Fabrication of core–shell TiO 2 @CuS nanocomposite via a bifunctional linker-assisted synthesis and its photocatalytic performance

Monodisperse anatase TiO2 microspheres were prepared by a modified sol–gel method and then coupled with CuS nanoparticles (NPs) to prepare non-core–shell TiO2/CuS composite (denoted as TiO2/CuS) and core–shell TiO2@CuS composite (denoted as TiO2@CuS), respectively, by two different fabricating methods, namely direct deposition and bifunctional linker-assisted assembly. The morphological, structural, and optical properties of both the TiO2/CuS and TiO2@CuS composites were characterized using TEM, HR-TEM, EDS mapping images, XRD, XPS, and UV–Vis DRS. Their visible-light-driven photocatalytic performance for degradation of methylene blue was comparatively studied. Results indicate: (1) as bifunctional linker between CuS and TiO2, 2,3-dimercapto-succinic acid (DMSA) enables CuS NPs to be anchored tightly onto the DMSA-functionalize TiO2 surface with small particle size, narrow size distribution, conformal coverage, intimate contact, and strong interaction with TiO2 to form TiO2@CuS. (2) Without using DMSA, the directly deposited CuS NPs tend to aggregate and are loaded randomly and loosely on the bare TiO2 without forming well-defined heterojunction due to the lattice mismatch between CuS and TiO2, even some CuS NPs are detached from the surface of TiO2 and thus TiO2/CuS was obtained. (3) TiO2@CuS exhibits superior synergistic effect and corresponding photocatalytic activity to TiO2/CuS, and the significant difference between their photocatalytic properties is mainly attributed to their distinct microstructure caused by the different assembling methods.