Electrochemical sensor for detecting quercetin as well as preparation method and application of electrochemical sensor

Abstract

The invention discloses an electrochemical sensor for detecting quercetin as well as a preparation method and application of the electrochemical sensor, and relates to the technical field of electrochemical sensors. According to the method, g-C3N4 and molybdenum selenide are combined in a Van der Waals heterojunction mode to obtain the g-C3N4 and MoSe2 composite material, a glassy carbon electrode is used as a working electrode, the g-C3N4 and MoSe2 composite material is modified on the working electrode to construct the electrochemical sensor for detecting quercetin, and the sensor is high in selectivity, high in sensitivity, good in electrochemical stability and good in reproducibility and can be applied to detection of quercetin. The detection efficiency of quercetin can be greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical sensors, and in particular to an electrochemical sensor for detecting quercetin, a preparation method thereof, and applications thereof. Background Art

[0002] Quercetin, also known as quercetin yellow, is a natural compound belonging to the flavonoid class. It is widely distributed in plants and is an important component of the human diet. Its main functions include expectoration, cough relief, heat-clearing and detoxification, and asthma relief. In recent years, quercetin has been found to possess multiple carcinogenic and cancer-promoting properties. Quercetin detection is of great significance for health management, food processing, and case analysis. Current methods for quercetin detection include high-performance liquid chromatography (HPLC), ultrahigh performance liquid chromatography-mass spectrometry (UHPLC-MS / MS), ultraviolet-visible spectrophotometry, and reversed-phase HPLC, all of which are relatively complex to operate. Since the detection of quercetin in dietary supplements, fruits, vegetables, and pharmaceutical samples requires a low-cost, rapid, and portable method, electrochemical methods offer advantages such as low cost, ease of use, high sensitivity, fast response, and low detection limits. Therefore, it is necessary to develop an electrochemical sensor for quercetin detection.

[0003] g-C3N4 boasts low cost, excellent thermal and chemical stability, and maintains structural stability under high temperatures and strong acid and alkali conditions. However, g-C3N4 has limitations, such as low quantum efficiency and small specific surface area, which restrict its future development. However, g-C3N4 can be combined with other materials to create heterojunctions, which can overcome these limitations. Structurally, molybdenum selenide and graphene share similar layered structures. Molybdenum selenide offers superior performance compared to graphene in terms of bandgap width and low-power electronics. Molybdenum selenide also possesses optical and electrical properties, along with a tunable bandgap, enabling improved electron-hole separation. It also holds promising application prospects in catalysis and adsorption, and has been studied in recent years for its outstanding performance in electrocatalysis, photocatalysis, and energy storage. However, its weak molecular binding capacity makes its preparation difficult, and MoSe has a low current carrying rate, resulting in limited performance in the resulting devices. Combining g-C3N4 and MoSe to achieve synergy could maximize the advantages of each. However, there is currently no report on electrochemical sensors based on g-C3N4@MoSe2 composite materials that can be used to detect quercetin. Summary of the Invention

[0004] To address the above shortcomings, the present invention provides an electrochemical sensor for detecting quercetin, its preparation method, and application. This method combines g-C3N4 and molybdenum selenide in the form of a van der Waals heterojunction to obtain a g-C3N4@MoSe2 composite material. A glassy carbon electrode is used as the working electrode, and the g-C3N4@MoSe2 composite material is modified onto the working electrode to construct an electrochemical sensor for detecting quercetin. The sensor has high selectivity and sensitivity, and can greatly improve the detection efficiency of quercetin. The specific technical solution is as follows:

[0005] A method for preparing an electrochemical sensor for detecting quercetin comprises the following steps:

[0006] (1) Preparation of g-C3N4;

[0007] (2) preparing molybdenum selenide;

[0008] (3) Preparation of g-C3N4@MoSe2 composite material: After mixing equal amounts of the g-C3N4 and the molybdenum selenide, DMF (N,N-dimethylformamide) was added to the mixture, and ultrasonication was performed to dissolve and mix the materials to obtain the g-C3N4@MoSe2 composite material;

[0009] (4) Preparation of electrochemical sensor g-C3N4@MoSe2 / GCE: Weigh g-C3N4 and MoSe2 and add them to DMF, disperse them evenly by ultrasonication to obtain a suspension, drop the suspension onto the surface of a clean glassy carbon electrode, and dry it under an infrared lamp to obtain the g-C3N4@MoSe2 / GCE.

[0010] Furthermore, in step (1), the preparation method of the g-C3N4 is: weighing melamine and placing it in a high-temperature tube furnace, and heating it at a rate of 5-8°C / min. When the temperature rises to 450-550°C, calcining it at a constant temperature of 450-550°C for 3.5-5h to obtain the g-C3N4.

[0011] Furthermore, in step (2), the preparation method of the molybdenum selenide is as follows: first, sodium molybdate is added to a mixed solution of anhydrous ethanol and deionized water, and then selenium powder is added, the mixture is covered with plastic wrap and stirred, and after the sodium molybdate is completely dissolved, sodium borohydride is added, and the mixture is covered with plastic wrap and stirred vigorously. When the solution changes from light brown to reddish brown, the reddish brown solution is placed in a high-pressure reactor, sealed firmly, and reacted at 180-250°C for 45-50h. After the reaction is completed, the temperature is lowered to room temperature to obtain a reaction material; the reaction material is centrifuged at 7000-8000r / min for 3-5min, the lower layer of material is washed 3-5 times, and then vacuum-dried at 50-60°C for 10-12h to obtain a finely divided black material; the black material is placed in a tubular furnace, after introducing an inert gas, the temperature is raised to 400-500°C at a rate of 5-8°C / min, and calcined and maintained under this environment for 2-3h to obtain the molybdenum selenide.

[0012] Furthermore, in the mixed solution of anhydrous ethanol and deionized water, the mass concentration of anhydrous ethanol is 50-55%.

[0013] Furthermore, the mass volume ratio of the sodium molybdate to the mixed solution is (0.8-1) g:25 mL.

[0014] Furthermore, the mass ratio of the sodium molybdate, selenium powder and sodium borohydride is (6-7):(5-6):1.

[0015] The present invention provides an electrochemical sensor g-C3N4@MoSe2 / GCE prepared according to the above preparation method.

[0016] The present invention provides an application of an electrochemical sensor prepared according to the above preparation method, wherein the application is for detecting quercetin, specifically: using the electrochemical sensor g-C3N4@MoSe2 / GCE as a working electrode, the electrochemical sensor g-C3N4@MoSe2 / GCE is immersed in a test solution that may contain quercetin for detection.

[0017] Furthermore, the test solution is prepared by adding the test sample into an electrolyte, and the electrolyte is a PBS buffer solution, the concentration of the PBS buffer solution is 0.20 mol / L, and the pH is 3.0-6.0.

[0018] Furthermore, the detection is performed using cyclic voltammetry with a potential window of -0.1 to 0.5 V and a scan rate of 0.01 to 1.0 v / s.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The method of the present invention first combines g-C3N4 and molybdenum selenide in the form of a van der Waals heterojunction to obtain a g-C3N4@MoSe2 composite material, and uses a glassy carbon electrode as a working electrode. The g-C3N4@MoSe2 composite material is modified onto the working electrode to construct an electrochemical sensor for detecting quercetin. The sensor has high selectivity, high sensitivity, good electrochemical stability, and good reproducibility, and can greatly improve the detection efficiency of quercetin.

[0021] 2. The present invention adopts a hydrothermal synthesis method to combine g-C3N4 and molybdenum selenide in the form of a van der Waals heterojunction, so that a large number of g-C3N4 particles are attached to the molybdenum selenide, and finally obtains a g-C3N4@MoSe2 composite material with a large volume, large specific surface area and high current carrying rate.

[0022] 3. The sensor of the present invention has a wide detection range for quercetin concentration and a low detection limit, which can detect quercetin more accurately in practical applications. -8 mol / L~9.90×10 -6 mol / L and 9.90×10 - 6 mol / L~4.76×10 -5 The corresponding peak currents in different concentration ranges of mol / L showed two good linear relationships, and their linear equations were expressed as Ip (μA) = 7.73 × 10 -2 C (μM) + 2.46 × 10 -8 (R 2 =0.9920) and Ip(μA)=3.54×10 -2 C (μM) +4.57×10 -7 (R 2 =0.9913), and the detection limit was found to be 5.34×10-9mol / L through experiments.

[0023] 4. The sensor of the present invention was tested continuously 11 times, and the current did not change much. The relative standard deviation of the measured peak current was 1.62%, indicating that the electrochemical stability of g-C3N4@MoSe2 / GCE was relatively good; 5 g-C3N4@MoSe2 / GCEs were measured once by square wave voltammetry, and 5 groups of peak current data were obtained. Their relative standard deviation was 1.92%, which was small, indicating that the quercetin electrochemical sensor constructed by g-C3N4@MoSe2 / GCE had good reproducibility; square wave voltammetry was used to explore the influence of different substances on the electrochemical response of quercetin when the g-C3N4@MoSe2 / GCE working electrode was used to determine the quercetin. The measured interference was extremely small at a multiple of 100 times, and the relative error was controlled within ±5%, indicating that the material had good selectivity; the actual samples were tested by the spike recovery method, and the average spike recovery rate was 95.89% to 104.85%, indicating that the g-C3N4 / MoSe2 / GCE sensor was accurate and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0025] Figure 1 Surface morphology comparison of g-C3N4 monomer, MoSe2 monomer and g-C3N4@MoSe2 composite material obtained in Example 1;

[0026] Figure 2 This is the energy spectrum characteristic diagram of the g-C3N4@MoSe2 composite material obtained in Example 1;

[0027] Figure 3 Comparison of electrochemical cyclic voltammetry of quercetin on four different material modified electrodes: bare electrode (Bare / GCE), g-C3N4 / GCE, MoSe2 / GCE, and g-C3N4@MoSe2 / GCE;

[0028] Figure 4 Cyclic voltammograms of quercetin in g-C3N4@MoSe2 / GCE in different pH solutions;

[0029] Figure 5 Cyclic voltammograms at different scan rates (0.01-1.0 v / s);

[0030] Figure 6 Electrochemical impedance spectroscopy of electrodes modified with different materials;

[0031] Figure 7 The response peak current diagram (A) and working curve diagram (B) of the same concentration;

[0032] Figure 8 The chrono-Coulomb curves of electrodes modified with different materials (A) and the Q~t1 / 2 linear equations of electrodes modified with different materials (B);

[0033] Figure 9 The electrochemical response stability analysis results of g-C3N4@MoSe2 / GCE to quercetin;

[0034] Figure 10 This is the reproducibility result diagram of g-C3N4@MoSe2 / GCE electrode. DETAILED DESCRIPTION

[0035] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0036] Example 1

[0037] A method for preparing an electrochemical sensor for detecting quercetin comprises the following steps:

[0038] (1) Preparation of g-C3N4: Melamine was weighed and placed in a high-temperature tube furnace, and the temperature was increased at a rate of 5°C / min. When the temperature reached 450°C, it was calcined at a constant temperature of 450°C for 3.5 hours to obtain the g-C3N4.

[0039] (2) Preparation of molybdenum selenide: First, 12.5 ml of anhydrous ethanol and 12.5 ml of deionized water (volume ratio of 1:1) were taken into a clean beaker and stirred to mix evenly. Then, 0.8225 g of sodium molybdate was accurately weighed and added to the mixed solution. Then, 0.7746 g of selenium powder was accurately weighed and added to the beaker containing molybdenum selenide. The mixture was covered with plastic wrap and stirred for 5 minutes. When the sodium molybdate was completely dissolved, 0.1296 g of sodium borohydride was accurately weighed and added. The mixture was covered with plastic wrap and stirred vigorously for 5 minutes to reduce the selenium. After reduction, the solution turned from light brown to reddish brown. The solution was then placed in a 100 ml high-pressure reactor, sealed securely, and the temperature was set to 200 ° C. The reaction was maintained in this environment for 48 hours. After the reaction was completed, the temperature was allowed to cool to room temperature. The reactants in the autoclave were transferred to a centrifuge tube and centrifuged at 8000 rpm for 3 minutes. The resulting material was then washed five times with distilled water and then ethanol. After washing, it was dried under vacuum at 60°C for 12 hours, resulting in a black, finely divided material. The resulting material was ground in an agate mortar and spread into a quartz boat. The resulting material was placed in a tube furnace, introduced with inert gas, and heated to 450°C at a rate of 5°C / min. Molybdenum selenide was obtained by calcining it under this environment and maintaining it for 3 hours.

[0040] (3) Preparation of g-C3N4@MoSe2 composite material: After mixing the g-C3N4 and the molybdenum selenide, DMF (N,N-dimethylformamide) is added to the mixture, and ultrasonication is performed to dissolve and mix the materials to obtain the g-C3N4@MoSe2 composite material.

[0041] (4) Accurately weigh 1 mg of g-C3N4 and 1 mg of MoSe2 in 1 ml of DMF and disperse them evenly under ultrasonication for 30 min to obtain a suspension. Then, 5 μL of the suspension was pipetted and dropped onto the surface of a clean glassy carbon electrode. The mixture was dried under an infrared lamp to obtain a g-C3N4@MoSe2 modified glassy carbon electrode (g-C3N4@MoSe2 / GCE). g-C3N4 / GCE and MoSe2 / GCE can be prepared according to the above method.

[0042] Example 2

[0043] A method for preparing an electrochemical sensor for detecting quercetin comprises the following steps:

[0044] (1) Preparation of g-C3N4: Melamine was weighed and placed in a high-temperature tube furnace, and the temperature was increased at a rate of 8°C / min. When the temperature reached 550°C, it was calcined at 550°C for 5 hours to obtain the g-C3N4.

[0045] (2) Preparation of molybdenum selenide: First, 12.5 ml of anhydrous ethanol and 12.5 ml of deionized water (volume ratio of 1:1) were taken into a clean beaker and stirred to mix evenly. Then, 0.8225 g of sodium molybdate was accurately weighed and added to the mixed solution. Then, 0.7746 g of selenium powder was accurately weighed and added to the beaker containing molybdenum selenide. The mixture was covered with plastic wrap and stirred for 5 minutes. When the sodium molybdate was completely dissolved, 0.1296 g of sodium borohydride was accurately weighed and added. The mixture was covered with plastic wrap and stirred vigorously for 5 minutes to reduce the selenium. After reduction, the solution turned from light brown to reddish brown. The solution was then placed in a 100 ml high-pressure reactor, sealed securely, and the temperature was set to 200 ° C. The reaction was maintained in this environment for 48 hours. After the reaction was completed, the temperature was allowed to cool to room temperature. The reactants in the autoclave were transferred to a centrifuge tube and centrifuged at 8000 rpm for 3 minutes. The resulting material was then washed five times with distilled water and then ethanol. After washing, it was dried under vacuum at 60°C for 12 hours, resulting in a black, finely divided material. The resulting material was ground in an agate mortar and spread into a quartz boat. The resulting material was placed in a tube furnace, introduced with inert gas, and heated to 450°C at a rate of 5°C / min. Molybdenum selenide was obtained by calcining it under this environment and maintaining it for 3 hours.

[0046] (3) Preparation of g-C3N4@MoSe2 composite material: After mixing the g-C3N4 and the molybdenum selenide, DMF (N,N-dimethylformamide) is added to the mixture, and ultrasonication is performed to dissolve and mix the materials to obtain the g-C3N4@MoSe2 composite material.

[0047] (4) Accurately weigh 1 mg of g-C3N4 and 1 mg of MoSe2 in 1 ml of DMF and disperse them evenly under ultrasonication for 30 min to obtain a suspension. Then, 5 μL of the suspension was pipetted and dropped onto the surface of a clean glassy carbon electrode. The mixture was dried under an infrared lamp to obtain a g-C3N4@MoSe2 modified glassy carbon electrode (g-C3N4@MoSe2 / GCE). g-C3N4 / GCE and MoSe2 / GCE can be prepared according to the above method.

[0048] Example 3

[0049] A method for preparing an electrochemical sensor for detecting quercetin comprises the following steps:

[0050] (1) Preparation of g-C3N4: Melamine was weighed and placed in a high-temperature tube furnace, and the temperature was increased at a rate of 6°C / min. When the temperature reached 500°C, it was calcined at 500°C for 4 hours to obtain the g-C3N4.

[0051] (2) Preparation of molybdenum selenide: First, 12.5 ml of anhydrous ethanol and 12.5 ml of deionized water (volume ratio of 1:1) were taken into a clean beaker and stirred to mix evenly. Then, 0.8225 g of sodium molybdate was accurately weighed and added to the mixed solution. Then, 0.7746 g of selenium powder was accurately weighed and added to the beaker containing molybdenum selenide. The mixture was covered with plastic wrap and stirred for 5 minutes. When the sodium molybdate was completely dissolved, 0.1296 g of sodium borohydride was accurately weighed and added. The mixture was covered with plastic wrap and stirred vigorously for 5 minutes to reduce the selenium. After reduction, the solution turned from light brown to reddish brown. The solution was then placed in a 100 ml high-pressure reactor, sealed securely, and the temperature was set to 200 ° C. The reaction was maintained in this environment for 48 hours. After the reaction was completed, the temperature was allowed to cool to room temperature. The reactants in the autoclave were transferred to a centrifuge tube and centrifuged at 8000 rpm for 3 minutes. The resulting material was then washed five times with distilled water and then ethanol. After washing, it was dried under vacuum at 60°C for 12 hours, resulting in a black, finely divided material. The resulting material was ground in an agate mortar and spread into a quartz boat. The resulting material was placed in a tube furnace, introduced with inert gas, and heated to 450°C at a rate of 5°C / min. Molybdenum selenide was obtained by calcining it under this environment and maintaining it for 3 hours.

[0052] (3) Preparation of g-C3N4@MoSe2 composite material: After mixing the g-C3N4 and the molybdenum selenide, DMF (N,N-dimethylformamide) is added to the mixture, and ultrasonication is performed to dissolve and mix the materials to obtain the g-C3N4@MoSe2 composite material.

[0053] (4) Accurately weigh 1 mg of g-C3N4 and 1 mg of MoSe2 in 1 ml of DMF and disperse them evenly under ultrasonication for 30 min to obtain a suspension. Then, 5 μL of the suspension was pipetted and dropped onto the surface of a clean glassy carbon electrode. The mixture was dried under an infrared lamp to obtain a g-C3N4@MoSe2 modified glassy carbon electrode (g-C3N4@MoSe2 / GCE). g-C3N4 / GCE and MoSe2 / GCE can be prepared according to the above method.

[0054] Product testing:

[0055] The surface morphologies of g-C3N4 monomer, MoSe2 monomer and g-C3N4@MoSe2 composite material obtained in Example 1 were characterized by scanning electron microscopy (SEM). Figure 1 As shown, Figure 1 In the figure, (a) is the electron micrograph of the synthesized g-C3N4 monomer, (b) is the electron micrograph of the synthesized MoSe2 monomer, (c) and (d) are the electron micrographs of the g-C3N4@MoSe2 composite materials. The figure shows that g-C3N4 has a block structure and the stacking clusters are aggregated ( Figure 1 a), MoSe2 is in the shape of small flowers with uniform layers and has a large specific surface area, which is conducive to the dispersion of g-C3N4 on its surface ( Figure 1 b), there are many blocky substances attached to the surface of MoSe2, and the volume becomes larger, indicating that the synthesis of g-C3N4@MoSe2 is relatively successful ( Figure 1 c. Figure 1 d).

[0056] The g-C3N4@MoSe2 composite material obtained in Example 1 was subjected to EDS spectrum analysis, and the analysis results are shown in Figure 2 , Figure 2 It shows that the composite material of g-C3N4@MoSe2 contains C, N, Se and Mo elements. Figure 1 The bulk material attached to MoSe2 in (c) is g-C3N4 particles.

[0057] Example 4

[0058] The photoelectrochemical sensor prepared in Example 1 was applied to the detection of quercetin, specifically:

[0059] Using a g-C3N4@MoSe2 / GCE as the working electrode, the g-C3N4@MoSe2 / GCE was immersed in a test solution potentially containing quercetin. The test solution was prepared by adding the test sample to an electrolyte solution consisting of a 0.20 mol / L PBS buffer solution with a pH range of 3.0-6.0. Cyclic voltammetry was used for detection in a potential window of -0.1 to 0.5 V at a scan rate of 0.01-1.0 v / s.

[0060] Electrochemical response of quercetin at electrodes modified with different materials:

[0061] Quercetin was detected using four modified electrodes made of different materials: bare electrode (Bare / GCE), g-C3N4 / GCE, MoSe2 / GCE, and g-C3N4@MoSe2 / GCE prepared in Example 1. The detection method was as follows: a 3.85×10-10 mol / L PBS buffer solution with a pH of 7 and a volume of 10 ml was added. -4 mol·L -1 The quercetin standard solution was used, and cyclic voltammetry (CV) was selected and the potential was set to -0.10~0.50V for detection. The results are shown in Figure 3 The figure shows that the oxidation peak current of g-C3N4@MoSe2 / GCE is 6.482μA, which is about 2.5 times the oxidation peak current of MoSe2 / GCE 2.607μA, and about 1.8 times the peak current of g-C3N4 / GCE 3.691μA, while the oxidation peak current of Bare / GCE is only 1.752μA. It can be seen that the g-C3N4@MoSe2 composite material has an obvious oxidation peak current response to quercetin. This composite material has a good chemical response to quercetin, which also shows that the electrochemical catalysis of the composite material on the current response of quercetin is promoting.

[0062] Effect of pH of PBS buffer solution:

[0063] The concentration to be tested is 3.85×10 -4 mol·L -1 The quercetin standard solution was added to PBS buffer solutions of equal concentration but different pH values, and cyclic voltammetry (CV) was used to explore and discover the electrochemical response of g-C3N4@MoSe2 / GCE at different pH values. The pH range of the measured pH was 3.0 to 9.0. Figure 4As shown in the figure, under the conditions of the same concentration and different pH, the electrochemical peak size of g-C3N4@MoSe2 / GCE measured will vary with the change of pH value. In the pH range of 3.0 to 6.0, the peak value of g-C3N4@MoSe2 / GCE increases; while in the pH range of 6.0 to 9.0, the peak value of g-C3N4@MoSe2 / GCE response decreases. It can be seen that the highest pH value of the buffer solution is 6.0, and the response peak at this time is 3.24μA. It can be seen that at pH = 6.0, the detection of quercetin shows the best peak. In addition, when the pH value of the PBS solution increases, the potential of the oxidation peak of quercetin will become smaller, and there is a certain linearity between them. The linear equation can be expressed as Ep(V) = -7.00×10 -2 pH = 5.89 × 10 -1 (R 2 =0.9930), the absolute value of the slope of this linear equation is 70.00 mV, and the theoretical value calculated by the Nernst equation should be 59.20 mV. The results calculated by them are not much different, indicating that in the electrochemical reaction process of quercetin, the number of transferred electrons is equal to the number of transferred protons.

[0064] Analysis of the impact of scan rate:

[0065] Under the optimal pH=6 condition, 3.85×10 -4 mol·L -1 The quercetin standard solution was prepared and cyclic voltammetry (CV) was used in the potential window of -0.1 to 0.5 V to study the effect of scan rate on the response of g-C3N4@MoSe2 / GCE to detect quercetin. Figure 5 It can be seen that under the same experimental conditions, as the scan rate increases from 0.01 to 1.0, the response peak current and peak potential of g-C3N4@MoSe2 / GCE also change, and there is a certain linear relationship between the peak potential and the logarithm of the scan rate, and between the peak current and the scan rate. Figure 5 Insert Figure 1 There is a linear relationship between the peak potential (Ep) of g-C3N4@MoSe2 / GCE response and the logarithm of the scan rate (lnv), and its linear equation is E p a(V)=1.72×10 -2 lnv(Vs -1 )+24.41×10 -2 (R 2 =0.9921), E p b(V)=-0.27×10 - 2lnv(Vs -1 )+0.14(R 2 =0.9719), it can be seen from the equation that their relationship is a proportional relationship. Figure 5 in Figure 2 This is the linear equation data diagram of the peak current (Ip) and scan rate (V) response of g-C3N4@MoSe2 / GCE. The linear relationship can be expressed as I p a(μA)=12.62V(Vs -1 )+1.38×10 -6 (R 2 =0.9927) and I p b=-10.25V(Vs -1 )+8.00×10 -8 (R 2 =0.9975), it can be seen that the peak current (Ip) of g-C3N4@MoSe2 / GCE response is proportional to the scan rate, indicating that the redox reaction of quercetin on the g-C3N4@MoSe2 / GCE working electrode is an adsorption-controlled process; in addition, Figure 5 It can be seen that the peak heights of the oxidation peak and the reduction peak of g-C3N4@MoSe2 / GCE are different, and the difference is a bit large, which is not completely symmetrical, indicating that the chemical reaction of quercetin on the g-C3N4@MoSe2 / GCE electrochemical sensor is irreversible. p a(V)=1.72×10 -2 lnv(Vs -1 )+24.41×10 -2 (R 2 =0.9921) into the formula K = RT / (αnF), where α = 47.7 / (E p -E p / 2 ), and finally we can get α = 0.87, n = 1.72 ≈ 2, that is, the number of electron transfers of quercetin on the electrode is 2, from which we can infer that the chemical reaction equation can be expressed as:

[0066]

[0067] Impedance analysis of electrodes modified with the same material:

[0068] Under the same experimental conditions, the impedance of the electrodes modified with each material was detected by electrochemical impedance spectroscopy (IMP). Figure 6The following is the result of an experiment using four different modified glassy carbon electrodes as working electrodes: Bare / GCE, g-C3N4 / GCE, MoSe2 / GCE, and g-C3N4@MoSe2 / GCE. From the figure, it can be seen that the radius detected by the electrodes modified by each material is Bare / GCE>g-C3N4 / GCE>MoSe2 / GCE>g-C3N4@MoSe2 / GCE. It can be seen that the composite material g-C3N4@MoSe2 has the smallest radius, which shows that the electrochemical resistance is reduced after the g-C3N4 and MoSe2 are combined. In summary, it is concluded that the conductive properties of the g-C3N4@MoSe2 composite are better than those of the two monomer materials g-C3N4 and MoSe2.

[0069] Investigation of linear relationship and detection limit:

[0070] Under the optimal conditions, the g-C3N4@MoSe2 / GCE prepared in Example 1 was used for determination using square wave voltammetry (SWV) with a sensitivity of 1.0×10 -5 , set the potential window parameter to -0.1~0.5V, and use it to detect quercetin standard solutions of different concentrations. The test results are shown in Figure 7 ,from Figure 7 It can be seen that quercetin is 1.00×10 -8 mol / L~9.90×10 -6 mol / L and 9.90×10 -6 mol / L~4.76×10 -5 The corresponding peak currents in different concentration ranges of mol / L showed two good linear relationships, and their linear equations were expressed as Ip (μA) = 7.73 × 10 -2 C (μM) + 2.46 × 10 -8 (R 2 =0.9920) and Ip(μA)=3.54×10 -2 C (μM) +4.57×10 -7 (R 2 =0.9913). Under the optimal conditions, the detection limit was found to be 5.34×10 -9 mol / L is calculated by the formula LOD = 3S / K. It can be seen that the sensor constructed with g-C3N4@MoSe2 material has a wide detection range for quercetin concentration and a low detection limit, which can be used to more accurately detect quercetin in practical applications.

[0071] Chronocoulometry analysis:

[0072] In a solution containing 0.1 mol / L potassium chloride, 1.0 mmol / L potassium ferrocyanide and potassium ferrocyanide, the chronocoulometry (CC) was used to study the chronocoulometry of four different modified electrodes: Bare / GCE, g-C3N4 / GCE, MoSe2 / GCE, and g-C3N4@MoSe2 / GCE prepared in Example 1. The chronocoulometry curves of the modified electrodes of different materials are shown in Fig. Figure 8 (A) Q~t of four different modified electrodes: Bare / GCE, g-C3N4 / GCE, MoSe2 / GCE, and g-C3N4@MoSe2 / GCE 1 / 2 The curve equation is Figure 8 (B) is represented as:

[0073] Q1=5.55×10 -5 t 1 / 2 +6.61×10 -6 (R 2 =0.9996);

[0074] Q2=8.07×10 -5 t 1 / 2 +7.53×10 -6 (R 2 =0.9995);

[0075] Q3=1.16×10 -4 t 1 / 2 +3.27×10 -6 (R 2 =0.9999);

[0076] Q4=1.57×10 -4 t 1 / 2 +5.62×10 -7 (R 2 =0.9999);

[0077] The electrochemical effective area (A) of the four modified electrodes can be calculated using the formula:

[0078]

[0079] In formula (1), D is 1 mmol / L and the diffusion coefficient (D) of the measured solution is 7.6×10 -6 cm 2 / s, Faraday constant F = 96480C / mol. The effective areas of Bare / GCE, g-C3N4 / GCE, MoSe2 / GCE, and g-C3N4@MoSe2 / GCE are calculated to be 0.185cm 2 、0.269cm 2 、0.386cm2 、0.523cm 2 The effective area of ​​g-C3N4@MoSe2 / GCE is 2.8 times that of Bare / GCE, which shows that the g-C3N4@MoSe2 / GCE composite material obviously provides more active sites than other monomer materials.

[0080] Stability and reproducibility:

[0081] In a PBS buffer solution with a pH of 6, the modified glassy carbon electrode of Example 1 was placed in an electrolytic cell, and 3.85×10 -4 mol·L -1 The quercetin standard solution was tested 11 times in a row using square wave voltammetry (SWV). The electrochemical response of g-C3N4@MoSe2 / GCE to quercetin is shown in Figure 9 , Figure 9 The current does not change much, and the relative standard deviation of the measured peak current is 1.62%, indicating that the electrochemical stability of g-C3N4@MoSe2 / GCE is relatively good, which can reduce the experimental error and thus improve the accuracy of the experimental results.

[0082] Square wave voltammetry (SWV) was used to test whether the response value of the g-C3N4@MoSe2 / GCE sensor to quercetin in Example 1 had good reproducibility. Under the optimal pH = 6, the concentration of 3.85×10 -4 mol·L -1 Quercetin standard solution was used to modify five g-C3N4@MoSe2 / GCE as working electrodes. The five working electrodes were measured once by square wave voltammetry (SWV) to obtain five sets of peak current data, as shown in Figure 2. Figure 10 As shown in the figure, their relative standard deviation is small, with a value of 1.92%. It can be seen that the data measured by the five electrodes have a small gap, and the g-C3N4@MoSe2 / GCE constructed quercetin electrochemical sensor has good reproducibility.

[0083] Interference experiment analysis

[0084] Table 1 shows the effects of different interfering substances on the electrochemical behavior of the g-C3N4@MoSe2 / GCE working electrode. The data were obtained using square wave voltammetry (SWV) under optimal conditions to explore the effects of different substances on the electrochemical response of quercetin at the g-C3N4@MoSe2 / GCE working electrode (prepared in Example 1). In a buffer solution with the same concentration and pH, a quercetin standard solution was first added for measurement and the peak current data was recorded. The interfering substance solution was then added for measurement and the peak current data was recorded. The peak current obtained by adding the interfering substance was then subtracted from the peak current obtained by adding the quercetin standard solution but without the interfering substance. This difference was then divided by the peak current obtained by adding only the quercetin standard solution to obtain the relative error. The experimental results showed that the interference of the measured interfering substances was minimal even at a 100-fold multiplication factor, with the relative error being within ±5%, indicating the material's good selectivity.

[0085] Table 1 Effects of different interfering substances on the electrochemical behavior of g-C3N4@MoSe2 / GCE working electrode

[0086]

[0087]

[0088] Detection and analysis of sample spike recovery rate:

[0089] Under optimal conditions, the sensor prepared in Example 1 was used to detect the quercetin content in treated grape juice, ginkgo biloba leaves, and human urine using square wave voltammetry (SWV). Within the range of the experimental linear equation, a certain volume of treated actual sample was first added, and the peak current was measured and recorded. Then, a certain volume of quercetin standard solution was added, and the peak current was measured and recorded. The two recorded peak currents were substituted into the linear equation to calculate C1 and C2. The formula (C2-C1) / C 标 ×100% to calculate the spike recovery (C1: actual concentration of the sample in the buffer solution, C2: actual concentration of quercetin solution, C 标 : Theoretical concentration of quercetin standard solution). The experimental test results are shown in Table 2 below. Using this experimental method to determine quercetin samples, the average spiked recovery range is between 95.89% and 104.85%. The recoveries of quercetin detected in the experiment are all within a reasonable error range, and their relative standard deviations are between 0.36% and 7.35%. The experimental results show that the electrochemical sensor can be applied to the detection of quercetin in actual samples.

[0090] Table 2 Analysis of actual sample spike recovery

[0091]

[0092]

[0093] In summary, the electrochemical sensor constructed from the g-C3N4@MoSe2 / GCE composite material synthesized in the present invention is used to detect quercetin, and its electrochemical performance in the above experiments shows good phenomena. The above experiments found that under the optimal conditions, the electrochemical sensor can detect quercetin at a concentration of 1.00×10 -8 mol / L~9.90×10 -6 mol / L and 9.90×10 - 6 mol / L~4.76×10 -5 The electrochemical response current exhibited a good linear relationship in the mol / L range, with a wide linear range and a low detection limit. Furthermore, interference experiments revealed negligible interference with the detection of quercetin among 25 common interfering substances. Furthermore, using a spike-in recovery method for real-world samples, the g-C3N4 / MoSe2 / GCE sensor successfully detected quercetin in grape juice, ginkgo biloba leaves, and urine, demonstrating promising application prospects.

[0094] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing an electrochemical sensor for detecting quercetin, characterized in that: The following steps are involved: (1) Preparation of g-C3N4; (2) preparing molybdenum selenide; (3) Preparation of g-C3N4@MoSe2 composite material: After mixing equal amounts of the g-C3N4 and the molybdenum selenide, DMF was added to the mixture, and ultrasonication was performed to dissolve and mix the materials to obtain the g-C3N4@MoSe2 composite material; (4) Preparation of electrochemical sensor g-C3N4@MoSe2 / GCE: Weigh g-C3N4 and MoSe2 and add them to DMF, disperse them evenly by ultrasonication to obtain a suspension, drop the suspension onto the surface of a clean glassy carbon electrode, and dry it under an infrared lamp to obtain the g-C3N4@MoSe2 / GCE.

2. The method for preparing an electrochemical sensor for detecting quercetin according to claim 1, wherein: In step (1), the preparation method of g-C3N4 is as follows: weigh melamine, place it in a high-temperature tube furnace, and heat it at a rate of 5-8°C / min. When the temperature rises to 450-550°C, calcinate it at a constant temperature of 450-550°C for 3.5-5h to obtain g-C3N4.

3. The method for preparing an electrochemical sensor for detecting quercetin according to claim 1, wherein: In step (2), the preparation method of the molybdenum selenide is as follows: first, sodium molybdate is added to a mixed solution of anhydrous ethanol and deionized water, and then selenium powder is added, the mixture is covered with plastic wrap and stirred, and after the sodium molybdate is completely dissolved, sodium borohydride is added, and the mixture is covered with plastic wrap and stirred vigorously. When the solution changes from light brown to reddish brown, the reddish brown solution is placed in a high-pressure reactor, sealed firmly, and reacted at 180-250° C. for 45-50 hours. After the reaction is completed, the temperature is lowered to room temperature to obtain a reaction material; the reaction material is centrifuged at 7000-8000 r / min for 3-5 minutes, the lower layer of material is washed 3-5 times, and then vacuum-dried at 50-60° C. for 10-12 hours to obtain a finely divided black material; the black material is placed in a tubular furnace, after introducing an inert gas, the temperature is raised to 400-500° C. at a rate of 5-8° C. / min, and calcined in this environment and maintained for 2-3 hours to obtain the molybdenum selenide.

4. The method for preparing an electrochemical sensor for detecting quercetin according to claim 3, wherein: In the mixed solution of anhydrous ethanol and deionized water, the mass concentration of anhydrous ethanol is 50-55%.

5. The method for preparing an electrochemical sensor for detecting quercetin according to claim 3, wherein: The mass volume ratio of the sodium molybdate to the mixed solution is (0.8-1) g:25 mL.

6. The method for preparing an electrochemical sensor for detecting quercetin according to claim 3, wherein: The mass ratio of the sodium molybdate, selenium powder and sodium borohydride is (6-7):(5-6):

1.

7. The electrochemical sensor g-C3N4@MoSe2 / GCE prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the electrochemical sensor prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The application is for the detection of quercetin, specifically: using the electrochemical sensor g-C3N4@MoSe2 / GCE as a working electrode, the electrochemical sensor g-C3N4@MoSe2 / GCE is immersed in a test solution that may contain quercetin for detection.

9. The use according to claim 8, characterized in that: The test solution is prepared by adding a test sample into an electrolyte, wherein the electrolyte is a PBS buffer solution, the concentration of the PBS buffer solution is 0.20 mol / L, and the pH is 3.0-6.

0.

10. The use according to claim 8, characterized in that: The detection is performed by cyclic voltammetry, with a potential window of -0.1 to 0.5 V and a scan rate of 0.01 to 1.0 v / s.

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