CN111072013A

CN111072013A - Green method for preparing graphene quantum dots by using phloroglucinol

Info

Publication number: CN111072013A
Application number: CN201911341481.1A
Authority: CN
Inventors: 陈卫丰; 吕果; 申佳露; 李德江; 李永双; 刘湘; 代忠旭
Original assignee: China Three Gorges University CTGU
Current assignee: China Three Gorges University CTGU
Priority date: 2019-12-24
Filing date: 2019-12-24
Publication date: 2020-04-28

Abstract

The invention provides a green synthesis method for preparing graphene quantum dots by adopting phloroglucinol as a carbon source and deionized water as a solvent. In the whole synthesis process, only phloroglucinol and deionized water are used as raw materials, other strong acid or strong base oxidants and any other chemical reagents are not required to be introduced, the preparation process is simple and effective, green, safe and environment-friendly, and large-scale industrial production is hopefully realized. The preparation process comprises the following steps: dissolving phloroglucinol in a certain proportion in deionized water, adding the deionized water into a high-pressure hydrothermal kettle, placing the hydrothermal kettle in a forced air drying oven, carrying out hydrothermal reaction at high temperature and high pressure, carrying out centrifugal separation on the obtained liquid under a high-speed centrifuge to obtain supernatant, and filtering the supernatant by using a filtering membrane to obtain light yellow filtrate, namely the aqueous solution of the graphene quantum dots. The graphene quantum dot prepared by the invention has stable fluorescence property, good water solubility and biocompatibility, and is hopeful to be applied to various fields such as photoelectric devices, biological medicines and the like.

Description

Green method for preparing graphene quantum dots by using phloroglucinol

Technical Field

The invention relates to a green method for synthesizing graphene quantum dots by phloroglucinol, and belongs to the field of nano material preparation. More specifically, the method is a green method for preparing the graphene quantum dots by taking phloroglucinol as a carbon source and deionized water as a solvent. The graphene quantum dot prepared by the method has stable fluorescence property, good water solubility and biocompatibility, and wide application prospect in various fields such as photoelectric devices, biological medicines and the like.

Background

In 2004, researchers prepared and found a novel two-dimensional carbon nanomaterial, namely graphene (graphene), for the first time, the material has very excellent electronic properties, optical properties and outstanding mechanical properties, and the properties make the material have very wide application in high-tech fields such as nanotechnology, photoelectric technology, biomedicine and the like. However, graphene is a zero band gap material, limiting its application in the semiconductor industry. Therefore, how to regulate the size of the band gap attracts great attention. In recent years, graphene segments with the dimension within 100nm, namely Graphene Quantum Dots (GQDs), are prepared by various physical or chemical methods, and the band gap of the graphene quantum dots can be well adjusted by controlling the particle size and the type of surface functional groups. As a novel carbon nano material, GQDs are widely researched and applied in the fields of electronic devices, biological imaging, biological sensing and the like. Compared with other semiconductor quantum dots, GQDs have the advantages of good water solubility and biocompatibility and the like. At present, methods for preparing GQDs mainly include an oxidative cleavage method, a microwave synthesis method, an electrochemical synthesis method, a laser ablation method, an arc discharge method, and the like. However, the traditional preparation methods often have the defects of complicated preparation steps, strict requirements on equipment, low final yield, certain harm to the environment and the like, so that industrial large-scale preparation cannot be realized. The preparation method provided by the invention is simple and effective in process, convenient in post-treatment and environment-friendly. According to the method, phloroglucinol is used as a precursor, and is subjected to hydrothermal reaction with deionized water in a hydrothermal kettle to prepare GQDs. The method has simple and effective preparation process, is green, environment-friendly and safe, and the prepared GQDs have good quality, thereby being very hopeful to realize industrial production.

Disclosure of Invention

Adding a certain amount of phloroglucinol into deionized water, stirring and dissolving, then adding a phloroglucinol aqueous solution into a hydrothermal kettle, then placing the hydrothermal kettle into an air-blast drying oven, carrying out hydrothermal reaction at high temperature and high pressure, and naturally cooling to obtain a brownish yellow liquid. And (3) carrying out centrifugal separation on the brown yellow solution to obtain supernatant which is yellow brown transparent liquid, and finally filtering the liquid by using a filter membrane to obtain light yellow clear liquid which is the aqueous solution of the graphene quantum dots.

The method for preparing the graphene quantum dots by adopting phloroglucinol is characterized by comprising the following steps of:

(1) adding a certain amount of phloroglucinol into deionized water, stirring for dissolving, then adding a phloroglucinol aqueous solution into a hydrothermal kettle, then placing the hydrothermal kettle into a forced air drying box, carrying out hydrothermal reaction for 2-15h at the temperature of 130-;

(3) and adding the brown yellow solution into a centrifuge tube, carrying out centrifugal separation at the speed of 3000-15000r/min to obtain a supernatant which is a yellow brown transparent liquid, and finally filtering the liquid by using a 220nm filter membrane to obtain a light yellow clear liquid which is the aqueous solution of the graphene quantum dots.

The green method for preparing the graphene quantum dots by using phloroglucinol is characterized in that the mass ratio of phloroglucinol to deionized water is 10-200: 10-25, preferably 50-100: 15-20.

The green method for preparing the graphene quantum dots by using phloroglucinol is characterized in that the reaction temperature of the phloroglucinol and deionized water is 130-220 ℃, and the preferred value is 150-200 ℃.

The green method for preparing the graphene quantum dots by using phloroglucinol is characterized in that the reaction time of the phloroglucinol and deionized water is 2-15h, and the optimal value is 5-10 h.

According to the method for preparing the graphene quantum dots by using phloroglucinol, raw materials are only phloroglucinol and deionized water, no strong acid, strong base or strong oxidant is required to be added in the reaction process, the preparation process is simple, and the method is suitable for large-scale industrial production. The graphene quantum dot prepared by the method has stable fluorescence property, good water solubility and biocompatibility, and wide application prospect.

Compared with other methods, the method has the advantages that the cheap and easily-obtained phloroglucinol is used as a precursor to prepare the graphene quantum dots with extremely high additional value creatively, the reaction process is simple and effective, the production process is green and environment-friendly, the prepared product only contains the graphene quantum dots, water and carbide precipitates, and the post-treatment is easy.

Drawings

Fig. 1 is a TEM photograph of the graphene quantum dot prepared in example 1.

Fig. 2 is an AFM photograph of the graphene quantum dot prepared in example 1.

Fig. 3 is a raman spectrum of the graphene quantum dot prepared in example 1.

Fig. 4 is a uv absorption spectrum of the graphene quantum dot prepared in example 1.

Fig. 5 is a fluorescence spectrum of the graphene quantum dot prepared in example 1.

Fig. 6 is a real image of the graphene quantum dot prepared in example 1.

FIG. 7 is a schematic diagram of a liquid obtained in example 4.

FIG. 8 is a schematic diagram of a liquid obtained in example 5.

Detailed Description

Example 1

Adding 25mL of deionized water into 25mg of phloroglucinol in a 50mL beaker, and stirring to dissolve the phloroglucinol to obtain a clear solution; transferring the obtained solution into a lining of a 50mL high-pressure hydrothermal kettle, placing the kettle in an air-blast drying oven, and adjusting the temperature to 1The drying oven is closed after 8 hours of reaction at the temperature of 80 ℃, and the hydrothermal kettle is taken out to be naturally cooled; transferring the brownish yellow solution obtained by the reaction to a centrifuge tube, putting the centrifuge tube into a high-speed centrifuge for centrifugation at the speed of 10000r/min for 30 min, taking out the supernatant by using a rubber head suction tube, and finally filtering the liquid by using a 220nm filter membrane to obtain the aqueous solution of the graphene quantum dots. The graphene quantum dots are characterized by means of Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Raman spectroscopy (Raman), ultraviolet-visible spectroscopy (UV-Vis), fluorescence spectroscopy (PL) and the like. Through TEM observation (figure 1), we find that the distribution of the graphene quantum dots is relatively uniform, no agglomeration phenomenon exists, and the size particle diameter is about 14-29 nm. According to AFM observation (figure 2), the thickness of the graphene quantum dot is about 0.6-1.8nm, and the number of layers is 1-3. The Raman spectrum test shows that (figure 3) the Raman shifts of the graphene quantum dots are 1370 and 1586cm^-1Two peaks are respectively corresponding to a D peak (representing a defect) and a G peak (representing a graphite crystal structure) of the graphene quantum dot, and the G peak is far higher than the D peak, which shows that the graphene quantum dot prepared by the invention has a good crystal structure. Uv-vis spectroscopy studies showed (fig. 4) two peaks at 202nm and 224nm, corresponding to the pi-pi transition of the graphene quantum dot electron, and a low peak at 268 nm corresponding to the n-pi transition of its electron. Fluorescence spectrum (PL) studies show (fig. 5) that the position of the graphene quantum dot fluorescence is red-shifted with increasing excitation wavelength, and has the maximum fluorescence intensity at 380 nm excitation wavelength. Fig. 6 is a photograph of graphene quantum dots under a fluorescent lamp and an ultraviolet lamp.

Example 2

Adding 30mg of phloroglucinol into 50mL of a beaker, adding 50mL of deionized water, and stirring to dissolve the mixture to obtain a clear solution; transferring the obtained solution into a 100mL high-pressure hydrothermal kettle lining, placing the lining in a forced air drying oven, adjusting the temperature to 170 ℃, closing the drying oven after reacting for 11 hours, and taking out the hydrothermal kettle to be naturally cooled; transferring the brown yellow solution obtained by the reaction to a centrifuge tube, placing the centrifuge tube into a high-speed centrifuge for centrifugation at 8000r/min for 30 min, taking out the supernatant by using a rubber head straw, and finally filtering the liquid by using a 220nm filter membrane to obtain the aqueous solution of the graphene quantum dots.

Example 3

Adding 50mg of phloroglucinol into 40mL of deionized water in a 50mL beaker, and stirring for dissolving to obtain a clear solution; transferring the obtained solution into a 100mL high-pressure hydrothermal kettle lining, placing the hydrothermal kettle in a forced air drying oven, adjusting the temperature to 190 ℃, closing the drying oven after reacting for 6h, and taking out the hydrothermal kettle to be naturally cooled; transferring the brown yellow solution obtained by the reaction to a centrifuge tube, placing the centrifuge tube into a high-speed centrifuge for centrifugation at 12000r/min for 30 min, taking out supernatant liquid by using a rubber head suction tube, and finally filtering the liquid by using a 220nm filter membrane to obtain the aqueous solution of the graphene quantum dots.

Example 4

Adding 60mg of phloroglucinol into 50mL of a beaker, adding 50mL of deionized water, and stirring to dissolve the mixture to obtain a clear solution; transferring the obtained solution into a 100mL high-pressure hydrothermal kettle lining, placing the hydrothermal kettle in a forced air drying oven, adjusting the temperature to 120 ℃, closing the drying oven after reacting for 5 hours, and taking out the hydrothermal kettle to be naturally cooled; transferring the obtained solution to a centrifuge tube, placing the centrifuge tube into a high-speed centrifuge for centrifugation at 12000r/min for 30 min until no precipitate is found, and finally filtering the liquid by using a 220nm filter membrane to obtain transparent liquid without generating graphene quantum dots, as shown in fig. 7.

Example 5

Taking 40mg of phenol, adding 50mL of deionized water into a 50mL beaker, and stirring to dissolve the phenol to obtain a clear solution; transferring the obtained solution into a 100mL high-pressure hydrothermal kettle lining, placing the lining in a forced air drying oven, adjusting the temperature to 170 ℃, closing the drying oven after reacting for 6h, and taking out the hydrothermal kettle to be naturally cooled; transferring the obtained solution to a centrifuge tube, placing the centrifuge tube into a high-speed centrifuge for centrifugation at 12000r/min for 30 min until no precipitate is found, and finally filtering the liquid by using a 220nm filter membrane to obtain transparent liquid without generating graphene quantum dots, as shown in fig. 8.

Claims

1. The green method for preparing the graphene quantum dots by using phloroglucinol is characterized by comprising the following steps of:

(1) adding a phloroglucinol aqueous solution into a hydrothermal kettle, carrying out hydrothermal reaction for 2-15h in an air-blast drying box at the temperature of 160-220 ℃, and naturally cooling to obtain a brown-yellow solution;

(3) and adding the brown yellow solution into a centrifuge tube, and carrying out centrifugal separation at the speed of 3000-15000r/min to obtain a supernatant which is brown yellow clear transparent liquid, namely the aqueous solution of the graphene quantum dots.

2. The green method for preparing graphene quantum dots by using phloroglucinol according to claim 1, wherein the mass ratio of phloroglucinol to deionized water is 50-100: 10 to 25.

3. The green method for preparing graphene quantum dots by using phloroglucinol according to claim 1, wherein the hydrothermal reaction temperature is 180 ℃ and the hydrothermal reaction time is 8 hours.