Synthesis And Properties Of Photochromic Materials Based On Heteropolyacids And Fulgides

The design and attainment of functional molecular materials have been a main challenge for scientists in now world when science and technology competition is becoming more and more drastic. Polyoxometalates (POMs) have been found to be extremely versatile inorganic building blocks for the construction of novel functional materials owing to their defined structure and predominant physical properties, in particular electrical, magnetic, and optical properties. After POMs are introduced into nanocomposite films by virtue of intermolecular weak acting force, the cooperative action from inorganic and organic components can induce and bring novel functional characteristics. We prepared a series of inorganic-organic photoelectric functional nanocomposite films based on non-covalent bonds and studied the composition, microstructure and photoelectric properties in detail. Some creative results were obtained from the experiments mentioned above. Potochromic indolylfulgides have been identified as potential candidates for a wide range of applications including optical switches, photoregulators of biological processes, and optical memory media.The main results were outlined as following: (1)A series of reversible photochromic sol-gel composite films with good mechanical and chemical stabilities through entrapping silicotungstic acid, phosphotungstic acid and phosphomolybdic acid into a kind of organoaminomodified silica network, respectively. The photochromic mechanism involving the transfer of electron and proton of the sol-gel films has a correlation with the redox potential of heteropolyanions. Owing to the order of redox potential of heteropolyanions: phosphomolybdic acid > phosphotungstic acid > silicotungstic acid, so the phosphomolybdic acid sol-gel composite film has the highest photochromic efficiency and the slowest bleaching speed and the silicotungstic acid sol-gel composite film has the lowest photochromic efficiency and the fast bleaching speed. In addition, the photochromic response speed of the phosphotungstic acid sol-gel composite film is faster than that of common amorphous WO3 films. ( 2 ) A novel reversible photochromic film containing polyoxotungstoeuropate K12[EuP5W30O110]?54H2O (EPW) entrapped in polyvinylpyrrolidone has been prepared through a nanocomposite technique. The composite film has a very strong photosensitivity and can change from colorless to blue under the irradiation of weak sunlight. The composite film shows very fast photochromic response speed. It can show blue after one second with irradiation by 500W high-pressure mercury lamp and the color becomes saturation after thirty seconds. It also shows very good reversibility in the coloration-decoloration process. The photochromism of the composite...