Wu Kaifeng, Rodríguez-Córdoba William, Lian Tianquan
Department of Chemistry, Emory University , Atlanta, Georgia 30322, United States.
J Phys Chem B. 2014 Dec 11;118(49):14062-9. doi: 10.1021/jp504703t. Epub 2014 Jul 1.
One-dimensional colloidal multicomponent semiconductor nanorods, such as CdSe-CdS dot-in-rod, have been extensively studied as a promising class of new materials for solar energy conversion because of the possibilities of using the band alignment of component materials and the rod-diameter-dependent quantum confinement effect to control the location of electrons and holes and to incorporate catalysts through the growth of Pt tips. Here we used CdS nanorods as an example to study the effect of nonuniform diameters along the rod on the exciton localization and dissociation dynamics in CdS and (platinum tipped) CdS-Pt nanorods. We showed that, in CdS nanorods prepared by seeded growth, the presence of a bulb with a larger diameter around the CdS seed resulted in an additional absorption band lower in energy than the exciton in the CdS rod. As a result, excitons generated in the CdS rod could undergo ultrafast localization to the bulb region in addition to trapping on the CdS rod. We observed that the Pt tip led to fast exciton dissociation by electron transfer. However, excitons localized on the CdS bulb showed slower average ET rates than those localized in the rod region. Our findings suggested that the effect of rod morphology should be carefully considered in designing multicomponent nanorods for solar energy conversion applications.
一维胶体多组分半导体纳米棒，如CdSe-CdS核壳纳米棒，由于可以利用组成材料的能带排列和与棒直径相关的量子限制效应来控制电子和空穴的位置，并通过生长Pt尖端来引入催化剂，作为一类有前途的太阳能转换新材料已得到广泛研究。在这里，我们以CdS纳米棒为例，研究了沿棒的直径不均匀对CdS和（带铂尖端的）CdS-Pt纳米棒中激子局域化和解离动力学的影响。我们表明，在通过种子生长制备的CdS纳米棒中，CdS种子周围存在直径较大的球茎会导致出现一个能量低于CdS棒中激子的附加吸收带。因此，在CdS棒中产生的激子除了会被捕获在CdS棒上之外，还可能超快地局域到球茎区域。我们观察到Pt尖端通过电子转移导致激子快速解离。然而，局域在CdS球茎上的激子的平均电子转移速率比局域在棒区域的激子慢。我们的研究结果表明，在设计用于太阳能转换应用的多组分纳米棒时，应仔细考虑棒形态的影响。
