Photochemical preparation of CdS nanoparticles on carboxyl- functionalized copolymer microspheres and their visible-light photocatalytic activities

CdS nanoparticles were prepared on the surface of copolymer of methyl methacrylate and methacrylic acid [Poly(MMA-co-MAA)] microspheres by a photochemical route, using Na₂S₂O₃ and CdSO₄ as source of sulfur and cadmium, respectively. Because of the coordinate effect of -COOH groups on the surface of Poly(MMA-co-MAA) microspheres, the Cd²⁺ would be adsorbed and then react with sulfur to produce CdS nanoparticles without coalescence under the irradiation of low power UV-light. The XRD spectra demonstrated that CdS nanoparticles on surface of Poly(MMA-co-MAA) microspheres have good crystallinity and the SEM results showed that CdS nanoparticles on microspheres were spherical and uniform with around 100 nm in sizes. At the same time, the photocatalytic activity of the nanoparticle/microsphere composite was studied by taking the photodegradation of methylene blue (MB) as an example. The degradation rate of MB solution could be up to 93.0% after irradiating 100 minutes by 500 W Xenon lamps and that would be up to77.5% if irradiating 180 minutes by sunlight. Comparing with the corresponding pure CdS nanoparticles, the composites have much higher photocatalytic activities.