Ultra-stable 4H-gold nanowires up to 800 °C in a vacuum

Abstract

Crystal phase engineering allows the growth of important noble metal structures with superior optical, electronic, or catalytic functional properties. However, the thermodynamic phase stabilities of nano-sized materials at high temperature are still largely unknown. Here, we reported atomic-scale structural analysis during heating hexagonal 4H-gold nanowires to high temperatures ∼850 °C using in situ transmission electron microscopy (TEM). The 4H phase can withstand high temperature till 800 °C and maintain a typical ABCB 4H stacking order. Further heating to 850 °C led to melting of the 4H-phase nanowires to form particles. After cooling the as-formed particles to room temperature, atomic-scale scanning TEM characterization revealed an fcc crystal structure of these particles. The 4H-gold nanowires with only 12 nm diameter showed remarkable phase stability up to 800 °C, making various applications possible in electronics, catalytic reactions, and optical fields.