CN114105124A - Preparation method and application of graphene quantum dot and polyphenylene sulfide/graphene quantum dot composite material - Google Patents
Preparation method and application of graphene quantum dot and polyphenylene sulfide/graphene quantum dot composite material Download PDFInfo
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Abstract
The invention relates to the technical field of carbon nano materials, in particular to a graphene quantum dot and a preparation method thereof, and further comprises a polyphenylene sulfide/graphene quantum dot composite material and a preparation method thereof, and a product of the polyphenylene sulfide/graphene quantum dot composite material, wherein the preparation method comprises the following steps: and (3) placing the brown black humic acid with the particle size of 40-180 micrometers in a hydrogen peroxide solution for oxidation reaction to obtain a graphene quantum dot solution, and filtering, dialyzing and freeze-drying the graphene quantum dot solution to obtain the graphene quantum dot. The preparation method of the graphene quantum dots provided by the invention is mild in reaction conditions, short in time consumption, simple and convenient to operate, and environment-friendly. The prepared graphene quantum dot has the characteristics of good water solubility, high fluorescence intensity and the like, the polyphenylene sulfide/graphene quantum dot composite material can be prepared by using the graphene quantum dot as a raw material through a thermoplastic processing method, the preparation process is environment-friendly, the performance of the processed material can be fully exerted, and the production efficiency is high.
Description
Technical Field
The invention relates to the technical field of carbon nano materials, in particular to a graphene quantum dot and a preparation method thereof, and further relates to a polyphenylene sulfide/graphene quantum dot composite material and a preparation method thereof, and a product of the polyphenylene sulfide/graphene quantum dot composite material.
Background
The Graphene Quantum Dots (GQDs) are graphene segments with the two-dimensional plane size smaller than 100 nanometers, oxygen-containing groups on the surface can provide active sites for the combination of foreign molecules, and the graphene quantum dots have wide application prospects in the fields of polymer composites, solar cells, optoelectronic devices, biological imaging, medicines and the like. The graphene quantum dots are used as an important carbon material, can effectively reduce heat transfer and mass transfer in the material combustion process due to the characteristics of high stability, strong barrier and the like, can be used as a flame retardant to improve the flame retardant property of a high polymer material, have the characteristics of low toxicity, environmental friendliness and the like, and are increasingly widely applied to energy sources and environments. Humic acid as a natural organic macromolecular substance exists in mineral resources such as weathered coal, peat, lignite, bituminous coal and the like and other biomass resources, is widely distributed and low in cost, takes condensed aromatic rings as a core and is connected with hydroxyl, carboxyl, carbonyl and epoxy groups, and has certain similarity with graphite oxide in structure. According to classification, humic acid can be classified into humic acid, humic acid black and humic acid yellow, wherein humic acid black and humic acid black are called humic acid brown, humic acid black is insoluble in acid and water, and humic acid yellow is soluble in acid and water.
The preparation method of the Graphene Quantum Dots (GQDs) is mainly divided into a top-down method and a bottom-up method. The top-down method mainly includes a strong acid oxidation method, a hydrothermal method, an electrochemical oxidation method, and the like. The bottom-up method is mainly divided into controllable organic synthesis and carbonization reaction. Among these methods, there are many researchers using coal as a raw material. YeR, etc. (Ye R, Xiaong C, Lin J, et al, Coal as an absolute source of graphene quatum dots [ J R]Coal is considered to be a rich source of graphene quantum dots, and the graphene quantum dots are obtained by standing the coal for 24 hours at 100 to 120 ℃ after being subjected to ultrasonic treatment in concentrated sulfuric acid and nitric acid. Then Dong Y (Dong Y, Lin J, Chen Y, et al. Graphene quatum dots, Graphene oxide, carbon quatum dots and Graphene nanocrystals in crystals [ J]Etc. (sujie, zhangli, zhuangyuan), a preparation method of coal-based graphene quantum dots [ P]. Publication number "CN 103803540 a"), pool concessions, etc. (pool concessions, director, penny. Method for extracting graphene quantum dots from coal [ P ]]. Publication No. CN 103922329 a), lissinpro, etc. (lissinpro, Zhang showy, Huangyanchun, etc. Preparation method [ P ] of high-dispersion graphene oxide quantum dots]. Publication number "CN 106430173 a") by stirring coal in concentrated sulfuric acid, concentrated nitric acid, or the like for a long time or oxidizing the coal at high temperature and high pressure to prepare graphene quantum dots. The method has high experimental condition requirement, large energy consumption and long reaction period, coal needs to be treated in concentrated acid for a long time, some methods also need to use medicines such as sodium nitrate and containers such as a high-pressure reaction kettle, the experiment has certain danger, the subsequent treatment is complex, and the use of a large amount of concentrated acid has certain adverse effect on the environment. Method for preparing coal-based graphene quantum dots with high yield by hydrothermal cutting in order to avoid using concentrated acid, such as Mingshemang (Mingshemang, Liuqiong, Wang Fang, etc.)]. Publication number "CN 107804840 a") water instead of concentrated acid in a high-pressure reactor at 200 ℃ for 6 hours, but the time is long and the high pressure is dangerous. Preparation method of Zhang Asian (Zhang Asian, Reshao shogao, Dangyongqiang, etc. [ P ] of coal-based graphene quantum dot]Publication No. "CN 106744861 a") mixing pulverized coal and dimethylformamideGraphene quantum dots are also obtained after 2-6 hours of ultrasonic treatment, but the time is long, and subsequent organic solvent is difficult to remove. Followed by He M et al (He M, Guo X, Huang J, et al. Mass production of tunable multicolor graphics gene dots from an array resource of co-by a one-step electrochemical evolution [ J M]That is) graphene quantum dots are obtained from coal derivative coke through electrochemical stripping, the stripping time is 1 hour, but the coke is treated by organic solvents such as methanol and isopropanol in the early stage, and the early treatment process is complicated. Liu X et al (Liu X, Hao J, Liu J, et al. Green synthesis of carbon four dots from lithium cobalt and the application in Fe3+ detection[J]A.) brown coal was oxidized with ozone, and carbon quantum dots were obtained after 2 hours of oxidation time. Researchers have also found that humus contains a large amount of graphene oxide nanosheets and oxygen-containing modified graphene nanosheets (Dong Y, Wan L, Cai J, et al. Natural carbon-based dots from human substructures [ J]The humic acid quantum dots show unique optical characteristics after being reduced in size, have quantum confinement and edge effects, and thus prove that the carbon quantum dots can be formed after the humic acid is reduced in size. After the publication of the discovery, researchers have used for reference to a method for obtaining graphene quantum dots from coal to prepare the graphene quantum dots from humic acid. Shi W (Shi W, Fan H, Ai S, et al, Preparation of fluorescent graphene dots from fluidic acid for biological application [ J]Et al) mixing humic acid and water, and reacting in a high-pressure reaction kettle at 180 ℃ for 5 hours to obtain the graphene quantum dots. Saikia M et al (Saikia M, Das T, Dihingia N, et al. Formation of carbon quaternary dots and graphene nanosheets from differential carbonaceous materials [ J]Similarly, humic acid and water are mixed by a high-pressure reaction kettle and then react for 2 hours at 200 ℃ to obtain the graphene quantum dots. For more effective oxidative exfoliation of humic acid structure, Liu X et al (Liu X, Han J, Hou X, et al, One-point synthesis of graphene quaternary ammonium salts using humic acid and acid application for copperon removal [ J]A.) replacing the aqueous solution in the autoclave with a mixture of sodium hydroxide and aqueous ammonia, and adjusting the pH of the solution to 10 and then at 200 ℃Reacting for 12 hours to obtain the graphene quantum dots. However, the method increases the investment of reagents, has long reaction time, makes the experiment more complicated, and also uses a high-pressure reaction kettle, so the experiment has certain dangerousness. In conclusion, the method for oxidizing coal by using concentrated acid has high experimental condition requirements, high energy consumption and long reaction period, coal needs to be treated in concentrated acid for a long time, some methods also need to use medicines such as sodium nitrate and containers such as a high-pressure reaction kettle, and the like, so that the experiment has certain dangerousness, the subsequent treatment is complex, and the use of a large amount of concentrated acid has certain adverse effect on the environment; the method for obtaining the graphene quantum dots by reacting the organic solvent with the coal requires long reaction time and is complex in subsequent separation; the graphene quantum dots can be obtained by using coal derivatives such as coke and humic acid, but most of the existing methods utilize a high-pressure reaction kettle for reaction, and have the disadvantages of high temperature, high pressure, high energy consumption and certain dangerousness.
Polyphenylene Sulfide (PPS), one of the special engineering materials which has been known to be hot to the hands in recent years, is wholly called polyphenylene sulfide, and is a thermoplastic semi-crystalline resin with a thiophenyl group in a molecular main chain. PPS is a semicrystalline thermoplastic polymer, the main chain structure of the PPS is formed by the alternate arrangement of benzene rings and sulfur atoms, a large number of benzene rings endow the PPS with rigidity, the PPS has good solvent resistance and flame retardance and is often used as a flame retardant material, but the PPS has the defects of brittleness, low elongation at break and poor impact resistance. For crystalline polymers, the strength, dimensional stability and other properties of the material are closely related to its crystallization behavior. Therefore, the PPS needs to be modified to improve the crystallization behavior and improve the mechanical properties thereof, so as to expand the application field thereof. The filling modification of polymers with inorganic materials is a common method in the field of polymer processing. For example, diamond (Deng S, Cao L, Lin Z, et al, Nanodiamond as an influencing nucleic acid for polyphenylene sulfate [ J]) Calcium carbonate (Liang J. Analysis on interfacial stress in impact of polyphenylene sulfide/CaCO)3composites[J]) Carbon fibers (Liu B, Wang X, Long S, et al. Interfacial micromechanics of carbon fiber-reinforced polyphenylene sulfide composites [ J]) Carbon nanotube（Ribeiro B, Pipes R B, Costa M L, et al. Electrical and rheological percolation behavior of multiwalled carbon nanotube-reinforced poly(phenylene sulfide) composites[J]) Silicon dioxide (Yang Y, Yu W, Duan H, et al. regeneration of regeneration and ligation poly (phenylene sulfide) with a perpendicular silica nanoparticles [ J]) And carrying out crystallization modification on the polyphenylene sulfide by using the materials. The auxiliary agent has poor dispersibility in the polyphenylene sulfide and is easy to agglomerate, so that the mechanical property of the polyphenylene sulfide is influenced. The graphene quantum dots serving as the novel carbon nano material have unique mechanical, thermal, electrical and other properties, can be completely dissolved in a related solvent, are uniformly dispersed and not easily agglomerated, and can better solve the problem and endow the material with a certain function. For example, Guo & bin et al (Guo & bin, Guo & lid, et al]Application of graphene quantum dot/polyphenylene sulfide composite material as preservative [ P110194839 a ], (Guo rui bin, jaqian, Mozun theory, etc. ]]Publication "CN 111662584 a") polyphenylene sulfide was added to HNO3/H2SO4The method comprises the steps of heating and nitrifying in mixed acid to obtain nitrified polyphenylene sulfide, adding the nitrified polyphenylene sulfide and a reducing agent into a DMF (dimethyl formamide) solvent, refluxing for 5.5 to 6 hours at 70 to 75 ℃ in a nitrogen atmosphere, precipitating in acidified methanol to obtain aminated polyphenylene sulfide, performing ultrasonic dispersion on the aminated polyphenylene sulfide, nitrified graphene quantum dots, a condensing agent and a catalyst in DMF uniformly, and performing condensation reaction to obtain the graphene quantum dot/polyphenylene sulfide composite material. Likewise, mozuki et al (mozuki, maryan, mazaro, etc.. a method for preparing a polyphenylene sulfide/graphene quantum dot composite [ P]Publication No. "CN 109852057A") dispersing lamellar polyphenylene sulfide and graphene quantum dots into N-methyl pyrrolidone, stirring and reacting for 3.5-4 hours at 200-220 ℃, then heating to 270-275 ℃, and continuing stirring and reacting for 1.5-275%The polyphenylene sulfide/graphene quantum dot composite material is obtained in 2 hours, the heat resistance of the polyphenylene sulfide is improved, but the preparation process takes a long time. The polyphenylene sulfide/graphene quantum dot composite material is prepared by adopting a solvent film-forming method, the preparation process is complex, the energy consumption is high, the production efficiency is low, a large amount of organic solvent is used and discharged in the production process, the environment is harmed, and the solvent remains in the prepared composite material. In addition, the above patent does not relate to the improvement of mechanical properties such as impact toughness of the graphene quantum dot/polyphenylene sulfide composite material.
Disclosure of Invention
The invention provides a graphene quantum dot, a polyphenylene sulfide/graphene quantum dot composite material, a preparation method and an application thereof, which can effectively solve the problems of difficulty in preparation of the graphene quantum dot, high raw material cost and long time consumption in the prior art, and the problems of long production period, environmental pollution, low efficiency and solvent residue in preparation of the polyphenylene sulfide/graphene quantum dot composite material by a solvent film forming method in the prior art.
One of the technical schemes of the invention is realized by the following measures: a preparation method of graphene quantum dots comprises the following steps: and (3) placing the brown black humic acid with the particle size of 40-180 micrometers in a hydrogen peroxide solution for oxidation reaction to obtain a graphene quantum dot solution, and filtering, dialyzing and freeze-drying the graphene quantum dot solution to obtain the graphene quantum dot.
The following is a further optimization or/and improvement of one of the above-mentioned technical solutions of the invention:
adding 20 ml to 100 ml of hydrogen peroxide solution into each gram of the brown black humic acid. The mass fraction of the hydrogen peroxide solution is 10-30%.
The above oxidation reaction is carried out at a temperature of 50 to 90 ℃.
The oxidation time is 20 to 60 minutes.
The second technical scheme of the invention is realized by the following measures: the graphene quantum dot prepared by the preparation method is one of the technical schemes.
The third technical scheme of the invention is realized by the following measures: according to the second technical scheme, the polyphenylene sulfide/graphene quantum dot composite material prepared by taking the graphene quantum dots as raw materials comprises, by weight, 100 parts of polyphenylene sulfide and 0.1-5 parts of graphene quantum dots.
The fourth technical scheme of the invention is realized by the following measures: a preparation method of the polyphenylene sulfide/graphene quantum dot composite material in the third technical scheme comprises the following steps: the polyphenylene sulfide resin and the graphene quantum dots are uniformly mixed in proportion to obtain a mixed raw material, and the mixed raw material is extruded at the temperature of 285-320 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material.
The following is further optimization or/and improvement of the fourth technical scheme of the invention:
the above extrusion is extrusion using a screw extruder at a screw rotation speed of 15 to 30 revolutions per minute.
The fifth technical scheme of the invention is realized by the following measures: a product of the polyphenylene sulfide/graphene quantum dot composite material comprises the polyphenylene sulfide/graphene quantum dot composite material.
The sixth technical scheme of the invention is realized by the following measures: the polyphenylene sulfide/graphene quantum dot composite material is applied to the fields of electronic appliances, communication equipment or automobiles.
The preparation method of the graphene quantum dots provided by the invention is mild in reaction conditions, short in time consumption, simple and convenient to operate, and environment-friendly. The method has rich raw material sources and low price, and has important promoting significance for the development of high added value of humic acid resources. The graphene quantum dot has the characteristics of good water solubility, high fluorescence intensity and the like, and the polyphenylene sulfide/graphene quantum dot composite material can be prepared by using the graphene quantum dot as a raw material through a thermoplastic processing method. The impact strength, crystallization property and thermal stability of the prepared polyphenylene sulfide/graphene quantum dot composite material are obviously improved, so that the polyphenylene sulfide composite material is widely applied to the fields of electronic appliances, communication equipment, automobiles and the like.
Drawings
Fig. 1 is a fluorescence emission spectrum of the graphene quantum dot obtained in example 10 at different excitation wavelengths.
Fig. 2 is a UV-vis absorption spectrum of the graphene quantum dot obtained in example 10.
Fig. 3a is a TEM image of the surface topography of the graphene quantum dot obtained in example 10.
Fig. 3b is a lattice fringe pattern of the graphene quantum dot obtained in example 10.
Fig. 3c is a particle size distribution diagram of the graphene quantum dots obtained in example 10.
Fig. 4 is a fluorescence spectrum of the graphene quantum dot obtained in example 10.
Fig. 5 is a raman spectrum of the graphene quantum dots obtained in example 10 and raw material brown black humic acid.
FIG. 6a is an SEM image of an impact cross-section of pure polyphenylene sulfide.
Fig. 6b is an SEM image of an impact cross section of the polyphenylene sulfide/graphene quantum dot composite material.
FIG. 7 is a graph showing the relative crystallinity of polyphenylene sulfide/graphene quantum dot composite material and pure polyphenylene sulfide as a function of time during non-isothermal crystallization.
Fig. 8a is a DTG diagram of a differential thermal gravimetry curve of a polyphenylene sulfide and polyphenylene sulfide/graphene quantum dot composite.
Fig. 8b is a thermogravimetric curve TG diagram of the polyphenylene sulfide and polyphenylene sulfide/graphene quantum dot composite material.
Detailed Description
The present invention is not limited by the following examples, and specific embodiments may be determined according to the technical solutions and practical situations of the present invention. The various chemical reagents and chemical articles mentioned in the invention are all the chemical reagents and chemical articles which are well known and commonly used in the prior art, unless otherwise specified; the percentages in the invention are mass percentages unless otherwise specified; the solution in the present invention is an aqueous solution in which the solvent is water, for example, a hydrochloric acid solution is an aqueous hydrochloric acid solution, unless otherwise specified; the normal temperature and room temperature in the present invention generally mean a temperature of 15 ℃ to 25 ℃, and are generally defined as 25 ℃.
In the present invention, unless otherwise specified, all the devices and apparatuses used are conventionally known and used in the art.
The invention is further described below with reference to the following examples:
example 1: the preparation method of the graphene quantum dot comprises the following steps: and (3) placing the brown black humic acid with the particle size of 40-180 micrometers in a hydrogen peroxide solution for oxidation reaction to obtain a graphene quantum dot solution, and filtering, dialyzing and freeze-drying the graphene quantum dot solution to obtain the graphene quantum dot.
Adding 20 ml to 100 ml of hydrogen peroxide solution into each gram of the brown black humic acid, wherein the mass fraction of the hydrogen peroxide solution is 10% to 30%.
The above oxidation reaction is carried out at a temperature of 50 to 90 ℃.
The oxidation time is 20 to 60 minutes.
The brown-black humic acid in the invention refers to a substance which is insoluble in acid and water and is black or brown-black in humic acid products, and comprises brown humic acid and black humic acid, and does not contain yellow humic acid. The brown black humic acid can be obtained from mineral resources such as weathered coal, peat, lignite, bituminous coal, anthracite and the like or other biomass resources. In the invention, the filtration and the dialysis are all carried out by the prior art. The freeze drying of the invention adopts cold trap freezing, the freezing temperature is-20 ℃, the cold trap temperature (namely the surface temperature of a cooler in the cold trap) is-50 ℃, the vacuum degree is 20Pa, and the freeze drying time is 72 hours.
According to the method, a green oxidant hydrogen peroxide solution is adopted to oxidize and strip brown black humic acid, and the graphene quantum dots with excellent fluorescence performance are obtained by reaction in a normal pressure environment. The mechanism is that hydrogen peroxide solution is heated and then decomposed to generate hydroxyl radicals with strong oxidizing property, carbon chains among the molecular structures of the brown black humic acid are attacked, more or less microcrystalline carbons with functional groups are left, some microcrystalline carbons are continuously oxidized by the hydroxyl radicals to form graphene quantum dots, and some microcrystalline carbons are self-assembled under the action of the functional groups, so that the graphene nanosheets are formed. The graphene nanosheets continue to form graphene quantum dots under the attack of hydroxyl radicals. The method has rich raw material sources, the brown black humic acid can be obtained from mineral resources such as peat, lignite, weathered coal, bituminous coal and the like or other biomass resources, the price is low, and compared with coal, the brown black humic acid has relatively simple components and structure, the preparation difficulty is reduced, the investment of a large amount of oxidation reagents is saved, and the experimental time is reduced; the method does not need high pressure, the reaction temperature is lower than 100 ℃, the oxidation time is short, graphene quantum dots with the size of about 12 nm can be obtained by oxidizing for 20-60 minutes at the temperature of 50-90 ℃ under normal pressure, and the method is simple, safe and good in effect.
Example 2: the preparation method of the graphene quantum dot comprises the following steps: and (3) placing the brown black humic acid with the particle size of 40 micrometers or 180 micrometers in a hydrogen peroxide solution for oxidation reaction to obtain a graphene quantum dot solution, and filtering, dialyzing and freeze-drying the graphene quantum dot solution to obtain the graphene quantum dot.
The ratio of the brown black humic acid to the hydrogen peroxide solution is 1 g to 20 ml or 1 g to 100 ml.
The mass fraction of the hydrogen peroxide solution is 10% or 30%.
The above oxidation reaction is carried out at a temperature of 50 ℃ or 90 ℃.
The above oxidation time is 20 minutes or 60 minutes.
Example 3: the graphene quantum dot prepared by the preparation method of the graphene quantum dot in the embodiment is provided.
Example 4: the polyphenylene sulfide/graphene quantum dot composite material prepared by taking the graphene quantum dots as the raw materials in the embodiment comprises, by weight, 100 parts of polyphenylene sulfide and 0.1-5 parts of graphene quantum dots.
Example 5: the polyphenylene sulfide/graphene quantum dot composite material prepared by taking the graphene quantum dots as the raw materials in the embodiment comprises 100 parts by weight of polyphenylene sulfide and 0.1 part or 5 parts by weight of graphene quantum dots.
Example 6: the preparation method of the polyphenylene sulfide/graphene quantum dot composite material in the embodiment comprises the following steps: the polyphenylene sulfide resin and the graphene quantum dots are uniformly mixed according to the proportion of 100 parts of polyphenylene sulfide and 0.1-5 parts of graphene quantum dots to obtain a mixed raw material, and the mixed raw material is extruded at the temperature of 285-320 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material.
The above extrusion is extrusion using a screw extruder having a screw rotation speed of 15 to 30 rpm.
Example 7: the preparation method of the polyphenylene sulfide/graphene quantum dot composite material in the embodiment comprises the following steps: the polyphenylene sulfide resin and the graphene quantum dots are uniformly mixed according to the proportion of 100 parts of polyphenylene sulfide and 0.1 part or 5 parts of graphene quantum dots to obtain a mixed raw material, and the mixed raw material is extruded at the extrusion temperature of 285 ℃ or 320 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material.
The extrusion is performed by using a screw extruder, and the rotating speed of a screw of the screw extruder is 15 revolutions per minute or 30 revolutions per minute.
Example 8: an article comprising the polyphenylene sulfide/graphene quantum dot composite of the above embodiments.
Example 9: the polyphenylene sulfide/graphene quantum dot composite material is applied to the fields of electronic appliances, communication equipment or automobiles.
Example 10: preparing graphene quantum dots: ball-milling 1 g of brown black humic acid until the particle size is 40 micrometers, placing the ball-milled brown black humic acid into 20 ml of hydrogen peroxide solution for oxidation, wherein the mass fraction of the hydrogen peroxide is 10%, the oxidation temperature is 50 ℃, the oxidation time is 20 minutes, obtaining graphene quantum dot solution, and filtering, dialyzing and freeze-drying the graphene quantum dot solution to obtain the graphene quantum dots.
Preparing a polyphenylene sulfide/graphene quantum dot composite material: the polyphenylene sulfide/graphene quantum dot composite material comprises 100 parts by weight of polyphenylene sulfide and 0.1 part by weight of graphene quantum dots, and is prepared by the following method: uniformly mixing the required polyphenylene sulfide resin and graphene quantum dots to obtain a mixed raw material, and then extruding the mixed raw material at the extrusion temperature of 285 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material, wherein the rotating speed of a screw is 15 revolutions per minute.
Example 11: preparing graphene quantum dots: ball-milling 1 g of brown black humic acid until the particle size is 100 microns, placing the ball-milled brown black humic acid into 50 ml of hydrogen peroxide solution for oxidation, wherein the mass fraction of hydrogen peroxide is 25%, the oxidation temperature is 70 ℃, and the oxidation time is 40 minutes to obtain graphene quantum dot solution, and filtering, dialyzing and freeze-drying the graphene quantum dot solution to obtain the graphene quantum dot.
Preparing a polyphenylene sulfide/graphene quantum dot composite material: the polyphenylene sulfide/graphene quantum dot composite material comprises 100 parts by weight of polyphenylene sulfide and 3 parts by weight of graphene quantum dots, and is prepared by the following method: uniformly mixing required polyphenylene sulfide resin and graphene quantum dots to obtain a mixed raw material, and then extruding the mixed raw material at an extrusion temperature of 310 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material, wherein the rotating speed of a screw is 20 revolutions per minute.
Example 12: preparing graphene quantum dots: ball-milling 1 g of brown black humic acid until the particle size is 180 micrometers, placing the ball-milled brown black humic acid into 100 ml of hydrogen peroxide solution for oxidation, wherein the mass fraction of the hydrogen peroxide is 30%, the oxidation temperature is 90 ℃, the oxidation time is 60 minutes, obtaining graphene quantum dot solution, and filtering, dialyzing and freeze-drying the graphene quantum dot solution to obtain the graphene quantum dots.
Preparing a polyphenylene sulfide/graphene quantum dot composite material: the polyphenylene sulfide/graphene quantum dot composite material comprises 100 parts by weight of polyphenylene sulfide and 5 parts by weight of graphene quantum dots, and is prepared by the following method: uniformly mixing the required polyphenylene sulfide resin and graphene quantum dots to obtain a mixed raw material, and then extruding the mixed raw material at an extrusion temperature of 320 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material, wherein the rotating speed of a screw is 30 revolutions per minute.
Example 13: the color effect and the fluorescence effect of the graphene quantum dots under visible light are as follows:
the graphene quantum dot solution obtained in example 10 appears brown-yellow under visible light irradiation, and appears bright cyan under ultraviolet lamp irradiation.
Example 14: fluorescence emission spectra of graphene quantum dots at different excitation wavelengths:
fig. 1 is a fluorescence emission spectrum of the graphene quantum dot obtained in example 10 at different excitation wavelengths, and it can be found that under the condition of changing the excitation wavelength (320-400 nm), the fluorescence intensity increases with the increase of the excitation wavelength and then decreases, and the position of the fluorescence peak gradually shifts red with the increase of the excitation wavelength, showing the excitation wave dependency.
Example 15: UV-vis absorption spectrum of graphene quantum dots:
FIG. 2 is a UV-vis absorption spectrum of the graphene quantum dot obtained in example 10, wherein the absorption peak at 227 nm corresponds to pi-pi on the aromatic ring*The peak at 300 nm corresponds to n-pi on C = O*Is detected.
Example 16: the morphology of the graphene quantum dots:
fig. 3a is a TEM image of the surface morphology of the graphene quantum dot obtained in example 10, and the quantum dot is approximately spherical, has good monodispersity, and has no obvious agglomeration phenomenon. Fig. 3b is a lattice fringe pattern of the graphene quantum dot obtained in example 10, wherein the lattice spacing is about 0.26nm, and the characteristic structure of graphitic carbon is shown. Fig. 3c is a particle size distribution diagram of the graphene quantum dots obtained in example 10, which shows that the particle size distribution of the quantum dots is mainly between 8nm and 14 nm.
Example 17: fluorescence spectrum of graphene quantum dots:
fig. 4 is a fluorescence spectrum of the graphene quantum dot obtained in example 10, and it can be seen from the graph that the maximum emission peak of the graphene quantum dot is 478nm, which is obtained when the excitation wavelength is 347 nm.
Example 18: the Raman spectra of the graphene quantum dots and the raw material of the brown black humic acid are as follows:
FIG. 5 is a Raman spectrum, D peak and sp peak of the graphene quantum dots obtained in example 10 and raw material of brown black humic acid3Associated with carbon atoms or defectsG peak indicates sp of graphene sheet2The planar relative intensity of the D peak of GQDs is reduced compared with the D peak of raw material brown black humic acid, which shows that the defect density is reduced, the G peak is widened, and the reduction of the intensity shows that a part of sp is2To sp carbon atoms3Carbon atom conversion, which indicates that there are some oxygen-containing functional groups around the carbon atom.
Example 19: the polyphenylene sulfide/graphene quantum dot composite material is compared with the existing pure polyphenylene sulfide material in a test:
the polyphenylene sulfide/graphene quantum dot composite material obtained in the embodiment 12 of the present invention and the existing pure polyphenylene sulfide material are subjected to a performance test, and the impact strength is tested according to the ASTM D256 standard, and the test results are as follows: the impact strength of the pure polyphenylene sulfide material in the prior art is 2.5kJ/m2And the impact strength of the polyphenylene sulfide/graphene quantum dot composite material obtained in example 12 is 12 kJ/m2. As can be seen from fig. 6a and 6b, compared with the impact section of the existing pure polyphenylene sulfide, the impact section of the polyphenylene sulfide/graphene quantum dot has more shear lip regions, rough section and increased dimples, which are obviously related to the yield process of absorbing energy in the composite material, and show the characteristic of typical ductile fracture; from DSC test, the crystallinity of the pure polyphenylene sulfide material of the prior art is 45%, while the crystallinity of the polyphenylene sulfide/graphene quantum dot composite material obtained in example 12 is 52%, as shown in fig. 7, the half-time period (t) of crystallization (PPS 3) of the polyphenylene sulfide/graphene quantum dot composite material (PPS 3) is shown1/2) The value is 1.05 minutes, while the crystallization half-life of the pure polyphenylene sulfide sample (PPS 0) is 1.28 minutes, the capability of the graphene quantum dots for accelerating the nucleation of the polyphenylene sulfide is verified, and the crystallization performance of the polyphenylene sulfide is improved.
The relative crystallinity of the polyphenylene sulfide/graphene quantum dot composite material obtained in example 12 and pure polyphenylene sulfide during non-isothermal crystallization is shown in fig. 7.
The results of the microtransom thermogravimetric curve (DTG) test of the polyphenylene sulfide and polyphenylene sulfide/graphene quantum dot composites are shown in fig. 8 a. Fig. 8a shows that the thermal decomposition temperature of the pure polyphenylene sulfide material of the prior art is 515 ℃, while the thermal decomposition temperature of the polyphenylene sulfide/graphene quantum dot composite material obtained in example 12 is 521 ℃, which shows that the thermal stability is improved. The thermogravimetric curve (TG) test results of the polyphenylene sulfide and polyphenylene sulfide/graphene quantum dot composites are shown in fig. 8 b. As can be seen from fig. 8b, the addition of the graphene quantum dots can increase the carbon residue rate of the polyphenylene sulfide/graphene quantum dot composite material after combustion, increase the condensed phase, and enhance the flame retardant effect.
The test results show that the impact strength (mechanical property), the crystallization property and the thermal stability of the polyphenylene sulfide/graphene quantum dot composite material are obviously improved and the flame retardant effect is enhanced compared with the existing pure polyphenylene sulfide material, so that the application of the polyphenylene sulfide composite material in the fields of flame retardant materials and the like is expanded.
According to the method, high-quality and low-cost brown black humic acid is used as a carbon source, the graphene quantum dots are prepared by using a green oxidant hydrogen peroxide, the reaction time is short, the operation is simple and convenient, the prepared graphene quantum dots are good in water solubility, high in fluorescence intensity and simple and convenient in post-treatment, and the method has an important promotion significance on the high-added-value development of humic acid resources. The method has rich raw material sources, the brown black humic acid can be obtained from mineral resources such as peat, lignite, weathered coal, bituminous coal and the like or other biomass resources, the price is low, and compared with coal, the brown black humic acid has no coal complexity in components and structure, the preparation difficulty is invisibly reduced, the investment of a large amount of oxidation reagents is saved, and the preparation time is reduced; compared with the previous method for preparing the graphene quantum dots by using the humic acid, the method does not need a high-pressure reaction kettle, and is simple, safe and good in effect. The polyphenylene sulfide/graphene quantum dot composite material prepared by using the graphene quantum dot prepared by the invention as an auxiliary agent through a thermoplastic processing method can effectively solve the problems of poor toughness of polyphenylene sulfide and the like, and overcomes the problems of long production period, environmental pollution, low efficiency, solvent residue and the like existing in the previous patent for preparing the polyphenylene sulfide/graphene quantum dot composite material through a solvent film-forming method.
In conclusion, the preparation method of the graphene quantum dots provided by the invention is mild in reaction conditions, short in time consumption, simple and convenient to operate, and environment-friendly. The method has rich raw material sources and low price, and has important promoting significance for the development of high added value of humic acid resources. The graphene quantum dot has the characteristics of good water solubility, high fluorescence intensity and the like, the polyphenylene sulfide/graphene quantum dot composite material can be prepared by using the graphene quantum dot as a raw material through a thermoplastic processing method, an organic solvent is not used in the preparation process, the environment friendliness is strong, the performance of the processed material can be fully exerted, and the production efficiency is high. The impact strength, crystallization property and thermal stability of the prepared polyphenylene sulfide/graphene quantum dot composite material are obviously improved, and the flame retardant property is favorably improved, so that the polyphenylene sulfide composite material is more widely applied to the fields of electronic appliances, communication equipment, automobiles and the like.
The technical characteristics form an embodiment of the invention, which has strong adaptability and implementation effect, and unnecessary technical characteristics can be increased or decreased according to actual needs to meet the requirements of different situations.
Claims (10)
1. A preparation method of graphene quantum dots is characterized by comprising the following steps: and (3) placing the brown black humic acid with the particle size of 40-180 micrometers in a hydrogen peroxide solution for oxidation reaction to obtain a graphene quantum dot solution, and filtering, dialyzing and freeze-drying the graphene quantum dot solution to obtain the graphene quantum dot.
2. The method for preparing graphene quantum dots according to claim 1, wherein 20 ml to 100 ml of hydrogen peroxide solution is added per gram of the brown black humic acid.
3. The method for preparing the graphene quantum dot according to claim 1 or 2, wherein the mass fraction of the hydrogen peroxide solution is 10% to 30%.
4. The method for preparing graphene quantum dots according to any one of claims 1 to 3, wherein the oxidation reaction is carried out at a temperature of 50 ℃ to 90 ℃; or/and the oxidation time is 20 minutes to 60 minutes.
5. The graphene quantum dot prepared by the preparation method of the graphene quantum dot according to any one of claims 1 to 4.
6. The polyphenylene sulfide/graphene quantum dot composite material prepared by taking the graphene quantum dot as the raw material of claim 5 is characterized in that the raw material comprises 100 parts by weight of polyphenylene sulfide and 0.1 to 5 parts by weight of graphene quantum dot.
7. The preparation method of the polyphenylene sulfide/graphene quantum dot composite material according to claim 6, which is characterized by comprising the following steps: the polyphenylene sulfide resin and the graphene quantum dots are uniformly mixed in proportion to obtain a mixed raw material, and the mixed raw material is extruded at the temperature of 285-320 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material.
8. The method for preparing polyphenylene sulfide/graphene quantum dot composite material according to claim 7, wherein the extrusion is extrusion using a screw extruder at a screw rotation speed of 15 to 30 rpm.
9. An article comprising the polyphenylene sulfide/graphene quantum dot composite of claim 6.
10. The polyphenylene sulfide/graphene quantum dot composite material according to claim 6, wherein the polyphenylene sulfide/graphene quantum dot composite material is applied to the fields of electronics, electric appliances, communication equipment and automobiles.
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