Jeong Jaeyoung, Shin Hyun-Hang, Kim Zee Hwan
Department of Chemistry, Seoul National University, Seoul 08826, Republic of Korea.
ACS Nano. 2024 Sep 10;18(36):25290-25301. doi: 10.1021/acsnano.4c08521. Epub 2024 Aug 26.
Plasmon photocatalysis reactions are thought to occur through vibrationally activated reactants, driven by nonthermal energy transfer from plasmon-induced hot carriers. However, a detailed quantum-state-level understanding and quantification of the activation have been lacking. Using anti-Stokes surface-enhanced Raman scattering (SERS) spectroscopy, we mapped the vibrational population distributions of reactants on plasmon-excited nanostructures. Our results reveal a highly nonthermal distribution with an anomalously enhanced population of multiquantum excited states ( ≥ 2). The shape of the distribution and its dependence on local field intensity and excitation wavelength cannot be explained by photothermal heating or vibronic optical transitions of the metal-molecule complex. Instead, it can be modeled by hot electron-molecule energy transfer mediated by the transient negative ions, establishing direct links among nonthermal reactant activation, plasmon-induced hot electrons, and negative ion resonances. Moreover, the presence of multiquantum excited reactants, which are far more reactive than those in the ground state or first excited state, presents opportunities for vibrationally controlling chemical selectivities.
表面等离子体光催化反应被认为是通过振动激活的反应物发生的，由表面等离子体激元诱导的热载流子的非热能转移驱动。然而，目前缺乏对这种激活过程的详细量子态水平的理解和量化。利用反斯托克斯表面增强拉曼散射（SERS）光谱，我们绘制了反应物在表面等离子体激元激发的纳米结构上的振动布居分布。我们的结果揭示了一种高度非热的分布，其中多量子激发态（≥2）的布居异常增强。这种分布的形状及其对局部场强和激发波长的依赖性不能用光热加热或金属 - 分子复合物的振动电子光学跃迁来解释。相反，它可以通过瞬态负离子介导的热电子 - 分子能量转移来建模，从而在非热反应物激活、表面等离子体激元诱导的热电子和负离子共振之间建立直接联系。此外，多量子激发反应物的存在，其反应性远比基态或第一激发态的反应物高，为振动控制化学选择性提供了机会。
