Mercury Ions In Aqueous Media Research Articles

Thiazole-Formulated Azomethine Compound for Three-Way Detection of Mercury Ions in Aqueous Media and Application in Living Cells

Heavy metal ions are extremely poisonous and cause long-term harm to living organisms. Among these ions, mercury is the most toxic metal and has no notorious purpose in the human body. In this regard, an elegant azomethine thiazole compound AM1 was synthesized, and it was found to be highly sensitive to three-way detection of mercury ions with detection limits of 0.1126 × 10–9 M (FL) and 0.64 × 10–6 M (UV–vis). AM1 highlighted the capability to detect mercury ions through the colorimetric method, the fluorometric method, and via the naked eye in three-way detection. In addition, the structure of AM1 was confirmed by single-crystal X-ray diffraction studies and crystallized in a monoclinic crystal system with a P21/c space group, and it shows numerous noncovalent interactions in the crystal packing. The high sensitivity of AM1 to Hg2+ ions was imputed to the quenching mechanism and was estimated by Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (1H-NMR), high-resolution mass spectrometry (HRMS), ultraviolet–visible (UV–vis) absorbance, fluorescence (FL) emission, Job’s plot, B-H plot, and DFT calculation. Naked eye color change of AM1 solution to yellow and turn-off FL by the addition of mercury ion is due to complex formation. In addition to mercury ions, the sensor displayed a new absorption peak at around 240 nm. Furthermore, an AM1-coated test strip is used as the solid support sensor, and real-time detection of Hg2+ ions in the HeLa cell line by fluorescence microscopy is performed.

Functionalized Silver Nanoparticles as Colorimetric and Fluorimetric Sensor for Environmentally Toxic Mercury Ions: An Overview.

Nanoscience is a multifaceted field which encompasses metal nanoparticles (MNPs) having novel and size-related optical properties significantly different from the bulk level as well as at the atomic level. Amongst noble MNPs, the silver nanoparticles (AgNPs) have unique properties for metal interaction. Presently, there have been expedite reports which are taken under the review in virtue of sensing the mercury ions in aqueous media. Mercury dissemination in various forms contaminates the ecosystem. Globally mercury is ranked as the most toxic element and an urgent threat to humans since it causes major health issues. Employing MNPs, especially AgNPs for the detection of mercury ions is the economic, handy and apt method in contrast to time-consuming methods that use expensive instrumentations. The review highlights a study of colorimetric and fluorimetric detection of the level of Hg (II) ions in aqueous media selectively with high sensitivity in different courses of conditions using AgNPs synthesized by various approaches. Graphical abstract.

Colorimetric detection of mercury ion using chlorophyll functionalized green silver nanoparticles in aqueous medium

This study presents an investigation of colorimetric sensing of mercury ions in aqueous medium using chlorophyll (Chl) functionalized green synthesized silver nanoparticles (AgNPs). Chl-AgNPs showed a high visually detectable color change for the selective detection of mercury ions, while the unmodified green synthesized silver nanoparticles did not show any remarkable color change. The surface plasmon resonance absorption band of Chl-AgNPs was obtained at 440 nm area and decreased with a blue shift by the addition of mercury ion. Furthermore, an increase was detected at the absorption band of 290 nm attributed to the blank silver ions. The possible mechanism relies on the redox reaction between the silver nanoparticles and mercury ions. The detection limit of the Chl-AgNPs was obtained as 2.7 µM and 60 µM by the UV-vis spectrophotometer and the naked eye, respectively. The response of Chl-AgNPs towards the mercury ion was excellent over other metal ions. The functionalization of green silver nanoparticles using chlorophyll pigment provided colorimetric detection advantage by the naked eye. The proposed method was successfully applied to river water samples spiked with known concentrations of mercury ions at the recovery values between 94 to 97%.

Chelation enhanced fluorescence of rhodamine based novel organic nanoparticles for selective detection of mercury ions in aqueous medium and intracellular cell imaging

A simple, quick and useful reprecipitation method was used to prepare rhodamine based fluorescent nanoparticles. The characterization techniques such as zeta-particle sizer and scanning electron microscopy were studied to investigate the formation of desired nanoparticles FONs-RSB along with its aqueous stability, surface charge, particle size, and morphological features. The comparative optical properties between parent molecule RSB and FONs-RSB were examined using absorption and fluorescence studies. The sphere morphology of FONs-RSB having 82 nm particle size and negative zeta potential (−33.5 mV) showed selective and sensitive interaction with only Hg2+ amongst the series of metal ion studied which was revealed by florescence titration results. The interaction between FONs-RSB and Hg2+ leads to enhance the fluorescence of FONs-RSB is because of chelation enhanced fluorescence (CHEF) phenomenon. The interference of foreign metal ions was found to be unaffected to the fluorescence enhancement induced by Hg2+. The binding stoichiometry and binding constant were evaluated using Job’s and modified Benesi-Hildebrand plot. The mechanism of binding interaction and nature of complexation were analyzed using Infrared (IR), Nuclear Magnetic Resonance (NMR), absorption and fluorescence lifetime titrations in the absence and presence of a variable amount of Hg2+ to FONs-RSB. Further, the reaction product of the sensing process in the present investigation was examined using mass analysis. The detection limits calculated using the present method were found to be 1.729 ng/mL (8.619 nM) and 1.68 ng/mL when linear concentration of Hg2+ additions were 0−2 μg/mL and 0−100 ng/mL, respectively. The practical application of the present method involves the quantitative determination of Hg2+ in environmental samples collected from the local campus and intracellular cell imaging of Hg2+ using A375 living cells with non-toxic behavior.

One-pot synthesis of highly fluorescent boron and nitrogen co-doped graphene quantum dots for the highly sensitive and selective detection of mercury ions in aqueous media

The doping of heteroatoms can radically alter the electronic properties of graphene quantum dots (GQDs), thereby realizing the adjustment of optical properties of GQDs, and further significantly improving quantum yield (QY) and other issues. In this paper, a simple, low-consumption and pollution-free synthesis strategy of boron and nitrogen co-doped graphene quantum dots (BGQDs) were developed by pyrolysis carbonization of citric acid (CA), boric acid and urea. The B,N-GQDs synthesized by this method showed bright blue fluorescence with a relatively high QY of 17.16%. The selective specificity of B,N-GQDs for Hg2+ was mainly attributed to the strong electron affinity of Hg2+ itself, which enabled it to perform kinetic chelation with boron, nitrogen, oxygen and other functional groups in B,N-GQDs more quickly. Therefore, the fluorescence of B,N-GQDs aqueous solution can be significantly quenched by aqueous solution containing Hg2+ or true water samples. B,N-GQDs fluorescent probe had high sensitivity to Hg2+. Moreover, it can respond quickly in a wide range of Hg2+ concentrations from 1 to 300 μM. The linear relationship was best at a concentration of 0∼4 μM, (R2 = 0.99753), and the minimum detection limit can achieve 4.3 nM (S/N = 3). The recoveries of Hg2+ in true water samples were between 99.6% and 104%, which indicated that B,N-GQDs can be successfully applied to the detection of Hg2+ in true water samples.

Using Gold Nanoparticles with Spectroscopic and Analytical Models for Rapid Colorimetric Detection of Mercury Ions in Aqueous Media

In this study, high-sensitively colorimetric detection of mercury ions was developed according to the surface plasmon resonance of modified gold nanoparticles. While in a citrate buffer solution, the selected modifier Bismuthiol II can cause gold nanoparticles to aggregate. Gold nanoparticles with a spherical shape and average diameter of about 13 nm were prepared. While mercury ions can inhibit gold nanoparticle aggregation, after the addition of mercury ions, the color of the gold nanoparticles solution changes from light violet to red with a hypochromatic shift at the absorption peak. By collecting the UV-Vis spectrum of the solution after the reaction, the characteristic bands are selected to build a partial least squares model. Both the 0.9477 correlation coefficient with a 0.0986 mg/L standard deviation for the calibration set, and 0.9274 correlation coefficient with a 0.1020 mg/L standard deviation for the prediction set were obtained via a partial least squares model.

Poly(adenine)-mediated DNA-functionalized gold nanoparticles for sensitive detection of mercury ions in aqueous media.

In this work, a facile and sensitive colorimetric sensor for Hg2+ ions based on poly (adenine)-mediated DNA-functionalized gold nanoparticles (Au NPs) is reported. One DNA sequence consisting of poly-A and T-rich DNA was designed rationally. Poly-A was used as an anchoring block to bind tightly to Au NPs, and T-rich DNA was utilized for specific recognition of Hg2+ ions. With the assistance of poly-A, T-rich DNA was easily introduced onto the surface of Au NPs and kept an upright orientation. In the presence of Hg2+ ions, T base binding with Hg2+ ions results in the formation of “T–Hg2+–T” among the Au NPs, which caused aggregation of the Au NPs and a subsequent change in the color of the solution, from wine red to grayish blue. On this occasion, the limit of detection (LOD) was 3.75 nM Hg2+ ions with a linear range from 5 nM to 200 nM, as measured by UV-Vis spectroscopy. Moreover, successful application of this method for the detection of Hg2+ ions in real samples was demonstrated.

Sensitive and Selective Detection of Mercury Ions in Aqueous Media Using an Oligonucleotide-functionalized Nanosensor and SERS Chip.

A surface-enhanced Raman scattering (SERS) platform for the selective trace analysis of Hg2+ ions was reported, based on poly-thymine (T) aptamer/2-naphthalenethiol (2-NT)-modified gold nanoparticles (AuNPs), which was an oligonucleotide-functionalized nanosensor and SERS chip. 2-NT was used as a Raman reporter, and T aptamer could form a T-Hg2+-T structure with Hg2+ ions making an SERS nanosensor absorbed to the SERS chip. The optimum concentrations of DNA and 2-NT were obtained. An average of 960 DNA molecules attached to each AuNP were measured. The limit of detection (LOD) was 1.0 ppt (1.0 × 10-12 g/mL), which is far below the limit of 10.0 ppb for drinking water, stipulated by the World Health Organization. The sensor has the advantages of low detection cost, a simple sample pretreatment, a green solution and reducing false positives. Furthermore, the nanosensor was used for the determination of trace Hg2+ in the water of a lake; a reliable result was obtained accurately.

Detection of Hg2+ ions in aqueous medium using an indole-based fluorescent probe: Experimental and theoretical investigations

Mercury pollution is a widespread danger to human health and environment. Due to limitations associated with the existing Hg2+ chemosensors, development of new, efficient and selective chemosensors capable of sensing mercury ions in aqueous medium remains a demanding area of research. In this regard, an indole-based fluorescent probe has been synthesized and characterized by detailed spectroscopic analysis. The probe showed a high selectivity and sensitivity towards Hg2+ by giving significant fluorescence quenching over other tested cations in H2O/DMF (7:3, v/v) medium. The association constant (Ka) was 6.4×103M−1 between sensor and Hg2+. The detection limit of sensor to Hg2+ was found to be 0.143μM (143nM). The experimental results have been verified with Density Functional Theory.

Rhodamine-based conjugated polymers: potentiometric, colorimetric and voltammetric sensing of mercury ions in aqueous medium

Herein, we report the synthesis and characterization of a new rhodamine-based monomer (RD-CZ), and an investigation of the optical and electrochemical properties of the corresponding polymer (P(RD-CZ)), which was electropolymerized on an ITO electrode. The resulting P(RD-CZ) polymer film was used as a simple and novel multi-signal sensor platform, which demonstrates ion-selective potentiometric, colorimetric and voltammetric responses in aqueous media for the first time. P(RD-CZ) exhibits excellent selectivity for Hg2+ ions compared with Cd2+, Cu2+ Zn2+, and Fe3+ using the potentiometric technique, which depends on the increasing charge carrier transport through rhodamine-bound Hg2+ with a limit of detection (LOD) of 9.77 × 10-8 M. The P(RD-CZ) polymer film also exhibits a distinct color change from orange to purple, which is detectable even by the naked eye, in the presence of Hg2+ ions. The LOD for Hg2+ ions obtained using the colorimetric method is 3.16 × 10-8 M. The same material has also been used for the voltammetric sensing of Hg2+ in aqueous media with a detection limit of 1 × 10-7 M. In this study, a conductive polymer-based sensor platform for detecting mercury ions via three different methods has been designed for the first time. By doing so, a disposable planar paper-based ion-sensing platform, which is suitable for low-cost point-of-care and in-field testing applications, could be fabricated with a highly reproducible and linear response towards different concentrations of analyte ions in aqueous and biological samples.

An unusual OFF–ON fluorescence sensor for detecting mercury ions in aqueous media and living cells

A novel azo derivative sensor (BDAA) based on alkynes was designed and utilized to direct detection of Hg(2+) in aqueous solution and living cells. The new strategy achieved off to on switchable fluorescence. permits the highly selective and sensitive detection of Hg(2+). This sensor can be used for imaging of Hg(2+) in living cells.

Photochemical functionalisation of optical nanotips with a rhodamine chemosensor for remote through-fiber detection of Hg2+

For remote Hg2+ detection, an array of nanotips was covalently functionalised using a versatile photochemical approach. After chemical etching of an optical fiber bundle to generate the nanotip array, a protected n-propyl amine was grafted onto the tip surface by silanisation and thereafter photodeprotected by irradiation at 365 nm. The new rhodamine-based probe 9 developed for detection of Hg2+ was linked to the liberated amino group using the HOBt/DCC protocol. The optical fiber bundles functionalised with 9 exhibited a high selectivity toward Hg2+in situ, in full analogy to its precursor 4 in solution. Titration of the functionalised optical fiber bundles using a remote detection mode showed a detection range from 10−5 to 5 × 10−3 M for mercury ions in aqueous medium.

Selective fluorescent sensor for mercury ions in aqueous media using a 1,4-dihydropyridine derivative

Novel 1,4-dihydropyridine (DHP) derivatives containing 3 carboxylic acid units are synthesized via cyclotrimerization of N-substituted β-aminoacrylates followed by basic hydrolysis of the triester. These DHP derivatives are readily soluble in aqueous media buffered at pH 8.0 and the solutions give blue fluorescent signals with quantum yields of 7–23%. One of these compounds, bearing a p-methoxyphenyl N-substituted group, shows specific fluorescent quenching with the mercuric ion (Hg2+). The fluorescent signal of the DHP derivative decays over a period of minutes to hours depending on the Hg2+ concentration, which implies that the sensing mechanism involves chemical reaction between the Hg2+ ion and the DHP compound. The 1H NMR and MS data suggest that Hg2+ mediates the oxidation of the DHP ring into a pyridinium ring. The event is useful for fluorescent detection of Hg2+ at the micromolar level within 30 min, with a detection limit of 0.2 μM in aqueous medium.

A cyclam-type “turn on” fluorescent sensor selective for mercury ions in aqueous media

The synthesis and spectral profile of a cyclam-type “turn on” fluorescent sensor selective for Hg2+ ions in aqueous media is described. Its properties are compared to those of a second probe with an N-deprotected cyclam system. The vast difference in ion selectivity between the two sensors reveals the influence of functional group modifications on the selectivity of fluorescent ion probes.

Facile and One Pot Synthesis of Gold Nanoparticles Using Tetraphenylborate and Polyvinylpyrrolidone for Selective Colorimetric Detection of Mercury Ions in Aqueous Medium

In this work, we reported for the first time, a facile and one step synthesis of gold nanoparticles from HAuCl4, employing tetraphenylborate as the reducing agent. The synthesis is not only facile but also yields “dumb-bell-shaped”particles. This shape appears to arise from a possible emulsion of the products of oxidation/decomposition of tetraphenylborate by HAuCl4, surrounding the particle. The size and shape of the AuNPs were characterized by Transmission electron microscopy (TEM) and UV-visible Spectroscopy. Interestingly, the addition of polyvinylpyrrolidone (PVP) during the synthesis was found to enhance the stability of the nanoparticle dispersion. The particles synthesized under these conditions assume “spherical” shape with the appearance of only transverse surface plasmon resonance band. The highlight of the observations is that the gold nanoparticles synthesized using tetraphenylborate as reducing agent and PVP as stabilizer are highly stable in alkaline medium, in contrast to the synthesis wherein borohydride is used as reducing agent. The AuNPs synthesized using tetraphenylborate and PVP show their mercury sensing behavior only in the alkaline medium. The color of the nanoparticle dispersion undergoes distinct color change from pink to blue with the addition of mercury ions. They also show dramatic selectivity to mercury ions in presence of other interfering ions, Pb2+, Zn2+ and Ca2+.

β-Cyclodextrin as the Vehicle for Forming Ratiometric Mercury Ion Sensor Usable in Aqueous Media, Biological Fluids, and Live Cells

The selective and sensitive detection methods for toxic transition-metal ions, which are rapid, facile, and applicable to the environmental and biological milieus, are of great importance. In this study, we designed a β-CD-based ratiometric sensor for detecting mercury ions in aqueous media, some biological fluids, and live cells. In this sensing platform, the thiocarbamido-containing probe dye was covalently linked onto the hydrophilic β-CD rim, which is conducive to complexing with metal ion, while the donor dye was anchored inside hydrophobic β-CD cavity via the adamantyl moiety, which is good for avoiding self-aggregation and enhancing the quantum yield of the donor dye. Upon associating with mercury ion, the probe dye undergoes ring-opening process and serves as the energy acceptor and constitutes the FRET system with the donor dye; by this way ratiometric detection of mercury ion in water can be realized with the detection limit of 10 nM. The cyclodextrin plays a crucial role for the sensing system; it not only accommodates both the donor dye and the probe dye which can form FRET system upon addition of Hg(2+) but also makes the sensor water-soluble and cell membrane permeable. This nontoxic sensing platform can be used for mercury ion detection in aqueous medium, biological fluids, and live cells (L929 and Hela). We also found that, upon being taken up by L929 cells, the sensor exhibited no cytotoxicity, and the cell proliferation was not affected.

Molecularly imprinted fluorescent polymers as chemosensors for the detection of mercury ions in aqueous media

AbstractThis article describes the investigation of molecularly imprinted fluorescent polymer membranes as sensing receptors for Hg2+ detection by an optical approach. The polymers were synthesized with 4‐vinylpyridine as a functional monomer and Hg2+ as a template; 9‐vinylcarbazole was used as both a complex‐forming agent and a fluorescence probe. The free‐radical polymerization was performed within a semicylindrical Teflon mold and was initiated by 2,2′‐azobisisobutyronitrile at 60°C. The template, ion‐bonded to pyridine and carbazole groups in the polymer membrane, was removed by acid treatment. Attenuated total reflectance–Fourier transform infrared (FTIR) spectroscopic measurements and scanning electron microscopy images were used to compare the chemistry and surface morphology, respectively, of both imprinted and nonimprinted polymer materials. The final polymer membranes with semicylindrical shapes were used directly to determine Hg2+ concentration in aqueous solutions by the monitoring of the fluorescence intensity of the carbazole groups quenched upon complex formation with metal ions. The values of the Hg2+ binding ratio for the imprinted and nonimprinted polymeric membranes were compared, and the results indicate the superior sensitivity and selectivity of the imprinted membranes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A “turn-on” coumarin-based fluorescent sensor with high selectivity for mercury ions in aqueous media

The synthesis and spectral profile of a "turn-on" fluorescent sensor selective for Hg(2+) ions in aqueous media is described.

Label-free aptamer-based colorimetric detection of mercury ions in aqueous media using unmodified gold nanoparticles as colorimetric probe

We report a simple and sensitive aptamer-based colorimetric detection of mercury ions (Hg(2+)) using unmodified gold nanoparticles as colorimetric probe. It is based on the fact that bare gold nanoparticles interact differently with short single-strand DNA and double-stranded DNA. The anti-Hg(2+) aptamer is rich in thymine (T) and readily forms T-Hg(2+)-T configuration in the presence of Hg(2+). By measuring color change or adsorption ratio, the bare gold nanoparticles can effectively differentiate the Hg(2+)-induced conformational change of the aptamer in the presence of a given salt with high concentration. The assay shows a linear response toward Hg(2+) concentration through a five-decade range of 1 x 10(-4) mol L(-1) to 1 x 10(-9) mol L(-1). Even with the naked eye, we could identify micromolar Hg(2+) concentrations within minutes. By using the spectrometric method, the detection limit was improved to the nanomolar range (0.6 nM). The assay shows excellent selectivity for Hg(2+) over other metal cations including K(+), Ba(2+), Ni(2+), Pb(2+), Cu(2+), Cd(2+), Mg(2+), Ca(2+), Zn(2+), Al(3+), and Fe(3+). The major advantages of this Hg(2+) assay are its water-solubility, simplicity, low cost, visual colorimetry, and high sensitivity. This method provides a potentially useful tool for the Hg(2+) detection.

Fluorescence detection of mercury ions in aqueous media with the complex of a cationic oligopyrene derivative and oligothymine

A water-soluble complex of a cationic oligopyrene derivative, oligo(N(1),N(1),N(1),N(4),N(4),N(4)-hexamethyl-2-(4-(pyren-1-yl) butanoyloxy) butane-1,4-diaminium bromide), and oligothymine has been prepared. The fluorescence sensor based on this complex showed high sensitivity and selectivity toward mercury(II) ions in aqueous media. The transduction mechanism of this sensor is based on the fluorescence self-quenching of oligopyrene in water via the interchain pi-stacking arising from the specific thymine-Hg-thymine complexation. The detection limit of this sensor was measured to be as low as 5 x 10(-9) mol L(-1). In addition, the fluorescent color change of the complex solution allows naked-eye detection of mercury(II) ions with an extremely low detection limit of 5 x 10(-6) mol L(-1).