Nanocrystalline SnO2 particles have been synthesized by a simple sol-gel method. The structural and optical properties of these SnO2 particles are investigated using X-ray powder diffraction, transmission electron microscopy, UV-visible absorption, and photoluminescence spectroscopy. The oxygen-vacancies-related photoluminescence of pure, cerium-, and manganese-doped SnO2 nanoparticles was systematically investigated. The origin of the luminescence is assigned to the recombination of electrons in a conduction band with holes in the Vo ** center. Experimental results reveal that increasing calcining temperature can decrease the oxygenvacanciesrelated luminescence intensity of the sample. After introducing Ce3+/Mn2+ ions into the host, the oxygenacancies-related luminescence has been enhanced remarkably resulting from the formation of many more oxygen vacancies. The dependence of the oxygen-vacancies-related luminescence intensity on the Ce3+/Mn2+ concentration is also discussed

Nanometer-scale ZnS, ZnS: Cu, ZnS:Pb, and Zns co-dopedwith Cu2+ and Pb2+ have been synthesized wusing a chemical preciptiation method. X-ray differation analysis shows that the diameter of the praticles is 2-4 nm. These nanocrystals can be doped with copper and lead during the syntheiss without altering the X-ray diffration pattern. However, doping has shifted the luminescence to 530nm (Cu2+ -doped) and 500-550nm (co-doped with Cu2+ and Pb2+). In the case of ZnS: Pb nanocrystals, a relatively broad emission band (color range form blue to yellow)has heen observed and ists excitation wavelength shows a red shift. The photouminescence intensity increases as the Zns nanoparticles co-dopedwith Pd2+ and Cu2+. The resultsstrongly suggest that doped Zns nanocrystals, especially two kinds of metals activated Zns nanocrystals, form a new class of luminescent materials.

PbS nanoparticles embedded in a novel silica glass have been achieved in the present sutdy by sol-gel processing. Their fluorescence properties have been evaluated nand compared with those of un-doped glass. A novel luminescent phenomenon has been observed from the composite of PbS nanoparticles and the sol-gel silica glass. The photoluminescence (PL) spectrum of the comosite consists of two emission peaks (440 and 605 nm). The Pb2+ions in the sol-gel silica glass show sharp emission band. This novel luminescene form the samples isassigned to the composite structure of Pbs nanoparticles and porous silica glasses.

Cubic ZnTiO3 nanocrystal doped with Ni2+ ion has been synthesized by sol-gel method at a lower temperature (600℃). The crystallinity of the doped sample was characterized by the X-ray diffraction (XRD) patterns and the infrared spectra (IR). The photoluminescence (PL) spectra of the sample measured at different excitation wavelength reveal a novel luminescent phenomenon in blue, green and red region, which can be attributed to the 3T1(3P)-3A2(3F), 1T2(1D)-3A2(3F) and 1T2(1D)-3T2(3F) transitions of Ni2+ ion, respectively. The position of the emission peak does not change greatly with the excitation wavelength. However, the luminescent intensities vary with changing the concentration of Ni2+ ion in ZnTiO3.

Nanocrystalline ZrO2 particles doped with Dy3+ ions have been synthesized by a simple co-precipitation method. The structural and optical properties of Dy3+-doped ZrO2 particles are investigated using the X-ray powder diffraction, transmission electron microscopy, and photoluminescence spectroscopy. The photoluminescence characteristics originating from Dy3+-doping in the ZrO2 nanoparticles were systematically investigated. Experimental results reveal that the luminescence can be affected by both the calcining temperature and the Dy3+ concentration in the ZrO2 nanoparticles.