Doping porous oxides with organic functionalities has become increasingly useful for the detection of many types of compounds and molecules. So far the detection of microorganisms by this process has not been firmly established. There is, however, a need to develop easy to use, sensitive devices for the detection of microorganisms in potable water supplies. For example, the need for a sensor that can detect a pathogenic parasite called Cryptosporidium parvum has emerged in the United States. In this report, we describe the production of such a device via the sol-gel method. The sol-gel sensor can detect trace amounts of Cryptosporidium parvum. The advantages of the porous oxide matrix lead to high sensitivity. The sensor is easy to use and inexpensive. The presence of Cryptosporidium parvum is indicated by a color change in an otherwise colorless gel. Absorbance intensities for the enzyme-linked antibody used in the study correlated appropriately to oocyst concentration in the solution.

Inorganic organic composite materials have been developed in the form of non-porous films on various substrates and as porous materials with specific surface areas of about 700 m2/ g. Both types of materials have been tested for absorption and adsorption of solvents from the gas phase (butyric acetate, benzene, toluene and xylene). The results show that the non-porous films could be loaded with solvents up to 30 wt.% and unloaded at 130 °C within a few minutes. The porous materials could be loaded up to 38 wt.%. The kinetics of desorption are slowed down to values of some hours, being however still fast compared to activated carbon. Adsorption in wet atmospheres do not affect adsorption capacity but leads to a decrease of adsorption kinetics due to a slowing down of the diffusion or a replacement of H2O against solvent within the pores.

IR and 13C NMR investigations of the hydrolytic stabilities of the saturated and unsaturated ß-keto ligands acetylacetone (ACAC), ethylacetoacetate (EAA), allylacetoacetate (AAA), methacryloxyethyl-acetoacetate (MEAA) of the Al-, Ti- and Zr-butoxide complexes show a strong dependence on the type of the metal alkoxide and the structure of the organic ligands. The hydrolytic stabilities of the ligands decrease in the order Al->Zr->Ti-alkoxide and ACAC>AAA>EAA≥MEAA. Sol-gel reactions of complexes having a weak ligand stability leads to a larger water consumption and to larger particle sizes in sols than those with stable ACAC ligands. Heterometal bonds, i.e. Si-O-Al, Si-O-Ti and Si-O-Zr, in the system diphenylsiloxanediol/ metal alkoxide (complex) proved by 29Si and 17O NMR are hydrolysed to a different extent depending on the water amount, the type of the Si-O-M bond and the structure of the heterometal species. The degradation of the heterometal bonds leads to a separation of MO-M and Si-O-Si bonds which can entail a decreased homogeneity of the materials at a molecular level.

The structure and properties of a series of modified polydimethylsiloxane (PDMS) elastomers reinforced by in situ generated silica particles were investigated. The PDMS elastomer was modified by systematically varying the molecular weight between reactive groups incorporated into the backbone. Tetraethoxysilane (TEOS) and partial hydrolyzate of TEOS were used to generate silica particles. The chemistry and phase structure of the materials were investigated by 29Si magic angle spinning nuclear magnetic resonance (NMR) spectroscopy and swelling experiments.

Hybrid materials presenting mechanical rubbery properties are prepared from silicon alkoxides modified by organic polymers [i.e. poly(propyleneoxide), poly(ethyleneoxide), poly(butadiene) of moderate molecular weight (MW ≈ 3000–4000)]. These materials were characterized by 29Si NMR. They can be swollen by deuterated probes which can be used with 2H NMR to follow the network structure. Under unidirectionnal mechanical strain, uniaxial anisotropy of the samples is obtained and the macroscopic ordering is evidenced by quadrupolar deuterium NMR of swelling probe.

Inorganic-organic hybrids were synthesized by the reaction of inorganic species of Ti(OC2H5)4, Nb(OC2H5)5, Ta(OC2H5)5 and Fe(OC2H5)3 with an organic polymer of ethyl cellulose. The studies of FT-IR spectroscopy revealed that M-O-cellulose bonds were formed by the reaction of ethoxy groups of metal ethoxides with hydroxy groups of ethyl cellulose. The dielectric constants of the resulting Ti-O-, Nb-O- and Ta-O-cellulose hybrids were higher than that of ethyl cellulose. The molar magnetic susceptibility of the Fe-O-cellulose hybrid was independent of iron content and was lower than that of Fe(OC2H5)3.

The non hydrolytic synthesis of several titanium oxo-alkoxo clusters Ti3O(OPri) 8(OR)2, Ti11O13(OPri)18, Ti7O4(OEt)20 and Ti16O16(OEt )32 have been performed via thermolysis of different titanium alkoxides (Ti(OEt)4, Ti(OPri)4). The structures of these clusters were mainly determined by X-ray diffraction, 17O NMR and 13 C NMR.

The reaction of tetraethylammonium salt with the nanocomposites K0.2(C2H4O)2.3M0.9PS3 (M = Mn, Cd) under ambient conditions results in the rapid and quantitative displacement of the polymer to form the alkylammonium intercalate. The displacement reactions go to completion with no polymer degradation after initial formation of the nanocomposite. Pseudo-reaction rates (0.0 to 7.8 min−1) are obtained using temporal XRD studies for different cations, concentrations, and polymer molecular weights. A strong rate dependence is observed for alkylammonium concentration, and displacement occurs very slowly, or only to a limited extent, for tetramethylammonium, tetrapropylammonium, and tetrabutylammonium salts. Rapid displacement is also reported for other layered nanocomposites containing poly(ethylene oxide), including those with LixMoS2, Na-montmorillonite, and LixMoO3.

Sol-gel processing of heteropolysiloxanes containing phosphate groups has been investigated for potential applications in the synthesis of facilitated transport solid membrane. The co-hydrolysis-condensation of SiP (diethylphosphatoethyltriethoxysilane) with each of the three following alkoxysilanes: tetraethoxysilane (TEOS), methyltrimethoxysilane (MTMOS) and C6H4[C(O)NH(CH2)3Si(CH3)(OEt)2] 2−1,4 (abbreviated P1) have been studied. The gels produced have been characterized by 29Si and 31P MAS NMR spectroscopy to determine Ihe chemical structure of these new materials. The connectivity and the hydrophilic properties of the materials are controlled by the chemical nature of the alkoxysilanes and the SiP concentration. Dense flexible membranes have been obtained by tape casting and have been used for the facilitated transport of Ni++ ions.

Random, graft, and block copolymers of polystyrene (PS) and poly(4-vinylphenol) (PVPh), and PVPh homopolymer are shown to act as compatibilizers for incompatible organic-inorganic composite materials. The VPh component reacts, or interacts strongly with the polymerizing inorganic (titanium or zirconium) alkoxide. The organic components studied were PS, poly(vinyl methyl ether), and poly(styrene-co-acrylonitrile). The use of such compatibilizers provides a means of combining in situ polymerized inorganic oxides and hydrophobic polymers. This is seen as a reduction in the size of the dispersed inorganic phase and results in improved optical and mechanical properties.

A linear, ethoxy-substituted polycarbosilane has been prepared by ring-opening polymerization of 1,1,3,3-tetraethoxy-1,3-disilacyclobutane. After hydrolysis, condensation and drying, the obtained gel was pyrolyzed under nitrogen to give a silicon oxycarbide glass. The gel and its pyrolysis chemistry were characterized by elemental analysis, thermogravimetric analysis, 29Si and 13C MAS NMR, FTIR and mass spectrometric analysis of the gaseous pyrolysis products. The conversion of the [SiOCH2]n network, which has a nearly pure SiC2O2 micro environment at the outset, into a silicon oxycarbide that contains a full distribution of the five possible SiC4−xOx environments occurs between 600 and 1000°C. This suggests the occurrence of redistribution reactions involving the exchange of Si-O and Si-C bonds during the pyrolysis.

Self assembled monolayers patterned by microcontact printing have been used in conjunction with sol-gel processing to selectively deposit oxide thin films with micron-scale lateral resolution. This simple, three step process allows ambient, lithography-free patterning of oxide thin films for integrated microelectronics, optoelectronics, and sensor applications. A variety of patterned structures, such as capacitors and waveguides, have been fabricated from LiNbO3, Ta2O5, PbTiO3, and BaTiO3 on technologically important substrates, including Si, Al, Pt, sapphire, and TiN. The technique involves functionalization of substrate surfaces by microcontact printing of octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs). Sol-gel precursors are then spin-coated on the SAMs-patterned surfaces and heat treated to deposit 20 nm-300 nm amorphous oxide layers. Oxide on derivatized regions is removed with mild polishing, yielding patterned films with features as small as 5 μm. For example, data are reported for 80–200nm Ta2O5 films to demonstrate the potential applications and mechanisms involved. The effects of sol-gel precursor chemistry, heat treatment, and other processing variables are reported. These results suggest unique potential for microfabrication of ceramic thin films using molecular self assembly and low temperature processing of solution-derived thin films.

We describe the synthesis and characterization of hybrid organicinorganic copolymer materials formed by the reaction of the transition metal alkoxide VO(OAmt)3 with the chelating monomer ligand acetoacetoxyethylmethacrylate (AAEM). By the simultaneous induction of the organic and inorganic polymerization reactions, covalent bonds are formed between both types of interpenetrating components. The organic chelating moiety of AAEM is linked through its ß-diketo function to the vanadium-oxo species.

Nanocomposite materials for application in photonics were developed by sol-gel processing and reverse micellar microemulsion techniques. The capability of incorporating many materials with different functional properties in sol-gel processed glass matrices has been explored in making these materials. The large pore volume fraction and the enormous surface area of the sol-gel glasses enables one to introduce many materials in a phase separated fashion, where the phase separation is in the nanometer range. It is possible to introduce an active material on to the pore surface by solution infiltration and subsequent removal of the solvent, then filling the pores with a monomer containing another active material, and polymerizing inside the pores. Using this approach we have developed composite materials for optical power limiting applications at different wavelengths and a tunable solid state dye lasing medium

Optically transparent polyimide:TiO2 composite waveguide materials were prepared by the dispersion of nano-sized TiO2 particles into a polyimide matrix. The particles were produced through reverse micelles using the sol-gel method, and were incorporated into the fluorinated polyimide solution. A polyimide:TiO2 (4 wt %) composite waveguide was produced from the solution. Since the particle size is so small, no noticeable scattering loss was observed. The measured optical propagation loss at 633 nm was 1.4 dB/cm, which is equivalent to that of the pure polyimide. The refractive index was increased from 1.550 to 1.560 by the incorporation of TiO2

A new class of perfluoroaryl substituted inorganic-organic copolymers (ORMOCERs) for integrated optics have been synthesized via hydrolysis and condensation (sol-gel processing) of novel perfluoroarylalkoxysilanes followed by organic crosslinking reactions. Curing leads to transparent coatings with low NIR optical loss factors. Patterned layers for optical interconnection were fabricated by photolithographic procedures.

New photopolymers have contributed significantly to the recent growth of holographic and lithographic applications. Photopolymerizable organic-inorganic hybrid materials, based on methacrylate functionalized silane and zirconia particles as holographic recording material, are presented. Thick films of this composite system were prepared and volume diffractive gratings were fabricated by a two laser beam interference technique. The formation of the gratings is based on the diffusion of high refractive index components (ZrO2-nanoparticles) to areas with high irradiation intensity with subsequent immobilization by full irradiation of the film. The influence of the zirconia particles as the main component for obtaining highly efficient gratings is presented and the correlation between particle concentration and refractive index profile is shown.

Organic-inorganic hybrids, with tailorable properties via control of their chemistries, offer great potential for many optical, electrical and mechanical applications. PDMS-based materials have been fabricated, having low optical losses of < 0.15 dB/cm but the dielectric properties of these hybrids have rarely been explored or reported. In the present study, the dielectric properties of PDMS:SiO2:TiO2 films are explored as a function of composition and curing temperature using an impedance analyzer. Dielectric spectroscopy was also performed to investigate the dielectric relaxation and dispersion behaviors. Results indicate that εr at 1 MHz ranges from 3 to 5. Residual hydroxyl and alkoxy species in the films contribute to the overall polarizabilities especially at low frequencies ( < 100 kHz).

The flexible solution chemistry of the sol-gel process has been used to encapsulate a wide variety of organic, organometallic, and biomolecules in inorganic solids. This paper reviews different types of photochemical reactions which we have used to produce specific products or to generate oxygen within sol-gel matrices. By controlling synthesis conditions, the molecules can be made to exhibit desired reactivities when trapped in the sol-gel matrix.

Three different examples of photochemical reactions are presented in this paper. An organometallic gold precursor compound, dimethyl (hexafluoroacetylacetonato)gold, dissolved in a silicate sol is used to produce gold nanoparticles of desired sizes. The second example is based on sol-gel encapsulated photochromic (and thermochromic) spiropyran, that converts to a colored form using thermal energy or UV radiation. The synthesis strategies for selectively isolating the colored or the colorless form in sol-gel materials are presented. Materials of these types may be useful in writeonce- read-many (WORM) optical data storage applications. The third example involves sol-gel matrices doped with a biosystem, the green plant photosystem H (PS II). The resulting aged gels and xerogels are photoactive and are capable of photooxidizing water. Oxygen illumination was measured under white light and there is an indication that PS II particles are stabilized by the encapsulation process.

Composite films containing solid state laser nanoparticles have been created which show optical amplification in the technologically important near IR range. The solid state laser materials studied, Cr-forsterite (Cr-Mg2SiO4) and Cr-diopside (Cr-CaMgSi2O6), were prepared using a dispersion polymerized polymer precursor. The nanoparticles produced during the polymer synthesis acted as size templates, creating fine crystalline powders of the Cr-forsterite and Crdiopside upon calcination. These fine powders were dispersed in a refractive index matched polymer matrix and cast as 5–10 μm thick films. The resulting composite containing Cr-forsterite showed optical amplification of 300 dB/m at 1.24 μm.

We report the synthesis and characterization of photorefractive sol-gel materials that possess covalently attached push-pull azobenzene and carbazole moieties. Molecular structural characterization of the modified silane monomers was achieved by 1H NMR and infra red spectroscopy. The second-order nonlinear optical properties of the organic-inorganic hybrid films prepared from modified silane monomers were evaluated by second-harmonic generation. The stabilized value of the second harmonic coefficient, d33, of films poled by corona discharge, at 1064 nm fundamental wavelenght was found to be 107 pm/V. Photorefractivity was clearly displayed from a two beam coupling experiment.