|場所||電子科学研究所 1F 会議室|
|所属等||Department of Chemistry, Rice University|
|タイトル||Steady-state absorption, scattering and time-resolved transient extinction spectra of single plasmonic nanoparticles|
Metallic nanoparticles possess unique optical properties and strong electric-field enhancements. These traits arise from surface plasmon resonances, which strongly depend of the size and shape of the nanoparticles and their surrounding media. The size and shape of nanoparticles that are chemically prepared are always heterogeneous. Single particle spectroscopy, correlated with high resolution electron microscopy, can take advantage of this heterogeneity, providing detailed spectroscopic information with respect to individual nanoparticle morphology. Optical characterization is usually performed using steady-state scattering methods, or extinction, which is the sum of absorption and scattering. However, separate measurements of the absorption and scattering are important. Absorption determines nanoparticle heating or hot electron generation, while scattering represents the strength of nanoparticle antenna. Complementary to steady-state spectroscopy methods, time-resolved transient spectroscopy provides additional dynamic information about electron thermalization, electron-phonon coupling, and acoustic vibration of the metallic nanoparticles after the surface plasmon decays.
In this talk, I will present steady-state absorption and scattering spectra on single gold nanospheres and nanorods. A comparison of the absorption spectra to the scattering spectra of the same individual gold nanoparticles reveals a blueshift of the absorption spectra. This is predicted by Mie theory but was previously not detectable in extinction measurements that measure the sum of absorption and scattering. We also found that the spectral shift between absorption and scattering for the longitudinal plasmon resonance decreases as a function of nanorod aspect ratio, in agreement with simulations. In addition, I will also discuss the acoustic properties of lithographically fabricated gold nanodisks on glass substrate where a thin titanium layer is required to promote the adhesion between gold and substrate. Using time-resolve transient extinction spectroscopy, we observed that the acoustic properties of gold nanodisks can be tuned by the titanium thickness that controls the binding strength of the nanostructures to the substrate.
|連絡先||世話人: グリーンフォトニクス研究分野 三澤 弘明・上野 貢生(内線9358)|