H2 sensing performance of optical fiber coated with nano-platelet WO3 film

For the first time, we have integrated nano-platelet Pd/WO3 films, which are formed using an acid etching method, with optical fibers to develop a hydrogen gas (H2) sensors. The tungsten films were firstly RF sputtered on top of optical fiber tips, and subsequently etched in 1.5M nitric acid to produce tungstite films. After annealing at 300 and 480°C, these films were coated with approximately 25Å thick Pd layers. The films were characterized using SEM, GADDS, EDX, and both Raman and UV–vis–NIR spectroscopy. H2 testing measurements were conducted when the sensors were interacting with 0.06–1% H2 in synthetic air at an optimum temperature of 100°C. It was found that the highly crystalline nano-platelet Pd/WO3 film based optical fiber H2 sensors show large reflectance responses in the NIR wavelength of 6% and 12% in the presence of 0.06% and 1% H2, respectively.