A new method for the preparation of phase-pure ferromagnetic Fe₃P films on quartz substrates is reported. This approach utilizes the thermal decomposition of the single-source precursors H₂Fe₃(CO)₉PR (R = ^tBu or Ph) at 400 °C. The films are deposited using a simple, home-built metal-organic chemical vapor deposition (MOCVD) apparatus and are characterized using a variety of analytical methods. The films exhibit excellent phase purity, as evidenced by X-ray diffraction, X-ray photoelectron spectroscopy, and field-dependent magnetization measurements, the results of which agree well with measurements obtained from bulk Fe₃P. Using scanning electron microscopy and atomic force microscopy techniques, the films are found to have thicknesses between 350 and 500 nm with a granular surface texture. As-deposited Fe₃P films are amorphous, and little or no magnetic hysteresis is observed in plots of magnetization versus applied field. Annealing the Fe₃P films at 550 °C results in improved crystallinity as well as the observation of magnetic hysteresis.

Ferromagnetic Fe₃P films are readily deposited on quartz substrates at 400 °C using the single-source molecular precursors H₂Fe₃(CO)₉PR (R = ^tBu or Ph) in a simple, low-pressure metal-organic chemical vapor deposition (MOCVD) apparatus. The films exhibit exceptional phase purity and the structural, spectroscopic, and magnetic data obtained from the films agree well with data obtained from pure bulk Fe₃P.

Switching and control of efficient red, green, and blue active matrix organic light-emitting devices (AMOLEDs) by printed organic thin-film electrochemical transistors (OETs) are demonstrated. These all-organic pixels are characterized by high luminance at low operating voltages and by extremely small transistor dimensions with respect to the OLED active area. A maximum brightness of ≈900 cd m⁻² is achieved at diode supply voltages near 4 V and pixel selector (gate) voltages below 1 V. The ratio of OLED to OET area is greater than 100:1 and the pixels may be switched at rates up to 100 Hz. Essential to this demonstration are the use of a high capacitance electrolyte as the gate dielectric layer in the OETs, which affords extremely large transistor transconductances, and novel graded emissive layer (G-EML) OLED architectures that exhibit low turn-on voltages and high luminescence efficiency. Collectively, these results suggest that printed OETs, combined with efficient, low voltage OLEDs, could be employed in the fabrication of flexible full-color AMOLED displays.

Active matrix organic light-emitting devices (AMOLEDs) based on printed organic thin-film electrochemical transistors (OETs) are demonstrated. These efficient light-emitting pixels are characterized by high luminance at low operating voltages and by extremely small transistor dimensions with respect to the OLED active area. The use of a high capacitance gel-electrolyte as the transistor gate dielectric layer and graded emissive layer (G-EML) OLED architectures are essential.

Very recently, wing scales of natural Lepidopterans (butterflies and moths) manifested themselves in providing excellent three dimensional (3D) hierarchical structures for surface-enhanced Raman scattering (SERS) detection. But the origin of the observed enormous Raman enhancement of the analytes on 3D metallic replicas of butterfly wing scales has not been clarified yet, hindering a full utilization of this huge natural wealth with more than 175 000 3D morphologies. Herein, the 3D sub-micrometer Cu structures replicated from butterfly wing scales are successfully tuned by modifying the Cu deposition time. An optimized Cu plating process (10 min in Cu deposition) yields replicas with the best conformal morphologies of original wing scales and in turn the best SERS performance. Simulation results show that the so-called “rib-structures” in Cu butterfly wing scales present naturally piled-up hotspots where electromagnetic fields are substantially amplified, giving rise to a much higher hotspot density than in plain 2D Cu structures. Such a mechanism is further verified in several Cu replicas of scales from various butterfly species. This finding paves the way to the optimal scale candidates out of ca. 175 000 Lepidopteran species as bio-templates to replicate for SERS applications, and thus helps bring affordable SERS substrates as consumables with high sensitivity, high reproducibility, and low cost to ordinary laboratories across the world.

Piled-up hotspots, which are engineered naturally by subwavelength structures in Cu butterfly wing scales, significantly enhance the Raman signals of analytes. These results will help identify the optimal scale morphologies out of ca. 175 000 butterfly species for biotemplates to replicate for surface-enhanced Raman scattering (SERS) applications and bring affordable high-quality SERS substrates as consumables to ordinary laboratories across the world.

Tough, dense polyelectrolyte complexes (PECs) with well-defined cross-sections are prepared using a laboratory extruder and plasticizing the complexes with salt water. Stoichiometric starting materials yield stoichiometric complexes of poly(diallyldimethylammonium) (PDADMA) and poly(styrene sulfonate) (PSS). As an example of this enabling technology, macroscopic tubes of PEC are produced. Microscopy images of cross-sections of rods, tape, and tubes show a pore volume of less than 10% in the bulk of the extruded complex and fully dense material towards the surface, where the shear is greatest. Thermal gravimetric analysis reveals the expected salt content for PECs doped with NaCl, and a lack of salt for PECs rinsed in water. The fact that doped PECs are transparent suggests they are supersaturated with salt. Residual stress following extrusion is relieved by exposure to solutions of NaCl. Stress relaxation experiments show decreasing equilibrium moduli as a function of increasing salt doping, consistent with prior results on multilayers of the same polymers.

Large, dense shapes of nanoblended polyelectrolyte complex are produced for the first time. Properties and processing are influenced by the salt concentration of solutions to which the complexes are exposed. A macroscopic tube, of dimensions similar to blood vessels, is an example of the new morphologies accessible.

Chemically synthesized nanocrystal quantum dots (NQDs) are promising materials for applications in solution-processable optoelectronic devices such as light emitting diodes, photodetectors, and solar cells. Here, we fabricate and study two types of p-n junction photodiodes in which the photoactive p-layer is made from PbS NQDs while the transparent n-layer is fabricated from wide bandgap oxides (ZnO or TiO₂). By using a p–n junction architecture we are able to significantly reduce the dark current compared to earlier Schottky junction devices without reducing external quantum efficiency (EQE), which reaches values of up to ∼80%. The use of this device architecture also allows us to significantly reduce noise and obtain high detectivity (>10¹² cm Hz^1/2 W⁻¹) extending to the near infrared past 1 μm. We observe that the spectral shape of the photoresponse exhibits a significant dependence on applied bias, and specifically, the EQE sharply increases around 500–600 nm at reverse biases greater than 1 V. We attribute this behavior to a “turn-on” of an additional contribution to the photocurrent due to electrons excited to the conduction band from the occupied mid-gap states.

A schematic structure of a p–n junction photodiode, which comprises a nearly fully depleted p-type layer of PbS nanocrystal quantum dots and an n-type layer of ZnO nanoparticles, is shown. This device architecture allows us to significantly reduce noise current and obtain high detectivity of more than 10¹² cm Hz^1/2 W⁻¹.

A novel interfacially active and magnetically responsive nanoparticle is designed and prepared by direct grafting of bromoesterified ethyl cellulose (EC-Br) onto the surface of amino-functionalized magnetite (Fe₃O₄) nanoparticles. Due to its strong interfacial activity, ethyl cellulose (EC) on the magnetic nanoparticles enables the EC-grafted Fe₃O₄ (M-EC) nanoparticles to be interfacially active. The grafting of interfacially active polymer EC on magnetic nanoparticles is confirmed by zeta-potential measurements, diffuse reflectance infrared Fourier-transform spectroscopic (DRIFTS) characterization, and thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) images show a negligible increase in particle size, confirming the thin silica coating and grafted EC layer. The magnetization measurements show a marginal reduction in saturation magnetization by silica coating and EC grafting of original magnetic nanoparticles, confirming the presence of coatings. The M-EC nanoparticles prepared in this study show excellent interfacial activity and highly ordered features at the oil/water interface, as confirmed using the Langmuir–Blodgett technique and atomic force microscopy (AFM). The magnetic properties of M-EC nanoparticles at the oil/water interface make the interfacial properties tunable by or responsive to an external magnetic field. The occupancy of M-EC at the oil/water interface allows rapid separation of the water droplets from emulsions by an external magnetic field, demonstrating enhanced coalescence of magnetically tagged stable water droplets and a reduced overall volume fraction of the sludge.

A novel interfacially active and magneticallyresponsive nanoparticle is designed and prepared by directly grafting bromoesterified ethyl cellulose (EC-Br) onto the surface of amine-functionalized magnetite (Fe₃O₄) nanoparticles. The tagging of stable emulsified water droplets by the resulting nanoparticles enhances coalescence and rapid separation of the emulsified water droplets by an external magnetic field.

A way to obtain macroscopic responsive materials from silicon-oxide polymer core/shell microstructures is presented. The microparticles are composed of a 60 nm SiO₂-core with a random copolymer corona of the temperature responsive poly-N-isopropylacrylamide (PNIPAAm) and the UV-cross-linkable 2-(dimethyl maleinimido)-N-ethyl-acrylamide. The particles shrink upon heating and form a stable gel in both water and tetrahydrofuran (THF) at 3–5 wt% particle content. Cross-linking the aqueous gel results in shrinkage when the temperature is increased above the lower critical solution temperature and it regains its original size upon cooling. By freeze drying with subsequent UV irradiation, thin stable layers are prepared. Stable fibers are produced by extruding a THF gel into water and subsequent UV irradiation, harnessing the cononsolvency effect of PNIPAAm in water/THF mixtures. The temperature responsiveness translates to the macroscopic materials as both films and fibers show the same collapsing behavior as the microcore/shell particle. The collapse and re-swelling of the materials is related to the expelling and re-uptake of water, which is used to incorporate gold nanoparticles into the materials by a simple heating/cooling cycle. This allows for future applications, as various functional particles (antibacterial, fluorescence, catalysis, etc.) can easily be incorporated in these systems.

Responsive core/shell microparticles are used for the production of macroscopic materials such as films, fibers, and gels. Both aqueous and tetrahydrofuran gels are formed. By cross-linking of the particles, the temperature responsiveness of the particles is translated to the aqueous gels, films, and fibers, making them shrink and swell. This is used for post-incorporation of nanoparticles that can be taken up from the surrounding solution during swelling.

Visible transparency is one of the attributes pursued in the advancement of display devices. Such a transparency can be realized in a plasma display device simply by applying Y(V,P)O₄:Eu red-, Y(V,P)O₄:Tm blue-, and LaPO₄:Ce,Tb green-emitting nanophosphors with a controlled particle size and reasonable luminescence. The nanophosphors of three primary colors are all hydrothermally synthesized and annealed at appropriate conditions. Highly transparent, uniform emissive layers are deposited by screen-printing the nanophosphor pastes. Using respective screen-printed nanophosphor layers of red, blue, and green, monochromatic transparent test panels of plasma display are fabricated and characterized. Ultimately, a white-luminescing full-color transparent panel is successfully demonstrated by line-patterning the individual nanophosphor layers. Furthermore, for an effort to extract more photons and thus improve the brightness of the test panel, polystyrene monolayer-based 2D photonic crystal is introduced as a scattering medium on the outer surface of the panel and its usefulness was proved.

Using hydrothermally synthesized red Y(V_0.5,P_0.5)O₄:Eu, blue Y(V_0.5,P_0.5)O₄:Tm, and green LaPO₄:Ce,Tb nanophosphors, highly transparent emissive layers are screen-printed. Monochromatic test panels of transparent plasma display are fabricated by the simple combination of the rear plate (nanophosphor/glass) with the front plate of the current ac-plasma display panels and a white luminescent full-color transparent panel is demonstrated.

Innovative memory switch devices require reliable bistable conductance properties. It would be desirable if such bistable characteristics were available in robust solid state materials, such as diamond, which benefit from outstanding physical properties. A bistable current with reversible switching effect from surface transfer doped ultrananocrystalline diamond thin films measured by electron field emission is reported. This switching is manifested by the appearance of huge jumps in the current emission, up to four orders of magnitude, that occur at specific extracting electric field values. Persistent hysteresis is exhibited whenever the field is ramped down. It is proposed that these phenomena are the result of resonant-tunneling through a double barrier junction composed of tetrahedral amorphous carbon (ta-C)/nanodiamond/adsorbent/vacuum. This finding may pave the way for the realization of novel types of memory switch devices with unprecedented performance.

Reversible bistable current with a switching effect of the electron field emission from surface transfer doped ultrananocrystalline diamond thin films is reported. This switching is manifested by abrupt jumps in the current emission at specific extracting electric field values. Persistent hysteresis is exhibited whenever the field is ramped down. This finding may lead the way to novel memory switch devices with unprecedented performance.

This paper aims to give an overview on the recent progress of controlled colloidal assembly as a unique experimental modeling system to study the general crystallization mechanism, i.e., the kinetics of nucleation, growth, and defects formation, and as a template for photonic crystals engineering. Such a system allows us not only to visualize some “atomic” details of the nucleation and surface process of crystallization, but also to treat quantitatively the previous models to an extent that has never been achieved before by other approaches. As such, the kinetic process of nucleation was quantitatively examined at the single particle level for the first time, allowing the identification of the deviations from the classical theories. The application of the electrically controlled colloidal crystallization to the modeling of the kinetics of some important processes of crystallization, i.e., multistep crystallization, supersaturation-driven structural mismatch nucleation, defect creation and migration kinetics, surface roughening, etc., has brought our knowledge to a new phase. Apart from the fundamental aspects, the controlled colloidal crystallization has attracted significant attention in many applications. In this regard, the application of colloidal crystallization to the fabrication of photonic crystals and the biomimicking of natural structure colors will be examined.

As a unique and new modeling approach, electrically controlled colloidal assembly enables the acquisition of comprehensive knowledge about nucleation, surface/kink kinetics, and crystal growth at the single growth unit level that has never been acquired before. In practical applications, colloidal crystallization can be adopted to produce structural colors on silk fabrics.

The preparation and characterization of new, tailor-made polymeric membranes using poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymers for gas separation are reported. Structural differences in the copolymer membranes, obtained by manipulation of the self-assembly of the block copolymers in solution, are characterized using atomic force microscopy, transmission electron microscopy, and the transport properties of three gases (CO₂, N₂, and CH₄). The CH₄/N₂ ideal selectivity of 7.2, the highest value ever reported for block copolymers, with CH₄ permeability of 41 Barrer, is obtained with a membrane containing the higher amount of polybutadiene (79 wt%) and characterized by a hexagonal array of columnar polystyrene cylinders normal to the membrane surface. Membranes with such a high separation factor are able to ease the exploitation of natural gas with high N₂ content. The CO₂/N₂ ideal selectivity of 50, coupled with a CO₂ permeability of 289 Barrer, makes SBS a good candidate for the preparation of membranes for the post-combustion capture of carbon dioxide.

Tuning the morphology of poly(styrene-b- butadiene-b-styrene) (SBS) co-polymer membranes by means of the preparation procedure enhances the selective permeation of methane and CO₂. New SBS membranes with outstanding gas separation properties are reported.

The unique combination of the gas like viscosity and liquid like density of supercritical CO₂ (scCO₂) is exploited to blend poly(D,L-lactic acid) (P_DLLA) and poly(ethylene glycol) (PEG) at near ambient temperatures. This novel process lowers the polymer blend viscosity and also permits incorporation of thermally and solvent labile protein based drugs. A series of blends are prepared with agitation in scCO₂. Differential scanning calorimetry (DSC) data shows that miscible blends can be produced at moderate temperatures. A surprising region of miscibility is revealed between 8 and 25%w/w PEG. The properties of this miscible region are probed with high pressure parallel plate rheological studies, showing that the viscosity in scCO₂ is directly related to the miscibility. Using the particles from gas saturated solutions (PGSS) method, microparticles of these P_DLLA/PEG blends are produced using scCO₂ and it is determined that the yields obtained are proportional to the miscibility of the polymers. Thus scCO₂ provides a unique route to low temperature, solvent free processing that accesses a window of miscibility that has not previously been observed. Finally, DSC analyses of these sprayed microparticles confirm the presence of the same high miscibility region observed in the bulk samples prepared under supercritical conditions.

Supercritical CO₂ (scCO₂) is used to blend polymers poly(D,L-lactic acid) (P_DLLA) and poly(ethylene glycol) (PEG) at surprisingly low temperatures. Differential scanning calorimetry (DSC) data highlight an unusual region of polymer miscibility between 8 and 25 wt% PEG. This miscibility region directly affects the viscosity of the blends in scCO₂ and the particle yield from spraying. The particles produced also confirm the presence of this miscibility region.

The local electrical properties of a conductive graphene/polystyrene (PS) composite sample are studied by scanning probe microscopy (SPM) applying various methods for electrical properties investigation. We show that the conductive graphene network can be separated from electrically isolated graphene sheets (GS) by analyzing the same area with electrostatic force microscopy (EFM) and conductive atomic force microscopy (C-AFM). EFM is able to detect the graphene sheets below the sample surface with the maximal depth of graphene detection up to ≈100 nm for a tip-sample potential difference of 3 V. To evaluate depth sensing capability of EFM, the novel technique based on a combination of SPM and microtomy is utilized. Such a technique provides 3D data of the GS distribution in the polymer matrix with z-resolution on the order of ≈10 nm. Finally, we introduce a new method for data correction for more precise 3D reconstruction, which takes into account the height variations.

The conductive graphene network in a conductive graphene/polystyrene composite sample is separated from electrically isolated graphene sheets by analyzing the same area with conductive atomic force microscopy (C-AFM) and electrostatic force microscopy (EFM). The novel technique based on combination of scanning probe microscope and microtome is utilized for 3D reconstruction of the graphene sheets in the polymer matrix with z-resolution in the order of ≈ 10 nm.

An improvement of the crystal quality of opal films self-assembled from polymer spheres in a moving meniscus using the agitation by white noise acoustic vibrations is demonstrated. A tenfold higher ordering of a hexagonal sphere packing in the (111) plane is achieved. This crystallization method, the mechanism of which is described in terms of the stochastic resonance, is a contrast to the widely used approach based on maintaining equilibrium conditions during the crystallization process. The precise quantification of the incremental lattice order improvement as a function of acoustic noise intensity is achieved by calculating the probability of finding an opposite partner for each sphere in the lattice. This method is examined against conventional and established techniques such as Fourier transforms and translational and bond-orientational correlation functions, and its advantages are demonstrated. Rotational symmetry analysis of diffraction resonances in measured and calculated optical transmission spectra as a function of the azimuth lattice orientation are carried out to confirm that the surface ordering translates into the bulk ordering of high index crystal planes, which are most sensitive to disorder.

A tenfold improvement of thein-plane lattice ordering in opal films is achieved using the non-equilibrium self-assembly of colloidal suspension under agitation by noise vibrations. A new and robust quantitative method of surface lattice ordering characterization is applied and results are compared with the optical diffraction at high-index crystal planes.

Formulation of therapeutic proteins into particulate forms is a main strategy for site-specific and prolonged protein delivery as well as for protection against degradation. Precise control over protein particle size, dispersity, purity, as well as mild preparation conditions and minimal processing steps are highly desirable. It is, however, hard to fit all these criteria with conventional preparation techniques. Here a one-step hard-templating synthesis of microparticles composed of functional, non-denatured protein is reported. The method is based on filling porous CaCO₃ microtemplates with the protein near to its isoelectric point (pI) followed by pH- or EDTA-mediated dissolution of the tempplates. In principle, a wide variety of proteins can be converted into microparticles using this approach. The main requirement is an overlap of the protein insolubility and a template solubility for a certain parameter (here pH or EDTA). Here the formulation of insulin particles is studied in detail and it is shown that particles consisting of high molecular weight protein (catalase) can also be prepared. In this context, the synthesis of CaCO₃ templates with controlled size, the mechanism of the protein microparticle formation and mechanical properties of the microparticles are discussed. For the first time, the fabrication of mesoporous monodispersed CaCO₃ microtemplates with identical porocity but tuned diameter from 3 to 20 μm is demonstrated. The protein particle diameter can be adjusted by choosing the appropriate template size that is critical for successful pulmonary delivery of insulin. As a first step towards insulin delivery, the in vitro release of insulin at physiological conditions is studied.

Monodisperse microparticles with adjustable diameter composed from pure protein (insulin or catalase) are prepared under gentle conditions by hard-templating on porous decomposable CaCO₃ microtemplates via isoelectric precipitation followed by pH- or EDTA-mediated template removal. The mechanism of the particle formation, mechanical properties, protein release, and potential for drug delivery applications are addressed.

The search for hard materials to extend the working life of sharp tools is an age-old problem. In recent history, sharp tools must also often withstand high temperatures and harsh chemical environments. Nanotechnology extends this quest to tools such as scanning probe tips that must be sharp on the nanoscale, but still very physically robust. Unfortunately, this combination is inherently contradictory, as mechanically strong, chemically inert materials tend to be difficult to fabricate with nanoscale fidelity. Here a novel process is described, whereby the surfaces of pre-existing, nanoscale Si tips are exposed to carbon ions and then annealed, to form a strong silicon carbide (SiC) layer. The nanoscale sharpness is largely preserved and the tips exhibit a wear resistance that is orders of magnitude greater than that of conventional silicon tips and at least 100-fold higher than that of monolithic, SiO-doped diamond-like-carbon (DLC) tips. The wear is well-described by an atom-by-atom wear model, from which kinetic parameters are extracted that enable the prediction of the long-time scale reliability of the tips.

A novel process is described whereby the surfaces of nanoscale Si tips are exposed to carbon ions and then annealed to form a strong silicon carbide (SiC) layer. The nanoscale sharpness is largely preserved and the tips exhibit a wear resistance orders of magnitude greater than conventional silicon tips and at least 100-fold higher than monolithic, SiO-doped diamond-like carbon (DLC) tips.

A unique delivery system to reversibly and controllably load and release proteins under physiological conditions is desirable for protein therapeutics. We fabricate an ultrafast exponentially growing nanoporous multilayer structure comprised of two weak polyelectrolytes, poly(ethyleneimine) and alginate with thickness and chemical composition controlled by the assembly pH. For the first time, the assembled multilayered structure demonstrates stimuli-free reversible protein loading and release capability at physiological conditions by a synthetic material. The protein loading and release time can also be controlled by the assembled bilayer number. The highest loading capacity for the target protein and longest release time of proteins for layer-by-layer films reported to date have been achieved with a 15-bilayered film fabricated in this work. The prominent properties of the assembled film provide great potential for various biomedical applications, especially as a delivery system for protein therapeutics.

A novel nanoporous multilayeredPEI/alginate film is fabricated by exponentially growing, layer-by-layer self-assembly to serve as a carrier for protein loading and release. It is demonstrated to be the first artificial system reported to have the capability of stimuli-free reversible loading and release of proteins under physiological conditions and thus has great potential for various biomedical applications.

Efficient local gene transfection on a tissue scaffold is of crucial importance in facilitating tissue repair and regeneration. In this work, the gelatin-functionalized polycaprolactone (PCL) film surfaces are prepared via surface-initiated atom transfer radical polymerization of glycidyl methacrylate. The resultant covalent attachment of gelatin could enhance the cell-adhesion and local gene transfection properties. The gelatin-functionalized PCL film surfaces exhibit excellent cell-adhesion ability to both adherent and suspension cells. The attached adherent cells demonstrate the characteristic elongated morphologies with good spreading capability, while the attached suspension cells can maintain the original status of the round morphologies without spreading. More importantly, the gelatin coupled on the PCL surface could be used to absorb the cationic vector/plasmid deoxyribonucleic acid (pDNA) complexes via electrostatic interaction. The local gene transfection property on the immobilized cells is dependent on both the density of the immobilized cells and the loading types of pDNA complexes. The transfection efficiency of different assemble methods of pDNA complex was compared. With the pre- and post-loading sandwich-like gene transfection, the gelatin-functionalized PCL film surface can substantially enhance the transfection properties to different cell lines. The present study is very useful to spatially control local gene delivery within PCL-based tissue scaffolds.

Efficient local gene transfection on a tissue scaffold is of crucial importance in facilitating tissue repair and regeneration. The gelatin-functionalized polycaprolactone (PCL) film surfaces are prepared via surface-initiated atom transfer radical polymerization (ATRP) of glycidyl methacrylate (GMA), which could enhance the cell-adhesion and local gene transfection properties. With the pre- and post-loading sandwich-like gene transfection, the gelatin-functionalized PCL film surface can substantially enhance the transfection properties to different cell lines.

Four series of new 1,2,4-oxadiazole derived bent-core liquid crystals incorporating one or two cyclohexane rings are synthesized and investigated by optical polarizing microscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD), electro-optical, and dielectric investigations. All the compounds exhibit wide ranges of nematic phases composed of tilted smectic (SmC-type) cybotactic clusters with strongly tilted aromatic cores (40–57°) and show a distinct peak in the current curves observed under a triangular wave field. Dielectric spectroscopy of aligned samples corroborates the previously proposed polar structure of the cybotactic clusters and the ferroelectric-like polar switching of these nematic phases. Hence, it is shown that this is a general feature of the nematic phases of structurally different 3,5-diphenyl-1,2,4-oxadiazole derivatives. In these uniaxial nematic phases there is appreciable local biaxiality and polar order in the cybotactic clusters. As a second point it is shown that electric field induced fan-like textures, as often observed for the nematic phases of bent-core liquid crystals, do not indicate the formation of a smectic phase, rather they represent special electro-convection patterns due to hydrodynamic instabilities.

1,2,4-Oxadiazole-derived bent-core liquid crystals incorporating one or two cyclohexane rings form nematic phases composed of cybotactic clusters that show ferroelectric-like polar switching and electric field induced fan-like textures, representing special electro-convection patterns.

An in situ technique for preparing composite nanoparticles from hydrophobic cellulose acetate and hydrophilic polysaccharides using nanoprecipitation is presented. This technique allows the nanoparticles’ surface properties to be tuned very specifically. Spherical, narrow-size-distributed composite nanoparticles of different size, charge, functionality, and increased stability can be generated by using hydroxyethyl cellulose, carboxymethyl cellulose, low molecular weight chitosan, and amino cellulose. The influence of the pH and hydrophilic polysaccharide content in the particle formation is shown. The pH- and ionic strength- effective zeta-potential functions are evidence of the presence of functional polysaccharides at the nanoparticle surface. The in situ technique is compared with the adsorption of hydrophilic polysaccharides onto cellulose acetate nanoparticles in two steps. The great potential of in situ prepared composite nanoparticles in the pharmaceutical industry and bio- or food technology, as carriers of hydrophobic substances in aqueous media and for specific surface modifications, e.g., to selectively introduce strong antimicrobial properties, is illustrated.

Composite nanoparticles from cellulose acetate and a hydrophilic polysaccharide are prepared in situ using a nanoprecipitation technique. Hydrophilic polysaccharides of different charge and functionality can be applied, which allow very specific modification of the nanoparticle surfaces. The composite nanoparticles can be used for solubilizing hydrophobic compounds in an aqueous environment and for the nanostructuring of surfaces in order to introduce strong antimicrobial activities.

A range of optical probes are used to study the nanoscale-structure and electronic-functionality of a photovoltaic-applicable blend of the carbazole co-polymer poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole) (PCDTBT) and the electronic accepting fullerene derivative (6,6)-phenyl C₇₀-butyric acid methyl ester (PC₇₀BM). In particular, it is shown that the glass transition temperature of a PCDTBT:PC₇₀BM blend thin-film is not sensitive to the relative blend-ratio or film thickness (at 1:4 blending ratio), but is sensitive to casting solvent and the type of substrate on which it is deposited. It is found that the glass transition temperature of the blend reduces on annealing; an observation consistent with disruption of π–π stacking between PCDTBT molecules. Reduced π–π stacking is correlated with reduced hole-mobility in thermally annealed films. It is suggested that this explains the failure of such annealing protocols to substantially improve device-efficiency. The annealing studies demonstrate that the blend only undergoes coarse phase-separation when annealed at or above 155 °C, suggesting a promising degree of morphological stability of PCDTBT:PC₇₀BM blends.

In poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole) (PCDTBT) :(6,6)-phenyl C₇₀-butyric acid methyl ester (PC₇₀BM) photovoltaic thin-films, the glass transition temperature is not sensitive to the relative blend-ratio or film thickness, but is sensitive to thermal treatment, casting solvent, and substrate. The π–π stacking between PCDTBT reduces upon thermal annealing, an observation that is correlate with reduced hole-mobility in thermally annealed devices. Coarse phase-separation in PCDTBT:PC₇₀BM occurs upon annealing at or above 155 °C.

Rationally designed polydiacetylene (PDA) molecules have been developed for rapid, selective, sensitive, and convenient colorimetric detection of organophosphate (OP) nerve agents, a mass destruction weapon. Oxime (OX) functionality was incorporated into diacetylene molecules to utilize its strong affinity toward organophosphates. The diacetylene molecules having an OX functional group (OX-PDA) were self-assembled to form PDA liposomes in an aqueous solution. Upon exposure to organophosphate nerve agent simulants, OX at the OX-PDA liposome surface interacts with nerve agent simulants, which results in intraliposomal repulsive stress due to steric repulsion between OP-occupied OX units at the liposome surface as well as interliposomal aggregation induced by increased hydrophobicity of the liposome surface via OP-OX complex formation. The resulting intra- and interliposomal stress causes disturbance of the conjugated backbone of OX-PDA, producing color change as a label-free and sensitive sensory signal. The effects of molecular structure on selectivity and sensitivity of OX-PDA liposome solution, OX-PDA liposome-embedded agarose gels, and OX-PDA liposome-coated cellulose acetate membranes were systematically investigated. The optimized OX-PDA liposome in the solid state showed selective and rapid optical transition upon exposure down to 160 ppb of diisopropylfluorophosphate (DFP), a nerve agent simulant. The results provide an insightful molecular design principle of PDA-based colorimetric sensor and suggest portable sensory patches for rapid, selective, sensitive, and convenient colorimetric detection of organophosphate nerve agents.

Polydiacetylene (PDA) liposomes having oxime (OX) functionality are rationally designed and synthesized to selectively and sensitively detect organophosphate (OP) nerve agents. Solutions, gel-pads, and solid films of OX-PDA liposome demonstrate convenient, rapid, selective, and sensitive colorimetric detection of nerve agent simulants through intra-liposomal repulsion and interliposomal hydrophobic aggregation.

Cu²⁺-based metal-organic framework (Cu−TCA) (H₃TCA = tricarboxytriphenyl amine) having triphenylamine emitters was assembled and structurally characterized. Cu−TCA features a three-dimensional porous structure consolidated by the well-established Cu₂(O₂CR)₄ paddlewheel units with volume of the cavities approximately 4000 nm³. Having paramagnetic Cu²⁺ ions to quench the luminescence of triphenylamine, Cu−TCA only exhibited very weak emission at 430 nm; upon the addition of NO up to 0.1 mM, the luminescence was recovered directly and provided about 700-fold fluorescent enhancement. The luminescence detection exhibited high selectivity – other reactive species present in biological systems, including H₂O₂, NO₃⁻, NO₂⁻, ONOO⁻, ClO⁻ and ¹O₂, did not interfere with the NO detection. The brightness of the emission of Cu−TCA also led to its successful application in the biological imaging of NO in living cells. As a comparison, lanthanide metal-organic framework Eu−TCA having triphenylamine emitters and characteristic europium emitters was also assembled. Eu−TCA exhibited ratiometric fluorescent responses towards NO with the europium luminescence maintained as the internal standard and the triphenylamine emission exhibited more than 1000-fold enhancement.

A new metal-organic framework (MOF)-based luminescence NO chemosensor with triphenylamine blue emitters is consolidated by the well-established Cu₂(O₂CR)₄ paddlewheel units and successfully applied in luminescene detection of NO in aqueous solution and bioimaging of NO in living cells. The quenched triphenylamine-based emission is recovered upon encapsulating NO directly. The sensor exhibits excellent selectivity for NO over other reactive species in biological systems.

Silaindacenodithiophene is copolymerized with benzo[c][1,2,5]thiadiazole (BT) and 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (DTBT), respectively their fluorinated counter parts 5,6-difluorobenzo[c][1,2,5]thiadiazole (2FBT) and 5,6-difluoro-4,7-di(thiophen-2-yl) benzo[c][1,2,5]thiadiazole (2FDTBT). The influence of the thienyl spacers and fluorine atoms on molecular packing and active layer morphology is investigated with regard to device performances. bulk heterojunction (BHJ) solar cells based on silaindacenodithiophene donor-acceptor polymers achieved PCE's of 4.5% and hole mobilities of as high as 0.28 cm²/(V s) are achieved in an organic field-effect transistor (OFET).

Fluorine is introduced into silaindacenodithiophene based semiconducting polymers with the aim to improve the photovoltaic as well as the charge carrier properties. The influence of the thienyl spacers and fluorine atoms on molecular packing and active layer morphology of the new polymers is investigated with regard to device performance.

The relationship between the exciton binding energies of several pure organic dyes and their chemical structures is explored using density functional theory calculations in order to optimize the molecular design in terms of the light-to-electric energy-conversion efficiency in dye-sensitized solar cell devices. Comparing calculations with measurements reveals that the exciton binding energy and quantum yield are inversely correlated, implying that dyes with lower exciton binding energy produce electric current from the absorbed photons more efficiently. When a strong electron-accepting moiety is inserted in the middle of the dye framework, the light-to-electric energy-conversion behavior significantly deteriorates. As verified by electronic-structure calculations, this is likely due to electron localization near the electron-deficient group. The combined computational and experimental design approach provides insight into the functioning of organic photosensitizing dyes for solar-cell applications. This is exemplified by the development of a novel, all-organic dye (EB-01) exhibiting a power conversion efficiency of over 9%.

A combined computational and experimental design approach provides insight into the functioning of organic photosensitizer dyes for solar cell applications. Comparing calculations with measurements reveals that the exciton binding energy and quantum yield are inversely correlated. When a strong electron-accepting moiety is inserted in the middle of the dye framework, the light-to-electric energy conversion behavior significantly deteriorates.

Laser ablation of solid targets in the liquid medium can be realized to fabricate nanostructures with various compositions (metals, alloys, oxides, carbides, hydroxides, etc.) and morphologies (nanoparticles, nanocubes, nanorods, nanocomposites, etc.). At the same time, the post laser irradiation of suspended nanomaterials can be applied to further modify their size, shape, and composition. Such fabrication and modification of nanomaterials in liquid based on laser irradiation has become a rapidly growing field. Compared to other, typically chemical, methods, laser ablation/irradiation in liquid (LAL) is a simple and “green” technique that normally operates in water or organic liquids under ambient conditions. Recently, the LAL has been elaborately developed to prepare a series of nanomaterials with special morphologies, microstructures and phases, and to achieve one-step formation of various functionalized nanostructures in the pursuit of novel properties and applications in optics, display, detection, and biological fields. The formation mechanisms and synthetic strategies based on LAL are systematically analyzed and the reported nanostructures derived from the unique characteristics of LAL are highlighted along with a review of their applications and future challenges.

Laser ablation of solid targets in liquid medium has been elaborately developed to prepare nanomaterials with special morphologies, microstructures, and to achieve one-step functionalization. The synthetic strategies based on laser ablation in liquid (LAL) are summarized and nanostructures derived from the peculiarity of LAL are highlighted along with a review of their applications and future challenges.

Electronic structure theory has recently been used to propose hypothetical compounds in presumed crystal structures, seeking new useful functional materials. In some cases, such hypothetical materials are metastable, albeit with technologically useful long lifetimes. Yet, in other cases, suggested hypothetical compounds may be significantly higher in energy than their lowest-energy crystal structures or competing phases, making their synthesis and eventual device-stability questionable. By way of example, the focus here is on the family of 1:1:1 compounds ABX called “filled tetrahedral structure” (sometimes called Half-Heusler) in the four groups with octet electron count: I-I-VI (e.g., CuAgSe), I-II-V (e.g., AgMgAs), I-III-IV (e.g., LiAlSi), and II-II-IV (e.g., CaZnSn). First-principles thermodynamics is used to sort the lowest-energy structure and the thermodynamic stability of the 488 unreported hypothetical ABX compounds, many of which were previously proposed to be useful technologically. It is found that as many as 235 of the 488 are unstable with respect to decomposition (hence, are unlikely to be viable technologically), whereas other 235 of the unreported compounds are predicted to be thermodynamically stable (hence, potentially interesting new materials). 18 additional materials are too close to determine. The electronic structures of these predicted stable compounds are evaluated, seeking potential new material functionalities.

First-principles thermodynamics is used to determine the lowest-energy structures and stability with respect to decomposition of 488 hypothetical ABX Half-Heusler compounds from the groups I-I-VI, I-II-V, I-III-IV, II-II-IV and it is found that 235 are unstable against decomposition and 18 are too close to determine. 235 other unreported (UR) compounds are predicted to be new stable phases. The electronic structures of these predicted new compounds are evaluated, seeking potential new material functionalities.

As one of the most promising negative electrode materials in lithium-ion batteries (LIBs), SnO₂ experiences intense investigation due to its high specific capacity and energy density, relative to conventional graphite anodes. In this study, for the first time, atomic layer deposition (ALD) is used to deposit SnO₂, containing both amorphous and crystalline phases, onto graphene nanosheets (GNS) as anodes for LIBs. The resultant SnO₂-graphene nanocomposites exhibit a sandwich structure, and, when cycled against a lithium counter electrode, demonstrate a promising electrochemical performance. It is demonstrated that the introduction of GNS into the nanocomposites is beneficial for the anodes by increasing their electrical conductivity and releasing strain energy: thus, the nanocomposite electrode materials maintain a high electrical conductivity and flexibility. It is found that the amorphous SnO₂-GNS is more effective than the crystalline SnO₂-GNS in overcoming electrochemical and mechanical degradation; this observation is consistent with the intrinsically isotropic nature of the amorphous SnO₂, which can mitigate the large volume changes associated with charge/discharge processes. It is observed that after 150 charge/discharge cycles, 793 mA h g⁻¹ is achieved. Moreover, a higher coulombic efficiency is obtained for the amorphous SnO₂-GNS composite anode. This study provides an approach to fabricate novel anode materials and clarifies the influence of SnO₂ phases on the electrochemical performance of LIBs.

Both amorphous and crystallineSnO₂ are deposited onto graphene nanosheets (GNS) using atomic layer deposition. The amorphous SnO₂-GNS is more effective than the crystalline SnO₂-GNS in overcoming electrochemical and mechanical degradation due to the intrinsically isotropic nature; it delivers a higher coulombic efficiency, higher energy capacity, and a superior cycling stability.

A general and versatile route to prepare hierarchical polymer microparticles via interfacial instabilities of emulsion droplets is demonstrated. Uniform emulsion droplets containing hydrophobic polymers and n-hexadecanol (HD) are generated through microfluidic devices. When organic solvent diffuses through the aqueous phase and evaporates, shrinking emulsion droplets containing HD and polystyrene (PS) will trigger interfacial instabilities to form microparticles with wrinkled surfaces. Interestingly, surface-textures of the particles can be accurately tailored from smooth to high textures by varying the HD concentration and/or the rate of solvent evaporation. Moreover, composite particles can be generated by suspending different hydrophobic species to the initial polymer solutions. This versatile approach for preparing particles with highly textured surfaces can be extended to other type of hydrophobic polymers which will find potential applications in the fields of drug delivery, tissue engineering, catalysis, coating, and device fabrication.

A facile, yet versatile approach to generate hierarchical polymer microparticles through interfacial instabilities of emulsion droplets is presented. This novel method allows a continuous fine tuning of surface textures and particle morphologies by varying cosurfactant content and/or solvent evaporation rate.

The ability to quickly store and deliver a significant amount of electrical energy at ultralow temperatures is critical for the energy-efficient operation of high altitude aircraft and spacecraft, exploration of natural resources in polar regions and extreme altitudes, and astronomical observatories exposed to ultralow temperatures. Commercial high-power electrochemical capacitors fail to operate at temperatures below –40 °C. According to conventional wisdom, mesoporous electrochemical capacitor electrodes with pores large enough to accommodate fully solvated ions are needed for sufficiently rapid ion transport at lower temperatures. It is demonstrated that strictly microporous carbon electrodes with much higher volumetric capacitance can be efficiently used at temperatures as low as –70 °C. The critical parameters, with respect to electrolyte properties and electrode porosity and microstructure, needed for achieving both rapid ion transport and efficient ion electroadsorption in porous carbons are discussed. As an example, the fabrication of an electrochemical capacitor with an outstanding performance at temperatures as low as –60 and –70 °C is demonstrated. At such low temperatures the capacitance of the synthesized electrodes is up to 123 F g⁻¹ (≈76 F cm⁻³), which is 50–100% higher than that of the most common commercial electrochemical capacitor electrode at room temperature. At –60 °C selected cells based on ≈0.2 mm electrodes exhibited characteristic charge–discharge time constants of less than 9 s, which is faster than the majority of commercial devices at room temperature. The achieved combination of high energy and power densities at such ultralow temperatures is unprecedented and extremely promising for the advancement of energy storage systems.

Uniform, microporous, zeolite-templated carbons produced at low pressures demonstrate excellent ion transport and electroadsorption in pores at low temperatures. When used with a carefully designed electrolyte, these properties allow for fabrication of supercapacitors with an unprecedented combination of high specific capacitance, rapid charging ability, and high energy density characteristics at ultralow temperatures.

Temperature-dependent studies of the electrical and optical properties of cross-linked PbS nanocrystal (NC) solar cells can provide deeper insight into their working mechanisms. It is demonstrated that the overall effect of temperature on the device efficiency originates from the temperature dependence of the open-circuit voltage and the short-circuit current, while the fill factor remains approximately constant. Extensive modeling provides signs of band-like transport in the inhomogeneously coupled NC active layer and shows that the charge transport is dominated by diffusion. Moreover, via low temperature absorption and photoluminescence (PL) measurements, it is shown that the optical properties of PbS thin films before and after benzenedithiol (BDT) treatment exhibit very distinct behavior. After BDT treatment, both the optical density (OD) and PL are shifted to lower energies, indicating the occurrence of electronic wave function overlap between adjacent NCs. Decrease of the temperature leads to additional red-shift of the OD and PL spectra, which is explained by the well-known temperature dependence of the PbS NCs' bandgap. Moreover, BDT treated PbS NCs show unusual properties, such as decrease of the PL signal and broadening of the spectra at low temperatures. These features can be attributed to the partial relaxation of the quantum confinement and the opening of new radiative and nonradiative pathways for recombination at lower temperatures due to the presence of trap states.

Peculiar temperature-dependentelectrical and optical properties of cross-linked PbS nanocrystal thin films are demonstrated. Extensive modeling suggests diffusion-dominated charge transport through the inhomogeneously coupled nanocrystal arrays. After benzenedithiol treatment, the thin films exhibit unusual optical properties that can be attributed to partial relaxation of the quantum confinement and opening of alternative recombination pathways.

A highly fluorescent triazine-bridged polymer, poly[(diphenylamino-s-triazine)-co-(2-methoxy-5-propyloxysulfonate-1,4-phenylene vinylene)] (DTMSPV), is synthesized from Wittig polycondensation of a triazine monomer with a water-soluble p-phenylene vinylene monomer. The fluorescent amphiphilic polymer in aqueous solution self-assembled into nanoassemblies of micelle-like nanostructure (MS) and π stacking nanostructure (πS), which have average sizes of 93 to 270 nm, depending on the concentration of DTMSPV. The micelle-like nanostructure of DTMSPV (MS) shows blue emission at 457 and 488 nm with a high emission quantum yield (Φ_E) of 31% in aqueous solution. On the other hand, the Φ_E of π stacking structures (πS), formed in a highly concentrated solution, is lower than the MS. The MS exhibits fluorescence quenching as well as color change from blue to green/yellow, depending on the kinds of metal ions. The metal ion sensitivity is larger in the order of the main group ions (Na⁺, K⁺) < dicationic transition metal ions (Zn²⁺, Cd²⁺, Pb²⁺, Cu²⁺, Pd²⁺) < trivalent transition metal ions (Fe³⁺, Ru³⁺), with an exception of Al³⁺. In particular, the fluorescence of MS is dramatically quenched with color change to yellow in response to Al³⁺ concentrations. The selectivity and sensitivity of MS to Al³⁺ are unusually high even in the presence of competitive metal ions, which can be attributed to the specific interaction of triazine units with Al³⁺.

Highly fluorescent conjugated polyelectrolyte (DTMSPV) with high fluorescence quantum yield is syntheiszed for Al³⁺ sensing in aqueous solutions. The DTMSPV with dual metal binding sites is self-assembled into stable fluorescent nanostructures in aqueous solution. DTMSPV micelle-like structure (DTMSPV-MS) is sensitive and selective to Al³⁺, showing a color change from blue to yellow. Al³⁺ in water is easily eliminated by filtration of precipitates formed by the complexation of the triazine units of the polymer and Al³⁺.

A novel intelligent “active defense” system that can specially respond to cancerous tissues for drug release was designed and prepared. The “active defense” system consists of a biodegradable dextran microgel core cross-linked by a Schiff's base and a surrounding layer formed by Layer-by-Layer (LbL) assembly. The loading and release of macromolecular model drug, dex-FITC, as well as antineoplastic drug, DOX, was investigated. The in vitro cell inhibition and drug release behavior of the drug delivery system were studied and the results showed that the entrapped drug could be explosively released from the microcapsules and thereafter taken up by cancer cells upon the trigger of the acidic environment around tumor tissues.

A novel intelligent “active defense” system that can specially respond to cancerous tissues and explosively release drugs is designed and demonstrated. This “active defense” system consists of a biodegradable dextran microgel core cross-linked by Schiff's base and a surrounding layer formed through layer by layer (LbL) assembly. It is triggered by the tumor environment to act as an exploding microcapsule.

The use of vapor phase polymerized poly(3,4-ethylenedioxythiophene) (VPP-PEDOT) as a metal-replacement top anode for inverted solar cells is reported. Devices with both i) standard bulk heterojunction blends of poly(3-hexylthiophene) (P3HT) donor and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C₆₀ (PCBM) soluble fullerene acceptor and ii) hybrid inorganic/organic TiO₂/P3HT acceptor/donor active layers are studied. Stamp transfer printing methods are used to deposit both the VPP-PEDOT top anode and a work function enhancing PEDOT:polystyrenesulphonate (PEDOT:PSS) interlayer. The metal-free devices perform comparably to conventional devices with an evaporated metal top anode, yielding power conversion efficiencies of 3% for bulk heterojunction blend and 0.6% for organic/inorganic hybrid structures. These encouraging results suggest that stamp transfer printed VPP-PEDOT provides a useful addition to the electrode materials tool-box available for low temperature and non-vacuum solar cell fabrication.

The use of vapor phase polymerized poly(3,4-ethylenedioxythiophene) (VPP-PEDOT) as a metal anode replacement in inverted bulk heterojunction and hybrid organic/inorganic solar cells is reported. The VPP-PEDOT and a work-function enhancing PEDOT:polystyrene sulphonate (PEDOT:PSS) layer are stamp transfer printed on top of the active photogeneration layer. The resulting device performance is equivalent to that for devices made with thermally evaporated Au anodes.

A novel drug-formulation protocol is developed to solve the delivery problem of hydrophobic drug molecules by using inorganic mesoporous silica nanocapsules (IMNCs) as an alternative to traditional organic emulsions and liposomes while preserving the advantages of inorganic materials. The unique structures of IMNCs are engineered by a novel fluoride-silica chemistry based on a structural difference-based selective etching strategy. The prepared IMNCs combine the functions of organic nanoemulsions or nanoliposomes with the properties of inorganic materials. Various spherical nanostructures can be fabricated simply by varying the synthetic parameters. The drug loading amount of a typical highly hydrophobic anticancer drug-camptothecin (CPT) in IMNCs reaches as high as 35.1 wt%. The intracellular release of CPT from carriers is demonstrated in situ. In addition, IMNCs can play the role of organic nanoliposome (multivesicular liposome) in co-encapsulating and co-delivering hydrophobic (CPT) and hydrophilic (doxorubicin, DOX) anticancer drugs simultaneously. The co-delivery of multi-drugs in the same carrier and the intracellular release of the drug combinations enables a drug delivery system with efficient enhanced chemotherapeutic effect for DOX-resistant MCF-7/ADR cancer cells. The special IMNCs-based “inorganic nanoemulsion”, as a proof-of-concept, can also be employed successfully to encapsulate and deliver biocompatible hydrophobic perfluorohexane (PFH) molecules for high intensity focused ultrasound (HIFU) synergistic therapy ex vivo and in vivo. Based on this novel design strategy, a wide range of inorganic material systems with similar “inorganic nanoemulsion or nanoliposome” functions will be developed to satisfy varied clinical requirements.

A simple and efficient drug-formulation protocol is developed to solve the delivery problem of hydrophobic agents. The protocol uses inorganic mesoporous silica nanocapsules as a promising alternative to traditional organic emulsions and liposomes while preserving the advantages of inorganic materials. This is demonstrated by delivery of drugs for cancer chemotherapy and surgery as well as the co-delivery of molecules for enhanced chemotherapy of drug-resistant cancer.

A novel approach for the direct synthetic diamond–GaN integration via deposition of the high-quality nanocrystalline diamond films directly on GaN substrates at temperatures as low as 450–500 °C is reported. The low deposition temperature allows one to avoid degradation of the GaN quality, which is essential for electronic applications The specially tuned growth conditions resulted in the large crystalline diamond grain size of 100–200 nm without coarsening. Using the transient “hot disk” measurements it is demonstrated that the effective thermal conductivity of the resulting diamond/GaN composite wafers is higher than that of the original GaN substrates at elevated temperatures. The thermal crossover point is reached at ≈95–125 °C depending on the thickness of the deposited films. The developed deposition technique and obtained thermal characterization data can lead to a new method of thermal management of the high power GaN electronic and optoelectronic devices.

A direct method to integrate nanocrystallinediamond (NCD)with gallium nitride (GaN) is demonstrated by tuning growth conditions to form nanocrystalline diamond thin films with grain sizes of 100–200 nm on GaN substrates at low temperature (450 °C), which is essential for maintaining the structural integrity of GaN. The thermal conductivity of the composite NCD/GaN wafer is higher than that of GaN substrates at temperatures characteristic for GaN electronics.

The development of soft pneumatic actuators based on composites consisting of elastomers with embedded sheet or fiber structures (e.g., paper or fabric) that are flexible but not extensible is described. On pneumatic inflation, these actuators move anisotropically, based on the motions accessible by their composite structures. They are inexpensive, simple to fabricate, light in weight, and easy to actuate. This class of structure is versatile: the same principles of design lead to actuators that respond to pressurization with a wide range of motions (bending, extension, contraction, twisting, and others). Paper, when used to introduce anisotropy into elastomers, can be readily folded into 3D structures following the principles of origami; these folded structures increase the stiffness and anisotropy of the elastomeric actuators, while being light in weight. These soft actuators can manipulate objects with moderate performance; for example, they can lift loads up to 120 times their weight. They can also be combined with other components, for example, electrical components, to increase their functionality.

Soft pneumatic actuators based on composites consisting of elastomers with embedded sheet or fiber structures that are flexible but not extensible combine soft lithography, for fabrication, with the principles of origami, for structural design. These actuators respond to pressurization with a wide range of motions, such as bending, extension, contraction, and twisting.

Atomic layer deposition is used to synthesize Al₂O₃:ZnO(1:x) nanolaminates with the number of deposition cycles, x, ranging from 5 to 30 for evaluation as optically transparent, electron-selective electrodes in polymer-based inverted solar cells. Al₂O₃:ZnO(1:20) nanolaminates are found to exhibit the highest values of electrical conductivity (1.2 × 10³ S cm⁻¹; more than six times higher than for neat ZnO films), while retaining a high optical transmittance (≥80% in the visible region) and a low work function (4.0 eV). Such attractive performance is attributed to the structure (ZnO crystal size and crystal alignment) and doping level of this intermediate Al₂O₃:ZnO film composition. Polymer-based inverted solar cells using poly(3-hexylthiophene) (P3HT):phenyl-C₆₁-butyric acid methyl ester (PCBM) mixtures in the active layer and Al₂O₃:ZnO(1:20) nanolaminates as transparent electron-selective electrodes exhibit a power conversion efficiency of 3% under simulated AM 1.5 G, 100 mW cm⁻² illumination.

The structural, electrical, and optical propertiesof Al₂O₃:ZnO(1:x) nanolaminates synthesized by atomic layer deposition are evaluated as a function of the relative number of cycles x. Al₂O₃:ZnO(1:20) nanolaminates exhibit a seven-fold increase in electrical conductivity compared with neat ZnO films, which is attributed to changes in the crystal structure of the films and doping effects. Efficient poly(3-hexylthiophene) (P3HT):phenyl-C61 -butyric acid methyl ester (PCBM) poly- mer-based inverted solar cells utilizing Al₂O₃:ZnO(1:20) nanolaminate electron-selective electrodes are demonstrated.

Hemoglobin-based capsules for use as blood substitutes are successfully fabricated by covalent layer-by-layer assembly. Dialdehyde heparin (DHP) is used both as one of the wall components and a cross-linker without employing other extraneous or toxic crosslinking agents. The biocompatibility of (Hb/DHP)₆ microcapsules is evaluated through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay and cell experiments. The hemocompatibility of (Hb/DHP)₆ microcapsules is characterized in terms of prothrombin time, thrombin time, activated partial thromboplastin time, and hemolysis rate. The oxygen-carrying capacity of the microcapsules is demonstrated by converting the deoxy-Hb state of the microcapsules into the oxy-Hb state. All these results demonstrate that the hemoglobin-based microcapsules exhibit oxygen-carrying capacity as well as biocompatibility and hemocompatility, indicating that the as-prepared capsules have great potential to function as blood substitutes.

Biocompatible, biodegradable, and blood-compatible hemoglobin-based microcapsules used as blood substitutes are successfully fabricated by covalent layer-by-layer assembly. Given the advantages of the layer-by-layer assembly technique, the construction and behavior of these hemoglobin-based capsules are controllable and adjustable, which makes the obtained capsules promising candidates for applications as blood substitutes, oxygen carriers, and in other biomedical fields.

Carbon-based, molecular semiconductors offer several attractive attributes for spintronics, such as exceptionally weak spin-orbit coupling and compatibility with bottom-up nanofabrication. In spite of the promising properties of organic spin valves, however, the physical mechanisms governing spin-polarized conduction remain poorly understood. An experimental study of C₆₀-based spin valves is presented and their behavior is modeled with spin-polarized tunneling via multiple intermediate states with a Gaussian energy distribution. It is shown that, analogous to conductivity mismatch in the diffusive regime, the magnetoresistance decreases with the number of intermediate tunnel steps, regardless of the value of the spin lifetime. This mechanism has been largely overlooked in previous studies of organic spin valves. In addition, using measurements of the temperature and bias dependence of the magnetoresistance, inhomogeneous magnetostatic fields resulting from interfacial roughness are identified as a source for spin relaxation and dephasing. These findings constitute a comprehensive understanding of the processes underlying spin-polarized transport in these structures and shed new light on previous studies of organic spin valves.

Organic spin valves show many promising features but remain poorly understood. An experimental study of C₆₀-based spin valves is presented and their behavior is modeled with spin-polarized tunneling via multiple intermediate states. Analogous to the conductivity mismatch in the diffusive regime, the magnetoresistance decreases with the number of intermediate tunnel steps, regardless of the value of the spin lifetime.

Molybdenum disulfide (MoS₂) is systematically studied using Raman spectroscopy with ultraviolet and visible laser lines. It is shown that only the Raman frequencies of and peaks vary monotonously with the layer number of ultrathin MoS₂ flakes, while intensities or widths of the peaks vary arbitrarily. The coupling between electronic transitions and phonons are found to become weaker when the layer number of MoS₂ decreases, attributed to the increased electronic transition energies or elongated intralayer atomic bonds in ultrathin MoS₂. The asymmetric Raman peak at 454 cm⁻¹, which has been regarded as the overtone of longitudinal optical M phonons in bulk MoS₂, is actually a combinational band involving a longitudinal acoustic mode (LA(M)) and an optical mode (). Our findings suggest a clear evolution of the coupling between electronic transition and phonon when MoS₂ is scaled down from three- to two-dimensional geometry.

Raman frequencies of and peaks can be used to identify the layer number of ultrathin molybdenum disulfide (MoS₂) flakes. The systemmatic Raman characterizations using various laser lines suggest a clear evolution of the coupling between electronic transition and phonon when MoS₂ is scaled down from three- to two-dimensional geometry.

Electronic devices process information and transduce energy with electrons, while biology performs such operations with ions and chemicals. To establish bio-device connectivity, we fabricate a redox-capacitor film from a polysaccharide (i.e., chitosan) and a redox-active catechol. We report that these films are rapidly and repeatedly charged and discharged electrochemically via a redox-cycling mechanism in which mediators shuttle electrons between the electrode and film (capacitance ≈ 40 F/g or 2.9 mF/cm²). Further, charging and discharging can be executed under bio-relevant conditions. Enzymatic-charging is achieved by electron-transfer from glucose to the film via an NADPH-mediated redox-cycling mechanism. Discharging occurs by electron-donation to O₂ to generate H₂O₂ that serves as substrate for peroxidase-mediated biochemical reactions. Thus, these films offer the capability of inter-converting electrochemical and biochemical inputs/outputs. Among potential applications, we anticipate that catechol–chitosan redox-capacitor films could serve as circuit elements for molecular logic operations or for transducing bio-based chemical energy into electricity.

Catechol-modified-chitosan films are redox-active and can exist in oxidized or reduced states. These films can be reductively-charged either electrochemically or enzymatically by mediated redox-cycling reactions. Oxidative-discharging is achieved by electrochemical mediator redox-cycling or by donating electrons to O₂ to generate a substrate (H₂O₂) for subsequent enzymatic (peroxidase) reactions. Thus, these films can inter-convert electrochemical and biochemical inputs/outputs.

This article presents a critical discussion of the various physical processes occurring in organic bulk heterojunction (BHJ) solar cells based on recent experimental results. The investigations span from photoexcitation to charge separation, recombination, and sweep-out to the electrodes. Exciton formation and relaxation in poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole) (PCDTBT) and poly-3(hexylthiophene) (P3HT) are discussed based on a fluorescence up-conversion study. The commonly accepted paradigm describing the conversion of incident photons into charge carriers in the BHJ material is re-examined in light of these femtosecond time-resolved measurements. Transient photoconductivity, time-delayed collection field, and time-delayed dual pulse experiments carried out on BHJ solar cells demonstrate the competition between carrier sweep-out by the internal field and the loss of photogenerated carriers by recombination. Finally, an emerging hypothesis is discussed: that bimolecular recombination accounts for the majority of recombination from short circuit to open circuit in optimized solar cells, and that bimolecular recombination is bias- and charge-density-dependent. The study of recombination loss processes in organic solar cells leads to insights into what must be accomplished to achieve the “ideal” solar cell.

Recent experiments that investigate the recombination loss processes in organic bulk heterojunction solar cells, ranging from photoexcitation to charge transfer, recombination, and collection, are described. The study of recombination loss processes in optimized and intentionally unoptimized systems leads to insights into what must be accomplished to achieve the “ideal” solar cell.

The application of ¹H spin diffusion nuclear magnetic resonance (NMR) is expanded to polymer-fullerene blends for bulk heterojunction (BHJ) organic photovoltaics (OPV) by developing a new experimental methodology for measuring the thin films used in poly-3-hexylthiophene–phenyl C61-butyric acid methyl ester (P3HT-PCBM) OPV devices and by creating an analysis framework for estimating domain size distributions. It is shown that variations in common P3HT-PCBM BHJ processing parameters such as spin-coating speed and thermal annealing can significantly affect domain size distributions, which in turn affect power conversion efficiency. ¹H spin diffusion NMR analysis reveals that films spin-cast at fast speeds in dichlorobenzene are primarily composed of small (<10 nm) domains of each component; these devices exhibit low power conversion efficiencies (η = 0.4%). Fast-cast films improve substantially by thermal annealing, which causes nanometer-scale coarsening leading to higher efficiency (η = 2.2%). Films spin-cast at slow speeds and then slowly dried exhibit larger domains and even higher efficiencies (η = 2.6%), but do not benefit from thermal annealing. The ¹H spin diffusion NMR results show that a significant population of domains tens of nanometers in size is a common characteristic of samples with higher efficiencies.

¹H spin diffusion NMR is demonstratedto be a valuable method for estimating the domain sizes in polymer:fullerene (poly-3-hexylthiophene:phenyl-C61-butyric acid methyl ester (P3HT:PCBM)) thin-film blends for bulk heterojunction photovoltaic devices. Variations in spin-casting speed and thermal annealing schedule have dramatic effects on the domain sizes observed in the blend films, which in turn affects the power conversion efficiency.

Sequence-independent or “click” chemistry is applied for the preparation of a series of novel and structurally similar π-conjugated oligomers. The new oligomers are prepared using Wittig–Horner chemistry from bifunctional building blocks that can be interconnected to one another at any desired sequence. The bifunctional building blocks consist of aromatic skeletons with acetal protected aldehyde groups on one side and a phosphonic acid diethyl ester group para to the aldehyde functionality. The first step in the arylenevinylene formation is a Wittig–Horner coupling of a functionalized aldehyde with the methyl phosphonate ester ylide of a bifunctional monomer. A stepwise protection–deprotection process is applied for the preparation of structurally similar π-conjugated oligo-phenylene vinylenes. New di-, tri-, penta-, and hepta-phenylenevinylenes are prepared and characterized. Selected penta-arylenevinylenes are incorporated as the semiconductor channel in organic field-effect transistors.

Wittig–Horner vinyl bond formation using bifunctional monomers provides an efficient, sequence-independent synthesis tool for the assembly by design and optimization according to performance (i.e., engineering) of complex π-conjugated structures.

A combination of impedance spectroscopy, device characterization, and modeling is used to pinpoint key processes in the operation of polymer light-emitting electrochemical cells (LECs). At low applied voltage, electric double layers with a thickness of ≈2–3 nm are shown to exist at the electrode interfaces. At voltages exceeding the bandgap potential of the conjugated polymer (V ≥ 2.5 V for superyellow), a light-emitting p–n junction forms in situ, with a steady-state structure that is found to depend strongly on the applied voltage. This is exemplified by that the effective p–n junction thickness (d_pn) for a device with an interelectrode gap of 90 nm decreases from ≈23 nm at 2.5 V to ≈6 nm at 3.9 V. The current increases with decreasing d_pn in a concerted manner, while the brightness reaches its peak at V = 3.4 V when d_pn ≈ 10 nm. The existence of an optimum d_pn for high brightness in LECs is attributed to an offset between an increase in the exciton formation rate with decreasing d_pn, due to an increasing current, and a simultaneous decrease in the exciton radiative decay rate, when an increasing fraction of excitons diffuses away from the p–n junction into the surrounding non-radiative doping regions.

The formation of electric double layers (EDLs)and an emissive p–n junction in light-emitting electrochemical cells are studied. At low applied voltage, EDLs with a thickness of ≈2–3 nm form at the electrode interfaces, and at voltages exceeding the bandgap potential of the emissive conjugated polymer, a light-emitting p–n junction forms in situ, with a steady-state structure that depends strongly on the applied voltage.

A novel approach for the fabrication of multifunctional microspheres integrating several advantages of mesoporous, luminescence, and temperature responses into one single entity is reported. First, the hollow mesoporous silica capsules are fabricated via a sacrificial template route. Then, Gd₂O₃:Eu³⁺ luminescent nanoparticles are incorporated into the internal cavities to form rattle-type mesoporous silica nanocapsules by an incipient-wetness impregnation method. Finally, the rattle-type capsules serve as a nanoreactor for successfully filling temperature-responsive hydrogel via photoinduced polymerization to form the multifunctional composite microspheres. The organic–inorganic hybrid microspheres show a red emission under UV irradiation due to the luminescent Gd₂O₃:Eu³⁺ core. The in vitro cytotoxicity tests show that the samples have good biocompatibility, which indicates that the nanocomposite could be a promising candidate for drug delivery. In addition, flow cytometry and confocal laser scanning microscopy (CLSM) confirm that the sample can be effectively taken up by SKOV3 cells. For in vitro magnetic resonance imaging (MRI), the sample shows the promising spin-lattice relaxation time (T₁) weighted effect and could potentially apply as a T₁-positive contrast agent. This composite drug delivery system (DDS) provides a positive temperature controlled “on-off”drug release pattern and the drug, indomethacin (IMC), is released fast at 45 °C (on phase) and completely shut off at 20 °C (off phase). Meanwhile Gd₂O₃:Eu³⁺ plays an important role as the luminescent tag for tracking the drug loading and release process by the reversible luminescence quenching and recovery phenomenon. These results indicate that the obtained multifunctional composite has the potential to be used as a smart DDS for biomedical applications.

Hydrogel-modifiedluminescent rattle-type mesoporous silica microspheres are prepared. The composites have good compatibility and can act as a magnetic resonance (MR) contrast agent because of the Gd³⁺ ions. The drug release behavior is regulared via a change in temperature.

Nanophotonic circuits meet exciton polaritons (EPs) in organic nanomaterials: Great possibilities for the use of organic 1D crystalline nanostructures as building blocks are emerging. These remarkable studies will contribute significantly to the development of EP-based on-chip photonic devices in the near future.

A study of how light-induced degradation influences the fundamental photophysical processes in the active layer of poly(3-hexylthiophene)/[6,6]-phenyl C₆₁-butyric acid methyl ester (P3HT/PCBM) solar cells is presented. Non-encapsulated samples are systematically aged by exposure to AM 1.5 illumination in the presence of dry air for different periods of time. The extent of degradation is quantified by the relative loss in the absorption maximum of the P3HT, which is varied in the range 0% to 20%. For degraded samples an increasing loss in the number of excitons within the P3HT domains is observed with longer ageing periods. This loss occurs rapidly, within the first 15 ps after photoexcitation. A more pronounced decrease in the population of polarons than excitons is observed, which also occurs on a timescale of a few picoseconds. These observations, complemented by a quantitative analysis of the polaron and exciton population dynamics, unravel two primary loss mechanisms for the performances of aged P3HT/PCBM solar cells. One is an initial ultrafast decrease in the polaron generation, apparently not related to the exciton diffusion to the polymer/fullerene interface; the second, less significant, is a loss in the exciton population within the photoexcited P3HT domains. The steady-state photoinduced absorption spectra of degraded samples exhibits the appearance of a signal ascribed to triplet excitons, which is absent for non-degraded samples. This latter observation is interpreted considering the formation of degraded sites where intersystem crossing and triplet exciton formation is more effective. The photovoltaic characteristics of same blends are also studied and discussed by comparing the decrease in the overall power conversion efficiency of solar cells.

The impact of light-induced degradationon the exciton and charge separation dynamics in the active layer of poly(3- hexylthiophene)/[6,6]-phenyl C₆₁-butyric acid methyl ester (P3HT/PCBM) organic solar cells is studied using optical pump-probe spectroscopy. The losses in excitons and polarons are quantified and compared to the degradation of solar cell performances in which the active layer has been selectively aged.

This article presents the synthesis and physicochemical behavior of dual-responsive plasmonic nanoparticles with reversible optical properties based on protein-coated gold nanoparticles grafted with thermosensitive polymer brushes by means of surface-initiated atom transfer radical polymerization (SI-ATRP) that exhibit pH-dependent thermo-responsive behavior. Spherical gold NPs of two different sizes (15 nm and 60 nm) and with different stabilizing agents (citrate and cetyltrimethylammonium bromide (CTAB), respectively) were first capped with bovine serum albumin (BSA). The resulting BSA-capped NPs (Au@BSA NPs) exhibited not only extremely high colloidal stability under physiological conditions, but also a reversible U-shaped pH-responsive behavior, similar to pure BSA. The ϵ-amine of the L-lysine in the protein coating was then used to covalently bind an ATRP-initiator, allowing for the SI-ATRP of thermosensitive polymer brushes of oligo(ethylene glycol) methacrylates with an LCST of 42 °C in pure water and around 37 °C under physiological conditions. Such protein coated nanoparticles grafted with thermosensitive polymers exhibit a smart pH-dependent thermosensitive behavior.

Protein-coated gold nanoparticles grafted with thermosensitive polymer brushes behave as truly smart dual-responsive materials. Proteins are naturally pH-sensitive and confer reversible U-shaped pH-responsive properties to the particles, whereas polymer brushes of oligo(ethylene glycol) methacrylates grafted by means of surface-initiated atom transfer radical polymerization add fully reversible thermoresponsive properties to the nanoparticles. Such Au@protein-g-polymer NPs exhibit pH-dependent thermoresponsive behavior with reversible optical properties.

Core/shell structured C₃N₄/BiPO₄ photocatalyst is fabricated via a facile ultrasonic dispersion method. The thickness of the shell may be controlled by tuning the amount of C₃N₄ in the dispersion, which determines the enhanced level of photocatalytic activity. The optimum photocatalytic activity of C₃N₄/BiPO₄ at a weight ratio of 4% (C₃N₄/BiPO₄) under UV irradiation is almost 4.5 times as high as that of reference P25 (TiO₂) and 2.5 times of BiPO₄. More attractively, the dramatic visible light photocatalytic activity is generated due to the C₃N₄ loaded. The enhancement in performance is demonstrated to be the match of lattice and energy level between the C₃N₄ and BiPO₄. This match facilitates the separation and transfer of photogenerated electron–hole pairs at the heterojunction interfaces and may be important for other core/shell structured materials. In addition, this method is expected to be extended for other C₃N₄ loaded materials.

A C₃N₄/BiPO₄ core/shell structured photocatalyst is synthesized via a facile ultrasonic dispersion method. The match of the lattice and energy levels between C₃N₄ and BiPO₄ facilitates the separation and transfer of photogenerated electron–hole pairs at the heterojunction interfaces so that it significantly enhances UV light photocatalytic activity and visible light photocatalytic activity.

Based on previous theoretical and experimental results on the electrochemical etching of silicon in HF-based aqueous electrolytes, it is shown for the first time that silicon microstructures of various shapes and silicon microsystems of high complexity can be effectively fabricated in any research lab with sub-micrometer accuracy and high aspect ratio values (about 100). This is well beyond any up-to-date wet or dry microstructuring approach and is achieved using a wet etching, low-cost technology: silicon electrochemical micromachining (ECM). Dynamic control of the etching anisotropy (from 1 to 0) as the electrochemical etching progresses allows the silicon dissolution to be switched in real-time from the anisotropic to the isotropic regime and enables advanced silicon microstructuring to be achieved through the use of high-aspect-ratio functional and sacrificial structures, the former being functional to the microsystem operation and the latter being sacrificed for accurate microsystem fabrication. World-wide dissemination of the ECM technology for silicon microstructuring is envisaged in the near future, due to its low cost and high flexibility, with high-potential impact on, though not limited to, the broad field of microelectronics and microfabrication.

The advanced fabrication of silicon microstructures of various shapes and silicon microsystems of high complexity using electrochemical micromachining (ECM) technology is described. ECM technology makes use of a dynamic control of the electrochemical etching anisotropy, which allows silicon dissolution to be switched in real-time from the anisotropic to the isotropic regime, to enable the low-cost fabrication of microstructures and microsystems using both functional and sacrificial structures.

Cell-instructive characteristics of extracellular matrices (ECM) resulting from a subtle balance of biomolecular and biophysical signals must be recapitulated in engineered biomaterials to facilitate regenerative therapies. However, no material explored so far allows the independent tuning of the involved molecular and physical cues due to the inherent correlation between biopolymer concentration and material properties. Addressing the resulting challenge, a rational design strategy for ECM-inspired biohybrid hydrogels based on multi-armed poly(ethylene glycol) and heparin, adapting a mean field approach to identify conditions at which the balance of elastic, electrostatic, and excluded volume forces results in constant heparin concentrations within swollen polymer networks with gradually varied physical properties is introduced. Applying heparin-based biofunctionalization schemes, multiple distinct combinations of matrix parameters could be identified to effectively stimulate the pro-angiogenic state of human endothelial cells and the differentiation of human mesenchymal stem cells. The study demonstrates the power of joint theoretical and experimental efforts in creating bioactive materials with specifically and independently controllable characteristics.

Amean field approach is applied to develop ECM-inspired biohybrid hydrogels that allow for the independent variation of physical and biomolecular properties. Using this material, multiple combinations of matrix parameters are identified to effectively stimulate morphogenesis of human endothelial cells and differentiation of human mesenchymal stem cells.

Processing flexibility and good mechanical properties are the two major reasons for SU-8 extensive applicability in the micro-fabrication of devices. In order to expand its usability down to the nanoscale, conductivity of ultra-thin SU-8 layers as well as its patterning by AFM are explored. By performing local electrical measurements outstanding insulating properties and a dielectric strength 100 times larger than that of SiO₂ are shown. It is also demonstrated that the resist can be nano-patterned using AFM, obtaining minimum dimensions below 40nm and that it can be combined with parallel lithographic methods like UV-lithography. The concurrence of excellent insulating properties and nanometer-scale patternability enables a valuable new approach for the fabrication of nanodevices. As a proof of principle, nano-electrode arrays for electrochemical measurements which show radial diffusion and no overlap between different diffusion layers are fabricated. This indicates the potential of the developed technique for the nanofabrication of devices.

Atomic force microscopy (AFM)-based lithography of SU-8 ultra-thin films and its applicability for the fabrication of nanodevices are investigated. It is shown that SU-8 presents outstanding insulating properties and extremely high dielectric strength. A physical-chemical mechanism responsible for the AFM-based patterning is proposed and the potential of this AFM nanopatterning demonstrated by the prototyping and testing of nano-electrode arrays.

Two donor-π-acceptor (D-π-A) dyes are synthesized for application in dye-sensitized solar cells (DSSC). These D-π-A sensitizers use triphenylamine as donor, oligothiophene as both donor and π-bridge, and benzothiadiazole (BTDA)/cyanoacrylic acid as acceptor that can be anchored to the TiO₂ surface. Tuning of the optical and electrochemical properties is observed by the insertion of a phenyl ring between the BTDA and cyanoacrylic acid acceptor units. Density functional theory (DFT) calculations of these sensitizers provide further insight into the molecular geometry and the impact of the additional phenyl group on the photophysical and photovoltaic performance. These dyes are investigated as sensitizers in liquid-electrolyte-based dye-sensitized solar cells. The insertion of an additional phenyl ring shows significant influence on the solar cells' performance leading to an over 6.5 times higher efficiency (η = 8.21%) in DSSCs compared to the sensitizer without phenyl unit (η = 1.24%). Photophysical investigations reveal that the insertion of the phenyl ring blocks the back electron transfer of the charge separated state, thus slowing down recombination processes by over 5 times, while maintaining efficient electron injection from the excited dye into the TiO₂-photoanode.

Two donor-π-acceptor dyes are synthesized for application in dye-sensitized solar cells (DSSCs). The introduction of a phenyl ring between benzothiadiazole and cyanoacrylic acid acceptors led to an over six times higher efficiency in DSSCs compared to the sensitizer without phenyl unit due to inhibition of back electron transfer and reduced recombination rate.

A novel and highly versatile synthetic route for the production of functionalized graphene dispersions in water, acetone, and isopropanol (IPA), which exhibit long-term stability and are easy to scale up, is reported. Both graphene functionalization (wherein the oxygen content can be varied from 4 to 16 wt%) and dispersion are achieved by the thermal reduction of graphite oxide, followed by a high-pressure homogenization (HPH) process. For the first time, binders, dispersing agents, and reducing agents are not required to produce either dilute or highly concentrated dispersions of single graphene sheets with a graphene content of up to 15 g L⁻¹. High graphene content is essential for the successful printing of graphene dispersions by 3D microextrusion. Free-standing graphene films and micropatterned graphene materials are successfully prepared using this method. Due to the absence of toxic reducing agents, the graphene exhibits no cytotoxicity and is biocompatible. Furthermore, the electrical conductivity of graphene is significantly improved by the absence of binders. Flexible microarrays can be printed on different substrates, producing microarrays that are mechanically stable and can be bent several times without affecting electrical conductivity.

A new process for the preparation of functionalized graphene dispersions without surfactants or additives is described. This simple process is suitable for large-scale production and a wide range of concentrations including highly viscous graphene pastes. These pastes can be used in a printing process based on 3D- microextrusion to form electrically conducting patterns and coatings.

There are distinct advantages to designing polymer systems that afford two distinct sets of material properties– an intermediate polymer that would enable optimum handling and processing of the material, while maintaining the ability to tune in different, final polymer properties that enable the optimal functioning of the material. In this study, by designing a series of non-stoichiometric thiol-acrylate systems, a polymer network is initially formed via a base catalyzed Michael addition reaction that proceeds stoichiometrically via the thiol-acrylate “click” reaction. This self-limiting reaction results in a polymer with excess acrylic functional groups within the network. At a later point in time, the photoinitiated, free radical polymerization of the excess acrylic functional groups results in a highly crosslinked, robust material system. These two stage reactive thiol-acrylate networks that have intermediate stage rubbery moduli and glass transition temperatures that range from 0.5 MPa and -10 °C to 22 MPa and 22 °C, respectively, are formulated and characterized. The same polymer networks can then attain glass transition temperatures that range from 5 °C to 195 °C and rubbery moduli of up to 200 MPa after the subsequent photocuring stage. The two stage reactive networks formed by varying the stoichiometric ratios of the thiol and acrylate monomers were shown to perform as substrates for three specific applications: shape memory polymers, impression materials, and as optical materials for writing refractive index patterns.

Within two-stage reactive polymer systems, the stage 1 reaction is a self-limiting “click” Michael addition between multifunctional thiols and acrylate monomers with excess of acrylate functional groups. It results in a loosely crosslinked low modulus polymer with idealized properties for intermediate polymer processing. The stage 2 reaction is a photoinduced acrylate polymerization that rapidly achieves a highly crosslinked high modulus polymer.

Robust hollow spheres consisting of molecular-scale alternating titania (Ti_0.91O₂) nanosheets and graphene (G) nanosheets are successfully fabricated by a layer-by-layer assembly technique with polymer beads as sacrificial templates using a microwave irradiation technique to simultaneously remove the template and reduce graphene oxide into graphene. The molecular scale, 2D contact of Ti_0.91O₂ nanosheets and G nanosheets in the hollow spheres is distinctly different from the prevenient G-based TiO₂ nanocomposites prepared by simple integration of TiO₂ and G nanosheets. The nine times increase of the photocatalytic activity of G-Ti_0.91O₂ hollow spheres relative to commercial P25 TiO₂ is confirmed with photoreduction of CO₂ into renewable fuels (CO and CH₄). The large enhancement in the photocatalytic activity benefits from: 1) the ultrathin nature of Ti_0.91O₂ nanosheets allowing charge carriers to move rapidly onto the surface to participate in the photoreduction reaction; 2) the sufficiently compact stacking of ultrathin Ti_0.91O₂ nanosheets with G nanosheets allowing the photogenerated electron to transfer fast from the Ti_0.91O₂ nanosheets to G to enhance lifetime of the charge carriers; and 3) the hollow structure potentially acting as a photon trap-well to allow the multiscattering of incident light for the enhancement of light absorption.

Robust hollow spheres consisting of molecular-scale alternating titania (Ti_0.91O₂) nanosheets and graphene (G) nanosheets are successfully fabricated using a layer-by-layer assembly technique. The nanostructures exhibit high efficiency of photocatalytic conversion of CO₂ into renewable fuels.

The 3D nanomorphology of blends of two different (organic and inorganic) solid phases as used in bulk heterojunction solar cells is described by a spatial stochastic model. The model is fitted to 3D image data describing the photoactive layer of poly(3-hexylthiophene)-ZnO (P3HT-ZnO) solar cells fabricated with varying spin-coating velocities. A scenario analysis is performed where 3D morphologies are simulated for different spin-coating velocities to elucidate the correlation between processing conditions, morphology, and efficiency of hybrid P3HT-ZnO solar cells. The simulated morphologies are analyzed quantitatively in terms of structural and physical characteristics. It is found that there is a tendency for the morphology to coarsen with increasing spin-coating velocity, creating larger domains of P3HT and ZnO. The impact of the spin-coating velocity on the connectivity of the morphology and the existence of percolation pathways for charge carriers in the resulting films appears insignificant, but the quality of percolation pathways, considering the charge carrier mobility, strongly varies with the spin-coating velocity, especially in the ZnO phase. Also, the exciton quenching efficiency decreases significantly for films deposited at large spin-coating velocities. The stochastic simulation model investigated is compared to a simulated annealing model and is found to provide a better fit to the experimental data.

A new multiscale stochastic model accurately describes and models the morphology of disordered polymer–zinc oxide solar cells as function of processing parameters in terms of structural and physical blend characteristics including domain connectivity, charge carrier mobility, and exciton quenching efficiency. A key result is that increasing the spin-coating velocity leads to coarse morphology.

For a variety of purposes, solid electrolytes with high ionic conductivity are believed to be an alternative to widely used liquid electrolytes. Most of them are developed based on the exploration of crystalline or amorphous structures. As a very rare example of the beneficial influence of glass/ceramic interfaces, we report the conductivity of LiF films on SiO₂. The LiF thin films are surprisingly found to be structurally disordered on the silica (0001) surface, leading to a remarkable enhancement of the Li-ion conductivity (6 × 10⁻⁶ S cm⁻¹ at 50 °C, with an activation energy of 0.55 eV) of three orders of magnitude. The resulting conductivity is not exceedingly high, but is comparable with that of the current, best thin-film solid electrolyte (Li_{(3 + x)}PO_{(4 - x)}N_x). The conductivity is highest if a significant density of glass/ceramic interfaces is achieved and percolation of the interfaces guaranteed.

Arrhenius plots of lithium fluoride thin films grown on silica substrates during various heating–stabilization–cooling cycles allow three Li⁺-migration paths in the inner film, with different local conductivities, to be distinguished. A remarkable enhancement of the Li-ion conductivity arises from the formation of a significant density of glass/ceramic interfaces, enabling percolation of interfacial or amorphous pathways.

Freestanding silicon nanocrystals (Si-ncs) offer unique optical and electronic properties for new photovoltaic, thermoelectric, and other electronic devices. A method to fabricate Si-ncs which is scalable to industrial usage has been developed in recent years. However, barriers to the widespread utilization of these nanocrystals are the presence of charge-trapping defects and an oxide shell formed upon ambient atmosphere exposure hindering the charge transport. Here, we exploit low-cost post-growth treatment routes based on wet-etching in hydrofluoric acid plus surface hydrosilylation or annealing enabling a complete native oxide removal and a reduction of the defect density by up to two orders of magnitude. Moreover, when compared with only H-terminated Si-ncs we report an enhancement of the conductivity by up to a factor of 400 for films of HF etched and annealed Si-ncs, which retain a defect density below that of untreated Si-ncs even after several months of air exposure. Further, we demonstrate that HF etched and hydrosilylated Si-ncs are extremely stable against oxidation and maintain a very low defect density after a long-term storage in air, opening the possibility of device processing in ambient atmosphere.

For crystalline silicon nanoparticles (Si-ncs), various low-cost post-growth treatments are presented that efficiently reduce the number of charge-trapping defects in the Si-ncs and remove the native oxide that forms upon exposure to air and hinders the charge transport. Particularly promising are HF etched plus vacuum annealed Si-ncs leading to a strong conductivity enhancement in thin films and HF etched plus hydrosilylated Si-ncs that are extremely stable against reoxidation.

A working electrode design based on a highly porous 1D photonic crystal structure that opens the path towards high photocurrents in thin, transparent, dye-sensitized solar cells is presented. By enlarging the average pore size with respect to previous photonic crystal designs, the new working electrode not only increases the device photocurrent, as predicted by theoretical models, but also allows the observation of an unprecedented boost of the cell photovoltage, which can be attributed to structural modifications caused during the integration of the photonic crystal. These synergic effects yield conversion efficiencies of around 3.5% by using just 2 μm thick electrodes, with enhancements between 100% and 150% with respect to reference cells of the same thickness.

Highly efficient, thin, dye-sensitized solar cells can be designed through the integration of 1D photonic structures of optimized porosity, with increases in both the device photocurrent and the photovoltage. Devices with enhanced efficiency are obtained while preserving the transparency, which is a topic of major interest due to possible applications in building integrated photovoltaics (BIPV).

A facile approach for the fabrication of monolayer SnO₂ nanonet is presented using polymer colloid monolayer nanofilms from oil–water interface self-assembly as sacrificial templates. The hole size of the nanonets can be adjusted easily by the mean diameter of polymer colloidal spheres. This method can be extended to the fabrication of a series of monolayer nanonets of semiconducting oxides such as TiO₂, ZnO, and CeO₂. Furthermore, the first photoresponse nanodevice based on monolayer SnO₂ nanonet is fabricated. This device presents ultrahigh photocurrent and sensitivity, excellent stability, and reproducibility.

2D ordered SnO₂ monolayer nanofilm and other semiconducting metal-oxide nanofilms such as TiO₂, ZnO, and CeO₂ can be easily fabricated using polymer monolayer nanofilms prepared by oil–water interfacial self-assembly as sacrificial templates. The first 2D ordered SnO₂ monolayer nanofilm-based UV photodetector is successfully constructed. This photodetector exhibits ultrahigh photocurrent and sensitivity, excellent stability, and reproducible characteristics.

The demand for advanced energy storage devices such as supercapacitors and lithium-ion batteries has been increasing to meet the application requirements of hybrid vehicles and renewable energy systems. A major limitation of state-of-art supercapacitors lies in their relatively low energy density compared with lithium batteries although they have superior power density and cycle life. Here, we report an additive-free, nano-architectured nickel hydroxide/carbon nanotube (Ni(OH)₂/CNT) electrode for high energy density supercapacitors prepared by a facile two-step fabrication method. This Ni(OH)₂/CNT electrode consists of a thick layer of conformable Ni(OH)₂ nano-flakes on CNT bundles directly grown on Ni foams (NFs) with a very high areal mass loading of 4.85 mg cm⁻² for Ni(OH)₂. Our Ni(OH)₂/CNT/NF electrode demonstrates the highest specific capacitance of 3300 F g⁻¹ and highest areal capacitance of 16 F cm⁻², to the best of our knowledge. An asymmetric supercapacitor using the Ni(OH)₂/CNT/NF electrode as the anode assembled with an activated carbon (AC) cathode can achieve a high cell voltage of 1.8 V and an energy density up to 50.6 Wh/kg, over 10 times higher than that of traditional electrochemical double-layer capacitors (EDLCs).

A high energy density asymmetric supercapacitor is developed based on an additive-free, nano-architectured Ni(OH)₂/CNT electrode with an ultra-high specific capacitance of 3300 F g⁻¹ and high areal capacitance of 16 F cm⁻². This asymmetric supercapacitor prototype is able to power up a 3 V mini-fan for 90 s by 10 s charging with an AA battery.

Cu-nanowire-doped graphene (Cu NWs/graphene) is successfully incorporated as the back contact in thin-film CdTe solar cells. 1D, single-crystal Cu nanowires (NWs) are prepared by a hydrothermal method at 160 °C and 3D, highly crystalline graphene is obtained by ambient-pressure CVD at 1000 °C. The Cu NWs/graphene back contact is obtained from fully mixing the Cu nanowires and graphene with poly(vinylidene fluoride) (PVDF) and N-methyl pyrrolidinone (NMP), and then annealing at 185 °C for solidification. The back contact possesses a high electrical conductivity of 16.7 S cm⁻¹ and a carrier mobility of 16.2 cm² V⁻¹ s⁻¹. The efficiency of solar cells with Cu NWs/graphene achieved is up to 12.1%, higher than that of cells with traditional back contacts using Cu-particle-doped graphite (10.5%) or Cu thin films (9.1%). This indicates that the Cu NWs/graphene back contact improves the hole collection ability of CdTe cells due to the percolating network, with the super-high aspect ratio of the Cu nanowires offering enormous electrical transport routes to connect the individual graphene sheets. The cells with Cu NWs/graphene also exhibit an excellent thermal stability, because they can supply an active Cu diffusion source to form an stable intermediate layer of CuTe between the CdTe layer and the back contact.

1D Cu-nanowire-doped graphene (Cu NWs/graphene) is used as the back contact for CdTe solar cells. The efficiency of cells with the Cu NWs/graphene reaches up to 12.1%, higher than for those with traditional back contacts using Cu-particle-doped graphite (10.5%) or Cu thin films (9.1%). The Cu-NW cells also exhibit an excellent thermal stability.

Porous silicon (pSi) surfaces have been chemically patterned via a UV initiated hydrosilylation reaction of an alkene through a photomask, introducing chemical functionality in the exposed surface areas. A secondary, UV initiated hydrosilylation reaction with a second alkene of different functionality is performed to backfill the silicon hydride terminated regions on the surface, thereby affording patterned porous films with dual, surface chemistry. UV initiated hydrosilylations were performed using the alkene undecylenic acid N-hydroxysuccinimide (NHS) ester, and the pSi surfaces were stabilized by a second hydrosilylation reaction with a polyethylene glycol (PEG) appended alkene. NHS ester and PEG functionalized surfaces were used for the selective immobilization of the cell adhesion mediator protein fibronectin (FN), in the NHS-functional regions. Matrix-assisted laser desorption/ionization mass spectrometry imaging on the protein functionalized pSi surface confirmed the patterned conjugation of the FN to the NHS functionalized regions. Mammalian cells cultured on these surfaces showed attachment that was confined to the patterned areas of FN on the pSi surface.

Porous silicon surfaces are patterned with dual alkene compounds by means of a UV-initiated hydrosilylation reaction through a photomask. Patterned surface attachment of an NHS ester functionalized alkene, with a PEG alkene attached in the surrounding areas allowed patterned conjugation of the cell adhesion mediator protein fibronectin to pSi surfaces. Protein functionalized surfaces are successfully used for the guided attachment of mammalian neuronal cells.

Wavy ribbons of carbon nanotubes (CNTs) are embedded in elastomeric substrates to fabricate stretchable conductors that exhibit excellent performance in terms of high stretchability and small resistance change. A CNT ribbon with a thin layer of sputtered Au/Pd film is transferred onto a prestrained poly(dimethylsiloxane) (PDMS) substrate and buckled out-of-plane upon release of the prestrain. Embedded in PDMS, the wavy CNT ribbon is able to accommodate large stretching (up to the prestrain) with little change in resistance. For a prestrain of 100%, the resistance increases only about 4.1% when the wavy CNT ribbon is stretched to the prestrain. A simple stretchable circuit consisting of a light-emitting diode and two wavy ribbons is demonstrated and shows constant response on significant twisting, folding, or stretching. Fabricated with a simple buckling approach, the wavy CNT-ribbon-based stretchable conductors (e.g., interconnects and electrodes) could play an important role in stretchable electronics, sensors, photovoltaics, and energy storage.

Wavy carbon nanotube ribbons coated with a thin layer of metal film are fabricated on poly(dimethylsiloxane) (PDMS) substrates through mechanical buckling. Covered with a top layer of PDMS, the wavy nanotube ribbons are able to accommodate large stretching (up to 100%) with little change in resistance. The resistance stabilizes upon further unloading and reloading.

Understanding the electrical transport properties of individual semiconductor nanostructures is crucial to advancing their practical applications in high-performance nanodevices. Large-sized individual nanostructures with smooth surfaces are preferred because they can be easily made into nanodevices using conventional photolithography procedures rather than having to rely on costly and complex electron-beam lithography techniques. In this study, micrometer-sized NiCo₂O₄ nanoplates are successfully prepared from their corresponding hydroxide precursor using a quasi-topotactic transformation. The Co/Ni atomic arrangement shows no changes during the transformation from the rhombohedral LDH precursor (space group Rm) to the cubic NiCo₂O₄ spinel (space group Fdm), and the nanoplate retains its initial morphology during the conversion process. In particular, electrical transport within an individual NiCo₂O₄ nanoplate is further investigated. The mechanisms of electrical conduction in the low-temperature range (T < 100 K) can be explained in terms of the Mott's variable-range hopping model. At high temperatures (T > 100 K), both the variable-range hopping and nearest-neighbor hopping mechanisms contribute to the electrical transport properties of the NiCo₂O₄ nanoplate. These initial results will be useful to understanding the fundamental characteristics of these nanoplates and to designing functional nanodevices from NiCo₂O₄ nanostructures.

Micrometer-sized NiCo₂O₄ platelets are prepared from their corresponding hydroxide precursor. Then, the electrical transport within an individual NiCo₂O₄ nanoplate is investigated for the first time. The mechanisms of electrical conduction in the low-temperature range (T < 100 K) can be explained in terms of the Mott's variable-range hopping model. At high temperatures (T > 100 K), both the variable-range hopping and nearest-neighbor hopping mechanisms contribute to the electrical transport properties of the NiCo₂O₄ nanoplate.

This paper shows how the self-assembled interlocking of two nanostructured materials can lead to increased photovoltaic performance. A detailed picture of the reticulated 6-DBTTC/C₆₀ organic photovoltaic (OPV) heterojunction, which produces devices approaching the theoretical maximum for these materials, is presented from near edge X-ray absorption spectroscopy (NEXAFS), X-ray photoelectron spectroscopy (XPS), Grazing Incidence X-ray diffraction (GIXD) and transmission electron microscopy (TEM). The complementary suite of techniques shows how self-assembly can be exploited to engineer the interface and morphology between the cables of donor (6-DBTTC) material and a polycrystalline acceptor (C₆₀) to create an interpenetrating network of pure phases expected to be optimal for OPV device design. Moreover, we find that there is also a structural and electronic interaction between the two materials at the molecular interface. The data show how molecular self-assembly can facilitate 3-D nanostructured photovoltaic cells that are made with the simplicity and control of bilayer device fabrication. The significant improvement in photovoltaic performance of the reticulated heterojunction over the flat analog highlights the potential of these strategies to improve the efficiency of organic solar cells.

This paper shows how self assembly can be exploited to engineer the interface and morphology between the single crystal cables of donor material (6-DBTTC) and polycrystalline acceptor (C₆₀) to create an interpenetrating network of pure phases expected to be optimal for photovoltaic device performance. These strategies facilitate 3-D nanostructured photovoltaic cells made with the simplicity and control of bilayer device fabrication.

A novel method is described for fabricating an all-solid-state flexible micro-supercapacitor. The microelectrodes of the supercapacitor are prepared by in situ electrodeposition of polyaniline (PANI) nanorods on the surface of reduced graphene oxide (rGO) patterns that are fabricated by micromolding in capillaries. The morphologies of PANI nanorods could be controlled by the concentration of aniline and the growth time in the electrodeposition process. The micro-supercapacitor possesses electrochemical capacitance as high as 970 F g⁻¹ at a discharge current density of 2.5 A g⁻¹, as well as good stability, retaining 90% of its initial capacitance after 1700 consecutive cycles for the synergistic effect of these new rGO/PANI nanostructures. The results show that the method could represent a route for translating the interesting fundamental properties of rGO and conducting polymers into technologically viable energy devices. Furthermore, this study might further guide the preparation of functional graphene-based materials.

Microelectrodes of an all-solid-state flexiblemicro-supercapacitor are prepared using in situ electrodeposition of polyaniline nanorods onto the surface of reduced graphene oxide patterns. The micro-supercapacitor possesses high electrochemical capacitance and good stability.

Gecko-inspired angled elastomer micropillars with flat or round tip endings are presented as compliant pick-and-place micromanipulators. The pillars are 35 μm in diameter, 90 μm tall, and angled at an inclination of 20°. By gently pressing the tip of a pillar to a part, the pillar adheres to it through intermolecular forces. Next, by retracting quickly, the part is picked from a given donor substrate. During transferring, the adhesion between the pillar and the part is high enough to withstand disturbances due to external forces or the weight of the part. During release of the part onto a receiver substrate, the contact area of the pillar to the part is drastically reduced by controlled vertical or shear displacement, which results in reduced adhesive forces. The maximum repeatable ratio of pick-to-release adhesive forces is measured as 39 to 1. It is found that a flat tip shape and shear displacement control provide a higher pick-to-release adhesion ratio than a round tip and vertical displacement control, respectively. A model of forces to serve as a framework for the operation of this micromanipulator is presented. Finally, demonstrations of pick-and-place manipulation of micrometer-scale silicon microplatelets and a centimeter-scale glass cover slip serve as proofs of the concept. The compliant polymer micropillars are safe for use with fragile parts, and, due to exploiting intermolecular forces, could be effective on most materials and in air, vacuum, and liquid environments.

Gecko-inspired angled elastomermicropillarswith flat or round tip endings are presented as compliant pick-and-place micromanipulators. The pillars are 35 μm in diameter, 90 μm tall, and angled at an inclination of 20°. Through shear displacement control, pick-to-release attachment force ratios of 39 to 1 is achieved and micromanipulation is demonstrated.

This work reports a resistive switching effect observed at rectifying Pt/Bi_1–δFeO₃ interfaces and the impact of Bi deficiencies on its characteristics. Since Bi deficiencies provide hole carriers in BiFeO₃, Bi-deficient Bi_1–δFeO₃ films act as a p-type semiconductor. As the Bi deficiency increased, a leakage current at Pt/Bi_1–δFeO₃ interfaces tended to increase, and finally, rectifying and hysteretic current–voltage (I–V) characteristics were observed. In I–V characteristics measured at a voltage-sweep frequency of 1 kHz, positive and negative current peaks originating from ferroelectric displacement current were observed under forward and reverse bias prior to set and reset switching processes, respectively, suggesting that polarization reversal is involved in the resistive switching effect. The resistive switching measurements in a pulse-voltage mode revealed that the switching speed and switching ratio can be improved by controlling the Bi deficiency. The resistive switching devices showed endurance of >10⁵ cycles and data retention of >10⁵ s at room temperature. Moreover, unlike conventional resistive switching devices made of metal oxides, no forming process is needed to obtain a stable resistive switching effect in the ferroelectric resistive switching devices. These results demonstrate promising prospects for application of the ferroelectric resistive switching effect at Pt/Bi_1–δFeO₃ interfaces to nonvolatile memory.

p-type Schottky-like Pt/BiFeO₃ interfaces show a bipolar-type resistive switching effect. A non-volatile resistive switching effect at Pt/BiFeO₃ interfaces induced by ferroelectric polarization reversal is reported. The devices show promising characteristics for use as non-volatile memories such as stable resistive switching without the need for any forming process, data retention of >10⁵ s at room temperature, and endurance of >10⁵ cycles.

An upscalable, self-aligned patterning technique for manufacturing high- performance, flexible organic thin-film transistors is presented. The structures are self-aligned using a single-step, multi-level hot embossing process. In combination with defect-free anodized aluminum oxide as a gate dielectric, transistors on foil with channel lengths down to 5 μm are realized with high reproducibility. Resulting on-off ratios of 4 × 10⁶ and mobilities as high as 0.5 cm² V⁻¹ s⁻¹ are achieved, indicating a stable process with potential to large-area production with even much smaller structures.

A self-aligned multi-level embossing patterning method for manufacturing bottom-gate, bottom-contact thin-film transistors on flexible substrates is demonstrated. The low temperature processed metal-insulator-metal stack includes an optimized defect-free, flat, and uniform gate dielectric layer based on aluminum anodization. Electrical measurements exhibit promising transfer characteristics of the devices, proving the feasibility of this technique.

Nanoparticular drug delivery systems may help to overcome the limitations of conventional chemotherapy. They have been reported to improve the specificity of distribution, the bioavailability, and the solubility of drugs, as well as the duration of drug efficacy, and helping to overcome multidrug resistance. Although various polymeric nanoparticles have been developed for delivery of anticancer agents, most nanoparticles still focus on solubilizing drugs, improving targeting ability, and reducing side effects. In particular, targeting to the tumor is typically improved through passive or active targeting. Despite great achievements in both strategies, yet to be resolved are issues of toxicity in normal cells and enhancement of tumor-specificity. A new approach combining the dual strategies of passive tumor targeting and cancer-selective efficacy is proposed. Recombinant human gelatin conjugated with lipoic acid (rHG-LA) developed in this study forms nanoparticles spontaneously in aqueous solution and encapsulates alpha-tocopheryl succinate (α-TOS), a well-known cancer-selective apoptosis-inducing agent, within a hydrophobic core during the self-assembly. This study describes the promising applicability of α-TOS-loaded rHG-LA nanoparticles with passive targeting ability and cancer-specificity.

Recombinant human gelatin conjugated with lipoic acid (rHG-LA) forms nanoparticles spontaneously in aqueous solution and encapsulates alpha-tocopheryl succinate (α-TOS), a well-known cancer-selective apoptosis-inducing agent. The promising applicability of α-TOS-loaded rHG-LA nanoparticles with passive targeting ability and cancer cell-specific apoptosis is described.

The preparation of uniform large-area highly crystalline organic semiconductor thin films that show outstanding carrier mobilities remains a challenge in the field of organic electronics, including organic field-effect transistors. Quantitative control over the drying speed during dip-coating permits optimization of the organic semiconductor film formation, although the kinetics of crystallization at the air–solution–substrate contact line are still not well understood. Here, we report the facile one-step growth of self-aligning, highly crystalline soluble acene crystal arrays that exhibit excellent field-effect mobilities (up to 1.5 cm V⁻¹ s⁻¹) via an optimized dip-coating process. We discover that optimized acene crystals grew at a particular substrate lifting-rate in the presence of low boiling point solvents, such as dichloromethane (b.p. of 40.0 °C) or chloroform (b.p. of 60.4 °C). Variable-temperature dip-coating experiments using various solvents and lift rates are performed to elucidate the crystallization behavior. This bottom-up study of soluble acene crystal growth during dip-coating provides conditions under which one may obtain uniform organic semiconductor crystal arrays with high crystallinity and mobilities over large substrate areas, regardless of the substrate geometry (wafer substrates or cylinder-shaped substrates).

Self-aligning, highly crystalline, uniform soluble acene crystal arrays are facilely grown via an optimized one-step dip-coating process. The optimized crystals grow only when a particular substrate lifting-rate in the presence of low boiling point solvents. This is because the rate of input/output flows at the contact line is well-balanced with the optimal substrate lifting rate. The study provides a simple and reproducible method for creating high-performance uniform organic semiconductor thin films over large areas of substrates with a variety of geometries.

Highly efficient and fully solution-processed white organic light-emitting diodes (WOLEDs) based on fluorescent small molecules and a polar conjugated polymer as electron-injection material are reported. The emitting layer in the WOLEDs is a blend of new blue-, green-, and red-fluorescent small molecules, with a blending ratio of 100:0.4:0.8 (B/G/R) by weight, and a methanol/water soluble conjugated polymerpoly[(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) acts as the electron-injection layer (EIL). All the organic layers are spin-coated from solution. The device exhibits pure white emission with a maximum luminous efficiency of 9.2 cd A⁻¹ and Commission Internationale d'Eclairage Coordinates of (0.35, 0.36). PFN acting as the EIL material plays a key role in the improvement of the device performance when used in solution-processed small-molecule WOLEDs.

Fully solution-processed fluorescent small-molecule white organic light-emitting diodes (WOLEDs) are fabricated. The methanol/water soluble conjugated polymer (PFN), as the electron-injection layer (EIL) material, plays a key role in the improvement of the device performance for solution-processed small-molecule-based WOLEDs. A high efficiency is obtained. The performance is the best ever reported for solution-processed fluorescent small-molecule WOLEDs using fully solution-processed techniques.

Electrical characterizations on webs of highly ordered semiconducting polymer nanofibers (NFs) are often performed with large electrodes devices (millimeter scale) for which the carrier transport is an average between transport within isolated NFs and transport at the intersection of two or more NFs. In order to assess the nanoscale electrical properties of the NFs, a field-effect transistor based on conductive atomic force microscopy is introduced that allows the visualization of the current distribution at the nanometer scale within a web of poly(3-butylthiophene) NFs. The contact resistance is evaluated to be ≈4 kΩ cm, which does not limit the charge transport process, and the mobility in one single NF is μ_NF = 0.07 ± 0.03 cm² V⁻¹ s⁻¹. One NF can carry a current density of 20 kA cm⁻² without being destroyed. Moreover, by observing the current maps in detail, it is found that the electrical resistance associated with the bridging of two or more individual NFs does not reduce the charge transport inside the web of NFs. Finally, different kinds of bridging geometries are shown and the role of tie molecules is discussed.

A transistor is developed in which one of the electrodes is the mobile Conductive AFM tip. This device allows for the measurement of the hole mobility in one single conjugated polymer nanofiber and the detailed observation of the current distribution in a web of nanofibers, leading to the conclusion that the interfiber transport is not reducing the charge transport. The structure of nanofibers bridging points is discussed.

Molecularly directed self-assembly has the potential to become a nanomanufacturing technology if the critical factors governing the kinetics and yield of defect-free self-assembled structures can be understood and controlled. The kinetics of streptavidin-functionalized quantum dots binding to biontinylated DNA origami are quantitatively evaluated and to what extent the reaction rate and binding efficiency are controlled by the valency of the binding location, the biotin linker length, and the organization, and spacing of the binding locations on the DNA is shown. Yield improvement is systematically determined as a function of the valency of the binding locations and as a function of the quantum dot spacing. In addition, the kinetic studies show that the binding rate increases with increasing linker length, but that the yield saturates at the same level for long incubation times. The forward and backward reaction rate coefficients are determined using a nonlinear least squares fit to the measured binding kinetics, providing considerable physical insight into the factors governing this type of self-assembly process. It is found that the value of the dissociation constant, K_d, for the DNA–nanoparticle complex considered here is up to seven orders of magnitude larger than that of the native biotin–streptavidin complex. This difference is attributed to the combined effect that the much larger size of the DNA origami and the quantum dot have on the translational and rotational diffusion constants.

Nanopatterns of quantum dots are generatedon DNA origami at molecular precision. The quantitative studies of their binding kinetics show that the yield can be greatly improved by controlling many factors including the valency of the binding location, the biotin linker length, and the organization and spacing of the binding locations on the DNA.

A systematic study of the photonic band gap (PBG) properties of 8-, 10- and 12-fold rotational symmetric quasicrystals (QCs) defined by level set equations with various phase parameters is reported. The optimized filling ratios corresponding to the largest PBGs for 19 types of QCs are found, which are useful for photonic QC fabrication design. The impact of filling ratio, rotational symmetry, and experimental fabrication parameters on the resultant PBGs are studied via PBG maps calculated by finite-difference time-domain (FDTD). Large area, high quality 8-, 10-, and 12-fold quasicrystalline pattern fabrication using multiple exposure interference lithography (MEIL) is also demonstrated.

A 10-fold rotational symmetric quasicrystal pattern can be fabricated by multiple exposure interference lithography. The photonic band gap of the structure is calculated via finite difference time domain. The impacts of rotational symmetry, filling ratio, and phase parameter on the photonic band gap are discussed.

Conjugated rod-coil block copolymers provide an interesting route towards enhancing the properties of the conjugated block due to self-assembly and the interplay of rod-rod and rod-coil interactions. Here, we demonstrate the ability of an attached semi-fluorinated block to significantly improve upon the charge carrier properties of regioregular poly(3-hexyl thiophene) (rr-P3HT) materials on bare SiO₂. The thin film hole mobilities on bare SiO₂ dielectric surfaces of poly (3-hexyl thiophene)-block-polyfluoromethacrylates (P3HT-b-PFMAs) can approach up to 0.12 cm² V⁻¹ s⁻¹ with only 33 wt% of the P3HT block incorporated in the copolymer, as compared to rr-P3HT alone which typically has mobilities averaging 0.03 cm² V⁻¹ s⁻¹. To our knowledge, this is the highest mobility reported in literature for block copolymers containing a P3HT. More importantly, these high hole mobilities are achieved without multistep OTS treatments, argon protection, or post-annealing conditions. Grazing incidence wide-angle x-ray scattering (GIWAX) data revealed that in the P3HT-b-PFMA copolymers, the P3HT rod block self-assembles into highly ordered lamellar structures, similar to that of the rr-P3HT homopolymer. Grazing incidence small-angle x-ray scattering (GISAXS) data revealed that lamellar structures are only observed in perpendicular direction with short PFMA blocks, while lamellae in both perpendicular and parallel directions are observed in polymers with longer PFMA blocks. AFM, GIWAXS, and contact angle measurements also indicate that PFMA block assembles at the polymer thin film surface and forms an encapsulation layer. The high charge carrier mobilities and the hydrophobic surface of the block copolymer films clearly demonstrates the influence of the coil block segment on device performance by balancing the crystallization and microphase separation in the bulk morphological structure.

The attachment of asemi-fluorinated block can significantly improve upon the charge carrier properties of regioregular poly(3-hexyl thiophene) on bare SiO₂. The mobilities of poly (3-hexyl thiophene)- block polyfluoromethacrylates can approach up to 0.12 cm² V⁻¹ s⁻¹ with only 33 wt% of the P3HT block incorporated in the copolymer.

Nanoscale diamond has recently received considerable attention due to the various possible applications such as luminescence imaging, drug delivery, quantum engineering, surface coatings, seeding etc. For most of these fields a suitable surface termination and functionalization of the diamond materials are required. In this feature article we discuss recent achievements in the field of surface modification of nanoscale diamond including the establishment of a homogeneous initial surface termination, the covalent and non-covalent immobilization of different functional moieties as well as the subsequent grafting of larger (bio)molecules onto previously functionalized nanodiamond.

Surface chemistry on nanodiamond has developed into a field in its own right in recent years. In this overview the large variety of possible functionalization reactions on the surface of this purportedly inert material is presented. These modifications enable the application of nanodiamond in areas such as bioimaging, composites or quantum engineering.

A new process is presented that combines nanoimprint lithography and soft lithography to assemble metal–bridge–metal crossbar junctions at ambient conditions. High density top and bottom metal electrodes with half-pitches down to 50 nm are fabricated in a parallel process by means of ultraviolet nanoimprint lithography. The top electrodes are realized on top of a sacrificial layer and are embedded in a polymer matrix. The lifting of the top electrodes by dissolving the sacrificial layer in an aqueous solution results in printable electrode stamps. Crossbar arrays are noninvasively assembled with high yield by printing the top electrode stamps onto bare or modified bottom electrodes. A semiconducting and a quasi metal like conducting type of polymer are incorporated in the cross points to form metal-polymer-metal junctions. The electrical characterization of the printed junctions revealed that the functional integrity of the electrically addressed conductive polymers is conserved during the assembling process. These findings suggest that printing of electrodes represents an easy and cost effective route to highly integrated nanoscale metal-bridge-metal junctions if imprint lithography is used for electrode fabrication.

Metal electrode crossbar arrays with feature sizes in the nanometer range are fabricated by combining nanoimprint lithography with a universal and gentle printing method. The feasibility of this process is demonstrated by assembling 8 bit × 8 bit crossbar arrays. Metal– molecule metal junctions are realized and electrically characterized by incorporating two types of conductive polymers into the crossbar structures.

A novel living hyaline cartilage graft (LhCG) with controllable dimensions and free of non-cartilaginous constituents for articular regeneration is developed. As a living graft for regenerative medicine, LhCG is purely living tissue based and truly scaffold-free. The process of neotissue formation in LhCG is mediated by an interim biomaterial-based novel scaffolding system. This design highlights a philosophy of using biomaterials in engineered regenerative medicine as a transient guiding facility rather than a permanent part of substitute. The fabrication is designed and practiced in a continuous and integrated process, which attributes to its simplicity in operation. Because of the intrinsic non-cell-adhesive property of hydrogel scaffolds, articular chondrocytes’ phenotype is always preserved throughout the whole procedure, which has been tested and approved both in vitro and in vivo. In situ grafting trials in a rabbit model showcase high success rates in both cartilage repair and graft-host integration. Beyond cartilage repair, this LhCG model may provide a living-tissue-based open platform or niche for multi-tissue regenerations.

The living hyaline cartilage graft (LhCG) fabrication process is studied. The microtissues undergoing phase transfer cell culture (PTCC) interact and secrete extracellular matrices (ECMs), forming an intricate interpenetrating network of ECM within the hydrogel scaffold. With the removal of the alginate scaffold, the structural integrity of the construct remains intact and a pure, scaffold-free LhCG is formed that is ready for implantation.

The work reports a new method for large-area growth of graphene films, which have been predicted to have novel and broad applications in the future. While chemical vapor deposition (CVD) is currently the preferred method, it suffers from a rather narrow processing window, and there is also much to be desired in the electrical properties of the CVD films. A new method for large-area growth of graphene films is reported to overcome the narrow processing window of the CVD method. A composite substrate made of a C-dissolving top (Ni) layer and a C-rejecting bottom (Cu) layer is designed, which evolves into a C-rejecting mixture, to autonomously regulate the C content at an elevated yet stable level at and near the surface over an extended duration. This “smart” substrate promotes graphene formation over a wide temperature-gas composition window, leading to reliable growth of wafer-sized graphene films of defined layer-thickness and superior electrical–optical properties. This “smart”-substrate strategy can also be implemented on Si and SiO₂ supports, paving the way toward the direct fabrication of large area, graphene-enabled electronic and photonic devices.