CN109704312B - Preparation method of water-soluble blue-green fluorescent graphene quantum dots - Google Patents
Preparation method of water-soluble blue-green fluorescent graphene quantum dots Download PDFInfo
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Abstract
The invention discloses a preparation method of water-soluble blue-green fluorescent graphene quantum dots. A top-down method is adopted, pyrene is used as a precursor, low-toxicity thiourea is used as a modifier, the blue-green fluorescent graphene quantum dots with good water solubility are hydrothermally synthesized in an alkaline environment in one step, the synthesis process is simple and environment-friendly, and the danger of the synthesis process is reduced. The peak wavelength of the emitted fluorescence spectrum is about 480nm and is in the beneficial long-wave blue light wave band (460-500 nm), and the fluorescent spectrum is expected to be better applied to the fields of blue light resistant illumination and display of LED lamps.
Description
Technical Field
The invention belongs to the technical field of nano fluorescent materials, and particularly relates to a preparation method of water-soluble blue-green fluorescent graphene quantum dots.
Background
In recent years, graphene has received increasing attention due to its unique properties, such as excellent mechanical flexibility, large specific surface area, good chemical stability, and environmental friendliness. As the latest member of graphene family, graphene quantum dots are quasi-zero-dimensional nanomaterials with the size of less than 100nm, and compared with two-dimensional graphene nanosheets and one-dimensional graphene nanowires, zero-dimensional Graphene Quantum Dots (GQDs) show stronger quantum confinement effect, size effect, boundary effect, surface effect and the like; the nano-silver nanoparticle has the advantages of excellent optical characteristics, low toxicity, good biocompatibility and the like, and has good application prospects in the fields of solar optoelectronic devices, biomedicines, biosensing, Light Emitting Diodes (LEDs) and the like.
The preparation method of the graphene quantum dot mainly comprises two main types: top-down and bottom-up. The top-down method is to cut large-size graphene into small-size GQDs by a physical or chemical method, and comprises a hydrothermal method, an electrochemical method and a chemical stripping carbon fiber method; the bottom-up method is to use small molecules as precursors to prepare GQDs by a molecular route, and mainly comprises a hydrothermal method, a solution chemical method, an ultrasonic method and a microwave method. At present, most of prepared blue light graphene quantum dots belong to oil-soluble quantum dots, and the solubility of the blue light graphene quantum dots in water is poor. Therefore, the development of a new method for preparing the blue-green fluorescent graphene quantum dots with good water solubility is of great significance.
Disclosure of Invention
The invention aims to provide a preparation method of water-soluble blue-green fluorescent graphene quantum dots. According to the method, a top-down method is adopted, pyrene is used as a precursor, low-toxicity thiourea is used as a modifier, and the blue-green fluorescent graphene quantum dots with good water solubility are hydrothermally synthesized in an alkaline environment in one step. The peak wavelength of the emitted fluorescence spectrum is about 480nm and is in the beneficial long-wave blue light wave band (460-500 nm), and the fluorescent spectrum is expected to be better applied to the fields of blue light resistant illumination and display of LED lamps.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of water-soluble blue-green fluorescent graphene quantum dots comprises the following steps:
1) weighing 12.5g of pyrene in a 5L glass reaction kettle, adding 1L of concentrated nitric acid for nitration reaction, wherein the reaction temperature is 80 ℃, fully stirring the solution, reacting for 24h, and cooling to room temperature;
2) adding 2L of ultrapure water for dilution, performing suction filtration by using a 0.22 mu m mixed cellulose filter membrane, washing the residual acid by using the ultrapure water for suction filtration, placing the solid on the filter paper in a culture dish after the suction filtration is finished, and drying in an oven at the temperature of 80 ℃ for 2 hours to obtain a yellow intermediate product 1.3.6-trinitropyrene;
3) dissolving a proper amount of alkaline substances in pure water to form an alkaline solution with the concentration of 0.01-1.0mol/L, dispersing 1.3.6-trinitropyrene and a modifier in the solution according to the mass ratio of 1:1-1:5 to form a mixed solution with the concentration of 1.3.6-trinitropyrene of 0.01-0.05mol/L, and then carrying out ultrasonic crushing for two hours;
4) transferring 100mL of the suspension after ultrasonic treatment to a 150mL polytetrafluoroethylene hydrothermal reaction kettle for hydrothermal reaction at 180-240 ℃ for 5-10 h, and performing suction filtration by using a 0.22 mu m filter membrane after the reaction kettle is cooled to room temperature;
5) and transferring the filtrate into a dialysis bag of 1000-3500D for dialysis for 2-4 days, changing water every 24 hours, and drying and collecting the obtained product in an oven at 80 ℃ after dialysis to obtain graphene quantum dot powder.
The alkaline substance in the step 3) is NaOH and NaHCO3One or more of ammonia water and KOH.
In the step 3), the modifier is thiourea.
Compared with the prior art, the invention has the advantages that:
according to the method, a top-down method is adopted, pyrene is used as a precursor, low-toxicity thiourea is used as a modifier, the blue-green fluorescent graphene quantum dot with good water solubility is hydrothermally synthesized in the alkaline environment in the next step, the synthesis process is simple and environment-friendly, and the danger of the synthesis process is reduced.
According to the invention, thiourea and NaOH are used as modifiers to be grafted onto the surfaces of quantum dots in the synthesis process to form surface hydrophilic groups, so that the water solubility of the synthesized quantum dots is improved, compared with the situation that the blue-green quantum dots prepared by the existing method are difficult to dissolve in water after being dried, the solubility of the water-soluble blue-green fluorescent quantum dots can reach 1.5-2.0mg/mL, and meanwhile, the modifiers can provide electron-withdrawing groups, so that the fluorescence wavelength of GQDS generates red shift (refer to fig. 4).
Drawings
FIG. 1 is a TEM spectrum of a quantum dot prepared by the present invention;
FIG. 2 is an absorption spectrum, an excitation spectrum and a fluorescence emission spectrum of the quantum dot prepared by the invention;
FIG. 3 is a fluorescence spectrum of quantum dot solutions prepared in examples 1 to 3 of the present invention measured under the same conditions;
fig. 4 is a fluorescence spectrum of quantum dots prepared in example 2 and comparative example 1 tested under the same conditions.
Detailed Description
In order to make the present invention more comprehensible, the technical solutions of the present invention are further described below with reference to specific embodiments, but the present invention is not limited thereto.
Example 1:
weighing 12.5g of pyrene in a 5L three-necked flask, adding 1L of concentrated nitric acid for nitration reaction at the reaction temperature of 80 ℃, and fully stirring the solution for reaction for 24 hours; after cooling to room temperature, 2L of ultrapure water is added for dilution, and the solution is filtered, washed and the residual acid is removed. After the suction filtration is finished, putting the product into a culture dish, and drying the product in an oven at the temperature of 80 ℃ for 2 hours to obtain a yellow intermediate product 1.3.6-trinitropyrene. 0.4g of NaOH, 1.1g of thiourea and 0.5g of 1.3.6-trinitropyrene are dispersed in 100ml of pure water in sequence, and ultrasonic treatment is carried out for 2 hours by an ultrasonic crusher to obtain fully mixed suspension; then transferring the reaction solution into a 150mL polytetrafluoroethylene reaction kettle, sealing the reaction kettle, and then putting the reaction kettle into an oven for hydrothermal reaction, wherein the reaction temperature is 200 ℃, and the reaction time is 10 hours; cooling to room temperature, taking out the solution, carrying out suction filtration, and collecting filtrate. And (3) performing fluorescence intensity comparison test on a part of filtrate after sampling, transferring the rest filtrate into a dialysis bag of 1000-3500D for dialysis for 2 days, changing water every 24 hours, and drying and collecting in an oven at 80 ℃ after dialysis to obtain the graphene quantum dot powder.
Example 2:
using the 1.3.6-trinitropyrene prepared in example 1, 0.4g of naoh, 2.2g of thiourea and 0.5g of 1.3.6-trinitropyrene were dispersed in 100mL of pure water in sequence, and ultrasonic treatment was performed for 2 hours by an ultrasonic pulverizer, and then the crushed suspension was transferred to a 150mL polytetrafluoroethylene reaction kettle, and after sealing, the reaction was performed in an oven at 200 ℃ for 10 hours; cooling to room temperature, taking out the solution, carrying out suction filtration, and collecting filtrate. And (3) performing fluorescence intensity comparison test on a part of filtrate after sampling, transferring the rest filtrate into a dialysis bag of 1000-3500D for dialysis for 2 days, changing water every 24 hours, and drying and collecting in an oven at 80 ℃ after dialysis to obtain the graphene quantum dot powder.
Example 3:
using 1.3.6-trinitropyrene prepared in example 1, 0g of naoh, 2.2g of thiourea, and 0.5g of 1.3.6-trinitropyrene were dispersed in 100ml of pure water in this order, and subjected to ultrasonication with an ultrasonic pulverizer for 2 hours to obtain a suspension; then transferring the suspension into a 150mL polytetrafluoroethylene reaction kettle, sealing the kettle, and then putting the kettle into an oven for hydrothermal reaction at the reaction temperature of 200 ℃ for 10 hours; cooling to room temperature, taking out the solution, carrying out suction filtration, and collecting filtrate. And (3) performing fluorescence intensity comparison test on a part of filtrate after sampling, transferring the rest filtrate into a dialysis bag of 1000-3500D for dialysis for 2 days, changing water every 24 hours, and drying and collecting in an oven at 80 ℃ after dialysis to obtain the graphene quantum dot powder.
Comparative example 1:
taking pure water as a solvent, taking 0.5g of 1.3.6-trinitropyrene dried in the embodiment 1, dispersing the 1.3.6-trinitropyrene in 100mL of ultrapure water, adding 2mL of hydrazine hydrate, and carrying out ultrasonic treatment for 2 hours by using an ultrasonic grinder; transferring the suspension after ultrasonic treatment into a 150mL polytetrafluoroethylene reaction kettle, sealing the reaction kettle, putting the reaction kettle into an oven for hydrothermal reaction, wherein the reaction temperature is 200 ℃, and the reaction time is 10 hours; cooling to room temperature, taking out the solution, performing suction filtration by using a 0.22 mu m filter membrane, and collecting filtrate; and (3) performing fluorescence intensity comparison test on a part of filtrate after sampling, transferring the rest filtrate into a dialysis bag of 1000-3500D for dialysis for 2 days, changing water every 24 hours, and drying and collecting in an oven at 80 ℃ after dialysis to obtain the graphene quantum dot powder.
Fig. 1 is a TEM spectrogram of the quantum dot prepared in example 1 of the present invention, and it can be seen that the quantum dot prepared in the present invention has obvious lattice fringes and good crystallization quality.
Fig. 2 is an absorption spectrum, an excitation spectrum and a fluorescence emission spectrum of the quantum dot prepared in example 1 of the present invention. The absorption spectrogram and the excitation spectrogram show that the quantum dot prepared by the method has obvious absorption in the wavelength bands of 270-300nm and 350-440nm, and the emission spectrogram curve shows that the quantum dot emits blue-green fluorescence with the peak value of about 480nm under the irradiation of excitation light with the wavelength of 370 nm.
FIG. 3 is a fluorescence spectrum of quantum dot solutions prepared in examples 1 to 3 of the present invention measured under the same conditions, from which it can be seen that the fluorescence intensity increases as the amount of thiourea used increases; after NaOH is added, the pH value of the solution is increased, the fluorescence intensity of the prepared quantum dots is enhanced, and the red shift of about 5-10nm is generated in the peak emission wavelength.
Fig. 4 is a fluorescence spectrum of quantum dots prepared in example 2 and comparative example 1 tested under the same conditions, from which it can be seen that: compared with the graphene quantum dot prepared by hydrazine hydrate, the quantum fluorescence emission peak wavelength red-shifted by about 20nm is in a beneficial long-wave blue-light wave band.
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.
Claims (1)
1. A preparation method of water-soluble blue-green fluorescent graphene quantum dots is characterized by comprising the following steps: the method comprises the following steps:
1) weighing 12.5g of pyrene in a 5L glass reaction kettle, adding 1L of concentrated nitric acid for nitration reaction, wherein the reaction temperature is 80 ℃, fully stirring the solution, reacting for 24h, and cooling to room temperature;
2) adding 2L of ultrapure water for dilution, performing suction filtration by using a 0.22 mu m mixed cellulose filter membrane, washing the residual acid by using the ultrapure water for suction filtration, placing the solid on the filter paper in a culture dish after the suction filtration is finished, and drying in an oven at the temperature of 80 ℃ for 2 hours to obtain a yellow intermediate product 1.3.6-trinitropyrene;
3) dissolving a proper amount of alkaline substances in pure water to form an alkaline solution with the concentration of 0.01-1.0mol/L, dispersing 1.3.6-trinitropyrene and a modifier in the solution according to the mass ratio of 1:1-1:5 to form a mixed solution with the concentration of 1.3.6-trinitropyrene of 0.01-0.05mol/L, and then carrying out ultrasonic crushing for two hours;
4) transferring 100mL of the suspension after ultrasonic treatment to a 150mL polytetrafluoroethylene hydrothermal reaction kettle for hydrothermal reaction at 180-240 ℃ for 5-10 h, and performing suction filtration by using a 0.22 mu m filter membrane after the reaction kettle is cooled to room temperature;
5) transferring the filtrate into a dialysis bag of 1000-3500D for dialysis for 2-4 days, changing water every 24 hours, drying and collecting in an oven at 80 ℃ after dialysis to obtain water-soluble blue-green fluorescent graphene quantum dot powder;
the alkaline substance in the step 3) is NaOH and NaHCO3One or more of ammonia water and KOH;
in the step 3), the used modifier is thiourea;
the solubility of the water-soluble blue-green fluorescent graphene quantum dot is 1.5-2.0 mg/mL.
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| CN104812697A (en) * | 2012-11-29 | 2015-07-29 | 北京奈艾斯新材料科技有限公司 | Method for forming nitrogen and sulfur co-doped graphene quantum dots |
| CN105670619A (en) * | 2016-02-25 | 2016-06-15 | 浙江理工大学 | Sulfur-doping graphene quantum dot, preparation method of sulfur-doping graphene quantum dot and application of lead ion detection |
| CN106883849A (en) * | 2017-03-29 | 2017-06-23 | 温州医科大学 | Graphene quantum dot that a kind of nitrogenous sulphur mixes and preparation method thereof and the application on lysine luciferase assay reagent is prepared |
| CN108529604A (en) * | 2018-07-10 | 2018-09-14 | 泉州师范学院 | A kind of preparation method of graphene quantum dot |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104812697A (en) * | 2012-11-29 | 2015-07-29 | 北京奈艾斯新材料科技有限公司 | Method for forming nitrogen and sulfur co-doped graphene quantum dots |
| CN105670619A (en) * | 2016-02-25 | 2016-06-15 | 浙江理工大学 | Sulfur-doping graphene quantum dot, preparation method of sulfur-doping graphene quantum dot and application of lead ion detection |
| CN106883849A (en) * | 2017-03-29 | 2017-06-23 | 温州医科大学 | Graphene quantum dot that a kind of nitrogenous sulphur mixes and preparation method thereof and the application on lysine luciferase assay reagent is prepared |
| CN108529604A (en) * | 2018-07-10 | 2018-09-14 | 泉州师范学院 | A kind of preparation method of graphene quantum dot |
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