High-performance and fast fiber-optic SPR gas sensor based on WO3/SnO2 nanocomposites films for room-temperature NH3 detection

Ammonia, a key biomarker existing in human breath, plays a critical role in non-invasive breath testing at room temperature. Among various ammonia sensors, reflective fiber-optic sensors based on surface plasmon resonance (SPR) offer significant advantages, including high sensitivity, small footprint, and portability, making them ideal for room-temperature gas sensing. In this work, WO3/SnO2 nanocomposites were synthesized via a solvothermal method to obtain sensitive materials for room-temperature NH3 detection. The WO3/SnO2 nanocomposites were deposited on the surface of the SPR fiber by dip-coating to form a uniform gas-sensitive film. The sensor exhibited exceptional performance, achieving a high sensitivity of −10.84 a.u./ppm, a fast response time of 2 s, and a theoretical limit of detection of 277 ppb at room-temperature. The enhanced sensing mechanism is attributed to the formation of WO₃-SnO₂ heterojunctions, which facilitate efficient charge transfer and amplify SPR signals via dielectric modulation. This work highlights the potential of low-dimensional material-integrated optical fiber platforms for non-invasive medical diagnostics through breath ammonia detection.