Guang Jun Zhou

Synthesis and luminescence properties of SnO2 nanoparticles

Abstract Nanometer-scale SnO 2 particles have been synthesized by a simple sol–gel method. The samples were characterized by X-ray diffraction, Fourier transform infrared (FTIR), UV–Vis absorption and photoluminescence spectroscopy. The as-prepared SnO 2 nanoparticles appear to be single tetragonal crystalline phase and the diameter is about 2.6 nm. The origin of luminescence is assigned to the recombination of electrons in singly occupied oxygen vacancies with photoexcited holes in the valence band.

Luminescent characteristics of Eu3+ in SnO2 nanoparticles

Abstract Nanometer-scale SnO2 particles have been synthesized by a simple coprecipitation method. X-ray diffraction analysis shows that the diameter of the particles is 2.6 nm after heat treatment at 400 °C for 2 h. The UV–visible absorptive spectra and photoluminescence spectra have been used to study the luminescence character of Eu3+ ions. The characteristic emission and concentration quenching of Eu3+ ions can be observed. The results also reveal that the Eu3+ ions can be situated not only at the surface of the SnO2 nanoparticles but also in the host lattice, though the relative quantity is very small.

The luminescence of PbS nanoparticles embedded in sol–gel silica glass

Abstract PbS nanoparticles embedded in a novel silica glass have been achieved in the present study by sol–gel processing. Their fluorescence properties have been evaluated and 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 composite consists of two emission peaks (440 and 605 nm). The Pb 2+ ions in the sol–gel silica glass show sharp emission band. This novel luminescence from the samples is assigned to the composite structure of PbS nanoparticles and porous silica glasses.

Luminescent properties of Mn2+-doped SnO2 nanoparticles

Abstract The room temperature photoluminescent properties of manganese-doped tin oxide nanoparticles are reported. The samples are crystalline with a tetragonal rutile structure of tin oxide. The FTIR and the UV–Vis absorptive spectra of the samples have also been investigated. The photoluminescence spectra are measured at room temperature as a function of different calcining temperatures and the Mn2+ concentration, respectively. The luminescence processes are associated with oxygen vacancies in the host and related with the recombination of electrons in singly occupied oxygen vacancies with photoexcited holes in the valence band.

Photoluminescence characteristics of Pb2+ ion in sol–gel derived ZnTiO3 nanocrystals

Abstract Pb 2+ ions doped ZnTiO 3 nanocrystal has been prepared by a sol–gel process. The X-ray diffraction patterns indicate that the doped sample exhibits a cubic ZnTiO 3 structure. From the luminescence spectra analysis, the introduction of Pb 2+ ions into ZnTiO 3 results in novel luminescent properties. A red emission band fixed at 620 nm has been observed. The relative intensities of the bands vary with the concentration of Pb 2+ ions. The luminescence due to Pb 2+ -involved centers can be ascribed to the Pb 2+ -related charge-transfer transition in ZnTiO 3 nanocrystals.

Preparation and luminescence characteristics of nanocrystalline SnO2 particles doped with Dy3

Abstract Nano-scaled SnO 2 particles doped with Dy 3+ have been synthesized by a simple sol–gel method. The samples were characterized by X-ray diffraction, transmission electron micrograph, UV-visible absorption and photoluminescence spectroscopy. The as-prepared SnO 2 nanoparticles appear to be single tetragonal crystalline phase and the diameter is about 2.6xa0nm. The hypersensitive transition ( 4 F 9/2 → 6 H 13/2 of Dy 3+ ) is dominated in the emission spectra resulting from the distorted crystal lattice at which Dy 3+ ions locate. And the dependence of the luminescence intensity on Dy 3+ concentration is also discussed.

Luminescence of Cu2+ and In3+ co-activated ZnS nanoparticles

Abstract Zinc sulfide (ZnS) nanoparticles co-doped with Cu2+ and In3+ ions have been prepared by precipitation from homogeneous solutions of zinc, copper and indium salt compounds, with S2− as precipitating anion formed by decomposition of thioacetamide. The estimated average crystallite size of doped and undoped ZnS nanometer scale samples is about 2–3 nm from X-ray diffraction patterns. Novel luminescence characteristics (green emission, λem∼530–550 nm) have been observed from the co-doped ZnS nanocrystals at room temperature. The emission wavelength and relative photoluminescense intensity of the co-doped samples vary with changing the impurity ratios of Cu2+ and In3+.

Strong visible-light emission of ZnS nanocrystals embedded in sol–gel silica xerogel

Abstract ZnS nanoparticles embedded in novel porous phosphor silica xerogel have been synthesized by sol–gel processing. Their fluorescence properties have been evaluated and compared with those of the Na + -doped and un-doped silica xerogels. Stable and strong visible-light emission of the doped samples has been observed. The relative fluorescence intensities of the samples doped with ZnS nanoparticles (S 2− ions have been obtained by the water solution of NaS) are the highest among all of the doped samples. Its relative fluorescence intensity is about 7.5 times of that of the un-doped silica xerogel and about 300 times of that of pure ZnS nanoparticles. The emission wavelength of the ZnS-doped and Na + -doped samples is the same as that of the un-doped silica xerogel and ZnS nanoparticles ( λ em =440–450 nm). This high efficiency luminescence of the doped silica xerogels has been assigned to the luminescence centers of ZnS nanoparticles and Na + in the porous phosphorescence silica xerogel.

Preparation and luminescent characteristics of Mn2+, Er3+ co-doped ZrO2 nanocrystals

Abstract ZrO 2 :Mn, Er nanocrystals have been prepared at different temperatures ranging from 400°C to 600°C by a coprecipitation method. The crystallinity of the samples was characterized by the X-ray diffraction (XRD) patterns and a transmission electron microscopy micrograph. The luminescent properties of the co-doped sample as a function of the doping concentration of Er 3+ and the heat-treated temperature have also been investigated. For all the doped samples, a red emission band centered at 638xa0nm was observed corresponding to the a 4 Γ– 6 S transition of Mn 2+ . Due to the energy transfer between Er 3+ and Mn 2+ , the relative intensity of the emission varies greatly with changing Er 3+ concentrations. The quenching of the PL intensity with increase in temperature is assigned to the decrease of residual chlorine in the sample.

Green emission from Cr, Dy co-doped sol/gel SiO2 glasses

Abstract Silica glasses singly doped and co-doped with Cr ions and Dy ions have been prepared by sol–gel method and their photoluminescence (PL) properties have been studied. The emission spectrum of Dy singly doped sample shows a band around 450 nm with a shoulder band around 480 nm, Cr singly doped sample consists of three bands around 450, 530 and 620 nm, and Cr, Dy co-doped samples show two bands around 450 and 530 nm. The relative PL intensity of the green emission at 530 nm in co-doped samples increases greatly compared with the singly doped. These two bands at 450 and 530 nm are respectively assigned to the defects in silica network and a complex luminescence centers associated with Cr ions. The quenching effect of metal ions and energy transfer process could be responsible for the change of PL properties in the co-doped samples.