Photoinduced relaxation processes in complexes based on semiconductor CdSe nanocrystals and organic molecules

Possible pathways and mechanisms of photoinduced relaxation processes in CdSe and CdSe/ZnS nanocrystals that are surface-passivated (as a result of two-point interactions) by nitrogen-containing ligands of different nature (pyridyl-substituted porphyrin molecules and their derivatives, 2,2′-dipyridyl, and 1,10-phenanthroline) are studied in toluene at 295 K by the methods of steady-state and time-resolved spectroscopy. In nanocrystal-organic ligand composites, a high luminescence-quenching efficiency of nanocrystals by molecules of tetrapyrrole compounds compared to 2,2′-dipyridyl, 1,10-shenanthroline, and pyridine can be associated with the electronic properties of a π conjugated macrocycle and anchor groups. The fundamental role that mesomeric effects and the partial overlap of HOMOs and LUMOs of porphyrin and meso-pyridyl rings play in the enhancement of nonradiative recombination of charges in a surface interface layer is substantiated.