Metal sulfide semiconductor nanoparticles of CdS and coprecipitated CdS-ZnS, when prepared in reverse micellar systems consisting of cetyl-p-vinylbenzyldimethylammonium chloride (CVDAC), were immobilized via an in situ polymerization of CVDAC, using 2,2'-azobisisobutyronitrile or visible light irradiation. The nanoparticles were incorporated successfully into the polymerized CVDAC (PCV) and retained their size and quantum size effect. Since PCV can both retain and cover the nanoparticles effectively, the stability of nanoparticles, versus photoirradiation, is improved as compared to CdS-containing polyurea (J. Phys. Chem. B 1999, 103, 10 120), but the photocatalytic activity is suppressed. PCV is soluble in polar solvents and a CdS nanoparticle-containing transparent film can therefore be prepared by means of casting an ethanol solution of CdS-PCV onto a quartz sheet. An Au nanoparticle-containing PCV was also prepared via in situ Au formation and polymerization by visible light irradiation.