A graphene / poly N, N-diethylacrylamide hydrogel film electrode and its preparation method and use

Abstract

The present application provides a method for preparing and using a graphene / poly N,N-diethylacrylamide hydrogel film electrode. The graphene / poly N,N-diethylacrylamide hydrogel film electrode is prepared by the preparation method provided by the present application. Phenylhydrazine is used as an active probe of environmental pollution molecules. The graphene / poly N,N-diethylacrylamide hydrogel film electrode exhibits pH, temperature, and salt-sensitive electrochemical responses and exhibits switch properties. Furthermore, the graphene / poly N,N-diethylacrylamide hydrogel film electrode is combined with phenylhydrazine molecular electrocatalysis, and the electrochemical catalytic oxidation of phenylhydrazine is controlled and regulated by utilizing the changes in various stimulating factors of the external environment, thereby realizing the monitoring and control of phenylhydrazine and the construction of a logic gate system.

Description

Technical Field

[0001] The present application relates to the technical field of hydrogel films, and in particular to a graphene / poly (N,N-diethylacrylamide) hydrogel film electrode and a preparation method and use thereof. Background Art

[0002] Phenylhydrazine is an important raw material in the pharmaceutical industry and is widely used as an anti-tuberculosis and anti-hypertensive drug. In addition, it is a chemical intermediate for the production of various useful chemicals (photographic chemicals) and agricultural chemicals (pesticides). However, phenylhydrazine is toxic and is a well-known hepatotoxic metabolite as a representative hydrazine derivative. Phenylhydrazine released due to leakage or untreated industrial wastewater can cause serious harmful effects on environmental ecosystems as well as humans and animals. Many studies have classified phenylhydrazine as a carcinogenic, neurotoxic and mutagenic substance. This is because phenylhydrazine can cause symptoms such as skin irritation, hemolytic anemia, dermatitis, kidney and liver damage in humans even when exposed to it at low concentrations. Therefore, it is of practical significance to develop a technical means to quickly detect the level of phenylhydrazine in the environment and take measures to control it below the permitted limit.

[0003] In recent years, switchable electrocatalysis of electrochemically active molecular probes induced by external stimuli has attracted increasing interest. It can not only control bioelectronic devices, but also provide a basis for information storage, signal amplification and conversion. The reason why Boolean logic gates are called "gates" is that they can control the path of current through binary codes to form different digital circuits. As a tool science, the rapid development of logic gates has laid a solid foundation for the construction of biosensors, environmental pollutant sensors, electronic devices for drug delivery and drug release, and the development of logic gate network platforms. As various chemical substances (such as organic compounds, heavy metal ions, phenols, etc.) are continuously discarded into the environment. These chemical pollutants are highly dangerous to the safety of ecosystems and public health due to their toxic properties, bioaccumulation and difficulty in degradation. Therefore, the electrochemical research of related environmental pollutants has attracted widespread attention from researchers. One of the great challenges is to develop controllable bioelectrocatalysis and its logic gates based on the electrochemistry of environmental pollutants.

[0004] At present, phenylhydrazine detection relies on large-scale instrument detection, such as gas chromatography and spectrophotometer. Although the detection limit is low and the detection range is wide, the solution is cumbersome, difficult to operate, expensive, and cannot achieve real-time monitoring. The electrochemical logic gate system monitoring system can solve the above problems well, but with the increase in the number of input and output signals of the electrochemical logic gate system and the enrichment and perfection of the complexity of the logic gate system, it is difficult to achieve simultaneous detection of multiple output signals. Summary of the invention

[0005] The purpose of this application is to provide a graphene / poly N, N-diethylacrylamide hydrogel film electrode (GDY / PDEA hydrogel film electrode) and its preparation method and use, for real-time detection of phenylhydrazine in the environment. The specific technical scheme is as follows:

[0006] The first aspect of the present application provides a method for preparing a Graphene / poly (N,N-diethylacrylamide) hydrogel film electrode, which comprises the following steps:

[0007] (1) dissolving graphene oxide (GDY) and perfluorosulfonic acid polymer (Nafion) solution in a solvent and ultrasonically dispersing for 20-40 minutes to obtain a GDY suspension;

[0008] The concentration of the Nafion solution is 4-6 vol%, the solvent is selected from a mixed solvent of ethanol and water, anhydrous ethanol, chloroform or toluene; the volume ratio of the Nafion solution to the solvent is 1:10; the final concentration of the graphyne is 0.1-0.3 mg / mL;

[0009] (2) applying the GDY suspension droplets on the surface of a pyrolytic graphite (PG) electrode and drying to obtain a GDY / PG electrode;

[0010] (3) drop-coating the pre-gel solution on the surface of the GDY / PG electrode under a nitrogen atmosphere for 10-30 minutes to obtain a GDY / PDEA hydrogel film electrode;

[0011] The pre-gel solution comprises N,N-diethylacrylamide (DEA) monomer, an initiator, a cross-linking agent and an accelerator; the concentration of the DEA monomer is 0.3-0.6 mol / L; the initiator is selected from 0.3-0.6 mg / mL sodium persulfate, the cross-linking agent is selected from 1-2 mg / mL N,N'-methylenebisacrylamide, and the accelerator is selected from 0.3-0.6 mg / mL N,N,N',N'-tetramethyloxalamide.

[0012] In some embodiments of the present application, the volume ratio of ethanol to water is 1:0.5-1.5, preferably 1:1.

[0013] In some embodiments of the present application, the geometric area of ​​the pyrolytic graphite electrode is 0.08-0.2 cm -1 The geometric area of ​​the pyrolytic graphite electrode and the volume ratio of the Graphene suspension are 0.008-0.02cm -1 : 1 μL; the drop-coating amount of the pre-gel solution is 6-10 μL.

[0014] In some embodiments of the present application, the initiator is selected from 0.4 mg / mL sodium persulfate, the cross-linking agent is selected from 1.5 mg / mL N,N'-methylenebisacrylamide, and the accelerator is selected from 0.46 mg / mL N,N,N',N'-tetramethyloxalamide.

[0015] In some embodiments of the present application, nitrogen is fully introduced into the pre-gel solution to remove oxygen before drop coating.

[0016] In some embodiments of the present application, it also includes:

[0017] (4) Immersing the GDY / PDEA hydrogel film electrode in a buffer solution to remove small molecules that do not participate in the reaction; wherein the buffer solution is selected from Britton-Robinson buffer solution (BR buffer solution), phosphate buffered saline solution (PBS buffer solution) or Tris-HCl buffered saline solution (Tris buffer solution).

[0018] The second aspect of the present application provides a GDY / PDEA hydrogel film electrode prepared by the preparation method described in the first aspect of the present application.

[0019] In some embodiments of the present application, the GDY / PDEA hydrogel film electrode uses a PG electrode as a substrate, and the upper surface of the substrate has an adjacent catalyst layer and an external stimulus response layer; the catalyst layer is GDY, and the external stimulus response layer is poly N,N-diethylacrylamide (PDEA).

[0020] The third aspect of the present application provides a logic gate system, wherein the logic gate system is constructed based on the GDY / PDEA hydrogel film electrode described in the second aspect of the present application.

[0021] The fourth aspect of the present application provides the use of the GDY / PDEA hydrogel film electrode described in the second aspect of the present application or the logic gate system described in the third aspect of the present application for phenylhydrazine detection.

[0022] The present application provides a preparation method and use of a GDY / PDEA hydrogel thin film electrode. The GDY / PDEA hydrogel thin film electrode prepared by the preparation method provided by the present application has been verified to use phenylhydrazine as an active probe of environmental pollution molecules. The GDY / PDEA hydrogel thin film electrode exhibits an electrochemical response that is sensitive to pH, temperature, and salt concentration, and exhibits switch properties. The GDY / PDEA hydrogel thin film electrode is combined with phenylhydrazine molecular electrocatalysis to control and regulate the electrochemical catalytic oxidation of phenylhydrazine. According to the response of the GDY / PDEA hydrogel thin film electrode provided by the present application to pH, temperature, salt concentration, and electrode type, accurate monitoring and control of phenylhydrazine can be achieved, thereby constructing a logic gate system that can accurately monitor phenylhydrazine.

[0023] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0025] Figure 1 Fourier transform infrared (FTIR) spectra of DEA monomer and PDEA hydrogel film;

[0026] Figure 2 The cyclic voltammetry (CV) response curves of phenylhydrazine as an electroactive pollutant molecule and GDY / PG electrode, GDY / PDEA hydrogel film electrode, PG electrode, and PDEA hydrogel film electrode;

[0027] Figure 3A The electrochemical impedance spectroscopy (EIS) response curves of K3[Fe(CN)6] as an electroactive probe with PG electrode, PDEA hydrogel film electrode, and GDY / PDEA hydrogel film electrode; Figure 3B for Figure 3A The EIS response enlarged curve of curve a in the middle;

[0028] FIG. 4A to FIG. 4D The pH sensitivity of phenylhydrazine in GDY / PDEA hydrogel film electrode was shown;

[0029] Figure 5 The pH sensitivity of GDY / PDEA hydrogel film was shown;

[0030] FIG. 6A to FIG. 6BThe temperature sensitivity of phenylhydrazine on GDY / PDEA hydrogel film electrode was shown;

[0031] FIG. 7A to FIG. 7C The salt sensitivity of phenylhydrazine in GDY / PDEA hydrogel film electrode was shown;

[0032] Figure 8 The scanning electron microscope (SEM) images of PDEA hydrogel films under different conditions;

[0033] Fig. 9A The 16 possible combinations of four inputs for scanning phenylhydrazine on the GDY / PDEA hydrogel film electrode are shown;

[0034] Fig. 9B A symbolic representation of the logic gate circuit for scanning phenylhydrazine on the GDY / PDEA hydrogel film electrode is shown. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field based on the present application belong to the scope of protection of the present application.

[0036] The first aspect of the present application provides a method for preparing a GDY / PDEA hydrogel film electrode, which comprises the following steps:

[0037] (1) Dissolving GDY and Nafion solution in a solvent and ultrasonically dispersing for 20-40 min to obtain a GDY suspension;

[0038] The concentration of the Nafion solution is 4-6 vol%, the solvent is selected from a mixed solvent of ethanol and water, anhydrous ethanol, chloroform or toluene; the volume ratio of the Nafion solution to the solvent is 1:10; the final concentration of the graphyne is 0.1-0.3 mg / mL;

[0039] (2) applying the GDY suspension droplets on the surface of the PG electrode and drying to obtain a GDY / PG electrode;

[0040] (3) drop-coating the pre-gel solution on the surface of the GDY / PG electrode under a nitrogen atmosphere for 10-30 minutes to obtain a GDY / PDEA hydrogel film electrode;

[0041] The pre-gel solution comprises DEA monomer, initiator, cross-linking agent and accelerator; the concentration of DEA monomer is 0.3-0.6 mol / L; the initiator is selected from 0.3-0.6 mg / mL sodium persulfate, the cross-linking agent is selected from 1-2 mg / mL N,N'-methylenebisacrylamide, and the accelerator is selected from 0.3-0.6 mg / mL N,N,N',N'-tetramethyloxalamide.

[0042] The inventors found in their research that when the concentration of the Nafion solution in step (1) is controlled within the range of the present application, the obtained GDY suspension has a moderate viscosity and excellent electrical conductivity.

[0043] The present application has no particular limitation on the geometric area of ​​the PG electrode in step (2), as long as the purpose of the present application can be achieved; in some embodiments of the present application, the geometric area of ​​the PG electrode is 0.08-0.2 cm -1 ; Further, the volume ratio of the geometric area of ​​the PG electrode to the GDY suspension is 0.008-0.02cm -1 : 1μL.

[0044] In this application, the geometric area refers to the electrochemically active area.

[0045] The present application has no particular limitation on the amount of the pre-gel solution to be applied in step (3), as long as the purpose of the present application can be achieved; in some embodiments of the present application, the amount of the pre-gel solution to be applied can be 6-10 μL.

[0046] The GDY / PDEA hydrogel film electrode prepared by the preparation method of the GDY / PDEA hydrogel film electrode provided in the present application uses phenylhydrazine as an active probe of environmental pollution molecules. The GDY / PDEA hydrogel film electrode responds to pH, temperature, salt concentration, and electrode type, thereby achieving accurate monitoring and control of phenylhydrazine.

[0047] In some embodiments of the present application, the volume ratio of ethanol to water is 1:0.5-1.5, preferably 1:1.

[0048] In some embodiments of the present application, the geometric area of ​​the pyrolytic graphite electrode is 0.08-0.2 cm -1 The geometric area of ​​the pyrolytic graphite electrode and the volume ratio of the Graphene suspension are 0.008-0.02cm -1 : 1 μL; the drop-coating amount of the pre-gel solution is 6-10 μL.

[0049] In some embodiments of the present application, the initiator is selected from 0.4 mg / mL sodium persulfate, the cross-linking agent is selected from 1.5 mg / mL N,N'-methylenebisacrylamide, and the accelerator is selected from 0.46 mg / mL N,N,N',N'-tetramethyloxalamide.

[0050] In some embodiments of the present application, nitrogen is fully introduced into the pre-gel solution to remove oxygen before drop coating.

[0051] In some embodiments of the present application, it also includes:

[0052] (4) Immersing the GDY / PDEA hydrogel film electrode in a buffer solution to remove small molecules that do not participate in the reaction; wherein the buffer solution is selected from BR buffer solution, PBS buffer solution or Tris buffer solution.

[0053] The second aspect of the present application provides a GDY / PDEA hydrogel film electrode prepared by the preparation method described in the first aspect of the present application.

[0054] In some embodiments of the present application, the GDY / PDEA hydrogel film electrode uses a PG electrode as a substrate, and the upper surface of the substrate has an adjacent catalyst layer and an external stimulus response layer; the catalyst layer is GDY, and the external stimulus response layer is PDEA.

[0055] The third aspect of the present application provides a logic gate system, wherein the logic gate system is constructed based on the GDY / PDEA hydrogel film electrode described in the second aspect of the present application.

[0056] The fourth aspect of the present application provides the use of the GDY / PDEA hydrogel film electrode described in the second aspect of the present application or the logic gate system described in the third aspect of the present application for phenylhydrazine detection.

[0057] In the present application, the GDY / PDEA hydrogel film electrode uses phenylhydrazine as an active probe of environmental pollution molecules, and the GDY / PDEA hydrogel film electrode exhibits electrochemical responses sensitive to pH, temperature, and salt concentration, and exhibits the properties of a switch; further, the GDY / PDEA hydrogel film electrode is combined with phenylhydrazine molecular electrocatalysis, and by utilizing the changes in various stimuli of the external environment, the electrochemical catalytic oxidation of phenylhydrazine is controlled and regulated, thereby realizing the monitoring and control of phenylhydrazine and the construction of a logic gate system. The GDY / PDEA hydrogel film exhibits responses to pH, temperature, salt concentration, and electrode type, and according to its electrochemical mechanism and its electrocatalytic behavior, a 4-input / 4-output logic gate system is built, which is for the advancement of future biological / environmental pollutant molecular computers, combining multiple sensitive interfaces with electrocatalysis to develop logic gate systems, and providing a new way to solve the problems of real-time monitoring of environmental pollutants, design of new environmental pollutant sensors, and molecular devices.

[0058] The terms used herein, unless otherwise specified or defined, have their general meanings known to those skilled in the art. The present application is described in detail below in conjunction with specific examples. The experimental materials and methods used in the following examples are conventional materials and methods unless otherwise specified.

[0059] Example 1

[0060] (1) Use 600-grit sandpaper to rub the pyrolytic graphite electrode (PG, geometric area 0.16 cm -1 ) indicates that it was polished, rinsed with pure water, and then ultrasonically treated for 10 seconds and then blown dry with an ear cleaning bulb;

[0061] (2) 0.22 g of GDY and 1 mL of 5 vol% Nafion solution were dissolved in 10 mL of a mixed solvent of ethanol and water (the volume ratio of ethanol to water was 1:1), and ultrasonically dispersed for 30 min to obtain a 0.2 mg / mL GDY suspension;

[0062] (3) Pipette 10 μL of GDY suspension droplet and apply it on the surface of PG electrode. After drying at room temperature, GDY / PG electrode is obtained.

[0063] (4) preparing a pregel solution containing 0.5 mol / L DEA monomer, 0.4 mg / mL sodium persulfate, 1.5 mg / mL N,N'-methylenebisacrylamide and 0.46 mg / mL N,N,N',N'-tetramethyloxalamide, wherein the pregel solution was freshly prepared each time and nitrogen was fully introduced to remove oxygen before drop coating;

[0064] (5) 8 μL of pre-gel solution was drop-coated on the surface of the GDY / PG electrode, and a PDEA hydrogel film layer was formed on the surface of the PG / GDY electrode under a nitrogen atmosphere for 10 min, thereby obtaining a GDY / PDEA hydrogel film electrode;

[0065] (6) The prepared GDY / PDEA hydrogel film electrode was immersed in BR buffer solution to remove small molecules that were not involved in the reaction.

[0066] It should be noted that the GDY / PDEA hydrogel film electrodes in the following characterizations and tests are all GDY / PDEA hydrogel film electrodes prepared in Example 1.

[0067] Characterization of GDY / PDEA hydrogel films

[0068] Fourier transform infrared spectroscopy (FTIR) characterization and analysis of PDEA hydrogel film

[0069] FTIR spectra of DEA monomer and PDEA hydrogel film are shown in Figure 1 As shown, curve a corresponds to DEA monomer, and curve b corresponds to PDEA hydrogel film. Comparison between curve a and curve b confirms the synthesis of PDEA hydrogel film. Figure 1 It can be seen that the DEA monomer is at 1606cm -1 There is a C=C stretching vibration peak at the PDEA hydrogel film, which cannot be detected in the PDEA hydrogel film. However, all characteristic peaks of DEA monomer can be observed in the spectrum of PDEA hydrogel film, and the positions of the two are the same or similar.

[0070] Electrochemical characterization by cyclic voltammetry (CV)

[0071] The CV method was used with a scan rate of 0.06 V s -1 The hydrogel membrane containing 0.001 mol / L phenylhydrazine as the electroactive pollutant molecule was characterized in a BR buffer solution containing 0.1 mol / L NaCl solution as the supporting electrolyte at pH 7.0 and temperature 25°C. The results are as follows Figure 2 As shown, curves ad correspond to the GDY / PG electrode, GDY / PDEA hydrogel film electrode, PG electrode, and PDEA hydrogel film electrode, respectively.

[0072] from Figure 2 It can be seen that the CV oxidation peak of phenylhydrazine molecules at about 0.25V can be observed on the PG electrode (see Figure 2 , curve c). After the PDEA hydrogel film is assembled on the electrode, the CV oxidation peak current signal (I pa) decreased, and the CV oxidation peak potential moved to the right, indicating that the PDEA hydrogel film has been successfully prepared on the PG electrode surface (see Figure 2 , curve d). When GDY was assembled on the PG surface, the CV oxidation peak current of phenylhydrazine increased significantly, indicating that the modification of GDY greatly increased the number of electrons exchanged by phenylhydrazine on the electrode surface, thereby amplifying the CV response signal (see Figure 2 , curve a). When the PDEA hydrogel film is formed on the surface of the PG / GDY electrode, the CV response of phenylhydrazine decreases significantly (see Figure 2 , curve b), this is because the PDEA hydrogel film forms a barrier on the electrode surface, and the diffusion of probe molecules in the entire film becomes more difficult, which indicates that the PDEA hydrogel film has been successfully assembled on the PG / GDY electrode surface.

[0073] Electrochemical impedance spectroscopy (EIS) was used to characterize the films.

[0074] In the EIS experiment with 1mmol / L K3[Fe(CN)6] as the electroactive probe, the responses of the PG electrode, the electrode modified with PDEA hydrogel film, and the electrode modified with GDY / PDEA hydrogel film at 0.17V were detected in a BR buffer solution with pH 7.0. The results are shown in Figure 2. Figure 3A-3B As shown, curves ac correspond to the PG electrode, PDEA hydrogel film electrode, and GDY / PDEA hydrogel film electrode, respectively.

[0075] Figure 3A Figure 3B The results show that the EIS response curve of K3[Fe(CN)6] on the PG electrode exhibits a smaller arc in the low frequency region (see Figure 3A , curve a, Figure 3B is the EIS response amplification curve of curve a), when PDEA (see Figure 3A , curve b) and GDY / PDEA hydrogel film (see Figure 3A , curve c) After being assembled on the PG electrode surface, the hydrogel film is a physical barrier that limits the electron exchange process of the probe molecules on the electrode surface. The GDY / PDEA hydrogel film curve is too large because GDY itself is a topological insulator. A topological insulator is a material with an internal electronic band structure similar to that of a conventional insulator, and the interface allows charge movement. The enlargement of the semicircle in the EIS response also indicates that the GDY / PDEA hydrogel film was successfully prepared on the PG electrode surface.

[0076] Environmental Sensitive Switching Electrochemical Behavior of GDY / PDEA Hydrogel Films

[0077] pH sensitive

[0078] The electrochemical behavior of phenylhydrazine can be used to characterize the pH sensitivity of the GDY-PDEA hydrogel film electrode. Figure 4A The GDY / PDEA hydrogel film was subjected to 0.001 mol / L phenylhydrazine at a scan rate of 0.06 V s at pH 4.0-9.0. -1 , CV response in BR buffer solution with 0.1 mol / L NaCl as supporting electrolyte at 25 °C; Figure 4B The peak current (I pa ) changes; Figure 4C CV responses of GDY / PDEA hydrogel film in 0.001 mol / L phenylhydrazine at pH = 7.0, 25 °C, and 0.1 mol / L NaCl as supporting electrolyte BR buffer solution at different scan rates. Curves a and b correspond to a scan rate of 0.14 V s -1 , 0.12V s -1 , 0.10V s -1 , 0.09V s -1 , 0.08V s -1 , 0.07V s -1 , 0.06V s -1 ; Figure 4D The standard curve of the peak value corresponding to the square root of the scanning rate: y = 4.23x-11.88R 2 =0.998.

[0079] The results show that the CV behavior of phenylhydrazine in the buffer of GDY-PDEA hydrogel film electrode is very sensitive to the solution pH at 25℃ (see Figure 4A ). At pH 7.0, the CV signal of phenylhydrazine is large, but it drops sharply when the pH drops from 7.0 to 4.0. At pH 4.0, it is even difficult to observe the CV response of the probe. Therefore, the GDY-PDEA hydrogel film is in the on state at pH 7.0 and in the off state at pH 4.0. After the modified electrode is regenerated, the pH-sensitive switching characteristics of phenylhydrazine on the GDY / PDEA hydrogel film electrode are reversible (see Figure 4B ). By switching the hydrogel film electrode in phenylhydrazine solution between pH 7.0 and 4.0, I pa It changes periodically between a relatively high value and a very small value. pa At pH 7.0 and temperature 25°C, the -1 The square root of the scan rate is linear, indicating that the response of phenylhydrazine on the electrode is diffusion controlled (see Figure 4C ).

[0080] In this study, we also performed CV responses of the pH value of the GDY / PDEA hydrogel film itself in BR buffer solution. Figure 5 Curve a in the middle is the GDY / PDEA hydrogel film at pH = 7.0 and a scan rate of 0.06 V s -1 , CV value of 0.001 mol / L phenylhydrazine in BR buffer solution supplemented with NaCl solution at 25 °C; Curve b is the CV value of GDY / PDEA hydrogel film at a scan rate of 0.06 V s -1 , CV value of BR buffer solution supplemented with NaCl solution without 0.001 mol / L phenylhydrazine at 25 °C and pH 7.0; Curve c is the CV value of GDY / PDEA hydrogel film at a scan rate of 0.06 V s -1 , CV values ​​of BR buffer solution supplemented with NaCl solution without 0.001 mol / L phenylhydrazine at 25°C and pH 4.0. The inset is the signal amplification of curve b and curve c.

[0081] Figure 5 The results showed that the GDY / PDEA hydrogel film did not exhibit sensitive behavior. Therefore, we speculate that the pH-responsive switch characteristics of the GDY / PDEA hydrogel film are mainly attributed to the characteristics of phenylhydrazine itself, and have little to do with the GDY / PDEA hydrogel film. a The value is 5.2. When the pH value of the BR buffer solution is lower than pK a When the pH value of the BR buffer solution is higher than the pK a When the pH value of the BR buffer solution is higher than 9, the analyte is mainly in the neutral form, which leads to a high response current. When the pH value of the BR buffer solution is higher than 9, phenylhydrazine will undergo deprotonation, which is kinetically less favorable, so a decrease in the current response is observed. Since the main purpose of the study is to distinguish a clear pH switch difference, pH 7.0 was selected as the optimal pH value for all electrochemical experiments.

[0082] Temperature sensitive

[0083] The CV response of phenylhydrazine on the GDY / PDEA hydrogel film electrode is also very sensitive to changes in ambient temperature. Fig. 6A The results of GDY / PDEA hydrogel films at different temperatures for 0.001 mol / L phenylhydrazine at a scan rate of 0.06 V s -1 , pH = 7, 0.1 mol / L NaCl as the supporting electrolyte BR buffer solution CV response, curves ae correspond to temperatures of 25 ° C, 29 ° C, 33 ° C, 37 ° C, and 41 ° C, respectively; Figure 6BIt shows that 0.001 mol / L phenylhydrazine has an I pa changes.

[0084] Fig. 6A The results show that when the temperature is 33℃, there is a significant difference between the peak value of the cyclic voltammetry curve and the peak value of the cyclic voltammetry curve at the adjacent temperature, and the temperature continues to rise, and basically no obvious peak appears. Therefore, it is judged that the GDY / PDEA hydrogel film has undergone a phase change at 33℃, causing the pores of the hydrogel to shrink or close; when the solution temperature is lower than 33℃, the CV signal of phenylhydrazine is larger. However, when the temperature is higher than 33℃, the peak current has a significant downward trend. It can be seen that the lowest critical solution temperature (LCST) of the GDY / PDEA hydrogel film is 33℃.

[0085] In addition, the switching characteristics of GDY / PDEA hydrogel film for phenylhydrazine at different temperatures were studied. We selected two typical temperatures: 25°C and 41°C. At 25°C, phenylhydrazine showed an obvious oxidation peak, indicating that the film was in the "ON" state. At 41°C, phenylhydrazine had almost no oxidation peak, indicating that the film was in the "OFF" state. After the modified electrode was regenerated, the temperature-sensitive switching characteristics of phenylhydrazine on the GDY / PDEA hydrogel film electrode were reversible (see Figure 6B ).

[0086] SEM images were used to observe the structural changes of the PDEA hydrogel film to determine the mechanism of its temperature-sensitive switching properties. At 25 °C, the PDEA hydrogel film exhibited a swollen and sparse network structure (see Figure 8 A in the figure leads to the easy diffusion of phenylhydrazine molecules into the membrane electrode and a large CV response. As the solution temperature rises to 41°C, the film shows a shrinkage and density state (see Figure 8 This prevents the phenylhydrazine molecules from passing through the hydrogel film and exchanging electrons with the overlying PG electrode.

[0087] Salt sensitivity

[0088] The CV response of phenylhydrazine on the GDY / PDEA hydrogel film electrode is also sensitive to the salt concentration in the solution. Fig. 7A The results show that the GDY / PDEA hydrogel film has a good performance in the presence of different concentrations of NaSO4 for 0.001 mol / L phenylhydrazine at a scan rate of 0.06 V s -1 , pH = 7 and 25 ° C CV response in BR buffer solution with 0.1 mol / L NaCl as supporting electrolyte, curve ag corresponds to NaSO4 concentrations of 0 mol / L, 0.05 mol / L, 0.10 mol / L, 0.15 mol / L, 0.20 mol / L, 0.30 mol / L, and 0.40 mol / L, respectively; Figure 7BWhen 0.001mol / L phenylhydrazine is in 0mol / L and 0.40mol / L NaSO4, pa changes; Figure 7C In a BR buffer solution containing Na2SO4, MgSO4, NaCl and NaBr, pH = 7.0, 25 °C, the scan rate is 0.06 V s -1 When 0.001mol / L phenylhydrazine is charged on the GDY / PDEA membrane electrode, pa The curves ad correspond to Na2SO4, MgSO4, NaCl, and NaBr respectively.

[0089] Selecting NaSO4 as the representative inorganic salt, under the conditions of pH 7.0 and solution concentration of 25°C, when there is no NaSO4 in the solution, a large oxidation peak will be shown when phenylhydrazine is detected by CV method, and the hydrogel film is in the "open" state ( Fig. 7A , curve a); under the same conditions, when the solution contains 0.4 mol / L NaSO4, the oxidation peak of phenylhydrazine becomes very small or even undetectable, and the hydrogel film is in the "off" state (see Fig. 7A , curve g). After the modified electrode is regenerated, the NaSO4-sensitive behavior of phenylhydrazine on the GDY / PDEA hydrogel film electrode is reversible (see Figure 7B ).

[0090] from Figure 7C It can be seen that the concentration of other salts can also cause phase transition of GDY / PDEA hydrogel film. For example, Na2SO4, MgSO4, NaCl and NaBr can be detected by environmental pollutant probe. Na2SO4, NaCl and NaBr all contain cationic Na + , and contains different anions, multiple tests have found that when SO4 2- =0.20mol / L, Cl -1 =0.42mol / L, Br -1 =0.8mol / L, there is a significant difference between the peak of the cyclic voltammetry curve and the peak of the salt concentration. Therefore, it is judged that the GDY / PDEA hydrogel film may undergo a phase transition at this concentration, resulting in the shrinkage or closure of the pores of the hydrogel. Therefore, the difference between them lies in that they have different critical phase transition concentrations (SO4 2- (0.20mol / L)<Cl -1 (0.42mol / L)<Br -1(0.8mol / L)), by comparing the dot-line graphs of the salt concentration changes of MgSO4 and Na2SO4, it can be concluded that at their different critical phase transition concentrations, anions play a greater role than cations in the GDY / PDEA hydrogel film. In this application, we choose Na2SO4 as a representative salt to discuss the sensitivity of the GDY / PDEA hydrogel film. When the concentration of Na2SO4 is lower than the critical phase transition concentration, the PDEA molecules form hydrogen bonds with the solution and present a cluster structure with multiple pores or channels. At this time, the phenylhydrazine molecules can easily pass through the gel surface to reach the electrode surface for electron exchange, so they show a larger CV response; when the concentration of Na2SO4 is higher than the critical phase transition concentration, the hydrogen bonds formed by the PDEA molecules with the solution are broken, and the pores and channels disappear with the increase in concentration, thereby hindering and limiting the phenylhydrazine molecules from reaching the electrode surface. This phenomenon can also be confirmed by SEM spectra (see Figure 8 CD in the figure, where C is a schematic diagram of the SEM results of the PDEA hydrogel film at pH = 7 and the Na2SO4 concentration is 0 mol / L; D is a schematic diagram of the SEM results of the PDEA hydrogel film at pH = 7 and the Na2SO4 concentration is 4 mol / L).

[0091] Electrocatalytic Oxidation of Phenylhydrazine

[0092] In this application, in order to increase the number and complexity of output, the electrocatalytic amplification method is used to increase the CV value and output number of environmental pollutants. GDY has good conductivity and large specific surface area. Its structure not only contains sp 2 The acetylenic bond (-C≡C≡C-) composed of sp-C connects the benzene ring, which can not only increase the specific surface area of ​​the electrode, but also improve the charge transfer rate, which helps to increase the number of logic gates through electrocatalytic amplification and increase the complexity of the logic gate system.

[0093] Based on the GDY / PDEA hydrogel film electrode of Example 1 of the present application, GDY was constructed as the catalyst layer and PDEA as the external stimulus response layer. In order to check the repeatability of the system, six GDY / PDEA hydrogel film electrodes were independently prepared under the same conditions, and each of the six sensors (all homemade in this laboratory, a, b, c, d, e, f) was used by repeated elution (grinding the GDY / PDEA hydrogel film modified on the surface of the PG electrode on 600-mesh sandpaper) and analytical detection (using the above-mentioned electrochemical method using cyclic voltammetry for detection) 10.00mmol / L phenylhydrazine, and each sensor was repeated three times. The relative standard deviation (RSD, RSD = standard deviation ÷ corresponding average value × 100%) of the peak values ​​of six randomly selected sensors was calculated, and the RSD values ​​were 3.5% and 3.7%, respectively, indicating that the system has good repeatability.

[0094] Building a 4-input / 4-output logic gate system based on GDY / PDEA film

[0095] The definition of the 4-input in the logic gate system is shown in Table 1. According to the electrocatalytic mechanism of GDY / PDEA hydrogel film and its triple switch electrocatalytic behavior, I pa The values ​​are divided into four thresholds, see Table 2. In Table 1, the state "1" (The "1" State) represents the "on" state, and its interpretation is, for example, when Input A (pH) is "1" in Table 3, it means that the set condition is "pH = 7.0", and the rest is deduced by analogy; the state "0" (The "0" State) represents the "off" state, and its interpretation is, for example, when Input A (pH) is "0" in Table 3, it means that the set condition is "pH = 4.0", and the rest is deduced by analogy. For GDY / PDEA hydrogel film electrodes, when the PDEA hydrogel film does not undergo phase change (the hydrogel pores are arranged regularly and open normally, which is conducive to the entry and exit of phenylhydrazine molecules to reach the electrode surface) and the phenylhydrazine molecules exist in molecular form (phenylhydrazine exists in molecular form at pH 7 and undergoes oxidation reaction when it reaches the electrode surface), the hydrogel is not only in a multi-pore and multi-channel state, but also has a GDY catalytic layer in the inner layer of the hydrogel film. Therefore, the threshold of output A (Output A) with a larger CV response is greater than 20μA; for PDEA hydrogel film, when the PDEA hydrogel film does not undergo phase change and phenylhydrazine exists in molecular form, the threshold of output B (Output B) is 10-20μA. The threshold of output C (Output C) is 5-10μA because although PDEA undergoes phase change due to changes in salt concentration or the hydrogel is not completely closed, the catalytic effect of GDY makes I pa The threshold value of output D is less than 5 μA. This may be due to the excessive phase change of PDEA hydrogel film under different environmental stimulation, which leads to the shrinkage or disappearance of PDEA hydrogel film pores and channels. It may also be due to the fact that phenylhydrazine no longer exists in the form of molecules. These will lead to the decrease or even disappearance of the oxidation peak current. Figure 9A-9B The truth table of the logic gate and the 4-input and corresponding output results are listed as follows: pa Resulting bar graph and logic gate circuit. Fig. 9A In the electrocatalytic oxidation peak current histogram, at 0.06 V s -1 The scanning speed scans 16 possible combinations of 4 inputs of 0.001 mol / L phenylhydrazine on the GDY / PDEA hydrogel film electrode, and the threshold is marked with a dotted line; Fig. 9BIt is a symbolic representation of the logic gate circuit for scanning phenylhydrazine on the GDY / PDEA hydrogel film electrode. In the present application, the monitoring and control of phenylhydrazine and the construction of the logic gate system are selected, and the phenylhydrazine concentration is 0.001mol / L. Phenylhydrazine with a concentration of ≥0.001mol / L can be monitored by the logic gate system, even if phenylhydrazine is found, and the phenylhydrazine is controlled below 0.001mol / L. In Table 1, "1" (The "1" State) represents the "on" state, indicating that phenylhydrazine is detected; "0" (The "0" State) represents the "off" state, indicating that phenylhydrazine is not detected.

[0096] Table 1. Definition of 4-input in logic gate system

[0097]

[0098] Table 2. Definition of the four thresholds in the logic gate system

[0099]

[0100] Table 3. Truth table for a 4-input / 4-output logic gate system

[0101]

[0102] The GDY / PDEA hydrogel film electrode prepared by the preparation method provided by the present application has been verified to use phenylhydrazine as an active probe of environmental pollution molecules. The GDY / PDEA hydrogel film electrode exhibits an electrochemical response sensitive to pH, temperature, and salt concentration, and exhibits the properties of a switch. Further, the GDY / PDEA hydrogel film electrode is combined with the electrocatalysis of phenylhydrazine molecules, and the electrochemical catalytic oxidation of phenylhydrazine is controlled and regulated by utilizing the changes in various stimulating factors of the external environment, thereby realizing the monitoring and control of phenylhydrazine and the construction of a logic gate system. The GDY / PDEA hydrogel film exhibits a response to pH, temperature, salt concentration, and electrode type. According to its electrochemical mechanism and its electrocatalytic behavior, a 4-input / 4-output logic gate system is built, which is for the advancement of future biological / environmental pollutant molecular computers, combining multi-sensitive interfaces with electrocatalysis to develop logic gate systems, and providing a new way to solve the problems of real-time monitoring of environmental pollutants, design of new environmental pollutant sensors, and molecular devices. The idea of ​​this work is universal and can be easily extended to other pollutants with electrochemical responses. This application provides a new method to increase the complexity of computing systems for monitoring environmental pollutants, thereby demonstrating its potential prospects and laying a solid foundation for solving complex practical problems such as real-time monitoring of pollutants.

[0103] The above description is only a preferred embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A method for preparing a graphene / poly (N,N-diethylacrylamide) hydrogel film electrode, comprising the following steps: (1) dissolving graphyne and a perfluorosulfonic acid polymer solution in a solvent, and ultrasonically dispersing for 20-40 minutes to obtain a graphyne suspension; The concentration of the perfluorosulfonic acid polymer solution is 4-6 vol%, the solvent is selected from a mixed solvent of ethanol and water, anhydrous ethanol, chloroform or toluene; the volume ratio of the perfluorosulfonic acid polymer solution to the solvent is 1:10; the final concentration of the graphyne is 0.1-0.3 mg / mL; (2) applying the graphyne suspension droplets on the surface of a pyrolytic graphite electrode, and drying to obtain a graphyne / graphite electrode; (3) dripping the pre-gel solution on the surface of the graphyne / graphite electrode, and standing for 10-30 minutes under a nitrogen atmosphere to obtain a graphyne / poly (N,N-diethylacrylamide) hydrogel film electrode; The pre-gel solution comprises N,N-diethylacrylamide monomer, initiator, cross-linking agent and accelerator; the concentration of N,N-diethylacrylamide monomer is 0.3-0.6 mol / L, the initiator is selected from 0.3-0.6 mg / mL sodium persulfate, the cross-linking agent is selected from 1-2 mg / mL N,N'-methylenebisacrylamide, and the accelerator is selected from 0.3-0.6 mg / mL N,N,N',N'-tetramethyloxalamide.

2. The preparation method according to claim 1, wherein The volume ratio of the ethanol to water is 1:0.5-1.

5.

3. The preparation method according to claim 1, wherein The geometric area of ​​the pyrolytic graphite electrode is 0.08-0.2 cm 2 The geometric area of ​​the pyrolytic graphite electrode and the volume ratio of the Graphene suspension are 0.008-0.02cm 2 : 1 μL; the drop-coating amount of the pre-gel solution is 6-10 μL.

4. The preparation method according to claim 1, wherein The N,N-diethylacrylamide monomer concentration is 0.5 mol / L, the initiator is selected from 0.4 mg / mL sodium persulfate, the crosslinker is selected from 1.5 mg / mL N,N'-methylenebisacrylamide, and the accelerator is selected from 0.46 mg / mL N,N,N',N'-tetramethyloxalamide.

5. The preparation method according to claim 1, wherein The pre-gel solution is fully purged with nitrogen before drop coating to remove oxygen.

6. The preparation method according to claim 1, wherein Also includes: (4) Immersing the graphyne / poly (N,N-diethylacrylamide) hydrogel film electrode in a buffer solution to remove small molecules that do not participate in the reaction; wherein the buffer solution is selected from BR buffer solution, PBS buffer solution or Tris buffer solution.

7. The graphene / poly (N,N-diethylacrylamide) hydrogel film electrode prepared according to the preparation method described in any one of claims 1 to 6.

8. The graphene / poly (N,N-diethylacrylamide) hydrogel film electrode according to claim 7, wherein: The graphyne / poly (N,N-diethylacrylamide) hydrogel film electrode uses a pyrolytic graphite electrode as a substrate, and an adjacent catalyst layer and an external stimulus response layer are provided on the upper surface of the substrate; the catalyst layer is graphyne, and the external stimulus response layer is poly (N,N-diethylacrylamide).

9. A logic gate system, wherein: The logic gate system is constructed based on the graphyne / poly (N,N-diethylacrylamide) hydrogel film electrode described in any one of claims 7 to 8.

10. Use of the graphyne / poly (N,N-diethylacrylamide) hydrogel film electrode according to any one of claims 7 to 8 or the logic gate system according to claim 9 for phenylhydrazine detection.

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