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A single and mixed-phases SnO2 (M-SnO2) nanostructures were synthesized by a simple spray pyrolysis method. The nanostructural crystallinity, surface morphology and optical evolution of Ba-doped tetragonal phase SnO2 with different Ba contents were studied by x-ray diffraction, atomic force microscopy, ultraviolet-visible spectroscopy and photoluminescence spectral measurements. The M-SnO2 with orthorhombic as well as tetragonal phases are formed in 6% Ba-doped SnO2 sample and it exhibits the highest average transmittance 86% with blue-shift of the optical band gap. The observed strong red emission at ∼ 615 nm might be encouraging for the implementation of red emission based on Ba-doped transparent conducting electrodes.

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A dual-channel propagation controlled photonic crystal fiber (PCF)-based plasmonic sensor was presented to detect multiple analytes simultaneously. Plasmonic micro-channels were placed on the outer surface of the PCF, which facilitates an easy sensing mechanism. The sensor was numerically investigated by the finite element method (FEM) with the perfectly matched layer (PML) boundary conditions. The proposed sensor performances were analyzed based on optimized sensor parameters, such as confinement loss, resonance coupling, resolution, sensitivity, and figure of merit (FOM). The proposed sensor showed a maximum wavelength sensitivity (WS) of 25,000 nm/refractive index unit (RIU) with a maximum sensor resolution (SR) of 4.0 × 10−6 RIU for channel 2 (Ch-2), and WS of 3000 nm/RIU with SR of 3.33 × 10−5 RIU for channel 1 (Ch-1). To the best of our knowledge, the proposed sensor exhibits the highest WS compared with the previously reported multi-analyte based PCF surface plasmon resonance (SPR) sensors. The proposed sensor could detect the unknown analytes within the refractive index (RI) range of 1.32 to 1.39 in the visible to near infrared region (550 to 1300 nm). In addition, the proposed sensor offers the maximum Figure of Merit (FOM) of 150 and 500 RIU−1 with the limit of detection (LOD) of 1.11 × 10−8 RIU2/nm and 1.6 × 10−10 RIU2/nm for Ch-1 and Ch-2, respectively. Due to its highly sensitive nature, the proposed multi-analyte PCF SPR sensor could be a prominent candidate in the field of biosensing to detect biomolecule interactions and chemical sensing.

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