Preparation of Cadmium Sulfide Ultrafine Particles in Various States with Aid of Cadmium Dioleylphosphate Microemulsion.

Microemulsion-assisted preparation of ultra-fine particles is important. There are, however, some problems to be solved: Control of particle size and its distribution, difficulty of preparing particles in denser state, and difficulty of preparing particles in dry state. Cadmium sulfide (CdS) particles prepared with the help of the microemulsions composed of cadmium dioleylphosphate and sodium dioleylphosphate are markedly stable. We demonstrate that these problems are solved using the above mixed surfactants microemulsion: 1) The size of ultra-fine CdS particles can be controlled by changing the water-to-surfactant mole-ratio in the microemulsion. 2) A dense dispersion and a film of the CdS ultrafine particles can be prepared with the help of the surfactants system. 3) Almost all CdS ultrafine particles can be precipitated from the microemulsion by addition of dodecanethiol, pyridine, and methanol to the microemulsion containing CdS particles, and the resultant precipitates can be filtrated. The separated particles can be redispersed in hexane without change in the primary size of CdS particles.