Fluorescence detection method for tin ion Sn < 4 + >

Abstract

The invention discloses a fluorescence detection method of tin ions Sn < 4 + >, which is characterized in that on the basis of a dual-emission ratio sensing mechanism of a europium metal organic framework, Eu < 3 + >, 2-hydroxyterephthalic acid (HTPA) and 1, 10-phenanthroline are coordinated and self-assembled to synthesize cubic EuMOF, and the cubic EuMOF simultaneously generates dual-emission fluorescence of HTPA and Eu < 3 + > at 430 nm and 614 nm respectively. When Sn < 4 + > exists, the EuMOF structure collapses, so that the antenna effect between the ligand and Eu < 3 + > is destroyed, the I614 / I430 fluorescence intensity ratio change is initiated, the Sn < 4 + > quantitative detection is realized, the detection limit is as low as 54.37 nM, and the linear range is 0.1-100 [mu] M. Aiming at field detection requirements, EuMOF test paper is further combined with RGB analysis application assisted by a smart phone to construct a portable visual sensing platform. The fluorescent sensor constructed by the invention can realize quantitative analysis and rapid detection of Sn < 4 + >, has high sensitivity, high selectivity and good anti-interference capability, and can be used for detecting Sn < 4 + > in an actual sample.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescence sensing of metal-organic framework materials, and particularly relates to a dual-emission europium metal-organic framework (EuMOF) for a ratiometric fluorescence and visual sensing platform for detecting tin ions (Sn 4+ ). Background Art

[0002] Sn 4+ is an essential trace element in the human body and plays an important role in physiological processes such as nucleic acid and protein synthesis, maintaining body homeostasis, and inhibiting the occurrence and development of cancer. Lack of Sn 4+ may lead to hearing loss, respiratory disorders, and reduced hemoglobin production, while excessive accumulation can cause gastrointestinal diseases, immunotoxicity, and neurotoxicity. Nevertheless, many canned foods are packaged with tin-containing materials, and the tin element contained therein may dissolve in foods, especially acidic foods. The maximum allowable amount of tin ions in canned foods is 2.105 mM. Therefore, detecting the content of Sn 4+ in canned foods is of great significance for food safety supervision. Currently, commonly used Sn 4+ detection methods include atomic absorption spectrometry (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), immunochromatography, and electrochemical methods. However, these methods require expensive instrument equipment, complex sample pretreatment, and professional technicians, which greatly limits their applications. Different from the above strategies, fluorescence-based analytical methods have higher sensitivity, faster response time, and simpler operation for target detection. Therefore, developing fluorescent materials with excellent performance is crucial for constructing efficient Sn 4+ sensors.

[0003] As an emerging porous crystalline material, metal-organic frameworks (MOFs) are formed by the coordination of metal ions and organic ligands, and have superior properties such as programmable structure, adjustable pores, and high specific surface area, and have great potential in gas storage, catalysis, and sensing applications. Among them, lanthanide metal-organic frameworks (LnMOFs) stand out due to their excellent lanthanide ion luminescence properties, such as bright visible fluorescence, large Stokes shift, and long fluorescence lifetime. In particular, LnMOFs with dual-emission characteristics have more advantages in terms of high sensitivity, high accuracy, and visualization ability, and can be used to construct sensors suitable for on-site detection, and thus have received increasing attention.

[0004] However, there has been no report on the use of dual-emission LnMOFs for Sn 4+There are few reports on detection, and existing fluorescence sensors generally lack the ability of portable visual detection. Inspired by the above research, a dual-emission europium metal-organic framework (EuMOF) was synthesized for the first time in this invention for the ratio fluorescence detection of Sn 4+ Meanwhile, in order to meet the detection needs under limited on-site conditions, a portable visual sensing platform was developed by combining EuMOF test paper with RGB color analysis application for the convenient, rapid and sensitive quantitative monitoring of Sn 4+ This invention provides a feasible strategy for the efficient detection of Sn 4+ and is expected to open up a new way for strengthening food safety supervision.

[0005] Based on this, a fluorescence detection method for tin ion Sn 4+ is now provided. Summary of the Invention

[0006] The purpose of this invention is to solve the technical bottleneck that the existing Sn 4+ detection methods rely on large instruments and cannot be quickly analyzed on-site, and provide a fluorescence detection method for tin ion Sn 4+ . By coordinating two ligands, 2-hydroxyterephthalic acid (HTPA) and 1,10-phenanthroline (Phen), with Eu 3+ , a cubic EuMOF is formed. This EuMOF exhibits the characteristic fluorescence of HTPA and Eu 3+ at 430 nm and 614 nm respectively. Using EuMOF directly as a fluorescence sensor for the ratio detection of Sn 4+ , and further preparing paper-based EuMOF, combined with smartphone RGB analysis software to construct a portable sensing platform, which can be used for the portable and rapid detection of Sn 4+ .

[0007] To achieve the above purpose, this invention provides the following technical solutions: In the first aspect of this invention, a sensor for the ratio fluorescence detection of Sn 4+ is provided, and the sensor is prepared by the following method: (1) Dissolve Eu(NO3)3·6H2O in ultrapure water, dissolve HTPA and Phen in ethanol, and ultrasonically process the two until completely dissolved; (2) Mix the solutions obtained in step (1), stir the reaction at a constant temperature and then cool to room temperature, centrifuge to collect the precipitate and wash it three times alternately with ethanol and ultrapure water; (3) Dry the product washed in step (2) to obtain the EuMOF fluorescence sensor.

[0008] Preferably, in step (1), the mass of Eu(NO3)3·6H2O is 0.1117 g, and the volume of ultrapure water is 5 mL; the masses of HTPA and Phen are 0.0364 g and 0.0541 g respectively, and the volume of ethanol is 15 mL.

[0009] Preferably, in step (1), the frequency of the ultrasonic wave is 60 kHz, and the ultrasonic time is 15 minutes.

[0010] Preferably, in step (2), the stirring temperature is 60 °C, the reaction condition is magnetic stirring in an oil bath, the reaction time is 4 hours, and the centrifugation condition is 8000 rpm for 10 minutes.

[0011] Preferably, in step (3), the drying condition is vacuum drying at 40 °C for 12 hours.

[0012] In the second aspect of the present invention, there is provided the application of the EuMOF fluorescence sensor in the detection of Sn 4+ The method is as follows: Disperse the EuMOF powder in DMF to obtain a dispersion liquid, mix it with Sn 4+ solutions with different concentrations, then measure the fluorescence emission spectrum, and record the fluorescence intensities at 430 nm and 614 nm. Use the ratio of the fluorescence intensities at 614 nm and 430 nm (I 614 / I 430 ) and the Sn 4+ concentration to establish a standard curve, and calculate the Sn 4+ concentration in the test solution according to the standard curve.

[0013] Preferably, the concentration of the EuMOF dispersion liquid is 1 mg / mL, the excitation wavelength of the fluorescence emission spectrum is 300 nm, the emission wavelength range is from 370 nm to 720 nm, the slit is 2 nm, the detection range is 0.1 - 15 μM, and the detection limit is 54.37 nM.

[0014] In the third aspect of the present invention, there is provided the application of the EuMOF portable test strip in the detection of Sn 4+ The method is as follows: Soak a 5 mm×5 mm round filter paper in a 1 mg / mL EuMOF solution, and dry it at 40 °C for 30 minutes to obtain a EuMOF test strip; soak the prepared EuMOF test strip in a solution containing different concentrations of Sn 4+ solution, then take a picture of the above test strip under ultraviolet light irradiation, and analyze its RGB value; use the ratio of R / (G + B) (y) and the Sn 4+The concentration (x) of the sample was used to establish a standard curve y = 0.694-0.006x. The Sn content in the solution to be tested was calculated based on the standard curve. 4+ concentration.

[0015] Preferably, the filter paper soaking time is 30 minutes, the wavelength of the ultraviolet lamp is 302 nm, the detection linear range is 1-100 μM, and the detection limit is 0.853 μM. Compared with the prior art, the beneficial effects of the present invention are as follows: The beneficial effects of the present invention are: 1. The detection method of the present invention is based on the ratio fluorescence signal (I 614 / I 430 )Realize Sn 4+ Quantitative analysis, easy operation (only two steps of mixing and detection), fast response (completed within 10 minutes), can meet the needs of high-precision and rapid detection.

[0016] 2. The EuMOF sensor prepared by the present invention exhibits excellent sensitivity (detection limit 54.37 nM), selectivity and anti-interference ability (to Ag + , K + , Hg 2+ , Cu 2+ , Ba 2+ ,Co 2+ , Pb 2+ , Ni 2+ The ratio fluorescence response of the plasma is almost unaffected), and it can detect trace amounts of Sn in canned fish and canned yellow peaches. 4+ Conduct analysis.

[0017] 3. The portable sensing platform based on EuMOF test paper and smartphone RGB analysis application prepared by the present invention realizes Sn 4+ Efficient detection of Sn 4+ The detection limit is 0.853 µM), which is a good method for the on-site detection of Sn 4+ Provides an easy-to-implement platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 (A) Scanning electron microscopy (SEM) image of EuMOF; Figure 1 (B) Element distribution diagram (C, N, O and Eu) corresponding to (A); Figure 1 (C) Powder X-ray diffraction (PXRD) pattern of EuMOF. Figure 1 (D) X-ray photoelectron spectroscopy (XPS) of EuMOF; Figure 2 (A) Adding different concentrations of Sn into EuMOF 4+ The fluorescence spectrum of Sn 4+The concentrations are successively: 0 µM, 0.1 µM, 0.25 µM, 0.5 µM, 1.0 µM, 2.5 µM, 5.0 µM, 10.0 µM, 15.0 µM, 20.0 µM, 25.0 µM, 35.0 µM, 50.0 µM, 100.0 µM; Figure 2 (B) Relationship diagram of the ratio fluorescence intensity (I 614 / I 430 ) and the concentration of Sn 4+ (0 - 100 µM). Insert: Linear fitting of I 614 / I 430 and the concentration of Sn 4+ within the range of 0.1 - 15 µM; Figure 2 (C) Time - related kinetic study of adding 25 µM Sn 4+ to EuMOF; Figure 2 (D) Selectivity and anti - interference ability of EuMOF for Sn 4+ detection; Figure 3 (A) CIE chromaticity diagram of EuMOF and EuMOF after reaction with 100 µM Sn 4+ . Insert: Corresponding pictures under 302 nm ultraviolet lamp irradiation; Figure 3 (B) Smartphone - assisted EuMOF test paper for visual quantitative detection of Sn 4+ ; R / (G + B) has a linear correlation with the concentration of Sn 4+ (1 - 100 µM), and the detected concentrations are respectively: 1.0 µM, 5.0 µM, 10.0 µM, 30.0 µM, 50.0 µM, 80.0 µM, 100.0 µM. Specific implementation manners

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] As described in the background technology, although existing analytical methods such as atomic absorption spectrometry (AAS), inductively coupled plasma - mass spectrometry (ICP - MS), immunochromatography, and electrochemical methods are used in detecting Sn 4+Some progress has been made in this regard, but these methods are greatly limited in their applications due to the requirements for expensive instruments and equipment, complex sample pretreatment, and professional technicians. Based on this, a dual-emission europium metal-organic framework (EuMOF) fluorescent sensor is developed, combining ratiometric fluorescence and test paper visualization technology to achieve highly sensitive, portable, and rapid detection of Sn 4+ of

[0021] In this fluorescence sensing strategy, two ligands, 2-hydroxyterephthalic acid (HTPA) and 1,10-phenanthroline (Phen), coordinate with Eu 3+ to form a cubic EuMOF. This material has dual-emission characteristics: it emits blue fluorescence of the HTPA ligand at 430 nm and characteristic red fluorescence of Eu 3+ at 614 nm. When Sn 4+ exists in the system, the fluorescence of EuMOF at 614 nm weakens, while the fluorescence at 430 nm significantly enhances, thus generating a ratiometric fluorescence signal. Based on this, the present invention provides a fluorescent sensor for highly efficient detection of Sn 4+ . In addition, an EuMOF test paper is further combined with RGB color analysis application to construct a portable visualization sensing platform for convenient, rapid, and highly sensitive quantitative detection of Sn 4+ .

[0022] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in conjunction with specific embodiments. If the specific experimental conditions are not specified in the embodiments, they are usually in accordance with conventional conditions or the conditions recommended by reagent companies; the reagents, consumables, etc. used in the following embodiments can be obtained through commercial channels without special instructions.

[0023] Example 1

[0024] Preparation of EuMOF Fluorescent Sensor 1. Dissolve Eu(NO3)3·6H2O in ultrapure water, dissolve HTPA and Phen in ethanol, and ultrasonically treat the two until completely dissolved; 2. Mix the solutions obtained in step (1), stir the reaction at a constant temperature, cool to room temperature, centrifuge to collect the precipitate, and wash it three times alternately with ethanol and ultrapure water; 3. Dry the product washed in step (2) to obtain the EuMOF fluorescent sensor.

[0025] The scanning electron microscope (SEM) of the EuMOF prepared in Example 1 is as shown in Figure 1 A, presenting a cubic structure. The elemental distribution map shows that C, N, O, and Eu elements are evenly distributed in EuMOF ( Figure 1B). The powder X-ray diffraction (PXRD) pattern shows distinct sharp diffraction peaks in the range of 5° to 55° ( Figure 1 C), indicating that the synthesized EuMOF has a high degree of crystallinity. In addition, X-ray photoelectron spectroscopy (XPS) shows characteristic peaks of C 1s, N 1s, O 1s, and Eu 3d ( Figure 1 D).

[0026] Example 2

[0027] EuMOF-based Ratiometric Fluorescence Detection of Sn 4+ Method Mix different concentrations of Sn 4+ (0 µM, 0.1 µM, 0.25 µM, 0.5 µM, 1.0 µM, 2.5 µM, 5.0 µM, 10.0 µM, 15.0 µM, 20.0 µM, 25.0 µM, 35.0 µM, 50.0 µM, 100.0 µM) evenly with the EuMOF fluorescence sensor prepared in Example 1. Determine the concentration of Sn 4+ according to the change in ratiometric fluorescence. Take the fluorescence intensity ratio (I 614 / I 430 ) as the ordinate and the concentration of Sn 4+ as the abscissa (unit: µM) to establish a standard curve y = 15.378 - 1.001x (R 2 = 0.994).

[0028] As Figure 2 shown, this fluorescence sensor has a good ratiometric fluorescence response to Sn 4+ , showing a wide linear range (0.1 - 15 µM), high sensitivity (detection limit 54.37 nM), and fast response time (10 minutes), fully indicating that this fluorescence sensor can be used for rapid detection of Sn 4+ with unknown concentration.

[0029] Example 3

[0030] Smartphone-Assisted EuMOF Test Strip for Portable Visual Quantitative Detection of Sn 4+ Portable Visual Quantitative Detection Soak the test strip in the EuMOF dispersion solution. After drying, drop solutions of different concentrations of Sn 4+ (1.0 µM, 5.0 µM, 10.0 µM, 30.0 µM, 50.0 µM, 80.0 µM, 100.0 µM) on the test strip. Place the above test strip in a dark box and take its picture with a smartphone under ultraviolet light (302 nm) irradiation. After RGB application recognition, perform quantitative analysis. Take R / (G + B) as the ordinate and the concentration of Sn 4+With the concentration as the abscissa (unit: μM), a standard curve y = 0.694 – 0.006x (R 2 = 0.996) was established.

[0031] As Figure 3 shown, the portable visual sensing platform showed a good linear relationship with Sn 4+ , with a wide linear range (1–100 µM) and high sensitivity (detection limit 0.853 µM), indicating that the fluorescence sensor can provide a convenient, rapid, and efficient strategy for Sn 4+ detection.

[0032] Test Example 1 Using the fluorescence intensity ratio (I 614 / I 430 ) of the EuMOF sensor to quantify Sn 4+ , the changes in the fluorescence intensity ratio corresponding to different concentrations of Sn 4+ were recorded, and the results are shown in Figure 2 .

[0033] As Figure 2 shown in Figure B, the EuMOF fluorescence sensor prepared in Example 1 could sensitively respond to low-concentration Sn 4+ , confirming the high-sensitivity detection ability of the ratio fluorescence sensing platform for trace Sn 4+ .

[0034] Test Example 2 The specificity and anti-interference of the fluorescence sensor prepared in Example 1 for detecting Sn 4+ were investigated: the ratio fluorescence changes of EuMOF to Sn 4+ with and without the addition of interfering ions were examined. The specific results are shown in Figure 2 Figure D; as Figure 2 shown in Figure D, except for the target Sn 4+ , other interfering ions hardly affected the fluorescence of EuMOF. In addition, when Sn 4+ coexisted with Ag + , K + , Hg 2+ , Cu 2+ , Ba 2+ , Co 2+ , Pb 2+ , Ni 2+ and other ions, the fluorescence ratio of EuMOF to Sn 4+ did not change significantly, thus excluding the interference of common cations.

[0035] Test Example 3 Using the change in the RGB value of the EuMOF test paper to detect Sn 4+Detection was carried out to record the changes in the R / (G+B) ratio corresponding to different concentrations of Sn 4+ The results are shown in Figure 3 .

[0036] As can be seen from Figure 3 B, the EuMOF test paper assisted by the smart phone developed in Example 3 has a dynamic color response to different concentrations of Sn 4+ which proves that this portable sensor can be used for on-site real-time monitoring of Sn 4+ .

[0037] Test Example 4 The accuracy of the fluorescence sensor prepared in Example 1 for the quantitative analysis method of Sn 4+ was investigated: Taking canned fish and canned yellow peaches as actual samples, different concentrations of Sn 4+ solutions were added to the actual samples by the standard addition method. The samples were pretreated by microwave digestion, and the prepared sensor in Example 1 was used to detect the obtained sample solutions. The analysis results are shown in Table 1

[0038] Table 1

[0039] As can be seen from Table 1, the recovery rates of the above ratio fluorescence and paper-based visual detection methods are between 95.96% and 108.16%, and the relative standard deviations are between 1.09% and 3.26%, indicating the reliability of the sensor constructed by the present invention for the detection of Sn 4+ in actual samples

[0040] In summary, the EuMOF ratio fluorescence and paper-based visual portable sensor based on the present invention can detect Sn 4+ with high sensitivity, high selectivity, accuracy and rapidity, and can be used for the determination of the content of Sn 4+ in canned fish and canned yellow peaches; in addition, the preparation cost of the fluorescence sensor of the present invention is low and the method is simple and easy to implement

[0041] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention

Claims

1. A tin ion Sn 4+ The fluorescence detection method is characterized in that The specific steps are: EuMOF powder was dispersed in DMF at 1 mg / mL, and 10 μL of the dispersion was mixed with different concentrations of Sn 4+ Mix in 2 mL system, react for 10 minutes, measure the fluorescence intensity at 430 nm and 614 nm, and take the ratio of the fluorescence intensity at 614 nm to that at 430 nm as I 614 / I 430 (y) and Sn 4+ The concentration (x) of the sample was used to establish a standard curve y = 15.378-1.001x. The Sn content in the solution to be tested was calculated based on the standard curve. 4+ concentration.

2. Sn according to claim 1 4+ The fluorescence detection method is characterized in that The excitation wavelength of the fluorescence emission spectrum is 300 nm, the emission wavelength range is 370 nm to 720 nm, the detection linear range is 0.1 to 15 μM, and the detection limit is 54.37 nM.

3. Sn according to claim 1 4+ The fluorescence detection method is characterized in that The EuMOF is composed of two ligands, 2-hydroxyterephthalic acid (HTPA) and 1,10-phenanthroline (Phen), and Eu 3+ The europium metal organic framework EuMOF was formed by coordination self-assembly, and the EuMOF exhibited HTPA and Eu at 430 nm and 614 nm, respectively. 3+ The characteristic fluorescence emission of 614 / I 430 With Sn 4+ The concentration was negatively correlated.

4. Sn according to claim 3 4+ The fluorescence detection method is characterized in that The preparation method of EuMOF is as follows: Step 1: Dissolve Eu(NO3)3·6H2O in ultrapure water, and dissolve ligands HTPA and Phen in ethanol, and both are treated by ultrasound until they are completely dissolved; Step 2: Mix the solutions obtained in step 1, stir at a constant temperature for reaction, cool to room temperature, collect the precipitate by centrifugation, and wash it three times alternately with ethanol and ultrapure water; Step 3: Dry the product after washing in step 2 to obtain the EuMOF fluorescent sensor.

5. Sn according to claim 4 4+ The fluorescence detection method is characterized in that In step 1, the mass of Eu(NO3)3·6H2O is 0.1117 g, and the volume of ultrapure water is 5 mL; the masses of HTPA and Phen are 0.0364 g and 0.0541 g, respectively, and the volume of ethanol is 15 mL.

6. Sn according to claim 4 4+ The fluorescence detection method is characterized in that In step 2, the stirring temperature is 60° C., the reaction condition is magnetic stirring in an oil bath, the reaction time is 4 hours, and the centrifugation condition is 8000 rpm for 10 minutes.

7. Sn according to claim 4 4+ The fluorescence detection method is characterized in that In the step three, the drying condition is vacuum drying at 40° C. for 12 hours.

8. A EuMOF portable test paper for detecting Sn 4+ The method is characterized in that A 5 mm × 5 mm circular filter paper was immersed in a 1 mg / mL EuMOF solution and dried at 40 °C for 30 minutes to obtain EuMOF test paper; Use the prepared test paper to measure Sn 4+ The steps for quantitative detection are as follows: The EuMOF test paper was immersed in water containing different concentrations of Sn 4+ The test paper was then photographed under UV light and its RGB value was analyzed; the R / (G+B) ratio (y) and Sn 4+ The concentration (x) of the sample was used to establish a standard curve y = 0.694-0.006x. The Sn content in the solution to be tested was calculated based on the standard curve. 4+ concentration.

9. The EuMOF portable test paper for detecting Sn according to claim 8 4+ The method is characterized in that The filter paper soaking time is 30 minutes, the wavelength of the ultraviolet lamp is 302 nm, the detection linear range is 1-100 μM, and the detection limit is 0.853 μM.

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