Fabrication of 2D ordered structure of self-assembled block copolymers containing gold nanoparticles

Two-dimensional (2D) ordered structure of metal or semiconducting nanoparticles has many applications in areas of optoelectronic and biomedical technologies. Traditional top–down patterning methods like photolithography and e-beam lithography has shown to be time-consuming and expensive processes. In this study, a bottom–up method to fabricate an ordered nanodot structure with entirely wet-chemical procedures is proposed by using an amphiphilic block copolymer self-assembled into well defined two/three-dimensional structures with gold nanoparticles evenly distributed in the hydrophilic domain of the copolymer. The nanodot array of micelle monolayer containing Au salts on substrates can be made by a simple dip coating process. The block copolymer micelles containing gold salts on substrates were used as nanoscale reactors for the in-situ synthesis of metal nanoparticles by chemical treatment of the film sample with hydrazine vapor. AFM was used to evaluate the uniformity of nanodots coated on a silicon wafer before and after hydrazine reduction. Transmission electron microscopy measurement showed that a monofilm of gold salts was reduced to one or a couple of gold nanoparticles inside the core volume of PVP domain by nucleation and growth mechanism upon hydrazine vapor exposure. For an exposure time longer than 5 min, aggregation of nanodots and disruption of 2D ordered structure were resulted due to the swelling of PVP core by hydrazine.