| Abstract
| - Mesoporous semiconducting films consisting of preferentially orientated monoclinic-phase nanocrystals of tungsten trioxide have been prepared using a novel version of the sol−gel method. Transformationsundergone by a colloidal solution of tungstic acid, stabilized by an organic additive such as poly(ethyleneglycol) (PEG) 300, as a function of the annealing temperature have been followed by means of a confocalRaman microscope. The shape and size of WO3 nanoparticles, the porosity, and the properties of the filmsdepend critically on preparation parameters, such as the tungstic acid/PEG ratio, the PEG chain length, andthe annealing conditions. Well-crystallized WO3 films combine excellent photoresponse to the blue region ofthe solar spectrum, up to 500 nm, with good transparency at wavelengths larger than 550 nm. Particularapplications of these nanocrystalline WO3 films include photoelectrochemical and electrochromic devices.
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