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

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

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
Volume7
Issue number19
DOIs
Publication statusPublished - Oct 6 2016

ASJC Scopus subject areas

  • Materials Science(all)

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