CN108456288B - Thermo-sensitive graphene-based electrochemical modification material and preparation method and application thereof - Google Patents
Thermo-sensitive graphene-based electrochemical modification material and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a temperature-sensitive graphene-based electrochemical modification material and a preparation method and application thereof. The temperature-sensitive graphene-based electrochemical modification material is Fe (CN)6 3‑The preparation method of the poly-rGO comprises the following steps: under the action of AIBN, taking DMF as a solvent, and generating a block copolymer poly (NIPAM-b-BVImBr) by ionic liquid BVImBr and PNIPAM; preparing poly-rGO by utilizing pi-pi non-covalent modification effect between graphene and ionic liquid, and synthesizing Fe (CN) through anion exchange reaction6 3‑poly-rGO. The prepared electrochemical modification material has good dispersibility, gives two intelligent responsibilities of temperature sensitivity and ionicity to the material when the graphene reaches a high reduction state, and expands the application in the fields of electrochemical analysis, biosensing, electronic devices, separation and purification and the like by applying the material to a biosensor.
Description
Technical Field
The invention relates to the field of nano composite materials, in particular to a temperature-sensitive graphene-based electrochemical modification material Fe (CN)6 3-poly-rGO and its preparation method and application.
Background
The biosensor is a detection device which takes enzyme, immune system, antibody, animal tissue, organelle and other bioactive substances as recognition elements, is combined with a physical-chemical converter and converts the concentration into an electric signal. The biosensor is one of chemical sensors, has high sensitivity, high efficiency, low detection limit, specific response to a target, and can perform on-line analysis and even in vivo analysis, and thus has attracted great attention.
The graphene nanocomposite material shows good electron transfer capacity on an electrochemical biosensor, so that the graphene is paid great attention to in the aspect of electrochemical enzyme sensors and has potential application value.
Graphene is a new carbonaceous material with a single-layer two-dimensional honeycomb lattice structure formed by tightly packing carbon atoms, and is the thinnest two-dimensional material discovered so far. As is well known, graphene has excellent properties such as high conductivity, good biocompatibility, and good chemical stability, and is widely used in the fields of electrochemistry and material science.
However, strong van der waals force and pi-pi interaction exist between graphene lamellar structures, and agglomeration is very easy to occur in the reduction process, so that the application of graphene in many aspects is limited. The graphene is combined with other materials with good water solubility, so that the problem of dispersibility of the nano composite material in an aqueous solution can be well solved; in addition, other functional substances can be introduced into the graphene-based nanocomposite material, so that some characteristics can be endowed to graphene. At present, functionalized graphene is various, and one of the functionalized graphene is a composite material prepared from graphene and organic macromolecules.
In recent years, the application of temperature sensitive polymers in the electrochemical field has been receiving wide attention. The intelligent material is a novel functional material which can quickly generate response to small changes of external environment (such as temperature, pH, salinity, light, magnetic field and the like). Poly-N-isopropylacrylamide is of particular interest because of its Low Critical Solution Temperature (LCST) in aqueous solution. With the rise of the temperature of the aqueous solution, intermolecular hydrogen bonds are changed into intramolecular hydrogen bonds, and phase separation is carried out to generate precipitation which is in a hydrophobic state; when the temperature is reduced below the critical temperature, the original hydrophilic extension state is reversibly recovered. That is, above the phase transition temperature, polymer chain collapse appears hydrophobic, and below the phase transition temperature, the polymer stretches and exhibits hydrophilicity, and this hydrophobic-hydrophilic state can be repeated all the time.
If the novel composite material is formed by compounding the graphene and the intelligent polymer, the original basic performance of the graphene nanocomposite material can be improved, and the graphene composite material can have certain intelligent environmental responsiveness.
Disclosure of Invention
The invention aims to provide a temperature-sensitive graphene-based electrochemical modification material Fe (CN) with double intelligent responsivity6 3-/poly-rGO。
The second purpose of the invention is to provide a temperature-sensitive graphene-based electrochemical modification material Fe (CN) with double intelligent responsivity6 3-Preparation method of poly-rGO.
Another object of the present invention is to provide a method for producing a high-purity Fe (CN)6 3-Preparation of electrochemical sensor Fe (CN) from poly-rGO6 3-The sensor not only preserves the original structure of graphene, but also has switchable on and off effects, and has electrical activity, and the electrochemical behavior of the sensor at different temperatures is researched, and ascorbic acid with different concentrations is detected. The result shows that the controllable electrochemical sensor has higher application value in the fields of electrochemical analysis, biosensing, electronic devices, separation and purification and the like.
The technical scheme adopted by the invention is as follows: a temperature-sensitive graphene-based electrochemical modification material is Fe (CN)6 3-/poly-rGO。
A preparation method of a temperature-sensitive graphene-based electrochemical modification material comprises the following steps: firstly, under the action of an azodiisobutyronitrile thermal initiator, dimethylformamide is taken as a reflux solvent, and 1-vinyl-3-butylimidazole bromide salt BVImBr and homopolymer PNIPAM are taken as ionic liquid to generate block copolymer poly (NIPAM-b-BVImBr); then, preparing a compound poly-rGO by utilizing pi-pi non-covalent modification between graphene and ionic liquid; synthesis of temperature-sensitive graphene group through anion exchange reactionElectrochemical modification material Fe (CN)6 3-/poly-rGO。
The preparation method specifically comprises the following steps:
1) synthesis of homopolymer PNIPAM: uniformly mixing N-isopropylacrylamide NIPAM, oxygen-ethyl dithiocarbonate ethylbenzene and azobisisobutyronitrile AIBN, adding dioxane, deoxidizing by argon for 30min, setting the oil bath temperature at 85 ℃, and heating and refluxing for 40 h; cooling, rotary evaporating, dropwise adding the reactant into anhydrous ether, filtering, and vacuum drying to obtain homopolymer PNIPAM;
2) synthesis of Block copolymer poly (NIPAM-b-BVImBr): uniformly mixing 1-vinyl-3-butylimidazole bromide, BVImBr, PNIPAM and azobisisobutyronitrile AIBN, adding dimethylformamide DMF, deoxidizing by argon for 30min, setting the oil bath temperature at 85 ℃, and heating and refluxing for 40 h; cooling, dropwise adding the reaction product into anhydrous ether, filtering, and drying to obtain block copolymer poly (NIPAM-b-BVImBr);
3) synthesis of complex poly-rGO: carrying out ultrasonic dispersion on a proper amount of graphene oxide GO powder and water, adding a block copolymer poly (NIPAM-b-BVImBr), dissolving, adding hydrazine hydrate to obtain a mixed solution, setting the oil bath temperature to be 110 ℃, heating and refluxing the mixed solution for 40 hours, cooling, taking an upper layer solution, and carrying out freeze drying to obtain a compound poly-rGO;
4) electrochemical modification material Fe (CN)6 3-Synthesis of poly-rGO: taking the complex poly-rGO and K3[Fe(CN)6]Dissolving in deionized water, ultrasonic dispersing, and dissolving K in deionized water3[Fe(CN)6]Dropwise adding the solution into poly-rGO solution, stirring and reacting for 24h at room temperature, washing, and freeze-drying to obtain Fe (CN)6 3-/poly-rGO。
In the preparation method, in the step 1), the mass ratio of the N-isopropylacrylamide NIPAM, the oxygen-ethyl dithiocarbonate ethylbenzene and the azobisisobutyronitrile AIBN is 48-52:1: 0.03-0.07.
The preparation method comprises the step 2) that the ratio of the amount of the 1-vinyl-3-butylimidazolium bromide BVImBr, the amount of the PNIPAM and the amount of the azodiisobutyronitrile AIBN is 78-82:1:0.13-0.17
In the preparation method, in the step 3), the mass ratio of GO to Poly (NIPAM-b-BVImBr) is 1: 18-22.
In the preparation method, in the step 3), after hydrazine hydrate is added, the pH value of the mixed solution is adjusted to be 9-10.
The application of the temperature-sensitive graphene-based electrochemical modification material in an electrochemical sensor. The electrochemical sensor is prepared by using the temperature-sensitive graphene-based electrochemical modification material Fe (CN)6 3-Poly-rGO is coated on a glassy carbon electrode GC and prepared into Fe (CN)6 3-a/poly-rGO/GC modified electrode.
Fe(CN)6 3-Application of a/poly-rGO/GC modified electrode in electrochemical detection of ascorbic acid.
According to the invention, the graphene nanocomposite is prepared by mainly utilizing pi-pi noncovalent modification effect between graphene and ionic liquid, the graphene nanocomposite prepared by the method has good dispersibility, and two intelligent responsivities of temperature sensitivity and ionic property are given to the graphene while the graphene reaches a high reduction state, so that the graphene composite has certain environmental responsivity on the basis of improving the original basic performance, the composite poly-rGO is prepared, and the morphology, structure and property of the composite are represented. Because the ionic liquid has ion exchange property, the composite material has double intelligent responsiveness, and the electroactive graphene-based functional material Fe (CN) is synthesized through anion exchange reaction6 3-The poly-rGO can be applied to the fields of electrochemical analysis, biosensing, electronic devices, separation and purification and the like.
The temperature-sensitive graphene-based electrochemical sensor prepared by the invention has temperature sensitivity and ionicity. Can be applied to the field of electrochemical analysis.
The invention has the following beneficial effects:
1. the invention relates to a temperature-sensitive graphene-based electrochemical sensor Fe (CN)6 3-The poly-rGO/GC mainly utilizes the pi-pi non-covalent modification effect between graphene and ionic liquid to prepare the graphene nano composite materialThe graphene nanocomposite prepared by the method is good in dispersibility, and two intelligent responsivities of temperature sensitivity and ionicity are given to the graphene while the graphene reaches a high reduction state, so that the graphene composite has the intelligent responsivity on the basis of improving the original basic performance, and the hydrophilicity and the hydrophobicity of a solution are reversibly changed when the temperature and the ions of the solution are changed.
2. The invention utilizes the unique ion exchange property of ionic liquid to prepare the graphene-based electrochemical sensor Fe (CN) with temperature sensitivity through an ion exchange reaction6 3-poly-rGO/GC. Proved by an electrochemical experiment, Fe (CN)6 3-the/poly-rGO/GC can be used as an intelligent responsive electrochemical sensor to realize the controllable detection of ascorbic acid.
Drawings
FIG. 1 is a transmission electron micrograph of GO (a) and poly-rGO (b).
FIG. 2 is a photograph of GO (a), rGO (b), and poly-rGO (c) dispersed in an aqueous solution.
FIG. 3 shows the UV-VIS absorption spectra of GO (a), rGO (b) and poly-rGO (c).
FIG. 4 is an infrared spectrum (FT-IR) of rGO (a), poly (NIPAM-b-BVImBr) (b) and poly-rGO (c).
FIG. 5a is the X-ray photoelectron spectrum of GO.
FIG. 5b is the X-ray photoelectron spectrum of rGO.
FIG. 5c is an X-ray photoelectron spectrum of poly-rGO.
FIG. 5d is Fe (CN)6 3-X-ray photoelectron spectrum of poly-rGO.
FIG. 6 is a digital photograph of poly-rGO at 20 deg.C (a), 45 deg.C (b) and restored to 20 deg.C (c).
FIG. 7 is a graph of the UV-VIS absorption spectra of poly-rGO at 20 deg.C (a), 45 deg.C (b) and restored to 20 deg.C (c), respectively.
FIG. 8 is a graph of the temperature-sensitive cycling of poly-rGO at 20 ℃ and 45 ℃.
FIG. 9 shows Fe (CN)6 3-Plot of cyclic voltammograms for poly-rGO/GC (a) versus poly-rGO/GC (b).
FIG. 10 shows Fe (CN)6 3-poly-rGO/GC was scanned for 50 cycles of cyclic voltammograms in PBS buffer (pH 7).
FIG. 11 shows Fe (CN)6 3-And (3) continuously scanning a peak current change trend graph corresponding to 50 cycles of cyclic voltammetry by the poly-rGO/GC.
FIG. 12 shows Fe (CN)6 3-Cyclic voltammograms of/poly-rGO/GC scanned in PBS at 20 deg.C (a) and 45 deg.C (b).
FIG. 13 shows Fe (CN)6 3-Temperature sensitivity response cycle plot in PBS (pH 7)/poly-rGO/GC.
FIG. 14 shows Fe (CN)6 3-Cyclic voltammograms of/poly-rGO/GC in PBS (pH 7) (a) and PBS containing 0.15mM ascorbic acid (pH 7) (b).
FIG. 15 shows Fe (CN)6 3-I-T curves for poly-rGO/GC against ascorbic acid.
FIG. 16 shows Fe (CN)6 3-Calibration curves for poly-rGO/GC versus the corresponding ascorbic acid concentration.
Detailed Description
For better understanding of the technical solution of the present invention, specific examples are described in further detail, but the solution is not limited thereto.
Example 1 temperature sensitive graphene-based electrochemical modification Material Fe (CN)6 3-/poly-rGO
Synthesis of (mono) oxy-ethyl dithiocarbonate ethylbenzene
Accurately weighing 0.80g of O-ethyl dithiocarbonate potassium salt, dissolving in 10mL of 50 ℃ ethanol, adding 1.0g of (1-bromoethyl) benzene at the temperature, stirring for 2.5h, adding 30mL of deionized water, extracting with diethyl ether, drying and filtering the organic extract, and removing the solvent to obtain a yellow oily substance, namely O-ethyl dithiocarbonate ethylbenzene.
Synthesis of (di) ionic liquid 1-vinyl-3-butylimidazolium bromide (BVImBr)
9.41g of 1-vinylimidazole, 16.68g of bromobutane and 30mL of methanol were measured and added to a round-bottomed flask in this order, and heated under reflux for 15h, the temperature of the reaction was set to 60 ℃. And cooling to room temperature after the reaction is stopped, pouring the reaction product into a beaker, recrystallizing with acetonitrile-ethyl acetate, filtering, and drying in vacuum to obtain white solid powder, namely the ionic liquid 1-vinyl-3-butylimidazole bromide (BVImBr).
Purification of (tri) N-isopropylacrylamide
10.0020g of NIPAM (N-isopropylacrylamide) monomer is weighed into a 200ml two-neck round-bottom flask, acetone is heated and dropwise until the NIPAM is completely dissolved, the mixture is cooled and refluxed, N-hexane is dropwise added, the volume ratio of the added acetone to the added N-hexane is about 1:6, and the heating is stopped. Cooling to room temperature and transferring into a refrigerator. After the crystal is separated out, taking out and filtering, and washing by using normal hexane. Drying in vacuum at room temperature, and storing in a dryer.
Synthesis of (tetra) homopolymer PNIPAM
6.4048g N-isopropylacrylamide (NIPAM), 0.2536g of ethyl benzene O-ethyldithiocarbonate and 0.0092g of Azobisisobutyronitrile (AIBN) were weighed accurately and added to a 100mL round-bottomed flask, 30mL of dioxane was added thereto, oxygen was removed by argon for 30min, and then the oil bath was heated under reflux for 40h with stirring, the oil bath temperature being set at 85 ℃. And cooling to room temperature after the reaction is finished, carrying out rotary evaporation on the reaction product to remove part of redundant dioxane, dropwise adding the reaction product into 200mL of anhydrous ether, observing that a white precipitate is separated out, filtering, and carrying out vacuum drying to obtain white solid powder, namely the homopolymer PNIPAM.
Synthesis of (penta) Block copolymer poly (NIPAM-b-BVImBr)
Accurately weighed 0.1836g of 1-vinyl-3-butylimidazolium bromide (BVImBr), 0.5081g of PNIPAM and 0.0025g of Azobisisobutyronitrile (AIBN) were added to a 100mL round bottom flask, 30mL of Dimethylformamide (DMF) were added thereto, argon was used for 30min of oxygen removal, and heating and refluxing were carried out for 40h with the oil bath temperature set at 85 ℃. After the reaction is finished, cooling by liquid nitrogen to stop quickly, removing the solvent, then dropwise adding the reactant into 200mL of anhydrous ether to observe that a light yellow precipitate is separated out, filtering, and drying in vacuum to obtain light yellow solid powder, namely the block copolymer poly (NIPAM-b-BVImBr).
Preparation of (VI) graphene oxide GO
67.5mL of concentrated sulfuric acid was accurately measured and added to a three-necked round-bottomed flask, the round-bottomed flask was placed in an ice-water bath to maintain a low temperature, and 2.0051g of high-purity graphite and 1.6057g of NaNO were added to the system3After stirring well, 9.0125g of KMnO was slowly added4Adding solid into round-bottom flask, keeping temperature in the flask below 5 deg.C all the time during adding medicine, heating to 35 deg.C, and reacting for 30 min. When the reaction was near the end, the black suspension became a grey brown viscous mass, which was then allowed to stand at room temperature for one week. Finally, the mixture was diluted with 560.0mL of hot water and 3% H was added dropwise2O2Reducing unreacted manganese ions, and dropwise adding H2O2Until it becomes bright yellow. Centrifugally washing with 0.01M NaOH solution to neutrality, centrifugally washing with deionized water to remove SO4 2-And (3) detecting with saturated barium acetate, washing until no white precipitate is generated, finally washing with ethanol twice, and vacuum drying to obtain graphene oxide GO for later use.
(VII) Synthesis of reduced graphene oxide rGO
Weighing 0.005g of graphene oxide GO powder, adding the graphene oxide GO powder into a 100mL round-bottom flask, adding 10mL of water, ultrasonically dispersing the GO to be dissolved, adding 10mL of ammonia water, stirring for 30min, and adding 1mL of hydrazine hydrate. The reaction was heated under reflux for 24 hours, and the temperature of the oil bath heating was set at 110 ℃. After the heating was stopped, the mixture was cooled and allowed to stand. And (4) freezing and drying the upper layer solution to obtain reduced graphene oxide rGO for later use.
Synthesis of (eight) Complex poly-rGO
Weighing 0.005g of graphene oxide GO powder, adding the graphene oxide GO powder into a 100mL round-bottom flask, adding 10mL of water into the round-bottom flask, carrying out ultrasonic dispersion for 30min, adding 1.0500g of block copolymer poly (NIPAM-b-BVImBr), fully oscillating and dissolving, adding 5mL of hydrazine hydrate into the round-bottom flask to obtain a mixed solution, and adjusting the pH value of the mixed solution to be 9-10. The reaction was heated under reflux for 40 hours, and the temperature of the oil bath heating was set at 110 ℃. Stopping heating, standing for one day, and freeze-drying the upper layer solution to obtain the poly-rGO compound for later use.
The synthesized poly-rGO is characterized by structure and morphology, and the related results are shown in FIGS. 1-4.
In FIG. 1, b is a transmission electron micrograph of poly-rGO, and through TEM electron micrograph observation, the morphology of poly-rGO is not obviously changed compared with GO, and is of an irregular sheet structure, and a large number of folds are formed on the surface.
In fig. 2, c is a photo picture of poly-rGO dispersed in an aqueous solution, as shown in the figure, the water solubility of reduced graphene oxide is greatly improved due to the compounding of the ionic liquid, so that the aqueous solution of poly-rGO of the compound is macroscopically represented as a black solution with good dispersibility.
In FIG. 3, c is the UV-VIS absorption spectrum of the complex poly-rGO, from which the characteristic peak of rGO at 273nm can be seen, indicating that the complex is fully reduced.
FIG. 4 is a graph representing the structure of the composite by using FT-IR, wherein a is an infrared spectrum curve of rGO, b is an infrared spectrum curve of poly (NIPAM-b-BVImBr), and c is an infrared spectrum curve of the composite poly-rGO, and the graph shows that the modified graphene is 1458cm-1And 1544cm-1The characteristic peak appears at 1649cm, and is the characteristic absorption peak of C ═ C on the imidazole ring-1The absorption peak is attributed to the secondary amide C ═ O stretching vibration absorption peak in PNIPAM, 1366cm-1And 1387cm-1The absorption peak is assigned to the characteristic peak of C-N stretching vibration absorption and N-H bending vibration absorption. Thereby the device is provided withIt can be seen that, compared with rGO, the reduced graphene nanosheet contains imidazole rings and amides on the polymer chain, and therefore, it can be inferred that the composite poly (NIPAM-b-BVImBr) is introduced into the graphene.
(nine) electrochemically modified Material Fe (CN)6 3-Synthesis of/poly-rGO
Electrochemical modification material Fe (CN)6 3-poly-rGO is synthesized by a simple anion exchange reaction. 0.05g of the complex poly-rGO synthesized in step (eight) was dissolved in 7mL of deionized water, and 0.15g of K was weighed3[Fe(CN)6]Dissolving in 3mL of deionized water, ultrasonically dispersing the two into a solution, and then adding K3[Fe(CN)6]The solution was added dropwise to the poly-rGO solution. After stirring at room temperature for 24 hours, the mixture was washed several times with hot deionized water. Finally, freeze drying to obtain the electrochemical modified material Fe (CN)6 3-/poly-rGO。
FIGS. 5 a-5 d are GO, rGO, poly-rGO and Fe (CN), respectively6 3-X-ray photoelectron spectrum of poly-rGO. From FIG. 5a, it can be seen that characteristic peaks of C1s and O1s appear at 287.0eV and 543.55eV, respectively. In contrast, in fig. 5b, the peak height of O1s was greatly reduced compared to fig. 5a, illustrating that GO was reduced. As can be seen in FIG. 5c, the composite poly-rGO shows characteristic orbital peaks ascribed to Br3d and N1s at 98.9eV and 396.8eV respectively, and the block copolymerization poly (NIPAM-b-BVImBr) successfully introduced into the graphene can be inferred by the element comparison analysis. Using Fe (CN)6 3-Ion exchange reaction with poly-rGO, FIG. 5d functional material Fe (CN)6 3-The X-ray photoelectron spectrum of poly-rGO shows the characteristic peak of the orbit of Fe2p at 708.2eV, which indicates that the functional material Fe (CN) is successfully synthesized6 3-poly-rGO, demonstrating good ionicity.
Example 2
(one) detection of the thermo-sensitivity of the complex poly-rGO
Taking 10ml of the poly-rGO aqueous solution of the compound prepared in the step (eight) of the example 1, putting the aqueous solution into a 15ml sample bottle, heating the sample bottle for 5min at the temperature of 60 ℃ in a water bath, observing experimental phenomena, and finding that the black solution with better dispersibility gradually changes into black turbid liquid to finally generate black precipitate, standing the sample bottle, wherein the upper layer in the sample bottle is colorless transparent solution, and the lower layer in the sample bottle is black precipitate. After the temperature is returned to room temperature, the black precipitate disappears by gently shaking the sample bottle, and becomes a black solution with good dispersibility, as shown in fig. 6. FIG. 6 is a digital photograph of an aqueous solution of poly-rGO at 20 deg.C (a), 45 deg.C (b) and then restored to 20 deg.C (c), and it can be seen from FIG. 6 that the complex poly-rGO has good temperature sensitivity.
FIG. 7 is a diagram showing the UV-VIS absorption spectra of poly-rGO aqueous solution at 20 deg.C (a), 45 deg.C (b) and restored to 20 deg.C (c), wherein the complex at 20 deg.C has a characteristic absorption peak at 273nm, when the temperature is raised to 45 deg.C, the black polymer is deposited at the bottom due to the change of PNIPAM hydrophilicity and hydrophobicity, resulting in disappearance of the characteristic peak at 273nm, and when the temperature is restored to 20 deg.C, the hydrophilicity is changed again, and the original solution with good dispersibility is restored, and the characteristic peak at 273nm appears, thus further proving that the synthesized complex poly-rGO has good temperature sensitivity, and the cycle is reversible, and embodies the "on" and "off" effects.
Ultraviolet test for temperature-sensitive reversibility of (II) compound poly-rGO
The absorbance value of the aqueous solution of the compound poly-rGO prepared in the step (eight) in the embodiment 1 is measured at the wavelength of 273nm under the conditions of room temperature of 20 ℃ and high temperature of 45 ℃, and the room temperature → high temperature → the room temperature → the high temperature are repeatedly tested for ten times in a circulating way, because the compound poly-rGO is in a hydrophobic state at the high temperature, the absorbance is approximately 0, the compound poly-rGO is changed into a hydrophilic state after the room temperature is recovered, and the circulation is reversible.
As shown in fig. 8, the thermo-sensitive cycle diagram of poly-rGO at room temperature 20 ℃ and high temperature 45 ℃ shows a peak → no peak → peak change in the uv absorption spectrum curve due to the hydrophilic → hydrophobic → hydrophilic state of the complex poly-rGO when the temperature is shifted between 20 ℃ and 45 ℃. As can be seen from FIG. 8, the synthesized complex poly-rGO has temperature sensitivity, is reversible in cycle, and has good on/off effects.
(III) Fe (CN)6 3-Preparation of/poly-rGO/GC
1. Pretreatment of glassy carbon electrodes
The experiment adopts a glassy carbon electrode with the diameter of 3mm, and uses Al with the diameters of 1.0, 0.3 and 0.05 mu m respectively2O3And polishing the glassy carbon electrode, and ultrasonically cleaning for 1min by using ultrapure water. A glassy carbon electrode (GC) is used as a working electrode, a platinum wire is used as a counter electrode, and an Ag/AgCl electrode is used as a reference electrode to form a three-electrode system. At 1mM K3Fe(CN)6The electrochemical Cyclic Voltammetry (CV) test is carried out in a 1M KCl solution, the scanning range is-200 and 800mV (vs. Ag/AgCl), and the scanning rate is 200 mV/s. When the peak position difference of the oxidation peak and the reduction peak of the electrode is less than 70.0mV, the electrode meets the requirement of activation cleaning. Taking out the glassy carbon electrode, cleaning with ultrapure water, and purifying with high-purity nitrogen (N)2) And drying for later use.
2、Fe(CN)6 3-Preparation of/poly-rGO/GC
7.0. mu.L of Fe (CN) prepared in example 1 was taken6 3-Dripping the poly-rGO solution on the surface of a pretreated glassy carbon electrode, covering a dry and clean beaker on the electrode, drying for 24 hours at room temperature, slowly evaporating water, and forming a layer of film on the surface of the electrode to obtain Fe (CN)6 3-a/poly-rGO/GC modified electrode.
This experiment was performed in 0.1M pH 7 PBS buffer. Adopts a three-electrode system, an Ag/AgCl electrode is taken as a reference electrode, a platinum electrode is taken as an auxiliary electrode, and Fe (CN)6 3-the/poly-rGO/GC modified electrode is used as a working electrode.
(IV) Fe (CN)6 3-Electrochemical characterization test of/poly-rGO/GC
In the electrochemical characterization test, the experiment was performed at a sweep rate of 200mV/s in a 0.1M buffer solution with a pH of 7.0. A three-electrode system is adopted, an Ag/AgCl electrode is taken as a reference electrode, a platinum electrode is taken as an auxiliary electrode, and Fe (CN) is respectively used6 3-the/poly-rGO/GC and poly-rGO/GC modified electrodes are working electrodes. Under the same experimental conditions, Fe (CN)6 3-Continuously scanning the poly-rGO/GC modified electrode as a working electrode for 50 circles to detect the stability of the electrode materialQualitative and applicability.
From FIG. 9, it can be observed that curves a and b are Fe (CN) compared to poly-rGO/GC (b)6 3-the/poly-rGO/GC (a) has a pair of redox peaks with good reversibility, the redox currents are-2.418 mu A and 3.334 mu A respectively, the peak difference is 75mV, and the redox peaks correspond to the redox peaks of potassium ferricyanide in the same environment, which shows that ferricyanide is successfully loaded on the surface of an electrode, so that the composite material shows the characteristic of electric activity in electrochemical detection.
As can be seen from FIGS. 10 and 11, the peak current changes within 5% after 50 consecutive scans, which indicates that the electrochemical sensor is Fe (CN)6 3-The poly-rGO/GC has good stability and can be used as an electrochemical sensor.
(V) Fe (CN)6 3-Thermo-sensitive reversible electrochemical cyclic voltammetry test of/poly-rGO/GC modified electrode
In a temperature-sensitive reversible electrochemical cyclic voltammetry test, the reaction is carried out at a sweep rate of 200mV/s in a buffer solution with a pH of 7.0 at 0.1M. Adopts a three-electrode system, an Ag/AgCl electrode is taken as a reference electrode, a platinum electrode is taken as an auxiliary electrode, and Fe (CN)6 3-the/poly-rGO/GC and the poly-rGO/GC modified electrodes are working electrodes, and the electrochemical cyclic voltammetry is used for carrying out cyclic detection at two temperatures under the two temperatures of 20 ℃ and 45 ℃ respectively.
In FIG. 12, Fe (CN)6 3-The poly-rGO/GC has a pair of reversible redox peaks at 20 ℃, the redox currents are-2.385 mu A and 3.295 mu A respectively, the peak difference is 72mV, and the peak current and the peak difference show that the electron transport performance on the surface of the electrode is better and the electrode is in an 'on' state. However, when the temperature is increased to 45 ℃, the cyclic voltammetry signal is greatly changed, the peak current is reduced, the oxidation-reduction peak of potassium ferricyanide disappears, and the electron transport process on the surface of the electrode is completely prevented, and the electrode is shown in an off state. The results indicate that the electron transport capability of such modified electrodes decreases with increasing temperature, presumably due to the increase in temperature, which hinders electron transport due to collapse of the poly-rGO chain.
FIG. 13 shows, by comparisonIt is known that, when the temperature is repeatedly changed at 20 ℃ and 45 ℃, Fe (CN)6 3-The poly-rGO/GC still well keeps the original circulating reversible temperature-sensitive intelligent response. This is particularly manifested in the reversibility of the peak current, and this reversible transition can be repeated well all the time. Thus proving Fe (CN)6 3-The poly-rGO can be used as a temperature sensitive graphene-based electrochemical sensor.
(VI) Fe (CN)6 3-Research on electrocatalytic response of/poly-rGO/GC modified electrode to ascorbic acid
Using Fe (CN)6 3-the/poly-rGO/GC modified electrode carries out electrochemical detection on ascorbic acid. As shown in fig. 14, the cathodic peak gradually decreased until it disappeared after the addition of 0.15mM ascorbic acid. Indicating that potassium ferricyanide undergoes a typical electrocatalytic reaction against ascorbic acid.
(VII) Fe (CN)6 3-Detection of ascorbic acid by poly-rGO/GC modified electrode
Fe(CN)6 3-Continuously adding current response curves of ascorbic acid with different concentrations into a poly-rGO/GC modified electrode pair, and testing Fe (CN) on the premise of not changing a three-electrode system6 3-I-T curve of/poly-rGO/GC modified electrode in PBS (pH 7.0).
As can be seen from FIG. 15, Fe (CN)6 3-the/poly-rGO/GC modified electrode showed a good linear relationship with the reduction peak current in the ascorbic acid concentration range of 30 μ M-0.3 mM with a linear regression equation of y-0.006 x-0.1517 (R-0.997, N-13) and a detection limit of 5 μ M (S/N).
From the slope of the straight line in the calibration curve of FIG. 16, the sensitivity of the modified electrode was 85.6mA ∙ cm-2∙M-1。Fe(CN)6 3-The detection limit of the/poly-rGO/GC modified electrode on ascorbic acid is low, and the sensitivity is high.
Claims (6)
1.Fe(CN)6 3-The application of/poly-rGO/GC modified electrode in electrochemical detection of ascorbic acid is characterized in that Fe (CN)6 3-Poly-rGO/GC modified electrodeIs prepared from thermo-sensitive graphene-based electrochemical modified material Fe (CN)6 3-Poly-rGO coated on glassy carbon electrode GC to prepare Fe (CN)6 3-a/poly-rGO/GC modified electrode; the thermo-sensitive graphene-based electrochemical modification material Fe (CN)6 3-The preparation method of the poly-rGO comprises the following steps: firstly, under the action of an azodiisobutyronitrile thermal initiator, dimethylformamide is taken as a reflux solvent, and 1-vinyl-3-butylimidazole bromide salt BVImBr and homopolymer PNIPAM are taken as ionic liquid to generate block copolymer poly (NIPAM-b-BVImBr); then, preparing a compound poly-rGO by utilizing pi-pi non-covalent modification between graphene and ionic liquid; finally synthesizing temperature-sensitive graphene-based electrochemical modification material Fe (CN) through anion exchange reaction6 3-/poly-rGO。
2. The use according to claim 1, wherein the temperature-sensitive graphene-based electrochemical modification material is Fe (CN)6 3-The preparation method of the poly-rGO comprises the following specific steps:
1) synthesis of homopolymer PNIPAM: uniformly mixing N-isopropylacrylamide NIPAM, oxygen-ethyl dithiocarbonate ethylbenzene and azobisisobutyronitrile AIBN, adding dioxane, deoxidizing by argon for 30min, setting the oil bath temperature at 85 ℃, and heating and refluxing for 40 h; cooling, rotary evaporating, dropwise adding the reactant into anhydrous ether, filtering, and vacuum drying to obtain homopolymer PNIPAM;
2) synthesis of Block copolymer poly (NIPAM-b-BVImBr): uniformly mixing 1-vinyl-3-butylimidazole bromide, BVImBr, PNIPAM and azobisisobutyronitrile AIBN, adding dimethylformamide DMF, deoxidizing by argon for 30min, setting the oil bath temperature at 85 ℃, and heating and refluxing for 40 h; cooling, dropwise adding the reaction product into anhydrous ether, filtering, and drying to obtain block copolymer poly (NIPAM-b-BVImBr);
3) synthesis of complex poly-rGO: carrying out ultrasonic dispersion on a proper amount of graphene oxide GO powder and water, adding a block copolymer poly (NIPAM-b-BVImBr), dissolving, adding hydrazine hydrate to obtain a mixed solution, setting the oil bath temperature to be 110 ℃, carrying out heating reflux reaction on the mixed solution for 40 hours, cooling, taking an upper layer solution, and carrying out freeze drying to obtain a compound poly-rGO;
4) electrochemical modification material Fe (CN)6 3-Synthesis of poly-rGO: taking the complex poly-rGO and K3[Fe(CN)6]Dissolving in deionized water, ultrasonic dispersing, and dissolving K in deionized water3[Fe(CN)6]Dropwise adding the solution into poly-rGO solution, stirring and reacting for 24h at room temperature, washing, and freeze-drying to obtain Fe (CN)6 3-/poly-rGO。
3. Use according to claim 2, characterized in that in step 1) the ratio of the amounts of substances of N-isopropylacrylamide NIPAM, ethyl-oxoethyldithiocarbonate ethylbenzene and azobisisobutyronitrile AIBN is 48-52:1: 0.03-0.07.
4. Use according to claim 2, characterized in that in step 2) the ratio of the amounts of the 1-vinyl-3-butylimidazolium bromide, BVImBr, PNIPAM and azobisisobutyronitrile AIBN is 78-82:1: 0.13-0.17.
5. The use according to claim 2, wherein in step 3), the mass ratio of GO to Poly (NIPAM-b-BVImBr) is 1: 18-22.
6. The use according to claim 2, wherein in step 3), after the addition of hydrazine hydrate, the pH of the mixed solution is adjusted to between 9 and 10.
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