Sensitive Detection Of Mercury Ions Research Articles

Electrochemical aptasensor based on Au@HS-rGO and thymine-Hg2+-thymine structure for sensitive detection of mercury ion

A sensitive electrochemical aptasensor was prepared on the basis of gold modified thiol reduced graphene (Au@HS-rGO) and thymine-Hg2+-thymine (T-Hg2+-T) constitution for the checkout of Hg2+. Firstly, Au@HS-rGO was fabricated as the substrate onto the glassy carbon electrode (GCE) surface, which facilitated the subsequent introduction of single-stranded DNA onto the electrode. Following that, thionine (Th) was immobilized on the electrode surface depend on the physical size effect of T and Hg2+. Finally, the amount of Hg2+ was determined by differential pulse voltammetry (DPV) of Th. Under the best conditions, the linear range of the aptasensor to Hg2+ was in the range of 1–200nmol/L and the detection limit was as low as 0.38nmol/L. Simultaneously, good selectivity and acceptable reproducibility were revealed in the designed aptasensor. Moreover, the design thought may provide an idea for the detection of other substances in the water sample.

Dandelion-like CuO microspheres decorated with Au nanoparticle modified biosensor for Hg2+ detection using a T-Hg2+-T triggered hybridization chain reaction amplification strategy

We fabricate a novel electrochemical biosensor based on the specific thymine-Hg2+-thymine (T-Hg2+-T) base pair for the highly sensitive detection of mercury ions (Hg2+) and utilize toluidine blue (TB) as a redox indicator that is combined with a hybridization chain reaction (HCR) for signal amplification. The dandelion-like CuO (D-CuO) microspheres that were assembled using Au nanoparticles were first introduced as support materials, which produced more active sites for the thiolated probe (P1) combination. Then, the presence of Hg2+ induced P1 to hybridize with the other oligonucleotide (P2) through Hg2+-mediated T-Hg2+-T complexes. In addition, the partial sequence of P2 acted as an initiator sequence, which led the two hairpin DNA (H1 and H2) strands to collectively form the extended double-strand DNA through the HCR process on the electrode surface. TB was employed to interact with the double strands and produce an efficient electrochemical signal. The proposed strategy combined the amplification of the HCR and the inherent redox activity of TB and utilized D-CuO/Au composites, which exhibited high sensitivity for Hg2+ determination. Under the optimum conditions, the proposed biosensor showed a prominent response for Hg2+, including a linear range from 1 pM to 100 nM and a detection limit of 0.2 pM (S/N = 3). Moreover, the new biosensor proved its potential application for trace Hg2+ determination in environmental water samples.

Gram-scale synthesis of nitrogen doped graphene quantum dots for sensitive detection of mercury ions and l-cysteine

Sensitive and reliable detection of mercury ions (Hg2+) and l-cysteine (l-Cys) is of great significance for toxicology assessment, environmental protection, food analysis and human health. Herein, we present gram-scale synthesis of nitrogen doped graphene quantum dots (N-GQDs) for sensitive detection of Hg2+ and l-Cys. The N-GQDs are one-step synthesized using bottom-up molecular fusion in a hydrothermal process with gram-scale yield at a single run. N-GQDs exhibit good structural characteristics including uniform size (∼2.1 nm), high crystallinity, and single-layered graphene thickness. Successful doping of N atom enables bright blue fluorescence (absolute photoluminescence quantum yield of 24.8%) and provides unique selectivity towards Hg2+. Based on the fluorescence quenching by Hg2+ (turn-off mode), N-GQDs are able to serve as an effective fluorescent probe for sensitive detection of Hg2+ with low limit of detection (19 nM). As l-Cys could recover the fluorescence of N-GQDs quenched by Hg2+, fluorescent detection of l-Cys is also demonstrated using turn-off-on mode.

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

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

Ratiometric fluorescence sensor based on dithiothreitol modified carbon dots-gold nanoclusters for the sensitive detection of mercury ions in water samples

Ratiometric fluorescence sensors can provide more accurate analysis of target objects because of their self-calibration function. Traditional methods often use steps of chemical coupling with two different fluorescent materials as the dual emission source, which make the construction process complicated and hard to control. Here, we report a convenient and effective way to construct a ratiometric fluorescence sensor based on dual-emission carbon dots-gold nanoclusters (C–AuNCs) functionalized with dithiothreitol (DTT) for the sensitive detection of mercury ions (Hg2+) in water samples. As a type of novel nanoparticle, C–AuNCs are synthesized via microwaving a mixture of gold seeds solution and carbon precursor. In the presence of Hg2+, the free thiol group of DTT would attract them around the surface of C–AuNCs, and owing to the strong 5d10–5d10 metallophilic interactions between Hg2+ and Au+, the fluorescence emission at 598 nm is quenched while the emission at 466 nm remains at a constant intensity. Thus, an obvious color change from orange-red to blue under ultraviolet irradiation can be observed by the naked eye. Moreover, the as-prepared fluorescence sensor has high sensitivity with a detection limit of 8.7 nM, and successfully applies to detect Hg2+ in real water samples with satisfactory recoveries at three spiking levels ranging from 95.9 − 103.5%. The good results imply that the developed DTT/C–AuNCs sensor is conducive to trace Hg2+ determination and possesses the great application potential for water-quality monitoring.

A technique for highly sensitive detection of mercury ions using DNA-functionalized gold nanoparticles and resonators based on a resonance frequency shift

Mercury is widely used in various research and industrial areas. However, due to the ionization of mercury to the mercury ion, the influence of this ion on human health and the environment is cause for concern. Gold nanoparticles (AuNPs) are the most widely studied nanomaterial because of their unique optical, chemical, electrical, and catalytic properties and have attracted much interest regarding the applications to detection of toxic metal ions. In this paper, we propose a technique for detection of divalent mercury using AuNPs and Mercury-specific-oligonucleotide–conjugated resonators (MSOIRs). The detection technique is based on the measurement of a resonance frequency shift in the resonators that results from a specific interaction between the thymine–thymine base pair and mercury ion as well as the adsorption of AuNPs that act as a mass amplifier. Our proposed method can quantify mercury ions with the limit of detection of 100 pM, which is 10-fold better than that of the existing assays. Furthermore, MSOIR can detect mercury ions in real tap water. These results imply that the mercury-detecting sensor may be used to enhance drinking-water quality.

Ultrasensitive electrochemical detection of Hg2+ based on an Hg2+-triggered exonuclease III-assisted target recycling strategy.

In the present work, a simple, rapid, isothermal, and ultrasensitive homogeneous electrochemical biosensing platform for target Hg2+ detection was developed on the basis of an exonuclease III (Exo III)-aided target recycling amplification strategy. In the assay, a label-free hairpin probe (HP1) was ingeniously designed, containing a protruding DNA fragment at the 3'-termini as the recognition unit for target Hg2+. Also, the DNA fragment in the loop region and 5'-termini (Helper) could be used when a secondary target analog is introduced, but it is caged in the stem region of HP1 when without such a target. The produced secondary target Helper opened the methylene blue (MB)-labeled hairpin probe (HP2) and triggered the Exo III cleavage process, accompanied with the secondary target recycling. This accordingly resulted in the autonomous reduction of the electroactive material MB on the electrode, inducing a distinct decrease in the electrochemical signal. The current developed homogeneous strategy provides a means for the ultrasensitive electrochemical detection of Hg2+ down to the 227 pM level, with high selectivity. It could be further used as a general autocatalytic and homogeneous strategy toward the detection of a wide spectrum of analytes and may be associated with more analytical techniques.

Histidine–dialkoxyanthracene dyad for selective and sensitive detection of mercury ions

Histidine-dialkoxyanthracene (HDA) was synthesised as a turn off type fluorescent sensor for fast and sensitive detection of mercury ions (Hg2+) in aqueous media. The two histidine moieties act as ‘claws’ to selectively complex Hg2+. The binding ratio of HDA to Hg2+ was 1:1 (metal-to-ligand ratio). The association constant for Hg2+ towards the receptor HDA obtained from Benesi–Hildebrand plot was found to be 3.22 × 104 M−1 with detection limit as low as 4.7 nM (0.94 μg/L).

Highly Sensitive Detection of Mercury Ion Based on Plasmon Coupling

Highly Sensitive Detection of Mercury Ion Based on Plasmon Coupling

Gas assisted method synthesis nitrogen-doped carbon quantum dots and Hg (II) sensing

ABSTRACTNitrogen-doped fluorescent carbon quantum dots (CQDs) was prepared by gas-assisted method using cellulose as precursors under ammonia atmosphere, which not only exhibited excellent photoluminescent properties, but also showed highly selective and sensitive detection of mercury ion. The nitrogen-doped CQDs displayed excitation wavelength dependent fluorescent behavior with outstanding dispersibility. Moreover, they exhibited high tolerance to various external conditions, such as storage time, pH value, and ionic strength. The rapid detection of Hg (II) by one-step operation within 1 min and the good linear correlation between I0/I and Hg (II) concentration in the range of 10–100 nM made the nitrogen-doped CQDs a promising nanoprobe for Hg (II) detection. The detection limit of the nitrogen-doped CQDs is about 7.7 nM. Such a nanoprobe has been successfully applied for the analysis of Hg (II) in natural water samples, demonstrating excellent practical feasibility.

Highly sensitive detection of mercury ion based on T-rich DNA machine using portable glucose meter

Mercury ion (Hg2+) has threats to human health and the environment even at a low concentration, thus it is desirable to propose a sensitive and portable method to detect it. In this work, it could realize detection of Hg2+ at low femtomolar concentration. Thymine-thymine (T-T) mismatches oligodeoxyribonucleotides were employed as specific recognition elements for selectively capturing Hg2+ to form hairpin structure and triggering the T-rich DNA machine operation to produce a large amount of product DNA for signal amplification. Product DNA connected capture DNA (Capt-DNA) with DNA-invertase conjugation which catalyzed sucrose into glucose. Thus, the output portable glucose meter (PGM) signals which came from glucose is related with the amount of product DNA, indirectly quantifying the concentration of Hg2+. It is shown that the detection limit of this method is as low as 10−17M and linear range is 10−6–10−17M without any complicated instrument. What’s more, this novel method could be applied in highly sensitive and selective Hg2+ detection in fish samples. Therefore, owing to the simple operability and portable use of PGM, this method is expected to have a wide application in routine detection the concentration of Hg2+ in environmental water and biologic samples in everyone’s home.

A reusable electrochemical biosensor for highly sensitive detection of mercury ions with an anionic intercalator supported on ordered mesoporous carbon/self-doped polyaniline nanofibers platform

In this paper, a reusable electrochemical biosensor was developed for highly sensitive detection of mercury ions (Hg2+) using an anionic intercalator, which was based on Hg2+-induced conformational change of a thymine-rich, single-stranded DNA (ssDNA) supported on the platform of ordered mesoporous carbon (OMC) and self-doped polyaniline (SPAN) nanofibers. In the presence of Hg2+, the mercury-specific oligonucleotides were induced and folded into hairpin structure through mismatched thymine-Hg2+-thymine (T-Hg2+-T) base pairs from random coils. Then, the indicators intercalated into the hairpin structure and increased electric signal. OMC and SPAN nanofibers possessed excellent electrical conductivity which synergistically accelerated electron transfer and greatly improved the efficiency of electrochemical reaction at the electrode interface. Meanwhile, SPAN nanofibers strongly adhered to the electrode surface and attached rod-like OMC homogeneously and firmly, which provided a stable platform for DNA immobilization. Under the optimal conditions, the detection limit (LOD) for Hg2+ was 0.6 fM (S/N=3). Furthermore, the biosensor could be easily regenerated by cysteine for cyclic utilization. Some environmental samples including lake sediment pore water and tap water were analyzed by the developed biosensor, the relatively satisfactory results indicated that it provided a green and promising strategy for detection of trace Hg2+ in the practical application.

A bright carbon-dot-based fluorescent probe for selective and sensitive detection of mercury ions

In this work, we demonstrated a convenient and green strategy for the synthesis of bright and water-soluble carbon dots (CDs) by carbonizing sodium citrate and glutathione together in a hydrothermal method for the first time. Without post surface modification, the as-synthesized CDs display fluorescence quantum yield (QY) as high as 21.03% and show superior stability not only in concentrated salt solutions but also in neutral and alkaline media. The probe exhibits selective and sensitive recognition capability towards mercury ion (Hg2+) in aqueous solution. The fluorescence of CDs can be quenched by Hg2+ through an effective electron energy transfer process. It displays a linear quenching effect toward mercury ion in the concentration range of 0–15μM with a correlation coefficient (R2) of 0.99. The limit of detection is determined to be 25nM at the signal to noise ratio of 3. These attractive merits would enable the extensive applications of this probe in environmental science and analytical chemistry in the future.

A Poly Adenine-Mediated Assembly Strategy for Designing Surface-Enhanced Resonance Raman Scattering Substrates in Controllable Manners.

In this article, we introduce a Poly adenine (Poly A)-assisted fabrication method for rationally designing surface-enhanced resonance Raman scattering (SERRS) substrates in controllable and reliable manners, enabling construction of core-satellite SERRS assemblies in both aqueous and solid phase (e.g., symmetric core (Au)-satellite (Au) nanoassemblies (Au-Au NPs), and asymmetric Ag-Au NPs-decorated silicon wafers (Ag-Au NPs@Si)). Of particular significance, assembly density is able to be controlled by varying the length of the Poly A block (e.g., 10, 30, and 50 consecutive adenines at the 5' end of DNA sequence, Poly A10/A30/A50), producing the asymmetric core-satellite nanoassemblies with adjustable surface density of Au NPs assembly on core NPs surface. Based on quantitative interrogation of the relationship between SERRS performance and assemble density, the Ag-Au NPs@Si featuring the strongest SERRS enhancement factor (EF ≈ 10(7)) and excellent reproducibility can be achieved under optimal conditions. We further employ the resultant Ag-Au NPs@Si as a high-performance SERRS sensing platform for the selective and sensitive detection of mercury ions (Hg(2+)) in a real system, with a low detection limit of 100 fM, which is ∼5 orders of magnitude lower than the United States Environmental Protection Agency (USEPA)-defined limit (10 nM) in drinkable water. These results suggest the Poly A-mediated assembly method as new and powerful tools for designing high-performance SERRS substrates with controllable structures, facilitating improvement of sensitivity, reliability, and reproducibility of SERRS signals.

Gold nanoparticle-based fluorescent “turn-on” sensing system for the selective detection of mercury ions in aqueous solution

A simple and straightforward fluorometric assay using dye-adsorbed gold nanoparticles (AuNPs) was used in the highly selective and sensitive detection of mercury ions in aqueous buffer solution.

A ratiometric electrochemical biosensor for sensitive detection of Hg2+ based on thymine–Hg2+–thymine structure

In this paper, a simple, selective and reusable electrochemical biosensor for the sensitive detection of mercury ions (Hg2+) has been developed based on thymine (T)-rich stem–loop (hairpin) DNA probe and a dual-signaling electrochemical ratiometric strategy. The assay strategy includes both “signal-on” and “signal-off” elements. The thiolated methylene blue (MB)-modified T-rich hairpin DNA capture probe (MB-P) firstly self-assembled on the gold electrode surface via Au–S bond. In the presence of Hg2+, the ferrocene (Fc)-labeled T-rich DNA probe (Fc-P) hybridized with MB-P via the Hg2+-mediated coordination of T–Hg2+–T base pairs. As a result, the hairpin MB-P was opened, the MB tags were away from the gold electrode surface and the Fc tags closed to the gold electrode surface. These conformation changes led to the decrease of the oxidation peak current of MB (IMB), accompanied with the increase of that of Fc (IFc). The logarithmic value of IFc/IMB is linear with the logarithm of Hg2+ concentration in the range from 0.5nM to 5000nM, and the detection limit of 0.08nM is much lower than 10nM (the US Environmental Protection Agency (EPA) limit of Hg2+ in drinking water). What is more, the developed DNA-based electrochemical biosensor could be regenerated by adding cysteine and Mg2+. This strategy provides a simple and rapid approach for the detection of Hg2+, and has promising application in the detection of Hg2+ in real environmental samples.

Intelligent and ultrasensitive analysis of mercury trace contaminants via plasmonic metamaterial-based surface-enhanced Raman spectroscopy.

Label-free molecular logic gates (AND, INHIBIT, and OR) are constructed based on specific conformation modulation of a guanine- and thymine-rich DNA, while the optical readout is enabled by the tunable metamaterials which serve as a substrate for surface enhanced Raman spectroscopy. The DNA logic is simple to operate, highly reproducible, and can be stimulated by ultra-low concentration of the external inputs, enabling an extremely sensitive detection of mercury ions down to 2 × 10(-4) ppb.

An autonomous T-rich DNA machine based lateral flow biosensor for amplified visual detection of mercury ions

An autonomous thymine rich DNA machine as an amplification unit was developed for the sensitive detection of mercury ions with high specificity.

Assembly of Gold Nanorods for Highly Sensitive Detection of Mercury Ions

A simple and cost-effective strategy for mercury ion sensing based on an easy and reliable colorimetric approach is investigated through L-cysteine functionalized gold nanorods (Au NRs). Detection tests are performed on several ions, such as Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Zn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Cd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Pb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , and As <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , and monitored by UV-Vis absorption spectroscopy, transmission electron microscopy (TEM), and infrared spectroscopy (ATR-FTIR). L-cysteine functionalized Au NRs demonstrated a remarkable sensitivity for Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> with limit of detection (LOD) at a few ppt level. A red-shift in the maximum of the typical longitudinal plasmon band of Au NRs is observed and recognized related to aggregation phenomena occurring among functionalized Au NRs and triggered only by the presence of Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions in solution. Interestingly, a significantly different response is recorded for the other tested ions. The results highlight that the functionalization of Au NRs with L-cysteine is an excellent route to implement a reliable colorimetric sensing device, able to push further down the LOD recorded for similar strategies based on spherical Au NPs.

Ratiometric Fluorescence Detection of Mercury Ions in Water by Conjugated Polymer Nanoparticles

We present dye-doped polymer nanoparticles that are able to detect mercury in aqueous solution at parts per billion levels via fluorescence resonance energy transfer (FRET). The nanoparticles are prepared by reprecipitation of highly fluorescent conjugated polymers in water and are stable in aqueous suspension. They are doped with rhodamine spirolactam dyes that are nonfluorescent until they encounter mercury ions, which promote an irreversible reaction that converts the dyes to fluorescent rhodamines. The rhodamine dyes act as FRET acceptors for the fluorescent nanoparticles, and the ratio of nanoparticle-to-rhodamine fluorescence intensities functions as a ratiometric fluorescence chemodosimeter for mercury. The light harvesting capability of the conjugated polymer nanoparticles enhances the fluorescence intensity of the rhodamine dyes by a factor of 10, enabling sensitive detection of mercury ions in water at levels as low as 0.7 parts per billion.