Fleischer Blake C, Petty Jeffrey T, Hsiang Jung-Cheng, Dickson Robert M
School of Chemistry and Biochemistry and Institute for Bioengineering & Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332-0400, United States.
Department of Chemistry, Furman University , Greenville, South Carolina 29613, United States.
J Phys Chem Lett. 2017 Aug 3;8(15):3536-3543. doi: 10.1021/acs.jpclett.7b01215. Epub 2017 Jul 17.
We harness the photophysics of few-atom silver nanoclusters to create the first fluorophores capable of optically activated delayed fluorescence (OADF). In analogy with thermally activated delayed fluorescence, often resulting from oxygen- or collision-activated reverse intersystem crossing from triplet levels, this optically controllable/reactivated visible emission occurs with the same 2.2 ns fluorescence lifetime as that produced with primary excitation alone but is excited with near-infrared light from either of two distinct, long-lived photopopulated dark states. In addition to faster ground-state recovery under long-wavelength co-illumination, this "repumped" visible fluorescence occurs many microsceconds after visible excitation and only when gated by secondary near-IR excitation of ∼1-100 μs-lived dark excited states. By deciphering the Ag nanocluster photophysics, we demonstrate that OADF improves upon previous optical modulation schemes for near-complete background rejection in fluorescence detection. Likely extensible to other fluorophores with photopopulatable excited dark states, OADF holds potential for drastically improving fluorescence signal recovery from high backgrounds.
我们利用少数原子银纳米团簇的光物理特性，制造出了首批能够产生光激活延迟荧光（OADF）的荧光团。类似于热激活延迟荧光（通常由氧或碰撞激活的从三重态的反向系间窜越产生），这种光学可控/可再激活的可见光发射具有与仅由一次激发产生的荧光相同的2.2纳秒荧光寿命，但由来自两个不同的、长寿命光致填充暗态之一的近红外光激发。除了在长波长共照射下更快的基态恢复外，这种“再泵浦”可见光荧光在可见光激发后许多微秒才出现，并且仅在由寿命约为1 - 100微秒的暗激发态的二次近红外激发选通时才发生。通过解读银纳米团簇的光物理特性，我们证明OADF在荧光检测中近乎完全消除背景方面比以前的光调制方案有所改进。OADF可能可扩展到其他具有可光致填充激发暗态的荧光团，在从高背景中大幅提高荧光信号恢复方面具有潜力。
