KR101865465B1 - Manufacturing device and method of the graphene - Google Patents

Abstract

 The present application relates to a manufacturing apparatus and a manufacturing method of graphene. According to the graphene manufacturing apparatus of the present application, graphene can be continuously produced through a simple and environmentally friendly process.

Description

TECHNICAL FIELD [0001] The present invention relates to a manufacturing apparatus and a manufacturing method of a graphen,

The present application relates to a manufacturing apparatus and a manufacturing method of graphene.

Due to its unique physical and chemical properties and a wide range of technical applications such as electrical devices, batteries, solar energy conversion and catalysts, graphene sheets have recently become a challenge, especially in practical applications, It is getting attention. Many methods have been developed for processing graphene materials such as micro-mechanical stripping, chemical vapor deposition, and reduction of oxidized graphene. Among these methods, chemical reduction has been considered as the most efficient and economical way to produce reduced graphene from oxidized graphene. However, such chemical reduction generally requires special devices and controls for the production of toxic compounds, batch slow reaction steps, high temperature and energy, reduced graphene, which limits practical application of graphene. Therefore, development of an environmentally friendly graphene manufacturing method is highly demanded.

Graphene-based hybrid nanomaterials have the potential to provide new properties that can potentially be used in a wide range of applications as well as the merits of each component, Research is actively being carried out. That is, considerable efforts have been made to develop binary materials of metals, semiconductors or sensitizing materials as possible alternatives to increase the efficiency of various catalyst and storage reactions in 2D scaffold and energy conversion applications ought. Recently, attention has been focused on gold nanoparticle-based hybrid materials. As a result, for the special intergranular properties of gold nanoparticles for catalysis, sensing, and biomaterial as well as electrical and optoelectronic devices, Deposition of gold particles on the surface of materials has been actively studied. The binding of gold nanoparticles on the surface of a material often requires the application of specific functionalities of the gold nanoparticles and the pretreatment of the surface of the material in order to find a suitable reactant for bonding of the hybrid material. In addition, nanometer sized graphene sheets, due to their size compatibility with their biological systems and the high stability of graphene in an aquatic environment, have recently attracted a great deal of attention, especially in cellular imaging and drug delivery. .

Therefore, there is a need to develop a technology capable of manufacturing gold-graphene hybrid materials by a simple, environmentally friendly, and continuous synthesis method.

The present application provides a manufacturing apparatus and a manufacturing method capable of manufacturing graphene in a simple, environmentally friendly, and continuous manner.

The present application relates to an apparatus for producing graphene. According to the exemplary graphene manufacturing apparatus of the present application, graphene can be continuously produced through a simple and environmentally friendly process.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, .

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram schematically showing an exemplary apparatus for producing graphene of the present application. Fig.

1, the manufacturing apparatus of the present application includes a discharge unit 10, a spray unit 20, and a reduction unit 30. As shown in FIG.

The discharge unit 10 is a part for generating metal nanoparticles by spark discharge. The discharge unit 10 includes a pair of conductive rods 11 spaced apart from each other by a predetermined distance, and a power supply unit 12 for applying a voltage to the conductive rods 11, (12).

The pair of conductive rods 11 are spaced apart from each other to form a gap. For example, a spark discharge occurs in the discharge unit 10, and metal nanoparticles are generated due to the high temperature locally generated between the conductive rods 11 due to the spark discharge. The term " gap " or " gap " as used in the present application means a gap between two parts that are moved or fixed. For example, the gap may be a space between a pair of conductive rods 11 . The term " nano " in this application is meant to indicate a size in nanometers (nm), for example, a size of 1 nm to 1000 nm, but is not limited thereto. The term " nanoparticle " in the present application may mean particles having a size in nanometers (nm), for example, an average particle diameter of 1 nm to 1000 nm, but the present invention is not limited thereto.

The material constituting the conductive rod 11 is not particularly limited as long as it is a metal having a work function of 6.0 eV or less. For example, a metal having a work function of 5.7 eV or less, 5.0 eV or less, 4.6 eV or 4.2 eV or less But is not limited thereto. In one example, the metal having a work function of less than 6.0 eV is selected from the group consisting of barium, silver, cadmium, aluminum, beryllium, cerium, cesium, cobalt, chromium, iron, gallium, gadolinium, hafnium, mercury, indium, magnesium, A metal selected from the group consisting of lead, niobium, neodymium, rubidium, rhenium, rhodium, ruthenium, scandium, tin, strontium, tantalum, terbium, tellurium, thorium, titanium, uranium, vanadium, yttrium, thallium, ytterbium, zinc, palladium, And zirconium. Preferably, gold may be used, but the present invention is not limited thereto.

In addition, the gap between the conductive rods 11, for example, the electrode gap (the shortest distance between the conductive rods 11), becomes lower as the distance decreases, and as the distance increases, High voltage is required. In addition, if the electrode gap is narrow, the voltage required to generate the spark is reduced, but the short spark can cause misfiring by transmitting the minimum ignition energy to the mixer, so it is necessary to set an appropriate distance by experiment. In one example, the gap between the electrodes may be from 0.1 to 10 mm, but is not limited thereto.

The power supply unit 12 is a portion for applying a voltage to each of the conductive rods 11. In one example, the voltage applied from the power supply unit 12 to the conductive rods 11 is 2 to 5 kV, The amount of current may be from 0.5 to 5 mA, but is not limited thereto. For example, the voltage applied to the pair of conductive rods 11 can be controlled to be constant in the power supply unit 12. Thus, metal nanoparticles can be prepared with good supply stability by quantitatively supplying metal nanoparticles.

In one example, the power supply unit 12 may include an electric circuit for applying a high voltage to the conductive rod 11. The electric circuit has a constant voltage source structure composed of a high voltage supply (HV), an external capacitor (C) and a resistor (R), and is capable of switching a plurality of resistors, a plurality of capacitors, Can be used to control the size of the metal nanoparticles.

Although not shown, the apparatus for manufacturing graphene of the present application may include a gas supply device such as a carrier gas supply system and a flow meter such as a mass flow controller (MFC). In addition, inert gas, oxygen or nitrogen can be quantitatively supplied at intervals between the conductive rods by the gas supply device and the flow meter.

Oxygen and nitrogen flowing through the gap between the conductive rods when the high voltage is applied to the conductive rod 11 by vaporizing or granulating the metal having a work function of 6.0 eV or less by spark discharge And may be flowed to the spraying portion 20 to be described later along one or more kinds of gas flows. For example, when a voltage is applied to the conductive rod 11 of the discharge unit 10, the metal is vaporized at a distance between the pair of conductive rods 11 of the discharge unit 10, and an inert gas or nitrogen Vaporized metal moved along the carrier gas, etc., is condensed as it goes beyond the above-mentioned interval, and thus metal nanoparticles are formed.

The particle size of the metal nanoparticles generated from the discharge unit 10 can be widely controlled from several nanometers to hundreds of nanometers in accordance with the flow rate or the flow rate of the inert gas or nitrogen. For example, when the flow rate or the flow rate of the supplied inert gas or nitrogen is increased, as the concentration of the metal nanoparticles decreases, the aggregation phenomenon between the particles also decreases. As a result, the size of the metal nanoparticles decreases . The particle size, shape, and density of the metal nanoparticles may be determined by spark generation conditions such as an applied voltage, a frequency, a current, a resistance, and a capacitance value; Type and flow rate of the inert gas; Or the shape of the spark electrode.

Examples of the inert gas include, but are not limited to, argon (Ar) or helium (He).

The spraying portion 20 is a portion for spraying the oxidized graphene solution on the metal nano-particles generated in the space between the conductive rods 11 to attach the oxidized graphene to the metal nano-particles.

1, the spraying portion 20 includes a spraying device 21 for spraying a graphene oxide solution.

In one example, the spraying device 21 may comprise a spray nozzle. The atomizing nozzle may consist of an upper atomizing nozzle and a lower atomizing nozzle. The particle size of the nozzle is not particularly limited, but may be 0.1 to 1.0 mm. In the spray unit 20, the graphene oxide solution is sprayed into the spray unit 20 through the spray nozzle 20 in the form of a droplet so that the metal nanoparticles generated in the discharge unit 10 It can be encapsulated by droplets.

The spraying unit 20 may further include a stirrer for mixing the graphene oxide and the solvent to produce a solution. The stirrer is not particularly limited as long as it is capable of high-speed stirring. For example, it may be 200 to 4000 rpm, and any device capable of stirring by applying ultrasonic waves may be used without limitation.

The solvent may be, for example, water or an organic solvent without limitation, preferably an organic solvent containing a hydroxyl group in the molecular structure, for example, ethanol or methanol, but is not limited thereto. For example, when an organic solvent containing a hydroxyl group is used in the molecular structure, a photo-induced OH radical, which is separated from the ethanol molecule in the reduction process, which will be described later in the reduction unit 30, .

The reducing unit 30 is a part for reducing the graphene oxide by irradiating ultraviolet light having a wavelength range of 200 nm or less to the metal nano-particle to which the oxide nano-particle is attached.

In one example, the reduction unit 30 may include a light source 31 that emits light to the reduction chamber. The type of the light source 31 is not particularly limited. For example, a device capable of irradiating light having a photon energy of 6.0 eV or more, for example, ultraviolet light having a short wavelength of 200 nm or less, It can be used without. For example, a well-known light source such as a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a halogen lamp, a black light lamp, a microwave-excited mercury lamp, various lasers or X-rays may be used, A similar reaction may be induced through irradiation of the soft X-ray during the flow. By using a light source capable of irradiating light having a short wavelength of 200 nm or less, the electrons on the surface of the metal nanoparticles having a work function of 6.0 eV or less can be released and the charge on the metal surface can be induced positively. Accordingly, the graphene oxide adhered to the metal nanoparticles can be reduced by receiving electrons separated from the metal nanoparticles, and the reduced graphene can be formed in the reducing unit 30.

The manufacturing apparatus of the present application may further include an extracting furnace or a drying apparatus for extracting the solvent between the atomizing unit and the reducing unit, although not shown.

The extraction path may include an inlet and an outlet. In one example, the extraction solvent may be introduced into the extraction furnace through the inlet and the outlet may discharge the mixture extracted by the extraction solvent. The term " extracted mixture " as used herein refers to a mixture comprising an extraction solvent and other materials extracted by the extraction solvent.

As the drying apparatus, a diffusion drier may be used. For example, the diffusion dryer may be filled with an adsorption-absorption type extraction bed containing activated carbon and silica, and a droplet encapsulated through the hollow of the extraction layer may pass through Solvent can be extracted.

In one example, the manufacturing apparatus of the present application may further include a collecting section 40. [ The collector 40 is a portion for collecting the reduced graphene by separating the reduced graphene from the metal nanoparticles in the reducing portion 30. For example, the collecting unit 40 may include a storage tank storing distilled water, a stirrer for applying centrifugal force to the distilled water, and a dispersing device for applying an ultrasonic wave or electric field to the distilled water. The distilled water The nanoparticles are separated from the reduced graphene while the metal particles are precipitated by the centrifugal force and the reduced graphene is separated from the metal nanoparticles by floating on the surface of the solution.

In the collecting unit 40, the reduced graphene can be collected using a substrate or a filter. The substrate is not particularly limited as long as it is a substrate capable of collecting reduced graphene. For example, the substrate may include aluminum foil, silicon, glass or mica.

In one example, an electric or thermal field may be applied to the substrate to increase particle collection efficiency. For example, when the electric field is applied, the electric charges between the particles and the substrate are reversed to increase the adhesion force of the particles to the substrate. When the temperature field is applied, a temperature difference between the particles and the substrate is induced, The adhesion force can be increased.

In one example, the discharge portion 10, the spray portion 20, and the reduction portion 30 may be maintained under an inert gas or a nitrogen atmosphere. In other words, the metal nanoparticles according to the present application are sequentially supplied to the discharge unit 10, the spray unit 20, and the reduction unit 30 according to the flow of the inert gas or nitrogen. It can mean moving.

The present application also relates to a method for producing graphene. The method of manufacturing the graphene of the present application can be performed by using the apparatus for producing graphene described above, and thus the description of the parts overlapping with those described in the apparatus for producing graphene will be omitted. According to the exemplary method for producing graphene of the present application, graphene can be continuously produced through a simple and environmentally friendly process.

Fig. 2 is a view exemplarily showing a method for producing graphene of the present application. As shown in Fig. 2, the method for producing graphene of the present application includes a discharging step, an encapsulating step and a reducing step.

The discharging step may be performed in the discharge part 10 of the above-described apparatus for producing graphene, and in one example, the discharging step may be performed by applying a voltage to the conductive rod 11 including a metal having a work function of 6.0 eV or less To generate spark discharge, thereby generating metal nanoparticles.

The pair of conductive rods 11 are spaced apart from each other at a predetermined interval, so that the pair of conductive rods 11 can form an interval. In the step of generating the metal nanoparticles, when a high voltage is applied to the conductive rod 11, the metal having a work function of 6.0 eV or less is vaporized or granulated by a spark discharge, And may be discharged to the spraying portion 20 in accordance with the gas or nitrogen flow. For example, when a voltage is applied to the conductive rod 11 of the discharge unit 10, the metal is vaporized at a distance between the pair of conductive rods 11 of the discharge unit 10, and an inert gas or nitrogen Vaporized metal moved along the carrier gas, etc., is condensed as it goes beyond the above-mentioned interval, and thus metal nanoparticles are formed.

The material constituting the conductive rod 11 is not particularly limited as long as it is a metal having a work function of 6.0 eV or less. For example, a metal having a work function of 5.7 eV or less, 5.0 eV or less, 4.6 eV or 4.2 eV or less But is not limited thereto. In one example, the metal having a work function of less than 6.0 eV is selected from the group consisting of barium, silver, cadmium, aluminum, beryllium, cerium, cesium, cobalt, chromium, iron, gallium, gadolinium, hafnium, mercury, indium, magnesium, A metal selected from the group consisting of lead, niobium, neodymium, rubidium, rhenium, rhodium, ruthenium, scandium, tin, strontium, tantalum, terbium, tellurium, thorium, titanium, uranium, vanadium, yttrium, thallium, ytterbium, zinc, palladium, And zirconium. Preferably, gold may be used, but the present invention is not limited thereto.

The spark discharge voltage can be appropriately adjusted by an electrode interval, an applied current, a capacitance, and the like. In one example, when the distance between the conductive rods 11 is 1 mm in the discharging step, a high temperature of about 5000 ° C may be generated when a voltage of 2.5 to 3.5 kV is applied, After the metal constituting the electrode is vaporized, metal nanoparticles may be formed while rapidly condensing at room temperature as the temperature is exceeded.

In one example, the manufacturing method of the present application may further include a gas supplying step of supplying an inert gas or nitrogen between the electrodes. Through the gas supplying step, the inert gas or nitrogen may be supplied while the metal particles are moved along the flow of the supplied inert gas or nitrogen to the encapsulation step and the light irradiation step described later.

The encapsulation step is a step of encapsulating the metal particles in the solution by spraying a solution containing the graphene oxide on the metal nanoparticles formed in the discharge step. The encapsulation step may be performed in the spraying unit 20 of the above-described apparatus for producing graphene. In one example, in the encapsulation step, the graphene solution is sprayed onto the metal nanoparticles generated in the discharging step, It is possible to form a droplet including the metal nanoparticles to which the graphene oxide is attached.

The reducing step is a step of irradiating ultraviolet rays of a wavelength range of 200 nm or less to the metal particles to which the graphene oxide is attached, and may be performed in the reducing unit 30 of the above-described apparatus for producing graphene.

In the reducing step, ultraviolet light of 200 nm or less, for example, 180 nm or less or 160 nm or less can be irradiated onto metal nanoparticles carried by an inert gas or nitrogen. As described above, by irradiating the metal nanoparticles with ultraviolet rays in the above range, light having a photon energy of 6.0 eV or more, for example, light having a short wavelength of 200 nm or less, such as ultraviolet light, electrons on the surface of the metal nanoparticles of less than or equal to eV can be released and the charge on the surface of the metal nanoparticles can be induced to be positively charged. Accordingly, the graphene oxide adhered to the metal nanoparticles can be reduced by receiving electrons separated from the metal nanoparticles, and the reduced graphene can be formed in the reducing unit 30.

The method for producing graphene may further include an extraction step for extracting the solvent before the light irradiation step. In one example, the extraction step may be carried out through a solvent extraction method. By extracting the solvent, the purity of the desired reduced graphene can be increased.

The manufacturing method of the present application may further comprise a collecting step of collecting the reduced graphene. The collecting step may be performed in the collecting part 40 of the apparatus for producing graphene described above, and may include separating the reduced graphene from the metal nanoparticles.

According to the graphene manufacturing apparatus of the present application, graphene can be continuously produced through a simple and eco-friendly process.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram schematically showing an apparatus for producing graphene of the present application. FIG.
Fig. 2 is a view exemplarily showing a method for producing graphene of the present application.
FIG. 3 shows the size distribution and the UV-vis spectrum of each of the graphene oxide graphene nanoflakes, the gold nanoparticles generated by sparks, and the gold nanoparticles to which the graphene grains are bound, respectively.
4 is a transmission electron microscope image of the gold nanoparticles, the oxidized graphene nanoflake, the gold / oxidized graphene, and the gold / reduced oxidized graphene of the example.
Figure 5 is an FT-IR spectrum of oxidized graphene and gold / graphene hybrid nano-flakes.
6 is a diagram schematically showing a reduction mechanism of graphene oxide through photoionization of gold nanoparticles.
FIG. 7 is a graph showing the charge distribution of photo-ionized gold particles under ultraviolet light of different wavelength ranges in Examples and Comparative Examples 1 and 2. FIG.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the scope of the present application is not limited by the following description.

Example

Graphene was prepared through the apparatus of Fig. 1 and the method of Fig.

Specifically, as shown in Fig. 2, nitrogen gas was passed through the discharge part, the spray part, and the reduction part in sequence. The flow rate of the nitrogen gas was maintained at 1.0 L / min and passed between a pair of electrodes made of gold (Au). At this time, a distance between the pair of electrodes was set to 1 mm, and gold nanoparticles were prepared by applying a voltage of 2.5 to 3.5 kV to the electrode. The generated gold nanoparticles were transferred to the spray part along with nitrogen gas. The graphene nano-particles were dispersed in an ethanol solvent to prepare a solution in which 1 wt% of graphene nanoflakes were mixed with 100 wt% of the total solution The mixture was stirred at 500 rpm to prepare a mixed solution. In the spraying part, the mixed solution was injected through a spray nozzle having a nozzle having a diameter of 0.3 mm by using a Collison type atomizer And spray grafting to attach the graphene oxide to the metal nanoparticles to prepare a hybrid droplet.

The graphene oxide-coated gold nanoparticles were irradiated with ultraviolet light having a wavelength of about 180 nm to reduce the graphene oxide. The reduced graphene-coated metal nanoparticles were collected by applying a working voltage of 5 kV using a Nano Particle Collector (NPC-10, HCT, Korea).

Comparative Example  One

Reduced graphene was prepared in the same manner as in Example 1 except that the hybrid droplet was irradiated with ultraviolet light having a wavelength of 250 nm.

Comparative Example  2

Reduced graphene was prepared in the same manner as in Example 1, except that the hybrid droplet was irradiated with ultraviolet light having a wavelength of 360 nm.

Measurement result

FIG. 3 shows the size distribution and the UV-vis spectra of each of the graphene oxide graphene nano-flakes, gold nanoparticles generated by sparking, and gold nanoparticles to which graphene oxide is bonded.

3A, the total number concentration (TNC), the geometric mean particle size (Geometric) of the gold nanoparticles measured using a mobile particle sizer (Scanning Mobility Particle Sizer, 3936, TSI, USA) Mean Diameter (GMD) and Geometric Standard Deviation (GSD) were measured as 8.32 × 10 ⁶ particles / cm ³ , 24.0 nm and 1.50, respectively.

According to the Gravimetric Measurements, it takes about 10 ⁶ J of energy to make 1 g of gold particles. During the spraying of the oxidized graphene solution, the gold / oxidized graphene hybrid nano-flakes were formed by the combination of the graphene oxide and gold nanoparticles. By measuring the size distribution of oxidized graphene and gold / oxidized graphene hybrid nano-flakes on the gas phase, the binding of graphene oxide to gold nanoparticles was confirmed. GMD, GSD and TNC of gold / oxidized graphene hybrid nano-flakes were measured to be 3.90 × 10 ⁶ particles / cm ³ , 30.0 nm and 1.61, respectively. The GMD, GSD and TNC of the graphene oxide were measured to be 2.74 x 10 ⁶ particles / cm ³ , 30.7 nm, and 1.57, respectively. The size distribution of the gold / oxide graphene hybrid nano-flakes was similar to that of the graphene graphene compared to the size distribution of the gold nanoparticles, and there was no bimodal distribution feature, indicating that the gold nanoparticles were almost quantitatively To form a gold / oxide graphene hybrid flake.

The ultraviolet-visible spectrum provides additional properties of the bond between gold nanoparticles and oxidized graphene flakes. Surface Plasmon Resonance Band was concentrated at 530 nm, a characteristic of gold nanoparticles. Spectrum of the graphene oxide exhibited a shoulder (Shoulder) at 240 nm, which corresponds to the n → π ^* transition associated with the C〓O π → π ^* transition of the aromatic C〓C bond. The gold / oxidized graphene hybrid nano-flakes exhibited a weak shoulder at 270 nm and a broad growth peak at about 500 nm, indicating that gold / oxide graphene hybrid nano- The presence of gold nanoparticles in the flake.

4 is a transmission electron microscope image of gold nanoparticles, oxidized graphene nano-flakes, gold / oxidized graphenes and gold / reduced oxidized graphenes. Images measured with a low magnification and high magnification transmission electron microscope (TEM, JEM-3010, JEOL, Japan) show the shapes of gold nanoparticles, oxidized graphenes, gold / oxidized graphenes and gold / reduced oxidized graphene samples. Transmission electron microscopy images of gold nanoparticles show that gold nanoparticles are agglomerates of some major particles (each about 3 nm in diameter) with a 0.23 nm lattice pattern corresponding to the (111) plane.

The shape of the oxidized graphene is flake, and the high resolution image of the oxidized graphene showed the antimicrobial structure predicted by graphene, while some internal defects were also found in the structure. While gold nanoparticles passed through the nozzles of the colison-type atomizer, most of the gold nanoparticles were attached to the oxidized graphene flakes and thus gold / oxide graphene hybrid nano-flakes were formed. Furthermore, the gold particles are redispersed in the oxidized graphene flakes due to the deagglomeration, and the size thereof can be obtained by the following general formula (1).

[Formula 1]

In the general formula 1, D _pr is the size of the restructured aggregate ,? Is a proportional constant, H is a lower marker constant, Δ P is the pressure difference between the front and back of the spray nozzle, and θ is a parameter that controls the maximum cohesion force between constituent particles in the aggregate.

Gold agglomerates pass through the orifices, and rapid changes in pressure, density, and velocity through the orifices create a stimulus that can give a massive impact to the aggregate. It is believed that the bond between gold and the oxidized graphene inhibits the dislocation of gold from the oxidized graphene while it is synthesized in the gas phase. This is due to the capillary force (F _cap ) represented by the following general formula (2) and the electrostatic attraction force (F _ea ) between the gold and the oxide graphene represented by the following general formula (3).

[Formula 2]

F _cap = 4? R _p? Cos?

In the above, r _p , γ and θ are the particle radius, the surface tension, and the contact angle between gold and the oxide graphene, respectively.

 [Formula 3]

In the above, ε ₀ is the dielectric constant, d is the distance between the gold and the oxide graphene, and q ₁ and q ₂ are the surface charge of the gold and the oxide graphene, respectively.

Particles produced by spark discharge usually have a positive charge due to the mineralized and / or electrically induced ionization of their surface during spark particle formation. Figure 4 also shows that, furthermore, oxidized graphene has a negative charge from its structural carboxylate. Figure 4 also shows gold / oxidized graphene hybrid nano-flakes after photo-induced reduction by electron emission from ionized gold nanoparticles. There is no significant difference in shape before and after reduction, but the distribution of gold nanoparticles on graphene flakes may change due to the different surface charge states of the gold particles.

Figure 5 is a spectral graph of Fourier infrared spectroscopy (FTIR, IFS 66 / S, Bruker Optics, Germany) of oxidized graphene and gold / reduced graphene oxide hybrid nano-flakes.

The oxidized graphene shows wide IR peaks near 3400 cm ^-1 and 1730 cm ^-1 , which correspond to OH stretching and C═C vibration, respectively, and the carboxyl group C ═O of the COOH group (1780 cm ^-1 ) and the hydroxyl group C-OH (1390 cm ^-1 ) stretching vibration. At a given absorbance scale, gold / graphene shows a characteristic spectrum that implies reduction for the function of oxygen.

6 is a diagram schematically showing a reduction mechanism of graphene oxide through photoionization of gold nanoparticles.

As shown in Figure 6, the first step of the mechanism shows the release of electrons during photoionization of gold nanoparticles on oxidized graphene flakes. In the second step, the emitted electrons are used to convert the oxidized graphene to graphene, which is a reduced form of oxidized graphene. Furthermore, the photo-induced OH radicals separated from the ethanol molecules during photoionization also affect the reduction of oxidized graphene.

FIG. 7 is a graph showing charge distributions of photo-ionized gold particles under ultraviolet light of different wavelength ranges in Examples and Comparative Examples 1 and 2. FIG. In order to confirm electron emission from gold nanoparticles, the charge distribution of gold nanoparticles after the photoionization process was measured using a tandem differential mobility analyzer (TDMA) system.

The different peaks appearing in the first image correspond to the number of different charges on the particle. The number q of basic charges of the photoionized particles is calculated using the following general formula (4).

[Formula 4]

In the above, Z _{p, NDMA1} and Z _{p, NDMA2} are the electric mobility measured by nanoDMA (NDMA, 3085, TSI, USA) 1 and 2, respectively.

The measurement results show that photoionization induces positive charge in the particles, suggesting that the electrons were released from the gold nanoparticles and used to reduce the oxidized graphene.

However, photoionization from different ultraviolet wavelengths such as Comparative Example 1 (250 nm) and Comparative Example 2 (360 nm) did not induce electron emission. The charge distributions measured at the 250 nm and 360 nm wavelengths were consistent with their initial distribution before UV irradiation, which means that there is little reduction of the graphene oxide through the emitted electrons.

1: reaction chamber
10: discharge unit
11: conductive rod
12:
20:
21: Spray device
30: reduction unit
31: Light source
40: collecting section

Claims (7)

A pair of conductive rods spaced apart from each other by a predetermined distance to form a gap and including a metal having a work function of 6.0 eV or less and a power source for applying a voltage to the conductive rod, A discharging part for generating metal nanoparticles in the electrode;
And a spraying device for spraying the oxidized graphene solution onto the metal nano-particles generated at the interval between the conductive rods, wherein the spraying part forms the metal nano-particles having the graphene oxide attached thereto; And
And a light source for irradiating ultraviolet rays having a wavelength of 200 nm or less to the metal nano-particles having the graphene oxide formed thereon, wherein the graphene oxide is reduced by receiving electrons separated from the surface of the metal nano- And a reducing portion forming a reduced graphene. The apparatus for producing graphene according to claim 1, wherein the discharging portion, the spraying portion and the reducing portion are maintained under an inert gas or a nitrogen atmosphere. The method of claim 1, wherein the metal having a work function of 6.0 eV or less is selected from the group consisting of barium, silver, cadmium, aluminum, beryllium, cerium, cesium, cobalt, chromium, iron, gallium, gadolinium, hafnium, mercury, indium, A metal selected from the group consisting of lead, niobium, neodymium, rubidium, rhenium, rhodium, ruthenium, scandium, tin, strontium, tantalum, terbium, tellurium, thorium, titanium, uranium, vanadium, yttrium, thallium, ytterbium, zinc, palladium, And zirconium. ≪ Desc / Clms Page number 24 > The apparatus for producing graphene according to claim 1, further comprising a collecting section for separating the reduced graphene from the metal nanoparticles in the reducing section and collecting the reduced graphene. A discharge step of generating a metal nanoparticle from the gap by applying a voltage to a pair of conductive rods spaced apart from each other to form an interval and including a metal having a work function of 6.0 eV or less and spark discharging;
An encapsulation step of forming a droplet containing the metal nano-particles to which the graphene oxide is attached by spraying a graphene oxide solution on the metal nano-particle; And
And a reducing step of irradiating ultraviolet rays having a wavelength range of not more than 200 nm to the metal nano-particles having the graphene oxide attached thereon to reduce the graphene oxide by receiving electrons separated from the surface of the metal nano-particles by ultraviolet rays . The method of claim 5, wherein the metal having a work function of 6.0 eV or less is selected from the group consisting of barium, silver, cadmium, aluminum, beryllium, cerium, cesium, cobalt, chromium, iron, gallium, gadolinium, hafnium, mercury, indium, A metal selected from the group consisting of lead, niobium, neodymium, rubidium, rhenium, rhodium, ruthenium, scandium, tin, strontium, tantalum, terbium, tellurium, thorium, titanium, uranium, vanadium, yttrium, thallium, ytterbium, zinc, palladium, And zirconium. ≪ Desc / Clms Page number 24 > 6. The method of claim 5, further comprising the step of separating the reduced graphene from the metal nanoparticles and collecting the reduced graphene.

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