Long-range and short-range interactions of gold nanoparticles irradiated by plane wave

This thesis studies, the light-driven interactions of the gold nanorods and nanoballs irradiated by linear or circular polarized light. Optical forces and torques on those nanoparticles based on Maxwell electromagnetic theory, with the Maxwell stress tensor and multiple multipole method (MMP). For gold nanoballs, there are two different interaction behaviors, which are categorized by the separation distance between nanoballs. If the separation distance of gold nanoballs is shorter than λ/2n, nanoballs behave as short-range interaction. Under linear polarized light, nanoballs attract each other and their line of centroid parallel to the polarization direction of the light. Under circular polarized light, nanoballs still attract each other, and get angular momentums for spin and revolution. If the separation distance of gold nanoballs is longer than λ/2n, nanoballs behave as long-range interaction. Under linear polarized light, nanoballs repulse each other until the distance of nanoballs reach the integer multiples of the wavelength in water, and their line of centroid perpendicular to the polarization direction of the light. Under circular polarized light, nanoballs still repulse each other until the distance between nanoballs reach mλ/n, and get angular momentums for spin and revolution. For gold nanorods, the key factors of the interaction are the wavelength and polarization of our incident light. If the wavelength is shorter than the longitudinal surface plasmon resonance (LSPR) of both nanorods, nanorods turn their longitudinal axes to be perpendicular to the polarization direction and combine side-by-side. If the wavelength is longer than the LSPR of both nanorods, nanorods turn their longitudinal axes to parallelize to the polarization direction and combine in end-to-end way. If the wavelength is between the LSPR of two different rods, the longer and shorter nanorods turn their longitudinal axes to be perpendicular and parallel to the polarization direction respectively, and combine in T-shape.