Enhancing the Plasmon Resonance Absorption of Multibranched Gold Nanoparticles in the Near-Infrared Region for Photothermal Cancer Therapy: Theoretical Predictions and Experimental Verification

Abstract

Multibranched gold nanoparticles (M-AuNPs) can serve as photothermal agents for near-infrared (NIR) photothermal therapy (PTT) of cancer, but a major shortcoming is that they tend to strongly scatter NIR light, causing a significant reduction in absorption. This work addresses this issue, based on theoretical simulations and experimental determinations, to enhance the absorption and reduce the scattering of these materials by screening their structural parameters. Our finite-difference time-domain simulations predict that M-AuNPs with a core size of ∼25 nm, a tip number of 5, and a tip height of ∼40 nm (i.e., an aspect ratio of ∼2) are optimal for trapping NIR light and yielding the highest light-to-heat conversion efficiency (η) and for trapping NIR light of various polarization and incident directions. The predicted M-AuNPs were synthesized by a seed-mediated growth method, and the measured optical properties agreed well with the simulation results. The M-AuNPs were further used as photothermal agents f...