U.S. patent application number 11/883179 was filed with the patent office on 2008-09-04 for carbon porous body, method of manufacturing carbon porous body, adsorbent and biomolecular element.
This patent application is currently assigned to National Institute For Materials Science. Invention is credited to Katsuhiko Ariga, Masahiko Miyahara, Toshiyuki Mori, Ajayan Vinu.
Application Number | 20080213557 11/883179 |
Document ID | / |
Family ID | 36740551 |
Filed Date | 2008-09-04 |
United States Patent
Application |
20080213557 |
Kind Code |
A1 |
Vinu; Ajayan ; et
al. |
September 4, 2008 |
Carbon Porous Body, Method of Manufacturing Carbon Porous Body,
Adsorbent and Biomolecular Element
Abstract
There are provided a carbon porous body having a larger pore
capacity and a larger specific surface area that can advantageously
diffuse the substance it adsorbs into the inside and a method of
manufacturing such a carbon porous body. The method of
manufacturing a carbon porous body is characterized by comprising a
step of mixing a cage-shaped silica porous body and a carbon
source, a step of heating the obtained mixture and a step of
removing the cage-shaped silica porous body from the reaction
product. The cage-shaped silica porous body contains a silica
skeleton, a plurality of pores formed by the silica skeleton and a
plurality of channels also formed by the silica skeleton to
mutually link the plurality of pores. The plurality of pores are
arranged three-dimensionally, regularly and symmetrically, the
diameter d.sub.1 of the plurality of pores and the diameter d.sub.2
of the plurality of channels satisfy the relationship of
d.sub.1>d.sub.2. The cage-shaped silica porous body and the
carbon source are mixed so as to make the mol ratio (C/Si) of the
silicon (Si) in the cage-shaped silica porous body and the carbon
(C) in the carbon source satisfy the relationship of
0.8<C/Si<3.0.
Inventors: |
Vinu; Ajayan; (Ibaraki,
JP) ; Ariga; Katsuhiko; (Ibaraki, JP) ;
Miyahara; Masahiko; (Ibaraki, JP) ; Mori;
Toshiyuki; (Ibaraki, JP) |
Correspondence
Address: |
KANESAKA BERNER AND PARTNERS LLP
1700 DIAGONAL RD, SUITE 310
ALEXANDRIA
VA
22314-2848
US
|
Assignee: |
National Institute For Materials
Science
Ibaraki
JP
|
Family ID: |
36740551 |
Appl. No.: |
11/883179 |
Filed: |
January 25, 2006 |
PCT Filed: |
January 25, 2006 |
PCT NO: |
PCT/JP2006/001596 |
371 Date: |
July 27, 2007 |
Current U.S.
Class: |
428/220 ;
264/340; 428/304.4 |
Current CPC
Class: |
B01J 20/28057 20130101;
C04B 38/0022 20130101; Y02E 60/50 20130101; B01J 20/28076 20130101;
C04B 35/14 20130101; C04B 35/6267 20130101; C04B 2235/80 20130101;
C01B 32/382 20170801; C04B 2235/422 20130101; C01B 32/00 20170801;
H01M 4/926 20130101; B01J 20/305 20130101; G01N 33/551 20130101;
C04B 35/524 20130101; C04B 35/6269 20130101; C04B 2235/6028
20130101; C04B 2235/616 20130101; H01M 4/96 20130101; C01B 32/306
20170801; Y10T 428/249953 20150401; H01M 4/8605 20130101; H01M
4/9083 20130101; B01J 20/3057 20130101; B01J 20/20 20130101 |
Class at
Publication: |
428/220 ;
264/340; 428/304.4 |
International
Class: |
B32B 3/26 20060101
B32B003/26; B29C 71/02 20060101 B29C071/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 2005 |
JP |
2005-022234 |
Claims
1. A method of manufacturing a carbon porous body (ICY),
characterized by comprising: a step of mixing a cage-shaped silica
porous body and a carbon source, the cage-shaped silica porous body
containing a silica skeleton, a plurality of pores formed by the
silica skeleton and a plurality of channels also formed by the
silica skeleton to mutually link the plurality of pores, the
plurality of pores being arranged three-dimensionally, regularly
and symmetrically, a diameter d.sub.1 of the plurality of pores and
a diameter d.sub.2 of the plurality of channels satisfying the
relationship of d.sub.1>d.sub.2, the cage-shaped silica porous
body and the carbon source being mixed so as to make the mol ratio
(C/Si) of the silicon (Si) in the cage-shaped silica porous body
and the carbon (C) in the carbon source satisfy the relationship of
0.8<C/Si<3.0; a step of heating the mixture obtained by the
mixing step; and a step of removing the cage-shaped silica porous
body from the reaction product obtained from the heating step.
2. The method according to claim 1, characterized in that the
cage-shaped silica porous body is KIT-5.
3. The method according to claim 2, characterized in that a
specific surface area s of the KIT-5 is 450<s
(m.sup.2/g)<690.
4. The method according to claim 3, characterized in that the
distance d.sub.2 of the KIT-5 is 4<d.sub.2 (nm)<6.
5. The method according to claim 4, characterized in that the
distance d.sub.1 of the KIT-5 is 10<d.sub.1 (nm)<14.
6. The method according to claim 1, characterized in that the
carbon source satisfies the chemical formula of
C.sub.lH.sub.mO.sub.n (where 1 is a positive integer and each of m
and n is 0 or a positive integer).
7. The method according to claim 6, characterized in that the
carbon source that satisfies the chemical formula of
C.sub.lH.sub.mO.sub.n is selected from a group of sugars, alcohols,
aldehydes, ketones, carboxylic acids, ethers and hydrocarbons.
8. The method according to claim 7, characterized in that the
sugars are cane sugar and grape sugar.
9. The method according to claim 7, characterized in that the
alcohols are a group of octanol, hexanediol and benzyl alcohol.
10. The method according to claim 7, characterized in that the
aldehydes are acetaldehyde and butylaldehyde.
11. The method according to claim 7, characterized in that the
ketones are dibutyl ketone and cyclohexanone.
12. The method according to claim 7, characterized in that the
carboxylic acids are butyric acid and valeric acid.
13. The method according to claim 7, characterized in that the
ethers are dibutyl ether and dioxane.
14. The method according to claim 7, characterized in that the
hydrocarbons are a group of dodecane, adamantane and
naphthalene.
15. The method according to claim 1, characterized in that the mol
ratio (C/Si) of the silicon (Si) in the cage-shaped silica porous
body and the carbon (C) in the carbon source satisfies the
relationship of 0.85.ltoreq.C/Si.ltoreq.0.95.
16. The method according to claim 1, characterized in that the
heating step includes a step of polymerizing the mixture at a first
temperature and a step of carbonizing the mixture at a second
temperature higher than the first temperature.
17. The method according to claim 16, characterized in that the
mixture is heated in the atmosphere at the first temperature
selected from the temperature range between 70.degree. C. and
150.degree. C. for 5 to 8 hours in the polymerizing step.
18. The method according to claim 17, characterized in that the
mixture is heated further in the atmosphere at a temperature
selected from the temperature range between 140.degree. C. and
160.degree. C. for 5 to 8 hours in the polymerizing step.
19. The method according to claim 16, characterized in that the
mixture is heated in a nitrogen atmosphere or in an inert gas
atmosphere at the second temperature selected from the temperature
range between 700.degree. C. and 900.degree. C. for 4 to 8 hours in
the carbonizing step.
20. The method according to claim 1, characterized in that the
reaction product is filtered by means of hydrofluoric acid or an
alkali aqueous solution in the removing step.
21. The method according to claim 1, characterized by further
comprising: a step of washing and drying the reaction product after
the removing step.
22. A carbon porous body (ICY) comprising a carbon skeleton
containing carbon atoms, characterized in that the carbon skeleton
includes carbon main sections and carbon linking sections mutually
linking the carbon main sections, that a distance D.sub.1 between
adjacent carbon main sections and a distance D.sub.2 between
adjacent carbon linking sections satisfy the relationship of
D.sub.1<D.sub.2, that the carbon main sections are arranged
three-dimensionally, regularly and symmetrically and that a
specific surface area of the carbon porous body is not less than
1,300 m.sup.2/g and/or the pore capacity of the carbon porous body
is not less than 1.5 cm.sup.3/g.
23. The carbon porous body according to claim 22, characterized in
that the distance D.sub.1 and the distance D.sub.2 are respectively
4.ltoreq.D.sub.1 (nm).ltoreq.6 and 9.ltoreq.D.sub.2
(nm).ltoreq.15.
24. The carbon porous body according to claim 22, characterized in
that the carbon main sections are arranged to form a face-centered
cube.
25. The carbon porous body according to claim 22, characterized in
that the specific surface area of the carbon porous body is not
less than 1,600 m.sup.2/g and/or the pore capacity of the carbon
porous body is not less than 2.0 cm.sup.3/g.
26. An adsorbent comprising a carbon porous body (ICY) including a
carbon skeleton containing carbon atoms, characterized in that the
carbon skeleton includes carbon main sections and carbon linking
sections mutually linking the carbon main sections, that a distance
D.sub.1 between adjacent carbon main sections and a distance
D.sub.2 between adjacent carbon linking sections satisfy the
relationship of D.sub.1<D.sub.2, that the carbon main sections
are arranged three-dimensionally, regularly and symmetrically and
that the specific surface area of the carbon porous body is not
less than 1,300 m.sup.2/g and/or the pore capacity of the carbon
porous body is not less than 1.5 cm.sup.3/g.
27. The adsorbent according to claim 26, characterized in that the
distance D.sub.1 and the distance D.sub.2 are respectively
4.ltoreq.D.sub.1 (nm).ltoreq.6 and 9.ltoreq.D.sub.2
(nm).ltoreq.15.
28. The adsorbent according to claim 26, characterized in that the
carbon main sections are arranged to form a face-centered cube.
29. The adsorbent according to claim 26, characterized in that the
specific surface area of the carbon porous body is not less than
1,600 m.sup.2/g and/or the pore capacity of the carbon porous body
is not less than 2.0 cm.sup.3/g.
30. A biomolecular element comprising a carbon porous body (ICY)
including a carbon skeleton containing carbon atoms and
biomolecules fixed to the carbon porous body, characterized in that
the carbon skeleton includes carbon main sections and carbon
linking sections mutually linking the carbon main sections, that a
distance D.sub.1 between adjacent carbon main sections and a
distance D.sub.2 between adjacent carbon linking sections satisfy
the relationship of D.sub.1<D.sub.2, that the carbon main
sections are arranged three-dimensionally, regularly and
symmetrically, that the specific surface area of the carbon porous
body is not less than 1,300 m.sup.2/g and/or the pore capacity of
the carbon porous body is not less than 1.5 cm.sup.3/g, that the
biomolecules are fixed to the inside of the pores formed by the
carbon main sections and the carbon linking sections and that the
biomolecules are adapted to react with a predetermined
substance.
31. The biomolecular element according to claim 30, characterized
in that the distance D.sub.1 and the distance D.sub.2 are
respectively 4.ltoreq.D.sub.1 (nm).ltoreq.6 and 9.ltoreq.D.sub.2
(nm).ltoreq.15.
32. The biomolecular element according to claim 30, characterized
in that the biomolecules are selected from a group of proteins,
nucleic acids and polysaccharides.
33. The biomolecular element according to claim 30, characterized
in that the predetermined substance is a protein.
34. The biomolecular element according to claim 33, characterized
in that the protein is an enzyme.
35. The biomolecular element according to claim 34, characterized
in that the enzyme is lysozyme.
36. The biomolecular element according to claim 30, characterized
in that the carbon main sections are arranged to form a
face-centered cube.
37. The biomolecular element according to claim 30, characterized
in that the specific surface area of the carbon porous body is not
less than 1,600 m.sup.2/g and/or the pore capacity of the carbon
porous body is not less than 2.0 cm.sup.3/g.
Description
TECHNICAL FIELD
[0001] The present invention relates to a carbon porous body and a
method of manufacturing the same. More particularly, the present
invention relates to a carbon porous body that is stable relative
to heat and water and has a large pore capacity and a large
specific surface area, a method of manufacturing the same and an
adsorbent and a biomolecular element using the same.
BACKGROUND ART
[0002] Research efforts have been and being made on porous
materials for the purpose of adsorption and removal of harmful
substances, adsorption and collection of useful substances and
fixation of biological substances. Particularly, carbon porous
bodies (meso porous carbon) that are stable under hydrothermal
conditions (e.g. in hot water) are attracting attention. Techniques
for manufacturing such carbon porous bodies by means of molds have
been proposed (see, inter alia, Patent Document 1).
[0003] FIG. 12 of the accompanying drawings is a flowchart of a
known method of manufacturing a carbon molecular body. This
manufacturing method will be described below on a step by step
basis.
[0004] Step S1210: A mold having gas holes (air holes) (meso porous
silica) is impregnated with a mixture containing a silica oligomer,
a carbon precursor substance that is a carbon-containing compound
liable to be subjected to condensation polymerization and a liquid
carrier. The mold has a structure where gas holes are irregularly
three-dimensionally linked to each other or a structure where
medium gas holes are linked to micro gas holes. The carbon
precursor substance is a carbohydrate or a monomer. The silica
oligomer is contained in order to raise the gas hole ratio in the
obtained carbon molecular body. The liquid carrier accelerates the
impregnation of the mixture to the mold.
[0005] Step S1220: The carbon precursor substance contained in the
mixture with which the mold is impregnated is polymerized. The
polymerization is realized by means of a heat treatment to produce
a carbon precursor substance polymer that is formed in the gas
holes of the mold. The liquid carrier is dried by the heat
treatment.
[0006] Step S1230: The carbon precursor substance polymer formed in
the gas holes is pyrolyzed and carbonized. The remaining liquid
carrier is also removed by the pyrolysis.
[0007] Step S1240: The mold and the silica oligomer are treated by
a solution that selectively dissolves them and removed. As a
result, a carbon molecular body having micro gas holes is
obtained.
[0008] Reference Document:
[0009] Patent Document 1: JP 2004-244311-A
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0010] However, while the carbon molecular porous body (carbon
porous body) obtained by the technique described in the Patent
Document 1 can be made to contain a large number of micro gas holes
by using a silica oligomer in order to produce a large specific
surface area, the capacity of the pores (gas holes) is limited (and
typically not greater than 1.7 cm.sup.3/g). In other words, the
size of a substance that the carbon porous body can adsorb is
limited and the carbon porous body may not be able to adsorb a
desired substance. Due to the structure of the mold (replica) used
in the Patent Document 1, the obtained carbon porous body shows a
structure produced by agglomeration of rod structures (e.g., a
hexagonal structure), which is disadvantageous to the diffusion of
the adsorbed substance into the inside of the carbon porous body.
Therefore, it is an object of the present invention to provide a
carbon porous body having a larger pore capacity and a larger
specific surface area that can advantageously diffuse the substance
it adsorbs into the inside and a method of manufacturing such a
carbon porous body. Another object of the present invention is to
provide applications (an adsorbent and a biomolecular element)
using a carbon porous body as described above.
Means for Solving the Problem
[0011] In an aspect of the present invention, the above first
object is achieved by providing a method of manufacturing a carbon
porous body (ICY), characterized by comprising: a step of mixing a
cage-shaped silica porous body and a carbon source, the cage-shaped
silica porous body containing a silica skeleton, a plurality of
pores formed by the silica skeleton and a plurality of channels
also formed by the silica skeleton to mutually link the plurality
of pores, the plurality of pores being arranged
three-dimensionally, regularly and symmetrically, a diameter
d.sub.1 of the plurality of pores and a diameter d.sub.2 of the
plurality of channels satisfying the relationship of
d.sub.1>d.sub.2, the cage-shaped silica porous body and the
carbon source being mixed so as to make the mol ratio (C/Si) of the
silicon (Si) in the cage-shaped silica porous body and the carbon
(C) in the carbon source satisfy the relationship of
0.8<C/Si<3.0; a step of heating the mixture obtained by the
mixing step; and a step of removing the cage-shaped silica porous
body from the reaction product obtained from the heating step.
[0012] The cage-shaped silica porous body may be KIT-5.
[0013] A specific surface area s of the KIT-5 may be 450<s
(m.sup.2/g)<690.
[0014] The distance d.sub.2 of the KIT-5 may be 4<d.sub.2
(nm)<6.
[0015] The distance d.sub.1 of the KIT-5 may be 10<d.sub.1
(nm)<14.
[0016] The carbon source may satisfy the chemical formula of
C.sub.lH.sub.mO.sub.n (where 1 is a positive integer and each of m
and n is 0 or a positive integer).
[0017] The carbon source that satisfies the chemical formula of
C.sub.lH.sub.mO.sub.n may be selected from a group of sugars,
alcohols, aldehydes, ketones, carboxylic acids, ethers and
hydrocarbons.
[0018] The sugars may be cane sugar and grape sugar.
[0019] The alcohols may be a group of octanol, hexanediol and
benzyl alcohol.
[0020] The aldehydes may be acetaldehyde and butylaldehyde.
[0021] The ketones may be dibutyl ketone and cyclohexanone.
[0022] The carboxylic acids may be butyric acid and valeric
acid.
[0023] The ethers may be dibutyl ether and dioxane.
[0024] The hydrocarbons may be a group of dodecane, adamantane and
naphthalene.
[0025] The mol ratio (C/Si) of the silicon (Si) in the cage-shaped
silica porous body and the carbon (C) in the carbon source may
satisfy the relationship of 0.85.ltoreq.C/Si.ltoreq.0.95.
[0026] The heating step may include a step of polymerizing the
mixture at a first temperature and a step of carbonizing the
mixture at a second temperature higher than the first
temperature.
[0027] The mixture may be heated in the atmosphere at the first
temperature selected from the temperature range between 70.degree.
C. and 150.degree. C. for 5 to 8 hours in the polymerizing
step.
[0028] The mixture may be heated further in the atmosphere at a
temperature selected from the temperature range between 140.degree.
C. and 160.degree. C. for 5 to 8 hours in the polymerizing
step.
[0029] The mixture may be heated in a nitrogen atmosphere or in an
inert gas atmosphere at the second temperature selected from the
temperature range between 700.degree. C. and 900.degree. C. for 4
to 8 hours in the carbonizing step.
[0030] The reaction product may be filtered by means of
hydrofluoric acid or an alkali aqueous solution in the removing
step.
[0031] A method according to the present invention may further
comprise a step of washing and drying the reaction product after
the removing step.
[0032] In another aspect of the present invention, there is
provided a carbon porous body (ICY) comprising a carbon skeleton
containing carbon atoms, characterized in that the carbon skeleton
includes carbon main sections and carbon linking sections mutually
linking the carbon main sections, that a distance D.sub.1 between
adjacent carbon main sections and a distance D.sub.2 between
adjacent carbon linking sections satisfy the relationship of
D.sub.1<D.sub.2, that the carbon main sections are arranged
three-dimensionally, regularly and symmetrically and that a
specific surface area of the carbon porous body is not less than
1,300 m.sup.2/g and/or the pore capacity of the carbon porous body
is not less than 1.5 cm.sup.3/g.
[0033] The distance D.sub.1 and the distance D.sub.2 may be
respectively 4<D.sub.1 (nm).ltoreq.6 and 9.ltoreq.D.sub.2
(nm).ltoreq.15.
[0034] The carbon main sections may be arranged to form a
face-centered cube.
[0035] The specific surface area of the carbon porous body may be
not less than 1,600 m.sup.2/g and/or the pore capacity of the
carbon porous body may be not less than 2.0 cm.sup.3/g.
[0036] In still another aspect of the present invention, there is
provided an adsorbent comprising a carbon porous body (ICY)
including a carbon skeleton containing carbon atoms, characterized
in that the carbon skeleton includes carbon main sections and
carbon linking sections mutually linking the carbon main sections,
that a distance D.sub.1 between adjacent carbon main sections and a
distance D.sub.2 between adjacent carbon linking sections satisfy
the relationship of D.sub.1<D.sub.2, that the carbon main
sections are arranged three-dimensionally, regularly and
symmetrically and that the specific surface area of the carbon
porous body is not less than 1,300 m.sup.2/g and/or the pore
capacity of the carbon porous body is not less than 1.5
cm.sup.3/g.
[0037] The distance D.sub.1 and the distance D.sub.2 may be
respectively 4.ltoreq.D.sub.1 (nm).ltoreq.6 and 9.ltoreq.D.sub.2
(nm).ltoreq.15.
[0038] The carbon main sections may be arranged to form a
face-centered cube.
[0039] The specific surface area of the carbon porous body may be
not less than 1,600 m.sup.2/g and/or the pore capacity of the
carbon porous body may be not less than 2.0 cm.sup.3/g.
[0040] In a further aspect of the present invention, there is
provided a biomolecular element comprising a carbon porous body
(ICY) including a carbon skeleton containing carbon atoms and
biomolecules fixed to the carbon porous body, characterized in that
the carbon skeleton includes carbon main sections and carbon
linking sections mutually linking the carbon main sections, that a
distance D.sub.1 between adjacent carbon main sections and a
distance D.sub.2 between adjacent carbon linking sections satisfy
the relationship of D.sub.1<D.sub.2, that the carbon main
sections are arranged three-dimensionally, regularly and
symmetrically, that the specific surface area of the carbon porous
body is not less than 1,300 m.sup.2/g and/or the pore capacity of
the carbon porous body is not less than 1.5 cm.sup.3/g, that the
biomolecules are fixed to the inside of the pores formed by the
carbon main sections and the carbon linking sections and that the
biomolecules are adapted to react with a predetermined
substance.
[0041] The distance D.sub.1 and the distance D.sub.2 may be
respectively 4.ltoreq.D.sub.1 (nm).ltoreq.6 and 9.ltoreq.D.sub.2
(nm).ltoreq.15.
[0042] The biomolecules may be selected from a group of proteins,
nucleic acids and polysaccharides.
[0043] The predetermined substance may be a protein.
[0044] The protein may be an enzyme.
[0045] The enzyme may be lysozyme.
[0046] The carbon main sections may be arranged to form a
face-centered cube.
[0047] The specific surface area of the carbon porous body may be
not less than 1,600 m.sup.2/g and/or the pore capacity of the
carbon porous body may be not less than 2.0 cm.sup.3/g.
ADVANTAGES OF THE INVENTION
[0048] A manufacturing method according to the present invention
employs a cage-shaped silica porous body containing a plurality of
pores arranged three-dimensionally, regularly and symmetrically as
replica. Since such a cage-shaped silica porous body has a specific
surface area and a pore capacity respectively smaller than the
specific surface area and the pore capacity of any known replica,
the obtained carbon porous body can be made to have a specific
surface area and a pore capacity greater than those of any known
carbon porous body. Additionally, since such a cage-shaped silica
porous body and a carbon source are mixed to satisfy a
predetermined mol ratio (namely 0.8<C/Si<3.0), it is possible
to obtain a highly regular carbon porous body that is free from
conglutination of carbon. A carbon porous body obtained in this way
can show an improved adsorbing force than ever and adsorb a large
substance that a conventional carbon porous body cannot adsorb.
Additionally, it is possible to diffuse the adsorbed substance into
the inside of the carbon porous body.
BRIEF DESCRIPTION OF DRAWINGS
[0049] FIG. 1 is a flowchart of a method of manufacturing a carbon
porous body (ICY) according to the present invention;
[0050] FIG. 2 is a schematic illustration of the structure of
KIT-5;
[0051] FIG. 3 is a schematic illustration of a carbon porous body
(ICY) according to the present invention;
[0052] FIG. 4 is a schematic illustration of a biomolecular element
according to the present invention;
[0053] FIG. 5(a) is a graph illustrating the X-ray diffraction
patterns of cage-shaped silica porous bodies KIT-5s (KIT-5-150,
KIT-5-130 and KIT-5-100) calcined at different temperatures;
[0054] FIG. 5(b) is a graph illustrating the X-ray diffraction
patterns of ICYs (ICY-1, ICY-2 and ICY-1');
[0055] FIG. 6(a) is a microscopic photograph of ICY-1 taken along a
surface parallel to the air holes thereof;
[0056] FIG. 6(b) is a microscopic photograph of ICY-1 showing a
cross section thereof;
[0057] FIG. 7(a) is a graph illustrating the nitrogen
adsorption-desorption isotherms of ICY-1, ICY-2 and ICY-1';
[0058] FIG. 7(b) is a graph illustrating the pore distributions of
ICY-1, ICY-2 and ICY-1';
[0059] FIG. 8 is a graph illustrating the X-ray diffraction
patterns of ICY-1, ICY-3, ICY-4 and ICY-2';
[0060] FIG. 9 is a graph illustrating the nitrogen
adsorption-desorption isotherms of ICY-1, ICY-3, ICY-4 and
ICY-2';
[0061] FIG. 10 is a graph illustrating the adsorption
characteristics of the protein (lysozyme) of ICY-3, ICY-4 and
CMK;
[0062] FIG. 11 is a graph illustrating the infrared absorption
spectrum of a protein (lysozyme) observed before and after a
protein (lysozyme) adsorption by ICY-3; and
[0063] FIG. 12 is a flowchart of a known method of manufacturing a
carbon molecular body.
EXPLANATION OF REFERENCE SYMBOLS
[0064] 200: cage-shaped silica porous body [0065] 210: silica
skeleton [0066] 220: pore [0067] 230: channel [0068] 300: carbon
porous body (ICY) [0069] 310: carbon main section [0070] 320:
carbon linking body [0071] 400: biomolecular element [0072] 410:
biomolecular material
BEST MODE FOR CARRYING OUT THE INVENTION
[0073] Now, the present invention will be described in greater
detail by referring to the accompanying drawings that illustrate
preferred embodiments of the invention.
Embodiment 1
[0074] FIG. 1 is a flowchart of a method of manufacturing a carbon
porous body (ICY) according to the present invention. The method
will now be described below on a step by step basis.
[0075] Step S110: A cage-shaped silica porous body and a carbon
source are mixed with each other. The mol ratio of the silicon (Si)
in the cage-shaped silica porous body and the carbon (C) in the
carbon source satisfies the relationship of 0.8<C/Si<3.0.
[0076] FIG. 2 is a schematic illustration of the structure of
KIT-5.
[0077] A structure 200 of KIT-5 is schematically illustrated as an
example of cage-shaped silica porous body. The KIT-5 shown as an
example of cage-shaped silica porous body includes a silica
skeleton 210 made of silica, a plurality of pores 220 and a
plurality of channels 230. The plurality of pores 220 and the
plurality of channels 230 are formed by the silica skeleton
210.
[0078] The plurality of pores 220 are arranged three-dimensionally
(although they are shown two-dimensionally in the drawing for the
purpose of simplicity), regularly and symmetrically. The plurality
of channels mutually link the plurality of pores 220. The diameter
d.sub.1 of the plurality of pores 220 and the diameter d.sub.2 of
the plurality of channels 230 satisfy the relationship of
d.sub.1>d.sub.2. Thus, the cage-shaped silica porous body has
cage-shaped (birdcage-shaped) spaces in the inside and each space
has such a structure that the inner diameter of the space is larger
than that of the entrances thereof.
[0079] When KIT-5 is employed as cage-shaped silica porous body,
the plurality of pores 220 show the symmetry of a face-centered
cube Fm3m. The KIT-5 is manufactured typically by means of the
technique described by Kleitz et al. in J. Phys. Chem. 107, 14296
(2003).
[0080] Note that the specific surface area, the lattice constant,
the diameter d.sub.1 and the diameter d.sub.2 can vary remarkably
depending on the manufacturing conditions (e.g., the baking
temperature).
[0081] The specific surface area s (m.sup.2/g), the lattice
constant a.sub.0 (nm), the pore diameter d.sub.1 (nm) and the
channel diameter d.sub.2 (nm) that are preferable for the purpose
of the present invention are respectively 450<s
(m.sup.2/g)<690, 17<a.sub.0 (nm)<22, 10<d.sub.1
(nm)<14 and 4<d.sub.2 (nm)<6.
[0082] Of the above-listed requirements, it is desirable that the
requirement of the specific surface area s and that of the channel
diameter d.sub.2 are satisfied. This is because the KIT-5 does not
operate as stable replica when the channel diameter d.sub.2 is too
small relative to the specific surface area s.
[0083] More preferably, the KIT-5 satisfies all the above-listed
requirements.
[0084] Note that the structure of the obtained carbon porous body
(ICY) depends on the structure of the selected cage-shaped silica
porous body. Therefore, it is possible to obtain a carbon porous
body having a desired profile, a desired pore diameter and a
desired specific surface area by appropriately selecting a
cage-shaped silica porous body.
[0085] Now, referring again to Step S110 in FIG. 1, the carbon
source is a compound C.sub.lH.sub.mO.sub.n (where 1 is a positive
integer and each of m and n is 0 or a positive integer) that is
made of all or part of carbon, hydrogen and oxygen. Such a carbon
source may be selected from a group of sugars, alcohols, aldehydes,
ketones, carboxylic acids, ethers and hydrocarbons.
[0086] Preferably, the sugars are cane sugar and grape sugar. The
alcohols may be a group of octanol, hexanediol and benzyl alcohol.
The aldehydes may be acetaldehyde and butylaldehyde. The ketones
may be dibutyl ketone and cyclohexanone. The carboxylic acids may
be butyric acid and valeric acid. The ethers may be dibutyl ether
and dioxane. The hydrocarbons may be a group of dodecane,
adamantane and naphthalene. The carbon source may be formed by
combining more than one of the above-listed materials. The carbon
source is not limited to the above-listed materials.
[0087] A cage-shaped silica porous body to be used for the purpose
of the present invention shows a specific surface area and a pore
capacity smaller than those of any conventional silica porous body.
Therefore, when a conventional method of manufacturing a carbon
porous body is employed, there arises a problem that the carbon
source is in short supply and hence carbon cannot be sufficiently
filled into the cage-shaped silica porous body or a problem that
carbon is excessively supplied and conglutination of carbon takes
place after removing the cage-shaped silica porous body. Then, it
is not possible to obtain a carbon porous body having a structure
where pores are arranged regularly. In short, the ratio of the
carbon source relative to the cage-shaped silica porous body is
important. According to the present invention, the cage-shaped
silica porous body and the carbon source are mixed in such a way
that the mol ratio (C/Si) of the silicon (Si) in the cage-shaped
silica porous body and the carbon (C) in the carbon source
satisfies the relationship of 0.8<C/Si<3.0.
[0088] It is possible to obtain a carbon porous body (ICY) having a
structure where pores are arranged regularly when the mol ratio is
within the above-defined range.
[0089] Preferably, the mol ratio satisfies the relationship of
0.85.ltoreq.C/Si.ltoreq.0.95. It is possible to control the pore
structure of the obtained carbon porous body (specifically in terms
of the pore capacity, the surface area, the pore diameter
(corresponding to distance D.sub.1, which will be described
hereinafter) and the diameter of the internal cage spaces
(corresponding to distance D.sub.2, which will be described
hereinafter)) by adjusting the mol ratio within the above-defined
range.
[0090] Step S120: The mixture obtained in Step S110 is heated. As a
result, the mixture gives rise to a chemical reaction to make it
possible to obtain a carbon porous body. More particularly, the
mixture is polymerized at a first temperature and subsequently
carbonized at a second temperature that is higher than the first
temperature.
[0091] The polymerization is realized by heating the mixture in the
atmosphere at the first temperature selected from the temperature
range between 70.degree. C. and 150.degree. C. for 5 to 8 hours.
Any heating means such as an oven or a hot plate may be used for
the heating. The carbon source is subjected to polymerization out
of the mixture by the heating. Subsequently, the carbon source is
placed in the pores of the cage-shaped silica porous body as the
mixture is agitated. The polymerization may be conducted further by
heating the mixture in the atmosphere at a temperature selected
from the temperature range between 140.degree. C. and 160.degree.
C. for 5 to 8 hours.
[0092] The carbonization is realized by heating the mixture in a
nitrogen atmosphere or in an inert gas atmosphere at the second
temperature selected from the temperature range between 700.degree.
C. and 900.degree. C. for 4 to 8 hours. Any heating means such as
an electric furnace may be used for the heating. The polymerized
carbon source is carbonized by as a result of the heating. The
reaction product obtained in the pores of the cage-shaped silica
porous body is a carbon porous body (ICY).
[0093] The polymer obtained as a result of the polymerization may
be dried and reduced to micro particles before the carbonization.
Then, it is possible to reduce the time necessary for the
carbonization.
[0094] Step S130: The cage-shaped silica porous body is removed
from the reaction product obtained as a result of Step S120. It is
possible to extract the ICY, or the reaction product, by filtering
the cage-shaped silica porous body by means of hydrofluoric acid or
an alkali aqueous solution. Any alkali aqueous solution that can
dissolve a cage-shaped silica porous body may be used.
[0095] After Step S130, the extracted reaction product may be
washed and dried. Pure water, distilled water or ethanol may be
used for the washing. The extracted reaction product may be dried
by any heating means such as an oven or a hot plate.
[0096] Thus, with a manufacturing method according to the present
invention, it is possible to obtain a novel cage-shaped carbon
porous body by means of a cage-shaped silica porous body where a
plurality of pores are arranged three-dimensionally, regularly and
symmetrically as replica.
[0097] Since the cage-shaped silica porous body has a specific
surface area and a pore capacity respectively smaller than those of
any conventional replica, the obtained carbon porous body has a
specific surface area and a pore capacity respectively greater than
those of any known carbon porous body.
[0098] Additionally, with a manufacturing method according to the
present invention, it is possible to obtain a carbon porous body
that is free from conglutination of carbon and shows a regularity
that reflects the structure of the cage-shaped silica porous body
because the cage-shaped silica porous body and the carbon source
are mixed so as to satisfy the above described predetermined mol
ratio.
[0099] FIG. 3 is a schematic illustration of a carbon porous body
(ICY) according to the present invention.
[0100] The carbon porous body (ICY) 300 illustrated in FIG. 3 is
formed by using KIT-5 as cage-shaped silica porous body by means of
a manufacturing method according to the present invention described
above by referring to FIG. 1. It should be noted, however, that the
structure of ICY 300 is not limited to the illustrated one.
[0101] A carbon porous body (ICY) 300 according to the present
invention is formed by using a carbon skeleton. The ICY 300
includes carbon main sections 310 and carbon linking sections 320
mutually linking the carbon main sections 310. The carbon main
sections 310 are arranged three-dimensionally (although they are
shown two-dimensionally in the drawing for the purpose of
simplicity), regularly and symmetrically. The distance D.sub.1
between adjacent carbon main sections 310 and the distance D.sub.2
between adjacent carbon linking sections 320 satisfy the
relationship of D.sub.1<D.sub.2.
[0102] Thus, the ICY 300 has a structure where large spaces
(separating the carbon linking sections 320) are linked by the
parts (separating the carbon main sections 310) where the thick
carbon skeleton forms narrow pores. Preferably, the carbon main
sections 310 are arranged so as to form a face-centered cube.
Preferably, the distance D.sub.1 (nm) is not smaller than 4 nm and
not greater than 6 nm. Preferably, the distance D.sub.2 (nm) is not
smaller than 9 nm and not greater than 15 nm.
[0103] Note that an ICY 300 having a specific surface area of not
smaller than 1,300 m.sup.2/g and/or a pore capacity of not smaller
than 1.5 cm.sup.3/g can be obtained by a method according to the
present invention described above by referring to FIG. 1.
[0104] It is possible to obtain an ICY 300 having a specific
surface area of not smaller than 1,600 m.sup.2/g and/or a pore
capacity of not smaller than 2.0 cm.sup.3/g by appropriately
selecting a cage-shaped silica porous body.
[0105] With an ICY 300 according to the present invention, it is
possible to effectively fix (absorb) a greater substance such as a
protein in the space having a cage diameter denoted by the distance
D.sub.2 if compared with the conventional art.
[0106] As described above by referring to FIG. 3, a cage-shaped
silica porous body according to the present invention has narrow
pores and large internal spaces to show a structure suitable for a
catalytic reaction.
[0107] A carbon porous body according to the present invention can
be utilized as a catalyst to be used as the anode or the cathode of
a fuel cell. It is possible to improve the catalytic activity and
the dispersion in the cell because a carbon porous body according
to the present invention provides a large specific surface area
and/or a large pore capacity if compared with the conventional art.
Therefore, a carbon porous body according to the present invention
can reduce the quantity of catalyst in the fuel cell and hence it
is possible to downsize the cell.
[0108] Additionally, a carbon porous body according to the present
invention can be utilized as an adsorbent. Particularly, different
from a silica porous body, a carbon porous body is highly
hydrophobic and can effectively operate to adsorb harmful
substances having hydrophobic groups. Such harmful substances
include PCB, environmental hormones that are endocrine disruptors
and odorous substances.
[0109] Now, an application of a cage-shaped silica porous body
according to the present invention as described above by referring
to Embodiment 1 to a biomolecular element (biomolecule identifier)
will be described below.
Embodiment 2
[0110] FIG. 4 is a schematic illustration of a biomolecular element
according to the present invention.
[0111] Biomolecular element 400 includes a cage-shaped silica
porous body 300 and a biomolecular material 410 adsorbed to the
inner wall surface of the cage-shaped silica porous body 300.
[0112] The biomolecular element 400 may be manufactured simply by
fixing a biomolecular material to a cage-shaped silica porous body
300. A biomolecular material 410 may be a substance that
selectively reacts on a specific substance (receptor), a substance
that selectively takes a catalytic action on a specific substance
or a substance that inactivates substances other than a specific
substance.
[0113] The biomolecular material 410 may typically be selected from
a group of proteins, nucleic acids and polysaccharides.
[0114] The above specific substance, or the biomolecular material
410, is a protein. More particularly, it is an enzyme. More
particularly, it is lysozyme.
[0115] For the purpose of fixation of the biomolecular material
410, a cage-shaped silica porous body 300 according to the present
invention is immersed into a solution where the biomolecular
material 410 is dissolved. Then, the biomolecular material 410 in
the solution is adsorbed by the cage-shaped silica porous body 300.
The cage-shaped silica porous body 300 that adsorbs the
biomolecular material may be appropriately dried to eliminate an
unnecessary solvent.
[0116] The operation of the biomolecular element 400 obtained in
the above-described manner will be described below.
[0117] The biomolecular element 400 may be used with a detection
means (not shown). Any detection means may be used for the purpose
of the present invention so long as it can display the fact that
the biomolecular element 400 detects the specific substance by way
of a change of electric current, voltage, quantity of light, mass,
calorie or the like. If the biomolecular material 410 of the
biomolecular element 400 can visualize such a change, the detection
means may be omitted.
[0118] An object solution of examination is provided to the
biomolecular element 400.
[0119] The object solution of examination passes through the
biomolecular element 400 and discharged. If the object solution of
examination contains a substance that reacts on the above described
biomolecular material 410, the biomolecular material 410 reacts on
the substance in the object solution of examination, takes a
catalytic action on the substance, inactivates substances other
than the specific substance or takes some other action.
[0120] A signal that indicates that the biomolecular element 400
detects a specific substance (and corresponds to a change of
electric current, voltage, quantity of light, mass, calorie or the
like) is notified to the detection means. The detection means can
display that the specific substance exists in the object solution
of examination according to the signal from the biomolecular
element 400.
[0121] If the object solution of examination does not contain a
substance that reacts on the above-described biomolecular material
410, the biomolecular material 410 notifies the detection means of
a signal indicating that the biomolecular element 400 does not
detect the specific substance (and corresponds to no change of
electric current, voltage, quantity of light, mass, calorie or the
like). The detection means can display that the specific substance
does not exist in the object solution of examination according to
the signal from the biomolecular element 400.
[0122] It is possible to detect several different substances at the
same time by combining a plurality of biomolecular elements 400
where respective biomolecular materials 410 that react on different
respective substances are fixed.
[0123] Now, the present invention will be described below by way of
specific examples. However, it should be noted that the present
invention is by no means limited to the examples.
EXAMPLE 1
[0124] A carbon porous body was prepared by means of the
manufacturing method according to the present invention that is
described above by referring to FIG. 1. 1 g of KIT-5 prepared at
150.degree. C. (to be referred to as KIT-5-150 hereinafter) and
selected as cage-shaped silica porous body and 0.75 g of cane sugar
selected as carbon source were brought in and mixed with 0.8 g of
concentrated sulfuric acid and 2.5 g of water. The mol ratio of the
silicon (Si) in the silica porous body and the carbon (C) in the
carbon source was C/Si=1.5. Thereafter, the mixture was heated in
the atmosphere in an oven at 100.degree. C. for 6 hours. Then, the
temperature was raised to 160.degree. C. and held to that
temperature for six hours to complete polymerization. The obtained
polymer was held to 877.degree. C. in a nitrogen flow of 50 ml/min
for carbonization. The KIT-5-150 was removed by means of 5 wt %
hydrofluoric acid and subsequently the reaction product ICY (to be
referred to as ICY-1 hereinafter) was washed with ethanol several
times and then dried at 120.degree. C.
[0125] The obtained reaction product ICY-1 was analyzed for
structure by means of an X-ray diffractometer (Siemens D5005,
Brucker AXS, UK). The operating conditions of the X-ray
diffractometer included the use of Cu-K.alpha. rays, 40 kV/50 mA
and a scanning rate of 0.5.degree.2.theta./min. The X-ray
diffraction pattern of the used KIT-5-150 and that of the ICY-1
were compared.
[0126] The ICY-1 was observed through high resolution transmission
type electron microscopes (JEOL-3000 and JEOL-3100-FEF, JEOL Ltd.,
Japan). The specimen was regulated by granulating it by means of a
mortar and dispersing the granules on a carbon film perforated at
positions located above a Cu-made lattice. The operating conditions
of the transmission type electron microscopes included an
acceleration voltage of 300 kV and a resolution of 150,000 to
1,200,000 times.
[0127] The nitrogen adsorption-desorption isotherms of the specimen
were observed by means of a specific surface area and pore size
distribution measuring instrument (Autosorb 1, Quantachrome, USA).
The ICY-1 was deaerated at 523K under pressure not higher than 10-5
hPa for 3 hours and subsequently observed at 77K. The presence or
absence of pores and, if present, the profiles of the pores can be
found by observing the absorption-desorption isotherms. Some of the
results of the above analysis and observation are illustrated in
FIGS. 5 through 9 and will be described below in detail.
EXAMPLE 2
[0128] ICY was prepared in this example under the same preparing
conditions by following the same preparation process as in Example
1 except that KIT-5 prepared at 130.degree. C. was used as
cage-shaped silica porous body (to be referred to as KIT-5-130
hereinafter).
[0129] The obtained reaction product ICY (to be referred to as
ICY-2 hereinafter) was analyzed for structure by means of an X-ray
diffractometer and observed for nitrogen adsorption-desorption
isotherms by means of a specific surface area and pore distribution
measuring instrument as in Example 1. Some of the results of the
above analysis and observation are illustrated in FIGS. 5 and 7 and
will be described below in detail.
COMPARATIVE EXAMPLE 1
[0130] ICY was prepared in this comparative example under the same
preparing conditions by following the same preparation process as
in Example 1 except that KIT-5 prepared at 100.degree. C. was used
as cage-shaped silica porous body (to be referred to as KIT-5-100
hereinafter). The obtained reaction product ICY (to be referred to
as ICY-1' hereinafter) was analyzed for structure by means of an
X-ray diffractometer and observed for nitrogen
adsorption-desorption isotherms by means of a specific surface area
and pore distribution measuring instrument. Some of the results of
the above analysis and observation are illustrated in FIGS. 5 and 7
and will be described below in detail.
EXAMPLE 3
[0131] The process of Example 1 was followed except that 0.45 g of
cane sugar was used as carbon source and hence the process of this
example will not be described here any further. The ratio of the
silicon (Si) in the silica porous body and the carbon (C) in the
carbon source showed a relationship of C/Si=0.9. The reaction
product ICY (to be referred to as ICY-3 hereinafter) obtained in
this Example 3 was analyzed for structure by means of an X-ray
diffractometer and observed for nitrogen adsorption-desorption
isotherms by means of a specific surface area and pore distribution
measuring instrument.
[0132] Then, the protein (lysozyme) adsorption characteristic of
the ICY-3 was observed. 20 mg of ICY-3 was dispersed in 4 g of a
lysozyme buffer aqueous solution (with a concentration within a
range between 17 .mu.mol/L and 280 .mu.mol/L) with pH 11. The
dispersion liquid was agitated at a rate of 160 turns per minute
for about 96 hours at 20.degree. C. After getting to an adsorption
equilibrium, the ultraviolet absorption (281.5 nm) of the
supernatant liquid was observed by means of an ultraviolet-visible
spectrometer (Shimadzu UV-3150, Shimadzu Corporation Japan). For
the purpose of reference, the adsorption characteristic of a known
carbon porous body CMK and that of the ICY-3 were compared.
[0133] Additionally, the infrared absorption spectrum of the
protein that was adsorbed by the ICY-3 was observed before and
after the adsorption of the protein by means of a Fourier transform
infrared spectrometer (Nicolet Nexus 670, Thermo Electron, USA) in
order to see the stability of the protein. The observation
wavelength range was 400 cm.sup.-1 through 950 cm.sup.-1. Some of
the results of the above analysis and observation are illustrated
in FIGS. 8 through 11 and will be described below in detail.
EXAMPLE 4
[0134] The process of Example 1 was followed except that 1.2 g of
cane sugar was used as carbon source and hence the process of this
example will not be described here any further. The ratio of the
silicon (Si) in the silica porous body and the carbon (C) in the
carbon source showed a relationship of C/Si=2.4. The reaction
product ICY (to be referred to as ICY-4 hereinafter) obtained in
this Example 4 was analyzed for structure by means of an X-ray
diffractometer and observed for nitrogen adsorption-desorption
isotherms by means of a specific surface area and pore distribution
measuring instrument and also for lysozyme adsorption
characteristic by means of an ultraviolet-visible spectrometer.
Some of the results of the above analysis and observation are
illustrated in FIGS. 8 through 11 and will be described below in
detail.
COMPARATIVE EXAMPLE 2
[0135] The process of Example 1 was followed except that 2.0 g of
cane sugar was used as carbon source and hence the process of this
example will not be described here any further. The ratio of the
silicon (Si) in the silica porous body and the carbon (C) in the
carbon source showed a relationship of C/Si=4.0. The reaction
product ICY (to be referred to as ICY-2' hereinafter) obtained in
this Comparative Example 2 was analyzed for structure by means of
an X-ray diffractometer and observed for nitrogen
adsorption-desorption isotherms by means of a specific surface area
and pore distribution measuring instrument. Some of the results of
the above analysis and observation are illustrated in FIGS. 8 and 9
and will be described below in detail.
[0136] FIG. 5A is a graph illustrating the X-ray diffraction
patterns of cage-shaped silica porous bodies KIT-5s (KIT-5-150,
KIT-5-130 and KIT-5-100). FIG. 5B is a graph illustrating the X-ray
diffraction patterns of ICYs (ICY-1, ICY-2 and ICY-1').
[0137] As shown in FIG. 5A, it was confirmed that all the KIT-5s
including the KIT-5-150 having a baking temperature of 150.degree.
C. that was used in Examples 1, 3 and 4 and Comparative Example 2,
the KIT-5-130 having a baking temperature of 130.degree. C. that
was used in Example 2 and the KIT-5-100 having a baking temperature
of 100.degree. C. that was used in Comparative Example 1 showed
peaks that correspond to diffractions of (111), (200) and (220) of
the face-centered cubic lattice (space group Fm3m). The diffraction
peaks were shifted to the low angle side and the diffraction
intensity was increased as the baking temperature rose.
[0138] The lattice constants a.sub.0 were determined from the
diffraction peak (111). Table 1 below shows the obtained results.
As shown in Table 1, the lattice constants a.sub.0 of KIT-5-100,
KIT-5-130 and KIT-5-150 are 18.1 nm, 19.0 nm and 20.7 nm
respectively. Thus, it was found that the lattice constant a.sub.0
is increased as the baking temperature is raised. The specific
surface area, the pore capacity, the pore diameter d.sub.1 (which
corresponds to the diameter d.sub.1 in FIG. 2) and the diameter
d.sub.2 (which corresponds to the diameter d.sub.2 in FIG. 2) of
each of the KIT-5s used in the examples were also looked into. The
obtained results are also shown in Table 1.
TABLE-US-00001 TABLE 1 baking specific pore temper- lattice surface
capacity channel ature constant area s v diameter diameter KIT-5
(.degree. C.) a.sub.0 (nm) (m.sup.2/g) (cm.sup.3/g) d.sub.1 (nm)
d.sub.2 (nm) KIT-5-100 100 18.1 701 0.44 10.8 3.8 KIT-5-130 130
19.0 675 0.69 12.3 4.3 KIT-5-150 150 20.7 470 0.75 13.5 5.7
[0139] As seen from Table 1, it was found that, as the baking
temperature rises, micro pores are removed to decrease the specific
surface while the value of d.sub.1 and that of d.sub.2 increase to
raise the pore capacity. Note that the structural difference among
the KIT-5s is also produced by detailed baking conditions (the rate
of temperature rise, the baking atmosphere, the baking time,
etc.)
[0140] As shown in FIG. 5B, the peaks that are similar to those of
the diffraction pattern of FIG. 5A and correspond to the
diffractions of (111), (200) and (220) of the face-centered cubic
lattice (space group Fm3m) were also confirmed. However, all the
peaks are rather broad and the diffraction intensity was reduced.
As in the case of KIT-5, the diffraction peaks were shifted and the
diffraction intensity was changed depending on the KIT-5 that was
used for the ICY. The lattice constants a.sub.0 were determined
from the diffraction peak (111) in the same manner. The obtained
results are shown in Table 2. The diffraction constants a.sub.0 of
ICY-1, ICY-2 and ICY-1' were 20.68 nm, 18.2 nm and 16.8 nm
respectively. It was found that they showed values similar to the
lattice constants of the KIT-5s that were respectively used for
them. This fact indicates that each of the carbon porous bodies
maintained the regular structure of the replica, or the cage-shaped
silica porous body (KIT-5 in the corresponding example), after
removing the replica.
[0141] Each of the ICYs was subjected to a thermogravimetric
analysis in an oxygen atmosphere in order to confirm that the
diffraction patterns shown in FIG. 5B are not produced by the
remaining KIT-5. As a result, it was found that the residual KIT-5
is about 1 wt % to 1.5 wt % for all the carbon porous bodies
including ICY-1, ICY-2 and ICY-1'. Thus, it was confirmed that the
X-ray diffraction patterns in FIG. 5B are not produced by the
residual KIT-5s.
[0142] From above, it was found the lattice constants of ICYs vary
as a function of the KIT-5s used for obtaining them. To be more
specific, it was found that an ICY having a large lattice constant
can be obtained by selecting a KIT-5 showing a large lattice
constant a.sub.0. The preferable range of lattice constant a.sub.0
of KIT-5 is 17<a.sub.0 (nm)<22.
[0143] FIG. 6A is a microscopic photograph of ICY-1 taken along a
surface parallel to the air holes thereof. FIG. 6B is a microscopic
photograph of ICY-1 showing a cross section thereof. In FIGS. 6A
and 6B, the light stripes indicate pore walls (e.g., 310 or 320 in
FIG. 3), whereas dark stripes indicate pores (e.g., spaces
indicated by distance D.sub.2 in FIG. 3). Thus, it was found from
FIGS. 6A and 6B that the obtained ICY-1 had a highly regular
structure and a micro pore distribution.
[0144] Light spots (like the enlarged ones at corners of FIGS. 6A
and 6B) are arranged regularly in the images illustrated in FIGS.
6A and 6B to prove that ICY-1 had a cage-shaped porous structure.
While similar microscopic images were obtained for ICY-2, no such
regularity was observed in the images of ICY-1' because pores had
been crushed there. This is because KIT-5-100 does not function
stably as replica due to the micro pores remaining in the inside
when KIT-5-100 baked at a relatively low temperature is
employed.
[0145] FIG. 7A is a graph illustrating the nitrogen
adsorption-desorption isotherms of ICY-1, ICY-2 and ICY-1' and FIG.
7B is a graph illustrating the pore distributions of ICY-1, ICY-2
and ICY-1'. As seen from FIG. 7A, the nitrogen
adsorption-desorption isotherms of ICY-1 and those of ICY-2 showed
the H2 type (the IV type in the IUPAC classification) hysteresis.
This fact means that meso pores (pores having a diameter of 2 to 50
nm) existed in ICY-1 and ICY-2 and nitrogen adsorption that is
attributable to capillary condensation took place under relative
pressure of 0.5 to 0.8.
[0146] On the other hand, the nitrogen adsorption-desorption
isotherms of ICY-1' was of the II type (in the IUPAC
classification) and did not show any hysteresis. This fact means
that no pores were found or micro pores (pores having a diameter
not greater than 2 nm) existed in ICY-1', leading to the fact that
the nitrogen adsorption amount of ICY-1' was remarkably smaller
than that of ICY-1 and that of ICY-2.
[0147] Subsequently, the specific surface area and the pore
capacity of ICY-1, those of ICY-2 and those of ICY-1' were
determined by means of the BET formula, using the nitrogen
adsorption-desorption isotherms of FIG. 7A. Table 2 shows the
obtained results.
[0148] The specific surface area and the pore capacity of ICY-1'
were respectively not greater than 500 m.sup.2/g and not greater
than 0.4 cm.sup.3/g because ICY-1' did not have any pores or only
micro pores existed there. However, it was found that both ICY-1
and ICY-2 had a specific surface area of not smaller than 1,400
m.sup.2/g and a pore capacity of not smaller than 1.5 cm.sup.3/g,
which were relatively large, because they had meso pores in the
inside. Particularly, ICY-1 showed a large pore capacity of not
smaller than 2.0 cm.sup.3/g, which is by far greater than that of
any conventional carbon porous body, and hence could be
advantageous for the purpose of adsorption (fixation) of a
substance having a large structure such as biomolecules. Referring
again to Tables 1 and 2, it was found that an ICY having a large
specific surface area can be obtained by using a KIT-5 having a
small specific surface area.
[0149] Accordingly, it was also found that an ICY having a large
pore capacity can be obtained by using a KIT-5 having a large pore
capacity. Preferably, the specific surface area of KIT-5 to be used
for the purpose of the present invention satisfies a requirement of
450<s (m.sup.2/g)<690.
[0150] FIG. 7B is a graph illustrating the pore distributions
determined respectively from the pore capacities of the ICYs as
determined from the nitrogen adsorption/desorption isotherms of
FIG. 7A. The determined pore diameter D.sub.1 is similar to the
distance D.sub.1, which is described above by referring to FIG. 3.
The obtained results are shown in Table 2.
[0151] From FIG. 7B, it was found that the pore diameter D.sub.1 of
ICY-1 was 5.2 nm and that of ICY-2 was 4.0 nm. On the other hand,
ICY-1' did not show any clear pore distribution. From FIGS. 7A and
7B and a microscopic photograph (not shown), it was found that
ICY-1' did not show any pores (except a small number of micro
pores) and its structure had been partly broken down.
[0152] This is because the channel diameter of KIT-5-100 used for
ICY-1' was too small relative to the specific surface area and
hence KIT-5-100 did not stably function as replica as seen from
Table 1. Thus, it is necessary to use a KIT-5 that has a preferable
specific surface area as described above and satisfies the
requirement for the channel diameter of 4<d.sub.2 (nm)<6 in
order to reliably obtain an ICY having a stable structure as shown
in FIG. 3.
[0153] Subsequently, the cage diameter D.sub.2 (that corresponds to
the distance D.sub.2 in FIG. 3) was determined by means of formula
(1) shown below from the pore diameter D.sub.1.
D.sub.2=a.sub.0.times.(6.epsilon./.pi..nu.).sup.1/3 (1)
[0154] In the formula (1), a.sub.0 is the lattice constant (nm) of
ICY and .epsilon. is the volume ratio of the pores, while .nu. is
the number of pores in a unit lattice (v=4 in the case of space
group Fm3m). Table 2 also shows the obtained results.
[0155] The cage diameter D.sub.2 of ICY-1 was 13.5 nm and that of
ICY-2 was 12.3 nm. Thus, it is possible to obtain an ICY having a
pore diameter D.sub.1 and a cage diameter D.sub.2 that are feasible
for practical applications (or respectively 4.ltoreq.D.sub.1
(nm).ltoreq.6 and 9.ltoreq.D.sub.2 (nm).ltoreq.15) by using a KIT-5
that satisfies the above-described requirements for the specific
surface area and the channel diameter.
[0156] Thus, it was shown from Examples 1 and 2 and Comparative
Example 1 that, when the mol ratio of the silicon (Si) in the
silica porous body and the carbon (C) in the carbon source is
constant (e.g., C/Si=1.5), it is important to select an appropriate
replica in order to obtain an ICY that is stable and has a large
specific surface area and a large pore capacity. Particularly, it
is effective to use a replica showing a large lattice constant in
order to obtain an ICY that has a large specific surface area, a
large pore capacity and a large cage diameter. More specifically,
it is desirable to use a KIT-5 that satisfies the requirement of
450<S (m.sup.2/g)<690 for the specific surface area s and
that of 4<d.sub.2 (nm)<6 for the channel diameter
d.sub.2.
[0157] FIG. 8 is a graph illustrating the X-ray diffraction
patterns of ICY-1, ICY-3, ICY-4 and ICY-2'. As in the case of ICY-1
shown in FIG. 5B, an X-ray diffraction pattern showing peaks that
correspond to diffractions of (111), (200) and (220) of the
face-centered cubic lattice (space group Fm3m) within the range of
2.theta.=between 0.7 and 3 was confirmed for ICY-3 and also for
ICY-4. No substantial shift of diffraction peaks was observed in
the X-ray diffraction patterns. On the other hand, ICY-2' did not
show any X-ray diffraction pattern of the face-centered
lattice.
[0158] The lattice constants a.sub.0 were determined from the
diffraction peak (111).
[0159] Table 2 also shows the obtained results. As described above
by referring to FIGS. 5A and 5B and Table 2, the lattice constant
a.sub.0 of the selected replica (KIT-5-150 here) was 20.7 nm. The
lattice constants of ICY-1, ICY-3 and ICY-4 were respectively 20.68
nm, 19.98 nm and 19.48 nm, which are close to the lattice constant
of KIT-5.
[0160] On the other hand, it was found that the lattice constant
a.sub.0 of ICY-2' was 7.03 nm and hence did not reflect the
structure of KIT-5. From the above, the mol ratio of the silicon
(Si) in the silica porous body and the carbon (C) in the carbon
source is important to the stability of the obtained crystal
structure when a same replica is used.
[0161] FIG. 9 is a graph illustrating the nitrogen
adsorption-desorption isotherms of ICY-1, ICY-3, ICY-4 and ICY-2'.
As seen from FIG. 9, all the nitrogen adsorption/desorption
isotherms showed the hysteresis of the H2 type (the IV type in the
IUPAC classification). This suggests that meso pores (pores having
a diameter between 2 and 50 nm) existed and nitrogen adsorption
attributable to capillary condensation took place under relative
pressure of 0.5 to 0.8 in ICY-1, ICY-3, ICY-4 and ICY-2'. However,
as described above by referring to FIG. 8, ICY-2' did not have any
structure that is based on KIT-5 and hence seems to have meso pores
that are structurally different from those of KIT-5.
[0162] The specific surface area, the pore capacity, the pore
diameter D.sub.1 and the cage diameter D.sub.2 of each of the ICYs
were determined from the nitrogen adsorption-desorption isotherms.
Table 2 shows the obtained results. As shown in Table 2, the
specific surface area, the pore capacity, the pore diameter D.sub.1
and the cage diameter D.sub.2 of ICY-1, ICY-3 and ICY-4 were
respectively 1,515 m.sup.2/g, 2.0 cm.sup.3/g, 5.2 nm and 15.0 nm,
1,600 m.sup.2/g, 2.1 cm.sup.3/g, 5.2 nm and 14.5 nm and 1,365
m.sup.2/g, 1.8 cm.sup.3/g, 5.6 nm and 14.0 nm. Particularly, it was
found that ICY-3 had a specific surface area and a pore capacity
that were the largest among the known carbon porous bodies.
[0163] From the above-described results, it became clear that, when
a same replica is used, the ICY structure, particularly the
specific surface area and the pore capacity thereof, can be changed
by changing the mol ratio of the silicon (Si) in the silica porous
body and the carbon (C) in the carbon source. More specifically, it
became clear that both the specific surface area and the pore
capacity decrease as the ratio of the carbon (C) in the carbon
source to the silicon (Si) in the silica porous body increases.
From the above, when KIT-5 is used, it is necessary for the mol
ratio to satisfy requirement of 0.8<C/Si<3.0, more preferably
the requirement of 0.85.ltoreq.C/Si.ltoreq.0.95.
TABLE-US-00002 TABLE 2 cane specific pore pore cage lattice
sugar/KIT-5 surface capac- diam- diam- constant mol ratio area ity
eter eter Example a.sub.0 (nm) (C/Si) (m.sup.2/g) (cm.sup.3/g)
D.sub.1 (nm) D.sub.2 (nm) Example 1 20.68 1.5 1515 2.0 5.2 15.0
Example 2 18.2 1.5 1410 1.5 4.0 12.8 Com. Ex 1 16.8 1.5 475 0.35 --
9.4 Example 3 19.98 0.9 1600 2.10 5.2 14.5 Example 4 19.48 2.4 1365
1.80 5.6 14.0 Com. Ex 2 7.03 4.0 1125 1.47 5.8 --
[0164] FIG. 10 is a graph illustrating the adsorption
characteristics of the protein (lysozyme) of ICY-3 and ICY-4. Each
of the adsorption characteristics agreed with the absorption
isotherm expressed by formula (2) below.
n.sub.s=Kn.sub.mc/(1+Kc) (2)
[0165] In the formula (2), n.sub.s is the adsorption amount of
lysozyme adsorbed to the carbon porous body and K is the Langmuir
constant, while nm is the saturated adsorption amount of the
mono-molecule layer and c is the lysozyme concentration. The
saturated adsorption amounts of ICY-3 and ICY-4 as determined by
means of the above formula (2) were respectively 26.5 .mu.mol/g and
23.8 .mu.mol/g. On the other hand, the saturated adsorption amount
of the known CMK was 22.9 .mu.mol/g.
[0166] The above-cited saturated adsorption amount of 26.5
.mu.mol/g was higher than the highest value attainable by any known
carbon porous body by more than 15%. Thus, from this fact, a carbon
porous body showing a large pore capacity and a large specific
surface area operates excellently for adsorption, collection,
removal and fixation of biomolecules (proteins, nucleic acids and
polysaccharides) having a large size.
[0167] FIG. 11 is a graph illustrating the infrared absorption
spectrum of a protein (lysozyme) observed before and after a
protein (lysozyme) adsorption by ICY-3. In FIG. 11, the dotted
chain line indicates the infrared absorption spectrum of the
lysozyme before the adsorption and the dotted line indicates the
infrared absorption spectrum of the lysozyme after the adsorption
by ICY-3. From FIG. 11, it was found that the infrared absorption
spectrum of the lysozyme after the adsorption by ICY-3 was similar
to that of the lysozyme before the adsorption. Besides, it was also
found that the absorbance in the amide I and amide II bands did not
change significantly before and after the adsorption. These facts
suggest that the lysozyme adsorbed by ICY does not react with the
ICY and hence is stable and that therefore the lysozyme adsorbed by
ICY can find applications as a molecule recognition element for
detecting a specific substance that reacts on the lysozyme.
Additionally, fixed biomolecules maintains their stability after
the fixation as described above and hence it is expected that such
biomolecules can find applications in the field of reactors for
digesting pollutants and sensors that are highly sensitive to
harmful substances.
INDUSTRIAL APPLICABILITY
[0168] A manufacturing method according to the present invention
employs a cage-shaped silica porous body where a plurality of pores
is arranged three-dimensionally, regularly and symmetrically as
replica. Since such a cage-shaped silica porous body has a specific
surface area and a pore capacity smaller than those of any
conventional replicas, the obtained carbon porous body can show a
specific surface area and a pore capacity greater than ever. Then,
such a cage-shaped silica porous body and a carbon source are mixed
to a predetermined mol ratio (namely 0.8<C/Si<3.0) and hence
it is possible to obtain a carbon porous body that is free from
conglutination of carbon and shows a high degree of regularity. The
carbon porous body that is obtained in this way can show an
improved adsorption effect than ever and adsorb large substances
that conventional carbon porous bodies cannot. Additionally, the
adsorbed substance can be dispersed into the inside of the carbon
porous body with ease. Such a carbon porous body can find
applications in the field of adsorbents, electrodes of fuel cells,
sensors of molecule recognition elements and so on.
* * * * *