Page 4 - Shimadzu Journal vol.4 Issue1

Insight from Customer

Professor Osamu Ishitani of the Graduate School of
Science and Engineering, Tokyo Institute of Technology, Japan

We interviewed Professor Osamu Ishitani of the Graduate School of Science and Engineering, Tokyo Institute of
Technology (Tokyo, Japan). His research is focused mainly on artificial photosynthesis. He and Shimadzu started a
collaborative relationship in 2012, which resulted in the QYM-01 photoreaction quantum yield evaluation system*
that permits accurate and simple quantitation measurements of absorbed photons.
* The QYM-01 system is not available in Europe and may not be available in some other countries. Please contact your local Shimadzu representative for availability.

Dr. Ishitani, thank you very much for sparing time for this
interview. First of all, could you explain the background
to this collaborative research with Shimadzu? Why did
you choose Shimadzu as your partner?

I have conducted research into the photochemistry of metal complexes,
and in particular into the development of artificial photosynthesis
systems, for many years, and in recent years the number of researchers
participating in this field of research has increased drastically. However,
it worries me that upon attending the presentations of these
researchers, it is not uncommon that many of them will not calculate
quantum yield, and will not pose their arguments based on quantum
yield results.
While quantum yield is the most important and fundamental
quantitative value for research into photoreactions, it is not simple,
experimentally, for a researcher that is researching photochemistry to
Could you provide a summary of this research and tell us
measure the quantum yield of a photoreaction. One of the first things what discoveries and achievements have been made so far?
taught to students in classes on photochemistry is the first law of
photochemistry. Simply put, this law states that light absorbed by a Basically, this research aims to enhance the functionality of, and improve
molecule gives rise to a photoreaction. Consequently, a measurement of the operability of equipment used in photoreactions, where the
quantum yield requires not a calculation of the quantity of light emitted, equipment in question is unique and was created by us. The three main
but a calculation of the number of photons absorbed by a substrate. topics of this research are as follows.
Calculating this number requires the preparation of various experimental First is ease-of-operability of light quantity measurement and
conditions and execution of a complicated procedure. In our laboratory, improvement of the precision. Two commonly used methods of
we prepare hand-made equipment and have summarized the research measuring light quantity employ a chemical actinometer and a
procedure in manual form so that all students are able to, without fail, photoelectric transducer. Our equipment previously employed a method
measure quantum yield. Nevertheless, I believe a fair number of students that used a chemical actinometer, but operation of this equipment was
find this research difficult to conduct, despite these preparations. Also, complex and required an experienced operator. This problem was
our equipment and methods have not always been totally satisfactory. resolved for us by Shimadzu. Second is measurement of the quantity of
For example, the equipment we developed could be used to calculate light transmitted through the reaction solution. Measuring the quantity
the number of photons entering the reaction vessel, but calculating the of light transmitted through the reaction vessel requires an extremely
number of photons that pass through the vessel has not been easy. complex procedure, a problem that was resolved by introducing a
Consequently, experiments had to be performed under the assumption system that takes constant measurements of the quantity of illuminating
that almost all incident light was absorbed by the solution inside the light during the photoreaction. By utilizing this equipment, we can now
reaction vessel. Furthermore, when a light source is emitting light change the substrate concentration (which affects the extent of
continuously for an extended period of time, the light source gradually absorbance by the reaction solution) at will and determine the quantum
degrades and the quantity of emitted light decreases. We were unable yield of the photoreaction. Third was the problem of canceling out error
to estimate this change. We needed to work together with engineers caused by degradation of the light source. This was resolved based on a
skilled at systemization of equipment as well as experts in spectroscopy proposal made by an engineer at Shimadzu. The mechanism devised
to make the improvements to our equipment required for resolution of introduces a beam splitter in front of the reaction vessel to take off part
these problems. of the illuminating light, which is directed into another system that
When approached by Shimadzu regarding the joint research into provides a constant measurement of the quantity of light. This allows us
development of equipment for photoreactions, two areas of equipment to perform measurements of quantum yield with good precision even
development occurred to me that I thought could be realized. One was during experiments using a light source for an extended period of time.
to enable people who conducted research into photochemical reactions A system that uses a photodiode detector to measure the absorption
but were not specialists in photochemistry to perform accurate yet spectra of the solution was added to the light illumination system we
simple measurements, and the other was to enable measurements of developed, and placed at right angles to the illuminating light used for
quantum yield with smaller errors than previously possible while under photoreactions. This system detects reaction intermediates that
diverse experimental conditions. accumulate in solution during the actual photoreaction, and has been

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