TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Film: The periodic lattice structure is at least 2-dimensional. (I) has thickness of 10 nm to 10 mum (preferably 50 nm to 5 mum); and is based on metal oxide(s). (II) are metal, chalcogenide, oxide, halide, phosphide or organic particles; and occupy 10-70% of the domain volume.Preferred Process: The liquid composition comprises at least one precursor for (II) (specifically a precursor for an oxide, especially a hydrolyzable compound such as a halide or alkoxide) and an organic structuring material (preferably a cationic surfactant, especially a quaternary ammonium salt; or a nonionic surfactant, especially a polyalkylene oxide copolymer) in an aqueous alcoholic medium.    TECHNOLOGY FOCUS - POLYMERS - Preferred Materials: (I) may be prepared using a polyalkylene oxide copolymer as structuring agent. EXAMPLE - A silica sol was prepared by mixing tetraethyl orthosilicate with water acidified to pH 1.25 with hydrochloric acid and ethanol in ratio 1:5:3.8 and aging for 1 h at 60 degrees C. The cationic surfactant cetyl trimethylammonium bromide (CTAB) was added to the sol at a CTAB to Si ratio 0.1, followed by dilution with ethanol in volume ratio 1:1. The solution was applied to 2.5 cm x 2.5 cm Pyrex glass slides by spin coating at 3000 rpm for 100 s. The CTAB was removed from the film by calcination in air at 450 degrees C with a temperature increase rate of 10 degrees C/h, giving a transparent, mesoporous silica film 300 nm thick with a pore lattice structure formed by elimination of the CTAB micelles. The pore volume was 55% of the total volume of the film. X-ray analysis showed a hexagonal 3-dimensional structure (space group p63/mmc with axis of symmetry perpendicular to the plane of the substrate) and the presence of spherical with a uniform diameter of ca. 3.5 nm. Electron microscopy showed a periodic lattice structure, with a domain scale of 200 nm. An impregnation solution was prepared by treating 1 M cadmium nitrate solution was treated with 1 equivalent of each of ammonia and sodium citrate and adjusting to pH 9.5 with ammonia. The coated Pyrex substrate was immersed in the solution for 1 minute, removed and washed with water. Cadmium ions were thus fixed on the pore surfaces by complexation with silanol moieties. The sample was placed in an evacuated container, followed by slowly injecting hydrogen sulfide gas up to atmospheric pressure, causing localized precipitation of calcium sulfide in the center of the pores. The impregnation and precipitation stages were repeated several times; after 9 cycles no more cadmium sulfide was introduced (i.e. the mesoporous layer was saturated with cadmium sulfide). X-ray investigations showed that the hexagonal 3-dimensional structure was preserved. The obtained composite film contained ca. 50 vol. % cadmium sulfide particles.