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Covalent attachment of 3,4,9,10-perylenediimides onto the walls of mesoporous molecular sieves MCM-41 and SBA-15

TRINDADE, Fabiane J.; FERNANDES, Glauber J. T.; ARAUJO, Antonio S.; FERNANDES JR., Valter J.; SILVA, Barbara P. G.; NAGAYASU, Rafael Y.; POLITI, Mario J.; CASTRO, Francisco L.; BROCHSZTAIN, Sergio
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
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This work describes the covalent grafting of 3,4,9,10-perylenediimides (PDI), which are fluorescent dyes with very interesting optical properties, onto the walls of mesoporous molecular sieves MCM-41 and SBA-15. The mesoporous materials were first treated with 3-aminopropyltriethoxysilane (APTES) in anhydrous toluene, generating amine-containing surfaces. The amine-containing materials were then reacted with 3,4,9,10-perylenetetracarboxylic dianhydride (PTCA), generating surface-grafted PDI. Infrared spectra of the materials showed that the reaction with amino groups took place at both anhydride ends of the PTCA molecule, resulting in surface attached diimides. No sign of unreacted anhydride groups were found. The new materials, designated as MCMN2PDI and SBAN(2)PDI, presented absorption and emission spectra corresponding to weakly coupled PDI chromophores, in contrast to the strongly coupled rings usually found in solid PDI samples. The materials showed a red fluorescence, which could be observed by the naked eye under UV irradiation or with a fluorescence microscope. The PDI-modified mesoporous materials showed electrical conductivity when pressed into a pellet. The results presented here show that the new materials are potentially useful in the design of nanowires. (C) 2007 Elsevier Inc. All rights reserved.

Morphology and topography analysis of mesoporous titania templated by micrometric latex sphere arrays

Barros Filho, D. A.; Benedetti, J. E.; Silva, Marcelo de Assumpção Pereira da; Seriacopi, V.; Gomes Silva, W. R.; Alonso, R. C. B.; Lewgoy, H. R.; Anido-Anido, A.; Amore, R.; Anauate-Netto, C.; Avellaneda, C. O.; Santilli, Celso V.; Nogueira, Ana F.
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.30933%
In this work, mesoporous titania is prepared by templating latex sphere arrays with four different sphere diameters at the micrometric scale (phi > 1 mu m). The mesoporous titania homogeneously covers the latex spheres and substrate, forming a thin coating characterized by N-2 adsorption isotherm, small angle X-rays scattering, atomic force, field emission and transmission electronic microscopies. Mesoporous titania has been templated into different shapes such as hollow particles and monoliths according to the amount of sol used to fill the voids of the close packed latex spheres. Titania topography strongly depends on the adsorption of polymeric segments over latex spheres surface, which could be decreased by changing the dimensions of latex spheres (phi = 9.5 mu m) generating a lamellar architecture. Thus, micrometric latex sphere arrays can be used to achieve new surface patterns for mesoporous materials via a fast and inexpensive chemical route for construction of functional devices in different technological fields such as energy conversion, inclusion chemistry and biomaterials. (C) 2011 Elsevier Inc. All rights reserved.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [2008/00463-2]; Chemistry Institute of the University of Sao Paulo...

Preparação e caracterização de pentóxido de vanádio mesoporoso e reações de intercalação; Synthesis and characterization of mesoporous vanadium pentoxide and intercalation reaction

Guerra, Elidia Maria
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/08/2007 PT
Relevância na Pesquisa
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A obtenção de pentóxido de vanádio mesoporoso, bem como a síntese, caracterização e estudo das propriedades de novos compostos híbridos, formado a partir do xerogel de pentóxido de vanádio e do pentóxido de vanádio mesoporoso, intercalados com espécies convidadas, foram os objetivos desta tese. O interesse nestes materiais, que apresentam uma considerável gama de modificações estruturais e químicas, é devido a possibilidade de arquitetar propriedades específicas e produzir novos materiais visando aplicações em óptica, catálise, dispositivos eletrônicos e sensores. Os compostos híbridos foram obtidos mediante a reação de intercalação utilizando espécies diretivas estruturais, como cloreto de cetilpiridínio, e materiais poliméricos, como óxido de polietileno e poli o-metoxianilina, introduzidos no interior do óxido em questão. O método de síntese é simples e relativamente rápido, uma vez que os materiais são obtidos em, no máximo, 10 dias, além de não ser necessário o monitoramento durante o período de preparação e secagem. Os resultados experimentais apontaram que houve uma expansão interplanar, bem como, as propriedades eletroquímicas dos compósitos apresentaram uma maior estabilidade de após vários ciclos quando comparados ao xerogel de pentóxido de vanádio...

Síntese e caracterização de catalisadores de níquel suportados em sílica mesoporosa altamente ordenada para hidrogenação de óleos vegetais; Synthesis and characterization of highly ordered mesoporous silica supported nickel catalysts for the hydrogenation of vegetable oils

Oliveira, Nara Andréa de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 14/04/2008 PT
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Este trabalho teve como objetivo a síntese e caracterização de sílicas mesoporosas suportadas com níquel para atuarem como catalisadores na hidrogenação de óleos vegetais. Foram escolhidas as sílicas mesoporosas ordenadas do tipo SBA-15 e FDU-1, sintetizadas a partir de TEOS como fonte de sílica e copolímeros triblocos como agentes direcionadores de estrutura em meio HCl. O Ni(NO3)2.6H2O foi utilizado como fonte de metal, cuja solução aquosa com a concentração de níquel desejada foi adicionada à sílica antes da remoção do molde polimérico, originando os precursores dos catalisadores. Após a impregnação, as amostras foram submetidas à calcinação sob atmosfera de ar, gerando o precursor na forma de óxido que ao ser tratado com H2 é reduzido Nio , forma ativa do catalisador. As técnicas de termogravimetria, termogravimetria derivada, difração de raios X a alto e baixo ângulo, isotermas de adsorção de nitrogênio e absorção atômica foram empregadas para a caracterização destes materiais. A TG/DTG foi utilizada para a simulação das melhores condições de calcinação/redução. As amostras foram calcinadas em um forno tubular com controlador de temperatura. Os ensaios de DRX confirmaram a fase NiO após calcinação e a fase Nio na redução...

Rhodamine 6G encapsuled mesoporous silica channels

Saran, Priscila Samara; Martines, Marco Antonio Utrera; Brito, Hermi Felinto de; Castro, Gustavo Rocha de; Messaddeq, Younes; Ribeiro, Sidney Jose Lima
Fonte: Trans Tech Publications Ltd Publicador: Trans Tech Publications Ltd
Tipo: Conferência ou Objeto de Conferência Formato: 62-67
ENG
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We report the effect of solvent on the rhodamine 6G encapsuled into channels of mesoporous silica, synthesized by two-step process that gives intermediary stable hybrid micelles. Mesoporous materials have been obtained by the method that involves surfactant micelles (mainly cationic) and inorganic precursor of the structure to be obtained. MSU-X type mesoporous silica has been synthesized with polyethylene oxide surfactant as the directing-structure agent and tetraethyl orthosilicate Si(OEt)(4) as the silica source. The influence of the solvent on the encapsulation of rhodamine dye was systematically explored, specially its influence on the luminescence properties. Rhodamine 6G encapsuled into mesoporous silica channel was characterized by UV-Vis and luminescence spectroscopies, scanning electron microscopy, small angle x ray scattering and N(2) sorption-desorption. The pore size and the solvent effects into luminescence dye encapsuled into mesoporous silica channels are observed in the visible absorption and emission spectra of rhodamine 6G. The intense photo luminescence band of rhodamine 6G dye is in 500 to 600 nm region. The observed shift of the absorption and emission bands can be assigned to the effect of the solvents dielectric constant and pore size of mesoporous silica.

Morphology and topography analysis of mesoporous titania templated by micrometric latex sphere arrays

Barros Filho, D. A.; Benedetti, J. E.; Pereira-da-Silva, M. A.; Seriacopi, V.; Gomes Silva, W. R.; Alonso, R. C. B.; Lewgoy, H. R.; Anido-Anido, A.; Amore, R.; Anauate-Netto, C.; Avellaneda, C. O.; Santilli, Celso V.; Nogueira, Ana F.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 84-95
ENG
Relevância na Pesquisa
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 08/00463-2; In this work, mesoporous titania is prepared by templating latex sphere arrays with four different sphere diameters at the micrometric scale (phi > 1 mu m). The mesoporous titania homogeneously covers the latex spheres and substrate, forming a thin coating characterized by N-2 adsorption isotherm, small angle X-rays scattering, atomic force, field emission and transmission electronic microscopies. Mesoporous titania has been templated into different shapes such as hollow particles and monoliths according to the amount of sol used to fill the voids of the close packed latex spheres. Titania topography strongly depends on the adsorption of polymeric segments over latex spheres surface, which could be decreased by changing the dimensions of latex spheres (phi = 9.5 mu m) generating a lamellar architecture. Thus, micrometric latex sphere arrays can be used to achieve new surface patterns for mesoporous materials via a fast and inexpensive chemical route for construction of functional devices in different technological fields such as energy conversion, inclusion chemistry and biomaterials. (C) 2011 Elsevier B.V. All rights reserved.

On the specific filtration mechanism of a mesoporous silica membrane, prepared with non-connecting parallel pores

Boissière, Cédric; Martines, Marco U.; Larbot, André; Prouzet, Eric
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 17-28
ENG
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We report the singular filtration properties of an ultrafiltration membrane made with mesoporous silica that exhibits cylindrical pores aligned mostly normal to the support. This membrane supported on tubular commercial macroporous alumina supports was prepared by the interfacial growth mechanism between stable silica-surfactant hybrid micelles made of the association of silica oligomers with polyethyleneoxide-based (PEO) surfactants and sodium fluoride, a well-known silica condensation catalyst [Boissière et al., An ultrafiltration membrane made with mesoporous MSU-X silica, Chem. Mater. 15 (2003) 460-463]. It appears that the combined effect of the silica nature of the membrane, whose surface charge can be easily adjusted by changing the pH and the non-connected cylindrical shape of the pores provides a new behavior in the retention properties, as proved by the filtration of polyoxyethylene polymers (PEO) with different molecular weights. Depending on the filtration conditions, a rejection rate of 80% and a steep cut-off at 2000 Da can be obtained or, on the reverse, polymers three times bigger than the pore diameter can diffuse through the membrane. This new filtration mechanism, which opens up new modes of separation modes, is explained in the light of both topology of the porous network and pH-dependent interactions between PEO polymers and silica porous media. © 2004 Elsevier B.V. All rights reserved.

Nanostructured materials based on mesoporous silica and mesoporous silica/apatite as osteogenic growth peptide carriers

Mendes, L. S.; Saska, S.; Martines, M. A U; Marchetto, R.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 4427-4434
ENG
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The aim of this work was the preparation of inorganic mesoporous materials from silica, calcium phosphate and a nonionic surfactant and to evaluate the incorporation and release of different concentrations of osteogenic growth peptide (OGP) for application in bone regeneration. The adsorption and release of the labeled peptide with 5,6-carboxyfluorescein (OGP-CF) from the mesoporous matrix was monitored by fluorescence spectroscopy. The specific surface area was 880 and 484 m2 g- 1 for pure silica (SiO) and silica/apatite (SiCaP), respectively; the area influenced the percentage of incorporation of the peptide. The release of OGP-CF from the materials in simulated body fluid (SBF) was dependent on the composition of the particles, the amount of incorporated peptide and the degradation of the material. The release of 50% of the peptide content occurred at around 4 and 30 h for SiCaP and SiO, respectively. In conclusion, the materials based on SiO and SiCaP showed in vitro bioactivity and degradation; thus, these materials should be considered as alternative biomaterials for bone regeneration. © 2013 Elsevier B.V.

Síntese de carbonos cerâmicos mesoporosos para aplicação como eletrodos em células a combustível a metanol direto; Synthesis of the novel mesoporous carbon ceramics for application on direct fuel cell electrodes

Jean Marcel Ribeiro Gallo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 16/03/2010 PT
Relevância na Pesquisa
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Esse trabalho teve como objetivo a aplicação de peneiras moleculares mesoporosas de sílica como suporte para metal em aplicações em eletrodos na Célula a combustível a metanol direto (DMFC). As peneiras moleculares mais importantes, MCM-41, MCM-48 e SBA-15, foram escolhidas. Em um primeiro momento a reprodutibilidade das sínteses foi verificada. Como pesquisa lateral foi estudada a acidez de superfície da SBA-15 contendo alumínio obtida por síntese direta. Além disso, foi desenvolvida a primeira síntese direta para a [Al]-SBA-15 Sílica é um isolante elétrico e, portanto, não pode ser utilizada como um eletrodo, deste modo, uma nova família de compósitos chamada Carbonos Cerâmicos Mesoporosos (MCC) foi preparada pela adição de grafite comercial na síntese das sílicas mesoporosas (MCM-41, MCM-48 ou SBA-15). A grafite não influenciou na formação da mesofase de sílica, de qualquer maneira, a MCC-MCM-41 e a MCC-MCM-48 cresceram na superfície da grafite. As MCCs preparadas com razão em massa sílica/carbono de 1/1 e 1/1.25 apresentaram condutividades elétricas similares enquanto MCCs com menos quantidade de carbono se mostraram isolantes elétricos. As MCCs(1/1) modificadas com 20 % em massa de paládio foram usadas na DMFC chegando no máximo a desempenhos 10 vezes menores que o do sistema usando o suporte comercia Vulcan XC-72R. Esse comportamento foi atribuida a menos condutividade elétrica dos MCCs. Para aumentar a condutividade elétrica dos MCCs(1/1)...

Morphology and topography analysis of mesoporous titania templated by micrometric latex sphere arrays

Barros Filho, D. A.; Benedetti, J. E.; Pereira-da-Silva, M. A.; Seriacopi, V.; Gomes Silva, W. R.; Alonso, R. C. B.; Lewgoy, H. R.; Anido-Anido, A.; Amore, R.; Anauate-Netto, C.; Avellaneda, C. O.; Santilli, Celso V.; Nogueira, Ana F.
Fonte: Elsevier; Amsterdam Publicador: Elsevier; Amsterdam
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.30933%
In this work, mesoporous titania is prepared by templating latex sphere arrays with four different sphere diameters at the micrometric scale (phi > 1 mu m). The mesoporous titania homogeneously covers the latex spheres and substrate, forming a thin coating characterized by N-2 adsorption isotherm, small angle X-rays scattering, atomic force, field emission and transmission electronic microscopies. Mesoporous titania has been templated into different shapes such as hollow particles and monoliths according to the amount of sol used to fill the voids of the close packed latex spheres. Titania topography strongly depends on the adsorption of polymeric segments over latex spheres surface, which could be decreased by changing the dimensions of latex spheres (phi = 9.5 mu m) generating a lamellar architecture. Thus, micrometric latex sphere arrays can be used to achieve new surface patterns for mesoporous materials via a fast and inexpensive chemical route for construction of functional devices in different technological fields such as energy conversion, inclusion chemistry and biomaterials. (C) 2011 Elsevier Inc. All rights reserved.; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Mesoporous carbons prepared by nano-casting with meso- or non-porous silica nanoparticles

Silva,Camila Ramos da; Wallau,Martin; Urquieta-González,Ernesto A.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2006 EN
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Mesoporous carbons were obtained by sequential nano-casting using the following hard templates: (i) mesoporous silica nanospheres with MCM-41 or MCM-48 analogous structure; (ii) non-porous silica nanospheres and (iii) pyrogenic silica (Aerosil 200). These silica templates (patrix) were impregnated with sucrose, carbonized at 800 ºC under nitrogen atmosphere and finally the silica dissolved with hydrofluoric acid. It was observed that the specific surface area of the carbon matrixes can be enhanced reducing the diameter of the silica nanospheres or the distance between them by agglomeration prior to the impregnation of the silica patrix with sucrose. Mesoporous carbons with specific surface areas higher than 500 m² g-1 were obtained using mesoporous silica spheres. In this case, the carbon matrixes contain mesopores with a narrow pore size distribution and with diameters in the order of the wall thickness of the mesoporous silica used as hard template.

Tailored adsorption of enzymes onto mesoporous silicates

Gaffney, Darragh
Fonte: University of Limerick Publicador: University of Limerick
Tipo: Doctoral thesis; all_ul_research; ul_published_reviewed; ul_theses_dissertations; none
ENG
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peer-reviewed; The objective of this research is to synthesise mesoporous silicates, incorporate metal complexes on to the surface of the silicates post synthesis and utilise these materials for the immobilisation of histidine-tagged enzymes to form stable, reusable biocatalysts. Studies in the synthesis of a range of mesoporous silicates and subsequent postsynthetic metal-cyclam functionalisation are presented. The generation of nickel-cyclam functionalised MCM-41/89, SBA-15 and MCF was successfully achieved in good yield. Post-synthetic methods for the metal-cyclam functionalisation of the mesoporous silicate mesocellular foam (MCF) are presented and compared. MCF functionalised using a one-pot functionalisation technique had a higher metal content than a step-wise functionalisation technique. Optimisation steps were required for the specific adsorption of histidine tagged proteins/enzymes onto metal functionalised mesoporous silicates. As a proof-of-concept system, the immobilisation of the histidine-tagged inhibitor protein Spi onto SBA-15- Ni-cyclam was investigated. Optimisation of the immobilisation using varying concentrations of NaCl and PEG400 demonstrated specific immobilisation. In the presence of 2 % PEG400...

Adsorption performance of VOCs in ordered mesoporous silicas with different pore structures and surface chemistry

Dou, B.; Hu, Q.; Li, J.; Qiao, S.; Hao, Z.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
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Ordered mesoporous silicas with different pore structures, including SBA-15, MCM-41, MCM-48 and KIT-6, were functionalized with phenyltriethoxysilane by a post-synthesis grafting approach. It was found that phenyl groups were covalently anchored onto the surface of mesoporous silicas, and the long-range ordering of the mesoporous channels was well retained after the surface functionalization. The static adsorption of benzene and the dynamic adsorption of single component (benzene) and bicomponent (benzene and cyclohexane) on the original and functionalized materials were investigated. As indicated by the adsorption study, the functionalized silicas exhibit improvement in the surface hydrophobicity and affinity for aromatic compounds as compared with the original silicas. Furthermore, the pore structure and the surface chemistry of materials can significantly influence adsorption performance. A larger pore diameter and cubic pore structure are favorable to surface functionalization and adsorption performance. In particular, the best adsorption performance observed with phenyl-grafted KIT-6 is probably related to the highest degree of surface functionalization, arising from the relatively large mesopores and bi-continuous cubic pore structure which allow great accessibility for the functional groups. In contrast...

Highly ordered mesoporous MoS₂ with expanded spacing of the (002) crystal plane for ultrafast lithium ion storage; Highly ordered mesoporous MoS(2) with expanded spacing of the (002) crystal plane for ultrafast lithium ion storage

Liu, H.; Su, D.; Zhou, R.; Sun, B.; Wang, G.; Qiao, S.
Fonte: Wiley - VCH Verlag GmbH & Co KGaA Publicador: Wiley - VCH Verlag GmbH & Co KGaA
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
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Highly ordered mesoporous MoS₂ with a high surface area and narrow pore-size distribution is synthesized by a vacuum assisted impregnation route. The mesoporous MoS₂ demonstrates an expanded d₀₀₂ spacing of 0.66 nm. The mesoporous MoS₂ electrode achieves an excellent high rate capacity of 608 mAh g⁻¹ at the discharge current of 10 A g⁻¹ (∼15C), which places MoS₂ as a viable next generation high power source for electric vehicles.; Hao Liu, Dawei Su, Ruifeng Zhou, Bing Sun, Guoxiu Wang, and Shi Zhang Qiao

Magnetic nanocomposites with mesoporous structures: synthesis and applications

Liu, J.; Qiao, S.; Hu, Q.; Lu, G.
Fonte: Wiley - VCH Verlag GmbH & Co KGaA Publicador: Wiley - VCH Verlag GmbH & Co KGaA
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
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Magnetic nanocomposites with well-defined mesoporous structures, shapes, and tailored properties are of immense scientific and technological interest. This review article is devoted to the progress in the synthesis and applications of magnetic mesoporous materials. The first part briefly reviews various general methods developed for producing magnetic nanoparticles (NPs). The second presents and categorizes the synthesis of magnetic nanocomposites with mesoporous structures. These nanocomposites are broadly categorized into four types: monodisperse magnetic nanocrystals embedded in mesoporous nanospheres, microspheres encapsulating magnetic cores into perpendicularly aligned mesoporous shells, ordered mesoporous materials loaded with magnetic NPs inside the porous channels or cages, and rattle-type magnetic nanocomposites. The third section reviews the potential applications of the magnetic nanocomposites with mesoporous structures in the areas of heath care, catalysis, and environmental separation. The final section offers a summary and future perspectives on the state-of-the art in this area.; Jian Liu, Shi Zhang Qiao, Qiu Hong Hu, and Gao Qing (Max) Lu

Tailored adsorption of enzymes onto mesoporous silicates.

O'Neill, Sarah
Fonte: University of Limerick Publicador: University of Limerick
Tipo: Master thesis (Research); all_ul_research; ul_published_reviewed; ul_theses_dissertations; none
ENG
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peer-reviewed; Enzymes often display high regio- and chemoselectivity and therefore are of great interest for industrial processes. However, in these processes, they can show low stability and are not reusable. Immobilisation can optimize stability and activity, providing controlled mass transport of substrate and enabling re-use of the biocatalyst. Immobilisation also allows for continuous processes. Mesoporous silicates provide a means of immobilizing proteins and enzymes in a stable environment while retaining physiological function. Mesoporous silicates possess large surface areas, highly ordered pore structures and a very narrow pore size distribution. Pore sizes range from 3-20nm making them ideal for protein encapsulation. One recurrent problem with physi-sorption onto mesoporous silicates is leaching of the enzyme. Covalent attachment can reduce leaching but can increase rigidity which could lead to a loss in activity. Methods of tailoring the properties of both the mesoporous silicate surface and the protein surface to improve adsorption and catalytic activity have been explored with a view to generate a stable biocatalyst. A biocatalyst has been generated through the tailored adsorption of a tagged enzyme onto a metal functionalized mesoporous silicate. By employing a standard method of protein purification...

Pore expansion in mesoporous silicas using supercritical carbon dioxide

Hanrahan, John P.; Copley, Mark P.; Ryan, Kevin M.; Spalding, Trevor R.; Morris, Michael A.; Holmes, Justin D.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: info:eu-repo/semantics/article; all_ul_research; ul_published_reviewed
ENG
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peer-reviewed; In this paper we report the controlled expansion of pores within mesoporous silicas using supercritical carbon dioxide (sc-CO2). Our method uses the tunable density of sc-CO2 to induce the controlled swelling of the triblock copolymer surfactant templating agents, P123 (PEO20PPO69PEO20) and P85 (PEO26PPO39PEO26). This swelling process ultimately leads to the control of pore diameters and hexagonal spacing within the mesoporous silicas. At pressures of approximately 482 bar, pore diameters of up to 100 Å can be achieved representing a pore expansion of 54 % compared to the conventionally formed mesoporous silicas. Powder X-ray diffraction (PXRD), transmission electron microscopy (TEM) and nitrogen adsorption techniques were used to establish pore diameters, silica wall widths and the hexagonal packing of the pores within the sc-CO2 treated mesoporous silicas. The sc-CO2 was shown not to effect the hexagonal ordering of the silica, a distinct advantage over conventional pore swelling techniques.

Organically Modified Mesoporous Silica as a Support for Synthesis and Catalysis

McEleney, Kevin
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 14165145 bytes; application/pdf
EN; EN
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Mesoporous silicates are excellent materials for supported catalysis due to their ease of functionalization, tunable pore size and high surface areas. Mesoporous silicates have been utilized in a variety of applications such as drug delivery scaffolds and catalyst supports. Functionalization of the surface can be achieved by either grafting of alkoxy silanes or co-condensation of the organosilane with the inorganic silica source. My research in this area can be divided into two components. In the first, we address the significant issue of metal contamination after reactions that are catalyzed by transition metals. In the second, we examine the design of new catalysts based on organic/inorganic composites. Ruthenium catalyzed processes such as olefin metathesis or asymmetric hydrogenation, are often underutilized due to the difficulty of removing the ruthenium by-products. Attempts to remove ruthenium involve treating the solution with a scavenging reagent followed by silica chromatography. Often these scavenging agents are expensive phosphines or toxic agents like lead tetra-acetate. SBA-15 functionalized with aminopropyl triethoxysilane displays a high affinity for ruthenium. Furthermore, it can be utilized to remove ruthenium by-products from olefin metathesis or hydrogenation reactions without the need for silica chromatography. We have also prepared sulfur-functionalized mesoporous silicates that have a high affinity for palladium. The materials after loading prove to be active catalysts for a variety of palladium catalyzed processes such as Suzuki-Miyaura and Sonogashira couplings. The catalysts are recyclable with moderate loss of activity and structure...

Síntese, caracterização e aplicação de novos adsorventes obtidos a partir da modificação de sílicas mesoporosas; Synthesis, characterization and application of new adsorbents materials obtained from chemically modified mesoporous silicas

Natália Fattori
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 21/07/2011 PT
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O presente trabalho descreve a preparação e caracterização de novos materiais adsorventes obtidos a partir da modificação química de dois diferentes substratos mesoporosos: uma sílica mesoporosa constituída de uma estrutura porosa altamente ordenada e uniforme, composta de poros ou canais cilíndricos dispostos paralelamente e empacotados em arranjo hexagonal (SBA-15), e uma sílica mesoporosa caracterizada por uma rede desordenada de poros, de tamanho e forma variados, distribuídos e interconectados aleatoriamente ao longo da estrutura porosa (SMD). Os dois substratos mesoporosos foram modificados com dois diferentes agentes funcionalizantes derivados da molécula 4,4´-bipiridina, imobilizados sobre a superfície da sílica tanto na forma monossubstituída (Bipy), como na forma dissubstituída (Bipy). A eficiência dos materiais obtidos como adsorventes de íons cobre (II) em solução etanólica foi testada, visando à utilização destas matrizes na purificação de etanol combustível. Os valores de capacidade efetiva de adsorção e constantes de equilíbrio heterogêneo foram obtidos. O processo de adsorção de CuCl2 ocorre na interface sólido-solução pela formação de complexos aniônicos de cobre (CuCl4 e CuCl3)...

Synthesis of mesoporous carbons of high surface area and porosity by using polymer blends as template

Lin, Yu-Chien; Wu, Sheng-Ho; Liu, Che-Wei; Lim, Zheng-Yi; Huang, Cheng-Wei; Lin, Hong-Pin; Deng, Shiensen; Yang, Ming-Chang; Tang, Chih-Yuan; Lin, Ching-Yeh
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.49862%
In this paper, we provided a new method to generate the carbonizable polymer-silica nanocomposite in one step by using different polymer blends of phenol formaldehyde (PF) and silica-gelling polymer (i.e., Pluronic F127, PEO6000 or gelatin) as the template. The PF-silica gelling polymer-silica nanocomposite was obtained from fast silicification in a highly diluted silica solution at pH∈≈∈5.0. Because the PF, one kind of carbon sources, was embedded in the as-synthesized nanocomposite, the mesoporous carbon was easily obtained from pyrolysis at 1,000°C and silica removal by diluted HF solution. The resulted mesoporous carbons possess a high surface area of 780-1,500 m2 g-1 and large pore size of 2.6-13.7 nm. In addition, the morphology of the mesoporous carbons can be tailored to nano-sized particles and hollow spheres by using different silica gelator-PF polymer blends. In practice, the electrically conducting mesoporous carbons of high surface area and large pore size can be considered as good material for preparing the supercapacitor. The mesoporous carbons exhibit electric capacity of 75-158 Fg-1 in 2.0 M H2SO4 electrolyte solution at scan rate of 1-50 mVs-1.