Two-Photon Oxygen Sensing with Quantum Dot-Porphyrin Conjugates

Supramolecular assemblies of a quantum dot (QD) associated to palladium­(II) porphyrins have been developed to detect oxygen (pO₂) in organic solvents. Palladium porphyrins are sensitive in the 0–160 Torr range, making them ideal phosphors for in vivo biological oxygen quantification. Porphyrins with <i>meso</i> pyridyl substituents bind to the surface of the QD to produce self-assembled nanosensors. Appreciable overlap between QD emission and porphyrin absorption features results in efficient Förster resonance energy transfer (FRET) for signal transduction in these sensors. The QD serves as a photon antenna, enhancing porphyrin emission under both one- and two-photon excitation, demonstrating that QD-palladium porphyrin conjugates may be used for oxygen sensing over physiological oxygen ranges