Detection of L-Cysteine Using Silver Nanoparticles and Graphene Oxide Immobilized Tapered SMS Optical Fiber Structure

A label-free highly sensitive tapered Single-Mode-Multimode-Single-Mode (TSMS) structure-based optical fiber sensors (OFSs) is presented in this study for the detection of L-cysteine (L-Cys). Well studied biocompatible nanomaterials (NMs) including silver nanoparticles (AgNPs) and graphene oxide (GO) were synthesized and immobilized over the surface of the sensing probe using self-assembly method. Configurations involving the excitation of localized surface plasmon resonance (LSPR) phenomena proposed in the work are investigated in detail. Further, a comparative study with tapered multimode fiber (TMMF) OFSs and pioneering investigations on previously reported sensors in this area over the last few years (notable advances only) is also presented in this study. The characterization of NMs and sensing probe are observed using in house high-resolution transmission electron microscope (HR-TEM), energy-dispersive X-ray spectroscopy(EDS), scanning electron microscope (SEM), and atomic force microscopy (AFM) facilities. The proposed method improves the performance of the L-Cys in various fronts, namely: (i) sensitivity, (ii) linearity range, (iii) correlation coefficient, and (iv) limit of detection (LoD). The calibration curve is found to be linear over the range of 10nM to1 mM with an LoD of 63.25 μM and sensitivity of 7.0 nm/mM for the proposed TSMS/AgNPs/GO/OFSs.