Preparation of photosensitized nanocrystalline TiO2 hydrosol by nanosized CdS at low temperature

A new method was developed for the fabrication of CdS-TiO2 semiconductor nanoparticles as visible-light-excitable photocatalyst at low temperatures. Nanosized CdS acting as an effective and stable sensitizer was incorporated into TiO2 by microemulsion-mediated solvothermal hydrolyzation followed by acidic peptization of the precipitate under 70 deg. C. The new method avoided the calcination or other pyrochemical treatments involved in traditional preparations, and thus eliminated the unwanted agglomeration of nanoparticles or the oxidation of CdS by oxygen. Compared to traditional methods, it was highly simplified, bypassing those miscellaneous steps like filtration, sintering, milling and redispersion in solutions. The crystal structure, configuration, element composition, as well as the light-absorption properties of the obtained CdS-TiO2 hydrosol were characterized in detail. The hydrosol consisting of uniform and small crystalline particles of about 2 nm in diameter was thermodynamically stable and showed good dispersibility. The photocatalytic activity of the 'coupled' material was confirmed through the photocatalytic degradation of methylene blue (MB) dye under visible light irradiation, and the cooperative photocatalytic mechanism is discussed