Achievement of long-lived higher excited state and its application to photochemical reaction

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K15522
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 32020:Functional solid state chemistry-related
• Research Institution: Shimane University
• Principal Investigator: Fujimura Takuya 島根大学, 学術研究院環境システム科学系, 助教 (80757063)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: S2発光 / Kasha則 / 高次励起状態 / ポルフィリン / 層状化合物 / 粘土鉱物 / 有機-無機複合体

Outline of Final Research Achievements

The excited molecules to higher excited state are relaxed to lowest excited state (S1) via fast internal conversion, thus generally, lifetime of higher excited state is short and photochemical/photophysical events from higher excited state are inefficient. In this research, in order to achieve the long-lived higher excited state and the enhancement of the emission from higher excited state, we investigate the hypothesis that the inorganic nanosheet surface may work as the field to decrease the magnitude of internal conversion from higher excited state by suppression of the molecular motion. The emission efficiency from metalloporphyrin in second excited (S2) state was enhanced, and lifetime of porphyrin in S2 state were extended by adsorption on inorganic nanosheet. Furthermore, obtained results indicated that S2 emission enhancement will depend on the magnitude of distortion of porphyrin ring.

Free Research Field

光化学

Academic Significance and Societal Importance of the Research Achievements

高次励起状態(紫外光など波長が短く、大きなエネルギーの光を吸収した状態)は独特な光反応を実現できる一方で、その寿命が短く利用が難しい。これを打破するために分子の設計等による解決が試みられているが、本研究では『分子を変更せず、分子が存在する“場”(固体表面)により長寿命化する』ことに成功した。依然として課題があるものの、当該技術は高次励起状態を長寿命化する汎用的技術となるポテンシャルを有しており、高次励起状態を利用した光反応の高効率化や光エネルギーの有効利用に資するものであると見込まれる。