A method for preparing pH-sensitive OECT based on PEDOT:PSS

Abstract

The invention provides a method for preparing a pH-sensitive OECT based on PEDOT:PSS, belonging to the technical field of organic electrochemical transistors; the method solves the problems of low stability and insufficient flexibility of existing PEDOT:PSS materials, and comprises the following steps: preparing a sensing electrode: manufacturing a gate electrode, and adopting a cyclic voltammetry method to electro-deposit a PEDOT:BTB film on the surface of the gate electrode; preparing a solution to be detected: using a phosphate buffer solution containing KNO3 and KH2PO4 as a pH reference solution, dripping HCl and NaOH to configure solutions to be detected with different pH values, and finally adding a KCl solution to adjust the conductivity of all pH solutions to 38±0.5 mS / cm; preparing a signal amplification chip: using a MEMS process to prepare a spare chip 1, the spare chip 1 comprising: a microelectrode layer including a source electrode, a drain electrode, a source PAD, and a drain PAD; preparing an organic semiconductor layer on the surface of the source electrode, the drain electrode and in the gap between the source electrode and the drain electrode; assembling a gate electrode, a gate dielectric, a source electrode, a drain electrode, and an organic semiconductor layer; the invention is applied to organic electrochemical transistors.

Description

Technical Field

[0001] The invention provides a method for preparing a pH-sensitive OECT based on PEDOT:PSS, belonging to the technical field of OECT preparation. Background Art

[0002] Organic electrochemical transistors (OECTs) are three-terminal signal amplifier devices that use permeable organic semiconductors as channel materials and liquid as gate dielectrics. Currently, the reported transconductance values ​​used to measure the signal amplification capability of OECTs can be as high as 57 mS. In addition, the commonly used organic semiconductor layer material PEDOT:PSS has good biocompatibility. Therefore, OECTs based on PEDOT:PSS are widely used in the fields of biosensing and electrophysiological monitoring.

[0003] In PEDOT:PSS materials, the PEDOT phase with regular regions is used for free carrier transport, and the amorphous PSS phase is used to improve the processability of PEDOT solutions. The PSS phase is insulating, and although it improves the solubility of PEDOT in a liquid environment, it seriously affects the charge transport of PEDOT in the solid state. Secondly, the PSS phase will come into contact with the aqueous solution during the biosensing process and interact with water molecules, causing the semiconductor to desorb and crack, reducing the stability of the OECT. The development of OECTs based on PEDOT:PSS semiconductor layers faces another technical bottleneck, namely the flexibility of PEDOT:PSS. In the paper published by Y. Wang, C. Zhu, R.Pfattner, H. Yan, L. Jin, S. Chen, F. Molina-Lopez, F. Lissel, J. Liu, and NI Rabiah, "A highly stretchable, transparent, and conductive polymer," Science advances, vol. 3, no. 3, p. e1602076, 2017, it is stated that PEDOT:PSS generally breaks when subjected to a strain of 5%-6%. This greatly limits its application in the field of wearable biosensors.

[0004] In view of these problems, the present invention proposes a method for preparing a PEDOT:PSS-based OECT with high stability, high flexibility and high transconductance. Summary of the invention

[0005] In order to solve the problems of low stability and insufficient flexibility of existing PEDOT:PSS materials, the present invention proposes a method for preparing pH-sensitive OECT based on PEDOT:PSS.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a pH-sensitive OECT based on PEDOT:PSS, wherein the pH-sensitive OECT comprises a sensing electrode used as a gate, a solution to be detected used as a gate dielectric layer, and a signal amplification chip, and the method for preparing the pH-sensitive OECT comprises the following steps:

[0007] S1: Preparation of sensing electrode: making gate electrode and electrodepositing PEDOT:BTB film on the gate electrode surface by cyclic voltammetry;

[0008] S2: Preparation of test solutions: Using phosphate buffer containing KNO3 and KH2PO4 as the pH reference solution, HCl and NaOH were added dropwise to prepare test solutions with different pH values, and finally KCl solution was added to adjust the conductivity of all pH solutions to 38±0.5 mS / cm;

[0009] S3: Preparation of signal amplification chip:

[0010] S3.1: Prepare a spare chip 1 using a MEMS process, wherein the spare chip 1 includes a microelectrode layer including a source electrode, a drain electrode, a source PAD, and a drain PAD;

[0011] S3.2: preparing an organic semiconductor layer on the surface of the source electrode, the drain electrode and in the gap between the source electrode and the drain electrode;

[0012] S3.3: Assemble the gate electrode, the gate dielectric, the source electrode, the drain electrode, and the organic semiconductor layer;

[0013] The steps of preparing the organic semiconductor layer are as follows:

[0014] S3.2.1: 0.15 mol / L ionic liquid with a water content of 0.5-1.5 wt% was mixed with PEDOT:PSS solution and stirred for 10-30 minutes, and then 0.1-1 Vol% GOPS was added to form solution No. 1;

[0015] S3.2.2: Take 0.1-1g of multi-walled carbon nanotubes with a diameter of 1-10 nanometers and a length of 2-7 micrometers, place them in a mixed solution consisting of 100-500 mL of concentrated sulfuric acid and 10-100 mL of concentrated nitric acid, and stir overnight; then, drain the mixed acid, and wash the multi-walled carbon nanotubes with deionized water until the pH value of the solution is 7, forming Solution No. 2;

[0016] S3.2.3: Add 99% pure methanesulfonic acid to solution No. 2 to form solution No. 3 with a concentration of 0.5-5 mg / mL;

[0017] S3.2.4: Mix solution No. 1 and solution No. 3 in a volume ratio of 1:1-1:10 to form solution No. 4;

[0018] S3.2.5: Spin-coat 30-50 μl of solution 4 between the source and drain of spare chip 1, and anneal on a hot plate at 50-200 degrees Celsius for 5-20 minutes to form spare chip 2;

[0019] S3.2.6: Place spare chip 2 on a hot plate, adjust the hot plate temperature to 50-200 degrees Celsius, cover the surface of the spare device with 5-10 mol / L sulfuric acid, let it stand, then cover the surface of spare chip 1 with 15-20 mol / L concentrated sulfuric acid, let it stand, to form spare chip 3;

[0020] S3.2.7: 1-vinyl-3-ethylimidazole dinitrile amine salt, deionized water, ammonium persulfate with a water content of 0.5-5wt% and N,N'-methylenebisacrylamide with a water content of 0.5-5wt% are mixed to prepare Solution No. 5;

[0021] S3.2.8: Spin-coat solution No. 5 on the surface of spare chip 3, and heat it in a vacuum drying oven at 50-100 degrees Celsius for 10-100 minutes to achieve coverage of the organic semiconductor layer on the surface of the source and drain electrodes and the gap between the source and drain electrodes, thereby forming spare chip 4.

[0022] The steps of preparing the micro-electrode layer including the source, drain, source PAD and drain PAD using the MEMS process:

[0023] Using quartz glass as a hard substrate, a PDMS flexible substrate was prepared on the surface of the hard substrate by spin coating.

[0024] Sputter titanium as an adhesion layer between PDMS and gold, and then sputter gold film;

[0025] Apply glue on the gold film and dry it, use a mask to perform photolithography and development, and finally perform wet etching to achieve the patterning of the microelectrode layer to form the source, drain, source PAD, and drain PAD.

[0026] The steps for preparing the spare chip 1 are as follows:

[0027] Laying a first insulating layer made of a flexible organic material on the surface of the microelectrode layer by vapor deposition;

[0028] Laying a second insulating layer made of a flexible organic material on the first insulating layer by vapor deposition;

[0029] Window structures corresponding to the source PAD, the drain PAD, the source, the drain, and the gap between the source and the drain are opened by a dry body etching method.

[0030] After the second insulating layer of the spare chip 4 is torn off, the flexible substrate and the micro-nano structure thereon are peeled off from the hard substrate to form a signal amplification chip.

[0031] The structure of the signal amplification chip is as follows: a source PAD, a drain PAD, a source electrode, and a drain electrode are processed on a PDMS flexible substrate;

[0032] Part of the surface of the source electrode and the drain electrode is covered by the first insulating layer, and part of the surface is covered by the organic semiconductor layer;

[0033] The gap between the source and drain electrodes is completely covered by the organic semiconductor layer;

[0034] Part of the surface of the first insulating layer and the entire surface of the organic semiconductor layer are covered by the gate dielectric.

[0035] The ionic liquid in step S3.2.1 is one of [EMIM][Cl], [EMIM][OTF], [EMIM][TFSI], [EMIM][TCM] or a mixture of any two or more thereof.

[0036] One or a mixture of any two or more of ethylene glycol, Triton X-100, dimethyl sulfoxide, sorbitol, DBSA, and GOPS can be added to the No. 1 solution as a dopant.

[0037] The specific preparation process of the sensing electrode is as follows:

[0038] S1.1: Use gold electrode as gate electrode;

[0039] S1.2: Electrodepositing a PEDOT:BTB film on the gate electrode surface by cyclic voltammetry, specifically comprising:

[0040] The EDOT monomer, BTB and PBS were dissolved in KNO3 aqueous solution to prepare the electrolyte;

[0041] The gate electrode was used as the working electrode, the saturated calomel electrode was used as the reference electrode, and the platinum wire was used as the counter electrode;

[0042] The potential scanning range and scanning rate of the working electrode were set so that after multiple CV cycles, the gate electrode appeared light blue.

[0043] The beneficial effects of the present invention compared with the prior art are as follows: the OETC prepared by the pH-sensitive OECT preparation method based on PEDOT:PSS provided by the present invention has high stability, high flexibility and high transconductance value, which can overcome the shortcomings of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below in conjunction with the accompanying drawings:

[0045] Figure 1 is a flow chart of the method for preparing pH-sensitive OECT of the present invention;

[0046] Figure 2 It is a schematic diagram of the structure of an organic electrochemical transistor;

[0047] Figure 3 It is a structural schematic diagram of the signal amplification chip of the present invention;

[0048] Figure 4 This is a flow chart of the preparation of the signal amplification chip of the present invention;

[0049] Figure 5 is a flow chart for preparing the organic semiconductor layer of the present invention;

[0050] Figure 6 This is a pH test diagram of OECT prepared by the method of the present invention;

[0051] In the figure: 10 is a sensing electrode, 11 is a solution to be detected, 12 is a signal amplifying chip, 1211 is a hard substrate, 1212 is a flexible substrate, 1221 is a source electrode, 1222 is a source electrode PAD, 1231 is a drain electrode, 1232 is a drain electrode PAD, 124 is an organic semiconductor layer, 125 is a first insulating layer, and 126 is a second insulating layer. DETAILED DESCRIPTION

[0052] The structure and preparation method of the OECT of the present invention are described in detail below with reference to the accompanying drawings.

[0053] Figure 2 It is a schematic diagram of the OECT structure of an embodiment of the present invention, comprising: a sensing electrode 10 used as a gate, a solution to be detected 11 used as a gate dielectric layer, and a signal amplification chip 12.

[0054] Figure 3 Schematic diagram of the structure of the signal amplifying chip 12, including: a flexible substrate 1212 made of PDMS material, a source electrode 1221, a source electrode PAD1222, a drain electrode 1231, a drain electrode PAD1232, an organic semiconductor layer 124, and a first insulating layer 125 made of Parylene C material.

[0055] Figure 1 The following is a preparation method of pH-sensitive OECT based on PEDOT:PSS with high stability, high flexibility and high transconductance. The specific process is as follows:

[0056] 1. The preparation method of the sensing electrode 10 is:

[0057] (1) The purchase area is 3.14 mm 2Commercial gold electrodes.

[0058] (2) PEDOT:BTB film was electrodeposited on the gate electrode surface by cyclic voltammetry (CV). Specifically, 10mmol / L EDOT monomer, 1mmol / L BTB and 1mmol / L PBS were dissolved in 0.1mol / L KNO3 aqueous solution to prepare the electrolyte; the gate electrode was used as the working electrode, saturated calomel electrode (SCE) as the reference electrode, and platinum wire as the counter electrode; the potential scanning range of the working electrode was (0-1Vvs.SCE) and the scanning rate was 100mV / s. After 5 CV cycles, the gate electrode showed light blue, indicating that its surface had been successfully modified with PEDOT:BTB film.

[0059] 2. The preparation method of the solution 11 to be tested is as follows: using phosphate buffer (PBS) 1× (pH=5.5) containing 10mmol / L KNO3 and 10mmol / L KH2PO4 as the pH reference solution, adding HCl and NaOH dropwise to prepare the test solutions with different pH values, and finally adding KCl solution to adjust the conductivity of all pH solutions to 38±0.5 mS / cm.

[0060] 3. If Figure 4 As shown, the preparation method of the signal amplification chip 12 is:

[0061] (1) Quartz glass is selected as a hard substrate 1211, the hard substrate 1211 is immersed in a chromic acid solution for 24 hours, washed with deionized water, dried for standby use, and then a flexible substrate 1212 made of PDMS is prepared by spin coating;

[0062] (2) sputtering a titanium (Ti) film with a thickness of 30 nm on the flexible substrate 1212 as an adhesion layer between PDMS and gold (Au), and then sputtering a gold (Au) film with a thickness of 200 nm;

[0063] (3) Applying glue on the gold film and drying it, using a mask to perform photolithography and development, and finally performing wet etching to achieve patterning of the microelectrode layer to form a source electrode 1221, a source electrode PAD1222, a drain electrode 1231, and a drain electrode PAD1232;

[0064] (4) The source electrode 1221 is connected to the source electrode PAD1222, the drain electrode 1231 is connected to the drain electrode PAD1232, and the distance between the source electrode 1221 and the drain electrode 1231 is 5 microns;

[0065] (5) using vapor deposition to lay Parylene C on the surface of the microelectrode layer as the first insulating layer 125;

[0066] (6) Laying Parylene C on the first insulating layer by vapor deposition as the second insulating layer 126;

[0067] (7) Opening a window structure corresponding to the source 1221, the source PAD 1222, the drain 1231, the drain PAD 1232, and the gap between the source 1221 and the drain 1231 by a dry body etching method to form a spare chip 1;

[0068] (8) Figure 5 As shown, 0.15 mol / L ionic liquid with a water content of 0.5-1.5 wt% was mixed with PEDOT:PSS solution and stirred for 10 minutes, and then 0.5 Vol% GOPS was added to form solution No. 1. The use of ionic liquid to dope PEDOT:PSS can not only make PEDOT have better crystallinity based on ion exchange, but also plasticize the amorphous region of PSS.

[0069] (9) Figure 5 As shown, 0.5 g of multi-walled carbon nanotubes with a diameter of 8 nanometers and a length of 5 microns were placed in a mixed solution consisting of 150 mL of concentrated sulfuric acid and 50 mL of concentrated nitric acid and stirred overnight. Afterwards, the mixed acid was drained and the multi-walled carbon nanotubes were washed with deionized water until the pH value of the solution was 7, forming solution No. 2;

[0070] (10) Figure 5 As shown, 99% pure methanesulfonic acid is added to solution No. 2 to form solution No. 3 with a concentration of 2 mg / mL;

[0071] (11) Figure 5 As shown, solution No. 1 and solution No. 3 are mixed in a volume ratio of 1:1 to form solution No. 4. The addition of carbon nanotubes can provide an adhesion body for PEDOT:PSS and improve the viscoelasticity of PEDOT:PSS. Some carbon nanotubes with high conductivity can also form a synergistic effect with the regionally regular PEDOT phase to accelerate the transport speed of free carriers.

[0072] (12) Figure 5 As shown, 30-50 μl of solution No. 4 is spin-coated between the source and drain of spare chip 1, and annealed on a hot plate at 150 degrees Celsius for 10 minutes to form spare chip 2;

[0073] (13) Figure 5 As shown, the spare chip 2 is placed on a hot plate, the temperature of the hot plate is adjusted to 140 degrees Celsius, the surface of the spare device is covered with 9.2 mol / L sulfuric acid, and it is allowed to stand for 10 minutes, and then the surface of the spare chip 1 is covered with 18.4 mol / L concentrated sulfuric acid, and it is allowed to stand for 10 minutes to form a spare chip 3. The use of sulfuric acid treatment can reduce the insulating and hydrophilic amorphous PSS phase, improve the aqueous solution stability of the OECT chip, and at the same time expand the regional regular space range of PEDOT, further improving the transport speed of free carriers;

[0074] (14) Figure 5 As shown, 1-vinyl-3-ethylimidazole dinitrile amine salt, deionized water, ammonium persulfate with a water content of 1 wt % and N,N'-methylenebisacrylamide with a water content of 1 wt % are mixed to prepare solution No. 5;

[0075] (15) Figure 4 and Figure 5 As shown, solution No. 5 is spin-coated on the surface of the spare chip 3 and heated at 80 degrees Celsius in a vacuum drying oven for 60 minutes to achieve coverage of the organic semiconductor layer on the surface of the source and drain electrodes and the gap between the source and drain electrodes, thereby improving the flexibility of the organic semiconductor layer and forming a spare chip 4.

[0076] (16) Figure 4 As shown, the second insulating layer 126 of the spare chip 4 is peeled off, and the flexible substrate 1212 and the micro-nano structure thereon are peeled off from the hard substrate 1211 to form the signal amplifying chip 12 .

[0077] The OETC prepared by the above method can be used as a biosensor. The sensing electrode 10, the solution to be detected 11, and the signal amplification chip 12 are assembled to form a Figure 2 The pH sensitive OECT structure is shown. The potentials of the sensor source PAD1222, drain PAD1232, and gate 10 are controlled by a semiconductor analyzer to be 0V, -0.6V, and 0.225V, respectively, and the curve of the current between the source PAD1222 and the drain PAD1232 changing with time is recorded, as shown in FIG. Figure 6 shown.

[0078] Regarding the specific structure of the present invention, it should be noted that the connection relationship between the various component modules adopted in the present invention is definite and feasible. Except for special instructions in the embodiments, the specific connection relationship can bring about corresponding technical effects, and solve the technical problems raised by the present invention without relying on the execution of corresponding software programs. The components, modules, models of specific components, the connection methods between each other, and the conventional use methods and expected technical effects brought about by the above-mentioned technical features, except for specific instructions, all belong to the disclosed contents in patents, journal articles, technical manuals, technical dictionaries, and textbooks that can be obtained by technical personnel in this field before the application date, or belong to the existing technologies such as conventional technologies and common knowledge in this field, and there is no need to elaborate, so that the technical solution provided in this case is clear, complete, and feasible, and the corresponding physical products can be reproduced or obtained according to the technical means.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing pH-sensitive OECT based on PEDOT:PSS, characterized in that: The pH sensitive OECT comprises a sensing electrode used as a gate, a solution to be detected used as a gate dielectric layer, and a signal amplification chip. The preparation method of the pH sensitive OECT comprises the following steps: S1: Preparation of sensing electrode: making gate electrode and electrodepositing PEDOT:BTB film on the gate electrode surface by cyclic voltammetry; S2: Preparation of test solutions: Using phosphate buffer containing KNO3 and KH2PO4 as the pH reference solution, HCl and NaOH were added dropwise to prepare test solutions with different pH values, and finally KCl solution was added to adjust the conductivity of all pH solutions to 38±0.5 mS / cm; S3: Preparation of signal amplification chip: S3.1: Prepare a spare chip 1 using a MEMS process, wherein the spare chip 1 includes a microelectrode layer including a source electrode, a drain electrode, a source PAD, and a drain PAD; S3.2: preparing an organic semiconductor layer on the surface of the source electrode, the drain electrode and in the gap between the source electrode and the drain electrode; S3.3: Assemble the gate electrode, the gate dielectric, the source electrode, the drain electrode, and the organic semiconductor layer; The steps of preparing the organic semiconductor layer are as follows: S3.2.1: 0.15 mol / L ionic liquid with a water content of 0.5-1.5 wt% was mixed with PEDOT:PSS solution and stirred for 10-30 minutes, and then 0.1-1 Vol% GOPS was added to form solution No. 1; The ionic liquid in step S3.2.1 is one of [EMIM][Cl], [EMIM][OTF], [EMIM][TFSI], [EMIM][TCM] or a mixture of any two or more thereof; The solution No. 1 may be added with one or a mixture of any two or more of ethylene glycol, Triton X-100, dimethyl sulfoxide, sorbitol, and DBSA as a dopant; S3.2.2: Take 0.1-1g of multi-walled carbon nanotubes with a diameter of 1-10 nanometers and a length of 2-7 micrometers, place them in a mixed solution consisting of 100-500 mL of concentrated sulfuric acid and 10-100 mL of concentrated nitric acid, and stir overnight; then, drain the mixed acid, and wash the multi-walled carbon nanotubes with deionized water until the pH value of the solution is 7, forming Solution No. 2; S3.2.3: Add 99% pure methanesulfonic acid to solution No. 2 to form solution No. 3 with a concentration of 0.5-5 mg / mL; S3.2.4: Mix solution No. 1 and solution No. 3 in a volume ratio of 1:1-1:10 to form solution No. 4; S3.2.5: Spin-coat 30-50 μl of solution No. 4 between the source and drain of spare chip 1, and anneal on a hot plate at 50-200 degrees Celsius for 5-20 minutes to form spare chip 2; S3.2.6: Place spare chip 2 on a hot plate, adjust the hot plate temperature to 50-200 degrees Celsius, cover the surface of the spare device with 5-10 mol / L sulfuric acid, let it stand, then cover the surface of spare chip 1 with 15-20 mol / L concentrated sulfuric acid, let it stand, to form spare chip 3; S3.2.7: 1-vinyl-3-ethylimidazole dinitrile amine salt, deionized water, ammonium persulfate with a water content of 0.5-5wt% and N,N'-methylenebisacrylamide with a water content of 0.5-5wt% are mixed to prepare Solution No. 5; S3.2.8: Spin-coat solution No. 5 on the surface of spare chip 3, and heat it in a vacuum drying oven at 50-100 degrees Celsius for 10-100 minutes to achieve coverage of the organic semiconductor layer on the surface of the source and drain electrodes and the gap between the source and drain electrodes, thereby forming spare chip 4.

2. The method for preparing a pH-sensitive OECT based on PEDOT:PSS according to claim 1, characterized in that: The steps of preparing the micro-electrode layer including the source, drain, source PAD and drain PAD using the MEMS process: Using quartz glass as a hard substrate, a PDMS flexible substrate was prepared on the surface of the hard substrate by spin coating. Sputter titanium as an adhesion layer between PDMS and gold, and then sputter gold film; Apply glue on the gold film and dry it, use a mask to perform photolithography and development, and finally perform wet etching to achieve the patterning of the microelectrode layer to form the source, drain, source PAD, and drain PAD.

3. The method for preparing a pH-sensitive OECT based on PEDOT:PSS according to claim 1, characterized in that: The steps for preparing the spare chip 1 are as follows: Laying a first insulating layer made of a flexible organic material on the surface of the microelectrode layer by vapor deposition; Laying a second insulating layer made of a flexible organic material on the first insulating layer by vapor deposition; Window structures corresponding to the source PAD, the drain PAD, the source, the drain, and the gap between the source and the drain are opened by a dry body etching method.

4. The method for preparing a pH-sensitive OECT based on PEDOT:PSS according to claim 1, characterized in that: After the second insulating layer of the spare chip 4 is torn off, the flexible substrate and the micro-nano structure thereon are peeled off from the hard substrate to form a signal amplification chip.

5. The method for preparing a pH-sensitive OECT based on PEDOT:PSS according to claim 4, characterized in that: The structure of the signal amplification chip is as follows: a source PAD, a drain PAD, a source electrode, and a drain electrode are processed on a PDMS flexible substrate; Part of the surface of the source electrode and the drain electrode is covered by the first insulating layer, and part of the surface is covered by the organic semiconductor layer; The gap between the source and drain electrodes is completely covered by the organic semiconductor layer; Part of the surface of the first insulating layer and the entire surface of the organic semiconductor layer are covered by the gate dielectric.

6. The method for preparing a pH-sensitive OECT based on PEDOT:PSS according to claim 1, characterized in that: The specific preparation process of the sensing electrode is as follows: S1.1: Use gold electrode as gate electrode; S1.2: Electrodepositing a PEDOT:BTB film on the gate electrode surface by cyclic voltammetry, specifically comprising: The EDOT monomer, BTB and PBS were dissolved in KNO3 aqueous solution to prepare the electrolyte; The gate electrode was used as the working electrode, the saturated calomel electrode was used as the reference electrode, and the platinum wire was used as the counter electrode; The potential scanning range and scanning rate of the working electrode were set so that after multiple CV cycles, the gate electrode appeared light blue.

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