Shape and Size Effect on Photothermal Heat Elevation of Gold Nanoparticles: Absorption Coefficient Experimental Measurement of Spherical and Urchin-Shaped Gold Nanoparticles

Gold nanoparticles (GNP) are very suitable agents for thermal destruction of cancer cells because of their photothermal heating ability. In this work, photothermal properties of different sizes and shapes of GNPs were studied regarding different parameters such as GNP concentration, laser excitation intensity, and exposure time. By using the heat transfer theory, the temperature elevation in the GNP solutions was converted in temperature elevation at the GNP surface. This allows us to determine the absorption cross section (sigma(abs)) of two different sizes of spherical gold nanoparticles (GNS), which were compared with the theoretical calculations based on the Mie theory, and both results were in a good agreement. sigma(abs) was determined also for gold nanourchins with different sizes (50, 80, and 90 nm) with high precision. Finally, the temperature elevation speeds were experimentally measured for all GNPs, and we have demonstrated that they are proportional to the GNP surface area as demonstrated in the classical diffusive heat transport theory. The proposed approaches can be used to monitor the local heat generation around the GNP and pave the way to the optimization of the photothermal properties of GNPs.