摘要
Generally,long wavelength absorbed near-infrared II(NIR-II)dyes have a low fluorescence efficiency in aggregate states for aggregate-caused quenching effect,simultaneously enhancing efficiency and extending absorption is a challenging issue for NIR-II dyes.Here,three benzo[1,2-c:4,5-c’]bis[1,2,5]thiadiazole(BBT)derivatives(TPA-BBT,FT-BBT,and BTBT-BBT)are used to clarify fluorescence quenching mechanisms.When the BBT derivatives are doped into a small molecule matrix,they show quite different fluorescence behaviors.Structuredistorted TPA-BBT displays fluorescence quenching originating from short-range exchange interaction,while FT-BBT and BTBT-BBT with a co-planar-conjugated backbone exhibit concentration-dependent quenching processes,namely changing from long-range dipole-dipole interaction to exchange interaction,which could be majorly ascribed to large spectral overlap between absorption and emission.By precisely tuning doping concentration,both FT-BBT and BTBT-BBT nanoparticles(NPs)present the optimal NIR-II fluorescence brightness at∼2.5 wt%doping concentration.The doped NPs have good biocompatibility and could be served as fluorescence contrast agents for vascular imaging with a high resolution under 980-nm laser excitation.Those paradigms evidence that molecular doping can promote fluorescence efficiency of long wavelength-absorbed NIR-II fluorophores via suppressing long-range energy migration.
基金
NNSF,Grant/Award Numbers:62120106002,22175089
Jiangsu Provincial Policy Key Research and Development Plan,Grant/Award Numbers:BE2021711,BE2022812
open research fund of State Key Laboratory of Organic Electronics and Information Displays
Startup Foundation for Introducing Talent of NUIST,Grant/Award Number:2021r089。
