Organic near infrared (NIR) persistent-luminescence systems with bright and long-lived emission are highly valuable for applications in communication, imaging, and sensors. However, realizing these materials (especially lifetime over 0.1 s) is a challenge, mainly because of non-radiative quenching of their long-lived excitons. Herein, a universal strategy of stepwise Förster resonance energy transfer (FRET) for a bright NIR system with remarkable persistent luminescence (up to 0.2 s at 810 nm) is presented, based on a new triphenylene-dye-doped polymer (triphenylene-2-ylboronic acid@poly(vinyl alcohol) (TP@PVA)) with a persistent blue phosphorescence of 3.29 s. This persistent NIR luminescence is demonstrated for application not only in NIR anti-counterfeiting but also NIR bioimaging with penetrating a piece of skin as thick as 2.0 mm. By co-doping a red dye (such as Nile red) and an NIR dye Cyanine 7 (Cy7) into this doped PVA film, the shortage of spectral overlap between TP emission and Cy7 absorbance is successfully solved, through a stepwise FRET process involving triplet to singlet (TS)-FRET from TP to the intermediate red dye and then singlet to singlet (SS)-FRET to Cy7. It is noted that the efficiency of the upper TS-FRET is enhanced significantly by the lower SS-FRET, leading to high efficiencies for the continuous FRETs.

中文翻译：

---

逐步能量转移：掺杂聚合物系统的近红外持续发光

具有明亮和长寿命发射的有机近红外 (NIR) 持续发光系统对于通信、成像和传感器的应用非常有价值。然而，实现这些材料（尤其是超过 0.1 s 的寿命）是一项挑战，主要是因为它们的长寿命激子会发生非辐射猝灭。在此，基于一种新的三苯并苯染料掺杂聚合物（triphenylene-2- ylboronic acid@poly(vinyl alcohol) (TP@PVA)) 具有持续 3.29 秒的蓝色磷光。这种持久的近红外发光不仅可用于近红外防伪，还可用于近红外生物成像，可穿透厚达 2.0 毫米的皮肤。通过将红色染料（如尼罗红）和 NIR 染料花青 7 (Cy7) 共掺杂到这种掺杂的 PVA 薄膜中，通过涉及三重态的逐步 FRET 过程，成功解决了 TP 发射和 Cy7 吸收之间光谱重叠不足的问题从 TP 到单线态 (TS)-FRET 到中间红色染料，然后从单线态到单线态 (SS)-FRET 到 Cy7。值得注意的是，上部 TS-FRET 的效率被下部 SS-FRET 显着提高，从而导致连续 FRET 的高效率。