Pinpointing the Cause of Platinum Tipping on CdS Nanorods

We computationally identify the precise mechanism by which metallic platinum aggregates at the tips of cadmium sulfide (CdS) nanostructures. Large-scale atomistic simulations of physically realistic nanorods are used to quantify the chemical, dispersive, and electrostatic contributions to platinum interaction with CdS. Crystallographic anisotropy as well as facet, edge, and tip effects are accounted for to show that Pt aggregation, known as "tipping", is not due to the dynamics of adhesion and diffusion. Instead, efficient tipping is found to be due to long-range electrostatic interactions of metallic ions with polar tips set up by CdS surface stoichiometry. The results are used to stipulate the physical conditions by which metallic decoration of ionic nanostructures can be optimized. This is expected to be useful in the realization of nanoscale metal-semiconductor devices.