SYNTHESIS AND ANALYSING SENSING APPLICATION FOR AMMONIA USING CR DOPED CUO/SNO₂/WO₃ METAL OXIDE NANOSTRUCTURED BY HYDROTHERMAL METHOD AT ROOM TEMPERATURE

Abstract

In the present study, the synthesis, structural and chemical characterization, and ammonia gas-sensing property of chromium (Cr)-doped metal oxide nanostructures synthesized by a hydrothermal method is presented. The nanostructures of Cr-doped SnO₂ and Cr-doped CuO were synthesized, respectively, initially, by varying the precursor concentration, pH, hydrothermal temperature, and reaction time. Next, an optimized Cr-doped SnO₂ and an optimized Cr-doped CuO were used to construct a “Cr-doped CuO/SnO₂/WO₃ ternary nanostructure. To understand the structural, morphological, elemental, and bonding features of the synthesized materials, they were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). The prepared materials were fabricated as sensing layer and were tested for ammonia detection at room temperature. The response to NH₃ was significantly enhanced for the ternary Cr-doped CuO/SnO₂/WO₃ sensor as compared to the individual Cr-doped SnO₂ and Cr-doped CuO sensors. The optimized ternary material exhibited a response of ~5.68 NH3 100 ppm, response time ~48 s and recovery time ~72 s NH3 50 ppm. The defect sites, surface-active sites and charge-transfer pathways generated by Cr were found to be responsible for the enhanced sensing performance at the CuO/SnO₂/WO₃ heterointerfaces. Selectivity and repeatability in successive ammonia exposure cycles were also tested and showed good characteristics of the sensor. These results show the strong potential of the Cr doped CuO/SnO₂/WO₃ nanostructures for sensitive and selective ammonia detection at room temperature.