Retrosynthetic Design of Morphologically Complex Metal Sulfide Nanoparticles Using Sequential Partial Cation Exchange and Chemical Etching
Auston G. Butterfield, Benjamin C. Steimle, Raymond E. Schaak
Abstract
Designer nanoparticles with complex morphologies are of growing interest for a wide range of applications, but making them rationally and scalably remains challenging. Here, we demonstrate a retrosynthetic approach to access morphologically complex colloidal nanoparticles by combining partial sequential cation exchange reactions with chemical etching. Rational synthesis of the targeted nanoparticles containing ZnS, CdS, or CoS began by identifying heterostructured nanorod precursors that contained precisely located regions of Cu1.8S, which were subsequently etched with trioctylphosphine in the presence of oxygen to generate the desired product. Appropriate heterostructured nanorod precursors were then synthesized by replacing some of the Cu+ cations in colloidal Cu1.8S nanorods with Zn2+, Cd2+, or Co2+, using exchange sequences that were known to produce the desired features. The residual Cu1.8S was then dissolved, converting the Cu1.8S regions into void space. Mixed-population samples were also used to explore and identify a wider swath of potential retrosynthetic pathways and targeted morphologies, as well as morphological tunability. Collectively, several new classes of complex nanoparticles were synthesized, including nanoparticles having a flat end on one side and a faceted tip on the other, nanoparticles having a different material on the top and bottom, and nanoparticles having various protrusions and notches.