Preparation method and application of amphiphilic carbon quantum dots

Abstract

The application discloses a preparation method of amphiphilic carbon quantum dots. The preparation process is as follows: citric acid is used as a precursor, and the precursor is reacted with amino acid and cetyl alcohol at high temperature to prepare the carbon quantum dots. The raw materials are widely sourced, and the method is simple and easy to operate. The carbon quantum dots prepared have polar functional groups and non-polar groups, and thus have hydrophilicity and lipophilicity, and can be dissolved in water and organic solvents. The amphiphilic carbon quantum dots have application value in the field of light emitting devices as light emitting materials.

Description

Technical Field

[0001] This invention relates to the field of carbon material synthesis technology, specifically to a method for preparing and applying amphiphilic carbon quantum dots. Background Technology

[0002] Carbon quantum dots (CQDs) are rising stars in the 21st-century family of carbon materials, following graphene and carbon nanotubes. CQDs are near-spherical, zero-dimensional carbon nanoparticles with a size less than 10 nm. Compared to traditional semiconductor quantum dots, carbon quantum dots not only possess similar luminescent properties and nanoscale characteristics, but also exhibit easy functionalization, low toxicity, and good biocompatibility, making them an ideal luminescent material.

[0003] In recent years, carbon quantum dots have been recognized as a potential luminescent material. Current research mainly focuses on the preparation and application of water-soluble carbon quantum dots. For example, patent application CN106829917A discloses a method for preparing carbon quantum dots, using polybasic acids and polyamines as raw materials to synthesize crude carbon quantum dots in one step via a hydrothermal method. After two purification processes, the prepared nanomaterials exhibit high quantum yield and excellent water solubility. Currently, the preparation and application of amphiphilic carbon quantum dots are almost non-existent. Researching simple, rapid, and efficient preparation methods for amphiphilic carbon quantum dots is of great significance and has attracted considerable attention from researchers. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing amphiphilic carbon quantum dots, which uses widely available raw materials, is simple and easy to operate, and produces carbon quantum dots that are both hydrophilic and lipophilic, and are soluble in water and organic solvents.

[0005] The present invention also aims to provide an application of amphiphilic carbon quantum dots as luminescent materials in the field of light-emitting devices.

[0006] To achieve the above objectives, the solution of the present invention is:

[0007] A method for preparing amphiphilic carbon quantum dots includes the following steps:

[0008] Step 1: Weigh 10-11 mmol of citric acid and 5-6 mmol of amino acids, and heat at 200℃ for 17-30 minutes;

[0009] Step 2: Then add 2-3 mmol of cetyl alcohol and continue heating for 6-10 minutes to carry out the reaction;

[0010] Step 3: After the reaction cools down, add 20-30 mL of toluene and stir for 10-15 min. Then add 20-30 mL of distilled water and let it stand to separate the layers. After a clear organic layer and water layer appear, separate the intermediate layer between the organic layer and the water layer, filter it, and wash away the toluene adsorbed on the surface of the product with a small amount of distilled water. Dry it to obtain amphiphilic carbon quantum dots.

[0011] In step 1, the amino acid is one of glycine, lysine, tyrosine, and alanine.

[0012] In step 3, the drying temperature is 70-80℃, and the drying time is 4-6 hours.

[0013] Application of amphiphilic carbon quantum dots as luminescent materials in the field of light-emitting devices.

[0014] With the above technical solution, the present invention provides a method for preparing amphiphilic carbon quantum dots, the preparation process of which is as follows: Figure 1 As shown (taking alanine as an example), carbon quantum dots are prepared by reacting citric acid as a precursor with amino acids and hexadecyl alcohol at high temperature. The raw materials are widely available, the method is simple and easy to operate, and the prepared carbon quantum dots contain polar functional groups (such as -OH, -NH). 2, C=O groups) and nonpolar groups (such as -(CH2) 15 (CH3 group), therefore it has both hydrophilic and lipophilic properties, and can be dissolved in water and organic solvents.

[0015] The amphiphilic carbon quantum dots prepared by this invention are luminescent materials and have promising applications in the field of light-emitting devices. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the preparation process of the present invention;

[0017] Figure 2 XRD powder diffraction pattern of amphiphilic carbon quantum dots;

[0018] Figure 3 Fourier transform infrared image of amphiphilic carbon quantum dots;

[0019] Figure 4 The images show the XPS spectra of amphiphilic carbon quantum dots, where (a) is the full spectrum, (b) is the O1s spectrum, (c) is the C1s spectrum, and (d) is the N1s spectrum.

[0020] Figure 5 The UV-Vis spectra of amphiphilic carbon quantum dots in water, acetone, and DMF are shown.

[0021] Figure 6 The fluorescence spectrum of amphiphilic carbon quantum dots in aqueous solution;

[0022] Figure 7 The fluorescence spectrum of amphiphilic carbon quantum dots in acetone solution;

[0023] Figure 8 The fluorescence spectrum of amphiphilic carbon quantum dots in DMF solution is shown. Detailed Implementation

[0024] To further explain the technical solution of the present invention, the present invention will be described in detail below through specific embodiments.

[0025] I. Preparation

[0026] Example 1

[0027] A method for preparing amphiphilic carbon quantum dots includes the following steps:

[0028] Step 1: Weigh 10.4 mmol (2 g) of citric acid and 5.6 mmol (0.50 g) of alanine, and heat at 200℃ for 17 min;

[0029] Step 2: Then add 2 mmol (0.48 g) of cetyl alcohol and continue heating for 6 min to carry out the reaction;

[0030] Step 3: After the reaction cools down, add 20 mL of toluene and stir for 10 min. Then add 20 mL of distilled water and let it stand to separate the layers. After a clear organic layer and water layer appear, separate the intermediate layer between the organic layer and the water layer, filter it, and wash away the toluene adsorbed on the surface of the product with a small amount of distilled water. Dry it at 70 °C for 6 h to obtain amphiphilic carbon quantum dots.

[0031] Example 2

[0032] A method for preparing amphiphilic carbon quantum dots includes the following steps:

[0033] Step 1: Weigh 10 mmol (1.92 g) of citric acid and 5.6 mmol (0.42 g) of glycine, and heat at 200℃ for 17 min;

[0034] Step 2: Then add 3 mmol (0.72 g) of cetyl alcohol and continue heating for 6 min to carry out the reaction;

[0035] Step 3: After the reaction cools down, add 20 mL of toluene and stir for 15 min. Then add 20 mL of distilled water and let it stand to separate the layers. After a clear organic layer and water layer appear, separate the intermediate layer between the organic layer and the water layer, filter it, and wash away the toluene adsorbed on the surface of the product with a small amount of distilled water. Dry it at 80 °C for 4 h to obtain amphiphilic carbon quantum dots.

[0036] II. Structural Characterization and Analysis

[0037] 1. Powder diffraction of the amphiphilic carbon quantum dots prepared in Example 1 as follows: Figure 2 As shown in the figure, there is a distinct broad absorption peak at around 22°, which is the (002) absorption peak of carbon, indicating that carbon quantum dots have been successfully synthesized.

[0038] 2. The Fourier transform infrared image of the amphiphilic carbon quantum dots prepared in Example 1 is shown below. Figure 3 As shown in the figure, at 3730cm -1 3442cm -1 2922cm -1 2840cm -1 1701cm -1 1467cm -1 1396cm -1 The presence of absorption at constant wavenumbers indicates the presence of various functional groups on the surface of amphiphilic carbon quantum dots, including those at 3730 cm⁻¹. -1 3442cm -1 The peak at 2922 cm⁻¹ corresponds to the stretching vibration peaks of NH and OH. -1 and 2840cm -1 The peak at position 1701 corresponds to the stretching vibration peak of CH. -1 This corresponds to the stretching vibration peak of the carbonyl group (C=O); 1467 cm⁻¹ -1 This corresponds to the antisymmetric bending vibration absorption of the methyl or methylene group, at 1396 cm⁻¹. -1 The absorption peak at 667 cm⁻¹ is due to in-plane bending of the symmetry plane of the methyl or methylene group. -1 The absorption peak at that point is caused by -(CH2)n-. These hydrophilic (NH, OH, C=O) and hydrophobic (CH, -(CH2)n-) functional groups endow the synthesized carbon quantum dots with amphiphilic properties.

[0039] 3. XPS analysis can further analyze the surface elemental composition and chemical state of amphiphilic carbon quantum dots. The XPS spectrum of the amphiphilic carbon quantum dots is shown below. Figure 4 .in Figure 4 Three different binding energies were shown: 284.8, 400.35 and 532.15 eV, corresponding to C1s, N1s and O1s, respectively, with a C:N:O element ratio of 80.96:2.49:16.15.

[0040] 4. The UV-Vis spectra of the amphiphilic carbon quantum dots prepared in Example 1 in water, acetone, and N,N-dimethylformamide are shown below. Figure 5 As shown in the figure, it is clear that the UV-Vis absorption peak is a typical absorption peak of carbon quantum dots. The changes in the absorption peak in different solvents indicate that there may be an interaction between the solvent and the carbon quantum dots.

[0041] III. Application

[0042] The amphiphilic carbon quantum dots prepared by this invention are luminescent materials. Optical performance tests were performed on them. The fluorescence spectra of the amphiphilic carbon quantum dots prepared in Example 1 in water, acetone, and DMF solutions are shown below. Figures 6-8 As shown, the test results indicate that amphiphilic carbon quantum dots exhibit strong emission peaks in three different solutions under different excitation wavelengths. In aqueous solution, the fluorescence intensity is strongest when excited at a wavelength of 350 nm, with an emission wavelength of 430 nm. The emission wavelength remains almost unchanged from 330 nm to 360 nm, but exhibits a redshift of approximately 20 nm when the excitation wavelength increases from 360 nm to 380 nm. In acetone solution, the fluorescence intensity is strongest when excited at a wavelength of 430 nm, with an emission wavelength of 490 nm. Furthermore, in acetone solution, a redshift of 90 nm occurs when the excitation wavelength increases from 430 nm to 470 nm. In DMF solution, the fluorescence intensity is strongest when excited at a wavelength of 400 nm, with an emission wavelength of 475 nm. Similarly, in DMF solution, a redshift of 55 nm occurs when the excitation wavelength increases from 400 nm to 460 nm.

[0043] The different redshifts of amphiphilic carbon quantum dots in three different solvents may be due to the fact that acetone is generally polar, DMF is a polar aprotic solvent, and water is a polar protic solvent capable of forming hydrogen bonds. This results in different interactions between the solvent and the amphiphilic carbon quantum dots, such as dipole-dipole interactions (aprotic) or hydrogen bonds, ultimately leading to different redshifts in the fluorescence spectra in different solvents. Therefore, the fluorescence of amphiphilic carbon quantum dots can be tunable simply by using different solvents without changing their inherent chemical structure. This allows amphiphilic carbon quantum dots to be used as luminescent materials in multifunctional sensing systems, photothermal and photodynamic therapy, photoacoustic imaging, and biosensing.

[0044] The above embodiments and figures are not intended to limit the product form and style of the present invention. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of the present invention.

Claims

1. A method for preparing amphiphilic carbon quantum dots, characterized in that: Includes the following steps: Step 1: Weigh 10-11 mmol of citric acid and 5-6 mmol of amino acids, and heat at 200℃ for 17-30 min; Step 2: Then add 2-3 mmol of cetyl alcohol and continue heating for 6-10 min to carry out the reaction; Step 3: After the reaction cools down, add 20-30 mL of toluene and stir for 10-15 min. Then add 20-30 mL of distilled water and let it stand to separate the layers. After a clear organic layer and water layer appear, separate the intermediate layer between the organic layer and the water layer, filter it, and wash away the toluene adsorbed on the surface of the product with a small amount of distilled water. Dry it to obtain amphiphilic carbon quantum dots. In step 1, the amino acid is one of lysine, tyrosine, and alanine.

2. The method for preparing amphiphilic carbon quantum dots according to claim 1, characterized in that: In step 3, the drying temperature is 70~80℃ and the drying time is 4~6 h.

3. The application of amphiphilic carbon quantum dots prepared by the method described in claim 1 as luminescent materials in the field of light-emitting devices.

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