The sol-gel process enables one to prepare oxide xerogels at room temperature. By using this method, it is possible to encapsulate a wide variety of organic, complex (organometallic) molecules and metallic nanoparticles stabilized by organic ligands in the inorganic or inorganic/organic hybrid matrix. Studies of this new type of inorganic/organic composite have evolved towards the deliberate doping of the supramolecular species. This review gives three examples of how doped xerogel materials prepared by the sol-gel method are emerging as an important means of producing new materials. The first part of this review is devoted to luminescent materials which are based on the antenna effect and are composed of Eu(III) complex (luminescence centre) entrapped in xerogel matrix. In this case results of the experiments concerning the coordination sphere composition show that a cryptand ligand with aromatic groups and an aromatic co-ligand, settle efficient action the antenna effect and isolate the central ion from each efficient quenchers, as e.g. water molecules. Secondly, silica xerogel samples with entrapped series of three fluorescent chemosensors of the Ant-R-Ant type, where Ant is an anthryl group and R is a receptor (spacer) with donor atoms, were prepared as chemical recognition phases. The recognition phase with fluorosensor of the type Ant- N-O-O-N-Ant, where N and O are donor atoms, can be regenerated many times and seems to be most promising system for the fluorescent chemical sensor. In the third part of this paper, ligand protected metal nanoclusters as immobilized catalysts are the point of interest. This type of heterogeneous catalysts are much less investigated than the bare metal particles on supports. The main interest is focused on the function of the ligands.
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For oxide xerogels of the types: Na/sub 2/O-B/sub 2/O/sub 3/-SiO/sub 2/ and SiO/sub 2/-TiO/sub 2/ prepared by the sol-gel procedure a correlation between one of the absorption bands of Cr/sup 3+/ ion (attributed to the /sup 4/A/sub 2g/(F) to /sup 4/T/sub 2g/(F) transition) and theoretical optical basicity has been found. The experimental results show that Cr/sup 3+/ ion can play the role of basicity probe in the Lewis sense for oxide xerogels. Additionally, its band position can be a relative measure of water content in the same material.