Photochromic Properties of Tungsten Bronze

Tungsten bronze has photochromic properties and can be applied to building windows films and automotive insulation films (smart glass). However, there are currently few studies on this.

Tungsten bronze can be prepared by hydrothermal method using hydrochloric acid and sodium tungstate as raw materials. Then, polyvinyl alcohol was added to the tungsten bronze sol, and after it was completely dissolved, it was transferred to a glass bottle. Finally, the sol is irradiated in an ultraviolet light of different wavelength bands, and then the photochromic property of the tungsten bronze is obtained by measuring the change of the transmittance of the sol before and after illumination by using a spectrophotometer.

The results show:

The tungsten bronze sol has no photochromic properties before the addition of polyvinyl alcohol, and the photochromism can be clearly observed after the addition of polyvinyl alcohol.

Photochromism - The purple tungsten bronze sol turns blue under ultraviolet light, and then the blue sol changes back to its original purple color in the dark. (Tungsten bronze powder is light blue and sol is purple.)

Later, some researchers mainly studied the relationship between the three types of alcohols (butanol, propanol, and the photochromic.) and properties of tungsten bronze. The results show that among the alcohols, the adsorption of propanol can maximize the photochromic properties of the tungsten bronze powder.

The photochromic mechanism of tungsten bronze:

W6+ in tungsten bronze can be reduced to W5+ by reducing alcohol under light, and W5+ can deepen the color of tungsten bronze powder. These studies have shown that tungsten bronze can be used as a photochromic material in the field of photochromic devices.

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