Conversion of Laser Light Energy into Heat with Gold Nanoparticles

K. Jiang and A.O. Pinchuk
University of Colorado - Colorado Springs, Colorado, United States

Keywords: plasmonics, hyperthermia, laser, nanoparticles

Laser light-to-heat energy transformation with gold nanoparticles was experimentally and theoretically studied by assessing the temperature profiles of laser-activated particle suspensions in water. Gold nanoparticles with sizes ranging from 10 nm to 54 nm were synthesized by chemical reduction using sodium borohydride, sodium citrate, or hydroquinone as reducing agents. As-synthesized gold nanoparticle solution (1 mL) was loaded into a quartz cuvette and exposed to a CW green laser (532 nm). The transducing efficiency was then determined by plotting temperature increase as a function of laser power extinction. The efficiency increase from 0.646 to 0.817 as the particle size decreases from 54 to 10 nm. The results indicate that the photothermal properties of gold nanoparticles are size-tunable, and smaller nanoparticles possess higher transduction efficiencies as they have higher absorption/extinction ratios according to Mie theory. We further expanded our Mie theory calculations of absorption/extinction ratios to a broader range of diameters and wavelengths. These studies are crucial for practical applications of gold nanoparticles in nanotechnology and bioengineering, such as enhancing the treatment efficiency of laser surgery.