摘要
Integrating multiple photosensitive properties into an“all-in-one”photosensitizer(PS)shows great promise for the treatment of cancers owing to synergistic effect among them.However,the development of such PSs,especially those that need a single laser source,remains a challenge.Herein,we report an orchestration of electron donors and acceptors in a propeller-like pentad,PBI-4Cz,where four carbazole(Cz)units are covalently linked to the ortho-positions of the perylene bisimide(PBI)core.Strong intramolecular donor-acceptor interaction significantly quenches the luminescence and largely extends the absorption spectra to near-infrared region.Excited-state dynamics investigated via femto-and nano-second transient absorption spectroscopy revealed exclusive charge separation of the PBI-4Cz within initial 0.5 ps when photoexcited regardless of which intermediate is involved.Energy dissipation of the resulting charge-separated state(PBI^(•−)-4Cz^(•−))is subjected to the toggle between intersystem-crossing toward excited triplet states and charge recombination toward ground states.Relative importance of the two pathways can be tuned by micro-environmental polarity,which endows PBI-4Cz remarkable performances of singlet-oxygen generation(>90.0%)in toluene and photothermal conversion(∼28.6%)in DMSO.Harnessing intrinsic photostability and excited-state processes of heavy-atom-free PBI derivatives not only holds a promise for multifunctional phototheranostics,but also provides a prototype for designing high-performance PSs with tunable photoconversion pathways.
基金
supported by the Natural Science Foundation of China(21820102005,22132002)
111 project(B14041)
the Fundamental Research Funds for the Central Universities of China(2019TS033,GK202001005 and GK202003034)
the Youth Innovation Team of Shaanxi Universities。
