Bio‐Derived Photonic Film With Switchable and High‐Asymmetry Circularly Polarized NIR Afterglow

ABSTRACT Near infrared (NIR) circularly polarized organic afterglow are highly attractive for information encryption, bio‐imaging/sensing. However, achieving both NIR afterglow and high optical asymmetry remains challenging. Here, a pure‐organic afterglow film with circularly polarized NIR emission is achieved through co‐assembly of chromophores with cellulose nanocrystals (CNCs). The film exhibits a strong NIR afterglow with a lifetime of 0.38 s at 808 nm and a high g lum of ‐0.15, 1–2 orders higher than reported performance. The CNCs matrix not only stabilizes triplet excitons via hydrogen bonding, facilitating phosphorescence from 1‐naphthylboronic acid, but also provides a cholesteric surrounding to enable circularly polarized luminescence (CPL). Further employing an intermediate dye, Rhodamine B (RB), and a NIR dye, Cyanine7, the CPL is extended from visible to NIR range via a two‐step Förster resonance energy transfer. Moreover, the film demonstrates dynamic switch of the NIR circularly polarized afterglow by modulating the pH‐responsive intermediate RB, showing potential for multi‐channel information encryption, bio‐imaging, and sensing.