Song Pei, Wang Jian-Hua, Zhang Miao, Yang Fan, Lu Hai-Jie, Kang Bin, Xu Jing-Juan, Chen Hong-Yuan
State Key Laboratory of Analytical Chemistry for Life Science and Collaborative Innovation Center of Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, 163 Xianlin Road, Nanjing 210023, P. R. China.
Sci Adv. 2018 Aug 17;4(8):eaat0292. doi: 10.1126/sciadv.aat0292. eCollection 2018 Aug.
The development of modern biological and medical science highly depends on advanced luminescent probes. Current probes typically have wide emission spectra of 30 to 100 nm, which limits the number of resolvable colors that are simultaneously labeled on samples. Spasers, the abbreviation for surface plasmon lasers, have ultranarrow lasing spectra by stimulated light amplification in the plasmon nanocavity. However, high threshold (>10 mJ cm) and short lasing lifetime (approximately picoseconds to nanoseconds) still remain obstacles for current two-level spaser systems. We demonstrated a new type of a three-level spaser using triplet-state electrons. By prolonging the upper state lifetime and controlling the energy transfer, high gain compensation was generated. This probe, named delayed spasing dots (dsDs), about 50 to 60 nm in size, exhibited a spectral linewidth of ~3 nm, an ultralow threshold of ~1 mJ cm, and a delayed lasing lifetime of ~10 μs. As the first experimental realization of the three-level spaser system, our results suggested a general strategy to tune the spasing threshold and dynamics by engineering the energy level of the gain medium and the energy transfer process. These dsDs have the potential to become new-generation luminescent probes for super-multiplex biological analysis without disturbance from short lifetime background emission.
现代生物医学科学的发展高度依赖于先进的发光探针。目前的探针通常具有30至100纳米的宽发射光谱，这限制了同时标记在样品上的可分辨颜色的数量。表面等离子体激元激光器（spasers）通过等离子体纳米腔中的受激光放大具有超窄激光光谱。然而，高阈值（>10 mJ/cm²）和短激光寿命（约皮秒到纳秒）仍然是当前两级spaser系统的障碍。我们展示了一种利用三重态电子的新型三级spaser。通过延长上能级寿命并控制能量转移，产生了高增益补偿。这种名为延迟发光点（dsDs）的探针尺寸约为50至60纳米，表现出约3纳米的光谱线宽、约1 mJ/cm²的超低阈值和约10微秒的延迟激光寿命。作为三级spaser系统的首次实验实现，我们的结果提出了一种通过设计增益介质的能级和能量转移过程来调节发光阈值和动力学的通用策略。这些dsDs有潜力成为用于超多重生物分析的新一代发光探针，而不受短寿命背景发射的干扰。
