Material-Driven Performance Enhancement in Composite Thin Films for Optical Hydrogen Sensing at Room Temperature

Hydrogen (H 2 ) detection is critical for ensuring safety in emerging clean energy systems. In this work, the material dependent optical response of MoS 2 and MoS 2 /NiS composite thin films integrated onto a side-polished plastic optical fiber (POF) is comparatively investigated. The sensing mechanism is governed by evanescent field interaction between guided light and the functional coating deposited on the exposed fiber surface. Both materials were synthesized via chemical bath deposition, forming nanostructured films with distinct surface characteristics. Upon exposure to varying H 2 concentrations, the MoS 2 /NiS composite demonstrated significantly higher absorbance variation compared to the MoS 2 film. The composite achieved a sensitivity of 0.4475 a.u./% H 2 , representing an enhancement of approximately 3.5-fold increase in sensitivity. The improved performance is attributed to synergistic interfacial effects, increased active adsorption sites, and enhanced charge transfer within the heterostructures composite. These findings highlight the role of material engineering in enhancing optical hydrogen sensing performance and demonstrate the potential of MoS 2 /NiS composites as smart functional sensing materials.