ja5b10254_si_001.pdf (4.3 MB)
Microscopic Investigation of Chemoselectivity in Ag–Pt–Fe3O4 Heterotrimer Formation: Mechanistic Insights and Implications for Controlling High-Order Hybrid Nanoparticle Morphology
journal contribution
posted on 2015-12-16, 00:00 authored by James
M. Hodges, James R. Morse, Mary Elizabeth Williams, Raymond E. SchaakThree-component
hybrid nanoparticle heterotrimers, which are important
multifunctional constructs that underpin diverse applications, are
commonly synthesized by growing a third domain off of a two-component
heterodimer seed. However, because heterodimer seeds expose two distinct
surfaces that often can both support nucleation and growth, selectively
targeting one particular surface is critical for exclusively accessing
a desired configuration. Understanding and controlling nucleation
and growth therefore enables the rational formation of high-order
hybrid nanoparticles. Here, we report an in-depth microscopic investigation
that probes the chemoselective addition of Ag to Pt–Fe3O4 heterodimer seeds to form Ag–Pt–Fe3O4 heterotrimers. We find that the formation of
the Ag–Pt–Fe3O4 heterotrimers
initiates with indiscriminate Ag nucleation onto both the Pt and Fe3O4 surfaces of Pt–Fe3O4, followed by surface diffusion and coalescence of Ag onto the Pt
surface to form the Ag–Pt–Fe3O4 product. Control experiments reveal that the size of the Ag domain
of Ag–Pt–Fe3O4 correlates with
the overall surface area of the Pt–Fe3O4 seeds, which is consistent with the coalescence of Ag through a
surface-mediated process and can also be exploited to tune the size
of the Ag domain. Additionally, we observe that small iron oxide islands
on the Pt surface of the Pt–Fe3O4 seeds,
deposited during the formation of Pt–Fe3O4, define the morphology of the Ag domain, which in turn influences
its optical properties. These results provide unprecedented microscopic
insights into the pathway by which Ag–Pt–Fe3O4 heterotrimer nanoparticles form and uncover new design
guidelines for the synthesis of high-order hybrid nanoparticles with
precisely targeted morphologies and properties.