A regenerative ratiometric electrochemical biosensor for selective detecting Hg based on Y-shaped/hairpin DNA transformation

Inspired by dual-signaling ratiometric mechanism which could reduce the influence of the environmental change, a novel, convenient, and reliable method for the detection of mercury ions (Hg²⁺) based on Y-shaped DNA (Y-DNA) was developed. Firstly, the Y-DNA was formed via the simple annealing way of using two different redox probes simultaneously, omitting the multiple operation steps on the electrode. The Y-DNA was immobilized on the gold electrode surface and then an obvious ferrocene (Fc) signal and a weak methylene blue (MB) signal were observed. Upon addition of Hg²⁺, the Y-DNA structure was transformed to hairpin structure based on the formation of T-Hg²⁺-T complex. During the transformation, the redox MB gets close to and the redox Fc gets far away from the electrode surface, respectively. This special design allows a reliable Hg²⁺ detection with a detection range from 1 nM to 5 μM and a low detection limit down to 0.094 nM. Furthermore, this biosensor exhibits good selectivity and repeatability, and can be easily regenerated by using l-cysteine. This study offers a simple and effective method for designing ratiometric biosensors for detecting other ions and biomolecules.     

A ratiometric electrochemical biosensor for sensitive detection of Hg based on thymine–Hg–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 (I_MB), accompanied with the increase of that of Fc (I_Fc). The logarithmic value of I_Fc/I_MB is linear with the logarithm of Hg²⁺ concentration in the range from 0.5 nM to 5000 nM, and the detection limit of 0.08 nM is much lower than 10 nM (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.     

Polythymine Oligonucleotide‐Modified Gold Electrode for Voltammetric Determination of Mercury(II) in Aqueous Solution

Polythymine oligonucleotide (PTO)‐modified gold electrode (PTO/Au) was developed for selective and sensitive Hg²⁺ detection in aqueous solutions. This modified electrode was prepared by self‐assembly of thiolated polythymine oligonucleotide (5′‐SH‐T₁₅‐3′) on the gold electrode via Au? S bonds, and then the surface was passivated with 1‐mercaptohexanol solution. The proposed electrode utilizes the specific binding interactions between Hg²⁺ and thymine to selectively capture Hg²⁺, thereby reducing the interference from coexistent ions. After exchanging the medium, electrochemical reduction at ?0.2 V for 60 s, voltammetric determination was performed by differential pulse voltammetry using 10 mM HEPES; pH 7.2, 1 M NaClO₄ as supporting electrolyte. This electrode showed increasing voltammetric response in the range of 0.21 nM Hg²⁺, with a relative standard deviation of 5.32% and a practical detection limit of 60 pM. Compared with the conventional stripping approach, the modified electrode exhibits good sensitivity and selectivity, and is expected to be a new type of green electrode.     

A novel electrochemical method to detect mercury (II) ions

A novel and sensitive electrochemical method for determination of mercury (II) ions (Hg²⁺) based on the formation of thymine–Hg²⁺–thymine complexes and gold nanoparticle-mediated signal amplification is reported. Two 5′ end thiolated complementary oligonucleotides containing six strategically placed thymine–thymine mistakes were introduced in this work. One of the two oligonucleotides was immobilized on a gold electrode and the other one on gold nanoparticles (AuNPs). Due to six thymine–thymine mistakes the two oligonucleotides were not able to be hybridized, so AuNPs could not be immobilized onto the electrode surface after the electrode was immersed in the DNA–AuNPs solution. However, if Hg²⁺ existed, T–Hg²⁺–T complexes could be formed and AuNPs could be immobilized onto the electrode surface. Meanwhile, large numbers of [Ru(NH₃)₆]³⁺ molecules as electrochemical species could be localized onto the electrode surface. The Hg²⁺ detection limit of this assay could be as low as 10 nM, which is the US Environmental Protection Agency (EPA) limit of Hg²⁺ for drinkable water. This method is proven to be simple, convenient, high sensitive and selective.     

Eco‐friendly Sensors Developed by Herbal Based Silver Nanoparticles for Electrochemical Detection of Mercury (II) Ion

In our study, the single‐use & eco‐friendly electrochemical sensor platform based on herbal silver nanoparticles (AgNPs) was developed for detection of mercury (II) ion (Hg²⁺). For this purpose, the surface of pencil graphite electrode (PGE) was modified with AgNPs and folic acid (FA), respectively. The concentrations of AgNPs and FA were firstly optimized by differential pulse voltammetry (DPV) to obtain an effective surface modification of PGE. Each step at the surface modification process was characterized by using cyclic voltammetry (CV) and electrochemical impedence spectroscopy (EIS). The limit of detection (LOD) for Hg²⁺ was estimated and found to be 8.43 μM by CV technique. The sensor presented an excellent selectivity for Hg²⁺ against to other heavy metal ions such as Ca²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Mg²⁺, Ni²⁺, Pb²⁺, Zn²⁺, Co²⁺ and Mn²⁺. Moreover, a rapid, selective and sensitive detection of Hg²⁺ was successfully performed in the samples of tap water within 1 min.     

In-situ electrochemical and piezogravimetric studies on the application of macrocyclic resorcinarene tetramer in the development of chemically-modified heavy metals ions detection platform in aqueous media

The new application of C-dec-9-enylcalix[4]resorcinarene (R₁), as an ionophore to detect heavy metals (HMs) cations (Cd²⁺, Hg²⁺, Cu²⁺, and Pb²⁺) in the aqueous media has been investigated through the preparation of an effective mass-sensitive sensor via the exploitation of a flow-type QCM-I technique. By adjusting the ions’ amounts in model solutions over a wide range of concentrations, acquired changes in the oscillating frequency related to the loading of metal ions on the sensor’s surface were gained, and thus favorable metrological parameters displaying the lowest detection limit (LOD) associated with copper ions (10 ppb). Simultaneously, a novel voltammetric sensor was prepared by modifying gold screen-printed electrodes (SPEs) with R₁. Electrochemical characterization employing CV, SWV, and EIS was carried out, showing the success of the electrode modification. Then, the experimental conditions of supporting electrolyte, pH, accumulation time, and accumulation potential were optimized to achieve an enhanced detection. The R₁@SPE sensor simultaneously detected the HMs (Cd²⁺, Hg²⁺, Cu²⁺, Pb²⁺), and the lowest LOD was associated with Pb²⁺ (0.19 ppb). The selectivity evaluation of the electrochemical sensor was performed by studying the effect of interferences majorly present in water sources (Mg²⁺, Ni²⁺, Zn²⁺, Al³⁺, and K⁺) on the SWV detection signals, and it was revealed that the interfering ions did not affect the simultaneous detection of the studied HMs (RSD less than 5%), the voltammetric sensors also presented excellent repeatability and reproducibility (RSD less than 5%).     

Highly Sensitive Electrochemical Bioassay for Hg(II) Detection Based on Plasma-Polymerized Propargylamine and Three-Dimensional Reduced Graphene Oxide Nanocomposite

In this study, a nanocomposite consisting of three-dimensional reduced graphene oxide (3D-rGO) and plasma-polymerized propargylamine (3D-rGO@PpPG) was prepared and used as a highly sensitive and selective DNA sensor for detecting Hg²⁺. Given the high density of amino groups in the resultant 3D-rGO@PpPG nanocomposite, thymine-rich and Hg²⁺-targeted DNA was preferentially immobilized on the fabricated sensor surface via the strong electrostatic interaction between DNA strands and the amino-functionalized nanocomposites, followed by detecting Hg²⁺ through T–Hg²⁺–T coordination chemistry between DNA and Hg²⁺. The results of electrochemical measurements revealed that the anchored amount of DNA strands anchored on the 3D-rGO@PpPG nanofilm surface affects the determination of Hg²⁺ in aqueous solution. It showed high sensitivity and selectivity toward Hg²⁺ within concentrations ranging from 0.1 to 200 nM and displayed a low detection limit of 0.02 nM. The new strategy proposed also provides high selectivity of Hg²⁺ against other interfering metal ions, good stability, and repeatability. The excellent applicability of the developed sensor confirms the potential use of plasma-modified nanofilms for the detection of heavy metal ions in real environmental samples and water.     

Label-free aptamer-based colorimetric detection of mercury ions in aqueous media using unmodified gold nanoparticles as colorimetric probe

We report a simple and sensitive aptamer-based colorimetric detection of mercury ions (Hg²⁺) using unmodified gold nanoparticles as colorimetric probe. It is based on the fact that bare gold nanoparticles interact differently with short single-strand DNA and double-stranded DNA. The anti-Hg²⁺ aptamer is rich in thymine (T) and readily forms T–Hg²⁺–T configuration in the presence of Hg²⁺. By measuring color change or adsorption ratio, the bare gold nanoparticles can effectively differentiate the Hg²⁺-induced conformational change of the aptamer in the presence of a given salt with high concentration. The assay shows a linear response toward Hg²⁺ concentration through a five-decade range of 1 × 10⁻⁴ mol L⁻¹ to 1 × 10⁻⁹ mol L⁻¹. Even with the naked eye, we could identify micromolar Hg²⁺ concentrations within minutes. By using the spectrometric method, the detection limit was improved to the nanomolar range (0.6 nM). The assay shows excellent selectivity for Hg²⁺ over other metal cations including K⁺, Ba²⁺, Ni²⁺, Pb²⁺, Cu²⁺, Cd²⁺, Mg²⁺, Ca²⁺, Zn²⁺, Al³⁺, and Fe³⁺. The major advantages of this Hg²⁺ assay are its water-solubility, simplicity, low cost, visual colorimetry, and high sensitivity. This method provides a potentially useful tool for the Hg²⁺ detection.     

Electrocatalytic assay of mercury(II) ions using a bifunctional oligonucleotide signal probe

Engineered nucleic acid probes containing recognition and signaling functions find growing interest in biosensor design. In this paper, we developed a novel electrochemical biosensor for sensitive and selective detecting of Hg²⁺ based on a bifunctional oligonucleotide signal probe combining a mercury-specific sequence and a G-quadruplex (G4) sequence. For constructing the electrochemical Hg²⁺ biosensor, a thiolated, mercury-specific oligonucleotide capture probe was first immobilized on gold electrode surface. In the presence of Hg²⁺, a bifunctional oligonucleotide signal probe was hybridized with the immobilized capture probe through thymine–mercury(II)–thymine interaction-mediated surface hybridization. The further interaction between G4 sequence of the signal probe and hemin generated a G4–hemin complex, which catalyzed the electrochemical reduction of hydrogen peroxide, producing amplified readout signals for Hg²⁺ interaction events. This electrochemical Hg²⁺ biosensor was highly sensitive and selective to Hg²⁺ in the concentration of 1.0 nM to 1 μM with a detection limit of 0.5 nM. The new design of bifunctional oligonucleotide signal probes also provides a potential alternative for developing simple and effective electrochemical biosensors capable of detecting other metal ions specific to natural or artificial bases.     

Development of a Sensor Based on Poly(1,2-diaminoanthraquinone) for Individual and Simultaneous Determination of Mercury (II) and Bismuth (III)

Contamination of natural water by mercury (Hg²⁺) and bismuth (Bi³⁺) metal ions have been extensively studied due to their toxic effects. A validated square-wave anodic stripping voltammetry (SW-ASV) method for determining Bi³⁺ and Hg²⁺ ions individually and simultaneously is described. A new electrochemical sensor was constructed using a gold (Au) electrode that has been modified with poly(1,2-diaminoanthraquinone) (p-1,2-DAAQ). Scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy were used to characterize the p-1,2-DAAQ/Au modified electrode. Factors such as the polymer film thickness, electrolyte, square wave parameters and preconcentration conditions were optimized to improve the performance of the modified Au electrode. Good linear responses were achieved in the concentration ranges of 1–200 μg L⁻¹ and 1–50 μg L⁻¹ forBi³⁺ and Hg²⁺, respectively, and the limits of detection were 0.27 μg L⁻¹ (Bi³⁺) and 0.29 μg L⁻¹ (Hg²⁺). The interference study results illustrated the high selectivity of the modified electrode for detection of Bi³⁺ and Hg²⁺. The proposed SW-ASV method was successfully applied for Bi³⁺ and Hg²⁺analyses in different real water samples.     

Rapid detection of trace Cu2+ using an l‐cysteine based interdigitated electrode sensor integrated with AC electrokinetic enrichment

Copper is an indispensable trace element for human health. Too much or too little intake of copper ion (Cu²⁺) can lead to its own adverse health conditions. Therefore, detection of Cu²⁺ is always of vital importance. In this work, a simple sensor was developed for rapid detection of trace Cu²⁺ in water, in which L‐cysteine (Cys) as a molecular probe was self‐assembled on a gold interdigital electrode to form a monolayer for specific capture of Cu²⁺. The interfacial capacitance of interdigital electrode was detected to indicate the target adsorption level under an AC signal working as the excitation to induce directed movement and enrichment of Cu²⁺ to the electrode surface. This sensor reached a limit of detection of 4.14 fM and a satisfactory selectivity against eight other ions (Zn²⁺, Hg²⁺, Pb²⁺, Cd²⁺, Mg²⁺, Fe²⁺, As³⁺, and As⁵⁺). Testing of spiked tap water was also performed, demonstrating the sensor's usability. This sensor as well as the detection method shows a great application potential in fields such as environmental monitoring and medical diagnosis.     

Target-induced formation of gold amalgamation on DNA-based sensing platform for electrochemical monitoring of mercury ion coupling with cycling signal amplification strategy

Heavy metal ion pollution poses severe risks in human health and environmental pollutant, because of the likelihood of bioaccumulation and toxicity. Driven by the requirement to monitor trace-level mercury ion (Hg²⁺), herein we construct a new DNA-based sensor for sensitive electrochemical monitoring of Hg²⁺ by coupling target-induced formation of gold amalgamation on DNA-based sensing platform with gold amalgamation-catalyzed cycling signal amplification strategy. The sensor was simply prepared by covalent conjugation of aminated poly-T₍₂₅₎ oligonucleotide onto the glassy carbon electrode by typical carbodiimide coupling. Upon introduction of target analyte, Hg²⁺ ion was intercalated into the DNA polyion complex membrane based on T–Hg²⁺–T coordination chemistry. The chelated Hg²⁺ ion could induce the formation of gold amalgamation, which could catalyze the p-nitrophenol with the aid of NaBH₄ and Ru(NH₃)₆³⁺ for cycling signal amplification. Experimental results indicated that the electronic signal of our system increased with the increasing Hg²⁺ level in the sample, and has a detection limit of 0.02 nM with a dynamic range of up to 1000 nM Hg²⁺. The strategy afforded exquisite selectivity for Hg²⁺ against other environmentally related metal ions. In addition, the methodology was evaluated for the analysis of Hg²⁺ in spiked tap-water samples, and the recovery was 87.9–113.8%.     

Zeptomolar detection of Hg2 + based on label-free electrochemical aptasensor: One step closer to the dream of single atom detection

An ultra-sensitive and highly selective electrochemical label-free aptasensor is proposed for the quantitation of Hg^2 + based on the hybridization/dehybridization of double-stranded DNA (dsDNA) on a gold electrode. Thiol-substituted single-stranded DNA (ssDNA) is self-assembled on the gold electrode surface through the SAu interaction. The hybridization of ssDNA with complementary DNA (cDNA) and the consequences of dehybridization in the presence of mercury ions are followed through differential pulse voltammetry (DPV) responses using a [Fe(CN)₆]^{3 −/4 −} redox probe. The formation of a thymine–Hg^2 +–thymine (T–Hg^2 +–T) complex is the key to producing a highly selective and sensitive aptasensor for Hg^2 + determination. Specifically, the present electrochemical aptasensor is able to quantify Hg^2 + ions in concentrations from 5 zeptomolar (zM) to 55 picomolar (pM) with a limit of detection of 0.6 zM, close to the dream of single atom detection, without requiring a complicated procedure or expensive materials.     

A Simple and Highly Sensitive Electrochemically Reduced p‐Nitrobenzoic Acid Film Modified Sensor for Determination of Mercury

Herein, a simple electrochemical sensor was fabricated for sensing Hg²⁺ ions by using electrochemically reduced p‐nitrobenzoic acid molecules modified (ERpNBA) glassy carbon electrode (GCE). The modified electrode was applied for the determination of Hg²⁺ ions by using differential pulse anodic stripping voltammetry (DPASV). Experimental parameters such as concentration of p‐nitrobenzoic acid used for electrode modification, pH, accumulation time and deposition potential used for the determination of Hg²⁺ ions were optimized. The strong interaction between the Hg²⁺ ions and the lone pair of electrons on the nitrogen atoms of ERpNBA molecules leads to highly selective adsorption of Hg²⁺ ions on the modified electrode. Under the optimum experimental conditions, the sensor showed higher sensitivity and very low detection limit for Hg²⁺ ions than other metal ions such as Cd²⁺, Pb²⁺ and Zn²⁺ ions. The LOD for Hg²⁺ ions was 240 pM which is below the guideline value given by the World Health Organization and the earlier reports.     

A High Efficient Electrocatalytic Activity of Metal-organic Frameworks ZnO/Ag/ZIF-8 Nanocomposite for Electrochemical Detection of Toxic Heavy Metal Ions

A novel electrochemical sensor on ZIF-8 nanocomposites (Ag/ZnO/ZIF-8) was developed to analyze the mercury ions (Hg²⁺). The ZIF-8 materials are one of the 3-dimensional porous metal-organic frameworks with highly accessible pores and great surface area. The ZIF-8 nanocomposites were prepared through simple sol-gel methods and their physio-chemical properties were characterized via different analytical analyses. As a result of cyclic voltammetry, Ag/ZnO/ZIF-8 exhibited a better electrocatalytic behavior towards the detection of mercury ions (Hg²⁺). Furthermore, the composite modified electrode was then inspected as a sensor for DPV detection of mercury ions. The nanocomposite sensor performed a wide linear range from 0.5 μM to 140 μM with a low detection limit of 40 nM, and high sensitivity of 56.06 μA μM⁻¹ cm⁻². Moreover, the ZIF-8 composite sensor showed a higher selectivity toward the detection of mercury ions (Hg²⁺). The real-time applications of the ZIF-8 composites sensor were inspected in various samples with good sensitivity.     

Modification of gold electrode by self-assembled 2-mercapto benzothiazole for the determination of Hg2+

An electrochemical method was developed for the determination of mercury using polycrystalline gold electrode modified by self-assembled monolayers (SAMs) of 2-mercaptobenzothiazole (MBTH). Morphological and electrochemical characterisation of the self-assembled structure of MBTH was performed using atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS) measurements. The monolayer of MBTH has shown high affinity for Hg²⁺. The limit of detection for the determination of Hg²⁺ using the MBTH SAMs modified gold electrode was obtained as 0.421 μg L^?1. The pre-concentration of Hg²⁺ at open circuit potential is beneficial for the onsite monitoring of mercury concentration in water samples.     

An Ultrasensitive DNA Sensor for Hg2+ Assay Based on Electrodeposited Au/Carbon Nanofibers-chitosan and Reduced Graphene Oxide

An ultrasensitive electrochemical DNA sensor was designed for Hg²⁺ assay using cooperative signal amplification effect of electrodeposited Au/carbon nanofibers-chitosan (DpAu/CNFs-CS) and reduced graphene oxide (RGO). CNFs-CS was prepared to modify gold electrode (AuE). Then, Au was electrodeposited on CNFs-CS/AuE to form DpAu/CNFs-CS/AuE for the first signal amplification. With TH as signal probe and ssDNA as recognition component, RGO/ssDNA and RGO/TH interaction were used for the second signal amplification. The prepared sensor had wider linear range of 0.0001–460 nM and lower detection limit of 5.7×10⁻⁵ nM, high selectivity, and performed well in Hg²⁺ assay of tap water.     

Simultaneous Determination of Lead,Copper, and Mercury Free from Macromolecule Contaminants by Square Wave Stripping Voltammetry

Abstract

A novel approach for the voltammetric determination of Pb²⁺, Cu²⁺, and Hg²⁺ in the presence of macromolecule contaminants was developed. An Au nanoparticles array was directly electrodeposited onto the gold electrode surface followed by a further modification of a mercaptoethanesulfonate (MES) monolayer. Square wave stripping voltammetry (SWSV) of Pb²⁺, Cu²⁺, and Hg²⁺ was performed on the doubly modified electrode. The electrodeposited gold nanoparticles provided a significantly improved sensitivity. Simultaneously, the MES monolayer efficiently prevented the macromolecules accessing the electrode surface. Compared with the bare gold electrode, the doubly modified electrode has the ability to detect metal ions in the presence of macromolecule contaminants, even when their concentration reach 100 ppm. Under the optimal conditions, the detection limits of 0.16, 0.15, and 0.14 ppb for Pb²⁺, Cu²⁺, and Hg²⁺ were obtained, respectively. The calibration graphs were linear in the concentration range of 1–100 ppb. The results of the analysis of a real metallurgy wastewater sample were reported. The electrode system has a great potential for the direct determination of trace metals in the complex environment and biological samples.     

An Electrochemical Sensor for the Detection of Cu2+ Based on Gold Nanoflowers‐modifed Electrode and DNAzyme Functionalized Au@MIL‐101 (Fe)

In this study, we developed an electrochemical sensor for sensitive detection of Cu²⁺ based on gold nanoflowers (AuNFs)‐modified electrode and DNAzyme functionalized Au@MIL‐101(Fe) (MIL: Materials of Institute Lavoisier). The AuNFs‐modified indium tin oxide modified conductive glass electrode(AuNFs/ITO) prepared via electrodeposition showed improved electronic transport properties and provided more active sites to adsorb large amounts of oligonucleotide substrate (DNA1) via thiol‐gold bonds. The stable Au@MIL‐101(Fe) could guarantee the sensitivity because of its intrinsic peroxidase mimic property, while the Cu²⁺‐dependent DNA‐cleaving DNAzyme linked to Au@MIL‐101(Fe) achieved the selectivity toward Cu²⁺. After the DNAzyme substrate strand (DNA2) was cleaved into two parts due to the presence of Cu²⁺, the oligonucleotide fragment linked to MIL‐101(Fe) was able to hybridize with DNA1 adsorbed onto the surface of AuNFs/ITO. Due to the peroxidase‐like catalytic activity of MIL‐101(Fe) and the affinity recognition property of DNAzyme toward Cu²⁺, the electrochemical biosensor showed a sensitive detection range from 0.001 to 100 μM, a detection limit of 0.457 nM and a high selectivity, demonstrating its potential for Cu²⁺ detection in real environmental samples.     

Sensitive pseudobienzyme electrocatalytic DNA biosensor for mercury(II) ion by using the autonomously assembled hemin/G-quadruplex DNAzyme nanowires for signal amplification

Herein, a novel sensitive pseudobienzyme electrocatalytic DNA biosensor was proposed for mercury ion (Hg²⁺) detection by using autonomously assembled hemin/G-quadruplex DNAzyme nanowires for signal amplification. Thiol functionalized capture DNA was firstly immobilized on a nano-Au modified glass carbon electrode (GCE). In presence of Hg²⁺, the specific coordination between Hg²⁺ and T could result in the assembly of primer DNA on the electrode, which successfully triggered the HCR to form the hemin/G-quadruplex DNAzyme nanowires with substantial redox probe thionine (Thi). In the electrolyte of PBS containing NADH, the hemin/G-quadruplex nanowires firstly acted as an NADH oxidase to assist the concomitant formation of H₂O₂ in the presence of dissolved O₂. Then, with the redox probe Thi as electron mediator, the hemin/G-quadruplex nanowires acted as an HRP-mimicking DNAzyme that quickly bioelectrocatalyzed the reduction of produced H₂O₂, which finally led to a dramatically amplified electrochemical signal. This method has demonstrated a high sensitivity of Hg²⁺ detection with the dynamic concentration range spanning from 1.0 ng L⁻¹ to 10 mg L⁻¹ Hg²⁺ and a detection limit of 0.5 ng L⁻¹ (2.5 pM) at the 3S_blank level, and it also demonstrated excellent selectivity against other interferential metal ions.