Self-assembly of hydrophobic gold nanoparticles and adhesion property of their assembled monolayer films

Abstract

Monodispersed gold nanoparticles had been successfully fabricated and they could form highly ordered two-dimensional (2D) film beyond a critical surface pressure by using Langmuir-Blodgett (LB) technology. To study adhesion property of these AuNPs films, atomic force microscope (AFM) has been used in measuring the interaction force between AFM tip and the gold nanoparticle films deposited on the silicon wafer, and defined the force at the breaking point as the adhesive force between nanoparticle films and the substrate. It has been found that the adhesive force was an exponential function of the packing density of the AuNPs in the film. When the packing density is near to the saturated value, the adhesive force of gold nanoparticle monolayer could reach 675nN which is approximately 30-fold of that for the nanoparticles on the substrate at low surface pressure (5mN/m). It shows that the adhesive force of assembled nanoparticle films is quantitative sensitive with their packing density and our method could be used to detect defact of assembled nanoparticle films, which presents great potential application.