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U. Schubert:
"In-orbit Contamination Traps Based on Sol-Gel Coatings";
in: "Austrian Space Applications Programme", herausgegeben von: Federal Ministry for Transport, Innovation and Technology; Projektfabrik Waldhör KG, Wien, 2010, (eingeladen), S. 66.

Control of molecular contamination for spacecraft is currently only pursued on ground. This is sufficient when the contamination levels at launch are significantly kept below end-of-life requirements. Due to increasingly sensitive optical payloads, even on-ground requirements become difficult to maintain leaving very little margin for nominal performance in orbit. Active control of contamination in orbit has already been demonstrated (e.g. at the Hubble Space Telescope) where zeolite-based cartridges have been placed near critical hardware. The drawback of this solution is a relatively small volume/surface ratio; the application of such a concept as coating would be most efficient.
In the project the feasibility of coatings as molecular contamination traps to protect optically sensitive or contamination critical payloads was investigated. The coatings were prepared by sol-gel processing. This is a wet-chemical technique, by which molecular precursors are converted to solid gels via colloidal dispersions, the sols. The precursors can be substituted by functional or non-functional organic groups, and inorganic-organic hybrid materials are thus obtained. Apart from the possibility to easily adjust the materials composition to the requirements of the anticipated application and to use simple deposition techniques, sol-gel processing also allows concomitant tailoring of other properties, such as porosity or optical performance.
Micrometer-thick, nanostructured hybrid films with very good adhesion to the housing materials were developed, which combined three levels of porosity (micro-, meso- and macropores), different metal centres (providing adsorption sites of different basicity and acidity) and multiple (functional) organic groups in one material. Macro-porosity was created by using selfassembled polystyrene spheres as templates or by the breath figure approach. Meso- and micropores were obtained by removing surfactant templates after film deposition. Different metal centres were introduced by using metal alkoxide mixtures. Organic groups with different polarity were incorporated either through organically modified precursors or by post-synthetic modification of the films.

http://www.bmvit.gv.at/innovation/downloads/asap_call_5_6.pdf