Advanced Functional Materials

An overall view of the mechanisms involved in the mesostructuring that takes place during the formation of surfactant-templated inorganic materials by evaporation is presented. Diagrams of textures, in which the stabilized structures are controlled by local minima, are proposed to explain the complex phenomena associated with mesostructuring induced by evaporation (see Figure).

Large differences in the conductive properties of alkylamino derivatives of Magnus' green salt, [Pt(NH₂R)₄][PtCl₄], parallel their dramatic color differences and thermochromism (see Figure, R = 2-ethylhexyl). Both phenomena are related to the intracolumnar Pt–Pt distance, d, with the one-dimensional charge mobility increasing inversely with d, from less than 0.001 cm² V^–1 s^–1 for d ≈ 3.6 Å up to ≥ 0.060 cm² V^–1 s^–1 for d ≈ 3.1 Å.

A pattern-forming state of a cholesteric liquid crystal is used as a template for the self-organization of spatially and orientationally ordered, acetylene-based semiconducting polymers (see Figure). The templating can be explained by a corrugation in polymer density determined by the spatially periodic profile of the orientational energy density associated with the cholesteric pattern-forming state.

A novel synthetic route for the production of thermally stable 2D hexagonal mesoporous nanocrystalline anatase has been developed using 1-butanol as an alternative solvent. This method provides a titania mesostructure containing large anatase crystallites in the channel walls together with a large pore size, narrow pore-size distribution, and high specific surface area in the form of bulk, large-area crack-free thin films (see Figure and cover).

The new concept of template-assisted synthesis of mesoporous magnetic nanocomposite particles is proposed to functionalize magnetic particles and increase their surface area. Characterization using transmission electron microscopy (TEM), FTIR, nitrogen adsorption–desorption, and zeta-potential measurements confirmed the deposition of mesoporous silica layers on the magnetite particles. The synthesized nanocomposite particles have a wide range of potential applications, for example in toxin removal, waste remediation, catalysis, nanoreactors, reactive sorbents, and biological cell separations.

Microwave-assisted protocols developed for the preparation of semiconducting polymers, in dramatically reduced reaction times and, in some cases, better yields and molecular weights, are reported. Synthesis is achieved via palladium-mediated Suzuki- and Stille-type reactions.

The photoinduced change in refractive index (Δn) of a series of diarylethenes has been investigated by ellipsometry (260–1700 nm), allowing examination of the influence of the resonance conditions on the refractive index. The largest Δn value, 0.005 ± 0.001 at λ=1.5 μm, was found for 1,2-bis(2-methyl-5-formyl-3-thienyl)perfluorocyclopentene phenyl hydrazone (see Figure) embedded in poly(methyl methacrylate).

Microstructures of hydrogen-bonded side-chain liquid-crystalline block copolymers can be rapidly aligned in AC electric fields (see Figure) at temperatures below the order–disorder transition but above the glass-transition temperature. The structures and their orientation were studied in real time with synchrotron X-ray scattering.

Electronic structure calculations from first principles have been performed to clarify structures, chemical bonding, and thermochemical stabilities of a series of CoN_xO_1–x phases, the first quasi-binary oxynitrides of a ferromagnetic transition metal. The non-stoichiometric zinc-blende-type compounds (see Figure) appear to be metallic, metastable materials that exhibit neither atomic ordering (N/O) nor significant magnetic moments (Co).

Blue-light-emitting polymer/dielectric nanolayer nanocomposites have been prepared (see Figure) and employed in an electroluminescent device. By reducing the probability that the excitons initially generated on the polyfluorenes will find keto-defects, both the color purity and the luminescence stability have been improved.

Hollow spheres of nickel sulfide (NiS) have been synthesized using room-temperature γ-irradiation of an aqueous poly(methyl methacrylate)-CS₂-ethanol solution that contains NiSO₄·6H₂O (see Figure). The spheres of 500 nm diameter and 20 nm thickness show a remarkable blue-shift in UV-vis absorbance.

3-Cyanocarbazole derivatives containing a 6-diarylamino substituent (see Figure) are reported. These compounds were demonstrated to act as emitting, hole-injecting, and hole-transporting materials. High-performance electroluminescence (EL) devices, including a single-layer device, were fabricated, a first step in the search for EL devices that can compete with liquid crystals in the display field.

Charge injection and transport can be tuned by end-capping polyfluorene (PFO) with hole-transporting moieties (HTM) and electron-transporting moieties (ETM), without significantly altering PFO's electronic properties. End-capping with ETM results in more closely balanced charge injection/transport with associated improvements in luminance and luminous efficiency of electrophosphorescence (see Figure).