2-dimensional MXene particle surface-modified with functional group containing saturated or unsaturated hydrocarbon, preparation method thereof and use thereof

Abstract

The present invention relates to a 2-dimensional MXene particle surface-modified with a functional group comprising a saturated or unsaturated hydrocarbon, a preparation method thereof, and a use thereof (e.g., a conductive film).

Claims

1. A passivated 2-dimensional MXene particle, comprising: a 2-dimensional MXene particle surface-modified with a functional group comprising a saturated or unsaturated hydrocarbon; and an organic protective film formed on a surface of the surface-modified 2-dimensional MXene particle, wherein the functional group is selected from the group consisting of a phosphonate and a silane, wherein the phosphonate is represented by Formula 1 or 2, and the silane represented by Formula 4: ##STR00005## wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently a saturated or unsaturated hydrocarbon, a C.sub.1 to C.sub.6 alkoxy, or a hydroxyl group, and R.sub.5 is a saturated or unsaturated hydrocarbon, with a proviso that each of R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is not a saturated or unsaturated hydrocarbon or each of R.sub.1, R.sub.2, R.sub.3, and R.sub.4 is not a hydroxyl group, wherein the surface-modified 2-dimensional MXene particle with a functional group comprising a saturated or unsaturated hydrocarbon is covered with an organic polymer, or dispersed in an organic polymer, forming the protective film.

2. The 2-dimensional MXene particle of claim 1, wherein the 2-dimensional MXene particle, as a subject of surface modification, is a 2-dimensional transition metal carbide, nitride, or combination thereof comprising at least one layer wherein a crystal cell having Empirical Formula 1 or 2 is formed in a 2-dimensional array:
M.sub.n+1X.sub.n  [Empirical Formula 1] wherein, each X is located within an octahedral array, M is a metal selected from the group consisting of Group IIIB metals, Group IVB metals, Group VB metals, and Group VIB metals, each X is C, N, or a combination thereof, and n is 1, 2, or 3; and
M′.sub.2M″.sub.nX.sub.n+1  [Empirical formula 2] wherein, each X is located within an octahedral array of M′ and M″, M′ and M″ are different metals selected from the group consisting of Group IIIB metals, Group IVB metals, Group VB metals, and Group VIB metals, each X is C, N, or a combination thereof, and n is 1 or 2.

3. The 2-dimensional MXene particle of claim 1, wherein the saturated or unsaturated hydrocarbon is independently selected from the group consisting of C.sub.1-25 alkyl, C.sub.2-25 alkenyl, C.sub.2-25 alkynyl, C.sub.6-25 aryl, and (C.sub.6-25 aryl)-(C.sub.1-4 alkyl).

4. The 2-dimensional MXene particle of claim 1, wherein the amount of surface charge of the MXene particle is determined by adjusting the molecular weight, composition, and/or substituent of the saturated or unsaturated hydrocarbon in the surface-modified 2-dimensional MXene particle.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a conceptual diagram which shows the synthesis of a MXene by etching a MAX phase according to a specific embodiment.

(2) FIG. 2a schematizes the method of preparing a MXene ink in which a 2-dimensional MXene particle surface-modified with phosphonate through an interfacial reaction is dispersed in an organic solvent, and FIG. 2b shows the method of preparing a MXene ink in which a 2-dimensional MXene particle surface-modified with an amine through an interfacial reaction is dispersed in an organic solvent, and the form of ink before and after the reaction and of the final product in which a MXene surface-modified with polystyrene-amine is dispersed in toluene.

(3) FIG. 3a shows the distribution of a MXene before and after surface modification reaction when using 1-hexanol as an organic solvent having a lower density than water in Examples 1 and 2. FIG. 3b shows the distribution of a MXene before and after surface modification reaction according to the kind of solvent, i.e., density, when using various organic solvents having a density higher or lower than water in Examples 4 and 5. FIG. 3c shows the distribution of a MXene before and after surface modification reaction when using hexanol as an organic solvent having a lower density than water in Examples 5.

(4) FIG. 4a shows inks in which a surface-modified MXene is dispersed in various organic solvents, and FIG. 4b shows inks in which a MXene surface-modified with aminated polystyrene (PS—NH.sub.2) is dispersed in various organic solvents.

(5) FIG. 5a shows the results of analyzing the composition of the surface-modified MXene using .sup.1H NMR with respect to the surface-modified MXene particle in Example 1-5 in which a MXene of Ti.sub.3C.sub.2T.sub.x composition as a subject of surface modification was used and a MXene was modified with dodecyl phosphonic acid. With respect to the surface-modified MXene particle in Example 1-5, FIG. 5b shows the results of analyzing the composition of the surface-modified MXene using .sup.31P NMR. With respect to the surface-modified MXene particle in which a MXene of Ti.sub.3C.sub.2T.sub.x composition as a subject of surface modification was used and MXene was modified with oleylamine, FIG. 5c shows the results of analyzing the composition of the surface-modified MXene using .sup.1H NMR.

(6) With regard to the aminated hydrophobic polymer according to Example 2, e.g., MXene particles surfaced-modified with aminated polystyrene, FIG. 6a shows the results of analyzing the composition of the surface-modified MXene using FT-IR. FIG. 6b shows the results of analyzing the composition of the surface-modified MXene with dodecyltriethoxysilane(DTES) using FT-IR.

(7) FIG. 7a shows the results of comparing the microstructure of a MXene (MXene of Ti.sub.3C.sub.2T.sub.x composition) before and after surface modification according to Examples 1-5 using a scanning electron microscope (SEM), a transmission electron microscope (TEM), and selected area electron diffraction (SAED). FIG. 7b shows the results of comparing the microstructure of a MXene (MXene of Ti.sub.3C.sub.2T.sub.x composition) before and after surface modification according to Example 4 using a scanning electron microscope (SEM), a transmission electron microscope (TEM), and selected area electron diffraction (SAED). (Top) before surface modification of MXene (Ti.sub.3C.sub.2T.sub.x); (bottom) after surface modification of MXene.

(8) FIG. 8a shows a comparison of the appearances of a water-dispersed Ti.sub.3C.sub.2T.sub.x MXene and a MXene dispersed in chloroform (CHCl.sub.3) after surface-modification with dodecyl phosphonic acid before and after 3 months' storage at room temperature. FIG. 8b shows a comparison of the appearances of a water-dispersed Ti.sub.3C.sub.2T.sub.x MXene and a MXene dispersed in toluene after surface-modification with aminated polystyrene before and after 3 months' storage at room temperature. FIG. 8c shows the appearances of a MXene dispersed in hexanol after surface-modification with dodecyltriethoxysilane(DTES) after 1 months' storage at room temperature.

(9) FIG. 9a shows a thin film prepared by a filtration method using a surface-modified MXene ink, which was dispersed in 1-hexanol according to Example 1-1 (surface-modified with dodecyl phosphonic acid), and a polypropylene membrane (pore size: 6 μm to 70 μm) and FIG. 9b shows a thin film prepared by a filtration method using a surface-modified MXene ink, which was dispersed in 1-hexanol by surface-modifying with hexylamine according to Example 1, and a polypropylene membrane (size: 6 μm to 70 μm).

(10) FIGS. 10a and 10b shows the conductivity and sheet resistance of each thin film prepared in FIGS. 9a and 9b.

(11) FIG. 11 shows a thin film prepared by spin-coating with a surface-modified MXene ink (concentration of 1 mg/mL) which was dispersed in 1-hexanol by surface-modifying with hexylamine prepared according to Example 5. It shows an image of depositing the coating layer with one layer at a time from the uncoated cover glass on the left side to the right side.

(12) FIG. 12 shows a large-area patterned thin film formed by applying a MXene ink, which was dispersed in chloroform prepared according to the present invention, to spray-coating.

DETAILED DESCRIPTION OF THE INVENTION

(13) Hereinafter, the present invention will be described in detail through exemplary embodiments so as to enable one of ordinary skill in the art to easily practice the present invention. However, these exemplary embodiments are provided for the purpose of illustration only and are not intended to limit the scope of the present invention.

Example 1-1 to Example 1-6: Surface Modification of MXene Using Alkyl Phosphonate

(14) A delaminated Ti.sub.3C.sub.2T.sub.x MXene aqueous solution which was prepared by treating Ti.sub.3AlC.sub.2 powder (average particle diameter ≤30 μm) with LiF—HCl was diluted to 1 mg/mL to prepare 10 mL, which was followed by adding hydrochloric acid to the aqueous solution to adjust the pH to the range of 2 to 3. 7 mg of each of propyl phosphonic acid, hexyl phosphonic acid, octyl phosphonic acid, decyl phosphonic acid, dodecyl phosphonic acid, and tert-butyl phosphonic acid, which are alkyl phosphonic acids, was dissolved in 10 mL of 1-hexanol, an organic solvent, to prepare each organic solution. The aqueous solution was mixed with each organic solution and stirred at room temperature to perform an interfacial reaction. The stirring was stopped after 6 hours and the mixture was allowed to stand until the aqueous solution and the organic solution had separated, which was followed by separating the organic solution, in which MXene particles surface-modified with alkyl phosphonate were dissolved.

Example 2-1 to Example 2-2: Surface Modification of MXene Using Aryl Phosphonate

(15) Except for a case where each of phenyl phosphonic acid and benzyl phosphonic acid, which are aryl phosphonic acids, was used instead of an alkyl phosphonic acid in 1-hexanol, which is an organic solvent, by using the same method as in Example 1 above, an organic solution, in which MXene particles surface-modified with an aryl phosphonate were dissolved, was separated by carrying out an interfacial reaction.

Example 3-1 to Example 3-2: Surface Modification of MXene Using Phosphonate Having Functional Group

(16) Except for a case where each of diethyl 3-butenyl phosphonate and diethyl (2-cyanoethyl) phosphonate, which are phosphates having a functional group, was used instead of an alkyl phosphonic acid in 1-hexanol, which is an organic solvent, an organic solution, in which MXene particles surface-modified with a phosphonate having a functional group were dissolved, was separated by carrying out a reaction using the same method as in Example 1 above.

Example 4-1: Surface Modification of MXene Using Alkylamine

(17) A delaminated Ti.sub.3C.sub.2T.sub.x MXene aqueous solution which was prepared by treating Ti.sub.3AlC.sub.2 powder (average particle diameter ≤40 μm) with LiF—HCl was diluted to 1 mg/mL to prepare 10 mL. The pH of the above aqueous solution was about 5. Each organic solution was prepared by dissolving 40 mg of an alkylamine such as hexylamine, dodecylamine, etc. in 10 mL of an organic solvent (dichloromethane, chloroform, chlorobenzene, benzene, toluene, and hexane). The above aqueous solution was mixed with each organic solution and stirred at room temperature to perform an interfacial reaction. The stirring was stopped after 24 hours and the mixture was allowed to stand until the aqueous solution and the organic solution had separated, which was followed by separating the organic solution, in which MXene particles surface-modified with an alkylamine were dispersed. In order to facilitate the separation, a step of breaking the emulsion formed was additionally carried out by applying ultrasonic waves prior to the separation of an organic solution as needed.

Example 4-2: Surface Modification of MXene Using Aminated Hydrophobic Polymer

(18) Except for a case where an aminated hydrophobic polymer (polystyrene comprising —NH.sub.2 at the end, MW=5,000) was used instead of an alkylamine, an organic solution, in which MXene particles surface-modified with an aminated hydrophobic polymer were dissolved, was separated by carrying out an interfacial reaction using the same method as in Example 4-1 above.

Example 5: Surface Modification of MXene Using Silane

(19) Except for a case where dodecyltriethoxysilane was used instead of an alkyl phosphonic acid in hexanol, which is an organic solvent, by using the same method as in Example 1 above, an organic solution, in which MXene particles surface-modified with a dodecyltriethoxysilane were dissolved, was separated by carrying out an interfacial reaction.

Experimental Example 1-1: Distribution of MXene Before and After Surface Modification Reaction

(20) FIG. 3a shows the distribution of a MXene before and after a surface modification reaction when 1-hexanol, having a lower density than water, was used as an organic solvent in Examples 1 and 2. Before the interfacial reaction, Ti.sub.3C.sub.2T.sub.x MXenes were dispersed in an aqueous solution. However, through an interfacial reaction, surface-modified MXenes were shown to be moved to an organic solvent. Accordingly, after the interfacial reaction, all surface-modified MXenes moved to an organic solvent (1-hexanol) having low density and distributed in the upper layer. Thereafter, the aqueous solution was separated to obtain a surface-modified MXene ink dispersed in an organic solvent.

Experimental Example 1-2: Distribution of MXene Before and After Surface Modification Reaction

(21) FIG. 3b shows the distribution of a MXene before and after a surface modification reaction using various organic solvents in Examples 4-1 and 4-2. This shows that although MXenes were dispersed in an aqueous solution before the reaction, surface-modified MXenes moved to an organic solvent through an interfacial reaction. Accordingly, after the interfacial reaction, all surface-modified MXenes moved to an organic solvent (dichloromethane, chloroform, chlorobenzene, hexanol, benzene, toluene, and hexane). Specifically, when dichloromethane, chloroform, and chlorobenzene, having a higher density than water, were used as an organic solvent, MXenes were distributed in the bottom layer, and when hexanol, benzene, toluene, and hexane, having a lower density than water, were used as an organic solvent, MXenes were distributed in the upper layer. Thereafter, the aqueous solution layer was separated and removed to obtain a surface-modified MXene ink dispersed in an organic solvent.

Experimental Example 1-3: Distribution of MXene Before and After Surface Modification Reaction

(22) FIG. 3c shows the distribution of a MXene before and after a surface modification reaction when hexanol, having a lower density than water, was used as an organic solvent in Examples 5. Before the interfacial reaction, Ti.sub.3C.sub.2T.sub.x MXenes were dispersed in an aqueous solution. However, through an interfacial reaction, surface-modified MXenes were shown to be moved to an organic solvent. Accordingly, after the interfacial reaction, all surface-modified MXenes moved to an organic solvent (hexanol) having low density and distributed in the upper layer. Thereafter, the aqueous solution was separated to obtain a surface-modified MXene ink dispersed in an organic solvent.

Example 6-1 to Example 6-8: MXene Dispersed in Various Organic Solvent

(23) As an organic solvent, dichloroethane, dichloromethane, chloroform, anisole, chlorobenzene, benzene, toluene, and hexane were used, and for each organic solvent, propyl phosphonic acid, hexyl phosphonic acid, octyl phosphonic acid, decyl phosphonic acid, dodecyl phosphonic acid, tert-butyl phosphonic acid, phenyl phosphonic acid, benzyl phosphonic acid, diethyl 3-butenyl phosphonate, and diethyl (2-cyanoethyl) phosphonate were used as a phosphonic acid to separate an organic aqueous solution in which surface-modified MXene particles were dissolved using the same method as in Example 1 above.

(24) As a representative example among these, FIG. 4a shows an ink dispersed in an organic solvent of dichloroethane, dichloromethane, chloroform, anisole, chlorobenzene, benzene, toluene, and hexane by MXene particles surface-modified with dodecyl phosphonic acid.

(25) FIG. 4a shows organic solutions in which surface-modified MXenes were separated by dispersing in various organic solvents. Accordingly, phosphonates comprising various alkyl groups, aryl groups, or functional groups can be used to obtain a MXene ink dispersed in various organic solvents having different polarity such as dichloroethane, dichloromethane, chloroform, toluene, etc.

Example 7-1 to Example 7-6: MXene Dispersed in Various Organic Solvents

(26) An ink was prepared by dispersing surface-modified MXene particles in an organic solvent, hexanol, dichloroethane (DCE), dichloromethane (DCM), chloroform (CHCl.sub.3), chlorobenzene, benzene, and toluene with an alkylamine or an aminated hydrophobic polymer prepared according to Example 4 or 5 above, and the same is shown in FIG. 4b.

Experimental Example 2-1: NMR Analysis of Composition of MXene Surface-Modified With Phosphonate

(27) As a subject of surface modification, a MXene of Ti.sub.3C.sub.2T.sub.x composition was used. With regard to the MXene particles surface-modified with dodecyl phosphonic acid in Example 1-5, as a result of analyzing the composition of a surface-modified MXene using .sup.1H NMR, a peak was observed near 0.8 ppm to 2.2 ppm, corresponding to an alkyl group of a phosphonic acid (FIG. 5a). Additionally, as the —OH peak (10.2 ppm) of a phosphonic acid disappeared after the reaction, it is considered that a Ti—O—P bond was formed.

(28) With regard to the surface-modified MXene particles in Example 1-5, as a result of analyzing the composition of a surface-modified MXene using .sup.31P NMR, it was confirmed that a peak (38 ppm) resulting from a phosphonic acid was shifted to 25 ppm (FIG. 5b). The results show that a Ti—O—P bond was formed (Reference: Langmuir 2005, 31, 10966).

Experimental Example 2-2: NMR Analysis of Composition of MXene Surface-Modified With Amine Comprising Saturated or Unsaturated Hydrocarbon

(29) As a subject of surface modification, a MXene of Ti.sub.3C.sub.2T.sub.x composition was used. With regard to the MXene particles surface-modified with oleylamine, as a result of analyzing the composition using .sup.1H NMR, a peak was observed near 1.26 ppm to 5.35 ppm, corresponding to an alkyl group of an amine (FIG. 5c).

Experimental Example 2-3: FT-IR Analysis of Composition of MXene Surface-Modified With Aminated Hydrophobic Polymer

(30) As a subject of surface modification, a MXene of Ti.sub.3C.sub.2T.sub.x composition was used. With regard to the MXene particles surface-modified with aminated polystyrene, as a result of analyzing the composition using FT-IR (FIG. 6a), peaks were observed near 2,800 cm.sup.−1 to 3,000 cm.sup.−1 and 1,400 cm.sup.−1 to 1,600 cm.sup.−1, corresponding to a hydrophobic polymer of an amine, i.e., C—H of polystyrene. In addition, peaks were observed near 3,000 cm.sup.−1 to 3,150 cm.sup.−1 and 700 cm.sup.−1 to 1,100 cm.sup.−1, which correspond to an aromatic ring.

Experimental Example 2-4: FT-IR Analysis of Composition of MXene Surface-Modified With Silane

(31) As a subject of surface modification, a MXene of Ti.sub.3C.sub.2T.sub.x composition was used. With regard to the MXene particles surface-modified with dodecyltriethoxysilane, as a result of analyzing the composition using FT-IR (FIG. 6b), peaks not present in MXene were observed and vibration peaks were observed near 1000 cm.sup.−1, corresponding to a T-O—Si bond. The results show that a covalent bond was formed on the MXene surface and the DTES.

Experimental Example 3: SEM and TEM Analysis of Microstructure of MXene Before and After Surface Modification

(32) The microstructure of a MXene (MXene of Ti.sub.3C.sub.2T.sub.x composition) before and after surface modification according to Example 1-5 and Example 4 was analyzed using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). As can be seen in FIGS. 7a and 7b, it was confirmed that a 2D flake structure before modification was maintained intact after surface modification.

(33) In particular, when a crystal structure was confirmed through an experiment of selected area electron diffraction (SAED), it was observed that the crystal structure of a MXene after surface modification was maintained intact as before modification (FIGS. 7a and 7b).

(34) The results show that reactions between a phosphonic acid and a MXene and between an amine and a MXene occurred on the surface of particles. Accordingly, even if a 2-dimensional MXene particle is surface-modified with a functional group comprising a saturated or unsaturated hydrocarbon according to the present invention, it is considered that the inherent properties of the particle would be maintained intact.

Experimental Example 4: Comparison of Degree of Oxidization of Water-Dispersed/Organic-Dispersed MXenes

(35) The appearance of a water-dispersed Ti.sub.3C.sub.2T.sub.x MXene and a MXene, which was dispersed in chloroform (CHCl.sub.3) after surface-modification with dodecyl phosphonic acid, after storage for 1 month or more at room temperature is shown in FIG. 8a.

(36) It was observed that the water-dispersed Ti.sub.3C.sub.2T.sub.x MXene became cloudy as time passed. This indicates that the MXene was oxidized and turned into TiO.sub.x particles. Meanwhile, it was observed that a MXene, which was dispersed in chloroform, maintained its original color even after 6 months. This indicates that it is easy to store surface-modified MXenes for a long period of time by limiting their contact with water to prevent oxidization.

Experimental Example 5: Comparison of Degree of Oxidation of Water-Dispersed/Organic-Dispersed MXenes

(37) A photo was taken of the appearance of a water-dispersed Ti.sub.3C.sub.2T.sub.x MXene and a MXene which was prepared according to Example 5 and dispersed in toluene after surface-modification with aminated polystyrene for 3 months or more at room temperature, and shown in FIG. 8b.

(38) It was observed that the water-dispersed Ti.sub.3C.sub.2T.sub.x MXene became cloudy as time passed, and this indicates that the MXene was oxidized and turned into TiO.sub.x particles. Meanwhile, it was observed that the MXene dispersed in an organic solvent, specifically, the MXene which was organically dispersed in toluene, maintained its original color over 6 months. This indicates that it is easy to store surface-modified MXenes for a long period of time by limiting their contact with water to prevent oxidization.

Experimental Example 6: Degree of Oxidation of Organic-Dispersed MXenes

(39) The appearances of a MXene dispersed in hexanol after surface-modification with dodecyltriethoxysilane(DTES), after 1 months' storage at room temperature is shown in FIG. 8c.

(40) It was observed that a MXene, which was dispersed in hexanol, maintained its original color even after 1 months. This indicates that it is easy to store surface-modified MXenes for a long period of time by limiting their contact with water to prevent oxidization.

Example 8-1: Preparation of Thin Film Using MXene Ink Dispersed in Organic Solvent

(41) A thin film was prepared using a surface-modified MXene ink, which was dispersed in 1-hexanol according to Example 1-1 (surface-modified with propyl phosphonic acid), and a polypropylene membrane (pore size: 6 μm to 70 μm) with a filtration method. As shown in FIG. 9a, the prepared thin film had a thickness of 13.6 μm and showed flexibility.

(42) As can be seen in FIG. 10a, the conductivity of the thin film prepared above was 800 S/cm or more, and the sheet resistance was 0.9 Ω/□.

Example 8-2: Preparation of Thin Film Using MXene Ink Dispersed in Organic Solvent

(43) A thin film was prepared using a surface-modified MXene ink, which was prepared by surface-modifying with hexylamine according to Example 4 and dispersing in hexanol according to Example 3, and a polypropylene membrane (pore size: 6 μm to 70 μm) with a filtration method. As shown in FIG. 9b, the prepared thin film had a thickness of 20.80 μm and showed flexibility.

(44) As can be confirmed in FIG. 10b, the conductivity of the thin film prepared above was 82 S/cm or more, and the sheet resistance was 5.9 Ω/□.

Example 8-3: Second Preparation of Thin Film Using MXene Ink Dispersed in Organic Solvent

(45) A thin film was prepared by spin-coating a MXene ink, which was prepared according to Example 7 and dispersed in hexanol by surface-modifying with hexylamine, and a MXene ink, which was prepared according to Example 7 and dispersed in toluene by surface-modifying with aminated polystyrene, on a cover glass. Representatively, a photo was taken of thin films which were prepared using a MXene ink dispersed in hexanol by surface-modifying with hexylamine, and is shown in FIG. 11.

Example 8-4: Third Preparation of Thin Film Using MXene Ink Dispersed in Organic Solvent

(46) Except for a case using CHCl.sub.3 instead of toluene as an organic solvent, large-area patterning was carried out by applying a MXene ink, which was prepared according to Example 7 and dispersed in chloroform by surface-modifying with oleylamine, to a substrate covered with a mask of a desired pattern with a spray-coating process, and the result thereof is shown in FIG. 12.