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JAPAN NANONET BULLETIN
-- 56th Issue -- October 27, 2005
Nanotechnology Researchers Network Center of Japan
Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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IN THIS ISSUE
Nanonet Interview:
"A new world expanding from nanospace
-- Dendrimer and Bucky plastics --"
Takuzo AIDA, Professor, Department of Chemistry and Biotechnology,
Graduate School of Engineering, The University of Tokyo
Young Researchers' Introduction:
"Silicon nanostructure fabrication and its application to
biomolecules"
Takashi TANII, Associate Professor, Graduate School of Science and
Engineering, Waseda University
-- NANO CALENDAR --
For information on nanotechnology related symposiums and conferences
held in the world,
http://www.nanonet.go.jp/english/calendar/
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NANONET INTERVIEW
A new world expanding from nanospace
-- Dendrimer and Bucky plastics --
(Issued in Japanese: February 17, 2004)
Takuzo AIDA, Professor, Department of Chemistry and Biotechnology,
Graduate School of Engineering, The University of Tokyo
Dendrimers are three-dimensional polymers characterized by a regular
tree-like array of branched units. The name originates from Dendron
which means trees in Greek. In 1991, Prof. Aida, who had been studying
plastics in his laboratory, decided to start studying dendrimers as a
new research subject. Although most of the research involved the
attachment of some substance to the periphery of a dendrimer to give
it new functions, Prof. Aida focused on the interior of the dendrimer.
Prof. Aida says, "A researcher is also a scriptwriter. It is
meaningless to write the same story as others. I thought that surely
there was something interesting to do with the interior that nobody
had done, yet."
"How can I make other researchers understand that the interior of the
dendrimer is important?" Prof. Aida then decided to investigate the
behavior of the iron porphyrin complex, or heme, encapsulated in the
center of the cavity created by a dendrimer molecule. The heme moiety
carries oxygen in your blood, and because it is surrounded by a
protein, heme stably binds oxygen. Prof. Aida found that, even if heme
is surrounded by a dendrimer, instead of a protein, it still functions
as a carrier. This phenomenon may lead to the development of
artificial blood.
While investigating what happens in the interior of a dendrimer, Prof.
Aida found that when azobenzene, which is encapsulated in the center
of the dendrimer cavity, is irradiated with low-energy light, the
azobenzene isomerizes. Normally, isomerization does not occur when low
-energy light is used, and thus, Prof. Aida discovered the light-
harvesting ability of dendrimers. Light-harvesting also occurs in
chlorophyll, which is ring-shaped, during photosynthesis. He prepared
dendrimers with a diameter of 15 nm and with light-harvesting units
similar to chlorophyll. When they were exposed to light, 70% of the
energy of the irradiated light was concentrated at the center of the
dendrimers. Recently, research involving hydrogen extraction from
water is progressing using light-harvesting. Because of his research
on dendrimers, he has become more interested in the nanospace within
molecules. He is now the leader of the Aida Nanospace Project of the
Exploratory Research for Advanced Technology (ERATO) of the Japan
Science and Technology Agency (JST). The aim of his project is to
research the potential functions of the nanospace of various large
molecules which is covered by the periphery of the molecule.
Prof. Aida regards the gelation of carbon nanotubes as an important
result from his project. Dispersing carbon nanotubes within polymers
improves the properties of the polymer, such as mechanical strength
and electrical conductivity, but so far no effective method has been
found to uniformly mix polymer materials and carbon nanotubes. However,
from Prof. Aida's project, it was discovered that, when nanotubes are
put into an ionic liquid, gelation occurs to form a paste, which is
more easily handled. Therefore, if a polymerizable component is
introduced into an ionic liquid, it can be molded like conventional
polymers. "This was a totally unexpected result from the project.
Interesting things are often found unexpectedly, outside the original
script," Prof. Aida says. Polymers containing carbon nanotubes were
named "Bucky plastic," and it has a mechanical strength 4 to 10 times
higher than polymers without nanotubes and is electrically conductive.
Prof. Aida has had some remarkable results through his study of
various types of nanospace. A particular type of silicate material
with a honeycomb-like porous framework was utilized as a nanoflask for
the polymerization of ethylene. The polymer chains were extruded from
mesopores with a diameter of 2 nm and then assembled to form extended-
chain crystalline polyethylene nanofibers with a diameter of 50 nm and
excellent mechanical properties. As well, Prof. Aida showed that a
chaperon, which is a cylindrical protein aggregate, absorbed nano-
sized cadmium sulfide particles, which are semiconductors, into its
4.5 nm sized holes. The nanoparticles were stably held within the
holes until the chaperon was activated by ATP to release the particles.
His findings may lead to the development of a new drug delivery system
and switches for electronic circuits. As for Prof. Aida's research
interests, both artificial and natural materials are included in his
concept of "nanospace". He says, "Among physicists, chemists and
biologists, chemists tend to adhere to a substance most. However, if
you are obsessed with a substance, you may end up becoming stuck and
unable to progress. Although I am a chemist, I want to adhere to
phenomena and concepts."
(Interviewer: Yu Tatsukawa, Cosmopia Inc.)
For more information,
http://www.nanonet.go.jp/english/mailmag/2005/056a.html
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YOUNG RESEARCHERS' INTRODUCTION
Silicon nanostructure fabrication and its application to
biomolecules
(Issued in Japanese: April 6, 2004)
Takashi TANII, Associate Professor, Graduate School of Science and
Engineering, Waseda University
During the 2001 academic year, Waseda University began a five year COE
(Center of Excellence) project entitled "Molecular nano-engineering"
with grants from the Ministry of Education, Sports, Culture, Science
and Technology (MEXT). Our aims in cooperation with molecular
biologists are the "Establishment of wafer-scale nanostructure
fabrication process", "Preferential immobilization of biomolecules
onto nanostructure array" and "Single molecule analysis by means of
near-field optical imaging via nano-hole wave-guides".
Biomolecules have sophisticated functions, such as self-assembly,
catalytic molecular recognition and self-restoration. By combining the
ability to self-assemble with conventional lithography processes, we
can fabricate well-designed nanostructured patterns for single
molecule immobilization, for example, high-density DNA nanostructured
patterns formed in a self-assembled monolayer (see Fig. 1). These well
-designed structures allow us also to observe the dynamics of
intramolecular interactions in real time. The nanohole arrays, in
which functional proteins are immobilized, serve as wave-guides for
near-field optical imaging (see Fig. 2). We can identify
intramolecular interactions in vitro using concentrations similar to
those found in real cells.
For more information,
http://www.nanonet.go.jp/english/mailmag/2005/056b.html
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