Photochromic organic-inorganic hybrid materials.

Photochromic organic-inorganic hybrid materials have attracted considerable attention owing to their potential application in photoactive devices, such as optical memories, windows, photochromic decorations, optical switches, filters or non-linear optics materials. The growing interest in this field has largely expanded the use of photochromic materials for the purpose of improving existing materials and exploring new photochromic hybrid systems. This tutorial review summarizes the design and preparation of photochromic hybrid materials, and particularly those based on the incorporation of organic molecules in organic-inorganic matrices by the sol-gel method.

Molecular configuration transitions of a nematic liquid crystal encapsulated in organically modified silicas.

The nematic liquid crystal (LC) 4-n-pentyl-4'-cyanobiphenyl (5CB) was encapsulated as spherical microdroplets dispersed in solid organically modified silica matrices (ORMOSIL), obtained by the sol-gel method. The organic functional groups used to modify the matrix were methyl, ethyl and propyl. The amount of the organic groups in the confining matrix was found to affect the LC surface anchoring properties, and therefore the molecular configurations in the LC droplets.

Ultrafast random laser emission in a dye-doped silica gel powder.

We report efficient random lasing in a ground powder of a novel solid-state material based on silica gel containing SiO(2) nanoparticles embedding rhodamine 6G (Rh6G) dye. Basic properties of random lasing such as emission kinetics, emission spectrum, and threshold of stimulated emission are investigated by using real-time spectroscopy. The laser-like emission dynamics can be accurately described by a light diffusive propagation model.

Preventing UV-light damage of light sensitive materials using a highly protective UV-absorbing coating.

One of the most important drawbacks of classical and new advanced functional materials for applications outdoors, or in environments with high UV irradiation, is the light induced damage that reduces drastically their effective operation lifetime or durability. This makes protecting light sensitive materials against UV irradiation a nowadays important technological demand in almost every industrial field. This tutorial review incorporates the main aspects of UV damage to materials and describes the recently developed highly effective thin UV-protective coatings, based on UV-absorber molecules entrapped in a Sol-Gel derived ormosil matrix.