Science.gov

Sample records for non-aqueous sol-gel route

  1. Synthesis of cobalt aluminate nanopigments by a non-aqueous sol-gel route

    NASA Astrophysics Data System (ADS)

    Karmaoui, Mohamed; Silva, Nuno J. O.; Amaral, Vitor S.; Ibarra, Alfonso; Milln, ngel; Palacio, Fernando

    2013-05-01

    Here we report the chemical synthesis of cobalt aluminum oxide (CoAl2O4) nanoparticles by a non-aqueous sol-gel route. The one-pot procedure is carried out at mild temperatures (in the 150 to 300 C range), and consists of the reaction between cobalt acetate and aluminium isopropoxide in benzyl alcohol. The resulting CoAl2O4 nanoparticles show an unusually low average size, between 2.5 and 6.2 nm, which can be controlled by the synthesis temperature. The colorimetric properties of the nanoparticles are also determined by the synthesis temperature and the characteristic blue color of CoAl2O4 pigments is achieved in samples prepared at T >= 200 C. The nanoparticles are antiferromagnetically ordered below ~27 K with an uncompensated configuration. The uncompensated moment shows the typical features of strongly interacting superparamagnetic nanoparticles and spin-glass systems.Here we report the chemical synthesis of cobalt aluminum oxide (CoAl2O4) nanoparticles by a non-aqueous sol-gel route. The one-pot procedure is carried out at mild temperatures (in the 150 to 300 C range), and consists of the reaction between cobalt acetate and aluminium isopropoxide in benzyl alcohol. The resulting CoAl2O4 nanoparticles show an unusually low average size, between 2.5 and 6.2 nm, which can be controlled by the synthesis temperature. The colorimetric properties of the nanoparticles are also determined by the synthesis temperature and the characteristic blue color of CoAl2O4 pigments is achieved in samples prepared at T >= 200 C. The nanoparticles are antiferromagnetically ordered below ~27 K with an uncompensated configuration. The uncompensated moment shows the typical features of strongly interacting superparamagnetic nanoparticles and spin-glass systems. Electronic supplementary information (ESI) available: Further microscopy, diffraction, spectroscopy and thermal data. See DOI: 10.1039/c3nr34229h

  2. The non-aqueous fluorolytic sol-gel synthesis of nanoscaled metal fluorides.

    PubMed

    Kemnitz, Erhard; Noack, Johannes

    2015-12-01

    This review article focuses on the mechanism of the non-aqueous fluorolytic sol gel-synthesis of nanoscopic metal fluorides and hydroxide fluorides. Based on MAS-NMR, XRD, WAXS and SAXS investigations in combination with computational calculations, it is shown that a stepwise replacement of alkoxide by F-ions takes place resulting in the formation of a large variety of metal alkoxide fluoride clusters, some of them being isolated and structurally characterised. It is shown that these nanoscopic metal fluorides obtained via this new synthesis approach exhibit distinctly different properties compared with their classically prepared homologues. Thus, extremely strong solid Lewis acids are available which give access to new catalytic reactions with sometimes unexpectedly high conversion degrees and selectivity. Even more interestingly, metal hydroxide fluorides can be obtained via this synthesis route that are not accessible via any other approach for which the hydroxide to fluoride ratios can be adjusted over a wide range. Optically fully transparent sols obtained in this way can be used for the first time to manufacture antireflective coatings, corundum ceramics with drastically improved properties as well as novel metal fluoride based organic-inorganic composites. The properties of these new fluoride based materials are presented and discussed in context with the above mentioned new fields of application. PMID:25952312

  3. Non-aqueous sol-gel synthesis of ultra small persistent luminescence nanoparticles for near-infrared in vivo imaging.

    PubMed

    Teston, Eliott; Richard, Sophie; Maldiney, Thomas; Lièvre, Nicole; Wang, Guillaume Yangshu; Motte, Laurence; Richard, Cyrille; Lalatonne, Yoann

    2015-05-11

    Ultra-small ZnGa2 O4 :Cr(3+) nanoparticles (6 nm) that exhibit near-infrared (NIR) persistent luminescence properties are synthesized by using a non-aqueous sol-gel method assisted by microwave irradiation. The nanoparticles are pegylated, leading to highly stable dispersions under physiological conditions. Preliminary in vivo studies show the high potential for these ultra-small ZnGa2 O4 :Cr(3+) nanoparticles to be used as in vivo optical nanotools as they emit without the need for in situ excitation and, thus, avoid the autofluorescence of tissues. PMID:25801438

  4. Synthesis of Carbon Nanotubes Using Sol Gel Route

    NASA Astrophysics Data System (ADS)

    Abdel-Fattah, Tarek

    2002-12-01

    Since 1990, carbon nanotubes were discovered and they have been the object of intense scientific study ever since. A carbon nanotube is a honeycomb lattice rolled into a cylinder. The diameter of a carbon nanotube is of nanometer size and the length is in the range of micrometer. Many of the extraordinary properties attributed to nanotubes, such as tensile strength and thermal stability, have inspired predictions of microscopic robots, dent-resistant car bodies and earthquake-resistant buildings. The first products to use nanotubes were electrical. Some General Motors cars already include plastic parts to which nanotubes were added; such plastic can be electrified during painting so that the paint will stick more readily. Two nanotube-based lighting and display products are well on their way to market. In the long term, perhaps the most valuable applications will take further advantage of nanotubes' unique electronic properties. Carbon nanotubes can in principle play the same role as silicon does in electronic circuits, but at a molecular scale where silicon and other standard semiconductors cease to work. There are several routes to synthesize carbon nanotubes; laser vaporization, carbon arc and vapor growth. We have applied a different route using sol gel chemistry to obtain carbon nanotubes. This work is patent-pending.

  5. Sol-gel route to the tunneled manganese oxide cryptomelane

    SciTech Connect

    Ching, S.; Roark, J.L.; Duan, N.; Suib, S.L.

    1997-03-01

    The sol-gel reaction between KMnO{sub 4} and fumaric acid in a 3:1 mole ratio generates a flocculant gel that serves as a precursor to the tunneled manganese oxide, cryptomelane. The elemental composition of sol-gel cryptomelane has been determined to be K{sub 0.12}MnO{sub 2.0-} (H{sub 2}O){sub 0.09}. Further characterization has been performed using powder X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy. The sol-gel process is heavily dependent on reactant concentration. Solutions that are too concentrated produce the layered manganese oxide birnessite, whereas overly dilute reactions yield mixtures of cryptomelane and Mn{sub 2}O{sub 3}. The preference for cryptomelane over birnessite correlates with low potassium content in the gel. The sol-gel procedure for synthesizing cryptomelane is not easily transferred to the preparation of analogous manganese oxides with different tunnel cations. Reactions that employ permanganates other than KMnO{sub 4} generally yield Mn{sub 2}O{sub 3}, with cryptomelane being a minor product at best. Thermal analyses of cryptomelane gels indicate that calcination proceeds through a series of stages that involve loss of water, loss of residual organics, conversion to cryptomelane, and finally degradation to Mn{sub 3}O{sub 4}. The extraction of potassium ions from sol-gel cryptomelane by various foreign cations is minimal, with the loss of K{sup +} being on the order of 10%. 49 refs., 7 figs., 3 tabs.

  6. Synthesis of Sol-Gel Matrices for Encapsulation of Enzymes Using an Aqueous Route

    SciTech Connect

    Ashley, C.S.; Bhatia, R.B.; Brinker, C.J.; Harris, T.M.

    1998-11-23

    Sol-gel matrices are promising host materials for potential chemical and biosensor applications. Previous studies have focused on modified sol-gel routes using alkoxides for encapsulation of enzymes. However the formation of alcohol as a byproduct during hydrolysis and condensation reactions poses limitations. We report the immobilization of glucose oxidase and peroxidase in silica prepared by an aqueous route which may provide a more favorable environment for the biomolecules. A two step aqueous sol-gel procedure using sodium silicate as the precursor was developed to encapsulate the enzymes and the dye precursor, o-dianisidine. Glucose oxidase catalyzes the oxidation of glucose to give gluconic acid and hydrogen peroxide. Peroxidase then catalyzes the reaction of the dye precursor with hydrogen peroxide to produce a colored product. The kinetics of the coupled enzymatic reactions were monitored by optical spectroscopy and compared to those occurring in tetramethyl orthosilicate (TMOS) derived silica matrices developed by Yamanaka. Enhanced kinetics in the aqueous silicate matrices were related to differences in the host microstructure as elucidated by microstructural comparisons of the corresponding aerogels.

  7. ZrO{sub 2} ultrafiltration membranes processed by the Sol-Gel route

    SciTech Connect

    Mueller, C.; Gottschling, S.; Kohl, R.; Tomandl, G.

    1995-09-01

    The sol-gel route was used to process thin porous ZrO{sub 2} layers on tubular x-alumina substrates. The hydrolysis of Zr-n-butoxide at room temperature and the subsequent peptization by an inorganic acid lead to stable colloidal sols. To achieve crack-free ultrafiltration membranes, mixtures of the sols with organic binders were optimized, deposited on the substrates, dried and heat treated at different temperatures. Thickness, morphology, phase composition, pore size distribution and filtration properties of the membranes were analyzed.

  8. Electrical properties of samarium cobaltite nanoparticles synthesized using SolGel autocombustion route

    SciTech Connect

    Sathyamoorthy, B.; Md Gazzali, P.M.; Murugesan, C.; Chandrasekaran, G.

    2014-05-01

    Highlights: The structural evolution and its electrical properties of samarium cobaltite nanograins are discussed. Optimization of SmCoO{sub 3} nanograins is achieved by post sintering as-prepared gel at 800 C. The impedance spectra indicate the semiconducting behavior SmCoO{sub 3} nanograins. - Abstract: Nanograins of SmCoO{sub 3} are prepared by citric acid assisted SolGel autocombustion route. The characterizations of crystal structure, surface morphology and electrical properties of SmCoO{sub 3} powder are done using XRD, HRSEM, FTIR and BDS. The structural evolution of SmCoO{sub 3} upon increasing the annealing temperature is followed using XRD and FTIR analyses. The powder sample contains polycrystalline grains with average size equal to 35 nm and orthorhombic perovskite structure with Pbnm space group. The vibrational bands observed in FTIR spectrum at 545 cm{sup ?1} and 439 cm{sup ?1} correspond to Co-O stretching modes in cobaltite system. HRSEM images of the sample show the formation of hexagonal shaped grains of samarium cobaltite. The AC electrical conductivity of 4.914 10{sup ?5} S cm{sup ?1} at 295 K is measured for SmCoO{sub 3} nanoparticles. The impedance spectra bring out the semiconducting behavior of the material.

  9. Effects of a protic ionic liquid on the reaction pathway during non-aqueous sol-gel synthesis of silica: a Raman spectroscopic investigation.

    PubMed

    Martinelli, Anna

    2014-01-01

    The reaction pathway during the formation of silica via a two-component "non-aqueou" sol-gel synthesis is studied by in situ time-resolved Raman spectroscopy. This synthetic route is followed with and without the addition of the protic ionic liquid 1-ethylimidazolium bis(trifluoromethanesulfonyl)imide (C2HImTFSI) in order to investigate its effect on the reaction pathway. We demonstrate that Raman spectroscopy is suitable to discriminate between different silica intermediates, which are produced and consumed at different rates with respect to the point of gelation. We find that half-way to gelation monomers and shorter chains are the most abundant silica species, while the formation of silica rings strongly correlates to the sol-to-gel transition. Thus, curling up of linear chains is here proposed as a plausible mechanism for the formation of small rings. These in turn act as nucleation sites for the condensation of larger rings and thus the formation of the open and polymeric silica network. We find that the protic ionic liquid does not change the reaction pathway per se, but accelerates the cyclization process, intermediated by the faster inclusion of monomeric species. PMID:24743891

  10. Production and characterization of spodumene dosimetric pellets prepared by a sol-gel route

    NASA Astrophysics Data System (ADS)

    Lima, H. R. B. R.; Nascimento, D. S.; Bispo, G. F. C.; Teixeira, V. C.; Valério, M. E. G.; Souza, S. O.

    2014-11-01

    Spodumene is an aluminosilicate that has shown good results for high-dose TL dosimetry for beta or gamma rays. Due to its chemical composition (LiAlSi2O6) it has potential to be used as a neutron dosimeter. The synthetic spodumene is usually produced by solid state reaction and conventional sol-gel, whose shortcomings arise from the need to employ high temperatures and high cost reagents, respectively. Proteic sol-gel method is promising, because it can reduce production costs and the possibility of environmental contamination. This work reports the production of the spodumene by the proteic sol-gel method using edible unflavored gelatin as a precursor. The product is characterized physically and morphologically, and investigated its applicability as a TL dosimeter. Two sets of samples were prepared using different sources of silicon, one with TEOS (Si(OC3H5)4) and one with SILICA (SiO2). The materials produced were characterized by X-ray diffraction, differential thermal analysis and thermogravimetry in order to evaluate the structural properties, as well as possible changes in physical or chemical properties depending on the temperature. The production of spodumene was successful, with generation of the crystals in the β-phase with tetragonal structure. Sintered pellets produced from these crystals were irradiated with a 90Sr-90Y source and their TL glow curves were evaluated. Although the samples prepared by the proteic sol-gel method with TEOS presented a lower forming temperature, the samples produced with SILICA showed higher sensitivity to radiation.

  11. Low-temperature deposition of the high-performance anatase-titania optical films via a modified sol gel route

    NASA Astrophysics Data System (ADS)

    Sheng, Yonggang; Liang, Liping; Xu, Yao; Wu, Dong; Sun, Yuhan

    2008-04-01

    Anatase-titania films with high optical performances have been deposited via a modified sol-gel route. This involved several precisely controlled processes including a sufficient hydrolysis of titanium tetraisopropoxide (TTIP) with excessive water, a peptization at pH value of 1-2, a restrained condensation under the hydrothermal conditions at 373 K, and finally a spin-coating process at 293 K. A full characterization of the sols and films indicated that such a well-controlled hydrolysis and condensation of TTIP enabled the formation of high-quality precursor sols consisting of anatase-titania colloidal particles with the mean hydrodynamic diameter of about 17.2 nm, and then endowed the as-deposited films with nanocrystalline structure and the corresponding high refractive index of 1.92 (at 632.8 nm). Moreover, the prepared films exhibited large optical bandgap of 3.38 eV and high laser-induced damage threshold of 16.3 J/cm 2 (at 1064 nm, 3 ns pulse duration and R/1 testing mode), which must be closely related to their homogeneous and nearly defect-free network structures derived from the low-temperature sol-gel deposition route.

  12. Effect of Annealing Temperature on Structural and Optical Parameters of Sol-Gel Routed Molybdenum Oxide Thin Film

    NASA Astrophysics Data System (ADS)

    Arasu, P. Adal; Williams, R. Victor

    2015-05-01

    The influence of annealing temperature on structural and optical properties of sol-gel routed spin-coated molybdenum tri oxide (MoO3) thin films are studied. The higher annealing temperatures improve the crystalline nature of the film. The X-ray diffraction (XRD) study reveals the formation of ?-orthorhombic phase at higher annealing temperature and amorphous nature at lower annealing temperature. The optical bandgap of molybdenum tri oxide (MoO3) film is found to be 3.3-3.8 eV, and the refractive index of the film is found to be 2.2-2.9. The dispersion curve of the refractive index shows that an abnormal dispersion in the absorption region and normal dispersion in the transparent region are observed. The optical polarizability, optical conductivity, dielectric constant, volume and surface energy loss parameters are evaluated.

  13. A convenient sol-gel route for the synthesis of salicylate-titania nanocomposites having visible absorption and blue luminescence

    NASA Astrophysics Data System (ADS)

    Mitra, Atanu; Bhaumik, Asim; Nandi, Mahasweta; Mondal, John; Roy, B. K.

    2009-05-01

    Syntheses of titania-based nanomaterials by simple sol-gel route using a mixture of CTAB and salicylate as well as salicylate ions as templates have been reported. The materials are characterized by the powder X-ray diffraction (XRD), thermal analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and spectroscopic (FT IR, UV-VIS) analyses. A disordered mesoscale orientation of nanoparticles (ca. 2-4 nm) composed of TiO 2-salicylate surface complex has been obtained when 1:1 mixing ratio of CTAB and salicylate at the CTAB concentration of 0.001 M was employed as a template. All these nanocomposites exhibit a considerable red shift at the onsets of their absorption band compared to pure (organic-free) nanocrystalline TiO 2 and show blue luminescence at room temperature. This assembly of nanoparticles is highly interesting in the context of visible light sensitization and nanodevice fabrication.

  14. Influence of transition metals on the surface acidic properties of titania prepared by sol-gel route

    SciTech Connect

    Shali, N.B.; Sugunan, S. . E-mail: ssg@cusat.ac.in

    2007-09-04

    A series of titania catalysts containing chromium, molybdenum as well as tungsten has been prepared by colloidal sol-gel route using metatitanic acid as the precursor. Structural characterization of the prepared catalysts was done with Energy dispersive X-ray analysis, X-ray diffraction, BET surface area and pore volume measurements. The influence of different transition metals like chromium, molybdenum and tungsten on the surface acidic properties of titania is investigated in detail. Two independent methods have been used to study the surface acidity of these catalyst systems: temperature programmed desorption of ammonia which is a measure of total acidity and thermodesorption studies using 2,6-dimethyl pyridine which is a measure of Bronsted acidity. Cumene cracking reaction is carried out over the prepared systems for further characterizing the acidity of the prepared catalysts. Remarkable enhancement in the surface acidity is observed after transition metal incorporation. The catalytic activity of the prepared catalysts was tested towards the dehydrogenation of cyclohexane.

  15. Thermo-optic characterization of neodymium/nickel doped silica glasses prepared via sol-gel route

    NASA Astrophysics Data System (ADS)

    Manuel, Ancy; Rajesh Kumar, B.; Shemeena Basheer, N.; Syamala Kumari, B.; Paulose, P. I.; Kurian, Achamma; George, Sajan D.

    2012-12-01

    Intrinsic as well as rare earth (Neodymium) doped silica glasses with various molar ratio of dopant and a metallic (Nickel) co-dopant is prepared via sol-gel route. The structural characterization of the sample is carried out using X-ray diffraction and Fourier Transform Infrared Spectroscopy. The influence of dopant and doping concentration on the optical properties of silica matrix is investigated via UV-VIS absorption spectroscopy. Effect of dopant on thermal effusivity value of the host matrix is carried out by laser induced open cell photoacoustic technique. Analysis of the results showed that doping affect the thermal effusivity value and results are interpreted in terms of structural modification of the lattice and phonon assisted heat transport mechanism.

  16. Aluminosilicates with varying alumina-silica ratios: synthesis via a hybrid sol-gel route and structural characterisation.

    PubMed

    Nampi, Padmaja Parameswaran; Moothetty, Padmanabhan; Berry, Frank John; Mortimer, Michael; Warrier, Krishna Gopakumar

    2010-06-01

    Aluminosilicates with varying Al2O3:SiO2 molar ratios (3:1, 3:2, 3:3 and 3:4) have been synthesized using a hybrid sol-gel route using boehmite sol as the precursor for alumina and tetraethyl orthosilicate (TEOS) as the precursor for silica. The synthesis of boehmite sol from aluminium nitrate, and its use as the alumina precursor, is cost effective compared to alkoxide precursors. Structural aspects, including bonding and coordination, are studied in detail for samples calcined in the temperature range 400-1400 C using both NMR and FTIR spectroscopy: the results are correlated with phase formation data (spinel and high temperature phases) obtained from XRD and thermal analysis. FTIR results show a broadening of peaks at 800 C indicating a disordered distribution of octahedral sites caused by crosslinking between AlO6 octahedral and SiO4 tetrahedral units prior to the formation of mullite. (27)Al MAS NMR spectra are consistent with a progressive decrease in the number of AlO6 polyhedra with increasing temperature corresponding to Al in these units being forced to adopt a tetrahedral coordination due to the increasing presence of similarly coordinated Si species. XRD results confirm the formation of pure mullite at 1250 C for a 3Al2O3:2SiO2 system. At 1400 C, phase pure mullite is observed for all compositions except 3Al2O3:SiO2 where ?-Al2O3 is the major phase with traces of mullite. The synthesis of aluminosilicates through a hybrid sol-gel route and the detailed insight into structural features gained from spectroscopic and diffraction techniques contributes further to the development of these materials in applications ranging from nanocatalysts to high-temperature ceramics. PMID:20411190

  17. A sol-gel route for the development of rare-earth aluminum borate nanopowders and transparent thin films

    SciTech Connect

    Maia, Lauro J.Q. Mastelaro, Valmor R.; Hernandes, Antonio C.

    2007-02-15

    A new sol-gel route was applied to obtain Y{sub 0.9}Er{sub 0.1}Al{sub 3}(BO{sub 3}){sub 4} crystalline powders and amorphous thin films by using Al(acac){sub 3}, B(OPr {sup i}){sub 3}, Y(NO{sub 3}){sub 3}.6H{sub 2}O, and Er(NO{sub 3}){sub 3}.5H{sub 2}O as starting materials dissolved in propionic acid and ethyl alcohol mixtures. Our study shows that propionic acid acts as good chelant agent for yttrium and erbium ions while ethyl alcohol allows to dissolve Al(acac){sub 3}. This process makes the resulting sols very stable to obtain homogeneous gels and transparent amorphous thin films. In addition, the propionic acid prevents the sol precipitation, making easy porous- and crack-free thin film depositions. Chemical reactions involved in the complexation were discussed. As-prepared powders and films are amorphous and present a good thermal stability due to their high glass transition (746 deg. C) and crystallization temperatures (830 deg. C). This new sol-gel route showed to be adequate to obtain dense and crack-free thin films free of organic and hydroxyl groups that can be considered as promising materials to be used in integrated optical systems. - Graphical abstract: SEM micrograph of Y{sub 0.9}Er{sub 0.1}Al{sub 3}(BO{sub 3}){sub 4} powders calcined at 400 and 700 deg. C during 24 h and heat-treated at 1150 deg. C.

  18. Synthesis of Yttria-Stabilized Zirconia Aerogels by a Non-Alkoxide Sol-Gel Route

    SciTech Connect

    Chervin, C N; Clapsaddle, B J; Chiu, H W; Gash, A E; Satcher, Jr., J H; Kauzlarich, S M

    2005-02-11

    Homogeneous, nanocrystalline powders of yttria-stabilized zirconia were prepared using a nonalkoxide sol-gel method. Monolithic gels, free of precipitation, were prepared by addition of propylene oxide to aqueous solutions of Zr{sup 4+} and Y{sup 3+} chlorides at room temperature. The gels were dried with supercritical CO{sub 2}(l), resulting in amorphous aerogels that crystallized into cubic stabilized ZrO{sub 2} following calcination at 500 C. The aerogels and resulting crystalline products were characterized using in-situ temperature profile X-ray diffraction, thermal analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and nitrogen adsorption/desorption analysis. TEM and N{sub 2} adsorption/desorption analysis of an aerogel indicated a porous network structure with a high surface area (409 m{sup 2}/g). The crystallized yttria-stabilized zirconia maintained high surface area (159 m{sup 2}/g) upon formation of homogeneous, nanoparticles ({approx}10 nm). Ionic conductivity at 1000 C of sintered YSZ (1500 C, 3 hours) prepared by this method, was 0.13 {+-} 0.02 {Omega}{sup -1} cm{sup -1}. Activation energies for the conduction processes from 1000-550 C and 550-400 C, were 0.95 {+-} 0.09 and 1.12 {+-} 0.05 eV, respectively. This is the first reported synthesis and characterization of yttria-stabilized zirconia via an aerogel precursor.

  19. A convenient sol-gel route for the synthesis of salicylate-titania nanocomposites having visible absorption and blue luminescence

    SciTech Connect

    Mitra, Atanu; Bhaumik, Asim; Nandi, Mahasweta; Mondal, John; Roy, B.K.

    2009-05-15

    Syntheses of titania-based nanomaterials by simple sol-gel route using a mixture of CTAB and salicylate as well as salicylate ions as templates have been reported. The materials are characterized by the powder X-ray diffraction (XRD), thermal analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and spectroscopic (FT IR, UV-VIS) analyses. A disordered mesoscale orientation of nanoparticles (ca. 2-4 nm) composed of TiO{sub 2}-salicylate surface complex has been obtained when 1:1 mixing ratio of CTAB and salicylate at the CTAB concentration of 0.001 M was employed as a template. All these nanocomposites exhibit a considerable red shift at the onsets of their absorption band compared to pure (organic-free) nanocrystalline TiO{sub 2} and show blue luminescence at room temperature. This assembly of nanoparticles is highly interesting in the context of visible light sensitization and nanodevice fabrication. - Graphical abstract: A new titania-salicylate nanostructure material has been synthesized, which exhibit a considerable red shift towards the visible region vis-a-vis nanocrystalline (organic-free) TiO{sub 2} and blue luminescence at room temperature.

  20. A new synthesis route to high surface area sol gel bioactive glass through alcohol washing: a preliminary study.

    PubMed

    Mukundan, Lakshmi M; Nirmal, Remya; Vaikkath, Dhanesh; Nair, Prabha D

    2013-01-01

    Bioactive glass is one of the widely used bone repair material due to its unique properties like osteoconductivity, osteoinductivity and biodegradability. In this study bioactive glass is prepared by the sol gel process and stabilized by a novel method that involves a solvent instead of the conventional calcinations process. This study represents the first attempt to use this method for the stabilization of bioactive glass. The bioactive glass stabilized by this ethanol washing process was characterized for its physicochemical and biomimetic property in comparison with similar composition of calcined bioactive glass. The compositional similarity of the two stabilized glass powders was confirmed by spectroscopic and thermogravimetric analysis. Other physicochemical characterizations together with the cell culture studies with L929 fibroblast cells and bone marrow mesenchymal stem cells proved that the stabilization was achieved with the retention of its inherent bioactive potential. However an increase in the surface area of the glass powder was obtained as a result of this ethanol washing process and this add up to the success of the study. Hence the present study exhibits a promising route for high surface area bioactive glass for increasing biomimicity. PMID:23512012

  1. The morphology, proliferation rate, and population doubling time factor of adipose-derived mesenchymal stem cells cultured on to non-aqueous SiO2, TiO2, and hybrid sol-gel-derived oxide coatings.

    PubMed

    Marycz, Krzysztof; Krzak-Ro?, Justyna; Donesz-Sikorska, Anna; ?mieszek, Agnieszka

    2014-11-01

    In recent years, much attention has been paid to the development of tissue engineering and regenerative medicine, especially when stem cells of various sources are concerned. In addition to the interest in mesenchymal stem cells isolated from bone marrow, recently more consideration has been given to stem cells isolated from adipose tissue (AdMSCs), due to their less invasive method of collection as well as their ease of isolation and culture. However, the development of regenerative medicine requires both the application of biocompatible material and the stem cells to accelerate the regeneration. In this study, we investigated the morphology, proliferation rate index (PRi), and population doubling time factor of adipose-derived mesenchymal stem cells cultured on non-aqueous sol-gel-derived SiO2, TiO2, and SiO2/TiO2 oxide coatings. The results indicated an increase in PRi of AdMSCs when cultured on to titanium dioxide, suggesting its high attractiveness for AdMSCs. In addition, the proper morphology and the shortest doubling time of AdMSCs were observed when cultured on titanium dioxide coating. PMID:24408867

  2. Low-temperature synthesis of SrAl{sub 2}O{sub 4} by a modified sol-gel route: XRD and Raman characterization

    SciTech Connect

    Escribano, Purificacion; Marchal, Monica; Luisa Sanjuan, Maria; Alonso-Gutierrez, Pablo; Julian, Beatriz; Cordoncillo, Eloisa . E-mail: cordonci@qio.uji.es

    2005-06-15

    Among other alkaline-earth aluminates, the monoclinic (M) polymorph of SrAl{sub 2}O{sub 4} can be used as host material for Eu{sup 2+} luminescence based phosphors. With the aim of reducing the synthesis temperature of this polymorph, we have produced and characterized by XRD and Raman scattering solid solutions of the SrAl{sub 2-x}B{sub x}O{sub 4} system (x=<0.3) obtained by two different methods, a ceramic route and a modified sol-gel synthesis. Though the addition of boron lowers the temperature of obtention of the M polymorph in both type of samples, lower B contents are needed to stabilize the M form as single phase for samples prepared by the sol-gel method than through the ceramic route. In the sol-gel method, the M polymorph can be obtained at temperatures as low as 1200 deg. C, with a Boron content of just 1%. Rietveld profile analysis allows us to conclude that coexistence of the monoclinic and hexagonal polymorphs of SrAl{sub 2}O{sub 4} occurs for samples synthesized below an onset temperature of about 1000-1100 deg. C, that depends on the sample composition. Above those temperatures, only the monoclinic phase is formed.

  3. Thin Films Derived by a Particulate Sol-Gel Route with Various Cr:Ti Molar Ratios

    NASA Astrophysics Data System (ADS)

    Mohammadi, M. R.; Fray, D. J.

    2014-11-01

    Nanocrystalline and nanostructured TiO2-Cr2O3 thin films and powders were prepared by a facile and straightforward aqueous particulate sol-gel route at low temperature of 400C. The prepared sols showed a narrow particle size distribution with hydrodynamic diameter in the range of 17.7 nm to 19.0 nm. Moreover, the sols were stable over 4 months, with constant zeta potential measured during this period. The effect of the Cr:Ti molar ratio on the crystallization behavior of the products was studied. X-ray diffraction (XRD) analysis revealed that the powders crystallized at low temperature of 400C, containing anatase-TiO2, rutile-TiO2, and Cr2O3 phases, depending on the annealing temperature and Cr:Ti molar ratio. Furthermore, it was found that Cr2O3 retarded the anatase to rutile transformation up to 800C. The activation energy of crystallite growth was calculated to be in the range of 1.3 kJ/mol to 2.9 kJ/mol. Transmission electron microscopy (TEM) imaging showed that one of the smallest crystallite sizes was obtained for TiO2-Cr2O3 binary mixed oxide, being 5 nm at 500C. Field-emission scanning electron microscopy (FESEM) analysis revealed that the deposited thin films had nanostructured morphology with average grain size in the range of 20 nm to 40 nm at 500C. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response towards low concentrations of NO2 gas at low operating temperature of 200C, resulting in increased thermal stability of sensing films as well as a decrease in their power consumption. Furthermore, calibration curves revealed that TiO2-Cr2O3 sensors followed the power law (where S is the sensor response, the coefficients A and B are constants, and [gas] is the gas concentration) for two types of gas, exhibiting excellent capability for detection of low gas concentrations.

  4. Structural investigation of nanomixed xSnO2-Al2O3 synthesized by sol-gel route

    NASA Astrophysics Data System (ADS)

    Kumar, C.; Mishra, N. K.; Kumar, A.; Bhatt, M.; Chaudhary, P.; Singh, R.

    2015-12-01

    Nanomixed SnO2-Al2O3 with variable composition has been synthesized by sol-gel technique using aluminium dichloride and stannous chloride as precursors. Synthesized nanocomposites have been characterized using various techniques such as X-ray diffraction (XRD), Fourier transform infrared, scanning electron microscopy and Energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET). XRD shows decrease in crystallinity as alumina component increases in following series of nanomixed oxides. The specific surface area calculated by Brunauer-Emmett-Teller (BET) method was about 191 m2/g and average pore diameter of 158 .

  5. Optical properties of undoped and Mg doped CuCrO{sub 2} powders synthesized by sol-gel route

    SciTech Connect

    Srinivasan, Radhakrishnan; Bolloju, Satish

    2014-01-28

    In this work, CuCrO{sub 2} was synthesized by sol-gel method using citric acid as a gelling agent. The different parameters like ratio of citric acid to metal ions, calcination temperature, and duration were studied. A green colored powder with particle size around 300 nm was formed at the calcination temperature of 800 °C for four hours duration. The increase in temperature has a profound impact on crystallite size and in turn effected the optical properties. Band gap of the obtained CuCrO{sub 2} has varied from 2.3 to 1.7 eV by increasing the temperature from 800 °C to 900 °C. Doping studies were performed by introducing Mg{sup 2+} ion to substitute Cr{sup 3+} in CuCrO{sub 2}. X-ray powder diffraction and SEM studies on 2% Mg doped samples indicated a clear formation of side phases. According to the X-ray powder patterns, the reflections from side phases were increasing with the increase in doping concentrations of Mg from 2 to 5%. The side phases were found to be MgCr{sub 2}O{sub 4} spinel and CuO. The band gap has decreased for doped samples in comparison to undoped one. In this paper, sol-gel synthesis and characterization by Xray powder diffraction, SEM studies and UV-Vis-Diffuse Reflectance spectra are presented.

  6. Structural, Optical and Magnetic Properties of Nickel-Silica Nanocomposite Prepared by a Sol-Gel Route

    NASA Astrophysics Data System (ADS)

    Saha, Mrinal; Soumya Mukherjee; Gayen, Arup; Siddhartha Mukherjee

    2015-10-01

    Nickel-silica nanocomposites have been synthesized by a sol-gel method using dextrose (C6H12O6) as the reducing agent. The dried gel is heat treated at 850 and 900 °C for 30 min in an inert atmosphere by N2 purging to obtain the composite material. The samples have been characterized by powder X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, transmission electron microscopy and selected area electron diffraction. Pure polycrystalline nickel granular particle has been found to form with face-centered cubic structure and is entrapped in amorphous silica matrix with particle sizes in between 10 and 30 nm and is almost spherical in shape. The strong ferromagnetic nature of Ni-SiO2 composite became evident from the M-H curve which is quite different from the bulk nickel. The band gap of the synthesized Ni-SiO2 nanocomposite is found to be 2.35 eV. The reported sol-gel technique is a convenient and effective method to prepare high purity nanopowders with uniform size distribution.

  7. A novel organic-free sol-gel route to ceria-zirconia-alumina thin films and glassy products

    NASA Astrophysics Data System (ADS)

    Frolova, Elena V.; Ivanovskaya, Mariya I.; Kosareva, Yuliya A.; Petranovskii, Vitalii P.; Fuentes, Sergio I.

    2004-10-01

    Successful preparation of the Ce-Zr-Al oxide thin films and glassy products by a newly developed organic-free modification of the sol-gel technique is reported. The structural composition and some properties of the samples obtained were investigated by TEM, XRD, FTIR, ESR, UV-Vis, PL and XPS. The optical investigation of the obtained films together with ESR data indicate the appearance of the bulk Ce3+-defects (g? = 1.962-1.967, g// = 1.938-1.940, assigned to 4f1 state, with concentration ~2"1018spin/g). The significant PL intensity rising at elevated temperature was related to spontaneous increasing of Ce3+ concentration in sol-gel samples under thermal dehydration. Also, an unexpected formation of intra-band gap states during thermal treatment of xerogels was manifested in UV-Vis spectra. This intra-band-gap states was attributed to the oxygen related defects that contribute to PL signal.

  8. Optical spectroscopy study of YVO4:Eu3+ nanopowders prepared by the proteic sol-gel route

    NASA Astrophysics Data System (ADS)

    dos Santos, B. F.; Araujo, R. M.; Valerio, M. E. G.; Rezende, M. V. dos S.

    2015-04-01

    In this study, computational and experimental methods are employed to study the optical properties of YVO4 induced by europium dopant. Atomistic modeling is used to predict the symmetry and the detailed geometry of the dopant site. This information is then used to calculate the crystal-field parameters. Eu-doped YVO4 nanopowders are prepared via a sol-gel proteic technique. Thereafter, multiple techniques including X-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to examine the structural properties and surface morphology of the YVO4:Eu3+ phosphors. The optical properties are studied using photoluminescence (PL) and radioluminescence (RL) spectroscopy performed at room temperature. The transition energy of the Eu3+-doped material is compared with the theoretical results. The intensity parameters ?2 and ?4 of Eu3+ in the YVO4 matrix are calculated with the Judd-Ofelt approach.

  9. Rh6G released from solid and nanoporous SiO2 spheres prepared by sol-gel route

    NASA Astrophysics Data System (ADS)

    Garca-Macedo, J. A.; Francisco S., P.; Franco, A.

    2015-10-01

    Porous silica nanoparticles are considering good systems for drug cargo and liquid separation. In this work we studied the release of rhodamine 6G (Rh6G) from solid and porous silica nanoparticles. Solid and porous SiO2 spheres were prepared by sol-gel method. Nanoporous channels were produced by using a surfactant that was removed by chemical procedure. Rh6G was incorporated into the channels by impregnation. The hexagonal structure of the pores was detected by XRD and confirmed by HRTEM micrographs. Rh6G released from the particles by stirring them in water at controlled speed was studied as function of time by photoluminescence. Released ratio was faster in the solid nanoparticles than in the porous ones. In the last case, a second release mechanism was observed. It was related with rhodamine coming out from the porous.

  10. Synthesis of CdS/CdSe core/shell ultra small nanostructures using new microwave assisted ultrasonic sol gel route

    NASA Astrophysics Data System (ADS)

    Goswami, Y. C.; Kumar, Vijay; Sharma, Ranjana; Singh, Rajeev

    2014-04-01

    Core-shell CdS/CdSe nanostructures have been synthesized by new microwave assisted ultrasonic sol gel route. The solution was obtained by dissolving cadmium acetate and Thiourea in the molar ratio 1:1 in Triethlioamine. The solution was Ultrasonically irradiated by Ultrasonic crystal at 40 Hz for 3 hours at 70C. The sol was kept for another 24 hours for gel formation. Selenium dioxide was used as a selenium source and added separately. The gel was spin coated on Quartz and Glass slides followed by microwave heat treatment. The samples were characterized by structural morphological and optical characterization. XRD studies confirm the zinc blende phase of the CdS nanoparticles. The mean nanocrystal sizes calculated using Scherrer equation is 1.2nm. Optical studies show the strong blue shift in the spectra due to very small size of the nanocrystals. TEM and HRTEM confirm the formation of core shell structures.

  11. Synthesis of CdS/CdSe core/shell ultra small nanostructures using new microwave assisted ultrasonic sol gel route

    SciTech Connect

    Goswami, Y. C. Kumar, Vijay; Sharma, Ranjana; Singh, Rajeev

    2014-04-24

    Core-shell CdS/CdSe nanostructures have been synthesized by new microwave assisted ultrasonic sol gel route. The solution was obtained by dissolving cadmium acetate and Thiourea in the molar ratio 1:1 in Triethlioamine. The solution was Ultrasonically irradiated by Ultrasonic crystal at 40 Hz for 3 hours at 70C. The sol was kept for another 24 hours for gel formation. Selenium dioxide was used as a selenium source and added separately. The gel was spin coated on Quartz and Glass slides followed by microwave heat treatment. The samples were characterized by structural morphological and optical characterization. XRD studies confirm the zinc blende phase of the CdS nanoparticles. The mean nanocrystal sizes calculated using Scherrer equation is ?1.2nm. Optical studies show the strong blue shift in the spectra due to very small size of the nanocrystals. TEM and HRTEM confirm the formation of core shell structures.

  12. EPR investigation on synthesis of Lithium zinc vanadate using sol-gel-combustion route and its optical properties

    NASA Astrophysics Data System (ADS)

    Pathak, Nimai; Gupta, Santosh K.; Prince, Angelina; Kadam, R. M.; Natarajan, V.

    2014-01-01

    The present work describes the synthesis of Lithium zinc vanadate (LiZnVO4) nanophosphor prepared by sol-gel-combustion method and its optical properties. The prepared sample was characterized by X-ray diffraction, SEM, electron paramagnetic resonance and photoluminescence spectroscopy. X-ray diffraction study showed the formation of pure LiZnVO4 at 600 C with distorted phenacite structure. SEM investigation revealed that the phosphor powder has spherical morphology with particle size of about 100-200 nm. EPR study showed the change of coordination sphere around vanadium from axially distorted octahedral symmetry to tetrahedral geometry along with the change in oxidation state of vanadium ion from +4 to +5. The emission spectrum showed a broad emission at 543 nm with ?ex = 375 nm. The decay time obtained on mono-exponential fitting was 8.3 ?s. The colour coordinates of the system were evaluated using CIE index diagram to be 0.31 and 0.41, which suggest that the prepared material is a potential green emitting phosphor. A bright green colour emission was also observed directly from this phosphor upon excitation with an UV source.

  13. Multiple-layered structure of obelisk-shaped crystalline nano-ZnO prepared by sol-gel route

    NASA Astrophysics Data System (ADS)

    Jurablu, Saeideh; Farahmandjou, Majid; Firoozabadi, Tahereh Pormirjaafari

    2015-08-01

    Zinc oxide nanopowders were synthesized by the simple sol-gel method from an ethanol solution of zinc nitrate hexahydrate. Structural and surface morphological investigations were carried out using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible (UV-Vis) spectrophotometry analyses. XRD pattern showed that the zinc oxide nanoparticles exhibited hexagonal wurtzite structure. A multiple-layered structure of obelisk-shaped ZnO nanoparticles was achieved after calcinations. The average particle size of ZnO was around 20 nm as estimated by direct HRTEM observation. The size of sphere-like shaped ZnO nanoparticles was measured in the range of 20-80 nm and the size of pyramid-like shaped annealed samples was achieved in the range of 40-100 nm with less agglomeration. The energy dispersive spectroscopy spectrum showed peaks of zinc and oxygen. The sharp peaks in FTIR spectrum determined the Zn-O stretching and absorbance peak of UV-Vis spectrum showed the wide bandgap energy of 3.35 eV.

  14. A New Route to Liposil Formation by an Interfacial Sol-Gel Process Confined by Lipid Bilayer.

    PubMed

    Shen, Shukun; Yang, Lu; Lu, Yaxing; Chen, Jian-Gang; Song, Shaofei; Hu, Daodao; Parikh, Atul

    2015-11-18

    We report a new and simple approach to prepare a class of silica-reinforced liposomes with hybrid core-shell nanostructures. The amphiphilic natural structure of lipids was exploited to sequester hydrophobic molecules, namely precursor TEOS and pyrene, in the hydrophobic midplane of liposomal bilayer assemblies in the aqueous phase. Subsequent interfacial hydrolysis of TEOS at the bilayer/water interface and ensuing condensation within the hydrophobic interstices of the lipid bilayer drives silica formation in situ, producing a novel class of silica-lipid hybrid liposils. Structural characterization by scanning- and transmission electron microscopy confirm that the liposils so generated preserve closed topologies and size-monodipersity of the parent lecithin liposomes, and DSC-TGA and XRD measurements provide evidence for the silica coating. Monitoring fluorescence measurements using embedded pyrene yield detailed information on microenvironment changes, which occur during sol-gel process and shed light on the structural evolution during silica formation. We envisage that liposils formed by this simple, new approach, exploiting the hydrophobic core of the lipid bilayer to spatially localize silica-forming precursors enables preparation of stable liposils exhibiting capacity for cargo encapsulation, bicompatibility, and fluorescence monitoring, more generally opening a window for construction of stable, functional hybrid materials. PMID:26197062

  15. A novel synthetic route for magnesium aluminate (MgAl2O4) nanoparticles using sol-gel auto combustion method and their photocatalytic properties.

    PubMed

    Nassar, Mostafa Y; Ahmed, Ibrahim S; Samir, Ihab

    2014-10-15

    In this paper a novel and inexpensive route for the preparation of spinel magnesium aluminate nanoparticles (MgAl2O4) is proposed. Magnesium aluminate photocatalyst was synthesized via sol-gel auto combustion method using oxalic acid, urea, and citric acid fuels at 350°C. Subsequently, the burnt samples were calcined at different temperatures. The pure spinel MgAl2O4 with average crystallite size 27.7, 14.6 and 15.65nm was obtained at 800°C calcinations using the aforementioned fuels, respectively. The obtained samples were characterized by powder X-ray diffraction, Fourier transform infrared, UV-Vis spectroscopy, transmission electron microscope, scanning electron microscope. The photo catalytic activity of MgAl2O4 product was studied by performing the decomposition of Reactive Red Me 4BL dye under UV illumination or sunlight irradiation. The dye considerably photocatalytically degraded by 90.0% and 95.45% under UV and sunlight irradiation, respectively, within ca. 5h with pseudo first order rate constants of 5.85×10(-3) and 8.38×10(-3)min(-1), respectively. PMID:24835935

  16. A novel synthetic route for magnesium aluminate (MgAl2O4) nanoparticles using sol-gel auto combustion method and their photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Nassar, Mostafa Y.; Ahmed, Ibrahim S.; Samir, Ihab

    2014-10-01

    In this paper a novel and inexpensive route for the preparation of spinel magnesium aluminate nanoparticles (MgAl2O4) is proposed. Magnesium aluminate photocatalyst was synthesized via sol-gel auto combustion method using oxalic acid, urea, and citric acid fuels at 350 C. Subsequently, the burnt samples were calcined at different temperatures. The pure spinel MgAl2O4 with average crystallite size 27.7, 14.6 and 15.65 nm was obtained at 800 C calcinations using the aforementioned fuels, respectively. The obtained samples were characterized by powder X-ray diffraction, Fourier transform infrared, UV-Vis spectroscopy, transmission electron microscope, scanning electron microscope. The photo catalytic activity of MgAl2O4 product was studied by performing the decomposition of Reactive Red Me 4BL dye under UV illumination or sunlight irradiation. The dye considerably photocatalytically degraded by 90.0% and 95.45% under UV and sunlight irradiation, respectively, within ca. 5 h with pseudo first order rate constants of 5.85 10-3 and 8.38 10-3 min-1, respectively.

  17. A novel low cost non-aqueous chemical route for giant dielectric constant CaCu3Ti4O12 ceramic

    NASA Astrophysics Data System (ADS)

    Singh, Laxman; Kim, Ill Won; Woo, Won Seok; Sin, Byung Cheol; Lee, Hyung-il; Lee, Youngil

    2015-05-01

    This paper reports a simple, fast, low cost and environment-friendly route for preparing a highly crystalline giant dielectric material, CaCu3Ti4O12 (CCTO), through combustion of metal nitrates in non-aqueous precursor solution using inexpensive solid TiO2 powder. The route to producing pure phase CCTO ceramic using stable solid TiO2 is better than other several sol-gel routes reported earlier in which expensive alkoxides, oxynitrates, or chlorides of titanium are used as the titanium sources. X-ray diffraction revealed the formation of cubic perovskite CCTO. Scanning electron microscopy image showed the average grain sizes in the range of 1.5-5 μm. At 10 kHz and room temperature, the best CCTO ceramic exhibited a high dielectric constant, ε‧ ∼43325.24, with low dielectric loss, tan δ ∼0.088. The dielectric relaxation behavior was rationalized from impedance and modulus studies and the presence of a non-Debye type of relaxation was confirmed.

  18. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A. (Los Alamos, NM); Klimov, Victor L. (Los Alamos, NM)

    2012-06-12

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites

  19. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A. (Los Alamos, NM); Klimov, Victor L. (Los Alamos, NM)

    2007-06-05

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites.

  20. Low temperature nanocrystalline TiO2-Fe2O3 mixed oxide by a particulate sol-gel route: Physical and sensing characteristics

    NASA Astrophysics Data System (ADS)

    Mohammadi, M. R.; Fray, D. J.

    2012-09-01

    Nanocrystalline TiO2-Fe2O3 thin films and powders were prepared by a straightforward aqueous particulate sol-gel route at the low temperature of 300 C. Titanium(IV) isopropoxide and iron(III) chloride were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powder crystallised at the low temperature of 300 C, containing anatase-TiO2 and hematite-Fe2O3 phases. Furthermore, it was found that Fe2O3 retarded the anatase-to-rutile transformation up to 500 C. The activation energies for crystallite growth of TiO2 and Fe2O3 components in the binary system were calculated 10.62 and 0.67 kJ/mol, respectively. Moreover, one of the smallest crystallite sizes was obtained for TiO2-Fe2O3 binary mixed oxide, being 6 nm at 300 C. Field emission scanning electron microscope (FE-SEM) analysis revealed that the deposited thin films had nanostructured morphology. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response towards low concentrations of CO gas (i.e., 25 ppm) at low operating temperature of 150 C, resulting in increased thermal stability of sensing films as well as a decrease in their power consumption. Furthermore, TiO2-Fe2O3 sensors follow the power law for the detection of CO gas.

  1. Synthesis of Nanostructured and Nanoporous TiO2-AgO Mixed Oxide Derived from a Particulate Sol-Gel Route: Physical and Sensing Characteristics

    NASA Astrophysics Data System (ADS)

    Mohammadi, M. R.; Fray, D. J.

    2011-08-01

    Nanocrystalline TiO2-AgO thin films and powders were prepared by an aqueous particulate sol-gel route at the low temperature of 573 K (300 C). Titanium tetraisopropoxide and silver nitrate were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the phase composition of the mixed oxide depends upon the annealing temperature, being a mixture of TiO2 and AgO in the range 573 K to 773 K (300 C to 500 C) and a mixture of TiO2, AgO, and Ag2O at 973 K (700 C). Furthermore, one of the smallest crystallite sizes was obtained for TiO2-AgO mixed oxide, being 4 nm at 773 K (500 C). Field emission-scanning electron microscopic (FE-SEM) and atomic force microscopic (AFM) images revealed that the deposited thin films had nanostructured and nanoporous morphology with columnar topography. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response toward low concentrations of CO gas ( i.e., 25 ppm) at low operating temperature of 473 K (200 C), resulting in an increase of the thermal stability of sensing films as well as a decrease in their power consumption. Furthermore, TiO2-AgO sensors follow the power law for the detection of CO gas.

  2. Magnetic and 57Fe Mössbauer study of magneto-electric GaFeO3 prepared by the sol-gel route.

    PubMed

    Sharma, Kavita; Raghavendra Reddy, V; Gupta, Ajay; Banerjee, A; Awasthi, A M

    2013-02-20

    This work reports the preparation of magneto-electric GaFeO(3) by the sol-gel route and its characterization by x-ray diffraction, dc-magnetization, ac-susceptibility, low temperature and high field (57)Fe Mössbauer spectroscopy and dielectric constant measurements. The prepared samples are found to be single phase from x-ray diffraction studies. The crystallite sizes are found to be in the nano-regime for the samples sintered at low temperatures. From the temperature dependent dc-magnetization (M-T) measurements, bifurcation of the zero-field cooled (ZFC)-field cooled data and a cusp in the ZFC data are observed. With the help of low-field ac-susceptibility, (57)Fe Mössbauer and detailed dc-magnetic measurements these features are explained in terms of the magnetic anisotropy of the sample ruling out phenomena like spin-glass and super-paramagnetism as quoted in the literature for this compound. Apart from this, very interesting and different M-H behavior mimicking composite two-phase magnets is observed for the samples sintered at different temperatures. A symmetric M-H loop is observed for samples sintered at low temperatures and a pinched M-H loop is observed for samples sintered at high temperatures. The observed magnetic properties are explained by estimating the Fe cation distribution using high field (57)Fe Mössbauer spectroscopy measurements. An anomaly in the dielectric constant data at the Curie temperature indicates the ME coupling of the samples. PMID:23327995

  3. Ternary transition-metal fluoride precursors for the fluorolytic sol-gel route: new insights into speciation and decomposition.

    PubMed

    Kohl, J; Wiedemann, D; Troyanov, S I; Palamidis, E; Lerch, M

    2015-08-01

    The nanoscaled ternary transition-metal fluorides Li3MF6 (M = V, Fe, Mn) and Li2NiF4 are promising candidates for cathode materials in high-voltage lithium-ion batteries. The fluorolytic route to these compounds relies on thermal decomposition of a hitherto uncharacterised precursor mixture produced from acetylacetonates and hydrofluoric acid. By addition of pyridine, different cationic, electroneutral and anionic complexes containing the motifs [MFn]((3-n)+) (n = 0-4) have been trapped and characterised by single-crystal X-ray diffraction and IR spectroscopy. Based on the results, a model of successive and incomplete fluorination is proposed for the speciation and formation of the precursor. The decomposition of the latter has been monitored via thermogravimetry (TG) and differential scanning calorimetry (DSC). PMID:26126969

  4. The Microscopic Magnetic Properties of W-type Hexaferrite Powder Prepared by A Sol-Gel Route

    SciTech Connect

    Jotania, Rajshree; Chauhan, Chetna; Sharma, Pooja

    2010-12-01

    Magnetic particles of W-type barium-calcium hexaferrite (BaCa{sub 2}Fe{sub 16}O{sub 27}) have been synthesized using a Stearic acid gel route. The gel precursors were dried at 100 deg. C for 2 hrs and then calcinated at 650 deg. C, 750 deg. C, 850 deg. C and 950 deg. C for 4 hrs in a furnace and slowly cooled to room temperature in order to obtain barium-calcium hexaferrite particles. The microscopic magnetic properties of prepared samples studying using Moessbauer spectroscopy. Moessbauer spectra of all samples were recorded at room temperature. Mossbauer parameters like Isomer shift, Quadruple splitting etc. were calculated with respect to iron foil. Barium calcium hexaferrite samples heated at 650 deg. C, 750 deg. C, 850 deg. C show relaxation type Moessbauer spectra along with paramagnetic doublet. The intensity of paramagnetic doublet increases with temperature confirm the presence of ferrous ions in the samples, where as sample calcinated at 950 deg. C confirm the presence of ferrimagnetic phase with partial super paramagnetic nature of prepared hexaferrite sample.

  5. Bioactive glass-ceramic coatings prepared by pulsed laser deposition from RKKP targets (sol-gel vs melt-processing route)

    SciTech Connect

    Rau, J.V.; Teghil, R.; CNR-IMIP U.O.S. di Potenza, Zona Industriale di Tito scalo ; Fosca, M.; Universita di Roma 'La Sapienza', Dipartimento di Chimica, Piazzale Aldo Moro, 5-00185 Rome ; De Bonis, A.; CNR-IMIP U.O.S. di Potenza, Zona Industriale di Tito scalo ; Cacciotti, I.; Bianco, A.; Albertini, V. Rossi; Caminiti, R.; Ravaglioli, A.

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Bioactive glass-ceramic coatings for bone tissue repair and regeneration. Black-Right-Pointing-Pointer Pulsed Lased Deposition allowed congruent transfer of target composition to coating. Black-Right-Pointing-Pointer Target was prepared by sol-gel process suitable for compositional tailoring. Black-Right-Pointing-Pointer Titanium, widely used for orthopaedics and dental implants, was used as substrate. Black-Right-Pointing-Pointer The physico-chemical properties of the prepared coatings are reported. -- Abstract: The deposition of innovative glass-ceramic composition (i.e. RKKP) coatings by Pulsed Lased Deposition (PLD) technique is reported. RKKP was synthesised following two methodologies: melt-processing and sol-gel, the latter being particularly suitable to tailor the compositional range. The PLD advantage with respect to other deposition techniques is the congruent transfer of the target composition to the coating. The physico-chemical properties of films were investigated by Scanning Electron and Atomic Force Microscopies, Fourier Transform Infrared Spectroscopy, Angular and Energy Dispersive X-ray Diffraction, and Vickers microhardness. The deposition performed at 12 J/cm{sup 2} and 500 Degree-Sign C allows to prepare crystalline films with the composition that replicates rather well that of the initial targets. The 0.6 {mu}m thin melt-processing RKKP films, possessing the hardness of 25 GPa, and the 4.3 {mu}m thick sol-gel films with the hardness of 17 GPa were obtained.

  6. Sol-gel derived sorbents

    DOEpatents

    Sigman, Michael E.; Dindal, Amy B.

    2003-11-11

    Described is a method for producing copolymerized sol-gel derived sorbent particles for the production of copolymerized sol-gel derived sorbent material. The method for producing copolymerized sol-gel derived sorbent particles comprises adding a basic solution to an aqueous metal alkoxide mixture for a pH.ltoreq.8 to hydrolyze the metal alkoxides. Then, allowing the mixture to react at room temperature for a precalculated period of time for the mixture to undergo an increased in viscosity to obtain a desired pore size and surface area. The copolymerized mixture is then added to an immiscible, nonpolar solvent that has been heated to a sufficient temperature wherein the copolymerized mixture forms a solid upon the addition. The solid is recovered from the mixture, and is ready for use in an active sampling trap or activated for use in a passive sampling trap.

  7. Morphology and optical properties of a porous silicon-doped sol-gel host

    NASA Astrophysics Data System (ADS)

    Khan, M. Naziruddin; Al Dwayyan, A. S.; Al Hoshan, M.

    2013-09-01

    Porous silicon (PSi) fabricated by a chemical route was successfully separated in 1,4-dioxane and then incorporated in a sol-gel host. The properties of PSi in both solution and a sol-gel environment were investigated using optical techniques, and strong luminescence was observed. The morphology of PSi was similar in solution and the sol-gel, with particles positioned close together. The PSi samples were highly crystalline. Transmission electron microscopy of PSi in solution revealed that the particles were monodisperse and roughly spherical in shape, with a diameter of around 5 nm. The effect of embedding PSi in a sol-gel matrix on its optical properties was investigated. Changes in the photoluminescence peaks of PSi during the phase transition from sol to dried gel were observed. PSi exhibited good photoluminescence stability in the sol-gel matrix, and crack-free sol-gel rods were obtained.

  8. Synthesis of YBa 2Cu 3O 7-x by sol-gel route formation of YBaCuO oxycarbonate intermediate

    NASA Astrophysics Data System (ADS)

    Gotor, F. J.; Odier, P.; Gervais, M.; Choisnet, J.; Monod, Ph.

    1993-12-01

    High- Tc superconducting powders of the Y-Ba-Cu-O system are prepared by a solution-polyacrylamide gel using citric acid as a complexing agent. This method provides an easy way to prepare reactive YBaCuO powders. However, sol-gel synthesis of this oxide involves the formation of intermediate phases which impedes the obtaining of the pure phase at low temperature. An intermediate oxycarbonate phase forms between 800 and 850°C in flowing oxygen. From powder X-ray diffraction, thermal analysis and IR spectroscopy, it is concluded that the intermediate oxycarbonate has an average tetragonal structure - SG P4/ mmm - similar to the parent oxide with a stoichiometry close to YBa 2Cu 2.95(CO 3) 0.35O 6.6. The carbonate group is located in the center of the basal CuO square. This compound has superconducting properties. A pure 123 phase is obtained when the sol-gel precursor is annealed at 925°C in O 2.

  9. Photobleaching in Y3Al5O12:Ce3+ macroporous monoliths prepared via sol - gel route accompanied by phase separation

    NASA Astrophysics Data System (ADS)

    Iwata, Koji; Fujita, Koji; Murai, Shunsuke; Tanaka, Katsuhisa

    2011-02-01

    Macroporous Y3Al5O12 doped with Ce3+ (YAG:Ce) ceramics has been prepared using the metal salt-derived sol-gel processing followed by the heat treatment at temperatures of 800 to 1500 C. The obtained YAG:Ce crystal exhibits a broad emission band around 530 nm ascribable to 5d-4f transitions of Ce3+. Irradiation of the samples with an intense laser light from a He-Cd laser (wavelength = 442 nm) leads to a decrease in the fluorescence intensity, indicating the occurrence of photoionization of Ce3+ and subsequent capture of excited electrons by some trapping sites. It is found that the rate of the photobleaching decreases with an increase in size of YAG crystallites, depending on the temperature of heat treatment; photobleaching takes place more rapidly when heat treatment is performed at lower temperatures, while the heat treatment at higher temperatures suppresses the bleaching.

  10. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Klimov, Victor L.; Petruska, Melissa A.

    2010-05-25

    The present invention is directed to a process for preparing a solid composite having colloidal nanocrystals dispersed within a sol-gel matrix, the process including admixing colloidal nanocrystals with an amphiphilic polymer including hydrophilic groups selected from the group consisting of --COOH, --OH, --SO.sub.3H, --NH.sub.2, and --PO.sub.3H.sub.2 within a solvent to form an alcohol-soluble colloidal nanocrystal-polymer complex, admixing the alcohol-soluble colloidal nanocrystal-polymer complex and a sol-gel precursor material, and, forming the solid composite from the admixture. The present invention is also directed to the resultant solid composites and to the alcohol-soluble colloidal nanocrystal-polymer complexes.

  11. Metal-silica sol-gel materials

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  12. Synthesis of magnetic FexOy@silica-pillared clay (SPC) composites via a novel sol-gel route for controlled drug release and targeting.

    PubMed

    Mao, Huihui; Liu, Xiaoting; Yang, Jihe; Li, Baoshan; Yao, Chao; Kong, Yong

    2014-07-01

    Novel magnetic silica-pillared clay (SPC) materials with an ordered interlayered mesopore structure were synthesized via a two-step method including gallery molecular self-assembly and sol-gel magnetic functionalization, resulting in the formation of FexOy@SPC composites. Small-angle XRD, TEM and N2 adsorption-desorption isotherms results show that these composites conserved a regular layered and ordered mesoporous structure after the formation of FexOy nanoparticles. Wide-angle XRD and XPS analyses confirmed that the FexOy generated in these mesoporous silica-pillared clay hosts is mainly composed of ?-Fe2O3. Magnetic measurements reveal that these composites with different ?-Fe2O3 loading amounts possess super-paramagnetic properties at 300K, and the saturation magnetization increases with increasing Fe ratio loaded. Compared to the pure SPC, the in vitro drug release rate of the FexOy@SPC composites was enhanced due to the fact that the intensities of the SiOH bands on the pore surface of SPC decrease after the generation of FexOy. However, under an external magnetic field of 0.15T, the drug release rate of the FexOy@SPC composites decreases dramatically owing to the aggregation of the magnetic FexOy@SPC particles triggered by non-contact magnetic force. The obtained FexOy@SPC composites imply the possibility of application in magnetic drug targeting. PMID:24857471

  13. Densely packed single-crystal Bi{sub 2}Fe{sub 4}O{sub 9} nanowires fabricated from a template-induced sol-gel route

    SciTech Connect

    Yang Zhi; Huang Yi; Dong Bin; Li Hulin; Shi Sanqiang . E-mail: mmsqshi@polyu.edu.hk

    2006-11-15

    Densely packed single-crystal Bi{sub 2}Fe{sub 4}O{sub 9} nanowires were successfully synthesized by a template-induced citrate-based sol-gel process. The structural properties of the nanowires were characterized using many techniques. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that Bi{sub 2}Fe{sub 4}O{sub 9} nanowires possessed a uniform length and diameter, which were controlled by the thickness and the pore diameter of the applied porous anodic aluminum oxide (AAO) template, respectively. The results of X-ray diffraction (XRD) and the selected area electron diffraction (SAED) indicated that Bi{sub 2}Fe{sub 4}O{sub 9} nanowires had an orthorhombic single-crystal structure. Furthermore, the energy-dispersive X-ray (EDX) spectroscopy demonstrated that the stoichiometric Bi{sub 2}Fe{sub 4}O{sub 9} was formed. The possible formation mechanism of nanowires was also discussed. - Graphical abstract: The top view in low magnification of SEM images of Bi{sub 2}Fe{sub 4}O{sub 9} nanowires after AAO template is partly dissolved.

  14. Structural, magnetic and hyperfine properties of single-phase SrFe12O19 nanoparticles prepared by a sol-gel route

    NASA Astrophysics Data System (ADS)

    Das, A.; Roychowdhury, A.; Pati, S. P.; Bandyopadhyay, S.; Das, D.

    2015-02-01

    Single-phase nanocrystalline strontium hexaferrite (SrFe12O19) powders have been synthesized by a sol-gel method and their structural, magnetic and hyperfine properties are discussed. The optimum annealing temperature of the as-prepared gel for formation of the single-phase SrFe12O19 structure has been found to be 800 C. X-ray diffraction and Fourier transform infrared studies confirmed formation of the hexaferrite phase. The cation distribution at crystallographic inequivalent sites of the hexaferrite structure has been examined by 57Fe Mssbauer spectroscopy and found to be identical to that reported earlier. Single-phase SrFe12O19 nanoparticles (NPs) showed a magnetic hysteresis loop with high coercivity and saturation magnetization denoting an irreversible magnetization character. The temperature dependent magnetization measurements reveal a difference between the zero-field-cooled and field-cooled curves throughout the measurement range 5-300 K that is attributed to superparamagnetic relaxation of finer hexaferrite particles and disordered spins at the surface of the NPs. Both hyperfine and magnetic studies confirm that magnetic anisotropy plays a crucial role in hexaferrite NPs.

  15. Absence of free carrier and paramagnetism in cobalt-doped ZnO nanoparticles synthesized at low temperature using citrate sol-gel route

    NASA Astrophysics Data System (ADS)

    Sivagamasundari, A.; Pugaze, R.; Chandrasekar, S.; Rajagopan, S.; Kannan, R.

    2013-10-01

    Cobalt-doped ZnO nanoparticles have been synthesized using a simple citrate sol-gel auto-combustion method. The XRD confirms nano-single phase and Wurtzite structure. Increased cobalt solubility from 15 to 20 % was observed in ZnO matrix due to low temperature synthesis. Room temperature paramagnetic contribution is observed for all the samples, since cobalt is a neutral dopant and no free carriers are produced. Normally, ferromagnetism is observed in ZnO due to carrier mediated interaction between transition metal ions and free carriers. Hence no ferromagnetism was observed and only paramagnetism was observed due to non-availability of free carriers for long range ferromagnetic interaction in our system. At higher doping, peak broadening of the highly intense XRD peak (101) was observed indicating formation of cobalt cluster (metal-metal) which reduces paramagnetism due to antiferromagnetic interaction and the magnetization value decreases to 0.00456 from 0.0076 emu/g. Absence of photoluminescence peak at 520 nm due to oxygen related defects also supports, the presence of paramagnetism in our samples, since oxygen defects are the another source of ferromagnetism in ZnO. Indirect evidence for the presence of cobalt clustering is also obtained from the photoluminescence studies which lead to concentration quenching of peaks. Photoluminescence studies exhibit NBE peak at 412 nm and defect peaks at 471 and 672 nm. The intensity of red emission peak at 672 nm remains constant whereas the intensity of the peaks at 412 and 471 nm increases and then decreases due to doping induced disorder leading to concentration quenching.

  16. Effect of Ni-Zr codoping on dielectric and magnetic properties of SrFe12O19 via sol-gel route

    NASA Astrophysics Data System (ADS)

    Kuruva, Praveena; Reddy Matli, Penchal; Mohammad, Bououdina; Reddigari, Sandhya; Katlakunta, Sadhana

    2015-05-01

    Nanocrystalline strontium hexaferrites [SrFe12-2x (Ni2+-Zr4+)xO19] nanoparticles were successfully synthesized by sol-gel process. For densification the powders were sintered at 950 C/4 h. The sintered samples were characterized by X-ray diffraction (XRD), surface area measurement, and field emission scanning electron microscope (FESEM). The lattice parameter a is almost constant but c increased with x upto 0.8 and then decreased. The frequency dependent complex permittivity (?? and ??) and permeability (?? and ??) and magnetic properties such as saturation magnetization (Ms), coercive field (Hc) were studied. It is observed that saturation magnetization increased gradually from 57.82 emu/g to 67.2 emu/g as x increased from 0.2 to 0.4 and then decreased from 67.2 emu/g to 31.63 emu/g for x=1.0. In present study, x=0.4 shows high value of Ms 67.2 emu/g. The real part of permittivity (??) remains constant upto a frequency 1 GHz and increases further with an increase of frequency, a resonance and anti-resonance peak was observed above 1 GHz for all the samples. In real part of permeability (??) the relaxation frequency is observed above 1 GHz for all the samples and it is attributed to the domain wall motion. It is well known that the permeability for polycrystalline ferrites can be described as the superposition of two different magnetizing mechanisms: spin rotation and domain wall motion. These low coercive strontium hexaferrites are suitable for magnetic recording applications in hard disks, floppy disks, video tapes, etc.

  17. Sol-gel chemistry by ring-opening polymerization

    SciTech Connect

    RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

    2000-02-07

    Sol-gel processing of materials is plagued by shrinkage during polymerization of the alkoxide monomers and processing (aging and drying) of the resulting gels. The authors have developed a new class of hybrid organic-inorganic materials based on the solventless ring-opening polymerization (ROP) of monomers bearing the 2,2,5,5-tetramethyl-2,5-disilaoxacyclopentyl group, which permits them to drastically reduce shrinkage in sol-gel processed materials. Because the monomers are polymerized through a chain growth mechanism catalyzed by base rather than the step growth mechanism normally used in sol-gel systems, hydrolysis and condensation products are entirely eliminated. Furthermore, since water is not required for hydrolysis, an alcohol solvent is not necessary. Monomers with two disilaoxacyclopentyl groups, separated by a rigid phenylene group or a more flexible alkylene group, were prepared through disilylation of the corresponding diacetylenes, followed by ring closure and hydrogenation. Anionic polymerization of these materials, either neat or with 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane as a copolymer, affords thermally stable transparent gels with no visible shrinkage. These materials provide an easy route to the introduction of sol-gel type materials in encapsulation of microelectronics, which they have successfully demonstrated.

  18. Encapsulation of enzymes and cells in sol-gel matrices for biosensor applications

    NASA Astrophysics Data System (ADS)

    Singh, Anup K.; Gupta, Alok; Mulchandani, Ashok; Chen, Wilfred; Bhatia, Rimple B.; Schoeniger, Joseph S.; Ashley, Carol S.; Brinker, C. J.

    1999-12-01

    Porous silicate materials made by low temperature sol-gel process are promising host matrices for encapsulation of biomolecules. Their mechanical strength, chemical inertness, hydrophilic nature, and above all, their optical transparency makes them an exciting platform for development of biosensors. To date, researchers have focused on sol-gel routes using alkoxides for encapsulation of biomolecules. However, formation of alcohol as a byproduct is an undesired complication as it can have detrimental effect on the activity of entrapped biomolecules. We have developed a novel sol-gel process to encapsulate biological molecules (such as enzymes, antibodies and cells) that uses neutral pH, room temperature, and does not generate alcohol as a byproduct. The process uses sodium silicate as precursor and is carried out in two steps--preparation of a low pH silicate sol followed by gelation at neutral pH in a buffer containing biomolecules. We developed a novel homogeneous immunoassay for 2,4,6-trinitrotoluene (TNT), and have encapsulated the immunoassay reagents in sol-gel matrices to product dispersible biosensors for the detection of TNT. Using the sol-gel doped with immunoassay reagents, we can detect TNT at low ppm levels. We also report encapsulation of E. Coli cells expressing the enzyme organophosphorus hydrolase on the cell surface in sol-gel matrices. The cell- doped sol-gel material can be used to develop biosensors for detection of organophosphates.

  19. Sol-gel antireflective coating on plastics

    DOEpatents

    Ashley, C.S.; Reed, S.T.

    1988-01-26

    An antireflection film made from reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

  20. Sol-gel deposited electrochromic coatings

    SciTech Connect

    Ozer, N.; Lampert, C.M.

    1995-06-01

    Electrochromic devices have increasing application in display devices, switchable mirrors and smart windows. A variety of vacuum deposition technologies have been used to make electrochromic devices. The sol- gel process offers an alternative approach to the synthesis of optical quality and low cost electrochromic device layers. This study summarizes the developments in sol-gel deposited electrochromic films. The sol-gel process involves the formation of oxide networks upon hydrolysis-condensation of alkoxide precursors. In this study we cover the sol-gel deposited oxides of WO[sub 3], V[sub 2]O[sub 5], TiO[sub 2], Nb[sub 2]O[sub 5], and NiO[sub x].

  1. Sol-gel antireflective coating on plastics

    DOEpatents

    Ashley, Carol S. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM)

    1990-01-01

    An antireflection film made from a reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

  2. Arylene-bridged 2,2,5,5-tetramethyl2,5-disila-1-oxacyclopentanes as precursors to non-shrinking polysiloxanes. A new route to sol-gel type polymers

    SciTech Connect

    Rahimian, K.; Loy, D.A.

    1998-11-01

    Sol-gel chemistry has been the focus of much attention in the design and preparation of highly crosslinked polysiloxane gels. Preparation of sol-gel processed silica or polysilesquioxane gels is carried out by the hydrolysis and condensation of alkoxysilyl monomers, usually in the presence of catalytic acid or base and an excess of water. Removal of the alcohol and water byproducts of the condensation reactions, in addition to the alcohol needed to co-dissolve the hydrophobic monomers with water, leads to substantial shrinkage during drying of the resulting gels. This limits the utility of sol-gel processing for applications requiring net-shape casting of artifacts, crack free coatings, or low vaporous organic contaminants (VOCs). It would be advantageous to have a sol-gel process based on an organosilicon monomer that would not require water as a reactant or produce water and alcohol condensation products and still result in siloxane network polymers capable of forming gels. Here, the authors show the synthesis and preparation of a novel sol-gel monomer which can easily be polymerized by ring opening polymerization to give highly crosslinked polysiloxane gels with no condensation byproducts.

  3. Sol-Gels for Optical Sensors

    NASA Astrophysics Data System (ADS)

    Podbielska, Halina; Ulatowska-Jarża, Agnieszka; Müller, Gerhard; Eichler, Hans J.

    Sol-gel process allows for formation of glassy and ceramics materials in temperatures much lower than offered by conventional melting techniques. The first paper on sol-gels was published over 150 years ago by Ebelmen, however, the rapid development of this technology and applications occurred in the last few years. There is a broad range of possible applications of solgel derived materials, what marked this technology as one of the most promising fields of contemporary material sciences

  4. The Influence of Microgravity on Silica Sol-Gel Formation

    NASA Technical Reports Server (NTRS)

    Sibille, L.; Smith, D. D.; Cronise, R.; Hunt, A. J.; Wolfe, D. B.; Snow, L. A.; Oldenberg, S.; Halas, N.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We discuss space-flight experiments involving the growth of silica particles and gels. The effect of microgravity on the growth of silica particles via the sol-gel route is profound. In four different recipes spanning a large range of the parameter space that typically produces silica nanoparticles in unit-gravity, low-density gel structures were instead formed in microgravity. The particles that did form were generally smaller and more polydisperse than those grown on the ground. These observations suggest that microgravity reduces the particle growth rate, allowing unincorporated species to form aggregates and ultimately gel. Hence microgravity favors the formation of more rarefied structures, providing a bias towards diffusion-limited cluster-cluster aggregation. These results further suggest that in unit gravity, fluid flows and sedimentation can significantly perturb sol-gel substructures prior to gelation and these deleterious perturbations may be "frozen" into the resulting microstructure. Hence, sol-gel pores may be expected to be smaller, more uniform, and less rough when formed in microgravity.

  5. Optimisation of a sol-gel synthesis route for the preparation of MgF2 particles for a large scale coating process.

    PubMed

    Scheurell, K; Noack, J; König, R; Hegmann, J; Jahn, R; Hofmann, Th; Löbmann, P; Lintner, B; Garcia-Juan, P; Eicher, J; Kemnitz, E

    2015-12-01

    A synthesis route for the preparation of optically transparent magnesium fluoride sols using magnesium acetate tetrahydrate as precursor is described. The obtained magnesium fluoride sols are stable for several months and can be applied for antireflective coatings on glass substrates. Reaction parameters in the course of sol synthesis are described in detail. Thus, properties of the precursor materials play a crucial role in the formation of the desired magnesium fluoride nanoparticles, this is drying the precursor has to be performed under defined mild conditions, re-solvation of the dried precursor has to be avoided and addition of water to the final sol-system has to be controlled strictly. Important properties of the magnesium fluoride sols like viscosity, particle size distribution, and structural information are presented as well. PMID:26402297

  6. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, J.M.

    1993-04-20

    Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

  7. Neutron detector using sol-gel absorber

    DOEpatents

    Hiller, John M. (Oak Ridge, TN); Wallace, Steven A. (Oak Ridge, TN); Dai, Sheng (Knoxville, TN)

    1999-01-01

    An neutron detector composed of fissionable material having ions of lithium, uranium, thorium, plutonium, or neptunium, contained within a glass film fabricated using a sol-gel method combined with a particle detector is disclosed. When the glass film is bombarded with neutrons, the fissionable material emits fission particles and electrons. Prompt emitting activated elements yielding a high energy electron contained within a sol-gel glass film in combination with a particle detector is also disclosed. The emissions resulting from neutron bombardment can then be detected using standard UV and particle detection methods well known in the art, such as microchannel plates, channeltrons, and silicon avalanche photodiodes.

  8. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, John M. (Albuquerque, NM)

    1992-01-01

    Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

  9. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, John M. (Albuquerque, NM)

    1993-01-01

    Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

  10. Sol-Gel Synthesis Of Aluminoborosilicate Powders

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey; Leiser, Daniel; Selvaduray, Guna

    1992-01-01

    Application of sol-gel process to synthesis of aluminoborosilicate powders shows potential for control of microstructures of materials. Development of materials having enhanced processing characteristics prove advantageous in extending high-temperature endurance of fibrous refractory composite insulation made from ceramic fibers.

  11. Sol-Gel Derived Hafnia Coatings

    NASA Technical Reports Server (NTRS)

    Feldman, Jay D.; Stackpoole, Mairead; Blum, Yigal; Sacks, Michael; Ellerby, Don; Johnson, Sylvia M.; Venkatapathy, Ethiras (Technical Monitor)

    2002-01-01

    Sol-gel derived hafnia coatings are being developed to provide an oxidation protection layer on ultra-high temperature ceramics for potential use in turbine engines (ultra-efficient engine technology being developed by NASA). Coatings using hafnia sol hafnia filler particles will be discussed along with sol synthesis and characterization.

  12. High specific surface area nickel mixed oxide powders LaNiO{sub 3} (perovskite) and NiCo{sub 2}O{sub 4} (spinel) via sol-gel type routes for oxygen electrocatalysis in alkaline media

    SciTech Connect

    El Baydi, M.; Chartier, P.; Koenig, J.F.; Poillerat, G.; Tiwari, S.K.; Singh, R.N.; Rehspringer, J.L.

    1995-04-01

    A novel sol-gel process of preparation of oxide electrocatalysts is investigated to prepare Ni-containing mixed oxides LaNiO{sub 3} and NiCo{sub 2}O{sub 4} at moderate temperatures. High surface area (20-55 m{sup 2} g{sup {minus}1}) powders and high roughness electrodes (30-1500) were obtained. Apparent and real electrocatalytical activity are compared and discussed.

  13. Novel carboxy functionalized sol-gel precursors

    SciTech Connect

    Wolter, H.; Storch, W.; Gellermann, C.

    1996-12-31

    A novel family of inorganic-organic copolymers (ORMOCER`s) derived from urethane- and thioether(meth)acrylate alkoxysilanes has been successfully exploited for a variety of diverse applications. In order to widen the range of applications an additional functionality (carboxy group) has been incorporated int his silane type. Conventional sol-gel processing facilitates the formation of an inorganic Si-O-Si-network via hydrolysis and polycondensation reactions of alkoxysilyl moieties and in addition, the (meth)acrylate groups are available for radically induced polymerization to obtain a complementary organic polymer structure. The presence of a carboxy group would appear to have great potential for a range of diverse areas of application, such as an internal catalyst for the sol-gel process, complexation of elements such as Zr and Ti, increasing the adhesion to various substrates and modification of solubility. A number of novel silanes and their syntheses will be described in this paper.

  14. Ring-Resonator/Sol-Gel Interferometric Immunosensor

    NASA Technical Reports Server (NTRS)

    Bearman, Gregory; Cohen, David

    2007-01-01

    A proposed biosensing system would be based on a combination of (1) a sensing volume containing antibodies immobilized in a sol-gel matrix and (2) an optical interferometer having a ring resonator configuration. The antibodies would be specific to an antigen species that one seeks to detect. In the ring resonator of the proposed system, light would make multiple passes through the sensing volume, affording greater interaction length and, hence, greater antibody- detection sensitivity.

  15. Sol-gel manufactured energetic materials

    DOEpatents

    Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

    2003-12-23

    Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

  16. Sol-gel based optical chemical sensors

    NASA Astrophysics Data System (ADS)

    Lobnik, Aleksandra; Korent Urek, pela; Turel, Matejka; Fran?i?, Nina

    2011-05-01

    The growing activity in the field of optical chemical sensors has resulted in numerous sensing schemes, new indicator dyes, various polymeric matrix, size and shapes and highly diversified methods of immobilization. The sensor characteristics are dependent upon the choice of indicator, polymer, immobilization technique, and also size. Sol-gel technology provides a low-temperature method for obtaining porous silicate glass matrices. It enables to obtain material in the form of films, powders, monoliths, fibres or nanoparticles. Organic reagents and molecular receptors can be easily immobilized in the matrices. Moreover, one of the unique features of the sol-gel process is that the properties of the final network structure, such as hydrophobicity, thickness, porosity, flexibility, reactivity and stability can be easily tailored by controlling the process conditions, the type and the size of the precursors and catalysis. Here we will report about several sensor designed over the years based on sol-gel materials for monitoring and controlling different parameters, such as heavy metals, amines, phosphates, organophosphates.

  17. Sol-Gel Manufactured Energetic Materials

    DOEpatents

    Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

    2005-05-17

    Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

  18. Strip-loaded sol-gel waveguides for optical amplifiers

    NASA Astrophysics Data System (ADS)

    Forastiere, Michele A.; Guglielmi, Massimo; Martucci, Alessandro; Ahmad, Munir M.; McCarthy, O.; Pelli, Stefano; Righini, Giancarlo C.; Vannucci, A.; Yeatman, Eric M.

    1999-04-01

    Among the various possible production techniques of silica- on-silicon integrated optical devices, sol-gel is the one which combines low cost with a great flexibility and the ease of doping the silica matrix with nonlinear and active compounds. In the frame of an European project, we have investigated the application of the sol-gel technique to the realization of an erbium-doped optical amplifier, operating in the third telecommunication window. Here, in particular, we refer to the development of an optimum fabrication strategy for the guiding structure. A strip-loaded configuration was chosen. Design optimization was carried out by means of a MATLAB software code, mainly based on the Effective Index Method. For what concerns the technical side, two different routes were followed: that of the Low Index Load and that of the High Index Load. Pros and cons of both structures were carefully evaluated through numerical simulations as well as experimental analysis, in order to choose the best performing one. Results of the design procedure and the characterization of the fabricated waveguides are described here.

  19. Ionogel Electrolytes through Sol-Gel Processing

    NASA Astrophysics Data System (ADS)

    Horowitz, Ariel I.

    Electrical energy needs have intensified due to the ubiquity of personal electronics, the decarbonization of energy services through electrification, and the use of intermittent renewable energy sources. Despite developments in mechanical and thermal methods, electrochemical technologies are the most convenient and effective means of storing electrical energy. These technologies include both electrochemical cells, commonly called batteries, and electrochemical double-layer capacitors, or "supercapacitors", which store energy electrostatically. Both device types require an ion-conducting electrolyte. Current devices use solutions of complex salts in organic solvents, leading to both toxicity and flammability concerns. These drawbacks can be avoided by replacing conventional electrolytes with room-temperature molten salts, known as ionic liquids (ILs). ILs are non-volatile, non-flammable, and offer high conductivity and good electrochemical stability. Device mass can be reduced by combining ILs with a solid scaffold material to form an "ionogel," further improving performance metrics. In this work, sol-gel chemistry is explored as a means of forming ionogel electrolytes. Sol-gel chemistry is a solution-based, industrially-relevant, well-studied technique by which solids such as silica can be formed in situ. Previous works used a simple acid-catalyzed sol-gel reaction to create brittle, glassy ionogels. Here, both the range of products that can be accomplished through sol-gel processing and the understanding of interactions between ILs and the sol-gel reaction network are greatly expanded. This work introduces novel ionogel materials, including soft and compliant silica-supported ionogels and PDMS-supported ionogels. The impacts of the reactive formulation, IL identity, and casting time are detailed. It is demonstrated that variations in formulation can lead to rapid gelation and open pore structures in the silica scaffold or slow gelation and more dense silica morphologies. The IL identity is shown to have an impact on the apparent strength of the acid catalyst, leading to significant shifts in gelation time. Delayed casting is proven to be an optimal technique for avoiding pore blockage when combining ionogels with high surface area electrodes for supercapacitor applications. Finally, a simple recycling process is proposed, establishing that ILs can be easily reclaimed from silica-supported ionogels and reused, thereby validating the reputation of ILs as "green" materials.

  20. Fabrication of Cu2ZnSn(S,Se)4 solar cells via an ethanol-based sol-gel route using SnS2 as Sn source.

    PubMed

    Zhao, Wangen; Wang, Gang; Tian, Qingwen; Yang, Yanchun; Huang, Lijian; Pan, Daocheng

    2014-08-13

    Cu2ZnSn(S,Se)4 semiconductor is a promising absorber layer material in thin film solar cells due to its own virtues. In this work, high quality Cu2ZnSn(S,Se)4 thin films have been successfully fabricated by an ethanol-based sol-gel approach. Different from those conventional sol-gel approaches, SnS2 was used as the tin source to replace the most commonly used SnCl2 in order to avoid the possible chlorine contamination. In addition, sodium was found to improve the short-circuit current and fill factor rather than the open-circuit voltage due to the decrease of the thickness of small-grained layer. The selenized Cu2ZnSn(S,Se)4 thin films showed large densely packed grains and smooth surface morphology, and a power conversion efficiency of 6.52% has been realized for Cu2ZnSn(S,Se)4 thin film solar cell without antireflective coating. PMID:25000474

  1. Sol-gel processing to form doped sol-gel monoliths inside hollow core optical fiber and sol-gel core fiber devices made thereby

    NASA Technical Reports Server (NTRS)

    Shaw, Harry C. (Inventor); Ott, Melanie N. (Inventor); Manuel, Michele V. (Inventor)

    2002-01-01

    A process of fabricating a fiber device includes providing a hollow core fiber, and forming a sol-gel material inside the hollow core fiber. The hollow core fiber is preferably an optical fiber, and the sol-gel material is doped with a dopant. Devices made in this manner includes a wide variety of sensors.

  2. Er3+-activated photonic structures fabricated by sol-gel and rf-sputtering techniques

    NASA Astrophysics Data System (ADS)

    Ferrari, M.; Alombert-Goget, G.; Armellini, C.; Berneschi, S.; Bhaktha, S. N. B.; Boulard, B.; Brenci, M.; Chiappini, A.; Chiasera, A.; Duverger-Arfuso, C.; Fron, P.; Gonalves, R. R.; Jestin, Y.; Minati, L.; Moser, E.; Nunzi Conti, G.; Pelli, S.; Rao, D. N.; Retoux, R.; Righini, G. C.; Speranza, G.

    2009-05-01

    The realization of photonic structures operating at visible and near infrared frequencies is a highly attractive scientific and technological challenge. Since optical fiber innovation, a huge of activity has been performed leading to interesting results, such as optical waveguides and planar lightwave circuits, microphotonic devices, optical microcavities, nanowires, plasmonic structures, and photonic crystals. These systems have opened new possibilities in the field of both basic and applied physics, in a large area covering Information Communication Technologies, Health and Biology, Structural Engineering, and Environment Monitoring Systems. Several materials and techniques are employed to successfully fabricate photonic structures. Concerning materials, Er3+-activated silica-based glasses still play an important role, although recently interesting results have been published about fluoride glass-ceramic waveguides. As far as regards the fabrication methods sol-gel route and rf sputtering have proved to be versatile and reliable techniques. In this article we will present a review of some Er3+-activated photonic structures fabricated by sol gel route and rf sputtering deposition. In the discussion on the sol-gel approach we focus our attention on the silica-hafnia binary system presenting an overview concerning fabrication protocols and structural, optical and spectroscopic assessment of SiO2-HfO2 waveguides activated by Er3+ ions. In order to put in evidence the reliability and versatility of the sol-gel route for photonics applications four different confined structures are briefly presented: amorphous waveguides, coated microspheres, monolithic waveguide laser, and core-shell nanospheres. As examples of rf sputtering technique, we will discuss Er3+-activated silica-hafnia and silica-germania waveguides, the latter system allowing fabrication of integrated optics structures by UV photo-imprinting. Finally, two examples of photonic crystal structures, one prepared by sol-gel process and the other one fabricated by rf sputtering deposition, will be illustrated.

  3. Substituent effects on the sol-gel chemistry of organotrialkoxysilanes

    SciTech Connect

    LOY, DOUGLAS A.; BAUGHER, BRIGITTA M.; BAUGHER, COLLEEN R.; SCHNEIDER, DUANE A.; RAHIMIAN, KAMYAR

    2000-05-09

    Silsesquioxanes have been the subject of intensive study in the past and are becoming important again as a vehicle for introducing organic functionalities into hybrid organic-inorganic materials through sol-gel processing. Depending on the application, the target hybrid material may be required to be a highly cross-linked, insoluble gel or a soluble polymer that can be cast as a thin film or coating. The former has applications such as catalyst supports and separations media; the latter is an economically important method for surface modification or compatiblization for applying adhesives or introducing fillers. Polysilsesquioxanes are readily prepared through the hydrolysis and condensation of organotrialkoxysilanes, though organotriaminosilane and organotrihalosilane monomers can also be used. This paper explores the kinetics of the preparation route.

  4. Laser processing of sol-gel coatings for infrared applications

    NASA Astrophysics Data System (ADS)

    Li, Guanming; Burggraf, Larry W.

    1997-10-01

    A new laser processing technique was proposed and demonstrated for producing high-temperature sol-gel coatings on substrates like ZnSe or chalcogenide infrared fibers which cannot be exposed to relatively high temperatures involved in most sol- gel processes. Our approach is similar to the 'indirect writing' technique except that an air gap is inserted between the sol-gel coating and the light absorber so as not to affect the optical coating. Our processing technique integrates optical sol-gel coatings having tailored properties of porosity, surface area, and surface affinity with substrate materials used for integrated and fiber optic infrared technologies such as optical sensors.

  5. Sol-gel method for encapsulating molecules

    DOEpatents

    Brinker, C. Jeffrey (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Bhatia, Rimple (Albuquerque, NM); Singh, Anup K. (San Francisco, CA)

    2002-01-01

    A method for encapsulating organic molecules, and in particular, biomolecules using sol-gel chemistry. A silica sol is prepared from an aqueous alkali metal silicate solution, such as a mixture of silicon dioxide and sodium or potassium oxide in water. The pH is adjusted to a suitably low value to stabilize the sol by minimizing the rate of siloxane condensation, thereby allowing storage stability of the sol prior to gelation. The organic molecules, generally in solution, is then added with the organic molecules being encapsulated in the sol matrix. After aging, either a thin film can be prepared or a gel can be formed with the encapsulated molecules. Depending upon the acid used, pH, and other processing conditions, the gelation time can be from one minute up to several days. In the method of the present invention, no alcohols are generated as by-products during the sol-gel and encapsulation steps. The organic molecules can be added at any desired pH value, where the pH value is generally chosen to achieve the desired reactivity of the organic molecules. The method of the present invention thereby presents a sufficiently mild encapsulation method to retain a significant portion of the activity of the biomolecules, compared with the activity of the biomolecules in free solution.

  6. Beta zeolite supported sol-gel TiO2 materials for gas phase photocatalytic applications.

    PubMed

    Lafjah, Mama; Djafri, Fatiha; Bengueddach, Abdelkader; Keller, Nicolas; Keller, Valrie

    2011-02-28

    Beta zeolite supported sol-gel TiO(2) photocatalytic materials were prepared according to a sol-gel route in which high specific surface area Beta zeolite powder was incorporated into the titanium isopropoxide sol during the course of the sol-gel process. This led to an intimate contact between the zeolite surface and the TiO(2) precursors, and resulted in the anchorage of large amounts of dispersed TiO(2) nanoparticles and in the stabilization of TiO(2) in its anatase form, even for high TiO(2) wt. contents and high calcination temperatures. Taking the UV-A photocatalytic oxidation of methanol as gas phase target reaction, high methanol conversions were obtained on the Beta zeolite supported TiO(2) photocatalysts when compared to bulk sol-gel TiO(2), despite lower amounts of TiO(2) within the photoactive materials. The methanol conversion was optimum for about 40 wt.% TiO(2) loading and calcination temperatures of 500-600C. PMID:21177024

  7. Biocatalysis with Sol-Gel Encapsulated Acid Phosphatase

    ERIC Educational Resources Information Center

    Kulkarni, Suhasini; Tran, Vu; Ho, Maggie K.-M.; Phan, Chieu; Chin, Elizabeth; Wemmer, Zeke; Sommerhalter, Monika

    2010-01-01

    This experiment was performed in an upper-level undergraduate biochemistry laboratory course. Students learned how to immobilize an enzyme in a sol-gel matrix and how to perform and evaluate enzyme-activity measurements. The enzyme acid phosphatase (APase) from wheat germ was encapsulated in sol-gel beads that were prepared from the precursor…

  8. Biocatalysis with Sol-Gel Encapsulated Acid Phosphatase

    ERIC Educational Resources Information Center

    Kulkarni, Suhasini; Tran, Vu; Ho, Maggie K.-M.; Phan, Chieu; Chin, Elizabeth; Wemmer, Zeke; Sommerhalter, Monika

    2010-01-01

    This experiment was performed in an upper-level undergraduate biochemistry laboratory course. Students learned how to immobilize an enzyme in a sol-gel matrix and how to perform and evaluate enzyme-activity measurements. The enzyme acid phosphatase (APase) from wheat germ was encapsulated in sol-gel beads that were prepared from the precursor

  9. Investigations of the small-scale thermal behavior of sol-gel thermites.

    SciTech Connect

    Warren, Mial E.; Farrow, Matthew; Tappan, Alexander Smith

    2009-02-01

    Sol-gel thermites, formulated from nanoporous oxides and dispersed fuel particles, may provide materials useful for small-scale, intense thermal sources, but understanding the factors affecting performance is critical prior to use. Work was conducted on understanding the synthesis conditions, thermal treatments, and additives that lead to different performance characteristics in iron oxide sol-gel thermites. Additionally, the safety properties of sol-gel thermites were investigated, especially those related to air sensitivity. Sol-gel thermites were synthesized using a variety of different techniques and there appear to be many viable routes to relatively equivalent thermites. These thermites were subjected to several different thermal treatments under argon in a differential scanning calorimeter, and it was shown that a 65 C hold for up to 200 minutes was effective for the removal of residual solvent, thus preventing boiling during the final thermal activation step. Vacuum-drying prior to this heating was shown to be even more effective at removing residual solvent. The addition of aluminum and molybdenum trioxide (MoO{sub 3}) reduced the total heat release per unit mass upon exposure to air, probably due to a decrease in the amount of reduced iron oxide species in the thermite. For the thermal activation step of heat treatment, three different temperatures were investigated. Thermal activation at 200 C resulted in increased ignition sensitivity over thermal activation at 232 C, and thermal activation at 300 C resulted in non-ignitable material. Non-sol-gel iron oxide did not exhibit any of the air-sensitivity observed in sol-gel iron oxide. In the DSC experiments, no bulk ignition of sol-gel thermites was observed upon exposure to air after thermal activation in argon; however ignition did occur when the material was heated in air after thermal treatment. In larger-scale experiments, up to a few hundred milligrams, no ignition was observed upon exposure to air after thermal activation in vacuum; however ignition by resistively-heated tungsten wire was possible. Thin films of thermite were fabricated using a dispersed mixture of aluminum and iron oxide particles, but ignition and propagation of these films was difficult. The only ignition and propagation observed was in a preheated sample.

  10. Sol-gel processing of energetic materials

    SciTech Connect

    Tillotson, T.M.; Hrubesh, L.H.; Fox, G.L.; Simpson, R.L.; Lee, R.W.; Swansiger, R.W.; Simpson, L.R.

    1997-08-18

    As part of a new materials effort, we are exploring the use of sol- gel chemistry to manufacture energetic materials. Traditional manufacturing of energetic materials involves processing of granular solids. One application is the production of detonators where powders of energetic material and a binder are typically mixed and compacted at high pressure to make pellets. Performance properties are strongly dependent on particle size distribution, surface area of its constituents, homogeneity of the mix, and void volume. The goal is to produce detonators with fast energy release rate the are insensitive to unintended initiation. In this paper, we report results of our early work in this field of research, including the preparation of detonators from xerogel molding powders and aerogels, comparing the material properties with present state-of-the-art technology.

  11. Effect of annealing temperature on optical properties of binary zinc tin oxide nano-composite prepared by sol-gel route using simple precursors: Structural and optical studies by DRS, FT-IR, XRD, FESEM investigations

    NASA Astrophysics Data System (ADS)

    Habibi, Mohammad Hossein; Mardani, Maryam

    2015-02-01

    Binary zinc tin oxide nano-composite was synthesized by a facile sol-gel method using simple precursors from the solutions consisting of zinc acetate, tin(IV) chloride and ethanol. Effect of annealing temperature on optical and structural properties was investigated using X-ray diffraction (XRD), diffuse reflectance spectra (DRS), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). XRD results revealed the existence of the ZnO and SnO2 phases. FESEM results showed that binary zinc tin oxide nano-composites ranges from 56 to 60 nm in diameter at 400 C and 500 C annealing temperatures respectively. The optical band gap was increased from 2.72 eV to 3.11 eV with the increasing of the annealing temperature. FTIR results confirmed the presence of zinc oxide and tin oxide and the broad absorption peaks at 3426 and 1602 cm-1 can be ascribed to the vibration of absorptive water, and the absorption peaks at 546, 1038 and 1410 cm-1 are due to the vibration of Zn-O or Sn-O groups in binary zinc tin oxide.

  12. Solid-state NMR study of geopolymer prepared by sol-gel chemistry

    SciTech Connect

    Tsai, Yi-Ling; Hanna, John V.; Lee, Yuan-Ling; Smith, Mark E.; Chan, Jerry C.C.

    2010-12-15

    Geopolymers are a new class of materials formed by the condensation of aluminosilicates and silicates obtained from natural minerals or industrial wastes. In this work, the sol-gel method is used to synthesize precursor materials for the preparation of geopolymers. The geopolymer samples prepared by our synthetic route have been characterized by a series of physical techniques, including Fourier-transform infrared, X-ray diffraction, and multinuclear solid-state NMR. The results are very similar to those obtained for the geopolymers prepared from natural kaolinite. We believe that our synthetic approach can offer a good opportunity for the medical applications of geopolymer. -- Graphical abstract: Geopolymer prepared by the sol-gel route has the same spectroscopic properties as the sample prepared from the natural kaolinite. Display Omitted

  13. Functionalized sol-gel coatings for optical applications.

    PubMed

    Pnard, Anne-Laure; Gacoin, Thierry; Boilot, Jean-Pierre

    2007-09-01

    Sol-gel processing is well-known to be a powerful technique for designing materials for optical applications. Here, some recent applications of functionalized sol-gel coatings in optics are briefly reviewed. Lanthanide-doped oxide nanocrystals form a new promising class of nanophosphors allowing the easy sol-gel preparation of transparent and luminescent films for the development of light-emitting devices. Recent experiments on organized mesoporous films show their potential applications in optics, such as stable low-index layers in interferential antireflective devices or as silica binders in TiO 2-photocatalytic devices. PMID:17330964

  14. A pure silica ytterbium-doped sol-gel-based fiber laser

    NASA Astrophysics Data System (ADS)

    Baz, Assaad; El Hamzaoui, Hicham; Fsaifes, Ihsan; Bouwmans, Graud; Bouazaoui, Mohamed; Bigot, Laurent

    2013-05-01

    In this letter it is demonstrated that the sol-gel route combined with fiber fabrication by the stack and draw method can be used to realize efficient fiber lasers. More precisely, a pure silica ytterbium-doped photonic crystal fiber with a core obtained by the sol-gel polymeric technique is studied, and a laser efficiency of more than 73% is achieved for a laser emission around 1034 nm. The optical and spectroscopic properties of the monolith and fiber are investigated, together with the sensitivity of the fiber to photodarkening. The dimensions of the ytterbium-doped monolith combined with the uniform doping and refractive index that are reported make this technique particularly interesting for the realization of large-mode area fibers.

  15. Electrophoretic Porosimetry of Sol-Gels

    NASA Technical Reports Server (NTRS)

    Snow, L. A.; Smith, D. D.; Sibille, L.; Hunt, A. J.; Ng, J.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    It has been hypothesized that gravity has an effect on the formation and resulting microstructure of sol-gels. In order to more clearly resolve the effect of gravity, pores may be non-destructively analyzed in the wet gel, circumventing the shrinkage and coarsening associated with the drying procedure. We discuss the development of an electrophoretic technique, analogous to affinity chromatography, for the determination of pore size distribution and its application to silica gels. Specifically a monodisperse charged dye is monitored by an optical densitometer as it moves through the wet gel under the influence of an electric field. The transmittance data (output) represents the convolution of the dye concentration profile at the beginning of the run (input) with the pore size distribution (transfer function), i.e. linear systems theory applies. Because of the practical difficulty in producing a delta function input dye profile we prefer instead to use a step function. Average pore size is then related to the velocity of this dye front, while the pore size distribution is related to the spreading of the front. Preliminary results of this electrophoretic porosimetry and its application to ground and space-grown samples will be discussed.

  16. Sol-gel-derived percolative copper film

    SciTech Connect

    Szu Sungping Cheng, C.-L.

    2008-10-02

    Cu-SiO{sub 2} films were prepared by the sol-gel method. Two-dimensional fractal copper films were formed after the films were thermally treated in reducing atmosphere. dc resistances of the films decrease 12 orders of magnitude as the content of copper increases from 70 to 80 mol%. During the resistance measurement under argon atmosphere, samples showed a sharp increase or decrease of resistance at a transition temperature which is ascribed to the oxidation of Cu into CuO. The oxidation was also observed in the in situ high temperature X-ray diffraction under vacuum condition. The evolution of the morphology of the films was studied by scanning electron microscopy. As the content of copper increases, the forms of copper particles change from discrete to aggregate then to interconnecting. The coverage coefficients of the copper range from 23 to 55% and the fractal dimensions range from 1.65 to 1.77. The percolation thresholds for the coverage coefficient and the fractal dimension are about 33% and 1.71, respectively, which corresponds to the sample containing 72.5 mol% of Cu.

  17. Dip coating of sol-gels

    SciTech Connect

    Schunk, P.R.; Hurd, A.J.; Brinker, C.J.

    1991-01-01

    Dip coating is the primary means of depositing sol-gel films for precision optical coatings. Sols are typically multicomponent systems consisting of an inorganic phase dispersed in a solvent mixture, with each component differing in volatility and surface tension. This, together with slow coating speeds (<1cm/s), makes analysis of the coating process complicated; unlike most high-speed coating methods, solvent evaporation, evolving rheology, and surface tension gradients alter significantly the fluid mechanics of the deposition stage. We set out to understand these phenomena with computer-aided predictions of the flow and species transport fields. The underlying theory involves mass, momentum, and species transport on a domain of unknown shape, with models and constitutive equations for vapor-liquid equilibria and surface tension. Due accounting is made for the unknown position of the free surface, which locates according to the capillary hydrodynamic forces and solvent loss by evaporation. Predictions of the effects of mass transfer, hydrodynamics, and surface tension gradients on final film thickness are compared with ellipsometry measurements of film thickness on a laboratory pilot coater. Although quantitative agreement is still lacking, both experiment and theory reveal that the film profile near the drying line takes on a parabolic shape. 2 refs., 2 figs.

  18. Production of continuous mullite fiber via sol-gel processing

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Sparks, J. Scott; Esker, David C.

    1990-01-01

    The development of a continuous ceramic fiber which could be used in rocket engine and rocket boosters applications was investigated at the Marshall Space Flight Center. Methods of ceramic fiber production such as melt spinning, chemical vapor deposition, and precursor polymeric fiber decomposition are discussed and compared with sol-gel processing. The production of ceramics via the sol-gel method consists of two steps, hydrolysis and polycondensation, to form the preceramic, followed by consolidation into the glass or ceramic structure. The advantages of the sol-gel method include better homogeneity and purity, lower preparation temperature, and the ability to form unique compositions. The disadvantages are the high cost of raw materials, large shrinkage during drying and firing which can lead to cracks, and long processing times. Preparation procedures for aluminosilicate sol-gel and for continuous mullite fibers are described.

  19. Sol-gel fluxes for flux cored welding consumables

    SciTech Connect

    Dunn, P.S.; Natalie, C.A.; Olson, D.L.

    1986-09-01

    The feasibility of producing high purity homogeneous welding fluxes by the sol-gel process and the effects that these fluxes have on the welding process were determined. Reagent grade sol-gel welding fluxes were produced by making systematic variations of the SiO/sub 2/-CaO-TiO/sub 2/-1 pct Na/sub 2/O flux system. The resulting fluxes were made into flux cored wires and used to make bead on plate welds on a niobium microalloyed HSLA steel. Sol-gel fluxes were shown to have excellent homogeneity, low residual hydrogen content, and no apparent water adsorption. The welding behaviour of the sol-gel fluxes was shown to have superior arc stability compared to a commercial flux cored wire and very low weld metal hydrogen content.

  20. Sol-gel-based biosensing applied to medicinal science.

    PubMed

    Moreira, Felismina T C; Moreira-Tavares, Ana P; Sales, M Goreti F

    2015-01-01

    Biosensors have opened new horizons in biomedical analysis, by ensuring increased assay speed and flexibility, and allowing point-of-care applications, multi-target analyses, automation and reduced costs of testing. This has been a result of many studies merging nanotechnology with biochemistry over the years, thereby enabling the creation of more suitable environments to biological receptors and their substitution by synthetic analogue materials. Sol-gel chemistry, among other materials, is deeply involved in this process. Sol-gel processing allows the immobilization of organic molecules, biomacromolecules and cells maintaining their properties and activities, permitting their integration into different transduction devices, of electrochemical or optical nature, for single or multiple analyses. Sol-gel also allows to the production of synthetic materials mimicking the activity of natural receptors, while bringing advantages, mostly in terms of cost and stability. Moreover, the biocompatibility of sol-gel materials structures of biological nature allowed the use of these materials in emerging in vivo applications. In this chapter, biosensors for biomedical applications based on sol-gel derived composites are presented, compared and described, along with current emerging applications in vivo, concerning drug delivery or biomaterials. Sol-gel materials are shown as a promising tool for current, emerging and future medical applications. PMID:25547971

  1. Enzyme renaturation to higher activity driven by the sol-gel transition: Carbonic anhydrase

    NASA Astrophysics Data System (ADS)

    Vinogradov, Vladimir V.; Avnir, David

    2015-09-01

    We describe a so-far unknown route for renaturing denatured enzymes, namely subjecting the denatured enzyme to an oxide sol-gel transition. The phenomenon was revealed in a detailed study of denatured carbonic anhydrase which was subjected to an alumina sol-gel transition, up to the thermally stabilizing entrapment in the final xerogel. Remarkably, not only that the killed enzyme regained its activity during the sol-gel process, but its activity increased to 180% of the native enzyme. To the best of our knowledge, this is the first report of enhanced activity following by renaturing (a Phoenix effect). Kinetic study which revealed a five-orders of magnitude (!) increase in the Arrhenius prefactor upon entrapment compared to solution. Circular dichroism analysis, differential scanning calorimetry, zeta potential analyses as well as synchronous fluorescence measurements, all of which were used to characterize the phenomenon, are consistent with a proposed mechanism which is based on the specific orienting interactions of the active site of the enzyme with respect to the alumina interface and its pores network.

  2. Enzyme renaturation to higher activity driven by the sol-gel transition: Carbonic anhydrase

    PubMed Central

    Vinogradov, Vladimir V.; Avnir, David

    2015-01-01

    We describe a so-far unknown route for renaturing denatured enzymes, namely subjecting the denatured enzyme to an oxide sol-gel transition. The phenomenon was revealed in a detailed study of denatured carbonic anhydrase which was subjected to an alumina sol-gel transition, up to the thermally stabilizing entrapment in the final xerogel. Remarkably, not only that the killed enzyme regained its activity during the sol-gel process, but its activity increased to 180% of the native enzyme. To the best of our knowledge, this is the first report of enhanced activity following by renaturing (a “Phoenix effect”). Kinetic study which revealed a five-orders of magnitude (!) increase in the Arrhenius prefactor upon entrapment compared to solution. Circular dichroism analysis, differential scanning calorimetry, zeta potential analyses as well as synchronous fluorescence measurements, all of which were used to characterize the phenomenon, are consistent with a proposed mechanism which is based on the specific orienting interactions of the active site of the enzyme with respect to the alumina interface and its pores network. PMID:26394694

  3. Conducting antimony-doped tin oxide films derived from stannous oxalate by aqueous sol gel method

    NASA Astrophysics Data System (ADS)

    Liu, Tong Jun; Jin, Zheng Guo; Feng, Li Rui; Wang, Tao

    2008-08-01

    Nanocrystalline SnO 2:Sb films were prepared by a sol-gel route using C 6H 8O 7-triethanolamine (TEA) mixing aqueous solution with pH 6.5-7.0. Stannous oxalate and antimony trichloride were used as tin and antimony sources. IR, XRD FESEM, FETEM, UV-vis and four-point probe measurement were used to characterize sol-gel chemistry, structure, morphologies, optical and electrical properties. Mechanism of sol-gel reaction illuminated that existence of TEA supplied large numbers of active tin hydrate and ionized state carboxyl groups for tin and antimony chelation through the amido association with the ionized H + on -COOH of H 3L and H 2C 2O 4. The 6 at.% Sb-doped films with film thickness of 600 nm had sheet resistance as low as 42.85 ?/ when annealed at 450 C for 10 min. Annealing temperature intensively altered sheet resistance and optimum was in the range of 450-500 C. The longer annealing time caused Sb volatilization which led to the optimum doping level shifted from 6 to 12 at.%.

  4. Hydrophilic and optical properties of nanostructured titania prepared by sol-gel dip coating

    NASA Astrophysics Data System (ADS)

    Ferrara, M. C.; Pilloni, L.; Mazzarelli, S.; Tapfer, L.

    2010-03-01

    Nanostructured titania thin films were prepared under controlled atmospheric conditions by the sol-gel dip-coating technique on glass, fused silica and (1 0 0)-silicon substrates. Two different sol-gel routes were employed by using different precursor solutions, a highly acid solution and a polymer-like solution. The influence of sol composition and of the substrate type on the morphology, coating porosity, surface roughness, crystalline phases and grain size of the titania films were investigated in detail. In addition, the relationship between microstructural/morphological properties and the optical properties (energy gap, refractive index and extinction coefficient) and the hydrophilic performance of the coatings were evaluated. Our experimental results clearly indicate that the sol composition and substrate type remarkably influence the films' morphology and microstructure; moreover, they consequently modify the optical response and hydrophilic performances of the samples, showing that superhydrophilic titania coatings can be obtained opportunely by choosing the composition of the precursor sol-gel solution. Blue shift of the band gap energy and a band structure mutation from indirect to direct were also revealed. The hydrophilic properties and the change in the band gaps transition can be attributed to oxygen vacancies on the surface of the titania nanocrystallites that gives rise to Ti3+ sites and, consequently, to structural changes/defects of the anatase nanoarchitecture. These findings allow us to design and tailor the optical and hydrophilic properties of the titania coatings.

  5. Chemical sensing of copper phthalocyanine sol-gel glass through organic vapors

    SciTech Connect

    Ridhi, R.; Gawri, Isha; Abbas, Saeed J.; Saini, G. S. S.; Tripathi, S. K.

    2015-05-15

    The sensitivities of metallophthalocyanine to vapor phase electron donors has gained significance in many areas and disciplines due to their sensing properties and ease of operation. In the present study the interaction mechanism of organic vapors in Copper Phthalocyanine (CuPc) sol-gel glass has been studied. The interaction mechanism is affected by many factors like morphology, electrical or optical properties of film. CuPc sol-gel glass has been synthesized using chemical route sol-gel method. Its structural characterization was conducted using XRD and the amorphous nature of the silicate glass was observed with characteristic α polymorph phase of CuPc at around 6.64° with 13.30Å interplanar spacing. The size of the particle as determined using Debbye Scherre’s formula comes out around 15.5 nm. The presence of α phase of CuPc was confirmed using FTIR with the appearance of crystal parameter marker band at 787 cm-1. Apart from this A2u and Eu symmetry bands of CuPc have also been observed. The UV absorption spectrum of CuPc exhibits absorption peaks owing to π→ π* and n→ π* transitions. A blue shift in the prepared CuPc glass has been observed as compared to the dopant CuPc salt indicating increase of band gap. A split in B (Soret) band and Q band appears as observed with the help of Lorentzian fitting. CuPc sol gel glass has been exposed with chemical vapors of Methanol, Benzene and Bromine individually and the electrical measurements have been carried out. These measurements show the variation in conductivity and the interaction mechanism has been analyzed.

  6. Sol-gel encapsulation for controlled drug release and biosensing

    NASA Astrophysics Data System (ADS)

    Fang, Jonathan

    The main focus of this dissertation is to investigate the use of sol-gel encapsulation of biomolecules for controlled drug release and biosensing. Controlled drug release has advantages over conventional therapies in that it maintains a constant, therapeutic drug level in the body for prolonged periods of time. The anti-hypertensive drug Captopril was encapsulated in sol-gel materials of various forms, such as silica xerogels and nanoparticles. The primary objective was to show that sol-gel silica materials are promising drug carriers for controlled release by releasing Captopril at a release rate that is within a therapeutic range. We were able to demonstrate desired release for over a week from Captopril-doped silica xerogels and overall release from Captopril-doped silica nanoparticles. As an aside, the antibiotic Vancomycin was also encapsulated in these porous silica nanoparticles and desired release was obtained for several days in-vitro. The second part of the dissertation focuses on immobilizing antibodies and proteins in sol-gel to detect various analytes, such as hormones and amino acids. Sol-gel competitive immunoassays on antibody-doped silica xerogels were used for hormone detection. Calibration for insulin and C-peptide in standard solutions was obtained in the nM range. In addition, NASA-Ames is also interested in developing a reagentless biosensor using bacterial periplasmic binding proteins (bPBPs) to detect specific biomarkers, such as amino acids and phosphate. These bPBPs were doubly labeled with two different fluorophores and encapsulated in silica xerogels. Ligand-binding experiments were performed on the bPBPs in solution and in sol-gel. Ligand-binding was monitored by fluorescence resonance energy transfer (FRET) between the two fluorophores on the bPBP. Titration data show that one bPBP has retained its ligand-binding properties in sol-gel.

  7. Investigations into the structural and down-shifting and up-conversion luminescence properties of Ba2Na1‑3x Er x Nb5O15 (0 ≤ x ≤ 0.06) nanocrystalline phosphor synthesized via sol-gel route

    NASA Astrophysics Data System (ADS)

    Kundu, Swarup; Bhimireddi, Rajasekhar; Mishra, Kavita; Rai, S. B.; Varma, K. B. R.

    2015-10-01

    The present work deals with the structural and efficient down-shifting (DS) and up-conversion (UC) luminescence properties of erbium ion (Er3+) doped nanocrystalline barium sodium niobate (Ba2Na1‑3x Er x Nb5O15, where x = 0, 0.02, 0.04 and 0.06) powders synthesized via novel citrate-based sol-gel route. The monophasic nature of the title compound was confirmed via x-ray powder diffraction followed by FT-IR studies. High-resolution transmission electron microscopy (HRTEM) facilitated the establishment of the nanocrystalline phase and the morphology of the crystallites. The Kubelka–Munk function, based on diffused reflectance studies and carried out on nano-sized crystallites, was employed to obtain the optical band-gap. The synthesized nanophosphor showed efficient DS/PL-photoluminescence and UC luminescence properties, which have not yet been reported so far in this material. The material emits intense DS green emission on excitation with 378 nm radiation. Interestingly, the material gives intense UC emission in the visible region dominated by green emission and relatively weak red emission on 976 nm excitation (NIR laser excitation). Such a dual-mode emitting nanophosphor could be very useful in display devices and for many other applications.

  8. Luminescence properties of Cr-doped silica sol gel glasses

    NASA Astrophysics Data System (ADS)

    Strek, Wieslaw; Lukowiak, Edward; Deren, Przemyslaw J.; Maruszewski, K.; Trabjerg, Ib; Koepke, Czeslaw; Malashkevich, G. E.; Gaishun, Vladimir E.

    1997-11-01

    The emission of Cr-doped silica glass obtained by the sol- gel method is characterized by an orange broad band with a maximum at 610 nm. Its nature is examined by the absorption, excited state absorption, emission, excitation and lifetime measurements over a wide range of temperature and for different concentration of Cr ions. Our measurement show that in spite of fact that the absorption properties of Cr- doped silica sol-gel glass are predominantly associated with Cr4+ centers, the observed in visible range emission can be assigned neither to Cr3+ nor to Cr4+ ions. The discussion of the nature of observed emission was carried out for all possible valencies of the Cr ions. In conclusion is suggested that it may be ascribed to the transitions on the monovalent Cr1+ ion. The reducing agents occurring during the sol-gel process and leading to lowering the Cr valency are discussed.

  9. Sol-gel processed materials in automotive exhaust reduction catalyst

    SciTech Connect

    Narula, C.K.

    1997-12-31

    The sol-gel process offers the advantage of the preparation of high purity materials with a mesoporous pore distribution and high surface area. Such materials have the ideal properties for applications as catalyst supports. However, sol-gel processed materials have not found applications in automotive catalysts due to (1) cost considerations and (2) the loss of beneficial properties of the materials at elevated temperatures. Thus the materials can be used only in applications where temperatures are not extreme or the cost is offset by a reduced use of platinum group metals. In this article, we review work from our laboratories on the application of heterometallic alkoxides as sol-gel precursors which can be employed in several new specialty applications such as electrically heatable catalyst devices, lean burn NO{sub x} catalysts, and microcalorimeter sensors.

  10. Dielectric Bilayer Films Comprising Polar Cyanolated Silica Sol-Gel and Nanoscale Blocking Layer for Energy Storage Applications

    NASA Astrophysics Data System (ADS)

    Kathaperumal, Mohanalingam; Kim, Yunsang; Smith, O'neil; Dindar, Amir; Fuentes-Hernandez, Canek; Hwang, Do-Kyung; Pan, Ming-Jen; Kippelen, Bernard; Perry, Joseph

    2013-03-01

    Organic-inorganic hybrid sol-gel containing polar groups, which can undergo orientational polarization under the influence of an electric field, provide a potential route to processable and rational design of materials for energy storage applications. However, the porous nature of sol-gel films, which significantly lowers breakdown strength, limits the potential of this material for energy storage particularly in high-field applications. In this work, we fabricate and characterize dielectric bilayer films comprising cyanolated silica sol-gel film prepared from 2-cyanoethyltrimethoxysilane (CNETMS) precursor and nanoscale blocking layers, which include amorphous fluoropolymer, SiO2, Al2O3 and ZrO2 deposited by spin casting, electron beam evaporation or atomic layer deposition (ALD). CNETMS films with 50 nm ZrO2 blocking layer exhibit an extractable energy density of 13 J/cm3, which is about a twofold enhancement compared to CNETMS films without blocking layer. The effect of the blocking layer will be discussed in terms of surface morphology, dielectric contrast, i.e. the ratio of relative permittivity between oxide layer and sol-gel film, electric field distribution, breakdown strength and statistics, bias polarity, and loss of the bilayer films.

  11. Optical Sensors for Biomolecules Using Nanoporous Sol-Gel Materials

    NASA Technical Reports Server (NTRS)

    Fang, Jonathan; Zhou, Jing C.; Lan, Esther H.; Dunn, Bruce; Gillman, Patricia L.; Smith, Scott M.

    2004-01-01

    An important consideration for space missions to Mars is the ability to detect biosignatures. Solid-state sensing elements for optical detection of biological entities are possible using sol-gel based biologically active materials. We have used these materials as optical sensing elements in a variety of bioassays, including immunoassays and enzyme assays. By immobilizing an appropriate biomolecule in the sol-gel sensing element, we have successfully detected analytes such as amino acids and hormones. In the case of the amino acid glutamate, the enzyme glutamate dehydrogenase was the immobilized molecule, whereas in the case of the hormone cortisol, an anti-cortisol antibody was immobilized in the sensing element. In this previous work with immobilized enzymes and antibodies, excellent sensitivity and specificity were demonstrated in a variety of formats including bulk materials, thin films and fibers. We believe that the sol-gel approach is an attractive platform for bioastronautics sensing applications because of the ability to detect a wide range of entities such as amino acids, fatty acids, hopanes, porphyrins, etc. The sol-gel approach produces an optically transparent 3D silica matrix that forms around the biomolecule of interest, thus stabilizing its structure and functionality while allowing for optical detection. This encapsulation process protects the biomolecule and leads to a more "rugged" sensor. The nanoporous structure of the sol-gel matrix allows diffusion of small target molecules but keeps larger, biomolecules immobilized in the pores. We are currently developing these biologically active sol-gel materials into small portable devices for on-orbit cortisol detection

  12. Sol-gel processing with inorganic metal salt precursors

    DOEpatents

    Hu, Zhong-Cheng

    2004-10-19

    Methods for sol-gel processing that generally involve mixing together an inorganic metal salt, water, and a water miscible alcohol or other organic solvent, at room temperature with a macromolecular dispersant material, such as hydroxypropyl cellulose (HPC) added. The resulting homogenous solution is incubated at a desired temperature and time to result in a desired product. The methods enable production of high quality sols and gels at lower temperatures than standard methods. The methods enable production of nanosize sols from inorganic metal salts. The methods offer sol-gel processing from inorganic metal salts.

  13. Silica scintillating materials prepared by sol-gel methods

    SciTech Connect

    Werst, D.W.; Sauer, M.C. Jr.; Cromack, K.R.; Lin, Y.; Tartakovsky, E.A.; Trifunac, A.D.

    1993-12-31

    Silica was investigated as a rad-hard alternative to organic polymer hosts for organic scintillators. Silica sol-gels were prepared by hydrolysis of tetramethoxysilane in alcohol solutions. organic dyes were incorporated into the gels by dissolving in methanol at the sol stage of gel formation. The silica sol-gel matrix is very rad-hard. The radiation stability of silica scintillators prepared by this method is dye-limited. Transient radioluminescence was measured following excitation with 30 ps pulses of 20 MeV electrons.

  14. Sol-gel derived PZT films doped with vanadium pentoxide

    SciTech Connect

    Shen Hongfang; Guo Qing; Zhao Zhiman; Cao Guozhong

    2009-11-15

    The present research investigated the sol-gel preparation, dielectric and ferroelectric properties of PZT films doped with 5 mol% vanadium oxide. Stable PZTV sols can be readily formed, and homogeneous, micrometer thick and pinhole-free PZTV films were obtained by using spin coating followed with rapid annealing. The X-ray diffraction patterns revealed that no parasitic or secondary phases were formed in the sol-gel PZT films with the addition of vanadium oxide. The material doped with vanadium pentoxide showed enhanced dielectric constant and remanent polarization with reduced loss tangent and coercive field.

  15. Solid-state NMR study of geopolymer prepared by sol-gel chemistry

    NASA Astrophysics Data System (ADS)

    Tsai, Yi-Ling; Hanna, John V.; Lee, Yuan-Ling; Smith, Mark E.; Chan, Jerry C. C.

    2010-12-01

    Geopolymers are a new class of materials formed by the condensation of aluminosilicates and silicates obtained from natural minerals or industrial wastes. In this work, the sol-gel method is used to synthesize precursor materials for the preparation of geopolymers. The geopolymer samples prepared by our synthetic route have been characterized by a series of physical techniques, including Fourier-transform infrared, X-ray diffraction, and multinuclear solid-state NMR. The results are very similar to those obtained for the geopolymers prepared from natural kaolinite. We believe that our synthetic approach can offer a good opportunity for the medical applications of geopolymer.

  16. Characterization of Hafnia Powder Prepared from an Oxychloride Sol Gel

    SciTech Connect

    McGilvery, Catriona M.; De Gendt, S; Payzant, E Andrew; MacKenzie, M; Craven, A J; McComb, D W

    2011-01-01

    Hafnium containing compounds are of great importance to the semiconductor industry as a replacement for Si(O,N) with a high- gate dielectric. Whilst Hf is already being incorporated into working devices1, much is still to be understood about it. Here we investigate the crystallisation processes and chemistry of bulk HfO2 powders which will aid in interpretation of reactions and crystallisation events occurring in thin films used as gate dielectrics. Amorphous HfO2 powder was prepared via a sol-gel route using hafnium oxychloride (HfOCl2 xH2O) as a precursor. The powders were subjected to various heat treatments and analysed using x-ray diffraction (XRD) and thermal analysis techniques. It was found that a large change in the crystallisation pathway occurred when the sample was heated in an inert environment compared with in air. Instead of the expected monoclinic phase (m-HfO2), tetragonal HfO2 (t-HfO2) also formed under these conditions and was observed up to temperatures of ~760 C. The t-HfO2 particles, which are less than 30nm in size, eventually transform into m-HfO2 on further heating. Possible mechanisms for the crystallisation of t-HfO2 are discussed. It is proposed that within this temperature range t-HfO2 is stabilised due to the presence of oxygen vacancies in the inert environment, forming by the reduction of HfIV to HfIII. As the crystal grows in size as the temperature increases there are too few oxygen vacancies left in the structure to continue stabilising the t-HfO2 phase and so transformation to m-HfO2 occurs.

  17. Distributed feedback dye-doped sol-gel silica lasers

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaolei

    Solid state dye lasers with narrow linewidth and short pulse duration have attracted increasing attention because of their potential applications. Distributed feedback (DFB) laser is an effective compact coherent light source capable of tunable output with narrow linewidth. In this dissertation, lasing characteristics of dye doped sol-gel silica distributed feedback lasers have been investigated. The optical properties of sol-gel silica deduced from measurements of DFB laser output have also been studied. High optical homogeneity sol-gel silica slabs doped with desired concentration of Rhodamine 6G (MG), Coumarin 460 (C460), or Exalite 377E (E377) dye have been fabricated. Spatial periodic gain modulation in the dye doped sol-gel silica slab was created by crossing the diffracted pump beams from a holographic grating (1800 lines/mm) used as a beam splitter. Tunable laser emission in the yellow, the blue, and in the near ultraviolet region has been generated from the distributed feedback geometry using sol-gel silica slabs doped with R6G, C460 or E377 dye respectively. Wavelength tuning range of approximately 20 nm around the emission centers (562 nm, 480 nm, 376 nm) has been realized by varying the pump beams intersection angle. The laser linewidth was of the order of 60~80 pm when pump energy was several times over the threshold. Laser pulse trains with sub-nanosecond spikes were induced. A slope efficiency of approximately 4.5% has been obtained. The time behavior of distributed feedback R6G doped sol- gel silica laser has been studied using a N2 laser as the pump source. Sub-nanosecond pulse duration has been obtained. The pulse number in the output pulse train is sensitive to the pump energy. Experimental results of the time behavior are in good agreement with theoretical calculations. The lasing performance of tunable distributed feedback dye-doped sol-gel silica laser operating at different Bragg scattering order (M = 1, 2, 3) has also been studied. Distributed feedback laser operating at higher Bragg scattering order was observed at higher pump energy threshold and with lower energy conversion efficiency. The energy conversion efficiency of 0.7% (for M = 3) and 11% (for M = 2) has been achieved. Based on the Bragg scattering condition and the temperature dependence of the refractive index (?) of the gain medium, temperature tuning of the laser output was realized in experiment from the distributed feedback R6G doped sol-gel silica/PMMA lasers. Wavelength tuning from 573 nm to 556 mm has been demonstrated by varying the temperature from 21C to 58C. The laser linewidth was kept below 0.5 mm within the whole tuning range. The thermal coefficient of the emission wavelength has been measured. Finally the thermal coefficient of refractive index of sol-gel silica has been derived from these experimental data. Discontinuity in d?/dT curve attributable to phase transition has been observed in dye doped sol-gel silica slab and PMMA bulk. Temperature tuning performance of DFB laser using high temperature treated sol-gel silica as the gain medium has also been investigated.

  18. Non-hydrolytic Sol-gel Synthesis of Tin Sulfides

    NASA Astrophysics Data System (ADS)

    Kaur, Rajvinder

    The non-hydrolytic sol-gel (NHSG) process is an effective low temperature route well known for preparing homogeneous metal oxides. Thermodynamically as well as kinetically favored products, which cannot be prepared with the traditional solid-state routes, can be produced using NHSG. This project is focused on the exploration of NHSG synthesis of binary tin sulfides. In the past few years, metal sulfides have been the subject of significant interest. Much effort has been devoted to understand these materials because of their potential applications in electronic, optical, and superconductor devices.4 Among these materials, tin sulfides are materials of technological importance, which are being explored as semiconductors, anode materials for Li ion batteries, photoconductors, photocatalysts and absorber layer materials in photovoltaic solar cell devices. All of these applications depend upon features like homogeneity, oxidation state, high surface area and purity of the materials. These properties can be difficult to achieve by employing traditional synthetic routes, which require high temperatures due to slow diffusion, limiting the products to thermodynamically stable phases and prohibiting control over properties like particle size and surface area. A variety of low temperature methods are being explored due to the increased demand for such advanced materials. This project is focused on exploring the NHSG approach to synthesize binary tin sulfides, with the main goal of establishing conditions for the targeted synthesis of different tin sulfide polymorphs with controlled particle size. Being non-oxide materials, tin sulfides can be air sensitive, which requires special attention in handling. All reactions were carried out in absence of oxygen. This project explores the reaction of tin halides with thioethers in a dry solvent medium, leading to the formation of tin sulfides. There are a number of synthetic parameters that can be varied for the NHSG approach. A systematic study was carried out to understand the influence of all reaction variables, which include tin halides, thioethers, solvents, time, temperature, stoichiometry and concentration. Fine tuning of all reaction variables was carried out. The crystallization and phase stability of the as-recovered products was further studied by heat treatments of the samples. A detailed investigation of synthetic variables during NHSG reactions resulted in controlled synthesis of two crystalline tin sulfide polymorphs, SnS and SnS2. A third polymorph, Sn2S3, could be obtained after heat treatments in the temperature range of 400 to 500 °C. Conditions for the targeted synthesis of particles with various sizes and morphologies were established. Samples were characterized by powder X-ray diffraction, electron microscopy in combination with EDS, CHNS analysis and thermo gravimetric/differential thermal analysis.

  19. Sol-gel matrices for direct colorimetric detection of analytes

    DOEpatents

    Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

    2000-01-01

    The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

  20. Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes

    DOEpatents

    Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

    2002-11-26

    The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

  1. Process of forming a sol-gel/metal hydride composite

    DOEpatents

    Congdon, James W. (Aiken, SC)

    2009-03-17

    An external gelation process is described which produces granules of metal hydride particles contained within a sol-gel matrix. The resulting granules are dimensionally stable and are useful for applications such as hydrogen separation and hydrogen purification. An additional coating technique for strengthening the granules is also provided.

  2. Inorganic Sensing Using Organofunctional Sol-Gel Materials

    PubMed Central

    Carrington, Nathan A.; Xue, Zi-Ling

    2007-01-01

    This Account describes recent work in the development and applications of sol-gel sensors for concentrated strong acids/bases and metal ions. The use of sol-gel films doped with organic indicators for the optical sensing of concentrated strong acids (HCl 1-10 M) and bases (NaOH 1-10 M) has been explored, and the development of dual optical sensor approaches for ternary systems (HCl-salt-H2O and NaOH-alcohol-H2O) to give acid and salt as well as base and alcohol concentrations is discussed. The preparation of transparent, ligand-grafted sol-gel monoliths is also described, and their use in the analysis of both metal cations (Cu2+) and anions [Cr(VI)] is presented. A new model using both metal ion diffusion and immobilization by the ligands in such monoliths has been developed to give metal concentrations using the optical monolith sensors. In addition to optical sensing, a method utilizing ligand-grafted sol-gel films for analyte preconcentration in the electrochemical determination of Cr(VI) has been explored and is discussed. PMID:17465520

  3. ARSENIC REMOVAL USING SOL-GEL SYNTHESIZED TITANIUM DIOXIDE NANOPARTICLES

    EPA Science Inventory

    In this study, the effectiveness of TiO2 nanoparticles in arsenic adsorption was examined. TiO2 particles (LS) were synthesized via sol-gel techniques and characterized for their crystallinity, surface area and pore volume. Batch adsorption studies were perf...

  4. New insights into uranium (VI) sol-gel processing

    SciTech Connect

    King, C.M.; Thompson, M.C.; Buchanan, B.R. ); King, R.B. . Dept. of Chemistry); Garber, A.R. . Dept. of Chemistry)

    1990-01-01

    Nuclear Magnetic Resonance (NMR) investigations on the Oak Ridge National Laboratory process for sol-gel synthesis of microspherical nuclear fuel (UO{sub 2}), has been extremely useful in sorting out the chemical mechanism in the sol-gel steps. {sup 13}C, {sup 15}N, and {sup 1}H NMR studies on the HMTA gelation agent (Hexamethylene tetramine, C{sub 6}H{sub 12}N{sub 4}) has revealed near quantitative stability of this adamantane-like compound in the sol-gel process, contrary to its historical role as an ammonia source for gelation from the worldwide technical literature. {sup 17}O NMR of uranyl (UO{sub 2}{sup ++}) hydrolysis fragments produced in colloidal sols has revealed the selective formation of a uranyl trimer, ((UO{sub 2}){sub 3}({mu}{sub 3}-O)({mu}{sub 2}-OH){sub 3}){sup +}, induced by basic hydrolysis with the HMTA gelation agent. Spectroscopic results will be presented to illustrate that trimer condensation occurs during sol-gel processing leading to layered polyanionic hydrous uranium oxides in which HMTAH{sup +} is occluded as an intercalation'' cation. Subsequent sol-gel processing of microspheres by ammonia washing results in in-situ exchange and formation of a layered hydrous ammonium uranate with a proposed structural formula of (NH{sub 4}){sub 2} ((UO{sub 2}){sub 8} O{sub 4} (OH){sub 10}) {center dot} 8H{sub 2}O. This compound is the precursor to sintered UO{sub 2} ceramic fuel. 23 refs., 10 figs.

  5. Influence of Heat Treatment on Structure and Charge Capacity of Sol-Gel Produced TiO2 Films

    NASA Astrophysics Data System (ADS)

    zdemir, Orhan; Gkdemir, Fatma P?nar; Keskin, Bahad?r; Kutlu, Kubilay

    Titanium dioxide thin films were synthesized by sol-gel route from titanium isopropoxide (TIP) with acetic acid. Prior to the heat treatment, the films were amorphous phase. Above 400 C, phase transition took place from amorphous into anatase phase. Electrochromic properties of each phase indicated reversible coloration upon Li+ ion intercalation in cyclic voltammetric measurements. Nevertheless, both charge capacity and energy band gap of films begun to decrease with increase in annealing temperature due to the crystallization.

  6. Sol-gel synthesis and characterization of silica polyamine composites: applications to metal ion capture.

    PubMed

    Allen, Jesse J; Rosenberg, Edward; Johnston, Erik; Hart, Carolyn

    2012-03-01

    A sol-gel method has been developed for the synthesis of composite materials analogous to the previously reported and commercialized silica polyamine composite (SPC) materials made from amorphous silica. Monolithic xerogels were formed using a two-step procedure with no templating agent using acid catalyzed followed by base catalyzed hydrolysis. This reaction was followed by (1)H NMR. Initial sol-gels were formed using a methyltrimethoxysilane (MTMOS) and 3-chloropropyltrimethoxysilane (CPTMOS) mixture. Elemental analyses and (13)C CPMAS NMR confirmed incorporation of both monomeric units into the surface structure. Some control over surface morphology was achieved by adjusting synthetic conditions. The resulting xerogels were reacted with poly(allylamine) (PAA) to give composite materials which showed much lower metal ion capacities than the commercially available amorphous silica analogs. The low degree of reaction of the chloropropyl groups indicated they were not surface-available to the polyamine. Addition of tetramethoxysilane (TMOS) produced a structural matrix and resulted in higher chloride utilization (reaction of surface chloropropyl groups with the polyamine). The ratio of the three siloxane monomeric components was varied until the resulting polyamine composite xerogels had metal capacities comparable with the commercialized SPC materials. These composites had narrower average pore size distributions and fewer small pores. Further modification of these composites with metal selective ligands showed material characteristics similar to those of commercially available SPC materials. Subjecting a composite made by the sol-gel route to one thousand load-strip cycles with Cu(2+) shows essentially no loss in metal capacity, and this robustness compares favorably with that observed for the SPC made from amorphous silica gels. PMID:22364267

  7. Synthesis of Sol-Gel Precursors for Ceramics from Lunar and Martian Soil Simulars

    NASA Technical Reports Server (NTRS)

    Sibille, L.; Gavira-Gallardo, J. A.; Hourlier-Bahloul, D.

    2004-01-01

    Recent NASA mission plans for the human exploration of our Solar System has set new priorities for research and development of technologies necessary to enable a long-term human presence on the Moon and Mars. The recovery and processing of metals and oxides from mineral sources on other planets is under study to enable use of ceramics, glasses and metals by explorer outposts. We report initial results on the production of sol-gel precursors for ceramic products using mineral resources available in martian or lunar soil. The presence of SO2, TiO2, and Al2O3 in both martian (44 wt.% SiO2, 1 wt.% TiO2, 7 wt.% Al2O3) and lunar (48 wt.% SiO2, 1.5 wt.% TiO2, 16 wt.% Al2O3) soils and the recent developments in chemical processes to solubilize silicates using organic reagents and relatively little energy indicate that such an endeavor is possible. In order to eliminate the risks involved in the use of hydrofluoric acid to dissolve silicates, two distinct chemical routes are investigated to obtain soluble silicon oxide precursors from lunar and martian soil simulars. Clear solutions of sol-gel precursors have been obtained by dissolution of silica from lunar soil similar JSC-1 in basic ethylene glycol (C2H4(OH)2) solutions to form silicon glycolates. Similarly, sol-gel solutions produced from martian soil simulars reveal higher contents of iron oxides. Characterization of the precursor molecules and efforts to further concentrate and hydrolyze the products to obtain gel materials will be presented for evaluation as ceramic precursors.

  8. Synthesis of Sol-Gel Precursors for Ceramics from Lunar and Martian Soil Simulars

    NASA Technical Reports Server (NTRS)

    Sibille, L.; Gavira-Gallardo, J. A.; Hourlier-Bahloul, D.

    2003-01-01

    Recent NASA mission plans for the human exploration of our Solar System has set new priorities for research and development of technologies necessary to enable a long-term human presence on the Moon and Mars. The recovery and processing of metals and oxides from mineral sources on other planets is under study to enable use of ceramics, glasses and metals by explorer outposts. We report initial results on the production of sol-gel precursors for ceramic products using mineral resources available in martian or lunar soil. The presence of SiO2, TiO2, and Al2O3 in both martian (44 wt.% SiO2, 1 wt.% TiO2,7 wt.% Al2O3) and lunar (48 wt.% SiO2, 1.5 wt.% TiO2, 16 wt.% Al2O3) soils and the recent developments in chemical processes to solubilize silicates using organic reagents and relatively little energy indicate that such an endeavor is possible. In order to eliminate the risks involved in the use of hydrofluoric acid to dissolve silicates, two distinct chemical routes are investigated to obtain soluble silicon oxide precursors from lunar and martian soil simulars. Clear solutions of sol-gel precursors have been obtained by dissolution of silica from lunar soil simular in basic ethylene glycol (C2H4(OH)2) solutions to form silicon glycolates. Similarly, sol-gel solutions produced from martian soil simulars reveal higher contents of iron oxides. The elemental composition and structure of the precursor molecules were characterized. Further concentration and hydrolysis of the products was performed to obtain gel materials for evaluation as ceramic precursors.

  9. Protic ionic liquid as additive on lipase immobilization using silica sol-gel.

    PubMed

    de Souza, Ranyere Lucena; de Faria, Emanuelle Lima Pache; Figueiredo, Renan Tavares; Freitas, Lisiane dos Santos; Iglesias, Miguel; Mattedi, Silvana; Zanin, Gisella Maria; dos Santos, Onlia Aparecida Andreo; Coutinho, Joo A P; Lima, lvaro Silva; Soares, Cleide Mara Faria

    2013-03-01

    Ionic liquids (ILs) have evolved as a new type of non-aqueous solvents for biocatalysis, mainly due to their unique and tunable physical properties. A number of recent review papers have described a variety of enzymatic reactions conducted in IL solutions, on the other hand, to improve the enzyme's activity and stability in ILs; major methods being explored include the enzyme immobilization (on solid support, sol-gel, etc.), protic ionic liquids used as an additive process. The immobilization of the lipase from Burkholderia cepacia by the sol-gel technique using protic ionic liquids (PIL) as additives to protect against inactivation of the lipase due to release of alcohol and shrinkage of the gel during the sol-gel process was investigated in this study. The in?uence of various factors such as the length of the alkyl chain of protic ionic liquids (monoethanolamine-based) and a concentration range between 0.5 and 3.0% (w/v) were evaluated. The resulting hydrophobic matrices and immobilized lipases were characterised with regard to specific surface area, adsorption-desorption isotherms, pore volume (V(p)) and size (d(p)) according to nitrogen adsorption and scanning electron microscopy (SEM), physico-chemical properties (thermogravimetric - TG, differential scanning calorimetry - DSC and Fourier transform infrared spectroscopy - FTIR) and the potential for ethyl ester and emulsifier production. The total activity yields (Y(a)) for matrices of immobilized lipase employing protic ionic liquids as additives always resulted in higher values compared with the sample absent the protic ionic liquids, which represents 35-fold increase in recovery of enzymatic activity using the more hydrophobic protic ionic liquids. Compared with arrays of the immobilized biocatalyst without additive, in general, the immobilized biocatalyst in the presence of protic ionic liquids showed increased values of surface area (143-245 m(2) g(-1)) and pore size (19-38 ). Immobilization with protic ionic liquids also favoured reduced mass loss according to TG curves (always less than 42.9%) when compared to the immobilized matrix without protic ionic liquids (45.1%), except for the sample containing 3.0% protic ionic liquids (46.5%), verified by thermogravimetric analysis. Ionic liquids containing a more hydrophobic alkyl group in the cationic moiety were beneficial for recovery of the activity of the immobilized lipase. The physico-chemical characterization confirmed the presence of the enzyme and its immobilized derivatives obtained in this study by identifying the presence of amino groups, and profiling enthalpy changes of mass loss. PMID:23410924

  10. Calcium hydroxyapatite, Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2} ceramics prepared by aqueous sol-gel processing

    SciTech Connect

    Bogdanoviciene, Irma; Beganskiene, Aldona; Tonsuaadu, Kaia; Glaser, Jochen; Meyer, H.-Juergen . E-mail: juergen.meyer@uni-tuebingen.de; Kareiva, Aivaras . E-mail: aivaras.kareiva@chf.vu.lt

    2006-09-14

    Aqueous sol-gel chemistry routes based on ammonium-hydrogen phosphate as the phosphorus precursor and calcium acetate monohydrate as source of calcium ions have been developed to prepare calcium hydroxyapatite samples with different morphological properties. In the sol-gel processes, an aqueous solutions of ethylene diamine tetra-acetic acid (EDTA) or tartaric acid (TA) as complexing agents were added to the reaction mixture. The monophasic Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2} samples were obtained by calcination of precursor gels for 5 h at 1000 deg. C. The phase transformations, composition and micro-structural features in the polycrystalline samples were studied by thermoanalytical methods (TGA/DTA), infrared spectroscopy (IR), X-ray powder diffraction analysis (XRD) and scanning electron microscopy (SEM). It was shown that adjusting the nature of complexing agent in the aqueous sol-gel processing can be used to control the morphology of the ceramic samples.

  11. Structural investigations of sol-gel-derived LiYF{sub 4} and LiGdF{sub 4} powders

    SciTech Connect

    Lepoutre, S.; Boyer, D. Potdevin, A.; Dubois, M.; Briois, V.; Mahiou, R.

    2007-11-15

    A soft synthesis route based on the sol-gel process was used for preparing rare-earth tetrafluoride powders from alkoxide precursors. In-situ fluorination was performed by decomposition of a fluorine containing organic compound named 1,1,1-trifluoro-5-methyl-2,4-hexanedione when sintering the as-prepared xerogel to produce crystallized samples. Both to insure complete departure of organic residues as well as to avoid any oxidation into oxyfluoride, annealing treatment was carried out under fluorine atmosphere. Free-oxygen content of resulting samples was evidenced by infrared and Raman spectroscopies. X-ray absorption spectroscopies (XAS) and {sup 19}F nuclear magnetic resonance (NMR) studies showed that samples heat treated at 300 deg. C are already crystallized but for a full crystallization in LiGdF{sub 4} and LiYF{sub 4} a thermal treatment at 550 deg. C is needed. Temperature dependence of powder morphology was analyzed by scanning electron microscopy (SEM). - Graphical abstract: The sol-gel route is a soft process, which allows developing versatile-shaped compounds. A fluorine organic compound named 1,1,1-trifluoro-5-methyl-2,4-hexadione was used to synthesis LiGdF{sub 4} and LiYF{sub 4} powders based on the sol-gel method. These materials can be used as host lattices for rare-earth ions to provide phosphors.

  12. Tunable Optical Properties of Metal Nanoparticle Sol-Gel Composites

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Snow, Lanee A.; Sibille, Laurent; Ignont, Erica

    2001-01-01

    We demonstrate that the linear and non-linear optical properties of sol-gels containing metal nanoparticles are highly tunable with porosity. Moreover, we extend the technique of immersion spectroscopy to inhomogeneous hosts, such as aerogels, and determine rigorous bounds for the average fractional composition of each component, i.e., the porosity of the aerogel, or equivalently, for these materials, the catalytic dispersion. Sol-gels containing noble metal nanoparticles were fabricated and a significant blue-shift in the surface plasmon resonance (SPR) was observed upon formation of an aerogel, as a result of the decrease in the dielectric constant of the matrix upon supercritical extraction of the solvent. However, as a result of chemical interface damping and aggregation this blue-shift does not strictly obey standard effective medium theories. Mitigation of these complications is achieved by avoiding the use of alcohol and by annealing the samples in a reducing atmosphere.

  13. Microstructured UV-sensitive luminescent sol gel layers

    NASA Astrophysics Data System (ADS)

    Bredol, M.; Schem, M.

    2004-12-01

    Carboxylic acid complexes of lanthanide ions may show an excellent sensitivity to UV radiation and often a luminescence quantum yield near unity. By incorporating them into an inert matrix such as a sol-gel layer, it is possible to prevent degradation of the complexes under atmospheric conditions or by UV irradiation. This work focuses on the lateral structuring of thin sol-gel layers which have been doped with two different luminescent complexes, namely terbium picolinate and europium picolinate. It is demonstrated that structuring of the doped layers with standard photolithographic processes is possible, without harming the luminescent properties of the incorporated complexes. Best results are achieved in an image reversal process, while the lift-off approach with a thick layer of photoresist leads to inhomogenities in the layer. Smallest features of 40 ?m were reproduced with excellent edge quality.

  14. Optical detection of parasitic protozoa in sol-gel matrices

    NASA Astrophysics Data System (ADS)

    Livage, Jacques; Barreau, J. Y.; Da Costa, J. M.; Desportes, I.

    1994-10-01

    Whole cell parasitic protozoa have been entrapped within sol-gel porous silica matrices. Stationary phase promastigote cells of Leishmania donovani infantum are mixed with a silica sol before gelation occurs. They remain trapped within the growing oxide network and their cellular organization appears to be well preserved. Moreover protozoa retain their antigenic properties in the porous gel. They are still able to detect parasite specific antibodies in serum samples from infected patients via an enzyme linked immunosorbent assay (ELISA). Antigen- antibody associations occurring in the gel are optically detected via the reactions of a peroxidase conjugate with ortho-phenylenediamine leading to the formation of a yellow coloration. A clear-cut difference in optical density is measured between positive and negative sera. Such an entrapment of antigenic species into porous sol-gel matrices avoids the main problems due to non specific binding and could be advantageously used in diagnostic kits.

  15. Ceramic fibers from Sol-Gel precursors

    SciTech Connect

    Glaubitt, W.; Sporn, D.; Jahn, R.

    1995-09-01

    Powderless methods for the preparation of continuously spirmable alumina, mullite, spinel, yttrium alumina garnet (YAG) and lead zirconium titanate (PZT) precursors are presented. The Al containing solutions are based on alcoholysis, carboxylation and hydrolysis reactions, which are described in detail. In addition, a synthesis route for the preparation of piezoelectric PZT long fibers has also been developed. This novel PZT precursor contains lead subcarboxylate and zirconium titanium oxohydroxocarboxylate. In all cases, continuously spinnable precursors which have been extruded with velocities up to 200 m/min, have been obtained. Gel fibers of several kilometer length could be drawn directly from sols. After drying, pyrolysis and sintering, each of the {alpha}-Al{sub 2}O{sub 3}, mullite. spinel, YAG and PZT, fibers have been obtained.

  16. Sol-Gel Thin Films for Plasmonic Gas Sensors

    PubMed Central

    Della Gaspera, Enrico; Martucci, Alessandro

    2015-01-01

    Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors. PMID:26184216

  17. Sol-Gel Thin Films for Plasmonic Gas Sensors.

    PubMed

    Della Gaspera, Enrico; Martucci, Alessandro

    2015-01-01

    Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors. PMID:26184216

  18. Synthesis of zirconium oxide nanoparticle by sol-gel technique

    SciTech Connect

    Lim, H. S.; Ahmad, A.; Hamzah, H.

    2013-11-27

    Zirconium oxide nanoparticle is synthesized using sol-gel technique. Various mole ratio of ammonia solution and nitric acid relative to zirconium propoxide is added in the reaction to study the effect on the crystallinity and particle size on zirconium oxide particle. Zirconium oxide synthesized with nitric acid have the smallest particle size under FESEM image and show the increasing formation of crystalline tetragonal phase under XRD diffractogram.

  19. Functional nucleic acid entrapment in sol-gel derived materials.

    PubMed

    Carrasquilla, Carmen; Brennan, John D

    2013-10-01

    Functional nucleic acids (FNAs) are single-stranded DNA or RNA molecules, typically generated through in vitro selection, that have the ability to act as receptors for target molecules (aptamers) or perform catalysis of a chemical reaction (deoxyribozymes and ribozymes). Fluorescence-signaling aptamers and deoxyribozymes have recently emerged as promising biological recognition and signaling elements, although little has been done to evaluate their potential for solid-phase assays, particularly with species made of RNA due to their lack of chemical stability and susceptibility to nuclease attack. Herein, we present a detailed overview of the methods utilized for solid-phase immobilization of FNAs using a sol-gel entrapment method that can provide protection from nuclease degradation and impart long-term chemical stability to the FNA reporter systems, while maintaining their signaling capabilities. This article will also provide a brief review of the results of such entrapment studies involving fluorescence-signaling versions of a DNA aptamer, selected RNA-cleaving deoxyribozymes, and two different RNA aptamers in a series of sol-gel derived composites, ranging from highly polar silica to hydrophobic methylsilsesquioxane-based materials. Given the ability to produce sol-gel derived materials in a variety of configurations, particularly as thin film coatings on electrodes, optical fibers, and other devices, this entrapment method should provide a useful platform for numerous solid-phase FNA-based biosensing applications. PMID:24025165

  20. Sol-gel Technology and Advanced Electrochemical Energy Storage Materials

    NASA Technical Reports Server (NTRS)

    Chu, Chung-tse; Zheng, Haixing

    1996-01-01

    Advanced materials play an important role in the development of electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. The sol-gel process is a versatile solution for use in the fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. This processing technique is particularly useful in producing porous materials with high surface area and low density, two of the most desirable characteristics for electrode materials. In addition,the porous surface of gels can be modified chemically to create tailored surface properties, and inorganic/organic micro-composites can be prepared for improved material performance device fabrication. Applications of several sol-gel derived electrode materials in different energy storage devices are illustrated in this paper. V2O5 gels are shown to be a promising cathode material for solid state lithium batteries. Carbon aerogels, amorphous RuO2 gels and sol-gel derived hafnium compounds have been studied as electrode materials for high energy density and high power density electrochemical capacitors.

  1. Piezoelectric Sol-Gel Composite Film Fabrication by Stencil Printing.

    PubMed

    Kaneko, Tsukasa; Iwata, Kazuki; Kobayashi, Makiko

    2015-09-01

    Piezoelectric films using sol-gel composites could be useful as ultrasonic transducers in various industrial fields. For sol-gel composite film fabrication, the spray coating technique has been used often because of its adaptability for various substrates. However, the spray technique requires multiple spray coating processes and heating processes and this is an issue of concern, especially for on-site fabrication in controlled areas. Stencil printing has been developed to solve this issue because this method can be used to fabricate thick sol-gel composite films with one coating process. In this study, PbTiO3 (PT)/Pb(Zr,Ti)O3 (PZT) films, PZT/PZT films, and Bi4Ti3O12 (BiT)/PZT films were fabricated by stencil printing, and PT/ PZT films were also fabricated using the spray technique. After fabrication, a thermal cycle test was performed for the samples to compare their ultrasonic performance. The sensitivity and signal-to-noise-ratio (SNR) of the ultrasonic response of PT/PZT fabricated by stencil printing were equivalent to those of PT/PZT fabricated by the spray technique, and better than those of other samples between room temperature and 300°C. Therefore, PT/PZT films fabricated by stencil printing could be a good candidate for nondestructive testing (NDT) ultrasonic transducers from room temperature to 300°C. PMID:26688872

  2. CdS nanoparticles and the sol-gel process

    NASA Astrophysics Data System (ADS)

    Gacoin, Thierry; Malier, Laurent; Counio, G.; Boilot, Jean-Pierre

    1997-10-01

    We present two approaches for the sol-gel synthesis of transparent solids in which CdS nanoparticles are homogeneously dispersed. In any case CdS nanocrystals are obtained by precipitation either in reverse micelles or in the presence of a complexing thiol. The grafting of the 4- fluorothiophenol at the surface of the particles leads to highly concentrated colloids in acetone. In a first approach, CdS/silica nanocomposites are prepared introducing this concentrated CdS colloid in a silica sol which contains 3- mercaptopropyltrimethoxysilane to ensure the homogeneity of the CdS dispersion. The luminescence properties of the materials are improved by using methyltriethoxysilane instead of tetraethoxysilane as the alkoxide precursor of the silica matrix. Further increase of the luminescence efficiency is also observed if a single Mn2+ ion is present inside the CdS particle. In a second approach, pure CdS nanocrystalline materials (bulk or thin films) are obtained from the sol-gel processing of the concentrated colloids stabilized by 4- fluorothiophenol. The mechanisms driving the aggregation of the particles and the gelation of the system are explicited. Thin films as well as monoliths can be produced. The general principles of this method are not restricted to chalcogenide materials, and should therefore enlarge the applications of the sol-gel proces to other non-oxide materials.

  3. Sol-gel optical coatings for lasers, 3

    SciTech Connect

    Floch, H.G.; Belleville, P.F.; Priotton, J.J.; Pegon, P.M.; Dijonneau, C.S.; Guerain, J.

    1995-12-01

    The planned megajoule-class neodymium-glass laser system will be the world`s largest. The proposed CEL-V design, based on the use of 240 beams, will use 50--150 times more optical material than did Phebus. Almost 10,000 m{sup 2} of coated area are required for optical coatings; this is a factor of almost 500 increase over Phebus. Lens, flashlamp, blastshield, harmonic converter, debris shield, window and cavity-end mirror coatings by the sol-gel process represent >96% of the entire coated area. The remaining <4% are high-rejection-ratio polarizers, pick-off cavity mirrors and transport mirrors. Cost estimates show that, for coating deposition, the sol-gel technique provides considerable saving compared to the more conventional e-beam deposition technique. Highly reflective and polarizing sol-gel-derived optical coatings have been prepared and tested for the proposed French megajoule neodymium-glass laser. Laser damage studies are reported here.

  4. A Sol-Gel Approach to the Insulation of Rutherford Cables

    SciTech Connect

    Buta, F.; Hascicek, Y.S.; Arda, L.; Aslanoglu, Z.; Akin, Y.; Sumption, M.D.; Collings, E.W.

    2004-06-28

    Two wind-and-react compatible variants for the electrical insulation of Rutherford cables by a sol-gel route have been investigated. The first variant involves the direct application of a sol-gel coating of SnO2-ZrO2 to the surface of the strands in the cable, whereas the second is an indirect approach consisting of coating stainless steel tapes with MgO-ZrO2 that are to be wrapped around or co-wound with the cable. Following the application of the insulation by one of the two methods, the insulation electrical resistance and breakdown voltage were determined for samples consisting of two 7 inches long cables pressed together and vacuum impregnated with epoxy (CTD-101K). With a notable exception, the breakdown voltages on directly insulated cables were too low for practical purposes. Better results, with breakdown voltages ranging from 20 to almost 200 V, were obtained for insulator coatings applied to stainless steel tapes. An additional sintering at 700-800 deg. C for 6-12h of the coatings deposited on stainless steel was found to increase the breakdown voltage.

  5. Morphology evolution of ZrB{sub 2} nanoparticles synthesized by sol-gel method

    SciTech Connect

    Zhang Yun; Li Ruixing; Jiang Yanshan; Zhao Bin; Duan Huiping; Li Junping; Feng Zhihai

    2011-08-15

    Zirconium diboride (ZrB{sub 2}) nanoparticles were synthesized by sol-gel method using zirconium n-propoxide (Zr(OPr){sub 4}), boric acid (H{sub 3}BO{sub 3}), sucrose (C{sub 12}H{sub 22}O{sub 11}), and acetic acid (AcOH). Clearly, it was a non-aqueous solution system at the very beginning of the reactions. Here, AcOH was used as both chemical modifier and solvent to control Zr(OPr){sub 4} hydrolysis. Actually, AcOH could dominate the hydrolysis by self-produced water of the chemical propulsion, rather than the help of outer water. C{sub 12}H{sub 22}O{sub 11} was selected, since it can be completely decomposed to carbon. Thus, carbon might be accounted precisely for the carbothermal reduction reaction. Furthermore, we investigated the influence of the gelation temperature on the morphology of ZrB{sub 2} particles. Increasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 deg. C to a particle chain at 75 deg. C, and then form rod-like particles at 85 deg. C. An in-depth HRTEM observation revealed that the nanoparticles of ZrB{sub 2} were gradually fused together to evolve into a particle chain, finally into a rod-like shape. These crystalline nature of ZrB{sub 2} related to the gelation temperature obeyed the 'oriented attachment mechanism' of crystallography. - Graphical Abstract: Increasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 deg. C to a particle chain at 75 deg. C, and then form rod-like particles at 85 deg. C. Highlights: > ZrB{sub 2} nanoparticles were synthesized by sol-gel method in an non-aqueous solution system. > AcOH was used as both chemical modifier and solvent to control Zr(OPr){sub 4} hydrolysis. > C{sub 12}H{sub 22}O{sub 11} was selected since it can be completely decomposed to carbon. > Increasing the gelation temperature, the particles changed from sphere-like to rod-like ones. > Crystalline nature of ZrB{sub 2} obeyed the 'oriented attachment mechanism' of crystallography.

  6. Phenyl Functionalized Sol-gel Silica Sorbent for Capillary Microextraction and Chromia-Based Sol-gel Ucon Stationary Phase for Capillary Gas Chromatography

    NASA Astrophysics Data System (ADS)

    McLean, Michael M.

    The first chapter of this thesis presents an introduction to sol-gel methodology whose usefulness as a synthetic route will be demonstrated with two applications in chromatography. The first application involves the fabrication of a capillary micro-extraction (CME) device by coating a phenyl functionalized extracting phase on the inner surface of a fused silica capillary for analyte pre-concentration. The device was coupled on-line to a RP-HPLC system and practicality was demonstrated using allergens as target analytes. The allergens chosen as model analytes are typically found in fragrance products and food. Most of the 26 fragrance allergens that are monitored by various government authorities have a phenyl organic moiety (a strong chromophore), thus making them appropriate probes for exploring the extraction efficiency of the coating using a UV detector. The CME device showed ppt level limit of detection which makes it suitable for trace analyses of allergens and similar compounds in a variety of matrices. The second application explores the feasibility of using sol-gel derived chromia-based stationary phase in gas chromatographic columns. The organic moiety of the stationary phase was derived from Ucon 75-H-90,000 while the inorganic backbone was prepared using chromium(III) dichloride hydroxide - methacrylic acid - aqua complex, 40% in isopropanol/acetone . Usefulness of prepared chromia-based GC stationary phase was examined for petrochemical application. Promising results were obtained using aliphatic-aromatics, polyaromatic hydrocarbons, BTEX test mixture, cycloalkanes, branched alkanes and akylbenzenes. The column was able to perform without degradation despite being rinsed multiples times sequentially with the following solvents: dichloromethane, methanol, water and finally methanol again. Maximum theoretical plate number calculated is around 2,400 plates/m. The plate number clearly needs improvement but is a promising result for the newly explored chromia-based stationary phase. The maximum programmable temperature is 250°C which is comparable with similar commercially available polar stationary phases.

  7. Sol-Gel materials for optical waveguide applications

    NASA Astrophysics Data System (ADS)

    Himmelhuber, Roland

    Sol-gel materials are an important material class, as they provide for easy modification of material properties, good processability and routine synthesis. This allows for the tailoring of the material properties to the needs of specific device designs. In the case of electro-optic modulators with a coplanar or coplanar strip (CPS) electrode design, sol-gel cladding materials can be used to confine the light to the electro-optic material as well as to concentrate the electrical field used for poling and driving the modulator. Another important material property that can influence the poling efficiency is the conductivity of the material surrounding the electro-optic material, and this property can also be controlled. In this dissertation I discuss several approaches to altering the material properties of sol-gel materials in order to achieve a specific performance objective. The optical loss in the telecom regime as well the refractive index will be discussed. I will introduce a novel titania-based family of sol-gel materials, which exhibit very high refractive indices, tuneability and high dielectric constant (epsilon). Coplanar electrode design is useful for device platforms that do not allow for a microstrip geometry, such as silicon and Si3N 4 devices. CPS electrodes however bring new challenges with them, especially optimizing the poling process. I will discuss a method for characterizing coplanar poled polymer films by a modified Teng-Man technique as well as with second harmonic microscope (SHM). SHM allows for an almost real-time mapping of the Pockels coefficient. The described method allows for quantitative measurements of the Pockels coefficient in a poled film with spatial resolution at the micron level. Finally, I will discuss the device design considerations for a silicon-EO hybrid modulator. Optimal dimensions for the silicon waveguide are shown and the feasibility of the proposed electrode design for high speed operation is theoretically shown. All design parameters, including electrode spacing and height are optimized towards the highest possible figure of merit. The functionality of a simple test device is shown. For Si3N 4 waveguides optimal dimensions are found as well and the influence of a high epsilon sol-gel side cladding is examined.

  8. Comparative study of nanocrystalline titanium dioxide obtained through sol-gel and sol-gel-hydrothermal synthesis.

    PubMed

    Seck, E I; Doa-Rodrguez, J M; Pulido Melin, E; Fernndez-Rodrguez, C; Gonzlez-Daz, O M; Portillo-Carrizo, D; Prez-Pea, J

    2013-06-15

    TiO2 particles were prepared by sol-gel method alone and by sol-gel method combined with hydrothermal treatment. The structural and photocatalytic properties of the two series of photocatalysts were compared. XRD studies revealed that rutilization was faster in the series of photocatalysts, which had been additionally subjected to a hydrothermal process (SG-HT). The hydrothermally treated photocatalysts also displayed a higher specific surface area than those which had only been synthesized using the sol-gel process (SG) and subjected to low calcination temperatures of up to 873 K, while this tendency was inverted at higher temperatures. In accordance with the above observation, the hydrothermally treated series of photocatalysts had a lower particle size than the SG series calcined immediately after the sol-gel process up to 873 K, with this relation being inverted for the highest two temperatures which were studied (973 K and 1023 K) and which saw the commencement of rutilization. Increases in average particle size were observed for both series, with a polyhedral morphology seen as calcination temperature rose. FTIR studies highlighted the presence of the band at 2351 cm(-1) in the SG-HT photocatalysts, characteristic of surface-adsorbed CO2. This was not seen in the SG or P25 photocatalysts. In terms of photoreactivity, the best photocatalyst in the SG-HT series was that calcined at 923 K and in the SG series at 1023 K (SG-1023). Comparing these two photocatalysts and the commercial P25 photocatalyst, SG-1023 was found to be the most photoactive in both the photodegradation and the mineralization of phenol. PMID:23582907

  9. Synthesis of phthalocyanine doped sol-gel materials

    NASA Technical Reports Server (NTRS)

    Dunn, Bruce

    1993-01-01

    The synthesis of sol-gel silica materials doped with three different types of metallophthalocyanines has been studied. Homogeneous materials of good optical quality were prepared and the first optical limiting measurements of dyes in sol-gel hosts were carried out. The properties of these solid state limiters are similar to limiters based on phthalocyanine (Pc) in solution. Sol-gel silica materials containing copper, tin and germanium phthalocyanines were investigated. The initial step in all cases was to prepare silica sols by the sonogel method using tetramethoxy silane (TMOS), HCl and distilled water. Thereafter, the synthesis depended upon the specific Pc and its solubility characteristics. Copper phthalocyanine tetrasulfonic acid tetra sodium salt (CuPc4S) is soluble in water and various doping levels (1 x 10 (exp -4) M to 1 x 10 (exp -5) M) were added to the sol. The group IV Pc's, SnPc(OSi(n-hexyl)3)2 and GePc(OSi(n-hexyl)3)2, are insoluble in water and the process was changed accordingly. In these cases, the compounds were dissolved in THF and then added to the sol. The Pc concentration in the sol was 2 x 10(exp -5)M. The samples were then aged and dried in the standard method of making xerogel monoliths. Comparative nanosecond optical limiting experiments were performed on silica xerogels that were doped with the different metallophthalocyanines. The ratio of the net excited state absorption cross section (sigma(sub e)) to the ground state cross section (sigma(sub g)) is an important figure of merit that is used to characterize these materials. By this standard the SnPc sample exhibits the best limiting for the Pc doped sol-gel materials. Its cross section ratio of 19 compares favorably with the value of 22 that was measured in toluene. The GePc materials appear to not be as useful as those containing SnPc. The GePc doped solids exhibit a higher onset energy (2.5 mj and lower cross section ratio, 7. The CuPc4S sol-gel material has a still lower cross section ratio, 4, however, the tetrasulfonate groups make the dye soluble in water which greatly facilitates its incorporation into the sol-gel matrix. The nonlinear transmission of CuPc4S in a pH 2 buffer solution and in a silica xerogel were compared. It is evident that the CuPc4S preserves its optical limiting behavior in the sol-gel matrix, indicating that the fundamental excited state absorption process is essentially the same for a molecule in solution or in the solid state. Although the spectroscopic details of energy level lifetimes are unknown, the significance is that passive optical limiting has been achieved in the solid state via incorporation of a dye into an inorganic host. The only compromise occurs at the extremely high energy regime where photobleaching is observed. This is a result of the limited mobility of the dye molecules in the solid silica host relative to a liquid host. The effects of photodegradation in the xerogel are additive, whereas the solution provides a supply of fresh molecules that are free to enter the active volume between pulses.

  10. A design of experiment approach to the solgel synthesis of titania monoliths for chromatographic applications.

    PubMed

    Abi Jaoud, Maguy; Randon, Jrme; Bordes, Claire; Lanteri, Pierre; Bois, Laurence

    2012-05-01

    A design of experiement approach is described for the optimization of the microscopic morphology of macro-mesoporous titania monoliths that were elaborated for the chromatographic enrichment of phosphorylated compounds. The monolithic titania gels were formed via an alkoxy-derived sol-gel route in association with a phase separation mechanism. The synthesis was performed at mild temperatures of gelation using starting mixtures of titanium n-propoxide, hydrochloric acid, N-methylformamide, water, and poly (ethylene oxide). The gelation temperature and the chemical compositions of N-methylformamide, water, and poly (ethylene oxide) were chosen as the most relevant experimental factors of the solgel process. Using the sizes of the skeletons and macropores as morphological descriptors of the dried porous monoliths, the statistical analyses simultaneously revealed the effects and interactions between the different factors. Crack-free TiO2 monolithic rods of 8 to 10 cm long with well-defined co-continuous macropores and micro-structured skeletons were obtained after selection of the sol-gel parameters and optimization of the drying and heat-treatment steps of the gels. The bimodal texture of the rods exhibited macropores of 1.5 ?m and mesopores centered at 5.2 nm with a total surface area of 140 m2 g(-1). The ability of the macro-mesoporous titania rods to selectively bind phosphorylated compounds was demonstrated for O-phosphoamino acids (P-Ser, P-Thr, P-Tyr). PMID:22286081

  11. Comparing nanostructured hydroxyapatite coating on AZ91 alloy samples via sol-gel and electrophoretic deposition for biomedical applications.

    PubMed

    Rojaee, Ramin; Fathi, Mohammadhossein; Raeissi, Keyvan

    2014-12-01

    Magnesium is one of the most critical elements in hard tissues regeneration and therefore causes speeding up the restoration of harmed bones, while high deterioration rate of magnesium in body fluid restricts it to be used as biodegradable implants. Alloying magnesium with some relatively nobler metals such as aluminium, zinc, rare earth elements, magnesium-bioceramics composites, and surface modification techniques are some of the routes to control magnesium corrosion rate. In this study AZ91 magnesium alloy had been coated by nanostructured hydroxyapatite via sol-gel dip coating and electrophoretical methods to survey the final barricade properties of the obtained coatings. In order to perform electrophoretic coating, powders were prepared by sol-gel method, and then the powders deposited on substrates utilizing direct current electricity. Zeta potentials of the electrophoresis suspensions were measured to determine a best mode for good quality coatings. Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM) were used to confirm nanoscale dimension, and the uniformity of the nanostructured hydroxyapatite coating, respectively. Fourier Transform-Infrared and X-ray diffraction analysis were utilized for functional group and phase structure evaluation of the prepared coatings, correspondingly. Electrochemical corrosion tests were performed in SBF at 371 ()C which revealed considerable increase in corrosion protection resistivity and corrosion current density for electrophoretic coated specimens versus sol-gel coated specimens. Results showed that both sol-gel and electrophoretical techniques seem to be suitable to coat magnesium alloys for biomedical applications but electrophoretic coating technique is a better choice due to the more homogeneity and more crystalline structure of the coating. PMID:25095258

  12. Solventless sol-gel chemistry through ring-opening polymerization of bridged disilaoxacyclopentanes

    SciTech Connect

    RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

    2000-04-04

    Disilaoxacyclopentanes have proven to be excellent precursors to sol-gel type materials. These materials have shown promise as precursors for encapsulation and microelectronics applications. The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared without the use of solvents and water, they have low VOC's and show little shrinkage during processing.

  13. Study on process development and property evaluation of sol-gel derived magnesia stabilized zirconia minispheres

    NASA Astrophysics Data System (ADS)

    Judes, J.; Kamaraj, V.

    2014-06-01

    In order to overcome limitations in the processing parameters of powder compaction method, a novel processing technique based on sol-gel route has been developed to produce near-net-shaped prototype fine zirconia minispheres with required properties that could potentially be used as grinding media. Impact of magnesia concentration and sintering temperature on the final product has been analyzed in detail. Zirconia minispheres have been characterized to establish a correlation between physical, structural and mechanical properties. Sintering temperature, soaking period, heating rate and viscosity of the sol apparently influence the characteristics of the magnesia stabilized zirconia minispheres. The phase identification, density variation, chemical decomposition, functional group specification, surface area, porosity, shrinkage and microstructural features of the dried and sintered final product have been studied. It has been observed that magnesia content, sintering temperature, density and the grain size of the sintered minispheres have a significant impact on the mechanical properties of the final product.

  14. Development of 3D photonic crystals using sol-gel process for high power laser applications

    NASA Astrophysics Data System (ADS)

    Benoit, F.; Dieudonn, E.; Bertussi, B.; Vall, K.; Belleville, P.; Mallejac, N.; Enoch, S.; Sanchez, C.

    2015-08-01

    Three-dimensional photonic crystals (PCs) are periodic materials with a modulated refractive index on a length scale close to the light wavelength. This optical property allows the preparation of specific optical components like highly reflective mirrors. Moreover, these structured materials are known to have a high laser-induced damage threshold (LIDT) in the sub-nanosecond range compared to multi-layered dielectric mirrors. This property is obtained because only one high LIDT material (silica) is used. The second material used in the layer stack is replaced by air. In this work, we present the development of 3D PCs with narrow-sized colloidal silica particles, prepared by sol-gel process and deposited with Langmuir-Blodgett technique. Different syntheses routes have been investigated and compared regarding the optical properties of the PCs. Finally a numerical model based on an ideal opal network including defect influence is used to explain these experimental results.

  15. Sol-gel derived porous bioactive nanocomposites: Synthesis and in vitro bioactivity

    NASA Astrophysics Data System (ADS)

    Shankhwar, Nisha; Kothiyal, G. P.; Srinivasan, A.

    2013-06-01

    Porous bioactive composites consisting of SiO2-CaO-Na2O-P2O5 bioactive glass-ceramic and synthetic water soluble polymer Polyvinylpyrrolidone [PVP (C6H9NO)n, MW˜40000 g/mol] have been synthesized by sol-gel route. As-prepared polymeric composites were characterized by X-ray diffraction (XRD) technique. Two major bone mineral phases, viz., hydroxyapatite [Ca10(PO4)6(OH)2] and wollastonite [calcium silicate (CaSiO3)] have been identified in the XRD patterns of the composites. Presence of these bone minerals indicates the bioactive nature of the composites. In vitro bioactivity tests confirm bioactivity in the porous composites. The flexibility offered by these bioactive polymer composites is advantageous for its application as implant material.

  16. Size effects in magnetotransport in sol-gel grown nanostructured manganites

    NASA Astrophysics Data System (ADS)

    Shah, N. A.; Solanki, P. S.; Ravalia, Ashish; Kuberkar, D. G.

    2015-02-01

    We report the results of the studies on polycrystalline nanostructured La0.7Pb0.3MnO3 (LPMO) manganites synthesized using sol-gel method employing metal acetate precursor route. Interestingly, it is observed that crystallite size decreases with increase in sintering temperature while microscopic investigations reveal the second grain growth in all the samples. A correlation between the grain morphology and secondary grain growth with the transport and magnetotransport in LPMO manganites has been established. Observation of large temperature sensitivity (~-28.29 %/K @ 0 T; >300 K) and field sensitivity (~-48.70 %/T @ 0.2 T; 5 K) in the samples sintered at higher temperature (~1150 C) has been understood in the light of observed secondary grain growth in the form of nanosized grains over the surface of primary grains.

  17. Sol-gel chirowaveguides investigated via MLine technique

    NASA Astrophysics Data System (ADS)

    Guy, S.; Stoita-Crisan, A.; Bensalah-Ledoux, A.; Vautey, T.; Guy, L.

    2011-12-01

    Chirowaveguides, planar waveguides with a chiral core, are made of a chiral organo-modified silane sol-gel material. The losses, optical rotation (OR), absorption spectra and circular dicroism (CD) are measured and discussed. The optical activity for the organic chiral molecule 1,1'-binaphtyl-2,2'-dyil hydrogen phosphate is preserved in solid thin films. The specific OR of the film material is 11°/mm at λ = 488 nm. It is shown that the prism coupling, known as m-line technique, is not appropriated to put into evidence the polarization feature of the chirowaveguides.

  18. Durable hydrophobic sol-gel finishing for textiles

    NASA Astrophysics Data System (ADS)

    Vihodceva, S.; Kukle, S.; Bitenieks, J.

    2015-03-01

    The surface of cotton textile was modified to create a water-repellent finishing by depositing a modifying coatings using the sol-gel technique. Treated textiles evaluated using scanning electron microscopy, X-Ray powder diffraction (XRD). The wettability of treated fabrics was characterized by water contact angle and drop test. The results showed that the cotton textile treated with 7.5 wt.% zinc acetate dihydrate sol showed excellent hydrophobic properties, water contact angle could reach 145°C without decreasing after 50 hydrothermal treatment cycles.

  19. Sol Gel-Derived SBA-16 Mesoporous Material

    PubMed Central

    Rivera-Muñoz, Eric M.; Huirache-Acuña, Rafael

    2010-01-01

    The aim of this article is to review current knowledge related to the synthesis and characterization of sol gel-derived SBA-16 mesoporous silicas, as well as a review of the state of the art in this issue, to take stock of knowledge about current and future applications. The ease of the method of preparation, the orderly structure, size and shape of their pores and control, all these achievable through simple changes in the method of synthesis, makes SBA-16 a very versatile material, potentially applicable in many areas of science and molecular engineering of materials. PMID:20957080

  20. Sol-gel materials as possible devices for tissue biomonitoring

    NASA Astrophysics Data System (ADS)

    Maruszewski, K.; Podbielska, Halina; Andrzejewski, Przemyslaw; Strek, Wieslaw

    1996-12-01

    Sol-gel techniques became very popular recently due to their high chemical homogeneity, lower processing temperatures, and the possibility of controlling the size and morphology of particles. We propose using the method of hydrolyzing TEOS and emerging different dyes into the solution. Different organic and inorganic dyes will be checked for pH and temperature measurement. Optical absorption spectra are measured, depending on the pH and temperature. The fist laboratory tests are reported. The final compound can be used as an optrode for fiberoptic sensor for tissue biomonitoring.

  1. Ultrafast Sol-Gel Synthesis of Graphene Aerogel Materials

    SciTech Connect

    Lim, Mathew; Hu, Matthew; Manandhar, Sandeep; Sakshaug, Avery; Strong, Adam; Riley, Leah; Pauzauskie, Peter J.

    2015-12-01

    Graphene aerogels derived from graphene-oxide (GO) starting materials recently have been shown to exhibit a combination of high electrical conductivity, chemical stability, and low cost that has enabled a range of electrochemical applications. Standard synthesis protocols for manufacturing graphene aerogels require the use of sol-gel chemical reactions that are maintained at high temperatures for long periods of time ranging from 12 hours to several days. Here we report an ultrafast, acid-catalyzed sol-gel formation process in acetonitrile in which wet GO-loaded gels are realized within 2 hours at temperatures below 45°C. Spectroscopic and electrochemical analysis following supercritical drying and pyrolysis confirms the reduction of the GO in the aerogels to sp2 carbon crystallites with no residual carbon–nitrogen bonds from the acetonitrile or its derivatives. This rapid synthesis enhances the prospects for large-scale manufacturing of graphene aerogels for use in numerous applications including sorbents for environmental toxins, support materials for electrocatalysis, and high-performance electrodes for electrochemical capacitors and solar cells.

  2. Sol-gel deposition of electrochromic copper oxide films

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; Tepehan, Fatma

    1993-10-01

    This paper discusses the optical and electrochromic properties of CuxO films deposited by sol-gel process. UV-VIS-NIR spectroscopy, SEM, X-ray Diffraction and X-ray Photoelectron spectroscopy have been employed in a study of structure and optical properties of coatings. The sol-gel process offers new approaches to optical properties of coatings prepared by the acid catalyzed reactions of alkoxides. CuxO polymeric solutions are formed upon hydrolysis-condensation of copper ethoxide. Transparent amorphous CuxO coatings ranging in the thickness from 43 to 615 nm, were deposited on Corning 7059 and transparent conducting plates from polymeric solutions. These films exhibited reversible electrochromism that their color turn from transparent to pale brown. The combined effect of firing temperature (in the range of 70 - 450 degree(s)C) on optical properties and response time of these films are investigated. Significant changes in optical properties and electrochromic properties have been observed with firing temperatures.

  3. Granulation of sol-gel-derived nanostructured alumina

    SciTech Connect

    Deng, S.G.; Lin, Y.S.

    1997-02-01

    A sol-gel granulation process was developed to prepare porous nanostructured {gamma}-alumina granules as supports for catalysts and adsorbents. The process, which starts with an aqueous sol of gelatinous boehmite, involves droplet formation, gelation in paraffin oil, conditioning in ammonia solution, and drying and calcination in air under controlled conditions. The {gamma}-Al{sub 2}O{sub 3} granules prepared are 1--3 mm-dia. spherical particles with large surface area (380 m{sup 2}/g) and pore volume (0.5 cm{sup 3}/g), uniform pore-size distribution (20--60 {angstrom}), and controllable average pore size (35 {angstrom}). These sol-gel-derived granules have excellent mechanical properties with crush strength (>100 N per granule) and attrition resistance (<0.01 wt.%/h), much better than the commercial alumina and zeolite granules. Supported CuO sorbents were prepared on these granules for SO{sub 2} removal applications. The alumina-supported CuO sorbents contain higher loading of well-dispersed CuO and better sulfation properties than similar sorbents reported in the literature.

  4. Sol-gel derived ceramic electrolyte films on porous substrates

    SciTech Connect

    Kueper, T.W.

    1992-05-01

    A process for the deposition of sol-gel derived thin films on porous substrates has been developed; such films should be useful for solid oxide fuel cells and related applications. Yttria-stabilized zirconia films have been formed from metal alkoxide starting solutions. Dense films have been deposited on metal substrates and ceramic substrates, both dense and porous, through dip-coating and spin-coating techniques, followed by a heat treatment in air. X-ray diffraction has been used to determine the crystalline phases formed and the extent of reactions with various substrates which may be encountered in gas/gas devices. Surface coatings have been successfully applied to porous substrates through the control of substrate pore size and deposition parameters. Wetting of the substrate pores by the coating solution is discussed, and conditions are defined for which films can be deposited over the pores without filling the interiors of the pores. Shrinkage cracking was encountered in films thicker than a critical value, which depended on the sol-gel process parameters and on the substrate characteristics. Local discontinuities were also observed in films which were thinner than a critical value which depended on the substrate pore size. A theoretical discussion of cracking mechanisms is presented for both types of cracking, and the conditions necessary for successful thin formation are defined. The applicability of these film gas/gas devices is discussed.

  5. Titanium (IV) sol-gel chemistry in varied gravity environments

    NASA Astrophysics Data System (ADS)

    Hales, Matthew; Martens, Wayde; Steinberg, Theodore

    Sol-gel synthesis in reduced gravity is a relatively new topic in the literature and further inves-tigation is essential to realise its potential and application to other sol-gel systems. The sol-gel technique has been successfully applied to the synthesis of silica systems of varying porosity for many diverse applications [1-5]. It is proposed that current methods for the synthesis of silica sol-gels in reduced gravity may be applied to titanium sol-gel processing in order to enhance desirable physical and chemical characteristics of the final materials. The physical and chemical formation mechanisms for titanium alkoxide based sol-gels, to date, is not fully understood. However, various authors [6-9] have described potential methods to control the hydrolysis and condensation reactions of titanium alkoxides through the use of chemical inhibitors. A preliminary study of the reaction kinetics of titanium alkoxide sol-gel reaction in normal gravity was undertaken in order to determine reactant mixtures suitable for further testing under varied gravity conditions of limited duration. Through the use of 1H Nuclear Magnetic Resonance spectroscopy (NMR) for structural analysis of precursor materials, Ultra-Violet-Visible spectroscopy (UV-VIS) and viscosity measurements, it was demonstrated that not only could the rate of the chemical reaction could be controlled, but directed linear chain growth within the resulting gel structure was achievable through the use of increased inhibitor concentrations. Two unique test systems have been fabricated to study the effects of varied gravity (reduced, normal, high) on the formation of titanium sol-gels. Whilst the first system is to be used in conjunction with the recently commissioned drop tower facility at Queensland University of Technology in Brisbane, Australia to produce reduced gravity conditions. The second system is a centrifuge capable of providing high gravity environments of up to 70 G's for extended periods of time. The test systems and experimental results obtained will be presented. 1. Okubo, T., Tsuchida, A., Okuda, T., Fujitsuna, K., Ishikawa, M., Morita, T., Tada, T. , Kinetic Analyses of Colloidal Crystallization in Microgravity -Aircraft Experiments. . Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999. 153: p. 515-524. 2. Okubo, T., Tsuchida, A., Kobayashi, K., Kuno, A., Morita, T., Fujishima, M., Kohno, Y., Kinetic Study of the Formation Reaction of Colloidal Silica Spheres in Microgravity Using Aircraft. Colloid Polymer Science, 1999. 277(5): p. 474-478. 3. Pienaar, C.L., Chiffoleau, G. J. A., Follens, L. R. A., Martens, J. A., Kirschhock, C. E. A., Steinberg, T. A., Effect of Gravity on the Gelation of Silica Sols. Chem. Mater., 2007. 19(4): p. 660-664. 4. Smith, D.D., et al., Effect of Microgravity on the Growth of Silica Nanostructures. Langmuir, 2000. 16(26): p. 10055-10060. 5. Zhang, X., Johnson, D.P., Manerbino, A.R., Moore, J.J., Schowengerdt, F. , Recent Mi-crogravity Results in the Synthesis of Porous Materials. AIP Conference Proceedings (Space Technology and Applications International Forum-1999, Pt. 1), 1999. 458: p. 88-93. 6. Dunbar, P.B., Bendzko, N.J.,, 1H and 13C NMR observation of the reaction of acetic acid with titanium isopropoxide. Materials Chemistry and Physics, 1999. 59: p. 26-35. 7. Krunks, M., Oja, I., T˜nsuaadu, K., Es-Souni, M., Gruselle, M., Niinistü,. L, Thermoanalytical study of acetylacetonate-modified titanium (iv) isopropoxide as precursor for TiO2 films. Journal of Thermal Analysis and Calorimetry, 2005: p. 483-488. 8. Moran, P.D., Bowmaker, G. A., Cooney, R. P., Vibrational Spectra and Molecular Associa-tion of Titanium Tetraisopropoxide. Inorg. Chem., 1998. 37(1): p. 2741-2748. 9. Somogyvari, A., Serpone, N.,, Evidence for five-coordination in titanium(1V) complexes. A nuclear magnetic resonance investigation. Canadian Journal of Chemistry, 1977. 56: p. 316-319.

  6. Novel hybrid sol-gel materials for smart sensor windows

    NASA Astrophysics Data System (ADS)

    Wencel, Dorota; Higgins, Clare; Guckian, Adrian; McDonagh, Colette; MacCraith, Brian D.

    2005-06-01

    Current sensor trends, such as multianalyte capability, miniaturisation and patternability are important drivers for materials requirements in optical chemical sensors. In particular, issues such as enhanced sensitivity and printablity are key in developing optimised sensor materials for smart windows for bioprocessing applications. This study focuses on combining novel sol-gel-based hybrid matrices with engineered luminescent complexes to produce stable luminescence-based optical sensors with enhanced sensitivity for a range of analytes including oxygen, pH and carbon dioxide. As well as optimising sensor performance, issues such as surface modification of the plastic substrate and compatibility with different deposition techniques were addressed. Hybrid sol-gel matrices were developed using a range of precursors including tetraethoxysilane (TEOS), methyltriethoxysilane (MTEOS), ethyltriethoxysilane (ETEOS), n-propyltriethoxysilane (PTEOS), phenyltriethoxysilane (PhTEOS), and n-octyltriethoxysilane (C8TEOS). Oxygen sensing, based on luminescence quenching of ruthenium phenanthroline complexes, has been realised with each of these hybrid materials. Furthermore, the possibility of immobilising pH-indicators for pH and carbon dioxide sensing has been investigated with some success. In the context of in-situ monitoring of bioprocesses, issues such as humidity interference as well as the chemical robustness of the multianalyte platform, were addressed.

  7. Study of silica sol-gel materials for sensor development

    NASA Astrophysics Data System (ADS)

    Lei, Qiong

    Silica sol-gel is a transparent, highly porous silicon oxide glass made at room temperature by sol-gel process. The name of silica sol-gel comes from the observable physical phase transition from liquid sol to solid gel during its preparation. Silica sol-gel is chemically inert, thermally stable, and photostable, it can be fabricated into different desired shapes during or after gelation, and its porous structure allows encapsulation of guest molecules either before or after gelation while still retaining their functions and sensitivities to surrounding environments. All those distinctive features make silica sol-gel ideal for sensor development. Study of guest-host interactions in silica sol-gel is important for silica-based sensor development, because it helps to tailor local environments inside sol-gel matrix so that higher guest loading, longer shelf-life, higher sensitivity and faster response of silica gel based sensors could be achieved. We focused on pore surface modification of two different types of silica sol-gel by post-grafting method, and construction of stable silica hydrogel-like thin films for sensor development. By monitoring the mobility and photostability of rhodamine 6G (R6G) molecules in silica alcogel thin films through single molecule spectroscopy (SMS), the guest-host interactions altered by post-synthesis grafting were examined. While physical confinement remains the major factor that controls mobility in modified alcogels, both R6G mobility and photostability register discernable changes after surface charges are respectively reversed and neutralized by aminopropyltriethoxysilane (APTS) and methyltriethoxysilane (MTES) grafting. The change in R6G photostability was found to be more sensitive to surface grafting than that of mobility. In addition, silica film modification by 0.4% APTS is as efficient as that by pure MTES in lowering R6G photostability, which suggests that surface charge reversal is more effective than charge neutralization in disrupting R6G/silica attraction. Similar post-grafting method was applied to highly hydrated silica hydrogel monoliths. Rhodamine 6G (R6G) and fluorescein (Fl) molecules were used as probes to monitor the surface modification inside silica hydrogel by measuring anisotropy values of doped dyes. Due to the larger pore sizes, pore surface modification inside hydrogel was more effective than in alcogel. Surface modification by chemical reactions of 3-Aminopropyltrimethoxysilane (APTS) and methyltriethoxysilane (MTES) showed dramatic effect on guest molecule mobility, whereas surface modification by physical method, that is to increase ionic strength by using 1.0 M sodium chloride or to neutralize pore surfaces by adding pH 2.0 hydrochloric acid, barely showed any effect. Charge-reversal by APTS is a more effective way to modify pore surfaces in hydrogel than hydrophobic capping from MTES. The ease of tracking surface modification inside hydrogel by simply locating R6G dye band, and the negligible pore fluid effect on R6G in modified hydrogel makes R6G a better probe than Fl to monitor the pore surface modification process in silica hydrogel monoliths. During the study of post-grafting on silica alcogel thin film, a new approach to produce stable silica hydrogel-like thin films was discovered. Homogeneous thin film hydrogel-like samples with thickness between 100 nm and 300 nm were produced, and they showed a very hydrophilic surface, high dye loading capacity, and the support of molecular diffusion. The reactive stage of starting silica gel matrix was elongated by increasing environmental humidity, the reproducibility of sample preparation was greatly improved by controlling environmental humidity, and the dye loading capacity of samples was improved more than ten times by using phosphate buffer solutions (PBS). The concentration of R6G trapped inside hydrogel-like thin film could reach as high as 900 times of its saturated aqueous solution. Dye encapsulation can simply be accomplished by dipping a chemically reactive alcogel thin film into a dye-doped buffer solution. Since alcohol exposure can be kept to a minimum during dye encapsulation, this new silica film makes a promising candidate for biomolecule encapsulation and thus biosensor development. A prototype silica hydrogel-like thin film pH sensor was also constructed and tested, and it showed faster response than the corresponding alcogel thin film sensor.

  8. Sol-gel optical coatings for lasers, 2

    SciTech Connect

    Floch, H.G.; Belleville, P.F.; Priotton, J.J.; Pegon, P.M.; Dijonneau, C.S.; Guerain, J.

    1995-11-01

    There are three basic types of antireflective (AR) coatings. The first is a single-layer coating in which the coating index is equal to the square root of the index of the substrate, assuming air is the external medium. The second type is a system of two or more layers of different indexes. The third type is a graded-index system, where the index is uniformly and continuously graded from the substrate to the external medium. Low reflection ranges from narrow for the single-layer to broad for the graded-layer and multilayered with a large number of layers. Four types of sol-gel AR coatings have been developed at CEL-V. They are based on single-layer or multilayer designs. They consist mainly of amorphous silica in the polymeric and/or colloidal state, combined in certain cases with other metallic oxides, binders, fillers, hydrophobic and lubricating agents, and adhesion promoters. These antireflective sol-gel-derived optical coatings have been prepared and tested for the proposed French megajoule neodymium-glass laser.

  9. Sol - Gel synthesis and characterization of magnesium peroxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Jaison, J.; Ashok raja, C.; Balakumar, S.; Chan, Y. S.

    2015-04-01

    Magnesium peroxide is an excellent source of oxygen in agriculture applications, for instance it is used in waste management as a material for soil bioremediation to remove contaminants from polluted underground water, biological wastes treatment to break down hydrocarbon, etc. In the present study, sol-gel synthesis of magnesium peroxide (MgO2) nanoparticles is reported. Magnesium peroxide is odourless; fine peroxide which releases oxygen when reacts with water. During the sol-gel synthesis, the magnesium malonate intermediate is formed which was then calcinated to obtain MgO2 nanoparticles. The synthesized nanoparticles were characterized using Thermo gravimetric -Differential Thermal Analysis (TG- DTA), X-Ray Diffraction studies (XRD) and High Resolution Transmission Electron Microscope (HRTEM). Our study provides a clear insight that the formation of magnesium malonate during the synthesis was due to the reaction between magnesium acetate, oxalic acid and ethanol. In our study, we can conclude that the calcination temperature has a strong influence on particle size, morphology, monodispersity and the chemistry of the particles.

  10. Manipulation and characterization of thin-film interfacial chemistry: Sol-gel deposition and single molecule tracking experiments

    NASA Astrophysics Data System (ADS)

    Barhoum, Moussa

    Single molecule trajectories of 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbo - cyanine perchlorate (DiI) fluorophores diffusing on planar supported 1,2-dimyristoyl-snglycero- 3-phosphocholine (DMPC) lipid bilayers imaged through total internal reflection fluorescence (TIRF) microscopy at different temperatures are investigated. The spatial resolution limit for detecting molecular motion is evaluated by characterizing the apparent motion which arises from the limited signal-to-noise ratio (S/N) of imaged and simulated stationary DiI molecules. Statistical criteria for reliably distinguishing molecular motion from stationary molecules using F-test statistics, including the computation of local signal-to-noise ratios are then established and used for reliably detecting subdiffraction motion of DiI molecules on DMPC. The same single molecule tracking concept is used in investigating the temperature dependence of subdiffraction diffusional confinement of single Rhodamine 6G molecules in polymer brushes of poly (N-isopropylacrylamide), pNIPAAm, above and below its lower critical solution temperature (LCST) of 32C. Reliably distinguishing subdiffraction molecular motion from stationary events is crucial in validating the application of single molecule tracking experiment in probing nanometersized hydrophobic environments of polymer structure. A versatile and rapid sol-gel technique for the fabrication of high quality one-dimensional photonic bandgap materials was developed. Silica/titania multilayer materials are fabricated by a sol-gel chemistry route combined with dip-coating onto planar or curved substrate. A shock-cooling step immediately following the thin film heat-treatment process is introduced. The versatility of this sol-gel method is demonstrated by the fabrication of various Bragg stack-type materials with fine-tuned optical properties. Measured optical properties show good agreement with theoretical simulations confirming the high quality of these sol-gel fabricated optical materials. Finally, magnetic functionalization studies of sol-gel derived Co-ion doped titania thin films using superconducting quantum interference device (SQUID) magnetometry and an attempt to measure their magneto-optical properties using a home-built Faraday rotation setup are discussed. The experimental limitations in reliably measuring magnetization responses of these thin films are introduced and discussed in detail. The summary and outlook chapters summarize the scientific significance of each research project and briefly introduce ongoing research based on the work and the results presented in this dissertation.

  11. Lasers based on dye-doped sol-gel composite glasses

    NASA Astrophysics Data System (ADS)

    Rahn, Mark D.; King, Terence A.

    1994-10-01

    Higher energy laser action in partially densified sol-gel glass, sol-gel glass composites and polymethylmethacrylate (PMMA) doped with laser dyes is reported. Post-doping, in which the active dye is diffused into the densified porous sol-gel matrix, has been developed into an effective method for the impregnation of organic species. The sol-gel glass composite is formed by refractive index matching the porous sol-gel glass by impregnation with polymethylmethacrylate. This is achieved by in-situ polymerization of methylmethacrylate. This reduced optical attenuation from 0.7 dB/cm to 0.4 dB/cm. By formation of the composite the chemical environment of some dyes is improved. Laser performance is described for the dyes rhodamine 590, pyrromethene 567, and the perylene derivatives perylene orange (KF 241) and perylene red (KF 856), in the three solid state hosts when pumped with the second harmonic of a Nd:YAG laser. As a comparison, their performance is also described in solution. For laser performance, the best combinations of dye and host in terms of both efficiency and photostability were found to be rhodamine 590 in sol-gel glass and perylene orange in sol-gel glass/PMMA composite. Long pulse lasing has also been demonstrated with rhodamine 590 in sol-gel glass and sol-gel glass/PMMA composite and pyrromethene 567 in sol-gel glass, using a flashlamp pumped coumarin 504 dye laser as a pump source, emitting 3 microsecond(s) pulses at 504 nm. We also give the first report on de-oxygenated pyrromethene 567 doped sol-gel glass/PMMA composites. De-oxygenation improved the photostability of this dye in the composite by a factor of four.

  12. Calcium and phosphate adsorption as initial steps of apatite nucleation on sol-gel-prepared titania surface.

    PubMed

    Coreo, Juan; Martnez, Antonia; Coreo, Oscar; Bolarn, Ana; Snchez, Flix

    2003-01-01

    Titania powders have been prepared by the sol-gel route from Ti (IV) ethoxide under acidic conditions. Adsorption experiments of calcium and phosphate ions on gel-derived titania suspensions were performed to suggest a likely initial step of apatite growth on its surface. Experiments were performed as a function of time and pH at 37 degrees C with and without NaCl present in the suspensions. Also, zeta (zeta) potential experiments were performed to determine the kind of calcium adsorption. Results suggest that, apparently, calcium and phosphate adsorption can act as two different initial steps for apatite growth. PMID:12483705

  13. Influence of processing parameters on the luminescence of sol-gel derived PrPO{sub 4}

    SciTech Connect

    Chadeyron-Bertrand, G. . E-mail: chadeyr@chimtp.univ-bpclermont.fr; Vial, S.; Cellier, J.; Boyer, D.; Mahiou, R.

    2005-09-01

    PrPO{sub 4} synthesis by the sol-gel process was carried out using an alkoxide route. Powders purity and morphology were analyzed by means of X-ray diffraction, laser granulometry and scanning electron microscopy. Moreover, praseodymium fluorescence in that lattice was recorded by laser induced spectroscopy at room temperature. Upon excitation into the {sup 3}P{sub 0} high energy level, emission in the red wavelength range is observed from this state as well as from the {sup 1}D{sub 2} level. Finally, dependence of the phosphorus precursor and hydrolysis rate on the quantum efficiency was investigated.

  14. Sol-gel based oxidation catalyst and coating system using same

    NASA Technical Reports Server (NTRS)

    Watkins, Anthony N. (Inventor); Leighty, Bradley D. (Inventor); Oglesby, Donald M. (Inventor); Patry, JoAnne L. (Inventor); Schryer, Jacqueline L. (Inventor)

    2010-01-01

    An oxidation catalyst system is formed by particles of an oxidation catalyst dispersed in a porous sol-gel binder. The oxidation catalyst system can be applied by brush or spray painting while the sol-gel binder is in its sol state.

  15. Radiation hardening in sol-gel derived Er3+-doped silica glasses

    NASA Astrophysics Data System (ADS)

    Hari Babu, B.; Ollier, Nadge; Len Pichel, Mnica; El Hamzaoui, Hicham; Poumellec, Bertrand; Bigot, Laurent; Savelii, Inna; Bouazaoui, Mohamed; Ibarra, Angel; Lancry, Matthieu

    2015-09-01

    The aim of the present paper is to report the effect of radiation on the Er3+-doped sol-gel silica glasses. A possible application of these sol-gel glasses could be their use in harsh radiation environments. The sol-gel glasses are fabricated by densification of erbium salt-soaked nanoporous silica xerogels through polymeric sol-gel technique. The radiation-induced attenuation of Er3+-doped sol-gel silica is found to increase with erbium content. Electron paramagnetic resonance studies reveal the presence of E'? point defects. This happens in the sol-gel aluminum-silica glass after an exposure to ?-rays (kGy) and in sol-gel silica glass after an exposure to electrons (MGy). The concentration levels of these point defects are much lower in ?-ray irradiated sol-gel silica glasses. When the samples are co-doped with Al, the exposure to ?-ray radiation causes a possible reduction of the erbium valence from Er3+ to Er2+ ions. This process occurs in association with the formation of aluminum oxygen hole centers and different intrinsic point defects.

  16. Development of sol-gel formulations for slow release of phermones

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new type of dispenser for slow-release of semiochemicals and sex pheromones was developed based on sol-gel polymers that can be useful in monitoring, mass trapping, and mating disruption in integrated pest management (IPM). Sol-gel matrices exhibit glass characteristics and allow control of the de...

  17. Infrared and Raman spectra of triacetoxyvinylsilane, aqueous sol-gel and xerogel.

    PubMed

    Li, Ying-Sing; Ba, Abdul; Mahmood, Maleeha S

    2009-04-01

    Triacetoxyvinylsilane (TAVS) has been used as a precursor to prepare sol-gel under aqueous conditions. The sol-gel product has been applied for the surface treatment of aluminum. Infrared and Raman spectra have been collected for TAVS and for TAVS sol-gel, xerogel and sol-gel-coated aluminum. Vibrational analyses have been suggested for the recorded spectra based essentially on the group frequencies and the spectral variation with the change of the sol-gel product states and the vibrational assignments of similar molecules. From the recorded infrared and Raman spectra of the sol-gel and xerogel, it is found that the sol-gel produced in the process with TAVS is essentially the same as that prepared from vinyltriethoxysilane. Thermo-gravimetric analysis (TGA) of TAVS xerogel has been conducted, and an explanation has been given in coordination with the results obtained from IR spectroscopic study of the xerogels cured at different temperatures. The study has demonstrated the thermal effect on the condensation of the sol-gel process and on the vinyl decomposition of TAVS xerogel. PMID:19110464

  18. Vibrational spectroscopic studies of vinyltriethoxysilane sol-gel and its coating

    NASA Astrophysics Data System (ADS)

    Li, Ying-Sing; Wright, Paul B.; Puritt, Rosalyn; Tran, Tuan

    2004-10-01

    Infrared and Raman spectra of vinyltriethoxysilane (VTES), the VTES sol-gel, and the sol-gel coated aluminum have been collected. The assignments of the vibrational modes for the silane, the sol-gel, and the sol-gel films have been made based on the group frequencies and the spectral variation collected at different physical and chemical states of the sol-gel samples. Applying the sol-gels onto the metal grids allowed the drying and the high temperature treatment of the samples for the collection of infrared transmission spectra. From the variation of the sol-gel and the sol-gel coated aluminum IR spectra with temperature, it was noticed that the samples partially decomposed when the temperature was higher than 100 C. Electrochemical experiments have demonstrated that the anticorrosion property of the coated aluminum has significantly increased. The water and the hexadecane contact angle measurements showed that the surface modified metal had a much higher hydrophobic property than the untreated metal.

  19. Bactericidal micron-thin sol-gel films prevent pin tract and periprosthetic infection.

    PubMed

    Qu, Haibo; Knabe, Christine; Burke, Megan; Radin, Shula; Garino, Jonathan; Schaer, Thomas; Ducheyne, Paul

    2014-08-01

    Orthopedic injuries constitute the majority of wounds sustained by U.S. soldiers in recent conflicts. The risk of infection is considerable with fracture fixation devices. In this pilot study, we examined the use of unique bactericidal micron-thin sol-gel films on fracture fixation devices and their ability to prevent and eradicate infections. External fixation was studied with micron-thin sol-gel coated percutaneous pins releasing triclosan and inserted medially into rabbit tibiae. A total of 11 rabbits received percutaneous pins that were either uncoated or sol-gel/triclosan coated. Internal fracture fixation was also studied using sol-gel coated intramedullary (IM) nails releasing vancomycin in the intramedullary tibiae. Six sheep received IM nails that were coated with a sol-gel film that either contained vancomycin or did not contain vancomycin. All animals were challenged with Staphylococcus aureus around the implant. Animals were euthanized at 1 month postoperative. Rabbits receiving triclosan/sol-gel coated percutaneous pins did not show signs of infection. Uncoated percutaneous pins had a significantly higher infection rate. In the sheep study, there were no radiographic signs of osteomyelitis with vancomycin/sol-gel coated IM nails, in contrast to the observations in the control cohort. Hence, the nanostructured sol-gel controlled release technology offers the promise of a reliable and continuous delivery system of bactericidals from orthopedic devices to prevent and treat infection. PMID:25102546

  20. Alkylthiol gold nanoparticles in sol-gel-based open tubular capillary electrochromatography.

    PubMed

    Yang, Li; Guihen, Elizabeth; Glennon, Jeremy D

    2005-05-01

    A novel open-tubular capillary electrochromatography (OTCEC) column was prepared by immobilizing dodecanethiol gold nanoparticles on prederivatised fused-silica capillary columns with sol-gel technology. 3-Mercaptopropyl-trimethoxysilane (MPTMS) was selected as sol-gel precursor to develop a sol-gel layer on the inner wall of the capillary, prior to assembly of dodecanethiol gold nanoparticles onto the generated sol-gel layer through specific interaction between the gold nanoparticles and surface terminating thiol groups. The electrochromatographic behaviour of the sol-gel gold nanoparticle capillary was compared with a gold nanoparticle capillary prepared via MPTMS surface functionalisation, through variation of the percentage of the organic modifier, pH, and separation voltage. Efficient separation for a "reversed-phase" test mixture of thiourea, naphthalene, and biphenyl and for selected polycyclic aromatic hydrocarbons (PAHs) was obtained on the sol-gel based gold nanoparticle capillaries. OTCEC separations of three selected drug substances (propiophenone, benzoin, and warfarin) were also demonstrated. Scanning electron microscopy was used for the characterization of the sol-gel gold nanoparticle capillary surface. The results confirm that dodecanethiol gold nanoparticles, bound on the sol-gel-based inner layer of fused-silica capillary, can provide sufficient solute-bonded phase interactions for OTCEC with reproducible retention as well as characteristic reversed-phase behaviour. PMID:15938184

  1. Sol-Gel Precursors for Ceramics from Minerals Simulating Soils from the Moon and Mars

    NASA Technical Reports Server (NTRS)

    Sibille, Laurent; Gavira-Gallardo, Jose-Antonio; Hourlier-Bahloul, Djamila

    2003-01-01

    Recent NASA mission plans for the human exploration of our Solar System has set new priorities for research and development of technologies necessary to enable a long-term human presence on the Moon and Mars. The recovery and processing of metals and oxides from mineral sources on other planets is under study to enable use of ceramics, glasses and metals by explorer outposts. We report some preliminary results on the production of sol-gel precursors for ceramic products using mineral resources available in Martian or Lunar soil. The presence of SiO2, TiO2, and A12O3 in both Martian (44 wt.% SiO2, 1 wt.% TiO2, 7 wt.% Al2O3) and Lunar (48 wt.% SiO2, 1.5 wt.% TiO2, 16 wt.% Al2O3) soils and the recent developments in chemical processes to solubilize silicates using organic reagents and relatively little energy indicate that such an endeavor is possible. In order to eliminate the risks involved in the use of hydrofluoric acid to dissolve silicates, two distinct chemical routes are investigated to obtain soluble silicon oxide precursors from Lunar and Martian simulant soils. Clear sol-gel precursors have been obtained by dissolution of silica from Lunar simulant soil in basic ethylene glycol (C2H4(OH)2) solutions to form silicon glycolates. Thermogravimetric Analysis and X-ray Photoelectron Spectroscopy were used to characterize the elemental composition and structure of the precursor molecules. Further concentration and hydrolysis of the products was performed to obtain gel materials for evaluation as ceramic precursors. In the second set of experiments, we used the same starting materials to synthesize silicate esters in acidified alcohol mixtures. Preliminary results indicate the presence of silicon alkoxides in the product of distillation.

  2. Optical fiber sensor having a sol-gel fiber core and a method of making

    DOEpatents

    Tao, Shiquan; Jindal, Rajeev; Winstead, Christopher; Singh, Jagdish P.

    2006-06-06

    A simple, economic wet chemical procedure is described for making sol-gel fibers. The sol-gel fibers made from this process are transparent to ultraviolet, visible and near infrared light. Light can be guided in these fibers by using an organic polymer as a fiber cladding. Alternatively, air can be used as a low refractive index medium. The sol-gel fibers have a micro pore structure which allows molecules to diffuse into the fiber core from the surrounding environment. Chemical and biochemical reagents can be doped into the fiber core. The sol-gel fiber can be used as a transducer for constructing an optical fiber sensor. The optical fiber sensor having an active sol-gel fiber core is more sensitive than conventional evanescent wave absorption based optical fiber sensors.

  3. Fabrication of advanced electrochemical energy materials using sol-gel processing techniques

    NASA Technical Reports Server (NTRS)

    Chu, C. T.; Chu, Jay; Zheng, Haixing

    1995-01-01

    Advanced materials play an important role in electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. They are being used as both electrodes and electrolytes. Sol-gel processing is a versatile solution technique used in fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. The application of sol-gel processing in the fabrication of advanced electrochemical energy materials will be presented. The potentials of sol-gel derived materials for electrochemical energy applications will be discussed along with some examples of successful applications. Sol-gel derived metal oxide electrode materials such as V2O5 cathodes have been demonstrated in solid-slate thin film batteries; solid electrolytes materials such as beta-alumina for advanced secondary batteries had been prepared by the sol-gel technique long time ago; and high surface area transition metal compounds for capacitive energy storage applications can also be synthesized with this method.

  4. Passive and active sol-gel integrated optics for heterogeneous integration

    NASA Astrophysics Data System (ADS)

    Fallahi, Mahmoud

    2004-08-01

    The advantage of hybrid organic-inorganic sol-gel as a simple, low-cost method for the fabrication of optoelectronic integration is described. High performance integrated optics using mulit-layer photo-patternable hybrid sol-gel on high-index InP compound semiconductor is achieved. An MMI based 1x12 beam splitter with low polarization sensitivity and high uniformity is demonstrated. The development of EO and NLO active sol-gels are described and the fabrication of active waveguides are presented. The chromophore doped active sol-gels demonstrate high stability which makes them attractive material for integrated optoelectronics. The results show the great potential of the hybrid sol-gel for heterogeneous integration with semiconductor lasers and optoelectronic components.

  5. Sol-gel multilayers applied by a meniscus coating process

    SciTech Connect

    Britten, J.A.; Thomas, I.M.

    1992-03-19

    We describe a meniscus coating method to produce high-laser damage threshold, silica/alumina sol-gel multilayer reflectors on 30 {plus} cm substrates for laser-fusion applications. This process involves forcing a small suspension flow through a porous applicator tube, forming a falling film on the tube. A substrate contacts this film to form a meniscus. Motion of the substrate relative to the applicator entrains a thin film on the substrate, which leaves behind a porous, optical quality film upon solvent evaporation. We develop a solution for the entrained film thickness as a function of geometry, flow and fluid properties by an analysis similar to that of the classical dip-coating problem. This solution is compared with experimental measurements. Also, preliminary results of multilayer coating experiments with a prototype coater are presented, which focus on coating uniformity and laser damage threshold (LDT).

  6. Photosensitivity in a silica-based sol-gel glass

    SciTech Connect

    Korwin, D.M.; Pye, L.D.

    1996-12-31

    Photosensitivity in glasses containing Au and Ce was first reported by Dalton in 1943 and later reaffirmed by Stookey. The photothermal reduction of Au ions to form metallic colloids was determined to be responsible for the {open_quotes}ruby{close_quotes} color produced in these glasses. In this work, the photosensitive effect has been confirmed for the first time in a silica sol-gel glass containing Au and Ce. Two methods of producing Au colloids in this glass were investigated, one involved a short ultraviolet (UV) exposure followed by a thermal treatment, the other a simultaneous UV irradiation and thermal treatment. Colloid formation was studied using optical absorption spectroscopy, whereas the role of Ce in the photosensitive process was elucidated using optical absorption and fluorescence spectroscopic techniques.

  7. Manufacture of Regularly Shaped Sol-Gel Pellets

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas; Johnston, James C.; Kinder, James D.

    2006-01-01

    An extrusion batch process for manufacturing regularly shaped sol-gel pellets has been devised as an improved alternative to a spray process that yields irregularly shaped pellets. The aspect ratio of regularly shaped pellets can be controlled more easily, while regularly shaped pellets pack more efficiently. In the extrusion process, a wet gel is pushed out of a mold and chopped repetitively into short, cylindrical pieces as it emerges from the mold. The pieces are collected and can be either (1) dried at ambient pressure to xerogel, (2) solvent exchanged and dried under ambient pressure to ambigels, or (3) supercritically dried to aerogel. Advantageously, the extruded pellets can be dropped directly in a cross-linking bath, where they develop a conformal polymer coating around the skeletal framework of the wet gel via reaction with the cross linker. These pellets can be dried to mechanically robust X-Aerogel.

  8. Sol-gel synthesis and characterization of mesoporous manganese oxide

    SciTech Connect

    Hong Xinlin; Zhang Gaoyong; Zhu Yinyan; Yang Hengquan

    2003-10-30

    Mesoporous manganese oxide (MPMO) from reduction of KMnO{sub 4} with maleic acid, was obtained and characterized in detail. The characterization of the material was confirmed by high-resolution transmission electron microscopy (HRTEM), X-ray powder diffractometry (XRD) and N{sub 2} sorptometry. The results showed that MPMO is a pseudo-crystalline material with complex network pore structure, of which BET specific surface area is 297 m{sup 2}/g and pore size distribution is approximately in the range of 0.7-6.0 nm. The MPMO material turns to cryptomelane when the calcinating temperature rises to 400 deg. C. The optimum sol-gel reaction conditions are KMnO{sub 4}/C{sub 4}H{sub 4}O{sub 4} molar ratio=3, pH=7 and gelation time>6 h.

  9. Fabrication of hybrid sol-gel glass diffractive elements

    NASA Astrophysics Data System (ADS)

    Rantala, Juha T.; Ayras, Pekka; Levy, Raviv; Descour, Michael R.; Honkanen, Seppo; Peyghambarian, Nasser

    1999-03-01

    Organically modified photosensitive hybrid glasses are synthesized and used for the fabrication of diffractive optical elements. The material synthesis is based on a sol-gel process. The materials are spin-deposited onto glass substrate that also have a significant role in the component assembly. The synthesized material has a negative tone property under UV-radiation and they can be patterned by a conventional UV- lithography process. Binary diffractive lenses are photoimprinted through an amplitude contact mask. Optical properties and surface roughness of the materials and elements are evaluated. Diffraction efficiencies of the elements are also measured. The process and material optimization for the reliable fabrication of integrated optics devices is carried out.

  10. Mayenite Synthesized Using the Citrate Sol-Gel Method

    SciTech Connect

    Ude, Sabina N; Rawn, Claudia J; Meisner, Roberta A; Kirkham, Melanie J; Jones, Gregory L.; Payzant, E Andrew

    2014-01-01

    A citrate sol-gel method has been used to synthesize mayenite (Ca12Al14O33). X-ray powder diffraction data show that the samples synthesized using the citrate sol-gel method contained CaAl2O4 and CaCO3 along with mayenite when fired ex-situ in air at 800 C but were single phase when fired at 900 C and above. Using high temperature x-ray diffraction, data collected in-situ in air at temperatures of 600 C and below showed only amorphous content; however, data collected at higher temperatures indicated the first phase to crystallize is CaCO3. High temperature x-ray diffraction data collected in 4% H2/96% N2 does not show the presence of CaCO3, and Ca12Al14O33 starts to form around 850 C. In comparison, x-ray powder diffraction data collected ex-situ on samples synthesized using traditional solid-state synthesis shows that single phase was not reached until samples were fired at 1350 C. DTA/TGA data collected either in a nitrogen environment or air on samples synthesized using the citrate gel method suggest the complete decomposition of metastable phases and the formation of mayenite at 900 C, although the phase evolution is very different depending on the environment. Brunauer-Emmett-Teller (BET) measurements showed a slightly higher surface area of 7.4 0.1 m2/g in the citrate gel synthesized samples compared to solid-state synthesized sample with a surface area of 1.61 0.02 m2/g. SEM images show a larger particle size for samples synthesized using the solid-state method compared to those synthesized using the citrate gel method.

  11. Composite sol-gel process for photocatalytic titanium dioxide

    NASA Astrophysics Data System (ADS)

    Keshmiri, Mehrdad

    Photocatalytic TiO2 decomposes organic and inorganic pollutants upon irradiation with UV light. TiO2 thin films and powder suspensions are used for purification treatments, but small surface area of TiO2 films, and difficult filtration of powders are the two major drawbacks in application of photocatalytic TiO2. The major objective of this work was to develop a novel process to combine the thin film coatings and the fine (sub-micron) powder anatase TiO2 to provide high photocatalytic efficiency thick films and self-supported membranes. The microstructural properties and photocatalytic efficiency of the developed materials were characterized and compared with that of the conventional TiO2 coatings and powders. Photocatalytic activity of CSG TiO 2 was measured through the ability to decompose organic compounds (trichloroethane, dioxane, toluene), as well as to destroy bacteria. The major achievement of this work is the development of a process wherein structurally sound, thick films and membranes of CSG anatase photocatalytic TiO2 can be produced in reproducible way. A novel method for the synthesis of monodispersed anatase TiO2 microspheres through colloidal precipitation has also been established. The microspheres were used as filler TiO2 in the composite microstructure, bonded with sot-gel derived TiO2, to produce the composite sol-gel (CSG) TiO2. A sol-gel-assisted sintering model for the CSG thick films and self-supported membranes was established and validated by experimental data. The model has the ability to predict the sintering behavior of the CSG-TiO2, in terms of the reduction of specific surface area versus the time of heating, particularly at the initial and intermediate stages of the sintering.

  12. Sol-Gel Glass Holographic Light-Shaping Diffusers

    NASA Technical Reports Server (NTRS)

    Yu, Kevin; Lee, Kang; Savant, Gajendra; Yin, Khin Swe (Lillian)

    2005-01-01

    Holographic glass light-shaping diffusers (GLSDs) are optical components for use in special-purpose illumination systems (see figure). When properly positioned with respect to lamps and areas to be illuminated, holographic GLSDs efficiently channel light from the lamps onto specified areas with specified distributions of illumination for example, uniform or nearly uniform irradiance can be concentrated with intensity confined to a peak a few degrees wide about normal incidence, over a circular or elliptical area. Holographic light diffusers were developed during the 1990s. The development of the present holographic GLSDs extends the prior development to incorporate sol-gel optical glass. To fabricate a holographic GLSD, one records a hologram on a sol-gel silica film formulated specially for this purpose. The hologram is a quasi-random, micro-sculpted pattern of smoothly varying changes in the index of refraction of the glass. The structures in this pattern act as an array of numerous miniature lenses that refract light passing through the GLSD, such that the transmitted light beam exhibits a precisely tailored energy distribution. In comparison with other light diffusers, holographic GLSDs function with remarkably high efficiency: they typically transmit 90 percent or more of the incident lamp light onto the designated areas. In addition, they can withstand temperatures in excess of 1,000 C. These characteristics make holographic GLSDs attractive for use in diverse lighting applications that involve high temperatures and/or requirements for high transmission efficiency for ultraviolet, visible, and near-infrared light. Examples include projectors, automobile headlights, aircraft landing lights, high-power laser illuminators, and industrial and scientific illuminators.

  13. Sol-gel processes and materials. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search

    SciTech Connect

    1995-12-01

    The bibliography contains citations of selected patents concerning sol-gel processes and sol-gel derived materials and products. Selected patents include sol-gel compositions, ceramic and refractory materials, fabrication of silica glass, sol-gel thin films and coatings, transparent inorganic oxide glass, luminescent quartz glass, catalysts and catalyst supports, nuclear fuels preparation, abrasives for grinding wheels, sol-gel production of microspheres, alumina composites, photographic materials, and dental materials. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  14. Solventless sol-gel chemistry through ring-opening polymerization of bridged disilaoxacyclopentanes

    SciTech Connect

    RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

    2000-05-01

    Ring-opening polymerization (ROP) of disilaoxacyclopentanes has proven to be an excellent approach to sol-gel type hybrid organic-inorganic materials. These materials have shown promise as precursors for encapsulation and microelectronics applications. The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared by an organic base or Bronsted acid (formic or triflic acid), without the use of solvents and water, they have low VOC's and show little shrinkage during processing.

  15. Sol-gel synthesis, characterization and luminescence properties of SrMgAl2 SiO7:Eu2+ as a novel nanocrystalline phosphor.

    PubMed

    Salimi, R; Sameie, H; Alvani, A A Sabbagh; Sarabi, A A; Moztarzadeh, F; Tahriri, M

    2011-01-01

    In this research, a new SrMgAl(2) SiO(7):Eu(2+) phosphor was synthesized via the sol-gel method. The phase-forming processes were studied by thermogravimetric-differential thermal analysis and X-ray diffraction technique. Scanning electron microscopy showed that there is uniform morphology and microstructure owing to the sol-gel route. Spectrophotometry and colorimetry analyses illustrated that, under short ultraviolet excitation, the main emission peak occurred at 421 nm and also a relatively pure blue color was observed that was ascribed to the 4f(6) 5d(1) ((2) D) → 4f(7) ((8) S(7/2)) transition of Eu(2+) with color coordination of x = 0.187, y = 0.077. Finally, it was found that the color and phase purity of the synthesized powder increased as calcinations time increased. PMID:20928926

  16. Extraordinarily water permeable sol-gel formed nanocomposite nanofibrous membranes.

    PubMed

    Homaeigohar, Seyed Shahin; Mahdavi, Hossein; Elbahri, Mady

    2012-01-15

    Electrospun nanofibrous membranes (ENMs) are considered as a state of the art in water filtration technology mainly owing to their high interconnected porosity and tunable pore size assumed to offer a very high permeability also selectivity. However, the extremely high surface area makes the ENMs prone to mechanical breakdown and lack of wettability lowering the filtration efficiency. Hence, any attempt to enhance both the mechanical properties and hydrophilicity of the ENMs is highly recommended. In the current study, the structural and transport properties of polyethersulfone (PES) ENMs were modified through incorporation of titania (TiO(2)) nanoparticles via a sol-gel approach. Presence of titania precursor increased the conductivity of the electrospun solution thereby optimized the structural features of the electrospun mat in terms of formation of very thin beadless nanofibers, a higher porosity and smaller pore size. Moreover, a significant rise in mechanical properties, thermal stability and switching from a highly hydrophobic membrane to a superhydrophilic one occur simultaneously. The combination of a more optimum porosity, very high mechanical properties and hydrophilicity leads to a significantly higher water permeability in the TiO(2)/PES ENMs encouraging us to propose it as a water filtration membrane with longer life span and lower energy consumption. PMID:21999961

  17. Processing, properties, and applications of sol-gel silica optics

    NASA Astrophysics Data System (ADS)

    Nogues, Jean-Luc R.; LaPaglia, Anthony J.

    1989-12-01

    For many years the market share maintained by U.S. optics manufacturers has been declining continuously caused in part by intense competition principally from countries in the Far East, and in part by the lack of a highly trained cadre of opticians to replace the current generation. This fact could place in jeopardy the defense system of the United States in case of international war. For example, in 1987, optical glass component imports accounted for approximately 50 percent of the Department of Defense (DOD) consumption. GELTECH's sol-gel technology is a new process for making a high quality optical glass and components for commercial and military uses. This technology offers in addition to being a local source of optics, the possibility to create new materials for high-tech optical applications, and the elimination of the major part of grinding and polishing for which the skill moved off-shore. This paper presents a summary of the solgel technology for the manufacture of high quality optical glass and components. Properties of pure silica glass made by solgel process (Type V and Type VI silicas) are given and include: ultraviolet, visible and near infrared spectrophotometry, optical homogeneity and thermal expansion. Many applications such as near net shape casting or Fresnel lens surface replication are discussed. Several potential new applications offered by the solgel technology such as organic-inorganic composites for non linear optics or scintillation detection are also reported in this paper.

  18. Cobalt silicon mixed oxide nanocomposites by modified sol gel method

    NASA Astrophysics Data System (ADS)

    Esposito, Serena; Turco, Maria; Ramis, Gianguido; Bagnasco, Giovanni; Pernice, Pasquale; Pagliuca, Concetta; Bevilacqua, Maria; Aronne, Antonio

    2007-12-01

    Cobalt-silicon mixed oxide materials (Co/Si=0.111, 0.250 and 0.428) were synthesised starting from Co(NO 3) 26H 2O and Si(OC 2H 5) 4 using a modified sol-gel method. Structural, textural and surface chemical properties were investigated by thermogravimetric/differential thermal analyses (TG/DTA), XRD, UV-vis, FT-IR spectroscopy and N 2 adsorption at -196 C. The nature of cobalt species and their interactions with the siloxane matrix were strongly depending on both the cobalt loading and the heat treatment. All dried gels were amorphous and contained Co 2+ ions forming both tetrahedral and octahedral complexes with the siloxane matrix. After treatment at 400 C, the sample with lowest Co content appeared amorphous and contained only Co 2+ tetrahedral complexes, while at higher cobalt loading Co 3O 4 was present as the only crystalline phase, besides Co 2+ ions strongly interacting with siloxane matrix. At 850 C, in all samples crystalline Co 2SiO 4 was formed and was the only crystallising phase for the nanocomposite with the lowest cobalt content. All materials retained high surface areas also after treatments at 600 C and exhibited surface Lewis acidity, due to cationic sites. The presence of cobalt affected the textural properties of the siloxane matrix decreasing microporosity and increasing mesoporosity.

  19. /dopamine films prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Valverde-Aguilar, G.; Prado-Prone, G.; Vergara-Aragón, P.; Garcia-Macedo, J.; Santiago, Patricia; Rendón, Luis

    2014-09-01

    Dopamine was encapsulated into nanoporous amorphous TiO2 matrix by sol-gel method under atmospheric conditions. A second sample was obtained by the addition of the crown-ether 15C5 in this previous sample. Thin films were spin-coated on glass wafers. No heat treatment was employed in both films. All films were characterized using infrared spectroscopy, high resolution transmission electronic microscopy, X-ray diffraction, optical absorption and scanning electronic microscopy. Despite the films prepared with 15C5 were no calcined, a partial crystallization was identified. Anatase and rutile nanoparticles with sizes of 4-5 nm were obtained. Photoconductivity technique was used to determine the charge transport mechanism on these films. Experimental data were fitted with straight lines at darkness and under illumination wavelengths at 320, 400, and 515 nm. It indicates an ohmic behavior. Photovoltaic and photoconductivity parameters were determined from the current density vs. the applied-electrical-field results. Amorphous film has bigger photovoltaic and photoconductive parameters than the partially crystalline film. Results observed in the present investigation prove that the nanoporous TiO2 matrix can protect the dopamine inhibiting its chemical instability. This fact modifies the optical, physical and electrical properties of the film, and is intensified when 15C5 is added.

  20. Sol-gel template synthesis of semiconductor nanostructures

    SciTech Connect

    Lakshmi, B.B.; Dorhout, P.K.; Martin, C.R.

    1997-03-01

    The template method for preparing nanostructures entails synthesis of the desired material within the pores of a nanoporous membrane or other solid. A nonofibril or tubule of the desired material is obtained within each pore. Methods used previously to deposit materials within the pores of such membranes include electrochemical and electroless deposition and in situ polymerization. This paper describes the first use of sol-gel chemistry to prepare semiconductor nanofibrils and tubules within the pores of an alumina template membrane. TiO{sub 2}, WO{sub 3}, and ZnO nanostructures have been prepared. TiO{sub 2} nanofibrils with diameters of 22 nm were found to be single crystals of anatase with the c-axis oriented along the fibril axis. Bundles of these fibrils were also found to be single crystalline, suggesting that the individual fibrils are arranged in a highly organized fashion within the bundle. Finally, 200 nm diameter TiO{sub 2} fibrils were used as photocatalysts for the decomposition of salicylic acid. 30 refs., 8 figs.

  1. Enantioselective, chirally templated sol-gel thin films.

    PubMed

    Fireman-Shoresh, Sharon; Popov, Inna; Avnir, David; Marx, Sharon

    2005-03-01

    Enantioselective surfactant-templated thin films were fabricated through the sol-gel (SG) process. The enantioselectivity is general in the sense that it discriminates between pairs of enantiomers not used for the imprinting process. The chiral cationic surfactant (-)-N-dodecyl-N-methylephedrinium bromide (1) was used as the surfactant template, and after its extraction chiral domains were created. The chiral discriminative feature of these films was examined by challenging with pure enantiomer solutions for rebinding. Selective adsorption was shown using (R)- and (S)-propranolol, (R)-2 and (S)-2, respectively, and (R)- and (S)-2,2,2-trifluoro-1-(9-anthryl)ethanol, (R)-3 and (S)-3, respectively, as the chiral probes. The selective adsorption was measured by fluorescence analysis, and the chiral selectivity factors were found to be 1.6 for 2 and 2.25 for 3. In both cases, (R)-enantiomer was adsorbed preferably. The resulting material was characterized by transmission electron microscopy, by diffraction, and by surface area measurements, and was found to be semicrystalline with short-range ordered domains (50 A) of hexagonal symmetry. PMID:15725022

  2. Dielectric properties of silicon dioxide and silicon-oxynitride sol/gel thin films

    SciTech Connect

    Carman, L.A.; Pantano, C.G.

    1986-03-01

    Sol-gel film coatings are considered as candidate abrasion resistant and anti-reflection coatings for photovoltaic concentrator solar cells. The studies described in this report concern the electrical breakdown potential as a function of processing in ammonia. It has previously been determined that large (5-40 atomic percent) amounts of nitrogen can be incorporated into silica sol-gels by ammonia exposure during the densification process to form an oxynitride. Most of the expected behavior of the nitrided sol/gel deposits were masked due to the presence of alkali impurities and interfacial defects. The dielectric strength of such films was no greater than silicon oxide films thermally grown. The distribution of breakdown potential was much narrower, however, for nitrided films. For the expected improved properties of nitrided sol gel films to be seen, more care with the purity of the deposition materials and atmosphere will need to be exercised.

  3. Enhanced piezoelectric performance of composite sol-gel thick films evaluated using piezoresponse force microscopy

    NASA Astrophysics Data System (ADS)

    Liu, Yuanming; Lam, Kwok Ho; Kirk Shung, K.; Li, Jiangyu; Zhou, Qifa

    2013-05-01

    Conventional composite sol-gel method has been modified to enhance the piezoelectric performance of ceramic thick films. Lead zirconate titanate (PZT) and lead magnesium niobate-lead titanate (PMN-PT) thick films were fabricated using the modified sol-gel method for ultrasonic transducer applications. In this work, piezoresponse force microscopy was employed to evaluate the piezoelectric characteristics of PZT and PMN-PT composite sol-gel thick films. The images of the piezoelectric response and the strain-electric field hysteresis loop behavior were measured. The effective piezoelectric coefficient (d33,eff) of the films was determined from the measured loop data. It was found that the effective local piezoelectric coefficient of both PZT and PMN-PT composite films is comparable to that of their bulk ceramics. The promising results suggest that the modified composite sol-gel method is a promising way to prepare the high-quality, crack-free ceramic thick films.

  4. Enhanced piezoelectric performance of composite sol-gel thick films evaluated using piezoresponse force microscopy.

    PubMed

    Liu, Yuanming; Lam, Kwok Ho; Kirk Shung, K; Li, Jiangyu; Zhou, Qifa

    2013-05-14

    Conventional composite sol-gel method has been modified to enhance the piezoelectric performance of ceramic thick films. Lead zirconate titanate (PZT) and lead magnesium niobate-lead titanate (PMN-PT) thick films were fabricated using the modified sol-gel method for ultrasonic transducer applications. In this work, piezoresponse force microscopy was employed to evaluate the piezoelectric characteristics of PZT and PMN-PT composite sol-gel thick films. The images of the piezoelectric response and the strain-electric field hysteresis loop behavior were measured. The effective piezoelectric coefficient (d33,eff) of the films was determined from the measured loop data. It was found that the effective local piezoelectric coefficient of both PZT and PMN-PT composite films is comparable to that of their bulk ceramics. The promising results suggest that the modified composite sol-gel method is a promising way to prepare the high-quality, crack-free ceramic thick films. PMID:23798771

  5. Optical pH detector based on LTCC and sol-gel technologies

    NASA Astrophysics Data System (ADS)

    Tadaszak, R. J.; ?ukowiak, A.; Golonka, L. J.

    2013-01-01

    This paper presents an investigation on using sol-gel thin film as a material for sensors application in LTCC (Low Temperature Co-fired Ceramics) technology. This material gives the opportunity to make new, low-cost highly integrated optoelectronic devices. Sensors with optical detection are a significant part of these applications. They can be used for quick and safe diagnostics of some parameters. Authors present a pH detector with the optical detection system made of the LTCC material. The main part of the device is a flow channel with the chamber and sol-gel active material. The silica sol-gel with bromocresol green indicator was used. As the absorbance of sol-gel layer changes with the pH value of a measured medium, the transmitted light power was measured. The pH detector was integrated with the electronic components on the LTCC substrate.

  6. Molecular receptors in metal oxide sol-gel materials prepared via molecular imprinting

    DOEpatents

    Sasaki, Darryl Y. (Albuquerque, NM); Brinker, C. Jeffrey (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Daitch, Charles E. (Charlottesville, VA); Shea, Kenneth J. (Irvine, CA); Rush, Daniel J. (Philadelphia, PA)

    2000-01-01

    A method is provided for molecularly imprinting the surface of a sol-gel material, by forming a solution comprised of a sol-gel material, a solvent, an imprinting molecule, and a functionalizing siloxane monomer of the form Si(OR).sub.3-n X.sub.n, wherein n is an integer between zero and three and X is a functional group capable of reacting with the imprinting molecule, evaporating the solvent, and removing the imprinting molecule to form the molecularly imprinted metal oxide sol-gel material. The use of metal oxide sol-gels allows the material porosity, pore size, density, surface area, hardness, electrostatic charge, polarity, optical density, and surface hydrophobicity to be tailored and be employed as sensors and in catalytic and separations operations.

  7. Preparation of oxide glasses from metal alkoxides by sol-gel method

    NASA Technical Reports Server (NTRS)

    Kamiya, K.; Yoko, T.; Sakka, S.

    1987-01-01

    An investigation is carried out on the types of siloxane polymers produced in the course of the hydrolysis of silicon tetraethoxide, as well as the preparation of oxide glasses from metal alkoxides by the sol-gel method.

  8. Enhanced piezoelectric performance of composite sol-gel thick films evaluated using piezoresponse force microscopy

    PubMed Central

    Liu, Yuanming; Lam, Kwok Ho; Kirk Shung, K.; Li, Jiangyu; Zhou, Qifa

    2013-01-01

    Conventional composite sol-gel method has been modified to enhance the piezoelectric performance of ceramic thick films. Lead zirconate titanate (PZT) and lead magnesium niobatelead titanate (PMN-PT) thick films were fabricated using the modified sol-gel method for ultrasonic transducer applications. In this work, piezoresponse force microscopy was employed to evaluate the piezoelectric characteristics of PZT and PMN-PT composite sol-gel thick films. The images of the piezoelectric response and the strain-electric field hysteresis loop behavior were measured. The effective piezoelectric coefficient (d33,eff) of the films was determined from the measured loop data. It was found that the effective local piezoelectric coefficient of both PZT and PMN-PT composite films is comparable to that of their bulk ceramics. The promising results suggest that the modified composite sol-gel method is a promising way to prepare the high-quality, crack-free ceramic thick films. PMID:23798771

  9. Heat treatment effect on the physical properties of cobalt doped TiO{sub 2} solgel materials

    SciTech Connect

    Samet, L.; Ben Nasseur, J.; Chtourou, R.; March, K.; Stephan, O.

    2013-11-15

    Cobalt doped and undoped TiO{sub 2} powders have been prepared by solgel technique and annealed at temperatures ranging from 400 C to 1000 C. The effects of annealing temperature on the structural, morphological and optical properties have been characterized by X-ray diffraction, transmission electron microscopy, electron energy-loss spectroscopy and diffuse reflectance spectroscopy. For all doped samples there is a general reduction of the band gap energy, in comparison with undoped samples prepared in the same conditions. More specifically, experimental results indicate that cobalt doping, occurring as Co{sup 2+} ion insertion into the TiO{sub 2} (Ti{sup 4+}) host lattice, inhibits the growth of the crystallites and delays the phase transformation from anatase to rutile. Moreover, at high temperature, a secondary phase (CoTiO{sub 3}) is found to coexist with highly crystalline rutile. These structural characteristics are discussed in relation with the observed general trends for the optical properties. - Highlights: Cobalt doped and undoped TiO{sub 2} powders have been prepared by solgel route. Doping makes the band gap narrower. Doping delays the phase transformation from anatase to rutile. Doping inhibits the growth of the crystallites. At high annealing temperature a CoTiO{sub 3} phase coexists with highly crystalline rutile.

  10. Rapid synthesis of low-fractal dimension titanium oxide polymers by a sol-gel technique using hydrazine monohydrochloride.

    PubMed

    Shimizu, Wataru; Sato, Takaaki; Matsumoto, Taki; Murakami, Yasushi

    2012-05-01

    Titanium oxide polymers having a low-fractal dimension (d(f) < 2) were rapidly synthesized from titanium tetra-n-butoxide via a catalytic sol-gel process with a hydrazine monohydrochloride catalyst. Different from conventional sol-gel processes aimed at producing low-fractal dimension titanium oxide polymers, the present synthetic strategy needed neither organic ligand to enhance the stability of titanium alkoxides nor an extremely long reaction time in a strongly acidic solution condition, thanks to a drastically accelerated polycondensation reaction. We pursued the structure evolution of the titanium oxide polymers by means of time-resolved small-angle X-ray scattering (Tr-SAXS). The SAXS data unambiguously demonstrate the generation of the expanded polymer-like structure characterized by the fractal dimension of d(f) approximately equal 5/3. The results offer an efficient route to the synthesis of the weakly-branched titanium oxide polymers, which are expected to be used to create a wide range of optical materials having a high refractive index, such as anti-glare coating. PMID:22852301

  11. Sol-gel derived ionic copper-doped microstructured optical fiber: a potential selective ultraviolet radiation dosimeter.

    PubMed

    El Hamzaoui, Hicham; Ouerdane, Youcef; Bigot, Laurent; Bouwmans, Graud; Capoen, Bruno; Boukenter, Aziz; Girard, Sylvain; Bouazaoui, Mohamed

    2012-12-31

    We report the fabrication and characterization of a photonic crystal fiber (PCF) having a sol-gel core doped with ionic copper. Optical measurements demonstrate that the ionic copper is preserved in the silica glass all along the preparation steps up to fiber drawing. The photoluminescence results clearly show that such an ionic copper-doped fiber constitutes a potential candidate for UV-C (200-280 nm) radiation dosimetry. Indeed, the Cu?-related visible photoluminescence of the fiber shows a linear response to 244 nm light excitation measured for an irradiation power up to 2.7 mW at least on the Cu-doped PCF core. Moreover, this response was found to be fully reversible within the measurement accuracy of this study ( 1%), underlying the remarkable stability of copper in the Cu? oxidation state within the pure silica core prepared by a sol-gel route. This reversibility offers possibilities for the achievement of reusable real-time optical fiber UV-C dosimeters. PMID:23388802

  12. Sol-gel hybrid materials for aerospace applications: Chemical characterization and comparative investigation of the magnetic properties

    NASA Astrophysics Data System (ADS)

    Catauro, Michelina; Mozzati, Maria Cristina; Bollino, Flavia

    2015-12-01

    In the material science field, weightless conditions can be successfully used to understand the relationship between manufacturing process, structure and properties of the obtained materials. Aerogels with controlled microstructure could be obtained by sol-gel methods in microgravity environment, simulated using magnetic levitation if they are diamagnetic. In the present work, a sol-gel route was used to synthesize class I, organic-inorganic nanocomposite materials. Two different formulations were prepared: the former consisted in a SiO2 matrix in which different percentages of polyethylene glycol (PEG) were incorporated, the latter was a ZrO2 matrix entrapping different amounts of poly (ε-caprolactone) (PCL). Fourier Transform Infrared Spectroscopy (FT-IR) detected that the organic and the inorganic components in both the formulation interact by means of hydrogen bonds. X-ray diffraction (XRD) analysis highlighted the amorphous nature of the synthesized materials and Scanning Electron Microscope (SEM) showed that they have homogeneous morphology and are nanocomposites. Superconducting Quantum Interference Device (SQUID) magnetometry confirmed the expected diamagnetic character of those hybrid systems. The obtained results were compared to those achieved in previous studies regarding the influence of the polymer amount on the magnetic properties of SiO2/PCL and ZiO2/PEG hybrids, in order to understand how the diamagnetic susceptibility is influenced by variation of both the inorganic matrix and organic component.

  13. Making MgO/SiO2 Glasses By The Sol-Gel Process

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1989-01-01

    Silicon dioxide glasses containing 15 mole percent magnesium oxide prepared by sol-gel process. Not made by conventional melting because ingredients immiscible liquids. Synthesis of MgO/SiO2 glass starts with mixing of magnesium nitrate hexahydrate with silicon tetraethoxide, both in alcohol. Water added, and transparent gel forms. Subsequent processing converts gel into glass. Besides producing glasses of new composition at lower processing temperatures, sol-gel method leads to improved homogeneity and higher purity.

  14. Preparation and characterization of conductive and transparent ruthenium dioxide sol-gel films.

    PubMed

    Allhusen, John S; Conboy, John C

    2013-11-27

    RuO2 conductive thin films were synthesized using the sol-gel method and deposited onto transparent insulating substrates. The optical transmission, film thickness, surface morphology and composition, resistivity, and spectroelectrochemical performance have been characterized. The optical transmission values of these films ranged from 70 to 89% in the visible region and from 56 to 88% in the infrared region. Resistivity values of the RuO2 sol-gel films varied from 1.02 10(-3) to 1.13 ? cm and are highly dependent on the initial solution concentration of RuO2 in the sol-gel. The RuO2 sol-gel films were used as electrodes for the electrochemical oxidation and reduction of ferrocenemethanol. The electrochemical behavior of our novel RuO2 sol-gel films was compared to that of a standard platinum disk electrode and showed no appreciable differences in the half-wave potential (E1/2). The mechanical and chemical stability of the coatings was tested by physical abrasion and exposure to highly acidic, oxidizing Piranha solution. Repeated exposure to these extreme conditions did not result in any appreciable decline in electrochemical performance. Finally, the use of the novel RuO2 sol-gel conductive and transparent films was demonstrated in a spectroelectrochemistry experiment in which the oxidation and reduction of ferrocenemethanol was monitored via UV-vis spectroscopy as the applied potential was cycled. PMID:24221640

  15. Controlled release of vancomycin from thin sol-gel films on implant surfaces successfully controls osteomyelitis.

    PubMed

    Adams, Christopher S; Antoci, Valentin; Harrison, Gerald; Patal, Payal; Freeman, Terry A; Shapiro, Irving M; Parvizi, Javad; Hickok, Noreen J; Radin, Shula; Ducheyne, Paul

    2009-06-01

    Peri-prosthetic infection remains a serious complication of joint replacement surgery. Herein, we demonstrate that a vancomycin-containing sol-gel film on Ti alloy rods can successfully treat bacterial infections in an animal model. The vancomycin-containing sol-gel films exhibited predictable release kinetics, while significantly inhibiting S. aureus adhesion. When evaluated in a rat osteomyelitis model, microbiological analysis indicated that the vancomycin-containing sol-gel film caused a profound decrease in S. aureus number. Radiologically, while the control side showed extensive bone degradation, including abscesses and an extensive periosteal reaction, rods coated with the vancomycin-containing sol-gel film resulted in minimal signs of infection. MicroCT analysis confirmed the radiological results, while demonstrating that the vancomycin-containing sol-gel film significantly protected dense bone from resorption and minimized remodeling. These results clearly demonstrate that this novel thin sol-gel technology can be used for the targeted delivery of antibiotics for the treatment of periprosthetic as well as other bone infections. PMID:19051247

  16. One-step sol-gel imprint lithography for guided-mode resonance structures.

    PubMed

    Huang, Yin; Liu, Longju; Johnson, Michael; C Hillier, Andrew; Lu, Meng

    2016-03-01

    Guided-mode resonance (GMR) structures consisting of sub-wavelength periodic gratings are capable of producing narrow-linewidth optical resonances. This paper describes a sol-gel-based imprint lithography method for the fabrication of submicron 1D and 2D GMR structures. This method utilizes a patterned polydimethylsiloxane (PDMS) mold to fabricate the grating coupler and waveguide for a GMR device using a sol-gel thin film in a single step. An organic-inorganic hybrid sol-gel film was selected as the imprint material because of its relatively high refractive index. The optical responses of several sol-gel GMR devices were characterized, and the experimental results were in good agreement with the results of electromagnetic simulations. The influence of processing parameters was investigated in order to determine how finely the spectral response and resonant wavelength of the GMR devices could be tuned. As an example potential application, refractometric sensing experiments were performed using a 1D sol-gel device. The results demonstrated a refractive index sensitivity of 50 nm/refractive index unit. This one-step fabrication process offers a simple, rapid, and low-cost means of fabricating GMR structures. We anticipate that this method can be valuable in the development of various GMR-based devices as it can readily enable the fabrication of complex shapes and allow the doping of optically active materials into sol-gel thin film. PMID:26822203

  17. Structural Modification of Sol-Gel Materials through Retro Diels-Alder Reaction

    SciTech Connect

    SHALTOUT,RAAFAT M.; LOY,DOUGLAS A.; MCCLAIN,MARK D.; PRABAKAR,SHESHASAYANA; GREAVES,JOHN; SHEA,KENNETH J.

    1999-12-08

    Hydrolysis and condensation of organically bridged bis-triethoxysilanes, (EtO){sub 3}Si-R-Si(OEt){sub 3}, results in the formation of three dimensional organic/inorganic hybrid networks (Equation 1). Properties of these materials, including porosity, are dependent on the nature of the bridging group, R. Flexible groups (akylene-spacers longer than five carbons in length) polymerize under acidic conditions to give non-porous materials. Rigid groups (such as arylene-, alkynylene-, or alkenylene) form non-porous, microporous, and macroporous gels. In many cases the pore size distributions are quite narrow. One of the motivations for preparing hybrid organic-inorganic materials is to extend the range of properties available with sol-gel systems by incorporating organic groups into the inorganic network. For example, organically modified silica gels arc either prepared by co-polymerizing an organoalkoxysilane with a silica precursor or surface silylating the inorganic gel. This can serve to increase hydrophobicity or to introduce some reactive organic functionality. However, the type and orientation of these organic functionalities is difficult to control. Furthermore, many organoalkoxysilanes can act to inhibitor even prevent gelation, limiting the final density of organic functionalities. We have devised a new route for preparing highly functionalized pores in hybrid materials using bridging groups that are thermally converted into the desired functionalities after the gel has been obtained. In this paper, we present the preparation and characterization of bridged polysilsesquioxanes with Diels-Alder adducts as the bridging groups from the sol-gel polymerization of monomers 2 and 4. The bridging groups are constructed such that the retro Diela-Alder reaction releases the dienes and leaves the dienophiles as integral parts of the network polymers. In the rigid architecture of a xerogel, this loss of organic functionality should liberate sufficient space to modify the overall porosity. Furthermore, the new porosity will be functionalized with the dienophilic olefin bridging group. We also demonstrate that by changing the type of Diels-Alder adduct used as the bridging group, we can change the temperature at which the retro-Diels-Alder reaction will occur.

  18. Large-area sol-gel highly-reflective coatings processed by the dipping technique

    SciTech Connect

    Belleville, P.; Pegon, P.

    1997-12-01

    The Centre d`Etudes de Limeil-Valenton is currently involved in a project which consists of the construction of a 2 MJ/500TW (351-nm) pulsed Nd:glass laser devoted to Inertial Confinement Fusion (ICF) research. With 240 laser beams, the proposed megajoule-class laser conceptual design necessitates 44-cm x 2 44-cm x 6-cm cavity-end mirrors (1053-nm) representing more than 50-m{sup 2} of coated area. These dielectric mirrors are made of quaterwave stacks of SiO{sub 2} and ZrO{sub 2}-PVP (PolyVinylPyrrolidone) and are prepared from colloidal suspensions (sols) using the sol-gel route. After a sustained search effort. we have prepared (SiO{sub 2}/ZrO{sub 2}-PVP){sup 10} mirrored coatings with up to 99% reflection at 1053-nm and for different incidence use. Adequate laser-conditioned damage thresholds ranging 14 - 15 J/cm{sup 2} at 1053-nm wavelength and with 3-ns pulse duration were achieved. Large-area mirrors with good coating uniformity and weak edge-effect were produced by dip-coating at room temperature and atmospheric pressure.

  19. Morphology of sol-gel derived nano-coated coralline hydroxyapatite.

    PubMed

    Ben-Nissan, B; Milev, A; Vago, R

    2004-09-01

    Current bone graft materials are mainly produced from coralline hydroxyapatite (HAp). Due to the nature of the conversion process, commercial coralline HAp has retained coral or CaCO(3,) and the structure possesses nanopores within the inter-pore trabeculae, resulting in high dissolution rates. Under certain conditions these features reduce durability and strength and are not utilised where high structural strength is required. To overcome these limitations, a new coral double-conversion technique has been developed. The technique involves a two-stage application route where, in the first stage, complete conversion of coral to pure HAp is achieved. In the second, a new sol-gel-derived HAp nano-coating is directly applied to cover the micro- and nano-pores within the intra-pore material, whilst maintaining the large pores. Biaxial strength was improved two-fold due to this unique double treatment. This application is expected to result in enhanced durability and longevity due to the monophasic hydroxyapatite structure and strength in the physiological environment. It is anticipated that this new material can be applied to load-bearing bone graft applications where high strength requirements are pertinent. PMID:15109858

  20. Glass-based confined structures fabricated by sol-gel and radio frequency sputtering

    NASA Astrophysics Data System (ADS)

    Chiappini, Andrea; Armellini, Cristina; Carpentiero, Alessandro; Vasilchenko, Iustyna; Lukowiak, Anna; Risti?, Davor; Varas, Stefano; Normani, Simone; Mazzola, Maurizio; Chiasera, Alessandro

    2014-07-01

    Some of the main results obtained in the field of glass-based photonic crystal (PC) systems using complementary techniques, such as radio frequency (RF) sputtering and sol-gel route, are presented. Initially, rare earth-activated one-dimensional PCs fabricated by RF-sputtering technique will be discussed, specifically the cavity is constituted by an Er-doped SiO active layer inserted between two Bragg reflectors consisting of 10 pairs of SiO2/TiO2 layers. Moreover, from near infrared, transmittance and variable angle reflectance spectra have verified the presence of a stop band from 1500 to 2000 nm with a cavity resonance centered at 1749 nm at 0 deg and quality factor of 890. In the second case, a composite system based on polystyrene colloidal nanoparticles assembled and embedded in an elastomeric matrix will be presented in detail. This system has been designed as a structure that displays an iridescent green color that can be attributed to the PC effect. This feature has been exploited to create a chemical sensor; in fact optical measurements have evidenced that this system presents a different optical response as a function of the solvent applied on the surface, showing: (1) high sensitivity, (2) fast response, and (3) reversibility of the signal change.

  1. Sol-gel synthesis of Fe-Co nanoparticles and magnetization study

    NASA Astrophysics Data System (ADS)

    Nautiyal, Pranjal; Seikh, Md. Motin; Lebedev, Oleg I.; Kundu, Asish K.

    2015-03-01

    We report the synthesis of carbon encapsulated Fe-Co nanoparticles using conventional sol-gel route and its magnetization studies. The x-ray diffraction indicates the formation of the single phase body centered cubic alloy Fe-Co phase with cell parameter of 2.857 . Nanoparticles are highly crystalline and exhibit low index faceting as determined from high-resolution transmission electron microscopy (HRTEM) investigation. The observed orthogonal lattice planes with lattice distance of 2.86 are attributed to (100) and (010). HRTEM image confirms the cube like Fe-Co nanoparticles with core-shell structure of carbon encapsulation, composed of carbon and graphite materials. The magnetometry results of the carbon encapsulated alloy Fe-Co nanoparticles with core-shell structure designate as a ferromagnetically ordered soft magnet with coercive field of 890 Oe (at 5 K). The coercive field and magnetization value depend on the size of nanoparticles as well as the diamagnetic contribution of carbon encapsulation.

  2. Aerogels, emulsions, and composites: Controlling structure with organic sol-gel chemistry

    SciTech Connect

    Pekala, R.W.; Alviso, C.T.; Hulsey, S.S.; Kong, F.M.

    1992-04-01

    The sol-gel polymerization of resorcinol with formaldehyde is a proven synthetic route for the formation of organic aerogels. These materials can also be pyrolyzed in an inert atmosphere to form vitreous carbon aerogels. Both resorcinol-formaldehyde and carbon aerogels are characterized by high porosity (50--98%), ultrafine cell/pore sizes (< 100 mn), high surface area (400--1000 m{sup 2}/g), and a solid matrix composed of interconnected colloidal-like particles or fibrous chains with characteristic diameters of 10 nm. While this nanostructure and the low Z (atomic number) composition are responsible for the unique optical, thermal, acoustic, mechanical, and electrical properties of organic aerogels, there are certain applications in which a larger scale structure is also desired in combination with the unique features of the aerogel. In order to achieve this goal, we have been emulsifying our resorcinol-formaldehyde sols to form foams which retain the aerogel framework but have some cells/pores as large as 2 {mu}m. In another approach, we have infused an emulsion-derived polystryene foam with a resorcinol-formaldehyde sol to form a new composite foam. This paper addresses the chemistry-structure-property relationships of organic aerogels, their emulsion-derived derivatives, and composite foams.

  3. Synthesis and Characterization of Sol-Gel Prepared Silver Nanoparticles

    NASA Astrophysics Data System (ADS)

    Ahlawat, Dharamvir Singh; Kumari, Rekha; Rachna; Yadav, Indu

    2014-03-01

    Silver nanoparticles (SNPs) have been successfully prepared using sol-gel method by annealing the sample at 550C for 30 min. The SNPs were not confirmed by X-ray diffraction (XRD) analysis when the annealing temperature was considered at 450C. They were also not confirmed without calcination of the sample. The physical mechanism of silver clusters formation in the densified silica matrix with respect to thermal treatment has been understood. The presence of silver metal in the silica matrix was confirmed by XRD analysis and TEM image of the samples. The average size of nanoparticles dispersed in silica matrix was determined as 10.2 nm by the XRD technique. The synthesized nanocomposites were also characterized by UV-Visible spectroscopy with a peak in the absorption spectra at around 375 nm. The distribution of particle size has been reported here in the range from 8 nm to 25 nm by TEM observations of the sample prepared at 550C. The spherically smaller size (?10 nm) SNPs have reported the surface plasmons resonance (SPR) peak less than or near to 400 nm due to blue-shifting and effect of local refractive index. Without annealing the silica samples the absorption spectra does not show any peak around 375 nm. The FTIR spectroscopy of the three types of samples prepared at different temperatures (room temperature, 450C and 550C) has also been reported. This spectra have provided the identification of different chemical groups in the prepared samples. It has been predicted that the size of SNPs by XRD, UV-Visible and TEM results have agreed well with each other. It may be concluded that formation of SNPs is a function of annealing temperature.

  4. Fabrication of highly uniform and porous MgF2 anti-reflective coatings by polymer-based sol-gel processing on large-area glass substrates

    NASA Astrophysics Data System (ADS)

    Raut, Hemant Kumar; Safari Dinachali, Saman; Konadu Ansah-Antwi, Kwadwo; Anand Ganesh, V.; Ramakrishna, Seeram

    2013-12-01

    Despite recent progress in the fabrication of magnesium fluoride (MgF2) anti-reflective coatings (ARCs), simple, effective and scalable sol-gel fabrication of MgF2 ARCs for large-area glass substrates has prospective application in various optoelectronic devices. In this paper, a polymer-based sol-gel route was devised to fabricate highly uniform and porous MgF2 ARCs on large-area glass substrates. A sol-gel precursor made of polyvinyl acetate and magnesium trifluoroacetate assisted in the formation of uniformly mesoporous MgF2 ARCs on glass substrates, leading to the attainment of a refractive index of 1.23. Systematic optimization of the thickness of the ARC in the sub-wavelength regime led to achieving 99.4% transmittance in the case of the porous MgF2 ARC glass. Precise control of the thickness of porous MgF2 ARC glass also resulted in a mere 0.1% reflection, virtually eliminating reflection off the glass surface at the target wavelength. Further manipulation of the thickness of the ARC on either side of the glass substrate led to the fabrication of relatively broadband, porous MgF2 ARC glass.

  5. Growth of epitaxial LaAlO{sub 3} and CeO{sub 2} films using sol-gel precursors

    SciTech Connect

    Shoup, S.S.; Paranthaman, M.; Beach, D.B.

    1996-04-01

    LaAlO{sub 3} and CeO{sub 2} films have been successfully grown using sol-gel precursors. LaAlO{sub 3} precursor solution has been prepared from a metal alkoxide route and spun-cast on a SrTiO{sub 3} (100) single crystal to yield an epitaxial film following pyrolysis at 800{degrees}C in a rapid thermal annealer. A CeO{sub 2} precursor solution has been made using both an aqueous and an alkoxide route.

  6. Quasi-one-dimensional nanostructured cobalt (Co) intercalated vanadium oxide (V{sub 2}O{sub 5}): Peroxovanadate sol gel synthesis and structural study

    SciTech Connect

    Langie da Silva, Douglas; Moreira, Eduardo Ceretta; Dias, Fábio Teixeira; Neves Vieira, Valdemar das; Brandt, Iuri Stefani; Cas Viegas, Alexandre da; Pasa, André Avelino

    2015-01-15

    Nanostructured cobalt vanadium oxide (V{sub 2}O{sub 5}) xerogels spread onto crystalline Si substrates were synthesized via peroxovanadate sol gel route. The resulting products were characterized by distinct experimental techniques. The surface morphology and the nanostructure of xerogels correlate with Co concentration. The decrease of the structural coherence length is followed by the formation of a loose network of nanopores when the concentration of intercalated species was greater than 4 at% of Co. The efficiency of the synthesis route also drops with the increase of Co concentration. The interaction between the Co(OH{sub 2}){sub 6}{sup 2+} cations and the (H{sub 2}V{sub 10}O{sub 28}){sup 4−} anions during the synthesis was suggested as a possible explanation for the incomplete condensation of the V{sub 2}O{sub 5} gel. Finally the experimental results points for the intercalation of Co between the bilayers of the V{sub 2}O{sub 5}. In this scenario two possible preferential occupation sites for the metallic atoms in the framework of the xerogel were proposed. - Graphical abstract: Quasi-one-dimensional nanostructured cobalt (Co) intercalated vanadium oxide (V{sub 2}O{sub 5}) nanoribbons synthesized by peroxovanadate sol gel route. - Highlights: • Nanostructured cobalt V{sub 2}O{sub 5} gel spread onto c{sub S}i were synthesized via peroxovanadate sol gel route. • The micro and nanostructure correlates with the cobalt content. • The efficiency of the synthesis route shows to be also dependent of Co content. • The experimental results points for the intercalation of Co between the bilayers of the V{sub 2}O{sub 5} xerogel.

  7. Sol-Gel Protective Coatings For Black Chrome Solar Selective Films

    NASA Astrophysics Data System (ADS)

    Pettit, R. B.; Brinker, C. J.

    1982-04-01

    Electrodeposited black chrome solar selective films degrade rapidly when heated to temperatures above 300°C in air. The application of sol-gel protective coatings to the black chrome films has been investigated as a possible means to improve the oxidation resistance of black chrome at high temperatures. The sol-gel coating process consists of applying an alcoholic solution containing polymeric glass precursors. After the coating is fired for about one-half hour at a moderate temperature (-450°C), a glass layer is obtained. Because of the wide range of sol-gel processing parameters, initial studies have concentrated on determining the effect of the following variables on the thermal stability of sol-gel coated black chrome: (1) sol-gel composition; (2) firing temperature; (3) firing atmosphere; (4) sol-gel coating thickness; (5) pre-aging of the black chrome films. Of the compositions studied, only Si02/B203 and Si02/B203/Al203/Na20/Ba0 resulted in improved thermal stability. Of the other processing parameters, the firing temperature had the most significant effect on the resulting black chrome thermal stability, with 500°C firing being optimum. For the best combination of process variables studied to date, the solar absorptance of a sol-gel coated sample decreased from 0.97 to 0.95 after 100 hrs at 400°C, while, for an uncoated control sample, the solar absorptance decreased to 0.89. For most of the solgel coated films, continued aging at 400°C resulted in continued protection of the black chrome film.*

  8. A new sol-gel process for producing Na(2)O-containing bioactive glass ceramics.

    PubMed

    Chen, Qi-Zhi; Li, Yuan; Jin, Li-Yu; Quinn, Julian M W; Komesaroff, Paul A

    2010-10-01

    The sol-gel process of producing SiO(2)-CaO bioactive glasses is well established, but problems remain with the poor mechanical properties of the amorphous form and the bioinertness of its crystalline counterpart. These properties may be improved by incorporating Na(2)O into bioactive glasses, which can result in the formation of a hard yet biodegradable crystalline phase from bioactive glasses when sintered. However, production of Na(2)O-containing bioactive glasses by sol-gel methods has proved to be difficult. This work reports a new sol-gel process for the production of Na(2)O-containing bioactive glass ceramics, potentially enabling their use as medical implantation materials. Fine powders of 45S5 (a Na(2)O-containing composition) glass ceramic have for the first time been successfully synthesized using the sol-gel technique in aqueous solution under ambient conditions, with the mean particle size being approximately 5 microm. A comparative study of sol-gel derived S70C30 (a Na(2)O-free composition) and 45S5 glass ceramic materials revealed that the latter possesses a number of features desirable in biomaterials used for bone tissue engineering, including (i) the crystalline phase Na(2)Ca(2)Si(3)O(9) that couples good mechanical strength with satisfactory biodegradability, (ii) formation of hydroxyapatite, which may promote good bone bonding and (iii) cytocompatibility. In contrast, the sol-gel derived S70C30 glass ceramic consisted of a virtually inert crystalline phase CaSiO(3). Moreover, amorphous S70C30 largely transited to CaCO(3) with minor hydroxyapatite when immersed in simulated body fluid under standard tissue culture conditions. In conclusion, sol-gel derived Na(2)O-containing glass ceramics have significant advantages over related Na(2)O-free materials, having a greatly improved combination of mechanical capability and biological absorbability. PMID:20447473

  9. Ionic conductivity of Bi{sub 2}Ni{sub x}V{sub 1−x}O{sub 5.5−3x/2} (0.1 ≤ x ≤ 0.2) oxides prepared by a low temperature sol-gel route

    SciTech Connect

    Rusli, Rolan; Patah, Aep Prijamboedi, Bambang Ismunandar; Abrahams, Isaac

    2014-03-24

    Solid oxides fuel cells (SOFCs) is one technology that could contribute toward future sustainable energy. One of the most important components of an SOFC is the electrolyte, which must have high ionic conductivity. Cation substitution of vanadium in Bi{sub 4}V{sub 2}O{sub 11} yields a family of fast oxide ion conducting solids known collectively as the BIMEVOXes (bismuth metal vanadium oxide), which have the potential to be applied as electrolytes in SOFCs. The purpose of this work is to study the effect of Ni concentration, when used as a dopant, on the ionic conductivity of Bi{sub 2}Ni{sub x}V{sub 1−x}O{sub 5.5−3x/2} (BINIVOX) oxides (0.1 ≤ x ≤ 0.2) when prepared by a sol gel method. The gels were calcined at 600 °C for 24 h to produce pure BINIVOX. These oxides were found to exhibit the γ-phase structure with tetragonal symmetry in space group I4/mmm. Ionic conductivity of BINIVOX at 300 °C were 6.9 × 10{sup −3} S cm{sup −1}, 1.2 × 10{sup −3} S cm{sup −1}, and 8.2 × 10{sup −4} S cm{sup −1}, for x = 0.1; 0.15; and 0.2; respectively; and at 600 °C were 1.1 × 10{sup −1} S cm{sup −1}, 5.3 × 10{sup −2} S cm{sup −1}, and 2.8 ×10{sup −2} S cm{sup −1}, for x = 0.1; 0.15; and 0.2; respectively.

  10. Enhanced photoelectrochemical performance of Ti-doped hematite thin films prepared by the sol-gel method

    NASA Astrophysics Data System (ADS)

    Lian, Xiaojuan; Yang, Xin; Liu, Shangjun; Xu, Ying; Jiang, Chunping; Chen, Jinwei; Wang, Ruilin

    2012-01-01

    Ti-doped ?-Fe2O3 thin films were successfully prepared on FTO substrates by the sol-gel route. Hematite film was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). The XRD data showed ?-Fe2O3 had a preferred (1 1 0) orientation which belonged to the rhombohedral system. Interestingly, the grains turned into worm-like shape after annealed at high temperature. The IPCE could reach 32.6% at 400 nm without any additional potential vs. SCE. Titanium in the lattice can affect the photo electro chemical performance positively by increasing the conductivity of the thin film. So the excited electrons and holes could live longer, rather than recombining with each other rapidly as undoped hematite. And the efficient carrier density on the Ti-doped anode surface was higher than the undoped anode, which contribute to the well PEC performance.

  11. Origin of the high tunability of BaTiSnO3 thin films deposited by sol-gel

    NASA Astrophysics Data System (ADS)

    Mascot, Manuel; Carru, Jean-Claude; Fasquelle, Didier

    2015-10-01

    Ba(Sn0.02Ti0.98)O3 thin films (BTS) were prepared by sol-gel route and deposited by spin-coating on commercial Pt/Ti/SiO2/Si substrates. By modifying the annealing conditions from 750°C at 1 h to 950°C at 15 min, the relative tunability nr at 100°C in the paraelectric state increased from 45 to 70% while the DC dielectric permittivity ɛ‧(0) increased as well. The evolutions of ɛ‧(E) and nr(E) are explained from Devonshire thermodynamic formalism. The very high value of tunability of 70% is explained by the grain size increase of our BTS thin films and the decrease of the dead layer effect when the annealing conditions are optimized.

  12. Recycling of chemicals from alkaline waste generated during preparation of UO 3 microspheres by sol-gel process

    NASA Astrophysics Data System (ADS)

    Kumar, Ashok; Vittal Rao, T. V.; Mukerjee, S. K.; Vaidya, V. N.

    2006-05-01

    Internal gelation process, one of the sol-gel processes for nuclear fuel fabrication, offers many advantages over conventional powder pellet route. However, one of the limitation of the process is generation of large volume of alkaline liquid waste containing hexamethylenetetramine, urea, ammonium nitrate, ammonium hydroxide etc. Presence of ammonium nitrate with hexamethylenetetramine and urea presents a fire hazard which prevents direct disposal of the waste as well as its recycle by evaporation. The paper describes the studies carried out to suitably process the waste. Nitrate was removed from the waste by passing through Dowex 1 4 anion exchange resin in OH - form. 1.0 M NaOH was used to regenerate the resin. The nitrate-free waste was further treated to recover and recycle hexamethylenetetramine, urea and ammonium hydroxide for preparation of UO 3 microspheres. The quality of the microspheres obtained was satisfactory. An optimized flow sheet for processing of the waste solution has been suggested.

  13. Investigation of corrosion protection performance of sol-gel surface treatments on AA2024-T3

    NASA Astrophysics Data System (ADS)

    Voevodin, Natalia Nikolajevna

    The dissertation research project addresses the technologically important problem of replacement of chromate based coatings for corrosion protection of aircraft. A review of corrosion processes in high-strength aluminum alloys indicated that the strengthening intermetallic precipitates provide local cathodic areas, which may initiate surface pitting. The mechanisms of chromate inhibition in these localized corrosion processes were identified. The environmental hazard of chromates was also highlighted, serves as the impetus for chromate coating replacement. Sol-gel coatings are shown as an excellent alternative, based on environment compliance, flexibility in the composition control, and reasonable costs. Several sol-gel coatings were formulated and applied to the surface of an AA2024-T3 alloy. The coating composition and bonding were analyzed with XPS and FTIR, surface morphology was studied with SEM and AFM, and corrosion protection properties were tested with EIS, PDS, salt water immersion, and salt-fog exposure. The results demonstrated that epoxy-zirconate sol-gel coatings can provide excellent barrier properties. A novel SVET technique was applied for studies of local electrochemical processes in the pitting formation. This technique was further refined in model studies of aluminum surfaces with artificially created local cathodic regions, experimental studies of chromate inhibition with pit formation, and pitting development studies in sol-gel coatings with artificially introduced defects. Mechanisms of pitting development and inhibition with the pit initiation and growth kinetics were established. The Zr-epoxy coatings are subjected to the pit development and undercutting in the absence of the corrosion inhibitors. Several organic and non-organic inhibitors were evaluated in the sol-gel coating composition. Organic inhibitors had a better compliance with sol-gel chemistry and were identified for future studies. Experiments were performed to verify that sol-gel coatings can be used as barrier layers in complex coating systems. The results clearly demonstrated that Zr-epoxy sol-gel coatings are a viable replacement for the currently used chromate-based surface treatments. This work expands the fundamental knowledge of chromate coating replacement with chromate-free sol-gel coatings and identifies possible ways to implement this goal.

  14. Sol-gel process from heterometallic alkoxides to incorporate alkaline- and rare earths in alumina for automotive applications

    SciTech Connect

    Narula, C.K.

    1996-12-31

    The high cost of materials prepared by sol-gel processing and the loss of useful surface properties at elevated temperature has prevented the application of sol-gel processed materials in automotive exhaust reduction catalyst formulations. In this report, the authors briefly describe the important developments needed in the next generation automotive catalysts and the role of sol-gel processed materials. They will also discuss the application of heterometallic alkoxides as sol-gel precursors to achieve the molecular distribution of lanthanides and alkaline earths in alumina matrices needed for the stabilization of alumina based materials at elevated temperatures.

  15. Mechanical compatibility of sol-gel annealing with titanium for orthopaedic prostheses.

    PubMed

    Greer, Andrew I M; Lim, Teoh S; Brydone, Alistair S; Gadegaard, Nikolaj

    2016-01-01

    Sol-gel processing is an attractive method for large-scale surface coating due to its facile and inexpensive preparation, even with the inclusion of precision nanotopographies. These are desirable traits for metal orthopaedic prostheses where ceramic coatings are known to be osteoinductive and the effects may be amplified through nanotexturing. However there are a few concerns associated with the application of sol-gel technology to orthopaedics. Primarily, the annealing stage required to transform the sol-gel into a ceramic may compromise the physical integrity of the underlying metal. Secondly, loose particles on medical implants can be carcinogenic and cause inflammation so the coating needs to be strongly bonded to the implant. These concerns are addressed in this paper. Titanium, the dominant material for orthopaedics at present, is examined before and after sol-gel processing for changes in hardness and flexural modulus. Wear resistance, bending and pull tests are also performed to evaluate the ceramic coating. The findings suggest that sol-gel coatings will be compatible with titanium implants for an optimum temperature of 500C. PMID:26691162

  16. Vibrational spectroscopic studies of (3-mercaptopropyl)trimethoxylsilane sol-gel and its coating

    NASA Astrophysics Data System (ADS)

    Li, Ying-Sing; Wang, Yu; Tran, Tuan; Perkins, Anshion

    2005-10-01

    Organosilane sol-gels have been prepared under different conditions from mercaptopropyltrimethoxysilane (MPTMS) and mercaptopropyltriethoxysilane (MPTES). These sol-gels were applied for the thin film coating on aluminum. Vibrational spectroscopy has been employed to trace and to study the proceeding of the sol-gel formation and the curing of the coated films on Al. Based on the group frequencies as well as their spectral behavior under different conditions, vibrational assignments have been made for most of the observed bands. Surface enhanced Raman scattering has revealed the chemical adsorption of MPTMS sol-gel on silver particles. Recorded reflection and absorption infrared (RAIR) spectra of coated tiles cured at different temperatures have indicated that surface reaction may occur at high temperature. The anticorrosion characters of the coated metals have been evaluated with the measured electrochemical data. Results from cyclic voltammographs have indicated that each layer of sol-gel coating would reduce the redox current across the electrode/electrolyte solution interface. Tafel plots have shown that the anodic current of the coated electrode decreases significantly and the corrosion potentials shift to the positive side.

  17. Roughness evolution of sol-gel optical coatings by ion beam sputtering

    NASA Astrophysics Data System (ADS)

    Gailly, P.; Dubreuil, O.; Fleury-Frenette, K.

    2015-12-01

    The surface roughness evolution of two silica-based sol-gel materials under 650 eV argon ion beam sputtering has been investigated. The liquid sol-gel solutions were applied on silicon substrates using the dip coating technique and thermally cured to obtain thin solid films and their thicknesses were then controlled over the samples surface using spectroscopic ellipsometry. The surface roughness of the sol-gel films was measured using both interferometric profilometry and atomic force microscopy depending on the obtained sputtering depths. We observed a significant increase of the roughness according to the sputtering depth, faster in the case of sol-gel layers than with bulk fused silica. Interestingly, the sputtering rates of the sol-gel layers were found much higher than the rate obtained on bulk fused silica. The development of micron scale holes with relatively stable interstices is supposed to rule the surface roughness evolution. AFM measurements revealed a regular submicron scale lateral structure which nanometric amplitude is amplified within sputtering.

  18. Optical pH sensor based on sol-gel-doped new luminescent dye

    NASA Astrophysics Data System (ADS)

    Lobnik, Aleksandra; Niederreiter, Karlheinz; Uray, Georg

    1999-11-01

    The sol-gel process is an exciting new technology that enables the production of gel glasses and ceramic materials at room temperature. Sol-gel technology offers simple methods for manipulation of the structure, configuration, composition and chemical characteristics of organic matrices. A novel longwave luminescent dye based on the europium luminescence initiated by a covalently bonded antenna fluorophore was designed, synthesized and characterized. The dye was successfully entrapped into various sol-gel and ormosil matrices and consequent optical- , leaching- and light fastness-properties were tested. Finally, sensor layer based on TMOS doped with Eu3+- complex and bromothymol blue was found to be most appropriate for purposes of sensing pH over the range 5-10.

  19. Highly efficient solid-state neutron scintillators based on hybrid sol-gel nanocomposite materials

    SciTech Connect

    Kesanli, Banu; Hong, Kunlun; Meyer, Kent; Im, Hee-Jung; Dai, Sheng

    2006-11-20

    This research highlights opportunities in the formulation of neutron scintillators that not only have high scintillation efficiencies but also can be readily cast into two-dimensional detectors. Series of transparent, crack-free monoliths were prepared from hybrid polystyrene-silica nanocomposites in the presence of arene-containing alkoxide precursor through room temperature sol-gel processing. The monoliths also contain lithium-6 salicylate as a target material for neutron-capture reactions and amphiphilic scintillator solution as a fluorescent sensitizer. Polystyrene was functionalized by trimethoxysilyl group in order to enable the covalent incorporation of aromatic functional groups into the inorganic sol-gel matrices for minimizing macroscopic phase segregation and facilitating lithium-6 doping in the sol-gel samples. Neutron and alpha responses of these hybrid polystyrene-silica monoliths were explored.

  20. Tantalum-tungsten oxide thermite composites prepared by sol-gel synthesis and spark plasma sintering

    SciTech Connect

    Kuntz, Joshua D.; Gash, Alexander E.; Cervantes, Octavio G.; Munir, Zuhair A.

    2010-08-15

    Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and the results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High-Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta-WO{sub 3}) energetic composite was consolidated to a density of 9.17 g cm{sup -3} or 93% relative density. In addition, those samples were consolidated without significant pre-reaction of the constituents, thus retaining their stored chemical energy. (author)

  1. Tantalum-Tungsten Oxide Thermite Composite Prepared by Sol-Gel Synthesis and Spark Plasma Sintering

    SciTech Connect

    Cervantes, O; Kuntz, J; Gash, A; Munir, Z

    2009-02-13

    Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO{sub 3}) energetic composite was consolidated to a density of 9.17 g.cm{sup -3} or 93% relative density. In addition those parts were consolidated without significant pre-reaction of the constituents, thus the sample retained its stored chemical energy.

  2. Photochromic organic-inorganic composite materials prepared by sol-gel processing: Properties and potentials

    SciTech Connect

    Hou, L.; Mennig, M.; Schmidt, H.

    1994-12-31

    The sol-gel method which features a low-temperature wet-chemical process opens vast possibilities to incorporating organic dyes into solid matrices for various optical applications. In this paper the authors present their experimental results on the sol-gel derived photochromic organic-inorganic composite (Ormocer) materials following an introductory description of the sol-gel process and a brief review on the state of the art of the photochromic solids prepared using this method. Their photochromic spirooxazine-Ormocer gels and coatings possess better photochromic response and color-change speed than the corresponding photochromic polymer coatings and similar photochemical stability to the latter. Further developments are proposed as to tackle the temperature dependence problem and further tap the potentialities of the photochromic dye-Ormocer material for practical applications.

  3. Laser-assisted sol-gel growth and characteristics of ZnO thin films

    SciTech Connect

    Kim, Min Su; Kim, Soaram; Leem, Jae-Young

    2012-06-18

    ZnO thin films were grown on Si(100) substrates by a sol-gel method assisted by laser beam irradiation with a 325 nm He-Cd laser. In contrast to conventional sol-gel ZnO thin films, the surface morphology of the laser-assisted sol-gel thin films was much smoother, and the residual stress in the films was relaxed by laser irradiation. The luminescent properties of the films were also enhanced by laser irradiation, especially, by irradiation during the deposition and post-heat treatment stages. The incident laser beam is thought to play several roles, such as annihilating defects by accelerating crystallization during heat treatment, enhancing the surface migration of atoms and molecules, and relaxing the ZnO matrix structure during crystallization.

  4. Thin film porous membranes based on sol-gel chemistry for catalytic sensors

    SciTech Connect

    Hughes, R.C.; Patel, S.V.; Jenkins, M.W.; Boyle, T.J.; Gardner, T.J.; Brinker, C.J.

    1998-05-01

    Nanoporous sol-gel based films are finding a wide variety of uses including gas separations and supports for heterogeneous catalysts. The films can be formed by spin or dip coating, followed by relatively low temperature annealing. The authors used several types of these films as coatings on the Pd alloy thin film sensors they had previously fabricated and studied. The sol-gel films have little effect on the sensing response to H{sub 2} alone. However, in the presence of other gases, the nanoporous film modifies the sensor behavior in several beneficial ways. (1) They have shown that the sol-gel coated sensors were only slightly poisoned by high concentrations of H{sub 2}S while uncoated sensors showed moderate to severe poisoning effects. (2) For a given partial pressure of H{sub 2}, the signal from the sensor is modified by the presence of O{sub 2} and other oxidizing gases.

  5. Ultrapure glass optical waveguide development in microgravity by the sol-gel process

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.; Holman, R. A.

    1981-01-01

    Multicomponent, homogeneous, noncrystalline oxide gels can be prepared by the sol-gel process and these gels are promising starting materials for melting glasses in the space environment. The sol-gel process referred to here is based on the polymerization reaction of alkoxysilane with other metal alkoxy compounds or suitable metal salts. Many of the alkoxysilanes or other metal alkoxides are liquids and thus can be purified by distillation. The use of gels offers several advantages such as high purity and lower melting times and temperatures. The sol-gel process is studied for utilization in the preparation of multicomponent ultrapure glass batches for subsequent containerless melting of the batches in space to prepare glass blanks for optical waveguides.

  6. Sol-gel transition accelerated by the co-assembly of two components in supramolecular hydrogels.

    PubMed

    Matsumoto, Keigo; Shundo, Atsuomi; Ohno, Masashi; Saruhashi, Kowichiro; Miyachi, Nobuhide; Tsuruzoe, Nobutomo; Tanaka, Keiji

    2015-10-28

    N-Palmitoyl-Gly-His (PalGH) and glycerol 1-monopalmitate (GMP) in water co-assembled into fibrils with twisted ribbon structures and formed a homogeneous network, resulting in gel formation. Shaking the gel easily broke the fibril network leading to a sol in which high and low fibril density regions exist. After a period at room temperature, the higher density regions became interconnected. The spontaneous sol-gel transition did not take place for a gel made from only PalGH. Also, during the transition, the aggregation state of the co-assembly remained unchanged at a molecular level, unlike the fibril network. Thus, it can be claimed that the sol-gel transition is not associated with the assembled molecular configuration, but with the change in the fibril network. This knowledge might be useful for understanding and controlling sol-gel transition, thereby leading to the design and functionalization of hydrogels. PMID:26394927

  7. Fluorescence enhancement of Er3 + -doped sol-gel glass by aluminum codoping

    NASA Astrophysics Data System (ADS)

    Zhou, Y.; Lam, Y. L.; Wang, S. S.; Liu, H. L.; Kam, C. H.; Chan, Y. C.

    1997-08-01

    Erbium-doped silica glasses prepared by the sol-gel process are desirable for applications in high-power lasers and integrated optical devices. However, its fluorescence could be quenched due to the high hydroxyl (OH-) content. Although this OH- content can be greatly reduced through special gas treatment [Y. Zhou, S. S. Wang, H. L. Liu, Y. L. Lam, Y. C. Chan, and C. H. Kam, EEE J. 8, 109 (1996).], the fluorescence is still considered weak for practical applications. We have used sol-gel aluminum codoping to increase the solubility of the Er3+ ions in a silica glass host and, consequently, significantly enhanced the fluorescence intensity of Er3+-doped sol-gel glass to the extent suitable for practical usage.

  8. A comparative synthesis and physicochemical characterizations of Ni/Al2O3-MgO nanocatalyst via sequential impregnation and sol-gel methods used for CO2 reforming of methane.

    PubMed

    Aghamohammadi, Sogand; Haghighi, Mohammad; Karimipour, Samira

    2013-07-01

    Carbon dioxide reforming of methane is an interesting route for synthesis gas production especially over nano-sized catalysts. The present research deals with catalyst development for dry reforming of methane with the aim of reaching the most stable catalyst. Effect of preparation method, one of the most significant variables, on the properties of the catalysts was taken in to account. The Ni/Al2O3-MgO catalysts were prepared via sol-gel and sequential impregnation methods and characterized with XRD, FESEM, EDAX, BET and FTIR techniques. The reforming reactions were carried out using different feed ratios, gas hourly space velocities (GHSV) and reaction temperatures to identify the influence of operational variables. FESEM images indicate uniform particle size distribution for the sample synthesized with sol-gel method. It has been found that the sol-gel method has the potential to improve catalyst desired properties especially metal surface enrichment resulting in catalytic performance enhancement. The highest yield of products was obtained at 850 degrees C for both of the catalysts. During the 10 h stability test, CH4 and CO2 conversions gained higher values in the case of sol-gel made catalyst compared to impregnated one. PMID:23901507

  9. Sol-gel deposited electrochromic films for electrochromic smart window glass

    SciTech Connect

    Oezer, N.; Lampert, C.M.; Rubin, M.

    1996-08-01

    Electrochromic windows offer the ability to dynamically change the transmittance of a glazing. With the appropriate sensor and controls, this smart window can be used for energy regulation and glare control for a variety of glazing applications. The most promising are building and automotive applications. This work covers the use of sol-gel deposition processes to make active films for these windows. The sol-gel process offers a low-capital investment for the deposition of these active films. Sol-gel serves as an alternative to more expensive vacuum deposition processes. The sol-gel process utilizes solution coating followed by a hydrolysis and condensation. In this investigation the authors report on tungsten oxide and nickel oxide films made by the sol-gel process for electrochromic windows. The properties of the sol-gel films compare favorably to those of films made by other techniques. A typical laminated electrochromic window consists of two glass sheets coated with transparent conductors, which are coated with the active films. The two sheets are laminated together with an ionically conductive polymer. The range of visible transmission modulation of the tungsten oxide was 60% and for the nickel oxide was 20%. The authors used the device configuration of glass/SnO{sub 2}:F/W0{sub 3}/polymer/Li{sub Z}NiO{sub x}H{sub y}/SnO{sub 2}:F glass to test the films. The nickel oxide layer had a low level of lithiation and possibly contained a small amount of water. Lithiated oxymethylene-linked poly(ethylene oxide) was used as the laminating polymer. Commercially available SnO{sub 2}:F/glass (LOF-Tec glass) was used as the transparent conducting glass. The authors found reasonable device switching characteristics which could be used for devices.

  10. Effect of calcium source on structure and properties of sol-gel derived bioactive glasses.

    PubMed

    Yu, Bobo; Turdean-Ionescu, Claudia A; Martin, Richard A; Newport, Robert J; Hanna, John V; Smith, Mark E; Jones, Julian R

    2012-12-18

    The aim was to determine the most effective calcium precursor for synthesis of sol-gel hybrids and for improving homogeneity of sol-gel bioactive glasses. Sol-gel derived bioactive calcium silicate glasses are one of the most promising materials for bone regeneration. Inorganic/organic hybrid materials, which are synthesized by incorporating a polymer into the sol-gel process, have also recently been produced to improve toughness. Calcium nitrate is conventionally used as the calcium source, but it has several disadvantages. Calcium nitrate causes inhomogeneity by forming calcium-rich regions, and it requires high temperature treatment (>400 C) for calcium to be incorporated into the silicate network. Nitrates are also toxic and need to be burnt off. Calcium nitrate therefore cannot be used in the synthesis of hybrids as the highest temperature used in the process is typically 40-60 C. Therefore, a different precursor is needed that can incorporate calcium into the silica network and enhance the homogeneity of the glasses at low (room) temperature. In this work, calcium methoxyethoxide (CME) was used to synthesize sol-gel bioactive glasses with a range of final processing temperatures from 60 to 800 C. Comparison is made between the use of CME and calcium chloride and calcium nitrate. Using advanced probe techniques, the temperature at which Ca is incorporated into the network was identified for 70S30C (70 mol % SiO(2), 30 mol % CaO) for each of the calcium precursors. When CaCl(2) was used, the Ca did not seem to enter the network at any of the temperatures used. In contrast, Ca from CME entered the silica network at room temperature, as confirmed by X-ray diffraction, (29)Si magic angle spinning nuclear magnetic resonance spectroscopy, and dissolution studies. CME should be used in preference to calcium salts for hybrid synthesis and may improve homogeneity of sol-gel glasses. PMID:23171477

  11. Development of novel Sol-Gel Indicators (SGI's) for in-situ environmental measurements: Part 1, Program and a new pH Sol-Gel Indicator

    SciTech Connect

    Livingston, R.R.; Baylor, L.; Wicks, G.G.

    1992-11-03

    The feasibility of incorporating analytical indicators into a sol-gel glassy matrix and then coating substrates with this composite material has bee demonstrated. Substrates coated include paper, wood, glass, and the lens of an analytical probe. The first SRTC sol-gel indicator, comprising bromophenol blue dispersed in a silica matrix, was fabricated and successfully used to measure solution pH in the range of pH 3.0 to 7.5. material exhibited a quick response time, as measured by color changes both qualitatively and quantitatively, and the measuring device was reversible or reusable. Additional indicators with responses over other ranges as well as indicators sensitive to the presence of elements of interest, are also under development. The new SGI composites possess promising properties and an excellent potential for performing a variety important in-situ environmental measurements and area discussed in this report.

  12. Novel Sol-Gel Based Pt Nanocluster Catalysts for Propane Dehydrogenation

    SciTech Connect

    Boespflug, Elaine; Kawola, Jeffrey S.; Martino, Anthony; Sault, Allen G.

    1999-08-09

    We report propane dehydrogenation behavior of catalysts prepared using two novel synthesis strategies that combine inverse micelle Pt nanocluster technology with silica and alumina sol-gel processing. Unlike some other sol-gel catalyst preparations. Pt particles in these catalysts are not encapsulated in the support structure and the entire Pt particle surface is accessible for reaction. Turnover frequencies (TOF) for these catalysts are comparable to those obtained over Pt catalysts prepared by traditional techniques such as impregnation, yet the resistance to deactivation by carbon poisoning is much greater in our catalysts. The deactivation behavior is more typical of traditionally prepared PtSn catalysts than of pure Pt catalysts.

  13. The sol-gel entrapment of noble metals in hybrid silicas: a molecular insight

    PubMed Central

    2013-01-01

    Background Why are metal nanoparticles sol-gel entrapped in ORMOSIL so active and stable? In other words, why ORMOSIL-entrappedmetal nanoparticles are more active and selective than many heterogenized counterparts, including silica-entrapped noble metals? Results Unveiling specific interactions between MNPs and the molecular structure of ORMOSIL, this work investigatessubtle structural aspects through DRIFT spectroscopy. Conclusions The results point to interactionsbetween entrapped Pd and Pt nanocrystallites with the organosilica sol-gel cagessimilar to those taking place in enzymes. PMID:24079552

  14. Sol-gel silica films embedding NIR- emitting Yb-quinolinolate complexes

    SciTech Connect

    Figus, Cristiana Quochi, Francesco Piana, Giacomo; Saba, Michele; Mura, Andrea; Bongiovanni, Giovanni; Artizzu, Flavia; Mercuri, Maria Laura; Serpe, Angela; Deplano, Paola

    2014-10-21

    Sol-gel silica thin films embedding an ytterbium quinolinolato complex (YbClQ{sub 4}) have been obtained using different alkoxides. Homogeneous, crack- and defect-free thin films of optical quality have been successfully deposited on glass substrate by dip-coating. The silica thin films have been characterized by time-resolved photoluminescence. The luminescence properties of the YbClQ{sub 4} are preserved in silica films prepared through an optimized sol-gel approach. The excited state lifetime of the lanthanide is comparable to those observed in bulk and longer than the corresponding ones in solution.

  15. Ion-irradiation-induced densification of zirconia sol-gel thin films

    SciTech Connect

    Levine, T.E.; Giannelis, E.P.; Kodali, P.; Tesmer, J.; Nastasi, M.; Mayer, J.W.

    1994-02-01

    We have investigated the densification behavior of sol-gel zirconia films resulting from ion irradiation. Three sets of films were implanted with neon, krypton, or xenon. The ion energies were chosen to yield approximately constant energy loss through the film and the doses were chosen to yield similar nuclear energy deposition. Ion irradiation of the sol-gel films resulted in carbon and hydrogen loss as indicated by Rutherford backscattering spectrometry and forward recoil energy spectroscopy. Although the densification was hypothesized to result from target atom displacement, the observed densification exhibits a stronger dependence on electronic energy deposition.

  16. Synthesis of superhydrophobic alumina membrane: Effects of sol-gel coating, steam impingement and water treatment

    NASA Astrophysics Data System (ADS)

    Ahmad, N. A.; Leo, C. P.; Ahmad, A. L.

    2013-11-01

    Ceramic membranes possess natural hydrophilicity thus tending to absorb water droplets. The absorption of water molecules on membrane surface reduces their application in filtration, membrane distillation, osmotic evaporation and membrane gas absorption. Fluoroalkylsilane (FAS) grafting allows the conversion of hydrophilic ceramic membranes into superhydrophobic thin layer, but it usually introduces a great increment of mass transfer resistance. In this study, superhydrophobic alumina membranes were synthesized by dip coating alumina support into sol-gel and grafted with the fluoroalkylsilane (FAS) named (heptadecafluoro-1,1,2,2-tetra hydrodecyl) triethoxysilane. Steam impingement and water treatment acted as additional steps to generate surface roughness on sol-gel and most importantly to reduce mass transfer resistance. Superhydrophobic alumina membrane with high water contact angle (158.4°) and low resistance (139.5 ± 24.9 G m-1) was successfully formed when the alumina membrane was dip coated into sol-gel for 7 s, treated with steam impingement for 1 min and immersed in hot water at 100 °C. However, the mass transfer resistance was greatly induced to 535.6 ± 23.5 G m-1 when the dip coating time was increased to 60 s. Long dip coating time contributes more on the blockage of porous structure rather than creates a thin film on the top of membrane surface. Reducing the pore size and porosity significantly due to increase of coating molecules deposited on the membrane. Steam impingement for 1 min promoted the formation of cones and valleys on the sol-gel, but the macro-roughness was destroyed when the steam impingement duration was extended to more than 3 min. The immersions of membranes into hot water at temperatures higher than 60 °C encouraged the formation of boehmite which enhances the formation of additional roughness and enlarges pore size greatly. Thus, this work showed that the formation of superhydrophobic alumina membrane with low resistance is influenced by three factors; sol-gel dip coating time, steam impingement time and temperature of water treatment. The optimum dip coating time could promote appropriate thickness of the sol-gel layer on the membrane support. The highest surface roughness and porosity could be created when the sol-gel layer was further treated with optimum steam impingement duration and immersed in hot water at 100 °C. The presence of appropriate sol-gel thickness can reduce the penetration of FAS during the grafting and reduce the membrane resistance.

  17. Porous Silica Sol-Gel Glasses Containing Reactive V2O5 Groups

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E.

    1995-01-01

    Porous silica sol-gel glasses into which reactive vanadium oxide functional groups incorporated exhibit number of unique characteristics. Because they bind molecules of some species both reversibly and selectively, useful as chemical sensors or indicators or as scrubbers to remove toxic or hazardous contaminants. Materials also oxidize methane gas photochemically: suggests they're useful as catalysts for conversion of methane to alcohol and for oxidation of hydrocarbons in general. By incorporating various amounts of other metals into silica sol-gel glasses, possible to synthesize new materials with broad range of new characteristics.

  18. Silica/quercetin sol-gel hybrids as antioxidant dental implant materials

    NASA Astrophysics Data System (ADS)

    Catauro, Michelina; Papale, Ferdinando; Bollino, Flavia; Piccolella, Simona; Marciano, Sabina; Nocera, Paola; Pacifico, Severina

    2015-06-01

    The development of biomaterials with intrinsic antioxidant properties could represent a valuable strategy for preventing the onset of peri-implant diseases. In this context, quercetin, a naturally occurring flavonoid, has been entrapped at different weight percentages in a silica-based inorganic material by a sol-gel route. The establishment of hydrogen bond interactions between the flavonol and the solid matrix was ascertained by Fourier transform infrared spectroscopy. This technique also evidenced changes in the stretching frequencies of the quercetin dienonic moiety, suggesting that the formation of a secondary product occurs. Scanning electron microscopy was applied to detect the morphology of the synthesized materials. Their bioactivity was shown by the formation of a hydroxyapatite layer on sample surface soaked in a fluid that simulates the composition of human blood plasma. When the potential release of flavonol was determined by liquid chromatography coupled with ultraviolet and electrospray ionization tandem mass spectrometry techniques, the eluates displayed a retention time that was 0.5 min less than quercetin. Collision-activated dissociation mass spectrometry and untraviolet-visible spectroscopy were in accordance with the release of a quercetin derivative. The antiradical properties of the investigated systems were evaluated by DPPH and ABTS methods, whereas the 2,7-dichlorofluorescein diacetate assay highlighted their ability to inhibit the H2O2-induced intracellular production of reactive oxygen species in NIH-3T3 mouse fibroblast cells. Data obtained, along with data gathered from the MTT cytotoxicity test, revealed that the materials that entrapped the highest amount of quercetin showed notable antioxidant effectiveness.

  19. Studies of (3-mercaptopropyl)trimethoxylsilane and bis(trimethoxysilyl)ethane sol-gel coating on copper and aluminum

    NASA Astrophysics Data System (ADS)

    Li, Ying-Sing; Lu, Weijie; Wang, Yu; Tran, Tuan

    2009-09-01

    Bis(trimethoxysilyl)ethane (BTMSE) and (3-mercaptopropyl)trimethoxysilane (MPTMS) have been used as precursors to prepare sol-gels and hybrid sol-gel under acidic condition. From the X-ray photoelectron spectroscopy data on MPTMS sol-gel coated aluminum and copper, it has been shown that the silane film is covalently bonded to Al surface through the interfacial condensation. There is no evidence of bonding interaction between the thiol group and the Cu. The recorded reflection adsorption IR (RAIR) spectrum has provided evidence that the coating BTMSE film covalently interacts with Al. Vibrational assignments have been suggested for pure BTMSE, BTMSE sol-gel, BTMSE xerogel, and BTMSE coated Al panel based on the group frequencies and the variation of frequencies with the sample treatment conditions. The progression of condensation reaction has been observed from the IR spectra of the BTMSE sol-gel and the sol-gel coated film after the treatments at different temperatures with different lengths of time. The corrosion protection of the sol-gel coated Al and Cu has been characterized in NaCl solutions by cyclic voltammetric, potentiodynamic polarization and impedance spectroscopy methods. All these electrochemical measurements indicate that the sol-gel coated metals have better corrosion protection than the corresponding uncoated metals.

  20. THERMALLY STABLE NANOCRYSTALLINE TIO2 PHOTOCATALYSTS SYNTHESIZED VIA SOL-GEL METHODS MODIFIED WITH IONIC LIQUID AND SURFACTANT MOLECULES

    EPA Science Inventory

    Recently, sol-gel methods employing ionic liquids (ILs) have shown significant implications for the synthesis of well-defined nanostructured inorganic materials. Herein, we synthesized nanocrystalline TiO2 particles via an alkoxide sol-gel method employing a water-immi...

  1. Electrochemical and In Vitro Behavior of Nanostructure Sol-Gel Coated 316L Stainless Steel Incorporated with Rosemary Extract

    NASA Astrophysics Data System (ADS)

    Motalebi, Abolfazl; Nasr-Esfahani, Mojtaba

    2013-06-01

    The corrosion resistance of AISI 316L stainless steel for biomedical applications, was significantly enhanced by means of hybrid organic-inorganic sol-gel thin films deposited by spin-coating. Thin films of less than 100 nm with different hybrid characters were obtained by incorporating rosemary extract as green corrosion inhibitor. The morphology, composition, and adhesion of hybrid sol-gel coatings have been examined by SEM, EDX, and pull-off test, respectively. Addition of high additive concentrations (0.1%) did not disorganize the sol-gel network. Direct pull-off test recorded a mean coating-substrate bonding strength larger than 21.2 MPa for the hybrid sol-gel coating. The effect of rosemary extract, with various added concentrations from 0.012 to 0.1%, on the anticorrosion properties of sol-gel films have been characterized by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in simulated body fluid (SBF) solution and has been compared to the bare metal. Rosemary extract additions (0.05%) have significantly increased the corrosion protection of the sol-gel thin film to higher than 90%. The in vitro bioactivity of prepared films indicates that hydroxyapatite nuclei can form and grow on the surface of the doped sol-gel thin films. The present study shows that due to their excellent anticorrosion properties, bioactivity and bonding strength to substrate, doped sol-gel thin films are practical hybrid films in biomedical applications.

  2. Environmentally benign sol-gel antifouling and foul-releasing coatings.

    PubMed

    Detty, Michael R; Ciriminna, Rosaria; Bright, Frank V; Pagliaro, Mario

    2014-02-18

    Biofouling on ships and boats, characterized by aquatic bacteria and small organisms attaching to the hull, is an important global issue, since over 80000 tons of antifouling paint is used annually. This biofilm, which can form in as little as 48 hours depending on water temperature, increases drag on watercraft, which greatly reduces their fuel efficiency. In addition, biofouling can lead to microbially induced corrosion (MIC) due to H2S formed by the bacteria, especially sulfate-reducing bacteria. When the International Maritime Organization (IMO) international convention banned the use of effective but environmentally damaging coatings containing tributyl tin in 2008, the development of clean and effective antifouling systems became more important than ever. New nonbiocidal coatings are now in high demand. Scientists have developed new polymers, materials, and biocides, including new elastomeric coatings that they have obtained by improving the original silicone (polydimethylsiloxane) formulation patented in 1975. However, the high cost of silicones, especially of fluoropolymer-modified silicones, has generally prevented their large-scale diffusion. In 2009, traditional antifouling coatings using cuprous oxide formulated in copolymer paints still represented 95% of the global market volume of anti-fouling paints. The sol-gel nanochemistry approach to functional materials has emerged as an attractive candidate for creating low fouling surfaces due to the unique structure and properties of silica-based coatings and of hybrid inorganic-organic silicas in particular. Sol-gel formulations easily bind to all types of surfaces, such as steel, fiberglass, aluminum, and wood. In addition, they can cure at room temperature and form thin glassy coatings that are markedly different from thick silicone elastomeric foul-releasing coatings. Good to excellent performance against biofouling, low cure temperatures, enhanced and prolonged chemical and physical stability, ease of application, and the waterborne nature of sol-gel coatings all support the diffusion of these paints to efficiently reduce the accumulation of fouling layers on valued surfaces immersed in marine or fluvial waters. Furthermore, sol-gel glassy coatings are transparent and can be effectively applied to optical devices, windows, and solar panels used in lake, fluvial, or marine environments. Sol-gel technology is eminently versatile, and the first generation sol-gel paints have already shown good performance. Even so, vast opportunities still exist for chemists to develop novel sol-gel derived coatings to both prevent biofouling and enhance the hydrodynamic properties of boat and ship hulls. Moreover, researchers have prepared and applied multifunctional sol-gel coatings providing protection against both biofouling and corrosion. They have tested these in the marine environment with good preliminary results. In this Account, we discuss some of our new strategies for the controlled functionalization of surfaces for the development of efficient antifouling and foul-releasing systems and summarize the main achievements with biocidal and nonbiocidal sol-gel coatings. We conclude by giving insight into the marine coatings and sol-gel products markets, providing arguments to justify our conclusion that the sol-gel coatings technology is now a mature platform for the development of economically viable and environmentally friendly antifouling and foul-release formulations of enhanced performance. PMID:24397288

  3. Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment

    PubMed Central

    Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

    2015-01-01

    Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits. PMID:26322304

  4. Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment.

    PubMed

    Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

    2015-01-01

    Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits. PMID:26322304

  5. Ternary Phase-Separation Investigation of Sol-Gel Derived Silica from Ethyl Silicate 40

    PubMed Central

    Wang, Shengnan; Wang, David K.; Smart, Simon; Diniz da Costa, João C.

    2015-01-01

    A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H2O/Si ratios. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H2O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification. PMID:26411484

  6. Foldable and Cytocompatible Sol-gel TiO2 Photonics

    PubMed Central

    Li, Lan; Zhang, Ping; Wang, Wei-Ming; Lin, Hongtao; Zerdoum, Aidan B.; Geiger, Sarah J.; Liu, Yangchen; Xiao, Nicholas; Zou, Yi; Ogbuu, Okechukwu; Du, Qingyang; Jia, Xinqiao; Li, Jingjing; Hu, Juejun

    2015-01-01

    Integrated photonics provides a miniaturized and potentially implantable platform to manipulate and enhance the interactions between light and biological molecules or tissues in in-vitro and in-vivo settings, and is thus being increasingly adopted in a wide cross-section of biomedical applications ranging from disease diagnosis to optogenetic neuromodulation. However, the mechanical rigidity of substrates traditionally used for photonic integration is fundamentally incompatible with soft biological tissues. Cytotoxicity of materials and chemicals used in photonic device processing imposes another constraint towards these biophotonic applications. Here we present thin film TiO2 as a viable material for biocompatible and flexible integrated photonics. Amorphous TiO2 films were deposited using a low temperature (<250 °C) sol-gel process fully compatible with monolithic integration on plastic substrates. High-index-contrast flexible optical waveguides and resonators were fabricated using the sol-gel TiO2 material, and resonator quality factors up to 20,000 were measured. Following a multi-neutral-axis mechanical design, these devices exhibit remarkable mechanical flexibility, and can sustain repeated folding without compromising their optical performance. Finally, we validated the low cytotoxicity of the sol-gel TiO2 devices through in-vitro cell culture tests. These results demonstrate the potential of sol-gel TiO2 as a promising material platform for novel biophotonic devices. PMID:26344823

  7. A Sol-Gel-Modified Poly(methyl methacrylate) Electrophoresis Microchip with a Hydrophilic Channel Wall

    SciTech Connect

    Chen, Gang; Xu, Xuejiao; Lin, Yuehe; Wang, Joseph

    2007-07-27

    A sol-gel method was employed to fabricate a poly(methyl methacrylate) (PMMA) electrophoresis microchip that contains a hydrophilic channel wall. To fabricate such a device, tetraethoxysilane (TEOS) was injected into the PMMA channel and was allowed to diffuse into the surface layer for 24 h. After removing the excess TEOS, the channel was filled with an acidic solution for 3 h. Subsequently, the channel was flushed with water and was pretreated in an oven to obtain a sol-gel-modified PMMA microchip. The water contact angle for the sol-gel-modified PMMA was 27.4 compared with 66.3 for the pure PMMA. In addition, the electro-osmotic flow increased from 2.1310-4 cm2 V-1 s-1 for the native-PMMA channel to 4.8610-4 cm2 V-1 s-1 for the modified one. The analytical performance of the sol-gel-modified PMMA microchip was demonstrated for the electrophoretic separation of several purines, coupled with amperometric detection. The separation efficiency of uric acid increased to 74 882.3 m-1 compared with 14 730.5 m-1 for native-PMMA microchips. The result of this simple modification is a significant improvement in the performance of PMMA for microchip electrophoresis and microfluidic applications.

  8. Sol-gel chemical sensors for surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Vincent Y.; Farquharson, Stuart; Kwon, Hueong-Chan; Shahriari, Mahmoud R.; Rainey, Petrie M.

    1999-02-01

    Surface-enhanced Raman spectroscopy (SERS) promises to be one of the most sensitive methods for chemical detection. Unfortunately, the inability of SERS to perform quantitative chemical analysis has slowed its general use in laboratories. This is largely due to the difficulty of manufacturing either active surfaces that yield reproducible enhancements, or surfaces that are capable of reversible chemical adsorption, or both. In an effort to meet this need, we have developed metal-doped sol-gels that provide surface-enhancement of Raman scattering. The porous silica network offers a unique environment for stabilizing SER active metal particles and the high surface area increases the interaction between the analyte and metal particles. This eliminates the need to concentrate the analyte on the surface by evaporating the solvent. The sol-gel is easily coated on a variety of surfaces, such as fiber optics, glass slides, or glass tubing, and can be designed into sample flow systems. Here we present the development of both gold- and silver-doped sol-gels, which have been used to coat the inside walls of glass sample vials for SERS applications. The performance of the metal-doped sol-gels was evaluated using p-aminobenzoic acid, to establish enhancement factors, detection limits, dynamic response range, reversibility, reproducibility, and suitability to commercial spectrometers. Measurements of trace chemicals, such as adenine and cocaine, are also presented.

  9. Foldable and Cytocompatible Sol-gel TiO2 Photonics

    NASA Astrophysics Data System (ADS)

    Li, Lan; Zhang, Ping; Wang, Wei-Ming; Lin, Hongtao; Zerdoum, Aidan B.; Geiger, Sarah J.; Liu, Yangchen; Xiao, Nicholas; Zou, Yi; Ogbuu, Okechukwu; Du, Qingyang; Jia, Xinqiao; Li, Jingjing; Hu, Juejun

    2015-09-01

    Integrated photonics provides a miniaturized and potentially implantable platform to manipulate and enhance the interactions between light and biological molecules or tissues in in-vitro and in-vivo settings, and is thus being increasingly adopted in a wide cross-section of biomedical applications ranging from disease diagnosis to optogenetic neuromodulation. However, the mechanical rigidity of substrates traditionally used for photonic integration is fundamentally incompatible with soft biological tissues. Cytotoxicity of materials and chemicals used in photonic device processing imposes another constraint towards these biophotonic applications. Here we present thin film TiO2 as a viable material for biocompatible and flexible integrated photonics. Amorphous TiO2 films were deposited using a low temperature (<250?C) sol-gel process fully compatible with monolithic integration on plastic substrates. High-index-contrast flexible optical waveguides and resonators were fabricated using the sol-gel TiO2 material, and resonator quality factors up to 20,000 were measured. Following a multi-neutral-axis mechanical design, these devices exhibit remarkable mechanical flexibility, and can sustain repeated folding without compromising their optical performance. Finally, we validated the low cytotoxicity of the sol-gel TiO2 devices through in-vitro cell culture tests. These results demonstrate the potential of sol-gel TiO2 as a promising material platform for novel biophotonic devices.

  10. The influence of surfactants on the roughness of titania sol-gel films

    SciTech Connect

    Medina-Valtierra, Jorge . E-mail: jormeval@yahoo.com; Frausto-Reyes, Claudio . E-mail: cfraus@cio.mx; Calixto, Sergio . E-mail: scalixto@cio.mx; Bosch, Pedro . E-mail: lacv@xanum.uam.mx

    2007-03-15

    Substrate dipping in a composite sol-gel solution was used to prepare both smooth and rough thin films of titanium dioxide (TiO{sub 2}) on commercial fiberglass. The deposition of a composite film was done in a beaker using a solution of titanium (IV) isopropoxide as the sol-gel precursor and cetyltrimethyl ammonium bromide as the surfactant. In order to establish a correlation between experimental conditions and the titanium oxide produced, as well as the film quality, the calcined samples were characterized using Raman spectroscopy, UV-vis spectrophotometry, scanning electron microscopy and atomic force microscopy. One of the most important results is that a 61-nm TiO{sub 2} film was obtained with a short immersion of fiberglass into the sol-gel without surfactant. In other cases, the deposited film consisted of a titanium precursor gel encapsulating micelles of surfactant. The gel films were converted to only the anatase phase by calcining them at 500 deg. C. The resulting films were crystalline and exhibited a uniform surface topography. In the present paper, it was found that the TiO{sub 2} films prepared from the sol-gel with a surfactant showed a granular microstructure, and are composed of irregular particles between 1.5 and 3 {mu}m. Smooth TiO{sub 2} films could have useful optical and corrosion-protective properties and, on other hand, roughness on the TiO{sub 2} films can enhance the inherent photocatalytic activity.

  11. Foldable and Cytocompatible Sol-gel TiO2 Photonics.

    PubMed

    Li, Lan; Zhang, Ping; Wang, Wei-Ming; Lin, Hongtao; Zerdoum, Aidan B; Geiger, Sarah J; Liu, Yangchen; Xiao, Nicholas; Zou, Yi; Ogbuu, Okechukwu; Du, Qingyang; Jia, Xinqiao; Li, Jingjing; Hu, Juejun

    2015-01-01

    Integrated photonics provides a miniaturized and potentially implantable platform to manipulate and enhance the interactions between light and biological molecules or tissues in in-vitro and in-vivo settings, and is thus being increasingly adopted in a wide cross-section of biomedical applications ranging from disease diagnosis to optogenetic neuromodulation. However, the mechanical rigidity of substrates traditionally used for photonic integration is fundamentally incompatible with soft biological tissues. Cytotoxicity of materials and chemicals used in photonic device processing imposes another constraint towards these biophotonic applications. Here we present thin film TiO2 as a viable material for biocompatible and flexible integrated photonics. Amorphous TiO2 films were deposited using a low temperature (<250 °C) sol-gel process fully compatible with monolithic integration on plastic substrates. High-index-contrast flexible optical waveguides and resonators were fabricated using the sol-gel TiO2 material, and resonator quality factors up to 20,000 were measured. Following a multi-neutral-axis mechanical design, these devices exhibit remarkable mechanical flexibility, and can sustain repeated folding without compromising their optical performance. Finally, we validated the low cytotoxicity of the sol-gel TiO2 devices through in-vitro cell culture tests. These results demonstrate the potential of sol-gel TiO2 as a promising material platform for novel biophotonic devices. PMID:26344823

  12. Two substrate-confined sol-gel coassembled ordered macroporous silica structures with an open surface.

    PubMed

    Guo, Wenhua; Wang, Ming; Xia, Wei; Dai, Lihua

    2013-05-21

    A sol-gel cooperative assembly method was demonstrated for the fabrication of inverse opal films with an open surface. In this method, a sol-gel silicate precursor was cooperatively assembled into the interstitial spaces of microspheres at the same time when polystyrene templates formed in between two desired substrates. Silica inverse opals with a three-dimensional ordered macroporous (3DOM) structure were obtained after selective removing the colloidal templates by calcination. The open surfaces with a high degree of interconnected porosity and extremely uniform pore size were characterized by scanning electron microscope (SEM). Optical transmission spectra reveals the existence of considerable deep band gaps of up to 70% and steep band edges of up to 6%/nm in the [111] directions of the 3DOM silica samples. A little shrinkage confirmed by transmission spectra is not larger than 3%, in consistent with the results measured by SEM, which revealing the sufficient and compact infiltration into the interstitial spaces by our confined sol-gel coassembly method. With different incidence angles, the positions of pseudogaps can be easily tuned in the wide range from 720 nm to 887 nm, agreed well with the calculated values by the Bragg law. All the results prove that the sol-gel coassembly method with two substrates confinement is a simple, low cost, convenient and versatile method for the fabrication of silica inverse opals without overlayers in large domains. PMID:23614663

  13. Improving the temperature performance of low-density ceramic heatshields through sol-gel processing

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey; Leiser, Daniel; Sommers, Jeneen; Esfahani, Lili

    1991-01-01

    The performance of rigid insulations for use as thermal protection materials on reentry vehicles can be characterized by their resistance to dimensional and morphological change when exposed to an isothermal environment equivalent to that generated in entry. Improvements in these material characteristics for alumina-enhanced thermal barrier insulation by compositional modification through sol-gel processing are reported.

  14. Sol-gel deposition of buffer layers on biaxially textured metal substances

    DOEpatents

    Shoup, Shara S. (Woodstock, GA); Paranthamam, Mariappan (Knoxville, TN); Beach, David B. (Knoxville, TN); Kroeger, Donald M. (Knoxville, TN); Goyal, Amit (Knoxville, TN)

    2000-01-01

    A method is disclosed for forming a biaxially textured buffer layer on a biaxially oriented metal substrate by using a sol-gel coating technique followed by pyrolyzing/annealing in a reducing atmosphere. This method is advantageous for providing substrates for depositing electronically active materials thereon.

  15. Investigation of optical properties of anthocyanin doped into sol-gel based matrix

    NASA Astrophysics Data System (ADS)

    Hashim, Hasrina; Abdul Aziz, Nik Mohd Azmi Nik; Isnin, Aishah

    2012-06-01

    Anthocyanin dye was extracted from petal of Hibiscus rosasinensis (Bunga Raya) and doped into sol-gel based matrix to investigate an effect of pH change on its optical properties. Sol-gel matrix based on Vinyl triethoxysilene (VTES) as a precursor was prepared through Sol-gel process at pH 7. The sol was doped with 0.1% of Anthocyanin and the same amount of dye was also dissolved in ethanol as a comparative sample. Hydrochloric Acid, HCl and Tetramethylammonium Hydroxide, TMAH were used to change the pH value by adding them at various concentrations into each sample. The emission spectra and chemical structures of the samples were measured by Spectrofluorometer and Fourier Transform Infrared (FTIR) respectively. When excited at 410 nm, two emission peaks at about 492 and 574 nm were observed for Anthocyanin in acidic environment both in ethanol and VTES sol. In base environment however, only Anthocyanin dissolved in ethanol produced emission peak with a single peak at about 539 nm. The sensitivity of Anthocyanin dye toward pH changes in VTES open a possibility to use it as sensing element in which sol-gel based matrix are known to have higher mechanical strength and thermal stability.

  16. Ternary Phase-Separation Investigation of Sol-Gel Derived Silica from Ethyl Silicate 40

    NASA Astrophysics Data System (ADS)

    Wang, Shengnan; Wang, David K.; Smart, Simon; Diniz da Costa, Joo C.

    2015-09-01

    A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H2O/Si ratios. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H2O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification.

  17. OPTIMIZATION OF ALKYL ESTER PRODUCTION FROM GREASE USING A PHYLLOSILICATE SOL-GEL IMMOBILIZED LIPASE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Simple alkyl ester derivatives of restaurant grease were prepared using a lipase from Pseudomonas cepacia immobilized within a phyllosilicate sol-gel matrix as biocatalyst. Alcoholysis reactions of grease were carried out in solvent-free media using a one step addition of alcohol to reaction mixtur...

  18. Lanthanide nanoparticle doped low-loss sol-gel amplifier materials

    NASA Astrophysics Data System (ADS)

    Gan, Haiyong; Norwood, Robert A.; Li, Li; DeRose, Christopher T.; Wu, Jianfeng; Thomas, Jayan; Fardad, M. Amir; Schuelzgen, Axel; Peyghambarian, Nasser N.; De Silva, Channa R.; Zheng, Zhiping

    2005-08-01

    Organic-inorganic hybrid sol-gel materials have attracted increasing attention in recent years as low-cost, rugged materials for integrated optical devices such as optical couplers, splitters, and electro-optic modulators. These materials can be easily processed by spin-coating, wet-etching photolithography, and low-temperature baking. Precise control of waveguide core-cladding refractive indices produces well-confined low-loss propagation and good matching of the absolute refractive index to that of fused silica results in low optical coupling loss to optical fiber. The increased thermal and mechanical stability of these materials, relative to optical polymers, results in numerous packaging options and improved reliability. However organic-inorganic hybrid sol-gel materials have not yet been often used as host of active dopants such as erbium (III) ions for 1550nm optical amplification. This limitation owes primarily to matrix and chelate dominated nonradiative relaxation processes, as high phonon energy OH and OH-like oscillators can bridge off the energy from the excited erbium (III) ions at very high rates. Different strategies have been proposed to protect erbium (III) ions from matrix and chelate quenching, including host and ligand fluorination, and inorganic microstructure shielding. Here we report on our work of encapsulating erbium (III) ions in transparent, refractive index matched, and highly re-dispersible lanthanum phosphate nanoparticles and the work of examining the optical properties of these nanoparticles as active dopants in organic-inorganic hybrid sol-gels adopting 2-methacryloxypropyl trimethoxysilane (MAPTMS) as a precursor. 980nm laser pumped photoluminescence at 1535nm was obtained from solid bulk samples of 300mg La.99Er.01PO4 nanoparticles doped in 1mL hybrid sol-gel. Thick bulk samples of this composition exhibited exceptional clarity and little trace of nanoparticle scattering effects. The lifetime of the nanoparticle doped hybrid sol-gel composite was measured to be 220?s, indicating an intermediate relaxation rate between that of an erbium organic complex and annealed erbium doped glass. La.99Er.01PO4 nanoparticle doped hybrid sol-gel films were also prepared and the refractive index was measured to be 1.4966 at 1550nm, which is very close to that of optical fiber and provides a suitable index difference from an undoped and metal oxide tuned sol-gel at 1.4870 to comprise an efficient single-mode waveguide system.

  19. Conformal sol-gel coatings on three-dimensional nanostructured templates

    NASA Astrophysics Data System (ADS)

    Weatherspoon, Michael R.

    Sol-gel processing techniques, such as spin coating and dip coating, have successfully been utilized over the past several decades to apply conformal coatings on planar substrates; however, controlled film growth on three-dimensional (3-D) nanostructured templates using the sol-gel process remains a significant challenge. Obstacles such as, uncontrolled hydrolyzation and condensation of metal alkoxide precursors on nanostructured surfaces are a few of the obstacles which lead to coatings with undesirable thicknesses and excess inorganic particles. A little over a decade ago, a surface sol-gel process was developed which utilizes stepwise film growth of anhydrous metal alkoxide precursors with hydroxylated surfaces. The surface sol-gel process provides control over the applied coating thickness and is viewed as a wet chemical analog to atomic layer deposition (ALD). The work presented in this dissertation has focused on applying conformal sol-gel derived coatings with controlled thicknesses on 3-D nanostructured templates. The templates utilized in this work were derived from biological species, such as diatoms and butterflies, as well as a synthetic photoresist polymer (SU-8). Coatings were applied on the templates using a conventional reflux/evaporation deposition process and a custom-built computer controlled surface sol-gel pumping system. The coatings applied using the reflux/evaporation process yielded conformal coatings with uncontrolled film thicknesses whereas the coatings applied using the surface sol-gel process yielded conformal coatings with controlled thicknesses. Barium titanate and europium-doped barium titanate coatings were applied on diatom frustules using the reflux/evaporation deposition process. The silica-based diatom frustules had to first be converted into magnesia/silicon composite replicas using a gas/solid displacement reaction to render the template chemically compatible with the barium titanate-based coating. Conformal titanate-based coatings were obtained on the magnesia frustule replicas possessing uncontrolled thicknesses and excess inorganic particles using the reflux/evaporation deposition process. The europium-doped barium titanate coated frustules exhibited bright red photoluminescent properties upon stimulation with an ultraviolet light source. Silica-based diatom frustules were also utilized as 3-D nanostructured templates for fabrication of a micro-scale nitric oxide gas sensor. Tin oxide coatings were applied on the silica frustules using the automated surface sol-gel pumping system. An organic dendrimer method was developed for amplifying hydroxyl groups on the silica frustule surfaces to enhance the surface sol-gel deposition process. Conformal coatings with controlled thicknesses were obtained on the hydroxyl amplified frustule surfaces; however, little if any deposition was observed on the frustules that were not subjected to the hydroxyl amplification process. A single tin oxide coated diatom frustule served as a gas sensor component which was sensitive to very low concentrations of nitric oxide gas. The automated surface sol-gel system was also used to apply multicomponent tin oxide-doped titania alkoxide chemistries on the wing scales of a blue Morpho butterfly. The alkoxide solutions reacted directly with the OH functionalities provided by the native chitin chemistry of the scales. The tin oxide served as a rutile nucleating agent which allowed the titania to completely crystallize in the high refractive index rutile titania phase with doping concentrations of tin oxide as low as 7 mol% after annealing at 450C. The tin oxide-doped titania coatings were both nanocrystalline and nanothick and replicated the nanostructured scales with a high degree of accuracy. Undoped titania coatings applied on the scales required a heat treatment of 900C to crystallize the coating in the rutile titania phase which led to adverse coarsening effects which destroyed the nanostructed features of the scales. Tin oxide-doped titania coatings were also deposited on synthetic polymer (SU-8) pho

  20. Magnetic resonance as a structural probe of a uranium (VI) sol-gel process

    SciTech Connect

    King, C.M.; Thompson, M.C.; Buchanan, B.R.; King, R.B.; Garber, A.R.

    1989-12-31

    NMR investigations on the ORNL process for sol-gel synthesis of microspherical nuclear fuel (UO{sub 2}), has been useful in sorting out the chemical mechanism in the sol-gel steps. {sup 13}C, {sup 15}N, and {sup 1}H NMR studies on the HMTA gelation agent (Hexamethylene tetramine, C{sub 6}H{sub l2}N{sub 4}) has revealed near quantitative stability of this adamantane-like compound in the sol-Gel process, contrary to its historical role as an ammonia source for gelation from the worldwide technical literature. {sub 17}0 NMR of uranyl (UO{sub 2}{sup ++}) hydrolysis fragments produced in colloidal sols has revealed the selective formation of a uranyl trimer, [(UO{sub 2}){sub 3}({mu}{sub 3}-O)({mu}{sub 2}-OH){sub 3}]{sup +}, induced by basic hydrolysis with the HMTA gelation agent. Spectroscopic results show that trimer condensation occurs during sol-gel processing leading to layered polyanionic hydrous uranium oxides in which HMTAH{sup +} is occluded as an ``intercalation`` cation. Subsequent sol-gel processing of microspheres by ammonia washing results in in-situ ion exchange and formation of a layered hydrous ammonium uranate with a proposed structural formula of (NH{sub 4}){sub 2}[(UO{sub 2}){sub 8}O{sub 4}(OH){sub 10}] {center_dot} 8H{sub 2}0. This compound is the precursor to sintered U0{sub 2} ceramic fuel.

  1. Magnetic resonance as a structural probe of a uranium (VI) sol-gel process

    SciTech Connect

    King, C.M.; Thompson, M.C.; Buchanan, B.R. ); King, R.B. . Dept. of Chemistry); Garber, A.R. . Dept. of Chemistry)

    1989-01-01

    NMR investigations on the ORNL process for sol-gel synthesis of microspherical nuclear fuel (UO{sub 2}), has been useful in sorting out the chemical mechanism in the sol-gel steps. {sup 13}C, {sup 15}N, and {sup 1}H NMR studies on the HMTA gelation agent (Hexamethylene tetramine, C{sub 6}H{sub l2}N{sub 4}) has revealed near quantitative stability of this adamantane-like compound in the sol-Gel process, contrary to its historical role as an ammonia source for gelation from the worldwide technical literature. {sub 17}0 NMR of uranyl (UO{sub 2}{sup ++}) hydrolysis fragments produced in colloidal sols has revealed the selective formation of a uranyl trimer, ((UO{sub 2}){sub 3}({mu}{sub 3}-O)({mu}{sub 2}-OH){sub 3}){sup +}, induced by basic hydrolysis with the HMTA gelation agent. Spectroscopic results show that trimer condensation occurs during sol-gel processing leading to layered polyanionic hydrous uranium oxides in which HMTAH{sup +} is occluded as an intercalation'' cation. Subsequent sol-gel processing of microspheres by ammonia washing results in in-situ ion exchange and formation of a layered hydrous ammonium uranate with a proposed structural formula of (NH{sub 4}){sub 2}((UO{sub 2}){sub 8}O{sub 4}(OH){sub 10}) {center dot} 8H{sub 2}0. This compound is the precursor to sintered U0{sub 2} ceramic fuel.

  2. Nonlinear solid-state filter based on photochromism induced by 2-photon absorption in a dye-doped sol-gel

    NASA Astrophysics Data System (ADS)

    Gvishi, Raz; Zhao, Peng; Hu, Honghua; Strum, Galit; Tal, Amir; Grinvald, Shmuel; Bar, Galit; Bekere, Laura; Lokshin, Vladimir; Khodorkovsky, Vladimir; Sigalov, Mark; Hagan, David; Van Stryland, Eric

    2014-10-01

    There is much interest in enhancement of the absorbance performance of nonlinear absorber solid-state filters. In this work we present an advanced reversible nonlinear filter based on a dye-doped sol-gel matrix. The absorbance enhancement was achieved by using a combination of two absorption mechanisms in the same molecule; a photochromic absorption which is induced by 2-photon absorption (2PA). The 2PA serves as the trigger for initiating the photochromism through Förster-resonance-energy-transfer (FRET) between the fluorescent donor and the photochromic acceptor. We synthesized a new bifunctional-chromophore that incorporated a carbazole-derived 2PA fluorescent donor and a chromene-derived photochromic acceptor, covalently linked together in a single molecule by a ~6 Å carboxyl group or oxygen bridge. The bifunctional-chromophore was doped in an inorganic-organic hybrid matrix prepared by the fast-sol-gel process. These materials solidify without shrinkage or formation of cracks and present promising properties as optical matrices for smart filters. The dye-doped sol-gel disc presents high transparency in the visible region ("colorless"), which under UV-irradiation (one-photon absorption in the photochromic part of the molecule), transforms into a strongly absorbing filter ("dark colored"), due to the conversion of the photochromic moiety to its "open" absorbing form. We have demonstrated that this ring-opening can also be induced by visible-light (620 nm) using the 2PA carbazole-derived moiety of the molecule. We have studied the fabrication routes and optical performance of these filters. We present studies of the 2PA mechanism of the carbazole derivative, FRET efficiency of the combined-molecule as well as in solutions of the individual moieties, and reversible dynamics of the photochromic moiety.

  3. Non-Aqueous Capillary Electrophoresis

    NASA Astrophysics Data System (ADS)

    Szumski, Michał; Buszewski, Bogusław

    Non-aqueous capillary electrophoresis and capillary electrochromatography are special variants of these techniques. Here, organic solvents or their mixtures with or without dissolved electrolytes are used as separation buffer or mobile phase, respectively. The most important features of non-aqueous systems are: better solubility of more hydrophobic ionic substances (many natural products) than in water, much less current and Joule heating allows for using highly concentrated buffers and/or larger capillary internal diameters, polar interactions are enhanced in organic solvents which is often highly advantageous in chiral separation systems. This chapter presents most frequently used solvents, their properties, as well as shows pH* scale which is often used in non-aqueous systems.

  4. Fluorescence properties of rare-earth doped sol-gel silica glasses

    NASA Astrophysics Data System (ADS)

    Stone, Brandon Thomas

    Rare earth doped silica glasses find numerous applications ranging from fiber amplifiers for optical communications to high power lasers for inertial confinement fusion research. The performance of rare earth doped optical devices would be improved by better understanding of relationships among glass structure, composition and dopant ion optical properties. The specific problem of rare earth ion clustering limits the efficiency of rare earth optical devices by limiting optimal rare earth ion concentrations. The fluorescence properties of rare earth ions were studied in sol-gel silica in order to determine the mechanism of rare earth ion clustering and evaluate synthesis procedures designed to prevent clustering. Fluorescence line narrowing measurements were used to identify rare earth clustering. While aluminum co-doping in rare earth doped silica has been found to eliminate rare earth ion clusters, it has also been found to increase the residual hydroxyl content and hydroxyl quenching. The use of an alternate aluminum precursor expected to reduce the hydroxyl content in sol-gel silica and the use of other co-dopant ions to reduce rare earth ion clustering were considered. Hydroxyl quenching due to the large residual hydroxyl content in sol-gel silica lowers optical efficiencies through non-radiative decay of ions in excited states. Excited state lifetime measurements were used to qualitatively assess the hydroxyl content of rare earth doped sol-gel silica with different compositions and prepared with different procedures. Fluorinated dopant ion precursors were used to produce in situ dehydroxylation in rare earth doped sol-gel silica. Additionally, rare earth doped hybrid organic/inorganic gels were prepared in an effort to reduce the hydroxyl content of the final silica glass. The influence of these synthesis schemes on rare earth ion clustering was also determined. The effects of energy transfer between rare earth ions in sol-gel silica were examined with lifetime, fluorescence, and upconversion measurements. Rare earth ion clustering was expected to have a beneficial effect on upconversion. Green and red upconversion fluorescence was detected, and models of the upconversion processes were developed.

  5. Fiber-optic chemical sensors using sol-gel membranes and photocatalysts

    NASA Astrophysics Data System (ADS)

    Nivens, Delana Amber Gajdosik

    Fiber-optic sensors have been developed that incorporate multi-layer organo-silica sol-gel membranes. Multilayer sol-gel sensors have been designed to offer improved stability over other sol-gel membranes and to measure COsb2 and the unreactive analytes trichloroethylene and perchloroethylene. Single layer pH sensors were fabricated using a base-catalyzed organo-silica sol-gel containing organosilane coupling agents. A base catalyst was found to be better suited for complete incorporation of the aminopropyltriethoxysilane used to attach dye molecules. This allows the production of optically transparent gels that respond to pH in less than 15 seconds. Dual layer COsb2 sensors use the pH sol-gel layer overcoated with a hydrophobic ORganically MOdified SIlica sol-gel membrane (ORMOSIL). The ORMOSIL reduces much of the pH cross sensitivity found in gas sensors and allows fast, reversible diffusion of COsb2. The sensors respond to COsb2 gas within 10 seconds and dissolved COsb2 in 2 minutes. COsb2 sensors have been found to be stable and reproducible for 12 months when stored dry and at least 6 months when stored in buffer. Many volatile organochloride compounds (VOC's) have been difficult to measure using current fiber-optic sensor transduction schemes. The three-layer optical sensor described here incorporates a TiOsb2/SiOsb2 membrane to degrade VOC's into smaller, detectable products, Hsp+, Clsp- and COsb2. Upon exposure to UV light, TiOsb2, a semiconductor with a bandgap of 3.2 eV, produces highly reactive electron-hole pairs that photodegrade organic compounds. The products produced on the TiOsb2 surface diffuse into the nearby indicator membrane where they are detected. Carbon dioxide and protons produced are detected by the pH sensitive indicator layer described above. Preliminary data for the measurement of VOC's indicates that the detection limit for PCE is less than 1.65 ppm in the headspace (10 ppm in solution). Photocatalysis is also used to measure uranyl ion by the fluorescence quenching of a dye, calcein, followed by uranyl-induced photooxidative fluorescence recovery. The photooxidative degradation of uranyl-bound calcein leads to an increase in observable fluorescence. The limit of detection for UOsb2sp{2+} is 10 ppb based on both quenching and photooxidation fluorescence recovery.

  6. Synthesis and characterization of sol-gel-derived nanomaterials and nanocrystalline electroless metal coatings

    NASA Astrophysics Data System (ADS)

    Shukla, Satyajit Vishnu

    CuS (minimum size of 2.5 nm), Ag2S (minimum and average size of 2.5 nm and 26 nm respectively), and Au (with minimum size of <10 nm) nanoparticles dispersed within the sol-gel derived hydroxypropyl cellulose (HPC)-silica films are synthesized using the gas diffusion technique. The effectiveness of HPC polymer, as a 'compatibilizer', to synthesize semiconductor and metal nanoparticles distributed uniformly within the silica film is demonstrated. The sol-gel derived HPC-silica films containing dispersed nanoparticles are characterized using x-ray photoelectron spectroscopy (XPS) to understand the mechanism of formation of nanoparticles within the film. The XPS core-level binding energies (B.E.) for the nanoparticles are observed to be sensitive to the variation in the chemical composition at the surface and their size. The 'cluster size effect' is shown to be useful in predicting the average nanoparticle size. Nanocrystalline ZrO2 particles are successfully synthesized using sol-gel technique utilizing HPC polymer as a 'steric barrier'. The use of HPC polymer is demonstrated to synthesize submicron-sized, non-agglomerated, and spherical as well as nanocrystalline ZrO2 particles by adjusting the sol-gel synthesis parameters. The effect of sol-gel synthesis parameters on ZrO2 nanocrystallite size, its distribution, and the phase evolution behavior of ZrO2 is studied. The optimum sol-gel synthesis parameters for synthesizing nanocrystalline ZrO2 with 100% tetragonal phase are identified. Cu/CuO-ZrO2 composite powder is synthesized using the electroless metal deposition technique. The mechanism of electroless deposition of Cu over ZrO2 particle surface is investigated using XPS. On the basis of 'cluster size effect', it is suggested that, the electroless metal deposition process activates the non-catalytic ceramic substrate surface by depositing metallic Pd0 clusters and not by the accepted Pd-Sn alloy catalyst. Fly ash cenosphere particle surface is also activated by metallic Pd0 clusters under similar coating conditions. The cenosphere particles are further coated with Ag using Pd-activation. The Cu and Ag-coated cenosphere particles find application in manufacturing conducting polymers used for electromagnetic interference (EMI) shielding application. The use of cost-effective activator (AgNO3) is demonstrated for coating the cenosphere particles with Cu for commercialization. The use of Focussed Ion Beam (FIB) microscopy technique is demonstrated to directly measure the coating-thickness.

  7. Aerogel and xerogel synthesis of solid oxide fuel cell materials by an epoxide assisted sol-gel method: Investigating high surface area ceramics for cathode applications

    NASA Astrophysics Data System (ADS)

    Chervin, Christopher N.

    In this work, an epoxide initiated sol-gel method was developed for the aerogel and xerogel synthesis of YSZ and LSM and the application of aerogel derived YSZ to SOFC cathodes was investigated. A brief review of SOFC cathodes and a background to sol-gel chemistry and the epoxide addition method are presented in Chapter l. Chapters 2 and 3 describe the synthesis of YSZ-precursor aerogels and xerogels by the epoxide method. The effects of epoxide, solvent, and drying method were examined. Aerogels calcined to 550 C, consisted of homogeneous, nanoparticles (10 nm) with spherical morphologies and high surface areas (125 to 150 m2/g), whereas xerogel processing produced coarse, highly agglomerated powders. YSZ sol-gel materials, from 3 to 25 mol% Y 2O3, were successfully prepared with either propylene oxide or trimethylene oxide in both aqueous and mixed ethanol-water solutions of Zr4+ and Y3+ chlorides. Elemental analysis, XRD, and electron microscopy indicated that Y2O3 and ZrO2 formed a homogeneous nanostructure over a wide range of Zr/Y ratios, corresponding from 3 to 25 MOM Y203. Chapter 4 details the sol-gel synthesis of LSM by the epoxide route. Unlike the YSZ gels, aerogel and xerogel processing of the gels produced remarkably similar mesoporous materials. Ambient drying resulted in high surface area xerogels (200 m 2/g) with nanostructured networks interconnecting particulate regions. The morphology of the resultant xerogels were intermediated between the networked structure of pure La xerogels and the particulate precipitates formed by the divalent cations. Calcination of the dried gels resulted in the crystallization of single-phase LSM nanoparticles (100 nm) by 700 C, subsequent to decomposition of intermediate hydroxide, chloride, and oxychloride compounds. Chapter 5 covers conventional electrochemical cell design and fabrication including results from a study on chemical degradation related to the fabrication process. In Chapter 6, the effect of YSZ surface area on composite YSZ-LSM cathodes was studied with respect to electrode fabrication, microstructure, and electrochemical performance is reported. High surface area aerogel derived YSZ powders were compared with relatively low-surface-area commercial YSZ powders.

  8. Sol-gel synthesis of nanocomposite materials based on lithium niobate nanocrystals dispersed in a silica glass matrix

    SciTech Connect

    Marenna, Elisa; Aruta, Carmela; Fanelli, Esther; Barra, Mario; Pernice, Pasquale; Aronne, Antonio

    2009-05-15

    With the final goal to obtain thin films containing stoichiometric lithium niobate nanocrystals embedded in an amorphous silica matrix, the synthesis strategy used to set a new inexpensive sol-gel route to prepare nanocomposite materials in the Li{sub 2}O-Nb{sub 2}O{sub 5}-SiO{sub 2} system is reported. In this route, LiNO{sub 3}, NbCl{sub 5} and Si(OC{sub 2}H{sub 5}){sub 4} were used as starting materials. The gels were annealed at different temperatures and nanocrystals of several phases were formed. Futhermore, by controlling the gel compositions and the synthesis parameters, it was possible to obtain LiNbO{sub 3} as only crystallizing phase. LiNbO{sub 3}-SiO{sub 2} nanocomposite thin films on Si-SiO{sub 2} and Al{sub 2}O{sub 3} substrates were grown. The LiNbO{sub 3} average size, increasing with the annealing temperature, was 27 nm for a film of composition 10Li{sub 2}O-10Nb{sub 2}O{sub 5}-80SiO{sub 2} heated 2 h at 800 deg. C. Electrical investigation revealed that the nanocrystals size strongly affects the film conductivity and the occurrence of hysteretic current-voltage curves. - Graphical abstract: Sol-gel synthesis of nanocomposite materials in the Li{sub 2}O-Nb{sub 2}O{sub 5}-SiO{sub 2} system is reported. The goal was to synthesize thin films containing lithium niobate nanocrystals embedded in a silica matrix. Starting from LiNO{sub 3}, NbCl{sub 5} and Si(OC{sub 2}H{sub 5}){sub 4,} it was possible to obtain LiNbO{sub 3} as only crystallizing phase, nanocrystals size was 27 nm for a film 10Li{sub 2}O-10Nb{sub 2}O{sub 5}-80SiO{sub 2} heated 2 h at 800 deg. C.

  9. β-Diketones and their derivatives in sol-gel processes

    NASA Astrophysics Data System (ADS)

    Zolotareva, N. V.; Semenov, V. V.

    2013-10-01

    Published data on the use of β-diketones, metal β-diketonates and some structurally related compounds in sol-gel synthesis of new organic-inorganic hybrid materials are analyzed. Functionalization methods of β-diketones with carbofunctional organosilicon compounds are considered. Ways of insertion of a metal cation into the organic-inorganic hybrid matrix using non-functionalized β-diketonates are demonstrated. Particular attention is devoted to luminescent lanthanide derivatives, which is due to the prospects of practical application of materials obtained from them in photonics, integrated optics and medical diagnosis. The types and properties of most widely used sol-gel monomers and oligomers and the luminescence behaviour of lanthanide β-diketonates and metal-free silica matrices are considered. The bibliography includes 220 references.

  10. Relaxation dynamics near the sol-gel transition: From cluster approach to mode-coupling theory

    NASA Astrophysics Data System (ADS)

    Coniglio, A.; Arenzon, J. J.; Fierro, A.; Sellitto, M.

    2014-10-01

    A long standing problem in glassy dynamics is the geometrical interpretation of clusters and the role they play in the observed scaling laws. In this context, the mode-coupling theory (MCT) of type-A transition and the sol-gel transition are both characterized by a structural arrest to a disordered state in which the long-time limit of the correlator continuously approaches zero at the transition point. In this paper, we describe a cluster approach to the sol-gel transition and explore its predictions, including universal scaling laws and a new stretched relaxation regime close to criticality. We show that while MCT consistently describes gelation at mean-field level, the percolation approach elucidates the geometrical character underlying MCT scaling laws.

  11. A Review of Photocatalysts Prepared by Sol-Gel Method for VOCs Removal

    PubMed Central

    Tseng, Ting Ke; Lin, Yi Shing; Chen, Yi Ju; Chu, Hsin

    2010-01-01

    The sol-gel process is a wet-chemical technique (chemical solution deposition), which has been widely used in the fields of materials science, ceramic engineering, and especially in the preparation of photocatalysts. Volatile organic compounds (VOCs) are prevalent components of indoor air pollution. Among the approaches to remove VOCs from indoor air, photocatalytic oxidation (PCO) is regarded as a promising method. This paper is a review of the status of research on the sol-gel method for photocatalyst preparation and for the PCO purification of VOCs. The review and discussion will focus on the preparation and coating of various photocatalysts, operational parameters, and will provide an overview of general PCO models described in the literature. PMID:20640156

  12. 3D Printed PEG-Based Hybrid Nanocomposites Obtained by Sol-Gel Technique.

    PubMed

    Chiappone, Annalisa; Fantino, Erika; Roppolo, Ignazio; Lorusso, Massimo; Manfredi, Diego; Fino, Paolo; Pirri, Candido Fabrizio; Calignano, Flaviana

    2016-03-01

    In this work, three-dimensional (3D) structured hybrid materials were fabricated combining 3D printing technology with in situ generation of inorganic nanoparticles by sol-gel technique. Those materials, consisting of silica nanodomains covalently interconnected with organic polymers, were 3D printed in complex multilayered architectures, incorporating liquid silica precursors into a photocurable oligomer in the presence of suitable photoinitiators and exposing them to a digital light system. A post sol-gel treatment in acidic vapors allowed the in situ generation of the inorganic phase in a dedicated step. This method allows to build hybrid structures operating with a full liquid formulation without meeting the drawbacks of incorporating inorganic powders into 3D printable formulations. The influence of the generated silica nanoparticle on the printed objects was deeply investigated at macro- and nanoscale; the resulting light hybrid structures show improved mechanical properties and, thus, have a huge potential for applications in a variety of advanced technologies. PMID:26871993

  13. Treatments of paper surfaces with sol-gel coatings for laminated plywood

    NASA Astrophysics Data System (ADS)

    Wang, Shaoxia; Jms, Saila; Mahlberg, Riitta; Ihalainen, Petri; Nikkola, Juha; Mannila, Juha; Ritschkoff, Anne-Christine; Peltonen, Jouko

    2014-01-01

    Two silane-based hybrid coatings were developed for surface modification of paper samples with an attempt to improve the hydrophobic properties of the paper surfaces. A phenolic resin was used along with the sol-gel coatings to impregnate the paper samples before they were pressed on to plywood surfaces. The surface characteristics of the sol-gel-coated paper were investigated by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), confocal laser scanning microscopy (CLSM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The surface chemical properties and water absorption of the laminated plywood was also evaluated. It was observed that the hybrid coatings had clearly different effect on the surface properties of the base paper compared to the industrially impregnated paper. The water absorption of the laminated plywood was decreased the most effectively by mixing the phenolic resin with the coating having an octyl group attached to the silane backbone.

  14. The Physics of Evaporation-Induced Assembly of Sol-Gel Materials

    SciTech Connect

    HURD,ALAN J.; STEINBERG,LEV

    2000-07-24

    Remarkable materials ordered at the nanoscale emerge when a sol-gel solution becomes co-organized with a surfactant. At sufficiently high concentration, the surfactant forms crystalline or liquid-crystalline arrays of micelles in the presence of the sol-gel, and as gelation proceeds the arrays become locked into the gel. Recent experiments demonstrate that the degree of order in the resulting mesoporous ceramic phase can be enhanced and controlled by continuous dip coating in which the solution, initially dilute, evolves through the critical micelle concentration by steady-state evaporation. The long-range order and microstructural orientation in these films suggest that the propagation of a critical-micelle-concentration transition front, with large physico-chemical gradients, promotes oriented self assembly of surfactant aggregates. This steep-gradient view is supported by results from unsteady evaporation of aerosols of similar solutions, in which internally well-ordered but complex particles are formed.

  15. Nanocrystalline indium tin oxide fabricated via sol-gel combustion for electrochemical luminescence cells.

    PubMed

    Chaoumead, Accarat; Kim, Tae-Woo; Park, Min-Woo; Sung, Youl-Moon

    2012-04-01

    Nanoporous indium tin oxide (ITO) was synthesized via a sol-gel combustion hybrid method using Ketjenblack as a fuel. The effects of the sol-gel combustion conditions on the structures and morphology of the ITO particles were studied. The size of the nanoporous powder was found to be 20-30 nm in diameter. The layer of the nanoporous ITO electrode (-10 microm thickness) with large surface area (-360 m2/g) was fabricated for an electrochemical luminescence (ECL) cell. At 4 V bias, the ECL efficiency of the cell consisting of the nanoporous ITO layer was approximately 1050 cd/m2, which is significantly higher than the cell using only the FTO electrode (450 cd/m2). The nanoporous ITO layer was effective in increasing the ECL intensities. PMID:22849163

  16. Sol gel based fiber optic sensor for blook pH measurement

    SciTech Connect

    Grant, S. A.; Glass, R. S.

    1996-12-19

    This paper describes a fiber-optic pH sensor based upon sol-gel encapsulation of a self-referencing dye, seminaphthorhodamine-1 carboxylate (SNARF-1C). The simple sol-gel fabrication procedure and low coating leachability are ideal for encapsulation and immobilization of dye molecules onto the end of an optical fiber. A miniature bench-top fluorimeter system was developed for use with the optical fiber to obtain pH measurements. Linear and reproducible responses were obtained in human blood in the pH range 6.8 to 8.0, which encompasses the clinically-relevant range. Therefore, this sensor can be considered for in vivo use.

  17. Optical and electrochromic properties of sol-gel-deposited tungsten oxide films

    NASA Astrophysics Data System (ADS)

    Ozkan, Esra; Lee, Se-Hee; Liu, Ping; Tracy, C. Ed; Tepehan, Fatma Z.; Pitts, J. Roland; Deb, Satyen K.

    2001-11-01

    The electrochromic properties of sol-gel and mesoporous tungsten oxide thin films were investigated. Tungsten oxide films were prepared by a spin coating technique from an ethanolic solution of tungsten hexachloride. A block copolymer (BASF Pluronic p123, (p1) was employed as a template to generate the mesoporous structure. The electrochromic and optical properties of such films are described and compared to standard sol-gel tungsten oxide films. A novel ultraviolet (UV) illumination method was developed to remove the polymer templates and was found to improve the coloration efficiency of tungsten oxide in general. All types of films were analyzed by transmission electron microscopy (TEM), atomic force microscopy (AFM), x- ray diffractometry and cyclic voltammetry.

  18. Effect of sol-gel modifications on formation and morphology of nanocrystalline lanthanum aluminate

    SciTech Connect

    Koc, S. Naci . E-mail: nacik@istanbul.edu.tr; Oksuzomer, Faruk; Yasar, Erdem; Akturk, Selcuk; Gurkaynak, M. Ali

    2006-12-14

    LaAlO{sub 3} powders are prepared by sol-gel method. The effect of preparation conditions on morphological properties and crystal formations are investigated. iso-Propanol/tert-butanol and ethyl acetoacetate/ethylene glycol monomethylether are used solvents and complexing agents, respectively. Samples are dried with conventional and freeze-drying methods and calcined between 600 and 1000 deg. C. TGA, DTA, XRD, SEM and TEM methods are used for characterization. It is observed that freeze-dried sample prepared with tert-butanol has the lowest LaAlO{sub 3} formation temperature and uniform rhombohedral crystals. But conventionally dried sample, prepared with iso-propanol has smallest agglomerates at 1000 deg. C and does not show clear crystallization temperature in DTA analysis. The XRD peaks of LaAlO{sub 3} crystal are observed at 600 deg. C for all samples prepared by various sol-gel conditions.

  19. Sol-gel co-assembly of hollow cylindrical inverse opals and inverse opal columns.

    PubMed

    Haibin, Ni; Ming, Wang; Wei, Chen

    2011-12-19

    A facile approach of fabricating hollow cylindrical inverse opals and inverse opal columns by sol-gel co-assembly method was proposed. Polystyrene (PS) colloidal suspension added with hydrolyzed silicate precursor solution was used to self-assemble composite colloidal crystals which consist of PS colloidal crystal template and infiltrated silica gel in the interstitial of microspheres. Continuous hollow cylindrical composite colloidal crystal films have been produced on capillaries' outside and internal surface. Composite colloidal crystal columns which filling up the interior of a capillary were fabricated by pressure assisted sol-gel co-assembly method. Hollow cylindrical inverse opals and inverse opal columns were obtained after removing PS colloidal crystal from the composite colloidal crystal. Optical properties of the silica hollow cylindrical inverse opals were characterized by transmission spectrum and a stop band was observed. Structure and optical properties of the inverse opal columns were investigated. PMID:22274178

  20. Moisture sensor based on evanescent wave light scattering by porous sol-gel silica coating

    DOEpatents

    Tao, Shiquan; Singh, Jagdish P.; Winstead, Christopher B.

    2006-05-02

    An optical fiber moisture sensor that can be used to sense moisture present in gas phase in a wide range of concentrations is provided, as well techniques for making the same. The present invention includes a method that utilizes the light scattering phenomenon which occurs in a porous sol-gel silica by coating an optical fiber core with such silica. Thus, a porous sol-gel silica polymer coated on an optical fiber core forms the transducer of an optical fiber moisture sensor according to an embodiment. The resulting optical fiber sensor of the present invention can be used in various applications, including to sense moisture content in indoor/outdoor air, soil, concrete, and low/high temperature gas streams.

  1. Cross-condensation reactions in an organically modified silica sol-gel

    SciTech Connect

    Prabakar, S.; Raman, N.K.; Assink, R.A.; Brinker, C.J. |

    1993-12-31

    High resolution {sup 29}Si NMR has been used to study the extent of cross condensation taking place in a hybrid organic/inorganic sol-gel system. Tetraethoxysilane (TEOS) and methltriethoxysilane (MTEOS) sol-gels were chosen for this purpose. The sols were prepared by acid catalyzed hydrolysis of TEOS and MTEOS with a H{sub 2}O/Si ratio of 0.3. {sup 29}Si NMR shows signals due to both self-condensation and cross-condensation between TEOS and MTEOS. Resonance assignments were made by comparing the positions and intensities of peaks in the spectra of single and multicomponent systems. It was found that, within experimental error, the self- and cross-condensation rates are equal and that extensive molecular level mixing takes place during the early stages of the reaction.

  2. The role of temperature in forming sol-gel biocomposites containing polydopamine

    PubMed Central

    Dyke, Jason Christopher; Hu, Huamin; Lee, Dong Joon; Ko, Ching-Chang; You, Wei

    2014-01-01

    To further improve the physical strength and biomedical applicability of bioceramicsbuilt on hydroxyapatite-gelatin (HAp-Gel) and siloxane sol-gel reactions, we incorporated mussel adhesive inspired polydopamine (PD) into our original composite based on HAp-Gel cross-linked with siloxane. Surprisingly, with the addition of PD, we observed that the processing conditions and temperatures play an important role in the structure and performance of these materials. A systematic study to investigate this temperature dependence behavior discloses that the rate of crosslinking of silane during the sol-gel process is significantly influenced by the temperature, whereas the polymerization of the dopamine only shows minor temperature dependence. With this discovery, we report an innovative thermal process for the design and application of these biocomposites. PMID:25485111

  3. Ultrapure glass optical waveguide development in microgravity by the sol-gel process

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Containerless melting of glasses in space for the preparation of ultrapure homogeneous glass for optical waveguides is discussed. The homogenization of the glass using conventional raw materials is normally achieved on Earth either by the gravity induced convection currents or by the mechanical stirring of the melt. Because of the absence of gravity induced convection currents, the homogenization of glass using convectional raw materials is difficult in the space environment. Multicomponent, homogeneous, noncrystalline oxide gels can be prepared by the sol-gel process and these gels are promising starting materials for melting glasses in the space environment. The sol-gel process is based on the polymerization reaction of alkoxysilane with other metal alkoxy compounds or suitable metal salts. Many of the alkoxysilanes or other metal alkoxides are liquids and thus can be purified by distillation.

  4. Rare-earth doped sol-gel materials for optical waveguides

    NASA Astrophysics Data System (ADS)

    Locher, Martin; Romano, Valerio; Weber, Heinz P.

    2005-03-01

    Neodymium doped SiO2-Al2O3 samples have been produced by the sol-gel method and characterized by refraction index and fluorescence measurements. TiO2 co-doping has been used to control the refraction index n up to a concentration of TiO2:SiO2 of 1:1 where n has increased from 1.46 to 1.73. Refraction index measurements of thin films have been done by white light interferometry. The fluorescence spectra and lifetimes upon 808 nm excitation have been measured. The results show that TiO2 co-doping of Nd3+:SiO2-Al2O3 sample does not lead to a significant decrease of the fluorescence lifetime. A fiber preform with a neodymium doped sol-gel core has been manufactured and successfully drawn to a fiber, which showed laser action.

  5. The porosity of sol-gel silica thin films for optrode applications

    SciTech Connect

    Harris, T.M.; Knobbe, E.T.

    1995-12-01

    Porous silica thin films produced by sol-gel processing are being considered for use in optical sensor (optrode) applications. In this study, thin films were produced by dip-coating onto glass slides. The porosity was then measured indirectly, by determining the amount of methylene blue adsorption on each slide. Using this technique, it has been determined that the {open_quotes}two-step{close_quotes} sol-gel process provides a greater surface area than the acid-catalyzed process. With the two-step process, increasing the amount of solvent (ethanol) and decreasing the rate of slide withdrawal from the sol provided increased surface area when normalized to the mass of the deposit.

  6. Sol-gel derived nanostructured cerium oxide film for glucose sensor

    NASA Astrophysics Data System (ADS)

    Ansari, Anees A.; Solanki, Pratima R.; Malhotra, B. D.

    2008-06-01

    Sol-gel derived nanostructured cerium oxide (CeO2) film deposited on gold (Au) electrode has been utilized for physisorption of glucose oxidase (GOx). X-ray diffraction, atomic force microscopy, UV-visible spectroscopy, and electrochemical techniques have been used to characterize sol-gel derived CeO2/Au electrode and GOx /CeO2/Au bioelectrode. The response characteristics of the glucose bioelectrode (GOx/CeO2/Au) indicate linearity, detection limit and shelf-life as 50-400mg/dL, 12.0μM, and 12weeks, respectively. The value of apparent Michaelis-Menten constant (Km) of GOx /CeO2/Au bioelectrode has been found to be 13.55μM.

  7. Regioselective hydroaminomethylation of vinylarenes by a sol-gel immobilized rhodium catalyst.

    PubMed

    Nairoukh, Zackaria; Blum, Jochanan

    2014-03-21

    In the course of our studies toward the development of new heterogeneous conditions for better controlling regioselectivity in organic reactions, we investigated the application of sol-gel immobilized organometallic catalyst for regioselective hydroaminomethylation of vinylarenes with aniline or nitroarene derivatives in an aqueous microemulsion. By immobilization of 6 mol % [Rh(cod)Cl]2 within a hydrophobic silica sol-gel matrix we were able to perform efficient hydroaminomethylation under mild conditions and isolate 2-arylpropylamines with high regioselectivity. The regioselectivity of the reaction was found to be mainly dependent on the hydrophobicity of the catalyst support. It is also significantly affected by the electronic nature of the substrates, by the reaction temperature, and by syngas pressure. The heterogenized catalyst can be reused for several times. PMID:24528141

  8. Nanoporous titania-coated alumina membranes: sol-gel synthesis and characterisation.

    PubMed

    Kermanpur, A; Dastjerdi, V H; Ghassemali, E; Abbasi, M H

    2010-09-01

    In this work, nanoporous titania top layers were deposited by dip-coating process on microporous alpha-alumina substrates using the sol-gel process. The alumina substrates were synthesized by slip casting method using Taguchi optimising approach. The microporous substrate was then used to coat nanoporous titania layers by the sol-gel method. The thickness, pore size, structure and permeability of the membranes were characterised using SEM, XRD, STA and Hg-Porosimetry. The process conditions to achieve defect-free nanoporous titania layers with the average pore size of about 4 nm coated on the microporous alumina substrates with the average pore size of about 270 nm were determined. PMID:21133178

  9. Temperature Dependence of CuGaO2 Films Fabricated by Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Alias, Afishah; Sakamoto, Masato; Kimura, Teppei; Uesugi, Katsuhiro

    2012-03-01

    P-type CuGaO2 films have been fabricated on silicon substrates by the sol-gel method. The stable sol solutions for CuGaO2 growth were developed by the mixing of Cu-O and Ga-O sol solutions using copper(II) acetate monohydrate and tris(acetylacetonato) gallium(III), respectively. Phase separation in CuGaO2 films depends on the sol solution temperature and postbake temperature and duration. CuGaO2 films without a CuO phase were fabricated by postbaking at temperatures of approximately 800 C for 1 h in N2 atmosphere. The sol-gel-derived CuGaO2 films show high transparency of more than 80% in the visible range, and the energy gap is approximately 3.6 eV.

  10. Oxide-based Synaptic Transistors Gated by Sol-Gel Silica Electrolytes.

    PubMed

    Shao, Feng; Yang, Yi; Zhu, Li Qiang; Feng, Ping; Wan, Qing

    2016-02-10

    Low-temperature sol-gel processed silica electrolyte films showed a high specific capacitance of 3.0 ?F/cm(2) due to the electric-double-layer (EDL) effect. Oxide-based transistors gated by such silica electrolyte films show a high on/off ratio (>10(7)) and a very low operation voltage (<2.0 V). The proton-related dynamic modulation in these devices makes them ideal candidates for biological synapse emulation. Short-term synaptic plasticity, such as paired pulse facilitation, was successfully emulated. Most importantly, spiking and logic operation were also demonstrated when two lateral in-plane gates were used as the presynaptic inputs. Our oxide-based EDL transistors gated by sol-gel processed silica electrolyte films provide an interesting approach for synaptic behavior emulation, which is interesting for brain-inspired neuromorphic systems. PMID:26775562

  11. Cotton Fabric Surface Modification by Sol-Gel Deposition of ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Vihodceva, S.; Kukle, S.

    2012-08-01

    One of the main tasks of research is to impact the additional value on natural textiles by adding to them ultraviolet (UV) absorption and antimicrobial protection properties with ZnO nano-level coatings. ZnO shows high absorption in the UV region of the light spectrum, in comparison with organic absorbers conventionally used in the textile industry shows no significant degradation, is stable and classified as non-toxic material. Nanosols were prepared by using the sol-gel process. In this work comparison of samples coated by nanosols with zinc acetate (Zn (CH3COO)2-2H2O) and zinc sulphate (ZnSO4) was made. Scanning electron microscopy (SEM) was used to examine the nature of the surface modification with ZnO coating by the sol-gel technique as also after exploitation of samples; energy dispersive X-ray spectroscopy was used for the analysis of elemental composition of coated fabric samples.

  12. Sol-gel solution-deposited InGaZnO thin film transistors.

    PubMed

    Street, Robert A; Ng, Tse Nga; Lujan, Ren A; Son, Inyoung; Smith, Matthew; Kim, Sangbok; Lee, Taegweon; Moon, Yongsik; Cho, Sungseo

    2014-03-26

    Thin film transistors (TFTs) fabricated by solution processing of sol-gel oxide semiconductor precursors in the group In-Ga-Zn are described. The TFT mobility varies over a wide range depending on the precursor materials, the composition, and the processing variables, with the highest mobility being about 30 cm(2)/(V s) for IZO and 20 cm(2)/(V s) for IGZO. The positive dark bias stress effect decreases markedly as the mobility increases and the high mobility devices are quite stable. The negative bias illumination stress effect is also weaker in the higher mobility TFTs, and some different characteristic properties are observed. The TFT mobility, threshold voltage, and bias stress properties are discussed in terms of the formation of self-compensated donor and acceptor states, based on the chemistry and thermodynamics of the sol-gel process. PMID:24593772

  13. Self-Protection of Electrochemical Storage Devices via a Thermal Reversible Sol-Gel Transition.

    PubMed

    Yang, Hui; Liu, Zhiyuan; Chandran, Bevita K; Deng, Jiyang; Yu, Jiancan; Qi, Dianpeng; Li, Wenlong; Tang, Yuxin; Zhang, Chenguang; Chen, Xiaodong

    2015-10-01

    Thermal self-protected intelligent electrochemical storage devices are fabricated using a reversible sol-gel transition of the electrolyte, which can decrease the specific capacitance and increase and enable temperature-dependent charging and discharging rates in the device. This work represents proof of a simple and useful concept, which shows tremendous promise for the safe and controlled power delivery in electrochemical devices. PMID:26294084

  14. The detection of hexavalent chromium by organically doped sol-gels

    SciTech Connect

    Wong, P.W.; Mackenzie, J.D.

    1994-12-31

    The sol-gel process can be used to produce porous inorganic matrices that are doped with organic molecules. These doped gels can be used as a quantitative method for the spectrophotometric determination of trace concentrations of metallic ions. For the detection of hexavalent chromium, malachite green was used as the dopant. Preliminary results indicate concentrations on the order of 5 ppb are detectable using this method.

  15. Room-temperature mirror preparation using sol-gel chemistry and laminar-flow coating technique

    NASA Astrophysics Data System (ADS)

    Belleville, Philippe F.; Bonnin, Claude; Lavastre, Eric; Pegon, Philippe; Rorato, Yannick

    2001-04-01

    The CEA/DAM megajoule-class pulsed Nd:glass laser devoted to Inertial Confinement Fusion (ICF) research is requiring 240 cavity-end mirrors. The mirror design is based on 44-cm square highly-reflective (HR)-coated deformable substrates. Such large dielectric mirrors are using interference quarterwave stacks of SiO2 and ZrO2-PVP (PolyVinylPyrrolidone) thin films starting from sol-gel colloidal suspensions (sols). The colloidal/polymeric ratio of the ZrO2-PVP composite system has been optimized regarding refractive index value, laser damage threshold and chemical interactions have been studied using FT-IR spectroscopy. Therefore a promising deposition technique so- called Laminar Flow Coating (LFC) has been associated to sol-gel chemistry for HR sol-gel coating development. The as-designed LFC prototype machine has been used for coating solution wave deposition by transportation of a tubular dispense unit under the substrate flat surface. Thin film so created by the solvent evaporation was then dried at room temperature or using short wavelength UV-curing built-in station. Optimization of parameters such as optical layer number, coating uniformity, coating edge effect, 1053-nm reflectance and laser damage threshold is discussed. Demonstration has been made that this novel coating method is a competitive way for large-area optical deposition compared to dipping or spinning techniques. Association of sol-gel colloidal suspensions to LFC process appear to be a promising cheap way of producing high power laser optical coatings.

  16. Li+ ions diffusion into sol-gel V2O5 thin films: electrochromic properties

    NASA Astrophysics Data System (ADS)

    Benmoussa, M.; Outzourhit, A.; Bennouna, A.; Ihlal, A.

    2009-10-01

    V{2}O{5} thin films were prepared by the sol-gel spin coating process. The Li+ ions insertion effect on optical and electrochromic properties of those films was studied. The diffusion coefficient was calculated using both cyclic voltammograms and chronoamperometric curves. The amount x of Li+ ions in LixV{2}O{5} was also calculated. Finally, the electrochromic performance evolution characteristics such as the reversibility, coloration efficiency, coloration memory stability and response time were studied.

  17. Development of novel sol-gel indicators (SGI`s) for in-situ environmental measurements

    SciTech Connect

    Livingston, R.R.; Wicks, G.G.; Baylor, L.C.; Whitaker, M.J.

    1993-10-01

    Organic indicator molecules have been incorporated in a porous sol- gel matrix coated on the end of a fiber-optic lens assembly to create sensors for in situ environmental measurements. Probes have been made that are sensitive to pH and uranyl concentration. The use of fiber optics allows the probe to be lowered into a well or bore hole, while support equipment such as a spectrophotometer and computer may be situated hundreds of meters away.

  18. Ultrapure glass optical waveguide: Development in microgravity by the sol gel process

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.; Debsikdar, J. C.; Beam, T.

    1983-01-01

    The sol-gel process for the preparation of homogeneous gels in three binary oxide systems was investigated. The glass forming ability of certain compositions in the selected oxide systems (SiO-GeO2, GeO2-PbO, and SiO2-TiO2) were studied based on their potential importance in the design of optical waveguide at longer wavelengths.

  19. Optical chemical sensors based on hybrid organic-inorganic sol-gel nanoreactors.

    PubMed

    Tran-Thi, Thu-Hoa; Dagnelie, Romain; Crunaire, Sabine; Nicole, Lionel

    2011-02-01

    Sol-gel porous materials with tailored or nanostructured cavities have been increasingly used as nanoreactors for the enhancement of reactions between entrapped chemical reactants. The domains of applications issued from these designs and engineering are extremely wide. This tutorial review will focus on one of these domains, in particular on optical chemical sensors, which are the subject of extensive research and development in environment, industry and health. PMID:21180764

  20. Characterization of Sol-gel Encapsulated Proteins using Small-angle Neutron Scattering

    SciTech Connect

    Luo, Guangming; Zhang, Qiu; Del Castillo, Alexis Rae; Urban, Volker S; O'Neill, Hugh Michael

    2009-01-01

    Entrapment of biomolecules in silica-derived sol-gels has grown into a vibrant area of research since it was originally demonstrated. However, accessing the consequences of entrapment on biomolecules and the gel structure remains a major challenge in characterizing these biohybrid materials. We present the first demonstration that it is possible with small-angle neutron scattering (SANS) to study the conformation of dilute proteins that are entrapped in transparent and dense sol-gels. Using deuterium-labeled green fluorescent protein (GFP) and SANS with contrast variation, we demonstrate that the scattering signatures of the sol-gel and the protein can be separated. Analysis of the scattering curves of the sol-gels using a mass-fractal model shows that the size of the colloidal silica particles and the fractal dimensions of the gels were similar in the absence and presence of protein, demonstrating that GFP did not influence the reaction pathway for the formation of the gel. The major structural difference in the gels was that the pore size was increased 2-fold in the presence of the protein. At the contrast match point for silica, the scattering signal from GFP inside the gel became distinguishable over a wide q range. Simulated scattering curves representing a monomer, end-to-end dimer, and parallel dimer of the protein were calculated and compared to the experimental data. Our results show that the most likely structure of GFP is that of an end-to-end dimer. This approach can be readily applied and holds great potential for the structural characterization of complex biohybrid and other materials.

  1. Photoresist-Free Fully Self-Patterned Transparent Amorphous Oxide Thin-Film Transistors Obtained by Sol-Gel Process

    NASA Astrophysics Data System (ADS)

    Lim, Hyun Soo; Rim, You Seung; Kim, Hyun Jae

    2014-04-01

    We demonstrated self-patterned solution-processed amorphous oxide semiconductor thin-film transistors (TFTs) using photosensitive sol-gels. The photosensitive sol-gels were synthesized by adding ?-diketone compounds, i.e., benzoylacetone and acetylacetone, to sol-gels. The chemically modified photosensitive sol-gels showed a high optical absorption at specific wavelengths due to the formation of metal chelate bonds. Photoreactions of the modified solutions enabled a photoresist-free process. Moreover, Zn-Sn-O with a high Sn ratio, which is hard to wet-etch using conventional photolithography due to its chemical durability, was easily patterned via the self-patterning process. Finally, we fabricated a solution-processed oxide TFT that included fully self-patterned electrodes and an active layer.

  2. Thermodynamic analysis of sol-gel transition of gelatin in terms of water activity in various solutions.

    PubMed

    Miyawaki, Osato; Omote, Chiaki; Matsuhira, Keiko

    2015-12-01

    Sol-gel transition of gelatin was analyzed as a multisite stoichiometric reaction of a gelatin molecule with water and solute molecules. The equilibrium sol-gel transition temperature, Tt , was estimated from the average of gelation and melting temperature measured by differential scanning calorimetry. From Tt and the melting enthalpy, ?Hsol , the equilibrium sol-to-gel ratio was estimated by the van't Hoff equation. The reciprocal form of the Wyman-Tanford equation, which describes the sol-to-gel ratio as a function of water activity, was successfully applied to obtain a good linear relationship. From this analysis, the role of water activity on the sol-gel transition of gelatin was clearly explained and the contributions of hydration and solute binding to gelatin molecules were separately discussed in sol-gel transition. The general solution for the free energy for gel-stabilization in various solutions was obtained as a simple function of solute concentration. PMID:26215282

  3. Research of materials for porous matrices in sol-gel systems based on silicon dioxide and metallic oxides

    NASA Astrophysics Data System (ADS)

    Maraeva, E. V.; Bobkov, A. A.; Maximov, A. I.; Moshnikov, V. A.; Nalimova, S. S.

    2015-11-01

    In this study silicon dioxide stannic oxide and silicon dioxide zinc nanomaterials oxide were obtained through sol-gel technology. The results of nitrogen thermal desorption measurements, atomic force microscopy measurements and particle sizes measurements are discussed.

  4. Increasing the activity and enantioselectivity of lipases by sol-gel immobilization: further advancements of practical interest

    NASA Astrophysics Data System (ADS)

    Tielmann, Patrick; Kierkels, Hans; Zonta, Albin; Ilie, Adriana; Reetz, Manfred T.

    2014-05-01

    The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of the sol-gel approach.The entrapment of lipases in hydrophobic silicate matrices formed by sol-gel mediated hydrolysis of RSi(OCH3)3/Si(OCH3)4 as originally reported in 1996 has been improved over the years by a number of modifications. In the production of second-generation sol-gel lipase immobilizates, a variety of additives during the sol-gel process leads to increased activity and enhanced stereoselectivity in esterifying kinetic resolution. Recent advances in this type of lipase immobilization are reviewed here, in addition to new results regarding the sol-gel entrapment of the lipase from Burkholderia cepacia. It constitutes an excellent heterogeneous biocatalyst in the acylating kinetic resolution of two synthetically and industrially important chiral alcohols, rac-sulcatol and rac-trans-2-methoxycyclohexanol. The observation that the catalyst can be used 10 times in recycling experiments without losing its significant activity or enantioselectivity demonstrates the practical viability of the sol-gel approach. Dedicated to the pioneer of sol-gel enzyme immobilization, Professor David Avnir, on the occasion of his 65th birthday.

  5. Low-power nonlinear optical interaction in dye-doped sol-gel glasses

    NASA Astrophysics Data System (ADS)

    Lam, Sio K.; Chan, Man-shih A.; Lo, Dennis Y.

    2000-11-01

    Organic dye-doped solids show strong third-order optical non-linearity due to the enhancement of the lifetime of the lowest triplet state of the dye in solid environment. The long triplet state lifetime leads to low absorption saturation intensity. As a result, the third order nonlinear optical behavior is observable at very low light power (i.e. tens of mW). Dye-doped solid of large third order nonlinearity finds application in many photonic devices. Boric acid glass, polymer (such as PMMA, PVA, PAA), sol-gel silica, and organically modified sol-get silicate (ORMOSIL) have been used as host materials for dyes. We will concentrate our interest on the dye-doped sol-gel silica and dye-doped ORMOSIL. We have performed degenerate four wave mixing (DFWM) experiment to demonstrate optical phase conjugation by eosin Y-doped sol-gel silica in vacuum ambient. We have also performed Z-scan measurement to study the nonlinear refractive index of fluorescein 548- doped ORMOSIL. Absorption saturation experiments are conducted to determine the absorption intensity and (chi) (3).

  6. Preparation and characterization of montmorillonite silica nanocomposites: A sol gel approach to modifying clay surfaces

    NASA Astrophysics Data System (ADS)

    Qian, Zhongzhong; Hu, Guangjun; Zhang, Shimin; Yang, Mingshu

    2008-09-01

    Montmorillonite-silica nanocomposites were prepared by a sol-gel approach involving hydrolysis reaction of alkoxysilanes (TEOS) and subsequent condensation reaction with hydroxyl groups of the clay, resulting in the formation of the mesoporous silica network and silica nanoparticles covered or attached on the clay surfaces. According to X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and nitrogen adsorption isotherms, the structure and surface properties of the sol-gel-modified clay can be controlled by varying the TEOS/clay mass ratio and/or adding trace amounts of acid as catalyst. In the case of acid-catalyzed procedures, large continuous mesoporous silica was covered on the clay surfaces, resulting in delamination of clay platelets in silica matrix at higher TEOS/clay ratio, and attaching of isolated mesoporous silica on the clay surface at lower TEOS/clay ratio, respectively. In the case of non-catalyzed procedures, silica nanoparticles were attached on the two-dimensional (2D) clay platelets, while the stack order of the clay was maintained regardless of the TEOS/clay ratios. This sol-gel modification approach combines the surface properties of mesoporous silica and nanoparticles with layered clay, while inheriting the structural properties of the pristine clay such as further intercalation with organic compounds and polymers.

  7. Synthesis of polymeric fluorinated sol-gel precursor for fabrication of superhydrophobic coating

    NASA Astrophysics Data System (ADS)

    Li, Qianqian; Yan, Yuheng; Yu, Miao; Song, Botao; Shi, Suqing; Gong, Yongkuan

    2016-03-01

    A fluorinated polymeric sol-gel precursor (PFT) is synthesized by copolymerization of 2,3,4,5,5,5-hexafluoro-2,4-bis(trifluorinated methyl)pentyl methacrylate (FMA) and 3-methacryloxypropyltrimethoxysilane (TSMA) to replace the expensive long chain fluorinated alkylsilanes. The fluorinated silica sol is prepared by introducing PFT as co-precursor of tetraethyl orthosilicate (TEOS) in the sol-gel process with ammonium hydroxide as catalyst, which is then used to fabricate superhydrophobic coating on glass substrate through a simple dip-coating method. The effects of PFT concentrations on the chemical structure of the formed fluorinated silica, the surface chemical composition, surface morphology, wetting and self-cleaning properties of the resultant fluorinated silica coatings were studied by using X-ray powder diffraction (XRD), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrophotometer (XPS), scanning electron microscopy (SEM) and water contact angle measurements (WCA). The results show that the fluorinated silica sols are successfully obtained. The size and size distribution of the fluorinated silica particles are found greatly dependent on the concentration of PFT, which play a crucial role in the surface morphology of the corresponding fluorinated silica coatings. The suitable PFT concentration added in the sol-gel stage, i.e. for F-sol-1 and F-sol-2, is helpful to achieve both the low surface energy and multi-scaled microstructures, leading to the formation of the superhydrophobic coatings with bio-mimicking self-cleaning property similar to lotus leaves.

  8. Thin-film silica sol-gels doped with ion responsive fluorescent lipid bilayers

    SciTech Connect

    Sasaki, D.Y.; Shea, L.E.; Sinclair, M.B.

    1999-01-12

    A metal ion sensitive, fluorescent lipid-b i layer material (5oA PSIDA/DSPC) was successfully immobilized in a silica matrix using a tetramethoxysilane (TMOS) sol-gel procedure. The sol-gel immobilization method was quantitative in the entrapment of seif-assembled Iipid-bilayers and yielded thin films for facile configuration to optical fiber piatforms. The silica matrix was compatible with the solvent sensitive lipid bilayers and provided physical stabilization as well as biological protection. Immobilization in the silica sol-gel produced an added benefit of improving the bilayer's metal ion sensitivity by up to two orders of magnitude. This enhanced performance was attributed to a preconcentrator effect from the anionic surface of the silica matrix. Thin gels (193 micron thickness) were coupled to a bifurcated fiber optic bundle to produce a metal ion sensor probe. Response times of 10 - 15 minutes to 0.1 M CUCIZ were realized with complete regeneration of the sensor using an ethylenediarninetetraacetic acid (EDTA) solution.

  9. Disinfection studies on TiO2 thin films prepared by a sol-gel method.

    PubMed

    Kambala, Venkata Subba Rao; Naidu, Ravi

    2009-02-01

    Transparent anatase TiO2 nanometer thin films were prepared by dip-coating on soda-lime glass plates via the sol-gel method. The un-calcined and the calcined films were characterized by X-ray diffraction (XRD), AFM, Nano-indentation (hardness and Young's modulus), UV-vis spectrometry, thickness and hydrophilicity (contact angle measurements). The photocatalytic activity of the thin films was evaluated by performing disinfection studies on the Gram-negative microorganisms like Escherichia coli, and Staphylococcus Aureus, a Gram-positive organism. The photocatalytic activity for both groups of organisms was studied in saline and nutrient broth. The leakage of potassium from the bacteria was observed parallel to cell viability. The activity of the sol-gel prepared TiO2 thin films were compared under UV lamps and natural day light (ND) lamps with Degussa P-25 TiO2 thin films prepared on soda-lime glass using a polymer support and the commercial self-cleaning glass (SC). The sol-gel prepared thin films which were annealed at 450 degrees C, show highest photocatalytic activity, the slowest conversion rate from hydrophilic to a hydrophobic state, light-induced hydrophilicity, and also higher disinfection activities compared to P-25 films and commercial self-cleaning glass. The films also show excellent activities when continuously reused for more than a month. PMID:20055115

  10. Sol gel ZnO films doped with Mg and Li evaluated for charged particle detectors

    NASA Astrophysics Data System (ADS)

    Murphy, John W.; Eddy, Alexander; Kunnen, George R.; Mejia, Israel; Cantley, Kurtis D.; Allee, David R.; Quevedo-Lopez, Manuel A.; Gnade, Bruce E.

    2013-05-01

    In this work we assess the feasibility of ZnO films deposited from a sol gel precursor as a material for thin film charged particle detectors. There are many reports of polycrystalline ZnO thin film transistors (TFTs) in the literature, deposited by sputtering, pulsed laser deposition, and sol gel. There are also reports of sol gel derived ZnO doped with Li or Mg to increase the resistivity, however, these works only measure resistivity of the films, without determining the effect of doping on the carrier concentration. We study the effects of doping the ZnO with Mg and Li as well as the effects of thickness on the films' resistivity, mobility, and carrier concentration, since these material parameters are critical for a charged particle sensor. Carrier concentration is particularly important because it must be kept low in order for the intrinsic region of a p-i-n diode to be depleted. In order to accomplish this we fabricate and electrically characterize test structures for resistivity, test structures for hall measurement, common back-gate TFTs, and metal-insulator-semiconductor (MIS) capacitors. We also conduct physical characterization techniques such as x-ray diffraction (XRD), atomic force microscopy (AFM), electron microscopy, UV-Vis spectroscopy, and ellipsometry to determine the effect of doping and film thickness on the microstructure and optical properties of the ZnO.

  11. Preparation and characterisation of a sol-gel process ?-Al?O? polycrystalline detector.

    PubMed

    Ferreira, H R; Santos, A

    2015-02-01

    This article presents the dosimetric characteristics of ?-Al2O3 detectors prepared through the sol-gel process, disc pressing and sintering in a highly reducing atmosphere. Comparative tests between the sol-gel process ?-Al2O3 polycrystalline and anion-defective ?-Al2O3:C single-crystal detectors indicate that the ones prepared through this approach present good dosimetric characteristics similar to those found in single-crystal detectors, such as a simple glow curve with the main peak at ?198 C (2 C s(-1)), high sensitivity, a detection threshold of 1.7 Gy, linearity of response, low fading, relatively low photon energy dependence, reusability without annealing and good reproducibility. However, the undesirable feature of heating rate dependence of the thermoluminescence (TL) output in ?-Al2O3:C single crystal is practically non-existent in the sol-gel process ?-Al2O3 polycrystalline detector. This characteristic renders it useful for the routine processing of large numbers of personal and environmental dosemeters at higher heating rates and also when it comes to the proposal for new approaches to thermal quenching investigation. PMID:24795396

  12. Formation and prevention of fractures in sol-gel-derived thin films.

    PubMed

    Kappert, Emiel J; Pavlenko, Denys; Malzbender, Jürgen; Nijmeijer, Arian; Benes, Nieck E; Tsai, Peichun Amy

    2015-02-01

    Sol-gel-derived thin films play an important role as the functional coatings for various applications that require crack-free films to fully function. However, the fast drying process of a standard sol-gel coating often induces mechanical stresses, which may fracture the thin films. An experimental study on the crack formation in sol-gel-derived silica and organosilica ultrathin (submicron) films is presented. The relationships among the crack density, inter-crack spacing, and film thickness were investigated by combining direct micrograph analysis with spectroscopic ellipsometry. It is found that silica thin films are more prone to fracturing than organosilica films and have a critical film thickness of 300 nm, above which the film fractures. In contrast, the organosilica films can be formed without cracks in the experimentally explored regime of film thickness up to at least 1250 nm. These results confirm that ultrathin organosilica coatings are a robust silica substitute for a wide range of applications. PMID:25466584

  13. Sol-Gel Material-Enabled Electro-Optic Polymer Modulators.

    PubMed

    Himmelhuber, Roland; Norwood, Robert A; Enami, Yasufumi; Peyghambarian, Nasser

    2015-01-01

    Sol-gels are an important material class, as they provide easy modification of material properties, good processability and are easy to synthesize. In general, an electro-optic (EO) modulator transforms an electrical signal into an optical signal. The incoming electrical signal is most commonly information encoded in a voltage change. This voltage change is then transformed into either a phase change or an intensity change in the light signal. The less voltage needed to drive the modulator and the lower the optical loss, the higher the link gain and, therefore, the better the performance of the modulator. In this review, we will show how sol-gels can be used to enhance the performance of electro-optic modulators by allowing for designs with low optical loss, increased poling efficiency and manipulation of the electric field used for driving the modulator. The optical loss is influenced by the propagation loss in the device, as well as the losses occurring during fiber coupling in and out of the device. In both cases, the use of sol-gel materials can be beneficial due to the wide range of available refractive indices and low optical attenuation. The influence of material properties and synthesis conditions on the device performance will be discussed. PMID:26225971

  14. Sol-Gel Material-Enabled Electro-Optic Polymer Modulators

    PubMed Central

    Himmelhuber, Roland; Norwood, Robert A.; Enami, Yasufumi; Peyghambarian, Nasser

    2015-01-01

    Sol-gels are an important material class, as they provide easy modification of material properties, good processability and are easy to synthesize. In general, an electro-optic (EO) modulator transforms an electrical signal into an optical signal. The incoming electrical signal is most commonly information encoded in a voltage change. This voltage change is then transformed into either a phase change or an intensity change in the light signal. The less voltage needed to drive the modulator and the lower the optical loss, the higher the link gain and, therefore, the better the performance of the modulator. In this review, we will show how sol-gels can be used to enhance the performance of electro-optic modulators by allowing for designs with low optical loss, increased poling efficiency and manipulation of the electric field used for driving the modulator. The optical loss is influenced by the propagation loss in the device, as well as the losses occurring during fiber coupling in and out of the device. In both cases, the use of sol-gel materials can be beneficial due to the wide range of available refractive indices and low optical attenuation. The influence of material properties and synthesis conditions on the device performance will be discussed. PMID:26225971

  15. Chemical sensing using sol-gel derived planar waveguides and indicator phases

    SciTech Connect

    Yang, L.; Saavedra, S.S.

    1995-04-15

    A new optical sensing platform based on a combination of planar waveguiding and sol-gel processing technologies is described. The sensing element consists of two, submicrometer thick glass layers supported on an optically thick glass substrate; both layers were fabricated using a sol-gel coating method. The lower layer is a densified glass that functions as a planar integrated optical waveguide (IOW). The upper layer is an undensified glass of lower index doped with an optical indicator that is immobilized, yet remains sterically accessible to analytes that diffuse into the pore network. Formation of a complex between the analyte and indicator is detected via attenuated total reflection (ATR) of light guided in the IOW. Feasibility was evaluated by constructing IOW-ATR sensors for Pb{sup 2+} and pH, based on immobilized xylenol orange and bromocresol purple, respectively. The response of both sensors was sensitive and rapid, features that are difficult to achieve simultaneously in monolithic sol-gel glass sensors. In the IOW-ATR geometry, these features are realized simultaneously because the primary axes of light propagation and analyte diffusion are orthogonal. The overall approach is technically simple, inexpensive, and applicable to a wide variety of indicator chemistries. 48 refs., 8 figs.

  16. Optical sensors based on sol-gel derived, laminate planar waveguide structures

    SciTech Connect

    Yang, Lin; Armstrong, N.R.; Dunphy, D.R.; Saavedra, S.S.

    1995-12-31

    A new optical sensing platform based on a combination of planar and sol-gel processing technologies is described. The sensing element is a planar integrated optical waveguide (IOW) composed of two, submicron thick glass layers coated on glass substrate; both layers are fabricated via the sol-gel method. The lower layer is a densified titania-silica composite. The upper layer is an undensified silica doped with an optical indicator that is physically entrapped yet sterically accessible to dissolved analytes that can diffuse into the pore network. Formation of an analyte-indicator complex is detected via attenuated total reflection (ATR) of light guided in the IOW. The sensor response is both sensitive and rapid, features that are difficult to achieve simultaneously in monolithic sol-gel glass sensors. In the IOW-ATR geometry, these features are realized simultaneously because the primary axes of light propagation and analyte diffusion are orthogonal. The overall approach is technically simple, inexpensive, and applicable to a wide variety of indicator chemistries.

  17. Sol-gel chemistry in biosensing devices of electrical transduction: application to CEA cancer biomarker.

    PubMed

    Truta, Liliana A A N A; Sales, M Goreti F

    2015-01-01

    Sol-gel chemistry allows the immobilization of organic molecules of biological origin on suibtable solid supports, permitting their integration into biosensing devices widening the possibility of local applications. The present work is an application of this principle, where the link between electrical receptor platform and the antibody acting as biorecognition element is made by sol-gel chemistry. The immunosensor design was targeted for carcinoembryonic antigen (CEA), an important biomarker for screening the colorectal cancer, by electrochemical techniques, namely electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SVW). The device displayed linear behavior to CEA in EIS and in SWV assays ranging from 0.50 to 1.5ng/mL, and 0.25 to 1.5ng/mL, respectively. The corresponding detection limits were 0.42 and 0.043 ng/mL. Raman spectroscopy was used to characterize the surface modifications on the conductive platform (FTO glass). Overall, simple sol-gel chemistry was effective at the biosensing design and the presented approach can be a potential method for screening CEA in point-of-care, due to the simplicity of fabrication, short response time and low cost. PMID:25547969

  18. Fabrication and characterization of sol-gel based nanoparticles for drug delivery

    NASA Astrophysics Data System (ADS)

    Yadav, Reeta

    Nanogels are cross linked polymeric sol-gel based nanoparticles that offer an interior network for incorporation and protection of biomolecules, exhibiting unique advantages for polymer based delivery systems. We have successfully synthesized stable sol-gel nanoparticles by means of [a] silicification reactions using cationic peptides like polylysine as gelating agents, and [b] lyophilization of sol-gels. Macromolecules such as Hemoglobin and Glucose Oxidase and small molecules such as Sodium Nitroprusside (SNP) and antibiotics were encapsulated within the nanogels. We have used transmission electron microscopy, dynamic light scattering, zeta potential analysis, and spectroscopy to perform a physicochemical characterization of the nanogels resulting from the two approaches. Our studies have indicated that the nanogel encapsulated proteins and small molecules remain intact, stable and functional. A Hydrogen Peroxide (H2O2) and Nitric Oxide (NO) generating drug carrier was synthesized using these nanogels and the effect of generation of H2O2 from Glucose Oxidase encapsulated nanogels and NO from SNP encapsulated nanogels was tested on E.coli. The results show that the nanoparticles exert antimicrobial activity against E.Coli, in addition NO generating nanogels potentiated H2O2 generating nanogels induced killing. These data suggest that these NO and H2O2 releasing nanogels have the potential to serve as a novel class of antimicrobials for the treatment of multidrug resistant bacteria. The unique properties of these protein/drug incorporated nanogels raise the prospect of fine tailoring to specific applications such as drug delivery and bio imaging.

  19. Raman investigation of germanium- and phosphorus-doping effects on the structure of sol-gel silica-based optical fiber preforms

    NASA Astrophysics Data System (ADS)

    El Hamzaoui, Hicham; Bouazaoui, Mohamed; Capoen, Bruno

    2015-11-01

    This works reports the structural investigation of homogeneously doped sol-gel-derived silica optical fiber preforms. Crack-free germanosilicate (2.7wt% Ge) and phosphosilicate (2.5wt% P) glasses, suitable for optical fiber fabrication, have been prepared using the polymeric sol-gel route combined with the sol-doping technique. Space homogeneity of the doping oxide (GeO2 or P2O5) in the cylindrical preforms has been checked by chemical analysis. The structure of these glasses have been studied using Raman spectroscopy and compared to pure silica glasses. It is shown that phosphorus has a much more sensitive effect on the glassy structure than germanium, both at small and medium scales. Indeed, in the low-wavenumber region (7-100cm-1), the phosphorus-doping was found to affect the intensity of the boson peak, suggesting an enhancement of heterogeneity at the nanometer scale. At a shorter scale, both germanium- and phosphorus-doping were found to reduce the number of three- and four-membered rings in the silica glass network.

  20. Coatings of titanium substrates with xCaO · (1 - x)SiO2 sol-gel materials: characterization, bioactivity and biocompatibility evaluation.

    PubMed

    Catauro, M; Papale, F; Bollino, F

    2016-01-01

    The objective of this study has been to develop low temperature sol-gel coatings to modify the surface of commercially pure titanium grade 4 (a material generally used in dental application) and to evaluate their bioactivity and biocompatibility on the substrate. Glasses of composition expressed by the following general formula xCaO · (1 - x)SiO2 (0.0sol-gel route starting from tetraethyl orthosilicate and calcium nitrate tetrahydrate. Those materials, still in the sol phase, have been used to coat titanium substrates by means of the dip-coating technique. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) allowed the materials to be characterized and a microstructural analysis of the coatings obtained was performed using scanning electron microscopy (SEM). The potential applications of the coatings in the biomedical field were evaluated by bioactivity and biocompatibility tests. The coated titanium was immersed in simulated body fluid (SBF) for 21 days and the hydroxyapatite deposition on its surface was subsequently evaluated via SEM-EDXS analysis, as an index of bone-bonding capability. To investigate cell-material interactions, mouse embryonic fibroblast cells (3T3) were seeded onto the specimens and the cell viability was evaluated by a WST-8 assay. PMID:26478379

  1. Effect of cerium on structure modifications of a hybrid solgel coating, its mechanical properties and anti-corrosion behavior

    SciTech Connect

    Cambon, Jean-Baptiste; Esteban, Julien; Ansart, Florence; Bonino, Jean-Pierre; Turq, Viviane; Santagneli, S.H.; Santilli, C.V.; Pulcinelli, S.H.

    2012-11-15

    Highlights: ? New solgel routes to replace chromates for corrosion protection of aluminum. ? Effect of cerium concentration on the microstructure of xerogel. ? Electrochemical and mechanical performances of hybrid coating with different cerium contents. ? Good correlation between the different results with an optimal cerium content of 0.01 M. -- Abstract: An organicinorganic hybrid coating was developed to improve the corrosion resistance of the aluminum alloy AA 2024-T3. Organic and inorganic coatings derived from glycidoxypropyl-trimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al(O{sup s}Bu){sub 3}, with different cerium contents, were deposited onto aluminum by dip-coating process. Corrosion resistance and mechanical properties were investigated by electrochemical impedance measurements and nano-indentation respectively. An optimal cerium concentration of 0.01 M was evidenced. To correlate and explain the hybrid coating performances in relation to the cerium content, NMR experiments were performed. It has been shown that when the cerium concentration in the hybrid is higher than 0.01 M there are important modifications in the hybrid structure that account for the mechanical properties and anti-corrosion behavior of the solgel coating.

  2. Sol-gel synthesis and characterization of SiO2/PCL hybrid materials containing quercetin as new materials for antioxidant implants.

    PubMed

    Catauro, Michelina; Bollino, Flavia; Papale, Ferdinando; Piccolella, Simona; Pacifico, Severina

    2016-01-01

    The development of biomaterials with intrinsic antioxidant properties could represent a valuable strategy for preventing peri-implant disease onset. In this context quercetin, a naturally occurring flavonoid, has been entrapped, at different weight percentages in a silica/poly(?-caprolactone)-based hybrid material by a sol-gel route. FT-IR and UV spectroscopic techniques were employed in order to characterize the hybrids. FT-IR analysis indicated changes in stretching frequencies of the quercetin dienonic moiety, suggesting that a flavonol oxidized derivative was formed during the sol-gel process. The establishment of hydrogen-bonded interactions between quercetin and silica and polymer matrices,was strongly affected by the amount of polymer. Poly(?-caprolactone) did not interact with quercetin when it was loaded at high doses (50 wt.%). The morphology of the synthesized materials was observed by using SEM. The obtained images proved that the materials are hybrid nanocomposites. Their bioactivity was shown by the formation of a hydroxyapatite layer on samples' surface soaked in a fluid simulating the composition of the human plasma. The antiradical properties of the investigated systems were evaluated by DPPH and ABTS methods and their cytotoxicity by the MTT assay. Data obtained revealed that the synthesized materials are biocompatible and that the hybrid system,with 6 wt.% of PCL and 15 wt.% of quercetin, produced the strongest antiradical efficacy. PMID:26478390

  3. Wideband tuning of XeCl laser-pumped dye-doped sol-gel silica laser

    SciTech Connect

    Lam, K.S.; Lo, D.; Wong, K.H.

    1995-03-01

    Doped and undoped silica slabs were fabricated using the sol-gel technique. Extended UV transmission was observed for HCl-catalyzed sol-gel silica. Under transverse pumping by a XeCi laser, narrowband (<0.9 nm) laser oscillation from Rhodamine Perchlorate (R640)-doped silica slabs was achieved in an echelle grating resonator cavity. Tuning of the R640 silica laser extended from 627 nm to 670 nm.

  4. Matrix molecularly imprinted mesoporous sol-gel sorbent for efficient solid-phase extraction of chloramphenicol from milk.

    PubMed

    Samanidou, Victoria; Kehagia, Maria; Kabir, Abuzar; Furton, Kenneth G

    2016-03-31

    Highly selective and efficient chloramphenicol imprinted sol-gel silica based inorganic polymeric sorbent (sol-gel MIP) was synthesized via matrix imprinting approach for the extraction of chloramphenicol in milk. Chloramphenicol was used as the template molecule, 3-aminopropyltriethoxysilane (3-APTES) and triethoxyphenylsilane (TEPS) as the functional precursors, tetramethyl orthosilicate (TMOS) as the cross-linker, isopropanol as the solvent/porogen, and HCl as the sol-gel catalyst. Non-imprinted sol-gel polymer (sol-gel NIP) was synthesized under identical conditions in absence of template molecules for comparison purpose. Both synthesized materials were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and nitrogen adsorption porosimetry, which unambiguously confirmed their significant structural and morphological differences. The synthesized MIP and NIP materials were evaluated as sorbents for molecularly imprinted solid phase extraction (MISPE) of chloramphenicol in milk. The effect of critical extraction parameters (flow rate, elution solvent, sample and eluent volume, selectivity coefficient, retention capacity) was studied in terms of retention and desorption of chloramphenicol. Competition and cross reactivity tests have proved that sol-gel MIP sorbent possesses significantly higher specific retention and enrichment capacity for chloramphenicol compared to its non-imprinted analogue. The maximum imprinting factor (IF) was found as 9.7, whereas the highest adsorption capacity of chloramphenicol by sol-gel MIP was 23 mg/g. The sol-gel MIP was found to be adequately selective towards chloramphenicol to provide the necessary minimum required performance limit (MRPL) of 0.3 μg/kg set forth by European Commission after analysis by LC-MS even without requiring time consuming solvent evaporation and sample reconstitution step, often considered as an integral part in solid phase extraction work-flow. Intra and inter-assay RSD values were less than 13% and accuracy expressed as relative recovery ranged from 85 to 106%. PMID:26965328

  5. Fiber-optic pH sensor based on sol-gel film immobilized with neutral red

    NASA Astrophysics Data System (ADS)

    Jeon, Dayeong; Yoo, Wook Jae; Seo, Jeong Ki; Shin, Sang Hun; Han, Ki-Tek; Kim, Seon Geun; Park, Jang-Yeon; Lee, Bongsoo

    2013-03-01

    In this study, we developed a fiber-optic pH sensor based on a sol-gel film immobilized with neutral red (NR). A solgel film was prepared by mixing tetramethylorthosilicate (TMOS), trimethoxymethylsilane (MTMS), ethanol (EtOH), distilled water (H2O), and NR powder. Accordingly, the thin pH sol-gel film was fabricated through a sol-gel process with a dip-coating method. The thickness and diameter of the fabricated pH sol-gel film are 0.11 and 0.6 mm, respectively. We measured the optical absorbance and the light intensity with the spectra of reflected light, which change with the color variation of the pH sol-gel film in the fiber-optic sensing probe. From the experimental results, we demonstrated that the proposed fiber-optic pH sensor has good reversibility, reproducibility, and a fast response time, in which the optical properties of the NR-based pH sol-gel film change with the pH value.

  6. Solid oxide fuel cells developed by the sol-gel process for oxygen generation

    NASA Astrophysics Data System (ADS)

    Finch, Joshua S.

    Electrochemical fuel cells convert chemical energy directly to electrical energy through the reaction of a fuel and an oxidant. Solid oxide fuel cells (SOFC) are solid-state devices that operate at temperatures around 800C, using a solid oxygen electrolyte. The goal of this thesis is to prepare a defect-free solid oxygen electrolyte by a sol-gel process that is capable of (a) functioning in a fuel cell; and (b) producing measurable oxygen when operated as an oxygen generator. Sol-gel processing was chosen for membrane development because it offers a means of applying high-purity layers with controlled doping and a variety of geometries. In this study, the sol-gel process was used to produce yttria-stabilized zirconia (YSZ) electrolyte membranes as well as the electrodes required for an operational fuel cell. Zirconium oxychloride (ZOC) was used as the precursor material for the electrolyte. The YSZ solution was prepared by mixing yttrium nitrate and ZOC in a 50/50 ETOH and water solvent. The reaction was catalyzed with 1.5M NH4OH. Viscosity and solution application techniques were varied to monitor the effect on membrane development. The YSZ layer was sintered to full density. The sol-gel process was used to synthesize supported lanthanum strontium manganate (LSM) electrodes separated by a YSZ electrolyte. The LSM solution was made by mixing strontium nitrate, lanthanum chloride, and manganese acetate solutions. The LSM layers were sintered but were porous. After the membranes were assembled by successive layering and sintering, the membranes and completed fuel cells were characterized using TGA, XRD, FE-SEM, a gas pressurization technique, and electrochemical testing. The YSZ membrane exhibited a stable tetragonal crystal phase and formed a triple phase boundary (TPB) with the cathode. The three phases are the electrode, the electrolyte, and air. Electrochemical testing showed successful membrane development. Although oxygen production was not measured quantitatively, voltage was produced during hydrogen testing. A maximum voltage of 0.352V was obtained using forming gas as a fuel. The relationship between the TPB and oxygen production is critical. By using the sol-gel process, it is possible to form a TPB where the YSZ electrolyte is dense.

  7. An unbreakable on-line approach towards sol-gel capillary microextraction.

    PubMed

    Bagheri, Habib; Piri-Moghadam, Hamed; Es'haghi, Ali

    2011-07-01

    In this work a novel unbreakable sol-gel-based in-tube device for on-line solid phase microextraction (SPME) was developed. The inner surface of a copper tube, intended to be used as a high performance liquid chromatography (HPLC) loop, was electrodeposited by metallic Cu followed by the self assembled monolayers (SAM) of 3-(mercaptopropyl) trimethoxysilane (3MPTMOS). Then, poly (ethyleneglycol) (PEG) was chemically bonded to the -OH sites of the SAM already covering the inner surface of the copper loop using sol-gel technology. The homogeneity and the porous surface structure of the SAM and sol-gel coatings were examined using the scanning electron microscopy (SEM) and adsorption/desorption porosimetry (BET). The prepared loop was used for online in-tube SPME (capillary microextraction) of some selected polycyclic aromatic hydrocarbons (PAHs), as model compounds, from the aquatic media. After extraction, the HPLC mobile phase was used for on-line desorption and elution of the extracted analytes from the loop to the HPLC column. Major parameters affecting the extraction efficiency including the sample flow rate through the copper tube, loading time, desorption time and sample volume were optimized. For investigating the sorbent efficiency, four loops based on the copper tube itself, the copper tube after electrodeposition with Cu and the tubes with the SAMs and SAMs-sol-gel coating were made and compared. The SAMs-sol-gel coated loop clearly shows a prominently lead of at least 20-100 times of higher efficiency. The linearity for the analytes was in the range of 0.01-500 μg L(-1). Limit of detection (LOD) was in the range of 0.005-0.5 μg L(-1) and the RSD% values (n=5) were all below 8.3% at the 5 μg L(-1) level. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples were from 90 to 104%. The prepared loop exhibited long life time due to its remarkable solvent and mechanical stability. Different solvents such as methanol, acetonitrile and acetone were passed through the loop for many days and it was also used for more than 100 extractions/desorption of the selected analytes and no decrease in the peak areas was observed. PMID:21616492

  8. Thermally stable supported metal catalysts and inorganic membranes prepared by sol-gel processing

    NASA Astrophysics Data System (ADS)

    Lambert, Christine Kay

    1998-12-01

    The application of sol-gel processing to the synthesis of supported metal catalysts, inorganic membranes and catalytic membranes was studied. Noble metals were supported on SiO2 and gamma-Al2O 3. These materials have high surface areas, well-defined pore size distributions, and average pore diameters around 4 nm. The effects of preparative variables such as pH, gelation temperature, metal precursor, metal loading and binder addition on the final properties of the materials were studied. The structure of the sol-gel derived support materials was used to stabilize the dispersion of the supported metal at elevated temperatures and enhance activity and selectivity of the catalyst. The thermal stability of a sol-gel Rh/SiO2 catalyst was tested at 650C in flowing O2 and compared to the stability of a similar sample prepared by the traditional method of ion-exchange. The ion-exchanged sample had an average pore diameter of 24 nm. The metal particle size distribution of the sol-gel catalyst was more stable due to the smaller pore diameter of that catalyst. The sol-gel samples were more active in the dehydrogenation of n-butane than the ion-exchanged sample. A similar effect of pore size was found for Pd/gamma-Al2O3 catalysts sintered in H 2 at 650C. The Pd/gamma-Al2O3 catalysts were found to be very active hydrogenation catalysts but were not selective to partially hydrogenated products. A boehmite sol was used as a coating on a porous alpha-Al 2O3 substrate to form a gamma-Al2O3 membrane that could act as a diffusion barrier for gases. A catalytic membrane was formed by adding a soluble palladium compound to the sol. The Pd/gamma-Al 2O3 membrane was used successfully in the selective hydrogenation reactions of acetylene and 1,3-butadiene to produce ethylene and butenes. This was accomplished by premixing the alkyne or diene with H2 and passing it through the membrane wall, therefore reducing the contact time between the reactants and the catalyst.

  9. Synthesis and Electrical Properties of ?-Na x Co2O4 via a Citrate Sol-Gel Method with Polyethylene Glycol 400

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Tang, Xinfeng; Gao, Wenbin

    2010-09-01

    In this work, a citrate sol-gel method (Sol-Gel) with polyethylene glycol 400 (Sol-Gel-PEG400) was developed to prepare ?-Na x Co2O4 by using sodium and cobalt nitrates as the raw materials, citric acid as a complexing agent, and PEG400 as a dispersant. At 800C, single-phase ?-Na x Co2O4 crystals were obtained using Sol-Gel-PEG400. With the addition of 1 vol.% PEG400, smaller, flaky particles exhibited a well-tiled structure along the plane direction of the flaky particles. Moreover, polycrystalline sintered bulk ?-Na x Co2O4 with more highly oriented crystals and greater compact density was fabricated using the Sol-Gel-PEG400 synthesized powders compared with the powders synthesized by citrate Sol-Gel. The electrical conductivity ( ?) values of Sol-Gel-PEG400 samples were higher than those of Sol-Gel samples between 400 K and 900 K. The ? value of Sol-Gel-PEG400 increased to 3.13 104 Sm-1 at 400 K and to 1.84 104 Sm-1 at 900 K. Between 400 K and 850 K, the Seebeck coefficient ( ?) values of Sol-Gel-PEG400 samples were slightly lower than those of Sol-Gel samples. Near 900 K, the ? values of these two methods were nearly equal, at 164 ?V K-1. Between 400 K and 900 K, the power factor ( P) of Sol-Gel-PEG400 was evidently larger than that of Sol-Gel.

  10. Effect of La substitution on structure and magnetic properties of sol-gel prepared BiFeO{sub 3}

    SciTech Connect

    Suresh, Pittala; Srinath, S.

    2013-05-07

    Detailed Rietveld analysis of the room temperature (RT) x-ray diffraction data of La{sub x}Bi{sub 1-x}FeO{sub 3} (LBFO) ceramics (0 {<=} x {<=} 0.4) prepared by sol-gel route revealed that the system retains distorted rhombohedral R3c structure of parent compound BiFeO{sub 3} (BFO) for x {<=} 0.2 but transforms to orthorhombic Pbnm structure for x > 0.2. The fundamental 12 Raman modes of pure BFO (x = 0.0) are reduced to 10 modes for x = 0.2 and further reduced to 7 modes for x = 0.4, which is a clear indication of structural modification and symmetry changes brought about by La doping. The coercive field, H{sub C}, increases remarkably with an increase in La doping and x = 0.4 exhibits the highest H{sub C} (19.5 kOe at RT) reported so far in any rare earth doped BFO, which will have a great potential for practical application in non-volatile memory devices. Moreover, high-field magnetization and remanence, M{sub r}, increase linearly with La doping content due to the gradual change in spin cycloid structure. M(T) curve shows an anomaly at 50 K, similar to that expected in a spin glass system. The Neel temperature (T{sub N}) of the LBFO increases with x, approaching that of the LaFeO{sub 3}.

  11. Remediation of waters contaminated with MCPA by the yeasts Lipomyces starkeyi entrapped in a sol-gel zirconia matrix.

    PubMed

    Sannino, Filomena; Pirozzi, Domenico; Aronne, Antonio; Fanelli, Esther; Spaccini, Riccardo; Yousuf, Abu; Pernice, Pasquale

    2010-12-15

    A single-stage sol-gel route was set to entrap yeast cells of Lipomyces starkeyi in a zirconia (ZrO(2)) matrix, and the remediation ability of the resulting catalyst toward a phenoxy acid herbicide, 4-chloro-2-methylphenoxyacetic acid (MCPA), was studied. It was found that the experimental procedure allowed a high dispersion of the microorganisms into the zirconia gel matrix; the ZrO(2) matrix exhibited a significant sorption capacity of the herbicide, and the entrapped cells showed a degradative activity toward MCPA. The combination of these effects leads to a nearly total removal efficiency (>97%) of the herbicide at 30 C within 1 h incubation time from a solution containing a very high concentration of MCPA (200 mg L(-1)). On the basis of the experimental evidence, a removal mechanism was proposed involving in the first step the sorption of the herbicide molecules on the ZrO(2) matrix, followed by the microbial degradation operated by the entrapped yeasts, the metabolic activity of which appear enhanced under the microenvironmental conditions established within the zirconia matrix. Repeated batch tests of sorption/degradation of entrapped Lipomyces showed that the removal efficiency retained almost the same value of 97.3% after 3 batch tests, with only a subsequent slight decrease, probably due to the progressive saturation of the zirconia matrix. PMID:21077667

  12. Sol-gel analogous aminolysis-ammonolysis of chlorosilanes to chlorine-free Si/(C)/N-materials.

    PubMed

    Wiltzsch, Conny; Wagler, Jrg; Roewer, Gerhard; Kroke, Edwin

    2009-07-28

    Large amounts of chlorosilanes, especially SiCl4 and CH3SiCl3, are produced as side-products of the industrial fabrication of solar or electronic grade silicon and the Mller-Rochow process. It was a goal of the present study to transform these compounds into useful chlorine-free precursors for Si/(C)/N ceramics via a sol-gel analogous liquid processing route. Chlorine substitution of the chlorosilanes (mixtures) with diethylamine did not yield chlorine-free products, complete reactions are only possible with lithium diethylamide. However, aminolyses with n-propylamine were successful. Transamination with ammonia was not possible with diethylaminosilanes but was with n-propylaminosilanes in various solvents. This result was attributed to steric reasons and polar interactions of the N-H groups. Colourless solid or liquid polysilazanes were obtained, depending on the silane (mixture) and the solvent. Transamination reactions of CH3Si(NH-n-Pr)3 in chloroform reproducibly yielded a cage-like oligosilazane of the composition (CH3)9Si9(NH)12N. Single crystal X-ray structure analysis revealed a seven-cyclic cluster containing four six- and three ten-membered silazane rings. This unique silazane cage as well as the other aminosilanes and the silazanes were comprehensively characterised using multi-nuclear solid state and solution NMR, elemental analyses and thermal gravimetry (TGA). PMID:19587990

  13. Optical and transport properties of Sn-doped ZnMn2O4 prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Gherbi, R.; Bessekhouad, Y.; Trari, M.

    2016-02-01

    The paper describes the effect of ZnMn2O4 doping with different Sn ratios. Snx-ZnMn2O4 is prepared with Sol-Gel route at 700 °C. The structural, optical and electrical properties were studied. The X-ray diffraction patterns indicate the formation of pure tetragonal phase for the ratios lower than 0.03%, while for other compositions, the secondary phases were observed. The attenuated total reflectance (ATR) analysis confirmed the localization of Sn in octahedral sites. The optical properties showed not only the increase of Eg, but also the improvement of the optical characteristics such as extinction coefficient (k), optical conductivity (σopt), dissipation factor (tan δ) and the relaxation time (τ). The latter has been improved by 50%. The Hall measurements confirmed the transition of the conductivity mode, i.e, from p to n-type. The formation of SnMn1+ point defects is evidenced; however, the transport properties indicate that the charge carriers are mainly localized.

  14. Preparation of surface-modified ZnO quantum dots through an ultrasound assisted sol-gel process

    NASA Astrophysics Data System (ADS)

    Moghaddam, E.; Youzbashi, AA; Kazemzadeh, A.; Eshraghi, MJ

    2015-08-01

    A synthetic process of zinc oxide quantum dots (QDs) is presented. It is based on a sol-gel process, carried out in an ultrasonic bath. It allows the formation of the stable colloids, containing surface-modified ZnO QDs with the aid of 3-aminopropyltriethoxysilane (APTES) as a capping agent. For this purpose, alcoholic solutions of zinc acetate dihydrate and potassium hydroxide were used as the reactants. Effect of KOH concentration, ultrasonic irradiation, and also the presence of capping agent on the characteristics of the final product were investigated. The synthesized samples were characterized by various analytical techniques such as XRD, TEM, FT-IR, UV-vis and PL spectroscopy. XRD analysis revealed the direct formation of hexagonal wurtzite nanocrystals with average size of ?3 nm confirmed by TEM and UV-vis spectroscopy. The PL spectroscopy indicated the influence of the capping agent on reducing the defects formation during the growth of the QDs. The present synthesis method was found to be a cost-effective and simple solution route for producing pure semiconductor ZnO QDs, exhibiting the quantum confinement effects, suitable for optical and optoelectronic applications.

  15. Sol-gel preparation of alumina stabilized rare earth areo- and xerogels and their use as oxidation catalysts.

    PubMed

    Neumann, Bjrn; Gesing, Thorsten M; Rednyk, Andrii; Matolin, Vladimir; Gash, Alexander E; Bumer, Marcus

    2014-05-15

    A new sol-gel synthesis route for rare earth (Ce and Pr) alumina hybrid aero- and xerogels is presented which is based on the so-called epoxide addition method. The resulting materials are characterized by TEM, XRD and nitrogen adsorption. The results reveal a different crystallization behavior for the praseodymia/alumina and the ceria/alumina gel. Whereas the first remains amorphous until 875C, small ceria domains form already after preparation in the second case which grow with increasing calcination temperature. The use of the calcined gels as CO oxidation catalysts was studied in a quartz tube (lab) reactor and in a (slit) microreactor and compared to reference catalysts consisting of the pure rare earth oxides. The Ce/Al hybrid gels exhibit a good catalytic activity and a thermal stability against sintering which was superior to the investigated reference catalyst. In contrast, the Pr/Al hybrid gels show lower CO oxidation activity which, due to the formation of PrAlO3, decreased with increasing calcination temperature. PMID:24655831

  16. Effect of the condensation of hybrid organic-inorganic sol-gel materials on the optical properties of tripan blue

    NASA Astrophysics Data System (ADS)

    Hicks, Craig; Morshed, Muhammad; Melia, Garrett; Barton, Killian; Duffy, Brendan; Oubaha, Mohamed

    2015-09-01

    The work reported in this paper highlights the effect of sol-gel structures on the optical properties of a typical organic dye (Trypan Blue, TB). Three transition-metal-based hybrid sol-gel materials with different structures and morphologies were developed and characterised by TEM. The optical properties of TB were investigated by incorporating it in the different sol-gel materials and the UV-Visible spectra recorded in both liquid and solid state, in thin-coatings cured at temperatures in the range 100-150 C. These studies revealed two relevant results. First, the sol-gel morphology plays a critical role in the optical properties of the dye. The effect of the sol-gel host matrix on the optical properties of the dye is attributed to the steric hindrance of the nanostructures, themselves intimately dependant on the reactivity of the transition metal. For instance, the less condensed system showed the highest reactivity with the dye, while the more condensed system exhibited limited interaction with the dye, symbolised by a significant change or quasi-unchanged UV-Visible spectra, respectively. It is also shown that the increase of the condensation degree of the sol-gel coatings by heat-curing can dramatically alter the optical properties of the dye especially for the most condensed sol-gel systems. This has been attributed to proximity effects enabled by the further increase of the materials densities. The results reported here aim to provide a better understanding of how material formulations can influence the optical properties of organic dyes and suggest that the structure of the host matrix along with the applied curing process have to be fully considered and assessed in the choice of organic dyes for a given application.

  17. Sol-gel derived C-SiC composites and protective coatings for sustained durability in the space environment

    NASA Astrophysics Data System (ADS)

    Haruvy, Yair; Liedtke, Volker

    2003-09-01

    Composites and coatings were produced via the fast sol-gel process of a mixture of alkoxysilane precursors. The composites were comprised of carbon fibers, fabrics, or their precursors as reinforcement, and sol-gel-derived silicon carbide as matrix, aiming at high-temperature stable ceramics that can be utilized for re-entry structures. The protective coatings were comprised of fluorine-rich sol-gel derived resins, which exhibit high flexibility and coherence to provide sustained ATOX protection necessary for LEO space-exposed elements. For producing the composites, the sol-gel-derived resin is cast onto the reinforcement fibers/fabrics mat (carbon or its precursors) to produce a 'green' composite that is being cured. The 'green' composite is converted into a C-SiC composite via a gradual heat-pressure process under inert atmosphere, during which the organic substituents on the silicon atoms undergo internal oxidative pyrolysis via the schematic reaction: (SiRO3/2)n -> SiC + CO2 + H2O. The composition of the resultant silicon-oxi-carbide is tailorable via modifying the composition of the sol-gel reactants. The reinforcement, when made of carbon precursors, is converted into carbon during the heat-and-pressure processing as well. The C-SiC composites thus derived exhibit superior thermal stability and comparable thermal conductivity, combined with good mechanical strength features and failure resistance, which render them greatly applicable for re-entry shielding, heat-exchange pipes, and the like. Fluorine rich sol-gel derived coatings were developed as well, via the use of HF rich sol-gel process. These coatings provide oxidation-protection via the silica formation process, together with flexibility that allows 18,000 repetitive folding of the coating without cracking.

  18. A new sol-gel synthesis of 45S5 bioactive glass using an organic acid as catalyst.

    PubMed

    Faure, J; Drevet, R; Lemelle, A; Ben Jaber, N; Tara, A; El Btaouri, H; Benhayoune, H

    2015-02-01

    In this paper a new sol-gel approach was explored for the synthesis of the 45S5 bioactive glass. We demonstrate that citric acid can be used instead of the usual nitric acid to catalyze the sol-gel reactions. The substitution of nitric acid by citric acid allows to reduce strongly the concentration of the acid solution necessary to catalyze the hydrolysis of silicon and phosphorus alkoxides. Two sol-gel powders with chemical compositions very close to that of the 45S5 were obtained by using either a 2M nitric acid solution or either a 5mM citric acid solution. These powders were characterized and compared to the commercial Bioglass®. The surface properties of the two bioglass powders were assessed by scanning electron microscopy (SEM) and by Brunauer-Emmett-Teller method (BET). The Fourier transformed infrared spectroscopy (FTIR) and the X-ray diffraction (XRD) revealed a partial crystallization associated to the formation of crystalline phases on the two sol-gel powders. The in vitro bioactivity was then studied at the key times during the first hours of immersion into acellular Simulated Body Fluid (SBF). After 4h immersion into SBF we clearly demonstrate that the bioactivity level of the two sol-gel powders is similar and much higher than that of the commercial Bioglass®. This bioactivity improvement is associated to the increase of the porosity and the specific surface area of the powders synthesized by the sol-gel process. Moreover, the nitric acid is efficiently substituted by the citric acid to catalyze the sol-gel reactions without alteration of the bioactivity of the 45S5 bioactive glass. PMID:25492213

  19. Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material

    DOEpatents

    Panitz, J.K.; Reed, S.T.; Ashley, C.S.; Neiser, R.A.; Moffatt, W.C.

    1999-07-20

    Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties. 6 figs.

  20. Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material

    DOEpatents

    Panitz, Janda K. (Sandia Park, NM); Reed, Scott T. (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Neiser, Richard A. (Albuquerque, NM); Moffatt, William C. (Albuquerque, NM)

    1999-01-01

    Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties.

  1. Preparation and mechanical properties of silicon oxycarbide fibers from electrospinning/sol-gel process

    SciTech Connect

    Wang, Xiaofei; Gong, Cairong; Fan, Guoliang

    2011-12-15

    Graphical abstract: Ceramic fibers, silicon oxycarbide (SiOC) fibers were demonstrated and showed higher mechanical properties from electrospinning/sol-gel process at 1000 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer SiOC fibers with low cost are promising to substitute the non-oxide fibers. Black-Right-Pointing-Pointer Successful preparation of SiOC fibers by electrospinning/sol-gel process. Black-Right-Pointing-Pointer Confirmation of the designed product using material characterization methods. Black-Right-Pointing-Pointer The SiOC fibers prepared at 1000 Degree-Sign C possess higher strength (967 MPa). -- Abstract: Silicon oxycarbide (SiOC) fibers were produced through the electrospinning of the solution containing vinyltrimethoxysilane and tetraethoxysilane in the course of sol-gel reaction with pyrolysis to ceramic. The effect of the amount of spinning agent Polyvinylpyrrolidone (PVP) on the dope spinnability was investigated. At a mass ratio of PVP/alkoxides = 0.05, the spinning sol exhibited an optimal spinnable time of 50 min and generated a large quantity of fibers. Electrospun fibers were characterized by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis-differential scanning calorimetry (TGA-DSC), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The SEM results revealed that the SiOC fibers had a smooth surface and dense cross-section, free of residue pores and cracks. The XPS results gave high content of SiC (13.99%) in SiOC fibers. The SiOC fibers prepared at 1000 Degree-Sign C had a high tensile strength of 967 MPa and Young's modulus of 58 GPa.

  2. "Smart" glasses: Design, synthesis, characterization and applications of organically-modified silica sol-gels

    NASA Astrophysics Data System (ADS)

    Rao, Mukti Shriprasad

    Critical design criteria for development of smart or intelligent materials include physicochemical responses that can be modulated by external stimuli. As a part of this work, sot-gel chemistry was used to design novel materials that constitute the first generation of sol-gel---derived 'smart' materials. The overall focus of this research was threefold. First, synthesis of new 'smart' sol-gel materials. Second, characterization of these materials by various physical and chemical methods to determine structure, composition, and morphology as well as evaluation of their environmental sensitivity. Finally, applications of these materials based on their unique properties. These glasses are characterized by an increased elasticity and porosity with a greater retention of water in their pores. Furthermore, it was established that these gels undergo swelling/shrinkage when subjected to different stimuli such as changes in temperature, pH, salt, solvent, and electrical potential. These dynamic responses mainly originate due to intake or expulsion of water as a result of its altered interactions with the gel when a stimulus is applied. The unique properties of these gels were investigated to establish their practical utility for different applications. First, the property of stimuli-induced swelling/shrinkage of the gels was exploited in the form of prototype tweezers to convert volume changes into mechanical action (grabbing objects like human fingers). Second, the unique combination of hydrophobic, and hydrophilic groups in the network imparts these gels with selectivity for certain molecules that exhibit preferential noncovalent interactions. Based on its selectivity, these gels were used as matrices for separation, release and controlled delivery of molecules. Third, owing to the presence of amino groups in the network these gels were used for sequestering metal ions to form metal-oxo nanoparticles, and act as terminal electron donor for a photoreduction reaction. Finally, soft-lithography was used to construct micro-scale sol-gel architectures with lateral and vertical separation, and dimensional resolution.

  3. Synthesis and characterization of sol gel silica films doped with size-selected gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Ferrara, M. C.; Mirenghi, L.; Mevoli, A.; Tapfer, L.

    2008-09-01

    Homogeneous nanocomposite silica films uniformly doped with size-selected gold nanoparticles (AuNPs) have been prepared by a combined use of colloidal chemistry and the sol-gel process. For this purpose, stable thiol-functionalized AuNPs (DDT-AuNPs) were first synthesized by a two-phase aqueous/organic system and, subsequently, dispersed in an acid-catalysed sol-gel silica solution. The microstructural morphology of the samples was investigated by x-ray diffraction and field emission scanning electron microscopy. X-ray photoelectron spectroscopy (XPS) and UV-vis optical spectrophotometry were instead employed to investigate the elemental chemical behaviour and the evolution of the surface plasmon resonance (SPR) band of the AuNPs from their synthesis up to the formation of the Au-doped silica films. The results show that the size, shape and crystalline domains of the AuNPs remain unchanged during the entire preparation process, indicating that their aggregation or decomposition was prevented. XPS results show that the DDT-AuNPs lose the capping shells and oxidize themselves when dispersed in acid-catalysed sol-gel solutions, and that bare AuNPs are embedded in the SiO2 films. A large broadening of the SPR band, observed for systems with DDT-AuNPs, suggests the presence of interface effects which cause a surface electron density lowering. Thiol chain detachment from the AuNPs determines an increase of the SPR peak intensity while the oxidation of the Au surfaces causes a red shift of its position. The latter is no longer observed in doped films, suggesting that no interfacial effects between bare AuNPs and the host medium are present.

  4. Mullite matrix continuous fibre reinforced composites by sol-gel processing

    SciTech Connect

    Wu, J.; Jones, F.R.; James, P.F.

    1994-12-31

    A fibre reinforced crystalline mullite matrix composite was prepared by sol-gel processing. The unidirectional fibre composite was synthesized by single stage infiltration of carbon fibres with an alumina-silica sol (3 Al{sub 2}O{sub 3}{center_dot}2SiO{sub 2}), followed by hot-pressing at 1550{degrees}C under 15 MPa to 95% of full density. The composite exhibited non-brittle failure with a mean flexural strength of 703 MPa.

  5. Switching of lasing wavelength in a sol-gel laser with dynamic distributed feedback

    SciTech Connect

    Balenko, V G; Trufanov, A N; Umanskii, B A; Dolotov, S M; Petukhov, V A

    2011-09-30

    A scheme of switching the lasing wavelength of active centres in a sol-gel matrix excited by external laser radiation is proposed. A distributed feedback is formed during pumping by using a right-angle prism due to the interference of the direct and reflected pump beams. The lasing wavelength is determined by the period of the interference pattern, which depends on the convergence angle of interfering beams. Control is performed by a liquid-crystal cell, which changes the pump radiation polarisation, and a birefringent prism. As a result, the convergence angle of interfering beams changes, leading to a change in the interference pattern period and the excited radiation wavelength.

  6. Controlling the porosity of microporous silica by sol-gel processing using an organic template approach

    SciTech Connect

    Lu, Y.; Cao, G.Z.; Kale, R.P.; Delattre, L.; Lopez, G.P.; Brinker, C.J.

    1996-12-31

    The authors use an organic template approach to prepare microporous silica with controlled pore size and narrow pore size distributions. This was accomplished by fabricating relatively dense hybrid silica matrices incorporating organic template ligands by sol-gel synthesis and then removing the organic ligands to create a microporous silica network. Comparison of computer simulation results and experimental data indicated that using this fugitive template approach, pore volume can be controlled by the amount of organic template added to the system, and pore size can be controlled by the size of the organic ligands.

  7. Green fluorescent protein-doped sol-gel silica planar waveguide to detect organophosphorus compound

    NASA Astrophysics Data System (ADS)

    Enami, Y.; Suye, S.

    2012-02-01

    We report novel living protein-doped planar waveguide, and real-time detection of an organophosphorus compound using a sol-gel silica planar waveguide doped with a green fluorescent protein and an organophosphorus hydrolase on a yeast-cell surface. The waveguide was pumped at 488 nm, and emitted green fluorescence at the far field. The green fluorescent light at 550 nm changed by 50% from the original power 1 min after application of the organophosphorus compound. The results enable the real-time detection of biochemical weapon and insecticide harmful for human body by using an in-line fiber sensor network.

  8. Synthesis and luminescence properties of encapsulated sol-gel glass samarium complexes.

    PubMed

    Zaitoun, M A; Momani, K; Jaradat, Q; Qurashi, I M

    2013-11-01

    Luminescence efficiency of lanthanide complexes generally largely depend on the choice of the organic ligand and the host matrix in which these complexes are doped. Two Sm(III) complexes, namely: Sm(III) dithicarbamate - Sm(L1)3B [L1=(R)2NCS2B, R=C2H5 and B=1,10-phenanthroline] and Sm(III) complex with the polytonic ligand L2=N', N'(2)-bis[(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide {Sm2-L2-(CH3COO)2; L2=C16H16N6O2} are synthesized, these complexes are then trapped in sol-gel glass. Room temperature luminescence of Sm(L1)3B and {Sm2-L2-(CH3COO)2} complexes encapsulated in sol-gel glass are studied using a spectrofluorometer. Up on excitation by a UV light, ligand L1B absorbs this light and transfers it into the Sm(III) ions and emission bands were observed in the visible region and were attributed to f-f transitions of Sm(III). The observed emission indicated an efficient L1B ligand as a sensitizer, while ligand L2 shows no ability to work as a sensitizer. The branching ratio I4G5/2?6H9/2/I4G5/2?6H7/2) of electric dipole transition to magnetic dipole transition was used as an effective spectroscopic probe to predict symmetry of the site in which Sm(III) is located. The encapsulation of the Samaium complexes was performed for three reasons: (i) before rare earth (RE)-doped sol-gel glasses can be used in applications such as laser materials, several fluorescence quenching mechanisms must be overcome, we show in this work that lanthanide fluorescence is greatly enhanced by chelation and selecting a suitable host matrix (sol-gel) to accommodate the lanthanide complex, (ii) to improve the stability of the phosphor with efficient and high color-purity characteristics under ultraviolet excitation and (iii) this work provides a framework for preparing transparent composite glasses that are robust hosts to study the fundamental interactions between nano-materials and light. PMID:23892122

  9. Hydrogen photochromism in V2O5 layers prepared by the sol-gel technology

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Pan, Lei; Li, Yao; Gavrilyuk, A. I.

    2014-09-01

    Here we report on hydrogen photochromism in V2O5 highly disordered layers, i.e., photochromism that occurs due to hydrogen atoms; the hydrogen being detached under the action of light from organic molecules adsorbed on the oxide surface, whereas the V2O5 layers have been prepared by the sol-gel technology. The comprehensive characterization of the layers has been carried out, as well as the investigation of the parameters influencing their photochromic sensitivity. The high photochromic sensitivity of the V2O5 layers is provided by the surface Grotthuss diffusion of the injected protons.

  10. Electroanalytical applications of screen-printable surfactant-induced sol-gel graphite composites

    DOEpatents

    Guadalupe, Ana R. (San Juan, PR); Guo, Yizhu (San Juan, PR)

    2001-05-15

    A process for preparing sol-gel graphite composite electrodes is presented. This process preferably uses the surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) and eliminates the need for a cosolvent, an acidic catalyst, a cellulose binder and a thermal curing step from prior art processes. Fabrication of screen-printed electrodes by this process provides a simple approach for electroanalytical applications in aqueous and nonaqueous solvents. Examples of applications for such composite electrodes produced from this process include biochemical sensors such as disposable, single-use glucose sensors and ligand modified composite sensors for metal ion sensitive sensors.

  11. Distributed feedback sol-gel zirconia waveguide lasers based on surface relief gratings

    NASA Astrophysics Data System (ADS)

    Ye, Chao; Wong, K. Y.; He, Yaning; Wang, Xiaogang

    2007-02-01

    Distributed feedback waveguide lasers based on dye-doped sol-gel zirconia films with permanent grating structures were demonstrated. The permanent grating was realized by employing a novel epoxy-based azo-polymer that generates a surface relief grating by a photo-isomerization process induced by two interfering writing beams. When employing the rhodamine 6G dye, tuning of the output wavelength of the distributed feedback waveguide laser from around 575 nm to 610 nm can be achieved by adjusting the tilting angle between the orientation of the grating and the pump beam.

  12. YAG:Ce3+ Nanophosphor Synthesized with the Salted Sol-Gel Method

    SciTech Connect

    D. Jia; C. V. Shaffer; J. E. Weyant; A. Goonewardene; X. Guo; Y. Wang; X. Z. Guo; K. K. Li; Y. K. Zou; W. Jia

    2006-05-01

    Nano-phosphors of Y3Al5O12:Ce3+ (YAG:Ce) were synthesized with a novel salted sol-gel method, in which aqueous solution of inorganic salts (yttrium/cerium nitrates) were used along with the metal alkoxide precursor, aluminum sec-butoxide, Al(OC4H9)3. YAG single phase was formed at temperature as low as 800 ?C. Luminescence of YAG:Ce reached the maximum intensity when calcined above 1350C. The SEM image reveals that the grain sizes of the nano-phosphors calcined at 1100 ?C are in a range of 50-150 nm.

  13. Dielectric function of sol-gel prepared nano-granular zinc oxide by spectroscopic ellipsometry

    SciTech Connect

    Gilliot, Mickaël Hadjadj, Aomar; Eypert, Céline

    2013-11-14

    ZnO thin films have been prepared by sol gel and deposited by spin coating. The dielectric function has been determined by spectroscopic ellipsometry. Ellipsometric spectra are inverted by a direct numerical method without using the standard fitting procedures. The obtained dielectric function presents a broad excitonic effect. The dielectric function is studied using Elliot excitonic theory including exciton plus band-to-band Coulomb interactions with standard Lorentzian broadening. A modification of this model dielectric function with independent bound and unbound exciton contributions is empirically proposed to improve modelling of the band gap excitonic peak.

  14. Tailoring the Microstructure of SolGel Derived Hydroxyapatite/Zirconia Nanocrystalline Composites

    PubMed Central

    2011-01-01

    In this study, we tailor the microstructure of hydroxyapatite/zirconia nanocrystalline composites by optimizing processing parameters, namely, introducing an atmosphere of water vapor during sintering in order to control the thermal stability of hydroxyapatite, and a modified solgel process that yields to an excellent intergranular distribution of zirconia phase dispersed intergranularly within the hydroxyapatite matrix. In terms of mechanical behavior, SEM images of fissure deflection and the presence of monoclinic ZrO2 content on cracked surface indicate that both toughening mechanisms, stress-induced tetragonal to monoclinic phase transformation and deflection, are active for toughness enhancement. PMID:24764458

  15. Barium hydroxyapatite nanoparticles synthesized by citric acid sol-gel combustion method

    SciTech Connect

    Xiu Zhiliang; Lue Mengkai . E-mail: mklu@icm.sdu.edu.cn; Liu Suwen; Zhou Guangjun; Su Benyu; Zhang Haiping

    2005-09-01

    Barium hydroxyapatite (BaHAP) nanoparticles have been synthesized by citric acid sol-gel combustion method using citric acid as a reductant/fuel and nitrate as an oxidant at a relatively low temperature of 600 deg. C. The thermal decomposition of nitrate-citrate xerogel was investigated by thermogravimetric/differential thermal analysis (TG/DTA) technique. The yielding powders calcined at 600 deg. C have been characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and transmission electron microscope (TEM). The possible combustion process was presented.

  16. Fabrication of inverted zinc oxide photonic crystal using solgel solution by spin coating method

    PubMed Central

    2013-01-01

    Inverted zinc oxide photonic crystal structures were fabricated from polystyrene sphere (PSS) template using the solgel solution of ZnO by spin-coating method. It is easily able to control and fabricate the photonic crystal structures using the self-organized PSS with a size of 193nm. The inverted ZnO photonic crystal structures observed show the (111) tendency of the hexagonal compact arrangement formation. The resulting structures possess the photonic band gaps in the near-ultraviolet range and exhibit an enhanced photoluminescence spectrum. The technology can effectively increase the light output intensity or efficiency for the applications of optoelectronic devices. PMID:23819709

  17. Synthesis and sintering of nanocrystalline hydroxyapatite powders by citric acid sol-gel combustion method

    SciTech Connect

    Han Yingchao; Li Shipu; Wang Xinyu; Chen Xiaoming

    2004-01-03

    The citric acid sol-gel combustion method has been used for the synthesis of nanocrystalline hydroxyapatite (HAP) powder from calcium nitrate, diammonium hydrogen phosphate and citric acid. The phase composition of HAP powder was characterized by X-ray powder diffraction analysis (XRD). The morphology of HAP powder was observed by transmission electron microscope (TEM). The HAP powder has been sintered into microporous ceramic in air at 1200 deg. C with 3 h soaking time. The microstructure and phase composition of the resulting HAP ceramic were characterized by scanning electron microscope (SEM) and XRD, respectively. The physical characterization of open porosity and flexural strength have also been carried out.

  18. Optoelectronic properties of sol-gel derived ZnO:Co: Effect of Co concentration

    NASA Astrophysics Data System (ADS)

    Bu, Ian Yi-Yu

    2014-11-01

    This paper studies the sol-gel synthesis of ZnO:Co thin films as function of Co doping concentration. The derived films were evaluated by using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction measurements, Raman spectroscopy and UV-Vis spectroscopy. SEM images show that the films are smooth with grains size ∼50 nm. It was also found that Co incorporation can decreased the preferential growth in the (0 0 2) orientation and optical transparency. Electrical characterization reveals that the derived films are n-type that can be paired with a p-type material to form rectifying pn junctions.

  19. Thin film of sol-gel deposited in photonic crystal fiber for cholesterol detection

    NASA Astrophysics Data System (ADS)

    Razo-Medina, D. A.; Alvarado-Mndez, E.; Trejo-Durn, M.

    2015-04-01

    In this work, the fabrication of thin films mixed with cholesterol enzyme as recognition component is shown, using solgel technique. The film was deposited at one end of photonic crystal fiber (optrode), which was used as carrier medium of sol-gel matrix. The concentration of cholesterol in the test sample was determined by the use of transmittance. Measuring device consists of a power source (laser diode), optrode and a light detector. The laser beam is transmitted through the optrode; the variations of intensity depending on cholesterol concentration are emitted to be detected by a photoresistor.

  20. Investigation of sol-gel yttrium doped ZnO thin films: structural and optical properties

    NASA Astrophysics Data System (ADS)

    Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B.

    2016-02-01

    Nanostructured metal oxide films are extensively studied due to their numerous applications such as optoelectronic devices, sensors. In this work, we report the Y-Zn-O nanostructured films prepared by sol-gel technology from sols with different concentration of yttrium precursor, followed by post-annealing treatment. The Y doped ZnO thin films have been deposited on Si and quartz substrates by spin coating method, then treated at temperatures ranging from 300-800oC. XRD analysis reveals modification of the film structure and phases in the doped ZnO films.

  1. Pyrochlore to perovskite phase transformation in sol-gel derived lead-zirconate-titanate thin films

    NASA Astrophysics Data System (ADS)

    Kwok, Chi Kong; Desu, Seshu B.

    1992-03-01

    Pyrochlore to perovskite phase transformation in sol-gel derived lead-zirconate-titanate (PZT) films was studied by x-ray diffraction and transmission-electron microscopy (TEM). X-ray diffraction studies of PZT films on sapphire substrates indicated that the pyrochlore to perovskite phase transformation was completed at 650 C. In contrast, TEM investigations of free-standing PZT films showed that the phase transformation was completed at much higher temperatures. This discrepancy in the behavior of free-standing films versus films on substrate can be related to the size effect.

  2. A hybrid sol-gel reverse-mesa waveguide using lanthanide phosphate nanoparticles for optical amplification

    NASA Astrophysics Data System (ADS)

    Gan, Haiyong; Li, Li; DeRose, Christopher T.; Norwood, Robert A.; De Silva, Channa R.; Zheng, Zhiping; Peyghambarian, Nasser

    2007-02-01

    Organic-inorganic hybrid sol-gel materials have been widely used for the fabrication of optoelectronic devices due to advantages such as low cost, low loss, low temperature fabrication, ease of processing, good thermal and mechanical stability, and large refractive index tunability. However, the residual OH-like groups remaining after low temperature treatment have hindered the development of the erbium doped waveguide amplifiers working at ~1550 nm. A variety of means have been adopted to overcome this problem: (1) low vibration energy deuterated or fluorinated polymers have been applied as matrix materials; (2) erbium ions have been incorporated into organic or inorganic complexes for protection and the ligands of the complexes have been further modified to reduce the vibrational energy or increase the pump energy transfer efficiency; and (3) the erbium ions have been shielded in inorganic nanoparticles or other micro-structures. Doping erbium ions along with ytterbium ions to increase the pumping efficiency in lanthanum phosphate nanoparticles appears to be a very promising approach since (i) the emission lifetime is fairly long; (ii) at ~1550 nm the nanoparticles are transparent and have a refractive index very close to that of standard optical fiber; and (iii) the nanoparticles are highly dispersible in most organic media. Here we demonstrate how Er 3+/Yb 3+ containing lanthanum phosphate nanoparticles dispersed in an organically modified sol-gel can be used in a reverse mesa waveguide to achieve optical signal enhancement. Er 3+/Yb 3+ containing lanthanum phosphate nanoparticles have been synthesized with a molar ratio of La:Yb:Er = 76:21:3 and dispersed in cyclopentanone with 30wt% hydrolyzed MAPTMS. The composite has been incorporated into a 4mm reverse mesa waveguide prepared using an organic-inorganic hybrid sol-gel material based on MAPTMS and zirconium n-propoxide. An optical signal enhancement of ~2 dB/cm at 1527 nm has been obtained using a 200 mW 980 nm pump laser. Modeling analyses have shown that the overall performance can be further improved. The results indicate that such hybrid sol-gel reverse mesa waveguides using Er 3+/Yb 3+ containing lanthanum phosphate nanoparticles are very promising for optical amplifiers in integrated optical systems.

  3. Evolution of Structural, Optical and Electrical Characteristics of Spin-Coated CdO Thin Films with the Gelation State of the Sol-Gel

    NASA Astrophysics Data System (ADS)

    Rajammal, R.; Anbarasu, V.; Savarimuthu, E.; Arumugam, S.

    2014-09-01

    The present work is intended to investigate the influence of the gelation state of the sol-gel on the properties of spin-coated cadmium oxide (CdO) thin films. The viscosity of the sol-gel increases at a slow uniform rate up to 5 days (break-off point) after which the rise becomes progressively more rapid and it attains saturation after 10 days of gelation. Films have been grown with gelation times of 2 days, 4 days, 6 days, 8 days, 9 days and 10 days. The visual characteristics of the films have been discussed in terms of the centrifugal force acting on the sol-gel. The sol-gel viscosity seems to be better suited to represent the gelation state of the sol-gel rather than the gelation time. The x-ray diffraction studies show that lower gelation times and lower sol-gel viscosities give rise to single crystalline CdO thin films while gelation times of 6 days and above (i.e. sol-gel viscosities of 2.92 10-3 N s m-2 and more) yield polycrystalline CdO thin films. The gelation state of the sol-gel has been found to have a strong bearing on the properties of CdO thin films, and highly conducting and transparent CdO thin films can be achieved by controlling the gelation state of the sol-gel and the results obtained have been reported.

  4. Sol-gel optical thin films for an advanced megajoule-class Nd:glass laser ICF-driver

    SciTech Connect

    Floch, H.G.; Belleville, P.F.; Pegon, P.M.; Dijonneau, C.S.; Guerain, J.

    1995-12-31

    It is well established by manufacturers and users that optical coatings are generally prepared by the well known Physical Vapor Deposition (PVD) technology. In the authors` opinion sol-gel technology is an effective and competitive alternative. The aim of this paper is to emphasize on the sol-gel thin film work carried out at Centre d`Etudes de Limeil-Valenton (CEL-V) and concerning the technology for high power lasers. The authors will briefly discuss the chemistry of the sol-gel process, the production of optical coatings and the related deposition techniques. Finally, the paper describes the preparation and performance of sol-gel optical coatings they have developed to fulfill the requirements of a future 2 MJ/500 TW (351 nm) pulsed Nd:glass laser so-called LMJ (Laser MegaJoules). This powerful laser is to be used for their national Inertial Confinement Fusion (ICF) program, to demonstrate at the laboratory scale, ignition of deuterium-tritium fusion fuel. Moreover, the aim of this article is, hopefully, to provide a convincing argument that coatings and particularly optical coatings, are some of the useful products available from sol-gel technology, and that exciting developments in other areas are almost certain to emerge within the coming decade.

  5. Pre-evaluation method for the spectroscopic properties of YAG bulk materials by sol-gel synthetic powder

    NASA Astrophysics Data System (ADS)

    Fujioka, K.; Fujimoto, Y.; Motokoshi, S.; Fujita, H.; Nakatsuka, M.

    2011-05-01

    The sol-gel synthetic powder evaluation method is the most effective and the easiest technique for pre-evaluating the spectroscopic properties of luminescent impurity doped YAG. The luminescent elements doped sol-gel powder agrees well with that of a single crystal or ceramic YAG regarding the luminescent spectra, the intensity, and the lifetime, even though the powder sintered at a low temperature of 1100C in comparison with the YAG crystal melting point of 1970C, because a good crystallinity of the sol-gel powder is led by the hard agglomerates of very small primary particles. It is considered that the significance of this method is to apply for not only of YAG but also of other oxides, for instance Y2O3, ZrO2, TiO2, and MgAl2O4

  6. Effect of chelating agent acetylacetone on corrosion protection properties of silane-zirconium sol-gel coatings

    NASA Astrophysics Data System (ADS)

    Yu, Mei; Liang, Min; Liu, Jianhua; Li, Songmei; Xue, Bing; Zhao, Hao

    2016-02-01

    The hybrid sol-gel coatings on AA2024-T3 were prepared with a silane coupling agent 3-glycidoxypropyltrimethoxysilane (GPTMS) and a metal alkoxide tetra-n-propoxyzirconium (TPOZ) as precursors. The effect of acetylacetone (AcAc) as a chelating agent on the corrosion protection properties of sol-gel coatings were evaluated and the optimal AcAc/TPOZ molar ratio was obtained. The sol-gel coatings were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The corrosion protection properties of the coatings were evaluated by means of potentiodynamic polarization study (PDS) and electrochemical impedance spectroscopy (EIS). It is demonstrated that AcAc avoids fast hydrolysis of TPOZ and benefits to form stable sols. The coating with AcAc/TPOZ molar ratio of 3 shows the best corrosion protection performance in 0.05 M NaCl solution.

  7. Flexo printed sol-gel derived vanadium oxide films as an interfacial hole-transporting layer for organic solar cells

    NASA Astrophysics Data System (ADS)

    Kololuoma, Terho; Lu, Jiangping; Alem, Salima; Graddage, Neil; Movileanu, Raluca; Moisa, Simona; Tao, Ye

    2014-03-01

    In this paper we report on the synthesis and development of vanadium oxide precursor flexographic ink for the printing of hole-transporting layers in organic solar cells. For the synthesis of vanadium oxide inks, a sol-gel methodology was utilized. By modifying the vanadium alkoxide precursor with a right type of coordinating ligands a stable and flexoprintable ink has been successfully developed. Flexo-printing afforded smooth and uniform vanadium oxide sol-gel films on top of PCDTBT:PC70BM films. The conversion of the synthesized sol-gel film into a corresponding vanadium oxide layer was followed by DSC/TGA and XPS analyses. The inks were used for the fabrication of inverted organic solar cells by flexo-printing. Power conversion efficiencies ranging between 3.5 % and 4.5 % were achieved, which are slightly lower than the reference cells using vacuum-deposited MoO3 as the hole-transporting layers.

  8. Luminescence of Eu(3+) doped SiO2 Thin Films and Glass Prepared by Sol-gel Technology

    NASA Technical Reports Server (NTRS)

    Castro, Lymari; Jia, Weiyi; Wang, Yanyun; Santiago, Miguel; Liu, Huimin

    1998-01-01

    Trivalent europium ions are an important luminophore for lighting and display. The emission of (5)D0 to (7)F2 transition exhibits a red color at about 610 nm, which is very attractive and fulfills the requirement for most red-emitting phosphors including lamp and cathode ray phosphorescence materials. Various EU(3+) doped phosphors have been developed, and luminescence properties have been extensively studied. On the other hand, sol-gel technology has been well developed by chemists. In recent years, applications of this technology to optical materials have drawn a great attention. Sol-gel technology provides a unique way to obtain homogeneous composition distribution and uniform doping, and the processing temperature can be very low. In this work, EU(3+) doped SiO2 thin films and glasses were prepared by sol-gel technology and their spectroscopic properties were investigated.

  9. Comparison of laser performance of dye molecules in sol-gel, polycom, ormosil, and poly(methyl methacrylate) host media.

    PubMed

    Rahn, M D; King, T A

    1995-12-20

    Laser performance is described for Rhodamine 590, Pyrromethene 567, Perylene red, and Perylene orange in inorganic porous sol-gel glass, poly(methyl methacrylate)(PMMA), a composite of porous sol-gel glass with PMMA and organically modified silicate ormosil glass. Lasers were excited with a flash-lamp-pumped dye laser in the long-pulse-length regime (3 s, 506 nm, 300 mJ) and a second-harmonic Nd:YAG laser in the short-pulse-length regime (6 or 15 ns, 532 nm, 60 mJ). The feasibility of long-pulse-length operation is demonstrated, detailed characteristics of short-pulse operation are described, and laser damage measurements are given. The nonpolar perylene dyes had better performance in partially organic hosts, and the ionic rhodamine and pyrromethene dyes performed best in the inorganic sol-gel glass host. PMID:21068943

  10. Comparison of laser performance of dye molecules in sol-gel, polycom, ormosil, and poly(methyl methacrylate) host media

    NASA Astrophysics Data System (ADS)

    Rahn, Mark D.; King, Terence A.

    1995-12-01

    Laser performance is described for Rhodamine 590, Pyrromethene 567, Perylene red, and Perylene orange in inorganic porous sol-gel glass, poly (methyl methacrylate) (PMMA), a composite of porous sol-gel glass with PMMA and organically modified silicate ormosil glass. Lasers were excited with a flash-lamp-pumped dye laser in the long-pulse-length regime (3 mu s, 506 nm, 300 mJ) and a second-harmonic Nd:YAG laser in the short-pulse-length regime (6 or 15 ns, 532 nm, 60 mJ). The feasibility of long-pulse-length operation is demonstrated, detailed characteristics of short-pulse operation are described, and laser damage measurements are given. The nonpolar perylene dyes had better performance in partially organic hosts, and the ionic rhodamine and pyrromethene dyes performed best in the inorganic sol-gel glass host.

  11. Electrochemical impedimetric sensor based on molecularly imprinted polymers/sol-gel chemistry for methidathion organophosphorous insecticide recognition.

    PubMed

    Bakas, Idriss; Hayat, Akhtar; Piletsky, Sergey; Piletska, Elena; Chehimi, Mohamed M; Noguer, Thierry; Rouillon, Régis

    2014-12-01

    We report here a novel method to detect methidathion organophosphorous insecticides. The sensing platform was architected by the combination of molecularly imprinted polymers and sol-gel technique on inexpensive, portable and disposable screen printed carbon electrodes. Electrochemical impedimetric detection technique was employed to perform the label free detection of the target analyte on the designed MIP/sol-gel integrated platform. The selection of the target specific monomer by electrochemical impedimetric methods was consistent with the results obtained by the computational modelling method. The prepared electrochemical MIP/sol-gel based sensor exhibited a high recognition capability toward methidathion, as well as a broad linear range and a low detection limit under the optimized conditions. Satisfactory results were also obtained for the methidathion determination in waste water samples. PMID:25159412

  12. Characterizations of maghemite thin films prepared by a sol-gel method

    NASA Astrophysics Data System (ADS)

    Lau, L. N.; Ibrahim, N. B.

    2015-09-01

    Iron is one of the abundant elements of Mother Nature and its compound, iron oxide is an interesting material to study since its discovery in the form of magnetite. It can exist in many phases such as hematite and maghemite, this unique nature has put it as a potential candidate in various applications. The aim of this work is to study the influence of different precursor concentrations on the microstructural and magnetic properties of iron oxide thin film. All samples were prepared via the sol-gel method followed by a spin coating technique on quartz substrates. Iron oxide films were confirmed as maghemite phase from X-ray diffraction patterns. The film morphology was examined by a field emission scanning electron microscope and it showed non-systematic value of average grain size and film thickness throughout the study. Hysteresis loop further confirmed that maghemite is a magnetic material when it was characterized by a vibrating sample magnetometer. The coercivity did not show any correlation with molarity. Nevertheless, it increased as the precursor concentration of the film increased due to the domain behaviour. In conclusion, maghemite thin films were successfully synthesized by the sol-gel method with different precursor concentrations in this work.

  13. Photonic crystal patterning of luminescent sol-gel films for light extraction.

    PubMed

    Revaux, Amelie; Dantelle, Geraldine; Decanini, Dominique; Guillemot, Francois; Haghiri-Gosnet, Anne-Marie; Weisbuch, Claude; Boilot, Jean-Pierre; Gacoin, Thierry; Benisty, Henri

    2011-09-01

    Structured luminescent thin films are investigated in the context of improved light extraction of phosphors for solid-state-lighting applications. Thin films composed of a sol-gel titania matrix doped with europium chelates are studied as a model system. These films, patterned with a square photonic lattice by soft nanoimprint lithography, are characterized by angle-resolved fluorescence. Modeling of this simple technique is shown to fit well the experimental data, revealing in great detail the guided modes of the film and their extraction parameters. An eightfold extraction enhancement factor of the film emission is measured. To further improve the extraction efficiency, we investigate the role of an additional low-index mesoporous silica underlayer through its influence on the guided modes of different polarizations and their interactions with the photonic crystal. Results obtained on model systems open the way towards the optimization of light-emitting devices, using a strategy of dielectric microstructure engineering using the sol-gel process. PMID:21836324

  14. Lead magnesium niobate-lead titanate fibres by a modified sol-gel method

    SciTech Connect

    Lam, K.-H. . E-mail: 02900857r@polyu.edu.hk; Li Kun; Chan, H.L.-W.

    2005-11-03

    Lead magnesium niobate-lead titanate (PMN-PT) ceramic fibres with the nominal composition of 0.65Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.35PbTiO{sub 3} have been fabricated by a modified sol-gel method. Due to the difficulty of dissolving the magnesium component, the mixed oxide method was used together with the traditional sol-gel method. To obtain crack-free fibres, pyrolysis was carried out at a very slow heating rate under specific atmosphere to control the organic burnout. The thermal and microstructural properties were investigated using thermogravimetric analysis, scanning electron microscopy and X-ray diffraction. The optimum sintering temperature is 1200 deg. C and yields a fibre with a final diameter of around 100 {mu}m. A single PMN-PT fibre has been poled and its electrical properties were measured. The properties of the fibre are found to be better than that of a ceramic disc.

  15. Sol-gel derived Ba(Fe, Ti)O3 ferroelectric materials for infrared sensors

    NASA Astrophysics Data System (ADS)

    Ray (Mal), Jayati; Hing, Peter

    2000-07-01

    In this article we report the development of Fe modified BaTiO3 using sol-gel technique and present results of structural and dielectric studies to establish its suitability for pyroelectric sensor applications. Fine powders of Fe modified BaTiO3 were prepared by sol-gel process using barium acetate, iron isopropoxide, and titanium isopropoxide. X-ray structural analyses of the BaTiO3 with different proportion of Fe ion suggest the formation of single-phase compounds having tetragonal structure at a relatively low temperature around 750 C for 4 h. The particle size of the powder was found to be in nm range. The sintering temperature of 1250 C for the above calcined powder was considerably lower than the powders made by the conventional methods. The ferroelectric to paraelectric phase transition of Ba(Fe, Ti)O3 ceramics was studied using the dielectric measurement. The value of dielectric constant for Fe modified BaTiO3 was found to be lower than pure BaTiO3 and the transition temperature shifted towards the lower temperature side with an increase in Fe ion concentration. A combination of low dielectric constant and a low transition temperature makes Fe modified BaTiO3 materials attractive for room temperature pyroelectric sensor applications.

  16. Combining inkjet printing and sol-gel chemistry for making pH-sensitive surfaces.

    PubMed

    Orsi, Gianni; De Maria, Carmelo; Montemurro, Francesca; Chauhan, Veeren M; Aylott, Jonathan W; Vozzi, Giovanni

    2015-01-01

    Today biomedical sciences are experiencing the importance of imaging biological parameters with luminescence methods. Studying 2D pH distribution with those methods allows building knowledge about complex cellular processes. Immobilizing pH sensitive nanoparticles inside hydrogel matrixes, in order to guarantee a proper SNR, could easily make stable and biocompatible 2D sensors. Inkjet printing is also well known as tool for printing images onto porous surfaces. Recently it has been used as a free-form fabrication method for building three-dimensional parts, and now is being explored as a way of printing electrical and optical devices. Inkjet printing was used either as a rapid prototyping method for custom biosensors. Sol-gel method is naturally bound with inkjet, because the picoliter-sized ink droplets evaporate quickly, thus allowing quick sol-gel transitions on the printed surface. In this work will be shown how to merge those technologies, in order to make a nanoparticles doped printable hydrogel, which could be used for making 2D/3D smart scaffolds able to monitor cell activities. An automated image analysis system was developed in order to quickly have the pH measurements from pH nanosensors fluorescence images. PMID:25547966

  17. In vitro release of cisplatin from sol-gel processed organically modified silica xerogels.

    PubMed

    Czarnobaj, Katarzyna; Lukasiak, Jerzy

    2007-10-01

    SiO2, SiO2/PEG and SiO2/PDMS xerogels were examined as polymeric carriers for the controlled release of cisplatin--an antineoplasmic medicine. Drug/carrier systems were prepared by the sol-gel method. The effect of organic substitution of the silica xerogel matrix and drying conditions on the release of cisplatin was evaluated. Based on the presented results of the study it may be stated that sol-gel method is useful for entrapping a cisplatin in the pores of organically modified silica gels and for releasing cisplatin mainly in the way of diffusion from the pores of the lattice under the in vitro conditions. The use of organic impurities in silica gel increased the release of cisplatin from xerogel (from 62% to 97% within 7 days), and thermal treatment of all xerogels with cisplatin at the temperature of 80 degrees C resulted in the acceleration of the drug release (2 days) and increase of the released drug (89-98%). PMID:17558477

  18. Dialkylenecarbonate-Bridged Polysilsesquioxanes. Hybrid Organic Sol-Gels with a Thermally Labile Bridging Group

    SciTech Connect

    Loy, D.A.; Beach, J.V.; Baugher, B.M.; Assink, R.A.; Shea, K.J.; Tran, J.; Small, J.H.

    1999-04-21

    In this paper, we introduce a new approach for altering the properties of bridged polysilsesquioxane xerogels using post-processing modification of the polymeric network. The bridging organic group contains latent functionalities that can be liberated thermally, photochemically, or by chemical means after the gel has been processed to a xerogel. These modifications can produce changes in density, volubility, porosity, and or chemical properties of the material. Since every monomer possesses two latent functional groups, the technique allows for the introduction of high levels of functionality in hybrid organic-inorganic materials. Dialkylenecarbonate-bridged polysilsesquioxane gels were prepared by the sol-gel polymerization of bis(triethoxysilylpropyl)carbonate (1) and bis(triethoxysilylisobutyl)-carbonate (2). Thermal treatment of the resulting non-porous xerogels and aerogels at 300-350 C resulted in quantitative decarboxylation of the dialkylenecarbonate bridging groups to give new hydroxyalkyl and olefinic substituted polysilsesquioxane monolithic xerogels and aerogels that can not be directly prepared through direct sol-gel polymerization of organotrialkoxysilanes.

  19. Sol-gel replicated optics made from single point diamond turned masters exhibit fractal surface roughness

    SciTech Connect

    Bernacki, B.E.; Miller, A.C. Jr.; Evans, B.M. III; Moreshead, W.V.; Nogues, J.L.R.

    1996-05-01

    Deterministic optics manufacturing, notably single point diamond turning (SPDT) has matured such that the current generation of machines is capable of producing refractive and reflective optics for the visible wavelength region that are quite acceptable for many applications. However, spiral tool marks are still produced that result in unwanted diffractive scattering from grating-like features having a spatial frequency determined by the machine feed, tool radius, and other influences such as vibration and material removal effects. Such regular artifacts are the characteristic of deterministic manufacturing methods such as SPDT. The authors present some initial findings suggesting that fractal, or non-deterministic surfaces can be produced by SPDT through sol-gel replication. The key is the large isotropic shrinkage that occurs through monolithic sol-gel replication (a factor of 2.5) that results in all features, including tooling marks, being reduced by that amount. The large shrinkage itself would be a laudable-enough feature of the replication process. However, by an as-yet-not understood manner, the replication process itself seems to alter the roughness character of the replicated surface such that it appears to be fractal when analyzed using contact profilometry and the power spectrum approach.

  20. Synthesis, characterization, and sol-gel entrapment of a crown ether-styryl fluoroionophore

    PubMed Central

    Sui, Zhijie; Hanan, Nathan J.; Phimphivong, Sam; Wysocki, Ronald J.; Saavedra, S. Scott

    2011-01-01

    The synthesis and initial evaluation of a new dye-functionalized crown-ether, 2-[2-(2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10.13.16-benzohexaoxacyclooctadecin)ethenyl]-3-methyl benzothiazolium iodide (denoted BSD), is reported. This molecule contains a benzyl 18-crown-6 moiety as the ionophore and a benzothiazolium to spectrally transduce ion binding. Binding of K+ to BSD in methanol causes shifts in the both absorbance and fluorescence emission maxima, as well as changes in the molar absorptivity and the emission intensity. Apparent dissociation constants (Kd) in the range of 30 65 ?M were measured. In water and neutral buffer, Kd values were approximately 1 mM. BSD was entrapped in sol-gel films composed of methyltriethoxysilane (MTES) and tetraethylorthosilicate (TEOS) with retention of its spectral properties and minimal leaching. K+ binding to BSD in sol-gels films immersed in pH 7.4 buffer causes significant fluorescence quenching, with an apparent response time of approximately 2 min and an apparent Kd of 1.5 mM. PMID:19253273

  1. Synthesis, characterization and sol-gel entrapment of a crown ether-styryl fluoroionophore.

    PubMed

    Sui, Zhijie; Hanan, Nathan J; Phimphivong, Sam; Wysocki, Ronald J; Saavedra, S Scott

    2009-01-01

    The synthesis and initial evaluation of a new dye-functionalized crown-ether, 2-[2-(2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,13,16-benzohexaoxacyclooctadecin)ethenyl]-3-methyl benzothiazolium iodide (denoted BSD), are reported. This molecule contains a benzyl 18-crown-6 moiety as the ionophore and a benzothiazolium to spectrally transduce ion binding. Binding of K(+) to BSD in methanol causes shifts in the both absorbance and fluorescence emission maxima, as well as changes in the molar absorptivity and the emission intensity. Apparent dissociation constants (K(d)) in the range 30-65 microm were measured. In water and neutral buffer, K(d) values were approximately 1 mm. BSD was entrapped in sol-gel films composed of methyltriethoxysilane (MTES) and tetraethylorthosilicate (TEOS) with retention of its spectral properties and minimal leaching. K(+) binding to BSD in sol-gel films immersed in pH 7.4 buffer causes significant fluorescence quenching, with an apparent response time of approximately 2 min and an apparent K(d) of 1.5 mm. PMID:19253273

  2. Interactions between DNA purines and ruthenium ammine complexes within nanostructured sol-gel silica matrixes.

    PubMed

    Lopes, Lus M F; Garcia, Ana R; Brogueira, Pedro; Ilharco, Laura M

    2010-03-25

    The interactions between DNA purines (guanine and adenine) and three ruthenium ammine complexes (hexaammineruthenium(III) chloride, hexaammineruthenium(II) chloride, and ruthenium-red) were studied in a confined environment, within sol-gel silica matrixes. Two encapsulation methods were rehearsed (differing in temperature and condensation pH), in order to analyze the effects of the sol-gel processes on the purines and on the Ru complexes separately. The extent of decomposition of the Ru complexes, as well as the interactions established with the purine bases, proved to be determined by the coencapsulation method. Combined results by diffuse reflectance UV-vis and infrared spectroscopies showed that, when coencapsulation is carried out at 60 degrees C, specific H bonding interactions are established between the amine group of Ade and the ammine groups of the Ru complex or the hydroxo group of an early decomposition product. These are responsible for the important role of the purine in inhibiting the oxidation reactions of the Ru(II) and Ru(III) complexes. In contrast, Gua establishes preferential H bonds with the matrix (mainly due to the carbonyl group), leading to higher yields in the final oxidation products of the Ru complexes, namely, trimers and dimers. Direct covalent bonding of either purine to the metal was not observed. PMID:20196584

  3. Low temperature self-agglomeration of metallic Ag nanoparticles on silica sol gel thin films

    NASA Astrophysics Data System (ADS)

    Akhavan, O.; Azimirad, R.; Moshfegh, A. Z.

    2008-10-01

    A facile sol-gel synthesis for self-agglomeration of metallic silver nanoparticles, with fcc crystalline structure, on the silica surface in a low annealing temperature has been introduced. X-ray photoelectron spectroscopy (XPS) revealed initial agglomeration (~30 times greater than the nominal concentration of Ag) of the nanoparticles on the surface of the dried film (100 C) and also their oxidation as well as easy diffusion (with 0.08 eV required activation energy) into the porous silica thin films, by increasing the annealing temperature (200-400 C). By raising the Ag concentration from 0.2 to 1.6 mol% in the sol, the average size of the Ag nanoparticles increased from ~5 to 37 nm corresponding to a redshift of the optical plasmon resonance absorption peak from 404 to 467 nm. The high concentration of Ag (1.6 mol%) in the sol resulted in a rough surface containing compact nanoparticles. Using power spectral density analysis of the atomic force microscopy images, we have found that the highest contributions in the surface roughness of the dried silica films were caused by the particles ranging from ~62 to 159 nm. The particles smaller than ~39 nm did not show any detectable contributions in the surface roughness of the dried silica film. Based on the XPS analysis, a mechanism has also been proposed for the self-agglomeration of the Ag nanoparticles on the surface of the aqueous sol-gel silica thin films.

  4. Sol gel derived hydroxyapatite coatings on titanium and its alloy Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Stoch, A.; Jastrzebski, W.; D?ugo?, E.; Lejda, W.; Trybalska, B.; Stoch, G. J.; Adamczyk, A.

    2005-06-01

    Titanium has been used for many medical and dental applications; however, its joining to a living bone is not satisfactorily good or the implant integration with bone tissue takes several months.The aim of this work is to produce hydroxyapatite (HAP) coatings on titanium and its alloy for facilitating and shortening the processes towards osseointegration. HAP coatings were obtained by sol-gel method with sol solutions prepared from calcium nitrate tetrahydrate and triammonium phosphate trihydrate as the calcium and phosphorous sources. Two types of gelatine were added to the sol: agar-agar or animals gelatine. Both were found to enhance the formation and stability of amorphous HAP using soluble salts as the sources of calcium and phosphate. HAP coatings were deposited from HAP-GEL sol using dip-withdrawal technique, then the plates were dried and annealed at temperatures 460-750 C. FTIR spectroscopy and XRD analysis were used to study the phase composition of phosphate coatings. Morphology and chemical analysis of HAP layers was performed using a scanning electron microscope equipped with an energy dispersive X-ray analyser (SEM+EDX). The biological activity of sol-gel phosphate coatings was observed during thermostatic held in simulated body fluid (SBF). It was found that chemical composition and structure of HAP coatings depends on pH and final thermal treatment of the layer.

  5. A modified sol-gel technique for pore size control in porous aluminum oxide nanowire templates.

    PubMed

    Kelly, Daniel N; Wakabayashi, Ryo H; Stacy, Angelica M

    2014-11-26

    A modified sol-gel technique was developed to continuously vary the pore diameters in porous alumina templates for the purpose of growing nanowires. To coat the pore walls, the porous alumina film is initially soaked in a methanol/water solution to fill the pores with the desired concentration of water. The porous alumina film is then exposed to a solution of 3-aminopropyltriethoxysilane (APTES) in toluene, creating a surface layer of APTES. The concentration of water in the pores correlates with the thickness of the APTES polymer coating that is obtained. This approach exerts greater control over the extent of silane polymerization than traditional sol-gel reactions by limiting the amount of water present for reaction. Factors such as the APTES concentration, exposure time, and organic cosolvent choice did not influence the coating thickness. However, the density and thickness of the APTES coating can be manipulated by varying the pH of the methanol/water solution as well as post-treatment annealing. Further modification of the pore size was achieved by subsequent reaction of the APTES coating with poly(methyl methacrylate) (PMMA). The PMMA couples to amine groups on the APTES polymer surface by an aminolysis reaction. Bismuth telluride nanowires were electrodeposited in the polymer-coated porous alumina templates using previously established methods. Nanowire diameters were smaller when the nanowires were prepared in modified templates as anticipated. PMID:25425125

  6. Solgel method to fabricate CaP scaffolds by robocasting for tissue engineering

    PubMed Central

    Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P.

    2012-01-01

    Highly porous calcium phosphate (CaP) scaffolds for bone-tissue engineering were fabricated by combining a robocasting process with a solgel synthesis that mixed Calcium Nitrate Tetrahydrate and Triethyl Phosphite precursors in an aqueous medium. The resulting gels were used to print scaffolds by robocasting without the use of binder to increase the viscosity of the paste. X-ray diffraction analysis confirmed that the process yielded hydroxyapatite and ?-tricalcium phosphate biphasic composite powders. Thus, the scaffold composition after crystallization of the amorphous structure could be easily modified by varying the initial Ca/P ratio during synthesis. The compressive strengths of the scaffolds are ~6 MPa, which is in the range of human cancellous bone (212 MPa). These highly porous scaffolds (~73 vol% porosity) are composed of macro-pores of ~260 ?m in size; such porosity is expected to enable bone ingrowth into the scaffold for bone repair applications. The chemistry, porosity, and surface topography of such scaffolds can also be modified by the process parameters to favor bone formation. The studied solgel process can be used to coat these scaffolds by dip-coating, which induces a significant enhancement of mechanical properties. This can adjust scaffold properties such as composition and surface morphology, which consequently may improve their performances. PMID:22311079

  7. Phospholipid fatty acids as physiological indicators of Paracoccus denitrificans encapsulated in silica sol-gel hydrogels.

    PubMed

    Trögl, Josef; Jirková, Ivana; Kuráň, Pavel; Akhmetshina, Elmira; Brovdyová, Taťjána; Sirotkin, Alexander; Kirilina, Tatiana

    2015-01-01

    The phospholipid fatty acid (PLFA) content was determined in samples of Paracoccus denitrificans encapsulated in silica hydrogel films prepared from prepolymerized tetramethoxysilane (TMOS). Immediately after encapsulation the total PLFA concentration was linearly proportional to the optical density (600 nm) of the input microbial suspension (R2 = 0.99). After 7 days this relationship remained linear, but with significantly decreased slope, indicating a higher extinction of bacteria in suspensions of input concentration 108 cells/mL and higher. trans-Fatty acids, indicators of cytoplasmatic membrane disturbances, were below the detection limit. The cy/pre ratio (i.e., ratio of cyclopropylated fatty acids (cy17:0 + cy19:0) to their metabolic precursors (16:1ω7 + 18:1ω7)), an indicator of the transition of the culture to a stationary growth-phase, decreased depending on co-immobilization of nutrients in the order phosphate buffer > mineral medium > Luria Broth rich medium. The ratio, too, was logarithmically proportional to cell concentration. These results confirm the applicability of total PLFA as an indicator for the determination of living biomass and cy/pre ratio for determination of nutrient limitation of microorganisms encapsulated in sol-gel matrices. This may be of interest for monitoring of sol-gel encapsulated bacteria proposed as optical recognition elements in biosensor construction, as well as other biotechnological applications. PMID:25690547

  8. Phospholipid Fatty Acids as Physiological Indicators of Paracoccus denitrificans Encapsulated in Silica Sol-Gel Hydrogels

    PubMed Central

    Trögl, Josef; Jirková, Ivana; Kuráň, Pavel; Akhmetshina, Elmira; Brovdyová, Tat′jána; Sirotkin, Alexander; Kirilina, Tatiana

    2015-01-01

    The phospholipid fatty acid (PLFA) content was determined in samples of Paracoccus denitrificans encapsulated in silica hydrogel films prepared from prepolymerized tetramethoxysilane (TMOS). Immediately after encapsulation the total PLFA concentration was linearly proportional to the optical density (600 nm) of the input microbial suspension (R2 = 0.99). After 7 days this relationship remained linear, but with significantly decreased slope, indicating a higher extinction of bacteria in suspensions of input concentration 108 cells/mL and higher. trans-Fatty acids, indicators of cytoplasmatic membrane disturbances, were below the detection limit. The cy/pre ratio (i.e., ratio of cyclopropylated fatty acids (cy17:0 + cy19:0) to their metabolic precursors (16:1ω7 + 18:1ω7)), an indicator of the transition of the culture to a stationary growth-phase, decreased depending on co-immobilization of nutrients in the order phosphate buffer > mineral medium > Luria Broth rich medium. The ratio, too, was logarithmically proportional to cell concentration. These results confirm the applicability of total PLFA as an indicator for the determination of living biomass and cy/pre ratio for determination of nutrient limitation of microorganisms encapsulated in sol-gel matrices. This may be of interest for monitoring of sol-gel encapsulated bacteria proposed as optical recognition elements in biosensor construction, as well as other biotechnological applications. PMID:25690547

  9. Epoxide opening versus silica condensation during sol-gel hybrid biomaterial synthesis.

    PubMed

    Gabrielli, Luca; Russo, Laura; Poveda, Ana; Jones, Julian R; Nicotra, Francesco; Jimnez-Barbero, Jess; Cipolla, Laura

    2013-06-10

    Hybrid organic-inorganic solids represent an important class of engineering materials, usually prepared by sol-gel processes by cross-reaction between organic and inorganic precursors. The choice of the two components and control of the reaction conditions (especially pH?value) allow the synthesis of hybrid materials with novel properties and functionalities. 3-Glycidoxypropyltrimethoxysilane (GPTMS) is one of the most commonly used organic silanes for hybrid-material fabrication. Herein, the reactivity of GPTMS in water at different pH?values (pH?2-11) was deeply investigated for the first time by solution-state multinuclear NMR spectroscopic and mass spectrometric analysis. The extent of the different and competing reactions that take place as a function of the pH?value was elucidated. The NMR spectroscopic and mass spectrometric data clearly indicate that the pH?value determines the kinetics of epoxide hydrolysis versus silicon condensation. Under slighly acidic conditions, the epoxy-ring hydrolysis is kinetically more favourable than the formation of the silica network. In contrast, under basic conditions, silicon condensation is the main reaction that takes place. Full characterisation of the formed intermediates was carried out by using NMR spectroscopic and mass spectrometric analysis. These results indicate that strict control of the pH?values allows tuning of the reactivity of the organic and inorganic moities, thus laying the foundations for the design and synthesis of sol-gel hybrid biomaterials with tuneable properties. PMID:23576425

  10. Preparation and optical properties of sol-gel-deposited electrochromic iron oxide films

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; Tepehan, Fatma; Tepehan, Galip

    1997-10-01

    The preparation and optical properties of sol-gel deposited iron oxide films are investigated in this study. The films are deposited on glass by spin-coating from polymeric sol-gel solutions. The coating solutions were prepared from Fe(OCH3H7)3 and isopropanol. Fe2O3 films were obtained at a firing temperature 180 degrees Celsius. The films were characterized by x-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and UV-Vis spectroscopy. The electrochemical properties of the films were studied in 0.5 M LiClO4/propylene carbonate (PC) solution. The CV results showed reversibility of the Li+/e- insertion/extraction process in the Fe2O3 films up to 200 cycles. Reduction and oxidation of the amorphous films in 0.5 M LiClO4-PC solution caused noticeable changes in optical absorption. XRD of the films showed that they had an amorphous structure. Fourier transform infrared spectroscopy (FTIR) measurements showed that the composition of the film is Fe2O3. In-situ spectrophotometric measurements indicated that these films show weak electrochromism in the spectral range of 350 - 800 nm. The optical band gap is estimated to be 1.92 eV for the amorphous film. The spectroelectrochemical properties clearly indicated that cyclic stability of the iron oxide films deteriorated above 200 cycles.

  11. Use of sol-gel systems for solid/liquid separation.

    SciTech Connect

    Chaiko, D. J.; Kopasz, J. P.; Elison, A. J. G.; Chemical Engineering

    1998-01-01

    A unique approach using sol-gel technology is presented for separating and recovering particulates and colloids from caustic waste slurries. The approach involves the addition of an alkali silicate and an organic gelling agent directly to the waste stream to immobilize particulates that range from macro sizes to submicron colloids. The particulates and colloids become trapped within a silica network that remains porous during the early stages of the sol-gel process. The freshly gelled monolith undergoes a process of syneresis, whereby the water and soluble salts are ejected from the monolith as it contracts. The approach has been illustrated by removal of ultrafine particulates from a Hanford Tank Waste simulant. Initial laboratory tests have shown that it is possible to produce silica monoliths in the presence of 4 M hydroxide. Analysis of the mother liquor produced during syneresis indicated quantitative recovery of the particulates within the monolith. The partitioning of ions between the silica gel and the mother liquor during syneresis correlates directly with the lyotropic series. Salt recoveries from the mother liquor in excess of 90% can be achieved. With a capability of recovering >99.999% of all particulates, including colloids, the process is more efficient than membrane filtration. This approach produces a rock-hard silica monolith that can be used directly as a feedstock to a glass melter or can be consolidated to near theoretical density by sintering.

  12. Sol-gel processed silica/titania/ÿ-Glycidoxypropyltrimethoxysilane composite materials for photonic applications

    NASA Astrophysics Data System (ADS)

    Que, Wenxiu; Zhou, Y.; Lam, Y. L.; Chan, Y. C.; Tan, H. T.; Tan, T. H.; Kam, C. H.

    2000-08-01

    Silica/titania/ÿ-Glycidoxypropyltrimethoxysilane composite materials processed by the sol-gel technique were studied for photonic applications. Waveguide thin films with thickness more than 1.7 µm were prepared by the sol-gel spin coating technique and low temperature heat treatment from this high titanium content composite materials. The films were analyzed by atomic force microscopy (AFM), ellipsometry, differential thermal analysis (DTA), thermal gravimetric analysis (TGA), UV-visible spectroscopy (UV-VIS), and Fourier transform infrared (FT-IR) spectroscopy. It was observed that the film becomes thinner as the titanium contents increase. A change of the refractive index through the range 1.52-1.61 at the optical wavelength of 633 nm was achieved by varying the molar ratio between silica and titanium. A dense, low absorption, and high transparency in the visible range waveguide films could be obtained at a low temperature. It was also noted that organic compounds in the film would decompose in the temperature range from 200°C to 480°C. Accordingly, purely inorganic silica-titania films with a thickness of about 0.7 µm could also be obtained by a single-coating process, when the film was baked at a temperature of 500°C or higher. The waveguides properties and photonic applications of the composite material solgel films were also investigated.

  13. Sol-gel method as a way of carbonyl iron powder surface modification for interaction improvement

    NASA Astrophysics Data System (ADS)

    Ma?ecki, P.; Kolman, K.; Pig?owski, J.; Kaleta, J.; Krzak, J.

    2015-03-01

    This article presents a method for modification of carbonyl iron particles' surface (CIP), (d50=4-9 ?m) by silica coatings obtained using the sol-gel method. Reaction parameters were determined to obtain dry magnetic powder with homogeneous silica coatings without further processing and without any by-product in the solid or liquid phase. This approach is new among the commonly used methods of silica coating of iron particles. No attempt has been made to cover a carbonyl iron surface by silica in a waste-free method, up to date. In the current work two different silica core/shell structures were made by the sol-gel process, based on different silica precursors: tetraethoxy-silane (TEOS) and tetramethoxy-silane (TMOS). The dependence between the synthesis procedure and thickness of silica shell covering carbonyl iron particles has been described. Surface morphology of the modified magnetic particles and the coating thickness were characterized with the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Determination of the physicochemical structure of the obtained materials was performed by the energy-dispersive X-ray spectroscope (EDS), and the infrared technique (IR). The surface composition was analyzed using X-ray photoelectron spectroscopy (XPS). Additionally, distribution of particle size was measured using light microscopy. The new, efficient process of covering micro-size CIP with a nanometric silica layer was shown. Results of a performed analysis confirm the effectiveness of the presented method.

  14. Patterning of sol-gel hybrid organic-inorganic film doped with luminescent semiconductor quantum dots.

    PubMed

    Buso, Dario; Della Giustina, Gioia; Brusatin, Giovanna; Guglielmi, Massimo; Martucci, Alessandro; Chiasera, Alessandro; Ferrari, Maurizio; Romanato, Filippo

    2009-03-01

    Two different sol-gel hybrid organic-inorganic films doped with luminescent CdS or PbS quantum dots (QDs) have been successfully synthesized and patterned using nanolithographic techniques. The feasibility of applying X-ray lithography and RIE to pattern hybrid materials doped with highly luminescent nanoparticles has been demonstrated for GPTMS-GeO2 (G-GeO2) and MPTMS-ZrO2 (M-ZrO2) hybrids obtained form 3-glycidoxypropyltrymethoxysilane (GPTMS), methacryloxy-propil-trimethoxysilane (MPTMS), germanium ethoxide and zirconium propoxide. Semiconductor doped film have been obtained by mixing ZrO2-SiO2 or GeO2-SiO2 sol-gel hybrid organic-inorganic matrix solution with CdS or PbS colloidal doping solution to obtain up to 20% molar concentration of QDs inside the films. Patterns consisting of pillars with different aspect ratio have been obtained by X-ray lithography and reactive ion etching (RIE). Structural and optical characterization of films before and after the lithographic process pointed out that both matrices and QDs retain their original properties without been affected by X-rays irradiation and RIE in the conditions here described. PMID:19435050

  15. Biocompatible Nb2O5 thin films prepared by means of the sol-gel process.

    PubMed

    Velten, D; Eisenbarth, E; Schanne, N; Breme, J

    2004-04-01

    Thin biocompatible oxide films with an optimised composition and structure on the surface of titanium and its alloys can improve the implant integration. The preparation of these thin oxide layers with the intended improvement of the surface properties can be realised by means of the sol-gel process. Nb2O5 is a promising coating material for this application because of its extremely high corrosion resistance and thermodynamic stability. In this study, thin Nb2O5 layers ( < 200 nm) were prepared by spin coating of polished discs of cp-titanium with a sol consisting of a mixture of niobium ethoxide, butanol and acetylacetone. The thickness, phase composition, corrosion resistance and the wettability of the oxide layers were determined after an optimisation of the processing parameters for deposition of oxide without any organic impurities. The purity of the oxide layer is an important aspect in order to avoid a negative response to the cell adhesion. The biocompatibility of the oxide layers which was investigated by in vitro tests (morphology, proliferation rate, WST-1, cell spreading) is improved as compared to uncoated and TiO2 sol-gel coated cp-titanium concerning the spreading of cells, collagen I synthesis and wettability. PMID:15332617

  16. In situ electrodeposition of an asymmetric sol-gel membrane based on an octadecyltrimethoxysilane Langmuir film.

    PubMed

    Hitrik, Maria; Lev, Ovadia; Mandler, Daniel

    2014-09-15

    The unique properties of Langmuir film formation were utilized in assembling a thin skin of an asymmetric membrane. An octadecyltrimethoxysilane (ODTMS) Langmuir monolayer was formed at the air-water interface and served as the substrate for growing a bulky sol-gel polymer in situ. The latter was based on the electrochemical deposition of tetramethoxysilane dissolved in the water subphase by means of horizontal touch electrochemistry. The resultant asymmetric layer that consisted of a thin hydrophobic ODTMS Langmuir film connected to a bulk hydrophilic sol-gel network was studied in situ and ex situ by using various techniques, such as cyclic voltammetry, electrochemical impedance spectroscopy (EIS), scanning electron microscopy, transmission electron microscopy (TEM), and goniometry. We found that a porous hydrophilic film grew on top of a hydrophobic layer as was evident from TEM, contact angle, and EIS analyses. The film thickness and film permeability could be controlled by changing the deposition conditions such as the potential window applied and its duration. Hence, this method offers an alternative approach for assembling asymmetric films for various applications. PMID:25111107

  17. The preparation of fluorine doped cadmium oxide thin film by sol-gel process.

    PubMed

    Kim, In Yea; Kim, Jong Sung

    2014-11-01

    During the several decades, CdO thin film has attracted many attentions as a candidate for the transparent conducting electrodes due to its high electrical conductivity and high optical transmittance. Various dopants such as F, In, Al, Sn, and Cr have been used to improve the optical and electrical properties of the film. Generally, the optical and electrical property of the thin film is dependent on its oxidation state, the amount of dopant materials, and the fabrication process. In this study, fluorine doped CdO thin films were prepared by using sol-gel process with various atomic ratios of Cd:F, and their electrical and optical properties were investigated. The precursor solution for sol-gel film was prepared with pH 5 and pH 8, and the film was annealed at 350 degrees C. X-ray diffraction pattern confirmed the cubic CdO:F phase formation, and the 10% fluorine doped film prepared with pH 8 precursor solution showed the lowest resistivity of 0.01574 Ω cm. PMID:25958514

  18. NiO-silica based nanostructured materials obtained by microemulsion assisted sol-gel procedure

    SciTech Connect

    Mihaly, M.; Comanescu, A.F.; Rogozea, A.E.; Vasile, E.; Meghea, A.

    2011-10-15

    Graphical abstract: TEM micrograph of NiO/SiO{sub 2} nanoparticles. Highlights: {yields} Microemulsion assisted sol-gel procedure for NiO silica nanomaterials synthesis. {yields} Controlling the size and shape of nanoparticles and avoiding their aggregation. {yields} Narrow band-gap semiconductors (energies <3 eV) absorbing VIS or near-UV light biologically and chemically inert semiconductors entrapping/coating in silica network. {yields} Low cost as the microemulsion is firstly used in water metallic cation extraction. -- Abstract: NiO-silica based materials have been synthesized by microemulsion assisted sol-gel procedure. The versatility of these soft nanotechnology techniques has been exploited in order to obtain different types of nanostructures, such as NiO nanoparticles, NiO silica coated nanoparticles and NiO embedded in silica matrix. These materials have been characterized by adequate structural and morphology techniques: DLS, HR-TEM/SAED, BET, AFM. Optical and semiconducting properties (band-gap values) of the synthesized materials have been quantified by means of VIS-NIR diffuse reflectance spectra, thus demonstrating their applicative potential in various electron transfer phenomena such as photocatalysis, electrochromic thin films, solid oxide fuel cells.

  19. Sol-gel antireflective spin-coating process for large-size shielding windows

    NASA Astrophysics Data System (ADS)

    Belleville, Philippe F.; Prene, Philippe; Mennechez, Francoise; Bouigeon, Christian

    2002-10-01

    The interest of the antireflective coatings applied onto large-area glass components increases everyday for the potential application such as building or shop windows. Today, because of the use of large size components, sol-gel process is a competitive way for antireflective coating mass production. The dip-coating technique commonly used for liquid-deposition, implies a safety hazard due to coating solution handling and storage in the case of large amounts of highly flammable solvent use. On the other hand, spin-coating is a liquid low-consumption technique. Mainly devoted to coat circular small-size substrate, we have developed a spin-coating machine able to coat large-size rectangular windows (up to 1 x 1.7 m2). Both solutions and coating conditions have been optimized to deposit optical layers with accurate and uniform thickness and to highly limit the edge effects. Experimental single layer antireflective coating deposition process onto large-area shielding windows (1000 x 1700 x 20 mm3) is described. Results show that the as-developed process could produce low specular reflection value (down to 1% one side) onto white-glass windows over the visible range (460-750 nm). Low-temperature curing process (120°C) used after sol-gel deposition enables antireflective-coating to withstand abrasion-resistance properties in compliance to US-MIL-C-0675C moderate test.

  20. Beating speckles via electrically-induced vibrations of Au nanorods embedded in sol-gel

    PubMed Central

    Ritenberg, Margarita; Beilis, Edith; Ilovitsh, Asaf; Barkai, Zehava; Shahmoon, Asaf; Richter, Shachar; Zalevsky, Zeev; Jelinek, Raz

    2014-01-01

    Generation of macroscopic phenomena through manipulating nano-scale properties of materials is among the most fundamental goals of nanotechnology research. We demonstrate cooperative speckle beats induced through electric-field modulation of gold (Au) nanorods embedded in a transparent sol-gel host. Specifically, we show that placing the Au nanorod/sol-gel matrix in an alternating current (AC) field gives rise to dramatic modulation of incident light scattered from the material. The speckle light patterns take form of beats, for which the amplitude and frequency are directly correlated with the voltage and frequency, respectively, of the applied AC field. The data indicate that the speckle beats arise from localized vibrations of the gel-embedded Au nanorods, induced through the interactions between the AC field and the electrostatically-charged nanorods. This phenomenon opens the way for new means of investigating nanoparticles in constrained environments. Applications in electro-optical devices, such as optical modulators, movable lenses, and others are also envisaged. PMID:24413086

  1. Characterization of ZnO Thin Film Deposited by Sol-Gel Process

    NASA Astrophysics Data System (ADS)

    Anand, Vijay Kumar; Sood, S. C.; Sharma, Anurekha

    2010-11-01

    ZnO is a wide band gap semiconductor which is used as transparent electrode in solar cells, chemical and gas sensors and light emitting diode etc. This paper reports the sol gel preparation and characterization of ZnO thin film. ZnO thin film was prepared by sol-gel process using zinc acetate dehydrate as a precursor, 2-methoxy ethanol as a solvent and monoethanolamine (MEA) as a stabilizer. The solution was deposited on n-type silicon (111) substrate by spin coating at 3000 rpm. Hydrolysis and condensation process produced a complex solution. After drying at 300 C, samples were annealed at 575 C in nitrogen ambient. Precise control of concentration of precursor, solvent used, spinning speed of the substrate and heat treatment conditions, are the factors which strongly affect the crystallographic orientation and morphology of the resultant ZnO films. The crystalinity of the film as found from X-ray diffraction (XRD) had different orientations, with (002) orientation as most intense having a grain size of 44 nm.

  2. Synthesis and characterization of NiO nanopowder by sol-gel process

    NASA Astrophysics Data System (ADS)

    Ningsih, Sherly Kasuma Warda

    2015-09-01

    Preparation of nickel oxide (NiO) nanopowder by sol-gel process has been studied. NiO nanopowders were obtained by sol-gel method by using nickel nitrate hexahydrate and sodium hydroxide and aquadest were used as precursor, agent precipitator and solvent, respectively. The powders were formed by drying at 110°C and followed by heating in the furnace at 400°C for 1.5 hours. The product was obtained black powder. The product was characterized by Energy Dispesive X-ray Fluorescence (ED-XRF), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The ED-XRF pattern shows the composition of NiO produced was 97.1%. The XRD pattern showed NiO forms were produced generally in monoclinic stucture. The crystalline size of NiO was obtained in the range 40-85 nm. SEM micrograph clearly showed that powder had a spherical with uniform distribution size is 0.1-1.0 µm approximately.

  3. Antimicrobial Activity of Thin Solid Films of Silver Doped Hydroxyapatite Prepared by Sol-Gel Method

    PubMed Central

    Iconaru, Simona Liliana; Chapon, Patrick; Le Coustumer, Philippe; Predoi, Daniela

    2014-01-01

    In this work, the preparation and characterization of silver doped hydroxyapatite thin films were reported and their antimicrobial activity was characterized. Silver doped hydroxyapatite (Ag:HAp) thin films coatings substrate was prepared on commercially pure Si disks by sol-gel method. The silver doped hydroxyapatite thin films were characterized by various techniques such as Scanning electron microscopy (SEM) with energy Dispersive X-ray attachment (X-EDS), Fourier transform infrared spectroscopy (FT-IR), and glow discharge optical emission spectroscopy (GDOES). These techniques have permitted the structural and chemical characterisation of the silver doped hydroxyapatite thin films. The antimicrobial effect of the Ag:HAp thin films on Escherichia coli and Staphylococcus aureus bacteria was then investigated. This is the first study on the antimicrobial effect of Ag:HAp thin films obtained by sol-gel method. The results of this study have shown that the Ag:HAp thin films with xAg = 0.5 are effective against E. coli and S. aureus after 24?h. PMID:24523630

  4. Sol-gel derived ZnO thin films: Effect of amino-additives

    NASA Astrophysics Data System (ADS)

    Hosseini Vajargah, P.; Abdizadeh, H.; Ebrahimifard, R.; Golobostanfard, M. R.

    2013-11-01

    Zinc oxide thin films were dip-coated from an alcoholic sol of zinc acetate with different amino-additives including monoethanolamine, diethanolamine, triethanolamine, triethylamine, and ethylenediamine. Sol-gel behavior, crystal structure, optoelectronic and morphological properties of thin films were investigated with focus on the effects of different amines and drying conditions. Investigations explicate the role of chemical and physical properties of amines such as organic chains, polarity, and boiling point as the main factors that cause distinct sol-gel behavior and film properties. It is shown that different amines in different molar ratios together with drying temperature cause dramatic impacts on sol transparency, stability, and consequently on structural, optoelectronic, and morphological properties of films. Notably, monoethanolamine and triethylamine films demonstrate a preferred orientation stimulated by increased molar ratio of amines. Further investigations indicated the positive effect of elevated drying temperature particularly on those films prepared from sols with high-boiling-point stabilizers. The variation of film optoelectronics seems to depend mainly on heat treatment, whereas sol chemistry influences the optical properties indirectly through the structural alteration. Peculiar morphologies in the ethylenediamine films disappeared with adjusting the drying conditions. The size of ZnO grains were approximately independent of amine types and primarily affected by the heat treatment

  5. Sol-Gel Derived Hydroxyapatite Coating on Mg-3Zn Alloy for Orthopedic Application

    NASA Astrophysics Data System (ADS)

    Singh, Sanjay; Manoj Kumar, R.; Kuntal, Kishor Kumar; Gupta, Pallavi; Das, Snehashish; Jayaganthan, R.; Roy, Partha; Lahiri, Debrupa

    2015-04-01

    In recent years, magnesium and its alloys have gained a lot of interest as orthopedic implant constituents because their biodegradability and mechanical properties are closer to that of human bone. However, one major concern with Mg in orthopedics is its high corrosion rate that results in the reduction of mechanical integrity before healing the bone tissue. The current study evaluates the sol-gel-derived hydroxyapatite (HA) coating on a selected Mg alloy (Mg-3Zn) for decreasing the corrosion rate and increasing the bioactivity of the Mg surface. The mechanical integrity of the coating is established as a function of the surface roughness of the substrate and the sintering temperature of the coating. Coating on a substrate roughness of 15-20 nm and sintering at 400C shows the mechanical properties in similar range of bone, thus making it suitable to avoid the stress-shielding effect. The hydroxyapatite coating on the Mg alloy surface also increases corrosion resistance very significantly by 40 times. Bone cells are also found proliferating better in the HA-coated surface. All these benefits together establish the candidature of sol-gel HA-coated Mg-3Zn alloy in orthopedic application.

  6. Fabrication of optical chemical ammonia sensors using anodized alumina supports and sol-gel method.

    PubMed

    Markovics, Akos; Kovács, Barna

    2013-05-15

    In this comparative study, the fabrication and the sensing properties of various reflectometric optical ammonia gas sensors are described. In the first set of experiments the role of the support material was investigated on four different sensor membranes. Two of them were prepared by the adsorption of bromocresol green indicator on anodized aluminum plates. The applied anodizing voltages were 12 V and 24 V, which resulted in different dynamic ranges and response times for gaseous ammonia. The sol-gel method was used for the preparation of the other batch of sensors. These layers were coated on anodized aluminum plates (24 V) and on standard microscope cover glasses. In spite of the identical sensing chemistry, slightly different response times were measured merely because of the aluminum surface porosity. Gas molecules can remain entrapped in the pores, which results in delayed recovery time. On the other hand, the porous oxide film provides excellent adhesion, making the anodized aluminum an attractive support for the sol-gel layer. PMID:23618145

  7. Post-deposition treatment of zirconia thermal barrier coatings using Sol-Gel alumina

    NASA Astrophysics Data System (ADS)

    Troczynski, T.; Yang, Q.; John, G.

    1999-06-01

    This article addresses the problem of gas permeability of thermal sprayed yttria-stabilized zirconia thermal barrier coatings (TBC)s. The objective of this study was to decrease the open porosity of TBCs through deposition of dense alumina ceramic on the surface of the pores. A simple infiltration technique was used, beginning with aluminum isopropoxide as sol precursor, subsequently hydrated to aluminum hydroxide sol, which decomposed at relatively low temperatures to extra-fine, readily sinterable aluminum oxide. In some experiments, the sol-gel (SG) precursor was combined with fine grains of calcined alumina, constituting high solid-yield composite sol-gel (CSG) deposits within the pores of TBCs. Sinterability in the model systems, including aluminum hydroxide sol-calcined alumina and aluminum hydroxide sol-calcined alumina-zirconia, has been studied. A number of TBC specimens were impregnated with suspensions of alumina sols and CSG. It is shown that these ceramics effectively penetrated into the pores and cracks of TBCs and reduced the coating permeability to gases. The overall reduction of porosity was however small (from 12 to 11%), preserving the strain and thermal shock tolerance of the coatings. Burner rig tests showed an increase in sealed coating lifetime under thermomechanical fatigue conditions.

  8. Preparation of the SnO2 gate pH-ISFET by sol gel technology

    NASA Astrophysics Data System (ADS)

    Chou, Jung Chuan; Wang, Yii Fang

    2001-10-01

    In this paper, the sol-gel prepared SnO2 thin film is first applied for the pH sensing. We use the SnCl2(DOT)2H2O as the precursor. It is cheaper than other methods. The resulting solution is dropped on the gate of the SiO2 gate pH-ISFET (ion sensitive field effect transistor). After baking, the thin film will convert to SnO2. We also use the thermal evaporation system to prepare the SnO2 gate MOSFET. Then, we use the Keithley 236 instrument to measure the IDS-VG curves of the SnO2 gate MOSFET and pH-ISFET for the different pH buffer solutions. Since the MOSFET and pH-ISFET are fabricated on the same silicon wafer, the properties of these devices are identical. Therefore, we can use the experimental results and theoretical model of the pH-ISFET to find the pH sensitivity and pHPZC (pH at the point of zero charge) of the sol-gel prepared SnO2 gate pH-ISFET, which are about 57.36 mV/pH and 11.3, respectively.

  9. Development of vapor deposited silica sol-gel particles for use as a bioactive materials system.

    PubMed

    Snyder, Katherine L; Holmes, Hallie R; VanWagner, Michael J; Hartman, Natalie J; Rajachar, Rupak M

    2013-06-01

    Silica-based sol-gel and bioglass materials are used in a variety of biomedical applications including the surface modification of orthopedic implants and tissue engineering scaffolds. In this work, a simple system for vapor depositing silica sol-gel nano- and micro-particles onto substrates using nebulizer technology has been developed and characterized. Particle morphology, size distribution, and degradation can easily be controlled through key formulation and manufacturing parameters including water:alkoxide molar ratio, pH, deposition time, and substrate character. These particles can be used as a means to rapidly modify substrate surface properties, including surface hydrophobicity (contact angle changes >15) and roughness (RMS roughness changes of up to 300 nm), creating unique surface topography. Ions (calcium and phosphate) were successfully incorporated into particles, and induced apatitie-like mineral formation upon exposure to simulated body fluid Preosteoblasts (MC3T3) cultured with these particles showed up to twice the adhesivity within 48 h when compared to controls, potentially indicating an increase in cell proliferation, with the effect likely due to both the modified substrate properties as well as the release of silica ions. This novel method has the potential to be used with implants and tissue engineering materials to influence cell behavior including attachment, proliferation, and differentiation via cell-material interactions to promote osteogenesis. PMID:23585242

  10. Rapid prototyping of integrated sol-gel devices for astronomical interferometry

    NASA Astrophysics Data System (ADS)

    Ghasempour, A.; Alexandre, D.; Brites, C.; Moreira, P. J.; Reynaud, F.; Marques, P. V. S.; Leite, A. M. P.; Garcia, P. J. V.

    2008-07-01

    Integrated optics is a mature technology with standard applications to telecommunications. Since the pioneering work of Berger et al. 1999 beam combiners for optical interferometry have been built using this technology. Classical integrated optics device production is very expensive and time consuming. The rapid production of devices using hybrid sol-gel materials in conjunction with UV laser direct writing techniques allows overcoming these limitations. In this paper this technology is tested for astronomical applications. We report on the design, fabrication and characterization of multiaxial two beam combiners and a coaxial beam combiner for astronomical interferometry. Different multiaxial two beam combiner designs were tested and high contrast (better than 90%) was obtained with a 1.3 ?m laser diode and with an SLD ( ?0 = 1.26 ?m, FWHM of 60 nm). High contrast fringes were produced with 1.3 ?m laser diode using the coaxial two beam combiner. These results show that hybrid sol-gel techniques produce devices with high quality, allowing the rapid prototyping of new designs and concepts for astronomy.

  11. "Beating speckles" via electrically-induced vibrations of Au nanorods embedded in sol-gel.

    PubMed

    Ritenberg, Margarita; Beilis, Edith; Ilovitsh, Asaf; Barkai, Zehava; Shahmoon, Asaf; Richter, Shachar; Zalevsky, Zeev; Jelinek, Raz

    2014-01-01

    Generation of macroscopic phenomena through manipulating nano-scale properties of materials is among the most fundamental goals of nanotechnology research. We demonstrate cooperative "speckle beats" induced through electric-field modulation of gold (Au) nanorods embedded in a transparent sol-gel host. Specifically, we show that placing the Au nanorod/sol-gel matrix in an alternating current (AC) field gives rise to dramatic modulation of incident light scattered from the material. The speckle light patterns take form of "beats", for which the amplitude and frequency are directly correlated with the voltage and frequency, respectively, of the applied AC field. The data indicate that the speckle beats arise from localized vibrations of the gel-embedded Au nanorods, induced through the interactions between the AC field and the electrostatically-charged nanorods. This phenomenon opens the way for new means of investigating nanoparticles in constrained environments. Applications in electro-optical devices, such as optical modulators, movable lenses, and others are also envisaged. PMID:24413086

  12. Conventional E-glass fibre light guides: self-sensing composite based on sol gel cladding

    NASA Astrophysics Data System (ADS)

    Wang, L.; Kister, G.; Ralph, B.; Talbot, J. D. R.; Fernando, G. F.

    2004-02-01

    The aim of this study was to modify conventional reinforcing E-glass fibres to enable them to act as optical waveguides and subsequently as sensor devices. This required the glass fibres to be coated with a relatively homogeneous coating with a corresponding refractive index that was lower than the E-glass fibre (1.56). Although a range of coating materials are available, this study focused on using materials that are generally used as sizing agents for glass fibres to improve the adhesion to the matrix. Two different methods based on conventional sol gel processing were used to obtain crack-free coatings. In the first method, tetraethoxysilane (TEOS) and polyvinyl alcohol were used as precursors. In the second method, acid-catalysed solutions of TEOS mixed with 3-glycidoxypropyltrimethoxysilane were used as precursors. UV visible transmission results showed that the films had low absorption and high transparency in the visible range. The refractive indices of the films were found to be a function of the molar fractions of the major chemical components. A simple impregnation procedure was used to apply the coating to the E-glass fibre bundles. The light transmission characteristics of the coated fibres along with their mechanical properties were evaluated. The sol gel coatings were shown to be effective in converting the conventional E-glass fibres into light guides.

  13. Surface acoustic wave characterization of optical sol-gel thin layers.

    PubMed

    Fall, Dame; Compoint, François; Duquennoy, Marc; Piombini, Hervé; Ouaftouh, Mohammadi; Jenot, Frédéric; Piwakowski, Bogdan; Belleville, Philippe; Ambard, Chrystel

    2016-05-01

    Controlling the thin film deposition and mechanical properties of materials is a major challenge in several fields of application. We are more particularly interested in the characterization of optical thin layers produced using sol-gel processes to reduce laser-induced damage. The mechanical properties of these coatings must be known to control and maintain optimal performance under various solicitations during their lifetime. It is therefore necessary to have means of characterization adapted to the scale and nature of the deposited materials. In this context, the dispersion of ultrasonic surface waves induced by a micrometric layer was studied on an amorphous substrate (fused silica) coated with a layer of ormosil using a sol-gel process. Our ormosil material is a silica-PDMS mixture with a variable polydimethylsiloxane (PDMS) content. The design and implementation of Surface Acoustic Wave InterDigital Transducers (SAW-IDT) have enabled quasi-monochromatic Rayleigh-type SAW to be generated and the dispersion phenomenon to be studied over a wide frequency range. Young's modulus and Poisson's ratio of coatings were estimated using an inverse method. PMID:26930248

  14. Solution chemistry optimization of sol-gel processed PZT thin films

    SciTech Connect

    Lockwood, S.J. Schwartz, R.W.; Tuttle, B.A.; Thomas, E.V.

    1992-12-31

    We have optimized the ferroelectric properties and microstructural characteristics of sol-gel PZT thin films used in a CMOS-integrated, 256 bit ferroelectric non-volatile memory. The sol-gel process utilized in our work involved the reaction of Zr n-butoxide, Ti isopropoxide, and Pb (IV) acetate in a methanol/acetic acid solvent system. A 10-factor screening experiment identified solution concentration, acetic acid addition, and water volume as the solution chemistry factors having the most significant effects on the remanent polarization, coercive field, ferroelectric loop quality, and microstructural quality. The optimal values for these factors were determined by running a 3-factor uniform shell design, modeling the responses, and testing the models at the predicted optimal conditions. The optimized solution chemistry generated 3-layer, 300--400 nm thick films on RuO{sub 2} coated silicon substrates with coercive fields of less than 25 kv/cm (a 40--50% improvement over the original solution chemistry), a remanent polarization of 25--30 {mu}C/cm, and a reduction in the pyrochlore phase content below observable levels.

  15. Evaporation induced self assembly and rheology change during sol-gel coating

    NASA Astrophysics Data System (ADS)

    Lee, Chang H.; Lu, Yunfeng; Shen, Amy Q.

    2006-05-01

    Thin films with self-assembled nanostructures are important in applications such as catalysis and biosensor technology. A major technique used to prepare such films is sol-gel processing. This technique involves depositing a complex fluid on a substrate by dip, spin, or spray coating, followed by allowing the film to evaporate and form self-assembled nanostructures. Since the composition of the film during coating is central to understanding how changing chemical and physical conditions affect the properties and microstructures of the films, we investigate the rheological properties of the entrained fluid film and its subsequent impact on the steady state film thickness during the evaporation-induced self-assembly process. We perform systematic experiments to measure the meniscus shape and film thickness during sol-gel dip coating. We observe that the experimental data of film thickness lie way below the Landau-Levich-Derjaguin prediction from the classic film-coating results. To explain this discrepancy, we present a thin film model based on the lubrication approximation with an evaporation effect. Our results show that evaporation-induced self-assembly leads to rheological variations in the entrained film and, consequently, alters the film thickness. The predicted film thickness based on the evaporation-induced rheology variation model compares well with the experiments.

  16. Percutaneous external fixator pins with bactericidal micron-thin sol-gel films for the prevention of pin tract infection.

    PubMed

    Qu, Haibo; Knabe, Christine; Radin, Shula; Garino, Jonathan; Ducheyne, Paul

    2015-09-01

    Risk of infection is considerable in open fractures, especially when fracture fixation devices are used to stabilize the fractured bones. Overall deep infection rates of 16.2% have been reported. The infection rate is even greater, up to 32.2%, with external fixation of femoral fractures. The use of percutaneous implants for certain clinical applications, such as percutaneous implants for external fracture fixation, still represents a challenge today. Currently, bone infections are very difficult to treat. Very potent antibiotics are needed, which creates the risk of irreversible damage to other organs, when the antibiotics are administered systemically. As such, controlled, local release is being pursued, but no such treatments are in clinical use. Herein, the use of bactericidal micron-thin sol-gel films on metallic fracture fixation pins is reported. The data demonstrates that triclosan (2,4,4'-trichloro-2'-hydroxydiphenylether), an antimicrobial agent, can be successfully incorporated into micron-thin sol-gel films deposited on percutaneous pins. The sol-gel films continuously release triclosan in vitro for durations exceeding 8 weeks (longest measured time point). The bactericidal effect of the micron-thin sol-gel films follows from both in vitro and in vivo studies. Inserting percutaneous pins in distal rabbit tibiae, there were no signs of infection around implants coated with a micron-thin sol-gel/triclosan film. Healing had progressed normally, bone tissue growth was normal and there was no epithelial downgrowth. This result was in contrast with the results in rabbits that received control, uncoated percutaneous pins, in which abundant signs of infection and epithelial downgrowth were observed. Thus, well-adherent, micron-thin sol-gel films laden with a bactericidal molecule successfully prevented pin tract infection. PMID:26036176

  17. SiO{sub 2} sol-gel composite films containing redox-active, polypyridyl-ruthenium polymers

    SciTech Connect

    Sykora, M.; Maxwell, K.A.; Meyer, T.J.

    1999-08-09

    SiO{sub 2}-based sol-gels have been utilized extensively as media for incorporating redox-active, luminescent, or catalytically active molecules. The mild preparative conditions allow for the incorporation of organic and inorganic dyes, and their glasslike optical properties make sol-gel composites attractive media for various optical applications. The high porosities and large surface areas of these materials have led to applications in chemical sensing and catalysis. The authors report here an approach which is based on the incorporation of Ru{sup II}-bpy derivatized polystyrene polymers and results in stable film structures on optically transparent ITO electrodes.

  18. Sol-gel derived Al and Ga co-doped ZnO thin films: An optoelectronic study

    NASA Astrophysics Data System (ADS)

    Ebrahimifard, Reza; Golobostanfard, Mohammad Reza; Abdizadeh, Hossein

    2014-01-01

    Al and Ga co-doped ZnO (AGZO) thin films with different doping contents of 0.5-4 at.% were synthesized via sol-gel route using dip coating method and the results were compared to the single doped specimens Al:ZnO (AZO) and Ga:ZnO (GZO). All samples were highly transparent in visible region (T > 85%) with band gap values around 3.3 eV. Introduction of Al and Ga to the ZnO crystal structure decreased the crystallinity and reduced the particle size of the films. Electrical resistivity was investigated and engineered in this study as the main parameter. Single doped samples showed reduction of resistivity compared to the un-doped ZnO. In this regard, Ga was more efficient than Al in decreasing the electrical resistivity. Furthermore, samples with 1 at.% Al and 1 at.% Ga showed the minimum amount of electrical resistivity. Co-doping was performed with two different approaches including variable doping content (Al + Ga ≠ cte) and constant doping content (Al + Ga = 0.5, 1, and 2 at.%) for the sake of the comparison with single doped samples. Samples with Al = 1 at.% and Ga = 1 at.% showed the lowest electrical resistivity in AGZO samples of former approach. However, in latter approach the lowest resistivity was obtained in Al + Ga = 2 at.% sample. The results proved the capability of co-doped samples in optoelectronic industry regarding partially substitution of expensive Ga with Al and obtaining co-doped AGZO transparent conductive thin films with lower resistivity compared to conventional AZO thin films and also achieving commercial advantages compared to costly GZO thin films.

  19. Transport and magnetotransport studies on Sol-Gel grown nanostructured La0.7Pb0.3MnO3 manganites.

    PubMed

    Solanki, P S; Doshi, R R; Thaker, C M; Pandya, Swati; Ganesan, V; Kuberkar, D G

    2009-09-01

    Sol-Gel synthesis offers relatively inexpensive scale processing of mixed oxide materials with a good control over the stoichiometry and morphology which helps to tailor the required materials on atomic scale to suit specific applications. Nanophasic polycrystalline samples of La0.7Pb0.3MnO3 (LPMO) manganites having perovskite type structure synthesized by novel Sol-Gel technique using acetate precursor route were sintered at various temperatures in the range 950-1150 degrees C for studying the effect of grain size modifications on their structural, transport and magnetotransport properties. X-ray diffraction (XRD) studies show that the samples exhibit rhombohedral structure crystallizing in space group R-3C. Microstructural investigations using Scanning Electronic Microscopy (SEM), Atomic Force Microscopy (AFM) and Lateral Force Microscopy (LFM) measurements reveal the observation of secondary grain growth behavior starting in the sample sintered at 1000 degrees C. The d.c. four probe resistivity measurements with and without applied magnetic field in the temperature range of 2-380 K, show the effect of secondary grain growth on the magnetoresistance (MR) behavior of LPMO manganites. The microstructural studies show the atomic scale engineering at nanoscale which is reflected in the improvement of surface to volume ratio (D(-1)) which in turn modifies the physical properties of samples under investigation. All the samples exhibit resistivity minima at approximately 30 K which can be explained in terms of e-e interaction at 0 Tesla field. There is a correlation between the parameters derived from e-e scattering model and the secondary grain growth present in the samples. The results of the microstructural and MR measurements on the nanostructured LPMO manganites have been discussed in detail. PMID:19928288

  20. Acrylate-silica polymer nanocomposites obtained by sol-gel reactions. Structure, properties and scaffold preparation

    NASA Astrophysics Data System (ADS)

    Rodriguez Hernandez, Jose Carlos

    The manuscript deals with the development and characterization of hybrid materials based on poly(hydroxyethyl acrylate) (hereafter PHEA) reinforced by the inclusion of an amorphous silica phase. Both phases were simultaneously synthesized: the organic phase underwent a free radical polymerization reaction induced by the small addition of a thermal initiator (benzoyl peroxide); besides, silica (SiO2) was polymerized by an acid catalyzed sol-gel reaction of the silicon alkoxide tetraethoxysilane (hereafter TEOS). The sol-gel reaction conditions where silicon dioxide is formed influence the final silica structure: degree of condensation, linear versus branched intermediate species, average size, and so on. Some of the key parameters to control SiO2 topology on sol-gel derived composites include the catalyst nature used to increase the alkoxide reactivity (as well as its amount, pH), the available water to hydrolyze the silica precursor (referred to the stoichiometric amount needed to fully hydrolyze one molecule of TEOS) and ratio between the organic and inorganic phases on the final hybrid. The former (catalyst) and the second (water) conditions were fixed so as to synthesize materials with silica average sizes around tens of nanometres (nanocomposites); the latter, the relative ratio between organic and inorganic phases, was systematically changed. Besides, it is introduced a methodology to prepare a new kind of scaffolds made by nanocomposites whose pore morphology consists of a cylindrical channel mesh, which are perpendicular between themselves. The procedure is based on the well-known method of intermediate templates, this time prepared by a stack of woven fabrics which are first pressed and afterwards sintered. After the filling of the holes left inside the template by the monomeric solution and subsequent thermal polymerization, templates are removed by the selective solvent of the material it is made up. A suitable template preparation is found to be crucial, since the sintering of localized points between neighbour fabrics gives rise to transversal holes which make that porous structure three-dimensionally interconnected. Porosity values equal 60%.

  1. Encapsulation of fluorescence vegetable extracts within a templated sol-gel matrix

    NASA Astrophysics Data System (ADS)

    Lacatusu, Ioana; Badea, Nicoleta; Nita, Rodica; Murariu, Alina; Miculescu, Florin; Iosub, Ion; Meghea, Aurelia

    2010-04-01

    The sol-gel encapsulation of labile substances with specific properties and recognition functions within robust polymer matrices remains a challenging task, despite the considerable research that has been focused on this field. Numerous studies have been reported in the field of sol-gel processes regarding different physical and chemical packing of sensitive biomolecules encapsulated in silica matrix. In this paper the classical sol-gel synthesis has been used under mild conditions in order to minimize denaturizing effects on encapsulated active vegetable extracts from flavones class. The silica templated matrix was obtained by using two types of surfactants with different alkyl chain (didodecyldimethyl-ammonium bromide and trioctadecylmetilammonium bromide) as structure-directing agents for the silicon oxide framework. An organic precursor of silicic acid (triethoxymethylsilane) has been used and it was processed by competitive hydrolysis and polycondensation reactions under controlled directions assured by the presence of oriented template. Silica materials thus obtained are used for encapsulation of two flavonoid samples containing as active principles two sources: rutin and a vegetable extract from Begonia plant. The synthesis of encapsulated nanocompounds has been achieved taking into consideration the specific interaction between the colloidal gel precursors and molecular structures of selected biomolecules. The main objective was to improve the encapsulation conditions for specific biomolecules, searching for the highest stability and functionality without loosing the quality of the flavonoid properties, particularly optical properties like fluorescence. The structural properties of the encapsulated samples have been studied by FT-IR and UV-VIS spectroscopy, thermal analysis and SEM/EDX analysis. The fluorescence experiments showed that, in the case of all four encapsulated samples, the fluorescence spectra manifest a significant increase in intensity signals, with more than 10 times for individual flavonoid and 50 times for Begonia extract. This behaviour are mainly assigned to the physical interaction of flavonoid molecules with the residual hydroxyl groups of silica, excellent synergistic properties of silica and the favourable conformation arrangement of organic molecules inside the silica network. The size distribution of synthesised polymeric silica materials have been investigated by dynamic light scattering (DLS) and optical microscopy.

  2. High surface area neodymium phosphate nano particles by modified aqueous sol-gel method

    SciTech Connect

    Sankar, Sasidharan; Warrier, Krishna Gopakumar; Komban, Rajesh

    2011-12-15

    Graphical abstract: Synthesis of nano rod shaped neodymium phosphate particles with specific surface area as high as 107 m{sup 2} g{sup -1} and particles could be compacted and sintered at as low as 1300 Degree-Sign C to a density of 98.5% (theoretical) with an average grain size of {approx}1 {mu}m. Highlights: Black-Right-Pointing-Pointer Nano size neodymium phosphate is synthesized and characterized using a novel modified aqueous sol gel process. Black-Right-Pointing-Pointer Specific surface area above 100 m{sup 2} g{sup -1} achieved without the addition of any complexing agents. Black-Right-Pointing-Pointer High sintered density reported than the density obtained for powder synthesized through conventional solid state reaction. Black-Right-Pointing-Pointer The particles are nano sized and have rod shape morphology and are retained at higher temperatures. Black-Right-Pointing-Pointer An average grain size of {approx}1 {mu}m obtained for sintered NdPO{sub 4} after thermal etching at 1400 Degree-Sign C. -- Abstract: Synthesis of nano rod shaped neodymium phosphate (NdPO{sub 4}) particles with specific surface area as high as 107 m{sup 2}g{sup -1} and an average length of 50 nm with aspect ratio 5 was achieved using modified sol gel method. Crystallite size calculated from the X-ray diffraction data by applying Scherer equation was 5 nm for the precursor gel after calcination at 400 Degree-Sign C. NdPO{sub 4} was first precipitated from neodymium nitrate solution using phosphoric acid followed by peptization using dilute nitric acid and further gelation in ammonia atmosphere. The calcined gel powders were further characterized by surface area (Brunauer-Emmet-Teller nitrogen adsorption analysis), Transmission electron microscopy, scanning electron microscopy, UV-vis and FT-IR analysis. Transmission electron microscopy confirms the formation of rod like morphology from the sol, gel and the calcined particles in nano size range. These particles could be compacted and sintered at as low as 1300 Degree-Sign C to a density of 98.5% (theoretical) with an average grain size of {approx}1 {mu}m.

  3. Stabilization of ZnMnO3 Phase from Sol-gel Synthesized Nitrate Precursors

    SciTech Connect

    Saraf, Laxmikant V.; Nachimuthu, Ponnusamy; Engelhard, Mark H.; Baer, Donald R.

    2010-02-01

    The stabilization and analysis of pure ZnMnO3 spinel phase may help to understand the solubility limits of Mn in ZnO in wurtzite and spinel cubic structures. In this report, synthesis and characterization of stable ZnMnO3 phase is discussed which is extracted from sol-gel synthesis of zinc and manganese nitrate precursors. The reflections at higher diffraction angles for this known cubic system with space group Fd3m were calculated with the help of JADE 8.0 program. High resolution X-ray photoelectron spectroscopy measurements of Mn3p position of ZnMnO3 compared with ZnMn2O4 showed a higher binding energy shift ~0.85 eV indicating Mn4+ valence state in ZnMnO3.

  4. Optical properties of ZnO powder prepared by using a proteic sol-gel process

    NASA Astrophysics Data System (ADS)

    Kwon, Bong-Joon; Woo, Hyun-Joo; Park, Ji-Yeon; Jang, Kiwan; Lim, Seung-Hyuk; Cho, Yong-Hoon

    2013-03-01

    We have studied the optical properties of ZnO powder synthesized by using a proteic sol-gel process with coconut water as the precursor. The energy dispersive X-ray spectrometer and X-ray diffraction results show high purity of the synthesized ZnO powder. From the low-temperature (12 K) and power-dependent PL spectra, the donor-bound exciton, the acceptor-bound exciton, the donor-to-acceptor pair (DAP), and the phonon-replica of the DAP transition have been observed at 3.38, 3.34, 3.26, and 3.19 eV, respectively. The free exciton emission (˜3.3 eV) is also observed at 300 K in the temperature-dependent PL spectra.

  5. Dynamical transition of heat transport in a physical gel near the sol-gel transition

    PubMed Central

    Kobayashi, Kazuya U.; Oikawa, Noriko; Kurita, Rei

    2015-01-01

    We experimentally study heat transport in a gelatin solution near a reversible sol-gel transition point where viscosity strongly depends on temperature. We visualize the temperature field and velocity field using thermochromic liquid crystals and polystyrene latex particles, respectively. During the initial stages of heating, we find that heat transport undergoes a dynamical transition from conductive to convective. Subsequently, during later stages, we observe that the transport dynamics are much more complex than conventional thermal convections. At the sample’s surface we observe the formation of stagnant domains, which lack fluid flow. Their formation is not due to the effects of local cooling. We determine that it is the dynamics of these stagnant domains that induce convective-conductive-convective transitions. PMID:26690696

  6. Towards new levels for stacking of sol-gel functional coatings.

    PubMed

    Dieudonn, X; Vall, K; Belleville, P

    2011-08-15

    High optical performance coatings prepared by a liquid deposition process have been studied with focus on the parameters playing a role on the layer stacking ability. During the development of multilayer optical coatings, defects such as cracks, scattering and a refractive index gradient could appear. In order to understand the origins of these limitations, the investigation was performed on colloidal stacks of single and multi-materials. This study has rendered it possible to define the main process parameters as well as the physical and chemical parameters of the suspensions influencing the stacking capacity. This work is a first step to obtaining evidence of a relationship between the thin film microstructure induced by deposition conditions and the ability to achieve sol-gel thick films with good optical (homogeneous) and mechanical (crack-free) properties. PMID:21934999

  7. Active fibers from sol-gel derived granulated silica: state of the art and potential

    NASA Astrophysics Data System (ADS)

    Romano, Valerio; Sandoz, Frederic

    2010-10-01

    In the recent past we have studied the granulated silica method as a versatile and cost effective way of fiber preform production. We have used the sol-gel technology combined with a laser-assisted remelting step to produce high homogeneity Rare Earth or Transition Metal - activated microsized particles for the fiber core. For the fiber cladding pure or index-raised granulated Silica has been employed. Silica glass tubes, appropriately filled with these granular materials, are then drawn to fibers, eventually after an optional quality enhancing vitrification step. The process offers a high degree of compositional flexibility with respect to dopants; it further facilitates to achieve high concentrations even in cases when several dopants are used. By this "rapid preform production" technique, that is also ideally suited for the preparation of microstructured optical fibers, several fibers ranging from broadband emitters, PCFs and large mode area fibers have been produced and will be presented here.

  8. Biocompatibility and Reduced Drug Absorption of Sol-Gel-Treated PDMS for Microfluidic Cell Culture Applications

    PubMed Central

    Gomez-Sjoberg, Rafael; Leyrat, Anne A.; Houseman, Benjamin T.; Shokat, Kevan; Quake, Stephen R.

    2010-01-01

    Poly(dimethyl siloxane) (PDMS) -based microfluidic devices are now commonly used for a wide variety of biological experiments, including cell culture assays. However, the porous, hydrophobic polymer matrix of PDMS rapidly absorbs small hydrophobic molecules, including hormones and most small-molecule drugs. This makes it challenging to perform experiments that require such substances in PDMS microfluidic devices. This study presents evidence that a sol-gel treatment of PDMS that fills the polymer matrix with silica nanoparticles is effective at reducing the absorption of drugs into the material while preserving its biocompatibility, transparency, and oxygen permeability. We show that the absorption of two anti-cancer drugs, Camptothecin and a kinase inhibitor, is reduced to such an extent that on-chip microfluidic cell culture experiments can recapitulate the results obtained off-chip. PMID:20936785

  9. Solar heat reflective glass by nanostructured sol-gel multilayer coatings

    NASA Astrophysics Data System (ADS)

    Nagamedianova, Z.; Ramrez-Garca, R. E.; Flores-Arvalo, S. V.; Miki-Yoshida, M.; Arroyo-Ortega, M.

    2011-10-01

    New 3-layer near-infrared reflective glasses were prepared by coating clear float soda-lime glass with nanostructured TiO 2 and SiO 2 films using a dip coating technique. Reflective interference filters at NIR region (800-1000 nm) were designed by simulation and prepared onto 4 mm clear glass. Optical, microstructural and mechanical properties were determined for the coated glasses. 3-layer sol-gel glasses show high visible transmittance >70% combined with high solar reflectance about 30% (with reflectivity up to 60% at region from 800 to 950 nm) and high UV blockage (transmittance <35%). Due to good abrasion resistance of the filters, application for monolithic windows in automotive and architectural areas is promising.

  10. Sol-gel-based doped granulated silica for the rapid production of optical fibers

    NASA Astrophysics Data System (ADS)

    Romano, Valerio; Pilz, Soenke; Etissa, Dereje

    2014-03-01

    In the recent past we have studied the granulated silica method as a versatile and cost effective way of fiber preform production. We have used the sol-gel technology combined with a laser-assisted remelting step to produce high homogeneity rare earth or transition metal-activated microsized particles for the fiber core. For the fiber cladding pure or index-raised granulated silica has been employed. Silica glass tubes, appropriately filled with these granular materials, are then drawn to fibers, eventually after an optional quality enhancing vitrification step. The process offers a high degree of compositional flexibility with respect to dopants; it further facilitates to achieve high concentrations even in cases when several dopants are used and allows for the implementation of fiber microstructures. By this "rapid preform production" technique, that is also ideally suited for the preparation of microstructured optical fibers, several fibers have been produced and three of them will be presented here.

  11. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, Richard W. (Pleasant Hill, CA)

    1996-01-01

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

  12. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, Richard W. (Pleasant Hill, CA)

    1995-01-01

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes.ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

  13. Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, R.W.

    1998-04-28

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes {<=}1000 {angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

  14. Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, Richard W. (Pleasant Hill, CA)

    1998-04-28

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000 .ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

  15. Mechanical properties of solgel derived SiO2 nanotubes

    PubMed Central

    Antsov, Mikk; Vlassov, Sergei; Dorogin, Leonid M; Vahtrus, Mikk; Zabels, Roberts; Lange, Sven; Lhmus, Rnno

    2014-01-01

    Summary The mechanical properties of thick-walled SiO2 nanotubes (NTs) prepared by a solgel method while using Ag nanowires (NWs) as templates were measured by using different methods. In situ scanning electron microscopy (SEM) cantilever beam bending tests were carried out by using a nanomanipulator equipped with a force sensor in order to investigate plasticity and flexural response of NTs. Nanoindentation and three point bending tests of NTs were performed by atomic force microscopy (AFM) under ambient conditions. Half-suspended and three-point bending tests were processed in the framework of linear elasticity theory. Finite element method simulations were used to extract Youngs modulus values from the nanoindentation data. Finally, the Youngs moduli of SiO2 NTs measured by different methods were compared and discussed. PMID:25383292

  16. H2-induced copper and silver nanoparticle precipitation inside sol-gel silica optical fiber preforms.

    PubMed

    Chahadih, Abdallah; El Hamzaoui, Hicham; Cristini, Odile; Bigot, Laurent; Bernard, Rmy; Kinowski, Christophe; Bouazaoui, Mohamed; Capoen, Bruno

    2012-01-01

    Ionic copper- or silver-doped dense silica rods have been prepared by sintering sol-gel porous silica xerogels doped with ionic precursors. The precipitation of Cu or Ag nanoparticles was achieved by heat treatment under hydrogen followed by annealing under air atmosphere. The surface plasmon resonance bands of copper and silver nanoparticles have been clearly observed in the absorption spectra. The spectral positions of these bands were found to depend slightly on the particle size, which could be tuned by varying the annealing conditions. Hence, transmission electron microscopy showed the formation of spherical copper nanoparticles with diameters in the range of 3.3 to 5.6 nm. On the other hand, in the case of silver, both spherical nanoparticles with diameters in the range of 3 to 6 nm and nano-rods were obtained. PMID:22937818

  17. Large low-field magnetoresistance in nanocrystalline magnetite prepared by sol-gel method.

    PubMed

    Lu, Z L; Zou, W Q; Lv, L Y; Liu, X C; Li, S D; Zhu, J M; Zhang, F M; Du, Y W

    2006-11-30

    Nanocrystalline magnetite Fe3O4 samples with a grain size of about 40 nm have been synthesized by an optimized sol-gel method. The single phase of spinel magnetite was confirmed by both X-ray diffraction and transmission electron microscopy. It has been found that the magnetoresistance of the samples at low field (LFMR) is relatively large, and with the decrease of temperature its value at a field of 0.5 T changes dramatically from -2.5% at 300 K to -17.0% at 55 K. With the further decrease of temperature a sharp drop occurs for the magnitude of the magnetoresistance (MR), regarded as a spin (cluster) glass transition in the surface region of the grains that can be confirmed by the zero-field-cooled and field-cooled magnetization and ac susceptibility measurement. The mechanism of the magnetic and transport properties was discussed. PMID:17125346

  18. Integrated optics structures on sol-gel derived organic-inorganic hybrids for optical communications

    NASA Astrophysics Data System (ADS)

    Andr, P. S.; Vicente, C. M. S.; Fernandes, V.; Marques, C. A. F.; Pecoraro, E.; Nogueira, R. N.; Wada, N.; Carlos, L. D.; Marques, P. G.; Ferreira, R. A. S.

    2011-05-01

    Organic-inorganic hybrid materials are a technologically key class of advanced multifunctional materials that fulfil the challenging strict requirements of the beginning of the century: higher levels of sophistication, miniaturisation, recyclability, reliability and low energy consumption with potential to be used as low-cost components in optical networks operating at high bit rates. In this work, high-rejection optical filters (19 dB) first-order Bragg gratings inscribed in channel waveguides written in thin films of sol-gel derived organic-inorganic hybrid based on methacrylic acid modified zirconium tetrapropoxide, Zr(OPrn)4, (so-called di-ureasils), using UV-laser direct-write method.

  19. Polyester-inorganic nanocomposite materials via sol-gel reactions: Synthesis and characterization of fundamental properties

    NASA Astrophysics Data System (ADS)

    Lambert, Alexander Adam, III

    A scheme was developed for producing poly(ethylene terephthalate (PET) ionomer)/silicate hybrid materials via polymer-in situ sol-gel reactions for tetraethylorthosilicate (TEOS) using different solvents. Scanning electron microscopy/EDAX studies revealed that silicate structures can be grown deep within PET ionomer films that were melt pressed from silicate-incorporated resin pellets. 29Si solid-state NMR spectroscopy revealed considerable, successful Si-O-Si bond formation, but also a significant fraction of uncondensed SiOH groups. 23Na solid-state NMR spectra suggested the presence of ionic aggregates within the unfilled PET ionomer and that these aggregates do not suffer major structural re-arrangements by silicate incorporation. For an ionomer treated with TEOS using MeCl2 solvent, Na + ions are less self-associated than in the unfilled control, suggesting silicate intrusion between PET-SO3- Na + ion pair associations. The ionomer treated with TEOS + tetrachloroethane had more poorly formed ionic aggregates, which illustrates the influence of solvent type on ionic aggregation. First-scan DSC thermograms for the ionomers demonstrate an increase in crystallinity after the incorporation of silicates, but solvent induced crystallization also appears to be operative. Second-scan DSC thermograms also suggest that the addition of silicate particles is not the only factor implicated in re-crystallization, and that solvent type is important even in second scan behavior. Silicate incorporation does not profoundly affect the second scan Tg vs. solvent type, i.e., chain mobility in the amorphous regions is not severely restricted by silicate incorporation. Re-crystallization and melting in these hybrids appears to be due to an interplay between a solvent induced crystallization that strongly depends on solvent type, and interactions between PET chains and in situ-grown, sol-gel-derived silicate particles. Isothermal studies confirmed that the crystallization rate and melting behavior of PET 5% Na+ ionomers depend on processing conditions. PET ionomer/ORMOSIL composites were formed via in situ sol-gel reactions using the ionic regions of PET as preferential reaction sites. TGA analysis revealed successful uptake for all three different solvents and TEOS:MTES composition ratios. TGA derivative curves suggest that for the THF and MeCl2 carrier solvent systems the MTES-generated network interacts more with the PET ionomer matrix. In the case of TCE, the TEOS-generated network interaction appears to be more operative. First scan DSC traces reveal that the in situ sol-gel processing of ORMOSIL phases induces PET ionomer crystallinity, although systems with higher silicate uptake have reduced induced crystallinity. Second scan DSC traces show that Tg is not effected by the incorporation of silicates into the PET ionomer. Also, for the ORMOSIL phases generated using THF and MeCl2 as the swelling solvent, only the pure silicate networks (synthesized using only TEOS) allow recrystallization and melting during the quick scan timeframe. It is thought that the presence of semi-organic MTES silicate networks do not allow fast nucleation onto the inorganic nuclei. (Abstract shortened by UMI.)

  20. Synthesis of nanosized platinum based catalyst using sol-gel process

    NASA Astrophysics Data System (ADS)

    Ingale, S. V.; Wagh, P. B.; Bandyopadhyay, D.; Singh, I. K.; Tewari, R.; Gupta, S. C.

    2015-02-01

    The nano-sized platinum based catalysts using high surface area silica support have been prepared by sol-gel method. Tetramethoxysilane (TMOS) diluted in methanol was hydrolyzed to form a porous silica gel. Platinum (2%) was loaded at sol state using platinum chloride solution. After gelation, the solvent from the gel pores was extracted at ambient temperature which resulted in porous silica matrix incorporated with nanosized platinum. X-ray diffraction studies indicated the presence of elemental platinum in the silica-platinum composites. Transmission electron microscopy of the platinum -silica composites revealed that nanosized platinum particles of about 5-10 nm are homogeneously dispersed in silica matrix. Chemisorptions studies showed high dispersion (more than 50%) of platinum on silica support with specific surface area of 400 m2/g which puts them as promising candidates as catalyst in heterogeneous reactions.

  1. Integrated ultrasonic transducers made by the sol gel spray technique for structural health monitoring

    NASA Astrophysics Data System (ADS)

    Kobayashi, M.; Jen, C.-K.; Moisan, J.-F.; Mrad, N.; Nguyen, S. B.

    2007-04-01

    Integrated piezoelectric-based ultrasonic transducers (UTs) have been developed for potential structural health monitoring. Fabrication techniques and performance evaluation of these transducers at selected monitoring sites are presented. Our novel transducer fabrication approach focuses on the use of handheld and readily accessible equipment to perform sol-gel spray coating, including the use of a heat gun or a torch, to carry out drying and firing, poling and electrode fabrication. The application of these integrated UTs for thickness measurement of graphite/epoxy composites, thickness monitoring of ice build up on aluminum plates at low temperatures, viscosity measurement of a cooling oil flow at temperatures up to 160 C and monitoring metal debris in cooling oil engines is demonstrated.

  2. Nanorods of Various Oxides and Hierarchically Structured Mesoporous Silica by Sol-Gel Electrophoresis

    SciTech Connect

    Limmer, Steven J.; Hubler, Timothy L.; Cao, Guozhong

    2003-01-02

    In this paper, we report the template-based growth of nanorods of oxides and hierarchically structured mesoporous silica, formed by means of a combination of sol-gel processing and elecrophoretic deposition. Both single metal oxides (TiO2) and complex oxides (Pb(Zr0.52Ti0.48)O3) have been grown by this method. This method has also been applied to the growth of nanorods of mesoporous silica having an ordered pore structure, where the pores are aligned parallel to the long axis of the nanorod. Uniformly sized nanorods of about 125-200 nm in diameter and 10 um in length were grown over large areas with near unidirectional alignment. Appropriate sol preparation yielded the desired stoichiometric chemical composition and crystal structure of the oxide nanorods, with a heat treatment (500-700 C for 15-30 min) for crystallization, densification and any necessary pyrolysis.

  3. TiO2 nanosized powders controlling by ultrasound sol-gel reaction.

    PubMed

    Latt, Kyaing Kyaing; Kobayashi, Takaomi

    2008-04-01

    We studied that anatase-TiO2 powders prepared from sol-gel process of titanium tetra-isopropoxide (TTIP) were developed under ultrasonic irradiation with different frequency of 28, 45 and 100 kHz. The irradiated ultrasound (US) was controlled by using semi-cylindrical reflection plate that was placed onto the vicinity of reaction vessel. The focused US influenced the reduction of particles size and increased the surface area of resultant nanosized TiO2 powders. We also examined photodegradation of rhodamine 640 dye (Rh-640) solution by the resultant TiO2 under UV light exposure. It was observed that low frequency for TiO2 photocatalyst preparation and low calcination temperature were more affected onto the photodegradation of the dye. PMID:17904404

  4. Tailoring the oxidation state of cobalt through halide functionality in sol-gel silica

    NASA Astrophysics Data System (ADS)

    Olguin, Gianni; Yacou, Christelle; Smart, Simon; Diniz da Costa, Joo C.

    2013-08-01

    The functionality or oxidation state of cobalt within a silica matrix can be tailored through the use of cationic surfactants and their halide counter ions during the sol-gel synthesis. Simply by adding surfactant we could significantly increase the amount of cobalt existing as Co3O4 within the silica from 44% to 77%, without varying the cobalt precursor concentration. However, once the surfactant to cobalt ratio exceeded 1, further addition resulted in an inhibitory mechanism whereby the altered pyrolysis of the surfactant decreased Co3O4 production. These findings have significant implications for the production of cobalt/silica composites where maximizing the functional Co3O4 phase remains the goal for a broad range of catalytic, sensing and materials applications.

  5. Synthesis of hybrid sol-gel materials and their biological evaluation with human mesenchymal stem cells.

    PubMed

    Hernndez-Escolano, M; Juan-Daz, M J; Martnez-Ibez, M; Suay, J; Goi, I; Gurruchaga, M

    2013-06-01

    Surface engineering of biomaterials could promote the osseointegration of implants. In this work, two types of hybrid sol-gel materials were developed to stimulate cell attachment, proliferation and differentiation of osteogenic cells. One type was synthesised from vinyl triethoxysilane (VTES) and tetraethyl-orthosilicate (TEOS) at different molar ratios, while the other from VTES and hydroxyapatite particles (HAp). Hybrid materials were systematically investigated using nuclear magnetic resonance, Fourier transform infrared spectroscopy and contact angle metrology. The biocompatibility and osseoinduction of the coatings were evaluated by measuring mesenchymal stem cell proliferation using MTT assays and analysing the mineralised extracellular matrix production by quantifying calcium-rich deposits. The results highlighted the versatility of these coatings in obtaining different properties by changing the molar ratio of the VTES:TEOS precursors. Thus, mineralisation was stimulated by increasing TEOS content, while the addition of HAp improved cell proliferation but worsened mineralisation. PMID:23475116

  6. Investigation of the Peroxovanadate Sol-Gel Process and Characterization of the Gels

    SciTech Connect

    Craig Joseph Fontenot

    2001-12-31

    In general, the peroxovanadate solution sol-gel process can be thought of as consisting of two parts: (1) the decomposition of the peroxo species and (2) cation hydrolysis leading to gelation. By controlling the synthesis conditions, both layered and amorphous compounds can be created. However, the type of water coordination observed in these gels was found to be identical no matter what the long-range order. The current work clarified many of the discrepancies found in the literature and offered much new valuable information. Highlights include the types of vanadium environments present at various stages of hydration, the role of adsorbed water, oxygen exchange from adsorbed water into the gel sites, and the ability to create metastable VMoO solid solution phases. These results could have a variety of impacts on future catalysis research.

  7. Optical and morphological properties of sol gel derived titanium dioxide films

    NASA Astrophysics Data System (ADS)

    Sharma, A. B.; Sharma, S. K.; M, Vishwas; Rao, K. Narasimha

    2015-08-01

    Titanium oxide (Titania) thin films were synthesized on different substrates via the sol-gel dip-coating method using alkoxide solution. Some selected samples were also prepared with different percentage of Lead (Pb). The influence of Pb addition in precursor sol on the optical properties of titanium dioxide thin films was studied. The optical transmittance in the visible region has increased with increase in weight percentage of lead. The refractive index was slightly decreased with Pb addition. Crystallization of these coatings was achieved through thermal annealing at temperatures above 400 C. The structural properties and surface morphology of the crystallized coatings were studied by Scanning Electron Microscopy. Increase in average grain size from 250 nm to 350 nm with increase in Pb concentration is observed. Films were appeared to more coarse with increase in Pb addition. An increase in Pb addition resulted increase in average roughness from 12 nm to 25 nm.

  8. Ionic conductivity of tantalum oxide films prepared by sol-gel process for electrochromic devices

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; He, Yongxiang; Lampert, Carl M.

    1994-09-01

    Tantalum oxide films were prepared by sol-gel process using tantalum ethoxide Ta(OC2H5)5. The dependence of deposition conditions (i.e. composition of polymeric solutions and spinning rate) on ionic conductivities for tantalum oxide films were studied. The best results achieved for films fabricated by the spin coating technique from clear polymeric solutions. These films had low packing density (rho) equals 3.2 g/cm3 and good proton conductivity (about 10-6 (Omega) -1/cm-1). X-ray photoelectron spectroscopy (XPS) was used for studying the compositions of the tantalum oxide films. We report on the use of tantalum oxide films as ion conductors in devices consisting of WO3/Ta2O5/H+ ion storage polymer structure. We found tantalum oxide to have very good properties for proton device applications.

  9. Hydroxyapatite/alumina nanocrystalline composite powders synthesized by sol-gel process for biomedical applications

    NASA Astrophysics Data System (ADS)

    Khorsand, S.; Fathi, M. H.; Salehi, S.; Amirkhanlou, S.

    2014-10-01

    Hydroxyapatite/alumina nanocrystalline composite powders needed for various biomedical applications were successfully synthesized by sol-gel process. Structural and morphological investigations of the prepared composite powders were performed using X-ray diffractometer (XRD), scanning electron microscopy (SEM), X'Pert HighScore software, and Clemex Vision image analysis software. The results show that the crystallite size of the obtained composite powders is in the range of 25 to 90 nm. SEM evaluation shows that the obtained composite powders have a porous structure, which is very useful for biomedical applications. The spherical nanoparticles in the range of 60 to 800 nm are embedded in the agglomerated clusters of the prepared composite powders.

  10. Sol-gel processing of drug delivery materials and release kinetics.

    PubMed

    De Gaetano, F; Ambrosio, L; Raucci, M G; Marotta, A; Catauro, M

    2005-03-01

    Silica, calcium (5 mol%) silicate and silica/polycaprolactone hybrid inorganic/organic amorphous materials, all mixed with sodium ampicillin, a broad-spectrum antibiotic, have been synthesized by sol-gel method. The amorphous nature of the gels was ascertained by X-ray diffraction analysis. Release kinetics in a simulate body fluid (SBF) have been subsequently investigated. The amount of sodium ampicillin released has been detected by UV-Vis spectroscopy and SEM. The release kinetics seems to occur in more than one stage. Finally FTIR measurements and SEM micrograph showed the formation of a hydroxyapatite layer on the surface of the samples soaked in SBF. All data showed that these materials could be used as drug delivery bioactive systems. PMID:15744618

  11. Photoluminescence from terbium doped silica-titania prepared by a sol-gel method

    SciTech Connect

    Ismail, Adel Ali; Abboudi, Mostafa . E-mail: abboudi14@hotmail.com; Holloway, Paul; El-Shall, Hassan

    2007-01-18

    Terbium doped (0.5 at.%) TiO{sub 2}-SiO{sub 2} (30%/70%) was prepared by a sol-gel method. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the powder calcined at two different temperatures. At a low temperature of 550 deg. C an amorphous phase was obtained, but at a higher temperature of 1000 deg. C, the anatase TiO{sub 2} phase was crystallized in the amorphous SiO{sub 2} phase. Green photoluminescence from ultraviolet excitation was detected after heating to either temperature, but the amorphous sample heated to 550 deg. C exhibited a higher intensity. X-ray diffraction and photoluminescence excitation data are discussed to explain these observations.

  12. Magnetization and Magnetocaloric Effect in Sol-Gel Derived Nanocrystalline Copper-Zinc Ferrite.

    PubMed

    Anwar, M S; Ahmed, Faheem; Koo, Bon Heun

    2015-02-01

    We report the sol-gel synthesis and magnetocaloric effect in nanocrystalline copper-zinc ferrite (Cu0.5Zn0.5Fe2O4). The synthesized powder was characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and magnetization measurements. The XRD results confirm the formation of single phase spinel structure. The average particle size was found to be ~58 nm. FE-SEM results suggested that the nanoparticles are agglomerated and spherical in shape. Magnetization measurement reveals that Cu0.5Zn0.5Fe2O4 nanoparticles exhibit transition temperature (Tc) above room temperature. The maximum magnetic entropy change (ΔSM)max shows interesting behaviour and was found to vary with the applied magnetic field. This nanopowder can be considered as potential material for magnetic refrigeration above room temperature. PMID:26353670

  13. Modified sol-gel method for patterned lithium niobate thin film preparation

    NASA Astrophysics Data System (ADS)

    Poghosyan, Armen R.; Guo, Ruyan; Grigoryan, Stepan G.; Manukyan, Aleksandr L.; Vardanyan, Eduard S.

    2008-08-01

    A key stage in production of the integrated optics devices is forming of microtopography on crystalline films. The current methods generally comprise two separate steps: producing of thin film and creation a topographical pattern on it. But the inherently large chemical stability of crystalline LiNbO3 has effectively precluded the use of standard photolithographic patterning techniques. We present new approach based on the modified sol-gel technology using the photosensitive gel. In this case, the photolithography is used on the stage of dried gel whereupon the direct crystallization of patterned precursor film allows to create integrated optical element without subsequent etching of crystalline film. Presented method of patterned thin film preparation involves synthesis of photo-reactive complex of metal, which undergoes change under the UV light. This technology has allowed to obtain first samples of different types of waveguide devices.

  14. Sol-gel synthesis and dilute magnetism of nano MgO powder doped with Fe

    NASA Astrophysics Data System (ADS)

    Nomura, Kiyoshi; Taya, Souichirou; Okazawa, Atsushi; Kojima, Norimichi

    2014-04-01

    Mg oxides doped with 1 % 57Fe were prepared by a sol-gel method, and annealed at various temperatures. Nano-size Mg oxides were characterized by Mssbauer spectrometry, magnetization and XRD measurements. The crystalline size of MgO increases with increase of annealing temperature. Samples annealed at 600 C and 800 C gave only doublet peaks of paramagnetic Fe3+ in Mssbauer spectra although Fe3+ doping into MgO induced a distorted structure and showed weak ferromagnetism. It is considered that the magnetic property is due to defect induced magnetism by doping Fe3+ into MgO. For a sample heated at 1000 C, it is found from low temperature Mssbauer spectra that Fe3+ species are located at the core and shell of fine MgFe2O4 grains and diluted in MgO matrix.

  15. A novel sol-gel method for preparing favorable TiO2 thin film

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoyi; Zhang, Dainan; Li, Jie; Zhong, Zhiyong; Jia, Lijun; Wen, Tianlong; Zhang, Huaiwu; Liao, Yulong

    2016-01-01

    Nanocrystalline TiO2 thin films were synthesized by the sol-gel spin-coating method with different variables. Tetrabutyl titanate (TBOT) proportion and C5H8O2: TBOT molar ratio were confirmed to be influential on the gelation time. X-ray diffraction analysis indicated that the samples presented rutile TiO2 phases, which is a basis for subsequent experiments. Scanning electron microscope results revealed that TiO2 thin films with homogeneous and compact surfaces were synthesized successfully when adding moderate TBOT. It was found the thickness of films could reach about 60 nm when sintered at 750 °C, and the influence of sintering temperature was also investigated.

  16. Electrical and Optical Properties of Copper Oxide Thin Films by Sol-Gel Technique

    NASA Astrophysics Data System (ADS)

    Hashim, H.; Shariffudin, S. S.; Saad, P. S. M.; Ridah, H. A. M.

    2015-11-01

    Copper oxide were prepared by sol-gel technique and deposited onto quartz substrates as thin films using spin coating method. The aim of this research was to study the effects of different spin coating speeds of copper oxide thin films on the electrical and optical properties of the thin films. Five samples of copper oxide thin films with different spin coating speeds of 1000, 1500, 2000, 2500 and 3000 rpm were annealed at 600°C for 30 minutes. UV-Vis spectrophotometer and two-point probe technique were used to characterize the optical and electrical properties of the deposited films. Based on the results obtained, it revealed that the electrical conductivity of the copper oxide thin films reduce as the spin coating speeds increase. The calculated optical band gap and the resistivity of the copper oxide thin films also decrease when the spin coating speeds are increased.

  17. Sol-gel synthesis and densification of aluminoborosilicate powders. Part 1: Synthesis

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey; Selvaduray, Guna; Leiser, Daniel

    1992-01-01

    Aluminoborosilicate powders high in alumina content were synthesized by the sol-gel process utilizing various methods of preparation. Properties and microstructural effects related to these syntheses were examined. After heating to 600 C for 2 h in flowing air, the powders were amorphous with the metal oxides comprising 87 percent of the weight and uncombusted organics the remainder. DTA of dried powders revealed a T(sub g) at approximately 835 C and an exotherm near 900 C due to crystallization. Powders derived from aluminum secbutoxide consisted of particles with a mean diameter 5 microns less than those from aluminum isopropoxide. Powders synthesized with aluminum isopropoxide produced agglomerates comprised of rod shaped particulates while powders made with the secbutoxide precursor produced irregular glassy shards. Compacts formed from these powders required different loadings for equivalent densities according to the method of synthesis.

  18. Boron doping effects in electrochromic properties of NiO films prepared by sol-gel

    SciTech Connect

    Lou, Xianchun; Zhao, Xiujian; He, Xin

    2009-12-15

    In this paper, NiO films doped with B{sub 2}O{sub 3} were first prepared by sol-gel. The effects of boron content on the structure and electrochromic properties of NiO films were studied with X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetric (CV) and UV-vis spectrophotometer, respectively. In addition, the roughness and phase of the bleached/colored were studied by atom force microscopy (AFM). B-doped prevent the crystallization of the films. The colored state transmittance could be significantly lowered when the boron added. The NiO film doped with boron exhibited a noticeable electrochromism with a variation of transmittance up to {proportional_to}60% at the wavelength range of 300-500 nm. (author)

  19. Structural and electrical properties of sol-gel spin coated indium doped cadmium oxide thin films

    SciTech Connect

    Rajammal, R.; Savarimuthu, E. Arumugam, S.

    2014-04-24

    The indium doped CdO thin films have been prepared by the sol-gel spin coating technique and the influence of indium doping concentration on the structural and electrical properties of the deposited films has been investigated. The indium doping concentration in the solution has been varied from 0-10 wt% insteps of 2wt%. A indium doping concentration of 6wt% has been found to be optimum for preparing the films and at this stage a minimum resistivity of 5.92×10{sup −4}Ω cm and a maximum carrier concentration of 1.20×10{sup 20}cm{sup −3} have been realized.

  20. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, R.W.

    1995-12-19

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes{<=}1000{angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

  1. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, R.W.

    1996-09-17

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes {<=}1,000{angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1,050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

  2. Direct visualization of changes in deacylated Na(+) gellan polymer morphology during the sol-gel transition.

    PubMed

    Atkin, N; Abeysekera, R M; Kronestedt-Robards, E C; Robards, A W

    2000-09-01

    Changes in gellan polymer morphology during the sol-gel transition were directly visualized by transmission electron microscopy and a model incorporating these changes and existing physical data is proposed. Our observations suggest that the most thermodynamically stable conformations of gellan polymers in solution, in the absence of added cations, are the double helix and double-helical duplexes. We have demonstrated two forms of lateral aggregation of gellan helices in the presence of Ca(2+) and K(+) ions. One type forms junction zones that lead to network formation and gelation, while the second type leads to the formation of isolated fibers of aggregated helices and inhibition of gelation. The proposed model of gellan gelation is based on these observations where thermoreversibility, gel strength, and endothermic transitions of gellan gels can be explained. PMID:10861381

  3. Physical Properties of Potassium Phosphate Glass Prepared by Sol Gel Method

    SciTech Connect

    Mat, Noorhidayah Che; Sahar, Md Rahim; Pauzi, Safwan Ahmad

    2010-07-07

    Series of glasses based on Al{sub 2}O{sub 3}-K{sub 2}O-P{sub 2}O{sub 5} have successfully been made by sol gel method. The amorphous state has been confirmed by X-ray diffraction (XRD) while the actual composition has been determined using Energy Dispersive X-ray (EDX) analysis. The glass density is determined using Archimedes method while the Vickers Micro hardness Test has been used to measure the hardness. It is found that all the samples are amorphous in nature with their actual composition contained phosphate in the range of 40-53% mol. It is also observed that the glass density is about 2.4 gcm{sup -3} while the hardness is in the range of 40-100 Hv, depending on composition.

  4. Preparation of long alumina fibers by sol-gel method using tartaric acid

    NASA Astrophysics Data System (ADS)

    Tan, Hong-Bin

    2011-12-01

    Long alumina fibers were prepared by sol-gel method. The spinning sol was obtained by mixing aluminum nitrate, tartaric acid, and polyvinylpyrrolidone with a mass ratio of 10:3:1.5. Thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to characterize the properties of the gel and ceramic fibers. A little of ?-Al2O3 phase is observed in the alumina precursor gel fibers sintered at 1273 K. The fibers with a uniform diameter can be obtained when sintered at 1473 K, and its main phase is also indentified as ?-Al2O3.

  5. Gel-sol-gel thermo-gelation behavior study of chitosan-inorganic phosphate solutions.

    PubMed

    Li, XingYi; Kong, XiangYe; Wang, XiuHong; Shi, Shuai; Guo, Gang; Luo, Feng; Zhao, Xia; Wei, YuQuan; Qian, ZhiYong

    2010-08-01

    In present study, the feasibility of developing a novel thermo-sensitive hydrogel suitable for injectable formulations based on chitosan and inorganic phosphate was demonstrated. The physicochemical and rheological changes of chitosan/dibasic sodium phosphate solutions as in function with temperature were investigated in order to gain a better understanding of gelation process. According to the result of rheological study, there are two phase transition points as in function with temperature, corresponding to 30 degrees C and 43 degrees C. The system is gel state at approximately 4 degrees C. With the temperature increased to 30 degrees C, the gel-sol transition as well as the decrease in turbidity was observed. The sol-gel transition as well as the increase in turbidity was observed again as the temperature was above 43 degrees C. And the gel obtained at approximately 4 degrees C is reversible, but the gel obtained at approximately 43 degrees C is irreversible. PMID:20434557

  6. Neutron diffraction study of the structure of water confined in a sol-gel silica glass

    NASA Astrophysics Data System (ADS)

    Venuti, Valentina; Crupi, Vincenza; Majolino, Domenico; Migliardo, Placido; Bellissent-Funel, Marie Claire

    2004-07-01

    During recent years, the understanding of the modification of the structural and dynamics of water confined in different environments has been the focus of much interest in scientific research. This topic is in fact of great relevance in a lot of technological areas and, in living systems, essential water related phenomena occur in restricted geometries in cells, and active sites of proteins and membranes, or at their surface. In this paper we report on neutron diffraction results on the microscopic structure of heavy water confined in a fully hydrated sol-gel silica glass (GelSil) as a function of the temperature, in comparison with that of bulk water. Furthermore, at low T, the nucleation of cubic ice superimposed to liquid water, already observed for water within Vycor glasses, is discussed.

  7. Parameters controlling silver nanoparticle growth in sol-gel silica coatings

    SciTech Connect

    Villegas, M.A. . E-mail: mavillegas@cenim.cisc.es; Garcia, M.A.; Paje, S.E.; LLopis, J.

    2005-07-12

    Silica based sol-gel coatings doped with different silver amounts have been prepared. Apart from silver concentration, other experimental parameters such as thermal densification conditions, presence of other co-dopants and the nature of the substrate have been varied in order to determine their influence on the final microstructure and properties. Characterisation of the materials prepared was carried out by optical spectroscopy (photoluminescence and absorption), secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). The study was oriented to determine the parameters governing the nucleation and growth of silver nanoparticles. The results showed that formation of silver nanoparticles was promoted when one or more of the following conditions were achieved: silver concentration in the initial sol over 5%, thermal densification under reducing atmosphere and use of pure silica substrate (in general, glass substrates without modifier ions and, therefore, with few non-bridging oxygen positions)

  8. Development of Metal Casting Molds By Sol-Gel Technology Using Planetary Resources

    NASA Technical Reports Server (NTRS)

    Sibille, L.; Sen, S.; Curreri, P.; Stefanescu, D.

    2000-01-01

    Metals extracted from planetary soils will eventually need to be casted and shaped in-situ to produce useful products. In response to this challenge, we propose to develop and demonstrate the manufacturing of a specific product using Lunar and Martian soil simulants, i.e. a mold for the casting of metal and alloy parts, which will be an indispensable tool for the survival of outposts on the Moon and Mars. Drawing from our combined knowledge of sol-gel and metal casting technologies, we set out to demonstrate the extraordinary potential of mesoporous materials such as aerogels to serve as efficient casting molds as well as fulfilling numerous other needs of an autonomous planetary outpost.

  9. Sol-gel synthesis and characterization of α-Fe2O3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Raja, K.; Mary Jaculine, M.; Jose, M.; Verma, Sunil; Prince, A. A. M.; Ilangovan, K.; Sethusankar, K.; Jerome Das, S.

    2015-10-01

    The α-Fe2O3 nanoparticles have been successfully synthesized via sol-gel technique. The lattice parameters, the lattice strain and crystallite size were investigated by X-ray diffraction (XRD) analysis. Fourier transform infrared spectroscopy (FT-IR) analysis has been carried out to confirm the presence of functional groups. Using UV-visible spectrum, the optical band gap energy is estimated as 2.55 eV. The morphology and chemical composition of the α-Fe2O3 nanoparticles were examined by high resolution scanning electron microscopy (HR-SEM) and energy dispersive X-ray diffraction analysis (EDX) respectively. The hysteresis loop was traced out using vibration sample magnetometer and the values of coercivity and saturation magnetization are found out to be 3891 G and 0.4193 emu/g respectively.

  10. Impact of temperature on zinc oxide particle size by using sol-gel process

    SciTech Connect

    Lee, Keanchuan Ching, Dennis Ling Chuan; Saipolbahri, Zulhilmi Akmal bin; Guan, Beh Hoe E-mail: hassan.soleimani@petronas.com.my; Soleimani, Hassan E-mail: hassan.soleimani@petronas.com.my

    2014-10-24

    Zinc oxide (ZnO) nanoparticles were prepared and synthesized via sol-gel method, by using citric acid as a precursor. The impact of annealing on the particle size was investigated. Based on the results from the Thermogravimetric Analysis (TGA), three different annealing temperature which is 500, 600 and 700 °C were chosen followed by the characterization of the ZnO nanoparticle by using Powder X-Ray Diffraction (PXRD), Transmission Electron Microscopy (TEM) and Field Emission Scanning Electron Microscopy (FESEM). Results showed that the crystallite size estimated from PXRD increased with the annealing temperature which was hexagonal structure for ZnO. TEM further revealed the same tendency which the Zn NPs size also increased with the annealing temperature.

  11. Synthesis of sol-gel mesoporous silica materials providing a slow release of doxorubicin.

    PubMed

    Prokopowicz, Magdalena; Przyjazny, Andrzej

    2007-11-01

    Samples of mesoporous base-catalysed silica xerogel materials made by the sol-gel process were impregnated with an anticancer drug--doxorubicin, followed by different times of ageing at room temperature. The effect of ageing time on the physical and structural properties as well as sorption-desorption of the drug was investigated. The obtained results suggest an inverse relationship with a solid density and surface area increasing as the pore size and volume decrease during ageing time. These results also revealed the effect of ageing time on the efficiency of sorption-desorption of the drug. An increase in ageing time results in an increase of the efficiency of drug sorption and a decrease in the rate of drug release. PMID:17763062

  12. Mechanical properties of sol-gel derived SiO2 nanotubes.

    PubMed

    Polyakov, Boris; Antsov, Mikk; Vlassov, Sergei; Dorogin, Leonid M; Vahtrus, Mikk; Zabels, Roberts; Lange, Sven; Lhmus, Rnno

    2014-01-01

    The mechanical properties of thick-walled SiO2 nanotubes (NTs) prepared by a sol-gel method while using Ag nanowires (NWs) as templates were measured by using different methods. In situ scanning electron microscopy (SEM) cantilever beam bending tests were carried out by using a nanomanipulator equipped with a force sensor in order to investigate plasticity and flexural response of NTs. Nanoindentation and three point bending tests of NTs were performed by atomic force microscopy (AFM) under ambient conditions. Half-suspended and three-point bending tests were processed in the framework of linear elasticity theory. Finite element method simulations were used to extract Young's modulus values from the nanoindentation data. Finally, the Young's moduli of SiO2 NTs measured by different methods were compared and discussed. PMID:25383292

  13. Durable superhydrophobic and antireflective surfaces by trimethylsilanized silica nanoparticles-based sol-gel processing.

    PubMed

    Manca, Michele; Cannavale, Alessandro; De Marco, Luisa; Aricò, Antonino S; Cingolani, Roberto; Gigli, Giuseppe

    2009-06-01

    We present a robust and cost-effective coating method to fabricate long-term durable superhydrophobic andsimultaneouslyantireflective surfaces by a double-layer coating comprising trimethylsiloxane (TMS) surface-functionalized silica nanoparticles partially embedded into an organosilica binder matrix produced through a sol-gel process. A dense and homogeneous organosilica gel layer was first coated onto a glass substrate, and then, a trimethylsilanized nanospheres-based superhydrophobic layer was deposited onto it. After thermal curing, the two layers turned into a monolithic film, and the hydrophobic nanoparticles were permanently fixed to the glass substrate. Such treated surfaces showed a tremendous water repellency (contact angle = 168 degrees ) and stable self-cleaning effect during 2000 h of outdoor exposure. Besides this, nanotextured topology generated by the self-assembled nanoparticles-based top layer produced a fair antireflection effect consisting of more than a 3% increase in optical transmittance. PMID:19466786

  14. New systems related to CdS nanoparticles in sol-gel matrices

    SciTech Connect

    Gacoin, T.; Malier, L.; Counio, G.; Esnouf, S.; Boilot, J.P.; Audinet, L.; Ricolleau, C.; Gandais, M.

    1996-12-31

    A process for the synthesis of CdS nanoparticles embedded in hybrid organic/inorganic silica matrices has been developed, based both on colloid and sol-gel chemistry. The large possibilities offered by these techniques allow the study of the influence of various parameters on the luminescence properties of the nanoparticles. Two directions were investigated: first, the authors characterized the surface of the nanoparticles complexed with an organic thiol using NMR spectroscopy. Then, they synthesized new systems to study the influence of chemical modifications, such as the composition of the aggregates (CdS:Mn), the surface (CdS/ZnS core/shell nanostructures) and the interface between the aggregate and the gel matrix.

  15. H2-induced copper and silver nanoparticle precipitation inside sol-gel silica optical fiber preforms

    NASA Astrophysics Data System (ADS)

    Chahadih, Abdallah; El Hamzaoui, Hicham; Cristini, Odile; Bigot, Laurent; Bernard, Rémy; Kinowski, Christophe; Bouazaoui, Mohamed; Capoen, Bruno

    2012-08-01

    Ionic copper- or silver-doped dense silica rods have been prepared by sintering sol-gel porous silica xerogels doped with ionic precursors. The precipitation of Cu or Ag nanoparticles was achieved by heat treatment under hydrogen followed by annealing under air atmosphere. The surface plasmon resonance bands of copper and silver nanoparticles have been clearly observed in the absorption spectra. The spectral positions of these bands were found to depend slightly on the particle size, which could be tuned by varying the annealing conditions. Hence, transmission electron microscopy showed the formation of spherical copper nanoparticles with diameters in the range of 3.3 to 5.6 nm. On the other hand, in the case of silver, both spherical nanoparticles with diameters in the range of 3 to 6 nm and nano-rods were obtained.

  16. Microencapsulation of probiotic bacteria using thermo-sensitive sol-gel polymers for powdered infant formula.

    PubMed

    Penhasi, Adel

    2015-01-01

    In this study the application of thermo-sensitive sol-gel polymers in microencapsulation formulation of probiotic bacteria, Bifidobacterium animalis spp lactis, for powdered infant formula (PIF), which is reconstituted at 70?C, has been assessed. A double-layered microcapsule containing hydroxypropyl methyl cellulose (HPMC) as an inner layer and an outer layer, as the smart coating layer, based on a combination of hydroxypropyl cellulose (HPC) and poloxamer was designed. Generally, this specific microencapsulation provided superior protection against the reconstitution temperature. A high molecular weight of HPC and a greater thickness of the smart coating layer resulted in a delayed release of the bacteria from the microcapsules especially in the PIF composition. However, this was compensated by a high stability of the bacteria at 70?C. Both the surface texture and particle size distribution of microcapsules have been respectively characterised by scanning electron microscopy and particle size analysis. PMID:26004368

  17. Sol-Gel-Prepared Nanoparticles of Mixed Praseodymium Cobaltites-Ferrites

    NASA Astrophysics Data System (ADS)

    Pekinchak, Olga; Vasylechko, Leonid; Lutsyuk, Iryna; Vakhula, Yaroslav; Prots, Yuri; Carrillo-Cabrera, Wilder

    2016-02-01

    Two series of nanocrystalline powders of PrCo1 - x Fe x O3 ( x = 0.1, 0.3, 0.5, 0.7 and 0.9) of high purity were obtained by sol-gel citrate method at 700 and 800 °C. The formation of continuous solid solution with an orthorhombic perovskite structure (sp. group Pbnm) was observed. A peculiarity of the PrCo1 - x Fe x O3 solid solution is the lattice parameter crossovers, which occurred at certain compositions and revealed in the pseudo-tetragonal or pseudo-cubic metric. An average crystallite size of the PrCo1 - x Fe x O3 samples estimated from the analysis of the angular dependence of the X-ray diffraction (XRD) line broadening varies between 30 and 155 nm, depending on the composition and synthesis temperature.

  18. Charge-transfer complexes of Cu(II)/HD analogue in sol gel sensors

    NASA Astrophysics Data System (ADS)

    Brinkley, J. F.; Kirkey, M. L.; Marques, A. D. S.; Lin, C. T.

    2003-01-01

    An optically transparent xerogel encapsulating Cu(II) acetate is fabricated to detect mustard gas (HD) analogues via a charge-transfer mechanism. A fast response (color change from sky blue to canary yellow) is observed for the chlorinated sulfide, and is accompanied by an absorption band at 370-420 nm. MO calculations revealed that the chlorinated HD analogue displays a charge-transfer transition extended from sulfur to chlorine atom. A 1:1 complex of Cu(II)/HD analogue is preferred. For a colorimetric sol-gel detector prepared at pH 3, the detection limit of HD analogue is calibrated at 0.03 ?l per 1.5 ml sensor volume.

  19. Titania-based molecularly imprinted polymer for sulfonic acid dyes prepared by sol-gel method.

    PubMed

    Li, Man; Li, Rong; Tan, Jin; Jiang, Zi-Tao

    2013-03-30

    A novel titania-based molecularly imprinted polymer (MIP) was synthesized through sol-gel process with sunset yellow (Sun) as template, without use of functional monomer. MIP was used as a solid-phase extraction material for the isolation and enrichment of sulfonic acid dyes in beverages. The results showed that MIP exhibited better selectivity, higher recovery and adsorption capacity for the sulfonic acid dyes compared to the non-imprinted polymer (NIP). MIP presented highest extraction selectivity to Sun when pH less than or equal to 3. The adsorption capacity was 485.9 mg g(-1), which was larger than that of NIP (384.7 mg g(-1)). The better clean-up ability demonstrated the capability of MIP for the isolation and enrichment of sulfonic acid dyes in complicated food samples. The mean recoveries for the sulfonic acid dyes on MIP were from 81.9% to 97.2% in spiked soft drink. PMID:23598213

  20. The enhancement of benzotriazole on epoxy functionalized silica sol-gel coating for copper protection

    NASA Astrophysics Data System (ADS)

    Peng, Shusen; Zhao, Wenjie; Li, He; Zeng, Zhixiang; Xue, Qunji; Wu, Xuedong

    2013-07-01

    The influence of the amount of benzotriazole (BTA) on the wetting and anticorrosion ability of the epoxy functionalized silica sol-gel (ESol) coating was studied by various complementary methods. IR results demonstrate that BTA reacted with ESol through a 1:1 addition reaction of Nsbnd H to epoxy group. The water contact angle of the ESol coating increases with an increase in the amount of BTA. SEM and adhesion tests reveal that BTA could improve the adhesion of ESol to copper surface. Moreover, the best protection was achieved when the amount of BTA equals to the molar number of epoxy group in the ESol coating according to the results of electrochemical measurements and salt spray test.