Synthesis of gold nanoparticle superlattice using seed-mediated method for size control

Abstract

Nanoparticles (NPs) have been widely researched in terms of their ability to self-assemble into ordered superlattice (SL). These SL displayed not only the intrinsic characteristics, which belong to individual NPs building blocks, but also unique collective optical, electronic, and mechanical properties which are tunable by the superlattice size. However, the limited size control of SL still remains a major obstacle for practical applications such as plasmon based sensing and optoelectronic coupling. Herein, we report a method to synthesize size tunable gold nanoparticle superlattices by using aldol reaction, a covalent bonding reaction, in conjunction with slow solvent evaporation by seed-mediated method concept. Gold nanoparticle functionalized with thiol polyethylene glycol formyl are linked to each other by carbon-carbon bonds formed by aldol reaction as the nanoparticle dispersion in aqueous NaOH solution is slowly evaporated, resulting in three dimensional NPSL. To further grow the as-preformed NPSL, we drop-cast the thiol polyethylene glycol formyl functionalized gold nanoparticle dispersed in aqueous NaOH solution on to the preformed NPSL. The seed-mediated growth concept of NPSL shows that it can control the resulting size of NPSL. The as-synthesized NPSL also show excellent structural stability in solvents of different polarities as well as dried condition and at temperature up to 185 oC. This new approach open-up new opportunities in the size control & stable synthesis of NPSL and its application.