Metal coordination type polyimide and laser direct writing electrochemical electrode prepared from metal coordination type polyimide

Abstract

The invention provides metal coordination type polyimide and a laser direct writing electrochemical electrode prepared from the metal coordination type polyimide. Cyano-containing diamine is used as a chelating ligand, metal ions are used as central atoms, aromatic diamine monomers and tetracarboxylic dianhydride monomers are used as raw materials, low-temperature reaction is performed under the anhydrous condition to synthesize a polyamide acid precursor solution, and programmed heating is performed to obtain the metal coordination polyimide film material. A lamellar porous graphene structure is generated through laser-induced patterning treatment, and the electrochemical electrode is prepared after the lamellar porous graphene structure is cut. The laser direct writing polyimide electrochemical electrode shows excellent conductivity, sensitivity and flexibility under the dispersion effect of metal coordination and the electrochemical catalysis effect, can keep good linear response to various biological small molecule solutions within the low concentration range of 10-1000 M, and can be applied to brain-computer electrochemical interfaces and in-vivo intestinal health monitoring.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of polyimide films, in particular to a preparation and application of a metal coordination type polyimide laser direct writing electrochemical electrode. Funding information

[0002] The application is supported by the National Key Research and Development Program, and the project number is 2024YFF0728502. BACKGROUND

[0003] Graphene is a two-dimensional carbon nanomaterial with excellent performance. It has been widely used due to its unique chemical, mechanical, optical and electrical properties. Since Tour et al. (Nature, 2022, 606(7912): 94-101) first proposed a method of preparing graphene by laser scanning the surface of polyimide (PI) in 2014, laser-induced graphene (LIG) technology has gradually become one of the mainstream methods for preparing graphene due to its simplicity, speed, low cost and the absence of chemical reactions. This method not only has applications in basic research, but is also widely used to prepare graphene materials with different functions. Today, LIG technology has important application prospects in many fields such as biosensors, wearable devices and medical monitoring.

[0004] PI is often used as a substrate material for LIG due to its excellent electrical insulation, mechanical strength and chemical stability. By precisely controlling the laser power, scanning speed and environmental atmosphere, the controllability of its physical and electrical properties and sensitivity can be achieved. However, traditional PI films are not ideal choices for flexible electrochemical electrodes and have certain limitations. Most PI materials have a main chain containing benzene groups, which makes PI materials generally exhibit strong rigidity, resulting in low elongation at break and poor toughness, thereby limiting their widespread application in the field of flexible electrochemical electrodes.

[0005] In addition, with the continuous advancement of technology, the demand for the detection of biologically relevant analytes such as dopamine, serotonin, etc. is growing, which also promotes the increasing demand for flexible electrochemical electrodes. In addition to requiring electrode materials to have excellent flexibility and stability, excellent electrical conductivity is also essential. However, traditional PI materials may generate oxides and nitrides and other by-products under laser irradiation, which may cause defects in the graphene layer (Nature Communications, 2024, 15(1): 2925), thereby affecting its electrical conductivity and leading to poor electrical conductivity of the electrode. Therefore, there is an urgent need to develop new PI materials as substrates for LIG to improve the electrical conductivity, selectivity and sensitivity of graphene electrodes. SUMMARY

[0006] The present application proposes a metal coordination type polyimide and a laser direct writing electrochemical electrode prepared therefrom to solve the problems in the background art. In the preparation of the polyimide material, the present application innovatively uses a diamine molecule containing a cyano group as a ligand and introduces metal ions such as Cu²⁺ and Ni²⁺ to form a coordination structure.

[0007] The cyano group is a strong polar group, which, as a strong electron donor, can form a strong coordination bond with metal ions, firmly fixing the metal ions on the ligand diamine molecule, avoiding the metal ions from approaching each other to form clusters, and further inhibiting the migration and aggregation of the metal ions, so that the metal ions are uniformly dispersed in the polyimide solution. Compared with the ligand structure without a cyano group, the diamine molecule structure containing a cyano group in the present application has a stronger spatial constraint ability on the metal ions, avoiding the local aggregation of the metal ions, so that the dispersibility is more excellent.

[0008] At the same time, the introduction of the metal coordination structure significantly enhances the mechanical strength and toughness of the material, and at the same time promotes the formation of metal ions into better dispersed nanoparticles, thereby effectively improving the conductivity of the LIG prepared by the laser direct writing patterning process. In addition, through the metal coordination effect, the metal ions are uniformly dispersed in the polyimide solution, and after laser treatment, monodisperse transition metal nanoparticles can be obtained, which promotes the absorption and electron transfer of biological molecules, thereby catalytically improving the selectivity and sensitivity of amine biological active molecule sensing.

[0009] According to one aspect of the present application, the present application provides a metal coordination type polyimide, characterized in that the repeating unit structure of the polyimide is shown in general formula (1) or (2):

[0010] (1)

[0011] (2)

[0012] wherein --- represents a coordination bond, the number of which is different when connected with different metal ions;

[0013] Ar 1 represents: ;

[0014] is a benzene ring-containing group, each being the same or different, and is selected from:

[0015] ;

[0016] is a benzene ring-containing group, each being the same or different, and is selected from:

[0017] ,

[0018] wherein * represents a connecting bond, which, when present on an aromatic ring, can be connected to any one of the carbon atoms of the aromatic ring;

[0019] Ligand units containing cyano groups, same or different, are selected from the group consisting of:

[0020] ;

[0021] Metal ions, same or different, are selected from the group consisting of: Cu 2+ , Ni 2+ , Mn 2+ , Co 3+ , Cr 3+ , Mo 3+ , Ru 2+ , Os 2+ , Ir 3 + .

[0022] According to another aspect of the present application, the present application provides a preparation method of metal coordination type polyimide, characterized in that, comprising the following steps:

[0023] 1) under the condition of inert gas protection, adding amino phenolic compound, meta-dihalogen nitrile-based aromatic heterocyclic compound, base and organic solvent, and reacting to obtain ligand diamine molecule;

[0024] 2) under the protection of anhydrous and oxygen-free inert gas, reacting the ligand diamine molecule obtained in step 1), diamine monomer, dianhydride monomer and metal ion donor in an organic solvent to obtain metal ion coordination polyamic acid precursor solution;

[0025] 3) the polyamic acid precursor solution obtained in step 2) is programmed to warm up for imidization reaction to obtain the metal coordination type polyimide.

[0026] According to the embodiments of the present application, the amino phenolic compound can include p-aminophenol, and the meta-dihalogen nitrile-based aromatic heterocyclic compound can include meta-dihalogen benzonitrile-based compound, but not limited thereto.

[0027] The ligand diamine molecule has H2N- -NH2 structure, wherein, Ligand units containing cyano groups, same or different, are selected from the group consisting of:

[0028] .

[0029] The dianhydride monomer is a tetracarboxylic dianhydride, and its structure is shown in general formula (3):

[0030] (3)

[0031] are benzene ring-containing groups, each the same or different, selected from the group consisting of:

[0032] .

[0033] The diamine monomer is an aromatic diamine, and its structure is shown in general formula (4):

[0034] (4)

[0035] are benzene ring-containing groups, each the same or different, selected from the group consisting of:

[0036] .

[0037] The metal ions are the same or different, and are selected from the group consisting of: Cu 2+ , Ni 2+ , Mn 2+ , Co 3+ , Cr 3+ , Mo 3+ , Ru 2+ , Os 2+ , Ir 3+ .

[0038] Preferably, the ligand diamine molecules are the same or different, and are selected from the group consisting of:

[0039] .

[0040] Preferably, the molar ratio of the amino phenol compound, the meta-dihalogen cyanophenyl heterocyclic compound, the base and the organic solvent in step 1) is 2:1:2:10 ~ 2:1:2:50.

[0041] Preferably, step 1) comprises: after refluxing at 100 ~ 120℃ for 24 ~ 48 h, removing the solid precipitate by filtration, and then recrystallizing to obtain the solid powder of the ligand diamine molecules.

[0042] Preferably, the recrystallization solvent is an alcohol / water system, and the alcohol is selected from one or a combination of methanol, ethanol, ethylene glycol, isopropanol, 1,2-propanediol, n-butanol, 2-butanol or 1,3-butanediol.

[0043] Preferably, the base in step 1) is selected from one or a combination of potassium carbonate, sodium carbonate, potassium phosphate, potassium hydroxide and sodium hydroxide.

[0044] Preferably, the organic solvent of step 1) is selected from one or a combination of 1,4-dioxane, acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone; the reflux temperature of the reaction is preferably 120°C, and the reaction time is preferably 36 h.

[0045] Preferably, the reaction conditions of step 2) are 2 ~ 6 h of reaction in an organic solvent under anhydrous and anaerobic conditions at -20 ~ 10°C.

[0046] Preferably, step 2) further comprises adding a stabilizer to the polyamic acid precursor solution and then storing and defoaming to obtain a bubble-free stable polyamic acid precursor solution. Preferably, the bubble-free stable polyamic acid precursor solution has a solid content of 7 ~ 15 wt%.

[0047] Preferably, the stabilizer is tetramethyldisilazane, and the amount of the stabilizer added is preferably 1 ~ 5 wt‰ of the solid content.

[0048] Preferably, the metal ion donor of step 2) is selected from metal salts or small molecule metal complexes, for example, can be selected from one or more of copper (II) acetylacetonate, cobalt (III) acetylacetonate, copper (II) chloride, nickel (II) chloride, nickel (II) sulfate, nickel (II) nitrate hexahydrate, manganese (II) chloride hexahydrate, cobalt (II) chloride hexahydrate, nickel (II) bromide ethylene glycol dimethyl ether, nickel (II) chloride ethylene glycol dimethyl ether.

[0049] Preferably, in step 2), the amount of the ligand diamine molecule is 10 ~ 50 mol% of the total amount of all diamine monomers. The total amount of all diamine monomers refers to the total amount of the ligand diamine molecule and the diamine monomer.

[0050] Preferably, in step 2), the molar ratio of the ligand diamine molecule to the metal ion donor is 2:1 ~ 10:1.

[0051] Preferably, the organic solvent of step 2) is selected from at least one of N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide.

[0052] Preferably, step 3) is to use a doctor blade to coat the bubble-free stable polyamic acid precursor solution obtained in step 2) on a substrate to form a film, and to perform an imidization reaction by programmed temperature rising to obtain a thin film of the metal-coordinated polyimide.

[0053] Preferably, the coating speed is 15 cm / min, the substrate is selected from one of a glass substrate, a polyether sulfone plate and a polyether ether ketone plate, and the thickness of the substrate can be 200 ~ 250 μm.

[0054] Preferably, step 2) further includes cleaning the substrate using oxygen plasma for 2 minutes.

[0055] Preferably, the programmed heating conditions are as follows: the programmed heating rate is 1~3℃ / min; heating at 60~90℃ for 1~3 h; heating to 100~140℃ for 0.5~2 h; heating to 160~180℃ for 0.5~2 h; heating to 220~260℃ for 0.5~1 h; heating to 280~320℃ for 0.5~2 h; heating to 350~380℃ for 0.5~1 h; and the programmed cooling rate is 1~5℃ / min, cooling to room temperature.

[0056] According to another aspect of the present invention, a metal-coordinated polyimide laser direct-write electrochemical electrode is provided, which is prepared by using the metal-coordinated polyimide of the present invention.

[0057] According to another aspect of the present invention, a method for preparing a metal-coordinated polyimide laser-written electrochemical electrode is provided, characterized by comprising the following steps:

[0058] 1') According to the above-described method for preparing metal-coordinated polyimide, a thin film of the metal-coordinated polyimide is prepared;

[0059] 2') Using a pulsed laser generated by a laser device, electrodes are directly patterned on the surface of the metal coordination polyimide film obtained in step 1') to obtain a patterned laser direct-write electrochemical electrode.

[0060] The laser direct-write electrochemical electrode prepared by the above method can realize the detection of small biological molecules such as dopamine.

[0061] Preferably, step 2') further includes: using a pulsed laser generated by a CO2 laser etching machine to directly perform laser carbonization on the surface of a metal coordination polyimide film on a substrate to form a conductive nanoporous graphene network modified with metal nanoparticles.

[0062] Preferably, step 2') further includes: using a 30 W laser power to perform laser cutting to remove unwanted parts and form a small, independent laser-written electrochemical electrode.

[0063] Preferably, the laser speed in step 2') is 500 mm / s, the laser focal length is 8 cm, the laser intensity is 2.4 ~ 7.2 W with an increment of 0.6 W, and the laser wavelength is 10.6 μm.

[0064] According to another aspect of the present invention, the present invention provides the application of the metal coordination polyimide laser direct writing electrochemical electrode in the detection of bioactive small molecules.

[0065] Specifically, using the laser-direct-writing electrochemical electrode prepared according to this invention and employing a three-electrode system, cyclic voltammetry (CV) tests were performed on bioactive small molecules such as dopamine, norepinephrine, epinephrine, serotonin, acetylcholine, and glutamate. The test voltage range was -0.6 to 1.2 V, the scan rate was 0.1 to 100 V / s, and the background solution was phosphate buffered saline (PBS) at pH 7.4. The metal-coordinated polyimide laser-direct-writing electrochemical electrode of this invention exhibits excellent sensitivity and linear response, enabling the detection of low concentrations of biomolecules.

[0066] The advantages of this invention are:

[0067] 1. From a polymer perspective: This invention utilizes cyano-containing diamine molecules as chelating ligands and metal ions as central atoms to achieve the synthesis of functional materials through metal coordination. Metal coordination enhances the interactions between polymer molecular chains, thereby significantly improving the mechanical properties of the materials.

[0068] 2. From the perspective of electrochemical sensing: Through metal coordination, metal ions are uniformly dispersed in a polyimide solution. After laser treatment, monodisperse transition metal nanoparticles are obtained, promoting biomolecular absorption and electron transfer, thereby catalyzing and improving the selectivity and sensitivity of amine-based bioactive molecules. The uniformly dispersed nanoparticles can also effectively improve the conductivity of the electrochemical electrode, reduce interfacial impedance and electrocatalytic activity. The flexible electrochemical electrode prepared in this way possesses excellent conductivity, sensitivity, flexibility, and durability, with a long service life, and shows promising application prospects in the field of flexible wearable sensors.

[0069] 3. From an industrial production perspective: This invention successfully prepared various graphene electrochemical electrodes based on the aforementioned metal-coordinated polyimide, and achieved good results in detecting the concentration of bioactive small molecules such as dopamine. Experimental results show that the electrochemical electrodes of this invention have broad application potential in the detection of biorelated analytes. The laser direct writing method for preparing patterned electrochemical electrodes has the advantages of speed and miniaturization, and is suitable for the preparation of micro electrochemical motors, with potential applications in areas such as brain-computer interfaces and in vivo intestinal health monitoring. Attached Figure Description

[0070] Figure 1 These are graphene surface morphology images (50 μm scale) under different laser powers.

[0071] Figure 2The present invention provides cyclic voltammetry (CV) curves for detecting dopamine biomolecules using a polyimide laser direct writing electrochemical electrode. (a) shows the polyimide laser direct writing electrochemical electrode with uncoordinated metal ions in Comparative Example 1, (b) shows the metal-coordinated polyimide laser direct writing electrochemical electrode in Example 1, and their respective electrochemical concentration-current signal graphs (c) and (d).

[0072] Figure 3 Cyclic voltammetry (CV) curves of four different biomolecules detected using the metal-coordinated polyimide laser direct-write electrochemical electrode of the present invention are shown, wherein (a) is dopamine, (b) is norepinephrine, (c) is epinephrine, and (d) is serotonin, and their respective electrochemical concentration-current signal graphs (e) to (h). Detailed Implementation

[0073] This invention can be implemented through the following embodiments:

[0074] Example 1:

[0075] 1) Under inert gas protection, 0.86 g of 2,6-dichlorobenzonitrile, 1.09 g of 4-aminophenol, and 2.76 g of anhydrous potassium carbonate were dissolved in 25 ml of dimethyl sulfoxide. The solution was stirred and heated at 120 °C for about 36 h, and then poured into water. The solid precipitate was removed by filtration, and the solution was then recrystallized using an ethanol-water mixed solvent to obtain a solid powder, namely the product 2,6-bis(4-aminophenoxy)benzonitrile.

[0076] 2) Under an anhydrous and oxygen-free inert gas atmosphere, 0.793 g of 2,6-bis(4-aminophenoxy)benzonitrile and 0.500 g of 4,4'-diaminodiphenyl ether were dissolved in 10 ml of N,N-dimethylacetamide. 1.470 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added at 10 °C, and the reaction was allowed to proceed for 2 h. Then, 0.131 g of copper(II) acetylacetonate was added, and the reaction was continued for another 2 h. During this period, N,N-dimethylacetamide was added to dilute the solution to 15% wt, yielding a polyamic acid precursor solution. After adding 2.5 mg of tetramethyldisilazane, the solution was allowed to stand for 24 h to remove bubbles, resulting in a bubble-free, stable polyamic acid precursor solution.

[0077] 3) Using a gap-type coating machine, the bubble-free, stable polyamic acid precursor solution obtained in step 2) was coated onto a borosilicate glass plate to form a film. The imidization reaction was then carried out using a programmed temperature rise. The programmed temperature rise was conducted under nitrogen atmosphere at a rate of 2 °C / min. The temperature was increased to 80 °C for 2 h, then increased to 100 °C for 1 h, then increased to 160 °C for 1 h, then increased to 220 °C for 1 h, then increased to 280 °C for 1 h, then increased to 320 °C for 0.6 h, then increased to 360 °C for 0.5 h. The programmed cooling rate was 5 °C / min, cooling to room temperature to obtain a metal-coordinated polyimide film.

[0078] Subsequently, using pulsed laser light generated by a laser device, electrodes were directly patterned on the surface of the obtained metal-coordinated polyimide film to obtain a patterned laser direct-write electrochemical electrode, thus completing the preparation of the metal-coordinated polyimide laser direct-write electrochemical electrode, and using this electrode to detect bioactive small molecules.

[0079] Example 2:

[0080] Except that in the synthesis of the ligand diamine molecule in step 1), 2,6-dibromobenzonitrile was used instead of 2,6-dichlorobenzonitrile as the m-dihalobenzonitrile compound, 4-amino-2,5-dimethylphenol was used instead of 4-aminophenol as the p-aminophenol, anhydrous sodium carbonate was used instead of anhydrous potassium carbonate as the base, and in the synthesis of the polyamic acid precursor in step 2), 2,6-bis(4-amino-2,5-dimethylphenoxy)benzonitrile prepared therefrom was added as the ligand diamine molecule, and cobalt acetylacetonate (III) was used instead of copper acetylacetonate (II) as the metal ion, the metal coordination type polyimide film and the laser direct writing electrochemical electrode were prepared in the same manner as in Example 1.

[0081] Example 3:

[0082] Except that in the synthesis of the ligand diamine molecule in step 1), 2,6-diiodo-4-methylbenzonitrile was used instead of 2,6-dichlorobenzonitrile as the m-dihalobenzonitrile compound, anhydrous potassium phosphate was used instead of anhydrous potassium carbonate as the base, and in the synthesis of the polyamic acid precursor in step 2), 2,6-di(4-aminophenoxy)-4-methylbenzonitrile prepared therefrom was added as the ligand diamine molecule, and ethylene glycol dimethyl ether nickel(II) chloride was used instead of copper(II) acetylacetonate as the metal ion, the metal coordination type polyimide film and laser direct writing electrochemical electrode were prepared in the same manner as in Example 1.

[0083] Example 4:

[0084] Except that in the synthesis of the ligand diamine molecule in step 1), 2,6-dibromobenzonitrile was used instead of 2,6-dichlorobenzonitrile as the m-dihalobenzonitrile compound, 4-amino-2,5-dimethylphenol was used instead of 4-aminophenol as the p-aminophenol, anhydrous potassium hydroxide was used instead of anhydrous potassium carbonate as the base, and in the synthesis of the polyamic acid precursor in step 2), 2,6-bis(4-amino-2,5-dimethylphenoxy)benzonitrile prepared therefrom was added as the ligand diamine molecule, and ethylene glycol dimethyl ether nickel(II) chloride was used instead of copper(II) acetylacetonate as the metal ion, the metal coordination type polyimide film and laser direct writing electrochemical electrode were prepared in the same manner as in Example 1.

[0085] Example 5:

[0086] Except that in the synthesis of the ligand diamine molecule in step 1), 2,6-diiodo-4-trifluoromethylbenzonitrile was used instead of 2,6-dichlorobenzonitrile as the m-dihalobenzonitrile compound, anhydrous sodium hydroxide was used instead of anhydrous potassium carbonate as the base, and in the synthesis of the polyamic acid precursor in step 2), 2,6-bis(4-aminophenoxy)-4-trifluoromethylbenzonitrile prepared therefrom was added as the ligand diamine molecule, and cobalt acetylacetonate (III) was used instead of copper acetylacetonate (II) as the metal ion, the metal coordination type polyimide film and the laser direct writing electrochemical electrode were prepared in the same manner as in Example 1.

[0087] Example 6:

[0088] Except that in the synthesis of the ligand diamine molecule in step 1), 2,6-dibromobenzonitrile was used instead of 2,6-dichlorobenzonitrile as the m-dihalobenzonitrile compound, 5-aminobenzofuran-2-hydroxy was used instead of 4-aminophenol as the aminophenol compound, anhydrous potassium hydroxide was used instead of anhydrous potassium carbonate as the base, and in the synthesis of the polyamic acid precursor in step 2), 2,6-bis(5-aminobenzofuranoxy)benzonitrile prepared therefrom was added as the ligand diamine molecule, and ethylene glycol dimethyl ether nickel(II) chloride was used instead of copper(II) acetylacetonate as the metal ion, the metal coordination type polyimide film and laser direct writing electrochemical electrode were prepared in the same manner as in Example 1.

[0089] Comparative Example 1:

[0090] Except for the absence of copper acetylacetonate (II) in the synthesis of the polyamic acid precursor in step 2), the polyimide film and the electrochemical electrode without metal particle doping were prepared in the same manner as in Example 1.

[0091] Experimental Example 1:

[0092] The metal-coordinated polyimide films prepared in Examples 1-6 and the polyimide film in Comparative Example 1 were cut into dumbbell-shaped strips for tensile testing. The thickness of the strips was measured to be 75 μm, and the tensile rate was 5 mm / min. The results are shown in Table 1 below, indicating that the polymer film materials of the embodiments of the present invention have excellent mechanical strength and high tensile strain.

[0093] Table 1. Maximum fracture stress and fracture strain for Examples 1-6 and Comparative Example 1

[0094]

[0095] Experimental Example 2:

[0096] The metal-coordinated polyimide laser-written electrochemical electrodes prepared in Examples 1-6 and the electrode prepared in Comparative Example 1 were subjected to resistance and conductivity tests. The electrodes were 2.5 cm long, 1.5 cm wide, and 75 μm thick. The results are shown in Table 2 below, indicating that the metal-coordinated polyimide laser-written electrochemical electrodes of the present invention have lower resistance and better conductivity.

[0097] Table 2. Resistance and conductivity of Examples 1-6 and Comparative Example 1

[0098]

[0099] Experimental Example 3:

[0100] The metal-coordinated polyimide laser direct-writing electrochemical electrode prepared in Example 1 and the electrochemical electrode without metal ion coordination prepared in Comparative Example 1 were used to detect the concentration of dopamine biomolecules. The test voltage range was -0.6 ~ 1.2 V, and the scan rate was 0.3 V / s. The results are as follows: Figure 2 As shown, it can be demonstrated that, compared with the uncoordinated polyimide laser direct writing electrochemical electrode prepared in Comparative Example 1, the metal-coordinated polyimide laser direct writing electrochemical electrode prepared in Example 1 of the present invention has superior sensitivity and can be used for the detection of biomolecule concentrations in a low concentration gradient range of 10 ~ 1000 μM.

[0101] Experimental Example 4:

[0102] Using any of the metal-coordinated polyimide laser direct-write electrochemical electrodes prepared in Examples 1-6, the concentrations of four small biomolecules—dopamine, norepinephrine, epinephrine, and serotonin—were detected. The test voltage range was -0.6 to 1.2 V, and the scan rate was 0.3 V / s. The results are as follows: Figure 3As shown, it can be demonstrated that the metal-coordinated polyimide laser direct-write electrochemical electrode prepared in the embodiments of the present invention can maintain a good linear response to a variety of small biological molecules in a low concentration range of 10 ~ 1000 μM, with high sensitivity, and can be applied to brain-computer interfaces and in vivo intestinal health monitoring.

[0103] Experimental Example 5:

[0104] To investigate the laser carbonization process, this invention treated the metal-coordinated polyimide in Example 1 with different laser powers to prepare a laser-written electrochemical electrode, and characterized its microstructure using SEM. The results showed that at the 50 μm scale, a laser power of 7.2 W could form a loose graphene structure with conductivity; while powers of 4.8 W and below could not form this structure and therefore did not exhibit conductivity. Based on this, a laser carbonization process can be designed.

[0105] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A metal-coordinated polyimide, characterized in that, The repeating unit structure of the metal-coordinated polyimide is shown in general formula (1) or (2): （1） （2） Where --- represents a coordinate bond; Ar 1 express: ; The groups are groups containing benzene rings, which may be the same or different, and are selected from: ； The groups are groups containing benzene rings, which may be the same or different, and are selected from: ， The ligands are cyano-containing units, which may be identical or different, and are selected from: ； Metal ions, whether the same or different, selected from: Cu 2+ Ni 2+ Mn 2+ Co 3+ Cr 3+ Mo 3+ Ru 2+ Os 2+ Ir 3+ .

2. A method for preparing the metal-coordinated polyimide as described in claim 1, characterized in that, Includes the following steps: 1) Under inert gas protection, aminophenolic compounds, m-dihalonitrile aromatic heterocyclic compounds, bases and organic solvents are added to react and give ligand diamine molecules; 2) Under the protection of anhydrous and oxygen-free inert gas, the ligand diamine molecule, diamine monomer, dianhydride monomer and metal ion donor obtained in step 1) are reacted in an organic solvent to obtain a polyamic acid precursor solution coordinated with metal ions. 3) The polyamic acid precursor solution obtained in step 2) is subjected to an imidization reaction with programmed temperature increases to obtain the metal-coordinated polyimide. The ligand diamine molecule has H2N- The -NH2 structure, in which, The ligands are cyano-containing units, which may be identical or different, and are selected from: ； The structure of the dianhydride monomer is shown in general formula (3): （3） The groups are groups containing benzene rings, which may be the same or different, and are selected from: ； The structure of the diamine monomer is shown in general formula (4): （4） The groups are groups containing benzene rings, which may be the same or different, and are selected from: ； The metal ions may be the same or different, and are selected from: Cu 2+ Ni 2+ Mn 2+ Co 3+ Cr 3+ Mo 3+ Ru 2+ Os 2+ Ir 3+ .

3. The method according to claim 2, characterized in that, The ligand diamine molecules may be the same or different, and are selected from: 。 4. The method according to claim 2, characterized in that, In step 1), the molar ratio of aminophenolic compounds, m-dihalonitrile aromatic heterocyclic compounds, base and organic solvent is 2:1:2:10 ~ 2:1:2:

50.

5. The method according to claim 2, characterized in that, Step 1) includes: after reflux reaction at 100 ~ 120℃ for 24 ~ 48 h, filtering to remove solid precipitate, and then recrystallizing to obtain the solid powder of the ligand diamine molecule.

6. The method according to claim 2, characterized in that, The metal ion donor is selected from metal salts or small molecule metal complexes.

7. The method according to claim 2, characterized in that, The metal ion donor is selected from one or more of the following: copper acetylacetonate (II), cobalt acetylacetonate (III), copper chloride (II), nickel chloride (II), nickel sulfate (II), nickel nitrate hexahydrate (II), manganese chloride hexahydrate (II), cobalt chloride hexahydrate (II), nickel bromide in ethylene glycol dimethyl ether (II), and nickel chloride in ethylene glycol dimethyl ether (II).

8. The method according to claim 2, characterized in that, The reaction conditions for step 2) are -20 ~ 10℃ anhydrous and oxygen-free conditions in the organic solvent for 2 ~ 6 h.

9. The method according to claim 2, characterized in that, Step 2) further includes adding a stabilizer to the polyamic acid precursor solution and then storing it to remove bubbles, thereby obtaining a bubble-free stable polyamic acid precursor solution.

10. The method according to claim 2, characterized in that, In step 2), the amount of the ligand diamine molecule is 10 to 50 mol% of the total amount of the ligand diamine molecule and the diamine monomer.

11. The method according to claim 2, characterized in that, In step 2), the molar ratio of the ligand diamine molecule to the metal ion donor is 2:1 to 10:

1.

12. The method according to claim 9, characterized in that, Step 3) involves using a doctor blade to coat the bubble-free, stable polyamic acid precursor solution obtained in step 2) onto a substrate to form a film, and then performing an imidization reaction by programmed temperature rise to obtain the metal-coordinated polyimide film.

13. A metal-coordinated polyimide laser-written electrochemical electrode, characterized in that, The metal-coordinated polyimide laser direct writing electrochemical electrode is prepared using the metal-coordinated polyimide described in claim 1.

14. A method for preparing a metal-coordinated polyimide laser-written electrochemical electrode, characterized in that, Includes the following steps: 1') The method for preparing metal-coordinated polyimide according to claim 12, wherein a thin film of the metal-coordinated polyimide is prepared; 2') Using a pulsed laser generated by a laser device, electrodes are directly patterned on the surface of the metal coordination polyimide film obtained in step 1') to obtain a patterned laser direct-write electrochemical electrode.

15. The method according to claim 14, characterized in that, Step 2') further includes using a pulsed laser generated by a CO2 laser etching machine to directly perform laser carbonization on the surface of the metal coordination polyimide film on the substrate, forming a conductive nanoporous graphene network modified with metal nanoparticles.

16. The application of the metal coordination polyimide laser direct writing electrochemical electrode as described in claim 13 in the detection of bioactive small molecules.

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