Novel Organic-inorganic Photochromic Film based on Mono-vacant Keggin-type Polyoxometalates

A novel SiWn/SiO2/PVA hybrid film was fabricated by using a sol-gel method. Mono-vacant Keggin-type polyoxometalates [Xn+W11O39](12-n)- (SiW11) were introduced into SiO2 network. The IR spectrum indicates that the covalent bond of W-O-Si is formed between SiW11 and SiO2 network, and SiWn anions still maintain Keggin structure basically in the hybrid film. However, the strong reaction between SiWn and matrix brings big shape changes on SiWn anions. The transparent film changes from colorless to dark blue under UV irradiation and shows a good photochromic behavior.