Highly stable and crystalline V(2)O(5) nanoparticles with an average diameter of 15 nm have been easily prepared by thermal treatment of a bariandite-like vanadium oxide, V(10)O(24)center dot 9H(2)O. Their characterization was carried out by powder X-ray diffractometry (XRD). Fourier transform infrared (FT-IR) and Raman spectroscopies, and transmission electron microscopy (TEM). The fibrous and nanostructured film obtained by electrophoretic deposition of the V(2)O(5) nanoparticles showed good electroactivity when submitted to cyclic voltammetry in an ionic liquid-based electrolyte. The use of this film for the preparation of a nanostructured electrode led to an improvement of about 50% in discharge capacity values when compared with similar electrodes obtained by casting of a V(2)O(5) xerogel. (C) 2009 Elsevier Inc. All rights reserved.; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq; FINEP; Financiadora de Estudos e Projetos (FINEP); CT-INFRA; Financiadora de Estudos e Projetos (FINEP); FAPESP; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); CAPES/PROCAD; LME-LNLS[HR-6777]; LME-LNLS; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[05/59135-6]
Raman spectra of polymer electrolytes based on poly(ethylene glycol) dimethyl ether (PEGdME) with LiClO(4), PEGdME/LiClO(4), and the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, PEGdME/[bmim]PF(6), are compared. Raman spectroscopy suggests stronger interactions in PEGdME/LiClO(4) than PEGdmE/[bmim]PF(6), thus corroborating previous results obtained by molecular dynamics simulations. Quantum Chemistry methods have been used to calculate vibrational frequencies and the equilibrium structure of segments of the polymer chain around the cation. A consistent picture has been obtained from Raman spectroscopy, density functional theory (DFT) calculations, and molecular dynamics simulations for these polymer electrolytes. (C) 2010 Elsevier B.V. All rights reserved.
The effect of the room temperature ionic liquid (1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BMMI][BF4])) on the immobilization of glucose oxidase (GOx) was studied. The electrochemical performance of biosensors prepared following different protocols indicated a beneficial effect of the ionic liquid on the analytical parameters. The chemical interaction between GOx, [BMMI][BF4] and glutaraldehyde was investigated using UV-visible spectroscopy (UV-vis) and circular dichroism (CD). Structural changes of the biomolecule were observed to depend on the method used for the immobilization. (C) 2011 Elsevier Ltd. All rights reserved.; CNPq; CNPq [554553/2008-2]; FAPESP [09/53199-3]; FAPESP; INCT of Bionalitica (CNPq/FAPESP/MCT); INCT of Bionalitica (CNPq/FAPESP/MCT)
A janela eletroquímica do líquido iônico trifluoroacetato de 1-n-butil-3-metilimidazólio foi estudada sobre eletrodos de carbono vítreo e platina em condições estática e dinâmica. Observouse uma drástica diminuição da janela eletroquímica ao trocar o eletrodo de carbono vítreo (4.50 V) pelo de platina (2.50 V). A variação da velocidade de rotação do eletrodo e da velocidade de varredura não afetaram o perfil dos voltamogramas, porém alteraram as densidades de corrente dos picos referentes aos processos anódicos e catódicos. A adsorção do cátion imidazólio durante o processo de transferência de carga na região catódica foi evidenciada, principalmente para baixas velocidades de rotação do eletrodo.; The 1-n-butyl-3-methylimidazolium trifluoroacetate ionic liquid electrochemical windows have been investigated at vitreous carbon and platinum disc electrodes under static and dynamic conditions. The electrochemical window abruptly decreases by changing vitreous carbon (4.50 V) by platinum electrode (2.50 V). Electrode rotation and potential sweep rate did not affect the current-potential profiles but alter the current values of both anodic and cathodic peaks. The adsorption of imidazolium cation involved in the charge transfer process during the cathodic sweep rate was evidenced...
The 1-n-butyl-3-methylimidazolium trifluoroacetate ionic liquid electrochemical windows have been investigated at vitreous carbon and platinum disc electrodes under static and dynamic conditions. The electrochemical window abruptly decreases by changing vitreous carbon (4.50 V) by platinum electrode (2.50 V). Electrode rotation and potential sweep rate did not affect the current-potential profiles but alter the current values of both anodic and cathodic peaks. The adsorption of imidazolium cation involved in the charge transfer process during the cathodic sweep rate was evidenced, mainly at low electrode rotation.
In this paper room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluoro-phosphate (BMIMPF6) was used as binder to fabricate a carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on the surface of CILE with clay and polyvinyl alcohol (PVA) composite film by layer to layer method. UV-Vis and FT-IR spectra showed that Hb in the film retained the essential features of its native structure. Electrochemical experiments indicated that a pair of well-defined quasi-reversible redox peak was obtained in pH 7.0 Britton-Robinson (B-R) buffer solution. The reduction and oxidation peak potentials were located at -0.405 V and -0.274 V (vs. SCE) with the formal potential as -0.340 V, which was contributed to the electrochemical reaction of heme Fe(III)/Fe(II) redox couples. The results suggested that the direct electron transfer of Hb in the PVA/Clay film with the CILE was accomplished. The direct electrochemical behaviors of Hb were carefully studied with the electrochemical parameters calculated. The PVA/Clay/Hb modified CILE gave excellent electrocatalytic ability to the reduction of H2O2 and the apparent Michaelis-Menten constant (K Mapp) value of Hb in the PVA/Clay film was calculated as 56.26 µmol L-1.
An efficient enantioselective approach for preparation of quaternary centers from proline 5 building block has been developed through [2,3]-sigmatropic Stevens rearrangement co-catalyzed by ionic liquid. The sigmatropic rearrangement was stereospecific because the [2,3]-migrations were restricted to the same face, and the stereoselectivity arose from the previous N-alkylation step in 8. The approach showed better yields than described in literature. The use of 1-butyl-3-methylimidazolium hexafluorophosphate showed an improvement in the yields of the Stevens rearrangement due to a possible stabilization and/or activatation of zwiterionicspecies in solution by the ionic liquid. Several indolizidine moieties were synthesized from quaternary proline derivative (S)-5.
Brilliant cresyl blue (BCB) was electropolymerized on the surface of a carbon ionic liquid electrode (CILE) by cyclic voltammetric sweep in the potential range from -0.5 to 1.0 V. CILE was prepared by using 1-ethyl-3-methyl- imidazolium tetrafluoroborate ([EMIM]BF4) as modifier. The stable polymer film of BCB was obtained on the CILE and a pair of redox peaks appeared. The characteristics of PBCB film was studied by different methods such as scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. This modified electrode showed excellent electrocatalytic response to ascorbic acid with the increase of the electrochemical responses. Under the optimal conditions a good linear voltammetric response could be obtained over the range of 2.0x10-5-3.0x10-3 mol L-1 and the detection limit was got as 6.5 µmol L-1 (3σ).
An improved procedure for the synthesis of indole-2-carboxylic acid esters in excellent yields has been achieved by the condensation of 2-halo aryl aldehydes or ketones and ethyl isocyanoacetate using ionic liquid under controlled microwave irradiation (100 W) at 50 °C. This method offers a number of advantages in terms of methodology, high-product yield, short period of conversion, mild reaction conditions and easy workup.
Dispersive liquid-liquid microextraction (DLLME) using ionic liquid (IL) as extraction solvent was developed as a new approach for the determination of four pyrethroid pesticides in environmental water and soil samples. High-performance liquid chromatography with ultraviolet detection (HPLC-UV) was employed on chromatographic analysis. The method is rapid, easy to operate and enviromentally-friendly. The highly toxic chlorinated solvent was replaced by the IL 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]), in which high extraction recovery and enrichment factors were obtained. The effects of IL volume, type and volume of disperser solvent, salt addition, pH and extraction time were investigated and optimized. Under optimum conditions, the method showed good linear response with correlation coefficient (R²) values in the range of 0.9943 to 0.9986. Relative standard deviation (RSD) varied from 3.9 to 10.1%. Enrichment factor, limit of detection and recovery ranged from 260 to 319, 0.94 to 1.97 µg L-1 and 89 to 98%, respectively. For real water samples, RSD ranged from 3.8 to 10.8%, and recovery from 83 to 99%. For soil sample analysis, RSD and recovery ranged from 3.7 to 8.9% and 88 to 98, respectively.
An efficient and reusable heterogeneous catalytic assembly of peroxotungstate held in a ionic liquid (IL) brush was synthesized and an environmentally-friendly procedure was developed for selective oxidation of sulfides at room temperature using 30 wt.% hydrogen peroxide as the terminal oxidant and water as a sole solvent. No organic co-solvent or other additive was needed. A 1.5-2.0 mol% (based on W atom) loading catalyst was found to be sufficient for a smooth and clean reaction. Both aliphatic and aromatic sulfides were efficiently and selectively transformed into their respective sulfoxides or sulfones by simply controlling of equivalents of hydrogen peroxide. In addition to the high catalytic activity, the catalyst exhibits excellent chemoselectivity. Sensitive functional groups, such as double bond and hydroxyl, remained under the oxidation conditions the reaction even with an excess hydrogen peroxide. The catalyst was easily recovered (via simple filtration) and reused at least eight times without a noticeable loss of activity.
The determination of nickel in food samples and well water using cold induced aggregation microextraction combined UV-Vis spectrophotometry is described. The extraction of nickel was performed in the presence of dimethylglyoxime (DMG) as the complexing agent. In this method, sodium hexafluorophosphate (NaPF6) was added to the sample solution containing small amounts of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF6] as extraction solvent. Parameters governing the extraction efficiency such as amount of ionic liquid, pH, temperature and ionic strength were optimized. The applicability of the technique was evaluated by the determination of trace nickel in different types of vegetables. Under the optimum conditions, the calibration curve was linear in the concentration range 8-200 ng mL-1 with correlation coefficient (r²) of 0.9996. The limit of detection (LOD) of 0.47 ng mL-1 and enhancement factor of 186 were obtained for nickel. The relative standard deviation (RSD) was 3.7% for 40 ng L-1 nickel (n = 10).
This paper is about an improved temperature-controlled ionic liquid dispersive liquid-phase microextraction method for pre-concentration of cadmium ions prior to determination by flame atomic absorption spectrometry. In this study, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]) was used as extraction solvent. Cadmium complexed with dithizone, and then entered into the dispersed ionic liquid droplets at 40 ºC. Some parameters affecting the extraction efficiency such as the volume of [C4MIM][PF6], dissolving temperature, sample pH, centrifuging time and salt effect have been investigated in detail. The calibration graph was linear in the range of 2-250 ng mL-1, the limit of detection (3Sb) was 0.62 ng mL-1. The enhancement factor was found to be 48.4 and the relative standard deviation (RSD) for 10 replicate determinations of 50 ng mL-1 Cd was 2.7%. The developed method successfully applied to the determination of cadmium in several real samples.
RESUMEN: La separación de proteínas de medios complejos como el lactosuero bovino suele representar entre el 50 y el 80 % de los costes de producción, por lo que se precisa de procesos eficientes y sostenibles de separación y purificación de proteínas que permitan su recuperación. La presente tesis doctoral tiene como objetivo desarrollar una técnica innovadora para la recuperación de proteínas denominada reparto en tres fases basado en líquidos iónicos (ILTPP, Ionic Liquid-based Three Phase Partitioning). ILTPP emplea sistemas líquido iónico/sal para acumular la proteína de interés en la interfase líquido-líquido y facilitar así su recuperación. Esta técnica se ha aplicado a la recuperación de lactoferrina, una proteína del lactosuero bovino que destaca por sus propiedades nutracéuticas. Los resultados obtenidos hacen de ILTPP una técnica muy prometedora por cuanto combina altas tasas de recuperación de proteína con selectividades variables que permiten tanto enriquecer proteínas individuales como conjuntos de ellas, empleando para ello sistemas líquido iónico/sal estables y que pueden llegar a reutilizarse en su totalidad.; ABSTRACT: The separation of proteins from complex mixtures such as bovine whey usually represents between 50 and 80 % of total production costs...
The ionic conductivity values of the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4) and ethylene glycol (EG) electrolytes in different concentrations and over a wide temperature range were determined. The results are discussed in terms of the interactions between the cations and anions of the ionic liquid and the organic solvent. The temperaturedependence of the ionic conductivity for BMI.BF4, as well as solutions containing BMI.BF4 and EG as electrolytes, in the temperature range of 248-358 K, obeys the Vogel-Tammann-Fulcher equation. The highest ionic conductivity was 42 mS cm-1 obtained with a solution of BMI.BF4 in EG at a molar fraction of 0.50 (358 K) due to the high ionic mobility. The critical micellar concentration (cmc) of 0.1 mol L-1 determined through the ionic conductivity indicates that BMI.BF4 behaves as a weak electrolyte above this value. The results obtained indicate that binary solutions based on BMI.BF4 and EG are appropriate for use in technological applications, such as capacitors.
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); The room temperature ionic liquid (IL) 1-butyl-3-methylimidazolium bis-(trifluorometanesulfonyl) imide BMIm[NTf2] was used as a novel medium for improvement of separation and quantization of 16 aromatic amines typically present as contaminants in consumer products and detected by HPLC coupled to an electrochemical detector. The aromatic amines, namely 4,4'-diaminodiphenylmethane, 4-chloroaniline, 2-methoxy-5-methyl-aniline, 3,3'-dimethylbenzidine, 2,4-diaminotoluidine, 2-chloro-4-nitroaniline, 4,4'-oxydianiline, aniline, 3,3'-dichlorobenzidine, benzidine, 4-aminobiphenyl, o-dianisidine, o-anisidine, o-toluidine, 4,4'-methylene-bis-2-chloroaniline and 2-naphthylamine are oxidized in methanol/BMIm[NTf2] at a potential around +0.68V to +0.93V vs. Ag/AgCl at a glassy carbon electrode, which is the base for their determination by HPLC/ED. Using the optimized conditions of methanol/BMIm[NTf2] 70: 30 (v/v) as mobile phase, flow-rate of 0.8 mL.min(-1), column CLC-ODS, E-ap = +1.0 V and T = 40 C analytical curves were constructed for each of the tested amines. Good linearity was obtained in the concentration range of 1.09 mg.L-1 to 217 mg.L-1...
Neste trabalho foi realizado o estudo de biorreduções utilizando microrganismos em sistema bifásico: água/líquido iônico. As reduções de (Z)-3-cloro-4-fenil-3-buten-2-ona, (E)-3-cloro-4-fenil-3-buten-2-ona e (Z)-3-bromo-4-fenil- 3-buten-2-ona a-haloenonas foram realizadas em meio aquoso e na presença de hexaflourofosfato de 1-butil-3-metilimidazólio, usando como biocatalisadores Saccharomyces cerevisiae CCT 3019, Pichia stipitis CCT 2617, Geotrichum candidum CCT 1205, Candida albicans CCT 0776, Rhodotorula glutinis CCT 0783 e Micrococcus luteus CCT 2283. Em geral, os resultados obtidos na redução das a-haloenonas catalisadas pelos microrganismos supracitados, em sistema bifásico: água/líquido iônico, foram melhores do que em meio aquoso, obtendo-se aumentos consideráveis nos excessos enantioméricos das correspondentes haloidrinas produzidas atingindo valores de até 97% ee. Esse fato pode ser devido as constantes de partição (K = 257 a 316) das a-haloenonas que indicam a presença da maior parte dessas enonas no líquido iônico, classificando essas reações como biocatálise extrativa in situ. A determinação da configuração das haloidrinas obtidas juntamente com o monitoramento dos produtos formados durante a biorredução...
O nosso trabalho envolveu a formação de íons N-acilimínios, gerados nas seguintes condições reacionais: sistema micelar SDS/água, na ausência de solvente e em líquido iônico. Os íons N-acilimínios foram originados dos carbamatos N-Boc-2-metoxipirrolidina e N-Boc-2-metoxipiperidina com o auxílio de um catalisador com acidez de Lewis ou de Bronsted. Para o sistema SDS/água foi empregado tanto HCI aquoso como tricloreto de índio em quantidades catalíticas. Os rendimentos obtidos da reação de a-amidoalquilação com a utilização de éter enólico de silício nesse meio foram moderados. No entanto, bons rendimentos foram obtidos utilizando-se N- Boc-2-metoxipirrolidina e compostos 1,3-dicarbonílicos, tendo como catalisador o tricloreto de índio. A reação de a-amidoalquilação utilizando éteres enólicos de silício e compostos 1,3-dicarbonílicos como nucleófilos, na ausencia de solvente e na presenca de tricloreto de índio como catalisador, gerou produtos em bons rendimentos. Nas reações envolvendo o líquido iônico (BMI.InCI4) bons rendimentos foram obtidos com o emprego de olefinas ativadas. Como uma aplicação do estudo foi realizado a síntese de um análogo da febrifugina visando a obtenção de um composto com melhor atividade antimalárica.; Our work involved the formation of N-acyliminium ions...
Neste trabalho, realizou-se o estudo da produção de etanol anidro por meio do processo de destilação extrativa, tomando por base uma usina sucroalcooleira que processa 15000 toneladas de cana por dia. Utilizou-se como ferramenta computacional o software Aspen Plus®, o qual possui recursos computacionais que permitem compatibilizar as simulações com processos reais. Nas simulações deste trabalho foram utilizados os solventes monoetilenoglicol e o líquido iônico cloreto de 1- metilimidazólio, assim como os modelos de estágios de equilíbrio e de não equilíbrio. Os resultados da análise de sensibilidade para utilização do solvente monoetilenoglicol na coluna de destilação extrativa, em alta temperatura, apresentou economia de até 0,04 kg de vapor/litro de etanol anidro e de 0,37 kg de vapor/litro de etanol anidro ao alimentar o etanol hidratado produzido em colunas de destilação diretamente em colunas extrativas, sem estocagem e sem necessidade de aquecimento deste etanol hidratado. As colunas de destilação extrativa e de recuperação, do processo de destilação extrativa, apresentaram eficiências globais de 71,68% e 64,25%, respectivamente, segundo a correlação de O¿Connell. Foi realizado o estudo do consumo energético em colunas que operavam com pressões de 1...
Densities of the aqueous solutions of ionic liquid 1-butyl-3 metilmidazolium chloride [Bmim+][Cl-] were determined using a vibrating tube densitometer Anton Paar DMA 5000 at a temperature range between (283.15 - 218.15) K. The apparent molar volumes of aqueous chloride1-butyl-3-methylimidazolium were calculated and adjusted to the Pitzer ion interaction model, obtaining the limiting apparent molar volumes and Pitzer volumetric parameters at temperatures of 283.15, 288.15, 293.15, 298.15, 303.15, 313.15 and 318.15K, proving that this model adequately represents the experimental volumetric data below an ionic strength of 0.6018 mol / kg. Finally the limiting apparent molar expansibilities were calculated from the limiting apparent molar volumes at various temperatures and the results are discussed in terms of the interactions occurring in solution.