Surfactant-Assisted WS2 Nanostructures for Enhanced NO2 Sensing Performance

A two-dimensional WS ₂ is considered the next-generation sensor material due to its high surface-to-volume ratio and a large number of active sites. These characteristics of the WS ₂ sensor can be efficiently tuned by varying the surface morphologies of the deposited WS ₂ . Here, we emphasize the role of surfactants (NaCl and CTAB) in the growth of various morphologies of WS ₂ nanostructures. Pristine-WS ₂ , NaCl-WS ₂ , and CTAB-WS ₂ exhibit nanorods, nanobelts, and flower-like morphologies, respectively, synthesized via a facile hydrothermal method. The NaCl-assisted WS ₂ nanostructure exhibits a three-fold increase in active surface area as compared to that by pristine-WS ₂ . Moreover, the NaCl-assisted WS ₂ sensor shows an eleven-fold enhancement in sensing performance as compared to that by pristine-WS ₂ and a five-fold improvement as compared to that by CTAB-assisted WS ₂ for 100 ppm NO ₂ exposure. The optimum operating temperature for the developed NaCl-WS ₂ sensor is 75 °C, making it suitable for use in portable sensor devices. At this optimal temperature, the NaCl-WS ₂ sensor exhibits an approximately eight-fold increase in sensing performance as compared to that by the same sensor at room temperature for 100 ppm NO ₂ exposure. Furthermore, the developed NaCl-WS ₂ sensor has demonstrated a significant response of 5.3 even at 250 ppb, with a limit of detection and quantification in the range of 0.5 and 1.5 ppb, respectively. The higher sensing response, shorter response-recovery time, excellent selectivity, and ultrasensitive and selective nature toward the target gas NO ₂ , even at sub-ppb levels, make NaCl-WS ₂ sensor a promising candidate for domestic and industrial applications.