Fluorescent probe of Eu < 3 + > and Tb < 3 + > lanthanide series metal doped organic framework material as well as preparation method and application of fluorescent probe

Abstract

The invention relates to a fluorescent probe of an Eu < 3 + > and Tb < 3 + > lanthanide series metal doped organic framework material as well as a preparation method and application of the fluorescent probe, and belongs to the technical field of fluorescent materials. According to the fluorescent probe, carboxylic acid organic matter serves as a ligand, lanthanide metal ions serve as a metal center, and the metal organic framework material fluorescent probe is synthesized. The molar ratio of the lanthanide metal salt to the carboxylic acid organic matter is 1: (1-2); carrying out crystallization reaction for 10-14 hours at the temperature of 110-130 DEG C through a solvothermal method; a solvent used in the solvothermal method is N, N-dimethylformamide. The fluorescent probe provided by the invention can be used for detecting ochratoxin A, and has good selectivity and stability. The invention further provides test paper for detecting ochratoxin A based on the fluorescent probe. The test paper can detect the concentration of OTA in a liquid sample to be detected under ultraviolet light.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent materials, and in particular to a Eu 3+ and Tb 3+ Fluorescent probes of lanthanide metal-doped organic framework materials, and their preparation methods and applications. Background Art

[0002] Ochratoxin A (OTA) is a secondary metabolite produced by Aspergillus and Penicillium fungi and is widely found in contaminated agricultural products such as grains, coffee, wine, and animal feed. Its toxic mechanism involves inhibition of the mitochondrial respiratory chain, induction of oxidative stress, and formation of DNA adducts, leading to renal fibrosis, hepatocyte necrosis, and immunosuppression. The International Agency for Research on Cancer (IARC) has classified it as a Group 2B potential human carcinogen, with a tolerable daily intake (TDI) of 14 ng / kg body weight. Given the ubiquity of OTA in the food supply chain and the cumulative effects of low-dose exposure, the development of highly sensitive, rapid, and on-site detection technologies is crucial.

[0003] Currently, OTA detection relies primarily on chromatography, electrophoresis, and immunoassays. Chromatography, including high-performance liquid chromatography (HPLC) coupled with mass spectrometry (HPLC-MS / MS), has become the gold standard due to its low limit of detection (LOD up to 0.01 μg / kg) and precise quantitative capabilities. However, it suffers from drawbacks such as reliance on expensive instrumentation (such as triple quadrupole mass spectrometry), complex pretreatment (such as immunoaffinity column cleanup), and the need for specialized operators, making it difficult to meet the demands of rapid on-site screening. While capillary electrophoresis (CE) offers the advantage of rapid separation (analysis time <10 min), it suffers from poor reproducibility (RSD >15%), low sensitivity (LOD approximately 1 μg / kg), and inadequate miniaturization technology. Enzyme-linked immunosorbent assay (ELISA) allows for semi-quantitative detection (LOD approximately 0.1 μg / kg), but its reliability is limited by a false-positive rate (approximately 10%-20%) due to antibody cross-reactivity and matrix interference with enzyme activity.

[0004] These methods are often plagued by bottlenecks such as strong equipment dependence, complex operations, and high costs, making it difficult to achieve on-site and timely detection of toxins. Therefore, developing new sensing technologies to achieve on-site OTA detection has become a research hotspot.

[0005] Metal-organic frameworks (MOFs) boast excellent performance, adjustable pore size, diverse morphologies, and variable structures. They can be functionalized through modification with various groups and applied in fields such as catalysis, separation, and fluorescence detection. In fluorescence detection, MOFs possess unique optoelectronic properties, especially when doped with europium and terbium, exhibiting characteristic emission spectra with excellent properties such as high monochromatic purity, large Stokes shift, high quantum yield, and long decay lifetime.

[0006] Therefore, seeking a metal-organic framework fluorescent probe suitable for detecting ochratoxin A has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a 3+ and Tb 3+ Double lanthanide metal-doped organic framework materials, their preparation methods and applications.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] In a first aspect, the present invention provides a Eu 3+ and Tb 3+ The fluorescent probe of the metal-doped organic framework material has the following chemical structure:

[0010]

[0011] In a second aspect, the present invention provides a method for preparing the fluorescent probe described in the first aspect, comprising the following steps:

[0012] (1) Synthesize a metal-organic framework fluorescent probe using carboxylic acid organic compounds as ligands and lanthanide metal ions as metal centers; the molar ratio of lanthanide metal salt to carboxylic acid organic compound is 1:(1-2);

[0013] (2) crystallizing the metal organic framework material fluorescent probe prepared in step (1) at 110-130° C. for 10-14 hours by a solvothermal method; the solvent used in the solvothermal method is N,N-dimethylformamide.

[0014] As a preferred embodiment of the second aspect of the present invention, the carboxylic acid organic compound is 3,5-dicarboxyphenylboronic acid.

[0015] As a preferred embodiment of the second aspect of the present invention, the lanthanide metal ions include lanthanum (La) ions, cerium (Ce) ions, praseodymium (Pr) ions, neodymium (Nd) ions, promethium (Pm) ions, samarium (Sm) ions, europium (Eu) ions, gadolinium (Gd) ions, terbium (Tb) ions, dysprosium (Dy) ions, holmium (Ho) ions, erbium (Er) ions, thulium (Tm) ions, ytterbium (Yb) ions and lutetium (Lu) ions.

[0016] As a preferred embodiment of the second aspect of the present invention, the metal center is composed of europium ions and terbium ions. The present invention has found that when europium ions and terbium ions are selected as the metal center, the detection effect of the fluorescent probe is better.

[0017] As a preferred embodiment of the second aspect of the present invention, the lanthanide metal salt includes Eu(NO)3·6H2O and Tb(NO)3·6H2O, wherein the molar ratio of Eu(NO)3·6H2O to Tb(NO)3·6H2O is 1:(8-10).

[0018] As a preferred embodiment of the second aspect of the present invention, the lanthanide metal salt includes Eu(NO)3·6H2O and Tb(NO)3·6H2O, wherein the molar ratio of Eu(NO)3·6H2O to Tb(NO)3·6H2O is 1:9.

[0019] The present invention found that when the molar ratio of Eu(NO)3·6H2O to Tb(NO)3·6H2O is 1:(8-10), the detection effect of the fluorescent probe is better, especially when the molar ratio is 1:9.

[0020] In a third aspect, the present invention provides the Eu described in the first aspect. 3+ and Tb 3+ Application of metal-doped organic framework materials as fluorescent probes for the detection of ochratoxin A.

[0021] By analyzing the structure of OTA, it was found that the carboxylic acid groups contained in it can react with Tb 3+ OTA can absorb light in the 365nm range and transfer energy to Tb through antenna effect as a sensitizer. 3+ , which can directly enhance Tb 3+ The fluorescence emission of Eu 3+ Therefore, under 365nm light excitation, the fluorescent probe prepared by the present invention is combined with OTA in the solution. As the OTA concentration increases, the solution changes color from red to yellow and then to green, thereby detecting the OTA concentration in the liquid sample to be tested.

[0022] As a preferred embodiment of the third aspect of the present invention, the method for detecting ochratoxin A with a fluorescent probe comprises:

[0023] (1) The fluorescent probe described in the first aspect was added to the same volume of ochratoxin A standard solution with different concentrations to obtain a series of mixed dispersions with known ochratoxin A concentrations. After sufficient reaction, the fluorescence intensity ratio I was measured at an excitation wavelength of 365 nm. 545 / I 615 , and obtain the ratio of ochratoxin A concentration to fluorescence intensity I 545 / I 615 The following relationship:

[0024] y = 2.608x + 0.613 (Formula 1), correlation coefficient R 2 =0.990;

[0025] y=0.107x+1.182(Formula 2), correlation coefficient R 2 =0.982;

[0026] y=0.0339x+1.158 (Formula 3), correlation coefficient R 2 =0.984;

[0027] y is the fluorescence intensity ratio I 545 / I 615 , x is the ochratoxin A concentration; wherein, Formula 1 is the relationship when the ochratoxin A concentration is 0-0.2 μg / mL, Formula 2 is the relationship when the ochratoxin A concentration is 0.2-6 μg / mL, and Formula 3 is the relationship when the ochratoxin A concentration is 6-20 μg / mL;

[0028] (2) The liquid sample to be tested is introduced under the same conditions as in step (1) to replace the ochratoxin A standard solution, and the fluorescence intensity ratio I of the mixed dispersion is also measured. 545 / I 615 Then, according to the ratio of ochratoxin A concentration to fluorescence intensity I 545 / I 615 The concentration of ochratoxin A in the liquid sample to be tested is calculated using the relationship (Formula 1)-(Formula 3).

[0029] The present invention found that under the excitation of 365nm ultraviolet light, the fluorescence of Eu-Tb-MOF at 545nm and 615nm increased simultaneously, and its fluorescence ratio signal I 545 / I 615 There is a good linear relationship between the concentration of OTA and Eu-Tb-MOF. When Eu-Tb-MOF is combined with OTA, the color of the solution changes from red to yellow and finally to green as the concentration of OTA increases. Therefore, the fluorescence ratio signal I 545 / I 615The concentration of OTA was detected in a linear relationship with the concentration of OTA.

[0030] In a fourth aspect, the present invention provides a test paper for detecting ochratoxin A, comprising a test paper body, a result control area, and a sample test area; the result control area comprises a plurality of paper-based sensors containing different concentrations of ochratoxin A, and the paper-based sensors are cut from circular filter paper with a diameter of 5-6 mm; the sample test area is loaded with the fluorescent probe described in the first aspect.

[0031] As a preferred embodiment of the fourth aspect of the present invention, the concentration of ochratoxin A includes 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 μg / mL.

[0032] The overall test paper of the present invention can be cut from ordinary filter paper into a size of 10-20 cm in length and 5-10 cm in width, and then cut from the ordinary filter paper into several circular filter paper pieces with a diameter of 5-6 mm. The several circular filter paper pieces are fixed to the result control area, and different concentrations of ochratoxin A, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 μg / mL, are sequentially dripped onto each circular filter paper piece.

[0033] Method 1 for using the test paper of the present invention: drop the liquid sample to be tested into the sample test area of ​​the test paper. After the test paper is dried at room temperature for 30 minutes, it is placed under 365nm ultraviolet light. The fluorescence color of the sample test area is compared with the fluorescence color of the paper-based sensor in the result control area. The color that is closest is the OTA concentration in the sample.

[0034] Method 2 for using the test paper of the present invention: drop the liquid sample to be tested onto the sample test area of ​​the test paper, dry the test paper at room temperature for 30 minutes, place it under 365nm ultraviolet light, obtain a fluorescence photo of the test paper through the rear camera of the mobile phone, and use ImageJ software to extract the RGB value of the fluorescence photo and calculate its G / R value. Substitute the G / R value into the relationship between G / R value and OTA concentration (G / R = 169090.88C OTA +0.4465,R 2 =0.9917, C OTA The concentration of OTA in the liquid sample to be tested can be obtained by

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) Luminescence performance regulation: ff transition of lanthanide ions produces narrow-band emission (half-peak width < 10 nm), Eu 3+ (red emission, 615nm) and Tb 3+The fluorescence intensity ratio of the two probes (emission in the green region, 545 nm) can be used to construct an internal reference system, significantly reducing environmental interference (such as light source fluctuations and probe concentration changes) and improving detection reliability.

[0037] (2) Synergistic mechanism: ① “Antenna effect” enhancement: The conjugated structure of the ligand 3,5-dicarboxyphenylboronic acid (5-Bop) transfers the excited state energy to Tb through the antenna effect. 3+ , and then through Tb 3+ Pass to Eu 3+ , so that Eu-Tb-MOF emits red light under 365nm light excitation; ②Specific recognition: The boric acid group of 5-Bop and the carboxylic acid group of OTA can enrich OTA through electrostatic interaction and hydrogen bonding, while Tb 3+ It can coordinate with the carboxylic acid group of OTA to further capture OTA. OTA can also act as a sensitizer to directly enhance the Tb 3+ The fluorescence of Eu 3+ The fluorescence of Eu-Tb-MOF can be detected by measuring the ratio fluorescence of Eu-Tb-MOF at 545nm and 615nm.

[0038] (3) Stability guarantee: The rigid skeleton of MOF can isolate the quenching effect of water molecules on lanthanide ions, maintain fluorescence stability within seven days, and is suitable for complex food analysis environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the characterization of Eu-Tb-MOF (a: TEM image of Eu-Tb-MOF; b: EDC element mapping of Eu-Tb-MOF; c: XPS full spectrum of Eu-Tb-MOF; d: FTIR spectrum of Eu-Tb-MOF);

[0040] Figure 2 Schematic diagram of the excitation spectrum and emission spectrum of Eu-Tb-MOF at 365 nm (Ex is the excitation spectrum, Em is the emission spectrum);

[0041] Figure 3 Schematic diagram of the antenna effect emission mechanism of Eu-Tb-MOF (“a” and “b” represent the process from T1 of 5-Bop to Eu 3+ and Tb 3+ The energy transfer, “c”, shows the energy transfer from Tb 3+ The process of transferring the excited state of α to Eu3+; Abbreviations: ET: energy transfer; S1: singlet state and T1: triplet state);

[0042] Figure 4 Schematic diagram of the Eu-Tb-MOF fluorescence stability test within seven days;

[0043] Figure 5 Schematic diagram of OTA detection in solution (a: fluorescence spectra of Eu-Tb-MOF at different OTA concentrations; b: I 545 / I 615 Linear relationship between fluorescence intensity ratio and OTA concentration);

[0044] Figure 6 The excitation spectrum and emission spectrum of OTA at 365 nm (the inset is the structural formula of OTA; Ex is the excitation spectrum, and Em is the emission spectrum);

[0045] Figure 7 The fluorescence spectra of Eu-MOF under different concentrations of OTA;

[0046] Figure 8 The fluorescence spectra of Tb-MOF under different concentrations of OTA;

[0047] Figure 9 Schematic diagram of the Eu-Tb-MOF selectivity verification results (a: fluorescence reaction of OTA and other mycotoxins; b: fluorescence reaction of various interfering ions);

[0048] Figure 10 Schematic diagram of the test strip's detection principle (a: Photographs of the test strip's color changes under natural light and UV light when detecting OTA (0-10 μg / mL); b: The linear relationship between the G / R value of the test strip's color in the fluorescent photograph and OTA concentration).

[0049] Figure 11 Schematic diagram of the structure of the test paper. DETAILED DESCRIPTION

[0050] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0051] Example 1

[0052] This embodiment provides a Eu 3+ and Tb 3+ The preparation method of the fluorescent probe of the metal-doped organic framework material comprises the following specific steps:

[0053] A metal-organic framework fluorescent probe was synthesized using 3,5-dicarboxyphenylboronic acid (5-Bop) as a ligand and europium and terbium ions as metal centers. The molar ratio of the total europium and terbium salts to 5-Bop was 1:1. Crystallization was performed by a solvothermal method at 130°C for 12 hours. The solvent for the solvothermal method was N,N-dimethylformamide. The specific steps are as follows:

[0054] 0.01 mmol of Eu(NO)3·6H2O, 0.09 mmol of Tb(NO)3·6H2O and 0.1 mmol of 5-Bop were mixed in 10 mL of N,N-dimethylformamide (DMF) solution to form a mixture, which was vigorously stirred in a container and then transferred to an oven at 130°C for 12 hours to prepare a fluorescent probe solution, which was recorded as: Eu-Tb-MOF.

[0055] DMF solution configuration: the volume ratio of DMF to water is 7:3.

[0056] Comparative Example 1

[0057] The difference between Comparative Example 1 and Example 1 is that europium ions are used as the metal center, specifically as follows:

[0058] 0.1 mmol of Eu(NO)3·6H2O and 0.1 mmol of 5-Bop were mixed in 10 mL of N,N-dimethylformamide (DMF) solution to form a mixture, which was vigorously stirred in a container and then transferred to an oven at 130°C for 12 hours to prepare a fluorescent probe solution, which was recorded as: Eu-MOF.

[0059] Comparative Example 2

[0060] The difference between Comparative Example 2 and Example 1 is that terbium ions are used as the metal center, specifically as follows:

[0061] 0.1 mmol of Tb(NO)3·6H2O and 0.1 mmol of 5-Bop were mixed in 10 mL of N,N-dimethylformamide (DMF) solution to form a mixture, which was vigorously stirred in a container and then transferred to an oven at 130°C for 12 hours to prepare a fluorescent probe solution, which was recorded as: Tb-MOF.

[0062] Test Example 1: Characterization of Eu-Tb-MOF

[0063] TEM analysis of the Eu-Tb-MOF prepared in Example 1 showed that it was a nanobelt structure with a width of 20 nm, a length of more than 10 mm, and an aspect ratio of more than 500 ( Figure 1 a) EDC elemental analysis shows that Eu-Tb-MOF is composed of C, O, B, Tb and Eu, among which Eu 3+ :Tb 3+ The ratio is 1:9( Figure 1 b). At the same time, X-ray photoelectron spectroscopy (XPS) was used to characterize the presence of C, O, B, Tb and Eu elements, and Eu 3+ :Tb 3+ The ratio is 1:9( Figure 1c), further proving that Eu-Tb-MOF has been successfully synthesized.

[0064] In FTIR spectroscopy ( Figure 1 d), Eu-Tb-MOF at 1680 cm -1 No stretching vibration peak of ligand CO was observed at 3+ and Eu 3+ The metal node is successfully coordinated. -1 The absorption peak of the boronic acid group of 5-Bop was observed at 100 nm, indicating that the boronic acid group was still an active group and did not participate in the formation of the MOF structure. The above series of characterizations confirmed the successful synthesis of Eu-Tb-MOF.

[0065] Test Example 2: Eu-Tb-MOF Optical Property Detection

[0066] The fluorescence spectrum of Eu-Tb-MOF was tested using a fluorescence spectrometer, and it was found that it can absorb light in the range of 270nm-365nm, and under the excitation of 365nm light, Eu-Tb-MOF has a fluorescence spectrum of 590nm ( 5 D0→ 7 F1) and 615nm( 5 D0→ 7 Eu is shown at F2) 3+ The characteristic emission at 490nm ( 5 D4→ 7 F6) and 545nm( 5 D4→ 7 F5) displays Tb 3+ The characteristic emission peak of Eu 3+ The emission peak intensity at 615nm is greater than that of Tb 3+ The peak emission intensity at 545 nm ( Figure 2 ), and it appears red under 365nm ultraviolet light. The energy transfer diagram of Eu-Tb-MOF under 365nm light is as follows Figure 2 The specific energy transfer process is as follows: under ultraviolet light irradiation, the conjugated π electron system of 5-Bop ligand is excited to form a singlet excited state (S1), and its S1 state is converted to a triplet state (T1) through intersystem crossing (ISC), and the T1 state can transfer energy to Eu 3+ and Tb 3+ ( Figure 3 a process and b process). Tb 3+ After absorbing energy, it transitions to an excited state ( 5 D4), Tb 3+ of 5 D4→ 7 F jThe transition produces green fluorescence (main peak 545nm). 3+ of 5 D4 energy level and Eu 3+ of 5 There is an energy difference between the D0 energy levels, which is matched by multi-phonon relaxation. 3+ ( 5 D4) and Eu 3+ ( 7 F0) coupled via dipole-dipole interaction, Tb 3+ of 5 Most of the energy of D4 level is transferred to Eu 3+ ( Figure 3 c process), stimulate it to 5 D0 energy level, while Tb 3+ Return to the low energy state, so that Eu 3+ of 5 D0→ 7 F j The transition produces red fluorescence (main peak 615nm). At the same time, energy is efficiently transferred to Eu 3+ , significantly reducing Tb 3+ of 5 D4→ 7 F j transition probability, resulting in its 545nm emission intensity being weaker than that of Eu 3+ The 615nm peak of Eu-Tb-MOF results in red fluorescence under 365nm light excitation.

[0067] Test Example 3: Eu-Tb-MOF fluorescence stability test

[0068] We investigated the fluorescence stability of the synthesized Eu-Tb-MOF and repeatedly tested the UV fluorescence spectrum of the synthesized Eu-Tb-MOF for seven days. The results are as follows Figure 4 As shown, it was found that its fluorescence intensity at 545 nm and 615 nm could remain stable within seven days.

[0069] Test Example 4: Detection Performance of Fluorescent Probe for Ochratoxin A

[0070] Direct detection of OTA using the prepared Eu-Tb-MOF: 20 μL of OTA standard solution with different concentrations (0.0001-20 μg / mL) was mixed with 180 μL of Eu-Tb-MOF solution and vortexed for 10 s until fully mixed before direct detection.

[0071] The results are as follows Figure 5 As shown in a, it was found that with the increase of OTA concentration, the fluorescence of Eu-Tb-MOF at 545nm and 615nm increased simultaneously under 365nm ultraviolet excitation ( Figure 5 a), causing the solution color to change from red to yellow and finally to green. 545 / I 615 The standard curve was drawn with OTA concentration as the vertical axis and OTA concentration as the horizontal axis. 545 / I 615 There was a good linear relationship between the OTA concentration and the OTA concentration in the ranges of 0-0.2μg / mL, 0.2-6μg / mL and 6-20μg / mL ( Figure 5 b), the linear equation is y=2.608x+0.613(R 2 =0.990), y=0.107x+1.182(R 2 =0.982) and y = 0.0339x + 1.158 (R 2 =0.984), and the detection limit was calculated to be 3.7 ng / mL (3σ / k).

[0072] Test Example 5: Mechanism of Eu-Tb-MOF Detection of OTA

[0073] In order to study the mechanism of OTA detection by Eu-Tb-MOF, we measured the excitation spectrum of OTA and the emission spectrum at 365 nm ( Figure 6 ). Analysis of the spectral data shows that OTA has a broad absorption at 340nm-365nm, corresponding to the conjugated π→π* electron transition of the isocoumarin group and the phenylalanine derivative in its molecule. Under 365nm light excitation, the emission spectrum peak of OTA is located at 440nm-460nm (blue light range). By analyzing the structure of OTA, it was found that the carboxylic acid group it contains can react with Tb 3+ OTA can absorb light in the 365nm range and transfer energy to Tb through antenna effect as a sensitizer. 3+ , which can directly enhance Tb 3+ The fluorescence emission of Eu 3+ With the increase of OTA concentration, the color of the solution changes from red to yellow and then to green under 365nm light excitation.

[0074] The Eu-MOF in Comparative Example 1 and the Tb-MOF in Comparative Example 2 were mixed with different concentrations of OTA, and their fluorescence spectra under 365 nm light excitation were tested ( Figure 7 and Figure 8). It was found that as the OTA concentration increased, the fluorescence intensity of Eu-MOF at 615nm remained essentially unchanged, while the fluorescence intensity of Tb-MOF at 545nm gradually increased. This indicates that Eu-MOF cannot directly detect OTA, and its fluorescence intensity at 615nm does not change with OTA concentration. Although Tb-MOF can directly detect OTA, it can only show a single change in the intensity of green fluorescence when the OTA concentration changes, resulting in low detection sensitivity. In contrast, the fluorescence color of the synthesized Eu-Tb-MOF changes from red to yellow and then to green as the OTA concentration increases. The naked eye can judge the concentration of OTA, improving detection sensitivity and making it more practical.

[0075] Test Example 6: Selectivity of Eu-Tb-MOF for OTA detection

[0076] In this test case, we investigated the effects of other mycotoxins, such as zearalenone (ZEN), aflatoxin B1 (AFB1), and aflatoxin G1 (AFG1), as well as various metal cations, on the detection of Eu-Tb-MOF. Standard solutions of these mycotoxins (0.1 mg / mL, 20 μL) were added to 180 μL of the Eu-Tb-MOF solution. After thorough mixing by vortexing for 10 seconds, the fluorescence spectrum was measured under 365 nm UV light.

[0077] The results are as follows Figure 9 As shown in a, in the case of only OTA, I 545 / I 615 The ratio of OTA to OTA increased significantly, while the addition of other mycotoxins did not change the ratio signal, which proves that the fluorescent probe of the present invention has good specificity for OTA.

[0078] The results are as follows Figure 9 As shown in Figure b, under the same conditions, 10-fold concentration of interfering ions had no significant effect on OTA detection, demonstrating that the fluorescent probe of the present invention has good anti-interference ability.

[0079] Application example: Building a test strip detection platform

[0080] Leveraging the excellent OTA sensing performance of Eu-Tb-MOF, we designed a portable test paper that enables on-site, instant OTA detection via smartphone imaging. The specific preparation method for the test paper is as follows:

[0081] (1) Cut ordinary qualitative filter paper into pieces of 10 cm in length and 5 cm in width, and set up a result control area and a sample test area; also take another piece of ordinary qualitative filter paper and cut it into several discs with a diameter of 6 mm;

[0082] (2) Each wafer was immersed in the Eu-Tb-MOF solution of Example 1 for 30 min and dried at room temperature. This immersion-drying process was repeated five times to obtain a wafer uniformly loaded with Eu-Tb-MOF, and a paper-based sensor and a sample test area were prepared respectively;

[0083] (3) 30 μL of OTA solution with different concentrations (including 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 μg / mL) was added to the paper-based sensor for 30 minutes and then allowed to dry naturally;

[0084] (4) Fix the paper-based sensor of step (3) in the result control area and fix the sample test area disc in the sample test area to obtain the OTA test paper.

[0085] Method 1 for using the test paper of the present invention: Figure 10 As shown in (a), the test paper of the present invention does not show a color change under natural light, and the test paper retains its original color. However, when placed under 365nm ultraviolet light, the color change of the test paper can be observed by the naked eye (OTA concentrations of 0-10μg / mL display different colors). Therefore, the liquid sample to be tested is added dropwise to the sample test area of ​​the test paper, dried at room temperature for 30 minutes, and then placed under 365nm ultraviolet light. The fluorescent color of the sample test area can be observed by the naked eye. By comparing it with the fluorescent color of the paper-based sensor in the result control area, the range of OTA concentration in the sample can be obtained.

[0086] The second method of using the test paper of the present invention: Figure 10 As shown in (b), under 365 nm ultraviolet light, the G / R ratio (G / R refers to the ratio of the green and red color intensities extracted in the fluorescence photograph) of the test paper of the present invention has a good linear relationship with the OTA concentration (in the range of 0-10 μg / mL), and the relationship is G / R = 169090.88C OTA +0.4465,R 2 =0.9917, where C OTA Indicates the concentration of OTA. Therefore, the following method can be used to detect OTA:

[0087] (1) The liquid sample to be tested was dropped onto the test area of ​​the test paper sample. After drying at room temperature for 30 minutes, the test paper was exposed to 365nm ultraviolet light. Fluorescence images of the test paper were obtained using the rear camera of a smartphone. As the OTA concentration increased, the color of the fluorescence image gradually changed from red to yellow and then to green. The RGB values ​​of each fluorescence image were analyzed using the image processing software ImageJ to obtain the G / R ratio.

[0088] (2) With the G / R ratio as the ordinate and the OTA standard concentration as the abscissa, a standard curve of the G / R ratio and OTA concentration was drawn. The G / R ratio value obtained from the test area of ​​the test paper sample was substituted into the formula: G / R = 169090.88C OTA +0.4465, the OTA concentration in the sample test area can be obtained.

[0089] In summary, the above two methods can both detect the concentration of OTA in the liquid sample to be tested. It has been verified that the LOD value (limit of detection) of the test paper of the present invention is 0.319 μg / mL.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A kind of Eu 3+ and Tb 3+ A fluorescent probe of a metal-doped organic framework material, characterized in that It has the following chemical structure:

2. A method for preparing a fluorescent probe according to claim 1, characterized in that: The preparation method comprises the following steps: (1) Synthesize a metal-organic framework fluorescent probe using carboxylic acid organic compounds as ligands and lanthanide metal ions as metal centers; the molar ratio of lanthanide metal salt to carboxylic acid organic compound is 1:(1-2); (2) crystallizing the metal organic framework material fluorescent probe prepared in step (1) at 110-130° C. for 10-14 hours by a solvothermal method; the solvent used in the solvothermal method is N,N-dimethylformamide.

3. The method for preparing a fluorescent probe according to claim 2, wherein: The carboxylic acid organic compound is 3,5-dicarboxyphenylboronic acid.

4. The method for preparing a fluorescent probe according to claim 2, wherein: The lanthanide metal ions include lanthanum ions, cerium ions, praseodymium ions, neodymium ions, promethium ions, samarium ions, europium ions, gadolinium ions, terbium ions, dysprosium ions, holmium ions, erbium ions, thulium ions, ytterbium ions and lutetium ions.

5. The method for preparing a fluorescent probe according to claim 2, wherein: The metal center consists of europium ions and terbium ions.

6. The method for preparing a fluorescent probe according to claim 2, wherein: The lanthanide metal salt includes Eu(NO)3·6H2O and Tb(NO)3·6H2O; wherein the molar ratio of Eu(NO)3·6H2O to Tb(NO)3·6H2O is 1:(8-10).

7. Eu as claimed in claim 1 3+ and Tb 3+ Application of metal-doped organic framework materials as fluorescent probes for the detection of ochratoxin A.

8. The use according to claim 7, characterized in that The method for detecting ochratoxin A using a fluorescent probe comprises: (1) The fluorescent probe described in claim 1 was added to the same volume of ochratoxin A standard solution with different concentrations to obtain a series of mixed dispersions with known ochratoxin A concentrations. After sufficient reaction, the fluorescence intensity ratio I was measured at an excitation wavelength of 365 nm. 545 / I 615 , and obtain the ratio of ochratoxin A concentration to fluorescence intensity I 545 / I 615 The following relationship: y = 2.608x + 0.613 (Formula 1), correlation coefficient R 2 =0.990; y=0.107x+1.182(Formula 2), correlation coefficient R 2 =0.982; y=0.0339x+1.158 (Formula 3), correlation coefficient R 2 =0.984; y is the fluorescence intensity ratio I 545 / I 615 , x is the ochratoxin A concentration; wherein, Formula 1 is the relationship when the ochratoxin A concentration is 0-0.2 μg / mL, Formula 2 is the relationship when the ochratoxin A concentration is 0.2-6 μg / mL, and Formula 3 is the relationship when the ochratoxin A concentration is 6-20 μg / mL; (2) The water sample to be tested is introduced to replace the ochratoxin A standard solution under the same conditions as in step (1), and the fluorescence intensity ratio I of the mixed dispersion is also measured. 545 / I 615 Then, according to the ratio of ochratoxin A concentration to fluorescence intensity I 545 / I 615 The concentration of ochratoxin A in the water sample to be tested is calculated using the relationship (Formula 1)-(Formula 3).

9. A test paper for detecting ochratoxin A, characterized in that: The test paper includes a test paper body, a result control area and a sample test area; the result control area includes several paper-based sensors containing different concentrations of ochratoxin A, and the paper-based sensors are cut from circular filter paper with a diameter of 5-6 mm; the sample test area is loaded with the fluorescent probe described in claim 1.

10. The test paper for detecting ochratoxin A according to claim 9, wherein The concentrations of ochratoxin A on the paper-based sensor included 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 μg / mL.

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