ZnOCdS

ZnO/CdS refers to a heterostructure or composite material formed by combining zinc oxide (ZnO) and cadmium sulfide (CdS) in various architectures such as core–shell nanoparticles, nanorods, or thin films, as well as at bulk interfaces. The combination leverages the wide band gap of ZnO and the narrower band gap of CdS to extend light absorption into the visible region and to promote charge separation across the interface.

Structure and properties: ZnO is a wide-band-gap semiconductor (about 3.3–3.4 eV) and CdS is a direct band-gap semiconductor (~2.4 eV). When paired, they form a type-II or quasi-type-II heterojunction that facilitates transfer of photoexcited electrons from CdS to ZnO and holes in CdS, reducing recombination. This can enhance photocatalytic activity and broaden the optical response compared with either component alone.

Synthesis: ZnO/CdS junctions can be prepared by sequential deposition methods such as chemical bath deposition, hydrothermal or solvothermal growth, as well as by sputtering or electrodeposition to create ZnO cores with a CdS shell or CdS/ZnO multilayers. In core–shell variants, CdS is deposited on ZnO nanorods or nanoparticles to maximize interfacial area.

Applications: The ZnO/CdS interface is studied for photocatalysis (degradation of pollutants, water splitting), quantum dot-sensitized or heterojunction solar cells, and gas sensing. CdS provides visible light absorption, while ZnO supports charge transport.

Safety and environmental considerations: Cadmium-containing compounds are toxic and require proper handling, encapsulation, and disposal to prevent environmental release. Research often seeks methods to stabilize CdS and minimize cadmium usage.

See also: ZnO, CdS, ZnO/CdS heterojunctions.