Synthesis and characterization of Cd-DMSO complex capped CdS nanoparticles

We report here the capping of cadmium sulfide nanoparticles (Q-CdS) with a Cd-DMSO complex as a consequence of particle preparation in dimethyl sulfoxide (DMSO). A characteristic sharp peak at 367 nm in the UV-vis for Q-CdS showed a gradual blue shift of ca. 41 nm, indicating the decrease in the particle size with time instead of the expected red shift for flocculation. Erosion of the particles was attributed to the reaction of CdS with DMSO to form a Cd-DMSO complex. FTIR spectra recorded for flocculated Q-CdS gave major peaks at 617, 800, 1109, 1261, 1408, and 1561 cm(-1) which were attributed to the presence of Cd-DMSO complex and acetate ions on the particle surface. The anti-stoke shift of S=O stretching frequency for particle-associated DMSO indicated that the bonding is through a sulfur moiety. On the basis of results from thermal and postannealed IR spectral analyses, the formation of a stable Cd-DMSO complex on the particle surface was inferred. The observed solution stability was attributed to the particle surface passivation by the complex. The kinetic studies of the reaction between Q-CdS and DMSO revealed that the reaction is second order with a rate constant of ca. 2 x 10(-6) L mol(-1) s(-1).