A SONOCHEMICAL APPROACH TO THE SURFACE SYNTHESIS OF CADMIUM-SULFIDE NANOPARTICLES ON SUBMICRON SILICA

A sonochemical procedure for the preparation of cadmium sulfide (CdS) nanoparticles coated on submicron spherical silica particles has been described. Ultrasonic irradiation of a slurry of silica microspheres, cadmium sulfate, and thiourea in an aqueous medium for 3 h under ambie nt air yields cadmium sulfide-silica (CSS) composite. Heating the init ial amorphous CSS nanocomposite at 150 degrees C for 1 h under a N-2 a tmosphere yields diffraction peaks assignable to the CdS phase. The tr ansmission electron microscopy image of CSS shows that the CdS nanopar ticles homogeneously coated on the silica (SiO2) carrier. The infrared spectroscopy illustrated the structural changes that occur when the a morphous SiO2 is coated with CdS nanoparticles ultrasonically. The pho toluminescence spectrum of the CdS and CSS shows a broadband with a ma ximum centered around 560 nm, which is similar to that of quantum CdS particles. The sharp onset of a CSS emission band compared to that of the CdS emission band in the red region indicates that the SiO? carrie r provides a medium for controlling the aggregation of CdS nanoparticl es. (C) 1998 American Institute of Physics. [S0003-6951(98)02320-1].