Determination Of Hg Research Articles

A structure-switching electrochemical aptamer sensor for mercury ions based on an ordered assembled gold nanorods-modified electrode

In this paper, an electrochemical aptamer sensor with high sensitivity and selectivity was proposed for the detection of mercury ion (Hg2+). The ordered assembled gold nanorods-modified screen-printed electrode (AuNRs/SPE) was used to improve the sensor with higher sensitivity and data reproducibility. The sensor was designed based on the specific recognition of Hg2+ with aptamer to form T-Hg2+-T binding structure. Two aptamer chains were applied in the designed sensor, aptamer S1 with terminal thiolate group was self-assembled on the AuNRs/SPE via Au–S bond, and complementary S2 labeled with ferrocene (Fc) would generate a strong redox electrical signal. The addition of Hg2+ would mediate the folding of the T-base of S1 to form a hairpin structure, resulting in the dissociation of the Fc-labeled S2 from the sensing system and a significant reduction in the redox current. The electrochemical properties of the sensor were further investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The effects of aptamer reaction time, concentration, and target incubation time on the sensor response were also investigated. The results showed that the sensor had a sensitive response to Hg2+ at concentrations ranging from 1 pM to 1 μM, with a detection limit of 0.3 pM. Furthermore, the proposed sensor was applied in the determination of Hg2+ in real samples, demonstrating its potential practical value.

Investigation of Electrochemical Properties and Behaviors of NBITEP Molecule; Availability of Sensor Electrode in Determination of Hg2+ with SWAdSV Technique

This Master's Thesis focuses on the synthesis and structural elucidation of 4-(2-((6-nitro-1h-benzo[d]imidazol-2-yl)thio)ethyl)phenol (NBITEP) molecule, along with its electrochemical behaviors. Electrochemical studies were carried out employing a glassy carbon (GC) electrode as the working electrode. The cyclic voltammetry (CV) technique was utilized for modification and characterization processes. Furthermore, the potential of the modified surface as a sensor electrode for Hg2+ ion detection was investigated using square wave adsorptive stripping voltammetry (SWAdSV). Detailed examinations were conducted in a phosphate buffer solution (PBS) medium specifically for Hg2+ ion detection, demonstrating the suitability of the reduced NBITEP modified GC electrode surface as a sensor electrode.

A novel approach to Hg2+ determination in water samples using carbon dots based on paper and fluorescence digital image analysis

AbstractBACKGROUNDThis work proposes the use of a simple, inexpensive method for the hydrothermal synthesis of fluorescent carbon dot nanoparticles (CDs) from rice starch aimed at the determination of Hg2+ in water. The proposed method involved using a paper‐based analytical device coupled to a 3D plate, with a UV‐LED chamber and a smartphone for the acquisition and analysis of the fluorescence digital images of the CDs.RESULTSThe size of the carbon dots ranged from 0.5 to 3 nm, with an average particle size of ~1 nm. The functionalization of carbon dots with methimazole allowed a high selective for Hg2+ determination. The results obtained showed a linear response R2 of 0.997 and Hg2+ concentration in the range of 0.5–45.0 μmol L−1 with a limit of detection and limit of quantitation of 0.23 and 0.62 μmol L−1, respectively. The results of the study show that there were no significant differences, at 95% confidence level, between the data obtained from the application of the proposed method and the reference method.CONCLUSIONThe proposed method is in line with the principles of green chemistry, as it involves the use of renewable sources for starch extraction and a hydrothermal synthesis process that does not employ toxic reagents. In addition, the method employs only 15 μL reagent/sample. © 2024 Society of Chemical Industry (SCI).

Enhancing peroxidase-like activity of AuNPs through headspace reaction: A signal amplification strategy for colorimetric and fluorescent sensing of trace Hg2+

BackgroundRecently, headspace single-drop microextraction (HS-SDME) has attracted some attention for developing sensitive and selective colorimetric assays due to its excellent capability to reduce matrix interference and enrich analytes. However, the single droplet limits direct visual observation of color change and its quantitative measurement suffers from reduced optical path length. Therefore, amplifying the detection signals in both volume and intensity is an important and challenging task for improving the sensitivity, stability, and accuracy of such colorimetric analysis. ResultsIn this study, a "headspace-nanoenzyme" (HS-NE) strategy was proposed that successfully addressed these challenges and enabled the colorimetric and fluorescent dual-mode detection of trace Hg2+. Atomic Hg0, generated via chemical vapor generation (CVG), underwent headspace reaction with AuNPs droplet to form Au@HgNPs, thus catalyzing the oxidation of o-phenylenediamine (OPD) in the presence of H2O2. The absorbance and fluorescence intensity of oxidized OPD were proportion to the concentration of Hg2+ in the sample solution. Due to the greatly enhanced peroxidase-like activity by Au@HgNPs, the limit of detection was as low as 0.98 nM and 0.21 nM for the colorimetric and fluorescent modes, respectively. The applicability of this assay was further demonstrated with determination of Hg2+ in real environmental and biological samples. Moreover, a convenient and cost-effective paper-based sensing platform was fabricated for rapid on-site detection of Hg2+. Significance and noveltyThis novel HS-NE strategy combines HS-SDME and nanoenzyme-based sensing to achieve dual effects of eliminating matrix interference and amplifying the measurement signal, resulting in improved accuracy, enhanced stability, high sensitivity, and exceptional selectivity, with great potential for on-site determination of trace Hg2+.

A rare salamo-salophen type “on-off-on” fluorescent probe for relay recognition of Hg2+ and phosphate ions and its applications

A rare salamo-salophen type fluorescent probe SS with ICT effect was designed and synthesized, in which a salophen moiety with enlarged conjugation surface and a flexible long-chain salamo moiety were introduced into the probe SS molecule in order to make it strongly fluorescent and selectively recognize metal ions with larger radii. The fluorescence test showed that the probe SS has a bright blue fluorescence in DMF/H2O (v/v, 9:1) solution, and it is a relay fluorescent probe that recognizes Hg2+ and phosphate ions sequentially by switching ``on-off-on''. The introduction of a salophen moiety with an enlarged conjugation surface and a flexible long-chain salamo moiety in the design of this probe results in excellent fluorescence properties. Due to its relay recognition property, it has the advantages of simple operation and reduced workload for probe synthesis as well as versatility compared with single recognition probes. Probe SS showed highly selective and sensitive recognition of Hg2+ in DMF/H2O (v/v, 9:1) solution, and the identification mechanism was established through the study optical properties and high resolution mass spectrometry (HRMS), and verified further by DFT theoretical calculations. The SS-Hg2+ complex was also highly selective and sensitive to PO43−, with the lowest detection limits of the probe SS to Hg2+ and SS-Hg2+ complex to PO43− being 5.70 × 10−9 M and 2.44 × 10−8 M, respectively. Additionally, the SS probe was used successfully for the detection of real water samples, which is potentially applicable in the determination of Hg2+ and phosphate ions in the environment.

A novel pyrene‐based “off–on” fluorescent probe with high selectivity and sensitivity for Hg2+

AbstractIn this article, a novel “off–on” fluorescent probe 2‐(pyren‐1‐ylmethylene)‐1H‐indene‐1,3(2H)‐dione (PID) for Hg2+ was designed and synthesized. The selectivity, concentration titration, pH titration, time dependence, limit of detection, and recognition mechanism of PID for Hg2+ in CH3CH2OH/H2O solution were also investigated. The results indicated that PID exhibited high selectivity, sensitivity, and fast response to Hg2+, and the limit of detection was as low as 20.7 nmol/L. In addition, PID could work in a wide pH range, and the determination of Hg2+ in water samples showed that it could be used as a potential detection tool in practical application.

Folic Acid Adjustive Polydopamine Organic Nanoparticles Based Fluorescent Probe for the Selective Detection of Mercury Ions.

Polydopamine fluorescent organic nanomaterials present unique physicochemical and biological properties, which have great potential application in bio-imaging and chemical sensors. Here, folic acid (FA) adjustive polydopamine (PDA) fluorescent organic nanoparticles (FA-PDA FONs) were prepared by a facile one-pot self-polymerization strategy using dopamine (DA) and FA as precursors under mild conditions. The as-prepared FA-PDA FONs had an average size of 1.9 ± 0.3 nm in diameter with great aqueous dispersibility, and the FA-PDA FONs solution exhibit intense blue fluorescence under 365 nm UV lamp, and the quantum yield is ~8.27%. The FA-PDA FONs could be stable in a relatively wide pH range and high ionic strength salt solution, and the fluorescence intensities are constant. More importantly, here we developed a method for rapidly selective and sensitive detection of mercury ions (Hg2+) within 10 s using FA-PDA FONs based probe, the fluorescence intensities of FA-PDA FONs presented a great linear relationship to Hg2+ concentration, the linear range and limit of detection (LOD) were 0-18 µM and 0.18 µM, respectively. Furthermore, the feasibility of the developed Hg2+ sensor was verified by determination of Hg2+ in mineral water and tap water samples with satisfactory results.

A difunctional electrochemiluminescence sensor based on Ru-MOFs and strand-displacement-amplification reaction for ultrasensitive detection of Hg2+ and Ag+

A label free difunctional electrochemiluminescence (ECL) sensor for the ultrasensitive detection of mercury ions (Hg2+) and silver ions (Ag+) was constructed based on Ru(bpy)32+-functionalized metal-organic frameworks (Ru-MOFs) and the strand-displacement-amplification (SDA) reaction. Electrodeposited Ru-MOFs not only overcome the disadvantage of poor stability of traditional Ru2+ in aqueous solution, but also serve as an excellent carrier for hairpin DNA H1 during sensor construction. The SDA technology can transform extremely low concentrations of Hg2+ and Ag+ into a large number of the same alternative target DNA (tDNA). By combining SDA with Ru-MOFs, the detection sensitivity of the sensor is further improved. Meanwhile, the generated same alternative target tDNA can realize the detection of Hg2+ and Ag+ ions on this same sensing platform, which is beneficial to solve the common problems of high cost, long time and complicated operation in the detection of metal ion. The detection limits for Hg2+ and Ag+ are as low as 0.00032 pM and 0.00298 pM, respectively. And the corresponding linear detection range (LDR) is 0.001–1000 pM and 0.01–10000 pM, respectively. This ECL sensor has also been successfully used in the determination of Hg2+ and Ag+ in seawater, indicating an ideal platform for the simultaneous detection of trace heavy metal ions.

Selective chromogenic and fluorogenic signalling of Hg2+ ions using a benzothiazole-quinolinyl acrylate conjugate and its applications in the environmental water samples and living cells

We have developed a new chromogenic and fluorogenic chemosensor (L) based on benzothiazole conjugated with quinolinyl acrylate for the detection of Hg2+ ions with excellent selectivity and sensitivity. In the presence of Hg2+, the fluorescence of L was quenched from light blue to colorless. The L could work in the wide pH range of 5.0–8.0 without considerable interference from other tested ions. UV–Visible and fluorometric investigations revealed that the limit of detection (LOD) for Hg2+ was 1.0 μM (202 ppb) and 11.8 nM (2.38 ppb), respectively. Further, the applicability of probe L in the determination of Hg2+ in various water samples and biological samples were tested. Human Bone Osteosarcoma cell lines (HOS) were utilized for this study and satisfying results were obtained. These cell line results also further support the ‘on-off’ properties of probe L. Based on the colorimetric and fluorescent results we have designed a Boolean logic gate for futuristic applications.

Fluorescent Determination of Mercury(II) and Glutathione with Binding to Thymine–Guanine Base Pairs

It has been demonstrated that thymine–guanine (T–G) mismatches in duplex DNA specifically coordinate with mercury ion (Hg2+), forming T–Hg2+–G base pairs. However, the binding performance of T–G mismatches with Hg2+ and its application in biosensors have been rarely reported so far. In this study, the binding between T–G mismatches and Hg2+ was investigated and efforts were made to systematical characterize the analytical performance of T–G mismatches in the determination of Hg2+ and glutathione (GSH), where the thymine–thymine (T–T) mismatches were used as the reference. In specific, Hg2+ induced the conformational change of the fluorescently labeled DNA (FDNA) consisted of seven T–T mismatches, resulting in the dissociation of FDNA with its complementary sequence labeled with a quencher, followed by the disappearance of the fluorescence resonance energy transfer (FRET). The experimental results suggest that the T–G mismatch showed faster signaling kinetics and high sensitivity in sensing Hg2+ with a limit of detection of 4.72 nM for Hg2+. Moreover, the platform based on the T–Hg2+–G structure was successfully applied to determine glutathione with a detection limit of 18.96 nM. These findings of this study may describe the interactions between Hg2+ and nucleobases and extend the applications of Hg2+–mediated base pairs.

Rapid Determination of Mercury Ions in Environmental Water Based on an N-Rich Covalent Organic Framework Potential Sensor

In this article, an N-rich covalent organic framework (COFTFPB-TZT) was successfully synthesized using 4,4′,4′-(1,3,5-triazine-2,4,6-triyl) trianiline (TZT), and 4-[3,5-bis (4-formyl-phenyl) phenyl] benzaldehyde (TFPB). The as-prepared COFTFPB-TZT possesses irregular cotton wool patches with a large specific surface area. A novel selective electrode based on COFTFPB-TZT was used for the determination of Mercury ions. The abundance of N atoms in COFTFPB-TZT provides more coordination sites for Hg2+ adsorption, resulting in a change in the surface membrane potential of the electrode to selectively recognize Hg2+. Under optimal experimental conditions, the ion-selective electrode shows a good potential response to Hg2+, with a linear range of 1.0 × 10−9∼1.0 × 10−4, a Nernst response slope of 30.32 ± 0.2 mV/-PC at 25°C and a detection limit of 4.5 pM. At the same time, the mercury-ion electrode shows a fast response time of 10 s and good reproducibility and stability. The selectivity coefficients for Fe2+, Zn2+, As3+, Cr6+, Cu2+, Cr3+, Al3+, Pb2+, NH4+, Ag+, Ba2+, Mg2+, Na+, and K+ are found to be small, indicating no interference in the detection system. The proposed method can be successfully applied to the determination of Hg2+ in 3 typical environmental water samples, with a recovery rate of 98.6–101.8%. In comparison with the spectrophotometric method utilizing dithizone, the proposed method is simple and fast and holds great potential application prospects in environmental water quality monitoring and other fields.

Biothiol-Functionalized Cuprous Oxide Sensor for Dual-Mode Sensitive Hg2+ Detection.

Hg2+ ions are one of the highly poisonous heavy metal ions in the environment, so it is urgent to develop rapid and sensitive detection platforms for detecting Hg2+ ions. In this work, a novel electrochemical and photoelectrochemical dual-mode sensor (l-Cys-Cu2O) was successfully fabricated, and the sensor exhibits a satisfactory detection limit (0.2 and 0.01 nM) for the detection of Hg2+, which is far below the dangerous limit of the U.S. Environmental Protection Agency. The linear ranges of dual-mode Hg2+ detections were 0.33-3.3 and 0.17-1.33 μM, respectively. Moreover, the sensor shows desirable stability, selectivity, and reproducibility for detecting Hg2+ ions. For river water samples, the recoveries of 96.6-101.4% (electrochemical data) and 93.0-105.6% (photoelectrochemical data) were obtained, indicating that the sensor could be successfully applied in the determination of Hg2+ ions in environmental water. Therefore, the designed sensor has a potential in the trace-level detection of Hg2+ ions.

Silver Nanoparticles for Colorimetric Detection and Discrimination of Mercury Ions in Lake Water

AbstractAs the most toxic heavy metal, mercury (Hg) has been considered as the greatest environmental threat and it reach ubiquitous in industrial waste water and extended to environment. The detection of Hg2+ in environmental water is a crucial work for both protecting the environment and human health. Colorimetric assay exhibits visual discriminating and simple readout. This work presents the selective sensing of metal ion (Hg2+) by silver particles (Ag NPs), which were functionalized by galactosamine and synthesized via simple one pot method, with the average particle diameter of 18.75±0.49 nm. The limit of detection (LOD) was calculated as low as 7.92 nM. The colorimetric probe can also be performed in real water sample with good selectivity, and recovery was found to be 95–102 %, indicating can be used for on‐line determination of Hg2+ in the complex aqueous solutions. Additionally, the good catalytic performance of Ag NPs was demonstrated by hydrogenation of p‐nitrophenol and potassium ferricyanide in water samples.

Spectrophotometric Determination of Hg2+ Ions Using Sols of Silver Nanoparticles Modified with Cysteamine

Spectrophotometric Determination of Hg2+ Ions Using Sols of Silver Nanoparticles Modified with Cysteamine

Síntesis de película delgada de microesferas abiertas de nanovarillas de TiO2 aplicado como sensor electroquímico de Hg2+

El mercurio (Hg) es uno de los contaminantes más tóxicos, se ha convertido en una amenaza seria para la salud humana y el ambiente. Su exposición, produce efectos tóxicos graves en seres vivos, afectando los sistemas: nervioso, digestivo e inmunitario, y otras partes del organismo. El impacto ambiental es significativo y requiere la atención de todas las partes involucradas. Por esta razón, el desarrollo de métodos analíticos para la detección de bajas concentraciones de Hg en diferentes muestras es un asunto de interés científico. Actualmente, el uso de óxido de titanio (TiO2) ha revolucionado diversos campos generando nuevas aplicaciones tecnológicas. El área de sensores no ha quedado ajena a esta revolución debido a las propiedades de este material. En este trabajo de investigación, se da a conocer el desarrollo de un sensor electroquímico novedoso para la determinación de ultratrazas de mercurio en agua, a partir de nano-flores de TiO2 orientados. La síntesis del material se realizó sobre un sustrato de carbono (grafito) por el método hidrotérmico. La determinación de Hg2+ en agua fue realizada mediante voltamperometría cíclica y de pulso diferencial. Las pruebas electroquímicas del sensor mostraron una sensibilidad, selectividad y estabilidad alta, así como un amplio intervalo de detección en ppb

A New Highly Selective Colorimetric and Fluorometric Coumarin-based Chemosensor for Hg2.

A novel colorimetric and fluorometric method based on coumarin as signalling unit wasdeveloped for Hg2+ recognition and quantification. Initially, the alkyne functionality wasincorporated into a coumarin system and the resulting molecule showed higher specificity andsensitivity for Hg2+ over other cations in both absorption and emission sensing assays. TheHg2+ recognition was detected as visible colour change from colourless to yellow and asfluorescence quenching. The colour change was assigned to the increased intramolecularcharge transfer (ICT) in the signalling unit upon Hg2+ binding whereas a decline in thefluorescence intensity was ascribed to the heavy atom effect from Hg2+. In order to generate amaterial with high sensing performance level, alkyne-functionalized molecule was hosted intoa polymeric material. The resulting functionalized polymer showed higher sensitivity andselectivity for Hg2+ over its corresponding coumarin molecule. The investigation of thepossible binding modes for Hg2+ suggested both alkyne and triazole functionalities as potentialbinding sites for Hg2+. The limit of detection (LOD) and limit of quantification (LOQ) of theproposed method were evaluated and values less than a recommended maximum level of Hg2+contaminant in drinking water (2.00 μg/L) were obtained (LOD = 0.44 μg/L and LOQ = 1.33μg/L). The real-life application of the method was investigated using natural water samples containing Hg2+ levels equivalent to the maximum tolerable concentration of Hg2+ in drinkingwater. The outcomes suggested that the method could be used in the sensing and determination of Hg2+ level of contaminant in the environment.

Growth of Carbonaceous Nanoparticles on Steel Fiber from Candle Flame for the Long-Term Preservation of Ultratrace Mercury by Solid-Phase Microextraction.

An extremely simple, cost-effective, and one-step method was developed for the preparation of solid-phase microextraction (SPME) fibers via the in situ synthesis of carbonaceous nanoparticles on the surface of stainless steel fiber from a candle flame. The prepared SPME fiber provided excellent adsorption capability toward Hg2+ derived with sodium tetraethylborate and was explored for the separation, preconcentration, and long-term preservation of ultratrace mercury in natural water samples. Moreover, the SPME fiber was further utilized for the highly sensitive routine analysis and field analysis of mercury with a commercial atomic fluorescence spectrometer (AFS) and a miniature point discharge optical emission spectrometer (μPD-OES), respectively. Under the optimum conditions, detection limits of 0.0005 μg L-1 and 0.007 μg L-1 together with relative standard deviations (RSDs) less than 5.8% were obtained for Hg2+ by headspace SPME-AFS and SPME-μPD-OES, respectively. The practicality of the prepared SPME fiber was validated via the determination of Hg2+ in real water samples with satisfactory recoveries (79-115%). Long-term preservation of mercury at parts per trillion level was undertaken at -20 °C and the sample loss rates were less than 5% after 9 days of storage, respectively, indicating that the storage performances of mercury provided by the proposed method are much better than that obtained by conventional methods. Notably, the extraction performance of the SPME fiber is not decreased obviously even after more than 100 times of operation. Due to its advantages of high sensitivity, high stability, simple operation, low cost, and low energy consumption, this method provides an avenue for the field analysis and long-term preservation of mercury in the field of environmental analytical chemistry.

Trace Mercury Ion Detection Sensor Employing SnO2/Rgo Nanocomposites Modified Electrode

Introduction Heavy metal pollution seriously affects human health. Mercury is one of the most hazardous pollution, it has been accumulated in the environment of the food chain, industrial waste and so on [1]. The adverse effects of the mercury on the enzymes in the living body result in strong toxicity, such as blindness, paralysis, nerve damage and seriously threatening the human health and animal life safety [2].Since the mercury ion has the above hazards, the World Health Organization (WHO) and the Environmental Protection Agency (EPA) provide that the concentration of the mercury ions in the drinking water cannot exceed 2 ppb [3], so it is of great significance to study highly sensitive sensors to detect Hg2+ [4].Electrochemical detection methods are cost-effective and miniaturizable with high sensitivity, selectivity, short analysis time, and low power consumption, so they are very attractive for trace analysis of heavy metals, making electrochemical method being emerged as a preferable detection means.Recent trends in development of various nanomaterials modification electrode have increasingly due to their improvement of the analytical performance. SnO2 CQWs is a kind of semiconductor nanocrystals that are synthesized and dispersed in the solution. It can be deposited onto various working electrode at room temperature due to its excellent solution processability. In addition, its excellent crystallinity and high surface-to-volume ratio ensure a large number of active sites for the solid-ion interaction. On the other hand, Reduced graphene oxide (rGO) have been utilized for electrochemical sensor development, attribute to its high electrical conductivity and versatile surface modification. In order to enhance the electrochemical performance, it is extremely attractive to develop heavy metal ion detection sensors based on the synergistic effect of rGO and SnO2 by using the good charge transfer of SnO2/rGO nanocomposites interface and the excellent transfer capacity of rGO.In this work, we believe that the benefits of SnO2/rGO nanocomposites for mercury ion detection can be improved by controlled material synthesis. We used a one-step colloidal synthesis scheme in which the morphology of SnO2/rGO nanocomposites was controlled by adjusting the concentration of rGO. The synthesized SnO2/rGO nanocomposites can be directly modified on the working electrode without further sintering due to its excellent solution processing properties. The SnO2/rGO nanocomposites modified electrode for trace mercury ion detection was studied by ASV method. It has a high sensitivity and a wide range of mercury ion detection linear ranges. Method For the synthesis of rGO, the graphene oxide (GO) synthesized from wormlike exfoliated graphite powder, were thermally reduced at 300 °C for 30 min in an argon atmosphere, resulting in the rGO nanosheets. In the one-step colloidal synthesis, typically, 0.6 g SnCl4·5H2O was dissolved into 20 mL of oleic acid (OA) and 2.5 mL of oleylamine to form a transparent solution. Then, 1.0-3.0 mg of rGO and 10 mL of ethanol were added with mild stirring. The mixture was transferred into a 50 mL Teflon-lined stainless steel autoclave to react at 180oC for 3-8 h and then transferred to a cold water bath for cooling to room temperature. The product was rinsed with toluene and finally dispersed in ethanol at a concentration of 20 mg mL-1.The bare sheet of screen printing electrode was prepared by printing gold paste on Al2O3 ceramic sheet and heat treatment at 600oC × 0.5 h. Subsequently, the electrode was rinsed with acetone solution, absolute ethanol in an ultrasonic bath for 15 min each wash. The SnO2/rGO nanocomposites was dripped on the working electrode of screen printing electrode (SPE), and the SnO2/rGO nanocomposites modified electrode was prepared after drying naturally.The dissolution current of the modified electrode in different concentrations of Hg2+ solution was detected by ASV method. The ASV method was conducted in 0.1 M phosphate buffer solution (PBS) (Ph=6.0) in the range from -0.15 V to +0.4 V with optimized parameters: accumulation time: 120 s, deposition potential: -0.15 V. Conclusions In this paper, SnO2/rGO nanocomposites modified electrode was used to detect mercury ions. SnO2/rGO nanocomposites was synthesized via a simple solvothermal process and decorated on the working electrode. In addition to the excellent mercury ion adsorption of SnO2 quantum wires, the superior sensing performance of SnO2/rGO nanocomposites can be attributed to the enhanced electron transport resulting from the favorable charge transfer of SnO2/rGO nanocomposites interfaces and the superb transport capability of rGO. Determination of Hg2+ was performed in buffer solution (PH=6.0) using anodic stripping voltammetry (ASV). During deposition, the mercury ions in the solution were concentrated on the electrode surface and reduced to mercury metal. After the enrichment for a period of time, the working electrode voltage was scanned from the negative direction to the positive direction, so that the metal mercury that has been enriched on the electrode was oxidized and dissolved back into the solution, producing a dissolution current.The results showed that the sensor has much higher sensitivity and wider detect range.

Determination of Hg2+ in water based on acriflavine functionalized AgNPs by SERS

We conducted a related study on the determination of Hg2+ in water by surface-enhanced Raman scattering (SERS). It is based on acriflavine as a signal probe with the assistance of aggregation agent MgSO4 for the SERS investigation. Moreover, the density functional theory (DFT) calculations of acriflavine were performed for interpreting the assignments of the vibrational normal modes. The interaction of acriflavine with AgNPs was inhibited because the citrate reduced Hg2+ to Hg and formed Ag amalgam on the AgNPs surface. The formation of Ag-Hg alloys reduced the SERS intensity of acriflavine. This sensing system displayed excellent sensitivity and a detection limit as low as 1.4 mol L − 1. The relationship between the SERS intensity and Hg2+ concentration was found in the range of 0.1–8.0 × 10−7 mol L − 1. This method for detecting Hg2+ is inexpensive, facile and sensitive.

Au–Ag Nanoclusters/3,3′,5,5′ Tetramethylbenzidine Complex as a Sensitive “Turn-On” Fluorescent Nanoplatform for Mercury (II) Ions Sensing

Fluorescent bimetallic Au-Ag nanoclusters (Au-AgNCs) were found to exhibit oxidase-like activity and could catalyze the oxidation of 3,3',5,5' tetramethylbenzidine (TMB) to oxTMB. On the basis of this property, we assembled a fluorescent nanoplatform as a turn-on probe for sensing mercury (II) ions (Hg2+) through the inner-filter effect (IFE). Au-AgNCs and oxTMB were chosen as IFE absorber and fluorophore pair for the first time. In the absence of Hg2+, the Au-AgNCs absorption band well. Covered the fluorescence emission band of oxTMB, and as a result, the fluorescence of oxTMB was reduced. In the presence of Hg2+, Hg2+ was reduced to Hg0 by extra BSA in Au-AgNCs probe system and anchored on the surface of Au-AgNCs. The absorption intensity for Au-AgNCs then decreased at 418 nm, resulting in the recovery of fluorescence from oxTMB. The formed Au-Hg thin amalgam layer obviously enhanced the oxidase-like activity of Au-AgNCs as well as hindered the IFE activity between Au-AgNCs and oxTMB. Therefore, based on the Hg2+ stimulating oxidaselike properties of Au-AgNCs, a fluorometric assay for determination of Hg2+ was developed in this study. The proposed sensing strategy showed a linear range from 10 nM to 500 nM, with ultralow LOD of ~0.7 nM for Hg2+. Moreover, the detection probe system was stable over a wide pH range, making it able to be applied in complex sample systems. We have successfully demonstrated the detection of Hg2+ in tap water samples. The fluorescent assay reported here, for sensitive and selective determination of Hg2+, may find great application in multiple areas, such as environmental and pharmaceutical analysis.