Photobrightening of CdSe/ZnS/TOPO nanocrystals
Photobrightening of CdSe/ZnS/TOPO nanocrystals
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DOI：
10.1016/j.jlumin.2006.01.282
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发表时间：
2007-01-01
影响因子：
3.6
通讯作者：
Tani, Toshiro
中科院分区：
文献类型：
--
作者：
Oda, Masaru;Tsukamoto, Junpei;Tani, Toshiro
研究了水分子饱和的氮气（H2O/N-2）中CdSe/ZnS/TOPO纳米晶（NC）的光致发光（PL）效应。连续光照射1200秒后，NC系综样品的PL强度增加了两倍多。这些增加大多恢复到他们以前的值在连续光照下，当我们抽空H2O/N-2气氛。这些结果表明，吸附到NC表面上的水分子提供了一些功能，几乎可逆地恢复PL淬火缺陷或陷阱网站或附近的NC表面。为了从微观上阐明这种恢复功能的机制，我们还测量了在H2O/N-2和真空中单个纳米碳的PL强度分布的时间演化。当在两种环境中观察到PL强度的闪烁行为时，我们发现在H_2O/N-2中的单次NC观测的PL开启时间比在真空中的显著增加。至于闪烁关断时间，其暂时与NC表面上或附近的陷阱位置处的载流子捕获的偶然事件相关联。因此，我们建议的H2O分子的光吸附灭活这些陷阱网站，并减少发生的捕获事件，这反过来又增加PL的时间，并最终提供的photoblizzenings。(c)2006 Elsevier B. V.保留所有权利。
We have investigated photobrightening effects of photoluminescence (PL) from CdSe/ZnS/TOPO nanocrystals (NCs) in ambient nitrogen gas saturated with water molecules (H2O/N-2). The PL intensities from NC ensemble samples increase more than twice after 1200-s irradiation of cw light. These increases mostly recover to their previous values under continuous light irradiation when we evacuate the H2O/N-2 atmosphere. These results indicate that the adsorption of H2O molecules onto NC surfaces provides some functions as to restore almost reversibly the PL-quenching defects or trap sites on or near the NC surfaces. To elucidate the mechanism of this restoring function microscopically, we have also measured time evolution of PL intensity profiles from single NCs both in H2O/N-2 and in vacuum. While blinking behaviors of the PL intensity being observed in both environments, we have found significant increase of PL on-times in case of single NC observations in the H2O/N-2 compared with those in vacuum. As for the blinking off-times, it is for the moment associated with the occasional events of carrier captures at the trap sites on or near the NC surfaces. Thus, we propose the photoadsorption of H2O molecules inactivates these trap sites and decreases the occurrence of the capturing events, which in turn increase PL on-times and eventually provide the photobrightenings. (c) 2006 Elsevier B.V. All rights reserved.