Electrochemical sensor constructed based on composite material as well as preparation method and application of electrochemical sensor

Abstract

The invention discloses an electrochemical sensor constructed based on a composite material and a preparation method and application thereof.The electrochemical sensor comprises a screen-printed electrode, the surface of the reaction end of a working electrode of the screen-printed electrode is loaded with a zirconium-based metal organic framework composite material, the composite material comprises UiO-66, and the surface of the composite material is modified with a polydopamine coating. The preparation method comprises the following steps: preparing the zirconium-based metal organic framework composite material and fixing the composite material on the working electrode of the screen-printed electrode. According to the invention, the zirconium-based metal organic framework composite material with many adsorption sites, good dispersibility, good conductivity and good hydrophilicity is used as a functional material, so that the sensor has the advantages of simple operation, low cost, rapid response, strong anti-interference capability, wide detection linear range, high detection sensitivity, long service life and the like, and can be widely used for detecting Mn < 2 + >, Mn < 2 + >, Mn < 2 + >, Mn < 2 + > and Mn < 2 + > in a water body. The method can realize rapid and accurate detection of Mn < 2 + > in a water body, and is high in use value and good in application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical sensing technology, and relates to an electrochemical sensor for heavy metal manganese ions in the environment, a preparation method thereof, and a use method thereof, and specifically relates to an electrochemical sensor constructed based on a composite material, a preparation method thereof, and an application thereof. Background Art

[0002] The severity of manganese (Mn) pollution in water is primarily manifested in health risks, water quality degradation, ecosystem impacts, and persistent accumulation. For example, long-term exposure to high concentrations of manganese can cause neurological dysfunction and affect the cognitive and intellectual development of infants and children. High manganese levels inhibit the growth and reproduction of aquatic organisms, resulting in adverse ecosystem impacts such as reduced species diversity, disrupted ecosystem chains, and degraded ecological functions. Manganese is persistent and cumulative, making it difficult to remove once it enters water bodies, exacerbating the pollution problem. Therefore, to mitigate manganese pollution in water, enhanced monitoring of manganese ions in water is necessary.

[0003] Traditional methods for detecting heavy metal ions include inductively coupled plasma mass spectrometry, atomic absorption spectrometry, X-ray fluorescence spectrometry and atomic emission spectrometry, but these methods have defects such as complexity, time-consuming and expensive, making them difficult to use on a large scale for detecting manganese ions in water bodies. Unlike them, electrochemical methods have the characteristics of low cost, short response time and simple detection process, and can be widely used to detect heavy metal ions in water bodies. However, traditional electrochemical methods mainly use glassy carbon electrodes as working electrodes to construct electrochemical sensors, which have defects such as complex electrode pretreatment, large sensor size and difficulty in portability, making them difficult to use on a large scale and having poor application prospects. Therefore, obtaining an electrochemical sensor that is simple to operate, low cost, fast in response, strong in anti-interference ability, wide linear detection range, high detection sensitivity and long service life will play an important role in promoting the rapid and accurate detection of manganese pollution sources in water bodies, especially high-concentration manganese pollution sources.

[0004] Compared with traditional electrochemical sensors based on glassy carbon electrodes, electrochemical sensors constructed with screen-printed electrodes (SPE) do not require pretreatment, are easy to use, and are low-cost, showing better application prospects. However, due to the poor electrochemical performance of screen-printed electrodes, it is difficult for electrochemical sensors to accurately detect heavy metals in water. To this end, existing researchers have proposed to deposit functional materials on the surface of screen-printed electrodes to improve the electrochemical performance of the electrodes. However, these functional materials deposited on the surface of screen-printed electrodes have defects such as small specific surface area, few active sites, easy agglomeration, and poor stability. As a result, the electrochemical sensors constructed in this way still have defects such as small detection linear range, long detection time, and low sensitivity when used to detect heavy metal ions. It is still difficult to obtain more accurate heavy metal concentration data. In particular, when the concentration of heavy metals in water is high, existing electrochemical sensors are not applicable. For example, when cyclic bismuth tungstate materials are loaded on the surface of screen-printed carbon electrodes, the bismuth tungstate materials still have defects such as easy agglomeration, small surface area, few active sites, and poor stability. When used to detect lead ions and cadmium ions in water, the detection linear range is 2ppb-100ppb, and the current response value is less than 90μA. There are still defects such as small detection linear range, long detection time, and low sensitivity, and it cannot be used to detect high-concentration heavy metal wastewater. In addition, UiO-66, as a metal-organic framework (MOFs) material, is an attractive material for electrochemical sensing due to its high surface area, porosity, large pore volume, and open metal sites. However, UiO-66 has shortcomings such as few adsorption sites, easy agglomeration, poor conductivity, and non-hydrophilicity. Therefore, when it is used as a functional material to construct an electrochemical sensor, it still has defects such as a small detection linear range, slow response speed, poor detection sensitivity, and poor detection accuracy. Therefore, it is still difficult to achieve rapid and accurate detection of manganese ions in water. Therefore, how to overcome the above technical defects and obtain a functional material with multiple adsorption sites, good dispersibility, good conductivity and good hydrophilicity is of great significance for promoting the widespread use of electrochemical sensors in heavy metal ions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide an electrochemical sensor based on composite materials, which is simple to operate, low in cost, quick in response, strong in anti-interference ability, wide in detection linear range, high in detection sensitivity and long in service life, as well as its preparation method and application.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] An electrochemical sensor constructed based on a composite material, the electrochemical sensor comprising a screen-printed electrode, the screen-printed electrode comprising a working electrode, the reaction end surface of the working electrode being loaded with a zirconium-based metal-organic framework composite material; the zirconium-based metal-organic framework composite material comprising a zirconium-based metal-organic framework, the surface of the zirconium-based metal-organic framework being modified with a polydopamine coating; the thickness of the polydopamine coating being nanometer-scale; the zirconium-based metal-organic framework being UiO-66.

[0008] As a general technical concept, the present invention also provides a method for preparing an electrochemical sensor based on a composite material, comprising the following steps:

[0009] S1. Preparation of zirconium-based metal-organic frameworks;

[0010] S2, dispersing the zirconium-based metal-organic framework into an aqueous solution, adding a dopamine aqueous solution, and stirring to obtain a zirconium-based metal-organic framework composite material;

[0011] S3, dispersing the zirconium-based metal-organic framework composite material into a mixed solution of naphthol and ethanol, and ultrasonicating to obtain a mixed solution;

[0012] S4. Drop the mixed solution on the working electrode of the screen-printed electrode and dry it to obtain the screen-printed electrode for constructing the electrochemical sensor.

[0013] The above preparation method is further improved in that in step S2, the mass ratio of the zirconium-based metal-organic framework to the dopamine in the dopamine aqueous solution is 1:1-3.

[0014] The above preparation method is further improved in that in step S2, the stirring time is 30 minutes.

[0015] The above preparation method is further improved in that in step S3, the ultrasonic time is 30 minutes.

[0016] The above preparation method is further improved in that in step S4, the drying is performed at a temperature of 60°C.

[0017] The above preparation method is further improved. In step S1, the zirconium-based metal-organic framework is UiO-66, and the preparation method of the zirconium-based metal-organic framework comprises the following steps: dispersing zirconium chloride and terephthalic acid in N,N-dimethylformamide, adding ethanol, and stirring until completely dissolved to obtain a precursor solution; placing the precursor solution in a reactor and maintaining it at 100°C to 150°C for 18h to 24h to obtain a zirconium-based metal-organic framework; the mass ratio of the terephthalic acid to the zirconium chloride is 1 to 1:2; the volume ratio of the ethanol to the N,N-dimethylformamide is 1:1 to 2.

[0018] The above preparation method is further improved. In step S4, the screen-printed electrode for constructing the electrochemical sensor includes a working electrode, and the reaction end surface of the working electrode is loaded with a zirconium-based metal-organic framework composite material; the zirconium-based metal-organic framework composite material includes a zirconium-based metal-organic framework, and the surface of the zirconium-based metal-organic framework is modified with a polydopamine coating; the thickness of the polydopamine coating is nanometer-scale; the zirconium-based metal-organic framework is UiO-66.

[0019] As a general technical concept, the present invention also provides an application of the above electrochemical sensor or the electrochemical sensor prepared by the above preparation method in detecting divalent manganese ions in water.

[0020] The above application is further improved, and the application includes the following steps:

[0021] (1) mixing water containing divalent manganese ions to be tested with acetic acid-sodium acetate buffer to obtain a sample to be tested;

[0022] (2) placing the sample to be tested on the surface of the working electrode for reaction and measuring the peak current of the sample to be tested;

[0023] (3) According to the peak current of the sample to be tested, the concentration of divalent manganese ions in the sample to be tested is calculated by combining the linear regression equation of the divalent manganese ion concentration and the peak current.

[0024] The above application is further improved, in step (3), the linear regression equation of the divalent manganese ion concentration and the peak current is shown in formula (1) or formula (2):

[0025] y= 0.017×x- 0.0624 (1),

[0026] In formula (1), y is the peak current of the solution to be tested, in μA; x is the Mn 2+ The concentration value is in ppb; the linear range of detection is 4 ppb to 100 ppb; the detection limit is 0.71 ppb; the correlation coefficient R 2 =0.9972;

[0027] y= 8.125×x+1.2854 (2),

[0028] In formula (2), y is the peak current of the solution to be tested, in μA; x is the Mn 2+ The concentration value is in ppm; the detection linear range is 0.1ppm to 1ppm; the correlation coefficient R 2 =0.9903.

[0029] The above application is further improved in that, in step (1), the concentration of the acetic acid-sodium acetate buffer solution is 0.1M to 0.2M.

[0030] The above application is further improved in that, in step (2), the reaction time is 100s to 400s; and the voltage is controlled at 0.5V during the reaction.

[0031] In the present invention, the unit M refers to mol / L.

[0032] Compared with the prior art, the advantages of the present invention are:

[0033] In response to the shortcomings of existing electrochemical sensors' working electrodes, such as few adsorption sites, easy agglomeration, and poor water stability, as well as the resulting defects of electrochemical sensors such as a small detection linear range, slow response speed, poor detection sensitivity, poor detection accuracy, and short service life, the present invention creatively proposes an electrochemical sensor constructed based on a composite material, including a screen-printed electrode, the screen-printed electrode including a working electrode, and a zirconium-based metal-organic framework composite material loaded on the reaction end surface of the working electrode, wherein the zirconium-based metal-organic framework composite material includes a zirconium-based metal-organic framework, the surface of the zirconium-based metal-organic framework is modified with a polydopamine coating, the thickness of the polydopamine coating is nanometer-scale, and the zirconium-based metal-organic framework is UiO-66. In the present invention, a nanometer-thick polydopamine coating is modified on the surface of UiO-66. On the one hand, since the thickness of the polydopamine coating is nanometer-thick, the original octahedral structure of UiO-66 can be maintained, thereby retaining its high specific surface area, porosity, large pore volume, and the number of open metal sites. On the other hand, since PDA contains rich amine and catechol functional groups, after the PDA coating is formed on the surface of UiO-66, the water stability of UiO-66 can be enhanced and its conductivity, hydrophilicity and manganese ion adsorption capacity can be improved, such as UiO-66@PDA adsorption of Mn 2+ The ability is stronger than that of UiO-66, which overcomes the problem of screen-printed electrodes directly detecting low concentrations of Mn in water. 2+ The problem of Mn 2+ The adsorption capacity of the screen-printed electrode is conducive to the adsorption of high concentration Mn 2+ Accurate detection of UiO-66 is possible. In particular, the significantly enhanced water stability of UiO-66 allows the screen-printed electrode to be stored for a long time, and the measurement error after 30 days is very small, overcoming the problem of long-term storage of electrochemical sensors. More importantly, the polydopamine coating is modified on the surface of UiO-66, making the surface of the zirconium-based metal-organic framework composite material have abundant active sites, showing stronger electrochemical activity, and the effect of Mn 2+The electrochemical detection has the characteristics of high sensitivity and rapid response. On this basis, in the present invention, UiO-66 with a surface modified with polydopamine coating is loaded on the working electrode surface of the screen-printed electrode to construct an electrochemical sensor. The electrochemical sensor can use the square wave voltammetry (SWV) of the electrochemical workstation to perform cathode stripping voltammetry (CSV) test, and can complete the detection of Mn under the action of an external power supply. 2+ Deposition and stripping, such as the deposition stage can be Mn 2+ Oxidation to Mn 4+ , a layer of MnO2 is formed on the surface of the working electrode, and the Mn 4+ Reduced to Mn 2+ Leave the electrode, especially when the system contains Mn 2+ When Mn is present, the sample shows a peak value at a voltage of 0.5 V after the reaction, and the peak current increases with the increase of Mn 2+ The concentration of Mn increases, so it can be established 2+ The linear relationship between the concentration and the peak current is detected, and the Mn content in the sample to be tested is calculated based on the linear regression equation. 2+ concentration, and finally the Mn 2+ Compared with conventional electrochemical sensors, the electrochemical sensor constructed based on the composite material of the present invention has the following advantages: (a) wide linear detection range, which can be used to detect Mn with a concentration of 1ppb-1ppm 2+ ; (b) High sensitivity to Mn 2+ (c) Rapid response, capable of detecting low concentrations of Mn in water within 100 seconds. 2+ ; (d) long service life, with very small error in the measurement results after storage for 30 days; (e) has the advantages of simple operation, low cost, miniaturization and portability. The electrochemical sensor constructed based on the composite material of the present invention has the advantages of simple operation, low cost, rapid response, strong anti-interference ability, wide detection linear range, high detection sensitivity and long service life. It is a new type of electrochemical sensor with excellent performance and can be widely used, and can be widely used to detect Mn in water. 2+ , which can realize the 2+ It has fast and accurate detection, high use value and good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0035] Figure 1 This is an SEM image of the zirconium-based metal-organic framework (UiO-66) prepared in Example 1 of the present invention.

[0036] Figure 2 This is an SEM image of the zirconium-based metal-organic framework composite material (UiO-66@PDA) prepared in Example 1 of the present invention.

[0037] Figure 3 The electrochemical sensor constructed in Example 1 of the present invention is Mn 2+ The linear fitting standard curve corresponding to the concentration range of 4 ppb to 100 ppb.

[0038] Figure 4 The electrochemical sensor constructed in Example 1 of the present invention is Mn 2+ The linear fitting standard curve corresponding to the concentration range of 0.1ppm to 1ppm. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0040] Example 1

[0041] An electrochemical sensor constructed based on a composite material includes a screen-printed electrode, the screen-printed electrode includes a working electrode, the reaction end surface of the working electrode is loaded with a zirconium-based metal-organic framework composite material, the zirconium-based metal-organic framework composite material includes a zirconium-based metal-organic framework, the surface of the zirconium-based metal-organic framework is modified with a polydopamine coating, the thickness of the polydopamine coating is nanometer-scale, with a thickness of 10 nm, and the zirconium-based metal-organic framework is UiO-66.

[0042] A method for preparing an electrochemical sensor based on a composite material comprises the following steps:

[0043] S1. Prepare a zirconium-based metal organic framework, wherein the zirconium-based metal organic framework is UiO-66, and its preparation process is as follows:

[0044] According to the mass ratio of terephthalic acid to zirconium chloride of 1:2 and the volume ratio of ethanol to N,N-dimethylformamide of 1:2, zirconium chloride and terephthalic acid are dispersed in N,N-dimethylformamide (DMF), ethanol is added, and stirred until completely dissolved to obtain a precursor solution; the precursor solution is placed in the lining of a reactor and maintained at 120°C for 24 hours to obtain a zirconium-based metal-organic framework, namely UiO-66.

[0045] Figure 1 This is a SEM image of the zirconium-based metal organic framework (UiO-66) prepared in Example 1 of the present invention. Figure 1 It can be seen that the shape of UiO-66 is a regular octahedron, indicating that UiO-66 was successfully prepared.

[0046] S2. According to the mass ratio of the zirconium-based metal-organic framework to dopamine in the dopamine aqueous solution of 1:1, the zirconium-based metal-organic framework is dispersed in the aqueous solution, and a dopamine aqueous solution with a concentration of 1 mg / mL is added. The mixture is stirred at room temperature for 6 hours, and a nanometer-thick polydopamine coating is modified on the surface of the zirconium-based metal-organic framework. The mixture is filtered and dried to obtain a zirconium-based metal-organic framework composite material, namely UiO-66@PDA.

[0047] Figure 2 This is a SEM image of the zirconium-based metal organic framework composite material (UiO-66@PDA) prepared in Example 1 of the present invention. Figure 2 It can be seen that UiO-66@PDA maintains a regular octahedral structure and has a smooth PDA coating on the surface, indicating that UiO-66@PDA was successfully prepared.

[0048] S3, zirconium-based metal organic framework composite material is scattered in the mixed solution of naphthol and ethanol, ultrasonic 30min, obtains mixed solution, and in this mixed solution, the concentration of zirconium-based metal organic framework composite material is 2mg / mL.In this step, the naphthol adopted and the mixed solution of ethanol are prepared after mixing by naphthol and ethanol, and in the mixed solution of this naphthol and ethanol, the mass fraction of naphthol is 0.5%.In this step, under the effect of naphthol, zirconium-based metal organic framework composite material can be stably adhered to the surface of electrode, be conducive to improving the stability of electrode, but, when the concentration of naphthol in mixed solution is too high, zirconium-based metal organic framework composite material can be caused to reunite, thus be difficult to be dispersed in electrode surface, and when concentration is too low, zirconium-based metal organic framework composite material can be caused to stably load in electrode surface.

[0049] S4. Drop 5 μL of the mixed solution prepared in step S3 on the working electrode of the screen-printed electrode, and dry it at a temperature of 60° C. to obtain a screen-printed electrode for constructing an electrochemical sensor.

[0050] In the present invention, the working electrode, the counter electrode and the calomel electrode of the screen-printed electrode are connected to an electrochemical workstation respectively to construct an electrochemical sensor.

[0051] An application of the electrochemical sensor constructed based on the composite material in the present embodiment for detecting divalent manganese ions in water comprises the following steps:

[0052] (1) Mix the water containing divalent manganese ions to be tested with 0.1M acetic acid-sodium acetate buffer to obtain a sample to be tested.

[0053] (2) The sample to be tested is placed on the surface of the working electrode for a reaction time of 100 s. The peak current of the sample to be tested is measured. Specifically, a cathode glass voltammetry (CSV) test is performed using square wave voltammetry (SWV) to record the peak current I of the sample to be tested at a voltage of 0.5 V after the reaction.

[0054] (3) According to the peak current of the sample to be tested, the concentration of divalent manganese ions in the sample to be tested is calculated by combining the linear regression equation of the divalent manganese ion concentration and the peak current.

[0055] In this embodiment, in step (3), the linear regression equation of the divalent manganese ion concentration and the peak current is shown in formula (1) or formula (2):

[0056] y= 0.017×x- 0.0624 (1),

[0057] In formula (1), y is the peak current of the solution to be tested, in μA; x is the Mn 2+ The concentration value is in ppb; the linear range of detection is 4 ppb to 100 ppb; the detection limit is 0.71 ppb; the correlation coefficient R 2 =0.9972;

[0058] y= 8.125×x+1.2854 (2),

[0059] In formula (2), y is the peak current of the solution to be tested, in μA; x is the Mn 2+ The concentration value is in ppm; the detection linear range is 0.1ppm to 1ppm; the correlation coefficient R 2 =0.9903.

[0060] In this embodiment, the method for constructing a linear regression equation of divalent manganese ion concentration and peak current includes the following steps:

[0061] (a) Using different concentrations of divalent manganese ion standard solutions mixed with 0.1M acetic acid-sodium acetate buffer, different concentrations of test samples were obtained. The divalent manganese ion (Mn 2+ ) concentrations are 4ppb, 6ppb, 8ppb, 10ppb, 20ppb, 30ppb, 40ppb, 60ppb, 80ppb, 100ppb, 0.15ppm, 0.2ppm, 0.4ppm, 0.6ppm, 0.8ppm, and 1ppm, respectively.

[0062] (b) Different test samples were placed on the working electrode surface for a reaction time of 100 s. The peak current of each test sample was measured by cathode glass voltammetry (CSV) testing using square wave voltammetry (SWV). The peak current I of each test sample at a voltage of 0.5 V after the reaction was recorded. The results showed that the peak currents I corresponding to 4ppb, 6ppb, 8ppb, 10ppb, 20ppb, 30ppb, 40ppb, 60ppb, 80ppb, 100ppb, 0.15ppm, 0.2ppm, 0.4ppm, 0.6ppm, 0.8ppm, and 1ppm were 0.03252μA, 0.05352μA, 0.08909μA, 0.12857μA, 0.24107μA, 0.554μA, 0.94257μA, 1.307μA, 1.66767μA, 2.39033μA, 3.062μA, 3.93533μA, 4.668μA, 6.51μA, 7.75μA, and 9.13867μA, respectively.

[0063] (c) Based on the peak current I of different samples, a linear relationship between divalent manganese ion concentration and peak current was established, and a linear regression equation between divalent manganese ion concentration and peak current was obtained. The results are shown in Figure 2. Figure 3 and Figure 4 shown.

[0064] Figure 3 The electrochemical sensor constructed in Example 1 of the present invention is Mn 2+ The linear fitting standard curve corresponding to the concentration range of 4 ppb to 100 ppb.

[0065] Figure 4 The electrochemical sensor constructed in Example 1 of the present invention is Mn 2+ The linear fitting standard curve corresponding to the concentration range of 0.1ppm to 1ppm.

[0066] Depend on Figure 3 and Figure 4 It can be seen that the electrochemical sensor constructed by the present invention is used to detect Mn 2+ The corresponding detection linear range is 4ppb to 1000ppb, and the detection limit is lower than 1ppb, which is far lower than the international standard of 50ppb.

[0067] An application of the electrochemical sensor prepared in the above embodiment of the present invention in detecting divalent manganese ions in water, specifically using the electrochemical sensor constructed in Example 1 to detect divalent manganese ions in surface water, wherein the concentration of divalent manganese ions in the surface water is 11 ppb.

[0068] Control group: The electrochemical sensor constructed with UiO-66 without polydopamine coating was used instead of the electrochemical sensor constructed based on the zirconium-based metal-organic framework composite material (UiO-66@PDA) in Example 1, and other conditions were the same.

[0069] After testing, the detection accuracy of the electrochemical sensor constructed based on the zirconium-based metal-organic framework composite material (UiO-66@PDA) was 89%, while the electrochemical sensor constructed based on UiO-66 without polydopamine coating was unable to detect.

[0070] From the above results, it can be seen that the electrochemical sensor based on the composite material of the present invention, when used to detect heavy metal manganese ions, can quantitatively detect the concentration of manganese ions in water with high sensitivity.

[0071] Stability assessment

[0072] To evaluate the stability of the electrochemical sensor in Example 1, a batch of electrodes was prepared and the sensor was used to detect the addition of 100 ppb Mn to blank drinking water every 5 days. 2+ The peak current of each sensor was measured three times, using the same testing method as in Example 1. After 5, 10, 15, 20, 25, and 30 days of storage, the average current values of the sensors were 1.45517 μA, 1.457 μA, 1.474 μA, 1.44 μA, 1.57233 μA, and 1.46167 μA, respectively. This indicates that the response current of the sensors of the present invention remained essentially unchanged after 30 days of storage, demonstrating the excellent stability of the sensors of the present invention.

[0073] Anti-interference capability assessment

[0074] To evaluate the stability of the electrochemical sensor in Example 1, a batch of electrodes were prepared and some possible interfering metal ions were added to the reaction system. Specifically, Cu 2+ was added to the solution with a concentration of 100 ppb. 2+ 、zn 2+ 、pb 2+ 、Co 2+ , their concentrations are higher than Mn 2+ The detection method is the same as that in Example 1. After testing, when no interfering ions are added, the corresponding current data average value is 1.45517μA, while when Cu is added 2+ 、zn 2+ 、pb 2+ 、Co 2+ After that, the corresponding average current data are 1.588μA, 1.45333μA, 1.49967μA, and 1.41167μA. Through comparison, it can be seen that even in the presence of interference from heavy metal ions, these sensors can still provide more than 90% accurate results.

[0075] Comparison of detection capabilities

[0076] The detection capability of the electrochemical sensor in Example 1 was evaluated and compared with electrodes reported in the literature, as shown in Table 1. As shown in Table 1, the electrochemical sensor constructed based on UiO-66@PDA and screen-printed electrodes in the present invention has the widest detection linear range (4 ppb-1000 ppb) and the lowest detection limit (0.71 ppb).

[0077] Table 1 Comparison of detection effects of different electrode materials

[0078] electrode Linear range (ppb) Deposition time (s) Detection limit (ppb) Boron-doped diamond electrode (BDD) 2.2-9.5 120 0.49 Screen Printed Electrodes (SPE) 5-98 30 3.52 Screen Printed Electrodes (SPE) 4-28 120 3.47 CNTS 33-369 60 5.12 Pd 25-600 600 18.37 Pt 5-50 900 0.9 Glassy carbon electrode (GC) 2.5-200 240 0.63 Pt 5-100 900 0.56 The present invention (UiO-66@PDA) 4-1000 100 0.71

[0079] From the above results, it can be seen that compared with conventional electrochemical sensors, the electrochemical sensor constructed based on the composite material of the present invention has the following advantages: (a) The detection linear range is wide and can be used to detect Mn with a concentration of 1ppb-1ppm. 2+ ; (b) High sensitivity to Mn 2+ (c) Rapid response, capable of detecting low concentrations of Mn in water within 100 seconds. 2+ (d) long service life, with very little error in the measurement results after 30 days of storage; (e) simple operation, low cost, miniaturization, and portability. Therefore, the electrochemical sensor constructed based on the composite material of the present invention has the advantages of simple operation, low cost, rapid response, strong anti-interference ability, wide detection linear range, high detection sensitivity, and long service life. It is a new type of electrochemical sensor with excellent performance and can be widely used, and can be widely used to detect Mn in water. 2+ , which can realize the 2+ It has fast and accurate detection, high use value and good application prospects.

[0080] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of protection of the present invention are within the scope of protection of the present invention. It should be noted that improvements and modifications that can be made by a person skilled in the art without departing from the principles of the present invention are also considered to be within the scope of protection of the present invention.

Claims

1. An electrochemical sensor constructed based on a composite material, the electrochemical sensor comprising a screen-printed electrode, the screen-printed electrode comprising a working electrode, characterized in that: The reaction end surface of the working electrode is loaded with a zirconium-based metal-organic framework composite material; the zirconium-based metal-organic framework composite material includes a zirconium-based metal-organic framework, and the surface of the zirconium-based metal-organic framework is modified with a polydopamine coating; the thickness of the polydopamine coating is nanometer-scale; the zirconium-based metal-organic framework is UiO-66.

2. A method for preparing an electrochemical sensor based on a composite material, characterized in that: The following steps are involved: S1. Preparation of zirconium-based metal-organic frameworks; S2, dispersing the zirconium-based metal-organic framework into an aqueous solution, adding a dopamine aqueous solution, and stirring to obtain a zirconium-based metal-organic framework composite material; S3, dispersing the zirconium-based metal-organic framework composite material into a mixed solution of naphthol and ethanol, and ultrasonicating to obtain a mixed solution; S4. Drop the mixed solution on the working electrode of the screen-printed electrode and dry it to obtain the screen-printed electrode for constructing the electrochemical sensor.

3. The preparation method according to claim 2, characterized in that In step S2, the mass ratio of the zirconium-based metal-organic framework to the dopamine in the dopamine aqueous solution is 1:1-3.

4. The preparation method according to claim 3, characterized in that In step S2, the stirring time is 30 min; In step S3, the ultrasonication time is 30 min; In step S4, the drying is performed at a temperature of 60°C.

5. The preparation method according to any one of claims 2 to 4, characterized in that In step S1, the zirconium-based metal-organic framework is UiO-66, and the preparation method of the zirconium-based metal-organic framework includes the following steps: dispersing zirconium chloride and terephthalic acid in N,N-dimethylformamide, adding ethanol, and stirring until completely dissolved to obtain a precursor solution; placing the precursor solution in a reactor and maintaining it at 100°C to 150°C for 18h to 24h to obtain a zirconium-based metal-organic framework; the mass ratio of the terephthalic acid to the zirconium chloride is 1 to 1:2; the volume ratio of the ethanol to the N,N-dimethylformamide is 1:1 to 2.

6. The preparation method according to any one of claims 2 to 4, characterized in that In step S4, the screen-printed electrode for constructing the electrochemical sensor includes a working electrode, and the reaction end surface of the working electrode is loaded with a zirconium-based metal-organic framework composite material; The zirconium-based metal-organic framework composite material comprises a zirconium-based metal-organic framework, the surface of the zirconium-based metal-organic framework is modified with a polydopamine coating; the thickness of the polydopamine coating is nanometer level; the zirconium-based metal-organic framework is UiO-66.

7. Use of the electrochemical sensor according to claim 1 or the electrochemical sensor prepared by the preparation method according to any one of claims 2 to 6 in detecting divalent manganese ions in water.

8. The use according to claim 7, characterized in that The application comprises the following steps: (1) mixing water containing divalent manganese ions to be tested with acetic acid-sodium acetate buffer to obtain a sample to be tested; (2) placing the sample to be tested on the surface of the working electrode for reaction and measuring the peak current of the sample to be tested; (3) According to the peak current of the sample to be tested, the concentration of divalent manganese ions in the sample to be tested is calculated by combining the linear regression equation of the divalent manganese ion concentration and the peak current.

9. The use according to claim 8, characterized in that In step (3), the linear regression equation of the divalent manganese ion concentration and the peak current is shown in formula (1) or formula (2): y= 0.017×x- 0.0624 (1), In formula (1), y is the peak current of the solution to be tested, in μA; x is the Mn 2+ The concentration value is in ppb; the linear range of detection is 4 ppb to 100 ppb; the detection limit is 0.71 ppb; the correlation coefficient R 2 =0.9972; y= 8.125×x+1.2854 (2), In formula (2), y is the peak current of the solution to be tested, in μA; x is the Mn 2+ The concentration value, in ppm; The linear range of detection is 0.1ppm~1ppm; the correlation coefficient R 2 =0.9903.

10. The use according to claim 8 or 9, characterized in that: In step (1), the concentration of the acetic acid-sodium acetate buffer is 0.1M to 0.2M; In step (2), the reaction time is 100s to 400s; and the control voltage during the reaction is 0.5V.

Images