Enhanced NO2 gas sensing performance of Ni-doped ZnO nanostructures

Abstract

Pure and 1–4 at.% Ni-doped ZnO (N0Z-N4Z) nanostructures have been successfully prepared by simple and cost-effective co-precipitation method. The prepared nanostructures were studied using XRD, FESEM, HRTEM, EDX, FTIR, UV–Visible absorption and XPS techniques. The XRD study revealed that the hexagonal wurtzite structure of pure and Ni doped ZnO nanostructures, and their preferred peak growth orientation is along (101) plane without inferior phases in Ni-doped ZnO samples. The morphological investigation of Ni doped ZnO samples by FESEM and HRTEM techniques exhibited nanorods. The average diameter and length of nanorods are 25–80 nm and 140–410 nm. The results of UV–Visible absorption spectroscopy of Ni-doped ZnO nanostructures indicate red shift with varying amounts of Ni concentration. The estimated band gaps were obtained 3.11, 3.06, 3.02, 2.99 and 2.97 eV of N0Z, N1Z, N2Z, N3Z and N4Z nanostructures respectively. The NO2 gas sensing performance of fabricated N0Z-N4Z sensors were tested at different working temperatures (120–280 °C) and concentrations (5–100 ppm). Among them, the N2Z sensor showed stable, reproducible and the highest response (356%) when exposed to 100 ppm NO2 gas at 200 °C working temperature. The probable sensing mechanism of NO2 gas by Ni-doped ZnO nanostructures is investigated and discussed. Sensing response of N2Z gas sensor was also studied for 100 ppm Cl2, SO2 and H2S gases at 200 °C operating temperature and it appeared for most selective towards NO2 gas. The present study reveals that N2Z nanostructure can be attractive material as a sensor for recognition of hazardous NO2 gas at low concentrations.