Synthesis, processing and forming gold structures from a 0.1 wt. % concentration solution

A very low concentration (similar to 0.1 wt. %) of spherical 15nm diameter gold nanoparticles were produced by the sodium citrate reduction method and later transferred to ethanol using poly vinyl pyrrolidone (PVP) as a stabilizing agent. The alcosol was then subjected to electrohydrodynamic atomisation to generate fine droplets with an average droplet diameter of < 30 mu m and deposited on substrates accordingly. With the assistance of various deposition methods, three different microstructures were produced. Firstly, the droplets produced by atomisation with the help of an electric field were deposited at various times on a substrate to fabricate gold films with a thickness range of similar to 500nm to 2000nm. Secondly, the droplets were deposited on a moving table which is computer controlled to form an array of inter-connected droplets, thus enabling us to pattern microstructures containing gold nanoparticles of different geometries (electrohydrodynamic atomisation printing). Thirdly, to reduce the track size as well as to form a dense assembly of particles in the microstructures templates were used in conjunction with electrohydrodynamic atomisation (template-assisted patterning). In order to encapsulate gold nanoparticles in a fibre a co-axial needle set-up was used with a polyethylene oxide (PEO) and polyethylene glycol (PEG) mixture as the encapsulating media. Lastly, a gold hydrosol was used to produce near-monodisperse gold microbubbles with the help of a T-junction device having an average diameter of similar to 150 mu m. The ability to generate such a range of structures starting from a very low concentration of gold is a significant achievement.