Sub-ppm level NO2 sensing properties of polyethyleneimine-mediated WO3 nanoparticles synthesized by a one-pot hydrothermal method

A novel sensing material of polyethyleneimine-mediated WO₃ nanoparticles was prepared by a simple and efficient one-pot hydrothermal method. The structure and morphology characteristics of the as-prepared WO₃ nanoparticles were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The results showed that the as-prepared WO₃ nanomaterials were composed of highly dispersible WO₃ nanoparticles, and these nanoparticles with the particle size in the range of 10–50 nm showed a monoclinic structure. NO₂ sensing measurements demonstrated that WO₃ nanoparticles-based gas sensor exhibited superior response, outstanding selectivity, excellent reversibility, and good long-term stability. The sensor response increased as NO₂ concentration increased. The highest response value of 251.7 was achieved to 5 ppm NO₂ at the optimal operating temperature of 100 °C. Especially, the sensor response could reach 3.2–50 ppb NO₂. It also exhibited fast response and recovery times with a high sensor response even in a high-humidity environment. The excellent gas sensing properties of WO₃ nanoparticles could be ascribed to their high effective surface areas as well as numerous oxygen vacancies, which foresee the great potential application for fast and effective detection of sub-ppm level NO₂ under different humidity environments.