Selective Hg(II) detection in aqueous solution with thiol derivatized fluoresceins

The syntheses and photophysical properties of mercury sensors 2 and 3 (MS2 and MS3), two asymmetrically derivatized fluorescein-based dyes designed for Hg(II) detection, are described. These sensors each contain a single pyridyl-amine-thiol metal-binding moiety, form 1:1 complexes with Hg(II), and exhibit selectivity for Hg(II) over other Group 12 metals, alkali and alkaline earth metals, and most divalent first-row transition metals. Both dyes display superior brightness (Phi x epsilon) and fluorescence enhancement following Hg(II) coordination in aqueous solution. At neutral pH, the fluorescence turn-on derives from greater brightness due to increased molar absorptivity. At higher pH, photoinduced electron transfer quenching of the free dye is enhanced, and the Hg(II)-induced turn-on also benefits from alleviation of this pathway. MS2 can detect ppb levels of Hg(II) in aqueous solution, demonstrating its ability to identify environmentally relevant concentrations of Hg(II).     

A "turn-on" fluorescent sensor for selective Hg(II) detection in aqueous media based on metal-induced dye formation

A Hg-promoted desulfurization reaction of a thiocarbazone derivative was introduced in the design of a fluorescent sensor for selective Hg(II) detection. Crystal structural and spectroscopic investigations demonstrated the formation of a triazanaphthalene ring and the "turn-on" responding for Hg(II) in aqueous media.     

Selective separation of Hg(II) from aqueous solutions by the precipitate flotation technique

Summary The flotation of Hg(II) ions as sulphide or iodide from aqueous solutions has been investigated, using oleic acid as surfactant. Selective separation from Cd ions has been achieved. There was no interference by Bi, Pb, Cu, Cd, Mn, Zn, Co or Ni.     

Tridentate lysine-based fluorescent sensor for Hg(II) in aqueous solution

A novel homoplastic podand fluorescent sensor based on flexible hydrophilic lysine was prepared. Lysine with two dansyl groups-appended at both ends supplied a possibility for a tridentate binding toward Hg(II) and finally resulted in a unique selectivity to Hg(II) over other transition-metal ions with a hypersensitivity (detection limit 2.0 nM) in neutral buffered aqueous solutions. Notably, the coordination of chloride ion to the complex of sensor-Hg(II) brought forth that the trend in the NMR chemical shift for hydrogen and carbon atoms of the sensor was contrary to the findings in the former reports, which shows upfield shifts for the hydrogens and the alkane carbons but downfield shifts for the dansyl carbons, respectively.     

Selectively chemodosimetric detection of Hg(II) in aqueous media

A new series of benzoylthiourea derivatives of 1, 3, and 5 were prepared, and their chemodosimetric behaviors toward metal cations were investigated in aqueous media at room temperature. Among various metal cations tested, exclusively Hg2+ ion responses to irreversible color changes of receptors, along with distinctive blue shifts in UV/vis spectra. The receptors can be applicable for the monitoring of Hg2+ ion in aqueous solution with a pH span 4-9.     

A novel highly selective fluorescent chemosensor for Hg（Ⅱ） in fully aqueous media

A novel fluorescent Hg~(2 ) chemosensor based on dithia-dioxa-monoaza crown ether was synthesized in four steps from inexpensive starting materials.This new sensor exhibited very strong fluorescence response to Hg~(2 ) (F_(Hg~(2 ))/F_(free)>130) and it was highly selective to Hg~(2 ) over the other metal ions by more than 45-fold.     

Cu(II)-Cu(Hg)体系在蔗糖水溶液中的电化学行为

糖及其聚合物有着重要的生理功能,研究它们的热力学性质具有重要的意义[1 5]。本文考察Cu(II)在蔗糖水溶液中的电化学行为,获得了一些重要信息。1　实验部分使用试剂均为分析纯。蔗糖(北京化学试剂总厂)在343K时真空干燥6h。LiClO4(上海化学试剂总厂)在403K时减压干燥后保存在干燥器中。硝酸铜(北京化学试剂总厂)。所用溶液均采用重量法用二次蒸馏水配制。配好的溶液测定前用通过焦性没食子酸溶液的氮气来除氧。测定温度为298±1K。极谱和伏安测定在微机电化学分析系统(LK98A型)上进行,该机由天津市兰力科化学电子高技术有限公司制…     

A potential fluorescent Hg(II) chemosensor

An imidazole-based ligand has been evaluated for a potential fluorescent Hg(II) sensing probe. In water-acetonitrile solvent system, the ligand exhibits a unique selectivity towards Hg(II), which not only modulates fluorescence intensity but also shifts the emission band. The fluorescence reduction and the emission shift correlate with Hg(II) concentrations.     

Novel fluorescent sensor for detection of Cu(II) in aqueous solution

A novel fluorescent chemosensor based on aminonaphthol, which can selectively recognize copper(II) over other metal ions in aqueous solution within a broad pH span, was synthesized.     

Detection of Hg2+ in aqueous solutions with a foldamer-based fluorescent sensor modulated by surfactant micelles

[structure: see text] A hybrid foldamer constructed from six cholate units and two methionines was labeled with a DANSYL (DNS) group. The foldamer was solubilized by surfactant micelles to allow its usage as a fluorescent sensor for mercury ions present in the micromolar range in aqueous solutions. Its sensitivity was largely independent of the concentration of nonionic surfactants but was strongly influenced by both the nature and the concentration of ionic surfactants.     

Sorption and filtration of Hg(II) ions from aqueous solutions with a membrane containing poly(ethyleneimine) as a complexing polymer

The performances of a PVA/PEI complexing membrane for the removal of Hg(II) from aqueous solutions were investigated by performing sorption and filtration experiments. This membrane, that was previously shown to ensure efficient sorption of the heavy metal ions Pb(II), Cd(II) and Cu(II) at pH 5, presented a higher affinity for Hg(II) at pH 2.5. The sorption equilibrium was satisfactorily represented by the Langmuir model. In view of possible application to the treatment of industrial wastewaters, the effects of parameters such as pH, temperature, water hardness, and the presence of complexing chloride anions were investigated. The effect of increasing temperature was not straightforward: the complexation equilibrium constant decreased, but the mass of mercury sorbed increased, probably due to the higher mobility of the polymer chains that made internal sites available for complexing mercury. The maximum retention capacity of the membrane was 311 mg Hg g⁻¹. Also, operating at large calcium or chloride concentrations was not detrimental to the membrane performances. For regeneration of the membrane, a 0.05 M solution of EDTA is recommended on the basis of limited performance loss. When used in the filtration mode, the elimination ratio of Hg(II) was close to 99%.     

Manganese(II) complexes with diethylamine in aqueous solutions

Interaction between MnCl₂ and diethylamine (DEA) in aqueous solutions has been studied by UV, IR, and EPR spectroscopy as part of the design and research program on models of natural photosystems. The composition of the precipitate for comparable concentrations of reagents and solute oxygen has been investigated. Mn(II) was found to be oxidized with oxygen to give MnO₂·H₂O as a precipitate. In the solution over the precipitate, Mn(III) complexes with DEA are formed; the complex molecule has four and six amine molecules in the coordination sphere.     

Degradation of a stilbene dye (SOTGL) in aqueous solutions under gamma-radiation

The effect of radiation on the colour intensity of aerated, oxygen and nitrogen-saturated aqueous solution of Solophenyl Orange TGL has been investigated. Experiments show that the absorption band decreases gradually with the increase of the dose in all cases and the destruction of the skeleton of the dye molecule is promoted, by the presence of oxygen. The kinetics of degradation of solution of (SOTGL) turned out to be of the first order with respect to the low dye concentration (<0.14 g/l) and of zero order for dye concentration (>0.14 g/l). The radiochemical degradation yield (Gd) was calculated and was found to decrease experimentally with the increase of dose for low concentrations, whereas for higher concentrations such a behaviour can be presented by a straight line parallel to the dose axis. The influence of pH on the degradation of the dye was studied. The specific bimolecular rate constant of the reaction of SOTGL with the hydroxyl radical was determined by studying the effect of ethanol concentration on Gd using competition kinetics and was found to be 1.055·10⁹ M^–1 s^–1. Suggestions are made for possible low radiation dosimetry (about 1.5 kGy) by means of spectrophotometric analysis of the absorption spectra.     

Highly sensitive and selective fluorescent chemosensors for Hg(II) in an aqueous environment based on carbamodithioate

Two highly sensitive (detection limits ∼20 nM) and selective (selectivity >30) fluorescent chemosensors were developed for detecting Hg²⁺ in a fully aqueous environment by using the rarely-studied carbamodithioate to create an Hg²⁺ binding site.     

Single-ion activities and Mn(Hg)/Mn(II) reactions in aqueous solutions of alkaline-earth chlorides

Combined thermodynamic and kinetic studies have yielded convenient single-ion activity coefficients for manganese(II), alkaline-earth, and chloride ions and standard exchange currents for the two steps of the Mn(Hg)/Mn(II) electrode in 0.005 M MnCl₂+0.495 M MeCl₂ (for Me=Mg, Ca, Sr, Ba, and Mn) at 25°C. The results indicate that the fall in mean ionic activity coefficient for the alkaline-earth chlorides along the sequence from magnesium to barium is carried to a larger extent by the cation than by the anion, that also the activity coefficient for the minority cation Mn(II) falls along this sequence, and that other than activity-coefficient effects on the Mn(Hg)/Mn(II) reactions appear only with barium ions, which retard the reactions additionally. The results are discussed with emphasis on ionic interactions and double-layer effects.     

Unfolding with mercury: anthracene-oxyquinoline dyad as a fluorescent indicator for Hg(II)

An anthracene-oxyquinoline dyad (HQ-AN) is synthesized which acts as a selective fluorescent reporter for Hg(II) with a detection limit of 3.2 × 10⁻⁶ M in acetonitrile-water system. The phenomenon of unfolding of HQ-AN from its initial folded conformation in acetonitrile-water system, selectively in the presence of Hg(II) is indicated from spectrofluorometric studies. The sensing event is monitored by the marked change in fluorescence emission occurring due to quenching of the excimer and retaining of the monomer emission of the two anthracene units in HQ-AN.     

Reduction of Hg(II) salts in aqueous acidic solutions by SO2

Kinetic studies of the reduction of Hg(II) salts in aqueous acidic solutions by SO₂ in mild conditions have revealed that SO₂ quantitatively reduces Hg(II) to metal in the examined HClO₄ concentration range (2–8M^–1).

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Hg(II) . , HClO₄ (2–8 .^–1) SO₂ Hg(II) .

     

Adsorption of Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II) from aqueous solutions on a 2-mercaptobenzimidazole-modified silica gel

The chemically modified silica, obtained by reacting 2-mercaptobenz-imidazole with 3-chloropropyl silica gel, was used to adsorb Cu(II), Zn(II), Cd(II) and Pb(II) from aqueous solutions at various pH. Between pH 3–5, the order of selectivity was Hg(II) > Cd(II) Cu(II) Zn(II) Pb(II). Under batch conditions retentions of 100% were achieved for all metals except for Pb(II) where 93% was attained. Under column conditions recoveries of 100% were obtained for all metals.     

Selective sensing of sulfate in aqueous solution using a fluorescent bis(cyclopeptide)

Fluorescence of a bis(cyclopeptide) in which two cyclohexapeptide moieties with alternating L-proline and 6-aminopicolinic acid subunits are attached to a 4,4'-bis(dimethylamino)biphenyl linker is quenched in 1:1 (v/v) water/methanol in the presence of sulfate. Of eight other anions tested, none produced a similar effect. This bis(cyclopeptide) allows the qualitative and quantitative detection of sulfate even in the presence of an excess of chloride anions. Calculations provided insight into the causes of fluorescence quenching and anion selectivity.     

Facile synthesis of water-soluble and size-homogeneous cadmium selenide nanoparticles and their application as a long-wavelength fluorescent probe for detection of Hg(II) in aqueous solution

Highly luminescent uncoated water-soluble and mono-disperse CdSe nanoparticles (NPs) have been prepared facilely. Uncoated CdSe core NPs possessing a good size distribution was accompanied with long wavelength of fluorescence emission. It is interesting to note that these functionalized NPs are soluble in water medium stably for more than 1 month, and no significant changes were found in the optical characteristics in comparison with fresh CdSe NPs prepared. The functionalized CdSe NPs exhibited strong specific affinity for mercury(II) through their surface functional groups. Based on the significant quenching of fluorescence emission of functionalized CdSe NPs with a long-wavelength 630nm, a simple, rapid and specific detection for Hg(II) was proposed. Under optimum conditions, the response of linearly proportional to the concentration of Hg(II) is between 0mol/L and 1.25x10(-6)mol/L, and the limit of detection is 4.50x10(-9)mol/L. The relative standard deviation (R.S.D.) of six replicate measurements is 2.0% for 2.0x10(-7)mol/L of Hg(II). In terms of fluorescence quenching at 630nm of CdSe NPs, no obvious wavelength shift or no new emission band in presence of Hg(II) at pH 7.50 of phosphate buffer solution were found; furthermore, a significant reduction in absorbance at 230nm of CdSe NPs was first observed in our work. We could speculate that Hg(II) as an effective quencher (even at low concentration) for functionalized CdSe NPs emission suggests that it is capable of directly intercepting one of the charge carriers, thus disrupting the recombination process.