Electrostatic Control of Excitonic Energies and Dynamics in a CdS Quantum Dot through Reversible Protonation of Its Ligands.
J Phys Chem Lett
; 7(19): 3954-3960, 2016 Oct 06.
Article
em En
| MEDLINE
| ID: mdl-27649043
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 â¼ 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 â¼4.3 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.
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Base de dados:
MEDLINE
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
J Phys Chem Lett
Ano de publicação:
2016
Tipo de documento:
Article
País de afiliação:
Estados Unidos