Assessment of the photothermal conversion efficiencies of tunable gold bipyramids under irradiation by two laser lines in a NIR biological window

Nanotechnology. 2019 Oct 4;30(40):405701. doi: 10.1088/1361-6528/ab2d90. Epub 2019 Jun 27.

Abstract

In this work, we present a thorough study on the evaluation of the photothermal conversion efficiencies of gold nanobipyramids (AuBPs) under irradiation by two phototherapeutic laser lines at 785 and 808 nm. Due to fine tunability of the longitudinal localized surface plasmon resonance (LSPR) of AuBPs along the entire biological window, AuBPs have great potential to be applied as efficient photothermal agents in specific hyperthermia applications. Aiming to identify the most suitable AuBPs for each laser line, here we synthetized AuBPs of six different aspect ratios with longitudinal LSPR ranging from 662 to 929 nm and compared their intrinsic photothermal properties in colloidal solutions under laser irradiation at various experimental parameters such as sample volume, optical density and laser power. In addition, the experimental plasmonic resonances of the as-prepared AuBPs were perfectly simulated and their theoretical extinction and absorption cross-sections provided by finite-difference time-domain technique. Finally, we found photothermal conversion efficiencies ranging from 40% to 97% for all AuBPs systems under both NIR irradiation laser lines concluding that for the 785 nm excitation wavelength the AuBPs with longitudinal LSPR at 802 nm are most efficient, whereas in the case of the 808 nm laser line the AuBPs with optical response at 812 nm exhibit the best thermal performance. These studies are crucial for designing AuBPs as effective phototherapy agents acting alone or in combination with other plasmon-based or plasmon-assisted therapies.