Tetrapod-shaped CdSe nanocrystals have been successfully synthesized in high yields using a simple method of controlling the protonic acidity of the reaction system. A possible growth mechanism is discussed on the basis of the surface modification of H+ present. The crystal structure of CdSe tetrapods is determined by high-resolution transmission electron microscopy analysis to have a zinc blende core at the center with four wurtzite arms growing out from the core along four [111] directions. The electronic structure of CdSe tetrapods is studied theoretically in comparison with that of spherical dots.

The Ce3+ → Tb3+ → Eu3+ energy-transfer process enables Eu3+5D0 → 7F J line emission to be sensitized by the allowed Ce3+ 4f1 → 5d1 absorption transition in near-ultraviolet (NUV) and violet spectral regions. This energy-transfer strategy is applied in Y2SiO5:Ce3+, Tb3+, Eu3+ powders, leading to line-emitting red phosphors that can be excited by short-wavelength InGaN LEDs. The blue, green, and red colors can be tuned by the ratio of Ce3+/Tb3+/Eu3+. Furthermore, the energy-transfer efficiencies and corresponding mechanisms are discussed in detail, and the thermal stability is evaluated. The results suggest that the optimal composition phosphor Y2SiO5: 0.01Ce3+, 0.50Tb3+, 0.01Eu3+, which exhibits an intense Eu3+ red 4f–4f sharp emission with a strong 4f–5d absorption band of Ce3+ at the NUV region, could serve as a potential broadband-excited and narrow line red phosphor for NUV LEDs.

In situ growth of ZnO nanobelt arrays from and on zinc substrates (foils and microparticles) has been accomplished by controlled thermal oxidation in the presence of oxygen. The nanobelts grow approximately perpendicular to the Zn substrate surface along the 110 direction of ZnO, which has a thickness of approximately 3-4 nm, a width tapering from about 50 to 300 nm, and a length of approximately 10-20 mum. On the basis of the structural analysis and kinetic studies, a tip-growth mechanism is proposed, which underlines the transport of Zn from the substrate to the growing tip. The ratio of UV to green photoluminescent emissions of the as-synthesized ZnO nanobelt arrays could be controlled by varying the reaction conditions. Sharp UV stimulated emission peak is also observed at moderate threshold excitation intensity ( approximately 0.7 mJ/cm(2)) showing the high quality of the ZnO nanobelts. The ZnO nanobelts array has also been tested for sensing NH(3) gas, and high sensitivity, reversibility, and rapid response have been demonstrated.