Iridium metal organic compound covalently functionalized graphene oxide ternary nano-hybrid material and preparation method thereof

Abstract

The invention discloses a ternary nano-hybrid material of iridium metal organic compound covalent functionalized graphene oxide and its preparation method, specifically first using phenylpyrazolyl cyclometal iridium dimer as metal organic precursor and auxiliary ligand 4,4' diamino-2,2'-bipyridine and 4-(2-quinolinyl methylene)-aminobenzoic acid for coordination, to obtain two iridium metal organic compounds with carboxylic acid functional group and amino functional group, then the two synthesized iridium metal organic compounds are respectively covalently linked to the carboxyl group at the edge of graphene oxide and the hydroxyl group on the surface by esterification reaction using their amino functional group. The iridium metal organic compound covalent functionalized graphene oxide ternary nano-hybrid material prepared by the present invention has obvious fluorescence quenching phenomenon compared with the two metal organic compound monomers, and can be applied to the field of electrochemical biosensing.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical biosensing, and in particular relates to an iridium metal organic compound covalently functionalized graphene oxide ternary nano-hybrid material and a preparation method thereof. Background Art

[0002] Compared to graphene, graphene oxide (GO) contains a large number of oxygen-containing groups on its surface and edge layers, mainly carboxyl groups located at the edge of GO and hydroxyl and epoxy groups on the surface of GO, which enables GO to exist stably in aqueous solutions and organic solvents. The presence of these oxygen-containing groups makes the originally single graphene structure diversified, provides the possibility of modification and reaction sites for GO, and also makes the application of GO more extensive. The materials for modifying GO mainly include metal particles, metal oxides, MOF materials and polymer materials, and the modification methods include in situ synthesis and doping. Since there are a large number of oxygen-containing functional groups such as hydroxyl groups, carboxyl groups and epoxy groups on the surface of graphene oxide, this provides reaction sites for the surface functionalization modification of graphene oxide. These oxygen-containing groups can be used to achieve covalent connection between GO and the modified material.

[0003] Iridium-containing organometallic compounds exhibit excellent luminescence properties due to their unique electronic structure, resulting in high photoluminescence quantum yields and short phosphorescence lifetimes. Their metal centers can be combined with different ligands to modulate fluorescence properties in different wavelength bands, attracting extensive research and attention in the fields of OLEDs, LECs, fluorescent probes, bioimaging, and nonlinear optics. Studies have shown that the conjugation of auxiliary ligands in iridium organometallic compounds can be regulated by introducing electron-donating and electron-withdrawing groups, thereby modifying the LUMO and HOMO energy levels of the system. Graphene oxide (GO) has a large π-conjugated system. By functionalizing the auxiliary ligands of iridium organometallic compounds, they can be covalently linked to GO. This allows for the simultaneous covalent modification of GO and conjugation regulation of the iridium organometallic compound, thereby constructing metal-organic-inorganic nanohybrid materials.

[0004] Therefore, by utilizing the large number of hydroxyl and carboxyl functional groups on the surface of graphene oxide (GO) and modifying the auxiliary ligands of iridium-containing metal organic compounds, we can prepare iridium metal organic compound covalently functionalized graphene oxide ternary nanohybrid materials, study their photoelectric properties, and ultimately apply them to fields such as fluorescent biosensors. Summary of the Invention

[0005] The present invention mainly comprises the following steps: based on a phenylpyrazole iridium metal dimer, two iridium metal organic compounds are coordinated with auxiliary ligands having carboxyl and amino functional groups, respectively, to synthesize two iridium metal organic compounds; then, carboxyl and hydroxyl groups on graphene oxide (GO) are covalently linked by carboxyl-amino dehydration condensation reaction and esterification reaction to prepare an iridium metal organic compound covalently functionalized graphene oxide ternary nano-hybrid material. Tests show that the hybrid material exhibits obvious fluorescence quenching compared with the two metal organic compound monomers, and the fluorescence is completely quenched within the range of 600 to 800 nm.

[0006] The present invention first provides a ternary nano-hybrid material of iridium metal organic compound covalently functionalized graphene oxide, the structural formula of which is shown in the figure below:

[0007]

[0008] In order to solve the above problems, the present invention also provides a method for preparing a ternary nano-hybrid material of iridium metal organic compound covalently functionalized graphene oxide, comprising the following steps:

[0009] Step (1) Synthesis of phenylpyrazole ring metal iridium dimer [Ir(ppz)2(μ-Cl)]2:

[0010] Hydrated iridium trichloride and 1-phenylpyrazole ligand were added to a reaction flask in proportion, and a mixed solvent of ethylene glycol ethyl ether and distilled water was added. The reaction was carried out under N2 protection at condensation reflux. The progress of the reaction was monitored by TLC during the reaction. After the reaction was completed, the solution was cooled to room temperature, filtered, washed, extracted and purified, and the organic phase was finally dried to obtain a light yellow solid [Ir(ppz)2(μ-Cl)]2.

[0011] Step (2) Synthesis of auxiliary ligand 4,4'-diamino-2,2'-bipyridine (bpd):

[0012] Add N,N′-dioxide-2,2′-bipyridine to a reaction flask, add concentrated sulfuric acid dropwise, cool with ice water, then add concentrated nitric acid. The resulting solution is heated to reflux. After the reaction is complete, place the mixture in a refrigerator to allow it to stand, forming a yellow precipitate, the intermediate product 4,4′-dinitro-N,N′-dioxide-2,2′-bipyridine. The collected intermediate product and the catalyst (5%) of Pd / C are mixed in a reaction flask, ethanol is added, and the mixture is heated to reflux under a nitrogen atmosphere. Hydrazine hydrate is slowly added dropwise to the solution during the reaction. After the reaction is complete, the solvent is evaporated to yield the yellow target product, 4,4′-diamino-2,2′-bipyridine (bpd).

[0013] Step (3) Synthesis of auxiliary ligand 4-(2-quinolinylmethylene)-aminobenzoic acid (baqma):

[0014] Weigh 2-quinolinecarboxaldehyde into a reaction flask, add methanol, and sonicate until completely dissolved. Then add p-aminobenzoic acid and stir to react. Monitor the reaction using TLC. After the reaction is complete, use a rotary evaporator to dry the solvent to obtain the orange target product, 4-(2-quinolinylmethylidene)-aminobenzoic acid (baqma).

[0015] Step (4) Synthesis of iridium metal organic compound [Ir(ppz)2(bpd)][PF6][CH2Cl2](Ir-bqd):

[0016] The phenylpyrazole ring metal iridium dimer prepared in step (1) and the auxiliary ligand 4,4'-diamino-2,2'-bipyridine (bpd) prepared in step (2) are added to a reaction bottle in a certain molar ratio, and then dichloromethane, methanol and potassium hexafluorophosphate are added in sequence. The reaction is placed in a light-proof environment under the protection of N2 for condensation reflux reaction. The degree of reaction is monitored by TLC during the reaction. After the reaction is completed, it is purified by column chromatography to obtain a solid iridium metal organic compound (Ir-bqd).

[0017] Step (5) Synthesis of iridium metal organic compound [Ir(ppz)2(baqma)][PF6][CH2Cl2](Ir-baqma):

[0018] The phenylpyrazole ring metal iridium dimer prepared in step (1) and the auxiliary ligand 4-(2-quinolinylmethylidene)-aminobenzoic acid (baqma) prepared in step (3) are added to a reaction flask in a certain molar ratio, and then dichloromethane, methanol and potassium hexafluorophosphate are added in sequence. The reaction is carried out in a light-proof environment under the protection of N2 and condensed reflux reaction is carried out. The progress of the reaction is monitored by TLC during the reaction. After the reaction is completed, it is purified by column chromatography to obtain a solid iridium metal organic compound (Ir-baqma).

[0019] Step (6) Preparation of ternary nano-hybrid materials of iridium metal organic compound covalently functionalized graphene oxide:

[0020] The iridium metal organic compound Ir-bqd obtained in step (4) and the iridium metal organic compound Ir-baqma obtained in step (5) are added to a reaction bottle in a certain proportion, and then N,N′-dicyclohexylcarbodiimide (DCC) is added, and then the reaction solvent DMF is added, ultrasonicated and heated to the reaction temperature, stirred and refluxed, first cooled and then distilled water is added for filtration, washed with CH2Cl2 and ethanol, and vacuum dried to obtain the final gray-black product iridium metal organic compound covalently functionalized graphene oxide ternary nanohybrid material.

[0021] Further,

[0022] In step (1), the molar ratio of the hydrated iridium trichloride to the 1-phenylpyrazole ligand is 1:2;

[0023] In the mixed solvent of ethylene glycol ethyl ether and distilled water, the volume ratio of ethylene glycol ethyl ether to distilled water is 5:1;

[0024] The temperature of the condensation reflux reaction is 130-140°C, and the reaction time is 24-36 hours;

[0025] The washing solvents were ethanol and petroleum ether; the extraction solvents were CH2Cl2 and H2O.

[0026] Furthermore, in step (2), the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 5:2; the mass ratio of the intermediate product to the catalyst Pd / C (5%) and hydrazine hydrate is 100:3:5, wherein the mass percentage of Pt in the catalyst Pd / C is 5%;

[0027] When preparing the intermediate product, the intermediate product is heated under reflux at a temperature of 90 to 100° C. and the reaction time is 24 to 36 hours;

[0028] When the intermediate product reacts with the catalyst Pd / C, the reaction temperature under reflux is 75-80° C. and the reaction time is 8-12 hours.

[0029] Furthermore, in step (3), the molar ratio of 2-quinolinecarboxaldehyde to p-aminobenzoic acid is 1:1, the stirring reaction temperature is 25° C., and the reaction time is 6 to 12 hours.

[0030] Furthermore, in step (4), the molar ratio of the phenylpyrazole ring metal iridium dimer to the auxiliary ligand 4,4'diamino-2,2'-bipyridine (bpd) is 1:2 to 1:3, the volume ratio of dichloromethane to methanol is 2:1 to 4:1, and the molar ratio of the amount of potassium hexafluorophosphate added to the amount of the auxiliary ligand 4,4'diamino-2,2'-bipyridine added is 2:1;

[0031] The condensation reflux temperature is 80-90°C, and the reaction time is 24-36h.

[0032] Furthermore, in step (5), the molar ratio of the phenylpyrazole ring metal iridium dimer to the auxiliary ligand 4-(2-quinolinylmethyl)-aminobenzoic acid (bapma) is 1:2 to 1:3, the volume ratio of dichloromethane to methanol is 2:1 to 4:1, and the molar ratio of the amount of potassium hexafluorophosphate added to the amount of the auxiliary ligand 4-(2-quinolinylmethyl)-aminobenzoic acid added is 2:1; when purified by column chromatography, V 二氯甲烷 :V 乙醇 =3:1; the stirring reaction temperature is 25°C and the reaction time is 24h.

[0033] Furthermore, in step (6), the molar ratio of the iridium metal organic compound [Ir(ppz)2(bpd)][PF6][CH2Cl2](Ir-bqd), [Ir(ppz)2(baqma)][PF6][CH2Cl2](Ir-baqma) and graphene oxide is 1:1:1 to 3:3:1, and the molar ratio of the amount of N,N-dicyclohexylcarbodiimide added to the amount of [Ir(ppz)2(bpd)][PF6][CH2Cl2] added is 3:2. The condensation reflux reaction temperature is 140-150°C, and the reaction time is 7-10 days.

[0034] The iridium metal organic compound covalently functionalized graphene oxide ternary nanohybrid material prepared by the present invention can be applied to the field of biosensing due to its unique fluorescence properties and chemical characteristics, has potential value as a fluorescent detection material, and is used to prepare a kit for detecting esterase in organisms.

[0035] Principle of the present invention:

[0036] Compared with graphene, graphene oxide (GO) contains a large number of oxygen-containing groups on its surface and edge layers, mainly carboxyl groups located at the edge of GO and hydroxyl and epoxy groups on the surface of GO, which enable GO to exist stably in aqueous solutions and organic solvents. This patent uses phenylpyrazole iridium dimer with good photothermal stability as a precursor building unit, and designs and synthesizes auxiliary ligands 4,4'diamino-2,2'-bipyridine and 4-(2-quinolinylmethyl)-aminobenzoic acid with carboxylic acid functional groups and amino functional groups, and coordinates to obtain two iridium metal organic compounds. Then, the carboxylic acid functional groups and amino functional groups on the two iridium metal organic compounds are used to react with the hydroxyl groups on the GO surface and the carboxyl groups on the edge of GO through carboxyl-amino dehydration condensation reaction and esterification reaction to form amide bonds and ester bonds, respectively, to achieve covalent connection between the iridium metal organic compound and GO, and obtain the corresponding iridium metal organic compound covalently functionalized graphene oxide ternary nanohybrid material.

[0037] Furthermore, the ternary nanohybrid material of iridium organometallic compound covalently functionalized graphene oxide prepared by the present invention exhibits significant fluorescence quenching compared to the two organometallic compound monomers within the 300-600 nm range, while fluorescence is completely quenched within the 600-800 nm range. Based on the hybrid material's properties of containing both amide and ester bonds and exhibiting fluorescence quenching compared to the monomers, it can be used to detect esterases, such as carboxylesterase, in organisms. By utilizing the esterase's ability to catalyze the hydrolysis of esters, sulfates, and amides, the hybrid material, when hydrolyzed by the esterase, breaks the covalent bond between the iridium organometallic compound and graphene oxide, allowing the fluorescence properties of the iridium organometallic compound to be observed again.

[0038] Beneficial effects of the present invention:

[0039] (1) The ternary nanohybrid material of iridium metal organic compound covalently functionalized graphene oxide prepared by the present invention realizes the double covalent connection of hydroxyl and carboxyl groups on the surface of graphene oxide.

[0040] (2) The present invention selects two iridium-containing metal organic compounds to covalently modify graphene oxide. The synthesis conditions of the iridium metal organic compounds are mild and the subsequent treatment is simple, and they have good photothermal stability.

[0041] (3) The ternary nanohybrid material of iridium metal organic compound covalently functionalized graphene oxide prepared by the present invention has a significant fluorescence quenching effect compared with the monomer of iridium metal organic compound, and can be used in the field of fluorescent biosensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The invention discloses a synthetic route for a ternary nanohybrid material of graphene oxide covalently functionalized with an iridium phenylpyrazole precursor (A), a 4,4′-diamino-2,2′-bipyridine auxiliary ligand (B), a 4-(2-quinolinylmethyl)-aminobenzoic acid auxiliary ligand (C), an iridium metal organic compound [Ir(ppz)2(bpd)][PF6][CH2Cl2] (D), an iridium metal organic compound [Ir(ppz)2(baqma)][PF6]-[CH2Cl2] (E), and an iridium metal organic compound covalently functionalized graphene oxide (F).

[0043] Figure 2 It is the unit structure of the iridium metal organic compounds [Ir(ppz)2(bpd)][PF6][CH2Cl2] and [Ir(ppz)2(baqma)][PF6][CH2Cl2].

[0044] Figure 3 The infrared spectra of two iridium metal organic compounds, graphene oxide and the iridium metal organic compound covalently functionalized graphene oxide ternary nano-hybrid material prepared by the present invention.

[0045] Figure 4 The diagram shows the ultraviolet-visible spectra of two iridium metal organic compounds, graphene oxide and the ternary nano-hybrid material of iridium metal organic compound covalently functionalized graphene oxide prepared by the present invention.

[0046] Figure 5 The fluorescence spectra of two iridium metal organic compounds and the iridium metal organic compound covalently functionalized graphene oxide ternary nano-hybrid material prepared by the present invention are shown.

[0047] Figure 6The thermogravimetric diagrams of two iridium metal organic compounds, graphene oxide and the iridium metal organic compound covalently functionalized graphene oxide ternary nano-hybrid material prepared by the present invention. DETAILED DESCRIPTION

[0048] The present invention is described or further illustrated below with reference to the accompanying drawings and specific examples, and detailed implementation methods and specific operating procedures are given for the purpose of better understanding the technical connotation of the present invention, but the protection scope of the present invention is not limited thereto.

[0049] Example 1:

[0050] (1) Synthesis of iridium precursor [Ir(ppz)2(μ-Cl)]2:

[0051] Figure 1 A is the synthetic route for the iridium precursor [Ir(ppz)2(μ-Cl)]2. A two-necked flask was charged with 300 mg (0.92 mmol) of hydrated iridium trichloride and 0.244 mL (1.84 mmol) of the chelating ligand 1-phenylpyrazole. Then, 40 mL of ethylene glycol ether and 8 mL of distilled water were added as reaction solvents. The mixture was refluxed at 135°C under nitrogen for 24 hours, with TLC monitoring the reaction progress. After the reaction was complete, the solution was cooled to room temperature and filtered using a small Buchner funnel. The resulting precipitate was washed with ethanol and petroleum ether to remove the starting materials and byproducts. The precipitate was then extracted and purified three times with CH2Cl2 and H2O. Finally, the organic phase was dried to yield 356 mg of the desired product, [Ir(ppz)2(μ-Cl)]2, as a pale yellow solid (40.7%).

[0052] (2) Synthesis of auxiliary ligand 4,4′-diamino-2,2′-bipyridine (bpd):

[0053] Figure 1 B is the synthetic route for the auxiliary ligand 4,4'-diamino-2,2'-bipyridine (bpd). Weigh 650.63 mg of N,N'-dioxide-2,2'-bipyridine (bpd) into a 10 mL round-bottom flask. Add 2.5 mL of concentrated sulfuric acid dropwise. Cool with ice water, then add 1 mL of concentrated nitric acid. The resulting solution is heated under reflux at 100°C for 24 hours. After the reaction, refrigerate the mixture overnight to form a yellow precipitate, the intermediate product being 4,4'-dinitro-N,N'-dioxide-2,2'-bipyridine. The collected intermediate product (about 250 mL) and 350 mg Pd / C (5%) were mixed into a 100 mL three-necked flask, 15 mL ethanol was added, and the mixture was heated to reflux at 75 ° C for 8 h under N2 atmosphere. During the reaction, 3 mL hydrazine hydrate was slowly added dropwise to the solution for about half an hour. After the reaction, the solvent was dried to obtain a yellow target product, which was weighed to obtain 213.51 mg after drying.

[0054] (3) Synthesis of auxiliary ligand 4-(2-quinolinylmethyl)-aminobenzoic acid (baqma):

[0055] Figure 1 C shows the synthetic route for the auxiliary ligand 4-(2-quinolinylmethylidene)-aminobenzoic acid (baqma). 2-Quinolinecarboxaldehyde (314.34 mg, 2 mmol) was weighed and placed in a 100 mL round-bottom flask. Ultrasonication was performed until completely dissolved. Then, p-aminobenzoic acid (220.10 mg, 2.015 mmol) was added and stirred at 25°C for 6 h. The reaction was monitored by TLC. After completion of the reaction, the solvent was evaporated using a rotary evaporator to obtain the orange target product, which was vacuum dried and weighed to yield 414.34 mg.

[0056] (4) Synthesis of iridium metal organic compound Ir-bqd:

[0057] Figure 1 D is the synthetic route for the iridium organometallic compound Ir-bqd. The iridium precursor [Ir(ppz)2(μ-Cl)]2 (103.00 mg, 0.1 mmol) and the auxiliary ligand 4,4′-diamino-2,2′-bipyridine (37.24 mg, 0.2 mmol) were weighed into a 150 mL eggplant-shaped flask. Potassium hexafluorophosphate (36.81 mg, 0.2 mmol) was then added. 40 mL of dichloromethane and 10 mL of methanol were added as solvents. The flask was completely wrapped with tin foil. The reaction was carried out in the dark. After connecting a condenser, nitrogen was introduced for 30 minutes, and the reaction was allowed to reflux at 85°C for 24 hours. After the reaction, the solution was golden yellow. The product was purified by column chromatography using pure dichloromethane as the eluent. The purified target product was spin-dried and vacuum-dried to obtain a yellow solid weighing 93.12 mg.

[0058] (5) Synthesis of iridium metal organic compound Ir-baqma:

[0059] Figure 1E is the synthetic route for the iridium organometallic compound Ir-baqma. The iridium precursor [Ir(ppz)2(μ-Cl)]2 (103.00 mg, 0.1 mmol) and the auxiliary ligand 4-(2-quinolinylmethylidene)-aminobenzoic acid (55.21 mg, 0.2 mmol) were weighed into a 100 mL eggplant-shaped flask. Potassium hexafluorophosphate (36.81 mg, 0.2 mmol) was then added, along with 80 mL of dichloromethane and 20 mL of methanol. After connecting a condenser, nitrogen was introduced for 30 minutes, and the reaction was stirred at 25°C for 24 hours. After the reaction, the solution turned dark red. The product was purified by column chromatography using a 200:1 dichloromethane:ethanol mixture as the eluent. The purified target product was spin-dried and vacuum-dried to yield a dark red solid weighing 89.80 mg.

[0060] (6) Preparation of ternary nanohybrid materials of iridium metal organic compound covalently functionalized graphene oxide:

[0061] Figure 1 F is the synthetic route for the ternary nanohybrid material. 40 mg of the iridium organometallic compound Ir-bqd, 40 mg of the iridium organometallic compound Ir-baqma, and 40 mg of GO were weighed into a 100 mL round-bottom flask. 15 mg of N,N-dicyclohexylcarbodiimide and 25 mL of anhydrous DMF were then added. Ultrasonic mixing was performed for 30 minutes, followed by a reflux system. The mixture was heated in an oil bath at 150°C for 7 days. After cooling to room temperature, 50 mL of distilled water was added to the reaction flask to precipitate the product. Filtration was then performed, yielding a black product on filter paper. The product was rinsed five times with distilled water and ethanol to remove the raw materials and impurities. The product was then dried under vacuum to yield 65 mg.

[0062] In order to determine the structure of the iridium metal organic compound, the crystal structure was determined by X-ray single crystal diffraction method, and the crystal structure of the iridium metal organic compound was obtained by direct analysis using the SHELXTL program. Figure 2 The main unit structures of two iridium organometallic compounds, [Ir(ppz)2(bpd)][PF6][CH2Cl2](Ir-bqd) and [Ir(ppz)2(baqma)][PF6][CH2Cl2](Ir-baqma). The crystallographic data of the iridium organometallic compounds are shown in Table 1.

[0063] Table 1. Crystallographic data of iridium organometallic compounds

[0064]

[0065] Example 2:

[0066] Step (1), step (2) and step (3) are the same as in Example 1, and the other steps are as follows:

[0067] (4) Synthesis of iridium metal organic compound [Ir(ppz)2(bpd)][PF6][CH2Cl2](Ir-bqd):

[0068] The iridium precursor [Ir(ppz)2(μ-Cl)]2 (103.00 mg, 0.1 mmol) and the auxiliary ligand 4,4′-diamino-2,2′-bipyridine (55.86 mg, 0.3 mmol) were weighed into a 150 mL eggplant-shaped flask. Potassium hexafluorophosphate (36.81 mg, 0.2 mmol) was then added, along with 60 mL of dichloromethane and 20 mL of methanol. The flask was completely wrapped with tin foil and the reaction was carried out in the dark. After connecting a condenser, nitrogen was introduced for 30 minutes, and the reaction was allowed to reflux at 85°C for 24 hours. After the reaction, the solution was golden yellow. The product was purified by column chromatography using pure dichloromethane as the eluent. The purified target product was spin-dried and vacuum-dried to obtain a yellow solid weighing 102.34 mg.

[0069] (5) Synthesis of iridium metal organic compound [Ir(ppz)2(baqma)][PF6][CH2Cl2](Ir-baqma):

[0070] The iridium precursor [Ir(ppz)2(μ-Cl)]2 (103.00 mg, 0.1 mmol) and the auxiliary ligand 4-(2-quinolinylmethylidene)-aminobenzoic acid (110.42 mg, 0.4 mmol) were weighed into a 100 mL eggplant-shaped flask. Potassium hexafluorophosphate (36.81 mg, 0.2 mmol) was then added, along with 80 mL of dichloromethane and 30 mL of methanol. After connecting a condenser, nitrogen was introduced for 30 minutes, and the reaction was stirred at 25°C for 24 hours. After the reaction, the solution turned dark red. The product was purified by column chromatography using a 200:1 dichloromethane:ethanol mixture as the eluent. The purified target product was spin-dried and vacuum-dried to yield a dark red solid weighing 96.71 mg.

[0071] (6) Preparation of ternary nanohybrid materials of iridium metal organic compound covalently functionalized graphene oxide:

[0072] 60 mg of the iridium organometallic compound Ir-bqd, 60 mg of the iridium organometallic compound Ir-baqma, and 30 mg of GO were weighed into a 100 mL round-bottom flask. 22.5 mg of N,N-dicyclohexylcarbodiimide and 30 mL of anhydrous DMF were then added. Ultrasonic mixing was performed for 30 minutes, followed by a reflux system. The mixture was heated in an oil bath at 150°C for 7 days. After cooling to room temperature, 50 mL of distilled water was added to the reaction flask to precipitate the product. Filtration was then performed, yielding a black product on filter paper. The product was rinsed five times with distilled water and ethanol to remove the raw materials and impurities. After vacuum drying, 72.8 mg of the product was obtained.

[0073] The infrared spectrum of metal organic compounds and hybrid materials is tested by Fourier infrared spectrometer. Figure 3 The infrared spectra of metal organic complexes Ir-bqd and Ir-baqma, GO, and hybrid materials are shown in the spectrum. O-H ),1727(ν C＝O ),1634(ν C＝C ),1043(ν C-O )cm –1 The characteristic absorption peaks of medium intensity were observed at 3491 and 3387 cm, which is consistent with the literature reports. –1 The double characteristic absorption peak at is the characteristic absorption peak of -NH2, with a wavelength of 2925cm –1 The stretching vibration of CH on the benzene ring is at a wavelength of 1482 cm –1 The wavelength is 1275cm –1 The stretching vibration of CN connecting the amino group and the benzene ring on the auxiliary ligand is shown in the Ir-baqma spectrum at 1601 and 1419 cm –1 The characteristic absorption peaks at the two locations are the C=N stretching vibration and C=C stretching vibration of quinoline on the auxiliary ligand. When the metal organic compounds Ir-bqd and Ir-baqma are bonded to the GO surface, the infrared spectra of Ir-bqd, Ir-baqma and GO are compared to find that the hybrid material after bonding has the characteristic absorption peaks of GO and metal organic compounds. In the hybrid material spectrum, -NH2 at 3491 and 3387 cm –1 The characteristic absorption peak at 1722cm –1 A new characteristic absorption peak appears at 1737 cm-1, which can be attributed to the stretching vibration of the amide bond, indicating that Ir-bqd has been covalently bonded to GO through the amide bond. In addition to the characteristic absorption peaks of GO and the complex in the hybrid material spectrum, there is a new characteristic absorption peak at 1737 cm-1. –1A new characteristic absorption peak appears at , which can be attributed to the stretching vibration of the C=O group on the generated ester group, proving that Ir-baqma and GO are connected by a covalent bond.

[0074] The iridium metal organic compound, graphene oxide (GO) and the iridium metal organic compound covalently functionalized graphene oxide ternary nanohybrid material prepared in this example were dissolved in dichloromethane for UV-visible absorption characterization. Figure 4 The UV-visible absorption spectrum obtained for measurement shows that GO has no obvious characteristic absorption peaks. Ir-bqd has obvious characteristic absorption peaks at 266nm and 330nm, which can be attributed to the charge transfer transition within the auxiliary ligand (1ILCT), the charge transfer transition between the chelating ligand and the auxiliary ligand (1LLCT), and the charge transfer transition from metal Ir to the auxiliary ligand (1MLCT). The hybrid material has a broad peak at 337nm, which is red-shifted compared to Ir-bqd. At the same time, its baseline intensity is increased above GO, indicating that there is obvious electron transfer between Ir-bqd as a donor and GO, proving the successful covalent connection of Ir-bqd and GO. Similarly, Ir-baqma has obvious characteristic absorption peaks at 275nm and 347nm, while the hybrid material has a narrower absorption peak at 280nm, which also shows a red shift compared to Ir-baqma. Similarly, its baseline absorption intensity is also increased to be comparable to that of GO, indicating that electronic transition occurs between Ir-baqma and GO, and further illustrates the successful covalent connection between Ir-baqma and GO.

[0075] The iridium metal organic compound covalently functionalized graphene oxide ternary nano-hybrid material prepared in this embodiment was placed in a dichloromethane solution for fluorescence emission. Figure 5 The steady-state fluorescence emission spectrum of the hybrid material shows that the ternary nanohybrid material of iridium metal organic compound covalently functionalized graphene oxide exhibits significant fluorescence quenching compared to both metal organic compound monomers in the 300-600nm range, and completely quenches fluorescence in the 600-800nm ​​range.

[0076] Example 3:

[0077] Step (1), step (2) and step (3) are the same as in Example 1, and the other steps are as follows:

[0078] (4) Synthesis of iridium metal organic compound [Ir(ppz)2(bpd)][PF6][CH2Cl2](Ir-bqd):

[0079] The iridium precursor [Ir(ppz)2(μ-Cl)]2 (103.00 mg, 0.1 mmol) and the auxiliary ligand 4,4′-diamino-2,2′-bipyridine (55.86 mg, 0.3 mmol) were weighed into a 150 mL eggplant-shaped flask. Potassium hexafluorophosphate (36.81 mg, 0.2 mmol) was then added, along with 60 mL of dichloromethane and 20 mL of methanol. The flask was completely wrapped with tin foil and the reaction was carried out in the dark. After connecting a condenser, nitrogen was introduced for 30 minutes, and the reaction was allowed to reflux at 85°C for 24 hours. After the reaction, the solution was golden yellow. The product was purified by column chromatography using pure dichloromethane as the eluent. The purified target product was spin-dried and vacuum-dried to obtain a yellow solid weighing 102.34 mg.

[0080] (5) Synthesis of iridium metal organic compound [Ir(ppz)2(baqma)][PF6][CH2Cl2](Ir-baqma):

[0081] The iridium precursor [Ir(ppz)2(μ-Cl)]2 (103.00 mg, 0.1 mmol) and the auxiliary ligand 4-(2-quinolinylmethylidene)-aminobenzoic acid (110.42 mg, 0.4 mmol) were weighed into a 100 mL eggplant-shaped flask. Potassium hexafluorophosphate (36.81 mg, 0.2 mmol) was then added, along with 80 mL of dichloromethane and 30 mL of methanol. After connecting a condenser, nitrogen was introduced for 30 minutes, and the reaction was stirred at 25°C for 24 hours. After the reaction, the solution turned dark red. The product was purified by column chromatography using a 200:1 dichloromethane:ethanol mixture as the eluent. The purified target product was spin-dried and vacuum-dried to yield a dark red solid weighing 96.71 mg.

[0082] (6) Preparation of ternary nanohybrid materials of iridium metal organic compound covalently functionalized graphene oxide:

[0083] 80 mg of the iridium organometallic compound Ir-bqd, 80 mg of the iridium organometallic compound Ir-baqma, and 50 mg of GO were weighed into a 100 mL round-bottom flask. 30 mg of N,N-dicyclohexylcarbodiimide and 50 mL of anhydrous DMF were then added. After ultrasonic mixing for 30 minutes, a reflux device was connected and the mixture was heated in an oil bath at 150°C for 7 days. After cooling to room temperature, 50 mL of distilled water was added to the reaction flask to precipitate the product. Filtering was then performed, and a black product was obtained on filter paper. This product was rinsed five times with distilled water and ethanol to remove the raw materials and impurities. After vacuum drying, 87.3 mg of the product was obtained.

[0084] In order to further test the thermal stability of GO, iridium metal organic compounds Ir-bqd and Ir-baqma, and hybrid materials, a comprehensive thermal analyzer was used to heat the sample from room temperature to 800 °C at a heating rate of 10 °C / min under a nitrogen atmosphere. Figure 6 Thermogravimetric analysis of four materials is shown in the figure. As shown in the figure, the thermal loss process of GO can be roughly divided into three stages. The first stage of thermal loss occurs between 30 and 153°C, with a weight loss of approximately 13.7%. The thermal loss in this stage can be attributed to the evaporation of some water in the GO molecular layer; the second stage of thermal loss occurs between 153 and 300°C, with a weight loss of approximately 37%. The thermal loss in this stage can be attributed to the loss of some oxygen-containing functional groups on GO that are easily decomposed by heat; the third stage of thermal loss occurs between 300 and 800°C, with a weight loss of approximately 9.3%. The thermal loss in this stage may be the loss of some oxygen-containing functional groups with good thermal stability. The remaining residue content may be the weight of the carbon element.

[0085] The heat loss process of the iridium metal organic compound Ir-bqd is mainly divided into two stages. The first stage is when heated to 343°C, the weight loss is about 9.1%. The heat loss in this stage is caused by the evaporation of some solvent molecules in the compound. The second stage is when continued to heat to 800°C, the weight loss is about 36.3%. The heat loss in this stage is due to the weight loss caused by the cracking of the chelating ligand ppz and the auxiliary ligand bpd due to heat. The remaining residue content may be the weight of the skeleton of the iridium metal organic compound that has not been completely cracked.

[0086] Similarly, the thermal loss process of the iridium metal organic compound Ir-baqma is similar to that of Ir-bqd, and is also divided into two stages. The first stage is when heated to 273°C, the weight loss is about 4.3%. The thermal loss in this stage is still caused by the evaporation of some solvent molecules in the compound. The second stage is when continued to heat to 800°C, the weight loss is about 38.1%. The thermal loss in this stage is the weight loss due to the cracking of the chelating ligand ppz and the auxiliary ligand baqma due to heat. The remaining residue content may be the weight of the skeleton of the compound that has not been completely cracked.

[0087] Comparing the thermogravimetric curves of Ir-bqd, Ir-baqma and GO, the thermogravimetric curve of the hybrid material tends to be a straight line, indicating that the heat loss process is very uniform and also shows that it has good thermal stability.

Claims

1. An iridium metal organic compound covalently functionalized graphene oxide ternary nanohybrid material, characterized in that: The structural formula is as follows:

2. The method for preparing the ternary nano-hybrid material of iridium metal organic compound covalent functionalized graphene oxide according to claim 1, wherein: The steps include: Step (1) Synthesis of phenylpyrazole ring metal iridium dimer [Ir(ppz)2(μ-Cl)]2: Iridium trichloride hydrate and 1-phenylpyrazole ligand were added to a reaction flask in proportion, and a mixed solvent of ethylene glycol ethyl ether and distilled water was added. The reaction was carried out under N2 protection under condensation reflux. The degree of reaction was monitored by TLC during the reaction. After the reaction was completed, the solution was cooled to room temperature, filtered, washed, extracted and purified, and the organic phase was finally dried to obtain a light yellow solid [Ir(ppz)2(μ-Cl)]2; Step (2) Synthesis of auxiliary ligand 4,4'-diamino-2,2'-bipyridine bpd: Add N,N′-dioxide-2,2′-bipyridine to a reaction flask, add concentrated sulfuric acid dropwise to the flask, cool with ice water, and then add concentrated nitric acid. Heat the resulting solution to reflux. After the reaction is complete, place the mixture in a refrigerator and let it stand to form a yellow precipitate, which is the intermediate product 4,4′-dinitro-N,N′-dioxide-2,2′-bipyridine. Mix the collected intermediate product and catalyst Pd / C into a reaction flask, add ethanol, and heat to reflux under a N2 atmosphere. During the reaction, slowly add hydrazine hydrate dropwise to the solution. After the reaction is complete, spin-dry the solvent to obtain the yellow target product 4,4′-diamino-2,2′-bipyridine bpd. Step (3) Synthesis of auxiliary ligand 4-(2-quinolinylmethylene)-aminobenzoic acid baqma: Weigh 2-quinolinecarboxaldehyde and place it in a reaction flask. Add methanol and sonicate until completely dissolved. Then add p-aminobenzoic acid and stir to react. The reaction process is monitored by TLC. After the reaction is completed, the solvent is dried on a rotary evaporator to obtain the orange target product 4-(2-quinolinylmethyl)-aminobenzoic acid baqma; Step (4) Synthesis of an iridium metal organic compound [Ir(ppz)2(bpd)][PF6][CH2Cl2], referred to as Ir-bqd: The phenylpyrazole ring metal iridium dimer prepared in step (1) and the auxiliary ligand 4,4'-diamino-2,2'-bipyridine bpd prepared in step (2) are added to a reaction bottle in a certain molar ratio, and then dichloromethane, methanol and potassium hexafluorophosphate are added in sequence. The reaction is carried out in a light-proof environment under the protection of N2 and condensed reflux reaction is carried out. The degree of reaction is monitored by TLC during the reaction. After the reaction is completed, it is purified by column chromatography to obtain a solid iridium metal organic compound Ir-bqd; Step (5) Synthesis of an iridium metal organic compound [Ir(ppz)2(baqma)][PF6][CH2Cl2], referred to as Ir-baqma: The phenylpyrazole ring metal iridium dimer prepared in step (1) and the auxiliary ligand 4-(2-quinolinylmethylidene)-aminobenzoic acid baqma prepared in step (3) are added to a reaction flask in a certain molar ratio, and then dichloromethane, methanol and potassium hexafluorophosphate are added in sequence. The reaction is carried out in a light-proof environment under the protection of N2 and condensed reflux reaction is carried out. The degree of reaction is monitored by TLC during the reaction. After the reaction is completed, the iridium metal organic compound Ir-baqma is purified by column chromatography to obtain a solid; Step (6) Preparation of ternary nano-hybrid materials of iridium metal organic compound covalently functionalized graphene oxide: The iridium metal organic compound Ir-bqd obtained in step (4) and the iridium metal organic compound Ir-baqma obtained in step (5) are added to a reaction bottle in a certain proportion, and then N,N′-dicyclohexylcarbodiimide DCC is added, and then the reaction solvent DMF is added. After ultrasonication and heating to the reaction temperature, stirring and refluxing, the mixture is first cooled and then distilled water is added for filtration, washed with CH2Cl2 and ethanol, and vacuum dried to obtain the final gray-black product iridium metal organic compound covalently functionalized graphene oxide ternary nanohybrid material.

3. The preparation method according to claim 2, wherein In step (1), The molar ratio of hydrated iridium trichloride and 1-phenylpyrazole ligand is 1:2; In the mixed solvent of ethylene glycol ethyl ether and distilled water, the volume ratio of ethylene glycol ethyl ether to distilled water is 5:1; The temperature of the condensation reflux reaction is 130-140°C, and the reaction time is 24-36 hours; The washing solvents were ethanol and petroleum ether; the extraction solvents were CH2Cl2 and H2O.

4. The preparation method according to claim 2, wherein In step (2), The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 5:2; The mass ratio of the intermediate product, the catalyst Pd / C, and the hydrazine hydrate is 100:3:5; wherein the mass percentage of Pd in ​​the catalyst Pd / C is 5%; When preparing the intermediate product, the heating reflux reaction temperature is 90-100°C and the reaction time is 24-36 hours; When the intermediate product reacts with the catalyst Pd / C, the reaction temperature under reflux is 75-80° C. and the reaction time is 8-12 hours.

5. The preparation method according to claim 2, wherein In step (3), the molar ratio of 2-quinolinecarboxaldehyde to p-aminobenzoic acid is 1:1, the stirring reaction temperature is 25° C., and the reaction time is 6 to 12 hours.

6. The preparation method according to claim 2, wherein In step (4), the molar ratio of the phenylpyrazole ring metal iridium dimer to the auxiliary ligand 4,4'-diamino-2,2'-bipyridine bpd is 1:2 to 1:3, the volume ratio of dichloromethane to methanol is 2:1 to 4:1, and the molar ratio of the amount of potassium hexafluorophosphate added to the amount of the phenylpyrazole ring metal iridium dimer added is 2:1; The condensation reflux temperature is 80-90°C, and the reaction time is 24-36h.

7. The preparation method according to claim 2, wherein In step (5), the molar ratio of the phenylpyrazole ring metal iridium dimer to the auxiliary ligand 4-(2-quinolinylmethyl)-aminobenzoic acid bapma is 1:2 to 1:3, the volume ratio of dichloromethane to methanol is 2:1 to 4:1, and the molar ratio of the amount of potassium hexafluorophosphate added to the amount of the phenylpyrazole ring metal iridium dimer added is 2:1; When purified by column chromatography, V 二氯甲烷 :V 乙醇 =3:1; The temperature of the condensation reflux reaction was 25°C and the reaction time was 24 h.

8. The preparation method according to claim 2, wherein In step (6), the mass ratio of the iridium metal organic compound [Ir(ppz)2(bpd)][PF6][CH2Cl2], [Ir(ppz)2(baqma)][PF6][CH2Cl2] and graphene oxide is 1:1:1 to 3:3:1, and the molar ratio of the added amount of N,N′-dicyclohexylcarbodiimide to the added amount of [Ir(ppz)2(bpd)][PF6][CH2Cl2] is 3:2; The temperature of the stirring reflux reaction is 140-150° C., and the reaction time is 7-10 days.

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