Ions In Aqueous Environment Research Articles

Synthesis of triazole linked fluorescent amino acid and carbohydrate bio-conjugates: a highly sensitive and skeleton selective multi-responsive chemosensor for Cu(ii) and Pb(ii)/Hg(ii) ions

A set of triazole-based chromogenic and fluorescent chemosensors with amino acid/carbohydrate–fluorophore conjugates have been designed and synthesized. The metal cation-sensing properties of glycine–anthracene, C24H24O4N4 (3), glycine–pyrene C26H24O4N4 (4), glucose–anthracene, C32H33O10N3 (5) and glucose–pyrene, C34H33O10N3 (6) bio-conjugates have been studied systematically. The significant changes in their absorption spectra are accompanied by a strong color change from light yellow to brown for 3 and 4 and colorless to greenish blue for 5 and 6. Receptors 3 and 4 have potential in the “naked eye” detection of Cu2+ and 5 and 6 for Pb2+/Hg2+ ion. The receptors 3 and 4 show fluorescence diminution following Cu2+ coordination within the limit of detection at 0.89 parts per billion (ppb) and this is unprecedented, whereas the receptors 5 and 6 present drastic fluorescence quenching upon addition of Hg2+ and Pb2+ within the limit of detection at 4 and 2 ppb respectively. Interestingly, their fluorescence and colorimetric responses are preserved in the presence of water that can be used for the selective colorimetric detection of these ions in aqueous environments. Along with the spectroscopic data, combined 1H NMR titration of the complexes and the DFT studies suggest the proposed coordination modes.

Design and Synthetic Scheme of Water Dispersible Graphene Oxide-Coumarin Complex for Ultra-Sensitive Fluorescence Based Detection of Copper (Cu2+) Ion in Aqueous Environment

Copper oxides and its salts are now widely used as pesticides to control fungal and bacterial diseases of field crops. Copper toxicity is often a major contributor of human health problems caused through accumulation of excess copper ions in various organs via drinking water, fruits and vegetables. So, detection and estimation of cupric ions in biological organs, drinking water, fruits and vegetables are extremely important. Recently, a fluorescence based sensor using coumarin dye (high quantum yield) has been proposed to detect micromolar Cu++ ion in biological organs. But major problem with coumarin dye is that it is insoluble in water and undergoes dye-dye aggregation in organic solvents. We proposed here a synthetic scheme of preparation of graphene oxide conjugated coumarin dye derivative which would be water dispersible and expected to be an ideal candidate for Cu2+ ion estimation in biological organs and drinking water.

Modulation of Quinone PCET Reaction by Ca2+ Ion Captured by Calix[4]quinone in Water

Calix[4]arene-triacid-monoquinone (CTAQ), a quinone-containing water-soluble ionophore, was utilized to investigate how proton-coupled electron transfer (PCET) reactions of quinones were influenced by redox-inactive metal ions in aqueous environment. This ionophoric quinone derivative captured a Ca(2+) ion that drastically altered the voltammetric behavior of quinone, showing a characteristic response to pH and unique redox wave separation. Spectroelectrochemistry verified significant stabilization of the semiquinone, and electrocatalytic currents were observed in the presence of Ca(2+)-free CTAQ. Using digital simulation of cyclic voltammograms to clarify how the thermodynamic properties of quinones were altered, a simple scheme was proposed that successfully accounted for all the observations. The change induced by Ca(2+) complexation was explained on the basis of the combined effects of the electrostatic influence of the captured metal ion and hydrogen bonding of water molecules with the support of DFT calculation.

Structure and dynamics of the Th4+-ion in aqueous solution – An ab initio QMCF-MD study

An ab initio quantum mechanical charge-field molecular dynamics simulation of the tetravalent thorium ion in aqueous environment is presented. Including the first and second hydration shell in the quantum mechanical treatment to enhance accuracy, this study yields very good results for a wide range of characteristics, as compared to experimental data. 20ps of simulation time were used to investigate structural and dynamical properties of the hydrate by numerous methods, including radial and angular distribution functions, three-body distribution functions, ligand exchange analysis and vibrational spectra. The hydrate proved stable during the simulation and did not show hydrolysis. The first solvation shell was found to be a very flexible one, with a number of intrashell ligand rearrangements occurring along the simulation. The data of the simulation also indicated the existence of a third hydration layer. Vibrational analysis yielded an average ion–oxygen frequency of 420cm−1, which is in excellent agreement with experimental data.

Probing the mechanisms of proton transfer in liquid water

Despite more than two centuries of experimental and theoretical investigations aimed at understanding the mechanisms by which hydronium (H3O+) and hydroxide (HO−) ions are transported through water (1⇓⇓⇓⇓–6), unique results published in PNAS (7) reveal that these can be complex processes that strongly couple to the structural and dynamic properties of the 3D hydrogen bond (H-bond) network in water. Water is well known as a very versatile and ubiquitous solvent, offering a rich environment for a multitude of complex reactions and processes. Its constituent hydronium and hydroxide ions exist as dynamic charge defects that can be viewed as representing the excess proton and proton hole, respectively. Importantly, these ions are known to exhibit anomalously high diffusion rates relative to other simple ions (e.g., Na+ or Cl−). The phenomena by which H3O+ and HO− move through water have enormous impacts on areas ranging from aqueous acid-base chemistry, enzymatic proton transfer, as well as proton transfer in biological channels, through fuel cell membranes and on ice surfaces facilitating atmospheric reactions (8). Marx (8) has reviewed recent progress in our understanding of the solvation and transport properties of hydronium and hydroxide ions in aqueous environments. To date, the accepted picture of an excess proton in water is that it … [↵][1]1To whom correspondence should be addressed. E-mail: pkusalik{at}ucalgary.ca. [1]: #xref-corresp-1-1

Preparation and Characterization of Poly(ethyl hydrazide) Grafted Oil Palm Empty Fruit Bunch for Removal of Ni(II) Ion in Aqueous Environment

Poly(ethyl hydrazide) grafted oil palm empty fruit bunch (peh-g-opefb) fiber has been successfully prepared by heating poly(methylacrylate)-g-opefb at 60 °C for 4 h in a solution of hydrazine hydrate in ethanol. The chelating ability of peh-g-opefb was evaluated based on removal of Ni(II) ions in aqueous solution. Adsorption of Ni(II) by peh-g-opefb was characterized based on effect of pH, isotherm, kinetic and thermodynamic study. This cheap sorbent based on oil palm empty fruit bunch fiber has a great future potential in water treatment industries based on high adsorption capacity, biodegradability and renewability.

Sorption of toxic metal ions in aqueous environment using electrospun polystyrene fibres incorporating diazole ligands

Electrospun polystyrene fibres incorporating potassium salts of pyrazole-1-carbodithioate and imidazole-1-carbodithioate were employed as sorbents for heavy metals from aqueous environments. The equilibrating time, initial metal concentrations and sorbent mass for optimal adsorption were 40 min, 5 mg/ℓ and 8 mg, respectively. The optimal pH for metal ion uptake was between 6.3 and 9.0 and was found to be dependent on the basicity of the ligands. Protonation constants for the ligands in aqueous solutions were determined potentiometrically; pK of the imidazole was 6.82 while that of the pyrazole was 3.36. The efficiencies of adsorption and desorption of metals on the imidazolyl-incorporated sorbents were more than 95%, up to the fifth cycle of usage. The limits of quantification were ≤ 0.0145 mg/ℓ for all the metals. Accuracy of the determinations, expressed as relative error between the certified and observed values of certified reference groundwater samples was ≤ 0.2% with relative standard deviations < 3%. Electrospun polystyrene fibres incorporating imidazoles proved to be efficient sorbents for divalent heavy metal ions in aqueous environments as their efficiencies exceeded those of chitosan microspheres, ion-imprinted composites, amino-functionalised mesoporous materials and most of the biomass-based sorbents previously reported on.Keywords: electrospinning, polystyrene, heavy metals, diazole

Algal polysaccharides on lipid Langmuir–Blodgett films and molecular effects upon metal ion contact

The capability of extracellular polysaccharides released from microorganisms to bind to metal ions is a potential molecular biotechnological tool to produce biosorbents as an alternative for the removal of heavy metals from aquatic environments. In this paper, we exploit the ability of polysaccharides from extracellular polymeric substances produced by phytoplankton adsorbed on lipid monolayers as Langmuir–Blodgett films to interact with silver ions in aqueous environments. The properties of the biomacromolecules after the interaction were investigated with polarisation modulation infrared reflection-absorption spectroscopy and atomic force microscopy. The vibrational spectroscopy technique applied to the Langmuir–Blodgett films before and after contact with silver ions indicated significant changes for the bands related to the chemical groups present in polypeptides and polysaccharides. These changes point to the influence of the metal interaction on the molecular organisation and on the structure of the Langmuir–Blodgett film. Therefore, the behaviour of these biomacromolecules adsorbed at bioinspired interfaces is better understood in terms of properties at the molecular level. This understanding leads to a model in which metal incorporation affects the molecular structure of the ultrathin film.

Colorimetric detection of Fe(III) ions using label-free gold nanoparticles and acidic thiourea mixture

We report colorimetric, label-free, and non-aggregation-based gold nanoparticle (AuNP) probes for the highly selective detection of Fe(III) ions in aqueous environments. This detection scheme relies on the ability of Fe(III) ions to catalyze the leaching of gold at room temperature in the presence of thiourea species and hydrochloric acid. The catalytic leaching of the AuNP probes results in rapid and remarkable damping of the surface Plasmon band and hence induces a visible color change which can be easily detected through naked eye. This simple and cost-effective probe provides rapid detection of Fe(III) ions at concentrations as low as 50ppm and expected to be effective to design efficient environmental and biological sensor.

Studies on the Effect of Temperature on Lead Ion in Aqueous Environment based on Pourbaix Diagram

Studies on the Effect of Temperature on Lead Ion in Aqueous Environment based on Pourbaix Diagram

Sensitive and Selective Redox, Chromogenic, and “Turn-On” Fluorescent Probe for Pb(II) in Aqueous Environment

The electrochemical, optical, and metal cation sensing properties of the triazole-tethered ferrocene-anthracene conjugates, C(48)H(40)FeO(2)N(6) (3) and C(52)H(40)FeO(2)N(6) (4), and the ferrocene-pyrene conjugates, C(29)H(25)FeON(3) (5) and C(31)H(25)FeON(3) (6), have been documented. All the compounds 3-6 behave as very selective redox, chromogenic, and "turn-on" fluorescent probes for Pb(2+) ion in an aqueous environment (CH(3)CN/H(2)O, 2/8). The significant changes in their absorption spectra are accompanied by a strong color change from yellow to greenish blue, which allows a prospective use for the "naked eye" detection of Pb(2+) ion over other competitor cations such as Hg(2+) and Cd(2+). These chemosensors present immense brightness and fluorescence enhancement (chelation-enhanced fluorescence = 85 for 3 and 92 for 4) following Pb(2+) coordination within the limit of detection at 2 ppb. Interestingly, their fluorescence, redox, and colorimetric responses are preserved in presence of water, which can be used for the selective colorimetric detection of Pb(2+) ion in aqueous environment over Hg(2+) and Cd(2+) cations. All the compounds have been characterized by (1)H, (13)C NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS) spectrometric analysis, and the solid-state structures of 5 and 6 have been unequivocally established by X-ray diffraction analysis.

Investigation of Conjugated Polymers for Metal Ion Sensing

Two carboxylate-containing fluorene-based anoinic water-soluble conjugated polymers, which are specially de- signed to link fluorene with alternating moieties such as 5% benzo(2,1,3)thiadiazole (BT) and amine groups have been syn- thesized via the Pd-catalyzed Suzuki-coupling reaction, respectively. The optical properties of the neutral precursory poly- mers in CHCl3 and final carboxylic-anionic conjugated polyelectrolytes in aqueous solution were investigated. These poly- mers had good solubility in water and showed different responses for metal ions in aqueous environments. The fluorescence of carboxylic-anionic polyfluorene (PFA) can be quenched by most of metal ions selected (except K + , Li

A triazole based triferrocene derivative as a multiresponsive chemosensor for Hg(II) ion and a redox chemosensor for H2PO4− ion

A triazole tethered triferrocene receptor, C40H40O2N6Fe33, has been synthesized from the reaction of mono-alkynyl substituted ferrocene, 1 and 1,1′-bis-(azidomethyl)ferrocene, 2. Consequently the cation and anion sensing properties of 3 have been examined. The receptor 3 was found to be highly selective electrochemical (ΔE1/21=145mV,ΔE1/22=92mV), optical and chromogenic chemosensor for Hg2+ ion in aqueous environment. The substantial changes in its absorption spectra are accompanied by the appearance of a new low-energy peak at 631 nm (ɛ = 3400 M−1 cm−1). This is also accompanied by a strong color change from yellow to purple, that allows a prospective for the “naked eye” detection of Hg2+ ion over other competitor cations such as Pb2+, Cd2+, Zn2+, etc. In addition, among various anions, 3 shows a distinct electrochemical recognition of dihydrogen phosphate anion by its multiple H-bonding (C–H⋯O), which is supported by electrochemical (large cathodic shift ΔE1/2 = −175 mV) and 1H NMR titration results.

Click-generated triazole based ferrocene-carbohydrate bioconjugates: A highly selective multisignalling probe for Cu(II) ions

Two Cu2+-specific colorimetric sensors, based on ferrocene-carbohydrate bioconjugates, 2, C46H56O20N6Fe and 3, C28H33O10N3Fe were designed and synthesized in good yields. Both the compounds, 2 and 3, behave as very selective and sensitive chromogenic and electrochemical chemosensor for Cu2+ ion in aqueous environment (CH3CN/H2O (2:8, v/v). The analytical detection limit (ADL) for receptor 2 was 7.5 × 10−7 M. The considerable changes in their absorption spectra of 2 and 3 are accompanied by the appearance of a new low energy (LE) peak at 630 nm (2: ε = 1600 M−1 cm−1 and 3: 822 M−1 cm−1). This is further accompanied by a strong colour change from yellow to dark green that allows the prospective for ‘naked eye’ detection of Cu2+ ion.

Surface-plasmon-based colorimetric detection of Cu(II) ions using label-free gold nanoparticles in aqueous thiosulfate systems

We report colorimetric, label-free and non-aggregation-based gold nanoparticle (AuNP) probes for the highly selective detection of Cu(II) ions in aqueous environments. This detection scheme relies on the ability of Cu(II) ions to catalyze the leaching of gold at room temperature in the presence of thiosulfate species and ammonia. This simple and cost-effective probe provides rapid detection of Cu(II) ions at concentrations as low as 10 ppm. A similar detection method using AuNPs in ammonia-free thiosulfate solution is also viable at moderate reaction temperature (50 °C). The ammonia-free method also leads to marked damping and red-shifting of the surface plasmon resonance signal of the AuNP dispersion. The two methods clearly differ in the nature of the surface plasmon damping phenomenon, and their working mechanisms are plausibly explained based on the experimental investigations.

Computational study of the cerium(III) ion in aqueous environment

This work comprises the first quantum chemical simulation study of the Ce3+ ion in aqueous environment. The structural and dynamical properties have been investigated by means of the quantum mechanical charge field (QMCF) molecular dynamics (MD) approach and the results, where applicable, have been compared to experimental data. Besides conventional analytical tools, angular radial distribution functions have been employed to gain deeper insight into the structure of the hydrate. The ion–oxygen stretching motion’s wavenumber, further characterising the CeO bond, is in excellent agreement with experimental results, same as the structural values obtained from the simulation.

An ion-imprinted polymer for the selective extraction of mercury(II) ions in aqueous media

A double-imprinted polymer exhibiting high sensitivity for mercury(II) in aqueous solution is presented. Polymer particles imprinted with mercury(II) were synthesised by copolymerising the functional and cross-linking monomers, N’–[3– (Trimethoxysilyl)–propyl]diethylenetriamine (TPET) and tetraethylorthosilicate (TEOS). A double-imprinting procedure employing hexadecyltrimethylammonium bromide (CTAB), as a second template to improve the efficiency of the polymer, was adopted. The imprinted polymer was characterised by FTIR, scanning electron microscopy (SEM) and the average size determined by screen analysis using standard test sieves. Relative selective coefficients (k`) of the imprinted polymer evaluated from selective binding studies between Hg 2+ and Cu 2+ or Hg 2+ and Cd 2+ were 10 588 and 3 147, respectively. These values indicated highly-favoured Hg2+ extractions over the 2 competing ions. The results of spiked and real water samples showed high extraction efficiencies of Hg 2+ ions, (over 84%) as evaluated from the detected unextracted Hg 2+ ions by ICP-OES. The method exhibited a dynamic response concentration range for Hg 2+ between 0.01 and 20 µg/ml, with a detection limit (LOD, 3σ) of 0.000036 µg/ml (36 ng/l) that meets the monitoring requirements for the USA EPA of 2 000 ng/l for Hg 2+ in drinking water. Generally, the data (n=10) had percentage relative standard deviations (%RSD) of less than 4%. Satisfactory results were also obtained when the prepared sorbent was applied for the pre-concentration of Hg2+ from an aqueous certified reference material. These findings indicate that the double-imprinted polymer has potential to be used as an efficient extraction material for the selective pre–concentration of mercury(II) ions in aqueous environments.

Electrochemical Detection of Copper Using a Gly-Gly-His Modified Carbon Nanotube Biosensor

Diazonium ion chemistry has been used to electrochemically graft aminophenyl layers onto p-type silicon (100) substrates. A condensation reaction was used to immobilise single-walled carbon nanotubes with high carboxylic acid functionality directly to this layer. The surface immobilised carbon nanotubes were then modified with the tripeptide Gly-Gly-His for the selective detection of copper ions in aqueous environments. The stepwise assembly and sensitivity of this biosensor to copper was characterised by X-ray photoelectron spectroscopy and differential pulse voltammetry, respectively. The ability to detect copper ion concentrations down to 1 μM was demonstrated. As this biosensor combines the advantages of a silicon substrate for easy integration into sophisticated electrical and electronic devices, diazonium salt derived films for stability in aqueous environments and carbon nanotubes for desirable electrochemical properties, it is expected to have important future applications in environmental sensing.

Selective Mercuration of 2-Hydroxy Nile Red and Its Application towards Chemodosimetric Hg2+-selective Signaling

Selective mercuration at the 1,6-positions of 2-hydroxy derivative of Nile Red and its application towards -selective signaling was investigated. The 2-hydroxy Nile Red exhibited a selective UV-vis absorption and fluorescent signaling behavior towards ions over common coexisting physiologically important metal ions in aqueous environment. NMR studies revealed that the mercuration was selectively effected at the 1,6-positions of 2-hydroxy Nile Red, which is quite different from that at the 6,8-positions for the parent Nile Red.

Highly Efficient Extraction of Sulfate Ions with a Tripodal Hexaurea Receptor

Fatal extraction: The Hofmeister bias for sulfate ions in aqueous environments can be overcome by using a tripodal hexaurea receptor (L) that completely encapsulates the sulfate ion in a complementary cavity protected by hydrophobic aromatic rings (see picture; C gray, N blue, O red, S yellow). Almost quantitative extraction of sulfate ions from an aqueous to an organic phase is achieved when this receptor is used as a liquid–liquid extractant.