Radiative properties of gold nanorod solutions and its temperature distribution under laser irradiation: Experimental investigation

Radiative properties of noble metal nanoparticle play important roles in enhanced photothermal conversion applications, and intensively affect the temperature distribution of the dispersed media. In order to investigate the radiative properties of two kinds of gold nanorods solutions (GNRs), a customized integrating sphere optical system is constructed to measure the hemispherical transmittance and reflectance of GNRs. The absorption and extinction coefficients of GNRs are acquired by solving an inverse radiation problem. The ratio of absorption coefficient to extinction coefficient is used to evaluate the photothermal conversion efficiency of GNRs. At the same time, the temperature distributions of GNRs under laser irradiation are measured by thermocouples and an infrared camera. The effects of particle concentration, laser incident power, and particle size on the temperature distribution of GNRs are analyzed. The results indicate that the particle concentration has an important effect on the temperature profile of GNRs. A suitably lower concentration can disperse more laser energy into the deeper tissue, thereby enhancing the effect of the plasmonic photothermal therapy. Moreover, for present two kinds of GNRs with identical extinction coefficient at 808 nm wavelength, the effect of particle size on the temperature distribution is relatively weaker, though it has a significant influence to their spectral radiative properties.

► The absorption and extinction coefficients of gold nanorod solutions are measured.
► The particle concentration has a great influence to the temperature profile.
► A suitably lower concentration can enhance the effect of photothermal therapy.
► The effect of particle sizes on the temperature distribution is weak.