In-situ deciphering the plasmon-boosted gas sensing behavior of orthogonally self-organized 3D cross-stacked Au/WO3 nanowire arrays on microchips.

Abstract

The development of highly sensitive and reliable gas sensors is crucial for environmental monitoring, industrial safety, and healthcare applications. We report a facile block copolymer self-assembly approach for fabricating plasmonic Au nanoparticle-decorated WO₃ three-dimensional cross-stacked nanowire arrays on microchips for enhanced gas sensing. The porous nanostructure of 3D WO₃ NW framework, coupled with the catalytic and surface plasmon resonance properties of Au NPs, synergistically boosts the NO₂ sensing performance. The Au/WO₃ sensor exhibits an exceptional response of 340.7 to 50 ppm NO₂ at 150 °C in dark conditions, which further increases to 980 under white light illumination, along with rapid response/recovery times, a low detection limit, and excellent stability. To elucidate the gas sensing mechanisms, we employ environmental operando micro-spectroscopy techniques, including conductive atomic force microscopy, Kelvin probe force microscopy, and diffuse reflectance infrared Fourier transform spectroscopy. These advanced characterizations, combined with theoretical calculations, provide direct evidence for the efficient generation and transfer of hot electrons from Au NPs to the WO₃ NW matrix under light irradiation, revealing their pivotal role in enhancing NO₂ adsorption and expanding the electron depletion layer. In-situ measurements also unveil the dynamic modulation of the Schottky barrier height at the Au/WO₃ junction, offering deeper insights into the interplay between environmental factors, hot electrons, and resistance alteration in the metal-semiconductor system. This work provides a promising strategy for designing high-performance gas sensors and paves the way for probing complex gas sensing mechanisms.