Synthesis of PbS-Al2O3 nanocomposites by sol-gel process and studies on their optical properties

PbS-Al2O3 nanocomposites were prepared by a single step sol-gel method starting from lead acetate, thiourea and aluminium isopropoxide. The crystallinity, shape of crystallites and optical properties of the nanocomposites were examined by various analytical techniques. X-ray diffraction indicates that the PbS-Al2O3 nanocomposites consist of small PbS crystallites (18.2-40.5 nm). Transmission electron microscopy images show cube-like and flake-like morphology for pure PbS and Al2O3, respectively and TEM images of the nanocomposites indicate uniform distribution of PbS nanoparticles on the Al2O3 matrix. Diffuse reflectance spectral (DRS) studies on the nanocomposites indicate near infrared (NIR) absorption and the nanocomposites exhibit blue shift of the band gap of PbS compared to pure PbS nanoparticles. Photoluminescence studies show characteristic peak due to excitonic emission of PbS nanoparticles in the nanocomposites.