Method for recovering solid carbon quantum dots

Abstract

The invention discloses a method for recycling solid carbon quantum dots, and relates to the technical field of solid carbon quantum dot recycling. Comprising the following steps: constructing a control model for controlling parameters of a carbon quantum dot vacuum freeze-drying process, optimizing a vacuum freeze-drying system, establishing a monitoring system for recovering solid carbon quantum dots, filtering, and performing vacuum freeze-drying. Passivating and functionally modifying the carbon quantum dot solution, and dynamically controlling the vacuum freeze drying temperature and time of the passivated carbon quantum dot solution with different product sub-packaging thicknesses by using a control model; the control model is used for dynamically controlling the vacuum freeze drying temperature and time of passivated carbon quantum dot solutions with different product sub-packaging thicknesses, so that the recovery efficiency and quality of solid carbon quantum dots can be improved; the problems that the recovered solid carbon quantum dots are poor in quality and easy to agglomerate due to the fact that a traditional recovery method cannot be dynamically controlled are solved; and the method can save energy to the maximum extent.

Description

Technical Field

[0001] The invention relates to the technical field of solid carbon quantum dot recovery, and in particular to a method for recovering solid carbon quantum dots. Background Art

[0002] In recent years, carbon quantum dots (Carbondots, particle size <10nm) have attracted great attention from researchers as a new type of fluorescent material because of their special zero-dimensional nanostructure with surface effect, small size effect and quantum effect, and will also produce special fluorescence characteristics. Compared with traditional semiconductor quantum dots and organic dyes, carbon dots not only maintain the advantages of carbon materials such as low toxicity and good biocompatibility, but also have incomparable advantages such as good photostability, adjustable luminescence wavelength, no light flicker, large two-photon absorption area, easy functionalization, low cost, and easy large-scale preparation. They are widely used in the fields of material detection, photocatalysis, bioimaging, and solar cells.

[0003] When freeze-drying a carbon quantum dot solution to recover solid carbon quantum dots, the traditional method lacks precise control of parameters during the recovery process and cannot achieve rapid and efficient recovery. Therefore, the present invention proposes a method for recovering solid carbon quantum dots to address the deficiencies in the prior art. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a method for recovering solid carbon quantum dots. By utilizing a control model to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution with different product packaging thicknesses, the recovery efficiency and quality of the solid carbon quantum dots can be improved, thereby avoiding the problem that the traditional recovery method cannot be dynamically controlled, resulting in the recovered solid carbon quantum dots having poor quality and easy agglomeration; and the method of the present invention can maximize energy savings.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for recovering solid carbon quantum dots comprises the following steps:

[0007] Step 1: construct a control model for controlling the parameters of the carbon quantum dot vacuum freeze-drying process;

[0008] Step 2: Optimize the vacuum freeze drying system;

[0009] Step 3: Establish a monitoring system for recycling solid carbon quantum dots;

[0010] Step 4: Filtration, passivation and functional modification of carbon quantum dot solution;

[0011] Step 5: Using the control model to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution with different product packaging thicknesses;

[0012] Step 6: According to the vacuum freeze-drying temperature and time parameters given by the control model, the passivated carbon quantum dot solution is dried using the optimized vacuum freeze-drying system, and the drying recovery process is monitored in real time according to the established monitoring system.

[0013] Further improvement is that when constructing the control model in step 1, first use full factorial design, fractional factorial design, Latin hypercube sampling or Box-Behnken design in response surface method (RSM) and other methods to rationally plan the experiment, determine the value range of carbon quantum dot packaging thickness (x), vacuum freeze-drying temperature (T) and drying time (t), and select the appropriate number of levels, then conduct experiments to obtain the value of maximizing product quality (Q) under each experimental condition, and establish a mathematical model based on the experimental data.

[0014] A further improvement is that when constructing the control model in step one, a machine learning library is used to fit the mathematical model, and the control mathematical model conforms to Q=f(x,T,t), and then the mathematical model Q=f(x,T,t) is verified and optimized to obtain a control model for controlling the parameters of the carbon quantum dot vacuum freeze-drying process.

[0015] Further improvement is: when verifying and optimizing the mathematical model Q=f(x,T,t), the prediction performance of the model is evaluated by using the holdout method or cross-validation method, the predicted value of the mathematical model Q=f(x,T,t) and the actual experimental value are judged, and then the optimization algorithm such as genetic algorithm, particle swarm optimization, simulated annealing, etc. is used to search for the optimal solution.

[0016] Further improvement is that when optimizing the vacuum freeze-drying system in step 2, the structural design of the freeze dryer used in the vacuum freeze-drying system is optimized, specifically, the freeze dryer pipeline is improved to reduce pipeline resistance, and the condenser is improved to improve heat and mass transfer efficiency.

[0017] A further improvement is that when a monitoring system for recovering solid carbon quantum dots is established in step three, the entire process of recovering solid carbon quantum dots is monitored using the established monitoring system, including constructing a variable detection module in the monitoring system that uses an electrochemical method to detect the impurity status of the carbon quantum dot solution.

[0018] A further improvement is that when the carbon quantum dot solution is passivated in step 4, the surface of the carbon quantum dot solution is passivated by introducing organic molecules, inorganic ions or polymers.

[0019] A further improvement is that when the carbon quantum dot solution is functionally modified in step 4, the carbon quantum dot solution is functionally modified by doping heteroatoms such as nitrogen and sulfur into the carbon quantum dot solution or connecting specific functional groups.

[0020] A further improvement is that when the control model is used in step five to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution with different product packaging thicknesses, it also includes using the results detected by the variable detection module as variable parameters of the control model to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution with different product packaging thicknesses.

[0021] A further improvement is that the step six also includes grinding and screening the recovered solid carbon quantum dots, and finally storing them in a light-proof and sealed manner.

[0022] The beneficial effects of the present invention are as follows: the present invention constructs a control model for controlling the parameters of the vacuum freeze-drying process of carbon quantum dots, optimizes the vacuum freeze-drying system, establishes a monitoring system for recovering solid carbon quantum dots, filters, passivates and functionally modifies the carbon quantum dot solution, and uses the control model to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution with different product packaging thicknesses, thereby improving the recovery efficiency and quality of solid carbon quantum dots, avoiding the problem that the traditional recovery method cannot be dynamically controlled, resulting in poor quality of the recovered solid carbon quantum dots and easy agglomeration; and the method of the present invention can maximize energy savings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0024] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0025] according to Figure 1 As shown, this embodiment provides a method for recovering solid carbon quantum dots, comprising the following steps:

[0026] Step 1: Construct a control model for controlling the parameters of the vacuum freeze-drying process of carbon quantum dots; when constructing the control model, first use full factorial design, fractional factorial design, Latin hypercube sampling or Box-Behnken design in response surface method (RSM) to rationally plan the experiment, determine the value range of carbon quantum dot packaging thickness (x), vacuum freeze-drying temperature (T) and drying time (t), and select the appropriate number of levels, then conduct experiments to obtain the value of maximizing product quality (Q) under each experimental condition, and establish a mathematical model based on the experimental data; use A machine learning library is used to fit a mathematical model, and the mathematical model is controlled to conform to Q=f(x, T, t), and then the mathematical model Q=f(x, T, t) is verified and optimized to obtain a control model for controlling parameters of the vacuum freeze-drying process of carbon quantum dots; when verifying and optimizing the mathematical model Q=f(x, T, t), a holdout method or a cross-validation method is used to evaluate the prediction performance of the model, and the predicted value of the mathematical model Q=f(x, T, t) is judged to be different from the actual experimental value, and then an optimization algorithm such as a genetic algorithm, a particle swarm optimization, and a simulated annealing is used to search for the optimal solution;

[0027] Step 2: Optimize the vacuum freeze drying system, including optimizing the freeze dryer structure design used in the vacuum freeze drying system, specifically: improve the freeze dryer pipeline to reduce pipeline resistance, and improve the condenser to improve heat and mass transfer efficiency;

[0028] Step three: Establish a monitoring system for recycling solid carbon quantum dots, and use the established monitoring system to monitor the entire process of recycling solid carbon quantum dots, including building a variable detection module in the monitoring system that uses electrochemical methods to detect the impurity situation of the carbon quantum dot solution; when the monitoring system monitors the entire process of recycling solid carbon quantum dots, it includes monitoring the standardization of the recycling operation steps. The monitoring system also has a reminder function, which is used to promptly prompt incorrect recycling operation steps.

[0029] Step 4: Filtration, passivation and functional modification of the carbon quantum dot solution. When passivating the carbon quantum dot solution, the surface of the carbon quantum dot solution is passivated by introducing organic molecules, inorganic ions or polymers. The organic molecule can be polyethylene glycol (PEG). PEG is one of the most commonly used organic molecules. Through the interaction between its functional groups and the surface of carbon quantum dots, the fluorescence quantum yield and stability of carbon quantum dots can be effectively improved. PEGs of different molecular weights (such as PEG2000, PEG1500N, etc.) have different passivation effects on carbon quantum dots and can be reasonably selected. The organic molecules can be amino-terminated polyethylene glycol and polyetherimide, which are combined with the surface of carbon quantum dots through amidation reaction to achieve surface passivation; the inorganic ions can be zinc oxide (ZnO) or zinc sulfide (ZnS), and the coating of inorganic substances can significantly improve the luminescence intensity of carbon quantum dots; the polymer can be polyindole boric acid or poly (3-hexylthiophene) (P3HT), which are combined with the surface of carbon quantum dots through different chemical reactions to form a stable composite structure, thereby improving the optical properties and stability of carbon quantum dots.

[0030] When functionally modifying the carbon quantum dot solution, the carbon quantum dot solution is functionally modified by doping heteroatoms such as nitrogen and sulfur into the carbon quantum dot solution or connecting specific functional groups; specifically:

[0031] When nitrogen doping is selected to functionalize the carbon quantum dot solution, nitrogen doping is a common method for functional modification of carbon quantum dots. The optical and electrical properties of carbon quantum dots can be regulated by introducing nitrogen atoms, including selecting an appropriate nitrogen source (such as ethylenediamine, urea, 3-dimethylaminopropylamine, etc.) to dissolve the carbon source and nitrogen source in a certain volume of deionized water to form a uniform mixed solution. Pay attention to controlling the molar ratio of the raw materials and the concentration of the solution, pour the mixed solution into a high-pressure reactor, seal it, and place it in a blast drying oven for hydrothermal reaction. The reaction temperature and time need to be optimized according to the specific raw materials and the desired product properties. Usually, the reaction is carried out at 160-220°C for 3-12 hours. After the reaction is completed, the high-pressure reactor is cooled to room temperature, and the resulting solution is centrifuged, washed, and dialyzed to finally obtain a nitrogen-doped carbon quantum dot solution.

[0032] When sulfur doping is selected to functionalize the carbon quantum dot solution, sulfur doping is similar to nitrogen doping, but the introduction of sulfur atoms can change the energy band structure and photoelectric properties of carbon quantum dots, including the selection of sulfur-containing compounds as sulfur sources (such as thiourea, sodium sulfide, etc.), and the selection of a suitable carbon source, dissolving the carbon source and sulfur source in deionized water, mixing them evenly, and then performing a hydrothermal reaction or other appropriate chemical reaction. The reaction conditions need to be adjusted according to the properties of the sulfur source and the carbon source. After the reaction is completed, centrifugation, washing, and dialysis steps are required to finally obtain a sulfur-doped carbon quantum dot solution.

[0033] When a specific functional group is selected to achieve functional modification of a carbon quantum dot solution, in order to give the carbon quantum dots specific functions, the specific functional group can be connected to the surface of the carbon quantum dot through a chemical reaction, and appropriate functional groups (such as carboxyl, amino, hydroxyl, etc.) are selected according to the required functions. First, an appropriate activator (such as EDC / NHS, etc.) is used to activate the functional groups on the surface of the carbon quantum dots to make them more easily react with other molecules, and the activated carbon quantum dots are coupled with molecules containing target functional groups to form stable chemical bonds. The reaction conditions need to be optimized according to the properties of the functional groups and coupling reagents, and purification is performed after the reaction to remove unreacted reagents and impurities, and the product is analyzed for structure and performance by appropriate characterization methods (such as infrared spectroscopy, fluorescence spectroscopy, transmission electron microscopy, etc.).

[0034] Step 5: using the control model to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution of different product packaging thicknesses, and also including using the results detected by the variable detection module as the variable parameters of the control model to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution of different product packaging thicknesses. If the impurity content in the carbon quantum dot solution of the same product packaging thickness is different, the product quality obtained by freeze-drying and recovering the solid carbon quantum dots using the same vacuum freeze-drying temperature and time is also different. Therefore, by detecting the impurity situation of the carbon quantum dot solution to adjust the vacuum freeze-drying temperature and time, high-quality solid carbon quantum dots can be obtained;

[0035] Step 6: According to the vacuum freeze-drying temperature and time parameters given by the control model, the passivated carbon quantum dot solution is dried using the optimized vacuum freeze-drying system, and the drying recovery process is monitored in real time according to the established monitoring system. The recovered solid carbon quantum dots are then ground and screened, and finally stored in a light-proof and sealed manner.

[0036] Verification Example

[0037] By using a conventional vacuum freeze-drying system (without freeze-drying machine structural design optimization), a carbon quantum dot solution with a mass of A (A=1L) and a product packaging thickness of B (B=3cm) was subjected to vacuum freeze-drying at a vacuum freeze-drying temperature (T)=-50°C, and the drying time (t) required for drying to be completed was recorded, and the value of the maximized product quality (Q) was determined; by using the method of the present invention, a carbon quantum dot solution with a mass of A and a product packaging thickness of B was subjected to vacuum freeze-drying at a vacuum freeze-drying temperature (T)=-50°C, and the drying time (t) required for drying to be completed was recorded, and the value of the maximized product quality (Q) was determined, and finally the results as shown in Table 1 were obtained:

[0038] Table 1

[0039]

[0040] It can be seen from the results in Table 1 that, at the same freeze-drying temperature, the method of the present invention takes a shorter time to recover solid carbon quantum dots, and the recovered solid carbon quantum dots have better quality and a lower agglomeration ratio.

[0041] The present invention constructs a control model for controlling the parameters of the vacuum freeze-drying process of carbon quantum dots, optimizes the vacuum freeze-drying system, establishes a monitoring system for recovering solid carbon quantum dots, filters, passivates and functionally modifies the carbon quantum dot solution, and uses the control model to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution with different product packaging thicknesses, thereby improving the recovery efficiency and quality of the solid carbon quantum dots, avoiding the problem that the traditional recovery method cannot be dynamically controlled, resulting in the poor quality of the recovered solid carbon quantum dots and easy agglomeration; and the method of the present invention can maximize energy savings.

[0042] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for recovering solid carbon quantum dots, characterized in that: The following steps are involved: Step 1: construct a control model for controlling the parameters of the carbon quantum dot vacuum freeze-drying process; Step 2: Optimize the vacuum freeze drying system; Step 3: Establish a monitoring system for recycling solid carbon quantum dots; Step 4: Filtration, passivation and functional modification of carbon quantum dot solution; Step 5: Using the control model to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution with different product packaging thicknesses; Step 6: According to the vacuum freeze-drying temperature and time parameters given by the control model, the passivated carbon quantum dot solution is dried using the optimized vacuum freeze-drying system, and the drying recovery process is monitored in real time according to the established monitoring system.

2. A method for recovering solid carbon quantum dots according to claim 1, characterized in that: When constructing the control model in the step 1, first use full factorial design, fractional factorial design, Latin hypercube sampling or Box-Behnken design in response surface method (RSM) and other methods to rationally plan the experiment, determine the value range of carbon quantum dot packaging thickness (x), vacuum freeze-drying temperature (T) and drying time (t), and select the appropriate number of levels, then conduct experiments to obtain the value of maximized product quality (Q) under each experimental condition, and establish a mathematical model based on the experimental data.

3. A method for recovering solid carbon quantum dots according to claim 2, characterized in that: When constructing the control model in step one, a machine learning library is used to fit the mathematical model, and the control mathematical model conforms to Q=f(x,T,t). Then, the mathematical model Q=f(x,T,t) is verified and optimized to obtain a control model for controlling the parameters of the carbon quantum dot vacuum freeze-drying process.

4. A method for recovering solid carbon quantum dots according to claim 3, characterized in that: When verifying and optimizing the mathematical model Q=f(x,T,t), the prediction performance of the model is evaluated by using the holdout method or the cross-validation method, the predicted value of the mathematical model Q=f(x,T,t) and the actual experimental value are judged, and then the optimization algorithms such as genetic algorithm, particle swarm optimization, simulated annealing, etc. are used to search for the optimal solution.

5. A method for recovering solid carbon quantum dots according to claim 1, characterized in that: When optimizing the vacuum freeze drying system in the second step, it includes optimizing the structural design of the freeze dryer used in the vacuum freeze drying system, specifically: improving the freeze dryer pipeline to reduce pipeline resistance, and improving the condenser to improve heat and mass transfer efficiency.

6. A method for recovering solid carbon quantum dots according to claim 1, characterized in that: When establishing a monitoring system for recovering solid carbon quantum dots in step three, the established monitoring system is used to monitor the entire process of recovering solid carbon quantum dots, including constructing a variable detection module in the monitoring system that uses an electrochemical method to detect the impurity situation of the carbon quantum dot solution.

7. A method for recovering solid carbon quantum dots according to claim 1, characterized in that: When the carbon quantum dot solution is passivated in step 4, the surface of the carbon quantum dot solution is passivated by introducing organic molecules, inorganic ions or polymers.

8. A method for recovering solid carbon quantum dots according to claim 7, characterized in that: When the carbon quantum dot solution is functionally modified in step 4, the carbon quantum dot solution is functionally modified by doping heteroatoms such as nitrogen and sulfur into the carbon quantum dot solution or connecting specific functional groups.

9. A method for recovering solid carbon quantum dots according to claim 6, characterized in that: In the step five, when the control model is used to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution with different product packaging thicknesses, it also includes using the results detected by the variable detection module as variable parameters of the control model to dynamically control the vacuum freeze-drying temperature and time of the passivated carbon quantum dot solution with different product packaging thicknesses.

10. A method for recovering solid carbon quantum dots according to claim 1, characterized in that: The step six also includes grinding and screening the recovered solid carbon quantum dots, and finally storing them in a light-proof and sealed manner.

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