Zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics and its preparation method

Abstract

The present invention belongs to the field of analytical detection and provides a zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics and a preparation method thereof, comprising: mixing a biomass material with a copper ion solution, adding a reducing agent to reduce the copper ions to zero-valent copper, filtering, and drying to obtain a mixture; carbonizing the mixture to obtain a zero-valent copper-loaded biochar material; forming the zero-valent copper-loaded biochar material into an electrochemical sensor electrode; and assembling an electrochemical sensor using the electrochemical sensor electrode as a working electrode. The electrochemical sensor of the present invention utilizes the peak voltage and peak current of the zero-valent copper oxidation process to detect antibiotics, overcoming the defects of conventional electrochemical sensors that, when detecting antibiotics based on their redox peaks, suffer from severe peak potential offsets due to reduced antibiotic concentration, as well as unclear peak currents for trace antibiotics and large errors, thereby improving the detection accuracy of the electrochemical sensor.

Description

Technical Field

[0001] The invention belongs to the field 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] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] With the development of society, the accumulation of antibiotics in the environment has led to serious problems such as the emergence 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, the oxidation current is very small, and quantitative detection cannot be achieved or the error is large, affecting the accuracy. On the other hand, when pollutants are detected through the redox peak of antibiotics, the value of its peak potential is related to the concentration of the pollutant. In particular, when the concentration of the pollutant is very low, the value of its peak potential is significantly different from the peak potential at constant concentration, which causes the electrochemical signal to shift and affects the accuracy of the detection.

[0004] Therefore, there is an urgent need to solve the problem of using biochar-based electrochemical sensors to detect trace amounts of antibiotics in water and ensure their accuracy. Summary of the Invention

[0005] To address the above-mentioned issues, the present invention provides a zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics and its preparation method. This invention utilizes the characteristic adsorption of zero-valent copper by the nitrogen (nitrogen) and sulfur (sulfur) functional groups in antibiotic molecules to achieve electrochemical detection of trace antibiotics. The zero-valent copper in the electrode material of the present invention generates an oxidation peak current when a potential is applied. When antibiotics containing amino, thiol, or other functional groups are present in the solution to be detected, the antibiotic molecules can adsorb on the copper surface, inhibiting the oxidation of the zero-valent copper. When the antibiotic content is low, the adsorption amount is low, and the oxidation inhibition of the zero-valent copper is weak. Therefore, the copper oxidation peak can maintain a high intensity, reducing errors and improving detection sensitivity. The electrochemical sensor of the present invention utilizes the peak voltage and peak current of the zero-valent copper oxidation process to detect antibiotics. This overcomes the shortcomings of traditional methods that detect antibiotics based on the redox peak of the antibiotic, which can cause significant peak potential shifts due to reduced antibiotic concentration, as well as unclear peak currents and large errors when detecting trace amounts of antibiotics. This improves the detection accuracy of the electrochemical sensor. The present invention significantly improves the sensitivity and accuracy of zero-valent copper / biochar-based electrochemical sensor detection through the strategy of in situ loading of zero-valent copper on the biochar surface, thereby realizing trace detection of antibiotic molecules in water.

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

[0007] The first aspect of the present invention provides a method for preparing a zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics, comprising:

[0008] mixing the biomass material with the copper ion solution, adding a reducing agent to reduce the copper ions to zero-valent copper, filtering, and drying to obtain a mixture;

[0009] carbonizing the mixture to obtain a zero-valent copper-loaded biochar material;

[0010] preparing the zero-valent copper-loaded biochar material into an electrochemical sensing electrode;

[0011] The electrochemical sensor is assembled using the electrochemical sensing electrode as a working electrode.

[0012] This invention utilizes biochar, a material with a large specific surface area, as the electrode material for the electrochemical sensor. Zero-valent copper is further loaded onto its surface, leveraging the unique adsorption interaction between zero-valent copper and functional groups containing nitrogen and sulfur elements in antibiotics to enhance electrochemical detection capabilities. Furthermore, under an applied potential, the oxidation peak of zero-valent copper is used as the detection signal, overcoming the signal offset caused by low pollutant concentrations, as well as the small peak current and large errors, thereby improving the detection accuracy of the electrochemical sensor.

[0013] The second aspect of the present invention provides an electrochemical sensor prepared by the above method.

[0014] Beneficial effects of the present invention

[0015] (1) This invention fully utilizes the advantages of biochar as an electrode material for electrochemical sensors and combines the characteristic 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, the redox properties of zero-valent copper are utilized to detect antibiotics through the oxidation peak potential and peak current of copper, thereby avoiding the influence of antibiotic concentration on the oxidation peak potential and current signal, and improving the accuracy of detection.

[0016] (2) The present invention first mixes the biomass raw material with copper ions modified with an ion dispersant, and uses a reducing agent to reduce the copper ions to zero-valent copper. Then, the biomass carbon material is prepared and the zero-valent copper is recrystallized through a one-step anaerobic high-temperature carbonization process, thereby improving the crystallinity of the zero-valent copper loaded on the surface of the biochar material and thereby enhancing the sensitivity of its electrochemical detection. The present invention significantly improves the electrochemical detection performance of the composite material by combining the in-situ loading of zero-valent copper on the biochar surface and the zero-valent copper recrystallization strategy. The prepared electrochemical sensor is capable of detecting trace amounts of antibiotics in water.

[0017] (3) The present invention uses polyvinyl pyrrolidone to modify copper ions, thereby avoiding the agglomeration of zero-valent copper particles and improving the dispersion of zero-valent copper particles on the surface of the carbon material;

[0018] (4) The present invention achieves recrystallization of zero-valent copper during the biochar preparation process, improves the crystallinity of zero-valent copper, and enhances the composite material's characteristic adsorption capacity for antibiotics;

[0019] (5) The zero-valent copper of the present invention has a strong adsorption capacity for antibiotics containing amino or thiol groups, and can adsorb small amounts or even trace amounts of antibiotics in the solution, thereby improving the detection efficiency and achieving the purpose of trace detection.

[0020] (6) The preparation method of the present invention is simple, practical, and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute 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 description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 These are characterization pictures of the zero-valent copper-loaded biochar material in Example 1 of the present invention, wherein: (a): high-resolution transmission electron microscopy picture 500nm, (b): high-resolution transmission electron microscopy picture 5nm, (c): lattice diffraction picture.

[0023] Figure 2 These are linear relationship diagrams for the detection of tetracycline in water by the zero-valent copper-loaded biochar material in Example 1 of the present invention, (a) current-voltage relationship diagram, and (b) current-concentration relationship diagram. DETAILED DESCRIPTION

[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0025] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in accordance with conventional methods in the art or according to product specifications. Similarly, unless otherwise specified, the test methods of the present invention are also tested in accordance with conventional methods in the art or the common methods or standards in the industry. In addition, any methods and materials similar to or equivalent to the described contents can be applied to the inventive method. The preferred embodiments and materials described herein are for demonstration purposes only.

[0026] The present invention provides a method for preparing a zero-valent copper / biochar-based electrochemical sensor for detecting antibiotics, comprising:

[0027] 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 a temperature of 500-700°C for 3-5 hours under the protection of a nitrogen atmosphere to obtain a zero-valent copper-loaded biochar material.

[0028] preparing the zero-valent copper-loaded biochar material into an electrochemical sensing electrode;

[0029] The electrochemical sensor is assembled using the electrochemical sensing electrode as a working electrode.

[0030] To enhance the loading of zero-valent copper onto the biochar surface, the present invention investigates mixing methods. Preferably, the mixing is performed under ultrasonic conditions. Ultrasonic mixing pre-adsorbs copper ions onto the surface of the biomass raw material, enhancing the dispersion of copper ions on the biochar surface. More preferably, the ultrasonic dispersion is performed at 50°C-60°C for 2-3 hours.

[0031] The degree of dispersion of zero-valent copper on the surface of biomass material can affect the performance of electrochemical sensors. To ensure uniform dispersion of synthesized zero-valent copper particles and prevent agglomeration, an ionic dispersant, preferably polyvinyl pyrrolidone, is added to the copper ion solution. The present invention adds an ionic dispersant (polyvinyl pyrrolidone) to the copper ion solution to control the size of the zero-valent copper particles and ensure uniform dispersion of the zero-valent copper on the biomass surface.

[0032] 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.

[0033] The concentration of the copper ion solution affects the content and structure of zero-valent copper in the final composite material. If the copper ion concentration is too low, the loaded zero-valent copper is insufficient, weakening the chemical adsorption of antibiotics and affecting trace detection capabilities. If the copper ion concentration is too high, the synthesized zero-valent copper will aggregate, affecting its activity. Therefore, the preferred concentration of the copper ion solution is 0.1-0.2 M.

[0034] Preferably, the mass ratio of the biomass material to the copper ion solution is 1-2:5.

[0035] Preferably, the copper ion solution is a copper sulfate solution.

[0036] 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 are studied in the present invention. Preferably, the carbonization condition is to react at 500°C-700°C for 3-5 hours under the protection of an inert atmosphere.

[0037] More specifically, the method comprises: adding biomass powder to a copper ion solution containing an ion dispersant and ultrasonically dispersing the biomass powder, then dropwise adding an excess of sodium borohydride solution, reacting the mixture under magnetic stirring for 1 hour at room temperature, and after the reaction is completed, performing solid-liquid separation, washing, and drying to obtain a mixture;

[0038] The mixture is placed in a tube furnace and heated at a temperature of 500-700° C. for 2-3 hours under the protection of a nitrogen atmosphere to obtain a zero-valent copper-loaded biochar material.

[0039] Preferably, the preparation method of the electrochemical sensor electrode is: preparing the zero-valent copper-loaded biochar material into a dispersion liquid, loading the dispersion liquid on a glassy carbon electrode, and drying to obtain the electrochemical sensor electrode.

[0040] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0041] The raw materials described in the examples and comparative examples are all conventional raw materials and commercially available products.

[0042] Example 1

[0043] 1. Synthesis of (biomass zero-valent copper) mixture:

[0044] Disperse 1 g of soybean straw powder in 5 mL of a 0.15 M copper sulfate solution containing 1 g / L polyvinylpyrrolidone K30 at 50°C for 2 hours. Then, under a nitrogen atmosphere, add 5 mL of a 0.6 M sodium borohydride solution prepared in ice water dropwise using a separatory funnel. The mixture is stirred magnetically for 1 hour, centrifuged, washed with water, and dried to obtain a mixture.

[0045] 2. Synthesis of Zero-valent Copper-Loaded Biochar Materials

[0046] One gram of the mixture was placed in a tube furnace under a nitrogen atmosphere for carbonization. The temperature was increased at a rate of 5°C / min and maintained at 500°C for 3 hours to obtain a zero-valent copper-loaded biochar.

[0047] 3. Characterization of Zero-valent Copper-Loaded Biochar Materials

[0048] The high-resolution transmission electron microscopy of the zero-valent copper-loaded biochar material prepared in this embodiment is as follows: Figure 1 As shown in (a) and (b), the lattice diffraction photos are as follows Figure 1 As shown in (c), it can be seen that a large amount of zero-valent copper with good crystallinity exists in the material prepared by the method of the present invention.

[0049] 4. Performance testing of zero-valent copper loaded biochar materials

[0050] 10 mg of the synthesized zero-valent copper-loaded biochar material was dispersed in 10 mL of ethanol and sonicated to obtain a uniform dispersion. 20 μL of the dispersion was then dropped onto a polished glassy carbon electrode (GCE) and dried under an infrared lamp to prepare an electrochemical sensing electrode.

[0051] Pulse voltammetry was used to detect trace amounts of tetracycline in water using a Chenhua CHI760E electrochemical workstation to evaluate the electrochemical performance of the prepared materials. The specific test conditions are as follows: All electrochemical measurements were performed using a three-electrode system, with an Ag / AgCl (silver / silver chloride) electrode and a Pt (platinum) electrode as the reference electrode and counter electrode, respectively, and the aforementioned electrochemical sensing electrode as the working electrode. Tetracycline was dissolved in acetic acid and sodium acetate buffer (HAc-NaAc, pH 5), and a series of solutions with concentrations ranging from 0.05 μM to 5 μM were prepared for electrochemical testing.

[0052] Figure 2 The detection data and linear relationship of tetracycline in water by the zero-valent copper loaded biochar material prepared in Example 1 are as follows: Figure 2 As shown in Figures (a) and (b), the material prepared in this invention can detect trace amounts of tetracycline in water with a linear range from 0.06 μM to 5 μM. Within this concentration range, the linear regression equation is y = 13.291lgx - 13.897, with a correlation coefficient of 0.980 and a detection limit of 0.005 μM.

[0053] Example 2

[0054] 1. Synthesis of (biomass zero-valent copper) mixture:

[0055] Disperse 1.5 g of soybean straw powder in 5 mL of a 0.2 M copper sulfate solution containing 1.2 g / L polyvinylpyrrolidone K30 at 50°C for 2 hours using ultrasonic technology. Then, under a nitrogen atmosphere, add 5 mL of a 0.8 M sodium borohydride solution prepared in ice water dropwise using a separatory funnel. The mixture is stirred magnetically for 1 hour, centrifuged, washed with water, and dried to obtain a mixture.

[0056] 2. Synthesis of Zero-valent Copper-Loaded Biochar Materials

[0057] One gram of the mixture was placed in a tube furnace under a nitrogen atmosphere for carbonization. The temperature was increased at a rate of 5°C / min and maintained at 600°C for 3 hours to obtain a zero-valent copper-loaded biochar.

[0058] The same detection method as in Example 1 was used to detect the properties of the material prepared in Example 2. The linear range was from 0.01 μM to 35 μM. Within the concentration range, the linear regression equation was y=14.472lgx-12.029, the correlation coefficient was 0.9952, and the detection limit was 0.004 μM.

[0059] Example 3

[0060] 1. Synthesis of (biomass zero-valent copper) mixture:

[0061] 2 g of soybean straw powder was dispersed in 5 mL of a 0.2 M copper sulfate solution containing 1.3 g / L polyvinylpyrrolidone K30 and ultrasonically dispersed at 50°C for 2 hours. Then, under a nitrogen atmosphere, 5 mL of a 0.8 M sodium borohydride solution prepared in ice water was added dropwise to the solution using a separatory funnel. The mixture was stirred magnetically for 1 hour, centrifuged, washed with water, and dried to obtain a biomass zero-valent copper mixture.

[0062] 2. Synthesis of Zero-valent Copper-Loaded Biochar Materials

[0063] One gram of the mixture was placed in a tube furnace under a nitrogen atmosphere for carbonization. The temperature was increased at a rate of 5°C / min and maintained at 700°C for 2 hours to obtain a zero-valent copper-loaded biochar.

[0064] The same detection method as in Example 1 was used to detect the properties of the material prepared in Example 3. The linear range was from 0.01 μM to 35 μM. Within the concentration range, the linear regression equation was y=12.292lgx-13.182, the correlation coefficient was 0.9910, and the detection limit was 0.004 μM.

[0065] Comparative Example 1

[0066] The difference from Example 1 is that pure water is used instead of the copper sulfate solution, and other conditions remain unchanged to prepare the biochar material.

[0067] The material prepared in Comparative Example 1 was tested for antibiotic concentration using the same detection method as in Example 1. Since the material prepared in Comparative Example 1 does not contain copper, the copper oxidation peak current cannot be used to detect the antibiotic. Therefore, the antibiotic's own oxidation peak current was used to detect its concentration. The linear range was from 0.9 μM to 10 μM. Within this concentration range, the linear regression equation was y = 1.753x + 0.584, with a correlation coefficient of 0.9952 and a detection limit of 0.418 μM.

[0068] Comparative Example 2

[0069] The difference from Example 1 is that a ferrous sulfate solution of equal concentration is used instead of a copper sulfate solution. Other conditions remain unchanged to prepare a zero-valent iron-loaded biochar material.

[0070] The material prepared in Comparative Example 2 was tested for antibiotic concentration using the same detection method as in Example 1. Because the material prepared in Comparative Example 2 contains zero-valent iron, the antibiotic concentration was determined by measuring the iron oxidation peak current. The linear range was from 0.4 μM to 10 μM. Within this concentration range, the linear regression equation was y = 0.892lgx + 0.284, with a correlation coefficient of 0.9896 and a detection limit of 0.079 μM.

[0071] Comparative Example 3

[0072] The difference from Example 1 is that the antibiotic tested is erythromycin. The presence of erythromycin is almost undetectable because the erythromycin molecule has no amino functional group and cannot be characteristically adsorbed on the zero-valent copper surface, so the copper oxidation peak is almost unchanged.

[0073] A comparison of Example 1 and Comparative Example 1 shows that zero-valent copper generates an oxidation peak current when a potential is applied. When antibiotics containing functional groups such as amino or thiol groups are present in the test solution, the antibiotic molecules can adsorb on the copper surface, inhibiting the oxidation of zero-valent copper. When the antibiotic content is low, the adsorption is minimal, and the inhibitory effect on zero-valent copper oxidation is weaker. Therefore, the copper oxidation peak can maintain a high intensity, reducing errors and improving detection sensitivity.

[0074] From the comparison between Example 1 and Comparative Example 2, it can be seen that the characteristic adsorption of iron element and amino functional group is relatively weak, and trace amounts of antibiotics cannot be effectively adsorbed, so the detection effect is poor.

[0075] From the comparison between Example 1 and Comparative Example 3, it can be seen that when the antibiotic does not have an amino functional group, characteristic adsorption cannot be performed on the zero-valent copper surface, so the copper oxidation peak hardly changes, and trace detection of the antibiotic cannot be performed.

[0076] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for detecting trace amounts of antibiotics, characterized in that: include: mixing the biomass material with the copper ion solution, adding a reducing agent to reduce the copper ions to zero-valent copper, filtering, and drying to obtain a mixture; An ion dispersant is also added to the copper ion solution, and the ion dispersant is polyvinyl pyrrolidone; 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; Assembling an electrochemical sensor using the electrochemical sensing electrode as a working electrode; The antibiotic is an antibiotic containing -NH2 / -SH functional group; The electrochemical sensor is used to perform electrochemical detection on antibiotics, and the copper oxidation peak current is used to detect the content of the antibiotics.

2. The method for detecting trace amounts of antibiotics according to claim 1, wherein The mixing is performed under ultrasonic conditions.

3. The method for detecting trace amounts of antibiotics according to claim 1, wherein In the copper ion solution, the mass concentration of the ion dispersant is 1-1.5 g / L.

4. The method for detecting trace amounts of antibiotics according to claim 1, wherein The concentration of the copper ion solution is 0.1M-0.2M.

5. The method for detecting trace amounts of antibiotics according to claim 1, wherein The mass ratio of the biomass material to the copper ion solution is 1-2:

5.

6. The method for detecting trace amounts of antibiotics according to claim 1, wherein The copper ion solution is a copper sulfate solution.

7. The method for detecting trace amounts of antibiotics according to claim 1, wherein The carbonization conditions are: reacting at 500° C.-700° C. for 3-5 hours under the protection of an inert atmosphere.

8. The method for detecting trace amounts of antibiotics according to claim 1, wherein The preparation method of the electrochemical sensor electrode is as follows: preparing the zero-valent copper-loaded biochar material into a dispersion liquid, loading the dispersion liquid on a glassy carbon electrode, and drying the mixture to obtain the electrochemical sensor electrode.

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