SLIDE 1
Pla lasmonic Nanoparticle les
SLIDE 2 Frequency of oscillation depends on
- composition
- geometrical shape and
- nature of their chemical environment.
2
light-induced collective oscillation of the conduction electrons at the surface of a metallic nanostructure.
Locali lized Surface Pla lasmon Resonance
- J. Phys. Chem. B 2003, 107, 668–677
SLIDE 3 light-induced collective oscillation of the conduction electrons at the surface of a metallic nanostructure.
3
- J. Am. Chem. Soc. 2000, 122, 12890.
Locali lized Surface Pla lasmon Resonance
- J. Phys. Chem. B 2003, 107, 668–677
SLIDE 4
Excited State Relaxation Processes
Electron-electron scattering: 100s of fs Electron-Phonon coupling: 1-4 ps Phonon-phonon coupling: 100 ps
SLIDE 5
Excited State Relaxation Processes
Electron-electron scattering: 100s of fs Electron-Phonon coupling: 1-4 ps Phonon-phonon coupling: 100 ps
SLIDE 6 Excited State Relaxation Processes
- Chem. Rev. 2011, 111, 3858-3887
SLIDE 7 Transient absorption spectra
Au nanoparticles (15 nm). Femtosecond laser pulse of 400nm. transient absorption signal at 520nm, plasmon bleach maximum
Link et al. Annu. Rev. Phys. Chem. 2003, 54, 331–366
7
Electron-phonon coupling: 3.1 ps Phonon-phonon coupling: 90 ps
SLIDE 8
Pump power dependence of tim ime constants
Hartland and coworkers, J. Chem. Phys. 2000, 112, 5942
Extrapolation to zero pump power: te-ph = 0.65 ps, same as bulk gold
SLIDE 9
Ele lectron-electron coupli ling in in Ag particles
Increases to saturation with particle size
Broyer and coworkers, Phys. Rev. Lett. 2000, 85, 2200
SLIDE 10
Gold nanorods
Transverse and Longitudinal Modes
Scherer and coworkers, J. Phys. Chem. C 2007, 111, 116
pulse energy τth (ps)Ath τe-ph (ps) Ae-ph τph-ph (ps) 0.42 nJ 0.20 4.7 1.6 1.5 120 0.63 nJ 0.18 7.3 1.8 2.1 120 0.84 nJ 0.16 10 2.0 2.8 120 1.05 nJ 0.17 12 2.1 3.3 120 1.6 nJ 0.16 18 2.6 4.7 120 2.1 nJ 0.75 25 2.9 6.2 120
SLIDE 11
Effect of cry rystallinity
Tang and Ouyang, Nat. Mater. 2007, 6, 754
Defects: electron-phonon coupling
20 nm
SLIDE 12 Absorption in in Au aggregates
- Broad red shifted absorption: nanoparticle aggregates
- Strong electromagnetic coupling between closely spaced aggregates
12
Link et al. J. Phys. Chem. B 1999, 103, 8410–8426
SLIDE 13 Transient ble leach dynamics
Increase in electron oscillation-phonon spectral overlap and interfacial scattering with increasing extent of aggregation leading to faster e-ph relaxation time
13
Link et al. J. Phys. Chem. B 1999, 103, 8410–8426
SLIDE 14 Multicomponent nanoparticle les
Hartner et al. J. Chem. Phys. 2001, 114, 2760
14
0.65 ps 0.21 ps Here, r(eF) = Density of states at Fermi level Electron-phonon coupling: Phonon emission from populated electronic states near the Fermi level. Its rate depends on the density of available electronic states at lower energy Pt-Au alloy
SLIDE 15 Multicomponent nanoparticle les
Hartner et al. J. Phys. Chem. B 2000, 104, 9954
15
Au-Ag alloy and core-shell
El Sayed et al. J. Chem. Phys. 1999, 111, 1255
High pump power: No change in electron-phonon coupling time
SLIDE 16 Multicomponent nanoparticle les
Hartner et al. J. Phys. Chem. B 2000, 104, 9954
16
High pump power: No change in electron-phonon coupling time Au-Ag alloy and core-shell
El Sayed et al. J. Chem. Phys. 1999, 111, 1255 Langot et al. Faraday Discuss. 2008, 138, 137
Low pump power: Electron-phonon resonance time varies linearly with composition r(eF)Au = r(eF)Ag So, aAu = xAu
SLIDE 17 Multicomponent nanoparticle les
17
Ni-Ag core-shell
Langot et al. Faraday Discuss. 2008, 138, 137
Why? Not clear
SLIDE 18 Photoluminescence from pla lasmonic nanoparticle les
18
Nano Lett. 2017, 17, 7914-7918
