Advanced Materials

Dye-bridged nanohybrids in which red and green luminescent dyes are covalently bridged to oligosi-loxane for white light-emitting diodes (LEDs) are reported on page 5767 by Byeong-Soo Bae and co-workers. The nanohybrid-based white LEDs have a high color rendering index and high thermal resistance due to the siloxane network and the chemically bridged hybrid structure. This organic luminescent material is a potential alternative to inorganic phosphors for high-performance white LEDs.

The photopolymerization of cholesteric liquid crystal droplets leads to the generation of solid chiral microspheres. The methodological approach of Cipparrone et al. reported on page 5773 enables control of the internal helical geometry of solid particles using dopant species in the precursor liquid crystal emulsion. The solid particles exhibit fascinating optical properties appropriate for applications in lab-on-a-chip technologies and colloidal science. Their unique capabilities are demonstrated by optical manipulation and lasing experiments.

The practical efficiency limits for nanostructured photovoltaics including organic small molecule, dye-sensitized, polymer, and colloidal-quantum-dot architectures estimated a posteriori are assessed. The specific challenges associated with improving the electrical power conversion efficiency of various nanostructured photovoltaic (nano-PV) technologies are discussed and several approaches to reduce their thermal losses beyond the single bandgap limit are reviewed. Critical considerations related to the module lifetime and cost that are unique to nano-PV architectures are also discussed.

Metal-to-ligand coordination is utilized in nanotechnology for the stabilization and directed self-assembly of nanometer-sized inorganic materials into highly ordered arrays. Moreover, hybrid materials for applications in nanoelectronics or catalysis are obtained when redox-active complexes are bound to (semi)conducting species (e.g., fullerenes, polyoxometalates). Among others, 2,2′:6′,2″-terpyridines, as chelating ligands, are widely applied for these purposes.

A coaxial nanohybrid consisting of a single-walled carbon nanotube (SWCNT), fullerodendron, and SiO₂ is created from a bottom-up approach by Yutaka Takaguchi and co-workers and shown to act as a photocatalyst, as reported on page 5750. The SWCNT/fullerodendron/SiO₂ coaxial nanohybrid demonstrates highly efficient hydrogen evolution from water upon visible-light irradiation in the presence of methyl viologen, benzyldihydroni-cotinamide, and a colloidal polyvinyl alcohol–Pt.

A coaxial nanohybrid consisting of a single-walled carbon nanotube (SWCNT), fullerodendron, and SiO₂ shows high-efficiency light-driven hydrogen evolution from water. Upon visible light irradiation, SWCNT/fullerodendron/SiO₂ coaxial nanohybrid shows hydrogen evolution activity in the presence of methyl viologen (MV²⁺), benzyldihydronicotinamide (BNAH), and a colloidal polyvinyl alcohol(PVA)-Pt.

The combination of solvent annealing, surface reconstruction, and a tone-reversal etching procedure provides an attractive approach to utilize block copolymer (BCP) lithography to fabricate highly ordered and densely packed silicon oxide nano-dots on a surface. The obtained silicon oxide nano-dots feature an areal density of 1.3 teradots inch⁻².

A hybrid approach to solar cells is demonstrated in which a silicon p–n junction, used in conventional silicon-based photovoltaics, is replaced by a room-temperature fabricated silicon/organic heterojunction. The unique advantage of silicon/organic heterojunction is that it exploits the cost advantage of organic semiconductors and the performance advantages of silicon to enable potentially low-cost, efficient solar cells.

Thermally stable red and green light-emitting nanohybrids are introduced as an organic luminescent converter with broad color tunability and a high color rendering index for white light-emitting diodes (LEDs). Nanohybrid-based white LEDs are thermally stable and the color coordination is not changed by heat exposure.

Solid chiral microspheres with unique and multifunctional optical properties are produced from cholesteric liquid crystal-water emulsions using photopolymerization processes. These self-organizing microspheres exhibit different internal configurations of helicoidal structures with radial, conical or cylindrical geometries, depending on the physicochemical characteristics of the precursor liquid crystal emulsion.

Uniform homeotropic and homogeneous alignment of liquid crystals (LCs) is facilely achieved by dispersing Ni nanoparticles (Ni NPs) into the LCs. The alignment mode depends on the morphology of the Ni NPs. The mechanism of NP-induced LC alignment is elucidated clearly, indicating that the perfect orientation arises from the adsorption of Ni NPs on the substrate.

A biomimetic substrate for cell-culture is fabricated by plasma treatment of a prestressed thermoplastic shrink film to create tunable multiscaled alignment “wrinkles”. Using this substrate, the functional alignment of human embryonic stem cell derived cardiomyocytes is demonstrated.

A near-infrared (NIR) absorbing contrast agent based on polypyrrole nanoparticles is described. Quantitative optical coherence tomography studies on tissue phantoms and Mie scattering calculations indicate their potential application for early-stage cancer diagnosis.

Based on conventional colloidal nanosphere lithography, we experimentally demonstrate novel graded-index nanostructures for broadband optical antireflection enhancement including the near-ultraviolet (NUV) region by integrating residual polystyrene antireflective (AR) nanoislands coating arrays with silicon nano-conical-frustum arrays. This is a feasible optimized integration method of two major approaches for antireflective surfaces: quarter-wavelength AR coating and biomimetic moth's eye structure.

The size of C-nanodots can be electrochemically tuned by changing the applied potential during their preparation. The higher the applied potential, the smaller the resulting C-nanodots. Moreover, the surface oxidation degree of the C-nanodots can also be electrochemically tuned. The red-shift of emission independent of the size provides an insight into the luminescence mechanism of C-nanodots.

A novel vacuum lamination approach to fabrication of high-performance single-crystal organic field-effect transistors has been developed. The non-destructive nature of this method allows a direct comparison of field-effect mobilities achieved with various gate dielectrics using the same single-crystal sample. The method also allows gating delicate systems, such as n -type crystals and SAM-coated surfaces, without perturbation.

Ultrafine grained aluminum alloys have restricted applicability due to their limited thermal stability. Metalized 7475 alloys can be soldered and brazed at room temperature using nanotechnology. Reactive foils are used to release heat for milliseconds directly at the interface between two components leading to a metallurgical joint without significantly heating the bulk alloy, thus preserving its mechanical properties.

Two thin-film assembly methods are coupled to address proteins. Electrodeposition confers programmability and generates a template for layer-by-layer (LbL) assembly. LbL enables precise control of film thickness and the incorporation of labile biological components. The capabilities are demonstrated using glucose oxidase (GOx) based electrochemical biosensing within a microfabricated fluidic device.

A prototype Mott transistor, the electric double layer transistor with a strained CaMnO₃ thin film, is fabricated. As predicted by the strain phase diagram of electron-doped manganite films, the device with the compressively strained CaMnO₃ exhibits an immense conductivity modulation upon applying a tiny gate voltage of 2 V.