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We demonstrate the use of photonic crystal fiber (PCF) joined in between two single mode fibers (SMF) as a concentration sensor. To realize this, one micrometer length PCF of hexagonal lattice is sandwiched between two SMF having one micrometer length each. To maximize the coupling between SMF and PCF, the core diameters are made equal. Then the output from a given input through this structure is analyzed with respect to different concentrations in the air holes of PCF using Finite Difference Time Domain (FDTD) method. It is found that the variation of electric field intensity at the output is linear with respect to concentration of alcohol.

Investigation of the interaction of nanostructures with sialic acid and effective detection and/or quantitative measurements of sialic acid have apparently been found to be sovereign research prospects toward chemical, biological, and scientific developments. Here, we have presented a Co3O4 magnetic nanoparticles (MNPs)-coated fiber-optic sialic acid sensor. Synthesized MNPs are of nearly monosize and single crystals and cubic-phase-stabilized, which is evidenced from a detailed structural investigation. Remarkably, the coated MNPs-based sensor exhibited a significant dynamic range in output current (190–159 μA) at the detector end with the working range/linear range of the sialic acid concentration from 10 to 30 mg/dL (i.e., 323.3–969.93 μM). In contrast, the output current appears to be the same for the uncoated configuration. Hence, among both configurations, the coated MNPs-based configuration more effectively validates the evidence for the detection of sialic acid. Captivatingly, the limit-of-detection value of this simple friendly sensor is found to be around 3.771 mg/dL, which is significantly less than the stated sialic acid concentration in cancer patients. In addition, the advantage of this sensor device is that the sensing response time is reflected within a few seconds, which is substantially less in relation to earlier-reported techniques. Finally, we used finite-difference-time-domain (FDTD) simulation to comprehend the sensing mechanism of this designed sensor. The findings from FDTD simulation and photoluminescence spectra of MNPs indeed signified that the field of light that emerges outside of the fiber can interact indisputably with sialic acid because of the emission peak of Co3O4 that is prevalent within the absorbance range of sialic acid. Thus, the present study unveils a Co3O4 MNPs-coated optical fiber as an efficient sensor for the detection of sialic acid.