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

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• 作者：Syed K. Islam ; Mohammad A. Sohel ; John R. Lombardi
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：August 21, 2014
• 年：2014
• 卷：118
• 期：33
• 页码：19415-19421
• 全文大小：410K
• ISSN：1932-7455

文摘

We report the observation of 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. The former is observed in 3, 4, and 5 nm diameter particles, while the latter is observed only in the 2 nm particles. Maximum enhancement of the phonon modes is 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鈥揟eller (vibronic) coupling are invoked to explain the observed enhancements.