Mercury ion detection electrochemical sensor, preparation method thereof and mercury ion detection method

Abstract

The invention belongs to the field of mercury ion detection, and provides a mercury ion detection electrochemical sensor, a preparation method thereof and a mercury ion detection method. The mercury ion detection electrochemical sensor is composed of a basic electrochemical electrode, a vertical mesoporous silica nano-channel film uniformly deposited on a sensing interface of the basic electrochemical electrode, and mercury ion recognition molecules connected to the nano-channel film, the mercury ion recognition molecules are connected to the surface of the nano-channel membrane and in the nano-channel through a silane coupling agent; the mercury ion recognition molecule is 1-(6-(hydroxymethyl)-2, 2-dimethyl tetrahydrofuran [3, 4-d] [1, 3] dioxacyclo-4-yl)-5-methylpyrimidine-2, 4 (1H, 3H)-diketone. According to the invention, the specific recognition capability of the existing electrochemical sensor on the mercury ions can be enhanced, the preparation difficulty and the preparation cost are reduced, and convenient, low-cost, high-efficiency and high-selectivity detection of the mercury ions is realized.

Description

Technical Field

[0001] The invention belongs to the field of mercury ion detection and relates to an electrochemical sensor for mercury ion detection and a preparation method thereof and a mercury ion detection method. Background Art

[0002] Mercury ions (Hg 2+ As a highly toxic heavy metal pollutant, Hg has high bioaccumulation, is difficult to degrade and has high neurotoxicity, which seriously threatens human health. With the rapid development of industries such as fossil energy and mining, Hg 2+ Hg in water bodies is discharged through large amounts of industrial wastewater and then enters the soil, causing serious damage to the ecological environment. 2+ It is easily captured by aquatic animals and gradually enriched through the food chain before entering the human body. Even trace amounts of Hg 2+ It can also cause serious damage to the reproductive system, digestive system and central nervous system, leading to the occurrence of various diseases, and even death in severe cases. Many countries and regions have Hg in drinking water. 2+ Therefore, the development of highly sensitive and selective Hg 2+ Detection technology has urgent practical significance for environmental pollution prevention and control and public health safety.

[0003] Traditional Hg 2+ The main detection methods include atomic fluorescence spectroscopy, inductively coupled plasma-mass spectrometry, atomic absorption / emission spectroscopy and high performance liquid chromatography, which can be used for trace or trace amounts of Hg 2+ However, these methods are limited by the cumbersome detection process, high operating costs, the lack of portability of detection equipment, and the reliance on specially trained personnel for operation. These methods are unable to meet the growing demand for on-site detection and immediate analysis. Electrochemical sensors have become important detection and analysis tools in fields such as environmental protection and public health due to their high sensitivity, fast response, minimal sample preparation steps, portability, and on-site detection capabilities. The key to improving the sensitivity of electrochemical detection and reducing its detection limit is signal amplification, and the key to signal amplification lies in the construction of a suitable sensing interface.

[0004] For Hg 2+As for electrochemical sensing detection, there are reports on electrochemical sensors based on nanochannel confined graphene quantum dots. The preparation process is as follows: first, hydroxyl functionalized graphene quantum dots (OH-GQDs) or amino functionalized graphene quantum dots (NH2-GQDs) are synthesized, and then the vertical ordered mesoporous silica nanochannel membrane (VMSF) is modified on the electrode surface. Then, the OH-GQDs or NH2-GQDs are confined in the nanochannels of the VMSF by electrophoresis. When detecting metal ions, the electrochemical sensor is used as the working electrode. Under negative voltage conditions, the hydroxyl groups of OH-GQDs or the amino groups of NH2-GQDs are used to coordinate with metal ions to enrich the metal ions in the nanochannels and reduce them to metal elements and deposit them on the surface of the working electrode. Then, a voltage is applied to the working electrode to dissolve the metal elements, and the dissolution signal is used as a quantitative basis (see ACS Nano 2018, 12, 12673-12681.). Although this method has achieved the 2+ 、Hg 2+ 、Cd 2+ However, on the one hand, it relies on the coordination effect of OH-GQDs or NH2-GQDs with metal ions to detect the target metal ions, and the specificity of OH-GQDs or NH2-GQDs in coordinating with metal ions is not high, and they will inevitably coordinate with other metal ions, resulting in the method being not selective for metal ions and easily interfered by other metal ions. On the other hand, OH-GQDs or NH2-GQDs are bound to VMSF by charge attraction, and their binding stability is easily affected by the voltage applied during the detection process, because a positive voltage is applied when confining OH-GQDs or NH2-GQDs in the nanochannel, while a negative voltage needs to be applied to deposit the target metal during detection, which will generate electrophoretic forces in opposite directions, causing the OH-GQDs or NH2-GQDs in the nanochannel to be lost, affecting the detection effect.

[0005] In order to improve the sensitivity of electrochemical sensors to Hg 2+ The specific recognition ability of Hg based on sulfur-nitrogen co-doped ordered mesoporous carbon and bioaptamer has been reported. 2+The preparation method of the electrochemical sensor is as follows: (1) preparing sulfur-nitrogen co-doped ordered mesoporous carbon (SN-OMC); (2) dropping SN-OMC suspension onto the electrode surface to obtain an electrode loaded with SN-OMC (GCE / SN-OMC); (3) electroplating gold nanoparticles on GCE / SN-OMC to obtain GCE / SN-OMC with a gold film (GCE / SN-OMC / AuNPs); (4) dissolving the probe P1 (5'-SH-(CH2)6-GGCGACGTTTTGTCGCC-3') in Tris-HCl buffer containing tris(2-carboxyethyl)phosphine hydrochloride, reacting for 1 h in the dark, dropping the obtained reaction solution onto the surface of GCE / SN-OMC / AuNPs, reacting for 12 h to assemble the probe P1 onto the gold film through gold-sulfur bonds, and then soaking in 6-mercaptohexanol solution for 1 h to obtain an electrochemical sensor. 2+ When the electrochemical sensor was immersed in the probe P2 (5'-GACTTTTCGTGCGG-(CH2)6-Fc-3', Fc = ferrocene) and Hg 2+ The reaction was carried out in phosphate buffer at 37 °C for 1 h and detected by differential pulse voltammetry. 2+ When Hg 2+ When probe P1 hybridizes with probe P2, the hairpin structure of probe P1 is opened, and the ferrocene signal molecule approaches the electrode surface; by analyzing the oxidation current change caused by the ferrocene signal molecule and the Hg 2+ The relationship between the concentrations of Hg 2+ Highly sensitive detection (see ACS Sens. 2018, 3, 2566−2573.). The electrochemical sensor was used to measure Hg 2+ The detection of Hg still has the following shortcomings: (1) The construction process of the electrochemical sensor is very cumbersome, which increases the complexity and cost of the preparation process; (2) In order to realize the connection of probe P1 on the gold film and the connection of ferrocene signal molecule on probe P2, the aptamer must be structurally modified, which will further increase the difficulty and cost of preparation; (3) Hg 2+ The detection process involves the pairing and disassembly of bioaptamers (probes P1 and P2), which results in the 2+The detection time is as long as 1 hour, and the detection efficiency is low; (4) the bioaptamer is easily affected by complex matrices such as nucleases during the detection process and inactivated, affecting the accuracy of the detection results; (5) in order to ensure the activity of the bioaptamer, the detection temperature needs to be specially regulated. The above factors seriously limit the convenient application of the electrochemical sensor in practical scenarios. At present, there is an urgent need to develop an electrochemical sensor with high selectivity and anti-interference, simple preparation method and low production cost to achieve Hg 2+ convenient, timely, low-cost and highly sensitive detection. Summary of the Invention

[0006] In response to the problems that existing electrochemical sensors based on nanochannel confined graphene quantum dots are easily interfered with by other metal ions when detecting mercury ions, and the problems that existing electrochemical sensors for mercury ion detection based on bioaptamers have a cumbersome preparation process, high preparation and detection costs, and low detection efficiency, the present invention provides an electrochemical sensor for mercury ion detection, a preparation method thereof, and a mercury ion detection method, so as to enhance the specific recognition ability of existing electrochemical sensors for mercury ions and reduce their preparation difficulty and preparation cost, thereby realizing convenient, low-cost, high-efficiency and highly selective detection of mercury ions.

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: A mercury ion detection electrochemical sensor comprises a basic electrochemical electrode, a vertical mesoporous silica nanochannel membrane uniformly deposited on the sensing interface of the basic electrochemical electrode, and a mercury ion recognition molecule connected to the nanochannel membrane. The mercury ion recognition molecule is connected to the surface of the nanochannel membrane and the nanochannel via a silane coupling agent. The mercury ion recognition molecule is 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxetane-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione. The electrochemical sensor is formed by the reaction of a mercury ion recognition molecule modified with a silane coupling agent with the nanochannel membrane on the sensing interface of the basic electrochemical electrode. The structure of the mercury ion recognition molecule modified with a silane coupling agent is shown in formula (I). (I) In formula (I), the R group is a triethoxysilyl group or a trimethoxysilyl group, m and n are both non-negative integers, and m+n=2-6.

[0008] In the technical solution of the aforementioned electrochemical sensor for mercury ion detection, the reaction between the mercury ion recognition molecule modified with a silane coupling agent and the nanochannel membrane at the sensing interface of the base electrochemical electrode is a condensation reaction between the silanol groups formed by hydrolysis of the R groups of the silane coupling agent-modified mercury ion recognition molecule and the silanol groups on the nanochannel membrane. This condensation reaction forms Si-O-Si bonds, effectively covalently linking the mercury ion recognition molecule to the surface of the nanochannel membrane and within the nanochannels via the silane coupling agent.

[0009] In the technical solution of the above-mentioned electrochemical sensor for mercury ion detection, the thickness of the nanochannel membrane is preferably 50-100 nm, and the diameter of the nanochannels of the nanochannel membrane is preferably 2-3 nm.

[0010] In the technical solution of the above-mentioned mercury ion detection electrochemical sensor, the value of m+n in the mercury ion recognition molecule modified with a silane coupling agent shown in formula (I) should ensure that under the action of mercury ions, the mercury ion recognition molecule connected in the same nanochannel of the nanochannel membrane can easily bind to the mercury ion to form a coordination complex with a molar ratio of 2:1. Specifically, the proton of the nitrogen atom at position 3 on the thymine base unit of two adjacent mercury ion recognition molecules connected in the same nanochannel of the nanochannel membrane is replaced by mercury ions to form a coordination complex. When the molecular chain of the silane coupling agent is too short, it will limit the rotation and swing ability of the mercury ion recognition molecule, resulting in its inability to bind to mercury ions, causing the electrochemical sensor to lose its ability to recognize mercury ions. When the molecular chain of the silane coupling agent is too long, the longer carbon chain will increase the surface hydrophobicity of the nanochannel membrane connected to the mercury ion recognition molecule, which is not conducive to the detection of mercury ions in an aqueous solution environment. It will also increase the steric hindrance of the channel of the nanochannel membrane connected to the mercury ion recognition molecule, which is not conducive to the detection of mercury ions. In addition, the longer carbon chain increases the steric hindrance within the silane coupling agent molecule, which will slow down the hydrolysis rate of the R group of the mercury ion recognition molecule modified by the silane coupling agent, resulting in a slower reaction rate between it and the nanochannel membrane on the sensing interface of the basic electrochemical electrode, reducing the preparation efficiency of the electrochemical sensor, and causing the mercury ion recognition molecule to tend to disorderly connect. The active site of the mercury ion recognition molecule may be blocked by disordered entanglement, unable to effectively bind to mercury ions or poor stability, which will also have an adverse effect on mercury ion detection. The value of m+n depends on the diameter of the nanochannel of the nanochannel membrane. When the diameter of the nanochannel of the nanochannel membrane is 2-3 nm, the value of m+n is preferably between 2-6.

[0011] In the technical scheme of the above-mentioned mercury ion detection electrochemical sensor, in the electrochemical sensor, the amount of the mercury ion recognition molecule connected on the nanochannel membrane can affect the amount of the coordination complex that the mercury ion recognition molecule forms after identifying mercury ions, and the amount of the coordination complex formed can affect the permeability of the nanochannel membrane to the electrochemical probe. Under the condition of the same mercury ion concentration, the more the amount of the mercury ion recognition molecule grafted on the nanochannel membrane is, the more the amount of the coordination complex that the mercury ion recognition molecule forms after identifying mercury ions is, and the permeability of the nanochannel membrane to the electrochemical probe is lower after identifying mercury ions. In order to realize the smooth detection of mercury ions, it is necessary to identify that the permeability of the nanochannel membrane to the electrochemical probe before and after the mercury ions are significantly changed, but the electrochemical probe can not be completely prevented from penetrating through the nanochannel membrane and reaching the basic electrochemical electrode. Therefore, the technical scheme of the present invention is required to the amount of the mercury ion recognition molecule connected on the nanochannel membrane. Preferably, the mass ratio of the mercury ion recognition molecule connected on the nanochannel membrane to the nanochannel membrane is (20~30):1.

[0012] In the technical solution of the above-mentioned electrochemical sensor for mercury ion detection, the basic electrochemical electrode includes an indium tin oxide electrode, a glassy carbon electrode, a fluorine-doped tin oxide electrode, a gold electrode, a screen-printed electrode, a graphite electrode or a carbon fiber electrode.

[0013] The present invention also provides a method for preparing the above-mentioned electrochemical sensor for mercury ion detection, comprising the following steps: (1) Depositing a vertical mesoporous silica nanochannel film on the sensing interface of the basic electrochemical electrode; (2) dissolving a mercury ion recognition molecule modified with a silane coupling agent having a structure as shown in formula (I) in an organic solvent to obtain a modified solution; (I) In formula (I), the R group is a triethoxysilyl group or a trimethoxysilyl group, m and n are both non-negative integers, and m+n=2 to 6; (3) placing the basic electrochemical electrode with the nanochannel membrane deposited on the sensing interface in a modification solution so that the nanochannel membrane is completely immersed in the modification solution, allowing it to fully react at 10-50°C under oscillation conditions, and then taking it out to obtain an electrochemical sensor for mercury ion detection.

[0014] In the technical solution of the above preparation method, the concentration of the mercury ion recognition molecule with a structure as shown in formula (I) in the modification solution is controlled to be 10-30 mg / mL, and preferably the concentration of the mercury ion recognition molecule with a structure as shown in formula (I) in the modification solution is controlled to be 15-25 mg / mL.

[0015] In the technical solution of the above preparation method, the organic solvent used in step (2) when preparing the modification solution is toluene, acetone or N,N-dimethylformamide.

[0016] In the technical solution of the above preparation method, the reaction time in step (3) is preferably controlled to be 2 to 10 h.

[0017] In the technical solution of the above preparation method, the oscillation speed in step (3) is preferably controlled to be 40~200 rpm.

[0018] In step (1) of the technical solution of the above-mentioned preparation method, a vertical mesoporous silica nanochannel membrane is uniformly deposited on the sensing interface of the basic electrochemical electrode with reference to the existing technology. For example, any one of the electrochemically assisted self-assembly method, Stöber solution growth method, two-phase layered growth method, evaporation-induced self-assembly method, π-π interaction induced method, epitaxial growth method, strong magnetic field method, electric field method, and organic solvent-induced self-assembly method can be used to uniformly deposit the vertical mesoporous silica nanochannel membrane on the sensing interface of the basic electrochemical electrode. Preferably, the electrochemically assisted self-assembly method is used to uniformly deposit the vertical mesoporous silica nanochannel membrane on the sensing interface of the basic electrochemical electrode.

[0019] When a vertical mesoporous silica nanochannel membrane is uniformly deposited on the sensing interface of a basic electrochemical electrode using an electrochemically assisted self-assembly method, the vertical mesoporous silica nanochannel membrane containing surfactant micelles in the pores is first deposited on the sensing interface of the basic electrochemical electrode using the electrochemically assisted self-assembly method, and then the surfactant micelles are removed by washing with a hydrochloric acid-ethanol mixture, thereby completing the operation of uniformly depositing the vertical mesoporous silica nanochannel membrane on the sensing interface of the basic electrochemical electrode. The hydrochloric acid-ethanol mixture refers to a mixture of a hydrochloric acid aqueous solution with a concentration of 3 to 10 mol / L and anhydrous ethanol in a volume ratio of (29 to 99):1. More specifically, the operation of uniformly depositing the vertical mesoporous silica nanochannel membrane on the sensing interface of the basic electrochemical electrode using the electrochemically assisted self-assembly method is as follows: (1) Ethanol and water were mixed in a volume ratio of (4-6):(6-4) as a solvent, sodium nitrate was added to the solvent to a concentration of 0.1-0.15 mol / L, hexadecyltrimethylammonium bromide was added to a concentration of 4-5 mmol / L, and tetraethyl orthosilicate was added to a concentration of 13.5-14 mmol / L. The mixture was stirred until all components were completely dissolved. The pH value of the solution was adjusted to 3-3.5 with hydrochloric acid, and the mixture was stirred at room temperature for 2-3 h to obtain a precursor solution. (2) Using the basic electrochemical electrode as the working electrode, the platinum electrode as the counter electrode, and the saturated Ag / AgCl electrode as the reference electrode, the precursor solution was used as the electrolyte solution, and constant current or constant potential was applied for deposition. The working electrode was removed, rinsed with water, and aged at 130~150℃ for 10~12 h. That is, a vertical mesoporous silica nanochannel membrane containing surfactant micelles in the pores was deposited on the sensing interface of the basic electrochemical electrode, and the surfactant micelles were washed with a hydrochloric acid-ethanol mixture. In this step, the constant current applied was -1~-0.7 mA, the constant voltage applied was -2~-1 V, and the deposition time was controlled to be 10~20 s.

[0020] In the technical solution of the above preparation method, a feasible method for preparing a mercury ion recognition molecule modified with a silane coupling agent having a structure as shown in formula (I) is as follows: 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxetane-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione, isocyanatepropyltriethoxysilane or isocyanatepropyltrimethoxysilane, and dibutyltin dilaurate are dissolved in a solvent to obtain a mixed solution, which is reacted at 65-80°C for 12-36 hours. The obtained reaction solution is then separated and purified by column chromatography to obtain a silane coupling agent-modified mercury ion recognition molecule having a structure shown in formula (I).

[0021] When preparing the mercury ion recognition molecule modified with a silane coupling agent, the solvent is tetrahydrofuran, N,N-dimethylformamide or 1,4-dioxane.

[0022] When preparing a mercury ion recognition molecule modified with a silane coupling agent, in the mixed solution, the molar ratio of 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxetane-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione, isocyanatepropyltriethoxysilane or isocyanatepropyltrimethoxysilane and dibutyltin dilaurate is (1-1.5):(1-2.5):(1-6).

[0023] Based on the above mercury ion detection electrochemical sensor, the present invention also provides a mercury ion detection method, comprising the following steps: (1) using the above-mentioned mercury ion detection electrochemical sensor as a working electrode, a platinum electrode as a counter electrode, and a silver / silver chloride electrode as a reference electrode, and forming a three-electrode system with the working electrode, the counter electrode, and the reference electrode; (2) placing the three-electrode system in a blank sample, maintaining ts, and then measuring the peak current response value of the electrochemical probe in the blank sample by electrochemical voltammetry; the blank sample is prepared by the electrochemical probe and the electrolyte solution; (3) replacing the blank sample of step (2) with standard samples having known mercury ion concentrations in order from low to high mercury ion concentrations in the standard samples, repeating the operation of step (2), and measuring the peak current response value of the electrochemical probe corresponding to each standard sample; the standard sample is prepared from an electrochemical probe, mercury ions, and an electrolyte solution; (4) Plotting a working curve with the peak current of the electrochemical probe corresponding to each standard sample as the ordinate and the logarithm of the mercury ion concentration corresponding to each standard sample as the abscissa, and determining the conversion relationship between the logarithm of the mercury ion concentration and the peak current response value; (5) replacing the blank sample in step (2) with the test sample, repeating the operation of step (2), measuring the peak current response value of the electrochemical probe corresponding to the test sample, and calculating the concentration of mercury ions in the test sample according to the conversion relationship between the logarithm of the mercury ion concentration and the peak current response value determined in step (4); the test sample is prepared by the test sample, the electrochemical probe and the electrolyte solution, and the test sample contains mercury ions; The t in step (2) is a constant value between 30 and 360 s, and the t value used in steps (2), (3), and (5) is the same; when preparing the blank sample, the standard sample, and the sample to be tested, the electrochemical probe used is the same, and the electrolyte solution used is the same; the pH value of the blank sample, the standard sample, and the sample to be tested is the same, all between 4 and 8; the concentration of the electrochemical probe in the blank sample, the standard sample, and the sample to be tested is the same; in step (5), before testing each sample to be tested, a mercury ion detection electrochemical sensor that is not bound to mercury ions is replaced, and the mercury ion detection electrochemical sensor used in steps (2), (3), and (5) is the same.

[0024] In the technical solution of the above-mentioned mercury ion detection method, the electrochemical probe is preferably a positively charged electrochemical probe, for example, methylene blue or hexaammineruthenium trichloride; the concentration of the electrochemical probe in the blank sample, standard sample and test sample is preferably 0.5~5 mmol / L.

[0025] In the technical solution of the above-mentioned mercury ion detection method, the electrolyte solution can be a potassium chloride aqueous solution, a potassium hydrogen phthalate aqueous solution, a phosphate buffer solution or an acetic acid-sodium acetate buffer solution; the concentration of the electrolyte solution is 0.01~0.1 mol / L.

[0026] In the technical solution of the above-mentioned mercury ion detection method, the mercury ion detection electrochemical sensors used in steps (2), (3), and (5) are the same, which means that the preparation method of the mercury ion detection electrochemical sensors used in steps (2), (3), and (5) and the process conditions used during the preparation are exactly the same.

[0027] The principle of the mercury ion detection electrochemical sensor provided by the present invention to achieve high selectivity, high efficiency and low-cost detection of mercury ions is mainly as follows: When the sample to be tested does not contain mercury ions, the mercury ion recognition molecules in the nanochannels of the nanochannel membrane of the mercury ion detection electrochemical sensor do not bind to mercury ions, the nanochannels have good permeability to the electrochemical probes, and the electrochemical probes in the sample to be tested can reach the basic electrochemical electrode through the nanochannels on the nanochannel membrane, where an electrochemical reaction occurs to produce a strong electrochemical signal. When the sample to be tested contains mercury ions, the mercury ion recognition molecules in the nanochannels of the nanochannel membrane specifically bind to the mercury ions and form a stable coordination complex. The coordination complex increases the steric hindrance in the nanochannels of the nanochannel membrane, thereby increasing the mass transfer resistance of the electrochemical probe through the nanochannel to the basic electrochemical electrode, resulting in a decrease in the number of electrochemical probes reaching the basic electrochemical electrode, causing the electrochemical signal to attenuate. The degree of attenuation of the electrochemical signal is negatively correlated with the mercury ion concentration in the sample to be tested. Therefore, by detecting the changes in the electrochemical signal of the electrochemical probe, electrochemical detection of mercury ions can be achieved.

[0028] On the one hand, mercury ion recognition molecules can specifically recognize mercury ions to form coordination complexes, but will not recognize other metal ions, including Na + , K + 、Li + Mg 2+ , Ca 2+ , Pb 2+ 、Fe 3+ 、Cd 2+ and Cu 2+ Common monovalent and polyvalent metal ions, including ions, do not interfere with mercury ion detection. Furthermore, the vertical mesoporous silica nanochannel membrane, with a pore size of 2 to 3 nm, can restrict substances larger than the nanochannel pore size from reaching the surface of the underlying electrochemical electrode through size exclusion. Furthermore, the pKa of the silanol groups in silica is around 2, resulting in deprotonation and negative charge at pH > 2. This electrostatic repulsion can prevent negatively charged substances from reaching the surface of the underlying electrochemical electrode. These two aspects give the present electrochemical sensor for mercury ion detection excellent anti-interference capabilities, enabling highly selective detection of mercury ions.

[0029] Because the mercury ion recognition molecule forms a coordination complex with mercury ions very quickly, the recognition process can reach reaction equilibrium within 30 to 360 seconds. Therefore, the mercury ion detection electrochemical sensor of the present invention can achieve rapid and efficient detection of mercury ions. Furthermore, the preparation method of this mercury ion detection electrochemical sensor is simple and the raw materials used are relatively low in cost, which helps reduce the difficulty and cost of its preparation, thereby reducing the cost of mercury ion detection.

[0030] Compared with the prior art, the technical solution provided by the present invention produces the following beneficial technical effects: 1. The present invention provides an electrochemical sensor for mercury ion detection, comprising a base electrochemical electrode, a vertical mesoporous silica nanochannel membrane uniformly deposited on the sensing interface of the base electrochemical electrode, and a mercury ion recognition molecule connected to the nanochannel membrane. The mercury ion recognition molecule is connected to the surface of the nanochannel membrane and the nanochannel via a silane coupling agent; the mercury ion recognition molecule is 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxetane-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione. Because the mercury ion recognition molecule can specifically recognize mercury ions, the present invention can solve the problem that existing electrochemical sensors based on nanochannel-confined graphene quantum dots are easily interfered with by other metal ions when detecting mercury ions. At the same time, through the size and charge exclusion properties of the nanochannel membrane, the present invention can avoid interference with mercury ion detection by macromolecules and negatively charged substances. Compared with the existing electrochemical sensor for mercury ion detection, the present invention effectively improves the selective detection capability of mercury ions and realizes highly selective detection of mercury ions.

[0031] 2. Since the process of mercury ion recognition molecules forming coordination complexes with mercury ions is very fast, the recognition process can reach reaction equilibrium within 30 to 360 seconds. Therefore, the mercury ion detection electrochemical sensor of the present invention can achieve rapid and efficient detection of mercury ions. Since it does not involve the pairing and disassembly process of bioaptamers, the mercury ion detection electrochemical sensor of the present invention can effectively improve the detection efficiency of mercury ions compared to existing bioaptamer mercury ion detection electrochemical sensors. In addition, the operation of mercury ion detection using it is also very simple, and there is no need to regulate the temperature of the detection process. This allows the mercury ion detection electrochemical sensor of the present invention to better meet the growing demand for on-site detection and real-time analysis.

[0032] 3. The present invention also provides a method for preparing the aforementioned electrochemical sensor for mercury ion detection. This method features simple operation, mild process conditions, and readily available, low-cost raw materials. The method exhibits a simple preparation process, high efficiency, and low production cost. Compared to existing electrochemical sensors for mercury ion detection, particularly those based on bioaptamers, the present invention significantly reduces the difficulty and cost of preparing such sensors.

[0033] 4. The present invention also provides a method for detecting mercury ions. The method utilizes the nanochannels on the nanochannel membrane of the mercury ion detection electrochemical sensor to pre-enrich the charged electrochemical probe through electrostatic action, and amplifies the electrical signal generated by the electrochemical probe to improve the detection sensitivity. The mercury ion recognition molecules connected in the nanochannel can quickly form a coordination complex after the mercury ions, so that the permeability of the nanochannel changes, causing the electrochemical signal generated by the electrochemical probe to decay, and the degree of attenuation of the electrochemical signal is correlated with the concentration of mercury ions. Thus, the method achieves high selectivity and high efficiency detection of mercury ions. At the same time, the preparation cost of the mercury ion detection electrochemical sensor on which the detection method relies is low, and the operation of the detection method is simple, which is conducive to achieving low-cost detection of mercury ions. Compared with the existing mercury ion detection method based on electrochemical sensors, the present invention not only achieves high selectivity detection of mercury ions, but also effectively improves detection efficiency and reduces detection cost, which is conducive to promotion and application in the field of convenient and low-cost detection of mercury ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 TEM images of the vertical mesoporous silica nanochannel membrane on SNM / ITO prepared in Example 1, wherein (a) and (b) are TEM top views and local magnified views thereof, and (c) is a TEM cross-sectional view.

[0035] Figure 2 Figures (a), (b), and (c) are the structures of ITO, CTAB@SNM / ITO, and SNM / ITO in the presence of Ru(NH3)6 3+ 、Fe(CN)6 3– , cyclic voltammetry curves in potassium chloride solution of FcMeOH.

[0036] Figure 3 This is the synthesis route of XXT-SiOH in Example 2.

[0037] Figure 4 This is the hydrogen nuclear magnetic resonance spectrum of XXT-SiOH prepared in Example 2.

[0038] Figure 5 These are the infrared spectra of ITO, CTAB@SNM / ITO, SNM / ITO, and XXT-SNM / ITO.

[0039] Figure 6 Figure (a) is the full spectrum of X-ray photoelectron spectra of SNM / ITO and XXT-SNM / ITO. Figure 6 Figure (b) is the test result of the signal ratio of N element to Si element in SNM / ITO and XXT-SNM / ITO.

[0040] Figure 7These are the water contact angle test results of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO.

[0041] Figure 8 Electrochemical impedance spectra of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO.

[0042] Figure 9 Figure 3 is the change in the differential pulse voltammetric response of XXT-SNM / ITO before and after the reaction with 10 μmol / L mercury ions. Figure 10 Figure (a) is the differential pulse voltammetry curve of XXT-SNM / ITO in blank sample and various standard samples. Figure 10 Figure (b) is the working curve drawn in Example 8.

[0043] Figure 11 Figure (a) shows the differential pulse voltammetric response of XXT-SNM / ITO to different types of metal ions. Figure 11 Figure (b) shows the effect of XXT-SNM / ITO on Hg in the presence of different metal ions. 2+ The differential pulse voltammetric response results are as follows: Figure 11 Figure (c) shows the effect of XXT-SNM / ITO on Hg in the presence of different macromolecular interfering substances. 2+ The differential pulse voltammetric response results. DETAILED DESCRIPTION

[0044] The following examples further illustrate the mercury ion detection electrochemical sensor, its preparation method, and mercury ion detection method provided by the present invention. It should be noted that the following examples are intended only to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by persons skilled in the art based on the above disclosure are still within the scope of protection of the present invention.

[0045] Unless otherwise specified, all reagents used in the following examples and comparative examples were purchased from TCI (Tokyo Chemical Industry) and used directly without special treatment. The electrochemical workstation used was PGSTAT-101.

[0046] Example 1 In this embodiment, a vertical mesoporous silica nanochannel film is grown on an indium tin oxide substrate electrode using electrochemically assisted self-assembly (EASA) method, and the steps are as follows: (1) Prepare the precursor solution: Mix equal volumes of ethanol and ultrapure water as the solvent, add sodium nitrate to the solvent to a concentration of 0.1 mol / L, add cetyltrimethylammonium bromide (CTAB) to a concentration of 4.35 mmol / L, and add tetraethyl orthosilicate to a concentration of 13.6 mmol / L. Stir until all components are completely dissolved. Adjust the pH value of the solution to 3 with hydrochloric acid and stir at room temperature for 2.5 h to obtain the precursor solution.

[0047] (2) Preparation of SNM / ITO electrode: A three-electrode system was used, with indium tin oxide electrode (ITO) as the working electrode, platinum electrode as the counter electrode, and saturated Ag / AgCl electrode as the reference electrode. The precursor solution was used as the electrolyte solution, and a constant current of -1 mA was applied for 10 s. After the deposition, the working electrode was quickly removed and rinsed with a large amount of ultrapure water, and then aged at 130 °C for 12 h to obtain an ITO electrode modified with a silica nanochannel membrane with CTAB micelles retained in the pores (CTAB@SNM / ITO). The CTAB@SNM / ITO was then soaked and cleaned in a 0.1 mol / L hydrochloric acid-ethanol solution for 5 min to obtain an electrode modified with a vertical mesoporous silica nanochannel membrane (SNM / ITO). The hydrochloric acid-ethanol mixture was obtained by mixing a 10 mol / L hydrochloric acid aqueous solution with anhydrous ethanol in a volume ratio of 99:1.

[0048] Figure 1 Figure 1 is a transmission electron microscope (TEM) image of the vertical mesoporous silica nanochannel film on SNM / ITO prepared in this embodiment, wherein (a) and (b) are TEM top views and partial magnified views thereof, and (c) is a TEM cross-sectional view. Figure 1 It can be seen that the pore size of the nanochannel on the vertical mesoporous silica nanochannel membrane is about 2~3 nm, the nanosilica is arranged in an orderly hexagonal shape, and no obvious large-area defects are found. The thickness of the vertical mesoporous silica nanochannel membrane is about 65 nm.

[0049] Prepare Ru(NH3)6 3+ 、Fe(CN)6 3– or potassium chloride solution of hydroxymethylferrocene (FcMeOH) and adjust the pH value of each solution to 4. In the prepared mixed solution, Ru(NH3)6 3+ 、Fe(CN)6 3– The concentrations of FcMeOH and KCl were 0.5 mmol / L and 50 mmol / L, respectively. The cyclic voltammetry curves of ITO, CTAB@SNM / ITO and SNM / ITO in the above three mixed solutions were tested respectively. The results are shown in Fig. Figure 2 shown.

[0050] Figure 2 Figures (a), (b), and (c) are the structures of ITO, CTAB@SNM / ITO, and SNM / ITO in the presence of Ru(NH3)6 3+ 、Fe(CN)6 3– Cyclic voltammetry curves in potassium chloride solution of FcMeOH. Figure 2 It can be seen that CTAB@SNM / ITO contains Ru(NH3)6 3+ and Fe(CN)6 3– In the potassium chloride solution, no Radius signal was found, only charging current was shown. This is because the micelles in the pores are hydrophilic due to hydrophobic interaction, and the charged probe Ru(NH3)6 3+ 、Fe(CN)6 3– The hydrophobic neutral probe FcMeOH can reach the electrode surface through micelle enrichment to generate redox signals, and compared with ITO, the redox peaks all move toward the positive potential direction. This is because the electrochemical reaction rate slows down and charge transfer becomes more difficult, requiring a higher potential for the reaction to occur. After removing the micelles in CTAB@SNM / ITO, the signals of the formed SNM / ITO in the three mixed solutions were restored. Compared with ITO, SNM / ITO has a better performance in the presence of Fe(CN)6 3– The signal in the potassium chloride solution was suppressed, and the signal in the solution containing Ru(NH3)6 3+ The signal in the potassium chloride solution was enhanced, which was due to the presence of Ru(NH3)6 3+ or Fe(CN)6 3– The pH value of the potassium chloride solution is 4. At this time, the deprotonation of the silanol groups in the nanopores makes the pore walls negatively charged, which repels the negatively charged probes and attracts the positively charged electrochemical probes.

[0051] The above experimental results show that the surface of the vertical mesoporous silica nanochannel membrane on SNM / ITO prepared in this example is intact, has no defects or cracks, and has obvious charge selective permeability.

[0052] Example 2 In this embodiment, a mercury ion recognition molecule (XXT-SiOH) modified with a silane coupling agent having a structure as shown in formula (II) was synthesized. The synthesis route is as follows: Figure 3 As shown, the steps are as follows: (II) (1) 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxet-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione, abbreviated as XXT, was synthesized according to the method in Zhou, X.-L. et al. Journal of Hazardous Materials, 445, 130610 (2023).

[0053] (2) XXT was dissolved in 50 mL of tetrahydrofuran (THF) at room temperature to obtain a 3 mmol / L XXT solution. 3 mL of isocyanatopropyltriethoxysilane (ICPTES) and 10 mL of dibutyltin dilaurate (DBDTL) were added to the XXT solution and the mixture was stirred under reflux at 66 °C. The reaction process was monitored by TLC (developing solvent was obtained by mixing equal volumes of petroleum ether and ethyl acetate). After the reaction was completed, the solvent was removed by rotary evaporation to obtain a crude product. The crude product was purified by silica gel column chromatography (eluent was obtained by mixing petroleum ether and ethyl acetate in a volume ratio of 2:1) to obtain XXT-SiOH, which was stored refrigerated.

[0054] Figure 4 This is the hydrogen NMR spectrum of XXT-SiOH prepared in this example. The peak at 11.40 ppm is attributed to the hydrogen of the secondary amine group at position 3 on the thymine base unit in XXT. Peaks at 5.80 ppm, 5.02 ppm, 4.76 ppm, and 3.75 ppm are attributed to the four single hydrogen atoms on the five-membered ring of XXT, respectively. The peak at 3.71 ppm is attributed to the ethyl hydrogen of the triethoxy group on the silane coupling agent ICPTES. The peak at 7.23 ppm is attributed to the hydrogen of the secondary amine group on the carbamate group connecting the two in XXT-SiOH. This hydrogen NMR spectrum confirms the successful synthesis of XXT-SiOH, whose structure is shown in Formula (II).

[0055] Example 3 In this example, an electrochemical sensor for mercury ion detection (XXT-SNM / ITO) was prepared in the following steps: (1) The XXT-SiOH prepared in Example 2 was added to anhydrous toluene and stirred thoroughly to dissolve to obtain a modification solution. The concentration of XXT-SiOH in the modification solution was 25 mg / mL.

[0056] (2) The SNM / ITO prepared in Example 1 was placed in a modification solution so that the silica nanochannel membrane on the SNM / ITO was completely immersed in the modification solution. The reaction was carried out at 40°C and 50 rpm for 6 h, and then the XXT-SNM / ITO was obtained.

[0057] Example 4 In this example, the chemical compositions of ITO, CTAB@SNM / ITO, SNM / ITO, and XXT-SNM / ITO prepared in Examples 1 to 3 were tested.

[0058] The infrared spectra of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO were tested. The results are as follows: Figure 5 As shown. Figure 5 It can be seen that compared with ITO, the infrared spectra of CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO are all at 1078 cm -1 and 801 cm -1 The asymmetric and symmetric stretching vibration peaks of Si-O-Si appeared at 2911 cm, corresponding to the intergrowth network of silica, indicating that a vertical mesoporous silica nanochannel membrane was successfully grown on the surface of the ITO electrode. -1 and 2843 cm -1 The peaks at 1470 cm-1 are the asymmetric and symmetric stretching vibration peaks of the CH bond in the CTAB molecule. -1 The peak at 851 cm is its deformation vibration peak. -1 The peak at 1692 cm is the stretching vibration peak of the C-N bond. In the infrared spectrum of SNM / ITO, the asymmetric and symmetric stretching vibration peaks of the C-H bond of the CTAB molecule disappeared, indicating that the CTAB micelles in the pores were successfully removed. Compared with SNM / ITO, the infrared spectrum of XXT-SNM / ITO has a peak at 1692 cm -1 The C=O stretching vibration peaks of -COO-NH- and -CO-NH- appeared at 1530 cm -1 The NH stretching vibration peak of the secondary amino group appeared at , indicating that Example 3 successfully covalently linked XXT to the silica nanochannel membrane of SNM / ITO.

[0059] The X-ray photoelectron spectroscopy of SNM / ITO and XXT-SNM / ITO was tested, and the results were as follows: Figure 6 shown. Figure 6 Figure (a) is the full spectrum of X-ray photoelectron spectra of SNM / ITO and XXT-SNM / ITO. Figure 6 Figure (b) shows the test results of the signal ratio of N element to Si element in SNM / ITO and XXT-SNM / ITO. Figure 6 The N / Si (i.e. N / Si atomic ratio) in Figure (b) is calculated based on the X-ray photoelectron spectroscopy test results. Figure 6As shown in Figure (b), after covalently linking XXT molecules, the N / Si ratio on the surface of the silica nanochannel membrane increased from 3.24 to 22.51. Further calculation of N / Si revealed that in XXT-SNM / ITO, the mass ratio of covalently linked XXT to silica nanochannel membrane was 24.93.

[0060] Example 5 In this example, the hydrophilicity and hydrophobicity of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO prepared in Examples 1 to 3 were tested.

[0061] The water contact angles of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO were tested. Figure 7 As shown. Figure 7 It can be seen that the water contact angle of ITO is 60.6°. After the vertical mesoporous silica nanochannel membrane is deposited on the sensing interface of ITO, the water contact angle of CTAB@SNM / ITO is significantly increased to 82.2° due to the presence of hydrophobic CTAB micelles in the pores. After the CTAB micelles in the pores are washed away with hydrochloric acid-ethanol solution, the water contact angle of the obtained SNM / ITO decreases to 71.9°. After covalently linking XXT to the vertical mesoporous silica nanochannel membrane, the water contact angle of the obtained XXT-SNM / ITO increases to 77.3° again. This is because the XXT molecule is a hydrophobic molecule and the silane coupling agent has a longer alkane chain, which increases the hydrophobicity of XXT-SNM / ITO.

[0062] Example 6 In this example, the electrochemical impedance spectroscopy (EIS) of ITO, CTAB@SNM / ITO, SNM / ITO, and XXT-SNM / ITO prepared in Examples 1 to 3 were tested.

[0063] ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO were used as working electrodes, platinum electrode as counter electrode and saturated Ag / AgCl electrode as reference electrode to form a three-electrode system. The three-electrode system was placed in a potassium chloride solution containing K3Fe(CN)6 and K4Fe(CN)6 at pH 4 (the concentration of potassium chloride was 50 mmol / L, and the concentrations of K3Fe(CN)6 and K4Fe(CN)6 were both 2.5 mmol / L). Electrochemical impedance spectroscopy (EIS) of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO was measured under the following test parameters: potential of -0.22 V, sinusoidal potential amplitude of 10 mV, and test frequency from 100 kHz to 0.001 Hz.

[0064] Figure 8 is the electrochemical impedance spectra of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO, where the horizontal axis is Z ′ is the real impedance, in units of K Ω, vertical axis - Z '' is the imaginary impedance, unit is K Ω. Figure 8 It can be seen that ITO has the smallest semicircle diameter in the high-frequency region, indicating the lowest charge transfer resistance. After growing the vertical mesoporous silica nanochannel membrane, CTAB@SNM / ITO has the largest semicircle diameter in the high-frequency region. This is because the micelles within the pores hinder the penetration of the electrochemical probe, resulting in electron transfer obstruction. After washing away the CTAB micelles in the pores with a hydrochloric acid-ethanol solution, the semicircle diameter of SNM / ITO decreases significantly, indicating that the open pores allow the electrochemical probe to enter the pores and promote its electron transfer. After covalently linking XXT to the vertical mesoporous silica nanochannel membrane of SNM / ITO, the semicircle diameter of XXT-SNM / ITO increases. This is because XXT is distributed within the pores of the silica nanochannel membrane, narrowing the pores and causing some mass transfer obstruction to the electrochemical probe, which in turn increases the charge transfer steric resistance.

[0065] Example 7 In this example, the changes in the differential pulse voltammetric response of the XXT-SNM / ITO prepared in Example 3 before and after the reaction with 10 μmol / L mercury ions were tested.

[0066] XXT-SNM / ITO was used as the working electrode, platinum electrode as the counter electrode, and saturated Ag / AgCl electrode as the reference electrode. The working electrode, counter electrode, and reference electrode formed a three-electrode system. Electrochemical probes methylene blue and Hg were added to PBS buffer with a concentration of 0.01 mol / L and pH = 7. 2+ (to methylene blue and Hg 2+ The samples were tested (concentrations of 1 mmol / L and 10 μmol / L, respectively), and methylene blue (to a concentration of 1 mmol / L) was added to a PBS buffer solution with a concentration of 0.01 mol / L and pH = 7 as a control sample. A three-electrode system was placed between the test samples and the control sample to measure the differential pulse voltammetric response of XXT-SNM / ITO. The test parameters were as follows: step potential of 0.005 V, pulse amplitude of 0.05 V, pulse time of 0.05 s, and interval time of 0.5 s. The test results are shown in Figure 2. Figure 9 shown.

[0067] Depend on Figure 9It can be seen that methylene blue has a higher oxidation peak current value in the control sample. This is because the methylene blue molecule is positively charged, while the surface of the vertical mesoporous silica nanochannel membrane is negatively charged due to the deprotonation of hydroxyl groups. It can attract methylene blue into the pores through electrostatic interaction, resulting in a pre-enrichment effect and achieving electrochemical signal amplification, thereby generating a high oxidation peak current value; while in the test sample, the oxidation peak current value of methylene blue is attenuated. This is because the covalently linked XXT on the vertical mesoporous silica nanochannel membrane can specifically recognize Hg in the solution. 2+ , Hg 2+ It will replace the proton of the nitrogen atom at position 3 on the thymine base units on the two adjacent XXTs to form a stable coordination complex, resulting in an increase in the steric hindrance in the nanochannel and a decrease in the permeability of the channel, which hinders the entry of methylene blue from the solution into the pore to undergo electrochemical reaction, causing its oxidation peak current value to attenuate.

[0068] Example 8 In this example, the differential pulse voltammetric response of the XXT-SNM / ITO prepared in Example 3 was tested in an electrolyte solution containing methylene blue and different concentrations of mercury ions, and a working curve was plotted to determine the conversion relationship between the logarithm of the mercury ion concentration and the peak current response value.

[0069] (1) Preparation of blank samples and standard samples Methylene blue was dissolved in PBS buffer with a concentration of 0.01 mol / L and a pH of 7.0 to obtain a blank sample. The concentration of methylene blue in the blank sample was 1 mmol / L.

[0070] Methylene blue was dissolved in PBS buffer with a concentration of 0.01 mol / L and pH = 7.0. Different amounts of mercury ion stock solution were added to the methylene blue solution to prepare a series of standard samples. The concentration of mercury ions in each standard sample was 10 -9 , 5×10 -9 , 10 -8 , 5×10 -8 , 10 -7 , 5×10 -7 , 10 -6 , 5×10 -6 , 10 -5 , 5×10 -5 mol / L (mol / L is abbreviated as M in the figure), and the concentration of methylene blue in each standard sample is 1 mmol / L.

[0071] (2) Using XXT-SNM / ITO as the working electrode, platinum electrode as the counter electrode, and saturated Ag / AgCl electrode as the reference electrode, the working electrode, counter electrode, and reference electrode form a three-electrode system.

[0072] (3) The three-electrode system was placed in a blank sample for 300 s, and then the peak current response value of methylene blue in the blank sample was measured by electrochemical voltammetry.

[0073] (4) Substituting the blank sample of step (3) with each standard sample in the order of the mercury ion concentration from low to high, repeating the operation of step (3), and measuring the peak current response value of methylene blue corresponding to each standard sample.

[0074] (5) Draw a working curve with the peak current of methylene blue corresponding to each standard sample as the ordinate and the logarithm (base 10) of the mercury ion concentration corresponding to each standard sample as the abscissa, and determine the conversion relationship between the logarithm of the mercury ion concentration and the peak current response value.

[0075] Figure 10 Figure (a) shows the differential pulse voltammetry curves of XXT-SNM / ITO in blank samples and standard samples. The peak current value of the oxidation of methylene blue increases with the change of Hg 2+ The concentration of Hg 2+ With the increase of Hg concentration, XXT in the nanochannel of vertical mesoporous silica nanochannel membrane can 2+ The formation of more coordination complexes leads to an increase in the steric hindrance of the nanochannel and a decrease in the permeability of the nanochannel, so the oxidation peak current value of methylene blue also decreases.

[0076] Figure 10 Figure (b) is the working curve drawn in step (5). It can be seen from the figure that Hg 2+ The logarithmic value of the concentration is related to the oxidation peak current of methylene blue at 10 -9 ~5×10 -7 mol / L concentration range shows two linear relationships. 2+ The concentration is 10 -9 ~5×10 -7 mol / L, Hg 2+ The conversion relationship between the logarithmic value of the concentration and the peak current response value is: Y = -1.254X + 33.134 (R 2 =0.996), when Hg 2+ The concentration is 5×10 -7 ~5×10 -5 mol / L, Hg 2+ The conversion relationship between the logarithmic value of the concentration and the peak current response value is: Y = -4.434X + 13.158 (R 2 =0.996), where Y is the peak current response value, X is lgC, and C is Hg 2+ concentration.

[0077] The method of the present invention can be used to calculate the Hg 2+ The detection limit is 0.5598 nmol / L, which has a high detection sensitivity for mercury ions. In the formula LOD=3σ / S, σ is the standard deviation of the peak current response value of the blank sample, the number of measurements is 12 times, and S is the above-mentioned Hg 2+ The concentration is 10 -9 ~5×10 -7 The slope of the conversion relationship when the value is mol / L.

[0078] Example 9 In this embodiment, the mercury ion detection method of the present invention is used to detect mercury ions in a sample to be tested, and the steps are as follows: (1) Preparation of test samples Methylene blue was dissolved in PBS buffer with a concentration of 0.01 mol / L and pH = 7.0, and then Hg 2+ mother liquor, prepared to obtain Hg 2+ The concentration is 2.5×10 −6 mol / L, and the test sample with a methylene blue concentration of 1 mmol / L.

[0079] (2) The XXT-SNM / ITO prepared in Example 3 was used as the working electrode, the platinum electrode was used as the counter electrode, and the saturated Ag / AgCl electrode was used as the reference electrode. The working electrode, the counter electrode, and the reference electrode formed a three-electrode system.

[0080] (3) The three-electrode system was placed in the test sample and maintained for 300 s. Then, the peak current response value of methylene blue in the test sample was measured by electrochemical voltammetry, and the result was 38.013 μA.

[0081] (4) The conversion relationship between the logarithm of the mercury ion concentration determined in Example 8 and the peak current response value is Y=-4.434X+13.158(R 2 =0.996) and the concentration of mercury ions in the test sample was calculated to be 2.48×10 −6 mol / L. The test results are basically consistent with the mercury ion concentration in the test sample solution, indicating that the method of the present invention can accurately detect Hg in the sample 2+ .

[0082] Example 10 In this example, the differential pulse voltammetric response of the XXT-SNM / ITO prepared in Example 3 to different types of metal ions was tested.

[0083] (1) Methylene blue was dissolved in PBS buffer with a concentration of 0.01 mol / L and pH = 7.0 to obtain a blank sample. The concentration of methylene blue in the blank sample was 1 mmol / L. Methylene blue was dissolved in PBS buffer with a concentration of 0.01 mol / L and pH = 7.0. Multiple portions of methylene blue solution were taken and Hg was added to each methylene blue solution. 2+ or interfering ions (Na + , K + 、Li + Mg 2+ , Ca 2+ , Pb 2+ 、Fe 3+ 、Cd 2+ or Cu 2+ ), a sample containing a single type of metal ion was obtained, and the concentration of methylene blue in each sample was 1 mmol / L. When the metal ion contained in the sample was Hg 2+ When Hg 2+ The concentration of Hg is 1 μmol / L. When the metal ions in the sample are interfering ions, the concentration of the interfering ions is 10 μmol / L. Methylene blue was dissolved in PBS buffer with a concentration of 0.01 mol / L and pH = 7.0, and then Hg 2+ 、Na + , K + 、Li + Mg 2+ , Ca 2+ , Pb 2+ 、Fe 3+ 、Cd 2+ and Cu 2+ , a sample containing multiple metal ions was obtained, the concentration of methylene blue in the sample was 1 mmol / L, Hg 2+ The concentration of Na + , K + 、Li + Mg 2+ , Ca 2+ , Pb 2+ 、Fe 3+ 、Cd 2+ and Cu 2+ The concentrations were all 10 μmol / L.

[0084] (2) Using XXT-SNM / ITO as the working electrode, platinum electrode as the counter electrode, and saturated Ag / AgCl electrode as the reference electrode, the working electrode, counter electrode, and reference electrode form a three-electrode system.

[0085] (3) The three-electrode system was placed in a blank sample, a metal ion sample containing a single metal ion, and a metal ion sample containing multiple metal ions for 300 s. The peak current response of methylene blue in each sample was then measured using electrochemical voltammetry. A new working electrode was replaced for each sample tested, and the working electrode after each replacement was the same as the working electrode used previously.

[0086] (4) Calculate the ratio (I / I0) of the peak current response value of methylene blue in each sample containing a single type of metal ion or a sample containing multiple metal ions to the peak current response value of methylene blue in the blank sample.

[0087] Figure 11 Figure (a) shows the differential pulse voltammetric response test results of XXT-SNM / ITO to different types of metal ions. When the metal ion in the sample is Hg 2+ When XXT is 2+ The specific recognition of methylene blue will cause the current peak of methylene blue to decay significantly; when the metal ions in the sample are 10 times the amount of interfering ions (Na + , K + 、Li + Mg 2+ , Ca 2+ , Pb 2+ 、Fe 3+ 、Cd 2+ or Cu 2+ ), the current peak of methylene blue did not show obvious attenuation or almost no attenuation; when the sample contained Hg 2+ When the amount of methylene blue was 10 times that of the interfering ions, the current peak of methylene blue still showed obvious attenuation, and the attenuation was similar to that of Hg 2+ The attenuation caused is basically the same, which shows that XXT-SNM / ITO only responds specifically to Hg in the environment. 2+ The corresponding electrochemical signal attenuation is generated, which has good selectivity and anti-interference properties.

[0088] Example 11 In this example, the XXT-SNM / ITO prepared in Example 3 was tested for its Hg 2+ The differential pulse voltammetric response.

[0089] (1) The blank sample was the same as that in Example 10. Methylene blue was dissolved in PBS buffer with a concentration of 0.01 mol / L and pH = 7.0. Then, several portions of the methylene blue solution were taken and Hg was added to each methylene blue solution. 2+ , or Hg 2+ and interfering ions (Na + , K+ 、Li + Mg 2+ , Ca 2+ , Pb 2+ 、Fe 3+ 、Cd 2+ or Cu 2+ ), and a single Hg 2+ Samples containing Hg 2+ and one interfering ion sample, the concentration of methylene blue in each sample was 1 mmol / L, Hg 2+ The concentration of Hg was 1 μmol / L and the concentration of interfering ions was 10 μmol / L. Methylene blue was dissolved in PBS buffer with a concentration of 0.01 mol / L and pH = 7.0, and then Hg 2+ 、Na + , K + 、Li + Mg 2+ , Ca 2+ , Pb 2+ 、Fe 3+ 、Cd 2+ and Cu 2+ , a sample containing multiple metal ions was obtained, the concentration of methylene blue in the sample was 1 mmol / L, Hg 2+ The concentration of Na + , K + 、Li + Mg 2+ , Ca 2+ , Pb 2+ 、Fe 3+ 、Cd 2+ and Cu 2+ The concentrations were all 10 μmol / L.

[0090] (2) Using XXT-SNM / ITO as the working electrode, platinum electrode as the counter electrode, and saturated Ag / AgCl electrode as the reference electrode, the working electrode, counter electrode, and reference electrode form a three-electrode system.

[0091] (3) The three-electrode system was placed on a blank sample, a sample containing a single Hg 2+ Samples containing Hg 2+ The sample containing a single interfering ion and a sample containing multiple metal ions was maintained for 300 seconds. Then, the peak current response of methylene blue in each sample was measured using electrochemical voltammetry. A new working electrode was replaced with each sample, and each replacement was the same working electrode as the previous one.

[0092] (4) Calculation of single Hg 2+Samples containing Hg 2+ The ratio of the peak current response value of methylene blue in samples containing one interfering ion and multiple metal ions to the peak current response value of methylene blue in the blank sample (I / I0).

[0093] Figure 11 Figure (b) shows the effect of XXT-SNM / ITO on Hg in the presence of different metal ions. 2+ The differential pulse voltammetric response results. When the sample contains a single Hg 2+ When XXT is 2+ The specific recognition of methylene blue will cause the current peak of methylene blue to decay significantly; when the sample contains Hg 2+ When the methylene blue current peak is significantly attenuated when 10 times the amount of an interfering ion is added, the attenuation degree is similar to that of HgCl2 alone. 2+ The attenuation degree caused is basically the same; when the sample contains Hg 2+ When the amount of multiple interfering ions was 10 times that of the ions, the current peak of methylene blue also decreased significantly. This shows that XXT-SNM / ITO can specifically respond to Hg in the environment in the presence of multiple interfering metal ions. 2+ It forms a coordination complex with it, produces corresponding electrochemical signal attenuation, and has good anti-interference and selectivity.

[0094] Example 12 In this example, the XXT-SNM / ITO prepared in Example 3 was tested for its effect on Hg in the presence of different macromolecular interferors. 2+ The differential pulse voltammetric response.

[0095] (1) The blank sample was the same as that in Example 10. Methylene blue was dissolved in PBS buffer with a concentration of 0.01 mol / L and pH = 7.0. Multiple portions of the methylene blue solution were taken and Hg 2+ , or Hg 2+ and a macromolecular interferor, wherein the macromolecular interferor is bovine serum albumin (BSA), hemoglobin (HGB), starch, hyaluronic acid (HA) or carboxymethyl cellulose (CMC), to obtain a single Hg 2+ Samples containing Hg 2+ and a sample containing a macromolecular interfering substance. The concentration of methylene blue in each sample was 1 mmol / L, Hg 2+ The concentration of Hg was 200 μg / L and the concentration of macromolecular interferors was 1 mg / L. Methylene blue was dissolved in PBS buffer with a concentration of 0.01 mol / L and pH = 7.0, and then Hg 2+and macromolecular interferors (BSA, HGB, Starch, HA and CMC) to obtain Hg 2+ The concentration of methylene blue in the sample was 1 mmol / L, Hg 2+ The concentration of the interfering substances was 200 μg / L and the concentration of the macromolecular interfering substances was 1 mg / L.

[0096] (2) Using XXT-SNM / ITO as the working electrode, platinum electrode as the counter electrode, and saturated Ag / AgCl electrode as the reference electrode, the working electrode, counter electrode, and reference electrode form a three-electrode system.

[0097] (3) The three-electrode system was placed on a blank sample, a sample containing a single Hg 2+ Samples containing Hg 2+ and a sample with a macromolecular interferent, containing Hg 2+ The sample was exposed to various macromolecular interferences for 300 seconds, and then the peak current response of methylene blue in each sample was measured using electrochemical voltammetry. A new working electrode was replaced with each sample, and the working electrode after each replacement was the same as the previous working electrode.

[0098] (4) Calculation of single Hg 2+ Samples containing Hg 2+ and a sample with a macromolecular interferent, containing Hg 2+ The ratio of the peak current response value of methylene blue in the samples with various macromolecular interferents to the peak current response value of methylene blue in the blank sample (I / I0).

[0099] Figure 11 Figure (c) shows the effect of XXT-SNM / ITO on Hg in the presence of different macromolecular interfering substances. 2+ The sample contains only Hg 2+ When XXT is 2+ The specific recognition of methylene blue will cause the current peak of methylene blue to decay significantly; when the sample also contains Hg 2+ When the amount of a macromolecular interfering substance was 5 times that of the methylene blue, the current peak of the methylene blue also showed a significant attenuation, and the attenuation degree was similar to that of Hg 2+ The attenuation degree caused is basically the same; when the sample contains Hg 2+ When the amount of multiple macromolecular interfering substances was 5 times that of the methylene blue, the current peak of the methylene blue also showed a significant attenuation, and the attenuation degree was similar to that of Hg 2+ The attenuation degree caused is basically the same. This shows that XXT-SNM / ITO is effective in detecting Hg 2+This is because the vertical mesoporous silica nanochannel membrane on XXT-SNM / ITO has a uniform pore size (about 2~3nm), which can prevent molecules with larger molecular size from entering the nanopores to react with Hg 2+ interference with detection.

[0100] Example 13 In this embodiment, the preparation method of the electrochemical sensor for mercury ion detection is as follows: (1) A vertical mesoporous silica nanochannel membrane was grown on an ITO electrode according to the method in Example 1. The operation was essentially the same as in Example 1, except that a constant current of -0.85 mA was applied for 10 s. The vertical mesoporous silica nanochannel membrane prepared in this step had a thickness of approximately 50 nm, and the pore size of the nanochannels on the vertical mesoporous silica nanochannel membrane was approximately 2-3 nm.

[0101] (2) An electrochemical sensor for mercury ion detection was prepared according to the procedure of Example 3. The operation was basically the same as that of Example 3, except that the concentration of XXT-SiOH in the modification solution was controlled to 10 mg / mL, and the reaction was carried out at 50°C and 80 rpm for 4 h, and then the product was taken out.

[0102] Example 14 In this embodiment, the preparation method of the electrochemical sensor for mercury ion detection is as follows: (1) A vertical mesoporous silica nanochannel membrane was grown on an ITO electrode according to the method of Example 1. The operation was essentially the same as in Example 1, except that a constant current of -1 mA was applied for 15 s. In the SNM / ITO prepared in this step, the vertical mesoporous silica nanochannel membrane had a thickness of approximately 100 nm, and the pore size of the nanochannels on the vertical mesoporous silica nanochannel membrane was approximately 2-3 nm.

[0103] (2) An electrochemical sensor for mercury ion detection was prepared according to the procedure of Example 3. The operation was basically the same as that of Example 3, except that the concentration of XXT-SiOH in the modification solution was controlled to 20 mg / mL, and the reaction was carried out at 30°C and 40 rpm for 6 h. The product was then taken out.

[0104] Example 15 In this embodiment, an electrochemical sensor for mercury ion detection is prepared in the following steps: (1) A vertical mesoporous silica nanochannel membrane was grown on a fluorine-doped tin oxide electrode according to the method of Example 1. The operation was basically the same as that of Example 1, except that the oxygen-fluorine-doped tin oxide electrode was used as the working electrode and a constant potential of -2 V was applied for deposition for 10 s.

[0105] (2) A mercury ion recognition molecule modified with a silane coupling agent having a structure as shown in formula (III) was synthesized according to the method in Example 2. The operation was basically the same as in Example 1, except that isocyanatepropyltriethoxysilane (ICPTES) was replaced with isocyanatepropyltrimethoxysilane (IPTS).

[0106] (III) (3) A mercury ion detection electrochemical sensor was prepared according to the procedures of Example 3. The procedures were basically the same as those of Example 3, except that the concentration of the mercury ion recognition molecule modified with the silane coupling agent in the modification solution was controlled to 30 mg / mL, and the reaction was carried out at 10°C and 200 rpm for 10 h. The sensor was then taken out to obtain the product.

[0107] Example 16 In this embodiment, the preparation method of the electrochemical sensor for mercury ion detection is as follows: (1) A vertical mesoporous silica nanochannel membrane was grown on a gold electrode according to the method of Example 1. The operation was basically the same as that of Example 1, except that the gold electrode was used as the working electrode and a constant potential of -1.3 V was applied for deposition for 15 s.

[0108] (2) A mercury ion detection electrochemical sensor was prepared according to the procedure of Example 3. The operation was basically the same as that of Example 3, except that the reaction was carried out at 50°C and 50 rpm for 4 h, and then the product was taken out.

[0109] Example 17 In this embodiment, the preparation method of the electrochemical sensor for mercury ion detection is as follows: (1) A vertical mesoporous silica nanochannel membrane was grown on a glassy carbon electrode according to the method of Example 1. The operation was basically the same as that of Example 1, except that the glassy carbon electrode was used as the working electrode and a constant current of -0.74 mA was applied for deposition for 15 s.

[0110] (2) A mercury ion detection electrochemical sensor was prepared according to the procedure of Example 3. The operation was basically the same as that of Example 3, except that the reaction was carried out at 20°C and 100 rpm for 8 h, and then the product was taken out.

[0111] Example 18 In this embodiment, the preparation method of the electrochemical sensor for mercury ion detection is as follows: (1) A vertical mesoporous silica nanochannel membrane was grown on a graphite electrode according to the method of Example 1. The operation was basically the same as that of Example 1, except that the graphite electrode was used as the working electrode and a constant current of -0.9 mA was applied for deposition for 12 s.

[0112] (2) A mercury ion detection electrochemical sensor was prepared according to the procedure of Example 3. The operation was basically the same as that of Example 3, except that the reaction was carried out at 25° C. and 150 rpm for 7 h, and then the product was taken out.

Claims

1. A mercury ion detection electrochemical sensor, characterized in that: The electrochemical sensor comprises a basic electrochemical electrode, a vertical mesoporous silica nanochannel membrane uniformly deposited on the sensing interface of the basic electrochemical electrode, and a mercury ion recognition molecule connected to the nanochannel membrane. The mercury ion recognition molecule is connected to the surface of the nanochannel membrane and the nanochannel via a silane coupling agent. The mercury ion recognition molecule is 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxetane-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione. The electrochemical sensor is formed by the reaction of a mercury ion recognition molecule modified with a silane coupling agent with the nanochannel membrane on the sensing interface of the basic electrochemical electrode. The structure of the mercury ion recognition molecule modified with a silane coupling agent is shown in formula (I). (I) In formula (I), the R group is a triethoxysilyl group or a trimethoxysilyl group, m and n are both non-negative integers, and m+n=2-6.

2. The electrochemical sensor for mercury ion detection according to claim 1, wherein The reaction between the mercury ion recognition molecule modified by the silane coupling agent and the nanochannel membrane on the sensing interface of the basic electrochemical electrode is a condensation reaction between the silanol group formed after the R group of the mercury ion recognition molecule modified by the silane coupling agent is hydrolyzed and the silanol group on the nanochannel membrane.

3. The electrochemical sensor for mercury ion detection according to claim 1, wherein: The thickness of the nanochannel membrane is 50-100 nm, and the diameter of the nanochannel of the nanochannel membrane is 2-3 nm.

4. The electrochemical sensor for mercury ion detection according to claim 1, wherein: In the electrochemical sensor, the mass ratio of the mercury ion recognition molecule connected to the nanochannel membrane to the nanochannel membrane is (20-30):

1.

5. The mercury ion detection electrochemical sensor according to any one of claims 1 to 4, characterized in that: The basic electrochemical electrode is an indium tin oxide electrode, a glassy carbon electrode, a fluorine-doped tin oxide electrode, a gold electrode, a screen-printed electrode, a graphite electrode or a carbon fiber electrode.

6. The method for preparing the electrochemical sensor for detecting mercury ions according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Depositing a vertical mesoporous silica nanochannel film on the sensing interface of the basic electrochemical electrode; (2) dissolving a mercury ion recognition molecule modified with a silane coupling agent having a structure as shown in formula (I) in an organic solvent to obtain a modified solution; (3) placing the basic electrochemical electrode with the nanochannel membrane deposited on the sensing interface in a modification solution so that the nanochannel membrane is completely immersed in the modification solution, allowing it to fully react at 10-50°C under oscillation conditions, and then taking it out to obtain an electrochemical sensor for mercury ion detection.

7. The method for preparing the electrochemical sensor for mercury ion detection according to claim 6, wherein: The concentration of the mercury ion recognition molecule modified with the silane coupling agent in the modification solution was controlled to be 10-30 mg / mL.

8. The method for preparing the electrochemical sensor for mercury ion detection according to claim 6 or 7, characterized in that: The reaction time in step (3) is controlled to be 2 to 10 h.

9. A method for detecting mercury ions, characterized in that: The following steps are involved: (1) The mercury ion detection electrochemical sensor according to any one of claims 1 to 5 is used as a working electrode, a platinum electrode is used as a counter electrode, and a silver / silver chloride electrode is used as a reference electrode, and the working electrode, the counter electrode, and the reference electrode form a three-electrode system; (2) placing the three-electrode system in a blank sample, maintaining ts, and then measuring the peak current response value of the electrochemical probe in the blank sample by electrochemical voltammetry; the blank sample is prepared by the electrochemical probe and the electrolyte solution; (3) replacing the blank sample of step (2) with standard samples having known mercury ion concentrations in order from low to high mercury ion concentrations in the standard samples, repeating the operation of step (2), and measuring the peak current response value of the electrochemical probe corresponding to each standard sample; the standard sample is prepared from an electrochemical probe, mercury ions, and an electrolyte solution; (4) Plotting a working curve with the peak current of the electrochemical probe corresponding to each standard sample as the ordinate and the logarithm of the mercury ion concentration corresponding to each standard sample as the abscissa, and determining the conversion relationship between the logarithm of the mercury ion concentration and the peak current response value; (5) replacing the blank sample in step (2) with the test sample, repeating the operation of step (2), measuring the peak current response value of the electrochemical probe corresponding to the test sample, and calculating the concentration of mercury ions in the test sample according to the conversion relationship between the logarithm of the mercury ion concentration and the peak current response value determined in step (4); the test sample is prepared by the test sample, the electrochemical probe and the electrolyte solution, and the test sample contains mercury ions; The t in step (2) is a constant value between 30 and 360 s, and the t value used in steps (2), (3), and (5) is the same; when preparing the blank sample, the standard sample, and the sample to be tested, the electrochemical probe used is the same, and the electrolyte solution used is the same; the pH value of the blank sample, the standard sample, and the sample to be tested is the same, all between 4 and 8; the concentration of the electrochemical probe in the blank sample, the standard sample, and the sample to be tested is the same; in step (5), before testing each sample to be tested, a mercury ion detection electrochemical sensor that is not bound to mercury ions is replaced, and the mercury ion detection electrochemical sensor used in steps (2), (3), and (5) is the same.

10. The mercury ion detection method according to claim 9, characterized in that: The electrochemical probe is methylene blue or hexaammineruthenium trichloride; the concentration of the electrochemical probe in the blank sample, standard sample and test sample is 0.5-5 mmol / L.

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