Prism-based surface plasmon resonance (SPR) optical sensors are extensively used in a variety of applications. In implementing a multilayer sensing structure, SPR phenomena are employed to detect gases in the proposed research. A BK7 glass prism is used as a sensing structure with decomposition on nano thin films based on different materials: silver (Ag), titanium dioxide (TiO2), and graphene. The methane gas is applied to the graphene sensing layer of the multilayer optical sensor. As the methane gas concentration rises around the sensor, the SPR angle varies, indicating that the refractive index of graphene layer is changed significantly due to absorption of the increasing methane gas concentration. The methane gas concentration measurement is based on an angle interrogation technique. TiO2, graphene, and Ag layers of different thicknesses have been optimised for sensor performance.
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