Preparation of semiconductor nanoparticle-polyurea composites using reverse micellar systems via an in situ diisocyanate polymerization

The polymerization of diisocyanates, such as hexamethylene diisocyanate, via reaction with water to form polyurea (PUA), has been utilized to immobilize nanoparticles, when formed in reverse micelles. Metal sulfide nanoparticles (CdS, ZnS, coprecipitated CdS-ZnS, and ZnS-coated CdS), as well as TiO2, AgI, and Ag nanoparticles, were immobilized successfully without undesirable particle coagulation, by the simple addition of diisocyanate to the micellar solution. The resulting PUA composites consist of powder of 0.01-0.1 mm in size and where the immobilized nanoparticles are more or less exposed to the external surface, such that they are utilizable as photocatalysts for the generation of H-2 from 2-propanol aqueous solution. With tolylene 2,4-diisocyanate used as monomer, the resulting PUA composite is soluble in both DMF and DMSO, and a nanoparticle-containing transparent film can therefore be prepared by casting the resulting DMSO solution onto a quartz sheet.