  We assess the potentiality of several geometries of metallic nanodimers (one
of the simplest thermoplasmonic systems) as candidates for active particles
(nanoswimmers) propelled and controlled by light (phototaxis). The studied
nanodimers are formed by two spherical nanoparticles of gold, silver, or copper
with radii ranging from 20 to 100 nm. Contrary to most proposals, which assume
the asymmetry of the systems as a requirement for self-propulsion, our results
show that nanodimers made of identical nanoparticles are excellent candidates
for phototactic self-thermophoretic systems. Nonsymmetrical nanodimers,
although having a tunable effective diffusion, possess much lower or zero
average thermophoretic forces. We show that the effective diffusion and the net
thermophoretic force in both types of systems depend strongly on the wavelength
of the incident light, which makes these properties highly tunable. Our study
may be useful for the design of simple-to-make but controllable self-propelled
nanoparticles. This can find numerous applications ranging from autonomous
drug-carrying to controlling the self-assembly of complex nanomaterials.
