Highly sensitive carbon monoxide (CO) gas sensors based on Ni and Zn doped SnO2 nanomaterials

Herein, a facile single-step hydrothermal method is reported for the synthesis of Ni and Zn doped SnO2 nanomaterials, i.e. nanoparticles and nanosheets. The synthesized pure and doped SnO2 nanomaterials were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The diffraction planes from the XRD analysis correspond to the tetragonal rutile crystal phase of doped SnO2. A slight shift in the diffraction angles for doped SnO2 nanomaterials as compared to pure SnO2 confirms the replacement of the Sn4+ with Ni2+ and Zn2+ ions. The SEM analysis revealed that SnO2 and Ni-doped SnO2 possess nanoparticle shaped morphologies while the Zn doped SnO2 exhibited sheet-like structures. The compositions of the pure SnO2, Ni and Zn doped SnO2 nanomaterials were ascertained by XPS studies which confirmed the purity and doping of SnO2 nanomaterials. Further, gas sensor applications of synthesized Ni and Zn doped SnO2 nanomaterials were evaluated at different operating temperatures and concentrations of the CO gas. The optimized temperatures for pure SnO2 and doped SnO2 nanomaterials based gas sensors were 310 °C and 280 °C, respectively. For an even very low concentration of 50 μL/L, Ni and Zn doped SnO2 gas sensors showed gas responses of 7.28 and 5.90, respectively at 280 °C. Thus, Ni-doped SnO2 nanoparticles based gas sensor exhibited better gas response than pure SnO2 and Zn doped SnO2 based gas sensors though response and recovery times were comparable with those of Zn doped SnO2 gas sensor.