Chelating the Surface of Zinc in Zinc Oxide Nanocrystals: Spectroscopic Characterization of ZnO Surface-Bound Eriochrome Black T and 8-Hydroxyquinoline

The surface binding of eriochrome black T (ErT) and 8-hydroxyquinoline (HQ) with zinc oxide nanocrystals is studied with UV-vis absorption and fluorescence spectroscopy. Stern-Volmer analysis of the quenching dynamics in neutral water leads to binding constants of 2.52(1) x 10(-6) and 7.14(1) x 10(-6')M(-1) for the binding of HQ and ErT, respectively. ErT coordinates in a 1:1 tetrahedral geometry for about 10% of the surface zinc sites, while HQ occupies a similar coordination geometry for half of the available sites. A new transient species forms during the interaction of ErT with the zinc oxide nanocrystals which is characterized by an absorption at 680 nm.