Synthesis of mercaptopropionic acid capped CdS nanoparticles

Results of the studies on the preparation and characterization of CdS nanoparticles using aqueous solutions of precursors in presence of Mercaptopropionic acid as a capping agent, is reported in this article. Aqueous solutions of Cadmium acetate and Sodium sulphide were used as precursors. The optical absorption edge shifting to smaller values than that for the bulk CdS indicated that the particles formed are in the nanometer size regime. The band gaps were calculated from the optical absorption studies and particle sizes were estimated from the band gap values using the relationship between particle size and band gap under effective mass approximation (EMA). Particles as small as 4.5 nm could be prepared by varying the concentration of the stabilizer, at a constant precursor concentration. Stability of the CdS particles formed were monitored for 15 days and good stability could be observed even at very low stabilizer concentrations. The particle size increases with decrease in stabilizer concentration. The increase is small at higher concentration region and at lower concentrations the increase is rapid with decreasing stabilizer concentration. Efficient capping can be achieved by the proper choice of the stabilizer concentration for a given precursor concentration. Higher precursor concentrations need higher stabilizer concentrations.,fraction (XRD) studies agree well with those estimated from the band gap values.