Graphene coated gold nanoparticles: an emerging class of nanoagents for photothermal therapy applications.

Graphene coated gold nanoparticles (GGNPs) have attracted great attention in recent years because of their high thermal stability and unique optical properties. In this paper, we study photothermal properties of GGNPs using the Mie and Gans theories combined with the Pennes bioheat equation. The effect of various sizes and different shapes of GGNPs such as nanosphere, nanorod and nanodisc are taken into account. The extinction efficiency and temperature distribution in tumor tissue show that graphene coated gold nanorods, because of the high temperature rise during laser irradiation, are more suitable candidates for photothermal therapy (PTT) applications. Also, we show that the extinction peak of graphene coated gold nanorods can be adjusted in the biological windows by increasing the graphene shell thickness and/or by changing their aspect ratio. Finally, we investigated the effect of the number of graphene layers upon the temperature rise in the tumor and found that the temperature rise increases with increasing number of graphene layers. Our findings introduce a new class of nanoagents which can be used in PTT applications.