AuNPs (at) CTS (at) NiCo2O4 composite material, preparation method and application

Abstract

The invention discloses an AuNPs (at) CTS (at) NiCo2O4 composite material and a preparation method and application thereof.The preparation method comprises the following steps that 1, sodium citrate is adopted for reducing chloroauric acid, and nanogold is obtained; step 2, adding NiCo2O4 into chitosan, so as to obtain a NiCo2O4 dispersing agent; the mass ratio of the NiCo2O4 to the chitosan is 1: 1; 3, the NiCo2O4 dispersing agent obtained in the step 2 and the nanogold solution obtained in the step 1 are fully mixed and dispersed, and an AuNPs (at) CTS (at) NiCo2O4 composite material can be obtained; the mass ratio of the chloroauric acid to the NiCo2O4 is 1: 25; the composite material is used for preparing an electrochemical sensor for detecting norfloxacin, and the prepared sensor has low LOD (0.0077 nM) and a wide linear range (0.02-1.09 nM); the sensor has good selectivity, good anti-interference performance and good stability.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical sensors, and particularly relates to an AuNPs@CTS@NiCo 2 O 4 composite material, a preparation method and an application thereof. Background Art

[0002] Norfloxacin (NOR), with the chemical name of 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolinecarboxylic acid, belongs to the third-generation fluoroquinolone antibacterial drugs and has a broad-spectrum antibacterial effect. NOR has a slow and incomplete metabolism in animals and is likely to remain in animal feces and animal-derived foods, which is harmful to the environment and human health and can lead to bacterial drug resistance. NOR has a slow and incomplete metabolism in animals and is likely to remain in animal feces and animal-derived foods, which is harmful to the environment and human health and can lead to bacterial drug resistance. In fact, the illegal use of NOR still exists. Therefore, it is still necessary to detect the residue of NOR, and at the same time, higher requirements are also put forward for the sensitivity of the method. Therefore, it is crucial to establish an effective method to monitor the residue of NOR in food, which is of great significance to human health.

[0003] Currently reported methods for detecting NOR residues include HPLC, HPLC-MS / MS, fluorescence, capillary electrophoresis, etc. The characteristics of these technologies are high sensitivity and good reproducibility, but they also have problems such as complexity, time-consuming, and the use of a large amount of organic solvents, with low cost-effectiveness and being harmful to the environment. Summary of the Invention

[0004] The present invention provides an AuNPs@CTS@NiCo 2 O 4 composite material, a preparation method and an application thereof in view of the problems existing in the prior art.

[0005] The technical solution adopted by the present invention is as follows: A preparation method of an AuNPs@CTS@NiCo 2 O 4 composite material, comprising the following steps:

[0006] Step 1: Reducing chloroauric acid with sodium citrate to obtain gold nanoparticles;

[0007] Step 2: Adding NiCo 2 O 4 to chitosan to obtain a NiCo 2 O 4 dispersant; the mass ratio of NiCo 2 O 4 to chitosan is 1:1;

[0008] Step 3: Mix and disperse the NiCo obtained in Step 2 2 O 4 with the dispersant and the nano-gold solution obtained in Step 1 to obtain the AuNPs@CTS@NiCo 2 O 4 composite material; the mass ratio of chloroauric acid to NiCo 2 O 4 is 1:25.

[0009] Furthermore, the reduction process in Step 1 is as follows:

[0010] Drop sodium citrate into the chloroauric acid solution heated to boiling, and stir and mix well.

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

[0012] Ultrasonically vibrate the mixture for 30 min.

[0013] An AuNPs@CTS@NiCo 2 O 4 composite material.

[0014] An application of an AuNPs@CTS@NiCo 2 O 4 composite material, wherein the AuNPs@CTS@NiCo 2 O 4 composite material is used for preparing an electrochemical sensor for detecting norfloxacin.

[0015] Furthermore, the AuNPs@CTS@NiCo 2 O 4 composite material is used for preparing a working electrode of the sensor.

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

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

[0018] S2: Coat the AuNPs@CTS@NiCo 2 O 4 composite material on the activated electrode and store it under refrigeration conditions to obtain the required electrode.

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

[0020] Polish the electrode with alumina powder and wash it;

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

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

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

[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 - 1.09 nM);

[0025] (2) The sensor of the present invention has good selectivity, good anti-interference ability and stability. Description of the Drawings

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

[0027] Figure 2 It is a CV diagram of the composite material obtained in Example 1 of the present invention and the composite material obtained in the comparative example as the working electrode.

[0028] Figure 3 It is an EIS diagram of the composite material obtained in Example 1 of the present invention and the composite material obtained in the comparative example as the working electrode.

[0029] Figure 4 It is a linear diagram obtained by detecting norfloxacin with the sensor prepared from the composite material obtained in Example 1 of the present invention. Detailed Embodiments

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

[0031] As Figure 1 shown, a preparation method of an AuNPs@CTS@NiCo 2 O 4 composite material includes the following steps:

[0032] Step 1: Sodium citrate is used to reduce chloroauric acid to obtain gold nanoparticles. The reduction process is as follows:

[0033] Sodium citrate is added dropwise to the boiling chloroauric acid solution, and stirred and mixed thoroughly.

[0034] Step 2: NiCo 2 O 4 is added to chitosan to obtain a NiCo 2 O 4 dispersant; the mass ratio of NiCo 2 O 4 to chitosan is 1:1;

[0035] Step 3: Mix and disperse the NiCo obtained in Step 2 2 O 4 dispersant and the nano-gold solution obtained in Step 1 thoroughly to obtain the AuNPs@CTS@NiCo 2 O 4 composite material. The mass ratio of chloroauric acid to NiCo 2 O 4 is 1:25. The dispersion process is as follows:

[0036] Ultrasonically vibrate the mixture for 30 min.

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

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

[0039] Polish the electrode with alumina powder and wash it;

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

[0041] S2: Coat the AuNPs@CTS@NiCo 2 O 4 composite material on the activated electrode and store it under refrigeration conditions to obtain the required electrode. The refrigeration temperature is 4 - 8 °C and the refrigeration time is 4 h.

[0042] Example 1

[0043] Prepare the AuNPs@CTS@NiCo 2 O 4 composite material according to the following steps:

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

[0045] Step 2: Take 0.0010 g of NiCo 2 O 4 powder, add the NiCo 2 O 4 powder to chitosan to obtain the NiCo 2 O 4 dispersant.

[0046] Step 3: Add 0.50 mL of the nano-gold solution to the dispersant obtained in Step 2, and continuously vibrate it with an ultrasonic cleaner for 30 min to disperse NiCo 2 O 4 in the dispersant and mix it evenly with chitosan. After dispersion, the AuNPs@CTS@NiCo 2 O 4 composite material can be obtained.

[0047] The working electrode for detecting norfloxacin electrochemical sensor is prepared by using the obtained AuNPs@CTS@NiCo 2 O 4 composite material as follows:

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

[0049] S2: Take 3.00 μL of the composite material obtained in Step 3, drop-coat it on the surface of the activated glassy carbon electrode, and place it in a refrigerator at 4 - 8 °C for about 4 h to form a uniform solid film. Then the required working electrode GCE-NiCo 2 O 4 -CTS-AuNPs can be obtained.

[0050] The following comparative examples are set to illustrate the beneficial effects of the present invention

[0051] Comparative Example 1

[0052] The process of the working electrode for detecting norfloxacin electrochemical sensor is the same as that in Example 1, except that the activated electrode is coated with NiCo 2 O 4 solution. The obtained electrode is GCE-NiCo 2 O 4 .

[0053] Comparative Example 2

[0054] Other steps are the same as those in Example 1, except that Step 1 is not included; The process of preparing the electrode is the same as that in Example 1, and the obtained electrode is GCE-NiCo 2 O 4 -CTS.

[0055] The detection of norfloxacin using the above electrode is as follows:

[0056] 1) Prepare PBS buffer solution: Weigh a certain amount of disodium hydrogen phosphate into a beaker, add deionized water to the beaker to dissolve and make up the volume to prepare PBS buffer solution A with a concentration of 0.10 mol / L. Weigh a certain amount of sodium dihydrogen phosphate into another beaker, add deionized water to this beaker to dissolve and make up the volume to prepare PBS buffer solution B with a concentration of 0.10 mol / L; mix solutions A and B in a certain ratio to form a PBS buffer solution with pH = 7.00.

[0057] 2) Prepare norfloxacin standard solution: Weigh a certain amount of norfloxacin into a beaker, dissolve it with hydrochloric acid and make up the volume to prepare a norfloxacin solution with a concentration of 0.01 M, and use ultrapure water for gradient dilution to prepare the standard solution for detection.

[0058] 3) Prepare potassium ferricyanide solution: Weigh a certain amount of potassium ferricyanide and dissolve it in ultrapure water, make up the volume to prepare a 0.4 M potassium ferricyanide solution.

[0059] 4) Prepare electrolyte solution: Use the PBS buffer solution with pH = 7.00 obtained in 2) and the potassium ferricyanide solution obtained in 3) as the base solution, and use a three - electrode system for detection and set the working conditions.

[0060] The three - electrode system is: a glassy carbon electrode modified with nickel cobalt oxide / chitosan / nano - gold composite material as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode 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 best ratio is NiCo 2 O 4 :CTS = 1:1. When the amount of NiCo 2 O 4 is 0.0010 g, it is best to add 0.50 mL of nano - gold solution. 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 condition of the optimal material ratio, use cyclic voltammetry to optimize the pH of PBS, and the best pH is 6.5. Use cyclic voltammetry to characterize the electrochemical properties of the electrode modification process.

[0062] 6) Make a norfloxacin standard curve: 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 successively take norfloxacin standard solutions starting from the lowest concentration (10 -7 M and 10 -8(M), 10 times of 10.00 μL were taken successively for each concentration, and each time it was taken, it was measured once and accumulated into the bottom solution, and differential pulse voltammetry (DPV) was used to find the linearity;

[0063] The CV diagram was obtained by the above method. The standing time for 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. As Figure 2 shown, in the figure, GCE is the glassy carbon electrode GCE. It can be seen from the figure that after adding the norfloxacin solution, a pair of obvious redox peaks appear.

[0064] The measured EIS is as Figure 3 shown. 9.00 mL of PBS (pH = 6.5), 1 mL of norfloxacin solution with a concentration of 0.001 M, and 1.00 μL of potassium ferricyanide solution with a concentration of 0.4 M were added to the electrolytic cell. The charge transfer resistance of NiCo 2 O 4 / CTS / AuNPs / GCE was measured by EIS method.

[0065] It can be seen from the figure that NiCo 2 O 4 nanoparticles have good electrocatalytic performance.

[0066] The linear diagram of norfloxacin (NOR) detected by the catalytic sensor obtained in Example 1 is as Figure 4 shown. 9 mL of PBS (pH = 6.5) was pipetted into the electrolytic cell, and 1.00 μL of potassium ferricyanide solution (0.4 M) was added. Starting from the lowest concentration, norfloxacin standard solutions (10 -7 M and 10 -8 M) were successively taken. 10 times of 10.00 μL were taken successively for each concentration, and each time it was taken, it was measured once and accumulated into the bottom solution, and the oxidation peak current was detected by DPV method. As shown in the figure, it can be obtained that there is a good linear relationship between the oxidation peak current and its concentration. When the concentration is in the range of 9.9×10 -11 mol / L to 2.0×10 -11 mol / L, the linear regression equation is y = 14.7418x + 3.4170, and the correlation coefficient is R 2 = 0.9926. The detection limit of the lowest concentration is 7.659×10 -12 mol / L.

[0067] The present invention utilizes the large conductivity, large active surface area, fast electron transfer ability and electrolyte ion penetration ability of NiCo 2 O 4 to construct a nano-composite electrode together with chitosan nanogold to realize the detection of NOR residues in animal-derived foods.

Claims

1. A method for preparing a AuNPs@CTS@NiCo2O4 composite material, characterized in that: The following steps are involved: Step 1: using sodium citrate to reduce chloroauric acid to obtain nano-gold; 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 nano-gold 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.

2. The method for preparing the AuNPs@CTS@NiCo2O4 composite material according to claim 1, characterized in that: The restoration process in step 1 is as follows: Add sodium citrate dropwise to the boiling chloroauric acid solution and stir thoroughly to mix.

3. The method for preparing the AuNPs@CTS@NiCo2O4 composite material according to claim 1, characterized in that: The dispersion process in step 3 is as follows: The mixture was sonicated for 30 min.

4. The AuNPs@CTS@NiCo2O4 composite material obtained by the preparation method as described in any one of claims 1 to 3.

5. The use of an AuNPs@CTS@NiCo2O4 composite material as claimed in claim 4, characterized in that: The AuNPs@CTS@NiCo2O4 composite material is used to prepare an electrochemical sensor for detecting norfloxacin.

6. The use of an AuNPs@CTS@NiCo2O4 composite material according to claim 5, characterized in that: The AuNPs@CTS@NiCo2O4 composite material is used to prepare the working electrode of the sensor.

7. The use of an AuNPs@CTS@NiCo2O4 composite material according to claim 6, 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.

8. The use of an AuNPs@CTS@NiCo2O4 composite material according to claim 7, characterized in that: The method of activating the electrode is as follows: Grind the electrode with aluminum oxide powder and clean it; Place it in a sulfuric acid solution and scan 50 times in the potential range of -0.6 to 1.0 V to activate the electrode.

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

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