Departmental Bulletin Paper シクロデキストリン水溶液中におけるクリセンとフェナントレンの2光子イオン化

竹下, 達哉  ,  Takeshita, Tatsuya  ,  笠羽, 祐太  ,  Kasaba, Yuuta  ,  窪田, 恭平  ,  Kubota, Kyouhei  ,  矢野, 篤  ,  Yano, Atsushi  ,  原, 道寛  ,  Hara, Michihiro

(45)  , pp.277 - 284 , 2015-08-06
Formations of chrysene (Ch) and phenanthrene (PH) radical cation and hydrated electrons during two-photon ionization (TPI) of Chand PH in the presence of cyclodextrins (CD) were studied by transient absorption measurement using 266-nm laser flash photolysis (LFP) technique. Ionization of Ch occurred within the time interval of the laser flash (5 ns) to give the radical cation, which was confirmed by the observation of hydrated electrons at 720 nm in the presence ofα-, β-and γ-CD in water. The electron was generated by two-photon excitation by means of simultaneous irradiation from a 266-nm laser. The ionization quantum yield (Φion) of Ch obtained by LFP in the presence ofα-, β-and γ-CD(1.0×10-2M)were 36.2±2.2%,1.2±0.7%and 0.8±0.4%, respectively. Additionally, Φion of Ch in the presence of CDs was due to the stabilization energy of solvation. These behaviors suggest that the useful two-photon ionization results from the complexes of Ch and α-, β-and γ-CD, respectively. In the case of changed concentration of CDs (from 1.0×10-2M to 1.0×10-3M), Φion of Ch in the presence ofα-CD was dependent on the fluorescence lifetime (τ).In contrast, Φion of Ch in the presence of β-and γ-CD increased with decreasing β-and γ-CD concentration, and independent on the τ. This result suggested that increase of Φion was due to the stabilization energy of solvation with change of formation of inclusion complexes Chand CDs. In this study, we found that TPI of Ch depended on the properties of the complexes with CDs. Finally, we compared Φion of Ch and PH, which was observed two-photon ionization process of PH in the presence ofα-, β-and γ-CD in water.

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