Core–shell TiO2@ZnO nanorods for efficient ultraviolet photodetection

Abstract

Core–shell TiO₂@ZnO nanorods (NRs) have been fabricated by a simple two step method: growth of ZnO NRs' array by an aqueous chemical technique and then coating of the NRs with a solution of titanium isopropoxide [Ti(OC₃H₇)₄] followed by a heating step to form the shell. The core–shell nanocomposites are composed of single-crystalline ZnO NRs, coated with a thin TiO₂ shell layer obtained by varying the number of coatings (one, three and five times). The ultraviolet (UV) emission intensity of the nanocomposite is largely quenched due to an efficient electron–hole separation reducing the band-to-band recombinations. The UV photoconductivity of the core–shell structure with three times TiO₂ coating has been largely enhanced due to photoelectron transfer between the core and the shell. The UV photosensitivity of the nanocomposite becomes four times larger while the photocurrent decay during steady UV illumination has been decreased almost by 7 times compared to the as-grown ZnO NRs indicating high efficiency of these core–shell structures as UV sensors.