Eu@sof fluorescent nanoprobes, preparation method and application thereof

Abstract

The application provides a Eu@SOF fluorescent nanoprobe, which is prepared by the following method: first, preparing a supramolecular organic framework (SOF) by reacting trimesic acid (TMA) and melamine (ME), and then preparing the Eu@SOF fluorescent nanoprobe by reacting the SOF and europium (III) nitrate hexahydrate. The Eu@SOF fluorescent nanoprobe provided by the application presents a sensitive and efficient fluorescence quenching response to TeA, and can be used for rapid detection of TeA in fruit and vegetable samples.

Description

Technical Field

[0001] This invention belongs to the field of biotoxin detection technology, specifically relating to an Eu@SOF fluorescent nanoprobe, its preparation method, and its application. Background Technology

[0002] Tenuazonic acid (TeA) is a fungal toxin mainly produced by *Alternaria* fungi, and is the only nitrogenous metabolite among them. TeA can grow and reproduce under low-temperature, humid conditions, thus contaminating vegetables, grains, fruits, and other foods, causing spoilage during refrigeration or long-distance transportation, resulting in significant economic losses. Studies have shown that TeA has the highest toxicity among *Alternaria* mycotoxins, exhibiting not only acute toxicity but also teratogenicity and carcinogenicity through inducing DNA damage, and has a potential link to hematologic disorders. Long-term exposure to TeA can cause tissue hemorrhage, motor dysfunction, circulatory failure, severe developmental delays, and even shock and death in animals.

[0003] Currently, the main detection technology for TeA is UHPLC-MS / MS. Although this method has high sensitivity and accuracy, it requires expensive instruments, professional operators, and complex and time-consuming pretreatment procedures, which limits its application in practical detection. Given the potential risks of TeA to human health and the economic losses it causes, it is necessary to research and develop a technology that can detect TeA quickly, accurately, easily, and at low cost. Summary of the Invention

[0004] This invention first provides a method for preparing Eu@SOF fluorescent nanoprobes, which includes the following steps: Trimeric pyromellitic acid (TMA) and melamine (ME) were dissolved separately in pure water, with a molar ratio of TMA to ME of 1:2-15. The mixture was heated at 80°C and stirred. After the solution was fully dissolved, the TMA and ME solutions were mixed and stirred. The reaction product was collected by centrifugation, washed with pure water, and finally dried in an oven to obtain a white powder, SOF. Take SOF and europium(III) nitrate hexahydrate (Eu(NO3)3) 6H2O) is added to water, where SOF reacts with Eu(NO3)3 The weight ratio of 6H2O was 5:1-5; after sonication for 3 min, the mixture was reacted at 50℃ for 3 h, and a white precipitate was obtained by filtration; after washing with pure water and drying, a white Eu@SOF fluorescent nanoprobe was obtained. The preferred molar ratio of TMA to ME is 1:5-10, and the ratio of SOF to Eu(NO3)3 is... The preferred weight ratio of 6H2O is 5:2-4; Furthermore, the preferred molar ratio of TMA to ME is 1:10, and the ratio of SOF to Eu(NO3)3 is... The preferred weight ratio of 6H2O is 5:2.

[0005] This invention also provides Eu@SOF fluorescent nanoprobes prepared by the above method.

[0006] The Eu@SOF fluorescent nanoprobe provided by this invention can be used to detect TeA in fruits, vegetables, and grains. The specific detection method is as follows: (1) Sample pretreatment: Weigh the sample accurately, soak it in acetonitrile solution containing 1% (volume ratio) formic acid for 5-30 min, and extract it by ultrasonication for 30-60 min; then centrifuge and collect the supernatant; take the supernatant into a centrifuge tube, blow it to near dryness with nitrogen, add pure water to reconstitute it; then filter it with a 0.22 μm microporous membrane to obtain the sample solution. (2) The Eu@SOF fluorescent nanoprobe was dispersed in pure water and sonicated to form a uniform suspension. The concentration of Eu@SOF was 0.1-1 mg / mL and the pH was 6.5-7.4. The Eu@SOF suspension and the sample solution were mixed in a centrifuge tube at a volume ratio of 8-10:1. After reacting at room temperature for 1-3 min, the mixture was transferred to a quartz cuvette and detected using an F-7000 fluorescence spectrophotometer. The emission spectrum was obtained at an excitation wavelength of 260 nm, and the fluorescence intensity (F) at the emission wavelength of 616 nm was recorded. The quantitative detection of TeA was achieved by fluorescence quenching efficiency (F0 / F), where F0 and F represent the fluorescence intensity of the sample solution containing TeA and the sample solution containing TeA, respectively.

[0007] This invention also provides a method for detecting TeA in fruits, vegetables, and grains, the method comprising the following steps: (1) Sample pretreatment: Weigh the sample accurately, soak it in acetonitrile solution containing 1% formic acid for 5-30 min, and extract it by sonication for 30-60 min; then centrifuge and collect the supernatant; take the supernatant into a centrifuge tube, blow it to near dryness with nitrogen, add pure water to reconstitute it; then filter it with a 0.22 μm microporous membrane to obtain the sample solution. (2) The Eu@SOF fluorescent nanoprobe was dispersed in pure water and sonicated to form a uniform suspension. The concentration of Eu@SOF was 0.1-1 mg / mL and the pH was 6.5-7.4. The Eu@SOF suspension and the sample solution were mixed in a centrifuge tube at a volume ratio of 8-10:1. After reacting at room temperature for 1-3 min, the mixture was transferred to a quartz cuvette and detected using an F-7000 fluorescence spectrophotometer. The emission spectrum was obtained at an excitation wavelength of 260 nm, and the fluorescence intensity at the emission wavelength of 616 nm was recorded. The quantitative detection of TeA was achieved by the fluorescence quenching efficiency F0 / F, where F0 and F represent the fluorescence intensity of the sample solution without TeA and containing TeA, respectively.

[0008] The Eu@SOF-based fluorescent nanoprobe provided by this invention combines lanthanide ions with SOFs, which not only provides a stable coordination environment for lanthanide ions and reduces interference from the external environment on their luminescence performance, but also utilizes the organic ligands of SOFs as "antenna molecules" to absorb excitation light energy and transfer energy to lanthanide ions through an efficient "antenna effect", thereby significantly improving the sensitivity of the probe.

[0009] The Eu@SOF fluorescent nanoprobe provided by this invention can be used for the rapid detection of TeA. Eu@SOF is a supramolecular organic framework modified with lanthanides. SOF acts as an antenna molecule, effectively transferring absorbed light energy to the luminescent center, Eu(III) ions, through the antenna effect, thereby enhancing the luminescence intensity of Eu(III) ions. When TeA binds to SOF, the lowest unoccupied molecular orbital (LUMO) energy level of TeA is lower than that of SOF. Therefore, a photoinduced electron transfer (PET) process occurs from SOF to TeA, leading to the attenuation of the antenna effect between the ligand and Eu(III) ions. The constructed Eu@SOF nanoprobe exhibits a sensitive and efficient fluorescence quenching response to TeA, and can be used for the rapid detection of TeA in fruit and vegetable samples.

[0010] The Eu@SOF fluorescent nanoprobe provided by this invention utilizes the antenna effect of Eu(III) ions and supramolecular organic frameworks to achieve highly selective recognition of TeA through a photoinduced electron transfer (PET) mechanism. Non-covalent interactions between Eu@SOF and TeA (such as hydrogen bonding, electrostatic interactions, and π-π stacking) significantly enhance the recognition ability and quenching response of the fluorescent nanoprobe. Experimental results show that this fluorescent nanoprobe exhibits good linear response to TeA in the concentration range of 5–200 ng / mL, with a detection limit (LOD) of 1.67 ng / mL, and demonstrates excellent fluorescence performance, stability, and selectivity. Attached Figure Description

[0011] Figure 1Characterization images of Eu@SOF fluorescent nanoprobes. (A) SEM image of Eu@SOF fluorescent nanoprobe; (B) TEM image of Eu@SOF; (C) Elemental distribution of Eu@SOF: C, N, O, Eu.

[0012] Figure 2 (A) Fluorescence emission spectra of Eu@SOF fluorescent nanoprobes at 5, 10, 15, 20, 50, 100, and 200 ng / mL TeA (λ) ex = 260 nm); (B) Linear fitting of fluorescence quenching efficiency (F0 / F) of Eu@SOF fluorescent nanoprobes to different concentrations of TeA (5, 10, 15, 20, 50, 100, 200 ng / mL) (λex = 260 nm, λem = 616 nm); (C) Selectivity of Eu@SOF fluorescent nanoprobes for different toxins (TeA, AOH, AME, ALT, TEN, AFB1, DON, PAT, OTA, ZEN) and mixed toxins (MIX); (D) Stability of Eu@SOF fluorescent nanoprobes.

[0013] Figure 3 (A) UV-Vis absorption spectra of Eu@SOF fluorescent nanoprobe, TeA, and Eu@SOF fluorescent nanoprobe mixed with TeA; (B) Zeta potential of Eu@SOF, TeA, and Eu@SOF mixed with TeA.

[0014] Figure 4 Excitation and emission spectra of Eu@SOF fluorescent nanoprobes.

[0015] Figure 5 (A) Optimization of the ratio of TMA to ME; (B) Eu(NO3)3 (C) Optimization of 6H2O addition amount; (D) Optimization of Eu@SOF fluorescent nanoprobe concentration; (E) Optimization of dispersion; (F) Optimization of dispersion pH; (G) Optimization of reaction time. Detailed Implementation

[0016] The embodiments described herein are merely examples of the present invention and are not intended to limit the scope of the present invention.

[0017] The sources of materials and instruments used in the following embodiments are shown in Tables 1 and 2 below: Table 1 Main Reagents

[0018] Table 2 Main Instruments and Equipment

[0019] Example 1: Synthesis and Characterization of Eu@SOF Fluorescent Nanoprobes (1) Synthesis of Eu@SOF fluorescent nanoprobes.

[0020] Trimeric pyromellitic acid (TMA) (105.1 mg) and melamine (ME) (631 mg) were dissolved separately in 50 mL of pure water, heated at 80 °C and stirred. After the solutions were fully dissolved, the TMA and ME solutions were mixed and stirred at room temperature for 1 h. The reaction product was collected by centrifugation and washed three times with pure water. Finally, it was dried in a 50 °C oven for 12 h to obtain a white powder, SOF. Take SOF (50 mg) and europium(III) nitrate hexahydrate (Eu(NO3)3). Add 20 mg of Eu@SOF (6H2O) to a beaker and add 10 mL of deionized water. After sonication for 3 min, react at 50 °C for 3 h, and filter to obtain a white precipitate. Wash three times with ultrapure water and dry at 50 °C for 12 h to obtain a white Eu@SOF fluorescent nanoprobe.

[0021] (2) Characterization of Eu@SOF fluorescent nanoprobes Figure 1 The morphology, structure, and elemental distribution of the Eu@SOF fluorescent nanoprobe are shown. Among them, such as... Figure 1 As shown in Figure A, the scanning electron microscope (SEM) image reveals that the Eu@SOF fluorescent nanoprobe is formed by stacking multiple columnar nanorods. Figure 1 Image B is a transmission electron microscope (TEM) image of the Eu@SOF fluorescent nanoprobe, which shows that it has a uniform internal structure, further verifying the stability and uniformity of the material. Figure 1 C is the elemental distribution diagram of the Eu@SOF fluorescent nanoprobe. Energy dispersive spectroscopy (EDS) analysis shows that carbon (C), nitrogen (N), oxygen (O) and europium (Eu) are uniformly distributed, indicating that Eu has been successfully incorporated into the SOF structure.

[0022] Example 2: Detection of fluorescence sensing performance of Eu@SOF fluorescent nanoprobes 1 mg of Eu@SOF fluorescent nanoprobe was dispersed in 2 mL of pure water and sonicated for 3 min to form a homogeneous suspension. 270 μL of the Eu@SOF suspension (0.5 mg / mL, pH 7.0) was mixed with 30 μL of TeA standard solution in a 1.5 mL centrifuge tube and reacted at room temperature for 1 min. The suspension was then transferred to a quartz cuvette, and the emission spectrum was obtained using an F-7000 fluorescence spectrophotometer at an excitation wavelength of 260 nm.

[0023] The fluorescence intensity of the Eu@SOF fluorescent nanoprobe was investigated after the addition of different concentrations of TeA (5, 10, 15, 20, 50, 100, 200 ng / mL). Figure 2 As shown in Figure A, the fluorescence intensity of Eu@SOF gradually decreased with increasing TeA concentration, indicating that TeA has a good fluorescence quenching effect on Eu@SOF. The fluorescence quenching efficiency showed a good linear relationship with TeA concentration and high sensitivity, such as... Figure 2 As shown in B, the linear equation is F0 / F = 0.99688C + 0.00449 (R0). 2 =0.993), and the limit of detection (LOD) was 1.67 ng / mL (S / N=3).

[0024] The selectivity of the Eu@SOF fluorescent nanoprobe was evaluated by measuring the fluorescence quenching efficiency (F0 / F) of 100 ng / mL TeA and other interfering toxins AOH, AME, ALT, TEN, AFB1, DON, PAT, OTA, ZEN, and a mixed solution containing TeA. Figure 2 As shown in Figure C, only the sample containing TeA exhibited a significant fluorescence quenching response, while other samples showed no significant change. This demonstrates that the fluorescent nanoprobe can specifically recognize TeA and possesses strong anti-interference capabilities. Furthermore, to evaluate the stability of the Eu@SOF fluorescent nanoprobe, its fluorescence quenching efficiency over 14 days was compared, such as... Figure 2 As shown in Figure D, the fluorescence quenching efficiency F0 / F of Eu@SOF showed minimal variation between days 0 and 14, decreasing by only 1.37%. This indicates that Eu@SOF exhibits good stability with no significant decay in fluorescence performance over a period of at least two weeks.

[0025] Example 3: Interaction Mechanism between Eu@SOF and Alternaria alterniflora Ketoacid (1) UV-Vis absorption spectroscopy analysis like Figure 3 As shown in Figure A, in UV-Vis absorption spectroscopy analysis, the UV absorption peak of TeA is at approximately 276 nm. When TeA is mixed with Eu@SOF, the absorption peak of the mixed sample shows a significant redshift to approximately 280 nm. This redshift may be due to the hydrogen bonding and π-π interactions between the ketone groups (-C=O) and hydroxyl groups (-OH) of TeA and the amino (-NH2) and carboxyl groups (-COOH) of ME and TMA in Eu@SOF, leading to a redistribution of electron cloud density and thus affecting the electronic transition properties of the molecules.

[0026] (2) Zeta potential analysis like Figure 3As shown in Figure B, the Zeta potential measurements indicate that the Zeta potentials of the Eu@SOF fluorescent nanoprobe and TeA are +1.98 mV and... 5.94 mV. After adding TeA to the Eu@SOF dispersion, the Zeta potential changed to... The value of 2.93 mV indicates that TeA can bind to Eu@SOF through hydrogen bonding or electrostatic interactions, thereby affecting the charge distribution on its surface.

[0027] The redshift in the UV-Vis absorption spectrum and the change in the Zeta potential suggest that TeA and Eu@SOF may be bonded through hydrogen bonds, π-π interactions, or electrostatic interactions, leading to a redistribution of electron cloud density and changes in surface charge properties.

[0028] (3) Luminescence properties and quenching mechanism of Eu@SOF fluorescent nanoprobes The fluorescence properties of the Eu@SOF fluorescent nanoprobes were investigated at room temperature, such as... Figure 4 As shown, the peak value of the photoluminescence excitation spectrum of Eu@SOF is approximately 260 nm. At an excitation wavelength of 260 nm, Eu@SOF exhibits strong emission peaks at 592 nm and 616 nm, which are attributed to Eu(III) ions. 5 D0→ 7 F 1,2 Transition. This phenomenon indicates that an antenna effect occurs between SOF and Eu(III) ions, that is, the ligand (SOF) absorbs energy and transfers it to Eu(III) ions, thereby exciting the characteristic luminescence of Eu(III) ions.

[0029] The energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of ME, TMA, and TeA were calculated using density functional theory (DFT). ME in SOF exhibits a higher LUMO level. 0.374 eV), capable of transferring electrons to TMA via a photoinduced electron transfer (PET) process ( 3.342 eV). The ligand (SOF) then absorbs ultraviolet light and transfers energy to the Eu(III) ion, causing the Eu(III) ion to emit characteristic red light, thus forming a ligand-to-metal charge transfer-electron transfer (LMCT-ET) process. Upon addition of the target compound TeA, the fluorescence of Eu@SOF is quenched. This is due to the low LUMO level of TeA (…). The 2.681 eV value is lower than ME but higher than TMA, which allows ME to effectively transfer energy to TeA, thereby hindering the energy transfer of ME to TMA, thus reducing the emission of Eu(III) ions and ultimately leading to fluorescence quenching.

[0030] Example 4: Optimization of fluorescence sensing method for Eu@SOF fluorescent nanoprobes To achieve better sensing performance, the experimental conditions of the Eu@SOF fluorescence sensing method were optimized, including the ratio of reactants TMA to ME and Eu(NO3)3. The amount of 6H2O added, the concentration of Eu@SOF, the dispersion, the pH value of the dispersion, and the reaction time.

[0031] To improve the quenching efficiency of Eu@SOF on TeA, this embodiment optimizes the molar ratio of TMA and ME during the SOF synthesis process in Example 1 (1:1, 1:2, 1:5, 1:10, and 1:15). Figure 5 As shown in Figure A, when the molar ratio of TMA to ME is 1:10, the fluorescence quenching efficiency F0 / F is the highest (F0 is the fluorescence intensity without TeA, and F is the fluorescence intensity after adding 100 ng / mL TeA), and the sensing performance of Eu@SOF is optimal. This may be because the amino groups (-NH2) in higher concentrations of ME can bind to TeA through hydrogen bonding. When the ratio of TMA to ME is 1:10, there are more effective -NH2 sites in the SOF that can bind to TeA. However, when the ME content is too high, hydrogen bonds may form between ME molecules, hindering effective bonding to TeA. Furthermore, the SOF prepared at this optimized ratio may have a highly efficient energy or electron transport pathway, thus exhibiting the highest quenching efficiency for TeA. Therefore, a molar ratio of 1:10 was chosen for further research.

[0032] Eu(NO3)3 The amount of 6H2O added significantly affected the fluorescence intensity of Eu@SOF. During the synthesis of Eu@SOF, 1, 10, 20, 30, and 40 mg of Eu(NO3)3 were added respectively. 6H2O, such as Figure 5 As shown in Figure B, the fluorescence quenching efficiency (F0 / F) significantly improved when the dosage was gradually increased from 1 mg to 20 mg. However, when the dosage was further increased to 40 mg, the fluorescence quenching efficiency tended to plateau or even slightly decreased, indicating that the optimal effect was achieved at a dosage of 20 mg, and further increasing the amount of Eu(NO3)3·6H2O no longer significantly improved the fluorescence performance. This may be because when Eu(NO3)3·6H2O is added... When the amount of 6H2O is low, the concentration of Eu(III) ions is insufficient to effectively bind to sites in SOF or initiate quenching reactions. With the increase of Eu(NO3)3... Increasing the amount of 6H₂O leads to an increase in the concentration of Eu(III) ions, thus improving the quenching efficiency. However, further increasing the amount of Eu(NO₃)₃... Regarding the 6H2O content, since the Eu element in Eu@SOF has reached saturation, it is impossible to further improve the fluorescence quenching efficiency. Therefore, 20 mg Eu(NO3)3 was chosen. 6H2O is the optimal amount to add.

[0033] The fluorescence quenching efficiency of Eu@SOF pairs with different concentrations was investigated. Figure 5 As shown in Figure C, the fluorescence intensity initially increased and then slightly decreased with increasing Eu@SOF suspension concentration. Simultaneously, the fluorescence quenching efficiency F0 / F peaked at an Eu@SOF concentration of 0.5 mg / mL, indicating the most significant quenching effect. Therefore, 0.5 mg / mL of Eu@SOF was determined to be the optimal concentration; excessively high concentrations would actually reduce the quenching efficiency.

[0034] The suspension of Eu@SOF was optimized, and the experimental results are as follows: Figure 5 As shown in Figure D, the fluorescence quenching efficiency F0 / F is highest in pure water, while it is lower in ethanol, acetonitrile, and ethyl acetate. Therefore, pure water was chosen as the dispersion.

[0035] The pH of the Eu@SOF dispersion was optimized, and the experimental results are as follows: Figure 5 As shown in Figure E, the fluorescence quenching efficiency F0 / F reaches its highest value at pH 7. This is likely because at pH 7, the electronic structure of TeA reaches its most stable state. Eu@SOF, acting as an electron donor, exhibits optimal electron-donating capabilities due to its surface functional groups, such as -COOH and -NH2, promoting electron migration from Eu@SOF to TeA and thus effectively enhancing the photoinduced electron transfer (PET) process. Furthermore, the neutral solvent conditions may provide an ideal dielectric constant, which is beneficial for electron transfer. In contrast, acidic or alkaline conditions may cause Eu@SOF to undergo protonation or deprotonation reactions more readily, thereby affecting its fluorescence properties. Therefore, experiments determined that pH 7 is the optimal condition for conducting Eu@SOF photoinduced electron transfer experiments.

[0036] The fluorescence intensity changes of Eu@SOF and TeA at different reaction times were investigated, such as... Figure 5 F. It was found that the fluorescence intensity gradually increased with increasing reaction time, reaching a maximum at 1 min, and then tended to stabilize. Therefore, 1 min was selected as the optimal reaction time between the Eu@SOF fluorescent nanoprobe and the target substance TeA.

[0037] Through the above system optimization, the optimal experimental conditions for the Eu@SOF fluorescent nanoprobe were finally determined to be: a molar ratio of TMA to ME of 1:10, and Eu(NO3)3 of 50 mg SOF. The amount of 6H2O added was 20 mg, the concentration of Eu@SOF was 0.5 mg / mL, the dispersion of Eu@SOF was pure water, the pH of the dispersion was 7, and the reaction time was 1 min.

[0038] Example 5: Sample detection using the Eu@SOF fluorescent nanoprobe prepared in Example 1. The fruit samples used in this embodiment are all ordinary commercially available products from Shanghai farmers' markets.

[0039] Sample pretreatment: Accurately weigh 2.0 g of fruit sample, soak it in 10 mL of acetonitrile solution containing 1% formic acid for 5 min, and then sonicate for 30 min. Centrifuge at 8000 r / min for 5 min and collect the supernatant. Transfer 5 mL of the supernatant to a centrifuge tube, nearly dry it under nitrogen, and then reconstitute it with 1 mL of pure water. Filter the solution through a 0.22 μm microporous membrane to obtain the sample solution.

[0040] 1 mg Eu@SOF was dispersed in 2 mL of pure water and sonicated for 3 min to form a homogeneous suspension. 270 μL of the Eu@SOF suspension (0.5 mg / mL, pH 7) was mixed with 30 μL of the sample solution in a 1.5 mL centrifuge tube and reacted at room temperature for 1 min. The suspension was then transferred to a quartz cuvette and detected using an F-7000 fluorescence spectrophotometer at an excitation wavelength of 260 nm.

[0041] The fluorescence intensity (F) emitted at 616 nm was recorded, and the quantitative detection of TeA was achieved by the fluorescence quenching efficiency (F0 / F), where F0 and F represent the fluorescence intensity of the sample solution containing and without TeA, respectively.

[0042] (1) The applicability of Eu@SOF fluorescent probe in food safety analysis was evaluated by spiked recovery experiments on different concentrations of TeA (10, 50, and 100 μg / kg) in strawberry, tomato, and pear samples (n=3). The results are shown in Table 3. The recoveries of Eu@SOF fluorescent probe in different samples ranged from 87.2% to 110.2%, with relative standard deviations of 0.7% to 6.5%, indicating that Eu@SOF fluorescent probe can be used for the rapid detection of trace amounts of TeA in fruits.

[0043] Table 3. Determination of TeA in fruit samples by Eu@SOF fluorescent nanoprobe.

[0044] (2) The concentration of TeA in three different fruit samples (strawberry, tomato, and pear) was determined using Eu@SOF fluorescent nanoprobes (n=3), and the results were compared with those reported in the literature [Wang J, Huang Q, Guo W, et al. Fe3O4@COF(TAPT–DHTA) Nanocomposites as Magnetic Solid-Phase Extraction Adsorbents for Simultaneous Determination of 9 Mycotoxins in Fruits by UHPLC–MS / MS [J]. Toxins, 2023, 15(2): 117]. As shown in Table 4, there was no significant difference between the results obtained by the two methods (p>0.05), demonstrating that Eu@SOF fluorescent nanoprobes have good reliability in the detection of actual samples.

[0045] Table 4 Comparison of the detection results of TeA in actual samples by the two detection methods

[0046] It should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Modifications of the present invention in various equivalent forms by those skilled in the art all fall within the protection scope of the present invention.

Claims

1. A method for preparing Eu@SOF fluorescent nanoprobes, characterized in that... The method includes the following steps: Tristyric acid (TMA) and melamine (ME) were dissolved separately in pure water at a molar ratio of 1:2-15. The mixture was heated at 80°C and stirred. After the solution was fully dissolved, the TMA and ME solutions were mixed and stirred. The reaction product was collected by centrifugation, washed with pure water, and finally dried in an oven to obtain a white powder, SOF. Take SOF and europium(III) nitrate hexahydrate Eu(NO3)3 When 6H2O is added to water, SOF reacts with Eu(NO3)3. The weight ratio of 6H2O was 5:1-5; after sonication for 3 min, the mixture was reacted at 50℃ for 3 h, and a white precipitate was obtained by filtration; after washing with pure water and drying, a white Eu@SOF fluorescent nanoprobe was obtained.

2. The method for preparing Eu@SOF fluorescent nanoprobes according to claim 1, characterized in that... The molar ratio of TMA to ME is 1:5-10, and the molar ratio of SOF to Eu(NO3)3 is... The weight ratio of 6H2O is 5:2-4.

3. The Eu@SOF fluorescent nanoprobe prepared by the method according to any one of claims 1 and 2.

4. The application of the Eu@SOF fluorescent nanoprobe according to claim 3 for the detection of TeA in fruits, vegetables, and grains.

5. The application according to claim 4, characterized in that... The specific testing method is as follows: (1) Sample pretreatment: Weigh the sample accurately, soak it in acetonitrile solution containing 1% formic acid for 5-30 min, and extract it by sonication for 30-60 min; then centrifuge and collect the supernatant; take the supernatant into a centrifuge tube, blow it to near dryness with nitrogen, add pure water to reconstitute it; then filter it with a 0.22 μm microporous membrane to obtain the sample solution. (2) Disperse Eu@SOF in pure water and sonicate to form a uniform suspension. The concentration of Eu@SOF is 0.1-1 mg / mL and the pH is 6.5-7.

4. Mix the Eu@SOF suspension and the sample solution in a centrifuge tube at a volume ratio of 8-10:

1. After reacting at room temperature for 1-3 min, transfer the mixture to a quartz cuvette and use an F-7000 fluorescence spectrophotometer for detection. Obtain the emission spectrum at an excitation wavelength of 260 nm and record the fluorescence intensity at the emission wavelength of 616 nm. Quantitatively detect TeA by fluorescence quenching efficiency F0 / F, where F0 and F represent the fluorescence intensity of the sample solution containing TeA and the sample solution containing TeA, respectively.

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