A MOF-based composite material for the simultaneous detection of Fe 3+ , MnO4 - and picric acid and a method for preparing the same

Abstract

The application belongs to the technical field of fluorescent sensing detection, and particularly relates to a MOF-based composite material for multiple detection of Fe 3+ , MnO4 ‑ and picric acid and a preparation method thereof. The application prepares ZIF-8 by taking Zn(NO3)6H2O and 2-methyl imidazole as raw materials; and then the MOF-based composite material Flu@ZIF-8 is obtained by soaking in a Flu methanol solution. The application is the first multi-element fluorescent sensor based on the confinement effect of ZIF-8, and can realize efficient detection of Fe 3+ , MnO4 ‑ and PA synchronously, break through the limitation of traditional single target detection, effectively inhibit the ACQ effect of Flu, avoid solution pollution problems, and retain excellent optical properties. The material still maintains structural integrity and fluorescent response ability after multiple regeneration cycles, and reduces the cost of actual application.

Description

Technical Field

[0001] This invention belongs to the field of fluorescence sensing technology, specifically relating to a method for detecting Fe. 3+ MnO4 - MOF-based composite materials with picric acid multi-component detection and their preparation methods. Background Technology

[0002] Limitations of fluorescent dyes: Fluorescent dye molecules are widely used in imaging and sensing, but there are two major problems: First, the aggregation-induced quenching (ACQ) effect at high concentrations leads to a sharp decline in the solid-state fluorescence quantum yield; second, they are prone to solution contamination during detection and are difficult to completely separate, which limits their practical applications.

[0003] Metal-organic frameworks (MOFs) possess three-dimensional periodic pore structures, ultra-high specific surface areas, and tunable pore size / surface functional groups, making them ideal carriers: they can suppress dye aggregation through physical confinement effects and provide a stable chemical environment; and enhance the recognition of target analytes through pore size exclusion and surface group interactions.

[0004] With the increasing demands for environmental pollution control and public safety, ions (such as Fe) are becoming more important. 3+ MnO4 - The detection of trace amounts of nitro explosives (such as PA) and nitro explosives (such as PA) is critical, and detection technologies with both high sensitivity and selectivity need to be developed. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for treating Fe 3+ MnO4 - This study describes a MOF-based composite material for the multi-emission detection of picric acid and its preparation method. Fluorescent (Flu) molecules were encapsulated within the nanopores of ZIF-8 via an impregnation method to construct a ratiometric fluorescence sensor Flu@ZIF-8 with dual emission characteristics, enabling the detection of Fe... 3+ MnO4 - And high-efficiency detection of PA.

[0006] The technical solution of the present invention is as follows: A type of Fe 3+ MnO4 - The preparation method of MOF-based composite materials with picric acid multi-component detection is as follows: (1) Preparation of ZIF-8 Zn(NO3) in a molar ratio of 1:8 6H₂O and 2-methylimidazole are dissolved in methanol, respectively, and Zn(NO₃)₂ is added. The mass ratio of 6H2O to methanol is 1:28-30, and the mass ratio of 2-methylimidazole to methanol is 1:23-25. After mixing, stir at room temperature for 5-6 hours; centrifuge at 7000 rpm for 10 minutes to collect the white precipitate, wash with methanol 3-5 times; dry in a vacuum oven at 100℃ for 8-12 hours to obtain white ZIF-8 powder. (2) Preparation of Flu@ZIF-8 ZIF-8 was immersed in a Flu methanol solution at room temperature, with a ZIF-8 to Flu methanol solution mass ratio of 1:160 and a Flu methanol solution mass concentration of 0.2 g / L; the solution was kept for 68-72 hours; the precipitate was collected by centrifugation at 7000 rpm for 10 minutes and washed with DMF and methanol to remove unbound Flu from the surface; the precipitate was dried at 60 ℃ for 12 hours to obtain orange-yellow MOF-based composite Flu@ZIF-8 powder.

[0007] This invention also provides the above-mentioned MOF-based composite material Flu@ZIF-8 in the presence of Fe 3+ MnO4 - And its application in the detection of picric acid.

[0008] Material design: The nanopore confinement effect of ZIF-8 is used to suppress the aggregation-induced quenching (ACQ) of Flu, while the fluorescence performance is enhanced by fluorescence resonance energy transfer (FRET) between ZIF-8 and Flu.

[0009] Sensing mechanism: Based on the dynamic response difference of the dual emission peaks of Flu@ZIF-8 (ZIF-8 intrinsic emission at 440 nm and Flu characteristic emission at 545 nm), a ratio signal output mode is established to improve the detection self-calibration capability.

[0010] Performance characteristics: This sensor is sensitive to Fe 3+ MnO4 - PA exhibits ultra-high fluorescence quenching sensitivity, as well as excellent stability, selectivity, anti-interference ability and reversibility, which can meet the actual detection needs.

[0011] The beneficial effects of this invention are as follows: 1. First Multi-Target Detection Platform: The first multi-element fluorescence sensor based on the ZIF-8 confinement effect, capable of simultaneously detecting Fe... 3+ MnO4 - The high-efficiency detection of PA breaks through the limitations of traditional single-target detection.

[0012] 2. Overcoming inherent defects of fluorescent dyes: The ACQ effect of Fluor is effectively suppressed through the physical confinement effect of the ZIF-8 channels, while avoiding solution contamination and preserving its excellent optical properties.

[0013] 3. Enhanced energy transfer performance: By utilizing the spectral overlap between ZIF-8 emission and Flu absorption, efficient FRET is achieved, making the fluorescence performance of Flu@ZIF-8 significantly better than that of single ZIF-8 or Flu.

[0014] 4. High stability and reversibility: The material retains its structural integrity and fluorescence response after multiple regeneration cycles, reducing the cost of practical applications. Attached Figure Description

[0015] Figure 1 XRD diffraction pattern of Flu@ZIF-8; Figure 2 Scanning electron microscope image of Flu@ZIF-8; Figure 3 Different amounts of Fe in aqueous solution 3+ The fluorescence emission spectrum changes with concentration; the inset shows the fluorescence emission spectrum after the addition of Fe. 3 + Optical photographs of the stimulated Flu@ZIF-8 suspension before and after aqueous solution (1 mM); Figure 4 Different concentrations of MnO4 in aqueous solution - The fluorescence emission spectrum varies with concentration; the inset shows the fluorescence emission spectrum after the addition of MnO4. - Optical photographs of the stimulated Flu@ZIF-8 suspension before and after aqueous solution (1 mM); Figure 5 The fluorescence emission spectra of PA with different concentrations in ethanol solution change with concentration; the inset shows optical photographs of the stimulated Flu@ZIF-8 suspension before and after the addition of PA ethanol solution (1 mM). Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] Example 1 A type of Fe 3+ MnO4 - Preparation method of MOF-based composite materials with picric acid multi-component detection 1. Preparation of ZIF-8 Raw material: Zn (NO3) 6H2O (1.0 mmol, 300 mg), 2-methylimidazole (Hmim, 8.0 mmol, 660 mg), methanol.

[0018] Procedure: Dissolve the two raw materials separately in 15 mL of methanol, mix and stir at room temperature for 5-6 hours; centrifuge at 7000 rpm for 10 minutes to collect the white precipitate, wash 5 times with methanol; dry overnight in a vacuum oven at 100℃ to obtain white ZIF-8 powder (yield 82%).

[0019] 2. Preparation of Flu@ZIF-8 Raw materials: ZIF-8 (500 mg), a methanol solution of Flu (100 mL, 200 mg / L). Procedure: Immerse ZIF-8 in the Flu methanol solution at room temperature for 68-72 hours; collect the precipitate by centrifugation, wash with a large amount of DMF and methanol to remove unbound Flu from the surface; dry at 60 °C for 12 hours to obtain orange-yellow Flu@ZIF-8 powder.

[0020] Experimental Example 1 1. Material Characterization Structure and morphology: such as Figure 1 As shown, PXRD confirms that the ZIF-8 and Flu@ZIF-8 crystal structures are intact and without shift; Figure 2 As shown, SEM revealed that both were hexagonal particles with a diameter of ~100 nm, and their morphology was not affected by the loading.

[0021] Chemical structure: FTIR showed that Flu@ZIF-8 coexisted with ZIF-8 (1575 cm⁻¹). -1 1390 cm -1 ) and Flu (500-1500 cm) -1 1600-1700 cm -1 It exhibits characteristic peaks and shows Zn-O coordination and π-π stacking.

[0022] Thermal stability: TGA shows that both are stable below 200°C (mass loss <5%).

[0023] Porosity and loading rate: The BET specific surface area of ​​ZIF-8 is 1923.8 m². 2 / g, Flu@ZIF-8 is 1323.0m 2 / g (the pore portion is filled with Flu); Flu loading rate is 5.21 wt%.

[0024] 2. Fluorescence properties Dual emission characteristics: ZIF-8 has a broad emission band at 440 nm, while Flu@ZIF-8 has emission peaks at 440 nm (weak) and 545 nm (strong), with the intensity at 545 nm being 6 times that at 440 nm (due to Flu, FRET enhancement).

[0025] Environmental stability: Fluorescence is stable in aqueous solutions with pH 4-12 and in highly polar solvents (water, ethanol, methanol).

[0026] 3. Sensing performance like Figure 3 As shown, in Fe 3+ The detection limit in water was 1.01 × 10⁻⁶. -6 mol / L, Stern-Volmer quenching constant (Ksv) 2.26 × 10⁻⁶ 4 M -1 It has excellent anti-interference capabilities.

[0027] like Figure 4 As shown, the detection limit in water for MnO4 is 1.31 × 10⁻⁶. -6 mol / L, Ksv 4.16×10 5 M -1 It has excellent anti-interference capabilities.

[0028] like Figure 5 As shown, the detection limit for ethanol in PA detection is 5.36 × 10⁻⁶. -7 mol / L, Ksv 1.81×10 5 M -1 It has the highest sensitivity.

[0029] Recyclability: It can be reused 7 times with minimal loss of fluorescence intensity and intact structure.

[0030] Sensing mechanism: mainly achieved through FRET (overlap of ZIF-8 emission and analyte absorption spectra), eliminating the influence of framework collapse.

Claims

1. A method for treating Fe 3+ MnO4 - The method for preparing MOF-based composite materials with picric acid multi-component detection is characterized by, The specific steps of the preparation method are as follows: (1) Preparation of ZIF-8: Zn(NO3) 6H2O and 2-methylimidazole were dissolved in methanol, mixed, stirred at room temperature, and the white precipitate was collected by centrifugation. The precipitate was washed with methanol 3-5 times and dried under vacuum to obtain white ZIF-8 powder. (2) Preparation of Flu@ZIF-8: ZIF-8 was immersed in Flu methanol solution at room temperature for 68-72 hours; the precipitate was collected by centrifugation and washed with DMF and methanol; after drying, orange-yellow MOF-based composite material Flu@ZIF-8 powder was obtained.

2. The preparation method according to claim 1, characterized in that, Zn(NO3) in step (1) The molar ratio of 6H2O to 2-methylimidazole is 1:

8.

3. The preparation method according to claim 1, characterized in that, In step (1), Zn(NO3) The mass ratio of 6H2O to methanol is 1:28-30; the mass ratio of 2-methylimidazole to methanol is 1:23-25.

4. The preparation method according to claim 1, characterized in that, The stirring time at room temperature in step (1) is 5-6 hours.

5. The preparation method according to claim 1, characterized in that, The centrifugation conditions in step (1) are 7000 rpm for 10 minutes.

6. The preparation method according to claim 1, characterized in that, In step (1), the vacuum drying conditions are 100℃ vacuum oven drying for 8-12 hours.

7. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of ZIF-8 to Flu methanol solution is 1:160; the mass concentration of Flu methanol solution is 0.2 g / L.

8. The preparation method according to claim 1, characterized in that, In step (2), the centrifugation conditions are 7000 rpm for 10 minutes; the drying conditions are 60 ℃ for 12 hours.

9. Flu@ZIF-8, a MOF-based composite material obtained by the preparation method according to any one of claims 1-8.

10. The MOF-based composite material Flu@ZIF-8 as described in claim 9, in the application of Fe... 3+ MnO4 - And its application in the detection of picric acid.

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