H2 sensor based on tapered optical fiber coated with MnO2 nanostructures

A novel hydrogen (H-2) sensor was developed using optical fiber coated with manganese dioxide (MnO2()) nanostructures. Optical multimode fiber (MMF) of 125 mu m in diameter as the transducing platform was tapered to 20 mu m to enhance the evanescent field of the light propagates in the fiber core. The tapered fiber was coated with MnO2 nanograins synthesised via chemical bath deposition (CBD) process. Catalytic Palladium (Pd) was sputtered onto the MnO2 layer to improve the H-2 detection. The sensing layer was characterized through Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), X-ray Diffraction (XRD) and Raman Spectroscopy to verify the properties of MnO2. Two sets of sensors consist of as-prepared MnO2 and 200 degrees C annealed MnO2 were tested towards H-2 gas. The tapered optical fiber coated with Pd/MnO2 nanograins was found to be sensitive towards H-2 with different concentrations in synthetic air at 240 degrees C operating temperature. The annealed sensor showed higher response and sensitivity as compared to the as-prepared sensors when measured in the visible to near infra-red optical wavelength range. The absorbance response of the annealed Pd/MnO2 on fiber has increased to 65% as compared to 20% for the as-prepared Pd/MnO2 upon exposure to 1% H-2 in synthetic air. (C)2017 Elsevier B.V. All rights reserved.