Electrochemical sensor based on monatomic catalyst as well as preparation method and application of electrochemical sensor

Abstract

The invention discloses an electrochemical sensor based on a monatomic catalyst and a preparation method and application thereof, and belongs to the technical field of electrochemical sensing. According to the electrochemical sensor based on the monatomic catalyst, the monatomic catalyst is dispensed on the surface of the working electrode, and the electrochemical sensor capable of detecting two bisphenol pollutants at the same time is prepared. The monatomic catalyst provided by the invention has a very large specific surface area, good conductivity and abundant catalytic active sites. The electrochemical sensor has the advantages of being simple in preparation process, low in cost, high in sensitivity, good in reproducibility and storage stability and the like, and a powerful tool is provided for sensitive and specific detection of bisphenol pollutants in the environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensors, and particularly relates to an electrochemical sensor based on a single-atom catalyst, a preparation method thereof, and an application thereof in the detection of bisphenol pollutants in the environment. Background Art

[0002] Endocrine disruptors are a class of exogenous chemical substances that are widely present in the environment and have endocrine disrupting effects. They can mimic the behavior of hormones in organisms, bind to hormone receptors, and interfere with processes such as the synthesis, transport, metabolism, and response of endogenous hormones. Long-term exposure to endocrine disruptors will affect the stability of the microenvironment in organisms and cause various diseases. Bisphenol compounds and their derivatives, as a typical endocrine disruptor, are widely used in the industrial production field. The phenolic wastewater discharged during the production process is enriched through the cycle of the ecosystem and the decomposition of other microorganisms, and is often detected in the environment. It accumulates in the environment and the ecological chain through the ingestion of wild animals and the absorption of plants, causing great harm to human health. At present, the methods for detecting bisphenol pollutants mainly include high-performance liquid chromatography, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, capillary electrophoresis, and spectroscopy. Although these traditional detection methods have high sensitivity and accuracy, they still have the disadvantages of complex and time-consuming sample pretreatment, large volume and high cost of instrument equipment, high technical requirements for operators, and large consumption of reagents. Therefore, there is an urgent need to develop a new method that can simply, quickly, and efficiently quantitatively detect bisphenol pollutants to help us monitor the environmental pollution status in real time.

[0003] Electrochemical sensors have the advantages of high sensitivity, good selectivity, and simple operation, and are widely used in the detection of environmental pollutants. In addition, their sample pretreatment is simple, the cost is low, and they are easy to miniaturize, which is suitable for on-site detection and continuous online monitoring.

[0004] To further improve the detection performance of electrochemical sensors, the selection of electrode modification materials is crucial. In recent years, single-atom catalysts (SACs) have received increasing attention due to their special structures, which exhibit significantly different activities, stabilities, and selectivities from conventional nanocatalysts. A single-atom catalyst refers to a catalyst in which active metal components are dispersed on a support in the form of single atoms, and there are no metal-metal bonds between the same atoms. The surface free energy and specific activity of nanomaterials increase sharply with the decrease in particle size. Therefore, single-atom catalysts have many unique advantages. For example, metal elements are dispersed on the substrate material at the atomic level, fully exposing all active sites, which is beneficial to improving the activity of the catalyst and achieving the highest atomic utilization rate. Individual metal atoms with extremely high surface free energy and high activity may cause quantum size effects. In addition, the special interaction between metal atoms and the substrate may promote charge transfer or provide an unsaturated coordination environment for metal atoms, which is conducive to improving catalytic activity and selectivity. Typical SACs are mainly dispersed on oxides, sulfides, carbon-based materials, or metal supports. Nowadays, single-atom catalysts have become a research hotspot in various fields due to their unique advantages and have been widely applied in a series of redox reaction systems, such as CO oxidation, CO 2 reduction, oxygen reduction reaction (ORR), selective hydrogenation, photocatalysts, water splitting, etc.

[0005] In electrochemical sensors, by using potential-resolved voltammetric detection and taking advantage of the different response peak potentials and peak currents of the phenolic hydroxyl functional groups of different bisphenols on the nanosensor, not only can the identification of target bisphenols be achieved, but also the rapid, low-cost, and highly sensitive quantitative detection of bisphenol S and bisphenol AF can be realized simultaneously by potential-resolved voltammetry. Bisphenol S and bisphenol AF are relatively common bisphenol compounds, and their individual quantitative detection can be achieved by traditional electrochemical sensors. However, their oxidation-reduction potentials are very close. When the sample to be measured contains both bisphenol S and bisphenol AF at the same time, ordinary electrodes cannot achieve the simultaneous accurate quantification of the two. By modifying the working electrode, the two can be separated to achieve the simultaneous quantitative detection of bisphenol S and bisphenol AF. At present, there are relatively few relevant reports at home and abroad on the application of single-atom catalysts in electrochemical sensors for the simultaneous detection of two bisphenol pollutants. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide an electrochemical sensor based on a single-atom catalyst, a preparation method thereof, and an application thereof in simply, rapidly and efficiently detecting BPS and BPAF in the environment. The single-atom catalyst on the electrochemical sensor of the present invention is formed by loading a large number of isolated Cu on graphene to form numerous catalytic active sites. Based on the high specific surface area and good conductivity of the single-atom catalyst, it is not only conducive to the large-scale loading of active sites, but also conducive to the diffusion and mass transfer of electroactive substances. At the same time, it can also improve the conductivity of the electrode and increase the current signal. The electrochemical sensor of the present invention has the advantages of high sensitivity, low detection limit, high selectivity, low cost, short time consumption, and simple and convenient preparation method, and can be used for on-site detection of BPS and BPAF.

[0007] The object of the present invention is achieved in the following way:

[0008] The present invention provides a preparation method of an electrochemical sensor based on a single-atom catalyst, which mainly includes the following steps:

[0009] (1) Ultrasonically disperse the single-atom catalyst into the aqueous phase to obtain a dispersion system, and the concentration of the dispersion system is 0.1-5 mg / mL;

[0010] (2) Add the film-forming material to the dispersion system and mix evenly to obtain a mixed solution, and the concentration of the film-forming material in the mixed solution is 0.05-3 mg / mL;

[0011] (3) Drop the mixed solution onto the surface of the modified electrode, and let it stand and dry at room temperature to obtain the electrochemical sensor.

[0012] Further, in step (1), the metal active center of the single-atom catalyst is partially or completely dispersed on the nitrogen-doped carbon material in the form of isolated single atoms, the metal includes Cu, and the loading amount of the metal is 0.1-10 wt%, preferably 1-3 wt%.

[0013] Further, the preparation of the single-atom catalyst mainly includes the following steps:

[0014] 1) Dissolve melamine and glucose in a solution containing CuCl 2 and stir evenly at room temperature;

[0015] 2) Transfer the solution of step 1) to a reaction kettle and react at 150-200 °C for 22-26 h;

[0016] 3) After drying the product obtained from the reaction in step 2), calcine it at 700-900 °C for 3-5 h under the protection of an inert atmosphere;

[0017] 4) The sample powder obtained in step 3) is in 7-9M H 2 SO4 Digest in solution for 10 - 14 h, then wash, dry, and finally calcine at 700 - 900 °C for 3 - 5 h under the protection of an inert atmosphere to obtain the Cu-N-C single-atom catalyst.

[0018] Further, in step 1), the mass ratio of melamine, glucose, and CuCl 2 is 100 - 120:50 - 60:1; the inert atmosphere in step 2) includes helium, argon, and neon; the washing in step 3) is to wash repeatedly with deionized water and ethanol.

[0019] Further, the film-forming material in step (2) is at least one of chitosan, Nafion, glutaraldehyde, carboxymethyl cellulose, polyamide, and polypyrrole.

[0020] Further, the modified electrode in step (3) includes a glassy carbon electrode, a gold electrode, a paper electrode, a polymer electrode, and an indium tin oxide electrode, and the volume of the mixed solution dropped on the modified electrode is 0.1 - 10 μL.

[0021] On the other hand, the present invention provides an electrochemical sensor based on a single-atom catalyst prepared by the above method, and the peak potential difference of the electrochemical sensor when detecting BPS and BPAF is higher than 80 mV.

[0022] The present invention also provides the application of the above electrochemical sensor based on a single-atom catalyst, and the electrochemical sensor is used to detect one or two bisphenol compounds of BPS and BPAF in water environmental samples, plastic products, or food contact materials.

[0023] Further, the detection includes the following steps: Immerse or drop a test solution containing bisphenol compounds on the surface of a three-electrode system or a chip electrode composed of the electrochemical sensor, a reference electrode, and a counter electrode, perform differential pulse voltammetry scanning, and record the response current signal; the scanning potential range of the differential pulse voltammetry is 0 - 1.2 V.

[0024] Further, for a test solution containing only BPS or BPAF, a standard curve is obtained through the relationship between the current intensity detected by the electrochemical sensor and the concentration of bisphenol compounds, and the content of bisphenol compounds in the sample is determined according to the response current intensity of the test solution.

[0025] Further, for a test solution containing both BPS and BPAF, the peak current detected in the test solution is deconvoluted and fitted, and the corrected current intensity is substituted into the standard curve of the corresponding bisphenol compound concentration and the current intensity detected by the electrochemical sensor to determine the content of each bisphenol compound.

[0026] The beneficial effects of the present invention compared with the prior art are as follows:

[0027] 1. The Cu-N-C single-atom catalyst of the present invention has a very high specific surface area, significantly increasing the number of active sites. The good electrical conductivity of the Cu-N-C single-atom catalyst can enhance the current response, thus effectively improving the sensitivity of the sensor.

[0028] 2. The electrochemical sensor prepared by the present invention has a simple preparation process, low cost, is easy to carry, has a short detection time, and does not require a complex pretreatment process for detecting actual samples, making it suitable for on-site detection.

[0029] 3. The electrochemical sensor prepared by the present invention has extremely high sensitivity for the detection of bisphenol pollutants in the environment. Compared with traditional chromatography and mass spectrometry methods, it has the advantages of simple sample pretreatment, fast detection speed, and low detection limit.

[0030] 4. The electrochemical sensor prepared by the present invention realizes the potential detection of two bisphenol pollutants respectively. By correcting the detected current, accurate quantification of bisphenol S and bisphenol AF with very close peak potentials can be achieved. Description of the Drawings

[0031] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments will be briefly introduced below.

[0032] Figure 1 It is the scanning electron microscope (SEM) image of the Cu-N-C single-atom catalyst prepared in Example 1 of the present invention;

[0033] Figure 2 It is the aberration-corrected transmission electron microscope (AC-TEM) image of the Cu-N-C single-atom catalyst prepared in Example 1 of the present invention;

[0034] Figure 3 It is the X-ray diffraction (XRD) pattern of the Cu-N-C single-atom catalyst prepared in Example 1 of the present invention;

[0035] Figure 4 It is the X-ray photoelectron spectroscopy (XPS) pattern of the Cu-N-C single-atom catalyst prepared in Example 1 of the present invention;

[0036] Figure 5 It is the differential pulse voltammogram of detecting different concentrations of BPS with the electrochemical sensor in Example 3 of the present invention;

[0037] Figure 6 It is the differential pulse voltammogram of detecting different concentrations of BPAF with the electrochemical sensor in Example 4 of the present invention;

[0038] Figure 7It is a linear correlation curve graph of the BPS concentration in Example 3 and the BPAF concentration in Example 4 of the present invention with the peak current of the electrochemical sensor;

[0039] Figure 8 It is the DPV graph of the electrochemical sensor for detecting two bisphenol pollutants, BPS and BPAF, in Example 5 of the present invention;

[0040] Figure 9 It is the peak splitting fitting graph of two bisphenol pollutants in Example 5 of the present invention;

[0041] Figure 10 It is the current correction curve graph of BPAF in Example 5 of the present invention;

[0042] Figure 11 It is the current correction curve graph of BPS in Example 5 of the present invention. Specific embodiments

[0043] The present invention will be described in detail below in conjunction with the embodiments. However, the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only part of the embodiments of the present invention. For those skilled in the art, without creative efforts, obtaining other similar embodiments will fall within the protection scope of the present invention.

[0044] Example 1 Preparation of Cu-N-C single-atom catalyst

[0045] Dissolve 4 g of melamine and 2 g of glucose in 15 mL of a solution containing 0.4 mmol of CuCl 2 After stirring evenly at room temperature; transfer the above solution to a polytetrafluoroethylene reaction kettle and react at 180 °C for 24 hours. After the reaction, dry it and place it in a tubular furnace for calcination at 800 °C for 4 hours. During the calcination process, introduce argon; digest the obtained powder sample in 9 M H 2 SO 4 solution for 10 - 14 h to remove excess elements. Wash the product repeatedly with deionized water and ethanol, dry it overnight in a vacuum oven, and finally calcine it in a tubular furnace at 800 °C for 4 hours to remove excess elements to obtain the Cu-N-C single-atom catalyst.

[0046] Example 2 Preparation of Cu-N-C single-atom electrochemical sensor

[0047] An electrochemical sensor was prepared by a simple method of drop-casting film formation. The specific operation steps are as follows: First, polish the surface of the glassy carbon electrode: polish the glassy carbon electrode successively on suede containing aluminum oxide powders with particle sizes of 1 μm, 0.3 μm, and 0.05 μm until its surface becomes mirror-like; then ultrasonically clean it in absolute ethanol and ultrapure water for 3 min respectively to remove the aluminum oxide powders adsorbed on the electrode surface; subsequently, in a 50 mmolL -1 potassium ferricyanide / potassium ferrocyanide solution, within the potential range of -0.1 to +0.6 V, scan the cyclic voltammogram curve at a scan rate of 50 mVs -1 until the potential difference between the oxidation and reduction peak potentials of the curve is less than 80 mV. Then wash the electrode surface with ultrapure water and dry it with ultrapure nitrogen. Drop the prepared aqueous solution of Cu-N-C single-atom catalyst (where the concentration of Cu-N-C single-atom catalyst is 0.2 mg / mL and the concentration of the film-forming material chitosan is 1.5 mg / mL) onto the surface of the glassy carbon electrode to obtain an electrochemical sensor modified with Cu-N-C single-atom catalysis.

[0048] Example 3 Detection of BPS by Cu-N-C single-atom electrochemical sensor

[0049] Add known concentrations of bisphenol S as the target analyte to phosphate buffer solutions (0 μM, 1 μM, 6 μM, 12 μM, 20 μM, 30 μM, 40 μM, 50 μM), and scan the differential pulse voltammogram curve between 0 and 1.2 V. Detect the relationship between the peak current intensity and the concentration of bisphenol compounds through the electrochemical sensor to obtain a linear fitting curve. Test the phosphate buffer solution containing unknown concentration of bisphenol S, and substitute the obtained peak current value into the standard curve to determine the content of bisphenol compounds therein.

[0050] Example 4 Detection of BPAF by Cu-N-C single-atom electrochemical sensor

[0051] Add known concentrations of bisphenol AF as the target analyte to phosphate buffer solutions (0 μM, 1.5 μM, 8 μM, 15 μM, 25 μM, 35 μM, 40 μM, 50 μM), and scan the differential pulse voltammogram curve between 0 and 1.2 V. Detect the relationship between the peak current intensity and the concentration of bisphenol compounds through the electrochemical sensor to obtain a linear fitting curve. Test the phosphate buffer solution containing unknown concentration of bisphenol AF, and substitute the obtained peak current value into the standard curve to determine the content of bisphenol compounds therein.

[0052] Example 5 Simultaneous detection of BPAF and BPS by Cu-N-C single-atom electrochemical sensor

[0053] Bisphenol AF (12 μM, 15 μM, 20 μM, 25 μM, 42 μM, 55 μM) and bisphenol S (7 μM, 10 μM, 15 μM, 20 μM, 32 μM, 40 μM) with known concentrations were added as target analytes to phosphate buffer, and the differential pulse voltammetry curve was scanned between 0 and 1.2 V. The curve was peak-fitted, and the relationship between the peak current value detected by the electrochemical sensor and the theoretical current calculated from the standard curve was used to obtain a calibration curve. A phosphate buffer containing bisphenol AF and bisphenol S with unknown concentrations was tested, and the obtained peak current value was corrected and substituted into the standard curve to determine the content of each bisphenol compound therein.

[0054] Example 6 Evaluation of the Specificity, Reproducibility and Storage Stability of the Electrochemical Sensor

[0055] The specificity of the electrochemical sensor of the present invention was studied by differential pulse. The prepared electrochemical sensor was exposed to a PBS buffer solution containing various interfering ions (Ga 2+ , Cu 2+ , Fe 3+ , Ni 2+ , CO 3 2- , Cl - , SO 4 2- , NO 3- , glucose, uric acid, with a concentration of 100 μM) and the component to be measured. There was no obvious change in the peak current obtained by differential pulse voltammetry testing, indicating that the sensor had good specificity.

[0056] To evaluate the reproducibility between different electrodes of the same batch of the electrochemical sensor of the present invention, 10 sensors were independently prepared under the same conditions. Bisphenol S at a concentration of 20 μM and bisphenol AF at a concentration of 20 μM were detected for every 5 sensors respectively. The results showed that the RSDs were 0.6% and 4.2% in turn, indicating that there was good reproducibility between the electrodes prepared in different batches.

[0057] To evaluate the storage stability of the electrochemical sensor of the present invention, the Cu-N-C single-atom catalyst modified electrode was stored at 4 °C for one week and then its current response to bisphenol pollutants was tested. The obtained potentials all remained above 85% of the original current, and there was no obvious attenuation compared with the original current, indicating that the electrochemical sensor developed by the present invention had good stability.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of an electrochemical sensor based on a single-atom catalyst, characterized in that, it mainly includes the following steps: (1) Ultrasonically disperse the single-atom catalyst into the aqueous phase to obtain a dispersion system, and the concentration of the dispersion system is 0.1 - 5 mg / mL; (2) Add the film-forming material into the dispersion system and mix evenly to obtain a mixed solution, and the concentration of the film-forming material in the mixed solution is 0.05 - 3 mg / mL; (3) Drop the mixed solution onto the surface of the modified electrode, and let it stand and dry at room temperature to obtain the electrochemical sensor.

2. The preparation method according to claim 1, characterized in that, in step (1), the metal active center of the single-atom catalyst is partially or completely dispersed on the nitrogen-doped carbon material in the form of isolated single atoms, the metal includes Cu, and the loading amount of the metal is 0.1 - 10 wt%, preferably 1 - 3 wt%.

3. The preparation method according to claim 2, characterized in that, the preparation of the single-atom catalyst mainly includes the following steps: 1) Dissolve melamine and glucose in a solution containing CuCl 2 and stir well at room temperature; 2) Transfer the solution in step 1) to a reaction kettle and react at 150 - 200 °C for 22 - 26 h; 3) After drying the product obtained from the reaction in step 2), calcine it at 700 - 900 °C for 3 - 5 h under the protection of an inert atmosphere; 4) Digest the sample powder obtained in step 3) in 7-9 M H 2 SO 4 solution for 10-14 h, then wash, dry, and finally calcine at 700-900 °C for 3-5 h under the protection of an inert atmosphere to obtain the Cu-N-C single-atom catalyst.

4. The preparation method according to claim 3, characterized in that, The mass ratio of melamine, glucose and CuCl described in step 1) 2 is 100-120:50-60:1; the inert atmosphere described in step 2) includes helium, argon and neon; the washing described in step 3) is to repeatedly wash with deionized water and ethanol in sequence.

5. The preparation method according to claim 1, characterized in that, in step (2), the film-forming material is at least one of chitosan, Nafion, glutaraldehyde, carboxymethyl cellulose, polyamide, and polypyrrole; in step (3), the modified electrode includes a glassy carbon electrode, a gold electrode, a platinum electrode, a screen-printed electrode, a paper electrode, a polymer electrode, and an indium tin oxide electrode, and the volume of the mixed solution dropped on the modified electrode is 0.1 - 10 μL.

6. An electrochemical sensor based on a single-atom catalyst prepared by the preparation method according to any one of claims 1 - 5, and the peak potential difference of the electrochemical sensor when detecting BPS and BPAF is higher than 80 mV.

7. The application of the electrochemical sensor based on a single-atom catalyst according to claim 6, characterized in that, the electrochemical sensor is used to detect one or two bisphenol compounds of BPS and BPAF in water environmental samples, plastic products or food contact materials.

8. The application according to claim 7, characterized in that, the detection includes the following steps: Immerse or drop the test solution containing bisphenol compounds on the surface of the three-electrode system or chip electrode composed of the electrochemical sensor, the reference electrode, and the counter electrode, perform differential pulse voltammetry scanning, and record the response current signal; the scanning potential range of the differential pulse voltammetry is 0 - 1.2 V.

9. The application according to claim 8, characterized in that, for the test solution containing only BPS or BPAF, the relationship between the current intensity detected by the electrochemical sensor and the concentration of the bisphenol compound is used to obtain a standard curve, and according to the response current intensity of the test solution, the content of the bisphenol compound in the sample is determined.

10. The application according to claim 8, wherein, for a test solution containing both BPS and BPAF, the peak current detected in the test solution is subjected to peak splitting and fitting, and the corrected current intensity is substituted into the standard curve of the concentration of each bisphenol compound and the current intensity detected by the electrochemical sensor, so as to determine the content of each bisphenol compound.

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