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

Abstract

The application 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 nanochannel membrane uniformly deposited on a sensing interface of the basic electrochemical electrode, and mercury ion recognition molecules connected to the nanochannel membrane. The mercury ion recognition molecules are connected to the surface and nanochannels of the nanochannel membrane through a silane coupling agent. The mercury ion recognition molecules are 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxol-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione. The application can enhance the specific recognition ability of an existing electrochemical sensor to mercury ions, reduce the preparation difficulty and cost, and realize convenient, low-cost, high-efficiency and high-selectivity detection of mercury ions.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of mercury ion detection, and relates to a mercury ion detection electrochemical sensor and a preparation method and mercury ion detection method thereof. BACKGROUND

[0002] Mercury ion (Hg 2+ ) as a kind of toxic heavy metal pollutants, has high biological accumulation, degradation and high neurotoxicity, which seriously threatens human health. With the rapid development of fossil energy, mining and other industries, Hg 2+ Through a large number of industrial wastewater emissions into the water, and then into the soil, causing serious damage to the ecological environment. Hg 2+ In water is easy to be captured by aquatic animals, gradually enriched through the food chain into the human body, even if trace amounts of Hg 2+ , also can cause serious damage to the reproductive system, digestive system and central nervous system, leading to the occurrence of many diseases, and even can cause death. Many countries and regions limit the content of Hg 2+ In drinking water. Therefore, developing high sensitivity and high selectivity Hg 2+ Detection technology has urgent practical significance for environmental pollution prevention and control and public health safety.

[0003] The traditional Hg 2+ Detection methods mainly include atomic fluorescence spectrometry, inductively coupled plasma-mass spectrometry, atomic absorption / emission spectrometry and high performance liquid chromatography, which can be used for detection of trace or trace Hg 2+ , But limited by the detection process is complicated, high operating cost, detection equipment is not easy to carry and depends on the operation of specially trained detection personnel, etc. These methods are difficult to meet the growing demand for on-site detection and real-time analysis. Electrochemical sensor has become an important detection and analysis tool in the field of environmental protection and public health, with the advantages of high sensitivity, fast response, less sample preparation steps, portability and on-site detection. The core of improving the sensitivity of electrochemical detection and reducing its detection limit is signal amplification, and the key to signal amplification is to construct a suitable sensing interface.

[0004] For Hg 2+For the electrochemical sensing detection, there are reports on the electrochemical sensor based on graphene quantum dots confined in nanochannels, and the preparation process is as follows: first, synthesize hydroxyl functionalized graphene quantum dots (OH-GQDs) or amino functionalized graphene quantum dots (NH2-GQDs), then modify the vertical ordered mesoporous silica nanochannel film (VMSF) on the surface of the electrode, and then confine OH-GQDs or NH2-GQDs in the nanochannel of VMSF by electrophoresis. When detecting metal ions, the electrochemical sensor is used as the working electrode, and under negative voltage conditions, the hydroxyl group of OH-GQDs or the amino group of NH2-GQDs is used to coordinate with metal ions to enrich metal ions in the nanochannel and reduce them to metal elements deposited on the surface of the working electrode, and then a voltage is applied to the working electrode to dissolve the metal elements, and the dissolution signal is used as the basis for quantification (see ACS Nano 2018, 12, 12673-12681.). Although this method realizes the detection of Cu 2+ , Hg 2+ , Cd 2+ , on the one hand, it relies on the coordination of OH-GQDs or NH2-GQDs with metal ions to realize the detection of target metal ions, and the specificity of the coordination of OH-GQDs or NH2-GQDs with metal ions is not high, which inevitably coordinates with other metal ions, resulting in the method not strong selectivity for metal ions, and is easily interfered by other metal ions, on the other hand, OH-GQDs or NH2-GQDs are combined on VMSF by charge attraction, and their combination stability is easily affected by the voltage applied in the detection process, because the positive voltage is applied when confining OH-GQDs or NH2-GQDs in the nanochannel, and the negative voltage is needed to deposit the target metal in the detection, which will produce electrophoretic force in the opposite direction, resulting in the loss of OH-GQDs or NH2-GQDs in the nanochannel, affecting the detection effect.

[0005] In order to improve the specific recognition ability of the electrochemical sensor for Hg 2+ , there are reports on the Hg 2+The electrochemical sensor is prepared by the following method: (1) preparing sulfur-nitrogen co-doped ordered mesoporous carbon (SN-OMC); (2) drop coating the SN-OMC suspension on the surface of an electrode to obtain an electrode loaded with SN-OMC (GCE / SN-OMC); (3) electrodepositing gold nanoparticles on the GCE / SN-OMC to obtain GCE / SN-OMC / AuNPs with a gold film; (4) dissolving probe P1 (5'-SH-(CH2)6-GGCGACGTTTTGTCGCC-3') in a Tris-HCl buffer containing tris(2-carboxyethyl)phosphine hydrochloride, and reacting in the dark for 1 h; dropwise adding the obtained reaction solution to the surface of the GCE / SN-OMC / AuNPs, and reacting for 12 h to assemble the probe P1 on the gold film through a gold-sulfur bond, and then soaking in a 6-mercaptohexanol solution for 1 h to obtain the electrochemical sensor. When detecting Hg 2+ , the electrochemical sensor is immersed in a phosphate buffer containing probe P2 (5'-GACTTTTCGTGCGG-(CH2)6-Fc-3', Fc=ferrocene) and Hg 2+ , and reacting at 37 °C for 1 h, and then detecting by differential pulse voltammetry; when Hg 2+ is not present, the probe P1 spontaneously forms a hairpin structure through base pairing; when Hg 2+ is present, the probe P1 hybridizes with the probe P2, the hairpin structure of the probe P1 is opened, and the ferrocene signal molecule is close to the electrode surface; by analyzing the relationship between the change of the oxidation current caused by the ferrocene signal molecule and the concentration of Hg 2+ , the high-sensitivity detection of Hg 2+ can be realized (see ACS Sens. 2018, 3, 2566−2573.). The detection of Hg 2+ by using the electrochemical sensor still has the following deficiencies: (1) the construction process of the electrochemical sensor is very complicated, which increases the complexity and cost of the preparation process; (2) in order to realize the connection of the probe P1 on the gold film and the connection of the ferrocene signal molecule on the probe P2, the structure of the aptamer needs to be modified, which further increases the preparation difficulty and cost; (3) the detection process of Hg 2+ involves the pairing and disassembly process of the biological aptamer (probes P1 and P2), which leads to the low detection efficiency of Hg 2+The detection time is as long as 1 hour, and the detection efficiency is low; (4) the biological aptamer is easily inactivated by complex matrices such as nucleases during the detection process, affecting the accuracy of the detection results; (5) in order to ensure the activity of the biological aptamer, the detection temperature needs to be specially controlled. The above factors seriously limit the convenient application of this 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, so as to realize Hg 2+ Convenient, timely, low-cost and highly sensitive detection. Summary of the Invention

[0006] To address 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, and that existing electrochemical sensors for mercury ion detection based on bioaptamers have cumbersome preparation processes, high preparation and detection costs, and low detection efficiency, this invention provides an electrochemical sensor for mercury ion detection, its preparation method, and a mercury ion detection method. This enhances the specific recognition ability of existing electrochemical sensors for mercury ions and reduces their preparation difficulty and cost, achieving convenient, low-cost, high-efficiency, and highly selective detection of mercury ions.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] An electrochemical sensor for mercury ion detection comprises a basic electrochemical electrode, a vertically 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]dioxane-4-yl)-5-methylpyrimidin-2,4(1H,3H)-dione.

[0009] This electrochemical sensor is formed by the reaction of a mercury ion recognition molecule modified with a silane coupling agent with the nanochannel membrane at the sensing interface of a basic electrochemical electrode. The structure of the mercury ion recognition molecule modified with the silane coupling agent is shown in formula (I).

[0010] (I)

[0011] In formula (I), the R group is triethoxysilyl or trimethoxysilyl, m and n are both non-negative integers, and m+n=2~6.

[0012] In the technical scheme of the above mercury ion detection electrochemical sensor, the reaction between the silane coupling agent modified mercury ion recognition molecule 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 silane coupling agent modified mercury ion recognition molecule is hydrolyzed and the silicon hydroxyl group on the nanochannel membrane. After the condensation reaction, a Si-O-Si bond is formed, that is, the mercury ion recognition molecule is covalently connected to the surface and nanochannel of the nanochannel membrane through the silane coupling agent.

[0013] In the technical scheme of the above mercury ion detection electrochemical sensor, the thickness of the nanochannel membrane is preferably 50-100 nm, and the diameter of the nanochannel of the nanochannel membrane is preferably 2-3 nm.

[0014] In the technical scheme of the above mercury ion detection electrochemical sensor, in the silane coupling agent modified mercury ion recognition molecule represented by formula (I), the value of m+n should ensure that the mercury ion recognition molecules connected in the same nanochannel of the nanochannel membrane can easily combine with mercury ions to form a coordination complex with a molar ratio of 2:1 under the action of mercury ions, specifically referring to the protons of the nitrogen atoms at position 3 of the thymine base units of the adjacent two mercury ion recognition molecules connected in the same nanochannel of the nanochannel membrane are replaced by mercury ions to form a coordination complex. When the molecular chain of the silane coupling agent is too short, the rotation and swing ability of the mercury ion recognition molecule will be limited, which will prevent it from combining with mercury ions, causing the electrochemical sensor to lose the ability to recognize mercury ions. When the molecular chain of the silane coupling agent is too long, the longer carbon chain will increase the hydrophobicity of the surface of the nanochannel membrane connected with the mercury ion recognition molecule, which is not conducive to the detection of mercury ions in an aqueous solution environment, and will also increase the steric hindrance of the channel of the nanochannel membrane connected with 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 silane coupling agent modified mercury ion recognition molecule, causing the reaction between the silane coupling agent modified mercury ion recognition molecule and the nanochannel membrane on the sensing interface of the basic electrochemical electrode to be slower, reducing the preparation efficiency of the electrochemical sensor, and causing the mercury ion recognition molecule to tend to be connected in disorder. The active site of the mercury ion recognition molecule may be blocked by disorderly winding, which cannot effectively combine with mercury ions or has poor stability, which will also adversely affect the detection of mercury ions. The value of m+n depends on the diameter of the nanochannel of the nanochannel membrane, and when the diameter of the nanochannel of the nanochannel membrane is 2-3 nm, the value of m+n is preferably between 2 and 6.

[0015] In the technical scheme of the above-mentioned mercury ion detection electrochemical sensor, the amount of the mercury ion recognition molecule connected to the nanochannel membrane in the electrochemical sensor affects the amount of the coordination complex formed after the mercury ion recognition molecule recognizes mercury ions, and the amount of the coordination complex affects the permeability of the nanochannel membrane to the electrochemical probe. Under the condition of the same concentration of mercury ions, the more the amount of the mercury ion recognition molecule grafted on the nanochannel membrane, the more the amount of the coordination complex formed after the mercury ion recognition molecule recognizes mercury ions, and the lower the permeability of the nanochannel membrane to the electrochemical probe after recognizing mercury ions. In order to realize the smooth detection of mercury ions, the permeability of the nanochannel membrane to the electrochemical probe before and after recognizing mercury ions should have a significant change, but the electrochemical probe should not be completely prevented from permeating through the nanochannel membrane to reach the basic electrochemical electrode. Therefore, the amount of the mercury ion recognition molecule connected to the nanochannel membrane in the technical scheme of the present application is required. Preferably, the mass ratio of the mercury ion recognition molecule connected to the nanochannel membrane to the nanochannel membrane is (20-30):1.

[0016] In the technical scheme of the above-mentioned mercury ion detection electrochemical sensor, 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.

[0017] The present application also provides a preparation method of the above-mentioned mercury ion detection electrochemical sensor, which comprises the following steps:

[0018] (1) depositing a vertical mesoporous silica nanochannel membrane on a sensing interface of a basic electrochemical electrode;

[0019] (2) dissolving a silane coupling agent-modified mercury ion recognition molecule with a structure as shown in formula (I) in an organic solvent to obtain a modification solution;

[0020] (I)

[0021] 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;

[0022] (3) placing the basic electrochemical electrode with the nanochannel membrane deposited on the sensing interface in the modification solution so that the nanochannel membrane is completely immersed in the modification solution, and fully reacting under oscillation at 10-50℃, and then taking out, to obtain the mercury ion detection electrochemical sensor.

[0023] In the technical scheme of the above-mentioned 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.

[0024] In the technical scheme of the preparation method, the organic solvent used in the preparation of the modification solution in step (2) is toluene, acetone or N,N-dimethylformamide.

[0025] In the technical scheme of the preparation method, the reaction time in step (3) is preferably controlled to be 2-10 h.

[0026] In the technical scheme of the preparation method, the oscillation speed in step (3) is preferably controlled to be 40-200 rpm.

[0027] In step (1) of the technical scheme of the preparation method, the vertical mesoporous silica nanochannel film is uniformly deposited on the sensing interface of the base electrochemical electrode according to the prior art, for example, any one of the following methods can be used to uniformly deposit the vertical mesoporous silica nanochannel film on the sensing interface of the base electrochemical electrode: electrochemical assisted self-assembly method, Stöber solution growth method, two-phase stratified growth method, evaporation-induced self-assembly method, π-π interaction induction method, epitaxial growth method, strong magnetic field method, electric field method, and organic solvent induced self-assembly method, and the electrochemical assisted self-assembly method is preferably used to uniformly deposit the vertical mesoporous silica nanochannel film on the sensing interface of the base electrochemical electrode.

[0028] When the electrochemical assisted self-assembly method is used to uniformly deposit the vertical mesoporous silica nanochannel film on the sensing interface of the base electrochemical electrode, first, the vertical mesoporous silica nanochannel film containing surfactant micelles in the channel is deposited on the sensing interface of the base electrochemical electrode by the electrochemical assisted self-assembly method, and then the surfactant micelles are removed by washing with a hydrochloric acid-ethanol mixed solution, thereby completing the operation of uniformly depositing the vertical mesoporous silica nanochannel film on the sensing interface of the base electrochemical electrode. The hydrochloric acid-ethanol mixed solution refers to a mixture of a hydrochloric acid aqueous solution with a concentration of 3-10 mol / L and anhydrous ethanol in a volume ratio of (29-99):1. More specifically, the operation of uniformly depositing the vertical mesoporous silica nanochannel film on the sensing interface of the base electrochemical electrode by the electrochemical assisted self-assembly method is as follows:

[0029] (1) Ethanol and water are mixed in a volume ratio of (4-6):(6-4) as a solvent, and sodium nitrate is added to the solvent to a concentration of 0.1-0.15 mol / L, cetyltrimethylammonium bromide is added to a concentration of 4-5 mmol / L, and tetraethyl orthosilicate is added to a concentration of 13.5-14 mmol / L, and stirred until all components are completely dissolved, and the pH value of the solution is adjusted to 3-3.5 with hydrochloric acid, and stirred at room temperature for 2-3 h to obtain a precursor solution;

[0030] (2) with the basic electrochemical electrode as a working electrode, a platinum electrode as a counter electrode, a saturated Ag / AgCl electrode as a reference electrode, a precursor solution as an electrolyte solution, a constant current or a constant voltage is applied for deposition, the working electrode is taken out, washed with water, and then placed in aging at 130-150 DEG C for 10-12 h, that is, a vertical mesoporous silica nanochannel membrane containing surfactant micelles in pores is deposited on the sensing interface of the basic electrochemical electrode, and the surfactant micelles are removed by washing with a hydrochloric acid-ethanol mixed solution; in the step, the applied constant current is-1--0.7 mA, the applied constant voltage is-2--1 V, and the controlled deposition time is 10-20 s.

[0031] In the technical scheme of the above preparation method, a feasible structure of the silane coupling agent modified mercury ion recognition molecule shown as formula (I) is prepared according to the following method:

[0032] 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxol-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione, propyl triethoxysilane isocyanate or propyl trimethoxysilane isocyanate, and dibutyl tin dilaurate are dissolved in a solvent to obtain a mixed solution, the reaction is carried out at 65-80 DEG C for 12-36 h, and then the obtained reaction solution is separated and purified by column chromatography to obtain the silane coupling agent modified mercury ion recognition molecule shown as formula (I).

[0033] In the preparation of the silane coupling agent modified mercury ion recognition molecule, the solvent is tetrahydrofuran, N,N-dimethylformamide or 1,4-dioxane.

[0034] In the preparation of the silane coupling agent modified mercury ion recognition molecule, the molar ratio of 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxol-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione, propyl triethoxysilane isocyanate or propyl trimethoxysilane isocyanate, and dibutyl tin dilaurate in the mixed solution is (1-1.5):(1-2.5):(1-6).

[0035] Based on the above mercury ion detection electrochemical sensor, the application further provides a mercury ion detection method, which comprises the following steps:

[0036] (1) the above mercury ion detection electrochemical sensor is used as a working electrode, a platinum electrode is used as a counter electrode, 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;

[0037] (2) placing the three-electrode system in a blank sample, keeping t s, and then determining 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 an electrolyte solution;

[0038] (3) replacing the blank sample in step (2) with the standard sample with a known mercury ion concentration in order from low to high, repeating the operation in step (2), and determining the peak current response value of the electrochemical probe corresponding to each standard sample; the standard sample is prepared by the electrochemical probe, the mercury ion, and the electrolyte solution;

[0039] (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;

[0040] (5) replacing the blank sample in step (2) with the test sample, repeating the operation in step (2), determining the peak current response value of the electrochemical probe corresponding to the test sample, and calculating the concentration of the mercury ion 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 the mercury ion;

[0041] The t in step (2) is a constant value between 30 s and 360 s, and the t values used in steps (2), (3), and (5) are the same; the electrochemical probe used when preparing the blank sample, the standard sample, and the test sample is the same, and the electrolyte solution used when preparing the blank sample, the standard sample, and the test sample is the same; the pH values of the blank sample, the standard sample, and the test sample are the same, and are between 4 and 8; the concentration of the electrochemical probe in the blank sample, the standard sample, and the test sample is the same; in step (5), a mercury ion detection electrochemical sensor that has not combined with the mercury ion is replaced before each test sample is tested, and the mercury ion detection electrochemical sensors used in steps (2), (3), and (5) are the same.

[0042] In the technical scheme of the mercury ion detection method, the electrochemical probe is preferably a positively charged electrochemical probe, for example, methylene blue or hexaammineruthenium chloride; and the concentration of the electrochemical probe in the blank sample, the standard sample, and the test sample is preferably between 0.5 mmol / L and 5 mmol / L.

[0043] In the technical scheme of the 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; and the concentration of the electrolyte solution is between 0.01 mol / L and 0.1 mol / L.

[0044] The technical scheme of the mercury ion detection method comprises the following steps: (1) preparing a mercury ion detection electrochemical sensor; (2) adding the mercury ion detection electrochemical sensor into a mercury ion detection system; (3) adding a test sample into the mercury ion detection system; (4) detecting the mercury ion in the test sample by using the mercury ion detection electrochemical sensor.

[0045] The mercury ion detection electrochemical sensor provided by the application can realize high-selectivity, high-efficiency and low-cost detection of mercury ions, and the principle is as follows:

[0046] When the test sample does not contain mercury ions, the mercury ion recognition molecules in the nanochannel of the nanochannel membrane of the mercury ion detection electrochemical sensor are not combined with the mercury ions, the nanochannel has good permeability to the electrochemical probe, the electrochemical probe in the test sample can reach the basic electrochemical electrode through the nanochannel on the nanochannel membrane, and a strong electrochemical signal is generated by the electrochemical reaction; when the test sample contains mercury ions, the mercury ion recognition molecules in the nanochannel of the nanochannel membrane are specifically combined with the mercury ions and form a stable coordination complex, the coordination complex increases the steric hindrance in the nanochannel of the nanochannel membrane, and then increases the mass transfer resistance of the electrochemical probe to the basic electrochemical electrode, so that the electrochemical probe reaching the basic electrochemical electrode is reduced, and the electrochemical signal is attenuated, and the attenuation degree of the electrochemical signal is negatively correlated with the concentration of the mercury ions in the test sample. Therefore, by detecting the change of the electrochemical signal of the electrochemical probe, the electrochemical detection of the mercury ions can be realized.

[0047] On the one hand, the mercury ion recognition molecules can specifically recognize the mercury ions to form a coordination complex, and will not recognize other metal ions, including common monovalent and multivalent metal ions such as Na + , K + , Li + , Mg 2+ , Ca 2+ , Pb 2+ , Fe 3+ , Cd 2+ and Cu 2+ will not interfere with the detection of mercury ions; on the other hand, the pore size of the vertical mesoporous silica nanochannel membrane is 2-3 nm, which can limit the substances with a size larger than the pore size of the nanochannel to reach the surface of the basic electrochemical electrode by size exclusion, and the pKa of the silicon hydroxyl group of the silica is about 2, which is deprotonated at pH>2 and is negatively charged, which can limit the negatively charged substances to reach the surface of the basic electrochemical electrode by electrostatic repulsion. The above two aspects make the mercury ion detection electrochemical sensor of the application have good anti-interference ability, and realize high-selectivity detection of mercury ions.

[0048] The mercury ion recognition molecule can specifically recognize mercury ions, so that the mercury ion detection electrochemical sensor can solve the problem that the existing electrochemical sensor based on nano-channel limited graphene quantum dots is easily interfered by other metal ions when detecting mercury ions. Meanwhile, by virtue of the size and charge repulsion of the nano-channel film, the mercury ion detection electrochemical sensor can avoid the interference of macromolecular substances and negatively charged substances on the detection of mercury ions. Compared with the existing mercury ion detection electrochemical sensor, the mercury ion detection electrochemical sensor can effectively improve the selective detection ability of mercury ions and realize high-selectivity detection of mercury ions.

[0049] Compared with the prior art, the technical scheme provided by the present application has the following beneficial technical effects:

[0050] 1. The mercury ion detection electrochemical sensor comprises a basic electrochemical electrode, a vertical mesoporous silica nanochannel film uniformly deposited on a sensing interface of the basic electrochemical electrode, and a mercury ion recognition molecule connected to the nanochannel film, wherein the mercury ion recognition molecule is connected to the surface and nanochannel of the nanochannel film through a silane coupling agent; the mercury ion recognition molecule is 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxol-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione. Since the mercury ion recognition molecule can specifically recognize mercury ions, the mercury ion detection electrochemical sensor can solve the problem that the existing electrochemical sensor based on nano-channel limited graphene quantum dots is easily interfered by other metal ions when detecting mercury ions. Meanwhile, by virtue of the size and charge repulsion of the nanochannel film, the mercury ion detection electrochemical sensor can avoid the interference of macromolecular substances and negatively charged substances on the detection of mercury ions. Compared with the existing mercury ion detection electrochemical sensor, the mercury ion detection electrochemical sensor can effectively improve the selective detection ability of mercury ions and realize high-selectivity detection of mercury ions.

[0051] 2. Since the process of forming a coordination complex between the mercury ion recognition molecule and mercury ions is very fast, the recognition process can reach reaction equilibrium within 30-360 s, so that the mercury ion detection electrochemical sensor can realize rapid and high-efficiency detection of mercury ions. Since the pairing and disintegration process of biological aptamers is not involved, compared with the existing biological aptamer mercury ion detection electrochemical sensor, the mercury ion detection electrochemical sensor can effectively improve the detection efficiency of mercury ions. In addition, the operation of using the mercury ion detection electrochemical sensor to detect mercury ions is very simple, and there is no need to regulate the temperature of the detection process. This makes the mercury ion detection electrochemical sensor better meet the growing demand for on-site detection and real-time analysis.

[0052] 3. The application further provides a preparation method of the above-mentioned mercury ion detection electrochemical sensor, which has the characteristics of simple operation, mild process conditions, low cost and easy availability of raw materials, simple preparation process, high efficiency and low preparation cost. Compared with the existing mercury ion detection electrochemical sensor, especially the mercury ion detection electrochemical sensor based on biological aptamer, the application effectively reduces the preparation difficulty and cost of the mercury ion detection electrochemical sensor.

[0053] 4. The application further provides a mercury ion detection method, which uses the nanochannel on the nanochannel membrane of the mercury ion detection electrochemical sensor to pre-enrich the charged electrochemical probes through electrostatic interaction, amplifies the electrical signal generated thereby, improves the detection sensitivity, and enables the mercury ion recognition molecules connected in the nanochannel to quickly form a coordination complex after the mercury ion, so that the permeability of the nanochannel changes, resulting in the attenuation of the electrochemical signal generated by the electrochemical probe, and the attenuation degree of the electrochemical signal has a correlation with the concentration of the mercury ion. Thus, the method realizes high selectivity and high efficiency detection of the mercury ion. At the same time, the preparation cost of the mercury ion detection electrochemical sensor relied on by the detection method is low, and the operation of the detection method is simple, which is also conducive to realizing low-cost detection of the mercury ion. Compared with the existing mercury ion detection method based on the electrochemical sensor, the application not only realizes high selectivity detection of the mercury ion, but also effectively improves the detection efficiency and reduces the detection cost, which is conducive to popularization and application in the field of convenient and low-cost detection of the mercury ion. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 Figure 1 is a TEM image of the vertical mesoporous silica nanochannel membrane on SNM / ITO prepared in Example 1, wherein (a) and (b) are TEM top view and its local enlarged view, and (c) is a TEM cross-sectional view.

[0055] Figure 2 Figures (a) (b) (c) are cyclic voltammograms of ITO, CTAB@SNM / ITO and SNM / ITO in KCl solution containing Ru(NH3)6 3+ , Fe(CN)6 3– , FcMeOH.

[0056] Figure 3 Figure 2 is a synthesis route diagram of XXT-SiOH in Example 2.

[0057] Figure 4 Figure 3 is the nuclear magnetic resonance hydrogen spectrum of XXT-SiOH prepared in Example 2.

[0058] Figure 5The infrared spectra of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO.

[0059] Figure 6 The (a) figure is the X-ray photoelectron spectroscopy full spectrum of SNM / ITO and XXT-SNM / ITO, Figure 6 The (b) figure is the test result of the signal ratio of N element and Si element in SNM / ITO and XXT-SNM / ITO.

[0060] Figure 7 The water contact angle test results of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO.

[0061] Figure 8 The electrochemical impedance spectrograms of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO.

[0062] Figure 9 The change of differential pulse voltammetry response of XXT-SNM / ITO before and after reacting with 10 μmol / L of mercury ion. Figure 10 The (a) figure is the differential pulse voltammetry curve of XXT-SNM / ITO in blank sample and each standard sample, Figure 10 The (b) figure is the working curve drawn by Example 8.

[0063] Figure 11 The (a) figure is the differential pulse voltammetry response result of XXT-SNM / ITO to different kinds of metal ions, Figure 11 The (b) figure is the differential pulse voltammetry response result of XXT-SNM / ITO to Hg 2+ in the presence of different kinds of metal ions, Figure 11 The (c) figure is the differential pulse voltammetry response result of XXT-SNM / ITO to Hg 2+ in the presence of different macromolecular interferents. DETAILED DESCRIPTION

[0064] The mercury ion detection electrochemical sensor provided by the present application and the preparation method and mercury ion detection method thereof are further described through the following examples. It is necessary to point out that the following examples are only used for further description of the present application and cannot be understood as the limitation of the protection scope of the present application. The skilled in the art can make some non-essential improvements and adjustments to the present application according to the above description, which still belongs to the protection scope of the present application.

[0065] In the following examples and comparative examples, the reagents used are purchased from TCI Corporation (Tokyo Chemical Industry) and used directly without special treatment, unless otherwise specified. The electrochemical workstation used is PGSTAT-101.

[0066] Example 1

[0067] In this example, a vertical mesoporous silica nanochannel membrane is grown on an indium tin oxide substrate electrode by electrochemical assisted self-assembly (EASA) method, and the steps are as follows:

[0068] (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 of the solution to 3 with hydrochloric acid, and stir at room temperature for 2.5 h to obtain the precursor solution.

[0069] (2) Prepare the SNM / ITO electrode: use a three-electrode system with an indium tin oxide electrode (ITO) as the working electrode, a platinum electrode as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode, use the precursor solution as the electrolyte solution, apply a constant current of -1 mA for 10 s, quickly remove the working electrode after deposition, and rinse it with a large amount of ultrapure water, then place it in an aging oven at 130 ℃ for 12 h to obtain a silica nanochannel membrane modified ITO electrode (CTAB@SNM / ITO) with CTAB micelles remaining in the pores. Then immerse the CTAB@SNM / ITO in a 0.1 mol / L hydrochloric acid-ethanol solution for 5 min to obtain a vertical mesoporous silica nanochannel membrane modified electrode (SNM / ITO). The hydrochloric acid-ethanol mixture is obtained by mixing a 10 mol / L hydrochloric acid aqueous solution with anhydrous ethanol in a volume ratio of 99:1.

[0070] Figure 1 Figure 1 is a transmission electron microscope (TEM) image of the vertical mesoporous silica nanochannel membrane on the SNM / ITO prepared in this example, where (a) and (b) are TEM top view and its local magnification, and (c) is a TEM cross-sectional view. It can be seen from Figure 1 that the pore size of the nanochannels on the vertical mesoporous silica nanochannel membrane is about 2-3 nm, the nanosilica is arranged in an ordered hexagonal pattern, and no obvious defects in large areas are found, and the thickness of the vertical mesoporous silica nanochannel membrane is about 65 nm.

[0071] Prepare Ru(NH3)6 3+ , Fe(CN)63– or potassium chloride solution of hydroxymethyl ferrocene (FcMeOH) and adjusting the pH value of each solution to 4. The concentrations of Ru(NH3)6 3+ , Fe(CN)6 3– and FcMeOH in each prepared mixed solution were 0.5 mmol / L, and the concentration of potassium chloride was 50 mmol / L. The cyclic voltammograms of ITO, CTAB@SNM / ITO and SNM / ITO in the above three mixed solutions were tested respectively, and the results are shown in Figs. (a) (b) and (c) of Figure 2 .

[0072] Figure 2 Figs. (a) (b) and (c) are cyclic voltammograms of ITO, CTAB@SNM / ITO and SNM / ITO in potassium chloride solutions containing Ru(NH3)6 3+ , Fe(CN)6 3– and FcMeOH. As can be seen from Figure 2 , CTAB@SNM / ITO cannot generate Randles signals in potassium chloride solutions containing Ru(NH3)6 3+ and Fe(CN)6 3– , but only charging current is presented, which is caused by the fact that the micelles in the channels cause hydrophilicity through hydrophobic interaction, so that the charged probes Ru(NH3)6 3+ and Fe(CN)6 3– cannot enter the channels and reach the electrode surface. However, the hydrophobic neutral probe FcMeOH can reach the electrode surface through micelle enrichment to generate redox signals, and compared with ITO, the redox peaks are all shifted to the positive direction, which is caused by the fact that the electrochemical reaction rate is slowed down and the charge transfer becomes more difficult, so that a higher potential is required to make the reaction occur. After the micelles in CTAB@SNM / ITO are removed, the signals of SNM / ITO in the three mixed solutions are all recovered. Compared with ITO, the signal of SNM / ITO in potassium chloride solution containing Fe(CN)6 3– is inhibited, and the signal in potassium chloride solution containing Ru(NH3)6 3+ is enhanced, which is caused by the fact that the pH value of potassium chloride solution containing Ru(NH3)6 3+ or Fe(CN)6 3– is 4, at which time the silicon hydroxyl groups in the nanopores are deprotonated to make the pore wall negatively charged, repelling the negatively charged probes and attracting the positively charged electrochemical probes.

[0073] The above experimental results show that the vertical mesoporous silica nanochannel membrane on SNM / ITO prepared in the embodiment has a complete surface without defects and cracks, and has obvious charge-selective permeability.

[0074] Example 2

[0075] In this example, a silane coupling agent modified mercury ion recognition molecule (XXT-SiOH) with the structure shown in formula (II) was synthesized, and the synthetic route is shown in Figure 3 The steps are as follows:

[0076] (II)

[0077] (1) Refer to the method in Zhou, X.-L. et al. Journal of Hazardous Materials, 445, 130610 (2023) to synthesize 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxol-4-yl)-5-methylpyrimidine-2,4(1H,3H)-dione, abbreviated as XXT.

[0078] (2) Dissolve XXT in 50 mL of tetrahydrofuran (THF) at room temperature to obtain a XXT solution with a concentration of 3 mmol / L. Add 3 mL of propyl triethoxysilane isocyanate (ICPTES) and 10 mL of dibutyltin dilaurate (DBDTL) to the XXT solution, and stir the reaction at 66 ℃ under reflux. Monitor the reaction process using TLC (developing agent obtained by mixing equal volumes of petroleum ether and ethyl acetate), and after the reaction is completed, remove the solvent by rotary evaporation to obtain the crude product. Purify the crude product by silica gel column chromatography (eluent obtained by mixing equal volumes of petroleum ether and ethyl acetate) to obtain XXT-SiOH, which is stored in a cold storage.

[0079] Figure 4 is the nuclear magnetic resonance hydrogen spectrum of XXT-SiOH prepared in this example, wherein the peak at 11.40 ppm belongs to the hydrogen of the secondary amine group at position 3 on the thymine base unit in XXT, the peaks at 5.80 ppm, 5.02 ppm and 4.76 ppm, 3.75 ppm belong to the four single hydrogen atoms on the five-membered ring of XXT, the peak at 3.71 ppm belongs to the ethyl hydrogen on the triethoxyl group of the silane coupling agent ICPTES, and the peak at 7.23 ppm belongs to the hydrogen of the secondary amine group on the urethane group connecting the two in XXT-SiOH. This nuclear magnetic resonance hydrogen spectrum confirms the successful synthesis of XXT-SiOH with the structure shown in formula (II).

[0080] Example 3

[0081] In this example, a mercury ion detection electrochemical sensor (XXT-SNM / ITO) was prepared, and the steps are as follows:

[0082] (1) The XXT-SiOH prepared in Example 2 was added into anhydrous toluene and dissolved by stirring to obtain a modification solution, in which the concentration of XXT-SiOH was 25 mg / mL.

[0083] (2) The SNM / ITO prepared in Example 1 was placed in the modification solution, so that the silica nanochannel membrane on the SNM / ITO was completely immersed in the modification solution. The reaction was oscillated at 40°C at a speed of 50 rpm for 6 h, and then removed to obtain XXT-SNM / ITO.

[0084] Example 4

[0085] In this example, the chemical compositions of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO prepared in Examples 1-3 were tested.

[0086] The infrared spectra of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO were tested, and the results are shown in FIG. 2. Figure 5 As shown in FIG. 2, compared with ITO, the infrared spectra of CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO all appeared asymmetric and symmetric stretching vibration peaks of Si-O-Si at 1078 cm -1 and 801 cm -1 , corresponding to the joint network of silica, indicating that the vertical mesoporous silica nanochannel membrane was successfully grown on the surface of the ITO electrode. In the infrared spectrum of CTAB@SNM / ITO, the peaks at 2911 cm -1 and 2843 cm -1 were asymmetric and symmetric stretching vibration peaks of C-H bond in CTAB molecules, the peak at 1470 cm -1 was a deformation vibration peak thereof, and the peak at 851 cm -1 was a stretching vibration peak of C-N bond. In the infrared spectrum of SNM / ITO, the asymmetric and symmetric stretching vibration peaks of C-H bond in CTAB molecules disappeared, indicating that the CTAB micelles in the channel were successfully removed. Compared with SNM / ITO, the infrared spectrum of XXT-SNM / ITO appeared C=O stretching vibration peaks of -COO-NH- and -CO-NH- at 1692 cm -1 , and N-H stretching vibration peaks of secondary amino group at 1530 cm -1 , indicating that XXT was successfully covalently connected to the silica nanochannel membrane of SNM / ITO in Example 3.

[0087] The X-ray photoelectron spectroscopy of SNM / ITO and XXT-SNM / ITO was tested, and the results are shown in FIG. 3. Figure 6 As shown in FIG. 3, compared with SNM / ITO, the X-ray photoelectron spectroscopy of XXT-SNM / ITO appeared C=O stretching vibration peaks of -COO-NH- and -CO-NH- at 1692 eV, and N-H stretching vibration peaks of secondary amino group at 1530 eV, indicating that XXT was successfully covalently connected to the silica nanochannel membrane of SNM / ITO in Example 3.Figure 6 As shown. Figure 6 Figure (a) shows the full 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 ratio (i.e., the N / Si atomic ratio) in Figure (b) is calculated based on X-ray photoelectron spectroscopy results. Figure 6 As shown in Figure (b), after covalently linking XXT molecules, the N / Si ratio on the surface of the silica nanochannel membrane increases from 3.24 to 22.51. Further calculations based on the N / Si ratio reveal that the mass ratio of covalently linked XXT to silica nanochannel membrane in XXT-SNM / ITO is 24.93.

[0088] Example 5

[0089] In this embodiment, the hydrophilicity and hydrophobicity of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO prepared in Examples 1 to 3 were tested.

[0090] The water contact angles of ITO, CTAB@SNM / ITO, SNM / ITO, and XXT-SNM / ITO were tested, and the results are as follows: Figure 7 As shown. By Figure 7 It is known that the water contact angle of ITO is 60.6°. After depositing a vertical mesoporous silica nanochannel film on the sensing interface of ITO, the water contact angle of CTAB@SNM / ITO increases significantly to 82.2° due to the presence of hydrophobic CTAB micelles in the channels. After washing away the CTAB micelles in the channels with hydrochloric acid-ethanol solution, the water contact angle of the resulting SNM / ITO decreases to 71.9°. After covalently linking XXT to the vertical mesoporous silica nanochannel film, the water contact angle of the resulting XXT-SNM / ITO increases again to 77.3°. This is because XXT molecules are hydrophobic and the silane coupling agent has a long alkane chain, leading to an increase in the hydrophobicity of XXT-SNM / ITO.

[0091] Example 6

[0092] In this embodiment, the electrochemical impedance spectroscopy of ITO, CTAB@SNM / ITO, SNM / ITO and XXT-SNM / ITO prepared in Examples 1 to 3 was tested.

[0093] ITO, CTAB@SNM / ITO, SNM / ITO, and XXT-SNM / ITO were used as working electrodes, with a platinum electrode as the counter electrode and a saturated Ag / AgCl electrode as the reference electrode. A three-electrode system was formed by combining the working electrode, counter electrode, and reference electrode. This system was placed in a potassium chloride solution containing K3Fe(CN)6 and K4Fe(CN)6 at pH 4 (potassium chloride concentration of 50 mmol / L, and K3Fe(CN)6 and K4Fe(CN)6 concentrations of 2.5 mmol / L each). Electrochemical impedance spectroscopy (EIS) of ITO, CTAB@SNM / ITO, SNM / ITO, and XXT-SNM / ITO was measured using the following parameters: potential of -0.22 V, sinusoidal potential amplitude of 10 mV, and test frequency from 100 kHz to 0.001 Hz.

[0094] Figure 8 This is the electrochemical impedance spectroscopy of ITO, CTAB@SNM / ITO, SNM / ITO, and XXT-SNM / ITO, where the horizontal axis... Z ′ is the real impedance, in units of K Ω, ordinate - Z ′′ is the imaginary impedance, with units of . K Ω. From Figure 8 It is evident that ITO exhibits the smallest semicircular diameter in the high-frequency region, indicating the lowest charge transfer resistance. After growing a vertical mesoporous silica nanochannel membrane, CTAB@SNM / ITO exhibits the largest semicircular diameter in the high-frequency region. This is because micelles within the pores impede the penetration of the electrochemical probe, thus hindering electron transfer. After washing away the CTAB micelles within the pores using a hydrochloric acid-ethanol solution, the semicircular diameter of SNM / ITO significantly decreases, indicating that the open pores allow the electrochemical probe to enter and promote electron transfer. After covalently linking XXT to the vertical mesoporous silica nanochannel membrane of SNM / ITO, the semicircular 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 resistance to the electrochemical probe, thereby increasing the charge transfer steric hindrance.

[0095] Example 7

[0096] In this embodiment, the changes in the differential pulse voltammetric response of XXT-SNM / ITO prepared in Example 3 before and after reacting with 10 μmol / L mercury ions were tested.

[0097] The XXT-SNM / ITO 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, to form a three-electrode system with the working electrode, the counter electrode and the reference electrode. The methylene blue and Hg 2+ (2) The methylene blue and Hg 2+ with concentrations of 1 mmol / L and 10 μmol / L respectively were added to the PBS buffer solution with a concentration of 0.01 mol / L and pH=7 as the sample to be tested. The methylene blue with a concentration of 1 mmol / L was added to the PBS buffer solution with a concentration of 0.01 mol / L and pH=7 as the control sample. The three-electrode system was placed in the sample to be tested and the control sample, and the differential pulse voltammetry response of the XXT-SNM / ITO was tested. The test parameters were as follows: the step potential was 0.005 V, the pulse amplitude was 0.05 V, the pulse time was 0.05 s, and the interval time was 0.5 s. The test results are shown in Figure 9 .

[0098] As can be seen from Figure 9 , the methylene blue in the control sample has a high oxidation peak current value. This is because the methylene blue molecule is positively charged, and the surface of the vertical mesoporous silica nanochannel membrane is negatively charged due to the deprotonation of the hydroxyl group. The methylene blue can be attracted into the channel by electrostatic interaction to achieve pre-enrichment effect and realize the amplification of the electrochemical signal, thereby generating a high oxidation peak current value. In the sample to be tested, the oxidation peak current value of the methylene blue decreases. This is because the covalently connected XXT on the vertical mesoporous silica nanochannel membrane can specifically recognize Hg 2+ in the solution, and Hg 2+ can replace the protons of the nitrogen atoms at position 3 on the two adjacent thymine base units of XXT to form a stable coordination complex, resulting in increased steric hindrance in the nanochannel, reduced permeability of the channel, and hindered electrochemical reaction of the methylene blue from the solution into the channel, thereby causing the oxidation peak current value to decrease.

[0099] Example 8

[0100] In this embodiment, the differential pulse voltammetry response of the XXT-SNM / ITO prepared in Example 3 in the electrolyte solution containing methylene blue and different concentrations of mercury ions was tested, and the working curve was drawn to determine the conversion relationship between the logarithmic value of the mercury ion concentration and the peak current response value.

[0101] (1) Preparation of blank sample and standard sample

[0102] The methylene blue was dissolved in the PBS buffer solution with a concentration of 0.01 mol / L and a pH value of 7.0 to obtain a blank sample. The concentration of the methylene blue in the blank sample was 1 mmol / L.

[0103] Methylene blue was dissolved in PBS buffer solution with a concentration of 0.01 mol / L and pH = 7.0, and different amounts of mercury ion mother liquor were added to the methylene blue solution to prepare a series of standards. In each standard, the concentration of mercury ion was 10 -9 , 5 x 10 -9 , 10 -8 , 5 x 10 -8 , 10 -7 , 5 x 10 -7 , 10 -6 , 5 x 10 -6 , 10 -5 , 5 x 10 -5 mol / L (mol / L is referred to as M in the figure), and the concentration of methylene blue in each standard was 1 mmol / L.

[0104] (2) The XXT-SNM / ITO 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 to form a three-electrode system.

[0105] (3) The three-electrode system was placed in the blank sample for 300 s, and then the peak current response value of methylene blue in the blank sample was determined by electrochemical voltammetry.

[0106] (4) The blank sample in step (3) was replaced by each standard in turn according to the order of the concentration of mercury ion in the standard from low to high, and the operation of step (3) was repeated to determine the peak current response value of methylene blue corresponding to each standard.

[0107] (5) The working curve was drawn with the peak current of methylene blue corresponding to each standard as the ordinate and the logarithm (base 10) of the concentration of mercury ion corresponding to each standard as the abscissa to determine the conversion relationship between the logarithm value of the concentration of mercury ion and the peak current response value.

[0108] Figure 10 Fig. (a) of the drawings is the differential pulse voltammogram of XXT-SNM / ITO in the blank sample and each standard. The oxidation peak current value of methylene blue decreases with the increase of the concentration of Hg 2+ , which is because with the increase of the concentration of Hg 2+ , more coordination complexes can be formed between XXT in the nanochannel of the vertical mesoporous silica nanochannel membrane and Hg 2+ , resulting in the increase of the steric hindrance of the nanochannel and the decrease of the permeability of the nanochannel, so the oxidation peak current value of methylene blue also decreases.

[0109] Figure 10 Fig. (b) of the drawings is the working curve drawn in step (5), and from the graph it can be seen that the logarithm of the concentration of Hg2+ The logarithm of the concentration and the oxidation peak current of methylene blue are in the range of 10. -9 ~5×10 -7 Within the concentration range of mol / L, there are two segments of linear relationship, when Hg 2+ The concentration is 10 -9 ~5×10 -7 At mol / L, Hg 2+ The conversion formula between the logarithm of the concentration and the peak current response is: Y = -1.254X + 33.134(R) 2 =0.996), when Hg 2+ The concentration is 5×10 -7 ~5×10 -5 At mol / L, Hg 2+ The conversion formula between the logarithm of the concentration and the peak current response 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.

[0110] The method described in this invention for Hg is calculated based on the formula LOD=3σ / S. 2+ The detection limit is 0.5598 nmol / L, indicating high sensitivity for mercury ions. In the formula LOD = 3σ / S, σ is the standard deviation of the peak current response of the blank sample, the number of measurements is 12, and S is the aforementioned Hg... 2+ Concentration of 10 -9 ~5×10 -7 The slope of the conversion formula for mol / L.

[0111] Example 9

[0112] In this embodiment, the mercury ion detection method described in this invention is used to detect mercury ions in the sample to be tested. The steps are as follows:

[0113] (1) Preparation of test sample

[0114] Dissolve methylene blue in 0.01 mol / L PBS buffer (pH 7.0), then add Hg. 2+ The mother liquor was used to prepare Hg. 2+ The concentration is 2.5 × 10⁻⁶. −6 The test sample was prepared with a concentration of 1 mmol / L of methylene blue.

[0115] (2) Using the XXT-SNM / ITO prepared in Example 3 as the working electrode, the platinum electrode as the counter electrode, and the saturated Ag / AgCl electrode as the reference electrode, the working electrode, the counter electrode, and the reference electrode are combined into a three-electrode system.

[0116] (3) Put the three-electrode system into the sample to be tested, keep for 300 s, and then determine the peak current response value of methylene blue in the sample to be tested by electrochemical voltammetry, and the result is 38.013 μA.

[0117] (4) According to the conversion relationship Y=-4.434X+13.158 (R 2 =0.996) of the logarithmic value of the mercury ion concentration and the peak current response value determined in Example 8, the concentration of the mercury ion in the sample to be tested is calculated as 2.48×10 −6 mol / L. The detection result is basically consistent with the concentration of the mercury ion in the sample solution to be tested, indicating that the method of the present application can accurately detect Hg 2+ in the sample.

[0118] Example 10

[0119] In this embodiment, the differential pulse voltammetry response of XXT-SNM / ITO prepared in Example 3 to different kinds of metal ions is tested.

[0120] (1) Dissolve methylene blue in a PBS buffer solution with a concentration of 0.01 mol / L and pH=7.0 to obtain a blank sample, and the concentration of methylene blue in the blank sample is 1 mmol / L. Dissolve methylene blue in a PBS buffer solution with a concentration of 0.01 mol / L and pH=7.0, take multiple portions of the methylene blue solution, and add Hg 2+ or interfering ions (Na + , K + , Li + , Mg 2+ , Ca 2+ , Pb 2+ , Fe 3+ , Cd 2+ or Cu 2+ ) into each portion of the methylene blue solution to obtain samples containing a single kind of metal ion, and the concentration of methylene blue in each sample is 1 mmol / L. When the metal ion contained in the sample is Hg 2+ , the concentration of Hg 2+ is 1 μmol / L, and when the metal ion in the sample is an interfering ion, the concentration of the interfering ion is 10 μmol / L. Dissolve methylene blue in a PBS buffer solution with a concentration of 0.01 mol / L and pH=7.0, and then add Hg 2+ , Na + , K + , Li + , Mg 2+ , Ca 2+ , Pb 2+ , Fe3+ , Cd 2+ and Cu 2+ , to obtain a sample containing multiple metal ions, the concentration of methylene blue in the sample being 1 mmol / L, the concentration of Hg 2+ being 1 μmol / L, the concentrations of Na + , K + , Li + , Mg 2+ , Ca 2+ , Pb 2+ , Fe 3+ , Cd 2+ and Cu 2+ all being 10 μmol / L.

[0121] (2) Taking 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, the counter electrode and the reference electrode form a three-electrode system.

[0122] (3) The three-electrode system is respectively placed in a blank sample, a metal ion sample containing a single kind of metal ion, and a metal ion sample containing multiple metal ions, and maintained for 300 s, and then the peak current response value of methylene blue in each sample is determined by electrochemical voltammetry. A new working electrode is replaced every time a sample is tested, and the working electrode after replacement is the same as the working electrode used before.

[0123] (4) The ratio (I / I0) of the peak current response value of methylene blue in each sample containing a single kind of metal ion or containing multiple metal ions to the peak current response value of methylene blue in the blank sample is calculated.

[0124] Figure 11 Fig. (a) of the drawings is the test result of the differential pulse voltammetry response of XXT-SNM / ITO to different kinds of metal ions. When the metal ion in the sample is Hg 2+ , the specific recognition of XXT to Hg 2+ will cause the current peak of methylene blue to obviously decrease; when the metal ion in the sample is 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 does not obviously decrease or basically does not decrease; when the sample contains Hg 2+The current peak of methylene blue still obviously attenuated in the presence of 10 times of various interfering ions, and the attenuation amount was basically the same as that caused by Hg 2+ The XXT-SNM / ITO only specifically responds to Hg 2+ in the environment and produces corresponding electrochemical signal attenuation, which has good selectivity and anti-interference.

[0125] Example 11

[0126] In this example, the differential pulse voltammetry response of the XXT-SNM / ITO prepared in Example 3 to Hg 2+ in the presence of different kinds of metal ions was tested.

[0127] (1) The blank sample was the same as that in Example 10. Methylene blue was dissolved in a PBS buffer solution with a concentration of 0.01 mol / L and pH=7.0, and then multiple portions of the methylene blue solution were taken, and Hg 2+ or Hg 2+ and interfering ions (Na + , K + , Li + , Mg 2+ , Ca 2+ , Pb 2+ , Fe 3+ , Cd 2+ or Cu 2+ ) were added to each of the methylene blue solutions, respectively, to obtain a sample containing single Hg 2+ or a sample containing Hg 2+ and one kind of interfering ion, and the concentration of methylene blue in each sample was 1 mmol / L, the concentration of Hg 2+ was 1 μmol / L, and the concentration of the interfering ion was 10 μmol / L. Methylene blue was dissolved in a PBS buffer solution 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+ were added to obtain a sample containing multiple metal ions, and the concentration of methylene blue in the sample was 1 mmol / L, the concentration of Hg 2+ was 1 μmol / L, and the concentrations of Na + , K + , Li + , Mg 2+ , Ca2+ Pb 2+ Fe 3+ Cd 2+ and Cu 2+ The concentrations were all 10 μmol / L.

[0128] (2) Using XXT-SNM / ITO as the working electrode, a platinum electrode as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode, the working electrode, counter electrode, and reference electrode are combined into a three-electrode system.

[0129] (3) The three-electrode system was placed in a blank sample and a sample containing only Hg, respectively. 2+ The sample containing Hg 2+ The samples were treated with one interfering ion and another containing multiple metal ions, and held for 300 s. Then, the peak current response of methylene blue in each sample was determined by electrochemical voltammetry. A new working electrode was used for each sample, and the working electrode used after each test was the same as the one used previously.

[0130] (4) Calculate the content of Hg alone 2+ The sample containing Hg 2+ The ratio (I / I0) of the peak current response of methylene blue in a sample containing one interfering ion and a sample containing multiple metal ions to the peak current response of methylene blue in a blank sample.

[0131] Figure 11 Figure (b) shows the effect of XXT-SNM / ITO on Hg in the presence of different types of metal ions. 2+ The differential pulse voltammetric response results. When the sample contains only Hg. 2+ At that time, XXT was related to Hg 2+ The specific recognition effect of Hg will cause a significant attenuation of the current peak of methylene blue; when the sample contains Hg 2+ When combined with a 10-fold increase in the amount of an interfering ion, the peak current of methylene blue also shows a significant decrease, and the degree of decrease is similar to that of Hg alone. 2+ The resulting attenuation levels are basically the same; when the sample contains Hg 2+ When subjected to 10 times the amount of various interfering ions, the peak current of methylene blue also showed a significant decrease. This indicates 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 the substance, resulting in corresponding electrochemical signal attenuation, exhibiting good anti-interference and selectivity.

[0132] Example 12

[0133] In this embodiment, the XXT-SNM / ITO prepared in Example 3 was tested for differential pulse voltammetry response to Hg 2+ in the presence of different macromolecular interferents.

[0134] (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 methylene blue solutions were prepared, and Hg 2+ or Hg 2+ and a macromolecular interferent were added to each methylene blue solution, respectively, to obtain a sample containing single Hg 2+ or a sample containing Hg 2+ and a macromolecular interferent. The concentration of methylene blue in each sample was 1 mmol / L, the concentration of Hg 2+ was 200 μg / L, and the concentration of the macromolecular interferent 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 the macromolecular interferent (BSA, HGB, Starch, HA, and CMC) were added to obtain a sample containing Hg 2+ and multiple macromolecular interferents. The concentration of methylene blue in the sample was 1 mmol / L, the concentration of Hg 2+ was 200 μg / L, and the concentration of the macromolecular interferent was 1 mg / L.

[0135] (2) The XXT-SNM / ITO 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 to form a three-electrode system.

[0136] (3) The three-electrode system was placed in the blank sample, the sample containing single Hg 2+ , the sample containing Hg 2+ and a macromolecular interferent, and the sample containing Hg 2+ and multiple macromolecular interferents, respectively, and maintained for 300 s. Then, the peak current response value of methylene blue in each sample was determined by electrochemical voltammetry. A new working electrode was used for each test, and the working electrode after each replacement was the same as the working electrode used before.

[0137] (4) The peak current response value of methylene blue in the sample containing single Hg 2+ , the sample containing Hg 2+ and a macromolecular interferent, and the sample containing Hg 2+The ratio (I / I0) of the peak current response value of methylene blue in the sample with various macromolecular interferents to the peak current response value of methylene blue in the blank sample.

[0138] Figure 11 (c) The figure is the differential pulse voltammetry response results of XXT-SNM / ITO to Hg 2+ in the presence of different macromolecular interferents. When the sample only contains Hg 2+ , the specific recognition of XXT to Hg 2+ will cause a significant attenuation of the current peak of methylene blue; when the sample contains Hg 2+ and one 5-fold macromolecular interferent, the current peak of methylene blue also significantly attenuates, and the attenuation degree is basically the same as that caused by Hg 2+ ; when the sample contains Hg 2+ and multiple 5-fold macromolecular interferents, the current peak of methylene blue also significantly attenuates, and the attenuation degree is basically the same as that caused by Hg 2+ . This shows that XXT-SNM / ITO is basically not interfered when detecting Hg 2+ , which is because the vertical mesoporous silica nanochannel film on XXT-SNM / ITO has a uniform pore size (about 2-3 nm), which can prevent molecules with larger molecular sizes from entering the nanopore to interfere with the detection of Hg 2+ .

[0139] Example 13

[0140] In this embodiment, the preparation method of the mercury ion detection electrochemical sensor is as follows:

[0141] (1) The vertical mesoporous silica nanochannel film is grown on the ITO electrode according to the method in Example 1, and the operation is basically the same as that in Example 1, except that a constant current of -0.85 mA is applied for 10 s. The SNM / ITO prepared in this step has a vertical mesoporous silica nanochannel film with a thickness of about 50 nm, and the nanopore of the vertical mesoporous silica nanochannel film has a pore size of about 2-3 nm.

[0142] (2) The mercury ion detection electrochemical sensor is prepared according to the operation of Example 3, and the operation is basically the same as that in Example 3, except that the concentration of XXT-SiOH in the modification solution is controlled to be 10 mg / mL, and the oscillation reaction is carried out at 50°C with a speed of 80 rpm for 4 h. Then, it is taken out, and the mercury ion detection electrochemical sensor is obtained.

[0143] Example 14

[0144] In this embodiment, the preparation method of the mercury ion detection electrochemical sensor is prepared, and the steps are as follows:

[0145] (1) According to the method of Example 1, the vertical mesoporous silica nanochannel membrane is grown on the ITO electrode, and the operation is basically the same as that of Example 1, except that a constant current of-1 mA is applied for 15 s. The SNM / ITO prepared in this step has a vertical mesoporous silica nanochannel membrane with a thickness of about 100 nm, and the nanochannel on the vertical mesoporous silica nanochannel membrane has a pore size of about 2-3 nm.

[0146] (2) According to the operation of Example 3, the mercury ion detection electrochemical sensor is prepared, and the operation is basically the same as that of Example 3, except that the concentration of XXT-SiOH in the modification solution is controlled to be 20 mg / mL, and the reaction is oscillated at 40 rpm at 30°C for 6 h. Take out, get.

[0147] Example 15

[0148] In this embodiment, the mercury ion detection electrochemical sensor is prepared, and the steps are as follows:

[0149] (1) According to the method of Example 1, the vertical mesoporous silica nanochannel membrane is grown on the fluorine-doped tin oxide electrode, and the operation is basically the same as that of Example 1, except that the oxygen-fluorine-doped tin oxide electrode is used as the working electrode, and a constant potential of-2V is applied for 10 s.

[0150] (2) According to the method in Example 2, the silane coupling agent modified mercury ion recognition molecule with the structure shown in formula (III) is synthesized, and the operation is basically the same as that of Example 1, except that isocyanate propyl triethoxysilane (ICPTES) is replaced by isocyanate propyl trimethoxysilane (IPTS).

[0151] (III)

[0152] (3) According to the operation of Example 3, the mercury ion detection electrochemical sensor is prepared, and the operation is basically the same as that of Example 3, except that the concentration of the silane coupling agent modified mercury ion recognition molecule in the modification solution is controlled to be 30 mg / mL, and the reaction is oscillated at 200 rpm at 10°C for 10 h. Take out, get.

[0153] Example 16

[0154] In this embodiment, the preparation method of the mercury ion detection electrochemical sensor is prepared, and the steps are as follows:

[0155] (1) The vertical mesoporous silica nanochannel membrane was grown on the gold electrode according to the method of Example 1, and 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.

[0156] (2) The mercury ion detection electrochemical sensor was prepared according to the operation of Example 3, and the operation was basically the same as that of Example 3, except that the reaction was oscillated at a speed of 50 rpm at 50°C for 4 h, and then taken out.

[0157] Example 17

[0158] In this example, the preparation method for preparing a mercury ion detection electrochemical sensor is as follows:

[0159] (1) The vertical mesoporous silica nanochannel membrane was grown on the glassy carbon electrode according to the method of Example 1, and 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.

[0160] (2) The mercury ion detection electrochemical sensor was prepared according to the operation of Example 3, and the operation was basically the same as that of Example 3, except that the reaction was oscillated at a speed of 100 rpm at 20°C for 8 h, and then taken out.

[0161] Example 18

[0162] In this example, the preparation method for preparing a mercury ion detection electrochemical sensor is as follows:

[0163] (1) The vertical mesoporous silica nanochannel membrane was grown on the graphite electrode according to the method of Example 1, and 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.

[0164] (2) The mercury ion detection electrochemical sensor was prepared according to the operation of Example 3, and the operation was basically the same as that of Example 3, except that the reaction was oscillated at a speed of 150 rpm at 25°C for 7 h, and then taken out.

Claims

1. An electrochemical sensor for mercury ion detection, characterized in that, The electrochemical sensor consists of a basic electrochemical electrode, a vertically 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 through a silane coupling agent. The mercury ion recognition molecule is 1-(6-(hydroxymethyl)-2,2-dimethyltetrahydrofuran[3,4-d][1,3]dioxane-4-yl)-5-methylpyrimidin-2,4(1H,3H)-dione. This electrochemical sensor is formed by the reaction of a silane coupling agent-modified mercury ion recognition molecule with the nanochannel membrane at the sensing interface of a basic electrochemical electrode. The structure of the silane coupling agent-modified mercury ion recognition molecule is shown in formula (I). (I) In formula (I), the R group is triethoxysilyl or trimethoxysilyl, 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, characterized in that, The reaction that occurs between the silane coupling agent-modified mercury ion recognition molecule and the nanochannel membrane at the sensing interface of the basic electrochemical electrode is a condensation reaction between the silanol group formed by the hydrolysis of the R group of the silane coupling agent-modified mercury ion recognition molecule and the silanol group on the nanochannel membrane.

3. The electrochemical sensor for mercury ion detection according to claim 1, characterized in that, The thickness of the nanochannel membrane is 50~100 nm, and the diameter of the nanochannels in the nanochannel membrane is 2~3 nm.

4. The electrochemical sensor for mercury ion detection according to claim 1, characterized in that, In this 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 electrochemical sensor for mercury ion detection 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. A method for preparing the electrochemical sensor for mercury ion detection according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Deposit vertical mesoporous silica nanochannel membranes on the sensing interface of a basic electrochemical electrode; (2) The mercury ion recognition molecule modified with the silane coupling agent shown in formula (I) is dissolved in an organic solvent to obtain the modified solution; (3) Place the basic electrochemical electrode on which the nanochannel membrane is deposited on the sensing interface in the modification solution, so that the nanochannel membrane is completely immersed in the modification solution, and react fully at 10~50 °C under oscillation conditions. Remove the electrode to obtain the mercury ion detection electrochemical sensor.

7. The method for preparing the electrochemical sensor for mercury ion detection according to claim 6, characterized in that, The concentration of the mercury ion recognition molecule modified with silane coupling agent in the modified 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, Includes the following steps: (1) Using the mercury ion detection electrochemical sensor described in any one of claims 1 to 5 as the working electrode, a platinum electrode as the counter electrode, and a silver / silver chloride electrode as the reference electrode, the working electrode, the counter electrode, and the reference electrode are combined to form a three-electrode system. (2) Place the three-electrode system in the blank sample, maintain ts, and then use electrochemical voltammetry to determine the peak current response value of the electrochemical probe in the blank sample; the blank sample is prepared by electrochemical probe and electrolyte solution; (3) Replace the blank sample in step (2) with a standard sample with known mercury ion concentration in order of increasing mercury ion concentration in the standard sample, repeat the operation of step (2), and measure the peak current response value of the electrochemical probe corresponding to each standard sample respectively; the standard sample is prepared by electrochemical probe, mercury ion and electrolyte solution. (4) Plot the 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 determine the conversion relationship between the logarithm of the mercury ion concentration and the peak current response value. (5) Replace the blank sample in step (2) with the test sample and repeat the operation of step (2). Measure the peak current response value of the electrochemical probe corresponding to the test sample. Calculate the concentration of mercury ions in the test sample according to the conversion formula between the logarithm of the mercury ion concentration and the peak current response value determined in step (4). The test sample is prepared from the test sample, electrochemical probe, and electrolyte solution. The test sample contains mercury ions. In step (2), t is a constant value between 30 and 360 s, and the t value used in steps (2), (3), and (5) is the same; the electrochemical probes used in preparing blank samples, standard samples, and test samples are the same, and the electrolyte solutions used are the same; the pH values ​​of blank samples, standard samples, and test samples are the same, all between 4 and 8; the concentrations of electrochemical probes in blank samples, standard samples, and test samples are the same; in step (5), before testing each test sample, a mercury ion detection electrochemical sensor that does not bind mercury ions is replaced, and the mercury ion detection electrochemical sensors used in steps (2), (3), and (5) are 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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