Zero-valent copper / charcoal-based electrochemical sensor for detecting antibiotics and preparation method of zero-valent copper / charcoal-based electrochemical sensor

Abstract

The invention belongs to the field of analysis and detection, and provides a zero-valent copper / charcoal-based electrochemical sensor for detecting antibiotics and a preparation method thereof.The preparation method comprises the steps that a biomass material and a copper ion solution are mixed, then a reducing agent is added, copper ions are reduced into zero-valent copper, filtering and drying are conducted, and a mixture is obtained; carbonizing the mixture to obtain a zero-valent copper loaded biochar material; preparing the zero-valent copper loaded biochar material into an electrochemical sensing electrode; the electrochemical sensor is assembled by taking the electrochemical sensing electrode as a working electrode. According to the electrochemical sensor, the antibiotics are detected by using the peak voltage and the peak current in the zero-valent copper oxidation process, so that the defects that the peak potential is seriously shifted, the trace antibiotic peak current is not obvious and the error is relatively large due to the reduction of the antibiotic concentration when the traditional electrochemical sensor is used for detecting the antibiotics according to the oxidation-reduction peak of the antibiotics are overcome; the detection accuracy of the electrochemical sensor is improved.

Description

Technical Field

[0001] The present invention belongs to the fields of electrochemical sensors and analytical detection, and relates to a zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics and a preparation method thereof. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and it is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] With the development of society, the accumulation of antibiotics in the environment has led to serious problems such as the generation of drug-resistant bacteria and the destruction of ecosystems. Traditional biochar-based electrochemical sensors achieve quantitative detection by detecting the oxidation peak of antibiotics. However, due to the weak physical adsorption force, when only trace amounts of antibiotics are present in the water body, the oxidation current is very small, making it impossible to achieve quantitative detection or resulting in large errors, affecting the accuracy. On the other hand, when detecting pollutants through the oxidation-reduction peak of antibiotics, the value of its peak potential is related to the concentration of the pollutants. Especially when the pollutant concentration is very low, the value of its peak potential is significantly different from that at a constant concentration, which leads to the deviation of the electrochemical signal and affects the accuracy of detection.

[0004] Therefore, it is urgent to solve the problems of trace detection of antibiotics in water bodies by biochar-based electrochemical sensors and ensuring their accuracy. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics and a preparation method thereof. The present invention realizes the electrochemical detection of trace antibiotics by utilizing the characteristic adsorption of the N (nitrogen) and S (sulfur) element functional groups in antibiotic molecules and zero-valent copper. In the present invention, zero-valent copper in the electrode material will generate an oxidation peak current under the applied potential. When there are antibiotics containing functional groups such as amino and mercapto in the solution to be detected, the antibiotic molecules can adsorb on the copper surface and inhibit the oxidation of zero-valent copper. When the antibiotic content is low, the adsorption amount is small, and the inhibitory effect on the oxidation of zero-valent copper is weak. Therefore, the oxidation peak of copper can maintain a high intensity, reducing errors and improving the detection sensitivity. The electrochemical sensor of the present invention uses the peak voltage and peak current of the zero-valent copper oxidation process to detect antibiotics, overcoming the defects that when detecting antibiotics by the traditional method based on the oxidation-reduction peak of antibiotics, the peak potential seriously deviates due to the decrease in antibiotic concentration and the peak current is not obvious and the error is large for trace antibiotics, and improving the detection accuracy of the electrochemical sensor. The present invention significantly improves the sensitivity and accuracy of the zero-valent copper / biochar-based electrochemical sensor detection through the strategy of in-situ loading of zero-valent copper on the biochar surface, realizing the trace detection of antibiotic molecules in water bodies.

[0006] To achieve the above object, the present invention adopts the following technical solutions: In the first aspect of the present invention, a preparation method of a zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics is provided, including: Mix a biomass material with a copper ion solution, then add a reducing agent to reduce the copper ions to zero-valent copper, filter and dry to obtain a mixture; Carbonize the mixture to obtain a biochar material loaded with zero-valent copper; Fabricate the biochar material loaded with zero-valent copper into an electrochemical sensing electrode; Use the electrochemical sensing electrode as a working electrode to assemble an electrochemical sensor.

[0007] The present invention uses a biochar material with a large specific surface area as the electrode material of the electrochemical sensor, further loads zero-valent copper on its surface, and utilizes the specific adsorption effect of zero-valent copper with the N- and S-containing functional groups in antibiotics to improve the electrochemical detection ability. At the same time, under the applied potential, the oxidation peak of zero-valent copper is used as the detection signal, overcoming the defects of signal offset, very small peak current and large error caused by low pollutant concentration, and improving the detection accuracy of the electrochemical sensor.

[0008] In the second aspect of the present invention, an electrochemical sensor prepared by the above method is provided.

[0009] Advantages of the present invention (1) The present invention makes full use of the advantages of biochar as the electrode material of the electrochemical sensor and combines the characteristics of specific adsorption of zero-valent copper with the N- and S-functional groups in antibiotic molecules to improve the detection sensitivity of the electrochemical sensor. At the same time, by using the redox characteristics of zero-valent copper itself, the detection of antibiotics is realized through the oxidation peak potential and peak current of copper, avoiding the influence of antibiotic concentration on the oxidation peak potential and current signal, and improving the detection accuracy.

[0010] (2) The present invention first mixes the biomass raw material with copper ions modified by an ionic dispersant, and uses a reducing agent to reduce the copper ions to zero-valent copper. Then, through one-step anaerobic high-temperature carbonization, the preparation of the biomass carbon material and the recrystallization of zero-valent copper are realized, improving the crystallinity of zero-valent copper loaded on the surface of the biochar material, and further enhancing the detection sensitivity of its electrochemistry. Through the combination of in-situ loading of zero-valent copper on the biochar surface and the zero-valent copper recrystallization strategy, the present invention significantly improves the electrochemical detection performance of the composite material, and the prepared electrochemical sensor can realize the trace detection of antibiotics in water.

[0011] (3) The present invention uses polyvinylpyrrolidone to modify copper ions, avoiding the agglomeration of zero-valent copper particles and improving the dispersion of zero-valent copper particles on the surface of the carbon material; (4) During the preparation of biochar in the present invention, the recrystallization of zero-valent copper is achieved, the crystallinity of zero-valent copper is improved, and the specific adsorption capacity of the composite material against antibiotics is enhanced. (5) The zero-valent copper of the present invention has a strong adsorption capacity for antibiotics containing amino or mercapto groups, and can adsorb a small amount or even trace amounts of antibiotics in the solution, thereby improving the detection efficiency and achieving the purpose of trace detection.

[0012] (6) The preparation method of the present invention is simple, highly practical, and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The attached drawings forming a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0014] Figure 1 It is a characterization picture of the biochar material loaded with zero-valent copper in Example 1 of the present invention. Among them, (a): High-resolution transmission electron microscope photo 500nm, (b): High-resolution transmission electron microscope photo 5nm, (c): Lattice diffraction photo.

[0015] Figure 2 It is a linear relationship diagram for detecting tetracycline in water by the biochar material loaded with zero-valent copper in Example 1 of the present invention, (a) Current-voltage relationship diagram, (b) Current-concentration relationship diagram. DETAILED DESCRIPTION OF THE INVENTION

[0016] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0017] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as familiar to those skilled in the art. The reagents or raw materials used in the present invention can be obtained through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in the conventional manner in the art or according to the product instructions. Similarly, unless otherwise specified, the test methods of the present invention are also tested in the conventional manner in the art or according to the general methods or standards in the industry. In addition, any methods and materials similar or equivalent to the described content can be applied to the method of the present invention. The preferred implementation methods and materials described herein are only for illustrative purposes.

[0018] The present invention provides a preparation method of a zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics, including: The biomass raw material powder is fully mixed with the copper ion solution, and then a reducing agent is added to the mixed solution to reduce the copper ions to zero-valent copper. The mixed solution is then filtered, and the product is dried in an oven. The resulting mixture is then placed in a tubular furnace and heated at 500-700°C for 3-5 hours under the protection of a nitrogen atmosphere to obtain a zero-valent copper-loaded biochar material.

[0019] The zero-valent copper-loaded biochar material is made into an electrochemical sensing electrode; The electrochemical sensor is assembled using the electrochemical sensing electrode as a working electrode.

[0020] In order to improve the loading effect of zero-valent copper on the surface of biochar, the present invention studies the mixing method. Preferably, the mixing is carried out under ultrasonic conditions. Ultrasonic mixing is used to pre-adsorb copper ions on the surface of biomass raw materials to improve the dispersibility of copper ions on the surface of biomass carbon materials. More preferably, the ultrasonic dispersion condition is 50°C-60°C for 2-3 hours.

[0021] The degree of dispersion of zero-valent copper on the surface of biomass materials will affect the performance of electrochemical sensors. In order to make the synthesized zero-valent copper particles dispersed evenly and avoid agglomeration. Preferably, an ion dispersant is also added to the copper ion solution, and the ion dispersant is polyvinyl pyrrolidone. The present invention adds an ion dispersant (polyvinyl pyrrolidone) to the copper ion solution to control the size of zero-valent copper particles and protect the zero-valent copper from being evenly dispersed on the surface of biomass.

[0022] In order to control the reduction rate and particle size of zero-valent copper, the present invention studies the concentration of the ion dispersant. More preferably, the mass concentration of the ion dispersant in the copper ion solution is 1-1.5 g / L. Further preferably, the polyvinyl pyrrolidone is polyvinyl pyrrolidone K30.

[0023] The concentration of the copper ion solution will affect the content and structure of zero-valent copper in the final composite material. If the copper ion concentration is too low, the zero-valent copper loaded is too little, the chemical adsorption of antibiotics is weak, and the trace detection ability is affected; if the copper ion concentration is too high, the synthesized zero-valent copper will agglomerate, affecting its activity. Therefore, preferably, the concentration of the copper ion solution is 0.1-0.2M.

[0024] Preferably, the mass ratio of the biomass material to the copper ion solution is 1-2:5.

[0025] Preferably, the copper ion solution is a copper sulfate solution.

[0026] The carbonization of biomass and the crystallization process of elemental copper can be regulated by changing the temperature and time. Therefore, the temperature and time of the carbonization reaction were studied in this invention. Preferably, the carbonization conditions are as follows: under the protection of an inert atmosphere, the reaction is carried out at 500°C - 700°C for 3 - 5 hours.

[0027] More specifically, it includes: adding biomass powder into a copper ion solution containing an ionic dispersant, ultrasonically dispersing it, then dropwise adding an excessive amount of sodium borohydride solution, magnetically stirring the reaction for 1 hour at room temperature. After the reaction is completed, solid-liquid separation, washing, and drying are carried out to obtain a mixture. Put the obtained mixture into a tubular furnace, and under the protection of a nitrogen atmosphere, heat it at a temperature of 500 - 700°C for 2 - 3 hours to obtain a zero-valent copper-loaded biochar material.

[0028] Preferably, the preparation method of the electrochemical sensing electrode is as follows: prepare a dispersion of the zero-valent copper-loaded biochar material, load the dispersion on a glassy carbon electrode, and dry it to obtain the electrode.

[0029] The following combines specific embodiments to further elaborate on this invention. It should be noted that the specific embodiments are explanations rather than limitations of this invention.

[0030] The raw materials described in the examples and comparative examples are all conventional raw materials, commercially available products.

[0031] Example 1 1. Synthesis of (biomass zero-valent copper) mixture: Disperse 1 g of soybean straw powder in 5 mL of 0.15 M copper sulfate solution, where the copper sulfate solution contains 1 g / L of polyvinylpyrrolidone K30, and ultrasonically disperse it at 50°C for 2 hours. Then, under the protection of a nitrogen atmosphere, use a separatory funnel to dropwise add 5 mL of 0.6 M sodium borohydride solution prepared with ice water into the above solution, magnetically stir the reaction for 1 hour, centrifuge, wash with water, and dry to obtain a mixture.

[0032] 2. Synthesis of zero-valent copper-loaded biochar material Put 1 g of the mixture prepared above into a tubular furnace, and under the protection of a nitrogen atmosphere, carry out a carbonization reaction. The heating rate is 5°C / min, and keep it at 500°C for 3 hours to obtain a zero-valent copper-loaded biochar material; 3. Characterization of zero-valent copper-loaded biochar material The high-resolution transmission electron microscope of the zero-valent copper-loaded biochar material prepared in this example is as shown in Figure 1 (a) and (b) in it, and the lattice diffraction photograph is as shown in Figure 1 (c) in it. It can be seen that there are a large number of well-crystallized zero-valent coppers in the material prepared by the method of this invention.

[0033] 4. Performance Testing of Zero-Valent Copper-Loaded Biochar Materials Disperse 10 mg of the synthesized zero-valent copper-loaded biochar material in 10 mL of ethanol and ultrasonicate to obtain a homogeneous dispersion. Drop 20 μL of the dispersion onto a polished glassy carbon electrode (GCE) and dry it under an infrared lamp to prepare an electrochemical sensing electrode.

[0034] Using differential pulse voltammetry, detect trace tetracycline in water through a CH Instrument CHI760E electrochemical workstation to evaluate the electrochemical performance of the prepared material. The specific test conditions are as follows: All electrochemical measurements are carried out using a three-electrode system, with an Ag / AgCl (silver / silver chloride) electrode and a Pt (platinum) electrode as the reference electrode and the counter electrode, respectively, and the above-mentioned electrochemical sensing electrode as the working electrode. Dissolve tetracycline in an acetic acid and sodium acetate buffer solution (HAc-NaAc, pH = 5) and prepare a series of solutions with concentrations ranging from 0.05 μM to 5 μM for electrochemical testing.

[0035] Figure 2 For the detection data and linear relationship of tetracycline in water detected by the zero-valent copper-loaded biochar material prepared in Example 1, from Figure 2 as shown in (a) and (b) below, it can be seen that the material prepared by the present invention can detect trace tetracycline in water, and the linear range can be from 0.06 μM to 5 μM. The linear regression equation within the concentration range is y = 13.291lgx - 13.897, the correlation coefficient is 0.980, and the detection limit is 0.005 μM.

[0036] Example 2 1. Synthesis of (biomass zero-valent copper) mixture: Disperse 1.5 g of soybean straw powder in 5 mL of 0.2 M copper sulfate solution, where the copper sulfate solution contains 1.2 g / L of polyvinylpyrrolidone K30, and ultrasonically disperse for 2 hours at 50°C. Then, under the protection of a nitrogen atmosphere, gradually add 5 mL of 0.8 M sodium borohydride solution prepared with ice water dropwise to the above solution using a separatory funnel, magnetically stir and react for 1 hour, centrifuge, wash with water, and dry to obtain the mixture.

[0037] 2. Synthesis of Zero-Valent Copper-Loaded Biochar Material Put 1 g of the above-prepared mixture into a tubular furnace and carry out a carbonization reaction under the protection of a nitrogen atmosphere. The heating rate is 5°C / min, and keep it at 600°C for 3 hours to obtain the zero-valent copper-loaded biochar material; Using the same detection method as in Example 1, the performance of the material prepared in Example 2 was detected. The linear range can be from 0.01 μM to 35 μM. In this concentration range, the linear regression equation is y = 14.472lgx - 12.029, the correlation coefficient is 0.9952, and the detection limit is 0.004 μM.

[0038] Example 3 1. Synthesis of (biomass zero-valent copper) mixture: Disperse 2 g of soybean straw powder in 5 mL of 0.2 M copper sulfate solution, where the copper sulfate solution contains 1.3 g / L of polyvinylpyrrolidone K30, and ultrasonically disperse for 2 hours at 50 °C. Then, under the protection of a nitrogen atmosphere, slowly add 5 mL of 0.8 M sodium borohydride solution prepared with ice water dropwise to the above solution using a separatory funnel, stir magnetically for 1 hour, centrifuge, wash with water, and dry to obtain a biomass zero-valent copper mixture.

[0039] 2. Synthesis of zero-valent copper-loaded biochar material Put 1 g of the mixture prepared above into a tubular furnace and carry out a carbonization reaction under the protection of a nitrogen atmosphere. The heating rate is 5 °C / min, and keep it at 700 °C for 2 hours to obtain a zero-valent copper-loaded biochar material; Using the same detection method as in Example 1, the performance of the material prepared in Example 3 was detected. The linear range can be from 0.01 μM to 35 μM. In this concentration range, the linear regression equation is y = 12.292lgx - 13.182, the correlation coefficient is 0.9910, and the detection limit is 0.004 μM.

[0040] Comparative Example 1 The difference from Example 1 is that pure water is used to replace the copper sulfate solution, and other conditions remain unchanged to prepare the biochar material.

[0041] Using the same detection method as in Example 1, the antibiotic concentration of the material prepared in Comparative Example 1 was detected. Since the material prepared in Comparative Example 1 does not contain copper and the detection of antibiotics cannot be carried out through the oxidation peak current of copper, the concentration of antibiotics is detected using the self-oxidation peak of antibiotics. The linear range can be from 0.9 μM to 10 μM. In this concentration range, the linear regression equation is y = 1.753x + 0.584, the correlation coefficient is 0.9952, and the detection limit is 0.418 μM.

[0042] Comparative Example 2 The difference from Example 1 is that an equal-concentration ferrous sulfate solution is used to replace the copper sulfate solution. Other conditions remain unchanged to prepare a zero-valent iron-loaded biochar material.

[0043] Using the same detection method as in Example 1, the antibiotic concentration of the material prepared in Comparative Example 2 was detected. Since the material prepared in Comparative Example 2 contains zero-valent iron, the concentration of the antibiotic was detected by measuring the oxidation peak current of iron. The linear range can be from 0.4 μM to 10 μM. In this concentration range, the linear regression equation is y = 0.892lgx + 0.284, the correlation coefficient is 0.9896, and the detection limit is 0.079 μM.

[0044] Comparative Example 3 The difference from Example 1 is that the detected antibiotic is erythromycin. The presence of erythromycin could hardly be detected because there is no amino functional group in the erythromycin molecule and it cannot be specifically adsorbed on the surface of zero-valent copper, so the oxidation peak of copper hardly changes.

[0045] From the comparison between Example 1 and Comparative Example 1, it can be seen that zero-valent copper will generate an oxidation peak current under the applied potential. When there are antibiotics containing functional groups such as amino and mercapto in the solution to be detected, the antibiotic molecules can be adsorbed on the copper surface and inhibit the oxidation of zero-valent copper. When the antibiotic content is low, the adsorption amount is small, and the inhibitory effect on the oxidation of zero-valent copper is weak. Therefore, the oxidation peak of copper can maintain a high intensity, reducing the error and improving the detection sensitivity.

[0046] From the comparison between Example 1 and Comparative Example 2, it can be seen that the specific adsorption of iron element and amino functional group is relatively weak, and it cannot effectively adsorb trace antibiotics, so the detection effect is poor.

[0047] From the comparison between Example 1 and Comparative Example 3, it can be seen that when there is no amino functional group in the antibiotic, it cannot be specifically adsorbed on the surface of zero-valent copper, so the oxidation peak of copper hardly changes and trace detection of antibiotics cannot be carried out.

[0048] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics, characterized in that, Including: Mix the biomass material with a copper ion solution, then add a reducing agent to reduce the copper ions to zero-valent copper, filter and dry to obtain a mixture; Carbonize the mixture to obtain a zero-valent copper-loaded biochar material; Fabricate the zero-valent copper-loaded biochar material into an electrochemical sensing electrode; Use the electrochemical sensing electrode as a working electrode to assemble an electrochemical sensor.

2. The preparation method of the zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics according to claim 1, wherein The mixing is carried out under ultrasonic conditions.

3. The preparation method of the zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics according to claim 1, wherein, An ionic dispersant is also added to the copper ion solution, and the ionic dispersant is polyvinylpyrrolidone.

4. The preparation method of the zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics according to claim 3, characterized in that, In the copper ion solution, the mass concentration of the ionic dispersant is 1 - 1.5 g / L.

5. The preparation method of the zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics according to claim 1, characterized in that, The concentration of the copper ion solution is 0.1 M - 0.2 M.

6. The preparation method of the zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics according to claim 1, characterized in that, The mass ratio of the biomass material to the copper ion solution is 1 - 2:

5.

7. The preparation method of the zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics according to claim 1, characterized in that, The copper ion solution is a copper sulfate solution.

8. The preparation method of the zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics according to claim 1, characterized in that, The conditions for carbonization are to react at 500°C - 700°C for 3 - 5 hours under the protection of an inert atmosphere.

9. The preparation method of the zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics according to claim 1, wherein, The preparation method of the electrochemical sensing electrode is: prepare the zero-valent copper-loaded biochar material into a dispersion, load the dispersion on a glassy carbon electrode, and dry to obtain it.

10. An electrochemical sensor prepared by the method according to any one of claims 1 - 9.

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