Gold nanoparticles as contrast agents for nonlinear microscopy

Abstract

Gold nanoparticles can be used as contrast agents for nonlinear optical microscopy because of their strong plasmon resonance. I have developed a numerical method which assumes that a scatterer is made of interacting dipoles. I have shown that the dipole coupling is necessary for predicting the effects of shape and size of a nanoparticle on its nonlinear optical properties. For a given material and excitation wavelength(s), this dipole model can be used to screen nanoparticles of different shapes for optimal nonlinear scattering of a particular kind. On the experimental side, I developed a generic methodology to conjugate gold nanoparticles to ligands so that these nanoparticles can be targeted to specific biological samples. Finally I demonstrated that multiphoton microscopy of gold nanorods with an excitation wavelength away from their plasmon resonance causes less photo-thermal damage without significantly compromising the multiphoton luminescence signal from the nanorods.