A sodium borohydride-reduced copper cobalt oxide nanomaterial and its application in an enzyme-free glucose sensor

Abstract

This invention discloses a highly active electrode material for an enzyme-free glucose sensor, its preparation method, and its application. The material is a copper-cobalt oxide nanomaterial treated with sodium borohydride reduction. First, a precursor CuCo oxide is prepared via a molten salt method, followed by in-situ reduction treatment with sodium borohydride solution. This treatment partially reduces the valence state of the metal ions, introducing abundant oxygen vacancies and defects onto the material surface, significantly enhancing its electrocatalytic activity. By modifying the surface of a working electrode (such as a glassy carbon electrode or a gold electrode) with the prepared material, a high-performance enzyme-free glucose electrochemical sensor can be constructed.

Description

Technical Field

[0001] This invention relates to the field of electrochemical sensor materials technology, specifically to a copper-cobalt oxide nanomaterial reduced by sodium borohydride and its application in an enzyme-free glucose sensor. Background Technology

[0002] Glucose detection plays an indispensable role in clinical medicine, the food industry, and the biotechnology field. Clinically, blood glucose monitoring is a crucial aspect of diabetes management; in the food industry, glucose concentration is a key parameter for monitoring fermentation processes and product quality. While traditional enzyme-based glucose sensors have been widely used due to their high selectivity and sensitivity, their inherent limitations significantly restrict their future development. The biological activity of enzymes (such as glucose oxidase) is easily affected by various environmental factors such as temperature, humidity, solution pH, and dissolved oxygen, resulting in poor sensor stability and limited lifespan. Furthermore, the enzyme immobilization process is complex and has poor reproducibility, and the enzyme materials themselves are expensive, significantly increasing the manufacturing cost and application threshold of the sensors.

[0003] To overcome these shortcomings of enzyme-based sensors, enzyme-free glucose sensors have emerged and become a research hotspot in the field of electrochemical sensors. Enzyme-free sensors eliminate the need for biological enzymes, directly utilizing the electrocatalytic oxidation activity of glucose molecules through nanomaterials for detection. This fundamentally avoids the instability issues associated with enzymes, exhibiting superior stability, longer lifespan, and better reproducibility. Furthermore, since they eliminate the need for expensive enzyme preparations, manufacturing costs are effectively reduced, and they have a wider tolerance range for operating conditions, making them more suitable for applications such as point-of-care testing.

[0004] However, the large-scale practical application of enzyme-free glucose sensors still faces two major challenges: sensitivity and selectivity need to be improved. The level of sensitivity and the width of the detection linear range directly determine whether the sensor can accurately cover the fluctuation range of blood glucose concentration under physiological and pathological conditions. More critical is the issue of selectivity, i.e., anti-interference capability. In complex real-world samples (such as blood), there are various electroactive substances such as ascorbic acid, uric acid, and dopamine, which may undergo redox reactions at the sensor's operating potential, severely interfering with the accurate measurement of glucose. Summary of the Invention

[0005] The purpose of this invention is to provide a sodium borohydride-reduced copper-cobalt oxide nanomaterial, its preparation method, and its application in an enzyme-free glucose sensor. This material possesses abundant oxygen vacancies and defects, which can significantly enhance its electrocatalytic oxidation activity for glucose. The technical solution of this invention is as follows.

[0006] A copper-cobalt oxide nanomaterial reduced by sodium borohydride is prepared by molten salt method to prepare CuCo oxide precursor, followed by in-situ reduction treatment with sodium borohydride solution to form nanomaterial with abundant oxygen vacancies and defects.

[0007] The molar ratio of copper to cobalt in the precursor CuCo oxide is 1:2~5.

[0008] The concentration of the sodium borohydride solution is 0.1~2 mol / L, the reduction treatment temperature is 30~100℃, and the reduction treatment time is 0.5~2 hours.

[0009] The method for preparing copper-cobalt oxide nanomaterials reduced by sodium borohydride includes the following steps: preparing a precursor CuCo oxide by molten salt method; mixing the precursor CuCo oxide with a sodium borohydride solution for in-situ reduction treatment; and washing and drying the reduced material to obtain the final product.

[0010] The molten salt method uses one or more of sodium chloride and potassium chloride, with a molten salt temperature of 700~900℃ and a reaction time of 2~6 hours.

[0011] An enzyme-free glucose sensor uses copper-cobalt oxide nanomaterials reduced by sodium borohydride as electrode modification materials.

[0012] The working electrode is a glassy carbon electrode, a gold electrode, or a carbon paste electrode.

[0013] Application of the enzyme-free glucose sensor in glucose detection. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the powder preparation, reduction treatment, and sensor electrode fabrication processes. Figure 2 SEM image of copper-cobalt oxide prepared by the molten salt method; Figure 3 The image is a restored SEM image. Figure 4 The CV curves of copper-cobalt oxide in glucose solutions of different concentrations are shown. Figure 5 The CV curves of copper-cobalt oxide after reduction with 0.5M sodium borohydride in glucose solutions of different concentrations are shown. Figure 6 The it response curve of the copper-cobalt oxide electrode after adding a certain concentration of glucose and the fitting curve of current versus glucose concentration are shown. Figure 7 The it response curve and the fitting curve of current versus glucose concentration of the modified copper-cobalt oxide electrode after adding a certain concentration of glucose are shown. Detailed Implementation Plan Example 1

[0015] Preparation of precursor CuCo oxide: Weigh 0.80 g (10 mmol) of copper oxide (CuO) and 3.75 g (50 mmol) of cobalt oxide (CoO), grind and mix them evenly in a mortar to obtain a mixed metal oxide with a copper-cobalt molar ratio of 1:5. Thoroughly mix the mixed oxide with a 4-fold equimolar ratio of 8 g of sodium chloride (NaCl) and 10.2 g of potassium chloride (KCl), transfer the mixture to an alumina crucible, and place it in a muffle furnace. Heat to 700 °C at a rate of 5 °C / min and hold at that temperature for 3 hours. After the reaction is complete, rapidly cool to room temperature, wash repeatedly with deionized water until no chloride ions are detected (using AgNO3 solution), and then dry in a vacuum drying oven at 60 °C for 6 hours to obtain the precursor CuCo oxide nanopowder.

[0016] Reduction treatment of sodium borohydride: 100 mg of the above precursor powder was dispersed in 50 mL of a 0.5 mol / L aqueous solution of sodium borohydride (NaBH4) and sodium hydroxide (NaOH), with a sodium hydroxide (NaOH) concentration of 0.1 mol / L. The mixture was stirred electrically at 30 ± 1 °C for 1 hour to carry out the in-situ reduction reaction. After the reaction, the material was washed three times alternately by centrifugation with deionized water and anhydrous ethanol to remove residual NaBH4 and byproducts. The washed material was then dried in a vacuum drying oven at 60 °C for 12 hours to obtain the final product—sodium borohydride-reduced copper cobalt oxide nanomaterials (denoted as NaBH4-CuCoO). x ). Example 2

[0017] The precursor preparation steps were exactly the same as in Example 1 (Cu:Co = 1:5).

[0018] The reduction procedure was exactly the same as in Example 1, using 0.1 mol / L NaBH4 solution and reducing for 1 hour at 30°C. Example 3

[0019] The precursor preparation steps were exactly the same as in Example 1 (Cu:Co = 1:5).

[0020] The reduction procedure was exactly the same as in Example 1, using 1 mol / L NaBH4 solution and reducing for 1 hour at 30°C. Electrode modification and sensor construction

[0021] Take 5 mg of the above NaBH4-CuCoOx The material was mixed with 1 mL of a solution of ethanol, deionized water, and Nafion reagent (volume ratio 48:48:4) and sonicated for 30 minutes to form a uniform modified slurry. 2 µL of the slurry was transferred using a microsyringe and drop-coated onto the surface of a pre-polished and cleaned glassy carbon electrode (2 mm in diameter). After air-drying at room temperature, the electrode was placed in a 60°C oven for 2 hours to dry. Performance testing

[0022] The sensor prepared in Example 1 was used as the working electrode, and together with the Ag / AgCl reference electrode and the platinum sheet counter electrode, a three-electrode system was formed to perform electrochemical detection of glucose in 0.1 M NaOH electrolyte.

[0023] Linear range and sensitivity: Cyclic voltammetry was used to test the potential from 0 to 0.65 V; Ampere current method (it curve) was used to test the intensity and linear range of the response current by continuously adding glucose standard solution of different concentrations at a working potential of +0.55 V.

[0024] The sensor prepared in Example 1 exhibits good linearity in the concentration range of 1 μM to 1 mM, with a sensitivity as high as 1604 μA·mM⁻¹·cm⁻².

[0025] Detection limit: Based on the signal-to-noise ratio S / N=3, the detection limit of the sensor in Example 1 is 0.3 μM. in conclusion

[0026] This invention successfully prepared copper-cobalt oxide nanomaterials with abundant oxygen vacancies and surface defects through a molten salt method combined with an in-situ reduction strategy using sodium borohydride. This material exhibits high electrocatalytic activity for glucose oxidation, and an enzyme-free glucose sensor constructed based on it possesses high sensitivity, low detection limit, good selectivity, and long-term stability, demonstrating excellent application potential in the detection of practical samples (such as serum and fruit juice).

Claims

1. A copper cobalt oxide nanomaterial reduced by sodium borohydride, characterized in that: The material is prepared by molten salt method to produce CuCo oxide precursor, which is then subjected to in-situ reduction treatment with sodium borohydride solution to form nanomaterials with abundant oxygen vacancies and defects at a specific temperature.

2. The sodium borohydride-reduced copper-cobalt oxide nanomaterial according to claim 1, characterized in that: The molar ratio of copper to cobalt in the precursor CuCo oxide is 1:2~5.

3. The sodium borohydride reduced copper cobalt oxide nanomaterial of claim 1, wherein: The concentration of the sodium borohydride solution is 0.1~2 mol / L, the reduction temperature is 30~100℃, and the reduction treatment time is 0.5~2 hours.

4. A method for preparing the copper cobalt oxide nanomaterial reduced by sodium borohydride according to any one of claims 1-3, characterized in that Includes the following steps: (1) Precursor CuCo oxide was prepared by molten salt method; (2) The precursor CuCo oxide was mixed with sodium borohydride solution and subjected to in-situ reduction treatment; (3) The reduced material is washed and dried to obtain the final product.

5. The method of claim 4, wherein: The molten salt method uses a mixture of sodium chloride and potassium chloride, with a mass ratio of 1:

1. The total mass of the two salts is four times the total mass of the oxides. The molten salt temperature is 700~900℃, and the reaction time is 2~6 hours.

6. An enzyme-free glucose sensor, characterized by: The copper-cobalt oxide nanomaterials reduced by sodium borohydride as described in any one of claims 1 to 3 are used as electrode modification materials.

7. The enzyme-free glucose sensor of claim 6, wherein: The working electrode is a glassy carbon electrode, a gold electrode, or a carbon paste electrode.

8. The application of the enzyme-free glucose sensor according to claim 6 or 7 in glucose detection.

Images