Preparation Method and Application of a (Au - Ag)-Ala-Gr / GCE Electrochemical Sensor

Abstract

The present invention relates to a preparation method and application of an (Au-Ag)-Ala-Gr / GCE electrochemical sensor. GO powder is added to ultrapure water and ultrasonicated to obtain a dispersion liquid. Alanine and chloroauric acid are successively added under stirring, and the pH of the mixed solution is adjusted to 10. Then it is transferred to a flask for water bath heating. When the mixed solution turns purplish red, silver nitrate is added, and the reaction is stopped when the mixed solution turns khaki. After the reaction mixture is cooled to room temperature, centrifugal separation is carried out, and the precipitate is washed repeatedly until the pH of the supernatant reaches 7, followed by centrifugal separation. After drying the precipitate, an alanine-functionalized graphene composite material (Au-Ag)-Ala-Gr loaded with Au-Ag alloy nanoparticles is obtained. The (Au-Ag)-Ala-Gr dispersion liquid is drop-coated onto the surface of a treated glassy carbon electrode (GCE) to obtain an (Au-Ag)-Ala-Gr / GCE electrochemical sensor. The present invention solves the problems of easy aggregation of noble metal nanoparticles and easy stacking of graphene sheets, does not use toxic and harmful reagents, is environmentally friendly, and the prepared sensor shows the characteristics of simple operation, accuracy and sensitivity in the detection of bisphenol A.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical analysis, particularly to the field of electrochemical sensors, and specifically to a preparation method and application of an (Au-Ag)-Ala-Gr / GCE electrochemical sensor. Background Art

[0002] The unique physical and chemical properties of noble metal nanoparticles lay the foundation for their use as materials for electrochemical sensors. However, the high surface energy makes noble metal nanoparticles prone to aggregation, thus hindering the exhibition of their excellent electrochemical properties. Composite of noble metal nanoparticles with carbon materials is an effective way to improve their dispersibility. Graphene has excellent charge mobility, a large specific surface area and good flexibility, and is an ideal substrate material for loading metal nanoparticles. The chemical reduction method is a commonly used graphene preparation method, but reducing agents such as hydrazine hydrate and sodium borohydride are harmful to humans and the environment, and the graphene sheets obtained using them are prone to stacking, resulting in a reduction in electrochemically active sites.

[0003] Bisphenol A can be used to prepare polymer materials such as polycarbonate and epoxy resin, and is thus widely used in the production of baby bottles, water cups, food packaging, etc. However, bisphenol A belongs to environmental estrogen compounds, which can cause disorders of the endocrine system and nervous system and reduce the body's immune function. Therefore, establishing an accurate and convenient bisphenol A detection technology is of great significance in protecting the environment, ensuring life health and food safety, etc. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and application of an (Au-Ag)-Ala-Gr / GCE electrochemical sensor. Using graphene oxide as the basic raw material, alanine (Ala)-functionalized graphene (Gr) modified with gold-silver alloy nanoparticles: (Au-Ag)-Ala-Gr is prepared by simple steps, solving the problems that noble metal nanoparticles are prone to agglomeration and graphene sheets are prone to stacking, without using toxic and harmful reagents, being environmentally friendly, and the sensor shows the characteristics of simple operation, accuracy and sensitivity in the detection of bisphenol A.

[0005] One of the purposes of the present invention is to provide a preparation method of an (Au-Ag)-Ala-Gr / GCE electrochemical sensor, and the method specifically includes the following steps:

[0006] (1) Add a certain mass of graphene oxide to ultrapure water, and ultrasonically treat the liquid until it is uniformly dispersed to obtain a graphene oxide dispersion;

[0007] (2) Add a certain mass of alanine to the graphene oxide dispersion, and stir to obtain a mixture A;

[0008] (3) Measure a certain amount of chloroauric acid solution with a concentration of 25 mmol·L -1 and add it to the mixed solution A, stir evenly to obtain the mixed solution B;

[0009] (4) Drop 1 mol·L -1 of NaOH solution into the mixed solution B until its pH reaches 10 to obtain the mixed solution C;

[0010] (5) Transfer the stirred mixed solution C to a flask, perform water bath heating on this flask, set the temperature of the water bath to 85 °C, and keep stirring the mixed solution C;

[0011] (6) Wait until the substance in the flask turns purple-red, add a certain mass of silver nitrate to it, continue water bath heating and stirring; wait until the substance in the flask turns yellowish-brown, then let it cool naturally to room temperature, centrifuge and separate, discard the supernatant, obtain the lower-layer precipitate, add high-purity water to the precipitate, shake and wash, and perform centrifugal separation again; repeat the washing and centrifugal separation steps until the pH of the supernatant reaches 7, then perform centrifugal separation, discard the filtrate, place the obtained precipitate in an oven for drying, set the oven temperature to 80 °C, and obtain alanine-functionalized graphene loaded with Au-Ag alloy nanoparticles (Au-Ag)-Ala-Gr after drying;

[0012] (7) Add a certain mass of the prepared (Au-Ag)-Ala-Gr to ultrapure water, perform ultrasonic treatment until it is evenly dispersed to obtain a (Au-Ag)-Ala-Gr dispersion with a concentration of 1 mg·mL -1 ;

[0013] (8) Polish the surface of the glassy carbon electrode in dilute paste-like Al2O3 until it becomes mirror-like, take it out, ultrasonically clean it in absolute ethanol, and then wash it again with ultrapure water;

[0014] (9) Drop 6 μL of the (Au-Ag)-Ala-Gr dispersion on the surface of the treated glassy carbon electrode, and dry it under an infrared lamp to obtain the (Au-Ag)-Ala-Gr / GCE electrochemical sensor.

[0015] Preferably, in step (1), the concentration of the graphene oxide dispersion is 1 mg·mL -1 .

[0016] Preferably, in step (2), the concentration of alanine in the mixed solution A is 4 mg·mL -1 .

[0017] Preferably, in step (1), the mass of graphene oxide is 35 mg, the amount of ultrapure water used is 35 mL, the mass of glycine added in step (2) is 140 mg, and the concentration of 25 mmol·L added in step (3)-1 The volume of the chloroauric acid solution is 0.5 - 1.0 mL, and the mass of silver nitrate added in step (6) is 2.2 - 4.4 mg.

[0018] Another object of the present invention is to provide an (Au - Ag)-Ala - Gr / GCE electrochemical sensor prepared according to the above method and the application of the (Au - Ag)-Ala - Gr / GCE electrochemical sensor in detecting bisphenol A. Linear sweep voltammetry is selected as the analysis method. The specific parameters for the (Au - Ag)-Ala - Gr / GCE electrochemical sensor to detect bisphenol A are as follows: The (Au - Ag)-Ala - Gr / GCE electrochemical sensor is used as the working electrode, a saturated calomel electrode and a platinum wire electrode are used as the reference electrode and the counter electrode respectively to form a three - electrode system together; PBS with pH = 3.0 is used as the buffer solution, the detection potential range is set to 0.3 - 1.1 V, and the scanning rate is 0.1 V·s -1 , and the enrichment time is 210 s; after the measurement is completed, the three - electrode system is immersed in PBS with a concentration of 0.1 mol·L -1 and pH = 8.0, the potential range is set to 0.3 - 1.1 V, and cyclic voltammetry is used to scan for two cycles to achieve the purpose of renewing the surface of the (Au - Ag)-Ala - Gr / GCE electrochemical sensor. The linear range of the (Au - Ag)-Ala - Gr / GCE sensor's response to bisphenol A is 3.0×10 -8 mol·L -1 ~4.0×10 -6 mol·L -1 , and the detection limit is 9.0×10 -9 mol L -1 (S / N = 3).

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

[0020] (1) The present invention uses graphene oxide as the basic raw material and prepares alanine-functionalized graphene modified with gold-silver alloy nanoparticles ((Au-Ag)-Ala-Gr) by a simple continuous reduction method. First, graphene oxide is uniformly dispersed in water by ultrasonic treatment. The oxygen-containing groups of graphene oxide can serve as the nucleation centers of nano-gold, improving the dispersion and stability of nano-gold. After the formation of gold nanoparticles, silver nitrate is added to form Au-Ag alloy nanoparticles. In this process, alanine acts as a reducing agent for metal ions and graphene oxide, avoiding the use of harmful reducing agents, and alanine is cheap; the covalent bonding of alanine to the surface of graphene is conducive to the formation of a homogeneous and stable aqueous dispersion of the composite material, exposing more electrochemically active sites of graphene. The covalent modification of alanine on the surface of graphene effectively changes the surface state of graphene, thereby reducing the stacking of graphene. In addition, compared with single metal nanoparticles, the synergistic effect of the bimetal makes it more advantageous in terms of the enrichment ability and conductivity of target molecules when used as a modification material for electrochemical sensors.

[0021] (2) The (Au-Ag)-Ala-Gr / GCE electrochemical sensor prepared by modifying the surface of a glassy carbon electrode with the (Au-Ag)-Ala-Gr composite material has a linear range of response to bisphenol A of 3.0×10 -8 mol·L -1 ~4.0×10 -6 mol·L -1 , and the detection limit is 9.0×10 -9 mol L -1 (S / N = 3). The present invention constructs a new type of electrochemical sensor for detecting bisphenol A, and when using this sensor to establish a bisphenol A detection method, it shows the characteristics of simple operation, accuracy, and sensitivity. Description of the Drawings

[0022] Figure 1 It is a photo of the (Au-Ag)-Ala-Gr aqueous dispersion obtained in Example 3 after being stored naturally for four weeks;

[0023] Figure 2 It is a TEM image of the (Au-Ag)-Ala-Gr composite material obtained in Example 3;

[0024] Figure 3 It is the STEM-EDS analysis diagram (a) and the line scan element distribution diagram (b) of the (Au-Ag)-Ala-Gr composite material obtained in Example 3.

[0025] Figure 4 It is the FT-IR spectra of GO and the (Au-Ag)-Ala-Gr composite material obtained in Example 3;

[0026] Figure 5 Cyclic voltammograms for the detection of bisphenol A (1.0×10 -4 mol·L -1 ) using different electrochemical sensors, where the electrodes corresponding to a→e are GCE (a), Ala-Gr / GCE (b), Ag-Ala-Gr / GCE (c), Au-Ala-Gr / GCE (d), and (Au-Ag)-Ala-Gr / GCE obtained in Example 3 (e) in sequence.

[0027] Figure 6 Linear voltammetric scanning curves for the determination of different concentrations of bisphenol A using the (Au-Ag)-Ala-Gr / GCE electrochemical sensor obtained in Example 3. The concentrations corresponding to the curves a→h are: 3.0×10 -8 , 7.0×10 -8 , 1.0×10 -7 , 3.0×10 -7 , 5.0×10 -7 , 7.0×10 -7 , 1.0×10 -6 , 2.0×10 -6 .

[0028] Figure 7 Relationship diagram of peak current and concentration for the determination of different concentrations of bisphenol A using the (Au-Ag)-Ala-Gr / GCE electrochemical sensor obtained in Example 3. Detailed implementation mode

[0029] To better understand the content of the present invention, the present invention will be further elaborated below in conjunction with specific examples and drawings. The following examples are implemented based on the technology of the present invention, and detailed implementation methods and operation steps are given, but the protection scope of the present invention is not limited to the following examples.

[0030] Example 1:

[0031] 1) Add 35 mg of graphene oxide to 35 mL of ultrapure water, and after ultrasonic treatment for 2 h, form a graphene oxide (GO)3 dispersion with a concentration of 1 mg·mL -1 ;

[0032] 2) Add 140 mg of alanine to the GO dispersion after ultrasonic treatment in step (1), and stir for 15 min to obtain a mixed solution A;

[0033] 3) Add 1.0 mL of chloroauric acid solution with a concentration of 25 mmol·L -1 to the mixed solution A in step (2), and continue to stir for 15 min to obtain a mixed solution B;

[0034] 4) Adjust the pH of the mixed solution B to 10 using a NaOH solution with a concentration of 1 mol·L -1 to obtain the mixed solution C;

[0035] 5) Stir the mixed solution C in step (4) for 15 min and then transfer it to a flask. Heat the flask in a water bath, set the temperature of the water bath to 85 °C, and keep stirring the mixed solution C;

[0036] 6) After the substance in the beaker in step (5) turns purplish red, add 2.2 mg of silver nitrate to it, continue heating in the water bath and stirring; after the substance in the beaker turns khaki, let it cool naturally to room temperature, perform centrifugal separation, discard the supernatant, and obtain the lower precipitate. Add high-purity water to the precipitate, shake and wash it, and perform centrifugal separation again. Repeat the washing and centrifugal separation steps until the pH of the supernatant reaches 7. After centrifugal separation, discard the filtrate, place the precipitate in an oven to dry, set the temperature to 80 °C, and dry for 10 h to obtain alanine-functionalized graphene loaded with Au-Ag alloy nanoparticles (Au-Ag)-Ala-Gr;

[0037] 7) Add a certain mass of (Au-Ag)-Ala-Gr to ultrapure water, and ultrasonically process the liquid for 2 h to form a (Au-Ag)-Ala-Gr dispersion with a concentration of 1 mg·mL -1 ;

[0038] 8) Polish the GCE interface in a thin paste of Al2O3 (0.5 μm) for several weeks until it becomes mirror-like, take it out, ultrasonically clean it in absolute ethanol, and then wash it again with ultrapure water;

[0039] 9) Pipette 6 μL of the (Au-Ag)-Ala-Gr dispersion in step (7) and drop it onto the surface of the glassy carbon electrode (GCE) ultrasonically cleaned in step (8), and dry it under an infrared lamp for 15 min to obtain the (Au-Ag)-Ala-Gr / GCE electrochemical sensor.

[0040] Dilute different volumes of bisphenol A standard solutions to 10 mL respectively using a PBS buffer solution with pH = 3.0 to prepare bisphenol A test solutions with different concentrations. Select linear sweep voltammetry. The specific parameters for detecting bisphenol A with the electrochemical sensor (Au-Ag)-Ala-Gr / GCE are: use the electrochemical sensor (Au-Ag)-Ala-Gr / GCE as the working electrode, use a saturated calomel electrode and a platinum wire electrode as the reference electrode and the counter electrode respectively to form a three-electrode system together, set the potential range to 0.3 - 1.1 V, the scanning speed to 0.1 V·s -1 , the enrichment time to 210 s, and record the peak current at different concentrations of bisphenol A. After each measurement, immerse the three-electrode system in a solution with a concentration of 0.1 mol·L-1 , in PBS with pH = 8.0, set the potential range from 0.3 V to 1.1 V, and use cyclic voltammetry to scan for two cycles to update the surface of the electrochemical sensor (Au - Ag)-Ala - Gr / GCE. In the concentration range of 6.0×10 -8 mol·L -1 ~2×10 -6 mol·L -1 , the peak current value shows a linear relationship with the concentration of bisphenol A. The detection limit of this method is 2.0×10 -8 mol·L -1 .

[0041] The standard addition method was used to determine the recovery rate of bisphenol A in lake water and mineral water in plastic bottles. The spiked recovery rate of bisphenol A in the lake water sample was 98.2% - 103.9%, and the spiked recovery rate of bisphenol A in the mineral water in plastic bottles was 95.9% - 101.1%.

[0042] Example 2:

[0043] 1) Add 35 mg of graphene oxide to 35 mL of ultrapure water. After ultrasonic treatment of this liquid for 2 h, a graphene oxide dispersion with a concentration of 1 mg·mL -1 is formed;

[0044] 2) Add 140 mg of alanine to the GO dispersion after ultrasonic treatment in step (1), and stir for 15 min to obtain a mixed solution A;

[0045] 3) Add 0.5 mL of chloroauric acid solution with a concentration of 25 mmol·L -1 to the mixed solution A in step (2), and continue to stir for 15 min to obtain a mixed solution B;

[0046] 4) Use a NaOH solution with a concentration of 1 mol·L -1 to adjust the pH of the mixed solution B to 10 to obtain a mixed solution C;

[0047] 5) After stirring the mixed solution C in step (4) for 15 min, transfer it to a flask, heat this flask in a water bath, set the temperature of the water bath to 85 °C, and keep stirring the mixed solution C;

[0048] 6) After the substance in the beaker in step (5) turns purplish red, add 4.4 mg of silver nitrate to it, continuously heat it in a water bath and stir; after the substance in the beaker turns khaki, let it cool naturally to room temperature, perform centrifugal separation, discard the supernatant, and obtain the precipitate at the bottom. Add high-purity water to the precipitate, shake and wash it, and perform centrifugal separation again. Repeat the washing and centrifugal separation steps until the pH of the supernatant reaches 7. After centrifugal separation, discard the filtrate, place the precipitate in an oven to dry, set the temperature at 80 °C for 10 h to obtain alanine-functionalized graphene loaded with Au-Ag alloy nanoparticles (Au-Ag)-Ala-Gr;

[0049] 7) Add a certain mass of (Au-Ag)-Ala-Gr to ultrapure water, and ultrasonically treat this liquid for 2 h to form a (Au-Ag)-Ala-Gr dispersion with a concentration of 1 mg·mL -1 ;

[0050] 8) Polish the GCE interface in dilute paste of Al2O3 (0.5 μm) for several weeks until it becomes mirror-like, take it out, ultrasonically clean it in absolute ethanol, and then wash it again with ultrapure water;

[0051] 9) Pipette 6 μL of the (Au-Ag)-Ala-Gr dispersion in step (7) and drop it onto the surface of the glassy carbon electrode (GCE) ultrasonically cleaned in step (8), and place it under an infrared lamp to dry for 15 min to obtain the (Au-Ag)-Ala-Gr / GCE electrochemical sensor.

[0052] Dilute different volumes of bisphenol A standard solutions to 10 mL respectively with PBS buffer solution with pH = 3.0 to prepare bisphenol A test solutions with different concentrations. Select linear sweep voltammetry, and the specific parameters for the electrochemical sensor (Au-Ag)-Ala-Gr / GCE to detect bisphenol A are: Take the electrochemical sensor (Au-Ag)-Ala-Gr / GCE as the working electrode, use the saturated calomel electrode and platinum wire electrode as the reference electrode and counter electrode respectively to form a three-electrode system, set the potential range to 0.3 - 1.1 V, the scanning speed to 0.1 V·s -1 , the enrichment time to 210 s, and record the peak current at different bisphenol A concentrations. After each measurement, immerse the three-electrode system in PBS with a concentration of 0.1 mol·L -1 and pH = 8.0, set the potential range to 0.3 - 1.1 V, and use cyclic voltammetry to scan for two cycles to update the surface of the electrochemical sensor (Au-Ag)-Ala-Gr / GCE. In the concentration range of 8.0×10 -8 mol·L -1 ~4×10 -6 mol·L -1Within, the peak current value shows a linear relationship with the concentration of bisphenol A. The detection limit of this method is 3.0×10 -8 mol·L -1 .

[0053] The standard addition method was used to determine the recovery rate of bisphenol A in lake water and mineral water in plastic bottles. The spiked recovery rate of the lake water sample was 96.4% - 102.8%, and the spiked recovery rate of bisphenol A in mineral water in plastic bottles was 97.1% - 104.2%.

[0054] Example 3:

[0055] 1) Add 35 mg of graphene oxide to 35 mL of ultrapure water. After ultrasonic treatment of this liquid for 2 h, a graphene oxide dispersion with a concentration of 1 mg·mL -1 is formed;

[0056] 2) Add 140 mg of alanine to the graphene oxide dispersion after ultrasonic treatment in step (1), and stir for 15 min to obtain mixture A;

[0057] 3) Add 0.5 mL of chloroauric acid solution with a concentration of 25 mmol·L -1 to mixture A in step (2), and continue to stir for 15 min to obtain mixture B;

[0058] 4) Use a NaOH solution with a concentration of 1 mol·L -1 to adjust the pH of mixture B to 10 to obtain mixture C;

[0059] 5) After stirring mixture C in step (4) for 15 min, transfer it to a flask, and heat this flask in a water bath. Set the temperature of the water bath to 85 °C, and keep stirring mixture C;

[0060] 6) After the substance in the beaker in step (5) turns purplish red, add 2.2 mg of silver nitrate to it, and continue heating in the water bath and stirring; after the substance in the beaker turns khaki, let it cool naturally to room temperature, perform centrifugal separation, discard the upper clear liquid, obtain the lower precipitate, add high-purity water to the precipitate, shake and wash, and perform centrifugal separation again. Repeat the washing and centrifugal separation steps until the pH of the upper clear liquid reaches 7. After centrifugal separation, discard the filtrate, place the precipitate in an oven to dry, set the temperature to 80 °C for 10 h to obtain alanine-functionalized graphene loaded with Au-Ag alloy nanoparticles ((Au-Ag)-Ala-Gr);

[0061] 7) Add a certain mass of (Au-Ag)-Ala-Gr to ultrapure water, and ultrasonic treat this liquid for 2 h to form a (Au-Ag)-Ala-Gr dispersion with a concentration of 1 mg·mL -1 ​

[0062] 8) Polish the GCE interface in a thin paste of Al2O3 (0.5 μm) for several weeks until it becomes mirror-like, take it out, ultrasonically clean it in absolute ethanol, and then clean it again with ultrapure water.

[0063] 9) Pipette 6 μL of the (Au-Ag)-Ala-Gr dispersion in step (7) and drop-coat it onto the surface of the glassy carbon electrode (GCE) ultrasonically cleaned in step (8), and place it under an infrared lamp to dry for 15 min to obtain the (Au-Ag)-Ala-Gr / GCE electrochemical sensor.

[0064] Dilute different volumes of bisphenol A standard solutions to 10 mL with PBS buffer solution at pH = 3.0 to prepare bisphenol A test solutions with different concentrations. Select linear sweep voltammetry, and the specific parameters for detecting bisphenol A with the electrochemical sensor (Au-Ag)-Ala-Gr / GCE are as follows: Use the electrochemical sensor (Au-Ag)-Ala-Gr / GCE as the working electrode, and use a saturated calomel electrode and a platinum wire electrode as the reference electrode and the counter electrode respectively to form a three-electrode system. Set the potential range to 0.3 - 1.1 V, the scanning speed to 0.1 V·s -1 、The enrichment time is 210 s, and record the peak currents at different bisphenol A concentrations. After each measurement, immerse the three-electrode system in PBS with a concentration of 0.1 mol·L -1 、pH = 8.0, set the potential range to 0.3 - 1.1 V, and use cyclic voltammetry to scan for two cycles to update the surface of the electrochemical sensor (Au-Ag)-Ala-Gr / GCE. In the concentration range of 3.0×10 -8 mol·L -1 ~2×10 -6 mol·L -1 , the peak current value has a linear relationship with the concentration of bisphenol A, and the detection limit of this method is 9.0×10 -9 mol·L -1 .

[0065] The standard addition method was used to determine the recovery rate of bisphenol A in lake water and mineral water in plastic bottles. The spiked recovery rate of the lake water sample was 99.2% - 103.2%, and the spiked recovery rate of bisphenol A in mineral water in plastic bottles was 98.9% - 102.7%.

[0066] Figure 1 This is a photo of the (Au-Ag)-Ala-Gr aqueous dispersion obtained in this example after standing naturally for 4 weeks. No precipitation occurred in the dispersion, and it still showed a uniform texture, indicating that the material can maintain good dispersion stability in water.

[0067] Figure 2This is the TEM image of the (Au-Ag)-Ala-Gr composite material obtained in this example. As Figure 2 shown, the graphene presents a single-layer structure, indicating that the functional modification of alanine effectively prevents the agglomeration and stacking of graphene. The Au-Ag alloy nanoparticles are distributed on the surface of the graphene sheets, and no metal nanoparticles appear in the space outside the graphene sheets, indicating that the Au-Ag alloy nanoparticles can be firmly loaded on the surface of graphene.

[0068] Figure 3 (a) This is the STEM-EDS analysis image of the (Au-Ag)-Ala-Gr composite material obtained in this example. The different contrasts of the nanoparticles indicate different metal elements. Figure 3 (b) This is the line scan elemental distribution image of the (Au-Ag)-Ala-Gr composite material obtained in this example, further indicating that the two metals are Au and Ag elements respectively, and it can be determined that the Au-Ag alloy nanoparticles are loaded on the surface of graphene.

[0069] Figure 4 These are the FT-IR spectra of graphene oxide (GO) and the (Au-Ag)-Ala-Gr composite material obtained in this example. Characteristic peaks of oxygen-containing groups appear in the curve of GO: C=O (1733 cm -1 ), C-O-H (1396 cm -1 ), C-O-C (1223 cm -1 ), C-O (1060 cm -1 ). In the curve of (Au-Ag)-Ala-Gr, some of the peaks at the corresponding positions disappear or weaken, indicating that GO is reduced. The absorption peak at 1470 cm -1 is caused by the bending vibration of N–H, and the absorption peak at 1407 cm -1 is attributed to the stretching vibration of C–N. The appearance of these peaks indicates that alanine is covalently bonded to graphene.

[0070] Figure 5 These are the cyclic voltammograms when detecting bisphenol A (1.0×10 -4 mol·L -1 ) using different electrochemical sensors. The electrodes corresponding to a→e are GCE (a), Ala-Gr / GCE (b), Ag-Ala-Gr / GCE (c), Au-Ala-Gr / GCE (d), (Au-Ag)-Ala-Gr / GCE (e) obtained in Example 3 in turn. From Figure 5It can be seen that when using GCE(a), the peak current of bisphenol A is 6.4 μA. When replaced with Ala-Gr / GCE(b), the peak current is 22.6 μA. The peak current of bisphenol A on Ala-Gr / GCE is greater than that on GCE, indicating that graphene has good electrical properties, and the modification of alanine can reduce the stacking degree of graphene, increase the specific surface area of the material, and thus enhance the enrichment ability for bisphenol A. Compared with Ala-Gr / GCE, when using Ag-Ala-Gr / GCE(c) and Au-Ala-Gr / GCE(d), the peak currents of bisphenol A both increase, with the values being 23.9 μA and 25.2 μA respectively. This shows that the introduction of Ag and Au nanoparticles increases the electroactive sites of the material. Compared with Ag-Ala-Gr / GCE and Au-Ala-Gr / GCE, the peak current of the curve corresponding to (Au-Ag)-Ala-Gr / GCE is larger, with a value of 29.9 μA, indicating that: compared with single-metal Ag and Au nanoparticles, the synergistic effect of the two metals further improves the electrochemical performance of the material.

[0071] Figure 6 Figure 4 shows the linear voltammetric scanning curves obtained when using the (Au-Ag)-Ala-Gr / GCE electrochemical sensor of this embodiment to measure bisphenol A at different concentrations. The concentrations corresponding to curves a→h are successively: 3.0×10 -8 、7.0×10 -8 、1.0×10 -7 、3.0×10 -7 、5.0×10 -7 、7.0×10 -7 、1.0×10 -6 、2.0×10 -6 . As the concentration increases, the oxidation peak current of bisphenol A increases.

[0072] Figure 7 Figure 5 shows the relationship between the peak current and the concentration when using the (Au-Ag)-Ala-Gr / GCE electrochemical sensor of this embodiment to measure bisphenol A at different concentrations. It can be seen from the figure that in the concentration range of 3.0×10 -8 ~2.0×10 -6 , the peak current shows a linear relationship with the concentration of bisphenol A.

[0073] The above are only embodiments of the present invention and do not impose any form of limitation on the present invention. The present invention can also have other forms of embodiments based on the above structures and functions, which will not be listed one by one. Any person skilled in the relevant art, without departing from the scope of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. Application of (Au - Ag)-Ala-Gr / GCE electrochemical sensor in detecting bisphenol A, selecting linear sweep voltammetry as the analysis method, characterized in that The specific parameters for detecting bisphenol A by the (Au-Ag)-Ala-Gr / GCE electrochemical sensor are as follows: PBS with pH = 3.0 is used as the buffer solution, the potential window is 0.3 - 1.1 V, and the scanning rate is 0.1 V·s -1 , the enrichment time is 210 s, and the linear range of the (Au-Ag)-Ala-Gr / GCE electrochemical sensor's response to bisphenol A is 3.0×10 -8 mol·L -1 ~ 4.0×10 -6 mol·L -1 , and the detection limit is 9.0×10 -9 mol L -1 (S / N = 3); the (Au-Ag)-Ala-Gr / GCE electrochemical sensor is prepared according to the following steps: (1) Add a certain mass of graphene oxide to ultrapure water, and ultrasonically treat the liquid until it is evenly dispersed to obtain a graphene oxide dispersion; (2) Add a certain mass of alanine to the graphene oxide dispersion, and stir to obtain a mixed solution A; (3)Measure a certain amount of chloroauric acid solution with a concentration of 25 mmol·L -1 and add it to the mixed solution A, and stir evenly to obtain the mixed solution B; (4) Add 1 mol·L -1 NaOH solution to mixture B until its pH reaches 10 to obtain mixture C; (5) Transfer the mixed solution C to a flask after stirring, and heat the flask in a water bath. Set the temperature of the water bath to 85 °C and keep stirring the mixed solution C; (6) Wait until the substance in the flask turns purplish red, add a certain mass of silver nitrate to it, and continue heating and stirring in the water bath; after the substance in the flask turns khaki, let it cool naturally to room temperature, centrifuge, discard the supernatant, obtain the lower precipitate, add high-purity water to the precipitate, shake and wash, and centrifuge again; Repeat the washing and centrifugation steps until the pH of the supernatant reaches 7, then centrifuge, discard the filtrate, place the obtained precipitate in an oven for drying, set the oven temperature to 80 °C, and obtain alanine-functionalized graphene (Au-Ag)-Ala-Gr loaded with Au-Ag alloy nanoparticles after drying; (7) Add a certain mass of the prepared (Au-Ag)-Ala-Gr to ultrapure water and perform ultrasonic treatment until it is evenly dispersed to obtain a (Au-Ag)-Ala-Gr dispersion with a concentration of 1 mg·mL -1 ; (8) Polish the surface of the glassy carbon electrode in dilute paste of Al2O3 until it becomes mirror-like, take it out, ultrasonically clean it in absolute ethanol, and then clean it again with ultrapure water; (9) Drop 6 μL of (Au-Ag)-Ala-Gr dispersion on the surface of the treated glassy carbon electrode, and dry it under an infrared lamp to obtain an (Au-Ag)-Ala-Gr / GCE electrochemical sensor.

2. Application of the (Au-Ag)-Ala-Gr / GCE electrochemical sensor as described in claim 1 in detecting bisphenol A, characterized in that The concentration of the graphene oxide dispersion formed in step (1) is 1 mg·mL -1 .

3. Application of the (Au-Ag)-Ala-Gr / GCE electrochemical sensor as described in claim 1 in the detection of bisphenol A, characterized in that In step (2), the concentration of alanine in mixture A is 4 mg·mL -1 .

4. Application of the (Au-Ag)-Ala-Gr / GCE electrochemical sensor according to claim 2 in detecting bisphenol A, characterized in that The amount of ultrapure water used in step (1) is 35 mL, and the added volume of chloroauric acid solution in step (3) is 0.5 - 1.0 mL.

5. Use of the (Au-Ag)-Ala-Gr / GCE electrochemical sensor according to claim 4 in the detection of bisphenol A, characterized in that The mass of silver nitrate added in step (6) is 2.2 - 4.4 mg.

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