Phenols electrochemical sensor based on ionic liquid-graphene oxide sensitive membrane

[0037] Example 1

[0038] A new type of ionic liquid 4-hydroxy-1-methyl-1-(3-pyrrolylpropyl)-piperidine bromide salt, and its synthesis method is as follows:

[0039] Weigh 4-hydroxy-N-methylpiperidine (0.4549g, 3mmol) in a 50mL three-necked flask, add 15mL toluene as a solvent, and add 1-(3-bromopropyl)pyrrole (0.5640g, 3.3mmol) dropwise Put it in a three-necked flask, place it in an oil bath at 80°C, and stir for 15 hours under nitrogen protection to form a yellow oily insoluble body. Cool to room temperature, separate the toluene layer, add water to dissolve the yellow oily liquid, and extract with ether. The water layer was evaporated to dryness to obtain a yellow oily liquid, that is, the product of the present invention 4-hydroxy-1-methyl-1-(3-pyrrolpropyl)-piperidine bromide ionic liquid 0.8510g (yield 93.9%), 1 H NMR (D 2 O) δ: 6.76 (d, 2H), 6.11 (d, 2H), 3.98 (t, 2H), 3.89 (d, 1H) 3.38 (t, 2H), 3.20 (d, 2H), 3.12 (d, 2H) ), 2.92 (s, 3H), 2.16 (t, 2H), 1.96 (d, 2H), 1.74 (d, 2H); m/z=222.92.

[0040] Synthetic route such as figure 1 As shown, the one-step method is adopted to synthesize 4-hydroxy-1-methyl-1-(3-pyrrolylpropyl)-piperidine bromide ionic liquid, the method is simple, the post-treatment operation is simple and the yield is high.

[0041] Example 2

[0042] A carboxylated graphene oxide-ionic liquid composite nano material, and its preparation method is as follows:

[0043] (1) Combine 10mg graphene oxide (GO), 0.5g sodium hydroxide solid (NaOH) and 0.5g chloroacetic acid (ClCH 2 COOH) was dissolved in 10 mL of water, sonicated uniformly, and stirred on a magnetic stirrer for 2 hours. After centrifugal separation, the solid was washed with water to neutrality, and dried under vacuum at 60°C to obtain 9.5 mg of carboxylated graphene oxide, which was recorded as GO-COOH. Add all the obtained carboxylated graphene oxide to 10mL0.01mol·L -1 In NaOH solution, the reaction was stirred on a magnetic stirrer for 2 hours, centrifuged, the solid was washed with water to neutrality, and dried under vacuum at 60°C to obtain 9.0 mg of carboxylated graphene oxide in an alkalized form, which was recorded as GO-COONa.

[0044] The graphene oxide used has no special requirements;

[0045] Specifically, the graphene oxide in this embodiment is self-made by the laboratory, and the preparation method is as follows:

[0046] Add 17mL98wt% concentrated sulfuric acid dropwise to 0.45g KNO under ice bath 3 In the mixture with 0.5g graphite powder, continue to stir, add 2.25g potassium permanganate within 1h, stir the reaction for 2h, then move the reaction flask to room temperature, stir for 5 days, get a black viscous liquid; Add 50mL of 5wt% sulfuric acid to the viscous liquid, stir for 2h, add 15g of 30wt% hydrogen peroxide, continue stirring for 2h, continue to stir, add 50mL of sulfuric acid and hydrogen peroxide mixed solution (in the mixed solution) The concentration of sulfuric acid is 3wt% and the concentration of hydrogen peroxide is 0.5wt%), stand for 2 days to settle, discard the upper layer to obtain a brown-black slurry, wash it with water until it is neutral, and ultrasonically peel for 30 minutes to obtain a clear yellow solution. Graphene oxide (GO) is obtained by drying.

[0047] (2) Add 9.0 mg of alkalized form of carboxylated graphene oxide (GO-COONa) and 0.2 g of the ionic liquid prepared in Example 1 to 10 mL of water, stir and react at 40°C for 1 hour, centrifuge for separation, and use water for solid Wash to remove excess ionic liquid and generated sodium bromide (NaBr), and vacuum dry at 60°C to obtain 8.0 mg of carboxylated graphene oxide-ionic liquid composite nanomaterial (GO-COO-IL).

[0048] figure 2 (A) and (b) are respectively the transmission electron micrographs of the carboxylated graphene oxide and the carboxylated graphene oxide-ionic liquid composite nanomaterial prepared in this embodiment. It can be seen from the figure that carboxylated graphene oxide (a) and carboxylated graphene oxide-ionic liquid composite nanomaterials (b) are both typical lamellar nanostructures, with a diameter of about several hundred nanometers and a thickness of about A few nanometers. Comparing the two structures, it is found that the surface of carboxylated graphene oxide is modified by a transparent ionic liquid, without changing the geometric structure of carboxylated graphene oxide, it can maintain its large specific surface area, high electronic conductivity and other characteristics, which is conducive to the construction of excellent electrical properties. Chemical sensor.

[0049] image 3 The middle curves a, b, and c are the infrared spectra of the carboxylated graphene oxide prepared in this embodiment, the ionic liquid prepared in embodiment 1, and the carboxylated graphene oxide-ionic liquid composite nanomaterial prepared in this embodiment, respectively. It can be seen from curve a that there is O-H stretching vibration in graphene oxide (ν O-H , 3411cm -1 ); C=O stretching vibration (ν C=O , 1735cm -1 ), C=C stretching vibration (ν C=C ,1627cm -1 ) And C-O stretching vibration (ν C-O ,1224cm -1 ). Curve b is the infrared spectrum curve of 4-hydroxy-1-methyl-1-(3-pyrrolylpropyl)-piperidine bromide ionic liquid. From the figure, the OH stretching vibration of piperidinol in the ionic liquid can be observed (Ν O-H , 3354cm -1 ); -CH 3 Antisymmetric stretching vibration (2946cm -1 ); backbone stretching vibration of pyrrole and piperidine heterocycles (1630cm -1 , 1464cm -1 ); the stretching vibration of the C-N bond on the pyrrole and piperidine groups (ν C-N , 1379cm -1 ); the stretching vibration of the C-O bond on the piperidinol group (ν C-O ,1280cm -1 ); Out-of-plane bending vibration of pyrrole ring (1090cm -1 );-CH 2 Plane rocking vibration (ν C-H , 742cm -1 ); C-H stretching vibration on the pyrrole ring (ν C-H , 618cm -1 ). Curve c is the infrared spectrum of the composite nanomaterial (GO-COO-IL) after carboxylated graphene oxide is combined with ionic liquid. It can be seen from curve c that 3399cm -1 The graphene oxide and the OH stretch vibration peaks on the ionic liquid overlap and are offset. The characteristic absorption peaks of GO and IL exist, and some characteristic absorption peaks are slightly shifted. It should be caused by the mutual influence after the two are combined. , Which shows that the ionic liquid has been successfully combined with graphene oxide.

[0050] Example 3

[0051] Such as Figure 4 As shown, a carboxylated graphene oxide-ionic liquid composite nano-material modified electrode includes an insulating layer 1, a glassy carbon substrate 3, an electrode lead 4 electrically connected to the glassy carbon substrate 3, and the surface of the glassy carbon substrate 3 is coated with carboxylation Graphene oxide-ionic liquid nano-composite nano-material film 2. The preparation method of the carboxylated graphene oxide-ionic liquid modified electrode includes the following steps in sequence:

[0052] (1) Pretreatment of glassy carbon electrode: first polish the glassy carbon electrode (3 mm in diameter) with alumina polishing powder with a particle size of 0.3 micron and 0.05 micron, rinse with water, and then use nitric acid solution (65wt% Nitric acid and water equal volume mixed solution), ethanol solution (95wt% ethanol and water equal volume mixed solution) and water are ultrasonically cleaned on the glassy carbon electrode for 1 minute, and the ultrasonic cleaning temperature is 20-30℃.

[0053] (2) Add 2.0 mg of the carboxylated graphene oxide-ionic liquid composite nano material prepared in Example 2 into 4.0 mL of water, and sonicate for 25 minutes to disperse uniformly, and obtain a concentration of 0.5 mg·mL -1 The carboxylated graphene oxide-ionic liquid dispersion.

[0054] (3) Apply 8 microliters of the carboxylated graphene oxide-ionic liquid dispersion obtained in step (2) to the surface of the glassy carbon electrode pretreated in step (1), and evaporate the solvent to obtain carboxylated graphene oxide-ion Liquid modified electrode.

[0055] Regarding step (2), the concentration of the carboxylated graphene oxide-ionic liquid dispersion applied on the surface of the glassy carbon electrode is the optimal concentration determined by the relationship between the concentration of the dispersion and the response current of honokiol. Respectively configure 0.1, 0.3, 0.5, 0.8, 1.0 mg·mL -1 The carboxylated graphene oxide-ionic liquid dispersion was drip-coated on the surface of the pre-treated glassy carbon electrode. The dripping volume was 8 microliters. -5 mol·L -1 Of Honokiol by differential pulse voltammetry, and it was found that when the concentration of the dispersion was 0.1 to 0.5 mg·L -1 During the period, the oxidation peak-to-peak current gradually increases to a concentration of 0.5 mg·mL -1 After that, as the concentration of the dispersion increases, the peak-to-peak current of oxidation decreases. It may be because the concentration is too large, which causes the electrode surface film to be too thick, which hinders electron transfer. Therefore, the subsequent detection of honokiol, The concentration of the carboxylated graphene oxide-ionic liquid dispersion applied on the surface of the glassy carbon is 0.5 mg·mL -1.

[0056] Regarding step (3), the amount of carboxylated graphene oxide-ionic liquid dispersion applied on the surface of the glassy carbon electrode is determined by the volume of the dispersion and the response current curve of honokiol Optimal dripping amount. Drop 1, 4, 6, 8, 10, 12, 14, 16 microliters 0.5mg·mL respectively -1 Carboxylated graphene oxide-ionic liquid dispersion on the surface of the pre-treated glassy carbon electrode, to 1.0×10 -5 mol·L -1 The differential pulse voltammetry scan of Honokiol showed that the oxidation peak current gradually increased when the volume of the dispersion liquid was between 1 and 8 microliters, and reached the maximum when the volume was 8 microliters. As the amount of droplet coating increased, the peak-to-peak oxidation current decreased. This may be due to the fact that the coating volume was too large, which caused the electrode surface film to be too thick and hindered the electron transfer. Therefore, the subsequent detection of honokiol should be applied to the glass. The volume of the carboxylated graphene oxide-ionic liquid dispersion on the carbon surface is 8 microliters.