Scalable fabrication of high-quality WS₂ thin films via solution processing for NO₂ sensing

Transition metal dichalcogenides are a family of semiconducting 2D nanomaterials. Among them, WS₂ stands out due to its theoretically high electron and hole mobilities making it a promising material for gas sensing. In this work, we studied the development of a highly sensitive chemiresistive gas sensor based on WS₂ nanosheets (NSs) for detecting NO₂ at sub-ppm levels under room-temperature. WS₂ NSs were synthesized using a highly efficient and eco-friendly liquid phase shear exfoliation method combined with centrifugation, with various parameters optimized to achieve a narrow sheet-size distribution. The structure and morphology of the WS₂ NSs and ultra-thin films were thoroughly characterized using complementary techniques. The experimental results confirmed the successful exfoliation of WS₂ into few-layer structures (1–5 layers) in an aqueous solution. The interfacial self-assembly method was employed to prepare a highly stacked, continuous WS₂ thin film with a thickness of 20–30 nm, making it promising for large-area surface fabrication. The WS₂-based NO₂ sensor exhibits remarkable sensitivity (23 % at 0.5 ppm), fast response (40 s), and reliable reversibility, with a theoretical limit of detection (LOD) estimated at 15.8 ppb at room temperature. The as-prepared sensor demonstrated excellent repeatability, stability, confirming its potential for NO₂ sensing applications. Additionally, the effects of humidity and temperature were investigated to assess the sensor’s performance under real-world conditions. Density Functional Theory calculations support the experimental results and provide insight into the interaction between NO₂ molecules and WS₂ NSs.