Fluorescence sensor based on Ln-BMOF and preparation method and application thereof

Abstract

The invention belongs to the technical field of fluorescence sensing detection, and particularly relates to a fluorescence sensor based on Ln-BMOF and a preparation method and application thereof. The preparation method comprises the following steps: mixing and dissolving Tb (NO3) 3.5 H2O, Eu (NO3) 3.5 H2O, 2-aminoterephthalic acid and o-fluorobenzoic acid in a DMF / H2O mixed solvent, heating, cooling to room temperature, filtering, and drying in vacuum to obtain the sensor Eu < 0.01 > Tb < 0.99 >-BDC-NH2. The device is quick in response, wide in application range and good in durability; in a wide pH range, the stable performance is still maintained after multiple times of recycling. The Eu < 0.01 > Tb < 0.99 >-BDC-NH2 obtained by the invention can be directly detected in an aqueous solution, is suitable for actual water sample analysis, can be repeatedly used, and provides a novel platform for on-site rapid screening of PA and Fe < 3 + > in the environment.

Description

Technical Field

[0001] This article belongs to the field of fluorescence sensing and detection technology, specifically involving a fluorescence sensor based on Ln-BMOF, its preparation method, and its application. Background Technology

[0002] Picric acid (PA) is an important chemical raw material widely used in dyes, explosives and other fields. However, its high water solubility and environmental accumulation can harm the ecological environment and human health (such as causing cancer and skin irritation).

[0003] Fe 3+ PA is a key ion in biological and environmental systems, and an imbalance in its content can lead to various diseases such as anemia and kidney failure. Therefore, efficient and sensitive detection of PA and Fe is crucial. 3+ It has significant practical implications.

[0004] Limitations of existing detection methods: Traditional detection methods (such as capillary electrophoresis, high performance liquid chromatography, gas chromatography-mass spectrometry, etc.) rely on expensive equipment, have complex sample pretreatment, and are difficult to achieve rapid on-site detection.

[0005] Fluorescence detection has advantages due to its ease of operation and rapid response, but there is a need to develop fluorescent sensing materials with high selectivity and high stability.

[0006] Advantages of lanthanide metal-organic frameworks: Metal-organic frameworks (MOFs) possess porous structures and tunability, making them highly promising for fluorescence sensing. Lanthanides (such as Eu and Tb) have unique advantages in the application of their bimetallic organic frameworks (Ln-BMOFs) in sensing due to their sharp emission peaks, long emission lifetimes, and large Stokes shifts. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a fluorescence sensor based on Ln-BMOF, its preparation method, and its application. This study synthesized a lanthanide bimetallic organic framework material Eu using a solvothermal method. 0.01 Tb 0.99 -BDC-NH2, with Eu 3+ 、Tb 3+ For metal nodes, 2-aminoterephthalic acid (H2BDC-NH2) is used as an organic ligand for PA and Fe in aqueous solution. 3+ Fluorescence sensing detection.

[0008] The technical solution of the present invention is as follows: A method for fabricating a fluorescence sensor based on Ln-BMOF, employing a solvothermal synthesis, is described below: (1) Pretreatment: Tb(NO3)3·5H2O, Eu(NO3)3·5H2O, 2-aminoterephthalic acid, and o-fluorobenzoic acid were dissolved in a mixed solvent with a molar ratio of 0.99:0.01:1:20 and a volume ratio of DMF / H2O of 1:0.8-1.2; the mixture was stirred at room temperature for 30-40 minutes to fully dissolve the mixture and obtain a mixed solution. (2) Solvothermal reaction: The mixture is placed in an oven preheated to 120°C and heated for 36-40 hours; (3) Post-processing: After cooling to room temperature, the product was filtered, washed three times each with DMF and ethanol, and vacuum dried overnight to obtain the fluorescence sensor Eu. 0.01 Tb 0.99 -BDC-NH2.

[0009] This invention also provides the above-mentioned material Eu 0.01 Tb 0.99 -BDC-NH2 in aqueous solution picric acid (PA) and Fe 3+ Applications in detection.

[0010] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention utilizes the unique luminescent properties of lanthanides and the porous structure of MOFs to, for the first time, apply a lanthanide bimetallic organic framework (Eu0.01Tb0.99-BDC-NH2) to PA and Fe. 3+ The simultaneous detection fills the gap in the application of Ln-BMOFs in this field, and at the same time enhances fluorescence performance through bimetallic synergy, achieving highly selective recognition of target analytes.

[0011] (2) The Eu0.01Tb0.99-BDC-NH2 sensor, under 344nm excitation, produces strong fluorescence emission at 430nm, PA and Fe 3+ It can be detected by fluorescence quenching effect, has a fast response, and is effective against PA and Fe. 3+ Its response time is only 10 seconds; it has a wide range of applications, good durability in a wide pH range, and maintains stable performance even after multiple cycles.

[0012] (3) Eu obtained by the present invention 0.01 Tb 0.99 -BDC-NH2 can be directly detected in aqueous solutions, making it suitable for actual water sample analysis. It is also reusable, better meeting the needs of real-world environmental sample analysis, and is ideal for detecting PA and Fe in the environment. 3+ This provides a new platform for rapid on-site screening.

[0013] (4) Experiments have confirmed that fluorescence quenching is due to energy competition between the target and the sensor, rather than structural collapse or ion exchange, providing a mechanism reference for the design of similar sensors. Attached Figure Description

[0014] Figure 1 For Eu 0.01 Tb 0.99 -BDC-NH2 photographs under natural light and ultraviolet light; Figure 2 For Eu 0.01 Tb 0.99 Scanning electron microscope image of -BDC-NH2; Figure 3 For Eu 0.01 Tb 0.99 Infrared spectrum of -BDC-NH2. Detailed Implementation

[0015] 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.

[0016] Example 1 A method for fabricating a fluorescence sensor based on Ln-BMOF, employing a solvothermal method to synthesize Eu. 0.01 Tb 0.99 -BDC-NH2, the specific steps are as follows: (1) Pretreatment: Tb(NO3)3·5H2O (430.7mg, 0.99mmol), Eu(NO3)3·5H2O (4.7mg, 0.01mmol), 2-aminoterephthalic acid (H2BDC-NH2, 181.2mg, 1mmol), and o-fluorobenzoic acid (2-FBA, 2.8g, 20mmol) were dissolved in a mixed solvent of DMF / H2O = 1: 0.8-1.2; the mixture was stirred at room temperature for 30 minutes to fully dissolve the mixture and obtain a mixed solution. (2) Solvothermal reaction: The mixture was placed in an oven preheated to 120°C and heated for 38 hours; (3) Post-processing: After cooling to room temperature, filter the product, wash three times each with DMF and ethanol, and vacuum dry overnight to obtain the target product Eu. 0.01 Tb 0.99 -BDC-NH2; Photos taken under natural light and UV light, as shown. Figure 1 As shown; Figure 2As shown, SEM revealed an octahedral structure; PXRD confirmed the complete crystal structure, exhibiting a similar crystal form to other MOFs.

[0017] Experimental Example 1 (1) The Eu obtained in Example 1 0.01 Tb 0.99 Characterized by -BDC-NH2 Chemical properties: such as Figure 3 As shown, the FT-IR spectrum reveals the presence of NH2 stretching vibration (3502 cm⁻¹). -1 C=C stretching vibration (1602cm) -1 1580cm -1 Characteristic peaks such as ) confirm that the ligand successfully coordinated with the metal ion.

[0018] Porosity and thermal stability: The specific surface area of ​​BET is 173.7144 m². 2 / g, with an average pore size of 7.8128 nm; TG analysis shows that the framework only begins to collapse above 480℃, indicating good thermal stability.

[0019] Elemental composition: ICP / OES analysis showed Eu content of 0.169% and Tb content of 35.20%; XPS confirmed the coordination of Eu, Tb with O in the ligands.

[0020] Experimental Example 2 Luminous properties Luminescence experiments were conducted at concentrations of 0.1 mg / 10 mL, 0.5 mg / 10 mL, 1.0 mg / 10 mL, 1.5 mg / 10 mL, 2.0 mg / 10 mL, and 2.5 mg / 10 mL. The concentration of 2.0 mg / 10 mL showed the best luminescence performance, and therefore, 2.0 mg / 10 mL was determined to be the optimal concentration (considering both fluorescence intensity and cost-effectiveness).

[0021] Emission characteristics: Fluorescence emission performance was tested using the above-mentioned optimal concentration as the sample, and the optimal excitation wavelength and emission intensity under this system were determined. Excitation sources of 304 nm, 314 nm, 324 nm, 334 nm, 344 nm, and 354 nm were used for testing. A strong and broad emission peak was observed at 430 nm (corresponding to the ICT fluorescence of the ligand H2BDC-NH2), and the emission was water-dependent (stable luminescence only in aqueous solution). The optimal excitation wavelength was 344 nm, at which the emission peak intensity at 430 nm was optimal.

[0022] Environmental stability: The fluorescence intensity is stable within the pH range of 5 to 12, making it suitable for detection in neutral aqueous solutions.

[0023] Experimental Example 3 Sensing performance Sensitivity: The limit of detection (LOD) for PA is 0.42 μM, and for Fe... 3+ The Stern-Volmer quenching constant (Ksv) is 0.85 μM; the Stern-Volmer quenching constant is 41000 M. -1 (PA) and 9100 M -1 (Fe) 3+ The higher the Ksv value, the stronger the quenching ability of the quencher on the fluorescent substance, and the more effective the interaction between the two. Therefore, this material can effectively detect PA and Fe. 3+ .

[0024] Response speed: Fluorescence signal can be recorded within 10 seconds after the target substance is added, and the fluorescence intensity remains constant within 1 hour, enabling rapid detection.

[0025] Selectivity and interference resistance: Compatible with various nitro compounds (such as TNT, RDX) and cations (such as Cu). 2+ Pb 2+ In ), only PA and Fe 3+ It can induce significant fluorescence quenching and has excellent anti-interference ability.

[0026] Repeatability: After 5 cycles, the fluorescence intensity did not decrease significantly, and the structure remained intact (PXRD verification).

[0027] Practical application: Analysis of PA and Fe in lake water samples 3+ The spiked recoveries were 97.23%–106.8% and 95.5%–106.0%, respectively, with relative standard deviations (RSD) ≤3.9%, confirming that they can be used for actual water sample testing.

[0028] Fluorescence quenching mainly stems from energy-competitive absorption: the excitation spectrum of the sensor is related to PA and Fe. 3+ The absorption spectra of the target analytes overlap, leading to competition for absorption excitation energy and a shortened fluorescence lifetime (from 16.0 ns to 13.7 ns in the presence of PA, Fe). 3+ (When present, it drops to 15.7 ns).

[0029] The possibilities of structural collapse (PXRD confirmed structural integrity) and ion exchange (stable in cyclic experiments) were ruled out.

Claims

1. A method for fabricating a fluorescence sensor based on Ln-BMOF, characterized in that, The preparation method employs a solvothermal synthesis, and the specific steps are as follows: (1) Pretreatment: Tb(NO3)3·5H2O, Eu(NO3)3·5H2O, 2-aminoterephthalic acid, and o-fluorobenzoic acid were dissolved in a mixed solvent of DMF / H2O at a molar ratio of 0.99:0.01:1:20; the mixture was stirred at room temperature to obtain a mixed solution. (2) Solvothermal reaction: The mixture is placed in an oven and heated; (3) Post-processing: After cooling to room temperature, the product was filtered, washed three times each with DMF and ethanol, and vacuum dried for 8-12 h to obtain the Ln-BMOF-based fluorescence sensor Eu. 0.01 Tb 0.99 -BDC-NH2.

2. The preparation method according to claim 1, characterized in that, In step (1), the volume ratio of DMF / H2O is 1:0.8-1.

2.

3. The preparation method according to claim 1, characterized in that, In step (1), the mixture is stirred at room temperature for 30-40 minutes.

4. The preparation method according to claim 1, characterized in that, The heating temperature in step (2) is 120°C.

5. The preparation method according to claim 1, characterized in that, The heating time in step (2) is 36-40 hours.

6. The preparation method according to claim 1, characterized in that, The vacuum drying time in step (3) is 8-12 hours.

7. The Eu fluorescence sensor obtained by the preparation method according to any one of claims 1-6 0.01 Tb 0.99 -BDC-NH2.

8. The Eu as described in claim 7 0.01 Tb 0.99 -BDC-NH2 in aqueous solution contains picric acid and Fe 3+ Applications in detection.

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