KR20160066966A - Preparation method for nanosheet of layered strucutre compound - Google Patents

Abstract

The present invention relates to a method for preparing a nanosheet of a layered structure compound, which allows preparation of a nanosheet having a smaller thickness and a larger area with high yield from various metal-containing layered structure compounds. The method for preparing a nanosheet of a layered structure compound comprises the steps of: forming a dispersion containing a layered structure compound having a transition metal element or post-transition metal element and a dispersant; and passing the dispersion continuously through a high-pressure homogenizer including an inlet portion, an outlet portion and a fine flow path connecting the inlet portion with the outlet portion and having a micrometer-scale diameter, wherein the layered structure compound is exfoliated into a nanosheet while passing through the fine flow pass under the application of shear force.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing a nanostructure of a layered compound,

The present invention relates to a method for producing a nanosheet of a layered compound capable of producing a nanosheet having a thinner thickness and a larger area from a variety of metal-containing layered compounds in a high yield.

Since a nanostructure having a two-dimensional structure, for example, a nanosheet is easy to be synthesized in a relatively complicated structure, and it is relatively simple to change the characteristics of the material itself constituting the nanosheet, Research is being conducted.

Among the nanostructures having such a two-dimensional structure, graphene, which corresponds to a two-dimensional nanostructure of carbon, is one of the materials that have recently attracted the greatest attention. However, such graphenes do not have the band gap necessary for electrical and electronic applications such as transistors or semiconductor devices, and thus their application is limited. In order to overcome these limitations, a variety of related researches have been conducted, such as modification of graphene. However, this not only increases the complexity of the semiconductor device manufacturing process, but also causes many defects in the modification process, And the like. Therefore, attempts to apply the graphene to various devices have been limited.

For this reason, much research has been conducted on the properties and manufacture of nanosheets using metal-containing layered compounds such as metal chalcogenes, as well as various layered compounds, such as graphene, There is a trend. Unlike graphene composed of only carbon, the nanosheets of various layered compounds can provide a variety of structures, bonds and chemical functional polydispersities, and thus the nanosheets can be applied to various applications.

For example, in the case of a chalcogen nanosheet of a transition metal such as MoS ₂ or MoSe ₂ , it may have a band gap of 1.2 to 1.8 Ev according to the thickness, and may have a band gap of 200 to 500 cm ² / (V? In plane carrier mobility, and the like, it has properties that can be suitably applied to various electric and electronic applications such as various semiconductor devices and electrode materials of lithium ion batteries.

For the above-mentioned reasons, there is a great interest in a technique of mass-producing nanosheets having a thinner thickness and a larger area by using a more various metal-containing layered compound. Previously known methods for producing nanosheets and the like include the following.

First, a method is known in which a nanosheet is peeled from a layered compound by a physical method such as using a tape. However, such a method is unsuitable for mass production, the separation yield is very low, and it is difficult to manufacture a large-sized nanosheet.

Further, there is known a method of obtaining a nanosheet in which an acid, a base, or a metal such as lithium is interposed between layers constituting a layered compound to peel off from an intercalation compound. However, this method requires additional processes such as the use and treatment of an intercalation compound, so that the whole process becomes complicated, the yield is not sufficient, and the economical efficiency of the process may deteriorate. Furthermore, the phase transformation of the layered compound occurs during the insertion of lithium and the like, so that it becomes difficult to obtain a nanosheet having desired properties, and it is not possible to control the insertion process. Thus, a nanosheet having a thinner thickness and a larger area It may be difficult to produce it at a high yield.

In addition to these methods, recently, there has been known a method for producing nanosheets by delaminating each layer constituting a layered compound by ultrasonic irradiation or a milling method using a ball mill in a state in which a layered compound or the like is dispersed in a liquid phase. However, in the method using ultrasonic irradiation, since the separation efficiency is low, a nanosheet having a thin thickness close to a single molecule layer can not be obtained in a high yield, and it is difficult to obtain a nanosheet having a large area and a defect There are many disadvantages that can occur. Further, in the method using the ball mill or the like, it is difficult to obtain a nanosheet with a sufficiently thin thickness, and a thin nanosheet having a thickness close to a single molecular layer can not be obtained with a high yield.

As a result, there is a continuing need for a method for producing nanosheets of various layered compound compounds having a thinner thickness and a larger area, reducing the occurrence of defects, and maintaining excellent properties, at a high yield.

Accordingly, the present invention provides a method for producing a nanosheet of a layered compound capable of producing a nanosheet having a thinner thickness and a larger area from a variety of metal-containing layered compounds in a high yield.

The present invention relates to a method for manufacturing a semiconductor device, comprising: forming a dispersion containing a layered compound having a transition metal element or a metal element after the transition; And passing the dispersion continuously through an inlet, an outlet, a high pressure homogenizer comprising a microchannel having a micrometer scale diameter connecting between the inlet and outlet, And the layered structural compound is peeled off while passing through the microchannel under application of a shear force to form a nanosheet.

In the method for producing a nanosheet of the layered compound, the layered compound is a compound represented by the following formula: Mo, Bi, Nb, W, Ti, Ta, Fe, Co, Ni, Ga, In, Re, Sn, Sb, Pb, Or one or more transition metal elements selected from the group consisting of transition metal elements. In one example, the layered structural compound can be a metal chalcogen compound, and examples of such a metal chalcogen compound include MoS ₂ , MoSe ₂ , MoTe ₂ , Bi ₂ Te ₃ , Bi ₂ Se ₃ , Bi ₂ Te _{3 , NbS 2, NbSe 2, WS} 2, WSe 2, NiTe 2, TaS 2, TaSe 2, TiS 2, MoWS 2, MoWSe 2, ReS 2, ReSe 2, SnSe 2, SnTe 2, Sb 2 Se 3, PbSnS 2 in, GaSe, GaTe, GaTe, CuS , GeSe, FeTe, FeTeSe, FeSe 2, CoSe 2, InS, InSe, InTe, in ₂ Se ₃ and the group consisting of ZrS ₂ may be selected ones.

In addition, in the nanosheet production method, the dispersion may be a dispersion in which the layered structural compound and the dispersant are dissolved or dispersed in a water solvent or a polar organic solvent.

At this time, as the dispersing agent, a pyrene-based derivative; Cellulosic polymers; Cationic surfactants; Anionic surfactants; Gum Arabic; n-Dodecyl b-D-maltoside; Amphoteric surfactants; Polyvinylpyrrolidone type polymers; Polyethylene oxide type polymers; Ethylene oxide-propylene oxide copolymer; Tannic acid; Or a mixture of plural kinds of polyaromatic hydrocarbon oxides, which contains a polyaromatic hydrocarbon oxide having a molecular weight of 300 to 1000 in an amount of not less than 60% by weight.

In the nanosheet manufacturing method, the micro-channel of the high-pressure homogenizer may have a diameter of about 50 to 300 mu m, and the dispersion may be supplied to the high-pressure homogenizer at a high pressure of about 500 to 3,000 bar So that the peeling can be performed while passing through the fine flow path.

The nanosheet prepared by the above method can be in the form of a nanosheet flake of a layered compound having a thickness of about 1 to 50 nm, and the nanosheet flake has a diameter of about 0.1 to 10 mu m, Lt; / RTI > to 10000 diameters / thickness ratio.

In addition, in the method of manufacturing a nanosheet, after the nanosheet is formed, the step of recovering and drying the nanosheet may be further performed from the dispersion containing the nanosheet. At this time, the recovering step may be performed by centrifugation, vacuum filtration or pressure filtration, and the drying step may be performed by vacuum drying at a temperature of about 30 to 200 ° C.

According to the present invention, it is possible to produce nanosheets of various layered compounds by optimizing the peeling method in a state where various metal-containing layered compounds are uniformly dispersed due to the use of a dispersant and the use of a high-pressure homogenizer. Particularly, according to the present invention, nanosheets having a thinner thickness and a larger area can be easily manufactured at a high yield by optimizing the dispersion state and the peeling efficiency of the layered structural compound.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram showing the principle of a high-pressure homogenizer usable in the method of manufacturing graphene in one embodiment.
2A and 2B (an enlarged view of a region having a molecular weight of 400 to 500) is a diagram showing the molecular weight distribution of a pitch used for the preparation of the dispersant of Production Example by analyzing by MALDI-TOF mass spectrum.
3A and 3B (an enlarged view of a region having a molecular weight of 400 to 500) is a diagram showing the molecular weight distribution of the dispersant obtained in Production Example 1 analyzed by MALDI-TOF mass spectrum.
4 is a graph showing the analysis results of the pitch and the dispersant of Production Example 1 analyzed by 13C CPMAS NMR, respectively.
5 is a graph showing the results of analysis of the pitch and the dispersant of Production Example 1 by FT-IR analysis, respectively.
Fig. 6 is a diagram showing the results of analysis of the molecular weight distributions of the dispersants obtained in Production Examples 2 to 4, respectively, in the MALDI-TOF mass spectrum.
7A shows an electron micrograph of a layered structural compound (a), a Bi ₂ Te ₃ layered structural compound (b) and an NbSe ₂ layered structural compound (c) of MoS ₂ used as a raw material for producing nanosheet flakes of the embodiment .
7 (a) and 7 (b) show SEM and TEM photographs of the MoS ₂ nanosheet flake of Example 1 prepared using the dispersant of Production Example 1, respectively.
(A) and (d) show SEM and TEM photographs of the MoS ₂ nanosheet flakes of Example 2 prepared using a polyvinylpyrrolidone dispersant, and (b) and (e) (C) and (f) show the SEM and TEM photographs of the Bi ₂ Te ₃ nanosheet flake of Example 3 prepared using the pyrrolidone dispersant, 4 shows SEM and TEM photographs of NbSe ₂ nanosheet flakes, respectively.
Figs. 8 to 10 show results of AFM analysis for measuring the diameter and thickness of the nanosheet flakes of Examples 2 to 4. Fig.

Hereinafter, a method for producing a nanosheet of a layered compound according to a specific embodiment of the present invention will be described in more detail.

Some of the terms used in the following specification can be defined as follows.

First, in the following specification, the term "dispersant" may refer to any component for uniformly dispersing another component, for example, a layered compound having a metal element, in a solvent, an organic solvent or other liquid medium. Such a " dispersion "or" dispersion composition ", which may be referred to as a " Solution, slurry or paste, and the like. Such a "dispersion liquid" or "dispersion composition" can refer not only to a composition used in the production of the nanosheet described below, but also to an ink or paste composition applied to various other applications Dispersion "or" dispersion composition "regardless of its state or use, as long as its use is not particularly limited, and the" dispersant "and the object component to be dispersed are contained together in the liquid medium. .

In the following specification, the term "polyaromatic hydrocarbon" may refer to an aromatic hydrocarbon compound having two or more, or five or more, aromatic rings, for example, a benzene ring, . Further, the "polyaromatic hydrocarbon oxide" may refer to any compound in which the above-mentioned "polyaromatic hydrocarbon" reacts with an oxidizing agent to form one or more oxygen-containing functional groups in its chemical structure. At this time, the oxygen-containing functional groups which can be introduced into the "polyaromatic hydrocarbon" by reaction with the oxidizing agent may be bonded to aromatic rings such as a hydroxyl group, an epoxy group, a carboxyl group, a nitro group or a sulfonic acid, Lt; / RTI >

On the other hand, according to one embodiment of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming a dispersion containing a layered compound having a transition metal element or a pre-metal element; And passing the dispersion continuously through an inlet, an outlet, a high pressure homogenizer comprising a microchannel having a micrometer scale diameter connecting between the inlet and outlet, And the layered structural compound is peeled off while passing through the fine flow path under the application of a shear force to form a nanosheet.

In the nanosheet manufacturing method of one embodiment, the use of the dispersing agent in the pre-peeling step and the use of the high-pressure homogenizer in the peeling step cause the transition metal or the post-metal-containing layered structure compound to be more uniformly dispersed And the nanosheet of the layered structural compound can be prepared by optimizing the peeling method thereof.

As a result of experiments conducted by the inventors of the present invention, it has been found that, by manufacturing the nanosheet by the above-mentioned method, the nanosheets of the layered compound having a thinner thickness and a larger area can be separated into a simplified process It was confirmed that it can be obtained. In addition, it was confirmed that the occurrence of defects on the nanosheet during the process was reduced, and the yield of the nanosheet was also increased.

Accordingly, it has been confirmed that nanosheets of the metal-containing layered compound which can exhibit various properties and can be used for various purposes can be preferably prepared. In particular, nanosheets of layered compounds including transition metals or transition metals such as metal chalcogen compounds, which can be preferably used for semiconductor devices, high-temperature lubricants, electrode materials for lithium ion batteries, catalyst materials, etc., It was confirmed that it can be produced with improved yield while exhibiting excellent properties more effectively.

Hereinafter, a method of manufacturing a nanosheet according to an embodiment will be described in more detail.

In the method of manufacturing a nanosheet of one embodiment described above, a dispersion containing a layered compound and a dispersant having a transition metal element or a metal element after the transition can be formed first.

At this time, the kind of the layered structural compound which can be formed into a nanosheet by the method of one embodiment is not particularly limited, and it is manufactured in nanosheet form and exhibits electrical characteristics, semiconductor characteristics, conductivity or catalytic activity, , It is possible to appropriately prepare nanosheets of such layered compounds by using them as raw materials without any limitation, as long as they are a transition metal or a metal compound containing a post-transition metal that can be used for various purposes.

For example, the layered compound may be at least one selected from the group consisting of Mo, Bi, Nb, W, Ti, Ta, Fe, Co, Ni, Ga, In, Re, Sn, Sb, Pb, A transition metal element or a metal element after the transition. In a more specific example, the layered structural compound may be a metal chalcogen compound. Examples of the metal chalcogen compound include MoS ₂ , MoSe ₂ , MoTe ₂ , Bi ₂ Te ₃ , Bi ₂ Se ₃ , Bi _{2 Te 3, NbS 2, NbSe 2} , WS 2, WSe 2, NiTe 2, TaS 2, TaSe 2, TiS 2, moWS 2, MoWSe 2, reS 2, reSe 2, SnSe 2, SnTe 2, Sb 2 Se 3, PbSnS ₂ , GaSe, GaTe, GaTe, CuS, GeSe, FeTe, FeTeSe, FeSe ₂ , CoSe ₂ , InS, InSe, InTe, In ₂ Se ₃ and ZrS ₂ .

Such a nanosheet of a layered compound such as a metal chalcogen compound can be prepared in a thinner thickness and a larger area by the method of one embodiment, and can be used for the above-mentioned various uses by taking advantage of its excellent properties.

The dispersion may be a dispersion in which the layered structural compound and the dispersing agent are dissolved or dispersed in a water solvent or a polar organic solvent. In such a dispersion, the layered structural compound may exist in a uniformly dispersed state due to the action of the dispersing agent. Therefore, in the optimized dispersion state, the subsequent peeling step is carried out to form a nanosheet having a thinner thickness and a larger area, For example, nanosheet flakes and the like can be effectively formed.

In the dispersion used as the raw material, the water solvent or the polar organic solvent may be water, N-methyl-2-pyrrolidone (NMP), acetone, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), cyclohexyl-pyrrolidinone (CHP), N-dodecyl-pyrrolidone N12P), benzyl benzoate, N-octyl-pyrrolidone (N8P), dimethylimidazolidinone (DMEU), cyclohexanone, dimethylacetate Amides such as dimethylacetamide (DMA), N-methylformamide (NMF), bromobenzene, chloroform, chlorobenzene, benzonitrile, quinolinone, Benzyl ether, ethanol, isopropyl alcohol, methanol, butanol, 2-ethoxyethanol, 2-butoxyethanol, (1) selected from the group consisting of 2-methoxypropanol, tetrahydrofuran, THF, ethylene glycol, pyridine, N-vinylpyrrolidone, methyl ethyl ketone (butanone), alpha-terpineol, formic acid, ethyl acetate and acrylonitrile A variety of polar organic solvents, water solvents, and mixed solvents thereof may be used.

Examples of the dispersing agent include low-molecular-weight pyrene-based derivatives; Cellulosic polymers; Cationic surfactants; Anionic surfactants; Gum Arabic; n-Dodecyl b-D-maltoside; Amphoteric surfactants; Polyvinylpyrrolidone type polymers; Polyethylene oxide type polymers such as a dispersing agent represented by trade name Triton X-100 and the like; Ethylene oxide-propylene oxide (block) copolymers such as a dispersant represented by Pluronics F-127, etc.; Or tannic acid. Any other substance or water-soluble dispersant known to be usable for previously uniformly dispersing the metal-containing layered compound in a polar solvent may be used.

Further, as a mixture of plural kinds of polyaromatic hydrocarbon oxides, a dispersant comprising a mixture containing a polyaromatic hydrocarbon oxide having a molecular weight of about 300 to 1000 in an amount of about 60% by weight or more may be used.

This specific dispersant has been newly manufactured by the present inventors and filed in Korean Patent Application No. 10-2013-0091625 (filed on August 1, 2013), which will be described in detail as follows.

The pitch discharged from the residue in the refining process of fossil fuels such as petroleum or coal is a by-product used for the production of asphalt, and it is in the form of a viscous mixture containing a plurality of polyaromatic hydrocarbons having a plurality of aromatic rings . However, if such an oxidation process using an oxidizing agent is applied to such a pitch, at least a part of the polyaromatic hydrocarbons having an excessively large molecular weight among the polyaromatic hydrocarbons contained in the pitch is decomposed and the polyaromatic hydrocarbons having a relatively narrow molecular weight distribution It was confirmed that a mixture was obtained. In addition, it has been confirmed that a mixture containing a plurality of polyaromatic hydrocarbon oxides is obtained, with one or more oxygen-containing functional groups introduced into the aromatic rings of the polyaromatic hydrocarbons.

Specifically, the mixture of polyaromatic hydrocarbon oxides obtained by this method has a molecular weight of about 300 to 1000, or about 300 to 700, as measured by MALDI-TOF MS, of at least about 60% by weight, or about 65% By weight or more, or about 70 to 95% by weight. The specific kind, structure, and distribution of the polyaromatic hydrocarbon oxides contained in such a mixture may vary depending on the type and origin of the pitch of the raw material, the kind of the oxidizing agent, and the like. However, at least the mixture of polyaromatic hydrocarbon oxides contained in the dispersing agent is a polyaromatic hydrocarbon having a structure in which at least one oxygen-containing functional group is introduced into a polyaromatic hydrocarbon each containing 5 to 30, or 7 to 20 benzene rings The polyaromatic hydrocarbon oxide in such a mixture has a molecular weight distribution in which the above-mentioned molecular weight distribution, that is, an oxide having a molecular weight of about 300 to 1000, or about 300 to 700, is at least about 60 wt% do.

At this time, the type of the oxygen-containing functional groups may vary depending on the kind of the oxidizing agent used in the oxidation process such as pitch, and the like, but may be one or more selected from the group consisting of a hydroxyl group, an epoxy group, a carboxyl group, .

The polyaromatic hydrocarbon oxides satisfying the above-mentioned structural characteristics and molecular weight distribution and the like and the mixture thereof can simultaneously have a hydrophobic? -Domain in which aromatic rings are gathered and a hydrophilic region by oxygen-containing functional groups bonded to the aromatic ring or the like have. Among these, the hydrophobic? -Domain can interact with the surface of the metal-containing layered compound or the like, and the hydrophilic region can cause the repulsion between the respective layered compound particles to be expressed. As a result, the above-described dispersing agent comprising a mixture of the polyaromatic hydrocarbon oxides is present between the molecules of the layered compound in a liquid medium such as a water solvent or a polar organic solvent to uniformly disperse the layered compound. Therefore, it has been confirmed that the dispersant can exhibit an excellent dispersing ability to disperse the layered structural compound more uniformly even if a relatively small amount is used.

Furthermore, the above-mentioned dispersant can exhibit water solubility by itself due to the presence of a hydrophilic region by an oxygen-containing functional group or the like, so that the layered structural compound can be uniformly dispersed even in an environmentally friendly water solvent. Particularly, it has been confirmed that the above-mentioned dispersant exhibits an excellent dispersing power capable of uniformly dispersing the layered compound in various polar organic solvents as well as an environmentally friendly water solvent.

Due to the excellent dispersing ability of such a dispersing agent, it becomes possible to more uniformly disperse the transition metal element as a starting material or the layered structural compound containing a metal element after the metal element in the manufacturing method of one embodiment. Therefore, nanosheets of various layered compound having a thinner thickness and a larger area can be more easily produced by stripping off the raw material in such an optimized dispersion state.

On the other hand, when the above-mentioned dispersant is subjected to an elemental analysis of a plurality of polyaromatic hydrocarbon oxides contained therein, the oxygen content of the whole mixture is about 12 to 50 wt%, or about 15 to 45 wt% of the total element content . This oxygen content reflects the degree to which the oxygen-containing functional groups have been introduced by the oxidation process in the polyaromatic hydrocarbon oxide, and the hydrophilic region described above can be appropriately included depending on the satisfaction of such oxygen content. As a result, in the method of one embodiment described above, it is possible to more uniformly disperse the layered structural compound as a raw material by using such a dispersant, and to obtain nanosheets having a thin thickness therefrom more effectively.

The oxygen content can be calculated by elemental analysis of plural kinds of polyaromatic hydrocarbon oxides contained in the above mixture. That is, if the mixture sample (for example, about 1 mg) is heated to a high temperature, for example, about 900 ° C on a thin foil, the foil may instantaneously melt and its temperature may rise to about 1500 to 1800 ° C , Gas can be generated from the mixture sample by such a high temperature, and the trapping and the element content can be measured and analyzed. As a result of this elemental analysis, the total element content of carbon, oxygen, hydrogen and nitrogen contained in the plural kinds of polyaromatic hydrocarbon oxides can be measured and analyzed, and the oxygen content with respect to the total element content can be obtained.

On the other hand, the above-mentioned dispersant can be prepared by a method comprising oxidizing a mixture containing polyaromatic hydrocarbons having a molecular weight of about 200 to 1500 in the presence of an oxidizing agent.

As already mentioned above, the pitch discharged from the residue in the refining process of fossil fuels such as petroleum or coal may include a plurality of polyaromatic hydrocarbons and may be in a mixture state having a viscous or powdery form. Of course, the specific kind, structure, compositional ratio, or molecular weight distribution of the polyaromatic hydrocarbon may vary depending on the raw material or the origin of pitch, but the pitch may be, for example, 5 to 50 aromatic rings, May contain a plurality of polyaromatic hydrocarbons contained in the structure and may include polyaromatic hydrocarbons generally having a molecular weight of about 200 to 1500. For example, a mixture (e.g., pitch) comprising polyaromatic hydrocarbons having a molecular weight of about 200 to 1500 used as a starting material in the method of preparing the dispersant may comprise about 80 wt% or more of polyaromatic hydrocarbons in the molecular weight range, About 90% by weight or more.

However, when an oxidation process using an oxidizing agent is applied to a mixture containing polyaromatic hydrocarbons such as pitch, polyaromatic hydrocarbons having an excessively large molecular weight among the polyaromatic hydrocarbons contained in the pitch are decomposed and a polyaromatic hydrocarbon having a relatively narrow molecular weight distribution Mixtures of polyaromatic hydrocarbons can be obtained. For example, polyaromatic hydrocarbons having a molecular weight greater than about 1000, or greater than about 700, can be decomposed to have small molecular weights. Also, with the introduction of one or more oxygen-containing functional groups into the aromatic ring of each polyaromatic hydrocarbon, a mixture comprising a plurality of polyaromatic hydrocarbon oxides, i. E. The dispersant used in the method of one embodiment, can be prepared very simply .

In the method for producing such a dispersant, the oxidizing agent is not particularly limited in its kind, and can be used without any limitation as far as it can cause an oxidation reaction to introduce oxygen-containing functional groups into aromatic hydrocarbons. Specific examples of such oxidizing agent is nitric acid (HNO _3), sulfuric acid (H ₂ SO _4), hydrogen peroxide (H ₂ O _2), ammonium cerium (IV) sulfate (Ammonium cerium (IV) sulfate; (NH 4) 4 Ce ( SO _{4) 4)} or ammonium cerium (IV) nitrate (ammonium cerium (IV) nitrate; that _{(NH 4) 2 Ce (NO} 3) 6) and the like, may be of two or more thereof selected among these are Of course.

This oxidation step may be carried out in a water solvent at a reaction temperature of about 10 to 110 DEG C for about 0.5 to 20 hours. In a specific example, a certain amount of the mixture containing the polyaromatic hydrocarbons is added in the presence of a solution phase oxidizing agent such as sulfuric acid and / or nitric acid, and the mixture is stirred at room temperature, for example, at about 20 DEG C or 80 DEG C for about 1 to 12 hours Oxidation step can proceed. By controlling the reaction temperature or time of the oxidation step, a dispersant having desired characteristics can be prepared by appropriately controlling the properties of the dispersant, for example, the degree of oxidation of the polyaromatic hydrocarbons.

Further, as already mentioned above, the mixture containing the polyaromatic hydrocarbons having a molecular weight of about 200 to 1500 as a starting material of the above-mentioned production method may originate from a pitch obtained from the fossil fuel or its product, Depending on the kind, the kind, structure or molecular weight distribution of the polyaromatic hydrocarbons may be different from each other. Nevertheless, as the oxidation process is proceeded for a mixture containing polyaromatic hydrocarbons having a molecular weight of about 200 to 1500 derived from the above-mentioned pitch and the like, the above-mentioned dispersant exhibiting an excellent dispersing ability for the metal-containing layered compound can be simply produced have.

On the other hand, the above-mentioned production method may further include a step of purifying the resultant after the oxidation step to obtain a mixture of plural kinds of polyaromatic hydrocarbon oxides, wherein the purification step comprises centrifuging the result of the oxidation step ≪ / RTI > With the progress of the purification step, it is possible to obtain a mixture of polyaromatic hydrocarbon oxides satisfying the above-mentioned molecular weight distribution and the like at a higher purity and suitably, and by using the dispersant containing the same, The nanosheet can be produced more effectively.

On the other hand, in the nanosheet manufacturing method of one embodiment, after the dispersion is formed and provided, the dispersion is continuously passed through a high pressure homogenizer having a predetermined structure to form a metal-containing layer The structural compound can be peeled off, and the nanosheets can be appropriately prepared through this.

Conventionally, a method of performing the peeling process using a ball mill or an ultrasonic wave irradiator is known. However, as already mentioned above, with this conventional method, it has been difficult to produce nanosheets of a thinner thickness and a larger area at a higher yield.

On the contrary, when the peeling step using the high-pressure homogenizer is performed, it is possible to easily produce nanosheets of a layered compound having a thinner, uniform thickness and a relatively large area, thereby solving the problems of the existing methods described above .

FIG. 1 is a schematic diagram showing the principle of a high pressure homogenizer usable in the nanosheet production method of one embodiment.

1, the high-pressure homogenizer includes a microfluidic channel having a micrometer scale diameter and connecting the inlet portion of the raw material, the outflow portion of the peeled product such as nanosheet flake, and the inflow portion and the outflow portion, Lt; / RTI > When a feedstock in the form of a dispersion containing a layered compound is introduced through the inlet of such a high pressure homogenizer while applying a high pressure of, for example, about 500 to 3,000 bar, the feedstock may have a micron (um) scale, While passing through a microfluidic channel having a diameter of about 50 to 300 占 퐉, or about 50 to 200 占 퐉, the speed of such a raw material can be accelerated to supersonic speed and a high shear force can be applied.

In the course of the passage of the microfluidic channels, due to the collision on the layered compounds caused by the high pressure at the inlet, these layered compounds can be crushed into a small flake form in the form of a two-dimensional plate, The additional peeling of the layered structural compound having the form of the two-dimensional flaky flake or the like can proceed due to the rapid flow rate and the shear force generated on the in-plane surface of the two-dimensional flaky flake. On the outlet side, the nanosheets of the layered compound having the form of the peeled product, for example, nanosheet flake, can be uniformly dispersed due to cavitation.

As a result, nanosheets of various layered compounds having a thinner and larger area transition metal or a pre-metal can be prepared very easily with a high yield, with reduced defects.

Meanwhile, the nanosheet manufacturing method of one embodiment may further include a step of recovering and drying the nanosheet from the dispersion containing the nanosheet after the nanosheet is formed, and the recovering step may include centrifugation, Or by pressure filtration. The drying step may be conducted by vacuum drying at a temperature of about 30 to 200 ° C.

According to the method of one embodiment described above, nanosheets of various metal-containing layered compounds having a very thin thickness and a relatively large area (diameter) corresponding to the respective molecular layer thicknesses of the layered compound are easily mass-produced at a high yield .

For example, such nanosheets can have various forms, such as flakes, plates or sheets, in which one or more molecular layers of a layered compound are laminated, more specifically about 1 to 50 nm, or about 1 to 25 nm, or about Can be mainly manufactured in the form of nanosheet flakes having a thickness of 5 to 20 nm. Further, such nanosheet flakes can have a large diameter of about 0.1 to 10 占 퐉, or about 0.1 to 5 占 퐉. The nanosheet flakes can have a diameter / thickness ratio of about 50 to 10000, or about 50 to 6000, or about 50 to 1000, because the area (diameter) of the nanosheet flakes is very large. Here, the "diameter" of the nanosheet flake refers to "diameter " of the nanosheet flake as " the longest distance among straight lines connecting two arbitrary points on the plane of each particle when viewed on a plane having the widest area & Can be defined.

Thus, as nanosheets of various metal-containing layered compounds having thinner and larger areas are produced by the method of one embodiment, such nanosheets can be expressed by maximizing their excellent conductivity, electrical or semiconductor properties have.

Because of the excellent properties of such nanosheets, they can be used in various fields and applications such as semiconductor devices such as FETs, high-temperature lubricants, electrode materials or catalyst materials of lithium ion batteries, etc. In addition, transition metals such as metal chalcogenides, Nanosheets of layered compounds can be used very advantageously for any field or application known to be applicable.

Best Mode for Carrying Out the Invention Hereinafter, the function and effect of the present invention will be described in more detail through specific examples of the present invention. It is to be understood, however, that these embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention.

Production Example 1: Preparation of dispersant

The following oxidation and purification processes were carried out on pitch, which is an oil byproduct obtained from POSCO, to prepare the dispersant of Preparation Example 1.

First, 0.5 to 1.5 g of a pitch was added to 75 ml of a mixed solution of sulfuric acid / nitric acid (volume ratio 3: 1), and the oxidation reaction was conducted at 70 캜 for about 3.5 hours.

After the oxidation reaction, the pitch reaction solution was cooled to room temperature, diluted with distilled water five times, and centrifuged at about 3500 rpm for 30 minutes. Subsequently, the supernatant was removed, and the same amount of distilled water was added thereto and re-dispersed. Then, the supernatant was centrifuged again under the same conditions, and the precipitate was finally recovered and dried. Thus, the dispersant of Preparation Example 1 was prepared.

First, the molecular weight distribution of the pitch used as a raw material in the process of producing such a dispersant was analyzed by MALDI-TOF mass spectrum and shown in FIGS. 2A and 2B (an enlarged view of the molecular weight range of 400 to 500) The molecular weight distribution was similarly analyzed and shown in Figs. 3A and 3B (an enlarged view of the molecular weight range of 400 to 500). This analysis was carried out by using the MALDI-TOF mass spectrum equipment (Ultraflex II, Bruker), mixing the pitch or dispersant into the matrix, mixing and drying.

Referring to FIGS. 2A and 2B (enlarged view), it has been confirmed that pitch includes polyaromatic hydrocarbons having a molecular weight of 200 to 1500, particularly peaks at a molecular weight of 14 Da in an enlarged view of FIG. It was confirmed that aliphatic hydrocarbons were connected to plural kinds of polyaromatic hydrocarbons having different numbers of aromatic rings (benzene rings). 3A and 3B (enlarged view), large peaks were observed in the dispersant of Production Example 1 at intervals of 44 Da and 16D in the polyaromatic hydrocarbons, respectively. This indicates that these aromatic hydrocarbons have? OOH, ? H or? O3H in the form of a mixture of polyaromatic hydrocarbon oxides into which oxygen-containing functional groups have been introduced such that oxides having a molecular weight of about 300 to 1000, or about 300 to 700, .

Pitch (upper) used as the raw material and dispersant (lower) used in Production Example 1 were analyzed by 13C CPMAS NMR (Varian 400MHz Solid-State NMR), respectively, and the results of the analysis are shown in FIG. 4, the carbon-derived peak of the aromatic hydrocarbon and the carbon-derived peak of the aliphatic hydrocarbon were confirmed in the pitch, but the presence of the oxygen-containing functional group was not confirmed. On the other hand, as a result of NMR analysis for the dispersant of Production Example 1, a peak of an oxygen-containing functional group was confirmed. The kind of oxygen-containing functional groups was confirmed to be an epoxy group, a hydroxyl group, a carboxyl group, or the like.

In addition, the pitch used as the raw material and the dispersant of Production Example 1 were analyzed by FT-IR (Agilent 660-IR) as a powder state, respectively, and the results of the analysis are shown in comparison with FIG. 5, it was confirmed that a peak of an oxygen-containing functional group was produced in the dispersant of Production Example 1. [

Production Examples 2 to 4: Preparation of dispersant

(Production Example 2), 3.5 hours (Production Example 3) and 7 (Production Example 3), respectively, using the pitch, which is an oil byproduct obtained from POSCO (using a pitch of a sample different from that of Production Example 1) The dispersants of Production Examples 2 to 4 were prepared in the same manner as in Production Example 1, except that the time was changed.

These dispersants were analyzed by MALDI-TOF mass spectrum in the same manner as in Production Example 1, and are shown together in comparison with FIG. Referring to FIG. 6, as the oxidation time increases, the content of components (polyaromatic hydrocarbon oxides) of about 1,000 or more than about 700 in the dispersant is reduced, and the polyaromatics having a molecular weight of about 300 to 1000, It was confirmed that a dispersant in the form of a mixture containing a higher content of hydrocarbon oxides was obtained.

Test Example 1: Measurement of oxygen content of dispersant

About 1 mg of the dispersant sample obtained in Preparation Examples 3 and 4 was heated to a high temperature of about 900 캜 on a thin foil. At this time, as the foil melted momentarily, the temperature rose to about 1500 to 1800 ° C, and gas was generated from the sample at such a high temperature. The contents of carbon, oxygen, hydrogen and nitrogen were measured and analyzed by trapping and elemental analysis of these gases. The results of this analysis are shown in Table 1 below in comparison with the analysis results of the pitches used for the preparation of each dispersant.

Name of sample C (wt%) H (wt%) N (wt%) O (wt%) pitch 95.5 4.5 - - Production Example 3 40.0 1.8 7.6 38.0 Production Example 4 40.0 1.5 7.8 39.2

Referring to Table 1, when the content of each element in the dispersant of Production Examples 3 and 4 was analyzed, it was confirmed that the oxygen content was about 12 to 50% by weight or about 30 to 40% by weight of the total element content .

Examples 1 and 2: Preparation of MoS ₂ nanosheet flakes

0.1 g of MoS ₂ layered compound was added to 100 ml of an aqueous dispersion in which 0.015 g of the dispersant (PAO) obtained in Production Example 1 was dispersed, to form a dispersion. Separately, 2.5 g of the layered compound of MoS ₂ was added to 500 ml of an aqueous dispersion in which 1.0 g of polyvinylpyrrolidone Mw 58,000 was dispersed to form a dispersion. Each of these dispersions was introduced into the inlet portion of the high-pressure homogenizer at a high pressure of about 1600 bar to pass a micro channel having a thickness of about 75 μm. This process was repeated ten times. Thus, the MoS ₂ nanosheet flakes of Examples 1 and 2 were prepared.

FIG. 7A shows electron microscope photographs of the layered structural compound of MoS ₂ before stripping used as a raw material. FIGS. 7 (a) and 7 (b) show SEM and TEM photographs of the MoS ₂ nanosheet flakes of Example 1 after being peeled off using the dispersant of Production Example 1, respectively. 7C and 7D are SEM and TEM photographs of the MoS ₂ nanosheet flakes of Example 2 after peeling off with a polyvinylpyrrolidone dispersant, respectively. Referring to FIGS. 7 (a) and 7 (d), it was confirmed that nanosheet flakes having very thin thickness and large area and minimized defects were formed very well.

In addition, the nanosheet flakes of Example 2 were subjected to AFM analysis and the results are shown in Fig. 8, respectively. Referring to this, it was confirmed that the nanosheet flakes of Example 2 had a very thin thickness of about 5 to 20 nm and a large area of 100 to 500 nm in diameter.

Example 3: Preparation of Bi ₂ Te ₃ nanosheet flakes

Instead of the layer structure compound of MoS ₂ in the same manner as in Example 2 except for using Bi ₂ Te ₃ layer structure compound 2.5g, the polyvinylpyrrolidone used in the money dispersant Example ₃ Bi ₂ Te 3 nanosheets flakes .

Fig. 7 (b) shows an electron micrograph of the layered structural compound of Bi ₂ Te ₃ used as a raw material before peeling. 7B and 7E show SEM and TEM photographs of the Bi ₂ Te ₃ nanosheet flake of Example 3 after peeling, respectively. Referring to FIGS. 7 (b) and 7 (e), it has been confirmed that nanosheet flakes having very thin thicknesses and large areas and minimizing defects are formed very well.

In addition, the nanosheet flakes of Example 3 were subjected to AFM analysis and the results are shown in Fig. Referring to this, it was confirmed that the nanosheet flakes of Example 3 had a very thin thickness of about 5 to 20 nm and a large area of 100 to 500 nm in diameter.

Example 4: Preparation of NbSe ₂ nanosheet flakes

Instead of the layer structure compound of MoS _2, NbSe ₂ was prepared in the layered structure in the same manner as in Example 2 except for using the compound 2.5g, polyvinylpyrrolidone performed using the money dispersing agent of Example 4 NbSe ₂ nanosheets flakes.

FIG. 7 (c) shows an electron micrograph of the layered structural compound of NbSe ₂ used as a raw material before peeling. 7C and 7F are SEM and TEM photographs of the NbSe ₂ nanosheet flake of Example 4 after peeling, respectively. Referring to FIGS. 7C and 7F, it was confirmed that nanosheet flakes having very thin thicknesses and large areas and minimizing defects were formed very well.

In addition, the nanosheet flakes of Example 4 were subjected to AFM analysis and the results are shown in Fig. 10, respectively. Referring to this, it was confirmed that the nanosheet flakes of Example 4 had a very thin thickness of about 5 to 20 nm and a large area of 100 to 500 nm in diameter.

Claims (13)

Forming a dispersion containing a layered compound having a transition metal element or a metal element after the transition and a dispersant; And
Passing the dispersion continuously through an inlet, an outlet, a high pressure homogenizer comprising a microchannel having a micrometer scale diameter connecting between the inlet and outlet, ,
Wherein the layered structural compound is formed as a nanosheet by being peeled off while passing through the micro flow path under the application of a shear force.
The method of claim 1, wherein the layered structural compound is selected from the group consisting of Mo, Bi, Nb, W, Ti, Ta, Fe, Co, Ni, Ga, In, Re, Sn, Sb, Pb, A method for producing a nanostructure of a layered compound having at least one transition metal element or a transition metal element.
The method of claim 1, wherein the layered structural compound is a metal chalcogen compound.
The method of claim 3, wherein the metal chalcogen compound is selected from the group consisting of MoS ₂ , MoSe ₂ , MoTe ₂ , Bi ₂ Te ₃ , Bi ₂ Se ₃ , Bi ₂ Te ₃ , NbS ₂ , NbSe ₂ , WS ₂ , WSe ₂ , NiTe _{2 , TaS 2, TaSe 2, TiS} 2, MoWS 2, MoWSe 2, ReS 2, ReSe 2, SnSe 2, SnTe 2, Sb 2 Se 3, PbSnS 2, GaSe, GaTe, GaTe, CuS, GeSe, FeTe, FeTeSe, Wherein the layered compound is selected from the group consisting of FeSe ₂ , CoSe ₂ , InS, InSe, InTe, In ₂ Se ₃ and ZrS ₂ .
The method of claim 1, wherein the dispersion is a dispersion in which the layered compound and the dispersant are dissolved or dispersed in a water solvent or a polar organic solvent.
The method of claim 1, wherein the dispersant is selected from the group consisting of a pyrene-based derivative; Cellulosic polymers; Cationic surfactants; Anionic surfactants; Gum Arabic; n-Dodecyl bD-maltoside; Amphoteric surfactants; Polyvinylpyrrolidone type polymers; Polyethylene oxide type polymers; Ethylene oxide-propylene oxide copolymer; Tannic acid; Or a mixture of plural kinds of polyaromatic hydrocarbon oxides, wherein the mixture contains a polyaromatic hydrocarbon oxide having a molecular weight of 300 to 1000 in an amount of 60 wt% or more.
The method of claim 1, wherein the microchannel has a diameter of 50 to 300 mu m.
The method according to claim 1, wherein the dispersion liquid flows into an inlet portion of the high-pressure homogenizer under a pressure of 500 to 3000 bar and passes through a microchannel.
The method of claim 1, wherein the nanosheet comprises a nanosheet flake of a layered compound having a thickness of 1 to 50 nm.
11. The method of claim 10, wherein the nanosheet flake has a diameter of 0.1 to 10 mu m and a diameter / thickness ratio of 50 to 10,000.
The method of claim 1, further comprising, after forming the nanosheet, recovering and drying the nanosheet from the dispersion containing the nanosheet.
12. The method of claim 11, wherein the recovering step is carried out by centrifugation, vacuum filtration or pressure filtration.
The method of claim 11, wherein the drying step is performed by vacuum drying at a temperature of 30 to 200 ° C.

Images