Luminescence properties of ZnO-M heterostructures fabricated by galvanic-submerged photosynthesis of crystallites

By adapting hetero-nanostructures in optoelectronic device, a prominent luminescence characteristic can be obtained. The challenge is to engineer the band bending if a semiconducting surface gets contact with a metal. A galvanic replacement method is versatile for bimetallic hetero-nanostructures synthesis. However, the nanostructures morphologies can be varied depending on the metals pair or their supporting template. In this study, we demonstrate a facile 1-D ZnO nanorods (NRs) growth fabricated by galvanic replacement reactions. Without using bimetallic solution, the galvanic replacement reaction was implemented by joining Zn metal to Au, Pt, Ag, Cu, W, and Ni metals substrate. The luminescence properties of ZnO NRs were characterized by photoluminescence (PL) and cathodoluminescence in scanning transmission electron microscopy (STEM-CL). Based on PL analysis result, oxygen vacancy (V-O) was responsible for the visible light region emission in all ZnO-M samples. Then, STEM-CL analysis highlighted the presence of zinc interstitial (Zn-i) at the interface of ZnO-M. Due to band bending, interaction between V-O and Zn-i resulted the formation of zinc antisite (Zn-O) at the interface. There was no shift in visible light emission of the NRs due to Fermi-level pinning. The findings will be useful for future large-scale synthesis and engineering of hetero-nanostructures luminescent devices

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 (ZnO). The G-SPSC method approach is versatile for other bimetallic system adaptation and is promising for large-scale environmentally friendly synthesis of optoelectronic devices