Nature Commun. 6, 8841 (2015)

There is substantial interest in the fabrication of porous Au due to its high catalytic activity. Khristosov et al. now demonstrate a new approach for the synthesis of micro-scale nanoporous Au particles devoid of grain boundaries. The approach they adopt is one of depositing Au and Ge at their eutectic composition on an SiO2 substrate, followed by heating to above the eutectic temperature; the melt dewets the substrate, forming solid spheres with a nanoscale eutectic structure, which is frozen by subsequent cooling. Ge is then etched away, yielding a single crystal of Au with nanoscale pores. The authors discern that the lack of grain boundaries is a result of the timescale for crystallization of one micro-droplet being shorter than the average timescale between two nucleation events. Importantly, the single-crystal structure makes the particles more thermally stable — as compared to dealloyed samples containing grain boundaries — potentially boosting the temperature at which they may be utilized.