Nanoparticles of CdS have been stabilized in aqueous medium by surface capping with 6-
dimethylaminopurine at pH 11.0 in the presence of excess Cd2+. The nucleation of the cluster is controlled
through coordination of 6-dimethylaminopurine via. -N(CH3)2 group. Excess 6-dimethylaminopurine binds
to the core structure through H-bonding involving protonated N(9). CdS capped with 6-dimethylaminopurine
produced relatively small sized particles (2 nm) having a narrow size distribution. These particles did not
exhibit any Ostwald's ripening and its solid sample could be fully redispersed in aqueous medium. Thermolysis
results in the growth of these particles but demonstrates a better photocatalytic activity. Relaxation
kinetics reveals the surface to contain a large number of surface states and the emission is originated by the
presence of sulfur vacancies on the particle. The addition of indole simply quenches the emission of CdS in
a bimolecular collisional process at a diffusion-controlled rate of about 9×109dm3mol−1s−1. Irradiation of the reaction mixture containing CdS and indole by light of λ>360 nm results in the formation of indigo
with a quantum efficiency of 0.1.
