Ferrocene-coated CdSe/ZnS quantum dots as electroactive nanoparticles hybrids

Electrochemical properties of core-shell CdSe/ZnS quantum dots (QDs) in a non-aqueous solution are presented. Cathodic reduction and anodic oxidation processes involving the QD HOMO and LUMO levels as well as defect states were identified by cyclic voltammetry. The electrochemical bandgap was estimated from the anodic and cathodic redox peaks and found to match well with the optical bandgap estimated from the absorption spectrum. The trioctylphosphine oxide ligands on the surface of the QDs were exchanged to electroactive ferrocenyl thiols and the resulting material was characterized by NMR and optical spectroscopy. Cyclic voltammetry showed that the redox potentials of the QDs are modified due to the presence of ferrocene on the surface of the QD. The QD oxidation peak decreased and the reduction peak shifted to more negative potentials. The concurrent shift of the ferrocene redox peaks indicates that the system displays features of a 'molecular hybrid', where both the QD and the ligand influence each other.