Recently, gold nanoparticles have attracted a lot of interest in research because of their unique properties. this is mainly a consequence of the localized surface plasmonic resonance defined by collective oscillations of free electrons of gold nanoparticles under an external electromagnetic field. Due of their plasmonic resonances, gold nanoparticles absorb strongly photonic energy at visible or infrared frequencies, and converting it into heat, leading to an increase in lattice temperature. As a result gold nanoparticles can be used as effective nano-heat sources, making the possibility of selectively targeting cancer cells to induce highly localized thermal destruction.

The present work deals with numerical study of the ultrafast thermal dynamics of exchange of electron-phonon energy inside Gold nanoparticle with a diameter of 40 nm heated by femtosecond pulses laser. In order to present a descriptive analysis, a unique spherical Gold nanoparticle is assumed heated by one single Gaussian pulse laser and cooled in water (the properties of water are comparable to biological tissues). Two temperatures model is used to describe the energy exchange dynamics of gold nanoparticle. Electron and phonon temperatures were computed for 100 femtoseconds duration pulse. The temperature at the gold nanoparticle/water interface is calculated and the effect of laser fluence on this temperature is reported.