Anions In Aqueous Solution Research Articles

New fluorescent chemosensors based on mononuclear copper complex for highly selective and sensitive detection of phosphate anion in aqueous solution and living cells.

Three new probes, named, [Cu(L1)2]Cl2 (C1), [Cu(L2)2]Cl2 (C2) and [Cu(L3)2]Cl2 (C3) were synthesized and well characterized. The probes C1, C2 and C3 were successfully achieved for the efficient detection of PO43- as turn-on fluorescence chemosensors in DMSO/H2O (v:v = 2:8, Tris-HCl pH = 7.20). The limit of detection (LOD) of probes C1, C2 or C3 for PO43- could be as low as 0.029 μM, 0.048 μM, 0.079 μM, respectively, which were effectively applied for the determination of the PO43- concentration in environmental water of swimming pool. What's more, the binding constant between probes C1, C2, C3 and PO43- are estimated to be 3.11 × 107 M-1 (R2 = 0.9992), 1.84 × 107 M-1 (R2 = 0.9956), 1.93 × 107 M-1 (R2 = 0.9976), respectively. The proposed mechanism for the "on-off-on" fluorescence response was confirmed by ESI-MS and fluorescence spectrum. Moreover, the membrane-permeable probe C1 was successfully demonstrated in monitoring of PO43- in cultured HepG2 cells.

Ratiometric fluorescence turn-on sensing of perrhenate anion, a non-radioactive surrogate of hazardous pertechnetate, in aqueous solution

Fluorescent sensor for the perrhenate/pertechnetate anions in aqueous media are rarely reported in literature as their large size and low charge density poses great challenge to their detection. Herein, we report the first fluorescent turn-on ratiometric sensor for perrhenate anion, exploiting its weak hydration property which leads to an advantageous formation of a contact ion-pair of perrhenate anion with a well-known cationic ultrafast molecular rotor dye, Auramine O. This ion-pair formation, in turn, leads to a fluorescent aggregate assembly that provides an excellent opportunity to detect perrhenate anion in aqueous solution.

Highly reduced and protonated aqueous solutions of [P2W18O62]6- for on-demand hydrogen generation and energy storage.

As our reliance on renewable energy sources grows, so too does our need to store this energy to mitigate against troughs in supply. Energy storage in batteries or by conversion to chemical fuels are the two most flexible and scalable options, but are normally considered mutually exclusive. Energy storage solutions that can act as both batteries and fuel generation devices (depending on the requirements of the user) could therefore revolutionize the uptake and use of renewably generated energy. Here, we present a polyoxoanion, [P2W18O62]6-, that can be reversibly reduced and protonated by 18 electrons/H+ per anion in aqueous solution, and that can act either as a high-performance redox flow battery electrolyte (giving a practical discharged energy density of 225 Wh l-1 with a theoretical energy density of more than 1,000 Wh l-1), or as a mediator in an electrolytic cell for the on-demand generation of hydrogen.

Aromatic 3,5-Di(2′,4′-dicarboxylphenyl)benozoic acid based coordination polymers as luminescent sensor for the sensitive detection of chromate anions in aqueous solution

Based on the mixed ligands of aromatic pentacarboxylate of 3,5-di(2′,4′-dicarboxylphenyl)benozoic acid (H5L) and 1,4-bis(imidazol-1-yl) benzene (bib), two novel coordination polymers, namely, [Ni1.5(H2L)(bib)1.5(H2O)2]n (1), and {[Pb2(HL)(bib)1.5(H2O)]·H2O}n (2) have been synthesized and characterized by EA, IR, TG, PXRD. Structure analyses reveal that complexes 1 and 2 are both (3,4,4)-connected structures with the same stoichiometry of (3-c)2(4-c)2(4-c), the 2D {63}2{64.8.10}{64.82}2 trilayer for 1, and 3D {6.82}2{64.82}2{8.104.12} network for 2. Complexes 1 and 2 exhibit excellent recyclable, selective, and sensitive detection of Cr(VI) anions in aqueous solution. The possible mechanism for selective luminescence quenching responses toward Cr(VI) anions is also discussed in detail.

Electrovalent chitosan functionalized methyl-orange/metal nanocomposites as chemosensors for toxic aqueous anions

Chitosan functionalized methyl orange (CFMO) nanocomposites of iron (CFMO-FeNPs) and copper (CFMO-CuNPs) were successfully prepared as simple and selective chemosensors for CN − and AsO43− anions in aqueous solution. The initially synthesized chitosan-dye-metal complexes (CFMO-Fe(II) and CFMO-Cu(II) were nanosized via chemical reduction methods. The imminent IR bands shift especially of νC−C aromatic rings and CFMO azo bond suggest the formation of cyclometaled metal-azo complexes. Plasmon resonance bands at 473 and 469 nm were observed for the nanocomposites of Fe and Cu respectively indicating successful nano reduction of the metal ions. The semi-crystalline nature of the composites was revealed from the XRD analysis which ranged from broad to sharp peaks. More so, the varying linear orientation to monodispersed distribution of the nanoparticles on the biopolymeric substrate was displayed in the SEM micrographs. The electrostatic attraction between the metal induced cationic N,N-dimethylbenzenamine end and the test anions provides remarkable colorimetric responses with high selectivity for the test anions in an aqueous solution with LOD of 1.0 and 2.0 μg/mL for CN− and AsO43− respectively. Consequently, the obvious selective color changes can be exploited for real time and on site applications.

Selective and sensitive fluorescent and colorimetric chemosensor for detection of CO32- anions in aqueous solution and living cells

A new colorimetric and fluorescent chemosensor for visual determination of carbonate ions was developed by the microwave assisted solvent free synthesis of 7,8-dihydroxy-3-(4-methylphenyl) coumarin (DHMC). The structural characterization of DHMC was confirmed by microanalysis and spectroscopy methods (MALDI-TOF, FT-IR, 1H NMR, 13C NMR, and 2D HETCOR). The binding behaviors of DHMC were investigated towards various anions by UV–vis and fluorescence spectroscopy. DHMC showed a selective and sensitive fluorometric and colorimetric responses towards carbonate ion over other anions. The detection limit of CO32- was found to be 1.03 µM. Moreover, the fluorescence imaging in living cells suggests that DHMC has a great potential in the biological imaging application. It has been demonstrated that DHMC can be used as a rapid and reliable sensor for the determination of carbonate anion in a variety of practical applications.

An efficient strategy for sensing pyrophosphate based on nitrogen-rich quantum dots combined with graphene oxide

A facile approach was developed to prepare fluorescent nitrogen-rich quantum dots (NCQDs) using 2-azidoimidazole and ammonium hydroxide as reactants. The nitrogen and carbon elements of NCQDs form the frameworks of their nanostructures together and bear multiple active sites. By using NCQDs as fluorophores and graphene oxide (GO) as controllers, a hydrogen binding-based nanosensor was constructed for the detection of pyrophosphate (PPi). In NCQDs-GO sensing assemblies, the binding of GO to NCQDs results in the fluorescence quenching by FRET mechanism; while the addition of PPi leads to the fluorescence recovery of NCQDs because of the competitive binding between NCQDs and PPi to GO. The fluorescence intensity showed linearity with the added PPi concentration ranging from 0 to 400 μM with the detection limit of 8.3 nM (σ = 3). This procedure for the fabrication of amino-functionalized carbon quantum dots is simpler and more efficient compared to conventional doping and surface modification methods. The proposed NCQDs-GO sensing assemblies showed high selectivity and sensitivity to PPi over the competing anions in aqueous solution.

Structural diversity and luminescent sensing of three coordination polymers based on the hydrolysates of N,N′-bis(3,5-dicarboxylatophenyl)pyromelliticdi-imide)

Based on the hydrolysates of N,N′-bis(3,5-dicarboxylatophenyl)pyromelliticdi-imide) (H4L) and 1,3-bis(imidazol-1-ylmethyl)benzene (bimb), three coordination polymers, namely, {[Zn(BTC)0.5(bimb)]·4H2O}n (1), [Cu(BTC)0.5(bimb)]n (2), and {[Cd(AIP)(H2O)]·H2O}n (3), have been obtained under solvothermal conditions. The possible hydrolysis mechanism of H4L was investigated here. Structural analyses reveal that complex 1 is a 3D (4,4)-c {64.82}{66}2-bbf net. Complex 2 displays a 2D 4-c {32.62.72}-kgm sheet. While complex 3 exhibits a 3D (3,6)-c {4.62}2{42.610.83}-rtl net based on binuclear {Cd2(COO)4} SBUs. Besides, luminescent sensing investigation indicated that 1 and 3 exhibit highly sensitive and selective sensing of chromate anions in aqueous solution.

Hydro/solvo-thermal syntheses and characterization of a series of CuII and CuI coordination polymers with an asymmetric semi-rigid Bi-functional ligand: Temperature induced polymorphism and photo-luminescent sensing

In this work, a flexible asymmetric semi-rigid bi-functional ligand 5-(4-((1H-1,2,4- triazol-1-yl)methyl)phenyl)-1H-tetrazole (HL) has been employed. A series of unique CuII and CuI coordination compounds, namely [Cu(μ2-L)2(H2O)2]n (1), [Cu(μ2-L)2(H2O)2]n (2), [Cu(μ4-L)]n (3) and [Cu2.5(μ4-L)(CN)1.5]n (4), have been prepared under hydro(solvo)-thermal conditions. 1 and 2 present scarcely reported temperature induced polymorphic 1D (1) and 2D (2) copper(II)-L coordination frameworks. When HL and CuBr2 are employed to react in the mixed H2O/CH3CN (1:1) solvent system, the 3D CuI-HL coordination polymer 3 can be isolated. The CuI centers in 3 should be the reduction of CuII ions by CH3CN solvent. When CuBr is used to replace CuBr2 under similar synthetic conditions of 3, 4 can be isolated. 4 is a unique 3D CuI cluster-based coordination framework assembled from L− and CN−. PXRD patters of all the bulky samples 1–4 also have been determined, which agree well with theoretical PXRD patterns, confirming pure phases. Photo-luminescent measurements also show that complexes 3–4 can behave highly sensitive photo-luminescent sensing of small solvent molecules DMF and NMP. Additionally, 4 also exhibits highly selective and sensitive photo-luminescent discriminating of dichromate anions in aqueous solutions with excellent quenching efficiency (Ksv = 2.38 × 104 L mol-1). The experiment result also demonstrates the broad prospects in the preparation of these novel coordination frameworks using these flexible bi-functional asymmetric semi-rigid ligands as basic building blocks.

Robust Multilayer Graphene-Organic Frameworks for Selective Separation of Monovalent Anions.

The chemical and mechanical stability of graphene nanosheets was used in this work to design a multilayer architecture of graphene, grafted with sulfonated 4,4'-diaminodiphenyl sulfone (SDDS). Quaternized poly(phenylene oxide) (QPPO) was synthesized and mixed with SDDS (rGO-SDDS-rGO@QPPO), yielding a multilayer graphene-organic framework (MGOF) with positive as well as negative functional groups that can be applied as a versatile electrodriven membrane in electrodialysis (ED). Multilayer graphene-organic frameworks are a new class of multilayer structures, with an architecture having a tunable interlayer spacing connected by cationic polymer material. MGOF membranes were demonstrated to allow for an excellent selective separation of monovalent anions in aqueous solution. Furthermore, different types of rGO-SDDS-rGO@QPPO membranes were found to have a good mechanical strength, with a tensile strength up to 66.43 MPa. The membrane (rGO-SDDS-rGO@QPPO-2) also has a low surface electric resistance (2.79 Ω·cm2) and a low water content (14.5%) and swelling rate (4.7%). In addition, the selective separation between Cl- and SO42- of the MGOF membranes could be as high as 36.6%.

Insight into the mode of action of Pd-doped zero-valent iron nanoparticles @graphene (Pd/FePs@G) toward carbon tetrachloride dechlorination reaction in aqueous solution

Herein, Pd/Fe bimetallic nanoparticles (Pd/FePs) were uniformly distributed on the surface of graphene sheet structure, and had good combination with the multilayer substrate. The nanocomposites could maintain high reactivity even after five times degradation reactions of carbon tetrachloride (CT) in succession, indicating that the modified technology had a positive effect on achieving high surface activity and prolonging the longevity. The structure evolution and compositional changes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photo-electron spectroscopy (XPS). Also, humic acid (HA) as non-reactive adsorbate could preferentially occupy surface active sites of Pd/FePs to mediate the predominant radical species in the degradation process, which caused a 53% decrease in dechlorination rate of CT. These findings provided an important understanding of the stability and reactive mechanism involved in Pd/Fe bimetallic system toward CT degradation. Moreover, batch experiments were conducted to investigate the actual catalytic activity in view of the effects of common inorganic anions in aqueous solution. The results revealed that the presence of Cl−, HCO3−, and HPO42− was beneficial to the CT degradation while SO42- and NO3− exerted the negative effects. Based on the detection results by means of gas chromatography (GC) and ion chromatography (IC), a possible degradation pathway was propose.

Effects of Cations and Anions in Aqueous Solution on the Electroreduction of Carbon Dioxide

Electrolyte has a crucial effect on the performance of electrodes in the process of the electrochemical reduction of carbon dioxide (ERC). In this work, we added common cations including SO4 2 -/HSO4 -, NO3 -,H2PO4 -/HPO4 2-/PO4 3-, Cl-, Br-, I-, and CH3COO-) and common metal ions (Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, and Ba2+) in a 0.1M NaHCO3 aqueous solution to investigate the effects of their presence in electrolyte solution on the efficient ERC over single metallic Cu and Sn electrodes. The effect of these ions on the rate of the ERC, the distribution of the products, and the reaction mechanism of electroreduction of CO2 over Cu and Sn electrodes in electrolyte solution were studied. According to experimental results, we will be able to choose the appropriate electrolyte to enhance electrocatalytic activity and stability, and improve the prediction selectivity of single metallic Cu and Sn catalysts.

Ni(II)/Zn(II)-triazolate clusters based MOFs constructed from a V-shaped dicarboxylate ligand: Magnetic properties and phosphate sensing

Two isomorphous metal-organic frameworks (MOFs) {[M2(μ3-OH)(trz)(sdba)(H2O)]·3H2O}∞ (M = Ni for 1, Zn for 2, Htrz = 1,2,4-triazole, H2sdba = 4,4′-sulfonyldibenzoate) were obtained under the same reaction condition. Both of complexes present a three dimensional 8-c framework with whc1 topology based on M4-(μ3-OH) units. Moreover, the magnetic properties of 1 and anion sensing of 2 were investigated. The magnetic study show that the domain antiferromagnetic interactions exist in 1. However, complex 2 can be considered as a promising chemical sensor for detecting PO43¯by means of fluorescence enhancement among various anions in aqueous solutions.

Terphenyltetracarboxylate acid based 3D modular cobalt(II) coordination polymer with highly sensitive luminescent sensing of chromate anions

Based on the mixed ligands synthesis strategy, a 3D cobalt (II) coordination polymer, [Co(tptc)0.5(bib)]n (1), has been assembled from p-terphenyl-2,2″,5″,5″'-tetracarboxylate acid (H4tptc) and 1,3-bis((imidazol-1-yl) benzene (bib). Structural analysis revealed that complex 1 is a 3D framework, which can be simplified into a (4,4)-connected {64.82}{66}2bbf net. And the modular analysis reveals the tiling of 1 is [6.82] + [63.8] = [6c.8a.8b] + [6a.6b.6c.8a] with the transitivity is 2352. And the luminescent sensing investigation indicating complex 1 exhibits highly sensitive sensing of CrO42−/Cr2O72− anions in aqueous solution through strong luminescence quenching effects.

A Water-Stable Luminescent ZnII Metal-Organic Framework as Chemosensor for High-Efficiency Detection of CrVI -Anions (Cr2 O72- and CrO42- ) in Aqueous Solution.

A new luminescent ZnII -MOF with 1D triangular channels along the b axis, namely NUM-5, has been successfully assembled and well characterized, which features good stability, especially in aqueous solution. Interestingly, this compound exhibits a fast, sensitive and selective luminescence quenching response towards CrVI (Cr2 O72- /CrO42- ) in aqueous solution. The detection limits towards Cr2 O72- and CrO42- ions are estimated to be 0.7 and 0.3 ppm, respectively, which are among the lowest detection limits reported for the MOF-based fluorescent probes that can simultaneously detect Cr2 O72- and CrO42- in aqueous environment. The possible detection mechanism has been discussed in detail. Moreover, it can be easily regenerated after detection experiments, indicative of excellent recyclability. All these results suggest NUM-5 to be a highly selective and recyclable luminescent sensing material for the quantitative detection of CrVI anions in aqueous solution.

Two luminescent lanthanide(iii) metal-organic frameworks as chemosensors for high-efficiency recognition of Cr(vi) anions in aqueous solution.

Two new lanthanide(iii) metal-organic frameworks (MOFs) {[(CH3)2NH2]2[Ln4(FDA)7(DMF)2]·0.5DMF}n [Ln = Eu (1), and Tb (2)] based on furan-2,5-dicarboxylic acid (H2FDA) have been successfully assembled and well characterized in detail. These MOFs are isostructural and demonstrate 12-connected sqc15 topologies, which are rarely observed in MOF chemistry, especially in lanthanide(iii) MOFs. Moreover, these two MOFs could show a tolerance towards moisture and organic solvents and satisfactory chemical stabilities. More importantly, they exhibit sensitive and selective luminescence quenching response towards Cr2O72- and CrO42- anions in aqueous solution with the average quenching Ksv values of 1.25 × 104 L mol-1 (Cr2O72-) and 3.56 × 103 L mol-1 (CrO42-) for 1 and 1.46 × 104 L mol-1 (Cr2O72-) and 4.35 × 103 L mol-1 (CrO42-) for 2 and the detection limits of 1.14 × 10-4 mol L-1 (Cr2O72-) and 1.12 × 10-4 mol L-1 (CrO42-) for 1 and 7.42 × 10-5 mol L-1 (Cr2O72-) and 1.27 × 10-4 mol L-1 (CrO42-) for 2. The high quenching Ksv values and low detection limits make them more feasible in sensing Cr(vi) anions in aqueous solution. The possible detection mechanism has been discussed in detail.

Mobilities of iodide anions in aqueous solutions for applications in natural dye-sensitized solar cells.

Dye-sensitized solar cells (DSSCs) composed of aqueous electrolytes represent an environmentally friendly, low-cost, and concrete alternative to standard DSSCs and typical solar cells. Although flammable and toxic organic-solvent-based electrolytes have so far been employed more than simpler (iodide) aqueous solutions, recently recorded efficiencies of water-based DSSCs suggest a trend inversion in the near future. Here, we present a study, based on both experiments and ab initio molecular dynamics simulations, in which assessments on the efficiencies of three water electrolytes commonly employed in DSSCs (i.e., LiI, NaI, and KI) are reported. In particular, by atomistically tracing the ability of the iodides as charge carriers and by experimentally measuring the generated currents, we demonstrate that NaI aqueous solutions are more efficient electrolytes than LiI and KI - in descending order - in transporting electrons in DSSCs under bias. Monitoring the role played by the hydration shells of the ionic species under an electric field, we interpret, by first-principles, the various iodide mobilities. This finding, when combined with general considerations on the cation-induced effects on the TiO2 electronic structure, is able to account for the distinct efficiencies of the investigated electrolytes.

A fluorescent turn-on probe for cyanide anion detection based on an AIE active cobalt(ii) complex.

A new tetradentate polypyridine ligand that displays aggregation induced emission (AIE) characteristics has been synthesized. A coordination complex with CoCl2 has been prepared and characterized by X-ray crystallography. The Co(ii) complex retains the AIE activity of the ligand in aqueous solution while also exhibiting a selective turn-on fluorescence response in the presence of cyanide anion. A complex : CN- binding stoichiometry of 1 : 2 was indicated via Job plot analysis and the limit of detection for CN- was determined to be 0.59 μM. The fluorescence response is attributed to coordination of CN- by the AIE active Co(ii) complex, resulting in decreased solubility in aqueous medium and concomitant generation of larger nanoaggregates as revealed by dynamic light scattering (DLS) measurements. The sensitivity and selectivity displayed by this sensor for CN- over other anions renders it a candidate probe for CN- detection in aqueous environments.

A two-fold interpenetrated zinc–organic framework: luminescence detection of CrO42−/Cr2O72− and chemical conversion of CO2

A novel two-fold interpenetrated 3D framework can adsorb CO2 and serve as an efficient and recyclable catalyst for the conversion of CO2 with epoxides. Furthermore, it can also act as a sensitive and recyclable luminescent probe to detect CrO42−/Cr2O72− among many anions in aqueous solution.

Composition and structure of hydrates of CH3COOH molecules and CH3CO2− anions in aqueous solutions

The optimal configurations, energy parameters, and normal vibrational frequencies of hydrates of the acetic acid molecule and anion (CH3COOH·(H2O) n (n = 1-10) and CH3CO2−⋅(H2O) n (n = 1-8, 16)) are calculated by density functional theory (B3LYP/6-31++G(d,p)). The comparison of the calculation results with the known experimental data (Raman, NMR, and so on) gives arguments in favor of the existence of two stable heteroassociates (HAs) in СН3СООН–H2O solutions: previously found CH3COOH·(H2O)2 heterotrimer and CH3COOH·(H2O)8, and three complexes (CH3CO2−⋅(H2O)2, CH3CO2−⋅(H2O)6, and CH3CO2−⋅(H2O)16) in NaCH3CO2−–H2O solutions. Each of them is most stable in a series of isomers, contains unstrained H bonds, and is characterized by the maximum molecular packing density among HAs with similar n values. The structure of the subsequent complex formed in solution uniquely follows the structure of the preceding complex and is based on it.