Ultrathin two-dimensional conductive metal phthalocyanine organic framework nanosheet as well as preparation method and application thereof

Abstract

The invention belongs to the field of nano material preparation, and particularly relates to a two-dimensional conductive metal phthalocyanine organic framework nanosheet as well as a preparation method and application thereof. An organic ligand 2, 3, 9, 10, 16, 17, 23, 24-octahydroxy metal phthalocyanine containing a metal phthalocyanine unit is synthesized by adopting an organic synthesis method, and a two-dimensional metal phthalocyanine-organic framework is further synthesized by utilizing a solvothermal reaction of the ligand and a metal salt of acetylacetone. Stripping the two-dimensional metal phthalocyanine organic framework by adopting a ball milling method to obtain a two-dimensional metal phthalocyanine organic framework nanosheet; the two-dimensional metal phthalocyanine organic framework nanosheet is used for modifying a substrate electrode to obtain the electrode modified by the two-dimensional metal phthalocyanine organic framework nanosheet, and the electrode is used for constructing an electrochemical sensor for detecting dopamine, uric acid, 5-hydroxytryptamine and ascorbic acid and has an extremely low detection limit. By improving the conductivity of the organic framework material and increasing active sites, the sensitivity and resolution of electrochemical detection are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterial preparation, and particularly relates to a two-dimensional conductive metal phthalocyanine organic framework nanosheet, a preparation method thereof, and an application thereof. Background Art

[0002] Metal-organic frameworks (MOFs) represent a class of emerging porous materials with excellent properties, including ultra-high specific surface area, various chemical compositions, and customizable pore structures rich in catalytically active sites. These unique properties make MOFs highly promising in various electrochemical applications. This progress is largely attributed to the precise recognition of analytes by active sites within MOFs, which not only promotes a deeper understanding of the catalytic mechanism but also provides valuable insights to guide the development of more efficient catalytic systems. However, most MOFs mainly exhibit coordination-saturated three-dimensional (3D) MOFs, where metal sites are encapsulated by organic ligands. 3D MOFs typically exhibit extremely low electronic conductivity and even insulating behavior due to the inertness of bridging ligands. Therefore, this inherent electronic property leads to reduced utilization of internal active metal centers and slow reaction kinetics, severely limiting their feasibility in electrochemical catalysis and sensing applications.

[0003] Two-dimensional (2D) MOFs have their active metal centers fully exposed due to their layered structure. However, most 2D MOFs have a non-conjugated structure, which still results in low electronic conductivity. These materials have a graphene-like layered structure and can be easily exfoliated into sheets, showing strong in-plane π-π conjugation and relatively weak out-of-plane π-π interactions. In addition to having periodic pore structures, large specific surface areas, etc., 2D conductive MOFs also have excellent electrical conductivity and unique physical and chemical properties, which have prompted research on their electrochemical sensing capabilities. However, traditional 2D conductive MOFs only have one type of metal catalytic center, and in the field of electrochemical sensors, the acquisition of conductive materials with high-density metal active centers is still very limited.

[0004] Therefore, there is an urgent need for a new type of MOF material that combines the excellent layered structure and conductivity of 2D conductive MOFs and has a high density of exposed active metal centers. Summary of the Invention

[0005] Aiming at the above defects or improvement requirements of the prior art, the present invention provides a two-dimensional conductive metal phthalocyanine organic framework nanosheet, a preparation method thereof, and an application thereof, aiming to develop a 2D conductive MOFs material with a high density of metal active centers, thereby solving the technical problems of poor conductivity, insufficient active sites, or inability to fully expose active sites in traditional MOFs.

[0006] To achieve the above object, according to one aspect of the present invention, a method for preparing two-dimensional metal phthalocyanine organic framework nanosheets is provided, including the following preparation steps:

[0007] (1) Mix 4,5-dimethoxyphthalonitrile, urea, metal chloride salt and ammonium molybdate, then add anhydrous ethylene glycol, react under an inert gas, cool the obtained product, add a quenching agent to quench the reaction, and then collect the first precipitate produced by the reaction. The first precipitate is 2,3,9,10,16,17,23,24-octamethoxymetal phthalocyanine;

[0008] (2) Disperse the 2,3,9,10,16,17,23,24-octamethoxymetal phthalocyanine in dichloromethane, and react with a dichloromethane solution of BBr3 under an inert gas atmosphere; add a quenching agent to the reaction mixture to quench the reaction, and then collect the second precipitate in the solution. The second precipitate is 2,3,9,10,16,17,23,24-octahydroxymetal phthalocyanine;

[0009] (3) Dissolve the 2,3,9,10,16,17,23,24-octahydroxymetal phthalocyanine in a mixed solution of a first organic solvent and ammonia water to obtain solution A; dissolve the metal acetylacetonate in dimethylformamide to obtain solution B; mix solution A and solution B and carry out a solvothermal reaction; after the reaction is completed, cool and collect the third precipitate in the solution. The third precipitate is a two-dimensional metal phthalocyanine organic framework;

[0010] (4) Add abrasive particles to the two-dimensional metal phthalocyanine organic framework, mill under an inert gas atmosphere, mill and exfoliate the two-dimensional metal phthalocyanine organic framework, and then wash to obtain two-dimensional metal phthalocyanine organic framework nanosheets.

[0011] Preferably, in step (1), the mass ratio of the 4,5-dimethoxyphthalonitrile, urea, chloride salt and ammonium molybdate is (8-12):(3-3.5):(1.6-2):(0.5-1); the ratio of the mass of the 4,5-dimethoxyphthalonitrile to the volume of the anhydrous ethylene glycol is 20-33 g / L;

[0012] Preferably, the metal chloride salt is selected from one or more of cobalt chloride, nickel chloride, iron chloride, manganese chloride, zinc chloride, copper chloride, and the metal chloride salt does not contain crystal water; in step (1), the reaction temperature is 160-200 °C and the time is 3-5 days.

[0013] Preferably, in step (2), the reaction temperature is 20-50 °C and the time is 5-8 days;

[0014] Preferably, in steps (1) and (2), the quenching agents are independently selected from one or more of water, methanol, or ethanol;

[0015] Preferably, the concentration of BBr3 in the dichloromethane solution of BBr3 is 0.5 - 2 mol / L; the molar ratio of BBr3 to 2,3,9,10,16,17,23,24 - octamethoxymetallophthalocyanine is 20 - 40.

[0016] Preferably, in step (3), the mass - to - volume ratio of 2,3,9,10,16,17,23,24 - octahydroxymetallophthalocyanine to ammonia water is 7 - 10 mg / ml;

[0017] Preferably, the mass ratio of 2,3,9,10,16,17,23,24 - octahydroxymetallophthalocyanine to the acetylacetonate salt is 1 - 2;

[0018] Preferably, in solution B, the mass - to - volume ratio of the acetylacetonate salt to the organic solvent is 0.8 - 1.2 g / ml; the mass fraction of ammonia in the ammonia water is 20% - 50%.

[0019] Preferably, the first organic solvent is selected from one or two of dimethylformamide and dimethyl sulfoxide;

[0020] Preferably, in step (3), the metal acetylacetonate salt is selected from one or more of nickel acetylacetonate, copper acetylacetonate, zinc acetylacetonate, manganese acetylacetonate, and ferrous acetylacetonate;

[0021] Preferably, the temperature of the solvothermal reaction is 80 - 120 °C, and the time is 24 - 48 hours;

[0022] Preferably, in step (4), it further includes dispersing the obtained two - dimensional metal phthalocyanine organic framework nanosheets in dimethylformamide, ultrasonically treating and centrifuging in an ice bath, and collecting the centrifugate to obtain the two - dimensional metal phthalocyanine organic framework nanosheets.

[0023] According to another aspect of the present invention, there is provided a two - dimensional metal phthalocyanine organic framework nanosheet prepared by the above - mentioned preparation method.

[0024] According to another aspect of the present invention, there is provided a preparation method of an electrode modified with two - dimensional metal phthalocyanine organic framework nanosheets. The two - dimensional metal phthalocyanine organic framework nanosheets prepared by the above - mentioned preparation method are dispersed in a second organic solvent, and then a conductive binder is added to obtain a mixed solution; the mixed solution is coated on the surface of a substrate electrode, dried, and then the mixed solution is coated again and dried again to obtain the electrode modified with two - dimensional metal phthalocyanine organic framework nanosheets.

[0025] Preferably, the ratio of the mass of the two-dimensional metal phthalocyanine organic framework nanosheets to the volume of the dimethylformamide is 8-12 mg / mL; the mass ratio of the two-dimensional metal phthalocyanine organic framework nanosheets to the conductive binder is 100-200.

[0026] Preferably, the second organic solvent is selected from one or more of dimethylformamide, ethanol, and isopropanol.

[0027] According to another aspect of the present invention, there is provided an electrode modified with two-dimensional metal phthalocyanine organic framework nanosheets prepared by the preparation method described above.

[0028] According to another aspect of the present invention, there is provided a biosensor, which includes an electrode modified with the two-dimensional metal phthalocyanine organic framework nanosheets as a working electrode, a silver chloride electrode as a reference electrode, an inert conductive electrode as a counter electrode, and further includes an electrolyte, and the pH of the electrolyte is 6-7.

[0029] According to another aspect of the present invention, there is provided an application of a biosensor, which is used for the detection of dopamine, uric acid, 5-hydroxytryptamine or ascorbic acid.

[0030] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0031] 1. The present invention synthesizes an organic ligand 2,3,9,10,16,17,23,24-octahydroxy metal phthalocyanine (M1Pc-OH) with a metal phthalocyanine (M1Pc) structural unit through an organic synthesis method. The ligand molecule has a fully conjugated planar structure and contains an M1Pc unit, with an intrinsic single-atom structure, providing a basis for the high electrochemical activity of the subsequent organic framework. Further, a two-dimensional metal phthalocyanine organic framework (M1Pc-OM2) crystal is synthesized from M1Pc-OH and acetylacetonate through a solvothermal method; the M1Pc-OM2 is exfoliated into nanosheets (NSs) using sodium chloride-assisted ball milling. M1Pc-OM2 contains M1Pc and M2-O4 double redox active centers and has extremely high electrochemical activity. The metal phthalocyanine additionally introduces metal active centers, thereby preparing a two-dimensional conductive metal phthalocyanine-organic framework nanosheet (M1Pc-OM2 NSs) material with extremely high electrochemical activity. The high-density metal sites and conjugation ensure its high catalytic activity and excellent electronic conductivity, providing a high-performance catalytic effect for the subsequent preparation of biosensors.

[0032] 2. The present invention utilizes the characteristics that the lattice of the ball milling agent is small and easy to intercalate into the lattice of the two-dimensional metal phthalocyanine organic framework (M1Pc-OM2) and is easy to remove. During the ball milling process, NaCl is introduced to assist ball milling to obtain two-dimensional metal phthalocyanine organic framework nanosheets (M1Pc-OM2 NSs), and an ultrasonically assisted liquid-phase exfoliation strategy and centrifugation method are used to further obtain a dispersion of ultrathin organic framework nanosheets with uniform size. The morphology of the organic framework nanosheets is layered, and the full exposure of the crystal planes enables biomolecules to easily reach the metal active centers of M1Pc and M2-O4, significantly improving the overall electrocatalytic activity of the organic framework material.

[0033] 3. The two-dimensional conductive metal phthalocyanine-organic framework described in the present invention has a fully conjugated structure and good conductivity, thus better enhancing the electron transfer activity; the two-dimensional conductive metal phthalocyanine organic framework nanosheets contain M1Pc and M2-O4 dual redox active centers, have extremely high electrochemical activity and high-performance catalytic effects, and can be used as a highly active electrochemiluminescent biosensing electrode material for highly sensitive and selective detection of various biomarkers in different biological samples. The atomic-level precision controllability, high catalytic activity, and good biocompatibility of the two-dimensional conductive metal phthalocyanine-organic framework with dual redox active centers provide opportunities for the further development of highly modular, sensitive, selective, and highly stable electrochemical microfluidic chips. Brief Description of the Drawings

[0034] Figure 1 It is a scanning electron microscope image of the two-dimensional metal phthalocyanine-organic framework prepared in Example 1 of the present invention.

[0035] Figure 2 It is a transmission electron microscope image of the two-dimensional metal phthalocyanine-organic framework nanosheets prepared in Example 1 of the present invention.

[0036] Figure 3 It is an atomic force microscope image of the two-dimensional metal phthalocyanine-organic framework nanosheets NiPc-O-Ni NSs prepared in Example 1 of the present invention.

[0037] Figure 4 It is an X-ray powder diffraction pattern of the two-dimensional conductive metal phthalocyanine-organic framework nanosheets NiPc-O-Ni NSs prepared in Example 1 of the present invention.

[0038] Figure 5 It is a nuclear magnetic resonance hydrogen spectrum of NiPc-OH prepared in Example 1 of the present invention.

[0039] Figure 6Photograph of the two-dimensional conductive metal phthalocyanine-organic framework nanosheet solution prepared in Example 1 of the present invention; among them, (a) is a picture of NiPc-O-Ni NSs before dilution; (b) is a picture of NiPc-O-Ni NSs after being diluted 40 times; (c) is a picture of NiPc-O-Ni NSs under side illumination by daylight lamp.

[0040] Figure 7 Differential pulse voltammograms of the sensor prepared in Example 3 of the present invention for dopamine at different concentrations in phosphate buffered saline (PBS).

[0041] Figure 8 Differential pulse voltammograms of the sensor prepared in Example 3 of the present invention for uric acid at different concentrations in PBS.

[0042] Figure 9 Differential pulse voltammograms of the sensor prepared in Example 3 of the present invention for serotonin at different concentrations in PBS.

[0043] Figure 10 Differential pulse voltammograms of the sensor prepared in Example 3 of the present invention for ascorbic acid at different concentrations in PBS. Detailed implementation manners

[0044] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] The present invention provides a preparation method for two-dimensional metal phthalocyanine organic framework nanosheets, including the following preparation steps:

[0046] (1) Mix 4,5-dimethoxyphthalonitrile, urea, metal chloride salt and ammonium molybdate, then add anhydrous ethylene glycol, react under an inert gas, cool the obtained product to room temperature, add a quenching agent to quench the reaction, and collect the first precipitate by centrifugation. The first precipitate is 2,3,9,10,16,17,23,24-octamethoxymetal phthalocyanine.

[0047] In some embodiments, in step (1), the mass ratio of 4,5-dimethoxyphthalonitrile, urea, chloride salt and ammonium molybdate is (8-12):(3-3.5):(1.6-2):(0.5-1); the ratio of the mass of 4,5-dimethoxyphthalonitrile to the volume of anhydrous ethylene glycol is 20-33 g / L.

[0048] In some embodiments, the collected first precipitate is washed. Specifically, the first precipitate is washed successively with methanol and acetone and then dried under vacuum conditions.

[0049] In some embodiments, the volumes of the methanol and acetone are each 20 - 40 mL; the washing method is centrifugal washing, the rotation speed of centrifugation is 5000 - 8000 rpm, the centrifugation time is 5 - 10 min, and the number of washing times is 3 - 5 times.

[0050] In some embodiments, the drying temperature is 50 - 60 °C and the drying time is 2 - 3 hours.

[0051] In some embodiments, in step (1), the reaction is a stirring reaction under ultrasonic conditions. The ultrasonic time is 5 - 10 min, the stirring speed is 200 - 400 r / min, and the stirring time is 5 - 20 min.

[0052] In some embodiments, the chloride salt is selected from one or more of cobalt chloride, nickel chloride, iron chloride, manganese chloride, zinc chloride, copper chloride, etc., and the chloride salt does not contain crystal water;

[0053] In some embodiments, in step (1), the reaction temperature is 180 - 220 °C and the reaction time is 3 - 5 days.

[0054] In some embodiments, in step (1), the inert gas is one or both of nitrogen or argon.

[0055] In some embodiments, in step (1), the reactants are subjected to condensation reflux to recover ethylene glycol.

[0056] In some embodiments, in step (1), the volume of the added water or ethanol is 30 - 80 mL, the mixing time is 2 - 5 min; the centrifugation rotation speed is 5000 - 8000 rpm, and the centrifugation time is 5 - 10 min.

[0057] (2) Disperse 2,3,9,10,16,17,23,24 - octamethoxymetallophthalocyanine in dichloromethane, and react with a dichloromethane solution of BBr3 under an inert gas atmosphere; add a quenching agent to the reaction mixture to quench the reaction, and centrifuge to collect the second precipitate in the solution. The second precipitate is 2,3,9,10,16,17,23,24 - octahydroxymetallophthalocyanine (M1Pc - OH);

[0058] In some embodiments, in step (2), the reaction temperature is 20 - 50 °C and the reaction time is 5 - 8 days;

[0059] In some embodiments, in steps (1) and (2), the quenching agent is independently selected from one or more of water, methanol, or ethanol; the volume of the quenching agent is 50 to 100 mL.

[0060] In some embodiments, in step (2), the inert gas is one or both of nitrogen or argon; the volume of the quenching agent is 30 - 80 mL, and the time for adding the quenching agent and mixing and stirring is 5 - 15 min.

[0061] In some embodiments, in step (2), the rotation speed of the centrifugation is 5000 - 8000 rpm, and the centrifugation time is 5 - 10 min.

[0062] In some embodiments, in step (2), the obtained second precipitate is washed. Specifically, the washing is sequentially carried out with water, methanol, and acetone until the supernatant is almost colorless and transparent. The bottom product of the centrifugation is collected and dried at 60 - 80 °C under vacuum.

[0063] In some embodiments, the volumes of water, methanol, and acetone are 20 - 40 mL respectively; the washing method is centrifugal washing, the centrifugation speed is 5000 - 8000 rpm, and the centrifugation time is 5 - 10 min.

[0064] In some embodiments, in step (2), the temperature of the vacuum drying is 50 - 60 °C, and the drying time is 2 - 3 hours.

[0065] In some embodiments, the concentration of BBr3 in the dichloromethane solution of BBr3 is 0.5 - 2 mol / L; the molar ratio of BBr3 to 2,3,9,10,16,17,23,24 - octamethoxymetal phthalocyanine is 20 - 40; the dichloromethane is super dry.

[0066] (3) Dissolve 2,3,9,10,16,17,23,24 - octahydroxymetal phthalocyanine in a mixed solution of a first organic solvent and ammonia water to obtain solution A; dissolve metal acetylacetonate in dimethylformamide to obtain solution B; mix solution A and solution B and carry out a solvothermal reaction; after the reaction is completed, cool to room temperature and centrifuge to obtain a third precipitate, which is the two - dimensional metal phthalocyanine organic framework (M1Pc - OM2).

[0067] In some embodiments, in step (3), the mass ratio of 2,3,9,10,16,17,23,24 - octahydroxy metal phthalocyanine to the volume of the mixed solution of dimethylformamide and ammonia water is 7 - 10 g / ml; the mass ratio of 2,3,9,10,16,17,23,24 - octahydroxy metal phthalocyanine to the acetylacetonate is 1 - 2; the mass ratio of the acetylacetonate to the volume of dimethylformamide is 0.8 - 1.2 g / ml.

[0068] In some embodiments, the mass fraction of ammonia in the ammonia water is 20% - 50%.

[0069] In some embodiments, the first organic solvent is selected from one or two of dimethylformamide and dimethyl sulfoxide.

[0070] In some embodiments, the solution A is first stirred and then sonicated. The stirring speed is 200 - 300 rpm, the stirring time is 3 - 5 min, and the sonication time is 5 - 10 min.

[0071] In some embodiments, in step (3), the third precipitate is washed. The washing is specifically carried out by washing with DMF, deionized water, and acetone in sequence, and then dried under vacuum.

[0072] In some embodiments, the volumes of DMF, deionized water, and acetone are 20 - 40 mL respectively. The washing is centrifugal washing. The centrifugation rate is 5000 - 10000 rpm, and the centrifugation time is 5 - 15 min.

[0073] In some embodiments, the temperature of the vacuum drying is 50 - 60 °C, and the drying time is 2 - 6 hours.

[0074] In some embodiments, the mixing of solution A and solution B in step (3) is specifically that, with solution A in a stirred state, solution B is quickly added to obtain a mixture, and then the mixture is sonicated.

[0075] In some embodiments, in step (3), the acetylacetonate is selected from one or more of nickel acetylacetonate, copper acetylacetonate, zinc acetylacetonate, manganese acetylacetonate, and ferrous acetylacetonate.

[0076] In some embodiments, the temperature of the solvothermal reaction is 80 - 120 °C, and the reaction time is 24 - 48 hours;

[0077] In some embodiments, in step (3), the centrifugation rate is 5000 - 10000 rpm, and the centrifugation time is 5 - 15 min.

[0078] (4) Add abrasive particles to the two-dimensional metal phthalocyanine organic framework, and ball mill it under a nitrogen atmosphere. After ball milling and exfoliating the two-dimensional metal phthalocyanine organic framework, wash it to obtain two-dimensional metal phthalocyanine organic framework nanosheets (M1Pc-OM2NSs).

[0079] In some embodiments, in step (4), it further includes dispersing the obtained two-dimensional metal phthalocyanine organic framework nanosheets in dimethylformamide, sonicating in an ice bath and centrifuging to remove thick-layer nanosheets, and collecting the centrifugate to obtain two-dimensional metal phthalocyanine organic framework nanosheets.

[0080] In some embodiments, the sonication time in the ice bath is 20 - 60 min.

[0081] In some embodiments, for the sonication and centrifugation in the ice bath, the centrifugation speed is 1000 - 5000 rpm, and the centrifugation time is 5 - 20 min.

[0082] In some embodiments, in step (4), the grinding is carried out using grinding beads, the diameter of the grinding beads is 6 - 14 mm, and the mass is 20 - 50 g.

[0083] In some embodiments, in step (4), the ball milling speed is 200 - 500 rpm, and the ball milling time is 3 - 6 hours.

[0084] In some embodiments, in step (4), the washing is specifically carried out by washing with deionized water and DMF in sequence.

[0085] In some embodiments, in step (4), the volumes of the deionized water and DMF are 20 - 40 mL respectively, the washing method is centrifugal washing, the centrifugation speed is 8000 - 12000 rpm, and the centrifugation time is 5 - 15 min.

[0086] In some embodiments, the abrasive is selected from sodium chloride or potassium chloride.

[0087] According to another aspect of the present invention, a method for preparing an electrode modified with two-dimensional metal phthalocyanine organic framework nanosheets is provided. Disperse the two-dimensional metal phthalocyanine organic framework nanosheets in a second organic solvent, and then add a conductive binder to obtain a mixed solution; coat the mixed solution on the surface of a substrate electrode, dry it, and then coat the mixed solution again, and obtain the two-dimensional metal phthalocyanine organic framework nanosheet modified electrode after drying again.

[0088] In some embodiments, the ratio of the mass of the two-dimensional metal phthalocyanine organic framework nanosheets to the volume of the dimethylformamide is 8-12 mg / mL; the mass ratio of the two-dimensional metal phthalocyanine organic framework nanosheets to the mass of the conductive binder is 100-200; the second organic solvent is selected from one or more of dimethylformamide, ethanol, and isopropanol.

[0089] In some embodiments, the conductive binder is selected from perfluorosulfonic acid-based polymers (nafion).

[0090] In some embodiments, the substrate electrode is selected from a glassy carbon electrode, an Au electrode, a carbon fiber electrode, or a graphene fiber electrode.

[0091] According to another aspect of the present invention, there is provided an electrode modified with two-dimensional metal phthalocyanine organic framework nanosheets prepared by the preparation method described above.

[0092] According to another aspect of the present invention, there is provided a biosensor, which includes an electrode modified with the two-dimensional metal phthalocyanine organic framework nanosheets as a working electrode, a silver chloride electrode as a reference electrode, an inert conductive electrode as a counter electrode, and further includes an electrolyte, and the pH of the electrolyte is 6-7.

[0093] In some embodiments, the inert conductive electrode is a platinum wire, a gold wire, a carbon fiber, or a graphene fiber.

[0094] In some embodiments, the electrolyte is selected from a phosphate buffer solution or one of physiological fluids such as saliva, sweat, and tear fluid.

[0095] In some embodiments, the length of the working electrode immersed in the electrolyte is 0.5-2 cm.

[0096] According to another aspect of the present invention, there is provided an application of a biosensor, which is used for the detection of biomolecules such as dopamine, uric acid, 5-hydroxytryptamine, or ascorbic acid.

[0097] In some embodiments, the application specifically is to add the biomolecule into the electrolyte, measure the differential pulse voltammogram of different concentrations of the biomolecule by differential pulse voltammetry (DPV), fit the linear relationship between the concentration of the biomolecule and the corresponding current, and calculate the concentration of the corresponding biomolecule through the current value.

[0098] In some embodiments, the parameters of the differential pulse voltammetry are: pulse height 40-60 mV, step height 3-5 mV, pulse width 0.1-0.5 s, step length 0.1-1 s, scan rate 5-20 mV s -1 。

[0099] Example 1

[0100] This embodiment provides a method for preparing two-dimensional layered conductive metal phthalocyanine-organic framework nanosheets, which includes the following steps:

[0101] Step 1: Add reactants to a 100 mL round-bottom flask: 1 g of 4,5-dimethoxyphthalonitrile, 320 mg of urea, 181 mg of anhydrous NiCl2, and 60 mg of (NH4)6Mo7O 24 , and then add 30 mL of anhydrous ethylene glycol. After ultrasonic treatment for 10 min, stir at a speed of 300 r / min for 10 min until the mixture is homogeneous, and reflux for 4 days under a nitrogen atmosphere. Then cool the mixture to room temperature, add 50 mL of water, stir for 5 minutes, and centrifuge at a speed of 8000 rpm for 5 min to collect the precipitate. Then centrifuge and wash the precipitate (8000 rpm, 5 min) with 30 ml of methanol and 30 ml of acetone in sequence, and dry in vacuum at 70 °C for 2 hours to obtain a dark green solid of 2,3,9,10,16,17,23,24-octamethoxynickel phthalocyanine (NiPc-OCH3), with a mass of approximately 700 mg.

[0102] Step 2: Ultrasonically disperse 700 mg of NiPc-OCH3 obtained in Step 1 in 30 mL of ultra-dry dichloromethane, and add 30 mL of a dichloromethane solution of 1 mol / L BBr3 under a nitrogen atmosphere. The mixture is stirred and reacted at 25 °C for 6 days. After the reaction, slowly add 50 mL of methanol to the mixture and stir evenly for 15 min in the atmosphere. Collect the precipitate in the solution by centrifugation (centrifugation rate: 8000 rpm, centrifugation time: 10 min), and then centrifuge and wash with 30 mL of water, 30 mL of methanol, and 30 mL of acetone in sequence (the centrifugation rate is 8000 rpm, and the centrifugation time is 10 min) until the supernatant is almost transparent. Finally, dry in vacuum at 60 °C for 3 hours to obtain a dark green solid of 2,3,9,10,16,17,23,24-octahydroxynickel phthalocyanine (NiPc-OH) with a mass of approximately 500 mg;

[0103] Step 3: Take 35 mg of NiPc-OH from Step 2 and add it to a 250 mL blue mouth bottle. Then add 25 mL of DMF and 4.4 mL of ammonia water (mass fraction of ammonia water is 25%) and stir at 300 rpm for 5 min and ultrasonicate for 10 min to completely dissolve to obtain Solution A. Dissolve 25 mg of nickel acetylacetonate in 5 mL of DMF to obtain Solution B. While Solution A is being stirred at 200 rpm, quickly add Solution B. The mixture is ultrasonically treated for another 5 minutes, and then reacted at 85 °C for 45 hours under solvothermal conditions. After the reaction is completed, it is cooled to room temperature and centrifuged at 8000 rpm for 10 min to obtain a black precipitate, which is two-dimensional conductive nickel phthalocyanine-organic framework (NiPc-O-Ni). The product is successively centrifuged and washed with 30 mL of DMF, 30 mL of deionized water, and 30 mL of acetone (8000 rpm, 5 min). Then NiPc-O-Ni is dried in a vacuum oven at 60 °C for 3 hours.

[0104] Step 4: Add 50 mg of NiPc-O-Ni from Step 3 and 500 mg of NaCl to a 45 mL ball milling jar. Add 50 g of agate grinding beads with a diameter of 8 mm under a nitrogen atmosphere and tightly cover the ball milling jar. Ball mill at a speed of 300 rpm for 3 hours to exfoliate to obtain NiPc-O-Ni nanosheets. Then, the nanosheets are centrifuged and washed with 30 mL of deionized water and DMF (centrifugation speed is 10000 rpm, time is 10 min), and the precipitate is collected. Redisperse 10 mg of the synthesized NiPc-O-Ni nanosheets into 30 mL of DMF and ultrasonicate gently in an ice bath for 30 min. After centrifuging at 2000 rpm for 10 min to remove thick-layer nanosheets, the centrifugate is collected to obtain a uniform NiPc-O-Ni NSs dispersion.

[0105] Figure 1 This is the scanning electron microscope image of the two-dimensional metal phthalocyanine-organic framework prepared in Example 1 of the present invention. It can be seen from the figure that the morphology of the two-dimensional metal phthalocyanine-organic framework before ball milling is blocky.

[0106] Figure 2 This is the transmission electron microscope image of the two-dimensional metal phthalocyanine organic framework nanosheets NiPc-O-Ni NSs prepared in Example 1 of the present invention. It can be seen from the figure that the square network pore structure of NiPc-O-Ni.

[0107] Figure 3 This is the atomic force microscope image of the two-dimensional conductive metal phthalocyanine organic framework nanosheets NiPc-O-Ni NSs prepared in Example 1 of the present invention. It can be seen from the figure that the prepared nanosheets are ultrathin with a thickness of 3 - 5 nanometers.

[0108] Figure 4X-ray powder diffraction patterns of the original synthesized and ball-milled two-dimensional conductive metal phthalocyanine-organic framework nanosheets NiPc-O-Ni prepared in Example 1 of the present invention. In the XRD pattern of NiPc-O-Ni-milled, the peak of the (001) crystal plane is significantly enhanced, indicating that more of the (001) crystal plane of the MOF is exposed, corresponding to more exposure of the layered structure of the MOF.

[0109] Figure 5 1H nuclear magnetic resonance spectrum of NiPc-OH prepared in Example 1 of the present invention. As can be seen from the figure, the peak with a chemical shift of 10.33 ppm corresponds to the hydrogen on the hydroxyl group of NiPc-OH, and the peak with a chemical shift of 8.56 ppm corresponds to the hydrogen on the benzene ring of NiPc-OH. The peak area ratio of the two peaks is close to 1:1, proving the successful synthesis of NiPc-OH.

[0110] Figure 6 Photo of the solution of two-dimensional conductive metal phthalocyanine-organic framework nanosheets NiPc-O-Ni NSs prepared in Example 1 of the present invention. As can be seen from the figure, the solution of NiPc-O-Ni NSs is very homogeneous, and there are no visible large MOF particles under the light source, indicating the successful preparation of NiPc-O-Ni NSs.

[0111] Example 2

[0112] This example provides a method for preparing a two-dimensional metal phthalocyanine-organic framework nanosheet electrode. The specific steps are as follows: Weigh a certain mass of NiPc-O-Ni NSs prepared in Example 1, disperse it in a certain volume of DMF, after ultrasonic treatment for a period of time, then add a certain volume of nafion solution, and continue ultrasonic treatment for 5 min to form a uniform ink. The ratio of MOF to DMF is m:V = 5 mg:250 - 1000 μL, and the ratio of MOF to nafion is m:V = 5 mg:5 - 20 μL. Subsequently, take 2 - 5 μL of the ink and drop it on the surface of the electrode, dry it, and then drop 2 - 5 μL of the ink again and dry it to form a glassy carbon electrode modified with NiPc-O-Ni NSs.

[0113] Example 3

[0114] This embodiment provides a biosensor. The glassy carbon electrode modified with NiPc-O-Ni NSs prepared in Example 2 is used as the working electrode and immersed 1 cm in the electrolyte solution. The Ag / AgCl electrode in saturated potassium chloride solution is used as the reference electrode, and a platinum wire is used as the counter electrode. A 0.1 M phosphate buffer solution is used as the electrolyte. The biological molecule is added to the electrolyte solution, and differential pulse voltammetry (DPV) is used to measure the DPV curves (parameters: pulse height 50 mV, step height 4 mV, pulse width 0.2 s, step length 0.5 s, scan rate 8 mV s -1 .) of continuously adding different concentrations of biological small molecules, fitting the linear relationship between the concentrations of these biological small molecules and the corresponding currents, and constructing a ratio electrochemical sensor based on the sensing interface of the electrode modified with NiPc-O-Ni NSs.

[0115] Figure 7 This is the differential pulse voltammogram of the sensor prepared in Example 3 of the present invention for different concentrations of dopamine in phosphate buffered saline (PBS). Figure 8 This is the differential pulse voltammogram of the sensor prepared in Example 3 of the present invention for different concentrations of uric acid in PBS. Figure 9 This is the differential pulse voltammogram of the sensor prepared in Example 3 of the present invention for different concentrations of serotonin in PBS.

[0116] Figure 10 This is the differential pulse voltammogram of the sensor prepared in Example 3 of the present invention for different concentrations of ascorbic acid in PBS. It can be seen from the figure that the electrochemical sensor prepared from NiPc-O-Ni NSs / GF can ultrasensitively detect electroactive small molecule substances such as dopamine (DA), uric acid (UA), serotonin (5-HT), and ascorbic acid (AA). In a relatively wide concentration range (10 nM–200 μM), the detection limits for DA and 5-HT are as low as 10±4 nM and 50±17 nM respectively, and the detection limits for UA and AA are as low as 500±60 nM and 50±15 μM respectively.

[0117] Example 4

[0118] This embodiment provides a preparation method for two-dimensional layered conductive metal phthalocyanine-organic framework nanosheets, including the following steps:

[0119] Step 1: Add the reactants to a 100 mL round-bottom flask: 1 g of 4,5-dimethoxyphthalonitrile, 320 mg of urea, 181 mg of anhydrous CoCl2, and 60 mg of (NH4)6Mo7O 24, Subsequently, 30 mL of anhydrous ethylene glycol was added. After ultrasonic treatment for 10 min, the mixture was stirred at a speed of 300 r / min for 10 min until homogeneous, and then refluxed for 4 days under a nitrogen atmosphere. Subsequently, the mixture was cooled to room temperature, 50 mL of water was added, and after stirring for 5 min, the precipitate was collected by centrifugation at 8000 rpm for 5 min. Then the precipitate was successively centrifuged and washed with 30 mL of methanol and 30 mL of acetone (8000 rpm, 5 min), and dried under vacuum at 70 °C for 2 h to obtain a dark green solid of 2,3,9,10,16,17,23,24-octamethoxy cobalt phthalocyanine (CoPc-OCH3), with a mass of approximately 700 mg.

[0120] Step 2: 700 mg of CoPc-OCH3 obtained in Step 1 was ultrasonically dispersed in 30 mL of ultra-dry dichloromethane. Under a nitrogen atmosphere, 30 mL of a dichloromethane solution of 1 mol / L BBr3 was added, and the mixture was stirred and reacted at 25 °C for 6 days. After the reaction, 50 mL of methanol was slowly added to the mixture, and the mixture was stirred evenly for 15 min under an air atmosphere. The precipitate in the solution was collected by centrifugation (8000 rpm, 10 min), and then successively centrifuged and washed with 30 mL of water, 30 mL of methanol, and 30 mL of acetone (8000 rpm, 10 min) until the supernatant was almost transparent. Finally, it was dried under vacuum at 60 °C for 3 h to obtain a dark green solid of 2,3,9,10,16,17,23,24-octahydroxy cobalt phthalocyanine (CoPc-OH) with a mass of approximately 500 mg;

[0121] Step 3: 35 mg of CoPc-OH obtained in Step 2 was added to a 250 mL blue-mouth flask, and then 25 mL of DMF and 4.4 mL of ammonia water (25% - 28%) were added. The mixture was stirred at 300 rpm for 5 min and ultrasonically treated for 10 min to completely dissolve it to obtain Solution A. 25 mg of nickel acetylacetonate was dissolved in 5 mL of DMF to obtain Solution B. While Solution A was being stirred at 200 rpm, Solution B was quickly added. The mixture was ultrasonically treated for another 5 min, and then reacted at 85 °C for 45 h under solvothermal conditions. After the reaction, it was cooled to room temperature, and the black precipitate was obtained by centrifugation at 8000 rpm for 10 min, which was the two-dimensional conductive cobalt phthalocyanine organic framework (CoPc-O-Ni). The product was successively centrifuged and washed with 30 mL of DMF, 30 mL of deionized water, and 30 mL of acetone (8000 rpm, 5 min). Then CoPc-O-Ni was dried in a vacuum oven at 60 °C for 3 h.

[0122] Step 4: Add 50 mg of CoPc-O-Ni and 500 mg of NaCl from Step 3 into a 45 mL ball milling jar. Under a nitrogen atmosphere, add 50 g of agate grinding beads with a diameter of 8 mm and tightly cover the ball milling jar. Ball mill at a speed of 300 rpm for 3 hours to exfoliate CoPc-O-Ni nanosheets. Subsequently, wash the nanosheets with 30 mL of deionized water and DMF (10000 rpm, 10 min), and collect the precipitate. Redisperse the synthesized 10 mg of CoPc-O-Ni nanosheets into 30 mL of DMF and ultrasonically agitate gently in an ice bath for 30 min. After centrifuging at 2000 rpm for 10 min to remove thick-layer nanosheets, collect the centrifugate to obtain a uniform CoPc-O-Ni NSs dispersion.

[0123] Example 5

[0124] This example provides a method for preparing two-dimensional layered metal phthalocyanine-organic framework nanosheets, including the following steps:

[0125] Step 1: Add reactants into a 100 mL round-bottom flask: 1 g of 4,5-dimethoxyphthalonitrile, 320 mg of urea, 181 mg of anhydrous CuCl2, and 60 mg of (NH4)6Mo7O 24 , and then add 30 mL of anhydrous ethylene glycol. After ultrasonic agitation for 10 min, stir at a speed of 300 r / min for 10 min until the mixture is homogeneous, and reflux for 4 days under a nitrogen atmosphere. Subsequently, cool the mixture to room temperature, add 50 mL of water, stir for 5 minutes, and then centrifuge at 8000 rpm for 5 min to collect the precipitate. Then, centrifuge and wash the precipitate with 30 ml of methanol and 30 mL of acetone successively 3 times (8000 rpm, 5 min), and dry in vacuum at 70 °C for 2 hours to obtain a dark green solid, 2,3,9,10,16,17,23,24-octamethoxycopper phthalocyanine (CuPc-OCH3), with a mass of approximately 700 mg.

[0126] Step 2: Ultrasonically disperse 700 mg of CuPc-OCH3 in Step 1 in 30 mL of ultradry dichloromethane. Under a nitrogen atmosphere, add 30 mL of a dichloromethane solution of 1 mol / L BBr3. The mixture is stirred and reacted at 25 °C for 6 days. After the reaction is completed, slowly add 50 mL of methanol to the mixture and stir evenly for 15 min under an air atmosphere. Centrifuge to collect the precipitate in the solution (8000 rpm, 10 min), and then successively wash it centrifugally with 30 mL of water, 30 mL of methanol, and 30 mL of acetone multiple times (8000 rpm, 10 min) until the supernatant is almost transparent. Finally, dry it under vacuum at 60 °C for 3 hours to obtain a dark green solid of 2,3,9,10,16,17,23,24-octahydroxycopper phthalocyanine (CuPc-OH) with a mass of approximately 500 mg;

[0127] Step 3: Add 35 mg of CuPc-OH in Step 2 to a 250 mL blue-mouth bottle, and then add 25 mL of DMF and 4.4 mL of ammonia water (25% - 28%). Stir at 300 rpm for 5 min and ultrasonicate for 10 min to completely dissolve it to obtain Solution A. Dissolve 25 mg of nickel acetylacetonate in 5 mL of DMF to obtain Solution B. While Solution A is being stirred at 200 rpm, quickly add Solution B. The mixture is ultrasonically treated for another 5 minutes, and then reacted at 85 °C for 45 hours under solvothermal conditions. After the reaction is completed, cool it to room temperature and centrifuge at 8000 rpm for 10 min to obtain a black precipitate, which is the two-dimensional conductive copper phthalocyanine organic framework (CuPc-O-Ni). The product is successively washed centrifugally with 30 mL of DMF, 30 mL of deionized water, and 30 mL of acetone (8000 rpm, 5 min). Then dry CuPc-O-Ni in a vacuum oven at 60 °C for 3 hours.

[0128] Step 4: Add 50 mg of CuPc-O-Ni in Step 3 and 500 mg of NaCl to a 45 mL ball milling jar. Under a nitrogen atmosphere, add 50 g of agate grinding beads with a diameter of 8 mm and tightly cover the ball milling jar. Ball mill at a speed of 300 rpm for 3 hours to exfoliate to obtain CuPc-O-Ni nanosheets. Subsequently, wash the nanosheets with 30 mL of deionized water and DMF (10000 rpm, 10 min), and collect the precipitate. Redisperse the synthesized 10 mg of CuPc-O-Ni nanosheets in 30 mL of DMF and ultrasonicate gently in an ice bath for 30 min. After centrifuging at 2000 rpm for 10 min to remove the thick-layer nanosheets, collect the centrifugate to obtain a uniform CuPc-O-Ni NSs dispersion.

[0129] The present invention discloses a preparation method and application of two-dimensional metal phthalocyanine organic framework nanosheets. An organic ligand 2,3,9,10,16,17,23,24-octahydroxy metal phthalocyanine containing a metal phthalocyanine unit is synthesized by an organic synthesis method, and further a two-dimensional conductive nickel phthalocyanine-organic framework is synthesized by a solvothermal reaction of the organic ligand and a metal salt. Next, the two-dimensional conductive nickel phthalocyanine-organic framework is exfoliated into nanosheets by using a sodium chloride-assisted ball milling method and an ultrasonic-assisted liquid-phase exfoliation strategy, thereby preparing a two-dimensional conductive nickel phthalocyanine-organic framework nanosheet material with extremely high electrochemical activity; it is used as a working electrode to construct a novel electrochemical sensor for ultrasensitive and specific detection of multiple markers in different biological samples. Designing electrode materials with atomically precise controllability can regulate the interaction between the electrode active interface and the analyte, thus providing a new insight into improving the sensitivity and resolution of electrochemical detection.

[0130] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a two-dimensional metal phthalocyanine organic framework nanosheet, characterized in that: The method comprises the following preparation steps: (1) mixing 4,5-dimethoxyphthalonitrile, urea, a metal chloride salt and ammonium molybdate, then adding anhydrous ethylene glycol, reacting under an inert gas, cooling the obtained product, adding a quencher to quench the reaction, and collecting a first precipitate produced by the reaction, wherein the first precipitate is 2,3,9,10,16,17,23,24-octamethoxymetallophthalocyanine; (2) dispersing the 2,3,9,10,16,17,23,24-octamethoxymetal phthalocyanine in dichloromethane, adding a dichloromethane solution of BBr3 to react under an inert gas atmosphere; adding a quencher to the mixture after the reaction to quench the reaction, and collecting a second precipitate in the solution, wherein the second precipitate is 2,3,9,10,16,17,23,24-octahydroxymetal phthalocyanine; (3) dissolving the 2,3,9,10,16,17,23,24-octahydroxymetal phthalocyanine in a mixed solution of a first organic solvent and aqueous ammonia to obtain a solution A; dissolving acetylacetone metal salt in dimethylformamide to obtain a solution B; mixing the solution A and the solution B and performing a solvothermal reaction; cooling after the reaction, and collecting a third precipitate in the solution, wherein the third precipitate is a two-dimensional metal phthalocyanine organic framework; (4) adding ball milling agent particles to the two-dimensional metal phthalocyanine organic framework, ball milling under an inert gas atmosphere, and then washing the two-dimensional metal phthalocyanine organic framework after ball milling to obtain a two-dimensional metal phthalocyanine organic framework nanosheet.

2. The method for preparing a two-dimensional metal phthalocyanine organic framework nanosheet according to claim 1, characterized in that: In step (1), the mass ratio of the 4,5-dimethoxyphthalonitrile, urea, chloride and ammonium molybdate is (8-12): (3-3.5): (1.6-2): (0.5-1); the ratio of the mass of the 4,5-dimethoxyphthalonitrile to the volume of the anhydrous ethylene glycol is 20-33 g / L; The metal chloride salt is selected from one or more of cobalt chloride, nickel chloride, ferric chloride, manganese chloride, zinc chloride, and copper chloride, and the metal chloride salt does not contain crystal water; in step (1), the reaction temperature is 160-200° C. and the reaction time is 3-5 days.

3. The method for preparing a two-dimensional metal phthalocyanine organic framework nanosheet according to claim 1, characterized in that: In step (2), the reaction temperature is 20-50°C and the reaction time is 5-8 days; in step (1) and step (2), the quencher is independently selected from one or more of water, methanol or ethanol; the concentration of BBr3 in the dichloromethane solution of BBr3 is 0.5-2 mol / L; the molar ratio of BBr3 to the 2,3,9,10,16,17,23,24-octamethoxymetallophthalocyanine is 20-40.

4. The method for preparing a two-dimensional metal phthalocyanine organic framework nanosheet according to claim 1, characterized in that: In step (3), the mass ratio of the 2,3,9,10,16,17,23,24-octahydroxymetal phthalocyanine to the volume ratio of ammonia water is 7-10 mg / ml; the mass ratio of the 2,3,9,10,16,17,23,24-octahydroxymetal phthalocyanine to the acetylacetonate metal salt is 1-2; in solution B, the mass ratio of the acetylacetonate metal salt to the volume ratio of the organic solvent is (0.8-1.2) g / ml; the mass fraction of ammonia in the ammonia water is 20%-50%; the first organic solvent is selected from one or two of dimethylformamide and dimethyl sulfoxide; the acetylacetonate metal salt is selected from one or more of acetylacetonate nickel, acetylacetonate copper, acetylacetonate zinc, acetylacetonate manganese, and acetylacetonate ferrous iron; the temperature of the solvent thermal reaction is 80-120° C., and the time is 24-48 hours; Step (4) further comprises dispersing the obtained two-dimensional metal phthalocyanine organic framework nanosheets in dimethylformamide, ultrasonicating and centrifuging in an ice bath, and collecting the centrifuge liquid to obtain the two-dimensional metal phthalocyanine organic framework nanosheets.

5. The two-dimensional metal phthalocyanine organic framework nanosheet prepared by the preparation method according to any one of claims 1 to 4.

6. A method for preparing an electrode modified with a two-dimensional metal phthalocyanine organic framework nanosheet, characterized in that: The two-dimensional metal phthalocyanine organic framework nanosheets prepared by the preparation method according to any one of claims 1 to 5 are dispersed in a second organic solvent, and then a conductive adhesive is added to obtain a mixed solution; the mixed solution is coated on the surface of a base electrode, and after drying, the mixed solution is coated again, and after drying again, the electrode modified with the two-dimensional metal phthalocyanine organic framework nanosheets is obtained.

7. The method for preparing a two-dimensional metal phthalocyanine organic framework nanosheet modified electrode according to claim 6, characterized in that: The ratio of the mass of the two-dimensional metal phthalocyanine organic framework nanosheet to the volume of the dimethylformamide is 8 to 12 mg / mL; the mass ratio of the two-dimensional metal phthalocyanine organic framework nanosheet to the conductive adhesive is 100 to 200; and the second organic solvent is selected from one or more of dimethylformamide, ethanol, and isopropanol.

8. An electrode modified with two-dimensional metal phthalocyanine organic framework nanosheets prepared by the preparation method according to any one of claims 6 to 7.

9. A biosensor, characterized in that: The method comprises an electrode modified with the two-dimensional metal phthalocyanine organic framework nanosheet according to claim 8 as a working electrode, a silver chloride electrode as a reference electrode, an inert conductive electrode as a counter electrode, and an electrolyte having a pH of 6 to 7.

10. The use of a biosensor as claimed in claim 9, characterized in that: It is used for the detection of dopamine, uric acid, 5-hydroxytryptamine or ascorbic acid.

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