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Abstract:In this paper, we numerically demonstrate a two-layer circular lattice photonic crystal fiber (PCF) biosensor based on the principle of surface plasmon resonance (SPR). The finite element method (FEM) with circular perfectly matched layer (PML) boundary condition is applied to evaluate the performance of the proposed sensor. A thin gold layer is deposited outside the PCF structure, which acts as the plasmonic material for this design. The sensing layer (analyte) is implemented in the outermost layer, which permits easy and more practical fabrication process compared to analyte is put inside the air holes. It is demonstrated that, at gold layer thickness of 40 nm, the proposed sensor shows maximum sensitivity of 2200 nm/RIU using the wavelength interrogation method in the sensing range between 1.33-1.36. Besides, using an amplitude interrogation method, a maximum sensitivity of 266 RIU −1 and a maximum sensor resolution of 3.75 × 10 −5 RIU are obtained. We also discuss how phase matching points are varied with different fiber parameters. Owing to high sensitivity and simple design, the proposed sensor may find important applications in biochemical and biological analyte detection.

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In this study, nano-crystalline lead sulfide (PbS) and lead oxide (PbO) were synthesized using hassle-free and cost-effective chemical route. Lead oxalate (PbC 2 O 4 ) precursor was thermally decomposed to obtain the nanocrystalline PbO, while PbS nanoparticles were synthesized by microwave irradiation on a mixture of PbC 2 O 4 precursor and sodium thiosulfate. Resulting materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, ultraviolet-visible (UV-Vis) spectrophotometry, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). XRD confirmed the tetragonal structure for PbO and face-centered cubic for PbS with average crystallite sizes varying from 20 to 30 nm for both materials. From UV-Vis spectra, direct band gap energies were calculated to be 2.51 and 2.23 eV for PbO and PbS, respectively. Various decomposition stages during heat treatment of PbO and PbS, as revealed by TGA/DSC, are discussed in detail.