Ultrafast Dynamics of Colloidal Copper Nanorods: Intraband versus Interband Excitation
Ultrafast Dynamics of Colloidal Copper Nanorods: Intraband versus Interband Excitation
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DOI：
10.1002/smsc.202100103
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
B. Diroll;Soojin Jeong;Xingchen Ye
中科院分区：
文献类型：
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作者：
B. Diroll;Soojin Jeong;Xingchen Ye
胶体铜纳米棒（NR）显示横向和纵向局部表面等离子体共振。纵向局域表面等离子体激元模式可通过具有NR纵横比的近红外电磁辐射能量来调谐。在跨越带内和带间激发（0.79−3.50 eV）的激发条件下研究了铜NR的可见光和近红外瞬态光学响应。在可见光和近红外区域，样品在带内激发（<2 eV）下的光谱响应与它们在带间激发（>2 eV）下的响应显著不同。然而，根据泵浦能量密度相关测量估计的电子-声子耦合的时间尺度（τep）对激发条件的敏感性低于金的报告。τ ep从带内激发（在可见探针能量下）的1.616 fs略微缩短到带间激发的1.565 fs。观察到的动力学对应于样品的平均电子-声子耦合参数，在所有条件下从4.4 × 1016到6.4 × 1016 J m− 3 K −1变化，这与块状铜相似。此外，相干声学声子被观察到的纵向局域表面等离子体共振的振荡周期范围内反映样品尺寸色散。
Colloidal copper nanorods (NRs) display transverse and longitudinal localized surface plasmon resonances. The longitudinal localized surface plasmon modes are tunable through the near‐infrared electromagnetic radiation energies with NR aspect ratios. Visible and near‐infrared transient optical response of the copper NRs is investigated under excitation conditions spanning intraband and interband excitation (0.79−3.50 eV). In both the visible and near‐infrared regions, the spectral response of the samples under intraband excitation (<2 eV) differs substantially from their response under interband excitation (>2 eV). However, the timescale of the electron−phonon coupling estimated from pump fluence‐dependent measurements (τep) is less sensitive to excitation conditions than reports for gold.τepshortens slightly from ≈616 fs with intraband excitation (at visible probe energies) to ≈565 fs with interband excitation. The observed dynamics correspond to an average sample electron−phonon coupling parameter varying across all conditions from 4.4 × 1016to 6.4 × 1016J m−3K−1, which is similar to bulk copper. Furthermore, coherent acoustic phonons are observed for the longitudinal localized surface plasmon resonance with a range of oscillatory periods reflecting sample size dispersion.