Luminescent properties of synthesized PbS nanoparticle phosphors

[摘要] Luminescent lead sulphide (PbS) nanoparticles embedded in an amorphous silica (SiO2)matrix were synthesized at room temperature by a sol-gel process. The preparednanocomposite materials were crushed into powders and annealed in air at 200oC. Thechemical composition of the powders was analyzed with an energy dispersive x-rayspectrometer. Particle sizes, crystalline structure and morphology of the PbSnanoparticles were determined with transmission electron microscopy (TEM) and x-raydiffraction (XRD). The crystal particle sizes estimated from the XRD peaks and the TEMimages were in the range of 10 to 50 nm in diameter.The SiO2:PbS powders were then irradiated with 325 nm (He-Cd) and 458 nm (Ar+)lasers for photoluminescence (PL) measurement. PL spectra were obtained for pure SiO2as well as the encapsulated PbS nanoparticles at room temperature. Two strong broadbands, blue (450 nm) and yellow-orange (560 nm) from bulk SiO2 and PbS nanoparticles,respectively, were observed. The PL data show a blue shift from the normal emissionwavelength at 3200 nm in bulk PbS to 560 700 nm in nanoparticulate PbS powders.The blue-shift of the emission wavelengths is attributed to quantum confinement ofcharge carriers in the restricted volume of nanoparticles. Energy transfer from ZnOnanoparticles to PbS nanoparticles was also observed. The possible mechanism for theenergy transfer is reported.The powders were also subjected to prolonged 2 keV electron beam irradiation in avacuum chamber at and different O2 pressures (5 × 10-8 2 × 10-7 Torr O2). Thecathodoluminescence (CL) was measured with Ocean Optics S2000 spectrometer, andshowed the emission peak to be at a wavelength of 680 nm. Changes in the CL brightnessand the corresponding change in the surface chemical composition were investigated withOcean Optics S2000, Auger Electron Spectroscopy (AES) and X-ray PhotoelectronSpectroscopy (XPS). The oxygen Auger peak-to-peak height decreased simultaneouslywith the CL intensity. XPS analysis on the degraded spot showed the development of characteristic SiO, SiOx (0

[发布机构] University of the Free State