Sensing of ultra-ppm level NO2 gas via synergistic effects of Cr doping and e-beam irradiation in WO3 nanostructures

Abstract

Herein, we report the effects of Cr doping and electron beam irradiation (EBI) on WO₃ thin films towards low-level detection of NO₂. Structural, morphological, and defect correlations are presented to provide a comprehensive understanding of the film's properties. XRD and Raman analyses confirmed the formation of well-crystallized WO₃ films due to doping and irradiation. Photoluminescence analysis validated the presence of oxygen vacancy (V_o) defects in the films which was further corroborated by XPS studies. The EBI Cr–WO₃ film exhibited a higher concentration of V_o defects and smaller grain sizes, contributing to enhanced sensing performance. A maximum sensor response of 3.43 was achieved at an NO₂ concentration of 5 ppm. Theoretical limit of detection (LOD) calculations indicated ultra-low NO₂ detection capability at 0.4 ppm (400 ppb), highlighting the potential of the prepared film for applications in environmental monitoring, healthcare diagnostics, and industrial settings.