Au@CdSe heteroepitaxial nanorods: An example of metal nanorods fully covered by a semiconductor shell with strong photo-induced interfacial charge transfer effects.

Synthesis of metal@semiconductor heteroepitaxial nanorods fully covered by a semiconductor shell remains challenging due to the large lattice mismatch between the two components. Here, we prepared Au@CdSe heteroepitaxial nanorods by employing pre-growth of AgSe as an intermediate layer that favored the formation of a complete CdSe shell via a cation-exchange process. The optical properties of these hybrid nanostructures can be tailored by changing the shell thickness with thicker shells resulting in a redshift of the longitudinal surface plasmon resonance. The resonance energy, intensity, and linewidth of the longitudinal surface plasmon resonance were measured by single-particle dark-field scattering spectroscopy, confirming significant electron transfer from the Au nanorod to the CdSe shell. In addition, we also studied the dependence of the catalytic reactivity on shell thickness in photocatalysis of methylene blue under UV illumination. These studies revealed that a thinner shell thickness resulted in higher photocatalytic activity.