CN115872390A - Preparation method and application of coal-based asphaltene carbon quantum dots capable of being efficiently converted - Google Patents
Preparation method and application of coal-based asphaltene carbon quantum dots capable of being efficiently converted Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
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Abstract
The invention discloses a preparation method and application of a high-conversion high-yield carbon quantum dot, wherein the main preparation process comprises the following steps: (1) Putting coal-based asphaltene into a reactor, adding a pre-oxidant, stirring and performing ultrasonic treatment; (2) Washing the suspension to neutrality, filtering, rotary evaporating, and concentrating; (3) Adding the concentrated liquid into a chemical solution as required for grafting characteristic functional groups, and stirring; (4) Continuously filtering the suspension, and then performing rotary evaporation and concentration; (5) Dialyzing, drying and grinding the concentrated solution to obtain carbon quantum dots; the process has the advantages of simple operation, rich raw material sources, large-scale production, high carbon source conversion rate, high yield of the obtained carbon quantum dots, controllable functional groups and excellent optical performance.
Description
Technical Field
The invention relates to the technical field of carbon quantum dot preparation, in particular to a preparation method and application of coal-based asphaltene high-efficiency conversion carbon quantum dots.
Background
The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.
There are various carbon sources for carbon quantum dots, for example: carbon dust, carbon nanotubes, carbon fibers, graphite rods, activated carbon, ethanol, and in recent years, a small amount of biomass and low-rank coal exist; citric acid, glucose, polyethylene glycol, urea, ionic liquid and the like, and a small amount of biomass tar. The preparation methods of the carbon sources (such as an arc discharge method, a laser ablation method, an electrochemical synthesis method, a combustion method and the like) usually need strict experimental conditions due to the characteristic limitation of the carbon sources, the process is complicated, the raw material source cost is high, the conversion rate of the carbon sources is low (20-40%), the fluorescence quantum yield of the carbon quantum dots is low (20-30%), and large-scale production is difficult to realize. Further limiting the application of the material in the fields of biological medicine, biosensors, photocatalytic degradation of organic matters, electrocatalysis and the like.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a preparation method and application of coal-based asphaltene high-efficiency conversion carbon quantum dots.
The technical scheme of the invention is as follows:
in a first aspect of the present invention, a preparation method of a carbon quantum dot with high efficiency conversion from coal-based asphaltenes is provided, wherein coal-liquefied asphaltenes are used as carbon source materials, and the preparation method comprises the following steps:
(1) Putting coal-based asphaltene into a reactor, adding a pre-oxidant, stirring and performing ultrasonic treatment;
(2) Washing the suspension to neutrality, filtering, rotary evaporating, and concentrating;
(3) Adding the concentrated liquid into a chemical solution as required to perform grafting of characteristic functional groups, and stirring;
(4) Continuously filtering the suspension, and then performing rotary evaporation and concentration;
(5) And dialyzing, drying and grinding the concentrated solution to obtain the carbon quantum dots.
The carbon quantum dot raw material is a coal liquefaction intermediate product, the source is wide, the coal-based asphaltene is formed by coal liquefaction polycondensation, the carbon content is high, the aromatizing degree is high, the structure is regular, the carbon quantum dot with high conversion rate can be obtained through pre-oxidation treatment, the fluorescence characteristic is adjustable by grafting various functional groups, and the fluorescence quantum yield is high.
In a second aspect of the invention, the application of the carbon quantum dots prepared by the preparation method of the coal-based asphaltene high-efficiency conversion carbon quantum dots in the fields of biomedicine, biosensors and electrocatalysis is provided.
One or more technical schemes of the invention have the following beneficial effects:
(1) The invention provides a preparation method of coal-based asphaltene high-efficiency conversion carbon quantum dots, aiming at the problems in the existing preparation of carbon quantum dots, and compared with other preparation methods, the prepared carbon quantum dots have the advantages of high carbon source conversion rate of more than 80%, regular structure, high fluorescence quantum yield of more than 35%, simple operation, low cost and capability of realizing large-scale production.
(2) The fluorescence characteristic of the carbon quantum dots prepared by the preparation method can be adjusted according to the type and content of the oxidant and the content and content of the grafting functional group solution, and the carbon quantum dots have good stability.
(3) The carbon quantum dots prepared by the preparation method disclosed by the invention are wide in application, can be applied to the fields of biomedicine, biosensors, photocatalytic degradation of organic matters, electrocatalysis and the like, and have wide application prospects.
Drawings
FIG. 1 is a carbon quantum dot morphology map prepared in example 1 of the present invention;
FIG. 2 is a particle size distribution diagram of carbon quantum dots prepared in example 1 of the present invention;
FIG. 3 is a graph showing the fluorescence contrast between the carbon quantum dots containing carboxyl groups and water in example 1 of the present invention under an ultraviolet light source;
FIG. 4 carbon quantum dot stability test prepared in example 1 of the present invention;
FIG. 5 is a graph showing the effect of carbon quantum dots prepared in example 1 of the present invention on the degradation of phenol.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
As mentioned above, the invention provides a method for preparing carbon quantum dots from coal-based asphaltenes, aiming at the problems of complex preparation and low yield of the existing carbon quantum dots; the method specifically comprises the steps of utilizing coal-based asphaltene as a carbon source, oxidizing the asphaltene by an oxidation method, carrying out ultrasonic treatment, centrifuging, evaporating and drying to obtain the high-yield and high-quality carbon quantum dots.
Further, the method comprises the following steps:
(1) Putting coal-based asphaltene into a reactor, adding a pre-oxidant, stirring and performing ultrasonic treatment;
(2) Washing the suspension to neutrality, filtering, rotary evaporating, and concentrating;
(3) Adding the concentrated liquid into a chemical solution as required for grafting characteristic functional groups, and stirring;
(4) Continuously filtering the suspension, and then performing rotary evaporation and concentration;
(5) And dialyzing, drying and grinding the concentrated solution to obtain the carbon quantum dots.
The carbon quantum dot raw material is a coal liquefaction intermediate product, the source is wide, the coal-based asphaltene is formed by coal liquefaction and polycondensation, the carbon content is high, the aromatizing degree is high, the structure is regular, the carbon quantum dot with high conversion rate can be obtained through preoxidation treatment, the fluorescence characteristic can be adjusted by grafting various functional groups, and the fluorescence quantum yield is high (can reach more than 40%).
The pre-oxidant in the step (1) is one or a mixed oxidant of sulfuric acid and sulfate radical high-grade oxidants (potassium persulfate and sodium persulfate); the pre-oxidant mainly has the functions of pre-oxidizing the carbon source and oxidatively decomposing the condensed asphaltene carbon source, and the sulfuric acid, the sodium persulfate and the potassium persulfate have strong oxidizability, so that the pre-oxidizing effect on the carbon source can be improved.
The mass ratio of the coal-based asphaltene to the oxidant in the step (1) is 1:20-100 parts of; furthermore, the concentration of the oxidant is 20-50wt%, the oxidant generally has strong acid or strong oxidizing property, too much is not beneficial to post-harmless treatment, too little is not obvious in oxidizing effect, and the concentration of the oxidant is limited in the range, so that the oxidizing effect of the oxidant can be better exerted.
In the step (1), the stirring process is carried out at 40-50 ℃, the stirring time is 120-180min, the ultrasonic time is 60-120min, the ultrasonic frequency is 30-100kHz, the oxidation reaction can be accelerated through the stirring and ultrasonic processes, the stirring temperature and the ultrasonic frequency have obvious oxidation effect in the range, the oxidation effect is not obvious when the temperature and the frequency are too low, and the energy consumption is increased when the temperature and the frequency are too high.
In the step (2), the suspension is neutralized at room temperature, and then filtered by a 0.2 μm filter membrane to remove impurities in the suspension, wherein the neutralization process can be performed by 0.1 mol/L sodium hydroxide alkaline solution, and the neutralization can be performed to prevent the filter membrane from being oxidized by the pre-oxidant due to strong acidity and oxidizability of the pre-oxidant, so that the solution is kept neutral.
In the step (2), the filtered solution is further subjected to rotary evaporation and concentration to remove a large amount of water in the solution so as to be convenient for the next treatment.
In the step (3), the chemical solution is an oxygen-containing functional group, a water-soluble amide group or an oil-soluble amide group, and plays a role in grafting functional groups with different functional characteristics to the carbon dot fragments. The oxygen-containing functional group being H 2 O 2 、HNO 3 、H 2 SO 4 、HCOOH、CH3COOH、KMnO 4 One oxidizing agent, or a mixed oxidizing agent thereof; increasing water-soluble amide groups, such as tetraethylenepentamine solution, to improve the water solubility of the carbon quantum dots; or increasing oil-soluble amide groups, such as n-octylamine solution, to improve the oil solubility of the carbon quantum dots; the fluorescence characteristics can be adjusted according to the needs, and the fluorescence quantum yield is improved, such as the fluorescence quantum yield is improved by carboxyl and nitro; the water-soluble amide group improves the water solubility of the quantum dot, and the oil-soluble amide group improves the oil solubility of the quantum dot.
In the step (3), the stirring process is carried out at 50-80 ℃, the stirring time is 120-180min, too low temperature and too short reaction time are not beneficial to grafting functional groups, and too high temperature and too long time cause waste.
And (4) filtering the turbid solution, and then performing rotary evaporation and concentration.
In the step (5), the drying of the concentrated solution can be as follows: vacuum drying or freeze drying.
The carbon quantum dots prepared by the preparation method of the coal-based asphaltene high-efficiency conversion carbon quantum dots have wide application in the fields of biological medicine, biosensors, electrocatalysis and the like.
In order to make the technical solutions of the present disclosure more clearly understood by those skilled in the art, the technical solutions of the present disclosure will be described in detail below with reference to specific examples and comparative examples.
The method for calculating the fluorescence yield of the carbon quantum dots comprises the following steps:
quinine sulfate as standard (sulfuric acid concentration is 0.05mol/L, fluorescence yield psi under excitation wavelength of 360 nm) R = 0.54) the fluorescence yield of the carbon quantum dots to be detected is determined. The calculation formula is as follows:
Ψ＝ψ R ×(I/A)/(I R /A R )×(η/η R ) 2
in the formula, /) R Is quinine sulfate fluorescenceLight yield (psi) R =0.54, I/A is the ratio of the fluorescence integral peak area and the absorbance of quinine sulfate with different concentration gradients at the excitation wavelength of 360nm, IR/AR is the ratio of the fluorescence integral peak area and the absorbance of carbon quantum dots with different concentration gradients at the excitation wavelength of 360nm, eta and eta R The refractive indices of the carbon quantum dots and the quinine solution, respectively.
Example 1
The preparation method of the coal-based asphaltene high-efficiency conversion carbon quantum dot comprises the following steps:
(1) Coal-based asphaltene is taken as a carbon source material, 0.5g of coal-based asphaltene is placed in a reactor, 5g of concentrated sulfuric acid is added as a pre-oxidant, 120min is stirred at 40 ℃, and then the ultrasonic treatment is continued for 60min;
(2) Filtering the suspension with 0.2 μm filter membrane at room temperature, neutralizing with alkaline solution, and washing with deionized water to neutrality; carrying out rotary evaporation and concentration on the neutral solution;
(3) Adding 20ml of HCOOH into the concentrated solution for reaction, grafting carboxyl, and stirring at 70 ℃ for 180min;
(4) Continuously washing the suspension to be neutral, and performing rotary evaporation and concentration;
(5) And dialyzing, freeze-drying and grinding the concentrated solution to obtain a powdery product, wherein the carbon quantum dots with high conversion rate and high performance are obtained, the fluorescence yield of the carbon quantum dots is 38.23%, and the conversion rate of a carbon source is 80.55%.
As shown in fig. 1 and 2, the morphology and the particle size distribution of the carbon quantum dots prepared in this example show that the particle size of the nanoscale carbon quantum dots prepared in this example is between 2.5 nm and 8.5nm, and mostly about 5.5 nm. The carbon source conversion rate is up to 80.55 percent through calculation, and the carbon source of the asphaltene is effectively utilized.
The comparison graph of the carboxyl-containing carbon quantum dots prepared in the example and the fluorescence of water under an ultraviolet light source is shown in fig. 3, and as can be seen from the graph, the quantum dots are light yellow under visible light, have fluorescence characteristics under an ultraviolet lamp, and display bluish fluorescence.
The uv-vis absorption spectrum of the carbon quantum dot prepared in this example is shown in fig. 4, and the quantum dot has a distinct absorption peak at 237nm, which is related to Π - Π transition of C = C on the surface of the carbon quantum dot. The fluorescent characteristic of the carbon quantum dots is met, and the fluorescent yield is as high as 38.23%.
The degradation effect of the carbon quantum dots prepared in the examples on phenol is shown in fig. 5, and it can be seen from the figure that the unique electron-hole characteristics of the carbon quantum dots can generate active oxygen free radicals, which have the effect of degrading organic matters.
Example 2
A preparation method of coal-based asphaltene carbon quantum dots comprises the following steps:
(1) Taking coal-liquefied asphaltene as a carbon source material, placing 0.5g of coal-based asphaltene into a reactor, adding 30ml of 0.5mol/L sodium persulfate solution as a pre-oxidant, stirring at 70 ℃ for 180min, and continuing to perform ultrasonic treatment for 60min;
(2) Filtering the suspension with 0.2 μm filter membrane at room temperature, neutralizing with alkaline solution, and washing with deionized water to neutrality; carrying out rotary evaporation and concentration on the neutral solution;
(3) The concentrated solution was added to 20ml H 2 O 2 Reacting, grafting hydroxyl, and stirring at 70 ℃ for 180min;
(4) Continuously washing the suspension to be neutral, and performing rotary evaporation and concentration;
(5) And dialyzing, freeze-drying and grinding the concentrated solution to obtain a powdery product, thus obtaining the carbon quantum dots with high conversion rate and high performance, wherein the fluorescence yield of the carbon quantum dots is 39.44%, and the conversion rate of a carbon source is 85.43%.
Comparative example 1:
preparation method for preparing carbon quantum dots from citric acid
(1) Putting 1g ammonium dihydrogen citrate into a muffle furnace, heating at a temperature of 10 ℃/min, and reacting at 200 ℃ for 3h to obtain a cracking product;
(2) Grinding the cracking product, adding 50ml of ethanol, stirring for 5 hours, centrifuging, and removing insoluble substances to obtain a carbon-containing quantum dot ethanol solution;
(3) And (3) drying the ethanol solution obtained in the step (2) to obtain the carbon quantum dots. The fluorescence yield of the carbon quantum dots is 22%.
Comparative example 2
Preparation method for preparing carbon quantum dots from biomass tar
(1) Weighing 5g of P 2 O 5 In a beaker, an aqueous solution of biomass tar (1 mL of biomass tar + 100. Mu.L of H) 2 O) add quickly to the beaker.
(2) And (3) standing in a beaker, cooling to room temperature, adding water for dissolving, centrifuging for 5min, collecting supernatant, adding a certain amount of NaOH solution, adjusting the pH to 7.00, and finally obtaining the carbon quantum dot aqueous solution emitting green fluorescence under the excitation wavelength of 365 nm. The fluorescence yield of the carbon quantum dots is 24.3%.
As can be seen from the comparison of the data of the example 1 and the example 2 with the data of the comparative example 1 and the comparative example 2, the fluorescence yield of the carbon quantum dots obtained by the preparation method provided by the invention is more than 35%, the conversion rate of the carbon source is more than 80%, and the example 2 is upgraded and improved on the basis of the traditional oxidant, does not adopt a strong acid solution, but adopts a novel oxidation technology of sulfate radical (SO) free radical 4- Of) an advanced oxidation process with oxidizing agents, the degradation products of which are generally CO 2 、H 2 O and inorganic salt, and basically does not cause secondary pollution. Compared with the carbon quantum dots prepared in the comparative examples 1 and 2, the fluorescence yield of the carbon quantum dots is below 25%, and the preparation method disclosed by the invention can effectively improve the carbon source conversion rate and the fluorescence quantum yield, so that the effect of green preparation of the quantum dots is achieved.
The technical solutions of the present invention have been described in detail with reference to the above embodiments, it should be understood that the above embodiments are only specific examples of the present invention and should not be construed as limiting the present invention, and any modifications, additions or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A preparation method of coal-based asphaltene high-efficiency conversion carbon quantum dots is characterized in that coal liquefaction asphaltene is used as a carbon source material, and comprises the following steps:
(1) Putting coal-based asphaltene into a reactor, adding a pre-oxidant, stirring and performing ultrasonic treatment;
(2) Washing the suspension to neutrality, filtering, rotary evaporating, and concentrating;
(3) Adding the concentrated liquid into a chemical solution as required for grafting characteristic functional groups, and stirring;
(4) Continuously filtering the suspension, and then performing rotary evaporation and concentration;
(5) And dialyzing, drying and grinding the concentrated solution to obtain the carbon quantum dots.
2. The method for preparing the coal-based asphaltene high-efficiency conversion carbon quantum dots according to claim 1, wherein the pre-oxidant in the step (1) is one or a mixture of sulfuric acid, sodium persulfate and potassium persulfate.
3. The method for preparing the coal-based asphaltene-efficient conversion carbon quantum dots according to claim 1, wherein the mass ratio of the coal-based asphaltene and the oxidant in the step (1) is 1:20-100 parts of; further, the concentration of the oxidizing agent is 20 to 50wt%.
4. The method for preparing the coal-based asphaltene high-efficiency conversion carbon quantum dot according to claim 1, wherein in the step (1), the stirring process is performed at 40-50 ℃, the stirring time is 120-180min, and the ultrasonic time is 60-120min.
5. The method for preparing the coal-based asphaltene high-efficiency conversion carbon quantum dot according to claim 1, wherein in the step (2), the suspension is filtered through a 0.2 μm filter membrane at room temperature.
6. The method for preparing the coal-based asphaltene high-efficiency conversion carbon quantum dot according to claim 1, wherein in the step (2), the process of washing to neutrality is to neutralize with alkaline solution and then wash to neutrality with deionized water.
7. The method for preparing the coal-based asphaltene high-efficiency conversion carbon quantum dot according to claim 1, wherein in the step (3), the chemical solution is an oxygen-containing functional group, a water-soluble amide group or an oil-soluble amide group.
8. The method for preparing the coal-based asphaltene high-efficiency conversion carbon quantum dot according to claim 7, wherein the oxygen-containing functional group is H 2 O 2 、HNO 3 、H 2 SO 4 、HCOOH、CH3COOH、KMnO 4 Or a mixed oxidant thereof.
9. The method for preparing the coal-based asphaltene high-efficiency conversion carbon quantum dot according to claim 7, wherein in the step (3), the stirring process is performed at 50-80 ℃ for 120-180min.
10. The application of the carbon quantum dots prepared by the preparation method of the coal-based asphaltene high-efficiency conversion carbon quantum dots according to any one of claims 1 to 9 in the fields of biological medicine, biosensors and electrocatalysis.
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