A dual-emission metal-organic framework composite nanomaterial and its application in ratiometric detection of tetracycline antibiotics

Abstract

The present invention discloses a dual-emission metal organic framework composite nanomaterial and its application in ratiometric detection of tetracycline antibiotics. The dual-emission metal organic framework composite nanomaterial is loaded with blue carbon quantum dots, adenosine-5'-monophosphate sodium salt and Eu 3+ The UiO-66 metal organic framework material has a size of 20 to 50 nm. The present invention uses adenosine-5'-monophosphate sodium salt to modify the metal organic framework, which increases the rigidity of the material and ensures the Eu 3+ The stable loading of carbon quantum dots into a metal-organic framework material overcomes the difficulty of separating carbon quantum dots in practical applications. The composite nanomaterial utilizes the pre-enrichment effect of the metal-organic framework, using the blue carbon quantum dot signal as a reference signal and the red europium signal as a response signal to achieve ratiometric detection of tetracycline antibiotics. This method offers the advantages of high sensitivity and fast response speed, with a detection limit of 5.6 nM for tetracycline and a response time of only 10 seconds.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterial preparation and chemical analysis detection, and particularly relates to a dual-emission metal-organic framework composite nanomaterial and an application thereof in ratiometric detection of tetracycline antibiotics. Background Art

[0002] Tetracycline antibiotics were once widely used because they are cheap and easy to produce. Tetracycline antibiotics are difficult to biodegrade in the environment. Their accumulation in the natural environment can produce biological toxicity, causing microorganisms to develop bacterial resistance and disrupting the ecological balance. Residues in food can cause liver damage, neurological diseases and other diseases in humans. Existing studies have shown that tetracycline antibiotics are detected downstream of sewage treatment plants, marine aquaculture farms, drinking water sources, groundwater, surface water, etc., and there is a need to establish a rapid and accurate detection method. Current methods for detecting tetracycline antibiotics include high-performance liquid chromatography, liquid chromatography-mass spectrometry, enzyme-linked immunosorbent assay, capillary electrophoresis, etc. These detection methods rely on large-scale instruments and equipment, require professional technicians to operate, and are complex and time-consuming. Therefore, there is a need for a rapid, convenient, and low-cost detection method to detect low levels of antibiotics in the environment.

[0003] Synthesizing metal-organic frameworks (MOFs) with excellent fluorescence properties provides an effective strategy for the accurate determination of various trace substances. However, most MOFs reported so far use a single signal for detection, which is easily affected by environmental and instrumental noise, resulting in low accuracy of the detection results. Summary of the Invention

[0004] In response to the shortcomings of current technologies, the present invention provides a dual-emission metal-organic framework composite nanomaterial with dual signal response and rapid ratiometric detection of tetracycline antibiotics.

[0005] The dual-emission metal organic framework composite nanomaterial provided by the present invention is a UiO-66 metal organic framework (AMP-UiO-66@CDs) with internal blue carbon quantum dots (CDs) and adenosine-5'-monophosphate sodium salt (AMP) prepared by a solvothermal method as a carrier, using Eu 3+ The coordination effect between Eu and the carrier 3+ The dual-emission metal organic framework composite nanomaterial (AMP-UiO-66@CDs@Eu 3+ ).

[0006] The preparation method of the dual-emission metal-organic framework composite nanomaterial provided by the present invention comprises the following steps:

[0007] Step 1: Dissolve citric acid and polyethyleneimine in deionized water, then transfer the resulting mixture to a polytetrafluoroethylene high-pressure reactor, react at 120-150°C under closed conditions for 1-2 hours, naturally cool to room temperature, dialyze to obtain a carbon quantum dot aqueous solution, and freeze-dry to obtain carbon quantum dots.

[0008] Step 2: Zirconium tetrachloride, terephthalic acid, carbon quantum dots, and adenosine-5'-monophosphate sodium salt are mixed in N,N-dimethylformamide, uniformly dispersed, added with glacial acetic acid, and stirred at room temperature for 3 to 4 hours. The mixture is then transferred to a polytetrafluoroethylene autoclave and reacted at 120 to 150°C under closed conditions for 15 to 20 hours. After naturally cooling to room temperature, the mixture is centrifuged and washed, and the precipitate is collected and freeze-dried to obtain UiO-66 metal-organic framework composite nanomaterials loaded with blue carbon quantum dots and adenosine-5'-monophosphate sodium salt (AMP-UiO-66@CDs).

[0009] Step 3: AMP-UiO-66@CDs was added to deionized water and ultrasonicated to obtain a dispersion; then citric acid activation solution was added to the dispersion, and the mixture was stirred at room temperature for 4 to 6 hours. After the reaction was completed, the precipitate was collected by centrifugation, and the precipitate was dispersed in ethanol, and europium chloride hexahydrate was added. The mixture was stirred at 70 to 80 ° C for 5 to 6 hours; after the reaction was completed, the mixture was cooled to room temperature, centrifuged, washed, and finally freeze-dried to obtain a light yellow powdery dual-emission UiO-66 metal organic framework composite nanomaterial (AMP-UiO-66@CDs@Eu 3+ ).

[0010] Furthermore, in the above step 1, the mass ratio of polyethyleneimine to citric acid is 1:5-10, and the average molecular weight of polyethyleneimine is 600-10000 Da.

[0011] Furthermore, in step 1, the dialysis bag with a molecular weight cut-off of 10KDa was used for 48 hours.

[0012] Furthermore, in the above step 2, the mass ratio of the zirconium tetrachloride to terephthalic acid, carbon quantum dots, and adenosine-5'-monophosphate sodium salt is 6-12:4-9:1:6-14; the volume ratio of the N,N-dimethylformamide to glacial acetic acid is 5-10:1; and the mass ratio of the zirconium tetrachloride to glacial acetic acid is 1:10-18.

[0013] Furthermore, in the above step 3, the volume ratio of the citric acid activation solution to the dispersion solution is 1:1-8, and the mass ratio of the AMP-UiO-66@CDs to europium chloride hexahydrate is 1:1-5.

[0014] Furthermore, in the above step 3, the citric acid activation solution is a mixed aqueous solution of citric acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide in a mass ratio of 6:1:1.

[0015] The dual-emission metal-organic framework composite nanomaterial provided by the present invention can be used for rapid detection of tetracycline antibiotics. The specific detection method includes the following steps:

[0016] Step 1: Ultrasonic dispersion of the dual-emission metal-organic framework composite nanomaterial in a sodium carbonate-sodium bicarbonate buffer solution to obtain a stock solution; measuring the fluorescence intensity and spectrum of the stock solution under λex = 350nm excitation and λem in the range of 380-680nm; then adding tetracycline antibiotic standard solutions of different known concentrations, and again measuring the fluorescence intensity and spectral changes of the system, the fluorescence intensity is recorded as F 450 and F 617 ; Calculate the fluorescence intensity ratio F of the system 617 / F 450 , and plot the fluorescence intensity ratio F 617 / F 450 Standard curve with varying concentrations of tetracycline antibiotics.

[0017] Step 2: Measure the fluorescence spectrum and intensity of the tetracycline antibiotic sample according to the method in step 1, and determine the concentration of the tetracycline antibiotic in the sample by combining the linear equation of the standard curve.

[0018] In the above detection method, preferably, the concentration of the dual-emission metal-organic framework composite nanomaterial in the stock solution is 0.01-0.05 mg / mL; and the pH value of the sodium carbonate-sodium bicarbonate buffer solution is 9.0-9.5.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. The present invention uses zirconium tetrachloride as a metal unit, terephthalic acid as an organic ligand, and is mixed with blue carbon quantum dots and adenosine-5'-monophosphate sodium salt to prepare a carbon quantum dot and adenosine-5'-monophosphate sodium salt functionalized UiO-66 metal organic framework composite material by a solvent thermal method; then Eu 3+ The coordination effect between Eu and the carrier 3+It is further loaded on the surface of the carrier to obtain a dual-emission metal-organic framework composite nanomaterial. The dual-emission metal-organic framework composite nanomaterial encapsulates blue carbon quantum dots inside the organic framework. Due to the shielding and protection of the matrix material, tetracycline antibiotics have little effect on the fluorescence of blue carbon quantum dots, but based on the "antenna effect", the fluorescence of red europium is significantly enhanced. Accordingly, the present invention provides a dual-emission metal-organic framework composite nanomaterial that can be used for the ratio detection of tetracycline antibiotics. The present invention uses adenosine-5'-monophosphate sodium salt to modify the metal organic framework, which increases the rigidity of the material and ensures that Eu 3+ Stable loading; loading carbon quantum dots onto metal-organic frameworks solves the problem of difficult separation of carbon quantum dots in practical applications.

[0021] 2. The dual-emission metal-organic framework composite nanomaterial of the present invention was used to detect tetracycline antibiotics. As the concentration of tetracycline antibiotics increased, the fluorescence of the blue carbon quantum dots decreased slightly, while the fluorescence of the red europium significantly increased. The rich microporous structure and organic functional groups in the metal-organic framework material effectively pre-enriched tetracycline antibiotics, greatly improving detection sensitivity and analysis speed. Compared with traditional detection methods, the analysis speed was faster and more sensitive, with a detection limit of as low as 5.6 nM for tetracycline and a response time of only 10 seconds. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 AMP-UiO-66@CDs@Eu prepared in Example 1 3+ TEM image of.

[0023] Figure 2 AMP-UiO-66@CDs@Eu prepared in Example 1 3+ EDC energy spectrum distribution diagram.

[0024] Figure 3 AMP-UiO-66@CDs@Eu prepared in Example 1 3+ Emission spectra at different excitation wavelengths.

[0025] Figure 4 AMP-UiO-66@CDs@Eu prepared in Example 1 3+ The corresponding fluorescence spectrum changes after adding different concentrations of tetracycline.

[0026] Figure 5 AMP-UiO-66@CDs@Eu prepared in Example 1 3+ Standard curve of the relationship between the fluorescence intensity ratio and tetracycline concentration.

[0027] Figure 6AMP-UiO-66@CDs@Eu prepared in Example 1 3+ The fluorescence spectrum of α-tetracycline (α-tetracycline) changes with time after adding tetracycline (final concentration of the system is 5 μM).

[0028] Figure 7 AMP-UiO-66@CDs@Eu prepared in Example 1 3+ Selectivity diagram for different substances. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can more clearly understand the present invention. However, the following should not be construed as limiting the scope of protection claimed in the claims of the present invention. Example 1

[0030] The dual-emission metal-organic framework composite nanomaterial of this embodiment is prepared by a solvent method using zirconium tetrachloride as a metal unit and terephthalic acid as an organic ligand. In the process of generating the UiO-66 metal-organic framework material, blue carbon quantum dots and adenosine-5'-monophosphate sodium salt are simultaneously coated. On this basis, red europium is further loaded. The preparation method of the dual-emission metal-organic framework composite nanomaterial is as follows:

[0031] Step 1: Dissolve 1g of citric acid and 0.1g of polyethyleneimine (average molecular weight of 10,000Da) in 15mL of ultrapure water, stir continuously for 3 to 5 minutes to fully mix them, then transfer the resulting mixture to a polytetrafluoroethylene-lined high-pressure reactor and heat the reaction at 150°C under closed conditions for 1.5 hours; after the reaction is completed, naturally cool to room temperature, transfer the reaction solution to a dialysis bag with a molecular weight cutoff of 10KDa and dialyze for 48 hours to obtain a carbon quantum dot aqueous solution. After freeze-drying, blue carbon quantum dots (CDs) are obtained.

[0032] 2. Take 0.116g of zirconium tetrachloride and dissolve it in 15mL of N,N-dimethylformamide (DMF). Then add 0.084g of terephthalic acid. After ultrasonication for 5 minutes, add 10mg of CDs and 0.132g of adenosine-5'-monophosphate sodium salt (AMP) in sequence. After uniform dispersion, add 2mL of glacial acetic acid. After continuous stirring at room temperature for 3 hours, the mixture is transferred to a polytetrafluoroethylene-lined autoclave and heated at 120℃ for 20 hours under closed conditions. After the reaction is completed, it is naturally cooled to room temperature, centrifuged, and washed twice with anhydrous ethanol and water respectively. The precipitate is collected and freeze-dried to obtain AMP-UiO-66@CDs.

[0033] 3. Weigh 10 mg of AMP-UiO-66@CDs and add it to 10 mL of deionized water. After ultrasonication, a dispersion was obtained. Then, 2 mL of citric acid activation solution (2 mL of a mixed aqueous solution containing 60 mg of citric acid, 10 mg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 10 mg of N-hydroxysuccinimide) was added. After stirring at room temperature for 4 hours, the mixture was centrifuged and washed twice with anhydrous ethanol and ultrapure water, respectively, and the precipitate was collected. The obtained precipitate was ultrasonically dispersed in 10 mL of anhydrous ethanol, 15 mg of europium chloride hexahydrate was added, the mixture was thoroughly mixed, and the mixture was stirred and reacted at 70 ° C for 5 hours. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the precipitate was washed twice with ultrapure water. After vacuum drying, a light yellow powder AMP-UiO-66@CDs@Eu was obtained. 3+ .

[0034] Depend on Figure 1 It can be seen that AMP-UiO-66@CDs@Eu 3+ It is spherical and has a size of about 20 to 50 nm. Figure 2 is the energy spectrum distribution diagram obtained using a transmission electron microscope. Figure 2 DisplayAMP-UiO-66@CDs@Eu 3+ The composite material is composed of Zr, Cl, P, Eu, C, N and O elements, and each element is basically evenly dispersed in the composite material. Figure 3 Show AMP-UiO-66@CDs@Eu 3+ It has two characteristic emission peaks, of which the characteristic emission peak at around 450nm shows an excitation wavelength-dependent characteristic, that is, as the excitation wavelength gradually redshifts, the maximum emission wavelength also redshifts. When the excitation wavelength is 350nm, the emission peak is the strongest. This property is a unique property of carbon quantum dots. The results show that carbon quantum dots have been successfully loaded into the UiO-66 metal-organic framework material; a weaker emission peak appears at 617 nm, which is Eu 3+ The characteristic emission peak of AMP-UiO-66@CDs@Eu 3+ Successfully prepared. Example 2

[0035] AMP-UiO-66@CDs@Eu prepared in Example 1 3+ Application of rapid detection of tetracycline

[0036] Weigh 5 mg of AMP-UiO-66@CDs@Eu 3+Add to 250mL of sodium carbonate-sodium bicarbonate buffer solution with a pH of 9.17, and ultrasonicate for 10 minutes to evenly disperse it to obtain a stock solution. Measure the fluorescence intensity and spectrum of 2mL of the stock solution with the instrument slit width set to 5nm, λex=350nm excitation, and λem range of 380~680nm. Then, add a series of tetracycline standard solutions of known concentrations (the final concentrations of the system are 0.05, 0.1, 0.5, 1, 3, 5, 7, 10, 14, 16, 18, 22, 26 and 30µM) to the 2mL stock solution, and measure the fluorescence intensity and spectral changes of the system again. The fluorescence intensity is recorded as F 450 and F 617 ; Calculate the fluorescence intensity ratio F of the system 617 / F 450 , establish the fluorescence intensity ratio F 617 / F 450 The linear relationship between the concentration of tetracycline and C was obtained, and a standard curve and linear equation for rapid detection of tetracycline were obtained.

[0037] like Figure 4 As shown in the figure, when the concentration of tetracycline changes from 0 to 30 μM, AMP-UiO-66@CDs@Eu 3+ The fluorescence intensity at 617nm increased significantly with the increase of tetracycline concentration, while the fluorescence intensity at 450nm decreased slightly. With the tetracycline concentration C as the horizontal axis, the fluorescence intensity ratio F 617 / F 450 As the vertical axis, the standard curve is obtained. Figure 5 It can be seen that the tetracycline concentration has a good linear correlation in the range of 0.01 to 16 μM. The linear equation is: y = 2.1080x + 1.1567, and the correlation coefficient is R 2 =0.9923, the linear equation of tetracycline concentration in the range of 16-30 μM is: y=0.6700x+22.340, and the correlation coefficient is R 2 =0.9964, the detection limit is 5.6nM. Figure 6 It can be seen that when the concentration of tetracycline is 5 μM and AMP-UiO-66@CDs@Eu 3+ After the reaction, the fluorescence at 617nm was significantly enhanced within 10s. 3+ When used to determine tetracycline, the analysis speed is only about 10 seconds. Figure 7 The AMP-UiO-66@CDs@Eu 3+ When used to determine tetracycline antibiotics, tetracycline antibiotics (represented by tetracycline, oxytetracycline, and doxycycline) significantly change the ratio of the fluorescence intensity of the system; however, metal ions (Al 3+ 、Zn2+ , Ca 2+ 、Cu 2+ Mg 2+ 、Fe 3+ As a representative, amino acids (L-lysine, L-serine, D-aspartic acid), sugars (glucose, lactose), and other antibiotics (ampicillin, azithromycin, gentamicin, streptomycin sulfate, neomycin sulfate, kanamycin, amoxicillin) were added, and the ratio of the fluorescence intensity of the system remained basically unchanged. This shows that the AMP-UiO-66@CDs@Eu 3+ It has good selectivity for the determination of tetracycline antibiotics.

[0038] The fluorescence spectrum and intensity of the tetracycline sample to be tested are measured according to the above method, and the concentration of tetracycline in the sample to be tested can be determined by combining the linear equation of the standard curve.

Claims

1. A dual-emission metal-organic framework composite nanomaterial, characterized by: The composite nanomaterial is prepared by a solvothermal method and uses a UiO-66 metal organic framework loaded with blue carbon quantum dots and adenosine-5'-monophosphate sodium salt as a carrier. 3+ The coordination effect between Eu and the carrier 3+ The obtained powder is further loaded on the surface of the carrier to form a light yellow powder with a size of 20 to 50 nm.

2. The dual-emission metal-organic framework composite nanomaterial according to claim 1, characterized in that The composite nanomaterial is prepared by the following method: Step 1: Dissolve citric acid and polyethyleneimine in deionized water, then transfer the resulting mixture into a polytetrafluoroethylene autoclave, react at 120-150°C for 1-2 hours under closed conditions, cool naturally to room temperature, dialyze to obtain a carbon quantum dot aqueous solution, and freeze-dry to obtain carbon quantum dots; Step 2: zirconium tetrachloride, terephthalic acid, carbon quantum dots, and adenosine-5'-monophosphate sodium salt are mixed in N,N-dimethylformamide, uniformly dispersed, glacial acetic acid is added, and the mixture is stirred at room temperature for 3 to 4 hours. The mixture is then transferred to a polytetrafluoroethylene autoclave and reacted at 120 to 150° C. under closed conditions for 15 to 20 hours. After naturally cooling to room temperature, the mixture is centrifuged and washed, and the precipitate is collected and freeze-dried to obtain a UiO-66 metal-organic framework composite nanomaterial loaded with blue carbon quantum dots and adenosine-5'-monophosphate sodium salt. Step 3: Adding the UiO-66 metal-organic framework composite nanomaterial loaded with blue carbon quantum dots and adenosine-5'-monophosphate sodium salt to deionized water, and obtaining a dispersion after ultrasonication; then adding citric acid activation solution to the dispersion, stirring and reacting at room temperature for 4 to 6 hours, collecting the precipitate by centrifugation after the reaction is completed, dispersing the precipitate in ethanol, adding europium chloride hexahydrate, and continuously stirring and reacting at 70 to 80° C. for 5 to 6 hours; cooling to room temperature after the reaction is completed, centrifuging, washing the precipitate, and finally freeze-drying to obtain a light yellow powdery dual-emission UiO-66 metal-organic framework composite nanomaterial.

3. The dual-emission metal-organic framework composite nanomaterial according to claim 2, characterized in that: In step 1, the mass ratio of polyethyleneimine to citric acid is 1:5-10, and the average molecular weight of polyethyleneimine is 600-10000 Da.

4. The dual-emission metal-organic framework composite nanomaterial according to claim 2, characterized in that: In step 1, the dialysis was performed using a dialysis bag with a molecular weight cut-off of 10 KDa for 48 hours.

5. The dual-emission metal-organic framework composite nanomaterial according to claim 2, characterized in that: In step 2, the mass ratio of the zirconium tetrachloride to terephthalic acid, carbon quantum dots, and adenosine-5'-monophosphate sodium salt is 6-12:4-9:1:6-14; the volume ratio of the N,N-dimethylformamide to glacial acetic acid is 5-10:1; and the mass ratio of the zirconium tetrachloride to glacial acetic acid is 1:10-18.

6. The dual-emission metal-organic framework composite nanomaterial according to claim 2, characterized in that: In step 3, the volume ratio of the citric acid activation solution to the dispersion is 1:1-8, and the mass ratio of the UiO-66 metal organic framework composite nanomaterial loaded with blue carbon quantum dots and adenosine-5'-monophosphate sodium salt to europium chloride hexahydrate is 1:1-5.

7. The dual-emission metal-organic framework composite nanomaterial according to claim 2 or 6, characterized in that: In step 3, the citric acid activation solution is a mixed aqueous solution of citric acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide in a mass ratio of 6:1:

1.

8. Use of the dual-emission metal-organic framework composite nanomaterial according to claim 1 in ratiometric detection of tetracycline antibiotics.

9. Use of the dual-emission metal-organic framework composite nanomaterial according to claim 8 in ratiometric detection of tetracycline antibiotics, characterized in that: Step 1: Ultrasonic dispersion of the dual-emission metal-organic framework composite nanomaterial in a sodium carbonate-sodium bicarbonate buffer solution to obtain a stock solution; measuring the fluorescence intensity and spectrum of the stock solution under λex = 350nm excitation and λem in the range of 380-680nm; then adding tetracycline antibiotic standard solutions of different known concentrations, and again measuring the fluorescence intensity and spectral changes of the system, and recording the fluorescence intensity as F 450 and F 617 ; Calculate the fluorescence intensity ratio F of the system 617 / F 450 , and plot the fluorescence intensity ratio F 617 / F 450 Standard curve with varying concentrations of tetracycline antibiotics; Step 2: Measure the fluorescence spectrum and intensity of the tetracycline antibiotic sample according to the method in step 1, and determine the concentration of the tetracycline antibiotic in the sample by combining the linear equation of the standard curve.

10. Use of the dual-emission metal-organic framework composite nanomaterial according to claim 9 in ratiometric detection of tetracycline antibiotics, characterized in that: The concentration of the dual-emission metal organic framework composite nanomaterial in the stock solution is 0.01-0.05 mg / mL; the pH value of the sodium carbonate-sodium bicarbonate buffer solution is 9.0-9.5.

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