KR20160012403A - Transparent graphene-nanocombosite thin film with high-conductivity, and method thereof - Google Patents

Abstract

The present invention relates to a transparent conductive graphene-nanocomposite thin film and a manufacturing method thereof and, more specifically, to a transparent conductive graphene-nanocomposite thin film, wherein the nanocomposite is a metal nanoparticle-reducing graphene or metal nanoparticle-reducing graphene oxide, and the thin film has ultralow-surficial resistance, and to a method for manufacturing the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent conductive graphene nanocomposite thin film and a method of manufacturing the same. BACKGROUND ART [0002] Transparent conductive graphene nanocomposite thin films,

More particularly, the present invention relates to a transparent conductive graphene nanocomposite thin film capable of simultaneously improving the electrical conductivity and improving the transmittance by significantly lowering the sheet resistance, . ≪ / RTI >

BACKGROUND OF THE INVENTION [0002] Transparent electrodes are widely used in various electronic devices that simultaneously require light transmission characteristics and electrical conductivity, such as image sensors, solar cells, liquid crystal display devices, organic EL displays, and touch screen panels. The transparent electrode is composed of a transparent substrate and a conductive film formed on the transparent substrate.

Such a conductive film is required to have a transparent conductive film having high conductivity and an excellent transmittance in the visible light region. A thin film of tin oxide (SnO 2), zinc oxide (ZnO) or indium oxide (In 2 O 3) is known as such a transparent conductive film have. In the tin oxide system, antimony is contained as an impurity (ATO) or fluorine is contained as an impurity (FTO). As the zinc oxide-based system, there are used (AZO) containing aluminum as an impurity and (GZO) containing gallium as an impurity. Indium oxide containing tin as an impurity is referred to as an ITO (Indium-Tin-Oxide) film, and a film with a low resistance can be easily obtained. Therefore, the transparent conductive film which is most industrially used is indium oxide- It has been widely used so far.

However, the use of such ITO is disadvantageous in that it has a high manufacturing cost and low flexibility, which causes surface resistance to increase and durability to degrade when used in a flexible display.

In recent years, attempts have been made to apply graphene, which has high electrical conductivity and flexibility, to transparent electrodes. However, when a conductive thin film composed of only graphene is used as a transparent electrode under the same conditions, there is a problem that the electrical conductivity is relatively higher than that of the carbon nanotube, but the transmittance is low.

Also, with respect to the large-scale synthesis technology of graphene, it has been difficult to mass-produce graphene due to problems such as restriction of the use of reducing agent, low efficiency, and impurities. In particular, when graphene oxide is reduced using a reducing agent such as hydrazine hydrate, sodium borohydrate (NaBH ₄ ), sodium borohydrate (NaBH ₄ ), or sulfuric acid (H ₂ SO ₄ ) There is a problem that it is impossible to apply to a flexible substrate because a reaction at a high temperature is necessarily required.

Korean Patent Application No. 10-2011-0007965

In order to solve the above problems, the inventors of the present invention have studied a method of manufacturing a transparent conductive thin film applicable to a transparent electrode or the like, and have found that a conductive thin film composed of reduced graphene or a nanocomposite of graphene oxide and metal nanoparticles The sheet resistance can be remarkably lowered and the electrical conductivity can be improved while the transmittance can be improved at the same time, and the present invention has been completed.

Accordingly, it is an object of the present invention to provide a transparent conductive graphene nanocomposite thin film having ultra low-surface resistance.

The present invention also provides a method for producing a transparent conductive graphene nanocomposite thin film having ultra low-surface resistance applying a green synthetic method for reducing graphene or graphene oxide by ultrasonication at room temperature using vitamin C as a reducing agent, The problem is solved.

It is another object of the present invention to provide a transparent electrode manufactured using the transparent conductive graphene nanocomposite thin film having the ultra low-surface resistance.

Another object of the present invention is to provide a flat panel display device using the transparent conductive graphene nanocomposite thin film having ultra low-surface resistance.

According to a first aspect of the present invention for solving the above problems,

As a nanocomposite thin film,

Wherein the nanocomposite is a nanocomposite that is a metal nanoparticle-reduced graphene or a metal nanoparticle-reduced graphene oxide,

There is provided a transparent conductive graphene nanocomposite thin film characterized in that the thin film has ultra low-sheet resistance.

In the present invention, the thin film has a sheet resistance of 100 to 500 Ω / sq.

The metal nanoparticles may be any one selected from the group consisting of Ag, Al, Cu, and Pt.

The metal nanoparticles have a particle diameter of 10 to 30 nm.

Further, according to a second aspect of the present invention for solving the above problems,

A first step of mixing a metal salt aqueous solution with graphene or graphene oxide and vitamin C to prepare a mixed solution;

A second step of ultrasonically treating the mixed solution to form a metal nanoparticle-graphene or metal nanoparticle-graphene oxide complex;

A third step of forming a thin film on the substrate using the ultrasonic treated mixed liquid; And

And reducing the graphene or graphene oxide by heat treating the thin film to produce a thin film of a metal nanoparticle-reduced graphene or a metal nanoparticle-reduced graphene oxide composite, wherein the ultra low- A method for producing a transparent conductive graphene nanocomposite thin film is provided.

In the present invention, the thin film has a sheet resistance of 100 to 500 Ω / sq.

The ultrasonic treatment is performed for 1 to 5 minutes.

According to a third aspect of the present invention for solving the above problems,

A flat panel display device manufactured using the transparent conductive graphene nanocomposite thin film is provided.

The thin film of the graphene nanocomposite according to the present invention is characterized in that the composite is formed such that the metal nanoparticles are uniformly dispersed on the reduced graphene or graphene oxide and the electrical conductivity and the thin film characteristics of the graphene or graphene oxide are shown The metal nano-particles can further improve the transmittance, thereby providing a transparent conductive thin film exhibiting ultra-low-surface resistance.

The transparent conductive thin film may be used as an electrode of a flat display device such as a liquid crystal display (LCD), a plasma display panel (OLED), an organic light emitting diode (OLED) Can be usefully applied.

1 is a flow chart of a manufacturing process according to an embodiment of the present invention.
FIG. 2 is a graph showing the results of an AgNPs-GO nanocomposite formed using (a) an XRD pattern of GO, (b) 0.1M, (c) 0.2M and (d) XRD pattern.
FIG. 3 is a graph showing the results of measurement of silver nanoparticles on a GO sheet in (a) AgNPs-GO 0.6-30, (b) AgNPs-GO 0.2-30, and (c) AgNPs-GO 0.1-30 nanocomposite according to an embodiment of the present invention. (D) is a TEM image of the GO nanotube, (e) is the HRTEM image of the silver nanoparticles in the AgNPs-GO 0.2-30 nanocomposite, and (f) is the TEM image of the AgNPs-GO 0.2-30 nanocomposite A SAED image of silver nanoparticles is shown.
(A) AgNPs-GO 0.1-30, (b) AgNPs (a), and (b) AgNPs-GO, in which the complex is formed by varying the ultrasonic treatment time at 30 minutes, 20 minutes, 10 minutes, 5 minutes and 1 minute according to an embodiment of the present invention. -GO 0.1-20, (c) AgNPs-GO 0.1-10, (d) AgNPs-GO 0.1-5, and (e) AgNPs-GO 0.1-1 nanocomposite.
(B) AgNPs-GO 0.1-5, (c) AgNPs-GO 0.1-10, (d) AgNPs-GO 0.1 -20, (e) UV-Vis absorption spectrum of AgNPs-GO 0.1-30 nanocomposite.
FIG. 6 shows the transmittance (%) according to the wavelength of GO and AgNPs-GO 0.1-30 nanocomposite according to an embodiment of the present invention.
Figure 7 shows Raman spectra of GO and AgNPs-GO 0.1-30 nanocomposites according to one embodiment of the present invention.
Figure 8 shows UV-Vis spectra of rGO and AgNPs-rGO nanocomposites according to one embodiment of the present invention.
(A) AgNPs-rGO 0.1-30, (b) AgNPs (a), and (b) AgNPs-rGOs having a complex formed by varying the ultrasonic treatment time at 30 minutes, 20 minutes, 10 minutes, 5 minutes and 1 minute according to an embodiment of the present invention. rGO 0.1-20, (c) AgNPs-rGO 0.1-10, (d) AgNPs-rGO 0.1-5, (e) SEM image of AgNPs-rGO 0.1-1 nanocomposite, And (g) EDS analysis results of AgNPs-rGO nanocomposite.
(C) AgNPs-rGO 0.1-20, (d) AgNPs-rGO 0.1-10, (e) AgNPs-rGO 0.1-10, rGO 0.1-5, (f) XRD patterns of AgNPs-rGO 0.1-1 nanocomposite, (g) cross-sectional image of rGO thin film, and (h) cross-sectional image of AgNPs-rGO 0.1-1 nanocomposite thin film .
FIG. 11 shows (a) Raman spectrum and (b) FT-IR spectrum of GO and AgNPs-rGO 0.1-1 nanocomposite.
12 is a graph showing sheet resistance values of AgNPs-rGO nanocomposites formed by different rGO and ultrasonic time.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention.

Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise.

The term "rGO" also refers to reduced GRP oxide or graphene.

In addition, the term "NPs " means nanoparticles.

The present invention relates to a transparent conductive graphene nanocomposite thin film. According to a first aspect of the present invention,

A nanocomposite thin film, wherein the nanocomposite is a nanocomposite that is a metal nanoparticle-reduced graphene or a metal nanoparticle-reduced graphene oxide, and the thin film has an ultra-low-surface resistance. The transparent conductive graphene nanocomposite thin film / RTI >

The nanocomposite of the present invention can improve the electrical conductivity and thin film properties of graphene or graphene oxide by forming a composite in which the metal nanoparticles are uniformly dispersed on the reduced graphene or graphene oxide In addition, it is possible to provide a transparent conductive thin film exhibiting ultra low-sheet resistance because the metal nanoparticles further improve the transmittance.

Preferably, the thin film has a sheet resistance of 100 to 500 Ω / sq. Accordingly, the transparent conductive graphene nanocomposite thin film of the present invention exhibits ultra low-surface resistance as described above, and thus can be usefully used as a transparent electrode.

Preferably, the metal nanoparticles may be any one selected from the group consisting of Ag, Al, Cu, Sn, Pt, Au, and Ga as metal nanoparticles that can exhibit electrical conductivity and permeability.

Further, the thin film of the graphene nanocomposite should be made thin enough to exhibit optical transparency, and it must have a uniform optical density with respect to the entire thin film, and preferably the diameter of the metal nanoparticles is 10 to 30 nm . It is possible to uniformly disperse the graphene or graphene oxide in the above range to improve transparency. In addition, since the metal nanoparticles are uniformly dispersed, the electrical conductivity according to the nanocomposite thin film itself can be remarkably improved, so that ultra low-surface resistance can be exhibited. More preferably, the graphene nanocomposite thin film has a thickness of 100 to 200 nm.

According to a second aspect of the present invention, there is provided a method for manufacturing a transparent conductive graphene nanocomposite thin film having an ultra low-surface resistance,

A first step of mixing a metal salt aqueous solution with graphene or graphene oxide and vitamin C to prepare a mixed solution; A second step of ultrasonically treating the mixed solution to form a metal nanoparticle-graphene or metal nanoparticle-graphene oxide complex; A third step of forming a thin film on the substrate using the ultrasonic treated mixed liquid; And a fourth step of reducing the graphene or graphene oxide by heat treating the thin film to produce a thin film of a metal nanoparticle-reduced graphene or a metal nanoparticle-reduced graphene oxide complex.

The method of the present invention is divided into the following steps.

In the first step, a mixed solution is prepared by mixing graphene or graphene oxide with vitamin C in an aqueous metal salt solution. The vitamin C is added as a reducing agent to reduce metal particles. In this case, by using vitamin C as a reducing agent, it is possible to reduce the environmentally-friendly, besides, since the metal particles can be reduced at room temperature without requiring a reaction at high temperature, the method of the present invention can be applied to a flexible substrate or the like .

Next, the second step is a step of ultrasonifying the mixed solution, which nanopartizes the metal particles reduced by the vitamin C in the mixed solution by the ultrasonic treatment, and the nanoized metal nanoparticles are again graphened or graphene oxide To form a metal nanoparticle-graphene or metal nanoparticle-graphene oxide complex.

At this time, the nano size of the metal particles reduced by vitamin C can be controlled according to the ultrasonic treatment time. Particularly, the particle size increases in proportion to the increase of the ultrasonic treatment time. This mechanism can be understood as Ostwald ripening, in which large or small metal nanoparticles coexist on graphene or graphene oxide. Since the atoms on the surface of the metal nanoparticles are less stable than the atoms located inside, the surface atoms of the small metal nanoparticles are driven by the vibration effect and the heat generation during ultrasonic treatment, and are desorbed from the particles and dissolved into the solution. On the other hand, a long time ultrasonic treatment increases the concentration of free molecules in the solution, and when such free molecules are supersaturated, larger particles tend to be concentrated. Therefore, during the growth of larger particles, all small particles shrink, the average size increases, and the formation of metal nanoparticles also increases by a certain magnitude due to the agglomeration of the metal nanoparticles during the prolonged ultrasonic treatment. The uniform distribution of the metal nanoparticles on the pin or graphene oxide is reduced.

That is, when ultrasonic waves are exposed for a short time, small-sized metal nanoparticles are generated. However, when exposed to ultrasonic waves for a predetermined time, metal nanoparticles of large particles are freed and move to small particles in the liquid, . Therefore, when ultrasonication is performed for preferably 1 to 5 minutes, the reduced metal nano-particles are prevented from being recrystallized, and the size of the metal nano-particles is controlled to be uniformly dispersed on the graphene or graphene oxide, It becomes possible to have one optical density.

The metal nanoparticles may be any one selected from Ag, Al, Cu, Sn, Pt, Au, and Ga so as to be uniformly dispersed on the graphene or graphene oxide due to their conductivity and permeability.

More preferably, the diameter of the metal nanoparticles is 10 to 30 nm. It is possible to uniformly disperse the graphene or graphene oxide in the above range to improve transparency. In addition, since the metal nanoparticles are uniformly dispersed, the electrical conductivity according to the nanocomposite thin film itself can be remarkably improved, so that ultra low-surface resistance can be exhibited.

Next, the third step is a step of forming a thin film on the substrate using the ultrasonic treated mixed solution, and preferably a thin film is formed by spin coating. At this time, the spin coating speed is preferably 500 to 3000 rpm, preferably 10 to 40 seconds, more preferably 10 times or more.

Next, the fourth step is a step of heat-treating the thin film, wherein graphene or graphene oxide of the metal nanoparticle-graphene or metal nanoparticle-graphene oxide nanocomposite formed on the substrate by heat treatment is reduced to form a metal A nanoparticle-reduced graphene or a metal nanoparticle-reduced graphene oxide composite thin film is formed to produce a transparent conductive graphene nanocomposite thin film. Preferably, the reduction of the graphene or graphene oxide is performed by annealing in an N ₂ / H ₂ gas atmosphere at 450 to 550 ° C. for about 1 to 2 hours.

The nanocomposite thin film can improve the electrical conductivity and thin film properties of graphene or graphene oxide by forming a composite in which metal nanoparticles are uniformly dispersed on reduced graphene or graphene oxide , The metal nano-particles can further improve the transmittance and thus the transparent conductive thin film exhibiting ultra low-surface resistance can be produced. Preferably, the thin film has a sheet resistance of 100 to 500 Ω / sq.

According to a third aspect of the present invention, there is provided a flat panel display device manufactured using the transparent conductive graphene nanocomposite thin film. The transparent conductive graphene nanocomposite thin film according to the present invention is manufactured by an environmentally friendly method, and has an ultra-low-surface resistance, is excellent in electric conductivity, and has improved transmittance and is used in various liquid crystal displays (LCDs), plasma display panels Panel, an organic light emitting device (OLED), a solar cell, and the like.

Hereinafter, the present invention will be described in detail with reference to examples, but the scope of the present invention is not limited thereto.

Example

Preparation of materials

The graphite powder was purchased from UniChem Chemical Reagent (Korea), AgNO3, NaNO3 and vitamin C (ascorbic acid) were purchased from Guangdong Guanghua Sci-Tech Co., Ltd. (China). All solutions were prepared using ultrapure water (Millipore, 18.2 MΩ / cm) and ultrasonic cleaner (Model: UltraMet 2005) as ultrasonic source. The frequency of the ultrasonic waves was set to 20 kHz ± 50 kHz.

Examples 1 to 7 Synthesis of AgNPs-GO Nanocomposite

First, graphite oxide was prepared by slightly modifying the Humulus's method and peeled by ultrasonic treatment for 1 hour to prepare a GO (Graphenoxide) nanosheet.

 30 ml of aqueous silver nitrate solution at various concentrations (0.1, 0.2, 0.6 M) and 50 ml of GO (Graphenoxide) suspension (0.4 mg / ml) were mixed in a sonication bath for 30 minutes, Were added slowly, and they were reacted with the above mixed solution while subjecting them to ultrasonic treatment (1, 5, 10, 20, 30 minutes) with different sonication times. After the reaction, the suspension was washed three times with DI water and dried at 60 DEG C for 12 hours to prepare an AgNPs-GO complex.

Experimental conditions according to this embodiment are shown in Table 1 below.

Example
Name of sample Experimental conditions AgNO ₃
(mol / l) GO (mg) Vitamin C (mmol / l) Ultrasonic time (min) One AgNPs-GO 0.6-30 0.6 20 5 30 2 AgNPs-GO 0.2-30 0.2 20 5 30 3 AgNPs-GO 0.1-30 0.1 20 5 30 4 AgNPs-GO 0.1-20 0.1 20 5 20 5 AgNPs-GO 0.1-10 0.1 20 5 10 6 AgNPs-GO 0.1-5 0.1 20 5 5 7 AgNPs-GO 0.1-1 0.1 20 5 One

<Examples 8 to 13> Synthesis of AgNPs-rGO nanocomposite

The AgNPs-GO nanocomposite prepared in the above Example was dispersed in 5 ml of N-methyl-2-pyrrolidone (NMP) aqueous solution and stirred for 1 hour. Next, the dispersion liquid was spin-coated on a glass substrate. Spin coating was applied to the piranha solution at 1000 rpm for 20 seconds and at 2000 rpm for 30 seconds. The AgNPs / GO nanocomposite thin film was annealed at 500 ° C under a N ₂ / H ₂ gas flow for 1 hour after spin coating 10 times, thereby preparing an AgNPs-rGO nanocomposite thin film.

Experimental conditions according to this embodiment are shown in Table 2 below.

Example
Name of sample Experimental conditions AgNO ₃
(mol / l) GO
(mg) Vitamin C
(mmol / l) Ultrasonic time
(min) 8 AgNPs-rGO-30 0.1 20 5 30 9 AgNPs-rGO-20 0.1 20 5 20 10 AgNPs-rGO-10 0.1 20 5 10 11 AgNPs-rGO-5 0.1 20 5 5 12 AgNPs-rGO-1 0.1 20 5 One 13 rGO 0 0 0 30

Assessment Methods

The morphology, nanoscale, spectral and electrical properties of the AgNPs-GO or AgNPs-rGO nanocomposites according to the above examples were analyzed. At this time, the electrical properties were measured using the four-point probe method. The equipment used for the analysis is as follows.

- FESEM: Tescan, Mira 3

- SEM: JSM-6700F

- Raman spectrum: Dong-Woo Optron, Vector-01FX

- FT-IR spectrum: Tensor 27, Bruker, Germany

- UV-vis spectrum: HP 8453, Agilent

- X-ray diffraction: Bruker AXS D8 Discover

Evaluation results for AgNPs-GO nanocomposites

First, the silver nanoparticle size was measured by SEM observation of AgNPs-GO nanocomposite, and the results are shown in Table 3 below.

Example
Name of sample Experimental conditions Ag particle size (nm) AgNO ₃
(mol / l) GO (mg) Vitamin C (mmol / l) Ultrasonic time (min) One AgNPs-GO 0.6-30 0.6 20 5 30 20-120 2 AgNPs-GO 0.2-30 0.2 20 5 30 13-100 3 AgNPs-GO 0.1-30 0.1 20 5 30 45-55 4 AgNPs-GO 0.1-20 0.1 20 5 20 17-50 5 AgNPs-GO 0.1-10 0.1 20 5 10 35 6 AgNPs-GO 0.1-5 0.1 20 5 5 20-25 7 AgNPs-GO 0.1-1 0.1 20 5 One 15

Referring to Table 3, when the ultrasonic treatment time was changed to 30 minutes in Examples 1 to 3, it was not increased in direct proportion to the silver nitrate concentration (0.1M, 0.2M, 0.6M) It was confirmed that silver nanoparticles having a large particle size were formed.

Also, in Examples 3 to 7, when the concentration of silver nitrate was set to the same value (0.1 M) and the ultrasonic treatment time was increased to 1, 5, 10, 20 or 30 minutes, It was confirmed that the size gradually increased. However, it was found that the increase in the size of silver nanoparticles was not large, and it was confirmed that silver nanoparticles of smaller size were formed than in Examples 1 and 2 in which the silver nitrate concentration was increased.

Therefore, it can be seen from the above examples that the size of the silver nanoparticles can be controlled by controlling the concentration of the aqueous solution of silver nitrate or the ultrasonic treatment.

2 is a graph showing the results obtained by using AgNPs-GO nano-crystals formed using an aqueous solution of silver nitrate having (a) an XRD pattern of GO, (b) 0.1M, XRD pattern of the complex. Referring to FIG. 1, the diffraction peak of GO is 17.15 ㅀ and the diffraction peaks of AgNPs-GO nanocomposite are 2 罐 values of 38.1 ㅀ, 44.3 ㅀ, 64.5 ㅀ, and 77.5,, (200), (220) and (311) corresponding to the crystal plane of the nanoparticles (JCPDS card No. 07-0783).

The AgNPs-GO nanocomposites did not show large diffraction peaks of GO at 10.14 ㅀ and 22.5,, indicating that the combination of vitamin C and ultrasonic treatment completely exfoliated the GO and extended the rejoined GO. The sample (d) using an aqueous solution of silver nitrate with a concentration of 0.6 M showed a remarkable high-intensity diffraction peak at 38.1 고, and the peak indicated crystallized Ag, confirming that the nanoparticles were composed of crystallized Ag . Thus, the XRD pattern demonstrates that AgNPs successfully bind to GO, which serves as a space to prevent re-deposition of GO sheet.

FIG. 3 is a graph showing the effect of the silver nanoparticles on the GO sheet in (a) AgNPs-GO 0.6-30, (b) AgNPs-GO 0.2-30 and (c) AgNPs-GO 0.1-30 nanocomposite according to the embodiment of the present invention (D) is a TEM image of AgNPs-GO 0.1-30 nanocomposite thin film, (e) is HRTEM image of silver nanoparticles in AgNPs-GO 0.2-30 nanocomposite, (f) is AgNPs-GO The SAED image of the silver nanoparticles in the 0.2-30 nanocomposite is shown. Referring to FIG. 2, as the concentration of the silver nitrate solution decreases, the size of the silver nanoparticles decreases and it is confirmed that a transparent thin film is formed. In FIG. 3E, the measured peripheral lattice of the Ag nanoparticles was confirmed to be 0.236 nm, which corresponds to the (111) crystal face. In addition, the SAED image of Fig. 3f shows that diffraction dots are well dissolved, which strongly demonstrates the simple crystallinity of these nanoparticles.

(A) AgNPs-GO 0.1-30, (b) AgNPs (a), and (b) AgNPs-GO, in which the complex was formed by varying the ultrasonic treatment time at 30 minutes, 20 minutes, 10 minutes, 5 minutes and 1 minute according to the above- -GO 0.1-20, (c) AgNPs-GO 0.1-10, (d) AgNPs-GO 0.1-5 and (e) AgNPs-GO 0.1-1 nanocomposite. Referring to FIG. 3, As the ultrasonic treatment time was decreased, the size of the silver nanoparticles decreased and it was confirmed that the grains were well dispersed on the graphene oxide and deposited.

FIG. 5 is a graph showing the results of a comparison between GO, (a) AgNPs-GO 0.1-1, (b) AgNPs-GO 0.1-5, (c) AgNPs- -20, (e) UV-Vis absorption spectrum of AgNPs-GO 0.1-30 nanocomposite. Referring to FIG. 5, the UV-vis spectrum of GO can observe two characteristic peaks. One of them is due to the π-π transition of the CAC bond at the peak observed at 231 nm in aromatics, and the N-P transition of the C 1 O bond observed at 300 nm. Conversely, no peak was observed at 231 nm for AgNPs-GO. This implies charge transfer interaction between GO and Ag nanoparticles. The formation of Ag nanoparticles shows the surface plasmon resonance peak of Ag nanoparticles at 431 nm. The charge-transporting complex between the Ag nanoparticles and the GO absorbs light at the excitation frequency, resulting in a chemical surface enhanced Raman scattering (SERS) effect. And the chemical SERS effect depends on the nanoparticle size, shape, chemical perimeter, and species absorbed on the surface. It shows that the intensity of the surface plasmon resonance peak at 431 nm increases with decreasing dimension of Ag nanoparticles (Table 1). This is due to an increase in the contact area between the Ag nanoparticles and the GO in the composite when the Ag nanoparticle size decreases. Thus, an increase in the contact area causes an increase in the charge-transport complex and increases the chemical SERS effect.

6 shows the transmittance (%) according to the wavelength of GO and AgNPs-GO 0.1-30 nanocomposite according to the embodiment of the present invention, and it was confirmed that the transmittance was remarkably improved as compared with graphene oxide.

FIG. 7 shows Raman spectra of the GO and AgNPs-GO 0.1-30 nanocomposite according to the embodiment of the present invention, and it was confirmed that the intensity of the D and G bands was remarkably improved to about 680% as compared with the GO.

Evaluation results of AgNPs-rGO nanocomposite

The results of measuring the size and the sheet resistance of the silver nanoparticles of the AgNPs-rGO nanocomposite prepared in the above Examples are shown in Table 4 below. The sheet resistance to reduced graphene oxide (rGO) was also measured for comparison.

Example
Name of sample Experimental conditions Ag
particle
you
(nm) Resistivity
(/ sq) AgNO ₃
(mol / l) GO
(mg) Vitamin
C
(mmol / l) Ultrasonic
time
(min) 8 AgNPs-rGO-30 0.1 20 5 30 45-55 6.94 k 9 AgNPs-rGO-20 0.1 20 5 20 17-50 6.72 k 10 AgNPs-rGO-10 0.1 20 5 10 35 4.19 k 11 AgNPs-rGO-5 0.1 20 5 5 20-25 427 12 AgNPs-rGO-1 0.1 20 5 One 15 270 control rGO 0 0 0 30 / 10.93 k

Referring to Table 4, when the concentration of silver nitrate is set to the same value (0.1 M) and the ultrasonic treatment time is increased to 1, 5, 10, 20 or 30 minutes, the increase in the size of the silver nanoparticles , But it was found to increase gradually.

In the case of the sheet resistance, in the case of Examples 8 to 10 in which the ultrasonic treatment time was 10 minutes or more, the sheet resistance was 6 k? Or more. In the case of Examples 11 and 12 in which the ultrasonic treatment time was 1 and 5 minutes, 427 Ω, 270 Ω. Regarding this sheet resistance value, it is confirmed that the sheet resistance is lowered also in the case of Examples 8 to 10 as compared with the case where the sheet resistance of the reduced graphene oxide (rGO) of Example 13 measured as a control group is 10.93 k? / Sq However, in the case of Examples 11 and 12, it was lowered to about 1/40 as compared with rGO, and it was confirmed that the sheet had extremely low-surface resistance.

8 shows the UV-Vis spectra of rGO and the AgNPs-rGO nanocomposite of Examples 8 to 12, wherein the AgNPs-rGO nanocomposite is the same as the reduced graphene oxide Peak, and the peak increased as the ultrasonic treatment time increased.

(A) AgNPs-rGO 0.1-30, (b) AgNPs-rGO (a) and (b) AgNPs-rGO in which the complex was formed by varying the ultrasonic treatment time by 30 minutes, 20 minutes, 10 minutes, 5 minutes, (D) AgNPs-rGO 0.1-5, (e) SEM image of AgNPs-rGO 0.1-1 nanocomposite, (f) EDS analysis result of GO and g) EDS analysis results of AgNPs-rGO nanocomposite. Referring to FIG. 9, it can be seen that as the ultrasonic treatment time is reduced, the size of the silver nanoparticles forming the complex with reduced graphene is reduced and more uniformly hybridized. In addition, it was confirmed that the reduction of oxygen content from 2.57 wt% to 0.94 wt% in comparison with the results of EDS analysis of GO showed that C, O and Ag derived from the rGO sheet could be confirmed in all of the EDS analysis results. In the AgNPs-rGO nanocomposite film, Si semiconductor wafers and Si and Pt derived from Pt were detected.

(A) GO, (b) AgNPs-rGO 0.1-30, (c) AgNPs-rGO 0.1-20, (d) AgNPs-rGO 0.1-10, (e) AgNPs rGO 0.1-5, (f) XRD patterns of AgNPs-rGO 0.1-1 nanocomposite, (g) cross-sectional image of rGO thin film, and (h) cross-sectional image of AgNPs-rGO 0.1-1 nanocomposite thin film Respectively. 9, the diffraction peak of GO is 17.15 ㅀ and the diffraction peaks of AgNPs-rGO nanocomposite are 2 罐 values of 38.1 ㅀ, 44.3 ㅀ, 64.5 ㅀ and 77.5,, which are (111), 200), (220), and (311). Comparing (g) and (h) show cross-sectional images of the rGO thin film and the AgNPs-rGO 0.1-1 nanocomposite thin film, it can be seen that silver nanoparticles were inserted into the layer structure of rGO when nanocomposite was formed. The thickness of the rGO thin film and the AgNPs-rGO 0.1-1 nanocomposite thin film were 115.86 nm and 199.73 nm, respectively, and the thickness was increased to 83.87 nm. As a result, it was confirmed that the AgNPs-rGO 0.1-1 nanocomposite thin film has structurally the existence of a layered structure of silver nanoparticles in rGO.

FIG. 11 shows (a) Raman spectrum and (b) FT-IR spectrum of GO and AgNPs-rGO 0.1-1 nanocomposite.

FIG. 12 is a graph showing sheet resistance values of AgNPs-rGO nanocomposites formed by different rGO and ultrasonic time, and it was confirmed that as the ultrasonic treatment time is reduced, the sheet resistance is remarkably lowered (see Table 4).

Specifically, the sheet resistance value of rGO is 10.93 k? / Sq, and the AgNPs-rGO sheet resistance value decreases with decreasing AgNPs size. That is, AgNPs-rGO-1 exhibited the lowest sheet resistance value of 270? / Sq as silver nanoparticles were controlled to about 15 nm (see Table 3), and this result shows improved conductivity due to the contribution of the AgNPs size effect on the rGO network It means import.

From the above results, it can be seen that as the ultrasonic treatment time is shortened, the size of AgNPs becomes smaller and homogeneous, so that uniform and small AgNPs are easily distributed on the rGO sheet when the AgNPs-rGO network is formed, and the AgNPs- Thereby providing a wider contact area. Therefore, as the ultrasonic treatment time is shortened, AgNPs of a small size are distributed on the rGO phase, resulting in improvement of electrical properties as compared with the case of distributing AgNPs of a large size.

On the other hand, the surface resistance of the GO thin film can not be measured because of high resistance, a characteristic improvement in the electrical conductivity of rGO films decomposition of the oxygen functionality through the handling thermal annealing with a GO film and the N ₂ / H ₂ gas, and sp ² CC Contributes to the immediate recovery of the binding (present in the GO structure).

From these results, it can be interpreted that it means that the sheet resistance can be lowered by controlling the size of the silver nanoparticles at the level of several tens of nanometers according to the ultrasonic treatment time. In the above embodiment, when the silver nanoparticles are controlled to 30 nm or less, it is confirmed that they can exhibit an ultra low-sheet resistance of 500? / Sq.

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 are to be construed as being included within the scope of the present invention do.

Claims (9)

As a nanocomposite thin film,
Wherein the nanocomposite is a nanocomposite that is a metal nanoparticle-reduced graphene or a metal nanoparticle-reduced graphene oxide,
Wherein the thin film has an ultra low-sheet resistance. The method according to claim 1,
Wherein the thin film has a surface resistance of 100 to 500? / Sq. The method according to claim 1,
Wherein the metal nanoparticles are selected from the group consisting of Ag, Al, Cu, Sn, Pt, Au, and Ga. The method according to claim 1,
The transparent conductive graphene nanocomposite thin film has a particle diameter of 10 to 30 nm. A first step of mixing a metal salt aqueous solution with graphene or graphene oxide and vitamin C to prepare a mixed solution;
A second step of ultrasonically treating the mixed solution to form a metal nanoparticle-graphene or metal nanoparticle-graphene oxide complex;
A third step of forming a thin film on the substrate using the ultrasonic treated mixed liquid; And
And reducing the graphene or graphene oxide by heat treating the thin film to produce a thin film of a metal nanoparticle-reduced graphene or a metal nanoparticle-reduced graphene oxide composite, wherein the ultra low- Wherein the transparent conductive graphene nanocomposite thin film has a thickness of 100 nm. 6. The method of claim 5,
Wherein the ultrasound treatment is performed for 1 to 5 minutes. 2. The method of claim 1, wherein the ultrasound treatment is performed for 1 to 5 minutes. 6. The method of claim 5,
Wherein the metal nanoparticles are selected from the group consisting of Ag, Al, Cu, Sn, Pt, Au, and Ga. 6. The method of claim 5,
Wherein the thin film has a sheet resistance of 100-500 OMEGA / sq. The method of manufacturing a thin film of transparent conductive graphene nanocomposite having ultra low-sheet resistance. A flat panel display device, comprising: a transparent conductive graphene nanocomposite thin film according to any one of claims 1 to 4.

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