Effects of Nanoscale Structures on Photothermal Heating Behaviors of Surface-Modified Fe₃O₄ Nanoparticles

In this investigation, the photothermal heating of superparamagnetic Fe3O4 nanoparticles was carried out by irradiating with either 785[Formula: see text]nm or 808[Formula: see text]nm near infrared (NIR) lasers. The effects of nanoparticle configuration, arrangement, and surface coating on the photothermal heating behavior were investigated for different Fe3O4 nanoparticle systems. Depending on the preparation method, Fe3O4 nanoparticles with mean hydrodynamic diameter ranging from 30[Formula: see text]nm to 250[Formula: see text]nm were synthesized. Photothermal transduction efficiency is a measure of light to thermal energy conversion; the highest efficiency obtained was 56% by 785[Formula: see text]nm and 42% by 808[Formula: see text]nm light irradiation for poly(acrylic) acid (PAA) coated Fe3O4 samples. With this conversion efficiency, the PAA-coated Fe3O4 nanoparticles raised the solution temperature [Formula: see text] [Formula: see text]C above physiological temperature, which is sufficient for cancer therapeutics. Photothermal transduction efficiency was found to decrease as the particle hydrodynamic diameter increased. Nanoparticle absorption and scattering properties were found different due to surface modifications. UV-VIS-NIR absorption spectroscopy was carried out and results were analyzed using the Mie scattering theory. Experimental photothermal transduction efficiency was found to scale with the theoretical results for a particular wavelength. These results have significance in the design and development of the Fe3O4 nanoparticle systems for effective cancer therapy with NIR light.