Advanced Materials

Fluorescent nanostructures within a transparent microstructure can be achieved via direct laser writing. On p. 781, Alexander Kuehne, Peter Skabara, Martin Dawson, Richard Pethrick, and co-workers report on a novel UV-transparent photoresist that incorporates star-shaped nanometer-sized oligofluorene truxenes. The method and materials will find applications in optical, electro-optical, and photonic devices. (Cover artwork by Leif Heuser).

Until recently, synthetic gels have been too weak for any engineering use. Strong double-network gels and other reinforced gels open the possibility of new biomedical devices, and may replace rubber in some applications. Immediate needs include a better understanding of the relationship between mechanical properties and structure in gels, and convenient methods for processing gels.

The introduction of a thin electronic sieve layer of a material with a wide bandgap, such as lithium fluoride (LiF) or silicon oxide (SiO_x), at the inorganic-organic interface of an organic photovoltaic device enhances the charge separation and improves the efficiency by more than an order to a maximum of 6.04%.

The solar-to-electric power-conversion efficiency (η) of dye-sensitized solar cells can be greatly enhanced by integrating a mesoporous, nanoparticle-based, 1D photonic crystal as a coherent scattering layer in the device. The photogenerated current is greatly improved without altering the open-circuit voltage of the cell, while keeping the transparency of the cell intact. Improved average η values between 15% and 30% are attained.

A liquid-crystal/polymer composite is used to produce a photonic bandgap system. Films of the composite show a large field-induced reversible color shift of the reflection band of over 150 nm. Intensity-controllable laser emission at relatively low lasing thresholds is generated from composite films doped with dye. Moreover, the laser exhibits omnidirectional emission propagation on application of an electric field.

Translucent composite films of poly(vinylidene fluoride), ionic liquid, and nickel complexes are successfully fabricated using thermal modulation of dissolution, casting, and drying. These films exhibit high stability in ambient storage and reversible thermochromic responses in air at temperatures achievable under sunlight, promising intelligent windows for controlling solar heat entering the built environment.

Recently developed star-shaped nanosized oligofluorene truxenes are dispersed in a novel vinyl ether based photoresist to produce microstructures via direct laser writing. The technique offers rapid and facile production of nanostructures whithin a microstructure, and ensures environmental protection from photo-oxidation of the fluorescent molecules.

Picoforce atomic force microscopy (AFM) and specific DNA hybridization have been used to lock on to synthetic nano-π-stacks, revealing the secrets of thermophilic, albeit weak, π–π interactions. A cone-shaped dendron created an appropriate lateral spacing to ensure that most times a single stack was confined between the tip and the substrate, eliminating undesired multi-molecular pulling and greatly simplifying data analysis.

Thin-film carbon-nanotube networks can interface with living neuroendocrine PC12 cells and support their growth and proliferation. Interestingly, as revealed by total-internal-reflection fluorescence microscopy, the nanoroughness created by the carbon-nanotube net physically deforms the 5 nm thick cell membrane with high local curvature, and significantly impedes the lateral motion of subplasmalemmal secretory vesicles.

The direct assembly of polymer blends on chemically functionalized surfaces is shown to produce a variety of nonuniform complex patterns. This method provides a powerful tool for easily producing nonuniform patterns in a rapid (30 s), one-step process with high specificity and selectivity for a variety of applications, such as nanolithography, polymeric optoelectronic devices, integrated circuits, and biosensors.

A light-emitting transistor (LEFET) architecture with a distributed feedback (DFB) resonator structure nanoimprinted into the gain medium offers a route to achieving an electrically pumped plastic laser. A 2D DFB laser provides lower lasing thresholds than a 1D DFB laser under identical conditions. The 2D DFB lasers exhibit excellent characteristics with lasing threshold and slope efficiency of 32 nJ/pulse and 1.2%, respectively.

A procedure for gram-scale synthesis of monodisperse Cu₂O nanocubes by a simple polyol process is demonstrated. The nanocubes are subsequently oxidized to form CuO hollow cubes, spheres, and urchin-like particles, through a sequential dissolution–precipitation process. The CuO urchin-like particles exhibited excellent electrochemical performance and stability, superior to those of hollow structures, for lithium-ion battery anode materials.

The formation and thermodynamic stability of silicon-vacancy (Si-V) color centers, intensively emitting at a wavelength of 738 nm, are demonstrated for the first time in nanodiamonds less than 10 nm in size. These findings open prospects for the production of stable and efficient optical nanoemitters (single-photon emitters) based on nanodiamond.

A facile, scalable, and low-cost gas-treatment method for selectively etching semiconductor single-walled carbon nanotubes (SWNTs) is developed. Using SO₃ gas as the etchant at a temperature of 400 °C, semiconductor SWNTs can be selectively and efficiently removed, and after this gas treatment samples enriched with metallic SWNTs can be obtained.

Two-variant stripe domains in BiFeO₃ films on miscut (001) SrTiO₃ substrates exhibit square-like, complete ferroelectric switching with low leakage current. Both the preferential distortion of BiFeO₃ unit cells and the persistent step-flow growth induced by the substrate anisotropy are the origins of the formation of the two-variant stripe domains in (001) BiFeO₃ films.

Carbon nanotube (CNT) composites have attracted much interest because of their potential applications in many fields. Herein, recent advances in the synthesis of CNT composites using supercritical (SC) fluids, including SC CO₂, SC-CO₂-based solutions, SC water, and SC methanol, are highlighted. Particular emphasis is placed on the synthesis of metal/CNT, metal-oxide/CNT (see figure), and polymer/CNT composites.