A dual-signal electrochemical uric acid sensor, its preparation method and application

Abstract

This invention discloses a dual-signal electrochemical uric acid sensor based on CoFe@NC composite material, its preparation method, and its application in uric acid detection, belonging to the field of nano-electrochemical sensor technology. The electrochemical uric acid sensor employs a three-electrode system, with the working electrode being an inert electrode modified with CoFe@NC composite material. The CoFe@NC composite material is nitrogen-doped carbon nanofibers modified with Co-Fe bimetallic materials. By modifying the surface of the inert electrode with Co-Fe bimetallic nitrogen-doped carbon nanofibers exhibiting excellent conductivity and electrocatalytic performance, and then using the prepared working electrode as a sensing platform to construct the electrochemical uric acid sensor, it demonstrates a wide linear range, low detection limit, and good selectivity and stability for uric acid detection.

Description

Technical Field

[0001] This invention belongs to the field of nano-electrochemical sensor technology, specifically a dual-signal electrochemical uric acid sensor based on CoFe@NC composite material, its preparation method, and its application in uric acid detection. Background Technology

[0002] With the rapid development of society and the economy, people's dietary structure has undergone tremendous changes. The continuous improvement of living standards has led to a significant increase in the proportion of high-purine foods in daily diets. Uric acid (UA), as the final product of purine metabolism, is a key biomolecule in human body fluids. In a healthy individual, uric acid 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 when excessive high-purine foods are ingested or when metabolic abnormalities occur.

[0003] Excessive uric acid accumulation can disrupt the body's physiological balance, leading 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.

[0004] Currently, various analytical methods such as capillary electrophoresis, chemiluminescence, colorimetry, and high-performance liquid chromatography are widely used for uric acid detection. However, these traditional methods have limitations such as expensive equipment, complex operation, and long detection time. In contrast, electrochemical methods, with their significant advantages of low cost, rapid response, and high sensitivity, have become a hot topic in the research of small molecule detection and show broad application prospects in clinical diagnosis, environmental monitoring, and other fields.

[0005] In electrochemical detection systems, the detection performance of electrochemical sensors largely depends on the characteristics of the electrode materials. Therefore, developing high-performance electrode materials has become a key research focus. In recent years, metal-organic frameworks (MOFs) derivatives have attracted widespread attention as novel electrode catalysts due to their unique structures and potential catalytic activities. However, in practical applications, the use of MOFs in sensing platforms still faces many challenges. For example, traditional MOF-based materials have limited active sites, resulting in low catalytic efficiency for target substances, making it difficult to meet the requirements of high sensitivity and high selectivity detection. Therefore, developing MOF-based nanocatalytic materials with abundant multi-active sites and improving their catalytic performance is of vital importance for preparing high-performance working electrodes and promoting the development of electrochemical sensing technology. Summary of the Invention

[0006] The purpose of this invention is to provide a dual-signal electrochemical uric acid sensor based on CoFe@NC composite material, its preparation method, and its application in uric acid detection. By modifying the surface of an inert electrode with Co-Fe bimetallic-modified nitrogen-doped carbon nanofibers (i.e., the electrocatalyst: CoFe@NC composite material), which possesses excellent conductivity and electrocatalytic properties, the working electrode is then used as a sensing platform to construct an electrochemical uric acid sensor. This sensor exhibits a wide linear range, low detection limit, and good selectivity and stability for uric acid detection.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A dual-signal electrochemical uric acid sensor based on CoFe@NC composite material is disclosed, employing a three-electrode system. The working electrode is an inert electrode modified with CoFe@NC composite material. The CoFe@NC composite material is nitrogen-doped carbon nanofiber modified with Co-Fe bimetallic material.

[0009] The electrochemical uric acid sensor of this invention employs a three-electrode system, with the core being the working electrode modified with CoFe@NC composite material. The CoFe@NC composite material consists of nitrogen-doped carbon nanofibers modified with Co-Fe bimetallic materials, possessing three core advantages:

[0010] First, the structure and catalytic activity inherited from MOFs lay the foundation for the reaction. Second, the high specific surface area of ​​nanofibers expands the contact space with uric acid, providing a large number of active sites. Third, nitrogen-doped carbon imparts good conductivity, ensuring rapid electron transport and promoting efficient electrochemical reactions. These three factors work synergistically to significantly improve the overall performance of the composite material.

[0011] This invention utilizes an innovative process to precisely load bimetallic CoFe nanoparticles with excellent catalytic activity onto the surface of one-dimensional nitrogen-doped carbon nanofibers, successfully preparing a CoFe@NC composite material that combines good conductivity and outstanding catalytic activity. Subsequently, this composite material is modified onto the surface of an inert electrode, forming a working electrode that serves as the core sensing platform for constructing a dual-signal electrochemical uric acid sensor. In actual detection, this working electrode, leveraging the unique properties of the CoFe@NC composite material, significantly enhances the sensor's sensitivity to uric acid (UA), enabling accurate detection of low concentrations of uric acid; it also enhances selectivity, effectively eliminating the influence of other interfering substances; and simultaneously accelerates the response rate and shortens the detection time, thereby comprehensively optimizing the overall detection performance of the sensor and providing strong technical support for the rapid and accurate diagnosis of uric acid-related diseases.

[0012] As some possible embodiments of this application, the method for preparing the working electrode is as follows:

[0013] S1. Weigh out cobalt nitrate and 2-methylimidazole separately, and dissolve them separately in a mixed solution of methanol and ethanol. Then mix the two solutions, and after thorough mixing, centrifuge, wash, and dry to obtain a purple solid ZIF-67. Separately, weigh out ferric chloride hexahydrate and terephthalic acid separately, and dissolve them separately in N,N-dimethylformamide. Then mix the two solutions and react them thoroughly. After centrifuge, wash, and dry, obtain a yellow solid MIL-53.

[0014] S2. Polyacrylonitrile and polystyrene were dispersed in DMF, and then ZIF-67 and MIL-53 were added and stirred evenly to prepare a spinning solution; the spinning solution was then spun, and the received fiber membrane was subjected to pre-oxidation, high-temperature calcination and cooling in sequence, and the product was ground into powder to obtain CoFe@NC composite material.

[0015] S3. The CoFe@NC composite material was prepared into a nanomaterial solution and dropped onto an inert electrode. It was then allowed to dry naturally at room temperature to obtain the working electrode.

[0016] As one possible implementation of this application, in step S2, the mass ratio of ZIF-67 to MIL-53 is 1:(1~3).

[0017] As some possible implementations of this application, in step S2, the pre-oxidation temperature is 200~250 °C and the time is 1.5~2.5h, and the pre-oxidation is carried out in air.

[0018] As some possible implementations of this application, in step S2, the high-temperature calcination step is as follows: under an argon atmosphere, the temperature is raised to 500-550°C at a heating rate of 4-7°C / min, held for 1.5-2.5 hours, and then raised to 800-850°C at a heating rate of 2-3°C / min.

[0019] As some possible implementations of this application, the inert electrode material is glassy carbon, platinum, gold, silver, lead, or conductive glass.

[0020] 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: firstly, a working electrode is prepared, and then the working electrode, the counter electrode, and the reference electrode are combined to form a three-electrode system.

[0021] Furthermore, to achieve the above objectives, the present invention also provides the application of a dual-signal electrochemical uric acid sensor based on CoFe@NC composite material in uric acid detection.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention employs electrospinning to precisely embed two types of MOFs into PAN / PS nanofibers. Following pre-oxidation and high-temperature calcination, Co-Fe bimetallic modified nitrogen-doped carbon nanofibers, i.e., the CoFe@NC composite material, were successfully prepared. This preparation method fully leverages the structural advantages of MOFs and the molding characteristics of PAN / PS nanofibers, endowing the composite material with a unique microstructure and thus imparting superior electrocatalytic performance. It not only significantly improves the conductivity of the working electrode but also significantly accelerates the electron transfer rate and interfacial reaction efficiency, providing a solid material basis for uric acid detection.

[0024] Building upon this foundation, this invention utilizes 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 significantly expands the linear range of uric acid (UA) detection, resulting in a wider detection concentration range. It achieves an extremely low limit of detection (LOD), enabling precise capture of trace amounts of uric acid. Simultaneously, it endows the sensor with excellent selectivity, effectively eliminating interference from other substances in bodily fluids, and exhibits outstanding stability, maintaining data reliability even after multiple detections. This provides an efficient and accurate detection method for clinical uric acid testing and related disease diagnosis. Attached Figure Description

[0025] Figure 1 FESEM images of CoFe@NC at different preparation stages: (A) precursor fibers, (B) pre-oxidation, (C) carbonization, and (D) elemental distribution.

[0026] 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.

[0027] Figure 3 CV curves (A) and linear relationship graphs (B) of GCE / CoFe@NC at different UA concentrations; CV curves (C) and linear relationship graphs (D) of GCE / CoFe@NC at different scan rates.

[0028] Figure 4 : CV (A) and DPV (B) plots of GCE / CoFe@NC in PBS solutions of different pH values; trend of peak current value with pH (C); linear relationship between peak potential value and scan rate (D).

[0029] Figure 5DPV 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.

[0030] Figure 6 : It curves of GCE / CoFe@NC at different UA concentrations (A); (A) Schematic diagram of the enlarged structure in the low concentration region (1−25.8 μM) (B); Linear relationship between peak current values ​​and UA concentration in the ranges of 0.001−0.04 and 0.04−0.35 mM (C−D); Selectivity of the nanosensor (E). Detailed Implementation

[0031] Example 1

[0032] This embodiment provides a nano-electrochemical uric acid sensor, the preparation method of which includes:

[0033] S1. Weigh 0.873 g of cobalt nitrate and 0.96 g of 2-methylimidazole, and dissolve them separately in a 1:1 mixture of methanol and ethanol (v / v) using ultrasonication. Then, rapidly mix the two solutions at room temperature, stir for 24 hours, and centrifuge to collect the precipitate. Wash three times with ethanol and dry overnight at 60 °C. 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 dissolve them separately in 15 mL of N,N-dimethylformamide (DMF) using ultrasonication. Mix the two solutions thoroughly and transfer them to a 50 mL round-bottom flask. Heat in a 150 °C oil bath for 2 hours. Wash by centrifugation and collect the precipitate. Dry overnight at 60 °C. The resulting yellow solid is designated MIL-53.

[0034] S2. Weigh 0.5 g of polyacrylonitrile (PAN) and 0.25 g of polystyrene (PS), disperse them in 5 mL of DMF under stirring, then add 0.25 g of ZIF-67 and 0.50 g of MIL-53 and continue stirring overnight to form a homogeneous spinning solution. Transfer the spinning solution to a 10 mL syringe and spin using a 19-gauge metal needle at a positive voltage of 18 kV and a negative voltage of −2 kV at a injection rate of 1 mL / h. Pre-oxidize the received fiber membrane in air at 200 °C for 2 hours, then raise the temperature to 500 °C at a heating rate of 5 °C / min under an argon atmosphere, hold for 2 hours, and then raise the temperature to 800 °C at a heating rate of 2 °C / min. Cool to room temperature and grind the black carbide into powder; the resulting product is denoted as CoFe@NC.

[0035] The surface morphology of the CoFe@NC composite fibers was characterized using field emission scanning electron microscopy (FESEM). Figure 1 As shown in (A), the presence of particulate matter on the nanofiber surface indicates that MOFs have been successfully loaded onto the NC surface. From Figure 1 As can be seen from (B) and (C), the beaded structure of CoFe@NC is preserved after pre-oxidation and high-temperature carbonization. Figure 1 The EDS elemental mapping of (D) in the diagram shows a uniform distribution of C, O, N, Co, and Fe elements.

[0036] In contrast, nanofibers (NC) without the addition of MOFs were prepared under the same conditions.

[0037] 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 onto a clean glass carbon electrode (GCE), and allow it to air dry at room temperature to obtain the working electrode GCE / CoFe@NC.

[0038] S4. A three-electrode system was constructed by the working electrode, the Ag / AgCl reference electrode, and the Pt wire counter electrode, and electrochemical tests were performed on a CHI 760E electrochemical workstation. During the tests, the pH of the phosphate buffer was adjusted to ensure that the nanoelectrochemical sensor could respond to the UA concentration and exhibit good electrochemical performance.

[0039] Experimental Example

[0040] 1. Electrocatalytic performance of UA by different working electrodes.

[0041] The electrocatalytic behavior of the working electrode for UA was investigated using CV and DPV methods. Figure 2 Figures (A) and (B) show the CV and DPV curves for GCE, GCE / NC, and GCE / CoFe@NC, respectively.

[0042] from Figure 2 It can be seen that GCE exhibits only a weak UA oxidation peak, but its current response is significantly limited due to its slow reaction kinetics. In contrast, both GCE / NC and GCE / CoFe@NC show more significant 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 compound (CoFe) greatly improves the electron transfer efficiency of UA through a synergistic effect and by providing more active sites.

[0043] 2. The effect of UA concentration.

[0044] To explore the feasibility of detecting UA using GCE / CoFe@NC, the current response at different UA concentrations was tested by CV method. The results are as follows: Figure 3 As shown in (A) in the figure. In 0.1 M PBS buffer, the oxidation peak current increases rapidly with increasing UA concentration. Figure 3 (B) shows that the current response is linearly positively correlated with UA concentration in the range of 0–0.5 mM. Therefore, the prepared GCE / CoFe@NC electrode can respond to changes in UA concentration and can be used for the quantitative analysis of UA.

[0045] 3. The effect of scan rate.

[0046] To investigate the reaction kinetics of UA on the GCE / CoFe@NC surface, CV tests were performed by varying the scan rate. Figure 3 As shown in (C), the irreversible oxidation peak current of UA gradually increases as the scan rate increases from 10 mV / s to 100 mV / s. Figure 3 (D) indicates that the current value is linearly related to the scan rate, with a correlation coefficient of 0.996, suggesting that the electrochemical reaction of UA on the GCE / CoFe@NC surface is an adsorption-controlled process.

[0047] 4. The effect of pH.

[0048] The pH of the solution directly affects the oxidation peak current and potential of UA; therefore, the CV curves of UA were measured in PBS solutions with different pH values. Figure 4 As shown in (A), the current response initially increases and then decreases with increasing pH. To further investigate the effect of pH on the UA oxidation process, the DPV method was used for testing. Figure 4 As shown in (B) and (C), the current response gradually increases as the pH increases from 5.4 to 6.8, reaching a maximum at pH = 6.8. Therefore, PBS with pH = 6.8 was chosen as the electrolyte solution for subsequent tests. Figure 4 As can be seen from (D), the oxidation peak potential decreases linearly with increasing pH, and this linear relationship can be expressed by the following equation:

[0049] E pa (V) = −0.063pH + 0.74 (R 2 = 0.996), and this 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 UA oxidation process on the working electrode is equal to the number of protons.

[0050] 5. Quantitative detection of DPV.

[0051] The sensitivity of this electrochemical sensor was investigated by detecting different concentrations of UA in 0.1 M PBS buffer solution using the DPV method. Figure 5 (A) in the figure shows the DPV curves for different UA concentrations (0.01–0.35 mM) on GCE / CoFe@NC. Figure 5 (B) 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:

[0052] I pa (μA) = 444.8 c – 1.53 (R 2 = 0.998).

[0053] 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 calculated LOD for UA with GCE / CoFe@NC was 26.8 μM.

[0054] To verify the reproducibility of the nanoelectrochemical sensor, six identical sensors were fabricated, 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 among different electrodes is less than 3.64%. Therefore, the nano-electrochemical sensor based on the CoFe@NC catalyst demonstrates excellent repeatability in UA detection.

[0055] For electrochemical sensors, a stable output electrical signal is crucial. Therefore, the stability of CoFe@NC for UA detection was tested using the iterative method. Figure 5 As shown in (D), the current response remained essentially unchanged over a time range of up to 1000 s after the addition of UA to 0.1 M PBS solution, indicating that the proposed electrochemical sensing platform has good stability.

[0056] 6. Quantitative analysis using the IT method.

[0057] The current response of the GCE / CoFe@NC working electrode at a constant potential of 0.35 V (relative to Ag / AgCl) was recorded using the iterative method. UA was added to the PBS buffer every 50 s under stirring conditions. The results are as follows: Figure 6As shown in (A), the current exhibits a steady increasing trend with the continuous addition of UA. Since the current signal in the low-concentration region (1–25.8 μM) is relatively weak and difficult to observe over a wider concentration range, it is not considered in [the following context]. Figure 6 (B) in the image shows a magnified view of this area. The sensor exhibits good linearity in UA detection within the range of 0.001–1.2 mM. From Figure 6 As can be seen from (C) and (D) in the diagram, the linear relationship exhibits a clear piecewise characteristic. This is because when the UA concentration is low, there are a large number of unoccupied active sites on the electrode surface, the electrode reaction is controlled 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 controlled by a dual diffusion-adsorption process, and the rate of increase in the current response decreases. Within the detection range, the linear equation for UA can be described as:

[0058] 0.001−0.04 mM: I pa (μA) = 60.14 c + 0.05 (R 2 = 0.999),

[0059] 0.04−1.20 mM: I pa (μA) = 56.13 c +1.08 (R) 2 = 0.995).

[0060] Based on the slope of the calibration curve, the LOD was calculated to be 2.40 μM, and the sensitivity was 0.85 mA∙mM. −1 ∙cm −2 .

[0061] Selectivity is an important parameter for evaluating sensor performance. Therefore, the it response of sodium chloride (NaCl), potassium chloride (KCl), sodium carbonate (Na₂CO₃), potassium carbonate (K₂CO₃), and glucose (Glu) was studied on GCE / CoFe@NC to test the selectivity of this electrochemical sensor. The concentration of the interfering substance was 10 times that of the UA concentration. Figure 6 As shown in (E), when uric acid (UA) was added sequentially to 0.1 M PBS solution (pH = 6.8), the it response of the electrochemical sensor gradually increased with increasing UA concentration. No significant current response was observed when interfering substances were added. Upon further addition of UA to the system, the it response continued to increase with increasing UA concentration. These results indicate that the sensor exhibits good selectivity for UA and can operate stably even in the presence of multiple potential interfering substances.

[0062] In summary, this invention constructs a dual-signal detection platform based on bimetallic modified nitrogen-doped carbon nanofibers (CoFe@NC composite material) for the quantitative analysis of UA concentration. The electrocatalyst CoFe@NC is prepared by electrospinning two MOF materials onto NC and then pyrolyzing them under inert gas protection. The synergistic effect between the bimetallic CoFe nanoparticles and NC fibers enhances the electrocatalytic activity of the nanocomposite material, exhibiting excellent analytical performance for UA, such as 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 repeatability, selectivity, and stability. Furthermore, the two signal modes are realized through different conduction channels, without interference, which not only improves detection sensitivity but also allows for mutual verification of the accuracy of the results. This nanoelectrochemical sensor can be used for the precise detection of small biomolecules, providing a new perspective for point-of-care testing and medical diagnostics.

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 CoFe@NC composite material; the CoFe@NC composite material is nitrogen-doped carbon nanofiber modified with Co-Fe bimetal; the microstructure of the CoFe@NC composite material is a beaded structure. The method for preparing the working electrode is as follows: S1. Weigh out cobalt nitrate and 2-methylimidazole separately, and dissolve them separately in a mixed solution of methanol and ethanol. Then mix the two solutions, and after thorough mixing, centrifuge, wash, and dry to obtain a purple solid ZIF-67. Separately, weigh out ferric chloride hexahydrate and terephthalic acid separately, and dissolve them separately in N,N-dimethylformamide. Then mix the two solutions and react them thoroughly. After centrifuge, wash, and dry, obtain a yellow solid MIL-53. S2. Polyacrylonitrile and polystyrene were dispersed in DMF, and then ZIF-67 and MIL-53 were added and stirred evenly to prepare a spinning solution; the spinning solution was then spun, and the received fiber membrane was subjected to pre-oxidation, high-temperature calcination and cooling in sequence, and the product was ground into powder to obtain CoFe@NC composite material. S3. The CoFe@NC composite material was prepared into a nanomaterial solution and dropped onto an inert electrode. It was then allowed to dry naturally at room temperature to obtain the working electrode.

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

3. The dual-signal electrochemical uric acid sensor based on CoFe@NC composite material according to claim 1, characterized in that, In step S2, the pre-oxidation temperature is 200~250 °C and the time is 1.5~2.5 h. The pre-oxidation is carried out in air.

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

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

6. The dual-signal electrochemical uric acid sensor based on CoFe@NC composite material according to any one of claims 1-5, characterized in that, First, prepare the working electrode, and then combine the working electrode with the counter electrode and the reference electrode to form a three-electrode system.

7. The application of the dual-signal electrochemical uric acid sensor based on CoFe@NC composite material according to any one of claims 1-5 in uric acid detection.

Images