KR20170107230A

KR20170107230A - Manufacturing Method for Graphene Ink by Non-oxidation/reduction Method

Info

Publication number: KR20170107230A
Application number: KR1020160030900A
Authority: KR
Inventors: 김석진; 진주
Original assignee: 김석진
Priority date: 2016-03-15
Filing date: 2016-03-15
Publication date: 2017-09-25

Abstract

The present invention relates to a method for producing a graphene ink having excellent dispersibility while being produced by a nonoxidizing method, and more particularly, to a method for producing graphene ink, which comprises (A) dispersing a graphite flake in an organic solvent and ultrasonic- (B) separating the supernatant by centrifugation of the ultrasonic treated dispersion to take a supernatant containing the exfoliated material (graphene); And (C) adding a C1-C5 alcohol to the supernatant, mixing the filter with a filter, vacuum-filtering the filter, immersing the filter in a C1-C5 alcohol, purified water or a mixture thereof, And a solvent substitution step of separating water (graphene) from the graphene ink.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphene ink,

The present invention relates to a process for producing graphene ink, and more particularly, to a process for producing graphene ink which is excellent in dispersibility while being produced in a non-oxidizing-reducing process.

Graphene is a structure consisting of six hexagons connected to each other to form a single layer of two-dimensional structure. The graphene is a carbon nanotube having a tubular one-dimensional structure or a three-dimensional structure It has a structure that is different from graphite.

Such graphene exhibits a velocity equal to the flux of light flowing as if the mass is zero when electrons move with an electron mobility of 50,000 cm 2 / Vs or more. It is characterized by structural, chemical stability and excellent thermal conductivity. It is also easy to process one- or two-dimensional nanopatterns composed of carbon, which is a relatively light element. Above all, graphene sheet is an inexpensive material and has excellent price competitiveness compared to conventional nanomaterials.

Graphene is expected to replace silicon-based semiconductor technology and transparent electrodes due to its electrical, structural, chemical, and economic properties, and it is expected to be applicable to flexible electronic devices due to its excellent mechanical properties.

As a method of producing graphene, there have been reported mechanical peeling, epitaxy, thermal expansion, chemical functionalization, gas phase, and dispersion in an organic solvent. From an industrial point of view, however, A method of directly growing graphene from a catalyst substrate and a method of producing reduced graphene by reducing graphene by oxidizing the graphene after preparing the oxidized graphene and separating it by a reducing agent or heat treatment are widely used.

However, the chemical vapor deposition method is difficult to apply to a large area, and in particular, it is difficult to transfer to a large area on a glass surface. According to the reduction graphene method of producing and reducing oxidized graphene from graphite, productivity is very low , The inherent physical properties of graphene are impaired, and the like.

On the other hand, in order to apply various types of graphene, the reduced graphene should be completely dispersed in an organic solvent or an aqueous solution, and dispersion stability of one month or more should be secured.

In order to solve the problem of graphene dispersion, recently, a chemical treatment method using a covalent bond of a graphene surface and a method of using a surfactant, a polymer, a nanoparticle, a low molecular weight and a polar solvent as a stabilizer have been studied. However, since graphene dispersion is not easy, it is practically limited to increase the concentration of the dispersion.

An object of the present invention is to provide a non-oxidation-reduction method of producing graphene ink which has high productivity and can maintain the inherent physical properties of graphene.

Another object of the present invention is to provide a method for producing graphene ink which is excellent in dispersibility even at a high concentration.

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: (A) a liquid phase separation step of dispersing graphite flakes in an organic solvent and then subjecting the mixture to sonication; (B) separating the supernatant by centrifugation of the ultrasonic treated dispersion to take a supernatant containing the exfoliated material (graphene); And (C) adding a C1-C5 alcohol to the supernatant, mixing the filter with a filter, vacuum-filtering the filter, immersing the filter in a C1-C5 alcohol, purified water or a mixture thereof, And a solvent substitution step of separating water (graphene) from the graphene ink.

As described above, according to the present invention, graphene can be directly prepared from graphite, unlike the conventional method of preparing graphene by oxidizing graphite and preparing graphene oxide from it and reducing it again. The manufacturing cost of the pin can be greatly reduced.

According to the present invention, the produced graphene can be stably dispersed and stored in a non-toxic solution at a high concentration, thereby increasing the utilization of graphene ink.

1 is a conceptual schematic flow diagram of a manufacturing method according to the present invention;
2 is a photograph of a graphene ink produced according to the method of the present invention.
FIGS. 3A and 3B are Raman analysis graphs of graphene and typical graphene of graphene ink prepared according to the method of the present invention, respectively. FIG.
4 is a graphene UV absorbance graph of a graphene ink prepared according to the method of the present invention.
FIG. 5 is a graphene electron microscope photograph of graphene ink prepared according to the method of the present invention. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the appended drawings illustrate only the contents and scope of technology of the present invention, and the technical scope of the present invention is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea of the present invention based on these examples.

As described above, the present invention relates to a non-oxidation-reduction method of producing a graphene ink including a liquid phase separation step, a separation step of removing a solvent and a solvent displacement step. FIG. 1 schematically shows the manufacturing method according to the present invention.

In the liquid phase exfoliation (LPE) step , the non-oxidized graphite flakes are dispersed in an organic solvent and then subjected to ultrasonic treatment to induce peeling of the graphite flakes, thereby separating the unoxidized graphene as an exfoliate into an organic solvent phase . The larger the size of the graphite flake, the better the productivity of graphene.

The organic solvent may be any one of NMP (N-methyl-2-pyrrolidone), DMSO (Dimethyl Sulfoxide) or DMF (Dimethylformamide) or a mixture thereof.

On the other hand, graphene peeled in the liquid phase peeling step is readjusted in the solvent phase. Therefore, although the mixing ratio of the graphite flake and the organic solvent is not important, it is preferably about 1:50 to 1: 200 (w / v), and the ultrasonic treatment is preferably carried out in a water tank at 80 ° C or lower.

The step of separating the exfoliated water is a step of separating the exfoliated material (graphene) from the graphite flakes, which has been ultrasonicated in the liquid phase exfoliation step and separated from the surface of the graphite flake and dispersed in the organic solvent. To this end, the dispersion is centrifuged to precipitate the graphite flakes and take up the supernatant in the presence of the exfoliated material (graphene). At this time, centrifugation can be performed at 2000 to 20000 rpm, and centrifugation time can be appropriately selected.

The solvent replacement step is a step of removing the toxic organic solvent used in the liquid phase separation step and dispersing the separated graphene in a non-toxic solvent. To this end, the C1-C5 alcohol is added to the supernatant obtained in the separation step, and then vacuum filtered using a filter. Then, the filter is immersed in a C1-C5 alcohol, purified water or a mixture thereof, (Graphene) attached to the filter is separated and dispersed. At this time, the ratio of the supernatant to the organic solvent is preferably about 1: 5 to 1: 30 (v / v).

On the other hand, it may be vacuum filtered so that the organic solvent does not remain, and then may be washed several times with C1 to C5 alcohol and vacuum filtered.

In the solvent replacement step, the C1-C5 alcohol is more preferably ethanol.

According to the present invention, it is possible to manufacture a non-oxidation-reduction type graphene ink that directly obtains unoxidized graphene from unoxidized graphite. The component of the graphene ink obtained by the present invention is 'graphene', which was confirmed by Raman analysis, UV absorption characteristic analysis and SEM observation performed in the following examples.

The concentration of the produced graphene ink is firstly adjusted according to the amount of C1 to C5 alcohol or purified water used for separating the graphene adhered to the filter or the amount of the mixed solution thereof, It is possible to obtain a desired concentration of graphene ink by concentrating the ink, adding C1 to C5 alcohol, purified water, or a mixture thereof.

[Example]

(1) Liquid peeling step

2.00 g of graphite flake was dispersed in N-methyl-2-pyrrolidone (NMP, 200 ml). Subsequently, the dispersion was sonicated for 10 hours in an ultrasonic water bath (maintained at 80 占 폚 or less).

(2) Separation step of separation

The supernatant was centrifuged at 2000 to 20,000 rpm for 1 hour to obtain a supernatant containing the exfoliated material. The precipitate (1.44 g after drying) can be reused in the manufacture of graphene.

(3) Solvent replacement step

To 100 ml of the supernatant was added 2 l of ethanol, followed by vacuum filtration with a filter having a pore size of 0.2 탆 (Millipore). The filter was then soaked in 10 ml of a mixture of ethanol and purified water (1: 1 by volume), sonicated for 10 minutes and the filter removed. [Residue upon drying of the filtrate was 0.07 g]

Thus, 45 mg / l of graphene ink was obtained (Fig. 2).

<Results analysis>

The graphene ink produced by the manufacturing method according to the present invention was analyzed by Raman analysis, UV absorption characteristic analysis and SEM observation.

(1) Raman Analysis

Excitation source 514nm Ar ion laser (1.3mW), grating groove / mm, exposure time 2sec, Raman analysis of graphene ink using CCD. A graphical representation of the results of Raman analysis of graphene (FIG. 3A) and typical graphene (FIG. 3B) produced by the present invention is attached.

As shown in the figure, the graphene ink prepared according to the method of the present invention can be considered to have a mixture of single-layer graphene and multi-layer graphene. For reference, the G-band shows the modification of the plane of graphene and the 2D-band is used to determine the number of layers of graphene.

(2) Analysis of UV absorption characteristics

The UV absorbance of the graphene ink prepared according to the present invention was measured (Fig. 4). As can be seen in the figure, graphene ink exhibited typical absorption properties of graphene showing peaks near 265 to 270 nm.

(3) SEM observation

The graphene ink prepared according to the method of the present invention was observed with an electron microscope (SEM) (Fig. 5). It can be seen that there is graphene in a finely flaky state as shown in the figure.

Claims

(A) a liquid phase separation step in which graphite flakes are dispersed in an organic solvent and then subjected to ultrasonic treatment;
(B) a separation step of separating the supernatant by centrifugation of the supersonic-wave dispersion to remove the supernatant; And
(C) a C1-C5 alcohol is added to the supernatant, followed by vacuum filtration using a filter, then the filter is immersed in a C1-C5 alcohol, purified water or a mixture thereof and ultrasonicated to remove the exfoliation A solvent substitution step of separating the solvent;
Wherein the non-oxidizing-reducing graphene ink is a non-oxidizing-reducing graphene ink.

The method according to claim 1,
The organic solvent may include,
Wherein the solvent is N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO) or dimethylformamide (DMF).

The method according to claim 1,
The method for producing graphene ink according to claim 1, wherein the step (C) further comprises vacuum filtration, followed by washing with C1 to C5 alcohol several times and vacuum filtration.

4. The method according to any one of claims 1 to 3,
Wherein the C1 to C5 alcohol is ethanol.

4. The method according to any one of claims 1 to 3,
In the liquid phase separation step, the mixing ratio of the graphite flake and the organic solvent is 1:50 to 1: 200 (w / v), the ultrasonic treatment is performed at 80 ° C or less,
In the separation step, the centrifugation is 2000 to 20000 rpm,
Wherein the ratio of the supernatant to the organic solvent is 1: 5 to 1: 30 (v / v) in the solvent substitution step.