ZnO/N:ZnO core-shell nanorods prepared via supercritical CO2-N process: Tunable doping and response reversal phenomena for gas sensing

Abstract

ZnO/N:ZnO core-shell nanorods (NRs) were prepared using chemical bath deposition followed by nitrogen doping via a proposed supercritical CO2-N process (SCCNP). The shells of the NRs upon the SCCNP at 120°C not only assume single-crystalline structures but the nitrogen content can reach up to 3.3at%. The bandgaps of the core-shell ZnO NRs are systematically red-shifted with increasing the incorporation of nitrogen. Gas sensing measurements show the ZnO/N:ZnO structures with tunable nitrogen doping concentration in the shell leads to response reversal phenomena and different level of sensitivities in exposure to NH3. The SCCNP is promising for preparing ZnO/N:ZnO nanostructures with controllable doping levels for multifunctional optoelectronics applications.