Advanced Materials

Functional hybrids are nanocomposite materials lying at the interface of organic and inorganic realms, whose high versatility offers a wide range of possibilities to elaborate tailor-made materials in terms of chemical and physical properties. The most striking examples of functional hybrids (see Figure) exhibiting emission, absorption, nonlinear optical, and sensing properties are summarized in this review.

A simple technique is introduced to pattern proteins and cells with precise control over the feature topography (see Figure, white bar indicates 20 μm). The technique uses a combination of a molding process and a novel poly(ethylene glycol) copolymer to form topographical features ranging from polymeric monolayers to microstructures via simple modifications to the fabrication process.

A high-quality (0001)-oriented ZnO layer that emits ultraviolet light at room-temperature has been prepared by electrodeposition on a (111) Au/(100) Si substrate. The ZnO layer emits ultraviolet light at a photon energy of around 3.3 eV due to the recombination of bound excitons and visible light at 2.34–2.8 eV at room temperature. The preparation temperature for this electrodeposition technique is several hundreds of degrees less than for other known techniques.

A new type of semiconducting material based on polymerizable oligothiophenes (see Figure) has been prepared. In field-effect transistors, a charge-carrier mobility of 10^–3 cm² V^–1 s^–1 is observed prior to polymerization. Photopolymerization to a polymer network provides mechanical stability and allows direct photopatterning of the semiconductor. These materials also appear more stable to oxidative doping than polythiophenes.

Unusual superhelix-like patterns on the surface of azopolymer films (see Figure) have been directly photofabricated by exposure to a laser interference pattern. Each superhelix-like pattern is aligned parallel to the others, with a diameter of micrometer scale that could be controlled by the laser interference periodicity.

Organic thin-film transistors with active layers of five different functionalized pentacene derivatives (see Figure) have been fabricated. The pentacene molecules are functionalized to encourage face-to-face molecular interactions and thus increase π-orbital overlap and carrier field-effect mobility. Devices fabricated using triisopropylsilyl pentacene have the highest field-effect mobility (0.4 cm² V^–1 s^–1) and on/off current ratio (10⁶).

One- and two-photon interferential patterning of photopolymerizable resin is demonstrated to lead to well-defined two-dimensional (2D) photonic crystal structures (which beat the diffraction limit) and also 3D nanonetworks, such as that shown in the Figure. The fiber-like features are probably formed by a novel self-assembly mechanism during drying. Applications in photonics are foreseen.

An inexpensive procedure to fabricate highly ordered, patterned through-hole nanopore arrays of anodic aluminum oxide (AAO, see Figure) with intermittent aluminum supports has been developed. Silica was used as the anodization barrier. Using a two-step anodization process, straight nanopores of AAO are formed in the unpatterned areas; no pores are found in the patterned areas.

A new electrochemical strategy has been developed for the production of mesoporous Pt films (see Figure). The method utilizes only a thin interfacial region of surfactant–inorganic assemblies formed on the working electrode to produce nanostructured films. The resulting films possess high surface areas that lead to enhanced electrocatalytic properties toward methanol oxidation compared to those of non-mesoporous Pt films.

Low-optical-reflectance cathodes (< 2 %, ∼ 45× lower than standard metal cathodes) utilizing a metal–organic mixed layer (MOML) have recently been developed and shown to dramatically enhance display contrast for organic light-emitting devices. MOML characterization reveals an organic matrix with embedded metal nanoparticles (see Figure), whose surface plasmon resonance is responsible for the layer's light-absorption properties.

A simple and effective method for the self-assembling of thin films with directional ordering perpendicular to the substrate surface (see Figure) is reported. These films are grown on amorphous glass substrates and show second-order nonlinear optical effects of the order of 5 pm V^–1. The ordering in these films can be maintained over large thicknesses (∼800 nm), and they are homogeneous over the area of the thin film.

A polymer nanofibrous matrix suitable for polymer electrolytes in high-performance lithium polymer batteries is presented. The poly(vinylidene fluoride) (PVdF) nanofibrous membrane (see Figure) was produced by electrospinning, which is briefly outlined. The characterization of the membrane—its porosity, network structure, mechanical strength, and electrochemical properties—is described.

Remarkable doughnut-shaped micrometer-sized aragonite particles with mesoporous sponge-like interiors (see Figure) are spontaneously assembled in water-in-oil microemulsions. The structures consist of an interlinked network of complex nanofilaments that arise from the surfactant-mediated mesoscale transformation and crystallization of amorphous CaCO₃ hybrid nanoparticles.