KR20090029409A - Complex of ionic liquid-carbon nanotubes support containing immobilized metallic nanoparticles and preparation method thereof - Google Patents

Abstract

An ionic liquid-carbon nanotube supporter composite in which metal nanoparticle is fixed is provided to increase dynamic stability of metal nanoparticle using the carbon nanotube as a supporter and to be separated without a surfactant. An ionic liquid-carbon nanotube supporter composite in which metal nanoparticle is fixed is indicated as a chemical formula 1. In the chemical formula, the carbon nanotube is a single-walled carbon nanotube or a multi-walled carbon nanotube; X is selected from a group consisting of Cl, Br, I, OH, AlCl4, BF4,ClO4, PF6 and N(OTf)2; Y is O or NR5; R5 is selected from a group consisting of hydrogen, substituted or non-substituted straight-chain of C1 ~ C5 or side chain alkyl and substituted or non-substituted aryl of C1 ~ C5; R1 to R4 are independently selectively H, non-substituted or substituted C1 ~ C10 selected from a group consisting of OH, COOH and SO3H or side chain alkyl group or non-substituted or substituted C5-C7 aryl selected from a group consisting of OH, Br, Cl, COOH, COO-,SO3H, SO3-, first, second, third amine and C1 ~ C10 straight-chain or the side chain alkyl group; M is one selected from a group consisting of Pd, Rh, Ir, Pt and Au; n is 0 ~ 10.

Description

Complex of ionic liquid-carbon nanotubes support containing immobilized metallic nanoparticles and preparation method

The present invention relates to an ionic liquid-carbon nanotube support composite having a metal nanoparticle immobilized thereon and a method for preparing the same.

Carbon nanotubes have excellent physical, chemical, mechanical and electrical properties, and thus are one of the important new materials that can be applied to a wide variety of industries.

In particular, the carbon nanotube-nanoparticle composite can apply not only the self-characteristics of the carbon nanotubes but also the properties of the nanoparticles, and thus can be applied to a catalyst, a chemical sense, or a nano-sized electromagnetic device.

For this application, various techniques have been developed for the preparation of carbon nanotube-nanoparticle composites in which nanoparticles are immobilized on carbon nanotubes while maintaining the unique properties of carbon nanotubes and nanoparticles.

Representative methods of the related art have been reported to immobilize nanoparticles on carbon nanotubes under supercritical carbon dioxide or aqueous solution. Since the carbon nanotubes have low solubility in an aqueous solution and require very violent conditions in order to apply the above technique, the carbon nanotubes not only impair the intrinsic properties of the carbon nanotubes, but also have low practicality. [(a) Ye, X.-R .; Lin, Y .; Wang, C .; Engelhard, MH; Wang, Y .; Wai, CM J. Mater . Chem . 2004 , 14, 908. (b) Xue, B .; Chen, P .; Hong, Q .; Lin, J .; Tan, KL J. Mater . Chem . 2001 , 11, 2378.]

In order to solve the problems of the prior art, metal halides such as palladium, rhodium and the like can be carried out without deterioration of the properties of carbon nanotubes under mild conditions under recent atmospheric pressure and water pressure using a water-oil microemulsion. By reducing the carbon nanotubes on which carbonyl acid functional groups are introduced, a method of immobilizing metal nanoparticles on carbon nanotubes on which carbonyl acid functional groups are introduced has been developed [Yoon, B .; Wai, CM J. Am . Chem . Soc . 2005 , 127, 17174.]. The method has the advantage of being effective in maintaining the properties of the carbon nanotubes, but in order to form a water-oil micro-emulsion, not only a large amount of organic solvents need to be used but also need a surfactant that is difficult to separate.

The present inventors have prepared the ionic liquid of the carbon nanotubes, the reforming was carried out a study to modify the ionic liquid based on the imidazole salt in order to solve the above problems, the carbon nanotube surface [Chemstry of Materials 2006 , 18, 1546].

In general, studies have been reported to stabilize metal nanoparticles by imidazole salt-based ionic liquids by electrostatically and coordinatively [(a) Dupont, J .; Fonseca, GS; Umpierre, AP; Fichtner, PFP; Teixeira, SR J. Am . Chem . Soc . 2002 , 124, 4228. (b) Fonseca, GS; Fonseca, AP; Teixeira, SR; Dupont, J. Chem .- Eur. J. 2003 , 9, 3263. (c) Scheeren, CW; Machado, G .; Dupont, J .; Fichtner, PFP; Teixeira, SR Inorg . Chem . 2003 , 42, 4738. (d) Silverira, ET; Umpierre, AP; Rossi, LM; Machado, G .; Morais, J .; Soares, GV; Baumvol, IJR; Teixeira, SR Fichtner, PFP; Dupont, J. Chem .- Eur. J. 2004 , 10, 3734.].

Therefore, using carbon nanotubes incorporating an ionic liquid having an imidazole salt structure not only increases the stability of the metal nanoparticles immobilized on the carbon nanotubes, but also carbon nanotube-metals under very mild conditions without the use of surfactants. Expecting the development of a composite of nanoparticles, and finding that it is possible to prepare a new metal nanoparticle-carbon nanotube support complex under very mild conditions using carbon nanotubes containing an ionic liquid, the present invention was completed. .

An object of the present invention is to provide an ionic liquid-carbon nanotube support complex in which carbon nanotubes are used as a support to increase the dynamic stability of the metal nanoparticles, and to which the metal nanoparticles that can be separated without a surfactant are immobilized. .

Another object of the present invention is to provide a method for immobilizing metal nanoparticles on the ionic liquid-carbon nanotube support composite.

In order to achieve the above object, the present invention provides an ionic liquid-carbon nanotube support complex immobilized metal nanoparticles and a method for immobilizing the metal nanoparticles to the complex.

The ionic liquid-carbon nanotube support complexes to which the metal nanoparticles of the present invention are immobilized are useful for manufacturing electronic devices having improved performance by increasing the efficiency of electronic devices using carbon nanotubes as well as catalysts using immobilized metals. Can be used.

Hereinafter, the present invention will be described in detail.

The present invention provides an ionic liquid-carbon nanotube support complex to which metal nanoparticles represented by Formula 1 are immobilized.

<Formula 1>

In the above formula,

The carbon nanotubes are single-walled carbon nanotubes or multiwalled carbon nanotubes;

X is selected from the group consisting of Cl, Br, I, OH, AlCl ₄ , BF ₄ , ClO ₄ , PF ₆ and N (OTf) ₂ ;

Y is O or NR ₅ , wherein R ₅ is selected from the group consisting of hydrogen, unsubstituted or substituted C ₁ to C ₅ straight or branched chain alkyl and unsubstituted or substituted C ₅ to C ₇ aryl, Preferably R ₅ is hydrogen, methyl, ethyl, propyl, butyl or benzyl;

R ¹ to R ⁴ are independently of one another or optionally C ₁ to C ₁₀ straight or branched chain alkyl group, unsubstituted or substituted with any one selected from the group consisting of H, unsubstituted or OH, COOH and SO ₃ H OH, Br, Cl, COOH, COO ^-, SO ₃ H, SO ₃ ^-, 1 primary, secondary and tertiary amines, and C ₁ ~ C ₁₀ straight-chain or by any member selected from the group consisting of branched alkyl substituted C ₅ -C ₇ aryl;

M is any one selected from the group consisting of Pd, Rh, Ir, Pt and Au;

N is from 0 to 10.

In addition, the ratio of the metal nanoparticles in the ionic liquid-carbon nanotube support composite to which the metal nanoparticles are immobilized is 5 to 60% by weight. If the ratio is less than 5% by weight, the efficiency may be reduced when applied as a catalyst, and if the ratio exceeds 60% by weight, the size of the metal nanoparticles is increased, so that the specific surface area is relatively decreased, thereby decreasing the efficiency of the catalyst. .

In addition, the present invention as shown in Scheme 1,

Step of modifying the carbon nanotubes with a carboxyl group in an acid solution (step 1)

Reacting the carbon nanotubes modified with the carboxyl group of step 1 with thionyl chloride, and then reacting with the ionic liquid to reform (step 2); And

In the step 2, the metal nanotube comprising the step of reducing the carbon nanotubes and metal precursors modified with an ionic liquid in water, alcohol or a mixed solvent of water and alcohol under a hydrogen pressure of 1 ~ 100 atmospheric pressure (step 3) Provided is a method for preparing an ionic liquid-carbon nanotube support composite to which particles are immobilized.

<Scheme 1>

(X, Y, R ¹ in Scheme ¹ R ⁴ and M are the same as defined in Formula 1 of claim 1,

M (Z) n is a metal precursor as Na ₂ PdCl ₄ , PdCl ₂ , Pd (OAc) ₂ , RhCl ₃ , [Rh (COD) Cl] ₂ , IrCl ₃ , [Ir (COD) Cl] ₂ , Na ₂ PtCl ₄ , PtCl ₂ And AuCl _3. )

Hereinafter, a method for preparing an ionic liquid-carbon nanotube support composite to which metal nanoparticles are immobilized according to the present invention will be described in detail step by step.

First, the step 1 according to the present invention is a step of modifying the carbon nanotubes with a carboxyl group in an acid solution.

The carbon nanotubes of step 1 may use purified single-walled or multi-walled carbon nanotubes. The acid solution may be sulfuric acid, nitric acid, or a mixed solution thereof. The acid solution may be heated to modify the carboxyl group on the surface of the carbon nanotubes.

Next, step 2 according to the present invention is a step of reforming by reacting the carbon nanotubes modified with the carboxyl group of step 1 with thionyl chloride, followed by reaction with an ionic liquid.

In the modification of step 2, the carbon nanotubes modified with carboxyl groups are reacted with thionyl chloride (SOCl ₂ ) to generate an acid chloride, followed by reaction with an ionic liquid to reform the surface of the carbon nanotubes. The carbon nanotube and the ionic liquid modified by reacting with the ionic liquid after the substitution with the acid chloride in step 2 form a covalent bond, whereas when the carboxyl group and the ionic liquid are reacted without replacing the carboxyl group with the acid chloride, Nanotubes and ionic liquids consist of relatively weak bonds of physical adsorption, which can cause removal of unreacted ionic liquids.

Next, step 3 is a step of immobilizing the metal nanoparticles on the carbon nanotubes by reacting the carbon nanotubes and the metal precursor modified with the ionic liquid in the step 2.

In the reduction of the step 3, the molar ratio of the carbon nanotubes to which the ionic liquid is modified in the step 2 and the metal precursor is in the range of 1: 1 to 50 or 1 to 50: 1. If it is out of the range there is a problem that the size of the metal nanoparticles increase to decrease the efficiency of the catalyst. Moreover, it is preferable that reaction pressure is the hydrogen pressure of 1-100 atm. Furthermore, it is preferable that reaction temperature is 0-100 degreeC, and reaction time is 30 minutes-24 hours. Water, alcohol or a mixed solvent thereof may be used as the reaction solvent, wherein the alcohol is preferably methanol or ethanol.

The metal precursors used in the present invention are Na ₂ PdCl ₄ , PdCl ₂ , Pd (OAc) ₂ , RhCl ₃ , [Rh (COD) Cl] ₂ , IrCl ₃ , [Ir (COD) Cl] ₂ , PtCl _{2 ,} AuCl ₃ may be used, but is not limited thereto as long as it is a metal nanoparticle precursor that can be reduced and immobilized on the surface of the metal nanoparticle.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely to illustrate the invention, the present invention is not limited by the following examples.

Example 1 Preparation of Ionic Liquid-Carbon Nanotube Support Composites Immobilized with Metal Nanoparticles

Step 1. With carboxyl group Modified  Manufacture of Carbon Nanotubes

1.0 g of multi-walled carbon nanotubes with purity of 95% or more was put in 60% nitric acid and subjected to ultrasonic treatment (Bransonic, model 1510R-PTH, 42 kHz) for 1.5 hours while maintaining 50 ° C. The carbon nanotubes sonicated in the nitric acid were cut and the surface was modified with a carboxyl group.

After mixing 2 L of distilled water to the solution containing the carbon nanotubes modified with carboxyl groups, the mixture was centrifuged at 14,000 rpm, and washed several times with distilled water and acetone. The carboxyl-modified carbon nanotubes were filtered and washed again with distilled water until the pH was 7.0. Thereafter, the carbon nanotubes modified with carboxyl groups were filtered and dried at 60 ° C. for 24 hours in a vacuum atmosphere.

Step 2. With ionic liquid Modified  Manufacture of Carbon Nanotubes

In step 1, 100 mg of the carboxyl-modified carbon nanotubes were mixed in 30.0 ml of SOCl ₂ , and stirred in a nitrogen atmosphere for 24 hours. The mixed solution was filtered, washed with anhydrous THF, and dried in a vacuum atmosphere at room temperature for 2 hours to prepare a carbon nanotube modified with -COCl. 99 mg of the -COCl group-modified carbon nanotube prepared above and 30 ml of 1-butyl-3- (3-aminopropyl) imidazolium bromide (1-Buthyl-3- (3-aminopropyl) imidazolium bromide) were mixed. The solution was stirred for 24 hours at 120 ° C. under a nitrogen atmosphere and then filtered using a polytetrafluoroethylene (PTFE) filtration membrane and washed sequentially with 1 N hydrochloric acid solution, concentrated sodium bicarbonate (NaHCo ₃ ) and anhydrous THF. All. Next, the mixture was washed with distilled water to pH 7.0 and filtered. The carbon nanotubes modified with the filtered ionic liquid were washed with alcohol, and then dried in vacuo at 60 ° C. overnight.

Step 3. Preparation of Carbon Nanotubes to Which Metal Nanoparticles are Fixed

In step 2, 10 mg of carbon nanotubes modified with 1-butyl-3- (3-aminopropyl) imidazolium and 0.9 ml of 0.1N sodium palladium tetrachloride (Na ₂ PdCl ₄ ) as metal precursors were dissolved in 6 ml of water. After the mixture was stirred for 1 hour at room temperature under hydrogen atmosphere at 1 atmosphere, reduced, washed several times with distilled water, and dried to prepare a carbon nanotube support complex having palladium nanoparticles immobilized thereon.

<Analysis>

1. Transmission Electron Microscopy (TEM)

Carbon nanotubes modified with an ionic liquid in which palladium metal nanoparticles are immobilized according to the present invention are shown in FIG. 1 by analyzing the shape of the immobilized palladium metal nanoparticles using a transmission electron microscope.

As shown in FIG. 1, it was confirmed that 3 to 20 nm-sized palladium metal nanoparticles were uniformly and densely distributed on the surface of the carbon nanotubes.

2. Inductively Coupled Plasma (ICP)

According to the present invention, the relative amount of the immobilized palladium metal nanoparticles was measured using an inductively coupled plasma of carbon nanotubes modified with ionic liquids.

As a result of the analysis, it was confirmed that 55 wt% of the palladium metal nanoparticles were immobilized on the carbon nanotubes.

3. X-ray photoelectron spectroscopy (XPS)

According to the present invention, the carbon nanotubes modified with the ionic liquid in which the palladium metal nanoparticles are immobilized are measured in X-ray photoelectron spectroscopy, and the binding energy of the palladium metal nanoparticles immobilized is shown in FIG. 2. Through this analysis, the oxidation state of the palladium metal nanoparticles was analyzed.

As shown in FIG. 2, the palladium metal nanoparticles were found to have peaks of 335.3 eV and 340.6 eV representing a typical structure of Pd (O) (PdO), and the palladium metal nanoparticles according to the present invention had a PdO structure. It was confirmed that the fixed on the surface of the carbon nanotubes.

4. X-ray Diffraction (XRD)

In order to confirm the crystallinity of the palladium metal nanoparticles immobilized on the carbon nanotubes modified with an ionic liquid according to the present invention was shown in Figure 3 by X-ray diffraction analysis.

As shown in FIG. 3, the peaks representing the crystals of the palladium metal nanoparticles appeared strongly and accurately, and it was confirmed that the palladium metal nanoparticles have excellent crystallinity and are fixed to the carbon nanotubes.

Experimental Example 1 Measurement of Catalytic Activity of Palladium Metal Nanoparticles Immobilized on Carbon Nanotubes Modified with Ionic Liquid

In order to examine the catalytic reaction of the palladium metal nanoparticles immobilized on the ionic liquid-modified carbon nanotubes according to the present invention, the reaction of hydrogenating a carbon-carbon double bond using a complex of the present invention is performed at 1 atm of hydrogen. Under pressure, it was performed at room temperature.

As a result, the reaction was completed in 10 minutes, resulting in a catalyst turnover frequency (TOF) of 600 h ⁻¹ , and the present invention can be repeatedly reused 50 times, resulting in a total conversion of 5000. appear. Thus, it was confirmed that the palladium metal nanoparticles immobilized on the carbon nanotubes modified with the ionic liquid according to the present invention have an excellent effect as a catalyst.

1 is a transmission electron microscope (TEM) photograph of an embodiment according to the present invention; ((a) ruler size 50 nm, (b) ruler size 20 nm)

2 is an X-ray photoelectron spectroscopic analysis graph of the metal nanoparticles included in one embodiment according to the present invention;

3 is an X-ray diffraction analysis graph of metal nanoparticles included in one embodiment according to the present invention.

Claims (8)

An ionic liquid-carbon nanotube support complex to which metal nanoparticles represented by Formula 1 are immobilized. <Formula 1>

In the above formula, The carbon nanotubes are single-walled carbon nanotubes or multiwalled carbon nanotubes; X is selected from the group consisting of Cl, Br, I, OH, AlCl ₄ , BF ₄ , ClO ₄ , PF ₆ and N (OTf) ₂ ; Y is O or NR ₅ , wherein R ₅ is selected from the group consisting of hydrogen, unsubstituted or substituted C ₁ to C ₅ straight or branched chain alkyl and unsubstituted or substituted C ₅ to C ₇ aryl; R ¹ to R ⁴ are independently of one another or optionally C ₁ to C ₁₀ straight or branched chain alkyl group, unsubstituted or substituted with any one selected from the group consisting of H, unsubstituted or OH, COOH and SO ₃ H OH, Br, Cl, COOH, COO ^-, SO ₃ H, SO ₃ ^-, 1 primary, secondary and tertiary amines, and C ₁ ~ C ₁₀ straight-chain or by any member selected from the group consisting of branched alkyl substituted C ₅ -C ₇ aryl; M is any one selected from the group consisting of Pd, Rh, Ir, Pt and Au; N is from 0 to 10. The ionic liquid-carbon nanotube support composite of claim 1, wherein R ₅ is hydrogen, methyl, ethyl, propyl, butyl or benzyl. The ionic liquid-carbon nanotube support composite of claim 1, wherein the ratio of the metal nanoparticles in the composite is 5 to 60 wt%. Reforming the carbon nanotubes to carboxyl groups in an acid solution (step 1) Reacting the carbon nanotubes modified with the carboxyl group of step 1 with thionyl chloride and then reacting with the ionic liquid to reform (step 2); In the step 2, a method for producing an ionic liquid-carbon nanotube support complex to which the metal nanoparticles are immobilized comprising the step of reducing the carbon nanotubes and metal precursors modified with an ionic liquid in a solvent (step 3). <Scheme 1>

X, Y, R ¹ in Scheme ¹ R ⁴ and M are the same as defined in Formula 1 of claim 1, M (Z) n is a metal precursor as Na ₂ PdCl ₄ , PdCl ₂ , Pd (OAc) ₂ , RhCl ₃ , [Rh (COD) Cl] ₂ , IrCl ₃ , [Ir (COD) Cl] ₂ , Na ₂ PtCl ₄ , PtCl ₂ And AuCl ₃ . The method of claim 4, wherein the acid solution of step 1 is sulfuric acid or nitric acid solution or a mixture thereof. 5. The method of claim 4, wherein the modifying of Step 2 comprises replacing the carboxyl group with an acid chloride and then modifying the ionic liquid. 6. The method of claim 4, wherein the reduction of the step 3 is a metal nano-molecular ratio of the carbon nanotubes and the metal precursor in which the ionic liquid is modified in the step 2 is 1: 1 to 50 or 1 to 50: 1 A method for preparing an ionic liquid-carbon nanotube support composite in which particles are immobilized. 5. The ionic liquid of claim 4, wherein the reduction of step 3 is performed for 30 minutes to 24 hours at a reaction temperature of 0 to 100 ° C. under a hydrogen pressure of 1 to 100 atm. 6. Method for preparing a carbon nanotube support composite.

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