CN101746745A

CN101746745A - Method for preparing and purifying carbon nano tubes, carbon nano tubes and carbon nano tube elements

Info

Publication number: CN101746745A
Application number: CN200810178857A
Authority: CN
Inventors: 梶浦尚志; 李勇明; 王钰; 刘云圻; 魏大程; 张洪亮; 黄丽平
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 2008-12-04
Filing date: 2008-12-04
Publication date: 2010-06-23
Also published as: JP2010132543A; US20100143234A1

Abstract

The invention discloses a method for preparing and purifying carbon nano tubes. The application also relates to carbon nano tubes and elements using the carbon nano tubes. The method for preparing and purifying carbon nano tubes comprises the steps that: (a) carbon nano tubes are produced in the atmosphere of catalyst and arbitrarily selected auxiliary cocatalyst in an arc charging manner; (b) materials which can react with metallic elements existing in the atmosphere of the catalyst and/or arbitrarily selected cocatalyst to produce complex compound complexes with the metallic elements existing in the atmosphere of the catalyst and/or arbitrarily selected cocatalyst to obtain the complex compound and (c) the complex compound is removed.

Description

Method, carbon nanotube and the carbon nano-tube element of preparation and purifying carbon nano-tube

Technical field

The application relates to the method for preparing carbon nanotube (CNT), the method for purifying carbon nano-tube (CNT), carbon nanotube that is obtained by these methods and the carbon nano-tube element that contains this carbon nanotube.More specifically, the application relates to via arc discharge method and prepares the method for carbon nanotube, the method for purifying carbon nano-tube, carbon nanotube that is obtained by these methods and the carbon nano-tube element that contains this carbon nanotube.Different with ordinary method, catalyzer that the application's preparation method or purification process adopt complexing technology to remove to adopt in the arc discharge method and/or optional promotor.

Background technology

Carbon nanotube (CNT) has electricity, mechanics and the chemical property of many excellences as one-dimensional carbon nano material, therefore is subjected to people's attention day by day.Along with to the deepening continuously of nano materials research, the broad prospect of application of carbon nanotube is also just constantly emerged in large numbers, and for example is used for field emitting electronic source, nano field-effect transistor, hydrogen storage material and high strength fibre etc.

Carbon nanotube can be divided into Single Walled Carbon Nanotube (SWNT) and multi-walled carbon nano-tubes (MWNT) according to the number of plies of the carbon atom that forms tube wall, and multi-walled carbon nano-tubes also is appreciated that to being formed by different diameter Single Walled Carbon Nanotube suit.In the research of reality and using, the less multi-walled carbon nano-tubes of Single Walled Carbon Nanotube, the number of plies is owing to having consequence at special performances that the aspect had such as electrical property, thermal characteristics, machinery and chemical properties.

The method for preparing carbon nanotube commonly used comprises arc discharge method, chemical Vapor deposition process (CVD) and laser evaporation method etc.Up to now, arc discharge method is one of most effectual way of scale operation high quality carbon nanotube.

Yet, prepare in the process of carbon nanotube at arc discharge method, all can generate some impurity simultaneously usually, for example carbon nano-particle of graphite particulate, decolorizing carbon and other form, and the promotor that has metal catalyst particles and choose wantonly.These impurity and carbon nano tube hybrid have all brought great inconvenience for more deep research of carbon nanotube and application together.Thereby generally all need to take various physico-chemical processes that the carbon nanotube head product of preparation gained is carried out purifying, to obtain the higher carbon nanotube of purity.Normally used chemical purification method has liquid phase oxidation and vapour phase oxidation process.For example, people such as K.Tohji.T.Goto have proposed to use the method (K.Tohji.T.Goto et al.J.Phys.Chem.1996,101,1974) of hot liquid.People such as Z.Shi have proposed vapour phase oxidation process (Z.Shi et al.SolidState Commun.1999,112,35), and people such as E.Mizoguti have proposed catalytic oxidation (E.Mizoguti et al.Chem.Phys.Lett.2000,321,297).And the nitric acid circumfluence method has obtained broad research, for example referring to people's such as J.L.Zimmerman article (J.L Zimmerman et al.Chem.Mater.2000,12,1361).In addition, have been found that by the initial selectivity oxidation and remove decolorizing carbon that then the purification process that refluxes can effectively be removed metal in the reaction product (referring to, K.Tohji et al.Nature 1996,383,679) in concentrated nitric acid.

These methods of purification are well known in the art, they utilized carbon nanotube more stable than impurity such as agraphitic carbon, metal catalyst particles, more be not easy to the character of oxidation, thereby can at first remove these impurity in the product, reach the purpose of purification.Vapour phase oxidation process can have oxygen (or air) oxidation style and carbonic acid gas oxidation style etc. according to the difference of oxidizing atmosphere.Liquid-phase oxidation agent commonly used in the liquid phase oxidation comprises potassium permanganate, salpeter solution or potassium bichromate etc.In addition, also have physical methods such as centrifugal method and micro-filtration to carry out separating of carbon nanotube.These methods can be used separately, also can use one or more combination.For example, can adopt vapour phase oxidation process such as air oxidation process to remove to be easy in the carbon nanotube impurity of removing such as decolorizing carbon; Adopt liquid phase oxidation such as nitric acid oxidation method to remove to be difficult in the carbon nanotube impurity of removing such as metal catalyst particles.Simultaneously, can also obtain carbon nanotube behind the purifying in conjunction with centrifuging.

Yet, at present the subject matter that exists how under the prerequisite of destroying carbon nanometer tube not with the carbon nanotube purifying of preparation.In the prior art, the liquid-phase oxidation of employing for example, refluxes in nitric acid and carries out the method for purifying, will cause the destruction of tube wall.Even the employing vapour phase oxidation process because the oxidizing temperature height that adopts is generally 470 ℃, can cause damage to carbon nanotube equally.

In addition, in arc discharge method, when for example using the Y-Ni alloy as catalyzer, after reaction was finished, this catalyzer was present on the inside or surface of reaction product, was difficult to remove by the method that mineral acid refluxes.Even removed most of granules of catalyst by long reaction, also can the while destroying carbon nanometer tube.Can cause the quality of carbon nanotube to descend like this, particularly electroconductibility reduces.

And the purification process that adopts strong acid to reflux causes the gained carbon nanotube to have following problem:

A. in carbon skeleton, there are 5 yuan or 7 yuan of rings, rather than 6 yuan of common rings, the carbon nanotube bending caused;

B.Sp ³Hydridization (R=H and OH) defective;

C. oxidizing condition causes carbon skeleton to be damaged, and fault location is introduced the COOH group; With

D. carbon nanotube is open-ended, and introduces the COOH group end capping.

Above problem is shown in Fig. 1.

Therefore, press for and a kind ofly can under the condition of not damaging carbon nanotube, prepare the method for carbon nanotube and purifying carbon nano-tube.

Summary of the invention

The application's method can prepare carbon nanotube and purifying carbon nano-tube, and carbon nanotube is not caused damage, particularly carbon nanotube side-wall is not caused damage.

The application's first aspect provides a kind of method for preparing carbon nanotube, said method comprising the steps of:

(a) in the presence of catalyzer and optional promotor by arc discharge method production carbon nanotube,

(b) use and can form the metallic element complexing that exists in the material of complex compound and catalyzer and/or the optional promotor with the metallic element that exists in catalyzer and/or the optional promotor, obtain complex compound and

(c) remove described complex compound.

In a kind of embodiment of the application's first aspect, in step (a), use promotor.

At this moment, preferred described promotor is FeS.

In a kind of embodiment of the application's first aspect, catalyzer is selected from the oxide compound of lanthanide series metal, transition metal, the perhaps mixture of nickel and rare earth element, and aforementioned mixture of catalysts.

At this moment, preferred described catalyzer is selected from Y-Ni alloy, Fe-Ni alloy, Fe-Co alloy, Co-Ni alloy, Rh-Pt alloy and Ce-Ni alloy.

In a kind of embodiment of the application's first aspect, step (b) may further comprise the steps:

(d) metallic element in catalyzer and/or the optional promotor is converted into ion, and

(e) use the described material that can form complex compound,, obtain complex compound with described ion complexation with the metallic element that exists in catalyzer and/or the optional promotor.

At this moment, preferred steps (d) may further comprise the steps:

(f), obtain the oxide compound of catalyzer and/or optional promotor with catalyzer and/or optional promotor oxidation.

At this moment, further preferably can be selected from the aminopolycanboxylic acid with the material that the metallic element that exists in catalyzer and/or the optional promotor forms complex compound.

In this embodiment, preferred employed aminopolycanboxylic acid is selected from ethylenediamine tetraacetic acid (EDTA) (EDTA), anti-form-1,2-diamino-cyclohexane-N, N, N ', N '-tetraacethyl hydrate (CYDTA), diethylene triaminepentaacetic acid(DTPA) (DTPA) and triethylenetetraaminehexaacetic acid (TTHA).

At this moment, further preferred aminopolycanboxylic acid is triethylenetetraaminehexaacetic acid (TTHA).

And, further preferably will change the form of salt into, so that promote removing of complex compound by the complex compound that the aminopolycanboxylic acid forms.

In a kind of embodiment of the application's first aspect, (d) is further comprising the steps of for step:

(g) use acid and described oxide compound reaction, obtain catalyzer and/or optional promoter metal element ion.

In a kind of embodiment of first aspect, for the material that can form complex compound, preferred tetrahydrofuran (THF), trialkyl phosphine, 6-caprolactone, ε-Ji Neixianan, dimethyl formamide and dimethyl sulfoxide (DMSO) with the metallic element that exists in catalyzer and/or the optional promotor.

In addition, in a kind of embodiment of first aspect, preferred complex compound be selected from M[(NC) ₂CC (OCH ₂CH ₂OH) C (CN) ₂] ₂(4,4 '-bPy) (H ₂O) ₂, double-core [M ' { (phen) ₂} ₂V ₄O ₁₂] C ₆H ₁₂OH ₂O and [Ni (L) (H ₂O) ₃2HO], wherein M is selected from Ni, Co and Fe, and M ' is selected from Ni and Co, and bPy is a dipyridyl, and phen is a phenyl, L is (a 2-methoxycarbonyl methyl-imino-5-methyl-thiazole-3-base-acetate).

In the another kind of variant in this embodiment of the application, step (f) comprises uses oxygen-containing gas to come oxide catalyst and/or optional promotor.

At this moment, time and the temperature of preferably using oxygen-containing gas to carry out oxidation is enough to catalyzer and/or optional promotor are changed into oxide compound.More preferably, described oxygen-containing gas is an air.Further preferredization temperature is 80-300 ℃, and also preferred oxidization time is 1-20 hour.

In a kind of embodiment of the application's first aspect, the application's method is carried out centrifugation step after also being included in and removing described complex compound.

At this moment, preferred centrifugation step was carried out 1-20 hour with 5000-30000rpm.

In all embodiments of the application's first aspect, preferred carbon nanotube is a Single Walled Carbon Nanotube.

The application's second aspect provide a kind of method of purifying carbon nano-tube, wherein said carbon nanotube be in the presence of catalyzer and optional promotor by arc discharge method production, the method for described purifying carbon nano-tube may further comprise the steps:

(I) use and can form the metallic element complexing that exists in the material of complex compound and catalyzer and/or the optional promotor with the metallic element that exists in catalyzer and/or the optional promotor, obtain complex compound and

(II) remove described complex compound.

In a kind of embodiment of the application's second aspect, arc discharge method has used promotor.

At this moment, preferred described promotor is FeS.

In a kind of embodiment of the application's second aspect, catalyzer is selected from the oxide compound of lanthanide series metal, transition metal, the perhaps mixture of nickel and rare earth element, and aforementioned mixture of catalysts.

In a kind of embodiment of the application's second aspect, step (I) may further comprise the steps:

(III) metallic element in catalyzer and/or the optional promotor is converted into ion, and

(IV) use the described material that can form complex compound,, obtain complex compound with described ion complexation with the metallic element that exists in catalyzer and/or the optional promotor.

At this moment, preferred steps (III) may further comprise the steps:

(V), obtain the oxide compound of catalyzer and/or optional promotor with catalyzer and/or optional promotor oxidation.

In a kind of embodiment of the application's second aspect, (III) is further comprising the steps of for step:

(VI) use acid and described oxide compound reaction, obtain catalyzer and/or optional promoter metal element ion.

In a kind of embodiment of second aspect, for the material that can form complex compound, preferred tetrahydrofuran (THF), trialkyl phosphine, 6-caprolactone, ε-Ji Neixianan, dimethyl formamide and dimethyl sulfoxide (DMSO) with the metallic element that exists in catalyzer and/or the optional promotor.

In addition, in a kind of embodiment of second aspect, preferred complex compound be selected from M[(NC) ₂CC (OCH ₂CH ₂OH) C (CN) ₂] ₂(4,4 '-bPy) (H ₂O) ₂, double-core [M ' { (phen) ₂} ₂V ₄O ₁₂] C ₆H ₁₂OH ₂O and [Ni (L) (H ₂O) ₃2HO], wherein M is selected from Ni, Co and Fe, and M ' is selected from Ni and Co, and bPy is a dipyridyl, and phen is a phenyl, L is (a 2-methoxycarbonyl methyl-imino-5-methyl-thiazole-3-base-acetate).

In a kind of embodiment of the application's second aspect, the application's method is carried out centrifugation step after also being included in and removing described complex compound.

In all embodiments of the application's second aspect, preferred carbon nanotube is a Single Walled Carbon Nanotube.

The application's the third aspect provides according to the prepared carbon nanotube of the method for the application's first aspect and second aspect.Compare with the carbon nanotube that the method that adopts prior art obtains, the tube wall of the carbon nanotube that the method by the application obtains is not damaged.

The application's fourth aspect provides the carbon nano-tube element that comprises according to the carbon nanotube of the application's third aspect.

In the application's all respects, carbon nanotube (CNT) is preferably Single Walled Carbon Nanotube (SWNT).

Detailed description hereinafter will make the application's other purpose and aspect become obvious.But should be appreciated that, though detailed description and specific embodiment show the application preferred embodiment, but they only are illustrative, and those skilled in the art clearly can make various changes and version by understanding following detailed description the in detail in the application's spirit and scope.

Description of drawings

Fig. 1 shows the synoptic diagram of the carbon nanotube that uses acid backflow acquisition;

Fig. 2 shows the synoptic diagram that the application is used to prepare the electric arc furnace of carbon nanotube;

Fig. 3 shows the synoptic diagram that uses the CYDTA purifying carbon nano-tube;

Fig. 4 shows the Raman spectrum that uses the carbon nanotube that EDTA and CYDTA purifying obtain.In Fig. 4, also show the spectrum of commercially available P3 carbon nanotube (P3, from Carbon Solutions.Inc. purity greater than 85%);

Fig. 5 shows the XPS collection of illustrative plates that uses the carbon nanotube that the EDTA purifying obtains;

Fig. 6 a is the SEM of not purified carbon nanotube, and Fig. 6 b is the SEM of the carbon nanotube that uses the TTHA purifying and obtain;

Fig. 7 shows the TEM that uses the carbon nanotube that the TTHA purifying obtains.In Fig. 7, Fig. 7 a is only different in existence aspect the magnification with Fig. 7 b;

Fig. 8 shows and is using TTHA purifying front and back, the Raman spectrum of carbon nanotube;

Fig. 9 shows the XPS collection of illustrative plates that uses TTHA purifying and the carbon nanotube that uses conventional acid treatment to obtain;

Figure 10 shows the carbon nano-tube film that uses the made of carbon nanotubes that obtains behind the TTHA purifying; With

Figure 11 shows the carbon nano-tube film of system film example 1 preparation and the sheet resistance of the film that Comparative Examples 1 prepares.

Figure 12 (a) shows the steam generator that uses in this application; (b) show glass bushing structural section synoptic diagram at steam generator shown in (a).

Embodiment

Describe some exemplary of the application below with reference to the accompanying drawings in detail.

The application's first aspect

In first aspect, the application provides a kind of method for preparing carbon nanotube, said method comprising the steps of:

(c) remove complex compound.

Below each step is described in detail.

(1) arc discharge method

Arc discharge method is to be used to one of processing method for preparing carbon nanotube the earliest.The application's the method for preparing carbon nanotube is not particularly limited for arc discharge method.The application can use conventional arc discharge method to obtain not purified carbon nanotube.Under regard to the employed equipment of arc discharge method, condition and raw material etc. and do simple description.

Fig. 2 shows the synoptic diagram of the electric arc furnace 100 that is used to prepare carbon nanotube in the application's the embodiment.This electric arc furnace comprises vacuum chamber 160, negative contact 110, negative electrode 120, anode 130, positive contact 140 and linear feeding device 150.Negative electrode 120 is generally the graphite rod of diameter thick (for example about 13mm), also can adopt for example metal electrode of copper; Anode 130 is the graphite rod of diameter less (for example about 6mm).

In a kind of embodiment of the application, be prepared as follows the graphite anode rod that is used for anode 130.Hole of center drill at graphite anode rod.With catalyzer, the optional promotor anode mixture that the back obtains with the graphite uniform mixing of claying into power, and then this mixture is filled in the hole of graphite anode rod and compacting to form the anode 130 of arc-over.This anode 130 can also form this mixture forming then by catalyzer and optional promotor being mixed in the graphite to obtain anode mixture to form graphite anode rod.

Before carrying out arc-over, vacuum chamber 160 is evacuated, and then to the mixture that wherein injects rare gas element (for example helium or argon gas), hydrogen, nitrogen or these gases as shielding gas.Connect after the power supply, (this distance remains a predetermined constant value usually, and for example about 1～5mm) with at anode 130 and the stable arc-over of negative electrode 120 generations can to adjust distance between negative electrodes 120 and the anode 130 by linear feeding device 150.In when beginning, negative electrode 120 should not contact with anode 130, thereby does not have initial current to produce, then gradually moving anode 120 with near negative electrode 130 up to producing electric arc.In discharge process, between anode 130 and negative electrode 120, produce the high speed plasma flow, make negative electrode 120 and anode 130 surfaces reach high temperature, for example can be respectively about more than 3000 ℃ and 5000 ℃, and cause anode 130 to evaporate carbon clusters and consumption gradually at a high speed.High-temperature area between negative electrode 120 and anode 130 bunch can form carbon nanotube from the carbon of anode 130 evaporation, and these carbon nanotubes are full of whole vacuum chamber, is deposited on vacuum chamber 160 walls and/or on the negative electrode 120.The carbon clusters of these evaporations can be full of whole vacuum chamber, thereby locates nucleation and grow to obtain carbon nanotube at negative electrode 120, vacuum-chamber wall etc. then.Anode only needed just be consumed in about ten minutes usually, thereby finished exoelectrical reaction, made the vacuum chamber cooling then.

After reaction finishes,, can in vacuum chamber 160, collect following several product: the cloth shape soot formation thing (cloth-like soot) on the locular wall of vacuum chamber 160 through fully cooling; Be suspended on the netted soot formation thing (web-like soot) between locular wall and the negative electrode; Settling (deposit) in cathode end; And " collar " shape soot formation thing (collar-like soot) around settling.Resulting carbon nanotube combines with Van der Waals force usually, is arranged as the hexagonal crystal structure.Carbon nanotube particularly Single Walled Carbon Nanotube mainly for example appears at three parts: cloth shape soot formation thing, netted soot formation thing and " collar " shape soot formation thing.In these three parts, particularly the purity of Single Walled Carbon Nanotube is the highest for carbon nanotube in the netted soot formation thing, minimum in cloth shape soot formation thing, falling between in " collar " shape soot formation thing.Carbon nanotube and some impurity, for example decolorizing carbon and metal catalyst particles etc. exist simultaneously.These impurity can be removed by follow-up purification step.This point will be discussed in more detail below.

Prepare in the process of carbon nanotube in the application, need to use catalyzer.Catalyzer plays an important role for the growth of carbon nanotube especially Single Walled Carbon Nanotube.Used in this application catalyzer can be the oxide compound of lanthanide series metal, transition metal, the perhaps mixture of nickel and rare earth element, and aforementioned mixture of catalysts.In addition, catalyzer can also be the mixture of metallic nickel (Ni) and rare earth element, and these rare earth elements are such as being Y, Ce, Er, Tb, Ho, La, Nd, Gd, Dy or their mixture etc.In a kind of embodiment of the application, catalyzer is preferably selected from Y-Ni alloy, Fe-Ni alloy, Fe-Co alloy, Co-Ni alloy, Rh-Pt alloy or Ce-Ni alloy.

Prepare in the method for carbon nanotube in the application, can choose the use promotor wantonly.It is generally acknowledged that promotor also plays an important role for the growth of carbon nanotube especially Single Walled Carbon Nanotube, particularly have important effect in the purity that improves carbon nanotube and the aspects such as diameter Distribution of controlling carbon nanotube.Therefore, in this application, preferably use FeS as promotor.

In this application, when using promotor, can use catalyzer and promotor with arbitrary proportion, condition is the growth that the ratio of used catalyzer and promotor does not influence carbon nanotube nocuously, and character such as the purity of carbon nanotube and diameter Distribution.

Generally, the weight ratio of catalyzer and promotor is generally 1～20: 1, be preferably 5～15: and 1, more preferably 10: 1.Yet, also can use weight ratio outside the above-mentioned scope according to actual conditions.

Prepare in the process of carbon nanotube at the application's arc discharge method, also need to use carbon source.Preferred carbon source is a graphite.In this application, can use catalyzer and carbon source with arbitrary proportion, condition is the growth that the ratio of used catalyzer and carbon source does not influence carbon nanotube nocuously, and character such as the purity of carbon nanotube and diameter Distribution.In one embodiment, the mol ratio of carbon source and catalyzer is 1～50: 1, is preferably 5～30: 1, and more preferably 15: 1.

In the application's preferred embodiment, carbon source is a graphite, and catalyzer is the Y-Ni alloy, and promotor is FeS.

In arc-over, usually need to use protection gas, for example the mixture of rare gas element (helium, argon gas or their mixed gas), hydrogen, nitrogen or these gases etc.Helium is the shielding gas of using always.If use hydrogen, then its air pressure can be less than the air pressure of helium, and because hydrogen has higher thermal conductivity, can form c h bond with carbon, and can the etching amorphous carbon etc., so can synthesize more purified carbon nanotube.The pressure of shielding gas can be about 6.67～203kPa, is preferably about 13.3～160kPa, more preferably about 66.7～120kPa, for example about 80.0～93.3kPa.

In order to realize discharge between anode and negative electrode, electric current is typically about 30A～200 ampere (A), is preferably about 70～120A, for example about 100A.Can not form stable electric arc if electric current is too little, the too high impurity such as decolorizing carbon, graphite particulate that then can make of electric current increase, and bring difficulty for the purification process of its back.Employed volts DS is about 20～40V, for example about 30V.Because carbon nanotube may be sintered into one with other by product such as impurity such as decolorizing carbon, graphite granule, and to subsequently separation and purify unfavorable, methods such as water-cooled therefore commonly used reduce the temperature of graphite cathode, thereby prepare more perfect, the purer carbon nanotube of structure.For example, the negative electrode graphite rod can be fixed on the water-cooled copper pedestal to reduce the temperature of graphite cathode.In addition, thus can be beneficial to form carbon nanotube as negative electrode by the metal that uses for example copper (Cu) that thermal conductivity better is easy to dispel the heat etc.In discharge process, can also extra use the temperature in the temperature regulating device control vacuum chamber 160, avoid temperature to cross low and cause impurity such as decolorizing carbon to increase.

In addition, though arc-over is to carry out between the opposing end faces between negative electrode and the anode in electric arc furnace shown in Figure 2 100, but also negative electrode and anode homonymy can be placed, between shape have a certain degree, discharge between negative electrode and the anode becomes discharge between points thus, resulting product is located attached to locular wall of vacuum chamber 160 etc. in flakes, can increase the output of carbon nanotube like this.

After arc-over reaction finishes, generally collect netted soot formation thing and carry out following purification step, this be because in this resultant carbon nanotube particularly the purity of Single Walled Carbon Nanotube is the highest.

(2) purification step-formation complex compound and remove complex compound

As mentioned above, in order to remove the impurity in the carbon nanotube, particularly, generally adopt the method for high temperature oxidation or strong acid oxidation (backflow) in order to remove remaining catalyzer and optional promotor.Yet these methods can particularly cause damage in the sidewall of carbon nanotube to carbon nanotube.

In order to eliminate available technology adopting high temperature oxidation or strong acid oxidation to destruction that carbon nanotube caused, the present inventor is through deep research, final discovery can be based on the complexing technology, remove catalyzer remaining in the carbon nanotube and optional promotor, and can the quality of carbon nanotube not damaged.

Purification step based on the complexing technology is gentle for the purification process of prior art, and the sidewall of carbon nanotube is not caused damage.Thus, the quality of the carbon nanotube by method of the present invention preparation is higher than the carbon nanotube that prior art obtains, and particularly is significantly improved on electroconductibility.

The present inventor finds, can use the material that can form complex compound with the metallic element that exists in catalyzer and/or the optional promotor, come with catalyzer and/or optional promotor in the metallic element complexing that exists so that remove catalyzer and/or optional promotor.

Term " can form the material of complex compound with the metallic element that exists in catalyzer and/or the optional promotor " and be meant the material that can form complex compound with employed metallic element in catalyzer or the promotor, perhaps can be simultaneously with catalyzer and promotor in employed metallic element form the material of complex compound.As mentioned above, used in this application catalyzer can be a transition metal, perhaps the oxide compound of lanthanide series metal.In addition, catalyzer can also be the mixture of metallic nickel (Ni) and rare earth element, and these rare earth elements are such as being Y, Ce, Er, Tb, Ho, La, Nd, Gd, Dy or their mixture etc.Therefore, should select the material that can form title complex for use with these transition metal, lanthanide series metal and rare earth metal etc., as " can form the material of complex compound ", so that from the carbon nanotube that obtains, remove catalyzer with the metallic element that exists in catalyzer and/or the optional promotor.

Owing in arc discharge method, adopt Y-Ni alloy, Fe-Ni alloy, Fe-Co alloy, Co-Ni alloy, Rh-Pt alloy or Ce-Ni alloy usually as catalyzer.Therefore, the application preferred those can with the material of formations complex compounds such as Y, Ni, F, Co, Rh, Pt and Ce as " can with the material of the metallic element formation complex compound that exists in catalyzer and/or the optional promotor ".

When using arc discharge method to prepare carbon nanotube, when using promotor, for catalyst consumption, the consumption of promotor can be ignored.Equally, the amount of the promotor that exists in the carbon nanotube that generates also is negligible with respect to the amount of catalyzer.Therefore, when selecting described material, can only consider that existing metallic element gets final product in the catalyzer.

However, consider that simultaneously employed metallic element is more preferably in catalyzer and the promotor.Further preferably selected material can be simultaneously with catalyzer and promotor in all metallic elements of existing form complex compounds, thereby can only pass through a kind of material, just can remove existing all catalyzer and promotor remnants.

Though some material can form complex compound with metal simple-substance (0 valency metal),, cause to be difficult to directly form complex compound between the element in this material and the alloy material owing in arc-over technology, use alloy material usually.Therefore, preferably the metallic element in catalyzer and/or the optional promotor is converted into its ionic species in the present invention, so that carry out complexing.

Be not particularly limited for the method that metallic element is converted into ionic species, can adopt several different methods.For example can adopt the strong acid oxidation style that metallic element is converted into metal ion.Yet, consider the damage minimum of the carbon nanotube that generates, can at first adopt the suitable oxidizing method that metallic element is converted into oxide compound, obtain metal ion with suitable acid then.Because at this moment therefore employed method for oxidation and acid, can not cause the remarkable reduction of carbon nanotube quality all than the mild condition of using in the conventional purge process.

In some cases, because " can form the material of complex compound with the metallic element that exists in catalyzer and/or the optional promotor " of being adopted is acidic substance, aminopolycanboxylic acid for example, it not only can be converted into metal ion with metal oxide, simultaneously can also with this complexing of metal ion, form complex compound.In this case, just do not need to use other acid to obtain metal ion.

In some cases, the solvability for the complex compound that increases formation (is generally in the water) in solvent so that promote removing of complex compound, can be converted into other suitable form with the complex compound that forms, and for example is converted into the form of salt.Like this, increased the solvability of complex compound, and helped leaching insoluble carbon nanotube, thereby removed complex compound, and made residual catalyzer and/or promotor few as much as possible by for example filtration method.In above-mentioned filtration method, can adopt any filtration medium, for example the tetrafluoroethylene filtering membrane.

For example, when the aminopolycanboxylic acid uses as this material, preferably the aminopolycanboxylic acid's complex compound that forms is converted into salt form.At this moment, can adopt the method that adds suitable alkaline solution, for example add NaOH, KOH etc., and make that pH is an alkalescence, is translated into the form of salt.

When using the aminopolycanboxylic acid, there is no particular limitation for the aminopolycanboxylic acid that can adopt, for example can be ethylenediamine tetraacetic acid (EDTA) (EDTA), anti-form-1,2-diamino-cyclohexane-N, N, N ', N '-tetraacethyl hydrate (CYDTA), diethylene triaminepentaacetic acid(DTPA) (DTPA) and triethylenetetraaminehexaacetic acid (TTHA).

The aminopolycanboxylic acid can form complex compound with Y.At this moment, preferred aminopolycanboxylic acid is ethylenediamine tetraacetic acid (EDTA) (EDTA), anti-form-1,2-diamino-cyclohexane-N, N, N ', N '-tetraacethyl hydrate (CYDTA), diethylene triaminepentaacetic acid(DTPA) (DTPA) and triethylenetetraaminehexaacetic acid (TTHA).Their structure is as follows:

The structure of Y and EDTA, CYDTA, DTPA and the formed complex compound of TTHA is as follows:

The structure of Y and the formed complex compound of EDTA

The structure of Y and the formed complex compound of CYDTA

The structure of Y and the formed complex compound of DTPA

The structure of Y and the formed complex compound of TTHA

In addition, Ni also can form following complex compound with TTHA:

Triethylenetetraaminehexaacetic acid (TTHA) most preferably wherein, this is because when adopting the aminopolycanboxylic acid, adopts TTHA to carry out the purity and the transparency optimum of the resulting carbon nanotube of purifying.

Fig. 3 shows the synoptic diagram that uses the CYDTA purifying carbon nano-tube.As can be seen from Figure 3, existing Y forms complex compound on CYDTA and the carbon nanotube, and and carbon nanotube separation.

In addition, can comprise with the material that Y forms complex compound: tetrahydrofuran (THF), trialkyl phosphine, 6-caprolactone, ε-Ji Neixianan, dimethyl formamide and dimethyl sulfoxide (DMSO) or the like.Will be appreciated that above enumerating do not have the qualification effect.For the material that can form complex compound with Y, and formed complex compound can be referring to " Anhydrous scandium; yttrium; lanthanide and actinide halide complexeswith neutral oxygen and nitrogen donor ligands " (Shashank Mishra, CoordinationChemistry Review 252 (2008) 1996-2025).Above-mentioned article is incorporated herein by reference.Can use that cited all can form the material of complex compound with Y in this article, remove catalyzer, for example the Y in the Y-Ni alloy.

For can enumerate with the example of Ni, Co and the formed complex compound of Fe M[(NC) ₂CC (OCH ₂CH ₂OH) C (CN) ₂] ₂(4,4 '-bPy) (H ₂O) ₂, M is selected from Ni, Co and Fe, referring to Inorganica Chemica Acta, and Vol.361, Issues 14-15,1 October 2008, Pages3856-3862.In the document, also propose, can adopt suitable material to obtain following complex compound, and double-core [M ' { (phen) ₂} ₂V ₄O ₁₂] C ₆H ₁₂OH ₂O, wherein M can be Co and Ni, referring to InorganicaChemica Acta, Vol.361, Issues 12-13,1September 2008, Pages 3681-3689, the application also can adopt in the document cited for obtaining the given material of above-mentioned complex compound.

The material that can adopt all can form complex compound with Ni, formed complex compound can be [Ni (L) (H ₂O) ₃2HO] (wherein L is (2-methoxycarbonyl methyl-imino-5-methyl-thiazole-3-yl)-acetate), Ni[P (Ph ₂)-N (H)-CH ₂Py] ₄, wherein Ph is a phenyl, Py is a pyridine.Other material that can adopt is included in Inorganica Chemica Acta, Vol.361, Issues 12-13,1September 2008, Pages 3723-3729 and at Journal of OrganometallicChemistry, Vol.693, Issue 12,1, and June 2008, Pages 2171-2176 and at InorganicChemistry Communications, In Press, Corrected Proof, Available on line 17, material described in the May 2008, and formed complex compound.

For forming the material of complex compound with Fe, can be referring at Inorganica Chimica Acta, Vol 361, Issues 14-15,1October 2008, Pages 3926-3930, CoordinationChemistry Reviews, Vol.229, Issues 1-2,9, July 2002, Pages 27-35, Coordination Chemistry Reviews, Vol.232, Issues 1-2, October 2002, Pages 151-171 and Coordination Chemistry Reviews, Vol.233-234,1November 2002, the described content of Pages 273-287.

Material for forming complex compound with Fe, Co and Ni sees also the Reviews at CoordinationChemistry, Vol.12, Issue 2April 1974, Pages 151-184 and Coordination Chemistry Reviews, Vol.11, Issue 4, December 1973, Pages343-402 and Coordination Chemistry Reviews, Vol.2, Issue 2, September 1967, the content described in the Pages 173-193.

All incorporate the above-mentioned document of quoting into this paper as a reference.

Can select the kind of described material according to the form (alloy, simple substance, compound or the like) of selected catalyzer and/or promotor and the kind of existing metallic element.

In addition, select the complexing step how to carry out according to the particular case of catalyzer and/or promotor.For example can select whether to carry out catalyzer and/or promotor are converted into the ionic step according to concrete catalyzer and/or promotor.When transforming, need also to determine whether that needs use the acid except that described material that the metallic element in catalyzer and/or the promotor is converted into ion by method for oxidation.

As mentioned above, for the metallic element in catalyzer and/or the promotor is converted into ion, can adopt the suitable oxidizing method that metallic element is converted into oxide compound earlier.At this moment preferably adopt oxygen-containing gas (preferred air) to come oxide catalyst and/or promotor.The oxidizing condition of this use oxygen-containing gas is compared with the condition of conventional gaseous oxidation purifying, is quite gentle.Generally speaking, oxygen-containing gas oxide catalyst and/or needed time of promotor and temperature are not concrete to be limited to using, as long as this time and temperature are enough to catalyzer and/or promotor are converted into its oxide compound.Usually, oxidizing temperature can be chosen as 80-300 ℃, more preferably, 100-200 ℃, most preferably 150 ℃-200 ℃.Oxidization time can change based on the selection of oxidizing temperature.Generally speaking, oxidization time can be 1-20 hour, preferred 5-15 hour, and more preferably 8-10 hour.As can be seen, compare with normally used high-temperature oxidation method (generally adopting 470 ℃ oxidizing temperature), the application prepares the oxidation of using in the method for carbon nanotube and belongs to low-temperature oxidation.Therefore, this low-temperature oxidation can not cause the destruction of carbon nanotube.

The method that the application prepares carbon nanotube is carried out centrifugation step after can also being included in and removing complex compound, removes decolorizing carbon remaining on the carbon nanotube, so that further improve the purity of carbon nanotube.For this centrifugation step, can adopt any centrifugal speed, yet preferably use the centrifugal of fair speed.For example, can adopt the speed of 5000-30000rpm, preferably adopt the centrifugal speed of 10000-20000.Centrifugal time of adopting and the centrifugal speed that adopts are closely related, generally speaking can centrifugal 1 minute-20 hour, and preferred 2-10 hour, for example 3 hours.

Preferably, the carbon nanotube that is obtained by method of the present invention is a Single Walled Carbon Nanotube.Comprise metallic single-wall carbon nano-tube (M-SWNT), semi-conductive single-walled carbon nanotubes (S-SWNT) and combination thereof.

The application's second aspect

The application's second aspect provides a kind of method of purifying carbon nano-tube, wherein said carbon nanotube be in the presence of catalyzer and optional promotor by arc discharge method production, the method for described purifying carbon nano-tube may further comprise the steps:

(I): the metallic element complexing that exists in the material that use can form complex compound with the metallic element that exists in catalyzer and/or the optional promotor and catalyzer and/or the optional promotor, the formation complex compound and

(II) remove described complex compound.

According to the purification process of the application's second aspect, can purifying be obtained from the carbon nanotube of arc discharge method, improve the purity of carbon nanotube, and improve its performance.

Be not particularly limited for the carbon nanotube that can be used for the application's second aspect, as long as this carbon nanotube is to obtain by arc discharge method.

Those skilled in the art are appreciated that, when arc discharge method prepares carbon nanotube, will adopt catalyzer and optional promotor.Generally speaking used catalyzer is transition metal, the perhaps oxide compound of lanthanide series metal, or its mixture.In addition, catalyzer can also be the mixture of metallic nickel (Ni) and rare earth element, and these rare earth elements are such as being Y, Ce, Er, Tb, Ho, La, Nd, Gd, Dy or their mixture etc.In a kind of embodiment of the application, catalyzer is preferably selected from Y-Ni alloy, Fe-Ni alloy, Fe-Co alloy, Co-Ni alloy, Rh-Pt alloy or Ce-Ni alloy.

Generally speaking, arc discharge method can use promotor, for example FeS.

According to the purification process of the application's second aspect, can effectively remove catalyzer residual in the carbon nanotube that arc discharge method obtains and/promotor, and can be to the quality of carbon nanotube, particularly conduction property causes any disadvantageous effect.

The method of the application's second aspect use " material that can form complex compound " with the metallic element that exists in catalyzer and/or the optional promotor come with catalyzer and/or optional promotor in the metallic element complexing that exists, form complex compound, and come purifying carbon nano-tube by removing complex compound.

In second aspect, should select the material that can form title complex for use with these transition metal, lanthanide series metal and rare earth metal etc., as " can form the material of complex compound ", so that from the carbon nanotube that obtains, remove catalyzer with the metallic element that exists in catalyzer and/or the optional promotor.

For example, when the aminopolycanboxylic acid uses as this material, preferably the aminopolycanboxylic acid's complex compound that forms is converted into salt form.At this moment, can adopt the method that adds suitable alkaline solution, for example add NaOH, KOH etc., be translated into the form of salt, and make that pH is an alkalescence.

The aminopolycanboxylic acid can form complex compound with Y.At this moment, preferred aminopolycanboxylic acid is ethylenediamine tetraacetic acid (EDTA) (EDTA), anti-form-1,2-diamino-cyclohexane-N, N, N ', N '-tetraacethyl hydrate (CYDTA), diethylene triaminepentaacetic acid(DTPA) (DTPA) and triethylenetetraaminehexaacetic acid (TTHA).Their structure (structural formula in the article is unclear, if you have clearly structural formula, please help is inserted in the presents) as follows:

The structure of Y and the formed complex compound of EDTA

The structure of Y and the formed complex compound of CYDTA

The structure of Y and the formed complex compound of DTPA

The structure of Y and the formed complex compound of TTHA

In addition, Ni also can form following complex compound with TTHA:

For can enumerate with the specific examples of Ni, Co and the formed complex compound of Fe M[(NC) 2CC (OCH2CH2OH) C (CN) 2] 2 (4,4 '-bPy) (H2O) 2}, referring to InorganicaChemica Acta, Vol.361, Issues 14-15,1October 2008, Pages 3856-3862.In the document, also propose, can adopt suitable material to obtain following complex compound, double-core [M{ (phen) ₂} ₂V ₄O ₁₂] C ₆H ₁₂OH ₂O, wherein M can be Co and Ni, referring to InorganicaChemica Acta, Vol.361, Issues 12-13,1September 2008, Pages 3681-3689, the application also can adopt in the document cited for obtaining the given material of above-mentioned complex compound.

For forming the material of complex compound with Fe, can be referring at Inorganica ChimicaActa, Vol 361, Issues 14-15,1October 2008, Pages 3926-3930, CoordinationChemistry Reviews, Vol.229, Issues 1-2,9, July 2002, Pages 27-35, Coordination Chemistry Reviews, Vol.232, Issues 1-2, October 2002, Pages 151-171 and Coordination Chemistry Reviews, Vol.233-234,1November 2002, the described content of Pages 273-287.

As mentioned above, for the metallic element in catalyzer and/or the promotor is converted into ion, can adopt the suitable oxidizing method that metallic element is converted into oxide compound earlier.At this moment preferably adopt oxygen-containing gas (preferred air) to come oxide catalyst and/or promotor.The oxidizing condition of this use oxygen-containing gas is compared with the condition of conventional gaseous oxidation purifying, is quite gentle.Generally speaking, oxygen-containing gas oxide catalyst and/or needed time of promotor and temperature are not concrete to be limited to using, as long as this time and temperature are enough to catalyzer and/or promotor are converted into its oxide compound.Usually, oxidizing temperature can be chosen as 80-300 ℃, more preferably, 100-200 ℃, most preferably 150 ℃-200 ℃.Oxidization time can change based on the selection of oxidizing temperature.Generally speaking, oxidization time can be 1-20 hour, preferred 5-15 hour, and more preferably 8-10 hour.As can be seen, compare with normally used high-temperature oxidation method, the oxidation of using in the method for the application's purifying carbon nano-tube belongs to low-temperature oxidation.Therefore, this low-temperature oxidation can not cause the destruction of carbon nanotube.

The method of the application's purifying carbon nano-tube is carried out centrifugation step after can also being included in and removing complex compound, removes decolorizing carbon remaining on the carbon nanotube, so that further improve the purity of carbon nanotube.For this centrifugation step, can adopt any centrifugal speed, yet preferably use the centrifugal of fair speed.For example, can adopt the speed of 5000-30000rpm, preferably adopt the centrifugal speed of 10000-20000.Centrifugal time of adopting and the centrifugal speed that adopts are closely related, generally speaking can centrifugal 1 minute-20 hour, and preferred 2-10 hour, for example 3 hours.

The application's the third aspect

The carbon nanotube that the application's the third aspect provides the carbon nanotube for preparing according to the application's first aspect and the application's second aspect purifying to obtain.

The term of Shi Yonging " carbon nanotube " comprises various carbon nanotube well known by persons skilled in the art in this article.The number of plies according to the carbon atom that forms tube wall can comprise for example Single Walled Carbon Nanotube and multi-walled carbon nano-tubes and combination thereof.According to its electrical property, can comprise metallic carbon nanotubes and semiconductive carbon nano tube and combination thereof again.But, carbon nanotube is preferably Single Walled Carbon Nanotube in this application, comprises metallic single-wall carbon nano-tube (M-SWNT), semi-conductive single-walled carbon nanotubes (S-SWNT) and combination thereof.

As above describe in detail, the application's the method for preparing carbon nanotube and the method for purifying carbon nano-tube can not cause damage to the sidewall of carbon nanotube, can not influence the quality, particularly electroconductibility of carbon nanotube.In this respect, the carbon nanotube that is obtained by the application's first aspect and second aspect is different from the carbon nanotube that is obtained by prior art.

What go out as shown in Figure 1 is such, because the restriction of preparation and purification condition, there is defective in carbon nanotube tube wall of the prior art.And the carbon nanotube of the application's third aspect, as shown in Figure 7, sidewall is smooth, is not damaged.And as Fig. 8 and shown in Figure 9, the carbon nano pipe purity that the method by the application obtains is very high, and quality is very good.

The application's fourth aspect

The application's fourth aspect provides carbon nano-tube element, and it comprises the carbon nanotube of the application's third aspect.

This carbon nano-tube element includes but not limited to, for example, the carbon nanotube conducting film, field emitting electronic source, transistor, lead (conductive wire), electrode materials is (for example transparent, porous or gaseous diffusion electrode material), nanoelectronic mechanical system (nano-electro-mechanic system) (NEMS), rotation conductive devices (spin conduction device), nanometer cantilever (nano cantilever), the quantum calculation device, photodiode, solar cell, the surface conduction electron emission display device, wave filter (for example high frequency or optical filter), doser, thermally conductive material, the nanometer shower nozzle, energy storage material (for example hydrogen storage material), space elevator (space elevator), fuel cell, transmitter (for example, gas, glucose or ionization sensor) or support of the catalyst etc.

Below provide the example of several carbon nano-tube elements, but the application is not limited to these examples.

1. carbon nanotube conducting film

Because carbon nanotube has intensity and flexibility simultaneously, so they are highly suitable for the flexible electronic assembly.Particularly the conductive film of the flexible and transparent of being made by carbon nanotube has obtained paying close attention to widely, and this is because they can be applied in electroluminescent, optical conductor and the photovoltaic device to a certain extent.

Though randomly transparent and indium tin oxide (ITO) high conductivity has been widely used in the photovoltaic applications, the intrinsic fragility of ITO has seriously limited the flexibility of film.The character of carbon nano-tube film makes them be suitable for replacing ITO.For example, can repeatedly crooked carbon nano-tube film and not broken.Carbon nano-tube film with low sheet resistance also is transparent at visible light and region of ultra-red.And low-cost and adjustable electronic property has given carbon nano-tube film further advantage.

Can be prepared as follows the application's carbon nanotube conducting film:

In ultrasonic bath, the carbon nanotube of 10mg is dispersed in octyl group-phenol-ethoxylate (being called Triton X-100) aqueous solution of 1 wt.% of 200ml, disperseed 20 minutes.In vacuum apparatus (Millipore), filter this dispersion with blended cellulose ester (MCE) membrane filter (Millipore, 0.2 μ m hole), and on membrane filter, form carbon nano-tube film.Through time two days later, with all basically Triton X-100 of three (hydroxymethyl) aminomethane hydrochloride (Tris-HCl) damping fluid (50mM, PH 7.5) this carbon nano-tube film of dialysing.Then wash the Tris-HCl damping fluid off, then this carbon nano-tube film is transferred on the quartz base plate with pure water.With this sample after 90 ℃ of dryings 1 hour, use the acetone steam to remove membrane filter.At last, with this carbon nano-tube film 100 ℃ of vacuum-dryings 1 hour.

For this method for preparing carbon nano-tube film, particularly use the acetone steam remove the step of membrane filter can be specifically referring to the associated description in the Chinese patent application of application on February 14th, 2008 numbers 200810005631.7, be introduced into this paper as a reference.

For example, can adopt steam generator shown in Figure 12 in this application.Figure 12 (a) shows the steam generator that uses in this application; (b) show glass bushing structural section synoptic diagram at steam generator shown in (a).

Described steam generator comprises:

The glass bushing that has condensing works, wherein the inlet of cooling medium exports up below sleeve pipe, and described sleeve pipe comprises porous support platform, and it is installed in inside pipe casing, and is highly general identical with the inlet of cooling medium, is used to place sample;

Container, for example round-bottomed flask is used to adorn solvent (as acetone);

Heating unit, for example the heating jacket of temperature controllable is used for the heating of solvent;

Optional whipping appts, for example magnetic stirring apparatus.

Described porous supports platform for example to be made by glass.The pore size of supporting platform is not strict with, if the steam that can guarantee q.s on the one hand by and can support sample on the other hand.The size of support platform depends on the internal diameter of glass bushing.

2. carbon nanotube field-effect pipe

Utilize single carbon nanotube and carbon nano-tube bundle can be used to construct the primary element-carbon nanotube field-effect pipe (carbon nanotube FET) of nanoelectronic element.Carbon nanotube in the product of preparation is not discrete one by one usually, but exist with the form of bundle (bundle), the carbon nanotube that is several even hundreds of root forms the carbon nano-tube bundle of several approximately nanometers of diameter to tens nanometers along parallel the combining of identical direction of principal axis.But for this carbon nanotube FET is applied in the nanoelectronic element, primary task is that the tube bank to carbon nanotube separates, to obtain single or undersized carbon nanotube.

In the tube bank of carbon nanotube, the diameter of carbon nanotube is homogeneous each other, and arranges with the form of Mi Dui, makes tube bank itself crystallization to a certain degree may occur.Separation method carries out long ultrasonication among normally carbon nanotube powder being dispersed in organic solvent again, thereby reaches the carbon nanotube purpose separated from one another in carbon nanotube tube bank or the tube bank.Isolating effect depends on factors such as solvent types and ultransonic time.Normally used organic solvent for example comprises ethanol, Virahol, acetone, tetracol phenixin, ethylene dichloride, dimethyl formamide (DMF, dimethyl formamide) etc.

3. transistor-nanoelectronic triode

For the nanoelectronic triode, single-electronic transistor is arranged at present, and (Single Electron Transistor is SET) with two kinds of patterns of carbon nanotube triode.The latter is also referred to as field-effect transistor (FET), is included in the source, leaks the interpolar carbon nanotube, and the electronics (or hole) by carbon nanotube transports the control that is subjected to gate voltage.

The preparation method of a typical FET is as follows.As mentioned above, the normally snarly tube bank of the primary product of this carbon nanotube, at first with they ultra-sonic dispersion fully in organic solvent (for example ethanol), to drip to the top layer be SiO to this liquid then ₂Silicon chip on, on this silicon chip, prepared a large amount of metal electrodes by traditional photolithography, evaporation of metal method or silk screen print method.Whether detection exists single-root carbon nano-tube or the tube bank that two electrodes are coupled together under atomic force microscope (AFM) then.These two electrodes will be as source electrode and the drain electrode of the FET that will prepare.Two interelectrode spacings typically are 100nm, and this interelectrode distance is such as changing in 0.1～1 micron scope.Be positioned at SiO ₂Another electrode below the layer or adulterated silicon base are crossed the electric current of carbon nanotube as the gate electrode of FET to apply the gate voltage controlling flow, and the FET that makes thus is bottom-gate FET.Certainly, also can prepare the top gate fet, promptly in substrate, prepare carbon nanotube or tube bank earlier to connect source electrode and drain electrode, deposit gate insulator then successively and above carbon nanotube or tube bank, on gate insulator, prepare gate electrode by for example method for printing screen.In addition, also can be earlier with single-root carbon nano-tube or restrain directed splash in substrate, re-use electron beam at the two ends of this carbon nanotube or tube bank depositing electrode, but this technology may cause the carbon nanotube between the electrode to be cut off.

The relation between detected transmission result and the gate voltage (I-V characteristic) at room temperature.In this detected, metallic carbon nanotubes did not show or demonstrates the faint linear conductance that influenced by gate voltage that semiconductive carbon nano tube then demonstrates stronger gate voltage dependency.

Embodiment

Following embodiment can be used for further describing the application.Except as otherwise noted, employed various raw materials of the application and reagent are commercially available or can prepare according to the technology of this area routine.

The source of present brief introduction main raw material:

The Y-Ni alloy catalyst is purchased in Beijing Non-Fervoous Metal Inst.,

Graphite rod is purchased in the carbon element factory, Shanghai,

FeS is available from Beijing Yili Fine Chemicals Co., Ltd.,

NaOH and neighbour-dichlorobenzene (o-DCB) be available from the Beijing Chemical Plant,

EDTA (ethylenediamine tetraacetic acid (EDTA)), CYDTA (anti-form-1,2-diamino-cyclohexane-N, N, N ', N '-tetraacethyl hydrate), DTPA (diethylene triaminepentaacetic acid(DTPA)) and TTHA (triethylenetetraaminehexaacetic acid) are available from Alfa Aesar.

Triton X-100 is available from Acros.

Three (hydroxymethyl) aminomethane is available from Acros, and 99%.

Hydrochloric acid is available from the Beijing Chemical Plant, and HCl content is 36-38%.

Characterizing method

For the carbon nanotube behind the purifying, can carry out analysis and characterization by following characterizing method:

Raman spectrum: use Renishaw 100micro-Raman system;

X-ray photoelectron spectroscopy: use the ESCALab220i-XL electronspectrometer of VG Scientific, use 300W AlK alpha-ray;

Scanning electronic microscope: use JEOL JSM-6700F;

Transmission electron microscope: use JEOL-2010,200kV.

For the film of carbon nanotube, use 4 pin probe Loresta-EP MCP-T360 to measure sheet resistance, use UV-vis-NIR spectrophotometer (JASCOV-570) the test transparency.

Raman spectrum is one of powerful measure that detects carbon nanotube, thereby not only can reflect the purity of the degree of order response sample of sample, can also characterize the diameter Distribution of carbon nanotube.When carrying out the Raman spectrum detection, for the pencil of getting rid of carbon nanotube is reunited to the influence of detected result, employed sample can carry out following processing in Raman test: in ethanol, carried out ultrasonication 5 minutes, then with resulting hanging drop on sheet glass and at air drying.

In the Raman spectrum, there are three zones or peak to need to pay close attention to: breathing pattern (Radial-BreathingMode, RBM) (about 100～300cm radially ^-1), D is with (～1350cm ^-1) and G band (～1570cm ^-1) (referring to M.S.Dresselhaus, et al., Raman Spectroscopy of Carbon Nanotubes in 1997and 2007, J.Phys.Chem.C, 111 (48), 2007,17887-17893).The RBM peak is one of feature backscatter mode corresponding to carbon nanotube, is that carbon nanotube is peculiar, and relevant with the diameter of carbon nanotube.According to relational expression (referring to Araujo, P.T., et al., Third and fourth opticaltransitions in semiconducting carbon nanotubes.Phys.Rev.Lett., 98,2007,067401.) ω _RBM=A/d _t+ B, wherein A=217.8 ± 0.3cm ^-1Nm, B=15.7 ± 0.3cm ^-1, ω _RBMBe that unit is cm ^-1The wave number at RBM peak, dt is that unit is the diameter of the carbon nanotube of nm, we can know the diameter Distribution of carbon nanotube.D band and G band correspond respectively to decolorizing carbon and graphited carbon.Can estimate the purity of carbon nanotube according to the G band and the strength ratio (G/D) of D band.G/D is big more, and graphited carbon is many more, thereby impurity or defective are few more, thereby purity is high more.

Preparation example 1

Use electric arc furnace 100 shown in Figure 2, anode 130 is the graphite rod of long 100mm, diameter 6mm, and negative electrode 120 is the graphite rod of diameter 8mm.Drill through the aperture that an internal diameter is 4mm, dark 80mm at anodic graphite rod one end, fill the mixture of following powder in the hole: high purity graphite powder, as the YNi of metal catalyst _4.2Powdered alloy and as the FeS powder of promotor, wherein the mol ratio of carbon and catalyzer is 15: 1, the weight ratio of catalyzer and promotor is 10: 1.With the weighting material compacting in the above-mentioned hole.Negative electrode is fixed on the water-cooled copper pedestal.Then electric arc furnace 100 is evacuated down to about 3.0Pa; Close vacuum valve afterwards, feed helium to about 0.07MPa.Connect after the power supply, make current control at about 80～120A, voltage is at 20～25V, and the manual regulation negative electrode makes two distance between electrodes remain about 3mm, produces stable arc-over.

Collect three sample segments: adhere to the cloth shape soot formation thing (cloth-like soot) on the locular wall; Be suspended on the netted soot formation thing (web-like soot) between locular wall and the negative electrode; And " collar " shape soot formation thing (collar-like soot) that adheres to negative electrode one end.In these three parts, the purity of carbon nanotube is the highest in the netted soot formation thing, minimum in cloth shape soot formation thing, falling between in " collar " shape soot formation thing.

Use netted soot formation thing to carry out the following examples as purification of samples not.

Purifying example 1

At first, purification of samples is not at 200 ℃ with 10mg, and the air velocity that used 20ml/ minute was calcined 10 hours.Afterwards, with the calcining after sample dispersion in deionized water, supersound process 30 minutes.The preparation 0.5M EDTA aqueous solution joins in the above-described carbon nanotube dispersion liquid then.Mixture was refluxed 18 hours at 110 ℃, use the 1M NaOH aqueous solution that the pH value is transferred to about 8.Then, the porous Teflon filtering membrane of dispersion liquid with 0.5 micron filtered, and with the hot water injection repeatedly.Then, with sample dispersion in o-DCB, at 15000rpm centrifugal 3 hours.With the supernatant liquor decant, and pass through blended cellulose ester (MCE) membrane filter with its filtration and collection.

Purifying example 2

Repeat the method for embodiment 1, difference is to use the 0.5M CYDTA aqueous solution to replace the 0.5MEDTA aqueous solution, carries out complexing.

Purifying example 3

Repeat the method for embodiment 1, difference is to use the 0.5M DTPA aqueous solution to replace the 0.5MEDTA aqueous solution, carries out complexing.

Purifying example 4

Repeat the method for embodiment 1, difference is to use the 0.5M TTHA aqueous solution to replace the 0.5MEDTA aqueous solution, carries out complexing.

At first respectively the sample that uses EDTA and CYDTA to carry out purifying is compared.The Raman spectrum of carbon nanotube is shown among Fig. 4 behind the purifying.In Fig. 4, also show commercially available P3 carbon nanotube (P3 uses the preparation of sour reflow method, from Carbon Solutions.Inc. purity greater than 85%).

As can be seen from Figure 4, three characteristic spectrum zones of all of carbon nanotube have all obviously obtained maintenance: (RBM) (150-250cm of breathing pattern (radial breathing mode) radially ^-1); D is with (1330cm ^-1) and G band (1520-1600cm ^-1).And the G/D of EDTA and CYDTA is than the G/D ratio greater than P3 as can be seen, and the purity of the carbon nanotube that this expression use EDTA and CYDTA purifying obtain is greater than P3.

In addition, it can also be seen that the carbon nano pipe purity that the CYDTA purifying obtains is higher than the carbon nano pipe purity that uses the EDTA purifying to obtain.This may be because CYDTA is more stable than the complex compound of EDTA and Y with the complex compound of Y.

Carry out XPS analysis for the carbon nanotube that uses the EDTA purifying to obtain, what obtain the results are shown among Fig. 5.

As can be seen from Figure 5, the 1s peak that has Na.Also have residual EDTA sodium salt in the carbon nanotube of this explanation behind purifying, that is EDTA is not removed fully.

Though do not illustrate, have the 1s peak of Na in the XPS collection of illustrative plates that uses the CYDTA purifying to obtain equally.

As can be seen, use CYDTA and EDTA not to remove catalyst impurities fully.This may be because EDTA sodium salt and the solvability of CYDTA sodium salt in water are bad.

Carry out sem analysis for the carbon nanotube that uses the TTHA purifying to obtain, obtain the collection of illustrative plates shown in Fig. 6 (Fig. 6 b).In Fig. 6, (Fig. 6 a) also to show the SEM of not purified carbon nanotube.

Equally, the carbon nanotube that uses the TTHA purifying to obtain is carried out tem analysis, obtain the collection of illustrative plates shown in Fig. 7.In Fig. 7, Fig. 7 a only is that the magnification existence is different with Fig. 7 b.

Comparison diagram 6a and Fig. 6 b pass through after the purifying of TTHA as can be seen, and most impurity have obtained removal, and only small amount of amorphous carbon sticks on the carbon nanotube.These residual impurity can be further by removing in conjunction with ultrasonic and supercentrifugal technology.

From Fig. 7 a and Fig. 7 b as can be seen, the sidewall of gained carbon nanotube is very smooth, and sidewall of this expression carbon nanotube does not damage in purge process.

Illustrated among Fig. 8 and used TTHA purifying front and back, the Raman spectrum of carbon nanotube.By comparing the G/D ratio of two curves in purifying front and back, obviously find out, carry out purifying by using TTHA, significantly increased purity.And, it can also be seen that the quality of carbon nanotube and purity are all very good.

Figure 9 illustrates the XPS collection of illustrative plates that uses TTHA purifying and the carbon nanotube that uses conventional acid treatment (P3) to obtain.From Fig. 9, can obviously find out, use TTHA to handle and removed Y fully, use the then remaining relatively large Y of sour reflow treatment.

System film example 1

In this embodiment, use the made of carbon nanotubes carbon nano-tube film that obtains through behind the TTHA purifying, the preparation of film is based on filtration method.Its preparation method is as described below.

In ultrasonic bath, the carbon nanotube of 10mg is dispersed in octyl group-phenol-ethoxylate (being called Triton X-100) aqueous solution of the 1wt.% of 200ml, disperseed 20 minutes.In vacuum apparatus (Millipore), filter this dispersion with blended cellulose ester (MCE) membrane filter (Millipore, 0.2 μ m hole), and on membrane filter, form carbon nano-tube film.Through time two days later, with all basically Triton X-100 of three (hydroxymethyl) aminomethane hydrochloride (Tris-HCl) damping fluid (50mM, PH 7.5) this carbon nano-tube film of dialysing.Then wash the Tric-HCl damping fluid off, then this carbon nano-tube film is transferred on the quartz base plate with pure water.With this sample after 90 ℃ of dryings 1 hour, use the acetone steam to remove membrane filter.At last, with this carbon nano-tube film 100 ℃ of vacuum-dryings 1 hour.

Comparative Examples 1

Mode according to system film example 1 prepares carbon nano-tube film, and difference is that the carbon nanotube (P3) that adopts conventional nitric acid backflow to obtain replaces the carbon nanotube that obtains through behind the TTHA purifying.

Figure 10 is to use the carbon nano-tube film of the made of carbon nanotubes that obtains behind the TTHA purifying.This film covers on the quartz base plate of ICCAS.As can be seen from Figure 10, can see through carbon nano-tube film (about 70 nanometers) and clearly see the ICCAS printed words on the substrate.This transparency of representing this film is very good.

Figure 11 has compared the carbon nano-tube film of embodiment 5 preparations and the sheet resistance of the film that Comparative Examples 1 prepares.As can be seen, compare with the film of Comparative Examples 1 preparation, the sheet resistance of the film of system film example 1 preparation significantly reduces.

Clearly, owing to avoided the tube wall of carbon nanotube is damaged, the carbon nanotube of the carbon nanotube of the method preparation by the application or the method purifying by the application has excellent character, can be widely used in during optical electron uses.

The numbering of continued presence in the application's method be (a) for example, (b), waits only to be intended to be distinguished from each other, and is not intended to represent not have any extra step between them.For example, in step (a) with (b) and/or (b) and (c) etc. extra step is arranged.These extra steps can be the common steps in this area, can comprise drying, washing etc., as long as they do not influence effect of the present invention nocuously.

Among the application practical term " choose wantonly " and subsequently incident or project (for example treatment step) of " randomly " expression can exist also and can not exist.And the present invention comprises this incident or project exists and non-existent situation.

Incorporate the application at this document with all references.

Though described the present invention with reference to embodiment, clearly it can change in many ways.Should think this variation without departing from the spirit and scope of the present invention, and all are this to those skilled in the art's obvious variation form also within the scope of the invention.

Claims

1. method for preparing carbon nanotube said method comprising the steps of:

(c) remove described complex compound.

2. according to the process of claim 1 wherein, in step (a), use promotor.

3. according to the method for claim 2, wherein, described promotor is FeS.

4. according to the process of claim 1 wherein, described catalyzer is selected from the oxide compound of lanthanide series metal, transition metal, the perhaps mixture of nickel and rare earth element, and aforementioned mixture of catalysts.

5. according to the process of claim 1 wherein, described catalyzer is selected from Y-Ni alloy, Fe-Ni alloy, Fe-Co alloy, Co-Ni alloy, Rh-Pt alloy and Ce-Ni alloy.

6. according to the process of claim 1 wherein that described step (b) may further comprise the steps:

7. according to the method for claim 6, wherein said step (d) may further comprise the steps:

8. the method for claim 7 is wherein used the material that can form complex compound with the metallic element that exists in catalyzer and/or the optional promotor, forms the corresponding metal ion from described oxide compound, and with described complexing of metal ion, obtain complex compound.

9. the method for claim 8 describedly can be selected from the aminopolycanboxylic acid with the material that the metallic element that exists in catalyzer and/or the optional promotor forms complex compound.

10. according to the method for claim 9, wherein, described aminopolycanboxylic acid is selected from ethylenediamine tetraacetic acid (EDTA) (EDTA), anti-form-1,2-diamino-cyclohexane-N, N, N ', N '-tetraacethyl hydrate (CYDTA), diethylene triaminepentaacetic acid(DTPA) (DTPA) and triethylenetetraaminehexaacetic acid (TTHA).

11. according to the method for claim 9, wherein, described aminopolycanboxylic acid is triethylenetetraaminehexaacetic acid (TTHA).

12. according to the process of claim 1 wherein that described step (c) comprises the form that described complex compound is converted into salt, and remove the complex compound of described salt form.

13. according to the method for claim 7, (d) is further comprising the steps of for wherein said step:

14. method according to claim 6, wherein, describedly can be selected from tetrahydrofuran (THF), trialkyl phosphine, 6-caprolactone, ε-Ji Neixianan, dimethyl formamide and dimethyl sulfoxide (DMSO) with the material that the metallic element that exists in catalyzer and/or the optional promotor forms complex compound.

15. according to the method for claim 6, wherein, described complex compound be selected from M[(NC) ₂CC (OCH ₂CH ₂OH) C (CN) ₂] ₂(4,4 '-bPy) (H ₂O) ₂, double-core [M ' { (phen) ₂} ₂V ₄O ₁₂] C ₆H ₁₂OH ₂O and [Ni (L) (H ₂O) ₃2HO], wherein M is selected from Ni, Co and Fe, and M ' is selected from Ni and Co, and bPy is a dipyridyl, and phen is a phenyl, L is (a 2-methoxycarbonyl methyl-imino-5-methyl-thiazole-3-base-acetate).

16. according to the method for claim 7, wherein, described step (f) comprises uses oxygen-containing gas to come oxide catalyst and/or optional promotor.

17. according to the method for claim 16, wherein, time and the temperature of using oxygen-containing gas to carry out oxidation are enough to catalyzer and/or optional promotor are changed into oxide compound.

18. according to the method for claim 16, wherein, described oxygen-containing gas is an air.

19. according to the method for claim 17, described oxidizing temperature is 80-300 ℃.

20. according to the method for claim 17, described oxidization time is 1-20 hour.

21. according to the process of claim 1 wherein, this method is carried out centrifugation step after also being included in and removing described complex compound.

22. according to the method for claim 21, wherein, this centrifugation step was carried out 1-20 hour with 5000-30000rpm.

23. according to each method in the claim 1 to 22, wherein, described carbon nanotube is a Single Walled Carbon Nanotube.

24. the method for a purifying carbon nano-tube, wherein said carbon nanotube be in the presence of catalyzer and optional promotor by arc discharge method production, the method for described purifying carbon nano-tube may further comprise the steps

(II) remove described complex compound.

25. according to the method for claim 24, wherein said step (I) may further comprise the steps:

26. according to the method for claim 25, wherein said step (III) may further comprise the steps:

27. the method for claim 26 is wherein used the material that can form complex compound with the metallic element that exists in catalyzer and/or the optional promotor, forms the corresponding metal ion from described oxide compound, and with described complexing of metal ion, obtain complex compound.

28., wherein, describedly can be selected from the aminopolycanboxylic acid with the material that the metallic element that exists in catalyzer and/or the optional promotor forms complex compound according to the method for claim 27.

29. according to the method for claim 28, wherein, described aminopolycanboxylic acid is selected from ethylenediamine tetraacetic acid (EDTA) (EDTA), anti-form-1,2-diamino-cyclohexane-N, N, N ', N '-tetraacethyl hydrate (CYDTA), diethylene triaminepentaacetic acid(DTPA) (DTPA) and triethylenetetraaminehexaacetic acid (TTHA).

30. according to the method for claim 28, wherein, described aminopolycanboxylic acid is triethylenetetraaminehexaacetic acid (TTHA).

31. according to the method for claim 24, wherein said step (II) comprises the form that described complex compound is converted into salt, and removes the complex compound of described salt form.

32. according to the method for claim 26, (V) is further comprising the steps of for wherein said step:

33. according to the method for claim 24, wherein said catalyzer is selected from Y-Ni alloy, Fe-Ni alloy, Fe-Co alloy, Co-Ni alloy, Rh-Pt alloy and Ce-Ni alloy.

34. method according to claim 25, wherein, describedly can be selected from tetrahydrofuran (THF), trialkyl phosphine, 6-caprolactone, ε-Ji Neixianan, dimethyl formamide and dimethyl sulfoxide (DMSO) with the material that the metallic element that exists in catalyzer and/or the optional promotor forms complex compound.

35. according to the method for claim 25, wherein said complex compound be selected from M[(NC) ₂CC (OCH ₂CH ₂OH) C (CN) ₂] ₂(4,4 '-bPy) (H ₂O) ₂, double-core [M ' { (phen) ₂} ₂V ₄O ₁₂] C ₆H ₁₂OH ₂O and [Ni (L) (H ₂O) ₃2HO], wherein M is selected from Ni, Co and Fe, and M ' is selected from Ni and Co, and bPy is a dipyridyl, and phen is a phenyl, L is (a 2-methoxycarbonyl methyl-imino-5-methyl-thiazole-3-base-acetate).

36. according to the method for claim 26, wherein, described step (V) comprises uses oxygen-containing gas oxide catalyst and/or optional promotor.

37. according to the method for claim 36, wherein, time and the temperature of using oxygen-containing gas to carry out oxidation are enough to catalyzer and/or optional promotor are changed into oxide compound.

38. according to the method for claim 36, wherein, described oxygen-containing gas is an air.

39. according to the method for claim 37, described oxidizing temperature is 80-300 ℃.

40. according to the method for claim 37, described oxidization time is 1-20 hour.

41. according to the method for claim 24, wherein, this method is carried out centrifugation step after also being included in and removing described complex compound.

42. according to the method for claim 41, wherein, this centrifugation step was carried out 1-20 hour with 5000-30000rpm.

43. according to each method in the claim 24 to 42, wherein, described carbon nanotube is a Single Walled Carbon Nanotube.

44. carbon nanotube by each method purifying in the claim 1 to 43.

45. carbon nano-tube element, it comprises the carbon nanotube of claim 44.

46. the carbon nano-tube element of claim 45, wherein said carbon nano-tube element are selected from carbon nanotube conducting film, field emitting electronic source, transistor, lead, nanoelectronic mechanical system, rotation conductive devices, nanometer cantilever, quantum calculation device, photodiode, solar cell, surface conduction electron emission display device, wave filter, drug delivery system, thermally conductive material, nanometer shower nozzle, accumulator system, space elevator, fuel cell, transmitter and support of the catalyst.