Purely organic near-infrared afterglow systems based on a triplet excimer donor

An efficient near-infrared (NIR) afterglow emission at over 750 nm is highly valuable for the advanced detection technology. Herein, a new kind of organic NIR afterglow system with persistent emission (0.16 s) at 808 nm is prepared by using a red room temperature phosphorescence (RTP) excimer as a donor and a NIR dye cyanine 7 (Cy7) as an acceptor. In the pyren-1-ylboronic acid@poly(vinyl alcohol) (PYB@PVA) system, its red persistent RTP emission at over 590 nm is proved to be derived from the triplet excimer of PYB. So, the bright NIR afterglow is achieved via only a single triplet-to-singlet Forster-resonance energy transfer process between PYB@PVA and Cy7. Moreover, PYB2@PVA with more triplet excimers is beneficial to improve NIR emission intensity with a quantum yield of 1.6%. This work demonstrates that exploiting triplet excimers is meaningful to develop purely organic red or NIR afterglow materials with the emission at a long wavelength. A kind of NIR afterglow with a lifetime of 0.16 s at 808 nm was prepared using triplet excimer (PVB@PVA) as the donor. PYB2@PVA containing more excimers is beneficial to improve luminescence of Cy7 acceptor via a triplet-to-singlet energy transfer.