Oleophilic hydrophobic carbon quantum dots and preparation method thereof

Abstract

This invention discloses an oleophilic-hydrophobic carbon quantum dot and its preparation method. The preparation method includes the following steps: (1) mixing oleic acid vegetable oil and amino acids in a certain proportion and stirring evenly to form a mixed reaction raw material; (2) placing the mixed reaction raw material in a sealed reaction container and reacting at 200~250℃ for at least 2 hours. After the reaction is completed, the mixture is cooled to room temperature, and the reaction product in the reaction container is taken out and subjected to ultrasonic dispersion, centrifugation, filtration purification, and freeze drying in sequence to obtain oleophilic-hydrophobic carbon quantum dots. The surface of the oleophilic-hydrophobic carbon quantum dots has alkyl long chains and amino groups, and the water contact angle of the oleophilic-hydrophobic carbon quantum dots is greater than 100°. This invention uses vegetable oil as a carbon source and amino acids as a nitrogen source to obtain oleophilic-hydrophobic carbon quantum dots that can be dissolved in non-polar systems such as oils through a one-step hydrothermal method, which solves the technical problem that existing carbon quantum dots have strong hydrophilicity and are difficult to disperse stably in non-polar systems and have functional applications.

Description

Technical Field

[0001] This invention relates to the field of carbon quantum dot preparation technology, specifically to an oleophilic and hydrophobic carbon quantum dot and its preparation method. Background Technology

[0002] Carbon quantum dots have been widely studied and applied in sensing, imaging, catalysis, and anti-counterfeiting fields due to their excellent optical properties, low toxicity, and good biocompatibility. However, current technologies for preparing carbon quantum dots have the following drawbacks: Traditional carbon quantum dots are mostly prepared by strong acid oxidation or high-temperature pyrolysis. Their surfaces are rich in hydrophilic groups such as carboxyl and hydroxyl groups, which makes them well dispersed in water. However, they are prone to agglomeration and deactivation in non-polar systems such as oils and fats. To realize the application of carbon quantum dots in non-polar systems such as oils and fats, complex surface modification or secondary modification processes are usually required, which are costly, have low yields, and may introduce chemical residues.

[0003] Therefore, developing a simple, environmentally friendly, and oleophilic carbon quantum dot that can be directly applied in nonpolar systems such as oils and fats is of great practical significance. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an oleophilic-hydrophobic carbon quantum dot and its preparation method. The oleophilic-hydrophobic carbon quantum dots prepared by this invention have alkyl long chains and amino groups on their surface, and can dissolve in nonpolar organic solvents such as oils and fats. This solves the technical problem that existing carbon quantum dots are highly hydrophilic, difficult to stably disperse in nonpolar systems, and have limited functional applications.

[0005] The technical solution adopted in this invention is as follows: In a first aspect, the present invention provides a method for preparing oleophilic and hydrophobic carbon quantum dots, comprising the steps of: (1) Mix oleic acid vegetable oil and amino acids in a certain proportion and stir evenly to form a mixed reaction raw material; (2) Place the mixed reaction raw materials in a closed reaction container and react at 200~250℃ for at least 2 hours. After the reaction is completed, cool to room temperature, take out the reaction product from the reaction container, and then perform ultrasonic dispersion, centrifugation, filtration purification and freeze drying in sequence to obtain oleophilic and hydrophobic carbon quantum dots.

[0006] Furthermore, in step (1), the mass ratio of oleic acid vegetable oil to amino acids is 1:0.05~0.5.

[0007] Furthermore, the oleic acid vegetable oil in step (1) includes at least one of camellia oil, tea seed oil, olive oil, rapeseed oil, and peanut oil.

[0008] In the above technical solution, oleic acid-based vegetable oil is used as the carbon source. During the hydrothermal reaction, the oleic acid contained in the vegetable oil is pyrolyzed to generate a carbon core + free alkyl long chain. The free alkyl long chain is spontaneously adsorbed on the surface of the carbon core to act as a hydrophobic ligand, so that the reaction product is naturally oil-soluble and there is no need to add external hydrophobic passivating agent or surface modifier.

[0009] Furthermore, the amino acid in step (1) includes at least one of lysine, proline, phenylalanine, and tyrosine.

[0010] Furthermore, during ultrasonic dispersion in step (2), the reaction product needs to be added to an organic solvent, which includes at least one of n-hexane, N,N-dimethylformamide, petroleum ether, and chloroform.

[0011] Furthermore, in step (2), a centrifuge is used for the centrifugation operation, and the centrifugation speed is 6000~10000 r / min, and the centrifugation time is 5~10 min.

[0012] Furthermore, the filtration and purification operation in step (2) uses a microporous filtration membrane or a dialysis membrane.

[0013] Furthermore, the pore size of the microporous filter membrane is 0.1~0.3μm.

[0014] Furthermore, the molecular weight cutoff of the dialysis membrane is 500–2000 Da.

[0015] Secondly, the present invention provides an oleophilic-hydrophobic carbon quantum dot, wherein the surface of the oleophilic-hydrophobic carbon quantum dot has alkyl long chains and amino groups, and the water contact angle of the oleophilic-hydrophobic carbon quantum dot is greater than 100°.

[0016] The beneficial effects of this invention are as follows: (1) This invention provides an oleophilic and hydrophobic carbon quantum dot, which uses oleic acid vegetable oil as carbon source and amino acid as nitrogen source. The oleophilic and hydrophobic carbon quantum dots with alkyl long chains and amino groups on the surface are obtained by a one-step hydrothermal method. The carbon quantum dots can be dissolved in non-polar systems such as oils and fats, which solves the technical problem that existing carbon quantum dots are highly hydrophilic and difficult to be stably dispersed and functionalized in non-polar systems such as oils and fats. (2) The preparation method of the present invention is simple and only requires one hydrothermal step to prepare the product. No hydrophobic modification is required in the later stage, which is suitable for large-scale production. At the same time, the raw materials are natural, safe and environmentally friendly. (3) The oleophilic and hydrophobic carbon quantum dots prepared by the present invention have fluorescence response characteristics and can be widely used for traceability in the fields of rapid anti-counterfeiting detection of fibers and fabrics, and fat-soluble functional materials. Attached Figure Description

[0017] Figure 1The images shown are radio electron microscope (RF) images and particle size distribution diagrams of the carbon quantum dots prepared in Example 1 of this invention, wherein (a) is a transmission electron microscope (TEM) image and (b) is a particle size distribution diagram. Figure 2 The images shown are radio electron microscope (RF) images and particle size distribution diagrams of the carbon quantum dots prepared in Example 2 of this invention, wherein (a) is a transmission electron microscope (TEM) image and (b) is a particle size distribution diagram. Figure 3 The images shown are radio electron microscope (RF) images and particle size distribution diagrams of the carbon quantum dots prepared in Example 3 of this invention, wherein (a) is a transmission electron microscope (TEM) image and (b) is a particle size distribution diagram. Figure 4 The images show radio electron microscopy (RFM) images and particle size distribution diagrams of the carbon quantum dots prepared in Comparative Example 1 of this invention, where (a) is a transmission electron microscopy (TEM) image and (b) is a particle size distribution diagram. Figure 5 The fluorescence emission spectrum of the carbon quantum dots prepared in Example 1 of this invention; Figure 6 The fluorescence emission spectrum of the carbon quantum dots prepared in Example 2 of this invention; Figure 7 The fluorescence emission spectrum of the carbon quantum dots prepared in Example 3 of this invention; Figure 8 The fluorescence emission spectrum of the carbon quantum dots prepared in Comparative Example 1 of this invention is shown below. Figure 9 The images show the infrared spectra of carbon quantum dots and camellia oil prepared in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0018] This invention provides an oleophilic-hydrophobic carbon quantum dot and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] Example 1 This embodiment provides an oleophilic and hydrophobic carbon quantum dot, the preparation process of which is as follows: (1) Mix 4g of camellia oil with 2g of lysine and stir evenly to form a mixed reaction raw material; (2) The mixed reaction raw materials were placed in a closed reaction vessel and reacted at 220°C for 3.5 h. After the reaction was completed, the mixture was cooled to room temperature. The reaction product in the reaction vessel was taken out and DMF was added for ultrasonic dispersion. Then, the mixture was centrifuged at 8000 r / min for 10 min. The supernatant was filtered and purified using a 0.22 μm microporous membrane to remove insoluble impurities. Finally, the filtered and purified supernatant was freeze-dried to obtain oleophilic and hydrophobic carbon quantum dots.

[0020] Example 2 This embodiment provides an oleophilic and hydrophobic carbon quantum dot, the preparation process of which is as follows: (1) Mix 4g of camellia oil with 2g of proline and stir evenly to form a mixed reaction raw material; (2) Place the mixed reaction raw materials in a closed reaction vessel and react at 200°C for 4 hours. After the reaction is completed, cool to room temperature, take out the reaction product from the reaction vessel, add DMF for ultrasonic dispersion, and then centrifuge at 10000 r / min for 5 minutes. Take the supernatant and filter it through a 0.22 μm microporous membrane to remove insoluble impurities. Finally, freeze-dry the filtered and purified supernatant to obtain oleophilic and hydrophobic carbon quantum dots.

[0021] Example 3 This embodiment provides an oleophilic and hydrophobic carbon quantum dot, the preparation process of which is as follows: (1) Mix 4g of camellia oil with 1g of lysine and stir evenly to form a mixed reaction raw material; (2) Place the mixed reaction raw materials in a closed reaction vessel and react at 250°C for 3.5 h. After the reaction is completed, cool to room temperature, take out the reaction product from the reaction vessel, add DMF for ultrasonic dispersion, and then centrifuge at 8000 r / min for 10 min. Take the supernatant and filter it through a 0.22 μm microporous membrane to remove insoluble impurities. Finally, freeze-dry the filtered and purified supernatant to obtain oleophilic and hydrophobic carbon quantum dots.

[0022] Comparative Example 1 This comparative example provides a carbon quantum dot, the preparation process of which is as follows: (1) Mix 2g of lysine with 4g of distilled water and stir until homogeneous to form a mixed reaction raw material; (2) Place the mixed reaction raw materials in a closed reaction vessel and react at 220°C for 3.5 h. After the reaction is completed, cool to room temperature, take out the reaction product from the reaction vessel, add DMF for ultrasonic dispersion, and then centrifuge at 8000 r / min for 10 min. Take the supernatant and filter it through a 0.22 μm microporous membrane to remove insoluble impurities. Finally, freeze-dry the filtered and purified supernatant to obtain carbon quantum dots.

[0023] The carbon quantum dots prepared in Examples 1-3 and Comparative Example 1 were subjected to the following tests: The average particle size was determined using transmission electron microscopy, and the particle size distribution was statistically analyzed to obtain the following results: Figure 1-4 Transmission electron microscope images and particle size distribution diagrams of carbon quantum dots prepared in Examples 1-3 and Comparative Example 1 are shown. Fluorescence properties were tested using a fluorescence spectrophotometer. The excitation wavelength was set to 395 nm, and the scanning range was 430–700 nm. The results were as follows: Figure 5-8 The fluorescence emission spectra of carbon quantum dots prepared in Examples 1-3 and Comparative Example 1 are shown. The fluorescence emission peaks of each quantum dot can be obtained from the fluorescence emission spectra. The carbon quantum dots prepared in Examples 1-3 and Comparative Example 1 were dissolved in water, oil, and organic solvents, respectively, using water, camellia oil, and peanut oil. The solubility of each carbon quantum dot in different solvents was compared, and the water contact angle of each carbon quantum dot was also tested.

[0024] The above test results are statistically analyzed and shown in Table 1 below.

[0025] Table 1. Detection results of carbon quantum dots prepared in Examples 1-3 and Comparative Example 1 Analysis of the test results in Table 1 above shows that the carbon quantum dots prepared in Examples 1-3 using camellia oil as the carbon source and amino acids as the nitrogen source are all oleophilic and hydrophobic, and can be dissolved in non-polar systems such as oils; while the carbon quantum dots prepared in Comparative Example 1 using amino acids directly as the carbon and nitrogen sources are hydrophilic and insoluble in non-polar systems such as camellia oil and peanut oil.

[0026] Additionally, refer to Figure 9 Infrared spectroscopy was performed on camellia oil and carbon quantum dots prepared in Example 1 and Comparative Example 1 to study the functional groups contained on the surface of the carbon quantum dots. Figure 1 The infrared spectroscopy results show that both the lipophilic-hydrophobic carbon quantum dots prepared in Example 1 and the hydrophilic carbon quantum dots prepared in Comparative Example 1 contain amino and carboxyl groups. However, the infrared spectrum of the lipophilic-hydrophobic carbon quantum dots prepared in Example 1 is consistent with that of camellia oil, and the lipophilic-hydrophobic carbon quantum dots prepared in Example 1 show a higher infrared spectrum at 1753 cm⁻¹. -1 There is a stretching vibration of the ester carbonyl group (C=O) at 1648 cm⁻¹. -1 The presence of bending vibration peaks of -CH2 and -CH3 indicates that the carbon quantum dots prepared in Example 1 contain long hydrophobic alkyl chains, thereby giving them oleophilic and hydrophobic properties.

[0027] It should be noted that any parts not mentioned in this invention can be achieved by using or referencing existing technologies.

[0028] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing oleophilic and hydrophobic carbon quantum dots, characterized in that, Including the following steps: (1) Mix oleic acid vegetable oil and amino acids in a certain proportion and stir evenly to form a mixed reaction raw material; (2) Place the mixed reaction raw materials in a closed reaction container and react at 200~250℃ for at least 2 hours. After the reaction is completed, cool to room temperature, take out the reaction product from the reaction container, and then perform ultrasonic dispersion, centrifugation, filtration purification and freeze drying in sequence to obtain oleophilic and hydrophobic carbon quantum dots.

2. The method for preparing oleophilic and hydrophobic carbon quantum dots according to claim 1, characterized in that, In step (1), the mass ratio of oleic acid vegetable oil to amino acids is 1:0.05~0.

5.

3. The method for preparing oleophilic and hydrophobic carbon quantum dots according to claim 1, characterized in that, In step (1), the oleic acid-containing vegetable oils include at least one of camellia oil, tea seed oil, olive oil, rapeseed oil, and peanut oil.

4. The method for preparing oleophilic and hydrophobic carbon quantum dots according to claim 1, characterized in that, The amino acids in step (1) include at least one of lysine, proline, phenylalanine, and tyrosine.

5. The method for preparing oleophilic and hydrophobic carbon quantum dots according to claim 1, characterized in that, In step (2), the reaction product needs to be added to an organic solvent during ultrasonic dispersion. The organic solvent includes at least one of n-hexane, N,N-dimethylformamide, petroleum ether, and chloroform.

6. The method for preparing oleophilic and hydrophobic carbon quantum dots according to claim 1, characterized in that, In step (2), a centrifuge is used for centrifugation, with a centrifugation speed of 6000~10000 r / min and a centrifugation time of 5~10 min.

7. The method for preparing oleophilic and hydrophobic carbon quantum dots according to claim 1, characterized in that, The filtration and purification operation in step (2) uses a microporous filtration membrane or a dialysis membrane.

8. The method for preparing oleophilic and hydrophobic carbon quantum dots according to claim 7, characterized in that, The pore size of the microporous filter membrane is 0.1~0.3μm.

9. The method for preparing oleophilic and hydrophobic carbon quantum dots according to claim 7, characterized in that, The dialysis membrane has a molecular weight cutoff of 500–2000 Da.

10. A hydrophobic carbon quantum dot, prepared by the method according to any one of claims 1-9, characterized in that, The surface of the oleophilic and hydrophobic carbon quantum dots has alkyl long chains and amino groups, and the water contact angle of the oleophilic and hydrophobic carbon quantum dots is greater than 100°.

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