Enhanced NO2 gas sensing performance of Ni-doped ZnO nanostructures

Pure and 1-4 at.% Ni-doped ZnO (N(0)Z-N(4)Z) 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 N(0)Z, N(1)Z, N(2)Z, N(3)Z and N(4)Z nanostructures respectively. The NO2 gas sensing performance of fabricated N(0)Z-N(4)Z sensors were tested at different working temperatures (120-280 degrees C) and concentrations (5-100 ppm). Among them, the N(2)Z sensor showed stable, reproducible and the highest response (356%) when exposed to 100 ppm NO2 gas at 200 degrees C working temperature. The probable sensing mechanism of NO2 gas by Ni-doped ZnO nanostructures is investigated and discussed. Sensing response of N(2)Z gas sensor was also studied for 100 ppm Cl-2, SO2 and H2S gases at 200 degrees C operating temperature and it appeared for most selective towards NO2 gas. The present study reveals that N(2)Z nanostructure can be attractive material as a sensor for recognition of hazardous NO2 gas at low concentrations.

Automated summary

Pure and Ni-doped ZnO nanostructures were prepared and characterized for their crystal structure, morphology, and gas sensing performance. Ni doping significantly influenced the band gap, absorption spectra, and gas sensing properties of ZnO nanostructures.