Background technology
Graphene is SP
2The hydridization carbon atom arrangement becomes cellular hexaplanar crystal, and thickness is merely the individual layer atom, is a kind of novel carbon nanomaterial, is the elementary cell that constitutes graphite, carbon nanotube and soccerballene etc., has the novel physical chemical property.Research shows that the specific surface area of Graphene can be up to 2600m
2/ g, Young's modulus is about 1100GPa, and breaking tenacity is 125GPa, and physical strength is 1060GPa, thermal conductivity 5000W/mK.Graphene also has excellent electron transport ability, and its electronic mobility is up to 15000cm under the room temperature
2/ VS.Graphene is (Novoselov since being found first in 2004; K.S.et al Science, 2004,306; 606); Cause the very big interest of scientific circles immediately, become in recent years one of active material of chemistry, Materials science and physics research, have a good application prospect in fields such as aerospace, novel material, electric power, electronics.
Prior art discloses multiple preparation method of graphene; Comprise that graphite oxide reduction method, micromechanics peel off method, chemical Vapor deposition process, SiC epitaxial growth method and electrochemical process etc.; Wherein, micromechanics is peeled off method, chemical Vapor deposition process, SiC epitaxial growth method and electrochemical process and is all had shortcomings such as complex process, cost height.Become the research focus and have graphite oxide reduction rule with low cost, as can to quantize advantages such as preparing, method is simple.The graphite oxide reduction method is usually at first with graphite oxidation and peel off into graphene oxide; Restore and obtain Graphene; Wherein, with graphite oxidation and peel off that to obtain graphene oxide be committed step, simultaneously; Because the graphene oxide good water-solubility has bigger advantage in the practical application of preparation matrix material.
At present; Supersound process is the method for peeling off graphite oxide that generally adopts; As CN201110065030.7 " a kind of chemical stripping prepares the method for graphene oxide " mentioned graphite oxide in organic solvent with the ultrasonic 0.5-1 of the frequency of 40-50kHz hour, later on also need be under 3000-5000 rev/min rotating speed obtain the graphene oxide lamella in centrifugal treating 20-90 minute; And for example CN200910062869.8 " a kind of method of realizing large-scale preparation of monolayer oxidized graphene " points out that the time that ultra-sonic dispersion is peeled off is 0.5-10 hour, also need filter not dispersive deposition; CN200910070735.0 " preparation method of single-layer graphene " mentions graphite oxide aqueous solution ultrasonic water bath under 150w power and handles 3h for another example, afterwards through the centrifugal graphene oxide that obtains.
In general, the ultrasonic method that uses at present all needs the long treatment time; And since hyperacoustic ununiformity to cause peeling off the graphene oxide size that obtains inhomogeneous; Cause the graphite oxide solution temperature to raise rapidly during supersound process easily; The laminated structure of high-power ultrasonic also easy disruptive oxidation Graphene; The use of organic solvent causes the pollution of environment easily.Therefore develop a kind of environmental protection, graphene oxide preparation technology is particularly important.
Summary of the invention
The objective of the invention is: provide a kind of cold expansion to peel off the method for preparing graphene oxide, with reach be beneficial to environmental protection, technology simple, peel off fully, graphite flake layer destroyed less, as to be convenient to scale operation purpose.
Technical scheme of the present invention is: a kind of preparation method of graphene oxide is characterized in that the step of preparation is:
1, preparation graphite oxide: adopt Hummer method or Staudenmaier method that crystalline flake graphite or highly oriented pyrolytic graphite are carried out the oxidation intercalation and obtain graphite oxide; The interlamellar spacing of oxidized graphite flake layer is 0.6nm~1.0nm;
2, the preparation graphite oxide aqueous solution: exsiccant graphite oxide powder is dissolved in the deionized water, stirs 20min~60min and be made into the graphite oxide aqueous solution, concentration is 0.1mg/ml~10mg/ml;
3, freezing: the graphite oxide aqueous solution that will be no less than 10ml places and is not higher than 0 ℃ freezer, places to be no less than 60min, makes it icing fully, forms hydrogen bond when utilizing water freezing and causes the big cold expansion principle of volume change to peel off graphite oxide;
4, thaw: after the freezing graphite oxide aqueous solution is taken out, at room temperature thaw, obtain the graphite oxide aqueous solution;
5, drying:, obtain graphene oxide with graphite oxide aqueous solution dry 8h~12h in 60 ℃~80 ℃ vacuum drying oven.
Advantage of the present invention is: provide a kind of cold expansion to peel off the method for preparing graphene oxide, avoided environmental pollution, helped environmental protection, technology is simple, and graphite oxide is peeled off fully, and is less to the destruction of graphite flake layer, is convenient to scale operation.
Embodiment
Explain further details in the face of the present invention down.A kind of preparation method of graphene oxide is characterized in that, the step of preparation is:
1, preparation graphite oxide: adopt Hummer method or Staudenmaier method that crystalline flake graphite or highly oriented pyrolytic graphite are carried out the oxidation intercalation and obtain graphite oxide; The interlamellar spacing of oxidized graphite flake layer is 0.6nm~1.0nm;
2, the preparation graphite oxide aqueous solution: exsiccant graphite oxide powder is dissolved in the deionized water, stirs 20min~60min and be made into the graphite oxide aqueous solution, concentration is 0.1mg/ml~10mg/ml;
3, freezing: the graphite oxide aqueous solution that will be no less than 10ml places and is not higher than 0 ℃ freezer, places to be no less than 60min, makes it icing fully, forms hydrogen bond when utilizing water freezing and causes the big cold expansion principle of volume change to peel off graphite oxide;
4, thaw: after the freezing graphite oxide aqueous solution is taken out, at room temperature thaw, obtain the graphite oxide aqueous solution;
5, drying:, obtain graphene oxide with graphite oxide aqueous solution dry 8h~12h in 60 ℃~80 ℃ vacuum drying oven.
More complete for graphite oxide is peeled off, after the freezing graphite oxide aqueous solution thawed, can carry out once more freezing with thaw operation, the number of times of repetitive operation is 1~5 time, and then carries out drying treatment.
Principle of work of the present invention is: utilize the graphite oxide good water-solubility; Be mixed with the homogeneous dispersive aqueous solution; When freezing, rely on water freezing to form hydrogen bond, and hydrogen bond action power is greater than the model ylid bloom action power of oxidized graphite flake interlayer; The big characteristics of volume change strut oxidized graphite flake layer when utilizing water freezing, obtain graphene oxide.The preparation process is simple, has avoided the use of organic solvent simultaneously, environmentally safe.The formation of hydrogen bond is more even, can not cause the destruction of graphite flake layer.
Embodiment 1
Adopt the Hummers method, in exsiccant single port flask, add 98% vitriol oil 100ml, be cooled to 0 ℃, add 4g natural flake graphite, 2g NaNO in the stirring successively with the cryogenic liquid recycle pump
3With 12g KMnO
4, control reacting liquid temperature at 10~15 ℃, stirring reaction 2h; Then beaker is placed the water bath with thermostatic control about 35 ℃, continue to stir 30min when the question response liquid temp rises to 35 ℃ of left and right sides; In stirring, add the 200ml deionized water at last, the control reacting liquid temperature continues to stir 2h in 100 ℃.Reaction solution is diluted to the H that adds 100ml 5% behind 800~1000ml again with deionized water
2O
2, filtered while hot, HCI with 5% and deionized water thorough washing be sulfate radical-free ion (detecting with BaC1 solution) in filtrating; With filter cake dry 12h in 80 ℃ of vacuum drying ovens; Obtain the exsiccant oxidized graphite flake, the interlamellar spacing of graphite oxide is 0.6nm, and its transmission electron microscope photo is shown in accompanying drawing 1.It is subsequent use that grinding obtains the graphite oxide powder.
Get the 0.1g graphite oxide and be dissolved in (graphite oxide concentration is 2mg/ml) in the 50ml deionized water, magnetic agitation 30min obtains the finely dispersed graphite oxide aqueous solution.Place-10 ℃ freezer 2h then, make it icing fully, take out then under the room temperature it is dissolved, dry 12h obtains graphene oxide in 60 ℃ of vacuum drying ovens, adopts transmission electron microscope to analyze, and sees accompanying drawing 2.
Embodiment 2
Adopt the Staudenmaier method in the concentrated nitric acid mixed solution of 98% the vitriol oil and 65%, to add natural flake graphite; Wherein the vitriol oil and concentrated nitric acid volume ratio are 3:1; Add SODIUMNITRATE under the magnetic agitation, normal temperature is reaction 24h down, obtains graphite oxide; With the reactant dilution, Hydrogen chloride with 5% and deionized water wash do not have SO to filtrating
4 2-And be neutral, obtain the graphite oxide powder after the drying and grinding, the graphite oxide interlamellar spacing is 1.0nm.
Get the 0.2g graphite oxide and be dissolved in (graphite oxide concentration is 4mg/ml) in the 50ml deionized water, magnetic agitation 40min obtains the finely dispersed graphite oxide aqueous solution.Place-5 ℃ of freezer 3h then, make it icing fully, it is dissolved, dry 8h obtains graphene oxide in 80 ℃ of vacuum drying ovens, and the graphene oxide for preparing among its transmission electron microscope photo and the embodiment is similar.
Embodiment 3
The graphite oxide preparation method is with embodiment 1.
Get the 0.3g graphite oxide and be dissolved in (graphite oxide concentration is 6mg/ml) in the 50ml deionized water, magnetic agitation 60min obtains the finely dispersed graphite oxide aqueous solution.Place-10 refrigerator-freezer 1h then, make it icing fully, it is dissolved, dry 10h obtains graphene oxide in 70 ℃ of vacuum drying ovens, and the graphene oxide for preparing among its transmission electron microscope photo and the embodiment is similar.
Embodiment 4
The graphite oxide preparation method is with embodiment 1.
Get the 0.1g graphite oxide and be dissolved in (graphite oxide concentration is 4mg/ml) in the 50ml deionized water, magnetic agitation 40min is mixed with the finely dispersed graphite oxide aqueous solution.Place-5 ℃ of refrigerator-freezer 3h then; Make it icing fully, it is dissolved, repeat the freezing-process of melting 5 times; Dry 12h obtains graphene oxide in 80 ℃ of vacuum drying ovens at last, and the graphene oxide for preparing among its transmission electron microscope photo and the embodiment is similar.