Core/Shell Approach to Dopant Incorporation and Shape Control in Colloidal Zinc Oxide Nanorods

Tunable aliovalent doping is critical to controlling the optoelectronic properties of semiconductor nanocrystal systems. However, unintentional dopant-induced shape evolution and kinetically limited doping reactions in low-temperature nanocrystal syntheses make it difficult to independently control shape and incorporate dopants in colloidal metal oxide nanocrystals. Here, we demonstrate a synthetic strategy for achieving simultaneous control of both nanorod shape and dopant concentration in colloidal zinc oxide nanorods. We show that this approach succeeds in doping zinc oxide nanorods using Group III dopants (indium or aluminum) in varying concentrations, and we quantify the effects of dopant incorporation on the structural, optical, and plasmonic properties of the nanorods. The synthesis of undoped zinc oxide nanorod templates and subsequent addition of dopant salts to the ongoing reaction enables both shape retention and dopant incorporation. Subsequent growth of an undoped shell on the nanorods incorporates surface segregated dopants with high efficiency. This “core/shell” doping strategy presents a general route to achieving controlled dopant incorporation and morphological retention in anisotropic metal oxide nanocrystal systems.