Science.gov

Sample records for non-aqueous sol-gel route

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

    PubMed

    Karmaoui, Mohamed; Silva, Nuno J O; Amaral, Vitor S; Ibarra, Alfonso; Millán, Ángel; Palacio, Fernando

    2013-05-21

    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. PMID:23552361

  2. 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; Millán, Ángel; 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

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

    PubMed

    Kemnitz, Erhard; Noack, Johannes

    2015-11-10

    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

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

    SciTech Connect

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

    1997-03-01

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

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

    PubMed

    Martinelli, Anna

    2014-01-01

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

  7. Effects of a Protic Ionic Liquid on the Reaction Pathway during Non-Aqueous Sol–Gel Synthesis of Silica: A Raman Spectroscopic Investigation

    PubMed Central

    Martinelli, Anna

    2014-01-01

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

  8. Electrical properties of samarium cobaltite nanoparticles synthesized using Sol–Gel autocombustion route

    SciTech Connect

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

    2014-05-01

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

  9. A new synthesis route to high surface area sol gel bioactive glass through alcohol washing

    PubMed Central

    M. Mukundan, Lakshmi; 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

  10. Preparation and nonlinear optical properties of indium nanocrystals in sodium borosilicate glass by the sol–gel route

    SciTech Connect

    Zhong, Jiasong; Xiang, Weidong; College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 ; Zhao, Haijun; Chen, Zhaoping; Liang, Xiaojuan; Zhao, Wenguang; Chen, Guoxin

    2012-11-15

    Graphical abstract: The sodium borosilicate glass doped with indium nanocrystals have been successfully prepared by sol–gel methods. And the indium nanocrystals in tetragonal crystal system have formed uniformly in the glass, and the average diameter of indium nanocrystals is about 30 nm. The third-order optical nonlinear refractive index ?, absorption coefficient ?, and susceptibility ?{sup (3)} of the glass are determined to be ?4.77 × 10{sup ?16} m{sup 2}/W, 2.67 × 10{sup ?9} m/W, and 2.81 × 10{sup ?10} esu, respectively. Highlights: ? Indium nanocrystals embedded in glass matrix have been prepared by sol–gel route. ? The crystal structure and composition are investigated by XRD and XPS. ? Size and distribution of indium nanocrystals is determined by TEM. ? The third-order optical nonlinearity is investigated by using Z-scan technique. -- Abstract: The sodium borosilicate glass doped with indium nanocrystals have been successfully prepared by sol–gel route. The thermal stability behavior of the stiff gel is investigated by thermogravimetric (TG) and differential thermal (DTA) analysis. The crystal structure of the glass is characterized by X-ray powder diffraction (XRD). Particle composition is determined by X-ray photoelectron spectroscopy (XPS). Size and distribution of the nanocrystals are characterized by transmission electron microscopy (TEM) as well as high-resolution transmission electron microscopy (HRTEM). Results show that the indium nanocrystals in tetragonal crystal structure have formed in glass, and the average diameter is about 30 nm. Further, the glass is measured by Z-scan technique to investigate the nonlinear optical (NLO) properties. The third-order NLO coefficient ?{sup (3)} of the glass is determined to be 2.81 × 10{sup ?10} esu. The glass with large third-order NLO coefficient is promising materials for applications in optical devices.

  11. 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 ?-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.

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

    NASA Astrophysics Data System (ADS)

    Arasu, P. Adal; Williams, R. Victor

    2015-05-01

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

  13. Al-doped ZnO nanocoatings obtained by sol-gel route

    NASA Astrophysics Data System (ADS)

    Mihaiu, S.; Toader, A.; Atkinson, I.; Anastasescu, M.; Vasilescu, M.; Zaharescu, M.; Plugaru, R.

    2010-11-01

    In recent years aluminum doped zinc oxide (AZO) film has attracted more attention due to many advantages including low cost, non-toxicity, and high stability to H2 plasma in comparison with indium tin oxide (ITO) film, the best known and used transparent conductive oxide (TCO) film. In this work, mono and multilayer Al-doped ZnO coatings have been obtained by dip coating sol-gel method on the glass and silicon supports. X-ray Diffraction, Atomic Force Microscopy (AFM) and Fluorescence Spectroscopy were used for the structural, morphological and optical characterization of the obtained coatings. The multilayer Al-doped ZnO coatings (after five layer depositions) on the silicon substrate present a polycrystalline wurtzite type structure with crystallite size of 20 nm. The AFM measurements have shown that no matter the support type, the Al-doped ZnO coatings present a similar morphology consisting in a smooth distribution of the circular grains leading also to similar values of the RMS roughness, around 2 nm. The photoluminescence properties of the Al-doped ZnO coatings depend on the number of depositions and type of substrate. Systematic study performed allows finding most suitable parameters for obtaining coatings with desired properties.

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

    PubMed

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

    2014-11-01

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

  15. 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.

  16. 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.

  17. 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 ?m) 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 ?m, 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 ?/?, respectively (??2×10(-3) ?-cm) for single layers. Similarly, ATO lines and films have Rs as low as 700 and 400 ?/? with ??7×10(-3) ?-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

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    García-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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  2. 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.

  3. 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

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

    PubMed

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

    2015-11-18

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

  5. 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

  6. Structural, optical and morphological analyses of pristine titanium di-oxide nanoparticles - Synthesized via sol-gel route

    NASA Astrophysics Data System (ADS)

    Praveen, P.; Viruthagiri, G.; Mugundan, S.; Shanmugam, N.

    2014-01-01

    Pure titanium di-oxide nanoparticles (TiO2) were synthesized by sol-gel technique at room temperature with appropriate reactants. The synthesis of anatase phase TiO2 nanoparticles was achieved by tetraisopropyl orthotitanate and 2-propanol as common starting materials and the product was annealed at 450 °C for 4 h. The synthesized product was characterized by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), UV-VIS-Diffuse reflectance spectroscopy (DRS), Photoluminescence (PL) spectroscopy and Scanning electron microscopy (SEM) with Energy dispersive X-ray (EDX) analysis. XRD pattern confirmed the crystalline nature and tetragonal structure of synthesized composition. Average grain size was determined from X-ray line broadening, using the Debye-Scherrer relation. The functional groups present in the sample were identified by FTIR spectroscopy. Diffuse reflectance measurement indicated an absorption band edge on UV-region. The allowed direct and indirect band gap energies, as well as the crystallite size of pure TiO2 nanoparticles are calculated from DRS analysis. The microstructure and elemental identification were done by SEM with EDX analysis.

  7. 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 ?m. At 10 kHz and room temperature, the best CCTO ceramic exhibited a high dielectric constant, ?? ?43325.24, with low dielectric loss, tan ? ?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.

  8. Nanocrystal/sol-gel nanocomposites

    DOEpatents

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

    2012-06-12

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

  9. Nanocrystal/sol-gel nanocomposites

    DOEpatents

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

    2007-06-05

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  11. 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

  12. Low-Temperature Anode-Supported SOFC with Ultra-Thin Ceria-Based Electrolytes Prepared by Modified Sol—Gel Route

    NASA Astrophysics Data System (ADS)

    Lin, Hongfei; Ding, Changsheng; Sato, Kazuhisa; Tsutai, Yoshifumi; Hashida, Toshiyuki

    The utilization of anode-supported electrolytes is a very promising strategy to improve the electrical performance in solid oxide fuel cells (SOFCs) application, because it is possible to decrease considerably the electrolytes thickness. In this paper, ultra-thin ceria-based electrolyte films were successfully prepared on porous NiO/GDC anode support. The electrolyte films with thickness of 0.5-1 µm were deposited by a novel citrate sol-gel route combined with a suspension spray coating technique. The characterization and microstructure of the ultra-thin films were investigated by DTA/TGA, XRD and FE-SEM. The results showed that ceria-based films prepared were pure fluorite type nanocrystalline, homogenous and almost fully dense. Electrochemical performance of single cells based on the ultra-thin electrolyte films was also tested. The single cell with electrolyte thickness of 1 µm provided an OCV of 0.832 V at 500 °C which was close to that of the reported single cell with thicker ceria-based electrolyte film of 10 µm, and maximum power densities of 59.6, 121.9 and 133.8 mW/cm2 at 500, 600, and 700 °C, respectively. These ultra-thin electrolyte films showed good combination with the porous NiO/GDC anode supports, and good insulating ability for inactive electron migration at temperatures less than 600 °C.

  13. Transparent, conducting ATO thin films by epoxide-initiated sol-gel chemistry: a highly versatile route to mixed-metal oxide films.

    PubMed

    Koebel, Matthias M; Nadargi, Digambar Y; Jimenez-Cadena, Giselle; Romanyuk, Yaroslav E

    2012-05-01

    A robust synthesis approach to transparent conducting oxide (TCO) materials using epoxide assisted sol-gel chemistry is reported. The new route utilizes simple tin and antimony chloride precursors in aqueous solution, thus eliminating the need for organometallic precursors. Propylene oxide acts as a proton scavenger and drives metal hydroxide formation and subsequent polycondensation reactions. Thin films of antimony-doped tin oxide (ATO) were prepared by dip-coating of mixed metal oxide sols. After annealing at 600 °C in air, structural, electrical and optical properties of undoped and Sb-doped tin oxide films were characterized. Single layer films with 5 mol % Sb doping exhibited an optical transparency which was virtually identical to that of the plain glass substrate and an electrical resistivity of 2.8 × 10(-2) ? cm. SEM and AFM analysis confirmed the presence of surface defects and cracks which increased with increasing Sb dopant concentration. Multiple depositions of identical ATO films showed a roughly 1 order of magnitude decrease in the film resistivity after the third layer, with typical values below 5 × 10(-3) ? cm. This suggests that a second and third deposition fill up residual cracks and defects in the first layer and thus brings out the full performance of the ATO material. The epoxide-assisted sol chemistry is a promising technique for the preparation of mixed oxide thin film materials. Its superiority over conventional alkoxide and metal salt-based methods is explained in the context of a general description of the reaction mechanism. PMID:22512285

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Composite sol-gel ceramics

    NASA Astrophysics Data System (ADS)

    Yang, Quanzu

    1999-11-01

    The fundamental goal of the present study was to develop an understanding of the mechanisms of dispersion, gelation, drying, interfacial bonding and densification of composite sol-gel (CSG) ceramics. The general applied objective was to fabricate high performance CSG ceramics and to produce novel, non-permeable, adherent CSG coatings on stainless steel substrates for high temperature corrosion and wear protection. The properties of the alumina sols and CSG were studied by measuring viscosity, conductivity, ionic strength, and pH of the sol. The dispersion and stability of ceramic particles in alumina sols were investigated by measuring particle size distributions, measuring zeta potentials, and calculating the interaction energy according to DLVO theory. The CSG technology has been developed to fabricate high performance engineering composite ceramics and coatings through dispersing ceramic fillers (alumina, zirconia, SiC) into alumina sols, gelcasting, drying, and pressureless sintering. A sintering model for CSG was developed and validated by experiment results. The model was then used successfully to predict sinterability and to optimize the processing technologies of CSG. The research results indicate that hydrated alumina sols can be used as a sintering and dispersion additive for alumina-based ceramics. The sol-gel matrix provides fast diffusion paths for mass transport during sintering CSG. Dispersion of alumina and SiC particles is substantially improved in alumina sols, as compared to pure water of similar acidity, e.g. the average agglomerate size is decreased by at least 50%. For alumina/alumina CSG ceramics sintered at 1400°C, the microhardness is 20 GPa and porosity is less than 1 vol%. The CSG composite with composition of 50vol%SiC-50vol%Al2O 3 has been sintered successfully to full densification and microhardness of 22.9 GPa. A novel process for ceramic coatings on the metallic substrates has been developed successfully by combining chemical bonding and CSG technologies. Non-permeable, crack-free, thick ceramic coatings (2--600 mum) on the substrates were fabricated by spraying and dipping, followed by low temperature (500--600°C) sintering. The correlations between the processing methods, microstructure, and mechanical properties of CSG coatings were investigated by varying the preparation methods, studying morphology, and measuring mechanical properties of the ceramics. The chemically bonded CSG coatings have the best performance. The bonding strength between the substrates and coatings is about 42 MPa, and the surface microhardness of the coatings is about 6.5 GPa.

  2. 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.

  3. 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].

  4. Sol-gel antireflective coating on plastics

    DOEpatents

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

    1990-01-01

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

  5. Biological response of human mesenchymal stromal cells to titanium grade 4 implants coated with PCL/ZrO? 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(?-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

  6. Non-aqueous spray drying as a route to ultrafine ceramic powders

    SciTech Connect

    Armor, J.N. ); Fanelli, A.J.; Marsh, G.M. ); Zambri, P.M. )

    1988-09-01

    Spray drying imparts unique powder handling features to a wide variety of dried products and is usually carried out in a heated air stream while feeding an aqueous suspension of some solid material. The present work, however, describes non-aqueous spray drying as a means of preparing fine powders of metal oxides. In this case an alcohol solvent was used in place of water and the slurry sprayed under an inert atmosphere. Using the non-aqueous technique, the product consists of distinct but loosely aggregated primary particles. Such materials have potential for use as catalysts or catalyst supports.

  7. Toward sol-gel-based sensors

    SciTech Connect

    Jordan, J.D.; Ingersoll, C.M.; Dunbar, R.A.

    1995-12-31

    Advances in biotechnology have produced a variety of antibodies and other biomolecules that possess selective recognition capabilities. Current techniques for the immobilization of these biomolecules typically involve multistep derivatization of a primary substrate, which is labor intensive and often requires large volumes of costly reagents. Further, these immobilization chemistries often adversely affect the characteristic properties of the protein (e.g., the binding affinity). As a result, the need for fast, accurate, inexpensive, and simple to operate diagnostic assays escalates. Because of their room temperature processing, transparency, inertness, and tunable pore structure, sol-gel-derived composites represent promising chemical and biosensing platforms. To date, many researchers have entrapped proteins and enzymes in sol-gel monoliths, and found that they retain some of their native properties. Our group first reported on the affinity of a sol-gel entrapped antibody. However, although these biogel monoliths were promising, analyte diffusion through the monolith matrix is slow, resulting in long response times. Thus, it is clear that the next level of sol-gel-derived biosensor must depend on thin film technology. In the current work, the affinity of fluorescein entrapped within a sol-gel derived thin film for the anti fluorescent hapten, 5- (and 6-)-carboxy 4{prime}, 5{prime}-dimethylfluorescein, is investigated. A novel film preparation technique will be introduced, and the response and response times of these films as a function of processing and storage conditions will be discussed.

  8. Chemical modification of TiO2 by H2PO{4/-}/HPO{4/2-} anions using the sol-gel route with controlled precipitation and hydrolysis: enhancing thermal stability

    NASA Astrophysics Data System (ADS)

    Elghniji, Kais; Saad, Mohamed El Khames; Araissi, Manel; Elaloui, Elimame; Moussaoui, Younes

    2014-12-01

    Two titanium phosphate materials (T p P and T h P) have been successfully synthesized by sol-gel route with controlled precipitation and hydrolysis. The T p P material was obtained from the reaction between precipitated titania and phosphate buffer solution H2PO{4/-} /HPO{4/2-} (pH = 7.3). The T p P material was prepared through hydrolysis of titanium in the presence of H2PO{4/-}/HPO{4/2}. The probable state of the phosphate anions in titania framework and their effect on the anatase-to-rutile transformation were characterized by ICP-AES, DTA-TG, 31P NMR, FT-IR, and Raman analysis HRTEM/SEM. FT-IR and 31P NMR analyses of titanium phosphate T p P calcined at low temperature showed that the phosphate species existed not only as Ti-O-P in the bulk TiO2 but also as amorphous titanium phosphates, including bidentate Ti(HPO4)2 and monodentate Ti(H2PO4)4. Increased calcination temperature only gave an enrichment of bidentate structure on the titania surface. For the T p P material, H2PO{4/-}/HPO{4/2-} anions were introduced into the initial solution, before precipitation, what promoted their lattice localization. At high temperatures, all the phosphorus inside the bulk of TiO2 migrated to the surface. The Raman analysis of both samples showed that the bidentate phosphates increased the temperature of the anatase-to-rutile phase transformation to more than 1000 °C with the formation of well crystalline TiP2O7 phase. This phenomenon was more evident for T p P sample.

  9. 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.

  10. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, John M. (Albuquerque, NM)

    1993-01-01

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

  11. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, John M. (Albuquerque, NM)

    1992-01-01

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

  12. Neutron detector using sol-gel absorber

    DOEpatents

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

    1999-01-01

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

  13. 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

  14. 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.

  15. Novel carboxy functionalized sol-gel precursors

    SciTech Connect

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

    1996-12-31

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

  16. 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.

  17. Sol-Gel Manufactured Energetic Materials

    DOEpatents

    Simpson, Randall L. (Livermore, CA); Lee, Ronald S. (Livermore, CA); Tillotson, Thomas M. (Tracy, CA); Hrubesh, Lawrence W. (Pleasanton, CA); Swansiger, Rosalind W. (Livermore, CA); Fox, Glenn A. (Livermore, CA)

    2005-05-17

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

  18. 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.

  19. Ionogel Electrolytes through Sol-Gel Processing

    NASA Astrophysics Data System (ADS)

    Horowitz, Ariel I.

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

  20. 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.

  1. 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.

  2. Sol-gel method for encapsulating molecules

    DOEpatents

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

    2002-01-01

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

  3. 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…

  4. Photopolymerized Sol-Gel Monoliths for Capillary Electrochromatography

    E-print Network

    Zare, Richard N.

    Photopolymerized Sol-Gel Monoliths for Capillary Electrochromatography Maria T. Dulay, Joselito P.d. capillary to prepare a porous monolithic sol-gel column by a one-step, in situ, process. The photopoly fabrication problems, surface-functionalized open-tubular capillary columns6,8-10 and monolithic capillaries6

  5. 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.

  6. 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.

  7. 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.

  8. Preparation of Nb-substituted titanates by a novel sol-gel assisted solid state reaction.

    PubMed

    Song, Haiyan; Sjåstad, Anja O; Vistad, Ørnulv B; Gao, Tao; Norby, Poul

    2009-07-20

    Single-phase layered Nb-substituted titanates, Na(2)Ti(3-x)Nb(x)O(7) (x = 0-0.06) and Cs(0.7)Ti(1.8-x)Nb(x)O(4) (x = 0-0.03), were for the first time synthesized by a novel sol-gel assisted solid state reaction (SASSR) route. Conventional solid state reactions as well as sol-gel synthesis did not succeed in producing phase pure Nb-substituted titanates. In the SASSR synthesis route we combine the advantages of traditional sol-gel technique (i.e., homogeneous products formed at low temperatures) and solid state reaction (i.e., formation of stable, crystalline phases) for preparing single-phase niobium-substituted layered titanates. The obtained products were characterized by X-ray powder diffraction, scanning electron microscopy, inductively coupled plasma-atomic emission spectrometry, Raman spectroscopy, and thermogravimetric analysis. Results indicate that the Ti(IV) in the host layer of the samples could be partially replaced by Nb(V) without structural deterioration. After proton-exchange, more water molecules were intercalated into the interlayer of H(0.7)Ti(1.8-x)Nb(x)O(4) x nH(2)O with increasing niobium content, whereas the interlayer distance of H(2)Ti(3-x)Nb(x)O(7) (x = 0-0.06) was unchanged. PMID:20507116

  9. 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.

  10. Structural and dielectric/ferroelectric properties of (La{sub 1-x}Nd{sub x}){sub 2}Ti{sub 2}O{sub 7} synthesized by sol-gel route

    SciTech Connect

    Shao Zhenmian; Saitzek, Sebastien; Roussel, Pascal; Mentre, Olivier; Prihor Gheorghiu, Felicia; Mitoseriu, Liliana; Desfeux, Rachel

    2010-07-15

    A series of compounds with the general formula (La{sub 1-x}Nd{sub x}){sub 2}Ti{sub 2}O{sub 7} (0.0{<=}x{<=}1.0) has been prepared by the sol-gel method. The decomposition of the gel was characterized by thermo-gravimetric analysis coupled to mass spectrometry, indicating the reaction is achieved above 850 {sup o}C. The lattice parameters versus x show an expected decrease in the a and b parameters while c and the {beta} angle remain almost unchanged with respect to the monoclinic symmetry conserved for the full solid solution. Dielectric, piezoelectric and ferroelectric properties were measured on the entire series. - Graphical abstract: XRD patterns of (La{sub 1-x}Nd{sub x}){sub 2}Ti{sub 2}O{sub 7} powders for various x values. The (hkl) peaks positions (with h and k{ne}0) change with x values while the (00l) peaks positions remain unaffected.

  11. 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.

  12. 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

  13. 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.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    Vinogradov, Vladimir V.; Avnir, David

    2015-09-01

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

  16. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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 ? 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 ? 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 ?? ?* and n? ?* 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.

  18. 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 ? 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 ? 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 ?? ?* and n? ?* 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  1. 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.

  2. 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.

  3. 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

  4. 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.

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

    DOEpatents

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

    2000-01-01

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

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

    DOEpatents

    Congdon, James W. (Aiken, SC)

    2009-03-17

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

  7. 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...

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

    DOEpatents

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

    2002-11-26

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

  9. Inorganic Sensing Using Organofunctional Sol-Gel Materials

    PubMed Central

    Carrington, Nathan A.; Xue, Zi-Ling

    2007-01-01

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

  10. 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 in?uence of various factors such as the length of the alkyl chain of protic ionic liquids (monoethanolamine-based) and a concentration range between 0.5 and 3.0% (w/v) were evaluated. The resulting hydrophobic matrices and immobilized lipases were characterised with regard to specific surface area, adsorption-desorption isotherms, pore volume (V(p)) and size (d(p)) according to nitrogen adsorption and scanning electron microscopy (SEM), physico-chemical properties (thermogravimetric - TG, differential scanning calorimetry - DSC and Fourier transform infrared spectroscopy - FTIR) and the potential for ethyl ester and emulsifier production. The total activity yields (Y(a)) for matrices of immobilized lipase employing protic ionic liquids as additives always resulted in higher values compared with the sample absent the protic ionic liquids, which represents 35-fold increase in recovery of enzymatic activity using the more hydrophobic protic ionic liquids. Compared with arrays of the immobilized biocatalyst without additive, in general, the immobilized biocatalyst in the presence of protic ionic liquids showed increased values of surface area (143-245 m(2) g(-1)) and pore size (19-38 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

  11. 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.

  12. 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.

  13. Structural and optical characterizations of sol-gel-derived europium-doped YAG materials: powders and films

    NASA Astrophysics Data System (ADS)

    Boyer, Damien; Bertrand-Chadeyron, Genevieve; Mahiou, Rachid

    2004-02-01

    Sol-gel route has been successfully achieved to obtain pure Y3Al5O12 and Y3Al5O12:Eu3+ powders and films. Advanced YAG coatings were achieved by two techniques, the spray and dip-coating methods, giving rise to different characteristics and properties. The materials structure and microstructure were analyzed by means of X-ray diffraction and scanning electron microscopy. It has been shown that sol-gel processed YAG powders crystallize around 900°C whereas a temperature much higher is necessary to obtain this compound by solid state synthesis (~ 1500°C). Additionally the surface of the films was observed by atomic force microscopy. Eventually, laser induced luminescence spectra, as well as luminescence decays of Eu3+ ions show undoubtedly the spectral features of a Eu3+ emitting centre embedded in a unique site of D2 symmetry.

  14. 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

  15. F-doped ZnO by sol-gel spin-coating as a transparent conducting thin film

    NASA Astrophysics Data System (ADS)

    Nam, Gil Mo; Kwon, Myoung Seok

    2011-06-01

    This paper reports a simple non-alkoxide sol-gel route for depositing F-doped ZnO thin film on glass substrates. Ammonium fluoride and zinc acetate were used as the dopant precursor and starting material for ZnO, respectively. After the first crystallization at 550°C in air, the sol-gel spin coated ZnO:F thin films at a F concentration < 5 at. % showed a nanosized polycrystalline structure with a c-plane preferred orientation. The structures, electrical resistivity, carrier concentration, mobility and optical transmittance were strongly dependent on the F concentration. The F concentration > 5 at. % degraded the microstructures, electrical conductivity, and optical transmittance. The second post-heat-treatment at 450°C in a reducing environment resulted in higher electrical resistivity than the first post-heat-treatment in air.

  16. 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.

  17. 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.

  18. Microstructured UV-sensitive luminescent sol gel layers

    NASA Astrophysics Data System (ADS)

    Bredol, M.; Schem, M.

    2004-12-01

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

  19. 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.

  20. Sol-gel derived photonic bandgap coatings for solar control

    NASA Astrophysics Data System (ADS)

    Almeida, Rui M.; Fortes, Luís M.; Clara Gonçalves, M.

    2011-10-01

    Sol-gel derived photonic bandgap films have been investigated as possible multilayer coatings for solar control glass applications. Multilayer Bragg mirrors, in particular, have been modelled by the Transfer Matrix method, designed to have either near-UV or near-IR reflectivity, but visible transparency, based on alternating aluminosilicate glass/titania quarter-wave stacks. Such composite multilayer structures have been deposited by sol-gel processing on selected glasses and other types of substrates and their optical characteristics have been measured by optical absorption and reflection spectroscopies, as well as spectroscopic ellipsometry to determine the single layer refractive index and thickness. The UV-visible-IR absorption and reflection characteristics of these multilayer coatings revealed solar control properties, due to the presence of peaks near ˜350-400 nm and ˜900-1000 nm, with reflectivities of the order of 70%, which appear promising for solar control application.

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Sol-gel processes and materials. (Latest citations from the Aerospace database). Published Search

    SciTech Connect

    Not Available

    1994-01-01

    The bibliography contains citations concerning design and development of sol-gel processes and sol-gel derived materials. Sol-gel derived materials include protective and transparent films, ceramic coatings, nanocomposites and microcomposites, porous and dense composites, fiber reinforced composites, oxides, and ductile ceramics. Topics include preparation of high temperature superconducting oxides and films, glass-ceramic composites and ceramic matrix composites for high temperature applications, sol-gel processes for advanced ceramics, coatings on semiconductors, infrared optical coatings, and coatings on carbon/carbon composites. (Contains 250 citations and includes a subject term index and title list.)

  13. Sol-gel processes and materials. (Latest citations from the Aerospace database). Published Search

    SciTech Connect

    Not Available

    1994-11-01

    The bibliography contains citations concerning design and development of sol-gel processes and sol-gel derived materials. Sol-gel derived materials include protective and transparent films, ceramic coatings, nanocomposites and microcomposites, porous and dense composites, fiber reinforced composites, oxides, and ductile ceramics. Topics include preparation of high temperature superconducting oxides and films, glass-ceramic composites and ceramic matrix composites for high temperature applications, sol-gel processes for advanced ceramics, coatings on semiconductors, infrared optical coatings, and coatings on carbon/carbon composites. (Contains 250 citations and includes a subject term index and title list.)

  14. 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.

  15. Magnetic properties of sol-gel derived Gd2O3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ray, R.; Biswas, Sumita; Das, S.; Patra, M.

    2012-06-01

    Nanocrystalline Gd2O3 particles of average particle size 25 nm (p25) and 18 nm (p18) are prepared through sol-gel route. Magnetization measurements in both samples show a linear variation of ?-1 with T having two different slopes in the temperature range 30 K- 260 K. In the temperature range 135 K ? T ? 260 K (TR1) the effective moment (?eff) per Gd3+ is estimated to be 7.70 ?B and 7.56 ?B whereas, in the temperature range 30 K ? T ? 135 K (TR2) they are estimated as 7.92 ?B and 7.79 ?B for p25 and p18, respectively. The enhancement of ?eff in the TR2 region may be related with the clustering of spins. Below 30 K, ?-1 deviates from the linearity. At 5K magnetization curve displays superparamagnetic like characteristic features.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. Sol-gel deposition of electrochromic copper oxide films

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; Tepehan, Fatma

    1993-10-01

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

  1. 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.

  2. 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

  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 based sensor for selective formaldehyde determination.

    PubMed

    Bunkoed, Opas; Davis, Frank; Kanatharana, Proespichaya; Thavarungkul, Panote; Higson, Séamus P J

    2010-02-01

    We report the development of transparent sol-gels with entrapped sensitive and selective reagents for the detection of formaldehyde. The sampling method is based on the adsorption of formaldehyde from the air and reaction with beta-diketones (for example acetylacetone) in a sol-gel matrix to produce a yellow product, lutidine, which was detected directly. The proposed method does not require preparation of samples prior to analysis and allows both screening by visual detection and quantitative measurement by simple spectrophotometry. The detection limit of 0.03 ppmv formaldehyde is reported which is lower than the maximum exposure concentrations recommended by both the World Health Organisation (WHO) and the Occupational Safety and Health Administration (OSHA). This sampling method was found to give good reproducibility, the relative standard deviation at 0.2 and 1 ppmv being 6.3% and 4.6%, respectively. Other carbonyl compounds i.e. acetaldehyde, benzaldehyde, acetone and butanone do not interfere with this analytical approach. Results are provided for the determination of formaldehyde in indoor air. PMID:20103132

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

    NASA Astrophysics Data System (ADS)

    Hales, Matthew; Martens, Wayde; Steinberg, Theodore

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

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Hari Babu, B.; Ollier, Nadège; León Pichel, Mónica; El Hamzaoui, Hicham; Poumellec, Bertrand; Bigot, Laurent; Savelii, Inna; Bouazaoui, Mohamed; Ibarra, Angel; Lancry, Matthieu

    2015-09-01

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

  8. Visualizing Chemical Compositions and Kinetics of Sol-Gel by Near-Infrared Multispectral Imaging

    E-print Network

    Reid, Scott A.

    Visualizing Chemical Compositions and Kinetics of Sol-Gel by Near-Infrared Multispectral Imaging, Milwaukee, Wisconsin 53201 Kinetics of sol-gel formation were studied using the recently developed near-infrared (NIR) multispectral im- aging instrument. This imaging spectrometer possesses all the advantages

  9. Hybrid Silica-PVA Nanofibers via Sol-Gel Electrospinning Tahira Pirzada,,

    E-print Network

    Khan, Saad A.

    Hybrid Silica-PVA Nanofibers via Sol-Gel Electrospinning Tahira Pirzada,,§ Sara A. Arvidson,,§ Carl: We report on the synthesis of poly(vinyl alcohol) (PVA)-silica hybrid nanofibers via sol-gel electro is under- taken and reveals a composition window in which defect-free hybrid nanofibers with diameters

  10. 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...

  11. 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); Ingram, 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Distributed feedback sol-gel zirconia channel waveguide lasers

    NASA Astrophysics Data System (ADS)

    Chen, Fei; Wang, Jun; Ye, Chao; Lo, Dennis; Zhu, Xiao-lei

    2004-11-01

    We fabricated dye-doped zirconia channel waveguides using wet or dry etching of quartz substrates followed by sol-gel deposition of the Rhodamine 6G-doped zirconia in the channel. Distributed feedback laser action was generated in the channel waveguides by crossing two nanosecond laser beams at 532nm. Maintaining the depth of the active zirconia layer at 3?m, narrow linewidth lasing was achieved for rectangular channel waveguides with widths at 5, 6.5, and 10?m. Wavelength tuning was achieved from 570to608nm. The output laser mode was identified as the fundamental E11x mode. The dispersion behavior of the laser output was checked by comparing experiments with the predictions of Marcatili's theory.

  18. 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.

  19. 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.

  20. Fabrication of high density UO 2 fuel pellets involving sol-gel microsphere pelletisation and low temperature sintering

    NASA Astrophysics Data System (ADS)

    Ganguly, C.; Basak, U.

    1991-02-01

    Powder-free sol-gel microsphere pelletisation and low temperature (1473 K) oxidative sintering processes were used in combination for fabrication of high density (? 96% TD) UO 2 fuel pellets for pressurised heavy water reactors. The "internal gelation of uranium" process of BARC was modified for preparation of hydrated gel-microspheres of UO 3 containing "carbon black" pore former. The gel-microspheres were subjected to controlled air-calcination at 973 K, followed by hydrogen reduction to obtain porous, dust-free and free-flowing UO 2 microspheres suitable for direct pelletisation at 225 MPa. Oxidative sintering of these pellets at 1473 K in CO 2 atmosphere followed by Ar+H 2 treatment led to high density (?96%TD) UO 2 pellets having equiaxed grains of < 10 ?m and uniformly distributed "closed" spherical pores in the diameter range of 2-5 ?m. Resintering of these pellets at high temperature (1973 K) for 8 hours in Ar+8% H 2 atmosphere did not show any significant change in pellet dimension or grain size. The UO 2 pellets prepared by sol-gel microsphere pelletisation route had higher thermal conductivity compared to pellets of equivalent density prepared by the "powder-pellet" route. UO 2 pellets of large grain size (45-55 ?m) and high density could be obtained with TiO 2 dopant and high temperature sintering in Ar+H 2 atmosphere. TiO 2 dopant was not effective for low temperature oxidative sintering.

  1. 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)

  2. 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.

  3. Heat treatment effect on the physical properties of cobalt doped TiO{sub 2} sol–gel materials

    SciTech Connect

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

    2013-11-15

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

  4. 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 (?-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.

  5. Production of cerium oxide microsheres by an internal gelation sol-gel process 

    E-print Network

    Wegener, Jeffrey J.

    2010-01-14

    The experiments performed for this research were completed to produce solid cerium oxide microspheres by an internal gelation sol-gel process. The motivation for this work was to develop a process that would enable the fabrication of a storage...

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

    DOEpatents

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

    2000-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  8. The physics and chemistry of semiconductor nanocrystals in sol-gel derived optical microcavities

    E-print Network

    Chan, Yinthai

    2006-01-01

    The incorporation of semiconductor nanocrystals (NCs) into sol-gel derived matrices presents both novel applications as well as a robust platform in which to investigate the nonlinear optical properties of NCs. This thesis ...

  9. 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.

  10. Investigation of the sol-gel transition of gelatin using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Kawabe, Shunsuke; Seki, Munetoshi; Tabata, Hitoshi

    2014-04-01

    The sol-gel transition temperature of gelatin is determined using viscoelasticity measurement and terahertz time-domain spectroscopy. From the results of the viscoelasticity measurement, the sol-gel transition temperature is determined to be 30-32 °C, and it strongly depended on the concentration. However, terahertz time-domain spectroscopy indicates a particular transition temperature of 36 °C. A distinction of these transition temperatures is attributed to the difference in the structural changes detected by these measurements.

  11. 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.

  12. 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

  13. Properties of trypsin and of acid phosphatase immobilized in sol-gel glass matrices.

    PubMed

    Shtelzer, S; Rappoport, S; Avnir, D; Ottolenghi, M; Braun, S

    1992-06-01

    Trypsin and acid phosphatase-containing silica sol-gel glasses were obtained by mixing a solution of an enzyme with polyethylene glycol (PEG) 6000 and tetramethoxy orthosilicate at room temperature, followed by gelation and drying. Activity of the immobilized trypsin toward small substrates, such as N-benzoyl-L-arginine-4-nitroanilide at its Km, for the best preparations equaled that of the soluble enzyme. Polylysine (M(r) less than or equal to 13,000) and aprotinin (M(r) = 6,500) inhibited this activity. Larger polylysines as well as soybean trypsin inhibitor (M(r) = 20,100) were ineffective. The sol-gel-entrapped trypsin activity was stable when sol-gel glasses were incubated at ambient temperature (pH 7.5) for several months. In comparison, trypsin, immobilized in sol-gel glass by surface adsorption and incubated under the same conditions overnight, was completely autodigested. The firm interaction between the protein molecules and the silica matrix stabilized the enzymes. Thus, the half-life of sol-gel-entrapped acid phosphatase at 70 degrees C (pH 8.0) was two orders of magnitude larger than that of the enzyme in solution. Transparent, mechanically and chemically stable bioactive sol-gel glasses may be used for the development of robust on-line biochemical photodetection sensors and for the purposes of chemical catalysis. PMID:1388818

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

    PubMed

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

    2012-01-15

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

  15. /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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    Cobalt-silicon mixed oxide materials (Co/Si=0.111, 0.250 and 0.428) were synthesised starting from Co(NO 3) 2·6H 2O and Si(OC 2H 5) 4 using a modified sol-gel method. Structural, textural and surface chemical properties were investigated by thermogravimetric/differential thermal analyses (TG/DTA), XRD, UV-vis, FT-IR spectroscopy and N 2 adsorption at -196 °C. The nature of cobalt species and their interactions with the siloxane matrix were strongly depending on both the cobalt loading and the heat treatment. All dried gels were amorphous and contained Co 2+ ions forming both tetrahedral and octahedral complexes with the siloxane matrix. After treatment at 400 °C, the sample with lowest Co content appeared amorphous and contained only Co 2+ tetrahedral complexes, while at higher cobalt loading Co 3O 4 was present as the only crystalline phase, besides Co 2+ ions strongly interacting with siloxane matrix. At 850 °C, in all samples crystalline Co 2SiO 4 was formed and was the only crystallising phase for the nanocomposite with the lowest cobalt content. All materials retained high surface areas also after treatments at 600 °C and exhibited surface Lewis acidity, due to cationic sites. The presence of cobalt affected the textural properties of the siloxane matrix decreasing microporosity and increasing mesoporosity.

  17. 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.

  18. 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.

  19. Sol-gel SiO2 film contained Au/SiO2/quantum dot core/shell/shell nanostructures with plasmonic enhanced photoluminescence.

    PubMed

    Yang, Ping; Zhang, Lipeng; Wang, Yingzi

    2012-12-01

    A sol-gel method has been developed to fabricate functional silica film with Au/SiO2/quantum dot (QD) core/shell/shell nanostructures which exhibited plasmonic enhanced photoluminescence (PL). Au nanoparticles (NPs) were homogeneously coated with a SiO2 shell by an optimal Stöber synthesis. Hydrophobic CdSe/ZnS QDs was transferred into water phase via a ligand exchange by a thin functional SiO2 layer consisted of partially hydrolyzed 3-aminopropyltrimethoxysilane (APS) sol. The Au/SiO2/QD core/shell/shell nanostructure was created by assembling the functional SiO2-coated QDs to the SiO2-coated Au NPs while QDs transferred into water phase. Those partially hydrolyzed APS molecules play an important role for the connection between the QDs and SiO2-coated Au NPs. The Au/SiO2/QD core/shell/shell nanostructures were embedded in functional sol-gel SiO2 films fabricated via spinning and dipping coating, in which the film revealed strong surface plasmon scattering and enhanced PL. Because of the dual functionality, the film is utilizable for various applications including biological and medical sensors, optical devices, and solar cells. This technique can serve as a general route for encapsulating a variety of nanomaterials in sol-gel films. PMID:23447950

  20. 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.

  1. 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.

  2. Sol gel based YAG : Tb3+ or Eu3+ phosphors for application in lighting sources

    NASA Astrophysics Data System (ADS)

    Potdevin, A.; Chadeyron, G.; Boyer, D.; Caillier, B.; Mahiou, R.

    2005-09-01

    Luminescent Y3Al5O12 : Eu3+ (YAG : Eu3+) and Y3Al5O12 : Tb3+ (YAG : Tb3+) powders with nanometre and micrometre-sized particles and films have been successfully synthesized by sol-gel route from alkoxide precursors. Advanced YAG coatings were achieved by spray and dip-coating methods, giving rise to different structural and optical properties. High temperature x-ray diffraction, x-ray powder diffraction, scanning electron microscopy and atomic force microscopy were used to investigate the materials structure and morphology. Pure polycrystalline YAG powder was obtained from 900°C. Laser induced luminescence spectra as well as luminescence decays of Tb3+ and Eu3+ ions were recorded. This study showed, undoubtedly, the spectral features of an Eu3+ emitting centre embedded in a unique site of D2 symmetry. Furthermore, the well-known cross-relaxation phenomenon was observed for Tb3+. Decay times were found to be exponential and shorter than 5 ms for both Eu3+ and Tb3+ activators. Finally, the spectroscopic properties of YAG : Tb3+ powders under vacuum ultra violet excitation were analysed and encouraging results were obtained regarding luminescence efficiency and time constants.

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

    PubMed

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

    2010-10-01

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

  4. 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 ??(0) increased as well. The evolutions of ??(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.

  5. 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.

  6. Flexible metal-oxide devices made by room-temperature photochemical activation of sol-gel films.

    PubMed

    Kim, Yong-Hoon; Heo, Jae-Sang; Kim, Tae-Hyeong; Park, Sungjun; Yoon, Myung-Han; Kim, Jiwan; Oh, Min Suk; Yi, Gi-Ra; Noh, Yong-Young; Park, Sung Kyu

    2012-09-01

    Amorphous metal-oxide semiconductors have emerged as potential replacements for organic and silicon materials in thin-film electronics. The high carrier mobility in the amorphous state, and excellent large-area uniformity, have extended their applications to active-matrix electronics, including displays, sensor arrays and X-ray detectors. Moreover, their solution processability and optical transparency have opened new horizons for low-cost printable and transparent electronics on plastic substrates. But metal-oxide formation by the sol-gel route requires an annealing step at relatively high temperature, which has prevented the incorporation of these materials with the polymer substrates used in high-performance flexible electronics. Here we report a general method for forming high-performance and operationally stable metal-oxide semiconductors at room temperature, by deep-ultraviolet photochemical activation of sol-gel films. Deep-ultraviolet irradiation induces efficient condensation and densification of oxide semiconducting films by photochemical activation at low temperature. This photochemical activation is applicable to numerous metal-oxide semiconductors, and the performance (in terms of transistor mobility and operational stability) of thin-film transistors fabricated by this route compares favourably with that of thin-film transistors based on thermally annealed materials. The field-effect mobilities of the photo-activated metal-oxide semiconductors are as high as 14 and 7?cm(2)?V(-1)?s(-1) (with an Al(2)O(3) gate insulator) on glass and polymer substrates, respectively; and seven-stage ring oscillators fabricated on polymer substrates operate with an oscillation frequency of more than 340?kHz, corresponding to a propagation delay of less than 210?nanoseconds per stage. PMID:22955624

  7. Carbon nanotube-coated solid-phase microextraction metal fiber based on sol-gel technique.

    PubMed

    Jiang, Ruifen; Zhu, Fang; Luan, Tiangang; Tong, Yexiang; Liu, Hong; Ouyang, Gangfeng; Pawliszyn, Janusz

    2009-05-29

    A novel carbon nanotube (CNT)-coated solid-phase microextraction fiber was prepared based on sol-gel technique. Commonly used fragile fused silica fiber was replaced with stainless steel wire, which made the fiber unbreakable. An approach was also proposed for batch producing, and good reproducibilities for fiber to fiber and between fibers were achieved. Experiments showed that the sol-gel-CNT fiber exhibited high thermal stability to resist 350 degrees C and excellent solvent durability in methanol and acetonitrile. Compared to commercial polydimethylsiloxane (PDMS) fiber, the sol-gel-CNT fiber represented significantly improved extraction efficiencies for both polar (phenols) and non-polar (benzene, toluene, ethylbenzene, and o-xylene) compounds. Meanwhile, no replacement effect, low carry-over and wide linear range demonstrated that the newly prepared sol-gel-CNT coating has liquid properties, which allow a relatively easy quantification procedure. Moreover, the characterization of the sol-gel-CNT coating was also evaluated with McReynold probe solutes. The results showed that the coating has better affinity for all the five types of solutes compared to commercial 7microm PDMS fiber, which suggested that the coating has the potential to be developed as GC stationary phase. PMID:19394026

  8. 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 500 °C. PMID:26691162

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

    PubMed

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

    2015-10-01

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

  10. Structural, optical and vibrational properties of sol gel titania valproic acid reservoirs

    NASA Astrophysics Data System (ADS)

    Lopez, T.; Ortiz-Islas, E.; Vinogradova, E.; Manjarrez, J.; Azamar, J. A.; Alvarado-Gil, J. J.; Quintana, P.

    2006-10-01

    Organically modified sol-gel derived titania xerogels were prepared by co-gellation of titanium n-butoxide and 2-propylpentanoic acid (valproic acid) at room temperature. Materials with different content of valproic acid were obtained varying the concentration of the drug, during the mixing stage of the sol-gel processing with two concentrations 400 and 800 mg/g of titania. Resulting xerogels were characterized by infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and electron microscopy techniques. Analysis of infrared spectra provides information on the interaction between titania and the adsorbed valproic acid. XRD show an amorphous structure at room temperature. SEM micrographs revealed that the nanoparticles of the xerogels form heterogeneous plates, meanwhile a homogeneous nanostructure was observed by TEM. This study shows the optical and structural properties of the materials and the chemical stability of the encapsulated drug, and suggests that these sol-gel titania are promising carriers for controlled drug release.

  11. Nonlinear optical properties of CdTe included in sol-gel by a new technique

    NASA Astrophysics Data System (ADS)

    Loicq, J.; Torrenti, C.; Renotte, Yvon L. M.; Calberg, C.; Delplancke, J. L.; Lion, Yves F.

    2000-05-01

    Sol-gel derived silica glasses are well suited as host for molecular dopants that show specific optical properties, such as laser action (high second and third order nonlinear coefficients). Such materials are of interest in optical waveguide and switching for telecommunication networks. The material is prepared by sol-gel technique in which some nanocrystallites of semiconductor (II-VI) are included, specially CdTe. Nanocrystallites are prepared out of the host matrix and included in the sol-gel after. The nanoparticles are prepared by sono-electrochemical technique. Sono-electrochemistry, or pulsed electrodeposition in presence of high intensity ultrasound, is used to product powders. The nanoparticles are characterized by scanning and transmission microscopy, electron diffraction, and x-ray fluorescence. The nonlinear refractive index and absorption are measured by the Z-scan method at 532 nm (Nd-YAG pulsed laser).

  12. 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.

  13. 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)

  14. 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.

  15. Cellulase immobilized by sol-gel entrapment for efficient hydrolysis of cellulose.

    PubMed

    Ungurean, Mihaela; Paul, Cristina; Peter, Francisc

    2013-10-01

    Cellulase from Trichoderma reesei (Celluclast 1.5 L, Novozyme) was immobilized by sol-gel encapsulation, using binary or ternary mixtures of tetramethoxysilane (TMOS) with alkyl- or aryl-substituted trimethoxysilanes as precursors. Optimization of immobilization conditions resulted in 92 % recovery of total enzymatic activity in the best immobilized preparate. The immobilized cellulase exhibiting the highest activity, obtained from tetramethoxysilane and methyltrimethoxysilane precursors at 3:1 molar ratio, was investigated in the hydrolysis reaction of microcrystalline cellulose (Avicel PH101). Although the optimal values did not change significantly, both temperature and pH stabilities of the sol-gel entrapped cellulase improved compared to the native enzyme. Immobilization also conferred superior resistance against the inactivation effect of glucose. Reuse of the sol-gel entrapped cellulase showed 40 % retention of the initial activity after five batch hydrolysis cycles, demonstrating the potential of this biocatalyst for large-scale application. PMID:23065015

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

    PubMed

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

    2012-12-18

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

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

    SciTech Connect

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

    1996-08-01

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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

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

    SciTech Connect

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

    1994-02-01

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

  3. 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.

  4. 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 ?-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.

  5. Sol-gel coated glass cells for spin-exchange polarized 3 Ming F. Hsu, G. D. Cates,a)

    E-print Network

    Aksay, Ilhan A.

    Sol-gel coated glass cells for spin-exchange polarized 3 He Ming F. Hsu, G. D. Cates,a) and I a high-purity sol-gel coating for the interior surface of glass cells used for polarizing 3 He by spin are typically polarized in glass vessels, and minimizing spin relaxation due to collisions with the vessel

  6. 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.

  7. 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...

  8. 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.

  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. Effect of matrix treatment on spectroscopic properties of HCl catalysed sol-gel glasses containing coumarin laser dyes.

    PubMed

    Deshpande, Aparna V; Jathar, Laxman V; Rane, Jayraj R

    2009-07-01

    Coumarin 1, Coumarin 2 and Coumarin 120 are embedded in transparent sol-gel glass samples prepared by sol-gel process using dip method. The sol-gel matrix is given dip treatment with Methanol /Distilled Water (50/50 vol) for 1 to 16 h before dipping into dye solution. The effect of dipping time of matrix in Methanol/ Distilled Water on spectroscopic properties of coumarin dye doped glass samples has been studied. The Optical Density (OD) at absorption maximum wavelength and Fluorescence Intensity (FI) at fluorescence maximum wavelength of all coumarin dyes increase with the time of dipping of the sol-gel sample. These absorption/fluorescence properties of coumarin dyes in sol-gel glass matrices are compared with its respective properties in methanolic solution in acidic environment. The cause of these changes in OD/FI with dipping time is discussed by taking into account the absorption / fluorescence of dye in acidified methanol. PMID:19067125

  11. 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

  12. 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

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

    NASA Astrophysics Data System (ADS)

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

    1999-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

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

    DOEpatents

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

    2000-01-01

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

  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. Sol-Gel-Encapsulated Alcohol Dehydrogenase as a Versatile, Environmentally Stabilized Sensor for Alcohols and Aldehydes

    E-print Network

    Sol-Gel-Encapsulated Alcohol Dehydrogenase as a Versatile, Environmentally Stabilized Sensor for Alcohols and Aldehydes Amy K. Williams and Joseph T. Hupp* Contribution from the Department of Chemistry alcohol dehydrogenase (ADH) can be employed as a sensor for short- chained alcohols in standard aqueous

  20. 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.

  1. 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

  2. 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.

  3. Enzyme Stabilization by Covalent Binding in Nanoporous Sol-Gel Glass for

    E-print Network

    Wang, Ping

    Enzyme Stabilization by Covalent Binding in Nanoporous Sol-Gel Glass for Nonaqueous Biocatalysis mate- rial for enzyme immobilization. A model enzyme, -chy- motrypsin, was efficiently bound onto the glass via a bifunctional ligand, trimethoxysilylpropanal, with an ac- tive enzyme loading of 0.54 wt

  4. 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.

  5. 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.

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

    PubMed

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

    2013-05-21

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

  7. Large-area sol-gel optical coatings for the Megajoule Laser prototype

    NASA Astrophysics Data System (ADS)

    Pegon, Philippe M.; Germain, Chantal V.; Rorato, Yannick R.; Belleville, Philippe F.; Lavastre, Eric

    2004-02-01

    In the field of thin film coatings, sol-gel (SG) process is an alternative to the conventional Physical Vapor Deposition (PVD) techniques. Sol-gel process is particularly competitive on large-area or fragile substates by taking advantage of various liquid phase deposition techniques performed at room temperature and atmospheric pressure, coupled with the versatility of organo-metallic chemistry. Developed by the French Commission for Atomic Energy (CEA) since 1985 for its former high-power lasers generation, optimized sol-gel coatings proved also very resistant to laser energy. In 1998, THALES Angenieux (TAGX) was selected by CEA to provide all the sol-gel coatings dedicated to the French Laser MegaJoule (LMJ) prototype, named Ligne d'Integration Laser (LIL). In cooperation with Saint-Etienne Pole Optique et Vision (POV), TAGX initiated the building of a sol-gel technological platform (SGPF) aimed at demonstrating the feasibility of production of optical and functional coatings on large area substrates. A technology transfer was performed by CEA (Le Ripault) to TAGX focusing on the manufacture mainly of single-layer antireflective coatings (SLAR), but also of multi-layer AR-coatings and of multi-layered highly reflective (HR)-coatings. Since beginning of 2001 and using SGPF equipments, TAGX successfully coated within specificaitons and schedule most of the 300 optics required for LIL activation. After this 2 years 1/2 production campaign in pre-industrial conditions, we can now analyse the advantages of each deposition technique used, the repeatability of the several processes, and the performance of the various coatings.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Shukla, Satyajit Vishnu

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

  10. 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.

  11. 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 21days 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

  12. 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.

  13. Effect of cerium on structure modifications of a hybrid sol–gel coating, its mechanical properties and anti-corrosion behavior

    SciTech Connect

    Cambon, Jean-Baptiste; Esteban, Julien; Ansart, Florence; Bonino, Jean-Pierre; Turq, Viviane; Santagneli, S.H.; Santilli, C.V.; Pulcinelli, S.H.

    2012-11-15

    Highlights: ? New sol–gel routes to replace chromates for corrosion protection of aluminum. ? Effect of cerium concentration on the microstructure of xerogel. ? Electrochemical and mechanical performances of hybrid coating with different cerium contents. ? Good correlation between the different results with an optimal cerium content of 0.01 M. -- Abstract: An organic–inorganic hybrid coating was developed to improve the corrosion resistance of the aluminum alloy AA 2024-T3. Organic and inorganic coatings derived from glycidoxypropyl-trimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al(O{sup s}Bu){sub 3}, with different cerium contents, were deposited onto aluminum by dip-coating process. Corrosion resistance and mechanical properties were investigated by electrochemical impedance measurements and nano-indentation respectively. An optimal cerium concentration of 0.01 M was evidenced. To correlate and explain the hybrid coating performances in relation to the cerium content, NMR experiments were performed. It has been shown that when the cerium concentration in the hybrid is higher than 0.01 M there are important modifications in the hybrid structure that account for the mechanical properties and anti-corrosion behavior of the sol–gel coating.

  14. 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 ?(B) fu(-1) (fu = formula unit) and 0.9 ?(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

  15. Thermodynamic analysis of sol-gel transition of gelatin in terms of water activity in various solutions.

    PubMed

    Miyawaki, Osato; Omote, Chiaki; Matsuhira, Keiko

    2015-12-01

    Sol-gel transition of gelatin was analyzed as a multisite stoichiometric reaction of a gelatin molecule with water and solute molecules. The equilibrium sol-gel transition temperature, Tt , was estimated from the average of gelation and melting temperature measured by differential scanning calorimetry. From Tt and the melting enthalpy, ?Hsol , the equilibrium sol-to-gel ratio was estimated by the van't Hoff equation. The reciprocal form of the Wyman-Tanford equation, which describes the sol-to-gel ratio as a function of water activity, was successfully applied to obtain a good linear relationship. From this analysis, the role of water activity on the sol-gel transition of gelatin was clearly explained and the contributions of hydration and solute binding to gelatin molecules were separately discussed in sol-gel transition. The general solution for the free energy for gel-stabilization in various solutions was obtained as a simple function of solute concentration. PMID:26215282

  16. Research of materials for porous matrices in sol-gel systems based on silicon dioxide and metallic oxides

    NASA Astrophysics Data System (ADS)

    Maraeva, E. V.; Bobkov, A. A.; Maximov, A. I.; Moshnikov, V. A.; Nalimova, S. S.

    2015-11-01

    In this study silicon dioxide – stannic oxide and silicon dioxide – zinc nanomaterials oxide were obtained through sol-gel technology. The results of nitrogen thermal desorption measurements, atomic force microscopy measurements and particle sizes measurements are discussed.

  17. Non-aqueous primary cell

    NASA Astrophysics Data System (ADS)

    James, S. D.; Smith, P. H.; Oneill, K. M.; Wilson, M. H.

    1986-05-01

    This patent application relates to electrochemical cells and especially to high-energy, liquid cathode, non-aqueous lithium electrochemical cells free from highly toxic materials. A non-aqueous lithium electrochemical cell is described which includes a halocarbon cathode depolarizer which is 1,2-dichloroethane, 1.1,2-trichloroethane, 1,1,2,2-tetrachloroethane, 1,2-dichloro-1,1-difluoroethane or mixtures thereof and a cathode catalyst which is copper, rhodium, palladium, cobalt phthalocyanine, nickel phthalocyanine, iron phthalocyanine, a cobalt tetraaza-(14)-annulene, a nickel tetraaza-(14)-annulene, a iron tetraaza-(14)-annulene, a cobalt porphyrin, a nickel porphyrin, a iron porphyrin, or a mixture thereof.

  18. 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.

  19. 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

  20. Versatile technique to functionalize optical microfibers via a modified sol-gel dip-coating method.

    PubMed

    Xu, Z Y; Li, Y H; Wang, L J

    2014-01-01

    We present a convenient and versatile technique to functionalize microfibers by depositing sol-gel jackets via a modified dip-coating method. This was elucidated by gain-functionalizing microfibers with erbium-ytterbium codoped silica sol-gel jackets. For a 4.5-cm-long coated microfiber, an internal gain of 1.8 dB and a net gain of 0.8 dB for a 1550 nm signal were observed, when combing together the gain of the doped jackets and low loss of microfibers. With benefits of convenience and versatility, this technique can be used for functionalizing microfibers with jackets showing gains in other spectral ranges, high nonlinearity, high sensitivity, and many other functions. PMID:24365815

  1. Transparent ultralow-density silica aerogels prepared by a two-step sol-gel process

    SciTech Connect

    Tillotson, T.M.; Hrubesh, L.W.

    1991-09-01

    Conventional silica sol-gel chemistry is limited for the production of transparent ultralow-density aerogels because (1) gelation is either slow or unachievable, and (2) even when gelation is achieved, the large pore sizes result in loss of transparency for aerogels <.020 g/cc. We have developed a two-step sol-gel process that circumvents the limitations of the conventional process and allows the formation of ultralow-density gels in a matter of hours. we have found that the gel time is dependent on the catalyst concentration. After supercritical extraction, the aerogels are transparent, uncracked tiles with densities as low as .003 g/cc. 6 figs., 11 refs.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

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

    SciTech Connect

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

    2006-12-14

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

  4. 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

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

    NASA Astrophysics Data System (ADS)

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

    2001-11-01

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

  6. 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

  7. 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.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Vihodceva, S.; Kukle, S.

    2012-08-01

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

  10. 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.

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

    PubMed

    Haibin, Ni; Ming, Wang; Wei, Chen

    2011-12-19

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

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

    PubMed

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

    2010-09-01

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

  14. 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

  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. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. Photocatalytic activity of titania coatings synthesised by a combined laser/sol–gel technique

    SciTech Connect

    Adraider, Y.; Pang, Y.X.; Nabhani, F.; Hodgson, S.N.; Sharp, M.C.; Al-Waidh, A.

    2014-06-01

    Highlights: • Sol–gel method was used to prepare titania coatings. • Titania thin films were coated on substrate surface by dip coating. • Fibre laser was employed to irradiate the titania coated surfaces. • Photocatalytic efficiency of titania coatings was significantly improved after laser processing. - Abstract: Titania coatings were prepared using sol–gel method and then applied on the substrate surface by dip coating. Fibre laser (? = 1064 nm) in continuous wave mode was used to irradiate the titania coated surfaces at different specific energies. The ATR-FTIR, XRD, SEM, EDS and contact angle measurement were employed to analyse surface morphology, phase composition and crystalline structure of laser-irradiated titania coatings, whilst the photocatalytic activity was evaluated by measuring the decomposition of methylene blue (MB) after exposure to the visible light for various illumination times. Results showed that the laser-irradiated titania coatings demonstrate significant different composition and microstructure in comparison with the as-coated from the same sol–gel titania. Photocatalytic efficiency of titania coatings was significantly improved after laser processing. The photocatalytic activity of laser-irradiated titania coatings was higher than that of the as-coated titania. The titania coating processed at laser specific energy of 6.5 J/mm{sup 2} exhibited the highest photocatalytic activity among all titania samples.

  2. 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.

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

    PubMed

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

    2011-04-15

    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 10? 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). PMID:21389579

  5. Laser cavity mirror preparation using sol-gel chemistry and laminar-flow coating technique

    NASA Astrophysics Data System (ADS)

    Belleville, Philippe F.; Pegon, Philippe M.

    1999-07-01

    The CEA/DAM megajoule-class pulsed Nd:glass laser devoted to Inertial Confinement Fusion (ICF) research will require 240 cavity-end mirrors. The approved laser design necessitates 44cm X 44cm X 6cm highly-reflective (HR)-coated substrates representing more than 50m2 of coated area. Prototypes of these dielectric mirrors were prepared with interference quarterwave stacks of SiO2 and ZrO2-PVP thin films starting from sol-gel colloidal suspensions. Low reflective index materials was based on nanosized silica particles and high refractive index coating solution was made of a composite system. The colloidal/polymeric ratio in the composite system has been optimized regarding refractive index value, laser damage threshold and chemical interactions have been studied using FTIR spectroscopy. A promising deposition technique so-called 'Laminar Flow Coating' has been associated to sol-gel chemistry for HR laser damage-resistant sol-gel coating development. This novel coating method confirmed its main advantages compared to dipping or spinning processes: coating large flat square substrates at room temperature with small solution consumption, good thickness uniformity, weak edge-effects, induced stress-free coating, good optical properties and laser damage resistance.

  6. 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.

  7. Optical sensors based on sol-gel derived, laminate planar waveguide structures

    SciTech Connect

    Yang, Lin; Armstrong, N.R.; Dunphy, D.R.; Saavedra, S.S.

    1995-12-31

    A new optical sensing platform based on a combination of planar and sol-gel processing technologies is described. The sensing element is a planar integrated optical waveguide (IOW) composed of two, submicron thick glass layers coated on glass substrate; both layers are fabricated via the sol-gel method. The lower layer is a densified titania-silica composite. The upper layer is an undensified silica doped with an optical indicator that is physically entrapped yet sterically accessible to dissolved analytes that can diffuse into the pore network. Formation of an analyte-indicator complex is detected via attenuated total reflection (ATR) of light guided in the IOW. The sensor response is both sensitive and rapid, features that are difficult to achieve simultaneously in monolithic sol-gel glass sensors. In the IOW-ATR geometry, these features are realized simultaneously because the primary axes of light propagation and analyte diffusion are orthogonal. The overall approach is technically simple, inexpensive, and applicable to a wide variety of indicator chemistries.

  8. 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.

  9. Charge Trapping in Sol-Gel-Derived Coatings on Si Wafers

    NASA Astrophysics Data System (ADS)

    Diaz, T.; Juárez, H.; Cuamatzi, M.; Olvera, J.; Martinez, J.; Juárez, R.

    Sol-gel techniques are particularly useful for the formation of thin oxide films on various substrates, which can be important for many technological applications. In microelectronic technology these films can be used as passivation layers, diffusion and oxidation barriers, intermetal dielectrics (IMD) and so on. Sol-gel-derived oxides are obtained from tetraethoxysilane, which is used as precursor and a two-step process involving acid catalysts. Varying the composition of the sol-gel solution, optical and electrical properties of the resulted films can be changed. In the present work, HF and HNO3 were used as catalyst in order to vary the electrical properties of the films. Oxides were deposited on Si substrates and MIS (metal-insulator-semiconductor) structures were fabricated. Electrical properties of the coatings were studied by the C-V (capacitance-voltage) method. Fourier transform infrared spectroscopy (FTIR) measurements ware employed to investigate the chemical bonding structure. The results show evidence of the existence of charge trapping in the TEOS/HNO3 films when MIS capacitors are biased from accumulation to inversion condition. This fact can be applied in the semiconductor device technology.

  10. 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

  11. 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).

  12. 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

  13. Preparation and characterisation of a sol-gel process ?-Al?O? polycrystalline detector.

    PubMed

    Ferreira, H R; Santos, A

    2015-02-01

    This article presents the dosimetric characteristics of ?-Al2O3 detectors prepared through the sol-gel process, disc pressing and sintering in a highly reducing atmosphere. Comparative tests between the sol-gel process ?-Al2O3 polycrystalline and anion-defective ?-Al2O3:C single-crystal detectors indicate that the ones prepared through this approach present good dosimetric characteristics similar to those found in single-crystal detectors, such as a simple glow curve with the main peak at ?198 °C (2 °C s(-1)), high sensitivity, a detection threshold of 1.7 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 ?-Al2O3:C single crystal is practically non-existent in the sol-gel process ?-Al2O3 polycrystalline detector. This characteristic renders it useful for the routine processing of large numbers of personal and environmental dosemeters at higher heating rates and also when it comes to the proposal for new approaches to thermal quenching investigation. PMID:24795396

  14. Antioxidant Sol-Gel Improves Cutaneous Wound Healing in Streptozotocin-Induced Diabetic Rats

    PubMed Central

    Lee, Yen-Hsien; Chang, Jung-Jhih; Chien, Chiang-Ting; Yang, Ming-Chien; Chien, Hsiung-Fei

    2012-01-01

    We examined the effects of vitamin C in Pluronic F127 on diabetic wound healing. Full-thickness excision skin wounds were made in normal and diabetic Wistar rats to evaluate the effect of saline, saline plus vitamin C (antioxidant sol), Pluronic F127, or Pluronic F127 plus vitamin C (antioxidant sol-gel). The rate of wound contraction, the levels of epidermal and dermal maturation, collagen synthesis, and apoptosis production in the wound tissue were determined. In vitro data showed that after 6 hours of air exposure, the order of the scavenging abilities for HOCl, H2O2, and O2?? was antioxidant sol-gel > antioxidant saline > Pluronic F127 = saline. After 7 and 14 days of wound injury, the antioxidant sol-gel improved wound healing significantly by accelerated epidermal and dermal maturation, an increase in collagen content, and a decrease in apoptosis formation. However, the wounds of all treatments healed mostly at 3 weeks. Vitamin C in Pluronic F127 hastened cutaneous wound healing by its antioxidant and antiapoptotic mechanisms through a good drug delivery system. This study showed that Pluronic F127 plus vitamin C could potentially be employed as a novel wound-healing enhancer. PMID:22919368

  15. Novel hybrid organic-inorganic sol-gel materials based on highly efficient heterocyclic push-pull chromophores

    NASA Astrophysics Data System (ADS)

    Abbotto, Alessandro; Bozio, Renato; Brusatin, Giovanna; Facchetti, Antonio; Guglielmi, Massimo; Innocenzi, Plinio; Meneghetti, Moreno; Pagani, Giorgio A.; Signorini, Raffaella

    1999-10-01

    We report the synthesis of sol-gel materials based on highly efficient heterocycle-based push-pull chromophores showing second- and third-order nonlinear optical activity. We show the proper functionalization of the best performing chromophores and their incorporation into a hybrid organic- inorganic sol-gel matrix. Different types of functionalization of the active molecule have been considered, including hydroxyl and alkoxysilyl end-groups. The functionalization strategy responded to different criteria such as stability and synthetic availability of the final molecular precursors, their solubility, and the used synthetic approach to the sol-gel material. The synthesis of the sol-gel materials has been tuned in order to preserve molecular properties and control important factors such as final concentration of the active dye in the matrix. Both acid- and base-catalyzed sol-gel synthesis has been taken into account. 3-Glycidoxypropyltrimethoxysilane and 3- aminopropyltriethoxysilane have been used as the organically modified alkoxides to prepare the hybrid organic-inorganic matrix. Characterization of the spectroscopic properties of the sol-gel materials is presented.

  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. Thick CeO2-TiO2 sol-gel coatings for Li-ion storage electrode in electrochromic devices

    NASA Astrophysics Data System (ADS)

    Choi, Kyo-Sook; Heusing, Sabine; Aegerter, Michel A.

    2002-10-01

    CeO2-TiO2 sol-gel coatings are well known as Li-ion storage electrode in electrochromic (EC) devices of the form glass/ TE /WO3/ electrolyte/ CeO2-TiO2/ TE/ glass (TE: transparent electrode, e.g. SnO2:F, FTO). The charge capacity of the CeO2-TiO2 coating is a limiting factor to get a high coloration intensity of such devices. In order to improve the charge capacity of these electrodes, new routes for the preparation of thick porous CeO2-TiO2 sol-gel layers were tested. One route was the preparation of thick porous TiO2 coatings on a conducting glass support (FTO) using a solution of colloidal TiO2 particles. After heat treatment at temperatures up to 550°C the coatings were soaked in a solution of a cerium-IV (Ce(NH4)2(NO3)6) or a cerium-III salt (Ce(NO3)3 6H2O) and heat treated again. Another route was the preparation of sols by mixing a solution of the cerium-IV or cerium-III salt or a colloidal CeO2-sol with the colloidal solution of TiO2. After dip coating on FTO-glass the coatings were also heat treated at temperatures up to 500°C. ALl these coatings were studied electrochemically in 1 M LiC1O4 in propylene carbonate electrolyte. Although thick porous single coatings could be obtained, typically 450 nm for TiO2 and 600 nm for cerium-titanium oxide, the intercalated and deintercalcated Li+ charges remain small and lie in the range of 2 mC/cm2 to 3 mC/cm2. The reasons for such low charge capacity is discussed.

  18. 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.

  19. 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

  20. Electrophoretically active sol-gel processes to backfill, seal, and/or densify porous, flawed, and/or cracked coatings on electrically conductive material

    DOEpatents

    Panitz, Janda K. (Sandia Park, NM); Reed, Scott T. (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Neiser, Richard A. (Albuquerque, NM); Moffatt, William C. (Albuquerque, NM)

    1999-01-01

    Electrophoretically active sol-gel processes to fill, seal, and/or density porous, flawed, and/or cracked coatings on electrically conductive substrates. Such coatings may be dielectrics, ceramics, or semiconductors and, by the present invention, may have deposited onto and into them sol-gel ceramic precursor compounds which are subsequently converted to sol-gel ceramics to yield composite materials with various tailored properties.

  1. 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.

  2. 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.

  3. 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.

  4. One- and three-dimensional growth of hydroxyapatite nanowires during sol-gel-hydrothermal synthesis.

    PubMed

    Costa, Daniel O; Dixon, S Jeffrey; Rizkalla, Amin S

    2012-03-01

    Nanoscale hydroxyapatite (HA) is an optimal candidate biomaterial for bone tissue engineering because of its bioactive and osteoconductive properties. In this study, micro- and nanoscale HA particles with rod- and wirelike morphology were synthesized by a novel sol-gel-hydrothermal process. Sol-gel chemistry was used to produce a dry gel containing amorphous calcium phosphate (ACP), which was used as a precursor material in a hydrothermal process. The sol-gel-hydrothermal products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to determine particle morphology, crystal structure, and the presence of chemical functional groups. A pure HA crystal was synthesized, which underwent both one- and three-dimensional growth, resulting in tunable microrod and nanorod, and wire morphologies. The effects of solution pH and reaction time on particle diameter and length were assessed. Particle diameter ranged from 25 to 800 nm and decreased with an increase in solution pH, whereas both particle length and diameter increased as the hydrothermal process was prolonged. Nanowire HA powders (10-50 wt %) were mixed with poly(?-caprolactone) (PCL) to produce PCL/HA composites. Fracture surfaces of PCL/HA composites showed a well-dispersed and homogeneous distribution of HA nanowires within the PCL matrix. Mechanical testing revealed a significant (p < 0.05) increase in the Young's and compressive moduli of PCL/HA composites compared to PCL alone, with 50 wt % HA producing a 3-fold increase in Young's modulus from 193 to 665 MPa and 2-fold increase in compressive modulus from 230 to 487 MPa. These HA nanowires can be used to reinforce polymer composites and are excellent biomaterials for tissue engineering of bone. PMID:22296410

  5. Preparation of ThO 2 pellets by sol-gel microsphere pelletization

    NASA Astrophysics Data System (ADS)

    Yamagishi, Shigeru; Takahashi, Yoshihisa

    1992-07-01

    The fabrication of high density ThO 2 pellets without any additives by the sol-gel microsphere pelletization (SGMP) process was studied. Source material for the pelletization was prepared by substituting isopropyl alcohol for the water in ThO 2 gel microspheres and thereafter by removing the alcohol with evacuating and heating. Thus dried microspheres were treated by heating at 450°C and rehumidifying up to 10-15% of overall moisture included. Through compacting the treated microspheres, the satisfactory pellets of 85-98% TD were obtained by sintering at 1300°C. The effects of the heat treating and the rehumidification on compaction and sintering are discussed.

  6. 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.

  7. Synthesis and sintering of nanocrystalline hydroxyapatite powders by citric acid sol-gel combustion method

    SciTech Connect

    Han Yingchao; Li Shipu; Wang Xinyu; Chen Xiaoming

    2004-01-03

    The citric acid sol-gel combustion method has been used for the synthesis of nanocrystalline hydroxyapatite (HAP) powder from calcium nitrate, diammonium hydrogen phosphate and citric acid. The phase composition of HAP powder was characterized by X-ray powder diffraction analysis (XRD). The morphology of HAP powder was observed by transmission electron microscope (TEM). The HAP powder has been sintered into microporous ceramic in air at 1200 deg. C with 3 h soaking time. The microstructure and phase composition of the resulting HAP ceramic were characterized by scanning electron microscope (SEM) and XRD, respectively. The physical characterization of open porosity and flexural strength have also been carried out.

  8. The development and characterization of sol-gel substrates for chemical and optical applications

    NASA Astrophysics Data System (ADS)

    Powers, Kevin William

    1998-12-01

    The sol gel process can be used to make monolithic porous glass for various scientific and engineering uses. The porosity of the material imparts a large surface area which is advantageous in applications such as catalyst supports or in the study of surface mediated chemical reactions. The chemical stability and transparency of the porous glass also make it suitable for use in the emerging field of optical sensors. In this study fluoride catalysis is used to produce sol gel monoliths with pore radii of up to 400 Angstroms, four times larger than any previously reported using conventional drying techniques. Gel monoliths with pore radii of 200 Angstroms were found to have the best combination of surface area, pore volume and optical transparency. Typical monoliths have surface areas of 150 m2/g and pore volumes of 1.60 cm3/g with good transparency. The monoliths are chemically stable, have good mechanical strength and can be easily rehydrated without cracking. The substrates are also suitable for sintering into dense high purity silica glass with little tendency towards foaming. An in-depth study of the catalytic effect of fluoride on the sol gel process is also included. It has been theorized that fluoride serves to expand the coordination sphere of the silicon center making it more subject to nucleophilic attack. In this work an ion-specific fluoride electrode is used to monitor free fluoride concentrations in HF catalyzed sols while silicic acid is added in the form of tetramethoxysilane (TMOS). It is found that fluoride is rapidly bound by the silicic acid in a ratio of four to one, indicating the formation of silicon tetrafluoride. A concurrent decrease in pH suggests that a pentacoordinate species is formed that is more stable than previously thought. A polymerization mechanism is proposed that explains the hydrophobicity of fluoride catalyzed gels and the difficulty in retaining structural fluoride in fluoride catalyzed sol gel glasses. Finally, several porous monoliths are doped with colloidal gold and the optical properties evaluated as a function of heat treatment. This demonstrates the feasibility of using porous glass nanocomposites in sensors and other optical components.

  9. Sol-gel synthesis of Pb-free thin-film nanomaterials for electrocaloric devices

    NASA Astrophysics Data System (ADS)

    Abrashova, E. V.; Kononova, I. E.; Moshnikov, V. A.; Nalimova, S. S.

    2014-12-01

    Lead-free BaxCa(1-x)TiO3, BaSnyTi(1-y)O3 and composite BaxCa(1-x)TiO3 / BaSnyTi(1-y)O3 thin films were synthesized by a sol-gel technique. A large electrocaloric effect is expected in the obtained films. Atomic force microscopy studies revealed that the thin films consists of ellipsoidal objects enclosed by an amorphous matrix. The electrical properties of synthesized nanomaterials were investigated by impedance spectroscopy.

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

    DOEpatents

    Guadalupe, Ana R. (San Juan, PR); Guo, Yizhu (San Juan, PR)

    2001-05-15

    A process for preparing sol-gel graphite composite electrodes is presented. This process preferably uses the surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) and eliminates the need for a cosolvent, an acidic catalyst, a cellulose binder and a thermal curing step from prior art processes. Fabrication of screen-printed electrodes by this process provides a simple approach for electroanalytical applications in aqueous and nonaqueous solvents. Examples of applications for such composite electrodes produced from this process include biochemical sensors such as disposable, single-use glucose sensors and ligand modified composite sensors for metal ion sensitive sensors.

  12. 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.

  13. 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.

  14. Micro-Composite Ceramic Coatings Prepared by Thermal Pressure Filtration of Sol-Gel Paints

    NASA Astrophysics Data System (ADS)

    He, Yedong; Zhang, Kun; Li, Liangjian; Wang, Deren

    A novel coating technique, thermal pressure filtration of sol-gel paints (TPFSP), has been developed to prepare nano-/micro-composite ceramic coatings with controllable thickness, structure, and excellent high temperature properties. In this paper, the fabrication of two typical coatings, nano-/micro-Al2O3-Y2O3 composite coating and Al2O3·SiO2 fibers reinforced nano-ZrO2-8wt.%Y2O3 composite coating was demonstrated and their structures and properties were studied.

  15. Development of an efficient large-aperture high damage-threshold sol-gel diffraction grating.

    SciTech Connect

    Ashley, Carol S.; Rambo, Patrick K.; Schwarz, Jens; Dunphy, Darren Robert; Branson, Eric D.; Smith, Ian Craig; Johnson, William Arthur; Reed, Scott T.; Cook, Adam W.

    2005-03-01

    In order to develop the next generation of high peak intensity lasers, new grating technology providing higher damage thresholds and large apertures is required. The current assumption is that this technical innovation will be multilayer dielectric gratings, wherein the uppermost layer of a thin film mirror is etched to create the desired binary phase grating. A variant of this is explored with the upper grating layer being a lower density gelatin-based volume phase grating in either sol-gel or dichromated gelatin. One key benefit is the elimination of the etching step.

  16. Photometric sensors based on sol-gel porous glass doped with organic reagents

    NASA Astrophysics Data System (ADS)

    Lev, Ovadia; Kuyavskaya, B. I.; Sacharov, Y.; Rottman, Claudio; Kuselman, A.; Avnir, David; Ottolenghi, M.

    1993-03-01

    A new class of sensitive disposable sensors for determination of trace concentrations of water pollutants has been developed. It utilizes porous transparent silica glasses doped with organic photometric reagents. The silica sensors are produced at room temperature by the sol-gel procedure, i.e. by hydrolysis followed by polycondensation of tetraalkoxysilanes. Thus, we produced porous glasses doped with organic photometric reagents for the determination of typical cations, anions, pH, oxidation agents (e.g. disinfection agents) as well as typical air pollutants. A mathematical model for a flat plate monolithic iron sensor was developed and the predicted calibration curves were compared with the experimental response.

  17. 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.

  18. 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.

  19. Optical Properties and Microstructure of Sol-Gel Derived NdAlO3 Thin Films

    NASA Astrophysics Data System (ADS)

    Wei, Tzu-Chun; Tseng, Ching-Fang

    Optical properties and microstructure of NdAlO3 thin films prepared by sol-gel method on glass substrates at different annealing temperatures have been investigated. The structure of the materials is studied using X-Ray diffraction, and the microstructure is analyzed using scanning electron microscopy. The diffraction pattern showed that the deposited films exhibited an amorphous microstructure. Optical transmittance spectroscopy further revealed high transparency in the visible region of the spectrum. The dependence of the physical, optical, and electrical characteristics on various annealing temperatures was also investigated.

  20. Optical and Structural Properties of Nanostructured Oxide Thin Films by Sol-Gel Technique

    NASA Astrophysics Data System (ADS)

    Kareem, K. S. A.; Rao, K. Narasimha; Phani, A. R.; Rani, R. Uma; Sharma, A. K.

    2011-10-01

    TiO2 and Al2O3 are commonly used materials in optical thin films in the visible and near-infrared wavelength region due to their high transparency and good stability. In this work, TiO2 and Al2O3 single, and nano composite thin films with different compositions were deposited on glass and silicon substrates at room temperature using a sol-gel spin coater. The optical properties like reflectance, transmittance and refractive index have been studied using Spectrophotometer, and structural properties using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM).

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

    SciTech Connect

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

    2014-04-24

    The indium doped CdO thin films have been prepared by the sol-gel spin coating technique and the influence of indium doping concentration on the structural and electrical properties of the deposited films has been investigated. The indium doping concentration in the solution has been varied from 0-10 wt% insteps of 2wt%. A indium doping concentration of 6wt% has been found to be optimum for preparing the films and at this stage a minimum resistivity of 5.92×10{sup ?4}? cm and a maximum carrier concentration of 1.20×10{sup 20}cm{sup ?3} have been realized.

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

    PubMed

    Zaitoun, M A; Momani, K; Jaradat, Q; Qurashi, I M

    2013-11-01

    Luminescence efficiency of lanthanide complexes generally largely depend on the choice of the organic ligand and the host matrix in which these complexes are doped. Two Sm(III) complexes, namely: Sm(III) dithicarbamate - Sm(L1)3B [L1=(R)2NCS2B, R=C2H5 and B=1,10-phenanthroline] and Sm(III) complex with the polytonic ligand L2=N', N'(2)-bis[(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide {Sm2-L2-(CH3COO)2; L2=C16H16N6O2} are synthesized, these complexes are then trapped in sol-gel glass. Room temperature luminescence of Sm(L1)3B and {Sm2-L2-(CH3COO)2} complexes encapsulated in sol-gel glass are studied using a spectrofluorometer. Up on excitation by a UV light, ligand L1B absorbs this light and transfers it into the Sm(III) ions and emission bands were observed in the visible region and were attributed to f-f transitions of Sm(III). The observed emission indicated an efficient L1B ligand as a sensitizer, while ligand L2 shows no ability to work as a sensitizer. The branching ratio I4G5/2?6H9/2/I4G5/2?6H7/2) of electric dipole transition to magnetic dipole transition was used as an effective spectroscopic probe to predict symmetry of the site in which Sm(III) is located. The encapsulation of the Samaium complexes was performed for three reasons: (i) before rare earth (RE)-doped sol-gel glasses can be used in applications such as laser materials, several fluorescence quenching mechanisms must be overcome, we show in this work that lanthanide fluorescence is greatly enhanced by chelation and selecting a suitable host matrix (sol-gel) to accommodate the lanthanide complex, (ii) to improve the stability of the phosphor with efficient and high color-purity characteristics under ultraviolet excitation and (iii) this work provides a framework for preparing transparent composite glasses that are robust hosts to study the fundamental interactions between nano-materials and light. PMID:23892122

  3. Thin film of sol-gel deposited in photonic crystal fiber for cholesterol detection

    NASA Astrophysics Data System (ADS)

    Razo-Medina, D. A.; Alvarado-Méndez, E.; Trejo-Durán, M.

    2015-04-01

    In this work, the fabrication of thin films mixed with cholesterol enzyme as recognition component is shown, using solgel technique. The film was deposited at one end of photonic crystal fiber (optrode), which was used as carrier medium of sol-gel matrix. The concentration of cholesterol in the test sample was determined by the use of transmittance. Measuring device consists of a power source (laser diode), optrode and a light detector. The laser beam is transmitted through the optrode; the variations of intensity depending on cholesterol concentration are emitted to be detected by a photoresistor.

  4. Diffraction gratings and diffusion coefficient determination of acrylamide and polyacrylamide in sol-gel glass

    NASA Astrophysics Data System (ADS)

    Blaya, S.; Murciano, A.; Acebal, P.; Carretero, L.; Ulibarrena, M.; Fimia, A.

    2004-06-01

    We describe the recording of holographic gratings in a photopolymerizable sol-gel glass based on acrylamide as monomer, triethanolamine as coinitiator, and yellowish eosin as photoinitiator. Although acrylic monomers have been introduced in silica glass by Cheben and Calvo [Appl. Phys. Lett. 78, 1490 (2001)], the well-known acrylamide based composition has not yet been produced by this method. Diffraction efficiencies close to 55% were obtained with an exposure of 8 mJ/cm2. The holographic gratings were not stable and we made use of this instability to determine the diffusion coefficients of acrylamide and polyacrylamide inside this glass.

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

    PubMed Central

    2013-01-01

    Inverted zinc oxide photonic crystal structures were fabricated from polystyrene sphere (PSS) template using the 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

  6. All-silica nanofluidic devices for DNA-analysis fabricated by imprint of sol-gel silica with silicon stamp.

    PubMed

    Mikkelsen, Morten Bo; Letailleur, Alban A; Søndergård, Elin; Barthel, Etienne; Teisseire, Jérémie; Marie, Rodolphe; Kristensen, Anders

    2012-01-21

    We present a simple and cheap method for fabrication of silica nanofluidic devices for single-molecule studies. By imprinting sol-gel materials with a multi-level stamp comprising micro- and nanofeatures, channels of different depth are produced in a single process step. Calcination of the imprinted hybrid sol-gel material produces purely inorganic silica, which has very low autofluorescence and can be fusion bonded to a glass lid. Compared to top-down processing of fused silica or silicon substrates, imprint of sol-gel silica enables fabrication of high-quality nanofluidic devices without expensive high-vacuum lithography and etching techniques. The applicability of the fabricated device for single-molecule studies is demonstrated by measuring the extension of DNA molecules of different lengths confined in the nanochannels. PMID:22081085

  7. 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.

  8. 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

  9. "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

  10. A modified sol-gel technique for pore size control in porous aluminum oxide nanowire templates.

    PubMed

    Kelly, Daniel N; Wakabayashi, Ryo H; Stacy, Angelica M

    2014-11-26

    A modified sol-gel technique was developed to continuously vary the pore diameters in porous alumina templates for the purpose of growing nanowires. To coat the pore walls, the porous alumina film is initially soaked in a methanol/water solution to fill the pores with the desired concentration of water. The porous alumina film is then exposed to a solution of 3-aminopropyltriethoxysilane (APTES) in toluene, creating a surface layer of APTES. The concentration of water in the pores correlates with the thickness of the APTES polymer coating that is obtained. This approach exerts greater control over the extent of silane polymerization than traditional sol-gel reactions by limiting the amount of water present for reaction. Factors such as the APTES concentration, exposure time, and organic cosolvent choice did not influence the coating thickness. However, the density and thickness of the APTES coating can be manipulated by varying the pH of the methanol/water solution as well as post-treatment annealing. Further modification of the pore size was achieved by subsequent reaction of the APTES coating with poly(methyl methacrylate) (PMMA). The PMMA couples to amine groups on the APTES polymer surface by an aminolysis reaction. Bismuth telluride nanowires were electrodeposited in the polymer-coated porous alumina templates using previously established methods. Nanowire diameters were smaller when the nanowires were prepared in modified templates as anticipated. PMID:25425125

  11. Surface Modification of Zirconia Substrate by Calcium Phosphate Particles Using Sol-Gel Method.

    PubMed

    Jin, So Dam; Um, Sang Cheol; Lee, Jong Kook

    2015-08-01

    Surface modification with a biphasic composition of hydroxyapatite (HA) and tricalcium phosphate (TCP) was performed on a zirconia substrate using a sol-gel method. An initial calcium phosphate sol was prepared by mixing a solution of Ca(NO3)2 · 4H20 and (C2H5O)3P(O), while both porous and dense zirconia were used as substrates. The sol-gel coating was performed using a spin coater. The coated porous zirconia substrate was re-sintered at 1350 °C 2 h, while coated dense zirconia substrate was heat-treated at 750 °C 1 h. The microstructure of the resultant HA/TCP coatings was found to be dependent on the type of zirconia substrate used. With porous zirconia as a starting substrate, numerous isolated calcium phosphate particles (TCP and HA) were uniformly dispersed on the surface, and the particle size and covered area were dependent on the viscosity of the calcium phosphate sol. Conversely, when dense zirconia was used as a starting substrate, a thick film of nano-sized HA particles was obtained after heat treatment, however, substantial agglomeration and cracking was also observed. PMID:26369177

  12. 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.

  13. Interactions between DNA purines and ruthenium ammine complexes within nanostructured sol-gel silica matrixes.

    PubMed

    Lopes, Luís M F; Garcia, Ana R; Brogueira, Pedro; Ilharco, Laura M

    2010-03-25

    The interactions between DNA purines (guanine and adenine) and three ruthenium ammine complexes (hexaammineruthenium(III) chloride, hexaammineruthenium(II) chloride, and ruthenium-red) were studied in a confined environment, within sol-gel silica matrixes. Two encapsulation methods were rehearsed (differing in temperature and condensation pH), in order to analyze the effects of the sol-gel processes on the purines and on the Ru complexes separately. The extent of decomposition of the Ru complexes, as well as the interactions established with the purine bases, proved to be determined by the coencapsulation method. Combined results by diffuse reflectance UV-vis and infrared spectroscopies showed that, when coencapsulation is carried out at 60 degrees C, specific H bonding interactions are established between the amine group of Ade and the ammine groups of the Ru complex or the hydroxo group of an early decomposition product. These are responsible for the important role of the purine in inhibiting the oxidation reactions of the Ru(II) and Ru(III) complexes. In contrast, Gua establishes preferential H bonds with the matrix (mainly due to the carbonyl group), leading to higher yields in the final oxidation products of the Ru complexes, namely, trimers and dimers. Direct covalent bonding of either purine to the metal was not observed. PMID:20196584

  14. Preparation and optical properties of sol-gel-deposited electrochromic iron oxide films

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; Tepehan, Fatma; Tepehan, Galip

    1997-10-01

    The preparation and optical properties of sol-gel deposited iron oxide films are investigated in this study. The films are deposited on glass by spin-coating from polymeric sol-gel solutions. The coating solutions were prepared from Fe(OCH3H7)3 and isopropanol. Fe2O3 films were obtained at a firing temperature 180 degrees Celsius. The films were characterized by x-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and UV-Vis spectroscopy. The electrochemical properties of the films were studied in 0.5 M LiClO4/propylene carbonate (PC) solution. The CV results showed reversibility of the Li+/e- insertion/extraction process in the Fe2O3 films up to 200 cycles. Reduction and oxidation of the amorphous films in 0.5 M LiClO4-PC solution caused noticeable changes in optical absorption. XRD of the films showed that they had an amorphous structure. Fourier transform infrared spectroscopy (FTIR) measurements showed that the composition of the film is Fe2O3. In-situ spectrophotometric measurements indicated that these films show weak electrochromism in the spectral range of 350 - 800 nm. The optical band gap is estimated to be 1.92 eV for the amorphous film. The spectroelectrochemical properties clearly indicated that cyclic stability of the iron oxide films deteriorated above 200 cycles.

  15. 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.

  16. 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

  17. Sol-gel method as a way of carbonyl iron powder surface modification for interaction improvement

    NASA Astrophysics Data System (ADS)

    Ma?ecki, P.; Kolman, K.; Pig?owski, J.; Kaleta, J.; Krzak, J.

    2015-03-01

    This article presents a method for modification of carbonyl iron particles' surface (CIP), (d50=4-9 ?m) by silica coatings obtained using the sol-gel method. Reaction parameters were determined to obtain dry magnetic powder with homogeneous silica coatings without further processing and without any by-product in the solid or liquid phase. This approach is new among the commonly used methods of silica coating of iron particles. No attempt has been made to cover a carbonyl iron surface by silica in a waste-free method, up to date. In the current work two different silica core/shell structures were made by the sol-gel process, based on different silica precursors: tetraethoxy-silane (TEOS) and tetramethoxy-silane (TMOS). The dependence between the synthesis procedure and thickness of silica shell covering carbonyl iron particles has been described. Surface morphology of the modified magnetic particles and the coating thickness were characterized with the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Determination of the physicochemical structure of the obtained materials was performed by the energy-dispersive X-ray spectroscope (EDS), and the infrared technique (IR). The surface composition was analyzed using X-ray photoelectron spectroscopy (XPS). Additionally, distribution of particle size was measured using light microscopy. The new, efficient process of covering micro-size CIP with a nanometric silica layer was shown. Results of a performed analysis confirm the effectiveness of the presented method.

  18. 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

  19. Improved Performances of Acoustic Energy Harvester Fabricated Using Sol/Gel Lead Zirconate Titanate Thin Film

    NASA Astrophysics Data System (ADS)

    Kimura, Shu; Tomioka, Syungo; Iizumi, Satoshi; Tsujimoto, Kyohei; Sugou, Tomohisa; Nishioka, Yasushiro

    2011-06-01

    Energy harvesters integrable on smart sensor systems have been strongly demanded. Microelectromechanical system (MEMS) acoustic energy harvesters using the first resonance vibration of a lead zirconate titanate (PZT) thin film as a diaphragm have recently been reported. Similar acoustic energy harvesters using the third resonance of a PZT diaphragm fabricated by sol/gel PZT thin film processes exhibited improved generated power density, and it was suggested that the PZT acoustic energy harvester might be suitable for use as a possible power source for silicon integrated circuits. We present further improved power generation performances of PZT MEMS acoustic energy harvesters fabricated by improved PZT capacitor fabrication processes. The PZT acoustic energy harvester with the diaphragm diameter of 1.2 mm fabricated by a sol/gel process generated an even higher energy density of 98 µW/m2 under the sound pressure level of 100 dB (0.01 W/m2) at 16.7 kHz.

  20. 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.

  1. Sol–gel method to fabricate CaP scaffolds by robocasting for tissue engineering

    PubMed Central

    Fu, Qiang; Saiz, Eduardo; Tomsia, Antoni P.

    2012-01-01

    Highly porous calcium phosphate (CaP) scaffolds for bone-tissue engineering were fabricated by combining a robocasting process with a sol–gel synthesis that mixed Calcium Nitrate Tetrahydrate and Triethyl Phosphite precursors in an aqueous medium. The resulting gels were used to print scaffolds by robocasting without the use of binder to increase the viscosity of the paste. X-ray diffraction analysis confirmed that the process yielded hydroxyapatite and ?-tricalcium phosphate biphasic composite powders. Thus, the scaffold composition after crystallization of the amorphous structure could be easily modified by varying the initial Ca/P ratio during synthesis. The compressive strengths of the scaffolds are ~6 MPa, which is in the range of human cancellous bone (2–12 MPa). These highly porous scaffolds (~73 vol% porosity) are composed of macro-pores of ~260 ?m in size; such porosity is expected to enable bone ingrowth into the scaffold for bone repair applications. The chemistry, porosity, and surface topography of such scaffolds can also be modified by the process parameters to favor bone formation. The studied sol–gel process can be used to coat these scaffolds by dip-coating, which induces a significant enhancement of mechanical properties. This can adjust scaffold properties such as composition and surface morphology, which consequently may improve their performances. PMID:22311079

  2. Synthesis, characterization, and sol-gel entrapment of a crown ether-styryl fluoroionophore

    PubMed Central

    Sui, Zhijie; Hanan, Nathan J.; Phimphivong, Sam; Wysocki, Ronald J.; Saavedra, S. Scott

    2011-01-01

    The synthesis and initial evaluation of a new dye-functionalized crown-ether, 2-[2-(2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10.13.16-benzohexaoxacyclooctadecin)ethenyl]-3-methyl benzothiazolium iodide (denoted BSD), is reported. This molecule contains a benzyl 18-crown-6 moiety as the ionophore and a benzothiazolium to spectrally transduce ion binding. Binding of K+ to BSD in methanol causes shifts in the both absorbance and fluorescence emission maxima, as well as changes in the molar absorptivity and the emission intensity. Apparent dissociation constants (Kd) in the range of 30 – 65 ?M were measured. In water and neutral buffer, Kd values were approximately 1 mM. BSD was entrapped in sol-gel films composed of methyltriethoxysilane (MTES) and tetraethylorthosilicate (TEOS) with retention of its spectral properties and minimal leaching. K+ binding to BSD in sol-gels films immersed in pH 7.4 buffer causes significant fluorescence quenching, with an apparent response time of approximately 2 min and an apparent Kd of 1.5 mM. PMID:19253273

  3. 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(?-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

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. Phospholipid Fatty Acids as Physiological Indicators of Paracoccus denitrificans Encapsulated in Silica Sol-Gel Hydrogels

    PubMed Central

    Trögl, Josef; Jirková, Ivana; Kurá?, 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 (16:1?7 + 18:1?7)), an indicator of the transition of the culture to a stationary growth-phase, decreased depending on co-immobilization of nutrients in the order phosphate buffer > mineral medium > Luria Broth rich medium. The ratio, too, was logarithmically proportional to cell concentration. These results confirm the applicability of total PLFA as an indicator for the determination of living biomass and cy/pre ratio for determination of nutrient limitation of microorganisms encapsulated in sol-gel matrices. This may be of interest for monitoring of sol-gel encapsulated bacteria proposed as optical recognition elements in biosensor construction, as well as other biotechnological applications. PMID:25690547

  9. Phospholipid fatty acids as physiological indicators of Paracoccus denitrificans encapsulated in silica sol-gel hydrogels.

    PubMed

    Trögl, Josef; Jirková, Ivana; Kurá?, Pavel; Akhmetshina, Elmira; Brovdyová, Ta?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 (16:1?7 + 18:1?7)), 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

  10. Sol-gel auto-combustion synthesis of zinc ferrite for moderate temperature desulfurization

    SciTech Connect

    Rongjun Zhang; Jiejie Huang; Jiantao Zhao; Zhiqiang Sun; Yang Wang

    2007-09-15

    Zinc ferrite as a desulfurization sorbent with an average crystallite size of about 36 nm was synthesized by a sol-gel auto-combustion method. The precursor for the sorbent was a gel obtained from metal nitrates and citric acid by a sol process. The nitrate-citrate gel exhibits a self-propagating combustion behavior, and after combustion, it can transform into a nanosized spinel structured zinc ferrite directly. The prepared sorbent has a larger specific surface area and higher reactivity when compared with the sorbent achieved by a solid mixing method, and it could efficiently reduce the H{sub 2}S concentration from 6000 ppm to less than 2 ppm at a moderate temperature range. The sulfur capacity at 400{sup o}C reaches about 38.5 g of sulfur/100 g of sorbent, which corresponds to 96.4% of the theoretical value. The temperature programmed oxidation test for the sulfided sorbent shows that the most sulfur is desorbed before 500{sup o}C. XRD results confirm that the sulfided sample after exposure to a 5% O{sub 2}/N{sub 2} gas mixture at 500{sup o}C can be regenerated completely, which indicates that the regeneration temperature of the sorbent prepared by the sol-gel auto-combustion method could be greatly reduced. 40 refs., 10 figs., 2 tabs.

  11. Filamentary Extension of the Mem-Con theory of Memristance and its Application to Titanium Dioxide Sol-Gel Memristors

    E-print Network

    Gale, Ella; Adamatzky, Andrew

    2012-01-01

    Titanium dioxide sol-gel memristors have two different modes of operation, believed to be dependent on whether there is bulk memristance, i.e. memristance throughout the whole volume or filamentary memristance, i.e. memristance caused by the connection of conducting filaments. The mem-con theory of memristance is based on the drift of oxygen vacancies rather than that of conducting electrons and has been previously used to describe bulk memristance in several devices. Here, the mem-con theory is extended to model memristance caused by small filaments of low resistance titanium dioxide and it compares favorably to experimental results for filamentary memristance in sol-gel devices.

  12. 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%.

  13. Brinker, C. J.; Harrington, M. S. SOL-GEL DERIVED ANTIREFLECTIVE COATINGS FOR SILICON. Solar Energy Materials 1981, 5, 159-172.

    E-print Network

    Brinker, C. Jeffrey

    Brinker, C. J.; Harrington, M. S. SOL-GEL DERIVED ANTIREFLECTIVE COATINGS FOR SILICON. Solar Energy Materials 1981, 5, 159-172. Brinker, C. J.; Mukherjee, S. P. COMPARISONS OF SOL-GEL-DERIVED THIN-FILMS WITH MONOLITHS IN A MULTICOMPONENT SILICATE GLASS SYSTEM. Thin Solid Films 1981, 77, 141-148. Brinker, C. J

  14. Rheology of Gastric Mucin Exhibits a pH-Dependent Sol-Gel Jonathan P. Celli, Bradley S. Turner,, Nezam H. Afdhal, Randy H. Ewoldt,

    E-print Network

    Rheology of Gastric Mucin Exhibits a pH-Dependent Sol-Gel Transition Jonathan P. Celli, Bradley S that gastric mucin undergoes a pH-dependent sol-gel transition from a viscoelastic solution at neutral pH to a soft viscoelastic gel in acidic conditions, with the transition occurring near pH 4. In addition to pH

  15. Size dependent structural and magnetic properties of Al substituted Co–Mg ferrites synthesized by the sol–gel auto-combustion method

    SciTech Connect

    Ahmad, Imran; Abbas, Tahir; Ziya, A.B.; Abbas, Ghazanfar; Maqsood, Asghari

    2014-04-01

    Highlights: • Well-crystalline Co{sub 0.7}Mg{sub 0.3}AlFeO{sub 4} nanoparticles with small grain size were obtained. • The approach is sol–gel auto-combustion technique for obtained nanoparticles. • The prepared Co{sub 0.7}Mg{sub 0.3}AlFeO{sub 4} ferrites are decent soft materials with low coercivity. • The minor decrease in lattice parameter with increase of temperature was observed. - Abstract: Single phased nanocrystalline Co{sub 0.7}Mg{sub 0.3}FeAlO{sub 4} ferrites having low coercivity were synthesized by the sol–gel auto-combustion route. The subsequent powder materials were sintered in a temperature range of 800–1200 °C for 2 h. The effects of sintering temperatures on the structure, morphology and magnetic properties of the prepared soft magnetic material were studied. X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and magnetic property measurement system (MPMS) were used to characterize the samples. X-ray diffraction analysis confirmed a single-phase cubic spinel structure and ruled out the presence of impurities like hematite. The higher sintering temperatures have caused in enhanced mark of crystallinity and bigger average grain size of the nanocrystals. A slight decrease in lattice parameters was noticed with a rise of grain size. Magnetic measurements revealed that grain size increase led to a decrease in the coercivity and, in difference, an increase in the saturation magnetization.

  16. 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.

  17. Luminescent properties of trivalent ytterbium ions in sol-gel produced alumina

    NASA Astrophysics Data System (ADS)

    Krebs, John Kenneth

    2000-10-01

    Solution growth of materials now offers a viable alternative to traditional high temperature melt growth processes. The sol-gel method, one such solution technique, chemically produces inorganic materials from aqueous solutions. The sol-gel process can be used to produce alumina, Al2O3 , in a variety of forms from porous, transparent monoliths to ceramics. Aluminum oxide, a large bandgap material (9 eV), has played important roles in the fields of impurity ion spectroscopy and catalysis. High quality single crystals, both natural and synthetic, can serve as a host for a variety of transition metal impurities, which are responsible for crystal coloration. Early studies of the spectroscopy of these crystals provided a proving ground for the quantum theory of solids. Meanwhile, the high surface area polycrystalline forms, referred to as transition aluminas, were finding wide application in the areas of catalysis. Despite the technological importance of solution grown materials, we know little about the role of impurities in these materials. The sol-gel growth technique enables the doping of transition aluminas with precise amounts of optically active impurity ions. These ions probe the structure and dynamics of the materials through interactions with the crystal field produced by the host ions. Recent work has begun to address this important class of materials. In this work, we report on the luminescent properties of trivalent ytterbium doped into alumina. Combining the results of optical measurements performed on single crystal and ceramic samples, we show that the dopants occupy identical sites in the two materials. We identify a set of crystal field parameters for ytterbium ions on the substitutional aluminum cation site. Comparison of the crystal field parameters with those of trivalent ytterbium in Bi4Ge3O12, a host with a larger cation site, shows that the ytterbium, the smallest of the lanthanides, sits near the center of the oxygen octahedron. Finally, studies of ytterbium in nanocrystalline gamma alumina demonstrate the role surfaces play in the relaxation of impurity ion excited states in the bulk. This work demonstrates a new method for studying metal oxide surfaces using optical probe ions.

  18. Anti-weathering treatments to protect mineral surfaces: Hybrid sol-gel and biomimetic strategies

    NASA Astrophysics Data System (ADS)

    Rao, Sudeep Motupalli

    1998-12-01

    The natural weathering of stone is accelerated by the combined effects of acid rain, salt crystallization and the freeze-thaw cycles of water. This dissertation describes the development of two anti-weathering preservation treatments that are specific to limestone surfaces. The first strategy involves the application of a surface-specific, bifunctional, passivating, coupling agent that binds to both the limestone surface and to a consolidating inorganic polymeric silica matrix by a sol-gel process. The second strategy involves biomimetic process that converts the exposed limestone surface into a nonreactive calcium oxalate hydrate ceramic layer found in kidney stones and lichen deposits. The microreactor environment of a scanning probe microscope (SPM) fluid cell was used to simulate acid rain effects on treated and untreated calcite surfaces, seen as etch pits and crystal step movement. The treatment process was also monitored at near molecular scale resolution using the SPM. Calcite crystals treated with aminoethylaminopropyltrimethoxysilane (25% AEAPS) passivating coupling agent and a silica consolidating solution (50%w/w), are resistant to the leaching action of deionized water equilibriated with atmospheric COsb2 to pH 5. The aminoalkoxylsilane coupling agent catalyses the condensation reaction and also reacts with the surface to offer the coupling mechanism. Modulus of rupture strength tests on limestone cores treated with the AEAPS and silica-based consolidant showed a 25-35% increase in strength. Environmental scanning electron microscopy of treated limestone exposed to concentrated sulfuric acid showed degradation of the surface except in areas where thick layers of the consolidant were deposited. Powder leach tests using a pH-stat apparatus yielded quantitative proof of the efficacy of the biomimetic calcium oxalate process. The dissolution rates (2.14×10sp{-9} mmol/cmsp2/sec) of treated calcite were two orders of magnitude less than untreated calcium carbonate (3.7×10sp{-7} mmol/cmsp2/sec) and an order of magnitude better than the sol-gel approach (3.5×10sp{-8} mmol/cmsp2/sec). Thus, we can extrapolate these results into a hybrid treatment of biomimetic calcium oxalate hydrate ceramic that provides the chemical leach resistance while a sol-gel passivation and consolidation step using aminoalkylsilane and silica, respectively, provides for improved strength and hydrophobicity.

  19. JOURNAL OF MATERIALS SCIENCE LETTERS 21, 2002, 251 255 Organic-inorganic sol-gel coating for corrosion protection

    E-print Network

    Cao, Guozhong

    for corrosion protection of stainless steel T. P. CHOU Department of Materials Science and EngineeringJOURNAL OF MATERIALS SCIENCE LETTERS 21, 2002, 251­ 255 Organic-inorganic sol-gel coating, Redmond, WA, USA S. LIMMER, C. NGUYEN, G. Z. CAO Department of Materials Science and Engineering

  20. 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

  1. 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.

  2. Photo-curable siloxane hybrid material fabricated by a thiol-ene reaction of sol-gel synthesized oligosiloxanes.

    PubMed

    Kim, Joon-Soo; Yang, SeungCheol; Park, HyungJin; Bae, Byeong-Soo

    2011-06-01

    The thiol-ene reaction of a sol-gel synthesized oligosiloxane thiol-ene mixture was processed through UV irradiation, resulting in transparency, high refractive index, good thermal stability and especially excellent electrical insulation materials. It provides new strong potential of the thiol-ene system for application in dielectric materials. PMID:21537501

  3. 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…

  4. ITO/poly(aniline)/sol-gel glass: An optically transparent, pH-responsive substrate for supported lipid bilayers.

    PubMed

    Al-Obeidi, Ahmed; Ge, Chenhao; Orosz, Kristina S; Saavedra, S Scott

    2013-01-01

    Described here is fabrication of a pH-sensitive, optically transparent transducer composed of a planar indium-tin oxide (ITO) electrode overcoated with a a poly(aniline) (PANI) thin film and a porous sol-gel layer. Adsorption of the PANI film renders the ITO electrode sensitive to pH, whereas the sol-gel spin-coated layer makes the upper surface compatible with fusion of phospholipid vesicles to form a planar supported lipid bilayer (PSLB). The response to changes in the pH of the buffer contacting the sol-gel/PANI/ITO electrode is pseudo-Nernstian with a slope of 52 mV/pH over a pH range of 4-9. Vesicle fusion forms a laterally continuous PSLB on the upper sol-gel surface that is fluid with a lateral lipid diffusion coefficient of 2.2 ?m(2)/s measured by fluorescence recovery after photobleaching. Due to its lateral continuity and lack of defects, the PSLB blocks the pH response of the underlying electrode to changes in the pH of the overlying buffer. This architecture is simpler to fabricate than previously reported ITO electrodes derivatized for PSLB formation, and should be useful for optical monitoring of proton transport across supported membranes derivatized with ionophores and ion channels. PMID:25328882

  5. ELISA AND SOL-GEL BASED IMMUNOAFFINITY PURIFICATION OF THE PYRETHROID BIOALLETHRIN IN FOOD AND ENVIRONMENTAL SAMPLES

    EPA Science Inventory

    The peer-reviewed article describes the development of a new sol-gel based immunoaffinity purification procedure and an immunoassay for the pyrethroid bioallethrin. The immunoaffinity chromatography procedure was applied to food samples providing an efficient cleanup prior to im...

  6. 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.

  7. A novel tantalum-based sol-gel packed microextraction syringe for highly specific enrichment of phosphopeptides in MALDI-MS applications.

    PubMed

    Çelikb?çak, Ömür; Atakay, Mehmet; Güler, Ülkü; Salih, Bekir

    2013-08-01

    A new tantalum-based sol-gel material was synthesized using a unique sol-gel synthesis pathway by PEG incorporation into the sol-gel structure without performing a calcination step. This improved its chemical and physical properties for the high capacity and selective enrichment of phosphopeptides from protein digests in complex biological media. The specificity of the tantalum-based sol-gel material for phosphopeptides was evaluated and compared with tantalum(V) oxide (Ta2O5) in different phosphopeptide enrichment applications. The tantalum-based sol-gel and tantalum(V) oxide were characterized in detail using FT-IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), and also using a surface area and pore size analyzer. In the characterization studies, the surface morphology, pore volume, crystallinity of the materials and PEG incorporation into the sol-gel structure to produce a more hydrophilic material were successfully demonstrated. The X-ray diffractograms of the two different materials were compared and it was noted that the broad signals of the tantalum-based sol-gel clearly represented the amorphous structure of the sol-gel material, which was more likely to create enough surface area and to provide more accessible tantalum atoms for phosphopeptides to be easily adsorbed when compared with the neat and more crystalline structure of Ta2O5. Therefore, the phosphopeptide enrichment performance of the tantalum-based sol-gels was found to be remarkably higher than the more crystalline Ta2O5 in our studies. Phosphopeptides at femtomole levels could be selectively enriched using the tantalum-based sol-gel and detected with a higher signal-to-noise ratio by matrix-assisted laser desorption/ionization-mass spectrometer (MALDI-MS). Moreover, phosphopeptides in a tryptic digest of non-fat bovine milk as a complex real-world biological sample were retained with higher yield using a tantalum-based sol-gel. Additionally, the sol-gel material was packed into a standard syringe (0.5 mL) to enhance the ease of use of the sol-gel material and for the elimination of additional mixing and separation procedures during the adsorption, washing and elution steps of the enrichment procedure. It was found that up to 28 phosphopeptides in milk digest were easily detectable by MALDI-MS at femtomole levels (around 20 fmol) using the microextraction syringe within less than one minute. PMID:23730683

  8. Development of Metal Casting Molds By Sol-Gel Technology Using Planetary Resources

    NASA Technical Reports Server (NTRS)

    Sibille, L.; Sen, S.; Curreri, P.; Stefanescu, D.

    2000-01-01

    Metals extracted from planetary soils will eventually need to be casted and shaped in-situ to produce useful products. In response to this challenge, we propose to develop and demonstrate the manufacturing of a specific product using Lunar and Martian soil simulants, i.e. a mold for the casting of metal and alloy parts, which will be an indispensable tool for the survival of outposts on the Moon and Mars. Drawing from our combined knowledge of sol-gel and metal casting technologies, we set out to demonstrate the extraordinary potential of mesoporous materials such as aerogels to serve as efficient casting molds as well as fulfilling numerous other needs of an autonomous planetary outpost.

  9. Optical and morphological properties of sol gel derived titanium dioxide films

    NASA Astrophysics Data System (ADS)

    Sharma, A. B.; Sharma, S. K.; M, Vishwas; Rao, K. Narasimha

    2015-08-01

    Titanium oxide (Titania) thin films were synthesized on different substrates via the sol-gel dip-coating method using alkoxide solution. Some selected samples were also prepared with different percentage of Lead (Pb). The influence of Pb addition in precursor sol on the optical properties of titanium dioxide thin films was studied. The optical transmittance in the visible region has increased with increase in weight percentage of lead. The refractive index was slightly decreased with Pb addition. Crystallization of these coatings was achieved through thermal annealing at temperatures above 400 °C. The structural properties and surface morphology of the crystallized coatings were studied by Scanning Electron Microscopy. Increase in average grain size from 250 nm to 350 nm with increase in Pb concentration is observed. Films were appeared to more coarse with increase in Pb addition. An increase in Pb addition resulted increase in average roughness from 12 nm to 25 nm.

  10. Synthesis of nano-sized lithium cobalt oxide via a sol-gel method

    NASA Astrophysics Data System (ADS)

    Li, Guangfen; Zhang, Jing

    2012-07-01

    In this study, nano-structured LiCoO2 thin film were synthesized by coupling a sol-gel process with a spin-coating method using polyacrylic acid (PAA) as chelating agent. The optimized conditions for obtaining a better gel formulation and subsequent homogenous dense film were investigated by varying the calcination temperature, the molar mass of PAA, and the precursor's molar ratios of PAA, lithium, and cobalt ions. The gel films on the silicon substrate surfaces were deposited by multi-step spin-coating process for either increasing the density of the gel film or adjusting the quantity of PAA in the film. The gel film was calcined by an optimized two-step heating procedure in order to obtain regular nano-structured LiCoO2 materials. Both atomic force microscopy (AFM) and scanning electron microscopy (SEM) were utilized to analyze the crystalline and the morphology of the films, respectively.

  11. Synthesis and characterization of biocompatible-nanohydroxyapatite crystals obtained by a modified sol-gel processing

    PubMed Central

    Figueroa, Ignacio A.; Novelo-Peralta, Omar; Flores-Morales, Carlos; González-Tenorio, Rodrigo; Piña-Barba, M. Cristina

    2012-01-01

    A modified sol-gel process for synthesizing nanocrystalline hydroxyapatite powders (nHA) for biomedical applications, using tetrahydrated calcium nitrate [Ca(NO3)2?4H2O] and phosphorous pentoxide [P2O5] as precursor, is presented and discussed. The powders were washed and heat-treated at different temperatures and then characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The total process time reached with this modified process was less than 16 h. The results showed that there was an increment in size of the HA nanocrystals (nHA) when treated at different temperatures, ranging from 30 nm for the sample treated at 600°C to 500 nm for the sample heat-treated at 1200°C. PMID:23507804

  12. Optical properties of ZnO powder prepared by using a proteic sol-gel process

    NASA Astrophysics Data System (ADS)

    Kwon, Bong-Joon; Woo, Hyun-Joo; Park, Ji-Yeon; Jang, Kiwan; Lim, Seung-Hyuk; Cho, Yong-Hoon

    2013-03-01

    We have studied the optical properties of ZnO powder synthesized by using a proteic sol-gel process with coconut water as the precursor. The energy dispersive X-ray spectrometer and X-ray diffraction results show high purity of the synthesized ZnO powder. From the low-temperature (12 K) and power-dependent PL spectra, the donor-bound exciton, the acceptor-bound exciton, the donor-to-acceptor pair (DAP), and the phonon-replica of the DAP transition have been observed at 3.38, 3.34, 3.26, and 3.19 eV, respectively. The free exciton emission (˜3.3 eV) is also observed at 300 K in the temperature-dependent PL spectra.

  13. Synthesis of high-surface-area titanium dioxide by sol-gel process for DSSC

    NASA Astrophysics Data System (ADS)

    Wahyuningsih, S.; Ramelan, A. H.; Juliana, G.; Khoirunisa, A. R.; Rahardjo, S. B.; Pramono, E.; Suharyana, S.; Suryana, R.; Supriyanto, A.

    2014-05-01

    Mesoporous TiO2 material was synthesized from dissolution ilmenite as well as from titanium chloride precursor via a sol-gel process in acidic aqueous solution. The properties of these materials were characterized with several analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), wide angle X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and Barrett-Joyner-Halenda (BJH) analysis. The mesoporous TiO2 materials calcinated at various temperatures were found to have high value surface areas. The photovoltaic of photo-anode build from the mesoporous TiO2 was characterized with I-V Keitley Multimeter, and it was found that photovoltaics fabricated using the mesoporous TiO2 have a good performance. Such a high photovoltaic activity is explained with large surface area and small crystal size.

  14. Impact of temperature on zinc oxide particle size by using sol-gel process

    SciTech Connect

    Lee, Keanchuan Ching, Dennis Ling Chuan; Saipolbahri, Zulhilmi Akmal bin; Guan, Beh Hoe E-mail: hassan.soleimani@petronas.com.my; Soleimani, Hassan E-mail: hassan.soleimani@petronas.com.my

    2014-10-24

    Zinc oxide (ZnO) nanoparticles were prepared and synthesized via sol-gel method, by using citric acid as a precursor. The impact of annealing on the particle size was investigated. Based on the results from the Thermogravimetric Analysis (TGA), three different annealing temperature which is 500, 600 and 700 °C were chosen followed by the characterization of the ZnO nanoparticle by using Powder X-Ray Diffraction (PXRD), Transmission Electron Microscopy (TEM) and Field Emission Scanning Electron Microscopy (FESEM). Results showed that the crystallite size estimated from PXRD increased with the annealing temperature which was hexagonal structure for ZnO. TEM further revealed the same tendency which the Zn NPs size also increased with the annealing temperature.

  15. Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, R.W.

    1998-04-28

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes {<=}1000 {angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

  16. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, R.W.

    1996-09-17

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes {<=}1,000{angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1,050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

  17. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, Richard W. (Pleasant Hill, CA)

    1996-01-01

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

  18. Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, Richard W. (Pleasant Hill, CA)

    1998-04-28

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000 .ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

  19. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, Richard W. (Pleasant Hill, CA)

    1995-01-01

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes.ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

  20. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, R.W.

    1995-12-19

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes{<=}1000{angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

  1. Mechanical properties of sol–gel derived SiO2 nanotubes

    PubMed Central

    Antsov, Mikk; Vlassov, Sergei; Dorogin, Leonid M; Vahtrus, Mikk; Zabels, Roberts; Lange, Sven; Lõhmus, Rünno

    2014-01-01

    Summary The mechanical properties of thick-walled SiO2 nanotubes (NTs) prepared by a sol–gel method while using Ag nanowires (NWs) as templates were measured by using different methods. In situ scanning electron microscopy (SEM) cantilever beam bending tests were carried out by using a nanomanipulator equipped with a force sensor in order to investigate plasticity and flexural response of NTs. Nanoindentation and three point bending tests of NTs were performed by atomic force microscopy (AFM) under ambient conditions. Half-suspended and three-point bending tests were processed in the framework of linear elasticity theory. Finite element method simulations were used to extract Young’s modulus values from the nanoindentation data. Finally, the Young’s moduli of SiO2 NTs measured by different methods were compared and discussed. PMID:25383292

  2. Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

    DOEpatents

    Martino, Anthony (Albuquerque, NM); Yamanaka, Stacey A. (Dallas, TX); Kawola, Jeffrey S. (Albuquerque, NM); Showalter, Steven K. (Albuquerque, NM); Loy, Douglas A. (Albuquerque, NM)

    1998-01-01

    A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5-10 nm in diameter with a monodisperse size distribution.

  3. Ionic conductivity of tantalum oxide films prepared by sol-gel process for electrochromic devices

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; He, Yongxiang; Lampert, Carl M.

    1994-09-01

    Tantalum oxide films were prepared by sol-gel process using tantalum ethoxide Ta(OC2H5)5. The dependence of deposition conditions (i.e. composition of polymeric solutions and spinning rate) on ionic conductivities for tantalum oxide films were studied. The best results achieved for films fabricated by the spin coating technique from clear polymeric solutions. These films had low packing density (rho) equals 3.2 g/cm3 and good proton conductivity (about 10-6 (Omega) -1/cm-1). X-ray photoelectron spectroscopy (XPS) was used for studying the compositions of the tantalum oxide films. We report on the use of tantalum oxide films as ion conductors in devices consisting of WO3/Ta2O5/H+ ion storage polymer structure. We found tantalum oxide to have very good properties for proton device applications.

  4. Spin-Coated Erbium-Doped Silica Sol-Gel Films on Silicon

    E-print Network

    Abedrabbo, Sufian; Shet, Sudhakar; Fiory, Anthony; Ravindra, Nuggehalli

    2012-01-01

    This work reports optical functionality contained in, as well as and produced by, thin film coatings. A sol-gel process, formulated with precursor active ingredients of erbium oxide and tetraethylorthosilicate (TEOS), was used for spin-coating thin (~130 nm) erbium-doped (~6 at. %) silica films on single-crystal silicon. Annealed films produce infrared emission in the 1.5-micron band from erbium ions in the film, as well as greatly enhancing (~100X) band-gap emission from the underlying silicon. The distinctly different mechanisms for the two modes of optical activities are interpreted in terms of optical emission theory and modeling; prospects for opto-electronic applications are discussed.

  5. Covalent Embedding of Ni2+/Fe3+ Cyanometallate Structures in Silica by Sol–Gel Processing

    PubMed Central

    Felbermair, Elisabeth; Sidorenko, Andrey; Paschen, Silke; Akbarzadeh, Johanna; Peterlik, Herwig; Schubert, Ulrich

    2014-01-01

    Compound [Ni(AEAPTS)2]3[Fe(CN)6]2 (AEAPTS=N-(2-aminoethyl)-3-aminopropyltrimethoxysilane), in which Ni2+ and Fe3+ ions are ferromagnetically coupled through cyano bridges, was prepared. Sol–gel processing of the AEAPTS derivative resulted in incorporation of the cyanometallate in silica. The obtained material is magnetically ordered below 22?K with an effective magnetic moment ?eff of 4.46??B at room temperature, a maximum of 8.60??B at approximately 15?K and a narrow hysteresis at 2?K, with a saturation remanence of about 300?emu?mol?1 and a coercitivity of 0.03?T. PMID:24867432

  6. Photoluminescence from terbium doped silica-titania prepared by a sol-gel method

    SciTech Connect

    Ismail, Adel Ali; Abboudi, Mostafa . E-mail: abboudi14@hotmail.com; Holloway, Paul; El-Shall, Hassan

    2007-01-18

    Terbium doped (0.5 at.%) TiO{sub 2}-SiO{sub 2} (30%/70%) was prepared by a sol-gel method. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the powder calcined at two different temperatures. At a low temperature of 550 deg. C an amorphous phase was obtained, but at a higher temperature of 1000 deg. C, the anatase TiO{sub 2} phase was crystallized in the amorphous SiO{sub 2} phase. Green photoluminescence from ultraviolet excitation was detected after heating to either temperature, but the amorphous sample heated to 550 deg. C exhibited a higher intensity. X-ray diffraction and photoluminescence excitation data are discussed to explain these observations.

  7. Thermo-optic coefficient in some hybrid organic/inorganic fast sol-gel glasses

    NASA Astrophysics Data System (ADS)

    Pokrass, M.; Burshtein, Z.; Gvishi, R.

    2010-07-01

    We have investigated the effect of organic content in hybrid organic/inorganic glasses prepared by the sol-gel process on the thermo-optic coefficient dn/ dT. The organic phase consisted of homogeneously dispersed methyl groups within an inorganic silica matrix. Analysis of Fresnel reflectance temperature dependence of an optically polished sample-surface yielded the desired value, with an accuracy of 10 -5/°C. A negative linear dependence of the thermo-optic coefficient on the volumetric thermal expansion coefficient ? was obtained, dn/ dT[10 -4/°C] = -1.1-0.45 ?[10 -4/°C]. Using Prod'homme's model, a negative value was derived for the electronic polarizability coefficient ? = (-1.8 ± 0.3) × 10 -4/°C. The negative sign of ? is attributed to isolation of the silica matrix sections by the methyl groups, causing the sections to distance upon increase in temperature.

  8. Integrated ultrasonic transducers made by the sol gel spray technique for structural health monitoring

    NASA Astrophysics Data System (ADS)

    Kobayashi, M.; Jen, C.-K.; Moisan, J.-F.; Mrad, N.; Nguyen, S. B.

    2007-04-01

    Integrated piezoelectric-based ultrasonic transducers (UTs) have been developed for potential structural health monitoring. Fabrication techniques and performance evaluation of these transducers at selected monitoring sites are presented. Our novel transducer fabrication approach focuses on the use of handheld and readily accessible equipment to perform sol-gel spray coating, including the use of a heat gun or a torch, to carry out drying and firing, poling and electrode fabrication. The application of these integrated UTs for thickness measurement of graphite/epoxy composites, thickness monitoring of ice build up on aluminum plates at low temperatures, viscosity measurement of a cooling oil flow at temperatures up to 160 °C and monitoring metal debris in cooling oil engines is demonstrated.

  9. Integrated optics structures on sol-gel derived organic-inorganic hybrids for optical communications

    NASA Astrophysics Data System (ADS)

    André, P. S.; Vicente, C. M. S.; Fernandes, V.; Marques, C. A. F.; Pecoraro, E.; Nogueira, R. N.; Wada, N.; Carlos, L. D.; Marques, P. G.; Ferreira, R. A. S.

    2011-05-01

    Organic-inorganic hybrid materials are a technologically key class of advanced multifunctional materials that fulfil the challenging strict requirements of the beginning of the century: higher levels of sophistication, miniaturisation, recyclability, reliability and low energy consumption with potential to be used as low-cost components in optical networks operating at high bit rates. In this work, high-rejection optical filters (19 dB) first-order Bragg gratings inscribed in channel waveguides written in thin films of sol-gel derived organic-inorganic hybrid based on methacrylic acid modified zirconium tetrapropoxide, Zr(OPrn)4, (so-called di-ureasils), using UV-laser direct-write method.

  10. Solar heat reflective glass by nanostructured sol-gel multilayer coatings

    NASA Astrophysics Data System (ADS)

    Nagamedianova, Z.; Ramírez-García, R. E.; Flores-Arévalo, S. V.; Miki-Yoshida, M.; Arroyo-Ortega, M.

    2011-10-01

    New 3-layer near-infrared reflective glasses were prepared by coating clear float soda-lime glass with nanostructured TiO 2 and SiO 2 films using a dip coating technique. Reflective interference filters at NIR region (800-1000 nm) were designed by simulation and prepared onto 4 mm clear glass. Optical, microstructural and mechanical properties were determined for the coated glasses. 3-layer sol-gel glasses show high visible transmittance >70% combined with high solar reflectance about 30% (with reflectivity up to 60% at region from 800 to 950 nm) and high UV blockage (transmittance <35%). Due to good abrasion resistance of the filters, application for monolithic windows in automotive and architectural areas is promising.

  11. Towards new levels for stacking of sol-gel functional coatings.

    PubMed

    Dieudonné, X; Vallé, K; Belleville, P

    2011-08-15

    High optical performance coatings prepared by a liquid deposition process have been studied with focus on the parameters playing a role on the layer stacking ability. During the development of multilayer optical coatings, defects such as cracks, scattering and a refractive index gradient could appear. In order to understand the origins of these limitations, the investigation was performed on colloidal stacks of single and multi-materials. This study has rendered it possible to define the main process parameters as well as the physical and chemical parameters of the suspensions influencing the stacking capacity. This work is a first step to obtaining evidence of a relationship between the thin film microstructure induced by deposition conditions and the ability to achieve sol-gel thick films with good optical (homogeneous) and mechanical (crack-free) properties. PMID:21934999

  12. Boron doping effects in electrochromic properties of NiO films prepared by sol-gel

    SciTech Connect

    Lou, Xianchun; Zhao, Xiujian; He, Xin

    2009-12-15

    In this paper, NiO films doped with B{sub 2}O{sub 3} were first prepared by sol-gel. The effects of boron content on the structure and electrochromic properties of NiO films were studied with X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetric (CV) and UV-vis spectrophotometer, respectively. In addition, the roughness and phase of the bleached/colored were studied by atom force microscopy (AFM). B-doped prevent the crystallization of the films. The colored state transmittance could be significantly lowered when the boron added. The NiO film doped with boron exhibited a noticeable electrochromism with a variation of transmittance up to {proportional_to}60% at the wavelength range of 300-500 nm. (author)

  13. Electrical and Optical Properties of Copper Oxide Thin Films by Sol-Gel Technique

    NASA Astrophysics Data System (ADS)

    Hashim, H.; Shariffudin, S. S.; Saad, P. S. M.; Ridah, H. A. M.

    2015-11-01

    Copper oxide were prepared by sol-gel technique and deposited onto quartz substrates as thin films using spin coating method. The aim of this research was to study the effects of different spin coating speeds of copper oxide thin films on the electrical and optical properties of the thin films. Five samples of copper oxide thin films with different spin coating speeds of 1000, 1500, 2000, 2500 and 3000 rpm were annealed at 600°C for 30 minutes. UV-Vis spectrophotometer and two-point probe technique were used to characterize the optical and electrical properties of the deposited films. Based on the results obtained, it revealed that the electrical conductivity of the copper oxide thin films reduce as the spin coating speeds increase. The calculated optical band gap and the resistivity of the copper oxide thin films also decrease when the spin coating speeds are increased.

  14. Biocompatibility and Reduced Drug Absorption of Sol-Gel-Treated PDMS for Microfluidic Cell Culture Applications

    PubMed Central

    Gomez-Sjoberg, Rafael; Leyrat, Anne A.; Houseman, Benjamin T.; Shokat, Kevan; Quake, Stephen R.

    2010-01-01

    Poly(dimethyl siloxane) (PDMS) -based microfluidic devices are now commonly used for a wide variety of biological experiments, including cell culture assays. However, the porous, hydrophobic polymer matrix of PDMS rapidly absorbs small hydrophobic molecules, including hormones and most small-molecule drugs. This makes it challenging to perform experiments that require such substances in PDMS microfluidic devices. This study presents evidence that a sol-gel treatment of PDMS that fills the polymer matrix with silica nanoparticles is effective at reducing the absorption of drugs into the material while preserving its biocompatibility, transparency, and oxygen permeability. We show that the absorption of two anti-cancer drugs, Camptothecin and a kinase inhibitor, is reduced to such an extent that on-chip microfluidic cell culture experiments can recapitulate the results obtained off-chip. PMID:20936785

  15. Surfactant-assisted sol-gel synthesis of forsterite nanoparticles as a novel drug delivery system.

    PubMed

    Hassanzadeh-Tabrizi, S A; Bigham, Ashkan; Rafienia, Mohammad

    2016-01-01

    In the present study, forsterite nanoparticles were synthesized via surfactant-assisted sol-gel method using cetyltrimethyl ammonium bromide (CTAB) as a surfactant. The effects of CTAB contents and heat treatment on the textural properties and drug release from nanoparticles were investigated. The synthesized powders were studied by X-ray diffraction, Fourier transform infrared spectra, Brunauer-Emmett-Teller surface area analysis and transmission electron microscope images. Mg2SiO4 materials demonstrated mesoporous characteristics and large specific surface area ranging from 159 to 30m(2)/g. The TEM results showed that forsterite nanorods had diameters about 4nm and lengths ranging from 10 to 60nm. It was found that the samples with 6g CTAB show slower drug release rate than the other specimens, which is due to smaller pore size. This study revealed that the drug delivery of forsterite can be tailored by changing the amount of surfactant. PMID:26478366

  16. Sol-gel synthesis and densification of aluminoborosilicate powders. Part 1: Synthesis

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey; Selvaduray, Guna; Leiser, Daniel

    1992-01-01

    Aluminoborosilicate powders high in alumina content were synthesized by the sol-gel process utilizing various methods of preparation. Properties and microstructural effects related to these syntheses were examined. After heating to 600 C for 2 h in flowing air, the powders were amorphous with the metal oxides comprising 87 percent of the weight and uncombusted organics the remainder. DTA of dried powders revealed a T(sub g) at approximately 835 C and an exotherm near 900 C due to crystallization. Powders derived from aluminum secbutoxide consisted of particles with a mean diameter 5 microns less than those from aluminum isopropoxide. Powders synthesized with aluminum isopropoxide produced agglomerates comprised of rod shaped particulates while powders made with the secbutoxide precursor produced irregular glassy shards. Compacts formed from these powders required different loadings for equivalent densities according to the method of synthesis.

  17. Synthesis of Novel Nanostructured Lanthanum Cobalt Ferrite Mixed Metal Oxides by Sol-Gel

    NASA Astrophysics Data System (ADS)

    Teresita, V. Mary; Jeseentharani, V.; Josephine, B. Avila; Antony, S. Arul

    2013-02-01

    Properties of nanoscale materials are very interesting and these are either comparable to or superior to those of bulk. These materials are interesting due to their exciting size dependent optical, electronic, magnetic, thermal, mechanical and chemical properties. Different mole ratios of nanostructured mixed metal oxides of LaCoxFe1-xO3-? (x = 0 to 1) were prepared by the sol-gel method by varying the mole ratios of iron and cobalt substrates. The compounds were sintered for 700°C in the tubular furnace for 8 h. The purity of the compounds was analyzed by TG-DTA. The compounds were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM) studies were employed to study the structural phases, vibrational frequencies, surface morphology of the highest humidity sensing compounds.

  18. Tailoring the oxidation state of cobalt through halide functionality in sol-gel silica

    PubMed Central

    Olguin, Gianni; Yacou, Christelle; Smart, Simon; Diniz da Costa, João C.

    2013-01-01

    The functionality or oxidation state of cobalt within a silica matrix can be tailored through the use of cationic surfactants and their halide counter ions during the sol-gel synthesis. Simply by adding surfactant we could significantly increase the amount of cobalt existing as Co3O4 within the silica from 44% to 77%, without varying the cobalt precursor concentration. However, once the surfactant to cobalt ratio exceeded 1, further addition resulted in an inhibitory mechanism whereby the altered pyrolysis of the surfactant decreased Co3O4 production. These findings have significant implications for the production of cobalt/silica composites where maximizing the functional Co3O4 phase remains the goal for a broad range of catalytic, sensing and materials applications. PMID:24022785

  19. Durable superhydrophobic and antireflective surfaces by trimethylsilanized silica nanoparticles-based sol-gel processing.

    PubMed

    Manca, Michele; Cannavale, Alessandro; De Marco, Luisa; Aricò, Antonino S; Cingolani, Roberto; Gigli, Giuseppe

    2009-06-01

    We present a robust and cost-effective coating method to fabricate long-term durable superhydrophobic andsimultaneouslyantireflective surfaces by a double-layer coating comprising trimethylsiloxane (TMS) surface-functionalized silica nanoparticles partially embedded into an organosilica binder matrix produced through a sol-gel process. A dense and homogeneous organosilica gel layer was first coated onto a glass substrate, and then, a trimethylsilanized nanospheres-based superhydrophobic layer was deposited onto it. After thermal curing, the two layers turned into a monolithic film, and the hydrophobic nanoparticles were permanently fixed to the glass substrate. Such treated surfaces showed a tremendous water repellency (contact angle = 168 degrees ) and stable self-cleaning effect during 2000 h of outdoor exposure. Besides this, nanotextured topology generated by the self-assembled nanoparticles-based top layer produced a fair antireflection effect consisting of more than a 3% increase in optical transmittance. PMID:19466786

  20. Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

    DOEpatents

    Martino, A.; Yamanaka, S.A.; Kawola, J.S.; Showalter, S.K.; Loy, D.A.

    1998-09-29

    A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis are disclosed. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5--10 nm in diameter with a monodisperse size distribution. 1 fig.

  1. Dynamical transition of heat transport in a physical gel near the sol-gel transition.

    PubMed

    Kobayashi, Kazuya U; Oikawa, Noriko; Kurita, Rei

    2015-01-01

    We experimentally study heat transport in a gelatin solution near a reversible sol-gel transition point where viscosity strongly depends on temperature. We visualize the temperature field and velocity field using thermochromic liquid crystals and polystyrene latex particles, respectively. During the initial stages of heating, we find that heat transport undergoes a dynamical transition from conductive to convective. Subsequently, during later stages, we observe that the transport dynamics are much more complex than conventional thermal convections. At the sample's surface we observe the formation of stagnant domains, which lack fluid flow. Their formation is not due to the effects of local cooling. We determine that it is the dynamics of these stagnant domains that induce convective-conductive-convective transitions. PMID:26690696

  2. Superparamagnetic calcium ferrite nanoparticles synthesized using a simple sol-gel method for targeted drug delivery.

    PubMed

    Sulaiman, N H; Ghazali, M J; Majlis, B Y; Yunas, J; Razali, M

    2015-08-17

    The calcium ferrite nano-particles (CaFe2O4 NPs) were synthesized using a sol-gel method for targeted drug delivery application. The proposed nano-particles were initially prepared by mixing calcium and iron nitrates that were added with citric acid in order to prevent agglomeration and subsequently calcined at a temperature of 550°C to obtain small particle size. The prepared nanoparticles were characterized by using an XRD (X-ray diffraction), which revealed the configuration of orthorhombic structures of the CaFe2O4 nano-particles. A crystallite size of ~13.59 nm was obtained using a Scherer's formula. Magnetic analysis using a VSM (Vibrating Sample Magnetometer analysis), revealed that the synthesized particles exhibited super-paramagnetic behavior having magnetization saturation of approximately 88.3emu/g. Detailed observation via the scanning electron microscopy (SEM) showed the calcium ferrite nano-particles were spherical in shape. PMID:26405858

  3. Physical Properties of Potassium Phosphate Glass Prepared by Sol Gel Method

    SciTech Connect

    Mat, Noorhidayah Che; Sahar, Md Rahim; Pauzi, Safwan Ahmad

    2010-07-07

    Series of glasses based on Al{sub 2}O{sub 3}-K{sub 2}O-P{sub 2}O{sub 5} have successfully been made by sol gel method. The amorphous state has been confirmed by X-ray diffraction (XRD) while the actual composition has been determined using Energy Dispersive X-ray (EDX) analysis. The glass density is determined using Archimedes method while the Vickers Micro hardness Test has been used to measure the hardness. It is found that all the samples are amorphous in nature with their actual composition contained phosphate in the range of 40-53% mol. It is also observed that the glass density is about 2.4 gcm{sup -3} while the hardness is in the range of 40-100 Hv, depending on composition.

  4. Nanorods of Various Oxides and Hierarchically Structured Mesoporous Silica by Sol-Gel Electrophoresis

    SciTech Connect

    Limmer, Steven J.; Hubler, Timothy L.; Cao, Guozhong

    2003-01-02

    In this paper, we report the template-based growth of nanorods of oxides and hierarchically structured mesoporous silica, formed by means of a combination of sol-gel processing and elecrophoretic deposition. Both single metal oxides (TiO2) and complex oxides (Pb(Zr0.52Ti0.48)O3) have been grown by this method. This method has also been applied to the growth of nanorods of mesoporous silica having an ordered pore structure, where the pores are aligned parallel to the long axis of the nanorod. Uniformly sized nanorods of about 125-200 nm in diameter and 10 um in length were grown over large areas with near unidirectional alignment. Appropriate sol preparation yielded the desired stoichiometric chemical composition and crystal structure of the oxide nanorods, with a heat treatment (500-700 C for 15-30 min) for crystallization, densification and any necessary pyrolysis.

  5. Dynamical transition of heat transport in a physical gel near the sol-gel transition

    PubMed Central

    Kobayashi, Kazuya U.; Oikawa, Noriko; Kurita, Rei

    2015-01-01

    We experimentally study heat transport in a gelatin solution near a reversible sol-gel transition point where viscosity strongly depends on temperature. We visualize the temperature field and velocity field using thermochromic liquid crystals and polystyrene latex particles, respectively. During the initial stages of heating, we find that heat transport undergoes a dynamical transition from conductive to convective. Subsequently, during later stages, we observe that the transport dynamics are much more complex than conventional thermal convections. At the sample’s surface we observe the formation of stagnant domains, which lack fluid flow. Their formation is not due to the effects of local cooling. We determine that it is the dynamics of these stagnant domains that induce convective-conductive-convective transitions. PMID:26690696

  6. Investigation of the Peroxovanadate Sol-Gel Process and Characterization of the Gels

    SciTech Connect

    Craig Joseph Fontenot

    2001-12-31

    In general, the peroxovanadate solution sol-gel process can be thought of as consisting of two parts: (1) the decomposition of the peroxo species and (2) cation hydrolysis leading to gelation. By controlling the synthesis conditions, both layered and amorphous compounds can be created. However, the type of water coordination observed in these gels was found to be identical no matter what the long-range order. The current work clarified many of the discrepancies found in the literature and offered much new valuable information. Highlights include the types of vanadium environments present at various stages of hydration, the role of adsorbed water, oxygen exchange from adsorbed water into the gel sites, and the ability to create metastable VMoO solid solution phases. These results could have a variety of impacts on future catalysis research.

  7. Anti-Stokes photoluminescence in Ga/Bi co-doped sol-gel silica glass.

    PubMed

    Laguta, Oleksii; Hamzaoui, Hicham El; Bouazaoui, Mohamed; Arion, Vladimir B; Razdobreev, Igor

    2015-04-01

    Unusual temperature dependence of the anti-Stokes photoluminescence (ASPL) at 734 nm was found in Ga/Bi co-doped sol-gel silica glass. While in the temperature range of 450-873 K, the behavior of ASPL is completely determined by the thermal population of the excited state levels, its intensity is continuously increasing with decreasing temperature in the range of 77-430 K. By measuring the pump power dependence of ASPL at 300 K, we show that the latter can be described via the two-step intracenter excitation process and subsequent relaxation. Based on the measurements of temperature dependence of the excitation spectra of near infrared band (at 1140 nm) and that corresponding to the ASPL (at 734 nm), we propose a simple rate equation model to explain the unusual behavior of ASPL. PMID:25831392

  8. Encapsulation of proteins in transparent porous silicate glasses prepared by the sol-gel method.

    PubMed

    Ellerby, L M; Nishida, C R; Nishida, F; Yamanaka, S A; Dunn, B; Valentine, J S; Zink, J I

    1992-02-28

    Novel sol-gel synthetic techniques were used to immobilize copper-zinc superoxide dismutase (CuZnSOD), cytochrome c, and myoglobin (Mb) by encapsulation in stable, optically transparent, porous silica glass matrices under mild conditions such that the biomolecules retained their characteristic reactivities and spectroscopic properties. The resulting glasses allowed transport of small molecules into and out of the glasses at reasonable rates but nevertheless retained the protein molecules within their pores. Chemical reactions of the immobilized proteins could be monitored by means of changes in their visible absorption spectra. Silica glasses containing the immobilized proteins were observed to have similar reactivities and spectroscopic properties to those found for the proteins in solution. For example, encapsulated CuZnSOD was demetallated and remetallated, encapsulated ferricytochrome c was reduced and then reoxidized, and encapsulated met Mb was reduced to deoxy Mb and then reacted either with dioxygen to make oxy Mb or with carbon monoxide to make carbonyl Mb. PMID:1312257

  9. Bandgap Modulation in ZnO Through Doping By Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Singh, Amanpal; Walia, Kiran; Kumar, Dinesh; Khanna, P. K.; Kumar, Anuj; Kumar, Mukesh

    2011-07-01

    Zinc oxide is a promising optical material for possible application in solid state lighting. Highly transparent and nanocrystalline Zinc Oxide thin films with different concentration of Cadmium and Magnesium are deposited on corning 7059 glass by sol-gel spin coating method. The transparent and homogeneous sol of 0.2 mol/l concentration is prepared by dissolving zinc acetate dihydrate in 2-methoxyethanol. Monoethanolamine is used as sol stabilizer. The calculated amounts of cadmium acetate dihydrarte and magnesium acetate tetrahydrarte are added for doping. All the samples are annealed at 550 °C in air ambient for an hour. The doping is confirmed by X-ray diffraction and the bandgap is measured by UV-Vis spectroscopy. The bandgap successfully modulated from near ultraviolet region (3.29 eV) to far ultraviolet region (3.83 eV).

  10. Spectroscopic study of protoporphyrin IX zinc(II) encapsulated in sol-gel glass.

    PubMed

    Zaitoun, Mohammed A

    2005-06-01

    Previous studies indicated that the organization of native porphyrins and their intentionally designated derivatives in solid substrates is of current interest because of the biological and practical importance of these compounds. In this paper, we report herein for the first time the incorporation of a functionalized diacid, protoporphyrin IX Zn(II) (Zn-pp-IX), successfully in a silica based transparent organic-inorganic hybrid material by choosing proper alkoxy silane containing amino-group via the sol-gel method. The entrapped guest was diagnosed using UV-vis sectrophotometry, emission spectroscopy, and infrared spectrometry; the properties of the encapsulated porphyrin were compared to those of the compound in solution. The results indicate that Zn-pp-IX is well distributed and homogeneously in the glass. PMID:15863039

  11. Optical and electrochemical properties of vanadium pentoxide porous film prepared by sol-gel technique

    NASA Astrophysics Data System (ADS)

    She, Shi-Feng; Wu, Guang-Ming; Yang, Hui-Yu; Shen, Jun; Gao, Guo-Hua

    2011-02-01

    Thin films of V2O5, especially vanadium oxide films with nano- and micro-structures, perform well as cathode material for Li ion batteries and charge storage devices. Thin films of V2O5 with different porosity were obtained by dip-coating sol-gel technique. V2O5 sols were prepared by dissolution of V2O5 powder in benzyl alcohol and isopropyl alcohol in proper proportion. Optical property and porosity of films were characterized by FTIR and ellipsometer. Electrochemical characterization was recorded by chronopotentiometry(CP) and cyclic voltammetry(CV). Furthermore, the study shows that the porous structures of V2O5 films had an effect on the stability and reversibility of the films.

  12. Optical and electrochemical properties of vanadium pentoxide porous film prepared by sol-gel technique

    NASA Astrophysics Data System (ADS)

    She, Shi-Feng; Wu, Guang-Ming; Yang, Hui-Yu; Shen, Jun; Gao, Guo-Hua

    2010-10-01

    Thin films of V2O5, especially vanadium oxide films with nano- and micro-structures, perform well as cathode material for Li ion batteries and charge storage devices. Thin films of V2O5 with different porosity were obtained by dip-coating sol-gel technique. V2O5 sols were prepared by dissolution of V2O5 powder in benzyl alcohol and isopropyl alcohol in proper proportion. Optical property and porosity of films were characterized by FTIR and ellipsometer. Electrochemical characterization was recorded by chronopotentiometry(CP) and cyclic voltammetry(CV). Furthermore, the study shows that the porous structures of V2O5 films had an effect on the stability and reversibility of the films.

  13. DEVELOPMENT OF A FABRICATION PROCESS FOR SOL-GEL/METAL HYDRIDE COMPOSITE GRANULES

    SciTech Connect

    Hansen, E; Eric Frickey, E; Leung Heung, L

    2004-02-23

    An external gelation process was developed to produce spherical granules that contain metal hydride particles in a sol-gel matrix. Dimensionally stable granules containing metal hydrides are needed for applications such as hydrogen separation and hydrogen purification that require columns containing metal hydrides. Gases must readily flow through the metal hydride beds in the columns. Metal hydrides reversibly absorb and desorb hydrogen and hydrogen isotopes. This is accompanied by significant volume changes that cause the metal hydride to break apart or decrepitate. Repeated cycling results in very fine metal hydride particles that are difficult to handle and contain. Fine particles tend to settle and pack making it more difficult to flow gases through a metal hydride bed. Furthermore, the metal hydrides can exert a significant force on the containment vessel as they expand. These problems associated with metal hydrides can be eliminated with the granulation process described in this report. Small agglomerates of metal hydride particles and abietic acid (a pore former) were produced and dispersed in a colloidal silica/water suspension to form the feed slurry. Fumed silica was added to increase the viscosity of the feed slurry which helped to keep the agglomerates in suspension. Drops of the feed slurry were injected into a 27-foot tall column of hot ({approx}70 C), medium viscosity ({approx}3000 centistokes) silicone oil. Water was slowly evaporated from the drops as they settled. The drops gelled and eventually solidified to form spherical granules. This process is referred to as external gelation. Testing was completed to optimize the design of the column, the feed system, the feed slurry composition, and the operating parameters of the column. The critical process parameters can be controlled resulting in a reproducible fabrication technique. The residual silicone oil on the surface of the granules was removed by washing in mineral spirits. The granules were dried in air at 40 C. The granules were heated to 230 C for 30 minutes in argon to remove the remaining water and organic materials. The resulting product was spherical composite granules (100 to 2000 micron diameter) with a porous silica matrix containing small agglomerates of metal hydride particles. Open porosity in the silica matrix allows hydrogen to permeate rapidly through the matrix but the pores are small enough to contain the metal hydride particles. Additional porosity around the metal hydride particles, induced using abietic acid as a pore former, allows the particles to freely expand and contract without fracturing the brittle sol-gel matrix. It was demonstrated that the granules readily absorb and desorb hydrogen while remaining integral and dimensionally stable. Microcracking was observed after the granules were cycled in hydrogen five times. The strength of the granules was improved by coating them with a thin layer of a micro-porous polymer sol-gel that would allow hydrogen to freely pass through the coating but would filter out metal hydride poisons such as water and carbon monoxide. It was demonstrated that if a thin sol-gel coating was applied after the granules were cycled, the coating not only improved the strength of the granules but the coated granules retained their strength after additional hydrogen cycling tests. This additional strength is needed to extend the lifetime of the granules and to survive the compressive load in a large column of granules. Additional hydrogen adsorption tests are planned to evaluate the performance of coated granules after one hundred cycles. Tests will also be performed to determine the effects of metal hydride poisons on the granules. The results of these tests will be documented in a separate report. The process that was developed to form these granules could be scaled to a production process. The process to form granules from a mixture of metal hydride particles and pore former such as abietic acid can be scaled up using commercial granulators. The current laboratory-scale external gelation column produc

  14. Magnetization and Magnetocaloric Effect in Sol-Gel Derived Nanocrystalline Copper-Zinc Ferrite.

    PubMed

    Anwar, M S; Ahmed, Faheem; Koo, Bon Heun

    2015-02-01

    We report the sol-gel synthesis and magnetocaloric effect in nanocrystalline copper-zinc ferrite (Cu0.5Zn0.5Fe2O4). The synthesized powder was characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and magnetization measurements. The XRD results confirm the formation of single phase spinel structure. The average particle size was found to be ~58 nm. FE-SEM results suggested that the nanoparticles are agglomerated and spherical in shape. Magnetization measurement reveals that Cu0.5Zn0.5Fe2O4 nanoparticles exhibit transition temperature (Tc) above room temperature. The maximum magnetic entropy change (?SM)max shows interesting behaviour and was found to vary with the applied magnetic field. This nanopowder can be considered as potential material for magnetic refrigeration above room temperature. PMID:26353670

  15. Hydroxyapatite/alumina nanocrystalline composite powders synthesized by sol-gel process for biomedical applications

    NASA Astrophysics Data System (ADS)

    Khorsand, S.; Fathi, M. H.; Salehi, S.; Amirkhanlou, S.

    2014-10-01

    Hydroxyapatite/alumina nanocrystalline composite powders needed for various biomedical applications were successfully synthesized by sol-gel process. Structural and morphological investigations of the prepared composite powders were performed using X-ray diffractometer (XRD), scanning electron microscopy (SEM), X'Pert HighScore software, and Clemex Vision image analysis software. The results show that the crystallite size of the obtained composite powders is in the range of 25 to 90 nm. SEM evaluation shows that the obtained composite powders have a porous structure, which is very useful for biomedical applications. The spherical nanoparticles in the range of 60 to 800 nm are embedded in the agglomerated clusters of the prepared composite powders.

  16. Sol-gel synthesis and characterization of ?-Fe2O3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Raja, K.; Mary Jaculine, M.; Jose, M.; Verma, Sunil; Prince, A. A. M.; Ilangovan, K.; Sethusankar, K.; Jerome Das, S.

    2015-10-01

    The ?-Fe2O3 nanoparticles have been successfully synthesized via sol-gel technique. The lattice parameters, the lattice strain and crystallite size were investigated by X-ray diffraction (XRD) analysis. Fourier transform infrared spectroscopy (FT-IR) analysis has been carried out to confirm the presence of functional groups. Using UV-visible spectrum, the optical band gap energy is estimated as 2.55 eV. The morphology and chemical composition of the ?-Fe2O3 nanoparticles were examined by high resolution scanning electron microscopy (HR-SEM) and energy dispersive X-ray diffraction analysis (EDX) respectively. The hysteresis loop was traced out using vibration sample magnetometer and the values of coercivity and saturation magnetization are found out to be 3891 G and 0.4193 emu/g respectively.

  17. Protective hybrid sol gel coatings containing bioactive particles on surgical grade stainless steel: Surface characterization

    NASA Astrophysics Data System (ADS)

    Ballarre, Josefina; López, Damián A.; Schreiner, Wido H.; Durán, Alicia; Ceré, Silvia M.

    2007-06-01

    Metallic materials are the most used materials as orthopaedic or dental implants for their excellent mechanical properties. However, they are not able to create a natural bonding with the mineralized bone and they could release metallic particles that could finally end in the removal of the implant. One way to avoid these effects is to protect the metallic implant with a biocompatible coating. In this work there are analyzed two kinds of protective organic-inorganic sol-gel made coatings with the adding of glass-ceramic particles with the aim of generating bioactivity. The samples are surface characterized by SEM, XRD and XPS. Amorphous hydroxyapatite (aHAp) deposited on the samples after 30 days of immersion in simulated body fluid (SBF) is detected on the samples and its presence is considered as a first signal of bioactivity.

  18. Synthesis and characterization of vinyl-bridged polysilsesquioxane sol-gel materials

    SciTech Connect

    Yamanaka, S.A.; Carpenter, J.P.; McClain, M.D.; Loy, D.A.

    1995-08-01

    Vinyl-bridged polysilsesquioxane gels were formed through the use of sol-gel polymerization methods. Acid- and base-catalyzed samples were prepared from both the pure cis-(l) and pure trans-(2) isomers of 1, 2-bis(triethoxysilyl)ethylene. Gelation times of the two isomers were compared. The trans monomer 2 formed gels within a week while the cis monomer I failed to gel-even after several months. Gelation of 1 could be promoted by the addition of a coordinating metal such as palladium. The resulting cis- and trans- vinyl-bridged polysilsesquioxane gels were then processed either by vacuum drying to afford xerogels or by extracting with supercritical carbon dioxide to afford aerogels. These vinylbridged polysilsesquioxanes were characterized by SEM, nitrogen sorption porosimetry, solid State {sub 29}Si and {sub 13}C NMR and x-ray powder diffraction.

  19. Sol-gel processing of highly transparent conducting Cd2SnO4 thin films

    NASA Astrophysics Data System (ADS)

    Bel-Hadj-Tahar, Radhouane; Bel-Hadj-Tahar, Noureddine; Belhadj Mohamed, Abdellatif

    2015-03-01

    Polycrystalline thin films of cadmium stannate (Cd2SnO4) (CTO) were coated on corning glass substrates by sol-gel method. The films were fired at different temperatures and annealed in inert ambient (N2) at 680°C. The structural, optical, and electrical properties of dip-coated cadmium-tin-oxide (CTO) thin films are discussed. CTO layers with a Hall mobility of 30 cm2/Vs and a carrier density of 1.4 × 1021 cm-3 resulting in a resistivity of 5 × 10-4 ? cm have been deposited. Dip-coating conditions must be carefully monitored to produce consistent films. The high electronic conductivity is due to two effective mechanisms of n-type doping: (i) stoichiometric deviation and (ii) self-doping.

  20. Sol-gel deposition of iridium oxide for biomedical micro-devices.

    PubMed

    Nguyen, Cuong M; Rao, Smitha; Yang, Xuesong; Dubey, Souvik; Mays, Jeffrey; Cao, Hung; Chiao, Jung-Chih

    2015-01-01

    Flexible iridium oxide (IrOx)-based micro-electrodes were fabricated on flexible polyimide substrates using a sol-gel deposition process for utilization as integrated pseudo-reference electrodes for bio-electrochemical sensing applications. The fabrication method yields reliable miniature on-probe IrOx electrodes with long lifetime, high stability and repeatability. Such sensors can be used for long-term measurements. Various dimensions of sol-gel iridium oxide electrodes including 1 mm × 1 mm, 500 µm × 500 µm, and 100 µm × 100 µm were fabricated. Sensor longevity and pH dependence were investigated by immersing the electrodes in hydrochloric acid, fetal bovine serum (FBS), and sodium hydroxide solutions for 30 days. Less pH dependent responses, compared to IrOx electrodes fabricated by electrochemical deposition processes, were measured at 58.8 ± 0.4 mV/pH, 53.8 ± 1.3 mV/pH and 48 ± 0.6 mV/pH, respectively. The on-probe IrOx pseudo-reference electrodes were utilized for dopamine sensing. The baseline responses of the sensors were higher than the one using an external Ag/AgCl reference electrode. Using IrOx reference electrodes integrated on the same probe with working electrodes eliminated the use of cytotoxic Ag/AgCl reference electrode without loss in sensitivity. This enables employing such sensors in long-term recording of concentrations of neurotransmitters in central nervous systems of animals and humans. PMID:25686309

  1. Fluorescence of Pentavalent Chromium in SiO2 Sol-Gel Glasses

    NASA Technical Reports Server (NTRS)

    Jia, Weiyi; Castro, Lymari; Wang, Yanyun; Liu, Huimin

    1998-01-01

    Chromium ions are very attractive to optical spectroscopy and laser physics. It is well known that the first laser in the history is a ruby laser activated with Cr(3+). It was found in early nineties that Cr(4+) was also an interesting lasing ion in the near infrared, and various Cr(4+) lasers have been developed. Very recently, it was reported that Cr(2+) doped in CdSe crystals showed lasing action in the infrared. The above achievement have stimulated an interest in searching for Cr(5+) and investigating its optical properties. Cr(5+) is isoelectronic with Ti(3+) and V(4+), having electron configuration 3d1. Ti(3+) is the active center of commercial cw and femtosecond sapphire lasers, tunable in the range 680-1100 nm. V(4+) doped in YAlO3 and Al2O3 showed broad band emission near 635 nm. Although EPR results of Cr(5+) were reported, the optical properties were less studied. Herren et al. reported an observation of luminescence from Cr doped in SiO2 sol-gel glass. The luminescence spectrum was assigned to pentavalent ions in their first paper, and later it was identified to be the emission from the charge transfer transition of Cr(6+). The first observation of photoluminescence from octahedrally coordinated Cr(5+) in BaCaMg aluminate glasses was reported very recently. In this work, we report luminescence results of Cr doped SiO2 sol-gel glasses. The fluorescence spectra are very different from Herrens' results, and we believe it originates from pentavalent Cr.

  2. Spectroscopic properties of Tm3+/Al3+ co-doped sol-gel silica glass

    NASA Astrophysics Data System (ADS)

    Wang, Xue; Lou, Fengguang; Wang, Shikai; Yu, Chunlei; Chen, Danping; Hu, Lili

    2015-04-01

    Tm3+/Al3+ co-doped silica glass was prepared by sol-gel method combined with high temperature sintering. Glasses with compositions of xTm2O3-15xAl2O3-(100 - 16x) SiO2 (in mol%, x = 0.1, 0.3, 0.5, 0.8 and 1.0) were prepared. The high thulium doped silica glass was realized. Their spectroscopic parameters were calculated and analyzed by Judd-Ofelt theory. Large absorption cross section (4.65 × 10-21 cm2 at 1668 nm) and stimulated emission cross section (6.00 × 10-21 cm2 at 1812 nm), as well as low hydroxyl content (0.180 cm-1), long fluorescence lifetime (834 ?s at 1800 nm), large ?em × ?rad (30.05 × 10-21 cm2 ms) and large relative intensity ratio of the 1.8 ?m (3F4 ? 3H6) to 1.46 (3H4 ? 3F4) emissions (90.33) are achieved in this Tm3+/Al3+ co-doped silica glasses. According to emission characteristics, the optimum thulium doping concentration is around 0.8 mol%. The cross relaxation (CR) between ground and excited states of Tm3+ ions was used to explain the optimum thulium doping concentration. These results suggest that the sol-gel method is an effective way to prepare Tm3+ doped silica glass with high Tm3+ doping and prospective spectroscopic properties.

  3. Sol-Gel Deposition of Iridium Oxide for Biomedical Micro-Devices

    PubMed Central

    Nguyen, Cuong M.; Rao, Smitha; Yang, Xuesong; Dubey, Souvik; Mays, Jeffrey; Cao, Hung; Chiao, Jung-Chih

    2015-01-01

    Flexible iridium oxide (IrOx)-based micro-electrodes were fabricated on flexible polyimide substrates using a sol-gel deposition process for utilization as integrated pseudo-reference electrodes for bio-electrochemical sensing applications. The fabrication method yields reliable miniature on-probe IrOx electrodes with long lifetime, high stability and repeatability. Such sensors can be used for long-term measurements. Various dimensions of sol-gel iridium oxide electrodes including 1 mm × 1 mm, 500 ?m × 500 ?m, and 100 ?m × 100 ?m were fabricated. Sensor longevity and pH dependence were investigated by immersing the electrodes in hydrochloric acid, fetal bovine serum (FBS), and sodium hydroxide solutions for 30 days. Less pH dependent responses, compared to IrOx electrodes fabricated by electrochemical deposition processes, were measured at 58.8 ± 0.4 mV/pH, 53.8 ± 1.3 mV/pH and 48 ± 0.6 mV/pH, respectively. The on-probe IrOx pseudo-reference electrodes were utilized for dopamine sensing. The baseline responses of the sensors were higher than the one using an external Ag/AgCl reference electrode. Using IrOx reference electrodes integrated on the same probe with working electrodes eliminated the use of cytotoxic Ag/AgCl reference electrode without loss in sensitivity. This enables employing such sensors in long-term recording of concentrations of neurotransmitters in central nervous systems of animals and humans. PMID:25686309

  4. Pr(III) luminescence enhancement by chelation in solution and in sol-gel glass

    NASA Astrophysics Data System (ADS)

    Zaitoun, M. A.; El-Qisairi, A. K.; Momani, K. A.; Qaseer, H. A.; Jaradat, Q. M.

    2015-02-01

    Due to the weak emission of lanthanide ions in solution, it is common practice to form complexes of the lanthanide ions with organic ligands that strongly absorbs light and transfers the energy to the lanthanide ion center via the antenna effect. The organic ligands 2-6-pyridinedicarboxylate (L1) and the polytonic diazine (N-N) ligand L2 (C22H16N12O2) were used to synthesize two Pr(III) complexes, namely: Pr-L1 (Na3[Pr(C7H3NO4)3]) and Pr-L2. The prepared complexes were further encapsulated in an optically transparent sol-gel glass. The synthesized ligands and complexes were characterized by FTIR and 1H NMR. Room temperature luminescence of Pr-L1 and Pr-L2 complexes in solution and in sol-gel glass were investigated using a spectrofluorometer. Excitation at the maximum absorption wavelength of the ligands (280 nm) resulted in the typical visible luminescence (centered at around 600 nm) resulting from the 1D2 ? 3H4 transition of the Pr(III) ion, which contributes to the efficient energy transfer from the absorbing ligand L1 to the chelated Pr(III) ion (an antenna effect) while the Pr(III) luminescence is not efficiently sensitized by ligand L2. The obtained emission spectra indicated that the excitation energy level for the central Pr(III) is in a slightly lower location than ligand L1 excitation triplet (T1) level and can accept the energy transfer from T1 efficiently.

  5. Pr(III) luminescence enhancement by chelation in solution and in sol-gel glass.

    PubMed

    Zaitoun, M A; El-Qisairi, A K; Momani, K A; Qaseer, H A; Jaradat, Q M

    2014-10-28

    Due to the weak emission of lanthanide ions in solution, it is common practice to form complexes of the lanthanide ions with organic ligands that strongly absorbs light and transfers the energy to the lanthanide ion center via the antenna effect. The organic ligands 2-6-pyridinedicarboxylate (L1) and the polytonic diazine (N-N) ligand L2 (C22H16N12O2) were used to synthesize two Pr(III) complexes, namely: Pr-L1 (Na3[Pr(C7H3NO4)3]) and Pr-L2. The prepared complexes were further encapsulated in an optically transparent sol-gel glass. The synthesized ligands and complexes were characterized by FTIR and (1)H NMR. Room temperature luminescence of Pr-L1 and Pr-L2 complexes in solution and in sol-gel glass were investigated using a spectrofluorometer. Excitation at the maximum absorption wavelength of the ligands (280nm) resulted in the typical visible luminescence (centered at around 600nm) resulting from the (1)D2?(3)H4 transition of the Pr(III) ion, which contributes to the efficient energy transfer from the absorbing ligand L1 to the chelated Pr(III) ion (an antenna effect) while the Pr(III) luminescence is not efficiently sensitized by ligand L2. The obtained emission spectra indicated that the excitation energy level for the central Pr(III) is in a slightly lower location than ligand L1 excitation triplet (T1) level and can accept the energy transfer from T1 efficiently. PMID:25467665

  6. Formulation and Performance of Novel Energetic Nanocomposites and Gas Generators Prepared by Sol-Gel Methods

    SciTech Connect

    Clapsaddle, B J; Zhao, L; Prentice, D; Pantoya, M L; Gash, A E; Satcher Jr., J H; Shea, K J; Simpson, R L

    2005-03-24

    In the field of composite energetic materials, properties such as ingredient distribution, particle size, and morphology affect both sensitivity and performance. Since the reaction kinetics of composite energetic materials are typically controlled by the mass transport rates between reactants, one would anticipate new and potentially exceptional performance from energetic nanocomposites. We have developed a new method of making nanostructured energetic materials, specifically explosives, propellants, and pyrotechnics, using sol-gel chemistry. A novel sol-gel approach has proven successful in preparing nanostructured metal oxide materials. By introducing a fuel metal, such as aluminum, into the nanostructured metal oxide matrix, energetic materials based on thermite reactions can be fabricated. Two of the metal oxides are tungsten trioxide and iron(III) oxide, both of which are of interest in the field of energetic materials. Due to the versatility of the preparation method, binary oxidizing phases can also be prepared, thus enabling a potential means of controlling the energetic properties of the subsequent nanocomposites. Furthermore, organic additives can also be easily introduced into the nanocomposites for the production of nanostructured gas generators. The resulting nanoscale distribution of all the ingredients displays energetic properties not seen in its micro-scale counterparts due to the expected increase of mass transport rates between the reactants. The unique synthesis methodology, formulations, and performance of these materials will be presented. The degree of control over the burning rate of these nanocomposites afforded by the compositional variation of a binary oxidizing phase will also be discussed. These energetic nanocomposites have the potential for releasing controlled amounts of energy at a controlled rate. Due to the versatility of the synthesis method, a large number of compositions and physical properties can be achieved, resulting in energetic nanocomposites that can be fabricated to meet specific safety and environmental considerations.

  7. Spectroscopic behavior of hybrid materials obtained by the sol-gel technique

    NASA Astrophysics Data System (ADS)

    Sokolnicki, J.; Wiglusz, R.; Radzki, S.; Graczyk, A.; Legendziewicz, J.

    2004-07-01

    The need for new, chemically and physically stable luminescent materials operating with UV excitations has stimulated research on luminescence properties of doped sol-gel material. In this work we present technology of production of silica gels doped with organic molecules, lanthanide compounds and organic/inorganic composites. Optical properties of these materials as functions of temperature, concentration and excitation wavelength are presented. Dynamics of the excited states is discussed based on the decay times and emission efficiencies data. Mechanisms of ligand-to-metal energy transfer as well as other processes affecting emission efficiency are considered. Silica sol-gels doped with di-aminoacid derivatives of porphyrins: PP(Ser) 2(Arg) 2, PP(Ala) 2(Arg) 2, PP(Met) 2(Arg) 2, where Met, Arg and Ser denote methionine, serine and arginine aminoacids, respectively, and H 2TTMePP {tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine} have been obtained and spectroscopically studied. The samples emit only from the lowest excited singlet state (S 1). Intensity of this emission depends on the concentration of the active molecule and time of the exposition to the excitation beam. The sample containing PP(Ser) 2 (Arg) 2 co-doped with Tb(III) ions exhibits only 5D 4 emission from the metal center. When co-doped with Pr(III) ions it displays only the S 1 emission and it has been shown that the metal ions affect the S 2 ? S 1 internal conversion. These materials can find applications as phosphors or sensors of UV irradiation. The efforts have been undertaken also to obtain chiral anisotropic materials.

  8. Sol-gel based optical sensor for determination of Fe (II): A novel probe for iron speciation

    NASA Astrophysics Data System (ADS)

    Samadi-Maybodi, Abdolraouf; Rezaei, Vida; Rastegarzadeh, Saadat

    2015-02-01

    A highly selective optical sensor for Fe (II) ions was developed based on entrapment of a sensitive reagent, 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ), in a silica sol-gel thin film coated on a glass substrate. The thin films fabricated based on tetraethoxysilane (TEOS) as precursor, sol-gel pH ? 3, water:alkoxyde ratio of 4:1 and TPTZ concentration of 0.112 mol L-1. The influence of sol-gel parameters on sensing behavior of the fabricated sensor was also investigated. The fabricated sensor can be used for determination of Fe (II) ion with an outstanding high selectivity over a dynamic range of 5-115 ng mL-1 and a detection limit of 1.68 ng mL-1. It also showed reproducible results with relative standard deviation of 3.5% and 1.27% for 10 and 90 ng mL-1 of Fe (II), respectively, along with a fast response time of ?120 s. Total iron also was determined after reduction of Fe (III) to Fe (II) using ascorbic acid as reducing agent. Then, the concentration of Fe (III) was calculated by subtracting the concentration of Fe (II) from the total iron concentration. Interference studies showed a good selectivity for Fe (II) with trapping TPTZ into sol-gel matrix and appropriately adjusting the structure of doped sol-gel. The sensor was compared with other sensors and was applied to determine iron in different water samples with good results.

  9. Sol-gel based optical sensor for determination of Fe (II): a novel probe for iron speciation.

    PubMed

    Samadi-Maybodi, Abdolraouf; Rezaei, Vida; Rastegarzadeh, Saadat

    2015-02-01

    A highly selective optical sensor for Fe (II) ions was developed based on entrapment of a sensitive reagent, 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ), in a silica sol-gel thin film coated on a glass substrate. The thin films fabricated based on tetraethoxysilane (TEOS) as precursor, sol-gel pH?3, water:alkoxyde ratio of 4:1 and TPTZ concentration of 0.112 mol L(-1). The influence of sol-gel parameters on sensing behavior of the fabricated sensor was also investigated. The fabricated sensor can be used for determination of Fe (II) ion with an outstanding high selectivity over a dynamic range of 5-115 ng mL(-1) and a detection limit of 1.68 ng mL(-1). It also showed reproducible results with relative standard deviation of 3.5% and 1.27% for 10 and 90 ng mL(-1) of Fe (II), respectively, along with a fast response time of ?120 s. Total iron also was determined after reduction of Fe (III) to Fe (II) using ascorbic acid as reducing agent. Then, the concentration of Fe (III) was calculated by subtracting the concentration of Fe (II) from the total iron concentration. Interference studies showed a good selectivity for Fe (II) with trapping TPTZ into sol-gel matrix and appropriately adjusting the structure of doped sol-gel. The sensor was compared with other sensors and was applied to determine iron in different water samples with good results. PMID:25448981

  10. The validity of the kinetic collection equation revisited - Part 3: Sol-gel transition under turbulent conditions

    NASA Astrophysics Data System (ADS)

    Alfonso, L.; Raga, G. B.; Baumgardner, D.

    2012-01-01

    In a coagulating system, a sol-gel transition occurs when a single giant particle (a gel) arises under certain conditions and begins to consume the mass of smaller but higher populated fraction (the sol). This single giant particle (also known as a runaway particle) is detached from the continuous spectrum. Since the kinetic collection equation (KCE) only models the evolution of the continuous size of the spectrum, as the largest particle continue to grow by accretion of smaller ones, the liquid water content predicted by the KCE will decrease. In this paper, the sol-gel transition is proposed as the mechanism that forms the large droplets that are needed to trigger warm rain development in cumulus clouds. By using a collection kernel enhanced by turbulence and a stochastic simulation method, the formation of a runaway droplet is modeled through the turbulent collection process. The model results show that the sol-gel transition (also called gelation) leads to the formation of a droplet with mass comparable to the mass of the initial system. The time when the sol-gel transition occurs is estimated with a Monte Carlo method when the parameter ? (the ratio of the standard deviation for the largest droplet mass over all the realizations to the averaged value) reaches its maximum value. Moreover, we show that without turbulence, the sol-gel transition will not occur. In the context of theoretical cloud microphysics, gelation can be interpreted as the formation of the "lucky droplet" that grows at a much faster rate than the rest of the droplet population and subsequently becomes the embryo for raindrops.

  11. Molybdenum chloride incorporated sol-gel materials for oxygen sensing above room temperature

    NASA Astrophysics Data System (ADS)

    Osborn, D. J., III

    Maximizing the efficiency of the combustion process requires the ability to sense oxygen levels over a broad range of concentrations with fast response times under rapidly varying conditions of pressure and temperature to maintain the correct fuel/oxygen ratio in real-time. Quenching of the luminescence from organometallic compounds by oxygen has been used to develop a number of fiber-based sensors. A major drawback of these organometallic indicators for combustion applications is that the chromophores degrade with time, have a limited operational temperature range, typically room temperature +/-25°C, and lack long-term reliability. This work investigates luminescent molybdenum clusters based on Mo6Cl12 were as replacements for organometallic indicators. A study of the high temperature stability of Mo6Cl 12 in air revealed irreversible changes in the optical absorption spectrum at T >250°C and a loss of the red luminescence characteristic of the pristine clusters. Thermal aging experiments run in air and under nitrogen point to oxidation of the clusters as the cause of the change in optical properties. X-ray powder diffraction measurements on samples annealed at 300°C under controlled conditions are consistent with oxidation of Mo6Cl 12 to form MoO3. Optical and thermal aging experiments show that K2Mo6Cl14•1H2O, the alkali metal salt of Mo6Cl12, has higher thermal stability and remains luminescent after long-term aging in air at 280°C. Methods were developed for depositing K2Mo6Cl14•1H 2O-incorporated sol--gel films on planar and optical fiber substrates by dip coating and spray coating. The mechanical properties of the films depended on the film thickness; thin films were stable, but cracks often formed in the thicker films needed for sensors. This problem was addressed using two strategies: altering the components of the sol--gel solutions used to embed the clusters and by devising a composite approach to sensing layers where a slurry of fully cured sol--gel particles containing K2Mo 6Cl14•1H2O in a sol--gel "binder" were deposited on substrates. The optical properties of a large number of fiber sensors were tested up to 102°C, with the best results obtained using the K2Mo6Cl14•1H2O/sol--gel composite sensing film. Fiber M demonstrated quenching of 4--6x between <0.001% and 21.1% (v/v) oxygen at 23, 42, 60, 81 and 102°C respectively. The sensor switches abruptly between two well defined levels with a response time of less than 10 s. Quenching of the cluster luminescence by oxygen obeys a two-site Stern-Volmer relationship based on measurements of fiber 121 at 42, 73, and 102°C, with sensitivity decreasing as temperature increases. The cycle-cycle variations for six cycles between nitrogen and oxygen at 58°C for fiber 45 corresponds to an uncertainty of +/-1% to +/-15% in oxygen concentration over the entire measurement range from 21.1% (v/v) to 2.1% (v/v) oxygen respectively. The long-term performance data from cycling fiber 70 between <0.001% (v/v) and 21.1% (v/v) oxygen for 14 hours was stable over the entire period and variations in sensor signal were found to be synchronous with the temperature fluctuations in the flow through cell. The magnitude of the sensor signal up to 102°C is ~3-nW for ~300 microW of incident excitation power. For the current 15-cm long fiber sensor, the autofluorescence (0.011 nW) is 40x smaller than the signal (~ 0.4 nW) in 20% (v/v) oxygen.

  12. 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.

  13. Sol-Gel Process for Making Pt-Ru Fuel-Cell Catalysts

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram; Valdez, Thomas; Kumta, Prashant; Kim, Y.

    2005-01-01

    A sol-gel process has been developed as a superior alternative to a prior process for making platinum-ruthenium alloy catalysts for electro-oxidation of methanol in fuel cells. The starting materials in the prior process are chloride salts of platinum and ruthenium. The process involves multiple steps, is time-consuming, and yields a Pt-Ru product that has relatively low specific surface area and contains some chloride residue. Low specific surface area translates to incomplete utilization of the catalytic activity that might otherwise be available, while chloride residue further reduces catalytic activity ("poisons" the catalyst). In contrast, the sol-gel process involves fewer steps and less time, does not leave chloride residue, and yields a product of greater specific area and, hence, greater catalytic activity. In this sol-gel process (see figure), the starting materials are platinum(II) acetylacetonate [Pt(C5H7O2)2, also denoted Pt-acac] and ruthenium(III) acetylacetonate [Ru(C5H7O2)3, also denoted Ru-acac]. First, Pt-acac and Ru-acac are dissolved in acetone at the desired concentrations (typically, 0.00338 moles of each salt per 100 mL of acetone) at a temperature of 50 C. A solution of 25 percent tetramethylammonium hydroxide [(CH3)4NOH, also denoted TMAH] in methanol is added to the Pt-acac/Ruacac/ acetone solution to act as a high-molecular-weight hydrolyzing agent. The addition of the TMAH counteracts the undesired tendency of Pt-acac and Ru-acac to precipitate as separate phases during the subsequent evaporation of the solvent, thereby helping to yield a desired homogeneous amorphous gel. The solution is stirred for 10 minutes, then the solvent is evaporated until the solution becomes viscous, eventually transforming into a gel. The viscous gel is dried in air at a temperature of 170 C for about 10 hours. The dried gel is crushed to make a powder that is the immediate precursor of the final catalytic product. The precursor powder is converted to the final product in a controlled-atmosphere heat treatment. Desirably, the final product is a phase-pure (Pt phase only) Pt-Ru powder with a high specific surface area. The conditions of the controlled- atmosphere heat are critical for obtaining the aforementioned desired properties. A typical heat treatment that yields best results for a catalytic alloy of equimolar amounts of Pt and Ru consists of at least two cycles of heating to a temperature of 300 C and holding at 300 C for several hours, all carried out in an atmosphere of 1 percent O2 and 99 percent N2. The resulting powder consists of crystallites with typical linear dimensions of <10 nm. Tests have shown that the powder is highly effective in catalyzing the electro-oxidation of methanol.

  14. Structural and magnetic properties of magnesium ferrite nanoparticles prepared via EDTA-based sol-gel reaction

    NASA Astrophysics Data System (ADS)

    Hussein, Shaban I.; Elkady, Ashraf S.; Rashad, M. M.; Mostafa, A. G.; Megahid, R. M.

    2015-04-01

    Magnesium ferrite (MgFe2O4) nanoparticles have been prepared, for the first time, by ethylene diamine tetraacetic acid (EDTA)-based sol-gel combustion method. The prepared ferrite system is calcined at 400, 500 and 600 °C. Thermo-gravimetric and differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometry (VSM) were applied for elucidating the structural and magnetic properties of the prepared system. XRD patterns revealed that the prepared system have two spinel MgFe2O4 structures, namely cubic and tetragonal phases that are dependent on calcination temperature (Tc). The crystallite sizes varied from 8.933 to 41.583 nm, and from 1.379 to 292.565 nm for the cubic and tetragonal phases respectively depending on Tc. The deduced lattice parameters for the cubic and (tetragonal) systems are a=8.368, 8.365 and 8.377 and (a=7.011, 5.922, 5.908 and c=6.622, 8.456, 8.364) Å at Tc=400, 500 and 600 °C respectively. While the cation distribution of the cubic phase is found to be mixed spinel and Tc-dependent, it is an inverse spinel in the tetragonal phase where the Fe3+ ions occupy both the tetrahedral A- and octahedral B-sites in almost equal amount; the Mg2+ ions are found to occupy only the B-sites. The HRTEM and selected-area electron diffraction (SAED) revealed the detailed morphology of the nanoparticles, and confirmed their crystalline spinel structure. VSM indicated the existence of an appreciable fraction of superparamagnetic particles at room temperature, with pure superparamagnetic behavior observed for samples calcined at 400 °C. Besides, the magnetic properties are found to change by thermal treatment as a result of the varied phase concentration, cation distribution and lattice parameters. Thus, the new synthesis route used in this study by applying EDTA as an organic precursor for preparing MgFe2O4 nanoparticles at rather low temperatures proved to be efficient in obtaining nanoparticles with favorable structural and magnetic properties. Such properties would qualify them for several potential applications including e.g. in hyperthermia treatment, as contrast agents in magnetic resonance imaging (MRI), and in ferroelastomers technology.

  15. A computational study of the structure and physical properties of sol-gel derived porous silica

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Sudin

    This dissertation endeavors to provide a comprehensive analysis of structure-property relationships in nano-porous materials, using silica aerogels as a model. Key to this study was the generation of realistic structures. Therefore, molecular dynamics simulations based on a reactive three-body potential with charge-transfer were used to reproduce the sol-gel condensation process that underlies the formation of these nano-porous gels. First we characterize the geometry of the simulated gel structure. The inherent self-similarity in these structures was established by evaluating the fractal dimension df from geometric correlations. Comparing the fractal dimensions of condensed gels with those of porous structures produced by rupturing dense silica glass, it was found that the fractal dimension is lower for the reacted gels than for the ruptured silica, indicating a wider pore size distribution for the former material. Supercritical drying of aerogels was modeled by a gradual extraction of water from the system with simultaneous relaxation of pressure, and found to have a negligible impact on df. The ruptured silica systems, on the other hand, undergo significant changes in density and fractal dimension upon pressure relaxation. The degree of branching in these disordered structures was measured in terms of the connectivity dimension: the ratio of the fractal dimension of the minimum path spanning the network to the fractal dimension of the entire structure. Unlike the fractal dimension df, the connectivity dimension is similar for the reacted and ruptured structures, suggesting that the degree of branching is independent of the generating process. Next, to study the effect of the chemical environment on gel structure, the sol-gel condensation process was simulated in an aqueous environment with varying water-to-silicon ratio r. A high value of r deters the condensation process, possibly by promoting the reverse (hydrolysis) reaction. Simulations reveal three distinct growth regimes in gel formation, depending on the system density and the water-to-silicon ratio. These regimes result in different structures, including (i) compact silica clusters with radius of gyration 5--17 A, (ii) well-percolated network structures, and (iii) branched clusters of widely varying size. Finally, a detailed investigation of the mechanical behavior of reacted gels and ruptured porous silica was undertaken. The structural stability of the condensed gels, as revealed by the change in their fractal dimension during supercritical drying, is strongest for the percolated network structures of regime (ii). The evolution of the bulk modulus and Young's modulus of the ruptured silica with density is well described by power-law scaling. (Abstract shortened by UMI.)

  16. Journal of Sol-Gel Science and Technology 36, 510, 2005 c 2005 Springer Science + Business Media, Inc. Manufactured in the United States.

    E-print Network

    Ghosh, Ruby N.

    Journal of Sol-Gel Science and Technology 36, 5­10, 2005 c 2005 Springer Science + Business Media dispersed in a polymer matrix at the tip of the fiber, the polymer/lumophore com- posite must have high

  17. Pre dye treated titanium dioxide nanoparticles synthesized by modified sol-gel method for efficient dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Ananth, S.; Vivek, P.; Arumanayagam, T.; Murugakoothan, P.

    2015-06-01

    Pure and pre dye treated titanium dioxide nanoparticles were prepared by sol-gel and modified sol-gel methods, respectively. The pre dye treatment has improved the properties of TiO2, such as uniform dye adsorption, reduced agglomeration, improved morphology and less dye aggregation. The brazilein pigment-rich Caesalpinia sappan heartwood extract was used as natural dye sensitizer for pure and pre dye treated TiO2 nanoparticles. Low cost and environment friendly dye-sensitized solar cells (DSSC) fabricated using pure and pre dye treated TiO2 nanoparticles sensitized by natural dye showed solar light to electron conversion efficiencies of 1.09 and 1.65 %, respectively. The pre dye treated TiO2-based DSSC showed 51 % improvement in efficiency when compared to that of conventionally prepared DSSC.

  18. Sintering and microstructure of silicon carbide ceramic with Y3Al5O12 added by sol-gel method.

    PubMed

    Guo, Xing-Zhong; Yang, Hui

    2005-03-01

    Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 1860 degrees C with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal 'bridging'. PMID:15682507

  19. Characterization and photoluminescence properties of sol-gel derived Bi2MoO6:Eu3+ phosphor

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Han, Bing; Li, Pengju; Li, Jianliang; Bian, Yang

    2015-05-01

    This work first reported the characterization and photoluminescence properties of Eu3+ doped Bi2MoO6 phosphor prepared by sol-gel method. The phosphor was characterized by X-ray diffraction, field emission scanning electron microscopic, fourier transform infrared spectrum, and fluorescence spectroscopy measurements in order to investigate the phase purity, surface morphology, and photoluminescence properties. The spectroscopic characteristics including excitation and emission spectrum, decay curve, and chromaticity coordinates were discussed. The as-prepared phosphor can be effectively excited with 345/465 nm light, and exhibit red emission belonging to the prevailing 5 D 0 ? 7 F 2 transition of Eu3+ with decay time of milliseconds. The above spectral characteristics indicate sol-gel derived Bi2MoO6:Eu3+ phosphor could be regarded as a potential red phosphor for application in white light-emitting diodes (w-LEDs) based on ultraviolet (UV)/blue LED chips.

  20. Sol–gel immobilization as a suitable technique for enhancement of ?-amylase activity of Aspergillus oryzae PP

    PubMed Central

    Evstatieva, Yana; Yordanova, Mariya; Chernev, Georgi; Ruseva, Yanislava; Nikolova, Dilyana

    2014-01-01

    Bioencapsulation of microbial cells in silica-based matrices has proved to be a good strategy to enhance the biosynthetic capabilities and viability of bioproducers. In the present study, mycelium and pellet cultures of strain Aspergillus oryzae PP were successfully immobilized in sol–gel hybrid matrices composed of tetraethylorthosilicate as an inorganic precursor, 5% (w/v) starch and 10 or 15% (w/v) polyethylene oxide, or 10% (w/v) calcium alginate as organic compounds. Biosynthetic activity of immobilized cultures was investigated by batch and fed-batch cultivation and the obtained results of 3042.04 IU cm?3 were comparable with the enzyme activity of the free cell culture. Immobilized cultures retained their viability and biosynthetic capabilities up to the 744th h during fed-batch fermentation processes. Consequently, sol–gel encapsulation in hybrid matrices could be considered as a promising technique for immobilization of Aspergillus oryzae PP in order to increase the ?-amylase production.

  1. Improved stability of organic-inorganic composite emitting film with sol-gel glass encapsulated Eu-complex

    NASA Astrophysics Data System (ADS)

    Fukuda, Takeshi; Yamauchi, Shuhei; Honda, Zentaro; Kijima, Naoto; Kamata, Norihiko

    2009-11-01

    A high-stability organic-inorganic composite emitting film has been realized via a sol-gel process using an optimized silane alkoxide and Eu-complex. We found that the long-term and thermal stabilities were improved by using a combined starting solution of phenyltrimethoxysilane and tetrametoxysilane as encapsulating agent. The resulting emitting film exhibited sharp red-luminescence under ultraviolet (UV) excitation and a high transparency in the visible wavelength region. In addition, no decrease in photoluminescence (PL) quantum yield was observed after thermal treatment up to 180 °C, and the reduction in PL intensity during UV irradiation was suppressed by encapsulating the Eu-complex within the sol-gel derived silica glass.

  2. On the sol-gel synthesis of strontium-titanate thin films and the prospects of their use in electronics

    SciTech Connect

    Sohrabi Anaraki, H.; Gaponenko, N. V. Rudenko, M. V.; Guk, A. F.; Zavadskij, S. M.; Golosov, D. A.; Kolosnitsyn, B. S.; Kolos, V. V.; Pyatlitskij, A. N.; Turtsevich, A. S.

    2014-12-15

    Strontium-titanate films obtained by the sol-gel technique are deposited onto silicon and silicon/oxide titanium/platinum substrates. The strontium-titanate phase is detected by the method of X-ray diffraction analysis after heat treatment at temperatures of 750 and 800°C. The thickness of the films obtained by the spin-on method increases from 50 to 250 nm as the number of deposited layers is increased and is accompanied with an increase in the grain size in the films. Prospects of the development of the sol-gel technique for the formation of film components of electronic devices based on SrTiO{sub 3} xerogels are discussed.

  3. Na-A (LTA) zeolite synthesis directly from alumatrane and silatrane by sol-gel microwave techniques

    E-print Network

    Gulari, Erdogan

    a sol-gel process and microwave heating technique using alu- matrane and silatrane as precursors. After fixing the SiO2:Al2O3 ratio at 1:1 and microwave heating temperature at 110 C, increasing the Na2O concentration by adding more NaOH exponentially reduces the microwave heating time from 160 min at a Na2O:SiO2

  4. Synthesis of Mixed Ceramic MgxZn1-xO Nanofibers via Mg2+ Using Sol-Gel Electrospinning

    E-print Network

    Khan, Saad A.

    Synthesis of Mixed Ceramic MgxZn1-xO Nanofibers via Mg2+ Doping Using Sol-Gel Electrospinning Yakup of tuned energy band gap MgxZn1-xO nanofibers (NFs) with different Mg2+ content via the sol-spun ZnAc/PVA and MgAc/ZnAc/ PVA nanofibers but also the crystal microstructure and optical properties

  5. Relationship between sol-gel conditions and enzyme stability: a case study with ?-galactosidase/silica biocatalyst for whey hydrolysis.

    PubMed

    Escobar, Sindy; Bernal, Claudia; Mesa, Monica

    2015-11-01

    The sol-gel process has been very useful for preparing active and stable biocatalysts, with the possibility of being reused. Especially those based on silica are well known. However, the study of the enzyme behavior during this process is not well understood until now and more, if the surfactant is involved in the synthesis mixture. This work is devoted to the encapsulation of ?-galactosidase from Bacillus circulans in silica by sol-gel process, assisted by non-ionic Triton X-100 surfactant. The correlation between enzyme activity results for the ?-galactosidase in three different environments (soluble in buffered aqueous reference solution, in the silica sol, and entrapment on the silica matrix) explains the enzyme behavior under stress conditions offered by the silica sol composition and gelation conditions. A stable ?-galactosidase/silica biocatalyst is obtained using sodium silicate, which is a cheap source of silica, in the presence of non-ionic Triton X-100, which avoids the enzyme deactivation, even at 40 °C. The obtained biocatalyst is used in the whey hydrolysis for obtaining high value products from this waste. The preservation of the enzyme stability, which is one of the most important challenges on the enzyme immobilization through the silica sol-gel, is achieved in this study. PMID:26313518

  6. Structural and electronic properties of indium-tin-oxide sol-gel films for various post-annealing treatment

    NASA Astrophysics Data System (ADS)

    Seo, Il Wan; Noh, Miru; Lee, Y. S.; Park, J.-H.; Chung, J.-S.; Park, J. H.; Kim, Hyuk Jin; Chang, Young Jun

    2015-08-01

    We investigated the change in the electronic properties of indium-tin-oxide sol-gel thin films for various annealing temperatures ( T anneal ) up to 800 °C. The X-ray diffraction (XRD) measurement showed that the crystallinity was enhanced continuously with increasing T anneal . From the electrodynamic analysis performed by using spectroscopic ellipsometry, in accord with the XRD result, the charge carrier density of the films was found to increase, and resultantly the DC conductivity was found to increase with thermal annealing at a higher T anneal . The optical absorption in the visible region was rather sizable in relation to the quite broad feature of the interband transition near 4 eV. This implies that high-temperature thermal annealing may induce some defects inside the film. Our findings for the thermally-annealed sol-gel films are compared with the optical properties of the photo-annealed sol-gel film and the commercially-used film fabricated by using a sputtering technique.

  7. Sol-Gel-Based Titania-Silica Thin Film Overlay for Long Period Fiber Grating-Based Biosensors.

    PubMed

    Chiavaioli, Francesco; Biswas, Palas; Trono, Cosimo; Jana, Sunirmal; Bandyopadhyay, Somnath; Basumallick, Nandini; Giannetti, Ambra; Tombelli, Sara; Bera, Susanta; Mallick, Aparajita; Baldini, Francesco

    2015-12-15

    An evanescent wave optical fiber biosensor based on titania-silica-coated long period grating (LPG) is presented. The chemical overlay, which increases the refractive index (RI) sensitivity of the sensor, consists of a sol-gel-based titania-silica thin film, deposited along the sensing portion of the fiber by means of the dip-coating technique. Changing both the sol viscosity and the withdrawal speed during the dip-coating made it possible to adjust the thickness of the film overlay, which is a crucial parameter for the sensor performance. After the functionalization of the fiber surface using a methacrylic acid/methacrylate copolymer, an antibody/antigen (IgG/anti-IgG) assay was carried out to assess the performance of sol-gel based titania-silica-coated LPGs as biosensors. The analyte concentration was determined from the wavelength shift at the end of the binding process and from the initial binding rate. This is the first time that a sol-gel based titania-silica-coated LPG is proposed as an effective and feasible label-free biosensor. The specificity of the sensor was validated by performing the same model assay after spiking anti-IgG into human serum. With this structured LPG, detection limits of the order of tens of micrograms per liter (10(-11) M) are attained. PMID:26548589

  8. Complete spectrum fiber optic pH sensor based on a novel fluorescent indicator doped porous sol-gel material

    NASA Astrophysics Data System (ADS)

    Manyam, U. H.; Shahriari, Mahmoud R.; Morris, Michael J.

    1999-02-01

    A new fiber optic sensor for monitoring pH made by doping of fluorescent dyes in a sol-gel matrix is demonstrated. The indicator, 5-(and6)-carboxy-2'7'-dichlorofluorescein (CDCF), has a lower average pKa than fluorescein due to a chloride functional modification. The absorption and fluorescence spectra of the immobilized dye at various pH levels show that the indicator is sensitive over a wide pH range. Porous sol-gel coatings are used to make the probes, which are incorporated into a bifurcated fiber optic sensor. The entire absorption and fluorescence spectra are continuously monitored using a miniature fiber optic spectrophotometer. The most responsive area of the fluorescence spectrum is selected and is referenced to a point which is insensitive to pH, so that any changes due to environmental effects and fluctuations in the light source are taken into account. Two approaches for referencing are shown, one involving the back-reflected light from the excitation source, and another utilizing the co-doping of the sol-gel with a second fluorescent dye with the same absorption characteristic as CDCF but which is insensitive to pH and fluoresces at a different wavelength.

  9. Yeast-based self-organized hybrid bio-silica sol-gels for the design of biosensors.

    PubMed

    Ponamoreva, O N; Kamanina, O A; Alferov, V A; Machulin, A V; Rogova, T V; Arlyapov, V A; Alferov, S V; Suzina, N E; Ivanova, E P

    2015-05-15

    The methylotrophic Pichia angusta VKM Y-2559 and the oleaginous Cryptococcus curvatus VKM Y-3288 yeast cells were immobilized in a bimodal silica-organic sol-gel matrix comprised of tetraethoxysilane (TEOS), the hydrophobic additive methyltriethoxysilane (MTES) and the porogen polyethylene glycol (PEG). Under carefully optimized experimental conditions, employing basic catalysts, yeast cells have become the nucleation centers for a silica-organic capsule assembled around the cells. The dynamic process involved in the formation of the sol-gel matrix has been investigated using optical and scanning electron microscopic techniques. The results demonstrated the influence of the MTES composition on the nature of the encapsulation of the yeast cells, together with the architecture of the three-dimensional (3D) sol-gel biomatrix that forms during the encapsulation process. A silica capsule was found to form around each yeast cell when using 85 vol% MTES. This capsule was found to protect the microorganisms from the harmful effects that result from exposure to heavy metal ions and UV radiation. The encapsulated P. angusta BKM Y-2559 cells were then employed as a biosensing element for the detection of methanol. The P. angusta-based biosensor is characterized by high reproducibility (Sr, 1%) and operational stability, where the biosensor remains viable for up to 28 days. PMID:25201014

  10. Acid-free sol-gel fabrication of glass thin films embedded with II-VI colloidal quantum dots

    NASA Astrophysics Data System (ADS)

    Jani, Hemang; Duan, Lingze

    2015-01-01

    II-VI colloidal quantum dots (QDs) are ideal for optical sensors thanks to their high fluorescent brightness and good size uniformity. However, embedding colloidal QDs into a glass matrix with the standard sol-gel process leads to the QDs being damaged by the acid catalyst. Here, we report an acid-free sol-gel technique, which proves to be both simple and effective in fabricating silica glass thin films embedded with commercial II-VI colloidal QDs. Octadecylamine ligands are used as a bifunctional aid to not only stabilize the QDs in solution, but also assist the formation of the SiO2 gel. We demonstrate that high-quality QD-embedded glass thin films can be developed with this technique, and our fluorescent tests indicate that, except for a small blueshift in the emission spectrum, the QDs are very well preserved through the sol-gel process. This method offers a fast and low-cost path towards thin-film QD sensors with good mechanical and thermal stabilities, which are desirable for applications involving highly focused laser beams, such as ultrafast nanophotonics.

  11. Biosynthesis of sucrose-6-acetate catalyzed by surfactant-coated Candida rugosa lipase immobilized on sol-gel supports.

    PubMed

    Zhong, Xiang; Qian, Junqing; Guo, Hui; Hu, Yuanyuan; Liu, Min

    2014-05-01

    Sucrose-6-acetate is an important intermediate in the preparation of sucralose (a finest sweetener). In our study, Candida rugosa lipase coated with surfactant was firstly immobilized on sol-gel supports. Then, the immobilized enzyme was used in the regioselective synthesis of sucrose-6-acetate by transesterification of sucrose and vinyl acetate. The screening results revealed that Tween 80 was an ideal surfactant to coat lipase immobilized in sol-gel and exhibited the highest yield of sucrose-6-acetate. Other factors that influenced the yield during the preparation process were also studied. Under optimal conditions, the yield of sucrose-6-acetate could reach up to 78.68 %, while free lipase was easily inactivated in polar solvent. Thermal and operational stabilities were also improved significantly. Surfactant-coated lipase immobilized in sol-gel remained stable when the temperature was higher than 60 °C. Moreover, they could maintain high catalytic activity after six recycles. This strategy is economical, convenient and promising for the food industry. PMID:24037039

  12. Dynamics around the sol-gel transition in thermoreversible polymer gels

    NASA Astrophysics Data System (ADS)

    Mattsson, Johan; Dasgupta, Bivash; Matic, Aleksandar; Bergman, Rikard; Nystrom, Bo; Weitz, David A.

    2004-03-01

    Recently, a number of intriguing similarities have been found between the dynamical behaviour of gel- and glass-forming materials [1-3]. For instance, both the glass and gel transitions are reversible, they show typical kinetic features and occur as a result of the physical arrest of either molecules or molecular structures. An obvious difference between glasses and gels is one of length and correspondingly time scales, with those of gels being much longer than those of glasses. In order to investigate what similarities and indeed differences that exist between thermoreversible gelation and glass formation we have investigated the dynamics around the sol-gel transition in two different thermoreversibly gelling systems: poly(N-acetamido acrylamide) in water and atactic polystyrene in toluene. The studies include a wide range of experimental techniques including dynamic light scattering, diffusing wave spectroscopy, rheology, calorimetry,quasi-elastic neutron scattering and dielectric spectrocopy. The results will be discussed in the light of models and theories suggested to describe gelation in these types of systems. [1] Ren, S.Z. And Sorensen, C.M., Phys. Rev. Lett., 70, 1727 (1993) [2] Ikkai, F. and Shibayama, M., Phys. Rev. Lett. 82, 4946 (1999) [3] Kumar, S. and Douglas, J.F., Phys. Rev. Lett., 87, 188301 (2001)

  13. Study of the Photoconductivity of Zinc Oxide Nanoparticles Synthesized by a Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Pandey, Nitin; Srivastava, Rajneesh Kumar

    2015-01-01

    ZnO nanoparticles (NPs) were synthesized by use of a sol-gel method at different temperatures, and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible absorption spectroscopy. XRD analysis showed crystallite size was of the order of few tens of nanometers and the NPs had a wurtzite structure. SEM micrographs showed the NPs were pseudo-spherical in shape. UV-visible absorption study revealed a blue shift of the absorption edge compared with that of bulk ZnO. With increasing temperature of synthesis, the absorption edge was red-shifted. The photoconductivity, in air, of all the samples was studied. Variation of the dark current with applied voltage was linear for NPs synthesized at low temperatures and became super-linear for NPs synthesized at high temperatures. The dark current decreased with increasing temperature of synthesis. Photosensitivity was maximum for NPs synthesized at 600°C. Anomalous behavior, a decrease in photocurrent even during steady illumination, was observed for all the samples.

  14. Porous MnO2 prepared by sol-gel method for electrochemical supercapacitor

    NASA Astrophysics Data System (ADS)

    Bazzi, K.; Kumar, A.; Jayakumar, O. D.; Nazri, G. A.; Naik, V. M.; Naik, R.

    2015-03-01

    MnO2 has attracted great attention as material for electrochemical pseudocapacitor due to its high theoretical specific faradic capacitance (~ 1370 F .g-1) , environmental friendliness and wide potential window in both aqueous and nonaqueous electrolytes. However, the MnO2 has a low surface area which depresses its electrochemical performance. The amorphous ?-MnO2 composite was synthesized by sol gel method in the presence of the tri-block copolymer P123. Our aim is to investigate the role of P123 on the electrochemical performance of MnO2. The samples with and without P123 were prepared and characterized by x-ray diffraction (XRD), SEM, TEM and Brunauer-Emmett-Teller (BET) method. The electrochemical performances of the amorphous MnO2 composites as the electrode materials for supercapacitors were evaluated by cyclic voltammetry and AC impedance measurements in a 1M Na2SO4 solution. The results show that the sample prepared without P123 exhibited a relatively low specific capacitance of 28F .g-1, whereas the porous MnO2 prepared with P123 exhibited 117 F .g-1at 5 mV/s. The results of crystalline MnO2 composites will also be presented. The authors acknowledge the support from the Richard J. Barber Foundation for Interdisciplinary Research.

  15. TiO2 Thin Film via Sol-Gel Method: Investigation on Molarity Effect

    NASA Astrophysics Data System (ADS)

    Mohamad Saad, Puteri Sarah; Sutan, Hanis Binti; Sobihana Shariffudin, Shafinaz; Hashim, Hashimah; Mohd Noor, Uzer

    2015-11-01

    We have systematically investigated the current-voltage (I-V), absorbance and optical band gap of TiO2 thin film prepared through varying the molarity of the TiO2 precursor by sol-gel spin coating technique. In addition to the electrical and optical characteristics, the surface morphology was examined by using Atomic Force Microscope (AFM). From the image of the AFM, we were able to observe the uniformity of the TiO2 thin film. From the experimental results, we found that the uniformity of the TiO2 thin film is optimized at 0.2M sample. It is also found that, as the molarity increased, there is tendency of the resistivity to decrease. Not only that, the absorbance measurement and optical band gap also gave its best value for 0.2M sample. Therefore, in this work it is concluded that 0.20M of TiO2 gave the best characteristics for all measurements.

  16. Preparation and Characterization of Nanostructured CuO Thin Films using Sol-gel Dip Coating

    NASA Astrophysics Data System (ADS)

    Shariffudin, S. S.; Khalid, S. S.; Sahat, N. M.; Sarah, M. S. P.; Hashim, H.

    2015-11-01

    Nanostructured CuO thin films were deposited onto quartz substrates by sol-gel dip coating technique. The precursor solution was prepared by dissolving copper acetate powder into isopropanol with molarity of 0.25M. Preheating and annealing temperature were fixed at 250°C and 600°C respectively. This study focused on various film thicknesses by varying the frequent number of deposited layers. The effect of thickness on electrical, surface morphology and optical properties of CuO thin film were studied. The surface morphology was examined using field emission scanning electron microscopy (FE-SEM), surface profiler for thickness measurement, optical properties of CuO thin film were characterized by using ultraviolet- visible spectroscopy (UV-VIS) for transmittance and absorbance, and the electrical property was examined by using two point probes method. The films were found to be denser at higher film thickness due to lesser porous observed on the surface. The thickness of these CuO thin films varied from 87.14 – 253.58 nm and the direct band gap energy was observed in between 1.9 to 2.35 eV. Lowest resistivity was found for sample with a thickness of 253.58 nm.

  17. Antimicrobial activity of hemocompatible silver doped hydroxyapatite nanoparticles synthesized by modified sol-gel technique

    NASA Astrophysics Data System (ADS)

    Jadalannagari, Sushma; Deshmukh, Ketaki; Ramanan, Sutapa Roy; Kowshik, Meenal

    2013-02-01

    Silver doped hydroxyapatite (Ag x Ca100-x (PO4)6 (OH)2) nanorods were synthesized using a modified sol gel method at a low temperature of 100 °C. Silver concentration was varied as x = 1, 3 and 5. X-ray diffraction studies showed that the synthesized silver doped hydroxyapatite (Ag-HAp) was fully crystalline with hexagonal structure and an average crystallite size of 25 nm. At all the doping concentrations, the nanoparticles were rod shaped with an average length of 110-180 nm and diameter of 20-25 nm as determined from transmission electron microscopy (TEM) studies. These compounds were tested for their antimicrobial activities against E. coli (MTCC 2345) and S. aureus (MTCC 737). Antimicrobial activity was observed for all the three silver doping concentrations with the highest activity for x = 3, in terms of the zone of inhibition and the percentage reduction in the number of colonies. Hemolysis ratios for x = 1 and 3 Ag-HAp samples were below 2 %, indicating that they are highly hemocompatible and can be a promising biomaterial for tissue engineering applications in orthopedics.

  18. Synthesis of LiCoO2 epitaxial thin films using a sol-gel method

    NASA Astrophysics Data System (ADS)

    Kwon, Taeri; Ohnishi, Tsuyoshi; Mitsuishi, Kazutaka; Ozawa, Tadashi C.; Takada, Kazunori

    2015-01-01

    Epitaxial LiCoO2 films are synthesized using a sol-gel method. The precursors are aqueous solutions of acetates or nitrates of Li and Co with polyvinylpyrrolidone as a thickener. The LiCoO2 films prepared from the solutions by spin coating are epitaxially grown on sapphire (0001) substrates with c-axis orientation and in-plane alignment of LiCoO2 [ 1 1 bar 0 ] ?sapphire [100]. A two-step heat treatment of the spin-coated films consisting of preheating on a hotplate at the crystallization temperature followed by a high-temperature treatment notably promotes the c-axis orientation. In addition, the crystal orientation is controllable on different planes of the SrTiO3 substrates; the LiCoO2 films are grown with epitaxial relationships of LiCoO2 (001)?SrTiO3 (111), LiCoO2 (018)?SrTiO3 (110), and LiCoO2 (104)?SrTiO3 (100).

  19. Hydroxyfullerene as a novel coating for solid-phase microextraction fiber with sol-gel technology.

    PubMed

    Yu, Jianxin; Dong, Li; Wu, Caiying; Wu, Lin; Xing, Jun

    2002-11-29

    Hydroxyfullerene (fullerol) as a novel coating for solid-phase microextraction (SPME) fiber was first prepared by a sol-gel technology. The coating procedure involving sol solution composition and conditioning process was presented. A fullerene polysiloxane surface-bonded porous coating on the fused-silica fiber surface was obtained and confirmed by IR spectra and scanning electron microscopy. The coating has stable performance at high temperature (even to 360 degrees C) and solvents (organic and inorganic) because of the properties of fullerene and the chemical binding between the coating and the fiber surface. The extraction properties of the new coatings to less volatile organic compounds, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons and polar aromatic amines were investigated using headspace SPME coupled with GC-electron-capture detection and GC-flame ionization detection. In addition, compared with commercial SPME stationary phases, the new coatings showed higher sensitivity, faster velocities of mass transfer for aromatic compound, and possessed planarity molecular recognition for PCBs. Moreover, this fiber was firm, inexpensive, durable and can be prepared simply. The fiber-to-fiber reproducibility was very good. PMID:12458943

  20. Study of annealing time on sol-gel indium tin oxide films on glass

    SciTech Connect

    De, A.; Biswas, P.K. . E-mail: pkbiswas@cgcri.res.in; Manara, J.

    2007-07-15

    Indium and tin salt-based precursors maintaining In:Sn atomic ratio as 90:10 were utilized for the development of sol-gel dip coated indium tin oxide films (ITO) on SiO{sub 2} coated ({approx} 200 nm thickness) soda lime silica glass substrate. The gel films were initially cured in air at {approx} 450 deg. C to obtain oxide films of physical thickness {approx} 250 nm. These were then annealed in 95% Ar-5% H{sub 2} atmosphere at {approx} 500 deg. C. The annealing time was varied from 0.5 h to 5 h. Variation of annealing time did not show any considerable change of transmittance in the visible region. Thermal emissivity ({epsilon} {sub d}, 0.67-0.79) of the films were evaluated from their hemispherical spectral reflectance. These passed through a minima with increasing annealing time as the reflectivity of the films in the mid-IR passed through a maxima. The microstructure of the films revealed systematic growth of the ITO grains. XRD and XPS studies revealed the presence of both In and Sn metals in addition to the metal oxides. The energy dispersive X-ray (EDX) analysis showed little lowering of tin content in the films with increasing annealing time.

  1. Transformations in Sol-Gel Synthesized Nanoscale Hydroxyapatite Calcined Under Different Temperatures and Time Conditions

    NASA Astrophysics Data System (ADS)

    Seema, Kapoor; Uma, Batra; Suchita, Kohli

    2012-08-01

    Nano-hydroxyapatite (HAP) has been synthesized using sol-gel technique. Calcium nitrate tetrahydrate and potassium dihydrogen phosphate were used as precursors for calcium and phosphorus, respectively. A detailed study on its transformation during calcination at two crucial temperatures has been undertaken. The synthesized nanopowder was calcined at 600 and 800 °C for different time periods. The results revealed that the obtained powders after calcining at 600 and 800 °C are composed of hydroxyapatite nanoparticles. The nano-HAP powders were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, thermal gravimetric analysis (TGA), and BET surface area analyzer techniques. The results indicate that crystallite size as well as crystallinity of synthesized HAP nanopowders increase with increase in calcination temperature as well as calcination time, but the effect of temperature is more prominent as compared to that of calcination time. TEM micrograph revealed the presence of majority of HAP powder particles as agglomerates and a few as individual particles. It also revealed that HAP produced after sintering at 600 °C is 26-45 nm in size, which is well in agreement with the crystallite size calculated using XRD data. TGA study showed the thermal stability of the as-synthesized nano-HAP powder. The BET surface area decreased with increase in calcination temperature and time. The results clearly demonstrate the significant role of calcination parameters on the characteristics of nano-HAP powders.

  2. Characterization of Copper Oxide Nanoparticles Fabricated by the Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Kayani, Zohra Nazir; Umer, Maryam; Riaz, Saira; Naseem, Shahzad

    2015-10-01

    Copper oxide nanoparticles were successfully prepared by a sol-gel technique. An aqueous solution of copper nitrate Cu(NO3)2 and acetic acid was used as precursor. On addition of sodium hydroxide (NaOH) a precipitate of copper oxide was immediately formed. The copper oxide nanoparticles were characterized by use of x-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential thermal analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometry, and scanning electron microscopy (SEM). The XRD pattern contained sharp peaks of copper oxide nanoparticles with mixed cuprite and tenorite phases. Use of the Debye-Scherer equation showed that the crystallite size of the copper oxide nanoparticles increased with increasing annealing temperature. FTIR spectra revealed vibration of the CuO band at 473 cm-1; a band at 624 cm-1 was attributed to Cu2O. Maximum coercivity and saturation magnetization of the nanoparticles were 276 Oe and 0.034 emu/g, respectively. SEM micrographs of the nanoparticles revealed the presence of spherical nanoparticles of the tenorite phase whereas the cuprite phase was in the form of a compact deposit.

  3. Structural and optical characterisation of tin dioxide thin films by sol-gel dip coating technique

    NASA Astrophysics Data System (ADS)

    Lekshmy, S. Sujatha; Berlin, I. John; Maneeshya, L. V.; Anitha; Joy, K.

    2015-02-01

    Tin oxide (SnO2) thin films were deposited on quartz substrates using sol-gel dip coating technique. X-ray diffraction (XRD) pattern indicated that the film annealed in air at 350°C was amorphous in nature, whereas, the films annealed in oxygen atmosphere at 350°C showed crystalline phase. The films were further annealed in oxygen atmosphere at 450°C and 550°C. All the diffraction peaks can be indexed to the tetragonal phase of SnO2 The surface morphology (SEM) showed that surface of all films were continuous and without micro cracks. The Energy dispersive X-ray spectroscopy (EDXS) spectra indicated an increase in the concentration of oxygen content with increase in annealing temperature. The energy band gap value for the film annealed in air was 3.88 eV. The optical band gap increased to 4.05 eV when annealed in O2 atmosphere. The photoluminescence (PL) spectra showed the presence of emission peaks in UV region and visible region of the electromagnetic spectra. Transparent oxide semiconductor SnO2 film finds potential application as an active channel layer for transparent thin film transistor.

  4. SiO2 coatings on glass containing copper colloids using the sol-gel technique

    NASA Astrophysics Data System (ADS)

    Mennig, Martin; Schmitt, Mike; Kutsch, Bernd; Schmidt, Helmut K.

    1994-10-01

    A sol-gel method for the preparation of transparent copper nano particle-containing SiO2 coatings on glass has been developed. The sol is synthesized from alkoxysilanes and tetra ethyl orthosilicate with copper ammine complexes, prepared from Cu2+ salts and amino alkoxy silanes. Glass substrates are coated by dipping and layers up to 1 micrometers in thickness are obtained after thermal densification at temperatures between 200 degree(s) - 500 degree(s)C. The Cu colloid formation can be achieved using a reducing atmosphere during densification. Thus reddish-brown colored coatings on glass with optical densities between 0.5 and 2 are obtained. Under ambient air the color turns from reddish-brown to dark green. This process is reversible and by re-heating under reducing conditions the reddish-brown color can be re- established. UV-VIS absorbance measurements and structural investigations by WAXS, TEM, ESCA and SNMS show that the green color is due to an oxide layer at the colloidal interface.

  5. Synergic combination of the sol–gel method with dip coating for plasmonic devices

    PubMed Central

    Patrini, Maddalena; Floris, Francesco; Fornasari, Lucia; Pellacani, Paola; Marchesini, Gerardo; Valsesia, Andrea; Artizzu, Flavia; Marongiu, Daniela; Saba, Michele; Marabelli, Franco; Mura, Andrea; Bongiovanni, Giovanni

    2015-01-01

    Summary Biosensing technologies based on plasmonic nanostructures have recently attracted significant attention due to their small dimensions, low-cost and high sensitivity but are often limited in terms of affinity, selectivity and stability. Consequently, several methods have been employed to functionalize plasmonic surfaces used for detection in order to increase their stability. Herein, a plasmonic surface was modified through a controlled, silica platform, which enables the improvement of the plasmonic-based sensor functionality. The key processing parameters that allow for the fine-tuning of the silica layer thickness on the plasmonic structure were studied. Control of the silica coating thickness was achieved through a combined approach involving sol–gel and dip-coating techniques. The silica films were characterized using spectroscopic ellipsometry, contact angle measurements, atomic force microscopy and dispersive spectroscopy. The effect of the use of silica layers on the optical properties of the plasmonic structures was evaluated. The obtained results show that the silica coating enables surface protection of the plasmonic structures, preserving their stability for an extended time and inducing a suitable reduction of the regeneration time of the chip. PMID:25821692

  6. Optical determination of Cr(VI) using regenerable, functionalized sol-gel monoliths

    PubMed Central

    Carrington, Nathan A.; Thomas, George H.; Rodman, D. Lynn; Beach, David B.; Xue, Zi-Ling

    2007-01-01

    Transparent, pyridine-functionalized sol-gel monoliths have been formed and their use in Cr(VI) sensing applications demonstrated. The monoliths were immersed in acidic Cr(VI)-containing solutions, and the Cr(VI) uptake was monitored using UV-visible and atomic absorption spectroscopies. At concentrations at the ppm level, the monoliths exhibit a yellow color change characteristic of Cr(VI) uptake, and this can be measured by monitoring the absorption change at about 350 nm using UV-vis spectroscopy. Concentrations at the ppb level are below the limit of detection using this wavelength of 350 nm for measurement. However, by adding a diphenylcarbazide solution to monoliths that have been previously immersed in ppb-level Cr(VI) solutions, a distinct color change takes place within the gels that can be measured at about 540 nm using UV-vis spectroscopy. Concentrations as low as 10 ppb Cr(VI) can be measured using this method. The monoliths can then be regenerated for subsequent sensing cycles by thorough washing with 6.0 M HCl. The factors affecting monolith uptake of Cr(VI) have been explored. In addition, the gels have been characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) measurements. PMID:17386449

  7. Ionic conductivity of tantalum oxide films prepared by sol-gel process for electrochromic devices

    SciTech Connect

    Ozer, N.; He, Y.; Lampert, C.M.

    1994-12-31

    Tantalum oxide films were prepared by sol-gel process using tantalum ethoxide Ta(OC{sub 2}H{sub 5}){sub 5}. The dependence of deposition conditions (i.e. composition of polymeric solutions and spinning rate) on ionic conductivities for tantalum oxide films were studied. The best results achieved for films fabricated by the spin coating technique from clear polymeric solutions. These films had low packing density {rho} = 3.2 g/cm{sup 3} and good proton conductivity (about 10{sup {minus}6} {Omega}{sup {minus}1}/cm{sup {minus}1}). X-ray photoelectron spectroscopy (XPS) was used for studying the compositions of the tantalum oxide films. The authors report on the use of tantalum oxide films as ion conductors in devices consisting of WO{sub 3}/Ta{sub 2}O{sub 5}/H{sup +} ion storage polymer structure. They found tantalum oxide to have very good properties for proton device applications.

  8. Electrochromic performance of sol-gel-deposited CeO2 films

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; Cronin, John P.; Akyuz, Sevim

    1999-10-01

    Ceria (CeO2) films were prepared by a sol-gel technique onto fluorine doped tin oxide coated glass substrates. The coating solution was derived from cerium ammonium nitrate dissolved in ethanol with diethanolamine used as a complexing agent. Lithium intercalating properties of the films were investigated using cyclic voltammetry (CV) and UV-visible spectroscopy. The electrochemical examinations were performed in a 0.5 M LiClO4 propylene carbonate electrolyte. The additional film characterizations were performed in X-ray diffractometry (XRD), x-ray photoelectron spectroscopy, scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy. XRD of the films showed that they had an cerianite structure for heat treatment temperatures at or above 450 degree(s)C. The SEM examinations showed that the surface texture was uniform and homogeneous. CV examinations showed a reversible electrochemical insertion or extraction of Li+/e- ions maintaining a high optical transmissivity. Spectroelectrochemistry showed that these films can be used as optically passive counter-electrode in transmissive electrochromic devices.

  9. Preparation of amorphous Al2O3 films by the sol-gel process

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; Cronin, John P.; Tomsia, Antoni P.

    1999-10-01

    Alumina, Al2O3, films were prepared by the sol-gel process and deposited by spin coating technique. The coating solutions were synthesized by using aluminum-sec butoxide, Al(OSBu)3, as a precursor, isopropanol as a solvent, acetylacetone, AcAcH, as a chelating agent and nitric acid, HNO3 as catalyzer. Highly transparent alumina coatings with thickness in the range of 100 - 700 nm were prepared at different spinning rates and heat treated at 400 degree(s)C. The morphology, microstructure, transmittance characteristics of the films were investigated. The investigations were performed by optical and Fourier infrared spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). SEM examinations and spectrophotometric measurements show that the films were homogeneous and uniform with a visible light transmittance higher than 90%. XRD of the alumina films heat treated at the temperatures below 500 degree(s)C showed that they had an amorphous structure. XPS examination showed that amorphous films were stoichiometric Al2O3.

  10. Study of electrochromism in Ti:WO3 films by sol-gel process

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; Dogan, Nilgun

    1998-09-01

    Electrochromism in sol-gel deposited WO3 films containing TiO2 has been observed. The films are deposited by spin coating from peroxo-polytungstic acid and titanium isopropoxide precursors. The films were fabricated on quartz and SnO2:F coated glass substrates. Films were heat treated at 150 degree(s)C. Morphology of the films was examined by scanning electron microscopy, which indicated that the films were smooth and had a pore free surface. Results will be presented detailing the optical switching during electrochemical lithium intercalation. These results will be used to compare the performance of the Ti doped WO3 films with other electrochromics. The Ti:WO3 films all color cathodically, and the color state is a neutral grayish blue color, while the bleached state is transparent and colorless. Results of the cyclic stability will also be presented. The neutral color of the Ti:WO3 films means that electrochromic windows based on Ti:WO3 may have significant advantages over WO3-based windows. A detailed analysis of the optical properties of the bleached and colored states of the films will be presented. The dynamics of coloration for these films is also under investigation, and preliminary results will be presented.

  11. Structural and optical properties of chromium doped zinc oxide nanoparticles synthesized by sol-gel method

    SciTech Connect

    Naqvi, Syed Mohd. Adnan; Irshad, Kashif; Soleimani, Hassan E-mail: noorhana-yahya@petronas.com.my; Yahya, Noorhana E-mail: noorhana-yahya@petronas.com.my

    2014-10-24

    Nanosized Cr-doped ZnO nano particles were synthesized by facile sol-gel auto combustion method. The structural and optical properties of Cr-doped ZnO nanoparticles have been investigated by XRD and UV-Vis spectroscopy at room temperature for 0% to 8% concentration. X-ray diffraction analysis reveals that the Cr-doped ZnO crystallizes in a single phase polycrystalline nature with wurtzite lattice. With every % of doping, the peaks are shifting scarcely and doping of Cr is possible up to 7%. After that, the last peak vanishes, that signifies its structure is transmuted from 8% doping. The average crystallite size decreases with increase in Cr concentration (i.e. 28.9 nm for 0% to 25.8 nm for 8%). The UV-Vis spectra of the nanoparticles betoken an incrementation in the band gap energy from 3.401, 3.415, 3.431, 3.437,3.453, 3.514,3.521, 3.530 and 3.538 eV respectively, for 0,1, 2, 3, 4, 5, 6, 7 and 8 % doping concentration.

  12. Mechanically stable and corrosion resistant superhydrophobic sol-gel coatings on copper substrate

    NASA Astrophysics Data System (ADS)

    Rao, A. Venkateswara; Latthe, Sanjay S.; Mahadik, Satish A.; Kappenstein, Charles

    2011-04-01

    Development of the anticorrosion coatings on metals having both passive matrix functionality and active response to changes in the aggressive environment has raised tremendous interest in material science. Using a sol-gel deposition method, superhydrophobic copper substrate could be obtained. The best hydrophobic coating sol was prepared with methyltriethoxysilane (MTES), methanol (MeOH), and water (as 7 M NH4OH) at a molar ratio of 1:19.1:4.31 respectively. The surface morphological study showed the ball like silica particles distributed on the copper substrate with particle sizes ranging from 8 to 12 ?m. The coatings showed the static water contact angle as high as 155° and the water sliding angle as low as 7°. The superhydrophobic nature was maintained even though the deposited copper substrate was soaked for 100 h in 50% of HCl solution. The coatings are stable against humidity and showed superhydrophobic behavior even after 90 days of exposure. The coatings are mechanically stable and water drops maintained the spherical shape on the bent copper substrate, which was bent more than 90°.

  13. Sol-gel, One Technology by Produced Nanohybrid with Anticorrosive Properties

    NASA Astrophysics Data System (ADS)

    Hernández-Padrón, Genoveva; García-Garduño, Margarita V.

    The evolution of nanotechnology has been allowed modify the material properties since of chemical architecture. In this work, we development nanohybrids sol-gel process, silica particles are incorporated a functionalized polymer resin (type epoxy and/or phenolic) with carboxylic groups. When the metallic plate is coating formed film ceramic glass. The incorporation this particles into to polymeric matrix, allowed to obtain performance corrosive properties. The structural characteristics of the different materials prepared, phenolic resin (RF), the resin functionalized (RFF) and its corresponding hybrids (RF-SiO2 and RFF- SiO2), were studied by infrared spectroscopy and morphological changes were analyzed by scanning electron microscopy. Then cooper plates were coated with these materials to evaluate their corrosion performance. The corrosion performance evaluation for each of these coatings RF, RFF, RE- SiO2 and RFF- SiO2 were determined by the following tests: a misty saline chamber operated under accelerated corrosive conditions for corrosion advance measurement, abrasion and adhesion.

  14. Vapor Phase Transport Synthesis of Zeolites from Sol-Gel Precursors

    SciTech Connect

    THOMA,STEVEN G.; NENOFF,TINA M.

    2000-07-14

    A study of zeolite crystallization from sol-gel precursors using the vapor phase transport synthesis method has been performed. Zeolites (ZSM-5, ZSM-48, Zeolite P, and Sodalite) were crystallized by contacting vapor phase organic or organic-water mixtures with dried sodium silicate and dried sodium alumino-silicate gels. For each precursor gel, a ternary phase system of vapor phase organic reactant molecules was explored. The vapor phase reactant mixtures ranged from pure ethylene diamene, triethylamine, or water, to an equimolar mixture of each. In addition, a series of gels with varied physical and chemical properties were crystallized using the same vapor phase solvent mixture for each gel. The precursor gels and the crystalline products were analyzed via Scanning Electron Microscopy, Electron Dispersive Spectroscopy, X-ray mapping, X-ray powder diffraction, nitrogen surface area, Fourier Transform Infrared Spectroscopy, and thermal analyses. The product phase and purity as a function of the solvent mixture, precursor gel structure, and precursor gel chemistry is discussed.

  15. Synthesis of silica nanoparticles from Vietnamese rice husk by sol–gel method

    PubMed Central

    2013-01-01

    Silica powder at nanoscale was obtained by heat treatment of Vietnamese rice husk following the sol–gel method. The rice husk ash (RHA) is synthesized using rice husk which was thermally treated at optimal condition at 600°C for 4 h. The silica from RHA was extracted using sodium hydroxide solution to produce a sodium silicate solution and then precipitated by adding H2SO4 at pH = 4 in the mixture of water/butanol with cationic presence. In order to identify the optimal condition for producing the homogenous silica nanoparticles, the effects of surfactant surface coverage, aging temperature, and aging time were investigated. By analysis of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, the silica product obtained was amorphous and the uniformity of the nanosized sample was observed at an average size of 3 nm, and the BET result showed that the highest specific surface of the sample was about 340 m2/g. The results obtained in the mentioned method prove that the rice husk from agricultural wastes can be used for the production of silica nanoparticles. PMID:23388152

  16. Hydroxyapatite coating by sol-gel on Ti-6Al-4V alloy as drug carrier.

    PubMed

    Avés, Eduardo Peón; Estévez, Gaston Fuentes; Sader, Marcia Soares; Sierra, Juan C Galván; Yurell, Julio C Llópiz; Bastos, Ivan N; Soares, Gloria D Almeida

    2009-02-01

    In this study Ti-6Al-4V samples were used as substrates and Ca-P layers were deposited using sol-gel technique and covered by spin-coating. The efficiency of hydroxyapatite (HA) coatings as drug carrier was also evaluated by immersion in gentamicin sulphate solution and the release profiles were obtained by cumulative method of the coating samples. Three non-linear mathematical methods were employed in order to discuss a possible mechanism to lead the drug release. Physical chemical techniques showed the presence of the typical absorption bands of calcium phosphates by infrared spectroscopy while X-ray diffraction peaks matched up with hydroxyapatite patterns. Microstructural techniques (SEM, EDS) help to confirm the hydroxyapatite coating by surface aspect and Ca/P ratio (1.64). The best fitting according statistical results explained each stage of the released profiles and correspond to a mixture of short initial burst effect plus drug dissolution with a specific kinetic and the diffusion of the gentamicin solid particles. PMID:19104913

  17. High-? TiO2 thin film prepared by sol-gel spin-coating method

    NASA Astrophysics Data System (ADS)

    Kumar, Arvind; Mondal, Sandip; Rao, K. S. R. Koteswara

    2015-06-01

    High-k TiO2 thin film on p-type silicon substrate was fabricated by a combined sol-gel and spin coating method. Thus deposited titania film had anatase phase with a small grain size of 16 nm and surface roughness of ? 0.6 nm. The oxide capacitance (Cox), flat band capacitance (CFB), flat band voltage (VFB), oxide trapped charge (Qot), calculated from the high frequency (1 MHz) C-V curve were 0.47 nF, 0.16 nF, - 0.91 V, 4.7x10-12 C, respectively. As compared to the previous reports, a high dielectric constant of 94 at 1 MHz frequency was observed in the devices investigated here and an equivalent oxide thickness (EOT) was 4.1 nm. Dispersion in accumulation capacitance shows a linear relationship with AC frequencies. Leakage current density was found in acceptable limits (2.1e-5 A/cm2 for -1 V and 5.7e-7 A/cm2 for +1 V) for CMOS applications.

  18. Chirality of Single-Handed Twisted Titania Tubular Nanoribbons Prepared Through Sol-gel Transcription.

    PubMed

    Wang, Sibing; Zhang, Chuanyong; Li, Yi; Li, Baozong; Yang, Yonggang

    2015-08-01

    Single-handed twisted titania tubular nanoribbons were prepared through sol-gel transcription using a pair of enantiomers. Handedness was controlled by that of the template. The obtained samples were characterized using field-emission electron microscopy, transmission electron microscopy, diffuse reflectance circular dichroism (DRCD), and X-ray diffraction. The DRCD spectra indicated that the titania nanotubes exhibit optical activity. Although the tubular structure was destroyed after being calcined at 700?°C for 2.0?h, DRCD signals were still identified. However, the DRCD signals disappeared after being calcined at 1000?°C for 2.0?h. The optical activity of titania was proposed to be due to chiral defects. Previous results showed that straight titania tubes could be used as asymmetric autocatalysts, indicating that titania exhibit chirality at the angstrom level. Herein, it was found that they also exhibit DRCD signals, indicating that there are no obvious relationships between morphology at the nano level and chirality at the angstrom level. The nanotube chirality should originate from the chiral defects on the nanotube inner surface. The Fourier transform infrared spectra indicated that the chirality of the titania was transferred from the gelators through the hydrogen bonding between N-H and Ti-OH. PMID:25994592

  19. Sol-gel synthesis and densification of aluminoborosilicate powders. Part 2: Densification

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey; Selvaduray, Guna; Leiser, Daniel

    1992-01-01

    Aluminoborosilicate (ABS) powders, high in alumina content, were synthesized by the sol-gel process utilizing four different methods of synthesis. The effect of these methods on the densification behavior of ABS powder compacts was studied. Five regions of shrinkage in the temperature range 25-1184 C were identified. In these regions, the greatest shrinkage occurred between the gel-to-glass transition temperature (T sub g approximately equal to 835 C) and the crystallization transformation temperature (T sub t approximately equal 900 C). The dominant mechanism of densification in this range was found to be viscous sintering. ABS powders were amorphous to x-rays up to T sub t at which a multiphasic structure crystallized. No 2Al2O3.B2O3 was found in these powders as predicted in the phase diagram. Above T sub t, densification was the result of competing mechanisms including grain growth and boria fluxed viscous sintering. Apparent activation energies for densification in each region varied according to the method of synthesis.

  20. Designing antimicrobial bioactive glass materials with embedded metal ions synthesized by the sol-gel method.

    PubMed

    Palza, Humberto; Escobar, Blanca; Bejarano, Julian; Bravo, Denisse; Diaz-Dosque, Mario; Perez, Javier

    2013-10-01

    Bioactive glasses (SiO2-P2O5-CaO) having tailored concentrations of different biocide metal ions (copper or silver) were produced by the sol-gel method. All the particles release phosphorous ions when immersed in water and simulated body fluid (SBF). Moreover, a surface layer of polycrystalline hydroxy-carbonate apatite was formed on the particle surfaces after 10 day immersion in SBF as confirmed by X-ray diffraction and scanning electron microscopy (SEM) showing the bioactive materials. Samples with embedded either copper or silver ions were able to further release the biocide ions with a release rate that depends on the metal embedded and the dissolution medium: water or SBF. This biocide ion release from the samples explains the antimicrobial effect of our active particles against Escherichia coli DH5? ampicillin-resistant (Gram-negative) and Streptococcus mutans (Gram-positive) as determined by the Minimum Bactericidal Concentration (MBC) method. The antimicrobial behavior of the particles depends on the bacteria and the biocide ion used. Noteworthy, although samples with copper are able to release more metal ion than samples with silver, they present higher MBC showing the high effect of silver against these bacteria. PMID:23910279

  1. Sol-Gel-Derived Hydroxyapatite-Carbon Nanotube/Titania Coatings on Titanium Substrates

    PubMed Central

    Ji, Xiaoli; Lou, Weiwei; Wang, Qi; Ma, Jianfeng; Xu, Haihong; Bai, Qing; Liu, Chuantong; Liu, Jinsong

    2012-01-01

    In this paper, hydroxyapatite-carbon nanotube/titania (HA-CNT/TiO2) double layer coatings were successfully developed on titanium (Ti) substrates intended for biomedical applications. A TiO2 coating was firstly developed by anodization to improve bonding between HA and Ti, and then the layer of HA and CNTs was coated on the surface by the sol-gel process to improve the biocompatibility and mechanical properties of Ti. The surfaces of double layer coatings were uniform and crack-free with a thickness of about 7 ?m. The bonding strength of the HA-CNT/TiO2 coating was higher than that of the pure HA and HA-CNT coatings. Additionally, in vitro cell experiments showed that CNTs promoted the adhesion of preosteoblasts on the HA-CNT/TiO2 double layer coatings. These unique surfaces combined with the osteoconductive properties of HA exhibited the excellent mechanical properties of CNTs. Therefore, the developed HA-CNT/TiO2 coatings on Ti substrates might be a promising material for bone replacement. PMID:22606041

  2. Influence of calcium precursors on the morphology and crystallinity of sol gel-derived hydroxyapatite nanoparticles

    NASA Astrophysics Data System (ADS)

    Vijayalakshmi Natarajan, U.; Rajeswari, S.

    2008-10-01

    Nanosized hydroxyapatite (HAP) particles were prepared by sol-gel method from the water-based solution of calcium and phosphorus precursor. In this study, two calcium precursors such as calcium nitrate tetrahydrate and calcium acetate were chosen as calcium precursors. The influence of aging period, pH, viscosity and sintering temperature on crystallinity and morphology of the HAP particles were investigated for the two calcium precursors with triethyl phosphate precursor. The morphology of nano-HAP towards phosphorous precursor was dependent on the type of calcium precursor used. The HAP prepared from calcium nitrate and triethyl phosphate was spherically shaped whereas the one from calcium acetate was found to be fibrous in structure. Both HAPs were stable up to 1200 °C and their crystallinity increased with respect to the sintering temperature. The obtained sample was characterized through X-ray diffraction (XRD), P 31 nuclear magnetic resonance (NMR), scanning electronic microscopy (SEM) and TEM analysis. The sol derived from the optimized aging period for the two different calcium precursors was coated on 316L stainless-steel (SS) implant and its corrosion resistivity during long-term implantation was studied by cyclic polarization in Ringer's solution. Both HAPs have their own desirable qualities and were found to be corrosion resistive.

  3. Study of alumosilicate porcelains: Sol-gel preparation, characterization and erosion evaluated by gravimetric method

    SciTech Connect

    Bogdanoviciene, Irma; Jankeviciute, Audrone; Pinkas, Jiri; Beganskiene, Aldona; Kareiva, Aivaras

    2008-11-03

    In this paper, the sol-gel synthesis and characteristic properties of kalsilite-type alumosilicates (KAlSiO{sub 4} and K{sub 0.5}Na{sub 0.5}AlSiO{sub 4}) are reported. The polycrystalline powders were characterized by thermal analysis (TG/DTA), powder X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Single-phase kalsilite oxides have been obtained after annealing precursor gels for 5 h in the temperature range of 750-850 deg. C. It was demonstrated that crystallinity of the samples slightly depends on the temperature of annealing. From the results obtained, it could be concluded that the KAlSiO{sub 4} solids are composed of the volumetric plate-like grains with no regular size (from 5 {mu}m to 30 {mu}m at 750 deg. C and around 5-50 {mu}m at 850 deg. C). Larger crystallites for mixed potassium-sodium kalsilite have formed (from 10 {mu}m to 80 {mu}m at 750 deg. C and >100 {mu}m at 850 deg. C) in comparison with potassium kalsilite samples). The erosion of obtained dental porcelain samples stored in saliva, beer and Coca-Cola was compared.

  4. Preparation of hydroxyapatite nanoparticles by sol-gel method with optimum processing parameters

    SciTech Connect

    Yusoff, Yusriha Mohd; Salimi, Midhat Nabil Ahmad; Anuar, Adilah

    2015-05-15

    Many studies have been carried out in order to prepare hydroxyapatite (HAp) by various methods. In this study, we focused on the preparation of HAp nanoparticles by using sol-gel technique in which few parameters are optimized which were stirring rate, aging time and sintering temperature. HAp nanoparticles were prepared by using precursors of calcium nitrate tetrahydrate, Ca(NO{sub 3}){sub 2}.4H{sub 2}O and phosphorous pentoxide, P{sub 2}O{sub 5}. Both precursors are mixed in ethanol respectively before they were mixed together in which it formed a stable sol. Fourier transform infrared (FTIR), X-ray diffraction (XRD) and Scanning electron microscopy (SEM) were used for its characterization in terms of functional group, phase composition, crystallite size and morphology of the nanoparticles produced. FTIR spectra showed that the functional groups that present in all five samples were corresponding to the formation of HAp. Besides, XRD shows that only one phase was formed which was hydroxyapatite. Meanwhile, SEM shows that the small particles combine together to form agglomeration.

  5. Thickness controlled sol-gel silica films for plasmonic bio-sensing devices

    SciTech Connect

    Figus, Cristiana Quochi, Francesco Artizzu, Flavia Saba, Michele Marongiu, Daniela Mura, Andrea; Bongiovanni, Giovanni; Floris, Francesco; Marabelli, Franco; Patrini, Maddalena; Fornasari, Lucia; Pellacani, Paola; Valsesia, Andrea

    2014-10-21

    Plasmonics has recently received considerable interest due to its potentiality in many fields as well as in nanobio-technology applications. In this regard, various strategies are required for modifying the surfaces of plasmonic nanostructures and to control their optical properties in view of interesting application such as bio-sensing, We report a simple method for depositing silica layers of controlled thickness on planar plasmonic structures. Tetraethoxysilane (TEOS) was used as silica precursor. The control of the silica layer thickness was obtained by optimizing the sol-gel method and dip-coating technique, in particular by properly tuning different parameters such as pH, solvent concentration, and withdrawal speed. The resulting films were characterized via atomic force microscopy (AFM), Fourier-transform (FT) spectroscopy, and spectroscopic ellipsometry (SE). Furthermore, by performing the analysis of surface plasmon resonances before and after the coating of the nanostructures, it was observed that the position of the resonance structures could be properly shifted by finely controlling the silica layer thickness. The effect of silica coating was assessed also in view of sensing applications, due to important advantages, such as surface protection of the plasmonic structure.

  6. AFM and XPS Study of Glass Surface Coated with Titania Nanofilms by Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Ji, Guo-Jun; Shi, Zhi-Ming

    2010-09-01

    Ce3+ -doped and undoped TiO2 nanofilms are prepared on glass surface using a sol-gel method. Crystal structure, surface morphology, chemical composition and element distribution of both glass substrates and TiO2 films were characterized by x-ray diffractometer (XRD), atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). The XRD results indicate that the Ce3+-doped TiO2 films are solely composed of the anatase phase whereas in the undoped films a small amount of the rutile phase of TiO2 is present. AFM observations show that there exist many micro-cracks and micro-holes on glass substrate surface. In contrast, the surface of pure titania films is crack-free and the average crystallite size of the films is less than 50 nm. For the films doped with Ce3+, not only does it appear to be more uniform and compact, but also the corresponding crystal size is decreased. XPS results indicate that element interdiffusion occurs between the titania nanofilm and the glass substrate during the sintering process. The film is firmly adhered onto the glass surface through the chemical combination of Ti-O-Si bonds, and the combination is more enhanced by Ce3+-doping.

  7. Robust superhydrophobic transparent coatings fabricated by a low-temperature sol-gel process

    NASA Astrophysics Data System (ADS)

    Huang, Wei-Heng; Lin, Chao-Sung

    2014-06-01

    A coating with robust, superhydrophobic, and transparent properties was fabricated on glass substrates by a sol-gel method at a temperature of 80 °C. The coating was formed in a solution containing silica nanoparticles and silicic acid, in which the ratio of silica nanoparticles and silicic acid was varied to tune the roughness of the coating. Subsequently, the as-deposited coating was dipped with a low surface energy material, 1H,1H,2H,2H-perfluorooctyltrichloro silane. The coated glass substrate was characterized in terms of surface morphology, optical transmittance, water- and CH2I2-contact angles, and its chemical as well as mechanical stability was evaluated by ultrasonication in ethanol for 120 min. The results showed that the coating had a water contact angle exceeding 160°, a sliding angle lower than 10°, a CH2I2 static contact angle of approximately 150°. The transmittance of the coating was reduced by less than 5% compared to that of the bare glass substrate at wavelengths above 500 nm. Moreover, the properties of the coating hardly changed after the ultrasonication test and still retained the superhydrophobicity after water dropping impact. Because the fabrication process is performed under low temperatures, it is feasible for scale-up production at low energy consumptions.

  8. Sol-gel synthesis of magnesium oxide-silicon dioxide glass compositions

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1988-01-01

    MgO-SiO2 glasses containing up to 15 mol pct MgO, which could not have been prepared by the conventional glass melting method due to the presence of stable liquid-liquid immiscibility, were synthesized by the sol-gel technique. Clear and transparent gels were obtained from the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) and magnesium nitrate hexahydrate when the water/TEOS mole ratio was four or more. The gelling time decreased with increase in magnesium content, water/TEOS ratio, and reaction temperature. Magnesium nitrate hexahydrate crystallized out of the gels containing 15 and 20 mol pct MgO on slow drying. This problem was partially alleviated by drying the gels quickly at higher temperatures. Monolithic gel samples were prepared using glycerol as the drying control additive. The gels were subjected to various thermal treatments and characterized by several methods. No organic groups could be detected in the glasses after heat treatments to approx. 800 C, but trace amounts of hydroxyl groups were still present. No crystalline phase was found from X-ray diffraction in the gel samples to approx. 890 C. At higher temperatures, alpha quartz precipitated out as the crystalline phase in gels containing up to 10 mol pct MgO. The overall activation energy for gel formation in 10MgO-90SiO2 (mol pct) system for water/TEOS mole ratio of 7.5 was calculated to be 58.7 kJ/mol.

  9. Phase and microstructural development in alumina sol-gel coatings on CoCr alloy.

    PubMed

    Bae, I J; Standard, O C; Roger, G J; Brazil, D

    2004-09-01

    Phase transformation of gamma-Al(2)O(3) to alpha-Al(2)O(3) in alumina sol gel coatings on biomedical CoCr alloy was studied as function of heat treatment temperature and time. Transformation in unseeded coatings was significant only above approximately 1200 degrees C. Addition of alpha-Al(2)O(3) seed particles having an average size of approximately 40 nm lowered the phase transformation temperature to around 800 degrees C. These particles were considered to act as heterogeneous nucleation sites for epitaxial growth of the alpha-Al(2)O(3) phase. The kinetics and activation energy (420 kJ/mol) for the phase transformation in the seeded coatings were similar to those reported for seeded monolithic alumina gels indicating that the transformation mechanism is the same in the two material configurations. Avrami growth parameters indicated that the mechanism was diffusion controlled and invariant over the temperature range studied but that growth was possibly constrained by the finite size of the seed particles and/or coating thickness. The phase transformation occurred by the growth of alpha-Al(2)O(3) grains at the expense of the precursor fine-grained gamma-Al(2)O(3) matrix and near-complete transformation coincided with physical impingement of the growing grains. The grain size at impingement was approximately 100 nm which agreed well with that predicted from the theoretical linear spacing of seed particles in the initial sol. PMID:15448403

  10. Preparation of Water-Repellent Glass by Sol-Gel Process Using Perfluoroalkylsilane and Tetraethoxysilane.

    PubMed

    Jeong, Hye-Jeong; Kim, Dong-Kwon; Lee, Soo-Bok; Kwon, Soo-Han; Kadono, Kohei

    2001-03-01

    Coating films on glass substrate were prepared by sol-gel process using alkoxide solutions containing perfluoroalkylsilane (PFAS) and tetraethoxysilane (TEOS). The physical properties of the coating films were characterized by SEM, FT-IR, and XRD. And their surface properties were investigated by measuring contact angles and atomic compositions. Transparent coating films with smooth surface and uniform thickness could be obtained. The contact angles of the coating films for water and methylene iodide are extremely high, at 118 degrees and 97 degrees, respectively, and their surface free energies are about 9.7 dyn/cm. It was found that the water-repellent glass prepared is very hydrophobic and exhibits excellent water-repellency. Hydrophobic perfluoroalkyl groups are preferentially enriched to the outermost layer at the coating film-air interface, and two layers probably exist in the coating film. The upper layer oriented toward the air is composed of mainly perfluoroalkyl groups originating from PFAS, and the lower layer is composed of mainly -OSiO- groups originating from TEOS. The heat treatment after drying step cannot influence the surface enrichment of the perfluoroalkyl group. The hydrolysis reaction should be more completely done before the dip coating step to obtain lower surface free energy. The burning temperature should be less than 300 degrees C because the perfluoroalkyl group begins to decompose from this temperature. Copyright 2001 Academic Press. PMID:11237451

  11. Synthesis of silica nanoparticles from Vietnamese rice husk by sol-gel method.

    PubMed

    Le, Van Hai; Thuc, Chi Nhan Ha; Thuc, Huy Ha

    2013-01-01

    Silica powder at nanoscale was obtained by heat treatment of Vietnamese rice husk following the sol-gel method. The rice husk ash (RHA) is synthesized using rice husk which was thermally treated at optimal condition at 600°C for 4 h. The silica from RHA was extracted using sodium hydroxide solution to produce a sodium silicate solution and then precipitated by adding H2SO4 at pH = 4 in the mixture of water/butanol with cationic presence. In order to identify the optimal condition for producing the homogenous silica nanoparticles, the effects of surfactant surface coverage, aging temperature, and aging time were investigated. By analysis of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, the silica product obtained was amorphous and the uniformity of the nanosized sample was observed at an average size of 3 nm, and the BET result showed that the highest specific surface of the sample was about 340 m2/g. The results obtained in the mentioned method prove that the rice husk from agricultural wastes can be used for the production of silica nanoparticles. PMID:23388152

  12. Synthesis of palladium-doped silica nanofibers by sol-gel reaction and electrospinning process

    SciTech Connect

    San, Thiam Hui; Daud, Wan Ramli Wan; Kadhum, Abdul Amir Hassan; Mohamad, Abu Bakar; Kamarudin, Siti Kartom; Shyuan, Loh Kee; Majlan, Edy Herianto

    2012-06-29

    Nanofiber is drawing great attention nowadays with their high surface area per volume and flexibility in surface functionalities that make them favorable as a proton exchange membrane in fuel cell application. In this study, incorporation of palladium nanoparticles in silica nanofibers was prepared by combination of a tetraorthosilane (TEOS) sol-gel reaction with electrospinning process. This method can prevent the nanoparticles from aggregation by direct mixing of palladium nanoparticles in silica sol. The as-produced electrospun fibers were thermally treated to remove poly(vinyl pyrrolidone) (PVP) and condensation of silanol in silica framework. PVP is chosen as fiber shaping agent because of its insulting and capping properties for various metal nanoparticles. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the silica fibers and Pd nanoparticles on the fibers. Spun fibers with average diameter ranged from 100nm to 400nm were obtained at optimum operating condition and distribution of Pd nanoparticles on silica fibers was investigated.

  13. Preparation and characterization of sol-gel-derived PZT thin films for microactuators

    NASA Astrophysics Data System (ADS)

    Wang, Zhanjie; Maeda, Ryutaro; Kikuchi, Kaoru M.

    1999-03-01

    Crack-free ferroelectric thin films of lead zirconate titanate with thickness of 3 micrometers for microactuators were fabricated using Sol-Gel spin-coating onto Pt/Ti/SiO2/Si substrates. The precursor solution was prepared from lead acetate, zirconium-n-propoxide and titanium tetraisopropoxide. 2-propanol was used as the solvent. The crystalline phase as well as preferred orientation in the PZT films were investigated using x-ray diffraction analysis. The microstructure and composition of the films were studied by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy, respectively. The well-crystallized perovskite phase and the preferred orientations in the direction of the (100) plane were obtained using the heat treatment for dry at 120 degrees C, for pyrolysis at 300 degrees C and for crystallization at 600 degrees C. The prepared films showed nanometer grains with smooth and uniform surface. The dielectric constants and loss values of these films measured at 1 kHz were approximately 1250 and 0.04, respectively, while the remnant polarization and the coercive field were 45.5 (mu) C/cm2 and 58.5 kV/cm. Our results suggest that fabrication of good structural quality PZT films of a few micrometers thick for use in micro actuators is possible.

  14. Sol-gel-derived hybrid materials multi-doped with rare-earth metal ions

    NASA Astrophysics Data System (ADS)

    Zelazowska, E.; Rysiakiewicz-Pasek, E.; Borczuch-Laczka, M.; Cholewa-Kowalska, K.

    2012-06-01

    Four different hybrid organic-inorganic materials based on TiO2-SiO2 matrices with organic additives and doped with rare-earth metal ions (III) from the group of europium, cerium, terbium, neodymium, dysprosium and samarium, were synthesized by sol-gel method. Tetraethyl orthosilicate, titanium (IV) isopropoxide and organic compounds, such as butyl acrylate, butyl methacrylate, ethyl acetoacetate, ethylene glycol dimethacrylate, ethyl acetate, propylene carbonate, organic solvents and certain inorganic salts were used in the synthesis. The inorganic part of the sols, which were used in the synthesis of all the hybrid materials, was prepared separately and then the organic parts were added. The materials obtained were aged for three weeks at room temperature and then heated in an electric oven for three hours at temperatures of 80 °C-150 °C. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDX); X-ray diffraction (XRD); Fourier transform infrared spectroscopy (KBr technique); 29Si magic-angle spinning nuclear magnetic resonance; and fluorescence spectroscopy were used for the examination of morphology, microstructure and luminescence properties, respectively. Photoluminescence properties with relatively intense narrow emission lines of Tb, Eu, Dy, Nd, Sm respectively to the RE-ions doping, were observed for all the hybrid materials.

  15. Microfabrication and Integration of a Sol-Gel PZT Folded Spring Energy Harvester

    PubMed Central

    Lueke, Jonathan; Badr, Ahmed; Lou, Edmond; Moussa, Walied A.

    2015-01-01

    This paper presents the methodology and challenges experienced in the microfabrication, packaging, and integration of a fixed-fixed folded spring piezoelectric energy harvester. A variety of challenges were overcome in the fabrication of the energy harvesters, such as the diagnosis and rectification of sol-gel PZT film quality and adhesion issues. A packaging and integration methodology was developed to allow for the characterizing the harvesters under a base vibration. The conditioning circuitry developed allowed for a complete energy harvesting system, consisting a harvester, a voltage doubler, a voltage regulator and a NiMH battery. A feasibility study was undertaken with the designed conditioning circuitry to determine the effect of the input parameters on the overall performance of the circuit. It was found that the maximum efficiency does not correlate to the maximum charging current supplied to the battery. The efficiency and charging current must be balanced to achieve a high output and a reasonable output current. The development of the complete energy harvesting system allows for the direct integration of the energy harvesting technology into existing power management schemes for wireless sensing. PMID:26016911

  16. Magnetic properties of high Li doped ZnO sol–gel thin films

    SciTech Connect

    Vettumperumal, R.; Kalyanaraman, S.; Santoshkumar, B.; Thangavel, R.

    2014-02-01

    Highlights: • Ferromagnetism in high Li doped ZnO films. • Magnetic properties observed by Guoy's and VSM method. • The rod and wrinkle like structures are observed from the surface of the films. • Band gap of ZnO does not get altered by high Li doping. - Abstract: Undoped and Li doped ZnO thin films were deposited on a glass substrate using the sol–gel dip coating method. The films were prepared at 5 mol.% and 10 mol.% of Li doped ZnO at 550 °C annealing temperature and the deposited films were characterized by X-ray diffraction (XRD), microscopic studies, Gouy's method, vibrating sample magnetometer (VSM) and UV–visible spectroscopy. All the deposited thin films had a hexagonal wurtzite structure with polycrystalline grains at random. Primarily magnetic properties of pure and Li doped ZnO films were observed by Guoy's method which depicted Dia and Para magnetic behavior at room temperature. VSM measurement reveals a coercivity of 97.7 Oe in the films. An inverse relative ferromagnetism was perceived in Li doped ZnO films which had an average transmission of <90%.

  17. Sol-gel metal oxide and metal oxide/polymer multilayers applied by meniscus coating

    SciTech Connect

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

    1993-10-01

    We are developing a meniscus coating process for manufacturing large-aperture dielectric multilayer high reflectors (HR`s) at ambient conditions from liquid suspensions. Using a lab-scale coater capable of coating 150 mm square substrates, we have produced several HR`s which give 99% + reflection with 24 layers and with edge effects confined to about 10 mm. In calendar 1993 we are taking delivery of an automated meniscus coating machine capable of coating substrates up to 400 mm wide and 600 mm long. The laser-damage threshold and failure stress of sol-gel thin films can be substantially increased through the use of soluble polymers which act as binders for the metal oxide particles comprising the deposited film. Refractive index control of the film is also possible through varying the polymer/oxide ratio. Much of our present effort present is in optimizing oxide particle/binder/solvent formulations for the high-index material. Films from colloidal zirconia strengthened with polyvinylpyrollidone (PVP) have given best results to date. An increase in the laser damage threshold (LDT) for single layers has been shown to significantly increase with increased polymer loading, but as yet the LDT for multilayer stacks remains low.

  18. Biocompatibility improvement of titanium implants by coating with hybrid materials synthesized by sol-gel technique.

    PubMed

    Catauro, M; Bollino, F; Papale, F

    2014-12-01

    Organic-inorganic hybrid materials based on zirconia and polyethylene glycol (PEG) have been synthesized via sol-gel method in the present study. Those materials, still in the sol phase, have been used to coat a titanium grade 4 (Ti-4) substrate to improve its biological properties. Dip-coating technique has been used to obtain thin films. PEG, a biocompatible polymer, used as the organic phase, has been incorporated with different percentages in an inorganic zirconium-based matrix. Those hybrids have been characterized by Fourier transform infrared spectroscopy (FTIR) to detect interactions between the two phases. The films have been examined using SEM to detect morphological changes with PEG percentages. The potential applications of the hybrid coatings in biomedical field have been evaluated by bioactivity and cytotoxicity tests. The coated titanium was immersed in simulated body fluid (SBF) for 21 days and the hydroxyapatite deposition on its surface was subsequently evaluated, as that feature can be used as an index of bone-bonding capability. SEM equipped with energy dispersive spectrometer (EDS) was used to examine hydroxyapatite formation. NIH 3T3 mouse embryonic fibroblast cells were seeded on specimens to evaluate cells-materials interactions and cell vitality was inspected using WST-8 Assay. PMID:24677575

  19. Corrosion behavior and mechanical properties of bioactive sol-gel coatings on titanium implants.

    PubMed

    Catauro, M; Bollino, F; Papale, F; Giovanardi, R; Veronesi, P

    2014-10-01

    Organic-inorganic hybrid coatings based on zirconia and poly (?-caprolactone) (PCL) were prepared by means of sol-gel dip-coating technique and used to coat titanium grade 4 implants (Ti-4) in order to improve their wear and corrosion resistance. The coating chemical composition has been analysed by ATR-FTIR. The influence of the PCL amount has been investigated on the microstructure, mechanical properties of the coatings and their ability to inhibit the corrosion of titanium. SEM analysis has shown that all coatings have a nanostructured nature and that the films with high PCL content are crack-free. Mechanical properties of the coatings have been studied using scratch and nano-indentation tests. The results have shown that the Young's modulus of the coatings decreases in presence of large amounts of the organic phase, and that PCL content affects also the adhesion of the coatings to the underlying Ti-4 substrate. However, the presence of cracks on the PCL-free coatings affects severely the mechanical response of the samples at high loads. The electrochemical behavior and corrosion resistance of the coated and uncoated substrate has been investigated by polarization tests. The results have shown that both the coatings with or without PCL don't affect significantly the already excellent passivation properties of titanium. PMID:25175226

  20. An investigation on sol-gel treatment to aramid yarn to increase inter-yarn friction

    NASA Astrophysics Data System (ADS)

    Chu, Yanyan; Chen, Xiaogang; Wang, Qing; Cui, Shizhong

    2014-11-01

    Inter-yarn friction helps to increase energy absorption in ballistic fabrics. This paper reports on the results of sol-gel treatment on aramid yarns to increase the inter-yarn friction. Two types of TiO2/ZnO hydrosols (submicro-sized and nano-sized) prepared using hydrolysis and peptization methods were used to treat aramid yarns with and without curing. SEM was used to characterize the change in morphology. FTIR and EDX analyses were applied to identify the coating substance. The inter-yarn friction was tested using Capstan method. Images from SEM showed that the surface of the yarn treated with TiO2/ZnO submicro-sized hydrosol was covered with lump-like coating whilst in the case of TiO2/ZnO nano-sized sol treatment, the coating on the fibres was more film-like. The substance in the coating was confirmed as titanium dioxide and zinc oxide by FTIR and EDX analyses. The test results for coefficient of friction revealed that the coefficient of friction between the yarns treated by submicro-sized hydrosol was 54% higher than the non-treated, and the nano-sized hydrosol was associated to a 10% increase. However, the curing process had little effect on the coefficient of friction between yarns. The study also showed that the tensile properties of the treated yarns and the weight add-on were not significantly affected.

  1. Preparation and Thermoelectric Properties of Co-Doped ZnO Synthesized by Sol-Gel.

    PubMed

    Wu, Zi-Hua; Xie, Hua-Qing; Zhai, Yong-Biao

    2015-04-01

    Zinc oxide (ZnO) has attracted increasing attention as one of the most promising n-type thermo-electric materials, but its practice use was limited by high thermal conductivity and low electrical conductivity. Therefore, we herein prepared Co-doped ZnO nanoparticles by sol-gel method and then compressed nanoparticles into bulk materials through spark plasma sintering. The thermo-electric properties, including electrical conductivity, Seebeck coefficient, thermal conductivity, and ZT value, have been investigated. We found that the substitution of Co2+ causes the decrease of bandgap and the increase of carrier concentration, thus the improvement of electrical conductivity. At the same time, the Co-induced lattice distortion and nanoparticles reduce the thermal conductivity by shortening the mean free path (MFP) of the phonons. The resultant ZT is 0.037 for Zn0.9Co0.1O, which is more than 23-fold higher than that of the pure ZnO samples. PMID:26353552

  2. Sol-gel-derived silica films with tailored microstructures for applications requiring organic dyes

    SciTech Connect

    Logan, M.N.; Prabakar, S.; Brinker, C.J. |

    1994-09-01

    A three-step sol-gel process was developed to prepare organic dye-doped thin films with tailored porosity for applications in chemical sensing and optoelectronics. Varying the acid- and base-catalyzed hydrolysis steps of sols prepared from tetraethoxysilane with identical final H{sub 2}O/Si ratios, dilution factors and pH resulted in considerably different distributions of the silicate polymers in the sol (determined by {sup 29}Si NMR) and considerably different structures for the polymer clusters (determined by SAXS). During film formation these kinetic effects cause differences in the packing and collapse of the silicate network, leading to thin films with different refractive indices and volume fraction porosities. Under conditions where small pore-plugging species were avoided, the porosities of as-deposited films could be varied by aging the sol prior to film deposition. This strategy, which relies on the growth and aggregation of fractal polymeric clusters, is compatible with the low temperature and near neutral pH requirements of organic dyes.

  3. Development of sol-gel icephobic coatings: effect of surface roughness and surface energy.

    PubMed

    Fu, Qitao; Wu, Xinghua; Kumar, Divya; Ho, Jeffrey W C; Kanhere, Pushkar D; Srikanth, Narasimalu; Liu, Erjia; Wilson, Peter; Chen, Zhong

    2014-12-10

    Sol-gel coatings with different roughness and surface energy were prepared on glass substrates. Methyl triethoxysilane (MTEOS), 3-Glycidyloxypropyl trimethoxysilane (GLYMO) and fluoroalkylsilane (FAS) were used to obtain a mechanically robust icephobic coating. Different amount of hydrophobic silica nano particles was added as fillers to introduce different roughness and surface energy to the coatings. The microstructure, roughness, and surface energy, together with elemental information and surface chemical state, were investigated at room temperature. The contact angle and sliding angle were measured at different temperatures to correlate the wetting behavior at low temperature with the anti-icing performance. The ice adhesion shear strength was measured inside an ice chamber using a self-designed tester. The factors influencing the ice adhesion were discussed, and the optimum anti-icing performance found in the series of coatings. It was found that lower surface energy leads to lower ice adhesion regardless of the roughness, while the roughness plays a more complicated role. The wetting behavior of the droplet on surface changes as temperature decreases. The anti-icing performance is closely related to the antiwetting property of the surfaces at subzero temperatures. PMID:25382856

  4. Leaching behavior of EDTA in a silica sol-gel matrix

    SciTech Connect

    Oka, K.S.; Mackenzie, J.D.

    1994-12-31

    Ethylene diamine tetra-acetic acid (EDTA) doped silica gels were made by the sol-gel process for the potential application as a filter for heavy metal ions in wastewater. The behavior of the organic molecule in the matrix was studied by investigating the percentage of EDTA leached out with a variation in the timing of addition of the EDTA molecule into the starting silica gel solution. Leach tests using water as the medium were performed for 2, 12 and 24 hours in order to determine the amount of EDTA trapped in the pores or in the matrix. A minimum amount of EDTA leached from the gels was detected in the samples to which EDTA was added 4 hours after initial hydrolysis of TEOS. This result was correlated to having a greater percentage of pore volume in the range of 15--20 {angstrom}, which was further substantiated with density measurements. The physical changes in the silica matrix altering the pore volume distribution were attributed to the addition of the water into which the EDTA molecule was initially dissolved.

  5. Radiation detection with CdTe quantum dots in sol-gel glass and polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Manickaraj, Kavin; Wagner, Brent K.; Kang, Zhitao

    2013-05-01

    Optically based radiation detectors in various fields of science still suffer from low resolution, sensitivity and efficiency that restrict their overall performance. Quantum dots (QD) are well-suited for such detectors due to their unique optical properties. CdTe QDs show fast luminescence decay times, high conversion efficiencies, and have band gaps strongly dependent on the particle radius. Since QD particle sizes are well below the wavelengths of their emissions, they remain optically transparent when incorporated in both polymer and sol-gel based silica glass due to negligible optical scattering. In addition, as these composite materials can greatly improve the mechanical robustness of alpha-particle detectors, conventionally known to have delicate components, CdTe QDs show high promise for radiation sensing applications. These properties are especially advantageous for alpha-particle and potentially neutron detection. In this work, CdTe QD-based glass or polymer matrix nanocomposites were synthesized for use as alpha-particle detection scintillators.. The fast photo-response and decay times provide excellent time resolution. The radiation responses of such nanocomposites in polymer or glass matrices were investigated.

  6. Annealing Treatment of ZnO Thin Films Deposited by Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Saleem, M.; Fang, L.; Huang, Q. L.; Li, D. C.; Wu, F.; Ruan, H. B.; Kong, C. Y.

    2012-10-01

    Highly transparent ZnO thin films were deposited on glass substrates by using a simple and inexpensive multi-step sol-gel spin coating process. This research investigated the effects of annealing temperature in the range from 350-600°C on the microstructure, surface morphology and optical properties of thin films by using XRD, SEM and transmittance spectra. The XRD results showed that the c-axis orientation of ZnO thin films was improved with the increase of annealing temperature. The grain size increases from 16.6-19.7 nm with the increase in temperature. The transmittance spectra indicated that the transmittance and direct optical band gap Eg of the films showed a decreased trend with annealing temperature. It is found that the tensile stress exist in the films, which decreases with the increase in annealing temperature up to 500°C, on further increasing the annealing temperature up to 600°C, the stress in the film changes from tensile to compressive nature.

  7. Transparent Superhydrophobic silica coatings on glass by sol-gel method

    NASA Astrophysics Data System (ADS)

    Mahadik, Satish A.; Kavale, Mahendra S.; Mukherjee, S. K.; Rao, A. Venkateswara

    2010-11-01

    Wetting behavior of solid surfaces is a key concern in our daily life as well as in engineering and science. In the present study, we demonstrate a simple dip coating method for the preparation of Thermally stable, transparent superhydrophobic silica films on glass substrates at room temperature by sol-gel process. The coating alcosol was prepared by keeping the molar ratio of methyltriethoxysilane (MTES), trimethylmethoxysilane (TMMS), methanol (MeOH), water (H2O) constant at 1:0.09:12.71:3.58, respectively with 13 M NH4OH throughout the experiments and the films were prepared with different deposition time varied from 5 to 25 h. In order to improve the hydrophobicity of as deposited silica films, the films were derivatized with 10% trimethylchlorosilane (TMCS) as a silylating agent in hexane solvent for 24 h. Enhancement in wetting behavior was observed for surface derivatized silica films which showed a maximum static water contact angle (172°) and minimum sliding angle (2°) for 25 h of deposition time. The superhydrophobic silica films retained their superhydrophobicity up to a temperature of 550 °C. The silica films were characterized by field emission scanning electron microscopy (FE-SEM), surface profilometer, Fourier transform infrared (FT-IR) spectroscopy, thermo-gravimetric and differential thermal analysis (TG-DTA), percentage of optical transmission, water contact angle measurements. The imperviousness behavior of the films was tested with various acids.

  8. Sol-gel transition of charged fibrils composed of a model amphiphilic peptide.

    PubMed

    Owczarz, Marta; Bolisetty, Sreenath; Mezzenga, Raffaele; Arosio, Paolo

    2015-01-01

    We characterized the sol-gel transition of positively charged fibrils composed of the model amphiphilic peptide RADARADARADARADA (RADA 16-I) using a combination of microscopy, light scattering, microrheology and rheology techniques, and we investigated the dependence of the hydrogel formation on fibril concentration and ionic strength. The peptide is initially present as a dispersion of short rigid fibrils with average length of about 100 nm. During incubation, the fibrils aggregate irreversibly into longer fibrils and fibrillar aggregates. At peptide concentrations in the range 3-6.5 g/L, the fibrillar aggregates form a weak gel network which can be destroyed upon dilution. Percolation occurs without the formation of a nematic phase at a critical peptide concentration which decreases with increasing ionic strength. The gel structure can be well described in the frame of the fractal gel theory considering the network as a collection of fibrillar aggregates characterized by self-similar structure with a fractal dimension of 1.34. PMID:25441357

  9. Raman study of oriented ZnO thin films deposited by sol-gel method

    NASA Astrophysics Data System (ADS)

    Yahia, S. Ben; Znaidi, L.; Kanaev, A.; Petitet, J. P.

    2008-12-01

    ZnO films with preferred orientation along the (0 0 2) plane were successfully deposited by the sol-gel method using Zn(CH 3COO) 2·2H 2O as starting material and inorganic precursor. A homogeneous and stable solution was prepared by dissolving the zinc acetate in a solution of ethanol and monoethanolamine. Thin films are obtained by spin-coating on glass substrates. ZnO films were obtained by preheating the spin-coated films at 300 °C for 10 min after each coating and postheating upto 550 °C for 2 h. The as-deposited films are transformed into mono-oriented ZnO upon thermal treatment. The films consist of spongy particles aggregates with an uniform size and homogenous surface. The films aim to be used in optoelectronic devices. Raman spectroscopy from ZnO films and deposit solutions has been investigated. New Raman results of the deposit solution suggest that Zn-O bond forms first in solution and that these entities play the role of germs initiating the crystallization mechanisms during films annealing. Raman spectra of the annealed films show the presence of a compressive stress within the film structure.

  10. Luminescence behavior of terbium sulphosalicylic acid complexes in sol-gel derived host materials

    SciTech Connect

    Fan, X.; Wang, M.; Wang, Z.; Hong, Z.

    1997-08-01

    The formation and luminescence behavior of terbium sulphosalicylic acid (TbSSA) complexes in sol-gel derived host materials have been investigated. The 5-sulphosalicylic acid (H{sub 3}SSA) was dissolved in ethanol in advance, and then the TbCl{sub 3} and ethanol containing H{sub 3}SSA were introduced into the initial precursor sol, respectively. The resulting sol exhibits intramolecular energy transfer from the coordinated sulphosalicylic acid to the terbium ion. The TbSSA complex has formed in the TbCl{sub 3} and H{sub 3}SSA codoped sol. The complexes were found to have notably higher fluorescence intensities than TbCl{sub 3} in both the sol and the gel. In the sol, the concentration quenching was a diffusion-controlled process due to aggregation and effective collision between molecules and the fluorescence was decreased with increase of H{sub 3}SSA concentration. On the other hand, the molecules in the gel were isolated in the pores of the silica network. The fluorescence intensities of TbSSA in the gel were increased with the increase of concentration ratio of H{sub 3}SSA/TbCl{sub 3}. Maximum fluorescence intensity was obtained at H{sub 3}SSA/TbCl{sub 3} = 2.

  11. Preparation and optical properties of iron-modified titanium dioxide obtained by sol-gel method

    NASA Astrophysics Data System (ADS)

    Hreniak, Agnieszka; Gryz?o, Katarzyna; Boharewicz, Bartosz; Sikora, Andrzej; Chmielowiec, Jacek; Iwan, Agnieszka

    2015-08-01

    In this paper twelve TiO2:Fe powders prepared by sol-gel method were analyzed being into consideration the kind of iron compound applied. As a precursor titanium (IV) isopropoxide (TIPO) was used, while as source of iron Fe(NO3)3 or FeCl3 were tested. Fe doped TiO2 was obtained using two methods of synthesis, where different amount of iron was added (1, 5 or 10% w/w). The size of obtained TiO2:Fe particles depends on the iron compound applied and was found in the range 80-300 nm as it was confirmed by SEM technique. TiO2:Fe particles were additionally investigated by dynamic light scattering (DLS) method. Additionally, for the TiO2:Fe particles UV-vis absorption and the zeta potential were analyzed. Selected powders were additionally investigated by magnetic force microscopy (MFM) and X-ray diffraction techniques. Photocatalytic ability of Fe doped TiO2 powders was evaluated by means of cholesteryl hemisuccinate (CHOL) degradation experiment conducted under the 30 min irradiation of simulated solar light.

  12. Preparation of hydroxyapatite nanoparticles by sol-gel method with optimum processing parameters

    NASA Astrophysics Data System (ADS)

    Yusoff, Yusriha Mohd; Salimi, Midhat Nabil Ahmad; Anuar, Adilah

    2015-05-01

    Many studies have been carried out in order to prepare hydroxyapatite (HAp) by various methods. In this study, we focused on the preparation of HAp nanoparticles by using sol-gel technique in which few parameters are optimized which were stirring rate, aging time and sintering temperature. HAp nanoparticles were prepared by using precursors of calcium nitrate tetrahydrate, Ca(NO3)2.4H2O and phosphorous pentoxide, P2O5. Both precursors are mixed in ethanol respectively before they were mixed together in which it formed a stable sol. Fourier transform infrared (FTIR), X-ray diffraction (XRD) and Scanning electron microscopy (SEM) were used for its characterization in terms of functional group, phase composition, crystallite size and morphology of the nanoparticles produced. FTIR spectra showed that the functional groups that present in all five samples were corresponding to the formation of HAp. Besides, XRD shows that only one phase was formed which was hydroxyapatite. Meanwhile, SEM shows that the small particles combine together to form agglomeration.

  13. Electrochemical Urea Biosensor Based on Sol-gel Derived Nanostructured Cerium Oxide

    NASA Astrophysics Data System (ADS)

    Ansari, Anees A.; Azahar, Md; Malhotra, B. D.

    2012-04-01

    Urease (Urs) and glutamate dehydrogenase (GLDH) have been co-immobilized onto a nanostructured-cerium oxide (Nano-CeO2) film deposited onto a indium-tin-oxide (ITO) coated glass substrate by dip-coating via sol-gel process for urea detection. This nanostructured film has characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning electron microscope (SEM) and electrochemical techniques, respectively. The particle size of the Nano-CeO2 film has been found to be 23 nm. Electrochemcial response (CV) studies show that Ur-GLDH/Nano-CeO2/ITO bioelectrode is found to be sensitive in the 10-80 mg/dL urea concentration range and can detect urea concentration upto 0.1 mg/dL level. The value of Michaelis-Menten constant (Km) estimated using Lineweaver-Burke plot found as 6.09 mg/dL indicates enhancement in the affinity and/or activity of enzyme attached to their nanobiocomposite. This bioelectrode retained 95% of enzyme activity after 6 months at 4°C.

  14. Microfabrication and integration of a sol-gel PZT folded spring energy harvester.

    PubMed

    Lueke, Jonathan; Badr, Ahmed; Lou, Edmond; Moussa, Walied A

    2015-01-01

    This paper presents the methodology and challenges experienced in the microfabrication, packaging, and integration of a fixed-fixed folded spring piezoelectric energy harvester. A variety of challenges were overcome in the fabrication of the energy harvesters, such as the diagnosis and rectification of sol-gel PZT film quality and adhesion issues. A packaging and integration methodology was developed to allow for the characterizing the harvesters under a base vibration. The conditioning circuitry developed allowed for a complete energy harvesting system, consisting a harvester, a voltage doubler, a voltage regulator and a NiMH battery. A feasibility study was undertaken with the designed conditioning circuitry to determine the effect of the input parameters on the overall performance of the circuit. It was found that the maximum efficiency does not correlate to the maximum charging current supplied to the battery. The efficiency and charging current must be balanced to achieve a high output and a reasonable output current. The development of the complete energy harvesting system allows for the direct integration of the energy harvesting technology into existing power management schemes for wireless sensing. PMID:26016911

  15. In situ preparation of Al-containing PVDF ultrafiltration membrane via sol-gel process.

    PubMed

    Pang, Ruizhi; Li, Jiansheng; Wei, Kajia; Sun, Xiuyun; Shen, Jinyou; Han, Weiqing; Wang, Lianjun

    2011-12-15

    Recently, inorganic nanoparticles blended within polymeric membranes have shown improved antifouling performance in wastewater treatment. However, agglomeration of nanoparticles remains as one of the major obstacles for generating a uniform surface. In this study, a new method for in situ preparation of Al-containing PVDF ultrafiltration membranes to improve the dispersion of nanoparticles is reported. The strategy of this method is to combine sol-gel process with traditional immersion precipitation process. Al sol was synthesized by the addition of anionic exchange resin in N,N-dimethylformamide (DMF) solvent containing aluminum chloride. Homogeneous Al-containing PVDF casting solution was then obtained by dissolving PVDF polymer in the Al sol. The membrane formation mechanism was investigated by precipitation kinetics and morphology. Results indicate that the addition of Al species can accelerate phase inversion of casting solution. Scanning electron microscopic images show that a typical transition from sponge-like structure to finger-like structure occurred with increasing Al species content. The existence and dispersion states of Al species in the resultant membrane matrix were further examined by transmission electron microscope and X-ray photoelectron spectrometer. The results indicate the Al species nanoparticles were well dispersed throughout PVDF matrix. Dynamic BSA fouling resistance experiments demonstrate the Al-containing PVDF membranes possess improved separation performances over the pure PVDF membranes. PMID:21955802

  16. Synthesis and electrochemical characterization of LiNi{sub 1{minus}y}Co{sub y}O{sub 2} powders obtained by complex sol-gel process

    SciTech Connect

    Croce, F.; D'Epifanio, A.; Deptula, A.; Lada, W.; Ciancia, A.; Di Bartolomeo, A.; Brignocchi, A.

    2000-07-01

    The layered oxides, among the wide family of intercalation compounds, have received considerable attention as positive electrode materials in high-energy density lithium and lithium ion batteries. Within this frame LiNiO{sub 2} and LiCoO{sub 2} oxides and their solid solutions have been extensively studied as they (and the LiMn{sub 2}O{sub 4} spinels) are the only known materials able to intercalate reversibly lithium at high cell voltage (3.5--4 V). Recently, solid solutions such as LiNi{sub 1{minus}x}Co{sub x}O{sub 2} have attracted the attention as alternative cathodes to the state of art LiCoO{sub 2} in commercial rechargeable Li-ion batteries. Here the authors have used the Complex Sol-Gel Process (CSGP) to prepare LiNi{sub 1{minus}x}Co{sub x}O{sub 2} (x = 0, 0.25, 0.5, 0.75, 1). Starting sols were prepared from Li{sup +}-(1{minus}x)Ni{sup 2+}-xCo{sup 2+} acetate aqueous solution in two different routes. According to route-A aqueous ammonia was added to a starting solution containing 0.2M ascorbic acid (ASC) on 1M total Me. According to route B the starting acetate solutions were first alkalized by ammonia and then the ascorbic acid was added. Regular sols were concentrated to 1/3 of their initial volume and dried slowly up to 170 C. Thermal transformation of the gels to solids was studied by XRD and IR. The electrochemical properties of the compound LiNi{sub 0.75}Co{sub 0.25}O{sub 2} prepared by the Route-A were evaluated and reported.

  17. Microstructure investigation on micropore formation in microporous silica materials prepared via a catalytic sol-gel process by small angle X-ray scattering.

    PubMed

    Shimizu, Wataru; Hokka, Junsuke; Sato, Takaaki; Usami, Hisanao; Murakami, Yasushi

    2011-08-01

    The so-called sol-gel technique has been shown to be a template-free, efficient way to create functional porous silica materials having uniform micropores. This appears to be closely linked with a postulation that the formation of weakly branched polymer-like aggregates in a precursor solution is a key to the uniform micropore generation. However, how such a polymer-like structure can precisely be controlled, and further, how the generated low-fractal dimension solution structure is imprinted on the solid silica materials still remain elusive. Here we present fabrication of microporous silica from tetramethyl orthosilicate (TMOS) using a recently developed catalytic sol-gel process based on a nonionic hydroxyacetone (HA) catalyst. Small angle X-ray scattering (SAXS), nitrogen adsorption porosimetry, and transmission electron microscope (TEM) allowed us to observe the whole structural evolution, ranging from polymer-like aggregates in the precursor solution to agglomeration with heat treatment and microporous morphology of silica powders after drying and hydrolysis. Using the HA catalyst with short chain monohydric alcohols (methanol or ethanol) in the precursor solution, polymer-like aggregates having microscopic correlation length (or mesh-size) < 2 nm and low fractal dimensions ?2, which is identical to that of an ideal coil polymer, can selectively be synthesized, yielding the uniform micropores with diameters <2 nm in the solid materials. In contrast, the absence of HA or substitution of 1-propanol led to considerably different scattering behavior reflecting the particle-like aggregate formation in the precursor solution, which resulted in the formation of mesopores (diameter >2 nm) in the solid product due to apertures between the particle-like aggregates. The data demonstrate that the extremely fine porous silica architecture comes essentially from a gaussian polymer-like nature of the silica aggregates in the precursor having the microscopic mesh-size and their successful imprint on the solid product. The result offers a general but significantly efficient route to creating precisely designed fine porous silica materials under mild condition that serve as low refractive index and efficient thermal insulation materials in their practical applications. PMID:21692454

  18. Influence of heat treatment on bond strength and corrosion resistance of sol-gel derived bioglass-ceramic coatings on magnesium alloy.

    PubMed

    Shen, Sibo; Cai, Shu; Xu, Guohua; Zhao, Huan; Niu, Shuxin; Zhang, Ruiyue

    2015-05-01

    In this study, bioglass-ceramic coatings were prepared on magnesium alloy substrates through sol-gel dip-coating route followed by heat treatment at the temperature range of 350-500°C. Structure evolution, bond strength and corrosion resistance of samples were studied. It was shown that increasing heat treatment temperature resulted in denser coating structure as well as increased interfacial residual stress. A failure mode transition from cohesive to adhesive combined with a maximum on the measured bond strength together suggested that heat treatment enhanced the cohesion strength of coating on the one hand, while deteriorated the adhesion strength of coating/substrate on the other, thus leading to the highest bond strength of 27.0MPa for the sample heat-treated at 450°C. This sample also exhibited the best corrosion resistance. Electrochemical tests revealed that relative dense coating matrix and good interfacial adhesion can effectively retard the penetration of simulated body fluid through the coating, thus providing excellent protection for the underlying magnesium alloy. PMID:25728582

  19. Influence of chitosan-PEG binary template on the crystallite characteristics of sol-gel synthesized mesoporous nano-titania photocatalyst

    NASA Astrophysics Data System (ADS)

    Preethi, T.; Abarna, B.; Rajarajeswari, G. R.

    2014-10-01

    Nano-titania is by far, the most studied material for its photocatalytic application in air and water pollution abatement. In this study, we have demonstrated the advantage offered by using a binary template of PEG and chitosan for the sol-gel synthesis of titania. Nano-titania samples were prepared using PEG, chitosan and the binary combination of these two as templates. XRD showed that all synthesized samples preserved the anatase structure. Titania sample prepared on 1% PEG and 3% chitosan as template (P1-C3 titania) possessed spherical shaped particles with an average particle size of 12.3 nm, a surface area of 82.9 m2/g and uniform dispersion. DRS UV-Vis spectra indicated that, P1-C3 titania showed blue shift in its absorption profile due to decrease in particle size. Consistent with the characteristics, the P1-C3 titania exhibited the highest photocatalytic activity for the degradation of 4-chlorophenol under UV irradiation, in comparison with all the synthesized photocatalytic systems and Degussa-P25. The chitosan bio template is believed to offer controlled growth of titania through Lewis base type interaction with Ti metallic centers in TiO2. Such controlled growth route will be significant in synthesizing custom-made titania for its advanced applications in catalytic processes.

  20. Reprint of "Influence of chitosan-PEG binary template on the crystallite characteristics of sol-gel synthesised mesoporous nanotitania photocatalyst"

    NASA Astrophysics Data System (ADS)

    Preethi, T.; Abarna, B.; Rajarajeswari, G. R.

    2014-11-01

    Nano-titania is by far, the most studied material for its photocatalytic application in air and water pollution abatement. In this study, we have demonstrated the advantage offered by using a binary template of PEG and chitosan for the sol-gel synthesis of titania. Nano-titania samples were prepared using PEG, chitosan and the binary combination of these two as templates. XRD showed that all synthesized samples preserved the anatase structure. Titania sample prepared on 1% PEG and 3% chitosan as template (P1-C3 titania) possessed spherical shaped particles with an average particle size of 12.3 nm, a surface area of 82.9 m2/g and uniform dispersion. DRS UV-Vis spectra indicated that, P1-C3 titania showed blue shift in its absorption profile due to decrease in particle size. Consistent with the characteristics, the P1-C3 titania exhibited the highest photocatalytic activity for the degradation of 4-chlorophenol under UV irradiation, in comparison with all the synthesized photocatalytic systems and Degussa-P25. The chitosan bio template is believed to offer controlled growth of titania through Lewis base type interaction with Ti metallic centers in TiO2. Such controlled growth route will be significant in synthesizing custom-made titania for its advanced applications in catalytic processes.

  1. Preparation of macroporous zirconia monoliths from ionic precursors via an epoxide-mediated sol-gel process accompanied by phase separation

    NASA Astrophysics Data System (ADS)

    Guo, Xingzhong; Song, Jie; Lvlin, Yixiu; Nakanishi, Kazuki; Kanamori, Kazuyoshi; Yang, Hui

    2015-04-01

    Monolithic macroporous zirconia (ZrO2) derived from ionic precursors has been successfully fabricated via the epoxide-mediated sol-gel route accompanied by phase separation in the presence of propylene oxide (PO) and poly(ethylene oxide) (PEO). The addition of PO used as an acid scavenger mediates the gelation, whereas PEO enhances the polymerization-induced phase separation. The appropriate choice of the starting compositions allows the production of a macroporous zirconia monolith with a porosity of 52.9% and a Brunauer-Emmett-Teller (BET) surface area of 171.9 m2 · g-1. The resultant dried gel is amorphous, whereas tetragonal ZrO2 and monoclinic ZrO2 are precipitated at 400 and 600 °C, respectively, without spoiling the macroporous morphology. After solvothermal treatment with an ethanol solution of ammonia, tetragonal ZrO2 monoliths with smooth skeletons and well-defined mesopores can be obtained, and the BET surface area is enhanced to 583.8 m2 · g-1.

  2. Broadband NIR emission in sol-gel Er(3+)-activated SiO2-Ta2O5 glass ceramic planar and channel waveguides for optical application.

    PubMed

    Ferrari, J L; Limal, K O; Maia, L J Q; Ribeiro, S J L; Gomes, A S L; Gonçalves, R R

    2011-03-01

    An Er(3+)-doped SiO2:Ta2O5 optical channel waveguide and nanocomposite were prepared by the sol-gel route at a Si:Ta 50:50 molar ratio. Channels with an excellent surface profile were easily and quickly fabricated by focusing a femtosecond laser onto the surface of multilayered films deposited on SiO2/Si substrates. In parallel, the same sol used to prepare the film was annealed at 900, 1000, and 1100 degrees C for 2 h, to get the nanocomposite materials. A broadband NIR emission around 1538 nm, assigned to the 4I13/2 --> 4I15/2 transition of the Er3+ ions was observed in the nanocomposites of amorphous SiO2 containing dispersed Ta2O5 nanocrystals. The 4I13/2 lifetime and emission bandwidth depend on the annealing temperature. In conclusion, Er(3+)-doped SiO2:Ta2O5 channel waveguides and nanocomposites are promising materials for photonic applications. PMID:21449421

  3. Effects of Cd concentration on structure and optical properties of the ternary Zn1-xCdxO nanopowder prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Sui, Y. R.; Cao, Y.; Li, X. F.; Yue, Y. G.; Yao, B.; Lang, J. H.; Li, X. Y.; Yang, J. H.

    2015-06-01

    Zn1-xCdxO nanocrystalline powder with different Cd contents (0?x?1) has been prepared by new facile sol-gel route. The crystal structure and optical properties were investigated by X-ray diffraction patterns, Transmission electron microscope, X-ray photoelectron spectroscopy, Photoluminescence. As x varied from x=0 to 0.25, the Zn1-xCdxO nanopowder exhibits a hexagonal wurtzite structure of pure ZnO without any significant formation of a separated CdO phase. For the samples with 0.5?x?0.85, the Zn1-xCdxO nanopowder exhibits the coexistence of hexagonal ZnO and cubic CdO phase, meanwhile, the content of ZnO phase decreases while that of CdO increases with increasing the Cd content x. The ultra-violet near-band-edge emission of the Zn1-xCdxO nanopowder was monotonously red-shifted from 389 nm (x=0) to 406 nm (x=0.25) due to the direct modulation of band gap caused by Cd substitution.

  4. Effect of Organic Blocking Layer on the Energy Storage Characteristics of High-Permittivity Sol-Gel Thin Film Based on Neat 2-Cyanoethyltrimethoxysilane

    NASA Astrophysics Data System (ADS)

    Kim, Yunsang; Kathaperumal, Mohanalingam; Pan, Ming-Jen; Perry, Joseph

    2014-03-01

    Organic-inorganic hybrid sol-gel materials with polar groups that can undergo reorientational polarization provide a potential route to dielectric materials for energy storage. We have investigated the influence of nanoscale polymeric layer on dielectric and energy storage properties of 2-cyanoethyltrimethoxysilane (CNETMS) films. Two polymeric materials, fluoropolymer (CYTOP) and poly(p-phenylene oxide, PPO), are examined as potential materials to control charge injection from electrical contacts into CNETMS films by means of a potential barrier, whose width and height are defined by thickness and permittivity. Blocking layers ranging from 20 nm to 200 nm were deposited on CNETMS films by spin casting and subjected to thermal treatment. Polarization-electric field measurements show 30% increase in extractable energy density with PPO/CNETMS bilayers, relative to CNETMS alone, due to improved breakdown strength. Conduction current of the bilayers indicate that onset of charge conduction at high field is much delayed, which can be translated into effective suppression of charge injection and probability of breakdown events. The results will be discussed in regards to film morphology, field partitioning, width and height of potential barrier, charge trapping and loss of bilayers.

  5. Synthesis, consolidation and characterization of sol-gel derived tantalum-tungsten oxide thermite composites

    NASA Astrophysics Data System (ADS)

    Cervantes, Octavio

    Energetic composite powders consisting of sol-gel (SG) 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 SG derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The SG derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO3) energetic composite was consolidated to a density of 9.17 g·cm-3 or 93% relative density. In addition, those samples were consolidated without significant pre-reaction of the constituents, thus retaining their stored chemical energy. The heat of combustion of two distinctly synthesized stoichiometric tantalum-tungsten oxide energetic composites was investigated by bomb calorimetry. One composite was synthesized using a sol-gel (SG) derived method in which micrometric-scale tantalum is immobilized in a tungsten oxide three-dimensional nanostructured network structure. The second energetic composite was made from the mixing of micrometric-scale tantalum and commercially available (CA) nanometric tungsten oxide powders. The energetic composites were consolidated using the spark plasma sintering (SPS) technique under a 300 MPa pressure and at temperatures of 25, 400, and 500°C. For samples consolidated at 25°C, the density of the CA composite is 61.65 +/- 1.07% in comparison to 56.41 +/- 1.19% for the SG derived composite. In contrast, the resulting densities of the SG composite are higher than the CA composite for samples consolidated at 400 and 500°C. The theoretical maximum density for the SG composite consolidated to 400 and 500°C are 81.30 +/- 0.58% and 84.42 +/- 0.62%, respectively. The theoretical maximum density of the CA composite consolidated to 400 and 500°C are 74.54 +/- 0.80% and 77.90 +/- 0.79%, respectively. X-ray diffraction analyses showed an increase of pre-reaction of the constituents with an increase in the consolidation temperature. The increase in pre-reaction results in lower stored energy content for samples consolidated to 400 and 500°C in comparison to samples consolidated at 25°C. The activation energy of a SG derived tantalum-tungsten oxide thermite composite was determined using the Kissinger isoconversion method. The SG derived powder was consolidated using the HPSPS technique at 300 and 400°C. The ignition temperatures were investigated under high heating rates (500--2000°C·min -1). Such heating rates were required in order to ignite the thermite composite. Samples consolidated at 300°C exhibit an abrupt change in temperature response prior to ignition of the main combustion reaction. This change in temperature response is attributed to the crystallization of the amorphous WO3 in the SG derived Ta-WO3 thermite composite and not to a pre-ignition reaction between the constituents. Ignition temperatures for the Ta-WO3 thermite ranged from approximately 465 to 670°C. The activation energies of the SG derived Ta-WO3 thermite composite consolidated at 300 and 400°C were determined to be 37.787 +/- 1.58 kJ·mol-1 and 57.381 +/- 2.26 kJ·mol -1, respectively.

  6. Nonlinear optical and electrical conductivity properties of Carbon Nanotubes (CNT) doped in Sol-Gel matrices

    NASA Astrophysics Data System (ADS)

    Pokrass, Mariana; Burshtein, Zeev; Bar, Galit; Gvishi, Raz

    2014-09-01

    Carbon-nanotubes (CNT) are fascinating compounds, exhibiting exceptional electrical, thermal conductivity, mechanical strength, and nonlinear optical (NLO) properties. Their unique structures involve large ?-?* electronic clouds. The energy level schemes thus created allow many electronic transitions between the ground and the excited states. The present work involves CNT-doped hybrid organic-inorganic glass composites prepared by a Fast-sol-gel method. Such composite glasses solidify without shrinkage or crack formation, and exhibit promising properties as optical devices. In this work we have studied nonlinear optical and electrical conductivity properties. The CNT composite glasses exhibited enhanced absorption at 532 nm, and saturable absorption at 1064 nm. The enhanced absorption at 532 was attributed to 2-photon absorption; saturable absorption was attributed to depletion of the absorbing ground-state, and was analyzed using the modified Frantz-Nodvik equation. Absorption cross-sections were extracted for the saturable absorption phenomenon. Such CNT composites glasses may be used as "optical limiting" filters in lasers near 532 nm, or as saturable absorbing filters for passive laser Q-switching near 1064 nm. The CNT composites electrical conductivity was studied as a function of the CNT concentration and modeled by a percolation theory. The maximal measured conductivity was ? ?10-3 (?cm)-1 for the CNT composites, representing a conductivity increase of at least 12 orders of magnitude compared to that of pure silica. A quite low percolation threshold was obtained, ?c = 0.22 wt.% CNT. Electrostatic Force Microscopy (EFM) and Conductive mode Atomic Force Microscopy (C-AFM) studies revealed that the conductivity occurs at the micro-level among the CNTs dispersed in the matrix.

  7. Characterization of nanocrystalline ZnO:Al films by sol-gel spin coating method

    SciTech Connect

    Gareso, P. L. Rauf, N. Juarlin, E.; Sugianto,; Maddu, A.

    2014-09-25

    Nanocrystalline ZnO films doped with aluminium by sol-gel spin coating method have been investigated using optical transmittance UV-Vis and X-ray diffraction (X-RD) measurements. ZnO films were prepared using zinc acetate dehydrate (Zn(CH{sub 3}COO){sub 2}@@‡2H{sub 2}O), ethanol, and diethanolamine (DEA) as a starting material, solvent, and stabilizer, respectively. For doped films, AlCl{sub 3} was added to the mixture. The ZnO:Al films were deposited on a transparent conductive oxide (TCO) substrate using spin coating technique at room temperature with a rate of 3000 rpm in 30 sec. The deposited films were annealed at various temperatures from 400°C to 600°C during 60 minutes. The transmittance UV-Vis measurement results showed that after annealing at 400°C, the energy band gap profile of nanocrystalline ZnO:Al film was a blue shift. This indicated that the band gap of ZnO:Al increased after annealing due to the increase of crystalline size. As the annealing temperature increased the bandgap energy was a constant. In addition to this, there was a small oscillation occurring after annealing compared to the as–grown samples. In the case of X-RD measurements, the crystalinity of the films were amorphous before annealing, and after annealing the crystalinity became enhance. Also, X-RD results showed that structure of nanocrystalline ZnO:Al films were hexagonal polycrystalline with lattice parameters are a = 3.290 Å and c = 5.2531 Å.

  8. Photocatalytic effect and Mössbauer study of iron titanium silicate glass prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Takahashi, Yusuke; Kubuki, Shiro; Akiyama, Kazuhiko; Sinkó, Katalin; Homonnay, Zoltán; Kuzmann, Ern?; Nishida, Tetsuaki

    2015-06-01

    A relationship between the photocatalytic effect and the local structure of 50Fe2O3? (50- x)SiO2? xTiO2 glass abbreviated as 50FS xTi prepared by sol-gel method was investigated by 57Fe-Mössbauer spectroscopy (FeMS), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible diffuse reflectance spectroscopy (UV-VIS). Mössbauer spectra of 50FS xTi glass before annealing showed a doublet with the isomer shift ( ?) and quadrupole splitting (?) of 0.41±0.01 mm s-1 and 0.75±0.02 mm s-1, indicating that Fe3+ formed FeO6 octahedra ( O h). A comparable ? of 0.36±0.02 mm s-1 and the larger ? of 0.92±0.02 mm s-1 values were confirmed for 50FS xTi after annealed at 400 ? C for 3 h. These results indicates that the coordination number of iron polyhedra decreases from 6 to 4 due to annealing. UV-VIS diffuse reflectance spectra of 50FS10Ti yielded two optical band gap energies ( E g's) of 2.05 eV and 3.55 eV. This result implied that 50FS10Ti has two optical band gaps in the visible area and UV area. A bleaching test performed by 10 mL of MB aqueous solution and 40 mg of powder 50FS10Ti glass sample showed that MB absorbance decreased from 3.16 to 0.43 after UV-visible light irradiation for 2 h with the first order rate constant ( k) of . These results prove that titanium containing iron silicate glass with the composition of 50Fe2O3?40SiO2?10TiO2 has the UV and visible light responsive photocatalytic effect.

  9. Preparation of MTMS based transparent superhydrophobic silica films by sol-gel method.

    PubMed

    Venkateswara Rao, A; Latthe, Sanjay S; Nadargi, Digambar Y; Hirashima, H; Ganesan, V

    2009-04-15

    Superhydrophobic surfaces with water contact angle higher than 150 degrees generated a lot of interest both in academia and in industry because of the self-cleaning properties. Optically transparent superhydrophobic silica films were synthesized at room temperature (27 degrees C) using sol-gel process by a simple dip coating technique. The molar ratio of MTMS:MeOH:H(2)O (5 M NH(4)OH) was kept constant at 1:10.56:4.16, respectively. Emphasis is given to the effect of the surface modifying agents on the hydrophobic behavior of the films. Methyl groups were introduced in the silica film by post-synthesis grafting from two solutions using trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDZ) silylating agents in hexane solvent, individually. The percentage of silylating agents and silylation period was varied from 2.5 to 7.5% and 1 to 3 h, respectively. The TMCS modified films exhibited a very high water contact angle (166+/-2 degrees) in comparison to the HMDZ (138+/-2 degrees) modified films, indicating the water repellent behavior of the surface. When the TMCS and HMDZ modified films were heated at temperatures higher than 350 degrees C and 335 degrees C, respectively, the films became superhydrophilic; the contact angle for water on the films was smaller than 5 degrees. Further, the humidity study was carried out at a relative humidity of 85% at 30 degrees C temperature over 30 days. The films have been characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), % optical transmission, humidity tests and contact angle (CA) measurements. PMID:19200554

  10. Development of durable self-cleaning coatings using organic-inorganic hybrid sol-gel method

    NASA Astrophysics Data System (ADS)

    Kumar, Divya; Wu, Xinghua; Fu, Qitao; Ho, Jeffrey Weng Chye; Kanhere, Pushkar D.; Li, Lin; Chen, Zhong

    2015-07-01

    Self-cleaning coatings with excellent water-repellence and good mechanical properties are in high demand. However, producing such coatings with resistance to mechanical abrasion and environmental weathering remains a key challenge. Mechanically robust coatings based on tetraethylorthosilicate (TEOS) and glycidoxypropyltriethoxysilane (Glymo) have been prepared using a sol-gel method. Emphasis is given to the addition of Glymo, an epoxy silane which creates an organic matrix that blends with the inorganic Sisbnd Osbnd Si matrix formed from the TEOS. The combination of the blended matrix produced coatings with good adhesion to substrates and improved mechanical properties. Fluoroalkylsilane (FAS) and silica fillers were introduced to increase the hydrophobicity of the coating. It was found that the water contact angle (CA) of these coatings increases from 115° to 164° upon decreasing filler size from 1-5 ?m to 10-20 nm. The sliding angle (SA) for coatings with 15 wt.% loading of 10-20 nm silica is around 2°. UV weathering does not show significant effect on the properties of the coatings. Mechanical properties and performances including hardness, Young's modulus, coating adhesion and abrasion resistance were systematically analyzed. In the current work, a simple self-cleaning test, which measures the extent of dirt accumulation and subsequent removal by water spray, was performed. The coatings with 15 wt.% loading of 10-20 nm silica particles show the best self-cleaning performance both before and after mechanical abrasion. The developed coating process is simple and can be easily scaled-up for large surfaces that require self-cleaning function.

  11. Preparation, characterization, and biological properties of organic-inorganic nanocomposite coatings on titanium substrates prepared by sol-gel.

    PubMed

    Catauro, Michelina; Bollino, Flavia; Papale, Ferdinando

    2014-02-01

    When surface-reactive (bioactive) coatings are applied to medical implants by means of the sol-gel dip-coating technique, the biological proprieties of the surface of the implant can be locally modified to match the properties of the surrounding tissues to provide a firm fixation of the implant. The aim of this study has been to synthesize, via sol-gel, organoinorganic nanoporous materials and to dip-coat a substrate to use in dental applications. Different systems have been prepared consisting of an inorganic zirconium-based matrix, in which a biodegradable polymer, the poly-?-caprolactone was incorporated in different percentages. The materials synthesized by the sol-gel process, before gelation, when they were still in sol phase, have been used to coat a titanium grade 4 (Ti-4) substrate to change its surface biological properties. Thin films have been obtained by means of the dip-coating technique. A microstructural analysis of the obtained coatings was performed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. The biological proprieties have been investigated by means of tests in vitro. The bone-bonding capability of the nanocomposite films has been evaluated by examining the appearance of apatite on their surface when plunged in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. The examination of apatite formation on the nanocomposites, after immersion in SBF, has been carried out by SEM equipped with energy-dispersive X-ray spectroscopy. To evaluate cells-materials interaction, human osteosarcoma cell line (Saos-2) has been seeded on specimens and cell vitality evaluated by WST-8 assay. PMID:23533196

  12. Structure and magnetic properties of SiO{sub 2}/PCL novel sol–gel organic–inorganic hybrid materials

    SciTech Connect

    Catauro, Michelina; Bollino, Flavia; Cristina Mozzati, Maria; Ferrara, Chiara; Mustarelli, Piercarlo

    2013-07-15

    Organic–inorganic nanocomposite materials have been synthesized via sol–gel. They consist of an inorganic SiO{sub 2} matrix, in which different percentages of poly(?-caprolactone) (PCL) have been incorporated. The formation of H-bonds among the carbonyl groups of the polymer chains and Si–OH group of the inorganic matrix has been proved by means of Fourier transform infrared spectroscopy (FT-IR) analysis and has been confirmed by solid-state nuclear magnetic resonance (NMR). X-Ray diffraction (XRD) analysis highlighted the amorphous nature of the synthesized materials. Scanning electron microscope (SEM) micrograph and atomic force microscope (AFM) topography showed their homogeneous morphology and nanostructure nature. Considering the opportunity to synthesize these hybrid materials under microgravity conditions by means of magnetic levitation, superconducting quantum interference device (SQUID) magnetometry has been used to quantify their magnetic susceptibility. This measure has shown that the SiO{sub 2}/PCL hybrid materials are diamagnetic and that their diamagnetic susceptibility is independent of temperature and increases with the PCL amount. - Graphical abstract: Characterization and magnetic properties of SiO{sub 2}/PCL organic–inorganic hybrid materials synthesized via sol–gel. FT-IR, Fourier transform infrared spectroscopy; solid-state NMR: solid-state nuclear magnetic resonance; SQUID: superconducting quantum interference device. - Highlights: • Sol–gel synthesis of SiO{sub 2}/PCL amorphous class I organic–inorganic hybrid materials. • FT-IR and NMR analyses show the hydrogen bonds formation between SiO{sub 2} and PCL. • AFM and SEM analyses confirm that the SiO{sub 2}/PCL are homogenous hybrid materials. • The SQUID measures show that the simples are diamagnetic. • Diamagnetic susceptibility of SiO{sub 2}/PCL materials increases with the PCL amount.

  13. Eu-Doped BaTiO3 Powder and Film from Sol-Gel Process with Polyvinylpyrrolidone Additive

    PubMed Central

    García-Hernández, Margarita; García-Murillo, Antonieta; de J. Carrillo-Romo, Felipe; Jaramillo-Vigueras, David; Chadeyron, Geneviève; De la Rosa, Elder; Boyer, Damien

    2009-01-01

    Transparent BaTiO3:Eu3+ films were prepared via a sol-gel method and dip-coating technique, using barium acetate, titanium butoxide, and polyvinylpyrrolidone (PVP) as modifier viscosity. BaTiO3:Eu3+ films ~500 nm thick, crystallized after thermal treatment at 700 ºC. The powders revealed spherical and rod shape morphology. The optical quality of films showed a predominant band at 615 nm under 250 nm excitation. A preliminary luminescent test provided the properties of the Eu3+ doped BaTiO3. PMID:19865533

  14. Plasmon mediated cathodic photocurrent generation in sol-gel synthesized doped SrTiO3 nanofilms

    NASA Astrophysics Data System (ADS)

    Sugavaneshwar, Ramu Pasupathi; Chen, Kai; Lakshminarayana, Gandham; Ishii, Satoshi; Dao, Thang Duy; Umezawa, Naoto; Nagao, Tadaaki

    2015-11-01

    Thin films of SrTiO3 (STO) and Rh-doped SrTiO3 (Rh-STO) were synthesized by sol-gel method and loaded with Ag nanoparticles. Pristine STO films exhibited anodic photocurrent while Rh-STO exhibited cathodic photocurrent. An enhancement in the overall cathodic photocurrent is observed with Ag nanoparticle loading and an additional enhancement in the visible light range is seen from the incident photon-to-current efficiency spectrum due to synergetic effect of Rh doping and Ag loading in STO.

  15. Novel sol-gel synthesis of cerium-doped ZnO thin films for photocatalytic activity

    SciTech Connect

    Senthilvelan, S.; Chandraboss, V. L.; Karthikeyan, B.; Murugavelu, M.; Loganathan, B.; Natanapatham, L.

    2012-07-23

    The Ce-doped ZnO films on silica glass plates were prepared by sol-gel dip coating technique. The surface morphology of thin films was characterized by means of scanning electron microscopy (SEM). Optical properties of films have been investigated using UV-visible spectroscopy. The photocatalytic activity was established by testing the degradation of Alizarin Red (AR) from aqueous solution. The test of photocatalytic activity of the heat-treated Ce-doped ZnO films were also carried out under visible light irradiation.

  16. Integrated optical devices based on solgel waveguides using the temperature dependence of the effective refractive index

    SciTech Connect

    Pavlov, S V; Trofimov, N S; Chekhlova, T K

    2014-07-31

    A possibility of designing optical waveguide devices based on solgel SiO{sub 2} – TiO{sub 2} films using the temperature dependence of the effective refractive index is shown. The dependences of the device characteristics on the parameters of the film and opticalsystem elements are analysed. The operation of a temperature recorder and a temperature limiter with a resolution of 0.6 K mm{sup -1} is demonstrated. The film and output-prism parameters are optimised. (fibreoptic and nonlinear-optic devices)

  17. Dielectric and magnetic properties of sol-gel-derived lead iron niobate ceramics

    SciTech Connect

    Majumder, S.B.; Bhattacharyya, S.; Katiyar, R.S.; Manivannan, A.; Dutta, P.; Seehra, M.S.

    2006-01-15

    In this work, we report the synthesis of sol-gel-derived lead iron niobate [Pb{sub 1.10}(Fe{sub 0.5}Nb{sub 0.5})O{sub 3}] (PFN) powders and sintered ceramics. The PFN powders were calcined at (T{sub a}), 973, 1073, 1173, 1273, and 1373 K for 3 h in air. As envisaged from x-ray-diffraction analyses, PFN powder calcined at 1173 K was crystallized into pure monoclinic perovskite phase whereas powders calcined at all other temperatures had varied amounts of retained pyrochlore (Pb{sub 3}Nb{sub 4}O{sub 13}) phase coexisted with dominant monoclinic perovskite phase. The PFN pellet (prepared using the phase pure powder calcined at 1173 K) sintered at 1373 K for 4 h in air also had a minute quantity of retained pyrochlore phase coexisting with desired perovskite phase. From the temperature dependence of measured capacitance and loss tangent at different frequencies, the ferroelectric to paraelectric phase-transition temperature of PFN ceramics was observed at T{sub c}{approx_equal}370 K. The diffused nature of this transition and high dielectric constant of PFN is related to the cation disorder at the B site of A(B{sub I}{sup +3}B{sub II}{sup +5})O{sub 3} lattice. For PFN powders, calcined at different temperatures, the temperature dependence of the magnetic susceptibility ({chi}) was measured in a temperature range of 2-360 K, whereas the magnetic hysteresis loops and electron magnetic resonance (EMR) spectra were measured at room temperature. Room-temperature ferromagnetism is observed in all the calcined powder samples and it was found that the magnetization increases with the increase in calcination temperature (T{sub a}). The symmetric EMR line shape with g{approx_equal}2.01 observed in all calcined samples was identified to be due to Fe{sup 3+} ions. It is suggested that the observed weak ferromagnetism, which increases with an increase in T{sub a}, may be due to canting of the Fe{sup 3+} spins. These observations suggest PFN to be a very attractive single-phase ferroelectric/ferromagnetic material for room-temperature applications.

  18. Optical Fiber Chemical Sensor with Sol-Gel Derived Refractive Material as Transducer for High Temperature Gas Sensing in Clean Coal Technology

    SciTech Connect

    Shiquan Tao

    2006-12-31

    The chemistry of sol-gel derived silica and refractive metal oxide has been systematically studied. Sol-gel processes have been developed for preparing porous silica and semiconductor metal oxide materials. Micelle/reversed micelle techniques have been developed for preparing nanometer sized semiconductor metal oxides and noble metal particles. Techniques for doping metal ions, metal oxides and nanosized metal particles into porous sol-gel material have also been developed. Optical properties of sol-gel derived materials in ambient and high temperature gases have been studied by using fiber optic spectroscopic techniques, such as fiber optic ultraviolet/visible absorption spectrometry, fiber optic near infrared absorption spectrometry and fiber optic fluorescence spectrometry. Fiber optic spectrometric techniques have been developed for investigating the optical properties of these sol-gel derived materials prepared as porous optical fibers or as coatings on the surface of silica optical fibers. Optical and electron microscopic techniques have been used to observe the microstructure, such as pore size, pore shape, sensing agent distribution, of sol-gel derived material, as well as the size and morphology of nanometer metal particle doped in sol-gel derived porous silica, the nature of coating of sol-gel derived materials on silica optical fiber surface. In addition, the chemical reactions of metal ion, nanostructured semiconductor metal oxides and nanometer sized metal particles with gas components at room temperature and high temperatures have also been investigated with fiber optic spectrometric methods. Three classes of fiber optic sensors have been developed based on the thorough investigation of sol-gel chemistry and sol-gel derived materials. The first group of fiber optic sensors uses porous silica optical fibers doped with metal ions or metal oxide as transducers for sensing trace NH{sub 3} and H{sub 2}S in high temperature gas samples. The second group of fiber optic sensors uses sol-gel derived porous silica materials doped with nanometer particles of noble metals in the form of fiber or coating for sensing trace H{sub 2}, NH{sub 3} and HCl in gas samples at for applications ambient temperature. The third classes of fiber optic sensors use sol-gel derived semiconductor metal oxide coating on the surface of silica optical fiber as transducers for selectively sensing H{sub 2}, CH{sub 4} and CO at high temperature. In addition, optical fiber temperature sensors use the fluorescence signal of rare-earth metal ions doped porous silica optical fiber or the optical absorption signal of thermochromic metal oxide materials coated on the surface of silica optical fibers have also been developed for monitoring gas temperature of corrosive gas. Based on the results obtained from this project, the principle of fiber optic sensor techniques for monitoring matrix gas components as well as trace components of coal gasification derived syngas has been established. Prototype sensors for sensing trace ammonia and hydrogen sulfide in gasification derived syngas have been built up in our laboratory and have been tested using gas samples with matrix gas composition similar to that of gasification derived fuel gas. Test results illustrated the feasibility of these sensors for applications in IGCC processes.

  19. Novel sol-gel methodology to produce LaCoO3 by acrylamide polymerization assisted by ?-irradiation

    NASA Astrophysics Data System (ADS)

    Carabalí, G.; Chavira, E.; Castro, I.; Bucio, E.; Huerta, L.; Jiménez-Mier, J.

    2012-05-01

    In this paper we report the synthesis of LaCoO3 (LCO) nano-particles with two methodologies: the conventional sol-gel reaction of acrylamide (AA) polymerization using a cross-linking agent (methylenebisacrylamide or MBA) with the activation of the polymerization reaction by thermo-chemical initiator (azobisisobutyrnitrile or AIBN). The second was a novel sol-gel methodology in which the polymerization of AA monomers was done without MBA and the initiation was achieved by gamma radiation. With thermochemical initiator a xerogel with a foam and porous structure was obtained, while the gamma-irradiation of the mixture leads to the formation of a compact resin with entrapped cations. X-ray diffraction (XRD) shows that formation of the product begins around 500 °C and according to analysis of microscopy images of powders calcined in 700 °C the average sizes of particles are 20 nm and 42 nm for samples obtained using ?-irradiation and AIBN as initiators, respectively. TEM images also show differences in particle morphology. Those synthesized using AIBN as initiator are dispersed, while those with ?-irradiation are in aggregates.

  20. A New Approach of Improving Rain Erosion Resistance of Nanocomposite Sol-Gel Coatings by Optimization Process Factors

    NASA Astrophysics Data System (ADS)

    Hojjati Najafabadi, Akbar; Shoja Razavi, Reza; Mozaffarinia, Reza; Rahimi, Hamed

    2014-05-01

    Erosion protection nanocomposite sol-gel coatings based on tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxisilane (GPTMS) are prepared and characterized to protect marine structures susceptible to damage caused by liquid impact, e.g., the submarine body. This study focuses on the optimization of compositional and process parameters of transparent hybrid nanocomposite sol-gel coatings resistant to rain erosion by using statistical design of experimental methodology (DoE) based on Taguchi orthogonal design. The impact of compositional and process parameters of the coatings on the erosion protection performance is investigated by five-factor-four-level design methodology. Hybrid coatings were deposited on AA5083 by a dip coating technique. Optimization coatings are analyzed regarding their adhesion (pull-off), flexibility (impact and mandrel bending), hardness (pencil), wear (Taber wear index), and rain erosion resistance (stationary sample erosion test). The surface morphology and roughness were studied by field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The optimization coatings showed excellent flexibility and adhesion to the substrate with smooth nanostructure surface; the RMS surface roughness was 1.85 nm. The evaluation of the result obtained from abrasion shows cohesive and interfacial wear with abrasive and adhesive mechanisms, respectively. Liquid impact results show cohesive failure of the coatings without any sign of delamination.