Advanced Functional Materials

Mono- and multilayer polyelectrolyte coatings are formed on gold nanoparticles (< 10 nm diameter) via electrostatic self-assembly. The core–shell nanoparticles can be adsorbed as thin films on substrates, with readily controlled particle density. The versatile strategy presented (see Figure) should be applicable to other nanoparticles, providing a facile means for their controlled surface modification and assembly.

The fractal morphogenesis of biomimetically grown fluorapatite–gelatin composite aggregates and their chemical and structural properties are reported, providing a deeper insight into the mechanisms of pattern formation and the development of hierarchical structures during the in-vitro biomineralization process. A model is developed describing the organization of the aggregates as a nanocomposite superstructure (see Figure and inside front cover).

Gate insulators in organic field-effect transistors (FETs) may influence not just the morphology of the semiconductor, but also the electronic states at the interface. Localized states may be distorted by random interface dipoles and their distribution broadened (see Figure and cover). In this communication it is shown that by using low-k materials as insulators, mobility can be increased and hysteresis reduced, and the underlying physics is discussed.

Near-infrared-emitting polymer light-emitting diodes (PLEDs) based on functionalized poly(p-phenylenes) with Yb³⁺ complexes show light output at ca. 1000 nm with concomitant quenching of the polymer host’s visible emission. The Figure shows one of the complexes used. A complex using porphyrin-based ligands was shown to have particularly enhanced near-IR output efficiency.

Core delocalization plays an important role in controlling intermolecular interactions for conjugated dendrimers with chromophores at the core (see Figure). This study of electrochemical, photo-, and electroluminescence measurements of four generations of dendrimers clearly demonstrates that the degree of aggregation is strongly dependent on both the dendrimer generation and the degree of delocalization across the central unit.

Nanostencils (shadow masks with submicrometer apertures in a thin silicon nitride membrane) may suffer from clogging of the apertures due to adhesion of evaporated material. Here it is shown that nanostencils coated with self-assembled monolayers show considerably less adhesion of gold compared to bare stencils, in turn producing better defined features (see Figure, gold features defined by uncoated (left) or coated (right) masks with 350 nm pores).

Tin dioxide opals have been fabricated utilizing a reverse templating strategy (see Figure, an electron microscopy image of the opals). The neck diameter between spheres in the SnO₂ opals can be controlled by variable sintering of the parent silica opals at temperatures between 700 and 1050 °C. The sensor response of the SnO₂ opals towards carbon monoxide has been examined and can be understood as a function of the final neck diameter.

Photoregulated phosphorescence switch behavior is shown by platinum complexes of mono- and multi-bisthienylethene-substituted ring-fused photochromic hybrids (such as the one whose structure is shown in the Figure) prepared via a concise synthesis route. The near-IR luminescence of the hybrids can be regulated in a reversible manner by the photoisomerization of the bisthienylethene moiety.

Brilliantly coloured pigments can be obtained by direct synthesis when layered double hydroxides (see Figure) are precipitated under controlled conditions in the presence of an organic perylene dye. The figure shows the structural arrangement of the dye molecules between the hydroxide layers. The stability of these organic–inorganic composite structures is not diminished compared to the pristine dye in a harsh application environment.