TWI408101B - Dispersion method of carbon nano materials, dispersion, and dispersion of nano carbon materials - Google Patents

Abstract

A Dispersion method of carbon nano materials, Dispersion, and Dispersion of nano carbon materials, it relates a novel noncovalent and inorganic method was used to disperse MWCNTs in aqueous solution. MWCNTs were directly dispersed into highly charged titanium dioxide nanoparticles aqueous solution without functionalization of their surfaces. The dispersed MWCNTs was characterized by transmission electron microscopy and atomic force microscopy. A series of experiments were carried out with the aid of ultrasonic agitation for 1.5 hr in order to investigeate the effects of solution pH value, amount of alumina-coated silica nanoparticles in aqueous solution, and amount of MWCNTs dispersed in aqueous solution.

Description

Nano carbon material dispersion method, dispersion liquid and nano carbon material obtained by the dispersion method

The present invention relates to a method of dispersing a nanocarbon material with titanium dioxide particles, which can be realized in a dispersion liquid and obtain a nano carbon material having mutually exclusive dispersion characteristics. The nano carbon materials described herein include, but are not limited to, carbon nanotubes and carbon spheres.

Due to the excellent properties of carbon nanotubes, the application of carbon nanotubes has been discussed in recent years. However, there is a strong van der Waals between the carbon nanotubes (Van der Waals). Attraction), it is easy to cause the carbon tubes to gather together and is not easily dissolved in an aqueous solution or an organic solvent, so that the carbon nanotubes are not easily dispersed. However, the dispersion of carbon nanotubes is closely related to its application effect, and poor dispersion will limit the development space of carbon nanotubes.

According to the literature, the method of dispersing a carbon nanotube can be roughly classified into two types: a covalent modification and a noncovalent modification.

Covalent modification, this method mainly uses strong acid as a strong oxidant, due to defects in the structure of the carbon nanotubes (such as five-membered ring or seven-membered ring), the long carbon tube can be shortened into Hundreds of nanometers of short carbon nanotubes, and during the reaction, the wall or tail end of the carbon nanotubes will react to oxygen-containing functional groups, including carboxyl groups (-COOH) and carbonyl groups. (carbonyl groups, >C=O) and hydroxyl groups (-OH), etc., there are other literature studies, such as fluorine or alkane (alkanes) and other functional groups attached to the side tube of the carbon nanotubes The wall does not cut the carbon nanotubes, reducing the damage to the carbon nanotube structure. The above-mentioned functionalized carbon nanotubes can be effectively dispersed in an aqueous solution or a different organic solvent, and the types and procedures of the functionalization of the carbon nanotubes are considerably recorded in the literature, and should be considered in the field of application. Choose what you want to pick up to The type of functional group on the surface of the carbon nanotube.

Although the covalent bond modification method can effectively disperse the carbon nanotubes, it may damage the structure of the carbon nanotubes during the functionalization process, and change the unique properties of some carbon nanotubes, so that The application was not as expected, so the study developed a non-covalent bond modification method to disperse the carbon nanotubes.

Noncovalent modification, mainly divided into two kinds, one is surfactants (surfactants) as a dispersing agent, the most common is sodium dodecyl sufate (SDS), First, the carbon nanotubes are ultrasonically oscillated to destroy the van der Waals attraction between the carbon nanotubes, and the carbon tubes are respectively coated in the micelles formed by the surfactant, and the hydrophobic of the micelles is hydrophobic. The end is internally coated with a carbon nanotube, and the hydrophilic end is externally contacted with the solution to form a stable dispersion.

The other type is mainly a polymer with polar side chains. Commonly used, such as polyvinylpyrolidone (PVP), polystyrene sulfonate (PSS), etc., the dispersion method is also the first to use ultrasonic waves. Oscillation destroys the van der Waals attraction between the carbon nanotubes, and then the main chain of the polymer is wrapped around the carbon nanotubes to form a dispersed nanocarbon tube supramolecular complex, while the polar side chains are Contact with the solution medium to achieve the dispersion effect, the thermodynamic driving force of the complex is excluded from the hydrophobic interface between the carbon nanotube wall and the solution medium. This method is also a reversible system, which can replace the solution with Less polar solvents (such as tetrahydrofuran (THF)) can cause entanglement failure due to changes in the solution system. The dispersion formed by this method can also be regarded as a composite material, which will improve the properties of the carbon nanotube itself and the polymer.

The above two non-covalent bond modification methods do not destroy the carbon nanotube structure, so the nanometer The nature of the carbon tube itself is less affected. However, in the case of surfactants, in the detection of biochemical sensors, the presence of surfactants may cause defects such as electrode passivation and signal interference, and polymers may be used as a barrier to these surfactants. Insulate the layer, but it will also slightly reduce the detected current signal.

De Heer, a professor of physics at the Georgia Institute of Technology in the United States, mentioned in 2002 that "the carbon nanotubes have not been effectively used after 10 years of discovery. The obstacles are not only the production cost of carbon nanotubes, but also the dispersion of applications. Sex, process limitations and self-assembly capabilities." This paragraph is pointing out the problems encountered by the nano industry today, so the inventor of this case studied the dispersibility of the carbon nanotubes.

The purpose of the present invention is to provide a method for dispersing nano carbon materials, which is a method for dispersing nano carbon materials without using covalent bonds and organic solvent modification, which can effectively reduce the operation steps and does not have surface functionalization of nano carbon materials. The basicity preserves the original excellent properties of the carbon nanotubes and enhances their applicability.

The purpose of the present invention is to provide a dispersion of nano carbon material, which is an aqueous solution with positively charged nano particles. After the carbon material is added to the aqueous solution, the nano particles with high charge will surround the nano. The surface of the rice carbon material is uniformly dispersed in the aqueous solution by the repulsive force by utilizing the same charge of the nano particles.

The method for achieving the above object comprises: mixing a nano carbon material with a positively charged titanium dioxide nano particle in a solution, so that the titanium dioxide nano particle is surrounded and bonded to the surface of the nano carbon material, and the titanium dioxide nano particle is positive. The charge mutual repulsion causes the nano carbon material to be uniformly dispersed in the aqueous solution.

The dispersion liquid for achieving the above object mainly comprises a titanium dioxide nano particle solution and a nano carbon material, wherein the nano carbon material is surrounded by the titanium dioxide nano particle, thereby uniformly dispersing in the solution. In the liquid.

In the present invention, a mutually exclusive nano carbon material is obtained by the above method, and the outer surface of the mutually exclusive nano carbon material is expressed in a solution around the titanium dioxide nano particles.

The method for dispersing a carbon nanotube of the present invention is to use a positively charged titanium dioxide nanoparticle aqueous solution to be added to a carbon nanotube, and the high-charged titanium dioxide nanoparticle will surround the carbon nanotube and finally utilize titanium dioxide. The nanoparticles are charged with the same charge, and the carbon nanotubes are uniformly dispersed in the aqueous solution by repulsive force.

In order to achieve the titanium dioxide nanoparticle surrounding the carbon nanotubes and uniformly dispersing the carbon nanotubes in the aqueous solution, the inventors explored the optimum conditions for the optimization scheme by the following experiments.

■Experimental drugs:

1. Multi-layered wall carbon nanotubes (purity of about 99%, TECO nano-materials)

Second, titanium dioxide nanoparticles (purity of about 99%, anatase, Aldrich)

Third, hydrogen chloride (purity about 96%, SHOWA)

■Experimental equipment:

1. Transmission electron microscope (TEM): used to observe the surface morphology of the carbon nanotubes before and after dispersion and to confirm whether the titanium dioxide nanoparticles surround Carbon nanotube surface (JEM-200CX from, JEOL)

Second, scanning probe microscope (SPM): using atomic force microscope tapping scanning mode, used to observe the surface morphology of the carbon nanotubes before and after dispersion and confirm whether the titanium dioxide nanoparticles surround the carbon nanotubes Surface (SPA-400 multiple function units together with SPI-3800N, Seiko).

■Experimental step - Discussion on changing the pH value of 5 wt% titanium dioxide nanoparticle aqueous solution

a. Four aqueous solutions of pH (1~4) 5 wt% titanium dioxide nanoparticles were prepared using hydrogen chloride.

b. Add 2.5 mg/mL multi-walled nanotubes to the above four aqueous solutions of pH 5 wt% titanium dioxide nanoparticles.

c. The multi-layered wall carbon nanotubes were completely dispersed in the aqueous solution of titanium dioxide nanoparticles by means of an ultrasonic oscillator, and then allowed to stand for several days.

d. Observe the dispersion of multi-walled carbon nanotubes in aqueous solution of 5 wt% titanium dioxide nanoparticles with different pH values.

As shown in Annex I, 2.5 mg/mL multi-walled carbon nanotubes at different pH values (a) pH = 1, (b) pH = 2, (c) pH = 3, (d) pH = 4 of 5 wt% titanium dioxide After the ultrasonic wave was shaken for 1.5 hours in an aqueous solution of nanoparticle, the dispersion was allowed to stand for another 12 hours. It can be found that the multi-walled carbon nanotubes are uniformly dispersed in the a bottle without any precipitation, and in the 5 wt% titanium dioxide nanoparticle aqueous solution with pH=2~4, the b~d bottle can be found to have delamination or precipitation. The phenomenon occurs, indicating that the phenomenon of multi-walled carbon nanotubes gathering together occurs.

As shown in Annex II, 2.5 mg/mL multi-walled carbon nanotubes at different pH values (a) pH=1, (b)pH=2, (c)pH=3, (d)pH=4 of 5 wt% titanium dioxide The dispersion of the nanoparticle aqueous solution after ultrasonic vibration for 1.5 hours was allowed to stand for another 24 hours. After standing for 24 hours, it was clearly seen that the multi-walled carbon nanotubes were uniformly dispersed in the solution in the 5 wt% titanium dioxide nanoparticle aqueous solution of pH=1. In the 5 wt% titanium dioxide nanoparticle aqueous solution with pH=2~4, delamination or precipitation can be found in the b~d bottle, indicating that the multi-walled carbon nanotubes are clustered together.

Through the results of this experiment, we can know that 5 wt% titanium dioxide nanoparticle aqueous solution is optimal. The pH of the dispersed multi-walled carbon nanotubes is 1.

■Experimental step - Discussion on the amount of carbon nanotubes in a 5 wt% titanium dioxide nanoparticle aqueous solution with pH=1

a. A 5 wt% aqueous solution of titanium dioxide nanoparticles having a pH of 1 was prepared using 0.1 M hydrogen chloride.

b. Different amounts of multi-walled nanotubes (0.5, 1.5, 2.5, 5 mg/mL, respectively) were added to a 5 wt% titanium dioxide nanoparticle aqueous solution of pH=1.

c. Different amounts of multi-walled nanotubes were completely dispersed in an aqueous solution of 5 wt% titanium dioxide nanoparticles having a pH of 1 using an ultrasonic oscillator and allowed to stand for 12 hours.

d. Dispersion of different amounts of multi-walled nanotubes in an aqueous solution of 5 wt% titanium dioxide nanoparticles having a pH of 1 was observed.

As shown in Annex III, the dispersion of different content of multi-walled carbon nanotubes after ultrasonic vibration for 1.5 hours in aqueous solution: (a) 0.5 mg/mL multi-walled carbon nanotubes dispersed in deionized water with pH=1 and ( b) 0.5 mg/mL; (c) 1.5 mg/mL; (d) 2.5 mg/mL; (e) 5 mg/mL multi-walled nanotubes dispersed in a 5 wt% titanium dioxide nanoparticle aqueous solution at pH=1 . It was found that the multilayered wall carbon nanotubes were uniformly dispersed in each aqueous solution without any precipitation.

As shown in Annex IV, the dispersion of different content of multi-walled nanocarbon tubes after ultrasonic vibration for 1.5 hours in aqueous solution, and then after standing for 12 hours: (a) 0.5 mg/mL multi-walled carbon nanotubes dispersed at pH= 1 deionized water with (b) 0.5 mg/mL; (c) 1.5 mg/mL; (d) 2.5 mg/mL; (e) 5 mg/mL multi-walled nanotubes dispersed at pH=1 5 A wt% aqueous solution of titanium dioxide nanoparticles. It can be found that the a bottle of multi-walled carbon nanotubes quickly aggregates to produce a precipitate, which proves that the multi-layered wall carbon nanotubes can be dispersed in the aqueous solution of 5 wt% titanium dioxide nanoparticles with pH=1, indeed because The effect of titanium oxide nanoparticles is not effective in dispersing multi-walled carbon nanotubes due to changes in the pH of the solution. The e-bottle has been clearly delaminated after 12 hours, and the multi-walled carbon nanotubes cannot be effectively dispersed because the amount of multi-walled carbon nanotubes (5 mg/mL) has exceeded 5 wt%. =1 The content of the titanium dioxide nanoparticle aqueous solution can be loaded, and the multi-layered wall carbon nanotubes can aggregate and can not maintain uniform dispersion. As for the b~d bottle, it can maintain good dispersion after 12 hours, no precipitation occurs, and the uniform dispersion can last for several days.

From the results of this experiment, it can be known that a 5 wt% titanium dioxide nanoparticle aqueous solution having a pH of 1 can disperse up to 2.5 mg/mL of multi-walled nanotubes.

■Experimental step - Discussion on the weight percentage of titanium dioxide nanoparticles in aqueous solution with pH=1

a. Use hydrogen chloride and deionized water to prepare different wt% (1~7) titanium dioxide nanoparticle aqueous solution with pH=1.

b. Add 2.5 mg/mL multi-walled nanotubes to an aqueous solution of different wt% titanium dioxide nanoparticles with a pH of 1.

c. The 2.5 mg/mL multi-walled nanotubes were completely dispersed in a different wt% titanium dioxide nanoparticle aqueous solution of pH=1 using an ultrasonic oscillator and allowed to stand for half a day.

d. Observe the dispersion of 2.5 mg/mL multi-walled carbon nanotubes in aqueous solution of different wt% titanium dioxide nanoparticles with pH=1.

As shown in Annex V, the dispersion of 2.5 mg/mL multi-walled carbon nanotubes in aqueous solution of titanium dioxide nanoparticles with pH=1 after ultrasonic vibration for 1.5 hours. Weight percent of titanium dioxide nanoparticles Ratio: (a) 1; (b) 2; (c) 5; (d) 7 wt%. It can be found that the a and b bottles of the multi-walled carbon nanotubes are not dispersible, and the c and d bottles of the multi-walled carbon nanotubes are uniformly dispersed in the respective aqueous solutions without any precipitation.

As shown in Annex VI, the dispersion of 2.5 mg/mL multi-walled carbon nanotubes in an aqueous solution of titanium dioxide nanoparticles at pH=1 was ultrasonically oscillated for 1.5 hours and allowed to stand for another 12 hours. Weight percentage of titanium dioxide nanoparticles: (a) 1; (b) 2; (c) 5; (d) 7 wt%. It can be found that a 7 wt% aqueous solution of titanium dioxide nanoparticles having a pH of 1 is precipitated because the weight percentage of the titanium dioxide nanoparticles is too high, resulting in significant delamination after the addition of the 2.5 mg/mL multi-walled carbon nanotubes. The phenomenon occurs, which means that excessive titanium dioxide nanoparticles are not conducive to the dispersion of multi-walled carbon nanotubes.

From the results of this experiment, it can be known that the 5 wt% titanium dioxide nanoparticle aqueous solution c bottle having a pH of 1 has a good effect on dispersing the multi-walled carbon nanotubes.

■Transmission electron microscope (TEM) analysis

The morphology of the multi-walled carbon nanotube-titanium dioxide nanoparticle composite was observed by transmission electron microscope (TEM). The undispersed multi-walled carbon nanotubes and the carbon nanotubes dispersed with the titanium dioxide nanoparticles were observed using a transmission electron microscope to observe the dispersion. From Annex VII, it can be seen that the multi-walled carbon nanotubes are gathered together to form a bundle. From Annex VIII, it can be seen that the multi-walled carbon nanotubes are dispersed one by one, which proves that the titanium dioxide nanoparticles can indeed disperse the multi-walled carbon nanotubes, and the surface of the multi-walled carbon nanotubes is also seen. The presence of nanoparticle means that the titanium dioxide nanoparticles actually surround the multi-walled nanotubes. From the partial enlarged view of Annex IX, it can be seen that the titanium dioxide nanoparticles have a particle diameter of about 10-20 nm, and the multilayer wall carbon nanotubes have a diameter of about 30. Nm, it is clear that the titanium dioxide nanoparticles surround the multi-walled carbon nanotubes.

■Atomic force microscope (AFM) analysis

Then observe by atomic force microscopy to see if the same result can be obtained. Annex IX is the surface topography of a single multi-walled carbon nanotube. It can be clearly seen from Annex IX that the multi-walled carbon nanotubes are straight round tubes with a diameter of 40 nm. The morphology is consistent with the arc discharge method. With the characteristics of straight rods and few structural defects, we will also scan a single multi-walled carbon nanotube surrounded by titanium dioxide nanoparticles to obtain the attachment 10 by atomic force microscopy. It can be clearly found that it surrounds the multi-walled carbon nanotubes. The titanium dioxide nanoparticles have a particle diameter of about 10-20 nm, which is consistent with the results of a transmission electron microscope. A single multi-walled nanocarbon tube surrounded by titanium dioxide nanoparticles is known from Annex X. The diameter is about 100 nm, which is much larger than the diameter of the multi-walled carbon nanotubes, which again proves that the titanium dioxide nanoparticles surround the multi-walled carbon nanotubes.

Through the proof of atomic force microscopy and transmission electron microscopy, it can be confirmed that the positively charged titanium dioxide nanoparticles can indeed surround the multi-walled carbon nanotubes, and the titanium dioxide nanoparticles have positive charges. A repulsive force is generated, so that the multilayered wall carbon nanotubes can be uniformly dispersed in the aqueous solution of titanium dioxide nanoparticles.

Although the above experiment uses multi-walled carbon nanotubes, it is not limited to this. Single-layer carbon nanotubes (SWNTs) and carbon nanocapsules are also achievable.

Although the present case is illustrated by a preferred embodiment, those skilled in the art can make various forms of changes without departing from the spirit and scope of the present invention. The above embodiments are only used to illustrate the present case and are not intended to limit the scope of the present invention. Any modification or change that does not violate the spirit of the case It is the scope of patent application in this case.

【annex】

Annex I: 2.5 mg/mL multi-walled nanotubes in different (a) pH = 1; (b) pH = 2; (c) pH = 3; (d) pH = 4 of 4 pH values of 4 wt% After dispersing for 1.5 hours in an aqueous solution of titanium dioxide nanoparticles, the dispersion was allowed to stand for another 24 hours.

Annex II: 2.5 mg/mL multi-walled carbon nanotubes at (a) pH = 1; (b) pH = 2; (c) pH = 3; (d) pH = 4 of 5 different pH values of 5 wt% After dispersing for 1.5 hours in an aqueous solution of titanium dioxide nanoparticles, the dispersion was allowed to stand for another 24 hours.

Annex III: Dispersion of different content of multi-walled nanocarbon tubes after ultrasonic vibration for 1.5 hours in aqueous solution: (a) 0.5 mg/mL multi-walled nanotubes dispersed in deionized water at pH=1 and (b) 0.5 mg/mL; (c) 1.5 mg/mL; (d) 2.5 mg/mL; (e) 5 mg/mL multi-walled nanotubes dispersed in a 5 wt% titanium dioxide nanoparticle aqueous solution at pH=1.

Annex 4: Dispersion of different content of multi-walled nanocarbon tubes after ultrasonic vibration for 1.5 hours in aqueous solution, after standing for another 12 hours: (a) 0.5 mg/mL multi-walled carbon nanotubes dispersed at pH=1 Deionized water with (b) 0.5 mg/mL; (c) 1.5 mg/mL; (d) 2.5 mg/mL; (e) 5 mg/mL multi-walled nanotubes dispersed at pH 1 of 5 wt % titanium dioxide nanoparticle aqueous solution.

Annex V: 2.5 mg/mL multi-walled carbon nanotubes in aqueous solution of titanium dioxide nanoparticles with pH=1 The dispersion of the ultrasonic wave after 1.5 hours. Weight percentage of titanium dioxide nanoparticles: (a) 1; (b) 2; (c) 5; (d) 7 wt%.

Annex VI: Dispersion of 2.5 mg/mL multi-walled carbon nanotubes in an aqueous solution of titanium dioxide nanoparticles at pH=1 after ultrasonic vibration for 1.5 hours and then allowed to stand for 12 hours. Weight percentage of titanium dioxide nanoparticles: (a) 1; (b) 2; (c) 5; (d) 7 wt%.

Annex VII: Transmission electron microscope (TEM) pattern before dispersion of multi-layered wall carbon nanotubes.

Annex VIII: Transmission electron microscope (TEM) pattern after dispersion of multi-layered wall carbon nanotubes.

Annex IX: Atomic Force Microscope (AFM) analysis of the multi-layered wall carbon nanotubes.

Annex X: Atomic force microscope (AFM) analysis pattern after dispersion of multi-layered wall carbon nanotubes.

Claims (9)

A method for dispersing a nano carbon material, comprising: mixing a nano carbon material with a positively charged titanium dioxide nano particle in a solution, and causing the titanium dioxide nano particle to surround the surface of the nano carbon material, and the titanium dioxide nano particle The positive charge mutual repulsion forces the nano carbon material to be uniformly dispersed in the aqueous solution. The method of claim 1, wherein the means for mixing is ultrasonic oscillating. A nano carbon material dispersion mainly comprises a titanium dioxide nano particle solution and a nano carbon material, wherein the nano carbon material is surrounded by the titanium dioxide nano particles to be uniformly dispersed in the solution. The nano carbon material dispersion according to claim 3, wherein the titanium dioxide nanoparticle solution has a pH of 1. The nano carbon material dispersion according to claim 4, wherein the titanium dioxide nanoparticle solution has a concentration of 5 wt%. The nano carbon material dispersion according to claim 5, wherein the titanium dioxide material of the titanium dioxide nanoparticle solution has a loading of at most 2.5 mg/mL. The nano carbon material dispersion according to claim 3, wherein the titanium dioxide nanoparticle has a diameter of 10 to 20 nm. The nano carbon material dispersion according to claim 3, wherein the nano carbon material is a multi-walled carbon nanotube, a single-layer carbon nanotube or a nanocarbon sphere. A nano carbon material in which the outer surface of the nano carbon material is expressed in a solution around the titanium dioxide nanoparticle.