Graphene–Gold–Au@Ag NPs-PDMS Films Coated Fiber Optic for Refractive Index and Temperature Sensing

A novel fiber-optic refractive index (RI) and temperature sensor based on a multimode-single-mode-multimode fiber (MMF-SMF-MMF) structure coated with graphene-metal hybrid films was proposed and investigated. The surface plasmon resonance (SPR)-based RI sensitivity is improved by the addition of the graphene layer above or below the gold coating of the fiber and then further enhanced with the addition of gold-silver core-shell nanoparticles (Au@Ag NPs). Furthermore, the surface of graphene-Au-Au@Ag NPs film was modified with polydimethylsiloxane (PDMS) for temperature sensing, achieving a high sensitivity of -1.02 nm/°C with good repeatability. This new structure with graphene-gold-Au@Ag NPs-PDMS hybrid films shows applications in many fields, including environmental protection, clean energy, and nano-medicine.