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Collective Behavior of Electrons and Atoms - Prashant K. Jain - Mardi 3 juin 2014 à 15 h 30

Prashant K. Jain - Department of Chemistry, University of Illinois Urbana Champaign

Mardi 3 juin 2014 à 15 h 30 - INSP - 4 place Jussieu - 75252 PARIS Cedex 05 - Barre 22-32, 2e étage, salle 201


Electrons : Plasmon resonances have captured the interest of the scientific community due to their strong interactions with light and applications in areas like sub-diffraction-limit imaging, chemical sensing, and photovoltaics. Whereas, it is popular to associate plasmon resonances with electron-dense metals, my talk will describe the ubiquity of plasmon resonances, as exemplified by the recent achievement of such resonances in nanostructures of semiconductors and oxides by artificial introduction of electronic carriers. More recently, we have found that a plasmon resonance can be sustained by as few as four carriers, much smaller in number than conventionally thought. This finding raises questions about the nature of these few-carrier plasmon resonances, and also about the very concept of a plasmon resonance. Therefore, we are now studying, using both experiment and theory, how a plasmon resonance emerges as charge carriers are progressively added to a semiconductor nanocrystal. My talk will share how non-metallic plasmon resonances are providing new insight into the collective nature of a plasmon excitation, while also expanding the technological domain of plasmonics.

Atoms : Time permitting, in the second part of my talk, I will describe the use of single-nanoparticle spectroscopy to uncover the rich dynamics of chemical transformations, otherwise hidden in bulk studies due to the process of ensemble averaging. By using plasmonic and photoluminescence spectroscopy, we have studied exchange reactions on the level of single noble metal and semiconductor nanocrystals. Our studies have revealed that collective dynamics of atoms is a hallmark of such chemical reactions.