Differentiate right-handed and left-handed particles by the force exerted by light

Chirality is the property that the structure is not superimposable on its mirror image. Chiral materials have the particularity of reacting differently to left and right circularly polarized light (optical activity). When a material is irradiated with strong laser light, an optical force is exerted on it. It was theoretically expected that the optical force exerted on chiral materials by left and right circularly polarized light would also be different.

The research group of the Institute for Molecular Science and three other universities used an experimental technique trapping to observe the circular polarization-dependent optical gradient force exerted on chiral gold nanoparticles. Chiral gold nanoparticles have a D-shape (right-handed) or L-shape (left-handed) structure, and the experiment was performed using both. Although the optical gradient force acting on chiral nanoparticles has been predicted theoretically, no observation of the force has been reported before. The research group succeeded in observing the optical gradient force arising from chirality (i.e. the difference between the gradient force by left and right circularly polarized light), by optical trapping of nanoparticles d chiral gold. The results showed that the optical gradient force was different for D-shape and L-shape particles. They also found, from the dependence of the force on the wavelength of the light used, that it There is a hitherto unknown effect on the mechanism of chirality-dependent optical forces.

The present study clarified the characteristics of circular polarization-dependent optical gradient force on the mechanics of chiral gold nanoparticles. It shows the possibility of separation of chiral materials by optical force, which can be achieved and can extend applications by using locally confined light generated on nanostructures to trap materials and/or by using optical force by other mechanisms. .

– This press release was provided by the National Institutes of Natural Sciences

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