Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
Nano Lett. 2015 Jun 10;15(6):4045-51. doi: 10.1021/acs.nanolett.5b01046. Epub 2015 May 29.
Single-particle photoluminescence blinking is observed in the copper-centered deep-trap luminescence of copper-doped CdSe (Cu(+):CdSe) nanocrystals. Blinking dynamics for Cu(+):CdSe and undoped CdSe nanocrystals are analyzed to identify the effect of Cu(+), which selectively traps photogenerated holes. Analysis of the blinking data reveals that the Cu(+):CdSe and CdSe nanocrystal "off"-state dynamics are statistically identical, but the Cu(+):CdSe nanocrystal "on" state is shorter lived. Additionally, a new and pronounced temperature-dependent delayed luminescence is observed in the Cu(+):CdSe nanocrystals that persists long beyond the radiative lifetime of the luminescent excited state. This delayed luminescence is analogous to the well-known donor-acceptor pair luminescence of bulk copper-doped phosphors and is interpreted as revealing metastable charge-separated excited states formed by reversible electron trapping at the nanocrystal surfaces. A mechanistic link between this delayed luminescence and the luminescence blinking is proposed. Collectively, these data suggest that electron (rather than hole) trapping/detrapping is responsible for photoluminescence intermittency in these nanocrystals.
在铜掺杂的 CdSe（Cu(+):CdSe）纳米晶体的铜中心深陷阱发光中观察到单粒子荧光闪烁。分析 Cu(+):CdSe 和未掺杂的 CdSe 纳米晶体的闪烁动力学，以确定 Cu(+)的影响，Cu(+)选择性地捕获光生空穴。闪烁数据分析表明，Cu(+):CdSe 和 CdSe 纳米晶体的“关闭”状态动力学在统计学上是相同的，但 Cu(+):CdSe 纳米晶体的“开启”状态寿命更短。此外，在 Cu(+):CdSe 纳米晶体中观察到一种新的、明显的温度相关延迟发光，其持续时间远远超过发光激发态的辐射寿命。这种延迟发光类似于体相铜掺杂荧光粉中众所周知的施主-受主对发光，并被解释为揭示了由纳米晶表面可逆电子俘获形成的亚稳态电荷分离激发态。提出了这种延迟发光与发光闪烁之间的机制联系。总的来说，这些数据表明，电子（而不是空穴）俘获/释放是这些纳米晶体中光致发光间歇性的原因。
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