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JAPAN NANONET BULLETIN
-- 82nd Issue -- October 26, 2006
Nanotechnology Researchers Network Center of Japan
Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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IN THIS ISSUE
Nanonet Interview:
"Observation of electrode surfaces
-- Developing an electrochemical STM --"
Kingo ITAYA, Professor, Department of Applied Chemistry, Graduate
School of Engineering, Tohoku University
Young Researchers' Introduction:
"Bio nano-tool fabrication by focused-ion-beam chemical vapor
deposition"
Reo KOMETANI, Doctoral student of University of Hyogo and Fellow,
Japan Society for the Promotion of Science (JSPS)
-- 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
Observation of electrode surfaces
-- Developing an electrochemical STM --
(Issued in Japanese: August 18, 2004)
Kingo ITAYA, Professor, Department of Applied Chemistry, Graduate
School of Engineering, Tohoku University
"We, electrochemists, all wished to observe directly the surface of
an electrode and to know what occurs on the surface," says Prof. Itaya.
In order to determine the surface structure of electrodes and what
reactions occur on the surface of the electrode using low energy
electron diffraction (LEED) or Auger electron spectroscopy (AES),
electrodes have to be taken from solution and placed into an ultra high
vacuum. However, this procedure may change the surface structure and
result in improper observations. It was impossible to observe electrode
surfaces in solution at the atomic and molecular level in real time
until Prof. Itaya developed an electrochemical STM (scanning tunneling
microscope).
In the early 80's, Prof. Itaya, who is an electrochemist, learned that
Prof. Binnig and Prof. Rohrer developed an STM, and he was fascinated
by the device, which was designed to directly observe surface
structures at the atomic and molecular level. However, he then thought
that the device could only be used in an ultra high vacuum, and it did
not fit any of his research objectives. As a result of his chance in
1985 to see the circuit diagram for the STM, he says, "In the circuit
diagram, I found that feedback loops were used to keep the tunneling
current constant. The circuit diagram was exactly the same as that used
in electrochemical measurements. I thought it was something that I
could make." Then, he decided to develop an electrochemical STM that
enables measurements in an electrolyte solution. He focused on the
similarities in the circuits for a galvanic electrochemical measurement,
which measures a change in electric potential by controlling the
current flowing between a sample and a counter electrode, and an STM,
which controls the tunneling current flowing between an STM probe and
a sample.
Electrical potentials control the reactions on the electrode surfaces.
In electrolyte solutions, not only the electrical potential of a sample
but also that of a probe must be controlled in order to conduct STM
measurements. Prof. Itaya devised a circuit, in which the electrical
potentials of a sample and a probe are controlled independently of each
other by using a reference electrode, and the tunneling current is
controlled by the potential difference between the sample and the probe.
In the circuit, the probe, except for its tip, is coated with glass or
polymers so that the current will not flow into the rest of the probe.
The largest obstacle in operating an STM in solution was the vibration
of the probe. Even a slight sound can cause vibrations in solution,
which will result in improper measurements. So, he covered the
equipment with thick boards to muffle any sound and conducted his
experiments while holding his breath at midnight.
In 1988, Prof. Itaya published the principles and system diagram of his
electrochemical STM and, in 1989, the STM images of a platinum (111)
single-crystalline surface in a sulfuric acid solution. The images had
monoatomic steps with a height of 0.23 nm intersecting each other at
the angles of integral multiplication of 60 degrees due to the tri-
symmetrical structure of the platinum (111) single-crystalline surface.
He says, "Researchers, who used STMs in ultra high vacuums, thought
that material surfaces in solution are dirty. However, we,
electrochemists, are sure that we could observe clean material surfaces
even in solution." In the STM images, clean and smooth electrode
surfaces in solution at the atomic level were observed for the first
time, and thus, he showed how effective his STM was.
In 1992, "ITAYA Electro-chemiscopy Project" at the Research Development
Corporation of Japan (Currently, Japan Science and Technology Agency,
JST) was launched. During the project, progress was made in the
electrochemical STM, and its resolution was high enough to identify
individual atoms, molecules and ions. As one of the project's
achievements, an adlattice structure of a sulfate ion on a rhodium
(111) single-crystalline surface was imaged. When the surface in
a sulfuric acid solution was measured using the electrochemical STM,
regular square root(3) x square root(7) lattices of a sulfate ion were
observed and small spots in the lattices were also imaged. These spots
proved the existence of water molecules. Till then, it was impossible
to determine how an adlattice structure was affected by water molecules.
"An adlattice structure affected by water molecules changes in an ultra
high vacuum. For this reason, I had to observe it in solution using an
in-situ STM," says Prof. Itaya. Meanwhile, he developed an ultra-high
-vacuum-electrochemical system, which enables structural analysis by
transporting electrodes from solution to an ultra high vacuum without
contaminating the electrode surfaces. He adds that he wanted to know
the difference between the adlattice structures in an ultra high vacuum
and in solution. The adlattice structures affected by water molecules
change in an ultra high vacuum, but the structures affected by organic
compounds containing no water molecules remain unchanged. He determined
the similarities and the differences between adlattice structures in
an ultra high vacuum and in solution.
Prof. Itaya says, "Nanotechnology had been a technology, which was
effective in ultra high vacuums. Now, it is at the stage where
nanofabrication is done by using chemical reactions in solution." He
has been trying to control surface structures at the atomic and
molecular level with electric potential in order to establish a method
to fabricate desired nanostructures. He says, "Generally, the
electrical potential of a sample is not considered when dealing with
adlattice structures. However, there are types of structures that
strongly depend on the electrical potential. Therefore, it is necessary
to think electrochemically when fabricating desired surface structures.
What is outstanding about electrochemistry is that it enables us to
precisely control chemical reactions including biological reactions."
(Interviewer: Aya Araoka, nanonet)
For more information including figures,
http://www.nanonet.go.jp/english/mailmag/2006/082a.html
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YOUNG RESEARCHERS' INTRODUCTION
Bio nano-tool fabrication by focused-ion-beam chemical vapor
deposition
(Issued in Japanese: February 8, 2006)
Reo KOMETANI, Doctoral student of University of Hyogo and Fellow,
Japan Society for the Promotion of Science (JSPS)
Bio nano-tools for highly accurate manipulation and analysis of single
cells and organelles are very useful and important in clarifying
unknown biological phenomena. We propose making tools for three-
dimensional (3-D) nano-structure devices towards achieving high
functionality. Therefore, we have been studying bio nano-tools with 3-D
structures using focused ion beam chemical vapor deposition (FIB-CVD).
Thus far, we have fabricated a bio nano-injector as a nano-tool (Fig.
1). The bio nano-injector has a nozzle with an inner diameter of 220 nm.
As a result, injection into an oocyte of Ciona Intestinalis was
possible. Mechanical stress on the injection target is reduced by using
the bio nano-injector, because the nozzle size is small. In addition,
the bio nano-injector is a very useful tool because the shape and size
of its tip can be freely adjusted for various functions.
In addition, a filtering tool was developed by using FIB-CVD ( Fig. 2).
In recent years, studies, such as those involving biological batteries,
which use chloroplasts, have been conducted. Therefore, it is important
to understand biological mechanisms at the single chloroplast level.
A technique to remove a single chloroplast from the plant cell was
necessary to research its biological mechanism. It is possible to
filter quickly and to capture arbitrarily sized organelles by using the
filtering tool. The filtering tool has a nano-net with a wire size of
200 nm to filter the various organelles, and we were able to capture
a chloroplast using the filtering tool. This result indicates that
single organelle manipulation can be carried out using bio nano-tools
fabricated by FIB-CVD.
By using FIB-CVD, we can develop novel nano-tools with high-performance.
We want to achieve free and highly accurate manipulation and analysis
of a single organelle in a cell by using the bio nano-tool fabricated
by FIB-CVD in the near future.
For more information including figures,
http://www.nanonet.go.jp/english/mailmag/2006/082b.html
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