Zeolites Toward Optical Materials
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The term zeolite comes from the two Greek words Zeo, meaning “to boil”, and Lithos meaning “stone”. They were so named by Swedish mineralogist Axel Cronstedt, who observed steam to be produced upon heating a sample of a naturally occurring mineral. Zeolites are built from corner sharing SiO44- and AlO45- tetrahedra, which give a large open framework structure. A large variety of different framework types can be produced in this way. It is the porosity of these framework that give rise to the many potential applications of zeolites, including catalysis and molecular sieves. These porous aluminosilicate frameworks can incorporate small molecules or charged species to produce optical compounds such as pigments, for example ultramarine. They are relatively non-toxic and chemically and thermally very stable, which would make zeolite based pigments a promising alternative to some conventional toxic pigments.
The LTA framework
Zeolite Films
Zeolite films have many applications. Once deposited on a substrate dyes can be incorporated into the pores of the zeolite to produce a film of an optically active species. Thermal conversion to other framework types can also be undertaken. This yields the potential application of using a zeolite layer deposited on a substrate as the basis of a high-throughput solid state array.
Films of zeolite can be synthesised by three different routes, depending on the properties of the final film that is required. Direct crystallisation, self-assembly using surfactants and binding to the substrate using chemical linkers can all be used. Films are characterised using the D8 discover diffractometer and the GADDS (General Area Detector Diffraction System) software, which has a flat sample stage allowing for mounting of films, and by SEM and EDAX.
Self assembly of films using surfactants
SEM image of a zeolite film
Zeolite film on substrate
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