High-sensitivity low-power tungsten doped niobium oxide nanorods sensor for nitrogen dioxide air pollution monitoring

摘要

The accurate sensing of air pollutants such as nitrous oxide gas (NO_x) has wide medical and industrial applications. For conventional polycrystalline film based sensors, achieving adequate sensitivity, especially at room temperature, still remains a challenge. In this paper, we present an investigation on the hydrothermal synthesis, device fabrication, and electronic properties, and NO_2 gas sensing performance of tungsten doped niobium oxide nanorods. The gas sensing capability of metal oxide nanorods can be significantly improved through doping, as the increase in electron density at the material surface results in a significant impedance change upon the presence of adsorbates. Results indicate that exposure to 9.9 ppm of NO_2 gas at 25 ℃ causes sensor outputs of 0.33 V and 3.4 V for 1 μA and 10 μA biases, respectively. For a 100 μA bias, the response at 410℃ and 450℃ demonstrated outputs of 16.1 V and 12.2V, respectively. Compared to the recent literature, the nanorod sensor demonstrated a several orders-of-magnitude improvement in voltage response toward ppb-level NO_2 gas under both room temperature (25℃) and elevated temperature (450℃), while keeping power consumption at the microwatt level. Such low powered operation enables the ubiquitous deployment of compact, portable and maintenance-free environmental sensors.