Reverse micelles

In this work, for the first time, the electrochemical behavior of hydroquinone (H 2 Q) by linear voltammetry in aqueous reverse micelles (RMs) of sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (AOT)/n-heptane, as well in homogenous media at different pH values, were studied. The choice of this molecular probe is because of its electrochemical response in water, strongly depend on the pH value thus, our goal is to know more about an intriguing issue in the soft matter field, what is the pH value for water encapsulated in the water pool of AOT RMs. Our work will demonstrate that the interfacial apparent pH value of AOT RMs is not strongly acidic as some of the literature works claim, but it is around a pH value of 6.7. Thus, through the electrochemistry technique, the present work reinforces the idea that the concept of is strongly dependent on the waterinterface interactions and the molecular probe location.

Los anfifilos ("surfactantes") cataniónicos, son la clase de surfactantes que resultan de la mezcla equimolar de algún surfactante aniónico y otro catiónico, donde se han removido completamente los contraiones. En nuestro grupo, se ha sintetizado por primera vez, el surfactante cataniónico: 1,4-bis-2etilhexilsulfosuccinato de bencil-n-hexadecildimetilamonio (BHD-AOT), el cual tiene gran utilidad dentro del campo que abarca la "materia blanda". Esto es así porque puede formar micelas inversas o vesículas unilaminares grandes, de manera espontánea, dependiendo del solvente utilizado. Las micelas inversas son agregados supramoleculares que se forman al disolver surfactantes en solventes de baja polaridad. En ellos, la parte polar se ubica hacia el interior mientras que las colas hidrocarbonadas se brought to you by CORE View metadata, citation and similar papers at core.ac.uk

The effect of the composition of the nonpolar organic media on the properties of sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles (RMs) at a fixed temperature were investigated. To monitor interfacial micropolarity and sequestrated water structure in n-heptane:benzene/AOT/ water RMs, the solvatochromic behavior of coumarin 343 (C343) as an absorption and emission probe was studied, and the size of the droplets was measured by dynamic light scattering (DLS). The DLS results confirm the formation of the nheptane:benzene/AOT/water RMs at every n-heptane mole fraction investigated. The data show that as the n-heptane content increases, the interdroplet attractive interactions and the droplet size both increase. With C343 spectroscopy, we determined the "operational" critical micellar concentration, the interfacial micropolarity of the RMs, the hydrogen-bond ability of the media, and the sequestrated water structure in every RM system studied. To verify the modulation of the interdroplet interactions by the external solvent, we have used a well-known synthetic method to create gold nanopar

Resumen Los anfifilos ("surfactantes") cataniónicos, son la clase de surfactantes que resultan de la mezcla equimolar de algún surfactante aniónico y otro catiónico, donde se han removido completamente los contraiones. En nuestro grupo, se ha sintetizado por primera vez, el surfactante cataniónico: 1,4-bis-2etilhexilsulfosuccinato de bencil-n-hexadecildimetilamonio (BHD-AOT), el cual tiene gran utilidad dentro del campo que abarca la "materia blanda". Esto es así porque puede formar micelas inversas o vesículas unilaminares grandes, de manera espontánea, dependiendo del solvente utilizado. Las micelas inversas son agregados supramoleculares que se forman al disolver surfactantes en solventes de baja polaridad. En ellos, la parte polar se ubica hacia el interior mientras que las colas hidrocarbonadas se brought to you by CORE View metadata, citation and similar papers at core.ac.uk

Herein we describe the synthesis of gold nanoparticles (Au-NPs) in presence of sulphonated imidazolium salts [1,3-bis(2,6-diisopropyl-4-sodiumsulfonatophenyl)imidazolium (L1), 1-mesityl-3-(3-sulfonatopropyl)imidazolium (L2) and 1-(3-sulfonatopropyl)imidazolium (L3)] in water and in a confinement environment created by reverse micelles (RMs). The Au-NPs were characterized-with an excellent agreement between different techniques-by UV-vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential. In homogeneous media, the Au-NPs interact with the imidazolium ring and the sulphonate groups were directed away from the NPs' surface. This fact is responsible for the Au-NPs' stability-over three months-in water. Based on the obtained zeta potential values we assume the degree of coverage of the Au-NPs by the imidazolium salts. In n-heptane/sodium 1,4-bis (2-ethylhexyl) sulfosuccinate (AOT)/water RMs, the Au-NPs formed in presence of sul...

Intact cells from Pseudomonas aeruginosa strain L10 containing amidase were used as biocatalysts both free and immobilized in a reverse micellar system. The apparent kinetic constants for the transamidation reaction in hydroxamic acids synthesis, were determined using substrates such as aliphatic, amino acid and aromatic amides and esters, in both media. In reverse micelles, K-m values decreased 2-7 fold relatively to the free biocatalyst using as substrates acetamide, acrylamide, propionamide and glycinamide ethyl ester. We have concluded that overall the affinity of the biocatalyst to each substrate increases when reactions are performed in the reversed micellar system as opposed to the buffer system. The immobilized biocatalyst in general, exhibits higher stability and faster rates of reactions at lower substrates concentration relatively to the free form, which is advantageous. Additionally, the immobilization revealed to be suitable for obtaining the highest yields of hydroxamic acids derivatives, in some cases higher than 80%.

Highlights  The photophysics of thionine was investigated in reverse micelles (RMs) of AOT and BHDC.  The dye molecules remain at the interface sensing a less polar medium in both RMs.  Apparent triplet quenching rate constants by tri-ethanolamine (TEOA) and tri-butylamine (TBA) were determined in RMs.  Triplet quenching by TEOA leads to a non-exponential decay in the RMs.  The triplet state is efficiently quenched by hydrophilic TEOA.

This work shows the feasibility of using the photoinitiating system composed by the xanthene dye Eosin-Y and triethanolamine on the polymerization of acrylamide in benzyl-hexadecyl-dimethylammonium chloride (BHDC) reverse micelles. Molecular weights of polyacrylamide (MW PAA) in the order of 10 5 and conversions up to 90 % are obtained. The size of the latex particles is in the range of the nanometers (d<50 nm). The effect of water content and concentrations of surfactant, amine, dye, and monomer on the particle size and MW PAA are examined. Only the amine and monomer concentrations affect the MW PAA. These results are interpreted on the basis of an exchange mechanism between micelles. Practically no effect on hydrodynamic diameters is observed when the value of MW PAA is doubled. This is ascribed to a supercoiled structure of PAA inside of micelles. Our results also suggest that the polymer properties can be modulated by appropriate combination of the dye/surfactant electrical charges.

We report the kinetic behavior of the enzyme aldehyde oxidoreductase (AOR) from the sulfate reducing bacterium Desulfovibrio gigas (Dg) encapsulated in reverse micelles of sodium bis-(2-ethylhexyl) sulfosuccinate in isooctane using benzaldehyde, octaldehyde, and decylaldehyde as substrates. Dg AOR is a 200-kDa homodimeric protein that catalyzes the conversion of aldehydes to carboxylic acids. Ultrasedimentation analysis of Dg AOR-containing micelles showed the presence of 100-kDa molecular weight species, confirming that the Dg AOR subunits can be dissociated. UV-visible spectra of encapsulated Dg AOR are indistinguishable from the enzyme spectrum in solution, suggesting that both protein fold and metal cofactor are kept intact upon encapsulation. The catalytic constant (k cat) profile as a function of the micelle size W 0 (W 0 ¼ ½H 2 O/[AOT]) using benzaldehyde as substrate showed two bell-shaped activity peaks at W 0 ¼ 20 and 26. Furthermore, enzymatic activity for octaldehyde and decylaldehyde was detected only in reverse micelles. Like for the benzaldehyde kinetics, two peaks with both similar k cat values and W 0 positions were obtained. EPR studies using spin-labeled reverse micelles indicated that octaldehyde and benzaldehyde are intercalated in the micelle membrane. This suggests that, though Dg AOR is found in the cytoplasm of bacterial cells, the enzyme may catalyze the reaction of substrates incorporated into a cell membrane.

Nitric acid extraction by tri-n-butyl phosphate (TBP) in dodecane is investigated by molecular dynamics (MD) simulation, for different concentrations of TBP in the range 0.1 M to 2 M with aqueous phase HNO 3 concentration of 1 M, 2 M and 3 M. The MD studies are carried out considering dissociated as well as molecular forms of HNO 3. The simulations showed formation of a third phase consisting of TBP, HNO 3 and water which is in agreement with reported experimental results. HNO 3 , in dissociated form, shows formation of NO 3 − and H 3 O + pockets in the third phase while HNO 3 in molecular form remains dispersed in the third phase without such specific formations. The impact of concentrations of the acid and TBP on the third phase formation, reverse micelles of TBP in dodecane and NO 3 − and H 3 O + pockets in the third phase, have been demonstrated. The estimated diffusion coefficient values of TBP and dodecane match well with the reported literature values.

Solution based synthesis of nanoparticles does not yield monodisperse particles, but rather a well-defined particle size distribution (PSD). There is currently no simple means to anticipate or model these size distributions, which critically affect the properties of the resulting nanomaterials. We simulate the temporal evolution of the PSD in the framework of a nucleation and growth model, with the critical postulate that the coagulation efficiency between two nanoparticles is quantitatively determined by the known, interparticle potential energy. Our simulation based on this ansatz, not only a-priori predicts experimentally obtained complete PSDs of uncoated or coated (with polyacrylic acid or dextran) iron oxide nanoparticles, but also accurately captures the influence of surface coverage of a coating agent on the resulting PSD.

Herein, a minimal model for the common case of W/O solubilization of badly soluble compounds present in an excess phase by reverse micellar aggregates in chemical equilibrium with its single compounds is introduced. A simple model of such liquid-liquid extractions is crucial for obtaining predictive parameter for the modelling of nuclear waste management and hydrometallurgic recycling strategies. The standard Gibbs free energy of aggregation and the concentration of the corresponding aggregate is calculated within a multiple-equilibria approach for a set of aggregate compositions of solute and amphiphilic extractant molecules. This minimal model provides potential surfaces estimating the stability of different aggregate compositions with 6.2 kJ mol À1 as a generalized bending constant. The complete concentrations of free and aggregated extractant species as well as the favored aggregation numbers, the polydispersity, the activity of the organic solvent, and the critical concentrations are captured by this thermodynamic model. An increase of the apparent critical micelle concentration for an increasing solute content in the aqueous phase is detected by this method.

Fe/Au nanoparticles have been chemically synthesized through a reverse micelle reaction and investigated by both conventional and synchrotron based x-ray diffraction and by magnetic and Mössbauer spectral studies. The powder x-ray diffraction patterns reveal both the presence of crystalline α-iron and gold and the absence of any crystalline iron oxides or other crystalline products. First-order reversal curves, along with the major hysteresis loops of the Fe/Au nanoparticles have been measured as a function of time in order to investigate the evolution of their magnetic properties. The iron-57 Mössbauer spectra of both uncoated iron nanoparticles and the Fe/Au nanoparticles have been measured at 78 and 295 K and indicate that two major iron containing components are present, namely the expected α-iron and the unexpected amorphous Fe 1-x B x alloy; several poorly crystallized ordered iron(III) oxide components as well as paramagnetic iron(II) and iron(III) components are also observed. These results indicate that the Fe-core/Aushell nanoparticles synthesized through reverse micelles are far more complex that had been believed.

The present paper aims to study the proprieties of water confined in water/AOT/ isooctane reverse micelles from their refractive indices at 298.5 K. The refractive indices of the microemulsions were investigated at increasing water concentration and at different micellar volume fractions, U d. The refractive index of micellar water was deduced for a large water to AOT molar ratio, W 0. The refractive index of interfacial water was also calculated. Then, the molar faction of interfacial water, a, was deduced for different W 0 values and compared with those measured by NMR as reported in the literature. The results show qualitative agreement. Finally, the average aggregation number, n agg , the area per surfactant headgroup, r, as well as the interfacial thickness, d i , of the reverse micelles were determined for the W 0 values studied. The values of these structural parameters also show good qualitative agreement with NMR and small angle X-ray scattering data reported in the literature. Thus, the refractive index method can be a cheap and fast alternative for these two methods.

Discrete water domains in hydrophobic environment find relevance in aerosols, oil refinery, the human body, etc. The interfacial microstructure plays a crucial role in the stability of such water domains. Over the decades, the amphiphile-induced electrostatic interaction is considered to be the major stabilizing factor operating at these interfaces. Here we take the representative water/AOT/oil microemulsion to show that creating a strong Hbonding network through suitable additive, such as protic ionic liquid (IL) at the interface, helps both the growth and stability of water domains in the hydrophobic phase. On the other hand, common electrolytes and aprotic ILs fail to replicate such behavior as seen by Raman, Fourier transform infrared spectroscopy, dynamic light scattering (DLS), and electron microscopy measurements. Experimental results are further supported by the all-atomic molecular dynamics (MD) simulations that showed extended Hbonding mediated by the protic IL cations that were localized at the interface. High temperature DLS and rheology studies have shown greater thermal stability and mechanical strengths of our biocompatible microemulsions, which have potential to become suitable templates for in situ synthesis of nanoparticle and various organic compounds.

Owing to superior surface‐activity and versatility in functionalization compared to conventional surfactants, surface‐active ionic liquids (SAILs) gained immense interest in recent years. Toxicity and biodegradation remain central issues while dealing with the SAILs and thus, the quest for synthesis of greener SAILs is increasing day by day. Keeping in view of the importance of SAIL&#39;s performance, we undertook the present study for the formulation of reverse micelles (RMs) using biodegradable L‐proline propyl ester lauryl sulfate ([ProC3][LS]) in cyclohexane (Cy). The formation of RMs was confirmed from the phase behavior and dynamic light scattering (DLS) studies. Fourier‐transform infrared spectroscopy (FTIR) study revealed the solvation of anionic head group through H‐bonding by added water. An increased micropolarity and reduced microviscosity were evidenced inside the RM droplets as a function of hydration level. Finally, the encapsulation of BSA protein in RMs was investig...

Resumen Los anfifilos ("surfactantes") cataniónicos, son la clase de surfactantes que resultan de la mezcla equimolar de algún surfactante aniónico y otro catiónico, donde se han removido completamente los contraiones. En nuestro grupo, se ha sintetizado por primera vez, el surfactante cataniónico: 1,4-bis-2etilhexilsulfosuccinato de bencil-n-hexadecildimetilamonio (BHD-AOT), el cual tiene gran utilidad dentro del campo que abarca la "materia blanda". Esto es así porque puede formar micelas inversas o vesículas unilaminares grandes, de manera espontánea, dependiendo del solvente utilizado. Las micelas inversas son agregados supramoleculares que se forman al disolver surfactantes en solventes de baja polaridad. En ellos, la parte polar se ubica hacia el interior mientras que las colas hidrocarbonadas se

Chitosan microparticles were synthesized by crosslinking chitosan and glycidyl trimethylammonium chloride modified chitosan inside the reverse micelles of Span and Tween 80. The particles were of uniform size with the average diameter of 10 μm. The particles swelled almost twice the original size in 20 min when dispersed in a buffer solution of pH 7.4. The feasibility of chitosan microparticles as drug sequestrant was tested using propafenone as the model drug. The particles sequestered free propafenone from a buffer solution of pH 7.4. In 20 min unmodified chitosan and modified chitosan microparticles sequestered 53% and 51.5% of the free drug respectively. The amount of drug sequestered increased with increase in the initial free drug concentration. The presence of normal saline also improved propafenone sequestration.

The interior water pool of aerosol OT (AOT) reverse micelles tends toward bulk water properties as the micelle size increases. Thus, deviations from bulk water behavior in large reverse micelles are less expected than in small reverse micelles. Probing the interior water pool of AOT reverse micelles with a highly charged decavanadate (V10) oligomer using 51 V NMR spectroscopy shows distinct changes in solute environment. For example, when an acidic stock solution of protonated V10 is placed in a reverse micelle, the 51 V chemical shifts show that the V10 is deprotonated consistent with a decreased proton concentration in the intramicellar water pool. Results indicate that a proton gradient exists inside the reverse micelles, leaving the interior neutral while the interfacial region is acidic.

The reverse micelle (RM) media are very good as nanoreactors because they can create a unique microenvironment for carrying out a variety of chemical and biochemical reactions. The aim of the present work is to determine the influence of different water-dimethyl sulfoxide (DMSO) mixtures encapsulated in 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/n-heptane RMs on the enzymatic hydrolysis of N-benzoyl-L-tyrosine p-nitroanilide (Bz-Try-pNA) by αchymotrypsin (α-CT). The reaction was first studied in homogeneous media at different DMSO-water mixture compositions and in DMSO-water/AOT/n-heptane RMs. The hydrolysis rates of Bz-Try-pNA catalyzed by α-CT were determined by UV−vis spectroscopy. The reaction follows the Michaelis-Menten mechanism and the kinetic parameters: k cat , K M , and k cat /K M were evaluated under different conditions. In this homogeneous media, DMSO plays an important role in the solubilization process of the peptide which is almost insoluble in water, but it has a tremendous impact on the inactivation of α-CT. It is shown that the enzyme dissolved in a 20% molar ratio of the DMSO-water mixture does not present enzymatic activity. Dynamic light scattering has been used to assess the formation of DMSO-water/AOT/heptane RMs at different DMSO compositions. The results also show that there is preferential solvation of the AOT RM interface by water molecules. To test the use of these RMs as nanoreactors, the kinetic parameters for the enzymatic reaction in these systems have been evaluated. The parameters were determined at fixed W S {W S = ([water] + [DMSO])/[AOT] = 20} at different DMSO-water compositions. The results show that the Michaelis−Menten mechanism is valid for α-CT in all the RM systems studied and that the reaction takes place at the RM interface. Surprisingly, it was observed that the enzyme encapsulated by the RMs show catalytic effects with similar k cat /K M values at any DMSO composition investigated, which evidence that DMSO molecules are localized far from the RM interface.

In this work, we have investigated the behavior of the cationic hemicyanine trans-4-[4-(dimethylamino)styryl]-N-methylpyridinium iodide (HC) in benzene/benzyl-n-hexadecyl dimethylammonium chloride (BHDC)/ water reverse micelle media using absorption and emission spectroscopy in addition to the steady-state and time-resolved fluorescence emission techniques and compare the results to those obtained in benzene/sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/water reverse micelle media (Moyano, F.; et al. J. Phys. Chem. B 2009, 113, 4284.) in order to gain more insight about reverse micelle interface properties. Our results show that HC spectroscopic behavior is completely different when dissolved in AOT or in BHDC reverse micelle media. While the dye experiences an intramolecular charge-transfer process upon excitation in the former media, in BHDC, this process is inhibited because of the cationic nature of the surfactant. Interestingly, we also show that the water properties are different for water molecules sequestrated inside of an anionic and cationic reverse micelle system. This come out because the water molecules entrapped inside of the BHDC reverse micelle media appear to be non-electron-donating because of its interaction with the cationic surfactant polar head group. On the other hand, the water molecules sequestrated inside of the AOT reverse micelle systems show its electron-donor ability enhanced in comparison with its water bulk structure. These results could also explain the lack of nucleophilicity shown by the water molecules entrapped in BHDC reverse micelle media reported in previous kinetic studies.

Nano-sized catalytic sites can be synthesized using reverse micelles to systematically deposit active metal species onto catalyst supports. The size of these metallic sites is influenced by the synthesis conditions, namely the water to surfactant molar ratio, the surfactant concentrations, and the surfactant type. These parameters can be adjusted to create tunable micro-structures that are catalytically active for specific chemical reactions. From a literature search, the size of catalytic sites was compiled against their respective synthesis conditions. A regression analysis was performed to investigate which parameters had significant effects on the size of the catalytic site. Initial laboratory tests were then carried out using the regression results to develop nano-nickel sites deposited onto TiO 2. According to the model, specific surfactant/solvent combinations (i.e. AOT/cyclohexane) and the water to surfactant molar ratio had profound impacts on the size of the produced catalytic site.

Agradeço em primeiro lugar a Deus, o Autor da vida. Sem Ele não haveria nada para ser estudado, nem quem o fizesse. Agradeço à minha família. Ao meu pai, pela incansável carona que me deu todos os dias desse trabalho, o que permitiu que eu dormisse uma preciosa hora a mais. À minha mãe por pacientemente ouvir meus lamentos e me impelir a continuar. Ao meu irmão pelo amor incondicional que ele dedica a mim e a minha família, e que faz toda a diferença. Ao meu noivo e futuro esposo Junior, pela paciência com que ouve minhas divagações científicas, pelo amor e carinho que dedica a mim (te amo). Agradeço ao meu orientador, Luiz Henrique Catalani, pela oportunidade de fazer parte de seu grupo de pesquisa, primeiro como aluna de Iniciação Científica e depois como aluna de Doutoramento; pela independência que permite aos seus alunos buscar suas próprias soluções, o que faz com que desenvolvamos maior senso crítico e maturidade científica; e pelo incentivo e amizade. Agradeço aos meus queridos amigos do laboratório (e de fora dele):

Molecular dynamics simulation of [Cd (II)] along with nitrate ions and water in dodecane was carried out for different nitric acid concentrations. The extraction process using N,N,N',N'tetraoctyldiglycolamide (TODGA) and tri-butyl phosphate (TBP), in biphasic systems, is also simulated at three nitric acid concentrations. In the TBP based system, the formation of a third phase was observed at 3M nitric acid concentration. Cd (II) ions form reverse micelles-like clusters with TODGA as an extractant in dodecane. The mass percentage of TODGA in these clusters decreases with increase in the acid concentration while increasing size of the aggregates at the same time.

The effect of nonionic cosurfactants on AOT reversed micellar interface and micelle/micelle interactions was studied. The change on the percolating temperature induced by these cosurfactants was determined for several water contents, micelle concentration, and cosurfactant type and concentration. Two types of cosurfactants were used, linear chained alkyl alcohols and poly(oxyethylene) alkyl ethers (CiEj). If an alcohol was added to the microemulsion, a shift in percolation to higher temperature was observed. The opposite was observed for the CiEj. The apparent hydrodynamic radius for the same systems was determined using dynamic light scattering. The apparent hydrodynamic radius of the alcohol-containing microemulsions was only slightly dependent on the concentration and chain size of the alcohol. The CiEj had the opposite effect, the apparent hydrodynamic radius increased for bigger head group sizes and higher concentrations. These results were interpreted in terms of a decrease or an increase of the fluidity of the interface layer. A solubilization site for the cosurfactants is proposed based on this interpretation of the results. Using the experimental results and an association model, the clustering enthalpy and entropy were determined. The clustering process was found to be endothermic and entropically driven.

Nafion membranes are polysulfonated teflon membranes and are selective towards cations. It is widely believed that there are water channels present in the membrane that are responsible for conducting cations. The conductivity of Nafion decreases by an order of magnitude upon decreasing the water content. The primary reason has been ascribed to the breaking up of water channels which are of hundreds of nanometers. On the contrary we have observed that proton transfer is hindered in molecular dimensions. We have even observed disruption of this proton transport even through one water molecule. 1,2 We ascribe the reason to enhanced electrostatic interactions upon reducing the water content. We have used Excited State proton transfer (ESPT) in Coumarin 102 (C102), 2-(2′-Pyridyl)-benzimidazole (2PBI) and (2,2′-Bipyridyl)-3,3′-diol to explore proton transfer process in the nafion membrane.

Synthesis of Eu 31-and Er 31 /Yb 31-doped GdVO 4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ,4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu 31-doped GdVO 4 nanoparticles emit red light through downconversion upon UV excitation. Er 31 /Yb 31-doped GdVO 4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from 2 H 11/2 R 2 I 15/2 and 4 S 3/2 R 4 I 15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K 21 , which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers. T he properties of nanoparticles (NPs) and nanostructured materials often drastically differ from those of bulk materials with the same chemical composition and are advantageous for numerous physical, biological, biomedical, and pharmaceutical applications 1. Therefore, the preparation of nanomaterials with wellcontrolled shape, size, phase purity, chemical composition, and with targeted, often multifunctional, properties is one of the most challenging problems in materials science. Because multifunctional NPs provide several functionalities in a single assembly, they are more applicable than conventional monofunctional NPs. Consequently, the design and preparation of multifunctional NPs have garnered considerable interest in recent years. In this respect, inorganic NPs doped with small amounts of activator ions such as transition-metal and/or rare-earth (RE) ions have attracted much attention because of their fascinating optical, magnetic, and thermal properties. Their potential as multifunctional materials is exceptionally broad. For example, they can be useful in improving photovoltaic cell efficiency through solar spectral conversion by shifting short-wavelength sunlight (ultraviolet and blue) to longer wavelengths (downshifting, quantum cutting), or by shifting long-wavelength near-infrared (NIR) radiation to visible light (upconversion), which provides more radiation in the spectral region wherein the solar cell shows the largest quantum efficiency 2. The luminescence decays of the majority of lanthanide and transition-metal ions (of the order of ms and larger) are much longer than those of biological materials (e.g., proteins and cells); therefore, NPs activated with these ions have high potential for biolabeling applications. Long-lasting emissions can be easily discriminated from the autofluorescence of biological materials using time-resolved measurements. Lanthanide-and transition-metal-ion-activated NPs do not show photobleaching and blinking, because the emission arises from many ions incorporated within the NPs. Also, these materials can be used in nanomedicine as anticancer drug carriers and magnetic resonance imaging (MRI) contrast agents, as well as in optical displays, cathode ray tubes, fluorescent lamps, light-emitting diodes, infrared detectors, scintillators, and fluorescent paints 3,4. Gadolinium orthovanadate (GdVO 4)-based materials have interesting luminescent and magnetic properties. Gd compounds can be easily doped with luminescent lanthanide ions because of the equal valence and similar ionic radii. They can be efficiently excited with UV radiation because of the strong absorption of the VO 4 32 groups and efficient energy transfer from GdVO 4 to lanthanide ions. Therefore, GdVO 4 is a used as a phosphor (doped with Eu 31 , Dy 31 , Sm 31), an upconvertor (doped with Er 31 /Yb 31 , Ho 31 /Yb 31 , or Tm 31 /Yb 31), and a laser (doped with Nd 31) 5,6. In addition, GdVO 4 NPs can act as T1-positive contrast agents for MRI, because Gd 31 ions possess unpaired electrons that efficiently alter the relaxation time of the surrounding water protons 3,4,7 .

Using THz absorption spectroscopy and ab initio molecular dynamics, we have investigated the water confined in a $Ga_4$$L_6$$^{-12}$ supramolecular tetrahedral assembly under ambient conditions. Based on the difference between the THz spectra of $Ga_4$$L_6$$^{-12}$ and a water-filled cavity compared to the nanocapsule occupied with a tetraethylammonium cation ($Et_4$N$^{+}$), we have experimentally determined that a small dynamically distinct network of 9$\pm$1 water molecules is present within the cavity of the $Ga_4$$L_6$$^{-12}$ supramolecular host. The low-frequency spectroscopic fingerprints and theoretical results of the water in the $Ga_4$$L_6$$^{-12}$ host assembly demonstrate that the structure of encapsulated water is different from that of ice and bulk water under cold temperatures or higher pressures, characterized by an isolated and arrested water cluster with significant translational and rotational entropy loss. In contrast to previous observations in crystals, the ab...

Triose phosphate isomerase (TIM) is responsible for the interconversion between GAP and DHAP in the glycolytic pathway. Two crystal forms belonging to space group P2 1 2 1 2 1 were obtained by the hanging-drop method and were designated A and B. Synchrotron X-ray diffraction data were collected for both forms. Form A had unit-cell parameters a = 65.14, b = 72.45, c = 93.24 A Ê and diffracted to 2.25 A Ê at 85 K, whereas form B had unit-cell parameters a = 73.02, b = 79.80, c = 172.85 A Ê and diffracted to 2.85 A Ê at room temperature. Molecular replacement was employed to solve the structures, using human TIM as a search model. Further re®nement of both structures is under way and is expected to shed light on the recently reported conformational studies for rabbit TIM.

Reverse micelles (RM) are nanopools of water surrounded by surfactant molecules in a non-polar solvent. Our studies investigated properties of RM probe molecules in the interfacial boundary between water and non-polar solvents. Reichardt’s dye, a probe molecule, was used to uncover properties of RM. UV/vis spectroscopy of Reichardt’s dye reveals information about polarity and the dye’s approximate residential location and also helps confirm molecular orbital energy diagram. We discovered an interesting phenomenon with Reichardt’s dye in RM. Surprisingly, the UV/vis spectrum of Reicahrdt’s dye in CTAB RM with octanol as a cosurfactant exhibits decreasing absorbance and a blue shift. Reichardt’s dye in solely octanol shows an irreversible color change and similar UV/vis spectrum. Consequently, we conclude that Reichardt’s dye resides near the interfacial layer/solvent boundary. Other cosurfactants do not result in the time dependent behavior suggesting a more dynamic interaction betwe...

Extraction and back-extraction of lysozyme are investigated using a mixed micellar system of sodium bis(2-ethylhexyl) sulfosuccinate and long chain alkyl amines. Either di-n-octylamine or di-2-ethylhexylamine is used as the amine added. In these systems, reverse micelles is not formed at acidic pH range. Lysozyme extracted at pH which is slightly lower than the isoelectric point of lysozyme is successfully back-extracted by destruction of the micelles at acidic pH range. By increasing the amine concentration, the pH values, at which the back-extraction of lysozyme began, are raised, and the activity of the back-extracted lysozyme decreases. Linear relationship between the concentration of the amine added in the system and that of lysozyme back-extracted exists .

Synthesis of Eu 31-and Er 31 /Yb 31-doped GdVO 4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ,4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu 31-doped GdVO 4 nanoparticles emit red light through downconversion upon UV excitation. Er 31 /Yb 31-doped GdVO 4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from 2 H 11/2 R 2 I 15/2 and 4 S 3/2 R 4 I 15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K 21 , which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers. T he properties of nanoparticles (NPs) and nanostructured materials often drastically differ from those of bulk materials with the same chemical composition and are advantageous for numerous physical, biological, biomedical, and pharmaceutical applications 1. Therefore, the preparation of nanomaterials with wellcontrolled shape, size, phase purity, chemical composition, and with targeted, often multifunctional, properties is one of the most challenging problems in materials science. Because multifunctional NPs provide several functionalities in a single assembly, they are more applicable than conventional monofunctional NPs. Consequently, the design and preparation of multifunctional NPs have garnered considerable interest in recent years. In this respect, inorganic NPs doped with small amounts of activator ions such as transition-metal and/or rare-earth (RE) ions have attracted much attention because of their fascinating optical, magnetic, and thermal properties. Their potential as multifunctional materials is exceptionally broad. For example, they can be useful in improving photovoltaic cell efficiency through solar spectral conversion by shifting short-wavelength sunlight (ultraviolet and blue) to longer wavelengths (downshifting, quantum cutting), or by shifting long-wavelength near-infrared (NIR) radiation to visible light (upconversion), which provides more radiation in the spectral region wherein the solar cell shows the largest quantum efficiency 2. The luminescence decays of the majority of lanthanide and transition-metal ions (of the order of ms and larger) are much longer than those of biological materials (e.g., proteins and cells); therefore, NPs activated with these ions have high potential for biolabeling applications. Long-lasting emissions can be easily discriminated from the autofluorescence of biological materials using time-resolved measurements. Lanthanide-and transition-metal-ion-activated NPs do not show photobleaching and blinking, because the emission arises from many ions incorporated within the NPs. Also, these materials can be used in nanomedicine as anticancer drug carriers and magnetic resonance imaging (MRI) contrast agents, as well as in optical displays, cathode ray tubes, fluorescent lamps, light-emitting diodes, infrared detectors, scintillators, and fluorescent paints 3,4. Gadolinium orthovanadate (GdVO 4)-based materials have interesting luminescent and magnetic properties. Gd compounds can be easily doped with luminescent lanthanide ions because of the equal valence and similar ionic radii. They can be efficiently excited with UV radiation because of the strong absorption of the VO 4 32 groups and efficient energy transfer from GdVO 4 to lanthanide ions. Therefore, GdVO 4 is a used as a phosphor (doped with Eu 31 , Dy 31 , Sm 31), an upconvertor (doped with Er 31 /Yb 31 , Ho 31 /Yb 31 , or Tm 31 /Yb 31), and a laser (doped with Nd 31) 5,6. In addition, GdVO 4 NPs can act as T1-positive contrast agents for MRI, because Gd 31 ions possess unpaired electrons that efficiently alter the relaxation time of the surrounding water protons 3,4,7 .

In this review, we deal with the formation and application of biocompatible water-in-oil microemulsions commonly known as reverse micelles (RMs). These RMs are extremely important to facilitate the dissolution of hydrophilic and hydrophobic compounds for biocompatibility in applications in drug delivery, food science, and nanomedicine. The combination of two wisely chosen types of compounds such as biocompatible non-polar solvents and ionic liquids (ILs) with amphiphilic character (surface-active ionic liquids, SAILs) can be used to generate organized systems that perfectly align with the Green Chemistry concepts. Thus, we describe the current state of SAILs (protic and aprotic) to prepare RMs using non-polar but safe solvents such as esters derived from fatty acids, among others. Moreover, the use of the biocompatible solvents as the external phase in RMs and microemulsions/nanoemulsions with the other commonly used biocompatible surfactants is detailed showing the diversity of pre...