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The structural and optoelectronic properties of ZnO nanopillars (ZnO-NPs) grown on Si substrates by the vapor transport deposition method were investigated. In particular, by varying the deposition duration and hence the morphology of the vertically aligned ZnO-NPs, the resultant field emission characteristics were systematically compared. In addition to identifying the advantageous field emission properties exhibited in the pencil-like ZnO-NPs, we observed that by adhering Au nanoparticles on the surface of the ZnO-NPs the turn-on field and the maximum current density can be drastically improved from 3.15 V/μm and 0.44 mA/cm(2) at 5 V/μm for the best ZnO-NPs to 2.65 V/μm and 2.11 mA/cm(2) at 5 V/μm for Au/ZnO-NPs, respectively. The enhancement of field emission characteristics that resulted from Au-nanoparticle decoration is discussed on the basis of charge-transfer-induced band structure modifications.

Single-crystalline mesoporous ZnO nanosheets were prepared with a green, deep eutectic solvent based antisolvent process followed by calcination at 300 uC. The antisolvent procedure led to formation of nanosheets of a mixed composition of zinc carbonate hydroxide and ZnO, calcination of which generated the product. The product nanosheets were ultrathin with a thickness of around 10 nm and pore sizes increasing from less than 10 nm to several tens nanometers with increasing calcination time and temperature. These nanosheets exhibited excellent photocatalytic efficiencies as good as that of a commercial photocatalyst, P-25 TiO 2 in terms of photocatalytic degradation of a model pollutant, methylene blue. The success is attributable to the structural advantages of the nanosheets of being ultrathin, mesoporous, and single-crystalline.

X-ray absorption spectroscopy measurements have been performed to elucidate local electronic and atomic structures of orthorhombic 3d-transition metal-doped yttrium manganites ͑YMnO 3 ͒ with chemical formulae YMn 2/3 Me 1/3 O 3 ͑Me= Co, Ni, and Cu͒. The Mn L 3 -and K-edges x-ray absorption near-edge structure ͑XANES͒ demonstrate the direct substitution of Me 2+ for Mn 3+ , so that the positive effective charge of Mn ions are increased. Me-doping is also found to induce substantial broadening of the Mn L 3 -edge feature, which suggests enhancement of the delocalization of Mn 3d e g subbands and conductivity. Local spin density approximation ͑LSDA͒ +U ͑Hubbard U parameter͒ calculations were used to understand their electronic structures.

X-ray absorption spectroscopy measurements have been made on 7-, 12-, and 23-nm palladium particles, along with bulk material as reference. With decreasing particle size, the extended x-ray absorption fine spectra reveal a substantial contraction of the nearest-neighbor distance and a reduction of the average coordination number, but an increasing Debye-Waller factor. Meanwhile, the x-ray absorption near edge spectra show a decreasing density of unoccupied states with decreasing particle size.