Enabling robust near-infrared afterglow polymers through cascade energy transfer

[Display omitted] •The NIR afterglow polymer is made by a cascade energy transfer strategy.•A high-efficiency cascade energy transfer process is achieved in the doped system.•NIR afterglow imaging with a high signal-to-background ratio is achieved.•The work offers a facile way for developing NIR afterglow polymers. Near-infrared afterglow materials, which can significantly reduce background fluorescence and improve penetration in living organisms, are vital for precision imaging. However, the practicability of near-infrared afterglow materials has been hindered by their short lifetime and low luminescence quantum efficiency. Herein, we propose an effective strategy for doping water-soluble afterglow polymer host materials with fluorescent dyes, leveraging the step-by-step Förster energy transfer principle to realize near-infrared afterglow. Benefiting from the ultralong lifetime of 4.2 s and high quantum efficiency of 20.1 % for the blue host PAMCz as well as efficient cascade energy transfer efficiency of 83.3 %, the developed NIR afterglow exhibits luminescence peaked at 750 nm, a lifetime of 1.4 s, and a quantum efficiency of 17.1 %. A successful demonstration of near-infrared afterglow biological imaging with a penetration depth of 3.4 mm and signal-to-background ratio of 48.3, has been established. These advancements expand the scope of near-infrared afterglow materials by combining an ultralong lifetime with high quantum efficiency, providing a roadmap for designing robust near-infrared materials.