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Photosynthetic light-harvesting (LH) systems consist of photosynthetic pigments, which are non-covalently self-assembled with protein scaffolds in many phototrophs and attain highly efficient excitation energy transfer via ultrafast dynamics. In this study, we constructed a biohybrid LH system composed of an LH complex (LH2) from Rhodoblastus acidophilus strain 10050 and a hydrophobic fluorophore ATTO647N (ATTO) as an extrinsic antenna in the lipid bilayer. Through the addition of ATTOs into a solution of LH2-reconstituted lipid vesicles, ATTOs were incorporated into the hydrophobic interior of the lipid bilayer to configure the non-covalently self-assembled biohybrid LH. Steady-state fluorescence spectroscopy clearly showed efficient energy transfer from ATTO to B850 bacteriochlorophylls in LH2. Femtosecond transient absorption spectroscopy revealed that the energy transfer took place in the time range of 3–13 ps, comparable to that of the covalently linked LH2-ATTO that we previously reported. In addition, the biohybrid LH system exhibited a much higher antenna effect than the LH2-ATTO system because of the higher loading level of ATTO in the membrane. These findings suggest that the facile self-assembled biohybrid LH system is a promising system for constructing LH for solar-energy conversion. [ABSTRACT FROM AUTHOR]

Phenol blue (PhB) is a dye that exhibits positive solvatochromism which is also nonfluorescent due to its ultrashort excited state lifetime. We have conducted femtosecond time‐resolved transient absorption (TA) spectroscopic measurements of a PhB solution using two distinct excitation wavelengths, at shorter and longer wavelength sides of the visible absorption band. The results revealed that a long‐lived heterogeneity exists in protic solvents whereas, in aprotic solvents, the system rapidly returns to the original thermal equilibrium on the ultrafast timescale. Interestingly, the lifetime of the heterogeneity is longer for methanol (MeOH) compared to ethanol (EtOH) solution suggesting stronger interaction between PhB and MeOH. Additionally, since the excited state lifetime of PhB was still in the sub‐picosecond domain even in a polymer matrix, we suggest a nonradiative decay mechanism through high‐frequency vibrational modes without involving large structural reconfiguration such as twisting of the benzoquinone (BzQ) moiety. [ABSTRACT FROM AUTHOR]

Coherent wavepacket oscillation accompanying the ultrafast photoexcited intramolecular charge separation (CS) of 9,9′-bianthryl (BA) and 10-cyano-9,9′-bianthryl (CBA) in a room temperature ionic liquid, N,N-diethyl-N-methyl-N-(methoxyethyl)ammonium tetrafluoroborate (DemeBF4), was investigated by femtosecond time-resolved transient absorption spectroscopy. The frequency of the coherent oscillation observed for CBA in nonpolar n-hexane solution (Hex) was 377 cm−1, while this oscillation was undetectable in DemeBF4. For BA in DemeBF4, coherent oscillation with a frequency of 394 cm−1 was observed, which is similar to that for CBA in Hex. CS of CBA occurs in the ultrashort time range of ≤100 fs, while that of BA occurs in a few picosecond range [E. Takeuchi et al., J. Phys. Chem. C 120, 14502–14512 (2016)]. Hence, the oscillation of CBA in Hex and that of BA in DemeBF4 are assigned to the molecular vibration in the locally excited state, while this oscillation dephases instantaneously for CBA in DemeBF4 due to the ultrafast CS and no oscillation was generated in the CS state. This result suggests that the CS reaction is not mediated by a specific intramolecular vibration in the CS state but occurs incoherently through higher levels of multiple vibrational modes. [ABSTRACT FROM AUTHOR]

A home-built cavity-dumped chromium:forsterite laser was used as light source for the development of the femtosecond near-infrared laser microscope to detect the multiphoton fluorescence of organic microcrystals. The application of this system explained the association of simultaneous three- and four-photon absorption processes with the production of the excited state for perylene and anthracene microcrystals, respectively.