Developed Low-Temperature Anionic 2H-MoS₂/Au Sensing Layer Coated Optical Fiber Gas Sensor

Carboxyl-functionalized molybdenum disulfide (COOH-MoS₂) nanosheets were prepared through a facile low-temperature hydrothermal method. The phase transformation of metallic-1T to 2H-semiconductor COOH-MoS₂ nanosheets was conducted through introducing Au thin film on the unclad optical fiber as a sensing layer in a low temperature. The developed structure successfully refined the loss of the semiconducting properties and poor adhesion of COOH-MoS₂ on the unclad polymer optical fiber, which provided limited semiconductor potential as the sensing layers on the optical fiber surfaces. The sensing performance of the as-prepared structure was tested for quantitative detection of three different volatile organic carbons (VOCs) of ethanol, propanol, and methanol gases as well as cross-sensitivity to relative humidity. The operating principle was based on intensity variation of the evanescent wave in the sensing region. The response of the proposed sensing system shows maximum response and better linearity (R² = 0.999) to methanol at room temperature. Finally, the comparative experimental cross-sensitivity to relative humidity and methanol was also studied to evaluate the potential of sensing range.