2D V<sub>2</sub>C MXene Based Flexible Gas Sensor for Highly Selective and Sensitive Toluene Detection at Room Temperature

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While the majority of the reports on toluene gas sensors are on rigid electrodes and based on composite materials, doping with additional noble metals, or a high temperature detection method, this work is the first demonstration of the vanadium carbide (V2C) MXene based flexible and room-temperature (RT) toluene gas sensor. The V2C MXene is synthesized by an HF etching route. The field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images exhibit a typical accordion-like multilayered structure of the V2C MXene, where the Fourier-transform infrared spectroscopy (FTIR), Raman, and X-ray photoelectron spectroscopy (XPS) data further ensured its successful growth. The V2C (band gap of 3.9 eV) based flexible gas sensor employing a polyester substrate, displays good reproducibility, quick response/recovery time (14 s/34 s), long-term stability, good cross-selectivity, and a low detection limit of 47.85 ppb over the linear region of 5-200 ppm toluene at RT (27 ± 1 °C). The effect of relative humidity (RH) toward RT toluene gas sensing has also been investigated here. This sensor shows an excellent response of 775% at 200 ppm toluene, with brilliant selectivity toward toluene over six other hazardous gases. The sensor’s plentiful surface functional groups (−F, −OH, −O) and superior electrical characteristics are responsible for its enhanced performance. In light of this, the flexible and RT toluene gas sensor based on the V2C MXene can be a smart way to fabricate the next-generation toluene gas sensors.