Assay Of Hg2 Research Articles

Spectroscopic detection of Hg2+ in water samples using fluorescent carbon quantum dots as sensing probe

Mercury (Hg2+) is remarked as toxic and hazardous element to global environment. Here, carbon quantum dots (CQDs) were synthesized by simple microwave assisted technique for Hg2+ detection in water samples via. fluorescence quenching and FT-IR spectroscopic approach. The morphology and chemical structure of synthesized CQDs was investigated by TEM, FT-IR, 13C-NMR, fluorescence and UV-vis spectroscopic technique. The resultant CQDs bears spherical morphology with an average size of 2–4 nm. The binding parameters, as Stern-Volmer quenching constant (Ksv) and binding constant for CQDs-Hg system was investigated by fluorescence method, whereas UV-vis techniques was employed for determination of thermodynamic parameters, as Gibb’s free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) at three different temperature (295, 298 and 305 K). Moreover, selectivity assay for Hg2+ detection has been studied in presence of other metal ions by FT-IR as well as fluorescence spectroscopy. Analytical assay was also successfully applied for Hg2+ in spiked water samples collected from different areas of Chhattisgarh, with 98–99 recovery %. The detection of Hg2+ has been demonstrated in the range of 0 to 5.0μM with 3.25 nM detection limit. The present method is found to be simple, highly sensitive and selective for sensing of Hg2+ in aquatic environmental samples using CQDs as sensing probe.

Chicken egg white and L-cysteine as cooperative ligands for effective encapsulation of Zn-doped silver nanoclusters for sensing and imaging applications

Herein, we report chicken egg white (CEW) and L-cysteine (L-Cys) as cooperative ligands for effective encapsulation of Zn-doped silver nanoclusters (Zn-doped Ag NCs) for enhancing optical properties in sensing of Hg2+ ion and bioimaging of fungal cells (Alternaria sp.). The emission peak at 657 nm was remarkably enhanced by doping of Zn-atom into Ag NCs, suggesting the proteins of CEW and L-Cys provide good architectures for supramolecular encapsulation of Zn-Ag NCs. The quantum yield (QY) of Ag NC was improved to 13.3% due to the doping of Zn atoms into Ag NCs. The “fluorescence-off” of Zn-doped Ag NCs is proceeded by the addition of Hg2+ ion, which exhibits detection limit of 68 nM. The other chemical species did not interfere with assay of Hg2+ ion. We also extended the application of Zn-doped Ag NCs as a probe in imaging of fungal cells (Alternaria sp.). The CEW-L-Cys encapsulated Zn-doped Ag NCs exhibited an excellent stability and shown to be a magnificent probe for sensing and bioimaging applications, which demonstrates that Zn-doped Ag NCs as potential candidates in analytical and bioanalytical sciences.

Simple and green synthesis of piperazine-grafted reduced graphene oxide and its application for the detection of Hg(II)

In this paper, piperazine-grafted reduced graphene oxide (NH-rGO) was synthesized via a simple and green two-step procedure: (i) opening of the resulting epoxides of graphene oxide (GO) with piperazine (NH) through nucleophilic substitution; (ii) reduction of GO with ascorbic acid. Its structure and morphology were characterized by scanning electron microscopy and x-ray photoelectron spectroscopy. The NH-rGO modified glassy carbon electrode was explored as an electrochemical sensor for the determination of Hg(II) using a differential pulse anodic stripping voltammetry technique. Hg(II) can be efficiently accumulated and deposited on the surface of a modified electrode by strong coordination chemical bonds formed between Hg(II) and NH. And then the anodic stripping current can be significantly enhanced by rGO with the merits of large specific surface area and high conductivity, which served as a signal amplifier, finally realizing the highly sensitive determination of Hg(II). The experimental parameters including the pH value of the acetate buffer, deposition potential and deposition time were optimized. Under optimal conditions, the developed sensor exhibited a wide linear range from 0.4–12 000 nM with a low limit of detection of 0.2 nM, which is well below the guideline value in drinking water set by the WHO. Moreover, the practical application of this method was confirmed by an assay of Hg(II) in tap water samples with acceptable results.

MnII-Doped ZnS Quantum Dots Modified with Tiopronin for Mercury(II) Detection

The simple, low-cost, and rapid detection of aqueous mercuric ions remains a challenge for environmental and biological monitoring and protection. We demonstrate herein a new analytical method to detect Hg2+ based on MnII-doped ZnS quantum dots modified with tiopronin. At pH 7.2, Hg2+ causes the fluorescence intensity of quantum dots modified with tiopronin to decrease linearly proportionally with the concentration of Hg2+. This method is non-responsive to general metal ions, surfactants, and some biomacromolecules even though their concentrations were greater than that of Hg2+. Therefore, a sensitive and selective fluorescence assay for Hg2+ with a low limit of detection (8.9 × 10–9 mol L–1) has been developed and its successful application in real samples such as tap water, lake water, and human serum are also discussed in detail.

Highly sensitive label-free fluorescent detection of Hg2+ ions by DNA molecular machine-based Ag nanoclusters

We present here a highly selective and sensitive label-free method to detect Hg(2+) ions in aqueous solution by using DNA molecular machine-based fluorescent Ag nanoclusters (AgNCs). This mechanism is based on the Hg(2+) ions triggering machine-like operations of DNA and the "product" of the machine being used to stabilize fluorescent AgNCs. In this method, a tailored DNA, containing a sequence for Hg(2+) ions recognition, a sequence-specific nicking site for Nb BbvC I and a sequence complementary to the DNA as a template for the synthesis of fluorescent AgNCs, was firstly designed. In the presence of Hg(2+) ions, the machine's function operations were triggered. A series of machine-like operations, including replication, scission, and displacement then occurred with the addition of polymerase/dNTPs/Nb BbvC I, which manufactured lots of "product" DNA. The "product" DNA could act as a template for the preparation of fluorescent AgNCs. Thus the fluorescence of the AgNCs could be used as a signal transduction of this DNA machine, which was related to the concentration of the Hg(2+) ions. The repeated synthesis of the "product" and its template effect for AgNCs synthesis led to signal amplification in the assay of Hg(2+) ions. A linear response to the concentration of Hg(2+) ions was observed in the range from 0.08 nM to 20 nM and a detection limit of 0.08 nM was obtained. By contrast, the operation of the machine could not be executed in an Hg(2+) ion-free system. Moreover, the detection was not only label-free but also specific for Hg(2+) ions without being affected by other metal ions.

Improved Detection of Hg<sup>2+</sup> in Aqueous Solution with High Sensitivity and Selectivity by Using Mercury-Specific DNA, Sybr Green I and Gold Nanoparticles

We report a label-free, fast, fluorescence turn on assay for Hg2+ detecton by using mercury-specific DNA (MSD), Sybr Green I (SG) and gold nanoparticles (AuNPs). SG efficiently discriminates MSD and MSD/Hg2+ complex. The addition of gold nanoparticle decreases the background fluorescence signal further for MSD. The fluorescence intensity of MSD/Hg2+ complex keeps constant after addition of AuNPs. This property improves the signal-to-background ratio and decreases the detection limitation further. In addition, the method shows improved selectivity compared with that in the absence of AuNPs. This strategy could be applied to the detection of potassium ions and showed good generality.

Highly sensitive and selective detection of Hg2+ in aqueous solution with mercury-specific DNA and Sybr Green I

Sybr Green I efficiently discriminates mercury-specific DNA and mercury-specific DNA/Hg(2+) complex, which provides a label-free, fast, fluorescence turn on assay for Hg(2+) detection with high sensitivity and selectivity.

'Hypocryoglobulins'

Three patients with cutaneous vasculitis and one patient with digital gangrene had a negative or equivocal test for cryoglobulins but a positive result in a modified assay for cryoproteins ( hypocryoglobulins [ HGs ]) in which serum is rendered hypotonic by dilution with an equal volume of distilled water before incubation in the cold. Each cryoprecipitate contained a mixture of immunoglobulins, and in two instances, a monoclonal component was demonstrated. Rheumatoid factor activity was found in two precipitates. All four patients improved with plasmapheresis, and two subsequently responded to alkylating agents. Seven patients with conventional cryoglobulins had precipitation from diluted serum as well, but none had a substantial increase in precipitation in the HG assay. Only two of five patients with seropositive rheumatoid arthritis had abnormal levels of HG. Hypocryoglobulins are a new category of abnormally insoluble serum proteins, probably closely related to conventional cryoglobulins, which are readily detected in a simple precipitation assay.