New gasochromic system: Nanoparticles in liquid

摘要

In this study, WO _3 nanocrystallites were first produced by laser ablation of W target in deionised water. To synthesize palladium, a PdCl _2 solution (0.2 g/L) was added to the liquid. Transmission electron microscope revealed successful synthesis of tungsten oxide nanocrystallites along with the production of Pd and core-shell Pd/WO3 nanoparticles. Gasochromic behavior was examined by hydrogen bubbling into Pd/WO _3 liquid in which a transition to blue absorbing state was observed. Optical absorption spectra of the colored liquid represented different sharp small polaron absorbing peaks below 3 eV and the peaks intensity was observed to be varied with Pd:WO _3 ratio. Time variations of optical density difference (δOD) were measured at constant wavelength of 632.8 nm by alternative bubbling hydrogen or oxygen gases. The δOD in the first coloring cycles were not completely reversible owing to the presence of some unreacted PdCl _2. The further coloring bleaching indicates a normal gasochromic behavior.