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Authors: E. Groeneveld, S. van Berkum, and C. de Mello Donegá Colloidal semiconductor nanocrystals (NCs) have opened up exciting new possibilities in the field of materials science. Control over the size and shape of the NCs makes it possible to tune the material's optoelectronic properties without changing its composition. Semiconductor heteronanocrystals offer even more exciting possibilities regarding property control. In these nanostructures the spatial localization of the photoexcited charge carriers can be tailored by manipulating the energy offsets between the valence and conduction band levels of the materials that are combined at the heterointerface. This offers the possibility of directly controlling the electron-hole overlap, which has important consequences for a number of technologies. In this work, we have synthesized highly luminescent ultranarrow (~2 nm in diameter) (Zn,Cd)Te/CdSe colloidal heteronanowires by a multistage approach in which ZnTe magic size clusters are used as seeds. The wire formation starts with a partial Zn for Cd cation exchange, followed by self-organization into segmented heteronanowires. Further growth occurs by inclusion of CdSe. The heteronanowires can be up to ~100 nm long and emit in the 530 to 760 nm range with high quantum yields (up to 50%). The electron-hole overlap decreases with increasing CdSe volume fraction, allowing the optical properties to be controlled by adjusting the heteronanowire composition. These properties make the colloidal (Zn,Cd)Te/CdSe heteronanowires prepared in this work potentially interesting as active elements in light harvesting and photovoltaic devices. |
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