A recently developed photochromic organic-inorganic nanocomposite (Nanomer®) coating system is investigated, which is based on an epoxysilane as network former, different bisepoxides as spacer and an organic amine as thermal cross-linker. This coating system is compatible with different photochromic dyes like oxazines, pyrans and fulgides and also with surface modified ceramic nanoparticles as filler in order to obtain macroscopic “hard properties” without changing the photochromic kinetics. In order to investigate the dye-spacer interactions and influence on the switching kinetic behavior, the matrix composition was diminished to the network former, the thermal cross-linker and two types (polar and nonpolar) of spacers in different concentrations. Four commercially available spirooxazines with different molecular sizes and polarities were incorporated into the matrices and coatings on glass slides were prepared by float-coating and cured at 130 °C for 2 h. The half darkening and half fading times of the coatings were measured by a fast diode array spectrometer as a function of spacer type and concentration for the four different dyes. The “nonpolar” spacer CHMG did not influence the switching kinetic of the dyes significantly and fast switching times of 2 s - 4 s were obtained. The “polar” spacer PCF (aromatic character) showed interactions with the dye molecules, which led to an increase in the switching times of up to 25 s. The retardation of the switching process increased with increasing spacer content and with increasing polar character of the dye molecule. From these results, it could be concluded that the photochromic behavior of the spirooxazines could be adjusted to different applications by interactions with polar spacers.

A new preparation route for an dielectric NIR-reflexion filter on glass is described. Coating sols are synthesized from SiO2 and TiO2 nanoparticles with photopolymerizable surface ligands. A 5-layer stack consisting of 2 SiO2 and 3 TiO2 layers was deposited on float glass by angledependent dip-coating (ADDC) with a fixed angle of 4° to the vertical and subsequent UV-curing. Finally, the whole stack was densified at 450 °C without cracking or discolouring. UV-vis-NIR transmittance and reflectance spectra show a steep increase of reflectance at 750 nm. In the range between 800 nm and 1200 nm, the reflectance is > 80 %. The visible transmittance is about 72 % due to single reflexion peaks. The bandwidth of the NIR reflection filter prepared by ADDC is about 200 nm larger and its maximum reflectance is only 5 % smaller compared to vertical dip-coating. The interference layer stack shows excellent stability in Taber Abraser, rubber, saline and UV tests, indicating a high potential for practical application.

A new approach to effective radial gradient refractive index (GRIN) lenses has been developed. It is based on the electrophoresis of ZrO2 nanoparticles with surface charges (ζ-potential) in a solvent free organic-inorganic hybrid matrix, synthesized from dodecandioldimethacrylate (DDDMA), methacryl silane (MPTS) and a complex of zirconium n-propylate (ZR) with methacrylic acid (MA). A DC-electric field of 2000 V/cm is applied by a set of ring electrodes on top and bottom of a cylindrical mould containing the matrix sol. The refractive index profile is measured in situ as a function of time by interferometry. The refractive index profile can be conserved by photopolymerisation of the matrix. The resulting refractive index profiles are calculated by computer simulation based on electrophoretical diffusion theory and they are measured by real time Mach-Zehnder Interferometry. The parabolic refractive index gradient of the lenses obtained by variation of concentration of ZrO2 is in very good agreement with the result of computer simulation. By this method, it is possible to obtain 1 cm radial GRIN lenses with a Δn=0.07 within 5 h.

We report the preparation of sol-gel waveguide films based on a newly developed recipe to incorporate organic molecules into the inorganic sol-gel glass matrix. The film was derived from a sol that has a higher titanium content in an organically modified silane (ORMOSIL), namely, ÿ-Glycidoxypropyltrimethoxysilane. We have shown that using spin-coating and low temperature baking, a single coating layer can have a thickness of more than 1.5 μm. When such a single layer film is deposited on a microscope glass slide or a piece of silicon with a buffercladding layer, it is able to support the guiding of optical waves. We have characterized the film using scanning electron microscopy, atomic force microscopy, X-ray diffractometry, thermal gravimetric analysis. differential thermal analysis and Fourier transform infrared spectroscopy and have studied the properties of the waveguide film, including the microstructural properties. the chemical bonding properties, and the optical properties. Based on these experimental results, we found that a heat-treatment at a temperature slightly below 200°C is necessary to attain a dense pore-free film. It has also been noted that a purely inorganic and crack-free silica-titania film can be obtained after baking the titania-ORMOSIL composite film at 500°C or higher.

The materials chemistry of sol-gel-derived inorganic-organic molecular composites offers significant potential for molecular-level systems design. One focus in this arena is the chemical design and microstructural engineering of optically-active systems. We report the generation of rare-earth-doped inorganic-organic hybrids, based on a bridged polysilsesquioxane architecture. Derived from lanthanide precursors such as Erbium isopropoxide, which we co-condense with the requisite silsesquioxane monomer, these systems exhibit significant optical activity. In experiments on hybrids doped with Erbium, we conclusively demonstrate strong fluorescence at wavelengths in the vicinity of 1540 nm, from stimulation with 488 nm radiation. We discuss materials-driven impacts of the bridged-silsesquioxane architecture on system complexities arising from the solution sol-gel route which would affect fluorescence efficiencies and luminescence levels, such as hydroxyl impurities and clustering-effects.

Semiconductor quantum dots are of great current interest for their optical properties. We have developed a method for preparing CdS quantum dots in commercially available PAMAM Starburst dendrimers. The resulting CdS-dendrimer nanocomposites are exceptionally stable and emit brightly in the blue. The size of the dendrimer (its “generation”) has a surprisingly small effect on the optical properties of the resulting nanocomposites. The dot-dendrimer nanocomposites can be captured in a silica sol-gel matrix to yield a stable, bright blue-emitting glass.

Silica-PEO hybrid materials which have both silica network and polymer network are synthesized from hydrolysis, condensation and polymerization of γ -glycidoxypropyltrimethoxysilane(GPTS). Polymerization of the epoxy groups to poly(ethylene oxide) units is achieved by using mixed triarylsulfonium hexafluorophosphate salt as a UV curing agent. The structural change of the hybrid solution is investigated by using NMR spectroscopy. The microstructure of silica hybrid film can be changed according to the degree of polymerization controlled by the UV curing conditions. The epoxide polymerization is confirmed by using FT-IR. The hybrid material is densified due to the epoxide polymerization as well as silica condensation with UV curing. The optical properties such as optcial absorbance and refractive index of the silica hybrid thin films are measured as functions of curing conditions. These optical properties are then correlated to the epoxide polymerization.

In this paper, the preparation, the characterization and the optical features of organicinorganic materials incorporating a trivalent europium organic chelate into a silicate network are described. The covalent grafting and the sol-gel process allow to obtain monophasic hybrid gels in which the structure and the activity of the organic molecules were retained. The Eu3+ coordination mode is not sensitive to the sol-gel processing conditions whereas the morphology of materials, their thermal resistance and their luminescence properties may be adjusted. Characteristics of hybrid compounds are compared to those of the corresponding organic species.