Graphene-antimonene coated tapered fiber optic surface plasmon resonance sensor for the detection of Hg2+ heavy metal ions

The environment has been severely polluted by heavy metal ions because of their high degree of toxicity. In this paper, we have designed a tapered fiber optic surface plasmon resonance sensor by depositing a thin film of gold (Au) on a tapered core followed by the deposition of graphene and antimonene overlayers. The fiber optic sensing probe was then utilized for the detection of mercury (Hg
²⁺
) heavy metal ions in water of concentration ranging from 70 ppm to 1000 ppm. For theoretical study, we have considered four different taper profiles i.e., exponential-linear, linear, parabolic, and quadratic. The sensitivity is calculated for each taper profile at taper ratios 1.0 and 1.5. The numerical results show that the sensitivity increases with increase in taper ratio and maximum value is observed for exponential-linear taper profile. For an exponential-linear taper profile at taper ratio 1.5, the average sensitivity was observed to be 0.0337 nm/ppm with limit of detection as 1 ppm for the detection of Hg
²⁺
heavy metal ions. The observed sensitivity is 26% higher than the sensitivity observed at taper ratio 1.0 (i.e., for untapered fiber core).