Heating Effects on Optical Properties of Metal Nano Particle

Abstract

Localized Surface Plasmon (LSPR) occurs on the interface of Metal Nano Particle (MNP) when illuminated with electromagnetic wave, at a specific electromagnetic energy (wavelength). In this work, we model the gold nanoparticle (AuNP) composite by its atomic polarizability, that is related to the absorption, and its dependence on temperature. To compare the resulted LSPR frequency shift when the AuNP system is heated, we synthesized the MNP composite of polymer (oleylamine) capped gold nanoparticle (AuOA) and measured the optical properties which is related to the LSPR resonance frequency through the atomic polarizability of the composite. The temperature dependence effect is observed by depositing the AuAO onto a thin film after mixing with a polymer solvent (P3HT : PCBM) and heating it. It is found that a perceptible blueshift of the LSPR signal is observed which is contrary to the prediction from the model. This effect can be attributed to the thermal expansion of the thin films due to the heating process. After heating, the relative distance between two nanoparticles becomes larger, thus the weakening of surface plasmon interaction between the particles.