Color-tunable ultralong room temperature afterglow in a wide excitation range from ultraviolet to visible light <i>via</i> doping boric acid with polyaromatic hydrocarbons

The development of ultralong organic room temperature afterglow (UL-RTA) materials has attracted tremendous attention owing to their great potential applications in optoelectronic areas. However, achieving UL-RTA, particularly under visible-light activation, remains a substantial challenge. Herein, we present an effective strategy to achieve excitation wavelength-dependent UL-RTA behavior covering a wide range from ultraviolet (UV) to the visible light region <i>via</i> embedding polycyclic aromatic hydrocarbons (PAHs containing triphenylene (TP) and coronene (CN)) into a boric acid (BA) matrix (denoted as PAHs-BA, TP-BA and CN-BA). Specifically, the TP-BA system exhibits a minute-level blue UL-RTA with an ultralong lifetime of 6744 ms, while the CN-BA system demonstrates a green afterglow with an ultralong lifetime of 3724 ms lasting up to 25 s under visible light excitation at 420 nm. Such outstanding afterglow performance has been rarely reported so far. Experiments and theoretical calculations indicate that the observed UL-RTA primarily originates from the rigid and confined environment provided by the formation of a metaboric acid (HBA) matrix under heat treatment, which effectively suppresses non-radiative transitions of the guest molecules. Furthermore, the excitation-dependent performance covering a wide range from UV to the visible light region mainly relies on the coexistence of the isolated individuals and J-aggregation of guest molecules. Inspired by these outstanding features, anti-counterfeiting and multilevel information encryption applications are demonstrated.