Vosch Tom, Antoku Yasuko, Hsiang Jung-Cheng, Richards Chris I, Gonzalez Jose I, Dickson Robert M
School of Chemistry and Biochemistry and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA.
Proc Natl Acad Sci U S A. 2007 Jul 31;104(31):12616-21. doi: 10.1073/pnas.0610677104. Epub 2007 May 22.
The water-soluble, near-IR-emitting DNA-encapsulated silver nanocluster presented herein exhibits extremely bright and photostable emission on the single-molecule and bulk levels. The photophysics have been elucidated by intensity-dependent correlation analysis and suggest a heavy atom effect of silver that rapidly depopulates an excited dark level before quenching by oxygen, thereby conferring great photostability, very high single-molecule emission rates, and essentially no blinking on experimentally relevant time scales (0.1 to >1,000 ms). Strong antibunching is observed from these biocompatible species, which emit >10(9) photons before photobleaching. The significant dark-state quantum yield even enables bunching from the emissive state to be observed as a dip in the autocorrelation curve with only a single detector as the dark state precludes emission from the emissive level. These species represent significant improvements over existing dyes, and the nonpower law blinking kinetics suggest that these very small species may be alternatives to much larger and strongly intermittent semiconductor quantum dots.
本文介绍的水溶性、近红外发射的DNA包裹银纳米簇在单分子和宏观水平上均表现出极其明亮且光稳定的发射。通过强度相关分析阐明了其光物理性质，表明银的重原子效应在被氧淬灭之前迅速使激发暗态去极化，从而赋予了极大的光稳定性、非常高的单分子发射速率，并且在实验相关的时间尺度（0.1至>1000毫秒）上基本不发生闪烁。从这些生物相容性物质中观察到强烈的反聚束现象，它们在光漂白前发射超过10^9个光子。显著的暗态量子产率甚至使得仅用单个探测器就能观察到从发射态到聚束的现象，表现为自相关曲线中的一个下降，因为暗态阻止了发射态的发射。这些物质相较于现有染料有显著改进，而非幂律闪烁动力学表明这些非常小的物质可能是比大得多且强烈间歇性的半导体量子点更好的替代品。
