Moving Kinetics of Nanocars with Hydrophobic Wheels on Solid Surfaces at Ambient Conditions

Abstract

Motivated by “driving” nanoscopic nanocars on solid substrate surfaces at ambient conditions, we studied the moving kinetics of nanocars on differently modified surfaces. Single molecule fluorescence imaging was used to track the nanocar movement so that the molecules were minimally perturbed. On freshly cleaned, hydroxylated glass surfaces, nanocars with hydrophobic adamantane wheels can diffuse with a relatively large diffusion coefficient of 7.6 × 10–16 m2/s. Both the number of moving molecules and the mobility of the moving molecules decreased over time when the sample was exposed in the air. Similar declinations in movement were observed on a poly(ethylene glycol) (PEG)-modified glass surface, but the declination rate was lowered. The slowing of molecular surface diffusion is correlated to the hydrophobicity of the surface and is likely caused by the adsorption of hydrophobic molecules from the air. A proposed sticky-spots model explains the decreasing apparent diffusion coefficient of the hydrophobi...