Plasmonic aluminum nanoparticles have emerged as an exciting new materials platform due to the high natural abundance of aluminum, their ability to be synthesized in the solution phase, and the potential of these materials to be used for photocatalysis and sensing. However, the photothermal properties of solution-processed aluminum nanoparticles, in particular, how phonon energy transfer depends on the particle size and surface properties, are critical for practical applications and are currently unexplored. Here we use transient absorption spectroscopy, in combination with simulations of phonon and thermal energy dissipation, to investigate the photoresponses of aluminum nanoparticles of various diameters (54, 85, 121, and 144 nm) suspended in 2-propanol. Fast thermal-transfer rates to the solvent (170–280 ps) are observed for particles of all sizes and are facilitated by native oxide coverage, as verified by a two-interface thermal energy-transfer model. Size-dependent phonon “breathing”/vibrational modes are also observed as oscillations in the total cross-section. We find that both the oscillation frequency and the damping rate increase as the diameter of the particles decreases. On the basis of the results of finite element calculations, we attribute the damping strength and oscillation period observed to a combination of the noncrystalline nature of the native oxide shell and the presence of surface-bound ligands, both of which increase the vibrational mode damping rates relative to bare Al and Al particles with a bare crystalline oxide shell. These insights should guide future work on controlling energy transfer through the use of size and surface tuning in sustainable aluminum nanomaterial systems for applications in catalysis and sensing.

中文翻译：

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溶液处理的铝纳米颗粒的尺寸和表面依赖性光响应

由于铝的自然丰富，在溶液相中合成的能力以及这些材料用于光催化和传感的潜力，等离子铝纳米颗粒已经成为令人兴奋的新材料平台。然而，溶液处理的铝纳米颗粒的光热性质，特别是声子能量转移如何取决于粒径和表面性质，对于实际应用是至关重要的，目前尚未得到开发。在这里，我们使用瞬态吸收光谱，结合声子和热能耗散的模拟，研究了悬浮在2-丙醇中的各种直径（54、85、121和144 nm）铝纳米颗粒的光响应。通过两界面热能转移模型验证，观察到各种尺寸的颗粒都有快速的热转移速率（170-280 ps），并且被天然氧化物覆盖所促进。与尺寸有关的声子“呼吸” /振动模式也被观察为整个横截面的振荡。我们发现随着颗粒直径的减小，振荡频率和阻尼率都增加。根据有限元计算的结果，我们将观察到的阻尼强度和振荡周期归因于天然氧化物壳的非晶性质和表面结合的配体的存在，两者都增加了振动模态阻尼率相对于裸露的Al和具有裸露的结晶氧化物壳的Al颗粒。