A terbium-tannic acid modified zeolitic imidazolate framework-8 nanoparticle, a preparation method and application thereof

Abstract

The application belongs to the field of composite materials, and particularly relates to terbium-tannic acid modified zeolitic imidazolate framework-8 nanoparticles and a preparation method and application thereof. The nanoparticles comprise zeolitic imidazolate framework-8 and a terbium-tannic acid compound modified on the surface of the zeolitic imidazolate framework-8; the terbium-tannic acid compound is Tb-TA, and the Tb-TA is modified on the surface of the ZIF-8 through electrostatic adsorption and hydrogen bonding. Compared with existing lanthanide series materials, the ZIF-8@Tb-TA contains more abundant Tb 3+ on the surface, provides a large number of DPA binding sites, and is beneficial to improve detection sensitivity. In the process of detecting DPA, other cations, anions or DPA analogs will not interfere with the detection of DPA, and the detection limit of the constructed ZIF-8@Tb-TA for DPA is 12.3 nM.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of composite materials, and particularly relates to a terbium-tannic acid modified zeolitic imidazolate framework-8 nanoparticle and a preparation method and application thereof. BACKGROUND

[0002] The anthrax spores produced by Bacillus anthracis are extremely harmful to humans and animals, and after inhaling about 10 4 anthrax spores, if not treated in time within 24 ~ 48 h, death will occur. At the same time, anthrax spores can survive in various special environments (such as high temperature, freezing, strong acid / strong base and ultraviolet radiation), and are a potential biological warfare agent. 2, 6-pyridinedicarboxylic acid (DPA) as the main component of bacterial spores has been used as a biomarker for detecting anthrax spores. At present, a large number of detection methods have been developed, including biological methods, electrochemical detection, polymerase chain reaction (PCR), surface enhanced Raman spectroscopy (SERS), etc., for the detection of DPA. However, the above methods often have the disadvantages of long detection period, complex pretreatment, expensive reagents, etc., and are not suitable for rapid and real-time detection. With the widespread concern about food safety, rapid and sensitive detection of DPA has become a research hotspot.

[0003] Zeolitic imidazolate framework-8 (ZIF-8) has highly ordered channels and pores, and has been widely used in the fields of gas storage, separation, sensing, catalysis and drug delivery, etc., thereby attracting extensive attention. However, the surface of ZIF-8 lacks high-affinity sites that can bind to lanthanides, and therefore, stable lanthanide-doped ZIF-8 (Ln-ZIF-8) cannot be formed, which greatly limits its application as a host substrate. SUMMARY

[0004] The present application provides a terbium-tannic acid modified zeolitic imidazolate framework-8 nanoparticle with strong anti-interference ability and high sensitivity to solve the problems of complex preparation method and low sensitivity of DPA detection in the prior art.

[0005] The present application also provides a preparation method of the above-mentioned terbium-tannic acid modified zeolitic imidazolate framework-8 nanoparticle.

[0006] Another object of the present application is to provide an application of the terbium-tannic acid modified zeolitic imidazolate framework-8 nanoparticle in DPA detection.

[0007] The technical scheme adopted by the present application to achieve the above-mentioned objects is as follows:

[0008] The application provides a terbium-tannic acid modified zeolitic imidazolate framework-8 nanoparticle, comprising a zeolitic imidazolate framework-8 and a terbium-tannic acid compound modified on the surface of the zeolitic imidazolate framework-8; the zeolitic imidazolate framework-8 is ZIF-8, and the terbium-tannic acid compound is Tb-TA.

[0009] Further, the terbium-tannic acid compound accounts for 1.28-2.12% of the mass of the zeolitic imidazolate framework-8 in terms of the mass of terbium ions.

[0010] The application further provides a preparation method of the terbium-tannic acid modified zeolitic imidazolate framework-8 nanoparticle.

[0011] (1) mixing a dimethyl imidazole methanol solution and a zinc nitrate methanol solution, stirring and reacting at room temperature, centrifuging to obtain the zeolitic imidazolate framework-8;

[0012] (2) taking the zeolitic imidazolate framework-8 and dispersing in a mixed solution of methanol and water to obtain a solution A;

[0013] (3) adding a tannic acid aqueous solution to the solution A under stirring, stirring at room temperature to obtain a solution B;

[0014] (4) adding a terbium chloride aqueous solution to the solution B under stirring, stirring at room temperature, and centrifuging and washing to obtain the ZIF-8@Tb-TA.

[0015] Further, in step (1), the mixing molar ratio of the dimethyl imidazole and the zinc nitrate is 2-5:1; the concentration of the dimethyl imidazole methanol solution is 0.03-0.05 g / mL; the concentration of the zinc nitrate methanol solution is 0.04-0.06 g / mL; and the stirring time is 30 min.

[0016] Further, in step (2), the volume ratio of the methanol and the water in the mixture is 2-4:1; and the concentration of the solution A is 0.35-0.5 mg / mL.

[0017] Further, in step (3), the ratio of the tannic acid aqueous solution (24 mmol / L) and the zeolitic imidazolate framework-8 is 10-20 μL:1-3 mg; and the stirring time is 3-10 min.

[0018] Further, in step (4), 10 μL of the terbium chloride aqueous solution with a concentration of 10 mg / mL-50 mg / mL is added to every milligram of the zeolitic imidazolate framework-8; and the stirring time at room temperature is 5-15 min.

[0019] This invention also provides the application of terbium-tannic acid modified zeolite imidazole framework-8 nanoparticles in the detection of DPA.

[0020] The specific process for detecting DPA using the nanoparticles provided by this invention is as follows:

[0021] (1) Preparation of DPA dilution sample: Dissolve solid DPA in fetal bovine serum diluted 10 times to prepare DPA with a concentration of 8 μM. Use this as the DPA sample to be tested. Take 10 μL of DPA with a concentration of 8 μM into centrifuge tube A.

[0022] (2) Binding of DPA with ZIF-8@Tb-TA: Resuspend ZIF-8@Tb-TA in HEPES buffer to prepare a suspension; add the ZIF-8@Tb-TA suspension to centrifuge tube A containing DPA, mix well, and react at room temperature in the dark.

[0023] (3) Detection of DPA: After the reaction is completed, the mixture is mixed and added to a glass dish. The emission spectrum of the ZIF-8@Tb-TA~DPA complex is measured by a fluorometer under excitation light of 345 nm to determine the concentration of DPA.

[0024] Furthermore, in step (2), the pH of the HEPES buffer is 3~10 and the concentration is 10~20 mM; the ZIF-8@Tb-TA is resuspended in the HEPES buffer and the concentration of the prepared suspension is 0.3~0.5 mg / mL; the time of the light-protected reaction is 20~120 s.

[0025] This invention uses tannic acid (TA) as a negative charge source to modify the surface of ZIF-8 to prepare tannic acid-zeolite imidazole structured nanoparticles; terbium chloride (TbCl3) is used as the Tb... 3+ Terbium-tannic acid-modified zeolite-imidazolium framework-8 nanoparticles were prepared by modifying the surface of tannic acid-zeolite-imidazolium framework nanoparticles. The binding of DPA to these nanoparticles was promoted in HEPES buffer solution, primarily due to the Tb content. 3+ Tb is an unsaturated coordination compound with the hydroxyl group. 3+ The remaining coordination sites of the ions may be occupied by H2O molecules, leading to a weakening of the fluorescence intensity of ZIF-8@Tb-TA in buffer solution. With the addition of DPA, the unique molecular structure of DPA can replace H2O molecules and bind to Tb. 3+ The ions coordinate to form a Tb-DPA complex, which excites strong green fluorescence from Tb ions; finally, at an excitation wavelength of 345 nm, the ZIF-8@Tb-TA~DPA complex excites four emission bands (483 nm ( 5 D4–7 F6), 544 nm ( 5 D4- 7 F5), 556 nm ( 5 D4- 7 F4), and 622 nm ( 5 D4- 7 F3), so that the fluorescence intensities of the four emission spectra are different at different concentrations, and sensitive detection of DPA is achieved.

[0026] The terbium ion in the terbium-tannic acid complex can form a stable coordination bond (O-Tb-O) with the oxygen atom in the DPA molecule. Therefore, the coordination of the Tb as a coordination atom with the DPA molecules in the solution forms the ZIF-8@Tb-TA~DPA complex, energy transfer occurs, which is conducive to exciting the fluorescence of the terbium ion. Compared with the terbium ion directly electrostatically adsorbed on the surface of the nanomaterial, the use of double coordination to detect DPA is conducive to exposing more Tb recognition sites, and the adsorbed DPA is not easy to fall off from the surface of the nanoparticle, which is more conducive to improving the detection sensitivity.

[0027] Compared with the prior art, the present application has the following remarkable advantages:

[0028] (1) The present application adopts terbium-tannic acid modified zeolite imidazole framework-8 nanoparticles ZIF-8@Tb-TA, and the obtained ZIF-8@Tb-TA has the characteristics of uniform particle size, uniform thickness of the surface Tb-TA layer and good stability;

[0029] (2) The ZIF-8@Tb-TA prepared by the present application has more abundant Tb 3+ on the surface compared with the existing lanthanide series materials in the application of DPA detection, which provides a large number of DPA binding sites and is conducive to improving the detection sensitivity. In the process of detecting DPA, other cations, anions or DPA analogues will not interfere with the detection of DPA, and the detection limit of the constructed ZIF-8@Tb-TA for DPA is 12.3 nM. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic diagram of the preparation process of ZIF-8@Tb-TA and its application in DPA detection;

[0031] Figure 2 is a TEM diagram of ZIF-8 and ZIF-8@Tb-TA prepared in Example 1 of the present application;

[0032] Figure 3 is an element mapping diagram of ZIF-8@Tb-TA prepared in Example 1 of the present application;

[0033] Figure 4 The fluorescence intensity fold line graph of ZIF-8@Tb-TA for detecting DPA with the concentration modification of terbium chloride in the embodiment 2 of the application;

[0034] Figure 5 The fluorescence intensity fold line graph of ZIF-8@Tb-TA for detecting DPA with different pH values of HEPES buffer in the embodiment 3 of the application;

[0035] Figure 6 The fold line graph of ZIF-8@Tb-TA for detecting the effect of different concentrations of DPA in the embodiment 4 of the application;

[0036] Figure 7 The column chart of ZIF-8@Tb-TA for detecting the anti-interference ability of DPA in the embodiment 5 of the application. DETAILED DESCRIPTION

[0037] The technical solutions of the application will be further described below with reference to the drawings.

[0038] Embodiment 1

[0039] The preparation method of terbium-tannic acid modified zeolitic imidazolate framework-8 nanoparticles is as follows:

[0040] (1) 20 mL of 0.041 g / mL dimethyl imidazole methanol solution and 20 mL of 0.038 g / mL zinc nitrate methanol solution are mixed, wherein the mixed molar ratio of dimethyl imidazole and zinc nitrate is 2:1, the above mixed solution is stirred at room temperature for 30 min, and ZIF-8 nanoparticles are obtained by centrifugation after the reaction is completed;

[0041] (2) 1 mg of ZIF-8 nanoparticles is dispersed in 2 mL of a mixed solution of methanol and water, wherein the mixed volume ratio of methanol and water is 4:1; the above solution is placed in an ultrasonic instrument and ultrasonically treated for 5 min; then 10 μL of tannic acid (TA) aqueous solution (24 mmol / L) and 10 μL of terbium chloride aqueous solution are added to the above solution under stirring, and stirring reaction is performed for 5 min; after the reaction is completed, the precipitate is obtained by centrifugation, washed with water for 3 times, and finally placed in a vacuum drying box for drying at 50°C for 12 h to obtain terbium-tannic acid modified zeolitic imidazolate framework-8 nanoparticles ZIF-8@Tb-TA.

[0042] The characterization of ZIF-8@Tb-TA is as follows: Figure 2 It can be seen from the TEM images of ZIF-8 and ZIF-8@Tb-TA in the above table that the particles of ZIF-8 and ZIF-8@Tb-TA are uniformly distributed, and the particle sizes of single particles are about 67 nm and 76 nm, respectively.Figure 3 The elemental mapping spectrum of ZIF-8@Tb-TA shows that Tb and O elements are uniformly distributed on the surface of ZIF-8@Tb-TA, indicating that ZIF-8 has been successfully modified with tannic acid and terbium chloride, and that it has abundant Tb. 3+ .

[0043] Example 2

[0044] Determining the use of ZIF-8@Tb-TA modified with different amounts of terbium chloride for the detection of DPA:

[0045] In this embodiment, the effects of different amounts of terbium ion (10 μL) modified ZIF-8@Tb-TA on DPA detection and capture are mainly investigated. The specific experimental steps are as follows:

[0046] A gradient of terbium chloride concentrations was set up, using terbium chloride at concentrations of 10 mg / mL, 20 mg / mL, 30 mg / mL, 40 mg / mL, and 50 mg / mL for subsequent DPA detection.

[0047] 10 μM DPA was placed in a 1.5 mL centrifuge tube. Subsequently, different amounts of terbium-modified ZIF-8@Tb-TA were resuspended in 800 μL HEPES buffer to form suspensions of 0.3 mg / mL. This suspension was then added to a 1.5 mL centrifuge tube containing DPA and inverted for 2 min at room temperature to bind. The fluorescence intensity of the solutions in different centrifuge tubes was measured using a fluorophotometer. Under an excitation spectrum of 345 nm, the fluorescence intensity values ​​at the emission wavelength of 483 nm were mainly recorded.

[0048] from Figure 4 It can be seen that the ZIF-8@Tb-TA~DPA complex exhibits the highest fluorescence intensity when the terbium chloride concentration is 30 mg / mL, and the fluorescence intensity is not significantly increased when the terbium chloride concentration is too high.

[0049] Example 3

[0050] Determine the pH of the HEPES buffer for ZIF-8@Tb-TA to detect DPA:

[0051] In this embodiment, the effect of the pH value of HEPES buffer on the detection of DPA by ZIF-8@Tb-TA is mainly investigated. The specific experimental steps are as follows:

[0052] A pH gradient was set in the HEPES buffer solution to achieve pH values ​​of 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0, which were used for subsequent ZIF-8@Tb-TA detection experiments on DPA.

[0053] Take 10 μM of DPA in a 1.5 mL centrifuge tube; then, the ZIF-8@Tb-TA prepared in Example 1 is resuspended in 800 μL of HEPES buffer to form a 0.3 mg / mL suspension, and the suspension is added to the 1.5 mL centrifuge tube containing DPA, and mixed uniformly by inverting at room temperature for 2 min.

[0054] The fluorescence intensity of the solution in different centrifuge tubes is measured by a fluorescence spectrometer, and the fluorescence intensity value at an emission wavelength of 483 nm is mainly recorded under an excitation spectrum of 345 nm.

[0055] Figure 5 The experimental results show that as the pH value of the HEPES buffer increases from 5.0 to 7.4, the fluorescence intensity of the ZIF-8@Tb-TA~DPA complex increases, and then, as the pH value increases from 8.0 to 10.0, the fluorescence intensity of the ZIF-8@Tb-TA~DPA complex increases slowly, and the fluorescence intensity at 7.4 is the strongest. Therefore, the optimal binding buffer pH for detecting DPA using ZIF-8@Tb-TA in subsequent experiments is 7.4.

[0056] Example 4

[0057] The detection effect of ZIF-8@Tb-TA for different concentrations of DPA is determined.

[0058] In this embodiment, the effect of ZIF-8@Tb-TA on the detection of different concentrations of DPA is mainly discussed, and the specific experimental steps are as follows:

[0059] The concentration of DPA is 0 μM, 0.1 μM, 0.2 μM, 0.5 μM, 1 μM, 4 μM, 8 μM, 12 μM, which is used for subsequent detection experiments of DPA.

[0060] Take 10 μM of DPA in a 1.5 mL centrifuge tube; then, the ZIF-8@Tb-TA prepared in Example 1 is resuspended in 800 μL of HEPES buffer to form a 0.3 mg / mL suspension, and the suspension is added to the 1.5 mL centrifuge tube containing DPA, and mixed uniformly by inverting at room temperature for 2 min.

[0061] The fluorescence intensity of the solution in different centrifuge tubes is measured by a fluorescence spectrometer, and the fluorescence intensity value at an emission wavelength of 483 nm is mainly recorded under an excitation spectrum of 345 nm.

[0062] Figure 6The experimental results show that the fluorescence intensity of the ZIF-8@Tb-TA~DPA complex gradually increases as the concentration of DPA increases from 0.1 μM to 12 μM, and therefore, the linear range of detection is 0 ~ 10 μM; in addition, the minimum detection limit of ZIF-8@Tb-TA for DPA is 12.3 nM.

[0063] Example 5

[0064] The anti-interference ability of ZIF-8@Tb-TA in detecting DPA is determined.

[0065] In this embodiment, different interference substances (Ca 2+ , Mg 2+ , Cl - , CO3 2- , phenylalanine (Phe), terephthalic acid (p-PA)) are added to the DPA solution to be detected to determine the specificity of ZIF-8@Tb-TA for DPA detection.

[0066] 10 μM of DPA is taken in a 1.5 mL centrifuge tube; then, ZIF-8@Tb-TA prepared in Example 1 is resuspended in 800 μL of HEPES buffer to form a 0.3 mg / mL suspension, a 0.3 mg / mL suspension is formed, and the suspension is added to the 1.5 mL centrifuge tube containing DPA, and the mixture is combined by inverting at room temperature for 2 min.

[0067] The fluorescence intensity of the solution in different centrifuge tubes is measured by a fluorescence spectrometer, and the fluorescence intensity value at an emission wavelength of 483 nm is mainly recorded under an excitation spectrum of 345 nm.

[0068] Figure 7 The experimental results show that different interference substances cannot be combined with ZIF-8@Tb-TA to excite strong fluorescence, and at the same time, the mixed solution of the interference substances and DPA can excite strong fluorescence after being incubated with ZIF-8@Tb-TA, which shows that the presence of the interference substances does not affect the detection of DPA by ZIF-8@Tb-TA.

[0069] In summary, the ZIF-8@Tb-TA prepared in the application can realize sensitive detection of DPA under the condition that the terbium chloride concentration is 30 mg / mL and the reaction buffer pH of ZIF-8@Tb-TA and DPA is 7.4, and has strong anti-interference ability, and therefore, the ZIF-8@Tb-TA has considerable application prospects for sensitive and rapid detection of DPA.

Claims

1. A method for preparing terbium-tannic acid modified zeolite imidazole framework-8 nanoparticles, characterized in that, The zeolite imidazole framework-8 nanoparticles include zeolite imidazole framework-8 and a terbium-tannic acid complex modified on the surface of zeolite imidazole framework-8; the zeolite imidazole framework-8 is ZIF-8, and the terbium-tannic acid complex is Tb-TA, which is modified on the surface of ZIF-8 by electrostatic adsorption and hydrogen bonding. Specifically, the following steps are included: (1) After mixing the methanol solution of dimethylimidazolium with the methanol solution of zinc nitrate, the mixture was stirred at room temperature. After the reaction was completed, the mixture was centrifuged to obtain zeolite imidazolium framework-8. (2) Take zeolite imidazole framework-8 dispersed in a methanol-water mixed solution and sonicate to obtain solution A; (3) Under stirring conditions, add tannic acid aqueous solution to solution A and stir at room temperature to obtain solution B; (4) Under stirring conditions, terbium chloride aqueous solution was added to solution B, stirred at room temperature, and after centrifugation and washing, ZIF-8@Tb-TA was obtained.

2. The terbium-tannic acid-modified zeolite imidazole framework-8 nanoparticles according to claim 1, characterized in that, The terbium-tannic acid complex contains 1.28 to 2.12% of the mass of zeolite imidazole framework-8 based on the mass of terbium ions.

3. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of dimethylimidazole to zinc nitrate is 2 to 5:1; the concentration of the methanol solution of dimethylimidazole is 0.03 to 0.05 g / mL; the concentration of the methanol solution of zinc nitrate is 0.04 to 0.06 g / mL; and the stirring time is 30 min.

4. The preparation method according to claim 1 or 2, characterized in that, In step (2), the volume ratio of methanol to water is 2 to 4:1; the concentration of solution A is 0.35 to 0.5 mg / mL.

5. According to the preparation method of claim 1, in step (3), the concentration of the tannic acid aqueous solution is 24 mmol / L; the ratio of the tannic acid aqueous solution to zeolite imidazole framework-8 is 10 ~ 20 μL: 1 ~ 3 mg; and the stirring time is 3 ~ 10 min.

6. The preparation method according to claim 1, characterized in that, In step (4), 10 μL of terbium chloride aqueous solution of 10 mg / mL to 50 mg / mL is added to each milligram of zeolite imidazole framework-8; the stirring time at room temperature is 5 to 15 min.

7. The application of terbium-tannic acid-modified zeolite imidazole framework-8 nanoparticles prepared by the preparation method according to any one of claims 1-6 in the detection of DPA.

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