Ultrafast electron dynamics in metal and metal-semiconductor nanoparticles

Dynamique ultrarapide dans les nanoparticules métalliques et métal-semiconducteur

 

The physical properties of materials at nanoscale are strongly modified as compared to the bulk one, due to the confinement of the electron and vibrational motion. These new properties are determined by both the characteristics of the constituting nano-objects (nature, size, form, structure, …) and of their environment (matrix, bound molecules, other nano-objects, …). Ultrafast electron interactions inside the nano-objects and with the environment (due to the increased role of surface effects and, in particular, energy and charge transfer), play a fundamental role here. Time-resolved optical techniques permit a direct and selective study of these mechanisms and of their modification due to confinement.

Through optical pump-probe spectroscopy we have characterized the ultrafast electron dynamics in noble metal nanoparticles (Au and Ag) and the dependence on the electron-electron and electron-lattice coupling with nanoparticle size and environment. We aim at extending our investigations to the very small size range (<3 nm) to elucidate a regime where a transition is expected from solid-like behavior (typical in metal nanoparticles of a few nanometers) to a molecular electronic description (expected for clusters with a small number of atoms).

 

 

While nano-objects formed by a single material have been extensively investigated, the optical properties of nano-hybrids formed by different materials are still little studied, though combination of the nanoscale responses of their components offer wide possibilities for developing novel plasmonic systems. In the case of semiconductor-metal hybrid nanosystems (CdS-Au nanomatchsticks) we have investigated the ultrafast (<20 fs) electron transfer from metal to semiconductor after selective photoexcitation of the metal component, with potential applications for solar energy harvesting.

The physical properties of materials at nanoscale are strongly modified as compared to the bulk one, due to the confinement of the electron and vibrational motion. These new properties are determined by both the characteristics of the constituting nano-objects (nature, size, form, structure, …) and of their environment (matrix, bound molecules, other nano-objects, …). Ultrafast electron interactions inside the nano-objects and with the environment (due to the increased role of surface effects and, in particular, energy and charge transfer), play a fundamental role here. Time-resolved optical techniques permit a direct and selective study of these mechanisms and of their modification due to confinement.

Through optical pump-probe spectroscopy we have characterized the ultrafast electron dynamics in noble metal nanoparticles (Au and Ag) and the dependence on the electron-electron and electron-lattice coupling with nanoparticle size and environment. We aim at extending our investigations to the very small size range (<3 nm) to elucidate a regime where a transition is expected from solid-like behavior (typical in metal nanoparticles of a few nanometers) to a molecular electronic description (expected for clusters with a small number of atoms).

 

 

While nano-objects formed by a single material have been extensively investigated, the optical properties of nano-hybrids formed by different materials are still little studied, though combination of the nanoscale responses of their components offer wide possibilities for developing novel plasmonic systems. In the case of semiconductor-metal hybrid nanosystems (CdS-Au nanomatchsticks) we have investigated the ultrafast (<20 fs) electron transfer from metal to semiconductor after selective photoexcitation of the metal component, with potential applications for solar energy harvesting.

 

Selection of publications on the investigations on the ultrafast electron dynamics

Selection of publications on the investigations on the ultrafast electron dynamics

 

T. Stoll, A. Crut, P. Maioli, N. Del Fatti, and F. Vallée

"Advances in femto-nano-optics: ultrafast nonlinearity of metal nanoparticles"

European Physical Journal B 87, 260 (2014) (colloquium paper)

 

D. Mongin, E. Shaviv, P. Maioli, A. Crut, U. Banin, N. Del Fatti, and F. Vallée

"Ultrafast Photoinduced Charge Separation in Metal–Semiconductor Nanohybrids"

ACS Nano 6, 7034-7043 (2012)

 

A. Arbouet, C. Voisin, D. Christofilos, P. Langot, N. Del Fatti, F. Vallée, J. Lermé, G. Celep, E. Cottancin, M. Gaudry, M. Pellarin, M. Broyer, M. Maillard, M. P. Pileni, and M. Treguer

"Electron-Phonon Scattering in Metal Clusters"

Physical Review Letters 90, 177401 (2003)

 

C. Voisin, D. Christofilos, N. Del Fatti, F. Vallée, B. Prével, E. Cottancin, J. Lermé, M. Pellarin, and M. Broyer

"Size-Dependent Electron-Electron Interactions in Metal Nanoparticles"

Physical Review Letters 85, 2200 (2000)

 

 

Full list of publications of the FemtoNanoOptics group

Liste complète des publications de l'équipe FemtoNanoOptics

 

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