Ratio-type Eu-MOF fluorescent material for ultrasensitive detection of sarin simulant and preparation method and application of ratio-type Eu-MOF fluorescent material

Abstract

The invention discloses a ratio-type Eu-MOF fluorescent material for super-sensitive detection of sarin simulants and a preparation method and application thereof, the Eu-MOF fluorescent material is prepared from 2-aminoterephthalic acid as an organic ligand and rare earth europium ions by utilizing the fluorescence change characteristic of a lanthanide MOF material, the material emits blue organic ligand and red europium ion fluorescence, and the ratio-type Eu-MOF fluorescent material can be applied to ultrasensitive detection of sarin simulants. When sarin simulant diethyl chlorophosphate interacts with europium ions, blue fluorescence of the ligand is enhanced while red fluorescence of the europium ions is almost unchanged, so that ratio-type fluorescence detection of diethyl chlorophosphate molecules in N, N-dimethylformamide is realized, the preparation method is simple, and the fluorescent probe has good stability in N, N-dimethylformamide, is sensitive and accurate in detection, and is suitable for industrial production. And the device can be recycled.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent materials technology, specifically relating to a ratiometric Eu-MOF fluorescent material for ultrasensitive detection of sarin simulants, its preparation method, and its application. Background Technology

[0002] Nerve agents exert toxic effects on humans by irreversibly inhibiting the activity of acetylcholinesterase. Sarin (GB), a key component of type G nerve agents, is highly volatile, rapidly evaporates, and poses an inhalation threat; 0.5 mg (skin contact) or inhalation of 100 mg / min / m³ can be fatal. Given the lethality of sarin, its control is extremely strict, making direct use in scientific research difficult. Therefore, diethyl chlorophosphate (DCP), a mimic with a highly similar chemical structure and physicochemical properties but lower toxicity, is typically used for detection experiments. Thus, developing highly sensitive, selective, and rapid-response detection methods has become a key focus for the scientific community in effectively mitigating the potential threat of nerve agents.

[0003] In recent years, fluorescence sensors have become one of the most valued detection tools due to their advantages of convenient operation, rapid analysis, and high sensitivity. Among them, luminescent metal-organic frameworks (LMOFs), as an important branch of fluorescence sensors, not only possess advantages such as high porosity and structural diversity, but also attract significant attention due to their unique luminescent properties. Rare earth elements, with their unique 4f electronic structure, can emit light in both the visible and near-infrared regions, exhibiting clearly visible emission spectra. However, due to the ff transition restriction of lanthanide metal ions, suitable organic ligands are needed to form complexes through the "antenna effect" before the characteristic emission peaks of rare earth ions can be detected. This unique "antenna effect" gives synthesized rare earth-based LMOFs large Stokes shifts, high quantum yields, and significant fluorescence color changes, thereby enabling the detection and analysis of target molecules and holding important applications in the field of fluorescence detection. Compared to the significant limitations of traditional single-signal LMOF sensors in practical applications, ratiometric fluorescence sensors can effectively eliminate interference from external environmental factors by constructing multiple interconnected and independently responding emission centers and establishing a self-calibration or self-reference mechanism. Ratiometric LMOF sensors not only significantly improve detection accuracy and reliability but also provide a new solution for trace substance detection in complex environments, offering practical significance for timely on-site detection. Therefore, synthesizing a ratiometric LMOF fluorescent material for ultrasensitive detection of sarin simulants will advance ultrasensitive on-site detection. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of traditional single-signal LMOF sensors, whose sensitivity is easily affected by various factors such as concentration fluctuations, changes in instrument parameters, ambient temperature and humidity, and excitation light source intensity. This invention provides an Eu-MOF fluorescent material with dual emission centers and its preparation method. The dual emission peaks effectively improve fluorescence efficiency and detection sensitivity.

[0005] To achieve the above objectives, the chemical formula of the dual-emission Eu-MOF fluorescent material provided by this invention is {[Eu(NH2-BDC]} 1.5 (OH) 0.5 (HCOO) 0.5 (DMF)]} n In this context, NH2-BDC represents 2-aminoterephthalic acid that has lost two protons from its carboxyl groups, and DMF represents N,N-dimethylformamide; this material crystallizes in a monoclinic crystal system with space group [space group number missing]. I 2 / m The unit cell parameters are a=13.2804(5) Å, b=15.4614(5) Å, c=16.9989(5) Å, α=90°, β=96.860(4)°, and γ=90°.

[0006] Furthermore, the asymmetric unit of the fluorescent material consists of an Eu... 3+ Ions, one DMF molecule, 1 / 2 HCOO - 3 / 2 NH2-BDC and 1 / 2 bridging OH - Composition; four Eu 3+ The ions are separated by the carboxyl oxygen atom and two OH groups of NH2-BDC. - The connection forms [Eu4(COO)] 10 The secondary building blocks of [(DMF)2(HCOO)2(OH)2], the secondary building blocks in NH2-BDC and HCOO - A three-dimensional framework structure is formed by the connection of these elements.

[0007] The preparation method of the above-mentioned dual-emission Eu-MOF fluorescent material is as follows: europium nitrate and 2-aminoterephthalic acid are completely dissolved in a mixed solvent of N,N-dimethylformamide, N,N-dimethylpropenylurea and water, then triethylamine is added, and the mixture is allowed to stand and react in a sealed manner at 110-130℃ for 5-6 days. After the reaction is complete, the mixture is cooled to room temperature, filtered, washed with N,N-dimethylformamide, and finally centrifuged and dried in air to obtain the dual-emission Eu-MOF fluorescent material.

[0008] Furthermore, in the above preparation method, the molar ratio of europium nitrate to 2-aminoterephthalic acid is preferably 1:1 to 2.

[0009] Furthermore, in the above preparation method, the volume ratio of N,N-dimethylformamide, N,N-dimethylpropenylurea and water in the mixed solvent is preferably 8:4:1.

[0010] Furthermore, in the above preparation method, the preferred volume ratio of water to triethylamine is 5:1 to 2.

[0011] Furthermore, in the above preparation method, it is preferable to allow the mixture to stand and be sealed at 120°C for 5 days for reaction.

[0012] This invention also provides the use of the above-mentioned ratiometric Eu-MOF fluorescent material in the sensing and detection of sarin simulant diethyl chlorophosphate, and the specific detection method includes the following steps: Step 1: Disperse the dual-emission Eu-MOF fluorescent material ultrasonically in N,N-dimethylformamide to obtain an Eu-MOF suspension with a concentration of 0.3–0.5 mg / mL.

[0013] Step 2: Transfer the Eu-MOF suspension to a quartz cuvette, add different concentrations of diethyl chlorophosphate, mix thoroughly, and let stand for 2–3 min. Detect the fluorescence spectrum of the mixed solution using a fluorescence spectrophotometer under 365 nm incident light excitation. Then, use I... 430 and I 614 The fluorescence intensity at 430 nm and 614 nm is represented by the concentration of diethyl chlorophosphate on the x-axis, and the ratio of the fluorescence intensity at 430 nm to 614 nm is represented by I. 430 / I 614 Plot a standard curve for the ordinate and perform a linear fit on the standard curve to obtain the standard equation.

[0014] Step 3: Add the sample to be tested according to the method in Step 2 above, and calculate the concentration of diethyl chlorophosphate in the sample by combining the standard equation.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention utilizes 2-aminoterephthalic acid (NH2-H2BDC) as an organic ligand with an "antenna effect" to interact with rare earth europium ions (Eu). 3+ Eu-MOF fluorescent materials with dual luminescent centers were synthesized via a hydrothermal method. These materials exhibit blue fluorescence emission from organic ligands and Eu... 3+ The ion emits red fluorescence, and when diethyl chlorophosphate (DCP) molecules interact with it, the blue emission of the ligand is enhanced, while Eu... 3+ The red fluorescence intensity remained almost unchanged, thus enabling the detection of DCP in N,N-dimethylformamide (DMF) solution.

[0016] 2. In the synthesis method of the Eu-MOF fluorescent material of the present invention, 2-aminoterephthalic acid and Eu 3+ The coordination ability of N,N-dimethylpropenylurea (DMPU) and triethylamine is very weak. Although they do not participate in coordination in the structure, they act as organic bases during synthesis, abstracting the carboxylic acid proton from 2-aminoterephthalic acid to generate a carboxylate anion (R-COO⁻). By adjusting the amount or rate of addition of triethylamine, the deprotonation rate can be controlled, thereby controlling the kinetics of MOF nucleation and crystal growth. Slow deprotonation often favors the formation of larger, higher-quality single crystals rather than microcrystalline powders. Furthermore, changing the amount of triethylamine can further regulate the compound structure by controlling the microenvironment of the synthesis process. The synthesis method of this invention has the advantages of being simple, easy to operate, highly safe, low in toxicity, and low in the cost of raw materials and equipment.

[0017] 2. The Eu-MOF fluorescent material of this invention exhibits excellent detection performance for DCP, a simulant of the nerve agent sarin, in a liquid environment: high sensitivity (detection limit down to 1 ppb), good selectivity, and rapid response. Furthermore, the material demonstrates good repeatability and stability, maintaining stable performance even after multiple cycles of detection. These characteristics make this Eu-MOF fluorescent material show outstanding application potential in the fields of rapid screening for nerve agents and public safety monitoring, with significantly superior performance compared to existing fluorescent sensing materials. Attached Figure Description

[0018] Figure 1 This is a diagram of the secondary building blocks of the Eu-MOF fluorescent material in Example 1.

[0019] Figure 2 This is a three-dimensional image of the Eu-MOF fluorescent material in Example 1.

[0020] Figure 3 These are the PXRD spectra of the Eu-MOF fluorescent material in DMF and after DCP detection in Example 1.

[0021] Figure 4 These are the fluorescence spectra of the Eu-MOF fluorescent material in different solvents in Example 1.

[0022] Figure 5 This is a fluorescence titration diagram of the Eu-MOF fluorescent material in DMF for DCP in Example 1.

[0023] Figure 6 The CIE coordinates are those corresponding to the Eu-MOF fluorescent material in Example 1 when 0-20 ppm DCP is added.

[0024] Figure 7The color change of the Eu-MOF fluorescent material in Example 1 under 365 nm ultraviolet light irradiation with the addition of 0 and 20 ppm DCP is shown.

[0025] Figure 8 This is a linear relationship between the emission intensity of the Eu-MOF fluorescent material in DMF and the DCP concentration in Example 1.

[0026] Figure 9 This is an experimental diagram showing the anti-interference performance of the Eu-MOF fluorescent material against DCP in Example 1.

[0027] Figure 10 This is a fluorescence sensing cycle test diagram of the Eu-MOF fluorescent material for DCP in Example 1. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments. Example 1

[0029] Eu(NO3)3·6H2O (0.0446 g, 0.01 mmol) and NH2-H2BDC (0.0181 g, 0.01 mmol) were placed in a 20 mL glass bottle. Then, DMF (4 mL), DMPU (2 mL), H2O (0.5 mL), and triethylamine (200 µL) were added. After sonication for 30 min, the glass bottle was sealed with a polytetrafluoroethylene shell and heated in a 120 ℃ oven for 5 days. After the reaction was complete, the mixed solution was filtered, washed repeatedly with DMF, centrifuged, and air-dried to obtain transparent blocky crystals, i.e., Eu-MOF fluorescent material. Example 2

[0030] Eu(NO3)3·6H2O (0.0446 g, 0.01 mmol) and NH2-H2BDC (0.0181 g, 0.01 mmol) were placed in a 20 mL glass bottle. Then, DMF (4 mL), DMPU (2 mL), H2O (1 mL), and triethylamine (300 µL) were added. After sonication for 30 min, the glass bottle was sealed with a polytetrafluoroethylene shell and heated in a 120 ℃ oven for 5 days. After the reaction was complete, the mixed solution was filtered, washed repeatedly with DMF, centrifuged, and air-dried to obtain transparent bulk crystals, i.e., Eu-MOF fluorescent material. Example 3

[0031] Eu(NO3)3·6H2O (0.0446 g, 0.01 mmol) and NH2-H2BDC (0.0181 g, 0.01 mmol) were placed in a 20 mL glass bottle. Then, DMF (4 mL), DMPU (2 mL), H2O (0.5 mL), and triethylamine (200 µL) were added. After sonication for 30 min, the glass bottle was sealed with a polytetrafluoroethylene shell and heated in a 120 ℃ oven for 5 days. After the reaction was complete, the mixed solution was filtered, washed repeatedly with DMF, centrifuged, and air-dried to obtain transparent blocky crystals, i.e., Eu-MOF fluorescent material. Example 4

[0032] Eu(NO3)3·6H2O (0.0446 g, 0.01 mmol) and ligand NH2-H2BDC (0.0362 g, 0.02 mmol) were placed in a 20 mL glass bottle. Then, DMF (4 mL), DMPU (2 mL), H2O (0.5 mL), and triethylamine (200 µL) were added. After sonication for 30 min, the glass bottle was sealed with a polytetrafluoroethylene shell and heated in a 120 °C oven for 5 days. After the reaction was complete, the mixture was filtered, washed repeatedly with DMF, centrifuged, and air-dried to obtain transparent bulk crystals, i.e., the Eu-MOF fluorescent material. Example 5

[0033] Eu(NO3)3·6H2O (0.0446 g, 0.01 mmol) and NH2-H2BDC (0.0181 g, 0.01 mmol) were placed in a 20 mL glass bottle. Then, DMF (8 mL), DMPU (4 mL), H2O (1 mL), and triethylamine (200 µL) were added. After sonication for 30 min, the glass bottle was sealed with a polytetrafluoroethylene shell and heated in a 120 ℃ oven for 5 days. After the reaction was complete, the mixed solution was filtered, washed repeatedly with DMF, centrifuged, and air-dried to obtain transparent blocky crystals, i.e., Eu-MOF fluorescent material.

[0034] The clear crystals from Example 1 were selected for X-ray single-crystal diffraction characterization. The results showed that the Eu-MOF fluorescent material crystallized in a monoclinic crystal system with space group [space group missing]. I 2 / m a=13.2804(5) Å, b=15.4614(5) Å, c=16.9989(5) Å, α=90°, β=96.860(4)°, γ=90°, chemical formula is {[Eu(NH2-BDC)} 1.5 (OH) 0.5(HCOO) 0.5 (DMF)]} n In this context, NH2-BDC represents 2-aminoterephthalic acid that has lost two protons from its carboxyl groups, and DMF represents N,N-dimethylformamide; its asymmetric unit consists of one Eu 3+ Ions, one DMF molecule, 1 / 2 HCOO - 3 / 2 NH2-BDC and 1 / 2 bridging OH - Composition (see) Figure 1 Four Eu 3+ The ions are separated by the carboxyl oxygen atom and two OH groups of NH2-BDC. - The connection forms [Eu4(COO)] 10 The secondary building block (SBU) of [(DMF)2(HCOO)2(OH)2], see Figure 1 SBU in NH2-BDC and HCOO - A three-dimensional frame structure is formed by the connection (see...). Figure 2 Furthermore, its powder X-ray diffraction (PXRD) pattern demonstrates that this Eu-MOF fluorescent material possesses good crystallinity and purity (see...). Figure 3 ).

[0035] Application Example 1 First, the fluorescence emission behavior of the Eu-MOF fluorescent material in Example 1 in different organic solvents was investigated. Solid-state fluorescence of the Eu-MOF fluorescent material at room temperature was found to be weak, so further analysis was not conducted. Under liquid-phase conditions, 1 mg of Eu-MOF fluorescent material was dispersed in 3 mL of different organic solvents, including acetonitrile (CH3CN), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), acetone (ACE), methanol (CH3OH), ethanol (C2H5OH), tetrahydrofuran (THF), and dichloromethane (CH2Cl2). The suspension was formed by sonication, and the fluorescence emission spectrum was measured under 365 nm excitation (see...). Figure 4 Since Eu-MOF fluorescent materials exhibit strong fluorescence intensity at around 430 nm and 614 nm in DMF, and also demonstrate good stability in DMF, DMF was chosen as the detection solvent for all subsequent fluorescence sensing tests.

[0036] Furthermore, the fluorescence sensing behavior of the Eu-MOF fluorescent material in DMF for DCP in Example 1 was evaluated. 1 mg of Eu-MOF fluorescent material was weighed into a 5 mL centrifuge tube, 3 mL of DMF was added, and the mixture was sonicated for 10 min to obtain a Eu-MOF suspension with a concentration of 0.33 mg / mL. The Eu-MOF suspension was transferred to a quartz cuvette, and 0–20 ppm of DCP was added to the suspension. After mixing thoroughly and standing for 2 min, the fluorescence spectrum of the mixed solution was detected using a fluorescence spectrophotometer under 365 nm incident light excitation. A fluorescence titration experiment was conducted to evaluate its sensing performance. Under 365 nm excitation, the Eu-MOF fluorescent material exhibited a significant "fluorescence-on" effect for DCP: the fluorescence color increased from a weak yellow-green to a bright yellow-green, and the emission peak intensity significantly increased (see...). Figures 5-7 As the DCP concentration increases, the fluorescence emission intensity ratio I... 430 / I 614 The correlation between DCP concentration and I2O concentration showed a good linear relationship in the range of 4–20 ppm. Plotting DCP concentration on the x-axis and I2O concentration on the y-axis... 430 / I 614 A standard curve was plotted on the ordinate, and a linear fit was performed on the standard curve. The fitting result was y = 2.454[DCP] - 7.181, R². 2 =0.995 (where I 430 and I 614 This indicates the fluorescence intensity at 430 and 614 nm with the addition of 0–20 ppm DCP. The limit of detection (LOD) for DCP by Eu-MOF fluorescent materials is calculated using the formula: LOD = 3σ / K (where σ is the standard deviation of 7 measurements of the blank sample, and K is the slope of the linear equation curve). The calculated LOD value is 1 ppb (see...). Figure 8 ).

[0037] Meanwhile, the specific response and recycling performance of the Eu-MOF fluorescent material in DMF solution to DCP in Example 1 were evaluated. The Eu-MOF fluorescent material was ultrasonically dispersed in N,N-dimethylformamide to obtain an Eu-MOF suspension with a concentration of 0.33 mg / mL. 10 ppm of DCP and 10 ppm of organophosphorus compounds with similar structures to DCP, including diethyl 2-bromoethylphosphonate (DEBEP), diethyl benzyl phosphate (DEBP), diethyl cyanophosphate (DECP), diisopropyl methyl phosphate (DIMP), tributyl phosphate (TBP), and triethyl phosphate (TEP), were added to this suspension. The fluorescence intensity changes at 430 nm showed that the addition of DCP resulted in approximately a 10-fold increase in fluorescence, and the addition of DECP caused approximately a 3-fold increase in fluorescence, while the other analytes showed no significant fluorescence changes (see [link to relevant documentation]). Figure 9 This indicates that Eu-MOF fluorescent materials in DMF exhibit outstanding selectivity for DCP. Furthermore, an equal amount of DCP was added to the above system, such as... Figure 9 As shown, the fluorescence enhancement change of the Eu-MOF fluorescent material is consistent with that without interfering substances, indicating good anti-interference performance. Subsequently, 20 ppm DCP was added to the Eu-MOF suspension to test its recyclability. To test the cycling performance, the Eu-MOF fluorescent material was washed with DMF and centrifuged after each round of testing, and five rounds of repeated testing were performed (see...). Figure 10 The fluorescence intensity of the Eu-MOF fluorescent material recovered in each round, demonstrating good reusability.

[0038] In summary, the Eu-MOF fluorescent material of this invention exhibits low detection limit, excellent selectivity, strong anti-interference ability, and good cyclic stability when detecting sarin simulant DCP. These outstanding properties highlight its great application potential in the field of efficient identification and visual detection of nerve agents.

Claims

1. A dual-emission Eu-MOF fluorescent material, characterized in that: The chemical formula of the fluorescent material is {[Eu(NH2-BDC)} 1.5 (OH) 0.5 (HCOO) 0.5 (DMF)]} n In this context, NH2-BDC represents 2-aminoterephthalic acid that has lost two protons from its carboxyl groups, and DMF represents N,N-dimethylformamide; this material crystallizes in a monoclinic crystal system with space group [space group number missing]. I 2 / m The unit cell parameters are a=13.2804(5) Å, b=15.4614(5) Å, c=16.9989(5) Å, α=90°, β=96.860(4)°, and γ=90°.

2. The dual-emission Eu-MOF fluorescent material according to claim 1, characterized in that: The asymmetric unit of the fluorescent material consists of an Eu 3+ Ions, one DMF molecule, 1 / 2 HCOO - 3 / 2 NH2-BDC and 1 / 2 bridging OH - Composition; four Eu 3+ The ions are separated by the carboxyl oxygen atom and two OH groups of NH2-BDC. - The connection forms [Eu4(COO)] 10 The secondary building blocks of [(DMF)2(HCOO)2(OH)2], the secondary building blocks in NH2-BDC and HCOO - A three-dimensional framework structure is formed by the connection of these elements.

3. A method for preparing the dual-emission Eu-MOF fluorescent material according to claim 1, characterized in that: Europium nitrate and 2-aminoterephthalic acid were completely dissolved in a mixed solvent of N,N-dimethylformamide, N,N-dimethylpropenylurea and water. Triethylamine was then added, and the mixture was allowed to stand and react in a sealed environment at 110–130 °C for 5–6 days. After the reaction was complete, the mixture was cooled to room temperature, filtered, washed with N,N-dimethylformamide, centrifuged, and dried in air to obtain the dual-emission Eu-MOF fluorescent material.

4. The method for preparing the dual-emission Eu-MOF fluorescent material according to claim 3, characterized in that: The molar ratio of europium nitrate to 2-aminoterephthalic acid is 1:1 to 2.

5. The method for preparing the dual-emission Eu-MOF fluorescent material according to claim 3, characterized in that: The volume ratio of N,N-dimethylformamide, N,N-dimethylpropenylurea, and water in the mixed solvent is 8:4:

1.

6. The method for preparing the dual-emission Eu-MOF fluorescent material according to claim 3, characterized in that: The volume ratio of water to triethylamine is 5:1 to 2.

7. The method for preparing the dual-emission Eu-MOF fluorescent material according to claim 3, characterized in that: The mixture was left to stand and react in a sealed container at 120°C for 5 days.

8. The use of the dual-emission Eu-MOF fluorescent material of claim 1 in ratiometric fluorescence sensing of sarin simulant diethyl chlorophosphate.

9. The use of the dual-emission Eu-MOF fluorescent material according to claim 8 in ratiometric fluorescence sensing of sarin simulant diethyl chlorophosphate, characterized in that: The specific testing methods are as follows: Step 1: The dual-emission Eu-MOF fluorescent material was ultrasonically dispersed in N,N-dimethylformamide to obtain an Eu-MOF suspension with a concentration of 0.3–0.5 mg / mL; Step 2: Transfer the Eu-MOF suspension to a quartz cuvette, add different concentrations of diethyl chlorophosphate, mix thoroughly, and let stand for 2–3 min. Detect the fluorescence spectrum of the mixed solution using a fluorescence spectrophotometer under 365 nm incident light excitation. Then, use I... 430 and I 614 The fluorescence intensity at 430 nm and 614 nm is represented by the concentration of diethyl chlorophosphate on the x-axis, and the ratio of the fluorescence intensity at 430 nm to 614 nm is represented by I. 430 / I 614 Plot a standard curve on the ordinate and perform a linear fit on the standard curve to obtain the standard equation; Step 3: Add the sample to be tested according to the method in Step 2 above, and calculate the concentration of diethyl chlorophosphate in the sample by combining the standard equation.

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