Formation of Highly Ordered Alloy Nanoparticles Based on Precursor-Filled Latex Spheres

Abstract

An experimental approach is presented, allowing the preparation of substrate supported, hexagonally arranged metallic alloy nanoparticles with narrow size distributions, well-defined interparticle distances, and controlled chemical composition. The method is based on miniemulsion polymerization and isotropic plasma etching. Polystyrene (PS) and poly(methyl methacrylate) (PMMA) colloids—in the present study containing Fe- and Pt-precursor complexes in a predefined ratio—are deposited onto hydrophilic Si/SiO 2 substrates by dip-coating, forming a highly ordered monolayer. Contrary to colloidal lithography, here, precursor-filled polystyrene colloids serve as carriers for the alloy forming elements. After reactive ion etching and annealing, hexagonally ordered arrays of crystalline FePt nanoparticles are formed exhibiting the desired 1:1 Fe–Pt ratio, as revealed by detailed analysis after each preparation step. Formation of stoichiometric binary alloy FePt nanoparticles is confirmed by determining magnetic hysteresis loops, as well as applying aberration-corrected high-resolution transmission electron microscopy.