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The development of new advanced sustainable materials for heterogeneous catalysis requires control of the structural parameters of the active sites. Mesoporous silica, especially SBA-15, has some unique and important features such as highly ordered mesopores, greater hydrothermal stability, greater wall thickness, large surface area, and adjustable pore volume. All these properties render it a promising material for catalysis, adsorption, supporting materials, biomedical applications, and environmental remediation. However, pure SBA-15 lacks acidic characteristics, which hinders its catalytic activity. Therefore, the functionalized SBA-15 improves the catalytic activity for versatile applications. Thus, in this study, we attempted to summarize the synthesis procedures, various functionalization processes, and application of metal-modified SBA-15 in organic synthesis, fine chemical synthesis, photocatalysis, and decontamination of water. Furthermore, the physicochemical properties, sustainability, and efficacy are discussed in detail for future reference and scope of studies. Key words: nanocomposite, metal-substituted SBA-15, organic transformation, environmental application. La mise au point de nouveaux materiaux de pointe durables pour la catalyse heterogene exige le controle des parametres structuraux des sites actifs. La silice mesoporeuse, en particulier le SBA-15, presente des caracteristiques uniques et importantes telles que des mesopores tres ordonnes, une grande stabilite hydrothermique, une paroi epaisse, une grande surface de contact et une porosite reglable. Toutes ces proprietes en font un materiau prometteur comme catalyseur ou comme materiau d'adsorption ou de support, dans des applications biomedicales ou d'assainissement environnemental. Cependant, le SBA-15 est depourvu de caractere acide, ce qui nuit a ses capacites de catalytiques. Ainsi, la fonctionnalisation du SBA-15 ameliore son activite catalytique pour differentes applications. Dans le present article, nous avons donc tente de resumer les methodes de synthese, les divers procedes de fonctionnalisation, et l'application de SBA-15 modifies par des metaux dans la synthese organique, la synthese de produits de chimie fine, la photocatalyse et l'assainissement des eaux. En outre, nous discutons en detail des proprietes physicochimiques, de la durabilite et de l'efficacite pour reference future et pour envisager la portee des etudes a venir. [Traduit par la Redaction] Mots-cles : nanocomposite, SBA-15 a substitution metallique, transformation organique, application environnementale., 1. Introduction Mesoporous materials, as classified by IUPAC nomenclature, are porous materials with pore sizes ranging from 2 to 50 nm. Mesoporous silica has been a popular class of two-dimensional [...]

How to get started in the process of identifying the problem source for column-related problems. Those of you who listen to the public radio program A Prairie Home Companion will [...]

This study explores how the presence of nanofillers with different structural and chemical characteristics, specifically silica nanoparticles and exfoliated graphite nanoplatelets (GNP), alters the crystallization behavior and polymorphism of a semicrystalline polymer, such as polypropylene (PP). The main focus of this research is to investigate how silica and GNP affect the nucleation and growth of PP crystals during isothermal crystallization. The nonisothermal crystallization behavior, including crystal structures, crystallization temperature, and rate, is also determined. PP composites with nanomaterial content up to 7 wt% were produced by melt mixing and injection molding. Both silica and graphite were found to be effective nucleating agents, significantly increasing the crystallization rate during isothermal crystallization, with greater changes observed in case of GNP composites. The effect of filler type and amount on the PP polymorphism and lamella thickness was studied by X-ray diffraction and modulated differential scanning calorimetry. Both silica and graphite were found to be effective nucleating agents for the less common β-phase of PP crystals even at low nanomaterial concentration, α--crystal perfection and the recrystallization of the β-form in the α-form and/ or at the transcrystalline regime were found to be responsible for the recrystallization occurring upon melting in nanocomposites at high silica or medium GNP content. POLYM. ENG. SCI., 55:672-680, 2015. © 2014 Society of Plastics Engineers, INTRODUCTION Isotactic polypropylene (PP) can crystallize in various forms or phases. In particular, depending on the crystallization conditions and molecular characteristics, different packing structures of the PP helices lead to [...]

Mixed matrix membranes of poly(vinyl alcohol) loaded with zeolite particles having different silica alumina ratio were prepared and used in the pervaporation dehydration of ethanol and isopropanol (IPA) from their aqueous mixtures. The membranes were characterized by physicochemical techniques that revealed higher interaction between polymer and zeolite particles having higher alumina than those with lower alumina in the zeolite framework. Both, membrane selectivity to water and flux were increased as the alumina content in the zeolite increases. Separation factors of zeolite with lower alumina incorporated membranes were, respectively, 236 and 334 for the feed mixture compositions of 4 wt% water in ethanol and 10 wt% water in IPA at 30°C. On the other hand, membranes containing zeolites with higher alumina content showed slightly higher separation factors of 349 and 568, respectively, for the same feed mixtures at 30°C. Such an incremental improvement in membrane performance with increase in alumina content in the zeolite framework is attributed to favorable interaction between zeolite particles and the polymer matrix., INTRODUCTION Ethanol and isopropanol (IPA) are the most commonly used solvents in organic synthesis as well as in pharmaceutical and chemical industries. Both the liquids form azeotropic mixtures at lower [...]

Nanoparticles with engineered surface chemistry represent novel means in controlling the in-situ formation of property-specific supramolecular structure in advanced processing technologies of semicrystalline polymers. Often, the published experimental data on effects of interfacial adhesion on the crystallization kinetics of polymer nanocomposites report contradictory results even for similar systems. Computer simulations allow separating structural and test variables, thus, can provide useful framework for understanding these apparent controversies. Our MD simulation of Regime II crystallization showed that adding non-nucleating spherical nanoparticles reduced the crystal growth rate, [G.sub.II] compared with the neat polymer with the extent of the reduction proportional to the strength of interfacial attraction. It also suggested that, regardless of the strength of the interfacial interactions, additional reduction of the [G.sub.II] was caused by topological constraints imposed by nanoparticles on the stem attachment. Both the Lauritzen-Hoffman model predicted and MD simulated [G.sub.II] reduction agreed fairly well with that obtained experimentally for monodisperse PE filled with nanometer-sized Si[O.sub.2]. POLYM. ENG. SCI., 53:2696-2704, 2013. © 2013 Society of Plastics Engineers, INTRODUCTION Polymer crystallization is kinetically controlled under conditions far from thermodynamic equilibrium involving molecular motions on various length and time scales. Many plastics processing technologies utilize this feature of plastics [...]

Poly(ethylene oxide)/silica (PEO/Si[0.sub.2]) nanocomposite films were modified, and nanocomposite gels were prepared by γ-irradiation up to 100 kGy. Thermal analysis, optical microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy revealed that the outcome mostly depended on the state of the PEO matrix on irradiation and that the state of the sample had a bearing on the effect of nanosilica addition. In unirradiated films, nanosilica induced heterogenous nucleation and increased crystallization temperatures proportional to its content. On irradiation of nanocomposite films, degradation prevailed, resulting in an increased crystallinity of samples irradiated to 50 kGy and a significant deterioration of mechanical properties at higher doses. In films irradiated in air, nanosilica did not provide radiation resistance. It enhanced oxidative degradation by increasing the content of a more radiation sensitive amorphous phase and probably facilitated the crystallization of broken chains resulting in an additional crystallinity increase. In the same dose range, the irradiation of PEO/nano-Si[0.sub.2] aqueous solutions produced cross-linked nanocomposite gels of much lower crystallinity and phase transformation temperatures and better mechanical properties. Interactions and radiation-induced effects in nanosilica likely contributed to a further crystallinity reduction in nanocomposite gels. Pronounced changes on the addition of 20 wt% of nano-Si[0.sub.2] to both nanocomposite films and gels indicate a possible synergism of γ-irradiation and nanoparticle addition. POLYM. ENG. SCI., 53:2318-2327, 2013. © 2013 Society of Plastics Engineers, INTRODUCTION Poly(ethylene oxide) (PEO) is a semicrystalline polymer with numerous applications (hydrogels for active substance release, polyelectrolytes, etc.). Among other characteristics, the degree of PEO crystallinity greatly influences its properties [...]

In this study influence of monomer ratio, butyl acrylate (BA), and methyl methacrylate (MMA) as well as silica nanofiller morphology (pyrogenic and colloidal) and concentration on the emulsion particle size distribution and properties of polyacrylate film (PA) synthesized by in situ emulsion polymerization were investigated. The ratios of the monomers BA/MMA were 100/0, 70/30, 50/50, 30/70, 0/100 and the filler concentration 0-10.0 mass%. PA nanocomposite films were characterized by using thermogravimetric analysis, differential scanning calorimetry, and tensile test. Research has shown that monomer ratio has significant influence on glass transition temperature ([T.sub.g]). The addition of both types of silica filler, pyrogenic and colloidal, has no effect on [T.sub.g]. Thermogravimetric analysis showed that systems with higher BA fraction have better thermal stability than systems with higher MMA fraction. Addition of the both type of silica nanofiller enhanced thermal stability of PAs, however, systems with colloidal silica are more stable. Pyrogenic silica and higher amounts of colloidal silica nanofiller increased PA emulsion particle size up to several micrometers. Addition of higher amounts of colloidal silica improved mechanical properties compared to the neat PA matrix. POLYM. ENG. SCI., 53:2292-2298, 2013. © 2013 Society of Plastics Engineers, INTRODUCTION Addition of tiller in polymer matrix affects matrix structure and hence affects final material properties. Organic/inorganic nanocomposites, because of their attractive mechanical, thermal, optical, electrical, and magnetic properties, are [...]

A method of the preconcentration of cadmium and lead as complexes with 2,3-dimercaptopropane-1-sulfonic acid (Unithiol) on a silica surface with the immobilized quaternary ammonium salt groups in the dynamic mode has been developed. The conditions of preconcentration (pH, flow rate and volume of solution) and the subsequent elution of cadmium and lead by a nitric acid solution have been optimized. The proposed method allows the separation of heavy metals from the cationic matrix ([Ca.sup.2+], [Mg.sup.2+], [Na.sup.+], [K.sup.+]) with the preconcentration coefficient equal to 100. The limits of detection for cadmium and lead by flame atomic absorption spectrometry are 0.3 and 2 µg/L, respectively. Keywords: Unithiol, flame atomic-absorption spectrometry, preconcentration, chemically modified silica gels, quaternary ammonium salt DOI: 10.1134/S1061934813030131, INTRODUCTION It is known that cadmium and lead are toxic elements that have detrimental effect on the environment and human health. In particular, compounds of Cd(II) and Pb(II) cause gastric [...]

Trace concentrations of Ti in quartz are used to indicate the pressure and temperature conditions of crystallization in the 'TitaniQ' geothermobarometer of Thomas et al. (Contrib Miner Petrol 160:743-759, 2010). It utilises the partitioning of Ti into quartz as an indicator of the pressures and/or temperatures of crystal growth. For a given value of Ti[O.sub.2] activity in the system, if temperatures are inferred to ± 20°C, pressure is constrained to ± 1 kbar and vice versa. There are significant contrasts, however, between the conclusions from TitaniQ and those for natural quartz (as well as other mineral phases) in volcanic rocks. Application of the TitaniQ model to quartz from the 27 ka Oruanui and 760 ka Bishop high-silica rhyolites, where the values of T, P and Ti[O.sub.2] activity are constrained by other means (Fe-Ti oxide equilibria, melt inclusion entrapment pressures in gas-saturated melts, melt and amphibole compositions), yields inconsistent results. If realistic values are given to any two of these three parameters, then the value of the third is wholly unrealistic. The model yields growth temperatures at or below the granite solidus, pressures in the lower crust or upper mantle, or Ti[O.sub.2] activities inconsistent with the mineralogical and chemical compositions of the magmas. CL imagery and measurements of Ti (and other elements) in quartz are of great value in showing the growth histories and changes in conditions experienced by crystals, but direct linkages to P, T conditions during crystal growth cannot be achieved. Keywords Ti-in-quartz * Oruanui * Bishop Tuff * Quartz * Geothermobarometer, Introduction The recent contribution by Thomas et al. (2010) represents a notable development in the use of trace concentrations of Ti in quartz as an indicator of the pressure and [...]

A cost-effective and efficient solid Br0nsted acid catalyst was synthesized by loading methanesulfonic acid (MSA) on silica and was used for the acid-catalyzed Pechmann reaction to test the catalytic activity and its reusability. Derivatives of 4-methylcoumarin were synthesized in good yields within short reaction times in the presence of environmentally friendly higher n-alkanes as solvents. The regeneration study of the spent catalyst showed satisfactory results. Key words: silica supported solid acids, methanesulfonic acid, Br0nsted acidity, Pechmann reaction, derivatives of 4-methylcoumarin. On a synthetise un catalyseur acide de Br0nsted efficace et rentable d'un point de vue cout en recouvrant de la silice avec de l'acide methanesulfonique (AMS) et on l'a utilise catalyseur acide pour la reaction de Pechmann dans le but d'evaluer son activite catalytique et la possibilite de le reutiliser. On a synthetise des derives de la 4-methylcoumarine avec de bons rendements, avec des temps de reaction relativement courts, dans des solvants a base d'alcanes superieurs ecologiques. L'etude de regeneration du catalyseur utilise a donne des resultats satisfaisants. Mots-cles : acides solides supportes par de la silice, acide methanesulfonique, acidite de Bronsted, reaction de Pechman, derives de la 4-methylcoumarine., Introduction Methanesulfonic acid (C[H.sub.3]S[O.sub.3]H; MSA) is a strong Br0nsted acid ([pK.sub.a] = -1.9) and has been reported as a potential acid catalyst for various acid-catalyzed reactions. (1-3) MSA is very [...]

Polydimethylsiloxanes, side functionalized in different degrees with chloromethyl groups, were reacted with 4,4'-bipyridyl and crosslinking occurred by the formation of ionic (bipyridinium) groups. The reactions were carried out in a silica sol-gel system, and thus, two networks were generated simultaneously: amphiphile siloxane-organic and silica networks. The samples, processed as films, were characterized by Fourier transform infrared spectroscopy to verify the occurrence of the crosslinking reactions. Different techniques were also used to evaluate the properties: differential scanning calorimetry for emphasizing the transitions, scanning electron microscopy, and atomic force microscopy for the evaluation of the morphology and surface topography. The modification of the film surface topography, which depends on the solvent polarity, was also emphasized. The sorption capacities of the water vapors and of liquid solvents (water and chloroform) were investigated, and the obtained values proved to be a function of the polar group's content. POLYM. ENG. SCI., 51:78-86, 2011. [C] 2010 Society of Plastics Engineers, INTRODUCTION For certain applications such as humidity sensors, the hydrophilicity of the materials must be limited or controlled. Thus, polymers containing hydrophilic groups, such as -COOH, [SO.sub.3]H, -[N.sup.+][R.sub.3]Cl, etc., are [...]

Adsorption of n-pentane on MCM-41 silica has been studied by neutron scattering on both the adsorption and desorption isotherms. Adsorption takes place without hysteresis in either the isotherm or the neutron scattering profile. Adsorption of contrast-matched pentane in porous MCM-41 silica at first increases the intensity of the (10) Bragg peak but reduces the (11) and (20) peaks, and as the pores are filled the intensities of all Bragg peaks are reduced to zero. The SANS background has a 1/Q dependence, typical of a material prepared with templates of one-dimensional character (cylinders). The initial increase of (10) intensity allows estimation of the cylindrical pore diameter to be 37 Å based on the variation of form factor as a function of the cylinder radius. PACS Nos: 61.43.Gt, 61.46.Bc, 81.05.Rm, 82.75.Fq Nous avons etudiee l'adsorption du ra-pentane sur de la silice MCM-41 par diffusion de neutrons sur les deux isothermes d'adsorption et de desorption. L'adsorption se produit sans hysterese soit dans l'isotherme ou le profil de diffusion de neutrons. Au debut, l'adsorption en appariement de contraste du n-pentane dans la silice MCM-41 augmente l'intensite du pic (10) de Bragg, mais reduit celle des pics (11) et (20). A mesure que les pores se remplissent, l'intensite de tous les pics de Bragg diminue a zero. Le bruit de fond de la diffusion de neutrons a petits angles (SANS) a une dependance en 1/ Q typique d'un materiau prepare avec des gabarits de type unidimensionnels (cylindres). L'augmentation initiale de l'intensite; du pic (10) permet d'estimer que le diametre des pores cylindriques est 37 A en se basant sur la variation du facteur de forme en fonction du rayon du cylindre. [Traduit par la Redaction], 1. Introduction The interaction between gases and porous solids is an important method for studying the nature of porosity. Although standard procedures are available for interpreting the shapes of the [...]

We report on a new approach to obtain highly homogeneous silica-monolithic columns, applying a sol-gel fabrication process inside a rectangular pillar-array column (1 mm in width, 29 [micro]m in height and 33.75 mm in length) having a cross-sectional area comparable to that of a 200 [micro]m diameter circular capillary. Starting from a silicon-based pillar array and working under high phase-separation-tendency conditions (low poly(ethylene glycol) (PEG)concentration), highly regular silica-based chromatographic systems with an external porosity in the order of 66-68% were obtained. The pillars, 2.4 [micro]m in diameter, were typically clad with a 0.5 [micro]m shell layer of silica, thus creating a 3.4 [micro]pm total outer pillar diameter and leaving a minimal through-pore size of 2.2 [micro]m. After mesopore creation by hydrothermal treatment and column derivatization with octyldimethylchlorosilane, the monolithic column was used for chip-based liquid-chromatographic separations of coumarin dyes. Minimal plate heights ranging between 3.9 [micro]m (nonretaining conditions) and 6 [micro]m (for a retention factor of 6.5) were obtained, corresponding to domain-size-reduced plate heights ranging between 0.7 and 1.2. The column permeability was in the order of 1.3 x [10.sup.13] [m.sup.s], lower than theoretically expected, but this is probably due to obstructions induced by the sol--gel process in the supply channels. 10.1021/ac100971a

We study time and length scales of eddy dispersion in 100 [micro]m i.d. capillary silica monoliths. First, the monolith's macropore morphology was visualized over complete column cross sections by confocal laser scanning microscopy, revealing a wall region with large voids (with a lateral dimension of up to ~ 15 [micro]m) and a homogeneous core region. A hulk segment from the core region was then physically reconstructed to receive a 60 x 12 x 12 [micro]m matrix consisting of ~3 x [10.sup.8] cubic voxels of 30 nm edge length for direct numerical simulations of fluid flow by the lattice-Boltzmann method and convective-diffusive mass transport by a random-walk particle-tracking technique on a high-performance computing platform. Pore-scale dispersion was analyzed in detail using the generalized Giddings equation. Eddy dispersion contributions originating in the bulk macropore heterogeneity were quantified and correlated with structural features of the monolith. To complement the simulation results, column scale dispersion was investigated by analysis of chromatographic plate heights. We found a much smaller bulk dispersion than generally assumed for silica monoliths (plate heights of ~2 pm over a wide velocity range), promising excellent separation efficiency also at high flow velocities (~1 cm/s). This potential is not realized by the capillary monolith in chromatographic practice because of the wall defect. 10.1021/ac101393b

We describe a protocol to create tissue phantoms with hydrophobic nanoporous particles. The nanopores of the particles are loaded with biological molecules at the desired compositions. Tissue phantoms are prepared by immersing dried particles into aqueous biological matrixes. The hydrophobicity of the pore surface prevents the solution from penetrating into the nanopores, thus preserving the designed molecular composition inside the particles. This protocol provides a unique approach to preparing biological systems in small domains, at micrometer and nanometer dimensions, with well-defined boundaries and tailored biological and optical properties. The nanoporeus particle approach is easy when compared to the common preparation methods such as with polymers and vesicles as it involves direct loading of the biological molecules into the pores and does not require complex synthetic steps. The method is adaptable, with tunable pore and particle sizes, and robust, with a rigid boundary to protect the designed biological domain. In addition to tissue phantom preparation, this approach is applicable in systems where a well-defined biological domain is desired. 10.1021/ac902442g

We present a fast, nondestructive, and quantitative approach to characterize the morphology of capillary silica-based monolithic columns by reconstruction from confocal laser scanning microscopy images. The method comprises column pretreatment, image acquisition, image processing, and statistical analysis of the image data. The received morphological data are chord length distributions for the bulk macropore space and skeleton of the silica monolith. The morphological information is shown to be comparable to that derived from transmission electron microscopy, but far easier to access. The approach is generally applicable to silica-based capillary columns, monolithic or particulate. It allows the rapid acquisition of hundreds of longitudinal and cross-sectional images in a single session, resolving a multitude of morphological details in the column. 10.1021/ac100909t

Mesoporous SBA-15 silica is an excellent support for constructing fluorescent surface sensors. In this letter, we reported a two-step surface reaction involved strategy to construct efficient fluorescent surface sensors for metal ions by clicking fluoroionophores onto azide-functionalized SBA-15. Our experimental results indicate that such a strategy exhibits an obviously higher loading efficiency within commercial SBA-15 than a previously reported strategy. As a proof-of-concept, a newly designed alkyne-functionalized [Hg.sup.2+] fluoroionophore was grafted onto SBA-15 to form a fluorescent [Hg.sup.2+] surface sensor. It shows improved sensitivity and selectivity than the fluoroinnophore itself working in the solution phase with a detection limit of 2.0 x [10.sup.-8] M for [Hg.sup.2+]. 10.1021/ac101305e

This paper describes a novel packing material for high selective reversed-phase high-performance liquid chromatography (RP-HPLC). The organic phase on silica is chemically designed in a way that the weak interaction sites are integrated with high orientation along the polymer main chain and high selectivity can be realized by multiple interactions with solutes. For the above purpose, we synthesized poly(octadecyl acrylate-alt-N-octadecylmaleimide)-grafted silica (Sil-poly(ODA-alt-OMI)) stationary phase. The alternating copolymerization was carried out from 3-marcaptopropytrimethoxysilane (MPS)-modified silica via surface-initiated radical-chain transfer reaction. Elemental analysis, diffuse reflectance infrared Fourier transform (DRIFT),[sup.1]H NMR, solid-state [sup.13]C cross polarization magic angle spinning (CP/MAS) NMR, and suspended-state [sup.1]H NMR were used to characterize the new organic phase. Aspects of shape selectivity was evaluated with Standard Reference Material (SRM 869b), Column Selectivity Test Mixture for Liquid Chromatography. Enhanced molecular shape selectivity was observed, that lead to the separation of SRM 1647e (16 polycyclic aromatic hydrocarbons, PAHs) in an isocratic elution. The effectiveness of this phase was also demonstrated by the separation of several [beta]-carotene and tocopherol isomers. The complete baseline separation of the tocopherol isomers was achieved using the Sil-poly(ODA-alt-OMI) phase. Chromatographic study revealed that Sil-poly(ODA-alt-OMI) has extremely high separation ability compared to monomeric and polymeric [C.sub.18] columns. Higher shape selectivity of the new RP material can be explained by a [pi]--[pi] and dipole--dipole interaction mechanism. 10.1021/ac1001178

Wollastonite is abundantly available in Rajasthan, Tamil Nadu, Uttarakhand, and Andhra Pradesh states of the Indian Union as a low-cost material. In this study, investigations were made on pastes and mortars to evaluate its potential as a new material for admixing with ordinary portland cement with or without microsilica. Its physical and chemical properties were analyzed. Wollastonite consists of 45.6% of CaO and 48% of Si[O.sub.2], mostly in amorphous form. It has an average specific surface area of 842.7 [m.sup.2]/kg and retention on 45-micron sieve of 3.20%. When ground to fine powder, it attains an average particle size of 4 microns which is about 4.5 times finer than ordinary portland cement. Scanning electron microscope images show that wollastonite particles were solid, acicular in shape, and have rough surfaces. Several cementitious mix proportions of ordinary portland cement, wollastonite, and microsilica were investigated for normal consistency, initial and final setting time of paste, and compressive strength of mortar. Test results indicate that the mortar, which contains 82.5% cement, 10% wollastonite, and 7.5% microsilica, as cementitious material attains the highest compressive strength. The mortar, which contains 77.5% cement, 15% wollastonite, and 7.5% microsilica, as cementitious material achieves compressive strength higher than the conventional OPC mortar along with rendering maximum cement replacement for better economy of concrete work. It was observed that the compressive strength of mortar varied logarithmically with the days of moist curing and linearly with the proportion of admixing. Suitable predictive models are presented accordingly. DOI: 10.1061/(ASCE)MT.1943-5533.0000019 CE Database subject headings: Mortars; Admixtures; Compressive strength; India. Author keywords: Wollastonite; Wollastonite-microsilica admixed mortar; Mineral admixtures; Consistency.

A new strategy for the fabrication of a sulfide sensor based on room-temperature phosphorescence (RTP) of PbO/ Si[O.sub.2] nanocomposite is proposed. The PbO/Si[O.sub.2] phosphor is prepared by a sol gel method, and it produces highly emissive broad-band RTP under the irradiation of UV light. The phosphorescence intensity of PbO/ Si[O.sub.2] nanocomposite could be quenched by sulfide, and the response behavior of the sensor is dependent on the value of pH of the solution. At pH 11.0, the sensor exhibits a linear response toward sulfide at the concentration range from 2.67 to 596 [micro]M. The detection limit for the sensor is estimated to be 0.138 pM (3 [sigma]), and the precision for five replication detections of 6 [micro]M sulfide is 1.82% (relative standard deviation). The color of the sensor and its phosphorescence intensity change obviously and could be observed with the naked eye when there was continuous addition of sulfide from the concentration of 50 [micro]M. The phosphorescence intensity of quenched PbO/Si[O.sub.2] phosphor can be recovered when dipping it into [H.sub.2][O.sub.2] solution, which demonstrates a good sulfide response characteristic of reusability. Furthermore, the sensor is easy to apply for trace hydrogen sulfide determination in the gas phase. 10.1021/ac921211

In this study, normal concrete (NC) and four types of self-compacting concrete (SCC), in which cement was partially replaced by 5%, 10%, 15%, and 20% of silica fume (SF), were used to evaluate the effect of SF content on the bond strength of tension lap-spliced bars embedded in NC and SCC specimens. Therefore, 15 full-scale beam specimens (2000 x 300 x 200 [mm.sup.3]) were tested and 20 mm reinforcing bars were used with a 300-mm splice length as tension reinforcement. Each beam was designed with bars spliced in a constant moment region at midspan. It was found that the bond strength of the reinforcement embedded in SCC beams was higher than that of the reinforcement in NC beams, whilst the bond strength increased with increase in the replacement of cement by SF from 5% to 10%. Moreover, the beam specimens produced from SCC containing 5% SF had the highest normalized bond strength of 1.07 followed by SCC beams with 10% SF. 15% SF. NC beams, and 20% SF. Key words: bond, splice, self-compacting concrete, silica fume, full-scale beam. Dans la presente etude, du beton normal et quatre types de beton autoplacant (BAP) dans lesquels le ciment a ete subslilue en partie par quatre proportions de fumee de silice (5, 10, 15 et 20 %) ont ete utilises pour evaluer l'effet des fumee de silice sur la resistance du liage des tiges en tension collees par chevauchement dans les echantillons de beton normal et de beton autoplacant. Ainsi, 15 echantillons de poutre a pleine echelle (2000 x 300 x 200 mm) ont ete mis a l'epreuve et des tiges d'armature de 20 mm ont ete utilisees avec une longueur de chevauchement de 300 mm servant de renforcement en tension. Chaque poutre incorporait des tiges chevauchant dans une zone a moment constant au milieu de la portee. II a ete decouvert que la resistance du liage du renforcement dans les poutres en beton autoplacant etait superieure a celle du renforcement dans les poutres en beton normal alors que la resistance de liage etait superieure avec un accroissement du pourcentage de remplacement du ciment par la fumee de silice de 5 a 10 %. De plus, les echantillons de poutre fabriques en beton autoplacant contenant 5 % de fumee de silice presentaient la plus forte resistance de liage normalisee avec 1,07 suivis des poutres en beton autoplacant comportant 10 % de fumee de silice, puis 15 % de fumee de silice, les poutres en beton normal et, finalement, le beton autoplacant comportant 20 % de fumee de silice. Mots-cles : lien, chevauchement, beton autoplacant, fumee de silice, poutre a pleine echelle. [Traduit par la Redaction], 1. Introduction In the reinforced concrete (RC) members, load is transferred between the main reinforcement and the surrounding concrete through adhesional and mechanical bond. An adequate bond in splice is [...]

A method is proposed for the selection of conditions for the preconcentration of polycyclic aromatic hydrocarbons (PAH) from aqueous solutions on octadecyl silica gel in an on-line adsorption--chromatographic system. Deterministic models of adsorption dynamics, based on partial differential equations, were used for a uniform mathematical description of all stages of adsorption preconcentration. The parameters of an adsorption system, such as dead volume, longitudinal dispersion coefficient, and distribution and mass transfer coefficients in adsorption and desorption, were calculated, and the adsorption isotherm was plotted. The conditions for the on-line determination of compounds were selected by simulation analysis, and the procedure was developed for determining PAH in natural and potable waters. The detection limits for PAH were 1-90 ng/L. DOI: 10.1134/S1061934810020048, The identification and quantification of the most hazardous pollutants, like phenols, aromatic and polycyclic aromatic hydrocarbons (PAH), chlorinated hydrocarbons, and others, are very important in the analysis of waters. Contemporary [...]

The guest-host interactions of poly(amidoamine) (PAMAM) dendrimers and porous silica surfaces were investigated by near-infrared (NIR) diffuse reflection spectroscopy. G0-G7 of amine-terminated PAMAM (PAMAM-N[H.sub.2]) dendrimers were analyzed comprising early, mid, and late generations. For early stages, the adsorption process of the partly protonated dendrimers to the negatively charged silica surface strongly depends on the size/shape characteristics of the guest (PAMAM-N[H.sub.2] dendrimers) and host (porous silica) materials. G0-G4 (15-45 [Angstrom]) show smaller particle sizes than the pore diameter of the silica (60 [Angstrom]) and thus have access to the interior surface of the host material. For mid and later stages (G5-G7; 54-81 [Angstrom]) only low amounts of the dendrimers adsorb to the silica surface due to the inaccessibility to the interior surface. The loading capacity of the silica material with adsorbed PAMAM-N[H.sub.2] was evaluated by means of capillary zone electrophoresis (CZE), whereas deviations from the theoretical to the effective particle size and molecular weight (MW) was determined by gas-phase electrophoretic mobility molecular analysis (GEMMA) and matrix-assisted laser desorption/ionization linear time-of-flight mass spectrometry (MALDI-lin TOF-MS). Deviations from the theoretical to the actual values showed a maximum of 13.8% and 28.0% for the particle size and MW, respectively. The NIR absorption spectra show a distinct band at 4932 [cm.sup.-1] ([v.sub.sym] (NH) + amide II) due to the adsorbed dendrimers. It was found that the absorbance tends to increase with decreasing generation number. On this basis multivariate calibration was performed with the theoretical data and the data obtained by GEMMA and MALDI-lin TOF-MS. All in all, the calculated partial least-squares regression (PLSR) model containing the GEMMA/MALDI-lin TOF-MS reference values showed better results than the models exclusively calculated from the theoretical values. This indicates that the theoretical values do not imply the structural imperfections arising during the synthesis that may be present in the PAMAM-N[H.sub.2] dendrimers.

Recent studies have shown that potassium acetate based deicers are capable of triggering deleterious expansion and cracking in concrete specimens containing alkali-silica reactive (ASR) aggregates. This paper presents the results and analysis from a research study conducted to evaluate the effectiveness of fly ash and ground granulated blast furnace slag (slag) in mitigating expansions induced by ASR in the presence of a potassium acetate based deicer. Standard and modified ASTM C 1260 and 1567 tests were conducted on mortar specimens prepared with five aggregates to study the mitigation behavior of fly ashes and slag. In this study, fly ash was evaluated at 15, 25, and 35%, and slag at 40 and 50% by mass replacement of cement. Changes in length, dynamic elastic modulus, and microstructure of the mortar bars were studied. Results from these studies indicate that low- and intermediate-lime fly ashes were more effective than high-lime fly ash at 25 and 35% cement replacement levels. High-lime fly ash was ineffective even at a replacement level of 35%. Slag at 50% cement replacement was more effective in mitigating expansions compared to 40% dosage level. DOI: 10.1061/(ASCE)0899-1561(2009)21:1(19) CE Database subject headings: Deicing; Fly ash; Slag; Aggregates; Silica; Chemicals.

This paper covers the design, fabrication, and characterization of two-layer microcoils wherein an unannealed plasma-enhanced CVD Si[O.sub.2] functions as the insulator between silicon-and photoresist-molded copper coils. This design overcomes the thermal limitations placed upon coils that are embedded within polymer molds and thereby enables higher current carrying capability. The fabrication process is compatible with deep reactive-ion etching and may be used to integrate coils with flexures/compliant mechanisms. Thermal and mechanical limitations were determined experimentally and used to create design rules that limit the coil design space. The breakdown strength of the unannealed Si[O.sub.2] was measured at 4.6 MV/cm. Experiments show that coils with 40-[micro]m pitch, 30 x 30-[micro][m.sup.2] winding cross section, and Si[O.sub.2] thickness of 1 [micro]m may carry more than 1 A (larger than [10.sup.9] A/[m.sup.2]) with less than 10[degrees]C temperature change. These characteristics make the coils useful in small-scale actuators and power systems. [2008-0170] Index Terms--Copper damascene, electroplating, magnetic microactuator, microcoil, microelectromechanical devices, silicon dioxide.

High spatial and spectral resolution reflectance data acquired by the Mars Reconnaissance Orbiter Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument reveal the presence of [H.sub.2]O-and SiOH-bearing phases on the Martian surface. The spectra are most consistent with opaline silica and glass altered to various degrees, confirming predictions based on geochemical experiments and models that amorphous silica should be a common weathering product of the basaltic Martian crust. These materials are associated with hydrated Fe sulfates, including [H.sub.3]O-bearing jarosite, and are found in finely stratified deposits exposed on the floor of and on the plains surrounding the Valles Marineris canyon system. Stratigraphic relationships place the formation age of these deposits in the late Hesperian or possibly the Amazonian, implying that aqueous alteration continued to be an important and regionally extensive process on Mars during that time.

The mechanisms by which amorphous silica dissolves have proven elusive because noncrystalline materials lack the structural order that allows them to be studied by the classical terrace, ledge, kink-based models applied to crystals. This would seem to imply amorphous phases have surfaces that are disordered at an atomic scale so that the transfer of Si[O.sub.4] tetrahedra to solution always leaves the surface free energy of the solid unchanged. As a consequence, dissolution rates of amorphous phases should simply scale linearly with increasing driving force (undersaturation) through the higher probability of detaching silica tetrahedra. By examining rate measurements for two amorphous Si[O.sub.2] glasses we find, instead, a paradox. In electrolyte solutions, these silicas show the same exponential dependence on driving force as their crystalline counterpart, quartz. We analyze this enigma by considering that amorphous silicas present two predominant types of surface-coordinated silica tetrahedra to solution. Electrolytes overcome the energy barrier to nucleated detachment of higher coordinated species to create a periphery of reactive, lesser coordinated groups that increase surface energy. The result is a plausible mechanism-based model that is formally identical with the classical polynuclear theory developed for crystal growth. The model also accounts for reported demineralization rates of natural biogenic and synthetic colloidal silicas. In principle, these insights should be applicable to materials with a wide variety of compositions and structural order when the reacting units are defined by the energies of their constituent species. biogenic silica | demineralization | glass | nucleation | surface energy

Solid-phase extraction of glycopeptides (SPEG) coupled with quantitative proteomic analysis using mass spectrometry has shown great potential for investigating glycoproteins in an effort to discover new diagnostic biomarkers or therapeutic targets. As a solid-phase approach, SPEG can be performed with a microtiter plate to provide a high-throughput platform for large-scale screening of clinical samples. Here we describe the synthesis of superparamagnetic silica particles with hydrazide groups on the surface and further evaluate their use as the solid support for SPEG. We produced nonspherical silica particles containing superparamagnetic iron oxide cores using a modified Stober method and then derivatized their surface with hydrazide-terminated silane. Such composite particles displayed a strong response to the external magnetic field, and this feature enabled us to capture and release the particles easily for automated, high-throughput sample preparation of glycopeptides. When measured with standard glycoproteins, the adsorption capacity of these particles was > 36 mg of glycoproteins per g of nanoparticles. The nanoparticles were used in a microtiter plate format for glycopeptide capture using a liquid handler. The captured glycopeptides were then analyzed by LC--MS and LC--MS/MS to determine the specificity and reproducibility of glycopeptide isolation. Our results demonstrate the potential of these superparamagnetic colloidal particles for high-throughput analysis of glycoproteins.

Silica and hybrid organic-inorganic films, ca. 100-200 nm thick, can be grown on glassy carbon electrodes through reactions initiated by electrogenerated hydroxide or hydronium ions in water under reductive and oxidative conditions, respectively. A variety of different alkoxysilanes (tetramethoxysilane and organoalkoxysilanes) and supporting electrolytes were used to evaluate whether film formation takes place on glassy carbon electrodes. The results of the study indicate that the acid-base properties of the supporting electrolyte are an important factor in determining whether film formation will take place. For cathodic electrodeposition, thin films can be formed using supporting electrolytes that are close to neutral, such as KCl, KN[O.sub.3], and NaCl[O.sub.4]. For anodic electrodeposition, thin films can be formed using supporting electrolytes that are acidic, such as, K[H.sub.2]P[O.sub.4], HN[O.sub.3], [H.sub.2]S[O.sub.4], etc. The acidity/basicity effects of the electrolytes arise in part from the strong dependence of the hydrolysis and condensation rates of the silicon alkoxide precursors on pH.

A new type of mesoporous silica with pore walls composed of a nonmicroporous silicate framework is described. The synthetic method is useful for designing the silicate framework of mesostructured and mesoporous materials with or without surface functional organic groups.

Sample pretreaanent is the most important procedure to remove the matrix for interfacing with mass spectrometry (MS). Additionally, for the samples with low concentration, the process of preconcentration is required before MS analysis. We have newly developed a solid-phase extraction stationary phase based on C60-fullerene covalently bound to silica for purification of biomolecules of different characteristics. Silica particles of different porosity are modified with aminopropyl linker and then covalently bound to C60-fullerenoacetic acid or C60-epoxy-fullerenes. The developed materials have been successfully applied as an alternative to commercially available reversed-phase materials for solid-phase extraction. C60-fullerene silica is able to retain small and hydrophilic molecules like phosphopeptides, which can be easily lost by reversed-phase sorbents. The novel materials are applied for desalting and preconcentration of proteins and peptides, especially phosphopeptides. In addition, the C60-fullerene silica is applied for the solid-phase extraction of selected flavonoids with recoveries of ~99%. The recoveries are compared with the commercially available solid-phase extraction materials.

This paper describes the development and study of a disposable and inexpensive microfluidic chip, fabricated from poly(dimethylsiloxane) (PDMS) incorporating conventional chromatographic reversed-phase silica particles (C18) without the use of frits, permanent physical barriers, tapers, or restrictors. The packing of C18 modified silica particles into the microfluidic channels is made possible by the hydrophobic nature and excellent elasticity of PDMS. Keystone-, clamping-, and anchor-effects provide the stability and the compactness of the packing and attenuated wall-effects were observed.

The application of the undissociated amorphous silica-water interface model is demonstrated to understand the surface properties of amorphous silica. The model could be used to understand the theory of electrochemical and electrokinetic phenomena.

The preparation and structural characterization of chiral mesoporous silica based on chiral block copolymers of poly(ethylene oxide) and of D-phenylalanine (PEO-b-D-Phe) as a surfactant template is described.

Using [sup.29]Si, [sup.1]H, and [sup.2]H magic-angle spinning (MAS) and [sup.29]Si{[sup.1]H} heteronuclear correlation (HetCor) nuclear magnetic resonance (NMR) spectroscopy the tetrahedral sheets of the 10 [Angstrom] phase are shown to contain [Q.sup.2]-type Si bonded to silanol groups that donate hydrogen bonds to interlayer [H.sub.2]O. [sup.29]Si NMR spectra of 10 [Angstrom] phase samples synthesized from oxide and from crystalline talc starting materials contain a peak near -87 ppm for [Q.sup.2] Si, in addition to the main peak at -98 ppm for the talc-like [Q.sup.3] of the tetrahedral sheet. The [sup.1]H MAS NMR spectra of the 10 [Angstrom] phase contain two distinct peaks, at chemical shifts of +7.8 and +3.2 ppm, in addition to a narrow peak near +0.9 ppm from the talc-like hydroxyl groups. [sup.29]Si{[sup.1]H} HetCor data indicate that the +7.8 ppm [sup.1]H resonance corresponds to silanol groups and that at +3.2 ppm arises from interlayer [H.sub.2]O. Comparison of the observed data with correlations of [sup.1]H NMR chemical shift and [sup.2]H quadrupolar coupling indicates that the silanol groups donate moderate hydrogen bonds to interlayer [H.sub.2]O, d(O ... O) [approximately equal to] 2.8 [Angstrom], whereas most interlayer [H.sub.2]O donate only very weak or no hydrogen bonds at ambient conditions. Our results suggest that formation of the 10 [Angstrom], phase involves formation of vacancies, which allow favorable hydrogen bond interaction between interlayer [H.sub.2]O and the normally hydrophobic talc-like 2:1 layers. Keywords: NMR, l0 [Angstrom] phase, talc, silanol, hydrogen bond

Solid-state NMR and infrared (IR) measurements are combined with computational analysis to examine the structures of major sites formed by grafting C[H.sub.3]Re[O.sub.3] onto amorphous silica-alumina and their relationships with olefin metathesis activity of this material. The results have suggested simple modifications in catalyst preparation, which has led to higher selectivity, less leaching and efficient use of the Re complex.

The synthesis and characterization of MCM-41-type mesoporous silica nanoparticle (MSN) material with a large average pore diameter is presented. It is shown that these MSNs with large pores have served as a transmembrane delivery vehicle for controlled release of membrane-impermeable proteins in live cells.

A surface functional monomer-directing strategy is described for the highly dense imprinting of 2,4,6-trinitrotoluene (TNT) molecules at the surface of silica nanoparticles. It is shown that the imprinting method at the surface of silica is applicable to imprinting various organic molecules such as estrone and amino acids and the monomer-directing approach has formed a basis of a new strategy for preparing various functional polymer-coating layers on silica support.

Silica colloidal crystals were investigated for their potential as high surface area materials to enhance sensitivity over planar surfaces for microarrays using fluorescence detection. A relation was derived showing how crystal thickness and transmission, as well as colloid size, combine to determine the optically accessible surface area for enhancing sensitivity. Experimentally, crystals of 250-nm colloids were prepared with thicknesses determined by SEM to be 1.6, 4.2, and 11.0 [micro]m. The material was sintered at 1000 [degrees]C to make it durable without affecting the crystalline structure, as confirmed by SEM. UV/visible spectrometry showed the depth of penetration (1/e) to be 8.4 [micro]m at 488 nm for these materials. Fluorescein-labeled streptavidin and biotin were used as a model ligand-receptor pair. For the fluorescence measurements, biotin was covalently bonded to the silica surfaces, and the fluorescence was detected from the captured streptavidin-fluorescein. The observed fluorescence enhancement agreed well with the theory developed here. Compared to a planar surface, the colloidal crystal of 11.0 [micro]m in thickness enhanced the fluorescence by nearly a factor of 80, with only a 0.3% increase in fluorescence background.

A Ti[O.sub.2]/Si[O.sub.2] composite prepared by the sol-gel route can produce highly emissive broadband room-temperature phosphorescence at an excitation wavelength of 403 nm. The white phosphorescence of Ti[O.sub.2]/Si[O.sub.2] could be quenched by [H.sub.2][O.sub.2]. The phosphorescence quenching effect demonstrated excellent sensitivity and high selectivity to [H.sub.2][O.sub.2]. Furthermore, the phosphorescence of Ti[O.sub.2]/ Si[O.sub.2] can be recovered when it is dipped in a hydroxylamine hydrochloride solution. Therefore, the Ti[O.sub.2]/Si[O.sub.2] was used to develop a reproducible phosphorescence sensor for [H.sub.2][O.sub.2]. It has been successfully applied to the determination of [H.sub.2][O.sub.2] in the enzymatic catalytic reaction and real samples.