Advanced Functional Materials

On page 3696, Wang et al. report on the nanoscale chemical surface patterning of different chemical species (amine, thiol, aldehyde, and biotin) in independent nanopatterns by the iterative application of thermochemical nanolithography. Due to the unique chemical stability of the patterns, the resultant substrates can be stored for weeks and subsequently be used for the selective attachment of nanometer-sized objects, such as proteins or DNA, using standard chemical protocols.

The inside cover image represents a novel azobenzene liquid-crystalline (LC) polymer with a block mesogenic side group, which exhibits a lamellar structure after annealing in an LC phase. Whereas irradiation with linearly polarized light aligns the lamellae parallel to the polarization, irradiation with unpolarized light erases the surface morphology accompanied by photochemical phase transition, as reported by K. Okano et al. on page 3804.

In order to maximize their unsurpassed physical properties, carbon nanotubes must be exfoliated down to individual tubes. Likewise, to access its unique properties graphene must be separated from its parent crystal. This article looks at liquid phase techniques to exfoliate both nanotubes and graphene.

Nanoscale chemical patterning of different chemical species in independent nanopatterns is achieved by iterative application of thermochemical nanolithography to inscribe amine patterns followed by their chemical conversion to other functional groups.

A clever solution to the problem of immobilization of PDA liposomes on a substrate for the use in biosensors is illustrated in the figure. This new immobilization method exploits crosslinking between the PDA liposomes through use of an ‘interlinker’, a bis-functional chemical capable of reacting with the functional groups on the PDA liposome surface. A PDA based biosensor chip for the simultaneous detection of multiple pathogens is demonstrated.

Graphene spintronics is currently regarded as one of the most pivotal research topics in group-IV spintronics. Here, an unprecedented robustness of the spin polarization in multilayer-graphene spin valves is revealed: the spin polarization of the injected spins into the graphene is constant at room temperature. This finding can expand the possibilities of device design for future spin transistors. Furthermore, an important accordance between theory and experiment in molecular spintronics is found, which provides construction of a steadfast physical basis in this field.

Pathogen-mimicking metal oxide nanoparticles with the ability to enter and to selectively target and activate the TLR9 pathway in cancer cells with optical and MR imaging capabilities are prepared. A multifunctional polymer is used as an interface for the nanoparticle surface modification that affords a protective organic biocompatible shell and provides an efficient and convenient means for loading the immunostimulatory oligonucleotides. These nanoparticles allow for monitoring of the nanoparticle cellular trafficking by optical and magnetic resonance imaging and can also be used for drug delivery.

Nucleation of silane SAMs at the surface of organic crystals occurs at molecular steps during the first few minutes of exposure to SAM vapor. The observed molecular step decoration results in macroscopically long nanoscale conducting channels at the crystal surface and opens intriguing possibilities for studies of nanoscale charge transport, as well as visualization and selective doping of surface defects in organic electronic devices.

A multifunctional TiO2 nanowire ultrafiltration (UF) membrane with a layered hierarchical structure is successfully fabricated via a simple and general method. The crystal phase, morphology, permeability and photocatalytic activity of the TiO₂ nanowire membrane are thoroughly investigated. Experimental results show that the membrane possesses unique properties, such as a high membrane flux and anti-fouling and anti-bacterial characteristics, making it promising for applications in environmental purification.

An in situ polymerization procedure is used to synthesize PPV inside the mesopores of monodisperse silica spheres. The composite displays properties that are superior to those of the unencapsulated polymer, including a higher fluorescence quantum yield, greater resistance to oxidative photobleaching, and increased processability. Self-assembly yields opaline films that exhibit overlap between the PPV emission band and the photonic bandgap.

MoO₃ deposition onto the polymer light-emitting material poly(dioctylfluorene-alt-benzothiadiazole) (F8BT) induces the following effects: upward band bending in the F8BT films accompanied by diffusion of MoO₃ ‘acceptors’ into F8BT, and the generation of an interface state near the Fermi level at the MoO₃-on-F8BT interfaces. These may be the origins of the improved hole-injection efficiency between F8BT and electrodes caused by MoO₃ interlayers.

The facile synthesis of a composite magnetic resonance contrast platform is described. It consists of Gd-labeled dendrimers encapsulated in porous polymersomes. These nanoparticles exhibit improval permeability to water flux and a large capacity to store chelated Gd within the aqueous lumen, resulting in enhanced longitudinal relaxivity.

When pH decreases from 7.0 to 6.9, a dark-to-bright optical response is observed in the liquid crystal (LC) comprising 4′-pentyl-biphenyl-4-carboxylic acid (5CB) doped with 4′-pentyl-biphenyl-4-carboxylic acid (PBA). The response can be explained by considering the orientational transitions of the LC induced by the protonation and deprotonation of PBA at the aqueous/LC interface. The high sensitivity to pH change can be further exploited for monitoring local pH changes resulting from enzymatic reactions.

A comprehensive density-functional theory study on a systematic series of organic thiols self-assembled on Au(111) surfaces (see figure) is presented. The authors derive relationships between the electronic structure of individual molecules and the properties of corresponding self-assembled monolayers (SAMs), namely the electrode work-function modification related to SAM adsorption and the alignment of the SAM conducting states relative to the metal Fermi level.

Single-crystalline copper-phthalocyanine (CuPc) nanowires in the metastable α-phase are synthesized by a simple, vapor-phase route through careful control of the growth temperature. α-CuPc nanowires are successfully incorporated as active semiconductors in field-effect transistors (FETs). Single nanowire devices exhibit carrier mobilities and current on/off ratios as high as 0.4 cm² V⁻¹ s⁻¹ and >10⁴, respectively, rendering them useful for organic photovoltaic cells, organic light-emitting diodes, FETs, memory devices, and gas sensors.

High metal content composite nanomaterials are produced following a facile method consisting of an organometallic synthesis of size-controlled Ru(0) nanoparticles as elemental bricks in the presence of a bifunctional ligand (see figure). Some of these nanocomposites display very interesting properties when applied as catalytic filters for gas sensors.

The charge dynamics in polymer/CdSe nanocrystal hybrid solar cells is examined by photo-induced absorption spectros copy and light-induced electron spin resonance (ESR). In contrast to polymer/PCBM ([6,6]-phenyl C₆₁-butyric acid methyl ester) systems, trapping of charge carriers dominates the dynamics. An increased amount of localized states in the polymer phase is found for the hybrid system, providing a reason for the limited efficiency of these systems.

The simple coating of poly(dimethylsiloxane) (PDMS) with a hybrid inorganic/organic polymer results in the creation of microfluidic channels that are chemically resistant to virtually any solvent. This novel modification method enables these microfluidic devices to be used for solvent-based applications such as oil-in-water and water-in-oil emulsions (see figure).

An azobenzene liquid-crystalline (LC) polymer with a block mesogenic side group is developed and exhibits a phase-separated structure after annealing in a LC phase. Whereas irradiation with linearly polarized light aligns the lamellae parallel to the polarization, irradiation with unpolarized light erases the surface morphology accompanied by photochemical phase transition.

The electronic structure at the hetero-interface between organic semiconductors is revealed by microelectrostatic calculations for the case of a junction of pentacene with C₆₀ fullerene. The strong discontinuity in quadrupole field provokes band bendings and level shifts, with consequences for geminate polaron-pair dissociation at such interfaces.

Nanorobots powered internally by a photovoltaic cell (PVC) are no longer a dream. Specially prepared PVCs irradiated by a 980-nm laser provide efficient electricity output, even when covered by layers of biological tissue, to power these nanodevices (see figure). These clever cells function through up-converting luminescence after excitation by the laser and because of the high penetration depth of 980-nm light in biological tissue the conversion efficiency is still high enough to power in-vivo nanodevices.

The synthesis of hyperbranched aminosilica (HAS) solid CO2 adsorbents is modified to obtain materials with varied amine loadings. The composition and structure of the materials, as well as the aminopolymers grown off of the support, are characterized by an array of techniques and correlated to their measured adsorption performance (see figure).