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Abbreviated Journal Title

J. Chem. Phys.

Keywords

Cadmium Alloys; Crystal Field Interactions; Density Functional Theory; Gaussian Processes; Light Absorption; Oxidation; Quantum Chemistry; Quantum Dots; Red Shift; Ultra-Stable Nanoparticles; Cdse Nanocrystals; Semiconductor; Nanocrystals; Electronic-Properties; Ab-Initio; Pseudopotential Theory; Surface-Structure; Clusters; Monodisperse; Growth; Physics; Atomic; Molecular & Chemical

Abstract

We report Gaussian basis set density functional theory (DFT) calculations of the structure and spectra of several colloidal quantum dots (QDs) with a (CdSe)(n) core (n=6,15,17), that are either passivated by trimethylphosphine oxide ligands, or unpassivated and oxidized. From the ground state geometry optimization results we conclude that trimethylphosphine oxide ligands preserve the wurtzite structure of the QDs. Evaporation of the ligands may lead to surface reconstruction. We found that the number of two-coordinated atoms on the nanoparticle's surface is the critical parameter defining the optical absorption properties. For (CdSe)(15) wurtzite-derived QD this number is maximal among all considered QDs and the optical absorption spectrum is strongly redshifted compared to QDs with threefold coordinated surface atoms. According to the time-dependent DFT results, surface reconstruction is accompanied by a significant decrease in the linear absorption. Oxidation of QDs destroys the perfection of the QD surface, increases the number of two-coordinated atoms and results in the appearance of an infrared absorption peak close to 700 nm. The vacant orbitals responsible for this near infrared transition have strong Se-O antibonding character. Conclusions of this study may be used in optimization of engineered nanoparticles for photodetectors and photovoltaic devices.

Journal Title

Journal of Chemical Physics

Volume

131

Issue/Number

4

Publication Date

1-1-2009

Document Type

Article

Language

English

First Page

6

WOS Identifier

WOS:000268613700007

ISSN

0021-9606

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