Fully fluorinated perfluorocarbon ligands are shown to modify the energetics and dielectric environment of quantum dots (QDs), resulting in a large hypsochromic shift in the optical gap. The original oleic acid (OA) ligands on PbS QDs can be completely replaced with thiolate and carboxylate-based perfluorocarbons, e.g., -SCF3 and CF3(CF2)14COOH (pFA), respectively. Ultraviolet photoelectron spectroscopy indicates that the work function varies by >1.3 eV depending on the electronegativity of the surface ligand, while cyclic voltammetry shows that an OA:pFA ratio of ∼2:1 increases the oxidation potential by 0.18 eV in solution. The diminished reduction potential of the conduction band is confirmed by photoinduced electron transfer experiments. The short thiolate ligands, -SCF3 and -SCH3, enhance the electron-donating ability of PbS QDs up to 7-fold because of an increase in the permeability of the ligand shell. This work shows that electron-withdrawing halogens like fluorine and chlorine can control the bandgap and band offsets of nanocrystals for the future design and optimization of functional organic/inorganic hybrid nanostructures.
|Number of pages||6|
|Journal||Chemistry of Materials|
|State||Published - Aug 14 2018|
Bibliographical noteFunding Information:
M.L.T. acknowledges support by the Alfred P. Sloan Foundation, National Science Foundation Grant CHE-1626673 for instrumentation, and Samsung GRO America. K.R.G. acknowledges the donors of the American Chemical Society Petroleum Research Fund for partial support of this research. The authors thank Prof. Valentine I. Vullev for use of his absorption spectrophotometer.
© 2018 American Chemical Society.
ASJC Scopus subject areas
- Chemistry (all)
- Chemical Engineering (all)
- Materials Chemistry