KR101744051B1

KR101744051B1 - A measurement method for number of functional groups bonded to the carbon nanotube surface

Info

Publication number: KR101744051B1
Application number: KR1020160005182A
Authority: KR
Inventors: 김우재
Original assignee: 가천대학교 산학협력단
Priority date: 2016-01-15
Filing date: 2016-01-15
Publication date: 2017-06-20

Abstract

More particularly, the present invention relates to a method for measuring the number of surface-bonding functional groups of carbon nanotubes,

(I ₁₂₈₉ / I ₁₅₈₂ ) for measuring the surface bonding functional group number of carbon nanotubes.

Description

Technical Field [0001] The present invention relates to a method for measuring the number of functional groups bonded to a surface of a carbon nanotube,

The present invention relates to a method of measuring the number of functional groups bonded to the surface of carbon nanotubes, and more particularly, to a method of measuring the number of functional groups bonded to the surface of carbon nanotubes

And a method for measuring the number of functional groups bonded to the surface of a carbon nanotube by using the density.

Carbon nanotubes have been studied since the discovery by Dr. Iijima of Meijo University in Japan, which handled electron microscopy in 1991. Carbon nanotubes have a structure in which a graphite surface is rounded, and a diameter of 1 to 20 nm is typical. Graphite has a unique hexagonal plate-like membrane structure, which is unique in its bonding arrangement. The upper and lower parts of the membrane are filled with free electrons, and electrons move in parallel with the membrane in a discrete state. Since these graphite layers are wound in a spiral shape to form carbon nanotubes, the electrical properties of the nanotubes are a function of structure and diameter. B46,1804 (1992) and Phys.Rev.Lett., 68, 1579 (1992). In other words, it has been proved that the electrical properties of the same material vary from insulator to semiconductor to metallic due to difference in structure and diameter.

Changing the spiral or chirality of carbon nanotubes changes the way the free electrons move, resulting in free movement of the free electrons, which can cause the carbon nanotubes to react like metal or to overcome barriers like semiconductors. Should be. The size of the barrier is determined by the diameter of the tube, and it is known that the diameter of the tube is as small as 1 eV.

Carbon nanotubes are excellent in mechanical durability and chemical stability, and can have both semiconductor and conductor properties. Due to their small diameter, long length, and hollow nature, they are excellent materials for flat panel display devices, transistors and energy storage materials. And it is very useful as a nano-sized electronic device.

However, despite the excellent properties of carbon nanotubes, the physical and electrical properties of currently manufactured carbon nanotube composites are not as expected. This is due to the strong electrostatic attraction between the carbon nanotubes, Or even dispersion in the polymer is difficult. Therefore, it is important that the carbon nanotube / polymer composite effectively disperses the carbon nanotubes in the polymer matrix to maximize the advantages of the nanotubes as a filler.

Conventionally, dispersion methods that have been studied for effective dispersion of carbon nanotubes include a physical method using ultrasonic waves and a surface modification method which introduces a low molecular substance or a polymer substance to the surface of a tube by a chemical method, Method. However, in the case of the physical method, it is difficult to maintain the excellent properties and characteristics of the tube because it damages the tube according to the intensity and the time of the ultrasonic wave. Therefore, the surface modification research using the more effective chemical method is being actively carried out.

In the surface modification using such a chemical method, the physical properties of the modified carbon nanotubes are greatly influenced by the number of functional groups chemically bonded to the surface, but the number of functional groups bonded to the surface of the carbon nanotubes can be quantified There has been no research on the method.

It is an object of the present invention to provide a new method for quantifying the number of functional groups bonded to the surface of carbon nanotubes in order to overcome the problems of the prior art.

The present invention provides a method for quantifying the number of functional groups bound to the surface of a carbon nanotube using a ratio D / G of D peak and G peak areas in Raman spectrum.

In the method of measuring the surface bonding functional group number of a carbon nanotube according to the present invention, the carbon nanotube is a single wall carbon nanotube.

In the method for measuring the surface bonding functional group number of carbon nanotubes according to the present invention, the number of functional groups n _f bonded to the surface of the carbon nanotubes by covalent bonding is determined by the ratio of the area of the D peak and the G peak

(1) by using the following equation (1).

In the method of measuring the number of surface bonding functional groups of a carbon nanotube according to the present invention, the covalent bonding functional group is not particularly limited as long as it is a functional group capable of being covalently bonded to the surface of the carbon nanotube, and is specifically a metal or a polymer .

In the method for measuring the number of surface bonding functional groups of a carbon nanotube according to the present invention, the functional group includes 4-nitrophenyl.

The number of functional groups bound to the surface of the carbon nanotube by covalent bonding can be easily measured by a simple method for measuring the Raman spectrum of the carbon nanotube according to the present invention. It is possible to quantitatively control the number of functional groups bonded to the surface of the carbon nanotubes by using the method of measuring the number of surface bonding functional groups of the carbon nanotubes.

FIG. 1 shows the UV-vis-NIR absorption spectra of single-walled carbon nanotubes functionalized with 4-nitrobenzene prepared in one embodiment of the present invention and a comparative example.
FIG. 2 shows Raman spectra of single-walled carbon nanotubes functionalized with 4-nitrobenzene prepared in one embodiment of the present invention and a comparative example.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited by the following examples.

< Example 1> Single wall Carbon nanotube preparation

CoMoCAT SWNT (SG65, SWeNT) was used as a sample. More than 90% of the carbon nanotubes have a diameter in the range of 0.7 to 0.9 nm.

CoMoCAT SWNTs were dissolved in deionized water using 1% (w / v) sodium dodecyl sulfate. Single walled carbon nanotubes (SWNTs) were dispersed for 2 hours using a homogenizer (T18 basic, ultra-turrax) and an ultra-sonicator (VCX-750, Sonics & Materials).

Single-walled carbon nanotubes (SWNTs) were then centrifuged (SW 32.1 Ti, Beckman Coulter) at 30,000 rpm for 4 hours and then separated into a supernatant and a suspension containing SWNTs.

< Example 2> Single wall Surface modification of carbon nanotubes

The 4-nitrobenzene diazonium salt was introduced into the 20-ml single-walled carbon nanotube (SWNTs) solution prepared in Example 1 to reform the surface of single-walled carbon nanotubes (SWNTs) into 4-nitrophenyl functional groups.

Specifically, 4-nitrobenzene diazonium salt solution was prepared at four concentrations (0.11, 0.17, 0.23, and 0.29 mM), put into single-walled carbon nanotubes (SWNTs) solution and reacted at 50 ° C. for 20 hours, The number of functional groups on the surface of the nanotubes (SWNTs) was varied.

Single walled carbon nanotubes (SWNTs) were reacted for 24 hours with an aqueous solution containing 2% (w / v) sodium cholate as a surfactant.

< Experimental Example > UV- vis - NIR absorption spectra measurement

The single-walled carbon nanotubes (SWNTs) prepared in Example 2, which were surface-modified with the 4-nitrophenyl functional group at concentrations of 0.11, 0.17, 0.23 and 0.29 mM, and the SWNTs ) Was measured for UV-vis-NIR absorption spectra and the results are shown in FIG.

For UV-vis-NIR absorption spectra metallic SWNTs is the first van Hove transition from _{^{(E 11 M, 400-500 nm)}} , the semiconducting SWNTs are each (E ₂₂ ^SC, 500-850 nm) and (E ₁₁ ^SC, 850-1350 nm), which is known to represent the first and second van Hove metastases.

Also compared to the comparative example that is not the modified surface in the first, for the four samples functionalized SWNT for semiconducting SWNTs characteristic (E ₂₂ ^SC, 500-850 nm) and (E ₁₁ ^SC, 850-1350 nm) It can be seen that the peak has completely disappeared.

From this, more than 90% of the SWNTs of the comparative example without the functional groups are composed of semiconducting SWNTs, and the minute metallic SWNTs completely react with the nitrobenzene diazonium reagent according to the embodiment of the present invention, and the nitrophenyl functional group Covalent bonding.

< Experimental Example > Raman spectrum measurement

(D) peak (disorder mode, 1289 cm ^& ^lt ; & quot ^; ¹ ^> ) with Raman spectra using 632.8 nm excitation for single-walled carbon nanotubes with nitrophenyl functional groups according to the present invention G peak (tangential mode, 1582 cm ^& ^lt ; ^-1 ^> ) was observed, and the results are shown in Fig.

In the comparative example of FIG. 2, no D peak was observed, indicating that the functional groups were not bonded. In contrast, four action by the embodiment of the present invention for a single-walled carbon nanotube sample vaporized G peak (tangential mode, 1582 cm - 1) and the D peak contrast ^{(disorder mode, 1289 cm - 1} ) can increase As the concentration of the diazonium reagent in the reaction sample increased from 0.11 mM to 0.29 mM

₍ D / G area ratio) is clearly increased.

< Example 3> Density difference by Reformed Single wall Separation of carbon nanotubes and Reformed Density measurement of single-walled carbon nanotubes

Single walled carbon nanotubes (SWNTs) increase in density of SWNTs as the number of functional groups per carbon atom increases and travels from the top to the bottom of the centrifuge tube.

Using this principle, the modified single-walled carbon nanotubes were centrifuged in order to separate the modified single-walled carbon nanotubes by the density difference according to the degree of modification.

3 ml of non-ionic medium iodixanol (optiprep, 60% (w / v) iodixanol, Sigma-Aldrich) was added as the first layer to the bottom of the centrifuge tube, Iodixanol was prepared by adding 1 ml of 50% (w / v) iodixanol of the functionalized SWNTs prepared in Examples and Comparative Examples and 29.5-48.5% (w / v) iodixanol in the third layer, , And deionized water was placed in the top layer and filled from the bottom to the top of the centrifuge tube.

All samples were centrifuged at 32,000 rpm for 22 hours at 22 ° C using a swinging bucket rotor (SW 32.1 Ti, Beckman Coulter), and each 200 μl sample was fractionated by centrifugation.

The density of the SWNT sample was measured through the final density of the solution and distance matching from each fraction to the meniscus, and the results are shown in FIG.

Each of the centrifugal tubes in Fig. 3 represents the result of centrifugation of the carbon nanotubes of the comparative example and the example. As shown in FIG. 3, the densities of the comparative examples containing 0.11 mM, 0.17 mM, 0.23 mM and 0.29 mM of the functional groups were measured at 1157, 1220, 1247, 1261 and 1266 kg / m ³ , respectively.

< Example 4> per carbon atom 디ason늄 Measurements

The density of the single-walled carbon nanotube (SWNT) measured in Example 3 can be expressed by Equation 1 below, where n _f is the amount of diazomium bonded per carbon atom.

Equation (1)

Here, a number of M _{(n, m)} and V _(n,m) are respectively (n, m) is the mass and volume of the SWNT, n _f is a carbon atom per one combined diazonium (diazonium), M _f, and V _f is the molecular weight and volume of the diazonium, respectively.

Thus, the amount of diazonium bonded per carbon atom n _f Can be expressed by the following equation (2).

Equation (2)

Where n _s is the number of surfactants present per nm of SWNT, n _c is the number of carbon atoms present per nm of SWNT, and d _eff is the diameter of the SWNT.

The number of surfactants present per 1 nm of SWNT is reduced because the surface area of the SWNT that the surfactant can adsorb decreases when the diazonium group is attached to the surface of the SWNT, The change of ns value can be expressed by the following equation.

(Equation 3)

The n _c and n _s values of the pure SWNT are substituted into Equation 2, and n _f After subtracting nf from the existing nc, the new nc value is obtained. The new nc value is obtained by substituting the new nc value into the equation (3), and the new ns value is substituted into the equation (2) The exact number of surfactants n _s present per nm of SWNT can be determined.

Using the densities measured in Example 3 above, the amount of diazomium per carbon atom measured in this manner is 0.0263 (0.11 mM), 0.0380 (0.17 mM), 0.0439 (0.23 mM), and 0.0464 (0.29 mM).

delete

Claims

Number of functional groups bonded to carbon nanotube surface

Is the ratio of the area of the D peak to the area of the G peak in the Raman spectrum

(I ₁₂₈₉ / I ₁₅₈₂ ) was used to measure the number of surface bonding functional groups of carbon nanotubes

The method according to claim 1,
The carbon nanotubes are single wall carbon nanotubes
Measurement of number of surface bonding functional groups of carbon nanotubes

delete

The method according to claim 1,
Wherein the functional group is a covalent bond functional group
Measurement of number of surface bonding functional groups of carbon nanotubes

The method according to claim 1,
Wherein said functional group comprises 4-nitrophenyl
Measurement of number of surface bonding functional groups of carbon nanotubes