Guided transport of nanoparticles by plasmonic nanowires.

Herein, we report the optical trapping and directional transport of nanoparticles in an aqueous solution by plasmonic nanowires. A laser illuminated one end of a silver nanowire and excited the localized and propagating surface plasmons. Optical forces were induced by the surface plasmons, which could trap the nanoparticles in an aqueous solution. Interestingly, the trapped nanoparticles moved along the silver nanowires from the trapping site to the excitation spot of the laser. Such movements of nanoparticles were also observed on curved nanowires, in which the trajectories of the particles were explicitly determined by the shape of the nanowires. More importantly, for a V-shaped silver nanowire, the direction of the movement could be modulated by the polarization of the incident laser. The direction of the movement was opposite to the prediction by the scattering force due to the propagation of surface plasmons, and the driving force could involve the thermal convection of local fluid due to a heating effect. Our findings indicate a novel approach to transport nanoparticles by plasmonic waveguides in aqueous solution.