Utilizing dip-coated graphene/nanogold to enhance SPR-based fiber optic sensor

Optical fiber sensing is an important sensing technique where combining the advantage of using new materials such as graphene and the features of the optical fibers. Previously, the sensing probes were prepared by different methods such as sputtering; we are seeking for a new, easy, low-cost and not complicated method with superior advantages over other methods. In this paper, dip-coated sensing probes of gold film (Au), graphene/gold film/core (Gn/Au/core), gold nanoparticles/core (AuNPs/core) and graphene/gold nanoparticles/core (Gn/AuNPs/core) are prepared. The structures of probes were examined via scanning electron microscope and Raman spectroscopy. In the Gn/AuNPs/core structure, the Gn surface and AuNP surface are rough enough to increase the surface area of the sensor. Lead ions in water with different concentrations were detected via optical fiber surface plasmon resonance with the prepared probes. Sensor performance parameters for the fabricated probes were calculated. The Gn/AuNPs/core probe shows a superior sensitivity (Sn), figure of merit, signal-to-noise ratio and limit of detection among other sensors, which make it available for chemical and biological applications. In this work, the dip-coated graphene is a promising method for enhancing performance parameters of optical fiber sensors, not complicated, low cost and easy in comparison with commonly used sputtering method.