Advanced Materials

Recent advances in the exploitation of localized surface plasmon resonance (see Figure) of metallic nanoparticles and nanostructures for waveguides, optical transmission, information storage and nanophotonic devices, switches, resonant light scatterers (employed in the different near-field scanning optical microscopies), sensors, and biosensors are reviewed.

Conducting polymer patterns are grown through flexible substrates using directional electropolymerization. An isolating gel layer between a polycarbonate membrane and a patterned anode allows reproduction of sub-ten-micrometer features (see Figure) throughout the volume of the membrane to the opposite side.

A 3,4-ethylenedioxythiophene derivative bearing a viologen unit has been synthesized and electropolymerized to form the corresponding polymer (see Figure). Electrochemical and spectroelectrochemical studies showed that the polymer has the characteristics of both PEDOT and viologen, and possesses high electrochromic contrast due to the cooperative electrochromic action of PEDOT and viologen.

Dyes inserted into the parallel nanochannels of a fully organic crystal show efficient light conversion over a wide visible spectral region, with 100 % conversion from UV to blue light. The Figure shows crystals containing either two (bottom) or three (top) dyes under UV illumination, and a top view of the structure of the dyes inserted into nanochannels (right).

A one-step synthesis of onion-like, shell-shaped carbon nanoparticles (SCNPs) is reported. Exposure of an acetylene flow to a continuous-wave infrared CO₂ laser produces SCNPs with continuous bent-graphene layers in bulk quantity, but only above a threshold laser power.

Microgrooves on self-assembled photonic-crystal (PC) films align liquid crystals (LCs) without any additional rubbing or surface treatment. Nematic (see Figure and inside cover) or twisted-nematic LCs can be formed, depending on the relative orientation of the microgrooved films. A LC Fabry–Perot (FP) cavity was fabricated using these PC films, and electro-optic tuning of FP cavity modes is demonstrated.

Paper-like membranes with a hierarchical microstructure (see Figure) are created from single-crystal cryptomelane-type manganese oxide (OMS-2) nanowires that aggregate and align spontaneously to self-organize into 2D arrays. The versatile material remains malleable, and can be written on, even under cryogenic conditions.

Lateral control of the fabrication of selectively inverted opals using polymer–silica composites is reported. Poly(methyl methacrylate)–SiO₂ composite opals obtained by chemical vapor deposition can be patterned by electron-beam lithography and developed to produce silica inverse opals with well-defined extrinsic defects (see Figure).

Thin supported films of cylinder-forming block copolymers, containing a single layer of microdomains (Figure top), ordinarily exhibit a highly defective texture with no long-range order (lower left). Shearing these 30 nm thick films aligns the cylinders, eliminates all orientational defects, and greatly reduces the density of translational defects (lower right), enhancing the utility of these films as lithographic templates. See also front cover.

A wurtzite-structured CdSe nanosaw (see Figure) is formed by a two-step process: a fast-growth process along [010] creates the main ribbon, while a subsequent side-growth process along [0001] creates the one-sided teeth. The growth of the teeth is suggested to be a combined result of secondary epitaxial nucleation processes resulting from a zinc-blende–wurtzite phase transformation and the self-catalytic effect of the Cd-terminated (0001) surface.

The growth of Cu₂O crystals that are electrochemically deposited as micrometer-size crystals with systematically varying fractions of {100} and {111} faces is reported (the Figure depicts cubic crystals). The methodical and homogeneous shape evolution is achieved by tuning the degree of preferential adsorption of sodium dodecyl sulfate on the {111} faces of growing Cu₂O crystals through pH variation. Scale bar: 1 μm.

A photoaddressable azobenzene-side-chain polymer (see Figure) optimized to exhibit a large optical birefringence of Δn = 0.5 at 650 nm is described. The birefringence extends well into the telecommunication wavelength region, which, together with the high optical transparency above 650 nm, promises applications for integrated photonic device applications. The writing dynamics of the polymer are examined, and it is shown that the rewriteability is limited by photobleaching.

The thermal stability of thin films of di-indenoperylene (DIP), an organic semiconductor is shown via thermal desorption spectroscopy (TDS) and in-situ X-ray diffraction to be strongly enhanced by aluminum oxide capping layers. Possible mechanisms for the eventual breakdown of the film (which remains crystalline up to 460 °C) at high temperatures are discussed (see Figure).

Increased overall efficiency in dye-sensitized solar cells (DSSCs) requires electrolytes with improved ionic conductivity and interfacial contact between the electrolyte and the dye-adsorbed semiconductor nanoparticles in the cell. The supramolecular electrolyte presented here (see Figure) achieves this due to its different behavior in the liquid and solid states.

A new transparent neutron-scintillating material has been developed based on polystyrene-block-poly(ethylene oxide). The unique self-assembly structure of the block copolymer makes it possible to dope hydrophilic Li⁺ in the ethylene-oxide domain and hydrophobic organic fluors in the styrene domain (see Figure).

Coarsening of 2D polycrystals of rod-like oligomers self-assembled at the solid–liquid interface can be visualized using scanning tunneling microscopy with sub-molecular resolution, providing insight into the thermodynamics and kinetics governing this 2D Ostwald- ripening phenomenon.

A stable-organic-radical-functionalized tetrathiapentalene organic conductor has been synthesized and studied using X-ray crystallography of very small single crystals. The crystal structure reveals alternating conducting and insulating layers (see Figure).