Talapin Dmitri V, Rogach Andrey L, Shevchenko Elena V, Kornowski Andreas, Haase Markus, Weller Horst
Institute of Physical Chemistry, University of Hamburg, 20146 Hamburg, Germany.
J Am Chem Soc. 2002 May 22;124(20):5782-90. doi: 10.1021/ja0123599.
The distribution of properties within ensembles of colloidally grown II-VI and III-V semiconductor nanocrystals was studied. A drastic difference in the photoluminescence efficiencies of size-selected fractions was observed for both organometallically prepared CdSe and InAs colloids and for CdTe nanocrystals synthesized in aqueous medium, indicating a general character of the phenomenon observed. The difference in the photoluminescence efficiencies is attributed to different averaged surface disorder of the nanocrystals originating from the Ostwald ripening growth mechanism when larger particles in the ensemble grow at the expense of dissolving smaller particles. At any stage of growth, only a fraction of particles within the ensemble of growing colloidal nanocrystals has the most perfect surface and, thus, shows the most efficient photoluminescence. This is explained by a theoretical model describing the evolution of an ensemble of nanocrystals in a colloidal solution. In an ensemble of growing nanocrystals, the fraction of particles with the highest photoluminescence corresponds to the particle size having nearly zero average growth rate. The small average growth rate leads to the lowest possible degree of surface disorder at any given reaction conditions.
研究了胶体生长的II-VI族和III-V族半导体纳米晶体集合体中的性质分布。对于有机金属制备的CdSe和InAs胶体以及在水介质中合成的CdTe纳米晶体，均观察到尺寸选择部分的光致发光效率存在显著差异，这表明所观察到的现象具有普遍性。光致发光效率的差异归因于纳米晶体不同的平均表面无序度，这源于奥斯特瓦尔德熟化生长机制，即集合体中的较大颗粒以溶解较小颗粒为代价生长。在生长的任何阶段，生长中的胶体纳米晶体集合体中只有一部分颗粒具有最完美的表面，因此表现出最有效的光致发光。这可以通过描述胶体溶液中纳米晶体集合体演化的理论模型来解释。在生长的纳米晶体集合体中，具有最高光致发光的颗粒分数对应于平均生长速率几乎为零的颗粒尺寸。在任何给定的反应条件下，小的平均生长速率导致最低可能程度的表面无序。
