Open AccessUltrafast Dynamics of Colloidal Copper Nanorods: Intraband versus Interband Excitation
Author(s) -
Diroll Benjamin T.,
Jeong Soojin,
Ye Xingchen
Publication year - 2022
Publication title -
small science
Language(s) - English
Resource type - Journals
ISSN - 2688-4046
DOI - 10.1002/smsc.202100103
Subject(s) - excitation , materials science , fluence , plasmon , copper , nanorod , phonon , molecular physics , surface plasmon resonance , ultrashort pulse , infrared , resonance (particle physics) , dispersion (optics) , surface plasmon , atomic physics , condensed matter physics , optics , optoelectronics , nanoparticle , chemistry , laser , physics , nanotechnology , quantum mechanics , metallurgy
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 ( τ ep ) is less sensitive to excitation conditions than reports for gold. τ ep shortens 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 × 10 16 to 6.4 × 10 16 J m −3 K −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.