CN114105124B - 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 also discloses 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 microns 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 dot provided by the invention has the advantages of mild reaction conditions, short time, simplicity and convenience in operation and environment friendliness. 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 taking 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 also discloses 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
Graphene Quantum Dots (GQDs) are graphene fragments with two-dimensional plane dimensions smaller than 100 nanometers, and oxygen-containing groups on the surfaces can provide active sites for combining foreign molecules with the graphene fragments, so that the graphene quantum dots have wide application prospects in the fields of polymer composite materials, solar cells, optoelectronic devices, biological imaging, medicines and the like. The graphene quantum dot is used as an important carbon material, has the characteristics of high stability, strong barrier and the like, can effectively reduce heat transfer and mass transfer in the material combustion process, can be used as a flame retardant to improve the flame retardant property of a high polymer material, has the characteristics of low toxicity, environmental friendliness and the like, and is 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 other biomass resources, has wide distribution and low cost, takes condensed aromatic rings as cores and is connected with hydroxyl, carboxyl, carbonyl and epoxy groups, and has certain structural similarity with graphite oxide. Humic acid can be classified into brown humic acid, black humic acid and fulvic acid according to classification, wherein brown humic acid and black humic acid are collectively called brown humic acid, brown humic acid is insoluble in acid and water, and fulvic acid is soluble in acid and water.
The preparation methods of the Graphene Quantum Dots (GQDs) are mainly divided into a top-down method and a bottom-up method. The top-down method mainly comprises 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 reactions. Among these methods, there are many researchers using coal as a raw material. Ye R et al (Ye R, xiang C, lin J, et al Coal as an abundant source of graphene quantum dots [ J)]Coal is considered to be a rich source of graphene quantum dots and is allowed to stand at 100 to 120 ℃ for 24 hours after being sonicated in concentrated sulfuric acid and nitric acid to yield graphene quantum dots. Then Dong Y (Dong Y, lin J, chen Y, et al Graphene quantum dots, graphene oxide),carbon quantum dots and graphite nanocrystals in coals[J]su Yanjie et al (Su Yanjie, zhang Liling, zhang Yafei. Preparation method of coal-based graphene quantum dot [ P ]]. Publication number "CN 103803540A"), chiwu, etc. (Chiwu, dong Yongjiang, lin Jianpeng. Method for extracting graphene quantum dots from coal [ P ]]. Publication number "CN 103922329A"), li Xinlu, etc. (Li Xinlu, zhang Yanyan, huang Yanchun, etc. Preparation method [ P ] of high-dispersion graphene oxide quantum dot]. Publication No. CN 106430173A ") prepares graphene quantum dots by stirring coal in a solution of concentrated sulfuric acid, concentrated nitric acid, etc. for a long time or oxidizing the coal at high temperature and high pressure. The method has the advantages of high experimental condition requirement, high energy consumption, long reaction period, long treatment time of coal in concentrated acid, sodium nitrate and other medicines, high-pressure reaction kettle and other containers, certain danger in the experiment, complex subsequent treatment and certain adverse effect on the environment due to the use of a large amount of concentrated acid. Method for preparing coal-based graphene quantum dots with high yield by hydrothermal cutting in order to avoid the use of concentrated acid, minshixiong et al (Minshixiong, liu Xiangyu, wang Fang, et al)]. Publication No. CN 107804840A ") was reacted with water instead of concentrated acid in a high-pressure reactor at 200 ℃ for 6 hours to obtain graphene quantum dots, but the time required was long and high pressure had a certain risk. Zhang Yating et al (Zhang Yating, ren Shaozhao, dang Yongjiang, et al. Preparation method of coal-based graphene quantum dot [ P ]]Publication No. CN 106744861A ") the graphene quantum dots were also obtained by ultrasound for 2 to 6 hours after mixing the coal dust and dimethylformamide, but the time required was longer and the subsequent removal of the organic solvent was difficult. Then HeM et al (HeM, guo X, huang J, et al Mass production of tunable multicolor graphene quantum dots from an energy resource of coke by a one-step electrochemical exfoliation [ J)]The graphene quantum dots are obtained from the coal derivative coke through electrochemical stripping, the stripping time is 1 hour, but the coke is treated by organic solvents such as methanol, isopropanol and the like in the earlier stage, and the earlier stage treatment process is complicated. Liu X et al (Liu X, hao J, liu J, et al Green synthesis of carbon quantum dots from lignite coal and the application in Fe) 3+ detection[J]Oxidation of lignite with ozone for 2 hours to obtain carbon quantum dots. Also researchers found that humus contains a large number of graphene oxide nanoplatelets and oxygen-containing modified graphene nanoplatelets (Dong Y, wan L, cai J, et al Natural carbon-based dots from humic substances [ J)]The carbon quantum dots have unique optical characteristics after the size of the carbon quantum dots is reduced, and have quantum constraint and edge effect, so that the carbon quantum dots can be formed after the size of the humus is reduced. After the discovery is published, researchers borrow and use 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 quantum dots from humic acid for bioimaging application [ J)]And then mixing humic acid and water, and reacting for 5 hours at 180 ℃ in a high-pressure reaction kettle to obtain the graphene quantum dots. Saikia M et al (Saikia M, das T, dihingia N, et al Formation of carbon quantum dots and graphene nanosheets from different abundant carbonaceous materials [ J)]And then mixing humic acid with water by using a high-pressure reaction kettle, and reacting for 2 hours at 200 ℃ to obtain the graphene quantum dots. To more effectively oxidize and exfoliate the structure of humic acid, liu X et al (Liu X, han J, hou X, et al One-pot synthesis of graphene quantum dots using humic acid and its application for copper ion detection [ J ]]The aqueous solution in the autoclave was replaced with a mixed solution of sodium hydroxide and ammonia water, and the solution was reacted at 200 ℃ for 12 hours after the pH was adjusted to 10, to obtain graphene quantum dots. However, the method increases the reagent investment, has long reaction time, makes the experiment more complex, and also uses a high-pressure reaction kettle, so that the experiment has a certain danger. In summary, the method for oxidizing coal by using the concentrated acid has high requirements on experimental conditions, high energy consumption and long reaction period, requires treating the coal in the concentrated acid for a long time, and also requires using medicines such as sodium nitrate and the like and containers such as a high-pressure reaction kettle and the like, has certain dangers in the experiment, is complicated in subsequent treatment, and has certain adverse effects on the environment due to the use of a large amount of concentrated acid; the method for obtaining the graphene quantum dots by using the reaction of the organic solvent and the coal requires longer reaction time, and the subsequent separation is more complex;graphene quantum dots can be obtained by using coal derivative coke, humic acid and the like, but most of the existing methods utilize a high-pressure reaction kettle for reaction, and the method has the disadvantages of higher temperature, higher pressure, higher energy consumption and certain danger.
Polyphenylene Sulfide (PPS) is one of the hot special engineering materials in recent years, and is a thermoplastic semicrystalline resin having a phenylthio group in the main chain. PPS is a semi-crystalline thermoplastic polymer, the main chain structure of which is formed by alternating arrangement of benzene rings and sulfur atoms, a large number of benzene rings endow rigidity, and PPS has good solvent resistance and flame retardance, and is often applied as a flame retardant material, but has the defects of brittleness, low elongation at break and poor impact resistance. For crystalline polymers, the strength, dimensional stability, and other characteristics of the material are closely related to its crystallization behavior. Therefore, the PPS needs to be modified, the crystallization behavior of the PPS is improved, and the mechanical property of the PPS is improved so as to expand the application field of the PPS. The use of inorganic materials to fill-modify polymers is a common method in the polymer processing arts. For example, diamond (Deng S, cao L, lin Z, et al Nanodiamond as an efficient nucleating agent for polyphenylene sulfide [ J)]) Calcium carbonate (Liang J. Analysis on interfacial stress in impact of polyphenylene sulfide/CaCO) 3 composites[J]) Carbon fiber (Liu B, wang X, long S, et al Interfacial micromechanics of carbon fiber-reinforced polyphenylene sulfide composites [ J)]) Carbon nanotubes (Ribeiro B, pins R B, costa M L, et al Electrical and rheological percolation behavior of multiwalled carbon nanotube-reinfored poly (phenylene sulfide) compositions [ J)]) Silica (Yang Y, yu W, duan H, et al Realization of reinforcing and toughening poly (phenylene sulfide) with rigid silica nanoparticles [ J)]) And the like, and the material is used for carrying out crystallization modification on the polyphenylene sulfide. The auxiliary agent has poor dispersibility in the polyphenylene sulfide and is easy to agglomerate, thereby affecting the mechanical property of the polyphenylene sulfide. The graphene quantum dot is used as an emerging carbon nano material, has unique mechanical, thermal and electrical properties, can be completely dissolved in a relevant solvent, is uniformly dispersed, is not easy to agglomerate, and can be used for preparing the graphene quantum dotThe problem can be solved well and the material is endowed with a certain function. For example Guo Rui et al (Guo Rui, ouyang Meixuan, chen Ying, et al. Preparation and use of a graphene quantum dot/polyphenylene sulfide composite [ P ]]Publication No. CN 110194839A ], (Guo Rui, gu Qianqian, mo Zun, etc.. Application of graphene Quantum dot/polyphenylene sulfide composite as preservative [ P ]]Publication number "CN 111662584A") to add polyphenylene sulfide to HNO 3 /H 2 SO 4 Heating and nitrifying in mixed acid to obtain nitrified polyphenylene sulfide, adding nitrified polyphenylene sulfide and a reducing agent into DMF solvent, refluxing for 5.5 to 6 hours at 70 to 75 ℃ in nitrogen atmosphere, precipitating in acidified methanol to obtain ammoniated polyphenylene sulfide, and performing condensation reaction with nitrified graphene quantum dots, a condensing agent and a catalyst after being uniformly dispersed in DMF in an ultrasonic manner to obtain the graphene quantum dot/polyphenylene sulfide composite material. Likewise, mo Zunli et al (Mo Zunli, ouyang Meixuan, dong Jibing, et al. Preparation method of polyphenylene sulfide/graphene Quantum dot composite Material [ P ]]Publication No. CN 109852057A ") to disperse lamellar polyphenylene sulfide and graphene quantum dots into N-methylpyrrolidone, stirring and reacting for 3.5 to 4 hours at 200 to 220 ℃, heating to 270 to 275 ℃ and continuing to stir and react for 1.5 to 2 hours to obtain the polyphenylene sulfide/graphene quantum dot composite material, and improving the heat resistance of the polyphenylene sulfide, but the preparation process is longer. The preparation method of the polyphenylene sulfide/graphene quantum dot composite material by adopting the solvent film-forming method is complex in preparation process, high in energy consumption and low in production efficiency, a large amount of organic solvents are required to be used and discharged in the production process, the environment is harmed, and the solvents remain in the prepared composite material. In addition, the above patent does not relate to whether the mechanical properties such as impact toughness and the like of the graphene quantum dot/polyphenylene sulfide composite material are improved.
Disclosure of Invention
The invention provides a graphene quantum dot, a polyphenylene sulfide/graphene quantum dot composite material, a preparation method and application thereof, which can effectively solve the problems of difficult preparation of the graphene quantum dot, higher raw material cost and longer time consumption in the prior art, and the problems of long production period, environmental pollution, low efficiency and solvent residue in the prior art that the polyphenylene sulfide/graphene quantum dot composite material is prepared by a solvent film forming method.
One of the technical schemes of the invention is realized by the following measures: 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 microns 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 are further optimizations and/or improvements to one of the above-described inventive solutions:
20 ml to 100 ml hydrogen peroxide solution is added to 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 above oxidation time is 20 minutes to 60 minutes.
The second technical scheme of the invention is realized by the following measures: a graphene quantum dot prepared by the preparation method according to one of the technical schemes.
The third technical scheme of the invention is realized by the following measures: the second technical scheme is that the polyphenylene sulfide/graphene quantum dot composite material is prepared from the graphene quantum dots serving as raw materials, wherein the raw materials comprise 100 parts of polyphenylene sulfide and 0.1 to 5 parts of graphene quantum dots in parts by weight.
The fourth technical scheme of the invention is realized by the following measures: the third technical scheme is that the preparation method of the polyphenylene sulfide/graphene quantum dot composite material comprises the following steps: the polyphenylene sulfide resin and the graphene quantum dots are uniformly mixed according to a 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 a further optimization and/or improvement of the fourth technical scheme of the invention:
the extrusion is extrusion using a screw extruder at a screw speed of 15 to 30 rpm.
The fifth technical scheme of the invention is realized by the following measures: an article comprising the polyphenylene sulfide/graphene quantum dot composite material of claim three.
The sixth technical scheme of the invention is realized by the following measures: the third technical proposal is the application of the polyphenylene sulfide/graphene quantum dot composite material in the fields of electronic appliances, communication equipment or automobiles.
The preparation method of the graphene quantum dot provided by the invention has the advantages of mild reaction conditions, short time, simplicity and convenience in operation and environment friendliness. The method has the advantages of rich raw material sources and low price, and has important promotion significance for the development of the 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 taking 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 a processed material can be fully exerted, and the production efficiency is high. The impact strength, crystallization performance and thermal stability of the prepared polyphenylene sulfide/graphene quantum dot composite material are obviously improved, so that the application of the polyphenylene sulfide composite material in the fields of electronic appliances, communication equipment, automobiles and the like is wider.
Drawings
Fig. 1 is a graph of fluorescence emission spectra of graphene quantum dots 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 morphology of the graphene quantum dots obtained in example 10.
Fig. 3b is a lattice fringe pattern of the graphene quantum dots obtained in example 10.
Fig. 3c is a graph showing a particle size distribution of 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 graphene quantum dots and raw material brown-black humic acid obtained in example 10.
FIG. 6a is an SEM of an impact section of a pure polyphenylene sulfide.
Fig. 6b is an impact cross-sectional SEM image of a polyphenylene sulfide/graphene quantum dot composite material.
Fig. 7 is a graph of relative crystallinity over time during non-isothermal crystallization of polyphenylene sulfide/graphene quantum dot composites and pure polyphenylene sulfide.
Fig. 8a is a graph of a differential thermogravimetric curve DTG of polyphenylene sulfide and polyphenylene sulfide/graphene quantum dot composites.
Fig. 8b is a thermogravimetric curve TG plot of polyphenylene sulfide and polyphenylene sulfide/graphene quantum dot composites.
Detailed Description
The present invention is not limited by the following examples, and specific embodiments can be determined according to the technical scheme and practical situations of the present invention. The various chemical reagents and chemical supplies mentioned in the invention are all commonly known and used in the prior art unless specified otherwise; the percentages in the invention are mass percentages unless specified otherwise; the solutions in the invention are aqueous solutions in which the solvent is water unless otherwise specified, for example, the hydrochloric acid solution is hydrochloric acid aqueous solution; the room temperature and the room temperature in the present invention generally refer to temperatures ranging from 15 ℃ to 25 ℃, and are generally defined as 25 ℃.
In the present invention, unless otherwise specified, the devices and apparatuses used are all known and commonly used in the art.
The invention is further described below with reference to 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 microns 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.
And adding 20 to 100 milliliters 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 percent.
The above oxidation reaction is carried out at a temperature of 50 to 90 ℃.
The above oxidation time is 20 minutes to 60 minutes.
The brown-black humic acid refers to substances which are insoluble in acid and water and are black or brown-black in humic acid products, and comprises brown humic acid and black humic acid, and does not contain fulvic acid. The brown-black humic acid can be obtained from mineral resources such as weathered coal, peat, lignite, bituminous coal and anthracite or other biomass resources. The filtration and dialysis in the invention are all the operations of the prior known technology. The freeze-drying process 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.
The invention adopts green oxidant hydrogen peroxide solution to oxidize and strip brown-black humic acid, and the graphene quantum dot with excellent fluorescence performance is obtained by reaction in normal pressure environment. The mechanism is that hydrogen peroxide solution is heated to decompose to generate hydroxyl free radical with strong oxidability, attack carbon chain among the molecular structures of the brown-black humic acid, leave microcrystalline carbon with larger or smaller functional groups, and the microcrystalline carbon forms graphene quantum dots because the functional groups are continuously oxidized by the hydroxyl free radical, and the microcrystalline carbon self-assembles through the function of the functional groups, so that the graphene nano-sheet is formed. The graphene nano-sheets continue to form graphene quantum dots under the attack of hydroxyl radicals. The method has the advantages that the raw material sources are rich, the brown-black humic acid can be obtained from mineral resources such as peat, lignite, weathered coal and bituminous coal or other biomass resources, the price is low, and compared with the brown-black humic acid and coal, the brown-black humic acid has relatively simple components and structures, the preparation difficulty is reduced, the investment of a large amount of oxidizing agents is saved, and the experimental time is shortened; the method does not need high-pressure conditions, the reaction temperature is lower than 100 ℃, the oxidation time is short, and graphene quantum dots about 12 nm can be obtained by oxidizing at 50-90 ℃ for 20-60 minutes under normal pressure, and the method is simple, safer and better 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 microns or 180 microns 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 oxidation time is 20 minutes or 60 minutes.
Example 3: the graphene quantum dot prepared by the preparation method of the graphene quantum dot is provided.
Example 4: the polyphenylene sulfide/graphene quantum dot composite material is prepared from the graphene quantum dots in the embodiment, and the raw materials comprise, by weight, 100 parts of polyphenylene sulfide and 0.1 to 5 parts of graphene quantum dots.
Example 5: the polyphenylene sulfide/graphene quantum dot composite material is prepared from the graphene quantum dots in the embodiment, wherein the raw materials comprise 100 parts of polyphenylene sulfide and 0.1 part or 5 parts of graphene quantum dots in parts by weight.
Example 6: the preparation method of the polyphenylene sulfide/graphene quantum dot composite material in the embodiment is carried out according to the following steps: and uniformly mixing the polyphenylene sulfide resin and the graphene quantum dots according to the proportion of 100 parts of polyphenylene sulfide and 0.1 to 5 parts of graphene quantum dots to obtain a mixed raw material, and extruding the mixed raw material at the temperature of 285 to 320 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material.
The extrusion is extrusion using a screw extruder having a screw speed of 15 to 30 rpm.
Example 7: the preparation method of the polyphenylene sulfide/graphene quantum dot composite material in the embodiment is carried out according to the following steps: and uniformly mixing 100 parts of polyphenylene sulfide resin and 0.1 part or 5 parts of graphene quantum dots to obtain a mixed raw material, and extruding the mixed raw material at an extrusion temperature of 285 ℃ or 320 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material.
The extrusion was performed using a screw extruder having a screw speed of 15 rpm or 30 rpm.
Example 8: the product comprising the polyphenylene sulfide/graphene quantum dot composite material in the embodiment above.
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 gram of brown-black humic acid to a particle size of 40 microns, placing the mixture into 20 milliliters of hydrogen peroxide solution for oxidization, wherein the mass fraction of the hydrogen peroxide is 10%, the oxidization temperature is 50 ℃, the oxidization 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 dot.
Preparation of a polyphenylene sulfide/graphene quantum dot composite material: the polyphenylene sulfide/graphene quantum dot composite material comprises, by weight, 100 parts of polyphenylene sulfide and 0.1 part of graphene quantum dot, wherein the polyphenylene sulfide/graphene quantum dot composite material is prepared by the following steps: uniformly mixing the needed polyphenylene sulfide resin and graphene quantum dots to obtain a mixed raw material, and extruding the mixed raw material at the extrusion temperature of 285 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material, wherein the screw speed is 15 revolutions per minute.
Example 11: preparing graphene quantum dots: ball-milling 1 gram of brown-black humic acid to a particle size of 100 microns, placing the mixture into 50 milliliters of hydrogen peroxide solution for oxidization, wherein the mass fraction of the hydrogen peroxide is 25%, the oxidization temperature is 70 ℃, the oxidization time is 40 minutes, obtaining graphene quantum dot solution, and filtering, dialyzing and freeze-drying the graphene quantum dot solution to obtain the graphene quantum dot.
Preparation of a polyphenylene sulfide/graphene quantum dot composite material: the polyphenylene sulfide/graphene quantum dot composite material comprises, by weight, 100 parts of polyphenylene sulfide and 3 parts of graphene quantum dots, wherein the polyphenylene sulfide/graphene quantum dot composite material is prepared by the following steps: uniformly mixing the needed polyphenylene sulfide resin and graphene quantum dots to obtain a mixed raw material, and extruding the mixed raw material at the extrusion temperature of 310 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material, wherein the screw speed is 20 revolutions per minute.
Example 12: preparing graphene quantum dots: ball-milling 1 gram of brown-black humic acid to a particle size of 180 microns, placing the mixture into 100 milliliters of hydrogen peroxide solution for oxidization, wherein the mass fraction of the hydrogen peroxide is 30%, the oxidization temperature is 90 ℃, the oxidization 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 dot.
Preparation of a polyphenylene sulfide/graphene quantum dot composite material: the polyphenylene sulfide/graphene quantum dot composite material comprises, by weight, 100 parts of polyphenylene sulfide and 5 parts of graphene quantum dots, wherein the polyphenylene sulfide/graphene quantum dot composite material is prepared by the following steps: uniformly mixing the needed polyphenylene sulfide resin and graphene quantum dots to obtain a mixed raw material, and extruding the mixed raw material at the extrusion temperature of 320 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material, wherein the screw speed is 30 revolutions per minute.
Example 13: color effect and fluorescence effect of graphene quantum dots under visible light:
the graphene quantum dot solution obtained in example 10 described above appears to be brown yellow under irradiation of visible light, and appears to be bright-eye cyan under irradiation of ultraviolet lamp.
Example 14: fluorescence emission spectra of graphene quantum dots at different excitation wavelengths:
fig. 1 is a graph of fluorescence emission spectra of graphene quantum dots obtained in example 10 at different excitation wavelengths, and it can be found that under the condition of changing the excitation wavelength (320-400 and nm), the fluorescence intensity increases with the increase of the excitation wavelength, then decreases, the position of the fluorescence peak gradually shifts red with the lengthening of the excitation wavelength, and the dependence of the excitation wave is shown.
Example 15: UV-vis absorption spectrum of graphene quantum dots:
FIG. 2 is a UV-vis absorption spectrum of graphene quantum dots obtained in example 10, the absorption peak at 227 nm corresponds to pi-pi on the aromatic ring * The peak at 300 nm corresponds to n-pi at c=o * Is a transition of (c).
Example 16: morphology of graphene quantum dots:
fig. 3a is a TEM image of the surface morphology of graphene quantum dots obtained in example 10, which is approximately spherical, good in monodispersity, and free from obvious agglomeration phenomenon. Fig. 3b is a lattice fringe pattern of the graphene quantum dot obtained in example 10, which has a lattice spacing of about 0.26nm, and shows a characteristic structure of graphitic carbon. Fig. 3c is a graph of particle size distribution of graphene quantum dots obtained in example 10, showing 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 at an excitation wavelength of 347 nm.
Example 18: raman spectra of graphene quantum dots and raw material brown-black humic acid:
FIG. 5 is a Raman spectrum of a graphene quantum dot and raw material brown-black humic acid obtained in example 10, D peak and sp 3 Carbon atom or defect related, G peak shows sp of graphene sheet 2 The relative intensity of the plane was lower than that of the D peak of the raw material brown-black humic acid, and the decrease of the intensity of the D peak of GQDs showed that the defect density was lower and the G peak was broader, and the decrease of the intensity showed that a part of sp was present 2 Sp of carbon atom 3 The carbon atom conversion indicates that there is some oxygen-containing functionality around the carbon atom.
Example 19: and comparing the polyphenylene sulfide/graphene quantum dot composite material with the existing pure polyphenylene sulfide material, and testing:
the polyphenylene sulfide/graphene quantum dot composite material obtained in the embodiment 12 of the invention is subjected to performance measurement with the existing pure polyphenylene sulfide materialThe impact strength was tested according to ASTM D256, and the test results were as follows: the impact strength of the prior art pure polyphenylene sulfide material is 2.5kJ/m 2 Whereas the polyphenylene sulfide/graphene quantum dot composite material obtained in example 12 has an impact strength of 12 kJ/m 2 . From fig. 6a and 6b, it can be seen that the impact section of the polyphenylene sulfide/graphene quantum dot presents more shear lip zones, the section is rough, the number of dimples is increased, the impact section is obviously related to the yield process of absorbing energy in the composite material, and the typical ductile fracture characteristics are shown; as can be seen from DSC test, the crystallinity of the prior art pure polyphenylene sulfide material was 45%, while the crystallinity of the polyphenylene sulfide/graphene quantum dot composite material obtained in example 12 was 52%, and as can be seen from FIG. 7, the crystallization half-life (t) 1/2 ) The value is 1.05 minutes, and the crystallization half-life of the pure polyphenylene sulfide sample (PPS 0) is 1.28 minutes, so that 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 results of the relative crystallinity over time during the non-isothermal crystallization of polyphenylene sulfide/graphene quantum dot composite material obtained in example 12 and pure polyphenylene sulfide are shown in fig. 7.
The results of the differential thermal gravimetric curve (DTG) test of polyphenylene sulfide and polyphenylene sulfide/graphene quantum dot composites are shown in fig. 8a. Fig. 8a shows that the thermal decomposition temperature of the prior art pure polyphenylene sulfide material is 515 ℃, and the thermal decomposition temperature of the polyphenylene sulfide/graphene quantum dot composite material obtained in example 12 is 521 ℃, indicating 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. 8b. As shown in fig. 8b, the addition of graphene quantum dots can improve the carbon residue rate after the combustion of the polyphenylene sulfide/graphene quantum dot composite material, increase the condensed phase and enhance the flame retardant effect.
The test results show that compared with the existing pure polyphenylene sulfide material, the polyphenylene sulfide/graphene quantum dot composite material has the advantages that the impact strength (mechanical property), the crystallization property and the thermal stability are obviously improved, and the flame retardant effect is enhanced, 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 invention, high-quality and low-cost brown-black humic acid is used as a carbon source, the graphene quantum dots are prepared by using the 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 to post-treat, and the method has important promotion significance for the development of the high added value of humic acid resources. The method has the advantages that the raw material sources are rich, the brown-black humic acid can be obtained from peat, lignite, weathered coal, bituminous coal and other mineral resources or other biomass resources, the price is low, and compared with the brown-black humic acid and coal, the brown-black humic acid has no complex components and structures, the difficulty in preparation is intangibly reduced, the investment of a large amount of oxidizing agents is saved, and the preparation time is shortened; compared with the previous method for preparing the graphene quantum dots by using humic acid, the method does not need to use a high-pressure reaction kettle, and is simple, safer and better in effect. The preparation method of the polyphenylene sulfide/graphene quantum dot composite material by taking the graphene quantum dot prepared by the preparation method as an auxiliary agent through a thermoplastic processing method can effectively solve the problems of poor toughness and the like of the polyphenylene sulfide, and overcomes the problems of long production period, environmental pollution, low efficiency, solvent residue and the like of the polyphenylene sulfide/graphene quantum dot composite material prepared by a solvent film-forming method in the prior art, the preparation process does not use an organic solvent, the environment friendliness is strong, the performance of the processed material can be fully exerted, the production efficiency is high, and the mass production is facilitated.
In conclusion, the preparation method of the graphene quantum dots provided by the invention has the advantages of mild reaction conditions, short time, simplicity and convenience in operation and environment friendliness. The method has the advantages of rich raw material sources and low price, and has important promotion significance for the development of the 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 taking 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 a processed material can be fully exerted, and the production efficiency is high. The impact strength, crystallization performance and thermal stability of the prepared polyphenylene sulfide/graphene quantum dot composite material are obviously improved, and the flame retardant performance is improved, so that the application of the polyphenylene sulfide composite material in the fields of electronic appliances, communication equipment, automobiles and the like is wider.
The technical characteristics form the embodiment of the invention, have stronger adaptability and implementation effect, and can increase or decrease unnecessary technical characteristics according to actual needs so as to meet the requirements of different situations.
Claims (9)
1. The preparation method of the graphene quantum dot is characterized by comprising the following steps of: and (3) placing the brown-black humic acid with the particle size of 40-180 micrometers in a hydrogen peroxide solution, carrying out oxidation reaction at normal pressure to obtain a graphene quantum dot solution, and filtering, dialyzing and freeze-drying the graphene quantum dot solution to obtain the graphene quantum dot, wherein the oxidation reaction is carried out at the temperature of 50-90 ℃ for 20-60 minutes.
2. The method for preparing the 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 preparation method of the graphene quantum dots according to claim 1 or 2, wherein the hydrogen peroxide solution is 10-30% by mass.
4. A graphene quantum dot produced by the production method of a graphene quantum dot according to any one of claims 1 to 3.
5. A polyphenylene sulfide/graphene quantum dot composite material prepared by taking the graphene quantum dots as raw materials, which is characterized by comprising, by weight, 100 parts of polyphenylene sulfide and 0.1 to 5 parts of graphene quantum dots.
6. A method for preparing the polyphenylene sulfide/graphene quantum dot composite material according to claim 5, which is characterized by comprising the following steps: and uniformly mixing the polyphenylene sulfide resin and the graphene quantum dots according to a proportion to obtain a mixed raw material, and extruding the mixed raw material at the temperature of 285-320 ℃ to obtain the polyphenylene sulfide/graphene quantum dot composite material.
7. The method for preparing the polyphenylene sulfide/graphene quantum dot composite material according to claim 6, wherein the extrusion is extrusion at a screw rotation speed of 15 to 30 revolutions per minute by using a screw extruder.
8. An article comprising the polyphenylene sulfide/graphene quantum dot composite material of claim 7.
9. Use of the polyphenylene sulfide/graphene quantum dot composite material according to claim 8 in the field of electronic appliances or communication equipment or automobiles.
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