JPH06298508A - Graphite-like carbon adsorbent - Google Patents

Abstract

PURPOSE:To provide a graphite-like carbon adsorbent capable of individually adsorbing molecules one by one or molecule groups which consist of several molecules, respectively. CONSTITUTION:A graphite-like carbon adsorbent comprises periodically arranging high electron density regions on the (011) lattice plane of a graphite-like thin film formed on a metal at distances of 1 nanometer or 10 nanometer and enabling to indiviually and periodically adsorb molecules such as enzymes or molecule groups when several molecules form a stable group in the high electron density region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a graphitic carbon adsorbent, and in particular, regions having a high electron density on the (001) lattice plane are arranged periodically, and one molecule or several groups of molecules are formed. It relates to adsorbents arranged at intervals, and as a result, if molecules such as enzymes are stable with one molecule or several molecules, it becomes possible to fix the molecule groups and observe the molecular image. The present invention relates to an adsorbent that does.

[0002]

BACKGROUND OF THE INVENTION Graphite is widely used as an electrode for industrial electrolytic electrodes to small dry batteries or lithium batteries because it is chemically stable and has electrical conductivity. It is also graphitized into fibers and is lightweight and has high strength. It is also widely used as a material.

As the carbon material as the adsorbent, amorphous carbon having a large surface area is used in many cases, but graphite pulverization is also used as the adsorbent utilizing the intercalation of the characteristic layered structure. .

The conventional technique of utilizing graphite found in graphite as an electrode material, graphitized fiber as a high-strength material, and graphite powder as an adsorbent is completely different from the technique of the present invention.

That is, while the conventional technology utilizes the characteristics of the entire structure having a so-called graphite structure,
The present invention utilizes the characteristics of a group of a small number of carbon atoms, which are specially caused by the graphitic surface structure.

From the viewpoint of utilizing a small number of carbon atom groups, it is similar to the fullerene represented by C60 which is a soccer ball-like carbon atom group, but the fullerene structure is spherical, whereas the graphite of the present invention is The shaped carbon is planar.

On the other hand, the societal demands for higher efficiency of drug development and sophistication of medical technology are combined with the scanning probe microscope technology, which is an observation method at the atomic and molecular level represented by the scanning tunnel microscope, which has been remarkably developed in recent years. However, there is a demand for a technique for observing and manipulating the drug at the molecular level, for example, confirming the drug effect by the three-dimensional structural change of biomolecules such as enzymes.

In order to observe and manipulate each molecule, at least that molecule must be immobilized.

In order to improve the resolution of the image of the fixed molecule, it is desirable that the molecules are dispersed independently.

Originally, fixing and dispersion were contradictory requirements,
When a low-concentration solution to be dispersed is introduced onto a substrate having a fixing function, a small number of aggregated molecules are formed,
I cannot reach my goal.

Further, the surface of the substrate used for fixing is, of course, smooth at the atomic level, but the relative position of the adsorbed molecule can be made clear at the nanometer level in the atomic or molecular level range or length unit. Is desirable.

That is, it is desired that the enzyme or the like is arranged not on a blank sheet of paper but on a surface of which the spacing is defined at the nanometer level, such as a graph paper.

From the viewpoint of providing a graph paper-like surface that is smooth at the atomic level and at the atomic / molecular level, graphite (00
1) The lattice plane is optimal.

However, the (001) lattice plane of graphite is chemically stable and is a typical surface because it is difficult for molecules to be adsorbed, and it is impossible to adsorb an enzyme or the like without surface treatment. Surface treatment loses the smoothness at the atomic level and the properties of graph paper that can determine the position at the atomic / molecular level.

[0015]

DISCLOSURE OF THE INVENTION The present inventors have completed the present invention as a result of extensive studies to achieve an adsorbent surface on which molecules can be regularly arranged.

That is, the object of the present invention is to have smoothness at the atomic level on the lattice plane of graphite, have periodicity at the nanometer level, and to adsorb one molecule or several molecule groups on it. It is to provide a graphite-like carbon adsorbent that enables it.

[0017]

The above-mentioned objects of the present invention can be achieved by a super-periodic structure of graphitic carbon surface.

The present invention has a periodic array of high electron density regions on the (001) lattice plane of graphitic carbon and adsorbs one molecule or several molecule groups in the high electron density region. It is a carbon adsorbent.

In the present invention, the interval of the high electron density regions periodically arranged on the surface of the graphitic carbon is from 1 nanometer to 10
It is in the nanometer range.

That is, the graphitic carbon of the present invention (00
1) The lattice plane is characterized by having atoms of graphite structure in addition to positions and having a super periodic structure of electron density.

The graphitic carbon of the present invention having such characteristics takes the form of a thin film formed on a metal.

The graphite-like carbon adsorbent of the present invention will be described in detail below.

FIG. 1 is a scanning tunneling microscope image of graphitic carbon formed on palladium, in which the periodically arranged bright areas are high electron density areas and the distance between them is about 2 nanometers.

As shown in FIG. 2, when further observing with higher resolution, bright spots are regularly arranged in the bright region, and the intervals are about 0.25 nanometer, and the (001) graphite structure is formed. Equal to the spacing of carbon atoms in the lattice plane.

That is, on the surface of the graphite-like carbon thin film formed on the palladium, a superperiodic structure in which the carbon atom arrangement of the graphite structure (001) lattice has an electron density distribution period of about 2 nanometers is seen.

Although it is not possible to clearly explain the manifestation mechanism of the electron periodicity super-periodic structure shown in FIGS. 1 and 2, one possible explanation is that the outermost lattice plane is several degrees from the next plane. It would just be rotating.

The expression of the super-periodic structure due to the rotation of the lattice planes will be explained in an easy-to-understand manner. When the lattice planes schematically shown in FIG. 3 are superposed at a rotation angle of 7 degrees, the super-periodic structure shown in FIG. Obtained and schematically reproducing the observation result of FIG.

As the rotation angle becomes smaller, the super-cycle interval becomes longer, and the brightness contrast is almost the same as that in the non-rotated case, and the interval at which a significant difference is recognized is 10 nanometers.

On the other hand, when the rotation angle becomes large, the interval of the super cycle becomes short, and when the interval is 1 nanometer or less, no significant difference can be recognized.

The super-periodic structure of the graphitic carbon surface is found in the graphitic thin film formed on the metal surface, but the manufacturing method thereof is various.

For example, there is a method in which carbon is previously solid-dissolved in a metal at a high temperature and then held at a temperature lower than that for a long time so that carbon atoms are surface-precipitated from the inside.

Here, it goes without saying that the process of solid solution and surface precipitation requires high vacuum conditions in which oxygen does not exist.

The type of metal is not particularly specified as long as it dissolves carbon atoms, but with nickel, palladium and platinum, a thin film of graphitic carbon can be obtained by heat treatment at a relatively low temperature.

The second method is a method in which carbon is deposited on the metal surface in an organic gas and then graphitized by heat treatment. This method requires higher temperatures than surface precipitation from solute carbon.

The metal used as the substrate for forming the graphitic carbon may be polycrystalline, but a single crystal or a polycrystalline body having large crystal grains can form a wide range of super-periodic region.

The bright portion of the super-period shown in FIGS. 1 and 2 is a region having a high electron density according to the principle of the scanning tunneling microscope. The super periodicity of this electron density is stable,
It can be observed not only in the air but also in an aqueous solution.

In the region where the electron density is high, the interaction with the molecules approaching the region is stronger, so that a stable adsorption state can be expected.

Furthermore, water molecules are adsorbed in the air or in an aqueous solution, and the originally hydrophobic graphite surface can increase the hydrophilicity in the local area of the nanometer level area with a periodicity of 1 nanometer to 10 nanometers.

By virtue of this feature, contact with a dilute solution of an enzyme molecule such as albumin, if one molecule or two if the dimer is stable, and if several molecules form a unique aggregate, For example, it is possible to disperse and adsorb the aggregate of molecules of that number.

The present invention will be described more specifically with reference to the following examples.

[0041]

Example 1 A single crystal plate of palladium was vacuum sealed with a carbon powder in a quartz tube and heated in an electric furnace at 1000 ° C. to dissolve carbon atoms in the crystal, followed by quenching in water to outside the tube. I took it out.

After polishing the palladium (100) surface, it was heated in a high vacuum environment at 700 ° C. to obtain a thin film of graphitic carbon on the surface.

As a result of observing this thin film in an atmosphere open to the atmosphere using a scanning tunneling microscope, the super-periodic structure in the high electron density region with a spacing of about 2 nanometers shown in FIG. 1 has the graphite structure (001) lattice shown in FIG. Observed in addition to the atomic arrangement of the plane. This superperiodic structure was stable in water.

[0044]

Example 2 By the same method as in Example 1, the (111) plane of a palladium single crystal in which carbon atoms were solid-solved was polished and heated at 800 ° C. in a high vacuum environment to obtain a thin film of graphitic carbon on the surface. It was

As a result of observing this thin film in an atmosphere open to the atmosphere with a scanning tunneling microscope, a superperiodic structure in a high electron density region with a spacing of about 7 nanometers was observed in addition to the atomic arrangement on the (001) lattice plane of the graphite structure. . This superperiodic structure was stable in water.

[0046]

Comparative Example 1 A (001) lattice plane obtained by cleaving a commercially available graphite plate (HOPG) in the atmosphere was observed by a scanning tunnel microscope under an atmosphere open to the atmosphere, and as a result, the super-periods found in Examples 1 and 2 were observed. No structure was observed, and only the atomic arrangement of the (001) lattice plane was observed.

[0047]

Example 3 A serum albumin aqueous solution was injected into the surface of the graphitic carbon having the superperiodic structure obtained in Example 1 and observed by a scanning atomic force microscope. As a result, albumin molecules dispersed and adsorbed on the surface could be observed. .

[0048]

[Comparative Example 2] The commercially available graphite plate (HOP
The same serum albumin aqueous solution as in Example 3 was injected into the cleaved surface of G) and observed with a scanning atomic force microscope, but no albumin molecule was observed on the surface. Albumin molecules float and are not fixed on the surface.

[0049]

As described above, the graphite-like carbon adsorbent of the present invention has (00) of the surface of the graphite-like carbon thin film formed on the metal.
1) It is based on the new discovery of a super-periodic structure of a region having a high electron density at intervals of 1 nanometer to 10 nanometers formed on a lattice plane, and it is possible to disperse one molecule or several groups of molecules such as an enzyme. It can be used as an adsorbent for precise in-situ observation of shape changes of enzyme molecules due to addition of other molecules or ions, and can confirm the efficacy of pharmaceuticals at the molecular level. It has a remarkable effect of developing into a method.

[Brief description of drawings]

FIG. 1 shows a scanning tunneling electron microscope image of a graphitic carbon thin film formed on palladium.

FIG. 2 shows an atomic image of a graphitic carbon thin film formed on palladium by a scanning tunneling electron microscope.

FIG. 3 is a schematic diagram showing a graphite (001) lattice model.

FIG. 4 is a schematic diagram showing a lattice model rotated by 7 degrees.

Claims (3)

[Claims] 1. A region having a high electron density is periodically arranged on a (001) lattice plane of graphitic carbon, and one molecule or a few molecule groups are adsorbed in the high electron density region. Graphite-like carbon adsorbent that makes possible. 2. The graphitic carbon adsorbent according to claim 1, wherein the intervals of the periodically arranged high electron density regions are in the range of 1 nanometer to 10 nanometers. 3. The graphitic carbon adsorbent according to claim 1, wherein the graphitic carbon is a thin film formed on a metal, and the surface thereof has a periodic high electron density region.