Selective ratiometric detection of Hg in pure water using a phenoxazinium-based probe

A ratiometric, near-infrared, and fully water-soluble probe, a phenoxazinium-based chemosensor bearing an anilino thiaazacrown, was successfully synthesized and characterized. The use of this probe for the selective ratiometric detection of Hg²⁺ in pure water is reported. The probe shows good selectivity for Hg²⁺, and a large blue shift (75 nm) of the complex’s absorption maximum was observed.     

Determination of Hg(II) ions in water samples by a novel Hg(II) sensor,based on calix[4]arene derivative

A PVC membrane electrode for Hg(II) ions, based on a new cone shaped calix[4]arene (L) as a suitable ionophore was constructed. The sensor exhibits a linear dynamic in the range of 1.0 × 10^?6–1.0 × 10^?1 M, with a Nernstian slope of 29.4 ± 0.4 mV decade^?1, and a detection limit of 4.0 × 10^?7 M. The response time is quick (less than 10 s), it can be used in the pH range of 1.5–4, and the electrode response and selectivity remained almost unchanged for about 2 months. The sensor revealed comparatively good selectivity with respect to most alkali, alkaline earth, and some transition and heavy metal ions. It was successfully employed as an indicator electrode in the potentiometric titration of Hg²⁺ ions with potassium iodide, and the direct determination of mercury content of amalgam alloy and water samples.     

Selective extraction of Hg(II) from aqueous mineral acid solution containing iodide ions using 2-benzylpyridine in benzene

A method for the selective extraction of mercury has been developed. The extraction of Hg(II) by 2-benzylpyridine (BPy) in benzene from dilute mineral acid solution containing iodide ions has been investigated, and variables such as concentration of acids, iodide and the extractant have been optimized. The optimum conditions for the extraction of Hg(II) by 0.1M BPy/benzene are: 0.01M (HCl, HNO₃, H₂SO₄)+0.01M KI. The distribution coefficients and separation factors of 19 elements relative to Hg(II), have been reported. Effect of anions such as ascorbate, acetate, citrate, oxalate and thiosulfate has also been studied. The method developed could find useful applications in selective extraction of small amounts of mercury from environmental samples.     

l-Valine-derived simple benzimidazole-based host in selective sensing of Hg(II) ions

A new and an easy-to-make simple benzimidazole-based chemosensor 1, derived from l -valine is reported. The chemosensor effectively recognises Hg²⁺ ion in the open cleft in CH₃CN containing 0.2% DMSO by exhibiting significant enhancement in fluorescence emission. In the selectivity, the steric isopropyl groups in 1 play the key role as confirmed by considering the model compound 2. The ensemble of 1.Hg²⁺, on the other hand, shows the fluorescence sensing of l -cysteine, homocysteine, and glutathione over the other amino acids with no thiol group in aq. DMSO (DMSO:H₂O = 4:1, v/v).     

Selective fluorescent Hg(II) detection in aqueous solutions with a dye intermediate

A dye intermediate, 1-amino-8-naphthol-3,6-disulfonic acid sodium (ANDS) was first used to selectively recognize Hg(II) in aqueous solutions with its fluorescence being strong quenched. The fluorescence quenching of ANDS was attributed to the formation of an inclusion complex between Hg(II) and ANDS by 2:1 complex ratio (K=6.2 x 10(9)), which has been utilized as the basis of the fabrication of the Hg(II)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed chemosensor were investigated. The sensor shows a linear response toward Hg(II) in the concentration range 2.9 x 10(-6) to 5.5 x 10(-5)M with a limit of detection of 5.3 x 10(-7)M, and a working pH range from 5.0 to 9.0. It shows excellent selectivity for Hg(II) over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed method was utilized successfully for the detection of Hg(2+) in water samples.     

Fabrication of a sensor chip containing Au and Ag electrodes and its application for sensitive Hg(II) determination using chronocoulometry

In this work, we explored a novel fabrication method to construct Au and Ag electrodes on chip, utilizing the different solubility of gold and silver in different etching solutions. KI-I₂ etching solution and 50% HNO₃ were chosen to dissolve the metal layers alternatively. Planar electrodes with gold and silver could be simultaneously and accurately patterned on chip using photolithographic technique. The as-prepared electrode could be directly served as integrated three-electrode system for electrochemical measurement. Based on it, a sensing strategy has been carried out using home-made electrochemical sensing (ECS) chip, which depended on the competition of double strand DNA and Hg(II)-mediated T–T base pairs (T-Hg(II)-T). Actually, a mercury specific oligonucleotide (MSO) was immobilized onto the thus-fabricated gold working electrode and employed as the sensing element. Chronocoulometry (CC) was chosen to monitor the differences of surface charge volume and quantify the concentrations of Hg(II) ions with a low detection limit down to 1 nM. Therefore, a facile method to fabricate Au and Ag electrodes has been demonstrated to simplify the production of ECS chip. The ECS chip was finally used for constructing an effective sensing platform for sensitive Hg(II) determination, which held promising potential for designing ECS chip in lab-on-a-chip device or point-of-care diagnosis.     

Highly sensitive perylene tetra-(alkoxycarbonyl) based colorimetric and ratiometric probes for fluorine detection

Fluoride anion (F^?) affects environmental, biological, and chemical processes significantly. Therefore, its detection has received increasing attention, and sensitive, effective, and convenient probes for F^? detection need to be developed urgently. In this work, two perylene tetra-(alkoxycarbonyl) (PTAC) based colorimetric and ratiometric probes, P1 and P2, were developed for the detection of F^?. The interactions between F^? and these two probes were investigated by absorption, electrochemistry, ¹H NMR, and density functional methods. Both the two probes were complexed with F^? with a ratio of 1:1. The detection limits of P1 and P2 were 0.22 μM and 0.87 μM, respectively. It was worth noting that the absorption peak of P1 showed a 190 nm red shift when sensing F^?, and P1 is the largest red shift value reported in F^? probes based on PTAC derivatives. This phenomenon was resulted from the unique configuration and deprotonation of P1 that can promote the intramolecular charge transfer (ICT). This strategy provides an example for the development of other ion probes based on D-A type ICT mechanism.     

Benzimidazolium-based new simple ratiometric fluorescent sensor for selective detection of dihydrogenphosphate

A series of pyridine-coupled benzimidazolium-based receptors 1, 2 and 3 have been designed and synthesised. In the series, only receptor 1 is structurally appealing in the selective recognition of H₂PO₄^?  in CHCl₃ as well as in CH₃CN over a series of other anions. The ratiometric change in emission with a triplet band at 420 nm is the distinctive feature of selective recognition of H₂PO₄^?  in CHCl₃. In CH₃CN, a ‘turn on’ response is selectively observed. Binding studies have been carried out using fluorescence, UV–vis, ¹H NMR and ³¹P NMR spectroscopic techniques. Experimental results have been correlated with the theoretical findings.     

A new fluorescent sensor bearing three dansyl fluorophores for highly sensitive and selective detection of mercury(II) ions

A novel fluorometric sensor bearing three dansyl moieties based on tris[2-(2-aminoethylthio)ethyl]amine was prepared by a simple approach using a conventional two-step synthesis. The sensor exhibits highly Hg²⁺-selective ON-OFF fluorescence quenching behavior in aqueous acetonitrile solutions and is shown to discriminate various competing metal ions, particularly Cu²⁺, Ag⁺, and Pb²⁺ as well as Ca²⁺, Cd²⁺, Co²⁺, Fe³⁺, Mn²⁺, Na⁺, Ni²⁺, and Zn²⁺, with a detection limit of 1.15 × 10⁻⁷ M or 23 ppb.     

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).     

Detection of toxic mercury ions using a ratiometric CdSe/ZnS nanocrystal sensor

We have developed a strategy for the ratiometric detection of toxic Hg(2+) ions using a semiconductor nanocrystal energy-transfer donor coupled to a mercury-sensitive "turn-on" dye acceptor. The results demonstrate a new paradigm of toxic metal sensing that resolves the difficulties with the use of semiconductor nanotechnology for this purpose.     

Thermoresponsive core cross-linked micelles for selective ratiometric fluorescent detection of Hg2+ ions

We report on the fabrication of core cross-linked (CCL) micelles possessing thermoresponsive cores and their application as sensitive and selective ratiometric Hg(2+) probes with thermo-tunable detection efficiency. Well-defined double hydrophilic block copolymer (DHBC) bearing naphthalimide-based Hg(2+)-reactive moieties (NUMA, 4), PEO-b-P(NIPAM-co-NAS-co-NUMA), was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, where PEO, NIPAM, and NAS represent poly(ethylene oxide), N-isopropylacrylamide, and N-acryloxysuccinimide. At 25 °C, PEO-b-P(NIPAM-co-NAS-co-NUMA) unimers in aqueous solution can act as ratiometric Hg(2+) probes with a detection limit of ～10.1 nM. After core cross-linking of the micellar nanoparticles formed at elevated temperatures, structurally stable CCL micelles with well-solvated PEO coronas and thermoresponsive cores embedded with Hg(2+)-reactive NUMA moieties were obtained. Upon Hg(2+) addition, the aqueous dispersion of CCL micelles exhibit a colorimetric transition from yellowish to colorless and a fluorometric emission transition from green to bright blue. Moreover, Hg(2+) detection limits of CCL micelles were considerably enhanced to 3.0 and 1.8 nM at 25 and 40 °C, when the thermoresponsive cores are at their swollen and collapsed state, respectively. The high selectivity of CCL micelles to Hg(2+) over other common cations was also demonstrated. Furthermore, in vitro studies revealed that CCL micelles can effectively enter into living cells and sensitively respond to the presence of Hg(2+) ions via the change of fluorescence emission color. This work represents the first example of DHBC-based CCL micelle acting as highly selective and sensitive ratiometric metal ion probes. The structural stability, water dispersibility, biocompatibility, and most importantly the thermo-tunable detection sensitivity of this novel type of CCL micelle-based sensing systems augur well for their future applications as multifunctional nanocarriers for drug delivery, sensing, imaging, and diagnosis.     

Theoretical studies of complexes between Hg(II) ions and l‐cysteinate amino acids

In this study, ab initio and density functional theory methods have been used to understand the structures and thermodynamic stabilities of complexes formed between l ‐cysteine and mercury (II) ions in neutral aqueous solution. To better understand the interaction between sulfur and mercury (II) ion, the MP2, B3LYP, M06‐2X, and TPSS methods have been used to optimize [HgSH_x]^2?x, x = 1–4, complexes and compared to benchmark QCISD(T) structures. Furthermore, energies from these same methods are compared to CCSD(T)/CBS(2,3) energies. From these benchmark calculations, the M06‐2X method was selected to optimize l ‐cysteinate‐Hg(II) complexes and the MP2 method for estimating complex energies. l ‐cysteinate‐mercury (II) ion complexes are formed primarily by forming a bond between cysteinate sulfur and the mercury ion. Stable complexes of l ‐cysteinate and mercury can be formed in 1:1, 2:1, 3:1, and 4:1 ratios. Each complex is stabilized further by interaction between carboxylate oxygen and mercury as well as hydrogen bonding among complex cysteinate ligands. The results indicate that at high cysteinate to Hg(II) ratios high‐coordinate complexes can be present but at lower ratios the 2:1 complex should be dominant. © 2013 Wiley Periodicals, Inc.     

A near IR di-styryl BODIPY-based ratiometric fluorescent chemosensor for Hg(II)

A novel BODIPY-based near-IR emitting probe as a selective and sensitive fluorophore for Hg(II) is synthesized. This versatile BODIPY fluorophore is functionalized for long wavelength emission at the 3 and 5 positions via a condensation reaction in which two dithiodioxomonoaza-based crown-containing phenyl units are conjugated to the BODIPY core as a chelating unit. This designed fluorophore, employing an ICT sensor can be used effectively to detect Hg(II) cations by way of a hypsochromic shift (∼90 nm) in both the absorption and emission spectra.     

A piezogravimetric sensor platform for sensitive detection of lead (II) ions in water based on calix[4]resorcinarene macrocycles: Synthesis,characterization and detection

The heavy metal ions detection is a foremost concern in water sources, the conventional detection methods are either time consuming or expensive, thus the need of fast, low-cost and accurate sensing methods is growing. Based on this direction, this paper describes the synthesis of newly enantiomeric calix[4]resorcinarenes, namely: C-dec-9-enylcalix[4]resorcinarene-O-(S-)-α-methylbenzylamine (Compound B) and C-dec-9-enylcalix[4]resorcinarene-O-(R+)-α-methylbenzylamine (Compound C), the two macrocycles were the subject of comparative characterization studies using (FTIR, ¹H NMR, ¹³C NMR, TG-DSC-MS, and P-XRD). The realization of modified quartz resonator-gold electrodes, and its introductory employment in the assembly of a novel QCM-I (Quartz Crystal Microbalance with Impedance measurements) based chemosensor for the detection of lead ions in the aqueous solutions is reported for the first time to the best of our knowledge, moreover both Calix-QCM based sensors presented good linearity, acceptable sensitivities, and wide linear ranges, as well as lower detection limits in the order of 0.45 and 0.30 ppm for compounds B and C, consecutively.     

Selective detection of bismuth(III) and iron(II) ions with certain new reagents

Isoperthiocyanic acid (3-amino-5-thione-1,2,4-dithiazole) (I), tetraethylthiuram monosulphide ("Tetmosol") (II), eosin (III), and mercurochrome (IV) are used as new qualitative reagents for bismuth, III and IV are also used for detection of iron(II). A conc. sulphuric acid solution of I, or an acctone solution of II, when treated with bismuth in presence of potassium iodide, gives a deep red or reddish-orange precipitate, characteristic of bismuth. Bismuth in presence of III or IV gives a heavy and characteristically bright deeppink precipitate on addition of ammonia. With I, 1 mug of bismuth may be detected with a dilution limit of 1:50,000. Sb(III) and As(III) do not interfere in any of these tests. Iodides interfere only when I and II are used as reagents. Pb, Cu(II). and Fe(III) interfere with III and IV. I and II are also proposed as reagents for iodide; nitrites would interfere. III and IV, with iron(II) on addition of ammonia, produce a precipitate with highly intense green fluorescence. No other common cation [including Fe(III)] or anion interferes. The limit of detection is 3 mug ml .     

Amplified fluorescence detection of mercury(II) ions (Hg2+) using target-induced DNAzyme cascade with catalytic and molecular beacons

In this work, a fluorescent sensing strategy was developed for the detection of mercury(II) ions (Hg(2+)) in aqueous solution with excellent sensitivity and selectivity using a target-induced DNAzyme cascade with catalytic and molecular beacons (CAMB). In order to construct the biosensor, a Mg(2+)-dependent DNAzyme was elaborately designed and artificially split into two separate oligonucleotide fragments. In the presence of Hg(2+), the specific thymine-Hg(2+)-thymine (T-Hg(2+)-T) interaction induced the two fragments to produce the activated Mg(2+)-dependent DNAzyme, which would hybridize with a hairpin-structured MB substrate to form the CAMB system. Eventually, each target-induced activated DNAzyme could catalyze the cleavage of many MB substrates through true enzymatic multiple turnovers. This would significantly enhance the sensitivity of the Hg(2+) sensing system and push the detection limit down to 0.2 nM within a 20 min assay time, much lower than those of most previously reported fluorescence assays. Owning to the strong coordination of Hg(2+) to the T-T mismatched pairs, this proposed sensing system exhibited excellent selectivity for Hg(2+) detection, even in the presence of 100 times of other interferential metal ions. Furthermore, the applicability of the biosensor for Hg(2+) detection in river water samples was demonstrated with satisfactory results. These advantages endow the sensing strategy with a great potential for the simple, rapid, sensitive, and specific detection of Hg(2+) from a wide range of real samples.     

Selective detection of ferric,cobalt(II) and molybdate ions usingm-(Mercaptoacetamido)-phenol as a reagent

Summary m-(Mercaptoacetamido)phenol (m-MAP) is used for the selective and characteristic detection of ferric ion, cobalt and molybdate. The reagent produces deep green precipitate at pH 6 with ferric ion in the absence of tartrate, purple red precipitate with cobalt around pH 7 even in the presence of tartrate, and reduces molybdate to a yellow green to blue solution below pH 3. The sensitivity of the cobalt test is exceptionally high. The three elements can be tested in the presence of each other and the related metal ions.

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Zusammenfassung m-Merkapto-acetamidophenol (m-MAP) wurde für den selektiven Nachweis von Eisen(III), Kobalt und Molybdat herangezogen. Das Reagens gibt bei pH 6 mit Eisen(III) in Abwesenheit von Tartrat einen tiefgrünen Niederschlag, bei pH 7 mit Kobalt auch in Gegenwart von Tartrat einen purpurroten Niederschlag. Es reduziert Molybdat unter pH 3 und führt so zu einer gelb-grünen bis blauen Lösung. Die Empfindlichkeit des Kobaltnachweises ist besonders groß. Die drei Elemente können nebeneinander und in Gegenwart verwandter Metalle nachgewiesen werden.

     

Selective picomolar detection of mercury(II) using optical sensors

The rational design of a mercury(II) ligand consisting in a 1-(4'-oxyphenyl)-4(1'-pyrenyl)-2,3-diaza-1,3-butadiene receptor unit, optimizes the sensitivity and reliability of a SPR sensor by the formation of a well packed SAM over the gold surface. SPR analysis allows detecting mercury(II) concentrations in aqueous systems in the picomolar range, meliorating on three orders of magnitude the EU mercury(II) detection limit in drinkable water.