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▲ [22a-D315-3] Optical Binding Outside the Focal Spot Leads to Swarming of Gold Nanoparticles
Keywords:Optical trapping, Optical binding, Gold nanoparticles
Previously, our group reported a large swarming assembly of 200 nm gold nanoparticles (Au NPs) formed by laser trapping at the glass/solution interface. The Au NPs in the swarms dynamically fluctuate while being spatially confined in a volume, indicating that the optical potential is expanded outside of the irradiated area of the incident laser.
In this work, we applied single particle tracking analysis to investigate the initial stage of the optical trapping and swarming of 400 nm Au NPs, tracing the origin of the optical potential expansion. As a result, correlated motion between particles is not only observed inside but also outside the laser focus. The external NPs show an expanding arc-shaped distribution with a characteristic half-wavelength inter-arc distance. The obtained results strongly support that optical binding can occur outside the irradiated area and extend its network through multiple scattering among more optically-bound NPs, leading to the dumbbell-shaped swarming assembly.
In this work, we applied single particle tracking analysis to investigate the initial stage of the optical trapping and swarming of 400 nm Au NPs, tracing the origin of the optical potential expansion. As a result, correlated motion between particles is not only observed inside but also outside the laser focus. The external NPs show an expanding arc-shaped distribution with a characteristic half-wavelength inter-arc distance. The obtained results strongly support that optical binding can occur outside the irradiated area and extend its network through multiple scattering among more optically-bound NPs, leading to the dumbbell-shaped swarming assembly.