Reversible photobluing of CdSe/ZnS/TOPO nanocrystals
Reversible photobluing of CdSe/ZnS/TOPO nanocrystals
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DOI：
10.1016/j.colsurfb.2006.12.012
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发表时间：
2007-04-15
影响因子：
5.8
通讯作者：
Tani, Toshiro
中科院分区：
文献类型：
--
作者：
Oda, Masaru;Hasegawa, Atsushi;Tani, Toshiro
在不同的环境下，研究了CdSe/ZnS/TOPO纳米晶(约1000个)的光致发光(PL)的光致校正和光致发蓝效应。在湿氮(H2O/N-2)气氛中连续光照下，发光强度增加一倍以上，蓝移，而在纯氮气氛和真空中，它们的行为没有什么特殊之处。此外，在H2O/N-2大气中，增亮和发蓝效应的增加速率取决于辐照强度。这些结果表明，这两种效应都应该与水分子在纳米晶体表面的光吸附有关。至于发光效应，我们认为水分子的光吸附对纳米晶体表面或附近的光致发光猝灭缺陷或陷阱位具有一定的恢复作用。另一方面，从系综测量的结果来看，蓝化效应的来源并不清楚。为了更深入地了解发蓝效应，在H2O/N-2气氛和真空交替的循环环境中，测量了单个纳米晶体在连续光照射下的荧光光谱。结果表明，在真空条件下，光在H2O/N-2气氛中产生的蓝移光致发光几乎可逆地恢复到初始光致发光。并在此基础上讨论了光致发蓝效应的机理。(C)2006爱思唯尔B.V.保留所有权利。
Photobrightening and photobluing effects of photoluminescence (PL) from CdSe/ZnS/TOPO nanocrystal ensembles, i.e. ca. 1000 nanocrystals, have been investigated in several environments. The PL intensity increases more than twice with blue shift under continuous light irradiation in a wet nitrogen (H2O/N-2) atmosphere, while in a pure nitrogen atmosphere and vacuum their behaviors are nothing particular. In addition, increasing rates of both the brightening and bluing effects in the H2O/N-2 atmosphere depend on irradiation intensities. These results suggest that both effects should be associated with photo-adsorption of water molecules onto nanocrystal surfaces. As for the brightening effect, we propose that the photoadsorption of water molecules provides some restoring functions to PL-quenching defects or trap-sites on or near nanocrystal surfaces. On the other hand, the origin of the bluing effect is not clear from the results of the ensemble measurements. To get further insight into the bluing effect, PL spectra from single nanocrystals are measured under continuous light irradiation in cyclic environments in which the H2O/N-2 atmosphere and vacuum are alternating. As a result, blue-shifted PL induced by the light irradiation in the H2O/N-2 atmosphere recovers almost to its initial one reversibly under evacuation. The mechanism of the photobluing effect will be discussed also on the bases of the photobrightening model introduced above. (c) 2006 Elsevier B.V. All rights reserved.