Photothermal characteristics of gold nanoparticles of different size, shape, and composition: application in photothermal therapy

Due to its safety and high efficiency, photothermal therapy has been actively explored as minimally invasive approach to cancer therapy. The selection of nanoparticles to achieve photo thermal conversion efficiently is based on the absorption properties of the nanoparticles. Finite difference time domain method (FDTD) was used to calculate spectral absorption efficiencies for seven common types of gold nanoparticles: nanospheres, nanoshells, nanorods, nanosheets, nanocages, nanostars, and nanoflowers. The calculated results clearly demonstrate the dependence of absorption efficiencies and resonance wavelengths on the geometrical parameters of the nanoparticles. Via the volume absorption efficiencies, photothermal performance of the seven types of gold nanoparticles is compared quantitatively. The gold nanosheets are proved to offer the most superior photothermal performance in the near-infrared region (NIR) among the seven types of nanoparticles. From the vector distributions of the electric current densities, it is clearly shown that the resonant electric currents in the gold nanoparticles play the major role on the ultra large absorption cross-section in the NIR.