Enhancing near-infrared II photothermal conversion through anchoring numerous nanospheres to the edge of a gold nanosheet†

Abstract

Anisotropic noble metal nanostructures have shown remarkable structural benefits in near-Infrared (NIR) light absorption and high efficiency in photothermal conversion. In this study, we employ the seed growth strategy to create two-dimensional gold (Au) in-plane hybrid nanostructures, specifically designed with numerous quasi-spherical particles adorning the edge of a single plate, showcasing promising use in NIR-II photothermal conversion. The key to our successful synthesis lies in the doping of plate-like Au seeds with elemental selenium (Se), which plays a crucial role in restricting the island-like deposition of Au nanoparticles predominantly to the edge regions. With this unique hybrid structure, we observed a notable red-shift in the absorption peak towards longer wavelengths, ensuring full coverage of the NIR-II regions. A photothermal conversion efficiency of 42% was achieved, as evaluated using a water suspension under a 1064 nm laser at a power density of 1.0 W cm⁻². Furthermore, our investigation into photothermal stability revealed excellent durability even after multiple heating and cooling cycles. Finite-difference time-domain (FDTD) simulations confirm that polarization of surface charges along the edge region is achieved by constructing such a “plate@ sphere” in-plane hybrid structure, thereby affirming successful hot spot engineering. This research demonstrates the potential to manipulate the growth mode of two-dimensional Au nanostructures through non-metal doping during seeded growth and validates the use of in-plane hybrid two-dimensional nanostructures for photothermal conversion, providing insights for the rational design of high-performance NIR-II photothermal nanomaterials tailored for biomedical applications.