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Surfactant-assisted intercalation of high molecular weight poly(ethylene oxide) into vanadyl phosphate di-hydrate

Ferreira, Joao Paulo L.; Oliveira, Herenilton Paulino
Fonte: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD Publicador: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD
Tipo: Artigo de Revista Científica
ENG
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A high molecular weight poly(ethylene oxide)/layered vanadyl phosphate di-hydrate intercalation compound was synthesized via the surfactant-assisted approach. Results confirmed that surfactant molecules were replaced with the polymer, while the lamellar structure of the matrix was retained, and that the material presents high specific surface area. In addition, intercalation produced a more thermally stable polymer as evidenced by thermal analysis. (C) 2011 Elsevier Ltd. All rights reserved.; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico); FAPESP (Fundacao de Amparo Pesquisa do Estado de So Paulo); FAPESP (Fundacao de Amparo Pesquisa do Estado de So Paulo); CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior); Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)

Hexaniobato lamelar: Estudos de esfoliação e intercalação"; Layered hexaniobate: studies of exfoliation and intercalation

Shiguihara, Ana Lucia
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 20/12/2004 PT
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O presente trabalho teve como objetivo principal estudar os processos de intercalação e esfoliação do niobato lamelar H2K2Nb6O17 em soluções aquosas de n-hexilamina, n-propilamina e hidróxido de tetrabutilamônio (TBAOH). Procurou-se avaliar a influência do agente esfoliante no processo de separação das lamelas do niobato. Para tanto, uma quantidade fixa de H2K2Nb6O17 foi suspensa em solução do agente esfoliante, nas razões molares amina/H+-niobato iguais a 0,25, 0,50, 0,75 e 1,0, e mantida sob agitação à temperatura ambiente por 2 semanas. O sólido depositado foi separado do sobrenadante opaco (isto é, do sólido esfoliado). Para a caracterização do sólido depositado, determinou-se a composição química e registrou-se o difratograma de raios-X, a curva termogravimétrica e os espectros vibracionais no IV e Raman. A dispersão de partículas esfoliadas foi caracterizada por espectroscopia eletrônica enquanto o sólido esfoliado, por DRX, medidas de área superficial, MEV e HRTEM. Nos sólidos depositados, as alquilaminas se encontram intercaladas em um arranjo de monocamada e praticamente orientadas perpendicularmente em relação às lamelas do niobato. As suspensões contendo as razões molares amina/H+-niobato = 0...

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
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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...

Intercalação de íons lantanídeos e de poli(óxido de etileno) assistida por tensoativo na matriz hospedeira VOPO4.2H2O; Intercalation of ions Lanthanides and Poly (ethylene oxide) assisted by surfactant in host matrix of VOPO4.2H2O

Ferreira, João Paulo Ligabó
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 02/10/2008 PT
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Compostos de vanádio são extensivamente estudados, devido suas propriedades redox, eletroquímicas, catalíticas, magnéticas e biológicas. Nesta dissertação tivemos como foco de nosso trabalho o composto VOPO4.2H2O que apresenta uma forma lamelar com suas lamelas unidas por interações de Van der Waals. Essas fracas interações interlamelares fazem do fosfato de vanadila e de seus componentes análogos excelentes matrizes para a síntese de compostos de intercalação. A morfologia do VOPO4.2H2O mostrou-se sensível a alterações de temperatura e tempo durante síntese. Através da alteração destes parâmetros obtivemos um sólido lamelar com um grau de organização inferior a matriz sintetizada à 130oC e 16 horas, devido a existência da fase II-VOPO4 que foi constatada por difração de raios-X. A quantidade de dois mols de água por mol de VOPO4 manteve-se constante segundo as análises termogravimétricas. As imagens de microscopia eletrônica de varredura confirmaram a estrutura lamelar dos produtos, no entanto uma forma rosácea foi constatada em VOPO4/160oC, sugerindo a presença da fase VOHPO4.0,5H2O, precursora da fase (VO)2P2O7 que atua como catalisador seletivo na reação de oxidação do n-butano à anidrido malêico. A intercalação de íons lantanídeos na matriz VOPO4.2H2O produziu sólidos lamelares com cristalinidade inferior a matriz hospedeira...

Investigação dos processos de intercalação e esfoliação de hexaniobato lamelar e preparação de materiais híbridos com biopolímeros; Investigation of the intercalation and exfoliation processes of layered hexaniobate and preparation of hybrid materials with biopolymers

Shiguihara, Ana Lucia
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 01/09/2010 PT
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A presente tese tem como objetivo principal a investigação do processo de intercalação e esfoliação do hexaniobato lamelar em soluções de hidróxidos de tetraalquilamônios e, também, do emprego das partículas do niobato na preparação de materiais híbridos com polissacarídeos. O material de composição H2K2Nb6O17 foi suspenso em soluções aquosas contendo diferentes concentrações dos hidróxidos de tetrametilamônio (TMA+), tetraetilamônio (TEA+) e tetrapropilamônio (TPA+). Após o tempo de reação foram separadas duas frações: o sólido depositado no recipiente e o sobrenadante turvo contendo as partículas não depositadas de características coloidais. Os resultados de difratometria de raios X, análise termogravimétrica, análise elementar, espectroscopia vibracional no infravermelho e Raman mostram que o processo de intercalação é promovido segundo a ordem: TMA+ > TEA+ > TPA+, isto é, a intercalação é facilitada para íons pouco volumosos. Já o processo de esfoliação do hexaniobato é promovido na ordem inversa: TPA+ » TEA+ > TMA+, ou seja, quanto mais volumoso o íon tetraalquilamônio, maior a extensão do processo de separação das lamelas. A formação das partículas cilíndricas, presentes em maior quantidade nas amostras tratadas com soluções de TPA+ e TBA+...

Lithium intercalation into double rare earth chromates

Melnikov, Petr
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 269-270
ENG
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Lithium intercalation into double rare earth chromates was carried out. It was found that the compounds NaxLi1-xLa(CrO4)2 belong to the NaLa(CrO4)2 structural type and may be recommended as fast ionic conductors. At small values of x a third polymorphous modification of LiLa(CrO4)2 can be stabilized. Attempts to intercalate lithium into CsLa(CrO4)2 lead to collapse of the lamellar network with the formation of LaCrO4 and alkaline chromates. Ion exchange Li+/H+ data are consistent with these considerations. © 1994.

Intercalation and thermochemistry of amines in lamellar titanium phenylarsonate

Ruiz,V. S. O.; Airoldi,C.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2005 EN
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The lamellar compound titanium phenylarsonate was synthesized and intercalated with alkylmonoamines (methyl to heptyl), diaminoethane, diaminobutane, lutidine and alpha-picoline. The host was characterized through elemental analysis, X-ray diffraction, surface analysis, porosity, infrared spectroscopy, thermogravimetry and electronic scanning microscopy. The intercalated compounds did not show significant increases in the interlamellar distances through X-ray diffractometry. The intercalation was confirmed by the thermogravimetric technique, indicating mass losses that correspond to the amines. The ideal intercalation was established by adding increments of 30.0x10-6 dm³ of 0.50 mol dm-3 of each amine into a suspension of about 10x10-3 g of matrix. The number of moles intercalated with alkylmonoamines followed an aleatory order in relation to the increase of the aliphatic chain and the enthalpic values gave -9.18 ± 0.07; -12.10 ± 0.20; -7.61 ± 0.02; -6.88 ± 0.01; -9.47 ± 0.03; -12.84 ± 0.10 and -14.78 ± 0.10 kJ mol-1 for the sequence of alkylmonoamines and varied from -3.66 ± 0.30 to -10.92 ± 1.50 kJ mol-1 for the alkyldiamines. The aromatic amines presented small thermal effects and the unfavorable intercalation is attributed to the large volume of the phenyl group inside the lamella...

Chemical modification of niobium layered oxide by tetraalkylammonium intercalation

Shiguihara,Ana L.; Bizeto,Marcos A.; Constantino,Vera R. L.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
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Chemical modification of the layered K4Nb6O17 material was systematically investigated through the reaction of its proton-exchanged form (H2K2Nb6O17) in alkaline solutions containing tetramethylammonium (tma+), tetraethylammonium (tea+) or tetrapropylammonium (tpa+) cations. The intercalated amount reaches 50% (for tma+), 25% (for tea+) and 15% (for tpa+) of the H2K2Nb6O17 negative charge (concerning the exchange at interlayer I) due to the steric hindrance of larger cations. Hexaniobate samples present (020) basal reflections equal to 23.0, 26.3 and 26.5 Å once intercalated respectively with tma+, tea+ and tpa+. When samples are heated above 200-250 ºC, CO2 evolution is observed; Hofmann elimination reaction is also detected for hexaniobate-tpa+ samples. Scanning electron microscopy images show the predominance of plate-like particles; stick-like particles are also observed for samples containing bulky ions. The intercalation reaction is promoted in the order tma+ > tea+ > tpa+, while the formation of a dispersion of colloidal particles is facilitated in the inverse order.

Intercalation and electrical behavior of Ta xMo1-xS2 (x > 0.5) layered mixed disulfides

Lara,Nelson; Aranda,Pilar; Ruiz,Ana I.; Manríquez,Víctor; Ruiz-Hitzky,Eduardo
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2012 EN
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This work reports a systematic study of the structural and electrical behavior of three ternary phases of the Ta xMo1-xS2 system (x = 0.55, 0.75 and 0.90) and their intercalation compounds resulting from both chemical and electrochemical lithium insertions, as well as from pyridine and poly(ethylene oxide) intercalations. The three ternary phases were prepared by direct reaction of their constituting elements, without any other additive, at 900 ºC in inert atmosphere. The resulting compounds were characterized by means of X-ray powder diffractometry (XRD), thermogravimetric and differential thermal (TGA/DTA) analyses, energy dispersive X-ray fluorescence (EDX) and field emission-scanning electron microscopy (FE-SEM). The electrical conductivity of the different products was measured in the 1.5-300 K temperature range using the conventional four probe van der Pauw method in the presence of a 9 T magnetic field in order to verify the occurrence of magnetoresistivity phenomena.

An intercalation inhibitor altering the target selectivity of DNA damaging agents: Synthesis of site-specific aflatoxin B1 adducts in a p53 mutational hotspot

Kobertz, William R.; Wang, David; Wogan, Gerald N.; Essigmann, John M.
Fonte: The National Academy of Sciences of the USA Publicador: The National Academy of Sciences of the USA
Tipo: Artigo de Revista Científica
Publicado em 02/09/1997 EN
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Aflatoxin B1 (AFB1) is a potent human carcinogen implicated in the etiology of hepatocellular carcinoma. Upon metabolic activation to the reactive epoxide, AFB1 forms DNA adducts primarily at the N7 position of guanines. To elucidate more fully the molecular mechanism of AFB1-induced mutagenesis, an intercalation inhibitor was designed to probe the effects of intercalation by AFB1 epoxide on its reaction with DNA. DNA duplexes were prepared consisting of a target strand containing multiple potentially reactive guanines and a nontarget strand containing a cis-syn thymidine-benzofuran photoproduct. Because the covalently linked benzofuran moiety physically occupies an intercalation site, we reasoned that such a site would be rendered inaccessible to AFB1 epoxide. By strategic positioning of this intercalation inhibitor in the intercalation site 5′ to a specific guanine, the adduct yield at that site was greatly diminished, indicating that intercalation by AFB1 epoxide contributes favorably to adduct formation. Using this approach it has been possible to simplify the production of site-specifically modified oligonucleotides containing AFB1 adducts in the sequence context of a p53 mutational hotspot. Moreover, we report herein isolation of site-specifically AFB1-modified oligonucleotides in sequences containing multiple guanines. Use of intercalation inhibitors will facilitate both investigation of the ability of other carcinogens to intercalate into DNA and the synthesis of specific carcinogen-DNA adducts.

Cooperative effects on the formation of intercalation sites

Trieb, Michael; Rauch, Christine; Wibowo, Fajar R.; Wellenzohn, Bernd; Liedl, Klaus R.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
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Daunomycin is one of the most important agents used in anticancer chemotherapy. It interacts with DNA through intercalation of its planar chromophore between successive base pairs. The effect of intercalation on structure, dynamics and energetics is the topic of a wealth of scientific studies. In the present study, we report a computational examination of the energetics of the intercalation process. In detail, we concentrate on the energetic penalty that intercalation of daunomycin introduces into DNA by disturbing it from its unbound conformation. For these means, we are analyzing already published molecular dynamics simulations of daunomycin–DNA complexes and present novel simulations of a bisdaunomycin–DNA and a 9-dehydroxydaunomycin–DNA intercalated complex using the MM-GBSA module implemented in the AMBER suite of programs. Using this molecular dynamics based, continuum solvent method we were able to calculate the energy required to form an intercalation site. Consequently, we compare the free energy of the duplex d(CGCGCGATCGCGCG)2 in the B-form conformation with the respective conformations when intercalated with daunomycin and a bisintercalating analog. Our results show that the introduction of one single intercalation site costs ∼32 kcal/mol. For double intercalation...

Non-directional radial intercalation dominates deep cell behavior during zebrafish epiboly

Bensch, Robert; Song, Sungmin; Ronneberger, Olaf; Driever, Wolfgang
Fonte: The Company of Biologists Publicador: The Company of Biologists
Tipo: Artigo de Revista Científica
Publicado em 03/06/2013 EN
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Epiboly is the first coordinated cell movement in most vertebrates and marks the onset of gastrulation. During zebrafish epiboly, enveloping layer (EVL) and deep cells spread over the vegetal yolk mass with a concomitant thinning of the deep cell layer. A prevailing model suggests that deep cell radial intercalations directed towards the EVL would drive deep cell epiboly. To test this model, we have globally recorded 3D cell trajectories for zebrafish blastomeres between sphere and 50% epiboly stages, and developed an image analysis framework to determine intercalation events, intercalation directionality, and migration speed for cells at specific positions within the embryo. This framework uses Voronoi diagrams to compute cell-to-cell contact areas, defines a feature-based spatio-temporal model for intercalation events and fits an anatomical coordinate system to the recorded datasets. We further investigate whether epiboly defects in MZspg mutant embryos devoid of Pou5f1/Oct4 may be caused by changes in intercalation behavior. In wild-type and mutant embryos, intercalations orthogonal to the EVL occur with no directional bias towards or away from the EVL, suggesting that there are no directional cues that would direct intercalations towards the EVL. Further...

Enhanced removal of triphosphate by MgCaFe-Cl-LDH: Synergism of precipitation with intercalation and surface uptake

Zhou, J.; Xu, Z.; Qiao, S.; Liu, Q.; Xu, Y.; Qian, G.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
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Triphosphate (TPP) is an important form of phosphate pollutants while its removal investigation has been just started now. This research examined the removal of triphosphate using Mg(2-x)Ca(x)FeCl-LDH (x = 0-2) as absorbents. We found that the removal of triphosphate over Mg(2)FeCl-LDH mainly underwent the surface adsorption and the near-edge intercalation, with the practical removal amount (9-11 mg(P)/g) corresponding to 10-15% of the theoretical one. In contrast, Ca(2)FeCl-LDH removed a higher amount of triphosphate (56.4 mg(P)/g). The comprehensive analysis of the triphosphate-uptake products with XRD/XPS/FTIR reveals that Ca(2)FeCl-LDH dissolves first and then released Ca(2+) ions react with triphosphate (TPP) to form insoluble Ca-TPP precipitate. Combination of these two different removal mechanisms enables Mg(0.5)Ca(1.5)FeCl-LDH to take up 84.2mg(P)/g from aqueous solution under similar conditions.; Jizhi Zhou, Zhi Ping Xu, Shizhang Qiao, Qiang Liu, Yunfeng Xu, Guangren Qian

Estrutura lamelar versus estrutura pirocloro : obtenção de compostos do tipo 'H IND.1-x' 'Ag IND.x' 'Ta' W'O IND.6' e reação de intercalação/inserção de amina linear; Lamellar structure versus pyrochlore structure: preparation of the compounds 'H IND.1-x' 'Ag IND.x' 'Ta' W'O IND.6' and intercalation/insertion reactions of linear amines

Marco Aurelio Culhari De Santis
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 29/05/2006 PT
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O presente Trabalho trata da obtenção do óxido HTaWO6.H2O nas formas: bidimensional (trirrutilo lamelar) e tridimensional (pirocloro com canais). Os compostos foram preparados a partir de reações de troca iônica do metal alcalino pelo próton nas respectivas fases (Li ou K)TaWO6. A síntese das fases precursoras envolveu típicas reações de estado sólido. Neste processo, foi estudada a evolução das estruturas em função da variação da temperatura e do tempo de síntese, no intervalo entre 350 e 850°C. As fases cristalinas com as estruturas trirrutilo e pirocloro apresentam propriedades estruturais e eletrônicas que as habilitam a aplicações tecnológicas. Por exemplo, na forma de matrizes hospedeiras para a obtenção de nanocompósitos orgânico/inorgânicos, assim como na forma de eletrólitos sólidos. Ambos os sólidos, obtidos na forma de pó, foram funcionalizados por reações de troca iônica do próton por íons Ag, conduzindo à formação dos compostos do tipo H1-xAgxTaWO6.H2O com estrutura bi- e tridimensional. Adicionalmente, o composto apresentando a estrutura trirrutilo (lamelar) foi utilizado como matriz hospedeira para a reação de intercalação de duas aminas lineares (n-butilamina e n-dodecilamina). As reações conduziram à formação dos compostos de intercalação: HTaWO6.H2O@C4H11N e HTaWO6.H2O@C12H27N. Os materiais preparados foram caracterizados por diferentes técnicas...

Capture of a Transition State Using Molecular Dynamics: Creation of an Intercalation Site in dsDNA with Ethidium Cation

Monaco, Regina R.
Fonte: SAGE-Hindawi Access to Research Publicador: SAGE-Hindawi Access to Research
Tipo: Artigo de Revista Científica
Publicado em 31/03/2010 EN
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The mechanism of intercalation and the ability of double stranded DNA (dsDNA) to accommodate a variety of ligands in this manner has been well studied. Proposed mechanistic steps along this pathway for the classical intercalator ethidium have been discussed in the literature. Some previous studies indicate that the creation of an intercalation site may occur spontaneously, with the energy for this interaction arising either from solvent collisions or soliton propagation along the helical axis. A subsequent 1D diffusional search by the ligand along the helical axis of the DNA will allow the ligand entry to this intercalation site from its external, electrostatically stabilized position. Other mechanistic studies show that ethidium cation participates in the creation of the site, as a ligand interacting closely with the external surface of the DNA can cause unfavorable steric interactions depending on the ligands' orientation, which are relaxed during the creation of an intercalation site. Briefly, such a site is created by the lengthening of the DNA molecule via bond rotation between the sugars and phosphates along the DNA backbone, causing an unwinding of the dsDNA itself and separation between the adjacent base pairs local to the position of the ligand...

Synthesis, functionalization, and properties of intercalation compounds

Benavente Espinosa, Eglantina; Lavayen, Vladimir; González, G.; Santa Ana, M. A.; Mirabal, N.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo de revista
EN
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Layered compounds are nanostructured, intrinsically anisotropic materials which often undergo intercalation reactions producing host– guest complexes. In this work examples from the molybdenum disulfide chemistry are used for discussing how the properties of the products may be regulated by appropriate selection of the guests species used for functionalizing the pristine sulfide. Special attention is given to new intercalates based in the intercalation of surfactants, which under special conditions may act as template promoting the conversion of the layered products into micro and nanotubes. The form how this kind of surfactants may be used for obtaining laminar derivatives of cadmium disulfide with the sulfide in a confined state is also described.; The authors thank to CYTED, Red IX.E, DID Universidad de Chile, FONDECYT (Contracts 1010924), and the Deutscher Academischen Austauschdienst (DAAD).

Intercalation of polyethylene oxide in layered thiophosphate of Bi and Sb

Manríquez, Víctor; Galdámez, Antonio; Ruiz León, Domingo
Fonte: SOC CHILENA QUIMICA Publicador: SOC CHILENA QUIMICA
Tipo: Artículo de revista
EN
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The intercalation compounds Li0.43(PEO)2.4(H2O)1.4K0.57BiP2S6 and Li0.38(PEO)2.1(H2O)1.6K0.62SbP2S6 have been synthesized by the insertion of polyethylene oxide PEO in LiKMP2S6 (M=Bi, Sb), that contained Li+ and K+ exchangeable cations in their interlayer space. The polymer PEO is able to associate interlayer Li+ cation modifying the ionic conductivity of pristine phases. These intercalation compounds constitute a new family of intercalates in the thiophosphate of Bi and Sb with Polyethylene oxide as guest species. They have been characterized by powder X-ray diffraction, FTIR-Raman, DTA/TGA analysis and electrical conductivity measurements. The studied nanocomposite shows values of electrical conductivity (σi ) of about 10-6 Ω-1 cm-1 at room temperature.; This work was supported by FONDECYT grant Nº 1061116

In-situ intercalation dynamics in inorganic-organic layered perovskite thin films

Ahmad, Shahab; Kanaujia, Pawan K.; Niu, Wendy; Baumberg, Jeremy J.; Prakash, G. Vijaya
Fonte: ACS Publications Publicador: ACS Publications
Tipo: Article; accepted version
EN
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This material is excerpted from a work that was published in ACS Applied Materials and Interfaces, copyright ? American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/am501568j; The properties of layered inorganic semiconductors can be manipulated by the insertion of foreign molecular species via a process known as intercalation. In the present study, we investigate the phenomenon of organic moiety (R-NH3I) intercalation in layered metal-halide (PbI2)-based inorganic semiconductors, leading to the formation of inorganic-organic (IO) perovskites [(R-NH3)2PbI4]. During this intercalation strong resonant exciton optical transitions are created, enabling study of the dynamics of this process. Simultaneous in-situ photoluminescence (PL) and transmission measurements are used to track the structural and exciton evolution. Based on the experimental observations, a model is proposed which explains the process of IO perovskite formation during intercalation of the organic moiety through the inorganic semiconductor layers. The interplay between precursor film thickness and organic solution concentration/solvent highlights the role of van der Waals interactions between the layers...

Cell motility driving mediolateral intercalation in explants of Xenopus laevis

Shih, John; Keller, Ray
Fonte: Company of Biologists Publicador: Company of Biologists
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /12/1992
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In Xenopus, convergence and extension are produced by active intercalation of the deep mesodermal cells between one another along the mediolateral axis (mediolateral cell intercalation), to form a narrower, longer array. The cell motility driving this intercalation is poorly understood. A companion paper shows that the endodermal epithelium organizes the outermost mesodermal cells immediately beneath it to undergo convergence and extension, and other evidence suggests that these deep cells are the most active participants in mediolateral intercalation (Shih, J. and Keller, R. (1992) Development 116, 887–899). In this paper, we shave off the deeper layers of mesodermal cells, which allows us to observe the protrusive activity of the mesodermal cells next to the organizing epithelium with high resolution video microscopy. These mesodermal cells divide in the early gastrula and show rapid, randomly directed protrusive activity. At the early midgastrula stage, they begin to express a characteristic sequence of behaviors, called mediolateral intercalation behavior (MIB): (1) large, stable, filiform and lamelliform protrusions form in the lateral and medial directions, thus making the cells bipolar; (2) these protrusions are applied directly to adjacent cell surfaces and exert traction on them...

Structural Aspects Related to Lithium Intercalation and Ionic Dynamics: Frequency Response Analysis of (Sn x,Ti1-x)O2 Based Systems

Bueno,Paulo R.; Bulhões,Luis O.S.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
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Diffusion models capable of describing the ionic diffusion inside host materials, e.g. oxides, during intercalation processes, have been reported in the literature. However, the majority of the models do not succeed in establishing a good correlation between diffusion and structural environment. What is frequently described is the influence of an addition solid state reaction. In this paper we discuss about such additional reaction and its influence on the diffusion. The responses were evaluated by means of impedance patterns analyzed in (Sn x,Ti1-x)O2 binary systems whose structural disorder control provides a way to evaluate how such structural disorder influences the global diffusion.