AuNPs@CTS@NiCo2O4 composite material, preparation method and application

Abstract

The invention discloses an AuNPs@CTS@NiCo2O4 composite material, a preparation method and an application thereof, comprising the following steps: step 1: reducing chloroauric acid with sodium citrate to obtain nano-gold; step 2: adding NiCo2O4 to chitosan to obtain a NiCo2O4 dispersant, wherein the mass ratio of NiCo2O4 to chitosan is 1:1; step 3: fully mixing and dispersing the NiCo2O4 dispersant obtained in step 2 and the nano-gold solution obtained in step 1 to obtain the AuNPs@CTS@NiCo2O4 composite material, wherein the mass ratio of chloroauric acid to NiCo2O4 is 1:25; the composite material is used to prepare an electrochemical sensor for detecting norfloxacin, and the prepared sensor has a low LOD (0.0077 nM) and a wide linear range (0.02-1.09 nM); and the sensor has good selectivity, good anti-interference and good stability.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical sensors, and in particular to an AuNPs@CTS@NiCo2O4 composite material, a preparation method and applications thereof. Background Art

[0002] Norfloxacin (NOR), chemically known as 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolinecarboxylic acid, is a third-generation fluoroquinolone antimicrobial drug with broad-spectrum antimicrobial activity. However, NOR is metabolized slowly and incompletely in animals, easily remaining in animal feces and animal-derived foods. This is harmful to the environment and human health, and can lead to bacterial resistance. The illegal use of NOR persists, necessitating the continued need for NOR residue detection, which in turn places higher demands on the sensitivity of the method. Therefore, establishing an effective method for monitoring NOR residues in food is crucial, as it is of great significance to human health.

[0003] Currently reported methods for detecting NOR residues include HPLC, HPLC-MS / MS, fluorescence, capillary electrophoresis, etc. These technologies are characterized by high sensitivity and good reproducibility, but they also have problems such as complexity, time-consuming, and the use of large amounts of organic solvents. They are not cost-effective and are harmful to the environment. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides an AuNPs@CTS@NiCo2O4 composite material, a preparation method and an application thereof.

[0005] The technical solution adopted by the present invention is: a method for preparing an AuNPs@CTS@NiCo2O4 composite material, comprising the following steps:

[0006] Step 1: Using sodium citrate to reduce chloroauric acid to obtain gold nanoparticles;

[0007] Step 2: adding NiCo2O4 to chitosan to obtain a NiCo2O4 dispersant; the mass ratio of NiCo2O4 to chitosan is 1:1;

[0008] Step 3: The NiCo2O4 dispersant obtained in step 2 and the nanogold solution obtained in step 1 are fully mixed and dispersed to obtain the AuNPs@CTS@NiCo2O4 composite material; the mass ratio of the chloroauric acid to NiCo2O4 is 1:25.

[0009] Furthermore, the restoration process in step 1 is as follows:

[0010] Add sodium citrate dropwise to the boiling chloroauric acid solution and stir thoroughly to mix.

[0011] Furthermore, the dispersion process in step 3 is as follows:

[0012] The mixture was ultrasonicated for 30 min.

[0013] An AuNPs@CTS@NiCo2O4 composite material.

[0014] An application of an AuNPs@CTS@NiCo2O4 composite material, wherein the AuNPs@CTS@NiCo2O4 composite material is used to prepare an electrochemical sensor for detecting norfloxacin.

[0015] Furthermore, the AuNPs@CTS@NiCo2O4 composite material is used to prepare a working electrode of a sensor.

[0016] Furthermore, the preparation method of the working electrode is as follows:

[0017] S1: Activate the electrode using cyclic voltammetry;

[0018] S2: Coat the AuNPs@CTS@NiCo2O4 composite material on the activated electrode and store it under refrigerated conditions to obtain the desired electrode.

[0019] Furthermore, the method for activating the electrode is as follows:

[0020] Polish the electrode with aluminum oxide powder and clean it;

[0021] Place it in sulfuric acid solution and scan 50 times in the potential range of -0.6 to 1.0 V to activate the electrode.

[0022] Furthermore, in step S2, the refrigeration temperature is 4-8° C., and the refrigeration time is 4 hours.

[0023] The beneficial effects of the present invention are:

[0024] (1) The composite material of the present invention is used to prepare an electrochemical sensor for detecting norfloxacin. The prepared sensor has a low LOD (0.0077 nM) and a wide linear range (0.02 to 1.09 nM);

[0025] (2) The sensor of the present invention has good selectivity, good anti-interference and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention provides a flow chart of a method for preparing a sensor from the composite material obtained in the present invention.

[0027] Figure 2CV graphs of the composite material obtained in Example 1 of the present invention and the composite material obtained in the comparative example as working electrodes.

[0028] Figure 3 These are EIS graphs of the composite material obtained in Example 1 of the present invention and the composite material obtained in the comparative example as working electrodes.

[0029] Figure 4 This is a linear graph obtained by detecting norfloxacin using a sensor prepared with the composite material obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, a method for preparing an AuNPs@CTS@NiCo2O4 composite material comprises the following steps:

[0032] Step 1: Use sodium citrate to reduce chloroauric acid to obtain gold nanoparticles; the reduction process is as follows:

[0033] Add sodium citrate dropwise to the boiling chloroauric acid solution and stir thoroughly to mix.

[0034] Step 2: adding NiCo2O4 to chitosan to obtain a NiCo2O4 dispersant; the mass ratio of NiCo2O4 to chitosan is 1:1;

[0035] Step 3: The NiCo2O4 dispersant obtained in step 2 and the nano-gold solution obtained in step 1 are fully mixed and dispersed to obtain the AuNPs@CTS@NiCo2O4 composite material. The mass ratio of chloroauric acid to NiCo2O4 is 1:25. The dispersion process is as follows:

[0036] The mixture was ultrasonicated for 30 min.

[0037] The obtained composite material can be used to prepare a working electrode of an electrochemical sensor for detecting norfloxacin. The preparation process is as follows:

[0038] S1: Activate the electrode using cyclic voltammetry. The method for activating the electrode is as follows:

[0039] Polish the electrode with aluminum oxide powder and clean it;

[0040] Place it in sulfuric acid solution and scan 50 times in the potential range of -0.6 to 1.0 V to activate the electrode.

[0041] S2: Coat the activated electrode with the AuNPs@CTS@NiCo2O4 composite material and store it in a refrigerator at 4-8°C for 4 hours to obtain the desired electrode.

[0042] Example 1

[0043] The AuNPs@CTS@NiCo2O4 composites were prepared by the following steps:

[0044] Step 1: Take 0.0010g of chloroauric acid in a beaker, add deionized water to the beaker and stir thoroughly with a glass rod; heat the chloroauric acid solution in the beaker to boiling, then add 5.00mL of sodium citrate with a mass concentration of 1wt.% dropwise, and stir until it turns purple-red to obtain a nanogold solution.

[0045] Step 2: Take 0.0010 g of NiCo2O4 powder and add the NiCo2O4 powder to chitosan to obtain a NiCo2O4 dispersant.

[0046] Step 3: Add 0.50 mL of nanogold solution to the dispersant obtained in step 2, and continuously vibrate for 30 minutes using an ultrasonic cleaner to mix the NiCo2O4 dispersant and chitosan evenly. After dispersion, the AuNPs@CTS@NiCo2O4 composite material can be obtained.

[0047] The process of preparing the working electrode of the electrochemical sensor for detecting norfloxacin using the AuNPs@CTS@NiCo2O4 composite material obtained above is as follows:

[0048] S1: First, activate the electrode: polish the glassy carbon electrode (GCE) with 0.02 μm diameter alumina powder and rinse it with deionized water and anhydrous ethanol ultrasonically; place the cleaned glassy carbon electrode in 0.5 M sulfuric acid solution and scan 50 cycles in the potential range of -0.6 to 1.0 V to activate the electrode.

[0049] S2: Take 3.00 μL of the composite material obtained in step 3 and drop-coat it on the surface of the activated glassy carbon electrode. Store in a refrigerator at 4-8°C for approximately 4 hours to form a uniform solid film. This will yield the desired working electrode, GCE-NiCo2O4-CTS-AuNPs.

[0050] To illustrate the beneficial effects of the present invention, the following comparative examples are provided:

[0051] Comparative Example 1

[0052] The process of detecting the working electrode of the norfloxacin electrochemical sensor is the same as in Example 1, except that the activated electrode is coated with a NiCo2O4 solution. The resulting electrode is GCE-NiCo2O4.

[0053] Comparative Example 2

[0054] The other steps are the same as those in Example 1, except that step 1 is not included; the process for preparing the electrode is the same as that in Example 1, and the obtained electrode is GCE-NiCo2O4-CTS.

[0055] The above-mentioned electrode is used to detect norfloxacin, and the process is as follows:

[0056] 1) Prepare PBS buffer solution: Weigh a certain amount of disodium hydrogen phosphate into a beaker and dissolve it in deionized water to a concentration of 0.10 mol / L as PBS buffer solution A. Weigh a certain amount of sodium dihydrogen phosphate into another beaker and dissolve it in deionized water to a concentration of 0.10 mol / L as PBS buffer solution B. Mix solutions A and B in a specific ratio to form a PBS buffer solution with a pH of 7.00.

[0057] 2) Prepare norfloxacin standard solution: Weigh a certain amount of norfloxacin into a beaker, dissolve it in hydrochloric acid, and then dilute to a 0.01 M norfloxacin solution. Then, use ultrapure water for gradient dilution to prepare a standard solution for detection.

[0058] 3) Prepare potassium ferrocyanide solution: Weigh a certain amount of potassium ferrocyanide and dissolve it in ultrapure water to make a 0.4 M potassium ferrocyanide solution.

[0059] 4) Preparation of electrolyte solution: The PBS buffer solution with pH = 7.00 obtained in 2) and the potassium ferricyanide solution obtained in 3) were used as base solutions, and detection was performed using a three-electrode system, and working conditions were set.

[0060] The three-electrode system is as follows: a glassy carbon electrode modified with nickel cobaltate / chitosan / nano-gold composite material is used as the working electrode, a platinum electrode is used as the counter electrode, and a saturated calomel electrode is used as the reference electrode.

[0061] 5) Optimize experimental conditions: Pipette 9.00 mL of PBS (pH = 7) into the electrolytic cell, add 1.00 mL of norfloxacin (0.001 M) and 1.00 μL of potassium ferricyanide solution (0.4 M), and use cyclic voltammetry to optimize the material ratio of the modified electrode. The optimal ratio is NiCo2O4:CTS = 1:1. When 0.0010 g of NiCo2O4 is taken, adding 0.50 mL of nanogold solution is the best. Pipette 9.00 mL of PBS solution into the electrolytic cell, add 1.00 mL of norfloxacin (0.001 M) and 1.00 μL of potassium ferricyanide solution (0.4 M). Under the optimal material ratio, the pH of PBS is optimized by cyclic voltammetry, and pH 6.5 is the best. The electrochemical properties of the electrode modification process are characterized by cyclic voltammetry.

[0062] 6) Prepare the standard curve of norfloxacin: Pipette 9.00 mL of PBS (pH=6.5) into the electrolytic cell, add 1.00 μL of potassium ferricyanide solution (0.4 M), and take the norfloxacin standard solution (10 -7 M and 10 -8 M), take 10.00 μL of each concentration 10 times, and measure once and add it to the bottom liquid to find the linearity by DPV method;

[0063] The CV graph was obtained by the above method. The rest time of CV detection was 2 min, the initial voltage was -0.7 V, the peak voltage was 0.7 V, the sampling interval was 0.001 V, the scanning speed was 0.1 V / s, and the sensitivity was 10 μA / V. Figure 2 As shown in the figure, GCE is a glassy carbon electrode GCE. It can be seen from the figure that after adding norfloxacin solution, a pair of obvious redox peaks appear.

[0064] The measured EIS is as follows Figure 3 As shown, 9.00 mL of PBS (pH = 6.5), 1 ml of 0.001 M norfloxacin solution and 1.00 μL of 0.4 M potassium ferricyanide solution were added to the electrolytic cell, and the charge transfer resistance of NiCo2O4 / CTS / AuNPs / GCE was measured by EIS method.

[0065] It can be seen from the figure that NiCo2O4 nanoparticles have good electrocatalytic performance.

[0066] The catalytic sensor obtained in Example 1 was used to detect the NOR linear graph of norfloxacin, as shown in FIG. Figure 4 As shown. Pipette 9mL of PBS (pH=6.5) into the electrolytic cell, add 1.00μL of potassium ferricyanide solution (0.4M), and take the norfloxacin standard solution (10 -7 M and 10 -8 M), 10.00 μL of each concentration was taken 10 times and measured once, and the oxidation peak current was detected by DPV method. As shown in the figure, it can be obtained that the oxidation peak current shows a good linear relationship with its concentration. -11 mol / L~2.0×10 -11 The linear regression equation for mol / L is y=14.7418x+3.4170, and the correlation coefficient is R 2 =0.9926. The minimum concentration detection limit is 7.659×10 -12 mol / L.

[0067] The present invention utilizes the high conductivity, large activated surface area, rapid electron transfer capability and electrolyte ion penetration capability of NiCo2O4 and chitosan nano-gold to construct a nano-composite electrode to detect NOR residues in animal-derived foods.

Claims

1. A method for preparing an AuNPs@CTS@NiCo2O4 composite material, characterized in that: The following steps are involved: Step 1: Add sodium citrate dropwise to a boiling chloroauric acid solution, stir thoroughly, and use sodium citrate to reduce the chloroauric acid to obtain gold nanoparticles; Step 2: adding NiCo2O4 to chitosan to obtain a NiCo2O4 dispersant; the mass ratio of NiCo2O4 to chitosan is 1:1; Step 3: The NiCo2O4 dispersant obtained in step 2 and the nanogold solution obtained in step 1 are thoroughly mixed and dispersed by ultrasonic vibration for 30 minutes to obtain an AuNPs@CTS@NiCo2O4 composite material; the mass ratio of chloroauric acid to NiCo2O4 is 1:

25.

2. The AuNPs@CTS@NiCo2O4 composite material obtained by the preparation method as described in claim 1.

3. The use of an AuNPs@CTS@NiCo2O4 composite material as claimed in claim 2, characterized in that: The AuNPs@CTS@NiCo2O4 composite material is used to prepare an electrochemical sensor for detecting norfloxacin.

4. The use of an AuNPs@CTS@NiCo2O4 composite material according to claim 3, characterized in that: The AuNPs@CTS@NiCo2O4 composite material is used to prepare the working electrode of the sensor.

5. The use of an AuNPs@CTS@NiCo2O4 composite material according to claim 4, characterized in that: The preparation method of the working electrode is as follows: S1: Activate the electrode using cyclic voltammetry; S2: Coat the AuNPs@CTS@NiCo2O4 composite material on the activated electrode and store it under refrigerated conditions to obtain the desired electrode.

6. The use of the AuNPs@CTS@NiCo2O4 composite material according to claim 5, characterized in that: The method for activating the electrode is as follows: polishing the electrode with aluminum oxide powder and cleaning it; placing it in a sulfuric acid solution and scanning it 50 times within a potential range of -0.6 to 1.0 V to activate the electrode.

7. The use of the AuNPs@CTS@NiCo2O4 composite material according to claim 5, characterized in that: In step S2, the refrigeration temperature is 4-8° C. and the refrigeration time is 4 hours.

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