Tunable 3D and 2D polystyrene nanoparticle assemblies using surface wettability, low volume fraction and surfactant effects

Polymer-based nanopatterning on metal surfaces is of increasing importance to a number of applications, including biosensors, bioelectronic devices and medical implants. Here we show that polycrystalline gold surfaces can be functionalized with monocomponent nanoparticle (NP) assemblies by a simple drop deposition method. Ordered 3D hexagonal close-packed structures consisting of 350 nm polystyrene (PS) NPs on hydrophobically modified gold surfaces from solutions of very low volume fraction (φ = 0.0006) were obtained as a result of capillary force induced self-assembly, whilst 2D self-assembly of PS NPs was generated over large area on hydrophilic gold and TiO₂ surfaces by spin coating. Furthermore, we show that when Triton X-100 is added to the PS NP suspending medium longer range ordering is obtained. Our observations may initiate interesting applications in the areas of nanoengineering of metal-based sensors and as a means to design new nanostructures for biocompatible implant surfaces.