Jin-Song Hu, Ling-Ling Ren, An-Min Cao, Li-Jun Wan* and Chun-Li Bai*

Environmental problems associated with organic pollutants and toxic water pollutants provide the impetus for sustained fundamental and applied research in the area of environmental remediation. Semiconductor photocatalysis offers the potential for complete elimination of toxic chemicals due to its efficiency and potentially broad applicability. Therefore, it is very essential to develop a cost-effective mass-production method of semiconductor photocatalysts with highly catalytic activity and easy separation.

Now, a simple, mass-production and low-cost self-assembly synthesis of ZnS nanoporous nanoparticles (NPNPs) composed of hexagonal ZnS nanocrystals with 3–5 nm size has been developed by Prof. Bai and Prof. Wan in Institute of Chemistry, CAS. The uniform, spherical NPNPs are monodisperse and possess surface areas on the order of 156 m²g^-1 (Fig. 1). The advantages of the ZnS NPNPs as semiconductor photocatalysts are (1) High surface-to-volume ratios and effectively preventing the nanoparticles from aggregation, so as to result in high catalytic activity; (2) The profitability of size-quantized, nanometer-sized semiconductor particles, involving the higher redox potentials due to the increase in band-gap energy (the energy difference between LUMO and HOMO), which in turn improves charge transfer rates in the system, and the drastically reduction of volume recombination (radiationless recombination of the electron–hole pair within the semiconductor particle); (3) Easier recycle and separation than common NCs due to the large diameter of NPNPs; (4) Good dispersity and proper dimension without the requirement of constant stirring or “dark” reaction for adsorption of substrates. As a result, the ZnS NPNPs show higher photocatalytic activity than Degussa P25 titania or ZnS nanocrystals in the photodegradation of eosin B at ambient temperature (Fig. 2).

ZnS photocatalysts have been used not only for photodegradation of organic dyes, also for photoreductive H₂ production and photoreduction of CO₂, phototransformation of various organic substrates, photoreductive dehalogenation of halogenated benzene derivatives, photocatalytic removal of water pollutants, and photocatalytic reduction of toxic metal ions, and so on. Therefore, the ZnS NPNPs are expected to find many interesting applications in semiconductor photocatalysis and environmental remediation, as well as nanodevices as a result of its high surface-to-volume ratios, monodispersion, rich photocatalytic and luminescent properties.

Angew. Chem. Int. Ed., 2005, 44(8), 1269-1273。