Concentration Of Mercury Ions Research Articles

Design and demonstration of a temperature-resistant aptamer structure for highly sensitive mercury ion detection with BioFETs

In this study, we developed a temperature-resistant aptamer coupled with extended gate electric double-layer Field-Effect Transistors (FETs) for highly sensitive mercury ion detection. The design of the temperature-resistant aptamer is based on the thermal and structural properties of the hairpin structure. Two aptamer sequences were designed with different melting temperatures (Tm) and compared for their sensitivity. The hairpin structure of the aptamer with a high melting temperature ensures the stable structure prior to the addition of the mercury ions, which allows the formation of thymine–mercury–thymine (T -Hg2+-T) complex in low concentrations of mercury ions. High sensitivity and low detection limit are achieved at elevated temperatures with the aptamer having a high melting temperature. The elevated temperature facilitates the reaction rate, resulting in high sensitivity and a low detection limit. The aptamer with a high melting temperature hairpin structure has shown a remarkable improvement in the limit of detection with a 4 orders of magnitude increase compared to the one with a low melting temperature. The sensor with the high melting temperature aptamer shows an extremely low detection limit of 4.68 × 10−12 M, surpassing previously reported results. The aptamer with a low melting temperature requires mercury ions to stabilize the hairpin structure by forming a T-Hg2+-T complex. The results show that if the melting temperature is lower than the ambient temperature, it is very difficult to detect low concentrations of mercury ions at the ambient temperature. The selectivity of this sequence was also tested against multiple heavy metals, including arsenic (As), lead (Pb), chromium (Cr), and cadmium (Cd) ions. This study has shown how the structural and thermal properties of the aptamer, and the ambient temperature affect the sensitivity. They are strongly correlated to the performance of the sensors and need to be considered in the design of the sequence.

On the mechanism and energetics of electrochemical alloy formation between mercury and platinum for mercury removal from aqueous solutions

Mercury pollution is an acute global concern threatening the health of humans and wildlife. Thus, there is a need for new and improved techniques to reduce emissions and remove toxic mercury from aqueous environments. Electrochemical alloy formation, specifically between mercury ions in aqueous solution and a platinum electrode, emerges as a promising solution. Through analysis of reaction mechanisms and energetics related to the formation and dissolution of the PtHg4 alloy, this study aims to deepen our understanding of the underlying processes of effective electrochemical mercury removal. Potentiodynamic measurements indicate rapid alloy formation at a clean platinum surface, proceeding with only trace amounts of metallic mercury on the surface. However, once the electrode surface has sufficient mercury coverage with an alloy thickness of around 1.5 nm, clear evidence of metallic mercury on the surface is observed. Furthermore, the amount of absorbed mercury on the cathode increases linearly in time. The onset potential for the alloy formation is experimentally determined using electrochemical quartz crystal microbalance with dissipation monitoring to be approximately 0.64 V vs. SHE, and the alloy dissolution (oxidation) onset potential is found to be approximately 0.98 V vs. SHE, at a mercury ion concentration of 10 mg/L. Density functional theory calculations are used to provide a theoretical value for the reversible potential from a thermodynamics perspective, yielding a value of 0.78 V vs. SHE at a mercury ion concentration of 10 mg/L. This value is in excellent agreement with the experimental results, suggesting an overpotential of about 0.14 and 0.20 V for the alloy formation and oxidation, respectively. These findings provide important information on the reaction mechanisms and overpotentials of the PtHg4 alloy formation and dissolution, which are key factors for development of large-scale mercury removal based on this technique, as well as fundamental understanding of the electrochemical alloy formation between mercury ions and platinum.

Accurate and rapid mercury susceptibility detection in aquatic samples using fluorescent probe integrated rhodamine with pyridyl isothiocyanate

Mercury, one of the various harmful metals, is particularly significant in affecting aquatic organisms, currently gaining more attentions and sparking discussions. In response to the limitations of traditional detections, fluorescent probes have emerged as a promising solution with some advantages, such as weaker background interference, shorter processing time, higher accuracy. Thus, a novel fluorescent probe, FS-Hg-1, has been developed for assessing mercury ion (Hg2+) concentrations in aquatic products. This probe displays specific recognition of mercury ions in fluorescence spectra. Notably, FS-Hg-1 exhibits a distinct color change to pink when combined with Hg2+ (with a 948-fold increase in absorption at 568 nm) and a substantial fluorescence change towards Hg2+ (361-fold increase, excitation at 562 nm, emission at 594 nm) in N, N-dimethylformamide. The probe boasts a detection limit of 0.14 μM and rapid reaction with Hg2+ within 10 s, showing an excellent linear correlation with [Hg2+] in the range of 0 to 10 μM. Through thorough analysis using FS-Hg-1, the results align with those from the standard method (P > 0.05), with spiked recovery rates ranging from 108.4% to 113.2%. With its precise recognition, low detection limit, and remarkable sensitivity, this fluorescent assay proves effective in mercury concentration determination in aquatic samples without interference. The potential of FS-Hg-1 is promising for speedy detection of residual Hg2+ and holds significance in ensuring food safety.

Genome-Scale Screening of Saccharomyces cerevisiae Deletion Mutants to Gain Molecular Insight into Tolerance to Mercury Ions.

Mercury (Hg) is a global pollutant and a bioaccumulative toxin that seriously affects the environment. Though increasing information has been obtained on the mechanisms involved in mercury toxicity, there is still a knowledge gap between the adverse effects and action mechanisms, especially at the molecular level. In the current study, we screened a diploid library of Saccharomyces cerevisiae single-gene deletion mutants to identify the nonessential genes associated with increased sensitivity to mercury ions. By genome-scale screening, we identified 64 yeast single-gene deletion mutants. These genes are involved in metabolism, transcription, antioxidant activity, cellular transport, transport facilitation, transport routes, and the cell cycle, as well as in protein synthesis, folding, modification, and protein destination. The concentration of mercury ions was different in the cells of yeast deletion mutants. Moreover, the disruption of antioxidant systems may play a key role in the mercurial toxic effects. The related functions of sensitive genes and signal pathways were further analyzed using bioinformatics-related technologies. Among 64 sensitive genes, 37 genes have human homologous analogs. Our results may provide a meaningful reference for understanding the action mode, cellular detoxification, and molecular regulation mechanisms of mercury toxicity.

NeMeHg, genetically encoded indicator for mercury ions based on mNeonGreen green fluorescent protein and merP protein from Shigella flexneri.

The detection of mercury ions is an important task in both environmental monitoring and cell biology research. However, existing genetically encoded sensors for mercury ions have certain limitations, such as negative fluorescence response, narrow dynamic range, or the need for cofactor supplementation. To address these limitations, we have developed novel sensors by fusing a circularly permutated version of the mNeonGreen green fluorescent protein with the merP mercury-binding protein from Gram-negative bacteria Shigella flexneri. The developed NeMeHg and iNeMeHg sensors responded to mercury ions with positive and negative fluorescence changes, respectively. We characterized their properties in vitro. Using the developed biosensors, we were able to successfully visualize changes in mercury ion concentration in mammalian cultured cells.

Electrochemical Hg2+ sensor based on electrospun cellulose acetate nanofibers doped with Ag nanoparticles

Mercury (Hg) sensors are critical for environmental monitoring, industrial processes, and public health. They are designed to measure the presence and concentration of mercury ions (Hg2+) in various matrices, including air, water, soil, and biological samples. Mercury in the environment raises concerns due to its toxicity and potential for bioaccumulation. Therefore, this work aims to develop an improved, eco-friendly mercury sensor to address the evolving need for monitoring and control of mercury. The electrochemical sensor for reported here is based on the ability of silver (Ag) to catalyze the reduction of the mercury species Hg2+ to elemental mercury (Hg0), forming an Ag/Hg amalgam. To optimize this sensor, the concentration of silver nanoparticles (AgNPs) on modified nanofibers is determined using differential pulse voltammetry (DPV). Morphological studies and chemical characterization reveal a fiber thickness ranging from 250 to 450 nm and characteristic functional groups, respectively. The sensoŕs analytical performance for detecting Hg2+ concentrations is evaluated through cyclic voltammetry (CV) and DPV in 0.1 M potassium chloride as a supporting electrolyte. The sensor’s detection limit (LOD) for Hg2+ was 0.43 μg/L, with a sensitivity of 0.33 mA/μg/L. In conclusion, the electrochemical sensor exhibits sensitivity and selectivity for Hg2+ detection in the presence of other interfering metal ions, along with eco-friendly and cost-effective features, making it a reliable and practical tool for detecting Hg2+ concentration in water samples.

Reflective optical fiber SPR sensor with DNA modification for high-sensitive Hg2+ concentration measurement

A reflective optical fiber surface plasmon resonance (SPR) sensor was proposed to measure the concentration of mercury ions (Hg2+). The specific single-stranded DNA was modified on the optical fiber sensing surface coated with Au film by the combination of covalent bond and charge adsorption. The Hg2+ can mismatch with T-T (thymine-thymine) base pairs in single-stranded DNA to form T-Hg2+-T structure, which led to the change of refractive index in sensing area and the wavelength shift of SPR spectrum. The measurement results showed that when the concentration of Hg2+ increased from 0 μM to 13 μM, the resonance spectrum shifted by 14.26 nm. In the linear range between 1–8 μM, the measurement sensitivity of the sensor could reach 1.51 nm/μM. The limit of detection (LOD) was found to be 0.28 μM. Besides, the sensor showed good stability, selectivity and reusability.

Different solvents accompanied by different structures: Catalyst-free one step construction of highly branched polythioureas and its properties

In this study, tris(2-aminoethyl)amine and carbon disulfide were used as raw materials for the construction of highly branched polythioureas. Firstly, a highly branched polythiourea adsorbent was synthesized through a heating condensation reaction using N, N-dimethylformamide (DMF) as solvent without any catalyst. Interestingly, this study also revealed that a highly branched polythiourea resin was successfully synthesized without any catalyst when water was used as the solvent. Through nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), gel chromatography column (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and other means to characterize the comprehensive properties of the polymer. Then, mercury ions were used as the adsorption model. The effects of adsorbent dosing, adsorption time, and different pH on the adsorption of mercury ions (Hg2+) were investigated by intermittent adsorption experiments. The adsorption kinetics, isotherm model, sensitivity test of mercury extraction, single metal ion test, and the adsorption capacity of the adsorbent for nine metal ions were studied. In addition, bond strength tests were utilized to explore the adhesive properties of the prepared aqueous phase highly branched polythioureas. The results show that in the adsorption performance test, when the dosage of highly branched polythiourea adsorbent is 10 mg, the pH is acidic or neutral, and the adsorption time is 60 min, the adsorption efficiency of P-DMF for Hg2+ is as high as 99.99 %. The adsorption follows the Langmuir isotherm model and fits well with the pseudo-second-order kinetic model. In addition, P-DMF has a certain selectivity for Hg2+, and the adsorption efficiency is positively correlated with the mercury ion concentration. When Hg2+ is 100 mg/L, the adsorption efficiency reaches 99.98 %. In the bond strength test, the dry shear strength of the plywood reached 1.6 MPa, and the strength after soaking in hot water and boiling water for 3 h was 1.5 MPa and 1.4 MPa respectively, exceeding the requirements of GB/T9846-2015 for type II plywood (≥0.7 MPa).

Controllable detection threshold achieved through the toehold switch system in a mercury ion whole-cell biosensor

Due to the toxicity of mercury and its harmful effects on human health, it is essential to establish a low-cost, highly sensitive and highly specific monitoring method with a wide detection range, ideally with a simple visual readout. In this study, a whole-cell biosensor with adjustable detection limits was developed for the detection of mercury ions in water samples, allowing controllable threshold detection with an expanded detection range. Gene circuits were constructed by combining the toehold switch system with lactose operon, mercury-ion-specific operon, and inducible red fluorescent protein gene. Using MATLAB for design and selection, a total of eleven dual-input single-output sensing logic circuits were obtained based on the basic logic of gene circuit construction. Then, biosensor DTS-3 was selected based on its fluorescence response at different isopropyl β-D-Thiogalactoside (IPTG) concentrations, exhibiting the controllable detection threshold. At 5–20 μM IPTG, DTS-3 can achieve variable threshold detection in the range of 0.005–0.0075, 0.06–0.08, 1–2, and 4–6 μM mercury ion concentrations, respectively. Specificity experiments demonstrated that DTS-3 exhibits good specificity, not showing fluorescence response changes compared with other metal ions. Furthermore spiked sample experiments demonstrated its good resistance to interference, allowing it to distinguish mercury ion concentrations as low as 7.5 nM by the naked eye and 5 nM using a microplate reader. This study confirms the feasibility and performance of biosensor with controllable detection threshold, providing a new detection method and new ideas for expanding the detection range of biosensors while ensuring rapid and convenient measurements without compromising sensitivity.

An excimer process induced a turn-on fluorescent probe for detection of ultra-low concentration of mercury ions.

The accumulation of mercury pollution in plants can induce severe injury to human beings. It is a great challenge to monitor ultra-low concentrations of mercury in complicated matrixes. In this study, we successfully developed a strategy via Hg2+-triggered naphthalene-based fluorescent probe 1, which formed excimer that subsequently emitted fluorescence for the successful detection of ultra-low concentrations of Hg2+. The coordination of N and S atoms with Hg2+ facilitated the formation of excimer from the naphthalene-conjugated planes that were in sufficiently close proximity. Suppression of CN bond rotation also induced the chelation-enhanced fluorescence (CHEF) effect, and the cumulative result of these effects was obvious fluorescent enhancement. Compared with probe 2, the other key factor for detection of Hg2+ is that the electrons of the hydroxyl group can easily transfer to a naphthalene moiety, resulting in an augmented π-electron density that enhanced the π-π stacking of the naphthalene-conjugated excimer. After detailed spectral studies and mechanism discussions, it was realized that probe 1 was able to detect ultra-low concentrations of Hg2+ in PBS buffer solution. The detection limit was calculated to be 1.98 nM. On account of the excellent performances, the probe was successfully applied in monitoring Hg2+ in water and pea sprouts with the potential for application as an advanced warning of contamination.

Voltammetry for quantitative determination of trace mercury ions in water via acetylene black modified carbon paste electrode

A sensitive acetylene black modified carbon paste electrode was fabricated for the determination of trace mercury ions in water samples. Nitric acid treatment of acetylene black (TAB) produced a porous structure with large surface area and defects, improving its performance as an electrode modifier. Under optimized conditions, the TAB/CPE showed good selectivity and sensitivity towards mercury ions. The peak current exhibited a linear relationship with mercury ion concentration from 10 nM to 0.1 mM, with a detection limit of 8.8 nM. The enhanced sensitivity results from a synergistic effect between the properties of TAB and carbon paste. The porous structure, large surface area and defects in TAB improve mercury ion adsorption and electron transfer kinetics. Meanwhile, the carbon paste provides a stable and conductive electrode base. The developed sensor showed good stability, repeatability and reproducibility, as well as acceptable recovery results when applied to detect mercury ions in simulated water samples. This simple and rapid electrochemical method holds potential for the determination of trace mercury ions in environmental water samples.

Electrochemiluminescence Sensor Based on CeO2 Nanocrystalline for Hg2+ Detection in Environmental Samples.

The excessive concentration of heavy-metal mercury ions (Hg2+) in the environment seriously affects the ecological environment and even threatens human health. Therefore, it is necessary to develop rapid and low-cost determination methods to achieve trace detection of Hg2+. In this paper, an Electrochemiluminescence (ECL) sensing platform using a functionalized rare-earth material (cerium oxide, CeO2) as the luminescent unit and an aptamer as a capture unit was designed and constructed. Using the specific asymmetric matching between Hg2+ and thymine (T) base pairs in the deoxyribonucleic acid (DNA) single strand, the "T-Hg-T" structure was formed to change the ECL signal, leading to a direct and sensitive response to Hg2+. The results show a good linear relationship between the concentration and the response signal within the range of 10 pM-100 µM for Hg2+, with a detection limit as low as 0.35 pM. In addition, the ECL probe exhibits a stable ECL performance and excellent specificity for identifying target Hg2+. It was then successfully used for spiked recovery tests of actual samples in the environment. The analytical method solves the problem of poor Hg2+ recognition specificity, provides a new idea for the efficient and low-cost detection of heavy-metal pollutant Hg2+ in the environment, and broadens the prospects for the development and application of rare-earth materials.

Advances in green materials derived from wood for detecting and removing mercury ions in water

The issue of mercury pollution in environmental remediation has garnered significant attention due to its severe health hazards to humans. Various strategies have been devised to mitigate the impact of toxic mercury ions, including coagulation, ion exchange, adsorption, membrane technology, and electrochemical treatment. Among these approaches, adsorption has emerged as an efficient and widely employed method for the uptake of low concentrations of mercury ions. It offers convenient operation, high removal efficiency, and facile regeneration of the adsorbent. Wood, being the most abundant renewable and sustainable bioresource, has garnered attention as a promising material for treating heavy metal wastewater. This is attributed to its unique physical and chemical characteristics, encompassing hierarchical pores, aligned channels, active functional groups, biodegradability, and cost-effectiveness. However, a comprehensive examination of the cutting-edge applications of wood and wood-derived biopolymers in the detection and removal of mercury ions from wastewater has yet to be undertaken. Consequently, this article presents a chronological overview of recent advancements in materials and structures derived from bulk wood and its constituents, including cellulose, lignin, hemicellulose, and tannin, with a specific focus on their utility in detecting and eliminating mercury from water sources. Subsequently, the most promising techniques and strategies involving wood and wood-derived biopolymers in addressing the predicament of mercury pollution are explored. Furthermore, this piece offers insights into the existing challenges and future prospects concerning environmentally friendly materials derived from wood, aiming to foster the development of cost-effective mercury adsorbents and detection devices.

Mercury Ion Sensing Using Aptamer-Modified Extended Gate Field-Effect Transistors and a Handheld Device

In this research, we have designed, fabricated, and characterized an Electrical double-layer (EDL) gated FET platform to detect heavy metals. The electrical double layer (EDL)-gated field-effect transistor-based sensor is garnering interest due to its sensitivity, portable configuration, selectivity, inexpensive operation, as well as their user-friendly nature. the sensing platform designed for rapid detection of Hg2+ using DNA-based aptamers. The investigation was carried out by introducing different concentrations of Mercury ions and a lower detection limit of 1 μM was achieved. The sensor surface was validated with Kelvin Probe Force Microscope (KPFM), which is consistent with the electrical response obtained. Sensor selectivity was studied and exhibited a high sensitivity toward Mercury ion detection. Considering its limit of detection, compatibility, and fast turnaround; the proposed system has the potential to be used to detect Mercury ions instantly for environmental monitoring, where quick and accurate detection of Mercury ions is essential.

Recyclable Multifunctional Magnetic Fe3O4@SiO2@Au Core/Shell Nanoparticles for SERS Detection of Hg (II)

Mercury ions can be enriched along the food chain and even low concentrations of mercury ions can seriously affect human health and the environment. Therefore, rapid, sensitive, and highly selective detection of mercury ions is of great significance. In this work, we synthesized Fe3O4@SiO2@Au three-layer core/shell nanoparticles, and then modified 4-MPy (4-mercaptopyridine) to form a SERS sensor. Mercury ions in water can be easily captured by 4-MPy which were used as the reporter molecules, and the concentration of mercury ions can be evaluated based on the spectral changes (intensification and reduction of peaks) from 4-MPy. After the mercury ion was combined with the pyridine ring, the peak intensity at 1093 cm−1 increased with the concentration of mercury ion in the range of 10 ppm–1 ppb, while the Raman intensity ratio I (416 cm−1)/I (436 cm−1) decreased with the increase of mercury ion concentration. This magnetically separatable and recyclable SERS sensor demonstrates good stability, accuracy, and anti-interference ability and shows the potential to detect actual samples. Furthermore, we demonstrate that the probe is applicable for Hg2+ imaging in macrophage cells.

The Effect of the Saudi Haloxylon ammodendron Shrub on Silver Nanoparticles: Optimal Biosynthesis, Characterization, Removability of Mercury Ions, Antimicrobial and Anticancer Activities

This research provides a sustainable way to treat water by removing heavy metal hazards (mercury ion) and biological pollutants (several strains of bacteria and fungi) through the eco-friendly synthesis of silver nanoparticles using the ethanol extract of the Saudi Haloxylon ammodendron shrub, which is planted in the Qassim desert. Further, this work confirms that these nanoparticles could be used as anticancer materials. The optimization factors of the biosynthesis of silver nanoparticles were studied and obtained (volume ratio = 1:2, pH = 7.5, and temperature = 60 °C). The scanning electron microscope micrographs showed the spherical shape and the huge numbers of silver nanoparticles accumulated, while X-ray diffraction measurements gave the crystal size of these nanoparticles in the range of 10.64 nm. The application findings of these biofabricated silver nanoparticles demonstrated effective detection and removal of different concentrations of mercury ions (0–2500 ppm) from the polluted aqueous solutions. The work revealed that Haloxylon ammodendron extract enhanced the antibacterial and antifungal activities of silver nanoparticles against different strains of bacteria and fungi. As well, the anticancer activity examinations of these nanoparticles and the extract showed good and reasonable results.

Temperature and concentration dependence of the electrochemical PtHg4 alloy formation for mercury decontamination

New and improved methods to remove toxic mercury from contaminated waters and waste streams are highly sought after. Recently, it was shown that electrochemical alloy formation of PtHg4 on a platinum surface with mercury ions from solution can be utilized for decontamination, with several advantages over conventional techniques. Herein, we examine the alloy formation process in more detail by mercury concentration measurements using inductively coupled plasma mass spectrometry in batch measurements as well as electrochemical quartz crystal microbalance analysis both in batch and in flowing water with initial mercury concentrations ranging from 0.25 to 75000 µg L−1 Hg2+. Results show that mercury is effectively removed from all solutions and the rate of alloy formation is constant over time, as well as for very thick layers of PtHg4. The apparent activation energy for the electrochemical alloy formation was determined to be 0.29 eV, with a reaction order in mercury ion concentration around 0.8. The obtained results give new insights that are vital in the assessment and further development of electrochemical alloy formation as a method for large scale mercury decontamination.

Tracking Silver Nanoparticles during Their Synthesis by Inductively Coupled Plasma Mass Spectrometry: Implications for Colorimetric Sensing of Mercury Ions

Silver nanoplates have been used in the colorimetric sensing of analytes through various mechanisms. Herein, we proposed the use of single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) for providing additional information on changes in nanoparticles during the colorimetric sensing of analytes. The information on equivalent spherical diameter and the number of particles obtained from SP-ICP-MS was employed for tracking the changes in silver nanoparticles during their synthesis process under various synthesis conditions and also during the colorimetric sensing of mercury. By comparing the edge size of triangular nanoplates observed by transmission electron microscopy, the information on the plate thickness of triangular silver nanoplates was also estimated by the size information from SP-ICP-MS. Four types of silver nanoplates were examined including bare silver nanoplates, silver nanoplates capped with glutathione, silver nanoplates capped with glutathione mixed with 0.05 mg L–1 mercury and bromide ions, and silver nanoplates capped with glutathione mixed with 1 mg L–1 mercury and bromide ions. The information on equivalent spherical diameter and the number of particles was used for understanding the sensing mechanism of the silver nanoplates toward mercury ions. The information from SP-ICP-MS was combinedly used with plasmon absorption data, as well as the information from field-flow fractionation-ICP-MS (FFF-ICP-MS), in order to study the changes in silver nanoparticles at various concentrations of mercury ions. A linear increase in particle concentrations was observed by SP-ICP-MS for the concentration range of 0.001–0.01 mg L–1 mercury ions. The particle concentrations were highest at 0.01 mg L–1 mercury ions and decreased to the same numbers as for the bare silver nanoplates without bromide etching. This study shows the potential use of SP-ICP-MS to provide additional information for tracking silver nanoparticles during their synthesis and colorimetric sensing of mercury ions. In addition, for SP-ICP-MS analysis of particle concentrations for the diluted silver nanoplates in contact with mercury ions before etching with diluted bromide ions, the limit of detection for mercury was pushed down to approximately 0.01 μg L–1, which would be very useful for the analysis of real samples under environmentally relevant conditions.

Synthesis of N,Si co-doped carbon dots to establish a fluorescent sensor for Hg(II) detection with triple signal output.

Mercury is a heavy metal with extreme toxicity. Thus, it is of significance to develop an effective method for mercury ion detection with high performance. In this study, carbon dots doped with nitrogen and silicon (N,Si/CQDs) were successfully prepared from folic acid and N-[3-(trimethoxysily)propyl]-ethylenediamine. The N,Si/CQDs show an obvious cyan fluorescence of 460 nm with the radiation of 350 nm. The existence of mercury ions induces the fluorescence quenching of N,Si/CQDs due to photoinduced electron transfer, which was applied for the sensitive sensing of Hg(II). More importantly, the practical application of the N,Si/CQD probe was confirmed by measurements of Hg(II) in real samples of lake water, sorghum and rice. In addition, the N,Si/CQD nanoprobe was integrated on a sensing strip for specific detection of Hg(II). Quantitative measurement of Hg(II) was realized by the outstanding linearity between the diameter (or fluorescence intensity) of the fluorescence quenching ring and the concentration of mercury ions. The sensor shows potential for rapid detection with a triple signal readout on-site and represents a larger step towards practical applications.

An electrochemiluminescence aptasensor based on highly luminescent silver-based MOF and biotin-streptavidin system for mercury ion detection.

In this study, for the first time, a silver-based metal-organic framework (Ag-MOF) was synthesized and used as the electrochemiluminescence (ECL) emitter for building an ECL sensor. After modification with chitosan (CS) and gold nanoparticles (Au NPs), the ECL stability of Ag-MOF was improved. To detect mercury ions, a biosensor was constructed using the mercury ion aptamer and steric effect of streptavidin. First, the capture strand (cDNA) with terminal-modified sulfhydryl group was attached to the electrode surface by the Au-S bond. Then, the mercury-ion aptamer (Apt-Hg) modified with biotin was anchored to the electrode by complementary pairing with cDNA. Streptavidin (SA) could be fixed on the electrode by linking with biotin, thereby reducing the ECL signal. However, in the presence of mercury ions, the aptamer was removed and streptavidin could not be immobilized on the electrode. Hence, the ECL signal of the sensor increased with the concentration of mercury ions, which was linear in the range from 1 μM to 300 fM. The detection limit could reach 66 fM (S/N = 3). The sensor provided a new method for the detection of mercury ions.