KR101543625B1 - Process for simultaneously preparing reduced graphene oxide and fluorescent carbon nanoparticles - Google Patents

Abstract

The present invention relates to a reduced graphene oxide having excellent electrical conductivity and a method for simultaneously producing fluorescent carbon nanoparticles having a high yield and a quantum yield. Reduced graphene oxide and fluorescent carbon nanoparticles are generally prepared through separate processes. Unlike the conventional method, according to one embodiment of the present invention, reduced graphene oxide having excellent electric conductivity and high- And the reduced graphene oxide can be applied to a supercapacitor because the reduced graphene oxide has excellent electrical properties. The carbon nanoparticles have a high stalk shift value, and thus form a complex with the polymer Thus, an effect that can be usefully used in fluorescent nanofibers, fluorescent nanofilms, and the like can be achieved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for simultaneously producing reduced graphene oxide and fluorescent carbon nanoparticles,

The present invention relates to a reduced graphene oxide having excellent electrical conductivity and a method for simultaneously producing fluorescent carbon nanoparticles having a high yield and a quantum yield.

Carbon nanoparticles are also commonly referred to as carbon quantum dots or nanodots. Carbon nanoparticles are not toxic and have a high potential for research on living cells and tissues because of their ability to emit fluorescence upon receiving light, so that they can be used as diagnostic probes or drug carriers for diagnostic purposes, as well as harmful substances such as cadmium, mercury and lead Compared with semiconducting nanoparticles containing heavy metals, they have excellent fluorescence properties and have a higher potential to be applied to various fields such as photocatalyst and LED.

Thus, semiconductor nanoparticles exhibit excellent optical, electrical properties and durability, but they are disadvantageous in that they require toxic and costly heavy metal raw materials and high-temperature synthesis processes. In the review paper of Baker et al. (Angew. Chem. Int. Ed., 2010, 49, 2.21), methods of producing carbon nanoparticles include electrophoresis, laser ablation, thermal oxidation, electrooxidation, pyrolysis And applications thereof. However, the conventional method of manufacturing carbon nanoparticles is complicated in manufacturing process, difficult to control the band gap, low quantum yield, and indeterminate process of internal chemical structure and optical characteristics, There is a problem that it is difficult.

Therefore, for the practical application of carbon nanoparticles, a synthesis method having high yield and quantum yield is devised, and a relatively simple synthesis process is also required.

On the other hand, reduced graphene oxide has excellent electrical conductivity, wide surface area and electrochemical stability, and various methods for producing reduced graphene oxide have been studied. In particular, a chemical reduction method or a reduction method by heat treatment is known.

The chemical reduction method can be carried out by using various reducing agents such as hydrazine, NaBH ₄ , HI / AcOH, NaOH / KOH / NH ₃ , metal, phenylhydrazine and the like to obtain graphene having an electrical conductivity of several tens to several hundreds S / It has been reported that toxic gas is generated in the reduction process and nitrogen atoms are adsorbed on the surface of the graphene sheet as well as the electrical properties are deteriorated by the impurities generated in the reduction process, In addition, a reduction method using a mixture of iodic acid and acetic acid has been developed, but the disadvantage is that the production time is more than 24 hours.

In the reduction method by heat treatment, graphene oxide is usually heat-treated at a high temperature (1,000 ° C or higher), and graphene having electric conductivity of 55,000-100,000 S / m can be obtained. However, the reduced graphene oxide The amount is small and is performed at a high temperature, which is not preferable due to an increase in energy loss and manufacturing cost.

The problems to be solved by the present invention are that, as described above, since the respective processes are different for producing reduced graphene oxide and carbon nanoparticles, the cost for the investment and management of materials and equipment according to each manufacturing process Which is different from the conventional method. It is another object of the present invention to provide a technique for more easily producing fluorescent carbon nanoparticles simultaneously with reduction of graphene oxide.

According to an exemplary aspect of the present invention, the present invention provides a method for simultaneously producing reduced graphene oxide and fluorescent carbon nanoparticles comprising the steps of:

(a) preparing a mixed solution by mixing graphene oxide, a first organic solvent and a second organic solvent;

(b) subjecting the mixed solution of step (a) to a first heat treatment;

(c) separating the reduced graphene oxide and the filtrate by filtering the first heat-treated mixed solution in the step (b); And

(d) obtaining a fluorescent carbon nanoparticle by performing a second heat treatment on the filtrate separated in the step (c).

Reduced graphene oxide and fluorescent carbon nanoparticles are generally prepared through separate processes. Unlike the conventional method, according to one embodiment of the present invention, reduced graphene oxide having excellent electric conductivity and high- And the reduced graphene oxide can be applied to a supercapacitor because the reduced graphene oxide has excellent electrical properties. The carbon nanoparticles have a high stalk shift value and thus form a complex with the polymer Thus, an effect that can be usefully used in fluorescent nanofibers, fluorescent nanofilms, and the like can be achieved.

FIG. 1 is a schematic view illustrating a process for producing reduced graphene oxide and fluorescent carbon nanoparticles according to an embodiment of the present invention. Referring to FIG.
FIG. 2 (a) is an X-ray photoelectron spectroscopy spectrum of carbon nanoparticles according to an embodiment of the present invention.
2 (b) is a C1s spectrum of carbon nanoparticles according to an embodiment of the present invention.
2 (c) is a C1s spectrum of graphene oxide according to one embodiment of the present invention.
Figure 2 (d) is the C1s spectrum of reduced graphene oxide according to one embodiment of the present invention.
3 (a) is an electron transmission microscope image of carbon nanoparticles according to one embodiment of the present invention.
FIG. 3 (b) is a distribution diagram of an electron transmission microscope image of carbon nanoparticles according to an embodiment of the present invention.
FIG. 3 (c) is an atomic force microscope image and height profile diagram of carbon nanoparticles according to one embodiment of the present invention.
FIG. 3 (d) is a graph showing the atomic force microscope image and the height profile of carbon nanoparticles according to one embodiment of the present invention.
4 (a) is a photograph of carbon nanoparticles according to an embodiment of the present invention dispersed in toluene and photographed under room light.
4 (b) is a photograph of carbon nanoparticles according to an embodiment of the present invention dispersed in toluene and photographed under an ultraviolet lamp in a dark room.
FIG. 4 (c) is an absorption, emission, and photoluminescence spectrum measured when carbon nanoparticles according to an embodiment of the present invention are dispersed in toluene.
4 (d) is a graph of luminescence according to various excitation wavelengths of carbon nanoparticles according to an embodiment of the present invention.
FIG. 4 (e) is a graph showing the result of summarizing the emission peak according to each excitation wavelength in FIG. 4 (d).
5 (a) and 5 (b) are images of carbon nanoparticle-PVDF composite nanofibers according to an embodiment of the present invention under bright light and fluorescent light of 488 nm, respectively.
FIG. 5 (c) is an image of a carbon nanoparticle-PMMA composite film according to an embodiment of the present invention taken under an ultraviolet lamp irradiation, and an illustration is an image of a carbon nanoparticle-PMMA composite film under an interior lamp.
FIG. 5 (d) is an image of a carbon nanoparticle-PMMA composite film according to an embodiment of the present invention, which is patterned by electron beam lithography, and then is observed under fluorescent light of 488 nm.
6A is a graph of a cyclic voltage-current measurement for a supercapacitor according to an embodiment of the present invention.
FIG. 6 (b) is a graph showing a capacitance per unit mass and a charge / discharge rate for a supercapacitor according to an embodiment of the present invention.
6 (c) is a graph of a constant current charge / discharge measurement for a supercapacitor according to an embodiment of the present invention.
6 (d) is a Nyquist plot for a supercapacitor according to an embodiment of the present invention.
7 (a) is a graph of capacitance and current density per mass for a supercapacitor according to an embodiment of the present invention.
FIG. 7 (b) is a graph of mass per cell energy density and mass per cell for a supercapacitor according to an embodiment of the present invention.
FIG. 7 (c) is a graph showing a capacitance per unit mass and a frequency of a supercapacitor according to an embodiment of the present invention.
FIG. 7 (d) is a graph showing a capacitance per unit mass and an oscillation frequency of an imaginary region for a supercapacitor according to an embodiment of the present invention.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

As used herein, the term "simultaneous" refers to a process for preparing two or more completely different materials of interest, wherein each of the materials is not produced through a separate process, but a series of processes are sequentially performed, Means producing another material.

The term "graphen oxide" means an oxide formed by oxidizing graphite, and "reduced graphen oxide" means a reduced product obtained by reducing graphen oxide.

Further, the term "fluorescent carbon nanoparticles" refers to nano-sized carbon particles having fluorescence properties.

According to an aspect of the present invention, a method for simultaneous production of reduced graphene oxide and fluorescent carbon nanoparticles comprising the steps of:

(a) at least one first organic solvent selected from the group consisting of graphene oxide, benzaldehyde and C ₁ -C ₆ aldehyde, and at least one second organic solvent selected from C ₁ -C ₆ alcohols and distilled water, Preparing a mixed solution;

(b) subjecting the mixed solution of step (a) to a first heat treatment;

(c) separating the reduced graphene oxide and the filtrate by filtering the first heat-treated mixed solution in the step (b); And

(d) obtaining a fluorescent carbon nanoparticle by performing a second heat treatment on the filtrate separated in the step (c).

Reduced graphene oxide and fluorescent carbon nanoparticles are generally prepared through separate processes. Unlike the conventional method, according to one embodiment of the present invention, reduced graphene oxide having excellent electric conductivity and fluorescent particles having excellent quantum yield Carbon nanoparticles can be produced simultaneously and more easily.

In one embodiment of the present invention, the first heat treatment process in the step (b) is performed at a temperature of 150-250 ° C.

In another embodiment of the present invention, the second heat treatment process in step (d) is performed at a temperature of 100-200 ° C.

In the step (d), it is preferable that the second heat treatment step is carried out with stirring.

In another embodiment of the present invention, the graphene oxide may include 0.1 to 10 wt% of at least one acid selected from sulfuric acid, nitric acid, and hydrochloric acid.

In another embodiment of the present invention, the graphene oxide is contained in an amount of 0.03 to 0.07 w / v% based on the total volume of the first organic solvent and the second organic solvent.

According to an embodiment of the present invention, in the production of the reduced graphene oxide and the fluorescent carbon nanoparticle, the graphene oxide preferably contains 0.1 to 10% by weight of an acid, There is a problem that the yield of the fluorescent carbon nanoparticles is lowered and the electrical conductivity of the reduced graphene oxide is lowered.

On the other hand, the graphene oxide may be contained in an amount of 0.03 to 0.07 w / v% based on the total volume of the first organic solvent and the second organic solvent, and when the ratio is out of the range, the yield of the reduced graphene oxide and the fluorescent carbon nanoparticles is There is a problem of deterioration.

In another embodiment of the present invention, the first organic solvent and the second organic solvent are added in a volume ratio of 1: 0.5-1.5.

According to one embodiment of the present invention, in the simultaneous production of the reduced graphene oxide and the fluorescent carbon nanoparticles, it is most preferable that the first organic solvent and the second organic solvent are added together at the same time, If the organic solvent is not included, the fluorescent carbon nano-particles may not be obtained at all. If only the first organic solvent is added without the second organic solvent, the yield of the fluorescent carbon nanoparticles may deteriorate There may be a problem that reduced graphene oxide having no electric conductivity is obtained.

Preferably, the first organic solvent and the second organic solvent may be added in a ratio of 1: 0.5-1.5. When the mixing ratio of the first organic solvent and the second organic solvent is less than 1: 0.5 by volume, carbon nanoparticles The fluorescence properties of the first organic solvent and the second organic solvent may be significantly reduced. When the mixing ratio of the first organic solvent and the second organic solvent is more than 1: 1.5 by volume, the fluorescent properties of the carbon nanoparticles may be deteriorated. The amount of the fluorescent carbon nanoparticles thus obtained is reduced.

In another embodiment of the present invention, the first organic solvent is added in an amount of 40 to 60% by volume based on the total volume of the mixed solvent.

In another embodiment of the present invention, the second organic solvent is added in an amount of 40 to 60% by volume based on the total volume of the mixed solvent.

According to one embodiment of the present invention, it is preferable that the second organic solvent is ethanol among C1-C6 alcohols. When alcohol other than ethanol is used, the fluorescence characteristic of the carbon nanoparticles and the electricity Conductivity may not be expressed.

Hereinafter, a method for simultaneously producing the reduced graphene oxide and the fluorescent carbon nanoparticle according to an embodiment of the present invention will be described in detail.

The step (a) may be performed by dispersing graphene oxide in an alcohol, adding benzaldehyde, and then treating the ultrasonic wave with the graphene oxide dispersion.

Also, the step (b) is a step of reducing graphene oxide. It is preferable that the dispersion obtained in the step (a) is reduced for 3 to 7 hours in a pressure processor at 150 to 250 캜.

Further, the step (c) may be a step of obtaining a reduced graphene oxide, wherein the reduced graphene oxide is reacted with acetone to form a reduced graphene oxide by an additional step of dispersing the reduced graphene oxide- And thus can be separated from the fluorescent carbon nanoparticles. The precipitate is completely separated by filtration through reduced graphene oxide and filtrate. The process can be repeatedly carried out until the filtrate becomes clear.

In the step (d), the fluorescent carbon nanoparticles are obtained from the filtrate obtained in the step (c), and the filtrate obtained in the step (c) And the mixture is cooled to obtain a fluorescent carbon nanoparticle powder.

In another embodiment of the present invention, the reduced graphene oxide has a carbon / oxygen atomic ratio of 4 to 7, and the reduced graphene oxide has an electrical conductivity of 250 to 300 S / m.

When graphene oxide is reduced through the production method according to an embodiment of the present invention, it is advantageous in that the reduced graphene oxide having an excellent yield and an excellent electrical conductivity of 250-300 S / m can be obtained .

Therefore, when the reduced graphene oxide is applied to a supercapacitor, compared with a supercapacitor using reduced graphene oxide obtained from propylene carbonate in the prior art, it exhibits similar performance with only a slight rate-limiting performance and capacitance difference, The reduced graphene oxide according to the present invention can be usefully used in future supercapacitors.

In another embodiment of the present invention, the fluorescent carbon nanoparticles are in the form of an elliptical amorphous form having a major axis length of 3-10 nm and a minor axis length of 1-5 nm.

In another embodiment of the present invention, the fluorescent carbon nanoparticles have an atomic ratio of carbon to oxygen of 95-99: 1-5.

In another embodiment of the present invention, the fluorescent carbon nanoparticle has an excitation wavelength of 300-400 nm and a Stokes shift value of 70 nm or less.

The fluorescent carbon nanoparticles prepared according to one embodiment of the present invention are excellent in quantum yield and have a Stoke's shift value of 70 nm or less, compared with the most widely used CdSe / ZnS nanocrystals (20 nm) Having been found to have a large Stokes shift value, it is possible to minimize the problems of self-absorption of fluorescent nanoparticles used in various optoelectronic and photovoltaic devices.

Therefore, the fluorescent carbon nanoparticles can be usefully used as a fluorescent nanofiber, a fluorescent film, a fluorescent light and the like by forming a complex together with a polymer.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope and content of the present invention can not be construed to be limited or limited by the following Examples. In addition, it is apparent that, based on the teachings of the present invention including the following examples, those skilled in the art can easily carry out the present invention in which experimental results are not specifically shown.

Manufacturing example  One

Graphene oxide was prepared by the modified Hummers method.

Graphite flakes (1 g) and sodium nitrate (1 g) were dispersed in sulfuric acid (50 ml), and potassium permanganate (6 g) was slowly added to the mixed solution in an ice bath. The mixed solution was stirred at a temperature of 35 ° C for 1 hour, then distilled water (80 ml) was further added to the mixed solution, and further stirred at 90 ° C for 1 hour.

Then, distilled water (200 mL) and sulfuric acid (6 mL) were continuously added to the mixed solution to terminate the reaction.

The brownish graphene oxide product produced by the above method was obtained by filtration through a glass microfiber filter and stored at room temperature in a vacuum state. The graphene oxide containing residual sulfuric acid was used to simultaneously produce carbon nanoparticles and reduced graphene oxide.

Example  One

1 g of graphene oxide obtained in Preparation Example 1 was dispersed in ethanol and the volume of the mixed solution was adjusted to 8 ml. To this was added 8 mL of benzaldehyde solution and sonicated for 1 hour. The mixed solution was heat-treated at a temperature of 200 ° C for 5 hours in a 20-mL Teflon-line stainless steel pressure processor, and then cooled to room temperature.

After the reaction, a black precipitate was obtained, which was dispersed in about 100 mL of acetone and filtered through a polytetrafluoroethylene (PTFE) membrane. This process was repeated 4-5 times until the filtrate became clear.

Through the above process, reduced graphene oxide in the form of a black powder was obtained on the membrane. The filtered solution was soaked in silicone oil at 140 ° C for about 12 hours to obtain 7 g of carbon nanopowder as fluorescent carbon quantum dots.

Comparative Example  One

The graphene oxide product prepared in Preparation Example 1 was dispersed in 5% by weight of aqueous HCl solution (1000 mL) and stirred slowly for 12 hours. Then, to precipitate graphene oxide in the mixed solution, .

After removing the float, an additional purification process was performed by dialysis to remove the residual acid of the graphene oxide precipitate for 3 days. After dialysis, ethanol was added to the solution and centrifuged at 13000 rpm for 1 minute to obtain the graphene oxide product from which sulfuric acid had been removed, followed by drying in air for 4-5 days.

The same procedure as in Example 1 was carried out except that graphene oxide in which sulfuric acid was removed was used.

division Mass (g) of CNP Quantum yield of CNP (%) RGO
Electrical Conductivity (S / m) Mass of RGO (mg) Example 1 7.0 19.9 282 260 Comparative Example 1 1.4 3.5 52 470

As shown in Table 1, it was confirmed that when sulfuric acid contained in graphene oxide was completely removed, the yield of carbon nanoparticles and proton was very low, and the electrical conductivity of the reduced graphene oxide was also extremely low.

Comparative Example 2

The same procedure as in Example 1 was carried out except that benzaldehyde was used instead of benzaldehyde and ethanol was added in an amount the same as that of benzaldehyde.

division Mass (g) of CNP Quantum yield of CNP (%) RGO
Electrical Conductivity (S / m) Mass of RGO (mg) Example 1 7.0 19.9 282 260 Comparative Example 2 - - 58 280

As shown in Table 2, it was confirmed that when no benzaldehyde was added at all, carbon nanoparticles were not generated at all and electrical conductivity of the reduced graphene oxide was also extremely low.

Comparative Example  3

The same procedure as in Example 1 was carried out except that ethanol was used instead of ethanol and benzaldehyde was added in the same amount as ethanol.

division Mass (g) of CNP Quantum yield of CNP (%) RGO
Electrical Conductivity (S / m) Mass of RGO (mg) Example 1 7.0 19.9 282 260 Comparative Example 3 7.0 2.1 - 300

As shown in Table 3, when ethanol was not added at all, carbon nanoparticles were formed, but the quantum yield thereof was very low, and reduced graphene oxide was not formed in the film, and it was confirmed that conductivity measurement became difficult.

Comparative Example 4

The same procedure as in Example 1 was carried out except that graphene oxide was not added and 1 mL of sulfuric acid was added.

division Mass (g) of CNP Quantum yield of CNP (%) RGO
Electrical Conductivity (S / m) Mass of RGO (mg) Example 1 7.0 19.9 282 260 Comparative Example 4 4.8 16.7 - -

As shown in Table 4, when sulfuric acid alone was added without using graphene oxide, it was confirmed that carbon nanoparticles were produced but no reduced graphene oxide was obtained.

Experimental Example 1: Photoelectron spectroscopy (XPS) experiment

The carbon and oxygen atomic ratios of the carbon nanoparticles obtained through the above examples were confirmed using an optoelectronic spectrometer (XPS).

As shown in Figs. 2a to 2d, the carbon 1s peak of the carbon nanoparticles is located at 285 eV, which means that carbon is mostly in the form of carbon-carbon bonds, and on the other hand, photoelectron spectroscopic analysis, It can be seen that graphene oxide was successfully reduced to reduced graphene oxide during the thermal reaction. In addition, graphene oxide shows the strongest C-C carbon peak at 285 eV and also a strong peak in the 286-289 eV region (meaning significant amounts of carbon are in the form of alcohols, aldehydes, ketones, and carboxylic acids).

However, when the graphene oxide was reduced to reduced graphene oxide, most of the carbonyl and carboxyl peaks disappeared and the hydroxyl peak was significantly reduced.

On the other hand, it was confirmed that the atomic ratio of carbon to oxygen due to reduction was increased from 1.4 to 5.7, and the atomic ratio of carbon to oxygen of the carbon nanoparticles was 97: 3.

Experimental Example 2: Confirmation of carbon nanoparticle morphology

The morphology of the carbon nanoparticles prepared according to the present invention was confirmed by an electron transmission microscope and an atomic force microscope.

As shown in FIGS. 3A and 3 D, the measured carbon nanoparticles had a round shape of a noncrystalline shape with a diameter of 6.1 ± 1.6 nm and a height of 2.4 ± 1.0 nm.

Experimental Example 3: Evaluation of optical properties of carbon particles

The synthesized carbon nanoparticles can be homogeneously dispersed in various organic solvents such as toluene, acetone, and dimethylformamide.

The carbon nanoparticle dispersion solution has been found to maintain a clean condition without any lumps or sediments observed over several months of observation, and the carbon nanoparticles have good solubility and can mix well with various organic materials.

As shown in FIGS. 4A and 4B, carbon nanoparticles can not confirm fluorescence in indoor illumination under room illumination and ultraviolet lamp in a dark room, but in a darkroom UV lamp, carbon nanoparticles dispersed in toluene emit blue light in solution Respectively.

Further, as shown in FIGS. 4C and 4E, in the ultraviolet-visible absorption spectrum, carbon nanoparticles strongly absorb light in the ultraviolet ray region. In the photoluminescence excitation spectrum, when the emission wavelength of 400 nm is detected, 336 nm. ≪ / RTI > It was also confirmed that the emission peak position in the photoluminescence spectrum measured at the excitation wavelength of 340 nm was 406 nm.

In this regard, the half-height width (FWHM) of the photoluminescence graph was confirmed to be 80 nm or less, and the Stokes shift value of the carbon nanoparticles synthesized by the present invention is most widely used at 70 nm or less CdSe / ZnS nanocrystals (less than 20 nm).

Having a large Stokes shift value is essential to minimize the self-absorption problem of nanocrystals used in various optoelectronic and photovoltaic devices, and the quantum yield of the measured carbon nanoparticles is 20%.

4D and 4E, the maximum emission intensity of the light emission intensity at 340 nm is shown in FIG. 4, and the peak position is red-shifted to the sigmoidal shape as the excitation wavelength increases.

Example 2: PVDF or carbon nanoparticle-PVDF nanofiber electrospinning

The nanofibers were prepared as follows through an electrospinning process.

PVDF nanofibers were prepared by electrospinning after dispersing polyfluorinated vinylidene (PVDF) in a mixed solution of 1: 1 volume ratio of dimethylformamide and acetone. At this time, the applied potential and feeding rate are 9 kV and 30 μL / min, respectively.

On the other hand, 300 mg of carbon nanoparticles were additionally added to the above-mentioned PVDF solution in the production of carbon nanoparticle-PVDF nanofibers. At this time, the applied potential and feeding rate are 10.5 kV and 30 μL / min, respectively.

Example  3: Carbon nanoparticles - PMMA  Film production and electron beam Lithography

PMMA (2 g) was dispersed in anisole, stirred for 24 hours, added with carbon nanoparticles (2 mg) dispersed in toluene (2 ml), and stirred for 2 hours. The carbon nanoparticle-PMMA layer was spin-coated at 3000 rpm for 30 seconds, followed by heat treatment at 170 ° C for 3 minutes, followed by electron beam lithography to perform patterning, and then the carbon nanoparticle- It was developed by a solution of isobutyl ketone: isopropyl alcohol (1: 3).

More carbon nanoparticles (40 mg) were used to demonstrate the transparency and fluorescence of carbon nanoparticle-PMMA films. The concentrated carbon nanoparticle-PMMA solution (400 μl) was dropped onto a SiO ₂ / Si slice (2 cm × 2 cm) and then heat treated at 170 ° C. for 5 minutes.

The carbon nanoparticle-PMMA-coated specimen was impregnated with hydrofluoric acid (5 wt%) for 1 hour, and then the carbon nanoparticle-PMMA film separated from the SiO ₂ / Si substrate was washed with distilled water.

Experimental Example  4: Evaluation of Optical Properties of Fluorescent Polymer Complex

As a result of evaluating the optical characteristics of the fluorescent carbon nanoparticle-polymer complexes prepared in Examples 2 and 3, bright light images of fluorescent confocal microscopes and their corresponding fluorescence images, as shown in Figs. 5A and 5B, It clearly shows that nanofibers have fluorescence properties. In particular, in FIG. 5A, the diameters of the carbon nanoparticles-PVDF were found to be 500-1000 nm, and as shown in the scanning electron microscope image, they were uniformly grown along the length direction.

Also, as shown in FIGS. 5C and 5D, the carbon nanoparticle-PMMA composite film photographed under the indoor light and the portable ultraviolet lamp in the dark room was transparent and fluorescent.

On the other hand, in Fig. 5D, the confocal microscope image can confirm the patterned carbon nanoparticle-PMMA layer under laser irradiation of 488 nm wavelength.

Example  4: Reduction Grapina Oxide  Super Capacitor Manufacturing

Reduced graphene oxide (30 mg) obtained in Example 1 was dispersed in propylene carbonate (30 ml) and ultrasonicated for 90 minutes. A portion of the solution was vacuum filtered over carbon paper. The reduced graphene oxide layer formed on the carbon paper was dried in an oven at 80 DEG C for 2 hours.

The PTFE membrane was used as a separator between the two reduced graphene oxide coated carbon paper electrodes prepared above.

The electrode / separator / electrode assembly was bundled with Para film, the assembly was placed in the electrolyte solution in the Teflon frame, and the electrolyte was prepared by adding 1 M tetraethylammonium tetrafluoroborate to the propylene carbonate solution.

The cell was placed in a glass container and measured in a vacuum atmosphere.

Experimental Example  5: Reduced oxidation Grapina  Supercapacitor measurement experiment

As a result of the measurement of the circulating voltage-current of the super capacitor manufactured in Production Example 2, a rectangular shape behavior is shown as shown in FIG. 6A, which means that it plays a role as a good capacitor. The capacitance of the reduced graphene oxide supercapacitor was slightly lower than that of the supercapacitor using reduced graphene oxide synthesized through propylene carbonate (83 F / g and 58 F / g, respectively, at 0.1 V).

Further, as shown in FIG. 6B, as the charge / discharge rate of the supercapacitor increases from 0.1 V / s to 8 V / s, the capacitance decreases from 57.5 F / g to 21.1 F / g, The reduced graphene oxide super-capacitor obtained from the present invention has a much higher rate performance than the reduced graphene oxide super-capacitor obtained from propylene carbonate in that the capacitance of about 1/3 is still obtained even at the charging / discharging speed of 8 V / s .

Further, as shown in Figs. 6C and 6D, the excellent capacitor behavior of the supercapacitor is shown by the triangular shape seen in the constant voltage charging / discharging curve and the line extending in the vertical direction (angle = 84.7 [deg.] ), And confirmed that the equivalent series resistance is 3.4 Ω.

As shown in FIG. 7, various other characteristics of the supercapacitor according to the present invention are compared with supercapacitors containing reduced graphene oxide obtained from propylene carbonate. As a result, It has been confirmed that it has performance.

Claims (16)

(a) at least one first organic solvent selected from the group consisting of graphene oxide, benzaldehyde and C ₁ -C ₆ aldehyde, and at least one second organic solvent selected from C ₁ -C ₆ alcohols and distilled water, Preparing a mixed solution;
(b) subjecting the mixed solution of step (a) to a first heat treatment;
(c) separating the reduced graphene oxide and the filtrate by filtering the first heat-treated mixed solution in the step (b); And
(d) subjecting the filtrate separated in the step (c) to a second heat treatment to obtain fluorescent carbon nanoparticles. The method for simultaneously producing reduced graphene oxide and fluorescent carbon nanoparticles. The method according to claim 1, wherein the first annealing process is performed at a temperature of 150-250 ° C in the step (b). The method of claim 1, wherein the second heat treatment in step (d) is performed at a temperature of 100-200 占 폚. The method according to claim 1, wherein the second heat treatment step in step (d) comprises boiling. The method of claim 1, wherein the graphene oxide comprises 0.1 to 10 wt% of an acid. 6. The method according to claim 5, wherein the acid is at least one selected from sulfuric acid, nitric acid and hydrochloric acid. The method according to claim 1, wherein the graphene oxide is contained in an amount of 0.03 to 0.07 w / v% based on the total volume of the first organic solvent and the second organic solvent. Way. The method of claim 1, wherein the first organic solvent and the second organic solvent are added in a ratio of 1: 0.5-1.5 by volume. The method of claim 1, wherein the first organic solvent is added in an amount of 40 to 60% by volume based on the total volume of the mixed solution of step (a)
Wherein the second organic solvent is added in an amount of 40 to 60 vol% based on the total volume of the mixed solution of step (a). The method of claim 1, wherein the reduced graphene oxide has a carbon / oxygen atomic ratio of 4-7,
Wherein the reduced graphene oxide has an electrical conductivity of 250-300 S / m. The method according to claim 1, wherein the fluorescent carbon nanoparticles have an elliptical amorphous form having a major axis length of 3 to 10 nm and a minor axis length of 1 to 5 nm, and a method for simultaneously producing the reduced graphene oxide and the fluorescent carbon nanoparticle . The method of claim 1, wherein the fluorescent carbon nanoparticles have an atomic ratio of carbon to oxygen of 95-99: 1-5. The method according to claim 1, wherein the fluorescent carbon nanoparticles have an excitation wavelength of 300-400 nm and a Stokes shift value of 70 nm or less. delete delete delete

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