Preparation method and application of ce cu ssqds / c@gce modified electrode

Abstract

The application discloses a preparation method of a CeCuSSQDs / C@GCE modified electrode, and the CeCuSSQDs / C composite material is prepared by taking copper nitrate and cerium nitrate as a pre-polymer in a porous carbon skeleton through a hydrothermal method; the CeCuSSQDs / C composite material is uniformly dispersed in anhydrous ethanol, then is drop-coated on the surface of a pretreated GCE electrode and dried to obtain the CeCuSSQDs / C@GCE modified electrode. The prepared modified electrode is applied to the detection of benzylpenicillin sodium in a water environment, and has an oxidation peak electrochemical signal when the electrochemical performance of the modified electrode is tested by using a cyclic voltammetry method, and has a low detection limit and a wide linear response range. The preparation method is simple, and the prepared modified electrode has high sensitivity for the detection of benzylpenicillin sodium in a complex water environment.

Description

Preparation method and application of CeCu SSQDs / C@GCE modified electrode Technical Field

[0001] This invention relates to the field of chemical analysis and detection, and in particular to the preparation method and application of CeCu SSQDs / C@GCE modified electrodes. Background Technology

[0002] Antibiotics can cause serious environmental pollution and increase bacterial resistance, especially quinolone antibiotics. These antibiotics accumulate in the body, gradually harming health and causing widespread concern. Sodium benzylpenicillin (NaBP) is a broad-spectrum β-lactam antibiotic used to treat animal diseases, resulting in residues in dairy products and farm wastewater. Due to its low price and excellent therapeutic effects, sodium benzylpenicillin has wide applications. However, it can cause allergic reactions and even severe shock, posing a potential threat to people allergic to penicillin. Furthermore, the overuse of sodium benzylpenicillin can lead to the emergence of superbugs and disrupt the balance of human gastrointestinal microbiota, causing harm to human health. Currently, many countries and organizations worldwide are paying close attention to this issue. Due to its high concentration, stability, resistance to degradation, and potential ecotoxicity in several wastewater samples, finding an accurate, convenient, effective, and low-cost method for detecting sodium benzylpenicillin is of great importance.

[0003] Currently, conventional methods for detecting benzylpenicillin sodium include spectrophotometry, capillary chromatography, and high-performance liquid chromatography (HPLC). While these methods each have their advantages, such as high selectivity and sensitivity, they also have many disadvantages, such as high equipment cost, long testing time, complex operation, and difficulty in online detection. Among various novel sensing methods, electrochemical sensors have attracted increasing attention due to their relatively simple sample preparation, small instrument size, and portability, making them an ideal method for detecting antibiotics in the aquatic environment. The core component of an electrochemical sensor is the electrode material. The electrode material affects the sensor's current or resistance, and can significantly reflect the sensor's quality.

[0004] Glassy carbon (GCE) electrodes are the most commonly used electrodes for electroanalysis due to their unique conductivity, chemical stability, biocompatibility, wide potential range, and extremely low gas permeability. Therefore, GCE is an excellent material for modification to stabilize the surface of electrodes used in electrochemical sensors.

[0005] Although research in the field of antibiotic electrochemical sensors has mainly focused on developing modified electrodes with improved sensitivity and selectivity, the detection sensitivity of electrochemical sensors for sodium benzylpenicillin is still not ideal for complex matrices, such as aquatic environments containing many impurities. Therefore, finding a NaBP detection method with higher sensitivity remains of great significance. Summary of the Invention

[0006] This application provides a method for preparing and applying a CeCu SSQDs / C@GCE modified electrode, solving the technical problem in existing technologies that cannot rapidly and sensitively detect NaBP in complex aquatic environments. The prepared CeCu SSQDs / C@GCE electrode exhibits an oxidation peak current response only to NaBP in actual complex aquatic environment detection, demonstrating not only extremely high sensitivity and reliability but also a low detection limit (6.31 × 10⁻⁶). -9 M) and a wider linear response range (6×10 - 8 M~1.2×10 -4 M).

[0007] The embodiments of this application adopt the following technical solutions:

[0008] A method for preparing a CeCu SSQDs / C@GCE modified electrode involves preparing a CeCu SSQDs / C composite material (copper oxide-doped cerium oxide solid solution quantum dots and bio-carbon composite material) in a porous carbon framework using copper nitrate and cerium nitrate as precursors via a hydrothermal method. The CeCu SSQDs / C composite material is then uniformly dispersed in anhydrous ethanol and drop-coated onto the surface of a pretreated GCE electrode, followed by drying to obtain the CeCu SSQDs / C@GCE modified electrode.

[0009] Quantum dot materials possess excellent electrochemical activity, high specific surface area, numerous active sites, and superior catalytic performance, making them widely applicable in electrochemical sensors. They easily combine with other materials to achieve synergistic effects and enhance performance, finding broad applications in the detection of amino acids, dopamine, organic matter in wastewater, harmful substances in food, and antibiotics. By introducing foreign elements into the CeO2 lattice to construct cerium oxide-based solid solutions, their application in electrochemical sensors exhibits superior redox capabilities and catalytic performance. This invention combines the advantages of solid solutions and quantum dots to design and develop a highly specific cerium oxide-based solid solution quantum dot (SSQD) electrode modification material for detecting NaBP antibiotics. Using a high-temperature carbonization method, treated bio-carbon sources are combined with SSQDs via impregnation and hydrothermal methods. The introduction of a new metal element—copper—forms a solid solution, altering the surface properties and electrochemical performance of the cerium oxide quantum dots and increasing internal defects and oxygen vacancies. Using bio-carbon as a dispersant in the preparation process, the micropores on the bio-carbon framework contribute to the uniform dispersion of SSQDs due to the confinement effect, providing a stable CeCu SSQDs loading and electron transport structure. Compared to other metal oxides, copper oxide is easier to use to obtain nanomaterials with high crystallinity, including their size and shape control, thereby realizing nanoelectronic devices with customized properties. Among a large number of different metal oxides, copper oxide belongs to the semiconductor group with p-type conductivity due to disordered doping caused by non-stoichiometry, and copper oxide is an abundant and non-toxic material that can be manufactured through sustainable and low-cost processes. This invention investigated and discovered that the surface properties, special electronic sequences, and spatial configurations of SSQDs exhibit significant specificity in response to a specific antibiotic (NaBP). By comparing the existing SSQD system with the SSQD system after reintroducing copper atoms, it was found that the cerium oxide unit cell further shrinks, the grain size decreases, defects and oxygen vacancies further increase, and the response current to the specific antibiotic is also enhanced.

[0010] Furthermore, transition metal oxides, due to their excellent stability, have brought new directions to the development of electrode modification materials. They not only possess high stability and good catalytic performance, but are also inexpensive and readily available. Copper oxide (CuO), as an important component of transition metal oxides, has gradually gained attention in electrochemical research. CuO is a metal semiconductor with a wide bandgap, possessing advantages such as high ion mobility, good chemical stability, simple preparation, and low cost, and is widely used in various fields. However, its poor conductivity, low dielectric constant, and rapid capacitance decay quickly hinder the further application of these electrodes. This invention introduces Cu atoms into the CeO2 crystal structure, which can improve the structural stability, ion diffusion, and conductivity of the composite material.

[0011] As a preferred option:

[0012] The method for preparing the CeCu SSQDs / C@GCE modified electrode as described above involves obtaining porous carbon from a bio-carbon source by high-temperature preparation in a tube furnace under N2 protection. The method for preparing porous carbon in this invention is not limited to this; other methods capable of forming a porous carbon framework are also applicable to this invention.

[0013] The method for preparing the CeCu SSQDs / C@GCE modified electrode as described above uses bio-carbon sources including fallen leaves, sawdust, wood fiber paper, cotton fabric, or cardboard. The types of bio-carbon sources used in this invention are not limited to these; other materials that contribute to the formation of porous carbon are also suitable for this invention.

[0014] As described above, the porous carbon and the precursor are prepared by an impregnation method, specifically by impregnating the porous carbon with a mixed solution containing copper nitrate and cerium nitrate by magnetic stirring.

[0015] The preparation method of the CeCu SSQDs / C@GCE modified electrode as described above specifically includes the following steps:

[0016] S1: Preparation of porous carbon:

[0017] After placing the biocarbon source in a container and pouring in ultrapure water and anhydrous ethanol at a molar ratio of 2:1, concentrated hydrochloric acid is added dropwise while stirring slowly in a fume hood until the biocarbon source is submerged. The pH of the soaking solution is 2-3, and the soaking time is 24 hours to remove impurity ions. Then, it is washed with ultrapure water and dried. Next, it is placed in a tube furnace and heated at 800℃ for 1 hour with N2. After naturally cooling to room temperature, porous carbon is obtained.

[0018] S2: Preparation of copper nitrate and cerium nitrate precursors:

[0019] (S21) Pour 1.3027g of cerium nitrate hexahydrate, 0.7248g of copper nitrate trihydrate, 50mL of ultrapure water and a clean magnetic stir bar into a glass container, seal it with plastic wrap, and then place it on a magnetic stirrer and stir for 30 minutes until the solids are completely dissolved and the mixture is uniform.

[0020] (S22) Weigh 1g of the porous carbon obtained in step S1 and pour it into the well mixed mixture. Seal it with plastic wrap and stir it slowly on a magnetic stirrer for 6 hours to allow the porous carbon to fully impregnate the metal ions in the solution. Then add concentrated ammonia in a fume hood to obtain a prepolymer solution with a pH of 9-10.

[0021] S3: Hydrothermal preparation of CeCu SSQDs / C composite materials:

[0022] The prepared prepolymer solution was poured into a polytetrafluoroethylene liner, then placed into a reaction vessel, and put into an electric thermostatic drying oven for hydrothermal reaction. After the reaction was completed, it was cooled to room temperature and then filtered. Impurities were removed by washing with ultrapure water and anhydrous ethanol. Then, it was dried and ground to obtain CeCu SSQDs / C composite material.

[0023] S4: Preparation of CeCu SSQDs / C@GCE modified electrode:

[0024] Weigh a certain amount of CeCu SSQDs / C composite material into a sample tube, and add a certain amount (generally 3-4 mL) of anhydrous ethanol to the sample tube (this invention does not specifically limit the amount of CeCu SSQDs / C and anhydrous ethanol added, as long as CeCu SSQDs / C is uniformly dispersed in anhydrous ethanol). After capping the sample tube, place it in an ultrasonic cleaner and sonicate for 15 minutes. After the CeCu SSQDs / C composite material is uniformly dispersed in anhydrous ethanol to form a dispersion, drop it onto the pretreated GCE electrode surface. After drying with an infrared lamp, add 0.5 wt% and 2 μL of Nafion solution to the modified electrode surface. After drying again, the CeCu SSQDs / C@GCE modified electrode is obtained.

[0025] In the preparation method of the CeCu SSQDs / C@GCE modified electrode as described above, in step S1, the biocarbon source is washed with ultrapure water, sterilized, and air-dried before being immersed in the solution. The main purpose is to remove impurities from the surface of the biocarbon source.

[0026] In the preparation method of the CeCu SSQDs / C@GCE modified electrode as described above, in step S2, the hydrothermal reaction refers to holding the electrode at 120℃ for 6 hours. During the hydrothermal reaction, the lower the holding temperature and the shorter the holding time, the less time a large number of Cu atoms have to enter the CeO2 unit cell to form a solid solution. Conversely, the higher the holding temperature and the longer the holding time, the more pronounced the agglomeration and stacking of the resulting CeO2-CuO composite material, which negatively impacts electrochemical performance. The drying treatment refers to drying in a drying oven at 55–65℃ for 20–28 hours, preferably at 60℃ for 24 hours. The grinding treatment refers to scraping the dried composite material from the filter paper and grinding it for 30 minutes using a clean and dried mortar.

[0027] The pretreatment of the CeCu SSQDs / C@GCE modified electrode as described above refers to the following steps: Alumina powder with a particle size of 0.01–0.05 μm is poured onto the surface of a polishing cloth adhered to a glass base, and ultrapure water is added. The GCE is then held perpendicular to the polishing cloth and polished at a uniform speed in a figure-eight pattern for 5–15 minutes. When the GCE exhibits a glassy luster, it is rinsed with pure water and then placed in a 1:1 mixture of ethanol and ultrapure water, sonicated for 30 seconds, washed, and dried. Next, the electrode is placed in a 1 mol / L H₂SO₄ solution and activated using the CV method. The electrode is repeatedly scanned within the range of -1.0–1.0 V until stable. Then, CV testing is performed in a mixed solution of 0.20 mol / L KNO₃ and 1 mmol / L K₃Fe(CN)₆ at a scan rate of 50 mV / s. This scanning is repeated until the potential difference between the oxidation and reduction peaks is within 100 mV, at which point the GCE electrode pretreatment is complete.

[0028] The present invention also provides the application of CeCu SSQDs / C@GCE modified electrodes, wherein the CeCu SSQDs / C@GCE modified electrodes prepared by the method described above are used for the detection of sodium benzylpenicillin in aquatic environments.

[0029] As a preferred technical solution:

[0030] As described above, the CeCu SSQDs / C@GCE modified electrode exhibits an oxidation peak electrochemical signal when its electrochemical performance is tested using cyclic voltammetry. The detection limit for the CeCu SSQDs / C@GCE modified electrode is 6.31 × 10⁻⁶. -9 M, linear response range is 6×10 -8 M~1.2×10 -4 M.

[0031] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0032] 1. The present invention prepares CeCu SSQDs / C composite material by drop-coating to modify the surface of a GCE electrode. A hydrothermal method is then used to synthesize the CeCu SSQDs / C composite material, constructing a novel and sensitive electrochemical sensor based on this material for the detection of sodium benzylpenicillin. This solves the problem of existing electrochemical sensors being unable to rapidly and sensitively detect NaBP in complex water conditions. The modified electrode prepared in this invention not only has extremely high sensitivity and reliability but also a low detection limit (6.31 × 10⁻⁶). -9 M) and a wider linear response range (6×10 -8 M~1.2×10 -4 M).

[0033] 2. The modified electrode prepared by the method of the present invention exhibits a significant oxidation peak electrochemical signal in a buffer solution containing NaBP when the electrochemical performance of the modified electrode is tested by cyclic voltammetry.

[0034] 3. The preparation method of this invention is simple, the raw material cost is low, and it has great application prospects. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 shows the comparison curves of cyclic voltammetry tests between the CeCu SSQDs / C@GCE electrode of the present invention and the bare GCE electrode.

[0037] Figure 2 shows the comparison curves of cyclic voltammetry tests performed on the CeCu SSQDs / C@GCE electrode of the present invention in buffer solutions containing NaBP and buffer solutions without NaBP.

[0038] Figure 3 shows the cyclic voltammetry comparison curves of the CeCu SSQDs / C@GCE electrode of the present invention and other modified electrodes in 0.12 mM NaBP buffer solution;

[0039] Figure 4 shows the differential pulse voltammetry of different concentrations of benzylpenicillin sodium detected by the CeCu SSQDs / C@GCE electrode of the present invention;

[0040] Figure 5 shows the linear relationship between different concentrations of NaBP and peak current in the CeCu SSQDs / C@GCE electrode of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The preparation method of CeCu SSQDs / C@GCE modified electrode includes the following steps:

[0043] S1: Preparation of porous carbon:

[0044] After washing, sterilizing, and air-drying the wood fiber paper (this embodiment uses wood fiber paper as an example, but the method for preparing porous carbon from other types of bio-carbon sources is also applicable), place it in a 100mL beaker and pour in ultrapure water and anhydrous ethanol in a volume ratio of 2:1. Then, while slowly stirring with concentrated hydrochloric acid dropwise in a fume hood, the wood fiber paper is submerged. The pH of the soaking solution is 2-3, and the soaking time is 24 hours. After washing with ultrapure water and drying, the paper is placed in a tube furnace and heated at 800℃ for 1 hour with N2. After naturally cooling to room temperature, porous carbon is obtained.

[0045] S2: Preparation of copper nitrate and cerium nitrate precursors:

[0046] (S21) Pour 1.3027g of cerium nitrate hexahydrate, 0.7248g of copper nitrate trihydrate, 50mL of ultrapure water and a clean magnetic stir bar into a glass container, seal it with plastic wrap, and then place it on a magnetic stirrer and stir for 30 minutes until the solids are completely dissolved and the mixture is uniform.

[0047] (S22) Weigh 1g of the porous carbon obtained in step S1 and pour it into the well mixed mixture. Seal it with plastic wrap and stir it slowly on a magnetic stirrer for 6 hours. Then add concentrated ammonia dropwise in a fume hood to obtain a prepolymer solution with a pH of 9-10.

[0048] S3: Hydrothermal preparation of CeCu SSQDs / C composite materials:

[0049] The prepared prepolymer solution was poured into a polytetrafluoroethylene liner, then placed into a reaction vessel, and placed in an electric thermostatic drying oven at 120°C for 6 hours for hydrothermal reaction. After the reaction was completed, the mixture was cooled to room temperature and then filtered. Impurities were removed by washing with ultrapure water and anhydrous ethanol, and then dried in a drying oven at 60°C for 24 hours. The dried composite material was scraped off the filter paper and ground for 30 minutes with a clean and dried mortar to obtain CeCu SSQDs / C composite material.

[0050] S4: Preparation of CeCu SSQDs / C@GCE modified electrode:

[0051] Weigh a certain amount of CeCu SSQDs / C composite material into a sample tube, add 3 mL of anhydrous ethanol to the sample tube, cover the sample tube, and place it in an ultrasonic cleaner for 15 min of sonication. After the CeCu SSQDs / C composite material is uniformly dispersed in anhydrous ethanol to form a dispersion, drop it onto the pretreated GCE electrode surface. After drying with an infrared lamp, add 0.5 wt% and 2 μL of Nafion solution to the modified electrode surface. After drying again, the CeCu SSQDs / C@GCE modified electrode is obtained.

[0052] The pretreatment process involves: 0.01–0.05 μm alumina powder, along with ultrapure water, is poured onto the surface of the polishing cloth adhered to the glass base. The GCE is then held perpendicular to the polishing cloth and polished at a constant speed in a figure-eight pattern for 5–15 minutes. When the GCE exhibits a glassy luster, it is rinsed with pure water and then ultrasonicated for 30 seconds in a 1:1 mixture of ethanol and ultrapure water. After rinsing and drying, the electrode is placed in a 1 mol / L H₂SO₄ solution and activated using the CV method. The electrode is repeatedly scanned within the range of -1.0 to 1.0 V until stable. CV testing is then performed in a mixed solution of 0.20 mol / L KNO₃ and 1 mmol / L K₃Fe(CN)₆ at a scan rate of 50 mV / s. This scanning is repeated until the potential difference between the oxidation and reduction peaks is within 100 mV, at which point the GCE electrode pretreatment is complete.

[0053] The CeCu SSQDs / C@GCE modified electrode prepared by the above method was used for the detection of sodium benzylpenicillin in an aqueous environment.

[0054] In this embodiment, cyclic voltammetry was used to test the electrochemical performance of CeCu SSQDs / C@GCE, and different modified electrodes were tested. Figure 1 shows the cyclic voltammetric curves of the CeCu SSQDs / C@GCE electrode and the bare GCE electrode in PBS phosphate buffer containing 0.12 mM sodium benzylpenicillin (NaBP). It can be seen that the bare GCE has no obvious electrochemical response signal to the sodium benzylpenicillin buffer. In contrast, the CeCu SSQDs / C@GCE modified electrode showed a significant oxidation peak electrochemical signal in the sodium benzylpenicillin buffer at 0.12 V, proving that CeCu SSQDs / C@GCE can detect sodium benzylpenicillin in a liquid environment. Figure 2 shows the cyclic voltammetry results of the CeCu SSQDs / C@GCE electrode in buffer solutions containing sodium benzylpenicillin and those without. It is easy to see that the CeCu SSQDs / C@GCE electrode did not show any oxidation or reduction peaks in the buffer solution without NaBP, but it did show an electrochemical response in the buffer solution containing NaBP. This indicates that it is feasible to use the CeCuSSQDs / C composite material to modify the GCE electrode for NaBP detection.

[0055] The CuO QDs / C@GCE electrode and CeO2QDs / C@GCE electrode, prepared using the same hydrothermal method as in the embodiments of this invention, were compared with the CeCu SSQDs / C@GCE modified electrode of this invention. The electrochemical performance results are shown in Figure 3, which is a cyclic voltammetric image in 0.12 μM NaBP buffer solution. As can be seen from the figure, the CuO QDs / C modified GCE electrode and the CeO2QDs / C modified GCE electrode did not show any electrochemical signal in the benzylpenicillin sodium buffer solution, while the CeCu SSQDs / C@GCE modified electrode clearly showed an oxidation peak signal during detection.

[0056] The above demonstrates that the CeCu SSQDs / C@GCE modified electrode is the best material for electrochemical detection of NaBP, exhibiting the highest sensitivity for NaBP detection.

[0057] To further analyze the detection sensitivity of the electrochemical sensor of the present invention for benzylpenicillin sodium, the linear range and detection limit of CeCuSSQDs / C@GCE were calculated at a CeCuSSQDs / C modifier concentration of 3 mg·mL⁻¹. -1 At a pH of 6.1 and a scan rate of 0.1 V / s, NaBP solutions of 0.06 μM, 0.6 μM, 3–12 μM gradients and 20 μM–120 μM solutions were prepared. Differential pulse voltammetry (DPV) was performed on different concentrations of benzylpenicillin sodium solutions within a potential range of -0.5 V to 0.1 V. Figure 4 shows the differential pulse voltammograms of CeCu SSQDs / C@GCE at different NaBP concentrations. It can be seen that the peak current increases with increasing benzylpenicillin sodium concentration, reaching a peak value at 6 × 10⁻⁶. -8 M to 1.2×10 -4 Within the range of M, there is a clear linear relationship between NaBP concentration and peak response. Figure 5 shows the linear relationship between different NaBP concentrations and peak current. The fitted equation can be expressed as y = 0.0384x + 0.4111 (correlation coefficient R). 2 =0.9978), the detection limit (LOD) is 6.31×10 -9 Therefore, CeCu SSQDs / C@GCE exhibits a low limit of detection (LOD) and a wide linear range for sodium benzylpenicillin. This is mainly due to the excellent electrochemical catalytic activity resulting from the composite material's large specific surface area, excellent electron transport capability, and high defect state. CeCu SSQDs / C@GCE can be used sensitively and efficiently for the detection of sodium benzylpenicillin in aquatic environments.

[0058] In summary, this invention synthesizes a CeCu SSQDs / C composite material via a hydrothermal method using lignocellulosic biochar prepared at high temperatures, and constructs a novel, sensitive electrochemical sensor based on this material for the detection of benzylpenicillin sodium. The electrochemical performance of this modified electrode was evaluated, demonstrating the successful synthesis of the cerium-copper solid solution quantum dot-supported biochar (CeCuSSQDs / C) composite material and the enhancement of various aspects of the material by biochar. The prepared electrode not only exhibits extremely high sensitivity and reliability but also a low detection limit (6.31 × 10⁻⁶). -9 M) and a wider linear response range (6×10 -8 M~1.2×10 -4 These characteristics can be attributed to the large specific surface area, excellent electron transfer capability, and superior electrochemical catalytic activity resulting from the biogenic carbon framework and highly defective solid solution quantum dot (SSQD) structure. These results indicate that this sensor has great application potential in water quality monitoring of NaBP.

[0059] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if such modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include such modifications and variations.

Claims

1. A method for preparing CeCu SSQDs / C@GCE modified electrodes, characterized in that, CeCu SSQDs / C composite material was prepared by hydrothermal method using copper nitrate and cerium nitrate as precursors in a porous carbon framework. The CeCu SSQDs / C composite material was uniformly dispersed in anhydrous ethanol and then drop-coated onto the surface of a pretreated GCE electrode and dried to obtain a CeCu SSQDs / C@GCE modified electrode. The specific steps are as follows: S1: Preparation of porous carbon: The bio-carbon source was placed in a container and ultrapure water and anhydrous ethanol were poured in at a volume ratio of 2:

1. Concentrated hydrochloric acid was added dropwise in a fume hood while stirring slowly until the bio-carbon source was submerged. The pH of the soaking solution was 2-3 and the soaking time was 24 hours. Then, it was washed with ultrapure water and dried. Then, it was placed in a tube furnace and N2 was introduced and kept at 800 °C for 1 h. After natural cooling to room temperature, porous carbon was obtained; S2: Preparation of copper nitrate and cerium nitrate precursors: (S21) 1.3027 g of cerium nitrate hexahydrate and 0.7248 g of cerium nitrate precursors were added respectively. (S22) Pour 1 g of copper nitrate trihydrate, 50 mL of ultrapure water and a clean magnetic stir bar into a glass container, seal it with plastic wrap, and then stir it on a magnetic stirrer for 30 min until the solid is completely dissolved and the mixture is uniform; (S3) Weigh 1 g of porous carbon obtained from step S1 and pour it into the mixed mixture, seal it with plastic wrap, stir it slowly on a magnetic stirrer for 6 h, and then add concentrated ammonia dropwise in a fume hood to obtain a prepolymer solution with a pH of 9-10; S3: Hydrothermal preparation of CeCu SSQDs / C composite material: Pour the prepolymer solution obtained from step S2 into a polytetrafluoroethylene liner, then put it into a reaction vessel, and put it into an electric thermostatic drying oven for hydrothermal reaction. After the reaction is completed, after cooling to room temperature, filter it, wash it with ultrapure water and anhydrous ethanol to remove impurities, and then dry and grind it to obtain CeCu SSQDs / C composite material; S4: Preparation of CeCu SSQDs / C@GCE modified electrode: Weigh a certain amount of CeCu SSQDs / C composite material into a sample tube, then add a certain amount of anhydrous ethanol to the sample tube. After capping the sample tube, place it in an ultrasonic cleaner and sonicate for 15 min. After the CeCu SSQDs / C composite material is uniformly dispersed in anhydrous ethanol to form a dispersion, drop it onto the pretreated GCE electrode surface. After drying with an infrared lamp, add 0.5wt% and 2 μL of Nafion solution to the modified electrode surface. After drying again, the CeCu SSQDs / C@GCE modified electrode is obtained.

2. The method for preparing the CeCu SSQDs / C@GCE modified electrode as described in claim 1, characterized in that, The porous carbon is prepared by placing a bio-carbon source in a tube furnace under N2 protection and subjecting it to high temperature.

3. The method for preparing the CeCu SSQDs / C@GCE modified electrode as described in claim 2, characterized in that, The biocarbon source includes fallen leaves, sawdust, wood fiber paper, cotton fabric, or cardboard.

4. The method for preparing the CeCu SSQDs / C@GCE modified electrode as described in claim 1, characterized in that, The porous carbon and the precursor are prepared by impregnation, specifically by impregnating the porous carbon with a mixed solution containing copper nitrate and cerium nitrate by magnetic stirring.

5. The method for preparing the CeCu SSQDs / C@GCE modified electrode as described in claim 1, characterized in that, In step S1, the biocarbon source is washed with ultrapure water, sterilized, and air-dried before being soaked in the solution.

6. The method for preparing the CeCu SSQDs / C@GCE modified electrode as described in claim 1, characterized in that, In step S2, the hydrothermal reaction refers to holding the material at 120°C for 6 hours, the drying treatment refers to drying the material in a drying oven at 60°C for 24 hours, and the grinding treatment refers to scraping the dried composite material off the filter paper and grinding it for 30 minutes with a clean and dried mortar.

7. The method for preparing the CeCu SSQDs / C@GCE modified electrode as described in claim 1, characterized in that, The pretreatment refers to the following steps: Alumina powder with a particle size of 0.01~0.05μm is poured onto the surface of the polishing cloth adhered to the glass base, and ultrapure water is added. The GCE is then held perpendicular to the polishing cloth and polished at a uniform speed in a figure-eight pattern for 5~15 minutes. When the GCE exhibits a glassy luster, it is rinsed with pure water and then placed in a 1:1 mixture of ethanol and ultrapure water, sonicated for 30 seconds, washed, and dried. Next, the electrode is placed in a 1mol / L H2SO4 solution and activated using the CV method. The electrode is repeatedly scanned within the range of -1.0~1.0 V until stable. Then, a CV test is performed in a mixed solution of 0.20 mol / L KNO3 and 1 mmol / L K3Fe(CN)6 at a scan rate of 50 mV / s. This is repeated until the potential difference between the oxidation peak and the reduction peak is within 100 mV, at which point the GCE electrode pretreatment is complete.

8. Application of CeCu SSQDs / C@GCE modified electrodes, characterized in that, The CeCu SSQDs / C@GCE modified electrode prepared by the method described in any one of claims 1 to 7 is used for the detection of sodium benzylpenicillin in an aqueous environment.

9. The application of the CeCu SSQDs / C@GCE modified electrode as described in claim 8, characterized in that, When the electrochemical performance of the CeCu SSQDs / C@GCE modified electrode was tested using cyclic voltammetry, an oxidation peak electrochemical signal was observed, and the detection limit of the CeCuSSQDs / C@GCE modified electrode was 6.31 × 10⁻⁶. -9 M, linear response range is 6×10 -8 M~1.2×10 -4 M.

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