Vapour confinement as a strategy to fabricate metal and bimetallic nanostructures

Metal nanostructures have attracted much attention in biomedical, plasmonic, hydrogen storage, and high-energy battery applications. However, the synthesis of various nanostructures of highly reactive elements (e.g. Mg) is still a difficult task and no single-approach has been reported for synthesizing such nanostructures. In this work, we produced magnesium nanoparticles (NPs), nanowires (NWs) and nanoneedles (NNs) in a single-approach, based on thermal evaporation without any carrier gas. Importantly, we employed rapid heating and cooling via a rapid thermal processing (RTP) furnace to control the nucleation and growth of nanostructures. The testing of Zn and Mg-Zn nanostructures was done to validate our approach and design for other metals and bimetallics. Interestingly, Cu and Ag nanoparticles were produced from metal salts (metal acetates and nitrates) with a reasonable control. The tuning of various nanostructures was possible by interplaying (i) with the curvature/outer diameter of the quartz bottle used for evaporation and (ii) by varying the position of the substrates. More specifically, the curvature of the quartz bottle increased the vapour collisions and effectively reduced the thermal energy of the vapour. Altogether, this favoured the control and confinement of vapour onto substrates and achieved supersaturation. Simultaneously, it led to the formation of various nanostructures without any carrier gas. The presented experimental set up is a versatile, simple, single-step and cost-effective solution for producing high-quality nanostructures.