RESUMO
Reported herein is the multi-scale supramolecular assembly (MSSA) process along with redox reactions driven by supramolecular interactions coupled with the spontaneous Marangoni effect in ionic liquid (IL)-based extraction systems. The black powder, the single sphere with a black exterior, and the single colorless sphere were formed step by step at the interface when an aqueous solution of KMnO4 was mixed with the IL phase 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (C2OHmimNTf2) bearing octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO). The mechanism of the whole process was studied systematically. The phenomena were related closely to the change in the valence state of Mn. The MnO4- ion could be reduced quickly to δ-MnO2 and further to Mn2+ slowly by the hydroxyl-functionalized IL C2OHmimNTf2. Based on Mn2+, Mn(CMPO)32+, elementary building blocks (EBBs), and [EBB]n clusters were generated step by step. The [EBB]n clusters with the large enough size that were transferred to the interface, together with the remaining δ-MnO2, assembled into the single sphere with a black exterior, driven by supramolecular interactions coupled with the spontaneous Marangoni effect. When the remaining δ-MnO2 was used up, the mixed single sphere turned completely colorless. It was found that the reaction site of C2OHmim+ with Mn(VII) and Mn(IV) was distributed mainly at the side chain with a hydroxyl group. The MSSA process presents unique spontaneous phase changes. This work paves the way for the practical application of the MSSA-based separation method developed recently. The process also provides a convenient way to observe in situ and characterize directly the continuous Marangoni effect.
RESUMO
Herein, we report a four-step mechanism for the spontaneous multi-scale supramolecular assembly (MSSA) process in a two-phase system concerning an ionic liquid (IL). The complex ions, elementary building blocks (EBBs), [EBB]n clusters and macroscopic assembly (MA) sphere are formed step by step. The porous large-sized [EBB]n clusters in the glassy state can hardly stay in the IL phase and they transfer to the IL-water interface due to both electroneutrality and amphiphilicity. Then, the clusters undergo random collision in the interface driven by the Marangoni effect and capillary force thereafter. Finally, a single MA sphere can be formed owing to supramolecular interactions. To our knowledge, this is the first example realizing spontaneous whole-process supramolecular assembly covering microscopic, mesoscopic and macroscopic scales in extraction systems. The concept of multi-scale selectivity (MSS) is therefore suggested and its mechanism is revealed. The selective separation and solidification of metal ions can be realized in a MSSA-based extraction system depending on MSS. In addition, insights into the physicochemical characteristics of ILs from microscopic, mesoscopic to macroscopic scales are provided, and especially, the solvation effect of ILs on the large-sized clusters leading to the phase-splitting is examined. It is quite important that the polarization of uranyl in its complex, the growing of uranyl clusters in an IL as well as the glassy material of uranyl are investigated systematically on the basis of both experiment and theoretical calculations in this work.
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The coordination of actinides and lanthanides, as well as strontium and cesium with graphdiyne (GDY) was studied experimentally and theoretically. On the basis of experimental results and/or theoretical calculations, it was suggested that Th4+ , Pu4+ , Am3+ , Cm3+ , and Cs+ exist in single-ion states on the special triangular structure of GDY with various coordination patterns, wherein GDY itself is deformed in different ways. Both experiment and theoretical calculations strongly indicate that UO2 2+ , La3+ , Eu3+ , Tm3+ and Sr2+ are not adsorbed by GDY at all. The distinguished adsorption behaviors of GDY afford an important strategy for highly selective separation of actinides and lanthanides, Th4+ and UO2 2+ , and Cs+ and Sr2+ , in the nuclear fuel cycle. Also, the present work sheds light on an approach to explore the unique functions and physicochemical properties of actinides in single-ion states.
RESUMO
The multi-scale supramolecular assembly (MSSA)-based extraction strategy with hydroxyl-functionalized ionic liquid (IL) is promising in the separation of metal ions from radioactive environments for which a comprehensive understanding toward the radiation stability of the MSSA system is necessary. Herein, we report on the analyses of the radiation stability of MSSA in extraction, especially the adopted ILs 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (IL-1) and 1-(2-hydroxyethyl)-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide (IL-2), by UV-vis, 1H NMR, and ESI-HRMS. It was found that the macroscopic assembly (MA) sphere could not be formed after γ irradiation on the extraction system with IL-1. On the contrary, the trisubstituted IL-2 instead of the disubstituted IL-1 remarkably improved the radiation stability of the MSSA system to guarantee the formation of the MA sphere. The high extraction efficiency could be kept, and the mechanism of such an improvement was revealed.
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We herein report a ß-cyclodextrin-based secondary assembly (ß-CD SA) obtained from an aqueous solution. It was found that the addition of a very small amount of organic molecule 2-phenyl-5-(4-diphenylyl) 1,3,4-oxadiazole (PBD) into an aqueous solution of 10 mM ß-CD led to the formation of a micrometer-sized rodlike SA, which made the mixture turbid immediately. After careful characterization, the structure and the formation mechanism of the ß-CD SA were suggested. PBD first induces ß-CDs to form rigid nanotubes through head-to-head or tail-to-tail routes. Using the "solid" nanotubes as recrystallization centers, other ß-CDs assembled to channel in the c axis direction and hexagonally aligned in the b axis direction, leading to the formation of a ß-CD SA. In the ß-CD SA, most of the ß-CDs were not occupied by PBD. In the course of formation , intermolecular hydrogen-bonding plays a prominent role. The results reported herein would be helpful in constructing cyclodextrin-based architectures in water.
RESUMO
Xuezhikang capsule (ethanol extract of red yeast rice) which produced by Beijing WBL Peking University Biotech Co., Ltd., is a traditional Chinese medication with 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibiting activity. Clinical trials indicated that Xuezhikang with lipid-lowering action could reduce the risk of cardiac events and total mortality of Chinese coronary heart disease patients. To exactly explain the clinical features of Xuezhikang, we undertook a complete study of the chemical constituents of Xuezhikang. This study resulted in the isolation of a new monacolin analogue, named alpha, beta-dehydromonacolin L (1), along with two known compounds: monacolin L (2) and 3-(2, 6-dimethyl-1, 2, 4a, 5, 6, 7, 8, 8a-octahydronaphthalen-1-yl)propanoic acid (3). The chemical structures were determined by extensive 1D and 2D NMR and MS spectroscopic analysis.
Assuntos
Medicamentos de Ervas Chinesas/química , Naftalenos/isolamento & purificação , Estrutura Molecular , Naftalenos/química , Propionatos/química , Propionatos/isolamento & purificaçãoRESUMO
We report herein the interaction of three ionic liquids, i.e., 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (11), 1-hexyl-2,3-dimethylimidazolium chloride (16), and 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (17), with beta-cyclodextrin (beta-CD). For 11 and 16, the 1:1 inclusion complexes were determined and the association constants were estimated through a competitive fluorescence method, conductivity, and (19)F NMR measurements. It was confirmed that the alkyl side chain on the imidazolium ring but not the imidazolium ring itself entered into the cavity of beta-CD. According to the association constants, the sequence of interaction strength of some ILs with beta-CD was obtained. We also found that the cation and the anion in 17 exhibited strong interactions with beta-CD simultaneously. Furthermore, a general interaction pattern of an IL with beta-CD was suggested.
RESUMO
A novel and efficient uranium capture strategy based on self-assembly is developed in an ionic liquid extraction system, by which the one-step separation and solidification of uranium are realized. This not only provides a promising method for separating metal ions but also promotes the development of a supramolecular assembly both in mechanism and application.
RESUMO
Cyclodextrin-based aggregates have been widely investigated with microscopies such as STM, AFM, SEM, TEM, and fluorescent microscopy to obtain the direct morphology and structure of samples. In the present review, we discuss various types of cyclodextrin aggregates, that is, native and modified cyclodextrins, inclusion complexes and their aggregates of cyclodextrins, cyclodextrin rotaxanes and polyrotaxanes, cyclodextrin nanotubes and their secondary assembly, and other high-order aggregates of cyclodextrins. Especially, we focus on the use of microscopy to characterize above aggregates. The application of modern microscopy tools promotes the investigation on cyclodextrins.
Assuntos
Ciclodextrinas/química , Microscopia de Força Atômica , Microscopia Eletrônica/métodos , Microscopia de Fluorescência , Modelos Moleculares , Nanotecnologia , Nanotubos , Rotaxanos/químicaRESUMO
A local ordered structure constructed from solid Cu(2)O nanocubes was obtained by the radiolytic reduction of Cu(NO(3))(2) in a water-in-oil (W/O) microemulsion composed of Triton X-100, n-hexanol, cyclohexane, and water in the presence of ethylene glycol (EG). However, when Triton X-100 was replaced with Brij 56 in the microemulsion, hollow Cu(2)O nanocubes were synthesized. The addition of toluene into the Brij 56 system could decrease the ratio of hollow nanocubes. It was suggested that the balance between the reduction rate of Cu(2+) depending on the yield of hydrated electrons (e(aq)(-)) and the escape rate of the mixed solvent determined their final morphologies. The presence of EG influenced the rigidity of the interface of the microemulsion and thus the above balance, which resulted in the different morphologies of Cu(2)O nanoparticles in the Brij 56-based microemulsion.
RESUMO
In the water-in-oil (W/O) microemulsions based on nonionic surfactants, i.e., Brij 30, Brij 56, or Triton X-100, the omega value (molar ratio of water to surfactant), anion, and surfactant could remarkably affect the radiolytic reduction of Cu2+ and the morphologies of the reduction products simultaneously. The addition of toluene or naphthalene could transform the reduction products from copper to cuprous oxide in the Brij 56-based microemulsion, and the efficiency of naphthalene was obviously higher than that of toluene. After the effects of pH value and cosurfactant were excluded, it could be concluded that the effects of the omega value, the anion, and the structure of the surfactant on the yield of hydrated electrons (eaq-) play a key role in the radiolytic reduction of Cu2+. It was also suggested that the morphology of the reduction product may be controlled by the yield of eaq-.
RESUMO
Cuprous oxide nanocubes were successfully prepared in w/o microemulsions by gamma-irradiation in the presence of ethylene glycol (EG). Absorption spectrum, XRD, TEM, HRTEM and SEM were used to characterize the as-prepared nanoparticles. The characteristic peak of Cu2O of absorption spectra of the irradiated microemulsions red-shifts apparently with the EG increasing, showing that the as-prepared Cu2O particle size becomes larger. TEM images verify this point and indicate that Cu2O nanoparticles become uniform with the increase of EG. The results indicated that EG played an important role in the structures of cuprous oxide nanoprticles. Firstly, EG increased the viscosity of water-pools of microemulsions which affected the reactivity of hydrated electrons and finally influenced the reduction of Cu2+ and the precipitation of Cu2O. Secondly, EG reduced the rigidity of the interface of microemulsions and enhanced the mass exchange among water pools which impacted the nucleation and precipitation of Cu2O. Thirdly, EG adsorbed certain crystal faces of Cu2O and influenced the final morphology of Cu2O.
RESUMO
In this work, we report the observation on the self-assembly of beta-CD nanotube induced by 2-phenyl-5-(4-diphenylyl)1,3,4-oxadiazole (PBD) molecule with fluorescence microscopy and transmission electron microscopy (TEM). Micrometer-sized rodlike structure is formed by the secondary assembly of cyclodextrin nanotube driven by the inter-nanotubular hydrogen bonding. The effects of pH value, urea, DMF and NaCl on the formation of the rodlike structure are investigated. Dynamic light scattering (DLS) is applied to further characterize the formation of the PBD-beta-CD nanotube. The effect of light scattering on the measurement of fluorescence anisotropy of PBD in the aqueous solutions of beta-CD is corrected. A new mechanism of cyclodextrin aggregation is proposed for this system.
Assuntos
Nanoestruturas/química , Nanotubos/química , beta-Ciclodextrinas/química , Microscopia Eletrônica de Transmissão/métodos , Microscopia de Fluorescência/métodos , Estrutura Molecular , Tamanho da Partícula , Espalhamento de Radiação , Sensibilidade e Especificidade , Soluções/química , Propriedades de SuperfícieRESUMO
Dynamic light scattering (DLS) measurement provides an effective way to investigate the formation of nanotube of gamma-cyclodextrin (gamma-CD) induced by N,N'-diphenylbenzidine (DPB) in water. With the combination of steady-state fluorescence and fluorescence anisotropy experiments, it was found that for alpha- and beta-CD, only 1:2 (guest:host) inclusion complexes were formed and for gamma-CD, cyclodextrin nanotube was formed involving 16 gamma-CD units at maximum. The pH effect studies with both DLS and fluorescence anisotropy measurements indicated that the hydrogen bonding between neighboring CDs was necessary to the formation of cyclodextrin nanotube. In the temperature experiment, we found that the nanotube of DPB-gamma-CD could exist stably at relatively high temperatures and the transition point for structural collapse was estimated to be around 54 degrees C. The aggregation states of both gamma-CD itself and DPB-gamma-CD nanotube were observed with TEM.
RESUMO
The solubility of water in the hydrophobic ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) increases significantly in the presence of HNO3. [C2mim][NTf2] is completely miscible with HNO3 but immiscible with water. The triangular phase diagram of the ternary system [C2mim][NTf2]-HNO3-H2O was determined at 300.1 K. The homogeneous [C2mim][NTf2]-HNO3-H2O phase is thermodynamically stable, while it can be separated into two phases with an increase of water content. Experiments (electrospray ionization mass spectrometry, Fourier transform infrared spectrometry, and (1)H-nuclear magnetic resonance spectrometry) and molecular dynamics simulations were carried out to investigate the interaction between [C2mim][NTf2], HNO3, and water in the homogeneous phase. It was found that NO3(-) ions interact with both C2mim(+) and water via H-bonding and act as a "bridge" to induce a large amount of water to be dissolved in the hydrophobic IL phase. This confirms that the complexes [C2mim-NTf2-C2mim](+) and [NTf2-C2mim-NTf2](-) exist in the homogeneous [C2mim][NTf2]-HNO3-H2O system at the concentration of HNO3 up to 27.01 wt % and of water as high as 20.74 wt %.
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We report herein the size-controlled preparation of monodispersed cuprous oxide octahedron nanocrystals smaller than 100 nm. The method is based on the reduction of copper nitrate in Triton X-100 water-in-oil (w/o) microemulsions by gamma-irradiation. The average edge length of the octahedron-shaped nanocrystals varies from 45 to 95 nm as a function of the dose rate. The quantum confinement effect was illustrated by the blueshift in the optical absorption. In addition, the growth process was also traced by absorption spectra.
RESUMO
The interactions between a fluorescent molecular probe, i. e., [2-(p-hexylamino) phenyl-3, 3-dimethyl-5-ethoxycarbonyl-3H-indole] methyldioctadecylammonium iodide (A) and Triton X-100/heptane/hexanol/water reverse micelle have been investigated by spectroscopy. Micropolarity of the environment, fluorescence anisotropy parameter and the pH effect of A in Triton X-100 reverse micelle were determined. Furthermore, the state of water in reverse micellar systems was studied by FTIR. According to the above experimental results, some information on the structure of Triton X-100 reverse micelle was obtained and the probable site of A in this system was discussed.
Assuntos
Corantes Fluorescentes/química , Indóis/química , Micelas , Octoxinol/química , Polarização de Fluorescência , Cinética , Estrutura Molecular , Espectrometria de Fluorescência , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
The binding between two surface-active substituted 3H-indole fluorescence probes, i. e., iodo-dihexadecyl methyl-2-(p-dodecyl amino phenyl)-3, 3-dimethyl-5-carboethoxy-3H-indole ammonium and iodo-dimethyloctadecyl-2-(p-dodecyl amino phenyl)-3,3-dimethyl-5-carboethoxy-3H-indole ammonium, and bovine serum albumin (BSA) in aqueous solution was studied using fluorescence. The binding constant and binding site number of molecule 1 and molecule 2 with BSA were obtained. It was confirmed that electrostatic interaction is the primary driving force for the combination of BSA with molecule 1 or molecule 2. According to the Förster resonance energy transfer theory, the distances between molecule 1, molecule 2 and tryptophan of BSA were calculated to be 2.90 nm and 4.02 nm, respectively.
Assuntos
Corantes Fluorescentes/química , Soroalbumina Bovina/química , Algoritmos , Animais , Bovinos , Corantes Fluorescentes/metabolismo , Indóis/química , Indóis/metabolismo , Cinética , Estrutura Molecular , Ligação Proteica , Soroalbumina Bovina/metabolismo , Espectrometria de Fluorescência , Eletricidade EstáticaRESUMO
A substituted 3H-indole quaternary ammonium molecule was designed and synthesized using hexamethylphosphoramide (HMPA) as a solvent. The products were purified and characterized by IR, 1H-NMR, MS and elemental analysis. The binding reaction of this compound with bovine serum albumin (BSA) in aqueous solution was studied using fluorescence. Their binding constant is Ka = 1.995 x 10(5) dm3 x mol(-1) and the binding site number is n = 1.12. It is confirmed that the combination is a single static quenching process.
Assuntos
Fluorescência , Indóis/química , Compostos de Amônio Quaternário/química , Soroalbumina Bovina/química , Algoritmos , Animais , Sítios de Ligação , Bovinos , Hempa/química , Cinética , Modelos Químicos , Estrutura Molecular , Ligação Proteica , Compostos de Amônio Quaternário/síntese química , Compostos de Amônio Quaternário/metabolismo , Soroalbumina Bovina/metabolismo , Espectrometria de Fluorescência , Água/químicaRESUMO
Steady-state fluorescence and anisotropy measurements have been used to investigate the interaction of 2,2'-biquinoline (BQ) and 1,1'-(methylenedi-1,4-phenylene)bismaleimide (MDP-BMI) with alpha-, beta-, and gamma-cyclodextrins (CDs). It was found that the reaction patterns between fluorescence molecules and CDs are remarkably different. They can form a simple inclusion complex with alpha-CD, while nanotubes can be formed in the presence of gamma-CD. Moreover, MDP-BMI can form nanotube with beta-CD at higher concentration.