Photoluminescence Quenching of CdSe/ZnS Quantum Dots by Molecular Ferrocene and Ferrocenyl Thiol Ligands

Photoluminescence quenching of CdSe/ZnS quantum dots (QDs) by molecular ferrocene and ferrocenyl thiols was investigated by steady-state absorption and emission spectroscopy. Modification of QD surfaces with ferrocenyl thiols exhibiting different lengths of the alkyl chains (6, 8, and 11 carbon units) was performed by ligand-exchange reaction. These alkyl chains function as spacers between the QDs and ferrocene. Diffusion-filtered NMR spectroscopy was applied to characterize the surface of the modified nanoparticles. Ferrocene and ferrocenyl thiols bound to the QD surface efficiently quenched the QD photoluminescence. Charge transfer between the photoexcited QD and ferrocene is ascribed as possible quenching mechanism. At maximum surface coverage the quenching efficiency of ferrocenyl thiols at the QD surface depends on the hydrocarbon spacer length.