Synthesis of Long Gold Nanorods as an Efficient Photothermal Agent in the Second Near-Infrared Window

Abstract

To date, intensive efforts have been devoted in the synthesis of various nanomaterials as photothermal agent in the first near-infrared (NIR) window (650-950 nm). Although the NIR-II window (1000-1350 nm) is recognized to offer more efficient tissue penetration and higher permissible exposure to excitation light, the corresponding photothermal agents have been scant. Here, we report a binary surfactant seeded growth method for high yield synthesis of long AuNRs (LAuNRs) as an efficient NIR-II photothermal agent. The as-synthesized LAuNRs with aspect ratio of 6.7 shows strong surface plasmon resonance band at 1064 nm, and demonstrates high photothermal conversion efficiency and excellent photothermal stability. When the AuNRs aqueous dispersion is covered with a 6 mm thick pork tissue as a model of biological tissues, its temperature can still be increased by 13.1 °C under a 1064 nm 1.0 W/cm2 laser irradiation. These results demonstrate the promising potential of the LAuNRs as an efficient photothermal agent in the NIR-II window.