Electrostatic Control of Excitonic Energies and Dynamics in a CdS Quantum Dot through Reversible Protonation of Its Ligands

Christopher M. Thompson, Mohamad Kodaimati, Dana Westmoreland, Raul Calzada, Emily A Weiss

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9 Citations (Scopus)


This paper describes the pH dependence of the excitonic energies and dynamics of CdS quantum dots (QDs) capped with phosphonopropionate (PPA) in water. QDs capped with PPA carry a negative charge on their surfaces upon deprotonation of PPA above pH ∼ 8.5; the resultant electric field induces large changes in the QD's optical properties. Between pH 5.6 and 12.0, an increase in pH is accompanied by a 47-meV bathochromic shift in the bandgap of the QDs and a decrease in the Stokes shift by ∼4.3 meV/pH unit. An increase in the radiative recombination rate by a factor of 20.9 occurs on increasing the pH from 5.6 to 9.4. These observations are attributed to a shifting of the energy levels within the first exciton manifold, and are simulated using time-dependent density functional theory calculations on model Cd29S29 clusters surrounded by point charges.

Original languageEnglish
Pages (from-to)3954-3960
Number of pages7
JournalJournal of Physical Chemistry Letters
Issue number19
Publication statusPublished - Oct 6 2016


ASJC Scopus subject areas

  • Materials Science(all)

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