Sol-gel derived coatings with completely reversible photochromism

Besides the photochromic glasses based on silver halides especially the cuprous halide containing materials are of practical importance. Due to their high absorption coefficient the cuprous halides are particularly suited for the preparation of thin photochromic films. Using the sol-gel technique silicon alkoxide based coating solutions with continuously distributed photoactive components were prepared. From these sols single or multilayer coatings were produced by dipping. The precipitation of the cuprous halide microcrystals as carriers of the photochromic properties of the coatings proceeded during a subsequent heat treatment (temperature range of 100 to 800 °C). Thus it was possible for the first time to produee photochromic coatings with a pronounced darkening and with complete reversibility of the photochromic reactions at room temperature

Photochromic materials via sol-gel process

Powders and thin films of photochromic glasses containing AgBr or AgCl microcrystals were synthesized via sol-gel process. Up to 10 wt%, of Ag⁺, bonded with suitable complexing agents, were introduced into the matrix system consisting of xSiO₂-(1 - x)Al₂O₃ (x = 0.7... 1). After drying and heat treatment the AgX microcrystals (X = Cl, Br) were characterized by X-ray diffraction and high-resolution TEM. The photochromic properties were measured using a diode array UV-VIS spectrometer

Lehrfilme Physikalische Chemie

Destillation, Kalorimetrie, Kritischer Punk