Galvanic-submerged photosynthesis of crystallites: Fabrication of ZnO nanorods@ Cu-surface

In this study, we report a facile fabrication method of 1-D ZnO nanorods (NRs) on a copper substrate surface by means of galvanic contact reactions. Instead of using bimetallic aqueous solution for the galvanic reactions, UV illumination on the Zn contacted with Cu surface in pure water environment was implemented, leading to galvanic combined submerged photo-synthesis of crystallites (G-SPSC) process. A pencil-like and flat-tip shape of NRs growth can be controlled as a function of UV irradiation time. In order to grow fine NRs, the galvanic process was essential for Zn²⁺ and OH⁻ ions production. In particular, OH⁻ accumulated at the vicinity surface of Cu to achieve a locally alkaline environment. Then, UV irradiation assisted the ZnO NRs initiated by water splitting process. Oxygen vacancy (V_O) was responsible for the growth of pencil-like shape NRs. A blue shift in visible light region of photoluminescence (PL) spectra was observed when the pencil-like NRs transformed into flat-tip shape. The successful heterojunction of ZnO-Cu also was observed in their PL spectra, which dictated by the formation of zinc antisite (Zn_O). The G-SPSC method approach is versatile for other bimetallic system adaptation and is promising for large-scale environmentally friendly synthesis of optoelectronic devices.