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The luminescence properties of ZnO nanorods and nanocrystals after high-temperature annealing in air and exposure to strong solar radiation were studied. Under UV radiation, as-prepared nanorods and nanocrystals exhibit the luminescence spectra with maxima at 380–384 and 560–570 nm. The thermal treatment and high-intensity solar radiation of both nanostructures results in an increase in the intensity of short-wave length luminescence bands. Moreover, the long-wave luminescence band (LB) vanishes in the spectra of nanorods, and a new band at 520 nm appears in the luminescence spectra of nanocrystals. The effect of solar radiation on the properties of nanorods is more pronounced than in the case of nanocrystals, it is possible due to predominately ray heating (annealing) of nanorods than nanocrystals. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) from ZnO nanocrystals deposited on silicon, sapphire and glass substrates was measured at different temperatures and UV-laser excitation densities. Our studies show that the PL properties of the nanocrystals are a strong function of the ultraviolet laser excitation density and the thermophysical properties of the substrates used. Even at low temperatures (10-30 K), high-power laser illumination can heat the top layer of nanocrystals up to 100 K. The heating effect induced by laser illumination results in a saturation behaviour of the PL intensity with increasing excitation density. It is determined that the degree of the saturation depends on the substrates' thermophysical properties. [ABSTRACT FROM AUTHOR]

ZnO nanocrystals grown by chemical solution deposition were studied by means of photoluminescence and cathodoluminescence spectroscopy. A postgrown annealing treatment significantly improved the UV emission efficiency and resulted in the clear appearance of a low temperature emission band around 3.31 eV (so-called A-line). Spatially and wavelength resolved cathodoluminescence measurements revealed a spotlike distribution of the A-line emission on a nanocrystal surface. It is found that there is a strong correlation between the emission around 3.31 eV and the specklike defects on the nanocrystal surface that appeared after annealing. The origin of the A-line and the specklike defects are discussed. [ABSTRACT FROM AUTHOR]