Science.gov

Sample records for microporous silica prepared

  1. Microporous silica prepared by organic templating: Relationship between the molecular template and pore structure

    SciTech Connect

    Lu, Y.; Brinker, C.J. |; Cao, G.; Kale, R.P.; Prabakar, S.; Lopez, G.P.

    1999-05-01

    Microporous silica materials with a controlled pore size and a narrow pore size distribution have been prepared by sol-gel processing using an organic-templating approach. Microporous networks were formed by pyrolytic removal of organic ligands (methacryloxypropyl groups) from organic/inorganic hybrid materials synthesized by copolymerization of 3-methacryloxypropylsilane (MPS) and tetraethoxysilane (TEOS). Molecular simulations and experimental measurements were conducted to examine the relationship between the microstructural characteristics of the porous silica (e.g., pore size, total pore volume, and pore connectivity) and the size and amount of organic template ligands added. Adsorption measurements suggest that the final porosity of the microporous silica is due to both primary pores (those present in the hybrid material prior to pyrolysis) and secondary pores (those created by pyrolytic removal of organic templates). Primary pores were inaccessible to N{sub 2} at 77 K but accessible to CO{sub 2} at 195 K; secondary pores were accessible to both N{sub 2} (at 77 K) and CO{sub 2} (at 195 K) in adsorption measurements. Primary porosity decreases with the amount of organic ligands added because of the enhanced densification of MPS/TEOS hybrid materials as the mole fraction of trifunctional MPS moieties increases. Pore volumes measured by nitrogen adsorption experiments at 77 K suggest that the secondary (template-derived) porosity exhibits a percolation behavior as the template concentration is increased. Gas permeation experiments indicate that the secondary pores are approximately 5 {angstrom} in diameter, consistent with predictions based on molecular simulations.

  2. 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

  3. 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.

  4. Synthesis of Pd particle-deposited microporous silica membranes via a vacuum-impregnation method and their gas permeation behavior.

    PubMed

    Lee, Dong-Wook; Yu, Chang-Yeol; Lee, Kew-Ho

    2008-09-15

    Pd particle-deposited microporous silica membranes were synthesized to improve hydrogen permselectivity of the microporous silica membrane and to overcome high cost of palladium and crack formation through hydrogen embrittlement. Pd particles below 400 nm in diameter were readily deposited on the microporous silica membrane via a vacuum-impregnation method by using a Pd(C(3)H(5))(C(5)H(5)) precursor. After deposition of Pd particles on the microporous silica membrane, hydrogen permselectivity over nitrogen considerably increased from 11-28 to 30-115 in a permeation temperature range of 25-350 degrees C due to plugging membrane defects and hydrogen adsorption diffusion through the interface between the Pd and silica layer. The activation energy of the Pd-deposited silica membrane (6.32 kJ mol(-1)) was higher than that of the microporous silica membrane (4.22 kJ mol(-1)). In addition, the Pd-particle deposition led to an increase in the permselectivity of He and CO(2) with little chemical affinity for the Pd particles, which indicates that Pd-particle deposition gives the effect of plugging defects such as pinholes or cracks, which could be formed during the membrane preparation. Therefore it is demonstrated that Pd-particle deposition on the silica membrane is effective for induction of the hydrogen adsorption diffusion and plugging membrane defects. PMID:18620361

  5. Highly hydrothermally stable microporous silica membranes for hydrogen separation.

    PubMed

    Wei, Qi; Wang, Fei; Nie, Zuo-Ren; Song, Chun-Lin; Wang, Yan-Li; Li, Qun-Yan

    2008-08-01

    Fluorocarbon-modified silica membranes were deposited on gamma-Al2O3/alpha-Al2O3 supports by the sol-gel technique for hydrogen separation. The hydrophobic property, pore structure, gas transport and separation performance, and hydrothermal stability of the modified membranes were investigated. It is observed that the water contact angle increases from 27.2+/-1.5 degrees for the pure silica membranes to 115.0+/-1.2 degrees for the modified ones with a (trifluoropropyl)triethoxysilane (TFPTES)/tetraethyl orthosilicate (TEOS) molar ratio of 0.6. The modified membranes preserve a microporous structure with a micropore volume of 0.14 cm3/g and a pore size of approximately 0.5 nm. A single gas permeation of H2 and CO2 through the modified membranes presents small positive apparent thermal activation energies, indicating a dominant microporous membrane transport. At 200 degrees C, a single H2 permeance of 3.1x10(-6) mol m(-2) s(-1) Pa(-1) and a H2/CO2 permselectivity of 15.2 were obtained after proper correction for the support resistance and the contribution from the defects. In the gas mixture measurement, the H2 permeance and the H2/CO2 separation factor almost remain constant at 200 degrees C with a water vapor pressure of 1.2x10(4) Pa for at least 220 h, indicating that the modified membranes are hydrothermally stable, benefiting from the integrity of the microporous structure due to the fluorocarbon modification. PMID:18613718

  6. Preparation and characterization of microporous SiO{sub 2}-ZrO{sub 2} pillared montmorillonite

    SciTech Connect

    Han, Yang-Su . E-mail: yshan@inanospace.com; Yamanaka, Shoji

    2006-04-15

    SiO{sub 2}-ZrO{sub 2} pillared montmorillonite (SZM) was prepared by the reaction of Na-montmorillonite with colloidal silica-zirconia particles which were prepared by depositing zirconium hydroxy cations on silica particles. By pillaring with the colloidal particles, the basal spacing of montmorillonite was expanded to ca. 45 A and the calcined SZM samples showed large specific surface areas up to 320 m{sup 2}/g at 400 deg. C. In spite of large interlayer separation, adsorption results indicated the presence of micropores generated between the colloidal particles. The microporous structure was maintained at least up to 600 deg. C and exhibited specific shape selectivity for the adsorption of large organic molecules, especially between toluene and mesitylene. According to the temperature-programmed-desorption (TPD) spectra of ammonia, the calcined SZM showed weakly acidic sites.

  7. Transport of pure components in pervaporation through a microporous silica membrane.

    PubMed

    Bettens, Ben; Dekeyzer, Sofie; Van der Bruggen, Bart; Degrève, Jan; Vandecasteele, Carlo

    2005-03-24

    The pervaporation mechanism of pure components through a commercial microporous silica membrane was studied by performing experiments using water, methanol, ethanol, 2-propanol, and n-propanol in the 40-80 degrees C temperature range. Experimental fluxes were correlated to feed temperature and viscosity. It was found that the permeation mechanism obeys the adsorption-diffusion description, covering both the microscopic models based on configurational (micropore) diffusion and on activated surface diffusion. The contribution of convection was negligible. Size parameters for the permeating molecules such as molecular weight, kinetic diameter, and effective diameter, which are expected to have an influence on diffusion, did not correlate with the flux, thus strongly emphasizing the importance of sorption as the rate-determining step for transport in the pervaporation process. This was confirmed by correlating parameters reflecting polarity with flux: an exponential relation between the Hansen polarity (especially the hydrogen bonding component) and the flux was observed. A similar correlation was found between the dielectric constant and the flux. Furthermore, the flux increases in the same direction as the hydrophilicity of the pure components (log P). The effects of membrane surface tension and contact angles are less outspoken, but experiments performed on glass supported and silica supported membrane top layers suggest an important influence of the sublayers on the flux. PMID:16863187

  8. Elaboration and Characterization of High Silica ZSM-5 and Mordenite Solid Microporous Materials

    NASA Astrophysics Data System (ADS)

    Khemaissia, Sihem; Nibou, Djamel; Amokrane, Samira; Lebaili, Nemcha

    In this study, we were interested to use a hydrothermally method of elaboration of ZSM-5 and Mordenite solid microporous materials. This method is based on crystallization of amorphous gels composed of silicon and aluminium solutions. The elaborations were carried out in stainless steel Teflon lined autoclave over different operation conditions: heating temperature, contact time, pH and agitation of the reactional medium. After crystallization, samples were characterized by several techniques as X ray diffraction, scanning microscopy, infrared spectroscopy. The used method was allowed the obtaining of pure phases of solids belonging to ZSM-5 and mordenite structures respectively. The crystal growth environment during nucleation and crystallization was occurred at the liquid-gel interface in the dispersed gel-solution mixtures. The composition of these structures was found as high silica zeolites.

  9. The hydrogen-storing microporous silica 'Microcluster' reduces acetaldehyde contained in a distilled spirit.

    PubMed

    Kato, Shinya; Miwa, Nobuhiko

    2016-12-01

    Acetaldehyde is a detrimental substance produced in alcoholic liquor aging. We assessed an ability of hydrogen-storing microporous silica 'Microcluster' (MC+) to reduce acetaldehyde, as compared with autoclave-dehydrogenated MC+ (MC-). Acetaldehyde was quantified spectrophotometrically by an enzymatic method. Authentic acetaldehyde was treated by MC+ for 20min, and decreased from 43.4ppm to 10.9ppm, but maintained at 49.3ppm by MC-. On the other hand, acetaldehyde contained in a distilled spirit was decreased from 29.5ppm to 3.1ppm at 20min by MC+, but not decreased by MC-. Addition of MC+ or MC- to distilled water without acetaldehyde showed no seeming effect on the quantification used. Accordingly acetaldehyde in a distilled spirit is reduced to ethanol by hydrogen contained in MC+, but not by the silica moiety of MC+. Hydrogen gas of 1.2mL was released for 20min from MC+ of 0.59g in water, resulting in dissolved hydrogen of 1.09ppm and an oxidation- reduction potential of -687.0mV indicative of a marked reducing ability. Thus, MC+ has an ability to reduce acetaldehyde in a distilled spirit due to dissolved hydrogen released from MC+. PMID:27612695

  10. An activated microporous carbon prepared from phenol-melamine-formaldehyde resin for lithium ion battery anode

    SciTech Connect

    Zhu, Yinhai; Xiang, Xiaoxia; Liu, Enhui; Wu, Yuhu; Xie, Hui; Wu, Zhilian; Tian, Yingying

    2012-08-15

    Highlights: ► Microporous carbon was prepared by chemical activation of phenol-melamine-formaldehyde resin. ► Activation leads to high surface area, well-developed micropores. ► Micropores lead to strong intercalation between carbon and lithium ion. ► Large surface area promotes to improve the lithium storage capacity. -- Abstract: Microporous carbon anode materials were prepared from phenol-melamine-formaldehyde resin by ZnCl{sub 2} and KOH activation. The physicochemical properties of the obtained carbon materials were characterized by scanning electron microscope, X-ray diffraction, Brunauer–Emmett–Teller, and elemental analysis. The electrochemical properties of the microporous carbon as anode materials in lithium ion secondary batteries were evaluated. At a current density of 100 mA g{sup −1}, the carbon without activation shows a first discharge capacity of 515 mAh g{sup −1}. After activation, the capacity improved obviously. The first discharge capacity of the carbon prepared by ZnCl{sub 2} and KOH activation was 1010 and 2085 mAh g{sup −1}, respectively. The reversible capacity of the carbon prepared by KOH activation was still as high as 717 mAh g{sup −1} after 20 cycles, which was much better than that activated by ZnCl{sub 2}. These results demonstrated that it may be a promising candidate as an anode material for lithium ion secondary batteries.

  11. Determination of phenolic compounds in air by using cyclodextrin-silica hybrid microporous composite samplers.

    PubMed

    Mauri-Aucejo, Adela R; Ponce-Català, Patricia; Belenguer-Sapiña, Carolina; Amorós, Pedro

    2015-03-01

    An analytical method for the determination of phenolic compounds in air samples based on the use of cyclodextrin-silica hybrid microporous composite samplers is proposed. The method allows the determination of phenol, guaiacol, cresol isomers, eugenol, 4-ethylphenol and 4-ethylguaiacol in workplaces according to the Norm UNE-EN 1076:2009 for active sampling. Therefore, the proposed method offers an alternative for the assessment of the occupational exposure to phenol and cresol isomers. The detection limits of the proposed method are lower than those for the NIOSH Method 2546. Storage time of samples almost reaches 44 days. Recovery values for phenol, guaiacol, o-cresol, m-cresol, p-cresol, 4-ethylguaiacol, eugenol and 4-ethylphenol are 109%, 99%, 102%, 94%, 94%, 91%, 95% and 102%, respectively with a coefficient of variation below 6%. The method has been applied to the assessment of exposure in different areas of a farm and regarding the quantification of these compounds in the vapors generated by burning incense sticks and an essential oil marketed as air fresheners. The acquired results are comparable with those provided from a reference method for a 95% of confidence level. The possible use of these samplers for the sampling of other toxic compounds such as phthalates is evaluated by qualitative analysis of extracts from incense sticks and essential oil samples. PMID:25618708

  12. Process for preparing polymer reinforced silica aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Capadona, Lynn A. (Inventor)

    2011-01-01

    Process for preparing polymer-reinforced silica aerogels which comprises a one-pot reaction of at least one alkoxy silane in the presence of effective amounts of a polymer precursor to obtain a silica reaction product, the reaction product is gelled and subsequently subjected to conditions that promotes polymerization of the precursor and then supercritically dried to obtain the polymer-reinforced monolithic silica aerogels.

  13. Preparation and Characterization of SiO 2/TiO 2 composite microspheres with microporous SiO 2 core/mesoporous TiO 2 shell

    NASA Astrophysics Data System (ADS)

    Zhao, Li; Yu, Jiaguo; Cheng, Bei

    2005-06-01

    SiO 2/TiO 2 composite microspheres with microporous SiO 2 core/mesoporous TiO 2 shell structures were prepared by hydrolysis of titanium tetrabutylorthotitanate (TTBT) in the presence of microporous silica microspheres using hydroxypropyl cellulose (HPC) as a surface esterification agent and porous template, and then dried and calcined at different temperatures. The as-prepared products were characterized with differential thermal analysis and thermogravimetric (DTA/TG), scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption. The results showed that composite particles were about 1.8 μm in diameter, and had a spherical morphology and a narrow size distribution. Uniform mesoporous titania coatings on the surfaces of microporous silica microspheres could be obtained by adjusting the HPC concentration to an optimal concentration of about 3.2 mmol L -1. The anatase and rutile phase in the SiO 2/TiO 2 composite microspheres began to form at 700 and 900 °C, respectively. At 700 °C, the specific surface area and pore volume of the SiO 2/TiO 2 composite microspheres were 552 and 0.652 mL g -1, respectively. However, at 900 °C, the specific surface area and pore volume significantly decreased due to the phase transformation from anatase to rutile.

  14. Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor)

    1992-01-01

    A microporous structure with layered interstitial surface treatments, and the method and apparatus for its preparation are disclosed. The structure is prepared by sequentially subjecting a uniformly surface treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

  15. Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor)

    1994-01-01

    A microporous structure with layered interstitial surface treatments, and method and apparatus for preparation thereof is presented. The structure is prepared by sequentially subjecting a uniformly surface-treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main atomic oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

  16. Procedure to prepare transparent silica gels

    NASA Technical Reports Server (NTRS)

    Barber, Patrick G. (Inventor); Simpson, Norman R. (Inventor)

    1987-01-01

    This invention relates to the production of silica gels and in particular to a process for the preparation of silica gels which can be used as a crystal growth medium that simulates the convectionless environment of space to produce structurally perfect crystals. Modern utilizations of substances in electronics, such as radio transmitters and high frequency microphones, often require single crystals with controlled purity and structural perfection. The near convectionless environment of silica gel suppresses nucleation, thereby reducing the competitive nature of crystal growth. This competition limits the size and perfection of the crystal; and it is obviously desirable to suppress nucleation until, ideally, only one crystal grows in a predetermined location. A silica gel is not a completely convectionless environment like outer space, but is the closest known environment to that of outer space that can be created on Earth.

  17. Effect of embedded metal compound on porosity of silica colloids prepared by spray reaction of silicon tetrachloride.

    PubMed

    Isobe, Hiroshi; Hattori, Yoshiyuki; Hayano, Tomoe; Kanoh, Hirofumi; Yamamoto, Kohzoh; Kaneko, Katsumi

    2006-03-15

    Attempts to prepare macroporous silica particles and metal-compound-nanoparticle-embedded silica microspheres were carried out using reactions between silicon tetrachloride and ultrasonic generating microdroplets including metal (Na, K, Al, Ni, Ti, Pt) compounds. Samples were collected by dry and wet processes. In the case of using nickel and aluminum compounds, acid-treated samples were also prepared. The obtained samples were characterized by scanning electron microscopy, X-ray fluorescence spectroscopy, powder X-ray diffractometry, mercury porosimetry, and the nitrogen adsorption method. The macroporous silica particles were prepared by removing the salt crystals, such as NaCl and KCl, formed in the silica frame. For acid-resistant metals, platinum- and titanium-compound nanoparticles are easily embedded in silica microspheres using these metal-compound solutions. For acid-soluble metals, aluminum- and nickel-compound-nanoparticle-embedded silicas were prepared by applying neutralization of the collection water. Micropores and mesopores were produced in wet-process samples. Acid treatment induced the increase of micropore volumes. PMID:16246356

  18. Phenomena affecting morphology of microporous poly(acrylonitrile) prepared via phase separation from solution

    SciTech Connect

    Legasse, R.R.; Weagley, R.J.; Leslie, P.K.; Schneider, D.A.

    1990-01-01

    This paper is concerned with controlling the morphology of microporous polymers prepared via thermal demixing of solutions. 2 wt % solutions of poly(acrylonitrile) in maleic anhydride, a poor solvent, are first cooled to produce separated polymer-rich and solvent-rich phases. Removing the solvent by freeze drying then produces a microporous material having a density of 33 mg/cm{sup 3}, a void fraction of 97%, and a pore size of about 10 {mu}m. We find that the morphology cannot be explained by existing models, which focus on phase diagrams and kinetics of phase transformations during cooling of the solution. In conflict with those models, we find that two radically different morphologies can be produced even when the polymer concentration and cooling path are held strictly constant. A hypothesis that polymer degradation causes the different morphologies is not supported by GPC, {sup 13}C NMR, and FTIR experiments. Instead, we offer evidence that the different microporous morphologies are caused by different polymer conformations in solutions having the same concentration and temperature. 11 refs., 3 figs.

  19. Modulation of microporous/mesoporous structures in self-templated cobalt-silica.

    PubMed

    Martens, Dana L; Wang, David K; Motuzas, Julius; Smart, Simon; da Costa, João C Diniz

    2015-01-01

    Finite control of pore size distributions is a highly desired attribute when producing porous materials. While many methodologies strive to produce such materials through one-pot strategies, oftentimes the pore structure requires post-treatment modification. In this study, modulation of pore size in cobalt-silica systems was investigated by a novel, non-destructive, self-templated method. These systems were produced from two cobalt-containing silica starting materials which differed by extent of condensation. These starting materials, sol (SG') and xerogel (XG'), were mixed with pure silica sol to produce materials containing 5-40 mol% Co. The resultant SG-series materials exhibited typical attributes for cobalt-silica systems: mesoporous characteristics developed at high cobalt concentrations, coinciding with Co3O4 formation; whereas, in the XG-series materials, these mesoporous characteristics were extensively suppressed. Based on an examination of the resultant materials a mechanism describing the pore size formation and modulation of the two systems was proposed. Pore size modulation in the XG-series was caused, in part, by the cobalt source acting as an autogenous template for the condensation of the silica network. These domains could be modified when wetted, allowing for the infiltration and subsequent condensation of silica oligomers into the pre-formed, mesoporous cages, leading to a reduction in the mesoporous content of the final product. PMID:25609189

  20. Modulation of microporous/mesoporous structures in self-templated cobalt-silica

    NASA Astrophysics Data System (ADS)

    Martens, Dana L.; Wang, David K.; Motuzas, Julius; Smart, Simon; da Costa, João C. Diniz

    2015-01-01

    Finite control of pore size distributions is a highly desired attribute when producing porous materials. While many methodologies strive to produce such materials through one-pot strategies, oftentimes the pore structure requires post-treatment modification. In this study, modulation of pore size in cobalt-silica systems was investigated by a novel, non-destructive, self-templated method. These systems were produced from two cobalt-containing silica starting materials which differed by extent of condensation. These starting materials, sol (SG') and xerogel (XG'), were mixed with pure silica sol to produce materials containing 5-40 mol% Co. The resultant SG-series materials exhibited typical attributes for cobalt-silica systems: mesoporous characteristics developed at high cobalt concentrations, coinciding with Co3O4 formation; whereas, in the XG-series materials, these mesoporous characteristics were extensively suppressed. Based on an examination of the resultant materials a mechanism describing the pore size formation and modulation of the two systems was proposed. Pore size modulation in the XG-series was caused, in part, by the cobalt source acting as an autogenous template for the condensation of the silica network. These domains could be modified when wetted, allowing for the infiltration and subsequent condensation of silica oligomers into the pre-formed, mesoporous cages, leading to a reduction in the mesoporous content of the final product.

  1. Modulation of microporous/mesoporous structures in self-templated cobalt-silica

    PubMed Central

    Martens, Dana L.; Wang, David K.; Motuzas, Julius; Smart, Simon; da Costa, João C. Diniz

    2015-01-01

    Finite control of pore size distributions is a highly desired attribute when producing porous materials. While many methodologies strive to produce such materials through one-pot strategies, oftentimes the pore structure requires post-treatment modification. In this study, modulation of pore size in cobalt-silica systems was investigated by a novel, non-destructive, self-templated method. These systems were produced from two cobalt-containing silica starting materials which differed by extent of condensation. These starting materials, sol (SG′) and xerogel (XG′), were mixed with pure silica sol to produce materials containing 5–40 mol% Co. The resultant SG-series materials exhibited typical attributes for cobalt-silica systems: mesoporous characteristics developed at high cobalt concentrations, coinciding with Co3O4 formation; whereas, in the XG-series materials, these mesoporous characteristics were extensively suppressed. Based on an examination of the resultant materials a mechanism describing the pore size formation and modulation of the two systems was proposed. Pore size modulation in the XG-series was caused, in part, by the cobalt source acting as an autogenous template for the condensation of the silica network. These domains could be modified when wetted, allowing for the infiltration and subsequent condensation of silica oligomers into the pre-formed, mesoporous cages, leading to a reduction in the mesoporous content of the final product. PMID:25609189

  2. Modeling of electro-osmosis of dilute electrolyte solutions in silica microporous media

    NASA Astrophysics Data System (ADS)

    Wang, Moran; Kang, Qinjun; Viswanathan, Hari; Robinson, Bruce A.

    2010-10-01

    Physicochemical transport due to electro-osmosis of dilute electrolyte solutions (<1 × 10-3 mol/L) through microporous media with granular random microstructures has been modeled in this work by our three-step numerical framework. First, the three-dimensional microstructures of porous media are reproduced by a random generation growth method. Second, the effects of chemical adsorption and electrical dissociation at the solid-liquid interfaces are modeled to determine the electrical boundary conditions, which vary with the ionic concentration, pH, and temperature. Finally, the nonlinear governing equations for electrokinetic transport are solved using a highly efficient lattice Poisson-Boltzmann algorithm. The simulation results indicate that the electro-osmotic permeability through the granular microporous media increases monotonically with the porosity, ionic concentration, pH, and temperature. When the surface electric potential is higher than about -50 mV, the electro-osmotic permeability exponentially increases with the electric potential. The electro-osmotic permeability increases with the bulk ionic concentration even though the surface zeta potential decreases correspondingly, which deviates from the conclusions based on the thin layer model. The electro-osmotic permeability increases exponentially with pH and linearly with temperature. The present modeling results improve our understanding of hydrodynamic and electrokinetic transport in geophysical systems and help guide the design of porous electrodes in microenergy systems.

  3. Comparison of the solid-phase extraction efficiency of a bounded and an included cyclodextrin-silica microporous composite for polycyclic aromatic hydrocarbons determination in water samples.

    PubMed

    Mauri-Aucejo, Adela; Amorós, Pedro; Moragues, Alaina; Guillem, Carmen; Belenguer-Sapiña, Carolina

    2016-08-15

    Solid-phase extraction is one of the most important techniques for sample purification and concentration. A wide variety of solid phases have been used for sample preparation over time. In this work, the efficiency of a new kind of solid-phase extraction adsorbent, which is a microporous material made from modified cyclodextrin bounded to a silica network, is evaluated through an analytical method which combines solid-phase extraction with high-performance liquid chromatography to determine polycyclic aromatic hydrocarbons in water samples. Several parameters that affected the analytes recovery, such as the amount of solid phase, the nature and volume of the eluent or the sample volume and concentration influence have been evaluated. The experimental results indicate that the material possesses adsorption ability to the tested polycyclic aromatic hydrocarbons. Under the optimum conditions, the quantification limits of the method were in the range of 0.09-2.4μgL(-1) and fine linear correlations between peak height and concentration were found around 1.3-70μgL(-1). The method has good repeatability and reproducibility, with coefficients of variation under 8%. Due to the concentration results, this material may represent an alternative for trace analysis of polycyclic aromatic hydrocarbons in water trough solid-phase extraction. PMID:27260440

  4. Charge transfer mechanism in titanium-doped microporous silica for photocatalytic water-splitting applications

    DOE PAGESBeta

    Sapp, Wendi; Koodali, Ranjit; Kilin, Dmitri

    2016-02-29

    Solar energy conversion into chemical form is possible using artificial means. One example of a highly-efficient fuel is solar energy used to split water into oxygen and hydrogen. Efficient photocatalytic water-splitting remains an open challenge for researchers across the globe. Despite significant progress, several aspects of the reaction, including the charge transfer mechanism, are not fully clear. Density functional theory combined with density matrix equations of motion were used to identify and characterize the charge transfer mechanism involved in the dissociation of water. A simulated porous silica substrate, using periodic boundary conditions, with Ti4+ ions embedded on the inner poremore » wall was found to contain electron and hole trap states that could facilitate a chemical reaction. A trap state was located within the silica substrate that lengthened relaxation time, which may favor a chemical reaction. A chemical reaction would have to occur within the window of photoexcitation; therefore, the existence of a trapping state may encourage a chemical reaction. Furthermore, this provides evidence that the silica substrate plays an integral part in the electron/hole dynamics of the system, leading to the conclusion that both components (photoactive materials and support) of heterogeneous catalytic systems are important in optimization of catalytic efficiency.« less

  5. Process for Preparing Epoxy-Reinforced Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B (Inventor)

    2016-01-01

    One-pot reaction process for preparing epoxy-reinforced monolithic silica aerogels comprising the reaction of at least one silicon compound selected from the group consisting of alkoxysilanes, orthosilicates and combination thereof in any ratio with effective amounts of an epoxy monomer and an aminoalkoxy silane to obtain an epoxy monomer-silica sol in solution, subsequently preparing an epoxy-monomer silica gel from said silica sol solution followed by initiating polymerization of the epoxy monomer to obtain the epoxy-reinforced monolithic silica aerogel.

  6. Immobilization of cross-linked phenylalanine ammonia lyase aggregates in microporous silica gel.

    PubMed

    Cui, Jian Dong; Li, Lian Lian; Bian, Hong Jie

    2013-01-01

    A separable and highly-stable enzyme system was developed by adsorption of phenylalanine ammonia lyase (PAL) from Rhodotorula glutinis in amino-functionalized macroporous silica gel and subsequent enzyme crosslinking. This resulted in the formation of cross-linked enzyme aggregates (PAL-CLEAs) into macroporous silica gel (MSG-CLEAs). The effect of adsorptive conditions, type of aggregating agent, its concentration as well as that of cross-linking agent was studied. MSG-CLEAs production was most effective using ammonium sulfate (40%-saturation), followed by cross-linking for 1 h with 1.5% (v/v) glutaraldehyde. The resulting MSG-CLEAs extended the optimal temperature and pH range compared to free PAL and PAL-CLEAs. Moreover, MSG-CLEAs exhibited the excellent stability of the enzyme against various deactivating conditions such as temperature and denaturants, and showed higher storage stability compared to the free PAL and the conventional PAL-CLEAs. Such as, after 6 h incubation at 60°C, the MSG-CLEAs still retained more than 47% of the initial activity whereas PAL-CLEAs only retained 7% of the initial activity. Especially, the MSG-CLEAs exhibited good reusability due to its suitable size and active properties. These results indicated that PAL-CLEAs on MSG might be used as a feasible and efficient solution for improving properties of immobilized enzyme in industrial application. PMID:24260425

  7. Sol-gel route to synthesis of microporous ceramic membranes: Preparation and characterization of microporous TiO[sub 2] and ZrO[sub 2] xerogels

    SciTech Connect

    Xu, Q.; Anderson, M.A. . Water Chemistry Program)

    1994-07-01

    This paper focuses on the preparation and characterization of pure TiO[sub 2] and ZrO[sub 2] xerogels. The preparation method is based on a sol-gel technique using metal tert-amyloxides as precursors to produce nano-sized metal oxide particles which are subsequently packed in a gelation process, eventually resulting in microporous xerogels. The unsupported TiO[sub 2]and ZrO[sub 2] xerogels produced in this manner have a mean pore diameter less than 2 nm and more than 50% microporosity. However, these gels, in their pure form, are thermally stable only to 350 C. Improved thermal stabilities of mixed metal oxide xerogels will be reported elsewhere.

  8. Preparation of uniform-sized agarose beads by microporous membrane emulsification technique.

    PubMed

    Zhou, Qing-Zhu; Wang, Lian-Yan; Ma, Guang-Hui; Su, Zhi-Guo

    2007-07-01

    Uniform-sized agarose beads were prepared by membrane emulsification technique in this study. Agarose was dissolved in boiling water (containing 0.9% sodium chloride) and used as water phase. A mixture of liquid paraffin and petroleum ether containing 4 wt% of hexaglycerin penta ester (PO-500) emulsifier was used as oil phase. At 55 degrees C, the water phase permeated through uniform pores of microporous membrane into the oil phase by a pressure of nitrogen gas to form uniform W/O emulsion. Then the emulsion was cooled down to room temperature under gentle agitation to form gel beads. The effect of oil phase, emulsifier, especially temperature on the uniformity of the beads were investigated and interpreted from interfacial tension between water phase and oil phase. Under optimized condition, the coefficient variation (C.V.) showing the size distribution of the beads was under 15%. This was the first report to prepare uniform agarose beads by membrane emulsification, and to investigate the effect of temperature on the size distribution of the droplets and beads. The beads with different size can be prepared by using membranes with different pore size, and the result showed that there was a linear relationship between the average diameter of beads and pore size of the membranes; beads with diameter from 15 to 60 microm were able to obtain in this study. PMID:17362974

  9. Preparation and supercapacitive behaviors of the ordered mesoporous/microporous chromium carbide-derived carbons

    NASA Astrophysics Data System (ADS)

    Wu, Chun; Gao, Jiao; Zhao, Qinglan; Zhang, Youwei; Bai, Yansong; Wang, Xingyan; Wang, Xianyou

    2014-12-01

    A series of ordered mesoporous/microporous carbon materials derived from chromium carbide-derived carbons (CDCs) are prepared by nanocasting the chromic acetate and furfuryl alcohol precursor into SBA-15 and subsequent chlorination. The structure and morphology of the CDCs are characterized by N2 adsorption/desorption isotherm, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that all of the synthesized CDCs present large specific surface area and pore volume. Especially, the CDCs-2 prepared at the mass ratio of 1/1 (chromic acetate/furfuryl alcohol) exhibits the chain-like morphology with high surface area (1236 m2 g-1), large pore volume (0.76 cm3 g-1), and the good mesopore size centered at 3.43 nm. The electrochemical properties of all the CDCs are studied by cyclic voltammetry, constant current charge/discharge, electrochemical impedance spectroscopy and cycle life measurements in 6 M KOH electrolyte. The results display that the sample CDCs-2 exhibits a high capacitance of 242.7 F g-1 at the current density of 1 A g-1 and good cycling stability with coulombic efficiency of 100% over 10000 cycles.

  10. Silica scintillating materials prepared by sol-gel methods

    SciTech Connect

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

    1993-12-31

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

  11. Preparation and Characterization of Silica-Enoxil Nanobiocomposites

    NASA Astrophysics Data System (ADS)

    Kuzema, Pavlo O.; Laguta, Iryna V.; Stavinskaya, Oksana N.; Kazakova, Olga A.; Borysenko, Mykola V.; Lupaşcu, Tudor

    2016-02-01

    Silica-Enoxil nanobiocomposites with 13 %w of Enoxil were prepared either by mechanical mixing of corresponding powders or by sorptive modification of fumed silica powder with aqueous Enoxil solution under fluidized bed conditions. The interaction of fumed silica with Enoxil and the properties of silica-Enoxil composites have been investigated using IR spectroscopy, thermogravimetric analysis, and quantum chemistry methods, as well as by means of water absorption, Enoxil desorption, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) test. It has been shown that the main biomolecules of Enoxil composition interact with silica involving their hydroxyl groups and surface silanol groups. The water absorption of silica-Enoxil nanocomposites was found to be less than that for the individual components. The Enoxil biomolecules are readily and completely desorbed from silica surface into water, and the antioxidant activity of desorbed Enoxil is practically the same as that for the just dissolved one.

  12. Preparation and Characterization of Silica-Enoxil Nanobiocomposites.

    PubMed

    Kuzema, Pavlo O; Laguta, Iryna V; Stavinskaya, Oksana N; Kazakova, Olga A; Borysenko, Mykola V; Lupaşcu, Tudor

    2016-12-01

    Silica-Enoxil nanobiocomposites with 13 %w of Enoxil were prepared either by mechanical mixing of corresponding powders or by sorptive modification of fumed silica powder with aqueous Enoxil solution under fluidized bed conditions. The interaction of fumed silica with Enoxil and the properties of silica-Enoxil composites have been investigated using IR spectroscopy, thermogravimetric analysis, and quantum chemistry methods, as well as by means of water absorption, Enoxil desorption, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) test. It has been shown that the main biomolecules of Enoxil composition interact with silica involving their hydroxyl groups and surface silanol groups. The water absorption of silica-Enoxil nanocomposites was found to be less than that for the individual components. The Enoxil biomolecules are readily and completely desorbed from silica surface into water, and the antioxidant activity of desorbed Enoxil is practically the same as that for the just dissolved one. PMID:26847694

  13. Compressible and monolithic microporous polymer sponges prepared via one-pot synthesis

    PubMed Central

    Lim, Yoonbin; Cha, Min Chul; Chang, Ji Young

    2015-01-01

    Compressible and monolithic microporous polymers (MPs) are reported. MPs were prepared as monoliths via a Sonogashira–Hagihara coupling reaction of 1,3,5-triethynylbenzene (TEB) with the bis(bromothiophene) monomer (PBT-Br). The polymers were reversibly compressible, and were easily cut into any form using a knife. Microscopy studies on the MPs revealed that the polymers had tubular microstructures, resembling those often found in marine sponges. Under compression, elastic buckling of the tube bundles was observed using an optical microscope. MP-0.8, which was synthesized using a 0.8:1 molar ratio of PBT-Br to TEB, showed microporosity with a BET surface area as high as 463 m2g–1. The polymer was very hydrophobic, with a water contact angle of 145° and absorbed 7–17 times its own weight of organic liquids. The absorbates were released by simple compression, allowing recyclable use of the polymer. MPs are potential precursors of structured carbon materials; for example, a partially graphitic material was obtained by pyrolysis of MP-0.8, which showed a similar tubular structure to that of MP-0.8. PMID:26534834

  14. Preparation and Characterization of Colloidal Silica Particles under Mild Conditions

    ERIC Educational Resources Information Center

    Neville, Frances; Zin, Azrinawati Mohd.; Jameson, Graeme J.; Wanless, Erica J.

    2012-01-01

    A microscale laboratory experiment for the preparation and characterization of silica particles at neutral pH and ambient temperature conditions is described. Students first employ experimental fabrication methods to make spherical submicrometer silica particles via the condensation of an alkoxysilane and polyethyleneimine, which act to catalyze…

  15. Preparing mesoporous carbon and silica with rosin-silica composite gel.

    PubMed

    Liu, Haidi; Du, Shangfeng; Chen, Yunfa

    2009-02-01

    Mesoporous carbon and mesoporous silica were prepared respectively with a same rosin-silica nanocomposite gel which was synthesized by cogelating tetra-ethyl-oxy-silane (silica source) and rosin (carbon source). Carbonizing the gel in nitrogen and then etching away silica with alkaline solution, mesoporous carbon with specific surface area larger than 800 m2/g was obtained. If calcining the gel at high temperature in air for given time, porous silica with surface area higher than 700 m2/g was done. BET measurement was employed to investigate the pore distribution and surface area of the samples. Most of the pores in both the porous carbon and porous silica were mesoscale, which makes the materials potential in enzyme supports for bio-catalyzed reaction or adsorbents for contaminants with large molecular size. PMID:19441395

  16. Preparation and characterization of silymarin synchronized-release microporous osmotic pump tablets

    PubMed Central

    Zeng, Qi-ping; Liu, Zhi-hong; Huang, Ai-wen; Zhang, Jing; Song, Hong-tao

    2016-01-01

    The pharmacological activity of herbal medicine is an overall action of each component in accordance with their original proportion. An efficient, sustained, and controlled-release drug delivery system of herbal medicine should ensure the synchronized drug release of each active component during the entire release procedure. In this study, silymarin (SM), a poorly soluble herbal medicine, was selected as a model drug to develop a synchronized-release drug delivery system: an SM microporous osmotic pump (MPOP) tablet. The SM was conjugated with phospholipid (SM phytosome complex, SM-PC) to improve the solubility, and the difference in the apparent octanol–water partition coefficient between the two components was significantly reduced. The dissolution rate of SM-PC was significantly higher than SM active pharmaceutical ingredients and was the same as that of the commercial SM capsule. The SM-PC was used to generate the MPOP tablet. SM was mixed with poly(ethylene) oxide and sodium chloride (an osmotic agent) to form the MPOP core, followed by coating with cellulose acetate and poly(ethylene) oxide to generate the SM MPOP. The results demonstrated that SM MPOP could synchronically and sustainably release the five active components within 12 hours (the similar coefficient f2 between two components was >65), and the average cumulative release rate was 85%. Fitting of the drug-release curve showed a zero-order release profile for SM MPOP. Our study showed that the phytosome complex technique combined with the MPOP system will achieve synchronized release of the various active components of herbal medicine and have potential applications in developing sustained release preparations in herbal medicine. PMID:26889080

  17. Preparation and characterization of silymarin synchronized-release microporous osmotic pump tablets.

    PubMed

    Zeng, Qi-ping; Liu, Zhi-hong; Huang, Ai-wen; Zhang, Jing; Song, Hong-tao

    2016-01-01

    The pharmacological activity of herbal medicine is an overall action of each component in accordance with their original proportion. An efficient, sustained, and controlled-release drug delivery system of herbal medicine should ensure the synchronized drug release of each active component during the entire release procedure. In this study, silymarin (SM), a poorly soluble herbal medicine, was selected as a model drug to develop a synchronized-release drug delivery system: an SM microporous osmotic pump (MPOP) tablet. The SM was conjugated with phospholipid (SM phytosome complex, SM-PC) to improve the solubility, and the difference in the apparent octanol-water partition coefficient between the two components was significantly reduced. The dissolution rate of SM-PC was significantly higher than SM active pharmaceutical ingredients and was the same as that of the commercial SM capsule. The SM-PC was used to generate the MPOP tablet. SM was mixed with poly(ethylene) oxide and sodium chloride (an osmotic agent) to form the MPOP core, followed by coating with cellulose acetate and poly(ethylene) oxide to generate the SM MPOP. The results demonstrated that SM MPOP could synchronically and sustainably release the five active components within 12 hours (the similar coefficient f 2 between two components was >65), and the average cumulative release rate was 85%. Fitting of the drug-release curve showed a zero-order release profile for SM MPOP. Our study showed that the phytosome complex technique combined with the MPOP system will achieve synchronized release of the various active components of herbal medicine and have potential applications in developing sustained release preparations in herbal medicine. PMID:26889080

  18. COUNTER-DIFFUSION OF ISOTOPICALLY LABELED TRICHLOROETHYLENE IN SILICA GEL AND GEOSORBENT MICROPORES: COLUMN RESULTS. (R822626)

    EPA Science Inventory

    To investigate counter-diffusion in microporous sorbents, the rate of
    exchange between deuterated trichloroethylene (DTCE) in fast desorbing sites and
    nondeuterated TCE (1HTCE) in slow desorbing sites was measured.
    Exchange rates were measured for a sili...

  19. Solid State Electrolytes Prepared from PEO (360) Silanated Silica

    NASA Technical Reports Server (NTRS)

    Maitra, P.; Ding, J.; Liu, B.; Wunder, S. L.; Lin, H.-P.; Chua, D.; Salomon, M.

    2002-01-01

    All solid state composite electrolytes were prepared using fumed silica (SiO2) silanated with an oligomeric polyethylene oxide (PEO) silane containing 6-9 ethylene oxide repeat units, a PEO matrix and LiClO4 (8/1 O/Li). The PEO-silane covalently attached to the silica was amorphous, with a T(sub g) that increased from -90 C to -53 C after attachment. The conductivity of films prepared using the PEO-silanated silica increased to approx. 6 x 10(exp -5) S/cm at RT compared with approx. 1 x 10(-5) S/cm for films prepared with unsilanated SiO2.

  20. Preparation of microporous films with sub nanometer pores and their characterization using stress and FTIR measurements

    SciTech Connect

    Samuel, J.; Hurd, A.J.; Swoll, F. van; Frink, L.J.D.; Contakes, S.C.; Brinker, C.J. |

    1996-06-01

    The authors have used a novel technique, measurement of stress isotherms in microporous thin films, as a means of characterizing porosity. The stress measurement was carried out by applying sol-gel thin films on a thin silicon substrate and monitoring the curvature of the substrate under a controlled atmosphere of various vapors. The magnitude of macroscopic bending stress developed in microporous films depends on the relative pressure and molar volume of the adsorbate and reaches a value of 180 MPa for a relative vapor pressure, P/Po = 0.001, of methanol. By using a series of molecules, and observing both the magnitude and the kinetics of stress development while changing the relative pressure, they have determined the pore size of microporous thin films. FTIR measurements were used to acquire adsorption isotherms and to compare pore emptying to stress development, about 80% of the change in stress takes place with no measurable change in the amount adsorbed. The authors show that for sol-gel films, pore diameters can be controlled in the range of 5--8 {angstrom} by ``solvent templating``.

  1. Drug silica nanocomposite: preparation, characterization and skin permeation studies.

    PubMed

    Pilloni, Martina; Ennas, Guido; Casu, Mariano; Fadda, Anna Maria; Frongia, Francesca; Marongiu, Francesca; Sanna, Roberta; Scano, Alessandra; Valenti, Donatella; Sinico, Chiara

    2013-01-01

    The aim of this work was to evaluate silica nanocomposites as topical drug delivery systems for the model drug, caffeine. Preparation, characterization, and skin permeation properties of caffeine-silica nanocomposites are described. Caffeine was loaded into the nanocomposites by grinding the drug with mesoporous silica in a ball mill up to 10 h and the efficiency of the process was studied by XRPD. Formulations were characterized by several methods that include FTIR, XRPD, SEM and TEM. The successful loading of caffeine was demonstrated by XRPD and FTIR. Morphology was studied by SEM that showed particle size reduction while TEM demonstrated formation of both core-shell and multilayered caffeine-silica structures. Solid-state NMR spectra excluded chemical interactions between caffeine and silica matrix, thus confirming that no solid state reactions occurred during the grinding process. Influence of drug inclusion in silica nanocomposite on the in vitro caffeine diffusion into and through the skin was investigated in comparison with a caffeine gel formulation (reference), using newborn pig skin and vertical Franz diffusion cells. Results from the in vitro skin permeation experiments showed that inclusion into the nanocomposite reduced and delayed caffeine permeation from the silica nanocomposite in comparison with the reference, independently from the amount of the tested formulation. PMID:22324371

  2. Janus Silica Hollow Spheres Prepared via Interfacial Biosilicification.

    PubMed

    Sheng, Li; Chen, Hong; Fu, Wenxin; Li, Zhibo

    2015-11-10

    A poly(ethylene glycol)-b-poly(L-lysine)-b-poly(styrene) (PEG-PLL-PS) triblock copolymer, which contains a cationic PLL block as the middle block, is synthesized via a combination of ring-opening polymerization (ROP) and atom-transfer radical polymerization (ATRP). The PEG-PLL-PS (ELS) triblock is employed as a macromolecular surfactant to form a stable oil-in-water (O/W) emulsion, which is subsequently used as the template to prepare Janus silica hollow spheres (JHS) via a one-pot biosilicification reaction. For the emulsion template, the middle PLL block assembles at the O/W interface and directs the biomimetic silica synthesis in the presence of phosphate buffer and silicic acid precursors. This biosilicification process takes place only in the intermediate layer between water and the organic interior phase, leading to the formation of silica JHSs with hydrophobic PS chains tethered to the inner surface and PEG attached to the outer surface. The three-layer JHSs, namely, PEG/silica-polylysine/PS composites, were verified by electron microscopy. Upon further breaking these JHSs into species, polymer-grafted Janus silica nanoplates (JPLs) can be obtained. Our studies provide an efficient one-step method for preparing hybrid silica Janus structures within minutes. PMID:26491973

  3. Ion channel mimetic membranes and silica nanotubes prepared from porous aluminum oxide templates

    NASA Astrophysics Data System (ADS)

    Mitchell, David Tanner

    Chapter 1 provides background information on the template synthesis of nanomaterials. The template synthesis method is examined with special attention to the use of membranes containing monodisperse cylindrical pores as templates. Several examples of the utility of template-synthesized nanomaterials are given. The production of one type of template membrane, nanopore alumina, is reviewed. Reviews of sol-gel and silane chemistry are also provided. In Chapter 2, a sol-gel template synthesis process is used to produce silica nanotubes within the pores of alumina templates. The nanotubes can be modified using a variety of chemistries, typically via a silanization process. Because the nanotubes are formed in a template, the interior and exterior surface can be modified independently. Modified nanotubes can be used for drug detoxification or as extractants for the removal of metal ions. The nanotube surface can also be biotinylated, which causes binding to avidinated surfaces. Composite microtubes of silica and various polymers are also prepared. Additionally, Au nanowires are shown to assemble with colloidal Au particles using dithiols as linkers. Chapter 3 describes the attachment of proteins onto template-synthesized silica nanotubes. The proteins are covalently linked via an aldehyde silane bridge that binds to pendant primary amino moieties on the protein. Protein-modified nanotubes function as highly specific extractants. Avidin-modified nanotubes extract biotin-coated Au nanoparticles from solution with high extraction efficiency. Immunoprotein-modified nanotubes extract the corresponding antibody from solution with high specificity. Antibody-modified nanotubes extract one enantiomer from a racemic mix. Enzymes, including drug detoxification enzymes, were also attached to the nanotubes and were shown to retain their catalytic activity. Immunoproteins on the outside of nanotubes can be used to direct nanotube binding, creating specific labeling agents. Chapter 4

  4. Bio-electrochemical characterization of air-cathode microbial fuel cells with microporous polyethylene/silica membrane as separator.

    PubMed

    Kircheva, Nina; Outin, Jonathan; Perrier, Gérard; Ramousse, Julien; Merlin, Gérard; Lyautey, Emilie

    2015-12-01

    The aim of this work was to study the behavior over time of a separator made of a low-cost and non-selective microporous polyethylene membrane (RhinoHide®) in an air-cathode microbial fuel cell with a reticulated vitreous carbon foam bioanode. Performances of the microporous polyethylene membrane (RhinoHide®) were compared with Nafion®-117 as a cationic exchange membrane. A non-parametric test (Mann-Whitney) done on the different sets of coulombic or energy efficiency data showed no significant difference between the two types of tested membrane (p<0.05). Volumetric power densities were ranging from 30 to 90 W·m(-3) of RVC foam for both membranes. Similar amounts of biomass were observed on both sides of the polyethylene membrane illustrating bacterial permeability of this type of separator. A monospecific denitrifying population on cathodic side of RhinoHide® membrane has been identified. Electrochemical impedance spectroscopy (EIS) was used at OCV conditions to characterize electrochemical behavior of MFCs by equivalent electrical circuit fitted on both Nyquist and Bode plots. Resistances and pseudo-capacitances from EIS analyses do not differ in such a way that the nature of the membrane could be considered as responsible. PMID:26073676

  5. Solar-grade silicon prepared by carbothermic reduction of silica

    NASA Technical Reports Server (NTRS)

    Aulich, H. A.; Schulze, F. W.; Urbach, H. P.; Lerchenberger, A.

    1986-01-01

    An advanced carbothermic reduction (ACR) process was developed to produce solar grade (SC) silicon from high purity silica and carbon. Preparation of starting materials and operation of the arc furnace to product high purity silicon is described. Solar cells prepared from single crystal SG-Si had efficiencies of up to 12.3% practically identical to cells made from electronic grade silicon. The ACR process is not in the pilot stage for further evaluation.

  6. Large- and small-nanopore silica prepared with a short-chain cationic fluorinated surfactant.

    PubMed

    Tan, Bing; Lehmler, Hans-Joachim; Vyas, Sandhya M; Knutson, Barbara L; Rankin, Stephen E

    2005-07-01

    A cationic partially fluorinated surfactant with four carbons in the chain 1-(3,3,4,4,4-pentafluorobutyl)pyridinium chloride is employed as a structure-directing agent to synthesize nanoporous silica. Samples are prepared in dilute ammonia solutions at room temperature with a range of surfactant:Si ratios. The sample with the largest surfactant:Si ratio forms particles with wormhole-like micropores with an average diameter of 1.6 nm, which corresponds to the anticipated small size of the surfactant aggregates. On the other hand, the sample with the smallest surfactant:Si ratio forms a gel that, upon drying, has uniform 11.1 nm pores. The formation and stabilization of the latter large-mesopore structure is unusual for a sample prepared and dried under ambient conditions, and may reflect favourable roles of the surfactant both in inducing gelation and in stabilizing the pore structure during drying. PMID:21727471

  7. Preparation of stable ultrahydrophobic and superoleophobic silica-based coating.

    PubMed

    Nimittrakoolchai, On-Uma; Supothina, Sitthisuntorn

    2012-06-01

    Silica-Based coatings having excellent water- and oil-repellent properties and good weathering stability have been deposited onto glass surface by a simple one-step dip coating technique. To achieve ultra water repellency and super oil repellency, the chemical composition of SiO2 nanoparticle employed as surface roughness enhancer and trichloro(1H,1H,2H,2H-perfluorooctyl)silane employed as surface-energy reducing substance was varied. At the optimum synthesis condition, the coating exhibited very high contact angles of 173.2, 146.7 and 147.6 degrees for water, ethylene glycol and seed oil, respectively. The achievement of excellent water- and oil-repellency is also described based on the presence of air trapped in micropore of the coating in addition to its high surface roughness and low surface free energy. The coatings have good weathering stability based on natural and accelerated weathering tests indicating feasibility for practical use. PMID:22905559

  8. Preparation of EPR/silica filler by a co-irradiation method forming PP/EPR/silica nanocomposites

    NASA Astrophysics Data System (ADS)

    Qian, Jun; Dang, Shuaiying; Huang, Zhijuan; Xu, Yongshen

    2012-01-01

    This paper presents a novel approach to prepare ethylene-propylene rubber (EPR)/silica filler by co-irradiation method forming polypropylene (PP)/EPR/silica nanocomposites. The grafting of maleic anhydride (MAH) on EPR was first studied by co-irradiation in the micro-suspension without any chemical initiator, and the effects of MAH concentration and the total co-irradiation dose on the graft degree of MAH were investigated. Then PP/EPR/silica nanocomposites were successfully prepared by blending of PP matrix and EPR/silica filler, which was obtained by co-irradiation using a mixture of EPR/MAH microsuspension in xylene and tetraethoxysilane/KH560 sol in formic acid. FTIR and SEM results showed that the reactions between MAH on EPR chains and KH560 surrounding silica particles were adopted to form the EPR/silica filler with strong bonding and well silica dispersion. Mechanical properties of PP/EPR/silica nanocomposites with different silica contents and the comparisons with PP, PP/EPR and PP/silica films were studied. The rigid silica particles were trapped in EPR shell and well dispersed in PP/EPR/silica nanocomposites with good compatibility and strong interfacial adhesion, achieving overall improvements in stiffness, strength and toughness compared with pure PP.

  9. Preparing two-dimensional microporous carbon from Pistachio nutshell with high areal capacitance as supercapacitor materials

    NASA Astrophysics Data System (ADS)

    Xu, Jiandong; Gao, Qiuming; Zhang, Yunlu; Tan, Yanli; Tian, Weiqian; Zhu, Lihua; Jiang, Lei

    2014-07-01

    Two-dimensional (2D) porous carbon AC-SPN-3 possessing of amazing high micropore volume ratio of 83% and large surface area of about 1069 m2 g-1 is high-yield obtained by pyrolysis of natural waste Pistachio nutshells with KOH activation. The AC-SPN-3 has a curved 2D lamellar morphology with the thickness of each slice about 200 nm. The porous carbon is consists of highly interconnected uniform pores with the median pore diameter of about 0.76 nm, which could potentially improve the performance by maximizing the electrode surface area accessible to the typical electrolyte ions (such as TEA+, diameter = ~0.68 nm). Electrochemical analyses show that AC-SPN-3 has significantly large areal capacitance of 29.3/20.1 μF cm-2 and high energy density of 10/39 Wh kg-1 at power of 52/286 kW kg-1 in 6 M KOH aqueous electrolyte and 1 M TEABF4 in EC-DEC (1:1) organic electrolyte system, respectively.

  10. Preparing two-dimensional microporous carbon from Pistachio nutshell with high areal capacitance as supercapacitor materials.

    PubMed

    Xu, Jiandong; Gao, Qiuming; Zhang, Yunlu; Tan, Yanli; Tian, Weiqian; Zhu, Lihua; Jiang, Lei

    2014-01-01

    Two-dimensional (2D) porous carbon AC-SPN-3 possessing of amazing high micropore volume ratio of 83% and large surface area of about 1069 m(2) g(-1) is high-yield obtained by pyrolysis of natural waste Pistachio nutshells with KOH activation. The AC-SPN-3 has a curved 2D lamellar morphology with the thickness of each slice about 200 nm. The porous carbon is consists of highly interconnected uniform pores with the median pore diameter of about 0.76 nm, which could potentially improve the performance by maximizing the electrode surface area accessible to the typical electrolyte ions (such as TEA(+), diameter = ~0.68 nm). Electrochemical analyses show that AC-SPN-3 has significantly large areal capacitance of 29.3/20.1 μF cm(-2) and high energy density of 10/39 Wh kg(-1) at power of 52/286 kW kg(-1) in 6 M KOH aqueous electrolyte and 1 M TEABF4 in EC-DEC (1:1) organic electrolyte system, respectively. PMID:24986670

  11. Preparing two-dimensional microporous carbon from Pistachio nutshell with high areal capacitance as supercapacitor materials

    PubMed Central

    Xu, Jiandong; Gao, Qiuming; Zhang, Yunlu; Tan, Yanli; Tian, Weiqian; Zhu, Lihua; Jiang, Lei

    2014-01-01

    Two-dimensional (2D) porous carbon AC-SPN-3 possessing of amazing high micropore volume ratio of 83% and large surface area of about 1069 m2 g−1 is high-yield obtained by pyrolysis of natural waste Pistachio nutshells with KOH activation. The AC-SPN-3 has a curved 2D lamellar morphology with the thickness of each slice about 200 nm. The porous carbon is consists of highly interconnected uniform pores with the median pore diameter of about 0.76 nm, which could potentially improve the performance by maximizing the electrode surface area accessible to the typical electrolyte ions (such as TEA+, diameter = ~0.68 nm). Electrochemical analyses show that AC-SPN-3 has significantly large areal capacitance of 29.3/20.1 μF cm−2 and high energy density of 10/39 Wh kg−1 at power of 52/286 kW kg−1 in 6 M KOH aqueous electrolyte and 1 M TEABF4 in EC-DEC (1:1) organic electrolyte system, respectively. PMID:24986670

  12. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, M.A.; Guangyao Sheng.

    1993-05-04

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  13. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  14. Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

    PubMed Central

    Gorka, Caroline A.

    2014-01-01

    A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10-3 molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes. PMID:24637334

  15. Preparing silica aerogel monoliths via a rapid supercritical extraction method.

    PubMed

    Carroll, Mary K; Anderson, Ann M; Gorka, Caroline A

    2014-01-01

    A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10(-3) molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes. PMID:24637334

  16. Preparation of silica or alumina pillared crystalline titanates

    SciTech Connect

    Udomsak, S.; Nge, R.; Dufner, D.C.; Anthony, R.G.; Lott, S.E.

    1994-05-01

    Layered crystalline titanates (CT) [Anthony and Dosch, US Patent 5 177 045 (1993)] are pillared with tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, and aluminum acetylacetonate to prepare porous and high surface area supports for sulfided NiMo catalyst. Tetra-ethyl orthosilicate or aluminum acetylacetonate intercalated CT are prepared by stepwise intercalation. First, the basal distance is increased by n-alkylammonium ions prior to intercalation with inorganic compounds. However, an aqueous solution of 3-aminopropyltrimethoxysilane could directly pillar CT without first swelling the titanate with n-alkylamine. The catalytic activities for hydrogenation of pyrene of sulfided NiMo supported silica or alumina pillared CT were higher than those of commercial catalysts (Shell324 and Amocat1C). The silicon and aluminum contents of the pillared CT, used as supports, have a considerable effect on the catalytic activities and physical properties of the supports.

  17. Effect of preparation parameters on the microporous structure of Ni/SiO{sub 2} catalysts

    SciTech Connect

    Castillon, F.F.; Bodganchikova, N.; Fuentes, S.; Avalos, M.

    1996-12-31

    In this work the authors report the synthesis of Ni/SiO{sub 2} catalysts promoted by group 2 (IIA) cations (calcium and barium) which are currently used as hydrogenation catalysts. The effect of the preparation parameters-aging, base agent, and type of cation, on the surface area of catalysts--is evaluated. Catalysts were prepared by precipitation of the precursor silicic acid, along with nickel nitrate and calcium and barium carbonates, with NaOH, NH{sub 4}OH and Na{sub 2}CO{sub 3} as precipitating agents. Catalysts were characterized by diffuse reflectance spectra (DRS) and by BET-surface area measurements. Results are discussed in terms of sol-gel chemistry.

  18. [Preparation and infrared spectral analysis of nanoporous silica thin film].

    PubMed

    Wang, Juan; Zhang, Chang-rui; Feng, Jian; Yang, Da-xiang

    2005-07-01

    Crack-free homogeneous nanoporous silica films on silicon wafer have been synthesized via supercritical drying of wet gel films obtained by spin-coating the polymeric silica sol, which was prepared using sol-gel method with tetraethoxysilane (TEOS) as precursor. The film is amorphous and nanoporous, and three-dimensional network, cross-linked by the primary particles whose sizes distribute between 10-20 nm showed respectively by XRD and SEM micrograph. The structure of the nanoporous SiO2 thin film was studied by FTIR spectra. The SiO2 thin film was composed of Si-O-Si and Si-OR, and was hydrophobic. The film contained Si-OH and became hydrophilic after being heat-treated at 250 degrees C or above in air. The heat-treated SiO2 thin film becomes hydrophobic by reacting with trimethylchlorosilane(TMCS). The TMCS-modified SiO2 thin film remains hydrophobic and can keep its nanoporous structure at a temperature lower than 450 degrees C in nitrogen. PMID:16241051

  19. Preparation and Application of Hollow Silica/magnetic Nanocomposite Particle

    NASA Astrophysics Data System (ADS)

    Wang, Cheng-Chien; Lin, Jing-Mo; Lin, Chun-Rong; Wang, Sheng-Chang

    The hollow silica/cobalt ferrite (CoFe2O4) magnetic microsphere with amino-groups were successfully prepared via several steps, including preparing the chelating copolymer microparticles as template by soap-free emulsion polymerization, manufacturing the hollow cobalt ferrite magnetic microsphere by in-situ chemical co-precipitation following calcinations, and surface modifying of the hollow magnetic microsphere by 3-aminopropyltrime- thoxysilane via the sol-gel method. The average diameter of polymer microspheres was ca. 200 nm from transmission electron microscope (TEM) measurement. The structure of the hollow magnetic microsphere was characterized by using TEM and scanning electron microscope (SEM). The spinel-type lattice of CoFe2O4 shell layer was identified by using XRD measurement. The diameter of CoFe2O4 crystalline grains ranged from 54.1 nm to 8.5 nm which was estimated by Scherrer's equation. Additionally, the hollow silica/cobalt ferrite microsphere possesses superparamagnetic property after VSM measurement. The result of BET measurement reveals the hollow magnetic microsphere which has large surface areas (123.4m2/g). After glutaraldehyde modified, the maximum value of BSA immobilization capacity of the hollow magnetic microsphere was 33.8 mg/g at pH 5.0 buffer solution. For microwave absorption, when the hollow magnetic microsphere was compounded within epoxy resin, the maximum reflection loss of epoxy resins could reach -35dB at 5.4 GHz with 1.9 mm thickness.

  20. Preparation and characterization of microporous layers on titanium by anodization in sulfuric acid with and without hydrogen charging.

    PubMed

    Tanaka, Shin-ichi; Fukushima, Yuriko; Nakamura, Isao; Tanaki, Toshiyuki; Jerkiewicz, Gregory

    2013-04-24

    The formation of microporous oxide layers on titanium (Ti) by anodization in sulfuric acid (H2SO4) solution and the influence of prior hydrogen charging on their properties are examined using electrochemical techniques, scanning electron microscopy, grazing incident X-ray diffraction, and X-ray photoelectron spectroscopy. When Ti is anodized in 1 M aqueous H2SO4 solution at a high direct current (DC) potential (>150 V) for 1 min, a porous surface layer develops, and the process takes place with spark-discharge. Under these conditions, oxygen evolution at the Ti electrode proceeds vigorously and concurrently with the formation of anodic oxide. The oxygen gas layer adjacent to the Ti surface acts as an insulator and triggers spark-discharge; the latter stimulates the development of pores. In the absence of spark-discharge, the oxide layer has extended surface roughness but low porosity. A porous oxide layer can be prepared by applying a lower DC voltage (130 V) and without spark-discharge, but Ti requires prior hydrogen charging by cathodic polarization in 1 M aqueous H2SO4 solution. Mott-Schottky measurements indicate that the oxide layers are n-type semiconductors and that the charge carrier density in the anodic oxide layer on the hydrogen-charged Ti is lower than in the case of untreated Ti. The hydrogen charging also affects the flat band potential of the anodic oxide layers on Ti by increasing its value. The reduced charge carrier density brought about by hydrogen charging decreases the oxide layer conductivity and creates favorable conditions for its electrical breakdown that stimulates the development of pores. The porous layer on the hydrogen-charged Ti consists of anatase and rutile phases of TiO2; it has the same chemical composition as the porous layer obtained on untreated Ti. X-ray photoelectron spectroscopy measurements show that prior hydrogen charging does not affect the thickness of anodic oxides on Ti. The porous oxide layer on Ti enables the

  1. Hollow Microporous Organic Capsules

    NASA Astrophysics Data System (ADS)

    Li, Buyi; Yang, Xinjia; Xia, Lingling; Majeed, Muhammad Irfan; Tan, Bien

    2013-07-01

    Fabrication of hollow microporous organic capsules (HMOCs) could be very useful because of their hollow and porous morphology, which combines the advantages of both microporous organic polymers and non-porous nanocapsules. They can be used as storage materials or reaction chambers while supplying the necessary path for the design of controlled uptake/release systems. Herein, the synthesis of HMOCs with high surface area through facile emulsion polymerization and hypercrosslinking reactions, is described. Due to their tailored porous structure, these capsules possessed high drug loading efficiency, zero-order drug release kinetics and are also demonstrated to be used as nanoscale reactors for the prepareation of nanoparticles (NPs) without any external stabilizer. Moreover, owing to their intrinsic biocompatibility and fluorescence, these capsules exhibit promising prospect for biomedical applications.

  2. Hollow Microporous Organic Capsules

    PubMed Central

    Li, Buyi; Yang, Xinjia; Xia, Lingling; Majeed, Muhammad Irfan; Tan, Bien

    2013-01-01

    Fabrication of hollow microporous organic capsules (HMOCs) could be very useful because of their hollow and porous morphology, which combines the advantages of both microporous organic polymers and non-porous nanocapsules. They can be used as storage materials or reaction chambers while supplying the necessary path for the design of controlled uptake/release systems. Herein, the synthesis of HMOCs with high surface area through facile emulsion polymerization and hypercrosslinking reactions, is described. Due to their tailored porous structure, these capsules possessed high drug loading efficiency, zero-order drug release kinetics and are also demonstrated to be used as nanoscale reactors for the prepareation of nanoparticles (NPs) without any external stabilizer. Moreover, owing to their intrinsic biocompatibility and fluorescence, these capsules exhibit promising prospect for biomedical applications. PMID:23820511

  3. Preparation and Characterization of Single Ion Conductors from High Surface Area Fumed Silica

    NASA Technical Reports Server (NTRS)

    Zhang, H.; Maitra, P.; Liu, B.; Wunder, S. L.; Lin, H.-P.; Salomon, M.; Hagedorn, Norman H. (Technical Monitor)

    2002-01-01

    Anions that can form dissociative salts with Li(+) have been prepared and covalently attached to high surface area fumed silica. When blended with polyethylene oxide (PEO), the functionalized fumed silica suppresses the crystallization of the PEO, provides dimensional stability, and serves as a single ion conductor. Since functionalized fumed silica is easily dispersed in common polar solvents, it can be incorporated in both the polymer electrolyte and the electrodes.

  4. Hollow Co@C prepared from a Co-ZIF@microporous organic network: magnetic adsorbents for aromatic pollutants in water.

    PubMed

    Hong, Seokjo; Yoo, Jin; Park, Nojin; Lee, Sang Moon; Park, Je-Geun; Park, Ji Hoon; Son, Seung Uk

    2015-12-28

    This work shows the new engineering strategy of magnetic adsorbents by the combination of zeolitic imidazolate framework (ZIF) and microporous organic network (MON) chemistry. ZIF-67 nanoparticles containing Co(2+) ions were coated with MON. The thermolysis of ZIF-67@MON under argon resulted in hollow carbon materials bearing cobalt nanoparticles which showed promising performance as magnetic adsorbents for aromatic pollutants in water. PMID:26490193

  5. Preparation and characterization of titania-deposited silica composite hollow fiber membranes with high hydrothermal stability.

    PubMed

    Kwon, Young-Nam; Kim, In-Chul

    2013-11-01

    Hydrothermal stability of a porous nickel-supported silica membrane was successfully improved by deposition of titania multilayers on colloidal silica particles embedded in the porous nickel fiber support. Porous nickel-supported silica membranes were prepared by means of a dipping-freezing-fast drying (DFF) method. The titania layers were deposited on colloidal silica particles by repeating hydrolysis and condensation reactions of titanium isopropoxide on the silica particle surfaces. The deposition of thin titania layers on the nickel-supported silica membrane was verified by various analytical tools. The water flux and the solute rejection of the porous Ni fiber-supported silica membranes did not change after titania layer deposition, indicating that thickness of titania layers deposited on silica surface is enough thin not to affect the membrane performance. Moreover, improvement of the hydrothermal stability in the titania-deposited silica membranes was confirmed by stability tests, indicating that thin titania layers deposited on silica surface played an important role as a diffusion barrier against 90 degrees C water into silica particles. PMID:24245310

  6. Preparation and processing of monodisperse colloidal silica-cadmium sulfide nanocomposites

    SciTech Connect

    Chang, S.Y.; Liu, L.; Asher, S.A.

    1994-12-31

    A novel synthetic methodology has been developed for preparing monodisperse colloidal silica-cadmium sulfide nanocomposite spheres in the 50--300 nm size regime. This methodology uses water-in-oil microemulsions as the reaction medium. Monosize silica colloids are first produced by the controlled hydrolysis of tetraethyl orthosilicate in the micro water droplets of the microemulsion. Cadmium sulfide quantum dots are incorporated into the silica colloids during synthesis by the introductions of Cd{sup 2+} and S{sup 2{minus}} microemulsions. Various morphologies of the nanocomposite are fabricated by controlling the heterogeneous coagulation of CdS and SiO{sub 2}. Unique high surface area silica particles can be prepared when nitric acid etches out the CdS and leaves behind topologically defined voids. The CdS nanocomposites are new materials useful for non-linear optics, while the high surface area silica particles should have novel applications in areas such as catalysis.

  7. Effect of vinyl-modified silica and raw silica particles on the properties of as-prepared polymer-silica nanocomposite foams.

    PubMed

    Yeh, Jui-Ming; Chang, Kung-Chin; Peng, Chih-Wei; Chiou, Sheng-Che; Hwang, Shyh-Shin; Yang, Jen-Chang; Lin, Hong-Ru

    2008-12-01

    In this study, the first comparative studies for the effect of vinyl-modified silica (VMS) and raw silica (RS) particles on the physical properties of as-prepared polymer-silica nanocomposite (PSN) foams are presented. First of all, the VMS particles were synthesized by performing conventional acid-catalyzed sol-gel reactions of TEOS in the presence/absence of MSMA molecules. The as-prepared VMS particles were then characterized through Fourier Transform Infrared (FTIR), solid-state 13C-nuclear magnetic resonance (13C-NMR) and 29Si-NMR spectroscopy. Subsequently, a series of PSN materials have been prepared through bulk polymerization of MMA monomers in the presence of VMS and RS particles with BPO as initiator. The dispersion capability of silica particles in polymer matrix was further observed by transmission electron microscopy (TEM) studies. The PSN foams can be further obtained by performing batch-foaming process on as-prepared bulky PSN materials with N2 as foaming agent. The cell structure analysis of the PSN foams was subsequently examined by the scanning electron microscopy (SEM) images. Gel permeation chromatography (GPC) was used to determine the molecular weights of as-prepared samples. It should be noted that the incorporated VMS and RS particles served as heterogeneous nucleation agent in polymer matrix under foaming process to reduce the cell size and increase the cell density of the PSN foams. Furthermore, the VMS particles exhibited a better dispersion capability of silica particles in PMMA matrix as compared to that of RS particles, leading to the PSN foams with smaller cell size and higher cell density. Effect of material composition on the thermal transport properties, thermal stability and mechanical strength of PSN foams were investigated by transient plane source (TPS) technique, thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA), respectively. PMID:19205197

  8. Preparation and characterization of silica nanoparticulate polyacrylonitrile composite and porous nanofibers

    NASA Astrophysics Data System (ADS)

    Ji, Liwen; Saquing, Carl; Khan, Saad A.; Zhang, Xiangwu

    2008-02-01

    In this study, polyacrylonitrile (PAN) composite nanofibers containing different amounts of silica nanoparticulates have been obtained via electrospinning. The surface morphology, thermal properties and crystal structure of PAN/silica nanofibers are characterized using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, wide-angle x-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The results indicate that the addition of silica nanoparticulates affects the structure and properties of the nanofibers. In addition to PAN/silica composite nanofibers, porous PAN nanofibers have been prepared by selective removal of the silica component from PAN/silica composite nanofibers using hydrofluoric (HF) acid. ATR-FTIR and thermal gravimetric analysis (TGA) experiments validate the removal of silica nanoparticulates by HF acid, whereas SEM and TEM results reveal that the porous nanofibers obtained from composite fibers with higher silica contents exhibited more nonuniform surface morphology. The Brunauer-Emmett-Teller (BET) surface area of porous PAN nanofibers made from PAN/silica (5 wt%) composite precursors is higher than that of pure nonporous PAN nanofibers.

  9. Preparation of silica sphere with porous structure in supercritical carbon dioxide.

    PubMed

    Chatterjee, Maya; Chatterjee, Abhijit; Ikushima, Yutaka; Kawanami, Hajime; Ishizaka, Takayuki; Sato, Masahiro; Suzuki, Toshishige; Yokoyama, Toshirou

    2010-08-01

    Silica sphere with porous structure has been synthesized in supercritical carbon dioxide. The structure originates from a delicate CO(2) trapping phenomenon intended for void formation in the inorganic framework. Silicate polymerization and subsequent removal of CO(2) by depressurization leaves the porous architecture. The key factor to obtain stable porous spherical structure was CO(2) pressure. Different characterization techniques such as X-ray diffraction, scanning and transmission electron microscopy and N(2) adsorption-desorption isotherm were used to determine the framework structure, morphology and porosity of the material. Microscopic visualization of calcined material suggested that the spherical structure was consisted of macroporous windows of diameter approximately 100 nm and the space between macropores presents a wormhole like mesoporous/microporous structure. The pore diameter of the mesoporous structure has been calculated as approximately 3 nm. X-ray diffraction and N(2) adsorption isotherm analysis confirmed the presence of micropores and also the macropores. In addition, the resulting material possess high thermal and hydrothermal stability associated with fully SiO(4) cross-linking. The spherical structure with different types of porosity was successfully obtained without using any molding agent. PMID:20417524

  10. Preparation and Characterization of Silica/Polyamide-imide Nanocomposite Thin Films

    NASA Astrophysics Data System (ADS)

    Ma, Xiaokun; Lee, Nam-Hee; Oh, Hyo-Jin; Hwang, Jong-Sun; Kim, Sun-Jae

    2010-11-01

    The functional silica/polyamide-imide composite films were prepared via simple ultrasonic blending, after the silica nanoparticles were modified by cationic surfactant—cetyltrimethyl ammonium bromide (CTAB). The composite films were characterized by scanning electron microscope (SEM), thermo gravimetric analysis (TGA) and thermomechanical analysis (TMA). CTAB-modified silica nanoparticles were well dispersed in the polyamide-imide matrix, and the amount of silica nanoparticles to PAI was investigated to be from 2 to 10 wt%. Especially, the coefficients of thermal expansion (CET) continuously decreased with the amount of silica particles increasing. The high thermal stability and low coefficient of thermal expansion showed that the nanocomposite films can be widely used in the enamel wire industry.

  11. Preparation and Characterization of Silica/Polyamide-imide Nanocomposite Thin Films

    PubMed Central

    2010-01-01

    The functional silica/polyamide-imide composite films were prepared via simple ultrasonic blending, after the silica nanoparticles were modified by cationic surfactant—cetyltrimethyl ammonium bromide (CTAB). The composite films were characterized by scanning electron microscope (SEM), thermo gravimetric analysis (TGA) and thermomechanical analysis (TMA). CTAB-modified silica nanoparticles were well dispersed in the polyamide-imide matrix, and the amount of silica nanoparticles to PAI was investigated to be from 2 to 10 wt%. Especially, the coefficients of thermal expansion (CET) continuously decreased with the amount of silica particles increasing. The high thermal stability and low coefficient of thermal expansion showed that the nanocomposite films can be widely used in the enamel wire industry. PMID:21124625

  12. Micro-PIXE and micro-RBS characterization of micropores in porous silicon prepared using microwave-assisted hydrofluoric acid etching.

    PubMed

    Ahmad, Muthanna; Grime, Geoffrey W

    2013-04-01

    Porous silicon (PS) has been prepared using a microwave-assisted hydrofluoric acid (HF) etching method from a silicon wafer pre-implanted with 5 MeV Cu ions. The use of microbeam proton-induced X-ray emission (micro-PIXE) and microbeam Rutherford backscattering techniques reveals for the first time the capability of these techniques for studying the formation of micropores. The porous structures observed from micro-PIXE imaging results are compared to scanning electron microscope images. It was observed that the implanted copper accumulates in the same location as the pores and that at high implanted dose the pores form large-scale patterns of lines and concentric circles. This is the first work demonstrating the use of microwave-assisted HF etching in the formation of PS. PMID:23388452

  13. Preparation of spherical ceria coated silica nanoparticle abrasives for CMP application

    NASA Astrophysics Data System (ADS)

    Peedikakkandy, Lekha; Kalita, Laksheswar; Kavle, Pravin; Kadam, Ankur; Gujar, Vikas; Arcot, Mahesh; Bhargava, Parag

    2015-12-01

    This paper describes synthesis of spherical and highly mono-dispersed ceria coated silica nanoparticles of size ∼70-80 nm for application as abrasive particles in Chemical Mechanical Planarization (CMP) process. Core silica nanoparticles were initially synthesized using micro-emulsion method. Ceria coating on these ultrafine and spherical silica nanoparticles was achieved using controlled chemical precipitation method. Study of various parameters influencing the formation of ceria coated silica nanoparticles of size less than 100 nm has been undertaken and reported. Ceria coating over silica nanoparticles was varied by controlling the reaction temperature, pH and precursor concentrations. Characterization studies using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Energy Dispersive X-ray analysis show formation of crystalline CeO2 coating of ∼10 nm thickness over silica with spherical morphology and particle size <100 nm. Aqueous slurry of ceria coated silica abrasive was prepared and employed for polishing of oxide and nitride films on silicon substrates. Polished films were studied using ellipsometry and an improvement in SiO2:SiN selective removal rates up to 12 was observed using 1 wt% ceria coated silica nanoparticles slurry.

  14. Preparation of silica-encapsulated ZnSe nanocrystals by mixed surfactant microemulsions.

    PubMed

    Liu, Kang; Ma, Sung Jin; Kim, Ji Hyeon; Choi, Hyung Wook; Kim, Kyung Hwan; Park, Sang Joon

    2013-11-01

    Silica-encapsulated ZnSe nanocrystals (NCs) have been prepared by employing sodium (2-ethylhexyl)sulfonate (AOT)/water/cyclohexane microemulsions containing ZnSe quantum dots with polyoxyethylenenonylphenylether (NP5)/water/cyclohexane microemulsions containing tetraethylorthosilicate (TEOS). Size tunable silica nanoparticles were achieved by using various water-to-surfactant ratios, W ([H2O]/[surfactant]). In order to characterize as-synthesized nanocrystals, photoluminescence (PL) spectroscopy, UV-visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) were employed. Cubic zinc blende quantum dots (QDs) (2.5 nm in diameter) were successfully encapsulated by silica nanoparticles (14.3-28.9 nm in diameter). The enhanced photoluminescence efficiency about 10% has been observed when compared with the results from the similar work using AOT microemulsions. The entire size of the silica-encapsulated nanocrystals increased with increasing W, then decreased slightly when free water exists in the core of the NP5/AOT microemulsion. On the other hand, the ZnSe NCs in the silica did not change their size during the synthesis. In addition, the possible mechanisms for growth of silica particles and the kinetics of silica particles formation were discussed. PMID:24245247

  15. Facile preparation of mesoporous carbon-silica-coated graphene for the selective enrichment of endogenous peptides.

    PubMed

    Zhang, Quanqing; Zhang, Qinghe; Xiong, Zhichao; Wan, Hao; Chen, Xiaoting; Li, Hongmei; Zou, Hanfa

    2016-01-01

    A sandwich-like composite composed of ordered mesoporous carbon-silica shell-coated graphene (denoted as graphene@mSiO2-C) was prepared by an in-situ carbonation strategy. A mesoporous silica shell was synthesized by a sol-gel method, and cetyltrimethyl ammonium bromide inside the mesopores were in-situ carbonized as a carbon source to obtain a carbon-silica shell. The resulting mesoporous carbon-silica material with a sandwich structure possesses a high surface area (600 m(2) g(-1)), large pore volume (0.587 cm(3) g(-1)), highly ordered mesoporous pore (3 nm), and high carbon content (30%). This material shows not only high hydrophobicity of graphene and mesoporous carbon but also a hydrophilic silica framework that ensures excellent dispersibility in aqueous solution. The material can capture many more peptides from bovine serum albumin tryptic digests than mesoporous silica shell-coated graphene, demonstrating great enrichment efficiency for peptides. Furthermore, the prepared composite was applied to the enrichment of low-abundance endogenous peptides in human serum. Based on Matrix-Assisted Laser Desorption/ Ionization Time of Flight Mass Spectrometry identification, the graphene@mSiO2-C could efficiently size-exclude proteins and enriches the low-abundant peptides on the graphene and mesoporous carbon. And based on the LC-MS/MS results, 892 endogenous peptides were obtained by graphene@mSiO2-C, hinting at its great potential in peptides analysis. PMID:26695263

  16. Fabrication of Hollow Microporous Carbon Spheres from Hyper-Crosslinked Microporous Polymers.

    PubMed

    Wang, Kewei; Huang, Liang; Razzaque, Shumaila; Jin, Shangbin; Tan, Bien

    2016-06-01

    Porous carbon materials prepared from the porous organic polymers are currently the subject of extensive investigation. On the basis of their interesting applications, it is highly desirable to develop new synthetic methodologies to obtain carbon materials with controllable pore size and morphology. Herein, a facile synthesis of hollow microporous carbon spheres (HCSs) from hollow microporous organic capsules (HMOCs) with a good control over the pore morphology, hollow cavity, and the shell thickness is reported. The highly porous hollow carbon spheres are prepared by the pyrolysis of HMOCs-based microporous polymers. The synthetic parameters, such as hypercrosslinking and pyrolysis conditions, are optimized to modify the porous structures and the properties. The morphology and porosity as well as energy storage applications of the microporous structures HCSs, derived through a combination of divinylbenzene-crosslinking and micropore-generating hypercrosslinking, are discussed. These findings provide a new benchmark for fabricating well-defined HCSs with great promise for various applications. PMID:27145206

  17. The preparation and properties of monodisperse core-shell silica magnetic microspheres.

    PubMed

    Lou, Min-yi; Jia, Qiu-ling; Wang, De-ping; Liu, Bing; Huang, Wen-hai

    2008-01-01

    The monodisperse core-shell silica magnetic microspheres (MMS) were synthesized by sol-gel method gelling in the emulsion. Optical microscope (OM), field emission scanning electron microscope (FESEM), nitrogen adsorption and desorption Brunauer Emmett Teller Procedure (BET) isotherms and Barrett-Joyner-Halenda (BJH) pore size distribution measurements, X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and vibrating sample magnetometer (VSM) were used to characterize the appearance, size distribution, phase, specific surface area, chemical composition and magnetic property of silica MMS. The results showed that silica MMS prepared through sol-gel method with acid-alkali two-step catalyze and gelling in emulsion exhibited the superior core-shell structure and size distribution of the microspheres concentrated in about 20 mum. The main phase of microspheres was amorphous silica and spinel ferroferric oxide. Meanwhile, the microspheres remained the superparamagnetic behavior and could be used as biomaterials. PMID:17597357

  18. Facile large scale preparation and electromagnetic properties of silica-nickel-carbon composite shelly hollow microspheres.

    PubMed

    An, Zhenguo; Zhang, Jingjie

    2016-02-21

    Silica-nickel-carbon composite microspheres with shelly hollow structures and tunable electromagnetic properties were prepared in large scale through a three-step route. Micron-sized precursor microspheres were prepared firstly by spray drying of water glass. Then a subsequent acid leaching with diluted hydrochloric acid was carried out to eliminate the Na2O in the precursor microspheres to get single shell silica hollow microspheres (SHMs). Afterwards, Ni-C composite shells were assembled on the surface of the previously formed SHMs through a calcination route in an inert atmosphere to form silica-nickel-carbon composite shelly hollow microspheres (CSHMs) through decomposition of the reactants and carbon thermal reduction. By properly tuning the calcination conditions, silica-nickel CSHMs with gradients in composition can also be prepared. The electromagnetic properties of the CSHMs were studied and the results demonstrate that they present ferromagnetic and microwave absorbing properties related to the shell composition. The DSHPs thus obtained may have some promising applications in the fields of low-density magnetic materials and microwave absorbers. This work provides a new strategy to fabricate shelly hollow particles, which can be expected to be extended to the controlled preparation of similar structures with various compositions. PMID:26726765

  19. Surfactant-free small Ni nanoparticles trapped on silica nanoparticles prepared by pulsed laser ablation in liquid

    NASA Astrophysics Data System (ADS)

    Mafuné, Fumitaka; Okamoto, Takumi; Ito, Miho

    2014-01-01

    Small Ni nanoparticles supported on silica nanoparticles were formed by pulsed laser ablation in liquid. Water dispersing surfactant-free silica particles was used here as a solvent, and a bulk Ni metal plate as a target. The nanoparticles formed by laser ablation in water were readily stabilized by the silica particles, whereas Ni nanoparticles prepared in water without silica were found to be precipitated a few hours after aggregation into 5-30 nm particles. The nanoparticles were characterized by TEM, dark-field STEM and optical absorption spectroscopy, which indicated that small 1-3 nm Ni nanoparticles were adsorbed on the surface of silica.

  20. Moisture Transport in Silica Gel Particle Beds: I. Theoretical Study

    SciTech Connect

    Pesaran, A. A.; Mills, A. F.

    1986-08-01

    Diffusion mechanisms of moisture within silica gel particles are investigated. It is found that for microporous silica gel surface diffusion is the dominant mechanism of moisture transport, while for macroporous silica gel both Knudsen and surface diffusion are important.

  1. Silica coating of luminescent quantum dots prepared in aqueous media for cellular labeling

    SciTech Connect

    Ma, Yunfei; Li, Yan Zhong, Xinhua

    2014-12-15

    Graphical abstract: A facile route based on modified Stöber method was used for the synthesis of silica coated QDs (QD@SiO{sub 2}) starting from aqueously prepared CdTe/CdS QDs. The resultant QD@SiO{sub 2} exhibited a significant increase in emission efficiency compared with that of the initial QDs, along with a small size (∼5 nm in diameter), great stability and low cytotoxicity, which makes it a good candidate as robust biomarker. - Highlights: • We present a facile modified Stöber method to prepare highly luminescent QD@SiO{sub 2}. • The PL efficiency of QDs increases significantly after silica coating. • QD@SiO{sub 2} exhibits small size (∼5 nm) and great dispersibility in aqueous solution. • QD@SiO{sub 2} presents extraordinary photo and colloidal stability. • The silica shell eliminates QD cytotoxicity, providing the access of bioconjugation. - Abstract: Silica coating is an effective approach for rendering luminescent quantum dots (QDs) with water dispersibility and biocompatibility. However, it is still challenging to prepare silica-coated QDs (QD@SiO{sub 2}) with high emission efficiency, small size and great stability in favor for bioapplication. Herein, we reported a modified Stöber method for silica coating of aqueously-prepared CdTe/CdS QDs. With the coexistence of Cd{sup 2+} and thioglycolic acid (TGA), a thin silica shell was formed around QDs by the hydrolysis of tetraethyl orthosilicate (TEOS). The resultant QD@SiO{sub 2} with a small size (∼5 nm in diameter) exhibits significantly higher emission efficiencies than that of the initial QDs. Also, QD@SiO{sub 2} has extraordinary photo and colloidal stability (pH range of 5–13, 4.0 M NaCl solution). Protected by the silica shell, the cytotoxicity of QDs could be reduced. Moreover, the QD@SiO{sub 2} conjugated with folic acid (FA) presents high specific binding toward receptor-positive HeLa cells over receptor-negative A549 cells.

  2. Ionic liquid-templated preparation of mesoporous silica embedded with nanocrystalline sulfated zirconia

    NASA Astrophysics Data System (ADS)

    Ward, Antony J.; Pujari, Ajit A.; Costanzo, Lorenzo; Masters, Anthony F.; Maschmeyer, Thomas

    2011-12-01

    A series of mesoporous silicas impregnated with nanocrystalline sulphated zirconia was prepared by a sol-gel process using an ionic liquid-templated route. The physicochemical properties of the mesoporous sulphated zirconia materials were studied using characterisation techniques such as inductively coupled optical emission spectroscopy, X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray microanalysis, elemental analysis and X-ray photoelectron spectroscopy. Analysis of the new silicas indicates isomorphous substitution of silicon with zirconium and reveals the presence of extremely small (< 10 nm) polydispersed zirconia nanoparticles in the materials with zirconium loadings from 27.77 to 41.4 wt.%.

  3. Preparation of Metalloporphyrin-Bound Superparamagnetic Silica Particles via "Click" Reaction.

    PubMed

    Hollingsworth, Javoris V; Bhupathiraju, N V S Dinesh K; Sun, Jirun; Lochner, Eric; Vicente, M Graça H; Russo, Paul S

    2016-01-13

    A facile approach using click chemistry is demonstrated for immobilization of metalloporphyrins onto the surface of silica-coated iron oxide particles. Oleic-acid stabilized iron oxide nanocrystals were prepared by thermal decomposition of iron(III) acetylacetonate. Their crystallinity, morphology, and superparamagnetism were determined using X-ray diffraction, transmission electron microscopy, and a superconducting quantum interference device. Monodisperse core-shell particles were produced in the silica-coating of iron oxide via microemulsion synthesis. Surface modification of these particles was performed in two steps, which included the reaction of silica-coated iron oxide particles with 3-bromopropyltrichlorosilane, followed by azido-functionalization with sodium azide. Monoalkylated porphyrins were prepared using the Williamson ether synthesis of commercially available tetra(4-hydroxyphenyl) porphyrin with propargyl bromide in the presence of a base. (1)H NMR and matrix-assisted laser desorption ionization confirmed the identity of the compounds. The prepared monoalkyne porphyrins were zinc-metalated prior to their introduction to azide-functionalized, silica-coated iron oxide particles in the click reaction. X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy were used to characterize the surface chemistry after each step in the reaction. In addition, particle size was determined using dynamic light scattering and microscopy. The presented methodology is versatile and can be extended to other photoreactive systems, such as phthalocyanines and boron-dipyrromethane, which may lead to new materials for optical, photonic, and biological applications. PMID:26691852

  4. Structured material combined HMO-silica fibers: preparation, optical and mechanical behavior

    NASA Astrophysics Data System (ADS)

    Schuster, K.; Kobelke, J.; Litzkendorf, D.; Schwuchow, A.; Lindner, F.; Kirchhof, J.; Bartelt, H.; Auguste, J.-L.; Humbert, G.; Blondy, J.-M.

    2011-03-01

    We report about preparation technique and characterization of structured fibers composed of HMO core glasses and silica cladding. Two processes as material preparation techniques have been developed based on glasses prepared by melting of SAL (e.g. 70SiO2-20Al2O3-10La2O3) glasses and the reactive powder sintering (REPUSIL) method. The melted glasses have been characterized by dilatometrical methods to find Tg values of 827-875°C and expansion coefficients between 4.3 and 7.0×10-6 K-1. The latter is one order of magnitude higher than the expansion coefficient of pure silica glass. Structured fibers (SAL core, silica cladding) were fabricated following the Rod-in-Tube (RIT) and Granulate-in-Tube (GIT) process. The HMO glasses were chosen due du their high lanthanum content and the expected high nonlinearity, suitable for nonlinear applications (e.g. supercontinuum sources). The partial substitution of lanthanum by other rare earth elements (e.g. Ytterbium) allows the preparation of fibers with extremely high rare earth concentration up to 5 mol% Yb2O3. The concentration of alumina in the HMO glasses as "solubilizer" for lanthanide was adjusted to about 20 mol%. So we overcame the concentration limits of rare earth doping of MCVD (maximum ca. 2 mol% RE2O3). Nevertheless, the investigated HMO glasses show their limits by integration in structured silica based fibers: Optical losses are typically in the dB/m range, best value of this work is about 600 dB/km. The mechanical stability of fibers is influenced by mechanical strain caused by the high thermal expansion of the core material and the lower network bonding stability of the HMO glasses, but partially compensated by the silica cladding.

  5. Preparation of resveratrol-loaded nanoporous silica materials with different structures

    NASA Astrophysics Data System (ADS)

    Popova, Margarita; Szegedi, Agnes; Mavrodinova, Vesselina; Novak Tušar, Natasa; Mihály, Judith; Klébert, Szilvia; Benbassat, Niko; Yoncheva, Krassimira

    2014-11-01

    Solid, nanoporous silica-based spherical mesoporous MCM-41 and KIL-2 with interparticle mesoporosity as well as nanosized zeolite BEA materials differing in morphology and pore size distribution, were used as carriers for the preparation of resveratrol-loaded delivery systems. Two preparation methods have been applied: (i) loading by mixing of resveratrol and mesoporous carrier in solid state and (ii) deposition in ethanol solution. The parent and the resveratrol loaded carriers were characterized by XRD, TEM, N2 physisorption, thermal analysis, and FT-IR spectroscopy. The influence of the support structure on the adsorption capacity and the release kinetics of this poorly soluble compound were investigated. Our results indicated that the chosen nanoporous silica supports are suitable for stabilization of trans-resveratrol and reveal controlled release and ability to protect the supported compound against degradation regardless of loading method. The solid-state dry mixing appears very effective for preparation of drug formulations composed of poorly soluble compound.

  6. Porous polylactic acid-silica hybrids: preparation, characterization, and study of mesenchymal stem cell osteogenic differentiation.

    PubMed

    Pandis, Christos; Trujillo, Sara; Matos, Joana; Madeira, Sara; Ródenas-Rochina, Joaquín; Kripotou, Sotiria; Kyritsis, Apostolos; Mano, João F; Gómez Ribelles, José Luis

    2015-02-01

    A novel approach to reinforce polymer porous membranes is presented. In the prepared hybrid materials, the inorganic phase of silica is synthesized in-situ and inside the pores of aminolyzed polylactic acid (PLA) membranes by sol-gel reactions using tetraethylorthosilicate (TEOS) and glycidoxypropyltrimethoxysilane (GPTMS) as precursors. The hybrid materials present a porous structure with a silica layer covering the walls of the pores while GPTMS serves also as coupling agent between the organic and inorganic phase. The adjustment of silica precursors ratio allows the modulation of the thermomechanical properties. Culture of mesenchymal stem cells on these supports in osteogenic medium shows the expression of characteristic osteoblastic markers and the mineralization of the extracellular matrix. PMID:25303745

  7. Feasibility of the preparation of silica monoliths for gas chromatography: fast separation of light hydrocarbons.

    PubMed

    Azzouz, Imadeddine; Essoussi, Anouar; Fleury, Joachim; Haudebourg, Raphael; Thiebaut, Didier; Vial, Jerome

    2015-02-27

    The preparation conditions of silica monoliths for gas chromatography were investigated. Silica-based monolithic capillary columns based on sol-gel process were tested in the course of high-speed gas chromatographic separations of light hydrocarbons mixture (C1-C4). The impact of modifying the amount of porogen and/or catalyst on the monolith properties were studied. At the best precursor/catalyst/porogen ratio evaluated, a column efficiency of about 6500 theoretical plates per meter was reached with a very good resolution (4.3) for very light compounds (C1-C2). The test mixture was baseline separated on a 70cm column. To our knowledge for the first time a silica-based monolithic capillary column was able to separate light hydrocarbons from methane to n-butane at room temperature with a back pressure in the range of gas chromatography facilities (under 4.1bar). PMID:25622518

  8. Preparation and characterization of poly (ethylene glycol)-coated Stoeber silica nanoparticles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Kopelman, Raoul; Xu, Hao; Yan, Fei; Monson, Eric E.; Tang, Wei; Schneider, Randy; Philbert, Martin A.

    2002-06-01

    Monodisperse, spherical, polyethylene glycol (PEG)-coated silica nanoparticles have been prepared in the size range of 50-350 nm, and their size distribution were characterized by SEM and multi-angle static light scattering experiments. The chemical binding of PEG to the silica nanoparticles was confirmed by IR spectroscopy. The biocompatibility of these PEGylated nanoparticles was also studied by non-specific protein binding tests and in-vivo toxicology studies in live animals. These silica nanoparticles, as a matrix for encapsulation of certain reagents, have been used for the fabrication of intracellular sensors and have potential for applications to in vivo diagnosis, analysis and measurements, due to their small physical size and their biocompatibility, both stemming from the specialized PEG coating.

  9. Preparation of fluorescent mesoporous hollow silica-fullerene nanoparticles via selective etching for combined chemotherapy and photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Yang, Yannan; Yu, Meihua; Song, Hao; Wang, Yue; Yu, Chengzhong

    2015-07-01

    Well-dispersed mesoporous hollow silica-fullerene nanoparticles with particle sizes of ~50 nm have been successfully prepared by incorporating fullerene molecules into the silica framework followed by a selective etching method. The fabricated fluorescent silica-fullerene composite with high porosity demonstrates excellent performance in combined chemo/photodynamic therapy.Well-dispersed mesoporous hollow silica-fullerene nanoparticles with particle sizes of ~50 nm have been successfully prepared by incorporating fullerene molecules into the silica framework followed by a selective etching method. The fabricated fluorescent silica-fullerene composite with high porosity demonstrates excellent performance in combined chemo/photodynamic therapy. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02769a

  10. Preparation and characterization of hydrophobic silica aerogel sphere products by co-precursor method

    NASA Astrophysics Data System (ADS)

    Yu, Huijun; Liang, Xiaofeng; Wang, Junxia; Wang, Minmin; Yang, Shiyuan

    2015-10-01

    In the present paper, silica aerogel balls were prepared using methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) co-precursor with different MTES/TEOS molar ratio (I) by two-step acid-base catalyzed sol-gel process and molding technology followed by the carbon dioxide supercritical drying. The physical properties of various silica aerogels whose I varied from 0 to 1.0 were studied by BET and SEM. Approving aerogel ball was obtained by using acetone as exchanging solvent at I of 0.8. Better properties are less crack, little shrinking percentage (17%), low apparent density (0.103 g/cm3), large surface area (996.35 m2/g) and high pore volume (3.32 cm3/g). Characterized by contact angle measurements and thermal stability, the characterizations of aerogel spheres were strongly affected by the MTES/TEOS molar ratio. Hydrophobic property increased with the increase in I value, and silica aerogels at I = 0.8 and 1.0 have a superhydrophobic characterization with the highest contact angle (152°). The TG-DTA analysis shows that the silica aerogel spheres transform hydrophobic to hydrophilic at around 450 °C, which is due to oxidation of Si-CH3 to Si-OH groups. The surface chemical modification was confirmed by FT-IR spectrums, which demonstrated that Si-CH3 groups be beneficial to molding of silica aerogels.

  11. Preparation, characterization, and in vivo evaluation of tanshinone IIA solid dispersions with silica nanoparticles

    PubMed Central

    Jiang, Yan-rong; Zhang, Zhen-hai; Liu, Qi-yuan; Hu, Shao-ying; Chen, Xiao-yun; Jia, Xiao-bin

    2013-01-01

    We prepared solid dispersions (SDs) of tanshinone IIA (TSIIA) with silica nanoparticles, which function as dispersing carriers, using a spray-drying method and evaluated their in vitro dissolution and in vivo performance. The extent of TSIIA dissolution in the silica nanoparticles/TSIIA system (weight ratio, 5:1) was approximately 92% higher than that of the pure drug after 60 minutes. However, increasing the content of silica nanoparticles from 5:1 to 7:1 in this system did not significantly increase the rate or extent of TSIIA dissolution. The physicochemical properties of SDs were investigated using scanning electron microscopy, differential scanning calorimetry, X-ray powder diffraction, and Fourier transforms infrared spectroscopy. Studying the stability of the SDs of TSIIA revealed that the drug content of the formulation and dissolution behavior was unchanged under the applied storage conditions. In vivo tests showed that SDs of the silica nanoparticles/TSIIA had a significantly larger area under the concentration-time curve, which was 1.27 times more than that of TSIIA (P < 0.01). Additionally, the values of maximum plasma concentration and the time to reach maximum plasma concentration of the SDs were higher than those of TSIIA and the physical mixing system. Based on these results, we conclude that the silica nanoparticle based SDs achieved complete dissolution, increased absorption rate, maintained drug stability, and showed improved oral bioavailability compared to TSIIA alone. PMID:23836971

  12. Preparation of antibacterial composite material of natural rubber particles coated with silica and titania

    NASA Astrophysics Data System (ADS)

    Wisutiratanamanee, Apisit; Poompradub, Sirilux; Poochinda, Kunakorn

    2014-06-01

    Silica coating, followed by titania coating, was performed over spray-dried natural rubber (NR) compound for physical and anti-bacterial characterizations. Titania has a strong photo-oxidative catalytic property, which can disinfect bacteria, but may degrade NR. Therefore, silica coating was intended to form a barrier between NR and titania. First, NR particles were prepared by spray-drying of NR compound latex, formulated for household glove products, mixed with sodium dodecyl sulfate (SDS) to reduce particle agglomeration. The factorial experimental design was employed to investigate the effects of nozzle flow rate (500-700 Lh-1), inlet air temperature (110-150 °C), SDS content (35-55 phr) and mass flow rate (1.2-1.7 g rubber/min) on NR yield and moisture content. Then, the NR compound particles prepared at the optimum condition were coated with silica, using tetraethoxysilane (TEOS) as the precursor, by chemical vapor deposition (CVD) at 60 °C for 2-48 hours. Next, the particles were coated with titania using titanium tetrafluoride (TiF4) by liquid phase deposition (LPD) at 60 ºC for 4-8 hours. The NR composites were characterized for surface morphology by SEM, silica and titania content by TGA and EDX. The NR composites were found to cause more than 99% reduction of Escherichia coli and Staphylococcus aureus under 1-hour exposure to natural light.

  13. Preparing hydrophobic nanocellulose-silica film by a facile one-pot method.

    PubMed

    Le, Duy; Kongparakul, Suwadee; Samart, Chanatip; Phanthong, Patchiya; Karnjanakom, Surachai; Abudula, Abuliti; Guan, Guoqing

    2016-11-20

    Hydrophobic nanocellulose-silica film was successfully prepared by a facile one-pot method using tetraethoxysilane (TEOS) and dodecyl triethoxylsilane (DTES). Morphological characterization of the hydrophobic nanocellulose-silica (NC-SiO2-DTES) film showed well self-assembled DTES modified silica spherical nanoparticles with the particle sizes in the range of 88-126nm over the nanocellulose film. The hydrophobicity of the NC-SiO2-DTES film was achieved owing to the improvement of roughness of the nanocellulose film by coating dodecyl- terminated silica nanoparticles. An increase in DTES loading amount and reaction time increased the hydrophobicity of the film, and the optimum condition for NC-SiO2-DTES film preparation was achieved at DTES/TEOS molar ratio of 2.0 for 8h reaction time. Besides, the NC-SiO2-DTES film performed superoleophilic property with octane and hexadecane contact angles of 0°. It also showed an excellent hydrophobic property over all pH values ranged from 1 to 14. PMID:27561496

  14. Preparation of resveratrol-loaded nanoporous silica materials with different structures

    SciTech Connect

    Popova, Margarita; Szegedi, Agnes; Mavrodinova, Vesselina; Novak Tušar, Natasa; Mihály, Judith; Klébert, Szilvia; Benbassat, Niko; Yoncheva, Krassimira

    2014-11-15

    Solid, nanoporous silica-based spherical mesoporous MCM-41 and KIL-2 with interparticle mesoporosity as well as nanosized zeolite BEA materials differing in morphology and pore size distribution, were used as carriers for the preparation of resveratrol-loaded delivery systems. Two preparation methods have been applied: (i) loading by mixing of resveratrol and mesoporous carrier in solid state and (ii) deposition in ethanol solution. The parent and the resveratrol loaded carriers were characterized by XRD, TEM, N2 physisorption, thermal analysis, and FT-IR spectroscopy. The influence of the support structure on the adsorption capacity and the release kinetics of this poorly soluble compound were investigated. Our results indicated that the chosen nanoporous silica supports are suitable for stabilization of trans-resveratrol and reveal controlled release and ability to protect the supported compound against degradation regardless of loading method. The solid-state dry mixing appears very effective for preparation of drug formulations composed of poorly soluble compound. - Graphical abstract: trans-Resveratrol was stabilized in the pores of BEA zeolite, MCM-41and KIL2 mesoporous silicas. - Highlights: • BEA, KIL-2 and MCM-41 materials were used as carriers for resveratrol loading. • Resveratrol encapsulation in ethanol solution and solid state procedure were applied. • The solid-state preparation appears very effective for stabilization of trans-resveratrol.

  15. Preparation of Composite Coating on AZ91D Magnesium Alloy by Silica Sol-Micro Oxidation

    NASA Astrophysics Data System (ADS)

    Shao, Zhongcai; Zhang, Feifei; Zhao, Ruiqiang; Shen, Xiaoyi

    2016-03-01

    Composite coating was prepared on AZ91D magnesium alloy with a new method which combined silica sol with micro-arc oxidation (MAO). The MAO coating was prepared on the basis of MAO solution, and then coated by sol-gel process. The composite coating was obtained after second MAO treatment. Scanning electron microscopy coupled with X-ray diffraction (XRD), energy spectrum analysis and electrochemical testing was applied to characterize the properties of MAO coating and composite coating. The experimental test results indicated that the Si element derived from SiO2 gel particle embedded into the MAO coating by second MAO treatment. The surface of composite coating became dense and the holes were smaller with silica sol sealing process. The corrosion resistance of composite coating was improved than the MAO coating.

  16. Incorporation of anti-inflammatory agent into mesoporous silica.

    PubMed

    Braz, Wilson Rodrigues; Rocha, Natállia Lamec; de Faria, Emerson H; Silva, Márcio L A E; Ciuffi, Katia J; Tavares, Denise C; Furtado, Ricardo Andrade; Rocha, Lucas A; Nassar, Eduardo J

    2016-09-23

    The unique properties of macroporous, mesoporous, and microporous systems, including their ability to accommodate molecules of different sizes inside their pores and to act as drug delivery systems, have been the object of extensive studies. In this work, mesoporous silica with hexagonal structure was obtained by template synthesis via the sol-gel process. The resulting material was used as support to accommodate the anti-inflammatory agent indomethacin. The alkaline route was used to prepare the mesoporous silica; cetyltrimethylammonium bromide was employed as porogenic agent. The silica particles were functionalized with 3-aminopropyltriethoxysilane alkoxide (APTES) by the sol-gel post-synthesis method. Indomethacin was incorporated into the silica functionalized with APTES and into non-functionalized silica. The resulting systems were characterized by x-ray diffraction (XRD), specific area, infrared spectroscopy, and thermal analyses (TGA). XRD attested to formation of mesoporous silica with hexagonal structure. This structure remained after silica functionalization with APTES and incorporation of indomethacin. Typical infrared spectroscopy vibrations and organic material decomposition during TGA confirmed silica functionalization and drug incorporation. The specific surface area and pore volume of the functionalized material incorporated with indomethacin decreased as compared with the specific surface area and pore volume of the non-functionalized silica containing no drug, suggesting both the functionalizing agent and the drug were present in the silica. Cytotoxicity tests conducted on normal fibroblasts (GM0479A) cells attested that the silica matrix containing indomethacin was less toxic than the free drug. PMID:27533108

  17. Properties of films prepared from low surface area/density alumina-silica

    SciTech Connect

    Hietala, S.L.; Smith, D.M. ); Hietala, V.M.; Frye, G.C.; Hurd, A.J.; Brinker, C.J. )

    1990-01-01

    A sol-gel method was use to prepare bulk, closed pore, amorphous alumina-silica. Films prepared from this 47wt% Al{sub 2}O{sub 3}- SiO{sub 2} composition were examined by SAW, elipsometry and electrical measurements. The films were found to have a surface area of 1.1 cm{sup 2}/cm{sup 2}, a refractive index of 1.44 at 633 nm, and a relative permittivity of 6.2 at 200 KHz. These properties indicate potential applications as hermetic seals, barrier coatings, dielectric layers for capacitors and passivation coatings for electronic circuits.

  18. Preparation, characterization and oxygen sensing properties of luminescent carbon dots assembled mesoporous silica microspheres.

    PubMed

    Wang, Li; Zhang, Haoran; Zhou, Xiaohua; Liu, Yingliang; Lei, Bingfu

    2016-09-15

    In this paper, our effort was focused on preparation and oxygen sensing of luminescence carbon dots (CDs) assembled hollow mesoporous silica microspheres (HMSMs) and mesoporous silica microspheres (MSMs). MSMs doped with CDs showed shorter response time and recovery time comparing with HMSMs doped with CDs. This feature can be attributed to ordered channel structure of mesoporous carrier which can promote the gas diffusion effectively. While HMSMs doped with CDs shows a higher oxygen quenching response and the degree of quenching reach 80.35%. The response time was determined to be about 7s and the emission intensities of the samples were effectively reduced as the concentration of oxygen increased. These results indicate that the system we have developed can be used for oxygen detection in wide concentration range and is especially accurate for very low oxygen concentrations. The obtained CDs grafted hollow mesoporous silica microspheres (HMSMs) and mesoporous silica microspheres (MSMs) samples appears to be a promising sensing material for environmental detection application and would also find applications in catalyst, electrode, or related fields. PMID:27309945

  19. Preparation and properties of aqueous castor oil-based polyurethane-silica nanocomposite dispersions through a sol-gel process.

    PubMed

    Xia, Ying; Larock, Richard C

    2011-09-01

    Waterborne castor oil-based polyurethane-silica nanocomposites with the polymer matrix and silica nanoparticles chemically bonded have been successfully prepared through a sol-gel process. The formation of silica nanoparticles in water not only reinforces the resulting coatings, but also increases the crosslink density of the nanocomposites. The (29)Si solid state NMR spectrum indicates the formation of silica and the TEM indicates that the nanoparticles are embedded in the polymers, resembling a core-shell structure. The silica nanoparticles in the polymer matrix play an important role in improving both the mechanical properties and the thermal stabilities of the resulting nanocomposites. This work provides an effective and promising way to prepare biorenewable, high performance nanocomposite coatings. PMID:25867899

  20. Preparation of highly anisotropic cobalt ferrite/silica microellipsoids using an external magnetic field.

    PubMed

    Abramson, Sébastien; Dupuis, Vincent; Neveu, Sophie; Beaunier, Patricia; Montero, David

    2014-08-01

    Magnetic cobalt ferrite/silica microparticles having both an original morphology and an anisotropic nanostructure are synthesized through the use of an external magnetic field and nanoparticles characterized by a high magnetic anisotropy. The association of these two factors implies that the ESE (emulsion and solvent evaporation) sol-gel method employed here allows the preparation of silica microellipsoids containing magnetic nanoparticles aggregated in large chains. It is clearly shown that without this combination, microspheres characterized by an isotropic distribution of the magnetic nanoparticles are obtained. While the chaining of the cobalt ferrite nanoparticles inside the silica matrix is related to the increase of their magnetic dipolar interactions, the ellipsoidal shape of the microparticles may be explained by the elongation of the sol droplets in the direction of the external magnetic field during the synthesis. Because of their highly anisotropic structure, these microparticles exhibit permanent magnetic moments, which are responsible, at a larger scale, for the existence of strong magnetic dipolar interactions. Therefore, when they are dispersed in water, the microellipsoids self-assemble into large and irregular chains. These interactions can be reinforced by the use of external magnetic field, allowing the preparation of very large permanent chains. This research illustrates how nanostructured particles exhibiting complex architectures can be elaborated through simple, fast, and low-cost methods, such as the use of external fields in combination with soft chemistry. PMID:25029515

  1. Consecutively Preparing D-Xylose, Organosolv Lignin, and Amorphous Ultrafine Silica from Rice Husk

    PubMed Central

    Zhang, Hongxi; Ding, Xuefeng; Wang, Zichen; Zhao, Xu

    2014-01-01

    Rice husk is an abundant agricultural by-product reaching the output of 80 million tons annually in the world. The most common treatment method of rice husk is burning or burying, which caused serious air pollution and resource waste. In order to solve this problem, a new method is proposed to comprehensively utilize the rice husk in this paper. Firstly, the D-xylose was prepared from the semicellulose via dilute acid hydrolysis. Secondly, the lignin was separated via organic solvent pulping from the residue. Finally, the amorphous ultrafine silica was prepared via pyrolysis of the residue produced in the second process. In this way, the three main contents of rice husk (semicellulose, lignin, and silica) are consecutively converted to three fine chemicals, without solid waste produced. The yields of D-xylose and organosolv lignin reach 58.2% and 58.5%, respectively. The purity and specific surface of amorphous ultrafine silica reach 99.92% and 225.20 m2/g. PMID:25140120

  2. Adsorption characterization of gaseous volatile organic compound on mesoporous silica particles prepared from spent diatomaceous earth.

    PubMed

    Bei, Lei-Lei; Tao, Hong; Ma, Chih-Ming; Shiue, Angus; Chang, Chang-Tang

    2014-04-01

    This study used spent diatomaceous earth (SDE) from drink processing as source of Si and cationic surfactant (CTAB) as a template for the synthesis of mesoporous silica Materials (MSM) through hydrothermal method. The MSM was characterized by Small-angle X-ray Diffraction (SXRD), Scanning Electron Microscopy (SEM), Thermo Gravimetric Analysis (TGA), Fourier Transform Infrared (FT-IR) spectroscopy and N2 adsorption-desorption analyzer. The results showed that the surface area, pore volume and pore size was roughly ranged from 880 to 1060 m2 g(-1), 1.05 cm3 g(-1) and 4.0 nm, respectively. The properties of the synthesized MSM were also compared with those prepared from pure silica sources (MCM-41) and got almost the same characteristics. The synthesized MSM was used as adsorbent at 25 degrees C with carrier gas of air. The adsorption equilibrium revealed that adsorption capacity of MSM was 59.6, 65.7, 69.6, 84.9 mg g(-1) while the acetone concentration was 600, 800, 1000 ppm, 1600 ppm respectively. Results showed that breakthrough curves correlate to the challenge vapor concentration, adsorbent loading, and the flow rate. The results obtained in the present work demonstrated that it was feasibility of using the SDE as a potential source of silica to prepare MSM. PMID:24734749

  3. Preparation and characterization of Ag nanoparticle-embedded blank and ligand-anchored silica gels.

    PubMed

    Im, Hee-Jung; Lee, Byung Cheol; Yeon, Jei-Won

    2013-11-01

    Ag nanoparticles, used for halogen (especially iodine) adsorption and an evaluation of halogen behavior, were embedded in synthesized inorganic-organic hybrid gels. In particular, an irradiation method using an electron beam plays a part in introducing Ag nanoparticles to the organofunctionalized silica gels from AgNO3 solutions in a simple way at atmospheric pressure and room temperature. For preparation of the Ag nanoparticle-embedded inorganic-organic hybrid gels, ligands of ethylenediamine (NH2CH2CH2NH-, TMSen) and mercapto (HS-) functionalized three-dimensional porous SiO2 sol-gels were first synthesized through hydrolysis and condensation reactions, and Ag nanoparticles were then embedded into the ethylenediamine- and mercapto-anchored silica gels each, through electron-beam irradiation. The addition of ligands yielded larger average pore sizes than the absence of any ligand. Moreover, the ethylenediamine ligand led to looser structures and better access of the Ag nanoparticles to the ethylenediamine-anchored gel. As a result, more Ag nanoparticles were introduced into the ethylenediamine-anchored gel. The preparation and characterization of Ag nanoparticle-embedded blank and ligand-anchored silica gels are discussed in detail. PMID:24245307

  4. Characterization of silica gel prepared by using sol-gel process

    NASA Astrophysics Data System (ADS)

    Besbes, M.; Fakhfakh, N.; Benzina, M.

    2009-11-01

    We studied the preparation of silica gels from sodium silicate solution mixed with hydrochloric acid by sol-gel process. The obtained gel is washed with water to obtain a 'hydrogel'. The immersion of the last one in alcohol, gives an 'alcogel'. A Hoke D6 experimental design was followed in order to limit the number of tests. pH and the silica concentration represent the most significant factors which control the obtaining of a significant specific surface and thus a great capacity of adsorption. A second order polynomial model was adopted in order to represent the results in the form of three-dimensional surfaces. These results are also topographically illustrated as isoresponses lines. The results showed that the pH effect is more significant than the silica concentration one. We obtained gels with great microporosity and presenting specific surfaces of 657 m2.g-1 when pH is equal to 2. The prepared gel without alcohol presents interesting characteristics for a potential industrial use since its production cost is lowest and has a high specific surface.

  5. Preparation and properties of PEC nanocomposite membranes with carboxymethyl cellulose and modified silica.

    PubMed

    Liu, Tao; An, Quan-Fu; Wang, Xue-San; Zhao, Qiang; Zhu, Bao-Ku; Gao, Cong-Jie

    2014-06-15

    Carboxymethyl cellulose (CMC)-modified silica nanocomposites were prepared via in situ incorporation of modified silica during the ionic complexation between CMC and poly(2-methacryloyloxy ethyl trimethylammonium chloride) (PDMC). Ionic bonds were introduced between the poly(2-acrylamido-2-methylproanesulfonic acid) modified silica (SiO2-PAMPS) and the polyelectrolyte complex (PEC) matrix. The PEC nanocomposites (PECNs) and their membranes (PECNMs) were characterized with Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and tensile testing. PECNM containing 5 wt.% SiO2-PAMPS showed a tensile strength of 68 MPa and elongation at break of 7.1%, which were 1.9 and 2.6 times as high as those of pristine PEC membranes, respectively. Moreover, the pervaporation performance of as-prepared PECNMs was evaluated with dehydration of 10 wt.% aqueous isopropanol mixtures, and the PECNMs exhibited a flux of 2,400 gm(-2)h(-1) with a high separation factor of 4491 at 70°C. PMID:24721095

  6. Consecutively preparing d-xylose, organosolv lignin, and amorphous ultrafine silica from rice husk.

    PubMed

    Zhang, Hongxi; Ding, Xuefeng; Wang, Zichen; Zhao, Xu

    2014-01-01

    Rice husk is an abundant agricultural by-product reaching the output of 80 million tons annually in the world. The most common treatment method of rice husk is burning or burying, which caused serious air pollution and resource waste. In order to solve this problem, a new method is proposed to comprehensively utilize the rice husk in this paper. Firstly, the D-xylose was prepared from the semicellulose via dilute acid hydrolysis. Secondly, the lignin was separated via organic solvent pulping from the residue. Finally, the amorphous ultrafine silica was prepared via pyrolysis of the residue produced in the second process. In this way, the three main contents of rice husk (semicellulose, lignin, and silica) are consecutively converted to three fine chemicals, without solid waste produced. The yields of D-xylose and organosolv lignin reach 58.2% and 58.5%, respectively. The purity and specific surface of amorphous ultrafine silica reach 99.92% and 225.20 m(2)/g. PMID:25140120

  7. Preparation of superhydrophobic and transparent micro-nano hybrid coatings from polymethylhydroxysiloxane and silica ormosil aerogels

    NASA Astrophysics Data System (ADS)

    Nagappan, Saravanan; Park, Jin Joo; Park, Sung Soo; Ha, Chang-Sik

    2014-12-01

    Superhydrophobic and transparent polymethylhydroxysiloxane (PMHOS)/silica ormosil aerogel hybrids were prepared successfully by mixing of PMHOS with various weight percentages of silica ormosil aerogels (as synthesized from methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS) precursors) in separate seal perfume glass vials. The hybrids were spin coated on glass substrate at 1000 rpm for 60 seconds and used for further analysis. The surface morphology and chemical compositions of the hybrids were analyzed by high resolution scanning electron microscopy, high resolution transmission electron microscopy, atomic force spectroscopy, adsorption and desorption isotherm, and X-ray photoelectron spectroscopy. The transparency, thermal decomposition and static contact angle (SCA) of each sample were measured by UV-Visible spectrophotometer, TGA and drop shape analysis system, respectively. The spin coated substrates showed good superhydrophobic properties, thermal stability as well as transparency on the glass substrates.

  8. Preparation of monolithic silica-chitin composite under extreme biomimetic conditions.

    PubMed

    Bazhenov, Vasilii V; Wysokowski, Marcin; Petrenko, Iaroslav; Stawski, Dawid; Sapozhnikov, Philipp; Born, René; Stelling, Allison L; Kaiser, Sabine; Jesionowski, Teofil

    2015-05-01

    Chitin is a widespread renewable biopolymer that is extensively distributed in the natural world. The high thermal stability of chitin provides an opportunity to develop novel inorganic-organic composites under hydrothermal synthesis conditions in vitro. For the first time, in this work we prepared monolithic silica-chitin composite under extreme biomimetic conditions (80°C and pH 1.5) using three dimensional chitinous matrices isolated from the marine sponge Aplysina cauliformis. The resulting material was studied using light and fluorescence microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy. A mechanism for the silica-chitin interaction after exposure to these hydrothermal conditions is proposed and discussed. PMID:25701776

  9. [Preparation and anti-cancer activity in vitro of curcumin loaded mesoporous silica nanoparticle].

    PubMed

    He, Li-li; Gu, Jian

    2015-11-01

    This paper is to prepare curcumin (Cur) loaded mesoporous silica nanoparticle (Cur-MSN), evaluate its release behavior and anti-cancer activity in vitro. Mesoporous silica nanoparticle (MSN) was prepared by polymerization method and Cur-MSN was obtained using solvent evaporation method and impregnation centrifugation method. The preparation method was optimized using entrapment efficiency (EE) and loading efficiency (LE) as indexes. Cur-MSN was characterized with scanning electron microscope and its particle size and zeta potential were determined. Finally, in vitro release behavior in 0.2% SDS solution and its cell-killing effect on HeLa cells were also evaluated. The Cur-MSN prepared with process optimization method was round and uniform and exhibited typical mesoporous characterization. The mean particle size and Zeta potential of Cur-MSN were 75.8 nm and -30.1 mV, respectively. EE and LE of three batches of Cur-MSN were (72.55 ± 2.01)% and (16.21 ± 1.12)%, respectively. In vitro release behavior of Cur-MSN showed a sustained release profile with 83.5% cumulative release within 96 h. The killing effect of Cur-MSN on HeLa cells was dose-dependent with IC50 of 19.40 mg x L(-1), which was similar to that of Cur. PMID:27071254

  10. All-acrylic film-forming colloidal polymer/silica nanocomposite particles prepared by aqueous emulsion polymerization.

    PubMed

    Fielding, Lee A; Tonnar, Jeff; Armes, Steven P

    2011-09-01

    The efficient synthesis of all-acrylic, film-forming, core-shell colloidal nanocomposite particles via in situ aqueous emulsion copolymerization of methyl methacrylate with n-butyl acrylate in the presence of a glycerol-functionalized ultrafine silica sol using a cationic azo initiator at 60 °C is reported. It is shown that relatively monodisperse nanocomposite particles can be produced with typical mean weight-average diameters of 140-330 nm and silica contents of up to 39 wt %. The importance of surface functionalization of the silica sol is highlighted, and it is demonstrated that systematic variation of parameters such as the initial silica sol concentration and initiator concentration affect both the mean particle diameter and the silica aggregation efficiency. The nanocomposite morphology comprises a copolymer core and a particulate silica shell, as determined by aqueous electrophoresis, X-ray photoelectron spectroscopy, and electron microscopy. Moreover, it is shown that films cast from n-butyl acrylate-rich copolymer/silica nanocomposite dispersions are significantly more transparent than those prepared from the poly(styrene-co-n-butyl acrylate)/silica nanocomposite particles reported previously. In the case of the aqueous emulsion homopolymerization of methyl methacrylate in the presence of ultrafine silica, a particle formation mechanism is proposed to account for the various experimental observations made when periodically sampling such nanocomposite syntheses at intermediate comonomer conversions. PMID:21776995

  11. Poromechanics of microporous media

    NASA Astrophysics Data System (ADS)

    Brochard, L.; Vandamme, M.; Pellenq, R. J.-M.

    2012-04-01

    Microporous media, i.e., porous media made of pores with a nanometer size, are important for a variety of applications, for instance for sequestration of carbon dioxide in coal, or for storage of hydrogen in metal-organic frameworks. In a pore of nanometer size, fluid molecules are not in their bulk state anymore since they interact with the atoms of the solid: they are said to be in an adsorbed state. For such microporous media, conventional poromechanics breaks down. In this work we derive poroelastic constitutive equations which are valid for a generic porous medium, i.e., even for a porous medium with pores of nanometer size. The complete determination of the poromechanical behavior of a microporous medium requires knowing how the amount of fluid adsorbed depends on both the fluid bulk pressure and the strain of the medium. The derived constitutive equations are validated with the help of molecular simulations on one-dimensional microporous media. Even when a microporous medium behaves linearly in the absence of any fluid (i.e., its bulk modulus does not depend on strain), we show that fluid adsorption can induce non-linear behavior (i.e., its drained bulk modulus can then depend significantly on strain). We also show that adsorption can lead to an apparent Biot coefficient of the microporous medium greater than unity or smaller than zero. The poromechanical response of a microporous medium to adsorption significantly depends on the pore size distribution. Indeed, the commensurability (i.e., the ratio of the size of the pores to that of the fluid molecules) proves to play a major role. For a one-dimensional model of micropores with a variety of pore sizes, molecular simulations show that the amount of adsorbed fluid depends linearly on the strain of the medium. We derive linearized constitutive equations which are valid when such a linear dependence of the adsorbed amount of fluid on the strain is observed. As an application, the case of methane and coal is

  12. Preparations for low-cost silica substrate of CIGS solar cell

    NASA Astrophysics Data System (ADS)

    Hsu, Ming-Seng; Chang, Chung Chih; Cheng, Hsiang Hshi; Ouyang, Yueh; Der Sheu, Shinn

    2008-08-01

    The production of CuInGaSe2 (CIGS) solar cell is based on vacuum processes, which requires a high manufacturing temperature and high cost. Our result show a simple method has been developed to prepare the silica substrates of CIGS solar cell. It's synthesized by sol-gel process from tetraethylorthosilicate (TEOS), methanol (CH3OH) and pure water (both ion-exchange and distillation) in the presence of ammonia as catalyst. The preparation procedure was elaborated as the flexible sequence to control chemical composition and properties of the particles in sol-gel-derived silica substrate. The morphology, particle size, and size distribution of CIGS substrate were characterized with dynamic light scattering (DLS) and atomic force microscopy (AFM). The results of AFM morphology and statistic evidence we find an easy way, non-vacuum and low temperature processes, to successfully prepare the CIGS solar cell substrates with surface roughness below 3 nm. It is powerful the advance study in low cost solar cell.

  13. Facile preparation of organic-silica hybrid monolith for capillary hydrophilic liquid chromatography based on "thiol-ene" click chemistry.

    PubMed

    Chen, Ming-Luan; Zhang, Jun; Zhang, Zheng; Yuan, Bi-Feng; Yu, Qiong-Wei; Feng, Yu-Qi

    2013-04-01

    In this work, a one-step approach to facile preparation of organic-inorganic hybrid monoliths was successfully developed. After vinyl-end organic monomers and azobisisobutyronitrile (AIBN) were mixed with hydrolyzed tetramethoxysilane (TMOS) and 3-mercaptopropyltrimethoxysilane (MPTMS), the homogeneous mixture was introduced into a fused-silica capillary for simultaneous polycondensation and "thiol-ene" click reaction to form the organic-silica hybrid monoliths. By employing this strategy, two types of organic-silica hybrid monoliths with positively charged quaternary ammonium and amide groups were prepared, respectively. The functional groups were successfully introduced onto the monoliths during the sol-gel process with "thiol-ene" click reaction, which was demonstrated by ζ-potential assessment, energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FT-IR) spectroscopy. The porous structure of the prepared monolithic columns was examined by scanning electron microscopy (SEM), nitrogen adsorption-desorption measurement, and mercury intrusion porosimetry. These results indicate the prepared organic-silica hybrid monoliths possess homogeneous column bed, large specific surface area, good mechanical stability, and excellent permeability. The prepared monolithic columns were then applied for anion-exchange/hydrophilic interaction liquid chromatography. Different types of analytes, including benzoic acids, inorganic ions, nucleosides, and nucleotides, were well separated with high column efficiency around 80,000-130,000 plates/m. Taken together, we present a facile and universal strategy to prepare organic-silica hybrid monoliths with a variety of organic monomers using one-step approach. PMID:23434082

  14. Preparation of silica coated cobalt ferrite magnetic nanoparticles for the purification of histidine-tagged proteins

    NASA Astrophysics Data System (ADS)

    Aygar, Gülfem; Kaya, Murat; Özkan, Necati; Kocabıyık, Semra; Volkan, Mürvet

    2015-12-01

    Surface modified cobalt ferrite (CoFe2O4) nanoparticles containing Ni-NTA affinity group were synthesized and used for the separation of histidine tag proteins from the complex matrices through the use of imidazole side chains of histidine molecules. Firstly, CoFe2O4 nanoparticles with a narrow size distribution were prepared in an aqueous solution using the controlled co-precipitation method. In order to obtain small CoFe2O4 agglomerates, oleic acid and sodium chloride were used as dispersants. The CoFe2O4 particles were coated with silica and subsequently the surface of these silica coated particles (SiO2-CoFe2O4) was modified by amine (NH2) groups in order to add further functional groups on the silica shell. Then, carboxyl (-COOH) functional groups were added to the SiO2-CoFe2O4 magnetic nanoparticles through the NH2 groups. After that Nα,Nα-Bis(carboxymethyl)-L-lysine hydrate (NTA) was attached to carboxyl ends of the structure. Finally, the surface modified nanoparticles were labeled with nickel (Ni) (II) ions. Furthermore, the modified SiO2-CoFe2O4 magnetic nanoparticles were utilized as a new system that allows purification of the N-terminal His-tagged recombinant small heat shock protein, Tpv-sHSP 14.3.

  15. Preparation of ultrafine silica from potash feldspar using sodium carbonate roasting technology

    NASA Astrophysics Data System (ADS)

    Liu, Jia-nan; Shen, Xiao-yi; Wu, Yan; Zhang, Jun; Zhai, Yu-chun

    2016-08-01

    A novel process was developed for the preparation of ultrafine silica from potash feldspar. In the first step, potash feldspar was roasted with Na2CO3 and was followed by leaching using NaOH solution to increase the levels of potassium, sodium, and aluminum in the solid residue. The leaching solution was then carbonated to yield ultrafine silica. The optimized reaction conditions in the roasting process were as follows: an Na2CO3-to-potash feldspar molar ratio of 1.1, a reaction temperature of 875°C, and a reaction time of 1.5 h. Under these conditions, the extraction rate of SiO2 was 98.13%. The optimized carbonation conditions included a final solution pH value of 9.0, a temperature of 40°C, a CO2 flow rate of 6 mL/min, a stirring intensity of 600 r/min, and an ethanol-to-water volume ratio of 1:9. The precipitation rate and granularity of the SiO2 particles were 99.63% and 200 nm, respectively. We confirmed the quality of the obtained ultrafine silica by comparing the recorded indexes with those specified in Chinese National Standard GB 25576―2010.

  16. Preparation and characterizaion of CTAB-templated large pore silica nanocomposite films

    NASA Astrophysics Data System (ADS)

    Yao, Lan-Fang; Tian, Lin-Lin; Wang, Shuo; Li, Lin; Xu, Ruiqing; Fang, Xueling

    2010-10-01

    CTAB-templated large pore silica nano-composite films were prepared by means of a two-step acid-catalyzed and solgel process using tetraethoxysilane (TEOS) as the precursor, Surfactant cetyltrimethy- ammonium bromide (CTAB) as an organic template to generate the uniformity pore structure and 1,3,5-trimethyl benzene (TMB) as organic swelling agent. The obtained samples were characterized by XRD, Fourier-transform infrared (FTIR) and Atomic Force Microscopy (AFM). We found that the TMB/CTAB mol ratio must be controlled well for producing large pore materials.

  17. Preparation and characterizaion of CTAB-templated large pore silica nanocomposite films

    NASA Astrophysics Data System (ADS)

    Yao, Lan-fang; Tian, Lin-lin; Wang, Shuo; Li, Lin; Xu, Ruiqing; Fang, Xueling

    2011-02-01

    CTAB-templated large pore silica nano-composite films were prepared by means of a two-step acid-catalyzed and solgel process using tetraethoxysilane (TEOS) as the precursor, Surfactant cetyltrimethy- ammonium bromide (CTAB) as an organic template to generate the uniformity pore structure and 1,3,5-trimethyl benzene (TMB) as organic swelling agent. The obtained samples were characterized by XRD, Fourier-transform infrared (FTIR) and Atomic Force Microscopy (AFM). We found that the TMB/CTAB mol ratio must be controlled well for producing large pore materials.

  18. Preparation of bio-compatible boron nanoparticles and novel mesoporous silica nanoparticles for bio-applications

    NASA Astrophysics Data System (ADS)

    Gao, Zhe

    This dissertation presents the synthesis and characterization of several novel inorganic and hybrid nanoparticles, including the bio-compatible boron nanoparticles (BNPs) for boron neutron capture therapy (BNCT), tannic acid-templated mesoporous silica nanoparticles and degradable bridged silsesquioxane silica nanoparticles. Chapter 1 provides background information of BNCT and reviews the development of design and synthesizing silica nanoparticles and the study of silica material degradability. Chapter 2 describes the preparation and characterization of dopamine modified BNPs and the preliminary cell study of them. The BNPs were first produced via ball milling, with fatty acid on the surface to stabilize the combustible boron elements. This chapter will mainly focus on the ligand-exchange strategy, in which the fatty acids were replaced by non-toxic dopamines in a facile one-pot reaction. The dopamine-coated BNPs (DA-BNPs) revealed good water dispersibility and low cytotoxicity. Chapter 3 describes the synthesis of tannic acid template mesoporous silica nanoparticles (TA-TEOS SiNPs) and their application to immobilize proteins. The monodispersed TA SiNPs with uniform pore size up to approximately 13 nm were produced by utilizing tannic acid as a molecular template. We studied the influence of TA concentration and reaction time on the morphology and pore size of the particles. Furthermore, the TA-TEOS particles could subsequently be modified with amine groups allowing them to be capable of incorporating imaging ligands and other guest molecules. The ability of the TA-TEOS particles to store biomolecules was preliminarily assessed with three proteins of different charge characteristics and dimensions. The immobilization of malic dehydrogenase on TA-TEOS enhanced the stability of the enzyme at room temperature. Chapter 4 details the synthesis of several bridged silsesquioxanes and the preparation of degradable hybrid SiNPs via co-condensation of bridged

  19. Enzyme encapsulation in silica gel prepared by polylysine and its catalytic activity

    NASA Astrophysics Data System (ADS)

    Kawachi, Yuki; Kugimiya, Shin-ichi; Nakamura, Hitomi; Kato, Katsuya

    2014-09-01

    Enzymes used in industrial applications are often immobilized onto different types of supports because they are sensitive to pH, temperature, and various other environmental conditions. However, many of the current immobilization approaches face problems such as the requirement of tedious multi-step procedures, loss of enzyme activity during immobilization, and poor reusability. In this study, we chose poly-L-lysine (Ki) as a catalyst for silica mineralization and attempted a one-step “leave to stand” synthesis method under mild conditions, so as to simultaneously maintain both high enzymatic activity and reusability. To examine the effect of Kx on the enzymatic reaction of lipase, we performed hydrolysis of 2-octylacetate without adding a silica precursor. Results indicate that Kx hardly exerts adverse influence on the enzymatic activity of lipase. The lipase encapsulated in the silica gel prepared by leave to stand (Gelstand) retained 70% of the activity compared to the free solution, which is two times higher than that obtained by mixing (Gelmix). However, the Km value was found to be similar to that of free enzymes. These results suggest that the leave to stand is a suitable procedure for immobilization, without any decrease in the mass transfer of substrate. The Gel-stand sample retained 100% activity even after the 5th cycle, and retained above 95% of its activity after 4 h of heat treatment at 65 °C. Using phenyltriethoxysilane as a silica precursor, tertiary structural stability of enzyme was obtained, and its Kcat value was improved when compared to a free solution.

  20. Dummy molecularly imprinted mesoporous silica prepared by hybrid imprinting method for solid-phase extraction of bisphenol A.

    PubMed

    Yu, Dan; Hu, Xiaolei; Wei, Shoutai; Wang, Qiang; He, Chiyang; Liu, Shaorong

    2015-05-29

    A novel hybrid dummy imprinting strategy was developed to prepare a mesoporous silica for the solid-phase extraction (SPE) of bisphenol A (BPA). A new covalent template-monomer complex (BPAF-Si) was first synthesized with 2,2-bis(4-hydroxyphenyl)hexafluoropropane (BPAF) as the template. The imprinted silica was obtained through the gelation of BPAF-Si with tetraethoxysilane and the subsequent removal of template by thermal cleavage, and then it was characterized by FT-IR spectroscopy, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. Results showed that the new silica had micron-level particle size and ordered mesoporous structure. The static binding test verified that the imprinted silica had much higher recognition ability for BPA than the non-imprinted silica. The imprinted silica also showed high extraction efficiencies and high enrichment factor for SPE of BPA. Using the imprinted silica, a SPE-HPLC-UV method was developed and successfully applied for detecting BPA in BPA-spiked tap water and lake water samples with a recovery of 99-105%, a RSD of 2.7-5.0% and a limit of detection (S/N=3) of 0.3ng/mL. The new imprinted silica avoided the interference of the residual template molecules and reduced the non-specific binding sites, and therefore it can be utilized as a good sorbent for SPE of BPA in environmental water samples. PMID:25892637

  1. Highly stabilized, polymer-lipid membranes prepared on silica microparticles as stationary phases for capillary chromatography

    PubMed Central

    Gallagher, Elyssia S.; Adem, Seid M.; Baker, Christopher A.; Ratnayaka, Saliya N.; Jones, Ian W.; Hall, Henry K.; Saavedra, S. Scott; Aspinwall, Craig A.

    2015-01-01

    The ability to rapidly screen complex libraries of pharmacological modulators is paramount to modern drug discovery efforts. This task is particularly challenging for agents that interact with lipid bilayers or membrane proteins due to the limited chemical, physical, and temporal stability of conventional lipid-based chromatographic stationary phases. Here, we describe the preparation and characterization of a novel stationary phase material composed of highly stable, polymeric-phospholipid bilayers self-assembled onto silica microparticles. Polymer lipid membranes were prepared by photochemical or redox initiated polymerization of 1,2-bis[10-(2′,4′-hexadieoyloxy)decanoyl]-sn-glycero-2-phosphocholine (bis-SorbPC), a synthetic, polymerizable lipid. The resulting polymerized bis-SorbPC (poly(bis-SorbPC)) stationary phases exhibited enhanced stability compared to particles coated with 1,2-dioleoyl-sn-glycero-phosphocholine (unpolymerized) phospholipid bilayers when exposed to chemical (50mM triton X-100 or 50% acetonitrile) and physical (15 min sonication) insults after 30 days of storage. Further, poly(bis-SorbPC)-coated particles survived slurry packing into fused silica capillaries, compared to unpolymerized lipid membranes, where the lipid bilayer was destroyed during packing. Frontal chromatographic analyses of the lipophilic small molecules acetylsalicylic acid, benzoic acid, and salicylic acid showed > 44% increase in retention times (P < 0.0001) for all analytes on poly(bis-SorbPC)-functionalized stationary phase compared to bare silica microspheres, suggesting a lipophilic retention mechanism. Phospholipid membrane-functionalized stationary phases that withstand the chemical and physical rigors of capillary LC conditions can substantially increase the efficacy of lipid membrane affinity chromatography, and represents a key advance towards the development of robust membrane protein-functionalized chromatographic stationary phases. PMID:25670414

  2. Impact of muffle furnace preparation on the results of crystalline silica analysis.

    PubMed

    Lee, R J; Van Orden, D R; Cox, L A; Arlauckas, S; Kautz, R J

    2016-10-01

    A prior report demonstrated an unacceptably low level of accuracy in silica analytical testing, with a general negative bias (i.e., underreporting) although other inaccuracies included false-positive results when analyzing blank filters. The possible bias may have been due to the loss of sample during shipping and or sample preparation. We report on a follow-up study that was designed to mimic the original study, but in which sources of variability were evaluated. We found no effect on silica recoveries due to shipping and confirmed the prior study results that the muffle furnace ashing process led to low overall recoveries (49-104%), depending on the adherence to the recommended preparation method. Plasma ashing recoveries ranged from 89 to 108%. Our results suggest that muffle-furnace ashing using a crucible should be restricted. More broadly, however, muffle-furnace ashing is only one source of analytical error that contributes to the relatively poor overall performance revealed by Cox et al. Whatever the case, OSHA should ensure that its proposed requirements to improve laboratory performance will actually lead to the discovery and correction of all major sources of error by participating laboratories. This is particularly important in light of OSHA's proposed reduction in the PEL and action level proposed by OSHA. PMID:27321060

  3. Preparation and characterization of mixed-mode monolithic silica column for capillary electrochromatography.

    PubMed

    Ye, Fanggui; Wang, Shun; Zhao, Shulin

    2009-12-18

    A silica-based monolithic stationary phase with mixed-mode of reversed phase (RP) and weak anion-exchange (WAX) for capillary electrochromatography (CEC) has been prepared. The mixed-mode monolithic silica column was prepared using the sol-gel technique and followed by a post-modification with hexadecyltrimethoxysilane (HDTMS) and aminopropyltrimethoxysilane (APTMS). The amino groups on the surface of the stationary phase were used to generate a substantial anodic EOF as well as to provide electrostatic interaction sites for charged compounds at low pH. A cathodic EOF was observed at pH above 7.3 due to the full ionization of residual silanol groups and the suppression in the ionization of amino groups. A variety of analytes were used to evaluate the electrochromatographic characterization and column performance. The monolithic stationary phase exhibited RP chromatographic behavior toward neutral solutes. The model anionic solutes were separated by the mixed-mode mechanism, which comprised RP interaction, WAX, and electrophoresis. Symmetrical peaks can be obtained for basic solutes because positively charged amino groups can effectively minimize the adsorption of positively charged analytes to the stationary phase. PMID:19913231

  4. Preparation of silica films on Ru(0001): A LEEM/PEEM study

    NASA Astrophysics Data System (ADS)

    Klemm, H. W.; Peschel, G.; Madej, E.; Fuhrich, A.; Timm, M.; Menzel, D.; Schmidt, Th.; Freund, H.-J.

    2016-01-01

    We use an aberration corrected spectro-microscope, the low energy electron microscope/photoelectron emission microscope (LEEM/PEEM) SMART, to follow the preparation and structure of a bilayer silica film on Ru(0001) as a function of temperature and oxidation conditions. This allows us to analyze the growth process at different length scales in order to judge on the overall quality and the morphology of the film. It is found that the film growth occurs in a crystalline and a vitreous phase as previously discovered using scanning tunneling microscopy. However, the present experiment allows an analysis on the sub-micron level to gain insight into the growth process at a mesoscopic scale. We find that the fully oxidized film can be prepared but that this film contains holes. These are unavoidable and are important to consider, if one wants to use the films for ensemble averaging experiments to investigate migration and reaction of molecules between the silica film and the Ru(0001) substrate.

  5. A highly efficient Yb-doped silica laser fiber prepared by gas phase doping technology

    NASA Astrophysics Data System (ADS)

    Unger, Sonja; Lindner, Florian; Aichele, Claudia; Leich, Martin; Schwuchow, Anka; Kobelke, Jens; Dellith, Jan; Schuster, Kay; Bartelt, Hartmut

    2014-03-01

    In this paper we report on an alternative technique for the preparation of ytterbium (Yb)-doped silica fibers and their characteristics compared to the conventional modified chemical vapor deposition (MCVD) process in combination with solution doping and powder sinter technology (REPUSIL). In the case of the technique applied here, the active core diameter in the preform can be significantly increased via the deposition of Yb and the most important codopant, aluminum (Al), in the gas phase through the high-temperature evaporation of the Yb chelate compound and Al chloride in the MCVD process. The prepared preform shows a homogenous distribution of the refractive index and dopant concentration. The background loss of the drawn fiber was measured to be 25 dB km-1 at 1200 nm. Efficient lasing up to 200 W, showing a slope efficiency of about 80%, was demonstrated, which is comparable to fibers made via MCVD/solution doping and the REPUSIL technique.

  6. Preparation of the narrow size distribution USPIO in mesoporous silica for magnetic field guided drug delivery and release

    NASA Astrophysics Data System (ADS)

    Zapotoczny, B.; Guskos, N.; Kozioł, J. J.; Dudek, M. R.

    2015-01-01

    Ultra-small superparamagnetic iron oxides (USPIO) with an average diameter of 2 nm were synthesized in mesoporous silica using the method of co-precipitation of Fe2+ and Fe3+ ions in aqueous solution directly in the silica nanopores. Two types of the silica material, hexagonal phase MCM-41 and mesoporous silica spheres (MSS), were used. The resulting magnetically modified silica samples show high-quality superparamagnetic properties which persist also at low temperatures near 2 K. Their magnetization saturation in an applied external magnetic field exceeds 15 emu/g. The magnetically modified silica samples were studied with the help of the ferromagnetic resonance (FMR), SQUID-magnetometry, X-ray diffraction (XRD), dynamic light scattering (DLS) and TEM/EDX microscopy. The studies were complemented by confirming the possibility of drug release by the modified silica samples where the standard fluorescent dye was used as an example. The prepared material is suggested to be considered for magnetic field guided drug delivery and release.

  7. Mesoporous Ta(3)N(5) microspheres prepared from a high-surface-area, microporous, amorphous precursor and their visible-light-driven photocatalytic activity.

    PubMed

    Cao, Jing; Ren, Ling; Li, Na; Hu, Changwen; Cao, Minhua

    2013-09-16

    A light Ta3N5: Mesoporous Ta3N5 microspheres were synthesized by thermally nitriding a high-surface-area, microporous, amorphous Ta2O5 precursor at 750 °C, which is lower than the 900 °C needed for the complete nitridation of micrometer-sized Ta2O5 powder. The mesoporous Ta3N5 microspheres show significantly enhanced visible-light photoactivity in the degradation of methylene blue (MB) compared with similar photocatalysts reported under similar conditions. PMID:24175337

  8. Preparation of double emulsions using hybrid polymer/silica particles: new pickering emulsifiers with adjustable surface wettability.

    PubMed

    Williams, Mark; Warren, Nicholas J; Fielding, Lee A; Armes, Steven P; Verstraete, Pierre; Smets, Johan

    2014-12-10

    A facile route for the preparation of water-in-oil-in-water (w/o/w) double emulsions is described for three model oils, namely, n-dodecane, isopropyl myristate, and isononyl isononanoate, using fumed silica particles coated with poly(ethylene imine) (PEI). The surface wettability of such hybrid PEI/silica particles can be systematically adjusted by (i) increasing the adsorbed amount of PEI and (ii) addition of 1-undecanal to the oil phase prior to homogenization. In the absence of this long-chain aldehyde, PEI/silica hybrid particles (PEI/silica mass ratio = 0.50) produce o/w Pickering emulsions in all cases. In the presence of 1-undecanal, this reagent reacts with the primary and secondary amine groups on the PEI chains via Schiff base chemistry, which can render the PEI/silica hybrid particles sufficiently hydrophobic to stabilize w/o Pickering emulsions at 20 °C. Gas chromatography, (1)H NMR and X-ray photoelectron spectroscopy provide compelling experimental evidence for this in situ surface reaction, while a significant increase in the water contact angle indicates markedly greater hydrophobic character for the PEI/silica hybrid particles. However, when PEI/silica hybrid particles are prepared using a relatively low adsorbed amount of PEI (PEI/silica mass ratio = 0.075) only o/w Pickering emulsions are obtained, since the extent of surface modification achieved using this Schiff base chemistry is insufficient. Fluorescence microscopy and laser diffraction studies confirm that highly stable w/o/w double emulsions can be achieved for all three model oils. This is achieved by first homogenizing the relatively hydrophobic PEI/silica hybrid particles (PEI/silica mass ratio = 0.50) with an oil containing 3% 1-undecanal to form an initial w/o emulsion, followed by further homogenization using an aqueous dispersion of relatively hydrophilic PEI/silica particles (PEI/silica mass ratio = 0.075). Dye release from the internal aqueous cores into the aqueous continuous

  9. Optical Properties of Silica-Encapsulated ZnSe Nanocrystals Prepared with Water-in-Oil Microemulsions

    NASA Astrophysics Data System (ADS)

    Liu, Kang; Kim, Ji Hyeon; Park, Sang Joon

    2013-01-01

    Silica-encapsulated ZnSe nanocrystals (NCs) were prepared by a safe and simple synthesis method, utilizing a sodium bis (2-ethylhexyl) sulfosuccinate (AOT)/water/cyclohexane microemulsion system and characterized by UV-vis analysis, photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). For the encapsulations, two reverse micellar solutions [one for tetraethyl orthosilicate (TEOS) and the other for ZnSe] containing different water volumes were employed. The size of silica particles containing ZnSe NCs could be controlled from 13-37 nm by varying the water content W (W=[H2O]/[AOT]). On the other hand, the size of encapsulated ZnSe NCs was almost unchanged (about 2.5 nm) even though the size of the silica particles was increased. At W = 7, the maximum PL efficiency of 6% was obtained and the photostability was increased markedly after ZnSe NCs were encapsulated by silica.

  10. Synthesis of silver nanoparticles deposited on silica by γ-irradiation and preparation of PE/Ag nano compound masterbatches

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi Kim Lan; Trinh Nguyen, Thuy Ai; Phu Dang, Van; Duy Nguyen, Ngoc; Le, Anh Quoc; Hien Nguyen, Quoc

    2013-12-01

    Silver nanoparticles (AgNPs) deposited on silica were synthesized by gamma Co-60 irradiation of Ag+ dispersion in silica/ethanol/water mixture (9/80/20:w/v/v). The reduction of Ag+ is occurred by hydrated electron (e-aq) and hydrogen atom (H•) generated during radiolysis of ethanol/water. The conversion doses (Ag+ → Ag0) were determined by UV-Vis spectroscopy. The synthesized AgNPs/silica were characterized by transmission electron microscopy (TEM) and x-ray diffraction (XRD), which showed the size of AgNPs to be in the range of 5-40 nm for Ag+ concentrations from 5 to 20 mM. Masterbatches of PE/AgNPs/silica compound with silver content from 250 to 1000 mg kg-1 were also prepared. These masterbatches can be suitably used for various applications such as antimicrobial food containers and packing films, etc.

  11. Preparation of magnetite-loaded silica microspheres for solid-phase extraction of genomic DNA from soy-based foodstuffs.

    PubMed

    Shi, Ruobing; Wang, Yucong; Hu, Yunli; Chen, Lei; Wan, Qian-Hong

    2009-09-01

    Solid-phase extraction has been widely employed for the preparation of DNA templates for polymerase chain reaction (PCR)-based analytical methods. Among the variety of adsorbents studied, magnetically responsive silica particles are particularly attractive due to their potential to simplify, expedite, and automate the extraction process. Here we report a facile method for the preparation of such magnetic particles, which entails impregnation of porous silica microspheres with iron salts, followed by calcination and reduction treatments. The samples were characterized using powder X-ray diffractometry (XRD), scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, and vibrating sample magnetometry (VSM). XRD data show that magnetite nanocrystals of about 27.2 nm are produced within the pore channels of the silica support after reduction. SEM images show that the as-synthesized particles exhibit spherical shape and uniform particle size of about 3 microm as determined by the silica support. Nitrogen sorption data confirm that the magnetite-loaded silica particles possess typical mesopore structure with BET surface area of about 183 m(2)/g. VSM data show that the particles display paramagnetic behavior with saturation magnetization of 11.37 emu/g. The magnetic silica microspheres coated with silica shells were tested as adsorbents for rapid extraction of genomic DNA from soybean-derived products. The purified DNA templates were amplified by PCR for screening of genetically modified organisms (GMOs). The preliminary results confirm that the DNA extraction protocols using magnetite-loaded silica microspheres are capable of producing DNA templates which are inhibitor-free and ready for downstream analysis. PMID:19632684

  12. Preparation of silica nanospheres and porous polymer membranes with controlled morphologies via nanophase separation

    PubMed Central

    2012-01-01

    We successfully synthesized two different structures, silica nanospheres and porous polymer membranes, via nanophase separation, based on a sol–gel process. Silica sol, which was in situ polymerized from tetraorthosilicate, was used as a precursor. Subsequently, it was mixed with a polymer that was used as a matrix component. It was observed that nanophase separation occurred after the mixing of polymer with silica sol and subsequent evaporation of solvents, resulting in organizing various structures, from random network silica structures to silica spheres. In particular, silica nanospheres were produced by manipulating the mixing ratio of polymer to silica sol. The size of silica beads was gradually changed from micro- to nanoscale, depending on the polymer content. At the same time, porous polymer membranes were generated by removing the silica component with hydrofluoric acid. Furthermore, porous carbon membranes were produced using carbon source polymer through the carbonization process. PMID:22873570

  13. Nanocellulose Derivative/Silica Hybrid Core-Shell Chiral Stationary Phase: Preparation and Enantioseparation Performance.

    PubMed

    Zhang, Xiaoli; Wang, Litao; Dong, Shuqing; Zhang, Xia; Wu, Qi; Zhao, Liang; Shi, Yanping

    2016-01-01

    Core-shell silica microspheres with a nanocellulose derivative in the hybrid shell were successfully prepared as a chiral stationary phase by a layer-by-layer self-assembly method. The hybrid shell assembled on the silica core was formed using a surfactant as template by the copolymerization reaction of tetraethyl orthosilicate and the nanocellulose derivative bearing triethoxysilyl and 3,5-dimethylphenyl groups. The resulting nanocellulose hybrid core-shell chiral packing materials (CPMs) were characterized and packed into columns, and their enantioseparation performance was evaluated by high performance liquid chromatography. The results showed that CPMs exhibited uniform surface morphology and core-shell structures. Various types of chiral compounds were efficiently separated under normal and reversed phase mode. Moreover, chloroform and tetrahydrofuran as mobile phase additives could obviously improve the resolution during the chiral separation processes. CPMs still have good chiral separation property when eluted with solvent systems with a high content of tetrahydrofuran and chloroform, which proved the high solvent resistance of this new material. PMID:27153055

  14. Facile preparation and characterization of modified magnetic silica nanocomposite particles for oil absorption

    NASA Astrophysics Data System (ADS)

    Yu, Liuhua; Hao, Gazi; Liang, Qianqian; Zhou, Shuai; Zhang, Ning; Jiang, Wei

    2015-12-01

    In this study, a novel environmental-friendly and superhydrophobic oil absorbent was fabricated by modifying magnetic silica nanocomposites. It was demonstrated that the modified rough magnetic silica nanocomposite particles possessed a number of superior features such as superhydrophobicity, superoleophilicity, and high oil-water separation efficiency etc. Moreover, the as-obtained material could be used as excellent absorbents for high density oils such as toluene and many organic liquids including viscous oils e.g. lubricating oil. The lubricating oil intake capacity for the nanocomposites was 7.15 times of its own weight. Importantly, the oil-absorption process of the nanocomposites was selective, fast and efficient when they were used in the purification of oil-contaminated water. Notably, the oil-absorbed nanocomposites could be renewed after suitable absolute ethanol washing and natural drying. In addition, the renewed nanocomposites still remained high oil-absorption capacity after the 20th cycle. These inspiring results show that the oil-absorbent material has good prospects for selection removal of oils and organic solvents on water surface. It is believed that the present work may have provided a novel and facile way for preparing environmental-friendly materials with ideal properties.

  15. Preparation, characterization and FE-simulation of the reinforcement of polycaprolactone with PEGylated silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Moussaif, N.; Viejo, I.; Bielsa, J. M.; Crespo, C.; Irusta, S.; Yagüe, C.; Meier, J. G.

    2012-09-01

    We recently published the preparation and characterization of polycaprolactone (PCL) nanocomposites with a 45% increased modulus reinforced with only 4 wt% PEGylated silica (polyethylene-glycol/SiO2) nanoparticles obtained by melt-extrusion [1]. The achieved reinforcement is related to an excellent dispersion of the nanoparticles due to the polyethylene-glycol graft of the nanoparticles which was obtained by a simple one-pot synthesis. X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR) analyses identified the location of the PEG at the PCL/silica interface. However, the extension of the interface could not be resolved. In an attempt to describe the effect of the interface on the reinforcement we applied several analytical micromechanical models. Models considering core-shell systems fitted the experimental data well and gave estimations of the modulus and extension of the interphase. However, different sets of parameters gave equally good representations. In an alternative approach, 3D representative volume elements (RVE) of the composite with spherical nanoparticles including the shell were built-up from the morphological data to carry out computational micromechanics based on finite elements (FE). The interphase was modeled in the RVE. Both approaches demonstrated the need of an interphase extension of roughly twice the radius of the particle. The FEM approach estimates the interface-modulus much higher than the analytical models.

  16. Preparation of glycerol carbonate esters by using hybrid Nafion-silica catalyst.

    PubMed

    Climent, María J; Corma, Avelino; Iborra, Sara; Martínez-Silvestre, Sergio; Velty, Alexandra

    2013-07-01

    Glycerol carbonate esters (GCEs), which are valuable biomass-derivative compounds, have been prepared through the direct esterification of glycerol carbonate and long organic acids with different chain lengths, in the absence of solvent, and with heterogeneous catalysts, including acidic-organic resins, zeolites, and hybrid organic-inorganic acids. The best results, in terms of activity and selectivity towards GCEs, were obtained using a Nafion-silica composite. A full reaction scheme has been established, and it has been demonstrated that an undesired competing reaction results in the generation of glycerol and esters derived from a secondary hydrolysis of the endocyclic ester group, which is attributed to water formed during the esterification reaction. The influence of temperature, substrate ratio, catalyst-to-substrate ratio, and the use of solvent has been studied and, under optimized reaction conditions and with the adequate catalyst, it was possible to achieve 95% selectivity for the desired product at 98% conversion. It was demonstrated that the reaction rate decreased as the number of carbon atoms in the linear alkyl chain of the carboxylic acid increased for both p-toluenesulfonic acid and Nafion-silica nanocomposite (Nafion SAC-13) catalysts. After fitting the experimental data to a mechanistically based kinetic model, the reaction kinetic parameters for Nafion SAC-13 catalysis were determined and compared for reactions involving different carboxylic acids. A kinetic study showed that the reduced reactivity of carboxylic acids with increasing chain lengths could be explained by inductive as well as steric effects. PMID:23754795

  17. Preparation of alumina nanoshell coated porous silica spheres for inorganic anions separation.

    PubMed

    Song, Zhihua; Wu, Dapeng; Ding, Kun; Guan, Yafeng

    2016-02-12

    It had been reported that alumina nanoshell coating could be obtained on the external surface of various substrates in one-nanometer precision in aqueous solution. In this work, alumina nanoshell coated mesoporous silica microbeads (nanoAl2O3/mesoSiO2) were prepared with the similar method, and were successfully applied to inorganic anions separation. As the mass transfer speed is largely constrained in the mesopore compared with that on the open surface, it was found that a complete alumina nanoshell coating could be obtained within the mesopore until the five-time coating was carried out. After characterization by BET, SEM and FTIR, it was found that the obtained nanoAl2O3/mesoSiO2 particles are smooth and well dispersed, and the mesopores are well reserved. In addition, the full coverage of nanoAl2O3 shell in mesopores was also confirmed by the binding capacity experiments with berberine. Finally, the nanoAl2O3/mesoSiO2 particles were packed in silica capillary for the separation of inorganic anions I(-), SCN(-), Br(-), NO2(-) and NO3(-) with ion chromatography (IC), and a column efficiency of 3.8 × 10(4) plates per meter was obtained for I(-). PMID:26803440

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

    PubMed

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

    2011-01-01

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

  19. Silica-coated iron nanocubes: preparation, characterization and application in microwave absorption.

    PubMed

    Ni, Xiaomin; Zheng, Zhong; Hu, Xiang; Xiao, Xiukun

    2010-01-01

    Novel cubic nanocapsules consisting of metallic iron core and amorphous silica shell were fabricated through a simple chemical reduction route followed by a Stöber process. Thus-prepared Fe@SiO(2) nanocubes were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectrometer (FTIR), thermogravimetry-differential thermal analysis (TG-DTA), vibrating sample magnetometer (VSM) and scalar network analysis (SNA). Comparing with that of pure iron counterparts, silica-coated iron nanocubes exhibited improved magnetic properties, oxidation resistance and microwave absorption performance. A reflection loss (RL) exceeding -12 dB was obtained in the frequency range of 8-14 GHz for an absorber thickness of 2 mm, with an optimal RL of -18.2 dB at 9 GHz. Mechanism of the improved microwave absorption properties of the Fe@SiO(2) composite was discussed based on their magnetic properties and electromagnetic theory. PMID:19833348

  20. Preparation of silica aerogels using CTAB/SDS as template and their efficient adsorption

    NASA Astrophysics Data System (ADS)

    Wa, Li; Fengyun, Li; Fanlu, Zhuo; Mengjing, Cao; Qiang, Cai; Jue, Huang; Weijun, Zhang; Mingwei, Mu

    2015-10-01

    Silica aerogels have been successfully synthesized using cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium dodecyl sulfate (SDS) as template. This study provides a novel approach to synthesize silica aerogels. The molar ratio of surfactant mixture was CTAB/SDS = 1.00. The obtained silica aerogels exhibit very low apparent density (0.044 g cm-3) and high specific surface area (856 m2 g-1). Surfactant packing parameter theory is used to explain the possible formation mechanism of the silica aerogels using mixed surfactant template. In addition, the adsorption capacity of Rhodamine B on the as-synthesized silica aerogels is as higher as that on the commercial silica aerogels.

  1. Binding behaviour of molecularly imprinted polymers prepared by a hierarchical approach in mesoporous silica beads of varying porosity.

    PubMed

    Baggiani, Claudio; Baravalle, Patrizia; Giovannoli, Cristina; Anfossi, Laura; Passini, Cinzia; Giraudi, Gianfranco

    2011-04-01

    One of the most interesting methods for preparing molecularly imprinted polymers with controlled morphology consists in filling the pores of silica beads with an imprinting mixture, polymerizing it and dissolving the support, leaving porous imprinted beads that are the "negative image" of the silica beads. The main advantage of such an approach consists in the easy preparation of spherical imprinted polymeric particles with narrow diameter and pore size distribution, particularly indicated for chromatographic applications. In this approach it has been shown that the resulting morphology of polymeric beads depends essentially on the porosity and surface properties of the silica beads that act as microreactors for the thermopolymerization process. Anyway, it is not yet clear if the porosity of the silica beads influences the binding properties of the resulting imprinted beads. In this paper, we report the effect of different porosities of the starting mesoporous silica beads on the resulting binding properties of imprinted polymers with molecular recognition properties towards the fungicide carbendazim. The morphological properties of the imprinted beads prepared through this hierarchical approach were measured by nitrogen adsorption porosimetry and compared with a reference imprinted material prepared by bulk polymerization. The chromatographic behaviour of HPLC columns packed with the imprinted materials were examined by eluting increasing amounts of carbendazim and extracting the binding parameters through a peak profiling approach. The experimental results obtained show that the resulting binding properties of the imprinted beads are strongly affected by the polymerization approach used but not by the initial porosity of the silica beads, with the sole exception of the binding site density, which appears to be inversely proportional to them. PMID:21349526

  2. N-doped mesoporous carbons supported palladium catalysts prepared from chitosan/silica/palladium gel beads.

    PubMed

    Zeng, Minfeng; Wang, Yudong; Liu, Qi; Yuan, Xia; Feng, Ruokun; Yang, Zhen; Qi, Chenze

    2016-08-01

    In this study, a heterogeneous catalyst including palladium nanoparticles supported on nitrogen-doped mesoporous carbon (Pd@N-C) is synthesized from palladium salts as palladium precursor, colloidal silica as template, and chitosan as carbon source. N2 sorption isotherm results show that the prepared Pd@N-C had a high BET surface area (640m(2)g(-1)) with large porosity. The prepared Pd@N-C is high nitrogen-rich as characterized with element analysis. X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), and Raman spectroscopy characterization of the catalyst shows that the palladium species with different chemical states are well dispersed on the nitrogen-containing mesoporous carbon. The Pd@N-C is high active and shows excellent stability as applied in Heck coupling reactions. This work supplies a successful method to prepare Pd heterogeneous catalysts with high performance from bulk biopolymer/Pd to high porous nitrogen-doped carbon supported palladium catalytic materials. PMID:27155234

  3. Preparation and characterization of phosphorylated Zr-doped hybrid silica/PSF composite membrane.

    PubMed

    Zhang, Yuqing; Jin, Zhenhua; Shan, Xing; Sunarso, Jaka; Cui, Ping

    2011-02-15

    Polysulfone (PSF) membranes are broadly applied in many fields owing to good physicochemical stability, resistance to oxidation and chlorine. But when treated with wastewater containing oil, PSF membranes are easy to be contaminated for its hydrophobicity, which can result in the declining of flux and lifespan of the membrane and limit their application in large scale. To enhance the capability of PSF membrane in the above circumstances, phosphorylated Zr-doped hybrid silica particles (SZP particles) were firstly prepared. SZP particles have various point defects inside their structure and lots of hydroxide radicals on their surface. SZP particles were added to the porous matrix of PSF to prepare a novel composite membrane (SZP/PSF) through a phase inversion process. Finally, the optimum preparation conditions of SZP/PSF composite membranes were determined. The optimum conditions are: the mass ratio of PSF, PEG400 and SZP is 12:10:10; ultrasound 10 min inside each 30 min; the pre-evaporating time is 10s. Optimized SZP/PSF composite membrane was characterized by scanning electron microscope (SEM) and ultrafiltration experiment. The results indicate that SZP particles can be uniformly dispersed in SZP/PSF composite membranes with excellent hydrophilic property, antifouling capability and tensile strength. Therefore, it can be concluded that the optimized SZP/PSF composite membrane is desirable in the treatment of wastewater containing oil and wastewater. PMID:21122987

  4. Preparation of nanoscale Bacillus thuringiensis chitinases using silica nanoparticles for nematicide delivery.

    PubMed

    Qin, Xu; Xiang, Xuemei; Sun, Xiaowen; Ni, Hong; Li, Lin

    2016-01-01

    A series of amino, carboxylic, and aldehydic surface-grafted silica nanoparticles (SNPs) was prepared based on SiO2 NYSi40 nanoparticles to develop an efficient, biocompatible, and cost-effective biopesticide delivery system. Bacillus thuringiensis chitinase (Chi9602) was immobilized onto SNP surface to prepare nanoscale chitinases (SNPCs) through electrostatic adsorption and covalent binding. The specimens were characterized by Fourier transform infrared, scanning electron microscopy, and zeta-potential analyses. The delivery capacity of the SNPs in Caenorhabditis elegans N2 was observed by immunofluorescence. Results demonstrated that amino-grafted SiO2 nanoparticles with Chi9602 electrostatically adsorbed onto their surface (SNPC2) exhibited a relatively high enzyme immobilization rate (80.2%) and the highest (94.1%) residual enzyme activity among all SNPCs. SNPC2 also showed wider pH tolerance and relatively higher thermostability and ultraviolet radiation resistance capacity than Chi9602. Bioassays further showed that SNPC2 synergistically enhanced the nematicidal effect of B. thuringiensis YBT-020 preparation against C. elegans, with a reduced LC50 of 8.35mg/mL and a shortened LT50 of 12.04h. Immunofluorescence assays showed that SNPC2 had considerable delivery capacity to carry a large protein into C. elegans. Therefore, SNP2 can serve as an efficient nanocarrier for the delivery of macromolecular proteic biopesticides or drugs, indicating potential agricultural or biotechnological applications. PMID:26476241

  5. A convenient sol-gel approach to the preparation of nano-porous silica coatings with very low refractive indices.

    PubMed

    Zhang, Yulu; Zhao, Chaoxia; Wang, Pingmei; Ye, Longqiang; Luo, Jianhui; Jiang, Bo

    2014-11-18

    Silica coatings with refractive indices as low as 1.10 were prepared via a one-step base-catalysed sol-gel process using methyltriethoxysilane and tetraethoxysilane as co-precursors. No expensive equipment was required and the method did not require etching or high-temperature calcination. PMID:25253239

  6. Capillary stress in microporous thin films

    SciTech Connect

    Samuel, J.; Hurd, A.J.; Frink, L.J.D.; Swol, F. van; Brinker, C.J. |; Raman, N.K.

    1996-06-01

    Development of capillary stress in porous xerogels, although ubiquitous, has not been systematically studied. The authors have used the beam bending technique to measure stress isotherms of microporous thin films prepared by a sol-gel route. The thin films were prepared on deformable silicon substrates which were then placed in a vacuum system. The automated measurement was carried out by monitoring the deflection of a laser reflected off the substrate while changing the overlying relative pressure of various solvents. The magnitude of the macroscopic bending stress was found to reach a value of 180 MPa at a relative pressure of methanol, P/Po = 0.001. The observed stress is determined by the pore size distribution and is an order of magnitude smaller in mesoporous thin films. Density Functional Theory (DFT) indicates that for the microporous materials, the stress at saturation is compressive and drops as the relative pressure is reduced.

  7. Preparation of Silica/Reduced Graphene Oxide Nanosheet Composites for Removal of Organic Contaminants from Water.

    PubMed

    Li, Wen; Liu, Wei; Wang, Haifei; Lu, Wensheng

    2016-06-01

    Graphene-based composites open up new opportunities as effective adsorbents for the removal of organic contaminants from water. In this article, we report a novel and facile process to synthesize well-dispersed silica/reduced graphene oxide (SiO2/RGO) nanosheet composites. The SiO2/RGO nanosheet composites are prepared through a modified sol-gel process with in situ hydrolysis of tetraethoxysilane (TEOS) on graphene oxide (GO) nanosheet, followed by reduction of GO to graphene. In comparison with the RGO nanosheets, the as-prepared SiO2/RGO nanosheet composites have a larger surface area and good aqueous disperse ability. In addition, the application of SiO2/RGO nanosheet composites was demonstrated on removing organic dyes from water. The SiO2/RGO nanosheet composites show rapid and stable adsorption performance on removal of Methylene Blue (MB) and thionine (TH) from water. It is indicated that the resulting SiO2/RGO composites can be utilized as efficient adsorbents for the removal of organic contaminants from water. PMID:27427624

  8. Preparation and Characterization of Rifampin Loaded Mesoporous Silica Nanoparticles as a Potential System for Pulmonary Drug Delivery

    PubMed Central

    Mohseni, Meysam; Gilani, Kambiz; Mortazavi, Seyed Alireza

    2015-01-01

    The goal of this research is to determine the feasibility of loading rifampin into mesoporous silica nanoparticles. Rifampin was selected as a model lipophilic molecule since it is a well-documented and much used anti tuberculosis drug. The mesoporous silica nanoparticles were prepared by using tetraethyl ortho silicate and cetyltrimethyl ammonium bromide (as surfactant). The prepared nanoparticles were characterized in terms of their particle size measurement and porosimetry. The results showed that the particle size is 218 ± 46 nm (mean ± SD) and surface area is 816 m2g-1. In order to load rifampin within the mesopores, adsorption experiments using three different solvents (methanol, water and dimethyl sulfoxide) were carried out. The loading procedure resulted in a significant improvement in the amount of rifampin loaded into mesoporous silica nanoparticles and methanol was found to be a suitable solvent, providing a drug entrapment efficiency of 52 %. Rifampin loaded nanoparticles underwent different in-vitro tests including, SEM and drug release. The in-vitro drug release was investigated using buffer phosphate (pH=7.4). Regarding the drug release study, a biphasic pattern of release was observed. The drug-loaded mesoporous silica nanoparticles were capable of releasing 95% of their drug content after 24 h, following a faster release in the first four hours. The prepared rifampin loaded nanoparticles seem to have potential for use as a pulmonary drug delivery. PMID:25561909

  9. Iron nanotube-silica composite (ZVI-S-PCAT modified silica composite) preparation, characterization and application as a recyclable catalytic system for 5-membered ring organic transformations.

    PubMed

    Kour, Gurpreet; Gupta, Monika; Vishwanathan, B; Thirunavukkarasu, K

    2015-09-01

    Iron nanotube silica composite have been synthesized and studied through particle-size analysis, FTIR, SEM-EDX, TEM, XRD, UV, VSM, TGA-DTA and XPS techniques. The application of nanoframeworks as sustainable recyclable catalytic systems has been observed for azole cyclic ring organic transformations. The good reaction yields and characterization through (1)H NMR, (13)C NMR and mass analysis support the performance of the nanoframeworks. We also present here the synthesis of two novel compounds. Also the prepared nanoframework has been observed to show soft magnetism which provides a scope to be used in sensing devices. PMID:26228908

  10. Preparation of composite with silica-coated nanoparticles of iron oxide spinels for applications based on magnetically induced hyperthermia

    NASA Astrophysics Data System (ADS)

    Andrade, Angela L.; Fabris, José D.; Pereira, Márcio C.; Domingues, Rosana Z.; Ardisson, José D.

    2013-04-01

    It is reported a novel method to prepare magnetic core (iron oxide spinels)-shell (silica) composites containing well-dispersed magnetic nanoparticles in aqueous solution. The synthetic process consists of two steps. In a first step, iron oxide nanoparticles obtained through co-precipitation are dispersed in an aqueous solution containing tetramethylammonium hydroxide; in a second step, particles of this sample are coated with silica, through hydrolyzation of tetraethyl orthosilicate. The intrinsic atomic structure and essential properties of the core-shell system were assessed with powder X-ray diffraction, Fourier transform infrared spectrometry, Mössbauer spectroscopy and transmission electron microscopy. The heat released by this ferrofluid under an AC-generated magnetic field was evaluated by following the temperature evolution under increasing magnetic field strengths. Results strongly indicate that this ferrofluid based on silica-coated iron oxide spinels is technologically a very promising material to be used in medical practices, in oncology.

  11. Supported microporous ceramic membranes

    DOEpatents

    Webster, E.; Anderson, M.

    1993-12-14

    A method for the formation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms. 4 figures.

  12. Supported microporous ceramic membranes

    DOEpatents

    Webster, Elizabeth; Anderson, Marc

    1993-01-01

    A method for permformation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms.

  13. Preparation of silica stabilized biological templates for the production of metal and layered nanoparticles

    DOEpatents

    Culver, James N; Royston, Elizabeth; Brown, Adam; Harris, Michael

    2013-02-26

    The present invention relates to a system and method providing for increased silica growth on a bio-template, wherein the bio-template is pretreated with aniline to produce a uniform silica attractive surface and yielding a significant silica layers of at least 10 nm, and more preferably at least 20 nm in thickness, thereby providing for a high degree of stability to the bio-template.

  14. Preparation of fused-silica columns with phases immobilized by cobalt-60 gamma radiation; application to essential oil analysis

    SciTech Connect

    Hubball, J.A.

    1987-01-01

    Cobalt-60 gamma-radiation was used to immobilize polymeric stationary phases in fused silica capillary columns for gas chromatography. Surface studies of the uncoated fused silica tubing by optical and scanning electron microscopy indicated some irregularities, but overall the tubing maintained its strength and flexibility at dosages up to 25 MRads. A polydimethylsiloxane phase (OV-1) and a polyethylene glycol phase (Carbowax 20 M) were effectively immobilized on the inner surface of fused silica capillary tubing without altering the properties of the phases. The optimum radiation dosage for OV-1 was 7 MRads, while Carbowax 20 M required 25 MRads to immobilize 33% of the coated layer. Fused silica capillary columns prepared with both phases were evaluated for deactivation, efficiency, and thermal stability. Immobilization of Carbowax 20 M extended the low and high temperature limits by 30 C in each direction. Columns prepared in this study were used to analyze the essential oil of Siparuna guianensis. Several key components of the oil were identified by GC/MS and gas chromatographic techniques.

  15. Preparation and in vitro characterisation of bioactive mesoporous silica microparticles for drug delivery applications.

    PubMed

    Prokopowicz, Magdalena; Czarnobaj, Katarzyna; Szewczyk, Adrian; Sawicki, Wiesław

    2016-03-01

    The aim of this study was to evaluate the surface mineralization activity and in vitro drug behaviour potential of new mesoporous silica microparticles (MSM). The unmodified MSM (MSM-0%Ca) and calcium-modified MSM (MSM-5%Ca, MSM-15%Ca, MSM-25%Ca) were prepared using the self-assembling method. Calcium diethoxide was used as a calcium precursor. Doxorubicin hydrochloride (DOX), used as an anticancer model drug, was selected to the drug loading and release studies. The DOX loading into the microparticles was performed by liquid adsorption process. The self-formation of carbonate hydroxyapatite (C-Hap) on the MSM surface was examined under in vitro biomimetic conditions. The samples were characterised by means of scanning-transmission electron microscopy (STEM) and energy dispersive X-ray spectrometry, powder X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption measurements. The results indicated an inverse relationship--while increasing the total amount of calcium in the MSM composition the surface area and pore volume decrease with a simultaneous increase in the pore size. This was correlated with a progressive increase in the surface mineralization ability--especially its initial promotion, and in the decrease in MSM drug loading efficiency. The release rate of the DOX can be effectively tailored by varying the amount of calcium, where the elution rate of DOX increases with an increasing amount of the Ca precursor. PMID:26706501

  16. The preparation of polypyrrole surfaces in the presence of mesoporous silica nanoparticles and their biomedical applications

    NASA Astrophysics Data System (ADS)

    Cho, Youngnam; Ben Borgens, Richard

    2010-05-01

    The deposition of carboxylic acid-terminated conducting polymer into two- or three-dimensional structures made up of colloidal particles has been successfully completed. This was accomplished using electrochemical deposition of ordered arrays of mesoporous silica nanoparticles (MSNs) as a template. Subsequent removal of the template yielded a porous polypyrrole surface. The co-polymerization of pyrrole with carboxylic acid-terminated pyrrole derivatives overcame the limitations of a lack of reactive functional groups—by facilitating the direct coupling of the film with biomolecules or drugs on the surface. Such Ppy films were characterized by several techniques: (1) scanning electron microscope (SEM) to evaluate surface topography, (2) x-ray photoelectron spectroscopy (XPS) to assess the chemical composition of the films, (3) four-point probe to measure the conductivity, and cyclic voltammogram to observe surface electroactivity. To assay the biological effectiveness of this preparation, we used phase-contrast light microscopy to compare neurite outgrowth from PC 12 cells grown on Ppy films in the presence and absence of electrical stimulation. These electrically functional, biocompatible composites show promise as novel neural implants that would deliver specific biologically active molecules in a highly localized manner to damaged or otherwise vulnerable cells such as found in the nervous system.

  17. Preparation and characterization of surface-engineered coarse microcrystalline cellulose through dry coating with silica nanoparticles.

    PubMed

    Zhou, Qun; Shi, Limin; Chattoraj, Sayantan; Sun, Changquan Calvin

    2012-11-01

    A popular grade of microcrystalline cellulose (MCC) exhibits excellent tabletability, but marginal flowability for high-speed tableting operations. Accordingly, an enhancement in flowability, while preserving its tabletability, will make it a more useful excipient in pharmaceutical tablet formulations, especially for the direct compression process. In this work, we show that surface coating by silica nanoparticles, using either a dry comilling process or simple mechanical blending, is a valid strategy for achieving the goal. The effects of milling intensity, either the number of comilling cycles or blending time, and silica loading level have been evaluated. Results show that surface deposition of 0.1% silica nanoparticles substantially improves the flowability of this grade of MCC while preserving a significant portion of its tabletability. Higher silica loading leads to better flowability, but at the cost of reduced tabletability. However, even up to 2.0% silica deposition, its tabletability remains superior. PMID:22927169

  18. Preparation of frustule-like 1,2-ethylene-silica nanospheres through a chiral amphiphile/organic solvent dual-templating approach

    SciTech Connect

    Zhao, Yanwei; Huang, Zhibin; Yan, Zhuojun; Wang, Sibing; Li, Baozong; Li, Yi; Yang, Yonggang

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Frustule-like 1,2-ethylene-silicas were prepared through a dual-templating approach. ► The morphologies and pore architectures of the 1,2-ethylene-silicas are tunable. ► Mesoporous 1,2-ethylene-silica nanotubes were also prepared. -- Abstract: Hollow silica nanospheres with mesopores in the walls have been widely studied because of their potential applications in catalysis and drug release. Hollow organosilica nanospheres also attracted much attention because of their tunable wall backbones and wider applications. Herein, frustule-like 1,2-ethylene-silicas were obtained using a chiral amphiphile, CHCl{sub 3}, and a dual-templating approach. The morphologies and pore architectures of the 1,2-ethylene-silicas are tunable by changing the amount of CHCl{sub 3} in the reaction mixture. With the addition of CHCl{sub 3} in the reaction mixtures, hollow 1,2-ethylene-silica nanospheres with opened mesopores in the walls were feasible. Moreover, 1,2-ethylene-silicas with mesopores on the surfaces and coiled pore channels within the walls were obtained using the chiral amphiphile in a single-templating approach. These 1,2-ethylene-silicas were characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and N{sub 2} sorptions.

  19. Ordered mesoporous silica prepared by quiescent interfacial growth method - effects of reaction chemistry

    PubMed Central

    2013-01-01

    Acidic interfacial growth can provide a number of industrially important mesoporous silica morphologies including fibers, spheres, and other rich shapes. Studying the reaction chemistry under quiescent (no mixing) conditions is important for understanding and for the production of the desired shapes. The focus of this work is to understand the effect of a number of previously untested conditions: acid type (HCl, HNO3, and H2SO4), acid content, silica precursor type (TBOS and TEOS), and surfactant type (CTAB, Tween 20, and Tween 80) on the shape and structure of products formed under quiescent two-phase interfacial configuration. Results show that the quiescent growth is typically slow due to the absence of mixing. The whole process of product formation and pore structuring becomes limited by the slow interfacial diffusion of silica source. TBOS-CTAB-HCl was the typical combination to produce fibers with high order in the interfacial region. The use of other acids (HNO3 and H2SO4), a less hydrophobic silica source (TEOS), and/or a neutral surfactant (Tweens) facilitate diffusion and homogenous supply of silica source into the bulk phase and give spheres and gyroids with low mesoporous order. The results suggest two distinct regions for silica growth (interfacial region and bulk region) in which the rate of solvent evaporation and local concentration affect the speed and dimension of growth. A combined mechanism for the interfacial bulk growth of mesoporous silica under quiescent conditions is proposed. PMID:24237719

  20. Preparation of Silica Nanoparticles Loaded with Nootropics and Their In Vivo Permeation through Blood-Brain Barrier

    PubMed Central

    Zaruba, Kamil; Kunes, Martin; Ulbrich, Pavel; Brezaniova, Ingrid; Triska, Jan; Suchy, Pavel

    2015-01-01

    The blood-brain barrier prevents the passage of many drugs that target the central nervous system. This paper presents the preparation and characterization of silica-based nanocarriers loaded with piracetam, pentoxifylline, and pyridoxine (drugs from the class of nootropics), which are designed to enhance the permeation of the drugs from the circulatory system through the blood-brain barrier. Their permeation was compared with non-nanoparticle drug substances (bulk materials) by means of an in vivo model of rat brain perfusion. The size and morphology of the nanoparticles were characterized by transmission electron microscopy. The content of the drug substances in silica-based nanocarriers was analysed by elemental analysis and UV spectrometry. Microscopic analysis of visualized silica nanocarriers in the perfused brain tissue was performed. The concentration of the drug substances in the tissue was determined by means of UHPLC-DAD/HRMS LTQ Orbitrap XL. It was found that the drug substances in silica-based nanocarriers permeated through the blood brain barrier to the brain tissue, whereas bulk materials were not detected in the brain. PMID:26075264

  1. Facile preparation of transparent and dense CdS-silica gel glass nanocomposites for optical limiting applications

    NASA Astrophysics Data System (ADS)

    Feng, Miao; Zhan, Hongbing

    2014-03-01

    To realize their practical and operable applications as a potential optical limiting (OL) material, quantum dots (QDs) need to have good processability by incorporating them into optical-quality matrices. This work reports a facile route for the room-temperature preparation of large, stable transparent monolithic CdS nanocomposites which can be easily extended to allow the introduction of acid-sensitive functional molecules/nanoparticles into a silica network by sol-gel chemistry. Our strategy involves a two-step sol-gel process (acid-catalyst hydrolysis and basic-catalyst condensation) and the co-condensation of the resulting alkoxysilane-capped CdS QDs with other alkoxysilanes, which allows the CdS QDs to become part of the silica covalent network. The degradation and agglomeration of CdS QDs were thereby effectively restrained, and large monolithic transparent CdS-silica gel glass was obtained. Using Z-scan theory and the resulting open-aperture Z-scan curves, the nonlinear extinction coefficient of the CdS-silica nanocomposite gel glass was calculated to be 1.02 × 10-14 cm W-1, comparable to that of the parent CdS QD dispersion, indicating their promise for OL applications.

  2. Preparation of silica nanoparticles loaded with nootropics and their in vivo permeation through blood-brain barrier.

    PubMed

    Jampilek, Josef; Zaruba, Kamil; Oravec, Michal; Kunes, Martin; Babula, Petr; Ulbrich, Pavel; Brezaniova, Ingrid; Opatrilova, Radka; Triska, Jan; Suchy, Pavel

    2015-01-01

    The blood-brain barrier prevents the passage of many drugs that target the central nervous system. This paper presents the preparation and characterization of silica-based nanocarriers loaded with piracetam, pentoxifylline, and pyridoxine (drugs from the class of nootropics), which are designed to enhance the permeation of the drugs from the circulatory system through the blood-brain barrier. Their permeation was compared with non-nanoparticle drug substances (bulk materials) by means of an in vivo model of rat brain perfusion. The size and morphology of the nanoparticles were characterized by transmission electron microscopy. The content of the drug substances in silica-based nanocarriers was analysed by elemental analysis and UV spectrometry. Microscopic analysis of visualized silica nanocarriers in the perfused brain tissue was performed. The concentration of the drug substances in the tissue was determined by means of UHPLC-DAD/HRMS LTQ Orbitrap XL. It was found that the drug substances in silica-based nanocarriers permeated through the blood brain barrier to the brain tissue, whereas bulk materials were not detected in the brain. PMID:26075264

  3. The formation of an ordered microporous aluminum-based material mediated by phthalic acid.

    PubMed

    Zhang, Wei; Cai, Jian-Hua; Huang, Pei-Pei; Hu, Lin-Lin; Cao, An-Min; Wan, Li-Jun

    2016-06-28

    By using phthalic acid as a soft template, we showed that it was possible to prepare a microporous aluminum-based material when the precipitation of Al(3+) was properly controlled. We also identified that this microporous aluminum-based material could be promising for the removal of fluoride ions in water treatment. PMID:27263661

  4. Silica-based nanocomposites via reverse microemulsions: classifications, preparations, and applications.

    PubMed

    Wang, Jiasheng; Shah, Zameer Hussain; Zhang, Shufen; Lu, Rongwen

    2014-05-01

    Silica-based nanocomposites with amorphous silica as the matrix or carrier along with a functional component have been extensively investigated. These nanocomposites combine the advantages of both silica and the functional components, demonstrating great potential for various applications. To synthesize such composites, one of the most frequently used methods is reverse microemulsion due to its convenient control over the size, shape, and structures. The structures of the composites have a decisive significance for their properties and applications. In this review, we tried to categorize the silica-based nanocomposites via reverse microemulsions based on their structures, discussed the syntheses individually for each structure, summarized their applications, and made some perspectives based on the current progress of this field. PMID:24562100

  5. Silica-based nanocomposites via reverse microemulsions: classifications, preparations, and applications

    NASA Astrophysics Data System (ADS)

    Wang, Jiasheng; Shah, Zameer Hussain; Zhang, Shufen; Lu, Rongwen

    2014-04-01

    Silica-based nanocomposites with amorphous silica as the matrix or carrier along with a functional component have been extensively investigated. These nanocomposites combine the advantages of both silica and the functional components, demonstrating great potential for various applications. To synthesize such composites, one of the most frequently used methods is reverse microemulsion due to its convenient control over the size, shape, and structures. The structures of the composites have a decisive significance for their properties and applications. In this review, we tried to categorize the silica-based nanocomposites via reverse microemulsions based on their structures, discussed the syntheses individually for each structure, summarized their applications, and made some perspectives based on the current progress of this field.Silica-based nanocomposites with amorphous silica as the matrix or carrier along with a functional component have been extensively investigated. These nanocomposites combine the advantages of both silica and the functional components, demonstrating great potential for various applications. To synthesize such composites, one of the most frequently used methods is reverse microemulsion due to its convenient control over the size, shape, and structures. The structures of the composites have a decisive significance for their properties and applications. In this review, we tried to categorize the silica-based nanocomposites via reverse microemulsions based on their structures, discussed the syntheses individually for each structure, summarized their applications, and made some perspectives based on the current progress of this field. Electronic supplementary information (ESI) available: The structures of all the surfactants included in this review are listed. See DOI: 10.1039/c3nr06025j

  6. The situ preparation of silica nanoparticles on the surface of functionalized graphene nanoplatelets

    NASA Astrophysics Data System (ADS)

    Li, Jiani; Yu, Kejing; Qian, Kun; Cao, Haijian; Lu, Xuefeng; Sun, Jie

    2014-04-01

    A method for situ preparing a hybrid material consisting of silica nanoparticles (SiO2) attached onto the surface of functionalized graphene nanoplatelets (f-GNPs) is proposed. Firstly, polyacrylic acid (PAA) was grafted to the surface of f-GNPs to increase reacting sites, and then 3-aminopropyltriethoxysilane (APTES) KH550 reacted with abovementioned product PAA-GNPs to obtain siloxane-GNPs, thus providing reaction sites for the growth of SiO2 on the surface of GNPs. Finally, the SiO2/graphene nanoplatelets (SiO2/GNPs) hybrid material is obtained through introducing siloxane-GNPs into a solution of tetraethyl orthosilicate, ammonia and ethanol for hours' reaction. The results from Fourier transform infrared spectroscopy (FTIR) showed that SiO2 particles have situ grown on the surface of GNPs through chemical bonds as Si-O-Si. And the nanostructure of hybrid materials was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). All the images indicated that SiO2 particles with similar sizes were grafted on the surface of graphene nanoplatelets successfully. And TEM images also showed the whole growth process of SiO2 particles on the surface of graphene as time grows. Moreover, TGA traces suggested the SiO2/GNPs hybrid material had stable thermal stability. And at 900°C, the residual weight fraction of polymer on siloxane-GNPs was about 94.2% and that of SiO2 particles on hybrid materials was about 75.0%. However, the result of Raman spectroscopy showed that carbon atoms of graphene nanoplatelets became much more disordered, due to the destroyed carbon domains during the process of chemical drafting. Through orthogonal experiments, hybrid materials with various sizes of SiO2 particles were prepared, thus achieving the particle sizes controllable. And the factors' level of significance is as follows: the quantity of ammonia > the quantity of tetraethyl orthosilicate (TEOS) > the reaction time.

  7. The situ preparation of silica nanoparticles on the surface of functionalized graphene nanoplatelets

    PubMed Central

    2014-01-01

    A method for situ preparing a hybrid material consisting of silica nanoparticles (SiO2) attached onto the surface of functionalized graphene nanoplatelets (f-GNPs) is proposed. Firstly, polyacrylic acid (PAA) was grafted to the surface of f-GNPs to increase reacting sites, and then 3-aminopropyltriethoxysilane (APTES) KH550 reacted with abovementioned product PAA-GNPs to obtain siloxane-GNPs, thus providing reaction sites for the growth of SiO2 on the surface of GNPs. Finally, the SiO2/graphene nanoplatelets (SiO2/GNPs) hybrid material is obtained through introducing siloxane-GNPs into a solution of tetraethyl orthosilicate, ammonia and ethanol for hours' reaction. The results from Fourier transform infrared spectroscopy (FTIR) showed that SiO2 particles have situ grown on the surface of GNPs through chemical bonds as Si-O-Si. And the nanostructure of hybrid materials was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). All the images indicated that SiO2 particles with similar sizes were grafted on the surface of graphene nanoplatelets successfully. And TEM images also showed the whole growth process of SiO2 particles on the surface of graphene as time grows. Moreover, TGA traces suggested the SiO2/GNPs hybrid material had stable thermal stability. And at 900°C, the residual weight fraction of polymer on siloxane-GNPs was about 94.2% and that of SiO2 particles on hybrid materials was about 75.0%. However, the result of Raman spectroscopy showed that carbon atoms of graphene nanoplatelets became much more disordered, due to the destroyed carbon domains during the process of chemical drafting. Through orthogonal experiments, hybrid materials with various sizes of SiO2 particles were prepared, thus achieving the particle sizes controllable. And the factors’ level of significance is as follows: the quantity of ammonia > the quantity of tetraethyl orthosilicate (TEOS) > the reaction time. PMID:24717037

  8. Effect of Sintering Temperature on the Properties of Fused Silica Ceramics Prepared by Gelcasting

    NASA Astrophysics Data System (ADS)

    Wan, Wei; Huang, Chun-e.; Yang, Jian; Zeng, Jinzhen; Qiu, Tai

    2014-07-01

    Fused silica ceramics were fabricated by gelcasting, by use of a low-toxicity N' N-dimethylacrylamide gel system, and had excellent properties compared with those obtained by use of the low-toxicity 2-hydroxyethyl methacrylate and toxic acrylamide systems. The effect of sintering temperature on the microstructure, mechanical and dielectric properties, and thermal shock resistance of the fused silica ceramics was investigated. The results showed that sintering temperature has a critical effect. Use of an appropriate sintering temperature will promote densification and improve the strength, thermal shock resistance, and dielectric properties of fused silica ceramics. However, excessively high sintering temperature will greatly facilitate crystallization of amorphous silica and result in more cristobalite in the sample, which will cause deterioration of these properties. Fused silica ceramics sintered at 1275°C have the maximum flexural strength, as high as 81.32 MPa, but, simultaneously, a high coefficient of linear expansion (2.56 × 10-6/K at 800°C) and dramatically reduced residual flexural strength after thermal shock (600°C). Fused silica ceramics sintered at 1250°C have excellent properties, relatively high and similar flexural strength before (67.43 MPa) and after thermal shock (65.45 MPa), a dielectric constant of 3.34, and the lowest dielectric loss of 1.20 × 10-3 (at 1 MHz).

  9. Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

    PubMed Central

    Lovingood, Derek D.; Owens, Jeffrey R.; Seeber, Michael; Kornev, Konstantin G.; Luzinov, Igor

    2013-01-01

    Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan δ solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials' morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by Stöber's methods, which have smooth surfaces. PMID:24379052

  10. Particle-filled microporous materials

    DOEpatents

    McAllister, Jerome W.; Kinzer, Kevin E.; Mrozinski, James S.; Johnson, Eric J.; Dyrud, James F.

    1990-01-01

    A microporous particulate-filled thermoplastic polymeric article is provided. The article can be in the form of a film, a fiber, or a tube. The article has a thermoplastic polymeric structure having a plurality of interconnected passageways to provide a network of communicating pores. The microporous structure contains discrete submicron or low micron-sized particulate filler, the particulate filler being substantially non-agglomerated.

  11. Particle-filled microporous materials

    DOEpatents

    McAllister, J.W.; Kinzer, K.E.; Mrozinski, J.S.; Johnson, E.J.; Dyrud, J.F.

    1990-09-18

    A microporous particulate-filled thermoplastic polymeric article is provided. The article can be in the form of a film, a fiber, or a tube. The article has a thermoplastic polymeric structure having a plurality of interconnected passageways to provide a network of communicating pores. The microporous structure contains discrete submicron or low micron-sized particulate filler, the particulate filler being substantially non-agglomerated. 3 figs.

  12. Particle-filled microporous materials

    DOEpatents

    McAllister, Jerome W.; Kinzer, Kevin E.; Mrozinski, James S.; Johnson, Eric J.

    1992-07-14

    A microporous particulate-filled thermoplastic polymeric article is provided. The article can be in the form of a film, a fiber, or a tube. The article has a thermoplastic polymeric structure having a plurality of interconnected passageways to provide a network of communicating pores. The microporous structure contains discrete submicron or low micron-sized particulate filler, the particulate filler being substantially non-agglomerated.

  13. Characterization of biocatalysts prepared with Thermomyces lanuginosus lipase and different silica precursors, dried using aerogel and xerogel techniques.

    PubMed

    Barão, Carlos Eduardo; Daniel de Paris, Leandro; Dantas, João Henrique; Pereira, Matheus Mendonça; Filho, Lucio Cardozo; Ferreira de Castro, Heizir; Zanin, Gisella Maria; Faria de Moraes, Flavio; Faria Soares, Cleide Mara

    2014-01-01

    The use of lipases in industrial processes can result in products with high levels of purity and at the same time reduce pollutant generation and improve both selectivity and yields. In this work, lipase from Thermomyces lanuginosus was immobilized using two different techniques. The first involves the hydrolysis/polycondensation of a silica precursor (tetramethoxysilane (TMOS)) at neutral pH and ambient temperature, and the second one uses tetraethoxysilane (TEOS) as the silica precursor, involving the hydrolysis and polycondensation of the alkoxide in appropriate solvents. After immobilization, the enzymatic preparations were dried using the aerogel and xerogel techniques and then characterized in terms of their hydrolytic activities using a titrimetric method with olive oil and by the formation of 2-phenylethyl acetate in a transesterification reaction. The morphological properties of the materials were characterized using scanning electron microscopy, measurements of the surface area and pore size and volume, thermogravimetric analysis, and exploratory differential calorimetry. The results of the work indicate that the use of different silica precursors (TEOS or TMOS) and different drying techniques (aerogel or xerogel) can significantly affect the properties of the resulting biocatalyst. Drying with supercritical CO2 provided higher enzymatic activities and pore sizes and was therefore preferable to drying, using the xerogel technique. Thermogravimetric analysis and differential scanning calorimetry analyses revealed differences in behavior between the two biocatalyst preparations due to the compounds present. PMID:24078188

  14. Thermodynamic investigation of trichloroethylene adsorption in water-saturated microporous adsorbents

    SciTech Connect

    Farrell, J.; Hauck, B.; Jones, M.

    1999-08-01

    Adsorption of trichloroethylene (TCE) in adsorbents containing hydrophilic and hydrophobic micropores was investigated in order to determine the mechanisms responsible for TCE adsorption on mineral solids. A high-pressure liquid chromatography method was used to measure TCE adsorption isotherms on three microporous adsorbents. Silica gel and zeolite type NaX were used as hydrophilic model adsorbents, and hexamethyldisilazane (HMDS)-treated silica gel was used as a model hydrophobic adsorbent. Batch uptake and desorption isotherms were also measured on the hydrophilic silica gel. Uptake of TCE by all three adsorbents was linear over the concentration range investigated. However, the silica gel desorption isotherm was highly nonlinear, as indicated by its Freundlich isotherm exponent of 0.58. Capillary phase separation into hydrophobic micropores was postulated as being responsible for the isotherm hysteresis. Supporting this hypothesis was the conformance of the TCE adsorption isotherm to Dubinin-Radushkevitch volume filling of micropores theory. The enthalpies for TCE adsorption on all three solids were determined by van't Hoff analysis of distribution coefficients measured over a temperature range from 5 to 90 C. The TCE adsorption enthalpies on the silica gel and HMDS silica gel were exothermic, but on the zeolite adsorption was endothermic. High exothermic adsorption enthalpies on the silica gel adsorbents indicated that TCE adsorption was occurring in hydrophobic micropores, and that adsorption on surfaces with large radii of curvature contributed only minimally to the total uptake. This indicates that the predominant mechanism for TCE adsorption on these mineral solids is not partitioning into the vicinal water layer.

  15. [Preparation and chromatographic performance of a eugenol-bonded silica gel stationary phase for high performance liquid chromatography].

    PubMed

    Xu, Lili; Zhong, Minghua; Chen, Xiaojing

    2015-05-01

    A eugenol-bonded silica gel stationary phase (EGSP) for high performance liquid chromatography ( HPLC) has been synthesized by the solid-liquid successive reaction method. The preparation process included two steps: firstly, γ-glycidoxypropyltrimethoxy-silane (KH-560) was covalently attached to the surface of spherical silica gel. Then the bonded silica gel continued to react with eugenol ligand, which was a plant active component, and obtained EGSP. The structure of EGSP was characterized by elemental analysis, thermogravimetric analysis and Fourier transform infrared spectroscopy. Using naphthalene as a probe, the column efficiency was tested under the mobile phase of acetonitrile-water (35:65, v/v) at a flow rate of 0.8 mL/min. The chromatographic properties and the retention mechanism of EGSP were evaluated by using neutral, basic and acidic analytes as solute probes. Meanwhile, the comparative study with C18 column and phenyl column was also carried out under the same chromatographic conditions. The result showed that the eugenol ligand was successfully bonded to the surface of silica gel with a 0.28 mmol/g of bonded amount, and the theoretical plate number of EGSP column was about 24 707 N/m. The EGSP appeared to be a kind of excellent reversed-phase stationary phase with suitable hydrophobicity and various synergistic sites. The eugenol ligand bonded on silica gel could first provide π-π interaction sites for different analytes because of its benzene ring and alkenyl. In addition, the methoxy groups of eugenol were responsible for dipole-dipole and hydrogen-bonding interactions between the ligand and solutes in the effective separation process. Comparing with traditional C18 column and phenyl column, EGSP has an advantage in the fast separation of polar compounds under simple experimental conditions. PMID:26387202

  16. SBA-15 mesoporous silica free-standing thin films containing copper ions bounded via propyl phosphonate units - preparation and characterization

    NASA Astrophysics Data System (ADS)

    Laskowski, Lukasz; Laskowska, Magdalena; Jelonkiewicz, Jerzy; Dulski, Mateusz; Wojtyniak, Marcin; Fitta, Magdalena; Balanda, Maria

    2016-09-01

    The SBA-15 silica thin films containing copper ions anchored inside channels via propyl phosphonate groups are investigated. Such materials were prepared in the form of thin films, with hexagonally arranged pores, laying rectilinear to the substrate surface. However, in the case of our thin films, their free standing form allowed for additional research possibilities, that are not obtainable for typical thin films on a substrate. The structural properties of the samples were investigated by X-ray reflectometry, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The molecular structure was examined by Raman spectroscopy supported by numerical simulations. Magnetic measurements (SQUID magnetometry and EPR spectroscopy) showed weak antiferromagnetic interactions between active units inside silica channels. Consequently, the pores arrangement was determined and the process of copper ions anchoring by propyl phosphonate groups was verified in unambiguous way. Moreover, the type of interactions between magnetic atoms was determined.

  17. Mesoporous silica/polyacrylamide composite: Preparation by UV-graft photopolymerization, characterization and use as Hg(II) adsorbent

    NASA Astrophysics Data System (ADS)

    Saad, Ali; Bakas, Idriss; Piquemal, Jean-Yves; Nowak, Sophie; Abderrabba, Manef; Chehimi, Mohamed M.

    2016-03-01

    MCM-41 ordered mesoporous silica was prepared, aminosilanized and grafted with polyacrylamide (PAAM) through in situ radical photopolymerization process. The resulting composite, denoted PAAM-NH2-MCM-41, the calcined and silanized reference MCM-41s were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N2 physisorption at 77 K. These complementary techniques brought strong supporting evidence for the silanization process followed by PAAM grafting. The surface composition was found to be PAAM-rich as judged by XPS. The composite was then employed for the uptake of Hg(II) from aqueous solutions. Adsorption was monitored versus pH, time, and temperature. The maximum adsorption capacity at 25 °C and pH 5.2 was 177 mg g-1. Kinetically, the equilibrium was reached within 60 min for a 100 mg L-1 mercury solution. The adsorption of Hg(II) on PAAM-NH2-MCM-41 composites followed second order kinetics. Thermodynamic parameters suggested that the favorable adsorption process is exothermic in nature and the adsorption is ascribed to a decrease in the degree of freedom of adsorbed ions which results in the entropy change. This work conclusively shows that mesoporous silica-polymer hybrid metal ion adsorbents (with robust silica-polymer interface) can be prepared in a simple way by in situ radical photopolymerization in the presence of aminosilanized silica acting as a support and a macro-hydrogen donor simultaneously.

  18. Preparation of silane-functionalized silica films via two-step dip coating sol-gel and evaluation of their superhydrophobic properties

    NASA Astrophysics Data System (ADS)

    Ramezani, Maedeh; Vaezi, Mohammad Reza; Kazemzadeh, Asghar

    2014-10-01

    In this paper, we study the two-step dip coating via a sol-gel process to prepare superhydrophobic silica films on the glass substrate. The water repellency of the silica films was controlled by surface silylation method using isooctyltrimethoxysilane (iso-OTMS) as a surface modifying agent. Silica alcosol was synthesized by keeping the molar ratio of ethyltriethoxysilane (ETES) precursor, ethanol (EtOH) solvent, water (H2O) was kept constant at 1:36:6.6 respectively, with 6 M NH4OH throughout the experiment and the percentages of hydrophobic agent in hexane bath was varied from 0 to 15 vol.%. The static water contact angle values of the silica films increased from 108° to 160° with an increase in the vol.% of iso-OTMS. At 15 vol%. of iso-OTMS, the silica film shows static water contact angle as high as 160°. The superhydrophobic silica films are thermally stable up to 440 °C and above this temperature, the silica films lose superhydrophobicity. By controlling the primer particle size of SiO2 about 26 nm, leading to decrease the final size of silica nanoparticles after modification of nanoparticles by isooctyltrimethoxysilane about 42 nm. The films are transparent and have uniform size on the surface. The silica films have been characterized by atomic force microscopy (AFM), fourier transform infrared spectroscopy (FT-IR), transparency, contact angle measurement (CA), Zeta-potential, Thermal stability by TG-DTA analysis.

  19. Core-shell-structured silica/polyacrylate particles prepared by Pickering emulsion: influence of the nucleation model on particle interfacial organization and emulsion stability

    PubMed Central

    2014-01-01

    This work reports a new evidence of the versatility of silica sol as a stabilizer for Pickering emulsions. The organization of silica particles at the oil-water interface is a function of the nucleation model. The present results show that nucleation model, together with monomer hydrophobicity, can be used as a trigger to modify the packing density of silica particles at the oil-water interface: Less hydrophobic methylmethacrylate, more wettable with silica particles, favors the formation of core-shell-structured composite when the composite particles are prepared by miniemulsion polymerization in which monomers are fed in batch (droplet nucleation). By contrast, hydrophobic butylacrylate promotes the encapsulating efficiency of silica when monomers are fed dropwise (homogeneous nucleation). The morphologies of polyacrylate-nano-SiO2 composites prepared from different feed ratio of methylmethacrylate/butylacrylate (with different hydrophobicity) and by different feed processes are characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. The results from SEM and TEM show that the morphologies of the as-prepared polyacrylate/nano-SiO2 composite can be a core-shell structure or a bare acrylic sphere. The stability of resulting emulsions composed of these composite particles is strongly dependent on the surface coverage of silica particles. The emulsion stability is improved by densely silica-packed composite particles. PMID:25313299

  20. Synthesis and adsorption properties of chitosan-silica nanocomposite prepared by sol-gel method.

    PubMed

    Budnyak, Tetyana M; Pylypchuk, Ievgen V; Tertykh, Valentin A; Yanovska, Elina S; Kolodynska, Dorota

    2015-01-01

    A hybrid nanocomposite material has been obtained by in situ formation of an inorganic network in the presence of a preformed organic polymer. Chitosan biopolymer and tetraethoxysilane (TEOS), which is the most common silica precursor, were used for the sol-gel reaction. The obtained composite chitosan-silica material has been characterized by physicochemical methods such as differential thermal analyses (DTA); carbon, hydrogen, and nitrogen (CHN) elemental analysis; nitrogen adsorption/desorption isotherms, scanning electron microscopy (SEM); and Fourier transform infrared (FTIR) spectroscopy to determine possible interactions between silica and chitosan macromolecules. Adsorption of microquantities of V(V), Mo(VI), and Cr(VI) oxoanions from the aqueous solutions by the obtained composite has been studied in comparison with the chitosan beads, previously crosslinked with glutaraldehyde. The adsorption capacity and kinetic sorption characteristics of the composite material were estimated. PMID:25852383

  1. Synthesis and adsorption properties of chitosan-silica nanocomposite prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Budnyak, Tetyana M.; Pylypchuk, Ievgen V.; Tertykh, Valentin A.; Yanovska, Elina S.; Kolodynska, Dorota

    2015-02-01

    A hybrid nanocomposite material has been obtained by in situ formation of an inorganic network in the presence of a preformed organic polymer. Chitosan biopolymer and tetraethoxysilane (TEOS), which is the most common silica precursor, were used for the sol-gel reaction. The obtained composite chitosan-silica material has been characterized by physicochemical methods such as differential thermal analyses (DTA); carbon, hydrogen, and nitrogen (CHN) elemental analysis; nitrogen adsorption/desorption isotherms, scanning electron microscopy (SEM); and Fourier transform infrared (FTIR) spectroscopy to determine possible interactions between silica and chitosan macromolecules. Adsorption of microquantities of V(V), Mo(VI), and Cr(VI) oxoanions from the aqueous solutions by the obtained composite has been studied in comparison with the chitosan beads, previously crosslinked with glutaraldehyde. The adsorption capacity and kinetic sorption characteristics of the composite material were estimated.

  2. Preparation and optical properties of silica@Ag Cu alloy core-shell composite colloids

    NASA Astrophysics Data System (ADS)

    Zhang, Jianhui; Liu, Huaiyong; Wang, Zhenlin; Ming, Naiben

    2007-04-01

    The silica@Ag-Cu alloy core-shell composite colloids have been successfully synthesized by an electroless plating approach to explore the possibility of modifying the plasmon resonance at the nanoshell surface by varying the metal nanoshell composition for the first time. The surface plasmon resonance of the composite colloids increases in intensity and shifts towards longer, then shorter wavelengths as the Cu/Ag ratio in the alloy shell is increased. The variations in intensity of the surface plasmon resonance with the Cu/Ag ratio obviously affect the Raman bands of the silica colloid core. The report here may supply a new technique to effectively modify the surface plasmon resonance.

  3. Preparation of Mesoporous Silica Templated Metal Nanowire Films on Foamed Nickel Substrates

    SciTech Connect

    Campbell, Roger; Kenik, Edward A; Bakker, Martin; Havrilla, George; Montoya, Velma; Shamsuzzoha, Mohammed

    2006-01-01

    A method has been developed for the formation of high surface area nanowire films on planar and three-dimensional metal electrodes. These nanowire films are formed via electrodeposition into a mesoporous silica film. The mesoporous silica films are formed by a sol-gel process using Pluronic tri-block copolymers to template mesopore formation on both planar and three-dimensional metal electrodes. Surface area increases of up to 120-fold have been observed in electrodes containing a templated film when compared to the same types of electrodes without the templated film.

  4. Preparation and In-vitro Evaluation of Rifampin-loaded Mesoporous Silica Nanoaggregates by an Experimental Design

    PubMed Central

    Mohseni, Meysam; Gilani, Kambiz; Bahrami, Zohreh; Bolourchian, Noushin; Mortazavi, Seyed Alireza

    2015-01-01

    The goal of this research is preparation, optimization and in-vitro evaluation of rifampin-loaded silica nanoparticles in order to use in the pulmonary drug delivery. Nanoparticles are exhaled because of their small size. Preparation of nanoaggregates in a micron-size scale and re-dispersion of them after deposition in the lung is an approach to overcome this problem. We used this approach in our research. Rifampin was selected as a model lipophilic molecule since it was a well-documented and much used anti tuberculosis drug. A half factorial design was used to identify significant parameters of the spray drying process. The results showed that feed concentration, feed pH and the interaction between feed flow rate and gas atomizer flow rate had statistically significant effects on the particle size of nanoaggregates. The Box-Behnken design was employed to optimize the spray drying process. Finally, a quadratic equation which explains the relation between independent variables and aerodynamic diameter of nanoaggregates was obtained. Rifampin-loaded silica nanoaggregates underwent different in-vitro tests including: SEM, Aerosol performance and drug release. The in-vitro drug release was investigated with buffer phosphate (pH=7.4). Regarding the drug release study, a triphasic pattern of release was observed. The rifampin-loaded silica nanoaggregates were capable of releasing 90% drug content after 24 h in combination patterns of release. The prepared rifampin-loaded nanoaggregates seem to have a potential to be used in a pulmonary drug delivery. PMID:25901143

  5. On-machine precision preparation and dressing of ball-headed diamond wheel for the grinding of fused silica

    NASA Astrophysics Data System (ADS)

    Chen, Mingjun; Li, Ziang; Yu, Bo; Peng, Hui; Fang, Zhen

    2013-09-01

    In the grinding of high quality fused silica parts with complex surface or structure using ball-headed metal bonded diamond wheel with small diameter, the existing dressing methods are not suitable to dress the ball-headed diamond wheel precisely due to that they are either on-line in process dressing which may causes collision problem or without consideration for the effects of the tool setting error and electrode wear. An on-machine precision preparation and dressing method is proposed for ball-headed diamond wheel based on electrical discharge machining. By using this method the cylindrical diamond wheel with small diameter is manufactured to hemispherical-headed form. The obtained ball-headed diamond wheel is dressed after several grinding passes to recover geometrical accuracy and sharpness which is lost due to the wheel wear. A tool setting method based on high precision optical system is presented to reduce the wheel center setting error and dimension error. The effect of electrode tool wear is investigated by electrical dressing experiments, and the electrode tool wear compensation model is established based on the experimental results which show that the value of wear ratio coefficient K' tends to be constant with the increasing of the feed length of electrode and the mean value of K' is 0.156. Grinding experiments of fused silica are carried out on a test bench to evaluate the performance of the preparation and dressing method. The experimental results show that the surface roughness of the finished workpiece is 0.03 μm. The effect of the grinding parameter and dressing frequency on the surface roughness is investigated based on the measurement results of the surface roughness. This research provides an on-machine preparation and dressing method for ball-headed metal bonded diamond wheel used in the grinding of fused silica, which provides a solution to the tool setting method and the effect of electrode tool wear.

  6. Preparation, characterization, and optical properties of gold, silver, and gold-silver alloy nanoshells having silica cores.

    PubMed

    Kim, Jun-Hyun; Bryan, William W; Lee, T Randall

    2008-10-01

    This report describes the structural and optical properties of a series of spherical shell/core nanoparticles in which the shell is comprised of a thin layer of gold, silver, or gold-silver alloy, and the core is comprised of a monodispersed silica nanoparticle. The silica core particles were prepared using the Stöber method, functionalized with terminal amine groups, and then seeded with small gold nanoparticles (approximately 2 nm in diameter). The gold-seeded silica particles were coated with a layer of gold, silver, or gold-silver alloy via solution-phase reduction of an appropriate metal ion or mixture of metal ions. The size, morphology, and elemental composition of the composite nanoparticles were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The optical properties of the nanoparticles were analyzed by UV-vis spectroscopy, which showed strong absorptions ranging from 400 nm into the near-IR region, where the position of the plasmon band reflected not only the thickness of the metal shell, but also the nature of the metal comprising the shell. Importantly, the results demonstrate a new strategy for tuning the position of the plasmon resonance without having to vary the core diameter or the shell thickness. PMID:18788760

  7. A new method of utilizing rice husk: consecutively preparing D-xylose, organosolv lignin, ethanol and amorphous superfine silica.

    PubMed

    Zhang, Hongxi; Ding, Xuefeng; Chen, Xue; Ma, Yuejia; Wang, Zichen; Zhao, Xu

    2015-06-30

    Rice husk is an abundant agricultural by-product with the annual output of 120 and 40 million tons in the world and China, respectively. The common disposal method of rice husk in China has caused the pollution. This manuscript deals with a new method of comprehensively utilizing rice husk, by which hazardous materials are avoided to release. 100.3, 219.4, 50.1 and 170.5 g of D-xylose, organosolv lignin, ethanol and superfine silica are consecutively prepared from 1000 g of rice husk. This new method is helpful to resolving the problem of pollution and waste aroused by rice husk. PMID:25768989

  8. Microporous bacterial cellulose as a potential scaffold for bone regeneration.

    PubMed

    Zaborowska, Magdalena; Bodin, Aase; Bäckdahl, Henrik; Popp, Jenni; Goldstein, Aaron; Gatenholm, Paul

    2010-07-01

    Nanoporous cellulose biosynthesized by bacteria is an attractive biomaterial scaffold for tissue engineering due to its biocompatibility and good mechanical properties. However, for bone applications a microscopic pore structure is needed to facilitate osteoblast ingrowth and formation of a mineralized tissue. Therefore, in this study microporous bacterial cellulose (BC) scaffolds were prepared by incorporating 300-500 microm paraffin wax microspheres into the fermentation process. The paraffin wax microspheres were subsequently removed, and scanning electron microscopy confirmed a microporous surface of the scaffolds while Fourier transform infrared spectroscopy verified the elimination of paraffin and tensile measurements showed a Young's modulus of approximately 1.6 MPa. Microporous BC and nanoporous (control) BC scaffolds were seeded with MC3T3-E1 osteoprogenitor cells, and examined by confocal microscopy and histology for cell distribution and mineral deposition. Cells clustered within the pores of microporous BC, and formed denser mineral deposits than cells grown on control BC surfaces. This work shows that microporous BC is a promising biomaterial for bone tissue engineering applications. PMID:20060935

  9. Development of novel biocompatible hybrid nanocomposites based on polyurethane-silica prepared by sol gel process.

    PubMed

    Rashti, Ali; Yahyaei, Hossein; Firoozi, Saman; Ramezani, Sara; Rahiminejad, Ali; Karimi, Roya; Farzaneh, Khadijeh; Mohseni, Mohsen; Ghanbari, Hossein

    2016-12-01

    Due to high biocompatibility, polyurethane has found many applications, particularly in development of biomedical devices. A new nanocomposite based on thermoset polyurethane and silica nanoparticles was synthesized using sol-gel method. Sol-gel process was fulfilled in two acidic and basic conditions by using tetraethylorthosilicate (TEOS) and trimethoxyisocyanatesilane as precursors. The hybrid films characterized for mechanical and surface properties using tensile strength, contact angle, ATR-FTIR and scanning electron microscopy. Biocompatibility and cytotoxicity of the hybrids were assessed using standard MTT, LDH and TUNEL assays. The results revealed that incorporation of silica nanoparticles was significantly improved tensile strength and mechanical properties of the hybrids. Based on the contact angle results, silica nanoparticles increased hydrophilicity of the hybrids. Biocompatibility by using human lung epithelial cell line (MRC-5) demonstrated that the hybrids were significantly less cytotoxic compared to pristine polymer as tested by MTT and LDH assays. TUNEL assay revealed no signs of apoptosis in all tested samples. The results of this study demonstrated that incorporation of silica nanoparticles into polyurethane lead to the enhancement of biocompatibility, indicating that these hybrids could potentially be used in biomedical field in particular as a new coating for medical implants. PMID:27612823

  10. Dry plant extracts loaded on fumed silica for direct compression: preparation and preformulation.

    PubMed

    Palma, S D; Manzo, R H; Allemandi, D A

    1999-01-01

    This paper describes the development of a method to load fumed silica with vegetal material (solid residue) from a liquid extract to obtain a solid loaded silica product (LSP) with satisfactory flow properties and compressibility to be processed by direct-compression technology. Extracts of Melissa officinalis L. (M.o.), Cardus marianus L. (C.m.), and Peumus boldus L. (P.b.) were used to load silica support. The release of boldine from LSP (P.b.) reached 100% in HCl 0.1 N solution and only approximately 70% in water. Some physical-mechanical properties of LSP (M.o. and C.m.) alone and LSP-excipient mixtures were determined. The densities (bulk and tap) of LSP were higher than those of fumed silica alone. Consequently, good flow properties of LSP products were observed. On the other hand, flowability, densities, and compactibility of directly compressible excipients (lactose, dicalcium phosphate dihydrate, and microcrystalline cellulose) were not adversely affected when mixed with LSP. PMID:10578506

  11. Preparation of chlorocholine chloride/urea deep eutectic solvent-modified silica and an examination of the ion exchange properties of modified silica as a Lewis adduct.

    PubMed

    Tang, Baokun; Park, Ha Eun; Row, Kyung Ho

    2014-07-01

    Chlorocholine chloride/urea (ClChCl-urea), a deep eutectic solvent (DES), was applied successfully to the modification of silica. The resulting modified silica was characterized by Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, and elemental analysis. Based on the ClChCl-urea modification of silica, the ClChCl-urea-modified silica is a Lewis adduct with ion exchange properties, and ferulic acid was adsorbed on the ClChCl-urea-modified silica via an ion exchange process. The adsorbed percentage of ferulic acid increased with the increasing amount of modified silica, and a high adsorbed percentage of 89% could be obtained by the ion exchange process. The Freundlich isotherm used to describe the adsorption of ferulic acid on the modified silica by ion exchange showed a good correlation (R(2) = 0.93). Based on the characterization of the structure and the analysis of the ion exchange property of the ClChCl-urea-modified silica, the modified silica as a potential medium can be applied in some analytical technologies such as solid phase extraction, chromatography, and so on. PMID:24748453

  12. Preparation and characterization of mesoporous silicas modified with chiral selectors as stationary phase for high-performance liquid chromatography.

    PubMed

    Pérez-Quintanilla, Damián; Morante-Zarcero, Sonia; Sierra, Isabel

    2014-01-15

    New hybrid materials were prepared as novel chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). Pure mesoporous silica (SM) and ethylene-bridged periodic mesostructured organosilica (PMO) were functionalized, by a post-synthesis method, with derivates of erythromycin and vancomycin. N2 adsorption-desorption measurements, XRD, FT-IR, MAS NMR, SEM, TEM and elemental analysis were used to characterize the physico-chemical properties of these mesostructured materials, before and after the modification process. The synthesized particles had non-symmetrical 3-D wormhole-like mesostructure, spherical morphology, and a mean pore diameter between 53 and 59 Å. CSPs prepared were tested for the separation of four chiral β-blockers (atenolol, metoprolol, pindolol and propranolol) in normal phase (NP) and polar organic phase (PO) elution modes. Much stronger chiral interaction was observed in vancomycin-modified silicas. Results obtained in these preliminary studies will permit in future works to improve the synthesis route in order to design mesoporous materials with better performance as a chiral stationary phase for HPLC. PMID:24231079

  13. Superhydrophobic Surfaces with Very Low Hysteresis Prepared by Aggregation of Silica Nanoparticles During In Situ Urea-Formaldehyde Polymerization.

    PubMed

    Diwan, Anubhav; Jensen, David S; Gupta, Vipul; Johnson, Brian I; Evans, Delwyn; Telford, Clive; Linford, Matthew R

    2015-12-01

    We present a new method for the preparation of superhydrophobic materials by in situ aggregation of silica nanoparticles on a surface during a urea-formaldehyde (UF) polymerization. This is a one-step process in which a two-tier topography is obtained. The polymerization is carried out for 30, 60, 120, 180, and 240 min on silicon shards. Silicon surfaces are sintered to remove the polymer. SEM and AFM show both an increase in the area covered by the nanoparticles and their aggregation with increasing polymerization time. Chemical vapor deposition of a fluorinated silane in the presence of a basic catalyst gives these surfaces hydrophobicity. Deposition of this low surface energy silane is confirmed by the F 1s signal in XPS. The surfaces show advancing water contact angles in excess of 160 degrees with very low hysteresis (< 7) after 120 min and 60 min polymerization times for 7 nm and 14 nm silica, respectively. Depositions are successfully demonstrated on glass substrates after they are primed with a UF polymer layer. Superhydrophobic surfaces can also be prepared on unsintered substrates. PMID:26682448

  14. Aptamer-based organic-silica hybrid affinity monolith prepared via "thiol-ene" click reaction for extraction of thrombin.

    PubMed

    Wang, Zheng; Zhao, Jin-cheng; Lian, Hong-zhen; Chen, Hong-yuan

    2015-06-01

    A novel strategy for preparing aptamer-based organic-silica hybrid monolithic column was developed via "thiol-ene" click chemistry. Due to the large specific surface area of the hybrid matrix and the simplicity, rapidness and high efficiency of "thiol-ene" click reaction, the average coverage density of aptamer on the organic-silica hybrid monolith reached 420 pmol μL(-1). Human α-thrombin can be captured on the prepared affinity monolithic column with high specificity and eluted by NaClO4 solution. N-p-tosyl-Gly-Pro-Arg p-nitroanilide acetate was used as the sensitive chromogenic substrate of thrombin. The thrombin enriched by this affinity column was detected with a detection of limit of 0.01 μM by spectrophotometry. Furthermore, the extraction recovery of thrombin at 0.15 μM in human serum was 91.8% with a relative standard deviation of 4.0%. These results indicated that "thiol-ene" click chemistry provided a promising technique to immobilize aptamer on organic-inorganic hybrid monolith and the easily-assembled affinity monolithic material could be used to realize highly selective recognition of trace proteins. PMID:25863371

  15. On the properties of silica-supported bimetallic Fe-Cu catalysts. Part 1. Preparation and characterization

    SciTech Connect

    Wielers, A.F.H.; Hop, C.E.C.A.; van Beijnum, J.; Geus, J.W. ); van der Kraan, A.M. )

    1990-02-01

    In this work a series of silica-supported bimetallic iron-copper catalysts has been prepared and characterized. The bimetallic catalysts were prepared via homogeneous deposition-precipitation involving a procedure in which first copper ions (as copper hydrosilicate) and consecutively iron(III) ions (as goethite) are precipitated onto the support. The results show that copper facilitates the reduction of iron(III) to iron(II) (which is present as iron(II)silicate) as well as the reduction to zero-valent iron. In the reduced iron/copper catalyst zero-valent iron is present as monometallic {alpha}-Fe particles and as iron clusters in bimetallic Fe-Cu particles. The relative amounts of the various iron species vary with the overall composition. Whereas the surfaces of the freshly reduced bimetallic particles are not extensively enriched in one of the constituents, prolonged CO exposure at room temperature leads to a considerable iron enrichment.

  16. Catalyzed oxidative degradation of methyl orange over Au catalyst prepared by ionic liquid-polymer modified silica

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Guo, J. S.

    2015-07-01

    A new type of hybrid material was prepared by grafting an ionic liquid monomer, 1-(p-vinylbenzyl)-3-methylimidazolium chloride, on the surface of the porous silica which was synthesized via sodium silicate hydrolysis. The as-synthesized products were characterized by scanning electron microscope, nitrogen physisorption experiment, thermogravimetric analysis and Fourier transform infrared spectra. A catalyst with Au was prepared using the hybrid material as carrier. The experimental results show that the catalyst exhibits a better catalytic effect of hydrogen peroxide on the degradation of methyl orange. The reason may be that the metal component of the catalyst facilitated the dissociation of hydrogen peroxide to produce abundant highly active free radicals which can rapidly ruin the structure of methyl orange molecules in water. Finally, a probable catalytic degradation mechanism based on diffusion was discussed.

  17. Mesoporous silica nanoparticles with controllable morphology prepared from oil-in-water emulsions.

    PubMed

    Gustafsson, Hanna; Isaksson, Simon; Altskär, Annika; Holmberg, Krister

    2016-04-01

    Mesoporous silica nanoparticles are an important class of materials with a wide range of applications. This paper presents a simple protocol for synthesis of particles as small as 40nm and with a pore size that can be as large as 9nm. Reaction conditions including type of surfactant, type of catalyst and presence of organic polymer were investigated in order to optimize the synthesis. An important aim of the work was to understand the mechanism behind the formation of these unusual structures and an explanation based on silica condensation in the small aqueous microemulsion droplets that are present inside the drops of an oil-in-water emulsion is put forward. PMID:26803604

  18. Carvedilol dissolution improvement by preparation of solid dispersions with porous silica.

    PubMed

    Planinšek, Odon; Kovačič, Borut; Vrečer, Franc

    2011-03-15

    Impregnation of porous SiO(2) (Sylysia) with carvedilol from acetone solution was used to improve dissolution of this poorly water-soluble drug. Solvent evaporation in a vacuum evaporator and adsorption from acetone solution were the methods used to load various amounts of carvedilol into the Sylysia pores. The impregnated carriers were characterized using nitrogen-adsorption experiments, X-ray diffraction, wettability measurements, attenuated total reflectance FTIR spectroscopy and thermal analysis. The impregnation procedures resulted in a significant improvement of drug release compared to dissolution of pure carvedilol or its physical mixtures with Sylysia. The results showed that when the drug precipitated in a thin layer within the carrier the dispersion retained a high specific surface area, micropore volume, and drug-release rate from the solid dispersion. Increasing the amount of drug in the solid dispersion caused particle precipitation within the pores that decreased the carrier's specific surface area and pore volume and decreased the release rate of the drug. The results also suggest that the amorphous form of carvedilol, the improved wettability and weak interactions between the drug and carrier in the solid dispersion also contribute to improved dissolution of the drug from the dispersion. PMID:21219991

  19. Preparation and characterization of a molecularly imprinted polymer by grafting on silica supports: a selective sorbent for patulin toxin.

    PubMed

    Zhao, Dayun; Jia, Jingfu; Yu, Xuelei; Sun, Xiangjun

    2011-10-01

    A new molecularly imprinted polymer (MIP) has been prepared on silica beads using the radical "grafting from" polymerization method for selective extraction of minor contaminant mycotoxin of patulin (PTL). After the introduction of amino groups onto the silica surface with 3-aminopropyltriethoxysilane, azo initiator onto the silica surface was achieved by the reaction of surface amino groups with 4,4'-azobis(4-cyanopentanoic acid). The scale-up synthesis of MIP was then carried out in the presence of 6-hydroxynicotinic acid as template substitute, functional, and cross-linking monomers. The prepared sorbent was characterized using FT-IR spectroscopy, scanning electron microscopy, elemental analysis, and the adsorption-desorption selectivity, and the capacity characteristic of the polymer was investigated by a conventional batch adsorption test and Scatchard plot analysis. The results indicated that coated polymers had specific adsorption to PTL as compared with its co-occurring 5-hydroxymethyl-2-furaldehyde (hydroxymethylfurfural (HMF)), at the same bulk concentration for solution of PTL and HMF, the maximum absorbance in the solid-phase extraction (SPE) method to PTL were 93.97% or 0.654 μg/mg while to HMF they were 76.89% or 0.496 μg/mg. Scatchard analysis revealed that two classes of binding sites were formed in PTL-MIP with dissociation constants of 3.2 × 10(-2) and 5.0 × 10(-3) mg/mL and the affinity binding sites of 8.029 and 1.364 mg/g, respectively. The recoveries of PTL were more than 90% for the developed MISPE and around 75% for the traditional liquid-liquid extraction in spiked apple juice samples. It was concluded that the method is suitable for the scale-up synthesis of PTL-MIP grafted on silica, and the polymer can be effectively applied as SPE coupled with high-performance liquid chromatography (HPLC) for the determination of PTL in apple juice or other related products. PMID:21870071

  20. Microporous biodegradable polyurethane membranes for tissue engineering.

    PubMed

    Tsui, Yuen Kee; Gogolewski, Sylwester

    2009-08-01

    Microporous membranes with controlled pore size and structure were produced from biodegradable polyurethane based on aliphatic diisocyanate, poly(epsilon-caprolactone) diol and isosorbide chain extender using the modified phase-inversion technique. The following parameters affecting the process of membrane formation were investigated: the type of solvent, solvent-nonsolvent ratio, polymer concentration in solution, polymer solidification time, and the thickness of the polymer solution layer cast on a substrate. The experimental systems evaluated were polymer-N,N-dimethylformamide-water, polymer-N,N-dimethylacetamide-water and polymer-dimethylsulfoxide-water. From all three systems evaluated the best results were obtained for the system polymer-N,N-dimethylformamide-water. The optimal conditions for the preparation of microporous polyurethane membranes were: polymer concentration in solution 5% (w/v), the amount of nonsolvent 10% (v/v), the cast temperature 23 degrees C, and polymer solidification time in the range of 24-48 h depending on the thickness of the cast polymer solution layer. Membranes obtained under these conditions had interconnected pores, well defined pore size and structure, good water permeability and satisfactory mechanical properties to allow for suturing. Potential applications of these membranes are skin wound cover and, in combination with autogenous chondrocytes, as an "artificial periosteum" in the treatment of articular cartilage defects. PMID:19301104

  1. Preparation and characterization of antibacterial Senegalia (Acacia) senegal/iron-silica bio-nanocomposites

    NASA Astrophysics Data System (ADS)

    Şişmanoğlu, Tuba; Karakuş, Selcan; Birer, Özgür; Soylu, Gülin Selda Pozan; Kolan, Ayşen; Tan, Ezgi; Ürk, Öykü; Akdut, Gizem; Kilislioglu, Ayben

    2015-11-01

    Many studies that research bio-nanocomposites utilize techniques that involve the dispersion of strengthening components like silica, metal and metal oxides through a host biopolymer matrix. The biggest success factor for the bio-nanocomposite is having a smooth integration of organic and inorganic phases. This interattraction between the surfaces of inorganic particles and organic molecules are vital for good dispersion. In this study, a novel biodegradable antibacterial material was developed using gum arabic from Senegalia senegal (stabilizer), silica (structure reinforcer) and zero valent iron particles. Silica particles work to not only strengthen the mechanical properties of the Senegalia senegal but also prevent the accumulation of ZVI nanoparticles due to attraction between hydroxyl groups and FeO. The gum arabic/Fe-SiO2 bio-nanocomposite showed effective antibacterial property against the Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Using Scanning electron microscopy, homogeneous dispersion and uniform particle size was viewed in the biopolymer. X-ray diffraction studies of iron particles organization in Senegalia senegal also showed that the main portion of iron was crystalline and in the form of FeO and Fe0. X-ray photoelectron spectroscopy was used to evaluate the chemical composition of the surface but no appreciable peak was measured for the iron before Ar etching. These results suggest that the surface of iron nanoparticles consist mainly of a layer of iron oxides in the form of FeO. Thermal gravimetric analysis was used to determine the thermal stability and absorbed moisture content.

  2. 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.

  3. Comparison of silver nanoparticles confined in nanoporous silica prepared by chemical synthesis and by ultra-short pulsed laser ablation in liquid

    NASA Astrophysics Data System (ADS)

    Szegedi, Á.; Popova, M.; Valyon, J.; Guarnaccio, A.; De Stefanis, A.; De Bonis, A.; Orlando, S.; Sansone, M.; Teghil, R.; Santagata, A.

    2014-10-01

    Hexagonally ordered mesoporous silica materials, MCM-41 and SBA-15, have been synthesized and loaded with Ag nanoparticles, utilizing both chemical synthesis and ultra-short pulsed laser ablation in liquid. In laser ablation, a silver target, immersed in aqueous suspension of ordered mesoporous silica SBA-15, was irradiated by ultra-short laser pulses to generate silver nanoparticles. For comparison, samples of similar silver contents were prepared either by incorporating silver into the SBA-15 during a hydrothermal synthesis or by introducing silver in MCM-41 by template ion-exchange. Samples were characterized by XRD, N2 physisorption, TEM and UV-vis spectroscopy. All preparations contained significant amount of 5-50 nm size silver agglomerates on the outer surface of the silica particles. The laser ablation process did not cause significant destruction of the SBA-15 structure and metallic silver (Ag0) nanoparticles were mainly generated. It is demonstrated that by laser ablation in aqueous silica suspension smaller and more uniform metallic silver particles can be produced and loaded on the surface of the silica support than by synthesis procedures. Catalytic properties of the samples have been tested in the total oxidation of toluene. Because of its favorable Ag dispersity, the Ag/SBA-15 catalyst, generated by the laser ablation method, had better catalytic stability and, relative to its Ag load, higher activity than the conventional Ag/SBA-15 preparations.

  4. PS-b-PEO/Silica Films with Regular and Reverse Mesostructures of Large Characteristic Length Scales Prepared by Solvent Evaporation-Induced Self-Assembly

    SciTech Connect

    YU,KUI; BRINKER,C. JEFFREY; HURD,ALAN J.; EISENBERG,ADI

    2000-11-22

    Since the discovery of surfactant-templated silica by Mobil scientists in 1992, mesostructured silica has been synthesized in various forms including thin films, powders, particles, and fibers. In general, mesostructured silica has potential applications, such as in separation, catalysis, sensors, and fluidic microsystems. In respect to these potential applications, mesostructured silica in the form of thin films is perhaps one of the most promising candidates. The preparation of mesostructured silica films through preferential solvent evaporation-induced self-assembly (EISA) has recently received much attention in the laboratories. However, no amphiphile/silica films with reverse mesophases have ever been made through this EISA procedure. Furthermore, templates employed to date have been either surfactants or poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers, such as pluronic P-123, both of which are water-soluble and alcohol-soluble. Due to their relatively low molecular weight, the templated silica films with mesoscopic order have been limited to relatively small characteristic length scales. In the present communication, the authors report a novel synthetic method to prepare mesostructured amphiphilic/silica films with regular and reverse mesophases of large characteristic length scales. This method involves evaporation-induced self-assembly (EISA) of amphiphilic polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymers. In the present study, the PS-b-PEO diblocks are denoted as, for example, PS(215)-b-PEO(100), showing that this particular sample contains 215 S repeat units and 100 EO repeat units. This PS(215)-b-PEO(100) diblock possesses high molecular weight and does not directly mix with water or alcohol. To the authors knowledge, no studies have reported the use of water-insoluble and alcohol-insoluble amphiphilic diblocks as structure-directing agents in the synthesis of mesostructured silica films through

  5. Preparation of Fe3O4 encapsulated-silica sulfonic acid nanoparticles and study of their in vitro antimicrobial activity.

    PubMed

    Naeimi, Hossein; Nazifi, Zahra Sadat; Amininezhad, Seyedeh Matin

    2015-08-01

    A simple and efficient method for the functionalization of silica-coated Fe3O4 magnetic nanoparticles (Fe3O4@SiO2) using chlorosulfonic acid is described. The prepared compounds were screened for antibacterial activity against Escherichia coli (E. coli ATCC 25922) and Staphylococcus aureus (S. aureus ATCC 25923) under UV-light and dark conditions. It was found that the Fe3O4@SiO2-SO3H was significantly indicated the higher photocatalytic inactivation than both Fe3O4 and Fe3O4@SiO2 against E. coli in compared with S. aureus. Furthermore, the inactivation efficiency against both organisms under light conditions has been higher than this efficiency under dark conditions. PMID:26092181

  6. Photochemical hole-burning study of 1,4-dihydroxyanthraquinone doped in amorphous silica prepared by alcoholate method

    NASA Astrophysics Data System (ADS)

    Tani, T.; Namikawa, H.; Arai, K.; Makishima, A.

    1985-11-01

    The preparation of 1,4-dihydroxyanthraquinone, an amorphous silica doped with organic dye molecules, is described. The amorphous structure of this system is studied using photochemical hole burning (PHB), and the results are reported together with absorption and fluorescence spectra measured at room temperature. The PHB results for this material are compared with those for alcoholic organic glass, and mechanisms which dominate the temperature dependence of the holewidth are discussed. The introduction of various organic molecules into inorganic oxide glasses may provide a new field in material science. These materials are promising for various optical and optoelectronic applications, including PHB memory, due to the rigidity and stability of the glassy matrices preserving the function of the organic molecules. These materials may also be highly significant for molecular electronic materials.

  7. Novel supports in chiral stationary phase development for liquid chromatography. Preparation, characterization and application of ordered mesoporous silica particles.

    PubMed

    Sierra, Isabel; Pérez-Quintanilla, Damián; Morante, Sonia; Gañán, Judith

    2014-10-10

    Recent advances in the development of new materials are having a major impact on analytical chemistry. For example, the unique properties of ordered mesoporous silicas (OMSs) have been shown to enhance the analytical performance of many existing techniques or allow new, exciting ones to be developed. Likewise, the introduction of organo-functional groups makes OMSs highly versatile and enables them to perform specialized tasks, such as the separation of chiral compounds. This review provides an overview with the most relevant achievements in the preparation of OMS particles functionalized with chiral selectors. In addition, some examples from the last fifteen years regarding the analytical applications of functionalized OMS for chiral separations by high-performance liquid chromatography, ultra-high pressure high-performance liquid chromatography and capillary electrochromatography have been reviewed. PMID:25015243

  8. [Preparation and chromatographic performance of a silica-bonded (4-cyclopentadienyl benzoic acid-iron-toluene) hexafluorophosphoric acid stationary phase].

    PubMed

    Cao, Aijuan; Li, Xiaole; Qiao, Lijun; Zhou, Xiaohua; Yu, Ajuan; Zhang, Shusheng; Wu, Yangjie

    2016-02-01

    Based on the unique molecular structure of ferrocene and its potential as a new liquid chromatography separation medium, a new silica-bonded (4-cyclopentadienyl benzoic acid-iron-toluene) hexafluorophosphoric acid stationary phase was prepared. The structure of this new material was characterized by infrared spectroscopy, elemental analysis, thermogravimetric analysis et al. The chromatographic performance and retention mechanism of this new stationary phase were evaluated using different solute probes, including polycyclic aromatic hydrocarbons (PAHs), positional isomers of naphthylamine, positional isomers of nitro-aniline, nitroimidazoles, organic phosphorus et al. It could provide various action sites for different solutes in normal-phase chromatography such as π electron transfer, π-π electron interactions, dipole-dipole interactions, and electrostatic interactions with the substrates. And the possible separation mechanisms are discussed. PMID:27382719

  9. [Preparation of 1 µm non-porous C18 silica gel stationary phase for chiral-pressurized capillary electrochromatography].

    PubMed

    Lu, Yangfang; Wang, Hui; Wang, Guiming; Wang, Yan; Gu, Xue; Yan, Chao

    2015-03-01

    Non-porous C18 silica gel stationary phase (1 µm) was prepared and applied to chiral separation in pressurized capillary electrochromatography (pCEC) for the enantioseparation of various basic compounds. The non-porous silica particles (1 µm) were synthesized using modified St6ber method. C18 stationary phase (1 µm) was prepared by immobilization of chloro-dimethyl-octadecylsilane. Using carboxymethyl-β-cyclodextrin (CM-β-CD) as the chiral additive, the pCEC conditions including the content of acetonitrile (ACN), concentration of buffer, pH, the concentration of chiral additive and flow rate as well as applied voltage were investigated to obtain the optimal pCEC conditions for the separation of four basic chiral compounds. The column provided an efficiency of up to 190,000 plates/m. Bupropion hydrochloride, clenbuterol hydrochloride, metoprolol tartrate, and esmolol hydrochloride were baseline separated under the conditions of 5 mmol/L ammonium acetate buffer at pH 4. 0 with 20% (v/ v) acetonitrile, and 15 mmol/L CM-β-CD as the chiral additive. The applied voltage was 2 kV and flow rate was 0.03 mL/min with splitting ratio of 300:1. The resolution were 1.55, 2.82, 1. 69, 1. 70 for bupropion hydrochloride, clenbuterol hydrochloride, metoprolol tartrate, esmolol hydrochloride, respectively. The C18 coverage was improved by repeating silylation method. The synthesized 1 µm C18 packings have better mechanical strength and longer service life because of the special, non-porous structure. The column used in pCEC mode showed better separation of the racemates and a higher rate compared with those used in the capillary liquid chromatography (cLC) mode. This study provided an alternative way for the method of pCEC enantioseparation with chiral additives in the mobile phase and demonstrated the feasibility of micron particle stationary phase in chiral separation. PMID:26182460

  10. Preparation and time-gated luminescence bioimaging applications of long wavelength-excited silica-encapsulated europium nanoparticles

    NASA Astrophysics Data System (ADS)

    Tian, Lu; Dai, Zhichao; Zhang, Lin; Zhang, Ruoyu; Ye, Zhiqiang; Wu, Jing; Jin, Dayong; Yuan, Jingli

    2012-05-01

    Silica-encapsulated luminescent lanthanide nanoparticles have shown great potential as biolabels for various time-gated luminescence bio-detections in recent years. The main problem of these nano-biolabels is their short excitation wavelengths within the UV region. In this work, a new type of silica-encapsulated luminescent europium nanoparticle, with a wide excitation range from UV to visible light in aqueous solutions, has been prepared using a conjugate of (3-isocyanatopropyl)triethoxysilane bound to a visible light-excited Eu3+ complex, 2,6-bis(1',1',1',2',2',3',3'-heptafluoro-4',6'-hexanedion-6'-yl)-dibenzothiophene-Eu3+-2-(N,N-diethylanilin-4-yl)-4,6-bis(pyrazol-1-yl)-1,3,5-triazine (IPTES-BHHD-Eu3+-BPT conjugate), as a functionalized precursor. The nanoparticles, which are prepared by the copolymerization of the IPTES-BHHD-Eu3+-BPT conjugate, tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane in a water-in-oil reverse microemulsion consisting of Triton X-100, n-octanol, cyclohexane and water in the presence of aqueous ammonia, are monodisperse, spherical and uniform in size. Their diameter is 42 +/- 3 nm and they are strongly luminescent with a wide excitation range from UV to ~475 nm and a long luminescence lifetime of 346 μs. The nanoparticles were successfully used for streptavidin labeling and the time-gated luminescence imaging detection of two environmental pathogens, cryptosporidium muris and cryptosporidium parvium, in water samples. The results demonstrated the practical utility of the new nanoparticles as visible light-excited biolabels for time-gated luminescence bioassay applications.

  11. Controlling surface energy of glass substrates to prepare superhydrophobic and transparent films from silica nanoparticle suspensions.

    PubMed

    Ogihara, Hitoshi; Xie, Jing; Saji, Tetsuo

    2015-01-01

    We fabricated superhydrophobic and transparent silica nanoparticle (SNP) films on glass plates via spray-coating technique. When suspensions containing 1-propanol and hydrophobic SNPs were sprayed over glass plates that were modified with dodecyl groups, superhydrophobic and transparent SNP films were formed on the substrates. Surface energy of the glass plates had a significant role to obtain superhydrophobic and transparent SNP films. SNP films did not show superhydrophobicity when bare glass plates were used as substrates, because water droplets tend to adhere the exposed part of the hydrophilic glass plate. Glass plates having extreme low surface energy were not also suitable because suspension solution was repelled from the substrates, which resulted in forming non-uniform SNP films. PMID:25310579

  12. [Preparation and stability of β-carotene loaded using mesoporous silica nanoparticles as carriers system].

    PubMed

    Liu, Jing; Ren, Zhi-hui; Wang, Hai-yuan; Jin, Xing-hua

    2015-09-01

    1,3,5-Trimethylbenzene (1,3,5-TMB) was used as the pore-enlarging modifier to expand the pore size of MCM-41 (mobil company of matter) mesoporous silica nanoparticles. The solvent impregnation method was adopted to assemble non-water-soluble β-carotene into the pore channel of MCM-41. The MCM-41 and drug assemblies were characterized by TEM, FT-IR, elemental analysis and N2 adsorption-desorption. The results showed that MCM-41 has good sphericity and regular pore structure. The research also investigated the optimal loading time, the drug loading and the vitro stability of the β-carotene. As a drug carrier, the modified MCM-41 showing a shorter drug loading time, the drug loading as high as 85.58% and the stability of β-carotene in drug assemblies has improved. The study of this new formulation provides a new way for β-carotene application. PMID:26983203

  13. Preparation of carboxymethyl chitosan-graft-β-cyclodextrin modified silica gel and preconcentration of cadmium.

    PubMed

    Lü, Haixia; An, Hongtao; Wang, Xiaoming; Xie, Zenghong

    2013-10-01

    Carboxymethyl chitosan (CMCS) grafted with β-cyclodextrin (CMCS-g-CD) modified silica gel as a new solid phase extraction (SPE) adsorbent for cadmium has been developed. The optimum batch experimental conditions (pH, amount of adsorbent and contact time) and column experimental conditions (concentration and volume of elution solution) were optimized, respectively. The kinetic models for Cd (II) were investigated and the results indicated that pseudo-second-order equation provided a better R(2) (R(2)>0.999) and agreement between calculated Qe value (10.6 mg/g) and the experimental Qe (exp) value (11.3 mg/g). The developed method was successfully applied to the determination of Cd(II) in lake water and tap water with recoveries ranging from 96.0% to 102.0%. PMID:23921207

  14. 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.

  15. Development of a simple method for the preparation of novel egg-shell type Pt catalysts using hollow silica nanostructures as supporting precursors

    SciTech Connect

    Wang Jiexin; Chen Jianfeng

    2008-04-01

    A simple method for the preparation of novel egg-shell type platinum catalysts was developed and achieved by utilizing unique hollow silica nanostructures, i.e., hollow silica nanospheres and nanotubes, as supports. The observation by transmission electron microscopy indicated that the well-dispersed hollow silica supported Pt catalysts with a Pt particle diameter of 8-14 nm can be successfully prepared by wet impregnation process and heat treatment. The Pt-loaded hollow silica nanostructures were also characterized by inductively coupled plasma, X-ray diffraction, specific surface area, Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy and energy dispersive spectroscopy. It was thus demonstrated that a higher Pt loading amount (0.392%) could be obtained under the same conditions except the addition of ammonia, which was found to be more effective than that (0.061%) with the addition of HCl in the immobilization of Pt. In addition, the effect of soaking time, Pt precursor concentration and calcination temperature on the loading of Pt in hollow silica nanostructures were investigated as well.

  16. Diol-linked microporous networks of cubic siloxane cages.

    PubMed

    Wada, Yuko; Iyoki, Kenta; Sugawara-Narutaki, Ayae; Okubo, Tatsuya; Shimojima, Atsushi

    2013-01-28

    A new class of inorganic-organic hybrid porous materials has been synthesized by a reaction between octa(hydridosilsesquioxane) (H(8)Si(8)O(12)), which has a double-four-ring (D4R) structure, and various diols, such as 1,3-propanediol (PD), 1,4-cyclohexanediol (CHD), and 1,3-adamantanediol (AD). Solid-state (29) Si magic-angle-spinning NMR spectroscopic analysis confirmed that most of the corner Si-H groups reacted with diols to form Si-O-C bonds with retention of the D4R cage. Nitrogen adsorption-desorption studies showed that the products are microporous solids with high BET surface areas (up to ≈580 m(2) g(-1) for CHD- and AD-linked products). If n-alkanediols are used as linkers, the surface area becomes smaller as the number of carbon atoms is increased. The thermal and hydrolytic stability of the products strongly depend on the type of diol linkers. The highest stabilities are found for the AD-linked products, which are thermally stable up to around 400 °C and remain intact even after being soaked in water for 1 day. In contrast, the PD-linked product is easily hydrolyzed in water to give microporous silica. These results offer a new route toward a series of silica-based porous materials with unique structures and properties. PMID:23203900

  17. One Polymorph and Various Morphologies of Phenytoin at a Silica Surface Due to Preparation Kinetics

    PubMed Central

    2014-01-01

    The preparation of solid crystalline films at surfaces is of great interest in a variety of fields. Within this work the preparation of pharmaceutically relevant thin films containing the active pharmaceutical ingredient phenytoin is demonstrated. The preparation techniques applied include drop casting, spin coating, and vacuum deposition. For the solution processed samples a decisive impact of the solution concentration and the applied film fabrication technique is observed; particular films form for all samples but with their extensions along different crystallographic directions strongly altered. Vacuum deposition of phenytoin reveals amorphous films, which over time crystallize into needle-like or particular-type structures whereby a nominal thickness of 50 nm is required to achieve a fully closed layer. Independent of all preparation techniques, the resulting polymorph is the same for each sample as confirmed by specular X-ray diffraction scans. Thus, morphologies observed via optical and atomic force microscope techniques are therefore a result of the preparation technique. This shows that the different time scales for which crystallization is obtained is the driving force for the various morphologies in phenytoin thin films rather than the presence of another polymorph forming. PMID:25593545

  18. Critical roles of cationic surfactants in the preparation of colloidal mesostructured silica nanoparticles: control of mesostructure, particle size, and dispersion.

    PubMed

    Yamada, Hironori; Urata, Chihiro; Higashitamori, Sayuri; Aoyama, Yuko; Yamauchi, Yusuke; Kuroda, Kazuyuki

    2014-03-12

    Mesoporous silica nanoparticles are promising materials for various applications, such as drug delivery and catalysis, but the functional roles of surfactants in the formation and preparation of mesostructured silica nanoparticles (MSN-as) remain to be seen. It was confirmed that the molar ratio of cationic surfactants to Si of alkoxysilanes (Surf/Si) can affect the degree of mesostructure formation (i.e., whether the mesochannels formed inside the nanoparticles actually pass through the outer surface of the particles), the particle diameter, and the dispersibility of MSN-as. Wormhole-like mesostructures formed with low Surf/Si ratios; however, the mesopores did not pass through the outer surface of the particles completely. At high Surf/Si ratios, the mesostructures extended. The particle diameter was 100 nm or larger at low Surf/Si ratios, and the primary particle diameter decreased as the Surf/Si ratio increased. This was because the surfactants enhanced the dispersity of the alkoxysilanes in water and the hydrolysis rate of the alkoxysilanes became faster, leading to an increased nucleation as compared to the particle growth. Moreover, primary particles aggregated at low Surf/Si ratios because of the hydrophobic interactions among the surfactants that were not involved in the mesostructure formation but were adsorbed onto the nanoparticles. At high Surf/Si ratios, the surfactant micelles were adsorbed on the surface of primary particles (admicelles), resulting in the dispersion of the particles due to electrostatic repulsion. In particular, molar ratios of 0.13 or higher were quite effective for the preparation of highly dispersed MSN-as. Surfactants played important roles in the mesostructure formation, decreasing the particle diameters, and the dispersibility of the particles. All of these factors were considerably affected by the Surf/Si ratio. The results suggested novel opportunities to control various colloidal mesostructured nanoparticles from the

  19. A nanosized Ag-silica hybrid complex prepared by γ-irradiation activates the defense response in Arabidopsis

    NASA Astrophysics Data System (ADS)

    Chu, Hyosub; Kim, Hwa-Jung; Su Kim, Joong; Kim, Min-Soo; Yoon, Byung-Dae; Park, Hae-Jun; Kim, Cha Young

    2012-02-01

    Silver nanoparticles have antimicrobial activity against many pathogenic microbes. Here, the preparation of a nanosized Ag-silica hybrid complex (NSS) prepared by γ-irradiation is described. The effects of both NSS and reduced Ag nanoparticles (Ag 0) on the growth of the model plant Arabidopsis thaliana were tested. The application of 1-10 ppm NSS complex improved Arabidopsis growth in soil, whereas 100 ppm NSS resulted in weakly curled leaves. In addition, supplementation of Murashige and Skoog (MS) growth medium with 1 ppm NSS promoted the root growth of Arabidopsis seedlings, but root growth was inhibited by supplementation with 10 ppm NSS. To investigate whether the NSS complex could induce plant defense responses, the expression of pathogenesis-related ( PR) genes that are implicated in systemic acquired resistance (SAR) in Arabidopsis plants was examined. PR1, PR2 and PR5 were significantly up-regulated by each application of 10 ppm NSS complex or Ag 0 to the rosette leaves. Furthermore, pretreatment with the NSS complex induced more pathogen resistance to the virulent pathogen Pseudomonas syringae pv. tomato DC3000 ( Pst) compared to water treatment in Arabidopsis plants.

  20. The hybrid photocatalyst of TiO2-SiO2 thin film prepared from rice husk silica

    NASA Astrophysics Data System (ADS)

    Klankaw, P.; Chawengkijwanich, C.; Grisdanurak, N.; Chiarakorn, Siriluk

    2012-03-01

    The TiO2-SiO2 thin film was prepared by self-assembly method by mixing SiO2 precursor with titanium precursor solution and aged to obtain a co-precipitation of silica and titanium crystals. Dip coating method was applied for thin film preparation on glass slide. The X-ray diffraction (XRD) of the self-assembly thin film had no characteristic property of SiO2 and even anatase TiO2 but indicated new crystal structure which was determined from the Fourier Transform Infrared Spectrophotometer (FTIR) as a hybridized Ti-O-Si bonding. The surface area and surface volume of the self-assembly sample were increased when SiO2 was incorporated into the film. The self-assembly TiO2-SiO2 thin film exhibited the enhanced photocatalytic decolorization of methylene blue (MB) dye. The advantages of SiO2 are; (1) to increase the adsorbability of the film and (2) to provide the hydroxyl radical to promote the photocatalytic reaction. The self-assembly thin film with the optimum molar ratio (SiO2:TiO2) as 20:80 gave the best performance for photocatalytic decolorization of MB dye with the overall efficiency of 81%.

  1. Preparation and adsorption behavior of berberine hydrochloride imprinted polymers by using silica gel as sacrificed support material

    NASA Astrophysics Data System (ADS)

    Li, Hui; Li, Yuzhuo; Li, Zhiping; Peng, Xiyang; Li, Yanan; Li, Gui; Tan, Xianzhou; Chen, Gongxi

    2012-03-01

    Preparation of berberine hydrochloride (B-Cl) imprinted polymers (MIPs) based on surface imprinting technique with silica gel as sacrificial support material was performed successfully by using B-Cl as template, methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) as functional monomer and cross-linker, respectively. The prepared polymers were characterized by Fourier transmission infrared spectrometry (FTIR) and scanning electron microscopy (SEM). Adsorption behavior of the MIPs for the template and its structural analogues was investigated. Sites distribution on the surface of MIPs was explored by using different isotherm adsorption models and thermodynamic parameters for the adsorption of B-Cl on the MIPs determined. Sample application and reusability for the MIPs was also evaluated. Results indicated the strong adsorption and high selectivity of the MIPs for B-Cl. Saturated adsorption capacity reached 27.2 μmol g-1 and the selectivity coefficient of the MIPs for B-Cl relative to jatrorrhizine hydrochloride (J-Cl) and palmatine palmatus hydrochloride (P-Cl) are 3.70 and 6.03, respectively. In addition, the MIPs were shown with good reusability and selectively retention ability in sample application.

  2. Preparation of amino-Fe(III) functionalized mesoporous silica for synergistic adsorption of tetracycline and copper.

    PubMed

    Zhang, Ziyang; Liu, Huijuan; Wu, Liyuan; Lan, Huachun; Qu, Jiuhui

    2015-11-01

    Finding effective methods for simultaneous removal of antibiotics and heavy metals has attracted increasing concern since both of them are frequently detected in aquatic environments. In this study, a novel mesoporous silica adsorbent (Fe-N,N-SBA15) contained dual-functional groups was synthesized by first grafting di-amino groups on SBA15, and then coordinating Fe(III) onto the adsorbent. The adsorbent was then used in the synchronous elimination of tetracycline (TC) and Cu(II) from water, which was deeply studied by solution pH, kinetics, equilibriums in sole and binary systems. It was found that the adsorbent had high affinity for both TC and Cu(II) and synergistic effects on the adsorption were found. The solution pH remarkably affected the adsorption due to pH-dependent speciation of TC, Cu(II), TC-Cu(II) complex and the surface properties of the adsorbent. Increasing adsorption amount of TC and Cu(II) on the adsorbent could be attributed to the formation of complex TC-Cu(II) bridging or the stronger affinity of the adsorbent for the TC-Cu(II) complex than that for TC or Cu(II) separately. FT-IR and XPS studies revealed that Fe(III) and amino groups on the adsorbent were complexed with the amide of TC and Cu(II), respectively. The recyclabilities of the adsorbent were also evaluated and the Fe-N,N-SBA15 exhibited good reusability for TC and Cu(II) removal. This study shows guidelines and offers an innovative, effective method for the synergistic removal of antibiotics and heavy metals from aquatic environments. PMID:26218342

  3. Preparation of monodisperse polystyrene/silica core-shell nano-composite abrasive with controllable size and its chemical mechanical polishing performance on copper

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Wang, Haibo; Zhang, Zefang; Qin, Fei; Liu, Weili; Song, Zhitang

    2011-11-01

    Monodisperse silica-coated polystyrene (PS) nano-composite abrasives with controllable size were prepared via a two-step process. Monodisperse positively charged PS colloids were synthesized via polymerization of styrene by using a cationic initiator. In the subsequent coating process, silica formed shell on the surfaces of core PS particles via the ammonia-catalyzed hydrolysis and condensation of tetraethoxysilane. Neither centrifugation/water wash/redispersion cycle process nor surface modification or addition surfactant was needed in the whole process. The morphology of the abrasives was characterized by scanning electron microscope. Transmission electron microscope and energy dispersive X-ray analysis results indicated that silica layer was successfully coated onto the surfaces of PS particles. Composite abrasive has a core-shell structure and smooth surface. The chemical mechanical polishing performances of the composite abrasive and conventional colloidal silica abrasive on blanket copper wafers were investigated. The root mean square roughness decreases from 4.27 nm to 0.56 nm using composite abrasive. The PS/SiO2 core-shell composite abrasives exhibited little higher material removal rate than silica abrasives.

  4. Composites of Eu(3+)-doped calcium apatite nanoparticles and silica particles: comparative study of two preparation methods.

    PubMed

    Isobe, Ayumu; Takeshita, Satoru; Isobe, Tetsuhiko

    2015-02-10

    We synthesized composites of Eu(3+)-doped calcium apatite (CaAp:Eu(3+)) nanoparticles and silica particles via two methods: (i) in situ synthesis of CaAp:Eu(3+) in the presence of silica particles and (ii) electrostatic adsorption of CaAp:Eu(3+) nanoparticles on silica particle surfaces. In both methods, submicrometer spherical silica particles were covered with CaAp:Eu(3+) nanoparticles without forming any impurity phases, as confirmed by X-ray diffractometry, Fourier-transform infrared spectroscopy, and scanning electron microscopy. In method i, part of the silica surface acted as a nucleation site for apatite crystals and silica particles were inhomogeneously covered with CaAp:Eu(3+) nanoparticles. In method ii, positively charged CaAp:Eu(3+) nanoparticles were homogeneously adsorbed on the negatively charged silica surface through electrostatic interactions. The bonds between the silica surface and CaAp:Eu(3+) nanoparticles are strong enough not to break under ultrasonic irradiation, irrespective of the synthetic method used. The composite particles showed red photoluminescence corresponding to 4f → 4f transitions of Eu(3+) under near-UV irradiation. Although the absorption coefficient of the forbidden 4f → 4f transitions of Eu(3+) was small, the red emission was detectable with a commercial fluorescence microscope because the CaAp:Eu(3+) nanoparticles accumulated on the silica particle surfaces. PMID:25616077

  5. Preparation and Acid Catalytic Activity of TiO2 Grafted Silica MCM-41 with Sulfate Treatment

    NASA Astrophysics Data System (ADS)

    Guo, Dai-shi; Ma, Zi-feng; Yin, Chun-sheng; Jiang, Qi-zhong

    2008-02-01

    TiO2 grafted silica MCM-41 catalyst with and without sulfate treatment were prepared. The structural and acid properties of these materials were investigated by XRD, N2 adsorption-desorption, element analysis, thermal analysis, Raman and FTIR measurements. Their acid-catalytic activities were evaluated using the cyclization reaction of pseudoionone. It was found that the obtained materials possess well-ordered mesostructure, and the grafted TiO2 components were in highly dispersed amorphous form. T/MCM41 without sulfation contained only Lewis acid sites, while Brønsted and Lewis acidities were remarkably improved for the sulfated materials ST/MCM41 and d-ST/MCM41. T/MCM-41 was not active for the cyclization reaction of pseudoionone, but ST/MCM-41 and d-ST/MCM-41 possessed favorable catalytic activities. The catalytic performance of ST/MCM-41 was comparable with that of the commercial solid acid catalyst of Amberlyst-15, and better than that of d-ST/MCM-41, although the latter underwent a second TiO2 grafting process and accordingly had higher Ti and S content. The specific surface structure of Si-O-Ti-O-S=O in ST/MCM-41 and the bilateral induction effect of Si and S=O on Si-O-Ti bonds were speculated to account for its higher acid catalytic activity.

  6. Preparation and evaluation of surface-bonded tricationic ionic liquid silica as stationary phases for high-performance liquid chromatography.

    PubMed

    Qiao, Lizhen; Shi, Xianzhe; Lu, Xin; Xu, Guowang

    2015-05-29

    Two tricationic ionic liquids were prepared and then bonded onto the surface of supporting silica materials through "thiol-ene" click chemistry as new stationary phases for high-performance liquid chromatography. The obtained columns of tricationic ionic liquids were evaluated respectively in the reversed-phase liquid chromatography (RPLC) mode and hydrophilic interaction liquid chromatography (HILIC) mode, and possess ideal column efficiency of 80,000 plates/m in the RPLC mode with naphthalene as the test solute. The tricationic ionic liquid stationary phases exhibit good hydrophobic and shape selectivity to hydrophobic compounds, and RPLC retention behavior with multiple interactions. In the HILIC mode, the retention and selectivity were evaluated through the efficient separation of nucleosides and bases as well as flavonoids, and the typical HILIC retention behavior was demonstrated by investigating retention changes of hydrophilic solutes with water volume fraction in mobile phase. The results show that the tricationic ionic liquid columns possess great prospect for applications in analysis of hydrophobic and hydrophilic samples. PMID:25890438

  7. Preparation, characterization and application of p-tert-butyl-calix[4]arene-SBA-15 mesoporous silica molecular sieves.

    PubMed

    Huang, Huayu; Zhao, Chuande; Ji, Yongsheng; Nie, Rong; Zhou, Pan; Zhang, Haixia

    2010-06-15

    p-tert-Butyl-calix[4]arene-SBA-15 mesoporous silica molecular sieves have been prepared and characterized by Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD) and nitrogen adsorption-desorption measurements. FT-IR spectra showed the presence of methylene (-CH(2)-), methyl (-CH(3)) and phenyl bands on the modified SBA-15. Powder XRD data indicated the structure of p-tert-butyl-calix[4]arene-SBA-15 remained the host SBA-15 structure. Brunauer-Emmett-Teller (BET) surface area analysis revealed a decrease in surface area and pore size. The adsorption capacity of the materials to diethylstilbestrol and bisphenol A was studied via the dynamic adsorption experiments. The maximum dynamic adsorption capacity on modified materials was 34.8 and 2.9 times higher than SBA-15 particles for diethylstilbestrol and bisphenol A, respectively. The results indicated that p-tert-butyl-calix[4]arene-SBA-15 particles could be used to the enrich the various compounds in water samples before the further analysis. PMID:20185235

  8. Preparation of robust biocatalyst based on cross-linked enzyme aggregates entrapped in three-dimensionally ordered macroporous silica.

    PubMed

    Jiang, Yanjun; Shi, Lianlian; Huang, Yan; Gao, Jing; Zhang, Xu; Zhou, Liya

    2014-02-26

    With the aim to provide a highly stable and active biocatalyst, cross-linked enzyme aggregates (CLEAs) of lipase Candida sp. 99-125 were prepared in three-dimensionally ordered macroporous silica materials (CLEAs-LP@3DOM-SiO2). Lipase Candida sp. 99-125 was first precipitated in the pores of 3DOM SiO2 (named EAs-LP@3DOM-SiO2), and further cross-linked by glutaraldehyde to form CLEAs-LP@3DOM-SiO2. Saturated ammonium sulfate was used as a precipitant and glutaraldehyde with a concentration of 0.25% (w/w) was employed as a cross-linker. Compared with EAs-LP@3DOM-SiO2 and native lipase, CLEAs-LP@3DOM-SiO2 exhibited excellent thermal and mechanical stability, and could maintain more than 85% of initial activity after 16 days of shaking in organic and aqueous phase. When CLEAs-LP@3DOM-SiO2 was applied in esterification and transesterification reactions, improved activity and reusability were achieved. This method can be used for the immobilization of other enzymes of interest. PMID:24484443

  9. 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.

  10. TiO{sub 2} supported on rod-like mesoporous silica SBA-15: Preparation, characterization and photocatalytic behaviour

    SciTech Connect

    Li, Yanjuan; Li, Nan; Tu, Jinchun; Li, Xiaotian; Wang, Beibei; Chi, Yue; Liu, Darui; Yang, Dianfan

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Rod-like SBA-15 and normal SBA-15 were used to prepare TiO{sub 2}/SBA-15 composites. Black-Right-Pointing-Pointer TiO{sub 2}/SBA-15 composites were studied as catalysts for methyl orange photodegradation. Black-Right-Pointing-Pointer TiO{sub 2}/Rod-SBA-15 exhibited higher photocatalytic activity than TiO{sub 2}/Nor-SBA-15. Black-Right-Pointing-Pointer The higher catalytic activity was a result of the controlled morphology of SBA-15. -- Abstract: TiO{sub 2} nanoparticles have been successfully incorporated in the pores of mesoporous silica SBA-15 with different morphologies by a wet impregnation method. The composites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma (ICP) emission spectroscopy, transmission electron microscopy (TEM), N{sub 2}-sorption and UV-Vis diffuse reflectance spectroscopy. The photodegradation of methyl orange (MO) was used to study their photocatalytic property. It is indicated that the morphology of SBA-15 had a great influence on the photocatalytic activity of the composites. When TiO{sub 2}/SBA-15 composite was prepared by loading TiO{sub 2} nanoparticles on uniform rod-like SBA-15 of 1 {mu}m length, it showed higher photocatalytic degradation rate than that on less regular but much larger SBA-15 support. This difference was rationalized in terms of the homogeneously distributed and shorter channels of rod-like SBA-15, which favored mass transport and improved the efficient utilization of the pore surface.

  11. Usefulness of Mesoporous Silica as a Template for the Preparation of Bundles of Bi Nanowires with Precisely Controlled Diameter Below 10 nm.

    PubMed

    Kitahara, Masaki; Kamila, Hasbuna; Shimojima, Atsushi; Wada, Hiroaki; Mori, Takao; Terasaki, Ichiro; Kuroda, Kazuyuki

    2016-03-18

    The reduction of the diameter of Bi nanowires below 10 nm has been an important target because of the theoretical prediction with regard to significant enhancement in thermoelectric performance by size reduction. In this study, we have demonstrated the usefulness of mesoporous silica with tunable pore size as a template for the preparation of thin Bi nanowires with diameters below 10 nm. Bi was deposited within the templates through a liquid phase deposition using hexane and 1,1,3,3-tetramethyldisiloxane as a solvent and reducing agent, respectively. Bundles of thin Bi nanowires with non-crystalline frameworks were successfully obtained after the template removal. The diameter was precisely controlled between about 6 nm and 9 nm. The judicious choices of mesoporous silica and deposition conditions are critical for the successful preparation. The reliable formation of such thin Bi nanowires reported here opens up exciting new possibilities. PMID:26812048

  12. Yb3+-doped large core silica fiber for fiber laser prepared by glass phase-separation technology.

    PubMed

    Chu, Yingbo; Ma, Yunxiu; Yang, Yu; Liao, Lei; Wang, Yibo; Hu, Xiongwei; Peng, Jinggang; Li, Haiqing; Dai, Nengli; Li, Jinyan; Yang, Luyun

    2016-03-15

    We report on the preparation and optical characteristics of an Yb3+-doped large core silica fiber with the active core prepared from nanoporous silica rod by the glass phase-separation technology. The measurements show that the fiber has an Yb3+ concentration of 9811 ppm by weight, a low background attenuation of 0.02 dB/m, and absorption from Yb3+ about 5.5 dB/m at 976 nm. The laser performance presents a high slope efficiency of 72.8% for laser emission at 1071 nm and a low laser threshold of 3 W within only 2.3 m fiber length. It is suggested that the glass phase-separation technology shows great potential for realizing active fibers with larger core and complex fiber designs. PMID:26977675

  13. Studies of the factors effecting the preparation of heterogeneous platinum-based catalyst on silica supports

    SciTech Connect

    Kim, Chang Young; Jung, Chi-Young; Jung, Jae-Woong; Jeong, Sung Hoon; Yi, Sung-Chul; Kim, Wha Jung

    2010-10-15

    Pt nanoparticles with an average size of {approx}3 nm were successfully immobilized on the surface of SiO{sub 2} functionalized with -NH{sub 2} and -SH groups through chemical reduction process using polyvinylpyrrolidone as a stabilizer and different reducing agents. The effects of molecular weight of polyvinylpyrrolidone, molar ratio of reducing agent to Pt salt, type of reducing agent on the size and degree of agglomeration of Pt nanoparticles on the SiO{sub 2} surface were investigated. The X-ray diffraction and transmission electron micrograph analyses were performed to identify the product phase, size and morphology of immobilized Pt onto SiO{sub 2}. UV-vis analysis was also conducted to identify the degree of reduction of Pt ions. The Pt-SiO{sub 2} nanocomposite prepared from both NH{sub 2}- and SH-functionalized SiO{sub 2} exhibited similar behavior. The number of immobilized Pt nanoparticles and their average size was increased with polyvinylpyrrolidone concentration while the number of immobilized Pt was decreased with its molecular weight.

  14. Preparation and characterization of ultrathin dual-layer ionic liquid lubrication film assembled on silica surfaces.

    PubMed

    Pu, Jibin; Wang, Liping; Mo, Yufei; Xue, Qunji

    2011-02-15

    A novel ultrathin dual-layer film, which contained both bonded and mobile phases in ionic liquids (ILs) layer, was fabricated successfully on a silicon substrate modified by a self-assembled monolayer (SAM). The formation and surface properties of the films were analyzed using ellipsometer, water contact angle meter, attenuated total reflectance Fourier transform infrared spectroscopy, multi-functional X-ray photoelectron spectroscopy, and atomic force microscope. Meanwhile, the adhesive and nanotribological behaviors of the films were evaluated by a homemade colloidal probe. A ball-on-plate tribometer was used to evaluate the microtribological performances of the films. Compared with the single-layer ILs film deposited directly on the silicon surface, the as-prepared dual-layer film shows the improved tribological properties, which is attributed to the special chemical structure and outstanding physical properties of the dual-layer film, i.e., the strong adhesion between bonded phase of ILs and silicon substrate via the chemical bonding with SAM, the interlinked hydrogen bonds among the molecules, and two-phase structure composed of steady bonded phase with load-carrying capacity and flowable mobile phase with self-replenishment property. PMID:21111428

  15. The microwave effect on the properties of silica-coated TiO{sub 2} fine particles prepared using sol-gel method

    SciTech Connect

    Furusawa, Takeshi; Honda, Kozue; Ukaji, Emi; Sato, Masahide; Suzuki, Noboru

    2008-04-01

    The silica coating of TiO{sub 2} fine particle was conducted using microwave assisted sol-gel method and conventional sol-gel method to suppress its photo-catalytic activity. The amount and uniformity of silica coating on TiO{sub 2} surface were characterized by X-ray photoelectron spectroscopy (XPS), X-ray fluorescence spectroscopy (XRF), infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and zeta potential measurements. XPS and XRF results showed that the presence of catalyst and reaction time were important factors to reach high silica amounts. SEM, TEM, and zeta potential results indicated that dense film coating of SiO{sub 2} layer formed on TiO{sub 2} surface in conventional sol-gel method, whereas the nucleation coating was observed on sample prepared by microwave assisted sol-gel method. When photo-catalytic activities and ultraviolet (UV) shielding abilities of these samples were evaluated, the sample prepared by microwave processing showed higher inhibition of photo-catalytic activity and better UV shielding ability than the sample prepared by conventional method. These results suggested that the coating method significantly affected the photo-catalytic activity and UV shielding ability of coated TiO{sub 2}.

  16. TiO2 supported over porous silica photocatalysts for pesticide degradation using solar light: Part 2. Silica prepared using acrylic acid emulsion.

    PubMed

    Sharma, Mangalampalli V Phanikrishna; Kumari, Valluri Durga; Subrahmanyam, Machiraju

    2010-03-15

    An acrylic acid emulsion mixture is used for synthesis of novel porous silica (E-Si) material. The photocatalytic activity of TiO2 under solar light irradiation for isoproturon (herbicide) degradation is drastically increased when dispersed over E-Si support using solid state dispersion (SSD) technique. The composite material is characterized by XRD, nitrogen adsorption-desorption isotherms, UV-vis DRS, SEM and TEM measurements. The photocatalytic activities of the composite catalysts are evaluated for different parameters. The 5 wt% TiO2/E-Si is found to be highly active for isoproturon degradation. PMID:19962829

  17. Preparation and photoluminescence of monolithic silica glass doped with Tb3+ ions using SiO2-PVA nanocomposite

    NASA Astrophysics Data System (ADS)

    Ikeda, Hiroshi; Murata, Takahiro; Fujino, Shigeru

    2014-05-01

    The monolithic silica glass doped with Tb3+ ions was fabricated using the SiO2-PVA nanocomposite as the glass precursor. In order to dope Tb3+ ions in the monolithic silica glass, the mesoporous SiO2-PVA nanocomposite was immersed in the Tb3+ ions contained solution and subsequently sintered at 1100 °C in air. Consequently the monolithic transparent silica glass was obtained, exhibiting green fluorescence attributed to 5D4 → 7F5 main transitions under UV excitation. The Tb concentration in the sintered glass could be controlled by immersion time of the nanocomposite in the solution.

  18. 21 CFR 177.2250 - Filters, microporous polymeric.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Filters, microporous polymeric. 177.2250 Section... Repeated Use § 177.2250 Filters, microporous polymeric. Microporous polymeric filters identified in... liquid food. (a) Microporous polymeric filters consist of a suitably permeable, continuous,...

  19. Sol-gel preparation of hydrophobic silica antireflective coatings with low refractive index by base/acid two-step catalysis.

    PubMed

    Cai, Shuang; Zhang, Yulu; Zhang, Hongli; Yan, Hongwei; Lv, Haibing; Jiang, Bo

    2014-07-23

    Hydrophobic antireflective coatings with a low refractive index were prepared via a base/acid-catalyzed two-step sol-gel process using tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as precursors, respectively. The base-catalyzed hydrolysis of TEOS leads to the formation of a sol with spherical silica particles in the first step. In the second step, the acid-catalyzed MTES hydrolysis and condensation occur at the surface of the initial base-catalyzed spherical silica particles, which enlarge the silica particle size from 12.9 to 35.0 nm. By a dip-coating process, this hybrid sol gives an antireflective coating with a refractive index of about 1.15. Moreover, the water contact angles of the resulted coatings increase from 22.4 to 108.7° with the increases of MTES content, which affords the coatings an excellent hydrophobicity. A "core-shell" particle growth mechanism of the hybrid sol was proposed and the relationship between the microstructure of silica sols and the properties of AR coatings was investigated. PMID:24979297

  20. Pyrocarbons prepared by carbonisation of polymers adsorbed or synthesised on a surface of silica and mixed oxides

    NASA Astrophysics Data System (ADS)

    Gun'ko, V. M.; Skubiszewska-Zi ęba, J.; Leboda, R.; Voronin, E. F.; Zarko, V. I.; Levitskaya, S. I.; Brei, V. V.; Guzenko, N. V.; Kazakova, O. A.; Seledets, O.; Janusz, W.; Chibowski, S.

    2004-04-01

    Initial oxides fumed silica, alumina/silica and titania/silica and silica gel and hybrid adsorbents with pyrocarbon formed on these oxide substrates by carbonisation of immobilised (adsorbed or synthesised) polymers such as starch, methyl cellulose, polyvinylpyrrolidone, polystyrene, and polybutylvinyl ether were studied by adsorption, AFM, TEM, and FTIR methods. Polymer/oxide materials were investigated by nitrogen and Pb(II) adsorption, FTIR, and potentiometric titration methods. Analysis of nitrogen adsorption-desorption isotherms by different methods, FTIR spectra, AFM and TEM images of the initial and hybrid adsorbents reveals that the morphology of the substrates significantly changes on carbonisation of oxygen-containing polymers because of hydrothermal treatment of them by water eliminated as a product of pyrolysis. Contribution of own microporosity of pyrocarbon deposits formed on carbonisation of immobilised polymers is greater (dependent on reaction conditions) than that on pyrolysis of low-molecular compounds at the same oxide substrates. Pyrocarbon particles formed on silica gel are larger than those formed on fumed oxides and larger than those formed on silica gel on pyrolysis of low-molecular compounds.

  1. Pressure induced swelling in microporous materials

    DOEpatents

    Vogt, Thomas; Hriljac, Joseph A.; Lee, Yongjae

    2006-07-11

    A method for capturing specified materials which includes contacting a microporous material with a hydrostatic fluid having at least one specified material carried therein, under pressure which structurally distorts the lattice sufficiently to permit entry of the at least one specified material. The microporous material is capable of undergoing a temporary structural distortion which alters resting lattice dimensions under increased ambient pressure and at least partially returning to rest lattice dimensions when returned to ambient pressure. The pressure of the fluid is then reduced to permit return to at least partial resting lattice dimension while the at least one specified material is therein. By this method, at least one specified material is captured in the microporous material to form a modified microporous material.

  2. Well-defined hollow nanochanneled-silica nanospheres prepared with the aid of sacrificial copolymer nanospheres and surfactant nanocylinders

    NASA Astrophysics Data System (ADS)

    Kim, Young Yong; Hwang, Bora; Song, Sungjin; Ree, Brian J.; Kim, Yongjin; Cho, Seo Yeon; Heo, Kyuyoung; Kwon, Yong Ku; Ree, Moonhor

    2015-08-01

    A new approach for synthesizing well-defined hollow nanochanneled-silica nanosphere particles is demonstrated, and the structural details of these particles are described for the first time. Positively charged styrene copolymer nanospheres with a clean, smooth surface and a very narrow size distribution are synthesized by surfactant-free emulsion copolymerization and used as a thermal sacrificial core template for the production of core-shell nanoparticles. A surfactant/silica composite shell with a uniform thickness is successfully produced and deposited onto the polymeric core template by charge density matching between the polymer nanosphere template surface and the negatively charged silica precursors and then followed by selective thermal decomposition of the polymeric core and the surfactant cylinder domains in the shell, producing the hollow nanochanneled-silica nanospheres. Comprehensive, quantitative structural analyses collectively confirm that the obtained nanoparticles are structurally well defined with a hollow core and a shell composed of cylindrical nanochannels that provide facile accessibility to the hollow interior space. Overall, the hollow nanochanneled-silica nanoparticles have great potential for applications in various fields.A new approach for synthesizing well-defined hollow nanochanneled-silica nanosphere particles is demonstrated, and the structural details of these particles are described for the first time. Positively charged styrene copolymer nanospheres with a clean, smooth surface and a very narrow size distribution are synthesized by surfactant-free emulsion copolymerization and used as a thermal sacrificial core template for the production of core-shell nanoparticles. A surfactant/silica composite shell with a uniform thickness is successfully produced and deposited onto the polymeric core template by charge density matching between the polymer nanosphere template surface and the negatively charged silica precursors and then

  3. Preparation of new catalysts by the immobilization of palladium(II) species onto silica: an investigation of their catalytic activity for the cyclization of aminoalkynes.

    PubMed

    Richmond, M K; Scott, S L; Alper, H

    2001-10-31

    Silica-immobilized palladium catalysts are readily prepared by treating partially dehydroxylated silica with solutions of the palladium(II) complexes, cis-[PdMeXL2] (X = Me, L2 = dmpe; X = Cl, L2 = dmpe, dppe, phen, bipy, 2PMe3), trans-[PdMeXL2] (X = Cl, NO3, OTf, L = PMe3; X = Cl, L = PPh3), or [PdPh(OH)L]2 (L = PPh3, PCy3), at room temperature. A chemisorption reaction is presumed to occur on the surface Si-OH groups, with elimination of 1 equiv of methane, benzene, or water and the initial formation of a covalent Pd-O bond to the silica surface. The amount of chemisorbed material is strongly dependent on the nature of the complex employed, and the Pd content of the materials, determined by ICP analysis, was found to vary widely (from 1.47 to 0.021 wt %). It appears that the complexes stabilized by more basic ligands undergo a more facile reaction with the surface. The catalytic activity of the materials was first tested in the cyclization of 6-aminohex-1-yne. Higher conversions were found for those catalysts containing more basic ligands, due to the higher loadings, and for those complexes containing more weakly coordinating anions. Silica/trans-[PdMe(NO3)(PMe3)2] was identified as the best catalyst and was used to test the generality of the catalytic cyclization method with two other alkynes, namely, 5-phenyl-4-pentyn-1-amine and 6-phenyl-5-hexyn-1-amine. The catalysts prepared here show rates comparable to, or greater than, those found for homogeneous late transition metal complexes, including their molecular precursors. Furthermore, the supported catalysts are only slightly air-sensitive and can be recycled, after filtration in air, with only moderate loss of activity. PMID:11673983

  4. [The activity of the lipid peroxidation processes in the mucosa of the rat small intestine and its morphofunctional state under acute irradiation and the administration of combined preparations created on a base of highly dispersed silica].

    PubMed

    Iakubovskiĭ, M M; Pentiuk, A A; Khmelnitskiĭ, O K; Oleĭnik, V N

    1997-01-01

    Morphofunctional and biochemical studies were carried out on bastard male rats (weight 200-240 g). The results showed that X-ray irradiation had induced structural alterations and elevation of lipid peroxidation in small intestine. Using of complex preparations defended this organ against pathological damages. The first preparation provided rat organisms with 100 ml/kg of silica, 2 mg/kg of beta-carotene, 30 mg/kg of alpha-tocopherol and 0.2 mg/kg of natrium selenite. The second preparation provided 100 mg/kg of silica, 10 mg/kg of dry Rhodiola extract, 0.1 mg/kg of tincture of Lagochilus [correction of Ladohilli] inebrians and 0.05 ml/kg of tincture of Aralia mandshurica. The third preparation provided organism with 100 mg/kg of silica and 20 mg/kg of thiobenzimidazole derivative. All these preparations had produced marked pharmacological effect. PMID:9244524

  5. Size and spacial distribution of micropores in SBA-15 using CM-SANS

    SciTech Connect

    Pollock, Rachel A; Walsh, Brenna R; Fry, Jason A; Ghampson, Tyrone; Centikol, Ozgul; Melnichenko, Yuri B; Kaiser, Helmut; Pynn, Roger; Frederick, Brian G

    2011-01-01

    Diffraction intensity analysis of small-angle neutron scattering measurements of dry SBA-15 have been combined with nonlocal density functional theory (NLDFT) analysis of nitrogen desorption isotherms to characterize the micropore, secondary mesopore, and primary mesopore structure. The radial dependence of the scattering length density, which is sensitive to isolated surface hydroxyls, can only be modeled if the NLDFT pore size distribution is distributed relatively uniformly throughout the silica framework, not localized in a 'corona' around the primary mesopores. Contrast matching-small angle neutron scattering (CM-SANS) measurements, using water, decane, tributylamine, cyclohexane, and isooctane as direct probes of the size of micropores indicate that the smallest pores in SBA-15 have diameter between 5.7 and 6.2 {angstrom}. Correlation of the minimum pore size with the onset of the micropore size distribution provides direct evidence that the shape of the smallest micropores is cylinderlike, which is consistent with their being due to unraveling of the polymer template.

  6. Preparation and physical characterization of calcium sulfate cement/silica-based mesoporous material composites for controlled release of BMP-2

    PubMed Central

    Tan, Honglue; Yang, Shengbing; Dai, Pengyi; Li, Wuyin; Yue, Bing

    2015-01-01

    As a commonly used implant material, calcium sulfate cement (CSC), has some shortcomings, including low compressive strength, weak osteoinduction capability, and rapid degradation. In this study, silica-based mesoporous materials such as SBA-15 were synthesized and combined with CSC to prepare CSC/SBA-15 composites. The properties of SBA-15 were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption–desorption isotherms. SBA-15 was blended into CSC at 0, 5, 10, and 20 wt%, referred to as CSC, CSC-5S (5% mass ratio), CSC-10S (10% mass ratio), and CSC-20S (20% mass ratio), respectively. Fourier-transform infrared spectroscopy and compression tests were used to determine the structure and mechanical properties of the composites, respectively. The formation of hydroxyapatite on composite surfaces was analyzed using scanning electron microscopy and X-ray diffraction after soaking in simulated body fluid. BMP-2 was loaded into the composites by vacuum freeze-drying, and its release characteristics were detected by Bradford protein assay. The in vitro degradation of the CSC/SBA-15 composite was investigated by measuring weight loss. The results showed that the orderly, nanostructured, mesoporous SBA-15 possessed regular pore size and structure. The compressive strength of CSC/SBA-15 increased with the increase in SBA-15 mass ratio, and CSC-20S demonstrated the maximum strength. Compared to CSC, hydroxyapatite that formed on the surfaces of CSC/SBA-15 was uniform and compact. The degradation rate of CSC/SBA-15 decreased with increasing mass ratio of SBA-15. The adsorption of BMP-2 increased and released at a relatively slow rate; the release rate of BMP-2 in CSC-20S was the slowest, and presented characteristics of low doses of release. In vitro experiments demonstrated that the physical properties of pure CSC incorporated with SBA-15 could be improved significantly, which made the CSC/SBA-15 composite more suitable for bone repair

  7. Preparation and physical characterization of calcium sulfate cement/silica-based mesoporous material composites for controlled release of BMP-2.

    PubMed

    Tan, Honglue; Yang, Shengbing; Dai, Pengyi; Li, Wuyin; Yue, Bing

    2015-01-01

    As a commonly used implant material, calcium sulfate cement (CSC), has some shortcomings, including low compressive strength, weak osteoinduction capability, and rapid degradation. In this study, silica-based mesoporous materials such as SBA-15 were synthesized and combined with CSC to prepare CSC/SBA-15 composites. The properties of SBA-15 were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. SBA-15 was blended into CSC at 0, 5, 10, and 20 wt%, referred to as CSC, CSC-5S (5% mass ratio), CSC-10S (10% mass ratio), and CSC-20S (20% mass ratio), respectively. Fourier-transform infrared spectroscopy and compression tests were used to determine the structure and mechanical properties of the composites, respectively. The formation of hydroxyapatite on composite surfaces was analyzed using scanning electron microscopy and X-ray diffraction after soaking in simulated body fluid. BMP-2 was loaded into the composites by vacuum freeze-drying, and its release characteristics were detected by Bradford protein assay. The in vitro degradation of the CSC/SBA-15 composite was investigated by measuring weight loss. The results showed that the orderly, nanostructured, mesoporous SBA-15 possessed regular pore size and structure. The compressive strength of CSC/SBA-15 increased with the increase in SBA-15 mass ratio, and CSC-20S demonstrated the maximum strength. Compared to CSC, hydroxyapatite that formed on the surfaces of CSC/SBA-15 was uniform and compact. The degradation rate of CSC/SBA-15 decreased with increasing mass ratio of SBA-15. The adsorption of BMP-2 increased and released at a relatively slow rate; the release rate of BMP-2 in CSC-20S was the slowest, and presented characteristics of low doses of release. In vitro experiments demonstrated that the physical properties of pure CSC incorporated with SBA-15 could be improved significantly, which made the CSC/SBA-15 composite more suitable for bone repair

  8. Sol-gel route to synthesis of microporous ceramic membranes: Thermal stability of TiO[sub 2]-ZrO[sub 2] mixed oxides

    SciTech Connect

    Qunyin Xu; Anderson, M.A. . Water Chemistry Program)

    1993-08-01

    In this paper concerning the synthesis of microporous ceramic membranes, the authors focus on the preparation and thermal stability of unsupported microporous TiO[sub 2]-ZrO[sub 2] mixed-oxide membranes. It has been observed that, by adding up to 20% ZrO[sub 2] into TiO[sub 2] or up to 10% TiO[sub 2] into ZrO[sub 2], these microporous membranes display improved thermal stability. They can be fired up to 500 C for 0.5 h without closing micropores. However, membranes containing almost equal percentages of each component have lost microporous features and have low surface areas and low porosities. A phase diagram of a two-component TiO[sub 2]-ZrO[sub 2] mixed-oxide membrane has been prepared based on DTA and X-ray diffraction data in order to better understand the microstructure changes upon firing.

  9. Preparation of aqueous colloidal mesostructured and mesoporous silica nanoparticles with controlled particle size in a very wide range from 20 nm to 700 nm

    NASA Astrophysics Data System (ADS)

    Yamada, Hironori; Urata, Chihiro; Ujiie, Hiroto; Yamauchi, Yusuke; Kuroda, Kazuyuki

    2013-06-01

    Particle size control of colloidal mesoporous silica nanoparticles (CMPS) in a very wide range is quite significant for the design of CMPS toward various applications, such as catalysis and drug delivery. Various types of CMPS and their precursors (colloidal mesostructured silica nanoparticles (CMSS)) with different particle sizes (ca. 20-700 nm) were newly prepared from tetraalkoxysilanes with different alkoxy groups (Si(OR)4, R = Me, Et, Pr, and Bu) in the presence of alcohols (R'OH, R' = Me, Et, Pr, and Bu) as additives. CMSS with larger particle size were obtained by using tetrabutoxysilane (TBOS) and by increasing the amount of BuOH, which is explained by both the difference in the hydrolysis rates of tetraalkoxysilanes themselves and the effect of added alcohols on the hydrolysis rates of tetraalkoxysilanes. Larger amounts of alcohols with longer alkyl chains decrease the hydrolysis rates of tetraalkoxysilanes and the subsequent formation rates of silica species. Thus, the preferential particle growth of CMSS to nucleation occurs, and larger CMSS are formed. Highly dispersed CMPS were prepared by the removal of surfactants of CMSS by dialysis which can lead to the preparation of CMPS without aggregation. Therefore, the particle size control through the tuning of the hydrolysis rate of tetraalkoxysilanes can be conducted by a one-pot and easy approach. Even larger CMPS (ca. 700 nm in size) show relatively high dispersibility. This dispersibility will surely contribute to the design of materials both retaining nanoscale characteristics and avoiding various nanorisks.Particle size control of colloidal mesoporous silica nanoparticles (CMPS) in a very wide range is quite significant for the design of CMPS toward various applications, such as catalysis and drug delivery. Various types of CMPS and their precursors (colloidal mesostructured silica nanoparticles (CMSS)) with different particle sizes (ca. 20-700 nm) were newly prepared from tetraalkoxysilanes with

  10. Stability of amorphous silica-alumina in hot liquid water.

    PubMed

    Hahn, Maximilian W; Copeland, John R; van Pelt, Adam H; Sievers, Carsten

    2013-12-01

    Herein, the hydrothermal stability of amorphous silica-alumina (ASA) is investigated under conditions relevant for the catalytic conversion of biomass, namely in liquid water at 200 °C. The hydrothermal stability of ASA is much higher than that of pure silica or alumina. Interestingly, the synthetic procedure used plays a major role in its resultant stability: ASA prepared by cogelation (CG) lost its microporous structure, owing to hydrolysis of the siloxane bonds, but the resulting mesoporous material still had a considerable surface area. ASA prepared by deposition precipitation (DP) contained a silicon-rich core and an aluminum-rich shell. In hot liquid water, the latter structure was transformed into a layer of amorphous boehmite, which protected the particle from further hydrolysis. The surface area showed relatively minor changes during the transformation. Independent of the synthetic method used, the ASAs retained a considerable concentration of acid sites. The concentration of acid sites qualitatively followed the changes in surface area, but the changes were less pronounced. The performance of different ASAs for the hydrolysis of cellobiose into glucose is compared. PMID:24124062

  11. Preparation of silica-supported porous sorbent for heavy metal ions removal in wastewater treatment by organic-inorganic hybridization combined with sucrose and polyethylene glycol imprinting.

    PubMed

    Li, Feng; Du, Ping; Chen, Wei; Zhang, Shusheng

    2007-03-01

    A new porous sorbent for wastewater treatment of metal ions was synthesized by covalent grafting of molecularly imprinted organic-inorganic hybrid on silica gel. With sucrose and polyethylene glycol 4000 (PEG 4000) being synergic imprinting molecules, covalent surface coating on silica gel was achieved by using polysaccharide-incorporated sol-gel process starting from the functional biopolymer, chitosan and an inorganic epoxy-precursor, gamma-glycidoxypropyltrimethoxysiloxane (GPTMS) at room temperature. The prepared porous sorbent was characterized by using simultaneous thermogravimetry and differential scanning calorimeter (TG/DSC), scanning electron microscopy (SEM), nitrogen adsorption porosimetry measurement and X-ray diffraction (XRD). Copper ion, Cu(2+), was chosen as the model metal ion to evaluate the effectiveness of the new biosorbent in wastewater treatment. The influence of epoxy-siloxane dose, buffer pH and co-existed ions on Cu(2+) adsorption was assessed through batch experiments. The imprinted composite sorbent offered a fast kinetics for the adsorption of Cu(2+). The uptake capacity of the sorbent imprinted by two pore-building components was higher than those imprinted with only a single component. The dynamic adsorption in column underwent a good elimination of Cu(2+) in treating electric plating wastewater. The prepared composite sorbent exhibited high reusability. Easy preparation of the described porous composite sorbent, absence of organic solvents, cost-effectiveness and high stability make this approach attractive in biosorption. PMID:17386667

  12. Preparation and application of functionalized cellulose acetate/silica composite nanofibrous membrane via electrospinning for Cr(VI) ion removal from aqueous solution.

    PubMed

    Taha, Ahmed A; Wu, Yi-na; Wang, Hongtao; Li, Fengting

    2012-12-15

    Novel NH(2)-functionalized cellulose acetate (CA)/silica composite nanofibrous membranes were successfully prepared by sol-gel combined with electrospinning technology. Tetraethoxysilane (TEOS) as a silica source, CA as precursor and 3-ureidopropyltriethoxysilane as a coupling agent were used in membrane preparation. The membrane's chemical and morphological structures were investigated by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) images, X-ray diffraction (XRD), element analyzer, Fourier-transform infrared spectroscopy (FTIR) and N(2) adsorption-desorption isotherms. The composite nanofibrous membranes exhibited high surface area and porosity. The membranes were used for Cr(VI) ion removal from aqueous solution through static and dynamic experiments. The adsorption behavior of Cr(VI) can be well described by the Langmuir adsorption model, and the maximum adsorption capacity for Cr(VI) is estimated to be 19.46 mg/g. The membrane can be conveniently regenerated by alkalization. Thus the composite membrane prepared from biodegradable raw material has potential applications in the field of water treatment. PMID:22858801

  13. Preparation of micron-sized spherical particles of mesoporous silica from a triblock copolymer surfactant, usable as a stationary phase for liquid chromatography

    NASA Astrophysics Data System (ADS)

    Mesa, Monica; Sierra, Ligia; López, Betty; Ramirez, Alejandro; Guth, Jean-Louis

    2003-09-01

    Spherical particles (∅>3 μm, with 5-10 nm pore size) of SBA15-type mesoporous silica, usable as stationary phase for HPLC, were prepared with tetraethoxysilane (TEOS) as silica source, triblock copolymer Pluronic P123 (EO 20PO 70EO 20) as surfactant S 0 and cetyltrimethylammonium bromide (CTMABr) as co-surfactant S +. The synthesis mechanism involves a surfactant-silica species self-assembly process in acidic medium under quiescent conditions, where S 0H 3O +X -I + and S +X -I + interactions occur. The syntheses were carried out using two procedures: (a) with one heating step and (b) with two heating steps. Synthesis conditions, such as the dilution, temperature and acidity of the reaction mixture and the temperature and duration of the reaction, influence the porous characteristics as well as the morphology and size of the particles. Spherical particles were obtained with one heating step under conditions that weaken the surfactants-silicate interactions such as high dilution, high temperature and low acidity. The modification of the micelle volume with the temperature and acidity allowed the adjustment of the pore size.

  14. Preparation of a nitro-substituted tris(indolyl)methane modified silica in deep eutectic solvents for solid-phase extraction of organic acids.

    PubMed

    Wang, Na; Wang, Jiamin; Liao, Yuan; Shao, Shijun

    2016-05-01

    A new sorbent for solid-phase extraction was synthesized by chemical immobilization of nitro-substituted tris(indolyl)methane on silica in new and green deep eutectic solvents. Elemental analysis results indicated that deep eutectic solvents could be an alternative to the traditional solvents in preparing nitro-substituted tris(indolyl)methane modified silica. Coupled with high performance liquid chromatography, the extraction performance of the sorbent was evaluated by using four organic acids as model analytes. The rebinding experiments results showed that the nitro-substituted tris(indolyl)methane modified silica sorbent had a good adsorption capacity towards the selected organic acids. Under the appropriate experimental conditions, good precision and wide linear ranges with coefficient of determination (R(2)) of higher than 0.9957 were obtained, and the limits of detection were in the range of 0.50-2.0μgL(-1) for the organic acids tested. The developed solid-phase extraction-high performance liquid chromatography-diode array detection (SPE-HPLC-DAD) method was successfully applied for the determination of organic acids in two drinking samples with recoveries ranging from 76.7% to 110.0% and 67.7% to 104.0% for all the selected organic acids, respectively. PMID:26946003

  15. Microporous polyurethane material for size selective heterogeneous catalysis of the Knoevenagel reaction.

    PubMed

    Dey, Sandeep Kumar; de Sousa Amadeu, Nader; Janiak, Christoph

    2016-06-14

    The first polyurethane material which is microporous (BET surface area of 312 m(2) g(-1)) is prepared by solvothermal synthesis and acts as highly efficient and recyclable heterogeneous catalyst in the Knoevenagel condensation showing size selectivity, and in the Henry reaction showing substrate selectivity under mild reaction conditions. PMID:27240738

  16. Micropore extrusion-induced alignment transition from perpendicular to parallel of cylindrical domains in block copolymers.

    PubMed

    Qu, Ting; Zhao, Yongbin; Li, Zongbo; Wang, Pingping; Cao, Shubo; Xu, Yawei; Li, Yayuan; Chen, Aihua

    2016-02-14

    The orientation transition from perpendicular to parallel alignment of PEO cylindrical domains of PEO-b-PMA(Az) films has been demonstrated by extruding the block copolymer (BCP) solutions through a micropore of a plastic gastight syringe. The parallelized orientation of PEO domains induced by this micropore extrusion can be recovered to perpendicular alignment via ultrasonication of the extruded BCP solutions and subsequent annealing. A plausible mechanism is proposed in this study. The BCP films can be used as templates to prepare nanowire arrays with controlled layers, which has enormous potential application in the field of integrated circuits. PMID:26816139

  17. CO2 capture using zeolite 13X prepared from bentonite

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Park, Dong-Wha; Ahn, Wha-Seung

    2014-02-01

    Zeolite 13X was prepared using bentonite as the raw material by alkaline fusion followed by a hydrothermal treatment without adding any extra silica or alumina sources. The prepared zeolite 13X was characterized by X-ray powder diffraction, N2-adsorption-desorption measurements, and scanning electron microscopy. The CO2 capture performance of the prepared zeolite 13X was examined under both static and flow conditions. The prepared zeolite 13X showed a high BET surface area of 688 m2/g with a high micropore volume (0.30 cm3/g), and exhibited high CO2 capture capacity (211 mg/g) and selectivity to N2 (CO2/N2 = 37) at 25 °C and 1 bar. In addition, the material showed fast adsorption kinetics, and stable CO2 adsorption-desorption recycling performance at both 25 and 200 °C.

  18. Hierarchical mesoporous/microporous carbon with graphitized frameworks for high-performance lithium-ion batteries

    SciTech Connect

    Lv, Yingying; Fang, Yin; Qian, Xufang; Tu, Bo; Wu, Zhangxiong; Asiri, Abdullah M.; Zhao, Dongyuan

    2014-11-01

    A hierarchical meso-/micro-porous graphitized carbon with uniform mesopores and ordered micropores, graphitized frameworks, and extra-high surface area of ∼2200 m{sup 2}/g, was successfully synthesized through a simple one-step chemical vapor deposition process. The commercial mesoporous zeolite Y was utilized as a meso-/ micro-porous template, and the small-molecule methane was employed as a carbon precursor. The as-prepared hierarchical meso-/micro-porous carbons have homogeneously distributed mesopores as a host for electrolyte, which facilitate Li{sup +} ions transport to the large-area micropores, resulting a high reversible lithium ion storage of 1000 mA h/g and a high columbic efficiency of 65% at the first cycle.

  19. Highly Monodisperse Microporous Polymeric and Carbonaceous Nanospheres with Multifunctional Properties

    PubMed Central

    Ouyang, Yi; Shi, Huimin; Fu, Ruowen; Wu, Dingcai

    2013-01-01

    Fabrication of monodisperse porous polymeric nanospheres with diameters below 500 nm remains a great challenge, due to serious crosslinking between neighboring nanospheres during pore-making process. Here we show how a versatile hypercrosslinking strategy can be used to prepare monodisperse microporous polystyrene nanospheres (MMPNSs) with diameters as low as ca. 190 nm. In our approach, an unreactive crosslinked PS outer skin as protective layer can be in-situ formed at the very beginning of hypercrosslinking treatment to minimize the undesired inter-sphere crosslinking. The as-prepared MMPNSs with a well-developed microporous network demonstrate unusual multifunctional properties, including remarkable colloidal stability in aqueous solution, good adsorption-release property for drug, and large adsorption capacity toward organic vapors. Surprisingly, MMPNSs can be directly transformed into high-surface-area monodisperse carbon nanospheres with good colloidal stability via a facile hydrothermal-assisted carbonization procedure. These findings provide a new benchmark for fabricating well-defined porous nanospheres with great promise for various applications. PMID:23478487

  20. A regenerable ruthenium tetraammine nitrosyl complex immobilized on a modified silica gel surface: preparation and studies of nitric oxide release and nitrite-to-NO conversion.

    PubMed

    Doro, Fabio Gorzoni; Rodrigues-Filho, Ubirajara P; Tfouni, E

    2007-03-15

    Silica gel bearing isonicotinamide groups was prepared by further modification of 3-aminopropyl-functionalized silica by a reaction with isonicotinic acid and 1,3-dicyclohexylcarbodiimide to yield 3-isonicotinamidepropyl-functionalized silica gel (ISNPS). This support was characterized by means of infrared spectroscopy, elemental analysis, and specific surface area. The ISNPS was used to immobilize the [Ru(NH(3))(4)SO(3)] moiety by reaction with trans-[Ru(NH(3))(4)(SO(2))Cl]Cl, yielding [Si(CH(2))(3)(isn)Ru(NH(3))(4)(SO(3))]. The related immobilized [Si(CH(2))(3)(isn)Ru(NH(3))(4)(L)](3+/2+) (L=SO(2), SO(2-)(4), OH(2), and NO) complexes were prepared and characterized by means of UV-vis and IR spectroscopy, as well as by cyclic voltammetry. Syntheses of the nitrosyl complex were performed by reaction of the immobilized ruthenium ammine [Si(CH(2))(3)(isn)Ru(NH(3))(4)(OH(2))](2+) with nitrite in acid or neutral (pH 7.4) solution. The similar results obtained in both ways indicate that the aqua complex was able to convert nitrite into coordinated nitrosyl. The reactivity of [Si(CH(2))(3)(isn)Ru(NH(3))(4)(NO)](3+) was investigated in order to evaluate the nitric oxide (NO) release. It was found that, upon light irradiation or chemical reduction, the immobilized nitrosyl complex was able to release NO, generating the corresponding Ru(III) or Ru(II) aqua complexes, respectively. The NO material could be regenerated from these NO-depleted materials obtained photochemically or by reduction. Regeneration was done by reaction with nitrite in aqueous solution (pH 7.4). Reduction-regeneration cycles were performed up to three times with no significant leaching of the ruthenium complex. PMID:17196216

  1. A simple and efficient frit preparation method for one-end tapered-fused silica-packed capillary columns in nano-LC-ESI MS.

    PubMed

    Tan, Feng; Chen, Shuo; Zhang, Yangjun; Cai, Yun; Qian, Xiaohong

    2010-04-01

    A novel frit preparation method for one-end tapered-fused silica-packed capillary columns in nano-LC-ESI MS was developed. A hollow-fused silica capillary column with a tapered tip as nano-spray emitter was filled with 5 microm C(18) beads, and then a sintered frit about 0.25 mm in length was prepared at the tip by butane flame. A stainless steel protection tube with 0.5 mm id was used to control the length of the frit and to protect the packed C(18) beads behind the sintered frit during the sintering. C(18) sintered frits were evaluated by BSA tryptic digests with nano-LC-LTQ. The sintered frits did not produce post-column band broadening due to very small volume (about 0.2 nL) and did not produce adsorption to sample. The sintered frit columns had good separation reproducibility and separation performance compared with self-assembled particles frit columns and commercial columns. PMID:20162556

  2. Preparation of magnetic photocatalyst nanoparticles—TiO{sub 2}/SiO{sub 2}/Mn–Zn ferrite—and its photocatalytic activity influenced by silica interlayer

    SciTech Connect

    Laohhasurayotin, Kritapas; Pookboonmee, Sudarat; Viboonratanasri, Duangkamon; Kangwansupamonkon, Wiyong

    2012-06-15

    Highlights: ► TiO{sub 2}/SiO{sub 2}/Mn–Zn ferrite acts as magnetic photocatalyst nanoparticle. ► SiO{sub 2} interlayer is used to prevent electron migration between photocatalyst and magnetic core. ► TiO{sub 2}/Mn–Zn ferrite without SiO{sub 2} interlayer shows poor magnetic and photocatalytic property. -- Abstract: A magnetic photocatalyst, TiO{sub 2}/SiO{sub 2}/Mn–Zn ferrite, was prepared by stepwise synthesis involving the co-precipitation of Mn–Zn ferrite as a magnetic core, followed by a coating of silica as the interlayer, and titania as the top layer. The particle size and distribution of magnetic nanoparticles were found to depend on the addition rate of reagent and dispersing rate of reaction. The X-ray diffractometer and transmission electron microscope were used to examine the crystal structures and the morphologies of the prepared composites. Vibrating sample magnetometer was also used to reveal their superparamagnetic property. The UV–Vis spectrophotometer was employed to monitor the decomposition of methylene blue in the photocatalytic efficient study. It was found that at least a minimum thickness of the silica interlayer around 20 nm was necessary for the inhibition of electron transference initiated by TiO{sub 2} and Mn–Zn ferrite.

  3. C18 silica packed capillary columns with monolithic frits prepared with UV light emitting diode: usefulness in nano-liquid chromatography and capillary electrochromatography.

    PubMed

    D'Orazio, Giovanni; Fanali, Salvatore

    2012-04-01

    In this paper the potential of fused silica capillaries packed with RP18 silica particles entrapped with monolithic frits using both nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) was investigated. Frits were prepared after removing a short part of the polyimide layer on the capillary wall and irradiating the polymerization mixture with an UV-light emitter diode (LED) at 370 nm. The capillary, was rotated during the polymerization procedure in order to obtain a homogeneous monolith. The distance of the LED from the capillary and the exposure time to UV light were studied in order to obtain frits with good porosity and high robustness. A mixture containing five alkylbenzenes was selected as sample and analyzed by both nano-LC and CEC. The standard mixture was baseline separated with good efficiency in the range 78,000-93,000 and 99,000-113,000 plates/m in nano-LC and CEC, respectively. The columns resulted to be very robust and the prepared monolithic frits allowed working with backpressure as high as 400 bar (nano-LC). In addition high voltages were applied in CEC (25-30 kV) without bubbles formation in absence of pressure assistance during runs. PMID:22189300

  4. Preparation and Characterization of Sulfonic Acid Functionalized Silica and Its Application for the Esterification of Ethanol and Maleic Acid

    NASA Astrophysics Data System (ADS)

    Sirsam, Rajkumar; Usmani, Ghayas

    2016-04-01

    The surface of commercially available silica gel, 60-200 mesh size, was modified with sulfonic acid through surface activation, grafting of 3-Mercaptopropyltrimethoxysilane, oxidation and acidification of 3-Mercaptopropylsilica. Sulfonic Acid Functionalization of Silica (SAFS) was confirmed by Fourier Transform Infra-red (FTIR) spectroscopy and thermal gravimetric analysis. Acid-base titration was used to estimate the cation exchange capacity of the SAFS. Catalytic activity of SAFS was judged for the esterification of ethanol with maleic acid. An effect of different process parameters viz. molar ratio, catalyst loading, speed of agitation and temperature were studied and optimized by Box Behnken Design (BBD) of Response Surface Methodology (RSM). Quadratic model developed by BBD-RSM reasonably satisfied an experimental and predicted values with correlation coefficient value R2 = 0.9504.

  5. New Method for Development of Carbon Coated Silica Phases for Liquid Chromatography Part I. Preparation of Carbon Phases

    PubMed Central

    Paek, Changyub; McCormick, Alon V.; Carr, Peter W.

    2011-01-01

    Owing to its combination of unique selectivity and mechanical strength, commercial carbon clad zirconia (C/ZrO2) has been widely used for many applications, including fast two-dimensional liquid chromatography (2DLC). However, the low surface area available (only 20 - 30 m2/g for commercial porous ZrO2) limits its retentivity. We have recently addressed this limitation by developing a carbon phase coated on the high surface area of HPLC grade alumina (C/Al2O3). This material provides higher retentivity and comparable selectivity, but its use is still limited by how few HPLC quality types of alumina particles (e.g., particle size, surface area, pore size) are available. In this work, we have developed useful carbon phases on silica particles, which are available in various particle sizes, pore sizes and forms of HPLC grade. To make the carbon phase on silica, we first treat the silica surface with a monolayer or less of metal cations that bind to deprotonated silanols to provide catalytic sites for carbon deposition. After Al (III) treatment, a carbon phase is formed on the silica surface by chemical vapor deposition at 700 °C using hexane as the carbon source. The amount of Al (III) on the surface was varied to assess its effect on carbon deposition, and the carbon loading was varied at different Al (III) levels to assess its effect on the chromatographic properties of the various carbon adsorbents. We observed that use of a concentration of Al (III) corresponding to a full monolayer leads to the most uniform carbon coating. A carbon coating sufficient to cover all the Al (III) sites, required about 4 – 5 monolayers in this work, provided the best chromatographic performance. The resulting carbon phases behave as reversed phases with reasonable efficiency (50,000 – 79,000 plates/meter) for non-aromatic test species. PMID:21295308

  6. Drug loaded and ethylcellulose coated mesoporous silica for controlled drug release prepared using a pilot scale fluid bed system.

    PubMed

    Hacene, Youcef Chakib; Singh, Abhishek; Van den Mooter, Guy

    2016-06-15

    The goal of this study was to test the feasibility to load non-ordered, non-spherical mesoporous silica with the model drug paracetamol, and subsequently coat the loaded particles using one single pilot scale fluid bed system equipped with a Wurster insert. Mesoporous silica particles (Davisil(®)) with a size ranging from 310 to 500μm and an average pore diameter of 15nm were loaded with paracetamol to 18.8% drug content. Subsequently, loaded cores were coated with ethylcellulose to obtain controlled drug release. Coating processing variables were varied following a full factorial design and their effect on drug release was assessed. Increasing coating solution feed rate and decreasing fluidizing air temperature were found to increase drug release rates. Increasing pore former level and decreasing coating level were found to increase drug release rates. The release medium's osmolality was varied using different sodium chloride concentrations, which was found to affect drug release rates. The results of this study clearly indicate the potential of non-ordered, non-spherical mesoporous silica as a reservoir carrier for the controlled release of drugs. Although non-spherical, we were able to reproducibly coat this carrier using a bottom spray fluid bed system. However, a major hurdle that needs to be tackled is the attrition the material suffers from during fluid bed processing. PMID:27107901

  7. Application of graphene nanoplatelets silica composite, prepared by sol-gel technology, as a novel sorbent in two microextraction techniques.

    PubMed

    Heidari, Mahmoud; Bahrami, Abdolrahman; Ghiasvand, Ali Reza; Shahna, Farshid Ghorbani; Soltanian, Ali Reza; Rafieiemam, Maryam

    2015-12-01

    In this study, the application of a novel nanomaterial composite was investigated in two microextraction techniques of solid-phase microextraction and a needle trap device in a variety of sampling conditions. The optimum sampling temperature and relative humidity were 10°C and 20%, respectively, for both techniques with two sorbents of graphene/silica composite and polydimethyl siloxane. The two microextraction techniques with the proposed sorbent showed recoveries of 95.2 and 94.6% after 7 days. For the needle trap device the optimums desorption time and temperature were 3 min at 290°C and for SPME these measures were 1 and 1.5 min at 240-250°C for the graphene/silica composite and polydimethyl siloxane, respectively. The relative standard division obtained in inter- and intra-day comparative studies were 3.3-14.3 and 5.1-25.4, respectively. For four sample the limit of detection was 0.021-0.25 ng/mL, and the limit of quantitation was 0.08-0.75 ng/mL. The results show that the graphene/silica composite is an appropriate extraction media for both techniques. Combining an appropriate sorbent with microextraction techniques, and using these in conjunction with a sensitive analytical instrument can introduce a strong method for sampling and analysis of occupational and environmental pollutants in air. PMID:26459611

  8. Nanomachines on Porous Silica Nanoparticles for Cargo Delivery

    NASA Astrophysics Data System (ADS)

    Tarn, Derrick

    The field of nanomachines based on mesoporous and microporous silica nanoparticles is a relatively new one, but has quickly gained widespread popularity due to their large potential applications. These porous nanomaterials can both carry and release a therapeutic drug molecule at a targeted location. In order to regulate the movement of cargo, nanomachines are designed and assembled onto the silica nanoparticle, ultimately creating a delivery system on the nanoscale that is capable of a stimulus-responsive delivery of its cargo. This dissertation focuses on the design, synthesis and assembly of nanomachines on both meso- and microporous silica nanoparticles to achieve the goal of cargo delivery. The six chapters of this dissertation are presented as follows: 1) the design, synthesis and modification of silica nanoparticles for their use in biology, 2) a light activated, reversible nanovalve assembled on mesoporous silica nanoparticles to achieve a size-selective cargo delivery, 3) biological applications and the delivery of anti-cancer drugs using a pseudorotaxane-based light activated nanovalve, 4) a nanogate machine that is capable of the storage and delivery of both small metal ions and useful organic cargo molecules, 5) biological applications of the nanogate machine in order to deliver calcium ions to cancerous cells to induce cell apoptosis, and 6) thin wax coated microporous silica nanoparticles that are capable of delivering small ions including oxidizers.

  9. Fabrication of silica-decorated graphene oxide nanohybrids and the properties of composite epoxy coatings research

    NASA Astrophysics Data System (ADS)

    Ma, Yu; Di, Haihui; Yu, Zongxue; Liang, Ling; Lv, Liang; Pan, Yang; Zhang, Yangyong; Yin, Di

    2016-01-01

    With the purpose of preparing anticorrosive coatings, solvent-based epoxy resins often serve as raw material. Unfortunately, plentiful micro-pores are fabricated via solvent evaporation in the resin' curing process, which is an intrinsic shortcoming and it is thus necessary to obstacle their micro-pore for enhancing antiseptic property. To reduce the intrinsic defect and increase the corrosion resistance of coating, we synthesize a series of SiO2-GO hybrids through anchoring silica (SiO2) on graphene oxide (GO) sheets with the help of 3-aminopropyltriethoxysilane and 3-glycidoxypropyltrimethoxysilane, and disperse the hybrids into epoxy resin at a low weight fraction of 2%. Furthermore, we investigate the appropriate preparation proportion of SiO2-GO hybrids (namely: SiO2-GO (1:5)). The electrochemical impedance spectroscopy (EIS) test and coatings' morphology monitoring in corrosion process reveal that the anticorrosive performance of epoxy coatings is significantly enhanced by incorporation of SiO2-GO (1:5) hybrids to epoxy compared with neat epoxy and other nanofillers including SiO2 or GO at the same contents. The superiority of the SiO2-GO (1:5) hybrids is related to their excellent dispersion in resin and sheet-like structure.

  10. Core–shell Ag@SiO{sub 2} nanoparticles of different silica shell thicknesses: Preparation and their effects on photoluminescence of lanthanide complexes

    SciTech Connect

    Kang, Jie; Li, Yuan; Chen, Yingnan; Wang, Ailing; Yue, Bin; Qu, Yanrong; Zhao, Yongliang; Chu, Haibin

    2015-11-15

    Highlights: • Ag@SiO{sub 2} nanoparticles of different silica shell thicknesses were prepared via the Stöber process. • Sm and Dy complexes with benzoate, 1,10-phenanthroline and 2,2′-bipyridine were synthesized. • The complex-doped Ag@SiO{sub 2} composites show stronger luminescent intensities than pure complexes. • The luminescent intensities of the composites strongly depend on the SiO{sub 2} shell thickness. - Abstract: Three kinds of almost spherical core–shell Ag@SiO{sub 2} nanoparticles of different silica shell thicknesses (10, 25 and 80 nm) were prepared via the Stöber process. The Ag core nanoparticles were prepared by reducing silver nitrate with sodium citrate. The size, morphology and structure of core–shell Ag@SiO{sub 2} nanoparticles were characterized by transmission electron microscopy. Subsequently, eight kinds of lanthanide complexes with benzoate, 1,10-phenanthroline and 2,2′-bipyridine were synthesized. The composition of the lanthanide complexes was characterized by elemental analysis, IR and UV spectra. Finally, lanthanide complexes were attached to the surface of Ag@SiO{sub 2} nanoparticles to form lanthanide-complex-doped Ag@SiO{sub 2} nanocomposites. The results show that the complex-doped Ag@SiO{sub 2} nanocomposites display much stronger luminescence intensities than the lanthanide complexes. Furthermore, the luminescence intensities of the lanthanide-complex-doped Ag@SiO{sub 2} nanocomposites with SiO{sub 2} shell thickness of 25 nm are stronger than those of the nanocomposites with SiO{sub 2} shell thickness of 10 and 80 nm.

  11. High-pressure-induced structural changes, amorphization and molecule penetration in MFI microporous materials: a review.

    PubMed

    Vezzalini, Giovanna; Arletti, Rossella; Quartieri, Simona

    2014-06-01

    This is a comparative study on the high-pressure behavior of microporous materials with an MFI framework type (i.e. natural mutinaite, ZSM-5 and the all-silica phase silicalite-1), based on in-situ experiments in which penetrating and non-penetrating pressure-transmitting media were used. Different pressure-induced phenomena and deformation mechanisms (e.g. pressure-induced over-hydration, pressure-induced amorphization) are discussed. The influence of framework and extra-framework composition and of the presence of silanol defects on the response to the high pressure of MFI-type zeolites is discussed. PMID:24892591

  12. Micropore extrusion-induced alignment transition from perpendicular to parallel of cylindrical domains in block copolymers

    NASA Astrophysics Data System (ADS)

    Qu, Ting; Zhao, Yongbin; Li, Zongbo; Wang, Pingping; Cao, Shubo; Xu, Yawei; Li, Yayuan; Chen, Aihua

    2016-02-01

    The orientation transition from perpendicular to parallel alignment of PEO cylindrical domains of PEO-b-PMA(Az) films has been demonstrated by extruding the block copolymer (BCP) solutions through a micropore of a plastic gastight syringe. The parallelized orientation of PEO domains induced by this micropore extrusion can be recovered to perpendicular alignment via ultrasonication of the extruded BCP solutions and subsequent annealing. A plausible mechanism is proposed in this study. The BCP films can be used as templates to prepare nanowire arrays with controlled layers, which has enormous potential application in the field of integrated circuits.The orientation transition from perpendicular to parallel alignment of PEO cylindrical domains of PEO-b-PMA(Az) films has been demonstrated by extruding the block copolymer (BCP) solutions through a micropore of a plastic gastight syringe. The parallelized orientation of PEO domains induced by this micropore extrusion can be recovered to perpendicular alignment via ultrasonication of the extruded BCP solutions and subsequent annealing. A plausible mechanism is proposed in this study. The BCP films can be used as templates to prepare nanowire arrays with controlled layers, which has enormous potential application in the field of integrated circuits. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09140c

  13. Characterization and acidic properties of Al-SBA-15 materials prepared by post-synthesis alumination of a low-cost ordered mesoporous silica

    SciTech Connect

    Gomez-Cazalilla, M.; Merida-Robles, J.M.; Gurbani, A.; Rodriguez-Castellon, E.; Jimenez-Lopez, A.

    2007-03-15

    A series of Al-containing SBA-15 type materials with different Si/Al ratio, were prepared by post-synthesis modification of a pure highly ordered mesoporous silica SBA-15 obtained by using sodium silicate as silica source, and amphiphilic block copolymer as structure-directing agent. A high level of aluminum incorporation was achieved, reaching an Si/Al ratio of up to 5.5, without any significant loss in the textural properties of SBA-15. These materials were fully characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), {sup 27}Al NMR spectroscopy, and N{sub 2} adsorption at 77 K. The acid properties of these materials have been evaluated by NH{sub 3}-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FTIR spectroscopy. The effective acidity of these materials was evaluated using two catalytic reactions: 2-propanol dehydrogenation and 1-butene isomerization. The adsorption of basic probe molecules and the catalytic behavior revealed an evolution of the acid properties with the Al content. These studies have shown that the Al-SBA-15 materials contain Bronsted and Lewis acid sites with medium acidity which makes them appropriate to be used as acid catalysts in heterogeneous catalysis, catalytic supports, and adsorbents. - Graphical abstract: Al KLL spectra of Al-SBA-15 materials with different Si/Al ratios.

  14. Preparation of perfluoro-1,3-propanedisulfonic acid/silica nanocomposites-encapsulated low molecular weight aromatic compounds possessing a nonflammable characteristic.

    PubMed

    Sawada, Hideo; Liu, Xinlai; Goto, Yuki; Kikuchi, Mieko; Tashima, Tsukasa; Nishida, Masakazu

    2011-04-01

    Perfluoro-1,3-propanedisulfonic acid/silica [PFPS/SiO(2)] nanocomposites were prepared by the sol-gel reactions of the corresponding disulfonic acid [PFPS] with tetraethoxysilane and silica nanoparticles under alkaline conditions. These fluorinated nanocomposites thus obtained can exhibit no weight loss behavior corresponding to the contents of PFPS in the composites after calcination at 800°C, although the parent PFPS can decompose completely around 270°C. In addition, we succeeded in encapsulation of a variety of low molecular weight aromatic compounds such as bisphenol-A, bisphenol-AF, bisphenol-F, 4,4'-biphenol and 1,1'-bi-2-naphthol into PFPS/SiO(2) nanocomposite cores. (1)H MAS NMR spectra, UV-vis spectra, fluorescence spectra and HPLC measurements of PFPS/SiO(2) nanocomposites-encapsulated bisphenol-A showed the presence of encapsulated bisphenol-A in the composites before and even after calcination at 800°C. Interestingly, it was verified that fluorescence spectra of PFPS/SiO(2) nanocomposites-encapsulated bisphenol-A after calcination at 800°C can exhibit an extremely red-shifted and enhanced fluorescence peak, compared to that before calcination or parent bisphenol-A. PMID:21256504

  15. Preparation and evaluation of monodispersed, submicron, non-porous silica particles functionalized with β-CD derivatives for chiral-pressurized capillary electrochromatography.

    PubMed

    Yangfang, Lu; Hui, Wang; Yun, Xue; Xue, Gu; Yan, Wang; Chao, Yan

    2015-09-01

    Submicron, non-porous, chiral silica stationary phase has been prepared by the immobilization of functionalized β-CD derivatives to isocyanate-modified silica via chemical reaction and applied to the pressurized capillary electrochromatography (pCEC) enantio-separation of various chiral compounds. The submicron, non-porous, cyclodextrin-based chiral stationary phases (sub_μm-CSP2) exhibited excellent chiral recognition of a wide range of analytes including clenbuterol hydrochloride, mexiletine hydrochloride, chlorpheniramine maleate, esmolol hydrochloride, and metoprolol tartrate. The synthesized submicron particles were regularly spherical and uniformly non-porous with an average diameter of around 800 nm and a mean pore size of less than 2 nm. The synthesized chiral stationary phase was packed into 10 cm × 100 μm id capillary columns. The sub_μm-CSP2 column used in the pCEC system showed better separation of the racemates and at a higher rate compared to those used in the capillary liquid chromatography mode (cLC) system. The sub_μm-CSP2 possessed high mechanical strength, high stereoselectivity, and long lifespan, demonstrating rapid enantio-separation and good resolution of samples. The column provided an efficiency of up to 170,000 plates/m for n-propylbenzene. PMID:25990895

  16. N-TiO2 nanoparticles embedded in silica prepared by Ti ion implantation and annealing in nitrogen

    SciTech Connect

    Xiang, Xia; Chen, Meng; Ju, Yongfeng; Zu, Xiaotao T.; Wang, Lumin M.; Zhang, Yanwen

    2010-05-01

    Room temperature Ti ion implantation and subsequent thermal annealing in N2 ambience have been used to fabricate the anatase and rutile structured N-doped TiO2 particles embedded in the surface region of fused silica. The Stopping and Range of Ions in Matter (SRIM) code simulation indicates a Gaussian distribution of implanted Ti, with a projected range of 74.4 nm and straggling of 16.5 nm. However, Rutherford backscattering spectrometry and transmission electron microscopy results show a much shallower distribution peaked at ~ 30 nm. Significant sputtering loss of silica substrates has occurred during implantation. Nanoparticles with size of 10-20 nm in diameter have formed after implantation. X-ray photoelectron spectroscopy indicates the coexistence of TiO2 and metallic Ti in the as-implanted samples. Metallic Ti is oxidized to anatase TiO2 after annealing at 600ºC, while rutile TiO2 forms by phase transformation after annealing at 900ºC. At the same time, N-Ti-O, Ti-O-N and/or Ti-N-O linkages have formed in the lattice of TiO2. A red shift of 0.34 eV in the absorption edge is obtained for N-doped anatase TiO2 after annealing at 600 ºC for 6 h. The absorbance increases in the ultraviolet and visible waveband.

  17. Preparation, characterization and luminescent properties of dense nano-silica hybrids loaded with 1,8-naphthalic anhydride.

    PubMed

    Wang, Jinpeng; Sun, Jihong; Li, Yuzhen; Wang, Feng

    2014-03-01

    Novel luminescent dense nano-silica hybrid materials (DNSS) modified with different amounts of (3-aminopropyl)triethoxysilane (APTES) and 1,8-naphthalic anhydride (NA) were successfully synthesized via two steps combined with post-grafting methods. Powder X-ray diffraction (XRD), N2-sorption analysis, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), photoluminescence (PL) spectroscopy and elemental analysis, as well as time-resolved decays were employed to characterize the resultant hybrid materials. The results revealed that luminescent organic molecules had been successfully loaded onto the amine-modified surface of nano-silica spheres. In addition, their fluorescence intensity and characteristic peak of emission spectra changed with increasing amount of APTES and NA additive. In particular, the characteristic peak showed a red shift from 390 to 450 nm, however, this was inconsistent with results calculated on the basis of the elemental analysis data, most probably because of the dispersion behaviors of NA molecules from the aggregating to the monolayer state. These observations demonstrated the existence of a quantum confinement effectiveness of NA-DNSS samples, and therefore a possible mechanism was put forward. PMID:23765586

  18. Synthesis and characterization of high-surface-area millimeter-sized silica beads with hierarchical multi-modal pore structure by the addition of agar

    SciTech Connect

    Han, Yosep; Choi, Junhyun; Tong, Meiping; Kim, Hyunjung

    2014-04-01

    Millimeter-sized spherical silica foams (SSFs) with hierarchical multi-modal pore structure featuring high specific surface area and ordered mesoporous frameworks were successfully prepared using aqueous agar addition, foaming and drop-in-oil processes. The pore-related properties of the prepared spherical silica (SSs) and SSFs were systematically characterized by field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), small-angle X-ray diffraction (SAXRD), Hg intrusion porosimetry, and N{sub 2} adsorption–desorption isotherm measurements. Improvements in the BET surface area and total pore volume were observed at 504 m{sup 2} g{sup −1} and 5.45 cm{sup 3} g{sup −1}, respectively, after an agar addition and foaming process. Despite the increase in the BET surface area, the mesopore wall thickness and the pore size of the mesopores generated from the block copolymer with agar addition were unchanged based on the SAXRD, TEM, and BJH methods. The SSFs prepared in the present study were confirmed to have improved BET surface area and micropore volume through the agar loading, and to exhibit interconnected 3-dimensional network macropore structure leading to the enhancement of total porosity and BET surface area via the foaming process. - Highlights: • Millimeter-sized spherical silica foams (SSFs) are successfully prepared. • SSFs exhibit high BET surface area and ordered hierarchical pore structure. • Agar addition improves BET surface area and micropore volume of SSFs. • Foaming process generates interconnected 3-D network macropore structure of SSFs.

  19. A dual-spatially-confined reservoir by packing micropores within dense graphene for long-life lithium/sulfur batteries

    NASA Astrophysics Data System (ADS)

    Li, Hongfei; Yang, Xiaowei; Wang, Xiaomin; He, Yu-Shi; Ye, Fangmin; Liu, Meinan; Zhang, Yuegang

    2016-01-01

    In lithium/sulfur batteries, micropores could bring about strong interactions with polysulfides, but could not alleviate the partial polysulfide overflowing outside because of the volume expansion of the lithiated sulfur. A dual-spatially-confined reservoir for sulfur by wrapping microporous carbon with dense graphene, micro@meso-porous DSC (dual-spatial carbon), is synthesized to solve this issue. Such a structure is prepared through two distinctive methods: graphene promoted in situ hydrothermal carbonization of organics to grow micropores on itself, and liquid mediated drying of graphene hydrogel to form mesoporous graphene frameworks. In contrast to previously reported hierarchical carbon/S, the inner micropores are mainly responsible for loading sulfur, which could help confine its particle size, thus increasing the electrical/ionic conductivity and the utilization of sulfur, and restrain lithium polysulfide dissolution because of strong interaction with pore walls; while the outer mesopores act as another reservoir to stabilize the overflowed polysulfide and to enhance the Li+ transport. The S-micro@meso-porous DSC cathode exhibits better discharge capacity and cycling performance than S-microporous AC and S-micro@macro-porous DSC, i.e., 59% and 37% higher capacity remaining at 0.5 C than the latter two, respectively.In lithium/sulfur batteries, micropores could bring about strong interactions with polysulfides, but could not alleviate the partial polysulfide overflowing outside because of the volume expansion of the lithiated sulfur. A dual-spatially-confined reservoir for sulfur by wrapping microporous carbon with dense graphene, micro@meso-porous DSC (dual-spatial carbon), is synthesized to solve this issue. Such a structure is prepared through two distinctive methods: graphene promoted in situ hydrothermal carbonization of organics to grow micropores on itself, and liquid mediated drying of graphene hydrogel to form mesoporous graphene frameworks. In

  20. Preparation and characterization of ammonium-functionalized silica nanoparticle as a new adsorbent to remove methyl orange from aqueous solution

    NASA Astrophysics Data System (ADS)

    Liu, Jinshui; Ma, Shi; Zang, Lingjie

    2013-01-01

    Quaternary ammonium polyethylenimine (PEI) was successfully modified to silica nanoparticle (QPEI/SiO2) as a new adsorbent to remove methyl orange from aqueous solution. The isotherm and kinetics of dye adsorption were studied, which showed that Langmuir isotherm fit the experimental results well. The maximum adsorption capacity of QPEI/SiO2 for methyl orange is 105.4 mg/g. The equilibrium time for methyl orange adsorption onto QPEI/SiO2 was as short as 10 min, indicating that the adsorbent has a strong affinity for methyl orange. The adsorption capacities of the methyl orange are slightly influenced by the pH in the range of 3.2-9.6. The QPEI/SiO2 adsorbent can be used in the wide pH range, which is different from other adsorbent. This may attribute to the quaternary ammonium carrying positive charges in acidic and basic solution.

  1. Characteristics of ultra low-k nanoporous and fluorinated silica based films prepared by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Abbasi-Firouzjah, M.; Shokri, B.

    2013-12-01

    Low dielectric constant (low-k) silica based films were deposited on p-type silicon and polycarbonate substrates by radio frequency (RF) plasma enhanced chemical vapor deposition method at low temperature. A mixture of tetraethoxysilane vapor, oxygen, and tetrafluoromethane (CF4) was used for the deposition of the films in forms of two structures called as SiOxCy and SiOxCyFz. Properties of the films were controlled by amount of porosity and fluorine content in the film matrix. The influence of RF power and CF4 flow on the elemental composition, deposition rate, surface roughness, leakage current, refractive index, and dielectric constant of the films were characterized. Moreover, optical emission spectroscopy was applied to monitor the plasma process at the different parameters. Electrical characteristics of SiOxCy and SiOxCyFz films with metal-oxide-semiconductor structure were investigated using current-voltage analysis to measure the leakage current and breakdown field, as well as capacitance-voltage analysis to obtain the film's dielectric constant. The results revealed that SiOxCy films, which are deposited at lower RF power produce more leakage current, meanwhile the dielectric constant and refractive index of these films decreased mainly due to the more porosity in the film structure. By adding CF4 in the deposition process, fluorine, the most electronegative and the least polarized atom, doped into the silica film and led to decrease in the refractive index and the dielectric constant. In addition, no breakdown field was observed in the electrical characteristics of SiOxCyFz films and the leakage current of these films reduced by increment of the CF4 flow.

  2. Characteristics of ultra low-k nanoporous and fluorinated silica based films prepared by plasma enhanced chemical vapor deposition

    SciTech Connect

    Abbasi-Firouzjah, M.; Shokri, B.

    2013-12-07

    Low dielectric constant (low-k) silica based films were deposited on p-type silicon and polycarbonate substrates by radio frequency (RF) plasma enhanced chemical vapor deposition method at low temperature. A mixture of tetraethoxysilane vapor, oxygen, and tetrafluoromethane (CF{sub 4}) was used for the deposition of the films in forms of two structures called as SiO{sub x}C{sub y} and SiO{sub x}C{sub y}F{sub z}. Properties of the films were controlled by amount of porosity and fluorine content in the film matrix. The influence of RF power and CF{sub 4} flow on the elemental composition, deposition rate, surface roughness, leakage current, refractive index, and dielectric constant of the films were characterized. Moreover, optical emission spectroscopy was applied to monitor the plasma process at the different parameters. Electrical characteristics of SiO{sub x}C{sub y} and SiO{sub x}C{sub y}F{sub z} films with metal-oxide-semiconductor structure were investigated using current-voltage analysis to measure the leakage current and breakdown field, as well as capacitance-voltage analysis to obtain the film's dielectric constant. The results revealed that SiO{sub x}C{sub y} films, which are deposited at lower RF power produce more leakage current, meanwhile the dielectric constant and refractive index of these films decreased mainly due to the more porosity in the film structure. By adding CF{sub 4} in the deposition process, fluorine, the most electronegative and the least polarized atom, doped into the silica film and led to decrease in the refractive index and the dielectric constant. In addition, no breakdown field was observed in the electrical characteristics of SiO{sub x}C{sub y}F{sub z} films and the leakage current of these films reduced by increment of the CF{sub 4} flow.

  3. Exploring meso-/microporous composite molecular sieves with core-shell structures.

    PubMed

    Qian, Xufang F; Li, Bin; Hu, Yuanyuan Y; Niu, Guoxing X; Zhang, D Yahong H; Che, Renchao C; Tang, Yi; Su, Dangsheng S; Asiri, Abdullah M; Zhao, Dongyuan Y

    2012-01-16

    A series of core-shell-structured composite molecular sieves comprising zeolite single crystals (i.e., ZSM-5) as a core and ordered mesoporous silica as a shell were synthesized by means of a surfactant-directed sol-gel process in basic medium by using cetyltrimethylammonium bromide (CTAB) as a template and tetraethylorthosilicate (TEOS) as silica precursor. Through this coating method, uniform mesoporous silica shells closely grow around the anisotropic zeolite single crystals, the shell thickness of which can easily be tuned in the range of 15-100 nm by changing the ratio of TEOS/zeolite. The obtained composite molecular sieves have compact meso-/micropore junctions that form a hierarchical pore structure from ordered mesopore channels (2.4-3.0 nm in diameter) to zeolite micropores (≈0.51 nm). The short-time kinetic diffusion efficiency of benzene molecules within pristine ZSM-5 (≈7.88×10(-19)  m(2)  s(-1)) is almost retainable after covering with 75 nm-thick mesoporous silica shells (≈7.25×10(-19)  m(2)  s(-1)), which reflects the greatly opened junctions between closely connected mesopores (shell) and micropores (core). The core-shell composite shows greatly enhanced adsorption capacity (≈1.35 mmol  g(-1)) for large molecules such as 1,3,5-triisopropylbenzene relative to that of pristine ZSM-5 (≈0.4 mmol  g(-1)) owing to the mesoporous silica shells. When Al species are introduced during the coating process, the core-shell composite molecular sieves demonstrate a graded acidity distribution from weak acidity of mesopores (predominant Lewis acid sites) to accessible strong acidity of zeolite cores (Lewis and Brønsted acid sites). The probe catalytic cracking reaction of n-dodecane shows the superiority of the unique core-shell structure over pristine ZSM-5. Insight into the core-shell composite structure with hierarchical pore and graded acidity distribution show great potential for petroleum catalytic processes. PMID

  4. Wear and Friction Behavior of Metal Impregnated Microporous Carbon Composites

    NASA Technical Reports Server (NTRS)

    Goller, Gultekin; Koty, D. P.; Tewari, S. N.; Singh, M.; Tekin, A.

    1996-01-01

    Metal-matrix composites have been prepared by pressure-infiltration casting of copper-base alloy melts into microporous carbon preforms. The carbon preforms contained varying proportions of amorphous carbon and graphite. Load dependence of the wear and friction behavior of the composite pins has been examined under ambient conditions against cast-iron plates, using a pin-on-plate reciprocating wear tester. The wear resistance of the composite is significantly improved, as compared with the base alloy. Contrary to the normally expected behavior, the addition of graphite to the amorphous carbon does not reduce the friction coefficient, especially at high loads. The wear and friction behavior of the composites is very sensitive to the size and distribution of the microstructural constituents.

  5. Method for making a microporous membrane

    NASA Technical Reports Server (NTRS)

    Gavalas, Lillian Susan (Inventor)

    2013-01-01

    A method for making a microporous membrane comprises the steps of: providing a plurality of carbon nanotubes having a hollow interior diameter of 20 Angstroms or less; sonicating the plurality of carbon nanotubes utilizing a solution comprising deionized, distilled water and a surfactant that coats at least one of the plurality of carbon nanotubes; collecting the coated carbon nanotubes; forming a matrix that supports the plurality of carbon nanotubes; embedding the coated carbon nanotubes into the matrix; rinsing the coated nanotubes to remove at least a portion of the surfactant; curing the nanotube-matrix assembly; and cutting the nanotube-matrix assembly to a particular thickness so as to open the ends of the embedded nanotubes. The hollow interiors of the plurality of embedded carbon nanotubes comprise the pores of the microporous membrane.

  6. Electron transfer reactions in microporous solids

    SciTech Connect

    Mallouk, T.E.

    1993-01-01

    Basic thrust the research program involves use of microporous solids (zeolites, clays, layered and tunnel structure oxide semiconductors) as organizing media for artificial photosynthetic systems. Purpose of the microporous solid is twofold. First, it induces spatial organization of photoactive and electroactive components (sensitizers, semiconductor particles, electron relays, and catalysts) at the solid-solution interface, enhancing the quantum efficiency of charge separation and separating physically the ultimate electron donor and acceptor in the electron transport chain. Second, since the microcrystalline solid admits only molecules of a certain charge and size, it is possible to achieve permanent charge separation by sieving chemical photoproducts (e.g., H[sub 2] and I[sub 3][sup [minus

  7. Cellulose-silica aerogels.

    PubMed

    Demilecamps, Arnaud; Beauger, Christian; Hildenbrand, Claudia; Rigacci, Arnaud; Budtova, Tatiana

    2015-05-20

    Aerogels based on interpenetrated cellulose-silica networks were prepared and characterised. Wet coagulated cellulose was impregnated with silica phase, polyethoxydisiloxane, using two methods: (i) molecular diffusion and (ii) forced flow induced by pressure difference. The latter allowed an enormous decrease in the impregnation times, by almost three orders of magnitude, for a sample with the same geometry. In both cases, nanostructured silica gel was in situ formed inside cellulose matrix. Nitrogen adsorption analysis revealed an almost threefold increase in pores specific surface area, from cellulose aerogel alone to organic-inorganic composite. Morphology, thermal conductivity and mechanical properties under uniaxial compression were investigated. Thermal conductivity of composite aerogels was lower than that of cellulose aerogel due to the formation of superinsulating mesoporous silica inside cellulose pores. Furthermore, composite aerogels were stiffer than each of reference aerogels. PMID:25817671

  8. Large-Pore Mesoporous Silica with Three-Dimensional Wormhole Framework Structures.

    PubMed

    Park, In; Pinnavaia, Thomas J

    2009-02-01

    Large-pore mesoporous silica with 3D wormhole framework structures (denoted MSU-J) are prepared through a supramolecular hydrogen-bonding assembly pathway from low-cost sodium silicate as the silica source and commercially available mono- and triamine Jeffamine and Surfonamine surfactants as structure-directing porogens. The calcined mesostructures exhibit large pore sizes (up to 8.2 nm), surface areas (632-1030 m(2)/g) and pore volumes (0.5-2.0 cm(3)/g), depending on the surfactant chain length and synthesis temperature (25-65 °C). The textural properties of these new wormhole mesostructures are comparable to those of hexagonal SBA-15 derivatives and large pore MCM-48. However, unlike the SBA-15 structure type, wherein the 3D pore network is formed by connecting 1D cylindrical mesopores through micropores, MSU-J mesophases have wormhole framework structures containing fully interconnected 3D mesopores that can minimize the diffusion limitations often encountered in adsorption and chemical catalysis. Also, unlike large pore MCM-48, which requires cost-intensive tetraethylorthosilicate as a silica source and the use of a co-surfactant as a pore expander under strong acid conditions, MSU-J mesostructures are assembled from low cost sodium silicate in the presence of a single Jeffamine or Surfonamine porogen at near-neutral pH. PMID:20126285

  9. Encapsulation of ruthenium nitrosylnitrate and DNA purines in nanostructured sol-gel silica matrices.

    PubMed

    Lopes, Luís M F; Garcia, Ana R; Fidalgo, Alexandra; Ilharco, Laura M

    2009-09-01

    The interactions between DNA purines (guanine and adenine) and the ruthenium complex Ru(NO)(NO(3))(3) were studied within nanostructured silica matrices prepared by a two-step sol-gel process. By infrared analysis in diffuse reflectance mode, it was proved that encapsulation induces a profound modification on the complex, whereas guanine and adenine preserve their structural integrity. The complex undergoes nitrate ligand exchange and co-condenses with the silica oligomers, but the nitrosyl groups remain stable, which is an unusual behavior in Ru nitrosyl complexes. In turn, the doping molecules affect the sol-gel reactions and eventually the silica structure as it forms: the complex yields a microporous structure, and the purine bases are responsible for the creation of macropores due to hydrogen bonding with the silanol groups of the matrix. In a confined environment, the interactions are much stronger for the coencapsulated pair guanine complex. While adenine only establishes hydrogen bonds or van der Waals interactions with the complex, guanine bonds covalently to Ru by one N atom of the imidazole ring, which becomes strongly perturbed, resulting in a deformation of the complex geometry. PMID:19499946

  10. Microporous polyimide films for reduced dielectric applications

    SciTech Connect

    Saunders, R.S.; Aubert, J.H.; McNamara, W.F.

    1996-08-01

    Limiting factor to computer chip speed and size is the dielectric constant of the interlayer insulating materials, which has been reduced going from inorganic to organic type materials. A further reduction, together with better mechanical properties, is still needed. We have developed a spincoating method in conjunction with a thermodynamic process (Non-solvent Induced Phase Separation) to create microporous polyimide films with both lower dielectric constant and better stress reduction properties compared to solid films. In this method, we spincoat a soluble polyimide solution in 1, 3-dimethoxybenzene solvent onto a Si wafer, and then immediately submerse the wet polymer film into a non-solvent bath, typically toluene. Phase separation of the polymer occurs on a micron size scale and the resulting microporous structure becomes locked in by the high glass transition temperature of the polyimide. Factors affecting film morphology, thickness, pore size, and % porosity include polymer concentration, spin speed, and non-solvent type. Morphology is explained in terms of thermodynamics and kinetics of phase separation and diffusion, using an idealized ternary phase diagram. One particular film having 68% porosity, 22 microns thickness, and 1.4 micron pore size had a dielectric constant of 1.88 and loss of 0.002. Stress measurements indicated that the microporous film reduced surface stress on the wafer by more than a factor of 10 compared to analogous solid polyimide film.

  11. Inorganic dual-layer microporous supported membranes

    DOEpatents

    Brinker, C. Jeffrey; Tsai, Chung-Yi; Lu, Yungfeng

    2003-03-25

    The present invention provides for a dual-layer inorganic microporous membrane capable of molecular sieving, and methods for production of the membranes. The inorganic microporous supported membrane includes a porous substrate which supports a first inorganic porous membrane having an average pore size of less than about 25 .ANG. and a second inorganic porous membrane coating the first inorganic membrane having an average pore size of less than about 6 .ANG.. The dual-layered membrane is produced by contacting the porous substrate with a surfactant-template polymeric sol, resulting in a surfactant sol coated membrane support. The surfactant sol coated membrane support is dried, producing a surfactant-templated polymer-coated substrate which is calcined to produce an intermediate layer surfactant-templated membrane. The intermediate layer surfactant-templated membrane is then contacted with a second polymeric sol producing a polymeric sol coated substrate which is dried producing an inorganic polymeric coated substrate. The inorganic polymeric coated substrate is then calcined producing an inorganic dual-layered microporous supported membrane in accordance with the present invention.

  12. Preparation, surface characterization and performance of a Fischer-Tropsch catalyst of cobalt supported on silica nanosprings

    NASA Astrophysics Data System (ADS)

    Kengne, Blaise-Alexis Fouetio; Alayat, Abdulbaset M.; Luo, Guanqun; McDonald, Armando G.; Brown, Justin; Smotherman, Hayden; McIlroy, David N.

    2015-12-01

    The reduction of cobalt (Co) catalyst supported on silica nanosprings for Fischer-Tropsch synthesis (FTS) has been monitored by X-ray photoelectron spectroscopy (XPS) and compared to FT catalytic activity. The cobalt is present in the starting catalyst as a Co3O4 spinel phase. A two-step reduction of Co3O4 to CoO and then to Co0 is observed, which is consistent with the results of H2-temperature programmed reduction. During the reduction the two steps occur concurrently. The deconvolution of the Co 2p core level state for the catalyst reduced at 385 °C and 1.0 × 10-6 Torr of H2 revealed signatures of Co0, CoO, and Co3O4. The reduction saturates at a Coo concentration of approximately 41% after 20 h, which correlates with the activity and lifetime of the catalyst during FTS testing. Conversely, at 680 °C and 10 Torr of H2, the catalyst is completely reduced after 10 h. The evolution of the Co d-band at the Fermi level in the valence band XPS spectrum definitively verifies the metallic phase of Co. FTS evaluation of the Co/NS catalyst reduced at 609 °C showed higher production rate (3-fold) of C6-C17 hydrocarbons than the catalyst reduced at 409 °C and is consistent with the XPS analysis.

  13. Preparation and characterization of micro-cell membrane chromatographic column with silica-based porous layer open tubular capillary as cellular membrane carrier.

    PubMed

    Zhang, Fugeng; Zhao, Xinchao; Xu, Bei; Cheng, Shuai; Tang, Cheng; Duan, Hongquan; Xiao, Xuefeng; Du, Wuxun; Xu, Liang

    2016-04-01

    Cell membrane chromatography (CMC) is a powerful tool to study membrane protein interactions and to screen active compounds extracted from natural products. Unfortunately, a large amount of cells are typically required for column preparation in order to carry out analyses in an efficient manner. Micro-CMC (mCMC) has recently been developed by using a silica capillary as a membrane carrier. However, a reduced retention of analytes is generally associated with mCMC mostly due to a low ligand (cellular membrane) capacity. To solve this common problem, in this work a silica-based porous layer open tubular (PLOT) capillary was fabricated and, to the best of our knowledge, for the first time applied to mCMC. The mCMC column was prepared by physical adsorption of rabbit red blood cell (rRBC) membranes onto the inner surface of the PLOT capillary. The effects of the PLOT capillaries fabricated by different feed compositions, on the immobilization amount of cellular membranes (represented by the fluorescence intensity of the capillary immobilized with fluorescein isothiocyanate isomer-labeled cellular membranes) and on the dynamic binding capacity (DBC) of verapamil (VP, a widely used calcium antagonist which specific interacts with L-type calcium channel proteins located on cellular membrane of rRBC) have been systematically investigated. The fluorescence intensity of the mCMC column when combined with the PLOT capillary was found to be more than five times higher than the intensity using a bare capillary. This intriguing result indicates that the PLOT capillary exhibits a higher cellular membrane capacity. The DBC of VP in the PLOT column was found to be more than nine times higher than that in the bare capillary. An rRBC/CMC column was also prepared for comparative studies. As a result, mCMC provides similar chromatographic retention factors and stability with common CMC; however, the cellular membrane consumption for mCMC was found to be more than 460 times lower than

  14. One-pot preparation of a mixed-mode organic-silica hybrid monolithic capillary column and its application in determination of endogenous gibberellins in plant tissues.

    PubMed

    Zhang, Zheng; Hao, Yan-Hong; Ding, Jun; Xu, Sheng-Nan; Yuan, Bi-Feng; Feng, Yu-Qi

    2015-10-16

    A newly improved one-pot method, based on "thiol-ene" click chemistry and sol-gel approach in microemulsion system, was developed for the preparation of C8/PO(OH)2-silica hybrid monolithic capillary column. The prepared monolith possesses large specific surface area, narrow mesopore size distribution and high column efficiency. The monolithic column was demonstrated to have cation exchange/reversed-phase (CX/RP) mixed-mode retention for analytes on nano-liquid chromatography (nano-LC). On the basis of the developed nano-LC system with MS detector coupled to pipette tip solid phase extraction (PT-SPE) and derivatization process, we then realized simultaneous determination of 10 gibberellins (GAs) with low limits of detection (LODs, 0.003-0.025 ng/mL). Furthermore, 6 endogenous GAs in only 5mg rice leaves (fresh weight) were successfully detected and quantified. The developed PT-SPE-nano-LC-MS strategy may offer promising applications in the determination of low abundant bioactive molecules from complex matrix. PMID:26365908

  15. Preparation of hybrid organic-inorganic mesoporous silicas applied to mercury removal from aqueous media: Influence of the synthesis route on adsorption capacity and efficiency.

    PubMed

    Pérez-Quintanilla, Damián; Sánchez, Alfredo; Sierra, Isabel

    2016-06-15

    New hybrid organic-inorganic mesoporous silicas were prepared by employing three different synthesis routes and mercury adsorption studies were done in aqueous media using the batch technique. The organic ligands employed for the functionalization were derivatives of 2-mercaptopyrimidine or 2-mercaptothiazoline, and the synthesis pathways used were post-synthesis, post-synthesis with surface ion-imprinting and co-condensation with ion-imprinting. The incorporation of functional groups and the presence of ordered mesopores in the organosilicas was confirmed by XRD, TEM and SEM, nitrogen adsorption-desorption isotherms, (13)C MAS-NMR, (29)Si MAS-NMR, elemental and thermogravimetric analysis. The highest adsorption capacity and selectivity observed was for the material functionalized with 2-mercaptothiazoline ligand by means the co-condensation with ion-imprinting route (1.03mmolg(-1) at pH 6). The prepared material could be potential sorbent for the extraction of this heavy metal from environmental and drinking waters. PMID:27023632

  16. Tailoring the properties of sub-3 μm silica core-shell particles prepared by a multilayer-by-multilayer process.

    PubMed

    Dong, Hanjiang; Brennan, John D

    2015-01-01

    Sub-3 μm silica core-shell particles (CSPs) were fabricated by a multilayer-by-multilayer method recently developed in our group. In this work, we report on methods to prepare and modify the properties of these CSPs by high temperature calcination, pore size enlargement under basic conditions, and rehydrolyzation in boiling water to make them more suitable as starting materials for preparation of HPLC columns. The chemical, physical and mechanical properties of these modified CSPs were characterized by scanning electron microscopy (SEM), infrared spectroscopy (IR), thermogravimetric analysis (TGA), and nitrogen sorption porosimetry. CSPs obtained after these treatments were observed to have the following properties: particle diameter ∼2.7 μm, shell thickness ∼0.5 μm, surface area ∼200 m(2)/g, pore diameter ∼10 nm (and almost no mesopores), pore volume ∼0.5 cc/g, and Si-OH group surface concentration ∼4 OH/nm(2). These properties are in line with those of commercially available sub-3 μm CSP products. PMID:25310582

  17. Encapsulation of biomolecules for bioanalytical purposes: preparation of diclofenac antibody-doped nanometer-sized silica particles by reverse micelle and sol-gel processing.

    PubMed

    Tsagkogeorgas, Fotios; Ochsenkühn-Petropoulou, Maria; Niessner, Reinhard; Knopp, Dietmar

    2006-07-28

    In recent years, the sol-gel technique has attracted increasing interest as a unique approach to immobilize biomolecules for bioanalytical applications as well as biochemical and biophysical studies. For this purpose, crushed biomolecule-doped sol-gel glass monoliths have been widely used. In the present work, for the first time, the encapsulation of anti-diclofenac antibodies in silica nanoparticles was carried out by a combination of reverse micelle and sol-gel technique. Cyclohexane was used for the preparation of the microemulsion as organic solvent, while surfactant Igepal CO-520 was found to be the optimal stabilizer. The antibody source was a purified IgG fraction originating from a polyclonal rabbit antiserum. Tetramethyl orthosilicate (TMOS) was used as precursor. Rather uniform, monodispersed and spherical silica particles of about 70nm diameter size were fabricated, as was demonstrated by transmission electron microscopy (TEM) and scanning electron microscopy/energy dispersive X-ray fluorescence analysis (SEM/EDX). The biological activity of the encapsulated antibodies was evaluated by incubation of the nanoparticles with a diclofenac standard solution and analysis of the filtrate and followed washing solutions by a highly sensitive enzyme-linked immunosorbent assay (ELISA), using non-doped particles as blanks. While only about 6% of the added diclofenac was nonspecifically retained by the blank, the corresponding amount of about 66% was much higher with the antibody-doped particles. An obvious advantage of this approach is the general applicability of the developed technique for a mild immobilization of different antibody species. PMID:17723516

  18. Micropores and methods of making and using thereof

    DOEpatents

    Perroud, Thomas D.; Patel, Kamlesh D.; Meagher, Robert J.

    2016-08-02

    Disclosed herein are methods of making micropores of a desired height and/or width between two isotropic wet etched features in a substrate which comprises single-level isotropic wet etching the two features using an etchant and a mask distance that is less than 2.times. a set etch depth. Also disclosed herein are methods using the micropores and microfluidic devices comprising the micropores.

  19. Macroporous Polymers with Aligned Microporous Walls from Pickering High Internal Phase Emulsions.

    PubMed

    Zhu, Yun; Zhang, Ranran; Zhang, Shengmiao; Chu, Yeqian; Chen, Jianding

    2016-06-21

    A novel class of macroporous polymers, open macroporous polymers with aligned microporous void walls, were prepared by combining particle-stabilized high internal phase emulsion (Pickering HIPE) and unidirectional freezing technique. These Pickering HIPEs were prepared by utilizing poly(urethane urea)/(vinyl ester resin) nanoparticles as the sole stabilizer, and this nanoparticles also acted as building blocks for the resulting macroporous polymers. Moreover, the morphology and compression modulus of the resulting porous materials could be tuned easily. This means now Pickering-HIPE templated open-cell foams can be prepared, and this route was normally achieved with surfactant and/or chemical reaction involved. PMID:27249538

  20. Preparation of periodic mesoporous silica-included divacant Keggin units for the catalytic oxidation of styrene to synthesize styrene oxide

    NASA Astrophysics Data System (ADS)

    Yu, Xiaodan; Xu, Leilei; Yang, Xia; Guo, Yingna; Li, Kexin; Hu, Jianglei; Li, Wei; Ma, Fengyan; Guo, Yihang

    2008-05-01

    Periodic mesoporous composite catalysts, [( n-C 4H 9) 4N] 4[γ-SiW 10O 34(H 2O) 2]/SBA-15 (TBA-1*/SBA-15, where TBA-1* = [( n-C 4H 9) 4N] 4[γ-SiW 10O 34(H 2O) 2]), with TBA-1* loadings of 4.3-14.8% were prepared by simultaneous hydrolysis and co-condensation of the tetraethoxysilane (TEOS) in the presence of divacant Keggin-type polyoxometalate and triblock copolymer surfactant (P123) followed by hydrothermal treatment process. Structure integrity of the Keggin unit in as-prepared composites was studied by Fourier transform infrared spectroscopy (FT-IR), Raman scattering spectra, and 29Si magic-angle spinning (MAS) NMR. Periodic mesoporous structure of the composites was evaluated by low-angle X-ray powder diffraction (LXRD) patterns, nitrogen porosimetry, and transmission electron microscope (TEM) measurements. As-prepared TBA-1*/SBA-15 was used as an heterogeneous oxidation catalyst for the styrene epoxidation reaction to synthesize styrene oxide in the presence of dilute H 2O 2 (30%), and influences of solvent, molar ratio of styrene to H 2O 2, TBA-1* loading on the styrene conversion, styrene oxide yield and selectivity were considered.

  1. Effects of CO2 activation on electrochemical performance of microporous carbons derived from poly(vinylidene fluoride)

    NASA Astrophysics Data System (ADS)

    Lee, Seul-Yi; Park, Soo-Jin

    2013-11-01

    In this work, we have prepared microporous carbons (MPCs) derived from poly(vinylidene fluoride) (PVDF), and the physical activation of MPCs using CO2 gas is subsequently carried out with various activation temperatures to investigate the electrochemical performance. PVDF is successfully converted into MPCs with a high specific surface area and well-developed micropores. After CO2 activation, the specific surface areas of MPCs (CA-MPCs) are enhanced by 12% compared with non-activated MPCs. With increasing activation temperature, the micropore size distributions of A-MPCs also become narrower and shift to larger pore size. It is also confirmed that the CO2 activation had developed the micropores and introduced the oxygen-containing groups to MPCs‧ surfaces. From the results, the specific capacitances of the electrodes in electric double layer capacitors (EDLCs) based on CA-MPCs are distinctly improved through CO2 activation. The highest specific capacitance of the A-MPCs activated at 700 °C is about 125 F/g, an enhancement of 74% in comparison with NA-MPCs, at a discharge current of 2 A/g in a 6 M KOH electrolyte solution. We also found that micropore size of 0.67 nm has a specific impact on the capacitance behaviors, besides the specific surface area of the electrode samples.

  2. Random lasing of microporous surface of Cr{sup 2+}:ZnSe crystal induced by femtosecond laser

    SciTech Connect

    Yang, Xianheng; Feng, Guoying E-mail: zhoush@scu.edu.cn; Yao, Ke; Yi, Jiayu; Zhang, Hong; Zhou, Shouhuan E-mail: zhoush@scu.edu.cn

    2015-06-15

    We demonstrate a random lasing emission based on microporous surface of Cr{sup 2+}:ZnSe crystal prepared by femtosecond pulsed laser ablation in high vacuum (below 5 × 10{sup −4} Pa). The scanning electron microscope results show that there are a mass of micropores with an average size of ∼13 μm and smaller ones with ∼1.2 μm on the surface of Cr{sup 2+}:ZnSe crystal. The adjacent micropore spacing of the smaller micropores ranges from 1 μm to 5 μm. Under 1750 nm excitation of Nd:YAG (355 nm) pumped optical parametric oscillator, a random lasing emission with center wavelength of 2350 nm and laser-like threshold of 0.3 mJ/pulse is observed. The emission lifetime of 2350 nm laser reduces from 800 ns to 30 ns as the pump energy increases above threshold. The emission spectra and decay time of smooth surface, groove and microporous surface of Cr{sup 2+}:ZnSe crystal are contrasted. The optional pump wavelength range is from 1500 nm to 1950 nm, which in accordance with the optical absorption property of Cr{sup 2+}:ZnSe crystal. The peak position of excitation spectra is almost identical to the strongest absorption wavelength.

  3. Self-formation of microporous polysulfone hollow fiber using a single nozzle spinneret and reduction of phase-inversion speed

    NASA Astrophysics Data System (ADS)

    Kim, Hyung Jin; Jang, Chang Sik; Kim, Byeong Hee; Seo, Young Ho

    2016-06-01

    This study proposed a simple fabrication technique for microporous hollow fibers whose inner channel was naturally formed because of a slow phase inversion speed. Conventionally, microporous hollow fibers have been fabricated by extruding a polymer solution through the outer nozzle and a bore liquid through the inner nozzle of a dual nozzle spinneret. Injecting a bore liquid played a key role for the formation of a hollow structure. In this study, the self-formation of a hollow structure of microporous fiber was developed using a single nozzle spinneret without a bore liquid. A sharp tip single nozzle spinneret of 200 µm in diameter was fabricated by the wetting effect of a liquid pre-polymer of polydimethylsiloxane, and polysulfone solution was extruded through the prepared single nozzle spinneret. The temperature of the coagulant bath was controlled in order to reduce the speed of phase change, because the phase-change speed depended on the temperature of the coagulant solution. An inner channel in the microporous fiber was successfully fabricated by reducing the phase-change speed and by increasing the solidification speed. The inner diameter of the microporous hollow fiber was decreased as the temperature of the coagulant bath was increased, and eventually the inner channel was not formed at the higher bath temperature rather than 25 °C.

  4. A dual-spatially-confined reservoir by packing micropores within dense graphene for long-life lithium/sulfur batteries.

    PubMed

    Li, Hongfei; Yang, Xiaowei; Wang, Xiaomin; He, Yu-Shi; Ye, Fangmin; Liu, Meinan; Zhang, Yuegang

    2016-01-28

    In lithium/sulfur batteries, micropores could bring about strong interactions with polysulfides, but could not alleviate the partial polysulfide overflowing outside because of the volume expansion of the lithiated sulfur. A dual-spatially-confined reservoir for sulfur by wrapping microporous carbon with dense graphene, micro@meso-porous DSC (dual-spatial carbon), is synthesized to solve this issue. Such a structure is prepared through two distinctive methods: graphene promoted in situ hydrothermal carbonization of organics to grow micropores on itself, and liquid mediated drying of graphene hydrogel to form mesoporous graphene frameworks. In contrast to previously reported hierarchical carbon/S, the inner micropores are mainly responsible for loading sulfur, which could help confine its particle size, thus increasing the electrical/ionic conductivity and the utilization of sulfur, and restrain lithium polysulfide dissolution because of strong interaction with pore walls; while the outer mesopores act as another reservoir to stabilize the overflowed polysulfide and to enhance the Li(+) transport. The S-micro@meso-porous DSC cathode exhibits better discharge capacity and cycling performance than S-microporous AC and S-micro@macro-porous DSC, i.e., 59% and 37% higher capacity remaining at 0.5 C than the latter two, respectively. PMID:26754080

  5. Microporous polyimide films for reduced dielectric applications

    SciTech Connect

    Saunders, R.S.; Aubert, J.H.; McNamara, W.F.

    1995-01-01

    With all the advances in the microelectronics industry, a limiting factor to computer chip speed and size is becoming the dielectric constant of the interlayer insulating materials. Dielectric constants of these layers have been reduced in going from inorganic to organic type materials. A further reduction in dielectric constant, coupled with better mechanical properties are still required for these types of materials. The authors have developed a technique involving spincoating in conjunction with a thermodynamic process called {open_quotes}Non-solvent Induced Phase Separation{close_quotes} (NSIPS) to create microporous polyimide films that exhibit both a lower dielectric constant and better stress reduction properties compared to their solid film counterparts. In this technique, the authors spincoat a soluble polyimide solution in 1,3-dimethoxybenzene solvent onto a silicon wafer, and then immediately submerse the {open_quotes}wet{close_quotes} polymer film into a non-solvent bath, typically toluene. Phase separation of the polymer occurs on a micron size scale and the resulting microporous structure becomes locked in by the high glass transition temperature of the polyimide. The authors have determined the factors affecting the film morphology, thickness, pore size, and percent porosity; these factors include the polymer concentration, spin speed, and the type of non-solvent used. The different morphologies obtained for the varying non-solvents are explained in terms of thermodynamics and kinetics of phase separation and diffusion, using an idealized ternary phase diagram. One particular film having a porosity of 68%, thickness of 22 microns and pore size of 1.4 microns had a measured dielectric constant of 1.88 and dielectric loss of 0.002. Stress measurements indicated that the microporous film reduced surface stress on the wafer by more than a factor of 10 when compared to the analogous solid polyimide film.

  6. Effect of the platinum content on the microstructure and micropore size distribution of Pt/alumina-pillared clays.

    PubMed

    Barrera-Vargas, M; Valencia-Rios, J; Vicente, M A; Korili, S A; Gil, A

    2005-12-15

    The aim of this work is to study the effect of the platinum content (0-1.8 wt % Pt) on the microstructure of an alumina-pillared clay. For this purpose, the nitrogen physisorption data at -196 degrees C, the micropore size distributions of the supported platinum catalysts, and the hydrogen chemisorption results at 30 degrees C have been analyzed and compared. The preparation of the catalysts has modified the textural properties of the Al-pillared clay support, giving rise to a loss of surface area and micropore volume. After reduction at 420 degrees C, the presence of dispersed metallic platinum with mean crystallite size in the 22-55 A range has been found by hydrogen adsorption. Comparison of all results reveals that the platinum species block the micropore entrances by steric hindrance to nitrogen access as the platinum content increases. PMID:16375319

  7. Thermodynamics and transport in microporous media

    SciTech Connect

    Glandt, E.D.

    1992-09-01

    Focus of this report is on the thermodynamic properties/behavior of fluids contained or adsorbed on the random microporus materials (disordered solids). The Madden-Glandt formalism for fluids in disordered matrices is applied to realistic systems (gas adsorption in carbons, polymer partitioning). Work on microgeometry of solids and their percolation and connectedness properties was continued; a study of the simplest model for microporous materials (random-pore or ''Swiss cheese'' model) was completed. Work on irreversible adsorption was continued; a simple model for correlated adsorption was studied.

  8. Gas adsorption on microporous carbon thin films

    SciTech Connect

    O'Shea, S.; Pailthorpe, B.A.; Collins, R.E.; Furlong, D.N. )

    1992-05-01

    A gas adsorption study was performed on amorphous hydrogenated carbon thin films which are deposited by reactive magnetron sputtering using acetylene gas. It is found that the films are highly microporous. Annealing significantly increases the adsorption capacity of the films and decreases the effects of low-pressure hysteresis in the adsorption isotherms. The general gas adsorption behavior closely resembles that of powdered activated carbons. The Dubinin-Radushkevich equation can be used to model the submonolayer adsorption isotherm for a variety of gases. 38 refs., 9 figs., 3 tabs.

  9. Solvent-resistant microporous polymide membranes

    DOEpatents

    Miller, W.K.; McCray, S.B.; Friesen, D.T.

    1998-03-10

    An asymmetric microporous membrane with exceptional solvent resistance and highly desirable permeability is disclosed. The membrane is made by a solution-casting or solution-spinning process from a copolyamic acid comprising the condensation reaction product in a solvent of at least three reactants selected from certain diamines and dianhydrides and post-treated to imidize and in some cases cross-link the copolyamic acid. The membrane is useful as an uncoated membrane for ultrafiltration, microfiltration, and membrane contactor applications, or may be used as a support for a permselective coating to form a composite membrane useful in gas separations, reverse osmosis, nanofiltration, pervaporation, or vapor permeation.

  10. Solvent-resistant microporous polymide membranes

    DOEpatents

    Miller, Warren K.; McCray, Scott B.; Friesen, Dwayne T.

    1998-01-01

    An asymmetric microporous membrane with exceptional solvent resistance and highly desirable permeability is disclosed. The membrane is made by a solution-casting or solution-spinning process from a copolyamic acid comprising the condensation reaction product in a solvent of at least three reactants selected from certain diamines and dianhydrides and post-treated to imidize and in some cases cross-link the copolyamic acid. The membrane is useful as an uncoated membrane for ultrafiltration, microfiltration, and membrane contactor applications, or may be used as a support for a permselective coating to form a composite membrane useful in gas separations, reverse osmosis, nanofiltration, pervaporation, or vapor permeation.

  11. Synthesis and modification of mesoporous silica and the preparation of molecular sieve thin films via pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Coutinho, Decio Heringer

    2001-07-01

    Hexagonal mesoporous DAM-1 (Dallas Amorphous Material-1) was prepared using Vitamin E TPGS as the structure-directing agent. Depending upon the temperature and gel composition, highly ordered and hydrothermally stable DAM-1 with various morphologies could be achieved including spheres, gyroids, discoid, hexagonal plates and rods. This synthesis was modified to prepare hybrid organic-inorganic amine and thiol bifunctionalized DAM-1 by direct co-condensation under acidic conditions. Patterned DAM-1 thin films were prepared on patterned transparencies utilizing pulsed laser deposition (PLD) and line patterning techniques. DAM-1 laser ablation onto the patterned substrate followed by hydrothermal treatment resulted in a densely packed film. Removal of the patterned lines by sonication revealed patterned DAM-1 films. Thin films of zeolite type X were also prepared using the PLD technique. Laser ablation of zeolite X onto TiN-coated silicon wafers followed by a hydrothermal treatment resulted in partially oriented, crystalline membranes. Hydrothermal treatment of PLD films on stainless steel mesh produced a coated wire mesh with a 3-mum thick zeolite X film. A novel strategy for imprinting mesoporous SBA-15 that combines a triblock copolymer template and a chiral ruthenium complex is reported. A chiral PEO helix was formed by the chiral ruthenium complex interaction with the block copolymer during the synthesis of SBA-15. Upon removal of the chiral ruthenium complex, a stereospecfic cavity was created. Preliminary results indicated stereoselective absorption of Delta or Λ-Ru(phen)3 2+ isomer from a racemic mixture could be achieved depending on the chirality of the PEO chain. Practicum Two. The industrial practicum report describes the process development unit (PDU) 3-pentenenitrile (3PN) refining operation. This distillation works was operated to refine crude 3PN product, which contained 3PN, 2-methyl-3-butenenitrile (2M3BN), and other byproducts. This report also

  12. Evaluation of colloidal silica suspension as efficient additive for improving physicochemical and in vitro biological properties of calcium sulfate-based nanocomposite bone cement.

    PubMed

    Borhan, Shokoufeh; Hesaraki, Saeed; Ahmadzadeh-Asl, Shaghayegh

    2010-12-01

    In the present study new calcium sulfate-based nanocomposite bone cement with improved physicochemical and biological properties was developed. The powder component of the cement consists of 60 wt% α-calcium sulfate hemihydrate and 40 wt% biomimetically synthesized apatite, while the liquid component consists of an aqueous colloidal silica suspension (20 wt%). In this study, the above mentioned powder phase was mixed with distilled water to prepare a calcium sulfate/nanoapatite composite without any additive. Structural properties, setting time, compressive strength, in vitro bioactivity and cellular properties of the cements were investigated by appropriate techniques. From X-ray diffractometer analysis, except gypsum and apatite, no further phases were found in both silica-containing and silica-free cements. The results showed that both setting time and compressive strength of the calcium sulfate/nanoapatite cement improved by using colloidal silica suspension as cement liquid. Meanwhile, the condensed phase produced from the polymerization process of colloidal silica filled the micropores of the microstructure and covered rodlike gypsum crystals and thus controlled cement disintegration in simulated body fluid. Additionally, formation of apatite layer was favored on the surfaces of the new cement while no apatite precipitation was observed for the cement prepared by distilled water. In this study, it was also revealed that the number of viable osteosarcoma cells cultured with extracts of both cements were comparable, while silica-containing cement increased alkaline phosphatase activity of the cells. These results suggest that the developed cement may be a suitable bone filling material after well passing of the corresponding in vivo tests. PMID:20972610

  13. Investigation of the sample preparation and curing treatment effects on mechanical properties and bioactivity of silica rich metakaolin geopolymer.

    PubMed

    Catauro, M; Bollino, F; Papale, F; Lamanna, G

    2014-03-01

    In many biomedical applications both the biological and mechanical behaviours of implants are of relevant interest; in the orthopaedic field, for example, favourable bioactivity and biocompatibility capabilities are necessary, but at the same time the mechanical characteristics of the implants must be such as to allow one to support the body weight. In the present work, the authors have examined the application of geopolymers with composition H24AlK7Si31O79 and ratio Si/Al=31 to be used in biomedical field, considering two different preparation methods: one of the activators (KOH) has been added as pellets in the potassium silicate solution, in the other as a water solution with 8M concentration. Moreover, a different water content was used and only some of the synthesized samples were heat treated. The chemical and microstructural characterizations of those materials have been carried out by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Subsequently, the effects of the adopted preparation on the mechanical and biological properties have been studied: compressive strength tests have demonstrated that more fragile specimens were obtained when KOH was added as a solution. The bioactivity was successfully evaluated with the soaking of the samples in a simulated body fluid (SBF) for 3 weeks. The formation of a layer of hydroxyapatite on the surface of the materials has been shown both by SEM micrographs and EDS analyses. PMID:24433882

  14. Preparation of magnetic core-shell iron oxide@silica@nickel-ethylene glycol microspheres for highly efficient sorption of uranium(VI).

    PubMed

    Tan, Lichao; Zhang, Xiaofei; Liu, Qi; Wang, Jun; Sun, Yanbo; Jing, Xiaoyan; Liu, Jingyuan; Song, Dalei; Liu, Lianhe

    2015-04-21

    We report a facile approach for the formation of magnetic core-shell iron oxide@silica@nickel-ethylene glycol (Fe3O4@SiO2@Ni-L) microspheres. The structure and morphology of Fe3O4@SiO2@Ni-L are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen sorption isotherm. The composite possesses a high specific surface area of 382 m(2) g(-1). The obtained core/shell structure is composed of a superparamagnetic core with a strong response to external fields, which are recovered readily from aqueous solutions by magnetic separation. When used as the adsorbent for uranium(vi) in water, the as-prepared Fe3O4@SiO2@Ni-L multi-structural microspheres exhibit a high adsorption capacity, which is mainly attributed to the large specific surface area and typical mesoporous characteristics of Fe3O4@SiO2@Ni-L microspheres. This work provides a promising approach for the design and synthesis of multifunctional microspheres, which can be used for water treatment, as well as having other potential applications in a variety of biomedical fields including drug delivery and biosensors. PMID:25773512

  15. Preparation of Ti(4+)-immobilized modified silica capillary trapping column for on-line selective enrichment of phosphopeptides.

    PubMed

    Yang, Huili; Deng, Chunhui; Zhang, Xiangmin

    2016-06-01

    In this work, we have developed Ti(4+)-immobilized capillary trapping column (250μm i.d.) for highly specific on-line enrichment of phosphopeptides in the bio-samples. It minimizes the sample loss and improves the effectiveness of phosphopeptide detection that the limit of detection is as low as 1fmol/μL. It is successfully applied to the detection of phosphopeptides from complex biological samples, such as skim milk, human serum and mouse brain. The results indicate that the Ti(4+)-immobilized capillary trapping column is time-effective and has the great potential of application in low-abundance phosphopeptides on-line analysis. The prepared Ti(4+)-immobilized capillary trapping column will be further used in LC/MS platform for phosphoproteome analysis. PMID:27130120

  16. Bactericidal activity and silver release of porous ceramic candle filter prepared by sintering silica with silver nanoparticles/zeolite for water disinfection

    NASA Astrophysics Data System (ADS)

    Trinh Nguyen, Thuy Ai; Phu Dang, Van; Duy Nguyen, Ngoc; Le, Anh Quoc; Thanh Nguyen, Duc; Hien Nguyen, Quoc

    2014-09-01

    Porous ceramic candle filters (PCCF) were prepared by sintering silica from rice husk with silver nanoparticles (AgNPs)/zeolite A at about 1050 °C to create bactericidal PCCF/AgNPs for water disinfection. The silver content in PCCF/AgNPs was of 300-350 mg kg-1 determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and the average pore size of PCCF/AgNPs was of 50-70 Å measured by Brunauer-Emmett-Teller (BET) method. The bactericidal activity and silver release of PCCF/AgNPs have been investigated by flow test with water flow rate of 5 L h-1 and initial inoculation of E. coli in inlet water of 106 CFU/100 mL. The volume of filtrated water was collected up to 500 L. Results showed that the contamination of E. coli in filtrated water was <1 CFU/100 mL and the content of silver released from PCCF/AgNPs into filtrated water was <1 μg L-1, it is low, far under the WHO guideline of 100 μg L-1 at maximum for drinking water. Based on the content of silver in PCCF/AgNPs and in filtrated water, it was estimated that one PCCF/AgNPs could be used to filtrate of ˜100 m3 water. Thus, as-prepared PCCF/AgNPs releases low content of silver into water and shows effectively bactericidal activity that is promising to apply as point-of-use water treatment technology for drinking water disinfection.

  17. Immersion Calorimetry: Molecular Packing Effects in Micropores.

    PubMed

    Madani, S Hadi; Silvestre-Albero, Ana; Biggs, Mark J; Rodríguez-Reinoso, Francisco; Pendleton, Phillip

    2015-12-21

    Repeated and controlled immersion calorimetry experiments were performed to determine the specific surface area and pore-size distribution (PSD) of a well-characterized, microporous poly(furfuryl alcohol)-based activated carbon. The PSD derived from nitrogen gas adsorption indicated a narrow distribution centered at 0.57±0.05 nm. Immersion into liquids of increasing molecular sizes ranging from 0.33 nm (dichloromethane) to 0.70 nm (α-pinene) showed a decreasing enthalpy of immersion at a critical probe size (0.43-0.48 nm), followed by an increase at 0.48-0.56 nm, and a second decrease at 0.56-0.60 nm. This maximum has not been reported previously. After consideration of possible reasons for this new observation, it is concluded that the effect arises from molecular packing inside the micropores, interpreted in terms of 2D packing. The immersion enthalpy PSD was consistent with that from quenched solid density functional theory (QSDFT) analysis of the nitrogen adsorption isotherm. PMID:26394883

  18. π-Conjugated Microporous Polymer Films: Designed Synthesis, Conducting Properties, and Photoenergy Conversions

    PubMed Central

    Gu, Cheng; Huang, Ning; Chen, Youchun; Qin, Leiqiang; Xu, Hong; Zhang, Shitong; Li, Fenghong; Ma, Yuguang; Jiang, Donglin

    2015-01-01

    Conjugated microporous polymers are a unique class of polymers that combine extended π-conjugation with inherent porosity. However, these polymers are synthesized through solution-phase reactions to yield insoluble and unprocessable solids, which preclude not only the evaluation of their conducting properties but also the fabrication of thin films for device implementation. Here, we report a strategy for the synthesis of thin films of π-conjugated microporous polymers by designing thiophene-based electropolymerization at the solution–electrode interface. High-quality films are prepared on a large area of various electrodes, the film thickness is controllable, and the films are used for device fabrication. These films are outstanding hole conductors and, upon incorporation of fullerenes into the pores, function as highly efficient photoactive layers for energy conversions. Our film strategy may boost the applications in photocatalysis, energy storage, and optoelectronics. PMID:26418672

  19. Preparation of high efficiency and low carry-over immobilized enzymatic reactor with methacrylic acid-silica hybrid monolith as matrix for on-line protein digestion.

    PubMed

    Yuan, Huiming; Zhang, Lihua; Zhang, Yukui

    2014-12-01

    In this work, a novel kind of organic-silica hybrid monolith based immobilized enzymatic reactor (IMER) was developed. The monolithic support was prepared by a single step "one-pot" strategy via the polycondensation of tetramethoxysilane and vinyltrimethoxysilane and in situ copolymerization of methacrylic acid and vinyl group on the precondensed siloxanes with ammonium persulfate as the thermal initiator. Subsequently, the monolith was activated by N-(3-dimethylaminopropyl) - N'-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS), followed by the modification of branched polyethylenimine (PEI) to improve the hydrophilicity. Finally, after activated by EDC and NHS, trypsin was covalently immobilized onto the monolithic support. The performance of such a microreactor was evaluated by the in sequence digestion of bovine serum albumin (BSA) and myoglobin, followed by MALDI-TOF-MS analysis. Compared to those obtained by traditional in-solution digestion, not only higher sequence coverages for BSA (74±1.4% vs. 59.5±2.7%, n=6) and myoglobin (93±3% vs. 81±4.5%, n=6) were obtained, but also the digestion time was shortened from 24h to 2.5 min, demonstrating the high digestion efficiency of such an IMER. The carry-over of these two proteins on the IMER was investigated, and peptides from BSA could not be found in mass spectrum of myoglobin digests, attributed to the good hydrophilicity of our developed monolithic support. Moreover, the dynamic concentration range for protein digestion was proved to be four orders of magnitude, and the IMER could endure at least 7-day consecutive usage. Furthermore, such an IMER was coupled with nano-RPLC-ESI/MS/MS for the analysis of extracted proteins from Escherichia coli. Compared to formerly reported silica hybrid monolith based IMER and the traditional in-solution counterpart, by our developed IMER, although the identified protein number was similar, the identified distinct peptide number was improved by 7% and 25% respectively

  20. Small-angle neutron scattering study of micropore collapse in amorphous solid water.

    PubMed

    Mitterdorfer, Christian; Bauer, Marion; Youngs, Tristan G A; Bowron, Daniel T; Hill, Catherine R; Fraser, Helen J; Finney, John L; Loerting, Thomas

    2014-08-14

    Vapor-deposited amorphous solid water (ASW) is the most abundant solid molecular material in space, where it plays a direct role in both the formation of more complex chemical species and the aggregation of icy materials in the earliest stages of planet formation. Nevertheless, some of its low temperature physics such as the collapse of the micropore network upon heating are still far from being understood. Here we characterize the nature of the micropores and their collapse using neutron scattering of gram-quantities of D2O-ASW of internal surface areas up to 230 ± 10 m(2) g(-1) prepared at 77 K. The model-free interpretation of the small-angle scattering data suggests micropores, which remain stable up to 120-140 K and then experience a sudden collapse. The exact onset temperature to pore collapse depends on the type of flow conditions employed in the preparation of ASW and, thus, the specific surface area of the initial deposit, whereas the onset of crystallization to cubic ice is unaffected by the flow conditions. Analysis of the small-angle neutron scattering signal using the Guinier-Porod model suggests that a sudden transition from three-dimensional cylindrical pores with 15 Å radius of gyration to two-dimensional lamellae is the mechanism underlying the pore collapse. The rather high temperature of about 120-140 K of micropore collapse and the 3D-to-2D type of the transition unraveled in this study have implications for our understanding of the processing and evolution of ices in various astrophysical environments. PMID:24963740

  1. [Recombinant strain producing thermostable lipase from Thermomyces lanuginosus immobilized into nanocarbon silica matrices and properties of the prepared biocatalyzers].

    PubMed

    Kovalenko, G A; Beklemishev, A B; Perminova, L V; Chuenko, T V; Ivanov, I D; Moiseenkov, S I; Kuznetsov, V L

    2013-01-01

    Multicomponent composite biocatalyzers with lipolytic activity have been studied. These biocatalyzers were prepared through the immobilization of a recombinant producer strain of thermostable lipase from Thermomyces lanuginosus into SiO2 xerogel, which contains a nanocarbon component, i.e., multilayered carbon nanotubes with varying diameters, and also bulblike structured carbon nanospheres ("nanobulb"). The properties of lipase were studied both in cell suspensions of a recombinant producer strain constructed based on E. coli BL21(DE3) and in the immobilized state with regard to the structure and dispersibility of the nanocarbon component used in the composition of the biocatalyzers. It was shown that the recombinant intracellular lipase exerted its activity in a reaction of tributirin hydrolysis on average comprising 50 U/mg of dried cells and had a high level of thermostability. Upon heating in olive oil at 100 degrees C, the inactivation constant and the period of semi-inactivation comprised 6 x 10(-3) min(-1) and 2 h, respectively, exceeding by one order the thermostability of lipase in a buffer solution. Biocatalyzers that contained aggregated "thick" nanotubes with a diameter of 20-22 nm had the maximum initial activity-250 U/g. PMID:23882949

  2. Preparation of a silica-based high-performance hydrophobic interaction chromatography stationary phase for protein separation and renaturation.

    PubMed

    Yang, Yicong; Qu, Qian; Li, Weimin; Yuan, Jie; Ren, Yi; Wang, Lili

    2016-07-01

    In this work, based on the structural characteristics of bio-membrane molecules, a novel type of high-performance hydrophobic interaction chromatography stationary phase was prepared using cholesterol as a ligand. Investigating the separation performance of this stationary phase, the effect of pH and salt concentration of the mobile phase on the retention time, the absorption capacity, and the hydrophobic ability revealed that this stationary phase had a high loading capacity and moderate hydrophobic interactions compared with four different hydrophobic interaction chromatography stationary phase ligands. Five types of standard proteins could be baseline separated with a great selection for protein separation. When 3.0 M urea was added to the mobile phase, it could be refolded with simultaneous purification of denatured lysozyme by one-step chromatography. The mass recovery of lysozyme reached 89.5%, and the active recovery was 96.8%. Compared with traditional hydrophobic interaction chromatography, this new stationary phase has a good hydrophobic ability and a significant refolding efficiency. PMID:27159821

  3. Molecular engineering of porous silica using aryl templates

    DOEpatents

    Loy, Douglas A.; Shea, Kenneth J.

    1994-01-01

    A process for manipulating the porosity of silica using a series of organic template groups covalently incorporated into the silicate matrix. The templates in the bridged polysilsesquioxanes are selectively removed from the material by oxidation with oxygen plasma or other means, leaving engineered voids or pores. The size of these pores is dependent upon the length or size of the template or spacer. The size of the templates is measured in terms of Si-Si distances which range from about 0.67 nm to 1.08 nm. Changes introduced by the loss of the templates result in a narrow range of micropores (i.e. <2 nm). Both aryl and alkyl template groups are used as spacers. Novel microporous silica materials useful as molecular seives, dessicants, and catalyst supports are produced.

  4. Molecular engineering of porous silica using aryl templates

    DOEpatents

    Loy, D.A.; Shea, K.J.

    1994-06-14

    A process is described for manipulating the porosity of silica using a series of organic template groups covalently incorporated into the silicate matrix. The templates in the bridged polysilsesquioxanes are selectively removed from the material by oxidation with oxygen plasma or other means, leaving engineered voids or pores. The size of these pores is dependent upon the length or size of the template or spacer. The size of the templates is measured in terms of Si-Si distances which range from about 0.67 nm to 1.08 nm. Changes introduced by the loss of the templates result in a narrow range of micropores (i.e. <2 nm). Both aryl and alkyl template groups are used as spacers. Novel microporous silica materials useful as molecular sieves, desiccants, and catalyst supports are produced. 3 figs.

  5. Silica nephropathy.

    PubMed

    Ghahramani, N

    2010-07-01

    Occupational exposure to heavy metals, organic solvents and silica is associated with a variety of renal manifestations. Improved understanding of occupational renal disease provides insight into environmental renal disease, improving knowledge of disease pathogenesis. Silica (SiO2) is an abundant mineral found in sand, rock, and soil. Workers exposed to silica include sandblasters, miners, quarry workers, masons, ceramic workers and glass manufacturers. New cases of silicosis per year have been estimated in the US to be 3600-7300. Exposure to silica has been associated with tubulointerstitial disease, immune-mediated multisystem disease, chronic kidney disease and end-stage renal disease. A rare syndrome of painful, nodular skin lesions has been described in dialysis patients with excessive levels of silicon. Balkan endemic nephropathy is postulated to be due to chronic intoxication with drinking water polluted by silicates released during soil erosion. The mechanism of silica nephrotoxicity is thought to be through direct nephrotoxicity, as well as silica-induced autoimmune diseases such as scleroderma and systemic lupus erythematosus. The renal histopathology varies from focal to crescentic and necrotizing glomerulonephritis with aneurysm formation suggestive of polyarteritis nodosa. The treatment for silica nephrotoxicity is non-specific and depends on the mechanism and stage of the disease. It is quite clear that further research is needed, particularly to elucidate the pathogenesis of silica nephropathy. Considering the importance of diagnosing exposure-related renal disease at early stages, it is imperative to obtain a thorough occupational history in all patients with renal disease, with particular emphasis on exposure to silica, heavy metals, and solvents. PMID:23022796

  6. Preparation and tribological properties of water-soluble copper/silica nanocomposite as a water-based lubricant additive

    NASA Astrophysics Data System (ADS)

    Zhang, Chunli; Zhang, Shengmao; Yu, Laigui; Zhang, Zhijun; Wu, Zhishen; Zhang, Pingyu

    2012-10-01

    Cu/SiO2 nanocomposite was synthesized by sol-gel method. The size, morphology and phase structure of as-prepared Cu/SiO2 nanocomposite were analyzed by means of X-ray diffraction and transmission electron microscopy, and its ultraviolet-visible light spectrum was measured in relation to surface plasmon excitation of Cu particles. The tribological properties of as-synthesized Cu/SiO2 nanocomposite as an additive in distilled water were investigated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined with a scanning electron microscope and an X-ray photoelectron spectroscope. Results show that as-synthesized Cu/SiO2 nanocomposite as a lubricant additive is able to significantly improve the tribological properties of distilled water. A protective and lubricious film composed of Cu and a small amount of FeS, FeSO4 and SiO2 is formed on steel sliding surfaces lubricated by distilled water containing Cu/SiO2 nanocomposite. During friction process Cu nanoparticles can be released from Cu/SiO2 nanocomposite to fill up micro-pits and grooves of steel sliding surfaces, resulting in greatly reduced friction and wear of steel frictional pair via self-repairing. The state and thickness of the film formed on the worn surface is closely related to applied load; and Cu/SiO2 nanocomposite might be a promising water-based lubricant additive for steel-steel contact subjected to moderate load.

  7. Preparation of phenothiazine bonded silica gel as sorbents of solid phase extraction and their application for determination of nitrobenzene compounds in environmental water by gas chromatography-mass spectrometry.

    PubMed

    Peng, Xi-Tian; Zhao, Xing; Feng, Yu-Qi

    2011-12-30

    In this paper, two phenothiazine bonded silica (PTZ-Si) sorbents were prepared and used as sorbents of solid-phase extraction (SPE) for the determination of nitrobenzene compounds in environmental water samples by gas chromatography-mass spectrometry (GC-MS). Different synthesis routes were proposed to obtain high bonded amount of PTZ on the surface of silica gel. PTZ molecule was derived to its amino or acyl chloride derivatives for reacting with isocyanate or amino silane coupling agent, which was further reacted with the surface silanol groups of silica gel to obtain the PTZ-Si sorbents. The resultant PTZ-Si sorbents were characterized by nitrogen sorption porosimetry (NSP), Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA) to assure the successful bonding of PTZ on the surface of silica gel. Then the PTZ-Si sorbents were served as SPE sorbents for the enrichment of nitrobenzene compounds. Several parameters affecting the extraction performance were investigated. Under the optimized conditions, the proposed method was applied to the analysis of six nitrobenzene compounds in environmental water samples. Good linearities were obtained for all nitrobenzene compounds with R(2) larger than 0.9958. The limits of detection were found to be in the range of 0.06-0.3 ng/mL. The method recoveries of nitrobenzene compounds spiked in water samples were from 71.4% to 124.3%, with relative standard deviations (RSDs) less than 10.1%. PMID:22129571

  8. Fabrication of GaN Microporous Structure at a GaN/Sapphire Interface as the Template for Thick-Film GaN Separation Grown by HVPE

    NASA Astrophysics Data System (ADS)

    Chen, Jianli; Cheng, Hongjuan; Zhang, Song; Lan, Feifei; Qi, Chengjun; Xu, Yongkuan; Wang, Zaien; Li, Jing; Lai, Zhanping

    2016-06-01

    In this paper, a microporous structure at the GaN/sapphire interface has been obtained by an electrochemical etching method via a selective etching progress using an as-grown GaN/sapphire wafer grown by metal organic chemical vapor deposition. The as-prepared GaN interfacial microporous structure has been used as a template for the following growth of thick-film GaN crystal by hydride vapor phase epitaxy (HVPE), facilitating the fabrication of a free-standing GaN substrate detached from a sapphire substrate. The evolution of the interfacial microporous structure has been investigated by varying the etching voltages and time, and the formation mechanism of interfacial microporous structure has been discussed in detail as well. Appropriate interfacial microporous structure is beneficial for separating the thick GaN crystal grown by HVPE from sapphire during the cooling down process. The separation that occurred at the place of interfacial microporous can be attributed to the large thermal strain between GaN and sapphire. This work realized the fabrication of a free-standing GaN substrate with high crystal quality and nearly no residual strain.

  9. Ultra-thin microporous/hybrid materials

    DOEpatents

    Jiang, Ying-Bing; Cecchi, Joseph L.; Brinker, C. Jeffrey

    2012-05-29

    Ultra-thin hybrid and/or microporous materials and methods for their fabrication are provided. In one embodiment, the exemplary hybrid membranes can be formed including successive surface activation and reaction steps on a porous support that is patterned or non-patterned. The surface activation can be performed using remote plasma exposure to locally activate the exterior surfaces of porous support. Organic/inorganic hybrid precursors such as organometallic silane precursors can be condensed on the locally activated exterior surfaces, whereby ALD reactions can then take place between the condensed hybrid precursors and a reactant. Various embodiments can also include an intermittent replacement of ALD precursors during the membrane formation so as to enhance the hybrid molecular network of the membranes.

  10. Oriented inorganic thin film channel structures with uni-directional monosize micropores

    SciTech Connect

    Cesarano, J. III; Sasaki, D.Y.; Singh, S.; Brinker, C.J.

    1997-10-01

    The goal of this project was to develop a novel technology that may be used to eventually manufacture a new generation of inorganic membranes and sensors with oriented, unidirectional monosized pores. The premise is that very thin membranes with oriented channels as pores will have a high flux in addition to being highly selective. Applications include: (1) gas separation membranes for oxygen enrichment, partial oxidation, dehydrogenation, and purification of natural gas; (2) refractory catalytic membrane reactors; and (3) molecular recognition sensors. The methodology for making such membranes was to combine Langmuir - Blodgett (LB) technology with sol-gel chemistry to engineer pore channels within the range 3 to 20 K The channel structure was fabricated of amorphous SiO{sub 2} because of its good thermal, chemical, and mechanical stability. Our approach was to use LB techniques to uniformly place organic molecular spacers throughout a thin silica precursor matrix and apply this film to a substrate. LB films of solid solutions of commercially available silane amphiphiles and organic amphiphiles were fabricated. The siloxane groups were then hydrolyzed to form silica and the organic portions of the amphiphiles removed by thermal decomposition. With the completely fugitive organic spacer amphiphiles removed, a thin silica film with micropores resulted. The pore size was in the range of 6 - 8 {angstrom} and in an ultra-thin configuration. With further development this technique may be useful for fabrication of inorganic membranes which satisfy all the criteria of the ideal membrane.

  11. Nanoscale assembly of lanthanum silica with dense and porous interfacial structures

    NASA Astrophysics Data System (ADS)

    Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R.; Smart, Simon; Diniz da Costa, João C.

    2015-02-01

    This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate.

  12. Nanoscale assembly of lanthanum silica with dense and porous interfacial structures

    PubMed Central

    Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R.; Smart, Simon; Diniz da Costa, João C.

    2015-01-01

    This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate. PMID:25644988

  13. Covalent attachment of microbial lipase onto microporous styrene-divinylbenzene copolymer by means of polyglutaraldehyde.

    PubMed

    Dizge, Nadir; Keskinler, Bülent; Tanriseven, Aziz

    2008-10-01

    A novel method for immobilization of Thermomyces lanuginosus lipase onto polyglutaraldehyde-activated poly(styrene-divinylbenzene) (STY-DVB), which is a hydrophobic microporous support has been successfully developed. The copolymer was prepared by the polymerization of the continuous phase of a high internal phase emulsion (polyHIPE). The concentrated emulsion consists of a mixture of styrene and divinylbenzene containing a suitable surfactant and an initiator as the continuous phase and water as the dispersed phase. Lipase from T. lanuginosus was immobilized covalently with 85% yield on the internal surface of the hydrophobic microporous poly(styrene-divinylbenzene) copolymer and used as a biocatalyst for the transesterification reaction. The immobilized enzyme has been fully active 30 days in storage and retained the activity during the 15 repeated batch reactions. The properties of free and immobilized lipase were studied. The effects of protein concentration, pH, temperature, and time on the immobilization, activity, and stability of the immobilized lipase were also studied. The newly synthesized microporous poly(styrene-divinylbenzene) copolymer constitutes excellent support for lipase. It given rise to high immobilization yield, retains enzymatic activity for 30 days, stable in structure and allows for the immobilization of large amount of protein (11.4mg/g support). Since immobilization is simple yet effective, the newly immobilized lipase could be used in several application including oil hydrolysis, production of modified oils, biodiesel synthesis, and removal of fatty acids from oils. PMID:18571389

  14. An ion-imprinted silica-supported organic-inorganic hybrid sorbent prepared by a surface imprinting technique combined with a polysaccharide incorporated sol-gel process for selective separation of cadmium(II) from aqueous solution.

    PubMed

    Li, Feng; Jiang, Hongquan; Zhang, Shusheng

    2007-03-15

    Ion-imprinting concept and polysaccharide incorporated sol-gel process were applied to the preparation of a new silica-supported organic-inorganic hybrid sorbent for selective separation of Cd(II) from aqueous solution. In the prepared shell/core composite sorbent, covalently surface coating on the supporting silica gel was achieved by using a Cd(II)-imprinting sol-gel process starting from an inorganic precursor, gamma-glycidoxypropyltrimethoxysiloxane (GPTMS), and a functional biopolymer, chitosan (CS). The sorbent was prepared through self-hydrolysis of GPTMS, self-condensation and co-condensation of silanol groups (Si-OH) from siloxane and silica gel surface, in combination with in situ covalent cross-linking of CS with partial amine shielded by Cd(II) complexation. Extraction of the imprinting molecules left a predetermined arrangement of ligands and tailored binding pockets for Cd(II). The prepared sorbent was characterized by using X-ray energy dispersion spectroscopy (EDX), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Batch experiments were conducted to study the sorption performance by removal of Cd(II) when present singly or in binary system, an aqueous Cd(II) and Zn(II) mixture. The ion-imprinted composite sorbent offered a fast kinetics for the sorption of Cd(II) and the maximum capacity was 1.14mmolg(-1). The uptake capacity of the imprinted sorbent and the selectivity coefficient were much higher than that of the non-imprinted sorbent. The imprinted sorbent exhibited high reusability. The prepared functional sorbent was shown to be promising for the preconcentration of cadmium in environmental and biological samples. PMID:19071480

  15. Preparation and characterization of glycidyl methacrylate organo bridges grafted mesoporous silica SBA-15 as ibuprofen and mesalamine carrier for controlled release.

    PubMed

    Rehman, Fozia; Rahim, Abdur; Airoldi, Claudio; Volpe, Pedro L O

    2016-02-01

    Mesoporous silica SBA-15 was synthesized and functionalized with bridged polysilsesquioxane monomers obtained by the reaction of 3-aminopropyltriethoxy silane with glycidyl methacrylate in 2:1 ratio. The synthesized mesoporous silica materials were characterized by elemental analysis, infrared spectroscopy, nuclear magnetic resonance spectroscopy, nitrogen adsorption, X-ray diffraction, thermogravimetry and scanning electron microscopy. The nuclear magnetic resonance in the solid state is in agreement with the sequence of carbon distributed in the attached organic chains, as expected for organically functionalized mesoporous silica. After functionalization with organic bridges the BET surface area was reduced from 1311.80 to 494.2m(2)g(-1) and pore volume was reduced from 1.98 to 0.89cm(3)g(-1), when compared to original precursor silica. Modification of the silica surface with organic bridges resulted in high loading capacity and controlled release of ibuprofen and mesalamine in biological fluids. The Korsmeyer-Peppas model better fits the release data indicating Fickian diffusion and zero order kinetics for synthesized mesoporous silica. The drug release rate from the modified silica was slow in simulated gastric fluid, (pH1.2) where less than 10% of mesalamine and ibuprofen were released in initial 8h, while comparatively high release rates were observed in simulated intestinal (pH6.8) and simulated body fluids (pH7.2). The preferential release of mesalamine at intestinal pH suggests that the modified silica could be a simple, efficient, inexpensive and convenient carrier for colon targeted drugs, such a mesalamine and also as a controlled drug release system. PMID:26652455

  16. Performance and Long Term Stability of Mesoporous Silica Membranes for Desalination

    PubMed Central

    Elma, Muthia; Yacou, Christelle; Diniz da Costa, João C.; Wang, David K.

    2013-01-01

    This work shows the preparation of silica membranes by a two-step sol-gel method using tetraethyl orthosilicate in ethanolic solution by employing nitric acid and ammonia as co-catalysts. The sols prepared in pH 6 resulted in the lowest concentration of silanol (Si–OH) species to improve hydrostability and the optimized conditions for film coating. The membrane was tested to desalinate 0.3–15 wt % synthetic sodium chloride (NaCl) solutions at a feed temperature of 22 °C followed by long term membrane performance of up to 250 h in 3.5 wt % NaCl solution. Results show that the water flux (and salt rejection) decrease with increasing salt concentration delivering an average value of 9.5 kg m–2 h–1 (99.6%) and 1.55 kg m–2 h–1 (89.2%) from the 0.3 and 15 wt % saline feed solutions, respectively. Furthermore, the permeate salt concentration was measured to be less than 600 ppm for testing conditions up to 5 wt % saline feed solutions, achieving below the recommended standard for potable water. Long term stability shows that the membrane performance in water flux was stable for up to 150 h, and slightly reduced from thereon, possibly due to the blockage of large hydrated ions in the micropore constrictions of the silica matrix. However, the integrity of the silica matrix was not affected by the long term testing as excellent salt rejection of >99% was maintained for over 250 h. PMID:24956942

  17. Effects of CO{sub 2} activation on electrochemical performance of microporous carbons derived from poly(vinylidene fluoride)

    SciTech Connect

    Lee, Seul-Yi; Park, Soo-Jin

    2013-11-15

    In this work, we have prepared microporous carbons (MPCs) derived from poly(vinylidene fluoride) (PVDF), and the physical activation of MPCs using CO{sub 2} gas is subsequently carried out with various activation temperatures to investigate the electrochemical performance. PVDF is successfully converted into MPCs with a high specific surface area and well-developed micropores. After CO{sub 2} activation, the specific surface areas of MPCs (CA-MPCs) are enhanced by 12% compared with non-activated MPCs. With increasing activation temperature, the micropore size distributions of A-MPCs also become narrower and shift to larger pore size. It is also confirmed that the CO{sub 2} activation had developed the micropores and introduced the oxygen-containing groups to MPCs′ surfaces. From the results, the specific capacitances of the electrodes in electric double layer capacitors (EDLCs) based on CA-MPCs are distinctly improved through CO{sub 2} activation. The highest specific capacitance of the A-MPCs activated at 700 °C is about 125 F/g, an enhancement of 74% in comparison with NA-MPCs, at a discharge current of 2 A/g in a 6 M KOH electrolyte solution. We also found that micropore size of 0.67 nm has a specific impact on the capacitance behaviors, besides the specific surface area of the electrode samples. - Graphical abstract: The A-MPC samples with high specific surface area (ranging from 1030 to 1082 m{sup 2}/g), corresponding to micropore sizes of 0.67 and 0.72 nm, and with the amount of oxygen-containing groups ranging from 3.2% to 4.4% have been evaluated as electrodes for EDLC applications. . Display Omitted - Highlights: • Microporous carbons (MPCs) were synthesized without activation process. • Next, we carried out the CO{sub 2} activation of MPCs with activation temperatures. • It had developed the micropores and introduced the O-functional groups to MPCs. • The highest specific capacitance: 125 F/g, an increase of 74% compared to MPCs.

  18. Organically Modified Silicas on Metal Nanowires

    PubMed Central

    2010-01-01

    Organically modified silica coatings were prepared on metal nanowires using a variety of silicon alkoxides with different functional groups (i.e., carboxyl groups, polyethylene oxide, cyano, dihydroimidazole, and hexyl linkers). Organically modified silicas were deposited onto the surface of 6-μm-long, ∼300-nm-wide, cylindrical metal nanowires in suspension by the hydrolysis and polycondensation of silicon alkoxides. Syntheses were performed at several ratios of tetraethoxysilane to an organically modified silicon alkoxide to incorporate desired functional groups into thin organosilica shells on the nanowires. These coatings were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. All of the organically modified silicas prepared here were sufficiently porous to allow the removal of the metal nanowire cores by acid etching to form organically modified silica nanotubes. Additional functionality provided to the modified silicas as compared to unmodified silica prepared using only tetraethoxysilane precursors was demonstrated by chromate adsorption on imidazole-containing silicas and resistance to protein adsorption on polyethyleneoxide-containing silicas. Organically modified silica coatings on nanowires and other nano- and microparticles have potential application in fields such as biosensing or nanoscale therapeutics due to the enhanced properties of the silica coatings, for example, the prevention of biofouling. PMID:20715881

  19. Exposure to crystalline silica in abrasive blasting operations where silica and non-silica abrasives are used.

    PubMed

    Radnoff, Diane L; Kutz, Michelle K

    2014-01-01

    Exposure to respirable crystalline silica is a hazard common to many industries in Alberta but particularly so in abrasive blasting. Alberta occupational health and safety legislation requires the consideration of silica substitutes when conducting abrasive blasting, where reasonably practicable. In this study, exposure to crystalline silica during abrasive blasting was evaluated when both silica and non-silica products were used. The crystalline silica content of non-silica abrasives was also measured. The facilities evaluated were preparing metal products for the application of coatings, so the substrate should not have had a significant contribution to worker exposure to crystalline silica. The occupational sampling results indicate that two-thirds of the workers assessed were potentially over-exposed to respirable crystalline silica. About one-third of the measurements over the exposure limit were at the work sites using silica substitutes at the time of the assessment. The use of the silica substitute, by itself, did not appear to have a large effect on the mean airborne exposure levels. There are a number of factors that may contribute to over-exposures, including the isolation of the blasting area, housekeeping, and inappropriate use of respiratory protective equipment. However, the non-silica abrasives themselves also contain silica. Bulk analysis results for non-silica abrasives commercially available in Alberta indicate that many contain crystalline silica above the legislated disclosure limit of 0.1% weight of silica per weight of product (w/w) and this information may not be accurately disclosed on the material safety data sheet for the product. The employer may still have to evaluate the potential for exposure to crystalline silica at their work site, even when silica substitutes are used. Limited tests on recycled non-silica abrasive indicated that the silica content had increased. Further study is required to evaluate the impact of product recycling

  20. Quantitative investigation of a hybrid Ziegler-Natta catalyst support prepared by grafting di(n-butyl)magnesium onto partially dehydroxylated silica.

    PubMed

    Lee, Ming-Yung; Scott, Susannah L

    2011-04-11

    MgCl(2)-modified silica is an important component of some Ziegler-Natta catalysts used in the manufacture of polyethylene. Information about the structure of the dispersed magnesium sites formed by the reaction of di-n-butylmagnesium (nBu(2)Mg) with silica was sought to provide a basis for understanding their subsequent interactions with transition-metal or co-catalyst components. From infrared spectra and elemental analysis, we deduced that nBu(2)Mg reacts with porous silica in two ways: about half (47%, 0.99 mmol g(-1)) is grafted through protonolysis by surface hydroxyl groups (≡SiOH), whereas the other half (53%, 1.11 mmol g(-1)) reacts directly with siloxane bonds (≡SiOSi≡). In the (29)Si and (13)C CP/MAS NMR spectra of Sylopol-2100 silica pretreated at 500 °C then modified with nBu(2)Mg at room temperature, both alkylsilicon and alkylmagnesium sites are evident. The alkylmagnesium-modified silica surface is proposed to contain dimers and/or tetramers with the empirical formula [≡SiOMg(nBu)](n). Upon exposure of nBu(2)Mg-modified silica to anhydrous HCl, alkanes are liberated, hydroxyl groups are regenerated, and water is formed. The appearance of water suggests condensation of hydroxyl group pairs, induced by the coordinatively unsaturated nanoclusters (MgCl(2))(n) that arise by ligand exchange on the silica-supported n-butylmagnesium oligomers. PMID:21433118

  1. The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes

    PubMed Central

    Akhmetshina, Alsu A.; Davletbaeva, Ilsiya M.; Grebenschikova, Ekaterina S.; Sazanova, Tatyana S.; Petukhov, Anton N.; Atlaskin, Artem A.; Razov, Evgeny N.; Zaripov, Ilnaz I.; Martins, Carla F.; Neves, Luísa A.; Vorotyntsev, Ilya V.

    2015-01-01

    Microporous polymers based on anionic macroinitiator and toluene 2,4-diisocyanate were used as a support for 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) immobilization. The polymeric support was modified by using silica particles associated in oligomeric media, and the influence of the modifier used on the polymeric structure was studied. The supported ionic liquid membranes (SILMs) were tested for He, N2, NH3, H2S, and CO2 gas separation and ideal selectivities were calculated. The high values of ideal selectivity for ammonia-based systems with permanent gases were observed on polymer matrixes immobilized with [bmim][PF6] and [emim][Tf2N]. The modification of SILMs by nanosize silica particles leads to an increase of NH3 separation relatively to CO2 or H2S. PMID:26729177

  2. Observation and Modelling of Micropore Formation in Active Network Regions

    NASA Astrophysics Data System (ADS)

    Berger, T. E.; Löfdahl, M. G.; Bercik, D. J.

    2002-06-01

    We present phase-diversity corrected G-band 4305 Å and 4364 Å continuum image time series showing the formation of a micropore in a small active region near disk center. The data were acquired at the Swedish Vacuum Solar Telescope on La Palma in June of 1997 and post-processed using the Phase Diverse Speckle (PDS) algorithm to produce diffraction limited images throughout the majority of both time series. The micropore dataset comprises a 29x29 Mm field of view and spans 5.1 hours with a 38 second cadence. The micropore forms in a strong sink area that can be seen to ``collect" many G-band bright points over the first 2 hours of the observation. During this time there is an occasional darkening at the sink point that may be the first unstable phase of the micropore formation. Once a stable dark pore forms in the flowfield, it grows to a maximum diameter of 1.2 Mm in approximately 1.9 hours. The pore persists for another 35 minutes before apparently being broken up by the intergranular flowfield. The total ``lifetime" of the stable pore phase is 2.5 hours. A separate nearby micropore of 1.5 Mm maximum diameter exists for the entire 5.2 hour data span. We show G-band and continuum movies of the micropore formation, correlation tracking flowfield analyses, G-band bright point tracking results, and area versus time plots for the micropore formation lifetime. The observational data are compared with fully compressible 3D MHD numerical simulations which show the development of a similar micropore structure within the computational domain. This research was supported by NASA SR&T grant NASW-98008, The Royal Swedish Academy of Sciences, NSF and NASA funding at Michigan State University, and Lockheed Martin IRAD funding.

  3. Microporous polymer films and methods of their production

    DOEpatents

    Aubert, J.H.

    1995-06-06

    A process is described for producing thin microporous polymeric films for a variety of uses. The process utilizes a dense gas (liquefied gas or supercritical fluid) selected to combine with a solvent-containing polymeric film so that the solvent is dissolved in the dense gas, the polymer is substantially insoluble in the dense gas, and two phases are formed. A microporous film is obtained by removal of a dense gas-solvent phase. 9 figs.

  4. Evaporative spray cooling of plain and microporous coated surfaces.

    SciTech Connect

    Kim, J. H.; You, S. M.; Choi, S. U.-S.; Energy Technology; Univ. of Texas at Arlington

    2004-07-01

    Experiments were performed on air and evaporative spray cooling of plain and microporous coated surfaces on flat and cylindrical heaters. Micron-size aluminum particles were used to build the microporous structures on the heated surfaces. To analyze the evaporative cooling, heat transfer curves were obtained in the form of the wall temperature difference versus heat flux. The heat transfer coefficients were also determined as a function of heat flux. Three water flow rates (1.25, 1.75 and 2.40 ml/min) were tested for the flat heater and one rate (3.0 ml/min) for the cylindrical heater, maintaining the air pressure of 7 psig (48 kPa) at the inlet of the nozzle. The effect of different particle sizes in the coating was also tested to optimize the microporous coating technique. Spraying water droplets on the microporous coating surface enhanced the heat removal due to the capillary pumping phenomenon through the microporous cavities connecting each other. The evaporative spray cooling increased the heat transfer coefficient by up to 400% relative to that of the uncoated surface cooled by dry air, and this enhancement was maintained at high heat fluxes by using microporous surfaces.

  5. SANS Investigations of CO2 Adsorption in Microporous Carbon

    DOE PAGESBeta

    Bahadur, Jitendra; Melnichenko, Yuri B.; He, Lilin; Contescu, Cristian I.; Gallego, Nidia C.; Carmichael, Justin R.

    2015-08-07

    The high pressure adsorption behavior of CO2 at T = 296 K in microporous carbon was investigated by small-angle neutron scattering (SANS) technique. A strong densification of CO2 in micropores accompanied by non-monotonic adsorption-induced pore deformation was observed. The density of confined CO2 increases rapidly with pressure and reaches the liquid –like density at 20 bar, which corresponds to the relative pressure of P/Psat ~0.3. At P > 20 bar density of confined CO2 increases slowly approaching a plateau at higher pressure. The size of micropores first increases with pressure, reaches a maximum at 20 bar,more » and then decreases with pressure. A complementary SANS experiment conducted on the same microporous carbon saturated with neutron-transparent and non-adsorbing inert gas argon shows no deformation of micropores at pressures up to ~200 bars. This result demonstrates that the observed deformation of micropores in CO2 is an adsorption-induced phenomenon, caused by the solvation pressure - induced strain and strong densification of confined CO2 .« less

  6. Diclofenac delays micropore closure following microneedle treatment in human subjects.

    PubMed

    Brogden, Nicole K; Milewski, Mikolaj; Ghosh, Priyanka; Hardi, Lucia; Crofford, Leslie J; Stinchcomb, Audra L

    2012-10-28

    Drugs absorbed poorly through the skin are commonly delivered via injection with a hypodermic needle, which is painful and increases the risk of transmitting infectious diseases. Microneedles (MNs) selectively and painlessly permeabilize the outermost skin layer, allowing otherwise skin-impermeable drugs to cross the skin through micron-sized pores and reach therapeutic concentrations. However, rapid healing of the micropores prevents further drug delivery, blunting the clinical utility of this unique transdermal technique. We present the first human study demonstrating that micropore lifetime can be extended following MN treatment. Subjects received one-time MN treatment and daily topical application of diclofenac sodium. Micropore closure was measured with impedance spectroscopy, and area under the admittance-time curve (AUC) was calculated. AUC was significantly higher at MN+diclofenac sodium sites vs. placebo, suggesting slower rates of micropore healing. Colorimetry measurements confirmed the absence of local erythema and irritation. This mechanistic human proof-of-concept study demonstrates that micropore lifetime can be prolonged with simple topical administration of a non-specific cyclooxygenase inhibitor, suggesting the involvement of subclinical inflammation in micropore healing. These results will allow for longer patch wear time with MN-enhanced delivery, thus increasing patient compliance and expanding the transdermal field to a wider variety of clinical conditions. PMID:22929967

  7. In situ formed lithium sulfide/microporous carbon cathodes for lithium-ion batteries.

    PubMed

    Zheng, Shiyou; Chen, Yvonne; Xu, Yunhua; Yi, Feng; Zhu, Yujie; Liu, Yihang; Yang, Junhe; Wang, Chunsheng

    2013-12-23

    Highly stable sulfur/microporous carbon (S/MC) composites are prepared by vacuum infusion of sulfur vapor into microporous carbon at 600 °C, and lithium sulfide/microporous carbon (Li2S/MC) cathodes are fabricated via a novel and facile in situ lithiation strategy, i.e., spraying commercial stabilized lithium metal powder (SLMP) onto a prepared S/MC film cathode prior to the routine compressing process in cell assembly. The in situ formed Li2S/MC film cathode shows high Coulombic efficiency and long cycling stability in a conventional commercial Li-ion battery electrolyte (1.0 M LiPF6 + EC/DEC (1:1 v/v)). The reversible capacities of Li2S/MC cathodes remain about 650 mAh/g even after 900 charge/discharge cycles, and the Coulombic efficiency is close to 100% at a current density of 0.1C, which demonstrates the best electrochemical performance of Li2S/MC cathodes reported to date. Furthermore, this Li2S/MC film cathode fabricated via our in situ lithiation strategy can be coupled with a Li-free anode, such as graphite, carbon/tin alloys, or Si nanowires to form a rechargeable Li-ion cell. As the Li2S/MC cathode is paired with a commercial graphite anode, the full cell of Li2S/MC-graphite (Li2S-G) shows a stable capacity of around 600 mAh/g in 150 cycles. The Li2S/MC cathodes prepared by high-temperate sulfur infusion and SLMP prelithiation before cell assembly are ready to fit into current Li-ion batteries manufacturing processes and will pave the way to commercialize low-cost Li2S-G Li-ion batteries. PMID:24251957

  8. Conjugated Microporous Networks on the Basis of 2,3,5,6-Tetraarylated Diketopyrrolo[3,4-c]pyrrolea

    PubMed Central

    Zhang, Kai; Tieke, Bernd; Vilela, Filipe; Skabara, Peter J

    2011-01-01

    π-Conjugated microporous networks have been prepared from the tetraarylated diketopyrrolo[3,4-c]pyrrole unit as a tetrafunctional building block. The reactions are carried out using microwave-assisted Yamamoto or Sonogashira cross-coupling. Red insoluble powders are obtained, showing intense fluorescence. The polymer networks exhibit a high gas storage capability, with BET surface areas up to about 500 m2 · g−1. PMID:21500301

  9. Nanoparticle-doped radioluminescent silica optical fibers

    NASA Astrophysics Data System (ADS)

    Mrazek, J.; Nikl, M.; Kasik, I.; Podrazky, O.; Aubrecht, J.; Beitlerova, A.

    2014-05-01

    This contribution deals with the preparation and characterization of the silica optical fibers doped by nanocrystalline zinc silicate. The sol-gel approach was employed to prepare colloidal solution of zinc silicate precursors. Prepared sol was thermally treated to form nanocrystalline zinc silicate disperzed inside amorphous silica matrix or soaked inside the porous silica frit deposed inside the silica substrate tube which was collapsed into preform and drawn into optical fiber. Single mode optical fiber with the core diameter 15 μm and outer diamer 125 μm was prepared. Optical and waveguiding properties of the fiber were analyzed. Concentration of the zinc silicate in the fiber was 0.93 at. %. Radioluminescence properties of nanocrystalline zinc silicate powder and of the prepared optical fiber were investigated. The nanoparticle doped samples appear a emission maximum at 390 nm.

  10. Structure-Property Relationships in Porous 3-D Nanostructures as a Function of Preparation Conditions: Isocyanate Cross-Linked Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Capadona, Lynn A.; McCorkle, Linda; Papadopoulos, Demetrios S.; Leventis, Nicholas

    2007-01-01

    Sol-gel derived silica aerogels are attractive candidates for many unique thermal, optical, catalytic, and chemical applications because of their low density and high mesoporosity. However, their inherent fragility has restricted use of aerogel monoliths to applications where they are not subject to any load. We have previously reported cross-linking the mesoporous silica structure of aerogels with di-isocyanates, styrenes or epoxies reacting with amine decorated silica surfaces. These approaches have been shown to significantly increase the strength of aerogels with only a small effect on density or porosity. Though density is a prime predictor of properties such as strength and thermal conductivity for aerogels, it is becoming clear from previous studies that varying the silica backbone and size of the polymer cross-link independently can give rise to combinations of properties which cannot be predicted from density alone. Herein, we examine the effects of four processing parameters for producing this type of polymer cross-linked aerogel on properties of the resulting monoliths. We focus on the results of 13C CP-MAS NMR which gives insight to the size and structure of polymer cross-link present in the monoliths, and relates the size of the cross-links to microstructure, mechanical properties and other characteristics of the materials obtained.

  11. Structure-Property Relationships in Porous 3-D Nanostructures as a Function of Preparation Conditions: Isocyanate Cross-Linked Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Capadona, Lynn A.; McCorkle, Linda; Padadopoulos, Demetrios S.; Leventis, Nicholas

    2007-01-01

    Sol-gel derived silica aerogels are attractive candidates for many unique thermal, optical, catalytic, and chemical applications because of their low density and high mesoporosity. However, their inherent fragility has restricted use of aerogel monoliths to applications where they are not subject to any load. We have previously reported cross-linking the mesoporous silica structure of aerogels with di-isocyanates, styrenes or epoxies reacting with amine decorated silica surfaces. These approaches have been shown to significantly increase the strength of aerogels with only a small effect on density or porosity. Though density is a prime predictor of properties such as strength and thermal conductivity for aerogels, it is becoming clear from previous studies that varying the silica backbone and size of the polymer cross-link independently can give rise to combinations of properties which cannot be predicted from density alone. Herein, we examine the effects of four processing parameters for producing this type of polymer cross-linked aerogel on properties of the resulting monoliths. We focus on the results of C-13 CP-MAS NMR which gives insight to the size and structure of polymer cross-link present in the monoliths, and relates the size of the cross-links to microstructure, mechanical properties and other characteristics of the materials obtained.

  12. Preparation of C60-functionalized magnetic silica microspheres for the enrichment of low-concentration peptides and proteins for MALDI-TOF MS analysis.

    PubMed

    Chen, Hemei; Qi, Dawei; Deng, Chunhui; Yang, Penyuan; Zhang, Xiangmin

    2009-01-01

    In this work, for the first time, a novel C60-functionalized magnetic silica microsphere (designated C60-f-MS) was synthesized by radical polymerization of C60 molecules on the surface of magnetic silica microspheres. The resulting C60-f-MS microsphere has magnetite core and thin C60 modified silica shell, which endow them with useful magnetic responsivity and surface affinity toward low-concentration peptides and proteins. As a result of their excellent magnetic property, the synthesized C60-f-MS microspheres can be easily separated from sample solution without ultracentrifuge. The C60-f-MS microspheres were successfully applied to the enrichment of low-concentration peptides in tryptic protein digest and human urine via a MALDI-TOF MS analysis. Moreover, they were demonstrated to have enrichment efficiency for low-concentration proteins. Due to the novel materials maintaining excellent magnetic properties and admirable adsorption, the process of enrichment and desalting is very fast (only 5 min), convenient and efficient. As it has been demonstrated in the study, newly developed fullerene-derivatized magnetic silica materials are superior to those already available in the market. The facile and low-cost synthesis as well as the convenient and efficient enrichment process of the novel C60-f-MS microspheres makes it a promising candidate for isolation of low-concentration peptides and proteins even in complex biological samples such as serum, plasma, and urine or cell lysate. PMID:19086100

  13. Monodisperse microporous carbon nanospheres: An efficient and stable solid phase microextraction coating material.

    PubMed

    Zheng, Juan; Wang, Kun; Luo, Erlun; Wu, Dingcai; Zhu, Fang; Jiang, Ruifen; Su, Chengyong; Wei, Chaohai; Ouyang, Gangfeng

    2015-07-16

    The monodisperse microporous carbon nanospheres (MMCNSs) were applied in solid phase microextraction for the first time. The MMCNSs-fiber was prepared by sol-gel technique and good repeatability and reproducibility were obtained, due to the excellent monodispersity of the MMCNSs. The sol-gel-MMCNSs fiber exhibited superior extraction ability for polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs), compared with the commercial polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber and the fiber prepared with its precursor, the monodisperse microporous polystyrene nanospheres (MMPNSs). Moreover, the fiber has good thermostability and strong acid/base durability. The sol-gel-MMCNSs fiber was then employed to detect PAHs and OCPs in aqueous samples by combining with gas chromatography-mass spectrometer (GC-MS). Under the optimized conditions, the detection limits of the proposed method ranged from 0.10 to 5.5 ng L(-1). Furthermore, the method was successfully utilized for the analysis of PAHs and OCPs in real samples, with satisfactory recoveries in the range of 81.0-120% for the Pearl River water samples and 72.8-118% for the coking wastewater samples. PMID:26073808

  14. Responsive Guest Encapsulation of Dynamic Conjugated Microporous Polymers

    NASA Astrophysics Data System (ADS)

    Xu, Lai; Li, Youyong

    2016-06-01

    The host-guest complexes of conjugated microporous polymers encapsulating C60 and dye molecules have been investigated systematically. The orientation of guest molecules inside the cavities, have different terms: inside the open cavities of the polymer, or inside the cavities formed by packing different polymers. The host backbone shows responsive dynamic behavior in order to accommodate the size and shape of incoming guest molecule or guest aggregates. Simulations show that the host-guest binding of conjugated polymers is stronger than that of non-conjugated polymers. This detailed study could provide a clear picture for the host-guest interaction for dynamic conjugated microporous polymers. The mechanism obtained could guide designing new conjugated microporous polymers.

  15. Responsive Guest Encapsulation of Dynamic Conjugated Microporous Polymers.

    PubMed

    Xu, Lai; Li, Youyong

    2016-01-01

    The host-guest complexes of conjugated microporous polymers encapsulating C60 and dye molecules have been investigated systematically. The orientation of guest molecules inside the cavities, have different terms: inside the open cavities of the polymer, or inside the cavities formed by packing different polymers. The host backbone shows responsive dynamic behavior in order to accommodate the size and shape of incoming guest molecule or guest aggregates. Simulations show that the host-guest binding of conjugated polymers is stronger than that of non-conjugated polymers. This detailed study could provide a clear picture for the host-guest interaction for dynamic conjugated microporous polymers. The mechanism obtained could guide designing new conjugated microporous polymers. PMID:27356483

  16. Responsive Guest Encapsulation of Dynamic Conjugated Microporous Polymers

    PubMed Central

    Xu, Lai; Li, Youyong

    2016-01-01

    The host-guest complexes of conjugated microporous polymers encapsulating C60 and dye molecules have been investigated systematically. The orientation of guest molecules inside the cavities, have different terms: inside the open cavities of the polymer, or inside the cavities formed by packing different polymers. The host backbone shows responsive dynamic behavior in order to accommodate the size and shape of incoming guest molecule or guest aggregates. Simulations show that the host-guest binding of conjugated polymers is stronger than that of non-conjugated polymers. This detailed study could provide a clear picture for the host-guest interaction for dynamic conjugated microporous polymers. The mechanism obtained could guide designing new conjugated microporous polymers. PMID:27356483

  17. Preparation of silica-sustained electrospun polyvinylpyrrolidone fibers with uniform mesopores via oxidative removal of template molecules by H{sub 2}O{sub 2} treatment

    SciTech Connect

    Kang, Haigang; Zhu, Yihua; Shen, Jianhua; Yang, Xiaoling; Chen, Cheng; Cao, Huimin; Li, Chungzhong

    2010-07-15

    Silica-sustained electrospun PVP fibers with uniform mesopores were synthesized via facile oxidative removal of template molecules by H{sub 2}O{sub 2} extraction. Tetraethyl orthosilicate, polyvinylpyrrolidone (PVP), and triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymer pluronic P{sub 123} compose the electrospinning sol to fabricate the silica-sustained PVP hybrid fibers. The effect of different post-treatment methods on the pore size distribution was investigated by calcination and extraction, respectively. Experimental results showed that oxidative removal of structure-directing agent P{sub 123} in the hybrid fibers by H{sub 2}O{sub 2} treatment can easily form narrow pore size distribution, and the incorporation of 3D silica skeleton built by hot steam aging facilitated preserving the original cylindrical morphology of fibers. Scanning electron microscopy (SEM), N{sub 2} adsorption-desorption isotherm, transmission electron microscopy (TEM), X-ray diffraction (XRD), FT-IR spectra and thermogravimetric analysis (TGA) were used to characterize the hybrid fibers. The hybrid fibers can be expected to have potential applications in drug release or tissue engineering because of their suitable pore size, large surface area and good biocompatibility.

  18. Distribution and Speciation of Nutrient Elements around Micropores

    SciTech Connect

    Jassogne, Laurence; Hettiarachchi, Ganga; Chittleborough, David; McNeill, Ann

    2009-07-21

    In Australia a class of soils known as duplex soils covers approximately 20% of the continent. Their defining characteristic is a sharp texture contrast between the A (or E) and B horizon. The upper B horizon at the point of contact with the E horizon is often highly sodic and of such a high strength that root growth and proliferation, water conductivity, aeration, water storage, and water uptake are restricted. Roots growing in these soils rely on channels created by previous roots or cracks arising from shrink-swell forces associated with seasonal wetting and drying. Although the characteristics of rhizospheres compared with the soil matrix are well documented there is a paucity of knowledge about how long these changes persist after roots decay. This knowledge is fundamental to our understanding of root growth in duplex soils in which plants rely on pore networks formed by previous plants to proliferate in the subsoil. In this study we investigated the heterogeneous chemistry of micropores in situ using synchrotron-based {mu}-x-ray fluorescence spectroscopy (XRF), {mu}-x-ray absorption near edge structure spectroscopy (XANES), and extended {mu}-x-ray absorption fine structure spectroscopy (EXAFS). The distribution maps of Ca, Mn, Fe, Cu, and Zn at micrometer resolution were collected using {mu}-XRF. Subsequently, specific locations with higher concentrations (hot spots) of Mn, Fe, Cu, or Zn were selected and XANES and EXAFS spectra were collected to study the speciation of these elements around the micropore compared with the soil matrix. The {mu}-XRF maps showed that Mn was depleted around one of the micropores studied but accumulated around another micropore. Copper and Zn accumulated around the micropores, whereas Ca was predominantly inside micropores. There was no difference between matrix and micropore surface with respect to the distribution of Fe. Around micropores Mn was present in reduced form (Mn II) and Fe was in its oxidized form (Fe III). Manganese

  19. Preparation of silicon@silicon oxide core-shell nanowires from a silica precursor toward a high energy density Li-ion battery anode.

    PubMed

    Zhang, Chuanjian; Gu, Lin; Kaskhedikar, Nitin; Cui, Guanglei; Maier, Joachim

    2013-12-11

    Bulk-quantity silicon@silicon oxide nanowires have been successfully synthesized via a facile high-temperature approach using environment-friendly silica mixed with titanium powders. It is confirmed that the obtained nanowires process a crystalline core and amorphous oxide sheath. The obtained nanowires grow along the [111] direction which catalyzed by spherical silicon@siilcon oxide nanoparticles. The unique one-dimensional structure and thin oxide sheath result in the favorable electrochemical performances, which may be beneficial to the high energy density silicon anode for lithium ion batteries. PMID:24229329

  20. Formation, Structure and Electrochemical Impedance Analysis of Microporous Polyelectrolyte Multilayers

    NASA Astrophysics Data System (ADS)

    Lutkenhaus, Jodie; McEnnis, Kathleen; Hammond, Paula

    2007-03-01

    Microporous networks are of interest as electrolyte materials, gas separation membranes and catalytic nanoparticle templates. Here, we create microporous polyelectrolyte networks of tunable pore size and connectivity using the layer-by-layer (LBL) technique. In this method, a film is formed from the alternate adsorption of oppositely charged polyelectrolytes from aqueous solution to create a cohesive thin film. Using poly(ethylene imine) (PEI) and poly(acrylic acid) (PAA), LBL thin films of variable composition and charge density were assembled; then, the films were treated in an acidic bath, which ionizes PEI and de-ionizes PAA. This shift in charge density induces morphological rearrangement realized by a microporous network. Depending on the assembly pH and acidic bath pH, we are able to precisely tune the morphology, which is characterized by atomic force microscopy and scanning electron microscopy. To demonstrate the porous nature of the polyelectrolyte multilayer, the pores were filled with non-aqueous electrolyte (i.e. ethylene carbonate, dimethyl carbonate and lithium hexafluorophosphate) and probed with electrochemical impedance spectroscopy. These microporous networks exhibited two time constants, indicative of ions traveling through the liquid-filled pores and ions traveling through the polyelectrolyte matrix.

  1. Rendering non-energetic microporous coordination polymers explosive.

    PubMed

    McDonald, Kyle A; Bennion, Jonathan C; Leone, Amanda K; Matzger, Adam J

    2016-09-18

    Adsorption of oxidizing guest molecules into a non-energetic microporous coordination polymer produces explosives with desirable oxygen balance, high heat released upon decomposition, and suppressed vapor pressure of the guest. Here, this results in primary explosives, materials very sensitive to impact, that have the potential to be used as replacements for lead-based initiators. PMID:27523573

  2. Fundamental Studies of Crystal Growth of Microporous Materials

    NASA Technical Reports Server (NTRS)

    Singh, Ramsharan; Doolittle, John, Jr.; Payra, Pramatha; Dutta, Prabir K.; George, Michael A.; Ramachandran, Narayanan; Schoeman, Brian J.

    2003-01-01

    Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include: (a) Nature of the molecular units responsible for the crystal nuclei formation; (b) Nature of the nuclei and nucleation process; (c) Growth process of the nuclei into crystal; (d) Morphological control and size of the resulting crystal; (e) Surface structure of the resulting crystals; and (f) Transformation of frameworks into other frameworks or condensed structures.

  3. Anisotropic microporous supports impregnated with polymeric ion-exchange materials

    DOEpatents

    Friesen, Dwayne; Babcock, Walter C.; Tuttle, Mark

    1985-05-07

    Novel ion-exchange media are disclosed, the media comprising polymeric anisotropic microporous supports containing polymeric ion-exchange or ion-complexing materials. The supports are anisotropic, having small exterior pores and larger interior pores, and are preferably in the form of beads, fibers and sheets.

  4. Anisotropic microporous supports impregnated with polymeric ion-exchange materials

    DOEpatents

    Friesen, D.; Babcock, W.C.; Tuttle, M.

    1985-05-07

    Novel ion-exchange media are disclosed, the media comprising polymeric anisotropic microporous supports containing polymeric ion-exchange or ion-complexing materials. The supports are anisotropic, having small exterior pores and larger interior pores, and are preferably in the form of beads, fibers and sheets. 5 figs.

  5. Preparation of a novel ionic hybrid stationary phase by non-covalent functionalization of single-walled carbon nanotubes with amino-derivatized silica gel for fast HPLC separation of aromatic compounds.

    PubMed

    Aral, Hayriye; Çelik, K Serdar; Aral, Tarık; Topal, Giray

    2016-03-01

    Single-walled carbon nanotubes (SWCNTs) were immobilized on spherical silica gel with a 4-μm average particle size and a 60-Å average pore size. The amino-derivatized silica gel was non-covalently coated with carboxylated SWCNTs to preserve the structure of the nanotubes and their physico-chemical properties. The novel ionic hybrid stationary phase was characterized by scanning electron microscopy (SEM), infra-red (IR) spectroscopy and elemental analysis, and then, it was used to fill an empty 150×4.6mm(2) high-performance liquid chromatography (HPLC) column. Chromatographic parameters, such as the theoretical plate number, retention factor and peak asymmetry factor, and analytical parameters, such as the limit of detection (LOD), limit of quantification (LOQ), linear range, calibration equation, and R(2) value, and quantitative analysis parameters were calculated for all of the analytes. Using different mobile phases, five different classes of aromatic hydrocarbons were separated in a very short analysis time of 4-8min. Furthermore, a high theoretical plate number (up to 25000) and an excellent peak asymmetry factor (1.0) were obtained. The results showed that the surface of the SWNTs had very strong interactions with aromatic groups, therefore providing high selectivity for the separation of different classes of aromatic compounds. This study indicates that SWCNTs enable the extension of the application range of the newly prepared stationary phases for the fast separation of aromatic compounds by HPLC. PMID:26717810

  6. Development of microporous structure and its application to optical film for cellulose triacetate containing diisodecyl adipate.

    PubMed

    Shimada, Hikaru; Nobukawa, Shogo; Yamaguchi, Masayuki

    2015-04-20

    Phase separation in plasticized cellulose triacetate (CTA) films is investigated to produce a microporous film that can be used in optical devices. Hot-stretched CTA films containing diisodecyl adipate (DIDA) show negative orientation birefringence similar to the hot-stretched pure CTA. After extracting DIDA from the stretched films by immersion into an organic solvent, however, the films exhibit positive birefringence. Moreover, the magnitude of the birefringence increases with the wavelength, known as extraordinary dispersion, which is an essential property in the preparation of an ideal quarter-wave plate. Numerous ellipsoidal pores with micro-scale were detected in the film after the immersion, indicating that DIDA were segregated and formed ellipsoidal domains in the CTA matrix during annealing and stretching. These results indicate that extraordinary wavelength dispersion is given by the combinations of orientation birefringence from CTA and form birefringence from micropores. Furthermore, it was found that annealing time and stretching condition affect the phase separation as well as the shape and size of pores. PMID:25662683

  7. Synthesis and Characterization of a New Microporous Material. 1. Structure of Aluminophosphate EMM-3

    SciTech Connect

    Afeworki,M.; Dorset, D.; Kennedy, G.; Strohmaier, K.

    2006-01-01

    Molecular sieves are extensively used in the chemical and petrochemical industry as catalysts, absorbents, and ion exchangers. New molecular sieve structures have the potential to improve the performance of these materials. We have discovered a new microporous material, EMM-3, prepared in both aluminophosphate and silicoaluminophosphate compositions by use of N,N,N,N{prime},N{prime},N{prime}-hexamethyl-1,6-hexanediammonium as a template at 160 C in 20 h. The structure of EMM-3 has been solved and refined from powder data by use of synchrotron X-ray radiation. The unit cell for the calcined AlPO form of EMM-3 has monoclinic space group symmetry, I2/m11, with cell dimensions a = 10.3132(2), b = 12.6975(3), and c = 21.8660(4) and {alpha}= 89.656(1). The microporous structure contains 12-ring, sinusoidal, unidimensional channels with pore openings of 6.1 x 6.5 Angstroms. This new framework contains two new building chains, not observed in other known framework structures. The {sup 31}P and {sup 27}Al NMR spectra of the calcined/dehydrated form are in agreement with a fully connected tetrahedral structure containing five unique phosphorus and five unique aluminum atoms. The material is stable upon calcination and absorbs 9-10 wt % hydrocarbons.

  8. Positively charged microporous ceramic membrane for the removal of Titan Yellow through electrostatic adsorption.

    PubMed

    Cheng, Xiuting; Li, Na; Zhu, Mengfu; Zhang, Lili; Deng, Yu; Deng, Cheng

    2016-06-01

    To develop a depth filter based on the electrostatic adsorption principle, positively charged microporous ceramic membrane was prepared from a diatomaceous earth ceramic membrane. The internal surface of the highly porous ceramic membrane was coated with uniformly distributed electropositive nano-Y2O3 coating. The dye removal performance was evaluated through pressurized filtration tests using Titan Yellow aqueous solution. It showed that positively charged microporous ceramic membrane exhibited a flow rate of 421L/(m(2)·hr) under the trans-membrane pressure of 0.03bar. Moreover it could effectively remove Titan Yellow with feed concentration of 10mg/L between pH3 to 8. The removal rate increased with the enhancement of the surface charge properties with a maximum rejection of 99.6%. This study provides a new and feasible method of removing organic dyes in wastewater. It is convinced that there will be a broad market for the application of charged ceramic membrane in the field of dye removal or recovery from industry wastewater. PMID:27266317

  9. [Preparation of xylitol and maltitol modified silica as novel stationary phases for hydrophilic interaction liquid chromatography and evaluation of their separation performance].

    PubMed

    Yong, Tian; Wu, Fan; Xiao, Hongbin; Wan, Boshun

    2015-09-01

    New types of stationary phases for hydrophilic interaction liquid chromatography (HILIC) with unique selectivity are very important for the separation of various polar and hydrophilic analytes. Two novel HILIC stationary phases based on sugar alcohol modified silica were synthesized by a simple two-step reaction in which xylitol and maltitol were bonded onto the surface of silica particles via the addition reaction between -NCO and -OH. The effect of acetonitrile content on the retention indicated that the two stationary phases were of typical HILIC character and exhibited strong retention for polar and hydrophilic analytes. They succeeded in the separation of a wide range of polar and hydrophilic analytes including water soluble vitamins, salicylic acid and its analogues, nucleic acid bases and nucleosides, and icariin and its analogues with unique selectivity. Especially, the maltitol stationary phase showed unique selectivity on glycosyl group, compared to xylitol stationary phase. Furthermore, the effects of buffer pH as well as salt concentration on the retention indicated that electrostatic interaction played an important role in the separation mechanism of the two stationary phases. For sure, the efficient stationary phases are of great potential applications in HILIC. PMID:26753275

  10. Facile large-scale preparation of mesoporous silica microspheres with the assistance of sucrose and their drug loading and releasing properties.

    PubMed

    Bi, Yanping; Wu, Chaonan; Xin, Ming; Bi, Shuyan; Yan, Chengxin; Hao, Jifu; Li, Fei; Li, Shou

    2016-03-16

    Mesoporous silica microspheres (MSMs) with a pore-size larger than 10nm and a large pore-volume have attracted considerable attention for their application in delivering poorly water-soluble drugs. Here we developed a simple method for large-scale synthesis of MSMs using sodium silicate as silica precursor. The novelty of this approach lies in the use of sucrose solution to achieve large size and volume of nanopores. The highest values of pore size and pore volume are 13.2 nm and 1.97 cm(3)/g, respectively. Importantly, the method is reliable and easily upscalable. The blank and drug-loaded MSMs were characterized by differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD). Ibuprofen and resveratrol were successfully loaded into the nanopores of MSMs in amorphous and nanocrystalline form and showed high drug-loadings and enhanced dissolution rates. This kind of MSMs appears to be a promising candidate as a new oral drug delivery vehicle providing a rapid drug release. PMID:26784977

  11. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    NASA Astrophysics Data System (ADS)

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  12. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    PubMed Central

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-01-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate. PMID:26235671

  13. Biodiesel production from sunflower, soybean, and waste cooking oils by transesterification using lipase immobilized onto a novel microporous polymer.

    PubMed

    Dizge, Nadir; Aydiner, Coskun; Imer, Derya Y; Bayramoglu, Mahmut; Tanriseven, Aziz; Keskinler, Bülent

    2009-03-01

    This study aims at carrying out lipase-catalyzed synthesis of fatty acid methyl esters (biodiesel) from various vegetable oils using lipase immobilized onto a novel microporous polymeric matrix (MPPM) as a low-cost biocatalyst. The research is focused on three aspects of the process: (a) MPPM synthesis (monolithic, bead, and powder forms), (b) microporous polymeric biocatalyst (MPPB) preparation by immobilization of lipase onto MPPM, and (c) biodiesel production by MPPB. Experimental planning of each step of the study was separately carried out in accordance with design of experiment (DoE) based on Taguchi methodology. Microporous polymeric matrix (MPPM) containing aldehyde functional group was synthesized by polyHIPE technique using styrene, divinylbenzene, and polyglutaraldehyde. Thermomyces lanuginosus lipase was covalently attached onto MPPM with 80%, 85%, and 89% immobilization efficiencies using bead, powder, and monolithic forms, respectively. Immobilized enzymes were successfully used for the production of biodiesel using sunflower, soybean, and waste cooking oils. It was shown that immobilized enzymes retain their activities during 10 repeated batch reactions at 25 degrees C, each lasting 24h. Since the developed novel method is simple yet effective, it could have a potential to be used industrially for the production of chemicals requiring immobilized lipases. PMID:19028094

  14. Encapsulation of silica nanoparticles by redox-initiated graft polymerization from the surface of silica nanoparticles.

    PubMed

    Wang, Huijun; Peng, Mao; Zheng, Jun; Li, Peng

    2008-10-01

    This study describes a facile and versatile method for preparing polymer-encapsulated silica particles by 'grafting from' polymerization initiated by a redox system comprising ceric ion (Ce(4+)) as an oxidant and an organic reductant immobilized on the surface of silica nanoparticles. The silica nanoparticles were firstly modified by 3-aminopropyltriethoxysilane, then reacted with poly(ethylene glycol) acrylate through the Michael addition reaction, so that hydroxyl-terminated poly(ethylene glycol) (PEG) were covalently attached onto the nanoparticle surface and worked as the reductant. Poly(methyl methacrylate) (PMMA), a common hydrophobic polymer, and poly(N-isopropylacrylamide) (PNIPAAm), a thermosensitive polymer, were successfully grafted onto the surface of silica nanoparticles by 'grafting from' polymerization initiated by the redox reaction of Ce(4+) with PEG on the silica surface in acid aqueous solutions. The polymer-encapsulated silica nanoparticles (referred to as silica@PMMA and silica@PNIPAAm, respectively) were characterized by infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy. On the contrary, graft polymerization did not occur on bare silica nanoparticles. In addition, during polymerization, sediments were observed for PMMA and for PNIPAAm at a polymerization temperature above its low critical solution temperature (LCST). But the silica@PNIPAAm particles obtained at a polymerization temperature below the LCST can suspend stably in water throughout the polymerization process. PMID:18684468

  15. The preparation of silver nanoparticle decorated silica nanowires on fused quartz as reusable versatile nanostructured surface-enhanced Raman scattering substrates.

    PubMed

    Hwang, Jih-Shang; Chen, Kuan-Yu; Hong, Shih-Jay; Chen, Shih-Wei; Syu, Wun-Shing; Kuo, Chi-Wen; Syu, Wei-Yi; Lin, Tai Yuan; Chiang, Hai-Pang; Chattopadhyay, Surojit; Chen, Kuei-Hsien; Chen, Li-Chyong

    2010-01-15

    We introduce a platform, comprised of silver nanoparticle decorated silica nanowires (SiONWs) dispersed on fused quartz substrates, for high sensitivity surface-enhanced Raman scattering (SERS) measurements using both frontal (through the analytes) and back-face (through the transparent substrate) excitation. Quasi-quantitative SERS performances on the specialized substrate, vis-à-vis a silver deposited bare fused quartz plate, showed: (i) the suitability of the Ag modified SiONW substrate for frontal as well as back-face excitation; (ii) a wider detection range with high sensitivity to Rhodamine 6G; and (iii) good underwater metal-oxide adhesion of the specialized substrates. Capable of surviving ultrasonic cleaning, the substrate introduced is one of the few reusable low-cost Ag-based nanostructured SERS substrates, requiring only a simple silver reload process (the silver mirror reaction). PMID:19955621

  16. Stable photoluminescence of zinc oxide quantum dots in silica nanoparticles matrix prepared by the combined sol{endash}gel and spray drying method

    SciTech Connect

    Mikrajuddin; Iskandar, F.; Okuyama, K.; Shi, F. G.

    2001-06-01

    A sol{endash}gel method was employed to produce a zinc oxide (ZnO) colloid consisting of ZnO nanocrystalline particles with an average diameter of {similar_to}3 nm, and subsequently mixed with a silica (SiO{sub 2}) colloid. The mixture was finally spray dried to form a powder nanocomposite. It was found that the green photoluminescence (PL) exhibited by the composite was very stable: the intensity, position, and shape do not change even after being aged over 30 days. Thus, the ZnO/SiO{sub 2} nanocomposite has a much improved PL stability over ZnO colloids, which is often found to undergo a significant redshift even after aging over a few days. Our results are expected to have significant technological implications. {copyright} 2001 American Institute of Physics.

  17. Sample Desorption/Onization From Mesoporous Silica

    DOEpatents

    Iyer, Srinivas; Dattelbaum, Andrew M.

    2005-10-25

    Mesoporous silica is shown to be a sample holder for laser desorption/ionization of mass spectrometry. Supported mesoporous silica was prepared by coating an ethanolic silicate solution having a removable surfactant onto a substrate to produce a self-assembled, ordered, nanocomposite silica thin film. The surfactant was chosen to provide a desired pore size between about 1 nanometer diameter and 50 nanometers diameter. Removal of the surfactant resulted in a mesoporous silica thin film on the substrate. Samples having a molecular weight below 1000, such as C.sub.60 and tryptophan, were adsorbed onto and into the mesoporous silica thin film sample holder and analyzed using laser desorption/ionization mass spectrometry.

  18. Chemically-bound xenon in fibrous silica.

    PubMed

    Kalinowski, Jaroslaw; Räsänen, Markku; Gerber, R Benny

    2014-06-21

    High-level quantum chemical calculations reported here predict the existence and remarkable stability, of chemically-bound xenon atoms in fibrous silica. The results may support the suggestion of Sanloup and coworkers that chemically-bound xenon and silica account for the problem of "missing xenon" (by a factor of 20!) from the atmospheres of Earth and Mars. So far, the host silica was assumed to be quartz, which is in contradiction with theory. The xenon-fibrous silica molecule is computed to be stable well beyond room temperature. The calculated Raman spectra of the species agree well with the main features of the experiments by Sanloup et al. The results predict computationally the existence of a new family of noble-gas containing materials. The fibrous silica species are finite molecules, their laboratory preparation should be feasible, and potential applications are possible. PMID:24807740

  19. Incorporating Nano-silica as a Binder to Improve Corrosion Resistance of High Alumina Refractory Castables

    NASA Astrophysics Data System (ADS)

    Ramezani, Abbas; Mohebi, Mohammad Masoud; Souri, Alireza

    2013-04-01

    In this study, four types of castables as calcium-aluminate cement (CAC)-bonded and nano-silica (NS)-bonded castables based on tabular-alumina and bauxite aggregates were prepared to investigate the replacement of the calcium-aluminate cement by NS. All samples were allowed to dry at 110 °C then fired at 800 and 1200 °C. Bulk density and apparent porosity of samples were measured. The molten aluminum static corrosion test (cup test) results showed that NS-bonded specimens had higher resistance to corrosion compared to CAC-bonded samples (based on the measured average aluminum penetration depth into the refractory texture). However no penetration was observed in bauxite NS-bonded samples. The results were consistent with dynamic corrosion test in aluminum melt carried out at 800 °C for 100 h. The small pore size in NS-bonded castables was found to be the main cause for high corrosion resistance as micro-pores prevented the melt to penetrate into the refractory.

  20. Engineering Surface Energy and Nanostructure of Microporous Films for Expanded Membrane Distillation Applications.

    PubMed

    Boo, Chanhee; Lee, Jongho; Elimelech, Menachem

    2016-08-01

    We investigated the factors that determine surface omniphobicity of microporous membranes and evaluated the potential application of these membranes in desalination of low surface tension wastewaters by membrane distillation (MD). Specifically, the effects of surface morphology and surface energy on membrane surface omniphobicity were systematically investigated by evaluating wetting resistance to low surface tension liquids. Single and multilevel re-entrant structures were achieved by using cylindrical glass fibers as a membrane substrate and grafting silica nanoparticles (SiNPs) on the fibers. Surface energy of the membrane was tuned by functionalizing the fiber substrate with fluoroalkylsilane (FAS) having two different lengths of fluoroalkyl chains. Results show that surface omniphobicity of the modified fibrous membrane increased with higher level of re-entrant structure and with lower surface energy. The secondary re-entrant structure achieved by SiNP coating on the cylindrical fibers was found to play a critical role in enhancing the surface omniphobicity. Membranes coated with SiNPs and chemically modified by the FAS with a longer fluoroalkyl chain (or lower surface energy) exhibited excellent surface omniphobicity and showed wetting resistance to low surface tension liquids such as ethanol (22.1 mN m(-1)). We further evaluated performance of the membranes in desalination of saline feed solutions with varying surface tensions by membrane distillation (MD). The engineered membranes exhibited stable MD performance with low surface tension feed waters, demonstrating the potential application omniphobic membranes in desalinating complex, high salinity industrial wastewaters. PMID:27391088

  1. Surface modification of silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Ranjan, Rajesh

    Surface modification of nanosized silica particles by polymer grafting is gaining attention. This can be attributed to the fact that it provides a unique opportunity to engineer the interfacial properties of these modified particles; at the same time the mechanical and thermal properties of the polymers can be improved. Controlled free radical polymerization is a versatile technique which affords control over molecular weight, molecular weight distribution, architecture and functionalities of the resulting polymer. Three commonly used controlled free radical polymerizations include nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP) and reversible addition fragmentation transfer (RAFT) polymerization. ATRP and RAFT polymerization were explored in order to modify the silica surface with well-defined polymer brushes. A novel click-functionalized RAFT chain transfer agent (RAFT CTA) was synthesized which opened up the possibility of using RAFT polymerization and click chemistry together in surface modification. Using this RAFT CTA, the surface of silica nanoparticles was modified with polystyrene and polyacrylamide brushes via the "grafting to" approach. Both tethered polystyrene and polyacrylamide chains were found in the brush regime. The combination of ATRP and click chemistry was also explored for surface modification. A combination of RAFT polymerization and click chemistry was also studied to modify the surface via the "grafting from" approach. Our strategy included the (1) "grafting from" approach for brush formation (2) facile click reaction to immobilize the RAFT agent (3) synthesis of R-supported chain transfer agent and (4) use of the more active trithiocarbonate RAFT agent. Grafting density obtained by this method was significantly higher than reported values in the literature. Polystyrene (PS) grafted silica nanoparticles were also prepared by a tandem process that simultaneously employs reversible addition fragmentation

  2. Hydrolysis of microporous polyamide-6 membranes as substrate for in situ synthesis of oligonucleotides

    NASA Astrophysics Data System (ADS)

    Tang, Jianxin; He, Nongyue; Nie, Libo; Xiao, Pengfeng; Chen, Hong

    2004-02-01

    This article provides a novel method of preparing substrate for in situ synthesis of oligonucleotide by hydrolyzing microporous polyamide-6 membranes in a 0.01 mol/l/NaOH/(H 2O-CH 3OH) mixture medium with refluxing about 36 h. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) demonstrated the emergence of amines (NH 2) on the surface. Optimum hydrolyzing conditions were determined through the ultra-violet (UV) spectra. A pH value of 12 and a hydrolysis time of 36 h are the preferred conditions for the modification. The treated membrane can be applied to in situ synthesis of oligonucleotide and, for example, the oligonucleotide probes of 5 '-AAC CAC CAA ACA CAC-3 ' were successfully synthesized on the hydrolyzed membrane. The single step coupling efficiency determined by ultraviolet (UV) spectra is above 98%.

  3. Titanium-containing zeolites and microporous molecular sieves as photovoltaic solar cells.

    PubMed

    Atienzar, Pedro; Valencia, Susana; Corma, Avelino; García, Hermenegildo

    2007-05-14

    Four titanium-containing zeolites and microporous molecular sieves differing on the crystal structure and particle size (Ti/Beta, Ti/Beta-60, TS-1 and ETS-10) are prepared, and their activity for solar cells after incorporating N3 (a commercially available ruthenium polypyridyl dye) is tested. All the zeolites exhibit photovoltaic activity, and the photoresponse is quite independent of the zeolite pore dimensions or particle size. The photoresponse increases with titanium content in the range 1-7% wt. In this way, cells are obtained that have open-circuit voltage Voc=560 mV and maximum short-circuit photocurrent density Isc=100 microA, measured for 1x1 cm2 surfaces with a solar simulator at 1000 W through and AM 1.5 filter. These values are promising and comparable to those obtained for current dye-sensitized titania solar cells. PMID:17410619

  4. Highly Conductive Anion-Exchange Membranes from Microporous Tröger's Base Polymers.

    PubMed

    Yang, Zhengjin; Guo, Rui; Malpass-Evans, Richard; Carta, Mariolino; McKeown, Neil B; Guiver, Michael D; Wu, Liang; Xu, Tongwen

    2016-09-12

    The development of polymeric anion-exchange membranes (AEMs) combining high ion conductivity and long-term stability is a major challenge for materials chemistry. AEMs with regularly distributed fixed cationic groups, based on the formation of microporous polymers containing the V-shape rigid Tröger's base units, are reported for the first time. Despite their simple preparation, which involves only two synthetic steps using commercially available precursors, the polymers provide AEMs with exceptional hydroxide conductivity at relatively low ion-exchange capacity, as well as a high swelling resistance and chemical stability. An unprecedented hydroxide conductivity of 164.4 mS cm(-1) is obtained at a relatively a low ion-exchange capacity of 0.82 mmol g(-1) under optimal operating conditions. The exceptional anion conductivity appears related to the intrinsic microporosity of the charged polymer matrix, which facilitates rapid anion transport. PMID:27505421

  5. Filtration characteristics of the polyester fiber micropore blood transfusion filter.

    PubMed

    Risberg, B I; Hurley, M J; Miller, E; deJongh, D S; Litwin, M S

    1979-06-01

    The filtration characteristics of a new polyester fiber (Fenwal II) micropore blood transfusion filter were investigated. Filtration of stored human whole blood and packed cells resulted in return of screen filtration pressure (SFP) of the blood to normal. Increased filter weights verified removal of large amounts of debris and microaggregates from the blood. Filtration of large quantities of blood accomplished at very high flow rates did not adversely affect the composition of the filtered blood. We conclude that the polyester fiber (Fenwal II) micropore blood transfusion filter is effective in removing microaggregates from stored whole blood and packed cells. It has a high volume capacity, allows rapid flow, and is reliable during pressure transfusion. PMID:451646

  6. A multifunctional role of trialkylbenzenes for the preparation of aqueous colloidal mesostructured/mesoporous silica nanoparticles with controlled pore size, particle diameter, and morphology

    NASA Astrophysics Data System (ADS)

    Yamada, Hironori; Ujiie, Hiroto; Urata, Chihiro; Yamamoto, Eisuke; Yamauchi, Yusuke; Kuroda, Kazuyuki

    2015-11-01

    Both the pore size and particle diameter of aqueous colloidal mesostructured/mesoporous silica nanoparticles (CMSS/CMPS) derived from tetrapropoxysilane were effectively and easily controlled by the addition of trialkylbenzenes (TAB). Aqueous highly dispersed CMPS with large pores were successfully obtained through removal of surfactants and TAB by a dialysis process. The pore size (from 4 nm to 8 nm) and particle diameter (from 50 nm to 380 nm) were more effectively enlarged by the addition of 1,3,5-triisopropylbenzene (TIPB) than 1,3,5-trimethylbenzene (TMB), and the enlargement did not cause the variation of the mesostructure and particle morphology. The larger molecular size and higher hydrophobicity of TIPB than TMB induce the incorporation of TIPB into micelles without the structural change. When TMB was used as TAB, the pore size of CMSS was also enlarged while the mesostructure and particle morphology were varied. Interestingly, when tetramethoxysilane and TIPB were used, CMSS with a very small particle diameter (20 nm) with concave surfaces and large mesopores were obtained, which may strongly be related to the initial nucleation of CMSS. A judicious choice of TAB and Si sources is quite important to control the mesostructure, size of mesopores, particle diameter, and morphology.Both the pore size and particle diameter of aqueous colloidal mesostructured/mesoporous silica nanoparticles (CMSS/CMPS) derived from tetrapropoxysilane were effectively and easily controlled by the addition of trialkylbenzenes (TAB). Aqueous highly dispersed CMPS with large pores were successfully obtained through removal of surfactants and TAB by a dialysis process. The pore size (from 4 nm to 8 nm) and particle diameter (from 50 nm to 380 nm) were more effectively enlarged by the addition of 1,3,5-triisopropylbenzene (TIPB) than 1,3,5-trimethylbenzene (TMB), and the enlargement did not cause the variation of the mesostructure and particle morphology. The larger molecular size

  7. NMR studies of methane and hydrogen in microporous materials

    NASA Astrophysics Data System (ADS)

    Ji, Yu; Hamida, J. A.; Tang, Yibing; Sullivan, N. S.

    2016-02-01

    We review the results of nuclear magnetic resonance studies of the molecular dynamics of the quantum gases HD and CH4 adsorbed in the cages of microporous structures. Measurements of the variation of the nuclear spin-lattice and nuclear spin-spin relaxation times with temperature provide detailed information about the translational and rotational dynamics of the adsorbed molecules over a wide temperature range.

  8. Cell trapping in activated micropores for functional analysis.

    PubMed

    Talasaz, AmirAli H; Powell, Ashley A; Stahl, Patrik; Ronaghi, Mostafa; Jeffrey, Stefanie S; Mindrinos, Michael; Davis, Ronald W

    2006-01-01

    This paper presents a novel device which provides the opportunity to perform high-throughput biochemical assays on different individual cells. In particular, the proposed device is suited to screen the rare cells in biological samples for early stage cancer diagnosis and explore their biochemical functionality. In the process, single cells are precisely positioned and captured in activated micropores. To show the performance of the proposed device, cultured yeast cells and human epithelial circulating tumor cells are successfully captured. PMID:17945673

  9. Origin of reduction in phonon thermal conductivity of microporous solids

    NASA Astrophysics Data System (ADS)

    Hopkins, Patrick E.; Rakich, Peter T.; Olsson, Roy H.; El-kady, Ihab F.; Phinney, Leslie M.

    2009-10-01

    Porous structures have strong tunable size effects due to increased surface area. Size effects on phonon thermal conductivity have been observed in porous materials with periodic voids on the order of microns. This letter explores the origin of this size effect on phonon thermal conductivity observed in periodic microporous membranes. Pore-edge boundary scattering of low frequency phonons explains the temperature trends in the thermal conductivity; further reduction in thermal conductivity is explained by the porosity.

  10. Fundamental Studies of Crystal Growth of Microporous Materials

    NASA Technical Reports Server (NTRS)

    Dutta, P.; George, M.; Ramachandran, N.; Schoeman, B.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include: (1) Nature of the molecular units responsible for the crystal nuclei formation; (2) Nature of the nuclei and nucleation process; (3) Growth process of the nuclei into crystal; (4) Morphological control and size of the resulting crystal; (5) Surface structure of the resulting crystals; (6) Transformation of frameworks into other frameworks or condensed structures. The NASA-funded research described in this report focuses to varying degrees on all of the above issues and has been described in several publications. Following is the presentation of the highlights of our current research program. The report is divided into five sections: (1) Fundamental aspects of the crystal growth process; (2) Morphological and Surface properties of crystals; (3) Crystal dissolution and transformations; (4) Modeling of Crystal Growth; (5) Relevant Microgravity Experiments.

  11. Reverse Micelle Based Synthesis of Microporous Materials in Microgravity

    NASA Technical Reports Server (NTRS)

    Dutta, Prabir K.

    2001-01-01

    Microporous materials include a large group of solids of varying chemical composition as well as porosity. These materials are characterized by channels and cavities of molecular dimensions. The framework structure is made up of interconnecting T-O-T' bonds, where T and T' can be Si, Al, P, Ga, Fe, Co, Zn, B and a host of other elements. Materials with Si-O-Al bonding in the framework are called zeolites and are extensively used in many applications. Ion-exchange properties of these materials are exploited in the consumer and environmental industries. Chemical and petroleum industries use zeolites as catalysts in hydrocarbon transform ations. Synthesis of new microporous frameworks has led to the development of new technologies, and thus considerable effort worldwide is expended in their discovery. Microporous materials are typically made under hydrothermal conditions. Influence of nature of starting reactants, structure directing agents, pH, temperature, and aging all have profound influence on the synthesis process. This is primarily because the most interesting open frameworks are not necessarily the stable structures in the reaction medium. Thus, the discovery of new frameworks is often tied to finding the right composition and synthesis conditions that allow for kinetic stabilization of the structure. This complexity of the synthesis process and limited understanding of it has made it difficult to develop directed is of microporous materials and most advances in this field have been made by trial and error. The basic issues in crystal growth of these materials include: (1) Nature of the nucleation process; (2) Molecular structure and assembly of nuclei; (3) Growth of nuclei into crystals; (4) Morphology control; and (5) Transformation of frameworks into other structures. The NASA-funded research described in this paper focuses on all the above issues and has been described in several publications. We present the highlights of our program, especially with the

  12. One-Step Synthesis of Microporous Carbon Monoliths Derived from Biomass with High Nitrogen Doping Content for Highly Selective CO2 Capture.

    PubMed

    Geng, Zhen; Xiao, Qiangfeng; Lv, Hong; Li, Bing; Wu, Haobin; Lu, Yunfeng; Zhang, Cunman

    2016-01-01

    The one-step synthesis method of nitrogen doped microporous carbon monoliths derived from biomass with high-efficiency is developed using a novel ammonia (NH3)-assisted activation process, where NH3 serves as both activating agent and nitrogen source. Both pore forming and nitrogen doping simultaneously proceed during the process, obviously superior to conventional chemical activation. The as-prepared nitrogen-doped active carbons exhibit rich micropores with high surface area and high nitrogen content. Synergetic effects of its high surface area, microporous structure and high nitrogen content, especially rich nitrogen-containing groups for effective CO2 capture (i.e., phenyl amine and pyridine-nitrogen) lead to superior CO2/N2 selectivity up to 82, which is the highest among known nanoporous carbons. In addition, the resulting nitrogen-doped active carbons can be easily regenerated under mild conditions. Considering the outstanding CO2 capture performance, low production cost, simple synthesis procedure and easy scalability, the resulting nitrogen-doped microporous carbon monoliths are promising candidates for selective capture of CO2 in industrial applications. PMID:27488268

  13. One-Step Synthesis of Microporous Carbon Monoliths Derived from Biomass with High Nitrogen Doping Content for Highly Selective CO2 Capture

    PubMed Central

    Geng, Zhen; Xiao, Qiangfeng; Lv, Hong; Li, Bing; Wu, Haobin; Lu, Yunfeng; Zhang, Cunman

    2016-01-01

    The one-step synthesis method of nitrogen doped microporous carbon monoliths derived from biomass with high-efficiency is developed using a novel ammonia (NH3)-assisted activation process, where NH3 serves as both activating agent and nitrogen source. Both pore forming and nitrogen doping simultaneously proceed during the process, obviously superior to conventional chemical activation. The as-prepared nitrogen-doped active carbons exhibit rich micropores with high surface area and high nitrogen content. Synergetic effects of its high surface area, microporous structure and high nitrogen content, especially rich nitrogen-containing groups for effective CO2 capture (i.e., phenyl amine and pyridine-nitrogen) lead to superior CO2/N2 selectivity up to 82, which is the highest among known nanoporous carbons. In addition, the resulting nitrogen-doped active carbons can be easily regenerated under mild conditions. Considering the outstanding CO2 capture performance, low production cost, simple synthesis procedure and easy scalability, the resulting nitrogen-doped microporous carbon monoliths are promising candidates for selective capture of CO2 in industrial applications. PMID:27488268

  14. One-Step Synthesis of Microporous Carbon Monoliths Derived from Biomass with High Nitrogen Doping Content for Highly Selective CO2 Capture

    NASA Astrophysics Data System (ADS)

    Geng, Zhen; Xiao, Qiangfeng; Lv, Hong; Li, Bing; Wu, Haobin; Lu, Yunfeng; Zhang, Cunman

    2016-08-01

    The one-step synthesis method of nitrogen doped microporous carbon monoliths derived from biomass with high-efficiency is developed using a novel ammonia (NH3)-assisted activation process, where NH3 serves as both activating agent and nitrogen source. Both pore forming and nitrogen doping simultaneously proceed during the process, obviously superior to conventional chemical activation. The as-prepared nitrogen-doped active carbons exhibit rich micropores with high surface area and high nitrogen content. Synergetic effects of its high surface area, microporous structure and high nitrogen content, especially rich nitrogen-containing groups for effective CO2 capture (i.e., phenyl amine and pyridine-nitrogen) lead to superior CO2/N2 selectivity up to 82, which is the highest among known nanoporous carbons. In addition, the resulting nitrogen-doped active carbons can be easily regenerated under mild conditions. Considering the outstanding CO2 capture performance, low production cost, simple synthesis procedure and easy scalability, the resulting nitrogen-doped microporous carbon monoliths are promising candidates for selective capture of CO2 in industrial applications.

  15. Synthesis of mesoporous silica nanoparticles.

    PubMed

    Wu, Si-Han; Mou, Chung-Yuan; Lin, Hong-Ping

    2013-05-01

    Good control of the morphology, particle size, uniformity and dispersity of mesoporous silica nanoparticles (MSNs) is of increasing importance to their use in catalyst, adsorption, polymer filler, optical devices, bio-imaging, drug delivery, and biomedical applications. This review discusses different synthesis methodologies to prepare well-dispersed MSNs and hollow silica nanoparticles (HSNs) with tunable dimensions ranging from a few to hundreds of nanometers of different mesostructures. The methods include fast self-assembly, soft and hard templating, a modified Stöber method, dissolving-reconstruction and modified aerogel approaches. In practical applications, the MSNs prepared by these methods demonstrate good potential for use in high-performance catalysis, antireflection coating, transparent polymer-MSNs nanocomposites, drug-release and theranostic systems. PMID:23403864

  16. Silicon Micropore based Electromechanical Transducer to Differentiate Tumor Cells

    NASA Astrophysics Data System (ADS)

    Ali, Waqas; Raza, Muhammad U.; Khanzada, Raja R.; Kim, Young-Tae; Iqbal, Samir M.

    2015-03-01

    Solid-state micropores have been used before to differentiate cancer cells from normal cells using size-based filtering. Tumor cells differ from normal ones not only in size but also in physical properties like elasticity, shape, motility etc. Tumor cells show different physical attributes depending on the stage and type of cancer. We report a micropore based electromechanical transducer that differentiated cancer cells based on their mechanophysical properties. The device was interfaced with a high-speed patch-clamp measurement system that biased the ionic solution across the silicon-based membrane. The bias resulted in the flow of ionic current. Electrical pulses were generated when cells passed through. Different cells depicted characteristic pulses. Translocation profiles of cells that were either small or were more elastic and flexible caused electrical pulses shorter in widths and amplitudes whereas cells with larger size or lesser elasticity/flexibility showed deeper and wider pulses. Three non-small cell lung cancer (NSCLC) cell lines NCI-H1155, A549 and NCI-H460 were successfully differentiated. NCI-H1155, due to their comparatively smaller size, were found quickest in translocating through. The solid-sate micropore based electromechanical transducer could process the whole blood sample of cancer patient without any pre-processing requirements and is ideal for point-of-care applications. Support Acknowledged from NSF through ECCS-1201878.

  17. On the physical adsorption of vapors by microporous carbons

    SciTech Connect

    Bradley, R.H. . Inst. of Surface Science and Technology); Rand, B. . Division of Ceramics)

    1995-01-01

    The physical adsorption of nonpolar and polar vapors by active carbons is discussed in relation to pore structure and pore wall chemistry. For nonpolar vapors the Dubinin-Radushkevich equation is used to derive micropore volumes (W[sub 0]), average adsorption energies (E[sub 0]), and micropore widths (L) for a number of systems. These parameters are used to interpret the adsorption behavior of nitrogen which, because it is a relatively small molecule, is frequently used at 77 K to probe porosity and surface area. Results are presented for three carbons from differing precursors, namely, coal, coconut shells, and polyvinylidene chloride (PVDC) to illustrate the applicability of the technique. For the latter carbon increases in micropore size, induced by activation in carbon dioxide, and reductions in accessible pore volume caused by heat treatment in argon are also characterized and related to structural changes. The approach is then extended to the adsorption of larger hydrogen vapors, where the resulting W[sub 0] values may require correction for molecular packing effects which occur in the lower relative pressure regions of the isotherms, i.e., during the filling of ultramicropores. These packing effects are shown to limit the use of the Polanyi characteristic curve for correlating isotherm data for several vapors, of differing molecular size, by one adsorbent. Data for the adsorption of water, which is a strongly polar liquid, have been interpreted using the Dubinin-Serpinsky equation.

  18. In situ ultra-small-angle X-ray scattering study under uniaxial stretching of colloidal crystals prepared by silica nanoparticles bearing hydrogen-bonding polymer grafts.

    PubMed

    Ishige, Ryohei; Williams, Gregory A; Higaki, Yuji; Ohta, Noboru; Sato, Masugu; Takahara, Atsushi; Guan, Zhibin

    2016-05-01

    A molded film of single-component polymer-grafted nanoparticles (SPNP), consisting of a spherical silica core and densely grafted polymer chains bearing hydrogen-bonding side groups capable of physical crosslinking, was investigated by in situ ultra-small-angle X-ray scattering (USAXS) measurement during a uniaxial stretching process. Static USAXS revealed that the molded SPNP formed a highly oriented twinned face-centered cubic (f.c.c.) lattice structure with the [11-1] plane aligned nearly parallel to the film surface in the initial state. Structural analysis of in situ USAXS using a model of uniaxial deformation induced by rearrangement of the nanoparticles revealed that the f.c.c. lattice was distorted in the stretching direction in proportion to the macroscopic strain until the strain reached 35%, and subsequently changed into other f.c.c. lattices with different orientations. The lattice distortion and structural transition behavior corresponded well to the elastic and plastic deformation regimes, respectively, observed in the stress-strain curve. The attractive interaction of the hydrogen bond is considered to form only at the top surface of the shell and then plays an effective role in cross-linking between nanoparticles. The rearrangement mechanism of the nanoparticles is well accounted for by a strong repulsive interaction between the densely grafted polymer shells of neighboring particles. PMID:27158507

  19. In situ ultra-small-angle X-ray scattering study under uniaxial stretching of colloidal crystals prepared by silica nanoparticles bearing hydrogen-bonding polymer grafts

    PubMed Central

    Ishige, Ryohei; Williams, Gregory A.; Higaki, Yuji; Ohta, Noboru; Sato, Masugu; Takahara, Atsushi; Guan, Zhibin

    2016-01-01

    A molded film of single-component polymer-grafted nanoparticles (SPNP), consisting of a spherical silica core and densely grafted polymer chains bearing hydrogen-bonding side groups capable of physical crosslinking, was investigated by in situ ultra-small-angle X-ray scattering (USAXS) measurement during a uniaxial stretching process. Static USAXS revealed that the molded SPNP formed a highly oriented twinned face-centered cubic (f.c.c.) lattice structure with the [11−1] plane aligned nearly parallel to the film surface in the initial state. Structural analysis of in situ USAXS using a model of uniaxial deformation induced by rearrangement of the nanoparticles revealed that the f.c.c. lattice was distorted in the stretching direction in proportion to the macroscopic strain until the strain reached 35%, and subsequently changed into other f.c.c. lattices with different orientations. The lattice distortion and structural transition behavior corresponded well to the elastic and plastic deformation regimes, respectively, observed in the stress–strain curve. The attractive interaction of the hydrogen bond is considered to form only at the top surface of the shell and then plays an effective role in cross-linking between nanoparticles. The rearrangement mechanism of the nanoparticles is well accounted for by a strong repulsive interaction between the densely grafted polymer shells of neighboring particles. PMID:27158507

  20. In situ ultra-small-angle X-ray scattering study under uniaxial stretching of colloidal crystals prepared by silica nanoparticles bearing hydrogen-bonding polymer grafts

    DOE PAGESBeta

    Ishige, Ryohei; Williams, Gregory A.; Higaki, Yuji; Ohta, Noboru; Sato, Masugu; Takahara, Atsushi; Guan, Zhibin

    2016-04-19

    A molded film of single-component polymer-grafted nanoparticles (SPNP), consisting of a spherical silica core and densely grafted polymer chains bearing hydrogen-bonding side groups capable of physical crosslinking, was investigated byin situultra-small-angle X-ray scattering (USAXS) measurement during a uniaxial stretching process. Static USAXS revealed that the molded SPNP formed a highly oriented twinned face-centered cubic (f.c.c.) lattice structure with the [11-1] plane aligned nearly parallel to the film surface in the initial state. Structural analysis ofin situUSAXS using a model of uniaxial deformation induced by rearrangement of the nanoparticles revealed that the f.c.c. lattice was distorted in the stretching direction inmore » proportion to the macroscopic strain until the strain reached 35%, and subsequently changed into other f.c.c. lattices with different orientations. The lattice distortion and structural transition behavior corresponded well to the elastic and plastic deformation regimes, respectively, observed in the stress–strain curve. The attractive interaction of the hydrogen bond is considered to form only at the top surface of the shell and then plays an effective role in cross-linking between nanoparticles. The rearrangement mechanism of the nanoparticles is well accounted for by a strong repulsive interaction between the densely grafted polymer shells of neighboring particles.« less

  1. Microporous Ni₁₁(HPO₃)₈(OH)₆ nanocrystals for high-performance flexible asymmetric all solid-state supercapacitors.

    PubMed

    Gao, Yanping; Zhao, Junhong; Run, Zhen; Zhang, Guangqin; Pang, Huan

    2014-12-01

    Microporous nickel phosphite [Ni11(HPO3)8(OH)6] nanocrystals were prepared using a hydrothermal method, and were successfully applied as a positive electrode in a flexible all solid-state asymmetric supercapacitor. Because of the specific micro/nanostructure, the flexible solid-state asymmetric supercapacitor can achieve a maximum energy density of 0.45 mW h cm(-3), which is higher than most reported supercapacitors. More importantly, the device performance remains efficient for 10,000 cycles. PMID:25329036

  2. Resolution and isolation of enantiomers of (±)-isoxsuprine using thin silica gel layers impregnated with L-glutamic acid, comparison of separation of its diastereomers prepared with chiral derivatizing reagents having L-amino acids as chiral auxiliaries.

    PubMed

    Bhushan, Ravi; Nagar, Hariom

    2015-03-01

    Thin silica gel layers impregnated with optically pure l-glutamic acid were used for direct resolution of enantiomers of (±)-isoxsuprine in their native form. Three chiral derivatizing reagents, based on DFDNB moiety, were synthesized having l-alanine, l-valine and S-benzyl-l-cysteine as chiral auxiliaries. These were used to prepare diastereomers under microwave irradiation and conventional heating. The diastereomers were separated by reversed-phase high-performance liquid chromatography on a C18 column with detection at 340 nm using gradient elution with mobile phase containing aqueous trifluoroacetic acid and acetonitrile in different compositions and by thin-layer chromatography (TLC) on reversed phase (RP) C18 plates. Diastereomers prepared with enantiomerically pure (+)-isoxsuprine were used as standards for the determination of the elution order of diastereomers of (±)-isoxsuprine. The elution order in the experimental study of RP-TLC and RP-HPLC supported the developed optimized structures of diastereomers based on density functional theory. The limit of detection was 0.1-0.09 µg/mL in TLC while it was in the range of 22-23 pg/mL in HPLC and 11-13 ng/mL in RP-TLC for each enantiomer. The conditions of derivatization and chromatographic separation were optimized. The method was validated for accuracy, precision, limit of detection and limit of quantification. PMID:25044026

  3. High-performance liquid chromatographic determination of mitoxantrone in plasma utilizing non-bonded silica gel for solid-phase isolation to reduce adsorptive losses on glass during sample preparation.

    PubMed

    Lin, K T; Rivard, G E; Leclerc, J M

    1989-03-10

    Mitoxantrone, a highly active antineoplastic agent, was found to bind strongly to non-bonded silica gel and glassware. When a Hamilton syringe was used to load and inject a mitoxantrone solution (0.4 microgram/ml in water) on to a high-performance liquid chromatographic (HPLC) system, about 95% of the loaded compound was found to bind to the glass surface of the syringe barrel and could not be removed by rinsing with water. It could, however, be removed slowly with an acidic solution and thus a small peak of mitoxantrone was present on the chromatogram whenever a blank acidic solution was injected with the syringe. The bound mitoxantrone could be removed effectively from the syringe surface with a solution of tetramethylammonium chloride, citric acid, methanol and water (elution solvent). This binding introduces a large error in assay results and might be one of the major factors responsible for contradictory pharmacokinetic data that have been reported. A new plasma preparation scheme and an HPLC method for mitoxantrone were developed to address this binding problem. Mitoxantrone was extracted directly from plasma samples with a plastic mini-column packed with non-bonded silica gel and eluted with the above elution solvent. The eluent was analysed by HPLC on an ODS column with an absorbance detector at 658 nm. The mobile phase was 0.1 M triethylamine phosphate (pH 3.0) in water-tetrahydrofuran-methanol (69:1:30) containing 0.02 M tetramethylammonium chloride. Methylene blue was added as an internal standard. Preliminary results showed that mitoxantrone levels in human plasma followed a triphasic decay curve after an intravenous bolus injection. The terminal elimination half-lives measured in three patients (mean t1/2 gamma = 25 min) were all shorter than the published values which ranged from 56 min to 9 days. PMID:2540217

  4. An ion-imprinted amino-functionalized silica gel sorbent prepared by hydrothermal assisted surface imprinting technique for selective removal of cadmium (II) from aqueous solution

    NASA Astrophysics Data System (ADS)

    Fan, Hong-Tao; Li, Jing; Li, Zhan-Chao; Sun, Ting

    2012-02-01

    A new ion-imprinted amino-functionalized silica gel sorbent was synthesized by the hydrothermal-assisted surface imprinting technique using Cd2+ as the template, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AAAPTS) as the functional monomer, and epichlorohydrin as the cross-linking agent (IIP-AAAPTS/SiO2) for the selective removal of Cd2+ from aqueous solution, and was characterized by FTIR, SEM, nitrogen adsorption and the static adsorption-desorption experiment method. The specific surface area of the IIP-AAAPTS/SiO2 sorbents was found to be 149 m2 g-1. The results showed that the maximum static adsorption capacities of IIP-AAAPTS/SiO2 sorbents by hydrothermal heating method and by the conventional heating method were 57.4 and 31.6 mg g-1, respectively. The IIP-AAAPTS/SiO2 sorbents offered a fast kinetics for the adsorption and desorption of Cd(II). The relative selectivity coefficients of IIP-AAAPTS/SiO2 sorbents for Cd2+/Co2+, Cd2+/Ni2+, Cd2+/Zn2+, Cd2+/Pb2+ and Cd2+/Cu2+ were 30.68, 14.02, 3.00, 3.12 and 6.17, respectively. IIP-AAAPTS/SiO2 sorbents had a substantial binding capacity in the range of pH 4-8 and could be used repeatedly. Equilibrium data fitted perfectly with Langmuir isotherm model compared to Freundlich isotherm model. Kinetic studies indicated that adsorption followed a pseudo-second-order model. Negative values of ΔG° indicated spontaneous adsorption and the degree of spontaneity of the reaction increased with increasing temperature. ΔH° of 26.13 kJ mol-1 due to the adsorption of Cd2+ on the IIP-AAAPTS/SiO2 sorbents indicated that the adsorption was endothermic in the experimental temperature range.

  5. Preparation and identification of multifunctional mesoporous silica nanoparticles for in vitro and in vivo dual-mode imaging, theranostics, and targeted tracking.

    PubMed

    Chan, Ming-Hsien; Lin, Hsiu-Mei

    2015-04-01

    Mesoporous silica nanoparticles (MSNs) can provide a structural foundation for a new generation of nanocarriers with a broad range of functionalities. Multifunctional MSNs can serve as all-in-one diagnostic and therapeutic tools that can be used to simultaneously visualize and treat various diseases, such as cancer. This research study is the first time that two lanthanide-based imaging systems have been combined to incorporate controlled drug release and targeted tracing into a single MSN-based nano-platform for a novel theranostic drug delivery system. Doping lanthanide ions, i.e., europium (Eu) and gadolinium (Gd) ions, into an MSN structure (EuGd-MSNs) imparts fluorescence and magnetism to the nanostructure that can be used to develop magnetic resonance imaging (MRI) and biological fluorescence tools. Current cancer research has revealed that most human cancer cells express a large number of folate receptors on their surface. Grafting folic acid (FA) onto the EuGd-MSN surface (EuGd-FA-MSNs) imparts a targeting function to the MSN because of the specificity of the binding of FA to cell surface receptors. Furthermore, grafting anticancer drugs, such as camptothecin (CPT), onto the surface of these MSNs by forming disulfide bonds (EuGd-SS-CPT-FA-MSNs) enables intracellular controlled drug release. A high concentration of intracellular glutathione cleaves the disulfide bond to release the drug and treat the disease. The results of in vitro and in vivo studies show that the functionalized MSNs can be successfully used as a platform to integrate dual-imaging, targeting, and therapeutic treatment in multifunctional diagnosis drug delivery systems. PMID:25678124

  6. Aminated hollow silica spheres for electrochemical DNA biosensor

    NASA Astrophysics Data System (ADS)

    Ariffin, Eda Yuhana; Heng, Lee Yook; Futra, Dedi; Ling, Tan Ling

    2015-09-01

    An electrochemical DNA biosensor for e.coli determination based on aminated hollow silica was successfully developed. Aminated hollow silica spheres were prepared through the reaction of Tween 20 template and silica precursor. The template was removed by the thermal decomposition at 620°C. Hollow silica spheres were modified with (3-Aminopropyl) triethoxysilane (APTS) to form aminated hollow silica spheres.Aminated DNA probe were covalently immobilized on to the amine functionalized hollow silica spheres through glutaradehyde linkers. The formation hollow silica was characterized using FTIR and FESEM. A range of 50-300nm particle size obtained from FESEM micrograph. Meanwhile for the electrochemical study, a quasi-reversible system has been obtain via cyclic voltammetry (CV).

  7. Multifunctional mesoporous silica catalyst

    DOEpatents

    Lin, Victor Shang-Yi; Tsai, Chih-Hsiang; Chen, Hung-Ting; Pruski, Marek; Kobayashi, Takeshi

    2015-03-31

    The present invention provides bifunctional silica mesoporous materials, including mesoporous silica nanoparticles ("MSN"), having pores modified with diarylammonium triflate and perfluoroaryl moieties, that are useful for the acid-catalyzed esterification of organic acids with organic alcohols.

  8. What Is Crystalline Silica?

    MedlinePlus

    ... silica, and requires a repirator protection program until engineering controls are implemented. Additionally, OSHA has a National ... silica materials with safer substitutes, whenever possible. ■ Provide engineering or administrative controls, where feasible, such as local ...

  9. Electron transfer reactions in microporous solids

    SciTech Connect

    Mallouk, T.E.

    1992-05-01

    We have studied electron transfer quenching of the excited state of Ru(bpy){sub 3}{sup 2+} in aqueous suspensions of zeolites Y, L, and mordenite. The internal pore network of the zeolite is ion-exchanged with methylviologen cations, which quench the excited state of the surface-bound sensitizer. A detailed study of the quenching and charge recombination kinetics, using time-resolved luminescence quenching and transient diffuse reflectance spectroscopies, shows to remarkable effects: first, the excited state quenching is entirely dynamic is large-pore zeolites (L and Y), even when they are prepared as apparently dry'' powders (which still contain significant amounts of internally sited water). Second, a lower limit for the diffusion coefficient of the MV{sup 2+} ion in these zeolites, determined by this technique, is 10{sup {minus}7} cm{sup 2}sec, i.e., only about one order of magnitude slower than a typical ion in liquid water, and 2--3 orders of magnitude faster than charge transfer diffusion of cations in polyelectrolyte films or membranes such as Nafion. Surface sensitization of internally platinized layered oxide semiconductors such as K{sub 4-x}H{sub x}Nb{sub 6}O{sub 17}{center dot}nH{sub 2}O (x {approx} 2.5) yields photocatalysts for the production of H{sub 2} and I{sub 3{minus}} in aqueous iodide solutions. Layered alkali niobates and titanates form a class of zeolitic wide-bandap semiconductors, and are the first examples of photocatalysts that evolve hydrogen from an electrochemically reversible (i.e., non-sacrificial) electron donor with visible light excitation.

  10. Electron transfer reactions in microporous solids

    NASA Astrophysics Data System (ADS)

    Mallouk, T. E.

    1992-05-01

    We have studied electron transfer quenching of the excited state of Ru3(2+) in aqueous suspensions of zeolites Y, L, and mordenite. The internal pore network of the zeolite is ion-exchanged with methylviologen cations, which quench the excited state of the surface-bound sensitizer. A detailed study of the quenching and charge recombination kinetics, using time-resolved luminescence quenching and transient diffuse reflectance spectroscopies, shows two remarkable effects: first, the excited state quenching is entirely dynamic is large-pore zeolites (L and Y), even when they are prepared as apparently 'dry' powders (which still contain significant amounts of internally sited water). Second, a lower limit for the diffusion coefficient of the MV(2+) ion in these zeolites, determined by this technique, is 10(exp -7) sq cm sec, i.e., only about one order of magnitude slower than a typical ion in liquid water, and 2 to 3 orders of magnitude faster than charge transfer diffusion of cations in polyelectrolyte films or membranes such as Nafion. Surface sensitization of internally platinized layered oxide semiconductors such as K(4-x)H(x)Nb6O17 - nH2O(x approx. = 2.5) yields photocatalysts for the production of H2 and I3(-) in aqueous iodide solutions. Layered alkali niobates and titanates form a class of zeolitic wide-bandap semiconductors, and are the first examples of photocatalysts that evolve hydrogen from an electrochemically reversible (i.e., non-sacrificial) electron donor with visible light excitation.

  11. Silica extraction from geothermal water

    SciTech Connect

    Bourcier, William L; Bruton, Carol J

    2014-09-23

    A method of producing silica from geothermal fluid containing low concentration of the silica of less than 275 ppm includes the steps of treating the geothermal fluid containing the silica by reverse osmosis treatment thereby producing a concentrated fluid containing the silica, seasoning the concentrated fluid thereby producing a slurry having precipitated colloids containing the silica, and separating the silica from the slurry.

  12. Bimodal mesoporous silica with bottleneck pores.

    PubMed

    Reber, M J; Brühwiler, D

    2015-11-01

    Bimodal mesoporous silica consisting of two sets of well-defined mesopores is synthesized by a partial pseudomorphic transformation of an ordered mesoporous starting material (SBA-15 type). The introduction of a second set of smaller mesopores (MCM-41 type) establishes a pore system with bottlenecks that restricts the access to the core of the bimodal mesoporous silica particles. The particle size and shape of the starting material are retained, but micropores present in the starting material disappear during the transformation, leading to a true bimodal mesoporous product. A varying degree of transformation allows the adjustment of the pore volume contribution of the two mesopore domains. Information on the accessibility of the mesopores is obtained by the adsorption of fluorescence-labeled poly(amidoamine) dendrimers and imaging by confocal laser scanning microscopy. This information is correlated with nitrogen sorption data to provide insights regarding the spatial distribution of the two mesopore domains. The bimodal mesoporous materials are excellent model systems for the investigation of cavitation effects in nitrogen desorption isotherms. PMID:26399172

  13. Silica nanoporous membranes and their applications

    NASA Astrophysics Data System (ADS)

    Khabibullin, Amir

    This thesis describes the development of novel silica and hybrid nanoporous membranes. Nanoporous membranes are widely used in various applications. This thesis focuses on their potential applications in the energy area, such as fuel cells and lithium batteries, and in separations and ultrafiltration. We use silica colloidal spheres and polymer-modified silica spheres to prepare the membranes in a time-, cost- and material-efficient manner. First, we prepared novel silica nanoporous membranes by pressing silica colloidal spheres followed by sintering. The pore size, the thickness, and the area of the membrane are precisely controlled by experiment parameters. The resulting membranes are mechanically and thermally durable, crack-free, and capable of size-selective transport. Next, to demonstrate the utility of the pressed membranes, described above, the proton-conductive pore-filled silica colloidal membranes were prepared and the fuel cells were constructed using these membranes. We modified these membranes by filling the membrane pores with surface-attached proton-conductive polymer brushes and prepared membrane-electrode assemblies to test fuel cell performance. We studied the proton conductivity and fuel cell performance as a function of the amount of sulfonic groups in the membrane. We also prepared and characterized reversible hybrid nanoporous membranes, self-assembled from solution containing polymer-modified silica colloidal spheres. Here we applied the new concept of noncovalent membranes, where the material is held together via noncovalent interactions of polymer brushes. This enables so-called reversible assembly of the membranes, in which membrane can be assembled in one solvent and dissolved in other. This approach provides advantages in recycling and reusing of the material. This work is one of the first of its kind and it opens a whole new area of research on reversible membranes made of polymer-modified nanoparticles. Finally, we applied our

  14. Hierarchical porous silicon carbide with controlled micropores and mesopores for electric double layer capacitors

    NASA Astrophysics Data System (ADS)

    Kim, Myeongjin; Oh, Ilgeun; Kim, Jooheon

    2015-05-01

    Three-dimensional hierarchical micro and mesoporous silicon carbide spheres (MMPSiC) are prepared by the template method and carbonization reaction via the aerosol spray drying method. The mesopores are generated by the self-assembly of the structure-directing agents, whereas the micropores are derived from the partial evaporation of Si atoms during carbonization. To investigate the effect of mesopore size on electrochemical performance, three types of MMPSiC with different mesopore size were fabricated by using three different structure directing agents (cetyltriethylammonium bromide (CTAB), Polyethylene glycol hexadecyl ether (Brij56), and Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123)). The MMPSiC electrode prepared with Brij56 exhibits the highest charge storage capacity with a specific capacitance of 253.7 F g-1 at a scan rate of 5 mV s-1 and 87.9% rate performance from 5 to 500 mV s-1 in 1 M Na2SO4 aqueous electrolyte. The outstanding electrochemical performance might be because of the ideal mesopore size, which effectively reduces the resistant pathways for ion diffusion in the pores and provides a large accessible surface area for ion transport/charge storage. These encouraging results demonstrate that the MMPSiC prepared with Brij56 is a promising candidate for high performance electrode materials for supercapacitors.

  15. Interface physics in microporous media : LDRD final report.

    SciTech Connect

    Yaklin, Melissa A.; Knutson, Chad E.; Noble, David R.; Aragon, Alicia R.; Chen, Ken Shuang; Giordano, Nicholas J.; Brooks, Carlton, F.; Pyrak-Nolte, Laura J.; Liu, Yihong

    2008-09-01

    This document contains a summary of the work performed under the LDRD project entitled 'Interface Physics in Microporous Media'. The presence of fluid-fluid interfaces, which can carry non-zero stresses, distinguishes multiphase flows from more readily understood single-phase flows. In this work the physics active at these interfaces has been examined via a combined experimental and computational approach. One of the major difficulties of examining true microporous systems of the type found in filters, membranes, geologic media, etc. is the geometric uncertainty. To help facilitate the examination of transport at the pore-scale without this complication, a significant effort has been made in the area of fabrication of both two-dimensional and three-dimensional micromodels. Using these micromodels, multiphase flow experiments have been performed for liquid-liquid and liquid-gas systems. Laser scanning confocal microscopy has been utilized to provide high resolution, three-dimensional reconstructions as well as time resolved, two-dimensional reconstructions. Computational work has focused on extending lattice Boltzmann (LB) and finite element methods for probing the interface physics at the pore scale. A new LB technique has been developed that provides over 100x speed up for steady flows in complex geometries. A new LB model has been developed that allows for arbitrary density ratios, which has been a significant obstacle in applying LB to air-water flows. A new reduced order model has been developed and implemented in finite element code for examining non-equilibrium wetting in microchannel systems. These advances will enhance Sandia's ability to quantitatively probe the rich interfacial physics present in microporous systems.

  16. Preparation of H{sub 2}-permselective silica membranes by alternating reactant deposition. Quarterly progress report, September 1, 1993--December 31, 1993

    SciTech Connect

    Kim, Soojin; Gavalas, G.R.

    1993-12-31

    Thin SiO{sub 2} layers were deposited on the surface of porous Vycor glass by alternating vapor phase reaction with SiCl{sub 4} and H{sub 2}O. The membranes prepared by this technique had H{sub 2} permeance of 0.3--0.4 cm{sup 3} (STP)/(min{center_dot}cm{sup 2}{center_dot}atm) and H{sub 2}:N{sub 2} selectivity of 500--1000 at 600{degrees}C. The SiCl{sub 4} dosage at each silylation cycle, the concentration of initial surface -OH groups, and the reaction temperature influence significantly the deposit layer thickness- After two weeks of heating at 550{degrees}C under 3 atmospheres of water vapor, the membrane H{sub 2} permeance decreased by about 20%, and the selectivity increased to more than 2000. The membrane properties after this hydrothermal treatment are superior to those of membranes prepared earlier by one-sided (steady flow) deposition. A simple model incorporating diffusion and surface reaction was used to study the effect of various parameters on the formation of the deposit layer.

  17. A single step technique for preparation of porous solid phase microextraction fibers by electrochemically co-deposited silica based sol-gel/Cu nanocomposite.

    PubMed

    Saber Tehrani, Mohammad; Aberoomand Azar, Parviz; Mohammadiazar, Sirwan

    2013-02-22

    In this study, electrochemically co-deposited 3-trimethoxysilyl propyl methacrylate (3TMSPMA)/Cu nanocomposite is introduced as a novel and single-step technique for preparation of efficient and unbreakable solid phase microextraction (SPME) fibers; having strong interaction between the substrate and the coating. The applicability of prepared nanocomposite films was evaluated through extraction of some aromatic pollutants as model compounds from the headspace of aqueous samples in combination with gas chromatography-mass spectrometry (GC-MS). Different parameters affecting the structure and composition of the deposited films including applied potential, electrodeposition time, and precursor concentration; and the parameters affecting extraction efficiency such as extraction temperature, extraction time, and salt content were investigated. The results showed that morphology and grain size of the films are strongly affected by the ratio between the sol-gel precursor and Cu(2+) ions. Furthermore, potential of deposition influences the composition of films as it controls the kinetics of sol-gel/Cu co-deposition. Finally, characterization of the deposited films was accomplished by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). PMID:23336939

  18. Thermodynamics and transport in microporous media. Progress report

    SciTech Connect

    Glandt, E.D.

    1992-09-01

    Focus of this report is on the thermodynamic properties/behavior of fluids contained or adsorbed on the random microporus materials (disordered solids). The Madden-Glandt formalism for fluids in disordered matrices is applied to realistic systems (gas adsorption in carbons, polymer partitioning). Work on microgeometry of solids and their percolation and connectedness properties was continued; a study of the simplest model for microporous materials (random-pore or ``Swiss cheese`` model) was completed. Work on irreversible adsorption was continued; a simple model for correlated adsorption was studied.

  19. Microporous coordination polymers as efficient sorbents for air dehumidification.

    PubMed

    Guo, Ping; Wong-Foy, Antek G; Matzger, Adam J

    2014-03-01

    Air drying is a widespread and critical industrial process. Removal of water from air is commonly accomplished by passage through a desiccant such as alumina; modest water capacity and energy intensive regeneration are limitations of currently used sorbents. Microporous coordination polymers (MCPs) are demonstrated here to be efficient desiccants for the dehumidification of air, and a comparison of their capacity, regenerability, and efficiency with commercial activated alumina is conducted. Complete regeneration using dry air with mild heating is achieved. The attainment of high capacity for the adsorption of water coupled to facile regeneration indicates that gas dehumidification may be an important application for MCPs. PMID:24517543

  20. The role of UHMW-PE in microporous PE separators

    SciTech Connect

    Wang, L.C.; Harvey, M.K.; Stein, H.L.; Scheunemann, U.

    1997-12-01

    Microporous PE separators have gained large popularity in the lead acid battery industry, particularly in SLI (Starting, Lighting and Ignition) Automotive Applications. The PE (Polyethylene) in battery separator is actually UHMW-PE (Ultra High Molecular Weight Polyethylene). UHMW-PE has a molecular weight more than ten times that of conventional HDPE (High Density Polyethylene). This paper gives an overview of the UHMW-PE`s contributions to the PE battery separator process, assembly, and performance, in comparison to other conventional separators, such as PVC (Polyvinyl Chloride), cellulose, and glass fiber.

  1. Method for rapidly producing microporous and mesoporous materials

    DOEpatents

    Coronado, P.R.; Poco, J.F.; Hrubesh, L.W.; Hopper, R.W.

    1997-11-11

    An improved, rapid process is provided for making microporous and mesoporous materials, including aerogels and pre-ceramics. A gel or gel precursor is confined in a sealed vessel to prevent structural expansion of the gel during the heating process. This confinement allows the gelation and drying processes to be greatly accelerated, and significantly reduces the time required to produce a dried aerogel compared to conventional methods. Drying may be performed either by subcritical drying with a pressurized fluid to expel the liquid from the gel pores or by supercritical drying. The rates of heating and decompression are significantly higher than for conventional methods. 3 figs.

  2. Method for rapidly producing microporous and mesoporous materials

    DOEpatents

    Coronado, Paul R.; Poco, John F.; Hrubesh, Lawrence W.; Hopper, Robert W.

    1997-01-01

    An improved, rapid process is provided for making microporous and mesoporous materials, including aerogels and pre-ceramics. A gel or gel precursor is confined in a sealed vessel to prevent structural expansion of the gel during the heating process. This confinement allows the gelation and drying processes to be greatly accelerated, and significantly reduces the time required to produce a dried aerogel compared to conventional methods. Drying may be performed either by subcritical drying with a pressurized fluid to expel the liquid from the gel pores or by supercritical drying. The rates of heating and decompression are significantly higher than for conventional methods.

  3. Microporous aluminium-oxide coatings for nonimpact printing applications

    NASA Astrophysics Data System (ADS)

    Farahbakhsh, Bahram; Steele, Don C.; Smits, Paul

    1993-06-01

    Aluminum can be anodized to form a microporous surface film consisting of uniform cylindrical pores normal to the substrate. This film may be engineered to permit detachment from its aluminum substrate, allowing the transfer of the film to a secondary substrate for printing. The film pores can act as vertical receivers of the toners and inks used in non-impact printing, thereby limiting in-plane spreading. If the film is formed on foil of a gauge compatible with printer media handling systems, the image and oxide may be transferred after printing. The use of such films for non-impact printing applications is proposed.

  4. Graphene-wrapped sulfur/metal organic framework-derived microporous carbon composite for lithium sulfur batteries

    NASA Astrophysics Data System (ADS)

    Chen, Renjie; Zhao, Teng; Tian, Tian; Cao, Shuai; Coxon, Paul R.; Xi, Kai; Fairen-Jimenez, David; Vasant Kumar, R.; Cheetham, Anthony K.

    2014-12-01

    A three-dimensional hierarchical sandwich-type graphene sheet-sulfur/carbon (GS-S/CZIF8-D) composite for use in a cathode for a lithium sulfur (Li-S) battery has been prepared by an ultrasonic method. The microporous carbon host was prepared by a one-step pyrolysis of Zeolitic Imidazolate Framework-8 (ZIF-8), a typical zinc-containing metal organic framework (MOF), which offers a tunable porous structure into which electro-active sulfur can be diffused. The thin graphene sheet, wrapped around the sulfur/zeolitic imidazolate framework-8 derived carbon (S/CZIF8-D) composite, has excellent electrical conductivity and mechanical flexibility, thus facilitating rapid electron transport and accommodating the changes in volume of the sulfur electrode. Compared with the S/CZIF8-D sample, Li-S batteries with the GS-S/CZIF8-D composite cathode showed enhanced capacity, improved electrochemical stability, and relatively high columbic efficiency by taking advantage of the synergistic effects of the microporous carbon from ZIF-8 and a highly interconnected graphene network. Our results demonstrate that a porous MOF-derived scaffold with a wrapped graphene conductive network structure is a potentially efficient design for a battery electrode that can meet the challenge arising from low conductivity and volume change.

  5. Graphene-wrapped sulfur/metal organic framework-derived microporous carbon composite for lithium sulfur batteries

    SciTech Connect

    Chen, Renjie E-mail: chenrj@bit.edu.cn; Zhao, Teng; Tian, Tian; Fairen-Jimenez, David; Cao, Shuai; Coxon, Paul R.; Xi, Kai E-mail: chenrj@bit.edu.cn; Vasant Kumar, R.; Cheetham, Anthony K.

    2014-12-01

    A three-dimensional hierarchical sandwich-type graphene sheet-sulfur/carbon (GS-S/C{sub ZIF8-D}) composite for use in a cathode for a lithium sulfur (Li-S) battery has been prepared by an ultrasonic method. The microporous carbon host was prepared by a one-step pyrolysis of Zeolitic Imidazolate Framework-8 (ZIF-8), a typical zinc-containing metal organic framework (MOF), which offers a tunable porous structure into which electro-active sulfur can be diffused. The thin graphene sheet, wrapped around the sulfur/zeolitic imidazolate framework-8 derived carbon (S/C{sub ZIF8-D}) composite, has excellent electrical conductivity and mechanical flexibility, thus facilitating rapid electron transport and accommodating the changes in volume of the sulfur electrode. Compared with the S/C{sub ZIF8-D} sample, Li-S batteries with the GS-S/C{sub ZIF8-D} composite cathode showed enhanced capacity, improved electrochemical stability, and relatively high columbic efficiency by taking advantage of the synergistic effects of the microporous carbon from ZIF-8 and a highly interconnected graphene network. Our results demonstrate that a porous MOF-derived scaffold with a wrapped graphene conductive network structure is a potentially efficient design for a battery electrode that can meet the challenge arising from low conductivity and volume change.

  6. Skeletal silica characterization in porous-silica low-dielectric-constant films by infrared spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Takada, Syozo; Hata, Nobuhiro; Seino, Yutaka; Fujii, Nobutoshi; Kikkawa, Takamaro

    2005-06-01

    Porous-silica low-dielectric-constant (low-k) films were prepared using a sol-gel method based on the self-assembly of surfactant templates. No change in the refractive index at 633 nm nor in the infrared-absorption intensities of C-H and O-H stretching vibrations at around 2900 and 3400cm-1 of porous-silica low-k films were observed after annealing at each temperature from 523 to 723 K. On the other hand, the Young's elastic modulus and hardness increased with the increase of annealing temperature. The structure in the complex dielectric function of porous-silica low-k films observed in between 1000 and 1400cm-1 is assigned as the asymmetric stretching vibration mode of the Si-O-Si bond. By applying the effective-medium theory by Bruggeman to the experimental results from infrared spectroscopic ellipsometry, we analyzed the skeletal silica structures. The peak positions of transverse (ωTO) and longitudinal (ωLO) vibration modes for Si-O-Si network in the silica skeleton of porous-silica films changed from 1061 to 1068cm-1 and from 1219 to 1232cm-1, respectively, with the annealing temperature. It is shown that the ωLO2/ωTO2 of skeletal silica correlates with Young's elastic modulus of porous-silica low-k films.

  7. Preparation and characterization of magnetic nanocomposite of Schiff base/silica/magnetite as a preconcentration phase for the trace determination of heavy metal ions in water, food and biological samples using atomic absorption spectrometry.

    PubMed

    Bagheri, Hasan; Afkhami, Abbas; Saber-Tehrani, Mohammad; Khoshsafar, Hosein

    2012-08-15

    A versatile and robust solid phase with both magnetic property and a very high adsorption capacity is presented on the basis of modification of iron oxide-silica magnetic particles with a newly synthesized Schiff base (Fe(3)O(4)/SiO(2)/L). The structure of the resulting product was confirmed by Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) spectrometry and transmission electron microscopy (TEM). We developed an efficient and cost-effective method for the preconcentration of trace amounts of Pb(II), Cd(II) and Cu(II) in environmental and biological samples using this novel magnetic solid phase. Prepared magnetic solid phase is an ideal support because it has a large surface area, good selectivity and can be easily retrieved from large volumes of aqueous solutions. The possible parameters affecting the enrichment were optimized. Under the optimal conditions, the method detection limit was 0.14, 0.19 and 0.12 μg L(-1) for Pb(II), Cd(II) and Cu(II) ions, respectively. The established method has been successfully applied to analyze real samples, and satisfactory results were obtained. All these indicated that this magnetic phase had a great potential in environmental and biological fields. PMID:22841051

  8. Preparation of Hollow N-Chloramine-Functionalized Hemispherical Silica Particles with Enhanced Efficacy against Bacteria in the Presence of Organic Load: Synthesis, Characterization, and Antibacterial Activity.

    PubMed

    Rahma, Hakim; Asghari, Sogol; Logsetty, Sarvesh; Gu, Xiaochen; Liu, Song

    2015-06-01

    The fabrication of highly effective antimicrobial materials is an important strategy for coping with the growing concern of bacterial resistance. In this study, N-chloramine-functionalized hollow hemispherical structures were designed and prepared to examine possible enhancement of antimicrobial performance. Antimicrobial testing was carried out on Gram-negative (Escherichia coli) and Gram-positive (Baccilus Cereus) bacteria in the presence and absence of biological medium. The efficacy of the hollow hemispherical particles functionalized with various N-chloramines in killing bacteria was compared among themselves with that of small organic molecules and spherical particles to investigate the effect of the surface charge, chemical structure, and shape of the particles. Results demonstrated that quaternary ammonium salt or amine functions in the chemical structure enhanced the antimicrobial activity of the particles and made the particles more effective than the small molecules in the presence of biological medium. The importance of particle shape in the killing tests was also confirmed. PMID:25941842

  9. Development of C18-functionalized magnetic silica nanoparticles as sample preparation technique for the determination of ergosterol in cigarettes by microwave-assisted derivatization and gas chromatography/mass spectrometry.

    PubMed

    Sha, Yunfei; Deng, Chunhui; Liu, Baizhan

    2008-07-11

    Ergosterol is one of the important precursors of tumorigenic polynuclear aromatic hydrocarbons. A large amount of ergosterol is present in mildewy cigarettes, which derives from fungal contaminations. In this paper, a novel approach based on C(18)-functionalized magnetic silica nanoparticles (C(18)-f-MS NPs) coupled with microwave-assisted derivatization and gas chromatography/mass spectrometry (GC/MS) was developed for the rapid enrichment and determination of ergosterol in cigarettes. Due to that, microwave-assisted derivatization requires very short time (several minutes), and the extraction and concentration of ergosterol become the key step in the sample preparation process. In this study, the prepared C(18)-f-MS NPs with its unique properties (high surface area and strong magnetism) provided an efficient way for extraction and concentration of ergosterol in the samples. Additionally, the analyte of ergosterol adsorbed with C(18)-f-MS NPs in cigarettes can be simply and rapidly isolated (only about 2s) through placing a strong magnet on the bottom of container. In this work, different parameters such as added amounts of C(18)-f-MS NPs, extraction temperature, and extraction time were optimized to enhance the extraction efficiency. Method validations (linear range, detection limit, precision, and recovery) were also studied. The results obtained by the optimal conditions showed that the proposed method based on C(18)-f-MS NPs was a simple, high efficient, and had a rapid approach for the enrichment of ergosterol in cigarettes and was successfully applied to the analysis of ergosterol in normal and mildewy cigarettes followed by microwave-assisted derivatization and GC/MS. PMID:18533171

  10. Microporous La0.8Sr0.2MnO3 perovskite nanorods as efficient electrocatalysts for lithium-air battery

    NASA Astrophysics Data System (ADS)

    Lu, Fanliang; Wang, Yarong; Jin, Chao; Li, Fan; Yang, Ruizhi; Chen, Fanglin

    2015-10-01

    Efficient electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the most critical factor to influence the performance of lithium-air batteries. We present La0.8Sr0.2MnO3 (LSM) perovskite nanorods as high active electrocatalyst fabricated via a soft template method for lithium-air batteries. The as-prepared LSM nanorods are microporous with numerous defects and large surface area (20.6 m2 g-1), beneficial to the ORR and OER in the discharge and charge processes, respectively. Lithium-air batteries based on the microporous LSM nanorods electrocatalysts show enhanced electrochemical performances, including high first discharge specific capacity (6890 mAh g-1(electrode) at 200 mA g-1), low overpotential, good rate capability (up to 400 mA g-1), and cycle stability (only 1.1% voltage loss after 30 circles of specific capacity limit of 1000 mAh g-1 tested at 200 mA g-1). The improved performance might be due to the synergistic effect of the unique microporous and one-dimensional structure and numerous defects of the prepared LSM catalyst.

  11. Electroosmosis in Non-homogeneously Charged Microporous Media

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Wang, M.

    2014-12-01

    Understanding electroosmosis in microporous media is important for species separation in electrochromatography, flooding control in fuel cells, contaminants removal in soil and electrokinetic displacement in oil extraction. Because of the complexity of transport and randomness of porous media, investigation of electroosmosis in porous media is mostly based on the assumption that the solid surface is homogeneously charged. However, based on the surface complexation model, the surface charge and zeta potential are much dependent on the local chemical environment of the solution. Therefore, variations of concentration, pH and temperature and so on will lead to a non-homogeneous charge distribution in the porous media. In addition, since the characteristic length of the pore is comparable to the characteristic length of the double layer in the microporous media, overlap of the double layer occurs and this will further regulate the surface charge distribution. In this work, we propose a 3-D lattice Poisson-Boltzmann model for electroosmosis in porous media with non-homogeneous charge for above reasons. We employ a generation-growth method to reproduce the 3-D random microstructures of natural porous media and solve the Navier-Stokes equation and Poisson-Boltzmann equation using lattice Boltzmann method. To determine the surface charge and zeta potential, we adopt the Basic-Stern model to describe the electrical double layer. Electroosmotic permeability is investigated for various cases with non-homogeneous charge and compared to the results with homogeneous charge to determine the validity of the homogeneous charge assumption.

  12. Tailored crystalline microporous materials by post-synthesis modification.

    PubMed

    Valtchev, Valentin; Majano, Gerardo; Mintova, Svetlana; Pérez-Ramírez, Javier

    2013-01-01

    Crystalline microporous solids are an important class of inorganic materials with uses in different areas impacting our everyday lives, namely as catalysts, adsorbents, and ion exchangers. Advancements in synthesis have been invaluable in expanding the classical aluminosilicate zeolites to new unique framework types and compositions, motivating innovative developments. However, the inexhaustible post-synthetic options to tailor zeolite properties have been and will continue to be indispensable to realize emerging and to improve conventional applications. Starting from the routine drying and template removal processes that every zeolite must experience prior to use, a wide spectrum of treatments exists to alter individual or collective characteristics of these materials for optimal performance. This review documents the toolbox of post-synthetic strategies available to tune the properties of zeolitic materials for specific functions. The categorisation is based on the scale at which the alteration is aimed at, including the atomic structure (e.g. the introduction, dislodgment, or replacement of framework atoms), the micropore level (e.g. template removal and functionalisation by inorganic and organic species), and the crystal and particle levels (e.g. the introduction of auxiliary porosity). Through examples in the recent literature, it is shown that the combination of post-synthetic methods enables rational zeolite design, extending the characteristics of these materials way beyond those imposed by the synthesis conditions. PMID:22996351

  13. Microporous and tight limestones in the Urgonian Formation (late Hauterivian to early Aptian) of the French Jura Mountains: Focus on the factors controlling the formation of microporous facies

    NASA Astrophysics Data System (ADS)

    Volery, Chadia; Davaud, Eric; Durlet, Christophe; Clavel, Bernard; Charollais, Jean; Caline, Bruno

    2010-10-01

    Microporous and tight limestones, with contrasting porosity and permeability values directly related to the microfabric of the micritic matrix, outcrop in the Urgonian Formation of the French Jura Mountains. This study investigates the factors controlling the differentiation between the microporous and tight facies, and proposes a diagenetic model for the development and preservation of the microporosity in these limestones. The petrophysical properties are not related to the depositional texture, the petrographical content or the mineralogical composition. However, the tight layers contain indications of emersion (e.g.: bird eyes, keystone vugs, and desiccation cracks). The sedimentation in very shallow conditions up to emersion is confirmed by the covariant more positive values of oxygen and carbon isotopes. The microporous intervals systematically occur a few meters below the tight layers affected by emersion. This position strongly suggests the importance of meteoric water input rapidly after sedimentation in the differentiation between tight and microporous limestones. The diagenetic model proposed for the development and preservation of the microporous facies involves partial early cementation of the interstitial mud, mainly composed of low-Mg calcite crystals (sedimentation during a calcite sea period), inside a meteoric phreatic lens by in situ dissolution-reprecipitation processes ("hybrid Ostwald ripening"). This early cementation partly preserves the original microfabric and intercrystalline microporosity and allows the carbonate sediment to resist compaction during burial. The identification of the conditions favorable to the development of microporosity in these Urgonian limestones may improve the knowledge and modeling of some microporous carbonate reservoir rocks.

  14. Preparation of dummy template imprinted polymers at surface of silica microparticles for the selective extraction of trace bisphenol A from water samples.

    PubMed

    Zhao, Wenhui; Sheng, Na; Zhu, Rong; Wei, Fangdi; Cai, Zheng; Zhai, Meijuan; Du, Shuhu; Hu, Qin

    2010-07-15

    Molecularly imprinted polymers for bisphenol A (BPA) were prepared by using surface molecular imprinting technique. Analogues of BPA, namely 4,4'-dihydroxybiphenyl and 3,3',5,5'-tetrabromobisphenol A, were used as the dummy templates instead of BPA, to avoid the leakage of a trace amount of the target analyte (BPA). The resulting dummy molecularly imprinted polymers (DMIPs) showed the large sorption capacity, high recognition ability and fast binding kinetics for BPA. The maximal sorption capacity was up to 958 micromol g(-1), and it only took 40 min for DMIPs to achieve the sorption equilibrium. The DMIPs were successfully applied to the solid-phase extraction coupled with HPLC/UV for the determination of BPA in water samples. The calibration graph of the analytical method was linear with a correlation coefficient more than 0.999 in the concentration range of 0.0760-0.912 ng mL(-1) of BPA. The limit of detection was 15.2 pg mL(-1) (S/N=3). Recoveries were in the range of 92.9-102% with relative standard deviation (RSD) less than 11%. The trace amounts of BPA in tap water, drinking water, rain and leachate of one-off tableware were determined by the method built, and the satisfactory results were obtained. PMID:20347520

  15. Carbothermal transformation of a graphitic carbon nanofiber/silica aerogel composite to a SiC/silica nanocomposite.

    PubMed

    Lu, Weijie; Steigerwalt, Eve S; Moore, Joshua T; Sullivan, Lisa M; Collins, W Eugene; Lukehart, C M

    2004-09-01

    Carbon nanofiber/silica aerogel composites are prepared by sol-gel processing of surface-enhanced herringbone graphitic carbon nanofibers (GCNF) and Si(OMe)4, followed by supercritical CO2 drying. Heating the resulting GCNF/silica aerogel composites to 1650 degrees C under a partial pressure of Ar gas initiates carbothermal reaction between the silica aerogel matrix and the carbon nanofiber component to form SiC/silica nanocomposites. The SiC phase is present as nearly spherical nanoparticles, having an average diameter of ca. 8 nm. Formation of SiC is confirmed by powder XRD and by Raman spectroscopy. PMID:15570963

  16. Physicochemical determinants in the cellular responses to nanostructured amorphous silicas.

    PubMed

    Gazzano, Elena; Ghiazza, Mara; Polimeni, Manuela; Bolis, Vera; Fenoglio, Ivana; Attanasio, Angelo; Mazzucco, Gianna; Fubini, Bice; Ghigo, Dario

    2012-07-01

    Amorphous silicas, opposite to crystalline polymorphs, have been regarded so far as nonpathogenic, but few studies have addressed the toxicity of the wide array of amorphous silica forms. With the advent of nanotoxicology, there has been a rising concern about the safety of silica nanoparticles to be used in nanomedicine. Here, we report a study on the toxicity of amorphous nanostructured silicas obtained with two different preparation procedures (pyrolysis vs. precipitation), the pyrogenic in two very different particle sizes, in order to assess the role of size and origin on surface properties and on the cell damage, oxidative stress, and inflammatory response elicited in murine alveolar macrophages. A quartz dust was employed as positive control and monodispersed silica spheres as negative control. Pyrogenic silicas were remarkably more active than the precipitated one as to cytotoxicity, reactive oxygen species production, lipid peroxidation, nitric oxide synthesis, and production of tumor necrosis factor-α, when compared both per mass and per unit surface. Between the two pyrogenic silicas, the larger one was the more active. Silanols density is the major difference in surface composition among the three silicas, being much larger than the precipitated one as indicated by joint calorimetric and infrared spectroscopy analysis. We assume here that full hydroxylation of a silica surface, with consequent stable coverage by water molecules, reduces/inhibits toxic behavior. The preparation route appears thus determinant in yielding potentially toxic materials, although the smallest size does not always correspond to an increased toxicity. PMID:22491428

  17. Preparation of a compressible and hierarchically porous polyimide sponge via the sol-gel process of an aliphatic tetracarboxylic dianhydride and an aromatic triamine.

    PubMed

    Lee, Jeongmin; Chang, Ji Young

    2016-08-16

    A compressible and monolithic microporous polyimide sponge was prepared from an aliphatic tetracarboxylic dianhydride and an aromatic triamine. The sponge had a hierarchical pore structure, in which spherical microporous polyimide particles were interconnected to form a macroscopic network. It showed an amphiphilic character, because of the balanced presence of hydrophobic and hydrophilic groups. PMID:27484707

  18. Silica-Ceria Hybrid Nanostructures

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Baer, Donald R.; Thevuthasan, Suntharampillai

    2012-04-25

    A new hybrid material system that consists of ceria attached silica nanoparticles has been developed. Because of the versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and antioxidant properties of ceria nanoparticles, this material system is ideally suited for biomedical applications. The silica particles of size ~50nm were synthesized by the Stöber synthesis method and ceria nanoparticles of size ~2-3nm was attached to the silica surface using a hetrocoagulation method. The presence of silanol groups on the surface of silica particles mediated homogenous nucleation of ceria which were attached to silica surface by Si-O-Ce bonding. The formations of silica-ceria hybrid nanostructures were characterized by X-photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The HRTEM image confirms the formation of individual crystallites of ceria nanoparticles attached to the silica surface. The XPS analysis indicates that ceria nanoparticles are chemically bonded to surface of silica and possess mixture of +3 and +4 chemical states.

  19. Sonochemical synthesis of silica particles and their size control

    NASA Astrophysics Data System (ADS)

    Kim, Hwa-Min; Lee, Chang-Hyun; Kim, Bonghwan

    2016-09-01

    Using an ultrasound-assisted sol-gel method, we successfully synthesized very uniformly shaped, monodisperse, and size-controlled spherical silica particles from a mixture of ethanol, water, and tetraethyl orthosilicate in the presence of ammonia as catalyst, at room temperature. The diameters of the silica particles were distributed in the range from 40 to 400 nm; their morphology was well characterized by scanning electron microscopy. The silica particle size could be adjusted by choosing suitable concentrations of ammonium hydroxide and water, which in turn determined the nucleation and growth rates of the particles during the reaction. This sonochemical-based silica synthesis offers an alternative way to produce spherical silica particles in a relatively short reaction time. Thus, we suggest that this simple, low-cost, and efficient method of preparing uniform silica particles of various sizes will have practical and wide-ranging industrial applicability.

  20. Silica powders for powder evacuated thermal insulating panel and method

    DOEpatents

    Harris, Michael T.; Basaran, Osman A.; Kollie, Thomas G.; Weaver, Fred J.

    1996-01-01

    A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2/ g is described. The silica powders are prepared by reacting a tetraakyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders.

  1. Silica powders for powder evacuated thermal insulating panel and method

    DOEpatents

    Harris, M.T.; Basaran, O.A.; Kollie, T.G.; Weaver, F.J.

    1996-01-02

    A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm{sup 3} and an external surface area in the range of about 90 to 600 m{sup 2}/g is described. The silica powders are prepared by reacting a tetraalkyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders. 2 figs.

  2. Silica powders for powder evacuated thermal insulating panel and method

    DOEpatents

    Harris, Michael T.; Basaran, Osman A.; Kollie, Thomas G.; Weaver, Fred J.

    1995-01-01

    A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2/ g is described. The silica powders are prepared by reacting a tetraakyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders.

  3. Silica powders for powder evacuated thermal insulating panel and method

    DOEpatents

    Harris, Michael T.; Basaran, Osman A.; Kollie, Thomas G.; Weaver, Fred J.

    1994-01-01

    A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2 /g is described. The silica powders are prepared by reacting a tetraakyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders.

  4. Characterization of sulfonated silica nanocomposite electrolyte membranes for fuel cell.

    PubMed

    Kim, Deuk-Ju; Nam, Sang-Yong

    2014-12-01

    Sulfonated poly(arylene ether sulfone) (SPAES) and sulfonated silica (silica-SO3H) prepared via sol-gel reaction are used as an organic polymer matrix and inorganic nanoparticles. The contents of the silica-SO3H particles in the composite membranes are controlled at 0.5, 1, 2, 3 and 5 wt.% in order to evaluate the appropriate content for high proton conductivity. Randomly dispersed silica particles are obtained from all composite membranes as a result of the hydrophilic domains in the polymer and silica-SO3H. In this study, the optimum silica-SO3H content for high proton conductivity is 3 wt.% in fully hydrated conditions and 0.5 wt.% in low humidity conditions. PMID:25970990

  5. A microporous silk carbon-ionic liquid composite for the electrochemical sensing of dopamine.

    PubMed

    Wang, Min; Bai, Lu; Zhang, Lingling; Sun, Guangping; Zhang, Xiaowei; Dong, Shaojun

    2016-04-21

    Porous silk carbon (Silk C) was obtained through carbonization and KOH activation of natural silk cocoons. The as-prepared Silk C presented the good characteristics of a large surface area (SBET: 2854.53 m(2) g(-1)) and a high volume of pores (1.54 cm(3) g(-1)) with uniform micropores (2.5 nm) and multiple defects. The metal-free silk carbon-ionic liquid (Silk C-IL) composite, synthesized by modifying Silk C with ionic liquid through non-covalent (π-π) interactions under grinding conditions, was prepared for electrochemical determination of dopamine (DA). The detection limit of DA was 79 nM (S/N = 3) with a linear range from 0.6 μM to 140 μM. Meanwhile, the as-made Silk C-IL/GCE presented good selectivity for DA detection from other possible interferences, such as ascorbic acid, glucose and uric acid. Furthermore, the Silk C-IL/GCE was also successfully used for the detection of DA in fetal bovine serum and dopamine hydrochloride injection samples. PMID:26979477

  6. Synthesis and characterization of polyaniline grafted multiwalled carbon nanotube loaded Nafion-silica nanocomposite membrane.

    PubMed

    Ragupathy, D; Gopalan, A; Kim, Kyeong-Wung; Lee, Kwang Pill

    2011-01-01

    The preparation and characterization results of a new nanocomposite, polyaniline (PANI) grafted multiwalled carbon nanotube (MWNT) loaded Nafion-silica, (designated as Nafion-silica/MWNT-g-PANI), are reported in this paper. The preparation involves the formation of a silica network in a Nafion membrane and the subsequent loading of polyaniline-grafted multiwalled carbon nanotubes (MWNT-g-PANI) onto the Nafion-silica nanocomposite. The new nanocomposite, Nafion-silica/ MWNT-g-PANI, was characterized as to its morphology, structure and properties. The conductivity and methanol permeability of the nanocomposite membranes were evaluated. PMID:21446537

  7. Poroelastic theory applied to the adsorption-induced deformation of vitreous silica.

    PubMed

    Coasne, Benoit; Weigel, Coralie; Polian, Alain; Kint, Mathieu; Rouquette, Jérome; Haines, Julien; Foret, Marie; Vacher, René; Rufflé, Benoit

    2014-12-11

    When vitreous silica is submitted to high pressures under a helium atmosphere, the change in volume observed is much smaller than expected from its elastic properties. It results from helium penetration into the interstitial free volume of the glass network. We present here the results of concurrent spectroscopic experiments using either helium or neon and molecular simulations relating the amount of gas adsorbed to the strain of the network. We show that a generalized poromechanical approach, describing the elastic properties of microporous materials upon adsorption, can be applied successfully to silica glass in which the free volume exists only at the subnanometer scale. In that picture, the adsorption-induced deformation accounts for the small apparent compressibility of silica observed in experiments. PMID:25383694

  8. Adsorption and desorption performance of benzene over hierarchically structured carbon-silica aerogel composites.

    PubMed

    Dou, Baojuan; Li, Jinjun; Wang, Yufei; Wang, Hailin; Ma, Chunyan; Hao, Zhengping

    2011-11-30

    Hierarchically structured carbon-silica aerogel (CSA) composites were synthesized from cheap water glass precursors and granulated activated carbon via a post-synthesis surface modification with trimethylchlorosilane (TMCS) and a low-cost ambient pressure drying procedure. The resultant CSA composites possess micro/mesoporous structure and hydrophobic surface. The adsorption and desorption performance of benzene on carbon-silica aerogel composite (CSA-2) under static and dynamic conditions were investigated, comparing with pure silica aerogel (CSA-0) and microporous activated carbon (AC). It was found that CSA-2 has high affinity towards aromatic molecules and fast adsorption kinetics. Excellent performance of dynamic adsorption and desorption observed on CSA-2 is related to its higher adsorption capacity than CSA-0 and less mass transfer resistance than AC, arising from the well-developed microporosity and open foam mesostructure in the CSA composites. PMID:21962860

  9. Synthesis and properties of porous silica obtained by the template method

    NASA Astrophysics Data System (ADS)

    Kuznetsova, T. F.; Rat'ko, A. I.; Eremenko, S. I.

    2012-10-01

    Micromesoporous samples of SiO2 were synthesized by the sol-gel method using tetraethoxysilane as a starting reagent and 1-5 wt % cetylpyridinium chloride as a template under the conditions of preadsorption of colloid silica by polyethyleneglycol macromolecules. The adsorption and texture of the samples were studied by the low-temperature nitrogen adsorption-desorption technique. Preadsorption of silica sol was shown to affect the adsorption and capillary-condensation properties of silica. The surface area and the volume of mesopores increased at cetylpyridinium concentrations higher than 1 wt %. The micropore volume increased to a maximum. The capillary-condensation hysteresis loop of H4 type transformed into an H3 loop according to the IUPAC classification.

  10. Temperature dependent thermal conductivity of pure silica MEL and MFI zeolite thin films

    NASA Astrophysics Data System (ADS)

    Fang, Jin; Huang, Yi; Lew, Christopher M.; Yan, Yushan; Pilon, Laurent

    2012-03-01

    This paper reports the temperature dependent cross-plane thermal conductivity of pure silica zeolite (PSZ) MFI and MEL thin films measured using the 3ω method between 30 and 315 K. PSZ MFI thin films were b-oriented, fully crystalline, and had a 33% microporosity. PSZ MEL thin films consisted of MEL nanoparticles embedded in a nonuniform and porous silica matrix. They featured porosity, relative crystallinity, and particle size ranging from 40% to 59%, 23% to 47%, and 55 to 80 nm, respectively. Despite their crystallinity, MFI films had smaller thermal conductivity than that of amorphous silica due to strong phonon scattering by micropores. In addition, the effects of increased relative crystallinity and particle size on thermal conductivity of MEL thin films were compensated by the simultaneous increase in porosity. Finally, thermal conductivity of MFI zeolite was predicted and discussed using the Callaway model based on the Debye approximation.

  11. Silazane to silica

    NASA Technical Reports Server (NTRS)

    Harvey, Gale A.

    1992-01-01

    Thin film silica and/or methyl silicone were detected on most external surfaces of the retrieved LDEF. Known sources of silicone in or on the LDEF appear inadequate to explain the ubiquitous presence of the silica and silicone films. Hexamethyldisilazane (HMDS) was used as the Challenger tile waterproofing compound for the Challenger/LDEF deployment mission. HMDS releases NH3 which depolymerizes silicone RTV's. Polyurethanes were also attacked. Much of the silica/silicone contamination of LDEF resulted from HMDS.

  12. A highly ordered cubic mesoporous silica/graphene nanocomposite.

    PubMed

    Lee, Chang-Wook; Roh, Kwang Chul; Kim, Kwang-Bum

    2013-10-21

    A highly ordered cubic mesoporous silica (KIT-6)/graphene nanocomposite and 2D KIT-6 nanoflakes were synthesized using a novel synthesis methodology. The non-ionic triblock copolymer, P123, played a dual role as a structure-directing agent in the formation of the cubic mesoporous structure and as a cross-linking agent between mesoporous silica and graphene. The prepared (KIT-6)/graphene nanocomposite could act as a template for the preparation of mesoporous material/graphene nanocomposites. PMID:24057016

  13. Silazine to silica

    NASA Technical Reports Server (NTRS)

    Harvey, Gale A.

    1993-01-01

    Thin film silica and/or methyl silicone were detected on most external surfaces of the retrieved LDEF. Both solar ultraviolet radiation and atomic oxygen can convert silicones to silica. Known sources of silicone in or on the LDEF appear inadequate to explain the ubiquitous presence of the silica and silicone films. Hexamethyldisilazane (HMDS) was used as the Challenger tile waterproofing compound for the Challenger/LDEF deployment mission. HMDS is both volatile and chemically reactive at STP. In addition, HMDS releases NH3 which depolymerizes silicone RTV's. Polyurethanes are also depolymerized. Experiments are reported that indicate much of the silicone and silica contamination of LDEF resulted directly or indirectly from HMDS.

  14. Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

    SciTech Connect

    Alyoshina, Nonna A.; Parfenyuk, Elena V.

    2013-09-15

    A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N{sub 2} adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption process of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica.

  15. Chitosan-silica hybrid porous membranes.

    PubMed

    Pandis, Christos; Madeira, Sara; Matos, Joana; Kyritsis, Apostolos; Mano, João F; Ribelles, José Luis Gómez

    2014-09-01

    Chitosan-silica porous hybrids were prepared by a novel strategy in order to improve the mechanical properties of chitosan (CHT) in the hydrogel state. The inorganic silica phase was introduced by sol-gel reactions in acidic medium inside the pores of already prepared porous scaffolds. In order to make the scaffolds insoluble in acidic media chitosan was cross-linked by genipin (GEN) with an optimum GEN concentration of 3.2 wt.%. Sol-gel reactions took place with Tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) acting as silica precursors. GPTMS served also as a coupling agent between the free amino groups of chitosan and the silica network. The morphology study of the composite revealed that the silica phase appears as a layer covering the chitosan membrane pore walls. The mechanical properties of the hybrids were characterized by means of compressive stress-strain measurements. By immersion in water the hybrids exhibit an increase in elastic modulus up to two orders of magnitude. PMID:25063153

  16. Surfactant removal and silica condensation during the photochemical calcination of thin film silica mesophases.

    PubMed

    Dattelbaum, Andrew M; Amweg, Meri L; Ruiz, Julia D; Ecke, Laurel E; Shreve, Andrew P; Parikh, Atul N

    2005-08-01

    The evolution of photochemical surfactant removal and silica condensation from organically templated thin film silica nanocomposites with mesoscopic ordering has been probed using a combined application of Fourier transform infrared (FT-IR) spectroscopy and single wavelength ellipsometry. Thin films of silica nanocomposites were prepared by a previously reported evaporation-induced self-assembly process. Specifically, oxidized silicon and gold substrates were withdrawn at 25 mm/min from a subcritical micelle concentration solution containing an ethylene oxide surfactant as a structure-directing agent and tetraethyl orthosilicate as a silica precursor. Real-time grazing incidence difference FT-IR spectra of the nanocomposite films on gold taken during exposure to short-wavelength ultraviolet light (184-257 nm) show that surfactant removal and silica condensation occur gradually and concomitantly. Surfactant removal and silica reconstructions were found to be nearly complete after 90 min of exposure. Further, a transient feature was observed in the FT-IR spectra around 1713 cm(-1) during the UV exposure process and was assigned to a carbonyl (C=O) stretching mode absorption, reflecting the transient formation of a partially oxidized surfactant intermediate. From these data we propose a stepwise model for surfactant removal from the nanocomposite films. Ellipsometrically determined index of refraction values collected as a function of UV exposure are also shown to support such a stepwise mechanism of surfactant removal from the ordered nanocomposite silica thin film mesophases studied here. PMID:16852834

  17. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    NASA Astrophysics Data System (ADS)

    Xu, Tiwen; Jia, Zhixin; Luo, Yuanfang; Jia, Demin; Peng, Zheng

    2015-02-01

    The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress-strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

  18. Development and characterization of chitosan/silica nanocomposite membranes

    NASA Astrophysics Data System (ADS)

    Kumar, Amit; Gahlot, Swati; Kulshrestha, Vaibhav; Shahi, V. K.

    2014-04-01

    Quaternized Chitosan/silica based composite membranes were prepared for pervaporation dehydration of water-ethanol mixture. Silica content in membrane matrix has been systematically optimized to control the nanostructure of the developed polymer matrix for studying the effects of molecular structure on the swelling, and PV performance. Among prepared membranes, 40% silica composite membrane shows the remarkable results for the water removal from water/ethanol mixture (80% ethanol + 20% water (w/w)). Contact angle measurement support the PV data as nature of CH-3 membrane is more hydrophilic comparative to others. SEM micrographs show the surface uniformity of the membranes.

  19. Silica-metal core-shell nanostructures.

    PubMed

    Jankiewicz, B J; Jamiola, D; Choma, J; Jaroniec, M

    2012-01-15

    Silica-metal nanostructures consisting of silica cores and metal nanoshells attract a lot of attention because of their unique properties and potential applications ranging from catalysis and biosensing to optical devices and medicine. The important feature of these nanostructures is the possibility of controlling their properties by the variation of their geometry, shell morphology and shell material. This review is devoted to silica-noble metal core-shell nanostructures; specifically, it outlines the main methods used for the preparation and surface modification of silica particles and presents the major strategies for the formation of metal nanoshells on the modified silica particles. A special emphasis is given to the Stöber method, which is relatively simple, effective and well verified for the synthesis of large and highly uniform silica particles (with diameters from 100 nm to a few microns). Next, the surface chemistry of these particles is discussed with a special focus on the attachment of specific organic groups such as aminopropyl or mercaptopropyl groups, which interact strongly with metal species. Finally, the synthesis, characterization and application of various silica-metal core-shell nanostructures are reviewed, especially in relation to the siliceous cores with gold or silver nanoshells. Nowadays, gold is most often used metal for the formation of nanoshells due to its beneficial properties for many applications. However, other metals such as silver, platinum, palladium, nickel and copper were also used for fabrication of core-shell nanostructures. Silica-metal nanostructures can be prepared using various methods, for instance, (i) growth of metal nanoshells on the siliceous cores with deposited metal nanoparticles, (ii) reduction of metal species accompanied by precipitation of metal nanoparticles on the modified silica cores, and (iii) formation of metal nanoshells under ultrasonic conditions. A special emphasis is given to the seed

  20. Suppression of secondary electron yield by micro-porous array structure

    SciTech Connect

    Ye, M.; He, Y. N.; Hu, S. G.; Wang, R.; Hu, T. C.; Yang, J.; Cui, W. Z.

    2013-02-21

    We study secondary electron yield (SEY) suppression for metal materials using a roughened surface with a micro-porous array. First, we perform a Monte Carlo simulation of the electron trajectory in a single cylindrical well using a phenomenological model of secondary electron emission and the SEY suppression efficiency of a micro-porous array. The simulation results show that the SEY of a roughened surface is affected significantly by the aspect ratio of the micro-pores and the surface porosity of the metal plate. Then, to verify the simulation results, we produce a micro-porous array on metal plates using photolithography and measure their SEYs. We show that the micro-porous array structure can efficiently suppress the SEY of metal materials, and the measurements agree quantitatively with the corresponding simulation results. Finally, we derive an analytical formula to evaluate easily the SEY suppression efficiency of the Ag micro-porous array. In total, the micro-porous array proposed in this paper offers an alternative to SEY suppression in related areas such as multipactor effects in satellite payloads or electron cloud effects in accelerators.

  1. Hydrophobic conjugated microporous polymers for sorption of human serum albumin

    NASA Astrophysics Data System (ADS)

    Zheng, Chunli; Du, Miaomiao; Feng, Shanshan; Sun, Hanxue; Li, An; He, Chi; Zhang, TianCheng; Wang, Qiaorui; Wei, Wei

    2016-02-01

    This paper investigated the sorption of human serum albumin (HSA) from water by three kinds of conjugated microporous polymers (CMPs) with surface hydrophobicity and intrinsic porosity. It was found that the three CMPs captured HSA with fast sorption kinetics and good working capacity. Equilibrium was obtained at 80 min for all the tests, and the maximum sorption quantity (qm) ranged from 0.07 to 0.14 mg/mg. With the increase in the particle external surface area of the CMPs, a greater extent of HSA sorption was achieved. Moreover, promoting the dispersion of CMPs in HSA aqueous solution was also beneficial to the extraction. Attenuated Total Reflection Fourier Transform Infrared spectroscopy verified the interactions between the CMPs and the Nsbnd H, Cdbnd O, and Csbnd N groups of HSA. This paper might provide fundamental guidance for the practical application of CMPs to proteins separation and recovery.

  2. A Three-Dimensional Microporous Metal-Metalloporphyrin Framework

    SciTech Connect

    Guo, Zhiyong; Yan, Dan; Wang, Hailong; Tesfagaber, Daniel; Li, Xinle; Chen, Yusheng; Huang, Wenyu; Chen, Banglin

    2015-01-14

    A new porphyrin-based microporous MOF, {Mn(II)0.5[Mn(II)4Cl(Mn(III)Cl-ttzpp)2(H2O)4]}·(DEF)20·(CH3OH)18·(H2O)12 (UTSA-57), has been constructed from {5,10,15,20-tetrakis[4-(2,3,4,5-tetrazolyl)phenyl]porphyrinato} manganese(III) chloride as the metalloligand. The MOF adopts the rare scu topology with one-dimensional square nanotube-like channels of about 20 Å. UTSA-57a exhibits permanent porosity and displays moderately high performance for C2H2/CH4 separation at room temperature.

  3. Functionalizing Microporous Membranes for Protein Purification and Protein Digestion

    NASA Astrophysics Data System (ADS)

    Dong, Jinlan; Bruening, Merlin L.

    2015-07-01

    This review examines advances in the functionalization of microporous membranes for protein purification and the development of protease-containing membranes for controlled protein digestion prior to mass spectrometry analysis. Recent studies confirm that membranes are superior to bead-based columns for rapid protein capture, presumably because convective mass transport in membrane pores rapidly brings proteins to binding sites. Modification of porous membranes with functional polymeric films or TiO2 nanoparticles yields materials that selectively capture species ranging from phosphopeptides to His-tagged proteins, and protein-binding capacities often exceed those of commercial beads. Thin membranes also provide a convenient framework for creating enzyme-containing reactors that afford control over residence times. With millisecond residence times, reactors with immobilized proteases limit protein digestion to increase sequence coverage in mass spectrometry analysis and facilitate elucidation of protein structures. This review emphasizes the advantages of membrane-based techniques and concludes with some challenges for their practical application.

  4. Reactive Infiltration of Silicon Melt Through Microporous Amorphous Carbon Preforms

    NASA Technical Reports Server (NTRS)

    Sangsuwan, P.; Tewari, S. N.; Gatica, J. E.; Singh, M.; Dickerson, R.

    1999-01-01

    The kinetics of unidirectional capillary infiltration of silicon melt into microporous carbon preforms have been investigated as a function of the pore morphology and melt temperature. The infiltrated specimens showed alternating bands of dark and bright regions, which corresponded to the unreacted free carbon and free silicon regions, respectively. The decrease in the infiltration front velocity for increasing infiltration distances, is in qualitative agreement with the closed-form solution of capillarity driven fluid flow through constant cross section cylindrical pores. However, drastic changes in the thermal response and infiltration front morphologies were observed for minute differences in the preforms microstructure. This suggests the need for a dynamic percolation model that would account for the exothermic nature of the silicon-carbon chemical reaction and the associated pore closing phenomenon.

  5. Synthetic Zeolites and Other Microporous Oxide Molecular Sieves

    NASA Astrophysics Data System (ADS)

    Sherman, John D.

    1999-03-01

    Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow "tailoring" of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol.

  6. Electrochemically Produced Graphene for Microporous Layers in Fuel Cells.

    PubMed

    Najafabadi, Amin Taheri; Leeuwner, Magrieta J; Wilkinson, David P; Gyenge, Előd L

    2016-07-01

    The microporous layer (MPL) is a key cathodic component in proton exchange membrane fuel cells owing to its beneficial influence on two-phase mass transfer. However, its performance is highly dependent on material properties such as morphology, porous structure, and electrical resistance. To improve water management and performance, electrochemically exfoliated graphene (EGN) microsheets are considered as an alternative to the conventional carbon black (CB) MPLs. The EGN-based MPLs decrease the kinetic overpotential and the Ohmic potential loss, whereas the addition of CB to form a composite EGN+CB MPL improves the mass-transport limiting current density drastically. This is reflected by increases of approximately 30 and 70 % in peak power densities at 100 % relative humidity (RH) compared with those for CB- and EGN-only MPLs, respectively. The composite EGN+CB MPL also retains the superior performance at a cathode RH of 20 %, whereas the CB MPL shows significant performance loss. PMID:27254459

  7. Nanoscale encapsulation: the structure of cations in hydrophobic microporous aluminosilicates

    SciTech Connect

    Wasserman, S.R.; Yuchs, S.E.; Giaquinta, D.; Soderholm, L.; Song, Kang

    1996-10-01

    Hydrophobic microporous aluminosilicates, created by organic surface modification of inherently hydrophilic materials such as zeolites and clays, are currently being investigated as storage media for hazardous cations. Use of organic monolayers to modify the surface of an aluminosilicate after introducing an ion into the zeolite/clay reduces the interaction of water with the material. Resulting systems are about 20 times more resistant to leaching of stored ion. XAS spectra from the encapsulated ion demonstrate that byproducts from the organic modifier can complex with the stored cation. This complexation can result in a decreased affinity of the cation for the aluminosilicate matrix. Changing the organic modifier eliminates this problem. XAS spectra also indicate that the reactivity and speciation of the encapsulated ion may change upon application of the hydrophobic layer.

  8. Kinetic modelling of molecular hydrogen transport in microporous carbon materials.

    SciTech Connect

    Hankel, M.; Zhang, H.; Nguyen, T. X.; Bhatia, S. K.; Gray, S. K.; Smith, S. C.

    2011-01-01

    The proposal of kinetic molecular sieving of hydrogen isotopes is explored by employing statistical rate theory methods to describe the kinetics of molecular hydrogen transport in model microporous carbon structures. A Lennard-Jones atom-atom interaction potential is utilized for the description of the interactions between H{sub 2}/D{sub 2} and the carbon framework, while the requisite partition functions describing the thermal flux of molecules through the transition state are calculated quantum mechanically in view of the low temperatures involved in the proposed kinetic molecular sieving application. Predicted kinetic isotope effects for initial passage from the gas phase into the first pore mouth are consistent with expectations from previous modeling studies, namely, that at sufficiently low temperatures and for sufficiently narrow pore mouths D{sub 2} transport is dramatically favored over H{sub 2}. However, in contrast to expectations from previous modeling, the absence of any potential barrier along the minimum energy pathway from the gas phase into the first pore mouth yields a negative temperature dependence in the predicted absolute rate coefficients - implying a negative activation energy. In pursuit of the effective activation barrier, we find that the minimum potential in the cavity is significantly higher than in the pore mouth for nanotube-shaped models, throwing into question the common assumption that passage through the pore mouths should be the rate-determining step. Our results suggest a new mechanism that, depending on the size and shape of the cavity, the thermal activation barrier may lie in the cavity rather than at the pore mouth. As a consequence, design strategies for achieving quantum-mediated kinetic molecular sieving of H{sub 2}/D{sub 2} in a microporous membrane will need, at the very least, to take careful account of cavity shape and size in addition to pore-mouth size in order to ensure that the selective step, namely passage

  9. Hierarchical fabrication of heterojunctioned SrTiO3/TiO2 nanotubes on 3D microporous Ti substrate with enhanced photocatalytic activity and adhesive strength

    NASA Astrophysics Data System (ADS)

    Zhou, Jie; Yin, Lu; Zha, Kang; Li, Huirong; Liu, Zhiyuan; Wang, Jianxin; Duan, Ke; Feng, Bo

    2016-03-01

    Recently, construction of three-dimensional (3D) architecture and design of heterostructure have been proved to be two important approaches for improving photocatalytic (PC) properties of TiO2-based catalysts. In this work, a 3D microporous surface on Ti substrate (MPT) was prepared by simple acid etching. Then, heterojunctioned SrTiO3/TiO2 nanotubes with dominant {001} facets of anatase TiO2were successfully fabricated on MPT by combining anodization with hydrothermal treatment. The 3D microporous-patterned SrTiO3/TiO2 nanotubes heterojunction shows significantly enhanced photo-current density and ∼200% improved PC effect in degradation of Rhodamine B owing to its higher specific surface area, stronger light-harvesting ability and positive heterojunction effect in comparison with TiO2 nanotubes formed on flat Ti substrate. Moreover, the 3D microporous structure on Ti substrate improved the adhesive strength between the nanotubes layer and Ti substrate, which can be ascribed to the effective release of internal stress. Therefore, this present strategy is expected to expand the application of TiO2-based catalysts in many fields which require excellent PC properties and mechanical stability.

  10. Nanowire-integrated microporous silicon membrane for continuous fluid transport in micro cooling device

    SciTech Connect

    So, Hongyun; Pisano, Albert P.; Cheng, Jim C.

    2013-10-14

    We report an efficient passive micro pump system combining the physical properties of nanowires and micropores. This nanowire-integrated microporous silicon membrane was created to feed coolant continuously onto the surface of the wick in a micro cooling device to ensure it remains hydrated and in case of dryout, allow for regeneration of the system. The membrane was fabricated by photoelectrochemical etching to form micropores followed by hydrothermal growth of nanowires. This study shows a promising approach to address thermal management challenges for next generation electronic devices with absence of external power.

  11. Output characteristics of a laser utilizing rhodamine 6G in microporous glass

    SciTech Connect

    Al'tshuler, G.B.; Dul'neva, E.G.; Krylov, K.I.; Meshkovskii, I.K.; Urbanovich, V.S.

    1983-06-01

    A study was made of the lasing characteristics of new active media in the form of microporous glass containing a dye. The efficiency of conversion of the pump radiation, and the spatial and frequency spectra of the output radiation were determined for lasers with dispersive and nondispersive resonators and with active elements in the form of an ethanol solution of rhodamine 6G or microporous glass containing either rhodamine 6G or its ethanol solution. It was found that the use of active elements made of microporous glass and containing rhodamine 6G improved considerably the spatial characteristics of the output radiation compared with those obtained using liquid active media.

  12. Silica, Silicosis, and Autoimmunity

    PubMed Central

    Pollard, Kenneth Michael

    2016-01-01

    Inhalation of dust containing crystalline silica is associated with a number of acute and chronic diseases including systemic autoimmune diseases. Evidence for the link with autoimmune disease comes from epidemiological studies linking occupational exposure to crystalline silica dust with the systemic autoimmune diseases systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Although little is known regarding the mechanism by which silica exposure leads to systemic autoimmune disease, there is a voluminous literature on silica exposure and silicosis that may help identify immune processes that precede development of autoimmunity. The pathophysiology of silicosis consists of deposition of silica particles in the alveoli of the lung. Ingestion of these particles by macrophages initiates an inflammatory response, which stimulates fibroblasts to proliferate and produce collagen. Silica particles are encased by collagen leading to fibrosis and the nodular lesions characteristic of the disease. The steps in the development of silicosis, including acute and chronic inflammation and fibrosis, have different molecular and cellular requirements, suggesting that silica-induced inflammation and fibrosis may be mechanistically separate. Significantly, it is unclear whether silica-induced inflammation and fibrosis contribute similarly to the development of autoimmunity. Nonetheless, the findings from human and animal model studies are consistent with an autoimmune pathogenesis that begins with activation of the innate immune system leading to proinflammatory cytokine production, pulmonary inflammation leading to activation of adaptive immunity, breaking of tolerance, and autoantibodies and tissue damage. The variable frequency of these immunological features following silica exposure suggests substantial genetic involvement and gene/environment interaction in silica-induced autoimmunity. However, numerous questions remain unanswered. PMID:27014276

  13. Silica, Silicosis, and Autoimmunity.

    PubMed

    Pollard, Kenneth Michael

    2016-01-01

    Inhalation of dust containing crystalline silica is associated with a number of acute and chronic diseases including systemic autoimmune diseases. Evidence for the link with autoimmune disease comes from epidemiological studies linking occupational exposure to crystalline silica dust with the systemic autoimmune diseases systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Although little is known regarding the mechanism by which silica exposure leads to systemic autoimmune disease, there is a voluminous literature on silica exposure and silicosis that may help identify immune processes that precede development of autoimmunity. The pathophysiology of silicosis consists of deposition of silica particles in the alveoli of the lung. Ingestion of these particles by macrophages initiates an inflammatory response, which stimulates fibroblasts to proliferate and produce collagen. Silica particles are encased by collagen leading to fibrosis and the nodular lesions characteristic of the disease. The steps in the development of silicosis, including acute and chronic inflammation and fibrosis, have different molecular and cellular requirements, suggesting that silica-induced inflammation and fibrosis may be mechanistically separate. Significantly, it is unclear whether silica-induced inflammation and fibrosis contribute similarly to the development of autoimmunity. Nonetheless, the findings from human and animal model studies are consistent with an autoimmune pathogenesis that begins with activation of the innate immune system leading to proinflammatory cytokine production, pulmonary inflammation leading to activation of adaptive immunity, breaking of tolerance, and autoantibodies and tissue damage. The variable frequency of these immunological features following silica exposure suggests substantial genetic involvement and gene/environment interaction in silica-induced autoimmunity. However, numerous questions remain unanswered. PMID:27014276

  14. Immobilization of L-lysine on microporous PVDF membranes for neuron culture.

    PubMed

    Young, Tai-Horng; Lin, Ui-Hsiang; Lin, Dar-Jong; Chang, Hsu-Hsien; Cheng, Liao-Ping

    2009-01-01

    Microporous poly(vinylidene fluoride) (PVDF) membranes with dense or porous surface were prepared by immersion precipitation of PVDF/TEP solutions in coagulation baths containing different amounts of water. Onto the membrane surface, poly(glycidyl methacrylate) (PGMA) was grafted by plasma-induced free radical polymerization. Then, L-lysine was covalently bonded to the as-grafted PGMA through ring-opening reactions between epoxide and amine to form amino alcohol. The highest attainable graft density of PGMA on a PVDF membrane was 0.293 mg/cm2. This was obtained when the reaction was carried out on a porous surface under an optimized reaction condition. For immobilization of L-lysine, the yield was found to depend on the reaction temperature and L-lysine concentration. The maximal yield was 0.226 mg/cm2, a value considerably higher than reported in the literature using other immobilization methods. Furthermore, neurons were cultured on L-lysine-immobilized PVDF membranes. The results indicated that these membrane surfaces were suited to the growth of neurons, with a MTT value higher than that of the standard culture dish. PMID:19323885

  15. Reactive Melt Infiltration of Silicon-Niobium Alloys in Microporous Carbons

    NASA Technical Reports Server (NTRS)

    Singh, M.; Behrendt, D. R.

    1994-01-01

    Studies of the reactive melt infiltration of silicon-niobium alloys in microporous carbon preforms prepared by the pyrolysis of a polymer precursor have been carried out using modeling, Differential Thermal Analysis (DTA), and melt infiltration. Mercury porosimetry results indicate a very narrow pore size distribution with virtually all the porosity within the carbon preforms open to infiltrants. The morphology and amount of the residual phases (niobium disilicide and silicon) in the infiltrated material can be tailored according to requirements by careful control of the properties (pore size and pore volume) of the porous carbon preforms and alloy composition. The average room temperature four-point flexural strength of a reaction-formed silicon carbide material (made by the infiltration of medium pore size carbon preform with Si - 5 at. % Nb alloy) is 290 +/- 40 MPa (42 +/- 6 ksi) and the fracture toughness is 3.7 +/- 0.3 MPa square root of m. The flexural strength decreases at high temperatures due to relaxation of residual thermal stresses and the presence of free silicon in the material.

  16. Thermomechanical analysis and durability of commercial micro-porous polymer Li-ion battery separators

    NASA Astrophysics Data System (ADS)

    Love, Corey T.

    2011-03-01

    Static and dynamic thermomechanical analysis was performed with a dynamic mechanical analyzer (DMA) to identify thermal and mechanical transitions for commercially available polymer separators under mechanical loading. Clear transitions in deformation mode were observed at elevated temperatures. These transitions identified the onset of separator "shutdown" which occurred at temperatures below the polymer melting point. Mechanical loading direction was critical to the overall integrity of the separator. Anisotropic separators (Celgard 2320, 2400 and 2500) were mechanically limited when pulled in tensile in the transverse direction. The anisotropy of these separators is a result of the dry technique used to manufacture the micro-porous membranes. Separators prepared using the wet technique (Entek Gold LP) behaved more uniformly, or biaxially, where all mechanical properties were nearly identical within the separator plane. The information provided by the DMA can also be useful for predicting the long-term durability of polymer separators in lithium-ion batteries exposed to electrolyte (solvent and salt), thermal fluctuations and electrochemical cycling. Small losses in mechanical integrity were observed for separators exposed to the various immersion environments over the 4-week immersion time.

  17. Functional gold nanoparticles coupled with microporous membranes: a flow controlled assay for colorimetric visualization of proteins.

    PubMed

    Chen, Yu-Yuan; Unnikrishnan, Binesh; Li, Yu-Jia; Huang, Chih-Ching

    2014-11-21

    We report a rapid and simple assay for colorimetric visualization of thrombin at nanomolar levels using functional gold nanoparticles (FAuNPs) coupled with microporous membranes. We used a 29-mer thiolated-thrombin-binding-aptamer (TBA29) to prepare TBA29 functionalized AuNPs (TBA29-AuNPs) for the selective detection of human thrombin. The sensing mechanism is based on the principle of TBA29-AuNPs flowing down through the nitrocellulose membrane (NCM) pores at different flow rates after binding to thrombin. Compared with free TBA29-AuNPs, when thrombin-TBA29-AuNPs were dropped on the NCM, the particles flowed down more easily through the NCM pores along with the buffer solution due to the increase in the gravity of particles. Therefore, color intensities of TBA29-AuNPs on the NCM depended on the concentration of thrombin; the color intensity was lighter when the concentration of thrombin was higher. Thrombin can be detected at the nanomolar level with the naked eye using this colorimetric probe. A protein G modified AuNP based probe (PG-AuNPs/NCM) was employed to detect human immunoglobulin G (hIgG) in plasma samples to demonstrate the practicality of our sensing system. Also, fibrinogen modified Au NPs were analyzed to demonstrate that this concept of detection could be extended to other proteins or systems, by functionalizing with suitable molecules. PMID:25267979

  18. Application of silica nanoparticles for increased silica availability in maize

    NASA Astrophysics Data System (ADS)

    Suriyaprabha, R.; Karunakaran, G.; Yuvakkumar, R.; Prabu, P.; Rajendran, V.; Kannan, N.

    2013-02-01

    Silica nanoparticles were extracted from rice husk and characterised comprehensively. The synthesised silica powders were amorphous in size with 99.7% purity (20-40 nm). Nanosilica was amended with red soil at 15 kg ha-1 along with micron silica. The influence of nanoscale on silica uptake, accumulation and nutritional variations in maize roots were evaluated through the studies such as root sectioning, elemental analysis and physiological parameters (root length and silica content) and compared with micron silica and control. Nanosilica treated soil reveals enhanced silica uptake and elongated roots which make the plant to resist in stress conditions like drought.

  19. High resolution patterning of silica aerogels

    SciTech Connect

    Bertino, M.F.; Hund, J.F.; Sosa, J.; Zhang, G.; Sotiriou-Leventis, C.; Leventis, N.; Tokuhiro, A.T.; Terry, J.

    2008-10-30

    Three-dimensional metallic structures are fabricated with high spatial resolution in silica aerogels. In our method, silica hydrogels are prepared with a standard base-catalyzed route, and exchanged with an aqueous solution typically containing Ag{sup +} ions (1 M) and 2-propanol (0.2 M). The metal ions are reduced photolytically with a table-top ultraviolet lamp, or radiolytically, with a focused X-ray beam. We fabricated dots and lines as small as 30 x 70 {micro}m, protruding for several mm into the bulk of the materials. The hydrogels are eventually supercritically dried to yield aerogels, without any measurable change in the shape and spatial resolution of the lithographed structures. Transmission electron microscopy shows that illuminated regions are composed by Ag clusters with a size of several {micro}m, separated by thin layers of silica.

  20. Fullerene-silica complexes for medical chemistry

    NASA Astrophysics Data System (ADS)

    Sheka, E. F.

    2007-06-01

    A quantum-chemical study of the interaction of C60 fullerene with nanosized silica was performed. It was demonstrated that a fullerene molecule forms a weakly bound complex with a pyrogenic silica (Aerosil) particle only via the interaction with the silanediol groups of the hydroxyl covering on the particle. By contrast, a fullerene molecule is not bonded to an individual siloxane cycle, and, therefore, fullerosilica gel is formed due to the retention of fullerene molecules in pores of silica gel as a result cooperative action of the siloxane cycles comprising the pore. In both cases, the predicted medico-biological action of medicinal preparations is due to the radical-like and donor-acceptor characteristics of the C60 molecule.

  1. Hollow silica sphere colloidal crystals: insights into calcination dependent thermal transport

    NASA Astrophysics Data System (ADS)

    Ruckdeschel, P.; Kemnitzer, T. W.; Nutz, F. A.; Senker, J.; Retsch, M.

    2015-05-01

    Colloidal crystals consisting of monodisperse hollow silica spheres represent a well-defined porous material class, which features a range of interesting optical, mechanical, and thermal properties. These hierarchically structured materials comprise micropores within the silica network, which are confined to a thin shell (tens of nanometers) of a hollow sphere (hundreds of nanometers). Using simple calcination steps, we markedly change the internal microstructure, which we investigate by a multitude of characterization techniques, while the meso- and macrostructure remains constant. Most importantly the rearrangement of the silica condensation network leads to a reduction in the total surface area and loss of micropores as demonstrated by N2 sorption and hyperpolarized 129Xe NMR studies. Spin-lattice relaxation shows a drastic increase of the rigidity of the amorphous network. These microstructural changes significantly influence the thermal conductivity through such a porous silica material. We demonstrate a remarkably low thermal conductivity of only 71 mW m-1 K-1 for a material of a comparatively high density of 1.04 kg m-3 at 500 °C calcination temperature. This thermal conductivity increases up to 141 mW m-1 K-1 at the highest calcination temperature of 950 °C. The great strength of hollow silica sphere colloidal crystals lies in their hierarchical structure control, which allows further investigation of how the internal microstructure and the interfacial contact points affect the transport of heat.Colloidal crystals consisting of monodisperse hollow silica spheres represent a well-defined porous material class, which features a range of interesting optical, mechanical, and thermal properties. These hierarchically structured materials comprise micropores within the silica network, which are confined to a thin shell (tens of nanometers) of a hollow sphere (hundreds of nanometers). Using simple calcination steps, we markedly change the internal microstructure

  2. Template-mediated Synthesis of Hollow Microporous Organic Nanorods with Tunable Aspect Ratio

    PubMed Central

    Li, Qingyin; Jin, Shangbin; Tan, Bien

    2016-01-01

    Hollow microporous organic nanorods (HMORs) with hypercrosslinked polymer (HCPs) shells were synthesized through emulsion polymerization followed by hypercrosslinking. The HMORs have tunable aspect ratios, high BET surface areas and monodispersed morphologies, showing good performance in gas adsorpion. PMID:27506370

  3. A luminescent microporous metal-organic framework for the recognition and sensing of anions.

    PubMed

    Chen, Banglin; Wang, Liangbo; Zapata, Fatima; Qian, Guodong; Lobkovsky, Emil B

    2008-05-28

    A luminescent microporous metal-organic framework Tb(BTC)G has been developed for the recognition and sensing of anions, exhibiting a high-sensitivity sensing function with respect to fluoride. PMID:18452294

  4. Characterization of the micropore structure of activated carbons by adsorptions of nitrogen and some hydrocarbons

    SciTech Connect

    Guezel, F.

    1999-02-01

    In the present study the effects of the duration of carbonization and physical activation properties of activated carbon from vegetable materials were investigated. Peanut shells were used to obtain active carbon. These shells were activated chemically with ZnCl{sub 2} and/or CO{sub 2} for different times, and the micropore structures of these active carbons were studied by measuring the adsorption isotherms for nitrogen and some hydrocarbons such as benzene, n-butane, isobutane, 2,2-dimethylbutane, and isooctane. As the physical activation time was increased, the primary micropores, which were measured at 0.01 relative pressure, were reduced, and they were replaced by larger secondary and tertiary micropores which were measured at 0.15--0.01 and 0.30--0.15 relative pressures. The ratios of the mesopore volume to the micropore volume also increased as the duration of physical activation increased.

  5. A highly crystalline layered silicate with three-dimensionally microporous layers

    NASA Astrophysics Data System (ADS)

    Jeong, Hae-Kwon; Nair, Sankar; Vogt, Thomas; Dickinson, L. Charles; Tsapatsis, Michael

    2003-01-01

    Layered silicates with three-dimensional microporosity within the layers have the potential to enable new applications in catalysis, adsorption and ion-exchange. Until now no such materials have been reported. However, here we present the synthesis and structure of AMH-3, a silicate with three-dimensionally microporous layers, obtained in high purity and crystallinity. AMH-3 is composed of silicate layers containing eight-membered rings in all three principal crystal directions, and spaced by strontium cations, sodium cations and water molecules. Because of its three-dimensional pore structure, acid and thermal stability, this layered material could find applications in polymer-silicate composites for membrane applications, for synthesis of combined microporous-mesoporous materials, and for the formation of new zeolites and microporous films. Its existence also opens new possibilities for the synthesis of other layered silicates with multidimensional microporous framework layers.

  6. Effect of pH and zinc stress on micropore system of rye roots

    NASA Astrophysics Data System (ADS)

    Szatanik-Kloc, A.

    2012-07-01

    After zinc stress the total micropore volume decreased remarkably while the average micropore radius increased remarkably for the rye roots. Pore size distribution functions of the roots after the additional zinc application showed the decrease of the small micropore fraction from ca 2 to 10 nm and the increase of the large micropore from ca 22 to 50 nm. The root surface pores were fractal. After the stress pore fractal dimension increased. The changes of the microporosity observed in the roots surface can be related to the high content of zinc in the cell wall and/or due to the shortage of Ca+2 the intercellular spaces particularly in the tissues of seminal cortex of the studied roots might have grown.

  7. Template-mediated Synthesis of Hollow Microporous Organic Nanorods with Tunable Aspect Ratio

    NASA Astrophysics Data System (ADS)

    Li, Qingyin; Jin, Shangbin; Tan, Bien

    2016-08-01

    Hollow microporous organic nanorods (HMORs) with hypercrosslinked polymer (HCPs) shells were synthesized through emulsion polymerization followed by hypercrosslinking. The HMORs have tunable aspect ratios, high BET surface areas and monodispersed morphologies, showing good performance in gas adsorpion.

  8. Effects of temperature on trichloroethylene desorption from silica gel and natural sediments. 1. Isotherms

    SciTech Connect

    Werth, C.J.; Reinhard, M.

    1997-03-01

    Aqueous phase isotherms were calculated from vapor phase desorption isotherms measured at 15, 30, and 60{degree}C for trichloroethylene on a silica gel, an aquifer sediment, a soil, a sand fraction, and a clay and silt fraction, all at 100% relative humidity. Isosteric heats of adsorption (Q{sub st}(q)) were calculated as a function of the sorbed concentration, q, and examined with respect to the following mechanisms: adsorption on water wet mineral surfaces, sorption in amorphous organic matter (AOM), and adsorption in hydrophobic micropores. Silica gel, sand fraction, and clay and silt fraction 60{degree}C isotherms are characterized by a Freundlich region and a region at very low concentrations where isotherm points deviate from log-log linear behavior. The latter is designated the non-Freundlich region. For the silica gel, values of Q{sub st}(q) (9.5-45 kJ/mol) in both regions are consistent with adsorption in hydrophobic micropores. For the natural solids, values of Q{sub st}(q) in the Freundlich regions are less than or equal to zero and are consistent with sorption on water wet mineral surfaces and in AOM. In the non-Freundlich regions, diverging different temperature isotherms with decreasing q and Q{sub st}(q) value of 34 kJ/mol for the clay and silt fraction suggest that adsorption is occurring in hydrophobic micropores. The General Adsorption Isotherm is used to capture this adsorption heterogeneity. 57 refs., 5 figs., 2 tabs.

  9. New antifouling silica hydrogel.

    PubMed

    Beltrán-Osuna, Ángela A; Cao, Bin; Cheng, Gang; Jana, Sadhan C; Espe, Matthew P; Lama, Bimala

    2012-06-26

    In this work, a new antifouling silica hydrogel was developed for potential biomedical applications. A zwitterionic polymer, poly(carboxybetaine methacrylate) (pCBMA), was produced via atom-transfer radical polymerization and was appended to the hydrogel network in a two-step acid-base-catalyzed sol-gel process. The pCBMA silica aerogels were obtained by drying the hydrogels under supercritical conditions using CO(2). To understand the effect of pCBMA on the gel structure, pCBMA silica aerogels with different pCBMA contents were characterized using scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) spectroscopy, and the surface area from Brauner-Emmet-Teller (BET) measurements. The antifouling property of pCBMA silica hydrogel to resist protein (fibrinogen) adsorption was measured using enzyme-linked immunosorbent assay (ELISA). SEM images revealed that the particle size and porosity of the silica network decreased at low pCBMA content and increased at above 33 wt % of the polymer. The presence of pCBMA increased the surface area of the material by 91% at a polymer content of 25 wt %. NMR results confirmed that pCBMA was incorporated completely into the silica structure at a polymer content below 20 wt %. A protein adsorption test revealed a reduction in fibrinogen adsorption by 83% at 25 wt % pCBMA content in the hydrogel compared to the fibrinogen adsorption in the unmodified silica hydrogel. PMID:22607091

  10. The use of Reactive Ion Etching for obtaining “free” silica nano test tubes

    NASA Astrophysics Data System (ADS)

    Buyukserin, Fatih; Martin, Charles R.

    2010-10-01

    Silica nano test tubes are one-dimensional inorganic nanostructures with several biotechnological applications including biosensing, magnetic resonance imaging, and targeted cancer therapeutics. They are generally prepared by sol-gel deposition of silica to nanoporous alumina templates. Preparing samples composed of isolated free silica nano test tubes can be a challenging process due to the conformal coating of silica on the template. This causes the formation of a top-surface silica layer which laterally connects the nano test tubes. Herein, we detailed the use of Reactive Ion Etching to remove this top-surface silica layer which yields free silica nano test tubes with template dissolution. Compared with the mechanical polishing approach, Reactive Ion Etching treatment allows a fine manipulation ability of the surface material at the nanoscale level. When used excessively, Reactive Ion Etching causes an orifice closing phenomenon that may be employed to create novel one-dimensional nanocapsules.

  11. Hard magnetism in structurally engineered silica nanocomposite.

    PubMed

    Song, Hyon-Min; Zink, Jeffrey I

    2016-09-21

    Creation of structural complexity by simple experimental control will be an attractive approach for the preparation of nanomaterials, as a classical bottom-up method is supplemented by a more efficient and more direct artificial engineering method. In this study, structural manipulation of MCM-41 type mesoporous silica is investigated by generating and imbedding hard magnetic CoFe2O4 nanoparticles into mesoporous silica. Depending on the heating rate and target temperature, mesoporous silica undergoes a transformation in shape to form hollow silica, framed silica with interior voids, or melted silica with intact mesostructures. Magnetism is governed by the major CoFe2O4 phase, and it is affected by antiferromagnetic hematite (α-Fe2O3) and olivine-type cobalt silicate (Co2SiO4), as seen in its paramagnetic behavior at the annealing temperature of 430 °C. The early formation of Co2SiO4 than what is usually observed implies the effect of the partial substitution of Fe in the sites of Co. Under slow heating (2.5 °C min(-1)) mesostructures are preserved, but with significantly smaller mesopores (d100 = 1.5 nm). In addition, nonstoichiometric CoxFe1-xO with metal vacancies at 600 °C, and spinel Co3O4 at 700 °C accompany major CoFe2O4. The amorphous nature of silica matrix is thought to contribute significantly to these structurally diverse and rich phases, enabled by off-stoichiometry between Si and O, and accelerated by the diffusion of metal cations into SiO4 polyhedra at an elevated temperature. PMID:27537252

  12. Silica-based cationic bilayers as immunoadjuvants

    PubMed Central

    Lincopan, Nilton; Santana, Mariana RA; Faquim-Mauro, Eliana; da Costa, Maria Helena B; Carmona-Ribeiro, Ana M

    2009-01-01

    Background Silica particles cationized by dioctadecyldimethylammonium bromide (DODAB) bilayer were previously described. This work shows the efficiency of these particulates for antigen adsorption and presentation to the immune system and proves the concept that silica-based cationic bilayers exhibit better performance than alum regarding colloid stability and cellular immune responses for vaccine design. Results Firstly, the silica/DODAB assembly was characterized at 1 mM NaCl, pH 6.3 or 5 mM Tris.HCl, pH 7.4 and 0.1 mg/ml silica over a range of DODAB concentrations (0.001–1 mM) by means of dynamic light scattering for particle sizing and zeta-potential analysis. 0.05 mM DODAB is enough to produce cationic bilayer-covered particles with good colloid stability. Secondly, conditions for maximal adsorption of bovine serum albumin (BSA) or a recombinant, heat-shock protein from Mycobacterium leprae (18 kDa-hsp) onto DODAB-covered or onto bare silica were determined. At maximal antigen adsorption, cellular immune responses in vivo from delayed-type hypersensitivity reactions determined by foot-pad swelling tests (DTH) and cytokines analysis evidenced the superior performance of the silica/DODAB adjuvant as compared to alum or antigens alone whereas humoral response from IgG in serum was equal to the one elicited by alum as adjuvant. Conclusion Cationized silica is a biocompatible, inexpensive, easily prepared and possibly general immunoadjuvant for antigen presentation which displays higher colloid stability than alum, better performance regarding cellular immune responses and employs very low, micromolar doses of cationic and toxic synthetic lipid. PMID:19152701

  13. Nature of =~SiOCrO(2)CI And (=~SiO)(2)CrO(2) Sites Prepared By Grafting CrO(2)CI(2) Onto Silica

    SciTech Connect

    Demmelmaier, C.A.; White, R.E.; Bokhoven, J.A.van; Scott, S.L.

    2009-05-14

    The room-temperature reaction between chromyl chloride and Sylopol 952 silicas pretreated at 200, 450, and 800 C was investigated using IR, XANES, and EXAFS spectroscopy, as well as by DFT modeling. On the silicas pretreated at 200 and 450 C, the structurally uniform sites formed by the reaction with one surface hydroxyl group are described as {triple_bond}SiOCrO{sub 2}Cl. Unreacted silanols persist on these silicas even in the presence of excess CrO{sub 2}Cl{sub 2}, and on the silica pretreated at 200 C some participate in hydrogen bonding with the grafted monochlorochromate sites. On the silica pretreated at 800 C, both {triple_bond}SiOCrO{sub 2}Cl and ({triple_bond}SiO){sub 2}CrO{sub 2} sites are formed. The latter are produced despite the absence of hydrogen-bonded hydroxyl pairs on the support. The origin of the chromate sites is proposed to be the reaction between CrO{sub 2}Cl{sub 2} and hydroxyl-substituted siloxane 2-rings. These rings are likely formed at 800 C by condensation between a pair of vicinal silanols in which one of the silanols is also a member of a geminal pair.

  14. Determination of Si/Al molar ratios in microporous zeolites using calibration-free laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Horňáčková, M.; Horňáček, M.; Rakovský, J.; Hudec, P.; Veis, P.

    2013-10-01

    In this paper, the potential application of a calibration-free laser-induced breakdown spectroscopy (CF-LIBS) method for the determination of the silicon-to-aluminum molar ratio in microporous zeolites (with both intermediate and high silica contents) is discussed. Three different zeolite types, i.e., mordenite and zeolites type Y and ZSM-5, were analyzed in this study and were shown to have Si/Al molar ratios in the range between 2.3 and 51.8. Many ionic and neutral atomic spectral lines of silicon and aluminum were detected in the measured LIBS spectra in the spectral range 200-1000 nm, but not all of the observed spectral lines are convenient for a CF-LIBS analysis. To increase the accuracy of the results, only lines with no or low self-absorption probability were selected. A systematic method is proposed to select spectral lines based on three main parameters: the transition probability (Einstein coefficient), the lower level energy of the observed transition and the number density ratio between singly ionized and neutral species (as calculated for Si and Al for the measured electron density and electron temperature). The calculated Si/Al molar ratios were close to that determined by wet chemical analysis with an average relative standard deviation of approximately 5% (maximum less than 15%). Our results point to the possibility of using CF-LIBS for analysis of these types of materials and for determination of Si/Al molar ratios.

  15. Direct formation of S-nitroso silica nanoparticles from a single silica source.

    PubMed

    Chou, Hung-Chang; Chiu, Shih-Jiuan; Liu, Ying-Ling; Hu, Teh-Min

    2014-01-28

    Nitric oxide (NO) is a ubiquitous molecule in the body. Because of its multiple pathophysiologic roles, the potential for treating various diseases by the exogenous administration of NO has been under intensive investigation. However, the unstable, radical nature of NO poses a major challenge to the effective delivery of NO. Previously, silica nanoparticles synthesized by the traditional method have been developed into NO-carrying systems. In the present study, for the first time NO-carrying silica nanoparticles were prepared from a single silica precursor using a simple nanoprecipitation method. (3-Mercaptopropyl)-trimethoxysilane (MPTMS) was used as the sole silane source, which was subjected to acid-catalyzed S-nitrosation and condensation reactions in a one-pot organic phase. S-Nitroso silica nanoparticles (SNO-SiNPs) were then produced by injecting a smaller quantity of the organic phase into a larger amount of water without surfactants. Various preparation parameters were tested to obtain optimized conditions. Moreover, a phase diagram demonstrating the ouzo effect was constructed. The prepared SNO-SiNPs were spherical particles with a tunable size in the range of 100-400 nm. The nanoparticles in aqueous dispersions exhibited high colloid stability, possibly resulting from highly negatively charged surfaces. The result of solid-state (29)Si NMR shows the predominance of T(2) and T(3) silicon structures, suggesting that nanoparticles were formed from polycondensed silica species. In conclusion, NO-loaded silica nanoparticles have been directly prepared from a single silane precursor using a surfactant-free, low-energy, one-step nanoprecipitation approach. The method precludes the need for the initial formation of bare particles and subsequent functionalization steps. PMID:24410024

  16. Silica Embedded Metal Hydrides

    SciTech Connect

    Heung, L.K.; Wicks, G.G.

    1998-08-01

    A method to produce silica embedded metal hydride was developed. The product is a composite in which metal hydride particles are embedded in a matrix of silica. The silica matrix is highly porous. Hydrogen gas can easily reach the embedded metal hydride particles. The pores are small so that the metal hydride particles cannot leave the matrix. The porous matrix also protects the metal hydride particles from larger and reactive molecules such as oxygen, since the larger gas molecules cannot pass through the small pores easily. Tests show that granules of this composite can absorb hydrogen readily and withstand many cycles without making fines.

  17. Oxygen configurations in silica

    SciTech Connect

    Chelikowsky, James R.; Chadi, D. J.; Binggeli, N.

    2000-07-15

    We propose a transition state for oxygen in silica. This state is produced by the insertion of an oxygen molecule into the Si-O-Si bond, i.e., it consists of producing a Si-O-O-O-Si bond. This state allows molecular oxygen diffusion in silica without breaking the molecular O{sub 2} bond and it is energetically more stable than a peroxy configuration. This configuration may allow for exchange of molecular oxygen with the oxygen in the silica framework. (c) 2000 The American Physical Society.

  18. Structure analysis and catalytic property of a microporous framework based on a flexible tripodal ligand with novel conformations

    NASA Astrophysics Data System (ADS)

    Shi, Xianju; Zhang, Xinhai; Li, Xiaoxia; Hou, Hongwei; Fan, Yaoting

    2011-06-01

    A microporous metal-organic framework {[Cu 3Cl 6(ttmb) 4]·6H 2O} n ( 1) (ttmb = 1,3,5-tris(1,2,4-triazol-1-ylmethyl)-benzene) with tetranodal (3,4)-connected topological type was prepared by the self-assembly reaction of the flexible tripodal ligand ttmb with CuCl 2·2H 2O. The ligand exhibits two infrequent coordination conformations in complex 1, and the framework has a large pore volume (remove the solvent molecules) of 1781.6 Å 3 (36.3% of the total). The test of 1 as the catalyst in the oxidative coupling reaction of 2,6-dimethylphenol indicates that it is catalytically active by showing high conversion of DMP under the optimized reaction condition.

  19. An NMR study on the mechanisms of freezing and melting of water confined in spherically mesoporous silicas SBA-16.

    PubMed

    Miyatou, Tatsuya; Ohashi, Ryutaro; Ida, Tomonori; Kittaka, Shigeharu; Mizuno, Motohiro

    2016-07-21

    Thermodynamic and dynamic properties of water confined in mesoporous silica glass SBA-16 were investigated by DSC, and (1,2)H NMR spectroscopy and (2)H NMR spin-lattice relaxation time (T1) as a function of pore size. SBA-16 possesses the main spherical pores, interconnecting channels and micropores (corona). Water in the characteristic spherical pores of SBA-16 freezes at the homogeneous nucleation temperature of water. Between room and freezing temperatures, the correlation time of the isotropic rotation of water in the pores of SBA-16 followed the Vogel-Fulcher-Tammann (VFT) relation, which reflects the formation and growth of clusters of fragile water for changing to the strong water. The vitrification of water in micropores around 200 K was observed by (2)H NMR. Above 200 K, the correlation time of the rotation of water in micropores exhibited non-Arrhenius behavior, which is correlated with the gradual decrease in the mobility of water due to the growth of hydrogen bonding, forming low density water before vitrification. After vitrification, the activation energy of the rotation of water in micropores was 25-33 kJ mol(-1), which was similar to that in ice Ih for all samples. The freedom of cluster formation and water rotation increased with the increasing the pore size. PMID:27346613

  20. Scattering and physical aging in intrinsically microporous polymers

    NASA Astrophysics Data System (ADS)

    McDermott, Amanda Grace

    Polymers of intrinsic microporosity (PIMs) form glassy, rigid membranes featuring a large concentration of pores smaller than 1 nm, a large internal surface area, and high gas permeability and selectivity. Porosity in these materials---closely related to free volume--- arises from an unusual chain structure combining rigid segments with sites of contortion. Linear PIMs can be easily solution-cast into films whose interconnected networks of micropores can be exploited for applications such as gas separation and storage. Like other glasses, though, PIMs are subject to physical aging: a slow increase in density over time. This is accompanied by a decrease in permeability that reduces their performance as gas separation membranes. Several characterization methods are routinely employed to measure the structural properties of microporous materials, but none are as widely available and as easily applied to film samples with varied sample histories as small- and wide-angle X-ray scattering (SAXS and WAXS). Although it is possible to derive useful information such as surface areas and pore sizes from the scattering patterns of many porous materials, scattering from PIMs includes some unusual features whose interpretation is not readily apparent. In this work, a robust interpretation of PIM SAXS and WAXS features is developed with support from molecular dynamics simulations. The sensitivity of these patterns to time, temperature and film thickness is shown to be qualitatively consistent with physical aging, demonstrating that high-free-volume, porous polymeric glasses present a unique opportunity to study structural changes during physical aging using scattering methods. Models for extracting quantitative information about changes in the sizes and volume fraction of pores are also explored. Although quantitative interpretation of scattering patterns remains challenging, results of the aging study suggest that there may be two distinct mechanisms of aging in PIMs. Several