Sol-gel chemistry enables the solution growth of oxide architectures whose size, morphology and mineral backbone functionality can be controlled by organic entities.
When the organic system provides the optical functionality, the properties are partially controlled by "molecule-oxide matrix" interactions. Dispersing organic photochromes in the mineral matrix, for example, produces films with a wide range of optical properties (adjustable refractive index, induced birefringence, controlled material migration). Potential applications include optical switches, guided optics, high-density optical storage and optical nanolithography.
Organic units can also be used to build nanometric crystalline architectures, stabilize them in colloidal form and control their surface properties (chemical and biological functionalization, energy transfer). Particular attention will be paid to the case of lanthanide-doped oxide nanoparticles (YVO4:Ln). When doped with Eu3+ ions, we show the influence of crystal defects, nanoparticle size and surface state on visible photon emission properties. With co-doping by Yb3+ and Er3+, we demonstrate the possibility of realizing relatively efficient nanoscale converters of infrared photons into visible photons. These luminescent nanoparticles can be used as light sources in visualization devices or as local probes in biology (localization of sodium channels, detection of intracellular hydrogen peroxide, dynamic tracking of individual biomolecules, etc.).
The last part concerns the realization of porous sol-gel films using nanometric organic porogens (latex nanoparticles, lyotropic mesophases...) The motivations are both fundamental, with the notion of model porous layers, and applicative, with the realization of photon-gap materials for light extraction, low-index coatings for anti-reflective devices and photocatalytic coatings for self-cleaning devices. These different properties can be combined in polyfunctional sol-gel coatings for photovoltaics or lighting.
