Highly stable, selective, and high-performance VOC sensor using SnS2 nano-lotus structures

This research demonstrates the design and development of a novel SnS2 nano-lotus structure (NLS) using a one-step eco-friendly solvothermal method which can detect volatile organic compounds (VOCs) and involves a 3-S approach, i.e., obtaining stability, sensitivity, and selectivity. As a unique feature, the UV-visible spectroscopy results showed an optical band gap of 2.25 eV and Urbach energy states at 630, 675, 751, and 793 meV. Thus, a gas sensing mechanism that is correlated with the optical band gap and Urbach energy states of SnS2 NLS, leading to selectivity with reference to a targeted VOC, is discussed in this research. This SnS2 NLS sensor demonstrates the highest response (sensitivity) of 93.5% to 25 ppm ethanol at 90 °C, compared with its responses to methanol (16.6%), propanol (14.8%), and n-butanol (11.4%). The SnS2 NLS sensor for ethanol shows rapid response (14.2 s) and quick recovery (16.6 s) times toward a concentration of 25 ppm at 90 °C. The SnS2 NLS sensor demonstrates better selectivity towards ethanol, with the response of 92.9% being much higher compared to its responses to other interfering gases, such as methanol (16.4%), propanol (14.8%), n-butanol (11.4%), benzene (4.1%), toluene (5.8%), and n-butylacetate (2.2%). The value of the selectivity coefficient with respect to n-butylacetate is high, 34.5, which indicates that the SnS2 NLS sensor response to ethanol is 34.5 times higher than the response to n-butylacetate. However, the value of the selectivity coefficient towards methanol is low, 4.3, which shows that the SnS2 NLS sensor response to ethanol is only 4.3 times higher than the response to methanol. In addition to selectivity, the SnS2 NLS sensor displays outstanding stability, with a response of 91.3% after 25 days (tested at 5 day intervals) to a concentration of 25 ppm ethanol at 90 °C. The SnS2 NLS sensor exhibits a theoretical detection limit of 7.9 ppb toward ethanol at 90 °C. Taking the sensing outcomes into consideration, the unique SnS2 NLS VOC sensor with tunable performance can be projected to act as an analytical tool to detect a category of VOCs efficiently.