KR101465205B1 - A preparing method of graphene using a surfactant containing aromatic functional group - Google Patents

Abstract

The present invention relates to a method for manufacturing a reduced graphene oxide using a surfactant containing an aromatic functional group, and to a reduced graphene oxide manufactured by the method. A graphene sheet, manufactured by reduction of graphene oxide (GO) by comprising the steps of manufacturing a graphene oxide dispersion solution including a surfactant containing two or more aromatic functional groups and a graphene oxide; obtaining a reduced graphene oxide laminate containing two or more aromatic functional groups by reducing the graphene oxide dispersion solution; and manufacturing multilayered reduced graphene oxide by dispersing the reduced graphene oxide laminate containing two or more aromatic functional groups in an aqueous solvent, can be non-covalent functional group under a condition of existence of the surfactant according to the present invention, and the reduced graphene oxide (rGO) containing the surfactant obtained as the result can be stably dispersed in water.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for preparing graphene using a surfactant containing an aromatic functional group,

The present invention relates to a process for preparing reduced graphene oxide using an aromatic functional group-containing surfactant, and a reduced graphene oxide produced by the process.

Graphene has great interest in the unique physical properties of graphene due to its rigid 2D structure and its potential applications in the fields of nanoelectronics, energy storage materials, polymer composites materials, and sensing . Among the technologies developed for the mass production of high quality graphene sheets, the mechanical stripping method has been used to produce pure graphene sheets for basic research, but the mechanical stripping method is not suitable for mass production of graphene . Therefore, developing alternative methods capable of mass synthesis of graphene sheets remains a challenge. In addition, the hydrophobic nature of the graphene nanosheet and the tendency to agglomerate in the solvent is a limiting factor in the development of the graphene fabrication process and severely limits the potential applicability of graphene in a variety of applications. Recently, it has been reported that a large amount of graphene sheet can be produced by the reduction of exfoliated graphene oxide. It has also been reported that graphene sheets can be stabilized by amphiphilic polymers and monomeric surfactants to form stable graphene dispersions in the presence of such surfactants. However, the use of surfactants in most applications of graphene is generally undesirable, since it is very difficult to remove the surfactant in the dispersion after formation of the stable graphene dispersion in the presence of the surfactant. Conventionally functionalized graphene sheets have been prepared by thermal expansion of graphene oxide without the use of surfactants, and stable dispersions of chemically modified graphene by alkylamines have also been reported. However, the thermal method of electrons is limited in the solution process, and the latter amine doping method is limited in application due to the purity of graphene. Therefore, in the functionalization of graphene sheets for application to devices, it has become an important issue to increase the dispersibility and self-assembling properties of graphene nanosheets. However, despite the fact that aromatic organic molecules are very commonly used reagents in organic chemistry, the non-covalent functionalization of graphene sheets through π-π interactions using aromatic organic molecules has not been previously reported . In addition, there has been no report on the removal of surfactants after the use of surfactants in the surface attachment or processing of graphene.

Korean Patent Laid-Open Publication No. 10-2013-0011099 discloses a related art document, and discloses a graphene dispersion and a manufacturing method thereof, but still has the disadvantages described above.

Accordingly, the present disclosure provides a process for preparing reduced graphene oxide using a surfactant containing two or more aromatic functional groups, and a reduced graphene oxide produced by the process.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

A first aspect of the present invention is a process for preparing a graphene oxide dispersion comprising: preparing a graphene oxide dispersion comprising a surfactant containing at least two aromatic functional groups and graphene oxide; Reducing the graphene oxide dispersion to obtain a reduced graphene oxide laminate containing at least two aromatic functional groups; And a step of dispersing the reduced graphene oxide laminate containing the two or more aromatic functional groups in an aqueous solvent to prepare a multilayered reduced graphene oxide, .

A second aspect of the present invention provides a reduced graphene oxide produced by the process according to the first aspect of the present invention.

According to the above-described task solution of the present invention, a graphene sheet produced by reduction of graphene oxide (GO) can be non-covalently functionalized in the presence of the surfactant according to the present invention, and the resultant Reduced graphene oxide (rGO) containing a surfactant can be dispersed stably in water. The reduced graphene oxide containing the surfactant may exhibit a long interlayer distance as observed using X-ray diffraction analysis (XRD). The surfactant can be completely removed by repeatedly washing with a solvent without affecting the graphene properties.

According to one embodiment of the present invention, a reduced graphene oxide can be prepared using a surfactant that can be completely removed without affecting the graphene properties.

In addition, the method described in one embodiment herein can be extended to obtain stably dispersed reduced graphene oxide in an organic solvent. Therefore, a large amount of reduced graphene oxide nanosheets dispersed in an organic solvent as well as water can be easily produced. In this way, graphene-free graphene can be usefully used in manufacturing flexible electrodes, biosensors, and hydrogen storage devices by producing reduced graphene oxide having a long interlayer distance and a surfactant removed.

Figure 1A shows a schematic structure of rGO and rGO containing a banne salt prepared according to one embodiment of the present invention.
Figure Ib is images dispersed in water of rGO (right) as a control and rGO (right) containing a Biolon salt prepared according to one embodiment of the invention.
Figure 2 shows the results of a solubility test (1 mg / mL) of rGO containing a bannon salt for several different solvents, prepared by sonication for 2 hours, according to one embodiment of the invention This is a picture showing.
3A is a C1s XPS spectrum of GO prepared according to one embodiment of the present invention.
Figure 3b is a C1s XPS spectrum of rGO containing a bionol salt prepared according to one embodiment herein.
3c is a C1s XPS spectrum of rGO prepared according to one embodiment of the present application.
FIG. 3D is a C1s XPS spectrum of the control sample (rGO).
Figure 4 is a high-resolution C1s XPS spectrum of a bionol salt prepared according to one embodiment of the invention.
5A is a powder XRD pattern of rGO (red) and rGO (black) containing a bannol salt, according to one embodiment of the invention.
Figure 5b is a powder XRD pattern of a bannol salt (red) and a binol (black) according to one embodiment of the invention.
6 is an XRD pattern of GO, rGO as a control, and graphite according to one embodiment of the present application.
Figure 7 is a graphical representation of the results of a comparison of GO (red), rGO (blue), rGO (cyan), binol (black), bionol salt (purple) (Green, rGO).
Figure 8 is a UV-vis spectra of rGO (0.04 mg / mL) and a banol salt (0.025 mg / mL) containing a banol salt prepared according to one embodiment of the present invention.
FIG. 9A is an AFM image of rGO (thickness: 20 nm) containing a bionol salt prepared according to one embodiment of the invention.
Figure 9b is an AFM image of rGO (thickness: 1.2 nm) containing a bionol salt prepared according to one embodiment of the invention.
10 is an image showing contact angle (73 °) of rGO containing (a) bannol salt prepared according to one embodiment of the present application and (b) contact angle (86 °) of rGO.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is "on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as "including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

The terms "about "," substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

The word " step (or step) "or" step "used to the extent that it is used throughout the specification does not mean" step for.

Throughout this specification, the term "combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

Throughout this specification, the term "graphene " means that a plurality of carbon atoms are linked together by a covalent bond to form a polycyclic aromatic molecule, wherein the carbon atoms linked by the covalent bond are 6-membered rings A 5-membered ring, and / or a 7-membered ring. Thus, the sheet formed by the graphene may be seen as a single layer of carbon atoms covalently bonded to each other, but may not be limited thereto. The sheet formed by the graphene may have various structures, and the structure may vary depending on the content of the 5-membered ring and / or the 7-membered ring which may be contained in the graphene. When the sheet formed by the graphene is a single layer, they may be laminated to form a plurality of layers, and the side end portion of the graphene sheet may be saturated with hydrogen atoms, but the present invention is not limited thereto.

Throughout the specification, the term "Graphene Oxide" is also referred to as graphene oxide and may be abbreviated as "GO ". But it may include, but is not limited to, a structure in which a functional group containing oxygen such as a carboxyl group, a hydroxyl group, or an epoxy group is bonded on a single layer graphene.

Throughout this specification, the term "reduced graphene oxide" refers to a reduced amount of oxygen-containing graphene oxide through reduction process, but may be abbreviated as "rGO" have.

Hereinafter, embodiments of the present invention are described in detail, but the present invention is not limited thereto.

A first aspect of the present invention is a process for preparing a graphene oxide dispersion comprising: preparing a graphene oxide dispersion comprising a surfactant containing at least two aromatic functional groups and graphene oxide; Reducing the graphene oxide dispersion to obtain a reduced graphene oxide laminate containing at least two aromatic functional groups; And a step of dispersing the reduced graphene oxide laminate containing the two or more aromatic functional groups in an aqueous solvent to prepare a multilayered reduced graphene oxide, .

In one embodiment of the invention, the two or more aromatic functionalities may each independently be selected from the group consisting of naphthyl, anthracene, pyrene, tetrahydropylene, and combinations thereof , But may not be limited thereto.

In one embodiment of the present invention, the preparation of the graphene oxide can be used without any particular limitation as long as it is a method known in the art. For example, the graphene oxide may be prepared from natural graphite powder by the modified Hummers and Offenman method using sulfuric acid, potassium permanganate, hydrochloric acid, and nitric acid, but may not be limited thereto. Generally, graphene oxide is produced by oxidation of graphene, and by oxidation, an oxygen atom is introduced into graphene to form a functional group containing oxygen such as a carboxyl group, a hydroxyl group, or an epoxy group on the graphene. The functional groups extend the gap between graphene monolayers to facilitate separation of each graphene layer. Also, since graphene oxide contains oxygen-containing functional groups, it can be dispersed better in water because it has hydrophilic properties.

 In one embodiment of the present invention, the surfactant containing two or more aromatic functional groups is adsorbed on the surface of graphene or graphene oxide through interaction with the [pi] -electron of the graphene structure to form graphene or graphene oxide Self-assembled with regular microstructures between the layers to prevent aggregation of the graphene or graphene oxide layers.

In one embodiment of the present invention, the graphene oxide dispersion may be formed by adding the graphene oxide to a solvent, or adding the graphene oxide to a solvent, followed by heating, stirring, or ultrasonic treatment. .

In one embodiment of the present invention, the surfactant containing two or more aromatic functional groups may include, but is not limited to, a bionol salt or a bionol derivative.

In one embodiment of the invention, the two naphthalene moieties of the Bynol salt have affinity to the basal plane of graphite and graphene through π-stacking. In addition, the bionol salt can be completely removed by washing without affecting the properties of graphene or graphene oxide because it has a weak? -Π interaction with graphene. By utilizing the properties of the Bynol salt, a stable aqueous dispersion solution of graphene sheet can be prepared by using the sodium salt of Bynol, a water-soluble banol derivative, as a stabilizer.

In one embodiment herein, the bionol derivative provides a very long interlayer distance to the graphene oxide using a very good dispersing power in water, and after complete function of the surfactant as a surfactant, .

In one embodiment of the invention, reducing the graphene oxide dispersion can be used without any particular limitation as long as it is a method known in the art. For example, the reduction of the graphene oxide dispersion may be performed by, but not limited to, the addition of a reducing agent, calcination, the use of microwaves, and combinations thereof.

In one embodiment of the invention, the reducing agent is sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH), sodium borohydride (NaBH _4), hydrazine (N ₂ H _4), hydroiodide But are not limited to, those selected from the group consisting of HI, H ₂ S, dimethylhydrazine, hydroquinone, H ₂ SO ₄ , aluminum powder, and combinations thereof. have. For example, the reducing agent may be hydrazine hydrate or a mixture of hydrazine hydrate and ammonia, but the present invention is not limited thereto. The method of reducing graphene oxide using hydrazine hydrate is a method that can most effectively reduce substances containing oxygen in graphene oxide.

In one embodiment of the invention, the reduction of the graphene oxide dispersion may be performed by additional heat treatment after addition of the reducing agent, but may not be limited thereto. For example, reduction of the graphene oxide dispersion may include, but is not limited to, heating to about 120 캜 or below after the addition of the reducing agent. For example, reducing the graphene oxide dispersion can include heating to about 90 ° C, about 100 ° C, about 110 ° C, or about 120 ° C after adding the reducing agent, But may not be limited.

In one embodiment of the present invention, the reduced graphene oxide laminate containing two or more aromatic functional groups is characterized in that the surfactant containing two or more aromatic functional groups is inserted between the layers of the reduced graphene oxide laminate As a result, the distance between graphene layers increases.

In one embodiment of the present invention, the step of preparing the multi-layer reduced graphene oxide comprises dispersing the reduced graphene oxide laminate containing the two or more aromatic functional groups in an aqueous solvent, / RTI > and / or < RTI ID = 0.0 > washing, < / RTI > and drying with an organic solvent. The surfactant may be removed from the reduced graphene oxide laminate by the washing.

In one embodiment of the invention, the aqueous solvent and / or organic solvent may be used without any particular limitation as long as it is known in the art. For example, the organic solvent is selected from the group consisting of acetone, methyl ethyl ketone, methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, ethylene glycol, polyethylene glycol, tetrahydrofuran, dimethyl sulfoxide, dimethyl formamide, dimethyl The organic solvent may be selected from the group consisting of acetamide, N-methylpyrrolidone, hexane, cyclohexane, toluene, xylene, chloroform, dichlorobenzene, dimethylbenzene, trimethylbenzene, pyridine, methylnaphthalene, nitromethane, dichloromethane, acetonitrile, octadecylamine, Dimethyl sulfoxide, dimethyl sulfoxide, and combinations thereof. The aqueous solvent may include, but is not limited to, for example, water.

In one embodiment of the present invention, the drying is not particularly limited as long as the drying is performed at a temperature of room temperature or higher. For example, the drying may be, but not limited to, drying in a vacuum oven at about 80 DEG C for about 24 hours.

In one embodiment of the present invention, in the process of dispersing the reduced graphene oxide laminate containing two or more aromatic functional groups in an aqueous solvent and then washing and drying the same using an aqueous solvent and / or an organic solvent, The two or more aromatic functional group-containing surfactants are removed between the layers of the reduced graphene oxide laminate containing the two or more aromatic functional groups, so that the reduced graphene oxide layer containing the two or more aromatic functional groups The distance between the graphene layers of the multi-layered reduced graphene oxide can be reduced.

In the exemplary embodiment of the present application, SiO ₂ of the reduced graphene oxide of the multi-layer to the drop casting method When formed on a substrate, due to the removal of the surfactant containing two or more aromatic functional groups between the layers of the reduced graphene oxide laminate containing the two or more aromatic functional groups, the two or more aromatic The thickness and sheet resistivity of the pellet of the multi-layer reduced graphene oxide can be reduced as compared with the reduced graphene oxide layered body containing the functional group.

A second aspect of the present invention provides a reduced graphene oxide produced by the process according to the first aspect of the present invention.

Although the description of the second aspect of the present invention has been omitted for the sake of clarity, the description of the first aspect of the present application may be applied equally to the second aspect of the present invention, have.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples are given for the purpose of helping understanding of the present invention, but the present invention is not limited to the following Examples.

[ Example ]

matter

(35%), s-binnol, sodium nitrate, potassium nitrate, sodium nitrate, hydrazine tetrahydrofuran, hydrazine hydrate (35%), natural graphite (Bay Carbon, SP-1 graphite), sulfuric acid (95-97%), hydrogen peroxide And sodium hydroxide were purchased from commercial sources and used as is.

Character analysis

All X-ray photoelectron spectroscopy (XPS) measurements were performed by SIGMA PROBE (ThermoVG, UK) using a monochromatic Al-Kα X-ray source at 100 W. Powder X-ray diffraction (XRD) patterns were obtained using the D8-Advance device (Germany) and Cu-Kα radiation. Thermal properties of all samples were analyzed by TGA 1000 plus (Polymer Laboratories) using thermogravimetric analysis (TGA). Atomic force microscope (AFM) was performed by using a SPA400 device (Seiko Instrument Industry Co.) containing SPI-3800 controller at room temperature. All UV-vis absorption spectra were recorded using a dual-beam UV-1650PC spectrophotometer (Shimadzu).

Grapina Of oxide (GO)  Produce

GO was prepared by the modified Hummers and Offenman method using natural graphite powders with sulfuric acid, potassium permanganate, and sodium nitrate.

Binol  Salt-containing rGO Manufacturing

15 mg of GO was dispersed in 10 mL of deionized water, and a fully dispersed solution was prepared by adding biol (60 mg) and NaOH (3 equivalents) and stirring at room temperature. Then, the temperature of the dispersion solution was adjusted to about 5 캜 to about 10 캜. Hydrazine hydrate (0.75 mL) was added to the dispersion solution, and the mixture was heated to about 100 캜 for 30 minutes. The heated product was filtered, washed several times with water, and dried in a vacuum oven at 80 ° C for 24 hours to obtain rGO containing a bionol salt. The rGO containing the obtained bannol salt was completely dispersed in water. The rGO containing the bannol salt dispersed in the water was filtered using a Buchner funnel. The rGO containing the bannol salt on the filtering Buchner funnel was washed several times with water, ethanol, and acetone, and then dried in a vacuum oven at 80 ° C for 24 hours to obtain rGO.

Control sample ( rGO )

A fully dispersed solution was prepared by adding 15 mg of GO to 10 mL of deionized water and maintaining the temperature between about 5 < 0 > C and about 10 < 0 > C, followed by the addition of NaOH (3 equivalents) and stirring at room temperature. Hydrazine hydrate (0.75 mL) was added to the dispersion solution, and the mixture was heated to about 100 캜 for 30 minutes. The heated product was filtered, washed several times with water, and dried in a vacuum oven at 80 DEG C for 24 hours to obtain a control sample (rGO).

Results and Discussion

According to the present embodiment, a stable aqueous dispersion solution of graphene sheet can be produced through exfoliation / in situ reduction of graphene oxide in the presence of a stabilizing surfactant, bionol salt, The activator banol salt can be completely removed without affecting the properties of the graphene sheet.

According to this embodiment, since the two naphthalene moieties of the biolin molecule have affinity to the basal plane of graphite and graphene through? -Stacking, the water-soluble A stable aqueous dispersion solution of graphene sheet was prepared using a bionol derivative and a sodium salt of bionol. The bionol derivatives provided a very long interlayer distance using a very good dispersing power in water and were completely removed after completing the function of the surfactant as a surfactant. X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), and ultraviolet- Spectra were used to characterize the material.

First, the GO sheet was synthesized from graphite powder using a modified Hummers method (Bay carbon, SP-2) and purified as previously reported. Binary and sodium hydroxide were mixed into the GO solution to prepare a completely dispersed aqueous solution. A large amount of hydrazine hydrate was added to the aqueous dispersion solution at about 5 캜 to about 10 캜 and then heat-treated at about 100 캜 for 15 to 20 minutes. Hydrazine hydrate was added at a relatively low temperature to slow down the rate of reduction of GO during the formation of a homogeneous graphene sheet (rGO containing the bionol salt of FIG. 1A) containing the Bynol salt mixture. The rGO containing the bannon salt prepared according to the above procedure was dispersed in the aqueous solution at a concentration of less than 1.5 mg / mL (Fig. 1B). The bannon salt of rGO containing the bannon salt does not affect the properties of the rGO nanosheet due to the weak π-π interaction due to the molecular structure of the bannol salt between the bannol salt and the graphene, And could be completely removed by washing with a solvent.

A possible route by which the rGO containing the bannon salt can become rGO is shown in Fig. The rGO containing the bannol salt may also be re-dispersed in various organic solvents (Fig. 2). FIG. 2 is a photograph showing the results of solubility test (1 mg / mL) of rGO containing the above-mentioned bannon salt for various solvents prepared by sonication for 2 hours according to this embodiment. (1), acetonitrile (2), toluene (3), and toluene (3) were used as the solvent for the solubility test. The rGO was dissolved in a solvent such as isopropyl alcohol , Dimethyl sulfoxide (4), dimethyl formamide (5), p-xylene (6), N-methylpyrrolidone (7), tetrahydrofuran (8), ethanol (9), and dichloromethane to be.

X-ray photoelectron spectroscopy (XPS) was used to analyze the GO, rGO, and rGO containing bionol salts. The C1s XPS spectrum of the GO (FIG. 3A) shows that the carbon of the different functional groups, ie, the carbon of the non-oxygenated ring (284.6 eV), the carbon in the CO bond (286.7 eV), the carbon of the carbonyl group (C = O, 288.4 eV), and the carbonyl of the carboxylate [C (O) OH, 290.1 eV]. However, for the same oxygen function corresponding to GO above, the C1s XPS spectrum of rGO and rGO containing the bannon salt (Fig. 3b and Fig. 3c) showed a much smaller peak density for this configuration, Indicating significant de-oxygenation by the reduction process. In addition, there was an additional configuration of the 285.7 eV to 286.0 eV region corresponding to the carbon of the C-N bond, which was formed by inserting nitrogen into the system. Of the XPS data, the rGO samples containing the bionol salt exhibited characteristic peaks at 1071.7 eV (Na 1s) and 495.9 eV (Na KLL), and these peaks were found to be absent in the XPS spectrum of other samples. On the basis of the analysis of the XPS, the prepared GO showed a very high oxygen atomic percent (C / O = 2.2). In contrast, the C / O ratio of the rGO containing the bannon salt and the C / O ratio of the rGO were 6.8 and 13.9, respectively. The C / O ratio (4.9) of the prepared bionol salt was very low (FIG. 4). The C / O ratio of the rGO containing the bannon salt was affected by the presence of the bannol salt. However, after complete removal of the bannol salt, the C / O ratio (13.9) of the prepared rGO was increased. To confirm the level of reduction, a control experiment was performed without a bionol salt. XPS data shows that the C / O ratio of the control sample was 14.2 (FIG. 3D), which is very close to the C / O ratio of the rGO. According to the above XPS data, it was concluded that the rGO produced by the method of the present invention is a good quality rGO containing a much smaller amount of oxygen.

A powder X-ray diffraction (XRD) pattern was used to confirm the distance between the graphene layers of the rGO containing the bannol salt and the rGO (Figs. 5A and 5B). The 2 &thetas; peak of the graphite powder was 26.71 DEG, which indicates that the interlayer distance of the graphite was 3.34 ANGSTROM (FIG. 6). The prepared GO showed a 2? Peak at 10.27 °, indicating that the graphite was completely oxidized to GO, resulting in an interlayer distance of 8.60 Å (FIG. 6). The XRD pattern of the sodium salt of binol and bionol was also measured (Fig. 5B). The binol exhibited several 2? Peaks, while the binolin salt showed a sharp peak at 6.2, indicating that the interlayer distance of the binolin salt was 14.24 Å. The XRD pattern of rGO containing the bionol salt exhibited a 2? Peak at 6.5 °, indicating that the interlayer distance was 13.6 Å (FIG. 5A). Therefore, it is believed that the interlayer distance increased to 13.6 Å due to the presence of the bannol salt between the rGO layers from the XRD pattern of rGO containing the bannon salt, which is in agreement with the interlayer distance of the bannol salt. However, when rGO containing the bannon salt was washed, a typical broad peak close to 25.5 ° was observed, indicating that the interlayer distance of the rGO was 3.49 Å. The abrupt shift of the 2? Peak from the rGO containing the bannon salt to the rGO indicates that the interlayer distance is reduced from 13.6 Å to 3.49 Å. In the rGO sample containing the bannon salt, Indicating complete removal of the salt. In contrast to the XRD pattern of the GO and rGO powders, shifting 2? Peaks from 10.27 ° to 25.5 ° show that the interlayer distance of the rGO is completely reduced. The interlayer distance of the rGO was 3.49 Å, which is very close to the interlayer distance of graphite powder (3.34 Å). The 2 &thetas; peak of the rGO was narrower than that observed in the conventional studies of the present inventors, which can be attributed to the well-ordered two-dimensional structure of the rGO sheet. From the long interlayer distance (13.6 Å) of the XRD data, rGO containing the bannol salt was found to contain rGO together with the bannol salt. After washing the rGO containing the bannon salt with several solvents, the interlayer distance decreased, indicating complete removal of the bannol salt and reformation of the typical rGO layer stack of graphite.

Thermogravimetric analysis (TGA) was used to assess the quality of the rGO and to confirm the presence of the binol salt. In FIG. 7, TGA plots of GO (red), rGO (blue), rGO (cyan), binol (black), bionol salt (purple), and control sample (green) containing bionol salts are shown. According to FIG. 7, the rGO had better thermal stability than the GO. All samples were heated from room temperature to 800 占 폚 at a heating rate of 1 占 폚 / min under a nitrogen atmosphere. In the case of the GO, most of the weight lost between 100 ° C and 200 ° C, indicating that CO, CO ₂ , and water vapor were released from the most unstable functional groups during pyrolysis and at a temperature below 800 ° C, The loss was about 77%. The weight loss of the rGO and rGO containing the bannon salts was 34% and 16.8%, respectively. The major weight loss for rGO containing the bannon salt occurred at about 600 ° C, which is similar to the bannon salt which had the maximum weight loss at 600 ° C. The TGA results showed that the rGO sample containing the bionol salt clearly contained the bionol salt. The binol was thermally volatile and weight loss occurred between 200 ° C and 300 ° C. The control sample showed a weight loss of about 16.2%, which is very similar to the rGO sample. These results showed that the rGO did not contain any bionol salts, and the rGO samples showed very high thermal stability. The weight loss of the rGO is due to the absence of most of the oxygen functional groups. In the UV-vis spectrum, the main absorption peak of rGO containing the bannon salt appeared at 228.6 nm, which was red shifted by 1.3 nm relative to the absorption peak of the bannol salt (Fig. 8). This is mainly due to the weak π-π interaction between graphene sheet and bionol salt. The AFM image of the rGO containing the bannon salt (Fig. 9a) showed that the average thickness of the rGO layer was 2.4 nm to 30 nm, indicating the presence of a bannol salt in the graphene sheet. After complete removal of the banneol salt, the thinnest film thickness of the rGO was about 1.2 nm (2 layers) (Fig. 9b), indicating complete removal of the bannol salt and the number of most rGO layers was 8-10 and higher . Also, an rGO pellet containing a bannol salt was prepared by drop casting the product on a SiO ₂ substrate, and the pellet of the pellet was dissolved in the rGO pellet containing the bannol salt, Lt; RTI ID = 0.0 > ohm / sq. ≪ / RTI > However, after washing and vacuum drying the rGO pellet-coated SiO ₂ substrate with water and organic solvent, the thickness and sheet resistivity of the prepared rGO pellets were about 10 μm and 40 Ω / sq. As the bannol salt was completely removed, the sheet resistance was reduced compared to the bannon salt containing rGO pellets. It is also possible to use poly (sodium-4-styrenesulfonate), PSS, sodium dodecylbenzene sulfonate (SDBS), and tetrasodium 1,3,6 , And tetrasodium 1,3,6,8-pyrenetetrasulfonic acid (TPA) surfactant were used for the control experiments. The thickness and sheet resistivity of the rGO pellet using PSS, SDBS, and TPA were about 16 [mu] m, 410 [Omega] / sq; About 12 μm, 635 Ω / sq; And about 15 μm, 489 Ω / sq, which were almost the same before and after washing. In addition, as the hydrophobicity increases due to the complete removal of the bannol salt, the water droplet contact angle (86 DEG) of the rGO compared with the water droplet contact angle (73 DEG, a in FIG. 10) , B) in FIG. 10), which supports the experimental results (FIG. 10).

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (8)

Preparing a graphene oxide dispersion comprising a surfactant containing at least two aromatic functional groups and graphene oxide;
Reducing the graphene oxide dispersion to obtain a reduced graphene oxide laminate containing at least two aromatic functional groups; And
Dispersing the reduced graphene oxide laminate containing the two or more aromatic functional groups in an aqueous solvent to prepare a multilayered reduced graphene oxide
Lt; / RTI >
Wherein the two or more aromatic functional groups each independently comprise a group selected from the group consisting of naphthyl, anthracene, pyrene, tetrahydropylene, and combinations thereof. .
delete The method according to claim 1,
Wherein the surfactant containing two or more aromatic functional groups comprises a bionol salt or a bionol derivative.
The method according to claim 1,
Wherein the reduction of the graphene oxide dispersion is carried out by the addition of a reducing agent.
5. The method of claim 4,
The reducing agent is sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH), sodium borohydride (NaBH _4), hydrazine (N ₂ H _4), hydrogen iodide (HI), hydrogen sulfide (H ₂ S ), Dimethylhydrazine, hydroquinone, sulfuric acid (H ₂ SO ₄ ), aluminum powder, and combinations thereof.
The method according to claim 1,
The step of preparing the multilayered reduced graphene oxide may include a step of dispersing the reduced graphene oxide laminate containing the two or more aromatic functional groups in an aqueous solvent and then washing it with an aqueous solvent and / ≪ / RTI > and further drying the resulting graphene oxide.
The method according to claim 6,
The organic solvent is selected from the group consisting of acetone, methyl ethyl ketone, methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, ethylene glycol, polyethylene glycol, tetrahydrofuran, dimethyl sulfoxide, dimethyl formamide, dimethylacetamide, N Methylpyrrolidone, hexane, cyclohexane, toluene, xylene, chloroform, dichlorobenzene, dimethylbenzene, trimethylbenzene, pyridine, methylnaphthalene, nitromethane, dichloromethane, acetonitrile, octadecylamine, aniline, dimethylsulfoxide and ≪ / RTI > and combinations thereof. ≪ Desc / Clms Page number 24 >
7. A reduced graphene oxide, produced by the process of any one of claims 1 and 3 to 7.

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