Fabrication of novel Ag-doped ZnO/CdO heterostructure for high-sensitive detection of formaldehyde at low temperature.

• Ag-doped ZnO/CdO ternary heterostructure have been synthesized. • The ternary composite exhibited enhanced HCHO sensing property at low temperature. • The AZC-2 sensor reached a high response value of 164 to 50 ppm HCHO at 150 °C. • A low experimental detection limit of 100 ppb can be achieved. • Both the Ag doping and multiple heterojunctions contribute to the property improvement. Novel Ag-doped ZnO/CdO ternary heterostructures (AZC composite) were fabricated and characterized by X-ray diffractometer (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and etc. The results showed that Ag nanoparticles were attached onto the ZnO/CdO surface and multiple heterojunctions including Ag/ZnO, Ag/CdO Schottky junctions and ZnO/CdO homo-type heterojunction were generated. The formaldehyde (HCHO)-sensing performance of the AZC composites was tested. Compared with the ZnO/CdO composite, the AZC composites demonstrated much higher response and faster response/recovery rate. In particular, the AZC sample with an Ag content of 3.04 wt% (AZC-2) exhibited a high response of 164 to 50 ppm HCHO at 150 °C, a ppb-level detection limit, and acceptable humidity resistance. This work illustrated that Ag nanoparticles is a promising candidate for improving the sensing property of transition metal oxide due to its catalytic sensitization effect and relatively low cost. [ABSTRACT FROM AUTHOR]