KR100999167B1 - Hollow graphene multilayed nanospheres - Google Patents

Abstract

The present invention relates to multilayer graphene hollow nanospheres formed in a layered structure by a graphene layer. The multilayer graphene hollow nanospheres not only retain the physicochemical properties of conventional carbon nanotubes or fullerenes, but the outer surface is hydrophilic and the inner surface forming the hollows is hydrophobic, including metallic carbides. Application is possible.

Graphene, Multishell, Hollow, Nanospheres

Description

Hollow graphene multilayed nanospheres

The present invention relates to multilayer graphene hollow nanospheres having not only the physicochemical properties of conventional waste-shell carbon nano allotropes (nanotubes and fullerenes), but also biochemical applications.

Carbon nanotubes (SWNTs, MWNTs), fullerenes (C ₆₀ ) and related closed-shell carbon nanoallotrope or their oxides are of ongoing interest due to their unique physical properties and potential technical applicability. This has been. Significant advances have been made in the last two decades in theoretical studies to produce carbon-based nanostructures with homogeneous topologies, and in physical or chemical synthesis methods. In particular, morphological control or surface modification from carbon precursors to graphene multilayered nanospheres in the form of colloids has been a major topic in many studies, due to their low toxicity and good biocompatibility due to their good biocompatibility. .

However, it is not known about the multilayer graphene hollow nanospheres that have not only the physicochemical properties of the existing shell-shell carbon allotrope (nanotubes and fullerenes) but also biochemical applications.

The present invention not only has the physicochemical properties of conventional waste shell carbon allotrope (nanotubes and fullerenes), but also enables biochemical applications, and provides multilayer graphene hollow nanospheres having high crystallinity and semiconducting properties. For the purpose of

The present invention,

The present invention provides a multilayer graphene hollow nanosphere formed in a layered structure by a graphene layer.

The multilayer graphene hollow nanospheres have an outer diameter of about 25 nm to 300 nm and an inner diameter of about 6 nm to 250 nm. In addition, the interlayer distance of the graphene is about 0.34 nm ~ 0.60 nm and the thickness of the multilayer graphene is about 3.4 nm ~ 60 nm.

In addition, the multilayer graphene hollow nanospheres are characterized in that the outer surface is hydrophilic including a hydroxyl group, the hollow interior is hydrophobic including a metal-based carbide.

The multilayer graphene hollow nanospheres of the present invention

(a) It has the property of expressing optical luminescence or electromagnetic characteristics by impurity introduction treatment such as deposition or supporting of specific metal ions, and thus can be used for specific applications requiring optical and electromagnetic applications.

(b) It possesses the physicochemical properties of existing carbon nanotubes or fullerenes and can be substituted for the same use.

(c) The outer surface shows the hydrophilicity including the hydroxyl group, and the inner curved surface forming the hollow shows the hydrophobicity including the metal carbide, thereby satisfying the biocompatibility without additional chemical and physical surface control or treatment,

(e) the hydrophilicity of the outermost surface of the carbon film can be easily converted to hydrophobic by physicochemical reduction,

(f) Metals with general metallic properties Compared with gold (Au) nanoparticles, they have semiconductor (semimetallic) properties and can be usefully used in related industries.

The present invention,

The present invention relates to a multilayer graphene hollow nanosphere formed in a layered structure by a graphene layer.

The multilayer graphene hollow nanospheres have an outer diameter of about 25 nm to 300 nm and an inner diameter of about 6 nm to 250 nm. The apparent size of the nominal inner diameter and nominal outer diameter of the entire nanosphere depends on the size of the mother template or the initial molar dosage of glucose.

In addition, the interlayer distance of the graphene is about 0.34 nm ~ 0.60 nm and the thickness of the multilayer graphene is about 3.4 nm ~ 60 nm.

In addition, the interlayer distance of graphite 2H as a reference for the minimum interlayer distance is about 0.34 nm. Therefore, the multilayer graphene layer includes about 10 to 100 single graphene layers.

The multilayer graphene hollow nanospheres of the present invention are characterized in that the outer surface exhibits hydrophilicity including a hydroxyl group, and the inner curved surface forming a hollow exhibits hydrophobicity including a metal carbide. In the hydroxy group of the outer surface is derived from the hydroxy group contained in the polysaccharide, the metal-based carbide is formed on the inner surface according to the type of metal or metal oxide applied in the synthesis, the fine form by the condensation reaction of silanol groups Si-O-Si hydrophobic film is formed.

However, the outer surface of the carbon base material can be easily converted to hydrophobicity by physical and chemical reduction treatment with a reducing gas and a reactive acetate group or the like. In particular, the graphene oxide surface layer is properly removed of the oxide upon heating to 600 ° C. in the presence of argon gas, and the graphene layer thus formed can be converted to hydrophobic upon solution phase reaction with reactive acetate.

The multilayer graphene hollow nanospheres of the present invention form optically asymmetrical and chemically active axes due to the introduction of impurities by metal ion deposition or supporting, such as chemical vapor deposition (CVD) or physical vapor deposition (PVD), to the specific solvent. Emission or electromagnetic expression is possible.

In principle, in contrast to the tetrahedral structure of tetravalent carbon, high-dimensional bonds such as octahedrons or, conversely, low-dimensional bonds can introduce asymmetric elements into the carbon bonds. Luminescence characteristics are exhibited by introduction of (II), Fe (III) and the like. In addition, the semiconducting properties of such compounds exhibit field emission characteristics in which electrons accumulated above a threshold voltage upon application of a battery field emit light.

The multi-layer graphene hollow nanospheres of the present invention satisfy the bio-friendliness of additives added to special purpose paints, which require optical and electromagnetic applications, and have bioavailability as almost pure carbon allotrope, thereby delivering substances such as drugs into the body. Since it has semiconductor (semimetallic) characteristics, it can be usefully used for applications such as a negative electrode of a battery.

Hereinafter, the manufacturing method of the multilayer graphene hollow nanospheres of the present invention will be described in detail.

The multilayer graphene hollow nanospheres of the present invention

(a) coating porous silica on metal (or metal oxide) nanoparticles to produce metal (or metal oxide) / silica composite nanoparticles,

(b) hydrothermal reaction of the metal (or metal oxide)) / silica composite nanoparticles in a polysaccharide dispersion with heating to obtain a carbonized product and to separate it; and

(c) etching the carbonized product of step (b) in an acidic solution.

The multilayer graphene hollow nanospheres of the present invention are dispersed in the carbonization product of step (b) or the etched carbonization product of step (c) in a polarity controlled solvent (or mixed solvent) to achieve uniform dispersion of nanospheres. The method may further include adjusting the photo exitation-emission sensitivity according to the dispersion degree.

In the above production method, the metal or the metal oxide may be prepared by a technique known in the art, or may be purchased and used commercially. Examples of the metal or metal oxide include Fe, Co, Mn, and oxides thereof, and in particular, Fe, Fe ₃ O ₄ Back It can be used preferably.

In the above method, the porous silica coating is a metal or metal oxide nanoparticles (dispersed in hexane solvent), ammonia water, and tetraalkyl orthosilicate (TAOS) in a cyclohexane solvent It is characterized by being formed by reacting. In the above, tetraethyl orthosilicate (TEOS) may be preferably used as TAOS.

In the above production method, the polysaccharide solution is preferably an aqueous solution prepared with deionized water, and purified alcohols or organic solvents may be used according to special uses and preparation methods. It is advantageous to use the polysaccharide solution of 5-10 M to efficiently induce an ionic non-diffusion effect (Kirkendall Effect). In addition, as the polysaccharide in the above, known polysaccharides can be used without limitation, for example, glucose, lactose, sucrose and the like.

In the above production method, the hydrothermal reaction of step (b) is preferably carried out by reacting 500 to 1000 parts by weight of the polysaccharide with respect to 100 parts by weight of the metal (or metal oxide) / silica composite nanoparticles. Reducing the polysaccharide to less than 500 parts by weight is not preferable in that the effective diffusion reaction is inhibited, if the reaction is more than 1000 parts by weight may cause a problem that the graphene layer locally abnormal growth.

The manufacturing method can adjust the thickness of the multilayered graphene hollow nanospheres obtained by adjusting the amount of polysaccharide within the above range.

In the above production method, the heating temperature for the hydrothermal reaction of step (b) is not particularly limited, but it is preferable to proceed at 160 ~ 250 ℃ in terms of efficiency and economic efficiency of the reaction. In the above temperature range, the hydrothermal reaction is performed for about 5 to 20 hours according to Fick's first diffusion law. If the temperature of the hydrothermal reaction is less than 160 ° C., the progress of the hydrothermal reaction follows the tendency to decrease exponentially with respect to the temperature. Therefore, it is necessary to extend the reaction time from the reaction time of up to 20 hours. Although the time is shortened and a high crystalline graphene multi-shell is obtained, the work becomes complicated, such as the durability of the hydrothermal reactor for high temperature operation, and the economic efficiency may be reduced.

In the above production method, the acidic aqueous solution serves to dissolve or wash the remaining porous silica or unreacted metal ions. To this end, the complex 3 is supported for 3 to 10 hours at room temperature, preferably using an acidic aqueous solution of 5 to 9 M, more preferably 7 M. If agitated for effective treatment, the treatment effect can be increased. The pH for the treatment should maintain strong acidity, and the pH range is appropriate. Therefore, non-oxygen based HF, HCl, or mixtures thereof are advantageous. When using oxygen acid sulfuric acid or nitric acid, graphene oxide may increase, which may affect electrical and optical properties. desirable.

The manufacturing method of the present invention is a silicate-coated nanoparticles in the form of metal or metal oxide as a template (template), the environmentally friendly polysaccarides hydrothermal route (polysaccarides hydrothermal route) and the ion ratio between the metal or metal oxide and polysaccharide It is characterized by using a Kirkendall Effect.

Hereinafter, the method for producing multilayer graphene hollow nanospheres of the present invention will be described in more detail.

Route 1. Synthetic route for the generation of multilayer graphene hollow nanospheres

Specifically, the method of the present invention will be described with reference to Path 1 as an example. First, a scalable metal or metal oxide nanoparticle (composite 1) having a diameter of 6 nm to 30 nm is known (Nature, 2004, 3). 891) or commercially available.

Next, the composite nanoparticles coated with porous silica were coated with a cyclohexane solvent and reacted with metal or metal oxide nanoparticles (dispersed in hexane solvent), ammonia water and tetraalkyl orthosilicate (TAOS, 25 to 30 nm in diameter). Make particles (composite 2). The reaction is preferably carried out at room temperature for 10 to 14 hours. In this case, the thickness of the coating layer of the porous silica can be modified up to several hundred nanometers by controlling the amount of TAOS. In the above, tetraethyl orthosilicate may be preferably used as TAOS.

The complex 2 is placed in a stainless steel autoclave finished with Teflon together with a polysaccharide solution previously dissolved in a solvent, and subjected to a hydrothermal reaction at 160 to 250 ° C. After the hydrothermal reaction, the obtained black precipitate is separated, washed and centrifuged to obtain a silica / carbon layer (compound 3) free of metal oxides (see schematic diagram of FIG. 1). The hydrothermal reaction is Fick's first diffusion law. Based on this, preferably 5 to 20 hours.

The polysaccharide solution is preferably made of deionized water and purified alcohols or organic solvents may be used according to special uses and preparation methods. The hydrothermal reaction is preferably carried out by reacting 500 to 1000 parts by weight of the polysaccharide with respect to 100 parts by weight of the composite 2. The thickness of the multilayered graphene hollow nanospheres obtained by adjusting the amount of the polysaccharide can be adjusted.

The complex 3 is etched and washed in an acidic aqueous solution to prepare a highly crystalline and metal-semiconductor transitionable multilayer graphene hollow nanosphere (composite 4). The acidic aqueous solution is loaded with the composite 3 for 3 to 10 hours at room temperature using an acidic aqueous solution of 5 to 9 M, more preferably 7 M. If agitated for effective treatment, the treatment effect can be increased. As the acidic aqueous solution, HF aqueous solution may be preferably used.

Hereinafter, the present invention will be described in detail through embodiments of the present invention. However, embodiments of the present invention may be modified in various forms, the scope of the present invention should not be construed in a way that is limited by the embodiments described below.

[ Example ]

Sizeable magnetite nanoparticles (Fe ₃ O ₄ nanoparticles) having an average diameter of 6 nm were prepared by known methods (Nature, 2004, 3, 891). 50 mg of the prepared particles were dispersed in 100 ml hexane. 1 ml of a hexane dispersion of Fe ₃ O ₄ nanoparticles, 1.3 ml of ammonia water, and 3 ml of liquid tetraethyl silicate (99.9%) were added to a 200 ml cyclohexane solvent by using a syringe, followed by reaction at room temperature for 12 hours. The obtained composite nanoparticles of magnetite / silica were recovered by centrifugation (6000 rpm x 20 min). Into a stainless autoclave finished with 100 ml Teflon, 40 ml of water, 4 g of glucose, 0.5 g of magnetite / silica were mixed, and the temperature was raised to 180 ° C. under stirring for 1 hour 30 minutes and hydrothermal reaction for 16 hours. Proceeded. After 16 hours of reaction, the pressure gauge was opened and the pressure was dropped rapidly. After the hydrothermal reaction, the obtained black precipitate was separated, washed and centrifuged (6000 rpm x 30 min) to recover Complex 3. The resultant complex 3 was reacted for 4 hours at room temperature in a 7 M HF aqueous solution, and then washed and centrifuged in the applied solvent to obtain a suspended complex 4, followed by drying at 120 ° C. for 12 hours to prepare a final product.

High-resolution transmission electron spectroscopy observation (HRTEM) and micro Raman spectra were observed to demonstrate that complexes 1, 2, 3 and 4 were formed at each step. The carbon / oxygen atomic ratio in the composites 3 and 4 was determined by ICP-MS. In addition, it is shown by measuring the electrical properties of the multilayer graphene hollow nanospheres prepared above. Hereinafter, the experimental results will be described with reference to the accompanying drawings.

HRTEM images of complexes 1, 2, 3 and 4 are shown in FIG. 2.

As shown in FIG. 2 all core / cell structures clearly exhibit discrete zero-dimentional (0-D) nanoparticle morphology.

The left image of Figure 2-1 is an image of a single dispersed 6 nm Fe ₃ O ₄ nanoparticles (Compound 1), the upper right image is an enlarged image of the particle measured in the (110) direction, the image of the lower right Are the corresponding SAED patterns, showing that they have good crystallinity.

The image of FIGS. 2-2 shows well separated 20 nm Fe ₃ O ₄ / SiO ₂ core / cell nanoparticles (Compound 2), and the images of the inserted single particles show that the average thickness of the silica is about 7 nm. .

2-3 show that SiO ₂ / C nanoparticles (composite 3) have an increased particle diameter.

2-4 show GMFs (composite 4) produced by etching treatment with HF.

In addition, FIG. 3 shows that nanocrystalline Fe ₃ O ₄ (composite 1) was well formed from the lattice fringe observed directly in the enlarged HRTEM image of complex 1. FIG.

4 shows that the hollow graphene multilayer fullerene was formed by an enlarged HRTEM image of the composite 4.

5 is confirmed by HRTEM that the hydrothermal reaction of glucose from complex 2 to complex 3 progresses over time.

FIG. 7 is a graph showing the carbon / oxygen atomic ratio of the composites 1 to 4 synthesized in the present invention. According to the graph, the C / O atomic ratio of the composite 3 is 2.3 and the C / O atomic ratio of the composite 4 is 3.6. It can be seen that the ratio increased.

8 shows micro Raman spectra for complexes 3 and 4 taken at room temperature.

9 is a graph showing Raman spectrum D / G band intensities of hollow nanospheres treated with palladium nanoparticles, wherein the ratio of D / G band intensities is 2 to 3, and these values are synthesized at a high temperature (1200 ° C. or higher). The characteristic Raman value of the highly oriented pyrolytic graphite (HOPG) can be confirmed that the multilayer graphene is formed from this. In particular, 1 is a direct coating of the graphene hollow nanospheres on the palladium nanoparticles, 2 is a palladium nanoparticles attached to the 200 nm graphene hollow nanospheres by self-assembly, 3 is a three-dimensional graphene composite Palladium nanoparticles were attached by self-assembly.

FIG. 10 illustrates the results obtained in the form of a single nanosphere in comparison with gold (Au) nanoparticles, which are metals having general metallic properties, in order to confirm electrical properties of the multilayer graphene hollow nanospheres prepared above. As a result shown in Figure 10, it can be seen that the multilayer graphene hollow nanospheres of the present invention exhibits semiconductor (semimetallic) characteristics.

1 is a conceptual diagram schematically showing that glucose is hydrothermally reacted to form a graphene multilayer fullerene.

2 is an HRTEM image of complexes 1, 2, 3 and 4. FIG.

3 is an enlarged HRTEM image of complex 1. FIG.

4 is an enlarged HRTEM image of complex 4. FIG.

5 is an HRTEM image confirming the hydrothermal glucose response of the Kirkendall Effect (Kirkendall Effect) over time.

FIG. 6 is a graph showing the results of measurement of the photoluminescence spectra of the composite 3 according to the UV-vis spectrum and the change of the solvent at room temperature in comparison with the conventional MWNT and C ₆₀ .

7 is a graph of qualitative and quantitative synthesis of the synthesized step 1, 2, 3, 4 using X-ray photoelectron spectroscopy (Photoelectron Spectroscopy).

FIG. 8 is a Raman spectra of the synthesized composites 3 and 4 (composite 4 adds the results of heat treatment at 700 ° C.).

FIG. 9 is a graph showing Raman spectrum D / G band intensities of hollow nanospheres treated with palladium nanoparticles (in FIG. 1, graphene hollow nanospheres are directly coated on palladium nanoparticles, and 2 is 200 nm graphene hollow) Palladium nanoparticles are attached to the nanospheres by self-assembly, and 3 is palladium nanoparticles attached to the three-dimensional graphene composite by self-assembly).

FIG. 10 illustrates the electrical properties of the composite 4 measured in the form of a single nanosphere in comparison with gold (Au) nanoparticles having a general metallicity, in order to confirm the electrical properties of the multilayer graphene hollow nanospheres.

FIG. 11 is a photograph confirming the possibility of photoliminescence (PL) by dispersing complex 4 in ethanol and irradiating with a UV lamp.

Claims (7)

A multi-layer graphene hollow nanosphere formed of a layered structure by a graphene layer, the outer surface of which is hydrophilic including a hydroxyl group, and the inner surface of which forms a hollow is hydrophobic including a metal carbide Multilayer graphene hollow nanospheres. The multilayer graphene hollow nanosphere of claim 1, wherein the outer diameter is 25 nm to 300 nm and the inner diameter is 6 nm to 250 nm. The multilayer graphene hollow nanosphere of claim 1, wherein the interlayer distance of the graphene is 0.34 nm to 0.60 nm and the thickness of the multilayer graphene is 3.4 nm to 60 nm. delete The multilayer graphene hollow nanosphere of claim 1, wherein the outer surface is converted to hydrophobicity by physicochemical reduction. The multilayer graphene hollow nanosphere of claim 1, wherein the metal carbide forms a fine Si-O-Si hydrophobic film by condensation reaction of silanol groups. The multilayer graphene hollow according to any one of claims 1 to 3, wherein the optically asymmetric and chemically active axes are formed in the structure by introducing impurities by deposition or supporting of metal ions, thereby enabling optical emission or electromagnetic expression. Nanospheres.

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