Zeolite imidazole frame-8 double-site loaded carbon dot and gold or gold and silver nanocluster fluorescent nanomaterial, preparation method and application of zeolite imidazole frame-8 double-site loaded carbon dot and gold or gold and silver nanocluster fluorescent nanomaterial

Abstract

The invention relates to a preparation method of a zeolite imidazole frame-8 double-site loaded carbon dot and gold or gold and silver nanocluster fluorescent material, which comprises the following steps of: 1, uniformly mixing a HAuCl4 aqueous solution and a GSH aqueous solution at room temperature, or uniformly mixing an AgNO3 aqueous solution, the HAuCl4 aqueous solution and the GSH aqueous solution, then stirring for 20-28 hours at 60-80 DEG C, cooling to room temperature, adding methanol, centrifuging, and drying to obtain a precursor solution of the zeolite imidazole frame-8 double-site loaded carbon dot and gold or gold and silver nanocluster; washing and drying to obtain gold or gold-silver nanoclusters, and dispersing the gold or gold-silver nanoclusters in water for later use; step 2, preparing carbon dots CDs; 3, zinc nitrate hexahydrate and 2-methylimidazole are added into methanol containing CDs under the stirring condition to react for 20-28 hours, centrifugation and washing are conducted, and a product ZIF coated CDs is obtained; and 4, mixing the gold or gold and silver nanocluster solution with the ZIF-coated CDs under an ultrasonic condition at room temperature to obtain the ZIF-coated CDs / gold / silver nanocluster composite material. The invention also provides an application of the zeolite imidazole frame-8 double-site loaded carbon dot and gold and silver nanocluster fluorescent material in detection of pesticide triazophos (TZP) and glucose.

Description

Technical Field

[0001] The present invention belongs to the field of fluorescence sensing technology, and specifically relates to a zeolite imidazole framework-8 dual-site loaded carbon dots and gold or gold-silver nanocluster fluorescent nanomaterial, a preparation method and an application. Among them, the zeolite imidazole framework-8 dual-site loaded carbon dots and gold nanocluster fluorescent nanomaterials construct a ratio-enhanced fluorescent composite nanomaterial and this material can be used as a probe to detect the pesticide triazophos (TZP), the zeolite imidazole framework-8 dual-site loaded carbon dots and gold-silver nanocluster fluorescent nanomaterial (based on Ag + The gold nanoclusters (gold nanoclusters) that are dually induced by restricted intramolecular motion and spatial confinement effects on the ZIF-8 surface to emit enhanced fluorescence (composite probes) can be used as probes to detect glucose. Background Art

[0002] Compared with other fluorescent materials, gold nanoclusters are cheap to prepare and have a mild and environmentally friendly synthesis process. They are widely used in fluorescence detection, bioimaging, catalysis and other fields. However, so far, the disadvantages of gold nanoclusters such as low fluorescence intensity and poor chemical stability have limited their application. Therefore, improving the fluorescence properties of gold nanoclusters is the key to their development. Using assembly technology to load AuNCs on the carrier structure can not only improve the luminescence efficiency through confinement or aggregation-induced fluorescence effect enhancement, but also increase the system loading capacity, which has the advantage of dual brightening.

[0003] ZIF-8@Au, which is constructed by loading AuNCs inside the zeolite imidazole framework-8 (ZIF-8) carrier using assembly technology, has been widely used in detection and analysis fields such as fluorescence detection and bioimaging. It can induce luminescence efficiency enhancement through confinement or aggregation effects, and increase the system loading, with the advantages of dual brightness enhancement. However, the synthesis of ZIF-8@Au is currently mainly based on two methods: late-stage and in-situ synthesis. Both methods embed AuNCs in the ZIF-8 structure. Due to internal space limitations and low space utilization, it is impossible to controllably prepare high-load ZIF-8@Au. At the same time, the outer space of ZIF-8 is not effectively used. Therefore, for the assembly of ZIF-8 and AuNCs, it is urgent to develop new strategies with high loading, emission efficiency and space utilization to improve detection sensitivity.

[0004] Gold nanoclusters (AuNCs) have been attracting much attention in the field of biosensing due to their low toxicity, ease of synthesis and good biocompatibility. However, the low luminescence efficiency of AuNCs compared to other fluorophores (such as carbon dots and quantum dots) severely limits their practical applications. Fortunately, the natural property of AuNCs, that is, the fluorescence efficiency can be improved by restricting their intermolecular or intramolecular motion, provides us with an ingenious blueprint for the rational design of high-brightness fluorescent composites.

[0005] At present, there are two main methods to improve the luminescence efficiency of nanomaterials based on AuNCs. The first method requires the use of metal cations, organic solvents and nanogels to inhibit intramolecular motion, thereby activating the AIE properties of AuNCs. Secondly, by selecting a specific type of nanomaterial as a carrier, integrating AuNCs together, and producing higher luminescence efficiency through large-scale aggregation of nanoclusters and restricting intramolecular motion, it is also widely used to improve fluorescence intensity. However, when the above two methods are used alone, there are corresponding shortcomings. Therefore, it is urgent to develop new strategies that combine the advantages of the above two methods for AuNCs to construct high-brightness fluorescent composite materials, thereby improving detection sensitivity.

[0006] Based on this, this application was developed. Summary of the invention

[0007] In view of the technical defects existing in the prior art, the present invention aims to provide a zeolite imidazole framework-8 dual-site loaded carbon dots and gold or gold-silver nanoclusters fluorescent nanomaterial, a preparation method and application.

[0008] In view of the technical problems of the space limitation and low space utilization of zeolite imidazole framework-8 (ZIF-8) in the prior art, the present invention proposes a method based on the characteristics that various objects such as drugs, enzymes, metal nanomaterials and carbon dots (CDs) can be encapsulated into the ZIF-8 cavity, and fluorescent CDs are encapsulated into ZIF-8 to synthesize ZIF@CDs. Furthermore, gold nanoclusters are electrostatically self-assembled on the surface of ZIF@CDs, and the surface spatial binding sites of ZIF-8 are used to electrostatically self-assemble with AuNCs, which greatly improves the effective utilization rate of the assembly space and the fluorescence performance, achieves a significant improvement in the fluorescence performance, and constructs ultra-high brightness ratio fluorescent composite nanomaterials for the detection of the pesticide triazophos.

[0009] Aiming at the technical problem of low luminescence efficiency of AuNCs in the prior art, the present invention proposes a method for constructing carbon dots@metal organic framework-gold and silver nanoclusters based on fluorescence quenching / enhancement effect, which utilizes Ag +The double enhancement of the restricted movement of Au molecules in AuNCs and the spatial confinement effect caused by the spatial binding sites on the surface of ZIF-8 and the electrostatic self-assembly of AuNCs achieves a significant improvement in fluorescence performance. At the same time, based on the characteristics of ZIF-8's cavity that can encapsulate various objects such as drugs, enzymes, metal nanomaterials and carbon dots (CDs), fluorescent CDs are encapsulated into ZIF-8 to synthesize CDs@ZIF, and the aggregation quenching characteristics of CDs induce the weakening of CDs fluorescence, and then CDs@ZIF is assembled with gold and silver nanoclusters (AuAgNCs) to prepare a multifunctional CDs@ZIF-AuAgNCs nanocomposite. Finally, the gluconic acid produced by glucose under the action of glucose oxidase can degrade ZIF-8, thereby causing the aggregation of AuNCs to disperse and the fluorescence enhancement effect caused by aggregation and CDs dispersion, and glucose is detected.

[0010] The invention also provides a preparation method of the composite nano material and application of the composite nano material as a probe in detecting the pesticide triazophos.

[0011] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme: A method for preparing a zeolite imidazole framework-8 dual-site loaded carbon dots and gold or gold-silver nanocluster fluorescent material, comprising the following steps: Step 1: At room temperature, HAuCl 4 The aqueous solution and the GSH aqueous solution are uniformly mixed, or the AgNO 3 Aqueous solution, HAuCl 4 The aqueous solution and the GSH aqueous solution are uniformly mixed, then stirred at 60-80°C for 20-28 hours, cooled to room temperature, added with methanol, centrifuged, washed, dried to obtain gold or gold-silver nanoclusters, dispersed in water and stored at 4°C for future use; Step 2: Preparation of carbon dots: Water-soluble carbon dots CDs were synthesized based on the hydrothermal polymerization reaction of citric acid and ethylenediamine. Citric acid and ethylenediamine were mixed with distilled water, then reacted at 200-260°C for 6-10 hours, cooled to room temperature, dialyzed and purified using a dialysis bag, and then dried to obtain carbon dots CDs; Step 3: Preparation of ZIF@CDs: Add zinc nitrate hexahydrate and 2-methylimidazole to methanol containing CDs under stirring conditions for 20-28 hours, centrifuge, wash, and obtain the product ZIF@CDs; Step 4: Mix the gold or gold-silver nanocluster solution with ZIF@CDs under ultrasonic conditions at room temperature.

[0012] Specifically, in step 1, the HAuCl 4 The molar ratio of AgNO to GSH is 1:1-2; 3HAuCl 4 The molar ratio of MgCl and GSH is 0.1:1:1-2.

[0013] Specifically, in step 2, 300-400 μL of ethylenediamine is added to every 1 g of citric acid, and the mixture is mixed and stirred at room temperature.

[0014] Further, in step 3, the zinc nitrate hexahydrate Zn(NO 3 ) 2 6H 2 The mass ratio of ZnO and 2-methylimidazole is 1: (2-16). The particle size of ZIF@CDs is 50-200 nm. The mass ratio of zinc nitrate hexahydrate to CDs is 140-160:1.

[0015] Furthermore, in step 4, the mass ratio of the gold nanoclusters or gold-silver nanoclusters to ZIF@CDs is 1:(6-10), preferably 1:8.

[0016] The present invention provides a zeolite imidazole framework-8 double-site loaded carbon point and gold or gold-silver nanocluster fluorescent material prepared by the preparation method.

[0017] Based on the same inventive concept, the present invention also provides the use of the above-mentioned zeolite imidazole framework-8 dual-site loaded carbon dots and gold nanocluster fluorescent materials (Au-ZIF@CDs) in the detection of the pesticide triazophos TZP. In specific applications, different concentrations of triazophos can be incubated with glutathione peroxidase, and then GSH, Cu 2+ , HEPES buffer solution, the zeolite imidazole framework-8 dual-site loaded carbon dots and gold nanocluster fluorescent materials are mixed and incubated, and the fluorescence spectrum of the mixture is measured at an excitation wavelength of 360 nm. More preferably, different concentrations of triazophos are incubated with glutathione peroxidase (GPx, 10 mU / mL) for 25 minutes, and then GSH (10 µM), Cu 2+ (1.5 µM), HEPES buffer solution (pH = 7.8), and the zeolite imidazole framework-8 dual-site loaded carbon dots and gold nanocluster fluorescent materials (40 µL) were mixed and incubated for 20 minutes, and the fluorescence spectrum of the mixture was measured at an excitation wavelength of 360 nm.

[0018] Based on the same inventive concept, the present invention also provides the use of the above-mentioned zeolite imidazole framework-8 dual-site loaded carbon dots and gold-silver nanocluster fluorescent materials (CDs@ZIF-AuAgNCs) in the detection of glucose. In specific applications, different concentrations of glucose can be incubated with glucose oxidase, and then the HEPES buffer solution and the zeolite imidazole framework-8 dual-site loaded carbon dots and gold-silver nanocluster fluorescent materials are mixed and incubated, and the fluorescence spectrum of the mixture is measured at an excitation wavelength of 360nm. Further preferably, different concentrations of glucose are incubated with glucose oxidase (GOx, 10 mU / mL) for 25 minutes, and then the HEPES buffer solution (pH=7.8) and the zeolite imidazole framework-8 dual-site loaded carbon dots and gold-silver nanocluster fluorescent materials (40µL) are mixed and incubated for 20 minutes, and the fluorescence spectrum of the mixture is measured at an excitation wavelength of 360nm.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing a ratio-enhanced fluorescence composite probe constructed by dual-site loading of carbon dots and gold nanoclusters on zeolite imidazole framework-8 and its application. The method is based on the internal and external double-sided space loading characteristics of zeolite imidazole framework-8 (ZIF-8). By encapsulating carbon dots (CDs) in the internal space of ZIF-8, a ratio fluorescence baseline control fluorescent group is formed. At the same time, gold nanoclusters (AuNCs) are self-assembled on the outer surface of ZIF-8 to increase the loading amount. Based on the spatial confinement or aggregation induction effect, the fluorescence performance of a single AuNCs nanogroup is improved, and the shortcomings of weak fluorescence intensity, poor stability and poor controllability of preparation of AuNCs are effectively overcome. Moreover, the accuracy of the detection target can be effectively enhanced by calibration in the ratio mode. Furthermore, based on the interaction between copper ions and the self-assembled AuNCs nanogroup, ultra-sensitive detection of the pesticide triazophos is achieved, and the detection limit is as low as 0.04 ng / ml. The novel ratio fluorescence composite probe obtained by the present invention has the advantages of simple and mild preparation method, short time consumption and high sensitivity.

[0020] The present invention provides a carbon dot@metal organic framework-gold and silver nanoclusters based on fluorescence quenching / enhancement effect and a preparation method and application thereof. +The fluorescence properties of AuNCs are improved by restricting the movement of Au molecules in AuNCs. AuAgNCs are further assembled on the surface of CDs@ZIF. Based on the spatial confinement or aggregation-induced effect, the fluorescence properties of individual nanogroups are improved and the loading amount is greatly increased, effectively overcoming the shortcomings of weak fluorescence intensity, poor stability and poor preparation controllability of gold nanoclusters. At the same time, based on the characteristics of ZIF-8 cavity that can encapsulate various objects such as drugs, enzymes, metal nanomaterials and carbon dots (CDs), fluorescent CDs are encapsulated into ZIF-8 to synthesize CDs@ZIF, and the aggregation quenching characteristics of CDs induce the weakening of CDs fluorescence. CDs@ZIF is then assembled with gold and silver nanoclusters (AuAgNCs) to prepare a multifunctional CDs@ZIF-AuAgNCs nanocomposite. Finally, the gluconic acid produced by glucose under the action of glucose oxidase can degrade ZIF-8, thereby causing the fluorescence weakening caused by the dispersion of aggregated AuNCs and the fluorescence enhancement effect caused by the aggregation and dispersion of CDs, and ultra-sensitive detection of glucose is performed. The novel fluorescent composite probe obtained by the present invention has the advantages of simple and mild preparation method, short time consumption, high sensitivity and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the preparation process of zeolite imidazole framework-8 dual-site loaded carbon dots and gold nanoclusters fluorescent nanomaterials (Au-ZIF@CDs); Figure 2 TEM characterization image of AuNCs; Figure 3 TEM characterization image of ZIF@CDs; Figure 4 TEM images of Au-ZIF@CDs. The right image is a partial enlarged image of the left image. Figure 5 The fluorescence intensity variation trend spectra of Au-ZIF@CDs assembled with different ratios (by weight, ZIF@CDs:AuNC) (the inset is the fluorescence emission spectrum); Figure 6 The corresponding EDS element map of Au-ZIF@CDs; Figure 7 Zeta potential diagrams of ZIP-8, AuNCs, and Au-ZIP; Figure 8 Au-ZIF@CDs / Cu at different TZP concentrations 2+ / GSH / H 2 O 2 Fluorescence emission spectra of the / GPx system; Fig. 9 Au-ZIF@CDs / Cu at different TZP concentrations2+ / GSH / H 2 O 2 / GPx system I 565 / I 445 intensity ratio (the inset is a linear fit plot of the logarithm of concentration versus intensity ratio); Fig.10 The repeatability of Au-ZIF@CDs-based TZP method; Fig.11 for the selectivity of the Au-ZIF@CDs-based TZP method; Fig.12 Schematic diagram of the preparation process of zeolite imidazole framework-8 dual-site loaded carbon dots and gold-silver nanoclusters fluorescent nanomaterials (CDs@ZIF-AuAgNCs); Fig.13 Transmission electron microscopy (TEM) image of AuAgNCs; Fig.14 Transmission electron microscopy (TEM) image of CDs@ZIF-AuAgNCs with a mass ratio of AuAgNCs / CDs@ZIF of 1:8; Fig.15 Fluorescence emission spectra of AuAgNCs, ZIF@CDs and CDs@ZIF-AuAgNCs; Fig.16 Zeta potential of CDs, ZIF-8, ZIF@CDs, AuAgNCs and composite probe; Fig.17 Fluorescence emission spectra of CDs@ZIF-AuAgNCs / GOx system under different glucose concentrations; Fig.18 F of CDs@ZIF-AuAgNCs / GOx system under different glucose concentrations 450 / F 570 intensity ratio (the inset in the figure shows the parameters of the linear relationship); Fig.19 is the reproducibility of the CDs@ZIF-AuAgNCs / GOx-based glucose method at different 600 μmol / L glucose concentrations; Fig. 20 The selectivity of the CDs@ZIF-AuAgNCs / GOx-based approach for glucose. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are further described by the following examples. The following are only preferred embodiments of the present invention, which are used to illustrate the present invention and do not limit the present invention in any way. Without departing from the technical solution of the present invention, any changes or modifications made to the present invention that are easily implemented by a person of ordinary skill in the art will fall within the scope of the claims of the present invention.

[0023] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. In the event of a conflict, the present specification takes precedence.

[0024] In the following examples, unless otherwise specified, the raw materials used are common commercial products that can be directly purchased, or can be prepared by conventional methods in the art. Room temperature refers to 25±5°C.

[0025] The preparation process of zeolite imidazole framework-8 dual-site loaded carbon dots and gold nanoclusters fluorescent nanomaterials (Au-ZIF@CDs) is as follows Figure 1 The preparation process of zeolite imidazole framework-8 dual-site loaded carbon dots and gold-silver nanoclusters fluorescent nanomaterials (CDs@ZIF-AuAgNCs) is shown in Fig.12 shown.

[0026] Example 1 Synthesis of gold nanoclusters (AuNCs): Freshly prepared glutathione (GSH) (0.3 mL, 100 mM) aqueous solution and HAuCl 4 The (1 mL, 20 mM) aqueous solution was added to 8.7 mL of distilled water, and the mixture was stirred at room temperature for 5 min. It was then stirred at 70 °C for 24 h, cooled to room temperature, an equal volume of methanol was added to precipitate AuNCs, and the suspension was centrifuged at 12000 rpm. The resulting precipitate was washed 3 times with methanol to remove unreacted precursors and then dried. The final precipitate was redispersed in distilled water and stored at 4 °C for future use.

[0027] Example 2 Synthesis of carbon dots (CDs): Citric acid (1.0507 g) and ethylenediamine (335 μL) were dissolved in distilled water (10 mL). The solution was then transferred to a polytetrafluoroethylene-lined autoclave and heated at 240 °C for 8 h. After the reaction was completed, the reactor was cooled to room temperature. The product was a brown-black and transparent liquid. The product was transferred to a dialysis bag (molecular weight cutoff 1000Da) and dialyzed with ultrapure water for 8 h. The dialyzed solution was dried to obtain carbon dots CDs, which were stored in a refrigerator at 4 °C for later use.

[0028] Example 3 Synthesis of ZIF@CDs: Zinc nitrate hexahydrate (149 mg) and 2-methylimidazole (328 mg) were added to 15 mL of methanol containing 1 mg of CDs under stirring conditions and reacted at room temperature for 24 h. After the reaction, the product was obtained by centrifugation at 8000 rpm for 10 min and washed three times with methanol. Finally, the product was dissolved in distilled water (4 mg / mL) and stored at 4 °C.

[0029] A similar procedure was used to synthesize pure ZIF-8 in the absence of CDs.

[0030] Example 4 Au-ZIF@CDs synthesis: Au-ZIF@CDs were prepared by mixing AuNCs (0.5 mg / mL, 500 μL) and ZIF@CDs (0.5 mg / mL, 4 mL) at room temperature for 10 min under ultrasonic treatment. The prepared Au-ZIF@CDs were kept at 4 °C for future use.

[0031] like Figure 5 As shown in Figure 2, the fluorescence emission spectra of Au-ZIF@CDs assembled in different ratios (by weight, ZIF@CDs:AuNCs) show that when the ratio of ZIF@CDs to AuNCs reaches 8:1, the fluorescence intensity reaches a plateau.

[0032] Characterization of Examples 1, 3, and 4 (1) Characterization of gold nanoparticles (AuNCs): Figure 2 The transmission electron microscope (TEM) image of AuNCs is given. Figure 2 As shown in Figure 2, TEM was used to analyze the particle size, morphology and surface morphology of AuNCs. In the TEM image, it was observed that the shape of AuNCs was spherical, with good dispersion, narrow particle size distribution, and an average particle size of about 1.85 nm. The above characterizations indicate the successful synthesis of AuNCs.

[0033] Figure 3 Transmission electron microscopy (TEM) images of ZIF@CDs are given. Figure 3 It can be seen that CDs were successfully embedded in ZIF-8.

[0034] (2) TEM characterization of Au-ZIF@CDs nanoparticles: like Figure 4 As shown in the TEM morphology of Au-ZIF@CDs nanoparticles, AuNCs and ZIF@CDs nanoparticles can also be seen to be composited, which indicates that Au-ZIF@CDs nanoparticles were successfully synthesized. Figure 4 As shown in the TEM image, when the mass ratio of ZIF@CDs to AuNCs reaches 8:1, the Au-ZIF@CDs nanoparticles maintain the same crystal morphology as ZIF@CDs. Figure 5 As shown in the figure, Au-ZIF prepared by mixing ZIF@CDs with AuNCs in different ratios has different fluorescence intensities. When the mass ratio of ZIF@CDs to AuNCs reaches 8:1, the fluorescence intensity reaches a plateau, and the fluorescence intensity of Au-ZIF@CDs is 16 times higher than that of AuNCs. Figure 6 The EDS elemental maps show that C, Zn, N, S, and Au exist throughout the entire architecture of Au-ZIF@CDs.

[0035] (3) Zeta potential characterization of AuNCs, ZIF@CDs and Au-ZIF@CDs nanoparticles: Zeta potential characterization can examine the charge on the particle surface. Figure 7 As shown in the figure, the average potentials of AuNCs, ZIF@CDs and Au-ZIF@CDs in water are -16.59, 17.83 and -3.67 mV respectively. This is because the surface of ZIF@CDs has a large amount of Zn, which is positively charged. After uniformly modifying a layer of AuNCs with a large amount of negative charge, the potential of ZIF@CDs is reduced from 17.83mV to -3.67mv. These results show that the surface of ZIF@CDs is successfully modified with a layer of AuNCs to form Au-ZIF@CDs nanoparticles.

[0036] Example 5 Au-ZIF@CDs / Cu 2+ / GSH / H 2 O 2 / GPx system for detection of triazophos: 0.1-1000 ng / ml triazophos was incubated with glutathione peroxidase (GPx, 10 mU / mL) at room temperature for 25 minutes. Then GSH (10µM), Cu 2+ (copper sulfate, 1.5µM), Au-ZIF@CDs (40µL, 4mg / mL) and HEPES buffer solution (pH=7.8) were mixed to form a 1mL reaction system and incubated for 20 minutes. The fluorescence spectrum of the mixture was measured at an excitation wavelength of 360 nm. As the concentration of triazophos gradually increased, the fluorescence intensity gradually increased, thereby achieving sensitive detection of triazophos.

[0037] The fluorescence emission spectra of the system with different concentrations of triazophos (0, 0.1, 0.5, 1, 5, 10, 50, 100, 500, 1000 ng / mL) are shown in Figure 2. Figure 8 . Figure 8The fluorescence emission spectra after adding different concentrations of triazophos to the system are shown. As the concentration of triazophos (TZP) increases, triazophos-induced GPx consumption of GSH is delayed, and the fluorescence intensity gradually increases. Fig. 9 It shows that the fluorescence enhancement factor (I 565 / I 445 ) has a good linear relationship with the logarithm of triazophos concentration, and the linear equation is: 565 / I 445 = 0.3714 + 0.07097LogC TZP (R 2 = 0.994), and the detection limit (LOD) of this method was 0.04 ng / mL. By introducing multiple interferences such as biological molecules, pesticides and ions, the recognition selectivity of the ratiometric fluorescent nanoprobe for triazophos was studied. Fig.10 As shown in the figure, at a TZP concentration of 100 ng / mL, there was almost no difference in the results of the seven concentration tests, indicating that the Au-ZIF@CDs-based TZP method has good repeatability. Fig.11 As shown in the figure, even when much higher concentrations of interfering substances than triazophos were added (such as atrazine, fomesafen, isoproturon, methacrylamid, cypermethrin, imidacloprid, chlorothiazide, bifenthrin, alanine, glutamic acid, histidine, glutamine, phenylalanine, fructose, glucose, sodium ion, calcium ion, magnesium ion, nitrate, etc.), I 565 / I 445 The response to interference was also negligible, indicating that this strategy has good selectivity toward triazophos.

[0038] Table 1. Actual sample detection results based on Au-ZIF@CDs-triazophos TZP method The test results of actual samples are given in Table 1. As shown in Table 1, the average recoveries ranged from 91.50% to 111.62%, and the relative standard deviation (RSD) was less than 6.61%, indicating that the accuracy of the quantitative determination of TZP in environmental and agricultural samples was satisfactory.

[0039] Example 6 Synthesis of gold-silver nanoclusters (AuAgNCs): Freshly prepared glutathione GSH (0.3 mL, 100 mM), AgNO 3 (0.2 mL, 10 mM) and HAuCl 4The (1 mL, 20 mM) aqueous solution was added to 8.5 mL of distilled water. The mixture was stirred at room temperature for 10 min and then at 70 °C for 24 h. After cooling to room temperature, an equal volume of methanol was added to precipitate AuAgNCs, and the suspension was centrifuged at 12000 rpm. The resulting precipitate was washed 3 times with methanol to remove unreacted precursors and then dried. The final precipitate was redispersed in distilled water and stored at 4 °C for future use.

[0040] Example 7 Synthesis of CDs@ZIF-AuAgNCs: AuAgNCs (0.5 mg / mL, 500 μL) and ZIF@CDs (0.5 mg / mL, 4 mL) were mechanically stirred and mixed at room temperature for 10 min under ultrasonic treatment conditions. AuAgNCs were successfully self-assembled on the surface of ZIF@CDs and washed three times with ultrapure water to obtain CDs@ZIF-AuAgNCs nanoparticles, which were freeze-dried and stored in a 4°C refrigerator for later use.

[0041] like Fig.15 As shown in Figure 2, the fluorescence emission spectra of CDs@ZIF-AuAgNCs assembled in different ratios (by weight, ZIF@CDs:AuNC). When the ratio of CDs@ZIF to AuAgNCs reached 8:1, the fluorescence intensity reached a plateau.

[0042] Characterization of Examples 6-7 (1) Characterization of AuAgNCs: The particle size, morphology and surface morphology of AuAgNCs were analyzed by TEM. Fig.13 The TEM image shows that the AuAgNCs are spherical in shape, well dispersed, with a narrow particle size distribution and an average particle size of about 2.13 nm. The above characterizations indicate the successful synthesis of AuAgNCs.

[0043] (2) Characterization of CDs@ZIF-AuAgNCs: like Fig.14 As shown in the figure, when the ratio of ZIF@CDs to AuAgNCs reaches 8:1, the structure of CDs@ZIF-AuAgNCs nanoparticles is complete. The composite of AuAgNCs and ZIF@CDs nanoparticles can also be seen in the TEM morphology of CDs@ZIF-AuAgNCs nanoparticles, which further proves that CDs@ZIF-AuAgNCs nanoparticles were successfully synthesized. Fig.15 As shown in the figure, the fluorescence intensity of CDs@ZIF-AuAgNCs (the ratio of ZIF@CDs to AuAgNCs is 8:1) is 12 times higher than that of AuAgNCs.

[0044] (4) Zeta potential characterization of CDs, ZIF-8, ZIF@CDs, AuAgNCs and composite probes: Zeta potential characterization can examine the charge on the particle surface. Fig.16 As shown in the figure, the average potentials of CDs, ZIF-8, ZIF@CDs, AuAgNCs and CDs@ZIF-AuAgNCs in water are -8.73, 12.70, 3.11, -22.51 and -20.02 mV, respectively. ZIF@CDs formed by the assembly of negatively charged CDs and positively charged ZIF-8 are positively charged, and then uniformly modified with a layer of AuAgNCs with a large amount of negative charge, resulting in the potential of ZIF@CDs decreasing to -20.02 mV. These results indicate that a layer of AuAgNCs was successfully modified on the surface of ZIF@CDs to form CDs@ZIF-AuAgNCs nanoparticles. The zeta potential decreased from 3.11 mV to -20.02 mv, proving that the negatively charged AuAgNCs were successfully attached to the positively charged ZIF@CDs surface.

[0045] Example 8 CDs@ZIF-AuAgNCs / GOx system for glucose detection: 10 μL of 0−20 mM glucose was incubated with glutathione peroxidase (GPx, 10 mU / mL) at room temperature for 25 min. Then GSH (10 μM), Cu 2+ (copper sulfate, 1.5µM), CDs@ZIF-AuAgNCs (40µL, 4mg / mL) and HEPES buffer solution (pH=7.8) were mixed to form a 1mL reaction system and incubated for 20 minutes. The fluorescence spectrum of the mixture was measured at an excitation wavelength of 360 nm. As the concentration of glucose gradually increased, the fluorescence intensity gradually decreased, thereby achieving sensitive detection of glucose.

[0046] Different concentrations of glucose (0, 50 µM, 100 µM, 200 µM, 300 µM, 400 µM, 500 µM, 600 µM, 800 µM, 1 mM, 1.2 mM, 1.4 mM) were taken. Fig.17 The fluorescence emission spectra after adding different concentrations of glucose into the system are shown. With the increase of glucose concentration, glucose oxidase induces the oxidation of glucose into gluconic acid, which leads to the cleavage of the CDs@ZIF-AuAgNCs structure. The fluorescence intensity of AuAgNCs gradually weakens, while the fluorescence intensity of CDs gradually increases. Fig.18 It shows that when the glucose concentration is in the range of 100~1000 μM / mL, the fluorescence reduction factor has a good linear relationship with the logarithm of the glucose concentration, and the linear equation is: F 450 / F 570= 0.612+0.0021x (R 2 = 0.998), the limit of detection (LOD) of this method is 20 µM. Fig.19 As shown in the figure, at a glucose concentration of 600 μmol / L, there was almost no difference in the results of the seven concentration tests, indicating that the CDs@ZIF-AuAgNCs-based glucose method has good repeatability. Fig. 20 As shown in the figure, the recognition selectivity of CDs@ZIF-AuAgNCs fluorescent nanoprobe for glucose was studied by introducing various interferents such as galactose, xylose, fructose, sucrose, alanine, histidine, barium chloride, calcium chloride, potassium chloride, sodium chloride, urease, glucose, etc. Even when a much higher concentration of interferents than glucose was added, the response of CDs@ZIF-AuAgNCs-based glucose method to interference was negligible, indicating that this strategy has good selectivity for glucose.

Claims

1. A method for preparing a zeolite imidazole framework-8 dual-site loaded carbon dots and gold or gold-silver nanocluster fluorescent material, characterized in that: The steps include: Step 1: at room temperature, uniformly mix HAuCl4 aqueous solution and GSH aqueous solution, or uniformly mix AgNO3 aqueous solution, HAuCl4 aqueous solution and GSH aqueous solution, and then stir at 60-80°C for 20-28 hours, cool to room temperature, add methanol, centrifuge, wash, dry, obtain gold or gold-silver nanoclusters, disperse in water, and set aside; Step 2: Preparation of carbon dots: citric acid and ethylenediamine were mixed with distilled water, and then reacted at 200-260°C for 6-10 hours, cooled to room temperature, dialyzed and purified using a dialysis bag, and then dried to obtain carbon dots CDs; Step 3: Preparation of ZIF@CDs: Add zinc nitrate hexahydrate and 2-methylimidazole to methanol containing CDs under stirring conditions for 20-28 hours, centrifuge, wash, and obtain the product ZIF@CDs; Step 4: Mix the gold or gold-silver nanocluster solution with ZIF@CDs under ultrasonic conditions at room temperature.

2. The method for preparing the zeolite imidazole framework-8 dual-site loaded carbon dots and gold or gold-silver nanocluster fluorescent material as claimed in claim 1, characterized in that: In step 1, the molar ratio of HAuCl4 to GSH is 1:1-2; the molar ratio of AgNO3, HAuCl4 and GSH is 0.1:1:1-2.

3. The method for preparing the zeolite imidazole framework-8 dual-site loaded carbon dots and gold or gold-silver nanoclusters fluorescent material as claimed in claim 1, characterized in that: In step 2, 300-400 μL of ethylenediamine was added for every 1 g of citric acid.

4. The method for preparing the zeolite imidazole framework-8 dual-site loaded carbon dots and gold or gold-silver nanocluster fluorescent material as claimed in claim 1, characterized in that: In step 3, the mass ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1: (2-16).

5. The method for preparing the zeolite imidazole framework-8 dual-site loaded carbon dots and gold or gold-silver nanocluster fluorescent material as claimed in claim 1, characterized in that: In step 4, the mass ratio of the gold nanoclusters or gold-silver nanoclusters to ZIF@CDs is 1: (6-10).

6. Zeolite imidazole framework-8 dual-site loaded carbon dots and gold or gold-silver nanocluster fluorescent material prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the zeolite imidazole framework-8 dual-site loaded carbon dots and gold nanocluster fluorescent material according to claim 6 in detecting the pesticide triazophos TZP.

8. The use of claim 7 in detecting the pesticide triazophos TZP, characterized in that: Different concentrations of triazophos were incubated with glutathione peroxidase, and then GSH, Cu 2+ , a HEPES buffer solution, the zeolite imidazole framework-8 dual-site loaded carbon dots and the gold nanocluster fluorescent material according to claim 6 are mixed and incubated, and the fluorescence spectrum of the mixture is measured at an excitation wavelength of 360 nm.

9. Use of the zeolite imidazole framework-8 dual-site loaded carbon dots and gold-silver nanocluster fluorescent material as described in claim 6 in detecting glucose.

10. The use of claim 9 in detecting glucose, characterized in that: Different concentrations of glucose were incubated with glucose oxidase, and then a HEPES buffer solution and the zeolite imidazole framework-8 dual-site loaded carbon dots and gold-silver nanocluster fluorescent materials as described in claim 6 were mixed and incubated, and the fluorescence spectrum of the mixture was measured at an excitation wavelength of 360 nm.

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