Trace Hg Research Articles

Three-dimensional macroporous Carbon/Zr-2,5-dimercaptoterephthalic acid metal-organic frameworks nanocomposites for removal and detection of Hg(II)

Mercury ion (Hg(II)) has serious destructive effects on organisms and environments even at extremely low concentration. Therefore, effective removal and highly sensitive determination of trace Hg(II) is very important. Herein, mercaptan functionalized metal-organic frameworks (MOFs) were prepared by the coordination between Zr (IV) and 2,5-dimercaptoterephthalic acid (Zr-DMBD MOFs) and attached to three-dimensional kenaf stem-derived carbon (3D-KSC) to form a novel nanocomposite for removal and electrochemical detection of Hg(II). The sensitivity of Hg(II) detection was 324.58 μA μM−1 cm-2, the linear range was 0.25 μM–3.5 μM and the detection limit was 0.05 μM. The good performances were because lots of Zr-DMBD MOFs were uniformly dispersed on 3D-KSC and the porous Zr-DMBD MOFs had a large number of mercaptan groups to enrich Hg(II) significantly on the electrode. The Hg(II) detection would not be interfered by other co-existing heavy metal ions, and the Zr-DMBD MOFs/3D-KSC also showed excellent stability and reproducibility. Furthermore, the Zr-DMBD MOFs/3D-KSC could effectively remove Hg(II) in real wastewater. The residues were lower than national discharge standard of industrial wastewater (GB30770-2014).

Black Phosphorus Quantum Dots: A Fluorescence Probe for Metal Ions Based on Black Phosphorus Quantum Dots (Adv. Mater. Interfaces 7/2020)

In article number 1902075, Yu-Jia Zeng and co-workers successfully prepared black phosphorus quantum dots with green fluorescence emission, which can directly detect trace Hg2+ and Cu2+ ions without the help of organic molecules in both aqueous and organic phases. The fluorescence quenching mechanism are further explained based on the calculation of the electronic structure and adsorption energy.

Label-free, sensitive colorimetric detection of mercury(II) by target-disturbed in situ seeding growth of gold triangular nanoprisms

Gold nanomaterials have been used extensively in colorimetric detection of mercuric ions (Hg2+) due to their shape- and size-dependent, ultrastrong localized surface plasmon resonance (LSPR). Conventional detection was performed by first synthesizing the nanomaterials, and then applying them to signal-transducing reactions. We herein report a convenient method for detecting Hg2+ based on gold triangular nanoprisms (AuTNPs). During the seeding-growth process, Hg2+ added to the growth solution was co-reduced and deposited on the high-energy facets of the gold seeds, affecting the deposition patterns of the subsequently generated Au0 and ultimately leading to the formation of defective AuTNPs. Morphological changes were reflected by the in-plane dipole LSPR wavelength shift, which was proportionally related to the concentration of Hg2+. To improve the selectivity, the interference from Ag+ was eliminated by a stepwise preparation-selective precipitation approach. Under the optimized conditions, Hg2+ could be selectively detected with 20 min, with a detection limit of 0.12 nM. Finally, the method was successfully applied to detecting trace Hg2+ in fortified drinking, mineral and rain water samples, with recoveries ranging from 95.17% to 110.6%.

Recyclable Raman chip for detection of trace Mercury ions

Due to enrichment effect of Mercury ions (Hg2+), even if the concentration of Hg2+ is very low, it will do harm to human health. Precise detection of trace Hg2+ is important for environment protection and human health monitoring. In this work, gold nanoparticles (AuNPs) are immobilized on the surface of ITO with aid of inositol-hexaphosphate as linker agent and then 4-pyridinethiol (4-MPy) is decorated to form a 4-MPy/AuNPs/ITO chip. 4-MPy in the chip acts two roles involving the capture agent for Hg2+ and Raman signal reporter. With the adding of Hg2+, the linear increase of SERS response of 4-MPy is in the range from 1.0 ppt to 100 ppb (R2 = 0.9896) and the limit of detection could be down to 1 ppt. The mechanism of the Raman chip was also explored by molecular simulation. It is found that the interaction between Hg2+ and the nitrogen atoms changes the electron distribution of pyridine ring and induces reorientation of the 4-MPy molecules tending to more perpendicular adsorption fashion with respect to AuNPs surface, which leads to enhancement of the intensity of the pyridine breathing vibration peak at 1093 cm−1. The as-prepared SERS sensor chip features excellent stability and reproducibility as well as could be reused. The rapid 4-MPy/AuNPs/ITO-chip-based Raman protocol with capability against interference is competent for monitoring trace Hg2+ in river water samples.

Preconcentration and Determination of Trace Hg(II) Using a Cellulose Nanofiber Mat Functionalized with MoS2 Nanosheets

Molybdenum disulfide (MoS2) nanoparticles were hydrothermally synthesized onto the surface of a cellulose nanofiber mat and demonstrated for the selective extraction and preconcentration of trace Hg(II) from aqueous media. Immobilization of MoS2 onto solid support restricts sorbent loss during a column operation. The surface morphology and chemical bonding of the prepared material were characterized by scanning electron microscopy, tunneling electron microscopy, and X-ray photoelectron microscopy. The selective sorption of Hg(II) is mainly attributed to the soft–soft interaction of Hg(II) with the S atoms of the MoS2. The experimental data shows good Hg(II) sorption capacity and was found to be 160.4 mg g–1. The limit of detection and limit of quantification of the proposed method were found to be 0.09 and 0.30 μg L–1, respectively. The accuracy of the method against the systematic and constant errors was confirmed by the analysis of the Standard Reference Material (>95% recovery with <5% RSD). Student’s ...

Miniature 3D-printed integrated electrochemical cell for trace voltammetric Hg(II) determination

This work describes an integrated miniature all-3D-printed device for the determination of trace Hg(II) by anodic stripping voltammetry (ASV). The device is fabricated through a single-step printing process using a dual-extruder 3D printer and is composed of a mini vessel (printed from a polylactic acid (PLA) filament) and of 3 thermoplastic electrodes printed from a carbon-loaded PLA conductive filament and integrated at the bottom of the vessel. The working electrode surface is modified with a thin gold film electroplated in situ. The formation of the gold deposit was studied by linear sweep voltammetry and optical microscopy and the electrode materials as well as the chemical and instrumental conditions for Hg(II) determination were optimized. The limit of detection for Hg(II) is 0.52 μg L−1, the within-sensor repeatability (expressed as the coefficient of variation of 8 measurements of 20 μg L−1 Hg(II) at the same device) is 3.9 % and the between-cell reproducibility (expressed as the coefficient of variation 5 measurements of 20 μg L−1 Hg(II) conducted at different cells) is 8.9 %. The 3D-printed device was successfully applied to the determination of Hg(II) in bottled water and fish oil samples.

A highly sensitive colorimetric sensor for Hg2+ detection based on the oxidative enzyme mimics-like activity of hierarchical porous carbon@chitosan-modified silver nanoparticles

In this paper, DMC was prepared via carbonization in nitrogen with plexiglass as the template and sucrose as the carbon source. The hierarchical porous carbon (DHPC) was prepared by treating DMC with potassium hydroxide. The DHPC was loaded on chitosan to prepare DHPC@CS, which was then doped into nanosilver via the one-pot process to prepare DHPC@CS-AgNPs. The morphology of DHPC@CS-AgNPs was characterized using the Scanning Electron Microscope (SEM) and the Transmission Electron Microscope (TEM). In the presence of Hg2+, DHPC@CS-AgNPs will catalyze the oxidation of TMB, resulting in an observable change of color, so a rapid, sensitive and highly selective method could be established to detect trace Hg2+ colorimetric sensors. The conditions of the TMB color reaction, characteristics of the Hg2+ -DHPC@CS-AgNPs oxidized enzyme mimics and their color reaction characteristics were studied. Under the optimized conditions, coloration could not be catalyzed in the DHPC@CS-AgNPs-TMB system, but with the addition of the mercury ions, the catalytic activity was enhanced and the oxidized enzyme mimic activity was observed. In the Hg2+-DHPC@CS-AgNPs-TMB system, when TMB was used as a substrate, Km = 0.0165 mM, and Vmax = 4.6512 × 10−8 M·s−1. Under the optimized conditions, the linear range of mercury ion was determined to be 1 × 10−8–1 × 10−6 mol·L−1 using the above method, the linear relationship was r = 0.99753, the detection limit (S/N = 3) was 7 × 10−9 mol·L−1, and the recoveries of spiked water sample and fish sample ranged from 84.4% to 103%.

"On-off" ratiometric fluorescent detection of Hg2+ based on N-doped carbon dots-rhodamine B@TAPT-DHTA-COF.

Covalent-organic frameworks (COFs) are new porous crystalline materials owning outstanding stability, adsorbability and hypotoxicity. The assembly of fluorescence probes into porous COF provides a good method for ratiometric fluorescence detection avoiding the toxic effects of fluorescence probes to the samples. Herein, a two-dimensional COF (TAPT-DHTA-COF) was employed as a host to encapsulate N-doped carbon dots (NCDs) and Rhodamine B (RhB) (NCDs-RhB@COF). NCDs and RhB were uniformly assembled into the pores of TAPT-DHTA- COF based on the hydrogen bond. The as-prepared NCDs-RhB@COF nanocomposites exhibited blue emission of NCDs at 440 nm and red emission of RhB at 570 nm at excitation of 340 nm. After the addition of Hg2+, the blue emission became weaker while the red emission was enhanced due to the strong coordination between NCDs-RhB@COF and Hg2+. This "on-off" fluorescence probe was applied in detection of trace Hg2+ with linear range of 0.048-10 μM and detection limit of 15.9 nM together with appropriate selectivity, acceptable sensitivity and stability. The work shreds some light for COF as platform to construct ratiometric fluorescent sensor for industrial and biological application.

Fibrous strips decorated with cleavable aggregation-induced emission probes for visual detection of Hg2+

The widespread contamination and high poisonousness have created significant concerns and thus demands for facile, rapid and selective monitoring of trace Hg2+. Inspired from the unique aggregation-induced emission (AIE) feature, in the current study, novel tetraphenylethylene (TPE) derivatives are prepared containing sulfonic groups for water solubility modulation and carboxyl dithioacetals for Hg2+ sensing. The TPE derivatives are grafted on electrospun fiber as test papers to initiate the AIE activities, while the Hg2+-specific cleavage of dithioacetal groups leads to the release of TPE derivatives and fluorescence turn-off. The decrease in the fluorescence intensities of fibrous mats could be fitted with Hg2+ levels for quantitative analysis, and the fibrous mats turn from green to bluish-green and then to blue in the presence of different Hg2+ levels. The limit of detection (LOD) reaches as low as 20 nM Hg2+, satisfying the threshold detection in drinking water, and the Hg2+ sensing indicates negligible interference from other metal ions and pH variations. The detected Hg2+ levels in lake water are consistent with the added amount with a recovery rate of over 98 %. It demonstrates a feasible strategy to integrate Hg2+-cleavable AIE probes on fibrous strips for real-time, highly specific and naked-eye detection of trace Hg2+.

Synthesis of graphene oxide nanosheets from sugar beet bagasse and its application for colorimetric and naked eye detection of trace Hg2+ in the environmental water samples

In the present study, an analytical method was developed by using graphene oxide (GO) stabilized silver nanoparticles (AgNPs) for colorimetric and naked eye detection of trace Hg2+ in the environmental water samples. In this regard, a stable aqueous dispersion of GO has been synthesized by employing sugar beet bagasse as carbon source. Subsequently, AgNPs were decorated on the surface of as-synthesized GO by in-situ reduction of Ag+. Follow by, Hg2+ detection process was performed by consideration of the influence of several key factors including sensor stability over time, sample pH, response time, selectivity and sensitivity of the sensor. The obtained results revealed that the produced nanosensor has a good sensitivity and selectivity to Hg2+ detection with response time of 2 min with linear range of 10 to 100 µM. The sensing mechanism of analyte was based on the selective amalgam reaction between AgNPs and Hg2+. Moreover, the naked eye detection was investigated by the sensor's color changed from yellow to colorless. The detection limit of the produced sensor was 0.64 nM. This sensor was also applied to detect Hg2+ in the environmental water samples with recoveries in the range of 92.17% to 105.57%. The produced nanosensor exhibited good selectivity of Hg2+ in the presence of high concentration of other ions.

Highly sensitive detection of trace Hg2+ via PdNPs/g-C3N4 nanosheet-modified electrodes using DPV

In this work, Pd nanoparticle (PdNP)-modified graphite carbon nitride (g-C3N4) porous nanosheets (PdNPs/g-C3N4) were synthesized via reduction by hydrazine hydrate. The morphology analysis of the PdNPs/g-C3N4 nanosheets indicated that PdNPs were uniformly distributed on the g-C3N4 surface. The PdNPs/g-C3N4 modified glassy carbon (GC) electrode (PdNPs/g-C3N4/GC) was used for the trace detection of Hg2+ by differential pulse voltammetry (DPV). Excellent sensitivity and selectivity toward the determination of trace Hg2+ were achieved, as well as excellent anti-interference, repeatability, and long term stability under similar optimal experimental conditions. The limit of detection (LOD) for Hg2+ was 0.009 µg/L, lower than WHO standard (1.0 µg/L) and previously reported values. Moreover, the PdNPs/g-C3N4/GC electrode was employed to detect Hg2+ ions in real water environments, including local tap, lake, and river water samples, aiming at manifesting the potential practical applications of the electrode. The outstanding electrochemical performance of the PdNPs/g-C3N4 GC electrode toward Hg2+ detection was mainly ascribed to the combined advantages of the large specific surface area of the nanosheets and improved electrical conductivity owing to the deposited PdNPs. The current study provides a green and feasible method for the detection of trace Hg2+ in real water environments.

Ultrasensitive colorimetric aptasensor for Hg2+ detection using Exo-III assisted target recycling amplification and unmodified AuNPs as indicators

Facile and ultrasensitive detection of Hg2+ in water environment remains challenging. Exonuclease III (Exo-III)-assisted target recycling is one of the most popular amplification strategies. Although the magnesium (II) ions are widely acting as cofactors of Exo-III, we recognized that Mg2+ cofactors would strongly disturb the charge distribution on citrate-stablized gold nanoparticles (in the general sense, unmodified AuNPs) surface, thus generate false positive colorimetric signals. To address this issue, we first put forward the view that the cobalt (II) ions can function as the Exo-III cofactor and successfully construct a novel label-free colorimetric aptasensor for facile and ultrasensitive detection of Hg2+ using Hg2+-triggered Exo-III-assisted signal amplification and unmodified AuNPs as indicators. A hairpin-looped DNA probe was rationally designed with thymine-rich recognition termini and specifically recognized trace Hg2+ by a stable T–Hg2+–T structure. A blue-to-red color change of AuNPs with the addition of Hg2+ provided the quantitative detection of Hg2+ with a limit of detection of 0.2 nM and a linear working range from 0.5 nM to 5.0 nM. The whole testing time for one assay was approximately 40 min. Real water samples, even containing Hg2+ at 1 nM, could be determined by the aptasensor with recovery rates from 97% to 103%.

An on-chip electrochemical sensor by integrating ITO three-electrode with low-volume cell for on-line determination of trace Hg(II)

In this paper, an on-chip electrochemical sensor was designed by integrating an indium tin oxide (ITO) three-electrode with a low-volume cell, and trace Hg2+ was detected by differential pulse anodic stripping voltammetry (DPASV) after online flow accumulation in the sensor. The working electrode of the ITO three-electrode was composed of in-situ electrodeposited flower-cluster gold nanoparticles (AuNPs) microarray on the surface of the ITO, the reference electrode was Ag/AgCl, and the auxiliary electrode was ITO. The in-situ flow accumulation in the on-chip electrochemical sensor was used to detect the linear range of Hg2+ from 0.63 to 80ppb with a detection limit of 0.11ppb (S/N=3). The sensors had good selectivity towards Hg2+ in the interferences of eight common cations. The recovery rates of 1ppb Hg2+ were 101% in the tap water and 106% in the lake water. Compared with the traditional detection method, the on-chip electrochemical sensor by the in-situ flow accumulation of Hg2+ required low-volume sample and got a more sensitive and stable signal, so it had excellent potential for on-site and on-line detection of mercuric pollutant.

Preparation 2-(anthracen-9-yl)-1,3-dithiolane as a novel dual-channel AIE-active fluorescent probe for mercury (II) ion with excellent performance

A novel fluorescent probe molecule, 2-(anthracen-9-yl)-1,3-dithiolane (AADT), is designed and synthesized for Hg2+ detection successfully, based on a good aggregation induced emission (AIE) fluorescent mechanism and a specific reaction type. DMF-H2O mixed solvent (Fw 80% V/V) is suitable to disperse AADT for forming 1 × 10−5 mol L−1 solution with an AIE-active fluorescence probe system. Meanwhile, 9-Anthraldehyde also presents good fluorescence at same condition. With the increase of trace Hg (II), the AADT probe shows dual-channel, (turn-off at 429 nm, and turn–on at 511 nm) fluorescence probe character. (R2 > 0.994), which does not interfere each other. The probe demonstrates excellent selectivity, anti-inference properties, and several metal ions and acid ions hardly affect its performance. The LOD of the AADT probe is lower than 2.34 × 10−8 mol L−1, and proper to many common AIE-active probes.

Colorimetric and naked eye detection of trace Hg2+ ions in the environmental water samples based on plasmonic response of sodium alginate impregnated by silver nanoparticles.

Water pollution with mercury is a global concern. Therefore, establishing a rapid and accurate detection method is urgently required. Nanosensors can be a perfect alternative to instrument detection. In order to overcome low sustainability of sensors, a new composite nanosensor of sodium alginate- silver nanoparticles (SA-AgNPs) was synthesized by solvent casting method and used in colorimetric and naked eye detection of trace Hg2+ ions in water samples. The structural features of the produced nanosensor were characterized by instrumental techniques. The obtained results confirmed the formation of AgNPs with an average size of 13.34 nm. The colorimetric sensing of Hg2+ was carried out under specific conditions (pH = 6 and reaction time of 7 min) with a linear correlation obtained between the absorbance at 402 nm and different Hg2+ ion concentrations within the range of 0.025 μM-60 μM. The synthesized composite nanosensor of SA-AgNPs detected Hg2+ ions with a detection limit (LOD) of 5.29 nM. In addition, this sensor was successfully applied to detect Hg2+ ions in the environmental water samples with recoveries within the range of 81.58% to 114.73%. The produced nanosensor exhibited good selectivity toward Hg2+ ions in the presence of several competing ions.

Preparation of CdTe/Alginate Textile Fibres with Controllable Fluorescence Emission through a Wet-Spinning Process and Application in the Trace Detection of Hg2+ Ions.

Fluorescent textile fibres (FTFs) are widely used in many industrial fields. However, in addition to fibres with good fluorescence, fibres with excellent colour controllability, structural stability and appropriate mechanical strength still need to be developed. In this work, CdTe/alginate composite FTFs are prepared by taking advantage of the interactions between CdTe nanocrystals (NCs) and alginate macromolecules via a wet-spinning machine with a CaCl2 aqueous solution as the coagulation bath. CdTe NCs were chemically fixed in the fibre due to the interactions among surface ligands, macromolecules and coagulators (calcium ions), which ensured the excellent dispersity and good stability of the fibres. Förster resonance energy transfer (FRET) between NCs in the fibre was found to be restricted, which means that the emission colour of the fibres was totally controllable and could be predicted. Other properties of alginate fibres, such as flame retardance and mechanical strength, were also well preserved in the fluorescent fibres. Finally, FTFs showed good selectivity toward trace Hg2+ ions over other metallic ions, and the detection could be identified by the naked eye.

Development and optimization of an immunoassay for the detection of Hg(II) in lake water.

In this paper, an indirect competitive enzyme‐linked immunosorbent assay (IC‐ELISA) has been developed and optimized to detect Hg(II) in tap water and lake water based on a monoclonal antibody (mAb‐A24). Some stabilizing additives (Gelatin, bovine serum albumin [BSA], polyvinyl alcohol [PVA], and polyvinyl pyrrolidone [PVP]) and surfactant (Tween‐20) have been investigated thoroughly in the optimization process. Under the optimal condition, the 50% half maximal inhibitory concentration (IC50) and limit of detection (LOD) were 1.68 and 0.079 ng/ml, respectively. These anti‐Hg mAbs also have some affinity with methyl mercury (CH3Hg) and with no cross‐reactivity with other thirteen metal ions. The developed method has shown satisfactory recovery of Hg(II), ranged between 91% and 116%, from tap water and lake water. Therefore, this immunoassay can be used to detect trace Hg(II) in environment water.

Selective removal behavior and mechanism of trace Hg(II) using modified corn husk leaves

Removal of Hg(II) from wastewater was beneficial to satisfy the discharge standards of China's mercury-containing wastewater (50 ppb). An adsorbent was prepared via modifying corn husk leaves with bismuthiol I. The results revealed that the mercury removal rate was more than 98.5% at pH 1.0–7.0. Moreover, the removal rate reached 96% at 5 min and the residual concentration decreased from 10 ppm to approximately 30 ppb. In addition, the adsorbent owned a conspicuous selective absorbability for trace Hg(II) from wastewater. The adsorption process followed a Hill isotherm model. The actual saturated adsorption quantity of the adsorbent was 707 mg/g. The repeatability experiment indicated that the mercury removal efficiency was still beyond 99% after three cycles. The X-ray photoelectron spectroscopy suggested that the main adsorption mechanism was chelation between nitrogen/sulfur groups and Hg(II). The adsorbent was hopeful to remove mercury from wastewater in a sustainability perspective.

Magnetic solid-phase extraction using sulfur-containing functional magnetic polymer for high-performance liquid chromatography-inductively coupled plasma-mass spectrometric speciation of mercury in environmental samples

1,2-Ethanedithiol was firstly involved in preparing sulfur-containing functional magnetic polymer material of Fe3O4@SiO2@ glycidyl methacrylate (GMA)-S-SH. The prepared Fe3O4@SiO2@GMA-S-SH magnetic nanoparticles (MNPs) show better adsorption capacity and adsorption/desorption dynamics for mercury species than other -SH functional materials due to the high affinity of both thioether and thiol group towards mercury. A new method of magnetic solid phase extraction (MSPE) using Fe3O4@SiO2@GMA-S-SH as sorbents combined with high performance liquid chromatography (HPLC)-inductively coupled plasma mass spectrometry (ICP-MS) was developed for the analysis of trace Hg2+, methylmercury (MeHg+) and phenylmercury (PhHg+). Variables affecting the simultaneous extraction of three target mercury species were investigated. It was found that Hg2+, MeHg+ and PhHg+ in 200 mL of water sample could be quantitatively adsorbed within 5 min and eluted by 0.5 mL 0.1 mol L−1 nitric acid and 4% thiocarbamide in 2 min. The developed method has high actual enrichment factors of 367, 380, 329-fold for Hg2+, MeHg+ and PhHg+, respectively. The detection limits were 0.40, 0.49 and 1.4 ng L−1 with the relative standard deviations (n = 5, inter-day) of 7.4, 8.1 and 8.3% for Hg2+, MeHg+ and PhHg+, respectively. The accuracy of the method was validated by the analysis of the Certified Reference Materials of GSS-11 soil, GSS-13 soil, GSB21 rice and DORM-2 fish. The established method was successfully used for the mercury speciation in farmland water, soil and rice samples collected from Wanshan, China, and satisfactory recoveries (84.3–116%) were obtained for the spiked samples.

Green preparation of CuI particles in dielectric barrier discharge for colorimetric determination of trace mercury in comparison with atomic fluorescence spectrometric determination

The present work describes a solution-free method for preparation of copper(I) iodide (CuI) particles on copper wire by dielectric barrier discharge (DBD). The prepared material was applied to develop a colorimetric semi-quantitative analysis for fast screening analysis of trace mercury (Hg) by combing mercury vapor generation with Hg/CuI chromogenic reaction. Under the optimized conditions, the proposed method was successfully explored for visual determination of trace Hg in natural water and certified reference samples, and the results were in good agreement with cold vapor generation-atomic fluorescence spectrometry (CVG-AFS). It was proved to be a green, fast, visual and portable method for the determination of trace Hg in these real samples. It is a potential field analytical method for fast screening analysis.