Dynamics of an optically confined nanoparticle diffusing normal to a surface.

ABSTRACT: Here we measure the hindered diffusion of an optically confined nanoparticle in the direction normal to a surface, and we use this to determine the particle-surface interaction profile in terms of the absolute height. These studies are performed using the evanescent field of an optically excited single-mode silicon nitride waveguide, where the particle is confined in a height-dependent potential energy well generated from the balance of optical gradient and surface forces. Using a high-speed cmos camera, we demonstrate the ability to capture the short time-scale diffusion dominated motion for 800-nm-diam polystyrene particles, with measurement times of only a few seconds per particle. Using established theory, we show how this information can be used to estimate the equilibrium separation

SUBMITTER: Schein P 

PROVIDER: S-EPMC5970563 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature