Etude des Plasmons de surface de nanoparticules métalliques et leurs applications dans le domaine médical.

Abstract

Advances in nanotechnology have recently led to the emergence of a completely new field of independent research, including plasmonics, which deals with the optical generation, manipulation and controlled transmission of localized or propagated plasmonic excitations in metal nanostructures interacting with light. These interesting characteristics have paved the way for exploiting the effects of surface plasmons in the photothermal therapy of cancer cells, photocatalytic reactions as well as in the surface-enhanced Raman spectroscopy. In this contribution, we are interested in the study of the localized surface plasmon resonance of metallic nanoparticles. In particular, the impact of various parameters such as the size, shape and environment surrounding nanoparticles on their optical response and thermal effect. We first became interested in calculating absorption and scattering according to these factors, in order to determine the best geometrical parameters (shape and size) for the good thermal characteristic. Then, we calculated numerically the spatiotemporal evolution of the temperature profile inside and around the gold nanoparticles using COMSOL multiphysics that based on the finite element method. Various parameters such as laser fluence and pulse duration on the temperature variation of these nanoparticles were examined. The results revealed that the temperature reached at the particle/water interface in the case of gold nanoshell is much higher than that obtained for other shapes. In particular, the case of nanoshell with Barium titanate (BaTiO3) core. Finally, we applied these nanoshells to a skin tumor, where the results showed that a large part of the tumor was damaged using a small concentration of nanoparticles with low laser intensity. In second time, we synthesized nanoparticles with small dimensions <100nm consisting of a silica core (SiO2) and a gold shell using two different methods. The first gave us a homogeneous gold shell, while the second allowed us to prepare a new type of nanoparticles in the form of raspberry. We investigated the size effect of silica particles, the concentration effect of gold nanoparticles and the effect of the degree of gold coverage on the morphology and optical properties of nanoshells. These studies revealed that the synthesized gold nanoshells are characterized by a broadened and exalted absorption extending to near-infrared region. These properties resulting from the inter-particles coupling due to the short distances between them, creating many hot spots between these nanoparticles, and that what has been demonstrated by numerical simulation. Finally, the results presented in this study can be used, we hope, for the synthesis of nanoparticles adapted to medical and biological applications.