Bi-quantum dots co-sensitized TiO ₂ nanocomposites: Templated synthesis and stabilized by polymer brushes

In this paper, a new strategy is reported to produce CdS-CdSe nanoparticles co-sensitized TiO ₂ nanocomposites via polymer brush template. The anonic functional polymer (polymethacrylate cadmium) are grafted on TiO ₂ surface via the surface-initiated atomic transfer radical polymerization using biomimetic anchor. The coordinated cadmium as the source precursor reacts with H ₂S to generate CdS nanocrystals on TiO ₂ surface. Interestingly, after reaction, the polymer brush can acts as the nanoreactor for generating and shaping CdSe nanoparticles via the absorption of cadmium ions by carboxylate groups and subsequent reaction with Na ₂SeSO ₃, the high density CdS or CdS-CdSe nanocrystals can be multiply uploaded on TiO ₂ surface by repeated steps. CdS nanoparticles have very small size of about 3-5 nm and the size of CdS-CdSe bi-nanocrystals is about 5-10 nm, which are stabilized by tether polymer brush. The light absorption of CdS/TiO ₂ and CdS-CdSe/TiO ₂ are investigated and both are expanded to visible light region.