PHOTOIRRADIATION EFFECT ON COLLOIDAL CADMIUM-SULFIDE FORMATION PROCESSES

Cadmium sulfide ultrafine particles of about 3 nm in diameter were prepared by introducing a H2S/He gas mixture into an acetonitrile solution of cadmium perchlorate, styrene monomer, and omicron-dicyanobenzene while irradiating the solution with light of wavelengths longer than 440 nm. The UV-vis spectral absorption onset wavelengths of the CdS colloidal solutions were blue-shifted in comparison with those of solutions not irradiated. The UV-vis spectra also showed the appearance of a shoulder due to the exciton absorption of quantum-confined CdS particles. These results demonstrate a new method for preparing size-regulated semiconductor ultrafine particles in the size range where quantum confinement of carriers occurs.