Control growth of PbS quantum dots doped sono-ormosil

Semiconductor PbS quantum dots doped-SiO2 organically modified silicate (ormosil) gels were synthesised via sol-gel by using high-power ultrasounds (sonogel). The effect of PbS crystal concentration and the addition of (3-mercaptopropyl)trimethoxysilane acting as surface capping agent (SCA) were investigated. By adjustment of the SCA to lead ratio, PbS nanoparticles of different sizes and morphologies were obtained. Textural parameters were calculated from N-2 physisorption isotherms. The PbS galena phase was identified by x-ray diffraction, the crystal size by high-resolution transmission electron microscopy, and the exciton confinement by ultraviolet-visible-near-infrared spectrophotometry. Crystallite mean sizes of spheres and cubes ranging from 6.5 to 10.5 nm and needles 7-nm wide and 15-20 nm long, for different PbS and SCA concentrations, were obtained. These results differ from those predicted by the effective mass approximation corroborating the band gap modifications in the smallest nanocrystals. The method allows the control of the crystal size and improves the stabilization of the PbS nanocrystals.