Preparation method and application of ratiometric fluorescent probe

Abstract

The invention discloses a preparation method and application of a ratiometric fluorescent probe, and the preparation method comprises the following steps: (1) in a closed container, reacting a mixture I containing citric acid and amino acid I to obtain a nitrogen and sulfur doped carbon dot material; and (2) reacting a mixture II containing terbium nitrate, 4, 4 '-diphenyldicarboxylic acid and the nitrogen and sulfur doped carbon dot material in a closed container, and drying to obtain the nitrogen and sulfur doped carbon dot (at) Tb-MOFs material. Under an optimized condition, the synthesized N, S-CDs (at) Tb-MOFs has relatively high sensitivity to norfloxacin, and the detection limit is 35.87 nM. The developed sensing platform has the characteristics of portability, low cost, specificity and the like, and has potential application prospects in the fields of food analysis and environmental monitoring.

Description

Technical Field

[0001] The present application relates to a preparation method and application of a ratiometric fluorescent probe, and belongs to the technical field of fluorescent sensing materials and environmental monitoring. Background Art

[0002] Norfloxacin (NOR) is a broad-spectrum antibacterial drug in the new generation of fluoroquinolone carboxylic acid antibiotics, which is widely used to treat bacterial infections such as Staphylococcus aureus and Escherichia coli. However, due to its abuse and difficulty in decomposition in surface water and food, it poses a serious threat to human health and environmental safety. Therefore, it is necessary to develop a simple and effective method to detect residual antibiotics of norfloxacin. At present, there are many methods for detecting NOR, such as high-performance liquid chromatography (HPLC), electrochemical analysis, and liquid chromatography tandem mass spectrometry (LC-MS). Although these methods have good accuracy, there are still some problems to be solved. These methods require complex sample preparation procedures, time-consuming, professional technicians and expensive equipment. Therefore, there is an urgent need to develop a simple and effective strategy to quickly and accurately monitor NOR in complex samples.

[0003] Fluorescence sensing technology is considered an important means of detecting antibiotics due to its good selectivity, high sensitivity and low cost. It is difficult for traditional fluorescence sensing systems to quantitatively analyze targets using only a single emission intensity. The detection process is easily affected by factors such as the microenvironment of the probe and light scattering of impurities, resulting in unreliable results. In order to overcome these shortcomings, another probe is introduced into the sensing system to form a ratiometric fluorescence sensor to detect the target by analyzing the changes in the fluorescence intensity of two different emission peaks. Ratiometric fluorescence detection is generally divided into two modes. One is a single signal response with a fixed reference. In this mode, during the detection process, only one signal has a specific response to the target. The other is a reverse change of dual signals, which means that both signals respond to the analyte and show reverse changes. In contrast, the second mode has a more sensitive signal change and is more suitable for the quantitative determination of low-concentration targets. In addition, dual-emission ratiometric fluorescent probes can provide rich color changes, showing a wider range of color changes by adjusting the reverse change of the emission peak intensity, making the visualization effect more obvious. Summary of the invention

[0004] Metal-organic frameworks (MOFs) are excellent materials for fluorescence detection due to their structural and functional diversity, high porosity, and large specific surface area. So far, many MOFs with fluorescent properties have been developed and applied to the sensing of various species. The tunable fluorescence properties of MOFs usually come from lanthanide ions or organic linkers, but the single signal response is still insufficient in terms of selectivity and sensitivity for quantitative detection of analytes. To overcome these shortcomings, fluorescent guests can be encapsulated in the cavities of MOFs to prepare dual-emission ratiometric fluorescent probes. Due to the tunable pores and high porosity of MOFs, they become host frameworks for various guest molecules.

[0005] Among the many luminophores, carbon dots are a type of zero-dimensional carbon nanoparticles with extremely small size. They have the advantages of easy synthesis, low toxicity, high photostability, and good biocompatibility, and have broad application prospects in the field of fluorescence sensing. Despite its advantages, aggregation-induced quenching is the main obstacle to its application. If the concentration of carbon dots is too high, there will be a tendency for aggregation and collision, leading to quenching. Studies have found that encapsulating CDs in porous materials can effectively inhibit the movement of CDs, greatly reduce the aggregation of CDs, and thus improve their fluorescence properties. Therefore, utilizing the synergistic effect between MOFs and CDs to prepare CDs@MOFs composites with excellent optical properties is a promising strategy for constructing new fluorescent sensing materials.

[0006] The purpose of the present invention is to provide a method for constructing a ratiometric fluorescent probe and apply the method to sensitive detection of antibiotics.

[0007] Based on this purpose, the present invention first prepared a ratiometric fluorescent probe N,S-CDs@Tb-MOFs and used it in antibiotic sensing experiments. The material showed excellent selectivity and sensitivity to norfloxacin, and the solution showed obvious color changes under ultraviolet light.

[0008] According to one aspect of the present application, a method for preparing a ratiometric fluorescent probe is provided, the preparation method comprising the following steps:

[0009] (1) In a sealed container, a mixture I containing citric acid and sulfur-containing amino acid substances is reacted to obtain nitrogen- and sulfur-doped carbon dot materials;

[0010] (2) In a sealed container, a mixture II containing terbium nitrate, 4,4'-biphenyldicarboxylic acid, and nitrogen- and sulfur-doped carbon dot materials is reacted and dried to obtain nitrogen- and sulfur-doped carbon dot@Tb-MOFs materials.

[0011] The ratio of carbon dots and MOFs, and the regulation of reaction temperature and reaction time during material synthesis.

[0012] Optionally, the ingredient ratio of the synthetic carbon dots is selected from any value of 1:1, 6:1, 10:1, 14:1, 18:1, 22:1 or a range value between any two of the above points.

[0013] Optionally, the proportion of the MOFs is selected from any value of 2:1, 1:1, 1:2 or a range between any two of the above points.

[0014] Optionally, the amount of CDs incorporated is selected from any value of 500 μL, 1000 μL, 2000 μL, 3000 μL, 4000 μL, or a range between any two of the above points.

[0015] Optionally, in step (1), the mass ratio of citric acid to sulfur-containing amino acid substances is 1:1 to 22:1.

[0016] Optionally, the sulfur-containing amino acid substance is selected from at least one of glutathione, glutathione, and methionine.

[0017] Optionally, in step (2), the molar ratio of the terbium nitrate to the 4,4'-biphenyldicarboxylic acid is 1:2 to 2:1.

[0018] Optionally, in step (2), the molar volume ratio of the terbium nitrate to the nitrogen and sulfur doped carbon dot material is 0.5-2.0 mmol: 500-4000 μL.

[0019] Optionally, the temperature of the reaction I is 160-220° C., and the time of the reaction I is 4-12 hours.

[0020] Optionally, the temperature of the reaction I is selected from any value of 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C or a range between any two of the above points.

[0021] Optionally, the reaction time I is selected from any value among 4h, 6h, 8h, 10h, 12h or a range value between any two of the above points.

[0022] Optionally, the temperature of the reaction II is 120-200° C., and the time of the reaction II is 6-12 h.

[0023] Optionally, the temperature of the reaction II is selected from any value of 120°C, 140°C, 160°C, 180°C, 200°C or a range between any two of the above points.

[0024] Optionally, the time of reaction II is selected from any value among 6h, 8h, 10h, 12h or a range between any two of the above points.

[0025] Optionally, the mixture II further comprises a solvent.

[0026] Optionally, the solvent is selected from at least one of N,N-dimethylformamide, ethanol and water.

[0027] Optionally, the N,S-CDs@Tb-MOFs solvent is at least one of DMF and H2O, DMF and C2H5OH, and DMF.

[0028] Optionally, in step (2), the drying temperature is 40 to 70° C., and the drying time is 3 to 12 hours.

[0029] Optionally, the drying temperature is selected from any value of 40°C, 50°C, 60°C, 70°C or a range between any two of the above points.

[0030] Optionally, the drying time is selected from any value among 3h, 6h, 9h, 12h or a range between any two of the above points.

[0031] According to another aspect of the present application, there is provided an application of a ratiometric fluorescent probe prepared by the preparation method described above in antibiotic detection.

[0032] Optionally, the ratiometric fluorescent probe has good selectivity for norfloxacin.

[0033] Optionally, the detection limit of the ratiometric fluorescent probe for norfloxacin is 30.00 nM to 40.00 nM.

[0034] As a specific implementation, the present invention is implemented by the following technical solutions:

[0035] 1. A ratiometric fluorescent probe N,S-CDs@Tb-MOFs is constructed and applied to the on-site detection of antibiotics. The preparation method comprises the following preparation steps:

[0036] Step a, preparing N, S-CDs carbon dot materials;

[0037] Step b, construction of N,S-CDs@Tb-MOFs;

[0038] Among them, the specific steps of preparing N,S-CDs carbon dot materials in step a are:

[0039] (1) Weigh 0.180 g of citric acid and 0.010 g of glutathione and dissolve them in distilled water. Ultrasonicate for 10 min to obtain a uniform solution.

[0040] (2) The mixed solution was transferred to a reactor and reacted in an oven at 200°C for 4 h.

[0041] (3) The product of step (2) was collected, filtered through a 0.22 μm filter to remove insoluble impurities, and purified using a dialysis bag for 12 hours to remove unreacted precursors.

[0042] Step b: The construction steps of N,S-CDs@Tb-MOFs are:

[0043] (1) Weigh 0.5 mmol of terbium nitrate and 1.0 mmol of 4,4'-biphenyldicarboxylic acid, dissolve them in DMF and H2O, sonicate for 10 min, and shake for 20 min to obtain a uniform solution.

[0044] (2) 3000 μL of N,S-CDs solution was added to the mixture. After ultrasonic treatment for 10 min, the mixture was shaken at 180 rpm for 20 min to obtain a uniform precursor solution.

[0045] (3) The obtained mixture was placed in a stainless steel autoclave lined with polytetrafluoroethylene, heated to 160°C, kept for 6 hours, and then cooled to room temperature.

[0046] (4) The product was collected by centrifugation and washed with ethanol several times. Finally, the N,S-CDs@Tb-MOFs were dried in a vacuum oven at 60 °C.

[0047] Based on the sensitive detection of the antibiotic norfloxacin by the ratiometric fluorescent probe, the specific detection method is characterized by:

[0048] (1) Under the same conditions, N, S-CDs@Tb-MOFs were dispersed in different types of antibiotic solutions, and the emission spectra of the mixtures were recorded.

[0049] (2) Disperse N,S-CDs@Tb-MOFs powder in deionized water to obtain a uniformly dispersed suspension. Add different concentrations of NOR to the above solution, react for 1.0 min, and then measure the fluorescence spectrum of the suspension. The relationship between the intensity ratio of the two peaks of CDs and Tb-MOFs and the NOR concentration is analyzed in detail.

[0050] (3) In the anti-interference experiment, the fluorescence response of N,S-CDs@Tb-MOFs to NOR was tested in the presence of interfering components such as anions, cations, and amino acids. The concentration of the interfering substances was three times that of NOR.

[0051] In this application, the constructed nitrogen- and sulfur-doped carbon dots encapsulated terbium-based metal-organic framework ratiometric fluorescent probe was used for highly sensitive sensing of the antibiotic norfloxacin (NOR). The Tb-MOFs alone emitted green fluorescence under ultraviolet light, and after the incorporation of blue carbon dots, the composite material as a whole appeared blue. As the concentration of norfloxacin increased, the fluorescence of CDs gradually weakened, and the Tb 3+The green fluorescence gradually increases, and finally realizes a multicolor fluorescence change from blue to green. Under optimized conditions, the synthesized N,S-CDs@Tb-MOFs has a high sensitivity to norfloxacin. The developed sensing platform has the characteristics of portability, low cost, and specificity, and has potential application prospects in the fields of food analysis and environmental monitoring.

[0052] The beneficial effects of this application include:

[0053] 1) The ratiometric fluorescent probe provided in this application is simple to prepare and easy to operate, and can achieve rapid, sensitive, and highly selective detection of norfloxacin. Its good stability makes it have market development prospects.

[0054] 2) The one-pot synthesis method of N,S-CDs@Tb-MOFs provided in this application.

[0055] Ratiometric fluorescent probes are compared with single-emission fluorescent sensors by using relative fluorescence intensity I Tb-MOFs / I CDs Instead of absolute fluorescence intensity as the output signal, the interference of external factors on the experiment is avoided, and the sensitivity and accuracy of the sensing are effectively improved. The ratiometric fluorescent probe based on N,S-CDs@Tb-MOFs not only shows changes in color brightness, but also exhibits hue differences that are easily recognizable by the naked eye. This probe provides a promising method for on-site detection of norfloxacin. In view of the above advantages, the ratiometric fluorescent probe N,S-CDs@Tb-MOFs has broad application prospects in environmental monitoring, food safety and other fields. In summary, the simple and effective preparation of this material has important scientific significance and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a diagram of the synthesis process of N,S-CDs@Tb-MOFs in Example 6 of the present application.

[0057] Figure 2 This is a graph showing the selectivity test of the ratiometric fluorescent probe N,S-CDs@Tb-MOFs for antibiotics in Example 14 of the present application.

[0058] Figure 3 This is a graph showing the concentration gradient test of the ratiometric fluorescent probe N,S-CDs@Tb-MOFs on norfloxacin in Example 15 of the present application. DETAILED DESCRIPTION

[0059] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0060] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0061] In the examples of the present application, the instruments used for characterization of the ratiometric fluorescent probe composite material are as follows:

[0062] Instrument Model Manufacturer Powder X-ray Diffractometer Malvern Panalytical Fluorescence Spectrometer Hitachi Manufacturing Co., Ltd. UV-Vis Spectrophotometer Beijing Puxi General Instrument Co., Ltd. digital camera Nikon Corporation

[0063] Example 1 Preparation of N,S-CDs carbon dot materials

[0064] (1) Weigh 0.180 g of citric acid and 0.010 g of glutathione and dissolve them in distilled water. Ultrasonicate for 10 min to obtain a uniform solution.

[0065] (2) The mixed solution was transferred to a reactor and reacted in an oven at 200°C for 4 h.

[0066] (3) The product of step (2) was collected, filtered through a 0.22 μm filter to remove insoluble impurities, and purified using a dialysis bag for 12 hours to remove unreacted precursors.

[0067] Example 2 Preparation of N,S-CDs carbon dot materials

[0068] (1) Weigh 0.100 g of citric acid and 0.010 g of glutathione and dissolve them in distilled water. Ultrasonicate for 10 min to obtain a uniform solution.

[0069] (2) The mixed solution was transferred to a reactor and reacted in an oven at 200°C for 4 h.

[0070] (3) The product of step (2) was collected, filtered through a 0.22 μm filter to remove insoluble impurities, and purified using a dialysis bag for 12 hours to remove unreacted precursors.

[0071] Example 3 Preparation of N,S-CDs carbon dot materials

[0072] (1) Weigh 0.180 g of citric acid and 0.010 g of glutathione and dissolve them in distilled water. Ultrasonicate for 10 min to obtain a uniform solution.

[0073] (2) The mixed solution was transferred to a reactor and reacted in an oven at 160°C for 4 h.

[0074] (3) The product of step (2) was collected, filtered through a 0.22 μm filter to remove insoluble impurities, and purified using a dialysis bag for 12 hours to remove unreacted precursors.

[0075] Example 4 Preparation of N,S-CDs carbon dot materials

[0076] (1) Weigh 0.180 g of citric acid and 0.010 g of glutathione and dissolve them in distilled water. Ultrasonicate for 10 min to obtain a uniform solution.

[0077] (2) The mixed solution was transferred to a reactor and reacted in an oven at 180°C for 4 h.

[0078] (3) The product of step (2) was collected, filtered through a 0.22 μm filter to remove insoluble impurities, and purified using a dialysis bag for 12 hours to remove unreacted precursors.

[0079] Example 5 Preparation of N,S-CDs carbon dot materials

[0080] (1) Weigh 0.180 g of citric acid and 0.010 g of glutathione and dissolve them in distilled water. Ultrasonicate for 10 min to obtain a uniform solution.

[0081] (2) The mixed solution was transferred to a reactor and reacted in an oven at 200°C for 6 h.

[0082] (3) The product of step (2) was collected, filtered through a 0.22 μm filter to remove insoluble impurities, and purified using a dialysis bag for 12 hours to remove unreacted precursors.

[0083] Example 6 Construction steps of N,S-CDs@Tb-MOFs

[0084] (1) Weigh 0.5 mmol of terbium nitrate and 1.0 mmol of 4,4'-biphenyldicarboxylic acid, dissolve them in DMF and H2O, sonicate for 10 min, and shake for 20 min to obtain a uniform solution.

[0085] (2) Add 3000 μL of the N,S-CDs solution prepared in Example 1 to the mixture. After ultrasonic treatment for 10 min, shake the mixture at 180 rpm for 20 min to obtain a uniform precursor solution.

[0086] (3) The obtained mixture was placed in a stainless steel autoclave lined with polytetrafluoroethylene, heated to 160°C, kept for 6 hours, and then cooled to room temperature.

[0087] (4) The product was collected by centrifugation and washed with ethanol several times. Finally, the N,S-CDs@Tb-MOFs were dried in a vacuum oven at 60 °C for 12 h. Figure 1 As can be seen in the figure, the construction process of the ratiometric fluorescent probe.

[0088] Example 7 Construction steps of N,S-CDs@Tb-MOFs

[0089] (1) Weigh 1.0 mmol of terbium nitrate and 1.0 mmol of 4,4'-biphenyldicarboxylic acid, dissolve them in DMF and H2O, sonicate for 10 min, and shake for 20 min to obtain a uniform solution.

[0090] (2) Add 3000 μL of the N,S-CDs solution prepared in Example 1 to the mixture. After ultrasonic treatment for 10 min, shake the mixture at 180 rpm for 20 min to obtain a uniform precursor solution.

[0091] (3) The obtained mixture was placed in a stainless steel autoclave lined with polytetrafluoroethylene, heated to 160°C, kept for 6 hours, and then cooled to room temperature.

[0092] (4) The product was collected by centrifugation and washed with ethanol several times. Finally, the N,S-CDs@Tb-MOFs were dried in a vacuum oven at 60 °C for 12 h.

[0093] Example 8 Construction steps of N,S-CDs@Tb-MOFs

[0094] (1) Weigh 0.5 mmol of terbium nitrate and 1.0 mmol of 4,4'-biphenyldicarboxylic acid, dissolve them in DMF and C2H5OH, sonicate for 10 min, and shake for 20 min to obtain a uniform solution.

[0095] (2) Add 3000 μL of the N,S-CDs solution prepared in Example 1 to the mixture. After ultrasonic treatment for 10 min, shake the mixture at 180 rpm for 20 min to obtain a uniform precursor solution.

[0096] (3) The obtained mixture was placed in a stainless steel autoclave lined with polytetrafluoroethylene, heated to 160°C, kept for 6 hours, and then cooled to room temperature.

[0097] (4) The product was collected by centrifugation and washed with ethanol several times. Finally, the N,S-CDs@Tb-MOFs were dried in a vacuum oven at 60 °C for 12 h.

[0098] Example 9 Construction steps of N,S-CDs@Tb-MOFs

[0099] (1) Weigh 0.5 mmol of terbium nitrate and 1.0 mmol of 4,4'-biphenyldicarboxylic acid, dissolve them in DMF and H2O, sonicate for 10 min, and shake for 20 min to obtain a uniform solution.

[0100] (2) Add 2000 μL of the N,S-CDs solution prepared in Example 1 to the mixture. After ultrasonic treatment for 10 min, shake the mixture at 180 rpm for 20 min to obtain a uniform precursor solution.

[0101] (3) The obtained mixture was placed in a stainless steel autoclave lined with polytetrafluoroethylene, heated to 160°C, kept for 6 hours, and then cooled to room temperature.

[0102] (4) The product was collected by centrifugation and washed with ethanol several times. Finally, the N,S-CDs@Tb-MOFs were dried in a vacuum oven at 60 °C for 12 h.

[0103] Example 10 Construction steps of N,S-CDs@Tb-MOFs

[0104] (1) Weigh 0.5 mmol of terbium nitrate and 1.0 mmol of 4,4'-biphenyldicarboxylic acid, dissolve them in DMF and H2O, sonicate for 10 min, and shake for 20 min to obtain a uniform solution.

[0105] (2) Add 3000 μL of the N,S-CDs solution prepared in Example 1 to the mixture. After ultrasonic treatment for 10 min, shake the mixture at 180 rpm for 20 min to obtain a uniform precursor solution.

[0106] (3) The obtained mixture was placed in a stainless steel autoclave lined with polytetrafluoroethylene, heated to 180°C, kept for 6 hours, and then cooled to room temperature.

[0107] (4) The product was collected by centrifugation and washed with ethanol several times. Finally, the N,S-CDs@Tb-MOFs were dried in a vacuum oven at 60 °C for 12 h.

[0108] Example 11 Construction steps of N,S-CDs@Tb-MOFs

[0109] (1) Weigh 0.5 mmol of terbium nitrate and 1.0 mmol of 4,4'-biphenyldicarboxylic acid, dissolve them in DMF and H2O, sonicate for 10 min, and shake for 20 min to obtain a uniform solution.

[0110] (2) Add 3000 μL of the N,S-CDs solution prepared in Example 1 to the mixture. After ultrasonic treatment for 10 min, shake the mixture at 180 rpm for 20 min to obtain a uniform precursor solution.

[0111] (3) The obtained mixture was placed in a stainless steel autoclave lined with polytetrafluoroethylene, heated to 160°C, kept for 12 hours, and then cooled to room temperature.

[0112] (4) The product was collected by centrifugation and washed with ethanol several times. Finally, the N,S-CDs@Tb-MOFs were dried in a vacuum oven at 60 °C for 12 h.

[0113] Example 12 Construction steps of N,S-CDs@Tb-MOFs

[0114] (1) Weigh 0.5 mmol of terbium nitrate and 1.0 mmol of 4,4'-biphenyldicarboxylic acid, dissolve them in DMF and H2O, sonicate for 10 min, and shake for 20 min to obtain a uniform solution.

[0115] (2) Add 3000 μL of the N,S-CDs solution prepared in Example 1 to the mixture. After ultrasonic treatment for 10 min, shake the mixture at 180 rpm for 20 min to obtain a uniform precursor solution.

[0116] (3) The obtained mixture was placed in a stainless steel autoclave lined with polytetrafluoroethylene, heated to 160°C, kept for 12 hours, and then cooled to room temperature.

[0117] (4) The product was collected by centrifugation and washed with ethanol several times. Finally, the N,S-CDs@Tb-MOFs were dried in a vacuum oven at 40 °C for 12 h.

[0118] Embodiment 13

[0119] The ratiometric fluorescent probes prepared in Examples 6 to 12 are applied to the detection of antibiotics, and the steps are as follows:

[0120] (1) The material constructed in Example 1 is used as nitrogen-sulfur doped carbon dots, and the composite material constructed in Example 6 is used as a ratiometric fluorescent probe;

[0121] (2) Under the same conditions, N,S-CDs@Tb-MOFs were dispersed in different types of antibiotic solutions, and the emission spectra of the mixtures were recorded.

[0122] (3) Disperse N,S-CDs@Tb-MOFs powder in deionized water to obtain a uniformly dispersed suspension. Add different concentrations of NOR to the above solution, react for 1.0 min, and then measure the fluorescence spectrum of the suspension. The relationship between the intensity ratio of the two peaks of CDs and Tb-MOFs and the NOR concentration was analyzed in detail. There is a good linear relationship between the two. At a lower concentration, the detection limit of N,S-CDs@Tb-MOFs for norfloxacin is 35.87nM.

[0123] Embodiment 14

[0124] Under the same conditions, N,S-CDs@Tb-MOFs were dispersed in different antibiotic solutions and the emission spectra of the mixtures were recorded. Figure 2 It can be seen that the ratiometric fluorescent probe has good selectivity for norfloxacin antibiotics.

[0125] Embodiment 15

[0126] To detect NOR antibiotics, 3.0 mg of N,S-CDs@Tb-MOFs powder was dispersed in 3.0 mL of deionized water by ultrasonic treatment to obtain a uniformly dispersed suspension (1 mg mL -1 ). Add NOR solution of different concentrations to the above solution, react for 1.0 min, and then measure the fluorescence spectrum of the suspension. Figure 3 It can be seen that the ratiometric fluorescent probe has a good linear relationship and high sensitivity to norfloxacin.

[0127] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a ratiometric fluorescent probe, characterized in that: The preparation method comprises the following steps: (1) In a sealed container, a mixture I containing citric acid and sulfur-containing amino acid substances is reacted to obtain nitrogen- and sulfur-doped carbon dot materials; (2) In a sealed container, a mixture II containing terbium nitrate, 4,4'-biphenyldicarboxylic acid, and nitrogen- and sulfur-doped carbon dot materials is reacted and dried to obtain nitrogen- and sulfur-doped carbon dot@Tb-MOFs materials.

2. The preparation method according to claim 1, characterized in that: In the step (1), the mass ratio of the citric acid to the sulfur-containing amino acid substance is 1:1 to 22:

1.

3. The preparation method according to claim 1, characterized in that: The sulfur-containing amino acid substance is selected from at least one of glutathione, cysteine ​​and methionine.

4. The preparation method according to claim 1, characterized in that: In the step (2), the molar ratio of the terbium nitrate to the 4,4'-biphenyldicarboxylic acid is 1:2 to 2:

1.

5. The preparation method according to claim 1, characterized in that: In the step (2), the molar volume ratio of the terbium nitrate to the nitrogen and sulfur doped carbon dot material is 0.5-2.0 mmol: 500-4000 μL.

6. The preparation method according to claim 1, characterized in that: The temperature of the reaction I is 160-220° C., and the time of the reaction I is 4-12 hours.

7. The preparation method according to claim 1, characterized in that: The temperature of the reaction II is 120-200° C., and the time of the reaction II is 6-12 hours.

8. The preparation method according to claim 1, characterized in that: The mixture II further comprises a solvent; Preferably, the solvent is selected from at least one of N,N-dimethylformamide, ethanol and water; Preferably, in step (2), the drying temperature is 40 to 70° C., and the drying time is 3 to 12 hours.

9. Use of the ratiometric fluorescent probe prepared by the preparation method according to any one of claims 1 to 8 in antibiotic detection.

10. The use according to claim 9, characterized in that: The detection limit of the ratiometric fluorescent probe for norfloxacin is 30.00 nM to 40.00 nM.

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