Oxyhydrogen and Hydrogen Detection by Gasochromic Coloration of Highly Porous Tungsten Oxide with Fractal-Like Pd Nanoparticles

WO3 thin films were deposited by pulsed laser deposition (PLD) on glass substrates at 100 mTorr oxygen pressure. Monodispersed palladium nanoparticles (50 nm) were synthesized by hydrogen reduction of PdCl2 drop-casted on the surface of the films. For oxyhydrogen detection, first a saturated coloration by 10%H2/Ar was prepared. Then different oxygen flow with certain O2:H2 ratios were exposed to the colored samples. Depending on this ratio, the optical density of samples was observed to drop into certain new values until vanishes for a ratio about 20. A desirable fast coloration with linear dependency on hydrogen concentration was also observed