Preparation and application of Zn-MOFs derived carbon nanosheet array / three-dimensional graphene composite material combined with molecular imprinting technology

Abstract

The invention discloses a preparation method of a Zn-MOFs derived carbon nanosheet array / three-dimensional graphene composite material combined with a molecular imprinting technology as an electrochemical sensor electrode material. The invention aims to solve the problems of low sensitivity, poor selectivity and the like of the existing sensor in detecting carbamazepine. The preparation method mainly comprises the following steps: 1, preparing three-dimensional graphene by a chemical vapor deposition method; 2, preparing a Zn-MOFs nanosheet array / three-dimensional graphene by a precipitation method; 3, preparing a carbon nanosheet array / three-dimensional graphene through heat treatment; and 4, preparing the molecularly imprinted polymer coated carbon nanosheet array / three-dimensional graphene. High conductivity and rich active sites of the Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene are combined with high selectivity of a molecular imprinting technology to jointly improve the electrochemical performance of the electrode, and the electrode has high sensitivity (1.41 [mu] A.[ mu] M <-1 >, 0-10 [mu] M and 0.559 [mu] A.[ mu] M <-1 >, 10-60 [mu] M) and low detection limit (31 nM) when being used for detecting carbamazepine.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterial preparation and relates to a Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene combined with molecular imprinting technology as an electrode material for electrochemical detection of carbamazepine with high sensitivity. Background Art

[0002] Epilepsy is one of the most common serious brain diseases, affecting more than 70 million people worldwide. Symptoms of epilepsy are usually loss of consciousness and tonic-clonic seizures. When tonic-clonic seizures occur, the mortality rate can be as high as 10% to 38%. Carbamazepine (CBZ) is a common and effective anti-epileptic drug that is widely used to treat epileptic disorders. However, its therapeutic window is narrow, and the normal therapeutic carbamazepine concentration in serum ranges from 17 to 51 μM. When the concentration is higher than 60 μM, patients will experience severe symptoms such as difficulty breathing and coma. Therefore, accurate detection of CBZ concentration is crucial.

[0003] Molecular imprinting technology (MIT) is an experimental technique that obtains molecularly imprinted polymers (MIPs) by polymerizing functional monomers in the presence of a template molecule. Removal of the template molecule leaves behind a cavity that specifically binds to the template molecule. MIT can improve electrode selectivity. In a potassium ferricyanide solution, the complexation of the cavity with the template molecule hinders the redox reaction of potassium ferricyanide, resulting in a decrease in peak current and enabling detection of the template molecule. Metal-organic framework (MOF) derivatives inherit the advantages of MOFs, such as large surface area, abundant active sites, excellent electrocatalytic performance, high conductivity, and stability. Aligned carbon nanosheet arrays provide direct electron transport and avoid nanosheet stacking. Furthermore, the -OH functional groups on the carbon nanosheet surface can form intermolecular hydrogen bonds with C6H6O2. ZnO nanoparticles formed on the carbon nanosheets can also coordinate with C6H6O2, improving the stability of the MIP coating. Three-dimensional graphene with excellent conductivity, prepared by chemical vapor deposition, can provide a stable support substrate for Zn-MOF-derived carbon nanosheet arrays. Therefore, the Zn-MOF-derived carbon nanosheet array / 3D GF combined with MIT technology is expected to significantly improve the electrochemical performance for detecting CBZ.

[0004] In summary, the present invention prepared a Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene combined with molecular imprinting technology, which exerted the synergistic effect of the three and was used to detect carbamazepine. The electrode has excellent electrochemical properties and has good clinical application prospects. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of low sensitivity and poor selectivity of existing materials in detecting carbamazepine. A Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene electrode material combined with molecular imprinting technology has been developed. The preparation method of the electrode material is as follows:

[0006] 1. Preparation of three-dimensional graphene by chemical vapor deposition

[0007] Three-dimensional graphene was prepared using chemical vapor deposition. For detailed parameters, please refer to our previous patent: CN109781822B.

[0008] 2. Preparation of Zn-MOFs Nanosheet Arrays / 3D Graphene by Precipitation Method

[0009] 250-350 mg of Zn(NO3)2·6H2O and 580-690 mg of C4H6N2 were ultrasonically dispersed in 15-30 mL of water, and 3D GF was inserted into the mixed solution of Zn(NO3)2 and C4H6N2. After standing at room temperature for 8-24 h, the Zn-MOFs nanosheet array / 3D graphene was obtained by washing and freeze-drying.

[0010] 3. Preparation of carbon nanosheet arrays / 3D graphene by heat treatment

[0011] The Zn-MOFs nanosheet array / 3D graphene obtained in step 2 was placed in a tube furnace and heated at a temperature of 400-600 °C under argon gas protection at a heating rate of 3-8 °C·min -1 Under the condition of 40 to 80 min, carbon nanosheet arrays / three-dimensional graphene are obtained;

[0012] 4. Preparation of Molecularly Imprinted Polymer-Coated Carbon Nanosheet Arrays / 3D Graphene

[0013] The carbon nanosheet array / 3D graphene obtained in step 3 was transferred to ITO glass as a working electrode and placed in [Fe(CN)6] 3- / 4- The solution was electropolymerized with 10 cycles, a voltage range of -0.1 to 0.6 V, and a scan rate of 10 to 100 mV·s -1 Then, 0.05-0.15 M NaOH solution was used for standing washing for 10-90 min to remove CBZ molecules, thereby obtaining molecularly imprinted polymer-coated carbon nanosheet arrays / three-dimensional graphene.

[0014] Compared with the existing technology, the present invention has the following beneficial effects:

[0015] (1) A Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene was prepared by molecular imprinting technology. The Zn-MOFs were grown at room temperature on the three-dimensional graphene surface prepared by chemical vapor deposition. The process is simple and environmentally friendly. Annealing treatment can derive the Zn-MOFs nanosheet array into a carbon nanosheet array. The nanosheet array has a large specific surface area, abundant active sites, and high electrical conductivity.

[0016] (2) The high conductivity and abundant active sites of Zn-MOFs-derived carbon nanosheet arrays / three-dimensional graphene combined with the high selectivity of molecularly imprinted polymers improve the electrochemical performance of the electrode, and the detection of carbamazepine has a high sensitivity (1.41 μA·μM -1 , 0~10μM and 0.559μA·μM -1 , 10-60 μM) and a low detection limit (31 nM). BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene morphology combined with molecular imprinting technology;

[0018] Figure 2 A Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene structure combined with molecular imprinting technology;

[0019] Figure 3 Electrochemical performance of a Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene electrode combined with molecular imprinting technology;

[0020] Figure 4 A Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene electrode combined with molecular imprinting technology was used to detect CBZ images using the DPV method;

[0021] Figure 5 A graph showing the anti-interference, reproducibility, repeatability, and stability tests of a Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene electrode combined with molecular imprinting technology;

[0022] Figure 6 Morphology of Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene. DETAILED DESCRIPTION

[0023] Specific embodiment 1: A method for preparing Zn-MOFs-derived carbon nanosheet arrays / three-dimensional graphene combined with molecular imprinting technology is specifically carried out according to the following steps:

[0024] 1. Preparation of three-dimensional graphene by chemical vapor deposition

[0025] Three-dimensional graphene was prepared using chemical vapor deposition. For detailed parameters, please refer to our previous patent: CN109781822B.

[0026] 2. Preparation of Zn-MOFs Nanosheet Arrays / 3D Graphene by Precipitation Method

[0027] 250-350 mg of Zn(NO3)2·6H2O and 580-690 mg of C4H6N2 were ultrasonically dispersed in 15-30 mL of water, and 3D GF was inserted into the mixed solution of Zn(NO3)2 and C4H6N2. After standing at room temperature for 8-24 h, the Zn-MOFs nanosheet array / 3D graphene was obtained by washing and freeze-drying.

[0028] 3. Preparation of carbon nanosheet arrays / 3D graphene by heat treatment

[0029] The Zn-MOFs nanosheet array / 3D graphene obtained in step 2 was placed in a tube furnace and heated at a temperature of 400-600 °C under argon gas protection at a heating rate of 3-8 °C·min -1 Under the condition of 40 to 80 min, carbon nanosheet arrays / three-dimensional graphene are obtained;

[0030] 4. Preparation of Molecularly Imprinted Polymer-Coated Carbon Nanosheet Arrays / 3D Graphene

[0031] The carbon nanosheet array / 3D graphene obtained in step 3 was transferred to ITO glass as a working electrode and placed in [Fe(CN)6] 3- / 4- The solution was electropolymerized with 10 cycles, a voltage range of -0.1 to 0.6 V, and a scan rate of 10 to 100 mV·s -1 Then, 0.05-0.15 M NaOH solution was used for standing washing for 10-90 min to remove CBZ molecules, thereby obtaining molecularly imprinted polymer-coated carbon nanosheet arrays / three-dimensional graphene.

[0032] Specific embodiment 2: A method for preparing Zn-MOFs-derived carbon nanosheet arrays / three-dimensional graphene combined with molecular imprinting technology. The difference between this embodiment and the first embodiment is that the amount of Zn(NO3)2·6H2O added in the second embodiment is 250mg~200g, and the rest is the same as the first embodiment;

[0033] Specific embodiment three: A method for preparing Zn-MOFs-derived carbon nanosheet arrays / three-dimensional graphene combined with molecular imprinting technology. The difference between this embodiment and the first and second embodiments is that the growth time in step 2 is 8h to 12h, and the other aspects are the same as the first and second embodiments;

[0034] Specific embodiment 4: A method for preparing Zn-MOFs-derived carbon nanosheet arrays / three-dimensional graphene combined with molecular imprinting technology. The difference between this embodiment and embodiment 1, embodiment 2 and embodiment 3 is that the heat treatment temperature in step 3 is 300°C to 600°C, and the rest is the same as embodiment 1, embodiment 2 and embodiment 3.

[0035] Specific embodiment five: A method for preparing Zn-MOFs-derived carbon nanosheet arrays / three-dimensional graphene combined with molecular imprinting technology. The difference between this embodiment and embodiment one, embodiment two, embodiment three and embodiment four is that in step four, CBZ is 0.5-1mM and C6H6O2 is 3-6mM, and the rest is the same as embodiment one, embodiment two, embodiment three and embodiment four.

[0036] The following test was used to verify the effect of the present invention:

[0037] The preparation method of Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene combined with molecular imprinting technology in this experiment is specifically carried out according to the following steps:

[0038] 1. Preparation of three-dimensional graphene (3D GF) by chemical vapor deposition

[0039] Three-dimensional graphene was prepared using chemical vapor deposition. For detailed parameters, please refer to our previous patent: CN109781822B.

[0040] 2. Preparation of Zn-MOFs Nanosheet Array / 3D Graphene (Zn-MOFs Nanosheet Array / 3D GF) by Precipitation Method

[0041] 298 mg of Zn(NO3)2·6H2O and 650 mg of C4H6N2 were ultrasonically dispersed in 20 mL of water, and 3D GF was inserted into the mixed solution of Zn(NO3)2 and C4H6N2. After standing at room temperature for 12 h, the Zn-MOFs nanosheet array / 3D graphene was obtained by washing and freeze-drying.

[0042] 3. Preparation of Carbon Nanosheet Array / 3D Graphene (CAN / 3D GF) by Heat Treatment

[0043] The Zn-MOFs nanosheet array / 3D graphene obtained in step 2 was placed in a tube furnace and heated to 500 °C at a rate of 5 °C min-1 under argon gas protection. -1 Under the condition of 500 nm, the carbon nanosheet array / three-dimensional graphene was obtained under the holding time of 60 min;

[0044] 4. Preparation of Molecularly Imprinted Polymer-Coated Carbon Nanosheet Array / 3D Graphene (MIP@CNA / 3DGF)

[0045] The carbon nanosheet array / 3D graphene obtained in step 3 was transferred to ITO glass as a working electrode and placed in [Fe(CN)6] 3- / 4- The solution was electropolymerized with 10 cycles, a voltage range of -0.1 to 0.6 V, and a scan rate of 50 mV·s -1 Then, 0.1 M NaOH solution was used for washing for 60 min to remove the CBZ molecules, and molecularly imprinted polymer-coated carbon nanosheet arrays / three-dimensional graphene were obtained.

[0046] The characterization and performance of the prepared imprinted polymer-coated carbon nanosheet array / three-dimensional graphene electrode are as follows:

[0047] The morphology of MIP@CNA / 3D GF is as follows Figure 1 As shown. Zn-MOFs nanosheet arrays with a thickness of ∼200 nm were uniformly grown on the surface of 3D GF ( Figure 1 ac). Zn-MOFs nanosheet array / 3D GF becomes CNA / 3D GF after annealing ( Figure 1 df), with the increase of temperature, Zn 2+ The coordination bond between C4H6N2 and nanosheets was destroyed, and the thickness of nanosheets became ∼100 nm. The surface of nanosheets changed from smooth edges to rough grain size and roundness due to thermal etching and carbonization. The surface of CNA / 3D GF became rough after electropolymerization ( Figure 1 This roughness originates from the growth process of MIPs, during which polymer chains form a certain thickness of texture on CNA / 3D GF. Transmission images show that the size of carbon nanosheets is ~2μm ( Figure 1 i). There are lattice stripes of about 0.260 nm on the carbon nanosheets, corresponding to the (002) of ZnO ( Figure 1 j). Figure 1 k shows three diffraction rings corresponding to the (200), (102) and (100) crystal planes of ZnO, indicating that ZnO is dispersed in an island-like manner on the surface of the carbon nanosheets. Due to the amorphous structure of carbon, no diffraction rings of carbon are observed. In addition, C, N, O and Zn elements are uniformly distributed in the CNA / 3D GF ( Figure 1 lp).

[0048] Figure 2 The crystal structure, chemical composition and elemental states of CAN / 3D GF are shown. Figure 2In a, the diffraction peaks of Zn-MOFs nanosheet array / 3D GF are highly consistent with those of the standard card (C5H7NO4Zn·2H2O, PDF#49-2015) and (carbon, PDF#26-1076). For CNA / 3DGF, the diffraction peaks at 31.8°, 34.4°, 36.3°, 47.5° and 56.6° correspond to (100), (002), (101), (102), (110) of ZnO (PDF#36-1451). After annealing, the diffraction peaks of Zn-MOFs disappear, the diffraction peaks of ZnO appear in CAN / 3D GF, and the diffraction peak of carbon is still at 26.6°. Figure 2 In the FTIR spectrum of b, 421 and 1584 cm -1 The vibration bands at 759, 1145 and 1306 cm correspond to the stretching vibrations of Zn-N and CN. -1 The peak at 1444 cm corresponds to the bending signal of the imidazole ring. -1 The peaks at 2927 and 3133 cm correspond to the stretching vibration of the imidazole ring. -1 The vibration peaks at 470 cm-1 belong to the stretching vibrations of aromatic and aliphatic CH, respectively. -1 The new vibration band that appears at belongs to the stretching vibration of Zn-O. Figure 2 As shown in c, C1s, O1s and Zn2p peaks can be observed in the XPS spectrum. The C1s spectrum consists of a CC peak at 284.7 eV and a COC peak at 286 eV ( Figure 2 d). The O1s spectrum is divided into three peaks (530.9, 531.1 and 532.1 eV), which are C=O, C-OH and COOH respectively. Figure 2 e). In the Zn2p spectrum, two peaks appear at 1022 and 1044.9 eV, which are Zn2p 1 / 2 and Zn2p 3 / 2 ( Figure 2 f).

[0049] The electrochemical performance of MIP@CNA / 3D GF is shown in Figure 3 As shown in Figure 2, with the increase of the number of electropolymerization cycles, the polymer film formed by C6H6O2 and CBZ on the CNA / 3D GF surface becomes thicker, hindering the [Fe(CN)6] 3- / 4- The redox of Fe(CN)6 results in the CV redox peak current [Fe(CN)6] 3- / 4- Gradually decrease ( Figure 3 a). Figure 3As shown in b, the redox peak current of CNA / 3D GF is the highest. Due to the low conductivity of polymer and CBZ, the redox peak current of CNA / 3D GF is significantly reduced when it is covered by polymer and CBZ. After removing the CBZ template from the polymer, the MIP@CNA / 3D GF electrode exposes the cavity, which makes [Fe(CN)6] 3- / 4- Reaching the electrode surface, resulting in an increase in the redox peak current. After recombining with CBZ, it will hinder the [Fe(CN)6] 3- / 4- The redox of , resulting in a decrease in the CV peak current. The corresponding EIS graph is shown in Figure 3 c, where the semicircle diameter represents the charge transfer resistance (RCT) and the linear part represents the diffusion process. The RCT of CAN / 3D GF is 12.69Ω, and due to the low conductivity of the polymer and CBZ, the RCT after electropolymerization increases to 280.9Ω. After NaOH removes the CBZ template, the RCT of MIP@CAN / 3D GF decreases to 115.5Ω. After recombining with CBZ, the RCT of MIP@CAN / 3D GF increases to 151Ω. The circuit consists of a solution resistance (Rs), a charge transfer resistance (RCT), a double layer capacitance (C1), a Warburg diffusion impedance (Zw) and an interface capacitance (C2). With the increase of the scan rate, the redox peak current gradually increases. Peak value and scan rate (v 1 / 2 ) square root correlation: I CBZ =(243.1±30.9)+(80.9±4.30)v 1 / 2 ,(R2=0.991);I CBZ =(-321.5±51.5)+(-83.6±6.49)v 1 / 2 , (R2=0.982), indicating that the diffusion-controlled process ( Figure 3 d-e). The electroactive area of ​​MIP@CNA / 3DGF was calculated to be 2.53 cm according to the Randles-Sevcik equation. 2 When the solution pH value increases from 3 to 12, the electrode oxidation peak current first increases and then decreases, reaching a maximum value at pH 7 ( Figure 3 f).

[0050] like Figure 4 As shown in Figure 2, CBZ was detected by split pulse voltammetry using the MIP@CNA / 3D GF electrode. As the CBZ concentration increased, the oxidation peak current of the MIP@CNA / 3D GF electrode decreased significantly ( Figure 4 a). The corresponding regression equation is divided into two parts: ΔI CBZ =(1.91±0.066)+(1.41±0.122)C CBZ (R2=0.993), ΔICBZ =(11.7±0.687)+(0.559±0.017)C CBZ (R 2 =0.995)( Figure 4 b) The sensitivity of the MIP@CNA / 3D GF electrode to CBZ in the range of 0-10 μM is 1.41 μA·μM -1 The sensitivity in the range of 10 to 60 μM is 0.56 μA·μM -1 , LOD is 31nm (S / N=3).

[0051] The selectivity, reproducibility, repeatability and stability of the MIP@CNA / 3D GF electrode are shown in Figure 2. Figure 5 shown. Figure 5 a is the structural formula of the test biomolecule. By testing CBZ and other biomolecules (including DA, PPZ, Glu, TCI and OLZ) ( Figure 5 b) and various ions (Na + , Ca 2+ 、Fe 3+ Mg 2+ and Zn 2+ )( Figure 5 c) to study the selectivity of the MIP@CNA / 3D GF electrode. At the same concentration, the response of the MIP@CNA / 3D GF electrode to CBZ was much higher than that of other interfering substances, indicating that the MIP@CAN / 3D GF electrode has good selectivity for CBZ. However, the NIP@CNA / 3D GF electrode showed almost no significant current difference when detecting all analytes. This is attributed to the ability of the specifically recognized cavity in MIPs to selectively bind CBZ, while NIPs lack this structure. Five MIP@CNA / 3D GF electrodes were prepared and tested in 60μM CBZ with an RSD of 1.34%, indicating that the electrode has good reproducibility ( Figure 5 d). When the electrode was tested five times in 60 μM CBZ every 10 min, the current only decreased by 3.1% with an RSD of 1.23%, indicating that the electrode had good repeatability ( Figure 5 e). The MIP@CNA / 3DGF electrode was tested once a day. After 5 days of CBZ detection, the current decreased by 7.7% and the RSD was 3.15%, indicating good stability ( Figure 5 f).

Claims

1. Preparation and application of Zn-MOFs-derived carbon nanosheet array / three-dimensional graphene composite material combined with molecular imprinting technology, characterized in that A method for preparing Zn-MOFs-derived carbon nanosheet arrays / three-dimensional graphene as sensor electrode materials combined with molecular imprinting technology is carried out in the following steps:

1. Preparation of three-dimensional graphene by chemical vapor deposition Three-dimensional graphene was prepared using chemical vapor deposition. For detailed parameters, please refer to our previous patent: CN109781822B.

2. Preparation of Zn-MOFs Nanosheet Arrays / 3D Graphene by Precipitation Method 250-350 mg of Zn(NO3)2·6H2O and 580-690 mg of C4H6N2 were ultrasonically dispersed in 15-30 mL of water, and 3D GF was inserted into the mixed solution of Zn(NO3)2 and C4H6N2. After standing at room temperature for 8-24 h, the Zn-MOFs nanosheet array / 3D graphene was obtained by washing and freeze-drying.

3. Preparation of carbon nanosheet arrays / 3D graphene by heat treatment The Zn-MOFs nanosheet array / 3D graphene obtained in step 2 was placed in a tube furnace under argon gas protection at a temperature of 400-600 °C and a heating rate of 3-8 °C min -1 Under the condition of 40-80 min, carbon nanosheet arrays / three-dimensional graphene were obtained; 4. Preparation of Molecularly Imprinted Polymer-Coated Carbon Nanosheet Arrays / 3D Graphene The carbon nanosheet array / 3D graphene obtained in step 3 was transferred to ITO glass as a working electrode and placed in [Fe(CN)6] 3- / 4- The solution was electropolymerized with 10 cycles, a voltage range of -0.1 to 0.6 V, and a scan rate of 10 to 100 mV·s. -1 Then, 0.05-0.15 M NaOH solution was used for standing washing for 10-90 min to remove CBZ molecules, and molecularly imprinted polymer-coated carbon nanosheet arrays / three-dimensional graphene were obtained.

2. The use of the molecularly imprinted polymer coated carbon nanosheet array / three-dimensional graphene / ITO electrode according to claim 1, characterized in that The molecularly imprinted polymer-coated carbon nanosheet array / three-dimensional graphene / ITO is used as an electrochemical sensor working electrode for highly sensitive and selective detection of carbamazepine.

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