Advanced Functional Materials

The most recent advances in polar-surface-dominated ZnO nanostructure synthesis are described: including nanocombs, nanosaws, nanosprings, nanorings, nanobows, and nanopropellers (see Figure). The synthesis, characterization, growth mechanisms, and possible applications as piezoelectric driven nanoscale sensors, transducers, and resonators have been reported. It is suggested that ZnO may be the next most important nanomaterial after carbon nanotubes.

A novel method using laser irradiation for the preparation of CdSe/ZnS quantum-rod films for robust lasing in a cylindrical microcavity is reported. A capillary tube, serving as the laser cavity, is filled with a solution of nanocrystals and irradiated with a series of intense nanosecond laser pulses to produce a nanocrystal film on the capillary surface. The Figure shows lasing in whispering-gallery modes at the film–capillary interface.

Layer-by-layer self-assembled polyelectrolyte films containing a charged cyclodextrin and lipopolysaccharide (LPS) are shown to be a potential model for local endotoxin antagonist delivery. When incorporated into multilayered polyelectrolyte architectures (poly-(L-lysine)/poly-(L-glutamic acid)), a polycationic cyclodextrin, heptakis(6-deoxy-6-pyridylamino)-β-cyclodextrin, showed molecular chaperone properties by enabling restoration of the LPS biological activity whenever lost upon interaction with poly-(L-lysine).

Photoluminescence (PL) and thermally stimulated luminescence (TSL) were investigated in highly ordered nanostructures of para-sexiphenyl (PSP) grown via hot wall epitaxy. A low-energy broad band is observed in PL spectra, which can be attributed to the emission from molecular aggregates. While the intrinsic exciton emission in steady state PL dominates at low temperatures, the emission from aggregates increases with elevating temperature and its magnitude is sensitively dependent upon film preparation conditions.

Rare earth chelates with identical organic ligands have been synthesized and characterized optically. The low- lying ligand triplet state prevents rare earth emission from the visible emitting rare earth ions, whilst a chemiluminescent process is feasible for Yb. The Figure shows a Yb chelate structure.

Potential candidates for electrochromic devices and lithium secondary microbatteries are the V₂O₅/chitosan/poly(ethylene oxide) nanoarchitectures presented here. Produced using the layer-by-layer method, these materials show good homogeneity and charge-storage capability. They are demonstrated to display superior performance to their V₂O₅/chitosan analogues. The influence of poly(ethylene oxide) on the migration/diffusion rate of lithium ions into the nanocomposite is investigated using spectroscopy and electrochemical techniques.

Charge-separation efficiency of 10 % on photoexcitation in a double layer of TiO₂ and a liquid-crystalline porphyrin is observed. Electron injection occurs both from the singlet and the long-lived triplet excited states; the latter can travel distances of at least 9.6 nm by Dexter energy transfer. Heating above the crystalline–discotic lamellar phase-transition temperature changes the morphology of the antenna layer, resulting in reduced efficiency (see Figure).

Carbon monoxide reduction of a palladium(II) compound in combination with stabilization by readily available amphiphilic hyperbranched polymers shape-selectively affords a dispersion of hexagonal palladium platelets (see Figure) in toluene, with an average breadth of thirty to several hundred nanometers, and thickness of only 1 to 2 nm.

The morphology of bulk-heterojunction conjugated polymer/fullerene-based plastic solar cells is investigated using atomic force micoscopy, scanning electron microscopy, and photoluminescence measurements. Nanostructures formed during casting have been analyzed and manipulated via heat treatment. Polymer and fullerene phases could be distinguished down to the nanometer scale.

Robust macroporous zeolitic membranes with three-dimensional (3D) interconnected pore structures were prepared (see Figure) and used as porous supports for the layer-by-layer immobilization of enzyme. The biofunctionalized membranes have significantly improved enzyme loadings and display enhanced activities, compared with their 3D closed macropore zeolite film counterparts.

Pure-silica-zeolites (PSZs) are promising low-dielectric-constant (low-κ) materials, with excellent mechanical strength due to their crystalline nature. A two-stage synthesis method that produces high-yield, small diameter zeolite nanoparticles is utilized to create highly crystalline spin-on PSZ MFI films (see Figure) with reduced κ values and low moisture sensitivity—two critical properties of a porous low-κ material.