Atomically Precise Au 42 Nanorods with Longitudinal Excitons for an Intense Photothermal Effect

作者：Yingwei Li, Yongbo Song, Xinwen Zhang, Tongyu Liu, Tingting Xu, He Wang, De‐en Jiang, Rongchao Jin · 发表于：Journal of the American Chemical Society · 年份：2022 · DOI：10.1021/jacs.2c03948 · 被引用次数：120 · 研究领域：Nanocluster Synthesis and Applications、Advanced Nanomaterials in Catalysis、Gold and Silver Nanoparticles Synthesis and Applications

Metallic-state gold nanorods are well known to exhibit strong longitudinal plasmon excitations in the near-infrared region (NIR) suitable for photothermal conversion. However, when the size decreases below ∼2 nm, Au nanostructures become nonmetallic, and whether the longitudinal excitation in plasmonic nanorods can be inherited is unknown. Here, we report atomically precise rod-shaped Au 42 (SCH 2 Ph) 32 with a hexagonal-close-packed Au 20 kernel of aspect ratio as high as 6.2, which exhibits an intense absorption at 815 nm with a high molar absorption coefficient of 1.4 × 10 5 M –1 cm –1 . Compared to other rod-shaped nanoclusters, Au 42 possesses a much more effective photothermal conversion with a large temperature increase of ∼27 °C within 5 min (λ ex = 808 nm, 1 W cm –2 ) at an ultralow concentration of 50 μg mL –1 in toluene. Density functional theory calculations show that the NIR transition is mainly along the long axis of the Au 20 kernel in Au 42, i.e., a longitudinal excitonic oscillation, akin to the longitudinal plasmon in metallic-state nanorods. Transient absorption spectroscopy reveals that the fast decay in Au 42 is similar to that of shorter-aspect-ratio nanorods but is followed by an additional slow decay with a long lifetime of 2400 ns for the Au 42 nanorod. This work provides the first case that an intense longitudinal excitation is obtained in molecular-like nanorods, which can be used as photothermal converters and hold potential in biomedical therapy, ...