Preparation method of fluorescent metal-organic framework and spray for visual detection of nitro-containing pesticides

Abstract

This invention discloses a fluorescent metal-organic framework for the visual detection of nitro-containing pesticides and a method for preparing its spray, belonging to the field of environmental protection technology, using Zn... 2+ Using 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole and 2-hydroxyterephthalic acid as organic ligands, [M] was prepared via a solvothermal method. x (L1) y (L2) z M is the metal ion Zn 2+ L1 is 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, L2 is 2-hydroxyterephthalic acid, x=1, y=1, z=1. This method allows for the visual detection of nitrate-containing pesticides on the surface of fruits, vegetables, and other agricultural products.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology, and particularly relates to a fluorescent metal-organic framework for visual detection of nitro-containing pesticides, and its preparation method and application in spray form. Background Technology

[0002] Nitrogen-containing pesticides (such as organophosphates and organochlorines) are widely used in agricultural production due to their highly effective and broad-spectrum insecticidal properties. However, their residues can accumulate in the human body through the food chain, leading to neurotoxicity, endocrine disorders, and carcinogenic risks. Currently, pesticide residue detection mainly relies on laboratory instruments such as chromatography and mass spectrometry. Although these methods offer high precision, they suffer from problems such as expensive equipment, complex operation, and long detection cycles, making it difficult to meet the needs of rapid screening in fields or markets. Especially in the fruit and vegetable supply chain and import / export links, there is an urgent need for a portable, low-cost, and visual detection technology to achieve real-time monitoring of pesticide residues and control of food safety risks.

[0003] In recent years, fluorescence sensing technology has become a research hotspot in the field of pesticide detection due to its advantages such as high sensitivity, real-time response, and intuitive signal output. However, traditional fluorescent probes (such as quantum dots and organic dyes) are easily interfered with in complex matrices, have poor photostability, and lack specificity for nitro pesticides, making accurate detection difficult. Furthermore, the synthesis of some probes involves toxic reagents, posing environmental and safety risks and limiting their practical application. Therefore, developing novel fluorescent materials that combine high selectivity, strong anti-interference properties, and environmental friendliness is crucial for improving the efficiency of pesticide residue detection.

[0004] Metal-organic frameworks (MOFs) exhibit unique potential in the field of sensing due to their customizable pore structures, high specific surface area, and abundant active sites. Some fluorescent MOFs can produce fluorescence quenching or enhancement responses to specific targets through host-guest interactions or electron transfer effects, and have been successfully used for the detection of heavy metal ions, explosives, and volatile organic compounds. However, the design of fluorescent MOFs for nitro pesticides still faces challenges: firstly, nitro groups (-NO2), as strong electron acceptors, easily interact non-specifically with MOF frameworks, leading to insufficient selectivity; secondly, existing materials often require complex modification or post-processing steps, making them difficult to adapt to portable detection scenarios and hindering their practical application.

[0005] To address the aforementioned problems, this invention proposes a fluorescent MOF (Medium-Oxide-Fluorescent Cell) specifically for the visual detection of nitro-containing pesticides, along with its sprayable preparation method. By directionally designing MOF structures containing electron-rich ligands, their electron transfer sensitivity to nitro-containing pesticides is enhanced, and selective recognition capabilities are improved by combining pore size control strategies. Simultaneously, a matching spray formulation is developed to disperse the MOF material into a stable suspension, which can be directly sprayed onto the surface of fruits and vegetables. In-situ, semi-quantitative detection of pesticide residues is achieved through changes in fluorescence signals. This technology combines high sensitivity, rapid response, and ease of operation, and is expected to provide a low-cost, widely applicable solution for pesticide residue monitoring. Summary of the Invention

[0006] The purpose of this invention is to provide a fluorescent metal-organic framework for the visual detection of nitro-containing pesticides and a method for preparing the same spray, wherein the material can enable the visual detection of nitro-containing pesticides on the surface of fruits and vegetables.

[0007] This invention provides a fluorescent metal-organic framework for the visual detection of nitro-containing pesticides and a method for preparing the same as a spray, wherein the fluorescent metal-organic framework is named Zn-MOF and its chemical formula is: [M x (L1) y (L2) z M is the metal ion Zn 2+ L1 is 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazolyl, L2 is 2-hydroxyterephthalic acid, x = 1, y = 1, z = 1.

[0008] Furthermore, Zn-MOF has a three-dimensional network structure, and its chemical formula is: [M x (L1) y (L2) z ],in,

[0009] L1 is the organic linker ligand 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazolyl, the structural formula of which is shown in Formula I;

[0010]

[0011] L2 is 2-hydroxyterephthalic acid, and its structural formula is shown in Formula II;

[0012]

[0013] M is the metal ion Zn. 2+ ;

[0014] x, y, and z represent the number of metal ions, 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, and 2-hydroxyterephthalic acid, respectively, where x = 1, y = 1, and z = 1.

[0015] A method for preparing a fluorescent metal-organic framework for the visual detection of nitro-containing pesticides, characterized in that it uses Zn metal ions... 2+ Using 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole and 2-hydroxyterephthalic acid as organic ligands, fluorescent metal-organic frameworks were prepared by a solvothermal method.

[0016] Furthermore, the method for preparing a fluorescent metal-organic framework for the visual detection of nitro-containing pesticides is characterized by comprising the following steps:

[0017] A soluble salt of 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, 2-hydroxyterephthalic acid, and zinc was mixed, added to a water / DMF solution, and stirred until homogeneous. The mixture was then reacted at a constant temperature of 85℃~95℃ for 8h~12h. After the reaction was completed, the mixture was cooled to obtain light yellow blocky crystals. These crystals were then filtered, washed, and dried to obtain a fluorescent metal-organic framework for the detection of nitrate pesticides.

[0018] Furthermore, the molar ratio of the soluble salts of 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, 2-hydroxyterephthalic acid, and zinc is 1:(0.9–1.1):(0.9–1.1).

[0019] Furthermore, the soluble salt of zinc is zinc nitrate hexahydrate, and the volume ratio of water to DMF is 1 / 1.

[0020] Furthermore, the drying temperature is 98℃~103℃, and the drying time is 8.5h~10h.

[0021] Furthermore, the preparation method of the fluorescent metal-organic framework spray for visual detection of nitro-containing pesticides involves dispersing the fluorescent metal-organic framework Zn-MOF in a 75% ethanol solution at a mass percentage of 0.5% to 0.6%, and placing the resulting uniform dispersion in a 10mL dispensing bottle to obtain the spray.

[0022] Furthermore, the aforementioned method for preparing a fluorescent metal-organic framework and its spray for visual detection of nitro-containing pesticides can visually detect nitro-containing pesticides on the surface of crops such as fruits and vegetables.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The designed fluorescent metal-organic frameworks (MOFs) have a three-dimensional network structure, combining high fluorescence quantum yield and chemical stability. They also exhibit strong resistance to photobleaching and can maintain fluorescence signal stability over a long period of time, which is significantly superior to traditional organic dyes or quantum dot probes.

[0025] This invention achieves material synthesis through a one-step solvothermal method, which is simple, has a high yield, low raw material cost, is environmentally friendly, requires no complicated post-processing, and is suitable for large-scale industrial production.

[0026] The spray-type design of this invention allows the material to be uniformly dispersed in the solvent. It enables in-situ visual detection of nitrate pesticides on the surface of fruits and vegetables through spraying, without the need for pretreatment. The detection limit is as low as nM, and the sensitivity and ease of operation are improved simultaneously. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 These are schematic diagrams of the metal-organic framework Zn-MOFs prepared in Examples 1-4 of this invention;

[0029] Figure 2 This is a fluorescence stability test diagram of the metal-organic framework Zn-MOF prepared in Example 1 of this invention;

[0030] Figure 3 This is a fluorescence titration diagram of adding different concentrations of nitrofuran to a suspension of Zn-MOF in water prepared in Example 1 of this invention. Detailed Implementation

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0034] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0035] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0036] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available pharmaceutical products.

[0037] In the embodiments of the present invention, unless otherwise specified, water refers to deionized water.

[0038] Example 1

[0039] Weigh 0.03 mmol of 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, 0.03 mmol of 2-hydroxyterephthalic acid, and 0.03 mmol of zinc nitrate hexahydrate into a 10 mL glass sample vial. Add 4 mL of water / DMF (v / v = 1 / 1). Then place the glass sample vial in a reaction vessel and place it in an electric heating drying oven at 90 °C for 10 h. After the reaction is complete, cool to obtain light yellow blocky crystals. Filter, wash, and dry at 100 °C for 9 h to obtain a fluorescent metal-organic framework Zn-MOF with the chemical formula: [M x (L1) y (L2) z M is the metal ion Zn 2+ L1 is 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, L2 is 2-hydroxyterephthalic acid, x=1, y=1, z=1, yield: 95%, its crystal structure is as follows. Figure 1 As shown, from Figure 1As can be seen, the asymmetric unit of Zn-MOF includes one zinc ion, one 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole coordination, and one deprotonated 2-hydroxyterephthalic acid ligand. Through four independent nitrogen coordinations of 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole and two monodentate coordinations of the carboxyl oxygen groups of 2-hydroxyterephthalic acid, deformed hexagonal nanopores are formed in space, with a size of [missing information]. The import and export of pesticides containing nitrates are permitted.

[0040] Fluorescence assay and fluorescence stability assay of Zn-MOF

[0041] Under 330 nm excitation, a 3 mL aqueous suspension of Zn-MOF showed an emission peak (black line) at 440 nm at which the emission peak was attributed to 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, indicating that Zn-MOF has good fluorescence properties. It also exhibited blue luminescence under 365 nm UV light, providing a good basis for subsequent visualization detection. Fluorescence tests were performed on uniformly dispersed Zn-MOF suspensions after 3 months, 6 months, and 1 year. The fluorescence intensity remained almost unchanged, indicating that Zn-MOF has excellent fluorescence stability. The fluorescence test results are attached. Figure 2 .

[0042] Fluorescence detection of nitrofurans by Zn-MOF

[0043] Weigh out the Zn-MOF material from Example 1 and prepare a suspension with a uniform dispersion of 0.33 mg / L water. Take 3 mL of the above suspension in a quartz cuvette, and then add 0.02 M nitrofuran solution dropwise (nitrofuran is used as an example; the fluorescence titration effect of other nitro-containing pesticides is similar) until the fluorescence intensity no longer changes. The total concentration of nitrofuran added is 0.72 mM. The excitation wavelength is 330 nm, and the fluorescence emission peak at 440 nm is recorded. The results are shown in the appendix. Figure 3 With increasing nitrofuran concentration, the fluorescence of Zn-MOF underwent significant quenching, reaching a quenching degree of 94.3%. Figure 3 The calculated detection limit of Zn-MOF for nitrofurans is 25.0 nM.

[0044] Example 2

[0045] Weigh 0.03 mmol of 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, 0.028 mmol of 2-hydroxyterephthalic acid, and 0.029 mmol of zinc nitrate hexahydrate into a 10 mL glass sample vial. Add 4 mL of water / DMF (v / v = 1 / 1). Then place the glass sample vial in a reaction vessel and place it in an electric heating drying oven at 95 °C for 8 h. After the reaction is complete, cool to obtain light yellow blocky crystals. Filter, wash, and dry at 100 °C for 9 h to obtain a fluorescent metal-organic framework Zn-MOF with the chemical formula: [M x (L1) y (L2) z M is the metal ion Zn 2+ L1 is 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, L2 is 2-hydroxyterephthalic acid, x=1, y=1, z=1, yield: 94%, its crystal structure is as follows. Figure 1 As shown.

[0046] Example 3

[0047] Weigh 0.03 mmol of 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, 0.03 mmol of 2-hydroxyterephthalic acid, and 0.031 mmol of zinc nitrate hexahydrate into a 10 mL glass sample vial. Add 4 mL of water / DMF (v / v = 1 / 1). Then place the glass sample vial in a reaction vessel and place it in an electric heating drying oven at 88 °C for 11 h. After the reaction is complete, cool to obtain light yellow blocky crystals. Filter, wash, and dry at 98 °C for 10 h to obtain a fluorescent metal-organic framework Zn-MOF with the chemical formula: [M x (L1) y (L2) z M is the metal ion Zn 2+ L1 is 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, L2 is 2-hydroxyterephthalic acid, x=1, y=1, z=1, yield: 95%, its crystal structure is as follows. Figure 1 As shown.

[0048] Example 4

[0049] Weigh 0.03 mmol of 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, 0.031 mmol of 2-hydroxyterephthalic acid, and 0.028 mmol of zinc nitrate hexahydrate into a 10 mL glass sample vial. Add 4 mL of water / DMF (v / v = 1 / 1). Then place the glass sample vial in a reaction vessel and place it in an electric heating drying oven at 95 °C for 8 h. After the reaction is complete, cool to obtain light yellow blocky crystals. Filter, wash, and dry at 103 °C for 10 h to obtain a fluorescent metal-organic framework Zn-MOF with the chemical formula: [M x (L1) y (L2) z M is the metal ion Zn 2+ L1 is 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, L2 is 2-hydroxyterephthalic acid, x=1, y=1, z=1, yield: 96%, its crystal structure is as follows. Figure 1 As shown.

[0050] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A fluorescent metal-organic framework for visual detection of nitro-containing pesticides and a method for preparing the same spray, wherein the metal-organic framework is characterized by having the chemical formula: [M x (L1) y (L2) z M is the metal ion Zn 2+ L1 is 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazolyl, L2 is 2-hydroxyterephthalic acid, x = 1, y = 1, z = 1.

2. A fluorescent metal-organic framework for visual detection of nitro-containing pesticides as described in claim 1, characterized in that, With metal ions Zn 2+ Using 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole and 2-hydroxyterephthalic acid as organic ligands, fluorescent metal-organic frameworks were prepared by a solvothermal method.

3. The method for preparing a fluorescent metal-organic framework for visual detection of nitro-containing pesticides according to claim 2, characterized in that, Includes the following steps: A soluble salt of 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, 2-hydroxyterephthalic acid, and zinc was mixed, added to a water / DMF solution, and stirred until homogeneous. The mixture was then reacted at a constant temperature of 85℃~95℃ for 8h~12h. After the reaction was completed, the mixture was cooled to obtain light yellow blocky crystals. These crystals were then filtered, washed, and dried to obtain a fluorescent metal-organic framework for the detection of nitrate pesticides.

4. The method for preparing a fluorescent metal-organic framework for visual detection of nitro-containing pesticides according to claim 3, characterized in that, The molar ratio of the soluble salts of 2,5-bis(pyridin-4-yl)thiazo[5,4-d]thiazole, 2-hydroxyterephthalic acid and zinc is 1:(0.9-1.1):(0.9-1.1), and the volume ratio of water / DMF is 1 / 1.

5. The method for preparing a fluorescent metal-organic framework for visual detection of nitro-containing pesticides according to claim 4, characterized in that, The soluble salt of zinc is zinc nitrate hexahydrate.

6. The method for preparing the fluorescent metal-organic framework for visual detection of nitro-containing pesticides according to claim 4, characterized in that, The drying temperature is 98℃~103℃, and the drying time is 8.5h~10h.

7. The preparation method of the fluorescent metal-organic framework and its spray for visual detection of nitro-containing pesticides according to claim 1 is to disperse the fluorescent metal-organic framework of claim 1 in a 75% ethanol solution at a mass percentage of 0.5% to 0.6%, and place the resulting uniform dispersion in a 10mL dispensing bottle to obtain the spray.

8. The fluorescent metal-organic framework and its spray preparation method for visual detection of nitrate-containing pesticides according to claim 1 can visually detect nitrate-containing pesticides on the surface of fruits and vegetables.

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