Anions In Aqueous Solution Research Articles

Accurate Vertical Electron Detachment Energies and Multiphoton Resonant Photoelectron Spectra of Biochromophore Anions in Aqueous Solution.

We introduce a new methodology for calculating vertical electron detachment energies (VDEs) of biologically relevant chromophores in their deprotonated anionic forms in aqueous solution. It combines a large-scale mixed DFT/EFP/MD approach with the high-level multireference perturbation theory XMCQDPT2 and the Effective Fragment Potential (EFP) method. The methodology includes a multiscale flexible treatment of inner (∼1000 water molecules) and outer (∼18000 water molecules) water shells around a charged solute, capturing both the effects of specific solvation and the properties of bulk water. VDEs are calculated as a function of system size for getting a converged value at the DFT/EFP level of theory. The XMCQDPT2/EFP approach, adapted for calculating VDEs, supports the DFT/EFP results. When corrected for a solvent polarization contribution, the XMCQDPT2/EFP method yields the most accurate estimate to date of the first VDE for aqueous phenolate (7.3 ± 0.1 eV), which agrees well with liquid-jet X-ray photoelectron spectroscopy data (7.1 ± 0.1 eV). We show that the geometry of the water shell and its size are essential for accurate VDE calculations of aqueous phenolate and its biologically relevant derivatives. By simulating photoelectron spectra of aqueous phenolate upon two-photon excitation at wavelengths resonant with the S0 → S1 transition, we also provide interpretation of recent multiphoton UV liquid-microjet photoelectron spectroscopy experiments. We show that its first VDE is consistent with our estimate of 7.3 eV, when experimental two-photon binding energies are corrected for the resonant contribution.

Molar-Ratio-Dependent Coordination Assembly of Organoiridium(III)-Octatungstate Complexes in Aqueous Solution

We scrutinized the speciation of Cp*Ir-containing tungsten oxide clusters (Cp* is pentamethylcyclopentadienyl anion) in aqueous mixtures of [(Cp*IrCl)2(μ-Cl)2] and Na2WO4 in varying molar ratios. 1H nuclear magnetic resonance (NMR) spectroscopy revealed the formation of three distinct Cp*Ir-polyoxotungstate species in the reaction solution, and they were isolated as Na4[(Cp*Ir)2(μ-OH)3]2[(Cp*Ir)2H2W8O30] (1), [(Cp*Ir)2(μ-OH)3]2[(Cp*Ir)2{Cp*Ir(OH2)}2H2W8O30] (2), and [(Cp*Ir)2{Cp*Ir(OH2)}2{Cp*Ir(OH2)2}2H2W8O30](NO3)2 (3) from the mixtures in which iridium concentration is less than, equal to, and more than the tungsten concentration, respectively. These results show the octatungstate [H2W8O30]10- anion is the major polyoxotungstate species in the presence of {Cp*Ir}2+ cations, and it has high nucleophilicity enough to bind up to six {Cp*Ir}2+ cations on its surfaces producing a cationic Cp*Ir-octatungstate complex. The octatungstate anion was also generated from the reaction of [(Cp*IrCl)2(μ-Cl)2] and methylammonium paratungstate-B, (CH3NH3)10[H2W12O42], and was isolated as a methylamine-coordinated complex (CH3NH3)2[(Cp*Ir)2{Cp*Ir(NH2CH3)}2H2W8O30] (4), indicating {Cp*Ir}2+ cations function as a structure-directing agent that converts tungsten species into octatungstate anions in aqueous solution. In addition, the coordination environment of {Cp*Ir}2+ can be further modified by coordination with pyridine forming [{Cp*Ir(NC5H5)}2(μ-OH)2][(Cp*Ir)2{Cp*Ir(NC5H5)}2H2W8O30] (5).

High-Resolution Ultrasonic Spectroscopy: Looking at the Interpolyelectrolyte Neutralization from a Different Perspective

In this study, the high-resolution ultrasonic spectroscopy (HR-US) technique was applied to examine interpolyelectrolyte neutralization. The mentioned method was tested on the example of complexation between poly(allylammonium) cations and poly(acrylate) anions in aqueous solutions at pH = 7. It was confirmed by HR-US that the type of titration (stepwise or abrupt), the direction of titration, and the type of background salt affect the outcome of interpolyelectrolyte neutralization. The obtained results were explained on the basis of ultrasonic velocity and attenuation changes in the context of suspension compressibility, a parameter that is extremely sensitive to molecular organization and intermolecular interactions. Moreover, the results of HR-US measurements proved to be consistent with previous results obtained by more traditional methods such as dynamic light scattering, microcalorimetry, and electrokinetics. This research demonstrates that HR-US is a convenient and reliable method that can be employed for the investigation of interpolyelectrolyte neutralization and polyelectrolyte-related processes.

A bis-chalcone based colorimetric probe for the selective detection of bisulfite/sulfite anions: exploring surfactant promoted Michael addition of anions to α, β-unsaturated ketones.

A probe, (1E,4E)-1,5-di(thiophen-2-yl)penta-1,4-dien-3-one, was developed for rapid, colorimetric, and selective detection of bisulfite/sulfite anions in aqueous solutions. This probe is based on the Michael addition reaction which is favoured in the presence of cationic micellar medium CTAB. CTAB promoted Michael addition is an effective tool to determine SO2 toxicity, which is mainly expressed in terms of collective concentration of bisulfite and sulfite anions. The probe showed high selectivity and sensitivity toward bisulfite and sulfite over other interfering anions, with a detection limit of 0.43 μM and 0.23 μM, respectively. The possible recognition mechanism of the probe and the analyte was illustrated by NMR, HR-MS, IR, and computational analysis. Moreover, this probe showed great potential for the detection of bisulfite/sulfite in real samples, such as crystal sugar and brown sugar.

Stability of highly soluble ferrocyanides at neutral pH for energy-dense flow batteries

Ferrocyanides and ferricyanides are among the most employed positive electrolyte materials in aqueous flow battery research, but the limited solubility of commonly available sodium and potassium salts is a critical factor limiting application at scale. Here, we systematically study the cation-dependent solubility of these materials and, importantly, the cation-dependent stability of the anion in aqueous solution. For Li4Fe(CN)6, we report a maximum solubility of 2.3 M and show stable cycling of a 2 M symmetric cell, corresponding to electrolyte capacities of 54 Ah L−1, over 200 days. We also demonstrate solubilities of 1.6 M for ammonium and calcium salts and investigate the pronounced anion decomposition observed in the presence of ammonium cations. Our observations lead to a discussion of challenges associated with the osmotic strength of concentrated electrolytes that employ ions with high charge states, such as ferrocyanide.

Photo-oxidation of nitrite anions in aqueous solution for the benchmarking of nano-TiO2 photocatalytic coatings

Photocatalytic coatings have potential as an air purifying technology for removal of pollutants such as NOx gases, which are converted into and immobilized as nitrate via photo-oxidation. This work is an investigation of the photocatalytic conversion of nitrite into nitrate in the aqueous phase. The study of this reaction is important to understand the mechanism through which the immobilization of the NOx species as nitrates takes place during NOx conversion, especially in humid environments. We investigate the photocatalytic performance of TiO2 nanoparticles (Aeroxide® P25) and the corresponding photocatalytic coatings prepared using acrylic binder (TiO2 NP-acrylic) towards the photo-conversion of nitrite. The combination of a simple colorimetric method (Griess test) for nitrite quantification and UV–vis spectroscopy for nitrite and nitrate analysis is shown to be a useful method for monitoring the nitrite conversion. Photocatalytic tests with suspended TiO2 nanoparticles show that the nitrite conversion benefits from lower pH, higher temperature and higher concentration of the photocatalyst. The advantage of lower pH is attributed to electrostatic attraction between TiO2 with adsorbed H3O+ and NO2−, which facilitates transport of nitrite to the active surface. When the photocatalyst is immobilized in a coating the factor of primary significance is the pigment volume concentration relative to critical pigment volume concentration (λ), as the nitrite conversion increases linearly with λ in the range 0.6–1.2. This is attributed to the creation of a more porous structure that facilitates the access of nitrite and light to the active TiO2 surface sites.

Synthesis of cationic carbon quantum dot-based dual emission fluorescence sensor for detecting perrhenate anions in aqueous solutions

This study developed a carbon quantum dot to selectively detect perrhenate anions, which was used as a surrogate for the radioactive pertechnetate anion, in aqueous solutions. A blue emission carbon dot (B-CD) was prepared using a simple microwave technique, whereas a dual-emission carbon dot (D-CD) was prepared using 1,3,6-trinitropyrene. When the concentration of the perrhenate anion was increased, both B-CD and D-CD exhibited a decrease in fluorescence brightness owing to the inner filter effect; however, no changes were observed in terms of color. Therefore, cationic D-CDs (C-CDs) were synthesized by introducing quaternary ammonium functional groups on the surface of D-CD to enhance the binding characteristics with the perrhenate anion. At an excitation wavelength of 350 nm, both B-CD and D-CD failed to exhibit a decrease in fluorescence brightness; however, the change in color and reduced brightness of fluorescence were observed in C-CD because of the perrhenate anion. The change in fluorescence color can be attributed to the difference in the intensity reduction in dual-emission wavelength regions. Furthermore, C-CD exhibited linear correlations for perrhenate anion concentrations of up to 1 mM, and the limits of detection were 87 and 208 μM at excitation wavelengths of 254 and 350 nm, respectively. Additionally, the results indicate that C-CD can be used as a sensor to detect perrhenate anions despite the presence of excess chloride anions. This fluorescence change can be attributed to the photoinduced electron transfer mechanism caused by the electrostatic interactions between the cationic surface functional groups of C-CD and perrhenate anions.

Multiconfigurational SCF and Short-Range DFT Combined with Polarizable Density Embedding: Comparison of Linear-Response and State-Specific Solvatochromic Shifts of Acrolein and Para-nitrophenolate in Water.

The polarizable density embedding model is combined with the multiconfigurational self-consistent field and MC-srDFT electronic structure methods to calculate solvatochromic shifts of the n-π* absorption of acrolein and the π-π* absorption of the para-nitrophenolate anion in aqueous solution. Differences between linear-response (LR) and state-specific (SS) solvent shifts are analyzed by assessing the contributions of different terms in the solvent potential. This comparison shows that the differences are not only due to the intrinsically different response of LR and SS excitation energies to the polarizability of the environment but also due to a different response to the static part of the environment potential. These observations show that even in nonpolarizable environments, LR and SS calculations based on SCF (orbital optimization) methods do not necessarily agree on the spectral shift. The difference can be as large as, or even dominate, the difference due to dynamical polarization.

Imidazolium-Modified Bispyrene-Based Fluorescent Aggregates for Discrimination of Multiple Anions in Aqueous Solution.

A great number of anions exist in biological systems and natural environment, and are highly relevant to human health and environment quality. It is necessary to develop simple and effective sensors to differentiate and identify those similar or different anions. Here, an imidazolium-modified bispyrene-based fluorescent amphiphilic probe DPyDIM was synthesized and its aggregates were applied to detect and discriminate various anions. The fluorescent aggregates exhibit ratiometric responses to different types of anions. Moreover, the ratiometric responses to different types of anions are featured with multiple-wavelength cross-reactivity. The collection of fluorescence variation at four typical wavelengths can generate distinct recognition patterns to specific anions. The heat map and principal component analysis results verify that this single fluorescent sensor system can effectively and sensitively identify 16 kinds of anions that belong to phosphorus-containing, sulfur-containing anions, and anionic surfactants. The cross-reactive sensing of the amphiphilic fluorescent aggregates was attributed to the different influences on the aggregation behaviors of the probes by different anions. The present work provides a promising strategy for effective detection and discrimination of multiple anions by employing dynamic fluorescent aggregates as a sensing platform.

Multi-responsive luminescent sensitivities of two pillared-layer frameworks towards nitroaromatics, Cr2O72−, MnO4− and PO43− anions

Combining Zn(II) with two dicarboxylic acids of different length and functional groups results in the 2D metal-carboxylate layer of different size and shape, which are further connected by the same bis-pyridyl-bis-amide pillar to afford two 4-fold and 3-fold interpenetrating pillared-layer networks (1 and 2). Luminescent properties of 1 and 2 have been systematically investigated and demonstrated multi-responsive luminescent sensitivities. 1 can be used for highly sensitive detection of nitroaromatics. In particular, 2 can be used turn-off sensing towards Cr2O72− and MnO4− anions as well as turn-on sensing towards PO43− anion in aqueous solution with high sensitivity and remarkable recyclability. The sensing mechanism is also discussed.

A dual-functional Zn(II) coordination polymer for detection of Cr(VI) and photocatalytic degradation of rhodamine B in aqueous solution

Herein, a new kind of zinc(II)-coordination polymer (CP-1) was constructed and structurally characterized. CP-1 features a 1D zigzag chain structure, and the 1D framework forms a 3D supramolecular network through intermolecular hydrogen bonding of C-H···Cl. It is worth mentioning that CP-1 can serve as a dual-functional material. First of all, It shows good selectivity, high sensitivity, and good recyclability in sensing CrO42· and Cr2O72· anions in aqueous solution through luminescence quenching effect. The high quenching efficiency can be attributed to the competitive absorption and the energy transfer. Meanwhile, it also exhibits high photocatalytic efficiency for the degradation of rhodamine B in aqueous solution under the irradiation of UV light, and the possible mechanism is also discussed.

Thermodynamic constants of formation of disulfide anion in aqueous solutions

This study is aimed at precise measurement of thermodynamic constants of disulfide (S22−) formation. It was demonstrated that these constants, K, for formation of longer polysulfides for reaction between hydrogen sulfide and orthorhombic cyclooctasulfur (α-S8) measured by independent techniques (potentiometry, spectrophotometry, chromatography) are in good agreement. For the most abundant polysulfides, S42−, S52− and S62−, the reported ranges of pK values are ≤0.72 pK units. On the other hand, pK2 values of the formation of S22− in this reaction measured by different techniques span from 11.46 to 14.43. The main difficulty in measurement of K2 is low abundance of disulfide in the solutions saturated with respect to α-S8. In this work, we applied chromatographic analysis for the samples, which are highly undersaturated with respect to α-S8. The results show that robust determination of K2 may be achieved at the molar ratio of S0 to S(II) ≤ 0.064. At these conditions the value of pK2 at 25 °C was found to be 12.77 ± 0.08. Based on this value, the standard Gibbs free energy of S22− formation was calculated. The standard enthalpy of formation and molar entropy were derived from the data obtained in experiments at the temperature range of 10 °C to 70 °C. Calculations based on these thermodynamic values show that while disulfide accounts for only a minor fraction of polysulfide zero-valent sulfur at saturation with α-S8, it can become the most abundant polysulfide at low S0 to S(II) molar ratios. In marine sediments and water columns low molar polysulfide S0 to S(II) ratio may exist in hydrogen sulfide-rich zero valent sulfur-poor systems as well as, due to kinetic constraints, in the zero valent sulfur-rich systems. Results of our work suggest that at the molar ratio of polysulfide S0 to S(II) > 0.064, the calculation of disulfide concentration should be based on concentrations of hydrogen sulfide and other polysulfides and the set of thermodynamic constants provided in this work. At the lower polysulfide S0 to S(II) ratios, the disulfide concentration should be either measured directly or calculated in case that it is below the detection limit of quantification method.

Probing Anion − π interactions between fluoroarene and carboxylate anion in aqueous solutions

Despite the much progress in developing π-conjugated fluoroarene moieties based functional materials in which anion − π interactions are commonly involved, it remains challenging to quantitatively characterize the nanomechanical interaction mechanism of these anion − π systems, particularly in aqueous solutions. In this study, we reported the first experimental quantification of the nanomechanics of anion − π interactions between π-conjugated fluoroarene moieties and carboxylate anions in aqueous solutions through direct molecular force measurements, with a special focus on the impact of the anion species, concentration and of the substitution effect of aromatic side group. The results using surface forces apparatus (SFA) and single-molecule force spectroscopy (SMFS) provide complementary evidences to demonstrate that the robust and reversible adhesion measured between the fluoroarene π systems and carboxylate anions was mainly attributed to anion − π interaction. Moreover, their nanomechanical properties were also systematically scrutinized, with the interaction strength being found to be significantly determined by the contact time, the type of fluoroarene systems (PFST > DFST) and the type of anions and ion concentration (HPO42- > CO32– > I- > Cl- ≈ NO3– > F-).

Di-(2-picolyl)amine functionalized tetraphenylethylene as multifunctional chemosensor

In this study, we successfully developed a new multifunctional chemosensor 4′,4‴-(2,2-diphenylethene-1,1-diyl)bis(N,N-bis (pyridin-2-ylmethyl)-[1,1′-biphenyl]-4-amine (T-D), based on the cooperation of tetraphenylethylene and di-(2-picolyl)amine (DPA), for sensitive, selective, and quick detection of Cu2+, PO43− and pesticide glyphosate in aqueous solution. In our research, we made full use of the Cu2+-indicator displacement strategy to achieve the construction of an “on-off-on” fluorescent switch platform. Due to the presence of the DPA moiety in T-D, Cu2+ could be captured quickly to form the complex T-D-Cu and caused fluorescence quenching. With the addition of PO43− and glyphosate, the system could rapidly restore the fluorescence by squeezing Cu2+ from T-D-Cu and blocking the photo induced electron transfer (PET) process to display the aggregation-induced emission. To demonstrate the possibility of practical applications, we detected PO43− and glyphosate in spiked real samples. The detection limit for PO43− and glyphosate reached 19 nM and 25 nM, respectively. Furthermore, test strips using T-D-Cu solution simplified the detection process of glyphosate. More importantly, the sensor could be used in visual semi-quantitative determination of PO43− concentrations in both living cells and living zebra fish. Therefore, the chemosensor presented here will not only be a powerful tool for the detection of phosphate anions in aqueous solution and biological systems, but also provides a new template for the design of other multifunctional chemosensors.

Biosorption of arsenite (As[III]) using Saccharomyces cerevisiae SRCM 501804 isolated from Korean turbid rice wine

The potentiality of Saccharomyces cerevisiae SRCM 501804 to remove arsenite (As[III]) in an aqueous solution was investigated in this study. The S. cerevisiae SRCM 501804 was isolated from Korean turbid rice wine (Makgeolli). The S. cerevisiae SRCM 501804 was characterized by phylogenetic analysis, Fourier transform infrared (FT-IR) spectroscopy, visual minerals technologies (MINTEQ) model, and point of zero charge (pHpzc). The relationship between the factors (pH, biosorbent dosage, contact time, and concentration) and biosorption capacity was investigated. The S. cerevisiae SRCM 501804 was removed 31.1–90.1% of the As(III) depending on the initial biomass dosage within 1 h. Co-existing anions in aqueous solution showed a negative influence on the biosorption performance of As(III) in the order Cl− > NO3 − > SO4 2− > CO3 2−. The results of isotherms and kinetics suggested the Langmuir (R 2 > 0.95) and Pseudo-second order (R 2 > 0.99) models fit well with the equilibrium experimental data. The maximum biosorption capacity (qm ) of S. cerevisiae SRCM 501804 biomass for As(III) was found to be 113.9 mg/g from Langmuir isotherm. Based on the results, it can be concluded that the biomass of S. cerevisiae SRCM 501804 could be used as an effective bio-sorbent for As(III) biosorption in an aqueous solution.

A New Determination of the Enthalpy of Formation of Fluoride Anions in Aqueous Solutions

A New Determination of the Enthalpy of Formation of Fluoride Anions in Aqueous Solutions

Comparative study of the interaction mechanisms between galena, cerussite and anglesite with benzohydroxamate and octanohydroxamate in aqueous solution

• The interaction mechanisms between lead ores with hydroxamate anions were suggested. • The identity of the formed metal complexes was determined by FTIR . • A lower BHA adsorption density on the lead active sites was found compared to OHA. • The collector anions are chemically adsorbed in most of the studied conditions. • Both anionic collectors are physisorbed onto anglesite conditioned at pH 5. Chelating agents have currently received particular attention in the search for reagents to improve the separation of oxidized minerals by froth flotation. Among chelating reagents, the hydroxamic acids outstand because they have shown a higher performance without the health, safety and environmental (HSE) concerns associated with the xanthates. In this study, the chemical adsorption of benzohydroxamic acid (BHA) and octanohydroxamic acid (OHA) onto galena (PbS), cerussite (PbCO 3 ) and anglesite (PbSO 4 ) surfaces was evaluated making use of infrared spectroscopy. Likewise, zeta potential measurements were carried out to determine the surface charge of the mineral particles before and after conditioning with the surfactant. Finally, the interaction mechanisms between galena, cerussite and anglesite with hydroxamate anions in aqueous solution were suggested; these mechanisms present the global reactions and help to understand the interaction of BHA and OHA with lead ores. It is suggested that the bezohydroxamate and octanohydroxamate anions are chemically adsorbed on the lead mineral surface in most of the studied conditions, except on the anglesite conditioned at pH 5, where the referred anions are physisorbed. The results obtained from infrared spectroscopy and zeta potential measurements suggest that P b 2 + dissolves from the crystal lattice and reacts with the anions to precipitate Pb–benzohydroxamate or Pb–octanohydroxamate, which are physically readsorbed on the anglesite surface vicinity. Additionally, the identity of the formed metal complexes was determined.

Synthesis and properties of a novel photochromic metal organic framework for rapid amine selective sensing and Cr2O72− detection

A new photochromic metal organic frameworks (MOFs) have been synthesized by using a viologen ligand, named 1,1′-bis(3,5-carboxylatobenzyl)-(4,4′-bipyridinium) dichloride (H4bdcbpy•2Cl) and Cd(NO3)2·4H2O. This MOF (Cd-bdcbpy) features a three-dimensional (3D) framework structure, exhibiting photochromic properties under the irradiation of white light, blue light, UV light and heat with obvious color change from light yellow to dark green. Meanwhile, Cd-bdcbpy displays a visible color change to the naked eye when exposed to different organic amine molecules (ammonia, aniline, o-methylaniline and diphenylamine). Moreover, the detection of ammonia has been confirmed by the visual color changing phenomenon and luminescence quenching experiment and it can detect ammonia in very low concentrations (10-6 ​M). Attractively, through luminescence quenching, Cd-bdcbpy can be used as a multi response sensor for Cr2O72− anion in aqueous solution.

Molecular Recognition of Biologically Relevant Anions with an Expanded Dinuclear Copper(II) Complex: An Efficient Sensor for Oxalate Anion in Aqueous Solution

AbstractAn expanded dinuclear copper(II) complex (1) derived from a biphenyl‐based hexaazamacrocyle (L) was synthesized and characterized by single crystal X‐ray analysis, exhibiting a boat‐shaped cavity with an elongated CuII⋅⋅⋅CuII distance of 11.01 Å. The dinuclear copper(II) complex was investigated for a verity of biologically relevant anions including carboxylates (oxalate, citrate, tartrate, glutamate, adipate, acetate and benzoate), oxoanions (phosphate, sulphate, perchlorate and nitrate), and halides (fluoride, chloride, bromide and iodide) by competitive fluorescence titrations via indicator displacement assay (IDA) using an external dye (Eosin Y) in water‐methanol solution at neutral pH. The receptor was shown to exhibit strong affinity for oxalate, providing the binding trend: oxalate (log K=6.07)>citrate (log K=5.74)>phosphate (log K=5.02)>tartrate (log K=4.78)>glutamate (log K=4.42)>adipate (log K=4.31)>acetate (log K=4.14)>benzoate (log K=4.01). No interaction was observed for other anions including sulphate, perchlorate, nitrate, fluoride, chloride, bromide and iodide under the identical conditions.

Enhanced photocatalytic degradation of sulfamethoxazole by stable hierarchical Fe2O3/Co3O4 heterojunction on nickel foam

A facile approach was successfully employed to prepare Fe2O3/Co3O4 nanosheet arrays on nickel foams (Fe2O3/Co3O4@NF), which owned such advantages as narrow band gap energies and high separation rate of photoexcited electron-hole pairs. The combination of Fe2O3 and Co3O4 dramatically enhanced the photocatalytic activity towards sulfamethoxazole (SMZ) degradation, with the highest catalytic efficiency of k = 0.0538 min−1, which was much higher than that of Fe2O3@NF (0.0098 min−1) and Co3O4@NF (0.0094 min−1). The introduction of Ni foam could not only act as the support to anchor photocatalyst, but also work as the electron mediator to promote the transition of electron-hole pairs. Reactive species trapping experiments combined with electron paramagnetic resonance analysis confirmed •O2− was primarily responsible for SMZ degradation. Furthermore, Fe2O3/Co3O4@NF was effective and almost unaffected by inorganic cations and anions in aqueous solution. This study could provide a facile and promising path for the construction of self-supported metal oxide-based heterojunction with high efficiency and strong stability.