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Coupled Exciton and Charge-Transfer Resonances in the Raman Enhancement of Phonon Modes of CdSe Quantum Dots (QDs)

NCJ Number
304221
Journal
Journal of Physical Chemistry C Volume: 118 Issue: 33 Dated: 2014 Pages: 19415–19421
Author(s)
Syed K. Islam ; Mohammad A. Sohel ; John R. Lombardi
Date Published
2014
Length
7 pages
Annotation

This article reports on a project that observed the enhancement of a transverse optical (TO) phonon mode of e1 symmetry and a normally forbidden surface optical (SO) phonon mode of b1 symmetry in CdSe quantum dots (QDs) due to adsorption of 4-mercaptopyridine molecules.

Abstract

The former was observed in 3, 4, and 5 nm diameter particles, while the latter was observed only in the 2 nm particles. Maximum enhancement of the phonon modes was obtained through a coupling of the charge-transfer transition and the exciton transition, which are in resonance with the laser energy. Selection rules, using Herzberg–Teller (vibronic) coupling, were invoked to explain the observed enhancements. (publisher abstract modified)