A highly stable, selective, and high-performance VOC sensor using a SnS2 nano-lotus structure

Abstract

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.