2005 Fiscal Year Final Research Report Summary
Molecular Science of Excitation Transfer Dynamics by Dynamic Near-Field Spectroscopy
| Project/Area Number |
16350015
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | Institute for Molecular Science |
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Principal Investigator |
OKAMOTO Hiromi Institute for Molecular Science, Department of Molecular Structure, Professor, 分子構造研究系, 教授 (20185482)
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| Co-Investigator(Kenkyū-buntansha) |
IMURA Kohei Institute for Molecular Science, Department of Molecular Structure, Research Associate, 分子構造研究系, 助手 (80342632)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Near-field microscope / Surface plasmon resonance / Metal nanoparticle / Nanorods / Wavefunction / Ultrafast phenomena / Spatial coherence |
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| Research Abstract |
Scanning near-field optical microscope enables optical measurements and observations with a spatial resolution far beyond the diffraction limit of light. This allows us to investigate spectroscopic characteristics with spatially resolving the positions point by point in nanoparticles. In this research, we have developed experimental methods and apparatuses of dynamic near-field spectroscopy, and applied them to time- and space-dynamics of excited states for plasmons in metal nanoparticles as well as molecular nanostructures.
For the studies of surface plasmon resonances in noble metal nanoparticles, we obtained notable achievements described in the following.
We utilized linear transmission/scattering as well as nonlinear two-photon excitation measurements in the near field to observe the nanoparticles, and found that the wavefunction of the plasmon excitation resonant with the incident radiation field can be optically visualized.
We succeeded in femtosecond time-resolved near-field imaging for gold nanorods, and found that the relaxation process depends on the position although the nanorod is a homogeneous crystalline material.
In the aggregated nanoparticles, strong electric-field enhancement localized in the interstitial sites, which had been theoretically predicted previously, was clearly imaged, and its major contribution to surface enhanced Raman scattering was also shown by the near-field images.
We also investigated nanomolecular systems by near-field spectroscopy. In the porphyrin wire (polymer) molecules, we have obtained an unexpected (and surprising) result that strongly suggests excitation energy migration of very long distance.
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