Ultra-selective hydrogen sensors based on CuO - ZnO hetero-structures grown by surface conversion

Synergistic effects of mixed oxides have the potential to improve sensing performances of environmental, domestic and industrial monitoring devices. However, mixed oxides often come in the form of separate particles and are thus addressed separately by the environment, instead of capitalizing on the interface between the metal oxides. This paper describes a new core@shell gas sensing material of tetrapodal zinc oxide with a surface coating of crystalline copper oxide(t-ZnO@CuO). The special surface conversion strategy yields a unique, self-assembled and pinhole-free coating of CuO nanoplatelets. The morphologies, structural, chemical and gas sensing properties of the heterostructure were investigated. To evaluate the sensing properties of the heterostructure, t-ZnO@CuO was fabricated as nanosensors, consisting of one core-shell rod of CuO-coated crystalline ZnO. The single core@shell rod showed high selectivity towards hydrogen already at comparatively low operation temperatures of 150 °C. Computational calculations based on the density functional theory (DFT) have been carried out to understand the interaction of the H₂ gas molecule with the surface of the CuO nanostructures. The surface conversion was done wet chemically and is a novel method for generating heterostructures that can be potentially transferred to heterojunctions with unique properties for chemosensors.