MoS2 sensitized tapered fiber optic evanescent wave sensor for refractive index based glucose sensing application

In this paper, a two-dimensional (2D) molybdenum disulfide (MoS₂) coated tapered multimode optical fiber sensor is proposed and its characteristics of refractive index sensing are investigated for the application of glucose monitoring. An highly efficient chemical etching approach has been carried out for tapering the multimode optical fiber. The tapered region is coated with MoS₂ nanosheets and they are synthesized by using a cost-effective liquid phase exfoliation [LPE] method. The ideal solvent for exfoliation has been chosen by comparing the deposition using isopropyl alcohol (IPA) and dimethyl formamide (DMF) solvents. It is found that DMF is an ideal solvent for the 2D MoS₂ nanosheet synthesis as well as for the deposition of the nanosheets over the optical fiber substrate. The optical deposition method is chosen for integrating the synthesized 2D MoS₂ with the tapered optical fiber. The sensitivity is 25, 297, and 525 %/RIU for the uniform multimode fiber, tapered multimode fiber, and MoS₂ coated tapered multimode optical fiber sensor, respectively. The MoS₂-coated tapered fiber exhibits the highest sensitivity of 1.7 times and 21 times more than that of the tapered and uniform optical fiber sensor probes. Along with the high sensitivity, the MoS₂-coated tapered optical fiber sensor probe also possesses high linearity for the change in the RI in the range of 1.33–1.41. It is found this sensor can be operated at any wavelength range from 400 to 1000 nm. Further, we believe that the proposed sensor probe using the intensity interrogation method would turn out to be a potential candidate for health monitoring as it exhibits high sensitivity, linearity, repeatability, and longevity.