Enhanced Humidity Sensing Characteristics of MoS₂ through Benzyl Viologen Dichloride Doping

Accurate humidity monitoring is essential for industries such as healthcare, agriculture, and manufacturing, where precise environmental control directly impacts quality and safety. Molybdenum disulfide (MoS₂) is a promising candidate for humidity sensors due to its high surface area and favorable electronic properties, but its response characteristics require further enhancement for real-time applications. In this study, we demonstrate that benzyl viologen dichloride (BVD) doping significantly improves the performance of MoS₂-based humidity sensors. BVD doping increases carrier concentration, enabling superoxide-mediated water dissociation and hydroxyl adsorption, which collectively enhance conductivity, proton transport, and surface hydrophilicity. The BVD-doped MoS₂ humidity sensor exhibited a 16-fold enhancement in relative response compared to undoped MoS₂, with response times reduced from 2.18 to 0.699 s and recovery times shortened from 15.2 to 6.56 s. Structural and electronic confirmation of successful n-type doping was obtained via Raman spectroscopy, UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrical measurements. Contact angle analysis further indicated enhanced hydrophilicity of BVD-doped MoS₂, supporting improved water adsorption. These results highlight BVD doping as an effective strategy to advance MoS₂-based humidity sensors toward next-generation applications in industrial, environmental, and medical fields.