Gamma radiation induced differential growth of CdS nanoparticles capped with aromatic and aliphatic thiols

Gamma radiation-induced growth of CdS nanoparticles in the presence of aromatic vis-à-vis aliphatic thiols has been thoroughly investigated in organic phase. Decanethiol (aliphatic) and thiophenol (aromatic) have been used as a source of sulfide and stabilizer in methanol as a solvent. CdS nanoparticles capped with thiophenol exhibited remarkable stability at neutral pH as compared to nanoparticles capped by decanethiol. Unlike aliphatic thiols, the average size of the thiophenol capped CdS nanoparticles did not vary with the radiation dose for a wide range of molar ratios of Cd2+:thiophenol (1:1–1:40). However, the particle concentration increased with increasing radiation doses at fixed molar ratios of Cd2+:thiophenol. These results suggest that the growth of the particles occurs till a particular size corresponding to certain magic agglomeration number with minimum energy configuration. On the contrary, the replacement of thiophenol (aromatic) by decanethiol (aliphatic) in the reaction mixture resulted in gradual change in the size as well as concentration of nanoparticles with the radiation dose and molar ratio of Cd2+:thiol. The differential ease of monolayer assembly of the planar aromatic moiety compared to the aliphatic one could be responsible for such an effect.