Double-signal electrochemical uric acid sensor based on CoFe-coated NC composite material, preparation method of double-signal electrochemical uric acid sensor and application of double-signal electrochemical uric acid sensor in uric acid detection

Abstract

The invention discloses a double-signal electrochemical uric acid sensor based on a CoFe-coated NC composite material, a preparation method of the double-signal electrochemical uric acid sensor and application of the double-signal electrochemical uric acid sensor in uric acid detection, and belongs to the technical field of nanometer electrochemical sensors. The electrochemical uric acid sensor adopts a three-electrode system, and a working electrode is an inert electrode modified with a CoFe-coated NC composite material; and the CoFe-coated NC composite material is nitrogen-doped carbon nanofibers modified by Co-Fe double metals. The surface of an inert electrode is modified with Co-Fe double-metal modified nitrogen-doped carbon nanofibers with excellent conductivity and electro-catalytic performance, and then a prepared working electrode serves as a sensing platform and is used for constructing an electrochemical uric acid sensor. A wide linear range, a low detection limit and good selectivity and stability can be shown on uric acid detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanoelectrochemical sensors, and specifically relates to a dual-signal electrochemical uric acid sensor based on a CoFe@NC composite material, a preparation method thereof, and an application thereof in uric acid detection. Background Art

[0002] With the rapid development of society and the economy, people's dietary patterns have undergone tremendous changes. The continuous improvement in living standards has led to a significant increase in the proportion of high-purine foods in the daily diet. Uric acid (UA), the end product of purine metabolism, is a key biomolecule in human body fluids. In healthy individuals, UA maintains a dynamic balance and participates in various physiological processes. However, due to its low solubility in aqueous solutions, uric acid easily accumulates in the body if excessive high-purine foods are consumed or if metabolic abnormalities occur. Excessive accumulation of uric acid can disrupt the body's physiological balance and lead to a series of serious diseases, such as gout, hyperuricemia, cardiovascular disease, coronary heart disease, and hypertension. Therefore, accurate and rapid detection of uric acid levels in body fluids is of great significance for the early diagnosis and treatment of related diseases. Currently, various analytical methods, including capillary electrophoresis, chemiluminescence, colorimetry, and high-performance liquid chromatography, are widely used for uric acid detection. However, these traditional methods suffer from limitations such as expensive instrumentation, complex procedures, and lengthy detection times. In contrast, electrochemical methods, with their significant advantages such as low cost, rapid response, and high sensitivity, have become a hot topic in small molecule detection research, showing broad application prospects in clinical diagnosis, environmental monitoring, and other fields. In electrochemical detection systems, the detection performance of electrochemical sensors depends largely on the characteristics of the electrode materials. Therefore, the development of electrode materials with excellent performance has become the key to current research. In recent years, Metal-Organic Frameworks (MOFs) derivatives have attracted widespread attention as new electrode catalysts due to their unique structure and potential catalytic activity. However, in practical applications, the application of MOFs in sensing platforms still faces many challenges. For example, the limited active sites of traditional MOFs-based materials result in low catalytic efficiency for target substances, making it difficult to meet the requirements of high-sensitivity and high-selectivity detection. Therefore, the development of MOFs-based nanocatalytic materials with rich and multiple active sites and the improvement of their catalytic performance are of vital importance for the preparation of high-performance working electrodes and the promotion of the development of electrochemical sensing technology. Summary of the Invention

[0003] The present invention aims to provide a dual-signal electrochemical uric acid sensor based on a CoFe@NC composite material, its preparation method, and its application in uric acid detection. This sensor is constructed by modifying the surface of an inert electrode with nitrogen-doped carbon nanofibers modified with a Co-Fe bimetallic (i.e., the electrocatalyst: CoFe@NC composite material), which exhibits excellent electrical conductivity and electrocatalytic properties. The prepared working electrode then serves as a sensing platform for the electrochemical uric acid sensor, demonstrating a wide linear range, low detection limit, and good selectivity and stability for uric acid detection.

[0004] The purpose of the present invention is achieved through the following technical solutions: A dual-signal electrochemical uric acid sensor based on CoFe@NC composite material adopts a three-electrode system, and the working electrode is an inert electrode modified with CoFe@NC composite material; the CoFe@NC composite material is a nitrogen-doped carbon nanofiber modified with Co-Fe bimetallic.

[0005] The electrochemical uric acid sensor of this invention utilizes a three-electrode system, centered around a working electrode modified with a CoFe@NC composite material. Composed of nitrogen-doped carbon nanofibers modified with a Co-Fe bimetallic, the CoFe@NC composite offers three key advantages: First, the inherited MOF structure and catalytic activity lay the foundation for the reaction. Second, the high surface area of ​​the nanofibers expands the contact space with uric acid, providing a large number of active sites. Third, the nitrogen-doped carbon imparts excellent conductivity, ensuring rapid electron transport and promoting efficient electrochemical reactions. These three factors work together to significantly improve the overall performance of the composite material.

[0006] Through an innovative process, the present invention precisely loads bimetallic CoFe nanoparticles with excellent catalytic activity onto the surface of one-dimensional nitrogen-doped carbon nanofibers, successfully preparing a CoFe@NC composite material with both good conductivity and excellent catalytic activity. Subsequently, this composite material is modified onto the surface of an inert electrode, and the resulting working electrode serves as the core sensing platform for constructing a dual-signal electrochemical uric acid sensor. During actual detection, the working electrode, thanks to the unique properties of the CoFe@NC composite material, can significantly improve the sensor's sensitivity to uric acid (UA), enabling accurate detection of low-concentration uric acid; enhance selectivity, effectively eliminating the influence of other interfering substances; and simultaneously accelerate the response rate and shorten the detection time, thereby comprehensively optimizing the sensor's overall detection performance and providing strong technical support for the rapid and accurate diagnosis of uric acid-related diseases.

[0007] As some possible implementation methods of the present application, the preparation method of the working electrode is as follows: S1. Cobalt nitrate and 2-methylimidazole were weighed and dissolved in a mixture of methanol and ethanol, respectively. The two solutions were then mixed, centrifuged, washed, and dried to obtain a purple solid, ZIF-67. Separately, ferric chloride hexahydrate and terephthalic acid were weighed and dissolved in N,N-dimethylformamide, respectively. The two solutions were then mixed and allowed to react fully, then centrifuged, washed, and dried to obtain a yellow solid, MIL-53. S2. Polyacrylonitrile and polystyrene were dispersed in DMF, followed by the addition of ZIF-67 and MIL-53, and stirred to form a spinning solution. The spinning solution was then spun, and the resulting fiber membrane was pre-oxidized, calcined at high temperature, cooled, and ground into a powder to obtain a CoFe@NC composite material. S3. Prepare the CoFe@NC composite material into a nanomaterial solution and drop it onto an inert electrode. Allow to dry naturally at room temperature to obtain a working electrode.

[0008] As some possible implementation methods of the present application, in step S2, the mass ratio of ZIF-67 to MIL-53 is 1:(1~3).

[0009] As some possible implementation methods of the present application, in step S2, the pre-oxidation temperature is 200~250 °C, the time is 1.5~2.5h, and the pre-oxidation is carried out in air.

[0010] As some possible implementation methods of the present application, in step S2, the high-temperature calcination step is: raising the temperature to 500~550°C at a heating rate of 4~7°C / min under an argon atmosphere, maintaining it for 1.5~2.5h, and then raising the temperature to 800~850°C at a heating rate of 2~3°C / min.

[0011] As some possible implementation methods of the present application, the inert electrode is made of glassy carbon, platinum, gold, silver, lead or conductive glass.

[0012] In addition, to achieve the above objectives, the present invention also provides a method for preparing a dual-signal electrochemical uric acid sensor based on CoFe@NC composite material, specifically: first preparing a working electrode, and then forming a three-electrode system by combining the working electrode, the counter electrode, and the reference electrode.

[0013] Furthermore, to achieve the above objectives, the present invention also provides an application of a dual-signal electrochemical uric acid sensor based on CoFe@NC composite material in uric acid detection.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This study uses electrospinning to precisely embed two MOFs into PAN / PS nanofibers. After pre-oxidation and high-temperature calcination, the resulting Co-Fe bimetallic-modified nitrogen-doped carbon nanofibers, or CoFe@NC composites, are successfully prepared. This preparation method leverages the structural advantages of MOFs and the molding properties of PAN / PS nanofibers, endowing the composite with a unique microstructure and, in turn, superior electrocatalytic properties. This significantly enhances the conductivity of the working electrode and significantly accelerates electron transfer and interfacial reaction efficiency, providing a solid foundation for uric acid detection.

[0015] On this basis, the present invention uses CoFe@NC composite material as a sensing platform to construct a dual-signal analysis mode nanoelectrochemical sensor based on differential pulse voltammetry (DPV) and chronoamperometry (IT). This greatly expands the linear range of the sensor for UA detection and makes the detection concentration range wider; it achieves an extremely low limit of detection (LOD) and can accurately capture trace uric acid; at the same time, it gives the sensor good selectivity, effectively eliminates interference from other substances in biological fluids, and has excellent stability. It can still maintain data reliability after multiple tests, providing an efficient and accurate detection method for clinical uric acid detection and related disease diagnosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 : FESEM images of CoFe@NC at different preparation stages: (A) precursor fiber, (B) pre-oxidation, (C) carbonization and (D) element distribution.

[0017] Figure 2 : CV (A) and DPV (B) plots of GCE, GCE / NC, and GCE / CoFe@NC in 0.1 PBS solution containing UA, with a CV scan rate of 50 mV / s.

[0018] Figure 3 : CV curves (A) and linear relationship diagram (B) of GCE / CoFe@NC at different UA concentrations; CV curves (C) and linear relationship diagram (D) of GCE / CoFe@NC at different scan rates.

[0019] Figure 4 : CV (A) and DPV (B) diagrams of GCE / CoFe@NC in PBS solutions with different pH values; trend diagram of peak current value changing with pH value (C); linear relationship diagram of peak potential value and scan rate (D).

[0020] Figure 5: DPV curves of GCE / CoFe@NC at different UA concentrations (A); linear relationship between peak current value and UA concentration in the range of 0.01−0.35 mM (B); repeatability (C) and stability (D) of the nanosensor.

[0021] Figure 6 :IT curves of GCE / CoFe@NC at different UA concentrations (A); (A) Schematic diagram of the enlarged structure of the low and medium concentration range (1−25.8 μM) (B); Linear relationship between the peak current value and UA concentration in the ranges of 0.001−0.04 and 0.04−0.35 mM, respectively (C−D); Selectivity of the nanosensor (E). DETAILED DESCRIPTION

[0022] Example 1 This embodiment provides a nano-electrochemical uric acid sensor, the preparation method of which includes: S1. Weigh 0.873 g of cobalt nitrate and 0.96 g of 2-methylimidazole and ultrasonically dissolve them in 20 mL of a mixture of methanol and ethanol (1:1, v / v). Then, rapidly mix the two solutions at room temperature, stir for 24 hours, and collect the precipitate by centrifugation. Wash the solution three times with ethanol and oven-dry at 60°C overnight. The resulting purple solid is designated ZIF-67. Separately, weigh 0.7481 g of ferric chloride hexahydrate and 0.5014 g of terephthalic acid and ultrasonically dissolve them in 15 mL of N,N-dimethylformamide (DMF). Then, thoroughly mix the two solutions and transfer them to a 50 mL round-bottom flask. Heat the mixture in an oil bath at 150°C for 2 hours. Wash and collect the precipitate by centrifugation and oven-dry at 60°C overnight. The resulting yellow solid is designated MIL-53.

[0023] S2. 0.5 g of polyacrylonitrile (PAN) and 0.25 g of polystyrene (PS) were weighed and dispersed in 5 mL of DMF with stirring. 0.25 g of ZIF-67 and 0.50 g of MIL-53 were then added and stirred overnight to form a uniform spinning solution. The spinning solution was transferred to a 10 mL syringe and spun using a 19-gauge metal needle at a positive voltage of 18 kV and a negative voltage of −2 kV, at a feed rate of 1 mL / h. The resulting fiber membrane was pre-oxidized at 200 °C in air for 2 hours. The temperature was then increased to 500 °C under an argon atmosphere at a heating rate of 5 °C / min. After holding for 2 hours, the temperature was increased to 800 °C at a heating rate of 2 °C / min. After cooling to room temperature, the black carbide was ground into a powder. The resulting product is designated as CoFe@NC.

[0024] The surface morphology of CoFe@NC composite fibers was characterized by field emission scanning electron microscopy (FESEM). Figure 1 As shown in (A), there are granular substances on the surface of nanofibers, indicating that MOFs have been successfully loaded on the NC surface. Figure 1 As can be seen from (B) and (C), the beaded structure of CoFe@NC is retained after pre-oxidation and high-temperature carbonization. Figure 1 The EDS elemental mapping in (D) shows the uniform distribution of C, O, N, Co, and Fe elements.

[0025] As a comparison, nanofiber NCs without adding MOFs were prepared under the same conditions.

[0026] S3. Weigh 4 mg of CoFe@NC material and ultrasonically disperse it in 2 mL of pure water to obtain a 2 mg / mL nanomaterial solution. Add 5 μL of this solution dropwise to a clean glassy carbon electrode (GCE). After air drying at room temperature, the GCE / CoFe@NC working electrode was obtained.

[0027] S4. A three-electrode system consisting of a working electrode, an Ag / AgCl reference electrode, and a Pt wire counter electrode was used for electrochemical testing on a CHI 760E electrochemical workstation. During the test, the pH of the phosphate buffer was adjusted to ensure that the nanoelectrochemical sensor could respond to UA concentration and exhibit good electrochemical performance.

[0028] Experimental example 1. Electrocatalytic performance of different working electrodes for UA.

[0029] The electrocatalytic behavior of the working electrode towards UA was studied by CV and DPV methods. Figure 2 (A) and (B) show the CV and DPV curves of GCE, GCE / NC, and GCE / CoFe@NC, respectively.

[0030] from Figure 2 As can be seen, GCE exhibits only a weak UA oxidation peak, but the current response is significantly limited due to the slow reaction kinetics. In contrast, both GCE / NC and GCE / CoFe@NC exhibit more pronounced UA oxidation peaks, confirming the successful modification of the nanomaterials. Furthermore, the oxidation peak current of GCE / CoFe@NC at 0.3 V is significantly higher than that of GCE / NC, indicating that the introduction of the bimetallic (CoFe) greatly improves the electron transfer efficiency of UA through synergistic effects and the provision of more active sites.

[0031] 2. Effect of UA concentration.

[0032] In order to explore the feasibility of GCE / CoFe@NC in detecting UA, the current response of different UA concentrations was tested by CV method. The results are shown in Figure 2. Figure 3 As shown in (A), in 0.1 M PBS buffer, the oxidation peak current increased rapidly with increasing UA concentration. Figure 3 (B) shows that the current response is linearly positively correlated with the UA concentration in the range of 0-0.5 mM. Therefore, the prepared GCE / CoFe@NC electrode is able to respond to changes in UA concentration and can be used for the quantitative analysis of UA.

[0033] 3. Influence of scanning rate.

[0034] In order to study the reaction kinetics of UA on the GCE / CoFe@NC surface, CV tests were performed by changing the scan rate. Figure 3 As shown in (C), as the scan rate increases from 10 mV / s to 100 mV / s, the irreversible oxidation peak current of UA gradually increases. Figure 3 (D) in the figure shows that the current value is linearly related to the scan rate with a correlation coefficient of 0.996, indicating that the electrochemical reaction of UA on the GCE / CoFe@NC surface is an adsorption-controlled process.

[0035] 4. Influence of pH.

[0036] The pH value of the solution directly affects the oxidation peak current and potential of UA, so the CV curves of UA were measured in PBS solutions with different pH values. Figure 4 As shown in (A), with the increase of pH value, the current response shows a trend of first increasing and then decreasing. In order to further explore the effect of pH on the UA oxidation process, the DPV method was used to test. Figure 4 As shown in (B) and (C), when the pH increases from 5.4 to 6.8, the current response gradually increases and reaches a maximum value at pH = 6.8. Therefore, PBS with pH = 6.8 was selected as the electrolyte solution for subsequent tests. Figure 4 As can be seen from (D) in the figure, the oxidation peak potential decreases linearly with increasing pH, and the linear relationship can be expressed by the following equation: E pa (V) = −0.063pH+ 0.74 (R 2 = 0.996), and the slope (−63 mV / pH) is close to the theoretical value (−59 mV / pH) calculated by the Nernst equation, indicating that the number of electrons transferred during the oxidation of UA on the working electrode is equal to the number of protons.

[0037] 5. DPV quantitative detection.

[0038] The sensitivity of the electrochemical sensor was studied by detecting different concentrations of UA in 0.1 M PBS buffer solution using the DPV method. Figure 5 (A) shows the DPV curves of different UA concentrations (0.01−0.35 mM) on GCE / CoFe@NC. Figure 5 (B) in the figure shows that as the UA concentration increases, there is a good linear relationship between the peak current value and the UA concentration, and the linear regression equation is: I pa (μA) = 444.8 c – 1.53 (R 2 = 0.998).

[0039] The limit of detection (LOD) was calculated using the formula LOD = 3σ / S, where σ is the standard deviation of three blank samples and S is the slope of the calibration curve. The LOD for GCE / CoFe@NC to UA was calculated to be 26.8 μM.

[0040] To verify the repeatability of the nanoelectrochemical sensor, six identical sensors were prepared, and the current response of GCE / CoFe@NC to 0.2 mM UA was recorded using the DPV method. Figure 5 The results in (C) show that the six electrodes exhibit similar oxidation peak current values ​​at 0.3 V, and the relative standard deviation (RSD) of the current response between different electrodes is less than 3.64%. Therefore, the nanoelectrochemical sensor based on CoFe@NC catalyst exhibits excellent repeatability in UA detection.

[0041] For electrochemical sensors, stable output of electrical signals is very important. Therefore, the stability of CoFe@NC for UA detection was tested by the IT method. Figure 5 As shown in (D), when UA was added to 0.1 M PBS solution, the current response remained basically unchanged for up to 1000 s, indicating that the proposed electrochemical sensing platform has good stability.

[0042] 6. Quantitative analysis by it method.

[0043] The current response of the GCE / CoFe@NC working electrode at a constant potential of 0.35 V (vs. Ag / AgCl) was recorded using the IT method. UA was added to the PBS buffer at 50 s intervals under stirring. The results are shown in Figure 2. Figure 6 As shown in (A), with the continuous addition of UA, the current shows a steady increasing trend. Since the current signal in the low concentration region (1-25.8 μM) is relatively weak and difficult to observe in a wide concentration range, Figure 6(B) in the figure shows the magnified area. The sensor showed good linearity in the detection of UA in the range of 0.001−1.2 mM. Figure 6 As can be seen in (C) and (D) of Figure 1, the linear relationship exhibits a distinct segmented characteristic. This is because when the UA concentration is low, a large number of unoccupied active sites exist on the electrode surface, the electrode reaction is dominated by the adsorption process, and the current response increases rapidly. When the UA concentration exceeds 0.04 mM, the active sites on the electrode surface tend to be saturated, the adsorption effect weakens, the electrode reaction is dominated by the dual process of diffusion and adsorption, and the growth rate of the current response decreases. Within the detection range, the linear equation for UA can be described as: 0.001−0.04 mM: I pa (μA) = 60.14 c + 0.05 (R 2 = 0.999), 0.04−1.20 mM: I pa (μA) = 56.13 c + 1.08 (R 2 = 0.995).

[0044] The LOD was calculated from the slope of the calibration curve to be 2.40 μM, and the sensitivity was 0.85 mA∙mM. −1 ∙cm −2 .

[0045] Selectivity is an important parameter for evaluating sensor performance. Therefore, the selectivity of the electrochemical sensor was tested by studying the IT responses of sodium chloride (NaCl), potassium chloride (KCl), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), and glucose (Glu) on the GCE / CoFe@NC. The concentration of the interfering substances was 10 times that of UA. Figure 6 Panel (E) shows that when uric acid (UA) is sequentially added to a 0.1 M PBS solution (pH = 6.8), the electrochemical sensor's it response gradually increases with increasing UA concentration. When an interfering substance is added, no significant current response is observed. Further addition of UA to the system reveals a continued increase in the it response with increasing UA concentration. These results demonstrate that the sensor exhibits excellent selectivity for UA and maintains stable operation even in the presence of multiple potential interfering substances.

[0046] In summary, this paper constructs a dual-signal detection platform based on bimetallic-modified nitrogen-doped carbon nanofibers (CoFe@NC composite) for the quantitative analysis of UA concentrations using both DPV and IT. The electrocatalyst CoFe@NC is prepared by electrospinning two MOFs onto NC and then pyrolyzing them under inert gas. The synergistic effect between the bimetallic CoFe nanoparticles and the NC fibers enhances the electrocatalytic activity of the nanocomposite, resulting in excellent analytical performance for UA, including a wide linear range (0.01−0.35 mM and 0.001−1.2 mM), low detection limits (26.8 μM and 2.40 μM), and good reproducibility, selectivity, and stability. Furthermore, the two signal modes are generated through different conduction channels, without mutual interference, which not only enhances detection sensitivity but also allows for cross-validation of the results. This nanoelectrochemical sensor can be used for the precise detection of small biomolecules, providing new insights into point-of-care testing and medical diagnosis.

Claims

1. A dual-signal electrochemical uric acid sensor based on CoFe@NC composite material, characterized in that: A three-electrode system is adopted, and the working electrode is an inert electrode modified with a CoFe@NC composite material; the CoFe@NC composite material is a nitrogen-doped carbon nanofiber modified with a Co-Fe bimetallic.

2. A dual-signal electrochemical uric acid sensor based on CoFe@NC composite material according to claim 1, characterized in that: The preparation method of the working electrode is as follows: S1. Cobalt nitrate and 2-methylimidazole were weighed and dissolved in a mixture of methanol and ethanol, respectively. The two solutions were then mixed, centrifuged, washed, and dried to obtain a purple solid, ZIF-67. Separately, ferric chloride hexahydrate and terephthalic acid were weighed and dissolved in N,N-dimethylformamide, respectively. The two solutions were then mixed and allowed to react fully, then centrifuged, washed, and dried to obtain a yellow solid, MIL-53. S2. Polyacrylonitrile and polystyrene were dispersed in DMF, followed by the addition of ZIF-67 and MIL-53, and stirred to form a spinning solution. The spinning solution was then spun, and the resulting fiber membrane was pre-oxidized, calcined at high temperature, cooled, and ground into a powder to obtain a CoFe@NC composite material. S3. Prepare the CoFe@NC composite material into a nanomaterial solution and drop it onto an inert electrode. Allow to dry naturally at room temperature to obtain a working electrode.

3. A dual-signal electrochemical uric acid sensor based on CoFe@NC composite material according to claim 2, characterized in that: In step S2, the mass ratio of ZIF-67 to MIL-53 is 1:(1~3).

4. A dual-signal electrochemical uric acid sensor based on a CoFe@NC composite material according to claim 2, characterized in that, in step S2, the pre-oxidation temperature is 200-250 ° C, the time is 1.5-2.5 h, and the pre-oxidation is carried out in air.

5. A dual-signal electrochemical uric acid sensor based on a CoFe@NC composite material according to claim 4, characterized in that, in step S2, the high-temperature calcination step is: under an argon atmosphere, the temperature is raised to 500-550°C at a heating rate of 4-7°C / min, maintained for 1.5-2.5 hours, and then the temperature is raised to 800-850°C at a heating rate of 2-3°C / min.

6. A dual-signal electrochemical uric acid sensor based on CoFe@NC composite material according to claim 1, characterized in that the inert electrode is made of glassy carbon, platinum, gold, silver, lead or conductive glass.

7. The method for preparing a dual-signal electrochemical uric acid sensor based on a CoFe@NC composite material according to any one of claims 2 to 6 is characterized in that a working electrode is first prepared, and then the working electrode, a counter electrode, and a reference electrode are combined to form a three-electrode system.

8. Use of the dual-signal electrochemical uric acid sensor based on the CoFe@NC composite material according to any one of claims 1 to 6 in uric acid detection.

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