Evaporation induced wrinkling of graphene oxide at the nanoparticle interface.

With the thickness of only a single atomic layer, graphene displays many interesting surface properties. A general observation is that wrinkles are formed on graphene oxide (GO) when it is dried in the presence of adsorbed inorganic nanoparticles. In this case, evaporation induced wrinkling is not an elastic deformation but is permanent. Understanding the nanoscale force of wrinkle formation is important for device fabrication and sensing. Herein, we employ surface functionalized gold nanoparticles (AuNPs) as a model system. All tested AuNPs induced wrinkling, including those capped by DNA, polymers and proteins. The size of AuNPs is less important compared to the properties of solvent. Wrinkle formation is attributed to drying related capillary force acting on the GO surface, and a quantitative equation is derived. After drying, the adsorption affinity between GO and AuNPs is increased due to the increased contact area.