WO2023159804A1 - Carbon quantum dot having high quantum yield and wide-spectrum photoelectric response, and preparation method - Google Patents

Abstract

The present invention relates to the technical field of nano luminescent materials. Disclosed are a carbon quantum dot having a high quantum yield and a wide-spectrum photoelectric response, and a preparation method. The method for preparing a carbon quantum dot of the present invention comprises the following steps: fully dissolving m-phenylenediamine in ethanol to obtain a precursor solution; then uniformly mixing the precursor solution and a dopant solid acid, and reacting at 175-185°C for 10-15 h; and after the reaction is finished, purifying, concentrating, and drying to obtain the carbon quantum dot having a visible-to-near-infrared wide-spectrum photoelectric response, wherein the concentration of m-phenylenediamine in ethanol is 8-12 mg/mL, and the concentration range of the solid acid in the precursor solution is 0.1-4 M. The carbon quantum dot of the present invention has good optical performance, comprises a high quantum yield, and excellent optical stability and anti-photobleaching effect, and has wide-spectrum photoelectric response performance from visible light to near infrared.

Description

A carbon quantum dot with high quantum yield and wide-spectrum photoelectric response and its preparation method technical field

The invention relates to a carbon quantum dot with high quantum yield and wide-spectrum photoelectric response and a preparation method, belonging to the technical field of nano-luminescent materials.

Background technique

As a new type of nanomaterial, carbon quantum dots usually have a diameter of less than 10nm. According to the crystal structure size of carbon quantum dots, they can be divided into carbon quantum dots, graphene quantum dots and polymer dots. Compared with traditional quantum dots, carbon quantum dots are mainly synthesized from readily available metal-free carbon-based materials. Due to their good biocompatibility and optical properties, such as excellent photostability and photobleaching resistance, carbon quantum dots are widely used in bioimaging, fluorescence sensing and other fields.

To improve the fluorescence performance and quantum yield of carbon quantum dots, a series of synthesis and structural modification methods have been developed. Typical synthesis methods mainly include the "bottom-up" method of hydrothermal, solvothermal, and microwave synthesis, and the "top-down" method of redox cleavage and physical grinding. Modifying the structure of carbon quantum dots can improve their optical properties. Current research mainly focuses on the doping of carbon quantum dots and the modification of functional groups. Among them, the doping of heteroatoms can improve the optical properties of carbon quantum dots, but its specific enhanced fluorescence mechanism and doping position have not yet been explained uniformly, and the structure and function of doped carbon quantum dots still need to be changed. further exploration.

Due to the wide optical absorption range of carbon quantum dots in the ultraviolet to visible region, excellent photoelectricity, including high electron mobility, long thermal electron lifetime and other characteristics, can significantly improve energy conversion efficiency and photoresponse rate, in solar energy It is widely used in the field of batteries and photodetectors. However, due to the low photon excitation energy and light absorption in the near, middle and far infrared regions, the photoelectric response based on carbon quantum dots is mainly concentrated in the deep ultraviolet to visible light region. Therefore, carbon quantum dots with photoresponse in the near infrared region are designed and prepared. is of great significance.

Contents of the invention

[technical problem]

The regulation of the fluorescence performance of carbon quantum dots and the improvement of quantum yield are the basis for later applications in the fields of sensing and imaging; at present, the photoelectric response of carbon quantum dots is mainly concentrated in the deep ultraviolet to visible light region, and the range is small, so the preparation Carbon quantum dots with photoelectric response in the near-infrared region are of great significance.

[Technical solutions]

In order to solve the above problems, the present invention provides a simple carbon quantum dot with high quantum yield and wide-spectrum photoelectric response and a preparation method thereof.

The first object of the present invention is to provide a kind of method for preparing carbon quantum dots with high quantum yield and visible to near-infrared broad-spectrum photoelectric response, comprising the steps:

Fully dissolve m-phenylenediamine in ethanol to obtain a precursor solution; then mix the precursor solution and dopant solid acid evenly, and react at 175-185°C for 10-15h; after the reaction, purify, concentrate, and dry , to obtain the carbon quantum dots with photoelectric response of the visible to near-infrared wide spectrum;

Wherein, the concentration of the m-phenylenediamine in ethanol is 8-12mg/mL;

The concentration range of the solid acid in the precursor solution is 0.1-4M.

In one embodiment of the present invention, the ethanol is absolute ethanol.

In one embodiment of the present invention, the full dissolution is carried out by ultrasonic-assisted dissolution.

In one embodiment of the present invention, the reaction method is a solvothermal method, specifically reacting at 180° C. for 12 hours.

In one embodiment of the present invention, the dopant solid acid is crystalline orthophosphoric acid.

In one embodiment of the present invention, the purification is to filter the solution after the reaction through a microporous membrane and a chromatographic column, remove unreacted precursors and impurities, and obtain purified carbon quantum dots; Wherein the pore diameter of the microporous membrane is 0.22 microns.

In one embodiment of the present invention, the chromatographic column eluent is dichloromethane and methanol, and the volume ratio thereof is 8-12:1, more preferably 10:1.

In one embodiment of the present invention, the concentration is obtained by concentrating the purified carbon quantum dots using a rotary evaporator.

In one embodiment of the present invention, the drying is vacuum drying, specifically placing the concentrated sample in a vacuum drying oven at 60° C. for 12-24 hours.

In one embodiment of the present invention, the prepared carbon quantum dots need to be redissolved, and then stored in the dark at 4°C; wherein the solvent for redissolving includes one or both of water and absolute ethanol .

The second object of the present invention is the carbon quantum dots with high quantum yield and wide spectrum photoelectric response from visible to near infrared prepared by the method of the present invention.

The third object of the present invention is the application of the carbon quantum dots with high quantum yield and wide-spectrum photoelectric response from visible to near-infrared in the fields of biological imaging, fluorescence sensing, solar cells, and photodetectors.

[beneficial effect]

(1) The carbon quantum dots of the present invention have better optical properties, including higher quantum yield, excellent photostability and photobleaching resistance, and still maintain better fluorescence properties after ultraviolet lamp irradiation for 24h, relatively The quantum yield reaches more than 67.3%, and can be as high as 102%. Compared with the carbon quantum dots before phosphoric acid regulation, the quantum yield is increased by 40 times.

(2) The present invention uses orthophosphoric acid as an acidity regulator and a dopant to make the carbon core structure more regular, and the doped phosphorus element is modified in the edge region of the carbon quantum dot in the form of dihydrogen phosphate, as a layer intercalation agent, A multi-layer carbon quantum dot structure is formed, and the interlayer potential energy is reduced to realize long-distance transport of electrons, thus improving the quantum yield of carbon quantum dots.

(3) The carbon quantum dots of the present invention can excite electrons under the irradiation of visible light, have photoconductivity, and lay the foundation for further preparation of solar cells and photodetectors.

(4) The carbon quantum dots obtained in the present invention respond to laser light from the visible light region to the near-infrared region, and have the characteristics of wide band and fast response. This characteristic has unique advantages for the development of new optoelectronic devices in the future.

Description of drawings

FIG. 1 is a high-resolution transmission electron micrograph of the carbon quantum dots of Example 1.

Fig. 2 is the carbon quantum dot fluorescence spectrogram of embodiment 1.

Fig. 3 is the carbon quantum dot photostability graph of embodiment 1.

4 is an electrochemical test diagram of the carbon quantum dots of Example 1.

FIG. 5 is a photoelectric response test diagram of the carbon quantum dots in the visible light region of Example 1. FIG.

6 is a photoelectric response test chart of the carbon quantum dots in Example 1 in the near-infrared region.

Detailed ways

Preferred embodiments of the present invention are described below, and it should be understood that the embodiments are for better explaining the present invention, and are not intended to limit the present invention.

Test Methods:

Transmission electron microscope test: Take dry carbon quantum dots and dissolve them in absolute ethanol. After ultrasonication for 10 minutes, take 2.5 μL of the solution and drop it on the ultra-thin carbon film, and observe its morphology with a high-resolution transmission electron microscope (200kV).

The test of relative quantum yield: with fluorescein isothiocyanate as a standard, the quantum yield of its 0.1M aqueous sodium hydroxide solution at 494nm excitation wavelength is 95%, according to the formula (1) can calculate the carbon quantum dot Relative quantum yield.

Among them, Φ represents the quantum yield, k is the slope of the linear relationship graph based on the absorbance of the standard and carbon quantum dots at 494nm and the intensity of the emission wavelength at the corresponding wavelength, n is the refractive index of the solvent, and s and r represent Analytes carbon quantum dots and standards.

Fluorescence performance test: 4 mg/mL carbon quantum dot solution was placed in a micro-volume fluorescence cuvette, using a Shimadzu RF 6000 fluorescence spectrophotometer, the excitation and emission slits were set to 5nm, and the excitation and emission wavelengths were measured. test.

Fluorescence stability performance test: After recording the fluorescence intensity of the 4mg/mL carbon quantum dot solution, place it under the ultraviolet lamp for continuous irradiation for 24 hours, and then test its fluorescence intensity under the same fluorescence test conditions.

Electrochemical test: Take 2.5 μL carbon quantum dot solution with a concentration of 2mg/ml and drop it on the ground glassy carbon electrode. After drying with an infrared lamp, use the three-electrode method to perform an electrochemical test on it.

Photoelectric response test: drop 1mg/mL carbon quantum dot aqueous solution on the silicon substrate with gold electrodes, and dry at 70°C to form carbon quantum dots into a film, evenly covering the middle of the gold electrodes, and apply 10mV between the two electrodes The photocurrent generated by carbon quantum dots was monitored in the dark and under different laser irradiation conditions.

Example 1

A method for preparing carbon quantum dots with high quantum yield and wide-spectrum photoelectric response from visible to near-infrared, comprising the steps of:

(1) Place 0.3g of m-phenylenediamine in 30mL of absolute ethanol to obtain a precursor solution; then add crystalline orthophosphoric acid so that the final concentration of orthophosphoric acid in the precursor solution is 2M. 200W, the time is 30 minutes) as the reaction solution after dissolving; then put the reaction solution into the reaction kettle, heat at 180°C for 12h in the blast drying oven, and cool to obtain the reacted carbon quantum dot solution;

(2) After the carbon quantum dot solution in step (1) is absorbed by a disposable syringe, the large particulate matter is removed by a 0.22 μm organic microporous filter membrane, and the eluent of dichloromethane/methanol (volume ratio is 10:1) Perform chromatographic column filtration to remove unreacted precursors and impurities, and finally obtain purified carbon quantum dots;

(3) Concentrate the purified carbon quantum dot solution to 5 mL using a rotary evaporator, and then dry it in a vacuum oven at 60° C. for 12 hours to obtain the carbon with high quantum yield and wide-spectrum photoelectric response from visible to near-infrared. Quantum dot solid samples.

The obtained carbon quantum dots with high quantum yield and wide-spectrum photoelectric response from visible to near-infrared were tested, and the test results are as follows:

Figure 1 is the morphological characterization. It can be seen from Figure 1 that the size of carbon quantum dots is uniformly dispersed, and the particle diameter is between 1-3nm.

Figure 2 shows the test results of fluorescence performance. It can be seen from Figure 2 that the optimal excitation wavelength of carbon quantum dots is 460nm, and the emission wavelength is 500nm.

Figure 3 shows the test results of fluorescence stability. It can be seen from Figure 3 that after long-time irradiation, carbon quantum dots still maintain good fluorescence performance, indicating the stability of their fluorescence.

Figure 4 shows the electrochemical performance test results. It can be seen from Figure 4 that the redox peak of carbon quantum dots increases under light conditions, indicating that they have photoconductivity.

Figure 5 and Figure 6 show the photoelectric response test results. It can be seen from Figure 5 and Figure 6 that carbon quantum dots produce photoelectric response in a wide spectral range from visible light to near infrared.

Example 2

Step (1) in the adjustment embodiment 1 is:

Put 0.15g of m-phenylenediamine in 15mL of absolute ethanol, add crystalline phosphoric acid so that the final concentration of orthophosphoric acid in the precursor solution is 2M, and dissolve it with the aid of ultrasound (power 200W, time 30 minutes) as a reaction solution; then put the precursor solution into the reaction kettle, heat it in a blast drying oven at 180°C for 15 hours, and cool it to obtain the reacted solution;

Others are consistent with Example 1, and the carbon quantum dots with high quantum yield and wide-spectrum photoelectric response from visible to near-infrared are obtained.

Example 3

Adjust the concentration of step (1) orthophosphoric acid in Example 1 relative to the precursor solution to be 1M; Others are consistent with Example 1, and the carbon quantum with high quantum yield and visible to near-infrared wide-spectrum photoelectric response is obtained. point.

Comparative example 1

The absolute ethanol in Example 1 was adjusted to be ultrapure water, and the others were kept the same as in Example 1 to obtain carbon quantum dots.

Comparative example 2

The crystalline orthophosphoric acid in Example 1 was omitted, and the others were kept the same as in Example 1 to obtain carbon quantum dots.

Comparative example 3

The crystalline orthophosphoric acid in Example 1 was replaced by phosphoric acid aqueous solution, so that the final concentration of phosphoric acid in the precursor solution was 2M, and the others were kept the same as in Example 1 to obtain carbon quantum dots.

Comparative example 4

Adjust the concentration of orthophosphoric acid relative to the precursor solution in step (1) in Example 1 to 8M, and keep the others consistent with Example 1 to obtain carbon quantum dots.

Comparative example 5

Adjust the concentration of orthophosphoric acid relative to the precursor solution in step (1) in Example 1 to 0.001M, and keep the others consistent with Example 1 to obtain carbon quantum dots.

Comparative example 6

The crystalline orthophosphoric acid in Example 1 was replaced with nitric acid solution, so that the final concentration of nitric acid in the precursor solution was 2M, and the others were consistent with Example 1 to obtain carbon quantum dots.

Comparative example 7

The crystalline orthophosphoric acid in Example 1 was replaced with hydrochloric acid solution, so that the final concentration of hydrochloric acid in the precursor solution was 2M, and the others were consistent with Example 1 to obtain carbon quantum dots.

Comparative example 8

The crystalline orthophosphoric acid in Example 1 was replaced with a sulfuric acid solution, so that the final concentration of sulfuric acid in the precursor solution was 2M, and the others were consistent with Example 1 to obtain carbon quantum dots.

The obtained carbon quantum dots were tested, and the test results were as follows:

Table 1 The test results of relative quantum yield and photoelectric range

example	Relative quantum yield (%)	Photoelectric response range
Example 1	102	Visible light - near infrared
Example 2	95.6	Visible light - near infrared
Example 3	67.3	Visible light - near infrared
Comparative example 1	1.61	—
Comparative example 2	2.62	visible light
Comparative example 3	21.6	—
Comparative example 4	46.2	Visible light - near infrared
Comparative example 5	31.1	Visible light - near infrared
Comparative example 6	17.9	—
Comparative example 7	24.2	—
Comparative example 8	15.6	—

Note: "—" means that the quantum yield is lower than 30%, and the photoelectric response test has not been carried out.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore The scope of protection of the present invention should be defined by the claims.

Claims (10)

1. A method for preparing carbon quantum dots with high quantum yield and wide-spectrum photoelectric response from visible to near-infrared, characterized in that it comprises the following steps:

   Fully dissolve m-phenylenediamine in ethanol to obtain a precursor solution; then mix the precursor solution and dopant solid acid evenly, and react at 175-185°C for 10-15h; after the reaction, purify, concentrate, and dry , to obtain the carbon quantum dots with photoelectric response of the visible to near-infrared wide spectrum;

   Wherein, the concentration of the m-phenylenediamine in ethanol is 8-12mg/mL;

   The concentration range of the solid acid in the precursor solution is 0.1-4M.
2. The method according to claim 1, characterized in that said dopant solid acid is crystalline orthophosphoric acid.
3. The method according to claim 1, wherein the purification is to filter the solution after the reaction through a microporous membrane and a chromatographic column, remove unreacted precursors and impurities, and obtain purified carbon quantum dots.
4. The method according to claim 3, characterized in that, the chromatographic column eluent is dichloromethane and methanol, and its volume ratio is 8-12:1.
5. The method according to claim 3, characterized in that the pore diameter of the microporous membrane is 0.22 microns.
6. The method according to claim 1, wherein the concentration is obtained by concentrating the purified carbon quantum dots using a rotary evaporator.
7. The method according to claim 1, characterized in that the drying is vacuum drying, specifically placing the concentrated sample in a vacuum oven at 60° C. for 12-24 hours.
8. The method according to claim 1, characterized in that the reaction method is a solvothermal method, specifically reacting at 180° C. for 12 hours.
9. The carbon quantum dots prepared by the method according to any one of claims 1-8 have high quantum yield and wide-spectrum photoelectric response from visible to near-infrared.
10. The application of the carbon quantum dots with high quantum yield and wide-spectrum photoelectric response from visible to near-infrared in claim 9 in the fields of biological imaging, fluorescence sensing, solar cells, and photodetectors.

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