Mohd. Hanif Yaacob

Comparative study of the gasochromic performance of Pd/WO 3 and Pt/WO 3 nanotextured thin films for low concentration hydrogen sensing

The gasochromic performance of WO<inf>3</inf> nanotextured thin films coated with catalytic Pd or Pt layers were investigated for low concentration H<inf>2</inf> sensing. The 25Å thick catalytic metals were deposited onto 200nm thick sputtered WO<inf>3</inf> films. It was found that the Pd/WO<inf>3</inf> thin films show superior gasochromic response when compared with Pt/WO<inf>3</inf> thin films. Integrating the absorbance change over a range of visible wavelengths (500–800nm), has enabled very low concentrations of H<inf>2</inf> (0.06%) to be easily sensed in real time for both Pd/WO<inf>3</inf> and Pt/WO<inf>3</inf> thin films. Pd/WO<inf>3</inf> T<inf>90%</inf> response towards 0.06% H<inf>2</inf> in a balance of synthetic air was 30 seconds at 100°C. Similarly, higher H<inf>2</inf> concentrations of 1% can be accurately sensed in as little as 20 seconds.

H2 Sensing Performance of Optical Fibers Coated with WO3 Film

Optical gas sensing performance of optical fibers coated with sputtered Pd/WO3 films was investigated for low concentration H2 sensing. This optical fiber H2 sensor was prepared by RF sputtering of WO3 on the tip of the multimode fiber at 260°C and subsequently depositing a Pd catalytic layer. Highly uniform nanotextured film, with individual crystallites having diameters in the range of 35-50 nm was observed. The sensing mechanism was based on the reflectance change of Pd/WO3 layers towards H2 reliant on the gasochromic effect. Under the conditions of different sensing layer thicknesses and different operating temperatures, full Vis-NIR spectra investigations were carried out during the sensor testing. It was found that the optical fiber H2 sensor coated with Pd/WO3 film show a remarkable optical reflectance response towards H2 concentrations as low as 0.06%. The optimum sensing layer thickness was 200 nm and the optimum operating temperature was found to be 100°C.