Message（16）From Laser Photolysis to Laser Nano Chemistry

１． Introduction
　　　I was a shy and slow-tempo student before I took a chemistry class in my third year of high school. The chemistry class changed my mind, and I decided to study chemistry as my special. I remember that there was an introduction at the end of the textbook used to what kind of work students could go after studying chemistry in Science and Engineering. One of the editor's advisors was Prof. Masao Koizumi of Tohoku University. In 1962, I was the only student who entered the Faculty of Science of Tohoku University in Sendai from Mikunigaoka High School in Osaka.
　　　I chose the chemistry department without hesitation when choosing a specialty for a sophomore in the Liberal Arts Department. When I was in my fourth year, I decided to participate in the laboratory of Prof. Masao Koizumi of Physical Chemistry and Photochemistry in the fourth year of undergraduate. Then I joined Prof. Koizumi's laboratory as a laboratory for graduation research. I think the reason why I participated in the Lab of Prof. Koizumi was that I was trying to read "Chemical Bonding Theory" written by Poling, and translated into Japanese by Prof. Koizumi, and a large book "Survey of Photochemistry" (Figure 1) written by Prof. Koizumi. At that time, Tohoku University had a strong presence in the field of Natural Products Chemistry. However, I thought that the intermediate between physics (research on the theory of things) and chemistry (research on the abundance of things) was very interesting, and I was fit to it. I received direct guidance from Assistant Prof. Michio Okuda (Late Director of the Institute of Environmental Science, Environment Agency, Japan). There was no direct discussion of the research with Prof. Koizumi until I finished my master thesis. However, his research life had a strong impression on me, a vague young man. Every morning, he walked from his home in Yagiyama to the Faculty of Science in Katahira and worked on a well-defined schedule. He sometimes rushed to the toilet with his shirt outside on his back. Prof. Koizumi was a real gentleman. I remember that I had a strong impression from him about what research is and what research life is like as if it were just yesterday. After that, I went on to a doctoral program at the Faculty of Engineering Science, Osaka University, and decided to try to get a degree under the guidance of Prof. Noboru Mataga. That was in 1968. In front of the nanosecond ruby laser that was installed in that year, Prof. Mataga said to me "All light sources will be replaced by lasers in the future, and photochemical research using lasers will have unlimited possibilities." I, a very young man, was much impressed by his words. I became the first graduate student at Mataga Lab who obtained a degree in laser-based research, and my first work was to oscillate a nanosecond ruby laser stably. I realized I could be awarded to PhD if I could write a paper unique to nanosecond lasers. So, I was very free to choose a theme. At this time, I think that I enjoyed the real (true) fun of exploratory research. Since then, I have been studying molecular systems unique to lasers, and working in the so-called interdisciplinary area, belonging to the departments of chemistry, synthetic chemistry, polymer science, applied physics, life science, and materials science. However, my research was consistently laser-based molecular science and photochemistry. I think that there is no other field that enables pioneering research and the real thrill of physics and chemistry as much as physical chemistry. In 2014 I turned 70 years old. I am still conducting exploratory research using lasers and microscopes at the National National Chiao Tung University in Hsinchu, Taiwan


 
Figure 1　Pauling, L. The Nature of the Chemical Bond (Translated to Japanese by Koizumi, M.; Kyoritu Shuppan Koizumi, M. Introduction to Photochemistry; Asakura Shoten

２．Tohoku University Koizumi Lab, flash photolysis method and molecular electronics structure calculation (1965-1968)
　　　In Koizumi Lab, in addition to kinetic analysis of photo-oxidation/reduction reaction of dyes, direct measurement and analysis of the initial reaction process by flash photolysis method. Koizumi Lab researched to clarify the electronic state of trapped reaction intermediates in a rigid solvent and spectroscopy. My theme was on the rigid solvent method, but I had no chance to touch upon the development of the flash photolysis method at Koizumi Lab and its application to the photoredox reaction. Time-resolved spectroscopy is now commonplace in all wavelength regions from X-rays to terahertz spectroscopy. However, in the early days, only the electronic spectrum measurement was technically possible. The flash photolysis method causes decomposition reaction with the first flashlight (photolysis), and the electronic spectrum is measured with the second flashlight to reveal the photoreaction. It was developed by Dr. Ronald George Wreyford Norrish and Dr. George Porter in England during the Second World War long before the 1960s when the laser was born, and they received the Nobel Prize in 1967 together with Eigen, the developer of the stopped flow method. According to Dr. Yoshiharu Usui (Prof. Emeritus of Ibaragi University) and Dr. Kengo Uchida (Prof. Emeritus of Hirosaki University) who were Assistant Profs at Koizumi Lab at that time, Dr. Shunji Kato was appointed as an associate Prof. at Koizumi Lab in 1957, and production of the spectroscopy system was started. Of course, the flash lamp, its electrodes, and the electric circuit are all made by themselves. In 1959, the results of transient absorption spectra and photoreduction of dyes observed by the flash method were published in Nature under the names of Drs. Shunji Kato, and Masao Koizumi (first paper), and Drs. Kengo Uchida, Shunji Kato, and Masao Koizumi (second paper). After that, it was improved by Mr. Akira Kira (RIKEN Senior Researcher, Director of Japan Synchrotron Radiation Research Institute (JASRI)) and Mr. Masaharu Morita (Late Prof. of Matsumoto Dental College) who were doctoral students. From 1966 to the first half of 1970, it was developed by Mr. Koichi Kikuchi (Prof. Emeritus of Kitasato University) as a two-step excitation flash method and a luminescence absorption flash method (named by Prof. Koizumi), which was a simultaneous measurement of delayed fluorescence and absorption. It was very effective in determining the rate constant of the elementary process. I did not belong to this flash photolysis method group at Koizumi Lab, but I feel that this research was a hint that I have been deeply involved in the relevant research later, development of laser photolysis system using nanosecond and picosecond lasers and its appreciation. According to Dr. Keitaro Yoshihara (Prof. Emeritus of Institute for Molecular Science), the flash photolysis system was in operation in the Nagakura Laboratory of the Institute for Solid State Physics, the University of Tokyo, led by Dr. Hiroshi Tsubomura in 1966.
　　　On the other hand, in the flow of research on reaction intermediates by the rigid solvent method, Assistant Prof. Shigeru Niizuma (Prof. Emeritus of Iwate University) was conducting research using ESR. At the time, Prof. Okuda gave me the theme of “stably capturing and spectroscopy of the pi-radical of the dye intermediate and assigning its electronic absorption spectrum”. I went to a computation center on the Katahira campus at the time, and decided to develop a program for calculating the open-shell electronic structure of the Pariser-Parr-Pople method. I sometimes went on a business trip to the large computer center in the Hongo campus of the University of Tokyo, and rushed to develop programs. Prof. Okuda went on a long-term business trip to the United States in 1966, and nobody in the department of chemistry had any experience in molecular electronic structure calculation. Therefore, I had to work alone. I asked Prof. Yuji Mori of Tokyo Institute of Technology, Prof. Kichisuke Nishimoto of Osaka City University and Prof. Shigeyuki Aono of Chiba University for guidance by letter. I read "Quantum Chemistry" written by members of Kenichi Fukui Laboratory and published by Kagakudojin. I also referred to the interpretation by Dr. Haruo Hosoya, which was published in every issue of "Chemistry" magazine (Kagakudojin). However, the calculation of the open-shell electronic state of the Pariser-Parr-Pople method had already been carried out in the Nagakura laboratory (I did not know it at all), and was previously published in the Spectra Chimica Acta magazine under the name of Dr. Ishitani and Prof. Nagakura. I realized the strength of the Nagakura Group of the University of Tokyo and the Fukui Group in the field of electronic state, and realized the limitations of my abilities. Then, while saying that the middle of physics (research on the theory of things) and chemistry (research on the abundance of things) is interesting, I wanted to shift toward the study of abundance of things.
 
Figure2　Mataga, N. Introduction to Photochemistry, Kyoritu Shuppan Mataga, N. Molecular Interactions and Electronic Spectra, Marcel-Dekker

3．Nano-picosecond laser photolysis in the Mataga Laboratory, Osaka University (1968-1984)
　　　Prof. Noboru Mataga became a Professor of the newly established Faculty of Engineering Science, and was already known worldwide as the proposer of the Mataga-Lippert formula and the Mataga-Nishimoto approximation at that time. Two reports on these works were later sited in Iwanami's "50 Years of Japanese Scientific Papers (Iwanami publish)," which summarizes typical examples of postwar research. Prof. Mataga published a famous paper in 1968 that proposed the concept of molecular ferromagnetism. I consider these three papers to be his most notable work before entering the brilliant era of laser photochemistry. At that time, a book on the electronic state and photochemistry of molecules was written by Prof. Mataga and published (Figure 2). I earned a master's degree from Koizumi Lab in 1968, and then started working as a PhD student at the Mataga Lab at Osaka University. I was instructed to move the laser and begin researching nanosecond photolysis. Until then, I had been studying quantum chemistry, creating a calculation program, and assigning data measured using existing equipment, so I started experimenting with making and running the equipment from scratch. Needless to say, at this time, we referred to the flow of research using the flash photolysis method by both Prof. Masao Koizumi and Prof. Shunji Kato. We managed to operate a ruby laser to measure nanosecond transient absorption spectra while learning vacuum tube circuits from Mr. Tadashi Okada (Prof. Emeritus of Osaka University), who was an Assistant Prof. at Mataga Lab joining from Department of Applied Physics, Osaka City University. The first system successfully measured was a charge-transfer complex of s-tetracyanobenzene and toluene, whose excited-state absorption, S1-Sn absorption, was very similar to the anion of the electron acceptor s-tetracyanobenzene. This result became one of the topics at that time as a direct indication that the excited state is an electronic state similar to an ion pair. Many debates have occurred in Japan and abroad, including exciplexes that form a charge-transfer complex only in an excited state. At the time, it was called hetero-excimer at the Mataga Lab, while excimers were formed for the same molecules). I remember there were sometimes intense debates between Mr. Tadashi Okada, Mr. Nobuaki Nakajima (Prof. of Osaka City University), Mr. Suehiro Iwata of Nagakura Lab (Prof. of the Institute of Molecular Science), Mr. Hisashi Hayashi (RIKEN), Mr. Takayoshi Kobayashi (Prof. of University of Tokyo) in Japan, and also between Profs. A. Weller, (refer to the Figure 3), M. Ottolenghi, Z. Grabowski, K. Zachariasse, Frans C. De Schryver, J. Verhoeve et al. abroad.  
Photo3　 Profs. Noboru Mataga and Albert Weller (Max-Planck-Institute fuer Biophysikalische Chemie) at Faculty of Engineering Science of Osaka University in 1981

　　　I used a nanosecond ruby laser at the Mataga Lab, but we needed a nitrogen gas laser with a high repetition frequency because it only oscillated once every three minutes. The Department of Electrical Engineering at Osaka University had a laboratory of laser pioneer Prof. Chiyoe Yamanaka, who had a close relationship with Prof. Mataga. Mr. Nobuaki Nakashima, a graduate student at the time, went there to study and learned laser technology, and began fluorescence lifetime measurement of a large number of charge-transfer complexes and exciplexes by the single-photon counting method using nitrogen gas laser as a light source. After that, a picosecond ruby laser was introduced to the Mataga Lab, and Nobuaki Nakajima also set up this for a picosecond absorption spectroscopy. However, he used all morning to set up his optical arrangement, while the set collapsed in the late afternoon. Also, he adjusted the optical system without a viewer to look at the beam. He measured picosecond absorption spectra using photographic film and ran into a dark room for developing the film. After that he knew whether or not it worked well, and he perform performed this procedure for more than 10 hours every day. In the early 1980s, we were able to install an Nd: YAG laser at Mataga Lab with Kakenhi (JSPS) grants. With the laser oscillating at 10Hz, streak cameras and diode array detectors, we were a bit relieved that we had finally reached some level in front of these modern advanced laser system. Many researchers not only in physical chemistry, but also in organic chemistry, polymer chemistry, photobiology, and solid state physics highly evaluated the research of the electron transfer dynamics and the excited state dynamics of charge transfer complexes and extended systematic collaborations with Mataga Lab. I just realized that something was interesting between physics (research on the theory of things) and chemistry (research on the abundance of things). Briefly leading collaborators include Prof. Soichi Misumi (The Institute of Scientific and Industrial Research, Osaka University), Kazuhiro Maruyama, Atsuhiro Osuga (Faculty of Science of Kyoto University), Hiroshi Mikawa, Narikazu Kusabayashi (Faculty of Engineering of Osaka university), Shigeo Tazuke (Tokyo Institute of Technology), Mikiharu Kamachi, Yotaro Morishima, Tomiyuki Hara (Faculty of Science of Osaka University), Toru Yoshizawa (Faculty of Science of Kyoto University), Masahiro Irie (Faculty of Engineering of Hokkaido University), Toshiaki Kakitani (Faculty of Science of Nagoya University) I think Prof. Mataga has just proved this proverb: the peach and the plum do not speak and try hard to appeal people, yet a path is born beneath them because of their flower and fruit.
　　　Prof. Tadashi Okada, Fumio Tanaka (Prof. of Mie Prefectural University), Yoshinori Hirata (Prof. of Kanagawa University) as staff member, Noriaki Ikeda (Prof. of Kyoto Institute of Technology), Hiroshi Miyasaka (Prof. of School of Engineering Science, Osaka University), Masato Migita (Hitachi Central Lab.), Seiji Nakatani (Prof. of Tsukuba University) and Tsuyoshi Asahi (Prof. of Ehime University) as student were in charge of what Prof. Mataga planned to do. I was relatively free to choose my research theme, while I had not found a possible subject enough convincing me. I studied photochemistry using a laser of the micellar solution and polymer solution, considering the development from charge-transfer complex system to higher-order assembly system. However, Prof. Mataga wrote about six papers in that direction in the mid-1950s while he worked at Koizumi Lab at Osaka City University. After all, I was on the palm of a giant. I thought that studying the excited state dynamics and reactions of solid molecular systems using time-resolved spectroscopy with a pulsed laser would be a good idea, and tried fluorescence spectroscopy of organic thin films and total reflection spectroscopy of polymer thin films. I did it. It was around 1980. At that time, Prof. Tazuke greatly encouraged me, and I applied for Kakenhi (JSPS) for the total reflection spectroscopy of polymer films. This application was approved, and my feelings were much better.
　　　Prof. Mataga did not say anything, but when I came to the Professor's office with the data, Prof. Mataga discussed with me for hours. After explaining and discussing the results of the experiment, I had more time to talk with Prof. Mataga about what to do next and what might be the future of this research. Prof. Mataga was often silent for a while, but on the other hand, the conversation with Prof. Mataga flourished, and I was sometimes moved to tears. I think that this discussion-style with the manuscript that was turned red by Prof. Mataga became the basis for my research life. In addition to the research on laser photolysis, Prof. Koichi Ito (Late Prof. of Faculty of Science of Osaka City University), who was an early Assistant Prof. at the Mataga Lab, showed me an excellent research style. He collaborated with Prof. Ichiro Moritani and Prof. Shunsuke Murahashi (School of Engineering Science of Osaka University) for synthesizing necessary compounds that produce carbene upon irradiation. He and Mr. Takeji Takui (Prof. of Osaka City University) had been studying multiples states such as triplet, quintet, and septet. They studied on holidays and late at night and had produced excellent results. Based on these achievements, Prof. Koichi Ito was awarded the 2003 Japan Academy Prize (jointly with Profs. Hiizu Iwamura and Minoru Kinoshita).

４．Time-resolved reflectance spectroscopy and ablation in Kyoto Institute of Technology Time-resolved reflection spectroscopy and ablation at Kyoto Institute of Technology (1984-1991)
　　　I was appointed a Prof. of the Department of Polymer Science, Faculty of Textile Science, Kyoto Institute of Technology, which was reorganized in April 1984. I started studying polymer solids by time-resolved solid-state spectroscopy. Since I was able to buy a nanosecond excimer laser, I used this laser to come up with many student themes. I asked Prof. Iwao Yamazaki (Prof. Emeritus of Hokkaido University) and Prof. Keitaro Yoshihara of the Institute for Molecular Science to conduct collaborative research for single-photon counting fluorescence spectroscopy and picosecond transient absorption spectroscopy. I asked them to use their lasers. As a young Prof. at a local university, I was very grateful to have collaborated with the Institute for Molecular Science, where I could afford to pay for my experiments and travel expenses. With my research funding, it was impossible to follow up with the development of transient absorption spectroscopy to picoseconds and even femtoseconds. Also, I could not compete with the laboratories by Profs. Saburo Nagakura, Noboru Mataga, Ikuzo Tanaka, and Keitaro Yoshihara. So, I decided to shift more and more towards the study of the abundance of things between physics (research on the theory of things) and chemistry (research on the abundance of things). In the summer of 1985, Dr. Hiroyuki Hiraoka of the IBM (IBM Research - Almaden) in the United States invited me as a Summer Faculty Fellow for three months, recommended by Prof. Haruo Shizuka of Gunma University. I thought that I could study anything freely, so I decided to try a spectroscopic study of polymer laser ablation as a new complex photochemical study in the future. Ablation itself was famous in Japan for the work of Dr. Susumu Namba of RIKEN. R. Srinivasan of the IBM (IBM Thomas J Watson Research Center) wrote a famous paper in 1982. Many researchers have been working on the development of optical lithography techniques, and there had been no molecular or electronic research. During my stay at IBM, I studied ablation of polymer films doped with aromatic molecules that could lead to spectroscopic research and posted the results to Prof. Mitsuo Ito, who was editing Chem. Phys. Lett. I wondered if this was not physical chemistry and would be refused by Prof. Ito. However, Prof. Ito accepted this as being new physical chemistry. If Prof. Ito refused at that time, I felt that my research attitude might have been more conservative. At Kyoto Institute of Technology, Prof. Akira Itaya (Prof. Emeritus of Kyoto Institute of Technology), Mr. Hiroshi Fukumura (Prof. of Tohoku University) and Mr. Noriaki Ikeda (Prof. of Kyoto Institute of Technology) greatly assisted me. We developed research on time-resolved reflection spectroscopy and ablation dynamics.

５．ERATO era, Micro Chemistry (1988-1994）
　　　In 1984, JST (at that time, Research Development Corporation of Japan (JRDC) invited me to apply for research supervision of the Exploratory Research for Advanced Technology (ERATO) project, which aims to create new science and technology. They are hoping for "picosecond chemistry" and preparing their budget, so they suggested me to write such a proposal. I argued that raising the time resolution from picosecond to femtoseconds is, of course, necessary and but already being challenged and this would not be an exploratory subject for creative science and technology trials. I proposed to pursue the "micro-conversion" project aiming at reaction control. In order to start from the research of spectroscopy and photochemistry using a microscope, it was common knowledge at the time to adopt a micrometer for spatial resolution, and microchemistry using a laser and a microscope was an issue for the project. The chief coordinator of the council to decide who should be the ERATO leaders and promote the research was Prof. Saburo Nagakura, and later changed to Prof. Ikuzo Tanaka. With the understanding and support of these two Profs., I significantly advanced my research. I was given two billion research funds and was able to hire 15 postdocs in five years. It was an exceptional project. Also, I was able to get a research place outside the university. Researchers of our project were a full-time researcher and could not concurrently hold other jobs. At that time, excellent researchers such as Profs. Junichi Nishizawa, Ken Masumoto, Osamu Hayaishi, and Chikara Hayashi were the leaders. On the other hand, I was only 44 years old and had been studying fundamental research fields until then. It was like walking in the dark. ERATO research begun by young researchers such as Noboru Kitamura (at that time, Assistant Prof. at Tokyo Institute of Technology, present Prof. of Hokkaido University), Hiroaki Misawa (at that time, Assistant Prof. of Tsukuba University, present Prof. of Hokkaido University), Keiji Sasaki (Prof. of Hokkaido University), Naoto Tamai (Prof. of Kwansei Gakuin University); Nobuyuki Ichinose (Prof. of Kyoto Institute of Technology); U. Pfeifer (Prof. of University of Applied Sciences Wiesbaden). Profs. Hiroyuki Sugimura (Prof. of Kyoto University), Seiji Nakatani (Prof. of the University of Tsukuba), and Kenji Kamata (Senior researcher of AIST) who gained positions in research institutes after participating from the private sector were also tremendous. They contributed very much to our project.
　　　The results of this Masuhara ERATO micro-conversion project include the development of a three-dimensional spatial and time-resolved spectroscopy system, the development of transient grating diffraction spectroscopy, the spectroscopy and photochemistry of single micrometer fine particles, the solid/solid and solid/liquid interface layers. Characterization, electrochemistry of single microdroplets, electrochemistry on microarrays, dynamics of photoresponsive polymer microgels, optical assembly, and optical drive of microparticle structures. To develop a method to create a field that makes these possible, we also worked on surface micromachining and modification by laser, electrochemical surface micromachining by scanning microscope, and micropatterning by CVD. The research on space- and time-resolved chemistry, which is now a major trend, using a combination of laser and microscope began with our ERATO project. A series of achievements was published in Japanese in 1993 and English in 1994 respectively, as the world's first books entitled Microchemistry. Since then, many researchers around the world have followed us. We pride ourselves on being ahead of the flow of microchemistry as a new area of science and technology along with microelectronics, micromachines, and microoptics. To confirm the results of this research, we organized an international conference on microchemistry in Brussels in 1993 with excellent cooperation by Prof. Frans C. De Schryver. Profs. G. Whiteside (Harvard), MS Wrighton (MIT), A. J. Bard (Texas Austin), J. Klafter (Tel Aviv), R. Srinivasan (IBM), D. D. Dlott (Illinois), Ikuzo Tanaka, Kenichi Honda et al. We could launch a new research stream of time- and space-resolved chemistry to the world.
   
Figure4　Masuhara, H.; Kitamura, N.; Misawa, H.; Tamai, N.; Sasaki, K. Microchemistry; Kagaku Dojin; Kyoto, 1993 Masuhara, H.; De Schryver，Kitamura, N.; Tamai, N. Microchemistry: Spectroscopy and chemistry in small domains; North-Holland; Amsterdam, 1994

６． Osaka University, Applied Physics, Laser Nanochemistry (1991−2007)
　　　During the development of ERATO research, Prof. Shigeo Minami of Osaka University (Prof. Emeritus of Osaka University) invited me to have a laboratory at Osaka University. I said that between physics (research on the theory of things) and chemistry (research on the abundance of things) was interesting, but I was hesitant whether I could live in the Department of Applied Physics. When I looked at departments at major universities across Japan, there were some instances where physicists moved to the chemistry department. Still, I could not find any cases where chemists became Professors in physics. However, Osaka University was known to be strong in optics and microscopy. Prof. Yoshiki Ichioka and Shinichiro Nakajima (Prof. Emeritus of Osaka University) were there in addition to Prof. Minami. If I moved to Osaka University, my lab was going to be the fourth lab related to light. Prof. Satoshi Kawata (Prof. of Osaka University, Director of Advanced Photonics Research Center) was an Assistant Prof. to Prof. Minami's laboratory at that time. He was already prominent. If I participated, the name of the laboratory in charge was Applied Physics 2nd Laboratory “Applied optics/Applied spectroscopy" and the lecture in charge was “Analytical instruments and Applied spectroscopy”. Prof. Hiroshi Yoshinaga, who was in charge of this course before, was an authority on far-infrared spectroscopy and had been collaborating on amino acids with Profs. Sanichiro Mizushima and Akiko Hirakawa of the University of Tokyo. His research results had been known around the world. Also, Prof. Minami said, "Applied physics is changing rapidly. Many people are now studying Raman spectroscopy of semiconductors, but in the future, research on the organic matter using lasers will become the mainstream." Before that, I heard lectures by profs. Koichi Shimada, Shigeo Shionoya, Susumu Namba, Chiyoe Yamanaka, Tatsuo Yajima, et al. through the Laser Workshop. The spirit of exploration and research has since revived within me, and I decided to move to the Department of Applied Physics. I thought it was an opportunity to be able to explore new research by putting myself in a different environment from others.
　　　In the ERATO project, I studied microchemistry. On the other hand, I developed laser-based spectroscopy and reaction in the small domains from micro to meso, and meso to nano at Osaka University. And I wanted to open up a new research area in laser nanochemistry, which would significantly change the conventional framework of light and chemical reactions. Regarding the development of nanospectroscopy and the study of reaction dynamics, I continued my work focusing on time-resolved reflection spectroscopy, which had been the theme since my research at Kyoto Institute of Technology. Also, I have developed femtosecond specular/total reflection spectroscopy for solid nano surfaces and interface layers, and femtosecond diffuse reflection spectroscopy for nanoparticle assemblies. And we have paved the way to analyze the photoreaction of a heterogeneous molecular solid system at exactly the same level as the solution. With the leadership of Assistant Prof. Hiroshi Fukumura, Mrs. Yui Ichikawa (Prof. of Shinshu University), Kazuya Watanabe (Prof. of Kyoto University), Akihiro Furube (AIST), and Mototsugu Suzuki (the Metropolitan Police Agency) had grown up as researchers. Regarding subsequent nanospectroscopy, Prof. Asahi launched a single nanoparticle spectrometer combining a microscope and AFM and clarified the correlation between the shape of the nanoparticles and fluorescence and light scattering spectroscopic data. These data ware valuable indicating the size effect of the electronic spectrum of organic solids. At that time, graduate student Mr. Tamitake Ito (AIST) developed the femtosecond single nanoparticle spectroscopy and clarified the relaxation dynamics of single gold nanoparticles.
　　　In the field of nanomanipulation and photon pressure chemistry, we have systematically clarified the dynamics in which various molecular aggregates, polymers, and nanoparticles in a solution at room temperature were captured at the focal position by the optical pressure of a focused laser beam under a microscope. In the early years, Prof. Keiji Sasaki constructed a new system and started new research, and then, Mr. Hiroyuki Yoshikawa (Prof. of Osaka University) continued Prof. Sasaki’s research and presented unique results one after another under topnotch ideas and guidance. From this trend, Mr. Junichi Hotta (Prof. of Yamagata University), Mrs. Shoji Ito (Prof. of Osaka University), Sadahiro Masuo (Prof. of Kwansei Gakuin), Yu Nabetani (Prof. of Tokyo Metropolitan University) , Ms. Chie Hosokawa (AIST) have grown up as researchers.
　　　Prof. Hiroshi Fukumura initially researched the dynamics and mechanism of nano ablation. After he moved to Tohoku University, Prof. Tsuyoshi Asahi proceeded as a leader in research on dynamics and mechanism elucidation. Then he developed a method for making nanoparticles in solution. Mrs. Yasuyuki Tsuboi (Prof. of Osaka City University), Hisashi Fujiwara (Prof. of Hiroshima City University), Hiroshi Furutani (Tokyo University), Koji Hatanaka (Academia Sinica, Taiwan), Yoichiro Hosokawa (Prof. of Nara Institute of Science and Technology) as graduate students. As a fundamental study, we proved that abrupt temperature rise in nanosecond excitation and local transient pressure in femtosecond excitation are the keys to understanding the ablation mechanism and dynamics. In particular, we succeeded in clarifying the process in which the electronic excitation of molecules evolves into the ablation of solids using a femtosecond laser. I like this work very much as a bridge between physics (research on the theory of things) and chemistry (research on the abundance of things). This result, led by Yoichiro Hosokawa, resulted in a method that attracted widespread attention, such as protein crystallization and non-invasive non-destructive manipulation of living cells. These achievements are also drawing attention from the field of bioscience, and Mr. Hiroshi Yoshikawa (Prof. of Saitama University) is playing an active role as one of the pioneers in this field.
　　　The stream of my research is often regarded as one of nanoscience and nanotechnology research, but the reason why nanotechnology began to gain social attention was that the US President Clinton issued a textbook in 2000 and invested in research. Early in the era, I was heading toward nano, and by focusing on the potential of lasers and focusing on the research of molecular nanos with light, I was able to create a unique stream as laser nanochemistry. At Osaka University, Prof. Satoshi Kawada, Prof. Toshio Yanagida, and Prof. Tomoji Kawai are playing a leading role in the world of nanoscience and nanotechnology. On the other hand, I think that I was able to demonstrate my uniqueness by focusing on lasers and molecular systems. Based on these achievements I organized a research project named "Molecular Nano Dynamics" with Profs. Hiroyasu Iwasawa, Masahiro Irie, Kohei Uosaki, and Hiroshi Fukumura, and worked with many researchers. Fortunately, I was able to summarize the activities of those three years as "Molecular Nano Dynamics" (Figure 5). These research developments had been evaluated, and Prof. G. Schatz, P. Kamat, Editor-in-Chief of J. Phys. Chem. He invited Profs. P. F. Barbara, J. Hofkens, Kei Murakoshi, Tsuyoshi Asahi, Hiroshi Miyasaka, Hiroaki Misawa as Guest Editors, and published my Festschrift in 2009 12. I read J. Phys. Chem. at Chemistry Department of Tohoku University in Sendai Katahira campus during my master's degree. At that time, I wondered if I could submit a paper to this journal in the future. I clearly remembered that time.
 
Figure 5　Fukumura, H.; Irie, M.; Iwasawa, Y.; Masuhara, H.; Uosakki, K. Molecular Nano Dynamics Vol. 1 & 2; VCH-Wiley; Berlin (2009)

7．Moved to Taiwan after retirement from Osaka University: Laser Ttrapping Chemistry (2007-）
　　　Fortunately, even after I retired from Osaka University, I was fortunate enough to have a laboratory in which I could maintain and develop my research activities. In 2007, at the 21 Life Science Research Institute of the Hamano Life Science Research Foundation established in Kobe, Yoichiro Hosokawa, Teruki Sugiyama (Research fellow of Instrument Technology Research Center (ITRC) (equivalent to Prof.)), Takayuki Uwada (Prof. of Josai University) We established a Laser Bio Nano Science Laboratory with our colleagues. From 2008, the foundation set up a three-year donation course at the Graduate School of Materials Science, Nara Institute of Science and Technology, and we moved to Nara. Even after I retired from Osaka University, I was fortunate enough to have a laboratory in which I could maintain and develop our research activities. At the same time, Prof. Y.-P. Lee of the National Chiao Tung University (NCTU) in Taiwan offered us to set up a laboratory. Prof. Souji Tsuchiya (Professor Emeritus of The University of Tokyo) helped me with this. Not only Taiwanese Profs. M.-C. Lin and S.-H. Lin who are both giants, but also Japanese Profs. such as Profs. Takayoshi Kobayashi, Hiroo Hamaguchi, Hiroki Nakamura, Hiroyuki Matsui, Koichi Narasaka were participating in research activities in NCTU. They were cooperating in the internationalization of the university. In addition, many foreign postdoctoral researchers, including Japanese, work at NCTU. Many foreign researchers visit NCTU to participate in Department Seminars, etc. NCTU research level is remarkably high and is comparable to that of big Japanese universities. I feel that Asian countries have been actively expanding their research in the world.
　　　I also named the Laser Bio nano Science Laboratory in my laboratory at NCTU in Hsinchu, Taiwan. Using the high potential of laser, we are developing methodologies for bioscience using laser, exploring new molecular phenomena unique to laser, and elucidating its molecular and electronic processes. In 2007, after I retiring from Osaka University, we succeeded in molecular crystallization by laser trapping, which I had been thinking about for many years. Currently, I am working with Profs. Teruki Sugiyama and Kenichi Yuyama (Assistant Research Fellow of NCTU) on the crystallization of amino acids and proteins, the dynamics of crystal growth, and their mechanisms. We are demonstrating that crystallization can be replaced by liquid-liquid phase separation depending on the conditions and that clusters of amino acids and proteins are assembled as precursors of this nucleation phenomenon and form hydrogen-bonded domains of large millimeter order. Researchers in condensed matter physics have praised these for suggesting the generation of new material states by laser trapping. Also, unique phenomena are observed; the crystallization from an unsaturated solution can be made possible, the crystal morphology can be controlled by adjusting the laser polarization and power, and amyloid formation rather than crystallization can be seen depending on the protein.
　　　Besides, recently, I have been working with Dr. Anwar Usman (Prof. of King Abdullah University of Science and Technology) to find highly efficient trapping of nanoparticles by a femtosecond laser pulse and the subsequent release phenomenon. This phenomenon is an interesting trapping behavior that depends on both pulse width and repetition late, and it is currently necessary to elucidate the trapping mechanism. In addition, since multiphoton absorption easily occurs, it was theoretically predicted that the trapping efficiency would increase through optical resonance with the electronic transition of nanoparticles, and we are succeeding in its experimental demonstration. Drs. Masayasu Muramatsu (Osaka University) and Tetsuhiro Kudo (Osaka Prefecture University) staying at NCTU as JSPS postdoctoral fellows, have been developing this research. They are showing the possibility of controlling mechanical nanomanipulation by exciting the electronic state of molecules. We may consider it as “Molecular Science” of “Nanotechnology”. I have been focusing on lasers, oscillating between physics (research on the theory of things) and chemistry (research on the abundance of thing), sometimes toward physics, and sometimes toward chemistry. I am satisfied that trapping chemistry is indeed a search for elucidation of new molecular phenomena. I believe that many molecular scientists will be born from this field in the future.

Reference:
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（６） The fifteenth anniversary of mataga Laboratory of faculty of Engineering Science, Osaka University (1979)
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（７） Fleming, G. R.; Chemical Applications of Ultrafast Spectroscopy: Oxford University Press: New York, 1996
（８） For the deeper meaning, it represents some people have high merit, honest, straightforward, so they don’t need to advocate or tell people around everyone just respect and think highly of them.
（９） Masuhara, H; Kitamura, N.; Misawa, H.; Tamai, N.; Sasaki, K. Microchemistry; kagakudojin, Kyoto, 1993.
（１０） Masuhara, H; De Schryver F. C.; Kitamura, N.; Tamai, N. Edt. Microchemistry: Spectroscopy and chemistry in small domains; North-Holland; Amsterdam, 1994.
（１１）Baba, H.; Tsuoi, M.; Tasum, M.，Reminescence , Mishima Laboratory, Kyoritsu Syuppan. Tokyo, 1990.
（１２）Hiroshi Masuhara Festschrift, J. Phys. Chem. C 2009, 113, 27, 11425-11974.

 

*This is the English version translated from the contributed article to Molecular Science (Electronic Journal of Japan Society of Molecular Science) A0066 (2014)

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