JP2002226209A - Lb film consisting of carbon nanotube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a thin film of a carbon nanotube which is homogeneous, and whose film thickness is controlled precisely. SOLUTION: The LB film consists of a solubilizing carbon nanotube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film (LB film) made of carbon nanotubes having a uniform thickness and a precisely controlled thickness.

[0002]

2. Description of the Related Art As a thin film of carbon nanotube,
So far, spray films have been known. The spray film is
Carbon nanotubes dispersed in a solvent such as ethanol using ultrasonic waves are sprayed on a substrate using a spray device, and the solvent is quickly evaporated to form a thin film. The spray film has many irregularities, it is difficult to form a uniform film, and it is impossible to control the film thickness. As another method, it has been reported that carbon nanotubes are dispersed in a surfactant, developed on a water surface, and transferred to a substrate to form a thin film. In this method, the concentration of the dispersible carbon nanotubes is extremely low, about 7% by weight or less, and only a single-layer film can be formed. Therefore, it is impossible to arbitrarily control the film thickness. In general, a vacuum deposition method, a spin coating method, or the like is used as a method for producing a thin film. However, since carbon nanotubes do not evaporate even when heated and do not dissolve in a solvent, it is not possible to produce a thin film using these methods. It was impossible.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a carbon nanotube thin film having a uniform thickness and a precisely controlled film thickness.

[0004]

Means for Solving the Problems The present inventors have completed the present invention by laminating solubilized carbon nanotubes on a substrate by the Langmuir Project (LB) method. . That is, according to the present invention, an LB film made of a solubilized carbon nanotube is provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The solubilized carbon nanotube used in the present invention contains an amide group represented by the following general formula (1). -CONHR (1) In the above formula, R represents an aliphatic group having 14 to 20 carbon atoms (indicating an alkyl group or an alkenyl group). Among the solubilized carbon nanotubes, those having 18 carbon atoms in the aliphatic group R are known compounds, for example, literature 1) [Chen, J. et al. Sci.
282, 95-98 (1998)]. Further, the carbon nanotube may be a single-walled carbon nanotube or a multi-walled carbon nanotube in which the carbon nanotubes are multiplexed concentrically. The diameter of the carbon nanotube may be 0.4 to 2.0 nm for a single-walled carbon nanotube, and may be larger for a multi-walled carbon nanotube. The length of the carbon nanotube is not limited, but is preferably about 1 micron or less in order to obtain good solubility.

In the present invention, the LB method is used to make the solubilized nanotube into a thin film. The solubilized nanotubes are dissolved in chloroform and placed on the surface of a commercially available Langmuir trough. In this case, the solubilized nanotube may be used alone, or the solubilized nanotube may be used as a mixture with a polymer such as poly (N-dodecylacrylamide) (PDDA). In the case of mixing, any mixing ratio in which the concentration of the solubilized carbon nanotube is more than 0% by weight and less than 100% by weight can be used. Since the surface pressure versus membrane area (π-A) curve when developed on the water surface shows a sharp rise and a high collapse pressure, the solubilized carbon nanotube or the mixture of the solubilized carbon nanotube and PDDA is It turns out that a stable monomolecular film is formed. When the concentration of the solubilized carbon nanotubes is changed, the occupied area of the condensed film obtained from the π-A curve increases in proportion to the concentration of the carbon nanotubes. It can be seen that they are homogeneously mixed.

A uniform thin film can be grown at a cumulative ratio of 1 by repeatedly developing a monomolecular film on a water surface, immersing the substrate in a direction perpendicular to the water surface, and lifting the substrate. In this case, the surface pressure of the monomolecular film is 20 to 45
It is kept at about mN / m. As the substrate, glass, quartz, conductive glass, silicon, or the like that has been subjected to a hydrophobic treatment or a hydrophilic treatment is used. The film thickness can be precisely controlled by changing the number of times the substrate is moved up and down. Mixing solubilized carbon nanotubes with PDDA
A more stable monomolecular film is formed, and the number of laminations can be increased. The number of laminations is usually 2 to 150 times, preferably 10 to 100 times. Further, in the thin film thus manufactured, it was found that the carbon nanotubes were oriented in the vertical direction of the substrate.

[0008]

Next, the present invention will be described in more detail by way of examples.

Example 1 Solubilized carbon nanotubes are dissolved in chloroform together with PDDA (37% by weight of solubilized carbon nanotubes) and developed as a monomolecular film on the water surface. The π-A curve of this monomolecular film has a favorable shape as shown in FIG. 1, and it can be seen that a stable monomolecular film is formed on the water surface.
The quartz substrate that had been subjected to the hydrophobic treatment in advance was immersed in the direction perpendicular to the water surface and pulled up repeatedly 10 to 50 times to produce five types of carbon nanotube thin films having different film thicknesses. These films are transparent without turbidity and have a very homogeneous appearance. FIG. 2 shows light absorption spectra of these five types of LB films. 182
Since the light absorption intensity at 0 nm increases in direct proportion to the number of laminations, it indicates that a thin film whose thickness is precisely controlled is formed. FIG. 3 is an X-ray diffraction diagram of the LB film stacked 50 times. A diffraction peak is observed at 2.37 degrees, which indicates that the LB film has a periodic structure of 3.72 nm. FIG. 4 shows a change in Raman spectrum when the polarization direction of the excitation laser is set to the vertical direction of the substrate and the direction perpendicular to the direction of the LB film having 90 stacked layers. The former gives a stronger Raman peak, indicating that the nanotubes are oriented in the vertical direction of the substrate.

Example 2 (LB film made of only solubilized carbon nanotubes without PDDA) The solubilized carbon nanotubes were dissolved in chloroform,
It develops as a monolayer on the water surface. Π- of this monolayer
The curve A has a favorable shape as shown in FIG. 5, and it can be seen that a stable monomolecular film is formed on the water surface. A glass substrate that had been subjected to hydrophilic treatment in advance was immersed in a direction perpendicular to the water surface, and was repeatedly pulled up to nine times, whereby a uniform carbon nanotube thin film could be produced. As shown in FIG. 6, since the light absorption intensity at 1820 nm increases in direct proportion to the number of laminations, it can be seen that a thin film whose thickness is precisely controlled is formed.

[0011]

The carbon nanotube thin film obtained according to the present invention is extremely uniform, and the film thickness can be precisely controlled. If this thin film is used, elements such as a solar cell, a photoelectric conversion element, a light emitting element, a field effect transistor, and a chemical sensor can be manufactured, and its application range is extremely wide.

[Brief description of the drawings]

FIG. 1 shows the relationship between the area (Area) (cm ² ) and the surface pressure (mN / m) of a solubilized carbon nanotube containing poly (N-dodecylacrylamide) as a monomolecular film developed on a water surface. It is a curve ((pi) -A curve) which shows a relationship.

FIG. 2 shows a light absorption spectrum of a solubilized carbon nanotube thin film (LB film) containing poly (N-dodecylacrylamide) and a relationship between absorbance at 1820 nm and the number of layers.

FIG. 3 shows an X-ray diffraction diagram of a laminated film when a solubilized carbon nanotube thin film is laminated 50 times.

FIG. 4 shows the change in Raman spectrum when the polarization direction of the excitation laser is set to the vertical direction of the substrate and the direction perpendicular to the direction of the laminated film when the solubilized carbon nanotube thin films are laminated 90 times.

FIG. 5 shows a π-A curve of a solubilized carbon nanotube containing no poly (N-dodecylacrylamide) when the film is developed as a monomolecular film on a water surface.

FIG. 6: LB consisting only of solubilized carbon nanotubes
The light absorption spectrum of the film and the relationship between the absorbance at 1820 nm and the number of layers are shown.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Masaru Yoshida 1-1 Higashi, Tsukuba, Ibaraki Pref. F-term (Reference) 4M035 AB24 BB63X CA48 DA06 DB13 DC21 EA07 EB20 4G046 CB03 CB08 CC05

Claims (2)

[Claims] 1. An L made of a solubilized carbon nanotube.
B film. 2. The LB film according to claim 1, wherein said carbon nanotubes are oriented in a certain direction.