WO₃ microtubules supported by nanoparticles to construct high-response and low-temperature nitric oxide sensor from...

A WO₃ sensor was prepared using discarded cotton towels to achieve a high response to NO at reasonably low temperatures, which not only turns cotton towels into treasures but also makes the preparation process green and environmentally friendly, which is very much in line with the concept of sustainable development of the society. We successfully replicated the microtubule morphology of discarded cotton towels by washing them with ultrapure water, cutting them into small squares, impregnating them with an ethanol solution of tungsten hexachloride (WCl₆) for 6 h, drying them, and then calcining them for 2 h under air atmosphere. Among them, the WO₃-CT-6 microtubules obtained by calcination at 600 °C are micron tube structures supported by nanoparticles, and the single tubes are uniformly distributed and morphologically intact, with a large specific surface area, a high content of adsorbed oxygen species, and oxygen vacancy defects, which together achieve the ability to exhibit a good sensitivity to trace NO. At a low temperature of 50 °C, the WO₃-CT-6 microtubular sensor has a response of 74.5 to 1 ppm NO and a fast response/recovery time (93 s /27 s), which is the best overall sensitivity performance of WO₃-based sensors available. The WO₃-CT-6 sensor also has good selectivity, reproducibility, long-term stability, and humidity resistance. In addition, we performed a detailed analysis of the sensitivity mechanism using X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), oxygen temperature-programmed desorption and nitrogen-air sensitivity tests.