Highly sensitive chemiresistive detection of NH3 by formation of WS2 nanosheets and SnO2 quantum dot heterostructures

Abstract

The development of chemiresistive ammonia (NH3) sensors has attracted considerable attention for health monitoring applications. In this study, we fabricated two-dimensional (2D) tungsten disulfide (WS2) nanosheets decorated with tin oxide (SnO2) quantum dots for detecting NH3 gas. We tuned the WS2 nanosheet:SnO2 quantum dot ratio to achieve the maximum interfacial area to enhance the sensitivity of NH3 detection. First, the liquid-phase exfoliation process for WS2 was optimized to prepare a stable, high-concentration dispersion comprising 5–6 layers of WS2 nanosheets. Furthermore, SnO2 quantum dots interfaced with WS2 nanosheets at different ratios were prepared to fabricate NH3 sensors. The maximum response of the WS2/SnO2 heterostructure to 10 ppm NH3 was ∼850 % for a WS2:SnO2 ratio of 10:1, which exceeds the response of previously reported NH3 sensors. This superior response led to high sensitivity (∼175 % ppm−1) at low NH3 concentrations and a low limit of detection (∼10 ppb). The electron transfer at the WS2-SnO2 interface has been discussed by studying the bond formation between WS2 and SnO2 at different ratios. This insight into the sensing mechanism could be useful for the development of heterostructured sensors, which can be implemented for NH3 detection in industrial and medical fields.