ISSN:
1573-4846
Keywords:
gasochromism
;
sol-gel prepared W-PTA
;
Pd doped W-PTA
;
polaron modes
;
in-situ infrared and in-situ UV-Vis spectra
;
Raman spectra
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The behavior of sol-gel prepared thin films exhibiting a gasochromic effect; i.e., a reversibly change in colour from transparent when in air to blue when in H2, has been studied. The films were prepared from a Pd (PdCl2) doped peroxopolytungstic acid sol using a dip-coating technique. Transmission electron microscopy together with selected area electron diffractrometry revealed that the films consist of monoclinic and hexagonal nanocrystalline grains (∼2–5 nm) embedded in an amorphous phase. This amorphous hydrated phase was established using Infrared (IR) and Raman spectroscopy. Characteristic vibrations observed in the in-situ IR spectra of the coloured and bleached states revealed the presence and the importance of terminal W=O and W—OH2 groups in the colouring of the films. Colouring/bleaching changes of Pd doped W-PTA films observed using in-situ UV-Vis spectroscopy are described in terms of Pd concentration, and the number of reducing/oxidising cycles. The rate of colouring/bleaching is greater for films containing a higher concentration of Pd but the change in the optical density does not increase, i.e., shows saturation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1008773614398
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