We report about the synthesis and optical properties of a composite metal-insulator-semiconductor nanowire system which consists of a wet-chemically grown silver wire core surrounded by a SiO2 shell of controlled thickness, followed by an outer shell of highly luminescent CdSe nanocrystals. With microphotoluminescence (micro-PL) experiments, we studied the exciton-plasmon interaction in individual nanowires and analyzed the spatially resolved nanocrystal emission for different nanowire length, SiO2-shell thickness, nanocrystal shape, pump power, and emission polarization. For an SiO2 spacer thickness of approximately 15 nm, we observed an efficient excitation of surface plasmons by excitonic emission of CdSe nanocrystals. For nanowire lengths up to approximately 10 microm, the composite metal-insulator-semiconductor nanowires ((Ag)SiO2)CdSe act as a waveguide for 1D-surface plasmons at optical frequencies with efficient photon outcoupling at the nanowire tips, which is promising for efficient exciton-plasmon-photon conversion and surface plasmon guiding on a submicron scale in the visible spectral range.

Porous polymer beads have been used as templates in which sol–gel chemistry was conducted for the formation of porous titanium dioxide and titania/aluminum, gallium, or indium oxide spheres. The addition of 5, 10, and 15 wt.‐% of the second metal oxide to titania was studied, resulting in little variation in the final porous‐sphere diameter, but in a decreased titania nanocrystal size and an increased specific surface area of the material. The crystallinity of the samples was observed after heating at 550, 750, and 950 °C as anatase to rutile phase transitions became apparent and peaks from the added metal oxide were observed with the increase in temperature. Photocatalytic decomposition of 2‐chlorophenol was monitored in the presence of the titania and titania/metal‐oxide spheres showing that a 5 wt.‐% addition of the second metal oxide gave best photocatalytic results for all the metal oxides studied. At a pH of 6 the pure titania spheres were less photocatalytically active than the Degussa P25 titania, however the mixed titania/5 wt.‐% metal‐oxide samples were more active than the standard in the order In (least active), Ga, then Al (most active). Variation of the solution pH (between pH 2 and 10) had little influence on the photocatalytic activity of the titania/5 wt.‐% aluminum oxide material, more effect on the titanium/5 wt. % gallium oxide, and the most pronounced effect on the titanium/5 wt.‐% indium oxide, with increased activity at higher pH values. The adsorption of pyridine to the titania samples containing the second metal oxide indicated the presence of Lewis‐acid sites.

Hollow and filled Ni microspheres are fabricated by a photocatalytic approach using polyelectrolyte capsules as templates. Because of the different crystallization conditions existing in the capsule shell and the interior volume, Ni nanorods are formed inside the capsule, whereas only small, spherical Ni nanoparticles are obtained in the capsule shell (see Figure). The metallized polyelectrolyte shell is sensitive to the pH and possesses pH‐controlled permeability.

Spatially confined photocatalytic microreactors for microheterogeneous photoreduction of metal ions from aqueous solutions have been developed. The microreactors consist of hollow micron-sized polyelectrolyte capsules with photoactive TiO2 nanoparticles incorporated in the walls. Additional improvements in metal photoreduction efficiency were achieved by filling the microcapsule cavity with a more effective electron donor.

We report on comparative experimental study of FRET efficiency in two different systems: organic dye molecules (donors) and CdSe-ZnS core-shell nanodots or nanorods (acceptors). Fluorescein isothiocyanate was bound chemically to the surface of nanocrystals using cysteine as a linker and the conjugates were embedded into the polymeric films. Contrary to intuitive presumptions based on the order of magnitude larger molar absorption coefficient for nanorods, the experiment demonstrated almost equal efficiency in the energy transfer from FITC to nanorods and nanodots. This effect is attributed to a distance-limited region of nanorod to which an efficient FRET from dye molecule can be achieved. These results may pave the way to hybrid materials with FRET efficiency controlled by the geometry of nanocrystals.