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Sample records for activated carbon silica

  1. Synthesis, characterization and catalytic activity of carbon-silica hybrid catalyst from rice straw

    NASA Astrophysics Data System (ADS)

    Janaun, J.; Safie, N. N.; Siambun, N. J.

    2016-07-01

    The hybrid-carbon catalyst has been studied because of its promising potential to have high porosity and surface area to be used in biodiesel production. Silica has been used as the support to produce hybrid carbon catalyst due to its mesoporous structure and high surface area properties. The chemical synthesis of silica-carbon hybrid is expensive and involves more complicated preparation steps. The presence of natural silica in rice plants especially rice husk has received much attention in research because of the potential as a source for solid acid catalyst synthesis. But study on rice straw, which is available abundantly as agricultural waste is limited. In this study, rice straw undergone pyrolysis and functionalized using fuming sulphuric acid to anchor -SO3H groups. The presence of silica and the physiochemical properties of the catalyst produced were studied before and after sulphonation. The catalytic activity of hybrid carbon silica acid catalyst, (H-CSAC) in esterification of oleic acid with methanol was also studied. The results showed the presence of silica-carbon which had amorphous structure and highly porous. The carbon surface consisted of higher silica composition, had lower S element detected as compared to the surface that had high carbon content but lower silica composition. This was likely due to the fact that Si element which was bonded to oxygen was highly stable and unlikely to break the bond and react with -SO3H ions. H-CSAC conversions were 23.04 %, 35.52 % and 34.2 7% at 333.15 K, 343.15 K and 353.15 K, respectively. From this research, rice straw can be used as carbon precursor to produce hybrid carbon-silica catalyst and has shown catalytic activity in biodiesel production. Rate equation obtained is also presented.

  2. Removing Dissolved Silica from Waste Water with Catechol and Active Carbon

    SciTech Connect

    Sasan, Koroush; Brady, Patrick; Krumhansl, James L.; Nenoff, Tina M.

    2017-01-01

    Fresh water scarcity is going to be a global great challenge in the near future because of the increasing population. Our water resources are limited and, hence, water treatment and recycling methods are the only alternatives for fresh water procurement in the upcoming decades. Water treatment and recycling methods serve to remove harmful or problematic constituents from ground, surface and waste waters prior to its consumption, industrial supply, or other uses. Scale formation in industrial and domestic installations is still an important problem during water treatment. In water treatment, silica scaling is a real and constant concern for plant operations. The focus of this study is on the viability of using a combination of catechol and active carbon to remove dissolved silica from concentrated cooling tower water (CCTW). Various analytical methods, such as ICP-MS and UV-vis, were used to understand the structure-property relationship between the material and the silica removal results. UV-Vis indicates that catechol can react with silica ions and form a silica-catecholate complex. The speciation calculation of catechol and silica shows that catechol and silica bind in the pH range of 8 – 10; there is no evidence of linkage between them in neutral and acidic pHs. The silica removal results indicate that using ~4g/L of catechol and 10g/L active carbon removes up to 50% of the dissolved silica from the CCTW.

  3. A sustainable route for the preparation of activated carbon and silica from rice husk ash.

    PubMed

    Liu, Yan; Guo, Yupeng; Zhu, Yanchao; An, Dongmin; Gao, Wei; Wang, Zhuo; Ma, Yuejia; Wang, Zichen

    2011-02-28

    An environmentally friendly and economically effective process to produce silica and activated carbon form rice husk ask simultaneously has been developed in this study. An extraction yield of silica of 72-98% was obtained and the particle size was 40-50 nm. The microstructures of the as-obtained silica powders were characterized by X-ray diffraction (XRD) and infrared spectra (IR). The surface area, iodine number and capacitance value of activated carbon could achieve 570 m(2)/g, 1708 mg/g, 180 F/g, respectively. In the whole synthetic procedure, the wastewater and the carbon dioxide were collected and reutilized. The recovery rate of sodium carbonate was achieved 92.25%. The process is inexpensive, sustainable, environmentally friendly and suitable for large-scale production.

  4. Silica decorated on porous activated carbon nanofiber composites for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Kim, So Yeun; Kim, Bo-Hye

    2016-10-01

    A hybrid of silica decorated on porous activated carbon nanofibers (ACNFs) is fabricated in the form of a web via electrospinning and an activation process as an electrode material for electrochemical capacitors in an organic electrolyte. The introduction of PhSiH3 (PS) into the polyacrylonitrile (PAN) solution induces a porous ACNF structure containing silica nanoparticles (NPs) via the spontaneous sol-gel process of PS by steam in the subsequent physical activation process. These inorganic-organic hybrid composites of porous ACNF containing silica NPs show superior specific capacitance and energy density in electrochemical tests, along with good rate capability and excellent cycle life in an organic electrolyte, which is attributed to the combination of ACNF's high surface area and silica's hydrophilicity. The electrochemical performance decreases with increasing PS concentration, and this trend is consistent with the specific surface area results, which reveal the rapid formation of a double layer.

  5. Impact of carbon on the surface and activity of silica-carbon supported copper catalysts for reduction of nitrogen oxides

    NASA Astrophysics Data System (ADS)

    Spassova, I.; Stoeva, N.; Nickolov, R.; Atanasova, G.; Khristova, M.

    2016-04-01

    Composite catalysts, prepared by one or more active components supported on a support are of interest because of the possible interaction between the catalytic components and the support materials. The supports of combined hydrophilic-hydrophobic type may influence how these materials maintain an active phase and as a result a possible cooperation between active components and the support material could occur and affects the catalytic behavior. Silica-carbon nanocomposites were prepared by sol-gel, using different in specific surface areas and porous texture carbon materials. Catalysts were obtained after copper deposition on these composites. The nanocomposites and the catalysts were characterized by nitrogen adsorption, TG, XRD, TEM- HRTEM, H2-TPR, and XPS. The nature of the carbon predetermines the composite's texture. The IEPs of carbon materials and silica is a force of composites formation and determines the respective distribution of the silica and carbon components on the surface of the composites. Copper deposition over the investigated silica-carbon composites leads to formation of active phases in which copper is in different oxidation states. The reduction of NO with CO proceeds by different paths on different catalysts due to the textural differences of the composites, maintaining different surface composition and oxidation states of copper.

  6. Experimental selectivity curves of gaseous binary mixtures of hydrocarbons and carbon dioxide on activated carbon and silica gel

    SciTech Connect

    Olivier, M.G.; Jadot, R.

    1998-07-01

    The selectivity curves of gaseous binary mixtures of ethane + ethylene, methane + carbon dioxide at 303 K and 700 kPa and butane + 2 methylpropane at 318 K and 200 kPa have been determined on activated carbon and silica gel using an original apparatus. In this paper, a brief description of this apparatus is given. The difference in behavior of these two adsorbents is discussed.

  7. Adsorption of CO{sub 2} on microporous materials. 1: On activated carbon and silica gel

    SciTech Connect

    Berlier, K.; Frere, M.

    1997-05-01

    Adsorption isotherms of carbon dioxide (CO{sub 2}) at temperatures ranging from 278 K to 328 K (seven temperatures) and at pressures up to 3300 kPa on activated carbon and on silica gel are presented. These experimental results are useful as they allow one to broaden, the T, P domain of CO{sub 2} adsorption. These data, together with more classical ones (obtained at low temperature and low pressure (Berlier and Frere, 1996)), will make possible the test of theoretical developments for the prediction of adsorption isotherms in a range of temperature and pressure conditions never studied before.

  8. Upgrading the rice husk char obtained by flash pyrolysis for the production of amorphous silica and high quality activated carbon.

    PubMed

    Alvarez, Jon; Lopez, Gartzen; Amutio, Maider; Bilbao, Javier; Olazar, Martin

    2014-10-01

    The overall valorization of rice husk char obtained by flash pyrolysis in a conical spouted bed reactor (CSBR) has been studied in a two-step process. Thus, silica has been recovered in a first step and the remaining carbon material has been subjected to steam activation. The char samples used in this study have been obtained by continuous flash pyrolysis in a conical spouted bed reactor at 500°C. Extraction with Na2CO3 allows recovering 88% of the silica contained in the rice husk char. Activation of the silica-free rice husk char has been carried out in a fixed bed reactor at 800°C using steam as activating agent. The porous structure of the activated carbons produced includes a combination of micropores and mesopores, with a BET surface area of up to 1365m(2)g(-1) at the end of 15min.

  9. Field Trip Guide to Serpentinite, Silica-Carbonate Alteration, and Related Hydrothermal Activity in the Clear Lake Region, California

    SciTech Connect

    Fraser Goff; George Guthrie

    1999-06-01

    This guide is designed to familiarize scientists with the geology, structure, alteration, and fluids typical of California serpentinites for purposes of carbon dioxide sequestration (Lackner et al., 1995). Goff et al. (1997) and Goff and Lackner (1998) describe the geology and geochemistry of some of the serpentinites from this area. Mechanisms of silica-carbonate alteration were outlined by Barnes et al. (1973). Donnelly-Nolan et al. (1993) most recently reviewed relations between regional hydrothermal alteration and Quarternary volcanic activity. Stanley et al. (1998) summarized geophysical characteristics of the region.

  10. Interfacial Reaction-Driven Formation of Silica Carbonate Biomorphs with Subcellular Topographical Features and Their Biological Activity.

    PubMed

    Wang, Guocheng; Zhao, Xiaobing; Möller, Marco; Moya, Sergio E

    2015-10-28

    We report the interfacial reaction-driven formation of micro/nanostructured strontium carbonate (SrCO3) biomorphs with subcellular topographical features on strontium zinc silicate (Sr2ZnSi2O7) biomedical coatings and explore their potential use in bone tissue engineering. The resulting SrCO3 crystals build a well-integrated scaffold surface that not only prevents burst release of ions from the coating but also presents nanotopographical features similar to cellular filopodia. The surface with biomorphic crystals enhances osteoblast adhesion, upregulates the alkaline phosphatase activity, and increases collagen production, highlighting the potential of the silica carbonate biomorphs for tissue regeneration.

  11. Microwave-assisted combustion synthesis of nano iron oxide/iron-coated activated carbon, anthracite, cellulose fiber, and silica, with arsenic adsorption studies

    EPA Science Inventory

    Combustion synthesis of iron oxide/iron coated carbons such as activated carbon, anthracite, cellulose fiber and silica is described. The reactions were carried out in alumina crucibles using a Panasonic kitchen microwave with inverter technology, and the reaction process was com...

  12. Thermal and catalytic degradation of polyethylene wastes in the presence of silica gel, 5A molecular sieve and activated carbon.

    PubMed

    González, Yovana Sander; Costa, Carlos; Márquez, M Carmen; Ramos, Pedro

    2011-03-15

    A comparative study of thermal and catalytic degradation of polyethylene wastes has been carried out with the aim of obtaining chemical compounds with potential use in the chemical industry and the energy production. Polyethylene wastes were obtained from polyethylene bags used in supermarkets. Catalysts utilized in the study were silica gel, 5A molecular sieve and activated carbon. The pyrolysis was performed in a batch reactor at 450, 500 and 700 °C during 2h for each catalyst. The ratio catalyst/PE was 10% w/w and the solid and gaseous products were analyzed by gas chromatography and mass spectrometry. The optimum operation temperature and the influence of the three catalysts are discussed with regards to the products formed. The best temperature for degradation with silica gel and activated carbon as catalysts was 450 °C and with 5A molecular sieve was 700 °C. Degradation products of PE (solid fraction and gas fraction) are depending on temperature and catalyst used. External surface and structure of catalysts were visualized by Scanning Electron Microscopy (SEM) and the contribution on product distribution is commented. All products from different degradations could be used as feed stocks in chemical industry or in energy production based on the value of heat of combustion for solid fraction (45000 J/g), similar to the heat of combustion of commercial fuels.

  13. Carbon in intimate contact with quartz reduces the biological activity of crystalline silica dusts.

    PubMed

    Ghiazza, Mara; Tomatis, Maura; Doublier, Sophie; Grendene, Francesca; Gazzano, Elena; Ghigo, Dario; Fubini, Bice

    2013-01-18

    To evaluate the effect of carbonaceous materials on the pathogenic activity of quartz dusts, mixtures of carbon soot (1 and 10%) and quartz (Min-U-Sil) were prepared and then milled so to attain an intimate association of carbon and the quartz surface. Both cellular and cell-free tests show that carbon associated to quartz completely inhibits the typical free radical generation of quartz dusts (through Fenton activity and homolytic cleavage of a C-H bond) and suppresses the oxidative stress and inflammation induced by quartz alone on MH-S murine macrophage cells (lipid peroxidation, nitric oxide release, and tumor necrosis factor-α synthesis). The cytotoxic response to quartz is also largely reduced. An extremely pure quartz milled with 10% of soot showed inactivating effects on the adverse reactions to quartz similar to Min-U-Sil quartz. None of these effects takes place when the same experiments are carried out with mechanically mixed samples, which suggests that carbon acts not just as a radical quencher but because of its association to the quartz surface.

  14. Carbon-Coated Silica and Silica-Coated Carbon for Elastomer Reinforcement

    NASA Astrophysics Data System (ADS)

    Kohls, D. J.; Beaucage, G.; Pratsinis, S. E.; Kammler, H.

    2000-03-01

    Recently several silica producers have introduced dual-phase grades of silica/carbon powders intended for use in elastomer reinforcement. These mass-produced, nano-structured materials have carbon content in excess of 75carbon aggregates, the intent being to enhance the strength of filler-filler networking in a nano-composite. We have recently developed pyrolytic, nano-scale silica aggregates with interfacial carbon (typically less than 3the aim of enhancing elastomer-filler interaction in green tires. Our carbon-coated silicas display improved processability in typical tire compounds and enhanced dynamic mechanical performance. We also have developed facilities to produce organically functionalized silicas using a novel, room-temperature, aerosol, chemical reactor (ASG reactor). This talk will present our results on dynamic mechanical properties of elastomer compounds with our carbon-coated silica; commercial dual-phase, silica-coated carbon; ASG-organically-modified silicas; conventional carbon black; conventional precipated and fumed silica; as well as blends of the conventional materials. The mass-fractal structure as determined by SAXS and SALS, as well as gas and DBP absorption measurements and microscopy will be presented.

  15. Adsorption of Pb(II) using silica gel composite from rice husk ash modified 3-aminopropyltriethoxysilane (APTES)-activated carbon from coconut shell

    NASA Astrophysics Data System (ADS)

    Yusmaniar, Purwanto, Agung; Putri, Elfriyana Awalita; Rosyidah, Dzakiyyatur

    2017-03-01

    Silica gel modified by 3-aminopropyltriethoxysilane (APTES) was synthesized from rice husk ash combined with activated carbon from coconut shell yielded the composite adsorbent. The composite was characterized by Fourier Transform Infra Red spectroscopy (FT-IR), Electron Dispersive X-Ray (EDX), Surface Area Analyzer (SAA) and adsorption test by Atomic Absorption Spectrometry (AAS). This composite adsorbent has been used moderately for the removal of lead ions from metal solutions and compared with silica gel modified APTES and activated carbon. The adsorption experiments of Pb -ions by adsorbents were performed at different pH and contact time with the same metal solutions concentration, volume solution, and adsorbent dosage. The optimum pH for the adsorption was found to be 5.0 and the equilibrium was achieved for Pb with 20 min of contact time. Pb ions adsorption by composite silica gel modified APTES-activated carbon followed by Langmuir isotherm model with qmax value of 46.9483 mg/g that proved an adsorbent mechanism consistent to the mechanism of monolayer formation.

  16. Cobalt- and iron-based nanoparticles hosted in SBA-15 mesoporous silica and activated carbon from biomass: Effect of modification procedure

    NASA Astrophysics Data System (ADS)

    Tsoncheva, Tanya; Genova, Izabela; Paneva, Daniela; Dimitrov, Momtchil; Tsyntsarski, Boyko; Velinov, Nicolay; Ivanova, Radostina; Issa, Gloria; Kovacheva, Daniela; Budinova, Temenujka; Mitov, Ivan; Petrov, Narzislav

    2015-10-01

    Ordered mesoporous silica of SBA-15 type and activated carbon, prepared from waste biomass (peach stones), are used as host matrix of nanosized iron and cobalt particles. The effect of preparation procedure on the state of loaded nanoparticles is in the focus of investigation. The obtained materials are characterized by Boehm method, low temperature physisorption of nitrogen, XRD, UV-Vis, FTIR, Mossbauer spectroscopy and temperature programmed reduction with hydrogen. The catalytic behaviour of the samples is tested in methanol decomposition. The dispersion, oxidative state and catalytic behaviour of loaded cobalt and iron nanoparticles are successfully tuned both by the nature of porous support and the metal precursor used during the samples preparation. Facile effect of active phase deposition from aqueous solution of nitrate precursors is assumed for activated carbon support. For the silica based materials the catalytic activity could be significantly improved when cobalt acetylacetonate is used during the modification. The complex effect of pore topology and surface functionality of different supports on the active phase formation is discussed.

  17. Improved Synthesis of Carbon Clad Silica Stationary Phases

    PubMed Central

    Ahmad, Imad A. Haidar; Carr, Peter W.

    2014-01-01

    Previously we described a novel method for clading elemental carbon onto the surface of catalytically activated silica by a chemical vapor deposition (CVD) method using hexane as the carbon source and its use as a substitute for carbon clad zirconia.1,2 In that method, we showed that very close to exactly one uniform monolayer of Al (III) was deposited on the silica by a process analogous to precipitation from homogeneous solution in order to preclude pore blockage. The purpose of the Al(III) monolayer layer is to activate the surface for subsequent CVD of carbon. In this work, we present an improved procedure for preparing the carbon clad silica (denoted CCSi) phases along with a new column packing process. The new method yields CCSi phases having better efficiency, peak symmetry and higher retentivity compared to carbon clad zirconia. The enhancements were achieved by modifying the original procedure in three ways: first. the kinetics of the deposition of Al(III) were more stringently controlled, second the CVD chamber was flushed with a mixture of hydrogen and nitrogen gas during the carbon cladding process to minimize generation of polar sites by oxygen incorporation, and third the fine particles generated during the CVD process were exhaustively removed by flotation in an appropriate solvent. PMID:24228897

  18. Silica-Based Carbon Source Delivery for In-situ Bioremediation Enhancement

    NASA Astrophysics Data System (ADS)

    Zhong, L.; Lee, M. H.; Lee, B.; Yang, S.

    2015-12-01

    Colloidal silica aqueous suspensions undergo viscosity increasing and gelation over time under favorable geochemical conditions. This property of silica suspension can potentially be applied to deliver remedial amendments to the subsurface and establish slow release amendment sources for enhanced remediation. In this study, silica-based delivery of carbon sources for in-situ bioremediation enhancement is investigated. Sodium lactate, vegetable oil, ethanol, and molasses have been studied for the interaction with colloidal silica in aqueous suspensions. The rheological properties of the carbon source amendments and silica suspension have been investigated. The lactate-, ethanol-, and molasses-silica suspensions exhibited controllable viscosity increase and eventually became gels under favorable geochemical conditions. The gelation rate was a function of the concentration of silica, salinity, amendment, and temperature. The vegetable oil-silica suspensions increased viscosity immediately upon mixing, but did not perform gelation. The carbon source release rate from the lactate-, ethanol-, and molasses-silica gels was determined as a function of silica, salinity, amendment concentration. The microbial activity stimulation and in-situ bioremediation enhancement by the slow-released carbon from the amendment-silica gels will be demonstrated in future investigations planned in this study.

  19. Carbon nanomaterials in silica aerogel matrices

    SciTech Connect

    Hamilton, Christopher E; Chavez, Manuel E; Duque, Juan G; Gupta, Gautam; Doorn, Stephen K; Dattelbaum, Andrew M; Obrey, Kimberly A D

    2010-01-01

    Silica aerogels are ultra low-density, high surface area materials that are extremely good thermal insulators and have numerous technical applications. However, their mechanical properties are not ideal, as they are brittle and prone to shattering. Conversely, single-walled carbon nanotubes (SWCNTs) and graphene-based materials, such as graphene oxide, have extremely high tensile strength and possess novel electronic properties. By introducing SWCNTs or graphene-based materials into aerogel matrices, it is possible to produce composites with the desirable properties of both constituents. We have successfully dispersed SWCNTs and graphene-based materials into silica gels. Subsequent supercritical drying results in monolithic low-density composites having improved mechanical properties. These nanocomposite aerogels have great potential for use in a wide range of applications.

  20. Biofunctionalization of carbon nanostructures through enzyme immobilization in colloidal silica

    NASA Astrophysics Data System (ADS)

    Goulet, Evan M.

    Multi-walled carbon nanotubes (MWNT) and carbon nanopipettes (CNP) provide interesting high aspect ratio scaffolds on which to base functionally gradient materials. In this dissertation, we present a general method for the production of an enzymatically active composite material based on MWNTs. Polyethyleneimine (PEI) was applied to purified MWNTs, generating a positive electrostatic potential on the MWNTs. This positive potential was used to apply negatively charged colloidal silica particle in the presence of a high concentration of enzyme. The silica coating continued to grow via localized condensation of silica particles driven by the buffered saline conditions, immobilizing the enzyme within the coating. The mesoporous nanostructure was characterized via transmission electron microscopy. Optical spectroscopy experiments on the material employed as an active suspension showed that the immobilized enzymes horseradish peroxidase (HRP) and tyrosinase (TV) retained their activity upon incorporation into the material. Using HRP as a model enzyme, it was determined that the MWNT-HRP-Silica material showed similar pH and temperature dependencies in activity to those of free HRP in solution. An examination of the Michaelis-Menten kinetics showed that the material had a slightly higher value of KM than did free HRP. The MWNT-HRP-Silica material was also employed as an active filter membrane, which allowed us to explore the reusable nature of the material. We were able to show the denaturation of the filter due to the loss of Ca2+ cations at low pH and then restore the activity by soaking the filter membrane in 1 mM CaCl2. The MWNT-HRP-Silica material was used to modify a carbon microelectrode and produce a functioning electrochemical sensor for H2O2 . Utilizing cyclic voltammetry, the sensor was shown to have a linear response in limiting current versus concentration of H2O2 of 4.26 pA/microM. We also determined a lower detection limit of 0.67 microM H2O2. CNPs were

  1. Amorphous silica-like carbon dioxide

    NASA Astrophysics Data System (ADS)

    Santoro, Mario; Gorelli, Federico A.; Bini, Roberto; Ruocco, Giancarlo; Scandolo, Sandro; Crichton, Wilson A.

    2006-06-01

    Among the group IV elements, only carbon forms stable double bonds with oxygen at ambient conditions. At variance with silica and germania, the non-molecular single-bonded crystalline form of carbon dioxide, phase V, only exists at high pressure. The amorphous forms of silica (a-SiO2) and germania (a-GeO2) are well known at ambient conditions; however, the amorphous, non-molecular form of CO2 has so far been described only as a result of first-principles simulations. Here we report the synthesis of an amorphous, silica-like form of carbon dioxide, a-CO2, which we call `a-carbonia'. The compression of the molecular phase III of CO2 between 40 and 48GPa at room temperature initiated the transformation to the non-molecular amorphous phase. Infrared spectra measured at temperatures up to 680K show the progressive formation of C-O single bonds and the simultaneous disappearance of all molecular signatures. Furthermore, state-of-the-art Raman and synchrotron X-ray diffraction measurements on temperature-quenched samples confirm the amorphous character of the material. Comparison with vibrational and diffraction data for a-SiO2 and a-GeO2, as well as with the structure factor calculated for the a-CO2 sample obtained by first-principles molecular dynamics, shows that a-CO2 is structurally homologous to the other group IV dioxide glasses. We therefore conclude that the class of archetypal network-forming disordered systems, including a-SiO2, a-GeO2 and water, must be extended to include a-CO2.

  2. Fibrous composites comprising carbon nanotubes and silica

    DOEpatents

    Peng, Huisheng; Zhu, Yuntian Theodore; Peterson, Dean E.; Jia, Quanxi

    2011-10-11

    Fibrous composite comprising a plurality of carbon nanotubes; and a silica-containing moiety having one of the structures: (SiO).sub.3Si--(CH.sub.2).sub.n--NR.sub.1R.sub.2) or (SiO).sub.3Si--(CH.sub.2).sub.n--NCO; where n is from 1 to 6, and R.sub.1 and R.sub.2 are each independently H, CH.sub.3, or C.sub.2H.sub.5.

  3. Nanoporous silica and carbon thin films: Synthesis and characterizations

    NASA Astrophysics Data System (ADS)

    Song, Lingyan

    Mesoporous carbons with different symmetries and mesoporous carbon-silica composites with hexagonal symmetry have been studied previously through polymer templating; however, those studies were only limited to powder materials. Here, by using polymer as a versatile platform, multiple routes including vapor infiltration of preformed templates and cooperative self-assembly were utilized to create nanoporous silica, carbon and carbon-silica composite films with the desired morphologies. Materials of different characteristics were developed and the potential applications were discussed. First, a facile method was investigated for patterning nanoporous silica, polymer and carbon films with structures on the order of ten nanometer, hundred nanometer and micron sizes from self assembly, phase separation and lithographic patterning, respectively. The methodology developed provides a simple, etch-free route to patterning nanoporous films utilizing commercially available materials. To improve the ordering of mesoporous carbon films, mesoporous polymer/carbon films with different symmetries were explored through the evaporation induced self-assembly (EISA) approach with water soluble resol as a carbon precursor and triblock copolymers as templates. Films exhibited well-defined orthorhombic and well-ordered rectangular symmetries after template removal by using two different block copolymers, respectively. The predominant difficulties in fabricating cylindrical mesopores were proposed, and a new composition window for obtaining ordered cylindrical mesopores in carbon films was obtained. A facile approach to improve the robustness of mesoporous polymer/carbon films by the addition of silica to a carbon matrix through the reactive co-assembly of resol and tetraorthosilicate with triblock copolymer template was then explored. The pyrolysis of the resol-silica-triblock copolymer film yielded a porous film with well defined pore size. The addition of silica to the matrix impacted

  4. Impregnation of Fenofibrate on mesoporous silica using supercritical carbon dioxide.

    PubMed

    Bouledjouidja, Abir; Masmoudi, Yasmine; Van Speybroeck, Michiel; Schueller, Laurent; Badens, Elisabeth

    2016-02-29

    Low oral bioavailability can be circumvented by the formulation of the poorly water soluble drug in ordered mesoporous silica (OMS-L-7). Fenofibrate is an orally administered, poorly water-soluble active pharmaceutical ingredient (API), used clinically to lower lipid levels. Fenofibrate was loaded into silica using two methods: incipient wetness and supercritical impregnation. This study investigates the impact of loading and the impact of varying supercritical carbon dioxide (scCO2) processing conditions. The objective is to enhance Fenofibrate loading into silica while reducing degree of the drug crystallinity, so as to increase the drug's dissolution rate and its bioavailability. The comparison of both impregnation processes was made in terms of impregnation yields and duration as well as physical characterization of the drug. While incipient wetness method led to a Fenofibrate loading up to 300 mgdrug/gsilica in 48 h of impregnation, the supercritical impregnation method yielded loading up to 485 mgdrug/gsilica in 120 min of impregnation duration, at 16 MPa and 308 K, with a low degree of crystallinity (about 1%) comparable to the crystallinity observed via the solvent method. In addition to the enhancement of impregnation efficiency, the supercritical route provides a solvent-free alternative for impregnation.

  5. Surface properties of mesoporous carbon-silica gel adsorbents

    SciTech Connect

    Leboda, R.; Turov, V.V.; Charmas, B.; Skubiszewska-Zieba, J.; Gun'ko, V.M.

    2000-03-01

    Carbon/silica (carbosil) samples prepared utilizing mesoporous silica gel (Si-60) modified by methylene chloride pyrolysis were studied by nitrogen adsorption, quasi-isothermal thermogravimetry, p-nitrophenol adsorption from aqueous solution, and {sup 1}H NMR methods. The structural characteristics and other properties of carbosils depend markedly on the synthetic conditions and the amount of carbon deposited. The changes in the pore size distribution with increasing carbon concentration suggest grafting of carbon mainly in pores, leading to diminution of the mesopore radii. However, heating pure silica gel at the pyrolysis temperature of 550 C leads to an increase in the pore radii. The quasi-isothermal thermogravimetry and {sup 1}H NMR spectroscopy methods used to investigate the water layers on carbosils showed a significant capability of carbosils to adsorb water despite a relatively large content of the hydrophobic carbon deposit, which represents a nonuniform layer incompletely covering the oxide surface.

  6. Cockade-textured cataclasite and silica gel from damage zone in carbonated ultramafics: markers of cycles of seismic activity?

    NASA Astrophysics Data System (ADS)

    Scarsi, Marco; Crispini, Laura; Garofalo, Paolo; Capponi, Giovanni

    2016-04-01

    Shallow crustal processes occurring during seismic slips and generating fracture networks are of great interest due to their complex interplay with a spectrum of other geological processes . Our study focuses on faults with peculiar core textures, similar to those of "cockade breccia" (Genna et al., 1996) and "clast cortex grains" (Rempe et al., 2014), and on their relation with syntectonic hydrothermal alteration linked with Au bearing-quartz and chalcedony veins. Our work aims to study the enviromental conditions for the formation of such peculiar texture, their relation with the hydrothermal vein system and their potential as shallow seismic indicators. We present field, microstructural and petrochemical data of a peculiar damage zone of fault rocks located in carbonated peridotites and serpentinites of the Ligurian Alps (Voltri Massif, Italy). These are mainly reverse faults, which are coeval with syntectonic Au-bearing quartz veins and chalcedony veins (Giorza et al., 2010), in which lherzolites occupy the hangingwall of the faults and serpentinites the footwall. The fault rocks show evidence for carbonation, as olivine and serpentine are clearly transformed into an assemblage made of magnesite, dolomite and minor ankerite. The damage zones of the faults are serpentinite-rich and about 10 m in thickness, while the cataclasite cores are carbonate-rich and ca. 1 m thick. The top of the fault core shows the occurrence of a chalcedony shear veins with chatter marks and slikenlines on the surface. The "cockade breccia" is made of spherical aggregates of Fe-Mg carbonates and are 1 mm to 3 cm in size. These aggregates show cores of microcrystalline Fe-Mg carbonates, and concentric outer layers of relatively coarser Fe-Mg carbonates with radial or laminated texture. In some cases, these aggregates show evidence for rotation along secondary slip zones. We interpret all these features as the products of chemical interaction between the olivine and serpentine initially

  7. 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.

  8. Fluorescent single walled carbon nanotube/silica composite materials.

    PubMed

    Satishkumar, B C; Doorn, Stephen K; Baker, Gary A; Dattelbaum, Andrew M

    2008-11-25

    We present a new approach for the preparation of single walled carbon nanotube silica composite materials that retain the intrinsic fluorescence characteristics of the encapsulated nanotubes. Incorporation of isolated nanotubes into optically transparent matrices, such as sol-gel prepared silica, to take advantage of their near-infrared emission properties for applications like sensing has been a challenging task. In general, the alcohol solvents and acidic conditions required for typical sol-gel preparations disrupt the nanotube/surfactant assembly and cause the isolated nanotubes to aggregate leading to degradation of their fluorescence properties. To overcome these issues, we have used a sugar alcohol modified silica precursor molecule, diglycerylsilane, for encapsulation of nanotubes in silica under aqueous conditions and at neutral pH. The silica/nanotube composite materials have been prepared as monoliths, at least 5 mm thick, or as films (<1 mm) and were characterized using fluorescence and Raman spectroscopy. In the present work we have investigated the fluorescence characteristics of the silica encapsulated carbon nanotubes by means of redox doping studies as well as demonstrated their potential for biosensing applications. Such nanotube/silica composite systems may allow for new sensing and imaging applications that are not currently achievable.

  9. Confinement Effects for Lithium Borohydride: Comparing Silica and Carbon Scaffolds.

    PubMed

    Suwarno; Ngene, Peter; Nale, Angeloclaudio; Eggenhuisen, Tamara M; Oschatz, Martin; Embs, Jan Peter; Remhof, Arndt; de Jongh, Petra E

    2017-03-02

    LiBH4 is a promising material for hydrogen storage and as a solid-state electrolyte for Li ion batteries. Confining LiBH4 in porous scaffolds improves its hydrogen desorption kinetics, reversibility, and Li(+) conductivity, but little is known about the influence of the chemical nature of the scaffold. Here, quasielastic neutron scattering and calorimetric measurements were used to study support effects for LiBH4 confined in nanoporous silica and carbon scaffolds. Pore radii were varied from 8 Å to 20 nm, with increasing confinement effects observed with decreasing pore size. For similar pore sizes, the confinement effects were more pronounced for silica than for carbon scaffolds. The shift in the solid-solid phase transition temperature is much larger in silica than in carbon scaffolds with similar pore sizes. A LiBH4 layer near the pore walls shows profoundly different phase behavior than crystalline LiBH4. This layer thickness was 1.94 ± 0.13 nm for the silica and 1.41 ± 0.16 nm for the carbon scaffolds. Quasi-elastic neutron scattering confirmed that the fraction of LiBH4 with high hydrogen mobility is larger for the silica than for the carbon nanoscaffold. These results clearly show that in addition to the pore size the chemical nature of the scaffold also plays a significant role in determining the hydrogen mobility and interfacial layer thickness in nanoconfined metal hydrides.

  10. Confinement Effects for Lithium Borohydride: Comparing Silica and Carbon Scaffolds

    PubMed Central

    2017-01-01

    LiBH4 is a promising material for hydrogen storage and as a solid-state electrolyte for Li ion batteries. Confining LiBH4 in porous scaffolds improves its hydrogen desorption kinetics, reversibility, and Li+ conductivity, but little is known about the influence of the chemical nature of the scaffold. Here, quasielastic neutron scattering and calorimetric measurements were used to study support effects for LiBH4 confined in nanoporous silica and carbon scaffolds. Pore radii were varied from 8 Å to 20 nm, with increasing confinement effects observed with decreasing pore size. For similar pore sizes, the confinement effects were more pronounced for silica than for carbon scaffolds. The shift in the solid–solid phase transition temperature is much larger in silica than in carbon scaffolds with similar pore sizes. A LiBH4 layer near the pore walls shows profoundly different phase behavior than crystalline LiBH4. This layer thickness was 1.94 ± 0.13 nm for the silica and 1.41 ± 0.16 nm for the carbon scaffolds. Quasi-elastic neutron scattering confirmed that the fraction of LiBH4 with high hydrogen mobility is larger for the silica than for the carbon nanoscaffold. These results clearly show that in addition to the pore size the chemical nature of the scaffold also plays a significant role in determining the hydrogen mobility and interfacial layer thickness in nanoconfined metal hydrides. PMID:28286596

  11. Adsorption of light hydrocarbons and carbon dioxide on silica gel

    SciTech Connect

    Olivier, M.G.; Jadot, R.

    1997-03-01

    The main component of natural gas is methane, but small quantities of other gases are also present. These compounds are in negligible quantities in natural gas but can become a problem for the storage of methane by adsorption, being less volatile than methane and so preferentially occupying the active sites of adsorbents. Adsorption isotherms of methane, ethane, ethylene, propane, propane, propadiene, butane, 2-methylpropane, and carbon dioxide on silica gel are given at three temperatures (278 K, 293 K, and 303 K). The results at pressures up to 0.8 P/P{sub s} for the subcritical compounds and up to 3,500 kPa for the supercritical compounds are measured using an automated apparatus.

  12. Growth behavior and kinetics of self-assembled silica-carbonate biomorphs.

    PubMed

    Kellermeier, Matthias; Melero-García, Emilio; Glaab, Fabian; Eiblmeier, Josef; Kienle, Lorenz; Rachel, Reinhard; Kunz, Werner; García-Ruiz, Juan Manuel

    2012-02-20

    Upon slow crystallization from silica-containing solutions or gels at elevated pH, alkaline-earth carbonates spontaneously self-assemble into remarkable nanocrystalline ultrastructures. These so-called silica biomorphs exhibit curved morphologies beyond crystallographic symmetry and ordered textures reminiscent of the hierarchical design found in many biominerals. The formation of these fascinating materials is thought to be driven by a dynamic coupling of the components' speciations in solution, which causes concerted autocatalytic mineralization of silica-stabilized nanocrystals over hours. In the present work, we have studied the precipitation kinetics of this unique system by determining growth rates of individual aggregates using video microscopy, and correlated the results with time-dependent data on the concentration of metal ions and pH acquired online during crystallization. In this manner, insight to the evolution of chemical conditions during growth was gained. It is shown that crystallization proceeds linearly with time and is essentially reaction controlled, which fits well in the proposed morphogenetic scenario, and thus, indirectly supports it. Measurements of the silica concentration in solution, combined with analyses of crystal aggregates isolated at distinct stages of morphogenesis, further demonstrate that the fraction of silica coprecipitated with carbonate during active growth is rather small. We discuss our findings with respect to the role of silica in the formation of biomorphs, and moreover, prove that the external silica skins that occasionally sheath the aggregates--previously supposed to be involved in the growth mechanism--originate from secondary precipitation after growth is already terminated.

  13. Stable and responsive fluorescent carbon nanotube silica gels

    SciTech Connect

    Dattelbaum, Andrew M; Gupta, Gautam; Doorn, Stephen K; Duque, Juan G

    2010-05-03

    Here we report a general route to prepare silica nanocomposite gels doped with fluorescent single walled carbon nanotubes (SWNT). We show that tetramethylorthosilicate (TMOS) vapors can be used to gel an aqueous suspension of surfactant-wrapped SWNT while maintaining fluorescence from the semiconducting nanotubes. The vapor phase silica process is performed at room temperature and is simple, reproducible, relatively quick, and requires no dilution of SWNT dispersions. However, exposure of aqueous SWNT suspensions to TMOS vapors resulted in an acidification of the suspension prior to gelation that caused a decrease in the emission signal from sodium dodecylsulfate (SDS) wrapped SWNT. We also show that although the SWNT are encapsulated in silica the emission signal from the encapsulated SWNT may be attenuated by exposing the nanocomposites to small aromatic molecules known to mitigate SWNT emission. These results demonstrate a new route for the preparation of highly luminescent SWNT/silica composite materials that are potentially useful for future sensing applications.

  14. Direct synthesis of mesoporous carbon from the carbonization of hydroxypropyl- β-cyclodextrin/silica composite and its catalytic performance

    NASA Astrophysics Data System (ADS)

    Wang, Hui Chun; Li, Bao Lin; Li, Jiang Tao; Lin, Pei; Bian, Xiao Bing; Li, Jiang; Zhang, Bo; Wan, Zhuan Xin

    2011-02-01

    A simple and efficient route is reported for the synthesis of mesoporous carbon materials by directly carbonizing hydroxypropyl-β-cyclodextrin-silica composites. The resulting carbon materials, with uniform wormlike mesoporous structure and certain degree graphitic phase characteristics in porous wall, possess narrow pore size distribution, high surface area (>1000 m2 g-1) and pore volume (>1.2 cm3 g-1). It is worth mentioning that the carbon materials have high catalytic activity for the reduction of p-nitrotoluene using hydrazine hydrate as the reducing agent; moreover, the catalytic activity is not reduced notably after being reused for six times.

  15. Solid-phase extraction of polar pesticides from environmental water samples on graphitized carbon and Empore-activated carbon disks and on-line coupling to octadecyl-bonded silica analytical columns.

    PubMed

    Slobodník, J; Oztezkizan, O; Lingeman, H; Brinkman, U A

    1996-10-25

    The suitability of Empore-activated carbon disks (EACD), Envi-Carb graphitized carbon black (GCB) and CPP-50 graphitized carbon for the trace enrichment of polar pesticides from water samples was studied by means of off-line and on-line solid-phase extraction (SPE). In the off-line procedure, 0.5-2 l samples spiked with a test mixture of oxamyl, methomyl and aldicarb sulfoxide were enriched on EnviCarb SPE cartridges or 47 mm diameter EACD and eluted with dichloromethane-methanol. After evaporation, a sample was injected onto a C18-bonded silica column and analysed by liquid chromatography with ultraviolet (LC-UV) detection. EACD performed better than EnviCarb cartridges in terms of breakthrough volumes (> 2 l for all test analytes), reproducibility (R.S.D. of recoveries, 4-8%, n = 3) and sampling speed (100 ml/min); detection limits in drinking water were 0.05-0.16 microgram/l. In the on-line experiments, 4.6 mm diameter pieces cut from original EACD and stacked onto each other in a 9 mm long precolumn, and EnviCarb and CPP-50 packed in 10 x 2.0 mm I.D. precolumn, were tested, and 50-200 ml spiked water samples were preconcentrated. Because of the peak broadening caused by the strong sorption of the analytes on carbon, the carbon-packed precolumns were eluted by a separate stream of 0.1 ml/min acetonitrile which was mixed with the gradient LC eluent in front of the C18 analytical column. The final on-line procedure was also applied for the less polar propoxur, carbaryl and methiocarb. EnviCarb could not be used due to its poor pressure resistance. CPP-50 provided less peak broadening than EACD: peak widths were 0.1-0.3 min and R.S.D. of peak heights 4-14% (n = 3). In terms of analyte trapping efficiency on-line SPE-LC-UV with a CPP-50 precolumn also showed better performance than when Bondesil C18/OH or polymeric PLRP-S was used, but chromatographic resolution was similar. With the CPP-50-based system, detection limits of the test compounds were 0.05-1 microgram

  16. Solvation forces between silica bodies in supercritical carbon dioxide.

    PubMed

    Vishnyakov, Aleksey; Shen, Yangyang; Tomassone, M Silvina

    2008-12-02

    We report Monte Carlo simulations of the solvation pressure between two planar surfaces, which represent the interface of spherical silica nanoparticles in supercritical carbon dioxide. Carbon dioxide (CO2) was modeled as an atomistic dumbbell or a spherical Lennard-Jones particle. The interaction between CO2 molecules and silica surfaces was characterized by the standard Steele potential with energetic heterogeneities representing the hydrogen bonds. The parameters for the solid-fluid interaction potentials were obtained by fitting our simulations to the experimental isotherms of CO2 sorption on mesoporous siliceous materials. We studied the dependence of the solvation force on the distance between planar silica surfaces at T = 318 K, at equilibrium bulk pressures p(bulk) ranging from 69 to 200 atm. At 69 atm, we observed a long-range attraction between the two surfaces, and it vanished when the pressure was increased to 102 and then 200 atm. The results obtained with different fluid models were consistent with each other. According to our observations, energetic heterogeneities of the surface have negligible influence on the solvation pressure. Using the Derjaguin approximation, we calculated the solvation forces between spherical silica nanoparticles in supercritical CO2 from the solvation pressures between the planar surfaces.

  17. Silica nanocontainers for active corrosion protection.

    PubMed

    Maia, Frederico; Tedim, João; Lisenkov, Aleksey D; Salak, Andrei N; Zheludkevich, Mikhail L; Ferreira, Mário G S

    2012-02-21

    Novel self-healing protective coatings with nanocontainers of corrosion inhibitors open new opportunities for long-term anticorrosion protection of different metallic materials. In this paper a new type of functional nanoreservoir based on silica nanocapsules (SiNC) synthesized and loaded with corrosion inhibitor 2-mercaptobenzothiazole (MBT) in a one-stage process is reported for the first time. Unlike conventional mesoporous silica nanoparticles, SiNC possess an empty core and shell with gradual mesoporosity, arising from the particular conditions of the synthetic route adopted, which confers significant loading capacity and allows prolonged and stimuli-triggered release of the inhibiting species. The kinetics of inhibitor release was studied at different pH values and concentrations of NaCl. The results show a clear dependence of the release profiles on corrosion relevant triggers such as pH and Cl(-) concentration. When SiNC loaded with MBT are dispersed in NaCl solution, there is a significant decrease of the corrosion activity on aluminium alloy 2024. More importantly, when SiNC-MBT is added to a conventional water-based coating formulation, the modified coating hampers corrosion activity at the metal interface, better than in the case of direct addition of corrosion inhibitor. Furthermore, self-healing is observed before and after artificially inflicting defects in the modified coatings. As a result, the developed nanocontainers show high potential to be used in new generation of active protective coatings.

  18. Silica nanocontainers for active corrosion protection

    NASA Astrophysics Data System (ADS)

    Maia, Frederico; Tedim, João; Lisenkov, Aleksey D.; Salak, Andrei N.; Zheludkevich, Mikhail L.; Ferreira, Mário G. S.

    2012-02-01

    Novel self-healing protective coatings with nanocontainers of corrosion inhibitors open new opportunities for long-term anticorrosion protection of different metallic materials. In this paper a new type of functional nanoreservoir based on silica nanocapsules (SiNC) synthesized and loaded with corrosion inhibitor 2-mercaptobenzothiazole (MBT) in a one-stage process is reported for the first time. Unlike conventional mesoporous silica nanoparticles, SiNC possess an empty core and shell with gradual mesoporosity, arising from the particular conditions of the synthetic route adopted, which confers significant loading capacity and allows prolonged and stimuli-triggered release of the inhibiting species. The kinetics of inhibitor release was studied at different pH values and concentrations of NaCl. The results show a clear dependence of the release profiles on corrosion relevant triggers such as pH and Cl- concentration. When SiNC loaded with MBT are dispersed in NaCl solution, there is a significant decrease of the corrosion activity on aluminium alloy 2024. More importantly, when SiNC-MBT is added to a conventional water-based coating formulation, the modified coating hampers corrosion activity at the metal interface, better than in the case of direct addition of corrosion inhibitor. Furthermore, self-healing is observed before and after artificially inflicting defects in the modified coatings. As a result, the developed nanocontainers show high potential to be used in new generation of active protective coatings.

  19. Sonochemical preparation of silica nanorods for gene delivery using single-walled carbon nanotubes as templates.

    PubMed

    Lee, Kyoung G; Min, Jung Sun; Wi, Rinbok; Kim, Jin Chul; Ahn, Jeong Keun; Kim, Do Hyun

    2011-01-01

    Silica nanorods were fabricated with single-walled carbon nanotubes (SWCNTs) via ultrasound. The diameter of the resulting SWCNT-silica particles ranged from 60 to 70 nm. The morphology of this composite material was investigated via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The individual SWCNTs are uniformly coated with silica and formed a unique nanocomposite material. The important role of ultrasound and the mechanism of silica layer formation on SWCNTs were explained via the hydrolysis of the silica source and the adsorption of the siloxane groups on the SWCNT surfaces under ultrasound irradiation. The amino-functionalized silica nanorods were demonstrated as non-viral vectors for gene delivery.

  20. Study of silica templates in the rice husk and the carbon-silica nanocomposites produced from rice husk

    NASA Astrophysics Data System (ADS)

    Larichev, Yu. V.; Yeletsky, P. M.; Yakovlev, V. A.

    2015-12-01

    Carbon-silica nanocomposites obtained by rice husk carbonization in a fluidized-bed reactor using a deep oxidation copper-chromium catalyst were studied. Dispersion characteristics of the silica phase in these systems were determined by small-angle X-ray scattering (SAXS) using the full contrast technique. SiO2 was found in the initial rice husk as compact nanoparticles having a wide size distribution. This distribution consists of a narrow fraction with particle sizes from 1 to 7 nm and a wider fraction with particle sizes from 8 to 22 nm. Oxidative heat treatment of rice husk in a fluidized bed in the presence of the catalyst decreased the fraction of small SiO2 particles and increased the fraction of large ones. It was demonstrated that the particle size of silica in the carbon matrix can be determined selectively for deliberate design of porous carbon materials with desired properties.

  1. Lung toxicities of core–shell nanoparticles composed of carbon, cobalt, and silica

    PubMed Central

    Al Samri, Mohammed T; Silva, Rafael; Almarzooqi, Saeeda; Albawardi, Alia; Othman, Aws Rashad Diab; Al Hanjeri, Ruqayya SMS; Al Dawaar, Shaikha KM; Tariq, Saeed; Souid, Abdul-Kader; Asefa, Tewodros

    2013-01-01

    We present here comparative assessments of murine lung toxicity (biocompatibility) after in vitro and in vivo exposures to carbon (C–SiO2-etched), carbon–silica (C–SiO2), carbon–cobalt–silica (C–Co–SiO2), and carbon–cobalt oxide–silica (C–Co3O4–SiO2) nanoparticles. These nanoparticles have potential applications in clinical medicine and bioimaging, and thus their possible adverse events require thorough investigation. The primary aim of this work was to explore whether the nanoparticles are biocompatible with pneumatocyte bioenergetics (cellular respiration and adenosine triphosphate content). Other objectives included assessments of caspase activity, lung structure, and cellular organelles. Pneumatocyte bioenergetics of murine lung remained preserved after treatment with C–SiO2-etched or C–SiO2 nanoparticles. C–SiO2-etched nanoparticles, however, increased caspase activity and altered lung structure more than C–SiO2 did. Consistent with the known mitochondrial toxicity of cobalt, both C–Co–SiO2 and C–Co3O4–SiO2 impaired lung tissue bioenergetics. C–Co–SiO2, however, increased caspase activity and altered lung structure more than C–Co3O4–SiO2. The results indicate that silica shell is essential for biocompatibility. Furthermore, cobalt oxide is the preferred phase over the zerovalent Co(0) phase to impart biocompatibility to cobalt-based nanoparticles. PMID:23658487

  2. Ordered mesoporous silica (OMS) as an adsorbent and membrane for separation of carbon dioxide (CO2).

    PubMed

    Chew, Thiam-Leng; Ahmad, Abdul L; Bhatia, Subhash

    2010-01-15

    Separation of carbon dioxide (CO(2)) from gaseous mixture is an important issue for the removal of CO(2) in natural gas processing and power plants. The ordered mesoporous silicas (OMS) with uniform pore structure and high density of silanol groups, have attracted the interest of researchers for separation of carbon dioxide (CO(2)) using adsorption process. These mesoporous silicas after functionalization with amino groups have been studied for the removal of CO(2). The potential of functionalized ordered mesoporous silica membrane for separation of CO(2) is also recognized. The present paper reviews the synthesis of mesoporous silicas and important issues related to the development of mesoporous silicas. Recent studies on the CO(2) separation using ordered mesoporous silicas (OMS) as adsorbent and membrane are highlighted. The future prospectives of mesoporous silica membrane for CO(2) adsorption and separation are also presented and discussed.

  3. Wettability alteration of oil-wet carbonate by silica nanofluid.

    PubMed

    Al-Anssari, Sarmad; Barifcani, Ahmed; Wang, Shaobin; Maxim, Lebedev; Iglauer, Stefan

    2016-01-01

    Changing oil-wet surfaces toward higher water wettability is of key importance in subsurface engineering applications. This includes petroleum recovery from fractured limestone reservoirs, which are typically mixed or oil-wet, resulting in poor productivity as conventional waterflooding techniques are inefficient. A wettability change toward more water-wet would significantly improve oil displacement efficiency, and thus productivity. Another area where such a wettability shift would be highly beneficial is carbon geo-sequestration, where compressed CO2 is pumped underground for storage. It has recently been identified that more water-wet formations can store more CO2. We thus examined how silica based nanofluids can induce such a wettability shift on oil-wet and mixed-wet calcite substrates. We found that silica nanoparticles have an ability to alter the wettability of such calcite surfaces. Nanoparticle concentration and brine salinity had a significant effect on the wettability alteration efficiency, and an optimum salinity was identified, analogous to that one found for surfactant formulations. Mechanistically, most nanoparticles irreversibly adhered to the oil-wet calcite surface (as substantiated by SEM-EDS and AFM measurements). We conclude that such nanofluid formulations can be very effective as enhanced hydrocarbon recovery agents and can potentially be used for improving the efficiency of CO2 geo-storage.

  4. Antioxidative and antiinflammatory activities of quercetin-loaded silica nanoparticles.

    PubMed

    Lee, Ga Hyun; Lee, Sung June; Jeong, Sang Won; Kim, Hyun-Chul; Park, Ga Young; Lee, Se Geun; Choi, Jin Hyun

    2016-07-01

    Utilizing the biological activities of compounds by encapsulating natural components in stable nanoparticles is an important strategy for a variety of biomedical and healthcare applications. In this study, quercetin-loaded silica nanoparticles were synthesized using an oil-in-water microemulsion method, which is a suitable system for producing functional nanoparticles of controlled size and shape. The resulting quercetin-loaded silica nanoparticles were spherical, highly monodispersed, and stable in an aqueous system. Superoxide radical scavenging effects were found for the quercetin-loaded silica nanoparticles as well as free quercetin. The quercetin-loaded silica nanoparticles showed cell viability comparable to that of the controls. The amounts of proinflammatory cytokines produced by macrophages, such as interleukin 1 beta, interleukin 6, and tumor necrosis factor alpha, were reduced significantly for the quercetin-loaded silica nanoparticles. These results suggest that the antioxidative and antiinflammatory activities of quercetin are maintained after encapsulation in silica. Silica nanoparticles can be used for the effective and stable incorporation of biologically active natural components into composite biomaterials.

  5. Silica dust exposures during selected construction activities.

    PubMed

    Flanagan, Mary Ellen; Seixas, Noah; Majar, Maria; Camp, Janice; Morgan, Michael

    2003-01-01

    This study characterized exposure for dust-producing construction tasks. Eight common construction tasks were evaluated for quartz and respirable dust exposure by collecting 113 personal task period samples for cleanup; demolition with handheld tools; concrete cutting; concrete mixing; tuck-point grinding; surface grinding; sacking and patching concrete; and concrete floor sanding using both time-integrating filter samples and direct-reading respirable dust monitors. The geometric mean quartz concentration was 0.10 mg/m(3) (geometric standard deviation [GSD]=4.88) for all run time samples, with 71% exceeding the threshold limit value. Activities with the highest exposures were surface grinding, tuck-point grinding, and concrete demolition (GM[GSD] of 0.63[4.12], 0.22[1.94], and 0.10[2.60], respectively). Factors recorded each minute were task, tool, work area, respiratory protection and controls used, estimated cross draft, and whether anyone nearby was making dust. Factors important to exposure included tool used, work area configuration, controls employed, cross draft, and in some cases nearby dust. More protective respirators were employed as quartz concentration increased, although respiratory protection was found to be inadequate for 42% of exposures. Controls were employed for only 12% of samples. Exposures were reduced with three controls: box fan for surface grinding and floor sanding, and vacuum/shroud for surface grinding, with reductions of 57, 50, and 71%, respectively. Exposures were higher for sweeping compound, box fan for cleanup, ducted fan dilution, and wetted substrate. Construction masons and laborers are frequently overexposed to silica. The usual protection method, respirators, was not always adequate, and engineering control use was infrequent and often ineffective.

  6. 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.

  7. Preference of multi-walled carbon nanotube (MWCNT) to single-walled carbon nanotube (SWCNT) and activated carbon for preparing silica nanohybrid pickering emulsion for chemical enhanced oil recovery (C-EOR)

    NASA Astrophysics Data System (ADS)

    AfzaliTabar, M.; Alaei, M.; Ranjineh Khojasteh, R.; Motiee, F.; Rashidi, A. M.

    2017-01-01

    The aim of this research was to determine the best nano hybrid that can be used as a Pickering emulsion Chemical Enhanced Oil Recovery (C-EOR). Therefore, we have prepared different carbon structures nano hybrids with SiO2 nano particles with different weight percent using sol-gel method. The as-prepared nano materials were characterized with X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and Thermal Gravimetric Analysis (TGA). Pickering emulsions of these nanohybrids were prepared at pH=7 in ambient temperature and with distilled water. Stability of the mentioned Pickering emulsions was controlled for one month. Emulsion phase morphology was investigated using optical microscopic imaging. Evaluation results demonstrated that the best sample is the 70% MWCNT/SiO2 nanohybrid. Stability of the selected nanohybrid (70% MWCNT/SiO2 nanohybrid) was investigated by alteration of salinity, pH and temperature. Results showed that the mentioned Pickering emulsion has very good stability at 0.1%, 1% salinity, moderate and high temperature (25 °C and 90 °C) and neutral and alkaline pH (7, 10) that is suitable for the oil reservoirs conditions. The effect of the related nano fluid on the wettability of carbonate rock was investigated by measuring the contact angle and interfacial tension. Results show that the nanofluid could significantly change the wettability of the carbonate rock from oil wet to water wet and can decrease the interfacial tension. Therefore, the 70% MWCNT/SiO2 nanohybrid Pickering emulsion can be used for Chemical Enhanced Oil Recovery (C-EOR).

  8. Acid-base bifunctional catalysis of silica-alumina-supported organic amines for carbon-carbon bond-forming reactions.

    PubMed

    Motokura, Ken; Tomita, Mitsuru; Tada, Mizuki; Iwasawa, Yasuhiro

    2008-01-01

    Acid-base bifunctional heterogeneous catalysts were prepared by the reaction of an acidic silica-alumina (SA) surface with silane-coupling reagents possessing amino functional groups. The obtained SA-supported amines (SA-NR2) were characterized by solid-state 13C and 29Si NMR spectroscopy, FT-IR spectroscopy, and elemental analysis. The solid-state NMR spectra revealed that the amines were immobilized by acid-base interactions at the SA surface. The interactions between the surface acidic sites and the immobilized basic amines were weaker than the interactions between the SA and free amines. The catalytic performances of the SA-NR2 catalysts for various carbon-carbon bond-forming reactions, such as cyano-ethoxycarbonylation, the Michael reaction, and the nitro-aldol reaction, were investigated and compared with those of homogeneous and other heterogeneous catalysts. The SA-NR2 catalysts showed much higher catalytic activities for the carbon-carbon bond-forming reactions than heterogeneous amine catalysts using other supports, such as SiO2 and Al2O3. On the other hand, homogeneous amines hardly promoted these reactions under similar reaction conditions, and the catalytic behavior of SA-NR2 was also different from that of MgO, which was employed as a typical heterogeneous base. An acid-base dual-activation mechanism for the carbon-carbon bond-forming reactions is proposed.

  9. 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.

  10. A two-enzyme immobilization approach using carbon nanotubes/silica as support.

    PubMed

    Du, Kun; Sun, Jian; Zhou, Xiaoyu; Feng, Wei; Jiang, Xia; Ji, Peijun

    2015-01-01

    Multiple enzyme mixtures are attractive for the production of many compounds at an industrial level. We report a practical and novel approach for coimmobilization of two enzymes. The system consists of a silica microsphere core coated with two layers of individually immobilized enzymes. The model enzymes α-amylase (AA) and glucoamylase (GluA) were individually immobilized on carbon nanotubes (CNTs). A CNT-GluA layer was formed by adsorbing CNT-GluA onto silica microsphere. A sol-gel layer with entrapped CNT-AA was then formed outside the CNT-GluA/silica microsphere conjugate. The coimmobilized α-amylase and glucoamylase exhibited 95.1% of the activity of the mixture of free α-amylase and glucoamylase. The consecutive use exhibited a good stability of the coimmobilized enzymes. The developed approach demonstrates advantages, including controlling the ratio of coimmobilized enzymes in an easy way, facilitating diffusion of small molecules in and out of the matrix, and preventing the leaching of enzymes.

  11. Influence of spatial configurations on electromagnetic interference shielding of ordered mesoporous carbon/ordered mesoporous silica/silica composites

    PubMed Central

    Wang, Jiacheng; Zhou, Hu; Zhuang, Jiandong; Liu, Qian

    2013-01-01

    Ordered mesoporous carbons (OMCs), obtained by nanocasting using ordered mesoporous silicas (OMSs) as hard templates, exhibit unique arrangements of ordered regular nanopore/nanowire mesostructures. Here, we used nanocasting combined with hot-pressing to prepare 10 wt% OMC/OMS/SiO2 ternary composites possessing various carbon mesostructure configurations of different dimensionalities (1D isolated CS41 carbon nanowires, 2D hexagonal CMK-3 carbon, and 3D cubic CMK-1 carbon). The electric/dielectric properties and electromagnetic interference (EMI) shielding efficiency (SE) of the composites were influenced by spatial configurations of carbon networks. The complex permittivity and the EMI SE of the composites in the X-band frequency range decreased for the carbon mesostructures in the following order: CMK-3-filled > CMK-1-filled > CS41-filled. Our study provides technical directions for designing and preparing high-performance EMI shielding materials. Our OMC-based silica composites can be used for EMI shielding, especially in high-temperature or corrosive environments, owing to the high stability of the OMC/OMS fillers and the SiO2 matrix. Related shielding mechanisms are also discussed. PMID:24248277

  12. Activated carbon from biomass

    NASA Astrophysics Data System (ADS)

    Manocha, S.; Manocha, L. M.; Joshi, Parth; Patel, Bhavesh; Dangi, Gaurav; Verma, Narendra

    2013-06-01

    Activated carbon are unique and versatile adsorbents having extended surface area, micro porous structure, universal adsorption effect, high adsorption capacity and high degree of surface reactivity. Activated carbons are synthesized from variety of materials. Most commonly used on a commercial scale are cellulosic based precursors such as peat, coal, lignite wood and coconut shell. Variation occurs in precursors in terms of structure and carbon content. Coir having very low bulk density and porous structure is found to be one of the valuable raw materials for the production of highly porous activated carbon and other important factor is its high carbon content. Exploration of good low cost and non conventional adsorbent may contribute to the sustainability of the environment and offer promising benefits for the commercial purpose in future. Carbonization of biomass was carried out in a horizontal muffle furnace. Both carbonization and activation were performed in inert nitrogen atmosphere in one step to enhance the surface area and to develop interconnecting porosity. The types of biomass as well as the activation conditions determine the properties and the yield of activated carbon. Activated carbon produced from biomass is cost effective as it is easily available as a waste biomass. Activated carbon produced by combination of chemical and physical activation has higher surface area of 2442 m2/gm compared to that produced by physical activation (1365 m2/gm).

  13. Carbon nanofibers decorated with poly(furfuryl alcohol)-derived carbon nanoparticles and tetraethylorthosilicate-derived silica nanoparticles.

    PubMed

    Zhang, Y; Yarin, A L

    2011-12-06

    The present paper introduces a novel method to functionalize nanofiber surfaces with carbon or silica nanoparticles by dip coating. This novel approach holds promise of significant benefits because dip coating of electrospun and carbonized nanofiber mats in poly(furfuryl alcohol) (abbreviated as PFA) is used to increase surface roughness by means of PFA-derived carbon nanoparticles produced at the fiber surface. Also, dip coating in tetraethylorthosilicate (abbreviated as TEOS) is shown to be an effective method for decorating carbon nanofibers with TEOS-derived silica nanoparticles at their surface. Furthermore, dip coating is an inexpensive technique which is easier to implement than the existing methods of nanofiber decoration with silica nanoparticles and results in a higher loading capacity. Carbon nanofiber mats with PFA- or TEOS-decorated surfaces hold promise of becoming the effective electrodes in fuel cells, Li-ion batteries and storage devices.

  14. Dissolution-rate enhancement of fenofibrate by adsorption onto silica using supercritical carbon dioxide.

    PubMed

    Sanganwar, Ganesh P; Gupta, Ram B

    2008-08-06

    Dissolution rate of a poorly water-soluble drug, fenofibrate, is increased by adsorbing the drug onto silica. The adsorption is achieved by first dissolving the drug in supercritical carbon dioxide and then depressurizing the solution onto silica. Loadings of up to 27.5 wt.% drug onto silica are obtained. Since solvents are not used in the loading process, the fenofibrate/silica formulation is free of any residual solvent, and carbon dioxide is freely removed upon depressurization. The formulation is characterized using infrared spectroscopy, ultraviolet spectroscopy, X-ray diffraction, differential scanning calorimetry and scanning electron microscopy. Based on in vitro dissolution study, a significant increase in the dissolution rate (approximately 80% drug release in 20 min) of drug-silica formulation is observed as compared to micronized fenofibrate (approximately 20% drug release in 20 min), which can be attributed to increase in the surface area and decrease in the crystallinity of drug after adsorption onto silica. Two different formulations are compared: (A) amorphous fenofibrate/silica and (B) slightly crystalline fenofibrate/silica. The second formulation is found to be more stable on storage.

  15. Stabilizing Surfactant Templated Cylindrical Mesopores in Polymer and Carbon Films through Composite Formation with Silica Reinforcement

    SciTech Connect

    Song, Lingyan; Feng, Dan; Lee, Hae-Jeong; Wang, Chengqing; Wu, Quanyan; Zhao, Dongyuan; Vogt, Bryan D.

    2010-10-22

    A facile approach to maintain the periodic mesostructure of cylindrical pores in polymer-resin and carbon films after thermal template removal is explored through the reactive coassembly of resol (carbon precursor) and tetraethylorthosilicate (silica precursor) with triblock copolymer Pluronic F127. Without silica, a low porosity, disordered film is formed after pyrolysis despite the presence of an ordered mesostructure prior to template removal. However for silica concentration greater than 25 wt %, pyrolysis at 350 C yields a mesoporous silica-polymer film with well-defined pore mesostructure. These films remain well ordered upon carbonization at 800 C. In addition to the mesostructural stability, the addition of silica to the matrix impacts other morphological characteristics. For example, the average pore size and porosity of the films increase from 3.2 to 7.5 nm and 12 to 45%, respectively, as the concentration of silica in the wall matrix increases from 0 to 32 wt %. The improved thermal stability of the ordered mesostructure with the addition of silica to the matrix is attributed to the reinforcement of the mechanical properties leading to resistance to stress induced collapse of the mesostructure during template removal.

  16. Functionalization effects of single-walled carbon nanotubes as templates for the synthesis of silica nanorods and study of growing mechanism of silica.

    PubMed

    Lee, Kyoung G; Wi, Rinbok; Imran, Muhammad; Park, Tae Jung; Lee, Jaebeom; Lee, Sang Yup; Kim, Do Hyun

    2010-07-27

    Silica nanorods were successfully prepared through a sol-gel process in the presence of carboxylic-functionalized single-walled carbon nanotubes (C-SWCNTs). The effect of chemical functionalization of single-walled carbon nanotubes (SWCNTs) on the growth of the silica layer was investigated using pristine SWCNTs (P-SWCNTs) and C-SWCNTS. The C-SWCNTs served as a unique template to fabricate silica hybrid composite materials. The crystalline formation and growing mechanism of the silica layer on C-SWCNTs were explained by the hydrolysis and chemical bonding between silica precursors and carboxylated SWCNTs. The C-SWCNTs, as templates, were successfully encapsulated using silica, and used templates were removed by oxidation at high temperature. Finally, silica nanorods/nanowires were synthesized in forms of mold, and this silica fabrication mechanism could be applied for large-scale production of silica nanomaterials and highly flexible nanocomposites. The sequence of a silica encapsulation process of C-SWCNTs and removed C-SWCNTs was characterized using SEM, TEM, EDX, FT-IR and Raman spectroscopy, XRD, and electrical analysis.

  17. Designing photobioreactors based on living cells immobilized in silica gel for carbon dioxide mitigation.

    PubMed

    Rooke, Joanna C; Léonard, Alexandre; Meunier, Christophe F; Su, Bao-Lian

    2011-09-19

    Atmospheric carbon dioxide levels have been rising since the industrial revolution, with the most dramatic increase occurring since the end of World War II. Carbon dioxide is widely regarded as one of the major factors contributing to the greenhouse effect, which is of major concern in today's society because it leads to global warming. Photosynthesis is Nature's tool for combating elevated carbon dioxide levels. In essence, photosynthesis allows a cell to harvest solar energy and convert it into chemical energy through the assimilation of carbon dioxide and water. Therefore photosynthesis is regarded as an ideal way to harness the abundance of solar energy that reaches Earth and convert anthropologically generated carbon dioxide into useful carbohydrates, providing a much more sustainable energy source. This Minireview aims to tackle the idea of immobilizing photosynthetic unicellular organisms within inert silica frameworks, providing protection both to the fragile cells and to the external ecosystem, and to use this resultant living hybrid material in a photobioreactor. The viability and activity of various unicellular organisms are summarized alongside design issues of a photobioreactor based on living hybrid materials.

  18. Microbial Activity and Silica Degradation in Rice Straw

    NASA Astrophysics Data System (ADS)

    Kim, Esther Jin-kyung

    Abundantly available agricultural residues like rice straw have the potential to be feedstocks for bioethanol production. Developing optimized conditions for rice straw deconstruction is a key step toward utilizing the biomass to its full potential. One challenge associated with conversion of rice straw to bioenergy is its high silica content as high silica erodes machinery. Another obstacle is the availability of enzymes that hydrolyze polymers in rice straw under industrially relevant conditions. Microbial communities that colonize compost may be a source of enzymes for bioconversion of lignocellulose to products because composting systems operate under thermophilic and high solids conditions that have been shown to be commercially relevant. Compost microbial communities enriched on rice straw could provide insight into a more targeted source of enzymes for the breakdown of rice straw polysaccharides and silica. Because rice straw is low in nitrogen it is important to understand the impact of nitrogen concentrations on the production of enzyme activity by the microbial community. This study aims to address this issue by developing a method to measure microbial silica-degrading activity and measure the effect of nitrogen amendment to rice straw on microbial activity and extracted enzyme activity during a high-solids, thermophilic incubation. An assay was developed to measure silica-degrading enzyme or silicase activity. This process included identifying methods of enzyme extraction from rice straw, identifying a model substrate for the assay, and optimizing measurement techniques. Rice straw incubations were conducted with five different levels of nitrogen added to the biomass. Microbial activity was measured by respiration and enzyme activity. A microbial community analysis was performed to understand the shift in community structure with different treatments. With increased levels of nitrogen, respiration and cellulose and hemicellulose degrading activity

  19. Molecular Modeling and Adsorption Properties of Ordered Silica-Templated CMK Mesoporous Carbons.

    PubMed

    Jain, Surendra Kumar; Pellenq, Roland J-M; Gubbins, Keith E; Peng, Xuan

    2017-03-07

    Realistic molecular models of silica-templated CMK-1, CMK-3, and CMK-5 carbon materials have been developed by using carbon rods and carbon pipes that were obtained by adsorbing carbon in a model MCM-41 pore. The interactions between the carbon atoms with the silica matrix were described using the PN-Traz potential, and the interaction between the carbon atoms was calculated by the reactive empirical bond order (REBO) potential. Carbon rods and pipes with different thicknesses were obtained by changing the silica-carbon interaction strength, the temperature, and the chemical potential of carbon vapor adsorption. These equilibrium structures were further used to obtain the atomic models of CMK-1, CMK-3, and CMK-5 materials using the same symmetry as found in TEM pictures. These models are further refined and made more realistic by adding interconnections between the carbon rods and carbon pipes. We calculated the geometric pore size distribution of the different models of CMK-5 and found that the presence of interconnections results in some new features in the pore size distribution. Argon adsorption properties were investigated using GCMC simulations to characterize these materials at 77 K. We found that the presence of interconnection results greatly improves the agreement with available experimental data by shifting the capillary condensation to lower pressures. Adding interconnections also induces smoother adsorption/condensation isotherms, and desorption/evaporation curves show a sharp jump. These features reflex the complexity of the nanovoids in CMKs in terms of their pore morphology and topology.

  20. Activated carbon material

    DOEpatents

    Evans, A. Gary

    1978-01-01

    Activated carbon particles for use as iodine trapping material are impregnated with a mixture of selected iodine and potassium compounds to improve the iodine retention properties of the carbon. The I/K ratio is maintained at less than about 1 and the pH is maintained at above about 8.0. The iodine retention of activated carbon previously treated with or coimpregnated with triethylenediamine can also be improved by this technique. Suitable flame retardants can be added to raise the ignition temperature of the carbon to acceptable standards.

  1. Larnite powders and larnite/silica aerogel composites as effective agents for CO2 sequestration by carbonation.

    PubMed

    Santos, A; Ajbary, M; Morales-Flórez, V; Kherbeche, A; Piñero, M; Esquivias, L

    2009-09-15

    This paper presents the results of the carbonation reaction of two sample types: larnite (Ca(2)SiO(4)) powders and larnite/silica aerogel composites, the larnite acting as an active phase in a process of direct mineral carbonation. First, larnite powders were synthesized by the reaction of colloidal silica and calcium nitrate in the presence of ethylene glycol. Then, to synthesize the composites, the surface of the larnite powders was chemically modified with 3-aminopropyltriethoxysilane (APTES), and later this mixture was added to a silica sol previously prepared from tetraethylorthosilicate (TEOS). The resulting humid gel was dried in an autoclave under supercritical conditions for the ethanol. The textures and chemical compositions of the powders and composites were characterized.The carbonation reaction of both types of samples was evaluated by means of X-ray diffraction and thermogravimetric analysis. Both techniques confirm the high efficiency of the reaction at room temperature and atmospheric pressure. A complete transformation of the silicate into carbonate resulted after submitting the samples to a flow of pure CO(2) for 15 min. This indicates that for this reaction time, 1t of larnite could eliminate about 550 kg of CO(2). The grain size, porosity, and specific surface area are the factors controlling the reaction.

  2. Entrapment of Enzymes and Carbon Nanotubes in Biologically Synthesized Silica: Glucose Oxidase-catalyzed Direct Electron Transfer, Preprint

    DTIC Science & Technology

    2007-08-01

    orthosilicate (TMOS), 99%, lysozyme from chicken egg white (EC3.2.1.17) and carboxylated single-walled carbon nanotubes were obtained from Sigma...provides significant mechanical stability to the resulting silica matrix. Lysozyme , for example, catalyzes the formation of silica particles when...demonstrated by entrapping GOx in a silica/CNT composite obtained through lysozyme -catalyzed synthesis of silica. 2. Results and discussion

  3. 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

  4. 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.

  5. Hydrothermal preparation of hybrid carbon/silica monolithic capillary column for liquid chromatography.

    PubMed

    Yang, Peiling; Wang, Wentao; Xiao, Xing; Jia, Li

    2014-08-01

    A simple, easy and economical approach for the preparation of a hybrid carbon/silica monolithic capillary column was described for the first time by using silica monolith as framework in combination with hydrothermal carbonization at 180°C. During the preparation process, formamide was introduced to the reaction solutions to reduce the dissolution rate of monolithic silica skeleton and its optimal concentration was 1.5 M. Fourier transform infrared spectrometry, scanning electron microscopy, energy dispersive X-ray spectrometry, and inverse size exclusion chromatography were carried out to characterize the as-prepared column. The results demonstrated that carbon spheres ranging from 150 to 1000 nm were successfully attached to the surface of silica skeleton. The prepared hybrid carbon/silica column had a permeability of 4.4 × 10(-14) m(2). Chromatographic performance of the column was evaluated by separation of various compounds including alkylbenzenes, nucleosides and bases, and aromatic acids. The column exhibited an efficiency of 75,000 plates/m for butylbenzene at the optimal linear velocity of 0.23 mm/s. The successful separation of these compounds and the study on mechanism indicated that the column can be applied in mixed-mode chromatography.

  6. Electrical stimuli to increase cell proliferation on carbon nanotubes/mesoporous silica composites for drug delivery.

    PubMed

    Vila, M; Cicuéndez, M; Sánchez-Marcos, J; Fal-Miyar, V; Manzano, M; Prieto, C; Vallet-Regi, M

    2013-01-01

    The development of smart materials as bone implants is nowadays a challenging task to optimize their fast osteointegration. Nevertheless, no attempts have been done in joining the possibility of using electrical stimulation and drug delivery together in a material intended for bone tissue engineering. Moreover, the use of this synergy to induce bone healing is still limited until novel drug reservoirs material formulations allow an efficient applicability of the electrical stimuli. Herein, we present the biological response of osteoblasts cells, cultured over carbon nanotubes-mesoporous silica composites while exposed to external electrical stimulus. Moreover, its ability to function as drug delivery systems is also demonstrated. Bone cell metabolism was stimulated and mitochondrial activity was increased up to seven times in the presence of these composites under electrical stimulus, suggesting their potential application in bone regeneration processes.

  7. Repetitive Dosing of Fumed Silica Leads to Profibrogenic Effects through Unique Structure–Activity Relationships and Biopersistence in the Lung

    DOE PAGES

    Sun, Bingbing; Wang, Xiang; Liao, Yu-Pei; ...

    2016-08-02

    Contrary to the notion that the use of fumed silica in consumer products can “generally (be) regarded as safe” (GRAS), the high surface reactivity of pyrogenic silica differs from other forms of synthetic amorphous silica (SAS), including the capacity to induce membrane damage and acute proinflammatory changes in the murine lung. Additionally, the chain-like structure and reactive surface silanols also allow fumed silica to activate the NLRP3 inflammasome, leading to IL-1β production. This pathway is known to be associated with subchronic inflammation and profibrogenic effects in the lung by α-quartz and carbon nanotubes. Different from the latter materials, bolus dosemore » instillation of 21 mg/kg fumed silica did not induce sustained IL-1β production or subchronic pulmonary effects. In contrast, the NLRP3 inflammasome pathway was continuously activated by repetitive-dose administration of 3 × 7 mg/kg fumed silica, 1 week apart. We also found that while single-dose exposure failed to induce profibrotic effects in the lung, repetitive dosing can trigger increased collagen production, even at 3 × 3 mg/kg. The change between bolus and repetitive dosing was due to a change in lung clearance, with recurrent dosing leading to fumed silica biopersistence, sustained macrophage recruitment, and activation of the NLRP3 pathway. These subchronic proinflammatory effects disappeared when less surface-reactive titanium-doped fumed silica was used for recurrent administration. Finally, these data indicate that while fumed silica may be regarded as safe for some applications, we should reconsider the GRAS label during repetitive or chronic inhalation exposure conditions.« less

  8. Repetitive Dosing of Fumed Silica Leads to Profibrogenic Effects through Unique Structure–Activity Relationships and Biopersistence in the Lung

    SciTech Connect

    Sun, Bingbing; Wang, Xiang; Liao, Yu-Pei; Ji, Zhaoxia; Chang, Chong Hyun; Pokhrel, Suman; Ku, Justine; Liu, Xiangsheng; Wang, Meiying; Dunphy, Darren R.; Li, Ruibin; Meng, Huan; Mädler, Lutz; Brinker, C. Jeffrey; Nel, André E.; Xia, Tian

    2016-08-02

    Contrary to the notion that the use of fumed silica in consumer products can “generally (be) regarded as safe” (GRAS), the high surface reactivity of pyrogenic silica differs from other forms of synthetic amorphous silica (SAS), including the capacity to induce membrane damage and acute proinflammatory changes in the murine lung. Additionally, the chain-like structure and reactive surface silanols also allow fumed silica to activate the NLRP3 inflammasome, leading to IL-1β production. This pathway is known to be associated with subchronic inflammation and profibrogenic effects in the lung by α-quartz and carbon nanotubes. Different from the latter materials, bolus dose instillation of 21 mg/kg fumed silica did not induce sustained IL-1β production or subchronic pulmonary effects. In contrast, the NLRP3 inflammasome pathway was continuously activated by repetitive-dose administration of 3 × 7 mg/kg fumed silica, 1 week apart. We also found that while single-dose exposure failed to induce profibrotic effects in the lung, repetitive dosing can trigger increased collagen production, even at 3 × 3 mg/kg. The change between bolus and repetitive dosing was due to a change in lung clearance, with recurrent dosing leading to fumed silica biopersistence, sustained macrophage recruitment, and activation of the NLRP3 pathway. These subchronic proinflammatory effects disappeared when less surface-reactive titanium-doped fumed silica was used for recurrent administration. Finally, these data indicate that while fumed silica may be regarded as safe for some applications, we should reconsider the GRAS label during repetitive or chronic inhalation exposure conditions.

  9. Designing an ultrathin silica layer for highly durable carbon nanofibers as the carbon support in polymer electrolyte fuel cells.

    PubMed

    Hwang, Sun-Mi; Park, Jae-Hyun; Lim, Seongyop; Jung, Doo-Hwan; Guim, Hwanuk; Yoon, Young-Gi; Yim, Sung-Dae; Kim, Tae-Young

    2014-10-21

    A critical issue for maintaining long-term applications of polymer electrolyte fuel cells (PEFCs) is the development of an innovative technique for the functionalization of a carbon support that preserves their exceptional electrical conductivity and robustly enriches their durability. Here, we report for the first time how the formation of a partially coated, ultrathin, hydrophobic silica layer around the surfaces of the carbon nanofiber (CNF) helps improve the durability of the CNF without decreasing the significant electrical conductivity of the virgin CNF. The synthesis involved the adsorption of polycarbomethylsilane (PS) on the CNF's sidewalls, followed by high temperature pyrolysis of PS, resulting in a highly durable, conductive carbon support in PEFCs. The Pt nanoparticles are in direct contact with the surface of the carbon in the empty spaces between unevenly coated silica layers, which are not deposited directly onto the silica layer. The presence of a Pt nanoparticle layer that was thicker than the silica layer would be a quite advantageous circumstance that provides contact with other neighboring CNFs without having a significant adverse effect that deeply damages the electrical conductivity of the neighboring CNF composites with the silica layer. Furthermore, the ultrathin, hydrophobic silica layer around the surfaces of the CNF provides great potential to reduce the presence of water molecules in the vicinity of the carbon supports and the ˙OH radicals formed on the surface of the Pt catalyst. As a result, the CNF with a 5 wt% silica layer that we prepared has had extremely high initial performance and durability under severe carbon corrosion conditions, starting up with 974 mA cm(-2) at 0.6 V and ending up with more than 58% of the initial performance (i.e., 569 mA cm(-2) at 0.6 V) after a 1.6 V holding test for 6 h. The beginning-of-life and end-of-life performances based on the virgin CNF without the silica layer were 981 and 340 mA cm(-2) at 0

  10. Tillage influence on soil organic carbon and silica relations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Walla Walla silt loam (coarse-silty, mixed, superactive, mesic Typic Haploxeroll) is one of many Mollisols in the Pacific Northwest (PNW) that contains a high concentration of potentially mobile silica (Si). Siliceous pans induced by cropping practices have been observed in the Palouse and Colum...

  11. Hierarchical control of porous silica by pH adjustment: Alkyl polyamines as surfactants for bimodal silica synthesis and its carbon replica

    SciTech Connect

    Abellan, G.; Carrillo, A.I.; Linares, N.; Serrano, E.

    2009-08-15

    Bimodal macro-mesoporous silica networks have been prepared in a simple one-pot synthesis using an inexpensive tetramine surfactant and tetraethoxysilane as a silica precursor. These novel materials show high pore volumes and templated mesopores (average pore size 3.0 nm) embedded in 20 nm thick walls forming interparticle large meso/macropores. The judicious control of the pH during the silica formation allows for the precise control of the interparticle condensation, likely due to the change in the interaction between the tetramine surfactant and the silica precursors. Finally, a highly porous carbon replica with bimodal porosity was prepared by using the bimodal silica as a hard sacrificial template. The microstructure of the silica template was accurately transferred to the carbon material obtaining high surface areas (up to 1300 m{sup 2} g{sup -1}) and total pore volumes >=2 cm{sup 3} g{sup -1}. - Graphical abstract: Hierarchical bimodal porous silica and its carbon replica prepared by nanocasting.

  12. Effect of silica sand on activation energy for diffusion of sodium ions in montmorillonite and silica sand mixture.

    PubMed

    Liu, Jinhong; Yamada, Hiromichi; Kozaki, Tamotsu; Sato, Seichi; Ohashi, Hiroshi

    2003-03-01

    The effect of silica sand on the diffusion of sodium ions in mixtures of montmorillonite and silica sand was studied by measuring the apparent diffusion coefficients, activation energies for diffusion, and the basal spacing of the mixed samples. These diffusion experiments suggest that the apparent diffusion coefficients of sodium ions in the mixed samples were almost the same as those of pure montmorillonite samples having the same partial dry densities of montmorillonite. The activation energy dependence for diffusion of sodium ions on the partial dry density was different between the mixed samples and the pure montmorillonite samples. The activation energy increased by adding silica sand at the partial dry density of 1.0 Mg m(-3), and decreased by adding silica sand at the partial dry densities higher than 1.2 Mg m(-3). A change in the XRD profile was observed after adding silica sand at the partial dry density of 1.6 Mg m(-3). Here, a three-water-layer hydrate state of montmorillonite was found in the mixed sample whereas only a two-water-layer hydrate state was observed in the pure montmorillonite sample. These experimental results suggest that silica sand changed the montmorillonite microstructure in the mixed samples, which then altered the sodium-ion diffusion process.

  13. Activation volumes of enzymes adsorbed on silica particles.

    PubMed

    Schuabb, Vitor; Czeslik, Claus

    2014-12-30

    The immobilization of enzymes on carrier particles is useful in many biotechnological processes. In this way, enzymes can be separated from the reaction solution by filtering and can be reused in several cycles. On the other hand, there is a series of examples of free enzymes in solution that can be activated by the application of pressure. Thus, a potential loss of enzymatic activity upon immobilization on carrier particles might be compensated by pressure. In this study, we have determined the activation volumes of two enzymes, α-chymotrypsin (α-CT) and horseradish peroxidase (HRP), when they are adsorbed on silica particles and free in solution. The experiments have been carried out using fluorescence assays under pressures up to 2000 bar. In all cases, activation volumes were found to depend on the applied pressure, suggesting different compressions of the enzyme-substrate complex and the transition state. The volume profiles of free and adsorbed HRP are similar. For α-CT, larger activation volumes are found in the adsorbed state. However, up to about 500 bar, the enzymatic reaction of α-CT, which is adsorbed on silica particles, is characterized by a negative activation volume. This observation suggests that application of pressure might indeed be useful to enhance the activity of enzymes on carrier particles.

  14. Catalyst free silica templated porous carbon nanoparticles from bio-waste materials.

    PubMed

    Kumar, Anuj; Hegde, Gurumurthy; Manaf, Shoriya Aruni Bt Abdul; Ngaini, Z; Sharma, K V

    2014-10-28

    Porous Carbon Nanoparticles (PCNs) with well-developed microporosity were obtained from bio-waste oil palm leaves (OPL) using single step pyrolysis in nitrogen atmosphere at 500-600 °C in tube-furnace without any catalysis support. The key approach was using silica (SiO2) bodies of OPL as a template in the synthesis of microporous carbon nanoparticles with very small particle sizes of 35-85 nm and pore sizes between 1.9-2 nm.

  15. Relationships Between Photosynthetic Activity and Silica Accumulation with Ages of Leaf in Sasa veitchii (Poaceae, Bambusoideae)

    PubMed Central

    Motomura, Hiroyuki; Hikosaka, Kouki; Suzuki, Mitsuo

    2008-01-01

    Background and Aims Bamboos have long-lived, evergreen leaves that continue to accumulate silica throughout their life. Silica accumulation has been suggested to suppress their photosynthetic activity. However, nitrogen content per unit leaf area (Narea), an important determinant of maximum photosynthetic capacity per unit leaf area (Pmax), decreases as leaves age and senescence. In many species, Pmax decreases in parallel with the leaf nitrogen content. It is hypothesized that if silica accumulation affects photosynthesis, then Pmax would decrease faster than Narea, leading to a decrease in photosynthetic rate per unit leaf nitrogen (photosynthetic nitrogen use efficiency, PNUE) with increasing silica content in leaves. Methods The hypothesis was tested in leaves of Sasa veitchii, which have a life span of 2 years and accumulate silica up to 41 % of dry mass. Seasonal changes in Pmax, stomatal conductance, Narea and silica content were measured for leaves of different ages. Key Results Although Pmax and PNUE were negatively related with silica content across leaves of different ages, the relationship between PNUE and silica differed depending on leaf age. In second-year leaves, PNUE was almost constant although there was a large increase in silica content, suggesting that leaf nitrogen was a primary factor determining the variation in Pmax and that silica accumulation did not affect photosynthesis. PNUE was strongly and negatively correlated with silica content in third-year leaves, suggesting that silica accumulation affected photosynthesis of older leaves. Conclusions Silica accumulation in long-lived leaves of bamboo did not affect photosynthesis when the silica concentration of a leaf was less than 25 % of dry mass. Silica may be actively transported to epidermal cells rather than chlorenchyma cells, avoiding inhibition of CO2 diffusion from the intercellular space to chloroplasts. However, in older leaves with a larger silica content, silica was also

  16. CCN activation of fumed silica aerosols mixed with soluble pollutants

    NASA Astrophysics Data System (ADS)

    Dalirian, M.; Keskinen, H.; Ahlm, L.; Ylisirniö, A.; Romakkaniemi, S.; Laaksonen, A.; Virtanen, A.; Riipinen, I.

    2015-04-01

    Particle-water interactions of completely soluble or insoluble particles are fairly well understood but less is known of aerosols consisting of mixtures of soluble and insoluble components. In this study, laboratory measurements were performed to investigate cloud condensation nuclei (CCN) activity of silica particles mixed with ammonium sulfate (a salt), sucrose (a sugar) and bovine serum albumin known as BSA (a protein). The agglomerated structure of the silica particles was investigated using measurements with a differential mobility analyser (DMA) and an aerosol particle mass analyser (APM). Based on these data, the particles were assumed to be compact agglomerates when studying their CCN activation capabilities. Furthermore, the critical supersaturations of particles consisting of pure and mixed soluble and insoluble compounds were explored using existing theoretical frameworks. These results showed that the CCN activation of single-component particles was in good agreement with Köhler- and adsorption theory based models when the agglomerated structure was accounted for. For mixed particles the CCN activation was governed by the soluble components, and the soluble fraction varied considerably with particle size for our wet-generated aerosols. Our results confirm the hypothesis that knowing the soluble fraction is the key parameter needed for describing the CCN activation of mixed aerosols, and highlight the importance of controlled coating techniques for acquiring a detailed understanding of the CCN activation of atmospheric insoluble particles mixed with soluble pollutants.

  17. Adsorption of dichlorodifluoromethane, chlorodifluoromethane, and chloropentafluoroethane on activated carbon

    SciTech Connect

    Berlier, K.; Frere, M.; Bougard, J.

    1995-09-01

    The CFCs (chlorofluorocarbons) are used as working refrigerant fluids. Recent concerns of the effects of CFCs on the ozone layer requires the development of efficient recovery methods. One technique is to adsorb the fluids onto a porous medium such as silica gel or activated carbon. Isotherms and enthalpies of adsorption curves of dichlorodifluoromethane (R12), chlorodifluoromethane (R22), and chloropentafluoroethane (R115) on three different activated carbons have been obtained at 303 K and at pressures to 602 kPa.

  18. Incorporation, oxidation and pyrolysis of ferrocene into porous silica glass: a route to different silica/carbon and silica/iron oxide nanocomposites.

    PubMed

    Schnitzler, Mariane C; Mangrich, Antônio S; Macedo, Waldemar A A; Ardisson, José D; Zarbin, Aldo J G

    2006-12-25

    This work reports the incorporation of ferrocene into a porous silica glass under ambient temperature and atmosphere. After or during the ferrocene incorporation, the spontaneous formation of ferricinium ions was observed by electron paramagnetic resonance (EPR), UV-visible, X-ray absorption near-edge structure (XANES), and 57Fe Mössbauer measurements. It was shown that the oxidation of ferrocene molecules to ferricinium ions was promoted by air and that the Si-O- groups on the surface of the pores act as counteranions. Pyrolysis of the porous glass/ferricinium material under argon atmosphere and variable temperature yields different glass/carbon nanocomposites, which were subsequently treated with an HF solution in order to remove the glassy fraction. The resulting insoluble carbon materials were characterized by transmission electron microscopy (TEM), Raman, and EPR spectroscopy and consisted of amorphous carbon when the pyrolysis was carried out at 900 or 1000 degrees C and of a mixture of carbon nanotubes and carbonaceous materials at a pyrolysis temperature of 1100 degrees C. When the pyrolysis was conducted under air, the incorporated ferricinium forms alpha-Fe2O3, and the resulting material is a transparent and highly homogeneous glass/iron oxide nanocomposite.

  19. Nanosilver on nanostructured silica: Antibacterial activity and Ag surface area

    PubMed Central

    Sotiriou, Georgios A.; Teleki, Alexandra; Camenzind, Adrian; Krumeich, Frank; Meyer, Andreas; Panke, Sven; Pratsinis, Sotiris E.

    2013-01-01

    Nanosilver is one of the first nanomaterials to be closely monitored by regulatory agencies worldwide motivating research to better understand the relationship between Ag characteristics and antibacterial activity. Nanosilver immobilized on nanostructured silica facilitates such investigations as the SiO2 support hinders the growth of nanosilver during its synthesis and, most importantly, its flocculation in bacterial suspensions. Here, such composite Ag/silica nanoparticles were made by flame spray pyrolysis of appropriate solutions of Ag-acetate or Ag-nitrate and hexamethyldisiloxane or tetraethylorthosilicate in ethanol, propanol, diethylene glucolmonobutyl ether, acetonitrile or ethylhexanoic acid. The effect of solution composition on nanosilver characteristics and antibacterial activity against the Gram negative Escherichia coli was investigated by monitoring their recombinantly synthesized green fluorescent protein. Suspensions with identical Ag mass concentration exhibited drastically different antibacterial activity pointing out that the nanosilver surface area concentration rather than its mass or molar or number concentration determine best its antibacterial activity. Nanosilver made from Ag-acetate showed a unimodal size distribution, while that made from inexpensive Ag-nitrate exhibited a bimodal one. Regardless of precursor composition or nanosilver size distribution, the antibacterial activity of nanosilver was correlated best with its surface area concentration in solution. PMID:23730198

  20. Nanosilver on nanostructured silica: Antibacterial activity and Ag surface area.

    PubMed

    Sotiriou, Georgios A; Teleki, Alexandra; Camenzind, Adrian; Krumeich, Frank; Meyer, Andreas; Panke, Sven; Pratsinis, Sotiris E

    2011-06-01

    Nanosilver is one of the first nanomaterials to be closely monitored by regulatory agencies worldwide motivating research to better understand the relationship between Ag characteristics and antibacterial activity. Nanosilver immobilized on nanostructured silica facilitates such investigations as the SiO2 support hinders the growth of nanosilver during its synthesis and, most importantly, its flocculation in bacterial suspensions. Here, such composite Ag/silica nanoparticles were made by flame spray pyrolysis of appropriate solutions of Ag-acetate or Ag-nitrate and hexamethyldisiloxane or tetraethylorthosilicate in ethanol, propanol, diethylene glucolmonobutyl ether, acetonitrile or ethylhexanoic acid. The effect of solution composition on nanosilver characteristics and antibacterial activity against the Gram negative Escherichia coli was investigated by monitoring their recombinantly synthesized green fluorescent protein. Suspensions with identical Ag mass concentration exhibited drastically different antibacterial activity pointing out that the nanosilver surface area concentration rather than its mass or molar or number concentration determine best its antibacterial activity. Nanosilver made from Ag-acetate showed a unimodal size distribution, while that made from inexpensive Ag-nitrate exhibited a bimodal one. Regardless of precursor composition or nanosilver size distribution, the antibacterial activity of nanosilver was correlated best with its surface area concentration in solution.

  1. The deposition of boron nitride and carbon films on silica glass fibers

    SciTech Connect

    Smith, W.L.; Michalske, T.A.; Rye, R.R.

    1993-11-01

    A chemical vapor deposition technique is used to produce amorphous boron nitride and carbon thin films on high strength silica glass fibers. In this method, the fiber is drawn under ultra high vacuum conditions and low pressure process gases, in the presence of a hot tungsten filament, are used to grow films at low substrate temperatures. Films deposited with this technique do not degrade the intrinsic pristine strength of the silica fibers under dry conditions and, when stressed in chemically aggressive environments, act as effective barrier coatings.

  2. Hybrid carbon nanoparticles modified core-shell silica: a high efficiency carbon-based phase for hydrophilic interaction liquid chromatography.

    PubMed

    Ibrahim, Mohammed E A; Wahab, M Farooq; Lucy, Charles A

    2014-04-11

    Hydrophilic interaction liquid chromatography (HILIC) is a fast growing separation technique for hydrophilic and polar analytes. In this work, we combine the unique selectivity of carbon surfaces with the high efficiency of core-shell silica. First, 5 μm core-shell silica is electrostatically coated with 105 nm cationic latex bearing quaternary ammonium groups. Then 50 nm anionic carbon nanoparticles are anchored onto the surface of the latex coated core-shell silica particles to produce a hybrid carbon-silica phase. The hybrid phase shows different selectivity than ten previously classified HILIC column chemistries and 36 stationary phases. The hybrid HILIC phase has shape selectivity for positional isomeric pairs (phthalic/isophthalic and 1-naphthoic/2-naphthoic acids). Fast and high efficiency HILIC separations of biologically important carboxylates, phenols and pharmaceuticals are reported with efficiencies up to 85,000 plates m(-1). Reduced plate height of 1.9 (95,000 plates m(-1)) can be achieved. The hybrid phase is stable for at least 3 months of usage and storage under typical HILIC eluents.

  3. Production of activated carbon from rice husk Vietnam

    NASA Astrophysics Data System (ADS)

    Korobochkin, V. V.; Tu, N. V.; Hieu, N. M.

    2016-09-01

    This work is dedicated to the production of activated carbon from rice husk from Delta of the Red River in Viet Nam. At the first stage, carbonization of a rice husk was carried out to obtain material containing 43.1% carbon and 25 % silica with a specific surface area of 51.5 m2/g. After separating of silica (the second stage), the specific surface area of the product increased to 204 m2/g and the silica content decreased to 1.23% by weight as well. The most important stage in the formation of the porous structure of the material is the activation. The products with the high specific surface area in the range of 800-1345 m2/g were obtained by activation of carbonized product with water vapour or carbon dioxide at temperatures of 700 °C and 850 °C, with varying the flow rate of the activating agent and activation time. The best results were achieved by activation of carbon material with water vapour at the flow rate of 0.08 dm3/min per 500 g of material and the temperature of 850 °C.

  4. Melting behavior of water in cylindrical pores: carbon nanotubes and silica glasses.

    PubMed

    Sliwinska-Bartkowiak, M; Jazdzewska, M; Huang, L L; Gubbins, K E

    2008-08-28

    We report a study of the effects of confinement in multi-walled carbon nanotubes and mesoporous silica glasses (SBA-15) on the solid structure and melting of both H(2)O and D(2)O ice, using differential scanning calorimetry, dielectric relaxation spectroscopy, and neutron diffraction. Multi-walled nanotubes of 2.4, 3.9 and 10 nm are studied, and the SBA-15 studied has pores of mean diameter 3.9 nm; temperatures ranging from approximately 110 to 290 K were studied. We find that the melting point is depressed relative to the bulk water for all systems studied, with the depression being greater in the case of the silica mesopores. These results are shown to be consistent with molecular simulation studies of freezing in silica and carbon materials. The neutron diffraction data show that the cubic phase of ice is stabilized by the confinement in carbon nanotubes, as well as in silica mesopores, and persists up to temperatures of about 240 K, above which there is a transition to the hexagonal ice structure.

  5. Effect of inorganic additives on the growth of silica-carbonate biomorphs

    NASA Astrophysics Data System (ADS)

    Nakouzi, Elias; Rendina, Ryan; Palui, Goutam; Steinbock, Oliver

    2016-10-01

    Silica-barium carbonate biomorphs are complex precipitate microstructures that form by purely inorganic processes. They display life-like morphologies with smoothly curved surfaces that are not restricted to crystallographic symmetries. We investigate the morphogenetic influence of inorganic dopants that compete with the barium carbonate precipitation. Trace deposition of alkaline earth or transition metal additives causes significant changes to the crystal morphologies. In the case of Pb2+ and Ag+ ions, biomorph growth is disrupted by the formation of competing precipitates. Similarly, the addition of Ca2+, Mg2+, and Zn2+ induces the rapid crystallization of witherite or amorphous silica-carbonate aggregates at enhanced growth rates. By comparison, the addition of strontium ions results in the assembly of classic biomorphs such as cardioid sheets and helices. The procedures reported here exemplify the use of co-depositing agents to influence the compositional and crystallographic properties in a manner similar to magnesium-doped biogenic calcites.

  6. Hierarchically structured activated carbon for ultracapacitors

    PubMed Central

    Kim, Mok-Hwa; Kim, Kwang-Bum; Park, Sun-Min; Roh, Kwang Chul

    2016-01-01

    To resolve the pore-associated bottleneck problem observed in the electrode materials used for ultracapacitors, which inhibits the transport of the electrolyte ions, we designed hierarchically structured activated carbon (HAC) by synthesizing a mesoporous silica template/carbon composite and chemically activating it to simultaneously remove the silica template and increase the pore volume. The resulting HAC had a well-designed, unique porous structure, which allowed for large interfaces for efficient electric double-layer formation. Given the unique characteristics of the HAC, we believe that the developed synthesis strategy provides important insights into the design and fabrication of hierarchical carbon nanostructures. The HAC, which had a specific surface area of 1,957 m2 g−1, exhibited an extremely high specific capacitance of 157 F g−1 (95 F cc−1), as well as a high rate capability. This indicated that it had superior energy storage capability and was thus suitable for use in advanced ultracapacitors. PMID:26878820

  7. Preparation, characterization, and catalytic activity of zirconocene bridged on surface of silica gel

    NASA Astrophysics Data System (ADS)

    El Majdoub, Lotfia; Shi, Yasai; Yuan, Yuan; Zhou, Annan; Abutartour, Abubaker; Xu, Qinghong

    2015-10-01

    Zirconocene catalyst supported on silica gel was prepared for olefin polymerization by surface modification of calcined silica with SiCl4, and the reaction between the modified silica and cyclopentadienyl sodium and ZrCl4. The catalyst was characterized by using Fourier-transform infrared (FT-IR) spectrometer, thermogravimetric (TG), and differential scanning calorimetric (DSC) analytic spectrometer. It was found that the metallocene structure could be formed and connected on silica surface by chemical bond. Initial catalytic tests showed that the supported metallocene was catalytically active (methylaluminoxane as a cocatalyst), producing polymer with higher molecular weight than the metallocene just immobilized on the surface of silica gel.

  8. Hollow silica-copper-carbon anodes using copper metal-organic frameworks as skeletons

    NASA Astrophysics Data System (ADS)

    Sun, Zixu; Xin, Fengxia; Cao, Can; Zhao, Chongchong; Shen, Cai; Han, Wei-Qiang

    2015-12-01

    Hollow silica-copper-carbon (H-SCC) nanocomposites are first synthesized using copper metal-organic frameworks as skeletons to form Cu-MOF@SiO2 and then subjected to heat treatment. In the composites, the hollow structure and the void space from the collapse of the MOF skeleton can accommodate the huge volume change, buffer the mechanical stress caused by lithium ion insertion/extraction and maintain the structural integrity of the electrode and a long cycling stability. The ultrafine copper with a uniform size of around 5 nm and carbon with homogeneous distribution from the decomposition of the MOF skeleton can not only enhance the electrical conductivity of the composite and preserve the structural and interfacial stabilization, but also suppress the aggregation of silica nanoparticles and cushion the volume change. In consequence, the resulting material as an anode for lithium-ion batteries (LIBs) delivers a reversible capacity of 495 mA h g-1 after 400 cycles at a current density of 500 mA g-1. The synthetic method presented in this paper provides a facile and low-cost strategy for the large-scale production of hollow silica/copper/carbon nanocomposites as an anode in LIBs.Hollow silica-copper-carbon (H-SCC) nanocomposites are first synthesized using copper metal-organic frameworks as skeletons to form Cu-MOF@SiO2 and then subjected to heat treatment. In the composites, the hollow structure and the void space from the collapse of the MOF skeleton can accommodate the huge volume change, buffer the mechanical stress caused by lithium ion insertion/extraction and maintain the structural integrity of the electrode and a long cycling stability. The ultrafine copper with a uniform size of around 5 nm and carbon with homogeneous distribution from the decomposition of the MOF skeleton can not only enhance the electrical conductivity of the composite and preserve the structural and interfacial stabilization, but also suppress the aggregation of silica nanoparticles and

  9. Carbon enters silica forming a cristobalite-type CO2-SiO2 solid solution

    NASA Astrophysics Data System (ADS)

    Santoro, Mario; Gorelli, Federico A.; Bini, Roberto; Salamat, Ashkan; Garbarino, Gaston; Levelut, Claire; Cambon, Olivier; Haines, Julien

    2014-04-01

    Extreme conditions permit unique materials to be synthesized and can significantly update our view of the periodic table. In the case of group IV elements, carbon was always considered to be distinct with respect to its heavier homologues in forming oxides. Here we report the synthesis of a crystalline CO2-SiO2 solid solution by reacting carbon dioxide and silica in a laser-heated diamond anvil cell (P=16-22 GPa, T>4,000 K), showing that carbon enters silica. Remarkably, this material is recovered to ambient conditions. X-ray diffraction shows that the crystal adopts a densely packed α-cristobalite structure (P41212) with carbon and silicon in fourfold coordination to oxygen at pressures where silica normally adopts a sixfold coordinated rutile-type stishovite structure. An average formula of C0.6(1)Si0.4(1)O2 is consistent with X-ray diffraction and Raman spectroscopy results. These findings may modify our view on oxide chemistry, which is of great interest for materials science, as well as Earth and planetary sciences.

  10. Carbon enters silica forming a cristobalite-type CO2-SiO2 solid solution.

    PubMed

    Santoro, Mario; Gorelli, Federico A; Bini, Roberto; Salamat, Ashkan; Garbarino, Gaston; Levelut, Claire; Cambon, Olivier; Haines, Julien

    2014-04-30

    Extreme conditions permit unique materials to be synthesized and can significantly update our view of the periodic table. In the case of group IV elements, carbon was always considered to be distinct with respect to its heavier homologues in forming oxides. Here we report the synthesis of a crystalline CO2-SiO2 solid solution by reacting carbon dioxide and silica in a laser-heated diamond anvil cell (P = 16-22 GPa, T>4,000 K), showing that carbon enters silica. Remarkably, this material is recovered to ambient conditions. X-ray diffraction shows that the crystal adopts a densely packed α-cristobalite structure (P4(1)2(1)2) with carbon and silicon in fourfold coordination to oxygen at pressures where silica normally adopts a sixfold coordinated rutile-type stishovite structure. An average formula of C0.6(1)Si0.4(1)O2 is consistent with X-ray diffraction and Raman spectroscopy results. These findings may modify our view on oxide chemistry, which is of great interest for materials science, as well as Earth and planetary sciences.

  11. The effect of glycine on the growth of calcium carbonate in alkaline silica gel

    NASA Astrophysics Data System (ADS)

    Gan, Xiong; He, Kunhuan; Qian, Baosong; Deng, Qin; Lu, Laixian; Wang, Yun

    2017-01-01

    Calcium carbonate was crystallized in alkaline silica gel with the presence of glycine. The crystallization proceeded with a counterdiffusion method by the reaction of calcium chloride and sodium carbonate. Optical microscopy observation showed a significant effect of glycine on the morphology control of calcite crystals. When the initial concentration of glycine was high enough (10 mg/mL, 20 mg/mL), spherical vaterite particles formed in alkaline silica gel concomitantly together with dumbbell shaped calcite particles. The in situ study by micro-Raman spectroscopy demonstrated that both vaterite and the concomitant calcite were stable phases during their growth processes since the initial appearance. A possible mechanism has been discussed to emphasize the effect of glycine on the nucleation of vaterite and the morphological control of calcite.

  12. Effect of gamma irradiation on the texture, acidity and catalytic activity of silica-aluminium and silica-magnesia catalysts

    NASA Astrophysics Data System (ADS)

    Youssef, A. M.; Samra, S. E.; Ahmed, Awad I.

    The textural properties of non-irradiated and γ-irradiated silica-aluminium and silica-magnesia catalysts were determined from nitrogen adsorption. The acidities of these catalysts were measured by the chemisorption of pyridine. Cracking of cumene and dehydration of isopropanol were investigated on non-irradiated and γ-irradiated catalysts. Irradiation with γ-rays enhanced sintering, i.e. decreased the surface area and increased pore size. For silica-magnesia, γ-irradiation enhanced crystallization of Forsterite and Enstatite. The surface acidity decreased upon γ-irradiation and consequently the activity of the catalysts towards cracking of cumene and dehydration of isopropanol was reduced. The former reaction is structure-sensitive, while the latter is structure-insensitive.

  13. Distribution and sources of carbon, nitrogen, phosphorus and biogenic silica in the sediments of Chilika lagoon

    NASA Astrophysics Data System (ADS)

    Nazneen, Sadaf; Raju, N. Janardhana

    2017-02-01

    The present study investigated the spatial and vertical distribution of organic carbon (OC), total nitrogen (TN), total phosphorus (TP) and biogenic silica (BSi) in the sedimentary environments of Asia's largest brackish water lagoon. Surface and core sediments were collected from various locations of the Chilika lagoon and were analysed for grain-size distribution and major elements in order to understand their distribution and sources. Sand is the dominant fraction followed by silt + clay. Primary production within the lagoon, terrestrial input from river discharge and anthropogenic activities in the vicinity of the lagoon control the distribution of OC, TN, TP and BSi in the surface as well as in the core sediments. Low C/N ratios in the surface sediments (3.49-3.41) and cores (4-11.86) suggest that phytoplankton and macroalgae may be major contributors of organic matter (OM) in the lagoon. BSi is mainly associated with the mud fraction. Core C5 from Balugaon region shows the highest concentration of OC ranging from 0.58-2.34%, especially in the upper 30 cm, due to direct discharge of large amounts of untreated sewage into the lagoon. The study highlights that Chilika is a dynamic ecosystem with a large contribution of OM by autochthonous sources with some input from anthropogenic sources as well.

  14. Rational design and synthesis of efficient Carbon and/or Silica functional nanomaterials for electrocatalysis and nanomedicine

    NASA Astrophysics Data System (ADS)

    Da Silva, Rafael

    In nanomaterials there is a strong correlation between structure and properties. Thus, the design and synthesis of nanomaterials with well-defined structures and morphology is essential in order to produce materials with not only unique but also tailorable properties. The unique properties of nanomaterials in turn can be taken advantage of to create materials and nanoscale devices that can help address important societal issues, such as meeting renewable energy sources and efficient therapeutic and diagnostic methods to cure a range of diseases. In this thesis, the different synthetic approaches I have developed to produce functional nanomaterials composed of earth-abundant elements (mainly carbon and silica) at low cost in a very sustainable manner are discussed. In Chapter 1, the fundamental properties of nanomaterials and their properties and potential applications in many areas are introduced. In chapter 2, a novel synthetic method that allows polymerization of polyaniline (PANI), a conducting polymer, inside cylindrical channel pores of nanoporous silica (SBA-15) is discussed. In addition, the properties of the III resulting conducting polymer in the confined nanochannel spaces of SBA-15, and more importantly, experimental demonstration of the use of the resulting hybrid material (PANI/SBA-15 material) as electocatalyst for electrooxidation reactions with good overpotential, close to zero, are detailed. In chapter 3, the synthetic approach discussed in Chapter 2 is further extended to afford nitrogen- and oxygen-doped mesoporous carbons. This is possible by pyrolysis of the PANI/SBA-15 composite materials under inert atmosphere, followed by etching away their silica framework. The high catalytic activity of resulting carbon-based materials towards oxygen reduction reaction despite they do not possess any metal dopants is also included. The potential uses of nanomaterials in areas such as nanomedicine need deep understanding of the biocompatibility/ toxicity of

  15. Mesoporous hollow nanospheres consisting of carbon coated silica nanoparticles for robust lithium-ion battery anodes

    NASA Astrophysics Data System (ADS)

    An, Weili; Fu, Jijiang; Su, Jianjun; Wang, Lei; Peng, Xiang; Wu, Kai; Chen, Qiuyun; Bi, Yajun; Gao, Biao; Zhang, Xuming

    2017-03-01

    SiO2 as lithium ion batteries (LIBs) anode has drawn considerable attentions because of its low cost, high theoretical specific capacity and low discharge potentials but been limited by its low conductivity and electrochemical kinetics, resulting in obvious capacity decay and poor rate performance. Herein, we developed a simple approach to synthesize mesoporous hollow nanosphere (MHSiO2@C) assembled by conformal carbon coating tiny silica nanoparticles through chemical polymerization of dopamine inside the shell of MHSiO2. The continuous carbon can conformally coat on the surface of all primary SiO2 nanoparticles in the shell, which not only enhances the conductivity but also improves the structural stability of the MHSiO2. Compared to raw MHSiO2 and non-conformal carbon coated MHSiO2, the MHSiO2@C demonstrate a high reversible capacity of 440.7 mA h g-1 at a current density of 0.5 A g-1 after 500 cycles and excellent rate performance due to synergetic effect of special structure of MHSiO2 and carbon conformal coating on each silica nanoparticle. Such a special structure will be a promising platform for LIBs. Significantly, this paper offers a direct evidence to prove the advantage of conformal carbon coating and provides consequentially guide in improving the energy storage performance of low-conductivity oxide based electrode materials.

  16. Development of a new separation media using ultra-thin glassy carbon film modified silica.

    PubMed

    Wang, Hui; Olesik, Susan V

    2015-01-30

    A self-polymerizable octatetrayne, 1,8-dialdehydebenzyl-1,3,5,7-octatetrayne, is synthesized and covalently attached to an amino-functionalized surface of silica particles. The silica particles with a monolayer coverage of octatetrayne were then thermally processed to various final temperatures of 200, 400 and 700°C. The amino-functionalization, covalent attachment of octatetrayne and thermal process of silica particles were monitored by scanning electron microscopy (SEM), infrared (IR) spectroscopy and thermogravimetric analysis (TGA). The thermally processed particles were then packed into a capillary column and evaluated as a stationary phase for HPLC. After chromatographic evaluation, the optimized temperature for thermal processing was determined to be 400°C, which provides the best modified silica particles SiO2-OCT-T400 with an ultra-thin glassy carbon film coating. The linear solvation energy relationship model indicated that the primary contributors in retention are dispersion and H-bond basicity. The application of SiO2-OCT-T400 as a stationary phase was further demonstrated by successful separation of nonpolar hydrocarbons mixture and a nucleosides mixture.

  17. Transparent silica glasses containing single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    DiMaio, Jeffrey R.; Rhyne, Suzette L.; Ballato, John M.; Czerw, Richard; Xu, Jianfeng; Webster, Scott; Carroll, David L.; Fu, Kefu; Sun, Ya-Ping

    2001-11-01

    Organic - Inorganic matrix nano composites have been created using an acid catalyzed, tetraethyl orthosilicate-based sol- gel technique with SWNTs. By utilizing nanotubes functionalized with the dendron methyl 3,5- di(methyltrigycoloxy)benzylic alcohol, ultrasonication blending in the sol phase prior to gelation yields excellent dispersion characteristics of the nanotube phase. Further, glasses could easily be dried by heating to 600 degrees C yielding 80 percent of theoretical density wit little change in the nanotube content. These materials exhibited intrinsic Rayleigh scattering, suggesting near ideal dispersion. Nonlinear optical transmissivity was observed for 1064 and 532 nm light suggesting that the matrix has a strong broad band coupling to the optical field. Such composites allow for a host of applications based on the novel confinement properties of carbon nanotubes in a robust host.

  18. Preferential oxidation of carbon monoxide catalyzed by platinum nanoparticles in mesoporous silica.

    PubMed

    Fukuoka, Atsushi; Kimura, Jun-ichi; Oshio, Tadashi; Sakamoto, Yuzuru; Ichikawa, Masaru

    2007-08-22

    Preferential oxidation (PROX) of CO is an important practical process to purify H2 for use in polymer electrolyte fuel cells. Although many supported noble metal catalysts have been reported so far, their catalytic performances remain insufficient for operation at low temperature. We found that Pt nanoparticles in mesoporous silica give unprecedented activity, selectivity, and durability in the PROX reaction below 353 K. We also studied the promotional effect of mesoporous silica in the Pt-catalyzed PROX reaction by infrared spectroscopy using the isotopic tracer technique. Gas-phase O2 is not directly used for CO oxidation, but the oxygen of mesoporous silica is incorporated into CO2. These results suggest that CO oxidation is promoted by the attack of the surface OH groups to CO on Pt without forming water.

  19. Dewatering Peat With Activated Carbon

    NASA Technical Reports Server (NTRS)

    Rohatgi, N. K.

    1984-01-01

    Proposed process produces enough gas and carbon to sustain itself. In proposed process peat slurry is dewatered to approximately 40 percent moisture content by mixing slurry with activated carbon and filtering with solid/liquid separation techniques.

  20. 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.

  1. Immobilization of Zidovudine Derivatives on the SBA-15 Mesoporous Silica and Evaluation of Their Cytotoxic Activity.

    PubMed

    Lewandowski, Dawid; Lewandowska, Marta; Ruszkowski, Piotr; Pińska, Anita; Schroeder, Grzegorz

    2015-01-01

    Novel zidovudine derivatives, able to be covalently conjugated to silica surface, have been obtained and grafted to SBA-15 mesoporous silica. Cytotoxic activity of the hybrid organic-inorganic (zidovudine derivatives-silica) systems against HeLa and KB cell lines has been analyzed. Addition of folic acid had a positive influence on the cytotoxicity. Up to 69% of HeLa and 65% of KB tumor cells growth inhibition has been achieved at low silica concentration used (10 μg/mL).

  2. Synthesis of bioethanol from biomass-derived syngas over carbon nanotube/silica supported catalyst.

    PubMed

    Feng, Wei; Yao, Jianqiang; Wu, Hailiang; Ji, Peijun

    2012-01-01

    Multi-walled carbon nanotubes (MWNTs) were functionalized with pyrogallol and used in a composite with silica as a support for a Cu-Co based catalyst. The catalysts were characterized using X-ray diffraction, transmission electron microscopy, and H(2) temperature programmed reduction. The effects of pyrogallol and the weight ratio of silica to MWNTs on the performance of the catalyst were studied in a fixed bed reactor. The increase of the amount of MWNTs in the catalyst support was found to favor decreased methanol production and increased production of C2+ alcohols. Using pyrogallol in catalyst preparation was also found to increase the production of C2+ alcohols. It was concluded that pyrogallol improves the distribution and uniformity of metal particles on the support, decreases the size of metal particles and increasing the rate of catalytic reduction.

  3. Concentration gradient induced morphology evolution of silica nanostructure growth on photoresist-derived carbon micropatterns

    PubMed Central

    2012-01-01

    The evolution of silica nanostructure morphology induced by local Si vapor source concentration gradient has been investigated by a smart design of experiments. Silica nanostructure or their assemblies with different morphologies are obtained on photoresist-derived three-dimensional carbon microelectrode array. At a temperature of 1,000°C, rope-, feather-, and octopus-like nanowire assemblies can be obtained along with the Si vapor source concentration gradient flow. While at 950°C, stringlike assemblies, bamboo-like nanostructures with large joints, and hollow structures with smaller sizes can be obtained along with the Si vapor source concentration gradient flow. Both vapor–liquid-solid and vapor-quasiliquid-solid growth mechanisms have been applied to explain the diverse morphologies involving branching, connecting, and batch growth behaviors. The present approach offers a potential method for precise design and controlled synthesis of nanostructures with different features. PMID:22938090

  4. Chitosan/silica coated carbon nanotubes composite proton exchange membranes for fuel cell applications.

    PubMed

    Liu, Hai; Gong, Chunli; Wang, Jie; Liu, Xiaoyan; Liu, Huanli; Cheng, Fan; Wang, Guangjin; Zheng, Genwen; Qin, Caiqin; Wen, Sheng

    2016-01-20

    Silica-coated carbon nanotubes (SCNTs), which were obtained by a simple sol-gel method, were utilized in preparation of chitosan/SCNTs (CS/SCNTs) composite membranes. The thermal and oxidative stability, morphology, mechanical properties, water uptake and proton conductivity of CS/SCNTs composite membranes were investigated. The insulated and hydrophilic silica layer coated on CNTs eliminates the risk of electronic short-circuiting and enhances the interaction between SCNTs and chitosan to ensure the homogenous dispersion of SCNTs, although the water uptake of CS/SCNTs membranes is reduced owing to the decrease of the effective number of the amino functional groups of chitosan. The CS/SCNTs composite membranes are superior to the pure CS membrane in thermal and oxidative stability, mechanical properties and proton conductivity. The results of this study suggest that CS/SCNTs composite membranes exhibit promising potential for practical application in proton exchange membranes.

  5. Concentration gradient induced morphology evolution of silica nanostructure growth on photoresist-derived carbon micropatterns

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Shi, Tielin; Xi, Shuang; Lai, Wuxing; Liu, Shiyuan; Li, Xiaoping; Tang, Zirong

    2012-09-01

    The evolution of silica nanostructure morphology induced by local Si vapor source concentration gradient has been investigated by a smart design of experiments. Silica nanostructure or their assemblies with different morphologies are obtained on photoresist-derived three-dimensional carbon microelectrode array. At a temperature of 1,000°C, rope-, feather-, and octopus-like nanowire assemblies can be obtained along with the Si vapor source concentration gradient flow. While at 950°C, stringlike assemblies, bamboo-like nanostructures with large joints, and hollow structures with smaller sizes can be obtained along with the Si vapor source concentration gradient flow. Both vapor-liquid-solid and vapor-quasiliquid-solid growth mechanisms have been applied to explain the diverse morphologies involving branching, connecting, and batch growth behaviors. The present approach offers a potential method for precise design and controlled synthesis of nanostructures with different features.

  6. Colloidal titania-silica-iron oxide nanocomposites and the effect from silica thickness on the photocatalytic and bactericidal activities

    NASA Astrophysics Data System (ADS)

    Chanhom, Padtaraporn; Charoenlap, Nisanart; Tomapatanaget, Boosayarat; Insin, Numpon

    2017-04-01

    New types of colloidal multifunctional nanocomposites that combine superparamagnetic character and high photocatalytic activity were synthesized and investigated. The superparamagnetic nanocomposites composed of anatase titania, silica, and iron oxide nanoparticles (TSI) were synthesized using thermal decomposition method followed by microemulsion method, without calcination at high temperature. Different techniques including X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to characterize and confirm the structure of the nanocomposites. These nanocomposites showed high photocatalytic activity when used in the photodegradation of methylene blue under irradiation with a black light lamp. Moreover, the nanocomposites exhibited high antibacterial properties. From our study, the nanocomposites can be useful in various applications such as removal of pollutants with readily separation from the environment using an external magnetic field. These composites could effectively photo-degrade the dye at least three cycles without regeneration. The effects of silica shell thickness on the photocatalytic activity was investigated, and the thickness of 6 nm of the silica interlayer is enough for the inhibition of electron translocation between titania and iron oxide nanoparticles and maintaining the efficiency of photocatalytic activity of titania nanoparticles.

  7. Silica hydride intermediate for octadecylsilica and phenyl bonded phase preparation via heterogeneous hydrosilation in supercritical carbon dioxide.

    PubMed

    Scully, N M; Ashu-Arrah, B A; Nagle, A P; Omamogho, J O; O'Sullivan, G P; Friebolin, V; Dietrich, B; Albert, K; Glennon, J D

    2011-04-15

    Investigations into the preparation of silica hydride intermediate in supercritical carbon dioxide (sc-CO(2)) that avoids the use of organic solvents such as toluene or dioxane are described. The effects of reaction temperature, pressure and time on the surface coverage of the supercritical fluid generated silica hydride intermediate were studied. Under optimised supercritical conditions of 120°C, 483 bar and 3 h reaction time, silica hydride (Si-H) conversion efficiencies of ca. 40% were achieved for the hydride intermediate prepared from a monofunctional silane reagent (dimethylmethoxysilane). Si-H conversion efficiencies (as determined from (29)Si CP-MAS NMR spectral analysis) for the hydride intermediate prepared from triethoxysilane (TES) in sc-CO(2) were found to be comparable to those obtained using a TES silanisation approach in an organic solvent. (13)C and (29)Si CP-MAS-NMR spectroscopy was employed to provide a complete structural assignment of the silica hydride intermediates. Furthermore, supercritical CO(2) was subsequently employed as a reaction medium for the heterogenous hydrosilation of silica hydride with octadecene and with styrene, in the presence of a free radical initiator. These supercritical fluid generated reversed-phase materials were prepared in a substantially reduced reaction time (3 h) compared to organic solvent based methods (100 h reaction time). Silica functionalisation in sc-CO(2) presents an efficient and clean alternative to organic solvent based methods for the preparation of important silica hydride intermediate and silica bonded stationary phases via a hydrosilation approach.

  8. Preparation of porous bio-char and activated carbon from rice husk by leaching ash and chemical activation.

    PubMed

    Ahiduzzaman, Md; Sadrul Islam, A K M

    2016-01-01

    Preparation porous bio-char and activated carbon from rice husk char study has been conducted in this study. Rice husk char contains high amount silica that retards the porousness of bio-char. Porousness of rice husk char could be enhanced by removing the silica from char and applying heat at high temperature. Furthermore, the char is activated by using chemical activation under high temperature. In this study no inert media is used. The study is conducted at low oxygen environment by applying biomass for consuming oxygen inside reactor and double crucible method (one crucible inside another) is applied to prevent intrusion of oxygen into the char. The study results shows that porous carbon is prepared successfully without using any inert media. The adsorption capacity of material increased due to removal of silica and due to the activation with zinc chloride compared to using raw rice husk char. The surface area of porous carbon and activated carbon are found to be 28, 331 and 645 m(2) g(-1) for raw rice husk char, silica removed rice husk char and zinc chloride activated rice husk char, respectively. It is concluded from this study that porous bio-char and activated carbon could be prepared in normal environmental conditions instead of inert media. This study shows a method and possibility of activated carbon from agro-waste, and it could be scaled up for commercial production.

  9. Supercritical Carbon Dioxide Assisted Processing of Silica/PMMA Nanocomposite Foams

    NASA Astrophysics Data System (ADS)

    Rende, Deniz; Schadler, Linda S.; Ozisik, Rahmi

    2012-02-01

    Polymer nanocomposite foams receive considerable attention in both scientific and industrial communities. These structures are defined as closed or open cells (pores) surrounded by bulk material and are widely observed in nature in the form of bone structure, sponge, corals and natural cork. Inspired by these materials, polymer nanocomposite foams are widely used in advanced applications, such as bone scaffolds, food packaging and transportation materials due to their lightweight and enhanced mechanical, thermal, and electrical properties compared to bulk polymer foams. The presence of the nanosized fillers facilitates heterogeneous bubble nucleation as a result, the number of bubbles increases while the average bubble size decreases. Therefore, the foam morphology can be controlled by the size, concentration, and surface chemistry of the nanofiller. In the current study, we used supercritical carbon dioxide as a foaming agent for silica/poly(methyl methacrylate), PMMA, foams. The silica nanoparticles were chemically modified by fluoroalkane chains to make them CO2-philic. The surface coverage was controlled via tethering density, and the effect of silica surface coverage and concentration on foam morphology was investigated through scanning electron microscopy and image processing. Results indicated that nanofiller concentration and filler surface chemistry (CO2-philicity) had tremendous effect on foam morphology but surface coverage did not have any effect.

  10. Fast and selective sugar conversion to alkyl lactate and lactic acid with bifunctional carbon-silica catalysts.

    PubMed

    de Clippel, Filip; Dusselier, Michiel; Van Rompaey, Ruben; Vanelderen, Pieter; Dijkmans, Jan; Makshina, Ekaterina; Giebeler, Lars; Oswald, Steffen; Baron, Gino V; Denayer, Joeri F M; Pescarmona, Paolo P; Jacobs, Pierre A; Sels, Bert F

    2012-06-20

    A novel catalyst design for the conversion of mono- and disaccharides to lactic acid and its alkyl esters was developed. The design uses a mesoporous silica, here represented by MCM-41, which is filled with a polyaromatic to graphite-like carbon network. The particular structure of the carbon-silica composite allows the accommodation of a broad variety of catalytically active functions, useful to attain cascade reactions, in a readily tunable pore texture. The significance of a joint action of Lewis and weak Brønsted acid sites was studied here to realize fast and selective sugar conversion. Lewis acidity is provided by grafting the silica component with Sn(IV), while weak Brønsted acidity originates from oxygen-containing functional groups in the carbon part. The weak Brønsted acid content was varied by changing the amount of carbon loading, the pyrolysis temperature, and the post-treatment procedure. As both catalytic functions can be tuned independently, their individual role and optimal balance can be searched for. It was thus demonstrated for the first time that the presence of weak Brønsted acid sites is crucial in accelerating the rate-determining (dehydration) reaction, that is, the first step in the reaction network from triose to lactate. Composite catalysts with well-balanced Lewis/Brønsted acidity are able to convert the trioses, glyceraldehyde and dihydroxyacetone, quantitatively into ethyl lactate in ethanol with an order of magnitude higher reaction rate when compared to the Sn grafted MCM-41 reference catalyst. Interestingly, the ability to tailor the pore architecture further allows the synthesis of a variety of amphiphilic alkyl lactates from trioses and long chain alcohols in moderate to high yields. Finally, direct lactate formation from hexoses, glucose and fructose, and disaccharides composed thereof, sucrose, was also attempted. For instance, conversion of sucrose with the bifunctional composite catalyst yields 45% methyl lactate in

  11. Silica-coated multi-walled carbon nanotubes impregnated with polyethyleneimine for carbon dioxide capture under the flue gas condition

    SciTech Connect

    Lee, Min-Sang; Park, Soo-Jin

    2015-03-15

    In this study, silica-coated multi-walled carbon nanotubes impregnated with polyethyleneimine (PEI) were prepared via a two-step process: (i) hydrolysis of tetraethylorthosilicate onto multi-walled carbon nanotubes, and (ii) impregnation of PEI. The adsorption properties of CO{sub 2} were investigated using CO{sub 2} adsorption–desorption isotherms at 298 K and thermogravimetric analysis under the flue gas condition (15% CO{sub 2}/85% N{sub 2}). The results obtained in this study indicate that CO{sub 2} adsorption increases after impregnation of PEI. The increase in CO{sub 2} capture was attributed to the affinity between CO{sub 2} and the amine groups. CO{sub 2} adsorption–desorption experiments, which were repeated five times, also showed that the prepared adsorbents have excellent regeneration properties. - Graphical abstract: Fabrication and CO{sub 2} adsorption process of the S-MWCNTs impregnated with PEI. - Highlights: • Silica coated-MWCNT impregnated with PEI was synthesized. • Amine groups of PEI gave CO{sub 2} affinity sites on MWCNT surfaces. • The S-MWCNT/PEI(50) exhibited the highest CO{sub 2} adsorption capacity.

  12. Isotherm, kinetic, and thermodynamic studies on Hg(II) adsorption from aqueous solution by silica- multiwall carbon nanotubes.

    PubMed

    Saleh, Tawfik A

    2015-11-01

    Silica combined with 2% multiwall carbon nanotubes (SiO2-CNT) was synthesized and characterized. Its sorption efficacy was investigated for the Hg(II) removal from an aqueous solution. The effect of pH on the percentage removal by the prepared material was examined in the range from 3 to 7. The adsorption kinetics were well fitted by using a pseudo-second-order model at various initial Hg(II) concentrations with R (2) of >0.99. The experimental data were plotted using the interparticle diffusion model, which indicated that the interparticle diffusion is not the only rate-limiting step. The data is well described by the Freundlich isotherm equation. The activation energy (Ea) for adsorption was 12.7 kJ mol(-1), indicating the process is to be physisorption. Consistent with an endothermic process, an increase in the temperature resulted in increasing mercury removal with a ∆H(o) of 13.3 kJ/mol and a ∆S(o) 67.5 J/mol K. The experimental results demonstrate that the combining of silica and nanotubes is a promising alternative material, which can be used to remove the mercury from wastewaters.

  13. Separating proteins with activated carbon.

    PubMed

    Stone, Matthew T; Kozlov, Mikhail

    2014-07-15

    Activated carbon is applied to separate proteins based on differences in their size and effective charge. Three guidelines are suggested for the efficient separation of proteins with activated carbon. (1) Activated carbon can be used to efficiently remove smaller proteinaceous impurities from larger proteins. (2) Smaller proteinaceous impurities are most efficiently removed at a solution pH close to the impurity's isoelectric point, where they have a minimal effective charge. (3) The most efficient recovery of a small protein from activated carbon occurs at a solution pH further away from the protein's isoelectric point, where it is strongly charged. Studies measuring the binding capacities of individual polymers and proteins were used to develop these three guidelines, and they were then applied to the separation of several different protein mixtures. The ability of activated carbon to separate proteins was demonstrated to be broadly applicable with three different types of activated carbon by both static treatment and by flowing through a packed column of activated carbon.

  14. Zero-valent iron particles embedded on the mesoporous silica-carbon for chromium (VI) removal from aqueous solution

    NASA Astrophysics Data System (ADS)

    Xiong, Kun; Gao, Yuan; Zhou, Lin; Zhang, Xianming

    2016-09-01

    Nanoscale zero-valent iron (nZVI) particles were embedded on the walls of mesoporous silica-carbon (MSC) under the conditions of high-temperature carbonization and reduction and used to remove chromium (VI) from aqueous solution. The structure and textural properties of nZVI-MSC were characterized by the powder X-ray diffraction, transmission electron microscopy and N2 adsorption and desorption. The results show that nZVI-MSC has highly ordered mesoporous structure and large surface area, indistinguishable with that of MSC. Compared with the support MSC and iron particles supported on the activated carbon (nZVI/AC), nZVI-MSC exhibited much higher Cr(VI) removal efficiency with about 98 %. The removal process obeys a pseudo first-order model. Such excellent performance of nZVI-MSC could be ascribed to the large surface and iron particles embedded on the walls of the MSC, forming an intimate contact with the MSC. It is proposed that this feature might create certain micro-electrode on the interface of iron particles and MSC, which prevented the formation of metal oxide on the surface and provided fresh Fe surface for Cr(VI) removal.

  15. Click on silica: systematic immobilization of Co(II) Schiff bases to the mesoporous silica via click reaction and their catalytic activity for aerobic oxidation of alcohols.

    PubMed

    Rana, Bharat S; Jain, Suman L; Singh, Bhawan; Bhaumik, Asim; Sain, Bir; Sinha, Anil K

    2010-09-07

    The systematic immobilization of cobalt(II) Schiff base complexes on SBA-15 mesoporous silica via copper catalyzed [3 + 2] azide-alkyne cycloaddition (CuAAC) "click reaction" involving either step-wise synthesis of silica-bound Schiff base ligand followed by its subsequent complexation with cobalt ions, or by the direct immobilization of preformed Co(II) Schiff base complex to the silica support is described. The catalytic activity of the prepared complexes was studied for the oxidation of alcohols to carbonyl compounds using molecular oxygen as oxidant. The immobilized complexes were recycled for several runs without loss in catalytic activity and no leaching was observed during this course.

  16. Enhanced antibacterial activity of silver/polyrhodanine-composite-decorated silica nanoparticles.

    PubMed

    Song, Jooyoung; Kim, Hyunyoung; Jang, Yoonsun; Jang, Jyongsik

    2013-11-27

    This work describes the synthesis of silver/polyrhodanine-composite-decorated silica nanoparticles and their antibacterial activity. Polymerization of polyrhodanine proceeded preferentially on the surface of the silica nanoparticles where Ag(+) ions were located. In addition, the embedded Ag(+) ions were reduced to form metallic Ag nanoparticles; consequently, silver/polyrhodanine-composite nanoparticles (approximately 7 nm in diameter) were formed on the surface of the silica nanoparticles. The resulting nanostructure was investigated using electron microscopy, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy. The silver/polyrhodanine-nanocomposite-decorated silica nanoparticles exhibited excellent antimicrobial activity toward gram-negative Escherichia coli and gram-positive Staphylococcus aureus because of the antibacterial effects of the silver nanoparticles and the polyrhodanine. The silver/polyrhodanine-composite nanoparticles may therefore have potential for use as a long-term antibacterial agent.

  17. Mesoporous CLEAs-silica composite microparticles with high activity and enhanced stability

    PubMed Central

    Cui, Jiandong; Jia, Shiru; Liang, Longhao; Zhao, Yamin; Feng, Yuxiao

    2015-01-01

    A novel enzyme immobilization approach was used to generate mesoporous enzymes-silica composite microparticles by co-entrapping gelatinized starch and cross-linked phenylalanine ammonia lyase (PAL) aggregates (CLEAs) containing gelatinized starch into biomemitic silica and subsequently removing the starch by α-amylase treatment. During the preparation process, the gelatinzed starch served as a pore-forming agent to create pores in CLEAs and biomimetic silica. The resulting mesoporous CLEAs-silica composite microparticles exhibited higher activity and stability than native PAL, conventional CLEAs, and PAL encapsulated in biomimetic silica. Furthermore, the mesoporous CLEAs-silica composite microparticles displayed good reusability due to its suitable size and mechanical properties, and had excellent stability for storage. The superior catalytic performances were attributed to the combinational unique structure from the intra-cross-linking among enzyme aggregates and hard mesoporous silica shell, which not only decreased the enzyme-support negative interaction and mass-transfer limitations, but also improved the mechanical properties and monodispersity. This approach will be highly beneficial for preparing various bioactive mesoporous composites with excellent catalytic performance. PMID:26374188

  18. A Comparative Study on Graphene Oxide and Carbon Nanotube Reinforcement of PMMA-Siloxane-Silica Anticorrosive Coatings.

    PubMed

    Harb, Samarah V; Pulcinelli, Sandra H; Santilli, Celso V; Knowles, Kevin M; Hammer, Peter

    2016-06-29

    Carbon nanotubes (CNTs) and graphene oxide (GO) have been used to reinforce PMMA-siloxane-silica nanocomposites considered to be promising candidates for environmentally compliant anticorrosive coatings. The organic-inorganic hybrids were prepared by benzoyl peroxide (BPO)-induced polymerization of methyl methacrylate (MMA) covalently bonded through 3-(trimethoxysilyl)propyl methacrylate (MPTS) to silica domains formed by hydrolytic condensation of tetraethoxysilane (TEOS). Single-walled carbon nanotubes and graphene oxide nanosheets were dispersed by surfactant addition and in a water/ethanol solution, respectively. These were added to PMMA-siloxane-silica hybrids at a carbon (CNT or GO) to silicon (TEOS and MPTS) molar ratio of 0.05% in two different matrices, both prepared at BPO/MMA molar ratios of 0.01 and 0.05. Atomic force microscopy and scanning electron microscopy showed very smooth, homogeneous, and defect-free surfaces of approximately 3-7 μm thick coatings deposited onto A1020 carbon steel by dip coating. Mechanical testing and thermogravimetric analysis confirmed that both additives CNT and GO improved the scratch resistance, adhesion, wear resistance, and thermal stability of PMMA-siloxane-silica coatings. Results of electrochemical impedance spectroscopy in 3.5% NaCl solution, discussed in terms of equivalent circuits, showed that the reinforced hybrid coatings act as a very efficient anticorrosive barrier with an impedance modulus up to 1 GΩ cm(2), approximately 5 orders of magnitude higher than that of bare carbon steel. In the case of GO addition, the high corrosion resistance was maintained for more than 6 months in saline medium. These results suggest that both carbon nanostructures can be used as structural reinforcement agents, improving the thermal and mechanical resistance of high performance anticorrosive PMMA-siloxane-silica coatings and thus extending their application range to abrasive environments.

  19. SBA-15 Mesoporous Silica Modified with Gallic Acid and Evaluation of Its Cytotoxic Activity

    PubMed Central

    Lewandowski, Dawid

    2015-01-01

    Gallic acid has been covalently conjugated to SBA-15 mesoporous silica surface through different linkers. Cytotoxic activity of the hybrid organic-inorganic systems against HeLa and KB cell lines has been analyzed. Up to 67% of HeLa or KB tumor cells growth inhibition has been achieved at low silica concentration used (10 μg mL-1). PMID:26151908

  20. Mineralogical characteristics of the silica polymorphs in relation to their biological activities

    SciTech Connect

    Guthrie, G.D. Jr.; Heaney, P.J.

    1993-10-01

    Numerous aspects of minerals (including the silica polymorphs) can effect their biological activities. These include periodic structures, compositional variations, dissolution characteristics, surface properties, and particle size/shape. In order to understand mineral-induced pathogenesis in a mechanistic way, the links between these properties and biochemical processes must be elucidated. This paper presents some of the basic properties of the silica polymorphs that may relate to pathogenicity and mineralogical strategies for designing biological assays to evaluate these properties.

  1. Performance and durability of carbon black-supported Pd catalyst covered with silica layers in membrane-electrode assemblies of proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Fujii, Keitaro; Ito, Mizuki; Sato, Yasushi; Takenaka, Sakae; Kishida, Masahiro

    2015-04-01

    Pd metal particles supported on a high surface area carbon black (Pd/CB) were covered with silica layers to improve the durability under severe cathode condition of proton exchange membrane fuel cells (PEMFCs). The performance and the durability of the silica-coated Pd/CB (SiO2/Pd/CB) were investigated by rotating disk electrode (RDE) in aqueous HClO4 and single cell test of the membrane-electrode assemblies (MEAs). SiO2/Pd/CB showed excellent durability exceeding Pt/CB during potential cycle in single cell test as well as in RDE measurement while Pd/CB significantly degraded. Furthermore, the MEA using SiO2/Pd/CB as the cathode catalyst showed higher performance than that using Pd/CB even in the initial state. The catalytic activity of SiO2/Pd/CB was higher than that of Pd/CB, and the drop of the cell performances due to the inhibition of electron conduction, proton conduction, and oxygen diffusion by the silica layer was not significant. It has been shown that the silica-coating is a very practical technique that can stabilize metal species originally unstable in the cathode condition of PEMFCs without a decrease in the cell performance.

  2. Electrochemistry and current control in surface films based on silica-azure redox nanoparticles, carbon nanotubes, enzymes, and polyelectrolytes.

    PubMed

    Karra, Sushma; Zhang, Maogen; Gorski, Waldemar

    2013-01-15

    The redox active nanoparticles were developed by covalently attaching redox dye Azure C (AZU) to commercial silica nanoparticles (SN) via the silylated amine and glutaric dialdehyde links. The SN-AZU nanoparticles were studied as redox mediators for the oxidation of reduced β-nicotinamide adenine dinucleotide (NADH) in two polymeric films. The first film (F1) was composed of SN-AZU, carbon nanotubes, and cationic polyelectrolyte chitosan. The second film (F2) contained also added enzyme glucose dehydrogenase and its cofactor β-nicotinamide adenine dinucleotide (NAD(+)). The films F1 and F2 were cast on the glassy carbon electrodes, covered with an anionic polyelectrolyte Nafion, and their electrochemical properties were probed with NADH and glucose, respectively, using voltammetry, amperometry, and potentiometry. The Nafion overcoat reduced the sensitivity of F1/Nafion film electrodes to NADH by >98%. In contrast, depending on the concentration of Nafion, the sensitivity of the F2/Nafion film electrodes (reagentless biosensors) to glucose increased by up to 340%. The amplification of glucose signal was ascribed to the Donnan exclusion and ensuing Nafion-gated ionic fluxes, which enhanced enzyme activity in films F2. The proposed model predicts that such signal amplification should be also feasible in the case of other enzyme-based biosensors.

  3. The impedance characterization of Carbon Nanotubes - Fumed Silica Poly (vinyl alcohol) Composites

    NASA Astrophysics Data System (ADS)

    Othman, R. N.; Wilkinson, A. N.

    2016-06-01

    Carbon Nanotube (CNT) was grown on the surface of fumed silica via chemical vapor deposition (CVD) method. In this work, silica acted as a site that holds CNT together, which prevents further agglomeration during composite processing. Iron catalyst at different loading (7.5 wt. % up to 25 wt. %) was introduced via impregnation method to synthesize CNT at 1000°C, under methane flow. Floating catalyst method was used where ferrocene (2.5 wt. % and 5 wt. %) was used as starting reactants together with toluene at 760°C. The reaction time was set at 1 hour for both methods. It was later confirmed via SEM images that the floating catalyst method is more suitable to produce a large amount of CNTs. The sample synthesized via floating catalyst method at both 2.5 wt.% and 5 wt. % ferrocene was later used to prepare composites. Composite films of the particles in poly (vinyl alcohol) (PVOH) were cast and their TEM images show that the dispersion is indeed uniform. From impedance measurement, it was found that the particles synthesized via floating catalyst method were found to form an electrically-conductive percolated network with percolation threshold of 1 wt. %, obtained via percolation equation.

  4. Investigation of the dielectric properties and defectoscopy of nanocomposites based on silica and polymers reinforced with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Osokin, C. S.; Eseev, M. K.; Goshev, A. A.; Horodek, P.; Kapustin, S. N.; Kobets, A. G.; Volkov, A. S.

    2016-11-01

    This work presents the results of experimental studies of the properties of nanocomposites based on silica and polypropylene reinforced with carbon nanotubes by dielectric relaxation and positron annihilation spectroscopy. On the basis of these results the technique of diagnosis and control of the investigated materials are proposed. This work was supported by the project of the Ministry of Education of Russian Federation №3635 "Investigation of the nanocomposites properties at controlled modification of the structure by reinforcement with carbon nanotubes".

  5. Interference sources in ATP bioluminescence assay of silica nanoparticle toxicity to activated sludge.

    PubMed

    Sibag, Mark; Kim, Seung Hwan; Kim, Choah; Kim, Hee Jun; Cho, Jinwoo

    2015-06-01

    ATP measurement provides an overview of the general state of microbial activity, and thus it has proven useful for the evaluation of nanoparticle toxicity in activated sludge. ATP bioluminescence assay, however, is susceptible to interference by the components of activated sludge other than biomass. This paper presents the interference identified specific to the use of this assay after activated sludge respiration inhibition test of silica nanoparticles (OECD 209). We observed a high degree of interference (90%) in the presence of 100 mg/L silica nanoparticles and a low level of ATP being measured (0.01 μM); and 30% interference by the synthetic medium regardless of silica nanoparticle concentration and ATP level in the samples. ATP measurement in activated sludge with different MLSS concentrations revealed interference of high biomass content. In conclusion, silica nanoparticles, synthetic medium and activated sludge samples themselves interfere with ATP bioluminescence; this will need to be considered in the evaluation of silica nanoparticle toxicity to activated sludge when this type of assay is used.

  6. Biological activation of carbon filters.

    PubMed

    Seredyńska-Sobecka, Bozena; Tomaszewska, Maria; Janus, Magdalena; Morawski, Antoni W

    2006-01-01

    To prepare biological activated carbon (BAC), raw surface water was circulated through granular activated carbon (GAC) beds. Biological activity of carbon filters was initiated after about 6 months of filter operation and was confirmed by two methods: measurement of the amount of biomass attached to the carbon and by the fluorescein diacetate (FDA) test. The effect of carbon pre-washing on WG-12 carbon properties was also studied. For this purpose, the nitrogen adsorption isotherms at 77K and Fourier transform-infrared (FT-IR) spectra analyses were performed. Moreover, iodine number, decolorizing power and adsorption properties of carbon in relation to phenol were studied. Analysis of the results revealed that after WG-12 carbon pre-washing its BET surface increased a little, the pH value of the carbon water extract decreased from 11.0 to 9.4, decolorizing power remained at the same level, and the iodine number and phenol adsorption rate increased. In preliminary studies of the ozonation-biofiltration process, a model phenol solution with concentration of approximately 10mg/l was applied. During the ozonation process a dose of 1.64 mg O(3)/mg TOC (total organic carbon) was employed and the contact time was 5 min. Four empty bed contact times (EBCTs) in the range of 2.4-24.0 min were used in the biofiltration experiment. The effectiveness of purification was measured by the following parameters: chemical oxygen demand (COD(Mn)), TOC, phenol concentration and UV(254)-absorbance. The parameters were found to decrease with EBCT.

  7. A silica-supported solid dispersion of bifendate using supercritical carbon dioxide method with enhanced dissolution rate and oral bioavailability.

    PubMed

    Cai, Cuifang; Liu, Muhua; Li, Yun; Guo, Bei; Chang, Hui; Zhang, Xiangrong; Yang, Xiaoxu; Zhang, Tianhong

    2016-01-01

    In this study, to enhance the dissolution rate and oral bioavailability of bifendate, a silica-supported solid dispersion (SD) of bifendate was prepared using supercritical carbon dioxide (ScCO2) technology. The properties of bifendate-silica SD were characterized by differential scanning calorimetry (DSC), X-ray diffraction (X-RD) and scanning electron microscopy. The pharmacokinetic study was carried out in beagle dogs using commercial bifendate dropping pills as a reference which is a conventional SD formulation of bifendate and PEG6000. A novel method of Ultra Performance Convergence Chromatography-tandem mass spectrometry (UPC(2)™-MS/MS) method was applied to determine bifendate concentration in plasma. The amorphous state of bifendate in bifendate-silica SD was revealed in X-RD and DSC when the ratios of bifendate and silica were 1:15 and 1:19, respectively. In vitro dissolution rate was significantly improved with cumulative release of 67% within 20 min relative to 8% for the physical mixture of bifendate and silica, and which was also higher than the commercial dropping pill of 52%. After storage at 75% relative humidity (RH) for 10 d, no recrystallization was found and reduced dissolution rate was obtained due to the absorption of moisture. In pharmacokinetic study, Cmax and AUC0-t for bifendate-silica SD were 153.1 ng/ml and 979.8 ng h/ml, respectively. AUC0-t of bifendate-silica SDs was ∼1.6-fold higher than that of the commercial dropping pills. These results suggest that adsorbing bifendate onto porous silica via ScCO2 technique could be a feasible method to enhance oral bioavailability together with a higher dissolution rate.

  8. Functionalized mesoporous silica films as a matrix for anchoring electrochemically active guests.

    PubMed

    Fattakhova Rohlfing, Dina; Rathouský, Jirí; Rohlfing, Yven; Bartels, Oliver; Wark, Michael

    2005-11-22

    Mesoporous silica thin films were shown to be an appropriate matrix for immobilization of discrete electroactive moieties, yielding uniform transparent thin film electrodes with defined texture and enhanced electrochemical activity. The mesoporous silica films prepared on conducting FTO-coated glass substrate were postsynthetically functionalized. Alkoxysilanes were used as precursors for subsequent grafting via ionic or covalent bonds of representative electroactive species, such as polyoxometalate PMo12O(40)3-, hexacyanoferrate(III), and ferrocene. The electrochemically active concentration within the silica-based composite electrodes achieves 90, 260, and 60 micromol cm(-3) for polyoxometalate, hexacyanoferrate(III), and ferrocene, respectively. The amount of molecules involved in the charge-transfer sequence is proportional to the film thickness and comparable to the total amount of embedded guests. Thus, eventually the whole bulk volume of the modified silica films is electrochemically accessible. Immobilization in the chemically modified silica matrix alters the redox potential of the electroactive molecules. Electron exchange between the adjacent redox centers (electron hopping) is proposed as a possible charge propagation pathway through the insulating silica matrix, which is supported by the fact that the high charge uptake is observed also for the hybrid electrodes with the covalently anchored redox guests.

  9. Fabrication of bulk-modified carbon paste electrode containing alpha-PW12O40(3-) polyanion supported on modified silica gel: Preparation, electrochemistry and electrocatalysis.

    PubMed

    Hamidi, Hassan; Shams, Esmaeil; Yadollahi, Bahram; Esfahani, Farhad Kabiri

    2008-01-15

    Alpha-PW(12)O(40)(3-) (PW(12)) supported on the surface of silica gel derivatized by 3-aminopropyl(triethoxy)silane (devoted briefly as SiNH(3)PW(12)) was synthesized and used as bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry. There is an ionic bonding character between PW(12) and the surface amino groups of modified silica, which greatly improves the stability of SiNH(3)PW(12)-modified carbon paste electrode due to insolubility of silica gel in water. The SiNH(3)PW(12) bulk-modified carbon paste electrode not only maintains the electrochemical activity of PW(12), but also exhibits remarkable advantages of renewability, as well as simple preparation and inexpensive material. The modified electrode offers an excellent and stable electrocatalytic response for the reduction of IO(3)(-) and hydrogen peroxide. The SiNH(3)PW(12)-CPE is successfully applied as an electrochemical detector to monitor IO(3)(-) in flow injection analysis (FIA). The catalytic peak current was found to be linear with the IO(3)(-) concentration in the range 5x10(-6) to 1x10(-3)molL(-1). The detection limit of the proposed method was found to be 3.1x10(-6)molL(-1) for IO(3)(-) determination.

  10. Practical tethering of vitamin B1 on a silica surface via its phosphate group and evaluation of its activity.

    PubMed

    Vartzouma, Ch; Louloudi, M; Butler, I S; Hadjiliadis, N

    2002-03-07

    A convenient immobilization of thiamine pyrophosphate molecules on a silica surface through the phosphate group is developed, leading to a very active heterogenized biocatalyst for pyruvate decarboxylation.

  11. Activated carbon to the rescue

    SciTech Connect

    Sen, S.

    1996-03-01

    This article describes the response to pipeline spill of ethylene dichloride (EDC) on the property of an oil company. Activated carbon cleanup proceedure was used. During delivery, changeout, transport, storage, thermal reactivation, and return delivery to the site, the carbon never came into direct contact with operating personnel or the atmosphere. More than 10,000 tones of dredge soil and 50 million gallons of surface water were processed during the emergency response.

  12. Insights into microstructure and chemistry of active fiber core material produced by the granulated silica method

    NASA Astrophysics Data System (ADS)

    Najafi, H.; Etissa, D.; Romano, V.

    2014-05-01

    The production of special fibers relies on new methods and materials to incorporate new functionalities into optical fibers by virtues of dopants and structure. In particular, the granulated silica method allows to rapidly produce active fibers with high dopant content and with virtually any microstructure. The implementation of this production method requires a multitude of process steps at various temperatures and temperature gradients that can significantly influence the optical properties of the produced preforms and fibers. To better understand and optimize the processes of active material production and fiber drawing parameters we have done a thorough analysis of microstructure, phase development, crystallinity and chemical mapping of active fiber cores produced by a combination of sol-gel process and granulated silica method with and without employment of a CO2 laser treatment. The microstructure of fibers have been analyzed with a diverse suite of techniques in Transmission Electron Microscopy (TEM), revealing formation of various silica polymorphs and distribution of active elements (i.e. Yb and P) into the core structure. Our results show the presence of another polymorph of silica with low crystallinity dispersed in the main amorphous polymorph (i.e. quartz). We conclude that in spite of importance of homogeneous distribution of Yb and P into the core, the formation of various silica polymorphs resulting from materials processing has to be considered.

  13. Carbon-dot-based dual-emission silica nanoparticles as a ratiometric fluorescent probe for Bisphenol A

    NASA Astrophysics Data System (ADS)

    Xiang, Guo-Qiang; Ren, Yue; Xia, Yin; Mao, Wenjie; Fan, Chao; Guo, Si-Yu; Wang, Pan-Pan; Yang, Deng-Hui; He, Lijun; Jiang, Xiuming

    2017-04-01

    A simple and effective strategy for designing a ratiometric fluorescent nanosensor is described in this work. A carbon dots (CDs) based dual-emission nanosensor for Bisphenol A (BPA) was prepared by coating CDs on the surface of dye-doped silica nanoparticles. The fluorescence of dual-emission silica nanoparticles was quenched in hydrochloric acid by potassium bromate (KBrO3) oxidation; BPA inhibited KBrO3 oxidation, resulting in the ratiometric fluorescence response of dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated and optimized. The detection limit of this nanosensor was 0.80 ng mL- 1 with a linear range from 10 to 500 ng mL- 1. This was applied successfully to determine BPA in the leached solution of different plastic products with satisfactory results.

  14. Interactions of Supercritical Carbon Dioxide with Porous Silica and Montmorillonite Clay

    NASA Astrophysics Data System (ADS)

    Rother, G.; Cole, D. R.; Ilton, E. S.; Anovitz, L.; Krukowski, E.

    2011-12-01

    The high and increasing level of carbon dioxide (CO2) in the atmosphere resulting from burning of fossil fuels is likely to cause global warming. Large-scale carbon capture and sequestration (CCS) of CO2 produced in power plants may play an important role in controlling the level of this greenhouse gas in the atmosphere. In this process, CO2 is stripped from the emissions, compressed, and stored in subsurface reservoirs in very large quantities. The specific CO2-rock interactions control the storage capacity of the reservoir and the fluid mobility. The dominant interactions of supercritical CO2 with reservoir rocks over the first couple of years after injection are sorption and capillary trapping. By combining sorption measurements and neutron scattering data in the Adsorbed Phase Model we obtain a full microstructural characterization of the pore fluid. We studied mesoporous CPG-10 silica materials with pore sizes of 75 Å and 350 Å at pressures from 0-200 bars and temperatures of 35°C and 50°C, covering a range typical for carbon storage sites. Porous silica glass serves as a proxy for quartz-rich rocks, including sandstones that may serve as reservoir rocks. The CO2 excess sorption isotherms were measured using a high-pressure sorption balance. Strong adsorption of CO2 to the silica was found at low fluid pressure and density, followed by formation of a maximum in the excess sorption isotherm. The excess sorption exhibited small or even negative values at high pressure. An inverse temperature dependence of the sorption strength was found in the adsorption region at low and intermediate pressure, while the excess sorption showed little temperature dependence at high pressure. A shift of the excess sorption maximum to higher fluid density was observed with increasing pore width. From small-angle neutron scattering data the density and volume of the sorption phase of CO2 is calculated. Caprocks overlying the porous reservoir rock serve to retain buoyant plumes

  15. Voltammetric determination of dopamine at a zirconium phosphated silica gel modified carbon paste electrode.

    PubMed

    Shams, Esmaeil; Babaei, Ali; Taheri, Ali Reza; Kooshki, Mojtaba

    2009-06-01

    Zirconium phosphated amorphous silica gel (devoted briefly as Si-ZrPH) modified carbon paste electrode (CPE) was used for detection of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). Cyclic voltammetry demonstrated improved reversibility of the DA on the modified electrode. Cyclic voltammetry of Fe(CN)(6)(3-/4-) as a negatively charged probe revealed that the surface of the Si-ZrPH modified CPE surface had a high density of negative charge. As a result, the modified carbon paste electrode could inhibit the voltammetric response of AA and UA while the redox reaction of dopamine was promoted. Based on this, a selective method has been developed to detect DA in the presence of 2500 and 1000 time higher concentration of AA and UA, respectively. The effect of various experimental parameters on the voltammetric response of dopamine was investigated. Under the chosen conditions, the differential pulse voltammetry peak current was found to be linear with DA concentration in the ranges of 0.04 to 50 microM and 50 to 400 microM. The detection limit of the proposed method in the presence of 100 microM of AA and 40 microM of UA was found to be 0.02 microM for DA determination. Satisfying results are achieved when detecting the DA in injection and human serum samples.

  16. Capturing the Local Adsorption Structures of Carbon Dioxide in Polyamine-Impregnated Mesoporous Silica Adsorbents.

    PubMed

    Huang, Shing-Jong; Hung, Chin-Te; Zheng, Anmin; Lin, Jen-Shan; Yang, Chun-Fei; Chang, Yu-Chi; Deng, Feng; Liu, Shang-Bin

    2014-09-18

    Interactions between amines and carbon dioxide (CO2) are essential to amine-functionalized solid adsorbents for carbon capture, and an in-depth knowledge of these interactions is crucial to adsorbent design and fabrication as well as adsorption/desorption processes. The local structures of CO2 adsorbed on a tetraethylenepentamine-impregnated mesoporous silica SBA-15 were investigated by solid-state (13)C{(14)N} S-RESPDOR MAS NMR technique and theoretical DFT calculations. Two types of adsorption species, namely, secondary and tertiary carbamates as well as distant ammonium groups were identified together with their relative concentrations and relevant (14)N quadrupolar parameters. Moreover, a dipolar coupling of 716 Hz was derived, corresponding to a (13)C-(14)N internuclear distance of 1.45 Å. These experimental data are in excellent agreement with results obtained from DFT calculations, revealing that the distribution of surface primary and secondary amines readily dictates the CO2 adsorption/desorption properties of the adsorbent.

  17. Progammed synthesis of magnetic mesoporous silica coated carbon nanotubes for organic pollutant adsorption

    NASA Astrophysics Data System (ADS)

    Tong, Yue; Zhang, Min; Xia, Peixiong; Wang, Linlin; Zheng, Jing; Li, Weizhen; Xu, Jingli

    2016-05-01

    Magnetic mesoporous silica coated carbon nanotubes were produced from hydrophilic monodisperse magnetic nanoparticles decorated carbon nanotubes using well controlled programmed synthesis method and were characterized by TEM, XRD, FTIR, TGA, N2 adsorption-desorption and VSM. The well-designed mesoporous magnetic nanotubes had a large specific area, a highly open mesoporous structure and high magnetization. Firstly, SiO2-coated maghemite/CNTs nanoparticles (CNTs/Fe3O4@SiO2 composites) were synthesized by the combination of high temperature decomposition process and an sol-gel method, in which the iron acetylacetonate as well as TEOS acted as the precursor for maghemite and SiO2, respectively. The CNTs/Fe3O4@SiO2 composites revealed a core-shell structure, Then, CNTs/Fe3O4@mSiO2 was obtained by extracting cetyltrimethylammonium bromide (CTAB) via an ion-exchange procedure. The resulting composites show not only a magnetic response to an externally applied magnetic field, but also can be a good adsorbent for the organic pollutant in the ambient temperature.

  18. Simultaneous determination of silica and alumina in bulk bauxite samples by fast neutron activation

    SciTech Connect

    Borsaru, M.; Eisler, P.L.

    1981-10-01

    A prototype of a bulk bauxite analyzer based on fast neutron activation analysis has been developed for simultaneously determining the chemical concentrations of alumina and silica in both dried and undried bulk bauxite samples (about 3.5 kg). The determination of alumina is based on measuring the count rate in the 0.844 MeV ..gamma..-ray peak emitted by /sup 27/Mg formed in the activation of aluminum. The determination of silica is based on measuring the count rate in the 1.78 MeV ..gamma..-ray peak emitted by /sup 28/Al formed in the activation of silicon. The interference from alumina in the determination of silica was eliminated by measuring an additional parameter, the thermal neutrons underneath the bulk sample. The technique enables up to 10 analyses per hour with an accuracy (1 sigma) of 0.28% silica and 0.9% alumina. The samples analyzed contained 48 to 62% alumina and 2 to 11% silica. The tests indicated that the accuracy of analysis was similar for samples which had been oven-dried (0 to 5% free moisture) and samples which were taken from the benefication plant with free moisture varying in a narrow range (10 to 14% free moisture). The results also indicated that crushing and grinding of samples did not significantly improve the accuracy.

  19. Uranium-series dating of pedogenic silica and carbonate, Crater Flat, Nevada

    USGS Publications Warehouse

    Ludwig, K. R.; Paces, J.B.

    2002-01-01

    A 230Th-234U-238U dating study on pedogenic silica-carbonate clast rinds and matrix laminae from alluvium in Crater Flat, Nevada was conducted using small-sample thermal-ionization mass spectrometry (TIMS) analyses on a large suite of samples. Though the 232Th content of these soils is not particularly low (mostly 0.1-9 ppm), the high U content of the silica component (mostly 4-26 ppm) makes them particularly suitable for 230Th/U dating on single, 10 to 200 mg totally-digested samples using TIMS. We observed that (1) both micro- (within-rind) and macro-stratigraphic (mappabe deposit) order of the 230Th/U ages were preserved in all cases; (2) back-calculated initial 234U/238U fall in a restricted range (typically 1.67??0.19), so that 234U/238U ages with errors of about 100 kyr (2??) could be reliably determined for the oldest, 400 to 1000 ka rinds: and (3) though 13 of the samples were >350 ka, only three showed evidence for an open-system history, even though the sensitivity of such old samples to isotopic disruption is very high. An attempt to use leach-residue techniques to separate pedogenic from detrital U and Th failed, yielding corrupt 230Th/U ages. We conclude that 230Th/U ages determined from totally dissolved, multiple sub-mm size subsamples provide more reliable estimates of soil chronology than methods employing larger samples, chemical enhancement of 238U/232Th, or isochrons. Copyright ?? 2002 Elsevier Science Ltd.

  20. Electron paramagnetic resonance study of paramagnetic centers in carbon-fumed silica adsorbent

    SciTech Connect

    Savchenko, D. V.; Shanina, B. D.; Kalabukhova, E. N.; Sitnikov, A. A.; Lysenko, V. S.; Tertykh, V. A.

    2014-04-07

    Fumed silica A-300 was carbonized by means of pyrolysis of CH{sub 2}Cl{sub 2}. The obtained initial SiO{sub 2}:C nanopowders of black color, with an average diameter of 14–16 nm and carbon (C) concentration 7 wt. %, subjected to the oxidation and passivation treatment were studied by electron paramagnetic resonance (EPR) in the temperature range 4–400 K. Two EPR signals of Lorentzian lineshape with nearly equal g-factors and different linewidth were observed in the initial, oxidized, and passivated SiO{sub 2}:C nanopowders. The two-component EPR spectrum was explained by the presence of C in two electronic states. The intensive narrow EPR signal, which has a temperature-dependent intensity, linewidth, and resonance field position, was attributed to the carbon-related defect with non-localized electron hopping between neighboring C-dangling bonds. The striking effect is that the temperature dependence of the EPR linewidth demonstrates the motional narrowing of the EPR signal at very low temperatures from 4 K to 20 K, which is not typically for nonmetallic materials and was explained by the quantum character of C layer conductivity in the SiO{sub 2}:C. The observed peaks in the temperature dependence of the conduction electron EPR signal integral intensity in the high-temperature range 200–440 K was explained by the presence of the C nanodots at the surface of SiO{sub 2} nanoparticles and the ejection of electrons from the confinement energy levels of C quantum dot when the temperature becomes comparable to the confinement energy.

  1. Preparation of silver nanoparticle containing silica micro beads and investigation of their antibacterial activity

    NASA Astrophysics Data System (ADS)

    Quang, Dang Viet; Sarawade, Pradip B.; Hilonga, Askwar; Kim, Jong-Kil; Chai, Young Gyu; Kim, Sang Hoon; Ryu, Jae-Yong; Kim, Hee Taik

    2011-05-01

    Silver nanoparticle containing silica micro beads (Ag-NPBs) were successfully prepared by using sodium silicate, a cheap precursor, involving chemical reductive method. First, silica gel was synthesized and crushed into micro beads which have sizes ranging from 0.5 to 1 mm. Silica micro beads were then modified with 3-aminopropyltriethoxysilane to graft amino functional groups onto their surface. Silver ions were loaded onto the surface of the modified silica and reduced to silver crystal by adding NaBH 4. The presence of silver nanoparticles as well as structure of materials was characterized with FT-IR, XRD, BET, FE-SEM, TEM, UV-vis spectrophotometer, and optical microscope. Silver nanoparticles with an average size about 5 nm were found in the pore and on the surface of amino functionalized silica beads. Ag-NPBs samples were tested for their antibacterial activity against Escherichia coli ( E. coli). The antibacterial activity was examined by both zone inhibition and test tube test method. Biological results indicated that the synthesized materials have an excellent antibacterial performance against E. coli which was completely inhibited after 5 min contact with Ag-NPBs.

  2. Interplay of carbon-silica sources on the formation of hierarchical porous composite materials for biological applications such as lipase immobilization.

    PubMed

    Higuita, Mario; Bernal, Claudia; Mesa, Monica

    2014-10-01

    The porous inorganic materials, with hierarchical structures, find application in many processes where the chemical stability and pore connectivity are key points, such as separation, adsorption and catalysis. Here, we synthesized carbon-silica composite materials, which combine hydrolytic stability of the carbon with the surface chemical reactivity of silica in aqueous media. The polycondensation of carbonaceous and siliceous species from sucrose, Triton X-100 surfactant and tetraethylortosilicate during the hydrothermal synthesis led to the formation of hydrochar composite materials. The subsequent carbonization process of these composite hydrochars gave carbon-silica hierarchical porous materials. The study of the micellar reaction system and the characterization of the derivate materials (carbon-silica composite, carbon and silica) were carried out. The results indicate that synthesis conditions allowed the formation of a silica network interpenetrated with a carbon one, which is produced from the incorporated organic matter. The control of the acidity of the reaction medium and hydrothermal conditions modulated the reaction yield and porous characteristics of the materials. The composite nature in conjunction with the hierarchical porosity increases the interest of these materials for future biological applications, such as lipase immobilization.

  3. C60 aminofullerene immobilized on silica as a visible-light-activated photocatalyst.

    PubMed

    Lee, Jaesang; Mackeyev, Yuri; Cho, Min; Wilson, Lon J; Kim, Jae-Hong; Alvarez, Pedro J J

    2010-12-15

    A new strategy is described to immobilize photoactive C(60) aminofullerene on silica gel (3-(2-succinic anhydride)propyl functionalized silica), thus enabling facile separation of the photocatalyst for recycling and repeated use. An organic linker moiety containing an amide group was used to anchor C(60) aminofullerene to the functionalized silica support. The linker moiety prevents aqueous C(60) aggregation/agglomeration (shown by TEM images), resulting in a remarkable enhancement of photochemical (1)O(2) production under visible light irradiation. With no loss in efficacy of (1)O(2) production plus insignificant chemical modification of the aminoC(60)/silica photocatalyst after multiple cycling, the system offers a promising new visible-light-activated photocatalyst. Under visible-light irradiation, the aminoC(60)/silica photocatalyst is capable of effective and kinetically enhanced oxidation of Ranitidine and Cimetidine (pharmaceutical pollutants) and inactivation of MS-2 bacteriophage compared to aqueous solutions of the C(60) aminofullerene alone. Thus, this photocatalyst could enable water treatment in less developed areas by alleviating dependence on major infrastructure, including the need for electricity.

  4. Active fibers from sol-gel derived granulated silica: state of the art and potential

    NASA Astrophysics Data System (ADS)

    Romano, Valerio; Sandoz, Frederic

    2010-10-01

    In the recent past we have studied the granulated silica method as a versatile and cost effective way of fiber preform production. We have used the sol-gel technology combined with a laser-assisted remelting step to produce high homogeneity Rare Earth or Transition Metal - activated microsized particles for the fiber core. For the fiber cladding pure or index-raised granulated Silica has been employed. Silica glass tubes, appropriately filled with these granular materials, are then drawn to fibers, eventually after an optional quality enhancing vitrification step. The process offers a high degree of compositional flexibility with respect to dopants; it further facilitates to achieve high concentrations even in cases when several dopants are used. By this "rapid preform production" technique, that is also ideally suited for the preparation of microstructured optical fibers, several fibers ranging from broadband emitters, PCFs and large mode area fibers have been produced and will be presented here.

  5. RADIOLOGICAL RELEASES DUE TO AIR AND SILICA DUST ACTIVATION IN EMPLACEMENT DRIFTS

    SciTech Connect

    J.S. Tang

    2003-05-07

    The purpose of this calculation is to determine the quantity and significance of annual Monitored Geologic Repository (MGR) subsurface normal radiological releases due to neutron activation of air and silica dust in emplacement drifts. This calculation includes the following items: (1) Calculate activation of ventilation airflow through emplacement drifts to quantify radioactive gaseous releases; and (2) Calculate the bounding potential activated silica dust concentration and releases. The sources of silica dust may arise from air supply to emplacement drifts as well as host rock around emplacement drifts. For this calculation, the source of dust is conservatively assumed to be the host rock (Assumption 3.6), which is subject to long-term neutron exposure resulting in saturated radioactivity. The scope of this calculation is limited to releases from activated air and silica dust only, excluding natural radioactive releases such as radon or releases from defective waste packages (breached or contaminated). This work supports the repository ventilation system design and Preclosure Safety Analysis. This includes MGR items classified as Quality Level 1, for example, the Uncanistered Spent Nuclear Fuel Waste Package (CRWMS M&O [Civilian Radioactive Waste Management and Operation Contractor] 1999a, page 7). Therefore, this calculation is subject to the requirements of the ''Quality Assurance Requirements and Description'' (DOE [U.S. Department of Energy] 2003). The performance of the calculation and development of this document are carried out in accordance with AP-3.12Q, ''Design Calculation and Analyses'' and LP-3.30Q-BSC, ''Hazards Analysis System''.

  6. Simultaneous determination of hydroquinone and catechol at gold nanoparticles mesoporous silica modified carbon paste electrode.

    PubMed

    Tashkhourian, J; Daneshi, M; Nami-Ana, F; Behbahani, M; Bagheri, A

    2016-11-15

    A new electrochemical sensor based on gold nanoparticles mesoporous silica modified carbon paste electrode (AuNPs-MPS) was developed for simultaneous determination of hydroquinone and catechol. Morphology and structure of the AuNPs-MPS were characterized by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical behavior of hydroquinone and catechol were investigated using square wave voltammetry and the results indicate that the electrochemical responses are improved significantly at the modified electrode. The observed oxidative peaks separation of about 120mV made possible the simultaneous determination of hydroquinone and catechol in their binary-mixture. Under the optimized condition, a linear dynamic range of 10.0μM-1.0mM range for hydroquinone with the detection limit of 1.2μM and from 30.0μM-1.0mM for catechol with the detection limit of 1.1μM were obtained. The applicability of the method was demonstrated by the recovery studies of hydroquinone and catechol in spiked tap water samples.

  7. A spectroscopic study on the absorption of carbonic anhydrase onto the nanoporous silica nanoparticle.

    PubMed

    Khameneh, Hannaneh Pourjabbari; Bolouri, Termeh Ghorbanian; Nemati, Fahimeh; Rezvani, Fatemeh; Attar, Farnoosh; Saboury, Ali Akbar; Falahati, Mojtaba

    2017-06-01

    Herein, KIT-6 nanoporous silica nanoparticles were used as a solid support for immobilization of bovine carbonic anhydrase, isoform II (BCA II). The zeta potential study revealed that KIT-6 and BCA II provided negative (-13.58±1.95mV) and positive (4.23±0.72mV) charge distribution, respectively. Dynamic light scattering (DLS) analysis also showed that the hydrodynamic radius of KIT-6 is less than 100nm. In addition, the structural studies of free and immobilized BCA II against urea-induced denaturation were investigated by circular dichroism (CD) and fluorescence spectroscopy. CD studies showed that the absorbed BCA II, in comparison with the free enzyme, demonstrated higher stability against rising urea concentration. Fluorescence spectroscopy showed lower values of Stern- Volmer constant (KSV) for immobilized BCA II relative to free enzyme, reflecting the relative enzyme stability of BCA II after immobilization. Melting temperature (Tm) measurement of free and immobilized BCA II showed that immobilized enzyme had a more stable structure (Tm=71.9°C) relative to the free counterpart (Tm=64.7°C). In addition, the immobilized BCA II showed pronounced stability against pH and thermal deactivation. This study may provide new and complementary details regarding the design and development of enzymes in industrial applications.

  8. Mapping local microstructure and mechanical performance around carbon nanotube grafted silica fibres: methodologies for hierarchical composites.

    PubMed

    Qian, Hui; Kalinka, Gerhard; Chan, K L Andrew; Kazarian, Sergei G; Greenhalgh, Emile S; Bismarck, Alexander; Shaffer, Milo S P

    2011-11-01

    The introduction of carbon nanotubes (CNTs) modifies bulk polymer properties, depending on intrinsic quality, dispersion, alignment, interfacial chemistry and mechanical properties of the nanofiller. These effects can be exploited to enhance the matrices of conventional microscale fibre-reinforced polymer composites, by using primary reinforcing fibres grafted with CNTs. This paper presents a methodology that combines atomic force microscopy, polarised Raman spectroscopy, and nanoindentation techniques, to study the distribution, alignment and orientation of CNTs in the vicinity of epoxy-embedded micrometre-scale silica fibres, as well as, the resulting local mechanical properties of the matrix. Raman maps of key features in the CNT spectra clearly show the CNT distribution and orientation, including a 'parted' morphology associated with long grafted CNTs. The hardness and indentation modulus of the epoxy matrix were improved locally by 28% and 24%, respectively, due to the reinforcing effects of CNTs. Moreover, a slower stress relaxation was observed in the epoxy region containing CNTs, which may be due to restricted molecular mobility of the matrix. The proposed methodology is likely to be relevant to further studies of nanocomposites and hierarchical composites.

  9. Genotoxicity evaluation of nanosized titanium dioxide, synthetic amorphous silica and multi-walled carbon nanotubes in human lymphocytes.

    PubMed

    Tavares, Ana M; Louro, Henriqueta; Antunes, Susana; Quarré, Stephanie; Simar, Sophie; De Temmerman, Pieter-Jan; Verleysen, Eveline; Mast, Jan; Jensen, Keld A; Norppa, Hannu; Nesslany, Fabrice; Silva, Maria João

    2014-02-01

    Toxicological characterization of manufactured nanomaterials (NMs) is essential for safety assessment, while keeping pace with innovation from their development and application in consumer products. The specific physicochemical properties of NMs, including size and morphology, might influence their toxicity and have impact on human health. The present work aimed to evaluate the genotoxicity of nanosized titanium dioxide (TiO2), synthetic amorphous silica (SAS) and multiwalled carbon nanotubes (MWCNTs), in human lymphocytes. The morphology and size of those NMs were characterized by transmission electron microscopy, while the hydrodynamic particle size-distributions were determined by dynamic light scattering. Using a standardized procedure to ensure the dispersion of the NMs and the cytokinesis-block micronucleus assay (without metabolic activation), we observed significant increases in the frequencies of micronucleated binucleated cells (MNBCs) for some TiO2 NMs and for two MWCNTs, although no clear dose-response relationships could be disclosed. In contrast, all forms of SAS analyzed in this study were unable to induce micronuclei. The present findings increase the weight of evidence towards a genotoxic effect of some forms of TiO2 and some MWCNTs. Regarding safety assessment, the differential genotoxicity observed for closely related NMs highlights the importance of investigating the toxic potential of each NM individually, instead of assuming a common mechanism and equal genotoxic effects for a set of similar NMs.

  10. Nanoemulsion drug delivery by ketene based polyester synthesized using electron rich carbon/silica composite surface.

    PubMed

    Swarnalatha, S; Selvi, P K; Ganesh Kumar, A; Sekaran, G

    2008-09-01

    A new carrier matrix for nanoemulsion drug delivery was synthesized from glycine as the raw material, using mesoporous/microporous electron rich carbon-silica composite surface (MAC(800)). MAC(800) was prepared from rice husk in two-stage carbonization. The surface area, pore volume, and pore size distribution of MAC(800) were measured, using nitrogen adsorption isotherms at 77K. The unpaired electron density of MAC(800) was measured in electron spin resonance spectroscopy (ESR), using TEMPOL (4-hydroxy-2,2,6,6-tetramethyl piperidine-1-oxyl) as the reference spin probe. Glycine was converted into ketene at the surface of MAC(800), which further underwent radical polymerization to form a low molecular weight ketene polymer (LMKP) of ester structure. The structure and the properties of LMKP were confirmed through (13)C, (1)H and DEPT nuclear magnetic resonance (NMR) spectroscopy, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and size exclusion chromatography (SEC). The two hydrophilic drugs namely ciprofloxacin hydrochloride (CPH) and gentamicin sulphate (GS) were chosen for the nanoemulsion preparation and characterization. They were characterized for morphology, interaction of drugs with the polymer and their crystallinity, using HR-TEM, DSC and XRD, respectively. The encapsulation efficiency of the LMKP towards the drugs ciprofloxacin hydrochloride and gentamicin sulphate were 26% and 12%, respectively. The dissolution studies of the nanoemulsion were carried out for the pH 6.5, 7.4 and 8.0. The cytocompatibility studies were done for LMKP as well as nanoemulsion using Hep2 epithelial cells.

  11. Photoconductivity of activated carbon fibers

    SciTech Connect

    Kuriyama, K.; Dresselhaus, M.S. )

    1990-08-01

    The photoconductivity is measured on a high-surface-area disordered carbon material, namely activated carbon fibers, to investigate their electronic properties. Measurements of decay time, recombination kinetics and temperature dependence of the photoconductivity generally reflect the electronic properties of a material. The material studied in this paper is a highly disordered carbon derived from a phenolic precursor, having a huge specific surface area of 1000--2000m{sup 2}/g. Our preliminary thermopower measurements suggest that this carbon material is a p-type semiconductor with an amorphous-like microstructure. The intrinsic electrical conductivity, on the order of 20S/cm at room temperature, increases with increasing temperature in the range 30--290K. In contrast with the intrinsic conductivity, the photoconductivity in vacuum decreases with increasing temperature. The recombination kinetics changes from a monomolecular process at room temperature to a biomolecular process at low temperatures. The observed decay time of the photoconductivity is {approx equal}0.3sec. The magnitude of the photoconductive signal was reduced by a factor of ten when the sample was exposed to air. The intrinsic carrier density and the activation energy for conduction are estimated to be {approx equal}10{sup 21}/cm{sup 3} and {approx equal}20meV, respectively. The majority of the induced photocarriers and of the intrinsic carriers are trapped, resulting in the long decay time of the photoconductivity and the positive temperature dependence of the conductivity. 54 refs., 11 figs., 3 tabs.

  12. Photoconductivity of Activated Carbon Fibers

    DOE R&D Accomplishments Database

    Kuriyama, K.; Dresselhaus, M. S.

    1990-08-01

    The photoconductivity is measured on a high-surface-area disordered carbon material, namely activated carbon fibers, to investigate their electronic properties. Measurements of decay time, recombination kinetics and temperature dependence of the photoconductivity generally reflect the electronic properties of a material. The material studied in this paper is a highly disordered carbon derived from a phenolic precursor, having a huge specific surface area of 1000--2000m{sup 2}/g. Our preliminary thermopower measurements suggest that this carbon material is a p-type semiconductor with an amorphous-like microstructure. The intrinsic electrical conductivity, on the order of 20S/cm at room temperature, increases with increasing temperature in the range 30--290K. In contrast with the intrinsic conductivity, the photoconductivity in vacuum decreases with increasing temperature. The recombination kinetics changes from a monomolecular process at room temperature to a biomolecular process at low temperatures. The observed decay time of the photoconductivity is {approx equal}0.3sec. The magnitude of the photoconductive signal was reduced by a factor of ten when the sample was exposed to air. The intrinsic carrier density and the activation energy for conduction are estimated to be {approx equal}10{sup 21}/cm{sup 3} and {approx equal}20meV, respectively. The majority of the induced photocarriers and of the intrinsic carriers are trapped, resulting in the long decay time of the photoconductivity and the positive temperature dependence of the conductivity.

  13. Preparation and characterization of kasuga-silica-conjugated nanospheres for sustained antimicrobial activity

    NASA Astrophysics Data System (ADS)

    Ding, Guanglong; Li, Deguang; Liu, Yao; Guo, Mingcheng; Duan, Yongheng; Li, Jianqiang; Cao, Yongsong

    2014-11-01

    Controlled release formulation of pesticides is highly desirable for attaining the most effective utilization of the pesticide as well as reducing environmental pollution. Nano-sized controlled release formulations can provide better penetration through cuticle and deliver the active ingredients efficiently to the targeted tissue. In this study, a novel strategy for the preparation of a nanoconjugate derived from kasugamycin with amino-modified silica was developed. The kasugamycin was connected with amino-modified silica matrix by an amide bond, which could avoid the initial burst release effectively and prolong the duration remarkably. The results showed the kasuga-silica can protect kasugamycin against photo-degradation effectively and the release rate of the active ingredient of nanoconjugate was related to the temperature, pH value, and the particle size (52.5-315.4 nm). With reduced particle size as well as increased temperature and acidity, the release of the active ingredient was faster. This amide linkage of kasuga-silica could be degraded by amidase effectively. This nanoconjugate displayed a better and a sustained bactericidal efficacy against E. coli than kasugamycin technical, which makes it a potential candidate as a controlled release conjugate for kasugamycin in the future.

  14. Chip electrochromatographic systems: Novel vertically aligned carbon nanotube and silica monoliths based separations

    NASA Astrophysics Data System (ADS)

    Goswami, Shubhodeep

    2009-12-01

    Miniaturized chemical analysis systems, also know as 'lab-on-a-chip' devices have been rapidly developing over the last decade. Capillary electrochromatography (CEC), a multidimensional separation technique combining capillary electrophoresis (CE) and liquid chromatography (LC) has been of great interest for chip based applications. Preliminary work has been undertaken to develop vertically aligned carbon nanotubes and photopolymerizable silica solgel as novel stationary phase materials for 'chip CEC' separations. Patterned growth of CNTs in a specific location of the channel has been carried out using a solid phase Fe-Al catalyst as well as a vapor deposited ferrocene catalyst. Characterization of the CNT "forests" was achieved using optical microscopy, secondary electron microscopy, high resolution tunneling electron microscopy and Raman spectroscopy. Proof-of-concept applications were demonstrated using reversed phase CEC separations as well as solid phase extraction of a glycosylated protein using concanavilin A immobilized onto the CNT bed. Photopolymerizable silica solgel materials were developed as stationary phase for microfluidic electrochromatographic separations in disposable polydimethylsiloxane (PDMS) chip devices. Effect on morphology and pore size of gels were studied as function of UV and solgel polymerization conditions, porogen, salt additives, geometry and hydrolyzable methoxy-ies. Structural morphologies were studied with Secondary Electron Microscopy (SEM). Pore size and pore volumes were characterized by thermal porometry, nitrogen BET adsorptions and differential scanning calorimetry. Computational fluid dynamics and confocal microscopy tools were employed to study the transport of fluids and model analytes. These investigations were directed towards evolving improved strategies for rinsing of uncrosslinked monomers to form porous monoliths as well as to effect a desired separation under a set of electrochromatograhic conditions

  15. Processing of surfactant templated nano-structured silica films using compressed carbon dioxide as interpreted from in situ fluorescence spectroscopy.

    PubMed

    Ghosh, Kaustav; Rankin, Stephen E; Lehmler, Hans-Joachim; Knutson, Barbara L

    2012-09-27

    The local environment and dynamics of compressed carbon dioxide (CO(2)) penetration in surfactant templated silica film synthesis is interpreted from the in situ fluorescence emission spectra of pyrene (Py) and a modified pyrene probe. Pyrene emission in cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB) templated silica films is monitored immediately after casting and during processing with gaseous and supercritical (sc) CO(2) (17-172 bar, 45 °C). The solvatochromic emission spectra of pyrene in CTAB templated films suggest CO(2) penetration in both the micelle interface and its interior. An anchored derivative of pyrene, 1-pyrenehexadecanoic acid (C(16)-pyr), is established for probing CPB films, where the pyrene moiety is preferentially oriented toward the micelle interior, thus limiting quenching by the pyridinium headgroup of CPB. CO(2) processing of CPB templated silica films results in an increase in the time scale for probe mobility, suggesting an increased time scale of silica condensation through CO(2) processing. The mobility of C(16)-pyr increases with pressure from gaseous to sc CO(2) processing and persists for over 5 h for sc CO(2) processing at 172 bar and 45 °C compared to about 25 min for the unprocessed film. The delivery of CO(2) soluble solutes to specific regions of surfactant templated mesoporous materials is examined via the nonradiative energy transfer (NRET) between pyrene and CO(2)-solubilized naphthalene.

  16. Solvent-regenerated activated carbon

    SciTech Connect

    McLaughlin, H. )

    1988-07-01

    This report summarizes the results of a University/Industry research project, sponsored by the New York State Energy Research and Development Authority and Fluids Design Corporation. The research project studied the solvent regeneration of activated carbon. Activate carbon was used to remove trace organics from aqueous streams, then regenerated by desorbing the adsorbates with organic solvents. The project included a survey of the potential applications in New York State industries, fundamental research on the adsorption/desorption phenomena, and design of a full-scale process. The economics of the full-scale process were evaluated and compared to alternate available technologies. The result of this work is a versatile process with attractive economics. A wide range of adsorbates and solvents were found to be acceptable for this process. The design methodologies are developed and the techniques for evaluating a new application are delineated. 13 refs., 12 figs., 4 tabs.

  17. Modified Activated Carbon Perchlorate Sorbents

    DTIC Science & Technology

    2007-01-25

    nitrosodimethylamine precursors in municipal wastewater treatment plants. Environ. Sci. Technol., 2004. 38: p. 1445-1454. 15. Shmidt, V., K. Rybakov...Engineering and Management, 1994. 141: p. 12. 33. Walker, G. and L. Weatherley, Biological Activated Carbon Treatment of Industrial Wastewater in... Treatment with Ammonia (NAC), Urea-formaldehyde Resin (UAC), and Hydrogen (HAC). Data are Indicated by the Symbol and Least Squares Fit of the Langmuir

  18. The burial of biogenic silica, organic carbon and organic nitrogen in the sediments of the East China Sea

    NASA Astrophysics Data System (ADS)

    Wang, Lisha; Zhang, Chuansong; Shi, Xiaoyong

    2015-06-01

    We sampled the sediments of the East China Sea during 2005 and 2006, and analysed the contents of the biogenic matters: biogenic silica, organic carbon, and organic nitrogen. From the surface distribution we found the contents of these substances to be in the ranges of 0.72%-1.64%, 0.043%-0.82%, and 0.006%-0.11%, respectively. Their distributions were similar to each other, being high inside the Hangzhou Bay and low outside the bay. The vertical variations of the contents were also similar. In order to discuss the relation between them we analysed the variations of content with depth. They increased in the first 7 cm and then decreased with depth. The peaks were found at depths between 20 to 25 cm. The distribution of carbonate showed an opposite trend to that of biogenic matters. The content of total carbon was relatively stable with respect to depth, and the ratio of high organic carbon to carbonate showed a low burial efficiency of carbonate, which means that the main burial of carbon is organic carbon. In order to discuss the source of organic matters, the ratio of organic carbon to organic nitrogen was calculated, which was 8.01 to 9.65, indicating that the organic matter in the sediments was derived mainly from phytoplankton in the seawater.

  19. Intrinsic catalytic role of mesoporous silica in preferential oxidation of carbon monoxide in excess hydrogen.

    PubMed

    Huang, Shengjun; Hara, Kenji; Fukuoka, Atsushi

    2012-04-10

    We have studied the intrinsic catalytic role of MCM-41 mesoporous silica in preferential oxidation of CO in excess H(2) (PROX). Two types of MCM-41 supports (MCM-41A and MCM-41B) were obtained from the same pristine as-synthesized materials by using different procedures for surfactant removal: one-step calcination or two-step extraction-calcination. Although two kinds of Pt catalysts prepared from the MCM-41 supports exhibit high similarity in apparent physicochemical parameters such as Pt morphology, particle-size distribution, electronic states, support architecture, and pore-size distribution, they show a dramatic difference in catalytic activity (ca. 100 % versus 10 % CO conversions at 298 K). This feature motivated us to investigate the catalytic role of MCM-41 in the PROX reaction. By means of infrared experiments with the isotope tracer technique, it was revealed that the reactive microenvironment at the interface between Pt and the MCM-41A support is the origin of the high activity. On the highly active Pt/MCM-41A catalyst, interfacial silanols play a decisive role in the ignition of CO oxidation, and gaseous O(2) and H(2) are dissociated on CO-free Pt sites created by the interfacial reaction. The dissociated oxygen and hydrogen are proposed to sustain the catalytic cycle in the form of regenerated silanols on the support, which is catalyzed by the Pt surface in the presence of H(2).

  20. Preparation of Self-Activated Fluorescence Mesoporous Silica Hollow Nanoellipsoids for Theranostics.

    PubMed

    Singh, Rajendra Kumar; Kim, Tae-Hyun; Mahapatra, Chinmaya; Patel, Kapil Dev; Kim, Hae-Won

    2015-10-20

    The newly developed multifunctional (self-activated fluorescent, mesoporous, and biocompatible) hollow mesoporous silica nanoellipsoids (f-hMS) are potentially useful as a delivery system of drugs for therapeutics and imaging purposes. For the synthesis of f-hMS, self-activated fluorescence hydroxyapatite (fHA) was used as a core template. A mesoporous silica shell was obtained by silica formation and subsequent removal of the fHA core, which resulted in a hollow-cored f-hMS. Although the silica shell provided a highly mesoporous structure, enabling an effective loading of drug molecules, the fluorescent property of fHA was also well-preserved in the f-hMS. Cytochrome c and doxorubicin, used as a model protein and anticancer drug, respectively, were shown to be effectively loaded onto f-hMS and were then released in a sustainable and controllable manner. The f-hMS was effectively taken up by the cells and exhibited fluorescent labeling while preserving excellent cell viability. Overall, the f-hMS nanoreservoir may be useful as a multifunctional carrier system for drug delivery and cell imaging.

  1. Kraft lignin/silica-AgNPs as a functional material with antibacterial activity.

    PubMed

    Klapiszewski, Łukasz; Rzemieniecki, Tomasz; Krawczyk, Magdalena; Malina, Dagmara; Norman, Małgorzata; Zdarta, Jakub; Majchrzak, Izabela; Dobrowolska, Anna; Czaczyk, Katarzyna; Jesionowski, Teofil

    2015-10-01

    Advanced functional silica/lignin hybrid materials, modified with nanosilver, were obtained. The commercial silica Syloid 244 was used, modified with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to increase its chemical affinity to lignin. Similarly, kraft lignin was oxidized using a solution of sodium periodate to activate appropriate functional groups on its surface. Silver nanoparticles were grafted onto the resulting silica/lignin hybrids. The systems obtained were comprehensively tested using available techniques and methods, including transmission electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, elemental analysis and atomic absorption spectroscopy. An evaluation was also made of the electrokinetic stability of the systems with and without silver nanoparticles. Conclusions were drawn concerning the chemical nature of the bonds between the precursors and the effectiveness of the method of binding nanosilver to the hybrid materials. The antimicrobial activity of the studied materials was tested against five species of Gram-positive and Gram-negative bacteria. The addition of silver nanoparticles to the silica/lignin hybrids led to inhibition of the growth of the analyzed bacteria. The best results were obtained against Pseudomonas aeruginosa, a dangerous human pathogen.

  2. Characterization of carbon silica hybrid fillers obtained by pyrolysis of waste green tires by the STEM–EDX method

    SciTech Connect

    Al-Hartomy, Omar A.; Al-Ghamdi, Ahmed A.; Al Said, Said A. Farha; Dishovsky, Nikolay; Ward, Michael B.; Mihaylov, Mihail; Ivanov, Milcho

    2015-03-15

    Dual phase carbon–silica hybrid fillers obtained by pyrolysis-cum-water vapor of waste green tires have been characterized by energy dispersive X-ray spectroscopy in a scanning transmission electron microscope, silicate analysis, weight analysis, atomic absorption spectroscopy and by inductively coupled plasma–optical emission spectroscopy. The results achieved have shown that the location and distribution of the phases in the carbon silica hybrid fillers as well as their most essential characteristics are influenced by the pyrolysis conditions. The carbon phase of the filler thus obtained is located predominantly in the space among silica aggregates which have already been existing while it has been formed by elastomer destruction in the course of pyrolysis. The presence of ZnS also has been found in the hybrid fillers investigated. - Highlights: • Dual phase fillers obtained by pyrolysis of waste green tires have been characterized. • The STEM–EDX method was used for characterization. • The phase distributions in the fillers are influenced by the pyrolysis conditions.

  3. Sol-gel derived silica/siloxane composite materials: The effect of loading level and catalyst activity on silica domain formation

    SciTech Connect

    Black, E.P.; Ulibarri, T.A.; Beaucage, G.; Schaefer, D.W.; Assink, R.A.; Bergstrom, D.F.; Giwa-Agbomeirele, P.A.; Burns, G.T.

    1993-11-01

    Currently, the production of in situ reinforcement in polymeric systems by sol-gel methods is undergoing rapid development. However, understanding of synthesis/structure/property relationships is still lacking. In order to produce sol-gel derived composite materials with sufficient mechanical properties for commercial applications, this deficit of information must be addressed. We have completed a detailed investigation of in situ silica growth in polydimethylsiloxane (PDMS)/tetraethylorthosilicate (TEOS) systems. Factors which affect the domain growth, such as catalyst activity and silica loading, have been examined by solid state {sup 29}Si NMR, SEM, mechanical testing and small angle neutron scattering.

  4. Bioresponsive carbon nano-gated multifunctional mesoporous silica for cancer theranostics

    NASA Astrophysics Data System (ADS)

    Prasad, Rajendra; Aiyer, Sandhya; Chauhan, Deepak S.; Srivastava, Rohit; Selvaraj, Kaliaperumal

    2016-02-01

    Designing bioresponsive nanocarriers for controlled and efficient intracellular drug release for cancer therapy is a major thrust area in nanomedicine. With recent recognition by the US FDA as a safe material for human trials, mesoporous silica nanoparticles (MSNPs) are being extensively explored as promising theranostic agents. Green fluorescent carbon quantum dots (CQDs), though known as possible alternatives for their more toxic and relatively less efficient predecessors, are less known as gate keepers for drug release control. We report for the first time an efficient bioresponse of CQDs when judiciously designed using glutathione cleavable (redox responsive) disulphide bonds. When the anticancer drug doxorubicin loaded MSNPs are capped with these CQDs, they display promising drug release control on exposure to a mimicked intracellular cancer environment. Their dual functionality is well established with good control on preventing the premature release and exceptional bio-imaging of HeLa cancer cells. Fluorescence images prove selective targeting of HeLa cells by overexpression of folate receptors from the surface functionalised folic acid ligand. Extensive characterisation using XRD, TEM, BET analysis, drug loading tests, drug release kinetics, MTT assay and fluoroscence cell imaging helps in understanding the multifunctionalities of the successful design, extending its scope with exciting prospects towards non-invasive targeted drug delivery and bio-imaging for effective cancer diagnosis and treatment.Designing bioresponsive nanocarriers for controlled and efficient intracellular drug release for cancer therapy is a major thrust area in nanomedicine. With recent recognition by the US FDA as a safe material for human trials, mesoporous silica nanoparticles (MSNPs) are being extensively explored as promising theranostic agents. Green fluorescent carbon quantum dots (CQDs), though known as possible alternatives for their more toxic and relatively less efficient

  5. A Thermally Conductive Composite with a Silica Gel Matrix and Carbon-Encapsulated Copper Nanoparticles as Filler

    NASA Astrophysics Data System (ADS)

    Lin, Jin; Zhang, Haiyan; Hong, Haoqun; Liu, Hui; Zhang, Xiubin

    2014-07-01

    Core-shell-structured nanocapsules with a copper core encapsulated in a carbon shell (Cu-C) were synthesized by a direct-current arc-discharge method. Morphological and microstructural characterization showed that the Cu-C consisted of a nanosized Cu core and carbon shell, with the carbon shells containing 6 to 15 ordered graphitic layers and amorphous carbon that effectively shield the metallic Cu core from oxidation. A thermally conductive composite was successfully fabricated using a silica gel matrix incorporated with Cu-C filler. The Cu-C nanoparticles were homogeneously dispersed in the silica gel. The effects of Cu-C on the thermal conductivity, electrical resistivity, and coefficient of thermal expansion (CTE) of the composite were investigated. For composites with 6.16 vol.%, 11.04 vol.%, 16.70 vol.%, and 23.34 vol.% Cu-C content, the thermal conductivity at 50°C was 0.32 W/(m K) to 0.77 W/(m K), the electrical resistivity was 1.98 × 109, 3.48 × 107, 302, and 1 Ω m, respectively, while the CTE at 200°C was 3.79 × 10-4 K-1 to 3.44 × 10-4 K-1. The results reveal that the ordered graphitic shells in the Cu-C increased both the thermal and electrical conduction, but decreased the CTE by preventing the Cu cores from expanding.

  6. Activated, coal-based carbon foam

    DOEpatents

    Rogers, Darren Kenneth; Plucinski, Janusz Wladyslaw

    2004-12-21

    An ablation resistant, monolithic, activated, carbon foam produced by the activation of a coal-based carbon foam through the action of carbon dioxide, ozone or some similar oxidative agent that pits and/or partially oxidizes the carbon foam skeleton, thereby significantly increasing its overall surface area and concurrently increasing its filtering ability. Such activated carbon foams are suitable for application in virtually all areas where particulate or gel form activated carbon materials have been used. Such an activated carbon foam can be fabricated, i.e. sawed, machined and otherwise shaped to fit virtually any required filtering location by simple insertion and without the need for handling the "dirty" and friable particulate activated carbon foam materials of the prior art.

  7. Activated, coal-based carbon foam

    SciTech Connect

    Rogers, Darren Kenneth; Plucinski, Janusz Wladyslaw

    2009-06-09

    An ablation resistant, monolithic, activated, carbon foam produced by the activation of a coal-based carbon foam through the action of carbon dioxide, ozone or some similar oxidative agent that pits and/or partially oxidizes the carbon foam skeleton, thereby significantly increasing its overall surface area and concurrently increasing its filtering ability. Such activated carbon foams are suitable for application in virtually all areas where particulate or gel form activated carbon materials have been used. Such an activated carbon foam can be fabricated, i.e. sawed, machined and otherwise shaped to fit virtually any required filtering location by simple insertion and without the need for handling the "dirty" and friable particulate activated carbon foam materials of the prior art.

  8. Low Ni olivine in silica-undersaturated ultrapotassic igneous rocks as evidence for carbonate metasomatism in the mantle

    NASA Astrophysics Data System (ADS)

    Ammannati, Edoardo; Jacob, Dorrit E.; Avanzinelli, Riccardo; Foley, Stephen F.; Conticelli, Sandro

    2016-06-01

    Subduction drags a large amount of CO2 into the Earth's interior, which is partly returned to the atmosphere by arc volcanism. Processes involved in the recycling of subducted carbon within the upper mantle are mainly related to mineralogical transformation. Subducted CO2 may dramatically affect the equilibria among peridotitic minerals (olivine vs. pyroxenes) changing their stability fields and hence their modal abundances. This process is accompanied by a subduction-induced change in the budget of some incompatible trace and major elements (e.g., K, Ca, HFSE), whereas it has a minimal effect on the mass balance of compatible elements (e.g., Ni). We report trace elements in olivine in subduction-related mafic alkaline ultrapotassic rocks from Italy, which are used as a proxy to define mantle wedge mineralogy and metasomatic processes. Minor element concentrations, and in particular the high Li and low Ti of all the olivines, confirm a major role for recycled sediment in the generation of Italian ultrapotassic magmas. The distinct contents of Ni, Mn, and Ca in olivine reflect the bimodal character of silica-rich and silica-poor ultrapotassic Italian rocks and constrain two distinct mineralogical reactions between metasomatic agents and peridotite. Olivine chemistry from silica-saturated rocks reflects the reaction of silicate melts with the ambient mantle, with consequent consumption of olivine in favour of orthopyroxene. In contrast, the low-Ni, high-Mn/Fe of olivine crystallised from silica-undersaturated leucitites require a mantle source enriched in olivine (and clinopyroxene) compared to orthopyroxene, as a result of the interaction between the ambient peridotitic mantle and CaCO3-rich metasomatic agents. The change from silica-oversaturated lamproites to silica-undersaturated leucitites and thus the difference in the olivine composition is due to a change in composition of the subducting sediment from pelitic to carbonate-rich. The results of this study

  9. Enhanced photocatalytic activity for titanium dioxide by co-modifying with silica and fluorine.

    PubMed

    Yang, Shaogui; Sun, Cheng; Li, Xinyong; Gong, Zhongqiang; Quan, Xie

    2010-03-15

    F-Si-co-modified TiO(2) (FST) samples with different ratios of fluorine to titanium (R(F)) and silica to titanium (R(x)), were successfully synthesized by ultrasound-assisted hydrolysis. The structure and properties of the as-prepared codoped titania were characterized by means of XRD, TEM, XPS, BET, UV-Vis diffuse reflectance spectra and ESR. XRD analysis showed that Si and F atoms prevented phase transition of anatase to rutile and suppressed the growth of titania crystalline. ESR results showed that the concentration of the active species (.OH) on 1%-FST(R(x)=10%) was higher than that on other FST samples and P25 titania. The improvement in photocatalytic activity relative to titania can be achieved by co-modifying fluorine and silica to fabricate FST composite material. The photocatalytic activity of FST powders for decomposition of methyl orange was affected by the content of fluorine and the content of silica. When the ratios of R(F) and R(x) were 1 and 10%, respectively, 1%-FST(R(x)=10%) shows the best among photocatalytic activity, which is much superior to P25 under UV-Vis irradiation. The possible reasons for the high photocatalytic activity of the FST powders were proposed in the paper. In addition, the stability of the FST powders in photocatalytic process was confirmed based on the XPS analysis.

  10. 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.

  11. Phosphate glass core/silica clad fibres with a high concentration of active rare-earth ions

    NASA Astrophysics Data System (ADS)

    Egorova, O. N.; Galagan, B. I.; Denker, B. I.; Sverchkov, S. E.; Semjonov, S. L.

    2016-12-01

    We report a study of silica-clad composite optical fibres having a phosphate glass core doped with active rare-earth elements. The phosphate glass core allows a high concentration of active rare-earth ions to be obtained, and the silica cladding ensures high mechanical strength and facilitates fusion splicing of such fibres to silica fibres. Owing to the high concentration of active rare-earth ions, this type of fibre is potentially attractive for applications where a small cavity length and high lasing efficiency are needed.

  12. Methanol Decomposition over Palladium Particles Supported on Silica: Role of Particle Size and Co-Feeding Carbon Dioxide on the Catalytic Properties

    SciTech Connect

    Hokenek, Selma; Kuhn, John N.

    2012-10-23

    Monodisperse palladium particles of six distinct and controlled sizes between 4-16 nm were synthesized in a one-pot polyol process by varying the molar ratios of the two palladium precursors used, which contained palladium in different oxidation states. This difference permitted size control by regulation of the nucleation rate because low oxidation state metals ions nucleate quickly relative to high oxidation state ions. After immobilization of the Pd particles on silica by mild sonication, the catalysts were characterized by X-ray absorption spectroscopy and applied toward catalytic methanol decomposition. This reaction was determined as structure sensitive with the intrinsic activity (turnover frequency) increasing with increasing particle size. Moreover, observed catalytic deactivation was linked to product (carbon monoxide) poisoning. Co-feeding carbon dioxide caused the activity and the amount of deactivation to decrease substantially. A reaction mechanism based on the formation of the {pi}-bond between carbon and oxygen as the rate-limiting step is in agreement with antipathetic structure sensitivity and product poisoning by carbon monoxide.

  13. Designed synthesis of carbon-functional magnetic graphene mesoporous silica materials using polydopamine as carbon precursor for the selective enrichment of N-linked glycan.

    PubMed

    Sun, Nianrong; Yao, Jizong; Deng, Chunhui

    2016-02-01

    Glycosylation, which has been confirmed to be associated with many diseases, is an important protein post-translation modification. Taking into account the low abundant of glycan, the purification of complex biological samples is considered to be very significant before mass spectrometry detection. In this work, carbon-functionalized magnetic graphene /mesoporous silica materials (C-Mag G@mSiO2 materials) with high content of carbon were designed and synthesized by using polydopamine as carbon precursor. Taking advantage of the special interaction between carbon and glycan, C-Mag G@mSiO2 materials were successfully applied to enrich N-linked glycans in different complex samples, such as standard glycoprotein digestion, the mixture of standard glycoprotein digestion, glycoprotein and non-glycoprotein, and human serum.

  14. Tuning the Interfacial Activity of Mesoporous Silicas for Biphasic Interface Catalysis Reactions.

    PubMed

    Xue, Fen; Zhang, Yabin; Zhang, Fengwei; Ren, Xiaomin; Yang, Hengquan

    2017-03-08

    Interface-active particle materials that are able to assemble at the oil/water interface so as to stabilize droplets, are gaining unprecedented interest due to the intriguing applications in catalysis and materials synthesis, etc. In contrast to these potential applications, this kind of materials are still limited and cannot meet some particular demands of practical utilizations such as rationally designed interfacial activity and high stability against concentrated salts. In this contribution, interface-active mesoporous silica nanospheres (MSS@CxZy) are synthesized through simultaneous incorporation of extremely hydrophilic zwitterionic moiety and hydrophobic octyl moiety in the shell. The textural properties of these materials are characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and nitrogen sorption. The successful decoration of these functionalities in the shell is confirmed by Fourier transform infrared spectra (FT-IR), (13)C nuclear cross-polar magnetic resonance ((13)C CP/MAS NMR), and (29)Si nuclear cross-polar magnetic resonance ((29)Si CP/MAS NMR). The prepared mesoporous silicas exhibit tunable interfacial activity, so that oil-in-water (O/W) and water-in-oil (W/O) Pickering emulsions can be easily obtained by varying the molar fraction of these two functionalities. The MSS@CxZy-stabilized Pickering emulsions exhibit high stability to coalescence even at 6.0 M NaCl and have relatively low surface coverage of droplets due to electrostatic repulsion, which is normally difficult to obtain for conventional particles. Interestingly, such interface-active mesoporous silicas can also carry polyoxometalate that is hosted in the nanopore to assemble at the oil/water interface and thus efficiently promotes biphasic epoxidation reactions without any external stirring, exemplifying an innovative application of theses developed mesoporous silicas.

  15. Date palm waste-derived biochar composites with silica and zeolite: synthesis, characterization and implication for carbon stability and recalcitrant potential.

    PubMed

    Ahmad, Munir; Ahmad, Mahtab; Usman, Adel R A; Al-Faraj, Abdullah S; Abduljabbar, Adel; Ok, Yong Sik; Al-Wabel, Mohammad I

    2017-03-23

    Engineered organo-mineral composites were synthesized from date palm waste biochar and silica or zeolite via mechanochemical treatments. Date palm tree rachis (leaves) waste biomass was pre-treated with silica or zeolite minerals via ball milling and sonication prior to pyrolysis at 600 °C. The resultant organo-mineral composites and pristine materials were characterized using X-ray diffraction, thermogravimetric-differential thermal (TG-DTA), Fourier transform infrared, scanning electron microscope analyses and surface area and porosity analyzer to investigate the variations in physiochemical and structural characteristics. Compared to the resultant composites derived from non-milled date palm biomass, ball milling increased surface area, while decreased crystallinity index and effective particle size of the biochar composites. Silica composited biochars were located near origin in the van Krevelen diagram indicating lowest H/C and O/C molar ratios, thus suggesting higher aromaticity and lower polarity compared to other biochars. TGA thermograms indicated highest thermal stability of silica composited biochars. Ash and moisture corrected TGA thermograms were used to calculate recalcitrance index (R 50) of the materials, which speculated high degradability of biomass (R 50 < 0.4), minimal degradability of biochars and zeolite composited biochars (0.5 < R 50 < 0.7) and high recalcitrant nature of silica composited biochars (R 50 > 0.7). Silica composited biochars exhibited highest carbon sequestration potential (64.17-95.59%) compared to other biochars. Highest recalcitrance and carbon sequestration potential of silica composited biochars may be attributed to changes in structural arrangements in the silica-biochar complex. Encapsulations of biochar particles with amorphous silica via Si-C bonding may have prevented thermal degradation, subsequently increasing recalcitrance potential of silica composited biochars.

  16. Preparation and evaluation of micro and meso porous silica monoliths with embedded carbon nanoparticles for the extraction of non-polar compounds from waters.

    PubMed

    Fresco-Cala, Beatriz; Cárdenas, Soledad; Valcárcel, Miguel

    2016-10-14

    A novel hybrid micro and meso porous silica monolith with embedded carbon nanoparticles (Si-CNPs monolith) was prepared inside a fused silica capillary (3cm in length) and used as a sorbent for solid-phase microextraction. The hybrid monolithic capillary was synthetized by hydrolysis and polycondensation of a mixture of tetraethoxysilane (TEOS), ethanol, and three different carbon nanoparticles such as carboxylated single-walled carbon nanotubes (c-SWCNTs), carboxylated multi-walled carbon nanotubes (c-MWCNTs), and oxidized single-walled carbon nanohorns (o-SWNHs) via a two-step catalytic sol-gel process. Compared with silica monolith without carbon nanoparticles, the developed monolithic capillary column exhibited a higher extraction efficiency towards the analytes which can be ascribed to the presence of the carbon nanoparticles. In this regard, the best performance was achieved for silica monolith with embedded c-MWCNTs. The resulted monolithic capillaries were also characterized by scanning electron microscopy (SEM), elemental analysis and nitrogen intrusion porosimetry. Variables affecting to the preparation of the sorbent phase including three different carbon nanoparticles and extraction parameters were studied in depth using polycyclic aromatic hydrocarbons (PAHs) as target analytes. Gas chromatography-mass spectrometry was selected as instrumental technique. Detection limits range from 0.1 to 0.3μgL(-1), and the inter-extraction units precision (expressed as relative standard deviation) is between 5.9 and 14.4%.

  17. Silica nanoparticles as indicator of hydrothermal activities at Enceladus ocean floor

    NASA Astrophysics Data System (ADS)

    Postberg, F.; Hsu, S.; Sekine, Y.; Kempf, S.; Juhasz, A.; Horanyi, M.; Moragas-Klostermeyer, G.; Srama, R.

    2013-12-01

    Silica nanoparticles as indicator of hydrothermal activities at Enceladus ocean floor F. Postberg, H.-W. Hsu, Y. Sekine, S. Kempf, A. Juhasz, M. Horanyi, G. Moragas-Klostermeyer, R. Srama Silica serves as a unique indicator of hydrothermal activities on Earth as well as on Mars. Here we report the Cassini Cosmic Dust Analyser (CDA) observation of nanosilica particles from the Saturnian system. Based on their interaction with the solar wind electromagnetic fields, these charged nanosilica particles, so-called stream particles, are found to be originated in Saturn's E ring, indicating Enceladus being their ultimate source. CDA stream particle mass spectra reveal a metal-free but silicon-rich composition that is only plausible for nearly pure silica particles. The size range derived from our measurements confines the size of these particles to a radius of 2 - 8 nm. The unique properties of nano-grains with the observed composition and size are a well-known phenomenon on Earth and their formation requires specific hydrothermal rock-water interactions. The observation of Saturnian nanosilica particles thus serves as an evidence of hydrothermal activities at the interface of Enceladus subsurface ocean and its rocky core. Considering plasma erosion as the major mechanism of releasing embedded nanosilica particles from their carriers, the much larger E ring ice grains, our dynamical model and CDA observation provide a lower limit on the average nanosilica concentration in E ring grains. Together with dedicated hydrothermal experiments (Sekine at al., 2013) this can be translated into constraints on the hydrothermal activities on Enceladus. Measurements and experiments both point at dissolved silica concentrations at the ocean floor in the order of 1 - 3 mMol. The hydrothermal reactions likely take place with a pristine, chondritic rock composition at temperature higher than 130°C (Sekine at al. 2013). Colloidal nano-silica forms upon supersaturation during cooling of the

  18. Innate Immune Activation Through Nalp3 Inflammasome Sensing of Asbestos and Silica

    PubMed Central

    Dostert, Catherine; Pétrilli, Virginie; Van Bruggen, Robin; Steele, Chad; Mossman, Brooke T; Tschopp, Jürg

    2008-01-01

    The inhalation of airborne pollutants, such as asbestos or silica, is linked to inflammation of the lung, fibrosis, and lung cancer. How the presence of pathogenic dust is recognized and how chronic inflammatory diseases are triggered are poorly understood. Here, we show that asbestos and silica are sensed by the Nalp3 inflammasome, whose subsequent activation leads to interleukin 1β secretion. Inflammasome activation is triggered by reactive oxygen species, which are generated by a NADPH oxidase upon particle phagocytosis (NADPH is the reduced form of nicotinamide adenine dinucleotide phosphate). In a model of asbestos inhalation, Nalp3−/− mice showed diminished recruitment of inflammatory cells to the lungs, paralleled by lower cytokine production. Our findings implicate the Nalp3 inflammasome in particulate matter–related pulmonary diseases and support its role as a major proinflammatory “danger” receptor. PMID:18403674

  19. Immobilization of ruthenium phthalocyanine on silica-coated multi-wall partially oriented carbon nanotubes: Electrochemical detection of fenitrothion pesticide

    SciTech Connect

    Canevari, Thiago C.; Prado, Thiago M.; Cincotto, Fernando H.; Machado, Sergio A.S.

    2016-04-15

    Highlights: • Hybrid material, SiO{sub 2}/MWCNTs containing ruthenium phthalocyanine (RuPc) synthesized in situ. • Silica containing multi-walled carbon nanotube partially oriented. • Determination of pesticide fenitrothion in orange juice. - Abstract: This paper reports on the determination of the pesticide fenitrothion using a glassy carbon electrode modified with silica-coated, multi-walled, partially oriented carbon nanotubes, SiO{sub 2}/MWCNTs, containing ruthenium phthalocyanine (RuPc) synthesized in situ. The hybrid SiO{sub 2}/MWCNTs/RuPc material was characterized by UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and differential pulse voltammetry. The modified electrode showed well-defined peaks in the presence of fenitrothion in acetate buffer, pH 4.5, with a sensitivity of 0.0822 μA μM{sup −1} mm{sup −2} and a detection limit of 0.45 ppm. Notably, the modified SiO{sub 2}/MWCNTs/RuPc electrodes with did not suffer from significant influences in the presence of other organophosphorus pesticides during the determination of the fenitrothion pesticide. Moreover, this modified electrode showed excellent performance in the determination of fenitrothion in orange juice.

  20. Treatment with activated carbon and other adsorbents as an effective method for the removal of volatile compounds in agricultural distillates.

    PubMed

    Balcerek, Maria; Pielech-Przybylska, Katarzyna; Patelski, Piotr; Dziekońska-Kubczak, Urszula; Jusel, Tomaš

    2017-02-08

    This study investigates the effect of treatment with activated carbon and other adsorbents on the chemical composition and organoleptics of a barley malt-based agricultural distillate. Contact with activated carbon is one of the methods by which the quality of raw distillates and spirit beverages can be improved. Samples placed in contact with 1 g activated carbon (SpiritFerm) per 100 ml distillate with ethanol content of 50% v/v for 1 h showed the largest reductions in the concentrations of most volatile compounds (aldehydes, alcohols, esters). Increasing the dose of adsorbent to over 1 g 100 ml(-1) did not improve the purity of the agricultural distillate significantly. Of the tested compounds, acetaldehyde and methanol showed the lowest adsorption on activated carbon. The lowest concentrations of these congeners (expressed in mg l(-1) alcohol 100% v/v) were measured in solutions with ethanol contents of 70-80% v/v, while solutions with an alcoholic strength by volume of 40% did not show statistically significant decreases in these compounds in relation the control sample. The reductions in volatile compounds were compared with those for other adsorbents based on silica or activated carbon and silica. An interesting alternative to activated carbon was found to be an adsorbent prepared from activated carbon and silica (Spiricol). Treatment with this adsorbent produced distillate with the lowest concentrations of acetaldehyde and isovaleraldehyde, and led to the greatest improvement in its organoleptics.

  1. A dual-emitting core-shell carbon dot-silica-phosphor composite for white light emission

    NASA Astrophysics Data System (ADS)

    Chen, Yonghao; Lei, Bingfu; Zheng, Mingtao; Zhang, Haoran; Zhuang, Jianle; Liu, Yingliang

    2015-11-01

    A unique dual-emitting core-shell carbon dot-silica-phosphor (CDSP) was constructed from carbon dots (CDs), tetraethoxysilane (TEOS) and Sr2Si5N8:Eu2+ phosphor through a one-pot sol-gel method. Blue emitting CDs uniformly disperse in the silica layer covering the orange emitting phosphor via a polymerization process, which makes CDSP achieve even white light emission. Tunable photoluminescence of CDSP is observed and the preferable white light emission is achieved through changing the excitation wavelength or controlling the mass ratio of the phosphor. When CDSP powders with a phosphor rate of 3.9% and 5.1% are excited at a wavelength of 400 nm, preferable white light emission is observed, with Commission Internationale de l'Eclairage (CIE) coordinates of (0.32, 0.32) and (0.34, 0.32), respectively. Furthermore, CDSP can mix well with epoxy resin to emit strong and even white light, and based on this, a CDSP-based white LED with a high colour rendering index (CRI) of 94 was fabricated.A unique dual-emitting core-shell carbon dot-silica-phosphor (CDSP) was constructed from carbon dots (CDs), tetraethoxysilane (TEOS) and Sr2Si5N8:Eu2+ phosphor through a one-pot sol-gel method. Blue emitting CDs uniformly disperse in the silica layer covering the orange emitting phosphor via a polymerization process, which makes CDSP achieve even white light emission. Tunable photoluminescence of CDSP is observed and the preferable white light emission is achieved through changing the excitation wavelength or controlling the mass ratio of the phosphor. When CDSP powders with a phosphor rate of 3.9% and 5.1% are excited at a wavelength of 400 nm, preferable white light emission is observed, with Commission Internationale de l'Eclairage (CIE) coordinates of (0.32, 0.32) and (0.34, 0.32), respectively. Furthermore, CDSP can mix well with epoxy resin to emit strong and even white light, and based on this, a CDSP-based white LED with a high colour rendering index (CRI) of 94 was fabricated

  2. The Impact of Silica Nanoparticle Design on Cellular Toxicity and Hemolytic Activity

    PubMed Central

    Yu, Tian; Malugin, Alexander; Ghandehari, Hamidreza

    2011-01-01

    Understanding the toxicity of silica nanoparticles (SiO2) on the cellular level is crucial for rational design of these nanomaterials for biomedical applications. Herein, we explore the impacts of geometry, porosity and surface charge of SiO2 on cellular toxicity and hemolytic activity. Nonporous Stöber silica nanospheres (115 nm diameter), mesoporous silica nanospheres (120 nm diameter, aspect ratio 1), mesoporous silica nanorods with aspect ratio of 2, 4 and 8 (width by length 80 × 200 nm, 150 × 600 nm, 130 × 1000 nm) as well as their cationic counterparts were evaluated on macrophages, lung carcinoma cells, and human erythrocytes. It was shown that the toxicity of SiO2 is cell-type dependent and that surface charge and pore size govern cellular toxicity. Using inductively coupled plasma mass spectrometry, the cellular association of SiO2 was quantitated with the association amount increasing in the following order: mesoporous SiO2 (aspect ratio 1, 2, 4, 8) < amine-modified mesoporous SiO2 (aspect ratio 1, 2, 4, 8) < amine-modified nonporous Stöber SiO2 < nonporous Stöber SiO2. Geometry did not seem to influence the extent of SiO2 association at early or extended time points. The level of cellular association of the nanoparticles was directly linked to the extent of plasma membrane damage, suggesting a biological cause-and-effect relationship. Hemolysis assay showed that the hemolytic activity was porosity- and geometry- dependent for bare SiO2 and surface charge-dependent for amine-modified SiO2. A good correlation between hemolytic activity and cellular association was found on a similar dosage basis. These results can provide useful guidelines for the rational design of SiO2 in nanomedicine. PMID:21630682

  3. Engineering catalytic activity via ion beam bombardment of catalyst supports for vertically aligned carbon nanotube growth

    SciTech Connect

    Islam, A. E.; Zakharov, D.; Stach, E. A.; Nikoleav, P.; Amama, P. B.; Sargent, G.; Saber, S.; Huffman, D.; Erford, M.; Semiatin, S. L.; Maruyama, B.

    2015-09-16

    Carbon nanotube growth depends on the catalytic activity of metal nanoparticles on alumina or silica supports. The control on catalytic activity is generally achieved by variations in water concentration, carbon feed, and sample placement on a few types of alumina or silica catalyst supports obtained via thin film deposition. We have recently expanded the choice of catalyst supports by engineering inactive substrates like c-cut sapphire via ion beam bombardment. The deterministic control on the structure and chemistry of catalyst supports obtained by tuning the degree of beam-induced damage have enabled better regulation of the activity of Fe catalysts only in the ion beam bombarded areas and hence enabled controllable super growth of carbon nanotubes. A wide range of surface characterization techniques were used to monitor the catalytically active surface engineered via ion beam bombardment. The proposed method offers a versatile way to control carbon nanotube growth in patterned areas and also enhances the current understanding of the growth process. As a result, with the right choice of water concentration, carbon feed and sample placement, engineered catalyst supports may extend the carbon nanotube growth yield to a level that is even higher than the ones reported here, and thus offers promising applications of carbon nanotubes in electronics, heat exchanger, and energy storage.

  4. Engineering catalytic activity via ion beam bombardment of catalyst supports for vertically aligned carbon nanotube growth

    DOE PAGES

    Islam, A. E.; Zakharov, D.; Stach, E. A.; ...

    2015-09-16

    Carbon nanotube growth depends on the catalytic activity of metal nanoparticles on alumina or silica supports. The control on catalytic activity is generally achieved by variations in water concentration, carbon feed, and sample placement on a few types of alumina or silica catalyst supports obtained via thin film deposition. We have recently expanded the choice of catalyst supports by engineering inactive substrates like c-cut sapphire via ion beam bombardment. The deterministic control on the structure and chemistry of catalyst supports obtained by tuning the degree of beam-induced damage have enabled better regulation of the activity of Fe catalysts only inmore » the ion beam bombarded areas and hence enabled controllable super growth of carbon nanotubes. A wide range of surface characterization techniques were used to monitor the catalytically active surface engineered via ion beam bombardment. The proposed method offers a versatile way to control carbon nanotube growth in patterned areas and also enhances the current understanding of the growth process. As a result, with the right choice of water concentration, carbon feed and sample placement, engineered catalyst supports may extend the carbon nanotube growth yield to a level that is even higher than the ones reported here, and thus offers promising applications of carbon nanotubes in electronics, heat exchanger, and energy storage.« less

  5. Preparation of aluminum-containing mesoporous silica with hierarchical macroporous architecture and its enhanced catalytic activities.

    PubMed

    Kamegawa, Takashi; Tanaka, Shota; Seto, Hiroki; Zhou, Dayang; Yamashita, Hiromi

    2013-08-28

    Aluminum-containing mesoporous silica with hierarchical macroporous architecture (Al-MMS) was successfully prepared using a solvent evaporation method through the combination of precursor solution for synthesis of Al-containing mesoporous silica (Al-MS) and poly(methyl methacrylate) (PMMA) colloidal crystals as a hard template. The porous structure and the state of aluminum were investigated using various characterization techniques. The construction of combined structure of Al-MMS, i.e., hierarchical macroporous architecture consisting of thin mesoporous silica frameworks, led to the formation of many mesopore entrances and the shortening of the mesoporous channels. In the tetrahydropyranylation of linear alcohols with dihydropyran (DHP), Al-MMS exhibited higher catalytic activities for the formation of corresponding tetrahydropyranyl ethers as compared to Al-MS. The advantageous structure of Al-MMS enables the efficient transport of reactants to the catalytically active sites, which realizes the significant enhancement of catalytic performances in the reaction of DHP with alcohols having longer alkyl chains.

  6. A porous silica rock ("tripoli") in the footwall of the Jurassic Úrkút manganese deposit, Hungary: composition, and origin through carbonate dissolution

    USGS Publications Warehouse

    Polgari, Marta; Szabo, Zoltan; Szabo-Drubina, Magda; Hein, James R.; Yeh, Hsueh-Wen

    2005-01-01

    The mineralogical, chemical, and isotopic compositions were determined for a white tripoli from the footwall of the Jurassic Úrkút Mn-oxide ore deposit in the Bakony Mountains, Hungary. The tripoli consists of quartz and chalcedony, with SiO2 contents up to 100 wt.%; consequently, trace-element contents are very low. Oxygen isotopes and quartz crystallinity indicate a low-temperature diagenetic origin for this deposit. The tripoli was formed by dissolution of the carbonate portion of the siliceous (sponge spicules) Isztimér Limestone. Dissolution of the carbonate was promoted by inorganic and organic acids generated during diagensis and left a framework composed of diagenetic silica that preserved the original volume of the limestone layer. The relative enrichment of silica and high porosity is the result of that carbonate dissolution. The silty texture of this highly friable rock is due to the structurally weak silica framework.

  7. Experimental study on heat transfer of supercritical carbon dioxide in a long silica-based porous-media tube

    NASA Astrophysics Data System (ADS)

    Hsieh, Jui-Ching; Lin, David T. W.; Lee, Bo-Heng; Chung, Ming-Che

    2017-03-01

    The heat transfer phenomena of supercritical carbon dioxide were experimentally investigated in a vertical tube containing silica-based porous media. The experiment was conducted at various levels of static pressure, flow rates, and initial wall temperatures as well as with silica sand of porous media in a long test section to study the heat transfer characteristics of supercritical carbon dioxide (CO2). The results indicated that the average heat transfer coefficient and outlet temperature at an initial wall temperature of 150 °C were higher and lower than that of 200 °C. The heat transfer performance was significantly influenced by flow rate of supercritical CO2. The porous media was provided large heat exchange surface between particles and CO2 to increase the heat transfer coefficient, especially when small diameter of particles. When the inlet temperature was higher than the pseudocritical temperature, the heat transfer coefficient sharply dropped when x/L ≥ 0.5, because of the development of a thermal boundary and the decrease of CO2 thermophysical properties of CO2 in a far pseudocritical temperature. When the pseudocritical temperature was higher than the inlet temperature of the fluid, the local heat transfer coefficient was affected by a thermal boundary and thermophysical properties of CO2 in pseudocritical point at a higher initial wall temperature or lower supercritical pressure when x/L ≤ 0.75; only the thermophysical properties of supercritical CO2 in pseudocritical point played a pivotal role when x/L > 0.75 at a lower initial wall temperature or higher supercritical pressure. In the present study, the supercritical pressure of 10.5 MPa constituted an optimal operating condition for supercritical CO2 a long silica-based porous-media tube because of the high heat transfer performance at 150 and 200 °C.

  8. Technique for surface oxidation of activated carbon

    SciTech Connect

    Sircar, S.; Golden, T.C.

    1987-10-27

    A method of activating a carbon adsorbent is described, which comprises oxidizing the surface of the carbon adsorbent with a mild oxidizing acid in the presence of a metal oxidation catalyst at an elevated temperature and boiling the mixture of the carbon adsorbent, mild oxidizing acid and metal oxidation catalyst to dryness. Then rinse the surface oxidizing carbon adsorbent with water; and dry the rinsed surface oxidized carbon adsorbent. In a process for the removal of water or carbon dioxide from a gas stream containing water or carbon dioxide of the type wherein the gas stream containing water or carbon dioxide is contacted with a solid phase adsorbent under pressure-swing adsorption or thermal-swing adsorption processing conditions, the improvement is described comprising utilizing an adsorbent produced by the activation of a carbon adsorbent. The activation comprises oxidizing the surface of the carbon adsorbent with a mold oxidizing acid in the presence of a metal oxidation catalyst at an elevated temperature and boiling the mixture of the carbon adsorbent, mild oxidizing acid and metal oxidation catalyst to dryness. Then rinse the surface oxidized carbon adsorbent with water; and dry the rinsed surface oxidized carbon adsorbent.

  9. Electrospun highly ordered mesoporous silica-carbon composite nanofibers for rapid extraction and prefractionation of endogenous peptides.

    PubMed

    Zhu, Gang-Tian; Chen, Xi; He, Xiao-Mei; Wang, Han; Zhang, Zheng; Feng, Yu-Qi

    2015-03-09

    A simple method was developed for the preparation of ordered mesoporous silica-carbon composite nanofibers (OMSCFs). The OMSCFs exhibited high carbon content, continuously long fibrous properties, uniform accessible mesopores, and a large surface area. The OMSCFs were also found to have ion-exchange capacity. On the basis of the size-exclusion effect of the mesopores and mixed-mode hydrophobic/ion-exchange interactions, the OMSCFs were applied for rapid enrichment of endogenous peptides by using a miniaturized solid-phase extraction format. The adsorption mechanism was studied, and the eluting solution was optimized with standard peptide/protein solutions and protein digests. Employing a successive three-step elution strategy, followed by LC-MS/MS analysis, led to excellent performance with this approach in the extraction and prefractionation of peptides from human serum.

  10. Tuning of an active photonic crystal cavity by an hybrid silica/silicon near-field probe.

    PubMed

    Le Gac, G; Rahmani, A; Seassal, C; Picard, E; Hadji, E; Callard, S

    2009-11-23

    The influence of a near-field tip on the spectral characteristics of a resonant mode of an active photonic crystal micro-cavity was investigated. The wavelength shift of the mode was theoretically and experimentally demonstrated and evaluated as a function of the nature and the position of the tip above the cavity. Experiment showed that the shift induced is ten times higher with a Si-coated silica probe than with a bare silica tip: a shift until 2 nm was reached with Si-coated tip whereas the shift with bare silica tip is in the range of the tenth of nanometer, for wavelengths around 1,55 microm.

  11. Adsorption of carbon monoxide on activated carbon tin ligand

    NASA Astrophysics Data System (ADS)

    Mohamad, A. B.; Iyuke, S. E.; Daud, W. R. W.; Kadhum, A. A. H.; Fisal, Z.; Al-Khatib, M. F.; Shariff, A. M.

    2000-09-01

    Activated carbon was impregnated with 34.57% SnCl 2·2H 2O salt and then dried at 180°C to produce AC-SnO 2 to improve its adsorptive interaction with CO. Besides the fact that activated carbon has its original different pore sizes for normal gas phase CO adsorption (as in the case of pure carbon), the impregnated carbon has additional CO adsorption ability due to the presence of O -(ads) on the active sites. AC-SnO 2 proved to be a superior adsorber of CO than pure carbon when used for H 2 purification in a PSA system. Discernibly, the high adsorptive selectivity of AC-SnO 2 towards gas phase CO portrays a good future for the applicability of this noble adsorbent, since CO has become a notorious threat to the global ecosystem due to the current level of air pollution.

  12. Nano-Welding of Multi-Walled Carbon Nanotubes on Silicon and Silica Surface by Laser Irradiation

    PubMed Central

    Yuan, Yanping; Chen, Jimin

    2016-01-01

    In this study, a continuous fiber laser (1064 nm wavelength, 30 W/cm2) is used to irradiate multi-walled carbon nanotubes (MWCNTs) on different substrate surfaces. Effects of substrates on nano-welding of MWCNTs are investigated by scanning electron microscope (SEM). For MWCNTs on silica, after 3 s irradiation, nanoscale welding with good quality can be achieved due to breaking C–C bonds and formation of new graphene layers. While welding junctions can be formed until 10 s for the MWCNTs on silicon, the difference of irradiation time to achieve welding is attributed to the difference of thermal conductivity for silica and silicon. As the irradiation time is prolonged up to 12.5 s, most of the MWCNTs are welded to a silicon substrate, which leads to their frameworks of tube walls on the silicon surface. This is because the accumulation of absorbed energy makes the temperature rise. Then chemical reactions among silicon, carbon and nitrogen occur. New chemical bonds of Si–N and Si–C achieve the welding between the MWCNTs and silicon. Vibration modes of Si3N4 appear at peaks of 363 cm−1 and 663 cm−1. There are vibration modes of SiC at peaks of 618 cm−1, 779 cm−1 and 973 cm−1. The experimental observation proves chemical reactions and the formation of Si3N4 and SiC by laser irradiation.

  13. Pd-N-Heterocyclic Carbene (NHC) Organic Silica: Synthesis and Application in Carbon-Carbon Coupling Reactions

    EPA Science Inventory

    The first Pd-N-heterocyclic carbene (NHC) complex in the form of organic silica was prepared using sol-gel method and its application in Heck and Suzuki reaction were demonstrated. These C-C coupling reactions proceeded efficiently under the influence of microwave irradiation, wi...

  14. Electrooxidation of nitrite on a silica-cerium mixed oxide carbon paste electrode.

    PubMed

    Silveira, Gustavo; de Morais, Andréia; Villis, Paulo César Mendes; Maroneze, Camila Marchetti; Gushikem, Yoshitaka; Lucho, Alzira Maria Serpa; Pissetti, Fábio Luiz

    2012-03-01

    A silica-cerium mixed oxide (SiCe) was prepared by the sol-gel process, using tetraethylorthosilicate and cerium nitrate as precursors and obtained as an amorphous solid possessing a specific surface area of 459 m(2) g(-1). Infrared spectroscopy of the SiCe material showed the formation of the Si-O-Ce linkage in the mixed oxide. Scanning electron microscopy/energy dispersive spectroscopy indicated that the cerium oxide particles were homogenously dispersed on the matrix surface. X-ray diffraction and (29)Si solid-state nuclear magnetic resonance implied non-crystalline silica matrices with chemical environments that are typical for silica-based mixed oxides. X-ray photoelectron spectroscopy showed that Ce was present in approximately equal amounts of both the 3+ and 4+ oxidation states. Cyclic voltammetry data of electrode prepared from the silica-cerium mixed oxide showed a peak for oxidation of Ce(3+)/Ce(4+) at 0.76 V and electrochemical impedance spectroscopy equivalent circuit indicated a porous structure with low charge transfer resistance. In the presence of nitrite, the SiCe electrode shows an anodic oxidation peak at 0.76 V with a linear response as the concentration of the analyte increases from 3×10(-5) at 3.9×10(-3) mol L(-1).

  15. Synthesis of Silica-Carbon Nanotube Composite Materials and Their Application for Laser Systems

    NASA Astrophysics Data System (ADS)

    Pilipavicius, J.; Sakalauskas, D.; Beganskiene, A.; Kareiva, A.

    2012-08-01

    Currently, fabrication of CNT and polymer composites for saturable absorbers is very popular. But due to nature of organic polymer matrix, these composites are unstable on higher temperatures or in high energy light exposition. Therefore a sol-gel process for the fabrication for inorganic (i.e. silica) or semi-organic (organic-modified silica) matrix can be a promising way to produce photo-chemically and thermally stable CNT composites. In this work we investigated SWCNT's solubility in ethanol using different surfactants - Triton, polyvinylpyrrolidone, and Poly(4-vinylpyridine). Most stable colloidal solution was obtained using a P4VP as surfactant - solutions were stable up to 6 weeks. Therefore this surfactant was used for the fabrication of SWCNT/Silica composite coatings. SWCNT's was directly dispensed in a colloidal silica sol and coatings made by spin-coating technique. Samples were investigated under optical, atomic force microscopy methods, and optical non-linearity was measured. Thermal stability was investigated using Raman spectroscopy.

  16. Study on Au nanoparticles, TiO2 nanoclusters, and SiO2 nanoshells coated multi-wall carbon nanotubes/silica gel-glass

    NASA Astrophysics Data System (ADS)

    Zheng, Chan; Chen, Wenzhe; Ye, Xiaoyun

    2012-05-01

    Multi-wall carbon nanotubes (MWCNTs) coated with crystalline Au nanoparticles, TiO2 nanoclusters, and amorphous SiO2 nanoshells, to represent conductors, semiconductors, and insulators, respectively, were embedded in transparent silica gel-glass. The coated MWCNT/silica gel-glasses were prepared by the sol-gel technique. Scanning electron microscopy (SEM), X-ray diffraction (XRD), UV/Vis spectroscopy, Fourier Transform Infrared (FT-IR) spectroscopy and pore structure measurements were used to investigate the morphology, structure, and texture properties of the coated MWCNT/silica gel-glasses. The hardness and elastic modulus of the silica gel-glasses were characterized using a Nanoindenter and found to depend on the coating materials. Coating the MWCNTs with crystalline Au nanoparticles, TiO2 nanoclusters, and amorphous SiO2 nanoshells leads to an increase in the hardness and elastic modulus, despite the higher specific surface area and pore volume of the coated MWCNT/silica gel-glasses. Consequently, we can conclude that the mechanical properties of coated MWCNT/silica gel-glass might be greatly dependent on the guest MWCNTs rather than the silica gel matrix.

  17. Preparation of a mercaptopropyl bonded silica intermediate in supercritical carbon dioxide: synthesis, characterisation and chromatography of a quinine based chiral stationary phase.

    PubMed

    Scully, Norma M; O'Sullivan, Gerard P; Healy, Liam O; Glennon, Jeremy D; Dietrich, Benjamin; Albert, Klaus

    2007-07-13

    This research examines the preparation of a mercaptopropyl bonded silica intermediate in supercritical carbon dioxide (sc-CO(2)) and the subsequent conversion in sc-CO(2) to a quinine derived chiral stationary phase (CSP). The effects of reaction temperature, pressure and time on the surface coverage of the silica intermediate were investigated when porous silica particles (Exsil-Avanti, 3microm) were reacted with 3-trimethoxymercaptopropylsilane in sc-CO(2). We present results which demonstrate that a stable mercaptopropyl bonded silica intermediate can be successfully prepared under supercritical conditions of 40 degrees C, 483bar, in a substantially reduced reaction time of 1h with superior surface coverages compared to organic solvent based methods. The further utility of this supercritical fluid technology was demonstrated by the free radical addition of a quinine derived chiral selector onto a mercaptopropyl bonded silica intermediate in sc-CO(2). This supercritical fluid generated chiral stationary phase (CSP) was utilised for the direct LC enantioseparation of a series of 3,5-dinitrobenzoyl (DNB) amino acids. Bonded silica samples were characterised using elemental analysis, diffuse reflectance infrared fourier transform (DRIFT) spectroscopy, solid state (13)C and (29)Si CP-MAS NMR spectroscopy, and thermogravimetric analysis (TGA). This supercritical fluid functionalisation approach offers an efficient and cleaner alternative to existing organic solvent based approaches for the preparation of bonded silica phases.

  18. Synthesis of N-halamine-functionalized silica-polymer core-shell nanoparticles and their enhanced antibacterial activity

    NASA Astrophysics Data System (ADS)

    Dong, Alideertu; Huang, Jinfeng; Lan, Shi; Wang, Tao; Xiao, Linghan; Wang, Weiwei; Zhao, Tianyi; Zheng, Xin; Liu, Fengqi; Gao, Ge; Chen, Yuxin

    2011-07-01

    N-halamine-functionalized silica-polymer core-shell nanoparticles with enhanced antibacterial activity were synthesized through the encapsulation of silica nanoparticles as support with polymeric N-halamine. The as-synthesized nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR). These N-halamine-functionalized silica-polymer core-shell nanoparticles displayed powerful antibacterial performance against both Gram-positive bacteria and Gram-negative bacteria, and their antibacterial activities have been greatly improved compared with their bulk counterparts. Therefore, these N-halamine-functionalized silica-polymer core-shell nanoparticles have the potential for various significant applications such as in medical devices, healthcare products, water purification systems, hospitals, dental office equipment, food packaging, food storage, household sanitation, etc.

  19. Silica-tin nanotubes prepared from rice husk ash by sol-gel method: Characterization and its photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Adam, Farook; Appaturi, Jimmy Nelson; Thankappan, Radhika; Nawi, Mohd Asri Mohd

    2010-11-01

    Silica-tin material has been synthesized by simple sol-gel method using rice husk ash as the source of silica and cetyltrimethylammonium bromide as the surfactant at room temperature. Calcination of the material at 500 °C for 5 h gave nanotubes with external diameter of 2-4 nm and an internal diameter of 1-2 nm. The BET specific surface area was found to be 607 m 2 g -1. Nitrogen sorption analysis exhibits a type IV isotherm with H3 hysteresis loop. The powder X-ray diffraction pattern showed that the material is amorphous. The photocatalytic activity of the prepared material was studied towards degradation of methylene blue under UV-irradiation. According to the experimental results the silica-tin nanotubes exhibit high photocatalytic activity compared to pure rice husk silica.

  20. [Study on influence between activated carbon property and immobilized biological activated carbon purification effect].

    PubMed

    Wang, Guang-zhi; Li, Wei-guang; He, Wen-jie; Han, Hong-da; Ding, Chi; Ma, Xiao-na; Qu, Yan-ming

    2006-10-01

    By means of immobilizing five kinds of activated carbon, we studied the influence between the chief activated carbon property items and immobilized bioactivated carbon (IBAC) purification effect with the correlation analysis. The result shows that the activated carbon property items which the correlation coefficient is up 0.7 include molasses, abrasion number, hardness, tannin, uniform coefficient, mean particle diameter and effective particle diameter; the activated carbon property items which the correlation coefficient is up 0.5 include pH, iodine, butane and tetrachloride. In succession, the partial correlation analysis shows that activated carbon property items mostly influencing on IBAC purification effect include molasses, hardness, abrasion number, uniform coefficient, mean particle diameter and effective particle diameter. The causation of these property items bringing influence on IBAC purification is that the activated carbon holes distribution (representative activated carbon property item is molasses) provides inhabitable location and adjust food for the dominance bacteria; the mechanical resist-crash property of activated carbon (representative activated carbon property items: abrasion number and hardness) have influence on the stability of biofilm; and the particle diameter size and distribution of activated carbon (representative activated carbon property items: uniform coefficient, mean particle diameter and effective particle diameter) can directly affect the force of water in IBAC filter bed, which brings influence on the dominance bacteria immobilizing on activated carbon.

  1. Antiproliferative effect of Antrodia camphorata polysaccharides encapsulated in chitosan-silica nanoparticles strongly depends on the metabolic activity type of the cell line

    NASA Astrophysics Data System (ADS)

    Kong, Zwe-Ling; Chang, Jenq-Sheng; Chang, Ke Liang B.

    2013-09-01

    Chitosan molecules interact with silica and encapsulate the Antrodia camphorata extract (ACE) polysaccharides to form composite nanoparticles. The nanoparticle suspensions of ACE polysaccharides encapsulated in silica-chitosan and silica nanoparticles approach an average particle size of 210 and 294 nm in solution, respectively. The encapsulation efficiencies of ACE polysaccharides are 66 and 63.5 %, respectively. Scanning electron micrographs confirm the formation of near-spherical nanoparticles. ACE polysaccharides solution had better antioxidative capability than ACE polysaccharides encapsulated in silica or silica-chitosan nanoparticles suspensions. The antioxidant capacity of nanoparticles increases with increasing dissolution time. The antitumor effects of ACE polysaccharides, ACE polysaccharides encapsulated in silica, or silica-chitosan nanoparticles increased with increasing concentration of nanoparticles. This is the first report demonstrating the potential of ACE polysaccharides encapsulated in chitosan-silica nanoparticles for cancer chemoprevention. Furthermore, this study suggests that antiproliferative effect of nanoparticle-encapsulated bioactive could significantly depend on the metabolic activity type of the cell line.

  2. Porous carbon-coated silica macroparticles as anode materials for lithium ion batteries: Effect of boric acid

    NASA Astrophysics Data System (ADS)

    Kim, Young-Kuk; Moon, Jong-Woo; Lee, Jung-Goo; Baek, Youn-Kyung; Hong, Seong-Hyun

    2014-12-01

    We report carbon-coated porous silica macroparticles (SiO2@C) prepared using polymeric templates and subsequent carbonization with sucrose for improved electrochemical energy storage in lithium-ion batteries (LIBs). In addition, boron is introduced to improve the stability of electrochemical cells by pyrolyzing mixtures of sucrose and boric acid (SiO2@C + B) under inert atmosphere. The initially large surface area of porous SiO2 (SBET ∼ 658 m2 g-1) is reduced to 102 m2 g-1 after carbonization and introduction of boric acid. Surface of both SiO2@C and SiO2@C + B are covered with amorphous carbon. In particular, SiO2@C + B particles containing borosilicate (Si-O-B) phase and B-O bondings and Si-C-O bondings are also detected from the X-ray photoelectron spectra. The SiO2@C + B macroparticles shows high reversible charge capacity up to 503 mAh g-1 after 103 cycles of Li intercalation/de-intercalation although initial capacity was 200 mAh g-1. The improved charge capacity of SiO2@C + B is attributed to formation of advantageous microstructures induced from boric acid.

  3. Enhanced adsorption of quaternary amine using modified activated carbon.

    PubMed

    Prahas, Devarly; Wang, M J; Ismadji, Suryadi; Liu, J C

    2014-01-01

    This study examined different methodologies to modify activated carbon (AC) for the removal of quaternary amine, tetramethylammonium hydroxide (TMAH), from water. Commercial carbon (WAC) was treated by nitric acid oxidation (NA-WAC), silica impregnation (SM-WAC0.5), and oxygen plasma (P10-WAC), and their characteristics and adsorption capacity were compared. The Langmuir model fitted the equilibrium adsorption data well under different pH. The maximum adsorption capacity of WAC was 27.77 mg/g, while those of NA-WAC, SM-WAC 0.5, and P10-WAC were 37.46, 32.83 and 29.03 mg/g, respectively. Nitric acid oxidation was the most effective method for enhancing the adsorption capacity of TMAH. Higher pH was favorable for TMAH adsorption. Desorption study revealed that NA-WAC had no considerable reduction in performance even after five cycles of regeneration by 0.1 N hydrochloric acid. It was proposed that electrostatic interaction was the main mechanism of TMAH adsorption on activated carbon.

  4. Carbon Nanofiber Incorporated Silica Based Aerogels with Di-Isocyanate Cross-Linking

    NASA Technical Reports Server (NTRS)

    Vivod, Stephanie L.; Meador, Mary Ann B.; Capadona, Lynn A.; Sullivan, Roy M.; Ghosn, Louis J.; Clark, Nicholas; McCorkle, Linda

    2008-01-01

    Lightweight materials with excellent thermal insulating properties are highly sought after for a variety of aerospace and aeronautic applications. (1) Silica based aerogels with their high surface area and low relative densities are ideal for applications in extreme environments such as insulators for the Mars Rover battery. (2) However, the fragile nature of aerogel monoliths prevents their widespread use in more down to earth applications. We have shown that the fragile aerogel network can be cross-linked with a di-isocyanate via amine decorated surfaces to form a conformal coating. (3) This coating reinforces the neck regions between secondary silica particles and significantly strengthens the aerogels with only a small effect on density or porosity. Scheme 1 depicts the cross-linking reaction with the di-isocyanate and exhibits the stages that result in polymer cross-linked aerogel monoliths.

  5. Surface Properties and Catalytic Performance of Activated Carbon Fibers Supported TiO2 Photocatalyst

    NASA Astrophysics Data System (ADS)

    Yang, Huifen; Fu, Pingfeng

    Activated carbon fibers supported TiO2 photocatalyst (TiO2/ACF) in felt-form was successfully prepared with a dip-coating process using organic silicon modified acrylate copolymer as a binder followed by calcination at 500°C in a stream of Ar gas. The photocatalyst was characterized by SEM, XRD, XPS, FTIR, and BET surface area. Most of carbon fibers were coated with uniformly distributed TiO2 clusters of nearly 100 nm. The loaded TiO2 layer was particulate for the organic binder in the compact film was carbonized. According to XPS and FTIR analysis, amorphous silica in carbon grains was synthesized after carbonizing organic silicon groups, and the Ti-O-Si bond was formed between the interface of loaded TiO2 and silica. Additionally, the space between adjacent carbon fibers still remained unfilled after TiO2 coating, into which both UV light and polluted solutions could penetrate to form a three-dimensional environment for photocatalytic reactions. While loaded TiO2 amount increased to 456 mg TiO2/1 g ACF, the TiO2/ACF catalyst showed its highest photocatalytic activity, and this activity only dropped about 10% after 12 successive runs, exhibiting its high fixing stability of coated TiO2.

  6. Novel silica surface charge density mediated control of the optical properties of embedded optically active materials and its application for fiber optic pH sensing at elevated temperatures.

    PubMed

    Wang, Congjun; Ohodnicki, Paul R; Su, Xin; Keller, Murphy; Brown, Thomas D; Baltrus, John P

    2015-02-14

    Silica and silica incorporated nanocomposite materials have been extensively studied for a wide range of applications. Here we demonstrate an intriguing optical effect of silica that, depending on the solution pH, amplifies or attenuates the optical absorption of a variety of embedded optically active materials with very distinct properties, such as plasmonic Au nanoparticles, non-plasmonic Pt nanoparticles, and the organic dye rhodamine B (not a pH indicator), coated on an optical fiber. Interestingly, the observed optical response to varying pH appears to follow the surface charge density of the silica matrix for all the three different optically active materials. To the best of our knowledge, this optical effect has not been previously reported and it appears universal in that it is likely that any optically active material can be incorporated into the silica matrix to respond to solution pH or surface charge density variations. A direct application of this effect is for optical pH sensing which has very attractive features that can enable minimally invasive, remote, real time and continuous distributed pH monitoring. Particularly, as demonstrated here, using highly stable metal nanoparticles embedded in an inorganic silica matrix can significantly improve the capability of pH sensing in extremely harsh environments which is of increasing importance for applications in unconventional oil and gas resource recovery, carbon sequestration, water quality monitoring, etc. Our approach opens a pathway towards possible future development of robust optical pH sensors for the most demanding environmental conditions. The newly discovered optical effect of silica also offers the potential for control of the optical properties of optically active materials for a range of other potential applications such as electrochromic devices.

  7. Separation of single-walled carbon nanotubes on silica gel. Materials morphology and Raman excitation wavelength affect data interpretation.

    PubMed

    Dyke, Christopher A; Stewart, Michael P; Tour, James M

    2005-03-30

    In this report, procedures are discussed for the enrichment of single-walled carbon nanotube (SWNT) types by simple filtration of the functionalized SWNTs through silica gel. This separation uses nanotube sidewall functionalization employing two different strategies. In the first approach, a crude mixture of metallic and semiconducting SWNTs was heavily functionalized with 4-tert-butylphenyl addends to impart solubility to the entire sample of SWNTs. Two major polarity fractions were rapidly filtered through silica gel, with the solvent being removed in vacuo, heated to 700 degrees C to remove the addends, and analyzed spectroscopically. The second approach uses two different aryldiazonium salts (one with a polar grafting group and one nonpolar), appended selectively onto the different SWNTs by means of titration and monitoring by UV analysis throughout the functionalization process. The different addends accentuate the polarity differences between the band-gap-based types permitting their partial separation on silica gel. Thermal treatment regenerated pristine SWNTs in enriched fractions. The processed samples were analyzed and characterized by Raman spectroscopy. A controlled functionalization method using 4-fluorophenyl and 4-iodophenyl addends was performed, and XPS analyses yielded data on the degree of functionalization needed to affect the van Hove singularities in the UV/vis/NIR spectra. Finally, we demonstrate that relative peak intensity changes in Raman spectra can be caused by morphological changes in SWNT bundling based on differing flocculation or deposition methods. Therefore a misleading impression of separations can result, underscoring the care needed in assessing efficacies in SWNT enrichment and the prerequisite use of multiple excitation wavelengths and similar flocculation or deposition methods in comparative analyses.

  8. Sorption of boron trifluoride by activated carbons

    SciTech Connect

    Polevoi, A.S.; Petrenko, A.E.

    1988-01-10

    The sorption of born trifluoride on AG-3, SKT, SKT-3, SKT-7, SKT-4A, SKT-6A, and SKT-2B carbons was investigated. The sorption isotherms for both vapors and gas were determined volumetrically. The coefficients of two equations described the sorption of BF/sub 3/ in the sorption of BF/sub 3/ on active carbons. Heats of sorption of BF/sub 3/ on the activated carbons are shown and the sorption isotherms and temperature dependences of the equilibrium pressure of BF/sub 3/ for activated carbons were presented. The values of the heats of sorption indicated the weak character of the reaction of BF/sub 3/ with the surface of the carbons. The equations can be used for calculating the phase equilibrium of BF/sub 3/ on carbons in a wider range of temperatures and pressures.

  9. Catalytic Growth of Macroscopic Carbon Nanofibers Bodies with Activated Carbon

    SciTech Connect

    Abdullah, N.; Muhammad, I. S.; Hamid, S. B. Abd.; Rinaldi, A.; Su, D. S.; Schlogl, R.

    2009-06-01

    Carbon-carbon composite of activated carbon and carbon nanofibers have been synthesized by growing Carbon nanofiber (CNF) on Palm shell-based Activated carbon (AC) with Ni catalyst. The composites are in an agglomerated shape due to the entanglement of the defective CNF between the AC particles forming a macroscopic body. The macroscopic size will allow the composite to be used as a stabile catalyst support and liquid adsorbent. The preparation of CNT/AC nanocarbon was initiated by pre-treating the activated carbon with nitric acid, followed by impregnation of 1 wt% loading of nickel (II) nitrate solutions in acetone. The catalyst precursor was calcined and reduced at 300 deg. C for an hour in each step. The catalytic growth of nanocarbon in C{sub 2}H{sub 4}/H{sub 2} was carried out at temperature of 550 deg. C for 2 hrs with different rotating angle in the fluidization system. SEM and N{sub 2} isotherms show the level of agglomeration which is a function of growth density and fluidization of the system. The effect of fluidization by rotating the reactor during growth with different speed give a significant impact on the agglomeration of the final CNF/AC composite and thus the amount of CNFs produced. The macrostructure body produced in this work of CNF/AC composite will have advantages in the adsorbent and catalyst support application, due to the mechanical and chemical properties of the material.

  10. Activation of the inflammasome by amorphous silica and TiO2 nanoparticles in murine dendritic cells.

    PubMed

    Winter, Meike; Beer, Hans-Dietmar; Hornung, Veit; Krämer, Ursula; Schins, Roel P F; Förster, Irmgard

    2011-09-01

    Nanomaterials are increasingly used in various food applications. In particular, nanoparticulate amorphous SiO2 is already contained, e.g., in spices. Since intestinal dendritic cells (DC) could be critical targets for ingested particles, we compared the in vitro effects of amorphous silica nanoparticles with fine crystalline silica, and micron-sized with nano-sized TiO2 particles on DC. TiO2- and SiO2-nanoparticles, as well as crystalline silica led to an upregulation of MHC-II, CD80, and CD86 on DC. Furthermore, these particles activated the inflammasome, leading to significant IL-1β-secretion in wild-type (WT) but not Caspase-1- or NLRP3-deficient mice. Silica nanoparticles and crystalline silica induced apoptosis, while TiO2 nanoparticles led to enhanced production of reactive oxygen species (ROS). Since amorphous silica and TiO2 nanoparticles had strong effects on the activation-status of DC, we suggest that nanoparticles, used as food additives, should be intensively studied in vitro and in vivo, to ensure their safety for the consumer.

  11. Artifactual prolongation of activated partial thromboplastin time with PEGylated compounds in silica-based assays.

    PubMed

    Murphy, Bethanne; Parrula, Maria C M; Perigard, Christopher J; Li, Jinze

    2014-12-01

    Conjugation of polyethylene glycol (PEG) to another molecule prolongs its half-life in the body, but has a potential to artifactually increase the activated partial thromboplastin time (aPTT) as measured with certain assays. Studies conducted in-house at Bristol-Myers Squibb using the STA-PTT Automate 5 assay, the routine assay used to measure aPTT, demonstrated prolongation of aPTT in plasma samples spiked in vitro with 40-kDa branched PEG (PEG40) conjugated compounds or PEG40 alone, but not in samples spiked with vehicle or non-PEGylated compound, suggesting that the interference is because of the PEG40 moiety. To investigate the cause of this phenomenon, cynomolgus monkey and rat plasma samples were spiked with different concentrations of PEG40 and the aPTT was measured using different proprietary assays. With one exception, prolongation of aPTT was observed with all assays containing silica as the contact activator. No changes in aPTT were noted in assays using kaolin as a contact activator. The findings indicated that the observed prolongation of aPTT is largely because of interference of PEG40 with the silica, but other features of the reagent mixture may also influence aPTT times.

  12. Heterogeneous copper-silica catalyst from agricultural biomass and its catalytic activity

    NASA Astrophysics Data System (ADS)

    Andas, Jeyashelly; Adam, Farook; Rahman, Ismail Ab.

    2013-11-01

    A series of highly mesoporous copper catalysts (5-20 wt.%) supported on silica rice husk were synthesized via sol-gel route at room temperature. The FT-IR and 29Si MAS NMR spectroscopic studies revealed the successful substitution of copper into the silica matrix. Copper in the +2 oxidation state was evidenced from the DR/UV-vis and XPS analyses. Introduction of copper up to 10 wt.% (RH-10Cu) results in a progressive enhancement in the BET surface area. The activity of the copper catalysts was studied in the liquid-phase oxidation of phenol with H2O2 yielding catechol (CAT) and hydroquinone (HQ). Phenol conversion was influenced by various experimental conditions such as temperature, catalyst dosage, molar ratio of reactants, nature of solvent and percentage metal loading. Excellent activity was achieved when 10 wt.% copper was used and decreased with further increase in the copper loading. RH-10Cu could be regenerated several times without significant loss in the catalytic activity.

  13. Antimicrobial activity of silica coated silicon nano-tubes (SCSNT) and silica coated silicon nano-particles (SCSNP) synthesized by gas phase condensation.

    PubMed

    Tank, Chiti; Raman, Sujatha; Karan, Sujoy; Gosavi, Suresh; Lalla, Niranjan P; Sathe, Vasant; Berndt, Richard; Gade, W N; Bhoraskar, S V; Mathe, Vikas L

    2013-06-01

    Silica-coated, silicon nanotubes (SCSNTs) and silica-coated, silicon nanoparticles (SCSNPs) have been synthesized by catalyst-free single-step gas phase condensation using the arc plasma process. Transmission electron microscopy and scanning tunneling microscopy showed that SCSNTs exhibited a wall thickness of less than 1 nm, with an average diameter of 14 nm and a length of several 100 nm. Both nano-structures had a high specific surface area. The present study has demonstrated cheaper, resistance-free and effective antibacterial activity in silica-coated silicon nano-structures, each for two Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) was estimated, using the optical densitometric technique, and by determining colony-forming units. The MIC was found to range in the order of micrograms, which is comparable to the reported MIC of metal oxides for these bacteria. SCSNTs were found to be more effective in limiting the growth of multidrug-resistant Staphylococcus aureus over SCSNPs at 10 μg/ml (IC 50 = 100 μg/ml).

  14. Catalytic activation of carbon-carbon bonds in cyclopentanones.

    PubMed

    Xia, Ying; Lu, Gang; Liu, Peng; Dong, Guangbin

    2016-11-24

    In the chemical industry, molecules of interest are based primarily on carbon skeletons. When synthesizing such molecules, the activation of carbon-carbon single bonds (C-C bonds) in simple substrates is strategically important: it offers a way of disconnecting such inert bonds, forming more active linkages (for example, between carbon and a transition metal) and eventually producing more versatile scaffolds. The challenge in achieving such activation is the kinetic inertness of C-C bonds and the relative weakness of newly formed carbon-metal bonds. The most common tactic starts with a three- or four-membered carbon-ring system, in which strain release provides a crucial thermodynamic driving force. However, broadly useful methods that are based on catalytic activation of unstrained C-C bonds have proven elusive, because the cleavage process is much less energetically favourable. Here we report a general approach to the catalytic activation of C-C bonds in simple cyclopentanones and some cyclohexanones. The key to our success is the combination of a rhodium pre-catalyst, an N-heterocyclic carbene ligand and an amino-pyridine co-catalyst. When an aryl group is present in the C3 position of cyclopentanone, the less strained C-C bond can be activated; this is followed by activation of a carbon-hydrogen bond in the aryl group, leading to efficient synthesis of functionalized α-tetralones-a common structural motif and versatile building block in organic synthesis. Furthermore, this method can substantially enhance the efficiency of the enantioselective synthesis of some natural products of terpenoids. Density functional theory calculations reveal a mechanism involving an intriguing rhodium-bridged bicyclic intermediate.

  15. Electrochemical determination of maltol in beverages with glassy carbon electrode and its silica sol-gel modified electrode.

    PubMed

    Di, Junwei; Bi, Shuping; Zhang, Feng

    2004-05-28

    The electrochemical behavior of maltol on a glassy carbon (GC) electrode was investigated. The results were applied to differential pulse voltammetric determination of maltol in beverages pretreated by ultrafiltration. Under the optimum experimental conditions, the linear range is 1x10(-5) to 6x10(-4)moll(-1) maltol and the relative standard deviation for 0.4mmoll(-1) maltol is 0.6% (n=9). The detection limit was 5mumoll(-1). Furthermore, silica sol-gel film on GC electrode could be used as suitable selective membrane, which integrated selective membrane on the electrode and substituted for the pretreatment of ultrafiltration. Under the above conditions, maltol was determined by semi-differential linear sweep voltammetry at a silica sol-gel modified GC electrode in the concentration range of 5x10(-6) to 5x10(-4)moll(-1). The detection limit was 2mumoll(-1) and the relative standard deviation for 0.1mmoll(-1) maltol was 0.7% (n=7). The proposed method is of sensitivity, simplicity, rapidness and no contamination. It had been applied to the direct determination of maltol in beverages such as grape wines, drinks and beers without any pretreatment. The results obtained with the present method were satisfactory with those obtained by spectrophotometry. It could be used as a simple and practical method for the determination of the flavor enhancer maltol in beverages.

  16. Making Activated Carbon by Wet Pressurized Pyrolysis

    NASA Technical Reports Server (NTRS)

    Fisher, John W.; Pisharody, Suresh; Wignarajah, K.; Moran, Mark

    2006-01-01

    A wet pressurized pyrolysis (wet carbonization) process has been invented as a means of producing activated carbon from a wide variety of inedible biomass consisting principally of plant wastes. The principal intended use of this activated carbon is room-temperature adsorption of pollutant gases from cooled incinerator exhaust streams. Activated carbon is highly porous and has a large surface area. The surface area depends strongly on the raw material and the production process. Coconut shells and bituminous coal are the primary raw materials that, until now, were converted into activated carbon of commercially acceptable quality by use of traditional production processes that involve activation by use of steam or carbon dioxide. In the wet pressurized pyrolysis process, the plant material is subjected to high pressure and temperature in an aqueous medium in the absence of oxygen for a specified amount of time to break carbon-oxygen bonds in the organic material and modify the structure of the material to obtain large surface area. Plant materials that have been used in demonstrations of the process include inedible parts of wheat, rice, potato, soybean, and tomato plants. The raw plant material is ground and mixed with a specified proportion of water. The mixture is placed in a stirred autoclave, wherein it is pyrolized at a temperature between 450 and 590 F (approximately between 230 and 310 C) and a pressure between 1 and 1.4 kpsi (approximately between 7 and 10 MPa) for a time between 5 minutes and 1 hour. The solid fraction remaining after wet carbonization is dried, then activated at a temperature of 500 F (260 C) in nitrogen gas. The activated carbon thus produced is comparable to commercial activated carbon. It can be used to adsorb oxides of sulfur, oxides of nitrogen, and trace amounts of hydrocarbons, any or all of which can be present in flue gas. Alternatively, the dried solid fraction can be used, even without the activation treatment, to absorb

  17. Silica-supported Au@hollow-SiO2 particles with outstanding catalytic activity prepared via block copolymer template approach.

    PubMed

    Shajkumar, Aruni; Nandan, Bhanu; Sanwaria, Sunita; Albrecht, Victoria; Libera, Marcin; Lee, Myong-Hoon; Auffermann, Gudrun; Stamm, Manfred; Horechyy, Andriy

    2017-04-01

    Catalytically active Au@hollow-SiO2 particles embedded in porous silica support (Au@hollow-SiO2@PSS) were prepared by using spherical micelles from poly(styrene)-block-poly(4-vinyl pyridine) block copolymer as a sacrificial template. Drastic increase of the shell porosity was observed after pyrolytic removal of polymeric template because the stretched poly(4-vinyl pyridine) chains interpenetrating with silica shell acted as an effective porogen. The embedding of Au@hollow-SiO2 particles in porous silica support prevented their fusion during pyrolysis. The catalytic activity of Au@hollow-SiO2@PSS was investigated using a model reaction of catalytic reduction of 4-nitrophenol and reductive degradation of Congo red azo-dye. Significantly, to the best of our knowledge, Au@hollow-SiO2@PSS catalyst shows the highest activity among analogous systems reported till now in literature. Such high activity was attributed to the presence of multiple pores within silica shell of Au@hollow-SiO2 particles and easy accessibility of reagents to the catalytically active sites of the ligand-free gold surface through the porous silica support.

  18. Immobilization of pectinase on silica-based supports: Impacts of particle size and spacer arm on the activity.

    PubMed

    Alagöz, Dilek; Tükel, S Seyhan; Yildirim, Deniz

    2016-06-01

    The pectinase was separately immobilized onto Florisil and nano silica supports through both glutaraldehyde and 3-glyoxypropyltrietoxysilane spacer arms. The effects of spacer arm, particle size of support and ionic liquids on the activities of pectinase preparations were investigated. The immobilization of pectinase onto Florisil and nano silica through 3-glyoxypropyltrietoxysilane spacer arm completely led to inactivation of enzyme; however, 10 and 75% pectinase activity were retained when it was immobilized through glutaraldehyde spacer arm onto Florisil and nano silica, respectively. The pectinase immobilized onto nano silica through glutaraldehyde spacer arm showed 6.3-fold higher catalytic efficiency than that of the pectinase immobilized onto Florisil through same spacer arm. A 2.3-fold increase in thermal stability of pectinase was provided upon immobilization onto nano silica at 35°C. The effects of IL/buffer mixture and volume ratio of IL/buffer mixture on the catalytic activities of free and immobilized pectinase preparations were also tested. All the pectinase preparations showed highest activity in 10% (v/v) 1-butyl-3-methylimidazolium hexafluorophosphate containing medium and their activities significantly affected from the concentration of 1-butyl-3-methylimidazolium hexafluorophosphate.

  19. Effects of silica fume, latex, methylcellulose, and carbon fibers on the thermal conductivity and specific heat of cement paste

    SciTech Connect

    Fu, X.; Chung, D.D.L.

    1997-12-01

    Due to their poor conductivity, latex (20--30% by weight of cement), methylcellulose (0.4--0.8% by weight of cement), and silica fume (15% by weight of cement) decreased the thermal conductivity of cement paste by up to 46%. In addition, these admixtures increased the specific heat of cement paste by up to 10%. The thermal conductivity decreased and the specific heat increased with increasing latex or methylcellulose content. Short carbon fibers (0.5--1.0% by weight of cement) either did not change or decreased the thermal conductivity of cement paste, such that the thermal conductivity decreased with increasing fiber content due to the increase in air void content. The fibers increased the specific heat due to the contribution of the fiber-matrix interface to vibration.

  20. Porous Silica-Coated Gold Nanorods: A Highly Active Catalyst for the Reduction of 4-Nitrophenol.

    PubMed

    Mohanta, Jagdeep; Satapathy, Smithsagar; Si, Satyabrata

    2016-02-03

    The successful coating of thin porous silica layers of various thicknesses [(10±1), (12±1), and (14±1) nm] on cetyl trimethylammonium bromide (CTAB) capped gold nanorods was achieved through a modified Stöber procedure. The resulting material was applied as a novel catalyst for the reduction of 4-nitrophenol. The catalytic activities of the gold nanorods increased up to eight times after coating with a layer of porous silica and the reaction followed a zero-order kinetics, having a rate constant as high as 2.92×10(-1) mol L(-1) min(-1). The spectral changes during the reduction reaction of 4-nitrophenol were observed within a very short span of time and a complete conversion to 4-aminophenol occured within 5-6 mins, including the induction period of ≈2 mins. The reusability of the catalyst was studied by running the catalytic reaction during five consecutive cycles with good efficiency without destroying the nanostructure. The methodology can be effectively applied to the development of composite catalysts with highly enhanced catalytic activity.

  1. Interpretation and application of carbon isotope ratios in freshwater diatom silica

    PubMed Central

    Webb, Megan; Wynn, Peter M.; Heiri, Oliver; van Hardenbroek, Maarten; Pick, Frances; Russell, James M.; Stott, Andy W.; Leng, Melanie J.

    2016-01-01

    ABSTRACT Carbon incorporated into diatom frustule walls is protected from degradation enabling analysis for carbon isotope composition (δ13Cdiatom). This presents potential for tracing carbon cycles via a single photosynthetic host with well‐constrained ecophysiology. Improved understanding of environmental processes controlling carbon delivery and assimilation is essential to interpret changes in freshwater δ13Cdiatom. Here relationships between water chemistry and δ13Cdiatom from contemporary regional data sets are investigated. Modern diatom and water samples were collected from river catchments within England and lake sediments from across Europe. The data suggest dissolved, biogenically produced carbon supplied proportionately to catchment productivity was critical in the rivers and soft water lakes. However, dissolved carbon from calcareous geology overwhelmed the carbon signature in hard water catchments. Both results demonstrate carbon source characteristics were the most important control on δ13Cdiatom, with a greater impact than productivity. Application of these principles was made to a sediment record from Lake Tanganyika. δ13Cdiatom co‐varied with δ13Cbulk through the last glacial and Holocene. This suggests carbon supply was again dominant and exceeded authigenic demand. This first systematic evaluation of contemporary δ13Cdiatom controls demonstrates that diatoms have the potential to supply a record of carbon cycling through lake catchments from sediment records over millennial timescales. PMID:27656013

  2. The transport properties of activated carbon fibers

    SciTech Connect

    di Vittorio, S.L. . Dept. of Materials Science and Engineering); Dresselhaus, M.S. . Dept. of Electrical Engineering and Computer Science Massachusetts Inst. of Tech., Cambridge, MA . Dept. of Physics); Endo, M. . Dept. of Electrical Engineering); Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons. 19 refs., 4 figs.

  3. Solvent recovery improved with activated carbon fibers

    SciTech Connect

    Not Available

    1982-11-01

    A non-woven net of activated carbon fibers as absorbing media, representing a major advancement in vapor recovery technology, is presented. The carbon fiber exhibits mass transfer coefficients for adsorption description of up to 100 times that of conventional systems.

  4. The Transport Properties of Activated Carbon Fibers

    DOE R&D Accomplishments Database

    di Vittorio, S. L.; Dresselhaus, M. S.; Endo, M.; Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons.

  5. Chemical activation of carbon mesophase pitches.

    PubMed

    Mora, E; Blanco, C; Pajares, J A; Santamaría, R; Menéndez, R

    2006-06-01

    This paper studies the chemical activation of mesophase pitches of different origins in order to obtain activated carbons suitable for use as electrodes in supercapacitors. The effect that the activating agent (NaOH, LiOH, and KOH), the alkaline hydroxide/pitch ratio, and the activation temperature had on the characteristics of the resultant activated carbons was studied. LiOH was found to be a noneffective activating agent, while activation with NaOH and KOH yielded activated carbons with high apparent surface areas and pore volumes. The increase of the KOH/pitch ratio caused an increase of the chemical attack on the carbon, producing higher burnoffs and development of porosity. Extremely high apparent surface areas were obtained when the petroleum pitch was activated with 5:1 KOH/carbon ratio. The increase of the activation temperature caused an increase of the burnoff, although the differences were not as significant as those derived from the use of different proportions of activating agent.

  6. ACTIVATED CARBON FROM LIGNITE FOR WATER TREATMENT

    SciTech Connect

    Edwin S. Olson; Daniel J. Stepan

    2000-07-01

    High concentrations of humate in surface water result in the formation of excess amounts of chlorinated byproducts during disinfection treatment. These precursors can be removed in water treatment prior to disinfection using powdered activated carbon. In the interest of developing a more cost-effective method for removal of humates in surface water, a comparison of the activities of carbons prepared from North Dakota lignites with those of commercial carbons was conducted. Previous studies indicated that a commercial carbon prepared from Texas lignite (Darco HDB) was superior to those prepared from bituminous coals for water treatment. That the high alkali content of North Dakota lignites would result in favorable adsorptive properties for the very large humate molecules was hypothesized, owing to the formation of larger pores during activation. Since no standard humate test has been previously developed, initial adsorption testing was performed using smaller dye molecules with various types of ionic character. With the cationic dye, methylene blue, a carbon prepared from a high-sodium lignite (HSKRC) adsorbed more dye than the Darco HDB. The carbon from the low-sodium lignite was much inferior. With another cationic dye, malachite green, the Darco HDB was slightly better. With anionic dyes, methyl red and azocarmine-B, the results for the HSKRC and Darco HDB were comparable. A humate test was developed using Aldrich humic acid. The HSKRC and the Darco HDB gave equally high adsorption capacities for the humate (138 mg/g), consistent with the similarities observed in earlier tests. A carbon prepared from a high-sodium lignite from a different mine showed an outstanding improvement (201 mg/g). The carbons prepared from the low-sodium lignites from both mines showed poor adsorption capacities for humate. Adsorption isotherms were performed for the set of activated carbons in the humate system. These exhibited a complex behavior interpreted as resulting from two types

  7. Mesoporous silica nanoparticles functionalized with folic acid/methionine for active targeted delivery of docetaxel

    PubMed Central

    Khosravian, Pegah; Shafiee Ardestani, Mehdi; Khoobi, Mehdi; Ostad, Seyed Naser; Dorkoosh, Farid Abedin; Akbari Javar, Hamid; Amanlou, Massoud

    2016-01-01

    Mesoporous silica nanoparticles (MSNs) are known as carriers with high loading capacity and large functionalizable surface area for target-directed delivery. In this study, a series of docetaxel-loaded folic acid- or methionine-functionalized mesoporous silica nanoparticles (DTX/MSN-FA or DTX/MSN-Met) with large pores and amine groups at inner pore surface properties were prepared. The results showed that the MSNs were successfully synthesized, having good pay load and pH-sensitive drug release kinetics. The cellular investigation on MCF-7 cells showed better performance of cytotoxicity and cell apoptosis and an increase in cellular uptake of targeted nanoparticles. In vivo fluorescent imaging on healthy BALB/c mice proved that bare MSN-NH2 are mostly accumulated in the liver but MSN-FA or MSN-Met are more concentrated in the kidney. Importantly, ex vivo fluorescent images of tumor-induced BALB/c mice organs revealed the ability of MSN-FA to reach the tumor tissues. In conclusion, DTX/MSNs exhibited a good anticancer activity and enhanced the possibility of targeted drug delivery for breast cancer. PMID:27980423

  8. Live diatom silica immobilization of multimeric and redox-active enzymes.

    PubMed

    Sheppard, V C; Scheffel, A; Poulsen, N; Kröger, N

    2012-01-01

    Living organisms are adept in forming inorganic materials (biominerals) with unique structures and properties that exceed the capabilities of engineered materials. Biomimetic materials syntheses are being developed that aim at replicating the advantageous properties of biominerals in vitro and endow them with additional functionalities. Recently, proof-of-concept was provided for an alternative approach that allows for the production of biomineral-based functional materials in vivo. In this approach, the cellular machinery for the biosynthesis of nano-/micropatterned SiO₂ (silica) structures in diatoms was genetically engineered to incorporate a monomeric, cofactor-independent ("simple") enzyme, HabB, into diatom silica. In the present work, it is demonstrated that this approach is also applicable for enzymes with "complex" activity requirements, including oligomerization, metal ions, organic redox cofactors, and posttranslational modifications. Functional expression of the enzymes β-glucuronidase, glucose oxidase, galactose oxidase, and horseradish peroxidase in the diatom Thalassiosira pseudonana was accomplished, and 66 to 78% of the expressed enzymes were stably incorporated into the biosilica. The in vivo incorporated enzymes represent approximately 0.1% (wt/wt) of the diatom biosilica and are stabilized against denaturation and proteolytic degradation. Furthermore, it is demonstrated that the gene construct for in vivo immobilization of glucose oxidase can be utilized as the first negative selection marker for diatom genetic engineering.

  9. Titanium dioxide encapsulation of supported Ag nanoparticles on the porous silica bead for increased photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Liu, Hui; Deng, Lu; Sun, Chaochao; Li, Junqi; Zhu, Zhenfeng

    2015-01-01

    A new synthetic strategy has been developed to encapsulate Ag nanoparticles in heterogeneous catalysts to prevent their dropping and sintering. Ag nanoparticles with diameters about 5-10 nm were first supported on the porous silica bead. These were then covered with a fresh layer of titanium dioxide with the thickness about 5 nm. SEM and TEM images were used to confirm the success of each synthesis step, and the photocatalytic activity of the as-synthesized samples was evaluated by photocatalytic decolorization of Rhodamine B (Rh B) aqueous solution at ambient temperature under both UV and visible light irradiation. The resulting titanium dioxide encapsulated Ag nanoparticles exhibited an enhanced photocatalytic activity under both UV and visible light irradiation, this can be attributed to effective charge separation and light harvesting of the plasmonic silver nanoparticles decoration, even the reducing of the exciton recombination rate caused by the small grain size of anatase TiO2 nanocrystals.

  10. Mesoporous silica-encapsulated gold nanoparticles as artificial enzymes for self-activated cascade catalysis.

    PubMed

    Lin, Youhui; Li, Zhenhua; Chen, Zhaowei; Ren, Jinsong; Qu, Xiaogang

    2013-04-01

    A significant challenge in chemistry is to create synthetic structures that mimic the complexity and function of natural systems. Here, a self-activated, enzyme-mimetic catalytic cascade has been realized by utilizing expanded mesoporous silica-encapsulated gold nanoparticles (EMSN-AuNPs) as both glucose oxidase- and peroxidase-like artificial enzymes. Specifically, EMSN helps the formation of a high degree of very small and well-dispersed AuNPs, which exhibit an extraordinarily stability and dual enzyme-like activities. Inspired by these unique and attractive properties, we further piece them together into a self-organized artificial cascade reaction, which is usually completed by the oxidase-peroxidase coupled enzyme system. Our finding may pave the way to use matrix as the structural component for the design and development of biomimetic catalysts and to apply enzyme mimics for realizing higher functions.

  11. Chemical acceleration of a neutral granulated blast-furnace slag activated by sodium carbonate

    SciTech Connect

    Kovtun, Maxim Kearsley, Elsabe P. Shekhovtsova, Julia

    2015-06-15

    This paper presents results of a study on chemical acceleration of a neutral granulated blast-furnace slag activated using sodium carbonate. As strength development of alkali-activated slag cements containing neutral GBFS and sodium carbonate as activator at room temperature is known to be slow, three accelerators were investigated: sodium hydroxide, ordinary Portland cement and a combination of silica fume and slaked lime. In all cements, the main hydration product is C–(A)–S–H, but its structure varies between tobermorite and riversideite depending on the accelerator used. Calcite and gaylussite are present in all systems and they were formed due to either cation exchange reaction between the slag and the activator, or carbonation. With accelerators, compressive strength up to 15 MPa can be achieved within 24 h in comparison to 2.5 MPa after 48 h for a mix without an accelerator.

  12. Monitoring by Control Technique - Activated Carbon Adsorber

    EPA Pesticide Factsheets

    Stationary source emissions monitoring is required to demonstrate that a source is meeting the requirements in Federal or state rules. This page is about Activated Carbon Adsorber control techniques used to reduce pollutant emissions.

  13. Non-metallic nanomaterials in cancer theranostics: a review of silica- and carbon-based drug delivery systems

    PubMed Central

    Chen, Yu-Cheng; Huang, Xin-Chun; Luo, Yun-Ling; Chang, Yung-Chen; Hsieh, You-Zung; Hsu, Hsin-Yun

    2013-01-01

    The rapid development in nanomaterials has brought great opportunities to cancer theranostics, which aims to combine diagnostics and therapy for cancer treatment and thereby improve the healthcare of patients. In this review we focus on the recent progress of several cancer theranostic strategies using mesoporous silica nanoparticles and carbon-based nanomaterials. Silicon and carbon are both group IV elements; they have been the most abundant and significant non-metallic substances in human life. Their intrinsic physical/chemical properties are of critical importance in the fabrication of multifunctional drug delivery systems. Responsive nanocarriers constructed using these nanomaterials have been promising in cancer-specific theranostics during the past decade. In all cases, either a controlled texture or the chemical functionalization is coupled with adaptive properties, such as pH-, light-, redox- and magnetic field- triggered responses. Several studies in cells and mice models have implied their underlying therapeutic efficacy; however, detailed and long-term in vivo clinical evaluations are certainly required to make these bench-made materials compatible in real bedside circumstances. PMID:27877592

  14. Comparison of the morphology of alkali–silica gel formed in limestones in concrete affected by the so-called alkali–carbonate reaction (ACR) and alkali–silica reaction (ASR)

    SciTech Connect

    Grattan-Bellew, P.E.; Chan, Gordon

    2013-05-15

    The morphology of alkali–silica gel formed in dolomitic limestone affected by the so-called alkali–carbonate reaction (ACR) is compared to that formed in a siliceous limestone affected by alkali–silica reaction (ASR). The particle of dolomitic limestone was extracted from the experimental sidewalk in Kingston, Ontario, Canada that was badly cracked due to ACR. The siliceous limestone particle was extracted from a core taken from a highway structure in Quebec, affected by ASR. Both cores exhibited marked reaction rims around limestone particles. The aggregate particles were polished and given a light gold coating in preparation for examination in a scanning electron microscope. The gel in the ACR aggregate formed stringers between the calcite crystals in the matrix of the rock, whereas gel in ASR concrete formed a thick layer on top of the calcite crystals, that are of the same size as in the ACR aggregate.

  15. Antimicrobial Activity of Carbon-Based Nanoparticles

    PubMed Central

    Maleki Dizaj, Solmaz; Mennati, Afsaneh; Jafari, Samira; Khezri, Khadejeh; Adibkia, Khosro

    2015-01-01

    Due to the vast and inappropriate use of the antibiotics, microorganisms have begun to develop resistance to the commonly used antimicrobial agents. So therefore, development of the new and effective antimicrobial agents seems to be necessary. According to some recent reports, carbon-based nanomaterials such as fullerenes, carbon nanotubes (CNTs) (especially single-walled carbon nanotubes (SWCNTs)) and graphene oxide (GO) nanoparticles show potent antimicrobial properties. In present review, we have briefly summarized the antimicrobial activity of carbon-based nanoparticles together with their mechanism of action. Reviewed literature show that the size of carbon nanoparticles plays an important role in the inactivation of the microorganisms. As major mechanism, direct contact of microorganisms with carbon nanostructures seriously affects their cellular membrane integrity, metabolic processes and morphology. The antimicrobial activity of carbon-based nanostructures may interestingly be investigated in the near future owing to their high surface/volume ratio, large inner volume and other unique chemical and physical properties. In addition, application of functionalized carbon nanomaterials as carriers for the ordinary antibiotics possibly will decrease the associated resistance, enhance their bioavailability and provide their targeted delivery. PMID:25789215

  16. Preparation, characterization and photocatalytic activity of manganese doped TiO(2) immobilized on silica gel.

    PubMed

    Xu, Yuehua; Lei, Bo; Guo, Laiqiu; Zhou, Wuyi; Liu, Youqin

    2008-12-15

    A series of Mn-TiO(2)/SiO(2) (silica gel loaded with manganese doped TiO(2)) photocatalysts have been prepared by sol-gel method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Photocatalytic activities were enhanced in photocatalytic degradation of methyl orange over Mn-TiO(2)/SiO(2). XPS analysis shows that a Ti-O-Si or Ti-O-Mn bond is formed on the surface of photocatalyst. Mn is doped as a mixture of Mn(2+) and Mn(3+) on the surface of 1.0mol% Mn-TiO(2)/SiO(2). Mn(3+) appears to trap electrons and prohibit the electron-hole recombination. The electrons trapped in Mn(3+) site are subsequently transferred to the adsorbed O(2). As a result, the combination of the electron-hole pair was reduced.

  17. Determination of anionic surface active agents using silica coated magnetite nanoparticles modified with cationic surfactant aggregates.

    PubMed

    Pena-Pereira, Francisco; Duarte, Regina M B O; Trindade, Tito; Duarte, Armando C

    2013-07-19

    The development of a novel methodology for extraction and preconcentration of the most commonly used anionic surface active agents (SAAs), linear alkylbenzene sulfonates (LAS), is presented herein. The present method, based on the use of silica-magnetite nanoparticles modified with cationic surfactant aggregates, was developed for determination of C10-C13 LAS homologues. The proposed methodology allowed quantitative recoveries of C10-C13 LAS homologues by using a reduced amount of magnetic nanoparticles. Limits of detection were in the range 0.8-1.9μgL(-1) for C10-C13 LAS homologues, while the repeatability, expressed as relative standard deviation (RSD), ranged from 2.0 to 3.9% (N=6). Finally, the proposed method was successfully applied to the analysis of a variety of natural water samples.

  18. Evidence of an oxidative mechanism for the hemolytic activity of silica particles.

    PubMed Central

    Razzaboni, B L; Bolsaitis, P

    1990-01-01

    The formation of reactive oxygen species resulting from the interaction of silica dust particles with red blood cell membranes was investigated; particularly, the effect of surface hydroxyl (silanol) group concentration on the rate of formation of such reactive oxygen species was investigated. The rate of formation was measured indirectly through the effect of catalase, a hemoprotein peroxidase, on silica-induced hemolysis. It was found that the addition of exogenous catalase to erythrocytes markedly reduces the hemolysis caused by silica particles. Furthermore, the amount of catalase required for deactivation of silica per unit area of particle surface is lower for fumed silica particles and calcined crystalline particles than for uncalcined, crystalline silica, suggesting a correlation between the concentration of OH groups at the silica particle surface and its potential for generation of H2O2. The addition of albumin, a copper chelator, also decreases hemolysis. These results suggest that the hemolysis caused by silica particles is at least partly related to the formation of H2O2 at the particle surface and its subsequent reaction with Cu+ ions. The relationship between the concentration of surface silanol groups on the silica surface and the amount of catalase required to decrease hemolysis may also provide a method for testing potential fibrogenicity of respirable dusts. PMID:2176590

  19. Precise size control over ultrafine rutile titania nanocrystallites in hierarchical nanotubular silica/titania hybrids with efficient photocatalytic activity.

    PubMed

    Gu, Yuanqing; Huang, Jianguo

    2013-08-12

    Hierarchical-structured nanotubular silica/titania hybrids incorporated with particle-size-controllable ultrafine rutile titania nanocrystallites were realized by deposition of ultrathin titania sandwiched silica gel films onto each nanofiber of natural cellulose substances (e.g., common commercial filter paper) and subsequent flame burning in air. The rapid flame burning transforms the initially amorphous titania into rutile phase titania, and the silica gel films suppress the crystallite growth of rutile titania, thereby achieving nano-precise size regulation of ultrafine rutile titania nanocrystallites densely embedded in the silica films of the nanotubes. The average diameters of these nanocrystallites are adjustable in a range of approximately 3.3-16.0 nm by a crystallite size increment rate of about 2.4 nm per titania deposition cycle. The silica films transfer the electrons activated by crystalline titania and generate catalytic reactive species at the outer surface. The size-tuned ultrafine rutile titania nanocrystallites distributed in the unique hierarchical networks significantly improve the photocatalytic performance of the rutile phase titania, thereby enabling a highly efficient photocatalytic degradation of the methylene blue dye under ultraviolet light irradiation, which is even superior to the pure anatase-titania-based materials. The facile stepwise size control of the rutile titania crystallites described here opens an effective pathway for the design and preparation of fine-nanostructured rutile phase titania materials to explore potential applications.

  20. Activated coconut shell charcoal carbon using chemical-physical activation

    NASA Astrophysics Data System (ADS)

    Budi, Esmar; Umiatin, Nasbey, Hadi; Bintoro, Ridho Akbar; Wulandari, Futri; Erlina

    2016-02-01

    The use of activated carbon from natural material such as coconut shell charcoal as metal absorbance of the wastewater is a new trend. The activation of coconut shell charcoal carbon by using chemical-physical activation has been investigated. Coconut shell was pyrolized in kiln at temperature about 75 - 150 °C for about 6 hours in producing charcoal. The charcoal as the sample was shieved into milimeter sized granule particle and chemically activated by immersing in various concentration of HCl, H3PO4, KOH and NaOH solutions. The samples then was physically activated using horizontal furnace at 400°C for 1 hours in argon gas environment with flow rate of 200 kg/m3. The surface morphology and carbon content of activated carbon were characterized by using SEM/EDS. The result shows that the pores of activated carbon are openned wider as the chemical activator concentration is increased due to an excessive chemical attack. However, the pores tend to be closed as further increasing in chemical activator concentration due to carbon collapsing.

  1. A General Silica-Templating Synthesis of Alkaline Mesoporous Carbon Catalysts for Highly Efficient H2S Oxidation at Room Temperature.

    PubMed

    Zhang, Zixiao; Jiang, Wuyou; Long, Donghui; Wang, Jitong; Qiao, Wenming; Ling, Licheng

    2017-01-25

    A general synthesis of alkaline mesoporous carbons (AMCs) is developed based on a simplified silica-templating method for room-temperature catalytic oxidation of H2S. The key to the success relies on dissolving the silica templates to create the interconnected mesoporous structure as well as leaving parts of the alkaline products in the pores; both of them are prerequisites for H2S oxidation. By adjusting the alkaline etching degree and organic/inorganic ratio, the porosity and basicity of the AMC could be simultaneously tuned, allowing the AMCs direct use for H2S catalytic oxidation with an unprecedented removal capacities of 4.49 ± 0.12 g/g. Such excellent catalytic performance should be attributed to the developed pore structure that stores the product sulfur and the strong basicity that promotes the dissociation of H2S into HS(-) ions. Moreover, this simplified silica-templating method could be easily extended to the preparation of various silica templated mesoporous carbon catalysts. All these AMCs demonstrate a successful combination of low cost with high performance, which may well be the answer for the technical development of industrial H2S removal.

  2. Poly(lactic) acid fibers loaded with mesoporous silica for potential applications in the active food packaging

    NASA Astrophysics Data System (ADS)

    Cacciotti, Ilaria; Nanni, Francesca

    2016-06-01

    Multifunctional fibrous systems based on poly(lactic) acid (PLA), mesoporous silica (SiO2) and ascorbic acid (AA) were produced by means of electrospinning technique, for potential applications in the active food packaging sector, as platform for the controlled release of antioxidant and/or antimicrobial agents with the additional filtering function. The ascorbic acid was physisorbed on the surface of mesoporous silica in order to stabilize it and to extend its antioxidant action. The influence of mesoporous silica and ascorbic acid on the microstructural and mechanical properties was investigated, revealing a revelant mechanical reinforcement in the case of fibers loaded only with SiO2 and a decrement in the case of SiO2 with physisorbed ascorbic acid, due to the worse interface between the fillers and the polymeric matrix.

  3. Sustainability of the Catalytic Activity of a Silica-Titania Composite (STC) for Long-Term Indoor Air Quality Control

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Levine, Lanfang H.; Richards, Jeffrey T.

    2011-01-01

    TiO2-assisted photocatalytic oxidation (PCO) is an emerging technology for indoor air quality control and is also being evaluated as an alternative trace contaminant control technology for crew habitats in space exploration. Though there exists a vast range of literature on the development of photocatalysts and associated reactor systems, including catalyst performance and performance-influencing factors, the critical question of whether photocatalysts can sustain their initial catalytic activity over an extended period of operation has not been adequately addressed. For a catalyst to effectively serve as an air quality control product, it must be rugged enough to withstand exposure to a multitude of low concentration volatile organic compounds (VOCs) over long periods of time with minimal loss of activity. The objective of this study was to determine the functional lifetime of a promising photocatalyst - the silica-titania composite (STC) from Sol Gel Solutions, LLC in a real-world scenario. A bench-scale STC-packed annular reactor under continuous irradiation by a UV-A fluorescent black-light blue lamp ((lambda)max = 365 nm) was exposed to laboratory air continuously at an apparent contact time of 0.27 sand challenged with a known concentration of ethanol periodically to assess any changes in catalytic activity. Laboratory air was also episodically spiked with halocarbons (e.g., octafluoropropane), organosulfur compounds (e.g., sulfur hexafluoride), and organosilicons (e.g., siloxanes) to simulate accidental releases or leaks of such VOCs. Total organic carbon (TOC) loading and contaminant profiles of the laboratory air were also monitored. Changes in STC photocatalytic performance were evaluated using the ethanol mineralization rate, mineralization efficiency, and oxidation intermediate (acetaldehyde) formation. Results provide insights to any potential catalyst poisoning by trace halocarbons and organosulfur compounds.

  4. Preliminary study of lead isotopes in the carbonate-silica veins of Trench 14, Yucca Mountain, Nevada

    SciTech Connect

    Zartman, R.E.; Kwak, L.M.

    1993-12-15

    The sub-vertical carbonate-silica veins filling the Bow Ridge Fault, where exposed in Trench 14 on the east side of Yucca Mountain, carry a lead isotopic signature that can be explained in terms of local sources. Two isotopically distinguishable--silicate and carbonate--fractions of lead are recognized within the vein system as well as in overlying surficial calcrete deposits. The acid-insoluble silicate fraction is contributed largely from the decomposing Miocene volcanic tuff, which forms the wall rock of the fault zone and is a ubiquitous component of the overlying soil. Lead contained in the silicate fraction approaches in isotopic composition that of the Miocene volcanic rocks of Yucca Mountain, but diverges from it in some samples by being more enriched in uranogenic isotopes. The carbonate fraction of lead in both vein and calcrete samples resides dominantly in the HCl- and CH{sub 3}COOH-soluble calcite. HCl evidently also attacks and removes lead from silicate phases, but the milder CH{sub 3}COOH dissolution procedure oftentimes identifies a significantly more radiogenic lead in the calcite. Wind-blown particulate matter brought to the area from Paleozoic and Late Proterozoic limestones in surrounding mountains may be the ultimate source of the calcite. Isotopically more uniform samples suggest that locally the basaltic ash and other volcanic rock have contributed most of the lead to both fractions of the vein system. An important finding of this study is that the data does not require the more exotic mechanisms or origins that have been proposed for the veins. Instead, the remarkably similar lead isotopic properties of the veins to those of the soil calcretes support their interpretation as a surficial, pedogenic phenomenon.

  5. Converting Poultry Litter into Activated Carbon

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Disposal of animal manure is one of the biggest problems facing agriculture today. Now new technology has been designed to covert manure into environmentally friendly and highly valued activated carbon. When pelletized and activated under specific conditions, the litter becomes a highly porous mat...

  6. Deposition of Magnetite Nanoparticles in Activated Carbons and Preparation of Magnetic Activated Carbons

    NASA Astrophysics Data System (ADS)

    Kahani, S. A.; Hamadanian, M.; Vandadi, O.

    2007-08-01

    Magnetic activated carbons (MACs) for gold recovery from alkaline cyanide solutions have been developed by mixing a magnetic precursor with a carbon source, and treating the mixture under controlled conditions. As would be expected, these activated carbons have high specific surface areas due to their microporous structure. In addition, the small particle size of the MACs produced allows rapid adsorption of gold in solution, and the magnetic character of these MACs enables recovery from suspension by magnetic separation.

  7. Solid-phase extraction using bis(indolyl)methane-modified silica reinforced with multiwalled carbon nanotubes for the simultaneous determination of flavonoids and aromatic organic acid preservatives.

    PubMed

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

    2015-12-01

    A novel bis(indolyl)methane-modified silica reinforced with multiwalled carbon nanotubes sorbent for solid-phase extraction was designed and synthesized by chemical immobilization of nitro-substituted 3,3'-bis(indolyl)methane on silica modified with multiwalled carbon nanotubes. Coupled with high-performance liquid chromatography analysis, the extraction properties of the sorbent were evaluated for flavonoids and aromatic organic acid compounds. Under optimum conditions, the sorbent can simultaneously extract five flavonoids and two aromatic organic acid preservatives in aqueous solutions in a single-step solid-phase extraction procedure. Wide linear ranges were obtained with correlation coefficients (R(2) ) ranging from 0.9843 to 0.9976, and the limits of detection were in the range of 0.5-5 μg/L for the compounds tested. Compared with the silica modified with multiwalled carbon nanotubes sorbent and the nitro-substituted 3,3'-bis(indolyl)methane-modified silica sorbent, the developed sorbent exhibited higher extraction efficiency toward the selected analytes. The synergistic effect of nitro-substituted 3,3'-bis(indolyl)methane and multiwalled carbon nanotubes not only improved the surface-to-volume ratio but also enhanced multiple intermolecular interactions, such as hydrogen bonds, π-π, and hydrophobic interactions, between the new sorbent and the selected analytes. The as-established solid-phase extraction with high-performance liquid chromatography and diode array detection method was successfully applied to the simultaneous determination of flavonoids and aromatic organic acid preservatives in grape juices with recoveries ranging from 83.9 to 112% for all the selected analytes.

  8. A novel activated carbon for supercapacitors

    SciTech Connect

    Shen, Haijie; Liu, Enhui; Xiang, Xiaoxia; Huang, Zhengzheng; Tian, Yingying; Wu, Yuhu; Wu, Zhilian; Xie, Hui

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer A novel activated carbon was prepared from phenol-melamine-formaldehyde resin. Black-Right-Pointing-Pointer The carbon has large surface area with microporous, and high heteroatom content. Black-Right-Pointing-Pointer Heteroatom-containing functional groups can improve the pseudo-capacitance. Black-Right-Pointing-Pointer Physical and chemical properties lead to the good electrochemical properties. -- Abstract: A novel activated carbon has been prepared by simple carbonization and activation of phenol-melamine-formaldehyde resin which is synthesized by the condensation polymerization method. The morphology, thermal stability, surface area, elemental composition and surface chemical composition of samples have been investigated by scanning electron microscope, thermogravimetry and differential thermal analysis, Brunauer-Emmett-Teller measurement, elemental analysis and X-ray photoelectron spectroscopy, respectively. Electrochemical properties have been studied by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 6 mol L{sup -1} potassium hydroxide. The activated carbon shows good capacitive behavior and the specific capacitance is up to 210 F g{sup -1}, which indicates that it may be a promising candidate for supercapacitors.

  9. A needle trap device packed with a sol-gel derived, multi-walled carbon nanotubes/silica composite for sampling and analysis of volatile organohalogen compounds in air.

    PubMed

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

    2013-06-27

    A needle trap device (NTD) packed with silica composite of multi-walled carbon nanotubes (MWCNTs) prepared based on sol-gel technique was utilized for sampling and analysis of volatile organohalogen compounds (HVOCs) in air. The performance of the NTD packed with MWCNTs/silica composite as sorbent was examined in a variety of sampling conditions and was compared with NTDs packed with PDMS as well as SPME with Carboxen/PDMS-coated fibers. The limit of detection of NTDs for the GC/MS detection system was 0.01-0.05 ng mL(-1) and the limit of quantitation was 0.04-0.18 ng mL(-1). The RSD were 1.1-7.8% for intra-NTD comparison intended for repeatability of technique. The NTD-MWCNTs/silica composite showed better analytical performances compared to the NTD-PDMS composite and had the same analytical performances when compared to the SPME-Carboxen/PDMS fibers. The results show that NTD-MWCNTs-GC/MS is a powerful technique for active sampling of occupational/environmental pollutants in air.

  10. Silica-templated synthesis of ordered mesoporous tungsten carbide/graphitic carbon composites with nanocrystalline walls and high surface areas via a temperature-programmed carburization route.

    PubMed

    Wu, Zhangxiong; Yang, Yunxia; Gu, Dong; Li, Qiang; Feng, Dan; Chen, Zhenxia; Tu, Bo; Webley, Paul A; Zhao, Dongyuan

    2009-12-01

    Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalline walls are fabricated for the first time by a temperature-programmed carburization approach with phosphotungstic acid (PTA) as a precursor and mesoporous silica materials as hard templates. The mesostructure, crystal phase, and amount of deposited graphitic carbon can be conveniently tuned by controlling the silica template (SBA-15 or KIT-6), carburizing temperature (700-1000 degrees C), the PTA-loading amount, and the carburizing atmosphere (CH(4) or a CH(4)/H(2) mixture). A high level of deposited carbon is favorable for connecting and stabilizing the WC nanocrystallites to achieve high mesostructural regularity, as well as promoting the carburization reaction. Meanwhile, large pore sizes and high mesoporosity of the silica templates can promote WC-phase formation. These novel, ordered, mesoporous WC/C nanocomposites with high surface areas (74-169 m(2) g(-1)), large pore volumes (0.14-0.17 cm(3) g(-1)), narrow pore-size distributions (centered at about 3 nm), and very good oxidation resistance (up to 750 degrees C) have potential applications in fuel-cell catalysts and nanodevices.

  11. Activation of the Solid Silica Layer of Aerosol-Based C/SiO₂ Particles for Preparation of Various Functional Multishelled Hollow Microspheres.

    PubMed

    Li, Xiangcun; Luo, Fan; He, Gaohong

    2015-05-12

    Double-shelled C/SiO2 hollow microspheres with an outer nanosheet-like silica shell and an inner carbon shell were reported. C/SiO2 aerosol particles were synthesized first by a one-step rapid aerosol process. Then the solid silica layer of the aerosol particles was dissolved and regrown on the carbon surface to obtain novel C/SiO2 double-shelled hollow microspheres. The new microspheres prepared by the facile approach possess high surface area and pore volume (226.3 m(2) g(-1), 0.51 cm(3) g(-1)) compared with the original aerosol particles (64.3 m(2) g(-1), 0.176 cm(3) g(-1)), providing its enhanced enzyme loading capacity. The nanosheet-like silica shell of the hollow microspheres favors the fixation of Au NPs (C/SiO2/Au) and prevents them from growing and migrating at 500 °C. Novel C/C and C/Au/C (C/Pt/C) hollow microspheres were also prepared based on the hollow nanostructure. C/C microspheres (482.0 m(2) g(-1), 0.92 cm(3) g(-1)) were ideal electrode materials. In particular, the Au NPs embedded into the two carbon layers (C/Au/C, 431.2 m(2) g(-1), 0.774 cm(3) g(-1)) show a high catalytic activity and extremely chemical stability even at 850 °C. Moreover, C/SiO2/Au, C/Au/C microspheres can be easily recycled and reused by an external magnetic field because of the presence of Fe3O4 species in the inner carbon shell. The synthetic route reported here is expected to simplify the fabrication process of double-shelled or yolk-shell microspheres, which usually entails multiple steps and a previously synthesized hard template. Such a capability can facilitate the preparation of various functional hollow microspheres by interfacial design.

  12. Amino-functionalized mesoporous silica modified glassy carbon electrode for ultra-trace copper(II) determination.

    PubMed

    Dai, Xingxin; Qiu, Fagui; Zhou, Xuan; Long, Yumei; Li, Weifeng; Tu, Yifeng

    2014-10-27

    This paper described a facile and direct electrochemical method for the determination of ultra-trace Cu(2+) by employing amino-functionalized mesoporous silica (NH2-MCM-41) as enhanced sensing platform. NH2-MCM-41 was prepared by using a post-grafting process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and fourier transform infrared (FTIR) spectroscopy. NH2-MCM-41 modified glassy carbon (GC) electrode showed higher sensitivity for anodic stripping voltammetric (ASV) detection of Cu(2+) than that of MCM-41 modified one. The high sensitivity was attributed to synergistic effect between MCM-41 and amino-group, in which the high surface area and special mesoporous morphology of MCM-41 can cause strong physical absorption, and amino-groups are able to chelate copper ions. Some important parameters influencing the sensor response were optimized. Under optimum experimental conditions the sensor linearly responded to Cu(2+) concentration in the range from 5 to 1000 ng L(-1) with a detection limit of 0.9 ng L(-1) (S/N=3). Moreover, the sensor possessed good stability and electrode renewability. In the end, the proposed sensor was applied for determining Cu(2+) in real samples and the accuracy of the results were comparable to those obtained by inductively coupled plasma optical emission spectrometry (ICP-OES) method.

  13. Influence of multi-walled carbon nanotubes on textural and adsorption characteristics of in situ synthesized mesostructured silica.

    PubMed

    Karim, A H; Jalil, A A; Triwahyono, S; Kamarudin, N H N; Ripin, A

    2014-05-01

    Carbon nanotubes-mesostructured silica nanoparticles (CNT-MSN) composites were prepared by a simple one step method with various loading of CNT. Their surface properties were characterized by XRD, N2 physisorption, TEM and FTIR, while the adsorption performance of the CNT-MSN composites were evaluated on the adsorption of methylene blue (MB) while varying the pH, adsorbent dosage, initial MB concentration, and temperature. The CNTs were found to improve the physicochemical properties of the MSN and led to an enhanced adsorptivity for MB. N2 physisorption measurements revealed the development of a bimodal pore structure that increased the pore size, pore volume and surface area. Accordingly, 0.05 g L(-1) CNT-MSN was able to adsorb 524 mg g(-1) (qm) of 60 mg L(-1) MB at pH 8 and 303 K. The equilibrium data were evaluated using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models, with the Langmuir model affording the best fit to the adsorption data. The adsorption kinetics were best described by the pseudo-first order model. These results indicate the potential of CNT-MSN composites as effective new adsorbents for dye adsorption.

  14. Waste-Glycerol-Directed Synthesis of Mesoporous Silica and Carbon with Superior Performance in Room-Temperature Hydrogen Production from Formic Acid

    PubMed Central

    Lee, Dong-Wook; Jin, Min-Ho; Park, Ji Chan; Lee, Chun-Boo; Oh, Duckkyu; Lee, Sung-Wook; Park, Jin-Woo; Park, Jong-Soo

    2015-01-01

    The development of easier, cheaper, and more ecofriendly synthetic methods for mesoporous materials remains a challenging topic to commercialize them, and the transformation of waste glycerol, as a biodiesel byproduct, into something useful and salable is one of the pending issues to be resolved. Here we first report that mesoporous silica (KIE-6) and carbon (KIE-7) can be simultaneously synthesized by using cheap and ecofriendly crude-waste-glycerol of biodiesel with or without glycerol purification, and we demonstrated the excellent performance of the mesoporous material as a catalyst support for formic acid decomposition. As a result, Pd-MnOx catalysts supported on NH2-functionalized KIE-6 showed the highest catalytic activity (TOF: 540.6 h−1) ever reported for room-temperature formic acid decomposition without additives. Moreover, we conducted life-cycle assessment (LCA) from biomass cultivation through biodiesel production to KIE-6 and KIE-7 preparation, and it was confirmed that CO2 emission during synthesis of KIE-6 and KIE-7 could be reduced by 87.1% and 85.7%, respectively. We believe that our study suggested more ecofriendly and industry-friendly approaches for preparation of mesoporous materials, and utilization of waste glycerol. PMID:26515193

  15. Waste-Glycerol-Directed Synthesis of Mesoporous Silica and Carbon with Superior Performance in Room-Temperature Hydrogen Production from Formic Acid

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Wook; Jin, Min-Ho; Park, Ji Chan; Lee, Chun-Boo; Oh, Duckkyu; Lee, Sung-Wook; Park, Jin-Woo; Park, Jong-Soo

    2015-10-01

    The development of easier, cheaper, and more ecofriendly synthetic methods for mesoporous materials remains a challenging topic to commercialize them, and the transformation of waste glycerol, as a biodiesel byproduct, into something useful and salable is one of the pending issues to be resolved. Here we first report that mesoporous silica (KIE-6) and carbon (KIE-7) can be simultaneously synthesized by using cheap and ecofriendly crude-waste-glycerol of biodiesel with or without glycerol purification, and we demonstrated the excellent performance of the mesoporous material as a catalyst support for formic acid decomposition. As a result, Pd-MnOx catalysts supported on NH2-functionalized KIE-6 showed the highest catalytic activity (TOF: 540.6 h-1) ever reported for room-temperature formic acid decomposition without additives. Moreover, we conducted life-cycle assessment (LCA) from biomass cultivation through biodiesel production to KIE-6 and KIE-7 preparation, and it was confirmed that CO2 emission during synthesis of KIE-6 and KIE-7 could be reduced by 87.1% and 85.7%, respectively. We believe that our study suggested more ecofriendly and industry-friendly approaches for preparation of mesoporous materials, and utilization of waste glycerol.

  16. Activated carbon monoliths for methane storage

    NASA Astrophysics Data System (ADS)

    Chada, Nagaraju; Romanos, Jimmy; Hilton, Ramsey; Suppes, Galen; Burress, Jacob; Pfeifer, Peter

    2012-02-01

    The use of adsorbent storage media for natural gas (methane) vehicles allows for the use of non-cylindrical tanks due to the decreased pressure at which the natural gas is stored. The use of carbon powder as a storage material allows for a high mass of methane stored for mass of sample, but at the cost of the tank volume. Densified carbon monoliths, however, allow for the mass of methane for volume of tank to be optimized. In this work, different activated carbon monoliths have been produced using a polymeric binder, with various synthesis parameters. The methane storage was studied using a home-built, dosing-type instrument. A monolith with optimal parameters has been fabricated. The gravimetric excess adsorption for the optimized monolith was found to be 161 g methane for kg carbon.

  17. Mesoporous silica coatings for cephalosporin active release at the bone-implant interface

    NASA Astrophysics Data System (ADS)

    Rădulescu, Dragoş; Voicu, Georgeta; Oprea, Alexandra Elena; Andronescu, Ecaterina; Grumezescu, Valentina; Holban, Alina Maria; Vasile, Bogdan Stefan; Surdu, Adrian Vasile; Grumezescu, Alexandru Mihai; Socol, Gabriel; Mogoantă, Laurenţiu; Mogoşanu, George Dan; Balaure, Paul Cătălin; Rădulescu, Radu; Chifiriuc, Mariana Carmen

    2016-06-01

    In this study, we investigated the potential of MAPLE-deposited coatings mesoporous silica nanoparticles (MSNs) to release Zinforo (ceftarolinum fosmil) in biologically active form. The MSNs were prepared by using a classic procedure with cetyltrimethylammonium bromide as sacrificial template and tetraethylorthosilicate as the monomer. The Brunauer-Emmett-Teller (BET) and transmission electron microscopy (TEM) analyses revealed network-forming granules with diameters under 100 nm and an average pore diameter of 2.33 nm. The deposited films were characterized by SEM, TEM, XRD and IR. Microbiological analyses performed on ceftaroline-loaded films demonstrated that the antibiotic was released in an active form, decreasing the microbial adherence rate and colonization of the surface. Moreover, the in vitro and in vivo assays proved the excellent biodistribution and biocompatibility of the prepared systems. Our results suggest that the obtained bioactive coatings possess a significant potential for the design of drug delivery systems and antibacterial medical-use surfaces, with great applications in bone implantology.

  18. Spacer intercalated disassembly and photodynamic activity of zinc phthalocyanine inside nanochannels of mesoporous silica nanoparticles.

    PubMed

    Ma, Xing; Sreejith, Sivaramapanicker; Zhao, Yanli

    2013-12-26

    Hydrophobic photosensitizer zinc(II) phthalocyanine (ZnPc) was loaded into adamantane (Ad) modified nanochannels of mesoporous silica nanoparticles (MSNPs). The Ad units on the surface of MSNPs were complexed with amino-substituted β-cyclodextrin to enhance the solubility of the hybrid in aqueous solution. The amino groups on β-cyclodextrin also provide functional sites for further conjugation with targeting ligands toward targeted cancer therapy. Since the intercalation of the Ad spacer isolates loaded ZnPc and prevents its aggregation inside MSNPs, ZnPc exhibits its monomeric characteristics to effectively generate cytotoxic singlet oxygen ((1)O2) upon light irradiation (675 nm) in aqueous conditions, leading to efficient photodynamic activity for successful cancer treatment in vitro. Current research presents a convenient approach to maintain the monomeric state of hydrophobic photosensitizer ZnPc by rationally utilizing multifunctional MSNPs as the carriers. The novel hybrid with targeting capability achieves active photodynamic property of monomeric ZnPc in aqueous solution under light irradiation, which may find its way for practical photodynamic therapy in the future.

  19. Template-activated strategy toward one-step coating silica colloidal microspheres with sliver.

    PubMed

    Wang, Ke; Zhang, Xiaoli; Niu, Chunyu; Wang, Yongqiang

    2014-01-22

    Template-activated strategy was developed to coat silica (SiO2) colloidal microspheres with silver in one step, based on one-pot hydrothermal treatment of silver nitrate, PVP (poly(vinyl pyrrolidone)), and SiO2 colloidal microspheres in ammonia solution. In our reaction system, the surface of SiO2 colloidal microspheres was continually activated with negative-charged SiO(-) groups in ammonia solution, which accumulated [Ag(NH3)2](+) or Ag(+) ions around the SiO2 colloidal microspheres through electrostatic attraction; thereafter these ions could be reduced into Ag nanoparticles in situ by the weak reducer PVP in the solution, and then acted as seeds for the subsequent complete silver coating with the reaction proceeding. Therefore, the traditional three steps for complete silver coating, including prior surface modification, seeding, and subsequent growing, were effectively integrated into one step. The experimental results exhibited that perfect SiO2/Ag core/shell composite microspheres were successfully synthesized through optimizing the reaction parameters like the solvent ingredient, reducer, and the reaction temperature. Additionally, these obtained uniform composite microspheres were further used as SERS substrate by using R6G and thiram as probe molecules, and showed excellent trace detection of these organic chemicals in solution.

  20. Promoting immobilization and catalytic activity of horseradish peroxidase on mesoporous silica through template micelles.

    PubMed

    Wan, Mi Mi; Lin, Wei Gang; Gao, Ling; Gu, Hui Cheng; Zhu, Jian Hua

    2012-07-01

    New concept on the promotion of immobilization and catalytic activity of enzyme on mesoporous silica through template micelles is proposed and realized in this paper. Proper P123 templates are controllable retained in the as-synthesized SBA-15, not only to anchor the horseradish peroxidase (HRP) guest, but also to establish the crowding-like microenvironment around the enzyme. The influence of retaining templates on the pore structure of SBA-15, immobilization, and catalytic activity of HRP is studied, and the possible process of template removal is proposed. Ethanol refluxing of 6 h is conformable to prepare the optimal mesoporous support characterized with the retained templates of about 8%. With the assistance of retained templates in SBA-15, up to 49 mg g(-1) of HRP can be immobilized, 100% more than that on calcined SBA-15. Furthermore, the thermal stability, the resistance of pH variation and denaturing agent urea, and the recycle usage of HRP immobilized are obviously elevated, paving a novel and low-cost route to develop enzyme catalysts.

  1. Preparation of activated carbons with mesopores by use of organometallics

    SciTech Connect

    Yamada, Yoshio; Yoshizawa, Noriko; Furuta, Takeshi

    1996-12-31

    Activated carbons are commercially produced by steam or CO{sub 2} activation of coal, coconut shell and so on. In general the carbons obtained give pores with a broad range of distribution. The objective of this study was to prepare activated carbons from coal by use of various organometallic compounds. The carbons were evaluated for pore size by nitrogen adsorption experiments.

  2. Infrared study of carbon monoxide hydrogenation over rhodium/ceria and rhodium/silica catalysts

    SciTech Connect

    Lavalley, J.C.; Saussey, J.; Lamotte, J. ); Breault, R.; Hindermann, J.P.; Kiennemann, A. )

    1990-07-26

    Carbon monoxide hydrogenation over ceria-promoted Rh or Rh/SiO{sub 2} catalysts was investigated by means of Fourier transform infrared spectroscopy. In the chemisorption of CO at room temperature, a new absorption band was observed near 1,725 or 1,696 cm{sup {minus}1} on a reduced 5% Rh-5% CeO{sub 2}/SiO{sub 2} or 5% Rh/CeO{sub 2} catalyst, respectively. This new absorption band was attributed to a C- and O-bonded species, located at the metal/support interface. The appearance of this species was related to the shift to lower temperatures of the peak ascribed to CO dissociation in the temperature-programmed desorption spectra after CO adsorption. A flow high-pressure IR cell allowed to study the surface species in situ during CO + H{sub 2} reaction and to follow the reactivity of these species toward pure H{sub 2}. The results suggest that the drop in methane formation may be related to a lower reactivity of surface carbon in the presence of the promoter.

  3. Activators generated by electron transfer for atom transfer radical polymerization of styrene in the presence of mesoporous silica nanoparticles

    SciTech Connect

    Khezri, Khezrollah; Roghani-Mamaqani, Hossein

    2014-11-15

    Graphical abstract: Effect of mesoporous silica nanoparticles (MCM-41) on the activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) is investigated. Decrement of conversion and number average molecular weight and also increment of polydispersity index (PDI) values are three main results of addition of MCM-41 nanoparticles. Incorporation of MCM-41 nanoparticles in the polystyrene matrix can clearly increase thermal stability and decrease glass transition temperature of the nanocomposites. - Highlights: • Spherical morphology, hexagonal structure, and high surface area with regular pore diameters of the synthesized MCM-41 nanoparticles are examined. • AGET ATRP of styrene in the presence of MCM-41 nanoparticles is performed. • Effect of MCM-41 nanoparticles addition on the polymerization rate, conversion and molecular weights of the products are discussed. • Improvement in thermal stability of the nanocomposites and decreasing T{sub g} values was also observed by incorporation of MCM-41 nanoparticles. - Abstract: Activator generated by electron transfer for atom transfer radical polymerization was employed to synthesize well-defined mesoporous silica nanoparticles/polystyrene composites. Inherent features of spherical mesoporous silica nanoparticles were evaluated by nitrogen adsorption/desorption isotherm, X-ray diffraction and scanning electron microscopy analysis techniques. Conversion and molecular weight evaluations were carried out using gas and size exclusion chromatography respectively. By the addition of only 3 wt% mesoporous silica nanoparticles, conversion decreases from 81 to 58%. Similarly, number average molecular weight decreases from 17,116 to 12,798 g mol{sup −1}. However, polydispersity index (PDI) values increases from 1.24 to 1.58. A peak around 4.1–4.2 ppm at proton nuclear magnetic resonance spectroscopy results clearly confirms the living nature of the polymerization. Thermogravimetric

  4. Supercritical Carbon Dioxide Regeneration of Activated Carbon Loaded with Contaminants from Rocky Mountain Arsenal Well Water.

    DTIC Science & Technology

    1982-05-01

    15 111-7 GRANULAR ACTIVATED CARBON ADSORPTION ISOTHERMS THERMALLY REACTIVATED CARBON .............. 16 I IV-1 PROCESS FLOW DIAGRAM FOR... PROCESSING COST OF ACTIVATED CHARCOAL REGENERATION BY SUPERCRITICAL CARBON DIOXIDE PROCESS ........................... 25 l IV-4 SENSITIVITY OF GAC...regenerate adsorbents such as granular activated carbon loaded with a broad variety of organic adsorbates. This regeneration process uses a supercritical

  5. Making Activated Carbon for Storing Gas

    NASA Technical Reports Server (NTRS)

    Wojtowicz, Marek A.; Serio, Michael A.; Suuberg, Eric M.

    2005-01-01

    Solid disks of microporous activated carbon, produced by a method that enables optimization of pore structure, have been investigated as means of storing gas (especially hydrogen for use as a fuel) at relatively low pressure through adsorption on pore surfaces. For hydrogen and other gases of practical interest, a narrow distribution of pore sizes <2 nm is preferable. The present method is a variant of a previously patented method of cyclic chemisorption and desorption in which a piece of carbon is alternately (1) heated to the lower of two elevated temperatures in air or other oxidizing gas, causing the formation of stable carbon/oxygen surface complexes; then (2) heated to the higher of the two elevated temperatures in flowing helium or other inert gas, causing the desorption of the surface complexes in the form of carbon monoxide. In the present method, pore structure is optimized partly by heating to a temperature of 1,100 C during carbonization. Another aspect of the method exploits the finding that for each gas-storage pressure, gas-storage capacity can be maximized by burning off a specific proportion (typically between 10 and 20 weight percent) of the carbon during the cyclic chemisorption/desorption process.

  6. Adsorption of Hydantoins on Activated Carbon,

    DTIC Science & Technology

    1985-05-01

    performed for single solute, bisolute, and trisolute solutions as well as an undiluted coal gasification wastewater containing predominantly hydantoin...hydantoin, 5,5-dimethylhydantoin, and 5-ethyl-5-methylhydantoin. Absorption using activated carbon did not appear to be an effective treatment process for the removal of hydantoins from the coal gasification wastewater.

  7. ENGINEERING BULLETIN: GRANULAR ACTIVATED CARBON TREATMENT

    EPA Science Inventory

    Granular activated carbon (GAC) treatment is a physicochemical process that removes a wide variety of contaminants by adsorbing them from liquid and gas streams [1, p. 6-3]. This treatment is most commonly used to separate organic contaminants from water or air; however, it can b...

  8. USING POWDERED ACTIVATED CARBON: A CRITICAL REVIEW

    EPA Science Inventory

    Because the performance of powdered activated carbon (PAC) for uses other than taste and odor control is poorly documented, the purpose of this article is to critically review uses that have been reported (i.e., pesticides and herbicides, synthetic organic chemicals, and trihalom...

  9. MODELING MERCURY CONTROL WITH POWDERED ACTIVATED CARBON

    EPA Science Inventory

    The paper presents a mathematical model of total mercury removed from the flue gas at coal-fired plants equipped with powdered activated carbon (PAC) injection for Mercury control. The developed algorithms account for mercury removal by both existing equipment and an added PAC in...

  10. Sol-gel derived mesoporous cobalt silica catalyst: Synthesis, characterization and its activity in the oxidation of phenol

    NASA Astrophysics Data System (ADS)

    Andas, Jeyashelly; Adam, Farook; Rahman, Ismail Ab.

    2014-10-01

    Highly mesoporous cobalt silica rice husk catalysts with (5-15 wt.%) Co2+ loading were prepared via a simple sol-gel technique at room temperature. The successful insertion of cobalt ions into silica matrix was evidenced from FT-IR, NMR, XPS and AAS analyses. Preservation of the mesoporosity nature of silica upon incorporating Co2+ was confirmed from the N2-sorption studies. The topography and morphology viewed by TEM analysis differs as the cobalt concentration varies from 5 to 15 wt.%. Parallel pore channels and spherical nanoparticles of 9.44 nm were achieved for cobalt silica catalysts with 10 and 15 wt.% respectively. Cobalt catalysts were active in the liquid-phase oxidation of phenol with H2O2 as an oxygen source. The performances of the catalysts were greatly influenced by various parameters such as reaction temperature, catalyst amount, molar ratio of substrate to oxidant, nature of solvent, metal loading and homogeneous precursor salt. Water served as the best reaction medium for this oxidation system. The regeneration studies confirmed cobalt catalyst could be reused for five cycles without experiencing large loss in the conversion. Both leaching and reusability studies testified that the catalysts were truly heterogeneous.

  11. Enhanced Pt utilization in electrocatalysts by covering of colloidal silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Zeng, Jianhuang; Chen, Jianjun; Lee, Jim Yang

    This work aims at enhancing Pt utilization in electrocatalysts by covering of preformed silica nanoparticles. Pt/C electrocatalysts were prepared by reductive deposition of Pt by citrate at moderate temperatures on silica nanoparticles with varying atomic silica to Pt ratios (1.7:1 and 3.3:1) to study the effects of silica to Pt ratio. Considerable voidages were created by inter-situated 10-20 nm silica nanoparticles between support carbon particulates to facilitate mass transfer of reactants and products. This particular method of catalyst preparation increases the Pt metal utilization, and generates a large amount of accessible voidage in the interpenetrating particle network of carbon and silica to support the facile transport of reactants and products. Electrochemical hydrogen adsorption/desorption has shown an increase in electrochemically active surface area by this approach. Methanol electro-oxidation was used as a test reaction to evaluate the catalytic activity. It was found that the Pt catalyst modified with silica at silica:Pt = 1.7:1 atomic ratio was more active than a catalyst prepared when silica to Pt ratio increased to 3.3:1.

  12. Probing Mechanisms for Enzymatic Activity Enhancement of Organophosphorus Hydrolase in Functionalized Mesoporous Silica

    SciTech Connect

    Chen, Baowei; Lei, Chenghong; Shin, Yongsoon; Liu, Jun

    2009-12-25

    We have previously reported that organophosphorus hydrolase (OPH) can be spontaneously entrapped in functionalized mesoporous silica (FMS) with HOOC - as the functional groups and the entrapped OPH in HOOC-FMS showed enhanced enzyme specific activity. This work is to study the mechanisms that why OPH entrapped in FMS displayed the enhanced activity in views of OPH-FMS interactions using spectroscopic methods. The circular dichroism (CD) spectra show that, comparing to the secondary structure of OPH free in solution, OPH in HOOC-FMS displayed increased a-helix/b-strand transition of OPH with increased OPH loading density. The fluorescence emission spectra of Trp residues were used to assess the tertiary structural changes of the enzyme. There was a 42% increase in fluorescence. This is in agreement with the fact that the fluorescence intensity of OPH was increased accompanying with the increased OPH activity when decreasing urea concentrations in solution. The steady-state anisotropy was increased after OPH entrapping in HOOC-FMS comparing to the free OPH in solution, indicating that protein mobility was reduced upon entrapment. The solvent accessibility of Trp residues of OPH was probed by using acrylamide as a collisional quencher. Trp residues of OPH-FMS had less solvent exposure comparing with free OPH in solution due to its electrostatical binding to HOOC-FMS thereby displaying the increased fluorescence intensity. These results suggest the interactions of OPH with HOOC-FMS resulted in the protein immobilization and a favorable conformational change for OPH in the crowded confinement space and accordingly the enhanced activity.

  13. The Fate and Transport of the SiO2 Nanoparticles in a Granular Activated Carbon Bed and Their Impact on the Removal of VOCs

    EPA Science Inventory

    Adsorption isotherm, adsorption kinetics and column breakthrough experiments evaluating trichloroethylene (TCE) adsorption onto granular activated carbon (GAC) were conducted in the presence and absence of silica nanoparticles (SiO2 NPs). Zeta potential of the SiO

  14. Engineering of Hollow Mesoporous Silica Nanoparticles for Remarkably Enhanced Tumor Active Targeting Efficacy

    PubMed Central

    Chen, Feng; Hong, Hao; Shi, Sixiang; Goel, Shreya; Valdovinos, Hector F.; Hernandez, Reinier; Theuer, Charles P.; Barnhart, Todd E.; Cai, Weibo

    2014-01-01

    Hollow mesoporous silica nanoparticle (HMSN) has recently gained increasing interests due to their tremendous potential as an attractive nano-platform for cancer imaging and therapy. However, possibly due to the lack of efficient in vivo targeting strategy and well-developed surface engineering techniques, engineering of HMSN for in vivo active tumor targeting, quantitative tumor uptake assessment, multimodality imaging, biodistribution and enhanced drug delivery have not been achieved to date. Here, we report the in vivo tumor targeted positron emission tomography (PET)/near-infrared fluorescence (NIRF) dual-modality imaging and enhanced drug delivery of HMSN using a generally applicable surface engineering technique. Systematic in vitro and in vivo studies have been performed to investigate the stability, tumor targeting efficacy and specificity, biodistribution and drug delivery capability of well-functionalized HMSN nano-conjugates. The highest uptake of TRC105 (which binds to CD105 on tumor neovasculature) conjugated HMSN in the 4T1 murine breast cancer model was ~10%ID/g, 3 times higher than that of the non-targeted group, making surface engineered HMSN a highly attractive drug delivery nano-platform for future cancer theranostics. PMID:24875656

  15. Activation of snap-top capped mesoporous silica nanocontainers using two near-infrared photons.

    PubMed

    Guardado-Alvarez, Tania M; Sudha Devi, Lekshmi; Russell, Melissa M; Schwartz, Benjamin J; Zink, Jeffrey I

    2013-09-25

    Photoactivation of "snap-top" stoppers over the pore openings of mesoporous silica nanoparticles releases intact cargo molecules from the pores. The on-command release can be stimulated by either one UV photon or two coherent near-IR photons. Two-photon activation is particularly desirable for use in biological systems because it enables good tissue penetration and precise spatial control. Stoppers were assembled by first binding photolabile coumarin-based molecules to the nanoparticle surface. Then, after the particles were loaded with cargo, bulky β-cyclodextrin (CD) molecules were noncovalently associated with the substituted coumarin molecule, blocking the pores and preventing the cargo from escaping. One-photon excitation at 376 nm or two-photon excitation at 800 nm cleaves the bond holding the coumarin to the nanopore, releasing both the CD cap and the cargo. The dynamics of both the cleavage of the cap and the cargo release was monitored using fluorescence spectroscopy. This system traps intact cargo molecules without the necessity of chemical modification, releases them with tissue-penetrating near-IR light, and has possible applications in photostimulated drug delivery.

  16. Supercapacitor Electrodes from Activated Carbon Monoliths and Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Dolah, B. N. M.; Othman, M. A. R.; Deraman, M.; Basri, N. H.; Farma, R.; Talib, I. A.; Ishak, M. M.

    2013-04-01

    Binderless monoliths of supercapacitor electrodes were prepared by the carbonization (N2) and activation (CO2) of green monoliths (GMs). GMs were made from mixtures of self-adhesive carbon grains (SACG) of fibers from oil palm empty fruit bunches and a combination of 5 & 6% KOH and 0, 5 & 6% carbon nanotubes (CNTs) by weight. The electrodes from GMs containing CNTs were found to have lower specific BET surface area (SBET). The electrochemical behavior of the supercapacitor fabricated using the prepared electrodes were investigated by electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD). In general an addition of CNTs into the GMs reduces the equivalent series resistance (ESR) value of the cells. A cell fabricated using electrodes from GM with 5% CNT and 5% KOH was found to have the largest reduction of ESR value than that from the others GMs containing CNT. The cell has steeper Warburg's slope than that from its respective non-CNT GM, which reflect the smaller resistance for electrolyte ions to move into pores of electrodes despite these electrodes having largest reduction in specific BET surface area. The cell also has the smallest reduction of specific capacitance (Csp) and maintains the specific power range despite a reduction in the specific energy range due to the CNT addition.

  17. Cooperative redox activation for carbon dioxide conversion

    NASA Astrophysics Data System (ADS)

    Lian, Zhong; Nielsen, Dennis U.; Lindhardt, Anders T.; Daasbjerg, Kim; Skrydstrup, Troels

    2016-12-01

    A longstanding challenge in production chemistry is the development of catalytic methods for the transformation of carbon dioxide into useful chemicals. Silane and borane promoted reductions can be fined-tuned to provide a number of C1-building blocks under mild conditions, but these approaches are limited because of the production of stoichiometric waste compounds. Here we report on the conversion of CO2 with diaryldisilanes, which through cooperative redox activation generate carbon monoxide and a diaryldisiloxane that actively participate in a palladium-catalysed carbonylative Hiyama-Denmark coupling for the synthesis of an array of pharmaceutically relevant diarylketones. Thus the disilane reagent not only serves as the oxygen abstracting agent from CO2, but the silicon-containing `waste', produced through oxygen insertion into the Si-Si bond, participates as a reagent for the transmetalation step in the carbonylative coupling. Hence this concept of cooperative redox activation opens up for new avenues in the conversion of CO2.

  18. The biomass derived activated carbon for supercapacitor

    NASA Astrophysics Data System (ADS)

    Senthilkumar, S. T.; Selvan, R. Kalai; Melo, J. S.

    2013-06-01

    In this work, the activated carbon was prepared from biowaste of Eichhornia crassipes by chemical activation method using KOH as the activating agent at various carbonization temperatures (600 °C, 700 °C and 800 °C). The disordered nature, morphology and surface functional groups of ACs were examined by XRD, SEM and FT-IR. The electrochemical properties of AC electrodes were studied in 1M H2SO4 in the potential range of -0.2 to 0.8 V using cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques in a three electrode system. Subsequently, the fabricated supercapacitor using AC electrode delivered the higher specific capacitance and energy density of 509 F/g at current density of 1 mA/cm2 and 17 Wh/kg at power density of 0.416 W/g.

  19. Facile and fast preparation of low-cost silica-supported graphitic carbon nitride for solid-phase extraction of fluoroquinolone drugs from environmental waters.

    PubMed

    Speltini, Andrea; Maraschi, Federica; Govoni, Roberta; Milanese, Chiara; Profumo, Antonella; Malavasi, Lorenzo; Sturini, Michela

    2017-03-17

    The analytical application of silica-supported graphitic carbon nitride (g-C3N4@silica) for solid-phase extraction (SPE) of fluoroquinolone (FQ) pollutants from water is presented for the first time. g-C3N4@silica was easily and quickly prepared by one-pot thermal condensation of dicyandiamide and characterized by powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and surface area measurements. The novel composite was applied as sorbent for SPE of FQs from water prior high-performance liquid chromatography with fluorescence detection. The extraction efficiency of g-C3N4 was tested in tap and surface waters at actual concentrations (10-100ngL(-1)). Quantitative adsorption was achieved using 100mg sorbent (20wt% g-C3N4) for pre-concentration of 50-500mL sample, at the native pH (∼7.5-8). Elution was performed with 25mM H3PO4 aqueous solution-acetonitrile (80:20), obtaining recoveries in the range 70-114%, enrichment factors up to 500 and inter-day RSDs≤12%. The batch-to-batch reproducibility was assessed on three independently synthesized g-C3N4@silica preparations (RSD 6-12%). g-C3N4 supported on silica microparticles proved to be of easy preparation, inexpensive, reusable for at least 4 extractions of raw surface waters, and suitable for determination in real matrices.

  20. Equilibrium and kinetics analysis of carbon dioxide capture using immobilized amine on a mesoporous silica

    SciTech Connect

    Monazam, E., Shadle, L., Pennline, H., Miller, D., Fauth, D., Hoffman, J., Gray, M.

    2012-01-01

    The equilibrium and conversion-time data on the absorption of carbon dioxide (CO{sub 2}) with amine-based solid sorbent were analyzed over the range of 303–373 K. Data on CO{sub 2} loading on amine based solid sorbent at these temperatures and CO{sub 2} partial pressure between 10 and 760 mm Hg obtained from volumetric adsorption apparatus were fitted to a simple equilibrium model to generate the different parameters (including equilibrium constant) in the model. Using these constants, a correlation was obtained to define equilibrium constant and maximum CO{sub 2} loading as a function of temperature. In this study, a shrinking core model (SCM) was applied to elucidate the relative importance of pore diffusion and surface chemical reaction in controlling the rate of reaction. Application of SCM to the data suggested a surface reaction-controlled mechanism for the temperature of up to 40°C and pore-diffusion mechanism at higher temperature.

  1. Amorphous Silica- and Carbon- rich nano-templated surfaces as model interstellar dust surfaces for laboratory astrochemistry

    NASA Astrophysics Data System (ADS)

    Pascual, Natalia; Dawes, Anita; González-Posada, Fernando; Thompson, Neil; Chakarov, Dinko; Mason, Nigel J.; Fraser, Helen Jane

    2015-08-01

    Experimental studies on surface astrochemistry are vital to our understanding of chemical evolution in the interstellar medium (ISM). Laboratory surface-astrochemists have recently begun to study chemical reactions on interstellar dust-grain mimics, ranging from graphite, HOPG and graphene (representative of PAHs or large C-grains in the ISM) to amorphous olivine (representative of silicate dust) and ablated meteoritic samples (representative of interplanetary dust). These pioneering experiments show that the nature of the surface fundamentally affects processes at the substrate surface, substrate-ice interface, and ice over-layer. What these experiments are still lacking is the ability to account for effects arising from the discrete nano-scale of ISM grains, which might include changes to electronic structure, optical properties and surface-kinetics in comparison to bulk materials. The question arises: to what extent are the chemical and optical properties of interstellar ices affected by the size, morphology and material of the underlying ISM dust?We have designed, fabricated and characterised a set of nano-structured surfaces, where nanoparticles, representative of ISM grains, are adhered to an underlying support substrate. Here we will show the nanoparticles that have been manufactured from fused-silica (FS), glassy carbon (GC) and amorphous-C (aC). Our optical characterisation data shows that the nanostructured surfaces have different absorption cross-sections and significant scattering in comparison to the support substrates, which has implications for the energetic processing of icy ISM dust. We have been able to study how water-ice growth differs on the nanoparticles in comparison to the “flat” substrates, indicating increased ice amorphicity when nanoparticles are present, and on C-rich surfaces, compared to Si-rich particles. These data will be discussed in the context of interstellar water-ice features.

  2. Morphogenetic activity of silica and bio-silica on the expression of genes controlling biomineralization using SaOS-2 cells.

    PubMed

    Müller, Werner E G; Boreiko, Alexandra; Wang, Xiaohong; Krasko, Anatoli; Geurtsen, Werner; Custódio, Márcio Reis; Winkler, Thomas; Lukić-Bilela, Lada; Link, Thorben; Schröder, Heinz C

    2007-11-01

    In a previous study (Schröder et al., J Biomed Mater Res B Appl Biomater 75:387-392, 2005) we demonstrated that human SaOS-2 cells, when cultivated on bio-silica matrices, respond with an increased hydroxyapatite deposition. In the present contribution we investigate if silica-based components (Na-silicate, tetraethyl orthosilicate [TEOS], silica-nanoparticles) (1) change the extent of biomineralization in vitro (SaOS-2 cells) and (2) cause an alteration of the expression of the genes amelogenin, ameloblastin, and enamelin, which are characteristic for an early stage of osteogenesis. We demonstrate that the viability of SaOS-2 cells was not affected by the silica-based components. If Na-silicate or TEOS was added together with ss-glycerophosphate, an organic phosphate donor, a significant increase in biomineralization was measured. Finally, expression levels of the amelogenin, ameloblastin, and enamelin genes were determined in SaOS-2 cells during exposure to the silica-based components. After exposure for 2 days, expression levels of amelogenin and enamelin strongly increased in response to the silica-based components, while no significant change was seen for ameloblastin. In contrast, exposure of SaOS-2 cells to ss-glycerophosphate resulted in increased expression of all three genes. We conclude that the levels of the structural molecules of the enamel matrix, amelogenin and enamelin, increase in the presence of silica-based components and substantially contribute to the extent of hydroxyapatite crystallite formation. These results demonstrate that silica-based components augment hydroxyapatite deposition in vitro and suggest that enzymatically synthesized bio-silica (via silicatein) might be a promising route for tooth reconstruction in vivo.

  3. Carbon nanomaterials: Biologically active fullerene derivatives.

    PubMed

    Bogdanović, Gordana; Djordjević, Aleksandar

    2016-01-01

    Since their discovery, fullerenes, carbon nanotubes, and graphene attract significant attention of researches in various scientific fields including biomedicine. Nano-scale size and a possibility for diverse surface modifications allow carbon nanoallotropes to become an indispensable nanostructured material in nanotechnologies, including nanomedicine. Manipulation of surface chemistry has created diverse populations of water-soluble derivatives of fullerenes, which exhibit different behaviors. Both non-derivatized and derivatized fullerenes show various biological activities. Cellular processes that underline their toxicity are oxidative, genotoxic, and cytotoxic responses.The antioxidant/cytoprotective properties of fullerenes and derivatives have been considered in the prevention of organ oxidative damage and treatment. The same unique physiochemical properties of nanomaterials may also be associated with potential health hazards. Non-biodegradability and toxicity of carbon nanoparticles still remain a great concern in the area of biomedical application. In this review, we report on basic physical and chemical properties of carbon nano-clusters--fullerenes, nanotubes, and grapheme--their specificities, activities, and potential application in biological systems. Special emphasis is given to our most important results obtained in vitro and in vivo using polyhydroxylated fullerene derivative C₆₀(OH)₂₄.

  4. Enhanced capacitive properties of commercial activated carbon by re-activation in molten carbonates

    NASA Astrophysics Data System (ADS)

    Lu, Beihu; Xiao, Zuoan; Zhu, Hua; Xiao, Wei; Wu, Wenlong; Wang, Dihua

    2015-12-01

    Simple, affordable and green methods to improve capacitive properties of commercial activated carbon (AC) are intriguing since ACs possess a predominant role in the commercial supercapacitor market. Herein, we report a green reactivation of commercial ACs by soaking ACs in molten Na2CO3-K2CO3 (equal in mass ratios) at 850 °C combining the merits of both physical and chemical activation strategies. The mechanism of molten carbonate treatment and structure-capacitive activity correlations of the ACs are rationalized. Characterizations show that the molten carbonate treatment increases the electrical conductivity of AC without compromising its porosity and wettability of electrolytes. Electrochemical tests show the treated AC exhibited higher specific capacitance, enhanced high-rate capability and excellent cycle performance, promising its practical application in supercapacitors. The present study confirms that the molten carbonate reactivation is a green and effective method to enhance capacitive properties of ACs.

  5. The world ocean silica cycle.

    PubMed

    Tréguer, Paul J; De La Rocha, Christina L

    2013-01-01

    Over the past few decades, we have realized that the silica cycle is strongly intertwined with other major biogeochemical cycles, like those of carbon and nitrogen, and as such is intimately related to marine primary production, the efficiency of carbon export to the deep sea, and the inventory of carbon dioxide in the atmosphere. For nearly 20 years, the marine silica budget compiled by Tréguer et al. (1995) , with its exploration of reservoirs, processes, sources, and sinks in the silica cycle, has provided context and information fundamental to study of the silica cycle. Today, the budget needs revisiting to incorporate advances that have notably changed estimates of river and groundwater inputs to the ocean of dissolved silicon and easily dissolvable amorphous silica, inputs from the dissolution of terrestrial lithogenic silica in ocean margin sediments, reverse weathering removal fluxes, and outputs of biogenic silica (especially on ocean margins and in the form of nondiatomaceous biogenic silica). The resulting budget recognizes significantly higher input and output fluxes and notes that the recycling of silicon occurs mostly at the sediment-water interface and not during the sinking of silica particles through deep waters.

  6. Kinetics of adsorption with granular, powdered, and fibrous activated carbon

    SciTech Connect

    Shmidt, J.L.; Pimenov, A.V.; Lieberman, A.I.; Cheh, H.Y.

    1997-08-01

    The properties of three different types of activated carbon, fibrous, powdered, and granular, were investigated theoretically and experimentally. The adsorption rate of the activated carbon fiber was found to be two orders of magnitude higher than that of the granular activated carbon, and one order of magnitude higher than that of the powdered activated carbon. Diffusion coefficients of methylene blue in the fibrous, powdered, and granular activated carbons were determined experimentally. A new method for estimating the meso- and macropore surface areas in these carbons was proposed.

  7. Mesoporous Silica Supported Pd-MnOx Catalysts with Excellent Catalytic Activity in Room-Temperature Formic Acid Decomposition

    NASA Astrophysics Data System (ADS)

    Jin, Min-Ho; Oh, Duckkyu; Park, Ju-Hyoung; Lee, Chun-Boo; Lee, Sung-Wook; Park, Jong-Soo; Lee, Kwan-Young; Lee, Dong-Wook

    2016-09-01

    For the application of formic acid as a liquid organic hydrogen carrier, development of efficient catalysts for dehydrogenation of formic acid is a challenging topic, and most studies have so far focused on the composition of metals and supports, the size effect of metal nanoparticles, and surface chemistry of supports. Another influential factor is highly desired to overcome the current limitation of heterogeneous catalysis for formic acid decomposition. Here, we first investigated the effect of support pore structure on formic acid decomposition performance at room temperature by using mesoporous silica materials with different pore structures such as KIE-6, MCM-41, and SBA-15, and achieved the excellent catalytic activity (TOF: 593 h‑1) by only controlling the pore structure of mesoporous silica supports. In addition, we demonstrated that 3D interconnected pore structure of mesoporous silica supports is more favorable to the mass transfer than 2D cylindrical mesopore structure, and the better mass transfer provides higher catalytic activity in formic acid decomposition. If the pore morphology of catalytic supports such as 3D wormhole or 2D cylinder is identical, large pore size combined with high pore volume is a crucial factor to achieve high catalytic performance.

  8. Mesoporous Silica Supported Pd-MnOx Catalysts with Excellent Catalytic Activity in Room-Temperature Formic Acid Decomposition

    PubMed Central

    Jin, Min-Ho; Oh, Duckkyu; Park, Ju-Hyoung; Lee, Chun-Boo; Lee, Sung-Wook; Park, Jong-Soo; Lee, Kwan-Young; Lee, Dong-Wook

    2016-01-01

    For the application of formic acid as a liquid organic hydrogen carrier, development of efficient catalysts for dehydrogenation of formic acid is a challenging topic, and most studies have so far focused on the composition of metals and supports, the size effect of metal nanoparticles, and surface chemistry of supports. Another influential factor is highly desired to overcome the current limitation of heterogeneous catalysis for formic acid decomposition. Here, we first investigated the effect of support pore structure on formic acid decomposition performance at room temperature by using mesoporous silica materials with different pore structures such as KIE-6, MCM-41, and SBA-15, and achieved the excellent catalytic activity (TOF: 593 h−1) by only controlling the pore structure of mesoporous silica supports. In addition, we demonstrated that 3D interconnected pore structure of mesoporous silica supports is more favorable to the mass transfer than 2D cylindrical mesopore structure, and the better mass transfer provides higher catalytic activity in formic acid decomposition. If the pore morphology of catalytic supports such as 3D wormhole or 2D cylinder is identical, large pore size combined with high pore volume is a crucial factor to achieve high catalytic performance. PMID:27666280

  9. Aqueous mercury adsorption by activated carbons.

    PubMed

    Hadi, Pejman; To, Ming-Ho; Hui, Chi-Wai; Lin, Carol Sze Ki; McKay, Gordon

    2015-04-15

    Due to serious public health threats resulting from mercury pollution and its rapid distribution in our food chain through the contamination of water bodies, stringent regulations have been enacted on mercury-laden wastewater discharge. Activated carbons have been widely used in the removal of mercuric ions from aqueous effluents. The surface and textural characteristics of activated carbons are the two decisive factors in their efficiency in mercury removal from wastewater. Herein, the structural properties and binding affinity of mercuric ions from effluents have been presented. Also, specific attention has been directed to the effect of sulfur-containing functional moieties on enhancing the mercury adsorption. It has been demonstrated that surface area, pore size, pore size distribution and surface functional groups should collectively be taken into consideration in designing the optimal mercury removal process. Moreover, the mercury adsorption mechanism has been addressed using equilibrium adsorption isotherm, thermodynamic and kinetic studies. Further recommendations have been proposed with the aim of increasing the mercury removal efficiency using carbon activation processes with lower energy input, while achieving similar or even higher efficiencies.

  10. Doxorubicin loaded silica nanorattles actively seek tumors with improved anti-tumor effects

    NASA Astrophysics Data System (ADS)

    Gao, Fuping; Li, Linlin; Liu, Tianlong; Hao, Nanjing; Liu, Huiyu; Tan, Longfei; Li, Hongbo; Huang, Xinglu; Peng, Bo; Yan, Chuanmiao; Yang, Liuqing; Wu, Xiaoli; Chen, Dong; Tang, Fangqiong

    2012-05-01

    Silica nanorattles (SNs) have proven to be promising vehicles for drug delivery. In order to further enhance efficacy and minimize adverse effects, active targeted delivery to tumors is necessary. In this work, SNs modified with a tumor specific targeting ligand, folic acid (FA), was used as carrier of doxorubicin (DOX) (DOX-FA-SNs). Drug loading, cytotoxicity and cellular uptake of DOX-FA-SNs in vitro in human cervical carcinoma cells (HeLa cells) were evaluated. DOX-FA-SNs showed a higher cytotoxicity in human cervical carcinoma cells (HeLa cells) than DOX loaded carboxyl (-COOH) and poly(ethylene glycol) (PEG) modified SNs (DOX-COOH-SNs and DOX-PEG-SNs, respectively). However, DOX-FA-SNs showed lower cytotoxicity in folate receptor negative normal mouse fibroblast cells (L929 cells) compared with free DOX. In vivo tumor-targeted fluorescence imaging indicated specific tumor targeting and uptake of FA-SNs in nude mice bearing subcutaneous HeLa cell-derived xenograft tumors. In vivo anti-tumor experiments demonstrated that DOX-FA-SNs (10 mg kg-1 of DOX) significantly regressed the tumor growth and reduced toxicity compared with free DOX. These results have great significance in developing and optimizing SNs as effective intracellular delivery and specific tumor targeting vehicles.Silica nanorattles (SNs) have proven to be promising vehicles for drug delivery. In order to further enhance efficacy and minimize adverse effects, active targeted delivery to tumors is necessary. In this work, SNs modified with a tumor specific targeting ligand, folic acid (FA), was used as carrier of doxorubicin (DOX) (DOX-FA-SNs). Drug loading, cytotoxicity and cellular uptake of DOX-FA-SNs in vitro in human cervical carcinoma cells (HeLa cells) were evaluated. DOX-FA-SNs showed a higher cytotoxicity in human cervical carcinoma cells (HeLa cells) than DOX loaded carboxyl (-COOH) and poly(ethylene glycol) (PEG) modified SNs (DOX-COOH-SNs and DOX-PEG-SNs, respectively). However, DOX

  11. Less-costly activated carbon for sewage treatment

    NASA Technical Reports Server (NTRS)

    Ingham, J. D.; Kalvinskas, J. J.; Mueller, W. A.

    1977-01-01

    Lignite-aided sewage treatment is based on absorption of dissolved pollutants by activated carbon. Settling sludge is removed and dried into cakes that are pyrolyzed with lignites to yield activated carbon. Lignite is less expensive than activated carbon previously used to supplement pyrolysis yield.

  12. 78 FR 13894 - Certain Activated Carbon From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-01

    ... COMMISSION Certain Activated Carbon From China Determination On the basis of the record \\1\\ developed in the... antidumping duty order on certain activated carbon from China would be likely to lead to continuation or... USITC Publication 4381 (February 2013), entitled Certain Activated Carbon from China: Investigation...

  13. Percolation-dominated superhydrophobicity and conductivity for nanocomposite coatings from the mixtures of a commercial aqueous silica sol and functionalized carbon nanotubes.

    PubMed

    Peng, Mao; Guo, Honglei; Liao, Zhangjie; Qi, Ji; Zhou, Zhi; Fang, Zhengping; Shen, Lie

    2012-02-01

    Superhydrophobic conductive nanocomposite coatings are prepared for the first time from the simple mixture of a commercial aqueous silica sol and functionalized multiwalled carbon nanotubes (MWNTs) by air-spraying at ambient conditions followed by fluorosilane treatment. The relationship between MWNT content and the structure and properties of the nanocomposite coatings is investigated systematically. An ultra-low threshold (<5 vol.%) for superhydrophobicity is observed, which suggests that MWNTs are superior to any other spherical fillers for the construction of superhydrophobic nanocomposite coatings. When the content of nanotubes is below the threshold, the surface roughness mainly caused by the silica nanoparticles is not enough for creating superhydrophobic surfaces. Only above the threshold, the multiscale hierarchical structure is enough for both high water contact angles (>165°) and extremely low sliding angles (<2°). The conductivity is also percolation dominated, while the threshold for conductivity is much higher than that for superhydrophobicity, which can be ascribed to the encapsulated structure and the agglomeration of nanotubes in the composite coatings during air-spraying. Moreover, the aqueous silica sols hold merits of great film-forming capability at relatively low calcination temperatures, and being free of organic solvents.

  14. Carbon Monoxide Dehydrogenase Activity in Bradyrhizobium japonicum

    PubMed Central

    Lorite, María J.; Tachil, Jörg; Sanjuán, Juán; Meyer, Ortwin; Bedmar, Eulogio J.

    2000-01-01

    Bradyrhizobium japonicum strain 110spc4 was capable of chemolithoautotrophic growth with carbon monoxide (CO) as a sole energy and carbon source under aerobic conditions. The enzyme carbon monoxide dehydrogenase (CODH; EC 1.2.99.2) has been purified 21-fold, with a yield of 16% and a specific activity of 58 nmol of CO oxidized/min/mg of protein, by a procedure that involved differential ultracentrifugation, anion-exchange chromatography, hydrophobic interaction chromatography, and gel filtration. The purified enzyme gave a single protein and activity band on nondenaturing polyacrylamide gel electrophoresis and had a molecular mass of 230,000 Da. The 230-kDa enzyme was composed of large (L; 75-kDa), medium (M; 28.4-kDa), and small (S; 17.2-kDa) subunits occurring in heterohexameric (LMS)2 subunit composition. The 75-kDa polypeptide exhibited immunological cross-reactivity with the large subunit of the CODH of Oligotropha carboxidovorans. The B. japonicum enzyme contained, per mole, 2.29 atoms of Mo, 7.96 atoms of Fe, 7.60 atoms of labile S, and 1.99 mol of flavin. Treatment of the enzyme with iodoacetamide yielded di(carboxamidomethyl)molybdopterin cytosine dinucleotide, identifying molybdopterin cytosine dinucleotide as the organic portion of the B. japonicum CODH molybdenum cofactor. The absorption spectrum of the purified enzyme was characteristic of a molybdenum-containing iron-sulfur flavoprotein. PMID:10788353

  15. Carbon monoxide dehydrogenase activity in Bradyrhizobium japonicum.

    PubMed

    Lorite, M J; Tachil, J; Sanjuán, J; Meyer, O; Bedmar, E J

    2000-05-01

    Bradyrhizobium japonicum strain 110spc4 was capable of chemolithoautotrophic growth with carbon monoxide (CO) as a sole energy and carbon source under aerobic conditions. The enzyme carbon monoxide dehydrogenase (CODH; EC 1.2.99.2) has been purified 21-fold, with a yield of 16% and a specific activity of 58 nmol of CO oxidized/min/mg of protein, by a procedure that involved differential ultracentrifugation, anion-exchange chromatography, hydrophobic interaction chromatography, and gel filtration. The purified enzyme gave a single protein and activity band on nondenaturing polyacrylamide gel electrophoresis and had a molecular mass of 230,000 Da. The 230-kDa enzyme was composed of large (L; 75-kDa), medium (M; 28.4-kDa), and small (S; 17.2-kDa) subunits occurring in heterohexameric (LMS)(2) subunit composition. The 75-kDa polypeptide exhibited immunological cross-reactivity with the large subunit of the CODH of Oligotropha carboxidovorans. The B. japonicum enzyme contained, per mole, 2.29 atoms of Mo, 7.96 atoms of Fe, 7.60 atoms of labile S, and 1.99 mol of flavin. Treatment of the enzyme with iodoacetamide yielded di(carboxamidomethyl)molybdopterin cytosine dinucleotide, identifying molybdopterin cytosine dinucleotide as the organic portion of the B. japonicum CODH molybdenum cofactor. The absorption spectrum of the purified enzyme was characteristic of a molybdenum-containing iron-sulfur flavoprotein.

  16. 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

  17. Thin-Layer Polymer Wrapped Enzymes Encapsulated in Hierarchically Mesoporous Silica with High Activity and Enhanced Stability

    NASA Astrophysics Data System (ADS)

    Zhang, Fang; Wang, Meitao; Liang, Chao; Jiang, Huangyong; Shen, Jian; Li, Hexing

    2014-03-01

    A novel soft-hard cooperative approach was developed to synthesize bioactive mesoporous composite by pre-wrapping Penicillin G amidase with poly(acrylaimde) nanogel skin and subsequently incorporating such Penicillin G amidase nanocapsules into hierarchically mesoporous silica. The as-received bioactive mesoporous composite exhibited comparable activity and extraordinarily high stability in comparison with native Penicillin G amidase and could be used repetitively in the water-medium hydrolysis of penicillin G potassium salt. Furthermore, this strategy could be extended to the synthesis of multifunctional bioactive mesoporous composite by simultaneously introducing glucose oxidase nanocapsules and horseradish peroxidase nanocapsules into hierarchically mesoporous silica, which demonstrated a synergic effect in one-pot tandem oxidation reaction. Improvements in the catalytic performances were attributed to the combinational unique structure from soft polymer skin and hard inorganic mesoporous silica shell, which cooperatively helped enzyme molecules to retain their appropriate geometry and simultaneously decreased the enzyme-support negative interaction and mass transfer limitation under heterogeneous conditions.

  18. Thin-Layer Polymer Wrapped Enzymes Encapsulated in Hierarchically Mesoporous Silica with High Activity and Enhanced Stability

    PubMed Central

    Zhang, Fang; Wang, Meitao; Liang, Chao; Jiang, Huangyong; Shen, Jian; Li, Hexing

    2014-01-01

    A novel soft-hard cooperative approach was developed to synthesize bioactive mesoporous composite by pre-wrapping Penicillin G amidase with poly(acrylaimde) nanogel skin and subsequently incorporating such Penicillin G amidase nanocapsules into hierarchically mesoporous silica. The as-received bioactive mesoporous composite exhibited comparable activity and extraordinarily high stability in comparison with native Penicillin G amidase and could be used repetitively in the water-medium hydrolysis of penicillin G potassium salt. Furthermore, this strategy could be extended to the synthesis of multifunctional bioactive mesoporous composite by simultaneously introducing glucose oxidase nanocapsules and horseradish peroxidase nanocapsules into hierarchically mesoporous silica, which demonstrated a synergic effect in one-pot tandem oxidation reaction. Improvements in the catalytic performances were attributed to the combinational unique structure from soft polymer skin and hard inorganic mesoporous silica shell, which cooperatively helped enzyme molecules to retain their appropriate geometry and simultaneously decreased the enzyme-support negative interaction and mass transfer limitation under heterogeneous conditions. PMID:24651701

  19. Thin-layer polymer wrapped enzymes encapsulated in hierarchically mesoporous silica with high activity and enhanced stability.

    PubMed

    Zhang, Fang; Wang, Meitao; Liang, Chao; Jiang, Huangyong; Shen, Jian; Li, Hexing

    2014-03-21

    A novel soft-hard cooperative approach was developed to synthesize bioactive mesoporous composite by pre-wrapping Penicillin G amidase with poly(acrylaimde) nanogel skin and subsequently incorporating such Penicillin G amidase nanocapsules into hierarchically mesoporous silica. The as-received bioactive mesoporous composite exhibited comparable activity and extraordinarily high stability in comparison with native Penicillin G amidase and could be used repetitively in the water-medium hydrolysis of penicillin G potassium salt. Furthermore, this strategy could be extended to the synthesis of multifunctional bioactive mesoporous composite by simultaneously introducing glucose oxidase nanocapsules and horseradish peroxidase nanocapsules into hierarchically mesoporous silica, which demonstrated a synergic effect in one-pot tandem oxidation reaction. Improvements in the catalytic performances were attributed to the combinational unique structure from soft polymer skin and hard inorganic mesoporous silica shell, which cooperatively helped enzyme molecules to retain their appropriate geometry and simultaneously decreased the enzyme-support negative interaction and mass transfer limitation under heterogeneous conditions.

  20. Monitoring annealing via carbon dioxide laser heating of defect populations in fused silica surfaces using photoluminescence microscopy

    SciTech Connect

    Raman, R N; Matthews, M J; Adams, J J; Demos, S G

    2010-02-01

    Photoluminescence (PL) microscopy and spectroscopy under 266 nm and 355 nm laser excitation are explored as a means of monitoring defect populations in laser-modified sites on the surface of fused silica and their subsequent response to heating to different temperatures via exposure to a CO{sub 2} laser beam. Laser-induced temperature changes were estimated using an analytic solution to the heat flow equation and compared to changes in the PL emission intensity. The results indicate that the defect concentrations decrease significantly with increasing CO{sub 2} laser exposure and are nearly eliminated when the peak surface temperature exceeds the softening point of fused silica ({approx}1900K), suggesting that this method might be suitable for in situ monitoring of repair of defective sites in fused silica optical components.

  1. Bio-active engineered 50 nm silica nanoparticles with bone anabolic activity: therapeutic index, effective concentration, and cytotoxicity profile in vitro

    PubMed Central

    Ha, Shin-Woo; Sikorski, James A.; Weitzmann, M. Neale; Beck, George R.

    2014-01-01

    Silica-based nanomaterials are generally considered to be excellent candidates for therapeutic applications particularly related to skeletal metabolism however the current data surrounding the safety of silica based nanomaterials is conflicting. This may be due to differences in size, shape, incorporation of composite materials, surface properties, as well as the presence of contaminants following synthesis. In this study we performed extensive in vitro safety profiling of ~50 nm spherical silica nanoparticles with OH-terminated or Polyethylene Glycol decorated surface, with and without a magnetic core, and synthesized by the Stöber method. Nineteen different cell lines representing all major organ types were used to investigate an in vitro lethal concentration (LC) and results revealed little toxicity in any cell type analyzed. To calculate an in vitro therapeutic index we quantified the effective concentration at 50% response (EC50) for nanoparticle-stimulated mineral deposition activity using primary bone marrow stromal cells (BMSCs). The EC50 for BMSCs was not substantially altered by surface or magnetic core. The calculated Inhibitory concentration 50% (IC50) for pre-osteoclasts was similar to the osteoblastic cells. These results demonstrate the pharmacological potential of certain silica-based nanomaterial formulations for use in treating bone diseases based on a favorable in vitro therapeutic index. PMID:24333519

  2. Activated carbon briquettes from biomass materials.

    PubMed

    Amaya, Alejandro; Medero, Natalia; Tancredi, Néstor; Silva, Hugo; Deiana, Cristina

    2007-05-01

    Disposal of biomass wastes, produced in different agricultural activities, is frequently an environmental problem. A solution for such situation is the recycling of these residues for the production of activated carbon, an adsorbent which has several applications, for instance in the elimination of contaminants. For some uses, high mechanical strength and good adsorption characteristics are required. To achieve this, carbonaceous materials are conformed as pellets or briquettes, in a process that involves mixing and pressing of char with adhesive materials prior to activation. In this work, the influence of the operation conditions on the mechanical and surface properties of briquettes was studied. Eucalyptus wood and rice husk from Uruguay were used as lignocellulosic raw materials, and concentrated grape must from Cuyo Region-Argentina, as a binder. Different wood:rice and solid:binder ratios were used to prepare briquettes in order to study their influence on mechanical and surface properties of the final products.

  3. Formation of periodic surface ripples under the action of pulsed carbon dioxide laser radiation on fused silica

    NASA Astrophysics Data System (ADS)

    Emel'Ianov, V. I.; Konov, V. I.; Tokarev, V. N.; Seminogov, V. N.

    1989-01-01

    Theoretical and experimental results on the formation of periodic surface ripples (PSR) on fused silica under the normal-incidence pulsed linearly-polarized light of a wavelength-tunable CO2 laser are reported. The dielectric permittivity of silica under conditions of PSR formation has been determined for the first time. Good agreement between theoretical and experimental results is achieved only if the complete theory of PSR is applied, taking into account electrodynamic and thermal processes along with growth rate calculations for capillary waves.

  4. Cooperative redox activation for carbon dioxide conversion

    PubMed Central

    Lian, Zhong; Nielsen, Dennis U.; Lindhardt, Anders T.; Daasbjerg, Kim; Skrydstrup, Troels

    2016-01-01

    A longstanding challenge in production chemistry is the development of catalytic methods for the transformation of carbon dioxide into useful chemicals. Silane and borane promoted reductions can be fined-tuned to provide a number of C1-building blocks under mild conditions, but these approaches are limited because of the production of stoichiometric waste compounds. Here we report on the conversion of CO2 with diaryldisilanes, which through cooperative redox activation generate carbon monoxide and a diaryldisiloxane that actively participate in a palladium-catalysed carbonylative Hiyama-Denmark coupling for the synthesis of an array of pharmaceutically relevant diarylketones. Thus the disilane reagent not only serves as the oxygen abstracting agent from CO2, but the silicon-containing ‘waste', produced through oxygen insertion into the Si–Si bond, participates as a reagent for the transmetalation step in the carbonylative coupling. Hence this concept of cooperative redox activation opens up for new avenues in the conversion of CO2. PMID:27981967

  5. Adsorbed natural gas storage with activated carbon

    SciTech Connect

    Sun, Jian; Brady, T.A.; Rood, M.J.

    1996-12-31

    Despite technical advances to reduce air pollution emissions, motor vehicles still account for 30 to 70% emissions of all urban air pollutants. The Clean Air Act Amendments of 1990 require 100 cities in the United States to reduce the amount of their smog within 5 to 15 years. Hence, auto emissions, the major cause of smog, must be reduced 30 to 60% by 1998. Natural gas con be combusted with less pollutant emissions. Adsorbed natural gas (ANG) uses adsorbents and operates with a low storage pressure which results in lower capital costs and maintenance. This paper describes the production of an activated carbon adsorbent produced from an Illinois coal for ANG.

  6. Charcoal and activated carbon at elevated pressure

    SciTech Connect

    Antal, M.J. Jr.; Dai, Xiangfeng; Norberg, N.

    1995-12-01

    High quality charcoal has been produced with very high yields of 50% to 60% from macadamia nut and kukui nut shells and of 44% to 47% from Eucalyptus and Leucaena wood in a bench scale unit at elevated pressure on a 2 to 3 hour cycle, compared to commercial practice of 25% to 30% yield on a 7 to 12 day operating cycle. Neither air pollution nor tar is produced by the process. The effects of feedstock pretreatments with metal additives on charcoal yield are evaluated in this paper. Also, the influences of steam and air partial pressure and total pressure on yields of activated carbon from high yield charcoal are presented.

  7. Visualization of Adsorption: Luminescent Mesoporous Silica-Carbon Dots Composite for Rapid and Selective Removal of U(VI) and in Situ Monitoring the Adsorption Behavior.

    PubMed

    Wang, Zhe; Xu, Chao; Lu, Yuexiang; Wu, Fengcheng; Ye, Gang; Wei, Guoyu; Sun, Taoxiang; Chen, Jing

    2017-03-01

    The removal and separation of uranium from aqueous solutions are quite important for resource reclamation and environmental protection. Being one of the most effective techniques for metal separation, adsorption of uranium by a variety of adsorbent materials has been a subject of study with high interest in recent years. However, current methods for monitoring the adsorption process require complicated procedures and tedious measurements, which hinders the development of processes for efficient separation of uranium. In this work, we prepared a type of luminescent mesoporous silica-carbon dots composite material that has high efficiency for the adsorption of uranium and allows simultaneous in situ monitoring of the adsorption process. Carbon dots (CDs) were prepared in situ and introduced onto amino-functionalized ordered mesoporous silica (SBA-NH2) by a facile microplasma-assisted method. The prepared CDs/SBA-NH2 nanocomposites preserved the high specific surface area of the mesoporous silica, as well as the fluorescent properties of the CDs. Compared with bare SBA-NH2, the CDs/SBA-NH2 nanocomposites showed much improved adsorption ability and excellent selectivity for uranyl ions. Moreover, the fluorescence intensity of the composites decreased along with the increase of uranium uptake, indicating that the CDs/SBA-NH2 nanocomposites could be used for on-site monitoring of the adsorption behavior. More interestingly, the adsorption selectivity of the composites for metal ions was in good agreement with the selective fluorescence response of the original CDs, which means that the adsorption selectivity of CDs-based composite materials can be predicted by evaluating the fluorescence selectivity of the CDs for metal ions. As the first study of CDs-based nanocomposites for the adsorption of actinide elements, this work opens a new avenue for the in situ monitoring of adsorption behavior of CDs-based nanocomposites while extending their application areas.

  8. Silica, hybrid silica, hydride silica and non-silica stationary phases for liquid chromatography.

    PubMed

    Borges, Endler M

    2015-04-01

    Free silanols on the surface of silica are the "villains", which are responsible for detrimental interactions of those compounds and the stationary phase (i.e., bad peak shape, low efficiency) as well as low thermal and chemical stability. For these reasons, we began this review describing new silica and hybrid silica stationary phases, which have reduced and/or shielded silanols. At present, in liquid chromatography for the majority of analyses, reversed-phase liquid chromatography is the separation mode of choice. However, the needs for increased selectivity and increased retention of hydrophilic bases have substantially increased the interest in hydrophilic interaction chromatography (HILIC). Therefore, stationary phases and this mode of separation are discussed. Then, non-silica stationary phases (i.e., zirconium oxide, titanium oxide, alumina and porous graphitized carbon), which afford increased thermal and chemical stability and also selectivity different from those obtained with silica and hybrid silica, are discussed. In addition, the use of these materials in HILIC is also reviewed.

  9. Novel adsorbent based on multi-walled carbon nanotubes bonding on the external surface of porous silica gel particulates for trapping volatile organic compounds.

    PubMed

    Wang, Li; Liu, Jiemin; Zhao, Peng; Ning, Zhanwu; Fan, Huili

    2010-09-10

    A novel adsorbent, 3-amino-propylsilica gel-multi-walled carbon nanotubes (APSG-MW), was prepared by chemical bonding multi-walled carbon nanotubes on silica gel. The surface area of APSG-MW was 98 m(2)/g, and the particle size was between 60 and 80 mesh with the average size of 215.0 microm. The adsorption capability of the new adsorbent to volatile organic compounds (VOCs) was measured. The effect of water to the adsorbent and its stability during storage were also investigated. Duplicate precision (DP) and distributed volume pair (DVP) on the basis of the EPA TO-17 criteria were estimated. The results showed that the sampling precision of the adsorbent was more superior compared to the MWCNTs because of the better air permeability. The new adsorbent was successfully applied in the determination of VOCs in ambient indoor air.

  10. Production of activated carbon from TCR char

    NASA Astrophysics Data System (ADS)

    Stenzel, Fabian; Heberlein, Markus; Klinner, Tobias; Hornung, Andreas

    2016-04-01

    The utilization of char for adsorptive purposes is known since the 18th century. At that time the char was made of wood or bones and used for decoloration of fluids. In the 20th century the production of activated carbon in an industrial scale was started. The today's raw materials for activated carbon production are hard coal, peat, wood or coconut shells. All these materials entail costs especially the latter. Thus, the utilization of carbon rich residues (biomass) is an interesting economic opportunity because it is available for no costs or even can create income. The char is produced by thermo-catalytic reforming (TCR®). This process is a combination of an intermediate pyrolysis and subsequently a reforming step. During the pyrolysis step the material is decomposed in a vapor and a solid carbon enriched phase. In the second step the vapor and the solid phase get in an intensive contact and the quality of both materials is improved via the reforming process. Subsequently, the condensables are precipitated from the vapor phase and a permanent gas as well as oil is obtained. Both are suitable for heat and power production which is a clear advantage of the TCR® process. The obtained biochar from the TCR® process has special properties. This material has a very low hydrogen and oxygen content. Its stability is comparable to hard coal or anthracite. Therefore it consists almost only of carbon and ash. The latter depends from input material. Furthermore the surface structure and area can be influenced during the reforming step. Depending from temperature and residence time the number of micro pores and the surface area can be increased. Preliminary investigations with methylene blue solution have shown that a TCR® char made of digestate from anaerobic digestion has adsorptive properties. The decoloration of the solution was achieved. A further influencing factor of the adsorption performance is the particle size. Based on the results of the preliminary tests a

  11. Size and surface modification of amorphous silica particles determine their effects on the activity of human CYP3A4 in vitro

    NASA Astrophysics Data System (ADS)

    Imai, Shunji; Yoshioka, Yasuo; Morishita, Yuki; Yoshida, Tokuyuki; Uji, Miyuki; Nagano, Kazuya; Mukai, Yohei; Kamada, Haruhiko; Tsunoda, Shin-ichi; Higashisaka, Kazuma; Tsutsumi, Yasuo

    2014-12-01

    Because of their useful chemical and physical properties, nanomaterials are widely used around the world - for example, as additives in food and medicines - and such uses are expected to become more prevalent in the future. Therefore, collecting information about the effects of nanomaterials on metabolic enzymes is important. Here, we examined the effects of amorphous silica particles with various sizes and surface modifications on cytochrome P450 3A4 (CYP3A4) activity by means of two different in vitro assays. Silica nanoparticles with diameters of 30 and 70 nm (nSP30 and nSP70, respectively) tended to inhibit CYP3A4 activity in human liver microsomes (HLMs), but the inhibitory activity of both types of nanoparticles was decreased by carboxyl modification. In contrast, amine-modified nSP70 activated CYP3A4 activity. In HepG2 cells, nSP30 inhibited CYP3A4 activity more strongly than the larger silica particles did. Taken together, these results suggest that the size and surface characteristics of the silica particles determined their effects on CYP3A4 activity and that it may be possible to develop silica particles that do not have undesirable effects on metabolic enzymes by altering their size and surface characteristics.

  12. RGD-conjugated silica-coated gold nanorods on the surface of carbon nanotubes for targeted photoacoustic imaging of gastric cancer

    NASA Astrophysics Data System (ADS)

    Wang, Can; Bao, Chenchen; Liang, Shujing; Fu, Hualin; Wang, Kan; Deng, Min; Liao, Qiande; Cui, Daxiang

    2014-05-01

    Herein, we reported for the first time that RGD-conjugated silica-coated gold nanorods on the surface of multiwalled carbon nanotubes were successfully used for targeted photoacoustic imaging of in vivo gastric cancer cells. A simple strategy was used to attach covalently silica-coated gold nanorods (sGNRs) onto the surface of multiwalled carbon nanotubes (MWNTs) to fabricate a hybrid nanostructure. The cross-linked reaction occurred through the combination of carboxyl groups on the MWNTs and the amino group on the surface of sGNRs modified with a silane coupling agent. RGD peptides were conjugated with the sGNR/MWNT nanostructure; resultant RGD-conjugated sGNR/MWNT probes were investigated for their influences on viability of MGC803 and GES-1 cells. The nude mice models loaded with gastric cancer cells were prepared, the RGD-conjugated sGNR/MWNT probes were injected into gastric cancer-bearing nude mice models via the tail vein, and the nude mice were observed by an optoacoustic imaging system. Results showed that RGD-conjugated sGNR/MWNT probes showed good water solubility and low cellular toxicity, could target in vivo gastric cancer cells, and obtained strong photoacoustic imaging in the nude model. RGD-conjugated sGNR/MWNT probes will own great potential in applications such as targeted photoacoustic imaging and photothermal therapy in the near future.

  13. RGD-conjugated silica-coated gold nanorods on the surface of carbon nanotubes for targeted photoacoustic imaging of gastric cancer.

    PubMed

    Wang, Can; Bao, Chenchen; Liang, Shujing; Fu, Hualin; Wang, Kan; Deng, Min; Liao, Qiande; Cui, Daxiang

    2014-01-01

    Herein, we reported for the first time that RGD-conjugated silica-coated gold nanorods on the surface of multiwalled carbon nanotubes were successfully used for targeted photoacoustic imaging of in vivo gastric cancer cells. A simple strategy was used to attach covalently silica-coated gold nanorods (sGNRs) onto the surface of multiwalled carbon nanotubes (MWNTs) to fabricate a hybrid nanostructure. The cross-linked reaction occurred through the combination of carboxyl groups on the MWNTs and the amino group on the surface of sGNRs modified with a silane coupling agent. RGD peptides were conjugated with the sGNR/MWNT nanostructure; resultant RGD-conjugated sGNR/MWNT probes were investigated for their influences on viability of MGC803 and GES-1 cells. The nude mice models loaded with gastric cancer cells were prepared, the RGD-conjugated sGNR/MWNT probes were injected into gastric cancer-bearing nude mice models via the tail vein, and the nude mice were observed by an optoacoustic imaging system. Results showed that RGD-conjugated sGNR/MWNT probes showed good water solubility and low cellular toxicity, could target in vivo gastric cancer cells, and obtained strong photoacoustic imaging in the nude model. RGD-conjugated sGNR/MWNT probes will own great potential in applications such as targeted photoacoustic imaging and photothermal therapy in the near future.

  14. Transport of oxidized multi-walled carbon nanotubes through silica based porous media: influences of aquatic chemistry, surface chemistry, and natural organic matter.

    PubMed

    Yang, Jin; Bitter, Julie L; Smith, Billy A; Fairbrother, D Howard; Ball, William P

    2013-12-17

    This paper provides results from studies of the transport of oxidized multi-walled carbon nanotubes (O-MWCNTs) of varying surface oxygen concentrations under a range of aquatic conditions and through uniform silica glass bead media. In the presence of Na(+), the required ionic strength (IS) for maximum particle attachment efficiency (i.e., the critical deposition concentration, or CDC) increased as the surface oxygen concentration of the O-MWCNTs or pH increased, following qualitative tenets of theories based on electrostatic interactions. In the presence of Ca(2+), CDC values were lower than those with Na(+) present, but were no longer sensitive to surface oxygen content, suggesting that Ca(2+) impacts the interactions between O-MWCNTs and glass beads by mechanisms other than electrostatic alone. The presence of Suwannee River natural organic matter (SRNOM) decreased the attachment efficiency of O-MWCNTs in the presence of either Na(+) or Ca(2+), but with more pronounced effects when Na(+) was present. Nevertheless, low concentrations of SRNOM (<4 mg/L of dissolved organic carbon) were sufficient to mobilize all O-MWCNTs studied at CaCl2 concentrations as high as 10 mM. Overall, this study reveals that NOM content, pH, and cation type show more importance than surface chemistry in affecting O-MWCNTs deposition during transport through silica-based porous media.

  15. High surface area silicon carbide-coated carbon aerogel

    DOEpatents

    Worsley, Marcus A; Kuntz, Joshua D; Baumann, Theodore F; Satcher, Jr, Joe H

    2014-01-14

    A metal oxide-carbon composite includes a carbon aerogel with an oxide overcoat. The metal oxide-carbon composite is made by providing a carbon aerogel, immersing the carbon aerogel in a metal oxide sol under a vacuum, raising the carbon aerogel with the metal oxide sol to atmospheric pressure, curing the carbon aerogel with the metal oxide sol at room temperature, and drying the carbon aerogel with the metal oxide sol to produce the metal oxide-carbon composite. The step of providing a carbon aerogel can provide an activated carbon aerogel or provide a carbon aerogel with carbon nanotubes that make the carbon aerogel mechanically robust. Carbon aerogels can be coated with sol-gel silica and the silica can be converted to silicone carbide, improved the thermal stability of the carbon aerogel.

  16. ENTRAINED-FLOW ADSORPTION OF MERCURY USING ACTIVATED CARBON

    EPA Science Inventory

    Bench-scale experiments were conducted in a flow reactor to simulate entrained-flow capture of elemental mercury (Hg) by activated carbon. Adsorption of Hg by several commercial activated carbons was examined at different carbon-to-mercury (C:Hg) ratios (by weight) (600:1 - 29000...

  17. Preparation of binderless activated carbon monolith from pre-carbonization rubber wood sawdust by controlling of carbonization and activation condition

    NASA Astrophysics Data System (ADS)

    Taer, E.; Deraman, M.; Taslim, R.; Iwantono

    2013-09-01

    Binderless activated carbon monolith (ACM) was prepared from pre-carbonized rubber wood sawdust (RWSD). The effect of the carbonization temperature (400, 500, 600, 700, 800 dan 900 °C) on porosity characteristic of the ACM have been studied. The optimum carbonization temperature for obtaining ACM with high surface area of 600 °C with CO2 activation at 800 °C for one hour. At this condition, the surface area as high as 733 m2 g-1 could be successfully obtained. By improved the activation temperature at 900 °C for 2.5 h, it was found that the surface area of 860 m2 g-1. For this condition, the ACM exhibit the specific capacitance of 90 F g-1. In addition the termogravimertic (TG)-differential termografimertic (DTG) and field emission scanning electron microscope (FESEM) measurement were also performed on the ACMs and the result has been studied. Finally, it was conclude that the high surface area of ACM from RWSD could be produced by proper selections of carbonization and activation condition.

  18. Plant diversity increases soil microbial activity and soil carbon storage.

    PubMed

    Lange, Markus; Eisenhauer, Nico; Sierra, Carlos A; Bessler, Holger; Engels, Christoph; Griffiths, Robert I; Mellado-Vázquez, Perla G; Malik, Ashish A; Roy, Jacques; Scheu, Stefan; Steinbeiss, Sibylle; Thomson, Bruce C; Trumbore, Susan E; Gleixner, Gerd

    2015-04-07

    Plant diversity strongly influences ecosystem functions and services, such as soil carbon storage. However, the mechanisms underlying the positive plant diversity effects on soil carbon storage are poorly understood. We explored this relationship using long-term data from a grassland biodiversity experiment (The Jena Experiment) and radiocarbon ((14)C) modelling. Here we show that higher plant diversity increases rhizosphere carbon inputs into the microbial community resulting in both increased microbial activity and carbon storage. Increases in soil carbon were related to the enhanced accumulation of recently fixed carbon in high-diversity plots, while plant diversity had less pronounced effects on the decomposition rate of existing carbon. The present study shows that elevated carbon storage at high plant diversity is a direct function of the soil microbial community, indicating that the increase in carbon storage is mainly limited by the integration of new carbon into soil and less by the decomposition of existing soil carbon.

  19. Preparation of activated carbons from bituminous coal pitches

    NASA Astrophysics Data System (ADS)

    Gañan, J.; González-García, C. M.; González, J. F.; Sabio, E.; Macías-García, A.; Díaz-Díez, M. A.

    2004-11-01

    High-porosity carbons were prepared from bituminous coal pitches by combining chemical and physical activation. The chemical activation process consisted of potassium hydroxide impregnation followed by carbonization in nitrogen atmosphere. The effect of the KOH impregnation ratio on the surface area and pore volumes evolution of the carbons derived from mesophase pitch was studied. The optimum KOH:pitch ratio was fixed to realize a physical activation process in order to increase the textural parameters of the KOH-activated carbons. Physical activation was performed by carbonizing the KOH-activated carbons followed by gasifying with air. The influence of the carbonization temperature and the residence time of the gasification with air were explored to optimize those preparation parameters.

  20. Design of porous silica supported tantalum oxide hollow spheres showing enhanced photocatalytic activity.

    PubMed

    Sharma, Manu; Das, Debashree; Baruah, Arabinda; Jain, Archana; Ganguli, Ashok K

    2014-03-25

    Silica-supported tantalum oxide (ST) hollow spheres were designed for photocatalytic applications in the UV range of 4.1 to 4.8 eV. These nanostructures with a variable diameter of 100-250 nm and shell thickness of 24-58 nm were obtained by the hydrothermal treatment of tantalum isopropoxide and tetraethylorthosilicate at 120 °C for 48 h in the presence of cetyl trimethyl ammonium bromide, which was used as a capping agent. The maximum observed surface area was found to be 610 m(2)/g and pore size distribution of ST hollow spheres varied from 13.4 to 19.0 nm. Lewis acidity of silica and the contact area between SiO2 and Ta2O5 plays a crucial role in controlling the photocatalytic properties of the ST hollow spheres. We observe a remarkable 6× enhancement in the photoactivity of silica-supported tantalum oxide hollow spheres compared to pure Ta2O5.

  1. Wettability of modified silica layers deposited on glass support activated by plasma

    NASA Astrophysics Data System (ADS)

    Terpiłowski, Konrad; Rymuszka, Diana; Goncharuk, Olena V.; Sulym, Iryna Ya.; Gun'ko, Vladimir M.

    2015-10-01

    Fumed silica modified by hexamethyldisilazane [HDMS] and polydimethylsiloxane [PDMS] was dispersed in a polystyrene/chloroform solution. To increase adhesion between deposited silica layers and a glass surface, the latter was pretreated with air plasma for 30 s. The silica/polystyrene dispersion was deposited on the glass support using a spin coater. After deposition, the plates were dried in a desiccator for 24 h. Water advancing and receding contact angles were measured using the tilted plate method. The apparent surface free energy (γS) was evaluated using the contact angle hysteresis approach. The surface topography was determined using the optical profilometry method. Contact angles changed from 59.7° ± 4.4 (at surface coverage with trimethylsilyl groups Θ = 0.14) to 155° ± 3.1 at Θ = 1. The value of γS decreased from 51.3 ± 2.8 mJ/m2 (for the sample at the lowest value of Θ) to 1.0 ± 0.4 mJ/m2 for the most hydrophobic sample. Thus, some systems with a high degree of modification by HDMS showed superhydrophobicity, and the sliding angle amounted to about 16° ± 2.1.

  2. Film-forming formulations containing porous silica for the sustained delivery of actives to the skin.

    PubMed

    Heck, Rouven; Hermann, Sabrina; Lunter, Dominique J; Daniels, Rolf

    2016-11-01

    The purpose of this study was to develop film-forming formulations facilitating long-term treatment of chronic pruritus with capsaicinoids. To this end, an oily solution of nonivamide was loaded into porous silica particles which were then suspended in the dispersion of a sustained release polymer. Such formulations form a film when applied to the skin and encapsulate the drug loaded silica particles in a dry polymeric matrix. Dermal delivery and permeation of the antipruritic drug nonivamide (NVA) are controlled by the matrix. The film-forming formulations were examined regarding homogeneity, storage stability, substantivity and ex vivo skin permeation. Confocal Raman spectral imaging proved the stability of silica-based film-forming formulations over a period of 6 months. Substantivity was found to be enhanced substantially compared to a conventional semisolid formulation. Permeation rates of nonivamide from film-forming formulations through the skin are much lower compared to those achieved with a conventional immediate release formulation with the same drug amount. Due to the drug reservoir in the polymer matrix, a sustained permeation is enabled. Film-forming formulations may therefore improve the treatment of chronic pruritus with capsaicinoids by enhancing patient compliance through a sustained release regime.

  3. REPEATED REDUCTIVE AND OXIDATIVE TREATMENTS ON GRANULAR ACTIVATED CARBON

    EPA Science Inventory

    Fenton oxidation and Fenton oxidation preceded by reduction solutions were applied to granular activated carbon (GAC) to chemically regenerate the adsorbent. No adsorbate was present on the GAC so physicochemical effects from chemically aggressive regeneration of the carbon coul...

  4. Reduction of bromate by granular activated carbon

    SciTech Connect

    Kirisits, M.J.; Snoeyink, V.L.; Kruithof, J.C.

    1998-07-01

    Ozonation of waters containing bromide can lead to the formation of bromate, a probable human carcinogen. Since bromate will be regulated at 10 {micro}g/L by the Stage 1 Disinfectants/Disinfection By-Products Rule, there is considerable interest in finding a suitable method of bromate reduction. Granular activated carbon (GAC) can be used to chemically reduce bromate to bromide, but interference from organic matter and anions present in natural water render this process inefficient. In an effort to improve bromate reduction by GAC, several modifications were made to the GAC filtration process. The use of a biologically active carbon (BAC) filter ahead of a fresh GAC filter with and without preozonation, to remove the biodegradable organic matter, did not substantially improve the bromate removal of the GAC filter. The use of the BAC filter for biological bromate reduction proved to be the most encouraging experiment. By lowering the dissolved oxygen in the influent to the BAC from 8.0 mg/L to 2.0 mg/L, the percent bromate removal increased from 42% to 61%.

  5. Activated Carbon Fibers For Gas Storage

    SciTech Connect

    Burchell, Timothy D; Contescu, Cristian I; Gallego, Nidia C

    2017-01-01

    The advantages of Activated Carbon Fibers (ACF) over Granular Activated Carbon (GAC) are reviewed and their relationship to ACF structure and texture are discussed. These advantages make ACF very attractive for gas storage applications. Both adsorbed natural gas (ANG) and hydrogen gas adsorption performance are discussed. The predicted and actual structure and performance of lignin-derived ACF is reviewed. The manufacture and performance of ACF derived monolith for potential automotive natural gas (NG) storage applications is reported Future trends for ACF for gas storage are considered to be positive. The recent improvements in NG extraction coupled with the widespread availability of NG wells means a relatively inexpensive and abundant NG supply in the foreseeable future. This has rekindled interest in NG powered vehicles. The advantages and benefit of ANG compared to compressed NG offer the promise of accelerated use of ANG as a commuter vehicle fuel. It is to be hoped the current cost hurdle of ACF can be overcome opening ANG applications that take advantage of the favorable properties of ACF versus GAC. Lastly, suggestions are made regarding the direction of future work.

  6. Electrochemical activation of carbon nanotube/polymer composites.

    PubMed

    Sánchez, Samuel; Fàbregas, Esteve; Pumera, Martin

    2009-01-07

    Electrochemical activation of carbon nanotube/polysulfone composite electrodes for enhanced heterogeneous electron transfer is studied. The physicochemical insight into the electrochemical activation of carbon nanotube/polymer composites was provided by transmission electron microscopy, Raman spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. Dopamine, ascorbic acid, NADH, and ferricyanide are used as a model redox system for evaluating the performance of activated carbon nanotube/polymer composite electrodes. We demonstrate that polymer wrapping of carbon nanotubes is subject to defects and to partial removal during activation. Such tunable activation of electrodes would enable on-demand activation of electrodes for satisfying the needs of sensing or energy storage devices.

  7. Gold nanoparticles supported on mesoporous silica: origin of high activity and role of Au NPs in selective oxidation of cyclohexane

    PubMed Central

    Wu, Pingping; Bai, Peng; Yan, Zifeng; Zhao, George X. S.

    2016-01-01

    Homogeneous immobilization of gold nanoparticles (Au NPs) on mesoporous silica has been achieved by using a one-pot synthesis method in the presence of organosilane mercapto-propyl-trimethoxysilane (MPTMS). The resultant Au NPs exhibited an excellent catalytic activity in the solvent-free selective oxidation of cyclohexane using molecular oxygen. By establishing the structure-performance relationship, the origin of the high activity of mesoporous supported Au catalyst was identified to be due to the presence of low-coordinated Au (0) sites with high dispersion. Au NPs were confirmed to play a critical role in the catalytic oxidation of cyclohexane by promoting the activation of O2 molecules and accelerating the formation of surface-active oxygen species. PMID:26729288

  8. DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

    SciTech Connect

    Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

    2003-09-30

    The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, the principal objective of this work was to characterize and utilize the unburned carbon in fly ash for the production of activated carbons. The unburned carbon samples were collected from different combustion systems, including pulverized utility boilers, a utility cyclone, a stoker, and a fluidized bed combustor. LOI (loss-on-ignition), proximate, ultimate, and petrographic analyses were conducted, and the surface areas of the samples were characterized by N2 adsorption isotherms at 77K. The LOIs of the unburned carbon samples varied between 21.79-84.52%. The proximate analyses showed that all the samples had very low moisture contents (0.17 to 3.39 wt %), while the volatile matter contents varied between 0.45 to 24.82 wt%. The elemental analyses show that all the unburned carbon samples consist mainly of carbon with very little hydrogen, nitrogen, sulfur and oxygen In addition, the potential use of unburned carbon as precursor for activated carbon (AC) was investigated. Activated carbons with specific surface area up to 1075m{sup 2}/g were produced from the unburned carbon. The porosity of the resultant activated carbons was related to the properties of the unburned carbon feedstock and the activation conditions used. It was found that not all the unburned carbon samples are equally suited for activation, and furthermore, their potential as activated carbons precursors could be

  9. Superhydrophobic activated carbon-coated sponges for separation and absorption.

    PubMed

    Sun, Hanxue; Li, An; Zhu, Zhaoqi; Liang, Weidong; Zhao, Xinhong; La, Peiqing; Deng, Weiqiao

    2013-06-01

    Highly porous activated carbon with a large surface area and pore volume was synthesized by KOH activation using commercially available activated carbon as a precursor. By modification with polydimethylsiloxane (PDMS), highly porous activated carbon showed superhydrophobicity with a water contact angle of 163.6°. The changes in wettability of PDMS- treated highly porous activated carbon were attributed to the deposition of a low-surface-energy silicon coating onto activated carbon (confirmed by X-ray photoelectron spectroscopy), which had microporous characteristics (confirmed by XRD, SEM, and TEM analyses). Using an easy dip-coating method, superhydrophobic activated carbon-coated sponges were also fabricated; those exhibited excellent absorption selectivity for the removal of a wide range of organics and oils from water, and also recyclability, thus showing great potential as efficient absorbents for the large-scale removal of organic contaminants or oil spills from water.

  10. Innovative Route to Prepare of Au/C Catalysts by Replication of Gold-containing Mesoporous Silicas

    NASA Astrophysics Data System (ADS)

    Kerdi, Fatmé; Caps, Valérie; Tuel, Alain

    Gold-catalyzed aerobic epoxidations in the liquid phase are generally performed in low-polarity solvents, in which conventional oxide-supported catalysts are poorly dispersed. To improve the wettability of the catalytic powder and, thus, the efficiency of the catalyst, gold nanoparticles (NPs) have been dispersed on meso-structured carbons. Gold is first introduced in functionalized mesostructured silica and particles are formed inside the porosity. Silica pores are then impregnated with a carbon precursor and the composite material is heated at 900 °C under vacuum or nitrogen. Silica is then removed by acid leaching, leading to partially encapsulated gold particles in mesoporous carbon. Carbon prevents aggregation of gold particles at high temperature, both the mean size and distribution being similar to those observed in silica. However, while Au@SiO2 exhibit significant catalytic activity in the aerobic oxidation of trans-stilbene in the liquid phase, its Au@C mesostructured replica is quite inactive.

  11. Recent Data Analysis of Carbon ACtivation

    NASA Astrophysics Data System (ADS)

    Jiang, Hui Ming; Smith, Elizabeth; Padalino, Stephen; Baumgart, Leigh; Suny Geneseooltz, Katie; Colburn, Robyn; Fuschino, Julia

    2002-10-01

    A method for measuring tertiary neutrons produced in Inertial Confinement Fusion reactions has been developed using carbon activation. Ultra pure samples of carbon, free from positron-emitting contaminants must be used in the detection. Our primary goal has been to reduce the contamination level by refining purification and packaging procedures. This process involves baking the disks in a vacuum oven to 1000¢XC @ 200 microns for a prescribed bake time without exposing the disks to nitrogen in the air which is a major contaminant. Recent experiments were conducted to determine the optimal bake time for purification. Disks were baked for varying times, from one hour to five hours, and then exposed to high-neutron-yield ( 5 x 1013) shots on OMEGA. Data collected was normalized to the same time interval and the same primary neutron yield, and no significant difference in the number of background counts was seen. Experimental results also indicated that disks that were exposed to air for short time intervals showed a significant increase in the number of contamination counts. This further supports our findings that the gaseous diffusion through graphite disks is very high. Experimental results of these findings will be presented. Research funded in part by the United States Department of Energy.

  12. Activated Carbon Composites for Air Separation

    SciTech Connect

    Baker, Frederick S; Contescu, Cristian I; Tsouris, Costas; Burchell, Timothy D

    2011-09-01

    Coal-derived synthesis gas is a potential major source of hydrogen for fuel cells. Oxygen-blown coal gasification is an efficient approach to achieving the goal of producing hydrogen from coal, but a cost-effective means of enriching O2 concentration in air is required. A key objective of this project is to assess the utility of a system that exploits porous carbon materials and electrical swing adsorption to produce an O2-enriched air stream for coal gasification. As a complement to O2 and N2 adsorption measurements, CO2 was used as a more sensitive probe molecule for the characterization of molecular sieving effects. To further enhance the potential of activated carbon composite materials for air separation, work was implemented on incorporating a novel twist into the system; namely the addition of a magnetic field to influence O2 adsorption, which is accompanied by a transition between the paramagnetic and diamagnetic states. The preliminary findings in this respect are discussed.

  13. Photocatalytic activity of erbium-doped TiO{sub 2} nanoparticles immobilized in macro-porous silica films

    SciTech Connect

    Castaneda-Contreras, J.; Maranon-Ruiz, V.F.; Chiu-Zarate, R.; Perez-Ladron de Guevara, H.; Rodriguez, R.; Michel-Uribe, C.

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Erbium-doped TiO{sub 2} nanoparticles were immobilized on macro-porous silica films. Black-Right-Pointing-Pointer The films were obtained by a phase separation process. Black-Right-Pointing-Pointer The samples exhibited photo-catalytic activity under visible light. Black-Right-Pointing-Pointer The sensitization of TiO{sub 2} was attributed to a red shift in the TiO{sub 2} band-gap. -- Abstract: A macro-porous silica film served as mechanical support to immobilize TiO{sub 2} nanoparticles, which were doped with erbium. The films and the nanoparticles were prepared by sol-gel route. The nanoparticles exhibited photocatalytic activity under visible light. We obtained a degradation rate of methylene blue that followed first order kinetics. The sensitization of the nanoparticles to visible light was attributed to a red shift in the band-gap of the TiO{sub 2} due to the addition of erbium ions.

  14. Recovery of silica from electronic waste for the synthesis of cubic MCM-48 and its application in preparing ordered mesoporous carbon molecular sieves using a green approach

    NASA Astrophysics Data System (ADS)

    Liou, Tzong-Horng

    2012-07-01

    The electronics industry is one of the world's fastest growing manufacturing industries. However, e-waste has become a serious pollution problem. This study reports the recovery of e-waste for preparing valuable MCM-48 and ordered mesoporous carbon for the first time. Specifically, this study adopts an alkali-extracted method to obtain sodium silicate precursors from electronic packaging resin ash. The influence of synthesis variables such as gelation pH, neutral/cationic surfactant ratio, hydrothermal treatment temperature, and calcination temperature on the mesophase of MCM-48 materials is investigated. Experimental results confirm that well-ordered cubic MCM-48 materials were synthesized in strongly acidic and strongly basic media. The resulting mesoporous silica had a high surface area of 1,317 m2/g, mean pore size of about 3.0 nm, and a high purity of 99.87 wt%. Ordered mesoporous carbon with high surface area (1,715 m2/g) and uniform pore size of CMK-1 type was successfully prepared by impregnating MCM-48 template using the resin waste. The carbon structure was sensitive to the sulfuric acid concentration and carbonization temperature. Converting e-waste into MCM-48 materials not only eliminates the disposal problem of e-waste, but also transforms industrial waste into a useful nanomaterial.

  15. A comparison study of carbon dioxide adsorption on polydimethylsiloxane, silica gel, and Illinois No. 6 coal using in situ infrared spectroscopy

    SciTech Connect

    A.L. Goodman

    2009-01-15

    Adsorption of supercritical carbon dioxide (CO{sub 2}) on polydimethylsiloxane (PDMS), silica gel (SiO{sub 2}), and Illinois No. 6 coal was compared using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy at pressures up to 14 MPa and temperatures at 40{sup o}C and 50{sup o}C. Only physical adsorption of CO{sub 2} was recorded for PDMS, SiO{sub 2}, and Illinois no. 6. There was no evidence of the formation of carbonic acid, bicarbonates, carbonates, or any other reaction product between CO{sub 2} and PDMS, SiO{sub 2}, and Illinois No. 6 coal. Carbon dioxide adsorption on PDMS and SiO{sub 2} produced a linear isotherm while a typical Langmuir-like isotherm was observed for Illinois No. 6 coal. Attempts to measure CO{sub 2} induced swelling of the three materials was unsuccessful due to the design of the ATR-FTIR cell. 51 refs., 7 figs., 1 tab.

  16. Highly porous activated carbons prepared from carbon rich Mongolian anthracite by direct NaOH activation

    NASA Astrophysics Data System (ADS)

    Byamba-Ochir, Narandalai; Shim, Wang Geun; Balathanigaimani, M. S.; Moon, Hee

    2016-08-01

    Highly porous activated carbons (ACs) were prepared from Mongolian raw anthracite (MRA) using sodium hydroxide as an activation agent by varying the mass ratio (powdered MRA/NaOH) as well as the mixing method of chemical agent and powdered MRA. The specific BET surface area and total pore volume of the prepared MRA-based activated carbons (MACs) are in the range of 816-2063 m2/g and of 0.55-1.61 cm3/g, respectively. The pore size distribution of MACs show that most of the pores are in the range from large micropores to small mesopores and their distribution can be controlled by the mass ratio and mixing method of the activating agent. As expected from the intrinsic property of the MRA, the highly graphitic surface morphology of prepared carbons was confirmed from Raman spectra and transmission electron microscopy (TEM) studies. Furthermore the FTIR and XPS results reveal that the preparation of MACs with hydrophobic in nature is highly possible by controlling the mixing conditions of activating agent and powdered MRA. Based on all the results, it is suggested that the prepared MACs could be used for many specific applications, requiring high surface area, optimal pore size distribution, proper surface hydrophobicity as well as strong physical strength.

  17. Reuse performance of granular-activated carbon and activated carbon fiber in catalyzed peroxymonosulfate oxidation.

    PubMed

    Yang, Shiying; Li, Lei; Xiao, Tuo; Zhang, Jun; Shao, Xueting

    2017-03-01

    Recently, activated carbon was investigated as an efficient heterogeneous metal-free catalyst to directly activate peroxymonosulfate (PMS) for degradation of organic compounds. In this paper, the reuse performance and the possible deactivation reasons of granular-activated carbon (GAC) and activated carbon fiber (ACF) in PMS activation were investigated. As results indicated, the reusability of GAC, especially in the presence of high PMS dosage, was relatively superior to ACF in catalyzed PMS oxidation of Acid Orange 7 (AO7), which is much more easily adsorbed by ACF than by GAC. Pre-oxidation experiments were studied and it was demonstrated that PMS oxidation on ACF would retard ACF's deactivation to a big extent. After pre-adsorption with AO7, the catalytic ability of both GAC and ACF evidently diminished. However, when methanol was employed to extract the AO7-spent ACF, the catalytic ability could recover quite a bit. GAC and ACF could also effectively catalyze PMS to degrade Reactive Black 5 (RB5), which is very difficult to be adsorbed even by ACF, but both GAC and ACF have poor reuse performance for RB5 degradation. The original organic compounds or intermediate products adsorbed by GAC or ACF would be possibly responsible for the deactivation.

  18. Enhanced Plasmonic Resonance Energy Transfer in Mesoporous Silica-Encased Gold Nanorod for Two-Photon-Activated Photodynamic Therapy

    PubMed Central

    Chen, Nai-Tzu; Tang, Kuo-Chun; Chung, Ming-Fang; Cheng, Shih-Hsun; Huang, Ching-Mao; Chu, Chia-Hui; Chou, Pi-Tai; Souris, Jeffrey S.; Chen, Chin-Tu; Mou, Chung-Yuan; Lo, Leu-Wei

    2014-01-01

    The unique optical properties of gold nanorods (GNRs) have recently drawn considerable interest from those working in in vivo biomolecular sensing and bioimaging. Especially appealing in these applications is the plasmon-enhanced photoluminescence of GNRs induced by two-photon excitation at infrared wavelengths, owing to the significant penetration depth of infrared light in tissue. Unfortunately, many studies have also shown that often the intensity of pulsed coherent irradiation of GNRs needed results in irreversible deformation of GNRs, greatly reducing their two-photon luminescence (TPL) emission intensity. In this work we report the design, synthesis, and evaluation of mesoporous silica-encased gold nanorods (MS-GNRs) that incorporate photosensitizers (PSs) for two-photon-activated photodynamic therapy (TPA-PDT). The PSs, doped into the nano-channels of the mesoporous silica shell, can be efficiently excited via intra-particle plasmonic resonance energy transfer from the encased two-photon excited gold nanorod and further generates cytotoxic singlet oxygen for cancer eradication. In addition, due to the mechanical support provided by encapsulating mesoporous silica matrix against thermal deformation, the two-photon luminescence stability of GNRs was significantly improved; after 100 seconds of 800 nm repetitive laser pulse with the 30 times higher than average power for imaging acquisition, MS-GNR luminescence intensity exhibited ~260% better resistance to deformation than that of the uncoated gold nanorods. These results strongly suggest that MS-GNRs with embedded PSs might provide a promising photodynamic therapy for the treatment of deeply situated cancers via plasmonic resonance energy transfer. PMID:24955141

  19. Enhanced adsorption of humic acids on ordered mesoporous carbon compared with microporous activated carbon.

    PubMed

    Liu, Fengling; Xu, Zhaoyi; Wan, Haiqin; Wan, Yuqiu; Zheng, Shourong; Zhu, Dongqiang

    2011-04-01

    Humic acids are ubiquitous in surface and underground waters and may pose potential risk to human health when present in drinking water sources. In this study, ordered mesoporous carbon was synthesized by means of a hard template method and further characterized by X-ray diffraction, N2 adsorption, transition electron microscopy, elemental analysis, and zeta-potential measurement. Batch experiments were conducted to evaluate adsorption of two humic acids from coal and soil, respectively, on the synthesized carbon. For comparison, a commercial microporous activated carbon and nonporous graphite were included as additional adsorbents; moreover, phenol was adopted as a small probe adsorbate. Pore size distribution characterization showed that the synthesized carbon had ordered mesoporous structure, whereas the activated carbon was composed mainly of micropores with a much broader pore size distribution. Accordingly, adsorption of the two humic acids was substantially lower on the activated carbon than on the synthesized carbon, because of the size-exclusion effect. In contrast, the synthesized carbon and activated carbon showed comparable adsorption for phenol when the size-exclusion effect was not in operation. Additionally, we verified by size-exclusion chromatography studies that the synthesized carbon exhibited greater adsorption for the large humic acid fraction than the activated carbon. The pH dependence of adsorption on the three carbonaceous adsorbents was also compared between the two test humic acids. The findings highlight the potential of using ordered mesoporous carbon as a superior adsorbent for the removal of humic acids.

  20. Synthesis and characterization of mesostructured silicas and gold frameworks as active matrices for biomolecule encapsulation.

    SciTech Connect

    Iton, L. E.; Crisci, A. J.; Vajdova, V.; Laible, P. D.; Burns, C. T.; Firestone, M. A.

    2006-01-01

    Interfacing of biomolecules to inorganic frameworks is essential for fabricating robust, functionally integrated biocomposites that may prove useful in a wide range of technologies including biocatalysis, biosensors or protein-based devices. Our work is directed at developing means to integrate biomolecules into mesostructured inorganics. These frameworks serve to both improve the mechanical stability of the proteins and to facilitate communication with them. Toward that end, we have synthesized and characterized mesoporous silicas and conductive metallic frameworks and have examined the encapsulation of both soluble (cytochrome c) and membrane proteins (bacteriorhodpsin) within them.

  1. Characterization of Activated Carbons from Oil-Palm Shell by CO2 Activation with No Holding Carbonization Temperature

    PubMed Central

    Herawan, S. G.; Hadi, M. S.; Ayob, Md. R.; Putra, A.

    2013-01-01

    Activated carbons can be produced from different precursors, including coals of different ranks, and lignocellulosic materials, by physical or chemical activation processes. The objective of this paper is to characterize oil-palm shells, as a biomass byproduct from palm-oil mills which were converted into activated carbons by nitrogen pyrolysis followed by CO2 activation. The effects of no holding peak pyrolysis temperature on the physical characteristics of the activated carbons are studied. The BET surface area of the activated carbon is investigated using N2 adsorption at 77 K with selected temperatures of 500, 600, and 700°C. These pyrolysis conditions for preparing the activated carbons are found to yield higher BET surface area at a pyrolysis temperature of 700°C compared to selected commercial activated carbon. The activated carbons thus result in well-developed porosities and predominantly microporosities. By using this activation method, significant improvement can be obtained in the surface characteristics of the activated carbons. Thus this study shows that the preparation time can be shortened while better results of activated carbon can be produced. PMID:23737721

  2. Characterization of activated carbons from oil-palm shell by CO2 activation with no holding carbonization temperature.

    PubMed

    Herawan, S G; Hadi, M S; Ayob, Md R; Putra, A

    2013-01-01

    Activated carbons can be produced from different precursors, including coals of different ranks, and lignocellulosic materials, by physical or chemical activation processes. The objective of this paper is to characterize oil-palm shells, as a biomass byproduct from palm-oil mills which were converted into activated carbons by nitrogen pyrolysis followed by CO2 activation. The effects of no holding peak pyrolysis temperature on the physical characteristics of the activated carbons are studied. The BET surface area of the activated carbon is investigated using N2 adsorption at 77 K with selected temperatures of 500, 600, and 700°C. These pyrolysis conditions for preparing the activated carbons are found to yield higher BET surface area at a pyrolysis temperature of 700°C compared to selected commercial activated carbon. The activated carbons thus result in well-developed porosities and predominantly microporosities. By using this activation method, significant improvement can be obtained in the surface characteristics of the activated carbons. Thus this study shows that the preparation time can be shortened while better results of activated carbon can be produced.

  3. Niobium-silica catalysts for the selective epoxidation of cyclic alkenes: the generation of the active site by grafting niobocene dichloride.

    PubMed

    Tiozzo, Cristina; Bisio, Chiara; Carniato, Fabio; Gallo, Alessandro; Scott, Susannah L; Psaro, Rinaldo; Guidotti, Matteo

    2013-08-28

    Niobium-containing silica materials obtained by deposition via liquid-phase grafting or dry impregnation of niobocene(iv) dichloride are active and selective catalysts in the epoxidation of alkenes in the presence of aqueous hydrogen peroxide. The generation of the catalytically-active Nb species was followed step-by-step, and investigated using a combined DR-UV-Vis, NIR, Raman, XRD, XANES and EXAFS analyses. At the end of the grafting procedure, the nature of the surface active species can be described as an oxo-Nb(v) site, tripodally grafted onto the silica surface in close proximity to other Nb(v) centres. The liquid-phase methodology provides a better dispersion of the metal sites onto the siliceous support than the dry-impregnation approach. The niobium-silica catalysts were then tested in the epoxidation of cyclohexene and 1-methylcyclohexene, as model substrates.

  4. Dual-emissive fluorescence measurements of hydroxyl radicals using a coumarin-activated silica nanohybrid probe.

    PubMed

    Liu, Saisai; Zhao, Jun; Zhang, Kui; Yang, Lei; Sun, Mingtai; Yu, Huan; Yan, Yehan; Zhang, Yajun; Wu, Lijun; Wang, Suhua

    2016-04-07

    This work reports a novel dual-emissive fluorescent probe based on dye hybrid silica nanoparticles for ratiometric measurement of the hydroxyl radical (˙OH). In the probe sensing system, the blue emission of coumarin dye (coumarin-3-carboxylic acid, CCA) immobilized on the nanoparticle surface is selectively enhanced by ˙OH due to the formation of a coumarin hydroxylation product with strong fluorescence, whereas the emission of red fluorescent dye encapsulated in the silica nanoparticle is insensitive to ˙OH as a self-referencing signal, and so the probe provides a good quantitative analysis based on ratiometric fluorescence measurement with a detection limit of 1.65 μM. Moreover, the probe also shows high selectivity for ˙OH determination against metal ions, other reactive oxygen species and biological species. More importantly, it exhibits low cytotoxicity and high biocompatibility in living cells, and has been successfully used for cellular imaging of ˙OH, showing its promising application for monitoring of intracellular ˙OH signaling events.

  5. Influence of Scaffold Size on Bactericidal Activity of Nitric Oxide Releasing Silica Nanoparticles

    PubMed Central

    Carpenter, Alexis W.; Slomberg, Danielle L.; Rao, Kavitha S.; Schoenfisch, Mark H.

    2011-01-01

    A reverse microemulsion synthesis was used to prepare amine functionalized silica nanoparticles of three distinct sizes (i.e., 50, 100, and 200 nm) with identical amine concentrations. The resulting hybrid nanoparticles, consisting of N-(6 aminohexyl) aminopropyltrimethoxysilane and tetraethoxysilane, were highly monodisperse in size. N-diazeniumdiolate nitric oxide (NO) donors were subsequently formed on secondary amines while controlling reaction conditions to keep the total amount of nitric oxide (NO) released constant for each particle size. The bactericidal efficacy of the NO releasing nanoparticles against Pseudomonas aeruginosa increased with decreasing particle size. Additionally, smaller diameter nanoparticles were found to associate with the bacteria at a faster rate and to a greater extent than larger particles. Neither control (non-NO-releasing) nor NO releasing particles exhibited toxicity towards L929 mouse fibroblasts at concentrations above their respective minimum bactericidal concentrations. This study represents the first investigation of the bactericidal efficacy of NO-releasing silica nanoparticles as a function of particle size. PMID:21842899

  6. Utilization of Enzyme-Immobilized Mesoporous Silica Nanocontainers (IBN-4) in Prodrug-Activated Cancer Theranostics

    PubMed Central

    Hung, Bau-Yen; Kuthati, Yaswanth; Kankala, Ranjith Kumar; Kankala, Shravankumar; Deng, Jin-Pei; Liu, Chen-Lun; Lee, Chia-Hung

    2015-01-01

    To develop a carrier for use in enzyme prodrug therapy, Horseradish peroxidase (HRP) was immobilized onto mesoporous silica nanoparticles (IBN-4: Institute of Bioengineering and Nanotechnology), where the nanoparticle surfaces were functionalized with 3-aminopropyltrimethoxysilane and further conjugated with glutaraldehyde. Consequently, the enzymes could be stabilized in nanochannels through the formation of covalent imine bonds. This strategy was used to protect HRP from immune exclusion, degradation and denaturation under biological conditions. Furthermore, immobilization of HRP in the nanochannels of IBN-4 nanomaterials exhibited good functional stability upon repetitive use and long-term storage (60 days) at 4 °C. The generation of functionalized and HRP-immobilized nanomaterials was further verified using various characterization techniques. The possibility of using HRP-encapsulated IBN-4 materials in prodrug cancer therapy was also demonstrated by evaluating their ability to convert a prodrug (indole-3-acetic acid (IAA)) into cytotoxic radicals, which triggered tumor cell apoptosis in human colon carcinoma (HT-29 cell line) cells. A lactate dehydrogenase (LDH) assay revealed that cells could be exposed to the IBN-4 nanocomposites without damaging their membranes, confirming apoptotic cell death. In summary, we demonstrated the potential of utilizing large porous mesoporous silica nanomaterials (IBN-4) as enzyme carriers for prodrug therapy. PMID:28347114

  7. Successful entrapment of carbon dots within flexible free-standing transparent mesoporous organic-inorganic silica hybrid films for photonic applications

    NASA Astrophysics Data System (ADS)

    Vassilakopoulou, Anastasia; Georgakilas, Vasilios; Vainos, Nikolaos; Koutselas, Ioannis

    2017-04-01

    The effective entrapment of Carbon dots (CDs) into a polymer-silica hybrid matrix, formed as free standing transparent flexible films, is presented. The composite's synthesis, characterization, device application and properties -mechanical, thermal and optical- are being provided and discussed. CDs of 3 nm mean size with strong photoluminescence are embedded into a silica matrix during the sol-gel procedure, using tetraethyl orthosilicate as the precursor and F127 triblock copolymer as the structure directing agent under acidic conditions. The final hybrid nanostructure forms free standing transparent films that show high flexibility and long term stable CDs luminescence indicating the protective character of the hybrid matrix. It is crucial that the photoluminescence of the hybrid's CDs is not seriously affected after thermal treatment at 550 °C for 30 min. Moreover, the herein reported hybrid is demonstrated to be suitable for the fabrication of advanced photonic structures using soft lithography processes due to its low shrinkage and distortion upon drying, both attributable to its porosity. Finally, it is reported that addition of F127 ethanolic solution in aqueous solution of CDs induces a blue-shift of their photoluminescence.

  8. Lead recovery and high silica glass powder synthesis from waste CRT funnel glasses through carbon thermal reduction enhanced glass phase separation process.

    PubMed

    Xing, Mingfei; Fu, Zegang; Wang, Yaping; Wang, Jingyu; Zhang, Zhiyuan

    2017-01-15

    In this study, a novel process for the removal of toxic lead from the CRT funnel glass and synchronous preparation of high silica glass powder was developed by a carbon-thermal reduction enhanced glass phase separation process. CRT funnel glass was remelted with B2O3 in reducing atmosphere. In the thermal process, a part of PbO contained in the funnel glass was reduced into metallic Pb and detached from the glass phase. The rest of PbO and other metal oxides (including Na2O, K2O, Al2O3, BaO and CaO) were mainly concentrated in the boric oxide phase. The metallic Pb phase and boric oxide phase were completely leached out by 5mol/L HNO3. The lead removal rate was 99.80% and high silica glass powder (SiO2 purity >95wt%) was obtained by setting the temperature, B2O3 added amount and holding time at 1000°C, 20% and 30mins, respectively. The prepared high silicate glass powders can be used as catalyst carrier, semipermeable membranes, adsorbents or be remelted into high silicate glass as an ideal substitute for quartz glass. Thus this study proposed an eco-friendly and economical process for recycling Pb-rich electronic glass waste.

  9. A disposable amperometric immunosensor for chlorpyrifos-methyl based on immunogen/platinum doped silica sol-gel film modified screen-printed carbon electrode.

    PubMed

    Wei, Wei; Zong, Xiaomin; Wang, Xuan; Yin, Lihong; Pu, Yuepu; Liu, Songqin

    2012-12-01

    A disposable amperometric immunosensor for sensitive detection of chlorpyrifos-methyl (CM) has been developed by combining dual signal amplification of platinum colloid with an enzymatic catalytic reaction. The immunosensor was fabricated by modification of the screen-printed carbon electrodes (SPCE) with nanocomposites made by skillful doping of bovine serum albumin conjugated chlorpyrifos-methyl antigen (BSA-Ag) and platinum colloid into silica sol-gel. The scanning electron microscope (SEM) images and electrochemical measurements showed that platinum colloid domains in the nanocomposite material could enhance electron transfer and change the brittleness of the silica sol-gel. The immobilisation of BSA-Ag on the nanocomposite retained its immunoactivities, which allowed the immobilised BSA-Ag to effectively capture unbound Ab-HRP in the detection solution. A linear response to CM concentration was exhibited, ranging from 0.4 to 20ng/mL. Detection of CM with the presented method in soil or grape samples treated with CM matched the reference values well, which indicated that the proposed disposable immunosensor hold promising applications in environmental and food monitoring.

  10. [Effects of different fertilizer application on soil active organic carbon].

    PubMed

    Zhang, Rui; Zhang, Gui-Long; Ji, Yan-Yan; Li, Gang; Chang, Hong; Yang, Dian-Lin

    2013-01-01

    The variation characteristics of the content and components of soil active organic carbon under different fertilizer application were investigated in samples of calcareous fluvo-aquic soil from a field experiment growing winter wheat and summer maize in rotation in the North China Plain. The results showed that RF (recommended fertilization), CF (conventional fertilization) and NPK (mineral fertilizer alone) significantly increased the content of soil dissolved organic carbon and easily oxidized organic carbon by 24.92-38.63 mg x kg(-1) and 0.94-0.58 mg x kg(-1) respectively compared to CK (unfertilized control). The soil dissolved organic carbon content under OM (organic manure) increased greater than those under NPK and single fertilization, soil easily oxidized organic carbon content under OM and NPK increased greater than that under single chemical fertilization. OM and NPK showed no significant role in promoting the soil microbial biomass carbon, but combined application of OM and NPK significantly increased the soil microbial biomass carbon content by 36.06% and 20.69%, respectively. Soil easily oxidized organic carbon, dissolved organic carbon and microbial biomass carbon accounted for 8.41% - 14.83%, 0.47% - 0.70% and 0.89% - 1.20% of the total organic carbon (TOC), respectively. According to the results, the fertilizer application significantly increased the proportion of soil dissolved organic carbon and easily oxidized organic carbon, but there was no significant difference in the increasing extent of dissolved organic carbon. The RF and CF increased the proportion of soil easily oxidized organic carbon greater than OM or NPK, and significantly increased the proportion of microbial biomass carbon. OM or RF had no significant effect on the proportion of microbial biomass carbon. Therefore, in the field experiment, appropriate application of organic manure and chemical fertilizers played an important role for the increase of soil active organic carbon

  11. Chitosan, Carbon Quantum Dot, and Silica Nanoparticle Mediated dsRNA Delivery for Gene Silencing in Aedes aegypti: A Comparative Analysis.

    PubMed

    Das, Sumistha; Debnath, Nitai; Cui, Yingjun; Unrine, Jason; Palli, Subba Reddy

    2015-09-09

    In spite of devastating impact of mosquito borne pathogens on humans, widespread resistance to chemical insecticides and environmental concerns from residual toxicity limit mosquito control strategies. We tested three nanoparticles, chitosan, carbon quantum dot (CQD), and silica complexed with dsRNA, to target two mosquito genes (SNF7 and SRC) for controlling Aedes aegypti larvae. Relative mRNA levels were quantified using qRT-PCR to evaluate knockdown efficiency in nanoparticle-dsRNA treated larvae. The knockdown efficiency of target genes correlated with dsRNA mediated larval mortality. Among the three nanoparticles tested, CQD was the most efficient carrier for dsRNA retention, delivery, and thereby causing gene silencing and mortality in Ae. aegypti.

  12. Simultaneous Detection of Cadmium, Copper, and Lead using A Carbon Paste Electrode Modified with Carbamoylphosphonic Acid Self-Assembled Monolayer on Mesoporous Silica (SAMMS)

    SciTech Connect

    Yantasee, Wassana ); Lin, Yuehe ); Fryxell, Glen E. ); Busche, Brad J. )

    2004-01-30

    A new sensor was developed for simultaneous detection of cadmium (Cd2+), copper (Cu2+), and lead (Pb2+), based on the voltammetric response at a carbon paste electrode modified with carbamoylphosphonic acid (acetamide phosphonic acid) self-assembled monolayer on mesoporous silica (Ac-Phos SAMMS). The adsorptive stripping voltammetry technique involves preconcentration of the metal ions onto Ac-Phos SAMMS under an open circuit, then electrolysis of the preconcentrated species, followed by a square wave potential sweep towards positive values. Factors affecting the preconcentration process were investigated. The voltammetric responses increased linearly with the preconcentration time from 1 to 30 minutes or with metal ion concentrations ranging from 10 to 200 ppb. The responses also evolved in the same fashion as adsorption isotherm in the pH range of 2-6. The metal detection limits were 10 ppb after 2 minutes preconcentration and improved to 0.5 ppb after 20 minutes preconcentration.

  13. Adsorption of aromatic compounds by carbonaceous adsorbents: a comparative study on granular activated carbon, activated carbon fiber, and carbon nanotubes.

    PubMed

    Zhang, Shujuan; Shao, Ting; Kose, H Selcen; Karanfil, Tanju

    2010-08-15

    Adsorption of three aromatic organic compounds (AOCs) by four types of carbonaceous adsorbents [a granular activated carbon (HD4000), an activated carbon fiber (ACF10), two single-walled carbon nanotubes (SWNT, SWNT-HT), and a multiwalled carbon nanotube (MWNT)] with different structural characteristics but similar surface polarities was examined in aqueous solutions. Isotherm results demonstrated the importance of molecular sieving and micropore effects in the adsorption of AOCs by carbonaceous porous adsorbents. In the absence of the molecular sieving effect, a linear relationship was found between the adsorption capacities of AOCs and the surface areas of adsorbents, independent of the type of adsorbent. On the other hand, the pore volume occupancies of the adsorbents followed the order of ACF10 > HD4000 > SWNT > MWNT, indicating that the availability of adsorption site was related to the pore size distributions of the adsorbents. ACF10 and HD4000 with higher microporous volumes exhibited higher adsorption affinities to low molecular weight AOCs than SWNT and MWNT with higher mesopore and macropore volumes. Due to their larger pore sizes, SWNTs and MWNTs are expected to be more efficient in adsorption of large size molecules. Removal of surface oxygen-containing functional groups from the SWNT enhanced adsorption of AOCs.

  14. Sol-gel thin-film based mesoporous silica and carbon nanotubes for the determination of dopamine, uric acid and paracetamol in urine.

    PubMed

    Canevari, Thiago C; Raymundo-Pereira, Paulo A; Landers, Richard; Benvenutti, Edilson V; Machado, Sérgio A S

    2013-11-15

    This work describes the preparation, characterization and application of a hybrid material composed of disordered mesoporous silica (SiO2) modified with multiwalled carbon nanotubes (MWCNTs), obtained by the sol-gel process using HF as the catalyst. This hybrid material was characterized by N2 adsorption-desorption isotherms, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission microscopy (HR-TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). This new hybrid material was used for the construction of a thin film on a glassy carbon electrode. The modified electrode using this material was designated SiO2/MWCNT/GCE. The electrocatalytic properties of the electrode toward dopamine, uric acid and paracetamol oxidation were studied by differential pulse voltammetry. Well-defined and separated oxidation peaks were observed in phosphate buffer solution at pH 7.0, in contrast with the ill-defined peaks observed with unmodified glassy carbon electrodes. The electrode had high sensitivity for the determination of dopamine, uric acid and paracetamol, with the limits of detection obtained using statistical methods, at 0.014, 0.068 and 0.098 µmol L(-1), respectively. The electrode presented some important advantages, including enhanced physical rigidity, surface renewability by polishing and high sensitivity, allowing the simultaneous determination of these three analytes in a human urine sample.

  15. Structural and optical properties of Eu3+ activated low cost zinc soda lime silica glasses

    NASA Astrophysics Data System (ADS)

    Omar, Nur Alia Sheh; Fen, Yap Wing; Matori, Khamirul Amin; Zaid, Mohd Hafiz Mohd; Samsudin, Nur Farhana

    A low cost method was employed to synthesize ZnO-SLS:xEu3+ phosphors using recyclable bottle glass as silica source. The structural and optical properties of ZnO-SLS:xEu3+ (x = 0, 1, 2, 3, 4 and 5 wt.%) glasses were determined using X-ray diffraction (XRD), Fourier transform infrared reflectance (FTIR), UV-visible (Uv-Vis) and photoluminescence (PL) spectroscopy. Structural investigation using XRD measurement had broadened the halo peak with the doping of dopants. FTIR spectra showed the glass system consists of -OH and SiO4 bands. Meanwhile, the optical measurement using UV-Vis absorption has been induced a blue shift of the electronic absorption edge. The emission peak intensity of ZnO-SLS:xEu3+ phosphors was enhanced with the progression of doping concentration and thus, revealed their potential as red emitting phosphors under 400 nm excitation.

  16. Characterization of highly photorefractive and active silica-germania sputtered thin films

    NASA Astrophysics Data System (ADS)

    Berneschi, S.; Brenci, M.; Chiasera, A.; Ferrari, M.; Nunzi Conti, G.; Pelli, S.; Sebastiani, S.; Tosello, C.; Righini, G. C.

    2006-02-01

    We report on the characterization of highly photorefractive Er 3+/Yb 3+-doped silica-germania planar waveguides deposited by radio-frequency-magnetron-sputtering technique. Details of the deposition process in order to get low loss, single mode waveguides at 1550 nm are described. The material presents an intense absorption band in the UV region and irradiation by a KrF excimer laser source produces large positive refractive index changes, without the need of particular sensitization procedures. Dark line spectroscopy of the waveguide modes at 635 nm was performed to calculate the index change under UV exposure. Highly efficient photo-induced phase gratings have been fabricated in the slab waveguide. Waveguides spectroscopic properties of the 4I 13/2 <=> 4I 15/2 transition of the Er 3+ ion, including lifetime and emission bandwidth, were examined. Photoluminescence excitation spectroscopy was also recorded to detect the Yb 3+ to Er 3+ energy transfer process.

  17. JPL Activated Carbon Treatment System (ACTS) for sewage

    NASA Technical Reports Server (NTRS)

    1976-01-01

    An Activated Carbon Treatment System (ACTS) was developed for sewage treatment and is being applied to a one-million gallon per day sewage treatment pilot plant in Orange County California. Activities reported include pyrolysis and activation of carbon-sewage sludge, and activated carbon treatment of sewage to meet ocean discharge standards. The ACTS Sewage treatment operations include carbon-sewage treatment, primary and secondary clarifiers, gravity (multi-media) filter, filter press dewatering, flash drying of carbon-sewage filter cake, and sludge pyrolysis and activation. Tests were conducted on a laboratory scale, 10,000 gallon per day demonstration plant and pilot test equipment. Preliminary economic studies are favorable to the ACTS process relative to activated sludge treatment for a 175,000,000 gallon per day sewage treatment plant.

  18. Activated Carbon Modified with Copper for Adsorption of Propanethiol

    PubMed Central

    Moreno-Piraján, Juan Carlos; Tirano, Joaquín; Salamanca, Brisa; Giraldo, Liliana

    2010-01-01

    Activated carbons were characterized texturally and chemically before and after treatment, using surface area determination in the BET model, Boehm titration, TPR, DRX and immersion calorimetry. The adsorption capacity and the kinetics of sulphur compound removal were determined by gas chromatography. It was established that the propanethiol retention capacity is dependent on the number of oxygenated groups generated on the activated carbon surface and that activated carbon modified with CuO at 0.25 M shows the highest retention of propanethiol. Additionally is proposed a mechanism of decomposition of propenothiol with carbon-copper system. PMID:20479992

  19. Preparation of nitrogen-enriched activated carbons from brown coal

    SciTech Connect

    Robert Pietrzak; Helena Wachowska; Piotr Nowicki

    2006-05-15

    Nitrogen-enriched activated carbons were prepared from a Polish brown coal. Nitrogen was introduced from urea at 350{sup o}C in an oxidizing atmosphere both to carbonizates obtained at 500-700{sup o}C and to activated carbons prepared from them. The activation was performed at 800{sup o}C with KOH in argon. It has been observed that the carbonization temperature determines the amount of nitrogen that is incorporated (DC5U, 8.4 wt % N{sup daf}; DC6U, 6.3 wt % N{sup daf}; and DC7U, 5.4 wt % N{sup daf}). X-ray photoelectron spectroscopy (XPS) measurements have shown that nitrogen introduced both at the stage of carbonizates and at the stage of activated carbons occurs mainly as -6, -5, and imine, amine and amide groups. On the other hand, the activation of carbons enriched with nitrogen results in the formation of pyridonic nitrogen and N-Q. The introduction of nitrogen at the activated carbon stage leads to a slight decrease in surface area. It has been proven that the most effective way of preparing microporous activated carbons enriched with nitrogen to a considerable extent and having high surface area ({approximately} 3000 m{sup 2}/g) is the following: carbonization - activation - reaction with urea. 40 refs., 1 fig., 6 tabs.

  20. Silica Fillers for elastomer Reinforement

    SciTech Connect

    Kohls, D.J.; Schaefer, D.W.

    2009-08-26

    This article summarizes recent work on the structure of precipitated silica used in the reinforcement of elastomers. Silica has a unique morphology, consisting of multiple structural levels that can be controlled through processing. The ability to control and characterize the multiple structures of precipitated silica is an example of morphological engineering for reinforcement applications. In this summary of some recent research efforts using precipitated silica, small-angle scattering techniques are described and their usefulness for determining the morphology of silica in terms of primary particles, aggregates, and agglomerates are discussed. The structure of several different precipitated silica powders is shown as well as the mechanical properties of elastomers reinforced with these silica particles. The study of the mechanical properties of filled elastomer systems is a challenging and exciting topic for both fundamental science and industrial application. It is known that the addition of hard particulates to a soft elastomer matrix results in properties that do not follow a straightforward rule of mixtures. Research efforts in this area have shown that the properties of filled elastomers are influenced by the nature of both the filler and the matrix, as well as the interactions between them. Several articles have reviewed the influence of fillers like silica and carbon black on the reinforcement of elastomers. In general, the structure-property relationships developed for filled elastomers have evolved into the following major areas: Filler structure, hydrodynamic reinforcement, and interactions between fillers and elastomers.

  1. Silica Fillers for elastomer Reinforement

    SciTech Connect

    Kohls, D.J.; Schaefer, D.W.

    2012-09-10

    This article summarizes recent work on the structure of precipitated silica used in the reinforcement of elastomers. Silica has a unique morphology, consisting of multiple structural levels that can be controlled through processing. The ability to control and characterize the multiple structures of precipitated silica is an example of morphological engineering for reinforcement applications. In this summary of some recent research efforts using precipitated silica, small-angle scattering techniques are described and their usefulness for determining the morphology of silica in terms of primary particles, aggregates, and agglomerates are discussed. The structure of several different precipitated silica powders is shown as well as the mechanical properties of elastomers reinforced with these silica particles. The study of the mechanical properties of filled elastomer systems is a challenging and exciting topic for both fundamental science and industrial application. It is known that the addition of hard particulates to a soft elastomer matrix results in properties that do not follow a straightforward rule of mixtures. Research efforts in this area have shown that the properties of filled elastomers are influenced by the nature of both the filler and the matrix, as well as the interactions between them. Several articles have reviewed the influence of fillers like silica and carbon black on the reinforcement of elastomers. In general, the structure-property relationships developed for filled elastomers have evolved into the following major areas: Filler structure, hydrodynamic reinforcement, and interactions between fillers and elastomers.

  2. Mitigation of Laser Damage Growth in Fused Silica NIF Optics with a Galvanometer Scanned Carbon Dioxide Laser

    SciTech Connect

    Bass, I L; Draggoo, V; Guss, G M; Hackel, R P; Norton, M A

    2006-04-06

    Economic operation of the National Ignition Facility at the Lawrence Livermore National Laboratory depends on controlling growth of laser damage in the large, high cost optics exposed to UV light at 351 nm. Mitigation of the growth of damage sites on fused silica surfaces greater than several hundred microns in diameter has been previously reported by us using galvanometer scanning of a tightly focused 10.6 {micro}m CO{sub 2} laser spot over an area encompassing the laser damage. Further investigation revealed that fused silica vapor re-deposited on the surface as ''debris'' led to laser damage at unexpectedly low fluences when exposed to multiple laser shots at 351 nm. Additionally, laser power and spatial mode fluctuations in the mitigation laser led to poor repeatability of the process. We also found that the shape of the mitigation pit could produce downstream intensification that could damage other NIF optics. Modifications were made to both the laser system and the mitigation process in order to address these issues. Debris was completely eliminated by these changes, but repeatability and downstream intensification issues still persist.

  3. Preparation and in vitro/in vivo Evaluation of Lacidipine by Adsorption onto Fumed Silica Using Supercritical Carbon Dioxide.

    PubMed

    Geng, Yajie; Fu, Qiang; Guo, Bei; Li, Yun; Zhang, Xiangrong; Wang, Xianglin; Zhang, Tianhong

    2016-01-01

    The aim of this study was to design a silica-supported solid dispersion of lacidipine (LCDP) to enhance the dissolution rate and oral absorption using supercritical CO2 (scCO2) as a solvent. The formulation was characterized using differential scanning calorimetry, powder X-ray diffraction, scanning electron microscopy and fourier transformed infrared spectroscopy. In the dissolution test, LCDP-scCO2 formulation showed a significantly enhanced dissolution compared with LCDPsilica physical mixture and a faster dissolution rate than Lacipil® under different dissolution conditions. In an in vivo test, the area under concentration-time curve and Cmax of LCDP-scCO2 formulation was 9.23 and 23.78 fold greater than LCDP-silica physical mixture (1:15, w/w), respectively, whereas the corresponding values were 1.92 and 2.80 fold greater than Lacipil®, respectively. Our results showed that the solid dispersion prepared by supercritical fluids technology is a feasible method to enhance the oral bioavailability of LCDP.

  4. Microbial Enzyme Activity and Carbon Cycling in Grassland Soil Fractions

    NASA Astrophysics Data System (ADS)

    Allison, S. D.; Jastrow, J. D.

    2004-12-01

    Extracellular enzymes are necessary to degrade complex organic compounds present in soils. Using physical fractionation procedures, we tested whether old soil carbon is spatially isolated from degradative enzymes across a prairie restoration chronosequence in Illinois, USA. We found that carbon-degrading enzymes were abundant in all soil fractions, including macroaggregates, microaggregates, and the clay fraction, which contains carbon with a mean residence time of ~200 years. The activities of two cellulose-degrading enzymes and a chitin-degrading enzyme were 2-10 times greater in organic matter fractions than in bulk soil, consistent with the rapid turnover of these fractions. Polyphenol oxidase activity was 3 times greater in the clay fraction than in the bulk soil, despite very slow carbon turnover in this fraction. Changes in enzyme activity across the restoration chronosequence were small once adjusted for increases in soil carbon concentration, although polyphenol oxidase activity per unit carbon declined by 50% in native prairie versus cultivated soil. These results are consistent with a `two-pool' model of enzyme and carbon turnover in grassland soils. In light organic matter fractions, enzyme production and carbon turnover both occur rapidly. However, in mineral-dominated fractions, both enzymes and their carbon substrates are immobilized on mineral surfaces, leading to slow turnover. Soil carbon accumulation in the clay fraction and across the prairie restoration chronosequence probably reflects increasing physical isolation of enzymes and substrates on the molecular scale, rather than the micron to millimeter scale.

  5. A Magnesium-Activated Carbon Hybrid Capacitor

    SciTech Connect

    Yoo, HD; Shterenberg, I; Gofer, Y; Doe, RE; Fischer, CC; Ceder, G; Aurbach, D

    2013-12-11

    Prototype cells of hybrid capacitor were developed, comprising activated carbon (AC) cloth and magnesium (Mg) foil as the positive and negative electrodes, respectively. The electrolyte solution included ether solvent (TBF) and a magnesium organo-halo-aluminate complex 0.25 M Mg2Cl3+-Ph2AlCl2-. In this solution Mg can be deposited/dissolved reversibly for thousands of cycles with high reversibility (100% cycling efficiency). The main barrier for integrating porous AC electrodes with this electrolyte solution was the saturation of the pores with the large ions in the AC prior to reaching the potential limit. This is due to the existence of bulky Mg and Al based ionic complexes consisting Cl, alkyl or aryl (R), and THF ligands. This problem was resolved by adding 0.5 M of lithium chloride (LiCl), thus introducing smaller ionic species to the solution. This Mg hybrid capacitor system demonstrated a stable cycle performance for many thousands of cycles with a specific capacitance of 90 Fg(-1) for the AC positive electrodes along a potential range of 2.4 V. (C) 2014 The Electrochemical Society. All rights reserved.

  6. Adsorption of EDTA on activated carbon from aqueous solutions.

    PubMed

    Zhu, Hai-song; Yang, Xiao-juan; Mao, Yan-peng; Chen, Yu; Long, Xiang-li; Yuan, Wei-kang

    2011-01-30

    In this study, the adsorption of EDTA on activated carbon from aqueous solutions has been investigated in a batch stirred cell. Experiments have been carried out to investigate the effects of temperature, EDTA concentration, pH, activated carbon mass and particle size on EDTA adsorption. The experimental results manifest that the EDTA adsorption rate increases with its concentration in the aqueous solutions. EDTA adsorption also increases with temperature. The EDTA removal from the solution increases as activated carbon mass increases. The Langmuir and Freundlich equilibrium isotherm models are found to provide a good fitting of the adsorption data, with R(2) = 0.9920 and 0.9982, respectively. The kinetic study shows that EDTA adsorption on the activated carbon is in good compliance with the pseudo-second-order kinetic model. The thermodynamic parameters (E(a), ΔG(0), ΔH(0), ΔS(0)) obtained indicate the endothermic nature of EDTA adsorption on activated carbon.

  7. Ozone Removal by Filters Containing Activated Carbon: A Pilot Study

    SciTech Connect

    Fisk, William; Spears, Mike; Sullivan, Douglas; Mendell, Mark

    2009-09-01

    This study evaluated the ozone removal performance of moderate-cost particle filters containing activated carbon when installed in a commercial building heating, ventilating, and air conditioning (HVAC) system. Filters containing 300 g of activated carbon per 0.09 m2 of filter face area were installed in two 'experimental' filter banks within an office building located in Sacramento, CA. The ozone removal performance of the filters was assessed through periodic measurements of ozone concentrations in the air upstream and downstream of the filters. Ozone concentrations were also measured upstream and downstream of a 'reference' filter bank containing filters without any activated carbon. The filter banks with prefilters containing activated carbon were removing 60percent to 70percent of the ozone 67 and 81 days after filter installation. In contrast, there was negligible ozone removal by the reference filter bank without activated carbon.

  8. 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.

  9. Synthesis, photophysical characterization, and photoinduced antibacterial activity of methylene blue-loaded amino- and mannose-targeted mesoporous silica nanoparticles.

    PubMed

    Planas, Oriol; Bresolí-Obach, Roger; Nos, Jaume; Gallavardin, Thibault; Ruiz-González, Rubén; Agut, Montserrat; Nonell, Santi

    2015-04-09

    Over the last 20 years, the number of pathogenic multi-resistant microorganisms has grown steadily, which has stimulated the search for new strategies to combat antimicrobial resistance. Antimicrobial photodynamic therapy (aPDT), also called photodynamic inactivation, is emerging as a promising alternative to treatments based on conventional antibiotics. We have explored the effectiveness of methylene blue-loaded targeted mesoporous silica nanoparticles (MSNP) in the photodynamic inactivation of two Gram negative bacteria, namely Escherichia coli and Pseudomonas aeruginosa. For E. coli, nanoparticle association clearly reduced the dark toxicity of MB while preserving its photoinactivation activity. For P. aeruginosa, a remarkable difference was observed between amino- and mannose-decorated nanoparticles. The details of singlet oxygen production in the nanoparticles have been characterized, revealing the presence of two populations of this cytotoxic species. Strong quenching of singlet oxygen within the nanoparticles is observed.

  10. The adsorption of sympathomimetic agents by activated carbon hemoperfusion.

    PubMed

    Horres, C R; Hill, J B; Ellis, F W

    1976-01-01

    Sympathomimetic agents with mixed and pure alpha and beta adrenergic activity are adsorbed by coconut shell activated carbon from blood, sufficiently rapidly to markedly reduce the activity of these agents. The results of this study suggest that the site of injection of sympathomimetic agents being considered for correcting hypotension during activated carbon hemoperfusion be selected to permit systemic mixing before circulation into the adsorption device.

  11. Fractal analysis of granular activated carbons using isotherm data

    SciTech Connect

    Khalili, N.R.; Pan, M.; Sandi, G.

    1997-08-01

    Utilization of adsorption on solid surfaces was exercised for the first time in 1785. Practical application of unactivated carbon filters, and powdered carbon were first demonstrated in the American water treatment plant, and a municipal treatment plant in New Jersey, in 1883 and 1930, respectively. The use of activated carbon became widespread in the next few decades. At present, adsorption on carbons has a wide spread application in water treatment and removal of taste, odor, removal of synthetic organic chemicals, color-forming organics, and desinfection by-products and their naturally occurring precursors. This paper presents an analysis of the surface fractal dimension and adsorption capacity of a group of carbons.

  12. Selecting activated carbon for water and wastewater treatability studies

    SciTech Connect

    Zhang, W.; Chang, Q.G.; Liu, W.D.; Li, B.J.; Jiang, W.X.; Fu, L.J.; Ying, W.C.

    2007-10-15

    A series of follow-up investigations were performed to produce data for improving the four-indicator carbon selection method that we developed to identify high-potential activated carbons effective for removing specific organic water pollutants. The carbon's pore structure and surface chemistry are dependent on the raw material and the activation process. Coconut carbons have relatively more small pores than large pores; coal and apricot nutshell/walnut shell fruit carbons have the desirable pore structures for removing adsorbates of all sizes. Chemical activation, excessive activation, and/or thermal reactivation enlarge small pores, resulting in reduced phenol number and higher tannic acid number. Activated carbon's phenol, iodine, methylene blue, and tannic acid numbers are convenient indicators of its surface area and pore volume of pore diameters < 10, 10-15, 15-28, and > 28 angstrom, respectively. The phenol number of a carbon is also a good indicator of its surface acidity of oxygen-containing organic functional groups that affect the adsorptive capacity for aromatic and other small polar organics. The tannic acid number is an indicator of carbon's capacity for large, high-molecular-weight natural organic precursors of disinfection by-products in water treatment. The experimental results for removing nitrobenzene, methyl-tert-butyl ether, 4,4-bisphenol, humic acid, and the organic constituents of a biologically treated coking-plant effluent have demonstrated the effectiveness of this capacity-indicator-based method of carbon selection.

  13. Two choices for the functionalization of silica nanoparticles with gallic acid: characterization of the nanomaterials and their antimicrobial activity against Paenibacillus larvae

    NASA Astrophysics Data System (ADS)

    Vico, Tamara A.; Arce, Valeria B.; Fangio, María F.; Gende, Liesel B.; Bertran, Celso A.; Mártire, Daniel O.; Churio, María S.

    2016-11-01

    Silica nanoparticles attached to gallic acid were synthesized from 7-nm diameter fumed silica particles by different functionalization methods involving the condensation of hydroxyl or carboxyl groups. The particles were characterized by thermal analyses and UV-vis, FTIR, NMR, and EPR spectroscopies. In comparison to free gallic acid, enhanced stability and increased antimicrobial activity against Paenibacillus larvae were found for the functionalized nanoparticles. Thus, both derivatization strategies result in improved properties of the natural polyphenol as antimicrobial agent for the treatment of honeybee pathologies.

  14. Enhancing the separation performance of the first-generation silica monolith using active flow technology: parallel segmented flow mode of operation.

    PubMed

    Soliven, Arianne; Foley, Dominic; Pereira, Luisa; Dennis, Gary R; Shalliker, R Andrew; Cabrera, Karin; Ritchie, Harald; Edge, Tony

    2014-03-21

    Active flow technology (AFT) columns are designed to minimise inefficient flow processes associated with the column wall and radial heterogeneity of the stationary phase bed. This study is the first to investigate AFT on an analytical scale 4.6mm internal diameter first-generation silica monolith. The performance was compared to a conventional first-generation silica monolith and it was observed that the AFT monolith had an increase in efficiency values that ranged from 15 to 111%; the trend demonstrating efficiency gains increasing as the volumetric flow to the detector was decreased, but with no loss in sensitivity.

  15. Preparation of activated carbon monolith by application of phenolic resins as carbon precursors

    NASA Astrophysics Data System (ADS)

    Sajad, Mehran; Kazemzad, Mahmood; Hosseinnia, Azarmidokht

    2014-04-01

    In the current work, activated carbon monoliths have been prepared by application of different phenolic hydrocarbons namely catechol and resorcinol as carbon precursors. For synthesis of carbon monolith, the precursors have been mixed with Genapol PF-10 as template and then polymerized in the presence of lysine as catalyst. Then the polymerized monolith carbonized in inert atmosphere at 700°C and activated by water steam at 550°C. It was found that resorcinol polymerization is easier than catechol and occurred at 90°C while for polymerization of catechol elevated temperature of 120°C at hydrothermal condition is necessary. The prepared activated carbon samples have been characterized by various analysis methods including scanning electron microscopy (SEM), surface area measurement, and transmission electron microscopy (TEM). The adsorptions of three different aromatic hydrocarbons by the prepared activated carbon samples have also been investigated by high performance liquid chromatography (HPLC) and UV-Vis spectroscopy. It was found that carbon monolith prepared by catechol as carbon precursor has higher adsorpability and strength in comparison with the other sample. The higher performance of carbon monolith prepared by catechol can be associated with its higher active sites in comparison with resorcinol.

  16. Production and characterization of lignocellulosic biomass-derived activated carbon.

    PubMed

    Namazi, A B; Jia, C Q; Allen, D G

    2010-01-01

    The goal of this work is to establish the technical feasibility of producing activated carbon from pulp mill sludges. KOH chemical activation of four lignocellulosic biomass materials, two sludges from pulp mills, one sludge for a linerboard mill, and cow manure, were investigated experimentally, with a focus on the effects of KOH/biomass ratio (1/1, 1.5/1 and 2/1), activation temperature (400-600 °C) and activation time (1 to 2 h) on the development of porosity. The activation products were characterized for their physical and chemical properties using a surface area analyzer, scanning electron microscopy and Fourier transform infrared spectroscopy. Experiments were carried out to establish the effectiveness of the lignocellulosic biomass-derived activated carbon in removing methylene blue (MB), a surrogate of large organic molecules. The results show that the activated carbon are highly porous with specific surface area greater than 500 m²/g. The yield of activated carbon was greater than the percent of fixed carbon in the dry sludge, suggesting that the activation process was able to capture a substantial amount of carbon from the organic matter in the sludge. While 400 °C was too low, 600 °C was high enough to sustain a substantial rate of activation for linerboard sludge. The KOH/biomass ratio, activation temperature and time all play important roles in pore development and yield control, allowing optimization of the activation process. MB adsorption followed a Langmuir isotherm for all four activated carbon, although the adsorption capacity of NK-primary sludge-derived activated carbon was considerably lower than the rest, consistent with its lower specific surface area.

  17. Preparation and characterization of activated carbon produced from pomegranate seeds by ZnCl 2 activation

    NASA Astrophysics Data System (ADS)

    Uçar, Suat; Erdem, Murat; Tay, Turgay; Karagöz, Selhan

    2009-08-01

    In this study, pomegranate seeds, a by-product of fruit juice industry, were used as precursor for the preparation of activated carbon by chemical activation with ZnCl 2. The influence of process variables such as the carbonization temperature and the impregnation ratio on textural and chemical-surface properties of the activated carbons was studied. When using the 2.0 impregnation ratio at the carbonization temperature of 600 °C, the specific surface area of the resultant carbon is as high as 978.8 m 2 g -1. The results showed that the surface area and total pore volume of the activated carbons at the lowest impregnation ratio and the carbonization temperature were achieved as high as 709.4 m 2 g -1 and 0.329 cm 3 g -1. The surface area was strongly influenced by the impregnation ratio of activation reagent and the subsequent carbonization temperature.

  18. Soil Inorganic Carbon in Deserts: Active Carbon Sink or Inert Reservoir?

    NASA Astrophysics Data System (ADS)

    Monger, H. C.; Cole, D. R.

    2011-12-01

    Soil inorganic carbon is the third largest C pool in the active global carbon cycle, containing at least 800 petagrams of carbon. Although carbonate dissolution-precipitation reactions have been understood for over a century, the role of soil inorganic carbon in carbon sequestration, and in particular pedogenic carbonate, is a deceptively complex process because it involves interdependent connections among climate, plants, microorganisms, silicate minerals, soil moisture, pH, and Ca supply via rain, dust, or in situ weathering. An understanding of soil inorganic carbon as a sink or reservoir also requires examination of the system at local to continental scales and at seasonal to millennial time scales. In desert soils studied in North America, carbon isotope ratios and radiocarbon dates were measured in combination with electron microscopy, lab and field experiments with biological calcite formation, and field measurements of carbon dioxide emissions. These investigations reveal that soil inorganic carbon is both an active sink and a inert reservoir depending on the spatial and temporal scale and source of calcium.

  19. Cellulosic carbon fibers with branching carbon nanotubes for enhanced electrochemical activities for bioprocessing applications.

    PubMed

    Zhao, Xueyan; Lu, Xin; Tze, William Tai Yin; Kim, Jungbae; Wang, Ping

    2013-09-25

    Renewable biobased carbon fibers are promising materials for large-scale electrochemical applications including chemical processing, energy storage, and biofuel cells. Their performance is, however, often limited by low activity. Herein we report that branching carbon nanotubes can enhance the activity of carbonized cellulosic fibers, such that the oxidation potential of NAD(H) was reduced to 0.55 V from 0.9 V when applied for bioprocessing. Coordinating with enzyme catalysts, such hierarchical carbon materials effectively facilitated the biotransformation of glycerol, with the total turnover number of NAD(H) over 3500 within 5 h of reaction.

  20. Grain-based activated carbons for natural gas storage.

    PubMed

    Zhang, Tengyan; Walawender, Walter P; Fan, L T

    2010-03-01

    Natural gas has emerged as a potential alternative to gasoline due to the increase in global energy demand and environmental concerns. An investigation was undertaken to explore the technical feasibility of implementing the adsorbed natural gas (ANG) storage in the fuel tanks of motor vehicles with activated carbons from biomass, e.g., sorghum and wheat. The grain-based activated carbons were prepared by chemical activation; the experimental parameters were varied to identify the optimum conditions. The porosity of the resultant activated carbons was evaluated through nitrogen adsorption; and the storage capacity, through methane adsorption. A comparative study was also carried out with commercial activated carbons from charcoal. The highest storage factor attained was 89 for compacted grain-based activated carbons from grain sorghum with a bulk density of 0.65 g/cm(3), and the highest storage factor attained is 106 for compacted commercial activated carbons (Calgon) with a bulk density of 0.70 g/cm(3). The storage factor was found to increase approximately linearly with increasing bulk density and to be independent of the extent of compaction. This implies that the grain-based activated carbons are the ideal candidates for the ANG storage.

  1. Acute Exposure to Crystalline Silica Reduces Macrophage Activation in Response to Bacterial Lipoproteins

    PubMed Central

    Beamer, Gillian L.; Seaver, Benjamin P.; Jessop, Forrest; Shepherd, David M.; Beamer, Celine A.

    2016-01-01

    Numerous studies have examined the relationship between alveolar macrophages (AMs) and crystalline silica (SiO2) using in vitro and in vivo immunotoxicity models; however, exactly how exposure to SiO2 alters the functionality of AM and the potential consequences for immunity to respiratory pathogens remains largely unknown. Because recognition and clearance of inhaled particulates and microbes are largely mediated by pattern recognition receptors (PRRs) on the surface of AM, we hypothesized that exposure to SiO2 limits the ability of AM to respond to bacterial challenge by altering PRR expression. Alveolar and bone marrow-derived macrophages downregulate TLR2 expression following acute SiO2 exposure (e.g., 4 h). Interestingly, these responses were dependent on interactions between SiO2 and the class A scavenger receptor CD204, but not MARCO. Furthermore, SiO2 exposure decreased uptake of fluorescently labeled Pam2CSK4 and Pam3CSK4, resulting in reduced secretion of IL-1β, but not IL-6. Collectively, our data suggest that SiO2 exposure alters AM phenotype, which in turn affects their ability to uptake and respond to bacterial lipoproteins. PMID:26913035

  2. The deep-sea natural products, biogenic polyphosphate (Bio-PolyP) and biogenic silica (Bio-Silica), as biomimetic scaffolds for bone tissue engineering: fabrication of a morphogenetically-active polymer.

    PubMed

    Wang, Xiaohong; Schröder, Heinz C; Feng, Qingling; Draenert, Florian; Müller, Werner E G

    2013-03-08

    Bone defects in human, caused by fractures/nonunions or trauma, gain increasing impact and have become a medical challenge in the present-day aging population. Frequently, those fractures require surgical intervention which ideally relies on autografts or suboptimally on allografts. Therefore, it is pressing and likewise challenging to develop bone substitution materials to heal bone defects. During the differentiation of osteoblasts from their mesenchymal progenitor/stem cells and of osteoclasts from their hemopoietic precursor cells, a lineage-specific release of growth factors and a trans-lineage homeostatic cross-talk via signaling molecules take place. Hence, the major hurdle is to fabricate a template that is functioning in a way mimicking the morphogenetic, inductive role(s) of the native extracellular matrix. In the last few years, two naturally occurring polymers that are produced by deep-sea sponges, the biogenic polyphosphate (bio-polyP) and biogenic silica (bio-silica) have also been identified as promoting morphogenetic on both osteoblasts and osteoclasts. These polymers elicit cytokines that affect bone mineralization (hydroxyapatite formation). In this manner, bio-silica and bio-polyP cause an increased release of BMP-2, the key mediator activating the anabolic arm of the hydroxyapatite forming cells, and of RANKL. In addition, bio-polyP inhibits the progression of the pre-osteoclasts to functionally active osteoclasts. Based on these findings, new bioinspired strategies for the fabrication of bone biomimetic templates have been developed applying 3D-printing techniques. Finally, a strategy is outlined by which these two morphogenetically active polymers might be used to develop a novel functionally active polymer.

  3. The Deep-Sea Natural Products, Biogenic Polyphosphate (Bio-PolyP) and Biogenic Silica (Bio-Silica), as Biomimetic Scaffolds for Bone Tissue Engineering: Fabrication of a Morphogenetically-Active Polymer

    PubMed Central

    Wang, Xiaohong; Schröder, Heinz C.; Feng, Qingling; Draenert, Florian; Müller, Werner E. G.

    2013-01-01

    Bone defects in human, caused by fractures/nonunions or trauma, gain increasing impact and have become a medical challenge in the present-day aging population. Frequently, those fractures require surgical intervention which ideally relies on autografts or suboptimally on allografts. Therefore, it is pressing and likewise challenging to develop bone substitution materials to heal bone defects. During the differentiation of osteoblasts from their mesenchymal progenitor/stem cells and of osteoclasts from their hemopoietic precursor cells, a lineage-specific release of growth factors and a trans-lineage homeostatic cross-talk via signaling molecules take place. Hence, the major hurdle is to fabricate a template that is functioning in a way mimicking the morphogenetic, inductive role(s) of the native extracellular matrix. In the last few years, two naturally occurring polymers that are produced by deep-sea sponges, the biogenic polyphosphate (bio-polyP) and biogenic silica (bio-silica) have also been identified as promoting morphogenetic on both osteoblasts and osteoclasts. These polymers elicit cytokines that affect bone mineralization (hydroxyapatite formation). In this manner, bio-silica and bio-polyP cause an increased release of BMP-2, the key mediator activating the anabolic arm of the hydroxyapatite forming cells, and of RANKL. In addition, bio-polyP inhibits the progression of the pre-osteoclasts to functionally active osteoclasts. Based on these findings, new bioinspired strategies for the fabrication of bone biomimetic templates have been developed applying 3D-printing techniques. Finally, a strategy is outlined by which these two morphogenetically active polymers might be used to develop a novel functionally active polymer. PMID:23528950

  4. Multifunctional Janus hematite-silica nanoparticles: mimicking peroxidase-like activity and sensitive colorimetric detection of glucose.

    PubMed

    Lu, Chang; Liu, Xiangjiang; Li, Yunfeng; Yu, Fang; Tang, Longhua; Hu, Yanjie; Ying, Yibin

    2015-07-22

    The design and engineering of multifunctional nanostructures with multiple components and synergistic properties are in urgent demand for variety of acceptable biosensing platforms, enabling users to fulfill multiple tasks in a single nanosystem. Herein, we report using an asymmetric hematite-silica hybrid of Janus γ-Fe2O3/SiO2 nanoparticles (JFSNs) as a multifunctional biosensing platform for sensitive colorimetric detection of H2O2 and glucose. It was demonstrated that JFSNs exhibit an intrinsic peroxidase-like catalytic activity. Compared with natural enzyme, JFSNs nanoenzymes could be used over a wider range of pH and temperatures and were more stable over time. Importantly, besides its excellent catalytic activity, the asymmetric properties of the Janus nanoparticle enable it to form the multiple functional utilities for various biosensing applications, including the ease of surface modification without deactivation of catalytic activity and recoverable use by magnetic separation. Thus, we utilized JFSNs with glucose oxidase (GOx) immobilization for glucose-sensitive colorimetric detection, which exhibited both catalytic activity of glucose oxidase and peroxidase with high selectivity and acceptable reproducibility. By combining these two analysis systems into Janus particles, an all-in-one and reusable sensor for blood glucose was formed and has the capability for determination of glucose in complex samples such as serum. These results suggest that such Janus nanosystems have the potential to construct robust nanoarchitecture with multiple functionalities for various biosensing applications.

  5. Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity

    NASA Astrophysics Data System (ADS)

    Erdmann, Martin; Koepke, Jürgen

    2016-10-01

    We experimentally investigated phase relations and phase compositions as well as the influence of water activity ( aH2O) and redox conditions on the equilibrium crystallization path within an oceanic dacitic potassium-depleted system at shallow pressure (200 MPa). Moreover, we measured the partitioning of trace elements between melt and plagioclase via secondary ion mass spectrometry for a highly evolved experiment (SiO2 = 74.6 wt%). As starting material, we used a dacitic glass dredged at the Pacific-Antarctic Rise. Phase assemblages in natural high-silica systems reported from different locations of fast-spreading oceanic crust could be experimentally reproduced only in a relatively small range of temperature and melt-water content ( T ~950 °C; melt H2O < 1.5 wt%) at redox conditions slightly below the quartz-fayalite-magnetite buffer. The relatively low water content is remarkable, because distinct hydrothermal influence is generally regarded as key for producing silica-rich rocks in an oceanic environment. However, our conclusion is also supported by mineral and melt chemistry of natural evolved rocks; these rocks are only congruent to the composition of those experimental phases that are produced under low aH2O. Low FeO contents under water-saturated conditions and the characteristic enrichment of Al2O3 in high aH2O experiments, in particular, contradict natural observations, while experiments with low aH2O match the natural trend. Moreover, the observation that highly evolved experimental melts remain H2O-poor while they are relatively enriched in chlorine implies a decoupling between these two volatiles during crustal contamination.

  6. Hydrogen adsorption on functionalized nanoporous activated carbons.

    PubMed

    Zhao, X B; Xiao, B; Fletcher, A J; Thomas, K M

    2005-05-12

    There is considerable interest in hydrogen adsorption on carbon nanotubes and porous carbons as a method of storage for transport and related energy applications. This investigation has involved a systematic investigation of the role of functional groups and porous structure characteristics in determining the hydrogen adsorption characteristics of porous carbons. Suites of carbons were prepared with a wide range of nitrogen and oxygen contents and types of functional groups to investigate their effect on hydrogen adsorption. The porous structures of the carbons were characterized by nitrogen (77 K) and carbon dioxide (273 K) adsorption methods. Hydrogen adsorption isotherms were studied at 77 K and pressure up to 100 kPa. All the isotherms were Type I in the IUPAC classification scheme. Hydrogen isobars indicated that the adsorption of hydrogen is very temperature dependent with little or no hydrogen adsorption above 195 K. The isosteric enthalpies of adsorption at zero surface coverage were obtained using a virial equation, while the values at various surface coverages were obtained from the van't Hoff isochore. The values were in the range 3.9-5.2 kJ mol(-1) for the carbons studied. The thermodynamics of the adsorption process are discussed in relation to temperature limitations for hydrogen storage applications. The maximum amounts of hydrogen adsorbed correlated with the micropore volume obtained from extrapolation of the Dubinin-Radushkevich equation for carbon dioxide adsorption. Functional groups have a small detrimental effect on hydrogen adsorption, and this is related to decreased adsorbate-adsorbent and increased adsorbate-adsorbate interactions.

  7. Select metal adsorption by activated carbon made from peanut shells.

    PubMed

    Wilson, Kermit; Yang, Hong; Seo, Chung W; Marshall, Wayne E

    2006-12-01

    Agricultural by-products, such as peanut shells, contribute large quantities of lignocellulosic waste to the environment each growing season; but few, if any, value-added uses exist for their disposal. The objective of this study was to convert peanut shells to activated carbons for use in adsorption of select metal ions, namely, cadmium (Cd2+), copper (Cu2+), lead (Pb2+), nickel (Ni2+) and zinc (Zn2+). Milled peanut shells were pyrolyzed in an inert atmosphere of nitrogen gas, and then activated with steam at different activation times. Following pyrolysis and activation, the carbons underwent air oxidation. The prepared carbons were evaluated either for adsorption efficiency or adsorption capacity; and these parameters were compared to the same parameters obtained from three commercial carbons, namely, DARCO 12x20, NORIT C GRAN and MINOTAUR. One of the peanut shell-based carbons had metal ion adsorption efficiencies greater than two of the three commercial carbons but somewhat less than but close to Minotaur. This study demonstrates that peanut shells can serve as a source for activated carbons with metal ion-removing potential and may serve as a replacement for coal-based commercial carbons in applications that warrant their use.

  8. Immobilization of enzymes to porous-bead polymers and silica gels activated by graft polymerization of 2,3-epoxypropyl methacrylate.

    PubMed

    Wójcik, A; Lobarzewski, J; Błaszczyńska, T

    1990-01-01

    Three types of organic polymers and bead-shape silica gels were activated by graft polymerization of 2,3-epoxypropyl methacrylate; in some cases, epoxide groups on the support surface were modified to NH2 groups. Eight active matrices so obtained were assessed as supports for immobilized enzymes using peroxidase, glucoamylase and urease. The immobilization yield of protein and specific activities of enzymes were better with supports containing NH2 groups than with those containing epoxide spacer arms. Maximum enzyme immobilization and storage stabilities were obtained with silica-gel beads activated by graft polymerization of 2,3-epoxypropyl methacrylate. With all eight matrices tested, the immobilized enzymes showed good stability with not less than 82% of the original activity persisting after 28 days. The developed matrices have potential for use in process-scale biotechnological operations.

  9. A solid paraffin-based carbon paste electrode modified with 2-aminothiazole organofunctionalized silica for differential pulse adsorptive stripping analysis of nickel in ethanol fuel.

    PubMed

    Takeuchi, Regina M; Santos, André L; Padilha, Pedro M; Stradiotto, Nelson R

    2007-02-19

    A solid paraffin-based carbon paste electrode modified with 2-aminothiazole organofunctionalized silica (SiAt-SPCPE) was applied to Ni(2+) determination in commercial ethanol fuel samples. The proposed method comprised four steps: (1) Ni(2+) preconcentration at open circuit potential directly in the ethanol fuel sample, (2) transference of the electrode to an electrochemical cell containing DMG, (3) differential pulse voltammogram registering and (4) surface regeneration by polishing the electrode. The proposed method combines the high Ni(2+) adsorption capacity presented by 2-aminothiazole organofunctionalized silica with the electrochemical properties of the Ni(DMG)(2) complex, whose electrochemical reduction provides the analytical signal. All experimental parameters involved in the proposed method were optimized. Using a preconcentration time of 20 min, it was obtained a linear range from 7.5 x 10(-9) to 1.0 x 10(-6) mol L(-1) with detection limit of 2.0 x 10(-9) mol L(-1). Recovery values between 96.5 and 102.4% were obtained for commercial samples spiked with 1.0 micromol L(-1) Ni(2+) and the developed electrode was totally stable in ethanolic solutions. The contents of Ni(2+) found in the commercial samples using the proposed method were compared to those obtained by graphite furnace atomic absorption spectroscopy by using the F- and t-test. Neither the F- nor t-values exceeded the critical values at 95% confidence level, confirming that there are not statistical differences between the results obtained by both methods. These results indicate that the developed electrode can be successfully employed to reliable Ni(2+) determination in commercial ethanol fuel samples without any sample pretreatment or dilution step.

  10. Role of nitrogen in pore development in activated carbon prepared by potassium carbonate activation of lignin

    NASA Astrophysics Data System (ADS)

    Tsubouchi, Naoto; Nishio, Megumi; Mochizuki, Yuuki

    2016-05-01

    The present work focuses on the role of nitrogen in the development of pores in activated carbon produced from lignin by K2CO3 activation, employing a fixed bed reactor under a high-purity He stream at temperatures of 500-900 °C. The specific surface area and pore volume obtained by activation of lignin alone are 230 m2/g and 0.13 cm3/g at 800 °C, and 540 m2/g and 0.31 cm3/g at 900 °C, respectively. Activation of a mixture of lignin and urea provides a significant increase in the surface area and volume, respectively reaching 3300-3400 m2/g and 2.0-2.3 cm3/g after holding at 800-900 °C for 1 h. Heating a lignin/urea/K2CO3 mixture leads to a significant decrease in the yield of released N-containing gases compared to the results for urea alone and a lignin/urea mixture, and most of the nitrogen in the urea is retained in the solid phase. X-ray photoelectron spectroscopy and X-ray diffraction analyses clearly show that part of the remaining nitrogen is present in heterocyclic structures (for example, pyridinic and pyrrolic nitrogen), and the rest is contained as KOCN at ≤600 °C and as KCN at ≥700 °C, such that the latter two compounds can be almost completely removed by water washing. The fate of nitrogen during heating of lignin/urea/K2CO3 and role of nitrogen in pore development in activated carbon are discussed on the basis of the results mentioned above.

  11. Hierarchically porous carbons with optimized nitrogen doping as highly active electrocatalysts for oxygen reduction.

    PubMed

    Liang, Hai-Wei; Zhuang, Xiaodong; Brüller, Sebastian; Feng, Xinliang; Müllen, Klaus

    2014-09-17

    Development of efficient, low-cost and stable electrocatalysts as the alternative to platinum for the oxygen reduction reaction is of significance for many important electrochemical devices, such as fuel cells, metal-air batteries and chlor-alkali electrolysers. Here we report a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation. Our protocol allows for the simultaneous optimization of both porous structures and surface functionalities of nitrogen-doped carbons. Accordingly, the prepared catalysts show the highest oxygen reduction reaction activity (half-wave potential of 0.85 V versus reversible hydrogen electrode with a low loading of 0.1 mg cm(-2)) in alkaline media among all reported metal-free catalysts. Significantly, when used for constructing the air electrode of zinc-air battery, our metal-free catalyst outperforms the state-of the-art platinum-based catalyst.

  12. Hierarchically porous carbons with optimized nitrogen doping as highly active electrocatalysts for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Liang, Hai-Wei; Zhuang, Xiaodong; Brüller, Sebastian; Feng, Xinliang; Müllen, Klaus

    2014-09-01

    Development of efficient, low-cost and stable electrocatalysts as the alternative to platinum for the oxygen reduction reaction is of significance for many important electrochemical devices, such as fuel cells, metal-air batteries and chlor-alkali electrolysers. Here we report a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation. Our protocol allows for the simultaneous optimization of both porous structures and surface functionalities of nitrogen-doped carbons. Accordingly, the prepared catalysts show the highest oxygen reduction reaction activity (half-wave potential of 0.85 V versus reversible hydrogen electrode with a low loading of 0.1 mg cm-2) in alkaline media among all reported metal-free catalysts. Significantly, when used for constructing the air electrode of zinc-air battery, our metal-free catalyst outperforms the state-of the-art platinum-based catalyst.

  13. Sink effect in activated carbon-supported hydrodesulfurization catalysts

    SciTech Connect

    Laine, J.; Labady, M.; Severino, F.; Yunes, S.

    1997-03-01

    A synergistic effect has been proposed in previous papers, attempting to explain the higher activity of activated carbon-supported hydrodesulfurization (HDS) catalysts with respect to conventional alumina-supported catalysts, reported earlier. However, activated carbon characteristics can be strongly affected by the raw material and the method of activation. Thus, previous work using Ni-Mo catalysts supported on two different activated carbons (one prepared by {open_quotes}physical{close_quotes} and the other by {open_quotes}chemical{close_quotes} activation) showed different optimal Ni concentrations for higher HDS activity, such difference being attributed to the predominance of Topsoe`s Type I {open_quotes}NiMoS{close_quotes} phase in one carbon and the predominance of Type II in the other. Due to the lack of proper characterization of the activated carbon supported catalysts of the previous work, this paper presents further data suggesting that microporosity provided by the activated carbon may be the responsible for the above referred synergism. 12 refs., 1 fig., 3 tabs.

  14. THE FATE AND TOXICITY OF RAMAN ACTIVE SILICA-GOLD NANOPARTICLES IN MICE

    PubMed Central

    THAKOR, AVNESH S; LUONG, RICHARD; PAULMURUGAN, RAMASAMY; LIN, FRANK I; KEMPEN, PAUL; ZAVALETA, CRISTINA; CHU, PAULINE; MASSOUD, TARIK F; SINCLAIR, ROBERT; GAMBHIR, SANJIV S

    2013-01-01

    Raman spectroscopy is an optical imaging modality which analyses the Raman effect in which energy is exchanged between light and matter. Although Raman spectroscopy has been widely used for chemical and molecular analysis, its use in clinical applications has been hindered by the inherently weak nature of the Raman effect. Raman-silica-gold-nanoparticles (R-Si-Au-NPs) overcome this limitation by producing high Raman signals via Surface Enhanced Raman Scattering. Targeted polyethylene glycol (PEG)-ylated R-Si-Au-NPs (e.g. PEG-R-Si-Au-NPs labeled with an affibody which binds specifically to the epidermal growth factor receptor) are currently being designed to detect colorectal cancer after administration into the bowel lumen. With this approach, PEG-R-Si-Au-NPs are not expected to enter the systemic circulation and would be removed from the body via defecation. We examined the acute toxicity and biodistribution of core PEG-R-Si-Au-NPs after different routes of administration in mice. After intravenous administration, PEG-R-Si-Au-NPs were removed from the circulation by marcophages in the liver and spleen (i.e. the reticuloendothelial system). At 24 hours, PEG-R-Si-Au-NPs elicited a mild inflammatory response and an increase in oxidative stress in the liver, which subsided by 2 weeks. No evidence of significant toxicity was observed by measuring clinical, histological, biochemical or cardiovascular parameters for 2 weeks. Notably, after administration per rectum, we observed no significant bowel or systemic toxicity and no PEG-R-Si-Au-NPs were detected systemically. Although additional studies are required to investigate the long-term effects of PEG-R-Si-Au-NPs, these initial results support the idea that they can be safely used in living subjects, especially when administered rectally. PMID:21508310

  15. Grafting of activated carbon cloths for selective adsorption

    NASA Astrophysics Data System (ADS)

    Gineys, M.; Benoit, R.; Cohaut, N.; Béguin, F.; Delpeux-Ouldriane, S.

    2016-05-01

    Chemical functionalization of an activated carbon cloth with 3-aminophthalic acid and 4-aminobenzoic acid groups by the in situ formation of the corresponding diazonium salt in aqueous acidic solution is reported. The nature and amount of selected functions on an activated carbon surface, in particular the grafted density, were determined by potentiometric titration, elemental analysis and X-ray photoelectron spectroscopy (XPS). The nanotextural properties of the modified carbon were explored by gas adsorption. Functionalized activated carbon cloth was obtained at a discrete grafting level while preserving interesting textural properties and a large porous volume. Finally, the grafting homogeneity of the carbon surface and the nature of the chemical bonding were investigated using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) technique.

  16. JV Task 90 - Activated Carbon Production from North Dakota Lignite

    SciTech Connect

    Steven Benson; Charlene Crocker; Rokan Zaman; Mark Musich; Edwin Olson

    2008-03-31

    The Energy & Environmental Research Center (EERC) has pursued a research program for producing activated carbon from North Dakota lignite that can be competitive with commercial-grade activated carbon. As part of this effort, small-scale production of activated carbon was produced from Fort Union lignite. A conceptual design of a commercial activated carbon production plant was drawn, and a market assessment was performed to determine likely revenue streams for the produced carbon. Activated carbon was produced from lignite coal in both laboratory-scale fixed-bed reactors and in a small pilot-scale rotary kiln. The EERC was successfully able to upgrade the laboratory-scale activated carbon production system to a pilot-scale rotary kiln system. The activated carbon produced from North Dakota lignite was superior to commercial grade DARCO{reg_sign} FGD and Rheinbraun's HOK activated coke product with respect to iodine number. The iodine number of North Dakota lignite-derived activated carbon was between 600 and 800 mg I{sub 2}/g, whereas the iodine number of DARCO FGD was between 500 and 600 mg I{sub 2}/g, and the iodine number of Rheinbraun's HOK activated coke product was around 275 mg I{sub 2}/g. The EERC performed both bench-scale and pilot-scale mercury capture tests using the activated carbon made under various optimization process conditions. For comparison, the mercury capture capability of commercial DARCO FGD was also tested. The lab-scale apparatus is a thin fixed-bed mercury-screening system, which has been used by the EERC for many mercury capture screen tests. The pilot-scale systems included two combustion units, both equipped with an electrostatic precipitator (ESP). Activated carbons were also tested in a slipstream baghouse at a Texas power plant. The results indicated that the activated carbon produced from North Dakota lignite coal is capable of removing mercury from flue gas. The tests showed that activated carbon with the greatest iodine number

  17. Activated carbon fibers and engineered forms from renewable resources

    DOEpatents

    Baker, Frederick S.

    2010-06-01

    A method of producing activated carbon fibers (ACFs) includes the steps of providing a natural carbonaceous precursor fiber material, blending the carbonaceous precursor material with a chemical activation agent to form chemical agent-impregnated precursor fibers, spinning the chemical agent-impregnated precursor material into fibers, and thermally treating the chemical agent-impregnated precursor fibers. The carbonaceous precursor material is both carbonized and activated to form ACFs in a single step. The method produces ACFs exclusive of a step to isolate an intermediate carbon fiber.

  18. Activated carbon fibers and engineered forms from renewable resources

    DOEpatents

    Baker, Frederick S

    2013-02-19

    A method of producing activated carbon fibers (ACFs) includes the steps of providing a natural carbonaceous precursor fiber material, blending the carbonaceous precursor material with a chemical activation agent to form chemical agent-impregnated precursor fibers, spinning the chemical agent-impregnated precursor material into fibers, and thermally treating the chemical agent-impregnated precursor fibers. The carbonaceous precursor material is both carbonized and activated to form ACFs in a single step. The method produces ACFs exclusive of a step to isolate an intermediate carbon fiber.

  19. Nickel adsorption by sodium polyacrylate-grafted activated carbon.

    PubMed

    Ewecharoen, A; Thiravetyan, P; Wendel, E; Bertagnolli, H

    2009-11-15

    A novel sodium polyacrylate grafted activated carbon was produced by using gamma radiation to increase the number of functional groups on the surface. After irradiation the capacity for nickel adsorption was studied and found to have increased from 44.1 to 55.7 mg g(-1). X-ray absorption spectroscopy showed that the adsorbed nickel on activated carbon and irradiation-grafted activated carbon was coordinated with 6 oxygen atoms at 2.04-2.06 A. It is proposed that this grafting technique could be applied to other adsorbents to increase the efficiency of metal adsorption.

  20. Activation of peroxymonosulfate by graphitic carbon nitride loaded on activated carbon for organic pollutants degradation.

    PubMed

    Wei, Mingyu; Gao, Long; Li, Jun; Fang, Jia; Cai, Wenxuan; Li, Xiaoxia; Xu, Aihua

    2016-10-05

    Graphitic carbon nitride supported on activated carbon (g-C3N4/AC) was prepared through an in situ thermal approach and used as a metal free catalyst for pollutants degradation in the presence of peroxymonosulfate (PMS) without light irradiation. It was found that g-C3N4 was highly dispersed on the surface of AC with the increase of surface area and the exposition of more edges and defects. The much easier oxidation of C species in g-C3N4 to CO was also observed from XPS spectra. Acid Orange 7 (AO7) and other organic pollutants could be completely degraded by the g-C3N4/AC catalyst within 20min with PMS, while g-C3N4+PMS and AC+PMS showed no significant activity for the reaction. The performance of the catalyst was significantly influenced by the amount of g-C3N4 loaded on AC; but was nearly not affected by the initial solution pH and reaction temperature. In addition, the catalysts presented good stability. A nonradical mechanism accompanied by radical generation (HO and SO4(-)) in AO7 oxidation was proposed in the system. The CO groups play a key role in the process; while the exposure of more N-(C)3 group can further increase its electron density and basicity. This study can contribute to the development of green materials for sustainable remediation of aqueous organic pollutants.

  1. Physicochemical and porosity characteristics of thermally regenerated activated carbon polluted with biological activated carbon process.

    PubMed

    Dong, Lihua; Liu, Wenjun; Jiang, Renfu; Wang, Zhansheng

    2014-11-01

    The characteristics of thermally regenerated activated carbon (AC) polluted with biological activated carbon (BAC) process were investigated. The results showed that the true micropore and sub-micropore volume, pH value, bulk density, and hardness of regenerated AC decreased compared to the virgin AC, but the total pore volume increased. XPS analysis displayed that the ash contents of Al, Si, and Ca in the regenerated AC respectively increased by 3.83%, 2.62% and 1.8%. FTIR spectrum showed that the surface functional groups of virgin and regenerated AC did not change significantly. Pore size distributions indicated that the AC regeneration process resulted in the decrease of micropore and macropore (D>10 μm) volume and the increase of mesopore and macropore (0.1 μm

  2. Preparation of activated carbons from agricultural residues for pesticide adsorption.

    PubMed

    Ioannidou, Ourania A; Zabaniotou, Anastasia A; Stavropoulos, George G; Islam, Md Azharul; Albanis, Triantafyllos A

    2010-09-01

    Activated carbons (ACs) can be used not only for liquid but also for vapour phase applications, such as water treatment, deodorisation, gas purification and air treatment. In the present study, activated carbons produced from agricultural residues (olive kernel, corn cobs, rapeseed stalks and soya stalks) via physical steam activation were tested for the removal of Bromopropylate (BP) from water. For the characterization of the activated carbons ICP, SEM, FTIR and XRD analyses were performed. Adsorption kinetics and equilibrium isotherms were investigated for all biomass activated carbons in aqueous solutions. Experimental data of BP adsorption have fitted best to the pseudo 2nd-order kinetic model and Langmuir isotherm. The study resulted that corn cobs showed better adsorption capacity than the other biomass ACs. Comparison among ACs from biomass and commercial ones (F400 and Norit GL50) revealed that the first can be equally effective for the removal of BP from water with the latter.

  3. Production and characterization of activated carbons from cereal grains

    SciTech Connect

    Venkatraman, A.; Walawender, W.P.; Fan, L.T.

    1996-12-31

    The term, activated carbon, is a generic name for a family of carbonaceous materials with well-developed porosities and consequently, large adsorptive capacities. Activated carbons are increasingly being consumed worldwide for environmental applications such as separation of volatiles from bulk gases and purification of water and waste-water streams. The global annual production is estimated to be around 300 million kilograms, with a rate of increase of 7% each year. Activated carbons can be prepared from a variety of raw materials. Approximately, 60% of the activated carbons generated in the United States is produced from coal; 20%, from coconut shells; and the remaining 20% from wood and other sources of biomass. The pore structure and properties of activated carbons are influenced by the nature of the starting material and the initial physical and chemical conditioning as well as the process conditions involved in its manufacture. The porous structures of charcoals and activated carbons obtained by the carbonization of kernels have been characterized.

  4. Hydrogen storage on activated carbon. Final report

    SciTech Connect

    Schwarz, J.A.

    1994-11-01

    The project studied factors that influence the ability of carbon to store hydrogen and developed techniques to enhance that ability in naturally occurring and factory-produced commercial carbon materials. During testing of enhanced materials, levels of hydrogen storage were achieved that compare well with conventional forms of energy storage, including lead-acid batteries, gasoline, and diesel fuel. Using the best materials, an electric car with a modern fuel cell to convert the hydrogen directly to electricity would have a range of over 1,000 miles. This assumes that the total allowable weight of the fuel cell and carbon/hydrogen storage system is no greater than the present weight of batteries in an existing electric vehicle. By comparison, gasoline cars generally are limited to about a 450-mile range, and battery-electric cars to 40 to 60 miles. The project also developed a new class of carbon materials, based on polymers and other organic compounds, in which the best hydrogen-storing factors discovered earlier were {open_quotes}molecularly engineered{close_quotes} into the new materials. It is believed that these new molecularly engineered materials are likely to exceed the performance of the naturally occurring and manufactured carbons seen earlier with respect to hydrogen storage.

  5. ELEMENTAL MERCURY CAPTURE BY ACTIVATED CARBON IN A FLOW REACTOR

    EPA Science Inventory


    The paper gives results of bench-scale experiments in a flow reactor to simulate the entrained-flow capture of elemental mercury (Hgo) using solid sorbents. Adsorption of Hgo by a lignite-based activated carbon (Calgon FGD) was examined at different carbon/mercury (C/Hg) rat...

  6. Activated carbon testing for the 200 area effluent treatment facility

    SciTech Connect

    Wagner, R.N.

    1997-01-17

    This report documents pilot and laboratory scale testing of activated carbon for use in the 200 Area Effluent Treatment Facility peroxide decomposer columns. Recommendations are made concerning column operating conditions and hardware design, the optimum type of carbon for use in the plant, and possible further studies.

  7. Influence of polymer matrix and adsorption onto silica materials on the migration of alpha-tocopherol into 95% ethanol from active packaging.

    PubMed

    Heirlings, L; Siró, I; Devlieghere, F; Van Bavel, E; Cool, P; De Meulenaer, B; Vansant, E F; Debevere, J

    2004-11-01

    In this study, the effect of polymer materials with different polarity, namely low density polyethylene (LDPE) and ethylene vinyl acetate (EVA), on the migration behaviour of alpha-tocopherol from active packaging was investigated. The antioxidant was also adsorbed onto silica materials, namely SBA-15 (Santa Barbara-15) and Syloblock, in order to protect the antioxidant during extrusion and to ensure a controlled and sufficient release during the shelf-life of the food product. Migration experiments were performed at 7.0 +/- 0.5 degrees C and 95% ethanol was used as fatty food simulant. All films contained a high concentration of alpha-tocopherol, approximately 2000 mg kg(-1), to obtain an active packaging. Polymer matrix had a small influence on the migration profile. The migration of 80% of total migrated amount of antioxidant was retarded for 2.4 days by using LDPE instead of EVA. When alpha-tocopherol was adsorbed onto both silica materials, the migration of 80% of total migrated amount of antioxidant was retarded for 3.4 days in comparison to pure alpha-tocopherol. No difference was seen between the migration profiles of alpha-tocopherol adsorbed onto both silica materials. In the case of pure alpha-tocopherol, 82% of the initial amount of alpha-tocopherol in the film migrated into the food simulant at a rather fast migration rate. In the case of adsorption on silica materials, a total migration was observed. These antioxidative films can have positive food applications.

  8. Selection and preparation of activated carbon for fuel gas storage

    DOEpatents

    Schwarz, James A.; Noh, Joong S.; Agarwal, Rajiv K.

    1990-10-02

    Increasing the surface acidity of active carbons can lead to an increase in capacity for hydrogen adsorption. Increasing the surface basicity can facilitate methane adsorption. The treatment of carbons is most effective when the carbon source material is selected to have a low ash content i.e., below about 3%, and where the ash consists predominantly of alkali metals alkali earth, with only minimal amounts of transition metals and silicon. The carbon is washed in water or acid and then oxidized, e.g. in a stream of oxygen and an inert gas at an elevated temperature.

  9. TESTING GUIDELINES FOR TECHNETIUM-99 ABSORPTION ON ACTIVATED CARBON

    SciTech Connect

    BYRNES ME

    2010-09-08

    CH2M HILL Plateau Remediation Company (CHPRC) is currently evaluating the potential use of activated carbon adsorption for removing technetium-99 from groundwater as a treatment method for the Hanford Site's 200 West Area groundwater pump-and-treat system. The current pump-and-treat system design will include an ion-exchange (IX) system for selective removal of technetium-99 from selected wells prior to subsequent treatment of the water in the central treatment system. The IX resin selected for technetium-99 removal is Purolite A530E. The resin service life is estimated to be approximately 66.85 days at the design technetium-99 loading rate, and the spent resin must be replaced because it cannot be regenerated. The resulting operating costs associated with resin replacement every 66.85 days are estimated at $0.98 million/year. Activated carbon pre-treatment is being evaluated as a potential cost-saving measure to offset the high operating costs associated with frequent IX resin replacement. This document is preceded by the Literature Survey of Technetium-99 Groundwater Pre-Treatment Option Using Granular Activated Carbon (SGW-43928), which identified and evaluated prior research related to technetium-99 adsorption on activated carbon. The survey also evaluated potential operating considerations for this treatment approach for the 200 West Area. The preliminary conclusions of the literature survey are as follows: (1) Activated carbon can be used to selectively remove technetium-99 from contaminated groundwater. (2) Technetium-99 adsorption onto activated carbon is expected to vary significantly based on carbon types and operating conditions. For the treatment approach to be viable at the Hanford Site, activated carbon must be capable of achieving a designated minimum technetium-99 uptake. (3) Certain radionuclides known to be present in 200 West Area groundwater are also likely to adsorb onto activated carbon. (4) Organic solvent contaminants of concern (COCs) will

  10. Process for sequestering carbon dioxide and sulfur dioxide

    DOEpatents

    Maroto-Valer, M. Mercedes; Zhang, Yinzhi; Kuchta, Matthew E.; Andresen, John M.; Fauth, Dan J.

    2009-10-20

    A process for sequestering carbon dioxide, which includes reacting a silicate based material with an acid to form a suspension, and combining the suspension with carbon dioxide to create active carbonation of the silicate-based material, and thereafter producing a metal salt, silica and regenerating the acid in the liquid phase of the suspension.

  11. Quality of poultry litter-derived granular activated carbon.

    PubMed

    Qiu, Guannan; Guo, Mingxin

    2010-01-01

    Utilization of poultry litter as a source material for generating activated carbon is a value-added and environmentally beneficial approach to recycling organic waste. In this study, the overall quality of poultry litter-derived granular activated carbon was systematically evaluated based on its various physical and chemical properties. Granular activated carbon generated from pelletized poultry litter following a typical steam-activation procedure possessed numerous micropores in the matrix. The product exhibited a mean particle diameter of 2.59 mm, an apparent density of 0.45 g cm(-3), a ball-pan hardness of 91.0, an iodine number of 454 mg g(-1), and a BET surface area of 403 m(2) g(-1). It contained high ash, nitrogen, phosphorus contents and the trace elements Cu, Zn, and As. Most of the nutrients and toxic elements were solidified and solution-unextractable. In general, poultry litter-based activated carbon demonstrated overall quality comparable to that of low-grade commercial activated carbon derived from coconut shell and bituminous coal. It is promising to use poultry litter as a feedstock to manufacture activated carbon for wastewater treatment.

  12. Natural gas storage with activated carbon from a bituminous coal

    USGS Publications Warehouse

    Sun, Jielun; Rood, M.J.; Rostam-Abadi, M.; Lizzio, A.A.

    1996-01-01

    Granular activated carbons ( -20 + 100 mesh; 0.149-0.84 mm) were produced by physical activation and chemical activation with KOH from an Illinois bituminous coal (IBC-106) for natural gas storage. The products were characterized by BET surface area, micropore volume, bulk density, and methane adsorption capacities. Volumetric methane adsorption capacities (Vm/Vs) of some of the granular carbons produced by physical activation are about 70 cm3/cm3 which is comparable to that of BPL, a commercial activated carbon. Vm/Vs values above 100 cm3/cm3 are obtainable by grinding the granular products to - 325 mesh (<0.044 mm). The increase in Vm/Vs is due to the increase in bulk density of the carbons. Volumetric methane adsorption capacity increases with increasing pore surface area and micropore volume when normalizing with respect to sample bulk volume. Compared with steam-activated carbons, granular carbons produced by KOH activation have higher micropore volume and higher methane adsorption capacities (g/g). Their volumetric methane adsorption capacities are lower due to their lower bulk densities. Copyright ?? 1996 Elsevier Science Ltd.

  13. Sustainable Regeneration of Nanoparticle Enhanced Activated Carbon in Water

    EPA Science Inventory

    The regeneration and reuse of exhausted granular activated carbon (GAC) is an appropriate method for lowering operational and environmental costs. Advanced oxidation is a promising environmental friendly technique for GAC regeneration. The main objective of this research was to ...

  14. [Influence of biological activated carbon dosage on landfill leachate treatment].

    PubMed

    Cui, Yan-Rui; Guo, Yan; Wu, Qing

    2014-08-01

    Effects of biological activated carbon (BAC) dosage on COD removal in landfill leachate treatment were compared. The COD removal efficiency of reactors with 0, 100 and 300 g activated carbon dosage per litre activated sludge was 12.9%, 19.6% and 27.7%, respectively. The results indicated that BAC improved the refractory organic matter removal efficiency and there was a positive correlation between COD removal efficiency and BAC dosage. The output of carbon dioxide after 8h of aeration in reactors was 109, 193 and 306 mg corresponding to the activated carbon dosages mentioned above, which indicated the amount of biodegradation and BAC dosage also had a positive correlation. The combination of adsorption and bioregeneration of BAC resulted in the positive correlation betweem organic matter removal efficiency and BAC dosage, and bioregeneration was the root cause for the microbial decomposition of refractory organics.

  15. Synthesis and characterization of perm-selective SERS-active silica-coated gold nanospheres for the direct detection of small molecules

    NASA Astrophysics Data System (ADS)

    Pierre-Bolivar, Marie Carmelle Serviane

    Noble metal nanomaterials have numerous uses in plasmonic and surface enhanced Raman scattering (SERS) detection applications; however, upon the addition of analytes, nanomaterials often undergo uncontrolled aggregation which leads to inconsistent signal intensities. To overcome this limitation, the effect of gold nanosphere concentration, column purification, and surface chemistry functionalization using internally etched silica stabilization methods was investigated on SERS assays for small molecule detection. Nanostructure composition, size, shape, stability, surface chemistry, optical properties, and SERS-activity were monitored using localized surface plasmon resonance (LSPR or extinction) spectroscopy, transmission electron microscopy (TEM), and Raman spectroscopy. First, the behavior of citrate-stabilized gold nanospheres was monitored as a function of molecular surface coverage. Both extinction and SERS spectral intensities increased linearly below monolayer functionalization. Above this value, however, uncontrolled nanoparticle aggregation occurred and large but irreproducible SERS signal intensities were monitored. Next, gold nanoparticles were encapsulated with varying silica shell thicknesses and purified using traditional centrifugation steps and/or column chromatography. Relative to the traditionally purified (i.e. centrifuged) samples, the SERS responses from small molecules using the column purified nanoparticle samples followed a well-known SERS distance-dependence model. Thus, surface chemistry cannot form more than a 2 nm thick layer on gold nanospheres if SERS applications were targeted. To overcome these challenges, gold nanospheres encapsulated with a thick silica shell were made SERS-active by etching the internal silica layer near the metal surface. During the synthesis of these internally etched silica-coated gold nanospheres, the LSPR wavelength shift, a parameter related to the effective local refractive index near the gold core, was

  16. Characterization of activated carbon fiber filters for pressure drop, submicrometer particulate collection, and mercury capture.

    PubMed

    Hayashi, T; Lee, T G; Hazelwood, M; Hedrick, E; Biswas, P

    2000-06-01

    The use of activated carbon fiber (ACF) filters for the capture of particulate matter and elemental Hg is demonstrated. The pressure drop and particle collection efficiency characteristics of the ACF filters were established at two different face velocities and for two different aerosols: spherical NaCl and combustion-generated silica particles. The clean ACF filter specific resistance was 153 kg m-2 sec-1. The experimental specific resistance for cake filtration was 1.6 x 10(6) sec-1 and 2.4 x 10(5) sec-1 for 0.5- and 1.5-micron mass median diameter particles, respectively. The resistance factor R was approximately 2, similar to that for the high-efficiency particulate air filters. There was a discrepancy in the measured particle collection efficiencies and those predicted by theory. The use of the ACF filter for elemental Hg capture was illustrated, and the breakthrough characteristic was established. The capacity of the ACF filter for Hg capture was similar to other powdered activated carbons.

  17. Silica-coated magnetic nanoparticles impair proteasome activity and increase the formation of cytoplasmic inclusion bodies in vitro

    PubMed Central

    Phukan, Geetika; Shin, Tae Hwan; Shim, Jeom Soon; Paik, Man Jeong; Lee, Jin-Kyu; Choi, Sangdun; Kim, Yong Man; Kang, Seong Ho; Kim, Hyung Sik; Kang, Yup; Lee, Soo Hwan; Mouradian, M. Maral; Lee, Gwang

    2016-01-01

    The potential toxicity of nanoparticles, particularly to neurons, is a major concern. In this study, we assessed the cytotoxicity of silica-coated magnetic nanoparticles containing rhodamine B isothiocyanate dye (MNPs@SiO2(RITC)) in HEK293 cells, SH-SY5Y cells, and rat primary cortical and dopaminergic neurons. In cells treated with 1.0 μg/μl MNPs@SiO2(RITC), the expression of several genes related to the proteasome pathway was altered, and proteasome activity was significantly reduced, compared with control and with 0.1 μg/μl MNPs@SiO2(RITC)-treated cells. Due to the reduction of proteasome activity, formation of cytoplasmic inclusions increased significantly in HEK293 cells over-expressing the α–synuclein interacting protein synphilin-1 as well as in primary cortical and dopaminergic neurons. Primary neurons, particularly dopaminergic neurons, were more vulnerable to MNPs@SiO2(RITC) than SH-SY5Y cells. Cellular polyamines, which are associated with protein aggregation, were significantly altered in SH-SY5Y cells treated with MNPs@SiO2(RITC). These findings highlight the mechanisms of neurotoxicity incurred by nanoparticles. PMID:27378605

  18. Silica-coated magnetic nanoparticles impair proteasome activity and increase the formation of cytoplasmic inclusion bodies in vitro.

    PubMed

    Phukan, Geetika; Shin, Tae Hwan; Shim, Jeom Soon; Paik, Man Jeong; Lee, Jin-Kyu; Choi, Sangdun; Kim, Yong Man; Kang, Seong Ho; Kim, Hyung Sik; Kang, Yup; Lee, Soo Hwan; Mouradian, M Maral; Lee, Gwang

    2016-07-05

    The potential toxicity of nanoparticles, particularly to neurons, is a major concern. In this study, we assessed the cytotoxicity of silica-coated magnetic nanoparticles containing rhodamine B isothiocyanate dye (MNPs@SiO2(RITC)) in HEK293 cells, SH-SY5Y cells, and rat primary cortical and dopaminergic neurons. In cells treated with 1.0 μg/μl MNPs@SiO2(RITC), the expression of several genes related to the proteasome pathway was altered, and proteasome activity was significantly reduced, compared with control and with 0.1 μg/μl MNPs@SiO2(RITC)-treated cells. Due to the reduction of proteasome activity, formation of cytoplasmic inclusions increased significantly in HEK293 cells over-expressing the α-synuclein interacting protein synphilin-1 as well as in primary cortical and dopaminergic neurons. Primary neurons, particularly dopaminergic neurons, were more vulnerable to MNPs@SiO2(RITC) than SH-SY5Y cells. Cellular polyamines, which are associated with protein aggregation, were significantly altered in SH-SY5Y cells treated with MNPs@SiO2(RITC). These findings highlight the mechanisms of neurotoxicity incurred by nanoparticles.

  19. Carbon Nanotube Materials for Substrate Enhanced Control of Catalytic Activity

    SciTech Connect

    Heben, M.; Dillon, A. C.; Engtrakul, C.; Lee, S.-H.; Kelley, R. D.; Kini, A. M.

    2007-05-01

    Carbon SWNTs are attractive materials for supporting electrocatalysts. The properties of SWNTs are highly tunable and controlled by the nanotube's circumferential periodicity and their surface chemistry. These unique characteristics suggest that architectures constructed from these types of carbon support materials would exhibit interesting and useful properties. Here, we expect that the structure of the carbon nanotube support will play a major role in stabilizing metal electrocatalysts under extreme operating conditions and suppress both catalyst and support degradation. Furthermore, the chemical modification of the carbon nanotube surfaces can be expected to alter the interface between the catalyst and support, thus, enhancing the activity and utilization of the electrocatalysts. We plan to incorporate discrete reaction sites into the carbon nanotube lattice to create intimate electrical contacts with the catalyst particles to increase the metal catalyst activity and utilization. The work involves materials synthesis, design of electrode architectures on the nanoscale, control of the electronic, ionic, and mass fluxes, and use of advanced optical spectroscopy techniques.

  20. Carbon-Carbon Bond Cleavage in Activation of the Prodrug Nabumetone

    PubMed Central

    Varfaj, Fatbardha; Zulkifli, Siti N. A.; Park, Hyoung-Goo; Challinor, Victoria L.; De Voss, James J.

    2014-01-01

    Carbon-carbon bond cleavage reactions are catalyzed by, among others, lanosterol 14-demethylase (CYP51), cholesterol side-chain cleavage enzyme (CYP11), sterol 17β-lyase (CYP17), and aromatase (CYP19). Because of the high substrate specificities of these enzymes and the complex nature of their substrates, these reactions have been difficult to characterize. A CYP1A2-catalyzed carbon-carbon bond cleavage reaction is required for conversion of the prodrug nabumetone to its active form, 6-methoxy-2-naphthylacetic acid (6-MNA). Despite worldwide use of nabumetone as an anti-inflammatory agent, the mechanism of its carbon-carbon bond cleavage reaction remains obscure. With the help of authentic synthetic standards, we report here that the reaction involves 3-hydroxylation, carbon-carbon cleavage to the aldehyde, and oxidation of the aldehyde to the acid, all catalyzed by CYP1A2 or, less effectively, by other P450 enzymes. The data indicate that the carbon-carbon bond cleavage is mediated by the ferric peroxo anion rather than the ferryl species in the P450 catalytic cycle. CYP1A2 also catalyzes O-demethylation and alcohol to ketone transformations of nabumetone and its analogs. PMID:24584631

  1. Carbon-carbon bond cleavage in activation of the prodrug nabumetone.

    PubMed

    Varfaj, Fatbardha; Zulkifli, Siti N A; Park, Hyoung-Goo; Challinor, Victoria L; De Voss, James J; Ortiz de Montellano, Paul R

    2014-05-01

    Carbon-carbon bond cleavage reactions are catalyzed by, among others, lanosterol 14-demethylase (CYP51), cholesterol side-chain cleavage enzyme (CYP11), sterol 17β-lyase (CYP17), and aromatase (CYP19). Because of the high substrate specificities of these enzymes and the complex nature of their substrates, these reactions have been difficult to characterize. A CYP1A2-catalyzed carbon-carbon bond cleavage reaction is required for conversion of the prodrug nabumetone to its active form, 6-methoxy-2-naphthylacetic acid (6-MNA). Despite worldwide use of nabumetone as an anti-inflammatory agent, the mechanism of its carbon-carbon bond cleavage reaction remains obscure. With the help of authentic synthetic standards, we report here that the reaction involves 3-hydroxylation, carbon-carbon cleavage to the aldehyde, and oxidation of the aldehyde to the acid, all catalyzed by CYP1A2 or, less effectively, by other P450 enzymes. The data indicate that the carbon-carbon bond cleavage is mediated by the ferric peroxo anion rather than the ferryl species in the P450 catalytic cycle. CYP1A2 also catalyzes O-demethylation and alcohol to ketone transformations of nabumetone and its analogs.

  2. Silicon, silica and its surface patterning/activation with alkoxy- and amino-silanes for nanomedical applications.

    PubMed

    Rother, Dag; Sen, Tapas; East, Daniel; Bruce, Ian James

    2011-02-01

    Silica and silicates are widely used in nanomedicine with applications as diverse as medical device coatings to replacement materials in tissue engineering. Although much is known about silica and its synthesis, relatively few biomedical scientists fully appreciate the link that exists between its formulation and its resultant structure and function. This article attempts to provide insight into relevant issues in that context, as well as highlighting their importance in the material's eventual surface patterning/activation with alkoxy- and organo-silanes. The use of aminosilanes in that context is discussed at some length to permit an understanding of the specific variables that are important in the reproducible and robust aminoactivation of surfaces using such molecules. Recent investigative work is cited to underline the fact that although aminosilanization is a historically accepted mechanism for surface activation, there is still much to be explained about how and why the process works in the way it does. In the last section of this article, there is a detailed discussion of two classical approaches for the use of aminosilanized materials in the covalent immobilization of bioligands, amino-aldehyde and amino-carboxyl coupling. In the former case, the use of the homobifunctional coupler glutaraldehyde is explored, and in the latter, carbodiimides. Although these chemistries have long been employed in bioconjugations, it is apparent that there are still variables to be explored in the processes (as witnessed by continuing investigations into the chemistries concerned). Aspects regarding optimization, standardization and reproducibility of the fabrication of amino functionalized surfaces are discussed in detail and illustrated with practical examples to aid the reader in their own studies, in terms of considerations to be taken into account when producing such materials. Finally, the article attempts to remind readers that although the chemistry and materials

  3. Preparation and characterization of activated carbon from sugarcane bagasse by physical activation with CO2 gas

    NASA Astrophysics Data System (ADS)

    Bachrun, Sutrisno; AyuRizka, Noni; Annisa, SolichaHidayat; Arif, Hidayat

    2016-01-01

    A series of experiments have been conducted to study the effects of different carbonization temperatures (400, 600, and 800oC) on characteristics of porosity in activated carbon derived from carbonized sugarcane bagassechar at activation temperature of 800oC. The results showed that the activated carbon derived from high carbonized temperature of sugarcane bagassechars had higher BET surface area, total volume, micropore volume and yield as compared to the activated carbon derived from low carbonized temperature. The BET surface area, total volume and micropore volume of activated carbon prepared from sugarcane bagassechars obtained at 800oC of carbonized temperature and activation time of 120 min were 661.46m2/g, 0.2455cm3/g and 0.1989cm3/g, respectively. The high carbonization temperature (800oC) generated a highly microporous carbonwith a Type-I nitrogen adsorption isotherm, while the low carbonization temperature (400 and 600oC) generated a mesoporous one with an intermediate between types I and IInitrogen adsorption isotherm.

  4. Waste polyvinylchloride derived pitch as a precursor to develop carbon fibers and activated carbon fibers.

    PubMed

    Qiao, W M; Yoon, S H; Mochida, I; Yang, J H

    2007-01-01

    Polyvinylchloride (PVC) was successfully recycled through the solvent extraction from waste pipe with an extraction yield of ca. 86%. The extracted PVC was pyrolyzed by a two-stage process (260 and 410 degrees C) to obtain free-chlorine PVC based pitch through an effective removal of chlorine from PVC during the heat-treatment. As-prepared pitch (softening point: 220 degrees C) was spun, stabilized, carbonized into carbon fibers (CFs), and further activated into activated carbon fibers (ACFs) in a flow of CO2. As-prepared CFs show comparable mechanical properties to commercial CFs, whose maximum tensile strength and modulus are 862 MPa and 62 GPa, respectively. The resultant ACFs exhibit a high surface area of 1200 m2/g, narrow pore size distribution and a low oxygen content of 3%. The study provides an effective insight to recycle PVC from waste PVC and develop a carbon precursor for high performance carbon materials such as CFs and ACFs.

  5. Water vapor adsorption on activated carbon preadsorbed with naphtalene.

    PubMed

    Zimny, T; Finqueneisel, G; Cossarutto, L; Weber, J V

    2005-05-01

    The adsorption of water vapor on a microporous activated carbon derived from the carbonization of coconut shell has been studied. Preadsorption of naphthalene was used as a tool to determine the location and the influence of the primary adsorbing centers within the porous structure of active carbon. The adsorption was studied in the pressure range p/p0=0-0.95 in a static water vapor system, allowing the investigation of both kinetic and equilibrium experimental data. Modeling of the isotherms using the modified equation of Do and Do was applied to determine the effect of preadsorption on the mechanism of adsorption.

  6. Activated carbon fiber composite material and method of making

    DOEpatents

    Burchell, Timothy D.; Weaver, Charles E.; Chilcoat, Bill R.; Derbyshire, Frank; Jagtoyen, Marit

    2000-01-01

    An activated carbon fiber composite for separation and purification, or catalytic processing of fluids is described. The activated composite comprises carbon fibers rigidly bonded to form an open, permeable, rigid monolith capable of being formed to near-net-shape. Separation and purification of gases are effected by means of a controlled pore structure that is developed in the carbon fibers contained in the composite. The open, permeable structure allows the free flow of gases through the monolith accompanied by high rates of adsorption. By modification of the pore structure and bulk density the composite can be rendered suitable for applications such as gas storage, catalysis, and liquid phase processing.

  7. Activated carbon fiber composite material and method of making

    DOEpatents

    Burchell, Timothy D.; Weaver, Charles E.; Chilcoat, Bill R.; Derbyshire, Frank; Jagtoyen, Marit

    2001-01-01

    An activated carbon fiber composite for separation and purification, or catalytic processing of fluids is described. The activated composite comprises carbon fibers rigidly bonded to form an open, permeable, rigid monolith capable of being formed to near-net-shape. Separation and purification of gases are effected by means of a controlled pore structure that is developed in the carbon fibers contained in the composite. The open, permeable structure allows the free flow of gases through the monolith accompanied by high rates of adsorption. By modification of the pore structure and bulk density the composite can be rendered suitable for applications such as gas storage, catalysis, and liquid phase processing.

  8. Differential Scanning Calorimetry (DSC) for the Analysis of Activated Carbon

    DTIC Science & Technology

    1991-10-01

    impregnation procedures . It is believed that Sutcliffe-Speakman is currently using coconut - shell as the carbon precursor (instead of the New Zealand coal...microstructure facilitate the adsorption process whereby all the undesirable materials are retained. For military deployment, the activated carbon is...AD-A245 899 H.P ’ l N dI dUenm / DIFFERENTIAL SCANNING CALORIMETRY (DSC) FOR THE ANALYSIS OF ACTIVATED CARBON (U) by S.H.C. a and L.E. Cameron DTIC x

  9. Activated Carbon Textile via Chemistry of Metal Extraction for Supercapacitors.

    PubMed

    Lam, Do Van; Jo, Kyungmin; Kim, Chang-Hyun; Kim, Jae-Hyun; Lee, Hak-Joo; Lee, Seung-Mo

    2016-12-27

    Carbothermic reduction in the chemistry of metal extraction (MO(s) + C(s) → M(s) + CO(g)) using carbon as a sacrificial agent has been used to smelt metals from diverse oxide ores since ancient times. Here, we paid attention to another aspect of the carbothermic reduction to prepare an activated carbon textile for high-rate-performance supercapacitors. On the basis of thermodynamic reducibility of metal oxides reported by Ellingham, we employed not carbon, but metal oxide as a sacrificial agent in order to prepare an activated carbon textile. We conformally coated ZnO on a bare cotton textile using atomic layer deposition, followed by pyrolysis at high temperature (C(s) + ZnO(s) → C'(s) + Zn(g) + CO(g)). We figured out that it leads to concurrent carbonization and activation in a chemical as well as mechanical way. Particularly, the combined effects of mechanical buckling and fracture that occurred between ZnO and cotton turned out to play an important role in carbonizing and activating the cotton textile, thereby significantly increasing surface area (nearly 10 times) compared with the cotton textile prepared without ZnO. The carbon textiles prepared by carbothermic reduction showed impressive combination properties of high power and energy densities (over 20-fold increase) together with high cyclic stability.

  10. Effects of CO 2 activation on porous structures of coconut shell-based activated carbons

    NASA Astrophysics Data System (ADS)

    Guo, Shenghui; Peng, Jinhui; Li, Wei; Yang, Kunbin; Zhang, Libo; Zhang, Shimin; Xia, Hongying

    2009-07-01

    In this paper, textural characterization of an activated carbon derived from carbonized coconut shell char obtained at carbonization temperature of 600 °C for 2 h by CO 2 activation was investigated. The effects of activation temperature, activation time and flow rate of CO 2 on the BET surface area, total volume, micropore volume and yield of activated carbons prepared were evaluated systematically. The results showed that: (i) enhancing activation temperature was favorable to the formation of pores, widening of pores and an increase in mesopores; (ii) increasing activation time was favorable to the formation of micropores and mesopores, and longer activation time would result in collapsing of pores; (iii) increasing flow rate of CO 2 was favorable to the reactions of all active sites and formation of pores, further increasing flow rate of CO 2 would lead carbon to burn out and was unfavorable to the formation of pores. The degree of surface roughness of activated carbon prepared was measured by the fractal dimension which was calculated by FHH (Frenkel-Halsey-Hill) theory. The fractal dimensions of activated carbons prepared were greater than 2.6, indicating the activated carbon samples prepared had very irregular structures, and agreed well with those of average micropore size.

  11. Comparison of toluene adsorption among granular activated carbon and different types of activated carbon fibers (ACFs).

    PubMed

    Balanay, Jo Anne G; Crawford, Shaun A; Lungu, Claudiu T

    2011-10-01

    Activated carbon fiber (ACF) has been demonstrated to be a good adsorbent for the removal of organic vapors in air. Some ACF has a comparable or larger surface area and higher adsorption capacity when compared with granular activated carbon (GAC) commonly used in respiratory protection devices. ACF is an attractive alternative adsorbent to GAC because of its ease of handling, light weight, and decreasing cost. ACF may offer the potential for short-term respiratory protection for first responders and emergency personnel. This study compares the critical bed depths and adsorption capacities for toluene among GAC and ACF of different forms and surface areas. GAC and ACF in cloth (ACFC) and felt (ACFF) forms were challenged in stainless steel chambers with a constant concentration of 500 ppm toluene via conditioned air at 25°C, 50% RH, and constant airflow (7 L/min). Breakthrough data were obtained for each adsorbent using gas chromatography with flame ionization detector. Surface areas of each adsorbent were determined using a physisorption analyzer. Results showed that the critical bed depth of GAC is 275% higher than the average of ACFC but is 55% lower than the average of ACFF. Adsorption capacity of GAC (with a nominal surface area of 1800 m(2)/g) at 50% breakthrough is 25% higher than the average of ACF with surface area of 1000 m(2)/g, while the rest of ACF with surface area of 1500 m(2)/g and higher have 40% higher adsorption capacities than GAC. ACFC with higher surface area has the smallest critical bed depth and highest adsorption capacity, which makes it a good adsorbent for thinner and lighter respirators. We concluded that ACF has great potential for application in respiratory protection considering its higher adsorption capacity and lower critical bed depth in addition to its advantages over GAC, particularly for ACF with higher surface area.

  12. Solid-state active media on the base of silica matrices doped with UV and visible laser dyes

    NASA Astrophysics Data System (ADS)

    Kuznetsova, R. T.; Manekina, Ju. A.; Telminov, E. N.; Mayer, G. V.; Arabei, S. M.; Pavich, T. A.; Solovyov, K. N.

    2007-06-01

    New results on the influence of the composition of a silica gel-matrix and the process of its production on the spectral, lasing and photochemical properties of embedded luminophores: rhodamine, phenalemine, oxazole, coumarine and other dyes series, which have lasing in the UV, blue-green and red spectral regions under excitation by poweful laser radiation of various wavelength (308 and 532 nm) and intensity (from 0,1 to 100 MW/cm2) have been obtained. The shortest-wavelength lasing is achieved for silica solid matrices with para-terphenyl (342 nm). Optimal conditions have been selected and the lasing of thin silica solid films doped with aminocoumarine (457 nm) with resource exceeding that in solutions has been obtained. It is established, that organic luminophores are fixed in nanodimensional pores of silica and hybrid matrices by specific interactions, that compete with the association of dyes.

  13. Explanation for the enhanced dissolution of silica column packing in high pH phosphate and carbonate buffers.

    PubMed

    Tindall, G W; Perry, R L

    2003-02-28

    It has been reported that at high pH, the rate of bonded phase packing degradation in methanol/water mobile phases is greater for carbonate and phosphate buffers than for amine buffers. This conclusion was based on buffer pH determined in the aqueous buffer before dilution with methanol. Changes in buffer species pKa, and therefore buffer pH, upon methanol dilution are consistent with the observed degradation results. Measurements of pH in the methanol/water solutions confirm that the carbonate and phosphate buffers were considerably more basic than the amine buffer, even though all the buffers were pH 10 before dilution with methanol. These results demonstrate that it can be misleading to extrapolate aqueous pH data to partially aqueous solutions. Measurements of pH in the mixed solvent provide more reliable predictions of column and sample stability.

  14. Electroadsorption of Arsenic from natural water in granular activated carbon

    NASA Astrophysics Data System (ADS)

    Beralus, Jean-Mackson; Ruiz Rosas, Ramiro; Cazorla-Amoros, Diego; Morallon, Emilia

    2014-11-01

    The adsorption and electroadsorption of arsenic from a natural water has been studied in a filter-press electrochemical cell using a commercial granular activated carbon as adsorbent and Pt/Ti and graphite as electrodes. A significant reduction of the arsenic concentration is achieved when current is imposed between the electrodes, especially when the activated carbon was located in the vicinity of the anode. This enhancement can be explained in terms of the presence of electrostatic interactions between the polarized carbon surface and the arsenic ions, and changes in the distribution of most stable species of arsenic in solution due to As(III) to As(V) oxidation. In summary, electrochemical adsorption on a filter press cell can be used for enhancement the arsenic remediation with activated carbon in the treatment of a real groundwater.

  15. Development of a CO2 Sequestration Module by Integrating Mineral Activation and Aqueous Carbonation

    SciTech Connect

    George Alexander; Parvana Aksoy; John Andresen; Mercedes Maroto-Valer; Harold Schobert

    2006-08-14

    Mineral carbonation is a promising concept for permanent CO{sub 2} sequestration due to the vast natural abundance of the raw materials and the permanent storage of CO{sub 2} in solid form as carbonates. The sequestration of CO{sub 2} through the employment of magnesium silicates--olivine and serpentine--is beyond the proof of concept stage. For the work done in this project, serpentine was chosen as the feedstock mineral due to its abundance and availability. Although the reactivity of olivine is greater than that of serpentine, physical and chemical treatments have been shown to increase greatly the reactivity of serpentine. The primary drawback to mineral carbonation is reaction kinetics. To accelerate the carbonation, aqueous processes are preferred, where the minerals are first dissolved in solution. In aqueous carbonation, the key step is the dissolution rate of the mineral, where the mineral dissolution reaction is likely to be surface-controlled. The relatively low reactivity of serpentine has warranted research into physical and chemical treatments that have been shown to greatly increase its reactivity. The use of sulfuric acid as an accelerating medium for the removal of magnesium from serpentine has been investigated. To accelerate the dissolution process, the mineral can be ground to very fine particle size, <37 {micro}m, but this is a very energy-intensive process. Previous work in our laboratory showed that chemical surface activation helps to dissolve magnesium from the serpentine (of particle size {approx} 100 {micro}m) and that the carbonation reaction can be conducted under mild conditions (20 C and 4.6 MPa) compared to previous studies that required >185 C, >13 MPa, and <37 {micro}m particle size. This work also showed that over 70% of the magnesium can be extracted at ambient temperature, leaving an amorphous silica with surface area of about 330 m{sup 2}/g. The overall objective of this research program is to optimize the active carbonation

  16. Gold nanorod@silica-carbon dots as multifunctional phototheranostics for fluorescence and photoacoustic imaging-guided synergistic photodynamic/photothermal therapy

    NASA Astrophysics Data System (ADS)

    Jia, Qingyan; Ge, Jiechao; Liu, Weimin; Liu, Sha; Niu, Guangle; Guo, Liang; Zhang, Hongyan; Wang, Pengfei

    2016-06-01

    Phototheranostics, which is the application of light in the diagnostic imaging and therapy of cancer, has shown great promise for multimodal cancer imaging and effective therapy. Herein, we developed multifunctional gold nanorod@silica-carbon dots (GNR@SiO2-CDs) as a phototheranostic agent by incorporating carbon dots (CDs) with gold nanorods (GNRs), using SiO2 as a scaffold. In GNR@SiO2-CDs, the GNRs act as both photoacoustic (PA) imaging and photothermal therapy (PTT) agents, and the CDs serve as fluorescence (FL) imaging and photodynamic therapy (PDT) agents. The introduction of SiO2 not only improves the chemical stability of the GNRs and CDs in the physiological environment but also prevents the absolute quenching of the fluorescence of the CDs by GNRs. These collective properties make GNR@SiO2-CDs a novel phototheranostic agent, in which high sensitivity and good spatial resolution of FL/PA imaging can be achieved to guide PDT/PTT treatments through i.v. administration. The combination of PDT and PTT proved to be more efficient in killing cancer cells compared to PDT or PTT alone under a low dose of laser irradiation (<=0.5 W cm-2). Furthermore, GNR@SiO2-CDs could be cleared out from the body of mice, indicating the low toxicity of this phototheranostic agent. Our work highlights the potential of using GNRs and CDs as novel phototheranostic agents for multifunctional cancer therapies.Phototheranostics, which is the application of light in the diagnostic imaging and therapy of cancer, has shown great promise for multimodal cancer imaging and effective therapy. Herein, we developed multifunctional gold nanorod@silica-carbon dots (GNR@SiO2-CDs) as a phototheranostic agent by incorporating carbon dots (CDs) with gold nanorods (GNRs), using SiO2 as a scaffold. In GNR@SiO2-CDs, the GNRs act as both photoacoustic (PA) imaging and photothermal therapy (PTT) agents, and the CDs serve as fluorescence (FL) imaging and photodynamic therapy (PDT) agents. The introduction

  17. Amperometric L-lactate biosensor based on screen-printed carbon electrode containing cobalt phthalocyanine, coated with lactate oxidase-mesoporous silica conjugate layer.

    PubMed

    Shimomura, Takeshi; Sumiya, Touru; Ono, Masatoshi; Ito, Tetsuji; Hanaoka, Taka-aki

    2012-02-10

    A novel amperometric biosensor for the measurement of L-lactate has been developed. The device comprises a screen-printed carbon electrode containing cobalt phthalocyanine (CoPC-SPCE), coated with lactate oxidase (LOD) that is immobilized in mesoporous silica (FSM8.0) using a polymer matrix of denatured polyvinyl alcohol; a Nafion layer on the electrode surface acts as a barrier to interferents. The sampling unit attached to the SPCE requires only a small sample volume of 100 μL for each measurement. The measurement of l-lactate is based on the signal produced by hydrogen peroxide, the product of the enzymatic reaction. The behavior of the biosensor, LOD-FSM8.0/Naf/CoPC-SPCE, was examined in terms of pH, applied potential, sensitivity and operational range, selectivity, and storage stability. The sensor showed an optimum response at a pH of 7.4 and an applied potential of +450 mV. The determination range and the response time for L-lactate were 18.3 μM to 1.5 mM and approximately 90s, respectively. In addition, the sensor exhibited high selectivity for L-lactate and was quite stable in storage, showing no noticeable change in its initial response after being stored for over 9 months. These results indicate that our method provides a simple, cost-effective, high-performance biosensor for l-lactate.

  18. The applicability of conventional cytotoxicity assays to predict safety/toxicity of mesoporous silica nanoparticles, silver and gold nanoparticles and multi-walled carbon nanotubes.

    PubMed

    Mannerström, Marika; Zou, Jing; Toimela, Tarja; Pyykkö, Ilmari; Heinonen, Tuula

    2016-12-01

    Developing new, validated methods for screening of the effects of nanomaterials is a huge and expensive task. It is therefore necessary to try to employ already existing and validated methods, developed for chemicals. In the present study cytotoxicity of gold (Au) and silver (Ag) nanoparticles (NP), two different mesoporous silica nanoparticles (MSNP), and multi-walled carbon nanotubes (MWCNT) were investigated in BALB/c 3T3 fibroblasts, NR8383 macrophages, and U937 monocytes using standard assays, namely WST-1 and NRU. In addition, preliminary attempts were made to investigate ENM-mediated effects on cell motility as a potential end point for NP toxicity. AgNPs were most toxic to BALB/c 3T3 fibroblasts while other ENMs were insignificantly toxic. NR8383 macrophages were most sensitive cells, as in addition to AgNPs, also MWCNTs were toxic to NR8383 cells. AgNP was toxic also to U937 cells, other ENMs had minor effect. Different media resulted in different-sized aggregates of the same ENMs. AgNP inhibited BALB/c motility most, whereas NR8383 motility was inhibited most by MWCNTs. In conclusion, conventional cytotoxicity assays are better suited to rank the order of toxicity of different nanoparticles instead of producing accurate IC50 data. Moreover, using immune cells, especially macrophages together with fibroblasts, would bring more relevant predictions of ENM cytotoxicity as immune cells may discover cytotoxicity that is not captured by BALB/c 3T3 cells alone.

  19. [Quickly enrichment of carbon in wastewater by activated sludge].

    PubMed

    Liu, Hong-Bo; Zhao, Fang; Wen, Xiang-Hua

    2011-10-01

    Pilot tests were carried out to investigate the absorption characteristics of the carbon source in urban wastewater by activated sludge and to analyze the carbon release from the carbon absorbed activated sludge in the settling process. The results indicated that carbon in wastewater could be quickly enriched by activated sludge. The absorption process of indissolvable organic matter could be finished as shortly as less than 10 min, while the absorption process of the dissolved organic matter was relatively slow and should consume up about 30 min. Moreover, carbon release was observed in the settling process of enriched sludge. In the period of 30-100 min, the release amount of total COD (TCOD) was 11.44 mg x g(-1), while in the period of 60-150 min, the release amount of dissolved COD (SCOD) was 6.24 mg x g(-1). Furthermore, based on the results of the bench-scale tests, a pilot-scale plant was built to investigate the absorption of carbon, nitrogen and phosphorus by activated sludge and the settleability of enriched sludge. The results indicated that under continuously operation mode, 60% of COD, 75% of TP and 10% of TN in the wastewater could be removed by the absorption of activated sludge, and the enriched sludge with SVI of 34.2 mL x g(-1) presented good settleability. Carbon enrichment by activated sludge could not only reclaim the carbon source in wastewater, but also reduce the loading of organic matter and give low C/N for the following nitrification unit and improving the nitrification efficiency.

  20. Track formation in two amorphous insulators, vitreous silica and diamond like carbon: Experimental observations and description by the inelastic thermal spike model

    NASA Astrophysics Data System (ADS)

    Rotaru, C.; Pawlak, F.; Khalfaoui, N.; Dufour, C.; Perrière, J.; Laurent, A.; Stoquert, J. P.; Lebius, H.; Toulemonde, M.

    2012-02-01

    Vitreous silica thin film (a-SiO 2) and mixed deuterated and hydrogenated amorphous carbon thin film (a-C:D,H), grown or deposited, respectively, on silicon, have been irradiated at GANIL in the MeV/u energy range with ions between C and U in order to reach electronic energy loss between 0.7 and 25 keV/nm. The evolution of Si-O bonds and C-D bonds contents was determined by infrared absorption spectroscopy. Complementary physico-chemical characterization was performed for a-C:D,H using Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA). For a-SiO 2, the band at 1076 cm -1 decreases with the appearance of a band at 1046 cm -1. In the case of the diamond like amorphous carbon, the main effects due to MeV/u ion irradiations are the decrease of sp 3 bonding content and of deuterium relative concentration (D/C atomic ratio) as a function of fluence with the appearance of the sp 1 bond. The cylinder radii in which these physical phenomena are confined can be deduced from a statistical analysis. Using the inelastic thermal spike model (i-TS) these track radii can be described using the electron-phonon mean free path which takes values equal to 3 and 0.9 nm for a-SiO 2 and a-C:D, respectively. Extrapolation to low energy range (˜1 MeV in total or ˜0.02 MeV/u) will be made.

  1. Composite electrodes of activated carbon derived from cassava peel and carbon nanotubes for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Taer, E.; Iwantono, Yulita, M.; Taslim, R.; Subagio, A.; Salomo, Deraman, M.

    2013-09-01

    In this paper, a composite electrode was prepared from a mixture of activated carbon derived from precarbonization of cassava peel (CP) and carbon nanotubes (CNTs). The activated carbon was produced by pyrolysis process using ZnCl2 as an activation agent. A N2 adsorption-desorption analysis for the sample indicated that the BET surface area of the activated carbon was 1336 m2 g-1. Difference percentage of CNTs of 0, 5, 10, 15 and 20% with 5% of PVDF binder were added into CP based activated carbon in order to fabricate the composite electrodes. The morphology and structure of the composite electrodes were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The SEM image observed that the distribution of CNTs was homogeneous between carbon particles and the XRD pattern shown the amorphous structure of the sample. The electrodes were fabricated for supercapacitor cells with 316L stainless steel as current collector and 1 M sulfuric acid as electrolyte. An electrochemical characterization was performed by using an electrochemical impedance spectroscopy (EIS) method using a Solatron 1286 instrument and the addition of CNTs revealed to improve the resistant and capacitive properties of supercapacitor cell.

  2. Development of a laser-activated mesoporous silica nanocarrier delivery system for applications in molecular and genetic research

    NASA Astrophysics Data System (ADS)

    Davidson, Lien M.; Barkalina, Natalia; Yeste, Marc; Jones, Celine; Coward, Kevin

    2016-11-01

    Nanoparticles have revolutionized medical research over the last decade. One notable emerging area of nanomedicine is research developments in the reproductive sciences. Since increasing evidence indicates links between abnormal gene expression and previously unexplained states of infertility, there is a strong impetus to develop tools, such as nanoparticle platforms, to elucidate the pathophysiological mechanisms underlying such states. Mesoporous silica nanoparticles (MSNPs) represent a powerful and safe delivery tool for molecular and genetic investigations. Nevertheless, ongoing progress is restricted by low efficiency and unpredictable control of cargo delivery. Here, we describe for the first time, the development of a laser-activated MSNP system with heat-responsive cargo. Data derived from human embryonic kidney cells (HEK293T) indicate that when driven by a heat-shock promoter, MSNP cargo exhibits a significantly increased expression following infrared laser stimulus to stimulate a heat-shock response, without adverse cytotoxic effects. This delivery platform, with increased efficiency and the ability to impart spatial and temporal control, is highly useful for molecular and genetic investigations. We envision that this straightforward stimuli-responsive system could play a significant role in developing efficient nanodevices for research applications, for example in reproductive medicine.

  3. Bis-clickable Mesoporous Silica Nanoparticles: Straightforward Preparation of Light-Actuated Nanomachines for Controlled Drug Delivery with Active Targeting.

    PubMed

    Noureddine, Achraf; Gary-Bobo, Magali; Lichon, Laure; Garcia, Marcel; Zink, Jeffrey I; Wong Chi Man, Michel; Cattoën, Xavier

    2016-07-04

    Bis(clickable) mesoporous silica nanospheres (ca. 100 nm) were obtained by the co-condensation of TEOS with variable amounts (2-5 % each) of two clickable organosilanes in the presence of CTAB. Such nanoparticles could be easily functionalized with two independent functions using the copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction to transform them into nanomachines bearing cancer cell targeting ligands with the ability to deliver drugs on-demand. The active targeting was made possible after anchoring folic acid by CuAAC click reaction, whereas the controlled delivery was performed by clicked azobenzene fragments. Indeed, the azobenzene groups are able to obstruct the pores of the nanoparticles in the dark whereas upon irradiation in the UV or in the blue range, their trans-to-cis photoisomerization provokes disorder in the pores, enabling the delivery of the cargo molecules. The on-command delivery was proven in solution by dye release experiments, and in vitro by doxorubicin delivery. The added value of the folic acid ligand was clearly evidenced by the difference of cell killing induced by doxorubicin-loaded nanoparticles under blue irradiation, depending on whether the particles featured the clicked folic acid ligand or not.

  4. The effect of surface modification of mesoporous silica micro-rod scaffold on immune cell activation and infiltration

    PubMed Central

    Li, Weiwei Aileen; Lu, Beverly Ying; Gu, Luo; Choi, Youngjin; Kim, Jaeyun; Mooney, David J

    2016-01-01

    Biomaterial scaffold based vaccines show significant potential in generating potent antigen-specific immunity. However, the role of the scaffold surface chemistry in initiating and modulating the immune response is not well understood. In this study, a mesoporous silica micro-rod (MSR) scaffold was modified with PEG, PEG-RGD and PEG-RDG groups. PEG modification significantly enhanced BMDC activation marker up-regulation and IL-1β production in vitro, and innate immune cell infiltration in vivo. PEG-RGD MSRs and PEG-RDG MSRs displayed decreased inflammation compared to PEG MSRs, and the effect was not RGD specific. Finally, the Nlrp3 inflammasome was found to be necessary for MSR stimulated IL-1β production in vitro and played a key role in regulating immune cell infiltration in vivo. These findings suggest that simply modulating the surface chemistry of a scaffold can regulate its immune cell infiltration profile and have implications for the design and development of new material based vaccines. PMID:26784009

  5. Specifically Formed Corona on Silica Nanoparticles Enhances Transforming Growth Factor β1 Activity in Triggering Lung Fibrosis.

    PubMed

    Wang, Zhenzhen; Wang, Chunming; Liu, Shang; He, Wei; Wang, Lintao; Gan, JingJing; Huang, Zhen; Wang, Zhenheng; Wei, Haoyang; Zhang, Junfeng; Dong, Lei

    2017-02-28

    A corona is a layer of macromolecules formed on a nanoparticle surface in vivo. It can substantially change the biological identity of nanomaterials and possibly trigger adverse responses from the body tissues. Dissecting the role of the corona in the development of a particular disease may provide profound insights for understanding toxicity of nanomaterials in general. In our present study, we explored the capability of different silica nanoparticles (SiNPs) to induce silicosis in the mouse lung and analyzed the composition of coronas formed on these particles. We found that SiNPs of certain size and surface chemistry could specifically recruit transforming growth factor β1 (TGF-β1) into their corona, which subsequently induces the development of lung fibrosis. Once embedded into the corona on SiNPs, TGF-β1 was remarkably more stable than in its free form, and its fibrosis-triggering activity was significantly prolonged. Our study meaningfully demonstrates that a specific corona component on a certain nanoparticle could initiate a particular pathogenic process in a clinically relevant disease model. Our findings may shed light on the understanding of molecular mechanisms of human health risks correlated with exposure to small-scale substances.

  6. Adsorption uptake of synthetic organic chemicals by carbon nanotubes and activated carbons

    NASA Astrophysics Data System (ADS)

    Brooks, A. J.; Lim, Hyung-nam; Kilduff, James E.

    2012-07-01

    Carbon nanotubes (CNTs) have shown great promise as high performance materials for adsorbing priority pollutants from water and wastewater. This study compared uptake of two contaminants of interest in drinking water treatment (atrazine and trichloroethylene) by nine different types of carbonaceous adsorbents: three different types of single walled carbon nanotubes (SWNTs), three different sized multi-walled nanotubes (MWNTs), two granular activated carbons (GACs) and a powdered activated carbon (PAC). On a mass basis, the activated carbons exhibited the highest uptake, followed by SWNTs and MWNTs. However, metallic impurities in SWNTs and multiple walls in MWNTs contribute to adsorbent mass but do not contribute commensurate adsorption sites. Therefore, when uptake was normalized by purity (carbon content) and surface area (instead of mass), the isotherms collapsed and much of the CNT data was comparable to the activated carbons, indicating that these two characteristics drive much of the observed differences between activated carbons and CNT materials. For the limited data set here, the Raman D:G ratio as a measure of disordered non-nanotube graphitic components was not a good predictor of adsorption from solution. Uptake of atrazine by MWNTs having a range of lengths and diameters was comparable and their Freundlich isotherms were statistically similar, and we found no impact of solution pH on the adsorption of either atrazine or trichloroethylene in the range of naturally occurring surface water (pH = 5.7-8.3). Experiments were performed using a suite of model aromatic compounds having a range of π-electron energy to investigate the role of π-π electron donor-acceptor interactions on organic compound uptake by SWNTs. For the compounds studied, hydrophobic interactions were the dominant mechanism in the uptake by both SWNTs and activated carbon. However, comparing the uptake of naphthalene and phenanthrene by activated carbon and SWNTs, size exclusion effects

  7. Adsorption uptake of synthetic organic chemicals by carbon nanotubes and activated carbons.

    PubMed

    Brooks, A J; Lim, Hyung-nam; Kilduff, James E

    2012-07-27

    Carbon nanotubes (CNTs) have shown great promise as high performance materials for adsorbing priority pollutants from water and wastewater. This study compared uptake of two contaminants of interest in drinking water treatment (atrazine and trichloroethylene) by nine different types of carbonaceous adsorbents: three different types of single walled carbon nanotubes (SWNTs), three different sized multi-walled nanotubes (MWNTs), two granular activated carbons (GACs) and a powdered activated carbon (PAC). On a mass basis, the activated carbons exhibited the highest uptake, followed by SWNTs and MWNTs. However, metallic impurities in SWNTs and multiple walls in MWNTs contribute to adsorbent mass but do not contribute commensurate adsorption sites. Therefore, when uptake was normalized by purity (carbon content) and surface area (instead of mass), the isotherms collapsed and much of the CNT data was comparable to the activated carbons, indicating that these two characteristics drive much of the observed differences between activated carbons and CNT materials. For the limited data set here, the Raman D:G ratio as a measure of disordered non-nanotube graphitic components was not a good predictor of adsorption from solution. Uptake of atrazine by MWNTs having a range of lengths and diameters was comparable and their Freundlich isotherms were statistically similar, and we found no impact of solution pH on the adsorption of either atrazine or trichloroethylene in the range of naturally occurring surface water (pH = 5.7-8.3). Experiments were performed using a suite of model aromatic compounds having a range of π-electron energy to investigate the role of π-π electron donor-acceptor interactions on organic compound uptake by SWNTs. For the compounds studied, hydrophobic interactions were the dominant mechanism in the uptake by both SWNTs and activated carbon. However, comparing the uptake of naphthalene and phenanthrene by activated carbon and SWNTs, size exclusion effects

  8. Enhancement of Alkaline Protease Activity and Stability via Covalent Immobilization onto Hollow Core-Mesoporous Shell Silica Nanospheres

    PubMed Central

    Ibrahim, Abdelnasser Salah Shebl; Al-Salamah, Ali A.; El-Toni, Ahmed M.; Almaary, Khalid S.; El-Tayeb, Mohamed A.; Elbadawi, Yahya B.; Antranikian, Garabed

    2016-01-01

    The stability and reusability of soluble enzymes are of major concerns, which limit their industrial applications. Herein, alkaline protease from Bacillus sp. NPST-AK15 was immobilized onto hollow core-mesoporous shell silica (HCMSS) nanospheres. Subsequently, the properties of immobilized proteases were evaluated. Non-, ethane- and amino-functionalized HCMSS nanospheres were synthesized and characterized. NPST-AK15 was immobilized onto the synthesized nano-supports by physical and covalent immobilization approaches. However, protease immobilization by covalent attachment onto the activated HCMSS–NH2 nanospheres showed highest immobilization yield (75.6%) and loading capacity (88.1 μg protein/mg carrier) and was applied in the further studies. In comparison to free enzyme, the covalently immobilized protease exhibited a slight shift in the optimal pH from 10.5 to 11.0, respectively. The optimum temperature for catalytic activity of both free and immobilized enzyme was seen at 60 °C. However, while the free enzyme was completely inactivated when treated at 60 °C for 1 h the immobilized enzyme still retained 63.6% of its initial activity. The immobilized protease showed higher Vmax, kcat and kcat/Km, than soluble enzyme by 1.6-, 1.6- and 2.4-fold, respectively. In addition, the immobilized protease affinity to the substrate increased by about 1.5-fold. Furthermore, the enzyme stability in various organic solvents was significantly enhanced upon immobilization. Interestingly, the immobilized enzyme exhibited much higher stability in several commercial detergents including OMO, Tide, Ariel, Bonux and Xra by up to 5.2-fold. Finally, the immobilized protease maintained significant catalytic efficiency for twelve consecutive reaction cycles. These results suggest the effectiveness of the developed nanobiocatalyst as a candidate for detergent formulation and peptide synthesis in non-aqueous media. PMID:26840303

  9. Enhancement of Alkaline Protease Activity and Stability via Covalent Immobilization onto Hollow Core-Mesoporous Shell Silica Nanospheres.

    PubMed

    Ibrahim, Abdelnasser Salah Shebl; Al-Salamah, Ali A; El-Toni, Ahmed M; Almaary, Khalid S; El-Tayeb, Mohamed A; Elbadawi, Yahya B; Antranikian, Garabed

    2016-01-29

    The stability and reusability of soluble enzymes are of major concerns, which limit their industrial applications. Herein, alkaline protease from Bacillus sp. NPST-AK15 was immobilized onto hollow core-mesoporous shell silica (HCMSS) nanospheres. Subsequently, the properties of immobilized proteases were evaluated. Non-, ethane- and amino-functionalized HCMSS nanospheres were synthesized and characterized. NPST-AK15 was immobilized onto the synthesized nano-supports by physical and covalent immobilization approaches. However, protease immobilization by covalent attachment onto the activated HCMSS-NH₂ nanospheres showed highest immobilization yield (75.6%) and loading capacity (88.1 μg protein/mg carrier) and was applied in the further studies. In comparison to free enzyme, the covalently immobilized protease exhibited a slight shift in the optimal pH from 10.5 to 11.0, respectively. The optimum temperature for catalytic activity of both free and immobilized enzyme was seen at 60 °C. However, while the free enzyme was completely inactivated when treated at 60 °C for 1 h the immobilized enzyme still retained 63.6% of its initial activity. The immobilized protease showed higher V(max), k(cat) and k(cat)/K(m), than soluble enzyme by 1.6-, 1.6- and 2.4-fold, respectively. In addition, the immobilized protease affinity to the substrate increased by about 1.5-fold. Furthermore, the enzyme stability in various organic solvents was significantly enhanced upon immobilization. Interestingly, the immobilized enzyme exhibited much higher stability in several commercial detergents including OMO, Tide, Ariel, Bonux and Xra by up to 5.2-fold. Finally, the immobilized protease maintained significant catalytic efficiency for twelve consecutive reaction cycles. These results suggest the effectiveness of the developed nanobiocatalyst as a candidate for detergent formulation and peptide synthesis in non-aqueous media.

  10. New non-toxic transition metal nanocomplexes and Zn complex-silica xerogel nanohybrid: Synthesis, spectral studies, antibacterial, and antitumor activities

    NASA Astrophysics Data System (ADS)

    Shebl, Magdy; Saif, M.; Nabeel, Asmaa I.; Shokry, R.

    2016-08-01

    A new chromone Schiff base and its complexes of Cu(II), Ni(II), Co(II), Fe(III), Zn(II), Cd(II), and UO2(VI) as well as Zn(II) complex-silica xerogel nanohybrid were successfully prepared in a nano domain with crystalline or amorphous structures. Structures of the Schiff base and its complexes were investigated by elemental and thermal analyses, IR, 1H NMR, electronic, ESR, mass spectra, XRD, and TEM, as well as conductivity and magnetic susceptibility measurements. The spectroscopic data revealed that the Schiff base ligand behaves as a monobasic tridentate ligand. The coordination sites with metal ions are γ-pyrone oxygen, azomethine nitrogen, and oxygen of the carboxylic group. The metal complexes exhibited octahedral geometry, except Cu(II) complex, which has a square planar geometry and UO2(VI) complex, in which uranium ion is hepta-coordinated. Transmission electron microscope (TEM) analysis showed that Ni(II) and Zn(II) complexes have aggregated spheres and rod morphologies, respectively. TEM images of Zn(II) complex-silica xerogel nanohybrid showed a nanosheet morphology with 46 nm average size and confirmed that the complex was uniformly distributed into the silica pores. The obtained nanocomplexes were tested as antimicrobial and antitumor agents. The results showed that Zn(II) nanocomplex and Zn(II) complex-silica xerogel nanohybrid have high activity. The toxicity test on mice showed that Zn(II) complex and Zn(II) complex-silica xerogel nanohybrid have lower toxicity than cisplatin.

  11. Granular Activated Carbon Performance Capability and Availability.

    DTIC Science & Technology

    1983-06-01

    5-11 Notes: 1. As total nitrobodies 2. Combined with RDX 3. Includes dissolved air flotation, sand filter, and GAC 4. Can be achieved with moderate...RDX-HMX Water and Air Research Inc Feoruary 1976 Facility Newoort Army Aunition Plant 0-27 ater Quality Assessment for the Proposed RDX-HMX Water and... Air Research Inc February 1976 Facility, McAlester Naval munition Depot. Vol I 0-28 luorovin Granular Carbon Treatment FMC Corp/EPA 1792-6D" N 07 71

  12. The ebb and flood of Silica: Quantifying dissolved and biogenic silica fluxes from a temperate salt marsh

    NASA Astrophysics Data System (ADS)

    Vieillard, Amanda M.; Fulweiler, Robinson W.; Hughes, Zoe J.; Carey, Joanna C.

    2011-12-01

    Salt marshes are widely studied due to the broad range of ecosystem services they provide including serving as crucial wildlife habitat and as hotspots for biogeochemical cycling. Nutrients such as nitrogen (N), phosphorus (P), and carbon (C) are well studied in these systems. However, salt marshes may also be important environments for the cycling of another key nutrient, silica (Si). Found at the land-sea interface, these systems are silica replete with large stocks in plant biomass, sediments, and porewater, and therefore, have the potential to play a substantial role in the transformation and export of silica to coastal waters. In an effort to better understand this role, we measured the fluxes of dissolved (DSi) and biogenic (BSi) silica into and out of two tidal creeks in a temperate, North American (Rowley, Massachusetts, USA) salt marsh. One of the creeks has been fertilized from May to September for six years allowing us to examine the impacts of nutrient addition on silica dynamics within the marsh. High-resolution sampling in July 2010 showed no significant differences in Si concentrations between the fertilized and reference creeks with dissolved silica ranging from 0.5 to 108 μM and biogenic from 2.0 to 56 μM. Net fluxes indicated that the marsh is a point source of dissolved silica to the estuary in the summer with a net flux of approximately 169 mol h -1, demonstrating that this system exports DSi on the same magnitude as some nearby, mid-sized rivers. If these findings hold true for all salt marshes, then these already valuable regions are contributing yet another ecosystem service that has been previously overlooked; by exporting DSi to coastal receiving waters, salt marshes are actively providing this important nutrient for coastal primary productivity.

  13. Targeting inflammasome by the inhibition of caspase-1 activity using capped mesoporous silica nanoparticles.

    PubMed

    García-Fernández, Alba; García-Laínez, Guillermo; Ferrándiz, María Luisa; Aznar, Elena; Sancenón, Félix; Alcaraz, María José; Murguía, José Ramón; Marcos, María D; Martínez-Máñez, Ramón; Costero, Ana M; Orzáez, Mar

    2017-02-28

    Acute inflammation is a protective response of the body to harmful stimuli, such as pathogens or damaged cells. However, dysregulated inflammation can cause secondary damage and could thus contribute to the pathophysiology of many diseases. Inflammasomes, the macromolecular complexes responsible for caspase-1 activation, have emerged as key regulators of immune and inflammatory responses. Therefore, modulation of inflammasome activity has become an important therapeutic approach. Here we describe the design of a smart nanodevice that takes advantage of the passive targeting of nanoparticles to macrophages and enhances the therapeutic effect of caspase-1 inhibitor VX-765 in vivo. The functional hybrid systems consisted of MCM-41-based nanoparticles loaded with anti-inflammatory drug VX-765 (S2-P) and capped with poly-L-lysine, which acts as a molecular gate. S2-P activity has been evaluated in cellular and in vivo models of inflammation. The results indicated the potential advantage of using nanodevices to treat inflammatory diseases.

  14. Adsorption Properties of Lignin-derived Activated Carbon Fibers (LACF)

    SciTech Connect

    Contescu, Cristian I.; Gallego, Nidia C.; Thibaud-Erkey, Catherine; Karra, Reddy

    2016-04-01

    The object of this CRADA project between Oak Ridge National Laboratory (ORNL) and United Technologies Research Center (UTRC) is the characterization of lignin-derived activated carbon fibers (LACF) and determination of their adsorption properties for volatile organic compounds (VOC). Carbon fibers from lignin raw materials were manufactured at Oak Ridge National Laboratory (ORNL) using the technology previously developed at ORNL. These fibers were physically activated at ORNL using various activation conditions, and their surface area and pore-size distribution were characterized by gas adsorption. Based on these properties, ORNL did down-select five differently activated LACF materials that were delivered to UTRC for measurement of VOC adsorption properties. UTRC used standard techniques based on breakthrough curves to measure and determine the adsorption properties of indoor air pollutants (IAP) - namely formaldehyde and carbon dioxide - and to verify the extent of saturated fiber regenerability by thermal treatments. The results are summarized as follows: (1) ORNL demonstrated that physical activation of lignin-derived carbon fibers can be tailored to obtain LACF with surface areas and pore size distributions matching the properties of activated carbon fibers obtained from more expensive, fossil-fuel precursors; (2) UTRC investigated the LACF potential for use in air cleaning applications currently pursued by UTRC, such as building ventilation, and demonstrated their regenerability for CO2 and formaldehyde, (3) Both partners agree that LACF have potential for possible use in air cleaning applications.

  15. Activated Carbon Composites for Air Separation

    SciTech Connect

    Contescu, Cristian I; Baker, Frederick S; Tsouris, Costas; McFarlane, Joanna

    2008-03-01

    In continuation of the development of composite materials for air separation based on molecular sieving properties and magnetic fields effects, several molecular sieve materials were tested in a flow system, and the effects of temperature, flow conditions, and magnetic fields were investigated. New carbon materials adsorbents, with and without pre-loaded super-paramagnetic nanoparticles of Fe3O4 were synthesized; all materials were packed in chromatographic type columns which were placed between the poles of a high intensity, water-cooled, magnet (1.5 Tesla). In order to verify the existence of magnetodesorption effect, separation tests were conducted by injecting controlled volumes of air in a flow of inert gas, while the magnetic field was switched on and off. Gas composition downstream the column was analyzed by gas chromatography and by mass spectrometry. Under the conditions employed, the tests confirmed that N2 - O2 separation occurred at various degrees, depending on material's intrinsic properties, temperature and flow rate. The effect of magnetic fields, reported previously for static conditions, was not confirmed in the flow system. The best separation was obtained for zeolite 13X at sub-ambient temperatures. Future directions for the project include evaluation of a combined system, comprising carbon and zeolite molecular sieves, and testing the effect of stronger magnetic fields produced by cryogenic magnets.

  16. FENTON-DRIVEN REGENERATION OF GRANULAR ACTIVATED CARBON: A TECHNOLOGY OVERVIEW

    EPA Science Inventory

    A Fenton-driven mechanism for regenerating spent granular activated carbon (GAC) involves the combined, synergistic use of two reliable and well established treatment technologies - adsorption onto activated carbon and Fenton oxidation. During carbon adsorption treatment, enviro...

  17. Dual yolk-shell structure of carbon and silica-coated silicon for high-performance lithium-ion batteries

    PubMed Central

    Yang, L. Y.; Li, H. Z.; Liu, J.; Sun, Z. Q.; Tang, S. S.; Lei, M.

    2015-01-01

    Silicon batteries have attracted much attention in recent years due to their high theoretical capacity, although a rapid capacity fade is normally observed, attributed mainly to volume expansion during lithiation. Here, we report for the first time successful synthesis of Si/void/SiO2/void/C nanostructures. The synthesis strategy only involves selective etching of SiO2 in Si/SiO2/C structures with hydrofluoric acid solution. Compared with reported results, such novel structures include a hard SiO2-coated layer, a conductive carbon-coated layer, and two internal void spaces. In the structures, the carbon can enhance conductivity, the SiO2 layer has mechanically strong qualities, and the two internal void spaces can confine and accommodate volume expansion of silicon during lithiation. Therefore, these specially designed dual yolk-shell structures exhibit a stable and high capacity of 956 mA h g−1 after 430 cycles with capacity retention of 83%, while the capacity of Si/C core-shell structures rapidly decreases in the first ten cycles under the same experimental conditions. The novel dual yolk-shell structures developed for Si can also be extended to other battery materials that undergo large volume changes. PMID:26039972

  18. Biofuel intercropping effects on soil carbon and microbial activity.

    PubMed

    Strickland, Michael S; Leggett, Zakiya H; Sucre, Eric B; Bradford, Mark A

    2015-01-01

    Biofuels will help meet rising demands for energy and, ideally, limit climate change associated with carbon losses from the biosphere to atmosphere. Biofuel management must therefore maximize energy production and maintain ecosystem carbon stocks. Increasingly, there is interest in intercropping biofuels with other crops, partly because biofuel production on arable land might reduce availability and increase the price of food. One intercropping approach involves growing biofuel grasses in forest plantations. Grasses differ from trees in both their organic inputs to soils and microbial associations. These differences are associated with losses of soil carbon when grasses become abundant in forests. We investigated how intercropping switchgrass (Panicum virgalum), a major candidate for cellulosic biomass production, in loblolly pine (Pinus taeda) plantations affects soil carbon, nitrogen, and microbial dynamics. Our design involved four treatments: two pine management regimes where harvest residues (i.e., biomass) were left in place or removed, and two switchgrass regimes where the grass was grown with pine under the same two biomass scenarios (left or removed). Soil variables were measured in four 1-ha replicate plots in the first and second year following switchgrass planting. Under switchgrass intercropping, pools of mineralizable and particulate organic matter carbon were 42% and 33% lower, respectively. These declines translated into a 21% decrease in total soil carbon in the upper 15 cm of the soil profile, during early stand development. The switchgrass effect, however, was isolated to the interbed region where switchgrass is planted. In these regions, switchgrass-induced reductions in soil carbon pools with 29%, 43%, and 24% declines in mineralizable, particulate, and total soil carbon, respectively. Our results support the idea that grass inputs to forests can prime the activity of soil organic carbon degrading microbes, leading to net reductions in stocks

  19. Oxidation of activated carbon: application to vinegar decolorization.

    PubMed

    López, Francisco; Medina, Francisco; Prodanov, Marin; Güell, Carme

    2003-01-15

    This article reports studies on the feasibility of increasing the decoloring capacity of a granular activated carbon (GAC) by using oxidation with air at 350 degrees C to modify its surface activity and porosity. The GAC, obtained from olive stones, had a maximum decolorization capacity of 92% for doses of 20 g/l, while the maximum decolorization capacity of the modified granular activated carbon (MGAC) was about 96% at a dose of 10 g/l. The increase in decoloring capacity is thought to be due to an increase in mesopore area (from 129 to 340 m2/g) in the MGAC. The maximum decoloring values and the doses needed to attain them are very close to values obtained in previous studies using coconut shell powder-activated carbon (94 and 98% for red and white vinegar for a dose of 10 g/l, respectively).

  20. Activated carbon and tungsten oxide supported on activated carbon catalysts for toluene catalytic combustion.

    PubMed

    Alvarez-Merino, M A; Ribeiro, M F; Silva, J M; Carrasco-Marín, F; Maldonado-Hódar, F J

    2004-09-01

    We have used activated carbon (AC) prepared from almond shells as a support for tungsten oxide to develop a series of WOx/AC catalysts for the catalytic combustion of toluene. We conducted the reaction between 300 and 350 degrees C, using a flow of 500 ppm of toluene in air and space velocity (GHSV) in the range 4000-7000 h(-1). Results show that AC used as a support is an appropriate material for removing toluene from dilute streams. By decreasing the GHSV and increasing the reaction temperature AC becomes a specific catalyst for the total toluene oxidation (SCO2 = 100%), but in less favorable conditions CO appears as reaction product and toluene-derivative compounds are retained inside the pores. WOx/AC catalysts are more selective to CO2 than AC due to the strong acidity of this oxide; this behavior improves with increased metal loading and reaction temperature and contact time. The catalytic performance depends on the nonstoichiometric tungsten oxide obtained during the pretreatment. In comparison with other supports the WOx/AC catalysts present, at low reaction temperatures, higher activity and selectivity than WO, supported on SiO2, TiO2, Al2O3, or Y zeolite. This is due to the hydrophobic character of the AC surface which prevents the adsorption of water produced from toluene combustion thus avoiding the deactivation of the active centers. However, the use of WOx/AC system is always restricted by its gasification temperature (around 400 degrees C), which limits the ability to increase the conversion values by increasing reaction temperatures.

  1. Cancer cell detection and therapeutics using peroxidase-active nanohybrid of gold nanoparticle-loaded mesoporous silica-coated graphene.

    PubMed

    Maji, Swarup Kumar; Mandal, Amal Kumar; Nguyen, Kim Truc; Borah, Parijat; Zhao, Yanli

    2015-05-13

    Development of efficient artificial enzymes is an emerging field in nanobiotechnology, since these artificial enzymes could overcome serious disadvantages of natural enzymes. In this work, a new nanostructured hybrid was developed as a mimetic enzyme for in vitro detection and therapeutic treatment of cancer cells. The hybrid (GSF@AuNPs) was prepared by the immobilization of gold nanoparticles (AuNPs) on mesoporous silica-coated nanosized reduced graphene oxide conjugated with folic acid, a cancer cell-targeting ligand. The GSF@AuNPs hybrid showed unprecedented peroxidase-like activity, monitored by catalytic oxidation of a typical peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB), in the presence of H2O2. On basis of this peroxidase activity, the hybrid was utilized as a selective, quantitative, and fast colorimetric detection probe for cancer cells. Finally, the hybrid as a mimetic enzyme was employed for H2O2- and ascorbic acid (AA)-mediated therapeutics of cancer cells. In vitro experiments using human cervical cancer cells (HeLa cells) exhibited the formation of reactive oxygen species (OH(•) radical) in the presence of peroxidase-mimic GSF@AuNPs with either exogenous H2O2 or endogenous H2O2 generated from AA, leading to an enhanced cytotoxicity to HeLa cells. In the case of normal cells (human embryonic kidney HEK 293 cells), the treatment with the hybrid and H2O2 or AA showed no obvious damage, proving selective killing effect of the hybrid to cancer cells.

  2. Silica Gel for Enhanced Activity and Hypochlorite Protection of Cyanuric Acid Hydrolase in Recombinant Escherichia coli

    PubMed Central

    Radian, Adi; Aukema, Kelly G.; Aksan, Alptekin

    2015-01-01

    ABSTRACT Chlorinated isocyanuric acids are widely used water disinfectants that generate hypochlorite, but with repeated application, they build up cyanuric acid (CYA) that must be removed to maintain disinfection. 3-Aminopropyltriethoxysilane (APTES)-treated Escherichia coli cells expressing cyanuric acid hydrolase (CAH) from Moorella thermoacetica exhibited significantly high CYA degradation rates and provided protection against enzyme inactivation by hypochlorite (chlorine). APTES coating or encapsulation of cells had two benefits: (i) overcoming diffusion limitations imposed by the cell wall and (ii) protecting against hypochlorite inactivation of CAH activity. Cells encapsulated in APTES gels degraded CYA three times faster than nonfunctionalized tetraethoxysilane (TEOS) gels, and cells coated with APTES degraded CYA at a rate of 29 µmol/min per mg of CAH protein, similar to the rate with purified enzyme. UV spectroscopy, fluorescence spectroscopy, and scanning electron microscopy showed that the higher rates were due to APTES increasing membrane permeability and enhancing cyanuric acid diffusion into the cytoplasm to reach the CAH enzyme. Purified CAH enzyme was shown to be rapidly inactivated by hypochlorite. APTES aggregates surrounding cells protected via the amine groups reacting with hypochlorite as shown by pH changes, zeta potential measurements, and infrared spectroscopy. APTES-encapsulated E. coli cells expressing CAH degraded cyanuric acid at high rates in the presence of 1 to 10 ppm hypochlorite, showing effectiveness under swimming pool conditions. In contrast, CAH activity in TEOS gels or free cells was completely inactivated by hypochlorite. These studies show that commercially available silica materials can selectively enhance, protect, and immobilize whole-cell biocatalysts for specialized applications. PMID:26530383

  3. Improvement of the activation of lipase from Candida rugosa following physical and chemical immobilization on modified mesoporous silica.

    PubMed

    Wang, Chunfeng; Li, Yanjing; Zhou, Guowei; Jiang, Xiaojie; Xu, Yunqiang; Bu, Zhaosheng

    2014-12-01

    Lipase from Candida rugosa (CRL) was chemically and physically immobilized onto four types of rod-shaped mesoporous silica (RSMS). RSMS prepared using surfactant P123 and poly(ethylene glycol) as co-templates was functionalized with (3-aminopropyl)triethoxysilane (APTES) to obtain P-RSMS by post-synthesis grafting. Tetraethoxysilane was hydrothermally co-condensed with APTES to obtain C-RSMS. A two-step process using APTES and glutaraldehyde was also performed to obtain G-RSMS. The effects of modification methods (including post-synthesis grafting and co-condensation) and glutaraldehyde on the mesoscopic order, interplanar spacing d100, cell parameter a0, mesoporous structure, and wall thickness of RSMS were studied in detail. Results showed that all samples were mesoporous materials with 2D mesostructures (p6mm). Pore size and d100 decreased, whereas the wall thickness increased after different modifications. CRL was used as a model enzyme to determine the effect of physical and chemical adsorption on loading amount and enzymatic activity. The possible mechanism of CRL immobilization on G-RSMS by chemical adsorption was systematically investigated. The chemical immobilization of CRL on G-RSMS increased the loading amount, hydrolytic activity, thermal stability, and reusability. Moreover, immobilized CRL was employed to catalyze the resolution of 2-octanol by esterification with caprylic acid. The enantiomeric excess of 2-octanol was 45.8% when the reaction was catalyzed by G-RSMS-CRL and decreased to about 38%-39% using the physically immobilized CRL, after 48 h of reaction in hexane.

  4. Encapsulation of Anti-Tuberculosis Drugs within Mesoporous Silica and Intracellular Antibacterial Activities

    PubMed Central

    Xia, Xin; Pethe, Kevin; Kim, Ryangyeo; Ballell, Lluis; Barros, David; Cechetto, Jonathan; Jeon, HeeKyoung; Kim, Kideok; Garcia-Bennett, Alfonso E.

    2014-01-01

    Tuberculosis is a major problem in public health. While new effective treatments to combat the disease are currently under development, they tend suffer from poor solubility often resulting in low and/or inconsistent oral bioavailability. Mesoporous materials are here investigated in an in vitro intracellular assay, for the effective delivery of compound PA-824; a poorly soluble bactericidal agent being developed against Tuberculosis (TB). Mesoporous materials enhance the solubility of PA-824; however, this is not translated into a higher antibacterial activity in TB-infected macrophages after 5 days of incubation, where similar values are obtained. The lack of improved activity may be due to insufficient release of the drug from the mesopores in the context of the cellular environment. However, these results show promising data for the use of mesoporous particles in the context of oral delivery with expected improvements in bioavailability.

  5. Testing Iodized Activated Carbon Filters with Non-Radio Active Methyl Iodide.

    DTIC Science & Technology

    1980-05-30

    and 4314, 4315, and 4316 are labora- to y impregnations using KI, KIO 3, hexamethylenetetramine and a pH 10 phosphate buffer (11). The agreement...14, Columbia Activated Carbon 207A 8 x 16, Sutcliffe, Speakman Co. Ltd. BPL 8 x 20, Activated Carbon Division, Calgon Corp. KITEG II Nuclear Consulting Services, Inc. TEDA triethylenediamine HMTA hexamethylenetetramine 52

  6. Decolorization of Cheddar cheese whey by activated carbon.

    PubMed

    Zhang, Yue; Campbell, Rachel; Drake, MaryAnne; Zhong, Qixin

    2015-05-01

    Colored Cheddar whey is a source for whey protein recovery and is decolorized conventionally by bleaching, which affects whey protein quality. Two activated carbons were studied in the present work as physical means of removing annatto (norbixin) in Cheddar cheese whey. The color and residual norbixin content of Cheddar whey were reduced by a higher level of activated carbon at a higher temperature between 25 and 55°C and a longer time. Activated carbon applied at 40g/L for 2h at 30°C was more effective than bleaching by 500mg/L of hydrogen peroxide at 68°C. The lowered temperature in activated-carbon treatments had less effect on protein structure as investigated for fluorescence spectroscopy and volatile compounds, particularly oxidation products, based on gas chromatography-mass spectrometry. Activated carbon was also reusable, removing more than 50% norbixin even after 10 times of regeneration, which showed great potential for decolorizing cheese whey.

  7. Treatment of activated carbon to enhance catalytic activity for reduction of nitric oxide with ammonia

    SciTech Connect

    Ku, B.J.; Rhee, H.K. . Dept. of Chemical Engineering); Lee, J.K.; Park, D. )

    1994-11-01

    Catalytic activity of activated carbon treated with various techniques was examined in a fixed bed reactor for the reduction of nitric oxide with ammonia at 150 C. Activated carbon derived from coconut shell impregnated with an aqueous solution of ammonium sulfate, further treated with sulfuric acid, dried at 120 C, and then heated in an inert gas stream at 400 C, showed the highest catalytic activity within the range of experimental conditions. The enhancement of catalytic activity of modified activated carbon could be attributed to the increase in the amount of oxygen function groups which increased the adsorption site for ammonia. Catalytic activity of activated carbons depended on the surface area and the oxygen content as well.

  8. A General Methodology for Evaluation of Carbon Sequestration Activities and Carbon Credits

    SciTech Connect

    Klasson, KT

    2002-12-23

    A general methodology was developed for evaluation of carbon sequestration technologies. In this document, we provide a method that is quantitative, but is structured to give qualitative comparisons despite changes in detailed method parameters, i.e., it does not matter what ''grade'' a sequestration technology gets but a ''better'' technology should receive a better grade. To meet these objectives, we developed and elaborate on the following concepts: (1) All resources used in a sequestration activity should be reviewed by estimating the amount of greenhouse gas emissions for which they historically are responsible. We have done this by introducing a quantifier we term Full-Cycle Carbon Emissions, which is tied to the resource. (2) The future fate of sequestered carbon should be included in technology evaluations. We have addressed this by introducing a variable called Time-adjusted Value of Carbon Sequestration to weigh potential future releases of carbon, escaping the sequestered form. (3) The Figure of Merit of a sequestration technology should address the entire life-cycle of an activity. The figures of merit we have developed relate the investment made (carbon release during the construction phase) to the life-time sequestration capacity of the activity. To account for carbon flows that occur during different times of an activity we incorporate the Time Value of Carbon Flows. The methodology we have developed can be expanded to include financial, social, and long-term environmental aspects of a sequestration technology implementation. It does not rely on global atmospheric modeling efforts but is consistent with these efforts and could be combined with them.

  9. Effect of silica nanoparticles with variable size and surface functionalization on human endothelial cell viability and angiogenic activity

    NASA Astrophysics Data System (ADS)

    Guarnieri, Daniela; Malvindi, Maria Ada; Belli, Valentina; Pompa, Pier Paolo; Netti, Paolo

    2014-02-01

    Silica nanoparticles could be promising delivery vehicles for drug targeting or gene therapy. However, few studies have been undertaken to determine the biological behavior effects of silica nanoparticles on primary endothelial cells. Here we investigated uptake, cytotoxicity and angiogenic properties of silica nanoparticle with positive and negative surface charge and sizes ranging from 25 to 115 nm in primary human umbilical vein endothelial cells. Dynamic light scattering measurements and nanoparticle tracking analysis were used to estimate the dispersion status of nanoparticles in cell culture media, which was a key aspect to understand the results of the in vitro cellular uptake experiments. Nanoparticles were taken up by primary endothelial cells in a size-dependent manner according to their degree of agglomeration occurring after transfer in cell culture media. Functionalization of the particle surface with positively charged groups enhanced the in vitro cellular uptake, compared to negatively charged nanoparticles. However, this effect was contrasted by the tendency of particles to form agglomerates, leading to lower internalization efficiency. Silica nanoparticle uptake did not affect cell viability and cell membrane integrity. More interestingly, positively and negatively charged 25 nm nanoparticles did not influence capillary-like tube formation and angiogenic sprouting, compared to controls. Considering the increasing interest in nanomaterials for several biomedical applications, a careful study of nanoparticle-endothelial cells interactions is of high relevance to assess possible risks associated to silica nanoparticle exposure and their possible applications in nanomedicine as safe and effective nanocarriers for vascular transport of therapeutic agents.

  10. Differences in both matrix metalloproteinase 9 concentration and zymographic profile between plasma and serum with clot activators are due to the presence of amorphous silica or silicate salts in blood collection devices.

    PubMed

    Mannello, Ferdinando; Tanus-Santos, Jose E; Meschiari, Cesar A; Tonti, Gaetana A

    2008-03-01

    Matrix metalloproteinases (MMPs) are promising diagnostic tools, and blood sampling/handling alters MMP concentrations between plasma and serum and between serum with and without clot activators. To explain the higher MMP-9 expression in serum collected with clot accelerators relative to serum with no additives and to plasma, we analyzed the effects of increasing amounts of silica and silicates (components of clot activators) in citrate plasma, serum, and buffy coats collected in both plastic and glass tubes from 50 healthy donors, and we analyzed the effects of silica and silicate on cultured leukemia cells. The levels of MMP-2 did not show significant changes between glass and plastic tubes, between serum and plasma, between serum with and without clot accelerators, or between silica and silicate treatments. No modification of MMP-9 expression was obtained by the addition of silica or silicate to previously separated plasma and serum. Increasing the amounts of nonsoluble silica and soluble silicate added to citrate and empty tubes prior to blood collection resulted in increasing levels of MMP-9 relative to citrate plasma and serum. Silica and silicate added to buffy coats and leukemia cells significantly induced MMP-9 release/secretion, demonstrating that both silica and silicate induce the release of pro- and complexed MMP-9 forms. We recommend limiting the misuse of serum and avoiding the interfering effects of clot activators.

  11. Trivalent chromium removal from wastewater using low cost activated carbon derived from agricultural waste material and activated carbon fabric cloth.

    PubMed

    Mohan, Dinesh; Singh, Kunwar P; Singh, Vinod K

    2006-07-31

    An efficient adsorption process is developed for the decontamination of trivalent chromium from tannery effluents. A low cost activated carbon (ATFAC) was prepared from coconut shell fibers (an agricultural waste), characterized and utilized for Cr(III) removal from water/wastewater. A commercially available activated carbon fabric cloth (ACF) was also studied for comparative evaluation. All the equilibrium and kinetic studies were conducted at different temperatures, particle size, pHs, and adsorbent doses in batch mode. The Langmuir and Freundlich isotherm models were applied. The Langmuir model best fit the equilibrium isotherm data. The maximum adsorption capacities of ATFAC and ACF at 25 degrees C are 12.2 and 39.56 mg/g, respectively. Cr(III) adsorption increased with an increase in temperature (10 degrees C: ATFAC--10.97 mg/g, ACF--36.05 mg/g; 40 degrees C: ATFAC--16.10 mg/g, ACF--40.29 mg/g). The kinetic studies were conducted to delineate the effect of temperature, initial adsorbate concentration, particle size of the adsorbent, and solid to liquid ratio. The adsorption of Cr(III) follows the pseudo-second-order rate kinetics. From kinetic studies various rate and thermodynamic parameters such as effective diffusion coefficient, activation energy and entropy of activation were evaluated. The sorption capacity of activated carbon (ATFAC) and activated carbon fabric cloth is comparable to many other adsorbents/carbons/biosorbents utilized for the removal of trivalent chromium from water/wastewater.

  12. Breakthrough CO₂ adsorption in bio-based activated carbons.

    PubMed

    Shahkarami, Sepideh; Azargohar, Ramin; Dalai, Ajay K; Soltan, Jafar

    2015-08-01

    In this work, the effects of different methods of activation on CO2 adsorption performance of activated carbon were studied. Activated carbons were prepared from biochar, obtained from fast pyrolysis of white wood, using three different activation methods of steam activation, CO2 activation and Potassium hydroxide (KOH) activation. CO2 adsorption behavior of the produced activated carbons was studied in a fixed-bed reactor set-up at atmospheric pressure, temperature range of 25-65°C and inlet CO2 concentration range of 10-30 mol% in He to determine the effects of the surface area, porosity and surface chemistry on adsorption capacity of the samples. Characterization of the micropore and mesopore texture was carried out using N2 and CO2 adsorption at 77 and 273 K, respectively. Central composite design was used to evaluate the combined effects of temperature and concentration of CO2 on the adsorption behavior of the adsorbents. The KOH activated carbon with a total micropore volume of 0.62 cm(3)/g and surface area of 1400 m(2)/g had the highest CO2 adsorption capacity of 1.8 mol/kg due to its microporous structure and high surface area under the optimized experimental conditions of 30 mol% CO2 and 25°C. The performance of the adsorbents in multi-cyclic adsorption process was also assessed and the adsorption capacity of KOH and CO2 activated carbons remained remarkably stable after 50 cycles with low temperature (160°C) regeneration.

  13. Synthesis of carbon fibers and activated carbon fibers from coal liquids

    SciTech Connect

    Fei, Y.Q.; Derbyshire, F.; Jagtoyen, M.; Kimber, G.

    1994-12-31

    The production and application of low-cost, general purpose carbon fibers and activated fibers are emerging technologies with exciting potential, although at present their cost is too high to find widespread use. Production and R and D have been limited and to data, only a small range of precursors has been studied: petroleum pitches, coal extracts and coal tar pitches. Both processing costs and the properties of the fiber products are dependent on the nature of the starting material. Commercial precursors have been limited to the pitches produced from high temperature pyrolysis or cracking processes and are similar in composition and molecular structure. Suitable coal-based precursors can be produced with a wide range of composition, and at moderate cost, by methods such as low temperature carbonization, solvent extraction, hydropyrolysis and mild coal liquefaction. It is of interest to investigate the synthesis of carbon fibers and activated carbon fibers from precursors of different origins to elucidate the influence of precursor materials on fiber formation and processing, and their structure and properties. It is also of practical importance to understand the relationships between the type of starting materials (for example, coals) and the processing methods, and the properties of fiber precursors that can be produced from them. In the present study, the authors describe the synthesis of carbon fibers and activated carbon fibers from the products of the first stage of coal liquefaction.

  14. Adsorption of aromatic organic contaminants by graphene nanosheets: comparison with carbon nanotubes and activated carbon.

    PubMed

    Apul, Onur Guven; Wang, Qiliang; Zhou, Yang; Karanfil, Tanju

    2013-03-15

    Adsorption of two synthetic organic compounds (SOCs; phenanthrene and biphenyl) by two pristine graphene nanosheets (GNS) and one graphene oxide (GO) was examined and compared with those of a coal base activated carbon (HD4000), a single-walled carbon nanotube (SWCNT), and a multi-walled carbon nanotube (MWCNT) in distilled and deionized water and in the presence of natural organic matter (NOM). Graphenes exhibited comparable or better adsorption capacities than carbon nanotubes (CNTs) and granular activated carbon (GAC) in the presence of NOM. The presence of NOM reduced the SOC uptake of all adsorbents. However, the impact of NOM on the SOC adsorption was smaller on graphenes than CNTs and activated carbons. Furthermore, the SOC with its flexible molecular structure was less impacted from NOM preloading than the SOC with planar and rigid molecular structure. The results indicated that graphenes can serve as alternative adsorbents for removing SOCs from water. However, they will also, if released to environment, adsorb organic contaminants influencing their fate and impact in the environment.

  15. High surface area activated carbon prepared from cassava peel by chemical activation.

    PubMed

    Sudaryanto, Y; Hartono, S B; Irawaty, W; Hindarso, H; Ismadji, S

    2006-03-01

    Cassava is one of the most important commodities in Indonesia, an agricultural country. Cassava is one of the primary foods in our country and usually used for traditional food, cake, etc. Cassava peel is an agricultural waste from the food and starch processing industries. In this study, this solid waste was used as the precursor for activated carbon preparation. The preparation process consisted of potassium hydroxide impregnation at different impregnation ratio followed by carbonization at 450-750 degrees C for 1-3 h. The results revealed that activation time gives no significant effect on the pore structure of activated carbon produced, however, the pore characteristic of carbon changes significantly with impregnation ratio and carbonization temperature. The maximum surface area and pore volume were obtained at impregnation ratio 5:2 and carbonization temperature 750 degrees C.

  16. Deactivation of photocatalytically active ZnO nanoparticle and enhancement of its compatibility with organic compounds by surface-capping with organically modified silica

    NASA Astrophysics Data System (ADS)

    Cao, Zhi; Zhang, Zhijun

    2011-02-01

    Tetraethyl orthosilicate (TEOS) and dimethyldiethoxysilane (DEDMS) were used as co-precursors to prepare organically modified silica (ormosil) via sol-gel process. The resultant ormosil was adopted for surface-capping of ZnO nanoparticle, where methyl (organic functional group) and silica (inorganic component) were simultaneously introduced onto the surface of the nanoparticles for realizing dual surface-modification. The ormosil-capped ZnO nanoparticle showed strong hydrophobicity and good compatibility with organic phases, as well as effectively decreased photocatalytic activity and almost unchanged ultraviolet (UV)-shielding ability. More importantly, the comprehensive properties of ormosil-capped ZnO nanoparticle could be manipulated by adjusting the molar ratio of TEOS to DEDMS during sol-gel process. This should help to open a wider window to better utilizing the unique and highly attractive properties such as high UV-shielding ability and high-visible light transparency of ZnO nanoparticle in sunscreen cosmetics.

  17. Facile, one-pot synthesis, and antibacterial activity of mesoporous silica nanoparticles decorated with well-dispersed silver nanoparticles.

    PubMed

    Tian, Yue; Qi, Juanjuan; Zhang, Wei; Cai, Qiang; Jiang, Xingyu

    2014-08-13

    In this study, we exploit a facile, one-pot method to prepare MCM-41 type mesoporous silica nanoparticles decorated with silver nanoparticles (Ag-MSNs). Silver nanoparticles with diameter of 2-10 nm are highly dispersed in the framework of mesoporous silica nanoparticles. These Ag-MSNs possess an enhanced antibacterial effect against both Gram-positive and Gram-negative bacteria by preventing the aggregation of silver nanoparticles and continuously releasing silver ions for one month. The cytotoxicity assay indicates that the effective antibacterial concentration of Ag-MSNs shows little effect on human cells. This report describes an efficient and economical route to synthesize mesoporous silica nanoparticles with uniform silver nanoparticles, and these nanoparticles show promising applications as antibiotics.

  18. The environmental applications of activated carbon/zeolite composite materials.

    PubMed

    Foo, K Y; Hameed, B H

    2011-02-17

    Over the past couple of years, the resurgence of placing an effective and sustainable amendment to combat against the auxiliary industrial entities, remains a highly contested agenda from a global point. With the renaissance of activated carbon, there has been a steadily growing interest in the research field. Recently, the adoption of zeolite composite, a prestigious advanced catalyst which formulates the enhancement of adsorption rate and hydrogen storage capability, has fore fronted to be a new growing branch in the scientific community. Confirming the assertion, this paper presents a state of art review of activated carbon/zeolite composite technology, its fundamental background studies, and environmental implications. Moreover, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expanding of activated carbon/zeolite composite represents a potentially viable and powerful tool, leading to the plausible improvement of environmental preservation.

  19. Detoxification of pesticide waste via activated carbon adsorption process.

    PubMed

    Foo, K Y; Hameed, B H

    2010-03-15

    Concern about environmental protection has increased over the years from a global viewpoint. To date, the percolation of pesticide waste into the groundwater tables and aquifer systems remains an aesthetic issue towards the public health and food chain interference. With the renaissance of activated carbon, there has been a consistent growing interest in this research field. Confirming the assertion, this paper presents a state of art review of pesticide agrochemical practice, its fundamental characteristics, background studies and environmental implications. Moreover, the key advance of activated carbon adsorption, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expanding of activated