Br In Aqueous Solutions Research Articles

Antiaggregation of NIR-II Probe Regulated by Amphiphilic Polypeptide with High Contrast Brightness for Phototheranostics and Vascular Microscopic Imaging under 1064nm Irradiation.

Thanks to deep penetration and high resolution, the second near-infrared window (NIR-II, 1000-1700nm)fluorescence (FL) imaging is expected to gain favor in clinical applications, including macroscopic imaging for cancer diagnosis and microangiography for vascular-related disease diagnosis. Nevertheless, most NIR-II fluorescent probes, especially cyanine, are highly susceptible to self-quenching in the aggregated state, which severely limits their application in bioimaging. Here, the Br-modified cyanine dye F4 -Br and the amphiphilic polypeptide poly(oligo[ethylene glycol]methacrylate)-b-poly(benzyl-L-aspartic acid) (POEGMA-PBLA) aresynthesized. By modulating the self-assembly of F4 -Br and POEGMA-PBLA to effectively inhibit the H-aggregation of F4 -Br in aqueous solutions, nanoprobe F4 -Br@P17 with outstanding antiquenching capability isdeveloped. This prominent feature allows it to perform vascular microscopic imaging with high spatiotemporal resolution and assess hemodynamic characteristics. F4 -Br@P17 nanoparticles (NPs) with good stability and satisfactory biocompatibility also enable high contrast brightness for NIR-II FL imaging of tumors. Given the efficient enrichment at tumor sites and the promising photothermal conversion efficiency (43.5%), F4 -Br@P17 NPs successfully conduct photothermal therapy and exhibit superior antitumor efficiency under 1064nm laser irradiation. These remarkable performances reveal the tremendous possibility of F4 -Br@P17 NPs for in vivomicroscopic imaging and FL imaging-guided photothermal therapy in the NIR-II region.

High capacity ethidium bromide removal by montmorillonites

Ethidium bromide (EtBr) is commonly used as a reagent to investigate DNA and RNA bonding in biochemistry. However, it is mutagenic and toxic; thus, its removal from the waste solution is of the top priority in lab safety practice. Although many products with high EtBr removal capacities are available on the market, developing new products with low material costs and high removal capacities is still an urgent priority. As the EtBr is in a cationic form Et+ balanced by counterion Br in aqueous solution, materials with high cation exchange capacity and large specific surface area may have great potential for efficient EtBr removal, Thus, several montmorillonites (MMTs) were evaluated for their EtBr removal capacity and methods of regeneration in this study. Results showed that both external and internal surfaces of MMTs were effective sorption sites for EtBr with a capacity up to 600mg/g. And the waste-laden materials could be regenerated or safely disposed after incineration at 500 °C for 2 h. As such, further tests on optimization and manufacturing kits or devices for practical EtBr removal in routine lab practice is of engineering priority, should MMTs be further explored as an effective material for EtBr removal.

Modulation of the aggregation behaviour and physicochemical properties of 1-dodecyl-3-methylimidazolium bromide in aqueous solutions by β-CD

ABSTRACTThe modulation of aggregation behaviour of ionic liquids (ILs) in aqueous media is one of the important research topics. In the present work, aggregation behaviour of 1-dodecyl-3-methylimidazolium bromide ([C12mim]Br) modulated by beta-cyclodextrin (β-CD) has been investigated by using conductivity, volume, fluorescence, dynamic light scattering and transmission electron microscopy techniques. The results suggested that the addition of β-CD significantly affects the aggregation of [C12mim]Br in aqueous solutions. For example, the apparent critical micelle concentration increases with the increase of β-CD concentration; the average micellar size reduced with the increasing concentration of β-CD, and the process for micelle formation of [C12mim]Br in aqueous β-CD solution is driven by entropy at lower temperature, while driven by enthalpy at higher temperature. It is expected that findings in this study would shed light on the potential applications of IL in supramolecular chemistry.

Interactions of sodium polystyrene sulfonate with 1-hexyl-3-methylimidazolium bromide in aqueous solution: conductometry and density functional theory studies

ABSTRACTConductivity measurements of sodium polystyrene sulfonate (NaPSS) were carried out in aqueous solutions of 1-hexyl-3-methylimidazolium bromide ([HMIm]Br) at three different temperatures. The scaling theory is used for the description of electrical conductance of polyelectrolytes. The fraction of uncondensed counterions is decreased by increasing temperature and concentration of [HMIm]Br. Conductivity measurements of ([HMIm]Br were accomplished in aqueous solutions of sodium polystyrene sulfonate. Data analysis was performed by the Quint–Viallard conductivity equation and low concentration chemical model. Molar conductivity of [HMIm]Br in aqueous solutions of NaPSS was increased with increasing temperature. The values of activation energy for viscous flow are higher than the values of activation enthalpy of charge transport; therefore, it can be concluded that in addition of ion transfer, the formation and breaking hydrogen has a portion in charge transfer. The results of Quantum chemical calculations confirm the existence of hydrogen bonding between [HMIm]+ and [PSS]–.

Conductometry and Density Functional Theory studies on the interactions of sodium polystyrenesulfonate with 1–butyl–3–methylimidazolium bromide in aqueous solution

Electrical conductance of sodium polystyrene sulfonate (NaPSS) have been measured in aqueous solutions of 1–butyl–3–methylimidazolium bromide ([BMIm]Br) at three different temperatures T=(288.15, 298.15 and 308.15) K. The scaling theory is applied for the explanation of electrical conductance of polyelectrolytes. From the obtained results can be seen that the fraction of uncondensed counterions is decreased by increasing temperature and concentration of [BMIm]Br. Also, conductivity measurements of 1–butyl–3–methylimidazolium bromide were carried out in aqueous solution of sodium polystyrene sulfonate. Data analysis was performed by the Quint-Viallard (QV) conductivity equation and low concentration chemical model (lcCM). Limiting molar conductivities of [BMIm]Br (Λ0) and the association constant (KA) were determined. Molar conductivity of [BMIm]Br in aqueous solutions of NaPSS was increased with increasing temperature. The values of activation energy for viscous flow and the values of activation enthalpy of charge transport were calculated. The results of Quantum chemical calculations were confirmed the existence of hydrogen bonding between [BMIm]+ and [PSS]−.

Solute-solvent interactions of amino acid l-phenylalanine in aqueous 1-butyl-2,3-dimethylimidazolium bromide ionic liquid solutions

Densities of l-phenylalanine in water and in aqueous1-butyl-2,3-dimethylimidazolium bromide solutions, at T=(283.15, 288.15, 293.15, 298.15 and 303.15)K and atmospheric pressure have been measured. The apparent molar volumes, VФ, standard partial molar volumes, VФ0, limiting apparent molar expansibilities, EФ0, and standard partial molar volumes of transfer, ΔVФ0, have been calculated. The values of ΔVФ0 are negative. These volumetric parameters are interpreted in terms of various mixing effects between l-phenylalanine and [BMMIm]Br in aqueous solution. The 1H NMR measurements of binary mixtures of l-phenylalanine and [BMMIm]Br in D2O solutions have been carried out to understand the possible interactions. The results show that the interactions between the hydrophobic-hydrophobic groups of [BMMIm]Br and l-phenylalanine may be dominant in the studied system. Furthermore, the density functional theory calculations provide stabilization energies and suggest possible interaction ways that support the volumetric and NMR measurements.

Interactions of Sodium Polystyrene Sulfonate with 1-Octyl-3-methylimidazolium Bromide in Aqueous Solution: Conductometric, Spectroscopic and Density Functional Theory Studies

Conductivity measurements were performed for aqueous mixtures of sodium polystyrene sulfonate (NaPSS) and 1-octyl-3-methylimidazolium bromide ([OMIm]Br) at 288.15, 298.15 and 308.15 K. Scaling theory is used for the description of the electrical conductance of the polyelectrolytes. The results indicate that the fraction of uncondensed counterions is decreased by increasing the temperature or concentration of [OMIm]Br. Conductivity measurements for 1-octyl-3-methylimidazolium bromide were performed in aqueous solutions of sodium polystyrene sulfonate. Data analysis was performed using the Quint–Viallard conductivity equation and the low concentration chemical model. Limiting molar conductivities of [OMIm]Br (Λ0) and the association constant (KA) were determined. The molar conductivity of [OMIm]Br in aqueous solutions of NaPSS increased with increasing temperature. Values of activation energy for viscous flow are higher than the values of activation enthalpy of charge transport; therefore, it can be concluded that, in addition to ion transfer, the formation and breaking of hydrogen bonds is responsible for a portion of the charge transfer. The results of UV–Vis spectroscopic and quantum chemical calculations confirmed the existence of hydrogen bonding between [OMIm]+ and [PSS]–.

Interactions of 1-butyl-2,3-dimethylimidazolium bromide ionic liquid with glycine, l-alanine and l-valine: A volumetric and NMR spectroscopic study

The densities of glycine, l-alanine and l-valine in aqueous and aqueous solutions of 1-butyl-2,3-dimethylimidazolium bromide [BMMIm]Br have been determined at (283.15, 288.15, 293.15, 298.15 and 303.15) K and atmospheric pressure. The apparent molar volumes, standard partial molar volumes, standard partial molar volume of transfer and hydration numbers have been calculated. The values of standard partial molar volume of transfer for three amino acids are negative at all temperatures studied. The values of standard partial molar volume of transfer become more negative with the increase of hydrophobicity of the amino acid side-chains. These volumetric parameters are interpreted in terms of various mixing effects between amino acids and [BMMIm]Br in aqueous solutions. Furthermore, the 1H NMR measurements of binary mixtures of amino acids and [BMMIm]Br dissolved in D2O have been carried out. The influence in electron density around the protons of [BMMIm]Br followed the order: l-valine>l-alanine>glycine. The results were interpreted on possible molecular interactions between the intrinsic hydrophilicity/hydrophobicity of amino acid side-chains and [BMMIm]Br.

Vapor-Pressure Osmometry and Conductivity Determination of Salting-Out Effects in Aqueous Surface-Active Ionic Liquid 1-Dodecyl-3-methylimidazolium Bromide Solutions

Systematic studies on the vapor-liquid equilibria (VLE) and conductometric properties of aqueous solutions of model surface-active ionic liquid 1-dodecyl-3-methylimidazolium bromide ([C12mim]Br) are performed in the absence and presence of a large series of electrolytes in order to achieve a deeper understanding about the molecular mechanism behind the specific salt effect on the aggregation behavior of [C12mim]Br in aqueous solution. For this purpose, 6 chloride electrolytes (NaCl, KCl, NH4Cl, (CH3)4NCl, MgCl2 and FeCl3) and 5 sodium electrolytes (NaCl, NaNO3, Na2CO3, Na2SO4, and Na3Cit.) were used in order to individualize the effect of the anion and the cation. The values of the critical aggregation concentration (CAC) were obtained and it was found that all the investigated electrolytes have salting-out effect on the aggregation of [C12mim]Br in aqueous solutions, leading to significant downward shifts of the CAC. The magnitude of the shifts depends on the water-structuring nature of the electrolyte and follows the Hofmeister series. Furthermore the effect of electrolyte on the degree of anionic binding and thermodynamic parameters of aggregation for [C12mim]Br in aqueous solutions were determined.

Study of salt effects on the aggregation behavior of ionic liquid 1-dodecyl-3-methylimidazolium bromide in aqueous solution

The effect of organic electrolytes Me4NBr, Et4NBr, Pr4NBr, Bu4NBr, Me4NCl and Me4NI on the aggregation behavior and thermodynamic properties of surface active ionic liquid (SAIL) 1-dodecyl-3-methylimidazolium bromide ([C12mim]Br) in aqueous solution was studied by volumetric, compressibility and conductometric measurements at different temperatures. The results show that all the electrolytes investigated effectively reduce critical micelle concentration and therefore have a salting-out effect on the aggregation of [C12mim]Br in aqueous solutions. It was also found that the salting-out-inducing anions are predominately responsible for the observed effect, while the cations have a very smaller effect on the salting-out strength. The ability of the anions to promote the aggregation of SAIL decreases in the order of I−>Br−>Cl−; however all the investigated cations Me4N+, Et4N+, Pr4N+ and Bu4N+ have a similar salting-out strength. Changes in the apparent molar volumes and isentropic compressibilities upon micellization were derived and the infinite dilution apparent molar properties of the monomer form of [C12mim]Br were determined. Furthermore the effect of electrolyte on the degree of anionic binding and the thermodynamic parameters of aggregation for [C12mim]Br in aqueous solutions were determined.

Salt-effects in aqueous surface-active ionic liquid 1-dodecyl-3-methylimidazolium bromide solutions: Volumetric and compressibility property changes and critical aggregation concentration shifts

Systematic studies on the volumetric and compressibility properties of aqueous solutions of model surface-active ionic liquid 1-dodecyl-3-methylimidazolium bromide ([C12mim]Br) are performed in the absence and presence of a large series of electrolytes in order to achieve a deeper understanding about the molecular mechanism behind the specific salt effect on the aggregation behavior of [C12mim]Br in aqueous solution. For this purpose, 6 chloride electrolytes (NaCl, KCl, NH4Cl, (CH3)4NCl, MgCl2 and FeCl3) and 5 sodium electrolytes (NaCl, NaNO3, Na2CO3, Na2SO4, and Na3Cit.) were used in order to individualize the effect of the anion and the cation. The values of the critical aggregation concentration (CAC) were obtained and it was found that all the investigated electrolytes have salting-out effect on the aggregation of [C12mim]Br in aqueous solutions, leading to significant downward shifts of the CAC. The magnitude of the shifts depends on the water-structuring nature of the electrolyte and follows the Hofmeister series. Changes in the apparent molar volumes and isentropic compressibilities upon micellization were derived using a pseudophase-transition approach and the infinite dilution apparent molar properties of the monomer and micellar form of [C12mim]Br were determined.

Effect of 1-Ethyl-3-methylimidazolium Bromide Ionic Liquid on the Volumetric Behavior of Some Aqueous l-Amino Acids Solutions

Densities of aqueous solutions of glycine, l-alanine, l-arginine, and l-phenylalanine containing 1-ethyl-3-methylimidazolium bromide, [EMIm]Br, have been determined at T = (298.15 and 308.15) K. From the experimental density data, the apparent molar volumes (VΦ) and the standard partial molar volumes (VΦ0) at (298.15 and 308.15) K have been calculated. The values of standard partial molar volumes of transfer (ΔtrVΦ0) are also obtained and are negative for glycine, l-alanine, and l-phenylalanine while positive for l-arginine. The ΔtrVΦ0 values all increased with the increase of the temperature and also the [EMIm]Br content. The obtained volumetric parameters will be helpful to understand mixing effects and other complex biological processes between head and side chain groups of amino acids and ionic liquid [EMIm]Br in aqueous solution.

Micelle Aggregation Numbers and Rheological Characterization of C12-3-C12·2Br and C12-3（OH）-C12·2 Br in Aqueous Solution

Micelle Aggregation Numbers and Rheological Characterization of C12-3-C12·2Br and C12-3（OH）-C12·2 Br in Aqueous Solution

Salt Effect on the Aggregation Behavior of 1-Decyl-3-methylimidazolium Bromide in Aqueous Solutions

Understanding of the specific salt effect on the aggregation behavior of ionic liquids (ILs) is relevant to multiple applications. In this work, the influence of a series of 15 salts on the aggregation behavior of [C(10)mim]Br in aqueous solutions has been investigated by conductivity, fluorescence, and dynamic light scattering. It was shown that NaCl, NaBr, NaI, CH(3)CO(2)Na, NaSCN, NaNO(3), NaBrO(3), NaClO(3), C(6)H(5)COONa, Na(2)CO(3), Na(2)SO(4), Na(2)C(4)H(4)O(6), and Na(3)CH(5)O(7) have salting-out effect, whereas FeBr(3) and AlBr(3) have salting-in effect on the aggregation of [C(10)mim]Br in aqueous solutions. The effect of anions of the added sodium salts on the critical aggregation concentration (CAC), degree of anionic binding (beta), and aggregation number (N(agg)) of the IL basically follows the Hofmeister series, and the CAC values decrease but the beta and N(agg) values increase with increasing concentration of the salts. Hydrophobicity of the anions is suggested to play important roles in the salt effect on the aggregation of [C(10)mim]Br in aqueous solutions. Furthermore, the IL aggregates were found to grow slowly as the increase of the salt concentrations under studied static conditions, and resulting in the increased aggregation number of the IL. These results are expected to be useful in the applications of ionic liquids.

Conductivities, Volumes, Fluorescence, and Aggregation Behavior of Ionic Liquids [C4mim][BF4] and [Cnmim]Br (n = 4, 6, 8, 10, 12) in Aqueous Solutions

Densities, conductivities, and polarity indexes of pyrene for aqueous solutions of a series of ionic liquids [C(n)mim]Br (n = 4, 6, 8, 10, 12) and [C4mim][BF4] have been determined at 298.15 K as a function of ionic liquid concentrations. It was shown that possible aggregation appeared for the ionic liquids in aqueous solutions except for [C4mim]Br. The critical aggregation concentration (CAC) of the ionic liquids, the ionization degree of aggregates (beta), the standard Gibbs energy of aggregation (Delta G(m)(o)), the limiting molar conductivity (Lambda(m)(o)), and the standard partial molar volume (V(m)(o)) for the ionic liquids were derived from the experimental data. The dependence of the CAC, Delta G(m)(o), Lambda(m)(o), and V(m)(o) on the length of the alkyl chain of the cations was examined. It was further suggested from volumetric data that a micelle was formed for [C8mim]Br, [C10mim]Br, and [C12mim]Br in aqueous solutions. Their apparent molar volumes at the critical micelle concentration (V Phi,CMC), apparent molar volumes in the micelle phase (V(Phi)(mic)), and the change of their apparent molar volume upon micellization (Delta V Phi,m) were calculated by application of the pseudophase model of micellization. In addition, the average aggregation number of [C(n)mim]Br (n = 8, 10, 12) has been determined by the steady-state fluorescence quenching technique, and predicted from a simple geometrical mode. It is found that the experimental values are in good agreement with the predicted ones.

π‐Complexes of Copper(I) with Terminal Alkynes. Synthesis and Crystal Structure of [(HC≡CCH2NH3)(Cu2Br3)] π‐Complex

AbstractCrystals of the zwitterionic copper(I) π‐complex [(HC≡CCH2NH3)Cu2Br3] have been synthesized by interaction of CuBr with [HC≡CCH2NH3]Br in aqueous solution (pH < 1) and X‐ray studied. The crystals are monoclinic: space group P21/n, a = 6.722(4), b = 12.818(8), c = 9.907(3) Å, β = 100.25(4)°, V = 840.0(8) Å3, Z = 4, R = 0.0592 for 3015 reflections. The crystal structure of the π‐complex contains isolated [(HC≡CCH2NH3)+(Cu2Br3)−]2 units which are incorporated into a framework by strong hydrogen N–H···Br and C≡C–H···Br bonds. The length of π‐coordinated propargylammonium C≡C bond is equal 1.216(8) Å and Cu(I)–(C≡C) distance equals 1.958(5) Å.

Thermodynamic modelling of the Br partition between aqueous solutions and halite

Experimental work in the ternary system NaCl–NaBr–H 2O at 25°C and 1 atm was carried out to determine the distribution of Br in halite and to close gaps in former sets of data. In order to model the incorporation of Br, a new link between the distribution coefficient D Br = (% Br in solid/% Br in aqueous solution) and the activity coefficient of the trace end-member in a solid solution system was developed. Because conventional solid solution models are not able to describe the behaviour of trace components satisfactory, a new generalized thermodynamic model for the extreme ends of such systems ( X trace < 0.01) was created. The basis of the model is the assumption that the activity coefficient of the trace component in the extreme ends can be sufficiently described by the following form: 2.303 RT log λ trace = p 1 X major 2 + p 2X major p 3 . The new model was implemented into the computer code EQ3/6. The influence of different alkali and earth alkali cations in aqueous solutions on the distribution coefficient was modelled. At a concentration of about 1% in the aqueous solution the distribution coefficient of Br in halite is reduced about 10% by K, 9.9% by Ca, 7% by Li, 4.5% by Rb, 3.5% by Sr and 2.5% by Mg. The model was validated by a comparison of calculated values for the Br concentration in halite precipitated from evaporating seawater and field observations of different authors. The calculated data are in good agreement with the experimental data as well as with other data from salt works.

Magnetic relaxation of23Na and81Br in aqueous solutions of the alkali halides

N.M.R. relaxation times of 81Br and 23Na have been measured as a function of temperature and concentration in aqueous solutions of LiBr, NaBr and CsBr. Linewidths of all ions vary linearly with viscosity over temperature, but are not directly proportional to this quantity in contradiction of the Debye equation. Striking similarity exists between the temperature dependence of N.M.R. linewidths and that of dielectric relaxation times in alkali halide solutions, suggesting that solvent reorientation or translation in the outer hydration region is the most efficient means of quadrupolar relaxation. On this assumption approximate solvent tumbling times in outer hydration spheres of Na+ and Br− are calculated. Contributions to relaxation due to ion-ion interactions are in accord with previous theory in that they possess an activation energy of the same approximate magnitude as that for ionic self-diffusion.