Adsorption of meso-tetra(3-pyridyl)porphyrin on InP/ZnS colloidal quantum dots

Interaction between InP/ZnS core/shell colloidal quantum dots (QDs) and meso -tetra(3-pyridyl)porphyrin (TPyP) was investigated by fluorescence and NMR spectroscopy. Density functional theory (DFT) calculations were used to interpret the NMR data. Formation of the QD-TPyP associate leads to an increase in the fluorescence intensity of the dye and to quenching of the nanocrystal photoluminescence mainly due to Förster resonance energy transfer (FRET). It was shown that the dye adsorption kinetics does not depend on its concentration, which testifies to the limitation of the adsorption rate by the rate of ligand detachment from the QD surface. The NMR data for concentrated solution of QD and TPyP with a 2:1 molar ratio reveal two different types of QD-TPyP associates. With the help of DFT calculations, this can be explained by taking into account that a dye molecule can be coordinated to a QD with one or two pyridine moieties. Associates of the former type are about two times more abundant than those of the latter. Graphical abstract