Influence of Gd doping on gas sensing performance of Gd-(ZnO/ TiO2) nanocomposites

The sol-gel method was applied to synthesized Gd-doped (0, 0.7, 1.4, and 2.1 wt%) ZnO/TiO2 nanocomposites (named G0, G1, G2, and G3). Herein, synthesized nanocomposites were examined against CO2 gas sensing ac-tivity. XRD patterns confirm the mixed phases for both metal oxides like ZnO and TiO2. The surface morphology of ZnO/TiO2 nanocomposites was observed in form of a nanorod-like structure which converts into nanocauliflower-like structures as Gd ions content increases. The average crystallite size was found to decrease as compared to undoped nanocomposites (20-13 nm) on increasing Gd ion content and was confirmed by XRD analysis. The optical bandgap found 3.16 eV for pure ZnO/TiO2 while augmenting the content of Gd it was observed to increase for G3 equal to 3.47 eV calculated by Tauc's plot. The gas sensing behavior of the nano-composites towards the CO2 gas was recorded as sensor resistance Vs time for all samples at different operating temperatures. Sensor G2 exhibits the best sensing behavior for CO2 gas at 50 degrees C. Which revealed that Gd ions enhanced the gas sensing activity of fabricated gas sensors of Gd doped ZnO/TiO2 nanocomposites as providing adsorbing surface sites for gas molecules. These findings represent that Gd(1.4 wt%)-(ZnO/TiO2) (G2) nano-composites is a good CO2 sensing candidates at low operating temperatures.