Pla lasmonic Nanoparticle les Locali lized Surface Pla lasmon - PowerPoint PPT Presentation

Pla lasmonic Nanoparticle les

Locali lized Surface Pla lasmon Resonance light-induced collective oscillation of the conduction electrons at the surface of a metallic nanostructure. Frequency of oscillation depends on  composition  geometrical shape and  nature of their chemical environment. 2 J. Phys. Chem. B 2003 , 107 , 668 – 677

Locali lized Surface Pla lasmon Resonance light-induced collective oscillation of the conduction electrons at the surface of a metallic nanostructure. 3 J. Phys. Chem. B 2003 , 107 , 668 – 677 J. Am. Chem. Soc. 2000 , 122 , 12890.

Excited State Relaxation Processes Electron-electron scattering: 100s of fs Electron-Phonon coupling: 1-4 ps Phonon-phonon coupling: 100 ps

Excited State Relaxation Processes Electron-electron scattering: 100s of fs Electron-Phonon coupling: 1-4 ps Phonon-phonon coupling: 100 ps

Excited State Relaxation Processes Chem. Rev. 2011 , 111 , 3858-3887

Transient absorption spectra Au nanoparticles (15 nm). Femtosecond laser pulse of 400nm. transient absorption signal at 520nm, plasmon bleach maximum Electron-phonon coupling: 3.1 ps Phonon-phonon coupling: 90 ps Link et al. Annu. Rev. Phys. Chem. 2003 , 54 , 331 – 366 7

Pump power dependence of tim ime constants Extrapolation to zero pump power: t e-ph = 0.65 ps, same as bulk gold Hartland and coworkers, J. Chem. Phys. 2000 , 112 , 5942

Ele lectron-electron coupli ling in in Ag particles Increases to saturation with particle size Broyer and coworkers, Phys. Rev. Lett . 2000 , 85 , 2200

Gold nanorods Transverse and Longitudinal Modes pulse energy τ th (ps) A th τ e-ph (ps) A e-ph τ ph-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 Scherer and coworkers, J. Phys. Chem. C 2007 , 111 , 116

Effect of cry rystallinity 20 nm Tang and Ouyang, Nat. Mater. 2007 , 6 , 754 Defects: electron-phonon coupling

Absorption in in Au aggregates • Broad red shifted absorption: nanoparticle aggregates • Strong electromagnetic coupling between closely spaced aggregates Link et al. J. Phys. Chem. B 1999 , 103 , 8410 – 8426 12

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 Link et al. J. Phys. Chem. B 1999 , 103 , 8410 – 8426 13

Multicomponent nanoparticle les Pt-Au alloy 0.65 ps 0.21 ps Here, r ( e F ) = 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 14 Hartner et al. J. Chem. Phys. 2001 , 114 , 2760

Multicomponent nanoparticle les Au-Ag alloy and core-shell High pump power: No change in electron-phonon coupling time El Sayed et al. J. Chem. Phys. 1999 , 111 , 1255 Hartner et al. J. Phys. Chem. B 2000 , 104 , 9954 15

Multicomponent nanoparticle les Au-Ag alloy and core-shell High pump power: No change in electron-phonon coupling time Low pump power: Electron-phonon resonance time varies linearly with composition r ( e F ) Au = r ( e F ) Ag So, a Au = x Au El Sayed et al. J. Chem. Phys. 1999 , 111 , 1255 Hartner et al. J. Phys. Chem. B 2000 , 104 , 9954 Langot et al. Faraday Discuss . 2008 , 138 , 137 16

Multicomponent nanoparticle les Ni-Ag core-shell Why? Not clear Langot et al. Faraday Discuss. 2008 , 138 , 137 17

Photoluminescence from pla lasmonic nanoparticle les Nano Lett. 2017 , 17 , 7914-7918 18