Electrochemical preparation method of all-optical color emission carbon quantum dots

Abstract

The invention particularly discloses an electrochemical preparation method of an all-optical color emission carbon quantum dot, which comprises the following steps: 1, mixing absolute ethyl alcohol and deionized water according to different proportions to form a mixed solvent; 2, quantitative NaOH is poured into the mixed solvent to be dissolved, stirring is conducted for 3-5 min, and the pH value of the solution is adjusted; 3, an electrochemical device is arranged, a carbon rod is selected as a working electrode, and the mixed solvent serves as electrolyte to be placed in the electrochemical device; 4, voltage is applied, in the electrolysis process, free radical groups generated through electrolysis are gathered on the surface of the working electrode under the action of current, and the all-optical-color carbon quantum dots are synthesized through oxidation, etching and stripping; and step 5, putting the obtained carbon quantum dot solution into a drying oven, and drying for 6-8 hours at the temperature of 70-80 DEG C to obtain powder capable of realizing solid-state luminescence, namely the full-light color emission carbon quantum dot.

Description

Technical Field

[0001] The invention relates to a material preparation method, in particular to an electrochemical preparation method of full-light-color emitting carbon quantum dots. Background Art

[0002] Carbon quantum dots are a new member of the carbon material family and are another new functional material after carbon nanotubes, nanodiamonds and graphene. As a newcomer in the carbon nanomaterial family, carbon dots not only have the advantages of carbon-based materials being non-toxic and having good biocompatibility compared to traditional organic dyes and semiconductor quantum dots, but also have many advantages such as excellent water solubility, adjustable luminescent area, good photostability, abundant material sources and easy preparation. With the continuous increase in research investment, carbon dots have also shown great research potential in energy, environment, sensors, light-emitting devices, biomarkers and nanomedicine, and have extremely broad application prospects.

[0003] At present, the reported preparation methods of carbon quantum dots are mainly divided into two categories: one is the bottom-up method, and the other is the top-down method. The bottom-up synthesis mainly covers water / solvothermal method, template method, microwave method and pyrolysis method. Usually, small molecule precursors are self-assembled to synthesize large-particle carbon quantum dots. The top-down method generally includes arc discharge, laser etching, chemical oxidation method and electrochemical synthesis method. Usually, larger carbon materials such as carbon black, graphite rods and carbon nanotubes are cracked to obtain small-particle fluorescent carbon quantum dots. Among them, the electrochemical method for preparing carbon quantum dots has the advantages of low preparation system cost, low energy consumption, timely monitoring of the formation of carbon quantum dots and large production scale. It is the first choice for synthesizing carbon quantum dots with high quantum efficiency and high fluorescence stability. The excellent properties of carbon quantum dots have made them widely used in ion detection, catalysis, solar cells, biological imaging and other fields. In addition, the excitation dependence, optical stability, electrochemical luminescence, emission upconversion fluorescence and other characteristics of carbon quantum dots make it possible to replace rare earth phosphors in LED or display fields.

[0004] Full-color emitting carbon quantum dots (CQDs), that is, carbon quantum dots that can cover all colors in the visible spectrum (from blue to red), are new phosphor materials for the development of LEDs. They can be used to construct various types of white light LEDs, covering warm, standard and cool colors. The carbon quantum dots are stable, low-cost and environmentally friendly, and are expected to replace traditional semiconductor quantum dots and rare earth fluorescent materials. Although studies have been able to prepare carbon quantum dots that emit full-color, their luminescence intensity and stability still have room for improvement in certain wavelength ranges. At present, most carbon quantum dots still mainly emit blue, green or yellow fluorescence, and it is still difficult to expand fluorescence to the entire visible light spectrum and achieve precise control. Therefore, exploring a simple, low-energy consumption and industrially friendly synthesis method for full-color emitting carbon quantum dots will help further promote the application of carbon quantum dots. For this purpose, an electrochemical preparation method for full-color emitting carbon quantum dots is provided. Summary of the invention

[0005] The purpose of the present invention is to provide an electrochemical preparation method of carbon quantum dots with full light color emission in view of the defects of the prior art, so as to solve the problems raised by the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: an electrochemical preparation method of carbon quantum dots with full light color emission, the specific steps are as follows:

[0007] Step 1: Mix anhydrous ethanol and deionized water in different proportions to form a mixed solvent;

[0008] Step 2: Pour a certain amount of NaOH into the mixed solvent to dissolve, stir for 3-5 minutes, and adjust the pH value of the solution;

[0009] Step 3: setting up an electrochemical device, selecting a carbon rod as a working electrode, and placing the mixed solvent as an electrolyte in the electrochemical device;

[0010] Step 4: Apply voltage. During the electrolysis process, the free radicals generated by electrolysis are gathered on the surface of the working electrode under the action of the current, and the full-color carbon quantum dots are synthesized through oxidation, etching and stripping;

[0011] Step 5: Place the obtained carbon quantum dot solution into an oven and bake it at 70-80°C for 6-8h to obtain a powder capable of achieving solid-state luminescence, i.e., full-light-color emitting carbon quantum dots.

[0012] As a preferred technical solution of the present invention, the electrochemical etching conditions in step 4 are: voltage 40-50V, current 0.1-0.3A, electrolysis time 2-3h, and room temperature.

[0013] As a preferred technical solution of the present invention, in step 1, the ratio of anhydrous ethanol and deionized water is adjusted to change the polarity of the solvent and the reaction rate, thereby generating carbon quantum dot solutions with different wavelengths.

[0014] A full-light color emitting carbon quantum dot prepared by an electrochemical preparation method.

[0015] As a preferred technical solution of the present invention, the diameter of the full-light-color-emitting carbon quantum dots is between 2.0 and 4.0 nm.

[0016] As a preferred technical solution of the present invention, the structure of the full-light color emitting carbon quantum dots contains a morphological graphite phase structure, the sample morphology is particles, contains C=C, C=O, OH chemical bonds, and the full-light color emitting carbon quantum dots absorb in the ultraviolet, blue and green light bands.

[0017] A full-color emission carbon quantum dot for cell imaging.

[0018] Compared with the prior art, the present invention has the following beneficial effects: the present invention adopts an electrochemical method, uses a carbon rod as a working electrode, and the electrolyte is a mixed solvent of anhydrous ethanol and deionized water, and sodium hydroxide is added; under room temperature conditions, the ratio of the mixed solvent and the electrolysis conditions (voltage, current) are mainly adjusted to optimize the fluorescence performance of the carbon quantum dots;

[0019] The carbon quantum dots obtained by the electrochemical synthesis method adopted in the present invention have many significant advantages.

[0020] First of all, it is non-toxic and pollution-free, and is extremely environmentally friendly; and the carbon quantum dots can emit different colors of fluorescence in the entire visible light range, which is colorful and lays the foundation for its application in multiple fields; compared with the currently reported carbon quantum dot preparation methods, the mixed solvent of anhydrous ethanol and deionized water used in the present invention plays a vital role; this mixed solvent can undergo a solvation reaction with the generated intermediate product, so that the intermediate product exists stably in the solution; in this process, the unsaturated carbon atoms on the surface will actively react with the hydroxide ions, oxygen atoms, etc. in the solution, thereby achieving surface passivation. The realization of surface passivation is of great significance, and it can significantly reduce the surface defects of carbon quantum dots and greatly improve their fluorescence performance and stability. This makes the carbon quantum dots prepared by the present invention more competitive in practical applications and brings new opportunities and possibilities for the development of related fields.

[0021] The present invention helps to improve the fluorescence intensity of carbon quantum dots and achieves regulation of the emission peak position of carbon quantum dots by adjusting the ratio of anhydrous ethanol and deionized water; in a mixed solvent system of anhydrous ethanol and deionized water, the carbon quantum dots can be evenly dispersed and are not easy to agglomerate, which helps to improve the stability and processability of the material and facilitates the application of carbon quantum dots in various practical scenarios.

[0022] In the reaction system, sodium hydroxide, as an electrolyte, can provide hydroxide ions (OH-), thereby adjusting the pH and ionic strength of the reaction system; appropriate pH and ionic strength can affect the rate and selectivity of the electrode reaction, thereby controlling the generation and properties of carbon quantum dots; hydroxide ions can participate in the oxidation reaction of the carbon source, promote the nucleation and growth of carbon quantum dots, and at the same time adjust the conductivity of the electrolyte and improve the efficiency of the electrochemical reaction; in addition, hydroxide ions can also react with unsaturated carbon atoms on the surface of carbon quantum dots to form functional groups such as hydroxyl groups (-OH), thereby achieving surface passivation of carbon quantum dots, reducing surface defects of carbon quantum dots, and improving their fluorescence performance and stability.

[0023] In terms of preparation, the present invention has the advantages of easy acquisition of raw materials and simple preparation process; by using different proportions of anhydrous ethanol and deionized water and adding sodium hydroxide, an electrochemical method is adopted to synthesize all-optical color carbon quantum dots; the invention has substantial characteristics such as a unique solvent system, the important role of sodium hydroxide and the advantages of the electrochemical synthesis method; these characteristics make the invention have important innovative value and broad application prospects in the field of synthesis of all-optical color carbon quantum dots.

[0024] The carbon quantum dot structure prepared by the technical solution of the present invention contains a morphological graphite phase structure. The sample has a particle morphology, the quantum dot size is several nanometers, and contains chemical bonds such as C=C, C=O, and OH. The prepared carbon quantum dots absorb in the ultraviolet, blue, and green light bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a high-magnification transmission electron microscopy image of the carbon quantum dots prepared in Example 2;

[0026] Figure 2 is the excitation spectrum of the full-color carbon quantum dot solution prepared in different proportions in Examples 1-5;

[0027] Figure 3 is the absorption spectrum of the full-color carbon quantum dot solution prepared in different proportions in Examples 1-5;

[0028] Figure 4 is the FTIR spectra of the full-color carbon quantum dot solutions prepared in different proportions in Examples 1-5;

[0029] Figure 5is a graph of element contents of the full-color carbon quantum dot solutions prepared in different proportions in Examples 1-5;

[0030] Figure 6 is the C1s and O1s atomic energy spectra of the X-ray photoelectron spectrum of the carbon quantum dots prepared in Example 1-5;

[0031] Figure 7 is a detailed spectrum of the X-ray photoelectron spectrum of C1s of the carbon quantum dots prepared in Examples 1-5;

[0032] Figure 8 This is a powdery picture of carbon quantum dots prepared by drying the full-color carbon quantum dot solutions prepared in different proportions in Examples 1-5. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0034] Example 1: Preparation method of all-optical carbon quantum dots;

[0035] Step 1: Anhydrous ethanol and deionized water are mixed in a ratio of 0:40 to form a mixed solvent;

[0036] Step 2: Pour a certain amount of NaOH into the mixed solvent to dissolve, stir for 3-5 minutes, and adjust the pH value of the solution;

[0037] Step 3: setting up an electrochemical device, selecting a carbon rod as a working electrode, and placing the mixed solvent as an electrolyte in the electrochemical device;

[0038] Step 4: Apply voltage. During the electrolysis process, free radicals and other groups generated by electrolysis are gathered on the surface of the working electrode under the action of current. Through oxidation, etching and stripping, all-optical carbon quantum dots are synthesized.

[0039] Step 5: Place the obtained carbon quantum dot solution into an oven and bake at 70-80°C for 6-8h to obtain powder, i.e., full-light-color emitting carbon quantum dots.

[0040] Example 2: The ratio in Example 1 is changed to 5:35, and the other steps are the same as in Example 1;

[0041] Example 3: The ratio in Example 1 is changed to 10:30, and the other steps are the same as in Example 1;

[0042] Example 4: The ratio in Example 1 is changed to 20:20, and the other steps are the same as in Example 1;

[0043] Example 5: The ratio in Example 1 is changed to 30:10, and the other steps are the same as Example 1.

[0044] The prepared carbon quantum dots were tested by the following methods: transmission electron microscopy (transmission electron microscope (JEOL, 2100)), infrared spectroscopy (Fourier transform infrared spectroscopy (Bruker, WQF-410), the test range is 500 to 3000 wavenumbers), X-ray photoelectron spectroscopy (PHI1600EXCA), excitation and emission spectroscopy (fluorescence spectrometer (Hitachi, F-7000), the emission spectrum test range is 350-700nm, the excitation light is 365nm monochromatic light, and the excitation spectrum range is 230-420nm).

[0045] Test results: From Figure 1 From the transmission image, it can be seen that the diameter of the carbon quantum dots is in the range of 2.0 to 4.0 nm. Figure 2 Shown are the excitation spectra of the full-color carbon quantum dot solutions prepared in different proportions in Examples 1 to 5, from which it can be seen that the wavelength range of 400nm to 800nm ​​covers the visible light and part of the near-infrared region. Figure 3 The absorption spectra of the full-color carbon quantum dot solutions prepared in different proportions in Examples 1 to 5 are shown in Table 1. By comparison, it can be found that the carbon quantum dots prepared by different proportions of alcohol and pure water mainly absorb in the ultraviolet-green band. Figure 4 In the experiment, the carbon quantum dots prepared by different proportions of ethanol and deionized water contained the same chemical bonds. They mainly included OH (3473.2 cm-1), C=O (1691.2 cm-1), and C=C (1562 and 1561.8 cm-1). In addition, as the proportion of ethanol increased, the C=O bond became more obvious. Considering that the emission of carbon quantum dots gradually red-shifted with the increase of the proportion of ethanol, it can be seen that C=O is closely related to red light emission. Figure 5 It is the element content of carbon quantum dots prepared with different ratios of ethanol to deionized water. It can be seen that with the increase of the proportion of alcohol, the oxidation degree corresponding to C=O of carbon quantum dots continues to increase, so the emission peak of CDs is constantly red-shifting. Considering that the color of the solution also changes from transparent to yellow and red in the process of increasing the proportion of alcohol, the red shift of emission is also related to the red shift of CDs caused by concentration. Figure 6 This is the C1s and O1s atomic energy spectra of the prepared carbon quantum dots in the X-ray photoelectron spectrum. The C1s peak is located at about 284nm, and there are two sub-peaks. Among them, the sub-peak with lower binding energy may correspond to the graphitized carbon structure on the surface of the carbon quantum dots, while the sub-peak with higher binding energy may be connected to the carbon in the oxygen-containing compound; the O1s peak is located at about 532nm. Figure 7In the graph, the sub-peak corresponding to "CC / C=C" may represent the graphitized carbon structure or the unoxidized carbon-carbon double bond region in the carbon quantum dots; the sub-peak corresponding to "CO" indicates that carbon and oxygen are combined in the form of single bonds, which may be due to the presence of functional groups such as hydroxyl and ether bonds on the surface of carbon quantum dots; the sub-peak corresponding to "C=O" indicates the presence of a carbon-oxygen double bond structure, which may be a functional group such as a carbonyl group. The distribution range of binding energy is between 280eV and 295eV. Regions with lower binding energy (such as around 280eV) may correspond to more stable carbon structures, while regions with higher binding energy (such as above 290eV) may be connected to carbon in oxygen-containing compounds, which reflects the degree of oxidation on the surface of carbon quantum dots. Figure 8 The figure shows the powder solid obtained after the carbon quantum dot solution is dried. This shows that the prepared photochromic carbon quantum dot solution not only has the ability to emit light in the liquid state, but also can emit light in the solid state.

[0046] According to the above results, the method for synthesizing all-light-emitting carbon quantum dots proposed in the present invention is extremely simple, efficient, convenient and fast, and has great potential for industrial production.

[0047] The above embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. An electrochemical preparation method of carbon quantum dots with full light color emission, characterized in that: The specific steps are as follows: Step 1: Mix anhydrous ethanol and deionized water in different proportions to form a mixed solvent; Step 2: Pour a certain amount of NaOH into the mixed solvent to dissolve, stir for 3-5 minutes, and adjust the pH value of the solution; Step 3: setting up an electrochemical device, selecting a carbon rod as a working electrode, and placing the mixed solvent as an electrolyte in the electrochemical device; Step 4: Apply voltage. During the electrolysis process, the free radicals generated by electrolysis are gathered on the surface of the working electrode under the action of the current, and the full-color carbon quantum dots are synthesized through oxidation, etching and stripping; Step 5: Place the obtained carbon quantum dot solution into an oven and bake it at 70-80°C for 6-8h to obtain a powder capable of achieving solid-state luminescence, i.e., full-light-color emitting carbon quantum dots.

2. The electrochemical preparation method of full-light color emitting carbon quantum dots according to claim 1, characterized in that: The electrochemical etching conditions in step 4 are: voltage 40-50 V, current 0.1-0.3 A, electrolysis time 2-3 h, and room temperature.

3. The electrochemical preparation method of full-light color emitting carbon quantum dots according to claim 1, characterized in that: In step 1, by adjusting the ratio of anhydrous ethanol and deionized water, the polarity of the solvent and the reaction rate are changed, thereby producing carbon quantum dot solutions with different wavelengths.

4. A full-light color emitting carbon quantum dot prepared by the method described in any one of claims 1 to 3.

5. The full-light color emitting carbon quantum dots according to claim 4, characterized in that: The diameter of the full-light-color-emitting carbon quantum dots is between 2.0 and 4.0 nm.

6. The full-light color emitting carbon quantum dots according to claim 4, characterized in that: The structure of the full-light color emitting carbon quantum dots contains a fixed-form graphite phase structure, the sample is in the form of particles, contains C=C, C=O, and OH chemical bonds, and the full-light color emitting carbon quantum dots absorb in the ultraviolet, blue, and green light bands.

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