A radially controlled ZnS interlayer on ultra-long ZnO–Gd2S3 core–shell nanorod arrays for promoting the visible photocatalytic degradation of antibiotics

Nanorod (NR) arrays offer commendable visible-light-driven photocatalytic performances. Herein, we describe the construction of a ternary ZnO–ZnS–Gd2S3 nanostructural array in which a sulfidation process is used to decorate the Gd2S3 shell layer with a ZnS interface over the vapor-phase-grown vertically-aligned ZnO. With control over the shell-wall thickness, the shell layer of ~25 nm wall thickness on the ultra-long ZnO NR arrays exhibited a higher catalytic efficiency close to 3.3, 2.0, 1.2, and 1.8 times those of the bare ZnO, the ZnO–ZnS, the Gd2S3-decorated (~10 nm) and Gd2S3 shell-layered (~40 nm) ZnO–ZnS core–shell structures, respectively. The core–shell geometry and the shell-wall thickness with maximized contact interface afforded increased light absorption in the visible region and effectively retarded the recombination rate of the photoinduced charge carriers by confining electrons and holes separately, thus providing advantages in terms of the degradation of the pharmaceutical residue tetracycline and the industrial pollutant 4-nitrophenol in wastewater.