2015 Fiscal Year Annual Research Report
Efficient utilization of the excitation energy of highly-excited quantum dots for photoreactions
Publicly Offered Research
| Project Area | Application of Cooperative-Excitation into Innovative Molecular Systems with High-Order Photo-functions |
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| Project/Area Number |
15H01099
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| Research Institution | National Institute of Advanced Industrial Science and Technology |
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Principal Investigator |
Biju V・Pillai 国立研究開発法人産業技術総合研究所, 健康工学研究部門, 主任研究員 (60392651)
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| Project Period (FY) |
2015-04-01 – 2017-03-31
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| Keywords | Quantum Dots / Photochemical reactions / Singlet oxygen / Excited state / Energy Transfer / Electron Transfer |
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| Outline of Annual Research Achievements |
In this project, I investigated efficient utilization of photoactivated QDs for photoreactions by generating singlet oxygen and utilizing singlet oxygen for photouncaging reactions. In these photoreactions, two singlet oxygen sensing samples were utilized. One is a commercially available singlet oxygen sensor green (SOSG) dye and the other is a homemade coumarin-anthracene conjugate singlet oxygen sensor blue (SOSB). SOSG has been found less specific to photochromic reactions triggered by QDs, which is becuase of self-sensitized reactions of SOSG triggered under visible light absorbption. On the other hand, SOSB does not undergo self-sensitized reaction. In other words, newly synthesized SOSB shows photocromic reaction, which is irrivesible, selectively in presence of singlet oxygen. Thus, selective and sensitive photoreaction was carried out by energy transfer from QDs to singlet oxygen and subsequently by singlet oxygen-mediated photouncaging of SOSB.
Currently, I am working on the creation of nanoscale molecular patterns by the above photoreactions using photoactivated quantum dots as the light source. In parallel, I am working on photoinduced energy transfer from quantum dots to diarylethenes for remote-excited photochromic reactions.
Unique outcome of this research until todate are twofold: (i) singelt oxygen-mediated reactions allow tapping of a portion of the energy of photoactivated quantum dots, and (ii) remote-excited photochromic reactions have become possible through energy transfer from quantum dots to a diarylethene molecule.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Research activities have been focusing in the direction that was proposed initially. To-date the results obtained are satisfactory with reference to the time I could spent. Indeed, because I have and had no other fund during the current research period, I expected to focus myself more on the proposed research under this category. However, I was relocated from AIST to Hokkaido University in the middle of the first year of the project, which was tedious and time consuming. In particular, I was fully focusing over two months on dismantling and packing of instruments, all by myself. Subsequently, the instruments were successfully moved in Hokkaido University. Thereafter, I have been resetting my labs, which is ongoing. As there isn't another fund or human resources, this relocation was the major challenge that I ever faced in my career if not in life. I take my effort positively and do all possible efforts to evolve into the proposed research, with which I am confident in achieving the aims proposed. In between, I planned collaboration with Prof. Naoto Tamai of A01 Group, Prof. Tsuyoshi Kawai of A02 Group, and Prof. Seiya Kobatake Prof. Martin Vacha of A03 Groups. Some parts of all these collaborations are investigated and some parts are delayed during my relocation. I restarted the collaboration and will take those to full-swing.
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| Strategy for Future Research Activity |
In this research, I will develop new methods for the efficient utilization of the energy of highly excited quantum dots (QDs) for energy and electron transfer reactions in the nanospace. With the electron and energy transfer reactions using highly excited QDs, this project will deliver new methods for controlled photochemical reactions in the nanospace confined by the distance of energy/electron transfer or diffusion length of singlet oxygen (1O2). Although energy transfer- mediated reactions are highly predictable, at first, we investigate it by the incorporation of CdSe/ZnS QDs in thin film polymer matrices enriched with a 1O2 sensor dye or an energy acceptor chromophore. Photoactivation of QDs results in both Auger recombination and energy transfer to oxygen or the chromophore. These processes result in the uncaging of the fluorescence or color of the dye, and creates nano-pattern in the close proximity of QDs. Such photouncaging phenomenon observed in solution phase will be translated into thin film samples. Next, in electron transfer reactions, highly excited QDs will be supplemented with amines of varying oxidation potentials. As a result of scavenging of the excess positive by amines, the non-radiative relaxations will be suppressed. Nevertheless, amines are expected to act as sacrificial electron donors, which will be exploited for Auger electron transfer therapy by replacing amines with DNA and proteins. Electron transfer reactions of DNA and proteins lead to their damage, which will be analyzed by using microscopy, gel electrophoresis, and mass spectroscopy.
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[Presentation] Singlet Oxygen Generation by Nanoparticles: Stability Vs Oxidation2015
Author(s)
Shin-ichi Yamashita, Morihiko Hamada, Hironobu Saito, Edakkattuparambil S. Shibu, Shin-ichi Wakida, Yoshio Nosaka, Shunsuke Nakanishi, Vasudevanpillai Biju
Organizer
International Conference on Photochemistry ICP2015
Place of Presentation
Jeju Convention Center, Republic of South Korea
Year and Date
2015-06-28 – 2015-07-03
Int'l Joint Research
