pH-Dependent shape changes of water-soluble CdS nanoparticles

In this study, a one-pot route was illustrated to synthesize stable water-soluble CdS nanoparticles stabilized by poly-(4-styrenesulfonic acid-co- maleic acid) (PSSMA). The CdS nanoparticles synthesized in alkaline solutions (pH 10.0) were irregular and small in size (similar to 1.1 nm), while those generated in acid solutions (pH 4.5) tended to aggregate to form larger particles (similar to 74.5 nm). Some bridge-like CdS wires linking several CdS particles were observed by tuning the molar ratio of elemental Cd to S. The ligand-detachment mechanism has been proposed to be the main reason for the formation of CdS assemblies synthesized in acid solutions. Further, photoluminescence (PL) studies confirmed that the use of the PSSMA stabilizer induces incomplete quenching of PL emissions in an acid solution, but complete quenching in an alkaline solution.