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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. 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.

  6. Synthesis of nano-titanium dioxide by sol-gel route

    NASA Astrophysics Data System (ADS)

    Kaler, Vandana; Duchaniya, R. K.; Pandel, U.

    2016-04-01

    Nanosized titanium dioxide powder was synthesised via sol-gel route by hydrolysis of titanium tetraisopropoxide with ethanol and water mixture in high acidic medium. The synthesized nanopowder was further characterized by X-ray Diffraction, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, and Ultraviolet Visible Spectroscopy in order to determine size, morphology and crystalline structure of the material. The synthesis of nano-TiO2 powder in anatase phase was realized by XRD. The optical studies of nano-TiO2 powder was carried out by UV-Vis spectroscopy and band gap was calculated as 3.5eV, The SEM results with EDAX confirmed that prepared nano-TiO2 particles were in nanometer range with irregular morphology. The FTIR analysis showed that only desired functional groups were present in sample. These nano-TiO2 particles have applications in solar cells, chemical sensors and paints, which are thrust areas these days.

  7. Nanoscopic yttrium oxide fluorides: non-aqueous fluorolytic sol-gel synthesis and structural insights by 19F and 89Y MAS NMR.

    PubMed

    Scholz, G; Dreger, M; Bertram, R; Kemnitz, E

    2015-08-14

    Nanoscopic yttrium acetate fluorides Y(CH(3)COO)(3-z)F(z) and yttrium oxide fluorides YO(3-z)/(2)F(z )were prepared with tunable Y/F molar ratios via the fluorolytic sol-gel route. All samples were characterized by X-ray diffraction, elemental analysis and thermal analysis. In addition, local structures of all samples were studied by (19)F MAS, (19)F-(89)Y CP MAS and (1)H-(89)Y CP MAS NMR spectroscopy and the respective chemical shifts are given. For both classes of compounds, only the fluorination using one equivalent of F (z = 1) leads to defined, well crystalline matrices: yttrium acetate fluoride Y(CH(3)COO)(2)F and r-YOF. PMID:26133504

  8. Porous titania films fabricated via sol gel rout - Optical and AFM characterization

    NASA Astrophysics Data System (ADS)

    Karasiński, Paweł; Gondek, Ewa; Drewniak, Sabina; Kajzer, Anita; Waczyńska-Niemiec, Natalia; Basiaga, Marcin; Izydorczyk, Weronika; Kouari, Youssef E. L.

    2016-06-01

    Mesoporous titania films of low refractive index ∼1.72 and thickness within the range of 57-96 nm were fabricated via sol-gel rout and dip-coating technique on a soda-lime glass substrate. Tetrabutylorthotitanate Ti(OBu)4 was used as a titania precursor. High porosity and consequently low refractive index were achieved using the polyethylene glycol (PEG 1100) as a template. Based on transmittance, using Tauc's relations, the optical energy band gaps and the Urbach energy were determined. The research shows that in the fabricated titania films there are two types of optical energy band gaps, connected with direct and indirect electron transitions and brought about by the presence of amorphous and crystalline phase respectively. Based on the quantum size effect, the diameters of nanocrystals versus film thickness were determined. AFM studies of the titania films have demonstrated that there are changes of surface morphology taking place with the change of thickness. We have demonstrated that the surface morphology of titania films has influence on wettability.

  9. Comparative study of potassium hexatitanate (K2Ti6O13) whiskers prepared by sol-gel and solid state reaction routes

    NASA Astrophysics Data System (ADS)

    Siddiqui, Mohd Asim; Chandel, Vishal Singh; Azam, Ameer

    2012-07-01

    Polycrystalline phases of the potassium hexatitanate (K2Ti6O13) were synthesized by conventional solid state reaction and sol-gel methods with a view to compare structural, electrical, optical and photocatalytic properties. Single phase K2Ti6O13 prepared by sol-gel method (PSG) revealed higher value of dielectric constant than same obtained by the solid state reaction method (PSS), attributed to smaller particle size in sol-gel method. Band gap (3.48 eV) of K2Ti6O13 prepared by sol-gel method was found higher than (3.06 eV), obtained in solid state reaction method. Additionally, K2Ti6O13 was tested as photocatalyst on the degradation of methyl orange (MO) under UV light and found better activity for sample PSG. Morphological characteristic exhibited formation of nanorods in sol-gel route and formation of microrods in solid state reaction method.

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

    NASA Astrophysics Data System (ADS)

    Maia, Lauro J. Q.; Mastelaro, Valmor R.; Pairis, Sebastien; Hernandes, Antonio C.; Ibanez, Alain

    2007-02-01

    A new sol-gel route was applied to obtain Y 0.9Er 0.1Al 3(BO 3) 4 crystalline powders and amorphous thin films by using Al(acac) 3, B(OPr i) 3, Y(NO 3) 3·6H 2O, and Er(NO 3) 3·5H 2O 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) 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 °C) and crystallization temperatures (830 °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.

  13. Formation of bimodal porous silica-titania monoliths by sol-gel route

    NASA Astrophysics Data System (ADS)

    Ruzimuradov, O. N.

    2011-10-01

    Silica-titania monoliths with micrometer-scale macroporous and nanometer-scale mesoporous structure and high titania contents are prepared by sol-gel process and phase separation. Titanium alkoxide precursor was not effective in the preparation of high titania content composites because of strong decrease in phase separation tendency. Bimodal porous gels with high titania content were obtained by using inorganic salt precursors such as titanium sulfate and titanium chloride. Various characterization techniques, including SEM, XRD, Hg porosimetry and N2 adsorption have been carried out to investigate the formation process and physical-chemical properties of silica-titania monoliths. The characterization results show that the silica-titania monoliths possess a bimodal porous structure with well-dispersed titania inside silica network. The addition of titania in silica improves the thermal stability of both macroporous and mesoporous structures.

  14. 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.

  15. DC electrical conductivity of nanocrystalline Mn3O4 synthesized through a novel sol-gel route

    NASA Astrophysics Data System (ADS)

    Bose, Vipin C.; Maniammal, K.; Madhu, G.; Veenas, C. L.; Aiswarya Raj, A. S.; Biju, V.

    2015-02-01

    Manganese oxides have generated considerable interest in recent years due to their electronic and magnetic properties with potential industrial applications. Among manganese oxides, Mn3O4 is one of the stable oxides with normal spinel structure and it has variety of important applications. In the present work nanocrystalline Hausmannite, Mn3O4 with phase purity and average crystallite size of 8 nm was synthesized through a novel sol-gel route at a temperature of 0-5°C. The samples were annealed at different temperatures to understand the thermal stability and the structural characterization was done using techniques such as X-ray powder diffraction (XRD), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR). The UV visible absorption spectra of the samples show that there are two types of transitions corresponding to Mn2+ ions and Mn3+ ions. The dc electrical conductivity of the samples increases in comparison with that of bulk.

  16. 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.

  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. 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-Roś, Justyna; Donesz-Sikorska, Anna; Śmieszek, 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

  20. 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.

  1. 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

  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 400°C. 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 400°C, 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 800°C. 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 500°C. 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 500°C. 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 200°C, 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. The sol-gel route: A versatile process for up-scaling the fabrication of gas-tight thin electrolyte layers

    NASA Astrophysics Data System (ADS)

    Viazzi, Céline; Rouessac, Vincent; Lenormand, Pascal; Julbe, Anne; Ansart, Florence; Guizard, Christian

    2011-03-01

    Sol-gel routes are often investigated and adapted to prepare, by suitable chemical modifications, submicronic powders and derived materials with controlled morphology, which cannot be obtained by conventional solid state chemistry paths. Wet chemistry methods provide attractive alternative routes because mixing of species occurs at the atomic scale. In this paper, ultrafine powders were prepared by a novel synthesis method based on the sol-gel process and were dispersed into suspensions before processing. This paper presents new developments for the preparation of functional materials like yttria-stabilized-zirconia (YSZ, 8% Y2O3) used as electrolyte for solid oxide fuel cells. YSZ thick films were coated onto porous Ni-YSZ substrates using a suspension with an optimized formulation deposited by either a dip-coating or a spin-coating process. The suspension composition is based on YSZ particles encapsulated by a zirconium alkoxide which was added with an alkoxide derived colloidal sol. The in situ growth of these colloids increases significantly the layer density after an appropriated heat treatment. The derived films were continuous, homogeneous and around 20 μm thick. The possible up-scaling of this process has been also considered and the suitable processing parameters were defined in order to obtain, at an industrial scale, homogeneous, crack-free, thick and adherent films after heat treatment at 1400 °C.

  5. Gravure-Printed Sol-Gels on Flexible Glass: A Scalable Route to Additively Patterned Transparent Conductors.

    PubMed

    Scheideler, William J; Jang, Jaewon; Ul Karim, Muhammed Ahosan; Kitsomboonloha, Rungrot; Zeumault, Andre; Subramanian, Vivek

    2015-06-17

    Gravure printing is an attractive technique for patterning high-resolution features (<5 μm) at high speeds (>1 m/s), but its electronic applications have largely been limited to depositing nanoparticle inks and polymer solutions on plastic. Here, we extend the scope of gravure to a new class of materials and on to new substrates by developing viscous sol-gel precursors for printing fine lines and films of leading transparent conducting oxides (TCOs) on flexible glass. We explore two strategies for controlling sol-gel rheology: tuning the precursor concentration and tuning the content of viscous stabilizing agents. The sol-gel chemistries studied yield printable inks with viscosities of 20-160 cP. The morphology of printed lines of antimony-doped tin oxide (ATO) and tin-doped indium oxide (ITO) is studied as a function of ink formulation for lines as narrow as 35 μm, showing that concentrated inks form thicker lines with smoother edge morphologies. The electrical and optical properties of printed TCOs are characterized as a function of ink formulation and printed film thickness. XRD studies were also performed to understand the dependence of electrical performance on ink composition. Printed ITO lines and films achieve sheet resistance (Rs) as low as 200 and 100 Ω/□, respectively (ρ≈2×10(-3) Ω-cm) for single layers. Similarly, ATO lines and films have Rs as low as 700 and 400 Ω/□ with ρ≈7×10(-3) Ω-cm. High visible range transparency is observed for ITO (86-88%) and ATO (86-89%). Finally, the influence of moderate bending stress on ATO films is investigated, showing the potential for this work to scale to roll-to-roll (R2R) systems. PMID:26018206

  6. 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 .

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  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 70°C. 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. Structural and cyclic volta metric investigations on BIPBVOX solid electrolyte synthesized by ethylene glycol-citric acid sol-gel route

    NASA Astrophysics Data System (ADS)

    Naqvi, Faria K.; Beg, Saba; Al-Areqi, Niyazi A. S.

    2016-05-01

    Samples of BIPBVOX.x (Bi2V1-xPbxO5.5-x/2) in the composition range 0.05 ≤ x ≤ 0.20 were prepared by ethylene glycol- citric acid sol-gel synthesis route. Structural investigations were carried out by X-ray diffraction, DTA. The highly conducting γ'- phase was effectively stabilized at room temperature for compositions with x ≥ 0.17. Cyclic voltammetric measurements showed reversible redox reactions of vanadium and irreversible redox reaction of Bi3+ in the BIPBVOX system during the first cathodic and anodic sweep. However, a higher stability against the reduction of Bi3+ to metallic bismuth was seen for x=0.20.

  13. Homoleptic gallium(III) and indium(III) aminoalkoxides as precursors for sol-gel routes to metal oxide nanomaterials.

    PubMed

    Mishra, Shashank; Daniele, Stéphane; Petit, Sarah; Jeanneau, Erwann; Rolland, Marc

    2009-04-14

    New homoleptic aminoalkoxides of gallium(III) and indium(III) of the types M4{(OC2H4)2NMe}6 [M = Ga (1), In (2)] and [Ga{(OC2H4)3N}]n (3), as well as a previously described Ga2(OC2H4NMe2)6 (A) have been prepared by isopropoxo(chloro)-aminoalkoxo exchange reactions and characterised by elemental analyses, FT-IR and 1H NMR spectroscopy. Formation of a star-shaped Ga[Ga{mu-eta3:eta1-(OC2H4)2NMe}2]3 (1.4CHCl3) and a zigzag linear In4{mu-eta3:eta1-(OC2H4)2NMe}6 (2.6CHCl3), as revealed by X-ray single crystal structures, reflects the structural diversity among N-methyldiethanolaminate derivatives. Their hydrolyses in boiling water, either in presence or absence of tetraalkylamonium bromide, have been studied and, for gallium derivatives, compared with similar hydrolytic reactions of Ga(OiPr)3. The hydrolysed products were studied by FT-IR, TG-DTA and XRD techniques. For gallium derivatives, transition from orthorhombic Ga(O)OH phase of as-prepared powder to phase pure rhombohedral- and monoclinic-Ga2O3 occurred at about 500 degrees C and 700 degrees C, respectively, whereas cubic In(OH)3 phase of as-prepared powder of 2 was converted to cubic In2O3 at 250 degrees C. Partial hydrolyses were also performed and evolution of the particle size in solution was recorded by light scattering measurements. Various sol-gel processing parameters such as concentration and hydrolysis ratio (h) were studied in order to stabilise nano-sized colloidal suspensions for access to thin films by spin coating. The N-methyldiethanolamine derivatives 1 and 2 were found to be the most suitable candidates for sol-gel processing. The transparent Ga2O3 and In2O3 films obtained on glass or Si wafers from spin-coating of 1 and 2, respectively, were characterised by SEM, EDX and XRD. PMID:19319402

  14. Development of injectable biocomposites from hyaluronic acid and bioactive glass nano-particles obtained from different sol-gel routes.

    PubMed

    Sohrabi, Mehri; Hesaraki, Saeed; Kazemzadeh, Asghar; Alizadeh, Masoud

    2013-10-01

    Bioactive glass nano-powders with the same chemical composition and different particle characteristics were synthesized by acid-catalyzed (the glass is called BG1) and acid-base catalyzed (BG2) sol-gel processes. Morphological characteristics of powders were determined by TEM and BET methods. The powders were separately mixed with 3% hyaluronic acid solution to form a paste. In vitro reactivity of pastes was determined by soaking them in simulated body fluid. Rheological behaviors of paste in both rotation and oscillation modes were also measured. The results showed that BG1 particles was microporous with mean pore diameter of 1.6 nm and particle size of ~300 nm while BG2 was mesoporous with average pore diameter of 8 and 17 nm and particle size of 20-30 nm. The paste made of BG2 revealed better washout resistance and in vitro apatite formation ability than BG1. According to the rheological evaluations, both pastes exhibited shear thinning but non-thixotropic behavior, meanwhile paste of BG2 had higher viscosity than BG1. The oscillatory tests revealed that the pastes were viscoelastic materials with more viscous nature. Both pastes could be completely injected through standard syringe using low compressive load of 5-50 N. Overall, The biocomposites can potentially be used as bioactive paste for the treatment of hard and even soft tissues. PMID:23910271

  15. 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.

  16. Sol-gel synthesis and characterization of nanocrystalline (Bi0.5Na0.5)TiO3 powders from the poly vinyl alcohol evaporation route

    NASA Astrophysics Data System (ADS)

    Haitao, Liu; xiaohui, Wang; Longtu, Li

    2009-09-01

    Nanocrystalline pure perovskite phase bismuth sodium titanate (Bi0.5Na0.5)TiO3(BNT) powders have been prepared by a sol-gel method from the poly vinyl alcohol evaporation route, bismuth nitrate [Bi(NO3)3], tetra-butyl titanate [Ti(OC4H9)4] and sodium acetate(CH3COONa) were used as raw materials and poly vinyl alcohol(PVA) as the sol-gel forming solvent. Stoichiometric amounts of the individual raw materials were thoroughly mixed in accordance with the BNT composition to form the stock solution. The pH of the stock was adjusted to 1-3 by adding acetate. Aqueous solution of PVA[10%(w/v)] was then added to the cationic mixture with thorough stirring. The weight ratio of the cationic mixture to the PVA aqueous solution was maintained at 2:1. The resulting viscous liquid was then heated over a hot crucible up to form a fluffy dry gel. The fluffy dry gels were calcined at different temperatures and times and then cooled to room temperature naturally. The X-ray powder diffraction(XRD) patterns of the heat-treated powders were obtained using a Bruker D8 Advance X-ray diffractometer with Cu Kα radiation and nickel filter. Scanning electron microscope (SEM) studies of the NBT powders were performed using a JSM-6700F electron microscope. Phase-pure BNT powders were obtained at 550°C for 2-2.5h which is relatively lower calcination temperature than other reports. The BNT powders consists of phase-pure perovskite nanocrystals with an average size of 100-200nm.

  17. Coupling sol-gel synthesis and microwave-assisted techniques: a new route from amorphous to crystalline high-surface-area aluminium fluoride.

    PubMed

    Dambournet, Damien; Eltanamy, Gehan; Vimont, Alexandre; Lavalley, Jean-Claude; Goupil, Jean-Michel; Demourgues, Alain; Durand, Etienne; Majimel, Jérôme; Rudiger, Stephan; Kemnitz, Erhard; Winfield, John M; Tressaud, Alain

    2008-01-01

    A non-aqueous sol-gel Al-based fluoride has been subjected to the microwave solvothermal process. The final material depends on the temperature heat treatment used. Three types of material have been prepared: 1) for low temperature heat treatment (90 degrees C) X-ray amorphous alkoxy fluoride was obtained; 2) for the highest temperature used (200 degrees C) the metastable form beta-AlF3 was obtained with a very large surface area of 125 m2 g(-1). The mechanism of the amorphous=crystalline transformation has been rationalised by the occurrence of a decomposition reaction of the gel fluoride induced by the microwave irradiation. 3) Finally, at intermediate temperature (180 degrees C) a multi-component material mixture exhibiting a huge surface area of 525 m2 g(-1) has been obtained and further investigated after mild post-treatment fluorination using F2 gas. The resulting aluminium-based fluoride still possesses a high-surface-area of 330 m2 g(-1). HRTEM revealed that the solid is built from large particles (50 nm) identified as alpha-AlF3, and small ones (10 nm), relative to an unidentified phase. This new high-surface-area material exhibits strong Lewis acidity as revealed by pyridine adsorption and catalytic tests. By comparison with other materials, it has been shown that whatever the composition/structure of the Al-based fluoride materials, the number of strong Lewis acid sites is related to the surface area, highlighting the role of surface reconstruction occurring on a nanoscopic scale on the formation of the strongest Lewis acid sites. PMID:18491305

  18. 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.

  19. Effect of annealing on the structural and optical properties of TiO2 powder prepared by sol-gel route

    NASA Astrophysics Data System (ADS)

    Halder, Nilanjan; Misra, Kamakhya Prakash

    2016-05-01

    Using titanium isopropoxide as the precursor, Titanium dioxide (TiO2) powder was synthesized via sol-gel method, a promising low temperature route for preparing nanosized metal oxide semiconductors with good homogeneity at low cost. The as-prepared nano powder was thermally treated in air at 550, 650, 750, 900 and 1100°C for 1hr after drying at room temperature and used for further characterization. X-ray diffraction measurements showed that the annealing treatment has a strong impact on the crystal phase of TiO2 samples. The crystallite size as calculated from Debye Scherer formula lies in the range 29-69 nm and is found to increase with increase in annealing temperature. Photoluminescence studies exhibit an improvement in the optical efficiency of the samples with post synthesis heat treatment. Annealing at temperature above 900°C results in a degradation of the structural and optical quality of the TiO2 nano powder samples.

  20. 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

  1. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A.; Klimov, Victor L.

    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

  2. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A.; Klimov, Victor L.

    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.

  3. 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

  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. Photoactive sol-gel biocoatings

    NASA Astrophysics Data System (ADS)

    Ulatowska-Jarża, A.; Bindig, U.; Podbielska, H.; Hołowacz, I.; Gersonde, I.; Beuthan, J.; Müller, G.; Eichler, H. J.

    2006-02-01

    In this work we investigated the photoactive properties sol-gel biocoatings doped with Protoporphyrin IX (PP IX). It was demonstrated that PP IX entrapped in sol-gel preserves it's chemical activity and may have contact with the external environment. The chemical reactions with zinc cations and pyridine, as well as protonation, occurred quite fast. This indicates, that the interconnected porous network could be easily penetrated by relatively large molecules (e.g. mentioned by pyridine molecule). Further, we observed that PP IX molecules do not leave the pores. Structural changes caused by the addition of PP IX to the sol-gel matrix influence not only on the optical properties, but also on durability of the coatings. The altering of PP IX doped silica sol-gel coatings is quite slow.

  6. 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.

  7. 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.

  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. Structural and magnetic properties of BaCoxZrxFe(12-2x)O19 prepared by citrate precursor sol-gel route

    NASA Astrophysics Data System (ADS)

    Chawla, S. K.; Mudsainiyan, R. K.; Meena, S. S.; Yusuf, S. M.

    2013-06-01

    The aim of this work is to investigate the correlation between the distribution of cations over five crystallographic positions and magnetic properties of Ba-hexaferrites in the coupled substitution of magnetic Co2+ and non-magnetic Zr4+ for Fe3+. We have accomplished the synthesis of Co-Zr doped BaCoxZrxFe(12-2xO19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) by citrate precursor sol-gel method under acidic conditions. Single phase M-type hexagonal ferrites are formed at 800 °C. The average size of hexagonal platelets is 34 nm. Mössbauer analysis suggests that site preferences depend upon the concentration of dopants. Dopant ions prefer 4f2 site at x = 0.4 while 12k site is largely substituted at higher dopant concentrations. Magnetic hysteresis data show that the coercive force is markedly reduced with increasing Co-Zr contents but net magnetization and coercivity are not correlated with dopant levels [MS = 61.02 emu/g, HC = 2790 Oe (x = 0); MS = 61.31 emu/g, HC = 100 Oe (x = 0.4); MS = 49.34, HC = 2134 Oe (x = 0.6); MS = 54.94 emu/g, HC = 1443 Oe (x = 1.0)]. Our results show that the magnetization and magnetocrystalline anisotropy are closely related to the distribution of Co-Zr on the five sites.

  13. 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 (ε‧ and ε″) and permeability (μ‧ and μ″) 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 (ε‧) 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 (μ‧) 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.

  14. 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.

  15. Preparation of nanostructured La0.7Ca0.3-xBaxMnO3 ceramics by a combined sol-gel and spark plasma sintering route and resulting magnetocaloric properties

    NASA Astrophysics Data System (ADS)

    Ayadi, F.; Regaieg, Y.; Cheikhrouhou-Koubaa, W.; Koubaa, M.; Cheikhrouhou, A.; Lecoq, H.; Nowak, S.; Ammar, S.; Sicard, L.

    2015-05-01

    This work proposes an original, easy to achieve and inexpensive route to synthesize manganite ceramics for magnetic refrigeration, combining sol-gel chemistry to Spark Plasma Sintering (SPS). The target La0.7Ca0.3-xBaxMnO3 (x=0, 0.1, 0.2) compounds are obtained as single phases which crystallize in the orthorhombic structure (Pnma space group). SPS allows a quick sintering at a relatively low temperature (700 °C in this work) compared to the conventional solid state method (≥1100 °C), leading to densified ultrafine grained pellets (85% of compactness). Magnetic studies show that Ba substitution does not affect significantly the relative cooling power (RCP) of these manganites, while it increases their Curie temperature (TC) by several tens of degrees. Typically, RCP values ranging between 267 and 270 J/kg (for a magnetic field change of 5 T) and TC between 205 and 245 K were measured when x was increased from 0 to 0.2, respectively. These results combined to the fact that the synthesis route is economically advantageous makes the obtained ceramics interesting as active refrigerants for magnetic refrigeration technology below room temperature.

  16. Biological response of human mesenchymal stromal cells to titanium grade 4 implants coated with PCL/ZrO₂ hybrid materials synthesized by sol-gel route: in vitro evaluation.

    PubMed

    Catauro, M; Bollino, F; Papale, F; Mozetic, P; Rainer, A; Trombetta, M

    2014-12-01

    The surface modification of implantable materials in order to improve their biological proprieties, including tissue tolerance and osseointegration ability, by means of functional coating deposition is a promising strategy to provide a firm fixation of the implants. In this study, organic/inorganic hybrid materials consisting of an inorganic zirconia-based matrix, in which a biocompatible polymer, poly(ε-caprolactone) (PCL), has been incorporated at different percentages, have been synthesized via sol-gel route. Developed materials have been used to coat titanium grade 4 substrates by means of dip coating technique. Scanning electron microscopy (SEM) analysis of the obtained coatings has shown that films crack-free can be obtained for high levels of PCL. Chemical composition and interactions between organic and inorganic moieties have been studied by Attenuated Total Reflectance Fourier Transform InfraRed spectroscopy. The bone-bonding capability of the nanocomposite films has been evaluated in vitro by examining the appearance of an apatite layer on their surface when soaked in a simulated body fluid by means of SEM equipped with EDS microanalysis. In vitro biocompatibility assessment was performed in combination with human mesenchymal stromal cells (hMSCs). Materials were found to be non-toxic and supporting cell proliferation. Additionally, the coating material was not hampering the differentiation of hMSCs in an osteogenic medium. PMID:25491844

  17. 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.

  18. 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].

  19. Sol-gel antireflective coating on plastics

    SciTech Connect

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

    1990-05-29

    This patent describes 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.

  20. Sol-gel antireflective coating on plastics

    DOEpatents

    Ashley, Carol S.; Reed, Scott T.

    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.

  1. 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.

  2. Non-aqueous energy storage devices using graphene nanosheets synthesized by green route

    NASA Astrophysics Data System (ADS)

    Mhamane, Dattakumar; Suryawanshi, Anil; Banerjee, Abhik; Aravindan, Vanchiappan; Ogale, Satishchandra; Srinivasan, Madhavi

    2013-04-01

    In this paper we report the use of triethylene glycol reduced graphene oxide (TRGO) as an electrode material for non-aqueous energy storage devices such as supercapacitors and Li-ion batteries. TRGO based non-aqueous symmetric supercapacitor is constructed and shown to deliver maximum energy and power densities of 60.4 Wh kg-1 and 0.15 kW kg-1, respectively. More importantly, symmetric supercapacitor shows an extraordinary cycleability (5000 cycles) with over 80% of capacitance retention. In addition, Li-storage properties of TRGO are also evaluated in half-cell configuration (Li/TRGO) and shown to deliver a reversible capacity of ˜705 mAh g-1 with good cycleability at constant current density of 37 mA g-1. This result clearly suggests that green-synthesized graphene can be effectively used as a prospective electrode material for non-aqueous energy storage systems such as Li-ion batteries and supercapacitors.

  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. 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

  5. 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.

  6. Sintering effects on dielectric properties of Zn-doped CaCu3Ti4O12 ceramic synthesized by modified sol-gel route

    NASA Astrophysics Data System (ADS)

    Singh, Laxman; Rai, U. S.; Rai, Alok Kumar; Mandal, K. D.

    2013-01-01

    CaCu2.90Zn0.10Ti4O12 ceramic was synthesized by a novel semi-wet route and calcined at 800°C in air for 8 h. The obtained powder was divided into three parts and sintered in air at 950°C for 6 h, 8 h, and 12 h, separately. XRD results confirmed the single phase formation of all the sintered samples with similar cubic structure of CaCu3Ti4O12 (CCTO). Scanning electron micrographs of the CaCu2.9Zn0.1Ti4O12 ceramic sintered for 6 h shows bimodal grain size distribution. Increasing the sintering time significantly promotes the grain growth and microstructural densification. The sintering duration was found to have tremendous influence on microstructure and dielectric properties of CaCu2.90Zn0.10Ti4O12 ceramic. The CaCu2.9Zn0.1Ti4O12 ceramic sintered for 12 h exhibited high dielectric constant ɛ r ˜ 5971 at 1 kHz and room temperature. It is found that ɛ r is independent at high frequency and weakly dependent on temperature.

  7. Patternable hybrid sol-gel glass

    NASA Astrophysics Data System (ADS)

    Jiang, HongJin; Yuan, XiaoCong; Chan, Yuen Chuen; Lam, Yee Loy

    2000-10-01

    The hybrid sol-gel materials have been extensively studied and widely used in the fabrication of optical devices due to their attractive properties. In this work, the synthesis of the UV sensitive organic- inorganic SiO2/TiO2 sol-gel glass is presented. The effect of the fabrication parameters such as doping concentration, bake temperature and UV light exposure time on the film characteristics (thickness and refractive index) are studied. A simple way of patterning the material by UV light radiation is also introduced. These demonstrate the material possesses high potential application for the micro-optics device fabrication.

  8. Neutron detector using sol-gel absorber

    DOEpatents

    Hiller, John M.; Wallace, Steven A.; Dai, Sheng

    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.

  9. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, John M.

    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.

  10. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, John M.

    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.

  11. 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.

  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. 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.

  14. 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.

  15. A sensitive fibre optic pH sensor using multiple sol-gel coatings

    NASA Astrophysics Data System (ADS)

    Lee, S. Thomas; Gin, Jose; Nampoori, V. P. N.; Vallabhan, C. P. G.; Unnikrishnan, N. V.; Radhakrishnan, P.

    2001-09-01

    The fabrication and characterization of a fibre optic pH sensor based on evanescent wave absorption is presented. The unclad portion of a multi-mode optical fibre is coated with a pH sensitive dye, which is immobilized by the sol-gel route. The sensitivity of the device has been found to increase when multiple sol-gel coatings are used as the sensing region. The dynamic range and the temporal response of the sensor are investigated for two different dyes, namely bromocresol purple and bromocresol green. The performance of the device is evaluated in terms of the results obtained during actual measurements.

  16. Droplet Spreading with Sol-Gel Transition

    NASA Astrophysics Data System (ADS)

    Jalaal, Maziyar; Stoeber, Boris; Balmforth, Neil J.

    2014-11-01

    The impact and spreading of liquid droplets on a smooth solid substrate is a classical subject with several industrial applications such as ink-jet printing, spray cooling, coating, and many others. For many of these deposition processes, controlling the final shape of the drop is critical. In the current research, a new technique for controlling the spreading of droplets impacting a substrate is presented. This technique exploits the rheology of a thermo-responsive polymer solution that undergoes a reversible sol/gel transition above a critical temperature. Experiments are conducted using a combination of shadowgraphy and micro-PIV to observe spreading drops. It is shown that the final diameter of a droplet can be controlled through the temperature of the substrate and the tunable sol/gel transition temperature of the fluid.A mathematical model is provided to further elucidate the flow dynamics.

  17. 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.

  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. 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.

  20. Sol-gel based optical chemical sensors

    NASA Astrophysics Data System (ADS)

    Lobnik, Aleksandra; Korent Urek, Špela; Turel, Matejka; Frančič, 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.; Féron, P.; Gonçalves, 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.

  6. 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.

  7. 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.

  8. Sol-gel method for encapsulating molecules

    DOEpatents

    Brinker, C. Jeffrey; Ashley, Carol S.; Bhatia, Rimple; Singh, Anup K.

    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.

  9. Spectroscopic studies of triethoxysilane sol-gel and coating process

    NASA Astrophysics Data System (ADS)

    Li, Ying-Sing; Ba, Abdul

    2008-10-01

    Silica sol-gels have been prepared under different conditions using triethoxysilane (TES) as precursor. The prepared sol-gels have been used to coat aluminum for corrosion protection. Vibrational assignments have been made for most vibration bands of TES, TES sol-gel, TES sol-gel-coated aluminum and xerogel. It has been noticed that air moisture may have helped the hydrolysis of the thin coating films. Xerogels have been obtained from the sol-gel under different temperature conditions and the resulting samples have been characterized by using infrared and Raman spectroscopic methods. IR data indicate that the sol-gel process is incomplete under the ambient conditions although an aqueous condition can have slightly improved the process. Two nonequivalent silicon atoms have been identified from the collected 29Si NMR spectra for the sol-gel, supporting the result derived from the IR data. The frequency of Si sbnd H bending vibration has been found to be more sensitive to the skeletal structure than that of the Si sbnd H stretching vibration. A higher temperature condition could favor the progression of hydrolysis and condensation. A temperature higher than 300 °C would cause sample decomposition without seriously damaging the silica network. From infrared intensity measurements and thermo-gravimetric analyses, the fractions of incomplete hydrolysis and condensation species have been estimated to be 4% and 3%, respectively. Electrochemical data have shown that the sol-gel coating significantly improves the corrosion protection properties of aluminum.

  10. 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…

  11. 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

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Sol-gel synthesis of protoenstatite

    SciTech Connect

    Jones, S.A.; Burlitch, J.M.

    1994-12-31

    Protoenstatite, a high-temperature polymorph of enstatite (MgSiO{sub 3}), is generally not stable at room temperature, and is difficult to synthesize. Using a recently developed, hydrogen peroxide assisted, sol-gel synthesis, protoenstatite was synthesized in a form that was stable at room temperature. Its crystallization was strongly dependent on processing conditions, particularly on the manner in which the xerogel was formed and fired. Xerogels prepared by evaporation, spray-drying and freeze-drying were compared by XRD, HTXRD, BET, TG/DTA, and {sup 29}Si NMR methods. When samples were prepared by evaporation or spray-drying, the result was a mixture of polymorphs. Only the freeze-dried precursor yielded protoenstatite at a lower temperature and within a shorter time than any previously reported.

  17. Ionic conductivity of Bi2NixV1-xO5.5-3x/2 (0.1 ≤ x ≤ 0.2) oxides prepared by a low temperature sol-gel route

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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 Bi4V2O11 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 Bi2NixV1-xO5.5-3x/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 × 10-3 S cm-1, 1.2 × 10-3 S cm-1, and 8.2 × 10-4 S cm-1, for x = 0.1; 0.15; and 0.2; respectively; and at 600 °C were 1.1 × 10-1 S cm-1, 5.3 × 10-2 S cm-1, and 2.8 ×10-2 S cm-1, for x = 0.1; 0.15; and 0.2; respectively.

  18. Raman and electrochemical impedance studies of sol-gel titanium oxide and single walled carbon nanotubes composite films.

    PubMed

    Rincón, M E; Trujillo-Camacho, M E; Miranda-Hernández, M; Cuentas-Gallegos, A K; Orozco, G

    2007-01-01

    Titanium oxide grown by a sol-gel route on single-walled carbon nanotubes was studied by Raman and Electrochemical Impedance techniques and compared with mixtures obtained by mechanical grinding. In spite of the superior dispersion of single-walled carbon nanotubes bundles in sol-gel composites, the lost of the small-diameter carbon nanotubes in the oxidizing sol-gel bath was inferred from their Raman spectra and the lower capacitive current of the voltammograms in 0.1 M H2SO4. We proposed proton electrosorption as the main charge storage mechanism for sol-gel composites, favoured by the hydroxylation and n-type conductivity of the oxide, while electrodes based on mixtures were dominated by double-layer charging, developing some pseudocapacitance with potential cycling due to the reversible oxidation of carbon nanotubes. Comparsion with TiO2/Carbon Blacks composites shows the effective role of single-walled carbon nanotubes as templates to control the mesoporous nature of sol-gel composite electrodes. PMID:17450931

  19. Wet powder processing of sol-gel derived mesoporous silica-hydroxyapatite hybrid powders.

    PubMed

    Andersson, Jenny; Johannessen, Espen; Areva, Sami; Järn, Mikael; Lindén, Mika

    2006-08-01

    This paper describes a method by which a porous silica coating layer can be obtained on different apatite particles through a simple sol-gel synthesis route. Sol-gel derived powders of hydroxyapatite (HAP) and beta tricalciumphosphate (beta-TCP) were coated with a mesoporous silica using C16TAB (hexadecyltrimethylammonium bromide) as a template in order to induce mesophase formation. Further calcination of the material removes the template from the mesophase and leaves a highly ordered hexagonal arranged mesoporous silica structure with a core of HAP/beta-TCP. The phase purity of the SiO2/apatite composites has been thoroughly investigated by the means of FT-IR, XRD, and solid state 31P MAS NMR. The phase purity of these materials is shown to be dependent on the solubility properties of the used apatites. The hybrid materials are suitable as a multifunctional biomaterial where osteoconductive properties can be combined with drug delivery. PMID:17037853

  20. Fabrication and Characterization of Lead Zirconate Titanate (PZT) Thin Films by Sol-Gel Technique

    NASA Astrophysics Data System (ADS)

    Rahman, M. F.; Miglioli, L.

    2016-02-01

    In this work, thin lead zirconate titanate, Pb[Zr0.52Ti0.48]O3 (PZT) films have been developed from a novel sol-gel route. The sol-gel films were deposited by spin coating method. Isopropanol-based solution was used for its less toxic property. Gold (Au), platinum (Pt) and indium tin oxide (ITO) were used as substrates. Homogeneous polycrystalline films with (110) preferred orientation were obtained from all the films. The films behaved as ferroelectric material where dielectric constant at 0V for the films obtained from Au, Pt and ITO substrates were 484, 770 and 655, respectively. The coercive field values were around 10-15KV/cm which revealed that the films were soft ferroelectric.

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

    NASA Astrophysics Data System (ADS)

    Baz, Assaad; El Hamzaoui, Hicham; Fsaifes, Ihsan; Bouwmans, Géraud; 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.

  2. Hybrid zirconium sol-gel thin films with high refractive index

    NASA Astrophysics Data System (ADS)

    Gorin, Arnaud; Copperwhite, Robert; Elmaghrum, Salem; Mc Donagh, Colette; Oubaha, Mohamed

    2011-08-01

    We describe the synthesis of optical quality thin film materials with high refractive index, employing zirconium based hybrid sol-gel precursors. As the zirconium propoxide precursor is unstable in the presence of a strong nucleophilic agent such as water, two synthesis routes have been performed employing a chelating agent and an organosilane precursor to avoid the formation of any undesired ZrO2 agglomerates, leading to organo-zirconate complexes and silicato-zirconate copolymers, respectively. The prepared hybrid sol-gel materials were deposited by spin-coating to form a transparent thin film on silicon substrates, and heat treated at 100 °C for the final stabilisation of the layer. The effect of the two synthesis routes on the optical properties of zirconium based hybrid sol-gel material is discussed. It was found that the nature and concentration of the organosilane precursor can significantly affect the structural properties of the deposited films. A correlation was also demonstrated between the concentration of the organosilane precursor and the refractive index of the material. By reducing the concentration of organosilane precursor, high refractive index materials were obtained. Similar behaviour was observed for the materials synthesised via chelating agent. The synthesis employing an organosilane precursor produces films with higher refractive index. A maximum refractive index of 1.746 was measured at 635nm for the deposited thin films.

  3. Neutron detector based on lithiated sol-gel glass

    NASA Astrophysics Data System (ADS)

    Wallace, Steven; Stephan, Andrew C.; Miller, Laurence F.; Dai, Sheng

    2002-05-01

    A neutron detector technology is demonstrated based on 6Li/ 10B doped sol-gel glass. The detector is a sol-gel glass film coated silicon surface barrier detector (SBD). The ionized charged particles from ( n, α) reactions in the sol-gel film enter the SBD and are counted. Data showing that gamma-ray pulse amplitudes interfere with identifying charged particles that exit the film layer with energies below the gamma-ray energy is presented. Experiments were performed showing the effect of 137Cs and 60Co gamma rays on the SBD detector. The reaction product energies of the triton and alpha particles from 6Li are significantly greater than the energies of the Compton electrons from high-energy gamma rays, allowing the measurement of neutrons in a high gamma background. The sol-gel radiation detection technology may be applicable to the characterization of transuranic waste, spent nuclear fuel and to the monitoring of stored plutonium.

  4. 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.

  5. 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.

  6. Dip coating of sol-gels

    NASA Astrophysics Data System (ADS)

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

    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 (less than 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. These phenomena were studied 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.

  7. 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.

  8. 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.

  9. 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

  10. Synthesis and characterization of transparent mesoporous materials by a non-aqueous sol gel method

    NASA Astrophysics Data System (ADS)

    Sediri, F.; Chine, M. K.; Gharbi, N.

    2008-06-01

    New inorganic-organic hybrid mesoporous materials were prepared by chemical modification of polymethylhydrosiloxane by 1,2-diaminopropane and 1,2-diaminocyclohexane, in tetrahydrofuran, using hexachloroplatinic acid (H2PtCl6· 6H2O) as catalyst at room temperature. This reaction leads to the formation of transparent and monolithic gels. The products have been characterized by infrared and 29Si CP MAS NMR spectroscopy. The results show that the organic components have reacted with the polymethylhydrosiloxane leading to colourless and coloured gels in which both organic-inorganic bridges are formed. The thermal treatment procedure was determined by TGA and DTA curves recorded on the hybrid gel powder drying at 100 °C during 24 h. Xerogels morphology and texture were performed by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller method (BET).

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Slow Release of Plant Volatiles Using Sol-Gel Dispensers.

    PubMed

    Bian, L; Sun, X L; Cai, X M; Chen, Z M

    2014-12-01

    The black citrus aphid, also known as the tea aphid, (Toxoptera aurantii Boyer) attacks economically important crops, including tea (Camellia sinensis (L.) O. Kuntze). In the current study, silica sol-gel formulations were screened to find one that could carry and release C. sinensis plant volatiles to lure black citrus aphids in a greenhouse. The common plant volatile trans-2-hexen-1-al was used as a model molecule to screen for suitable sol-gel formulations. A zNose (Electronic Sensor Technology, Newbury Park, CA) transportable gas chromatograph was used to continuously monitor the volatile emissions. A sol-gel formulation containing tetramethyl orthosilicate and methyltrimethoxysilane in an 8:2 (vol:vol) ratio was selected to develop a slow-release dispenser. The half-life of trans-2-hexen-1-al in the sol-gel dispenser increased slightly with the volume of this compound in the dispenser. Ten different volatiles were tested in the sol-gel dispenser. Alcohols of 6-10 carbons had the longest half-lives (3.01-3.77 d), while esters of 6-12 carbons had the shortest (1.53-2.28 d). Release of these volatiles from the dispensers could not be detected by the zNose after 16 d (cis-3-hexenyl acetate) to 26 d (3,7-dimethylocta-1,6-dien-3-ol). In greenhouse experiments, trans-2-hexen-1-al and cis-3-hexen-1-ol released from the sol-gel dispensers attracted aphids for ≍17 d, and release of these volatiles could not be detected by the zNose after ≍24 d. The sol-gel dispensers performed adequately for the slow release of plant volatiles to trap aphids in the greenhouse. PMID:26470065

  17. Optical spectroscopy of trivalent chromium in sol-gel lithium niobate

    SciTech Connect

    Krebs, J.K.; Happek, U.

    2005-12-19

    We report on the characterization of sol-gel derived lithium niobate via trivalent chromium probe ions, a study that is motivated by recent reports on the synthesis of high quality sol-gel lithium niobate (LiNbO{sub 3}). In order to assess the quality of sol-gel derived LiNbO{sub 3}, we incorporate Cr{sup 3+} during the hydrolysis stage of the sol-gel process. A comparison of the Cr{sup 3+} emission and photoexcitation data on both sol-gel and melt-grown LiNbO{sub 3} shows that the sol-gel derived material is highly stoichiometric.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Scanning electron microscopy analysis of sol-gel derived biocompatible glass

    NASA Astrophysics Data System (ADS)

    Holmes-Smith, A. S.; Hungerford, G.; Uttamlal, M.; Amaro, M.; Martins, P.; McBrearty, L.; Love, G.; Ferreira, M. I. C.

    2008-08-01

    Bioactive silica gels/polymer systems have been produced using a sol-gel route and their bio-compatibility has been investigated by immersing them in simulated body fluid (SBF). The porous monoliths have been characterised by SEM and EDX analysis where images obtained show pores on the surface of 10-200 μm. The silica gels are not homogeneous and distinct regions of silicon and calcium are observed. The growth of an apatite layer on the surface of the gels was evident after steeping in SBF.

  5. 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.

  6. 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.

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

    DOEpatents

    Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

    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.

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

    DOEpatents

    Congdon, James W.

    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.

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

    DOEpatents

    Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

    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.

  10. 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...

  11. Safe and Environmentally Acceptable Sol-gel Derived Pyrophoric Pyrotechnics

    SciTech Connect

    Simspon, R L; Satcher, J H; Gash, A

    2004-06-10

    It was demonstrated that highly porous sol-gel derived iron (III) oxide materials could be reduced to sub-micron-sized metallic iron by heating the materials to intermediate temperatures in a hydrogen atmosphere. Through a large number of experiments complete reduction of the sol-gel based materials was realized with a variety of hydrogen-based atmospheres (25-100% H{sub 2} in Ar, N{sub 2}, CO{sub 2}, or CO) at intermediate temperatures (350 C to 700 C). All of the resulting sol-gel-derived metallic iron powders were ignitable by thermal methods, however none were pyrophoric. For comparison several types of commercial micron sized iron oxides Fe2O3, and NANOCAT were also reduced under identical conditions. All resulting materials were characterized by thermal gravimetric analysis (TGA), differential thermal analysis (DTA), powder X-ray diffraction (PXRD), as well as scanning and transmission electron microscopies (SEM and TEM). In addition, the reduction of the iron oxide materials was monitored by TGA. In general the sol-gel materials were more rapidly reduced to metallic iron and the resulting iron powders had smaller particle sizes and were more easily oxidized than the metallic powders derived from the micron sized materials. The lack of pyrophoricity of the smaller fine metallic powders was unexpected and may in part be due to impurities in the materials that create a passivation layer on the iron. Several recommendations for future study directions on this project are detailed.

  12. Sol-gel synthesis and TEM-EDX characterisation of hydroxyapatite nanoscale powders modified by Mg, Sr or Ti

    NASA Astrophysics Data System (ADS)

    Qaisar, S. A.; Bilton, M.; Wallace, R.; Brydson, R.; Brown, A. P.; Ward, M.; Milne, S. J.

    2010-07-01

    Chemically modified hydroxyapatite nanoparticles have been prepared by a sol-gel route. Analysis by TEM-EDX confirmed that the dopants, Mg, Sr or Ti had been incorporated into the product. However each sample displayed variability in the level of dopant incorporation in different particles within the same sample. Particle sizes were <= 100 nm for samples modified by Mg or Ti. Doping with Sr produced an elongated particle morphology, with dimensions ~ 200nm × 50 nm.

  13. Effect of solute concentration on the structural and morphological properties of sol-gel derived CdO films

    NASA Astrophysics Data System (ADS)

    Rajammal, R.; Savarimuthu, E.; Arumugam, S.

    2013-06-01

    The present work deals with the preparation of cadmium oxide (CdO) thin films through the sol-gel spin coating route on to glass substrates. The structural and surface morphological properties of the deposited films have been investigated and the influence of precursor solute concentration on these properties studied. Smooth, uniform CdO films with good crystalline quality have been obtained by controlling the precursor solute concentration and the results have been presented.

  14. 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.

  15. Multinuclear NMR studies on the sol-gel preparation of sodium aluminophosphate glasses.

    PubMed

    Zhang, Long; Eckert, Hellmut

    2004-01-01

    Sodium aluminophosphate gels and glasses in the system NaPO(3)-Al(2)O(3) with P/Al ratios ranging from 9:1 to 1:1 have been synthesized by a novel sol-gel route based on the reaction of aluminum lactate with sodium polyphosphate in aqueous solution. The route from the solution to the gel and the final glass was monitored in situ by liquid and solid state NMR techniques, characterizing the influence of composition and pH on the hydrolysis, polymerization, and vitrification processes. The site distribution in the xerogels is strongly influenced by the gel-processing temperature. At temperatures near 150 degrees Celsius ligation with lactate groups can be nearly suppressed, resulting in maximum Al/P connectivity in the gel. Annealing the gels at temperatures near 400 degrees Celsius produces significant structural rearrangements, resulting in a glassy network that has close structural similarity to the glasses derived from the usual melt-cooling procedure at 1100-1450 degrees Celsius. This has been confirmed by extensive (27)Al, (31)P and (23)Na MAS NMR as well as (27)Al[(31)P] and (27)Al [(1)H] double resonance experiments. Compared to melt-cooling, the sol-gel process permits a significant extension of the glass-forming region towards higher alumina contents. PMID:15388177

  16. 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.

  17. 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.

  18. 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

  19. 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, Onélia Aparecida Andreo; Coutinho, João A P; Lima, Álvaro 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 influence 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 Å). 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

  20. 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.

  1. Synthesis of 45S5 Bioglass® via a straightforward organic, nitrate-free sol-gel process.

    PubMed

    Rezabeigi, Ehsan; Wood-Adams, Paula M; Drew, Robin A L

    2014-07-01

    More than four decades after the discovery of 45S5 Bioglass® as the first bioactive material, this composition is still one of the most promising materials in the tissue engineering field. Sol-gel-derived bioactive glasses generally possess improved properties over other bioactive glasses, because of their highly porous microstructure and unique surface chemistry which accelerate hydroxyapatite formation. In the current study, a new combination of precursors with lactic acid as the hydrolysis catalyst have been employed to design an organic, nitrate-free sol-gel procedure for synthesizing of 45S5 Bioglass®. This straightforward route is able to produce fully amorphous submicron particles of this glass with an appropriately high specific surface area on the order of ten times higher than that of the melt-derived glasses. These characteristics are expected to lead to rapid hydroxyapatite formation and consequently more efficient bone bonding. PMID:24857490

  2. 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.

  3. 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.

  4. 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.

  5. Nanostructured Energetci Matreials with sol-gel Chemistry

    SciTech Connect

    Gash, A; Satcher, J; Simpson, R; Clapsaddle, B

    2003-11-18

    The utilization of nanomaterials in the synthesis and processing of energetic materials (i.e., pyrotechnics, explosives, and propellants) is a relatively new area of science and technology. Previous energetic nanomaterials have displayed new and potentially beneficial properties, relative to their conventional analogs. Unfortunately some of the energetic nanomaterials are difficult and or expensive to produce. At LLNL we are studying the application of sol-gel chemical methodology to the synthesis of energetic nanomaterials components and their formulation into energetic nanocomposites. Here sol-gel synthesis and formulation techniques are used to prepare Fe{sub 2}O{sub 3}/Al pyrotechnic nanocomposites. The preliminary characterization of their thermal properties and the degree of mixing between fuel and oxidizer phases is contrasted with that of a conventional pyrotechnic mixture.

  6. New developments for sol-gel film and fiber processing

    SciTech Connect

    Hurd, A.J.

    1995-03-01

    New insights into the development of microstructure in sol-gel films have recently been revealed by several diagnostic techniques, including imaging ellipsometry, {open_quotes}chemical imaging{close_quotes} by fluorescent tracers, light scattering from capillary waves, and finite-element modeling. The evolution of porosity during the continuous transition from dilute sol to porous solid in restricted geometries such as films and fibers is becoming clearer through fundamental understanding of evaporation dynamics and capillarity.

  7. 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.

  8. Neodymium doped sol-gel tapered waveguide amplifier

    NASA Astrophysics Data System (ADS)

    Peled, Asher; Nathan, Menachem; Tsukernik, Alexander; Ruschin, Shlomo

    2007-04-01

    The authors report the design, fabrication, and study of a fully monolithic solid-state amplifier based on a neodymium doped sol-gel tapered rib waveguide with a thin guiding layer of 360nm. Signal (1064nm) and pump (803nm) light were coupled into and out of the amplifier by grating couplers. A gain of 4.8dB (3.75dB net internal gain) was obtained from a 1cm long device.

  9. 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

  10. Switchable vanadium oxide films by a sol-gel process

    NASA Astrophysics Data System (ADS)

    Partlow, D. P.; Gurkovich, S. R.; Radford, K. C.; Denes, L. J.

    1991-07-01

    Thin polycrystalline films of VO2 and V2O3 were deposited on a variety of substrates using a sol-gel process. The orientation, microstructure, optical constants, and optical and electrical switching behavior are presented. These films exhibited sharp optical switching behavior even on an amorphous substrate such as fused silica. The method yields reproducible results and is amenable to the coating of large substrates and curved surfaces such as mirrors and lenses.

  11. 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

  12. Control of the nanocrystalline zirconia structure through a colloidal sol-gel process

    NASA Astrophysics Data System (ADS)

    Gossard, A.; Grasland, F.; Le Goff, X.; Grandjean, A.; Toquer, G.

    2016-05-01

    A simple method to synthesize tetragonal zirconia stabilized at ambient temperature is developed and allows the monitoring of the tetragonal-monoclinic transition via a colloidal sol-gel process. By increasing the pH of an aqueous solution consisted of a zirconium precursor and a complexing agent (acetylacetone), a colloidal sol and then a gel can be formed under slightly acidic condition. After a drying step, tetragonal zirconia is easily obtained with an adequate thermal treatment at low temperature. The tetragonal-monoclinic transition occurs when the calcination temperature is increased. The relationship between the crystallite size, the crystallographic structure and the thermal treatment has been investigated by X-Ray Diffraction and the behaviour of the system from the gel state to the final powder has been studied by using Small Angle X-Ray Scattering and thermal analysis techniques. We demonstrate that compared to a chemical precipitation route, this colloidal sol-gel process allows the nanostructure of the material to be controlled due to the formation of primary nanoparticles. The presence of these nanoparticles makes possible the specific determination of the zirconia crystallographic phase through an accurate control of the nanostructure during the thermal treatment.

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

    NASA Astrophysics Data System (ADS)

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

    2004-06-01

    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°C for 6-12h of the coatings deposited on stainless steel was found to increase the breakdown voltage.

  14. 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.

  15. Band gap and FTIR studies for copper-zinc sol-gel glasses

    NASA Astrophysics Data System (ADS)

    Kaur, G.; Kaur, Navneet; Rawat, Mohit; Singh, K.; Kumar, Vishal

    2016-05-01

    Sol-gel technique was used for synthesis of Calcium phosphorous Borosilicate (CaO-SiO2-B2O3-P2O5-CuO-ZnO) glasses by varying composition of Copper oxide and Zinc oxide. Sol-gel route uses organic precursors which provide better homogeneity and uniform particle size compared to melt quenched glass. Four different glass stoichiometries were characterised using UV-visible spectroscopy and Fourier transforms infra-red spectroscopy (FTIR). Infra-red spectrum of transmittance of powdered glass samples is obtained by FTIR which measure the transmittance of wavelength in them and it also determines the presence of different functional group. Band gap has been obtained using UV-visible spectroscopy for all the glasses so as to study the effect of increasing ZnO content in glass composition. The change in band gap with ZnO content is indication of the change in number of non-bridging oxygen's (NBO).

  16. 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.

  17. Sol-gel-derived thick-film amperometric immunosensors.

    PubMed

    Wang, J; Pamidi, P V; Rogers, K R

    1998-03-15

    Sol-gel processing is used for the first time for the preparation of electrochemical immunosensors. One-step sensor fabrication, based on the coupling of sol-gel and screen-printing technologies, is employed. A low-temperature cured ink is prepared by dispersion of rabbit immunoglobulin G (RIgG), graphite powder, and a binder in the sol-gel solution. The enzyme-labeled antibody can readily diffuse toward the encapsulated antigen, which retains its binding properties, and the association reaction is easily detected at the dispersed graphite surface. Use of anti-RIgG labeled with alkaline phosphatase, naphthyl phosphate as the substrate, and amperometric detection at +400 mV (vs Ag/AgCl) results in a low detection limit of 5 ng/mL (32 pM) for the solution antigen. Tailoring the porosity of the ceramic-carbon matrix can be used for tuning the assay performance. The high sensitivity, low cost, durability, and simplicity of the new single-use immunosensors make them well suited for various on-site applications. PMID:9530007

  18. 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

  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. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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 37±1 (°)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

  6. Morphology evolution of ZrB 2 nanoparticles synthesized by sol-gel method

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

    Zirconium diboride (ZrB 2) nanoparticles were synthesized by sol -gel method using zirconium n-propoxide (Zr(OPr) 4), boric acid (H 3BO 3), sucrose (C 12H 22O 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) 4 hydrolysis. Actually, AcOH could dominate the hydrolysis by self-produced water of the chemical propulsion, rather than the help of outer water. C 12H 22O 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 2 particles. Increasing the gelation temperature, the particle shapes changed from sphere-like particles at 65 °C to a particle chain at 75 °C, and then form rod-like particles at 85 °C. An in-depth HRTEM observation revealed that the nanoparticles of ZrB 2 were gradually fused together to evolve into a particle chain, finally into a rod-like shape. These crystalline nature of ZrB 2 related to the gelation temperature obeyed the "oriented attachment mechanism" of crystallography.

  7. 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.

  8. Green synthesis of magnetic chitosan nanocomposites by a new sol-gel auto-combustion method

    NASA Astrophysics Data System (ADS)

    Ansari, Fatemeh; Sobhani, Azam; Salavati-Niasari, Masoud

    2016-07-01

    The Fe2O3/CuFe2O4/chitosan nanocomposites have been successfully synthesized via a new sol-gel auto-combustion route. To prepare the nanocomposites, copper ferrite (CuFe2O4) and iron (II) oxide (Fe2O3) nanostructures were first prepared utilizing onion as a green reductant for the first time, and characterized by SEM, TEM, XRD, IR and VSM. Then chitosan was added into the nanostructures dispersed in water. Chitosan was used to functionalize and modify the nanostructures and also to improve surface properties. The nanocomposites were also characterized by several techniques including SEM, TEM, XRD, IR and VSM. The effects of amount of onion and chitosan on the morphology and particle size of nanocomposites were evaluated.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Benoit, F.; Dieudonné, E.; Bertussi, B.; Vallé, 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.

  11. Preparation and characterisation of novel thick sol-gel titania film photocatalysts.

    PubMed

    Mills, Andrew; Elliott, Nicholas; Hill, George; Fallis, David; Durrant, James R; Willis, Richard L

    2003-05-01

    The preparation and characterization of thick (9 microns), clear, mechanically robust and photocatalytically active films of nanocrystalline anatase titania are described. XRD and SEM analysis show the films comprise 13 nm particles of anatase TiO2. Thin (54 nm) films of the 'paste' TiO2, along with sol-gel titania films made by a more traditional route are also prepared and characterised. All titania films mediate the photocatalytic destruction of stearic acid with a quantum yield of 0.0016 +/- 0.0003, using either 365 nm (i.e. BLB) or 254 nm (germicidal) light. P25 TiO2 films also appear to mediate the same process with a similar formal quantum efficiency. Of all the films tested, the thick paste TiO2 films are the most ideally suited for use with near UV light, for reasons which are discussed. All the titania films tested exhibit photoinduced superhydrophilicity. PMID:12803083

  12. 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.

  13. Sol-gel encapsulated horseradish peroxidase: a catalytic material for peroxidation.

    PubMed

    Smith, Kevyn; Silvernail, Nathan J; Rodgers, Kenton R; Elgren, Timothy E; Castro, Mauro; Parker, Robert M

    2002-04-24

    This study addresses the viability of sol-gel encapsulated HRP (HRP:sol-gel) as a recyclable solid-state catalytic material. Ferric, ferric-CN, ferrous, and ferrous-CO forms of HRP:sol-gel were investigated by resonance Raman and UV-visible methods. Electronic and vibrational spectroscopic changes associated with changes in spin state, oxidation state, and ligation of the heme in HRP:sol-gel were shown to correlate with those of HRP in solution, showing that the heme remains a viable ligand-binding complex. Furthermore, the high-valent HRP:sol-gel intermediates, compound I and compound II, were generated and identified by time-resolved UV-visible spectroscopy. Catalytic activity of the HRP:sol-gel material was demonstrated by enzymatic assays by using I(-), guaiacol, and ABTS as substrates. Encapsulated HRP was shown to be homogeneously distributed throughout the sol-gel host. Differences in turnover rates between guaiacol and I(-) implicate mass transport of substrate through the silicate matrix as a defining parameter in the peroxidase activity of HRP:sol-gel. HRP:sol-gel was reused as a peroxidation catalyst for multiple reaction cycles without loss of activity, indicating that such materials show promise as reusable catalytic materials. PMID:11960453

  14. Modified sol-gel coatings for biotechnological applications

    NASA Astrophysics Data System (ADS)

    Beganskiene, A.; Raudonis, R.; Zemljic Jokhadar, S.; Batista, U.; Kareiva, A.

    2007-12-01

    The modified sol-gel derived silica coatings were prepared and characterized. The amino and methyl groups were introduced onto the colloidal silica. The silica coatings with different wettability properties: coloidal silica (water contact angle 17°), polysiloxane (61°), methyl-modified (158° and 46°) coatings samples were tested for CaCo-2 cells proliferation. Methyl-modified coating (46°) proved to be the best substrate for cell proliferation. CaCo-2 cell proliferation two days post seeding was significantly faster on almost laminine, fibronectin and collagen-1 coated samples compared to corresponding controls.

  15. 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.

  16. 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.

  17. Optical bonding using silica nanoparticle sol-gel chemistry.

    PubMed

    Sivasankar, Sanjeevi; Chu, Steven

    2007-10-01

    A simple method is described to bond optical components using silica nanoparticle sol-gel chemistry. The silica nanoparticles polymerize into highly branched networks that link the surfaces together. The nanoparticle mediated bonding has several advantages to currently used optical joining technologies. The bonding is a room-temperature process and does not require any clean room facilities. The bonded interface has a high mechanical strength and low scattering. The bonding is resistant to organic solvents on silylation with hydrophobic surface groups. This method achieves 100% successful bonding rates between soda-lime glass slides. The bond-setting time can be tailored to allow time for precision optical alignment. PMID:17854226

  18. 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

  19. 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.

  20. Novel thermochromism in silica sol-gel materials

    NASA Astrophysics Data System (ADS)

    Gardener, Martin; Perry, Carole C.

    2000-05-01

    In this contribution we provide evidence for thermochromic color changes unique to silica based materials formed at low temperatures by the sol-gel process. The materials formed have potential application as temperature sensitive light filters, visual temperature indicators, self-diagnostic labels for electronic devices and IR recording media. The dopants, diamine complexes of copper(II)/nickel(II) chloride, change from purple to green following heating to 100 degrees C and revert to purple on cooling in the atmosphere. This color change has been explained by the substitution of water molecules by chloride ions in the first coordination sphere of the metal ions. When the same compounds are incorporated into a silica sol-gel matrix under acidic conditions the gel-glasses may be pale green, dark green, yellow, olive-yellow, blue or brown depending on the metal ion chosen and the extent of thermal treatment. Studies on the complexes themselves and on granular silicas doped with some of the complexes are assisting us in understanding the molecular mechanisms that give rise to these color changes.

  1. 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.

  2. Nanostructured energetic materials derived from sol-gel chemistry

    SciTech Connect

    Simpson, R L; Tillotson, T M; Hrubesh, L W; Gash, A E

    2000-03-15

    Initiation and detonation properties are dramatically affected by an energetic material's microstructural properties. Sol-gel chemistry allows intimacy of mixing to be controlled and dramatically improved over existing methodologies. One material goal is to create very high power energetic materials which also have high energy densities. Using sol-gel chemistry we have made a nanostructured composite energetic material. Here a solid skeleton of fuel, based on resorcinol-formaldehyde, has nanocrystalline ammonium perchlorate, the oxidizer, trapped within its pores. At optimum stoichiometry it has approximately the energy density of HMX. Transmission electron microscopy indicated no ammonium perchlorate crystallites larger than 20 nm while near-edge soft x-ray absorption microscopy showed that nitrogen was uniformly distributed, at least on the scale of less than 80 nm. Small-angle neutron scattering studies were conducted on the material. Those results were consistent with historical ones for this class of nanostructured materials. The average skeletal primary particle size was on the order of 2.7 nm, while the nanocomposite showed the growth of small 1 nm size crystals of ammonium perchlorate with some clustering to form particles greater than 10 nm.

  3. Nanostructured Energetic Materials with Sol-Gel Methods

    SciTech Connect

    Gash, A; Satcher, J; Simpson, R; Clapsaddle, B

    2003-11-25

    The utilization of sol-gel chemical methodology to prepare nanostructured energetic materials as well as the concepts of nanoenergetics is described. The preparation and characterization of two totally different compositions is detailed. In one example, nanostructured aerogel and xerogel composites of sol-gel iron (III) oxide and ultra fine grained aluminum (UFG Al) are prepared, characterized, and compared to a conventional micron-sized Fe{sub 2}O{sub 3}/Al thermite. The exquisite degree of mixing and intimate nanostructuring of this material is illustrated using transmission and scanning electron microscopies (TEM and SEM). The nanocomposite material has markedly different energy release (burn rate) and thermal properties compared to the conventional composite, results of which will be discussed. Small-scale safety characterization was performed aerogels and xerogels of the nanostructured thermite. The second nanostructured energetic material consists of a nanostructured hydrocarbon resin fuel network with fine ammonium perchlorate (NH{sub 4}ClO{sub 4}) oxidizer present.

  4. 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.

  5. Practical protocols for lipase immobilization via sol-gel techniques.

    PubMed

    Reetz, Manfred T

    2013-01-01

    Lipases can be efficiently entrapped in the pores of hydrophobic silicates by a simple and cheap sol-gel process in which a mixture of a hydrophobic alkylsilane RSi(OCH3)3 and Si(OCH3)4 is hydrolyzed under basic conditions in the presence of the enzyme. Additives such as isopropanol, polyvinyl alcohol, cyclodextrins, ionic liquids or surfactants enhance the efficiency of this type of lipase-immobilization. The main area of application of these heterogeneous biocatalysts concerns esterification or transesterification in organic solvents, ionic liquids, or supercritical carbon dioxide. Rate enhancements (relative to the traditional use of lipase powders) of several orders of magnitude have been observed, in addition to higher thermal stability. The lipase-immobilizates are particularly useful in the kinetic resolution of chiral esters, enantioselectivity often being higher than what is observed when using the commercial forms of these lipases (powder or classical immobilizates). Thus, due to the low price of sol-gel entrapment, the excellent performance of the lipase-immobilizates, and the ready recyclability, the method is industrially viable. PMID:23934809

  6. 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.

  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. 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.

  9. 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.

  10. Index modulation Bragg gratings directly imprinted on sol gel layers

    NASA Astrophysics Data System (ADS)

    Moreau, Yves; Arguel, Philippe; Coudray, Paul; Porque, Jerome; Etienne, Pascal

    1998-01-01

    Among the fabrication techniques of integrated optical devices, the sol-gel chemistry is now performant enough to make thin films of transparent materials with controlled purity and composition, at low temperature. Semi-mineral semi-organic solutions allow dip coating followed by low temperature baking to deposit vitreous films up to eight micrometers thick which are free from cracks. A local polymerization process through UV exposure enables hybrid components compatible with electronic planar silicon or III- V components. This UV imprinting method is used here to make index modulation gratings with use of a holographic equipment as an alternative to the use of a costly phase mask. Gratings have been imprinted on various sol-gel films; single layer, with a protective coating, and/or with an isolating buffer layer from the substrate, which is silicon and glass. Diffraction magnitude is measured in the various cases, as well as analysis and computer simulations are performed. Wavelength filters are experimented and studied. This shows the potential of this low cost technology in integrated optics, for application in telecommunications.

  11. 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 32°C. 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.

  12. Substituent-dominated structure evolution during sol-gel synthesis: a comparative study of sol-gel processing of 3-glycidoxypropyltrimethoxysilane and methacryloxypropyltrimethoxysilane.

    PubMed

    Shen, Shukun; Sun, Peipei; Li, Wei; Parikh, Atul N; Hu, Daodao

    2010-06-01

    The sol-gel processes of 3-glycidoxypropyltrimethoxysilane (GPTMS) and methacryloxypropyltrimethoxysilane (MAPTMS) have been followed by fluorescence spectroscopy with pyranine as a photophysical probe. The experimental results showed that this probe is sensitive to the structural evolution and microenvironment polarity. The specific comparison of the structural evolution in two substituted organotrialkoxysilanes, namely, MAPTMS and GPTMS, illustrates the ability of the substituents to interact with the microenvironment via electrostatic interactions. Interestingly, these interactions determine the kinds of intermediate supramolecular structures that form during the sol-gel process and hence control the structure of the ensuing sol-gel end product. In particular, the amphiphile-like character of the MAPTMS intermediates contrasts with the biamphiphilic character of their GPTMS counterparts, driving distinctly different transient and local molecular organizations, which in turn modulate the hydrolysis and condensation reactions during the sol-gel process. PMID:20443541

  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. 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

  15. 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.

  16. 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

  17. 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

  18. 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...

  19. Sol-gel microextraction phases for sample preconcentration in chromatographic analysis.

    PubMed

    Segro, Scott S; Tran, Minh Phuong; Kesani, Sheshanka; Alhendal, Abdullah; Turner, Erica B

    2010-10-01

    Sol-gel technology provides a simple and reliable method for solid-phase microextraction (SPME) fiber preparation through in situ creation of surface-bonded organic-inorganic hybrid coatings characterized by enhanced thermal stability and solvent-resistance properties that are important for the coupling of SPME with GC and HPLC, respectively. The sol-gel coating technology has led to the development of an extensive array of sol-gel sorbent coatings for SPME. In this article, sol-gel microextraction coatings are reviewed, with particular attention on their synthesis, characterization, and applications in conjunction with GC and HPLC analyses. In addition, the development of sol-gel-coated stir bars, their inherent advantages, and applications are discussed. Next, the development and applications of sol-gel capillary microextraction (CME) in hyphenation with GC and HPLC is extensively reviewed. The newly emerging germania- and titania-based sol-gel microextraction phases look promising, especially in terms of pH and hot solvent stability. Finally, sol-gel monolithic beds for CME are reviewed. Such monolithic beds are in a position to greatly improve the extracting capabilities and enhanced sensitivity in CME. PMID:21038461

  20. 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.

  1. 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.

  2. 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.

  3. Sol-gel derived nanoporous compositions for entrapping small molecules and their outlook toward aptamer screening.

    PubMed

    Ahn, Ji-Young; Lee, SangWook; Jo, Minjoung; Kang, Jeehye; Kim, Eunkyung; Jeong, Ok Chan; Laurell, Thomas; Kim, Soyoun

    2012-03-20

    This paper reports for the first time the application of sol-gel microarrays for immobilizing nonsoluble small chemicals (Bisphenol-A; BPA). Also, known problems of sol-gel adhesion to conventional microtiter well plate substrates are circumvented by anchoring the sol-gel microspots to a porous silion surface so-called, PS-SG chips. We confirmed low molecular weight chemical immobilization inside a sol-gel network using fluorescein. BPA and the BPA specific aptamer were utilized as a model pair to verify the affinity specific interaction in the PS-SG selection system. The aptamer interacted specifically with BPA in the sol-gel spots, as shown in microarrays forming the letters "L", "U", "N", and "D". Moreover, the bound aptamer was released by heat, recovered, and verified by gel electrophoresis. The developed PS-SG chip platform will be used for screening aptamers against numerous small molecules such as toxins, metabolites, or pesticide residues. PMID:22283623

  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. 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.

  6. Statistical Thermodynamics of Irreversible Aggregation: The Sol-Gel Transition

    PubMed Central

    Matsoukas, Themis

    2015-01-01

    Binary aggregation is known to lead, under certain kinetic rules, to the coexistence of two populations, one consisting of finite-size clusters (sol), and one that contains a single cluster that carries a finite fraction of the total mass (giant component or gel). The sol-gel transition is commonly discussed as a phase transition by qualitative analogy to vapor condensation. Here we show that the connection to thermodynamic phase transition is rigorous. We develop the statistical thermodynamics of irreversible binary aggregation in discrete finite systems, obtain the partition function for arbitrary kernel, and show that the emergence of the gel cluster has all the hallmarks of a phase transition, including an unstable van der Waals loop. We demonstrate the theory by presenting the complete pre- and post-gel solution for aggregation with the product kernel. PMID:25748055

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Sol-Gel processing of silica nanoparticles and their applications.

    PubMed

    Singh, Lok P; Bhattacharyya, Sriman K; Kumar, Rahul; Mishra, Geetika; Sharma, Usha; Singh, Garima; Ahalawat, Saurabh

    2014-11-01

    Recently, silica nanoparticles (SNPs) have drawn widespread attention due to their applications in many emerging areas because of their tailorable morphology. During the last decade, remarkable efforts have been made on the investigations for novel processing methodologies to prepare SNPs, resulting in better control of the size, shape, porosity and significant improvements in the physio-chemical properties. A number of techniques available for preparing SNPs namely, flame spray pyrolysis, chemical vapour deposition, micro-emulsion, ball milling, sol-gel etc. have resulted, a number of publications. Among these, preparation by sol-gel has been the focus of research as the synthesis is straightforward, scalable and controllable. Therefore, this review focuses on the recent progress in the field of synthesis of SNPs exhibiting ordered mesoporous structure, their distribution pattern, morphological attributes and applications. The mesoporous silica nanoparticles (MSNPs) with good dispersion, varying morphology, narrow size distribution and homogeneous porous structure have been successfully prepared using organic and inorganic templates. The soft template assisted synthesis using surfactants for obtaining desirable shapes, pores, morphology and mechanisms proposed has been reviewed. Apart from single template, double and mixed surfactants, electrolytes, polymers etc. as templates have also been intensively discussed. The influence of reaction conditions such as temperature, pH, concentration of reagents, drying techniques, solvents, precursor, aging time etc. have also been deliberated. These MSNPs are suitable for a variety of applications viz., in the drug delivery systems, high performance liquid chromatography (HPLC), biosensors, cosmetics as well as construction materials. The applications of these SNPs have also been briefly summarized. PMID:25466691

  12. A silica sol-gel design strategy for nanostructured metallic materials

    NASA Astrophysics Data System (ADS)

    Warren, Scott C.; Perkins, Matthew R.; Adams, Ashley M.; Kamperman, Marleen; Burns, Andrew A.; Arora, Hitesh; Herz, Erik; Suteewong, Teeraporn; Sai, Hiroaki; Li, Zihui; Werner, Jörg; Song, Juho; Werner-Zwanziger, Ulrike; Zwanziger, Josef W.; Grätzel, Michael; Disalvo, Francis J.; Wiesner, Ulrich

    2012-05-01

    Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol-gel process. The porous materials made by silica sol-gel chemistry are typically insulators, however, which has restricted their application. Here we present a simple, yet highly versatile silica sol-gel process built around a multifunctional sol-gel precursor that is derived from the following: amino acids, hydroxy acids or peptides; a silicon alkoxide; and a metal acetate. This approach allows a wide range of biological functionalities and metals—including noble metals—to be combined into a library of sol-gel materials with a high degree of control over composition and structure. We demonstrate that the sol-gel process based on these precursors is compatible with block-copolymer self-assembly, colloidal crystal templating and the Stöber process. As a result of the exceptionally high metal content, these materials can be thermally processed to make porous nanocomposites with metallic percolation networks that have an electrical conductivity of over 1,000 S cm-1. This improves the electrical conductivity of porous silica sol-gel nanocomposites by three orders of magnitude over existing approaches, opening applications to high-current-density devices.

  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. Non-Shrinking Sol-Gel Type Polymers by Ring Opening Polymerizations

    SciTech Connect

    Loy, D.A.; Rahimian, K.

    1999-04-05

    We have designed a new class of cyclic siloxane compounds that behave as sol-gel systems when ring open polymerized using a hydroxide base. These monomers polymerize through chain growth polymerization. unlike conventional alkoxysilane sol-gel precursors, to form sol-gel polymers. They do not require solvent or water for polymerization, show no visible shrinkage or cracking during polymerization and are thermally stable. We have successfully utilized these materials in encapsulation of microelectronics. Current efforts are focused toward expanding this family of ROP monomers and optimization of their mechanical properties.

  15. 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.

  16. Oxygen Permeability of 60-VOLUME% Bi1.6Y0.4O3 and 40-VOLUME% ag Composite Prepared by Citrate Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kiyoshi; Tsunoda, Tatsuo

    2002-12-01

    A composite membrane composed of 60-volume% Bi1.6Y0.4O3 and 40-volume% Ag was directly fabricated by a citrate sol-gel method. Oxygen permeation measurements were carried out as a function of the partial pressure difference of oxygen and temperature. A high oxide ionic conductor (δ-Bi2O3) phase and Ag composite could be obtained by heating above 1073 K and a well-sintered material was fabricated using the precursor powder prepared via the sol-gel route. We conclude that the rate-determining step in oxygen permeation is the ionic oxide transport in the Bi1.6Y0.4O3 component of the composite.

  17. 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

  18. Calcium phosphate sol-gel-derived coatings on titanium-aluminum-vanadium substrate for biomedical applications

    NASA Astrophysics Data System (ADS)

    Gan, Lu

    Osseointegration of implants to host bone is a necessary requirement for dental and orthopaedic implants. The rate and quality of osseointegration were enhanced through the use of calcium phosphate (Ca-P) films on metallic substrates. The present study investigates the characteristics of Ca-P films applied using sol-gel dip coating methods to sintered porous-surfaced implants. Ca-P films have been formed using Inorganic Route and Organic Route processes. It has been shown that both approaches resulted in the formation of carbonated hydroxyapatite but with different Ca/P ratios as well as different surface textures and film structures, the Inorganic Route-formed film being more porous at its outermost surface, and having a more irregular topography. An interfacial reaction product (calcium titanium oxide) was detected for the Inorganic Route-formed coatings while this interfacial phase was not detectable in the Organic Route-formed coatings. The interface tensile and shear adhesion strength properties of Ca-P films have been evaluated using an improved direct pull-off testing (ASTM C633) and a substrate straining method, respectively. For both Ca-P films, the adhesive tensile strength was higher than the failure stress of ˜38 MPa occurring between the Ca-P films and the glue or in the glue. A shear lag approach revealed a shear strength of 347 +/- 64MPa and 280 +/- 28MPa for the Inorganic Route and the Organic Route Ca-P films, respectively. In vivo animal model studies have been performed to compare the effect on early bone formation of sintered porous-surfaced implants that had been modified through the addition of Ca-P film. In Group I study (i.e. Inorganic Route-formed Ca-P-coated implants vs. non-coated implants), it has been found that the Inorganic Route-formed Ca-P film significantly enhances the early rate of bone ingrowth for sintered porous-surfaced implants. However, in Group II study (i.e. Organic Route-formed Ca-P-coated implants vs. non-coated implants), significant improvement was not observed for the Organic Route-formed Ca-P film. It is speculated that the slightly different surface topography and film density between the two Ca-P films result in a different amounts of protein adsorption on the implant surface at the early stage, which further affects the following processes leading to osseointegration.

  19. Surface treatment of cotton using β-cyclodextrins sol gel method

    NASA Astrophysics Data System (ADS)

    Wang, C. X.; Chen, Sh. L.

    2006-07-01

    β-Cyclodextrin can be added into sol-gel solution which consists of 3-glycidyloxypropyl-trimethoxysilane (GPTMS), tetraethoxysilane (TEOS), catalyzer and solvent. This β-cyclodextrianto sol-gel solution is able to anchor β-cyclodextrin on cotton fabrics in gelation process in order to impart new surface property of cotton. The suitable technical conditions of forming stable β-cyclodextrin sol-gel solution were presented. β-Cyclodextrins are able to form inclusion complexes with other guest components. As a result of the inclusions, the treated fabrics achieved new functional properties by the selective inclusion of the guest substances into the fixed cavities on fabrics. A novel functional surface treatment of fabrics is presented by sol-gel methods. The new functionalities were verified simply by decreasing the rate of volatile fragrance substances.

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

    DOEpatents

    Sasaki, Darryl Y.; Brinker, C. Jeffrey; Ashley, Carol S.; Daitch, Charles E.; Shea, Kenneth J.; Rush, Daniel J.

    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.

  1. 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.

  2. [Research of Hg2+ sol-gel membrane made of organically modified silicates].

    PubMed

    Guo, Liang-Qia; Zhang, Wei; Yan, Jian-Feng; Lin, Xu-Cong; Xie, Zeng-Hong; Chen, Guo-Nan

    2006-07-01

    A photochemical sensor for the determination of Hg2+ consisting of organically modified silicates (ormosils) was developed. Hg(2+)-sensitive fluorescent sol-gel films were prepared by co-condensation of tetramethoxysilane (TMOS) and dimethyldimethoxysilane (DMOS), and the fluorescent indicator 5,10,15, 20-tetra (p-sulfonatophenyl) porphyrin sodium was embedded in sol-gel in the form of ion pairs with cetyltrimethyl ammonium bromide. The optimization condition of preparation and response performance of sol-gel membrane were investigated. The experimental results showed a linear range of Hg2+ concentrations from 1.0 x 10(-5) to 1.0 x 10(-4) mol x L(-1) in a Tris-HCl buffer at pH 8.0 with fast response and good repetition. The indicators in the sol-gel membrane did not leak out and the sensor showed good selectivity over other metal ions. PMID:17020040

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

    SciTech Connect

    Sasaki, D.Y.; Brinker, C.J.; Ashley, C.S.; Daitch, C.E.; Shea, K.J.; Rush, D.J.

    2000-05-02

    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{minus}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.

  4. Barium hexaaluminate nanowhiskers synthesized by novel sol-gel process in reverse micellar media.

    PubMed

    Sahu, Prashant K; Kulkarni, B D; Khomane, R B; Pardhy, S A; Phalgune, U D; Rajmohanan, P; Pasricha, Renu

    2003-08-01

    Barium hexaaluminate (BHA) synthesized by coupling of sol-gel process in reverse microemulsions shows a unique nanowhisker morphology and high surface area, which are retained after calcination at 1300 degrees C. PMID:12932011

  5. 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.

  6. 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

  7. 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.

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

    NASA Astrophysics Data System (ADS)

    Tadaszak, R. J.; Łukowiak, 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.

  9. 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

  10. Control of rehydration in sol-gel glasses

    NASA Astrophysics Data System (ADS)

    Ortiz, Carlos; Boye, Daniel

    2007-11-01

    Optical properties of monoliths synthesized via the sol gel process result in a large number of residual silanol (Si-OH) groups, even after annealing at 900 C. High silanol content quenches emission from rare earth ions via excitation of vibrations of the silanol groups. Medium density glasses (1.5gcm-3) have a highly interconnected porous structure that allows the diffusion of molecules throughout the material. Diffusion of atmospheric water molecules results in chemiadsorption reactions that increase silanol group content, adding to quenching. By monitoring the intensity of terbium (Tb^3+) emissions from the ^5D3 level relative to the ^5D4 level, we report an 80% decrease in ratio within 12 hours. Monoliths prepared with of N,N-dimethylformamide, a drying control chemical additive (DCCA), were annealed at 1050 C and maintained good optical quality with nearly complete densification of the material (2.1gcm-3). DCCAs minimize the capillary stresses in the network during drying, even during the onset of viscous flow at the glass transition. Monoliths prepared with DMF and annealed at 1050 C for 6 hours showed no change in their ^5D3: ^5D4 intensity ratio upon exposure to the atmosphere.

  11. 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.

  12. /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.

  13. Switching property of sol-gel vanadium oxide thin films

    NASA Astrophysics Data System (ADS)

    Yuan, Ningyi; Li, Jinhua; Lin, Chenglu

    2001-10-01

    Highly orientated V2O5 thin film was prepared by sol-gel method on SiO2/Si substrate. When baked at temperature higher than 400°C and pressure lower than 2Pa, the V2O5 thin film can be converted to VO2 thin film. Annealing V2O5 thin film under 1-2Pa, 480°C for 20 minutes, the VO2 polycrystalline thin film with resistance change larger than 3 orders of magnitude and 6.2°C hysteresis width was obtained. Meanwhile the transition progress from V2O5 to VO2 was discussed in detail. It was observed that the valence of V was reduced by the sequence as V2O5 to V3O7 to V4O9 to V6O13 to VO2, namely from VnO2n+1(n=2,3,4,6) to VO2. It was confirmed that the key factors to obtain VO2 thin film with good switching property were the conditions of pre-heating and vacuum baking for V2O5 thin film.

  14. Thin Film Deposition Using SOL-GEL Technology

    NASA Astrophysics Data System (ADS)

    Puyane, R.; Gonzalez-Oliver, C. J. R.

    1983-11-01

    Sol-Gel technology can be used to deposit a wide variety of oxide coatings on substrates such as glass, ceramics or metals. This presentation outlines the fundamentals of the process and the possibilities offered by this technique. Several oxide layers have been prepared in our laboratories including single oxides like SiO2, TiO2, ZrO2, VO2+x, V205, as well as multicomponent systems such as SiO2-Ge02, SiO2-TiO2, SiO2-Y203 and SiO2-TiO2-Al203. The coatings are deposited by dipping the substrate into a solution containing the appropriate organometallic compound with control of the surrounding atmosphere. Subsequent thermal treatments are required to eliminate the volatile solvents, which are physically and chemically absorbed into the oxide layer and to densify the layers. The first thermal treatments are carried out at temperatures up to 150°C. Further treatments up to about 600°C (depending on oxide composition) are necessary to eliminate organic traces and residual moisture as well as to harden further the oxide coating.

  15. 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.

  16. Characterization and corrosion studies of titania-coated NiTi prepared by sol gel technique and steam crystallization

    NASA Astrophysics Data System (ADS)

    Chiu, K. Y.; Wong, M. H.; Cheng, F. T.; Man, H. C.

    2007-06-01

    Nickel titanium (NiTi) was dip-coated with titania via the sol-gel route using titanium butoxide (Ti(OC 4H 9) 4) as precursor. The as-coated titania film was crystallized to form anatase by treatment in steam at 105 °C. The crystallized film was relatively thick (about 750 nm) and even. Atomic force microscopy (AFM) revealed that the film was dense with a surface roughness of about 3 nm, and was composed of particles of about 100 nm. X-ray diffractometry (XRD) showed that these particles were composed of nanocrystallites of a few nanometers. Nanoindentation tests of the titania film indicated that the film was tough, possibly due to the nano-size of the crystallites. The mean hardness H and elastic modulus E of the coating were about 1.5 and 70 GPa, respectively. Direct pull-off test recorded a mean coating-substrate bonding strength larger than 17 MPa. Electrochemical impedance spectroscopic (EIS) study and cyclic polarization tests showed that the corrosion resistance of the coated NiTi samples in Hanks' solution was increased by about two orders of magnitude compared with the substrate. Taken together, the present study showed that steam crystallization is a feasible low-temperature treatment method for sol-gel derived titania coating on NiTi in biomedical applications.

  17. 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

  18. 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.

  19. 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.

  20. Strength of interactions between immobilized dye molecules and sol-gel matrices.

    PubMed

    Ismail, Fanya; Schoenleber, Monika; Mansour, Rolan; Bastani, Behnam; Fielden, Peter; Goddard, Nicholas J

    2011-02-21

    In this paper we present a new theory to re-examine the immobilization technique of dye doped sol-gel films, define the strength and types of possible bonds between the immobilized molecule and sol-gel glass, and show that the immobilized molecule is not free inside the pores as was previously thought. Immobilizing three different pH sensitive dyes with different size and functional groups inside the same sol-gel films revealed important information about the nature of the interaction between the doped molecule and the sol-gel matrix. The samples were characterized by means of ultraviolet-visible spectrophotometer (UV-VIS), thermal gravimetric analysis (TGA), mercury porosimetry (MP), nuclear magnetic resonance spectroscopy ((29)Si NMR) and field-emission environmental scanning electron microscopy (ESEM-FEG). It was found that the doped molecule itself has a great effect on the strength and types of the bonds. A number of factors were identified, such as number and types of the functional groups, overall charge, size, pK(a) and number of the silanol groups which surround the immobilized molecule. These results were confirmed by the successful immobilization of bromocresol green (BCG) after a completely polymerized sol-gel was made. The sol-gel consisted of 50% tetraethoxysilane (TEOS) and 50% methyltriethoxysilane (MTEOS) (w/w). Moreover, the effect of the immobilized molecule on the structure of the sol-gel was studied by means of a leaky waveguide (LW) mode for doped films made before and after polymerization of the sol-gel. PMID:21120245

  1. 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

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

    NASA Astrophysics Data System (ADS)

    Huang, Yin; Liu, Longju; Johnson, Michael; Hillier, Andrew C.; 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.

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. 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 Å. 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 Å 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.

  8. 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; Ristić, 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.

  9. 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.

  10. Development of electrochromic smart windows by sol-gel techniques

    NASA Astrophysics Data System (ADS)

    Munro, Brian; Kraemer, S.; Zapp, P.; Krug, Herbert; Schmidt, Helmut K.

    1997-10-01

    A novel nanocomposite lithium ion-conducting electrolyte has been developed, based on organically modified silanes, which is suitable for application in a sol-gel electrochromic system. The system developed consists of FTO-coated (fluorine doped tin oxide) glass coated with tungsten oxide, WO3, at one side of the device as the electrochromic layer, with a cerium oxide-titanium oxide layer, CeO2-TiO2, acting as ion-storage layer or counter electrode. The adhesive properties of the electrolyte enabled the manufacture of electrochromic devices in a laminated structure: glassFTOWO3nanocomp.elect.CeO2-TiO2FTOglass. The conductivity of the nanocomposite electrolyte system varies between 10-4 and 10-5 Scm-1 at 25 degrees Celsius depending on the exact composition. The temperature dependence of the conductivity exhibits typical Vogel-Tamman-Fulcher (VTF) behavior. The thickness of the electrolyte between the two halves of the device could be adjusted by the use of a spacer technique in the range 10 - 150 micrometer. Optoelectrochemical measurements were conducted on electrochromic devices to study the kinetics of coloration and bleaching as a function of the number of switching cycles. At present, cells are constructed in two formats: 10 multiplied by 15 cm2 and 35 multiplied by 35 cm2. Switching times under one minute were achieved for the smaller format with a corresponding optical modulation between 75% to 20% (at lambda equals 0.633 micrometer). In the case of the larger format the switching time increases to several minutes due to the increase in geometric area.

  11. 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.

  12. Antibacterial modification of an injectable, biodegradable, non-cytotoxic block copolymer-based physical gel with body temperature-stimulated sol-gel transition and controlled drug release.

    PubMed

    Wang, Xiaowen; Hu, Huawen; Wang, Wenyi; Lee, Ka I; Gao, Chang; He, Liang; Wang, Yuanfeng; Lai, Chuilin; Fei, Bin; Xin, John H

    2016-07-01

    Biomaterials are being extensively used in various biomedical fields; however, they are readily infected with microorganisms, thus posing a serious threat to the public health care. We herein presented a facile route to the antibacterial modification of an important A-B-A type biomaterial using poly (ethylene glycol) methyl ether (mPEG)- poly(ε-caprolactone) (PCL)-mPEG as a typical model. Inexpensive, commercial bis(2-hydroxyethyl) methylammonium chloride (DMA) was adopted as an antibacterial unit. The effective synthesis of the antibacterial copolymer mPEG-PCL-∼∼∼-PCL-mPEG (where ∼∼∼ denotes the segment with DMA units) was well confirmed by FTIR and (1)H NMR spectra. At an appropriate modification extent, the DMA unit could render the copolymer mPEG-PCL-∼∼∼-PCL-mPEG highly antibacterial, but did not largely alter its fascinating intrinsic properties including the thermosensitivity (e.g., the body temperature-induced sol-gel transition), non-cytotoxicity, and controlled drug release. A detailed study on the sol-gel-sol transition behavior of different copolymers showed that an appropriate extent of modification with DMA retained a sol-gel-sol transition, despite the fact that a too high extent caused a loss of sol-gel-sol transition. The hydrophilic and hydrophobic balance between mPEG and PCL was most likely broken upon a high extent of quaternization due to a large disturbance effect of DMA units at a large quantity (as evidenced by the heavily depressed PCL segment crystallinity), and thus the micelle aggregation mechanism for the gel formation could not work anymore, along with the loss of the thermosensitivity. The work presented here is highly expected to be generalized for synthesis of various block copolymers with immunity to microorganisms. Light may also be shed on understanding the phase transition behavior of various multiblock copolymers. PMID:27022875

  13. 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.

  14. 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.*

  15. Dynamics of proteins encapsulated in silica sol-gel glasses studied with IR vibrational echo spectroscopy.

    PubMed

    Massari, Aaron M; Finkelstein, Ilya J; Fayer, Michael D

    2006-03-29

    Spectrally resolved infrared stimulated vibrational echo spectroscopy is used to measure the fast dynamics of heme-bound CO in carbonmonoxy-myoglobin (MbCO) and -hemoglobin (HbCO) embedded in silica sol-gel glasses. On the time scale of approximately 100 fs to several picoseconds, the vibrational dephasing of the heme-bound CO is measurably slower for both MbCO and HbCO relative to that of aqueous protein solutions. The fast structural dynamics of MbCO, as sensed by the heme-bound CO, are influenced more by the sol-gel environment than those of HbCO. Longer time scale structural dynamics (tens of picoseconds), as measured by the extent of spectral diffusion, are the same for both proteins encapsulated in sol-gel glasses compared to that in aqueous solutions. A comparison of the sol-gel experimental results to viscosity-dependent vibrational echo data taken on various mixtures of water and fructose shows that the sol-gel-encapsulated MbCO exhibits dynamics that are the equivalent of the protein in a solution that is nearly 20 times more viscous than bulk water. In contrast, the HbCO dephasing in the sol-gel reflects only a 2-fold increase in viscosity. Attempts to alter the encapsulating pore size by varying the molar ratio of silane precursor to water (R value) used to prepare the sol-gel glasses were found to have no effect on the fast or steady-state spectroscopic results. The vibrational echo data are discussed in the context of solvent confinement and protein-pore wall interactions to provide insights into the influence of a confined environment on the fast structural dynamics experienced by a biomolecule. PMID:16551107

  16. 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.

  17. Effects of the sol-gel solution host on the chemical and optical properties of PbS quantum dots

    NASA Astrophysics Data System (ADS)

    Capoen, B.; Martucci, A.; Turrell, S.; Bouazaoui, M.

    2003-06-01

    PbS nanoparticles were prepared via a colloidal route using an organic capping agent, and were incorporated in both a silica and a titania sol-gel solution with a concentration of 10 mol%. The stability of the particles embedded in the sols was lengthened from 2 h to several days and their growth was considerably slowed down. The kinetics of the optical absorption allowed us to quantify the growth rate of the particles. Analysis of the optical emission in the three solutions (colloid, SiO 2/PbS and TiO 2/PbS) showed that the PbS nanocrystals are partially passivated by the silica chains and completely by the titania chains in the sols. Conjoint study of the optical absorption and emission measurements revealed a correlation between the presence of a structured exciton peak in the absorption spectra and the absence of shallow surface states.

  18. 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.

  19. Synthesis and characterization of monodispersed CdS nanoparticles in SiO 2 fibers by sol-gel method

    NASA Astrophysics Data System (ADS)

    Hullavarad, Nilima V.; Hullavarad, Shiva S.

    2007-11-01

    Cadmium sulfide (CdS) has been synthesized by a sol-gel route in order to obtain chemically protected, stable nanoparticles. The CdS nanoparticles in the SiO 2 gel matrix were dried to form monoliths of 1 in. diameter. The TEOS:H 2O:HCl:C 2H 5OH and TEOS/Cd mole ratios were varied to obtain narrow size distributed CdS nanoparticles. The UV absorption measurements indicated sharp absorption at 260 and 350 nm for different precursor compositions. SiO 2 gel containing the CdS nanoparticles was spin coated onto substrates in order to monitor the surface morphology of the samples. Scanning electron microscope measurements revealed formation of CdS nanoparticles within the branches of gel-network. Depending upon the mole ratio of additives and drying method, fibers or monolithic tablets of CdS nanoparticles could be produced.

  20. 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.

  1. 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.

  2. 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

  3. Screen-printable sol-gel enzyme-containing carbon inks.

    PubMed

    Wang, J; Pamidi, P V; Park, D S

    1996-08-01

    Enzymes usually cannot withstand the high-temperature curing associated with the thick-film fabrication process and require a separate immobilization step in connection with the production of single-use biosensors. We report on the development of sol-gel-derived enzyme-containing carbon inks that display compatibility with the screen-printing process. Such coupling of sol-gel and thick-film technologies offers a one-step fabrication of disposable enzyme electrodes, as it obviates the need for thermal curing. The enzyme-containing sol-gel carbon ink, prepared by dispersing the biocatalyst, along with the graphite powder and a binder, within the sol-gel precursors, is cured very rapidly (10 min) at low temperature (4 °C). The influence of the ink preparation conditions is explored, and the sensor performance is evaluated in connection with the incorporation of glucose oxidase or horseradish peroxidase. The resulting strips are stable for at least 3 months. Such sol-gel-derived carbon inks should serve as hosts for other heat-sensitive biomaterials in connection with the microfabrication of various thick-film biosensors. PMID:21619216

  4. Examination of light distribution from fibers coated with sol-gel films doped with porphyrine

    NASA Astrophysics Data System (ADS)

    Ulatowska-Jarża, A.; Bindig, U.; Podbielska, H.; Andrzejewski, D.; Müller, G.; Eichler, H. J.

    2006-02-01

    The modification of optical fibers by exploiting various coatings may be important for construction of fiberoptics, sensors or applicators for interstitial laser therapy. We report here on sol-gel films placed on fiber cores, replacing the original fiber coatings. The silica sol-gel coatings where prepared form silicate precursor TEOS (tetraethylorthosilicate) mixed with ethyl alcohol in acid catalyzed hydrolysis. The matrices were produced with various ratios R=5, 15, 20, 32, 40, 50, whereas R denotes the number of solvent moles (here ethanol) to the number of TEOS moles. Two types of coatings were produced: pure sol-gel matrices and sol-gel doped with Protophyrin IX in two various concentrations. The angular light intensity distribution was examined in order to find out the influence of R factor on the light intensity distribution near the fiber tip. Then, the light pattern was captured by means of CCD camera and the three dimensional luminances were calculated. The same experiments were repeated for silica sol-gel coatings doped with natural porphyrine Protoporphyrine IX and different patterns were observed.

  5. Spectroscopic and electrochemical characterization of cytochrome c encapsulated in a bio sol-gel matrix.

    PubMed

    Deriu, Daniela; Pagnotta, Sara Emanuela; Santucci, Roberto; Rosato, Nicola

    2008-08-01

    Sol-gel technique represents a remarkably versatile method for protein encapsulation. To enhance sol-gel biocompatibility, systems envisaging the presence of calcium and phosphates in the sol-gel composition were recently prepared and investigated. Unfortunately, the low pH at which solutions were prepared (pH < 2.5) dramatically limited their application to proteins, because the acidic environment induces protein denaturation. In this paper we apply a new protocol based on the introduction of calcium nitrate to the inorganic phase, with formation of a binary bioactive system. In this case protein encapsulation results versatile and secure, being achieved at a pH close to neutrality (pH 6.0); also, the presence of calcium is expected to enhance system biocompatibility. To determine the properties of the salt-doped sol-gel and the influence exerted on entrapped biosystems, the structural and functional properties of embedded cytochrome c have been investigated. Data obtained indicate that the salt-doped sol-gel induces no significant change in the structure and the redox properties of the embedded protein; also, the matrix increases protein stability. Interestingly, the presence of calcium nitrate appears determinant for refolding of the acid-denatured protein. This is of interest in the perspective of future applications in biosensoristic area. PMID:18163198

  6. 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.

  7. 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)

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-11-01

    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.

  10. Room temperature sol-gel fabrication and functionalization for sensor applications

    NASA Astrophysics Data System (ADS)

    Huyang, George; Canning, John; Petermann, Ingemar; Bishop, David; McDonagh, Andrew; Crossley, Maxwell J.

    2013-06-01

    The structure and physical properties of a thin titania sol-gel layer prepared on silicon and silica surfaces were examined. Spectroscopic (FTIR, UV-VIS spectroscopy), refractive index (ellipsometry) and microscopic (light microscopy and SEM/EDS) tools were used to examine both chemical uniformity and physical uniformity of the sol-gel glass layers. The conditions for the fabrication of uniform layers were established, and room temperature dopant incorporation was examined. The absorption bands of porphyrin-containing titania sol-gel layers were characterized. By addition of a metal salt to the titania layer, it was possible to metallate the free-base porphyrin within and change the UV-VIS absorbance of the porphyrin, the basis of metal detection using porphyrins. The metalloporphyrins were detected by localized laser ablation inductive coupled mass spectroscopy (LA-ICP-MS), indicating fairly uniform distribution of metals across the titania surface.

  11. 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.

  12. 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.

  13. 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.

  14. Development and characterization of molecularly imprinted sol-gel materials for the selective detection of DDT.

    PubMed

    Graham, Amy L; Carlson, Catherine A; Edmiston, Paul L

    2002-01-15

    Molecularly imprinting sol-gel materials for DDT using both a noncovalent and a covalent approach was examined. A nonpolar porous sol-gel network was created through the use of the bridged polysilsesquioxane, bis-(trimethoxysilylethyl)benzene (BTEB), as the principal sol-gel component. Noncovalent molecular imprinting was deemed unsuccessful, presumably because of the lack of strong intermolecular interactions that can be established between the DDT and the sol-gel precursor. A covalent imprinting strategy was employed by generating a sacrificial spacer through the reaction of two 3-isocyanatopropyltriethoxysilanes with one of two different template molecules: 4,4'-ethylenedianiline (EDA) or 4,4'-ethylidenebisphenol (EBP). After formation of the sol-gel, the bonds linking the spacer template to the matrix were cleaved in a manner that generated a pocket of the appropriate size bordered by amine groups that could aid in the binding of DDT through weak hydrogen bonding interactions. Experiments indicated that DDT could be bound selectively by such an approch. To generate a sensor, an environmentally sensitive fluorescent probe, 7-nitrobenz-2-oxa-1,3-diazole, (NBD) located adjacent to the DDT binding site was used to transduce the binding of analyte. EDA-imprinted sol-gels, deposited as films on glass microscope slides, were shown to quantitatively detect DDT in water to a limit-of-detection of 50 ppt with a response time of <60 s. Repeat measurements could be made with the same sensing films after rinsing with acetone between each measurement. The EDA sensing material was selective for DDT and other structurally similar molecules. However, the sensing film design was limited by the relatively minor changes in fluorescence intensity upon binding DDT. This situation may be remedied by an alternative methodology that can facilitate attachment of the NBD fluorophore in an optimal position proximal to the binding pocket. PMID:11811423

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Sol-gel-derived ferroelectric films as pyroelectric detectors in imaging applications

    NASA Astrophysics Data System (ADS)

    Teowee, Gimtong T.; McCarthy, K.; Uhlmann, Donald R.

    1996-06-01

    This paper reviews the latest developments in pyroelectric devices for IR detection based on sol-gel derived ferroelectric thin films, highlighted by recent results from our laboratories. The optimization of sol-gel processing has led to ferroelectric films with pyroelectric coefficients as high as 200 nC/cm2-K. Some modeling results of the thin film devices, which aid in device design, are also discussed. At the film level, various factors such as chemistries, microstructures and processing conditions all affect the final pyroelectric properties of the films. At the device level, processing compatibility and device layout need to be taken into account to optimize fully the device performance.

  20. 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-entrapped metal 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 investigates subtle structural aspects through DRIFT spectroscopy. Conclusions The results point to interactions between entrapped Pd and Pt nanocrystallites with the organosilica sol-gel cages similar to those taking place in enzymes. PMID:24079552

  1. 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.

  2. 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.

  3. 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.

  4. 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...

  5. 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.

  6. 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

  7. 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

  8. 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

  9. Effectiveness of silica based Sol-gel microencapsulation Method for odorants and flavours leading to sustainable Environment

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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 actives, thereby broadening the practical utilization of chemically unstable essential oils. Reviewing progress in the fabrication of diverse odorant and flavoured sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.

  10. 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

  11. 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.

  12. 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

  13. Sol-gel immunoaffinity chromatography for the clean up of ochratoxin A contaminated grains.

    PubMed

    Reiter, Elisabeth Viktoria; Cichna-Markl, Margit; Tansakul, Natthasit; Shim, Won-Bo; Chung, Duck-Hwa; Zentek, Jürgen; Razzazi-Fazeli, Ebrahim

    2011-10-21

    This paper describes the application of sol-gel immunoaffinity columns for clean up of ochratoxin A contaminated cereal crops. Monoclonal antibodies selective for OTA have been entrapped into the pores of a sol-gel matrix in order to prepare immunoaffinity columns. Different parameters such as amount of entrapped antibodies and loading conditions were optimized to obtain highest possible recoveries of OTA. The method has been found to be a suitable tool in sample preparation prior to HPLC-FLD determination and as selective as conventional commercially available immunoaffinity columns. In the clean up of different cereals mean recoveries of 82±5%, 90±6% and 91±3%, were obtained for wheat, barley and rye, respectively, with sol-gel columns containing 1mg of anti-OTA antibodies. The detection limit (signal-to-noise ratio, 3) was 0.5 μg/kg and the limit of quantification (signal-to-noise ratio, 10) determined to be 1 μg/kg. Sol-gel columns can be reused 7 times without significant loss of recovery. After 10 applications the recovery decreased to approx. 50%. PMID:21831391

  14. Preparation and complex characterization of silica holmium sol-gel monoliths.

    PubMed

    Cacaina, D; Areva, S; Laaksonen, H; Simon, S; Ylänen, H

    2011-01-01

    Amorphous, sol-gel derived SiO(2) are known to biocompatible and bioresorbable materials. Biodegradable and inert materials containing radioactive isotopes have potential application as delivery vehicles of the beta radiation to the cancer tumors inside the body. Incorporation of holmium in the sol-gel derived SiO(2) could lead to the formation of a biodegradable material which could be used as carrier biomaterial for the radiation of radioactive holmium to the various cancer sites. The homogeneity of the prepared sol-gel silica holmium monoliths was investigated by Back Scattered Electron Imaging of Scanning Electron Microscope equipped with Energy Dispersive X-ray Analysis, X-ray Induced Photoelectron Spectroscopy and Nuclear Magnetic Resonance Spectroscopy. The biodegradation of the monoliths was investigated in Simulated Body Fluid and TRIS (Trizma pre-set Crystals) solution. The results show that by suitable tailoring of the sol-gel processing parameters holmium can be homogeneously incorporated in the silica matrix with a controlled biodegradation rate. PMID:21132520

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

    DOEpatents

    Shoup, Shara S.; Paranthamam, Mariappan; Beach, David B.; Kroeger, Donald M.; Goyal, Amit

    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.

  16. 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.

  17. Amplification from Nd 3+ doped Si-Ti sol-gel channel waveguides

    NASA Astrophysics Data System (ADS)

    Peled, Asher; Nathan, Menachem; Arie, Ady; Tsukernik, Alexander; Ruschin, Shlomo

    2009-07-01

    We report the sol-gel chemistry reaction system and processes used to realize the first grating coupled monolithic solid state optical amplifier based on a Nd 3+ doped sol-gel tapered rib waveguide. The sol-gel matrix composition is 50SiO 2:50TiO 2:10AlO 1.5:1NdO 1.5. The signal (1064 nm) and pump (803 nm) beams were coupled via grating couplers into and out of the rib waveguide. A photoluminescence lifetime of 138 μs and a pump absorption cross-section of 1.79 × 10 -24 m -2 were measured. A net internal gain of 3.75 dB/cm was achieved. Theoretical simulations predict that this gain could be further improved. Analysis of the results suggests that the difference between achieved and predicted gain is due to low quantum efficiency caused by two-ion cross-relaxation and up-conversion, as manifestly evident by yellow light emitted from the device. The molecular-level processes during the doped sol-gel fabrication that could lead to these phenomena are discussed, and strategies are suggested to overcome these limitations in order to approach the full potential gain.

  18. 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

  19. Liquid core fibre versus doped sol-gel layered structured fibre for chemical sensing

    NASA Astrophysics Data System (ADS)

    Canning, John; Huyang, George; Åslund, Mattias L.; Naqshbandi, Masood; Stocks, Danial; Crossley, Maxwell J.

    2010-10-01

    We review recent work on evaluating the performance of a simple porphyrin-based acid sensor using structured fibre technology. Specifically, the same sensor in a multimode liquid core is compared to that in a sol-gel coated structured optical fibre. General implications for fibre chemical sensing are discussed.

  20. Myoglobin/sol-gel film modified electrode: direct electrochemistry and electrochemical catalysis.

    PubMed

    Wang, Quanlin; Lu, Gongxuan; Yang, Baojun

    2004-02-17

    Direct electrochemical and electrocatalytic behavior of myoglobin (Mb) immobilized on carbon paste electrode (CPE) by a silica sol-gel film derived from tetraethyl orthosilicate was investigated for the first time. Mb/sol-gel film modified electrodes show a pair of well-defined and nearly reversible cyclic voltammetric peaks for the Mb Fe(III)/Fe(II) redox couple at about -0.298 V (vs Ag/AgCl) in a pH 7.0 phosphate buffer solution. The formal potential of the Mb heme Fe(III)/Fe(II) couple shifted linearly with pH with a slope of 52.4 mV/pH, denoting that an electron transfer accompanies single-proton transportation. An FTIR and UV-vis spectroscopy study confirms that the secondary structure of Mb immobilized on an electrode by a sol-gel film still maintains the original arrangement. The immobilized Mb displays the features of a peroxidase and acts in an electrocatalytic manner in the reduction of oxygen, trichloroacetic acid (TCA), and nitrite. In comparison to other electrodes, the chemically modified electrodes used in this study for direct electrochemistry and electrocatalysis of Mb are easy to fabricate and fairly inexpensive. Consequently, the Mb/sol-gel film modified electrode provides a convenient way to perform electrochemical research on this kind of protein. It also has potential use in the fabrication of bioreactors and third-generation biosensors. PMID:15803717

  1. 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.

  2. Low-density nanoporous iron foams synthesized by sol-gel autocombustion

    PubMed Central

    2012-01-01

    Nanoporous iron metal foams were synthesized by an improved sol-gel autocombustion method in this report. It has been confirmed to be pure phase iron by X-ray diffraction measurements. The nanoporous characteristics were illustrated through scanning electron microscope and transmission electron microscope images. Very low density and quite large saturation magnetization has been performed in the synthesized samples. PMID:22333555

  3. 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 2.13×10-4 cm2 V-1 s-1 for the native-PMMA channel to 4.86×10-4 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.

  4. 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...

  5. 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 220μs, 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.

  6. 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.

  7. 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.

  8. Low temperature and UV curable sol-gel coatings for long lasting optical fiber biosensors

    NASA Astrophysics Data System (ADS)

    Otaduy, D.; Villar, A.; Gomez-Herrero, E.; Goitandia, A. M.; Gorritxategi, E.; Quintana, I.

    2010-04-01

    The use of optical fibers as sensing element is increasing in clinical, pharmaceutical and industrial applications. Excellent light delivery, long interaction length, low cost and ability not only to excite the target molecules but also to capture the emitted light from the targets are the hallmarks of optical fiber as biosensors. In biosensors based on fiber optics the interaction with the analyte can occur within an element of the optical fiber. One of the techniques for this kind of biosensors is to remove the fiber optic cladding and substitute it for biological coatings that will interact with the parameter to sensorize. The deposition of these layers can be made by sol-gel technology. The sol-gel technology is being increasingly used mainly due to the high versatility to tailor their optical features. Incorporation of suitable chemical and biochemical sensing agents have allowed determining pH, gases, and biochemical species, among others. Nonetheless, the relatively high processing temperatures and short lifetime values mean severe drawbacks for a successful exploitation of sol-gel based coated optical fibres. With regard to the latter, herein we present the design, preparation and characterization of novel sol-gel coated optical fibres. Low temperature and UV curable coating formulations were optimized to achieve a good adhesion and optical performance. The UV photopolymerizable formulation was comprised by glycidoxypropyltrimethoxysilane (GLYMO), Tetraethylorthosilicate (TEOS) and an initiator. While the thermoset coating was prepared by using 3-aminopropyltrimethoxysilane, GLYMO, and TEOS as main reagents. Both curable sol-gel coated fibres were analysed by FTIR, SEM and optical characterization. Furthermore, in the present work a new technique for silica cladding removal has been developed by ultra-short pulses laser processing, getting good dimensional accuracy and surface integrity.

  9. 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.

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

    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 2O-Nb 2O 5-SiO 2 system is reported. In this route, LiNO 3, NbCl 5 and Si(OC 2H 5) 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 3 as only crystallizing phase. LiNbO 3-SiO 2 nanocomposite thin films on Si-SiO 2 and Al 2O 3 substrates were grown. The LiNbO 3 average size, increasing with the annealing temperature, was 27 nm for a film of composition 10Li 2O-10Nb 2O 5-80SiO 2 heated 2 h at 800 °C. Electrical investigation revealed that the nanocrystals size strongly affects the film conductivity and the occurrence of hysteretic current-voltage curves.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Sol-gel technologies in thin film fabrication for integrated optics lasers and amplifiers

    NASA Astrophysics Data System (ADS)

    Almeida, Rui M.; Vasconcelos, H. C.

    1997-07-01

    There is a strong need for the development of cheap component technologies for optical functions such as switching, demultiplexing and amplification. Silica-on- silicon integrated optics using sol-gel processing is probably the best technology for such low cost applications. This review focuses on the sol-gel based thin film fabrication technologies for integrated optics (IO) lasers and amplifiers, using Nd3+ and Er3+ as the active species. Special emphasis is given to the work performed under the European Union sponsored projects NODES (ESPRIT) and CAPITAL (ACTS), in particular to the processing and characterization of Nd3+ and Er3+-doped silica-titania planar waveguides for IO lasers and amplifiers.

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

    PubMed

    Street, Robert A; Ng, Tse Nga; Lujan, René 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

  19. 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.

  20. 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.

  1. 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

  2. Porphyrinosilica and metalloporphyrinosilica: hybrid organic-inorganic materials prepared by sol-gel processing

    PubMed

    Iamamoto; Sacco; Biazzotto; Ciuffi; Serra

    2000-01-01

    New materials porphyrinosilica and metalloporphyrinosilica template have been obtained by a sol-gel processing where functionalyzed porphyrins and metalloporphyrins "building blocks" were assembled into a three-dimensional silicate network. The optimized conditions for preparation of these materials are revised. The monomer precursors porphyrinopropylsilyl and metalloporphyrinopropylsilyl preparation reactions and subsequent one pot sol-gel processing with tetraethoxysilane are discussed. In the case of metalloporphyrins the nitrogen base coordinates to the central metal and acts as a template in the molecular imprinting technique. UV-visible absorption spectroscopy, thermogravimetric analysis, electron paramagnetic resonance, nuclear magnetic spectra, infrared spectra, luminescence spectra, surface area and electron spectroscopy imaging of the materials are used to characterize the prepared materials. The catalytic activities of these metalloporphyrinosilica-template are compared. PMID:10932105

  3. 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.

  4. Glucose microbiosensor based on alumina sol-gel matrix/electropolymerized composite membrane.

    PubMed

    Chen, Xiaohong; Hu, Yibai; Wilson, George S

    2002-12-01

    A procedure is described that provides co-immobilization of enzyme and bovine serum albumin (BSA) within an alumina sol-gel matrix and a polyphenol layer permselective for endogenous electroactive species. BSA has first been employed for the immobilization of glucose oxidase (GOx) on a Pt electrode in a sol-gel to produce a uniform, thin and compact film with enhanced enzyme activity. Electropolymerization of phenol was then employed to form an anti-interference and protective polyphenol film within the enzyme layer. In addition, a stability-reinforcing membrane derived from (3-aminopropyl)-trimethoxysilane was constructed by electrochemically-assisted crosslinking. This hybrid film outside the enzyme layer contributed both to the improved stability and to permselectivity. The resulting glucose sensor was characterized by a short response time (<10 s), high sensitivity (10.4 nA/mM mm(2)), low interference from endogenous electroactive species, and a working lifetime of at least 60 days. PMID:12392950

  5. 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

  6. Enhanced optical band-gap of ZnO thin films by sol-gel technique

    NASA Astrophysics Data System (ADS)

    Raghu, P.; Naveen, C. S.; Shailaja, J.; Mahesh, H. M.

    2016-05-01

    Transparent ZnO thin films were prepared using different molar concentration (0.1 M, 0.2 M & 0.8 M) of zinc acetate on soda lime glass substrates by the sol-gel spin coating technique. The optical properties revealed that the transmittance found to decrease with increase in molar concentration. Absorption edge showed that the higher concentration film has increasingly red shifted. An increased band gap energy of the thin films was found to be direct allowed transition of ˜3.9 eV exhibiting their relevance for photovoltaic applications. The extinction coefficient analysis revealed maximum transmittance with negligible absorption coefficient in the respective wavelengths. The results of ZnO thin film prepared by sol-gel technique reveal its suitability for optoelectronics and as a window layer in solar cell applications.

  7. Silicon diffusion in sol-gel derived isotopically enriched silica glasses

    NASA Astrophysics Data System (ADS)

    Bracht, H.; Staskunaite, R.; Haller, E. E.; Fielitz, P.; Borchardt, G.; Grambole, D.

    2005-02-01

    We performed silicon diffusion experiments with sol-gel derived isotopically enriched silica glasses at temperatures between 1050 °C and 1300 °C. The diffusion profiles were measured by means of time-of-flight secondary ion mass spectrometry. Samples annealed in closed silica ampoules under argon or dry air reveal enhanced Si diffusion compared to Si diffusion in fused silica. On the other hand, annealing in a large alumina tube under O218 ambient yields Si and O diffusion coefficients which approach the results for thermally grown SiO2. The enhanced Si diffusion in sol-gel derived glass is proposed to be due to water residues which lead to the formation of silanol SiOH groups.

  8. Preparation and electrochemical characterization of lithium cobalt oxide nanoparticles by modified sol-gel method

    SciTech Connect

    Khomane, Ramdas B.; Agrawal, Amit C.; Kulkarni, B.D. Gopukumar, S. Sivashanmugam, A.

    2008-08-04

    Uniformly distributed nanoparticles of LiCoO{sub 2} have been synthesized through the simple sol-gel method in presence of neutral surfactant (Tween-80). The powders were characterized by X-ray diffractometry, transmission electron microscopy and electrochemical method including charge-discharge cycling performance. The powder calcined at a temperature of 900 deg. C for 5 h shows pure phase layered LiCoO{sub 2}. The results show that the particle size is reduced in presence of surfactant as compared to normal sol-gel method. Also, the sample prepared in presence of surfactant and calcined at 900 deg. C for 5 h shows the highest initial discharge capacity (106 mAh g{sup -1}) with good cycling stability as compared to the sample prepared without surfactant which shows the specific discharge capacity of 50 mAh g{sup -1}.

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. Secondary Crystal Growth on a Cracked Hydrotalcite-Based Film Synthesized by the Sol-Gel Method.

    PubMed

    Lee, Wooyoung; Lee, Chan Hyun; Lee, Ki Bong

    2016-05-01

    The sol-gel synthesis method is an attractive technology for the fabrication of ceramic films due to its preparation simplicity and ease of varying the metal composition. However, this technique presents some limitations in relation to the film thickness. Notably, when the film thickness exceeds the critical limit, large tensile stresses occur, resulting in a cracked morphology. In this study, a secondary crystal growth method was introduced as a post-treatment process for Mg/Al hydrotalcite-based films synthesized by the sol-gel method, which typically present a cracked morphology. The cracked hydrotalcite-based film was hydrothermally treated for the secondary growth of hydrotalcite crystals. In the resulting film, hydrotalcite grew with a vertical orientation, and the gaps formed during the sol-gel synthesis were filled with hydrotalcite after the crystal growth. The secondary crystal growth method provides a new solution for cracked ceramic films synthesized by the sol-gel method. PMID:27064301

  14. Photoresist-Free Fully Self-Patterned Transparent Amorphous Oxide Thin-Film Transistors Obtained by Sol-Gel Process

    PubMed Central

    Lim, Hyun Soo; Rim, You Seung; Kim, Hyun Jae

    2014-01-01

    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 β-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. PMID:24686314

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Monolithic rare-earth doped sol-gel tapered rib waveguide laser

    NASA Astrophysics Data System (ADS)

    Peled, A.; Chiasera, A.; Nathan, M.; Ferrari, M.; Ruschin, S.

    2008-06-01

    We report the design, fabrication, and characterization of a monolithic tapered rib waveguide laser made of Nd doped silica hafnia sol-gel. The laser has a 604nm thick guiding layer. CW pumping was coupled in via a grating which also coupled out the lasing signal output, while reflection gratings supported the feedback. A lasing threshold of 20mW and an output power of 2.45mW were measured in a 3cm long device.

  20. Sol-gel kinetics for the preparation of inorganic/organic siloxane copolymers

    SciTech Connect

    Rankin, S.E.; Macosko, C.W.; McCormick, A.V.

    1996-12-31

    A model is described which incorporates hydrolysis pseudo-equilibrium to quantify the evolution of silicon site distributions in sol-gel polymerization up to higher conversions than previously possible. {sup 29}Si nuclear magnetic resonance spectroscopy data are used (1) to provide a means of recognizing hydrolysis pseudo-equilibrium and (2) to provide examples where different substitution effects on condensation rate coefficients caused by branching are observed. Extension of the model to copolymerization is discussed.

  1. 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

  2. Volume Changes of a Thixotropic, Sodium Bentonite Suspension during Sol-Gel-Sol Transition.

    PubMed

    Anderson, D M; Leaming, G F; Sposito, G

    1963-09-13

    Dilatometric measurements during the sol-gel-sol transition of an air-free, thixotropic, sodium bentonite suspension revealed a reversible change in volume of about 2.4 X 10(-4) percent. The volume of the suspension increased during gelation and decreased when the gel was subsequently liquified. This is taken as evidence of a progressive building up, during gelation, of a water structure less dense than normal. PMID:17739493

  3. 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

  4. 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.

  5. Ultraviolet-light-imprinted sol-gel silica glass channel waveguides on silicon

    NASA Astrophysics Data System (ADS)

    Najafi, S. Iraj; Li, C.-Y.; Chisham, J. E.; Andrews, Mark P.; Coudray, Paul; Malek-Tabrizi, Alireza; Peyghambarian, Nasser

    1996-01-01

    We describe a new simplified process for inexpensive fabrication of low-loss (0.1 dB/cm) glass waveguides on silicon by ultraviolet light imprinting in photosensitive, organically modified sol-gel silica glass films prepared by one-step dip-coating process. The fabrication process is appealing because the buffer layer between waveguide and substrate is eliminated, and waveguides can be made in a few steps using low-cost equipment.

  6. 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.

  7. Synthesis and characterization of ordered and disordered polycrystalline La2NiMnO6 thin films by sol-gel.

    PubMed

    Zhang, Zhiqing; Jian, Hongbin; Tang, Xianwu; Yang, Jie; Zhu, Xuebin; Sun, Yuping

    2012-10-14

    Polycrystalline La(2)NiMnO(6) thin films are prepared on Pt/Ti/SiO(2)/Si substrates by the sol-gel method. Through controlling the processing parameters, the cation ordering can be tuned. The disordered and ordered thin films exhibit distinct differences for crystal structures as well as properties. The crystal structure at room temperature characterized by X-ray diffraction and Raman spectra is suggested to be monoclinic (P2(1)/n) and orthorhombic (Pbnm) for the ordered and disordered thin films, respectively. The ferromagnetic-paramagnetic transition is 263 K and 60 K for the ordered and disordered samples respectively, whereas the saturation magnetic moment at 5 K is 4.9 μ(B) fu(-1) (fu = formula unit) and 0.9 μ(B) fu(-1). The dielectric constant as well as magnetodielectric effect is higher for the ordered La(2)NiMnO(6) thin films. The magnetodielectric effect for the ordered thin film is dominantly contributed to the intrinsic coupling of electric dipole ordering and fluctuations and magnetic ordering and fluctuations, while it is mainly contributed to Maxwell-Wagner (M-W) effects for the disordered thin film. The successful achievements of ordered and disordered polycrystalline La(2)NiMnO(6) thin films will provide an effective route to fabricate double-perovskite polycrystalline thin films by the sol-gel method. PMID:22910689

  8. 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 (2.7 wt% Ge) and phosphosilicate (2.5 wt% 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 (7-100 cm-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.

  9. 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(ε-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(ε-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

  10. 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

  11. Sol-gel preparation and characterization of SiO2 coated VO2 films with enhanced transmittance and high thermochromic performance

    NASA Astrophysics Data System (ADS)

    Li, Dezeng; Shan, Yongkui; Huang, Fuqiang; Ding, Shangjun

    2014-10-01

    Vanadium dioxide (VO2) films prepared at low-temperature with a low cost are considerable for energy-saving applications. Here, SiO2 coated VO2 films with clearly enhanced visible transmittance by introducing antireflection coatings (ARCs) and excellent thermochromic performance were present. The VO2 films have been prepared via a stable and low-cost sol-gel synthesis route using vanadium pentaoxide powder as precursor, and their structural, morphological, optical and electrical properties and thermochromic performance were systemically characterized. The resistance of VO2 films varies by 4 orders of magnitude and the transmittance changes from 11.8% to 69.3% at 2500 nm while no significant deviation appears in the visible region during metal-insulator transition (MIT). Nanoporous SiO2 coating with good optical transparency was coated on the surface of VO2 film via sol-gel dip-coating technique to enhance its optical transmittance, and the visible transmittance is increased by 14.6% due to the significantly decreased reflectance. The critical transition temperature (63 °C) and infrared switching properties of VO2 films are not much deteriorated by applying SiO2 layer. The synergistic effect of antireflection and thermochromism on SiO2 coated VO2 films was investigated.

  12. 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 450°C. 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 900°C 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) photonic crystal structures using the automated surface sol-gel process. The hydroxyl concentration on the SU-8 surface was amplified using tris(hydroxymethyl)amino-methane which decreased the hydrophobicity of the SU-8 template and provided reactive OH functionalities for surface sol-gel deposition of the tin oxide-doped titania alkoxide precursor. The coating was crystallized in an acidic solution at 80°C which led to the formation of rutile titania inverse opal photonic crystal structures which maintained the overall structure and ordering of the template. The underlying SU-8 template was successfully removed using an oxygen plasma etch.

  13. Biological influence of Ca/P ratio on calcium phosphate coatings by sol-gel processing.

    PubMed

    Catauro, M; Papale, F; Sapio, L; Naviglio, S

    2016-08-01

    The objective of this work has been to develop low temperature sol-gel glass coatings to modify the substrate surface and to evaluate their bioactivity and biocompatibility. Glasses, based on SiO2·CaO·P2O5, were synthesized by the sol-gel technique using tetraethyl orthosilicate, calcium nitrate tetrahydrate and triethyl phosphate as precursors of SiO2, CaO and P2O5, respectively. Those materials, still in the sol phase, have been used to coat substrates by means of the dip-coating technique. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) has been used for characterize coatings and a microstructural analysis has been obtained using scanning electron microscopy (SEM). The potential applications of the coatings in the biomedical field were evaluated by bioactivity and biocompatibility tests. The coated substrate was immersed in simulated body fluid (SBF) for 21days and the hydroxyapatite deposition on its surface was subsequently evaluated via SEM-EDXS analysis, as an index of bone-bonding capability. In order to study the cell behavior and response to our silica based materials, prepared via the sol-gel method, with various Ca/P ratio and coating substrate, we have used the human osteoblast-like U2OS cell line. PMID:27157742

  14. 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

  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. Synthesis of garnet structure compounds using aqueous sol-gel processing

    NASA Astrophysics Data System (ADS)

    Leleckaite, A.; Kareiva, A.

    2004-07-01

    The sol-gel method based on metal chelates in aqueous solvents has been developed to prepare different oxides having garnet crystal structure. This synthetic approach has been used to prepare rare-earth doped yttrium aluminum garnet Y 3Al 5O 12:Ce, Y 3Al 5O 12:Nd, Y 3Al 5O 12:Ho, and Y 3Al 5O 12:Er samples (YAG:Ln). The polycrystalline powders sintered at 1000 °C are formed as single-phase garnet materials. The formation of pure and neodymium-doped lanthanum aluminum garnets (La 3Al 5O 12 (LAG), and La 3Al 5O 12:Nd (LAG:Nd)) at the same synthesis conditions, however, does not proceed. A systematic study of sol-gel technique synthesized Y 3Ga 5O 12 (YGG) is presented using six different complexing agents. These complexing agents were found to influence the characteristics of the end products, in particular the homogeneity. Finally, some specific features of sol-gel derived mixed-metal Y 3Sc xAl 5- x- yGa yO 12 (0⩽ x, y⩽5) (YSAGG) garnets are discussed in the present paper. The phase purity, composition and microstructural features in the polycrystalline samples were studied by XRD analysis, IR spectroscopy and scanning electron microscopy.

  17. Facile Fabrication of Gold Nanoparticle-Titanium Oxide Alternate Assemblies by Surface Sol-Gel Process

    NASA Astrophysics Data System (ADS)

    Arakawa, Taichi; Kawahara, Tomoaki; Akiyama, Tsuyoshi; Yamada, Sunao

    2007-04-01

    Multistructured assemblies consisting of gold nanoparticles and titanium oxide were alternately fabricated by a surface sol-gel process. First, a quartz glass substrate was immersed into an organic solution of titanium butoxide [Ti(OBu)4]. Then, the substrate was rinsed with water, and dried in air, giving ultra-thin titanium oxide [Ti(O)]-modified quartz glass substrate. This modified glass substrate was immersed into an aqueous colloidal solution of gold nanoparticles (AuPs) that were stabilized with citrate ions, giving a AuP-Ti(O)-modified glass substrate. By repeating these surface sol-gel processes, the multistructured assemblies of AuPs and Ti(O), [AuP/Ti(O)]n/Glass (n=1--4) were fabricated. Plasmon band intensity increased with the number of surface sol-gel process cycles. The resultant assemblies were stable even after 11 days, or after treatment with an aqueous electrolyte solution. The alternate assembling of AuPs and Ti(O) was confirmed by quartz crystal microbalance measurements and absorption and X-ray photoelectron spectroscopies. Accordingly, we have succeeded in the preparation of stable AuP-Ti(O) composite films on the substrates.

  18. Synthesization of Nanostructured Titanium Dioxide at Low Molarity of Sol-Gel Process

    NASA Astrophysics Data System (ADS)

    Maarof, S. K. M.; Abdullah, S.; Rusop, M.

    2013-06-01

    Titanium dioxide, TiO2 is one of the semiconductor materials. The aim of this paper is to determine the production of TiO2 by sol-gel method. The sol-gel method used because this method is quite simple compare to other methods such as dip-coated and refractive sputtering. The parameter will be used in this paper is the concentration. The sol-gel TiO2 solution then spin coated on the glass substrate to form homogenous and transparent thin film. The thin film was coated at 8 layers to adjust the refractive index characteristics and to get the clear images during characterize by spin coating technique. Other than that, this work also to get the band gap energy similar to the standard bandgap for TiO2. The optical properties such as absorption and transmittance of TiO2 can be done by Ultraviolet-visible Spectroscopy (UV-Vis). The changes on the surface morphology were observed using Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM). Based on the result, higher the molarity of TiO2, the uniformity of the surface morphology, and the energy bandgap is much better. Higher the molarity, the bandgap will be lower with 0.1M (3.78 eV) and its too large compare to the standard value (3.2 eV).

  19. A study on the effect factors of sol-gel synthesis of yttrium aluminum garnet nanopowders

    NASA Astrophysics Data System (ADS)

    Yang, Lin; Lu, Tiecheng; Xu, Hui; Zhang, Wei; Ma, Benyuan

    2010-03-01

    Yttrium aluminum garnet (YAG) nanopowders were synthesized by sol-gel method using aluminum nitrate, yttrium nitrate, and citric acid as starting materials, de-ionized water, ethanol, and ethylene glycol as solvents, respectively. The phase formation process, state of particle size distribution (PSD), compositions, morphological characteristics, and thermal behavior of the powders were investigated by means of x-ray diffractometry, PSD, Fourier transform infrared, transmission electronic microscope, and thermogravimetry-differential scanning calorimetry. Results indicate that the formation and characteristics of precursor gel and YAG powder, such as the rate of gelation, average particle size, and powder agglomerate state, strongly depend on the stoichiometric amount of citric acid, the solvent composition, and the precalcination process. Highly crystalline, well-dispersed YAG nanopowder was obtained by calcining at 800 °C for 2 h in the presence of citric acid to nitrate ratio of 3, ethanol solvent, and precalcination process. According to the analysis of experimental results, sol-gel chemistry, DLVO theory, and steric effect, the effects of stoichiometric amount of citric acid, solvent composition, and precalcination process on the formation and characteristics of precursor gel and YAG powder have been discussed. Meanwhile, the overall synthesis mechanism in sol-gel method has been suggested.

  20. 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.

  1. Preparation and characterisation of a sol-gel process α-Al₂O₃ polycrystalline detector.

    PubMed

    Ferreira, H R; Santos, A

    2015-02-01

    This article presents the dosimetric characteristics of α-Al2O3 detectors prepared through the sol-gel process, disc pressing and sintering in a highly reducing atmosphere. Comparative tests between the sol-gel process α-Al2O3 polycrystalline and anion-defective α-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 µGy, 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 α-Al2O3:C single crystal is practically non-existent in the sol-gel process α-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

  2. Use of sol-gel-derived titania coating for direct soft tissue attachment.

    PubMed

    Areva, Sami; Paldan, Hannu; Peltola, Timo; Närhi, Timo; Jokinen, Mika; Lindén, Mika

    2004-08-01

    A firm bond between an implant and the surrounding soft tissue is important for the performance of many medical devices (e.g., stents, canyls, and dental implants). In this study, the performance of nonresorbable and reactive sol-gel-derived nano-porous titania (TiO(2)) coatings in a soft tissue environment was investigated. A direct attachment between the soft tissue and the sol-gel-derived titania coatings was found in vivo after 2 days of implantation, whereas the titanium control implants showed no evidence of soft tissue attachment. The coated implants were in immediate contact with the connective tissue, whereas the titanium controls formed a gap and a fibrous capsule on the implant-tissue interface. The good soft tissue attachment of titania coatings may result from their ability to initiate calcium phosphate nucleation and growth on their surfaces (although the formation of poorly crystalline bonelike apatite does not occur). Thus, the formation of a bonelike CaP layer is not crucial for their integration in soft tissue. The formation of bonelike apatite was hindered by the adsorption of proteins onto the initially formed amorphous calcium phosphate growth centers, thus preventing the dissolution/reprecipitation processes required for the formation of poorly crystalline bonelike apatite. These findings might open novel application areas for sol-gel-derived titania-based coatings. PMID:15227661

  3. MOS solar cells with oxides deposited by sol-gel spin-coating techniques

    SciTech Connect

    Huang, Chia-Hong; Chang, Chung-Cheng; Tsai, Jung-Hui

    2013-06-15

    The metal-oxide-semiconductor (MOS) solar cells with sol-gel derived silicon dioxides (SiO{sub 2}) deposited by spin coating are proposed in this study. The sol-gel derived SiO{sub 2} layer is prepared at low temperature of 450 Degree-Sign C. Such processes are simple and low-cost. These techniques are, therefore, useful for largescale and large-amount manufacturing in MOS solar cells. It is observed that the short-circuit current (I{sub sc}) of 2.48 mA, the open-circuit voltage (V{sub os}) of 0.44 V, the fill factor (FF) of 0.46 and the conversion efficiency ({eta}%) of 2.01% were obtained by means of the current-voltage (I-V) measurements under AM 1.5 (100 mW/cm{sup 2}) irradiance at 25 Degree-Sign C in the MOS solar cell with sol-gel derived SiO{sub 2}.

  4. Investigation of novel sol-gel hydrophobic surfaces for desorption electrospray ionization-mass spectrometry analysis.

    PubMed

    Penna, Andrea; Elviri, Lisa; Careri, Maria; Mangia, Alessandro; Predieri, Giovanni

    2011-05-01

    Sol-gel-based materials were synthesized, characterized and finally tested as solid supports for desorption electrospray ionization-mass spectrometry (DESI-MS) analysis of a mixture of compounds of different polarity. Films with thickness in the 2-4 μm range were obtained by a dip-coating process using tetraethoxysilane (TEOS) and octyltriethoxysilane (OTES) as sol-gel precursors. Three types of surface with different hydrophobic character were obtained by varying the TEOS/OTES ratio in the sol-gel mixture. Each coating was characterized by atomic force microscopy investigations, gaining insight into homogeneity, smoothness and thickness of the obtained films. To study hydrophobicity of each surface, surface free energy measurements were performed. Different DESI-MS responses were observed when different solvent mixture deposition procedures and solvent spray compositions were investigated. Results were finally compared to those obtained by using commercial polytetrafluoroethylene-coated slides. It was found that surface free energy plays an important role in the desorption/ionization process as a function of the polarity of analytes. PMID:21465099

  5. 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.

  6. Direct electrochemistry and Raman spectroscopy of sol-gel-encapsulated myoglobin.

    PubMed

    Ray, Anandhi; Feng, Manliang; Tachikawa, Hiroyasu

    2005-08-01

    The direct electrochemistry of myoglobin (Mb) has been observed at a glassy carbon (GC) electrode coated with silica sol-gel-encapsulated Mb film. A well-behaved cyclic voltammogram is observed with a midpoint potential (E(1/2)) of -0.25 V vs Ag/AgCl in a pH 7.0 phosphate buffer. This potential, which is pH-dependent, is 70-90 mV more negative than the formal potential values obtained by using the spectroeletrochemical titration method at the same pH. Square wave voltametry (SWV) also shows a peak potential of -0.25 V for the reduction of Mb under the same experimental conditions. Both cathodic and anodic peak currents have a linear relationship with the scan rate. The midpoint potential decreases with pH, having a slope of -30 mV/pH. UV-vis and resonance Raman spectroscopic studies reveal that the sol-gel provides a bio-compatible environment where Mb retains a structure similar to its solution form, a 6-coordinated aquomet myoglobin. These results suggest that the silica sol-gel is a useful matrix for studying direct electrochemistry of other heme proteins. PMID:16042479

  7. Silica sol-gel matrix doped with Photolon molecules for sensing and medical therapy purposes.

    PubMed

    Podbielska, Halina; Ulatowska-Jarza, Agnieszka; Müller, Gerhard; Holowacz, Iwona; Bauer, Joanna; Bindig, Uwe

    2007-11-01

    Photolon is one of the new photosensitisers that has found application in photodynamic therapy (PDT). Its chemical structure has a partially reduced porphyrin moiety and its molecular structure is comparable to chlorin e(6), which can be isolated after hydrolysis of the 5-membered exocyclic beta-ketoester moiety of pheophorbide a. For this study, a Photolon doped sol-gel matrix was produced in the form of coatings deposited on silica fibers cores. The material was produced from sols prepared from the silicate precursor TEOS mixed with ethyl alcohol. The sol-gel films were prepared with factor R=20, where R denotes the solvent-to-precursor molar ratio. Hydrochloric acid was added as a catalyst in the correct proportion to ensure acid hydrolysis (pH approximately 2). The mixture was stirred at room temperature for 4h using a magnetic stirrer (speed 400 rpm). The coated fibers were examined in different environments, liquid and gaseous, at different pH values and with various zinc cation concentrations. The chemical reactions were studied by means of spectroscopic methods, whereby the fluorescence response was studied. It was demonstrated that Photolon immobilized in a sol-gel matrix is accessible for the environment and shows visible response to the external changes. Furthermore, it was observed that these reactions are reversible. These biomaterials are also examined as carriers for PDT. It was also proved that a toxic effect is observed an environment with microorganisms, meaning that doped coatings have photodynamic activity. PMID:17827060

  8. 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).

  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. Low-temperature sol-gel-derived nanosilver-embedded silane coating as biofilm inhibitor

    NASA Astrophysics Data System (ADS)

    Babapour, A.; Yang, B.; Bahang, S.; Cao, W.

    2011-04-01

    Silver nanocomposite coatings are prepared by the sol-gel method for the prevention of biofilm formation on the surface of medical implanted devices. High-temperature processing of such coatings can lead to diffusion of nanosilver and reduce the amount of available silver particles for long-term effects. Using a low-temperature sol-gel method, we have successfully prepared silane-based matrices, phenyltriethoxysilane (PhTEOS), containing different amounts of Ag nanoparticles. The incorporation of a silver salt into the sol-gel matrix resulted in a desired silver release rate, i.e. high initial release rate followed by a lower sustained release for more than 15 days, as determined by inductively coupled plasma mass spectrometry (ICP-MS). Scanning electron microscopy (SEM) has been employed to investigate the morphology of the film surfaces before and after immersion in a nutrient-rich bacterial suspension of approximately 108 CFU ml - 1, which was incubated for up to 30 days at 37 °C. It was found that thin films containing 35 nm particles could prevent the formation of biofilm for over 30 days. The presence of surface silver before and after 3, 9 and 15 days immersion was confirmed by x-ray photoelectron spectroscopy (XPS).

  11. A sol-gel-based microfluidics system enhances the efficiency of RNA aptamer selection.

    PubMed

    Ahn, Ji-Young; Jo, Minjoung; Dua, Pooja; Lee, Dong-Ki; Kim, Soyoun

    2011-01-01

    RNA and DNA aptamers that bind to target molecules with high specificity and affinity have been a focus of diagnostics and therapeutic research. These aptamers are obtained by SELEX often requiring many rounds of selection and amplification. Recently, we have shown the efficient binding and elution of RNA aptamers against target proteins using a microfluidic chip that incorporates 5 sol-gel binding droplets within which specific target proteins are imbedded. Here, we demonstrate that our microfluidic chip in a SELEX experiment greatly improved selection efficiency of RNA aptamers to TATA-binding protein, reducing the number of selection cycles needed to produce high affinity aptamers by about 80%. Many aptamers were identical or homologous to those isolated previously by conventional filter-binding SELEX. The microfluidic chip SELEX is readily scalable using a sol-gel microarray-based target multiplexing. Additionally, we show that sol-gel embedded protein arrays can be used as a high-throughput assay for quantifying binding affinities of aptamers. PMID:21413890

  12. Optical characterization of sol-gel ZnO:Al thin films

    NASA Astrophysics Data System (ADS)

    Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B.

    2015-09-01

    This work presents a sol-gel approach for ZnO:Al films deposition. The effect of Al component and annealing treatments (from 500 to 800 °C) on the film structural and optical properties has been studied. Sol-gel ZnO and Al2O3 films are used for comparative analyses. Structural evolution as a function of annealing temperatures is investigated by using X-ray diffraction (XRD). XRD analysis of ZnO:Al films revealed that the predominant crystal phase is a wurtzite ZnO. It can be seen that the addition of Al leads to decaying of the film crystallinity. Fourier Transform Infrared (FTIR) and UV-VIS spectrophotometry are applied for characterization of the vibrational and optical properties. The Al component influences the shapes of the absorption bands. The optical properties of the sol-gel ZnO, ZnO:Al and Al2O3 films reveal very interesting features. Increasing Al component results in significantly higher film transparency.

  13. Statistical description of the sol-gel transition in systems with thermoreversible chemical bonds

    SciTech Connect

    Ryltsev, R. E. Son, L. D.

    2010-03-15

    A general statistical model is proposed for describing network-forming systems. The model is based on the representation of the partition function for all possible configurations of a thermoreversible network in the form of a functional integral over a scalar field. According to this model, two types of first-order phase transitions can occur in the systems under consideration: macroscopic phase separation with the structural phase transition due to the change in the configuration of the spatial network and the sol-gel transition due to the formation of a thermoreversible percolation cluster consisting of bound structural units. A detailed analysis is performed of the thermodynamic and structural properties of a solution of monomers that have f functional groups and can form thermoreversible chemical bonds. The influence of specific features of the chemical and volume interactions on the phase diagram of the system is investigated. The mutual position of the sol-gel transition line and the phase diagram is determined for different model parameters. It is revealed that two substantially different regimes of the behavior of the sol-gel transition line in the 'temperature-volume fraction of structural units' plane are observed with a change in the rigidity of chemical bonds.

  14. 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

  15. 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.

  16. 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.

  17. Comparison of VO2 thin films prepared by inorganic sol-gel and IBED methods

    NASA Astrophysics Data System (ADS)

    Ningyi, Y.; Jinhua, L.; Chan, H. L. W.; Chenglu, L.

    VO2 thin films with semiconductor-to-metal phase-transition properties were prepared by inorganic sol-gel and IBED (ion-beam-enhanced deposition) methods on SiO2/Si substrate. The crystalline phase and the shape and width of the hysteresis curves of these VO2 films were significantly different. For sol-gel VO2 films, the transition started at close to 62 °C upon heating. The temperature interval needed to complete the phase transition was 8 °C, the ratio of resistance (R20 °C/R80 °C) reached three orders and the hysteresis width was 6 °C. However, the IBED film post-annealed in Ar at 700 °C underwent a phase transition from 45 °C to 80 °C, the ratio of resistance was more than two orders and the hysteresis width was 2 °C. In addition, the TCR (temperature coefficient of resistance) at 22 °C of the IBED film was 3.5%/K, much larger than the 0.7%/K TCR of the sol-gel film.

  18. Comparison of vanadium-dioxide films produced via sol-gel and sputtering techniques

    NASA Astrophysics Data System (ADS)

    Walker, Roy E.; Coath, John A.; Richardson, Mark A.

    2000-05-01

    The purpose of this work is to compare thin films of vanadium dioxide (VO2) produced via a sol-gel process and a reactive sputtering technique. The sol-gel process used was based on vanadium oxide triisopropoxide precursor. This was converted to soli n dried ethanol by adding water, and the substrates were then dip coated with a controlled draw method in an inert atmosphere. After drying this was followed by a final reduction stage in a low oxygen partial pressure atmosphere. The reactive sputtering technique used carefully controlled deposition rates from a vanadium metal target in argon/oxygen atmosphere to ensure correct stoichiometry. The films were deposited on silicon substrates and were tested optically and electrically above the below the transition temperature. Results of transmission and reflectivity in the IR region of the spectrum, and electrical conductivity are presented. The results show that the sol-gel technique provides a viable alternative method to sputtering for the production of thin films of vanadium dioxide.

  19. 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.

  20. 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

  1. 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

  2. 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

  3. 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.

  4. Investigations on photolon-and porphyrin-doped sol-gel fiberoptic coatings for laser-assisted applications in medicine

    NASA Astrophysics Data System (ADS)

    Bindig, U.; Ulatowska-Jarza, A.; Kopaczynska, M.; Müller, G.; Podbielska, H.

    2008-01-01

    In view of laser-assisted medical applications, the construction of silica-based sol-gel fiberoptic sensors based on photolon (Ph) and protoporphyrin IX (PP IX) is discussed. Electron microscopy and AFM were used to characterize the silica sol-gel coatings. AFM measurements indicate a change in the surface porosity. The PP IX-based sensors were constructed as a one-layer optode as well as a multilayered structure. An additional hybrid sensor made up of alternate layers of PP IX-and Ph-doped sol-gel was also constructed and examined. Sol-gel matrices were prepared from silicate precursor tetraethylorthosilicate (TEOS) mixed with ethanol in acid-catalyzed hydrolysis. The carrier matrices of photosensitive dyes were produced with factor R = 20, where R denotes the ratio of solvent moles (ethanol) to the number of TEOS moles. A multilayered coating was built up using the reverse-dipping technique. The overall coating thickness was determined by electron microscopy. Doped sol-gels with different PP IX concentrations were used to produce fiberoptic coatings. The film optodes with a different number of layers were examined by fluorescence spectroscopy. It was found that photolon and protoporphyrin IX entrapped in sol-gel preserve their chemical reactivity and have contact with the external environment. The hybrid sensor demonstrated clear fluorescence and a reversible behavior in gaseous environments.

  5. A sol-gel-integrated protein array system for affinity analysis of aptamer-target protein interaction.

    PubMed

    Ahn, Ji-Young; Kim, Eunkyung; Kang, Jeehye; Kim, Soyoun

    2011-06-01

    A sol-gel microarray system was developed for a protein interaction assay with high activity. Comparing to 2-dimensional microarray surfaces, sol-gel can offer a more dynamic and broad range for proteins. In the present study, this sol-gel-integrated protein array was used in binding affinity analysis for aptamers. Six RNA aptamers and their target protein, yeast TBP (TATA-binding protein), were used to evaluate this method. A TBP-containing sol-gel mixture was spotted using a dispensing workstation under high-humidity conditions and each Cy-3-labeled aptamer was incubated. The dissociation constants (K(d)) were calculated by plotting the fluorescent intensity of the bound aptamers as a function of the TBP concentrations. The K(d) value of the control aptamer was found to be 8 nM, which agrees well with the values obtained using the conventional method, electric mobility shift assay. The sol-gel-based binding affinity measurements fit well with conventional binding affinity measurements, suggesting their possible use as an alternative to the conventional method. In addition, aptamer affinity measurements by the sol-gel-integrated protein chip make it possible to develop a simple high-throughput affinity method for screening high-affinity aptamers. PMID:21749295

  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 800°C, 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. 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 650°C 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 650°C. 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.

  8. 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

  9. Stability High Salt Content Waste Using Sol Gel Process. Mixed Waste Focus Area. OST Reference Number 0236

    SciTech Connect

    None, None

    1999-09-01

    Mixed waste sludges, soils, and homogeneous solids containing high levels of salt ( ~ greater than 15% by weight ) have proven to be difficult to stabilize due to the soluble nature of the salts. The current stabilization technique for high salt waste, grouting with Portland cement, is limited to low waste loadings. The presence of salts interfere with the hydration and curing of the cement, cause waste form deteriorating mineral expansions, or result in an undesirable separate phase altogether. Improved technologies for the stabilization of salt waste must be able to accommodate higher salt loadings, while maintaining structural integrity, chemical durability, and leach resistance. In a joint collaboration supported by the Department of Energy’s (DOE’s) Mixed Waste Focus Area (MWFA), the Pacific Northwest National Laboratory (PNNL) and the Arizona Materials Laboratory (AML) at the University of Arizona have developed a sol-gel (wet-chemical) based, low-temperature-processing route for the stabilization of salt-containing mixed wastes. By blending and reacting liquid precursors at room temperature with salt waste, strong, impermeable “polyceram” matrices have been formed that encapsulate the environmentally hazardous waste components. As depicted by Figure 1, polycerams are hybrid organic/inorganic materials with unique properties derived from the chemical combination of polymer (organic) and ceramic (inorganic) components. For this application, the stabilizing polyceram matrices contain polybutadiene-based polymer components and silicon dioxide (SiO2) as the inorganic component. Polybutadiene (PBD) is a strong, tough, waterresistant plastic and its use in the polyceram promotes these same characteristics in the waste form. The PBD polymer component is modified to increase its reactivity with the SiO2 precursor during sol-gel processing. When combined, the polymer and SiO2 precursors react, gel, solidify, and encapsulate the salt waste components. The toxicity characterization leaching procedure (TCLP), Compressive Strength (ASTM C 39-94) and leachability tests (ANSI/ANS 16.1) confirm the efficacy of this approach, indicating that polyceram-based salt waste forms have the potential to provide end users with unique capabilities for disposing of salt-containing mixed wastes.

  10. The sol gel synthesis of perovskites by an EDTA/citrate complexing method involves nanoscale solid state reactions

    NASA Astrophysics Data System (ADS)

    Feldhoff, A.; Arnold, M.; Martynczuk, J.; Gesing, Th. M.; Wang, H.

    2008-06-01

    Nowadays, sol-gel procedures are well established in the synthesis of complex oxides as they allow to obtain phase pure products and to control precisely their stoichiometry. This quality makes them a tool of choice for the preparation of perovskite-type oxides. To optimize the functional properties of these materials, it is essential to set accurately their possible complex stoichiometries. However, details of the formation of the perovskite crystal remain obscure. Different stages of an ethylene-diamine-tetraacetic acid (EDTA)/citrate-gel based synthesis process for mixed conducting (Ba 0.5Sr 0.5)(Fe 0.8Zn 0.2)O 3- δ of cubic perovskite structure are elucidated. The combination of analytical transmission electron microscopy with X-ray diffraction reveals that the perovskite-type oxide is formed already at moderate temperatures at around 700 °C via nanoscale solid state reactions between finely-dispersed crystalline intermediates identified as a spinel and a carbonate. The reaction scheme, however, is intricate and includes stuffed tridymite structures as transient phases. The ultrafine intermixing of extremely small reactants makes EDTA/citrate-gel based procedures superior to classical solid state routes with respect to applications that demand phase purity and stoichiometry control.

  11. 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.

  12. 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

  13. Effect of La substitution on structure and magnetic properties of sol-gel prepared BiFeO3

    NASA Astrophysics Data System (ADS)

    Suresh, Pittala; Srinath, S.

    2013-05-01

    Detailed Rietveld analysis of the room temperature (RT) x-ray diffraction data of LaxBi1-xFeO3 (LBFO) ceramics (0 ≤ x ≤ 0.4) prepared by sol-gel route revealed that the system retains distorted rhombohedral R3c structure of parent compound BiFeO3 (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, HC, increases remarkably with an increase in La doping and x = 0.4 exhibits the highest HC (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, Mr, 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 Néel temperature (TN) of the LBFO increases with x, approaching that of the LaFeO3.

  14. Novel multifunctional titania-silica-lanthanum phosphate nanocomposite coatings through an all aqueous sol-gel process.

    PubMed

    Smitha, Venu Sreekala; Jyothi, Chembolli Kunhatta; Peer, Mohamed A; Pillai, Saju; Warrier, Krishna Gopakumar

    2013-04-01

    A novel nanocomposite coating containing titania, silica and lanthanum phosphate prepared through an all aqueous sol-gel route exhibits excellent self-cleaning ability arising from the synergistic effect of the constituents in the nanocomposite. A highly stable titania-silica-lanthanum phosphate nanocomposite sol having particle size in the range of 30-50 nm has been synthesized starting from a titanyl sulphate precursor, which was further used for the development of photocatalytically active composite coatings on glass. The coatings prepared by the dip coating technique as well as the nanocomposite powders are heat treated and characterized further for their morphology and multifunctionality. The nanocomposite containing 1.5 wt% LaPO4 has shown a surface area as high as 138 m(2) g(-1) and a methylene blue degradation efficiency of 94% in two hours of UV exposure. The composite coating has shown very good homogeneity evidenced by transparency as high as 99.5% and low wetting behaviour. The present novel approach for energy conserving, aqueous derived, self-cleaning coatings may be suitable for large scale industrial applications. PMID:23358559

  15. 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}.

  16. 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.

  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. 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.

  20. 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.

  1. 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.; Reed, Scott T.; Ashley, Carol S.; Neiser, Richard A.; Moffatt, William C.

    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.

  2. 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.

  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. Dielectric properties and alternating current conductivity of sol-gel made La0.8Ca0.2FeO3 compound

    NASA Astrophysics Data System (ADS)

    Benali, A.; Souissi, A.; Bejar, M.; Dhahri, E.; Graça, M. F. P.; Valente, M. A.

    2015-09-01

    In this work, single phase La0.8Ca0.2FeO3 nanomaterial has been synthesized by the sol-gel method using the citric acid route. By employing impedance spectroscopy, ac electrical properties have been measured over a temperature range from 300 to 673 K at various frequencies. With the analysis based on Debye's theory and a series of Arrhenius relations, the relaxation was argued to be associated with the hopping motions of charge carriers between Fe ions. The relaxation in the La0.8Ca0.2FeO3 compound was ascribed to be a polaronic relaxation. The ac electrical conduction was studied and associated to the non-overlapping small polaron tunneling (NSPT) model.

  5. 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.

  6. Enhanced piezoelectric properties of lead zirconate titanate (PZT) sol-gel derived ceramics using single crystal PZT cubes

    NASA Astrophysics Data System (ADS)

    Lin, Yirong; Andrews, Clark; Sodano, Henry A.

    2010-04-01

    Piezoceramic materials have attracted much attention for sensing, actuation, structural health monitoring and energy harvesting applications in the past two decades due to their excellent coupling between energy in the mechanical and electrical domains. Among all piezoceramic materials, lead zirconate titanate (PZT) has been the most broadly studied and implemented, in industrial applications due to its high piezoelectric coupling coefficients. Piezoceramic materials are most often employed as thin films or monolithic wafers. While there are numerous methods for the synthesis of PZT films, the sol-gel processing technique is the most widely used due to its low densification temperature, the ease at which the film can be applied without costly physical deposition equipment and the capability to fabricate both thin and thick films. However, the piezoelectric properties of PZT sol-gel derived films are substantially lower than those of bulk materials, which limit the application of sol-gel films. In comparison, single crystal PZT materials have higher piezoelectric coupling coefficients than polycrystalline materials due to their uniform dipole alignment. This paper will introduce a novel technique to enhance the piezoelectric properties of PZT sol-gel derived ceramics through the use of single crystal PbZr0.52Ti0.48O3 microcubes as an inclusion in the PZT sol-gel. The PZT single crystal cubes are synthesized through a hydrothermal based method and their geometry and crystal structure is characterized through scanning electron microscopy (SEM) and X-ray diffraction (XRD). A mixture of PZT cubes and sol-gel will then be sintered to crystallize the sol-gel and obtain full density of the ceramic. XRD and SEM analysis of the cross section of the final ceramics will be performed and compared to show the crystal structure and microstructure of the samples. The P-E properties of the samples will be tested using a Sawyer-Tower circuit. Finally, a laser interferometer will be used to directly measure the piezoelectric strain-coupling coefficient of the PZT sol-gel ceramics with and without PZT cube inclusions. The results will show that with the integration of PZ0.52T0.48 crystal inclusions the d33 coupling coefficient will increase more than 200% compared to that of pure PbZr0.52Ti0.48O3 sol-gel.

  7. 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.

  8. 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.

  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. 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.

  11. Tunable Bragg stacks from sol-gel derived Ta2O5 and MEL zeolite films

    NASA Astrophysics Data System (ADS)

    Gospodinov, B.; Dikova, J.; Mintova, S.; Babeva, T.

    2012-12-01

    In this paper we investigated sol-gel derived Ta2O5 and nanosized MEL zeolite films obtained by spin coating of Tantalum sol and colloidal zeolite solution, respectively. Refractive index and thickness of the films were determined using non-linear curve fitting of measured reflectance spectra. The influence of the post deposition annealing on the optical properties and thickness of the films was studied. Besides tunable Bragg stacks were designed and prepared by layer-by-layer deposition of Ta2O5 and MEL suspensions with quarter-wave thicknesses. The influence of water, acetone and methanol on the optical behavior of Bragg stacks was discussed.

  12. Synthesis and luminescence properties of encapsulated sol-gel glass samarium complexes

    NASA Astrophysics Data System (ADS)

    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.

  13. Flat ceramic ultrafiltration membranes and modules coated by the sol-gel technique

    SciTech Connect

    Pflanz, K.; Stroh, N.; Riedel, R.

    1994-12-31

    Sol-gel techniques are common in preparing inorganic ultrafiltration membranes. Since applicable membranes should exhibit improved chemical and thermal stability with respect to phase transition, pore size and particle growth, the authors developed a new method for preparing an inorganic ultrafiltration membrane made of magnesium aluminum spinel, MgAl{sub 2}O{sub 4}. This membrane is supported by a flat ceramic microfilter ({alpha}-Al{sub 2}O{sub 3}) produced via the tape casting process, which offers the opportunity of improved processing techniques and new module concepts compared to the widely used extruded multi channel modules. Membrane characteristics and some applications will be shown.

  14. 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.

  15. Structural and electrical properties of sol-gel spin coated indium doped cadmium oxide thin films

    NASA Astrophysics Data System (ADS)

    Rajammal, R.; Savarimuthu, E.; Arumugam, S.

    2014-04-01

    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 5.92×10-4Ω cm and a maximum carrier concentration of 1.20×1020cm-3 have been realized.

  16. Optical characterization of sol gel TiO2 monoliths doped with Brilliant Green

    NASA Astrophysics Data System (ADS)

    Tomás, S. A.; Zelaya, O.; Palomino, R.; Lozada, R.; García, O.; Yáñez, J. M.; Ferreira da Silva, A.

    2008-01-01

    Amorphous titanium dioxide monoliths doped with brilliant green (BG) were synthesized by the sol-gel process. The optical properties of the monoliths were characterized by Photoacoustic Spectroscopy and Photoluminescence Spectroscopy. The absorption spectra for the BG-doped TiO2 monoliths exhibited two well defined absorption regions: a band below 400 nm corresponding to TiO2 absorption and three absorption bands centered at 424 nm, 588 nm, and 632 nm due to brilliant green. While the undoped TiO2 monoliths showed no luminescence, the doped samples showed a strong luminescence band at 673 nm, which increased its intensity for increasing organic dye doping.

  17. Nonlinear absorption and emission of excited states in metalloporphyrin-doped sol gels

    NASA Astrophysics Data System (ADS)

    Dou, Kai; Sun, Xiaodong; Wang, Xiao-jun; Knobbe, Edward T.

    1997-10-01

    In this paper, we describe up-converted luminescence and reverse saturation absorption of metalloporphyrins of CuTPPS and ZnTPPS in aluminosilicate sol-gel materials. The photo- upconversion luminescence is believed to arise from the radiative recombination of the second excited singlet (singdoublet) state. These effects are attributed to the higher excited state absorption. The dynamic analysis for the excited state processes indicates that the saturation or reverse saturation absorption is dependent on the ratio of the average absorption cross-section of the excited states to that of the ground state. The absorption cross-sections of the excited states are estimated.

  18. Synthesis of porphyrin-introduced silica gels by sol-gel process.

    PubMed

    Tanaka, Hidekazu; Yamada, Toshiyuki; Sugiyama, Shinichiro; Shiratori, Hideo; Hino, Ryozi

    2005-06-15

    Using a hydroxyl group appended free base porphyrin derivative (HP), porphyrin-introduced silica gels were synthesized by a sol-gel process. The HP content in the materials linearly increased with increasing the HP concentration. Meanwhile, free base tetraphenylporphyrin (TPP) with no hydroxyl groups were almost not incorporated into the silica gels. These facts suggested that the interaction between hydroxyl groups of the HP molecules and silica network is considerably strong. The UV-vis characters of HP-introduced materials were almost the same as pure HP molecules. The Beer's plot indicated that the HP molecules in the materials are dispersed. PMID:15897099

  19. Porphyrin gels reinforced by sol-gel reaction via the organogel phase.

    PubMed

    Kishida, Takanori; Fujita, Norifumi; Sada, Kazuki; Shinkai, Seiji

    2005-10-11

    Porphyrins bearing four urea-linked dodecyl groups (3a) or four urea-linked triethoxysilylpropyl groups (3TEOS) at their peripheral positions were synthesized. 3a tends to assemble into a sheetlike two-dimensional structure due to the predominant hydrogen-bonding interaction among the urea groups and acts as a moderate gelator of organic solvents. On the other hand, its Cu(II) compelx (3a.Cu) tends to assemble into a fibrous one-dimensional structure due to the predominant porphyrin-porphyrin pi-pi stacking interaction and acts as an excellent gelator of many organic solvents. 3TEOS and 3TEOS.Cu, which also act as gelators, afforded similar superstructures as those of 3a and 3a.Cu, respectively, and as evidenced by SEM and TEM observations and XRD measurements, the original superstructures could be precisely immobilized by in situ sol-gel polycondensation of the triethoxysilyl groups. The TEM images of 3a gels and 3TEOS gels after sol-gel polycondensation showed a fine striped structure, the periodical distance of which was either 2 or 4 nm. X-ray crystallographic analysis of a single crystal obtained from a reference porphyrin bearing four urea-linked butyl groups revealed that there are two different porphyrin-stacked columns in the crystal and both the 2 nm distance and the 4 nm distance can appear, depending on the observation tilting angle. The hybrid gel prepared from 3TEOS.Cu by sol-gel polycondensation showed unique physicochemical properties such as a high sol-gel phase-transition temperature (>160 degrees C), sufficient elasticity, high mechanical strength, etc. Thus, the present study has established new concepts for molecular design of porphyrin-based gelators on the basis of cooperative and/or competitive actions of hydrogen-bonding and pi-pi stacking interactions and for immobilization of their superstructures leading to development of new functional organic/inorganic hybrid materials. PMID:16207018

  20. 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.

  1. 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.

  2. 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.

  3. Surface and catalytic properties of acid metal carbons prepared by the sol gel method

    NASA Astrophysics Data System (ADS)

    Aguado-Serrano, J.; Rojas-Cervantes, M. L.; Martín-Aranda, R. M.; López-Peinado, A. J.; Gómez-Serrano, V.

    2006-06-01

    The sol-gel method has been applied for the synthesis of a series of acid metal-carbon xerogels (with M = V, Cr, Mo and Ni) by polymerisation of resorcinol with formaldehyde in the presence of metallic precursors. A blank sample was also prepared without any metal addition. The xerogels were heated in nitrogen at 1000 °C to obtain the pyrolysed products. The samples were characterised by different techniques such as thermal-mass spectrometry analysis, gas physisorption, and mercury porosimetry. In addition, the acid character of the pyrolysed products was tested by the Claisen-Schmidt condensation between benzaldehyde and acetophenone for the formation of chalcones.

  4. Optical characterization of Sol-Gel ZnO:Al thin films

    NASA Astrophysics Data System (ADS)

    Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B.

    2016-03-01

    This paper presents a sol-gel technological process for preparing thin films of ZnO and ZnO:Al. The effect of annealing treatments (500, 600, 700 and 800 °C) on their properties was studied. The structural evolution with the temperature was investigated by using X-Ray diffraction (XRD). Fourier Transform Infrared (FTIR) and UV-VIS spectrophotometry were applied to characterizing the films' vibrational and optical properties. The ZnO and ZnO:Al films possessed a polycrystalline structure. The films studied are highly transparent in the visible spectral range. The optical band gap values and the haze parameter were also determined.

  5. 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.

  6. Fabrication of inverted zinc oxide photonic crystal using sol-gel solution by spin coating method.

    PubMed

    Huang, Kuo-Min; Ho, Chong-Lung; Chang, Heng-Jui; Wu, Meng-Chyi

    2013-01-01

    Inverted zinc oxide photonic crystal structures were fabricated from polystyrene sphere (PSS) template using the sol-gel 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 193 nm. 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

  7. Electroanalytical applications of screen-printable surfactant-induced sol-gel graphite composites

    DOEpatents

    Guadalupe, Ana R.; Guo, Yizhu

    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.

  8. Permeability measurements during the sol-gel transition: Direct determination of the ν exponent

    NASA Astrophysics Data System (ADS)

    Allain, C.; Amiel, C.

    1986-04-01

    We study the variation of the permeability in the vicinity of the sol-gel transition observed during free-radical copolymerization of acrylamide and bisacrylamide at low concentrations. The main difficulty of the experiment arises from the low values of the elastic moduli which can lead to deformation effects; these have been carefully analyzed. For the first time, the exponent ν and the prefactor ξtheta of the correlation length have been determined experimentally. We find that ν is equal to 0.9+/-0.1 independently of the concentration while ξtheta decreases as the concentration is increased.

  9. The photoconductivity of sol-gel derived TiO 2 films

    NASA Astrophysics Data System (ADS)

    Brajsa, A.; Szaniawska, K.; Barczyński, R. J.; Murawski, L.; Kościelska, B.; Vomvas, A.; Pomoni, K.

    2004-07-01

    TiO 2 films on silica substrate were prepared by the sol-gel method. The photoconductivity of these films has been studied in different ambient conditions. The photoconductivity in vacuum is much larger than that in air. In air the photoconductivity exhibits saturation after a short illumination time. In vacuum the maximum current is reached after hours of illumination and is more than three orders of magnitude larger than in air. This effect is attributed to a loss of oxygen adsorbed at the surface. Oxygen is known as electron scavenger, and its removal extends the electron lifetime and results in a much larger saturation photocurrent.

  10. 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.

  11. Comparison of bare and sol-gel coated of mitigated site on fused silica

    NASA Astrophysics Data System (ADS)

    Jiang, Y.; Mu, X. Y.; Qiu, R.; Yang, Y. J.; Zhou, Q.; Gao, X.

    2015-05-01

    The performance of mitigated site coated with antireflective (AR) coating is investigated, and its discrepancy is also investigated by comparing the bare site with substrate from surface morphology and profile, transmittance and laser induced damage threshold (LIDT). The results indicated that more SiO2 sol will be deposited in the crater of mitigated site during the dipping process, while the coated site does not seriously influence the performance of the entire sample. The LIDT results indicate that both the coated substrate and mitigated site are lower than that of un-coated substrate and mitigated site. Keywords: fused silica; mitigated site; coating; sol-gel.

  12. Ultraviolet light imprinted sol-gel silica glass waveguide devices on silicon

    NASA Astrophysics Data System (ADS)

    Coudray, P.; Chisham, J.; Malek-Tabrizi, A.; Li, C.-Y.; Andrews, M. P.; Peyghambarian, N.; Najafi, S. I.

    1996-02-01

    We describe a new simplified process for inexpensive fabrication of low-loss (0.1 dB/cm) glass waveguides on silicon by ultraviolet light imprinting in photosensitive, organically modified sol-gel silica glass films prepared by one-step dip-coating process. The fabrication process is appealing because the buffer layer between waveguide and substrate is eliminated, and waveguides can be made in a few steps using low-cost equipment. Also, a 1 × 8 power splitter is produced by this process. The splitter exhibits relatively uniform output and a configuration loss of 0.9 dB at 1.55 μm wavelength.

  13. Preparation of chitosan-graft-(β-cyclodextrin) based sol-gel stationary phase for open-tubular capillary electrochromatography.

    PubMed

    Lü, Haixia; Li, Qingyin; Yu, Xiaowei; Yi, Jiaojiao; Xie, Zenghong

    2013-07-01

    A novel open-tubular CEC column coated with chitosan-graft-(β-CD) (CDCS) was prepared using sol-gel technique. In the sol-gel approach, owing to the 3D network of sol-gel and the strong chemical bond between the stationary phase and the surface of capillary columns, good chromatographic characteristics and unique selectivity in separating isomers were shown. The column efficiencies of 55,000∼163,000 plates/m for the isomeric xanthopterin and phenoxy acid herbicides using the sol-gel-derived CDCS columns were achieved. Good stabilities were demonstrated that the RSD values for the retention time of thiourea and isoxanthopterin were 1.3 and 1.4% (run to run, n = 5), 1.6 and 2.0% (day to day, n = 3), 2.9 and 3.1% (column to column, n = 3), respectively. The sol-gel-coated CDCS columns have shown improved separations of isomeric xanthopterin in comparison with CDCS-bonded capillary column. PMID:23595578

  14. 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.

  15. Sol-gel entrapped Candida antarctica lipase B--a biocatalyst with excellent stability for kinetic resolution of secondary alcohols.

    PubMed

    Ursoiu, Anca; Paul, Cristina; Kurtán, Tibor; Péter, Francisc

    2012-01-01

    Sol-gel entrapment is an efficient immobilization technique that allows preparation of robust and highly stable biocatalysts. Lipase from Candida antarctica B was immobilized by sol-gel entrapment and by sol-gel entrapment combined with adsorption on Celite 545, using a ternary silane precursor system. After optimization of the immobilization protocol, the best enzyme loading was 17.4 mg/g support for sol-gel entrapped lipase and 10.7 mg/g support for samples obtained by entrapment and adsorption. Sol-gel immobilized enzymes showed excellent values of enantiomeric ratio E and activity when ionic liquid 1-octyl-3-methyl-imidazolium tetrafluoroborate was used as additive. Immobilization increased the stability of the obtained biocatalysts in several organic solvents. Excellent operational stability was obtained for the immobilized lipase, maintaining unaltered catalytic activity and enantioselectivity during 15 reuse cycles. The biocatalysts were characterized using scanning electron microscopy (SEM) and fluorescence microscopy. The improved catalytic efficiency of entrapped lipases recommends their application for large-scale kinetic resolution of optically active secondary alcohols. PMID:23124473

  16. 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.

  17. Single-step fabrication of diffraction gratings on hybrid sol-gel glass using holographic interference lithography

    NASA Astrophysics Data System (ADS)

    Jiang, H. J.; Yuan, X.-C.; Zhou, Y.; Chan, Y. C.; Lam, Y. L.

    2000-11-01

    Single-step fabrication of diffractive surface relief gratings on an ultraviolet (UV) sensitive hybrid sol-gel glass is presented. The gratings are imprinted on the negative-tone sol-gel glass based on a holographic interference lithographic system. Characteristics of the sol-gel glass including refractive index and film thickness have been discussed and experimental results are presented as a function of baking temperature and UV exposure time respectively. The grating relief profiles are measured by an atomic force microscope and the measured groove depths are found in good agreement with the theoretical results determined by the Gerchberg-Saxton phase retrieval algorithm. It is promising to utilise the new material for various diffractive optical elements fabrication.

  18. 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.

  19. Mesoporous sol-gel silica cladding for hybrid TiO2/electro-optic polymer waveguide modulators.

    PubMed

    Enami, Yasufumi; Kayaba, Yasuhisa; Luo, Jingdong; Jen, Alex K-Y

    2014-06-30

    We report the efficient poling of an electro-optic (EO) polymer in a hybrid TiO(2)/electro-optic polymer multilayer waveguide modulator on mesoporous sol-gel silica cladding. The mesoporous sol-gel silica has nanometer-sized pores and a low refractive index of 1.24, which improves mode confinement in the 400-nm-thick EO polymer film in the modulators and prevents optical absorption from the lower Au electrode, thereby resulting in a lower half-wave voltage of the modulators. The half-wave voltage (Vπ) of the hybrid modulator fabricated on the mesoporous sol-gel silica cladding is 6.0 V for an electrode length (Le) of 5 mm at a wavelength of 1550 nm (VπLe product of 3.0 V·cm) using a low-index guest-host EO polymer (in-device EO coefficient of 75 pm/V). PMID:24977890

  20. 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

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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 400°C 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.

  7. 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.

  8. 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.

  9. 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.

  10. Antimicrobial activity of thin solid films of silver doped hydroxyapatite prepared by sol-gel method.

    PubMed

    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 x(Ag) = 0.5 are effective against E. coli and S. aureus after 24 h. PMID:24523630

  11. 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.

  12. Chitosan-PEG hydrogel with sol-gel transition triggerable by multiple external stimuli.

    PubMed

    Tsao, Ching Ting; Hsiao, Meng Hsuan; Zhang, Mengying Y; Levengood, Sheeny Lan; Zhang, Miqin

    2015-02-01

    Smart hydrogels play an increasingly important role in biomedical applications, since materials that are both biocompatible and multi-stimuli-responsive are highly desirable. A simple, organic solvent-free method is presented to synthesize a biocompatible hydrogel that undergoes a sol-gel transition in response to multiple stimuli. Methoxy-poly(ethylene glycol) (mPEG) is modified into carboxylic-acid-terminated-methoxy-poly(ethylene glycol) (mPEG-acid), which is then grafted onto chitosan via amide linkages yielding mPEG-g-chitosan. Grafting of mPEG onto hydrophobic chitosan imparts hydrophilic properties to the resultant polymer. The mPEG-g-chitosan gel exhibits a controllable multi-stimuli-responsive property. The balance between hydrophilicity and hydrophobicity is believed to confer mPEG-g-chitosan with stimuli-responsive behavior. The effect of salt concentration, solute concentration, temperature, and pH on the sol-gel transition of mPEG-g-chitosan is evaluated and the underlying mechanisms of mPEG-g-chitosan polymer packing and gelation property is discussed. PMID:25522283

  13. Synthesis and characterization of NiO nanopowder by sol-gel process

    SciTech Connect

    Ningsih, Sherly Kasuma Warda

    2015-09-30

    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.

  14. TiO2/PCL hybrid materials synthesized via sol-gel technique for biomedical applications.

    PubMed

    Catauro, M; Bollino, F; Papale, F; Marciano, S; Pacifico, S

    2015-02-01

    The aim of the present work has been the synthesis of organic/inorganic hybrid materials based on titanium dioxide and poly(ε-caprolactone) (PCL) to be used in the biomedical field. Several materials have been synthesized using sol-gel methods by adding different amounts of polymer to the inorganic sol. The obtained gels have been characterized using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The FT-IR data allowed us to hypothesize that the structure formed was that of an interpenetrating network, realized by hydrogen bonds between TiOH groups in the sol-gel intermediate species and carbonyl groups in the polymer repeating units. SEM and AFM analyses highlighted that the obtained materials were nanostructurated hybrids. To evaluate the biological properties of the hybrids, their bioactivity and cytotoxicity were investigated as a function of the PCL amount. The bioactivity of the synthesized systems was proven by the formation of a hydroxyapatite layer on the surface of samples soaked in a fluid simulating human blood plasma (SBF). MTT cytotoxicity tests and Trypan Blue dye exclusion tests were carried out exposing NIH-3T3 mouse embryonic fibroblasts for 24 and 48h to extracts from the investigated hybrid materials. The results showed that all the hybrids had a non-cytotoxic effect on target cells. PMID:25492181

  15. 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.

  16. Biological evaluation of zirconia/PEG hybrid materials synthesized via sol-gel technique.

    PubMed

    Catauro, M; Papale, F; Bollino, F; Gallicchio, M; Pacifico, S

    2014-07-01

    The objective of the following study has been the synthesis via sol-gel and the characterization of novel organic-inorganic hybrid materials to be used in biomedical field. The prepared materials consist of an inorganic zirconia matrix containing as organic component the polyethylene glycol (PEG), a water-soluble polymer used in medical and pharmaceutical fields. Various hybrids have been synthesized changing the molar ratio between the organic and inorganic parts. Fourier transform spectroscopy suggests that the structure of the interpenetrating network is realized by hydrogen bonds between the Zr-OH group in the sol-gel intermediate species and both the terminal alcoholic group and ethereal oxygen atoms in the repeating units of polymer The amorphous nature of the gels has been ascertained by X-ray diffraction analysis. The morphology observation has been carried out by using the Scanning Electron Microscope and has confirmed that the obtained materials are nanostructurated hybrids. The bioactivity of the synthesized system has been shown by the formation of a hydroxyapatite layer on the surface of samples soaked in a fluid simulating the human blood plasma. The potential biocompatibility of hybrids has been assessed as performing indirect MTT cytotoxicity assay towards 3T3 cell line at 24, 48, and 72 h exposure times. PMID:24857491

  17. "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

  18. 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.

  19. Biocompatibility of sol-gel-derived titania-silica coated intramedullary NiTi nails.

    PubMed

    Muhonen, V; Kujala, S; Vuotikka, A; Aäritalo, V; Peltola, T; Areva, S; Närhi, T; Tuukkanen, J

    2009-02-01

    We investigated bone response to sol-gel-derived titania-silica coated functional intramedullary NiTi nails that applied a continuous bending force. Nails 26 mm in length, either straight or with a radius of curvature of 28 or 15 mm, were implanted in the cooled martensite form from a proximal to distal direction into the medullary cavity of the right femur in 40 Sprague-Dawley rats. Body temperature restored the austenite form, causing the curved implants to generate a bending force on the bone. The femurs were examined after 24 weeks. Bone length measurements did not reveal any bowing or shortening of the bone in the experimental groups. The results from histomorphometry demonstrated that the stronger bending force, together with sol-gel surface treatment, resulted in more bone deposition around the implant and the formation of significantly less fibrous tissue. Straight intramedullary nails, even those with a titania-silica coating, were poorly attached when compared to the implants with a curved austenite structure. PMID:18838349

  20. 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

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. NMR of molecules trapped in sol-gel glasses: Progressive closure of the nanoporosity during drying

    NASA Astrophysics Data System (ADS)

    Cros, F.; Malier, L.; Korb, J.-P.; Chaput, F.

    1998-02-01

    We characterize the closed porosity of porous hybrid organic-inorganic sol-gel matrices. 2H-nuclear relaxation of d16-adamantane confined in these pores evidences a molecular translational motion inside the porous network. The pores are shown to be interconnected at the submicrometric scale. By modelling the effect of interpore molecular jumps on the lineshape, we characterize the progressive closure of the nanoporosity during drying. Nous avons caractérisé la porosité de matrices hybrides organique-inorganiques poreuse, à porosité fermée, préparées par voie sol-gel. La relaxation nucléaire du deuterium de l'adamantane d16 confinée dans les pores de ces matériaux a mis en évidence un mouvement de translation de cette molécule à l'intérieur du système de pores, qui est en fait connexe à l'échelle sub-micrométrique. L'influence des sauts, d'un pore à un autre, sur la forme de raie nous a permis de caractériser la fermeture de ces pores au cours du séchage.

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. Sol-gel network silica/modified montmorillonite clay hybrid nanocomposites for hydrophobic surface coatings.

    PubMed

    Meera, Kamal Mohamed Seeni; Sankar, Rajavelu Murali; Murali, Adhigan; Jaisankar, Sellamuthu N; Mandal, Asit Baran

    2012-02-01

    Sol-gel silica/nanoclay composites were prepared through sol-gel polymerization technique using tetraethylorthosilicate precursor and montmorillonite (MMT) clay in aqueous media. In this study, both montmorillonite-K(+) and organically modified MMT (OMMT) clays were used. The prepared composites were coated on glass substrate by making 1 wt% solution in ethyltrichlorosilane. The incorporation of nanoclay does not alter the intensity of characteristic Si-O-Si peak of silica network. Thermogravimetric studies show that increasing clay content increased the degradation temperature of the composites. Differential scanning calorimetry (DSC) results of organically modified MMT nanoclay incorporated composite show a shift in the melting behavior up to 38°C. From DSC thermograms, we observed that the ΔH value decreased with increasing clay loading. X-ray diffraction patterns prove the presence of nanoclay in the composite and increase in the concentration of organically modified nanoclay from 3 to 5 wt% increases the intensity of the peak at 2θ=8° corresponds to OMMT. Morphology of the control silica gel composite was greatly influenced by the incorporation of OMMT. The presence of nanoclay changed the surface of control silica gel composite into cleaved surface with brittle in nature. Contact angle measurements were done for the coatings to study their surface behavior. These hybrid coatings on glass substrate may have applications for hydrophobic coatings on leather substrate. PMID:22056084

  11. 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

  12. 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

  13. New optical fiber type: microporous sol-gel-clad optical fibers

    NASA Astrophysics Data System (ADS)

    Skutnik, Bolesh J.

    1999-04-01

    A new type of optical fiber has been developed. It is made with all pure silica in both the core and cladding. This is possible because the cladding is a micro porous silica produced by a modified sol-gel technology. The formation and characteristics of this new optical fiber type are described. In particular the optical and mechanical properties are illustrated and described. The strength and fatigue of these optical fibers are very good, even without additional protective jackets. Unjacketed fibers have mean Weibull strengths in bending of 6.5 to 7.6 GPa with Weibull slopes in the 40 to 60 range. Fatigue results for fibers tested in ambient air, ambient water and boiling water are presented. The dynamic and static fatigue parameters are around 20. The micro porous structure of the sol-gel cladding provides sites for attaching different moieties which could activate biochemical reactions or be useful as sensing sites. Based on preliminary experiments, some possibilities are presented. In general this new structure can provide opportunities for as yet unidentified applications where chemicals and or light must be brought in close contact with body tissue to effect beneficial reactions there.

  14. 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

  15. Nonvolatile memory devices prepared from sol-gel derived niobium pentoxide films.

    PubMed

    Baek, Hyunhee; Lee, Chanwoo; Choi, Jungkyu; Cho, Jinhan

    2013-01-01

    We report on the resistive switching nonvolatile memory (RSNM) properties of niobium pentoxide (Nb(2)O(5)) films prepared using sol-gel chemistry. A sol-gel derived solution of niobium ethoxide, a precursor to Nb(2)O(5), was spin-coated on to a platinum (Pt)-coated silicon substrate, and was then annealed at approximately 620 and 450 °C to form a Nb(2)O(5) film of polycrystalline and amorphous structure, respectively. A top electrode consisting of Ag, W, Au, or Pt was then coated onto the Nb(2)O(5) films to complete the fabrication. After a forming process of limited current compliance up to 10 mA, known as "electroforming", a resistive switching phenomenon, independent of voltage polarity (unipolar switching), was observed at low operating voltages (0.59 ± 0.05 V(RESET) and 1.03 ± 0.06 V(SET)) with a high ON/OFF current ratio above 10(8). The reported approach offers opportunities for preparing Nb(2)O(5)-based resistive switching memory devices from solution process. PMID:23210494

  16. Sol gel derived hydroxyapatite coatings on titanium and its alloy Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Stoch, A.; Jastrzebski, W.; Długoń, 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.

  17. High-Tc superconductivity in nanostructured NaxWO3-y: sol gel route

    NASA Astrophysics Data System (ADS)

    Aliev, Ali E.

    2008-11-01

    Tungsten trioxide, WO3-y, infiltrated into various nanoporous matrix structures such as carbon inverse opal, carbon nanotube paper or platinum sponge, and then intercalated with alkaline ions (Li+, Na+) exhibits a pronounced diamagnetic onset in ZFC magnetization in a wide range of temperatures, 125-132 K. Resistivity measurements show nonzero jump and intensive fluctuations of electrical resistance below observed transition points. The observed magnetic and electrical anomalies in nanostructured tungsten bronzes (LixWO3-y and NaxWO3-y) suggest the possibility of localized non-percolated superconductivity.

  18. High-Tc superconductivity in nanostructured NaxWO3-y: Sol-gel route

    NASA Astrophysics Data System (ADS)

    Aliev, Ali

    2009-03-01

    Tungsten trioxide, WO3-y infiltrated into various nanoporous matrix structures such as carbon inverse opal, carbon nanotubes paper, or platinum sponge and then intercalated with alkaline ions (Li^+, Na^+) exhibits a pronounced diamagnetic onset in ZFC magnetization in a wide range of temperatures, 125-132 K. Resistivity measurements show non zero jump and intensive fluctuations of electrical resistance below observed transition points. The observed magnetic and electrical anomalies in nanostructured tungsten bronzes (LixWO3-y, NaxWO3-y) suggest the possibility of localized non-percolated superconductivity. The direct evidence of polaron formation from temperature dependence of EPR and photoemission spectra and formation of bipolarons in weakly reduced to WO3-y, with 3-y typically in the order of 2.95 suggest bipolarons mechanism of a Bose-Einstein condensation of trapped electron pairs in doped WO3-y. On the other hand the strong lattice instabilities in 2D systems like layered cuprates and tungsten bronzes place the upper limit on Tc. Than, the percolative self-organized mechanism on the metal/insulator interface like Na/WO3 and NaWO3/nanostructured matrix can facilitate the high Tc obtained in sodium bronzes infiltrated into inverted carbon opal or carbon nanotube matricies.

  19. Combined removal of SO2 and NO using sol-gel-derived copper oxide coated alumina sorbents/catalysts.

    PubMed

    Buelna, G; Lin, Y S

    2003-09-01

    The present paper reports experimental results on the removal of sulfur dioxide and nitrogen oxide from simulated flue gas using a copper oxide coated on alumina sorbent/catalyst prepared by the sol-gel method. Selective catalytic reduction of nitric oxide by ammonia over sol-gel derived CuO/gamma-Al2O3 sorbents/catalysts with different degrees of sulfation was studied in a fixed-bed packed reactor. The optimum temperature for NO reduction was found at 350 degrees C for both fresh and sulfated catalysts. The properties for simultaneous removal of SO2 and NO by the sol-gel-derived CuO/gamma-Al2O3 sorbents were studied using simulated dry flue gas. The optimum operating temperature for the combined deSO2/deNO operations was identified at 350 degrees C. At the space velocity of 5200 h(-1) and 350 degrees C, a fixed-bed reactor packed with the 7.9 wt% CuO/gamma-Al2O3 sorbent prepared by the sol-gel method offers SO2 sorption capacity of 2.3 mmol g(-1) and NO conversion of 92% with a dry simulated flue gas as the feed. Under these experimental conditions, the sol-gel derived sorbents/catalysts have comparable efficiency for removal of SO2 and NOx as their commercial counterparts. The significantly higher crush strength of the sol-gel derived sorbents/catalysts make them very promising for their use in the copper oxide process for combined removal of SO2 and NOx from flue gas in a single unit operation. PMID:14599142

  20. Distal heme pocket conformers of carbonmonoxy derivatives of Ascaris hemoglobin: evidence of conformational trapping in porous sol-gel matrices.

    PubMed

    Das, Tapan K; Samuni, Uri; Lin, Yu; Goldberg, Daniel E; Rousseau, Denis L; Friedman, Joel M

    2004-03-12

    We report the ligand dependence of the conformer distribution in the distal heme pocket of Ascaris suum hemoglobin (Hb) studied by resonance Raman spectroscopy. The heme-bound CO is used as a spectroscopic antenna to probe the original distribution of conformers in the dioxygen derivative of Ascaris Hb, by utilizing sol-gel encapsulation. The first step is to encapsulate the dioxygen derivative in the porous sol-gel and let the gel age, thus trapping the equilibrium conformational distribution of Ascaris dioxygen Hb. In the second step, the dioxygen ligand is replaced by CO. The sol-gel environment impedes any large scale movements, drastically slowing down the conformational relaxation triggered by the ligation change, essentially "locking in" the initial quaternary and even tertiary structure of the protein. Studying the Fe-CO frequencies of the latter sample allows evaluation of the distribution of the distal heme pocket conformers that was originally associated with the dioxygen derivative. Extending the study to the Ascaris mutants allows for examination of the effect of specific residues in the distal pocket on the conformational distribution. The choice of mutants was largely based on the anticipated variation in hydrogen bonding patterns. The results show that the sol-gel encapsulation can slow or prevent re-equilibration within the distal heme pocket of Ascaris Hb and that the distribution of distal heme pocket conformers for the CO derivative of Ascaris Hb in the sol-gel is highly dependent on the history of the sample. Additionally, we report a detailed study of the CO complex of the mutants in solution for assignment of the various heme pocket conformers, and we present a comparison of the sol-gel data with solution data. The results support a picture in which the dioxygen derivative biases the population strongly toward a tightly packed configuration that favors the network of strong hydrogen bonding interactions, and suggest that Ascaris Hb is uniquely designed for dioxygen capture. PMID:14688246

  1. 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

  2. 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.

  3. Crystal structure and luminescent properties of nanocrystalline YAG and YAG:Nd synthesized by sol-gel method

    NASA Astrophysics Data System (ADS)

    Zhydachevskii, Ya.; Syvorotka, I. I.; Vasylechko, L.; Sugak, D.; Borshchyshyn, I. D.; Luchechko, A. P.; Vakhula, Ya. I.; Ubizskii, S. B.; Vakiv, M. M.; Suchocki, A.

    2012-10-01

    The work describes results of synthesis of undoped and Nd-doped YAG nanopowders by sol-gel method using different complexing agents (ethylene glycol and citric acid) and characterization of the material by X-ray powder diffraction, scanning electron microscopy, photoluminescence and thermoluminescence techniques. Utilization of citrate sol-gel procedure using yttrium and aluminum nitrate nonahydrates as starting substances allowed to obtain highly stoichiometric and non-defected YAG and YAG:Nd nanocrystalline samples with good luminescence performance and low radiation storage efficiency.

  4. Efficiently Reflected Ultrasound on Production of Sol-Gel TiO2 Powder: Properties and Photodegradation to Rhodamine 640

    NASA Astrophysics Data System (ADS)

    Latt, Kyaing Kyaing; Kobayashi, Takaomi

    2007-05-01

    In 45 kHz ultrasound (US), sol-gel derived anatase-TiO2 powder was prepared using a stainless steel reflection plate. We found that reflected US reduced the particle size of TiO2 thereby increasing the reactive surface area for photodegradation to Rhodamine 640 (Rh-640). We found that the reflected US focused high sound intensity onto a part of the sol-gel reaction. When the surface area of TiO2 powder, which was prepared using reflected US, was increased, photodegradation to Rh-640 was enhanced.

  5. Development and characterization of a family of shape memory, biocompatible, degradable, porous (co)-polyurethanes via sol-gel chemistry

    NASA Astrophysics Data System (ADS)

    Lippincott, Hugh Walker

    In support of the goal of a tissue engineering scaffold that is moldable, biodegradable and has shape-memory, this work explored the space of polyurethane sol-gel formulations and solvents to create a biocompatible, porous xerogel with potential to be such a porous scaffold. The work has resulted in both a process and a sol-gel formulation to effectively create a family of degradable, biocompatible, shape memory, porous, block copolyurethane xerogels from polycaprolactone and castor oil. Formulations of the sol-gel family of potential scaffolds were characterized for their biocompatibility, hydrolytic degradability, porosity, and shape memory. Of the scaffolds tested in this fashion, the most successful supported the attachment and growth of 3T3 fibroblast cells at 72% of the rate of attachment and growth in the standard tissue culture plastic Petri dishes. A method was developed and explained that selects the solvent for creation of a porous xerogel by controlling the phase separation of the polymerizing polyurethane from the reaction solution. This method uses standard polymer solvent swelling and extraction test data. Solvent solutions plotted in the 3-D space of Hansen solubility parameters were used to select solvents that produced porous xerogels from two different polyurethane sol-gel formulations. The process effectively combines a set of methods that search the sol-gel formulation spaces for both shape-memory and porosity. Easily produced dense xerogels from trial sol-gel formulations are sufficient for DSC and initial DMA shape-memory test data, as well as standard solvent swelling and extraction test data to support the search for shape memory and the computation of rankings to select solvent(s) that is most likely to produce a porous xerogel. Accelerated degradation tests on the dense xerogels also produced results useful to guide further testing of the sol-gel formulations. Standard shape-memory research testing only characterizes the free return to shape or the shape memory force with no return from a tensile test. Characterization of the scaffold's compressive shape memory (percent strain recovery under stress) offers a clinical user design data for interactions with body tissue. Standard tensile shape memory ratios were translated to the compressive stress, strain, and temperature cycles used to characterize the shape-memory abilities of the two sol-gel families tested. The advantage of a thermoset polymer's ability to achieve 100% shape memory repeatability is demonstrated. This scaffold's compressive shape memory actuation energy density was above 6.0 KJ/m 3 over a range of recovery strains from 5% to 12%.

  6. 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.

  7. 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

  8. Reaction mechanism and optimal conditions for preparation of high-quality vanadium oxide films by organic sol-gel for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Sun, Minghui; Wen, Yuejiang; Xu, Xiangdong; Wang, Meng; He, Qiong; Jiang, Yadong; Dai, Zelin; Gu, Yu; Chen, Zhegeng

    2016-03-01

    Although vanadium oxides (VO x ) are important functional materials for academic research and industrial applications, the reaction mechanism of VO x prepared by organic sol-gel remains unclear. In order to investigate this mechanism, VO x organic sols were reacted at different temperatures, by which various VO x thin films were prepared. The products were systematically characterized by infrared spectroscopy, Raman spectroscopy, UV-vis spectroscopy, thermogravimetric analysis, scanning electron microscopy, x-ray diffraction, and a high resistance meter. Results reveal that vanadium alkoxides are created through an alcoholysis reaction of V2O5 powder and isobutyl alcohol, and then a condensation reaction of the vanadium alkoxides leads to the formation of VO x networks. The as-prepared sols are strongly temperature-dependent, causing different chemical structures and physical properties for the resulting VO x films. Particularly, a moderate temperature of 110 °C prompts both alcoholysis and condensation reactions, and thus the VO x films that are produced by the sol reacted at 110 °C possess a low resistivity of 23 Ω cm, a high temperature coefficient resistance (TCR) of  -3.2% K-1, and a low average transmittance of 54% in 580-1100 nm, compared with those prepared by the sols reacted at lower or higher temperatures. Therefore, 110 °C is a desirable sol temperature for producing VO x films serving as high-quality bolometric materials for uncooled infrared detectors. This work discloses not only the reaction mechanism of VO x films prepared by organic sol-gel, but also the route to yield desirable VO x films for optoelectronic applications.

  9. 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.

  10. 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.

  11. Fast and efficient proteolysis by reusable pepsin-encapsulated magnetic sol-gel material for mass spectrometry-based proteomics applications.

    PubMed

    Kayili, H Mehmet; Salih, Bekir

    2016-08-01

    Hydrophobic silicon-based material having magnetic properties was fairly synthesized by a classical sol-gel approach. Pepsin enzyme was encapsulated in the sol-gel material and the enzyme activity was evaluated in consequence of the digestion of some common proteins such as α- and β-casein, cytochrome c, myoglobin, and bovine serum albumin (BSA) both in a single protein batch and in the protein mixture. The optimum digestion time of the studied proteins using pepsin-encapsulated magnetic sol-gel material was found to be 20min. To produce the magnetic sol-gel material for convenient and easy proteomics applications, Fe3O4 was doped inside sol-gel material during the gelation step. It was observed that the activity of encapsulated pepsin was not affected by the amount of Fe3O4. Poly(ethylene glycol) was also inserted in sol-gel bulk to obtain suitable roughness and increase the hydrophilicity of the material surface to let protein molecules reach to the sol-gel material easily. The digestion of the protein mixture and non-fat bovine milk was performed with the pepsin-encapsulated magnetic sol-gel material and the digested solutions were analyzed using SDS-PAGE, MALDI-TOF-MS and LC-MS/MS for the protein identification. Reusability of the pepsin-encapsulated sol-gel material was examined and it was determined that they could be used at least 20 times. Finally, IgG digestions with a fast incubation time period were carried out using pepsin-encapsulated sol-gel material for generation of (Fab)2 product to evaluate the kinetic performance of the material. PMID:27216659

  12. Dense and optical transparent CdWO4 films by sol-gel processing for scintillation applications

    SciTech Connect

    Shang, Huamei; Bliss, Mary; Heald, S.; Sham, T. K.; Heigl, F.; Cao, Guozhong

    2007-06-01

    This paper reports the first success of fabricating dense and optical transparent cadmium tungstate (CWO) films by sol-gel processing and the study on their optical and X-ray scintillation properties. A new sol-gel processing was developed using tungstic acid and cadmium nitrate as precursors, hydrogen peroxide as solvent; homogeneous and stable CWO sol was synthesized and ready for fabricating CWO films. A rapid sintering process was investigated and found necessary in order to make dense and optically transparent nanocrystalline CWO films. CWO films were uniform, fully dense, and crack-free, with CWO as the only detectable crystalline phase as determined by XRD. The thickness, density, grain size and crystallinity of CWO films are all found to be strongly dependent on the sintering conditions and in turn impact on optical and X-ray scintillation properties. Sol-gel derived dense CWO films demonstrated high photoluminescence (PL) and X-ray excitation optical luminescence (XEOL) intensity. The relationships between sol-gel processing, nanostructures, and optical and X-ray scintillation properties were discussed in detail.

  13. Direct Evidence for Percolation of Immobilized Polymer Layer around Nanoparticles Accounting for Sol-Gel Transition in Fumed Silica Dispersions.

    PubMed

    Zheng, Zhong; Song, Yihu; Yang, Ruiquan; Zheng, Qiang

    2015-12-22

    Immobilized polymer fractions have been claimed to be of vital importance for sol-gel transitions generally observed in nanoparticle dispersions but remain a matter of debate regarding mechanism and difficulty for prediction. Here we investigate the immobilized layer structures of trifunctionality polyether polyol (PPG) near the surfaces of hydrophilic and hydrophobic fumed silica (FS) nanoparticles to reveal the role of surface chemistry on the molecular dynamics and sol-gel transitions of the dispersions. Using modulated differential scanning calorimetry, we measure the specific heat capacity during glass transition and the enthalpy during cold-crystallization. Comparing with hydrophobic FS that forms a fully immobilized (glassy) layer, we find that hydrophilic FS immobilizes more PPG, forming a partially immobilized outer layer being unable to crystallize next to the inner glassy layer. By correlating the thickness of the glassy layer with half of the minimum spacing between nanoparticles, we directly evidence the percolation of this layer along the nearest neighbor nanoparticles responsible for the sol-gel transition. Using effective volume fraction including the glassy layer, we successfully construct master curves of relative viscosity of both hydrophilic and hydrophobic FS dispersions, pointing to a common sol-gel transition mechanism mediated by the surface chemistry. PMID:26618390

  14. Photoluminescence studies of ZnO thin films prepared using a laser-assisted sol-gel method

    NASA Astrophysics Data System (ADS)

    Kim, Min Su; Lee, Jewon; Kim, Yangsoo; Leem, Jae-Young; Lee, Sang-heon; So, Wonshoup; Jung, Jae Hak; Kim, Jong Su

    2012-12-01

    ZnO thin films were grown on Si(100) substrates by using a laser-assisted sol-gel method involving irradiation from a 325-nm He-Cd laser. In contrast to conventionally-synthesized sol-gel ZnO thin films, the surfaces of those grown using the laser-assisted sol-gel method were much smoother. The optical properties of the ZnO thin films were investigated using temperature-dependent photoluminescence (PL). In the room-temperature PL spectra, the intensity of the blue-green emission was dramatically decreased by laser irradiation during the stages of deposition and post-heat treatment. Moreover, the full width at half maximum of the near-band-edge emission peaks was decreased by the laser irradiation. The activation energy of the laser-assisted sol-gel ZnO thin films was determined to be ˜99 meV, and the values of the fitting parameters α and β for Varshni's empirical equation were 4 × 10-3 eV/K and 4.9 × 103 K, respectively. Another fitting based on the thermal broadening effect of the excitonic emission peak revealed a decreased exciton-phonon interaction in the laser-assisted ZnO thin films.

  15. Sol-gel reaction of porphyrin-based superstructures in the organogel phase: creation of mechanically reinforced porphyrin hybrids.

    PubMed

    Kishida, Takanori; Fujita, Norifumi; Sada, Kazuki; Shinkai, Seiji

    2005-05-25

    We have demonstrated that a one-dimensional molecular assembly created by an H-aggregated porphyrin.Cu(II) stack can be immobilized, without a morphological change, by sol-gel polycondensation of the peripheral triethoxysilyl groups. The resultant gel prepared according to this flowchart has gained a very high thermal stability as well as a unique mechanical strength. PMID:15898763

  16. Hybrid optics for the visible produced by bulk casting of sol-gel glass using diamond-turned molds

    SciTech Connect

    Bernacki, B.E.; Miller, A.C.; Maxey, L.C.; Cunningham, J.P.; Moreshead, W.V.; Nogues, J.L.R.

    1995-07-01

    Recent combinations of diffractive and refractive functions in the same optical component allow designers additional opportunities to make systems more compact and enhance performance. This paper describes a research program for fabricating hybrid refractive/diffractive components from diamond-turned molds using the bulk casting of sol-gel silica glass. The authors use the complementary dispersive nature of refractive and diffractive optics to render two-color correction in a single hybrid optical element. Since diamond turning has matured as a deterministic manufacturing technology, techniques previously suitable only in the infrared are now being applied to components used at visible wavelengths. Thus, the marriage of diamond turning and sol-gel processes offers a cost-effective method for producing highly customized and specialized optical components in high quality silica glass. With the sol-gel casting method of replication, diamond-turned mold costs can be shared over many pieces. Diamond turning takes advantage of all of the available degrees of freedom in a single hybrid optical element: aspheric surface to eliminate spherical aberration, kinoform surface for control of primary chromatic aberration, and the flexibility to place the kinoform on non-planar surfaces for maximum design flexibility. The authors discuss the critical issues involved in designing the hybrid element, single point diamond-turning the mold, and fabrication in glass using the sol-gel process.

  17. Organic-inorganic hybrid superhydrophobic surfaces using methyltriethoxysilane and tetraethoxysilane sol-gel derived materials in emulsion

    NASA Astrophysics Data System (ADS)

    Wen, Xiu-Fang; Wang, Kun; Pi, Pi-Hui; Yang, Jin-Xin; Cai, Zhi-Qi; Zhang, Li-juan; Qian, Yu; Yang, Zhuo-Ru; Zheng, Da-feng; Cheng, Jiang

    2011-11-01

    By applying alkaline-catalyzed co-hydrolysis and copolycondensation reactions of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) in organic siloxane modified polyacrylate emulsion (OSPA emulsion), we are able to demonstrate the potential for developing a sol-gel derived organic-inorganic hybrid emulsion for a superhydrophobic surface research. TEOS and MTES derived sol-gel moieties can be designed for a physical roughness and hydrophobic characteristic (Si-CH3) of the hybrid superhydrophobic surface, while OSPA emulsion can be endowed for good film-forming property. The effect of formulation parameters on superhydrophobicity and film-forming property was analyzed. The water contact angle (WCA) on the sol-gel derived hybrid film is determined to be 156°, and the contact angle hysteresis is 5° by keeping the mole ratio of TEOS:MTES:C2H5OH:NH3·H2O:AMP-95 at 1:4:30:10:0.63 and the mass percentage of OSPA emulsion at 25%. The nanoparticle-based silica rough surface is observed as the mole ratio of MTES/TEOS at 4:1. The sol-gel derived organic-inorganic hybrid emulsion shows remarkable film-forming property when the mole ratio of MTES/TEOS reaches or exceeds 4:1. With the primer coating, the performance of superhydrophobic film achieve actual use standard. It reveals that this new procedure is an effective shortcut to obtain a superhydrophobic surface with potential applications.

  18. Sol-Gel Application for Consolidating Stone: An Example of Project-Based Learning in a Physical Chemistry Lab

    ERIC Educational Resources Information Center

    de los Santos, Desiree M.; Montes, Antonio; Sanchez-Coronilla, Antonio; Navas, Javier

    2014-01-01

    A Project Based Learning (PBL) methodology was used in the practical laboratories of the Advanced Physical Chemistry department. The project type proposed simulates "real research" focusing on sol-gel synthesis and the application of the obtained sol as a stone consolidant. Students were divided into small groups (2 to 3 students) to

  19. Sol-Gel Application for Consolidating Stone: An Example of Project-Based Learning in a Physical Chemistry Lab

    ERIC Educational Resources Information Center

    de los Santos, Desiree´ M.; Montes, Antonio; Sa´nchez-Coronilla, Antonio; Navas, Javier

    2014-01-01

    A Project Based Learning (PBL) methodology was used in the practical laboratories of the Advanced Physical Chemistry department. The project type proposed simulates "real research" focusing on sol-gel synthesis and the application of the obtained sol as a stone consolidant. Students were divided into small groups (2 to 3 students) to…

  20. Surface texture and specific adsorption sites of sol-gel synthesized anatase TiO{sub 2} nanoparticles

    SciTech Connect

    Zaki, Mohamed I.; Mekhemer, Gamal A.H.; Fouad, Nasr E.; Jagadale, Tushar C.; Ogale, Satishchandra B.

    2010-10-15

    The surface properties of sol-gel synthesized anatase titania (TiO{sub 2}) nanoparticles are probed by sorptiometry, infrared absorption spectroscopy, UV-vis diffuse reflectance spectroscopy and high resolution transmission electron microscopy. The results reveal strong correlations of the surface area, porosity, pyridine adsorption capacity and strength, and catalytic methylbutynol decomposition activity.