Thermal Diffusivity Determination of Protoporphyrin IX Solution Mixed with Gold Metallic Nanoparticles

Nanoparticles appear to be ideally suited for applications in targeted thermal effects in medical therapies and photothermally activated drug delivery; all depend critically on the thermal transport between the nanoparticles and the surrounding liquid. In this work thermal lens spectroscopy (TLS) was used to determine the thermal diffusivity of protoporphyrin IX (PpIX) solutions mixed with gold metallic nanoparticles. PpIX disodium salt (DS) was used in a HCl solution at 25%. Fluids containing gold (Au) nanoparticles at different concentrations were prepared and added to the PpIX solutions. For each solution, UV-Vis spectroscopy was used to obtain the optical absorption spectrum, and transmission electron microscopy (TEM) was used to obtain the gold nanoparticle size. From the TLS signal intensity, it was possible to determine the characteristic time constant of the transient thermal by fitting the theoretical expression to the experimental data. From this characteristic time, the thermal diffusivity was obtained for each solution. The results show that the thermal diffusivity of PpIX mixed with gold nanoparticles increases with an increase of the nanoparticle metallic concentration.