Showing papers on "Silica gel published in 2005"
TL;DR: A novel kind of magnetic core/mesoporous silica shell nanospheres with a uniform particle diameter of ca.
Abstract: A novel kind of magnetic core/mesoporous silica shell nanospheres with a uniform particle diameter of ca. 270 nm was synthesized. The inner magnetic core endues the whole nanoparticle with magnetic properties, while the outer mesoporous silica shell shows high enough surface area and pore volume. The synthesized material is expected to be applied to targeted drug delivery and multiphase separation. The storage and release of ibuprofen into and from the pore channels of the mesoporous silica shell, as a typical example, are demonstrated.
720 citations
19 Dec 2005
TL;DR: In this paper, Bergna et al. present an overview of the chemical properties of Silica surfaces and their application in a variety of applications, including the preparation of solvents.
Abstract: Colloid Science H.E. Bergna The Language of Colloid Science and Silica Chemistry H.E. Bergna Colloid Chemistry of Silica: An Overview H.E. Bergna Silicic Acids and Colloidal Silica H.E. Bergna PREPARATION OF SOLS B.A. Keiser Science and Art of the Formation of Uniform Solid Particles E. Matijevic Silica Nucleation, Polymerization, and Growth Preparation of Monodispersed Sols A. Yoshida The Formation and Interfacial Structure of Silica Sols J.D.F. Ramsay, S.W. Swanton, A. Matsumoto, and D.G.C. Goberdhan Synthesis and Characterization of Colloidal Model Particles Made from Organoalkoxysilanes A. van Blaaderen and A. Vrij Synthesis of Nanometer-Sized Silica by Controlled Hydrolysis in Reverse Micellar Systems F. J. Arriagada and K. Osseo-Asare Formation of Silica Gels Composed of Micrometer-Sized Particles by the Sol-Gel Method H. Kozuka and S. Sakka Silica Aquasol Process to Prepare Small Particle Size Colloidal Silica by Electrodialysis H.E. Bergna Manufacturing and Applications of Water-Borne Colloidal Silica W.O. Roberts Enterosorbent Silics: Properties and Clinical Application O.O. Chuiko, O.O. Pentyuk, and V.K. Pogorelyi Industrial Synthetic Silicas in Powder Form H.K. Ferch High Ratio Silicate Foundry Sand Binders H.E. Bergna Spray Dried Silica for Chromatography H.E. Bergna Preparation of Monodisperse Ultrafine Hybrid Silica Particles by Polymer Modification K. Yoshinaga, J. Shimada, and T. Kobayashi Monodisperse Core-Shell Silica Colloids from Alkoxysilanes A. van Blaaderen Preparation of Silica Solid Microspheres by Hydrolysis of Tetraethyl Ortho Silicate (TEOS) and Silica Porous Microspheres by Spray Drying Aggregated Colloidal Silica H.E. Bergna STABILITY OF SOLS F. Dumont Stability of Aqueous Silica Sols T.W. Healy Stabilization Against Particle Growth P.C. Yates SURFACE CHEMISTRY OF SILICA M.L. Hair The Surface Chemistry of Silica - The Zhuravlev Model L.T. Zhuravlev Surface Structure of Amorphous and Crystalline Porous Silicas: Status and Prospects K.K. Unger Infrared Study of Chemical and H-D Exchange Probes for Silica Surfaces B.A. Morrow and A.J. McFarlan Infrared Studies of Chemically Modified Silica B.A. Morrow and D.T. Molapo Fourier Transform Infrared and Raman Spectroscopic Study of Silica Surfaces B. Humbert, C. Carteret, A. Burneau and J.P. Gallas Adsorption on Silica and Related Materials L.E. Cascarini de Torre and E.J. Bottani Structure of Disperse Silica Surface and Electrostatic Aspects of Adsorption A.A. Chuiko, V.V. Lobanov, and A.G. Grebenyuk Variable-Temperature Diffuse Reflectance Fourier Transform Infrared Spectroscopic Studies of Amine Desorption from a Siliceous Surface D.E. Leyden and K.G. Proctor Surveying the Silica Gel Surface with Excited States R. Krasnansky and J.K. Thomas Surface Chemistry and Surface Energy of Silicas A.M. Vidal and E. Papirer Diffuse Reflectance FTIR Spectroscopic Study of Base Desorption from Thermally Treated Silica K.G. Proctot, S.J. Markway, M. Garcia, C.A. Brown, and C.P. Gonzales Salient Features of Synthesis and Structure of Surface of Functionalized Polysiloxane Xerogels Yu.L. Zub and A.A. Chuiko Multinuclear NMR Studies of Silica Surfaces G.E. Maciel and I. Chuang Modified Silicas: Synthesis and Applications A.A. Chuiko Electric Surface Properties of Silica in Non-aqueous Electrolyte Solutions A.N. Zhukov Chemical Reactions at Fumed Silica Surfaces V.M. Gun'ko and A.A. Chuiko Structural and Adsorptive Characteristics of Fumed Silicas in Different Media V.M. Gun'ko, V.I. Zarko, V.V. Turov, E.F. Voronin, I.F. Mironyuk, A.A. Chuiko Adsorption of Surfactants and Polymers on Silica P. Somasundaran and L. Zhang PARTICLE SIZE AND CHARACTERIZATION TECHNIQUES J.L. Bass New Separation Methods for Characterizing the Size of Silica Sols J. J. Kirkland Characterization of Colloidal and Particulate Silica by Field-Flow Fractionation J.C. Giddings, S.K. Ratanathanawongs, B.N. Barman, M.H. Moon, G. Liu, B.L. Tjelta, and M.E. Hansen Formation of Uniform Precipitates from Alkoxides C.F. Zukoski, J.L. Look, and G.H. Bogush SILICA GELS AND POWDERS W.A. Welsh Synthetic Amorphous Silicas U. Brinkmann, M. Ettlinger, D. Kerner and R. Schmoll Adsorptive Properties of Porous Silicas Martyn B. Kenny and K.S.W. Sing Silica Gels from Aqueous Silicate Solutions: Combined 29Si NMR and Small-Angle X-Ray Scattering Spectroscopic Study P.W.J.G. Wijnen, T.P.M. Beelen, and R.A. van Santen Interpretation of the Differences Between the Pore Size Distributions of Silica Measured by Mercury Intrusion and Nitrogen Adsorption A.R. Minihan, D.R. Ward, and W. Whitby SOL-GEL TECHNOLOGY G.W. Scherer Sol-Gel Processing of Silica C.J. Brinker The Chemistry of Hydrolysis and Condensation of Silica Sol-Gel Precursors B.K. Coltrain and L.W. Kelts Chemistry and Properties of Porous, Organically Modified Silica H. Schmidt and H. Boettner Evaporation and Surface Tension Effects in Dip Coating A.J. Hurd SILICA COATINGS M.R. Baloga Nanostructuring Metals and Semiconductors with Silica from Monolayers to Crystals L.M. Liz-Marzan and P. Mulvaney Surface Chemistry of Silica Coatings of Titania D.N. Furlong Dense Silica Coatings on Micro- and Nanoparticles by Deposition of Monosilicic Acid H.E. Bergna, L.E. Firment, and D.G. Swartzfager USES OF COLLOIDAL SILICAS R.E. Patterson and J.S. Falcone Applications of Colloidal Silica: Past, Present, and Future C.C. Payne The Uses of Soluble Silica J.S. Falcone, Jr. Attrition Resistant Catalysts, Catalyst Precursors and Catalyst Supports and Process for Preparing Same H.E. Bergna Some Important, Fairly New Uses of Colloidal Silica/Silica Sol J.E. Otterstedt and P. Greenwood Silicon-Aluminum Interactions and Biology J. D. Birchall Silica in Biology J.S. Falcone Preparation and Uses of Silica Gels and Precipitated Silicas R.E. Patterson Foundry Mold or Core Compositions and Method H.E. Bergna Silica Supported Catalysts and Method of Preparation H.E. Bergna Molded Amorphous Silica Bodies and Molding Powders for Manufacture of Same H.E. Bergna High Ratio Silicate Foundry Sand Binders H.E. Bergna NMR OF SILICA EDGE On the Silica Edge: An NMR Point of View A.P. Legrand, H. Hommel and J.B. d'Espinose de la Caillerie RESEARCH IN RUSSIA H.E. Bergna Colloid Chemistry of Silica: Research in the Former Soviet Union L.T. Zhuravlev ANALYTICAL METHODS H.E. Bergna Integrated Analytical Methods H.E. Bergna Index
503 citations
TL;DR: The functionalization of SBA-15 with mercaptopropyl trimethoxysilane leads to a material capable of absorbing Pd from organic and aqueous solutions, illustrating the importance of the thiol ligand to retain Pd on the surface.
Abstract: The functionalization of SBA-15 with mercaptopropyl trimethoxysilane leads to a material capable of absorbing Pd from organic and aqueous solutions. The resulting Pd-loaded material acts as a catalyst for the Suzuki−Miyaura and Mizoroki−Heck coupling reactions. Leaching studies show that the filtrate contains as little as 3 ppb Pd after reaction. Aminopropylated silica is an effective scavenger, and catalyst for the Mizoroki−Heck reaction, but leaching is significant (35 ppm), illustrating the importance of the thiol ligand to retain Pd on the surface. Heterogeneity tests such as hot filtration experiments and three-phase tests show that the reaction is occurring predominantly via surface-bound Pd.
500 citations
TL;DR: A new method using a microcolumn packed with immobilized nanometer TiO(2) as sorbent has been developed for the preconcentration of trace amounts of Cd, Cr, Cu and Mn prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES).
362 citations
TL;DR: In this paper, a novel high-capacity, water-tolerant adsorbent for CO2 was developed, which consisted of diethanolamine (DEA) loaded poreexpanded MCM-41 silica.
Abstract: A novel high-capacity, water-tolerant adsorbent for CO2 was developed. It consisted of diethanolamine (DEA) loaded pore-expanded MCM-41 silica (PE-MCM-41). Due to its very large pore volume, PE-MCM-41 silica was capable of accommodating a greater quantity of amine resulting in higher CO2 adsorption capacity compared to the other supports including activated carbon, silica gel, and standard MCM-41 silica. Adsorption measurements were conducted by gravimetry using dry CO2 to obtain uptake curves and apparent rate data. The capacity and uptake rate reached maxima with respect to amine content and then declined due to the deposition of excess amine on the particle's external surface and within the interparticle voids. At CO2 partial pressures below 0.15 atm, the current DEA loaded PE-MCM-41 adsorbent was found to be superior to the more conventional zeolite 13X. Adsorption studies with humid CO2 revealed that the adsorption capacity of the PE-MCM-41-based material was insensitive to the presence of moisture, ...
359 citations
TL;DR: The prepared ion-imprinted functionalized sorbent was shown to be promising for on-line, solid-phase extraction coupled with flame atomic absorption spectrometry for the determination of trace cadmium in environmental and biological samples.
Abstract: A new ion-imprinted thiol-functionalized silica gel sorbent was synthesized by a surface imprinting technique in combination with a sol−gel process for selective on-line, solid-phase extraction of Cd(II). The Cd(II)-imprinted thiol-functionalized silica sorbent was characterized by FT-IR, the static adsorption−desorption experiment, and the dynamic adsorption−desorption method. The maximum static adsorption capacity of the ion-imprinted functionalized sorbent was 284 μmol g-1. The largest selectivity coefficient for Cd(II) in the presence of Pb(II) was over 220. The static uptake capacity and selectivity coefficient of the ion-imprinted functionalized sorbent are higher than those of the nonimprinted sorbent. The breakthrough capacity and dynamic capacity of the imprinted functionalized silica gel sorbent for 4 mg L-1 of Cd(II) at 5.2 mL min-1 of sample flow rate were 11.7 and 64.3 μmol g-1, respectively. No remarkable effect of sample flow rate on the dynamic capacity was observed as the sample flow rate...
308 citations
TL;DR: The implications of organically modified silica-based materials in electrochemical science is reviewed along with some selected recent trends in the field of functionalized and sol-gel silica electrochemistry as discussed by the authors.
Abstract: The implications of organically-modified silica-based materials in electrochemical science is reviewed along with some selected recent trends in the field of functionalized and sol–gel silica electrochemistry. These recent trends include the electro-assisted generation of organosilica films on solid electrode surfaces, the preparation and applications of sol–gel derived composite (carbon, gold, nanotubes) electrodes, the electrochemical characterisation of mass transfer reactions in porous functionalized silicas, solid-state electrochemistry and gas sensors involving sol–gel materials, imprinted functionalized silica, and the electrochemical characterisation and applications of ordered mesoporous organosilicas.
274 citations
TL;DR: Magnesium silicate hydrate gels (M-S-H) have been prepared by precipitation and the range of gel compositions lie between Mg/Si molar ratios 0.67-1.0 as mentioned in this paper.
265 citations
TL;DR: Thermodynamic measurements and NMR spectroscopic analysis were used to show that it is possible to recover CO2 from flue gas by forming a mixed hydrate that removes CO2 preferentially from CO2/N2 gas mixtures using water dispersed in the pores of silica gel.
Abstract: Thermodynamic measurements and NMR spectroscopic analysis were used to show that it is possible to recover CO2 from flue gas by forming a mixed hydrate that removes CO2 preferentially from CO2/N2 gas mixtures using water dispersed in the pores of silica gel. Kinetic studies with 1H NMR microimaging showed that the dispersed water in the silica gel pore system reacts readily with the gas, thus obviating the need for a stirred reactor and excess water. Hydrate phase equilibria for the ternary CO2−N2−water system in silica gel pores were measured, which show that the three-phase hydrate−water-rich liquid−vapor equilibrium curves were shifted to higher pressures at a specific temperature when the concentration of CO2 in the vapor phase decreased. 13C cross-polarization NMR spectral analysis and direct measurement of the CO2 content in the hydrate phase suggested that the mixed hydrate is structure I at gas compositions of more than 10 mol % CO2, and that the CO2 molecules occupy mainly the more abundant 51262...
256 citations
TL;DR: In this paper, ordered macroporous silica, a silica gel microhoneycomb (SMH), has been prepared through a method which uses micrometer-sized ice crystals as a template.
Abstract: Ordered macroporous silica, a silica gel microhoneycomb (SMH), has been prepared through a method which uses micrometer-sized ice crystals as a template. Template ice crystals, which have a continuous rod shape, a polygonal cross section, and ordered diameters, were grown inside precursor silica hydrogels under a condition where the pseudo-steady-state growth of them continues. Besides their ordered macroporosity, micro-/mesopores develop inside the honeycomb walls through the freeze-drying of SMHs soaked in tert-butyl alcohol. SMHs have straight and polygonal macroporous voids, which are created and retained through the formation and removal of the ice crystals. Micromorphology including macropore size and wall thickness, micro-/mesoporosity inside the honeycomb walls, and thermal stability of SMHs were investigated in detail through scanning electron microscopy observation, nitrogen adsorption−desorption measurements, and thermogravimetric analysis. It was found that the macropore size of the SMHs can b...
250 citations
TL;DR: In this paper, the role of ozone was studied for two different configurations combining non-thermal plasma (NTP) and heterogeneous catalysis, namely the use of a gas phase plasma with subsequent exposure of the effluent to a catalyst in a packed-bed reactor (post-plasma treatment) and the placement of the catalyst directly in the discharge zone (inplasma catalysis).
Abstract: The role of ozone was studied for two different configurations combining non-thermal plasma (NTP) and heterogeneous catalysis, namely the use of a gas phase plasma with subsequent exposure of the effluent to a catalyst in a packed-bed reactor (post-plasma treatment) and the placement of the catalyst directly in the discharge zone (in-plasma catalysis). Non-porous and porous alumina and silica were deployed as model catalysts. The oxidation of immobilised hydrocarbons, toluene as a volatile organic compound and CO as an inorganic pollutant were studied in both operational modes. While conversion and selectivity of hydrocarbon oxidation in the case of catalytic post-plasma treatment can be fully explained by the catalytic decomposition of O3 on γ-Al2O3, the conversion processes for in-plasma catalysis are more complex and significant oxidation was also measured for the other three materials (α-Al2O3, quartz and silica gel). It became obvious that additional synergetic effects can be utilised in the case of in-plasma catalysis due to short-lived species formed in the NTP. The capability of porous alumina for ozone decomposition was found to be correlated with its activity for oxidation of carbon-containing agents. It could be clearly shown that the reaction product CO2 poisons the catalytic sites at the γ-Al2O3 surface. The catalytic activity for O3 decomposition can be partially re-established by NTP treatment. However, for practical purposes the additional reaction pathways provided by in-plasma catalytic processes are essential for satisfactory conversion and selectivity.
TL;DR: The PCP-imprinted amino-functionalized silica gel sorbent exhibited high selectivity and offered a fast kinetics for the adsorption and desorption of PCP and offered good linearity for on-line solid-phase extraction of trace levels ofPCP.
TL;DR: Catalytic activities were remarkably enhanced with much lower amounts of ionic liquids needed with respect to bulk ionic-liquid catalysts or silica-supported ionsic- liquid catalysts prepared with simple impregnation, in which the ionic liquid may be deposited as a thin layer on the support.
Abstract: A new concept of designing and synthesizing highly dispersed ionic-liquid catalysts was developed through physical confinement or encapsulation of ionic liquids (with or without metal complex) in a silica-gel matrix through a sol-gel process. We studied ionic liquids such as EMImBF4, BuMImBF4, DMImBF4, CMImBF4, BuMImPF6, either with or without [Pd(PPh3)2Cl2] and [Rh(PPh3)3Cl], in a silica-gel matrix (E = ethyl, Bu = butyl M = methyl, D = decyl, C = cetyl and Im = imidazolium). The contents of ionic liquids and loadings of Pd or Rh were 8-53 wt % and 0.1 approximately 0.15 wt %, respectively. Analyses of FT-Raman spectra showed that abnormal Raman spectra of the confined ionic liquids were observed in comparison with the bulk and pure ionic liquids. EMImBF4 and BuMImBF4 ionic liquids could be completely washed out from the silica-gel matrix under vigorous reflux conditions, but ionic liquids with larger molecular size, for example, DMImBF4 or CMImBF4, could be confined into the silica-gel nanopores relatively firmly. These results suggested that the ionic liquids were physically confined or encapsulated into the silica gel. The N2 adsorption measurements indicated that the silica-gel skeleton was mesoporous with 50-110 A pore size after the BuMImBF4 ionic liquid was removed completely. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis showed that the silica-gel matrix was amorphous and non-uniformly mesoporous. Carbonylation of aniline and nitrobenzene for synthesis of diphenyl urea, carbonylation of aniline for synthesis of carbamates, and oxime transformation between cyclohexanone oxime and acetone were used as test reactions for these catalysts. Catalytic activities were remarkably enhanced with much lower amounts of ionic liquids needed with respect to bulk ionic-liquid catalysts or silica-supported ionic-liquid catalysts prepared with simple impregnation, in which the ionic liquid may be deposited as a thin layer on the support. Such unusual enhancement in catalytic activities may be attributed to the formation of nanoscale and high-concentration ionic liquids due to the confinement of the ionic liquid in silica gel; this results in unusual changes in the symmetry and coordination geometry of the ionic liquids.
TL;DR: In this paper, the effects of grafting the alumina species at the surface of silica support on the H3PW12O40 (HPW) immobilization capacity and performance of loaded HPW in acid-catalyzed reactions were studied with regular silica-gel and ordered mesostructured silica SBA-15.
TL;DR: In this article, a thin-layer chromatographic separation of curcuminoid pigments was performed on silica gel 60G plates using dichloromethane:methanol, 99:1.
TL;DR: An array of small molecules that mimic the unique physiochemical environment found in the enzyme active site was investigated for catalytic activity in the formation of silica from silicon alkoxides at neutral pH and was used to encapsulate firefly luciferase, green and blue fluorescent proteins, and Escherichia coli cells expressing GFP in silica matrixes.
Abstract: Silicatein is an enzyme isolated from the biosilica produced by the marine demosponge, Tethya aurantia. Once isolated from the sponge, silicatein can be used in vitro to catalyze the hydrolysis and direct polycondensation of a wide variety of alkoxide, ionic, and organometallic precursors to the corresponding chalcogens at standard temperature and pressure and neutral pH. On the basis of these results, an array of small molecules that mimic the unique physiochemical environment found in the enzyme active site was investigated for catalytic activity in the formation of silica from silicon alkoxides at neutral pH. The most successful of these biomimetic catalysts (cysteamine) was used to encapsulate firefly luciferase, green and blue fluorescent proteins (GFP, BFP), and Escherichia coli cells expressing GFP in silica matrixes. The benign conditions required for the catalysis of synthesis of these silica composites does not impair the activities of the encapsulated enzyme, fluorescent proteins, or live cells as shown by fluorescence measurements. In conjunction with microcontact printing, this biomimetically catalyzed encapsulation method has been used to produce patterned functional arrays of silica nanoparticulate composite materials.
TL;DR: It is demonstrated that this DMAP-functionalized mesoporous silica material is an efficient heterogeneous catalyst for Baylis-Hillman, acylation, and silylation reactions with good reactivity, product selectivity, and recyclability.
Abstract: A new nucleophilic catalytic system comprised of dialkylaminopyridine-functionalized mesoporous silica nanosphere (DMAP-MSN) has been synthesized and characterized. We have demonstrated that this material is an efficient heterogeneous catalyst for Baylis-Hillman, acylation, and silylation reactions with good reactivity, product selectivity, and recyclability. We envision that this DMAP-functionalized mesoporous silica material can also serve as an effective heterogeneous catalyst for many other catalytic nucleophilic reactions.
TL;DR: In this paper, high-ordered mesoporous bioactive glasses (MBGs) with different compositions have been synthesized by a combination of surfactant templating, sol-gel method and evaporation-induced self-assembly (EISA) processes.
Abstract: Highly ordered mesoporous bioactive glasses (MBGs) with different compositions have been synthesized by a combination of surfactant templating, sol-gel method and evaporation-induced self-assembly (EISA) processes. The texture properties and compositional homogeneity of MBGs have been characterized and compared with conventional bioactive glasses (BGs) synthesized in the absence of surfactants by evaporation method. The formation mechanism (pore - composition dependence) and compositional homogeneity in the case of MBG materials are different from those in conventional BGs. Unlike conventional sol-gel-derived BGs that shows a direct correlation between their composition and pore architecture, MBGs with different compositions may possess similar pore volume and uniformly distributed pore size when the same structure-directing agent is utilized. The framework of MBG is homogeneously distributed in composition at the nanoscale and the inorganic species generally exists in the form of amorphous phase. MBGs calcined at temperatures <= 1073 K exhibit ordered mesopores; at higher temperature such as 1173 K, the inorganic wall becomes crystalline and the mesostructure is collapsed. The leaching test of MBG in water indicates that MBGs may have excellent degradability in body fluid, which is important for prospective bio-applications. (c) 2005 Elsevier B.V. All rights reserved.
TL;DR: This work investigates the mercury-binding mechanism for representative thiol-functionalized mesostructures by atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data and by Raman spectroscopy and results indicate that the complexation of mercury centers by thiolate depends on the mercury loading.
Abstract: Thiol-functionalized mesostructured silica with anhydrous compositions of (SiO2)1-x(LSiO1.5)x, where L is a mercaptopropyl group and x is the fraction of functionalized framework silicon centers, are effective trapping agents for the removal of mercuric(II) ions from water. In the present work, we investigate the mercury-binding mechanism for representative thiol-functionalized mesostructures by atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data and by Raman spectroscopy. The mesostructures with wormhole framework structures and compositions corresponding to x = 0.30 and 0.50 were prepared by direct assembly methods in the presence of a structure-directing amine porogen. PDF analyses of five mercury-loaded compositions with Hg/S ratios of 0.50−1.30 provided evidence for the bridging of thiolate sulfur atoms to two metal ion centers and the formation of chain structures on the pore surfaces. We find no evidence for Hg−O bonds and can rule out oxygen coordination o...
TL;DR: A novel method is presented for direct coupling of high-performance thin-layer chromatography (HPTLC) with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the analysis of biomolecules.
Abstract: A novel method is presented for direct coupling of high-performance thin-layer chromatography (HPTLC) with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the analysis of biomolecules. A first key feature is the use of a liquid matrix (glycerol), which provides a homogeneous wetting of the silica gel and a simple and fast MALDI preparation protocol. A second is the use of an Er:YAG infrared laser, which ablates layers of ∼10-μm thickness of analyte-loaded silica gel and provides a soft desorption/ionization of even very labile analyte molecules. The orthogonal time-of-flight mass spectrometer employed in this study, finally provides a high accuracy of the mass determination, which is independent of any irregularity of the silica gel surface. The analytical potential of the method is demonstrated by the compositional mapping of a native GM3 (II3-α-Neu5Ac−LacCer) ganglioside mixture from cultured Chinese hamster ovary cells. The analysis is characterized by a high relative sensi...
TL;DR: In this article, a mesoporous light solid material was prepared from the rice hull ash by sol-gel followed by supercritical carbon dioxide drying, and the prepared silica aerogel was characterized using SEM, TEM and BET measurements.
Abstract: Silica aerogel, which is a mesoporous light solid material, was prepared from the rice hull ash by sol–gel followed supercritical carbon dioxide drying. The rice hull ash, which is rich in silica, was extracted using sodium hydroxide solution to produce a sodium silicate solution. The solution was neutralized with sulfuric acid solution to form a silica gel. After washing with water and the solvent exchange with ethanol, the aged gel was dried to produce aerogel using supercritical carbon dioxide drying. The prepared silica aerogel was characterized using SEM, TEM and BET measurements. The specific surface area of the rice hull ash aerogel was as high as 597.7 m2/g with a bulk density of 38.0 kg/m3. The diameters of the pores inside the aerogel are between 10 and 60 nm.
TL;DR: The experimental results on the physical and hydrophobic properties of the ambient pressure dried silica aerogels as a function of sol-gel and drying conditions, are reported in this article.
Abstract: The experimental results on the physical and hydrophobic properties of the ambient pressure dried silica aerogels as a function of sol-gel and drying conditions, are reported.The aerogels have been produced by a two stage (acidic and basic) catalytic sol-gel process using tetraethylorthosilicate (TEOS) precursor, oxalic acid (OXA) and ammonium hydroxide (NH4OH) catalysts, ethanol (EtOH) solvent and hexamethyldisilazane (HMDZ) silylating agent at 200∘C.The molar ratios of HMDZ/TEOS (M), OXA/TEOS (A) NH4OH/TEOS (B), acidic H2O/TEOS (Wa) basic H2O/TEOS (Wb), EtOH/TEOS (S) were varied from 0.09 to 0.9, 3.115 × 10− 5 to 3.115 × 10−3, 4 × 10− 3 to 8 × 10− 2, 2 to 9, 1.25 to 5 and 1 to 16 respectively. The physical properties such as the percentage (%) of volume shrinkage, density, thermal conductivity, percentage of porosity, the percentage of optical transmission and contact angle have been found to be strongly dependent on the sol-gel parameters. It was found from the FTIR spectra of the aerogels that with the increase of M, the bands at 3500 and 1600 cm− 1 corresponding to H-OH and Si-OH respectively decreased and the bands at 840 and 1250 cm− 1 due to Si-C and 2900 and 1450 cm−1 due to C-H increased. The best quality silica aerogels in terms of low density, low volume shrinkage, low thermal conductivity, high hydrophobicity and high optical transmission have been obtained with the molar ratio of TEOS:EtOH:acidicH2O:basicH2O:OXA:NH4OH:HMDZ at 1:8:3.75:2.25:6.23 × 10− 5: 4 × 10− 2:0.36 respectively, by ambient pressure dried method.
TL;DR: It is demonstrated that relative peak intensity changes in Raman spectra can be caused by morphological changes in SWNT bundling based on differing flocculation or deposition methods, underscoring the care needed in assessing efficacies inSWNT enrichment and the prerequisite use of multiple excitation wavelengths and similar flocculating methods in comparative analyses.
Abstract: 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.
TL;DR: In this work, a hybrid silica/chitosan was synthesized and characterized by nitrogen elemental analysis and thermal analysis and demonstrated that the diffusion is the rate-controlling interaction mechanism.
TL;DR: In this article, the authors introduce the sol-gel reaction and the properties of the gel matrix and the applications of the matrix in the latter half of the 1970s, and present a review of the first half and the subsequent half.
Abstract: Sol-gel technology was first discovered in the late 1800s, but it was not until the early 1970s that renewed interest in the technique was generated, when monolithic inorganic gels were formed at low temperature. In this review, we introduce the sol-gel reaction and the properties of the gel matrix in the first half and the applications of the matrix in the latter half.
TL;DR: In this paper, an efficient synthesis of various substituted Hantzsch 1,4-dihydropyridines using silica gel-supported sodium bisulfate as heterogenous catalyst from an aldehyde, β-keto ester and ammonium acetate in acetonitrile is described.
TL;DR: The results obtained indicated that the dehydration reaction on the catalyst relies on surface acidity, whereas the ethylene production selectivity depends on the catalytic chemical constituents.
TL;DR: In recent years, proteomics has been a subject of intense research, and the need for more efficient and faster separations is addressed, which gives silica-based monoliths favourable properties for high-efficiency, fast separations, like a low-pressure drop across the column, fast mass transfer kinetics and a high binding capacity.
Abstract: In recent years, proteomics has been a subject of intense research. The complexity of proteomics samples has fostered technological developments. One of these addresses the need for more efficient and faster separations. Monolithic columns prepared from organic and silica monomers offer very efficient separations at low backpressure. Silica-based monoliths have small-sized skeletons and a bimodal pore size distribution with μm-sized throughpores and nm-sized mesopores. This gives silica-based monoliths favourable properties for high-efficiency, fast separations, like a low-pressure drop across the column, fast mass transfer kinetics and a high binding capacity.
TL;DR: The precision of the method, evaluated as the relative standard deviation in solutions containing 100mugl(-1) of chromium species, by analyzing a series of seven replicates, was lower than 3.0%.
TL;DR: The immobilized trypsin exhibits an increased stability even after continuous use compared with that in free solution, and this on-plate bioreactor was applicable to the digestion of protein with multiple cleavage sites.
Abstract: A miniaturized trypsin reactor was prepared by coating a trypsin-containing gel on a porous silica monolith. The trypsin-encapsulated gel was prepared by the sol-gel method. The sol-gel reaction was optimized so that the sol solution containing trypsin forms a thin film on the sol-gel monolith. The trypsin was encapsulated into the gel matrix without losing its activity. The silica monolith was fabricated to fit into a 96-well microtiter plate well and could then be easily removed. The trypsin-immobilized monolith was reacted in the 96-well microtiter plate. After the reaction, the monolith was removed, and the enzymatic activity was measured. The large surface area of the monolith enabled the immobilized trypsin to achieve a high catalytic turnover rate. Furthermore, the kinetic parameter of the immobilized trypsin indicates the absence of diffusional limitations. The durability and repeatability of the fabricated trypsin-coated monolith was tested and found to be satisfactory. The encapsulated trypsin exhibits an increased stability even after continuous use compared with that in free solution. Furthermore, this on-plate bioreactor was applicable to the digestion of protein with multiple cleavage sites.