CN107720734A - It is a kind of to prepare the method with fluorescent characteristic graphene quantum dot using waste biomass resource - Google Patents

Abstract

The invention discloses a method for preparing graphene quantum dots with fluorescent properties by utilizing waste biological resources. The method comprises drying longan branches or longan shells and then carbonizing them at high temperature to obtain carbon sources, and then undergoing simple nitrification, ultrasonic crushing and hydrothermal treatment. The graphene quantum dots with fluorescent properties are prepared. The invention turns waste into treasure, fully utilizes the local discarded biological resources in Fujian Province, not only can relieve the pressure of local environmental pollution to a certain extent, but also can change the fluorescence intensity of graphene quantum dots by adjusting parameters during the preparation process And wavelength to meet different needs, which will help promote the development of local graphene-related industries and increase economic benefits.

Description

A method of using waste biological resources to prepare graphene quantum dots with fluorescent properties method

technical field

The invention belongs to the technical field of nanomaterial preparation, and in particular relates to a method for preparing graphene quantum dots with fluorescent properties by using discarded longan branches or longan shells.

Background technique

Graphene quantum dots (GQDs) are graphene sheets with oxygen-containing groups on the surface when graphene becomes smaller than 10nm, commonly known as small-size graphene. In addition to the excellent performance of graphene, graphene quantum dots have many unique properties due to their quasi-zero-dimensional properties, which restrict the movement of internal electrons in all directions. , has important potential application value in the fields of solar cells, electronic devices, optical dyes, biomarkers and composite particle systems, and new semiconductor devices. At present, the synthesis methods of graphene quantum dots are mainly divided into two types: top-down and bottom-up. Top-down includes hydrothermal method, electrochemical method and chemical stripping carbon fiber method, bottom-up includes solution chemical method, ultrasonic method and microwave method, controllable pyrolysis method of polycyclic aromatic hydrocarbons, etc.

Longan branch refers to the small branches of longan, and longan shell refers to the peel of longan. In Fujian Province, longan branches and longan shells can be seen everywhere when longan is ripe. The present invention recycles discarded longan branches or longan shells, and carbonizes them at high temperature after drying as a green, environmentally friendly and low-cost carbon source, and then undergoes simple nitrification, ultrasonic crushing, and hydrothermal treatment to obtain different fluorescent Graphene quantum dots are expected to be better applied in fields such as solar cells.

Contents of the invention

The purpose of the present invention is to provide a method for preparing graphene quantum dots with fluorescent properties by utilizing waste biological resources, which can not only make full use of waste biological resources, but also obtain graphene quantum dots with different fluorescent properties easily and at low cost.

To achieve the above object, the present invention adopts the following technical solutions:

A method for preparing graphene quantum dots with fluorescent properties by using waste biological resources, which is to dry longan branches or longan shells and carbonize them at high temperatures as a carbon source, and then undergo simple nitrification, ultrasonic crushing, and hydrothermal treatment to obtain Described graphene quantum dot; It specifically comprises the following steps:

(1) After washing and drying the longan branch or longan shell, carbonize it under a protective atmosphere at high temperature for a period of time, then take it out, wash and dry it, and grind it into powder to obtain carbon powder;

(2) The obtained carbon powder is oxidized with nitric acid, then subjected to suction filtration, and then dried to obtain a black powder;

(3) Add the obtained black powder into N,N-dimethylformamide solvent, and transfer the suspension obtained after ultrasonic crushing to a high-temperature and high-pressure reactor for hydrothermal treatment;

(4) Cool to room temperature after treatment, take it out, and filter with suction, and the obtained filtrate is graphene quantum dots with different fluorescence intensities.

The protective atmosphere in step (1) is argon.

In step (1), the carbonization temperature is 600-800°C, preferably 800°C, and the carbonization time is 2-3h, preferably 3h. The temperature increase rate in carbonization is 5-10°C/min, preferably 5°C/min.

The reaction temperature of nitric acid oxidation in step (2) is 70-90°C, preferably 80°C, and the reaction time is 12-24h, preferably 12h; the mass concentration of nitric acid used is 65%-68%.

The drying temperature in step (2) is 70-90°C, preferably 80°C.

The power of ultrasonic crushing in step (3) is 100-400W, and the time is 1-2h, preferably 2h.

The temperature of the hydrothermal treatment in step (3) is 180-200°C, preferably 200°C, and the treatment time is 10-12h, preferably 10h.

Suction filtration was performed using a sand core funnel and a 0.22 µm microporous membrane during operation.

The remarkable advantage of the present invention is that: the present invention recycles and utilizes discarded longan branches and longan shells, and carbonizes them at high temperature after drying to obtain a green, environmentally friendly and low-cost carbon source, which is then produced after simple nitrification, ultrasonic crushing, and hydrothermal treatment into graphene quantum dots with different fluorescence intensities. The invention turns waste into treasure, fully utilizes the local discarded biological resources in Fujian Province, not only can relieve the pressure of local environmental pollution to a certain extent, but also can change the fluorescence intensity of graphene quantum dots by adjusting parameters during the preparation process And wavelength to meet different needs, which will help promote the development of local graphene-related industries and increase economic benefits.

Description of drawings

Fig. 1 is the X-ray diffraction diagram of the obtained longan stick carbon powder after high temperature carbonization.

Fig. 2 is the fluorescence spectrogram of the graphene quantum dot prepared in embodiment 1 and embodiment 2.

Fig. 3 is the fluorescence spectrogram of the graphene quantum dot prepared in embodiment 2 and embodiment 3.

detailed description

In order to make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

High-temperature carbonization adopts Bayek vacuum tube furnace.

SCIENTZ Ⅱ D ultrasonic cell pulverizer was used for ultrasonic crushing.

Suction filtration uses a sand core funnel and a 0.22 µm microporous membrane.

Example 1

(1) After washing and drying 7g longan branches, carbonize them at 800°C for 3 hours under an argon protective atmosphere, then take them out, wash them with ethanol and water for 3-5 times, dry them at 60°C for 5 hours, and grind them into Powder, get longan branch charcoal powder;

(2) Add 1 g of the obtained longan branch carbon powder into 150 mL of N,N-dimethylformamide solvent, and after 100 W ultrasonic crushing for 2 hours, transfer the resulting suspension to 100 mL of polytetrafluoroethylene as the lining for high temperature and high pressure reaction In the kettle, hydrothermal treatment at 200°C for 10h;

(3) Cool to room temperature after treatment, take out, and filter with suction, and the obtained filtrate is graphene quantum dots.

Example 2

(1) After washing and drying 7g longan branches, carbonize them at 800°C for 3 hours under an argon protective atmosphere, then take them out, wash them with ethanol and water for 3-5 times, dry them at 60°C for 5 hours, and grind them into Powder, get longan branch charcoal powder;

(2) Add 70mL of nitric acid with a mass concentration of 68% to 1g of the obtained longan stick carbon powder, oxidize it at 80°C for 12h with a magnetic stirrer, then filter it with suction, and then dry it at 80°C to obtain 0.753g of black powder ;

(3) Add the obtained black powder into 150mL N,N-dimethylformamide solvent, and after 100W ultrasonic crushing for 2 hours, transfer the obtained suspension to a 100mL polytetrafluoroethylene-lined high-temperature and high-pressure reactor. Hydrothermal treatment at 200°C for 10 hours;

(4) Cool to room temperature after treatment, take out, and filter with suction, and the obtained filtrate is graphene quantum dots.

Example 3

(1) After washing and drying 6g of longan shells, carbonize them at 800°C for 3 hours in an argon protective atmosphere, then take them out, wash them with ethanol and water for 3-5 times, dry them at 60°C for 5 hours, and grind them into Powder, get longan shell carbon powder;

(2) Add 70mL of nitric acid with a mass concentration of 65% to the obtained longan shell carbon powder, use a magnetic stirrer to oxidize at 80°C for 12 hours, then perform suction filtration, and then dry at 80°C to obtain 0.841g of black powder;

(3) Add the obtained black powder into 150mL N,N-dimethylformamide solvent, and after 100W ultrasonic crushing for 2 hours, transfer the obtained suspension to a 100mL polytetrafluoroethylene-lined high-temperature and high-pressure reactor. Hydrothermal treatment at 200°C for 10 hours;

(4) Cool to room temperature after treatment, take out, and filter with suction, and the obtained filtrate is graphene quantum dots.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (8)

1. A method utilizing waste biological resources to prepare graphene quantum dots with fluorescent properties, characterized in that: comprising the following steps: (1) After washing and drying the longan branch or longan shell, carbonize it under a protective atmosphere at high temperature for a period of time, then take it out, wash and dry it, and grind it into powder to obtain carbon powder; (2) The obtained carbon powder is oxidized with nitric acid, then subjected to suction filtration, and then dried to obtain a black powder; (3) Add the obtained black powder into N,N-dimethylformamide solvent, and transfer the suspension obtained after ultrasonic crushing to a high-temperature and high-pressure reactor for hydrothermal treatment; (4) Cool to room temperature after treatment, take it out, and filter with suction, and the obtained filtrate is graphene quantum dots with fluorescent properties. 2. The preparation method according to claim 1, characterized in that: the protective atmosphere in step (1) is argon. 3. The preparation method according to claim 1, characterized in that: in step (1), the carbonization temperature is 600-800°C, and the carbonization time is 2-3h. 4. The preparation method according to claim 1, characterized in that: the reaction temperature of nitric acid oxidation in step (2) is 70-90°C, the reaction time is 12-24h, and the mass concentration of nitric acid used is 65%-68%. 5. The preparation method according to claim 1, characterized in that: the drying temperature in step (2) is 70-90°C. 6. The preparation method according to claim 1, characterized in that: in step (3), the power of ultrasonic crushing is 100-400W, and the time is 1-2h. 7. The preparation method according to claim 1, characterized in that: the temperature of the hydrothermal treatment in step (3) is 180-200° C., and the treatment time is 10-12 hours. 8. The preparation method according to claim 1, characterized in that: sand core funnel and 0.22 μm microporous membrane are used for suction filtration in the suction filtration operation.