Preparation method of fluorescent hybrid probe for detecting ciprofloxacin

Abstract

The invention discloses a preparation method of a fluorescent hybrid probe for detecting ciprofloxacin, which comprises the following steps: citric acid and urea are used as raw materials to prepare carbon quantum dots, and the carbon quantum dots are in a blue luminous dark brown powder shape; the preparation method comprises the following steps: preparing a mesoporous molecularly imprinted polymer by taking ciprofloxacin as a raw material; the preparation method comprises the following steps: adding a rare earth chloride, an organic ligand, ethanol and 3-aminopropyltriethoxysilane into carbon quantum dots, then adding a mesoporous molecularly imprinted polymer into the carbon quantum dots, after full reaction, carrying out centrifugal treatment and washing on a reactant, and evaporating water to obtain a carbon quantum dot / rare earth molecularly imprinted composite material; and detecting the fluorescence property of the carbon quantum dot / rare earth molecularly imprinted composite material. The complex has double fluorescence emission centers and good fluorescence performance, and compared with pure carbon quantum dots and rare earth organic complexes, the fluorescence performance and the structural stability of the complex are relatively improved.

Description

Technical Field

[0001] The present application relates to a preparation method of a fluorescent hybrid probe, and particularly to a preparation method of a fluorescent hybrid probe for detecting ciprofloxacin. Background Art

[0003] Ciprofloxacin is a broad-spectrum antibiotic belonging to the fluoroquinolone class. It can inhibit bacterial DNA gyrase and topoisomerase, thereby inhibiting bacterial DNA replication and transmission, leading to bacterial death. Ciprofloxacin has been widely used to treat various infections caused by a variety of Gram-positive and Gram-negative bacteria, including respiratory tract infections, urinary tract infections, skin and soft tissue infections, osteoarticular infections, gastrointestinal infections, etc. In addition, ciprofloxacin is also used for the prevention and treatment of diarrhea in some travelers and anthrax exposure. However, overuse of ciprofloxacin can cause various side effects, such as nausea, diarrhea, headache, rash, central nervous system damage, peripheral neuropathy, arrhythmia, tendinitis, tendon rupture, etc. Therefore, accurate detection of ciprofloxacin is of great significance for identifying the drug tolerance of patients, studying the metabolic pathways and pharmacokinetics of ciprofloxacin, ensuring environmental and food safety, and checking the compliance of drug quality. To date, a variety of methods for detecting ciprofloxacin have been developed, including high performance liquid chromatography, liquid chromatography-tandem mass spectrometry, electrochemical methods, electrochemiluminescence, immunoassay, etc. However, these methods generally take a long time and involve complex and cumbersome sample processing procedures, etc.

[0004] Using fluorescence methods for ciprofloxacin detection has the advantages of high sensitivity, good selectivity, strong real-time monitoring ability, relatively simple operation process, low cost, etc. Existing literature has reported a variety of probes for ciprofloxacin fluorescence detection, including small molecule fluorescent probes, carbon quantum dots, nanoclusters, luminescent metal-organic framework materials. However, there is less research on carbon quantum dot / rare earth molecularly imprinted composites at present, mainly focusing on simply doping rare earth complexes or directly coordinating carbon quantum dots. The composites prepared by this method have problems such as weak anti-interference ability, instability of carbon quantum dots, and easy fluorescence quenching. Summary of the Invention

[0006] In order to solve the above technical problems, the embodiments of the present application provide a preparation method of a fluorescent hybrid probe for detecting ciprofloxacin. The specific technical solutions are as follows: In a first aspect, a method for preparing a fluorescent hybrid probe for detecting ciprofloxacin is provided, which includes the following steps: preparing carbon quantum dots from citric acid and urea, and the carbon quantum dots are dark brown powders showing blue luminescence; preparing a mesoporous molecularly imprinted polymer from ciprofloxacin; adding rare earth chloride, an organic ligand, ethanol, and 3-aminopropyltriethoxysilane to the carbon quantum dots, and then adding the mesoporous molecularly imprinted polymer to the carbon quantum dots. After sufficient reaction, the reactants are centrifuged, washed, and the water is evaporated to obtain a carbon quantum dot / rare earth molecularly imprinted composite material; detecting the fluorescence performance of the carbon quantum dot / rare earth molecularly imprinted composite material.

[0007] In one embodiment, the step of preparing carbon quantum dots from citric acid and urea includes: taking citric acid and urea as raw materials in a certain mass ratio, dissolving them in deionized water to obtain a mixture solution; transferring the mixture solution to a closed high-pressure reactor with a polytetrafluoroethylene substrate, and heating it in a vacuum oven; after cooling to room temperature, centrifuging and washing the mixture solution, and further purifying it using a filter membrane to remove large impurities in the mixture solution to obtain a blue solution; dialyzing the blue solution in a dialysis bag to remove excessive small molecule precursors and by-products in the blue solution; performing freeze-drying on the blue solution to obtain dark brown powders with blue luminescence.

[0008] In one embodiment, the mass ratio of citric acid to urea is 1:1.

[0009] In one embodiment, the pore size of the filter membrane is 0.22 μm, and the dialysis time of the blue solution is 2 days.

[0010] In one embodiment, the step of preparing a mesoporous molecularly imprinted polymer from ciprofloxacin includes: adding cetyltrimethylammonium bromide and ultrapure water to ciprofloxacin, and mixing and stirring for a certain time to obtain a mixture; adding 3-aminopropyltriethoxysilane, tetraethyl orthosilicate, and sodium hydroxide to the mixture, stirring for a certain time under light-shielded conditions, and then collecting the product; centrifuging the product and extracting the solid product; washing the solid product until it is neutral and drying it to obtain a mesoporous molecularly imprinted polymer.

[0011] In one embodiment, when extracting the solid product, a mixed solution prepared from ethanol and hydrochloric acid is used as the washing solution, and a Soxhlet extractor is used to extract the solid product.

[0012] In one embodiment, in the step of preparing the carbon quantum dot / rare earth molecularly imprinted composite material: the reaction conditions of the reactants are room temperature and light-shielded, the reaction time is 24 h, and the centrifugation time of the reactants is 10 min.

[0013] In one embodiment, the organic ligand is guanosine monophosphate or guanosine diphosphate or guanosine triphosphate, and the molar ratio of the organic ligand to the rare earth chloride is 3:4.

[0014] In one embodiment, the steps for detecting the fluorescence performance of the carbon quantum dot / rare earth molecularly imprinted composite material include: dispersing a certain amount of the carbon quantum dot / rare earth molecularly imprinted composite material in ciprofloxacin with different concentrations, and detecting its fluorescence performance.

[0015] In one embodiment, the steps for detecting the fluorescence performance of the carbon quantum dot / rare earth molecularly imprinted composite material further include: dispersing a certain amount of the carbon quantum dot / rare earth molecularly imprinted composite material in antibiotics with the same volume but different structures, and detecting its fluorescence performance.

[0016] In the embodiments of the present application, first, carbon quantum dots (CQDs) are prepared using citric acid and urea as raw materials, then mesoporous molecularly imprinted polymers are prepared using ciprofloxacin as a raw material, and then the carbon quantum dots (CQDs) and the mesoporous molecularly imprinted polymers are covalently bonded together to obtain a carbon quantum dot / rare earth molecularly imprinted composite material, which has dual fluorescence emission centers and good fluorescence performance. Moreover, compared with pure carbon quantum dots and rare earth organic complexes, its fluorescence performance and structural stability are relatively improved. In addition, different types of carbon quantum dots have different fluorescence centers due to their different structures, providing a new idea for the preparation of composite materials with different fluorescence emissions. The present application designs a structurally novel carbon quantum dot / rare earth molecularly imprinted composite material based on strong chemical bonds as a ratiometric fluorescence sensor to detect ciprofloxacin, broadening the types and research fields of carbon quantum dots and rare earth fluorescence materials. Based on a series of advantages of the molecularly imprinted polymer, such as simple synthesis method, cheap raw materials, large specific surface area, strong specific recognition, high stability, and strong resistance to environmental interference, a carbon quantum dot / rare earth molecularly imprinted composite material is obtained, breaking through the limitations of traditional solid fluorescence materials, providing a brand-new design idea for the development of novel multifunctional carbon quantum dot fluorescence composite materials, achieving a breakthrough in the performance of the composite material, and further broadening the application of green liquid devices in production and life. Description of the Drawings

[0018] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings: Figure 1 is a flowchart of the steps for the preparation method of the fluorescence hybrid probe for detecting ciprofloxacin in the present application.

[0019] Figure 2 is the fluorescence spectrum diagram of the carbon quantum dot / rare earth molecularly imprinted composite material in Example 1 of the present application.

[0020] Figure 3 It is the infrared spectrum of the carbon quantum dots / rare earth molecularly imprinted composite material in Example 1 of the present application.

[0021] Figure 4 It is the fluorescence spectrum of ciprofloxacin sensitivity of the carbon quantum dots / rare earth molecularly imprinted composite material in Example 1 of the present application.

[0022] Figure 5 It is the specific fluorescence spectrum of ciprofloxacin of the carbon quantum dots / rare earth molecularly imprinted composite material in Example 1 of the present application. Detailed implementation manners

[0024] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0025] As an emerging environmentally friendly nano-fluorescent material, carbon quantum dots (CQDs) are expected to replace traditional inorganic fluorescent materials, fluorescent organic small molecule materials and metal semiconductor nanoclusters and become a new type of fluorescent material due to their advantages such as low toxicity, stable chemical properties, low price, simple preparation method, and excellent optical properties. In recent years, they have received widespread attention and have been widely used in fields such as biomedicine and optoelectronic devices.

[0026] Rare earth complexes not only have good controllability and chemical stability, but also are rich in oxygen elements and double bonds inside the group. While perfectly retaining the excellent optical properties of rare earth ions, they are more conducive to the chemical grafting modification of rare earth elements. Currently, there are mainly two categories: rare earth inorganic complexes and rare earth organic complexes. Rare earth inorganic complexes are mainly composed of rare earth ions and inorganic salt coordination groups such as oxides, fluorides, oxysulfides, borates, phosphates, etc. Rare earth organic complexes often coordinate with rare earth ions as the center. There are many types, and the size of their ligands can be adjusted and designed to control the molecular size and surface characteristics of the complexes and achieve different luminescence properties and applications. Currently, many rare earth complexes have been successfully prepared into functional molecular devices and have shown good application prospects in fields such as chemistry, biology, medicine, and materials.

[0027] Molecularly imprinted polymers (MS / MIPs) are organic polymers with specific recognition ability. Due to advantages such as simple synthesis methods, inexpensive raw materials, and large specific surface area, they are widely used in analytical chemistry. The specific recognition mechanism of molecularly imprinted polymers is also like the concept of "guest - receptor" polymers. When synthesizing the polymer, first, the template molecule and the functional monomer are added and pre - polymerized, that is, the template molecule and the functional monomer are combined through covalent bonds, non - covalent bonds, or hydrogen bond interactions. Then the cross - linker and initiator are added to initiate the polymerization reaction to form a polymer containing the template molecule. Finally, the template molecule is eluted by a certain method (so that the template molecule falls off from the polymer layer), thus leaving three - dimensional spatial sites similar to the structure of the template molecule in the polymer. When the polymer with the three - dimensional configuration of the template molecule is added to a complex sample system again, the polymer can specifically recognize and adsorb the template molecule with similar spatial sites uniquely. Molecular imprinting technology is a recognition technology that combines many disciplines such as materials chemistry, polymer, and biology and has specific recognition. MIPs are also applied in many fields such as analytical separation, sensors, catalysts, and drug delivery due to a series of advantages such as their special selectivity, high stability, and strong resistance to environmental interference.

[0028] In the prior art, due to the aggregation - induced quenching phenomenon of carbon dots in the solid state or powder state, and the property of solid - state fluorescence quenching greatly hinders their application in optoelectronic devices and detectors. Therefore, the composite material formed by combining molecular imprinting technology with carbon quantum dots / rare - earth fluorescent materials in this application will bring together the advantages of both, resulting in a new type of fluorescent material with dual emission. It can not only utilize the advantage of the specific adsorption of molecularly imprinted polymer itself to make up for the two major disadvantages of low selectivity and sensitivity when carbon quantum dots are used as fluorescent probes to detect target substances. Moreover, compared with single - emission molecularly imprinted fluorescent probes, the constructed ratio - type fluorescent probe has stronger anti - interference ability. The beneficial effects of the preparation method of the fluorescence hybrid probe for detecting ciprofloxacin in this application will be described in detail below.

[0029] Please refer to Figure 1, which is a flow chart of the steps for the preparation method of the fluorescent hybrid probe for detecting ciprofloxacin in this application; as shown in the figure, the preparation method of the fluorescent hybrid probe for detecting ciprofloxacin in this embodiment includes the following steps S1 to S4. In step S1, carbon quantum dots (CQDs) are prepared: carbon quantum dots are prepared using citric acid and urea as raw materials, and the carbon quantum dots present as a dark brown powder with blue luminescence. First, citric acid and urea are taken as raw materials in a certain mass ratio, and citric acid and urea are dissolved in deionized water to obtain a mixture solution, where the mass ratio of citric acid to urea is preferably 1:1. Then the mixture solution is transferred to a closed high-pressure reactor with a polytetrafluoroethylene substrate and placed in a vacuum oven for heating. After heating and holding for a certain time, it is cooled to room temperature, and then the mixture solution is centrifuged, washed, and further purified using a filter membrane with a pore size of 0.22 μm to remove large impurities in the mixture solution, obtaining a blue solution. Then the blue solution is dialyzed in a dialysis bag for 2 days to remove excessive small molecule precursors and by-products in the blue solution. Finally, the blue solution is subjected to freeze-drying operation to obtain a dark brown powder with blue luminescence.

[0030] In step S2, mesoporous molecularly imprinted polymers (MS / MIPs) are prepared: mesoporous molecularly imprinted polymers are prepared using ciprofloxacin as a raw material. An appropriate amount of ciprofloxacin is placed in a clean and dry conical flask, and a certain amount of cetyltrimethylammonium bromide and ultrapure water are continuously added to it at room temperature and mixed and stirred for a certain time, usually 30 minutes, to obtain a mixture. Then 3-aminopropyltriethoxysilane, tetraethyl orthosilicate, and sodium hydroxide are added continuously, and stirring is continued in the dark at room temperature for 24 h, and then the product is collected. Then the product is centrifuged, and the solid product obtained by centrifugation is extracted. Then a mixed solution of ethanol / hydrochloric acid is prepared as a washing solution, and the solid product is extracted using a Soxhlet extractor, and the extraction time is usually two days. Finally, the product is washed with deionized water until neutral and dried for 24 hours to obtain mesoporous molecularly imprinted polymers.

[0031] In step S3, prepare the carbon quantum dot / rare earth molecularly imprinted composite material: Add rare earth chloride, organic ligand, ethanol, and 3-aminopropyltriethoxysilane to the carbon quantum dots, and then add the mesoporous molecularly imprinted polymer to the carbon quantum dots. After sufficient reaction, centrifuge the reactants, wash, and evaporate the water to obtain the carbon quantum dot / rare earth molecularly imprinted composite material. First, add rare earth chloride, organic ligand, ethanol, and 3-aminopropyltriethoxysilane to the carbon quantum dots prepared in step S1, and then add the mesoporous molecularly imprinted polymer prepared in step S2, and react at room temperature in the dark for 24 h. Then, centrifuge the solid product (reactants) at a specific speed for 10 minutes, wash the solid product alternately with ethanol and high-purity water multiple times, and evaporate the water to finally obtain the carbon quantum dot / rare earth molecularly imprinted composite material. The organic ligand is guanosine monophosphate or guanosine diphosphate or guanosine triphosphate, and the molar ratio of the organic ligand to the rare earth chloride is 3:4. At the same time, for comparison, a non-molecularly imprinted polymer was prepared under the same conditions.

[0032] In step S4, detect the fluorescence performance: Detect the fluorescence performance of the carbon quantum dot / rare earth molecularly imprinted composite material. Disperse a certain amount of the carbon quantum dot / rare earth molecularly imprinted composite material in ciprofloxacin with different concentrations and detect its fluorescence performance. Disperse a certain amount of the carbon quantum dot / rare earth molecularly imprinted composite material in antibiotics with the same volume but different structures and detect its fluorescence performance.

[0033] The preparation method of the fluorescence hybrid probe for detecting ciprofloxacin in this embodiment first uses citric acid and urea as raw materials to prepare carbon quantum dots (CQDs), then uses ciprofloxacin as a raw material to prepare a mesoporous molecularly imprinted polymer, and then combines the carbon quantum dots and the mesoporous molecularly imprinted polymer through covalent bonds to obtain a carbon quantum dot / rare earth molecularly imprinted composite material, which has dual fluorescence emission centers and good fluorescence performance. Moreover, compared with pure carbon quantum dots and rare earth organic complexes, its fluorescence performance and structural stability are relatively improved. In addition, different types of carbon quantum dots have different fluorescence centers due to their different structures, providing a new idea for the preparation of composite materials with different fluorescence emissions. This embodiment designs a novel carbon quantum dot / rare earth molecularly imprinted composite material based on strong chemical bonds as a ratiometric fluorescence sensor to detect ciprofloxacin, broadening the types and research fields of carbon quantum dots and rare earth fluorescence materials. Based on a series of advantages of the molecularly imprinted polymer, such as simple synthesis method, cheap raw materials, large specific surface area, strong specific recognition, high stability, and strong anti-environmental interference, a carbon quantum dot / rare earth molecularly imprinted composite material is obtained, breaking through the limitations of traditional solid fluorescence materials, providing a brand-new design idea for the development of new multifunctional carbon quantum dot fluorescence composite materials, achieving a breakthrough in the performance of the composite material, and further broadening the application of green liquid devices in production and life.

[0034] This embodiment mainly uses chemical modification means and organic synthesis methods to prepare carbon quantum dots by hydrothermal method. Through a simple one-pot silylation reaction, the carbon quantum dots and rare earth complexes are doped into the silica network obtained by the hydrolysis of tetraethyl orthosilicate under alkaline conditions. The precipitation polymerization method in molecular imprinting technology is used to form the imprinting site functional groups of the analyte ciprofloxacin on the polymer surface, so that when encountering the analyte ciprofloxacin, it can be effectively and quickly recognized. On the one hand, specific imprinting sites can reduce the interference of other structurally similar antibiotics to the analyte, thereby improving the anti-interference performance and effectively reducing the non-specific response of multiple substances in a complex environment. On the other hand, it overcomes the problems that the rare earth small molecule complexes are unstable when simply doped into the inorganic matrix, are easy to precipitate from the matrix and have fluorescence quenching, improves the luminescence performance and color purity of the material, and obtains a dual fluorescence system with both carbon quantum dot fluorescence emission and rare earth characteristic emission to meet the requirements of later ratio-type fluorescence sensing.

[0035] The following will illustrate the beneficial effects of the preparation method of the fluorescence hybrid probe for detecting ciprofloxacin of the present application with specific examples.

[0036] Example 1 The detection of ciprofloxacin based on the carbon quantum dot / rare earth molecularly imprinted composite material as a ratiometric fluorescence probe includes the following steps: (1) Preparation of carbon quantum dots by hydrothermal method: 300 mg of citric acid and 300 mg of urea were ultrasonically dissolved in 30 mL of deionized water. Then the mixture solution was transferred to a closed high-pressure reactor with a polytetrafluoroethylene substrate and heated in a vacuum oven at 160 °C for 4 hours. After cooling to room temperature, it was centrifuged at 6000 r / min for 20 minutes, and further purified with a 0.22 μm filter membrane to remove large impurities, obtaining a blue solution. Then the product was dialyzed with a dialysis bag (MWCO 500 - 1000) for 2 days to remove excessive small molecule precursors and by-products. Finally, a dark brown powder with blue luminescence was obtained by freeze-drying.

[0037] (2) Preparation of mesoporous molecularly imprinted polymer: Place 0.7484 g of ciprofloxacin in a clean and dry conical flask, and continuously add 0.6 g of cetyltrimethylammonium bromide and ultrapure water to it at room temperature, mix and stir. After 30 minutes, add 0.9 mL of 3-aminopropyltriethoxysilane (APTES), 3.6 mL of tetraethyl orthosilicate (TEOS) and an appropriate amount of sodium hydroxide solution. Continue to stir in the dark at room temperature for 24 hours, then collect the product, centrifuge the product for 10 min, and separate the supernatant to obtain the solid product. Prepare a mixed solution of ethanol / hydrochloric acid (2.0 M) (9:1, v / v) as the washing solution, and extract the solid product with a Soxhlet extractor at 110 °C for 48 hours. Finally, wash the product with deionized water until neutral, and dry it at 60 °C for 24 hours to obtain mesoporous molecularly imprinted polymers (MS / MIPs).

[0038] (3) Synthesis of carbon quantum dots / rare earth molecularly imprinted composites: First, dissolve an appropriate amount of carbon quantum dots in deionized water, then add dropwise 6 mL of europium chloride aqueous solution (10 mM) and 9.0 mL of organic ligand guanosine monophosphate (GMP) (10 mM). Subsequently, add 2.3 g of the MS / MIPs obtained in step (2), 5.0 mL of solvent ethanol and 2.0 mL of APTES, and react at room temperature in the dark for 24 hours. Then, centrifuge the solid product at 6000 rpm for 10 min, wash it alternately with ethanol and high-purity water for several times, and evaporate to finally obtain carbon quantum dots / rare earth (Eu 3+ ) molecularly imprinted composites. For comparison, non-molecularly imprinted polymers were prepared under the same conditions.

[0039] (4) Sensing detection of ciprofloxacin: Weigh 3 mg of the samples obtained in step (3) and disperse them in 1.5 mL of ciprofloxacin solution, and use an RF-5301PC fluorescence spectrometer to detect the fluorescence properties of each solution. Use an RF-5301 PC fluorescence spectrometer to measure the carbon quantum dots / rare earth molecularly imprinted composites obtained in step (3), and the obtained fluorescence spectra are as Figure 2 shown, where Figure 2 black and white processing has been carried out. It can be observed from Figure 2 that the composite material has two emission centers, namely the emission of carbon quantum dots at 438 nm and the characteristic emission of rare earth ions at 612 nm, indicating that the composite material can be applied to ratiometric fluorescence sensing.

[0040] Use a Perkin Elmer Spectrum 100 FTIR spectrophotometer to measure the samples of each step, and the obtained infrared spectra are as Figure 3 shown, where Figure 3Black and white processing was carried out. From Figure 3 a broad peak at 3419 cm −1 may be due to the stretching vibrations of O-H and N-H bonds; the peak at 1640 cm −1 can be attributed to the stretching vibration of the C=O bond of carbon quantum dots; in addition, the sharp band at 1400 cm −1 is caused by the in-plane bending vibration of C-N, indicating the presence of -NH 2 groups on the surface of carbon quantum dots; the rich surface functional groups of carbon quantum dots are of great significance for the further synthesis of MIPs and their coordination with Eu 3 + ions; the peaks of the molecularly imprinted polymer N-CQDs@Eu / MIPs are at 3419 cm −1 , 1640 cm −1 and 1400 cm −1 are weakened, indicating the interaction of -OH groups, -NH 2 groups and C=O groups on the surface of carbon quantum dots with APTES and Eu 3+ ions; the peak at 2940 cm −1 can be attributed to the stretching vibration of C-H bonds; the strong peak at 1095 cm −1 is the Si-O-Si bond, and the strong peaks at 799 cm −1 and 460 cm −1 are the Si-O bonds, indicating the successful formation of the composite material; in addition, as shown by curves b and c, there are no significant differences in the positions and intensities of the characteristic peaks between the molecularly imprinted polymer (N-CQDs@Eu / MIPs) and the non-molecularly imprinted polymer (N-CQDs@Eu / NIPs).

[0041] The mixed solution obtained in step (4) was measured using an RF-5301 PC fluorescence spectrometer, and the obtained fluorescence spectrum is as Figure 4 shown, where Figure 4 black and white processing was carried out. From Figure 4 it can be seen that for the above-mentioned carbon quantum dot / rare earth molecularly imprinted composite material, namely N-CQDs@Eu / MIPs, as the concentration of ciprofloxacin increases, the double emission centers show completely different fluorescence responses. The fluorescence emission peak of carbon quantum dots increases with the increase in the concentration of ciprofloxacin. On the contrary, the characteristic emission peak of rare earth ions decreases or remains unchanged with the increase in the concentration of ciprofloxacin. When the concentration of ciprofloxacin is 0, the fluorescent material shows red light emission, and it gradually changes to blue light emission with the increase in the concentration of ciprofloxacin. The change in color can more intuitively reflect the concentration of ciprofloxacin.

[0042] The specific determination of ciprofloxacin was carried out on the carbon quantum dot / rare earth molecularly imprinted composite using an RF-5301 PC fluorescence spectrometer, and the obtained emission spectra are as follows Figure 5 shown, where Figure 5 black and white processing was performed. From Figure 5 it can be seen that by selecting some antibiotics similar to or co-existing with ciprofloxacin (CIP) as interfering substrates, including tetracycline (TC), sulfamethoxazole (STX), ofloxacin (OFL), sulfadimidine (SM2), pefloxacin (PEF) and sparfloxacin (SPX), the selectivity of the composite for ciprofloxacin (CIP) was explored. The results showed that all antibiotics except CIP exhibited varying degrees of fluorescence enhancement responses. However, only the composite showed a significant signal for CIP. This indicates that although the analogues are very similar in structure to the target, the fluorescence probe has only a limited response to the analogues, which is attributed to the specific binding sites created by the molecular imprinting technique. Therefore, these results suggest that the composite has excellent selectivity for ciprofloxacin and can be used as a fluorescence probe for the detection of ciprofloxacin.

[0043] Example 2 A preparation method of a carbon quantum dot / rare earth molecularly imprinted composite, comprising the following steps: (1) Preparation of carbon quantum dots by hydrothermal method: 300 mg of citric acid and 300 mg of urea were ultrasonically dissolved in 30 mL of deionized water. Then the mixture solution was transferred to a closed high-pressure reactor with a polytetrafluoroethylene substrate and heated in a vacuum oven at 160 °C for 4 hours. After cooling to room temperature, it was centrifuged at 6000 r / min for 20 minutes and further purified with a 0.22 μm filter membrane to remove large impurities, obtaining a blue solution. Then the product was dialyzed with a dialysis bag (MWCO 500 - 1000) for 2 days to remove excessive small molecule precursors and by-products. Finally, a dark brown powder with blue luminescence was obtained by freeze-drying.

[0044] (2) Preparation of mesoporous molecularly imprinted polymers: Place 0.7484 g of ciprofloxacin in a clean and dry conical flask. Continuously add 0.6 g of cetyltrimethylammonium bromide and ultrapure water to it at room temperature, mix and stir. After 30 minutes, add 0.9 mL of 3-aminopropyltriethoxysilane (APTES), 3.6 mL of tetraethyl orthosilicate (TEOS) and an appropriate amount of sodium hydroxide solution. Continue to stir in the dark at room temperature for 24 hours, then collect the product. Centrifuge the product for 10 min, and separate the supernatant to obtain the solid product. Prepare a mixed solution of ethanol / hydrochloric acid (2.0 M) (9:1, v / v) as the washing solution, and extract the solid product with a Soxhlet extractor at 110 °C for 48 hours. Finally, wash the product with deionized water until neutral, and dry it at 60 °C for 24 hours to obtain mesoporous molecularly imprinted polymer (MS / MIPs).

[0045] (3) Synthesis of carbon quantum dots / rare earth molecularly imprinted composite materials First, dissolve an appropriate amount of carbon quantum dots in deionized water, then add dropwise 6 mL of terbium chloride aqueous solution (10 mM) and 9.0 mL of organic ligand guanosine diphosphate (GDP) (10 mM). Subsequently, add 2.3 g of the MS / MIPs obtained in step (2), 5.0 mL of solvent ethanol and 2.0 mL of APTES, and react at room temperature in the dark for 24 hours. Then, centrifuge the solid product at 6000 rpm for 10 min, wash it alternately with ethanol and high-purity water for several times, and evaporate to finally obtain carbon quantum dots / rare earth (Tb 3+ ) molecularly imprinted composite materials. For comparison, non-molecularly imprinted polymers were prepared under the same conditions.

[0046] Example 3 A preparation method of carbon quantum dots / rare earth molecularly imprinted composite materials, comprising the following steps: (1) Preparation of carbon quantum dots by hydrothermal method: Ultrasonically dissolve 300 mg of citric acid and 300 mg of urea in 30 mL of deionized water. Then transfer the mixture solution to a closed high-pressure reactor with a polytetrafluoroethylene substrate, and heat it in a vacuum oven at 160 °C for 4 hours. After cooling to room temperature, centrifuge at 6000 r / min for 20 minutes, and further purify it with a 0.22 μm filter membrane to remove large impurities, obtaining a blue solution. Then dialyze the product with a dialysis bag (MWCO 500-1000) for 2 days to remove excessive small molecule precursors and by-products. Finally, obtain a dark brown powder with blue luminescence by freeze-drying.

[0047] (2) Preparation of mesoporous molecularly imprinted polymer: Place 0.7484 g of ciprofloxacin in a clean and dry conical flask. Continuously add 0.6 g of cetyltrimethylammonium bromide and ultrapure water to it at room temperature, mix and stir. After 30 minutes, add 0.9 mL of 3-aminopropyltriethoxysilane (APTES), 3.6 mL of tetraethyl orthosilicate (TEOS) and an appropriate amount of sodium hydroxide solution. Continue to stir in the dark at room temperature for 24 hours, then collect the product. Centrifuge the product for 10 min to separate the supernatant to obtain the solid product. Prepare a mixed solution of ethanol / hydrochloric acid (2.0 M) (9:1, v / v) as the washing solution, and extract the solid product with a Soxhlet extractor at 110 °C for 48 hours. Finally, wash the product with deionized water until neutral, and dry it at 60 °C for 24 hours to obtain mesoporous molecularly imprinted polymers (MS / MIPs).

[0048] (3) Synthesis of carbon quantum dots / rare earth molecularly imprinted composites First, dissolve an appropriate amount of carbon quantum dots in deionized water, then add dropwise 6 mL of terbium chloride aqueous solution (10 mM) and 9.0 mL of organic ligand guanosine triphosphate (GTP) (10 mM). Subsequently, add 2.3 g of the MS / MIPs obtained in step (2), 5.0 mL of solvent ethanol and 2.0 mL of APTES, and react at room temperature in the dark for 24 hours. Then, centrifuge the solid product at 6000 rpm for 10 min, wash it repeatedly with ethanol and high-purity water, and evaporate to finally obtain carbon quantum dots / rare earth (Tb 3+ ) molecularly imprinted composites.

[0049] In summary, the present application provides a method for preparing a fluorescent hybrid probe for detecting ciprofloxacin. First, carbon quantum dots are prepared using citric acid and urea as raw materials. Then, mesoporous molecularly imprinted polymers are prepared using ciprofloxacin as a raw material. Subsequently, the carbon quantum dots and the mesoporous molecularly imprinted polymers are covalently bonded together to obtain a carbon quantum dot / rare earth molecularly imprinted composite material, which has dual fluorescence emission centers and good fluorescence properties. Moreover, compared with pure carbon quantum dots and rare earth organic complexes, its fluorescence properties and structural stability are relatively improved. In addition, different types of carbon quantum dots have different fluorescence centers due to their different structures, providing a new idea for the preparation of composite materials with different fluorescence emissions. The present application designs a novel carbon quantum dot / rare earth molecularly imprinted composite material based on strong chemical bonds as a ratiometric fluorescence sensor to detect ciprofloxacin, broadening the types and research fields of carbon quantum dots and rare earth fluorescent materials. Based on a series of advantages of the molecularly imprinted polymer, such as simple synthesis method, inexpensive raw materials, large specific surface area, strong specific recognition, high stability, and strong anti-environmental interference, a carbon quantum dot / rare earth molecularly imprinted composite material is obtained, breaking through the limitations of traditional solid fluorescent materials, providing a brand-new design idea for the development of novel multifunctional carbon quantum dot fluorescent composite materials, achieving a breakthrough in the performance of the composite materials, and further broadening the application of green liquid devices in production and life.

[0050] It should be noted that in this text, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "including a..." does not exclude the presence of additional identical elements in the process, method, article or device including that element.

[0051] The embodiments of the present application have been described above in conjunction with the accompanying drawings. However, the present application is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present application, those of ordinary skill in the art can also make many forms without departing from the purpose of the present application and the scope protected by the claims, and all belong to the protection scope of the present application.

Claims

1. A method for preparing a fluorescent hybrid probe for detecting ciprofloxacin, characterized in that: The following steps are involved: Carbon quantum dots are prepared using citric acid and urea as raw materials, and the carbon quantum dots are in the form of dark brown powder with blue light emission; Mesoporous molecularly imprinted polymers were prepared using ciprofloxacin as raw material; Adding rare earth chloride, organic ligand, ethanol and 3-aminopropyltriethoxysilane to the carbon quantum dots, and then adding the mesoporous molecular imprinting polymer to the carbon quantum dots, after sufficient reaction, centrifuging and washing the reactants, and evaporating water to obtain a carbon quantum dot / rare earth molecular imprinting composite material; The fluorescence property of the carbon quantum dot / rare earth molecular imprinting composite material is detected.

2. The method for preparing a fluorescent hybrid probe for detecting ciprofloxacin according to claim 1, characterized in that: The step of preparing the carbon quantum dots using the citric acid and the urea as raw materials comprises: Citric acid and urea are taken as raw materials in a certain mass ratio, and dissolved in deionized water to obtain a mixture solution; The mixture solution is transferred into a closed high-pressure reactor with a polytetrafluoroethylene bottom, and placed in a vacuum oven for heating; After cooling to room temperature, the mixture solution is centrifuged, washed, and further purified using a filter membrane to remove bulk impurities in the mixture solution to obtain a blue solution; Placing the blue solution in a dialysis bag for dialysis to remove excess small molecule precursors and byproducts in the blue solution; The blue solution was freeze-dried to obtain a dark brown powder with blue luminescence.

3. The method for preparing a fluorescent hybrid probe for detecting ciprofloxacin according to claim 2, characterized in that: The mass ratio of the citric acid to the urea is 1:

1.

4. The method for preparing a fluorescent hybrid probe for detecting ciprofloxacin according to claim 2, characterized in that: The pore size of the filter membrane is 0.22 μm, and the dialysis time of the blue solution is 2 days.

5. The method for preparing a fluorescent hybrid probe for detecting ciprofloxacin according to claim 1, characterized in that: The steps of preparing the mesoporous molecularly imprinted polymer using the ciprofloxacin as a raw material include: Adding cetyltrimethylammonium bromide and ultrapure water to the ciprofloxacin, and mixing and stirring for a certain period of time to obtain a mixture; Add 3-aminopropyltriethoxysilane, tetraethyl orthosilicate and sodium hydroxide to the mixture, stir for a certain period of time under light-proof conditions, and then collect the product; Centrifuging the product and extracting the solid product; The solid product is washed to neutrality and dried to obtain the mesoporous molecularly imprinted polymer.

6. The method for preparing a fluorescent hybrid probe for detecting ciprofloxacin according to claim 5, characterized in that: When extracting the solid product, a mixed solution prepared by ethanol and hydrochloric acid is used as a washing solution, and a Soxhlet extractor is used to extract the solid product.

7. The method for preparing a fluorescent hybrid probe for detecting ciprofloxacin according to claim 1, characterized in that: In the step of preparing the carbon quantum dot / rare earth molecular imprinting composite material: the reaction conditions of the reactants are room temperature and light-proof, the reaction time is 24 hours, and the centrifugation time of the reactants is 10 minutes.

8. The method for preparing a fluorescent hybrid probe for detecting ciprofloxacin according to claim 1, characterized in that: The organic ligand is guanosine monophosphate, guanosine diphosphate or guanosine triphosphate, and the molar ratio of the organic ligand to the rare earth chloride is 3:

4.

9. The method for preparing a fluorescent hybrid probe for detecting ciprofloxacin according to claim 1, characterized in that: The step of detecting the fluorescence performance of the carbon quantum dot / rare earth molecular imprinting composite material comprises: A certain amount of the carbon quantum dot / rare earth molecular imprinting composite material is dispersed in different concentrations of ciprofloxacin, and its fluorescence performance is detected.

10. The method for preparing a fluorescent hybrid probe for detecting ciprofloxacin according to claim 9, characterized in that: The step of detecting the fluorescence properties of the carbon quantum dot / rare earth molecular imprinting composite material also includes: A certain amount of the carbon quantum dot / rare earth molecular imprinting composite material is dispersed in the same volume of antibiotics with different structures, and the fluorescence properties thereof are detected.

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