A ratio-type fluorescent probe based on carbon quantum dot hybrid covalent organic framework and a preparation method thereof
By hybridizing covalent organic frameworks with carbon quantum dots, ratiometric fluorescent probes were prepared, solving the problems of self-aggregation quenching and complex sample processing of fluorescent nanomaterials, and realizing the visual detection and rapid response of α-dicarbonyl compounds.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA JILIANG UNIV
- Filing Date
- 2025-01-16
- Publication Date
- 2026-07-21
AI Technical Summary
Existing fluorescent nanomaterials suffer from fluorescence quenching due to self-aggregation in the fields of sensing and bioimaging, and the sample pretreatment and instrument analysis processes are complex.
A ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework was prepared by hybridizing covalent organic framework materials with carbon quantum dots using a bulk polymerization method. By utilizing nitrogen-doped bio-carbon quantum dots and a three-dimensional acylhydrazine-imine covalent organic framework, a dual fluorescent emission signal was formed, reducing signal drift and self-quenching.
This method enables the visual detection of α-dicarbonyl compounds in food, improving detection speed and stability, lowering the detection limit, and enhancing the selective binding ability to target compounds.
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Figure CN119875025B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of fluorescence sensing technology. Specifically, it relates to a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework and its preparation method, which can be used in the field of environmental analysis and testing. Background Technology
[0002] Currently, fluorescent nanomaterials have been widely applied in fields such as sensing and bioimaging. Carbon quantum dots, especially biomass carbon quantum dots, have attracted widespread attention as a novel fluorescent nanomaterial due to their low raw material cost, simple synthesis methods, good biocompatibility, and low toxicity. [1] Furthermore, their physicochemical properties can be further modulated through heteroatom doping. For example, doping carbon quantum dots with N heteroatoms can passivate their surface states, enabling a transition from excited correlated emission to excited uncorrelated emission, thereby improving their ability to detect metal ion fluorescence. [2] Studies have found that carbon quantum dots are prone to self-aggregation during use, which can cause fluorescence quenching. To improve their practical application performance, they are often doped with other materials.
[0003] Covalent organic framework materials have attracted widespread attention due to their excellent structural tunability, high specific surface area, good chemical stability, and rich functionalization potential. Extended π-conjugation in the backbone of covalent organic frameworks can generate useful luminescent properties. [3] Covalent organic frameworks are potential fluorescent materials. Furthermore, their high porosity makes them excellent supports, effectively avoiding fluorescence quenching caused by carbon quantum dot self-aggregation and improving the mass transfer rate of the target compound, thereby further enhancing the efficiency of fluorescence detection. [4] .
[0004] Therefore, we propose to develop a ratiometric fluorescent probe based on covalent organic framework carbon quantum dots by bulk polymerization to dope covalent organic framework materials with carbon quantum dots. This approach can maintain the excellent optical properties of quantum dots while leveraging the structural advantages of the covalent organic framework to regulate the surface properties of the probe and enhance its selective binding ability with the target analyte.
[0005] References
[0006] [1]TC Wareing,P.Gentile,ANPhan.Biomass-Based CarbonDots:CurrentDevelopmentandFuturePerspectives.ACSNano 15(2021)15471-15501.
[0007] [2]J.Ju,W.Chen.Synthesis of highly fluorescent nitrogen-dopedgraphene quantum dots for sensitive,label-free detection ofFe(III)inaqueousmedia.BiosensorsandBioelectronics58(2014)219-225.
[0008] [3]HWKral,MEM,WER,MPLThe luminescent and photophysicalproperties of covalent organic frameworks.Chem.Soc.Rev.49(2020)839-864.
[0009] [4] S. Wang, N. Liang, X. Hu, W. Li, Z. Guo, X. Zhang, X. Huang, Z. Li, Summary of the Invention
[0010] To address the complex processes required for sample pretreatment and instrumental analysis in existing technologies, this invention provides a method for preparing a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework, enabling the visual detection of α-dicarbonyl compounds in food.
[0011] This invention is achieved through the following technical solution:
[0012] This invention discloses a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework. The fluorescent probe comprises nitrogen-doped bio-carbon quantum dots synthesized using waste durian shells as a carbon source and a three-dimensional acylhydrazine-imine covalent organic framework generated by the hydrothermal reaction of 2,5-bis(allyloxy)terephthalohydrazide with 4',4”',4””',4”””-(ethylene-1,1,2,2-tetramethyl)tetra(([[1,1'-biphenyl]-4-carboxaldehyde)). The ratiometric fluorescence is synthesized by bulk polymerization, wherein the ratio of nitrogen-doped bio-carbon quantum dots to three-dimensional acylhydrazine-imine covalent organic framework is 2:1-3:1.
[0013] As a further improvement, the present invention also discloses a method for preparing a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework. The method uses carbon quantum dots and a covalent organic framework as fluorescent materials and prepares the ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework by curing and crosslinking.
[0014] As a further improvement, the carbon quantum dots described in this invention are nitrogen-doped carbon quantum dots generated by the hydrothermal reaction of waste durian shell powder and ethylenediamine.
[0015] As a further improvement, the covalent organic framework described in this invention is an acylhydrazine-imine type covalent organic framework generated by the hydrothermal reaction of 2,5-bis(allyloxy)terephthalohydrazide and 4',4”',4””',4”””'-(ethylene-1,1,2,2-tetramethyl)tetra(([[1,1'-biphenyl]-4-carboxaldehyde)).
[0016] As a further improvement, the specific preparation steps described in this invention are as follows:
[0017] 1) An appropriate amount of 2,5-bis(allyloxy)terephthalohydrazide and 4',4”',4””',4”””-(ethylene-1,1,2,2-tetramethyl)tetra(([[1,1'-biphenyl]-4-carboxaldehyde)) were ultrasonically dispersed in toluene, and acetic acid was added to obtain a homogeneous reaction solution;
[0018] 2) The reaction solution obtained in 1) was reacted under sealed conditions for a period of time, and then centrifuged to obtain a yellow powder, which is the covalent organic framework;
[0019] 3) Dry the durian peel at 80℃ overnight to remove as much moisture as possible, then grind it into durian peel powder;
[0020] 4) The durian peel powder obtained in 3) is mixed with ethylenediamine in water, and then transferred to a reaction vessel for hydrothermal reaction at a certain temperature to obtain a pale yellow solution;
[0021] 5) Centrifuge the pale yellow solution obtained in step 4) at high speed to obtain carbon quantum dots;
[0022] 6) Add the covalent organic framework obtained in 2) and the carbon quantum dots obtained in 5) to ethanol, sonicate, add acrylamide and stir until homogeneous, then add ethylene glycol dimethacrylate and azobisisobutyronitrile, seal and heat and stir under nitrogen.
[0023] As a further improvement, in step 1) of the present invention, the concentration of 2,5-bis(allyloxy)terephthalohydrazide is 9 mg / mL-10 mg / mL, the concentration of 4',4”',4””',4”””-(ethylene-1,1,2,2-tetramethyl)tetra(([[1,1'-biphenyl]-4-carboxaldehyde)) is 21 mg / mL-23 mg / mL, the concentration of acetic acid is 2 mol / L-3 mol / L, and the reaction temperature in step 2) is 120℃-140℃, and the reaction time is 60h-72h.
[0024] As a further improvement, in step 4) of the present invention, the concentration of durian peel powder is 7 mg / mL-10 mg / mL, the volume ratio of ethylenediamine to water is 5:100-15:100, the reaction temperature is 160℃-180℃, and the reaction time is 5h-7h.
[0025] As a further improvement, in step 6) of this invention, the concentration of the covalent organic framework is 0.1 mg / mL-0.3 mg / mL, the concentration of carbon quantum dots is 0.05 mg / mL-0.1 mg / mL, the concentration of acrylamide is 16 mg / mL-18 mg / mL, the volume ratio of ethylene glycol dimethacrylate to ethanol is 1:10-1.5:10, the concentration of azobisisobutyronitrile is 8 mg / mL-12 mg / mL, the reaction temperature is 150℃-170℃, and the reaction time is 20h-30h.
[0026] The present invention has the following advantages and effects:
[0027] 1. This invention uses carbon quantum dot hybrid covalent organic framework to prepare ratiometric fluorescent probes. Based on carbon quantum dots and covalent organic framework, two fluorescent emission signals with different wavelengths are formed, reducing errors caused by signal drift, instrument changes and other factors in the experiment.
[0028] 2. This invention uses a three-dimensional hydrazide-imine covalent organic framework as a substrate, and reduces the self-quenching of carbon quantum dots through fluorescence resonance energy transfer between the framework and quantum dots.
[0029] 3. 2,5-bis(allyloxy)terephthalohydrazide and 4',4”',4””',4”””-(ethylene-1,1,2,2-tetramethyl)tetra(([[1,1'-biphenyl]-4-carboxaldehyde)) were selected as reaction monomers. The strong adsorption capacity of the covalent organic framework synthesized by these monomers on the target compound was utilized to improve the detection speed of the ratiometric fluorescent probe.
[0030] 4. This invention uses ethylenediamine doping to prepare nitrogen-doped carbon quantum dots, thereby improving their fluorescence response capability.
[0031] 5. This invention uses waste durian peels to prepare nitrogen-doped carbon quantum dots, which is green and environmentally friendly.
[0032] 6. This invention is based on the color change of a ratiometric fluorescent probe in α-dicarbonyl compounds of different concentrations, enabling the visual detection of α-dicarbonyl compounds in videos.
[0033] 7. This invention uses a bulk curing method to prepare carbon quantum dot hybrid covalent organic framework fluorescent probes, which enables strong π-π conjugation and hydrogen bonds to form between carbon quantum dots and covalent organic frameworks, thereby improving the stability of the material and extending its service life.
[0034] 8. In the preparation of carbon quantum dots, this invention controls the concentration of durian peel powder to be 7 mg / mL-10 mg / mL, the volume ratio of ethylenediamine to water to be 5:100-15:100, the reaction temperature to be 160℃-180℃, and the reaction time to be 5h-7h, so that the synthesized nitrogen-doped carbon quantum dots have a suitable size and thus exhibit the best fluorescence response value.
[0035] 9. In the preparation of the fluorescent probe, the concentration of the covalent organic framework is controlled to be 0.1 mg / mL-0.3 mg / mL and the concentration of carbon quantum dots is controlled to be 0.05 mg / mL-0.1 mg / mL. This results in a good linear relationship between the response value ratio of the fluorescent probe at 510 nm and 670 nm and the concentration of the target analyte, and also exhibits a low detection limit. Attached Figure Description
[0036] Figure 1 This is a schematic diagram illustrating the preparation method of a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework. Detailed Implementation
[0037] This invention discloses a method for preparing a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework. The method involves dispersing the covalent organic framework and carbon quantum dots in ethanol, adding acrylamide and stirring for a period of time, then adding ethylene glycol dimethacrylate and azobisisobutyronitrile (AIBN), sealing the mixture under nitrogen atmosphere, and heating and stirring. After washing with methanol and drying, the ratiometric fluorescent probe based on the carbon quantum dot hybrid covalent organic framework is obtained. The specific preparation steps are as follows:
[0038] 1) An appropriate amount of 2,5-bis(allyloxy)terephthalohydrazide and 4',4”',4””',4”””'-(ethylene-1,1,2,2-tetramethyl)tetra(([[1,1'-biphenyl]-4-carboxaldehyde)) were ultrasonically dispersed in toluene, and an appropriate amount of acetic acid was added to obtain a homogeneous reaction solution. The concentration of 2,5-bis(allyloxy)terephthalohydrazide was 9 mg / mL-10 mg / mL, the concentration of 4',4”',4””’,4”””'-(ethylene-1,1,2,2-tetramethyl)tetra(([[1,1'-biphenyl]-4-carboxaldehyde)) was 21 mg / mL-23 mg / mL, and the concentration of acetic acid was 2 mol / L-3 mol / L;
[0039] 2) The reaction solution obtained in 1) was transferred to a reaction vessel and reacted at 120°C for 72 h. The yellow powder obtained by centrifugation was obtained, which is the covalent organic framework.
[0040] 3) Dry the durian peel at 80℃ overnight to remove as much moisture as possible, then grind it into durian peel powder;
[0041] 4) Mix the durian peel powder obtained in 3) with ethylenediamine in water, then transfer it to a reaction vessel and hydrothermally react at 180℃ for 5 hours to obtain a pale yellow solution. The concentration of the durian peel powder is 7mg / mL-10mg / mL, and the volume ratio of ethylenediamine to water is 5:100-15:100.
[0042] 5) Centrifuge the solution obtained in step 4) at 10000 r / min for 20 min, and then dry it at 60 degrees Celsius to obtain nitrogen-doped carbon quantum dots.
[0043] 6) Add the covalent organic framework obtained in step 2) and the carbon quantum dots obtained in step 5) to ethanol, sonicate for 10 min, add acrylamide and stir for 30 min, then add ethylene glycol dimethacrylate and azobisisobutyronitrile, seal and heat and stir under nitrogen. The concentration of covalent organic framework is 0.1 mg / mL-0.3 mg / mL, the concentration of carbon quantum dots is 0.05 mg / mL-0.1 mg / mL, the concentration of acrylamide is 16 mg / mL-18 mg / mL, the volume ratio of ethylene glycol dimethacrylate to ethanol is 1:10-1.5:10, the concentration of azobisisobutyronitrile is 8 mg / mL-12 mg / mL, the reaction temperature is 150℃-170℃, and the reaction time is 20 h-30 h.
[0044] Under 365 nm UV light irradiation, the ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework exhibits a purple color. When placed in a low concentration of α-dicarbonyl compound and then irradiated with a 365 nm UV light, the ratiometric fluorescent probe appears pale purple or bluish-gray. As the concentration of the α-dicarbonyl compound increases, the color of the ratiometric fluorescent probe changes to green. This is due to the strong π-π conjugation between the target compound, the carbon quantum dot aggregates, and the covalent organic framework, which restricts the rotation of the covalent organic framework and enhances its fluorescence response. The detection method established using the ratiometric fluorescent probe based on the carbon quantum dot hybrid covalent organic framework can complete adsorption and fluorescence response within 15 min, and the detection limit for α-dicarbonyl compounds can reach 0.1 μg / kg.
[0045] The detection method established using a fluorescent probe based on an ionic liquid-doped covalent organic framework completed adsorption and fluorescence response in 18 min, with a detection limit of 0.31 μg / kg for α-dicarbonyl compounds.
[0046] Comparing the two fluorescent probes, it can be seen that carbon quantum dots can more effectively fill the pores of covalent organic frameworks, reduce their interlayer stacking, and enhance their fluorescence performance. Therefore, ratiometric fluorescent probes based on carbon quantum dot hybrid covalent organic frameworks have faster response speeds and lower detection limits for α-dicarbonyl compounds.
[0047] In comparison, the covalent organic framework obtained in step 2) and the carbon quantum dots obtained in step 5) were added to N,N-dimethylformamide and stirred for 2 hours to directly obtain a carbon quantum dot hybrid covalent organic framework. After four adsorption-elution cycles, the fluorescence response value of this material decreased to 80% of its initial value. In contrast, the carbon quantum dot hybrid covalent organic framework prepared by the method described in this invention only decreased to 80% of its initial value after more than eight uses. This demonstrates that bulk polymerization can effectively hybridize carbon quantum dots onto the surface of a covalent organic framework, improving the material's stability and reusability.
[0048] The detection limits of ratiometric fluorescent probes for α-dicarbonyl compounds at different concentrations of covalent organic frameworks are shown in Table 1.
[0049] Table 1
[0050]
[0051]
[0052] As shown in Table 1, the detection limit first decreases and then increases with increasing covalent organic framework concentration. This may be because at excessively high covalent organic framework concentrations, quantum dots cannot effectively fill their pores, resulting in severe interlayer stacking and increased self-quenching. Consequently, the intensity ratio of the emission spectra at 510 nm and 670 nm decreases. The data in Table 1 indicate that fluorescent probes prepared with covalent organic framework concentrations of 0.1 mg / mL to 0.3 mg / mL exhibit lower detection limits and higher practical application value.
[0053] Table 2 shows the emission peak intensities of the ratiometric fluorescent probe at 510 nm and 670 nm under different nitrogen-doped carbon quantum dot concentrations.
[0054] Table 2
[0055]
[0056] As shown in Table 2, with the increase of carbon quantum dot concentration, the emission peak intensity of the ratiometric fluorescent probe at 510 nm remained basically unchanged, while the emission peak at 670 nm first increased and then remained unchanged. According to the experimental results, the carbon quantum dot concentration in the range of 0.05 mg / mL to 0.1 mg / mL had the best effect.
[0057] The technical solution of the present invention will be further described below with reference to the accompanying drawings:
[0058] This invention prepares a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework. Through the specific adsorption of α-dicarbonyl compounds by the covalent organic framework and the dual fluorescence response of the covalent organic framework and carbon quantum dots, the visual detection of α-dicarbonyl compounds in food is realized.
[0059] Figure 1 This is a schematic diagram illustrating a method for preparing a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework. The specific preparation process is as follows:
[0060] 18 mg of 2,5-bis(allyloxy)terephthalohydrazide and 42 mg of 4',4”',4””',4”””-(ethylene-1,1,2,2-tetramethyl)tetra(([[1,1'-biphenyl]-4-carboxaldehyde)) were ultrasonically dispersed in 2 mL of toluene. 1 mL of 6 mol / L acetic acid was added to obtain a homogeneous reaction solution, which was then transferred to a reaction vessel and reacted at 120 °C for 72 h. Centrifugation yielded a yellow powder, which was the covalent organic framework. Durian peel was dried overnight at 80 °C to remove as much moisture as possible, then ground into durian peel powder. 200 mg of durian peel powder and 2.5 mL of ethylenediamine were mixed in 25 mL of water. In a transfer reactor, a hydrothermal reaction was carried out at 180°C for 5 hours to obtain a pale yellow solution. The solution was centrifuged at 10,000 r / min for 20 minutes and then dried at 60°C to obtain nitrogen-doped carbon quantum dots. 1.0 mg of covalent organic framework and 0.35 mg of carbon quantum dots were added to 5 mL of ethanol and sonicated for 10 minutes. 85 mg of acrylamide was added and the mixture was stirred for 30 minutes. Then, 0.6 mL of ethylene glycol dimethacrylate and 50 mg of azobisisobutyronitrile were added. The mixture was sealed and heated and stirred at 160°C for 24 hours under nitrogen atmosphere. After centrifugation, the solution was washed three times with methanol and dried to obtain a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework.
[0061] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework, characterized in that, A ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework was prepared by using carbon quantum dots and covalent organic frameworks as fluorescent materials through a curing and crosslinking process. The carbon quantum dots were nitrogen-doped carbon quantum dots generated by the hydrothermal reaction of waste durian shell powder and ethylenediamine. The covalent organic framework was a hydrazide-imine type covalent organic framework generated by the hydrothermal reaction of 2,5-bis(allyloxy)terephthalohydrazide and 4',4''',4'''',4''''''-(ethylene-1,1,2,2-tetramethyl)tetra(([1,1'-biphenyl]-4-formaldehyde)). The specific preparation steps are as follows: An appropriate amount of 2,5-bis(allyloxy)terephthalohydrazide and 4',4''',4'''',4'''''''-(ethylene-1,1,2,2-tetramethyl)tetra(([1,1'-biphenyl]-4-formaldehyde)) were ultrasonically dispersed in toluene, and acetic acid was added to obtain a homogeneous reaction solution; The reaction solution obtained in 1) was reacted under sealed conditions for a period of time, and then centrifuged to obtain a yellow powder, which is the covalent organic framework; Dry the durian peel at 80°C overnight to remove as much moisture as possible, then grind it into durian peel powder; The durian peel powder obtained in step 3) was mixed with ethylenediamine in water, and then transferred to a reaction vessel for hydrothermal reaction at a certain temperature to obtain a pale yellow solution. The light yellow solution obtained in step 4) can be centrifuged at high speed to obtain nitrogen-doped carbon quantum dots; The covalent organic framework obtained in step 2) and the nitrogen-doped carbon quantum dots obtained in step 5) were added to ethanol, sonicated, and then acrylamide was added and stirred until homogeneous. Subsequently, ethylene glycol dimethacrylate and azobisisobutyronitrile were added, and the mixture was sealed and heated and stirred under nitrogen atmosphere. The concentration of the covalent organic framework was 0.1 mg / mL - 0.3 mg / mL, the concentration of the nitrogen-doped carbon quantum dots was 0.05 mg / mL - 0.1 mg / mL, the concentration of acrylamide was 16 mg / mL - 18 mg / mL, the volume ratio of ethylene glycol dimethacrylate to ethanol was 1:10 - 1.5:10, the concentration of azobisisobutyronitrile was 8 mg / mL - 12 mg / mL, the reaction temperature was 150℃ - 170℃, and the reaction time was 20 h - 30 h.
2. The method for preparing a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework according to claim 1, characterized in that, In step 1), the concentration of 2,5-bis(allyloxy)terephthalohydrazide is 9 mg / mL - 10 mg / mL, the concentration of 4',4''',4'''',4''''''-(ethylene-1,1,2,2-tetramethyl)tetra(([1,1'-biphenyl]-4-formaldehyde)) is 21 mg / mL - 23 mg / mL, and the concentration of acetic acid is 2 mol / L - 3 mol / L. In step 2), the reaction temperature is 120℃ - 140℃, and the reaction time is 60 h - 72 h.
3. The method for preparing a ratiometric fluorescent probe based on a carbon quantum dot hybrid covalent organic framework according to claim 2, characterized in that, In step 4), the concentration of durian peel powder is 7 mg / mL-10 mg / mL, the volume ratio of ethylenediamine to water is 5:100-15:100, the reaction temperature is 160℃-180℃, and the reaction time is 5 h-7 h.