Photoreactivity of a quantum dot-ruthenium nitrosyl conjugate.

We describe the use of cadmium telluride quantum dots (CdTe QDs) as antennas for the photosensitization of nitric oxide release from a ruthenium nitrosyl complex with visible light excitation. The CdTe QDs were capped with mercaptopropionic acid to make them water-soluble, and the ruthenium nitrosyl complex was cis-[Ru(NO)(4-ampy)(bpy)2](3+) (Ru-NO; bpy is 2,2'-bipyridine, and 4-ampy is 4-aminopyridine). Solutions of these two components demonstrated concentration-dependent quenching of the QD photoluminescence (PL) as well as photoinduced release of NO from Ru-NO when irradiated by 530 nm light. A NO release enhancement of ∼8 times resulting from this association was observed under longer wavelength excitation in visible light range. The dynamics of the quenching determined by both PL and transient absorption measurements were probed by ultrafast flash photolysis. A charge transfer mechanism is proposed to explain the quenching of the QD excited states as well as the photosensitized release of NO from Ru-NO