Plasmonic enhancement of absorption efficiency of nanoparticles for photothermal therapy applications

Abstract

Even though humanity is in a golden age when it comes to medical wonders, can cer is still one of the most common and deadly diseases in the world. One new treatment method is called photothermal therapy, which is the thermal ablation of cancer cells by the intravenous injection of plasmonic nanoparticles. Plasmonic nanoparticles absorb the incident light, converting almost all to heat, and increasing the temperature of the environment. But since the nanoparticles are taken intravenously, their placements in the tissue are randomized. In this thesis, the effects of adding dielectric nanoparticles to a plasmonic nanoparticle system on absorption are studied. Nanorods, nanocones, and bipyramid nanoparticles are considered as the dielectric nanoparticles due to their elongated shape. Effects of geometric parameters, such as the radius, on the absorption of the system are studied separately. Optimal parameters of each dielectric nanoparticle are identified. Multiple simulations are completed for each dielectric nanoparticle type where the nanoparticles is placed randomly in a control volume for an approximation of the randomly scattered nature of the nanoparticles in PTT. Nanocones are found to be the best dielectric nanostructure for improving absorption when the orientation of the dielectric nanoparticle can be controlled, with a 228.5% increase in absorption efficiency. However, the non-symmetric nature of the nanocone diminishes the ab sorption improvement greatly, with only a 68.1% improvement in absorption when the particles are placed randomly. Comparisons between the nanorods, nanocones and the bipyramid nanoparticles show that the slanted shaped dielectric nanoparticles are more suitable for PTT applications, while the symmetric geometry of the bipyramid nanoparticles provides more consistent improvements.