title: Characterization of adsorption and electronic excited states of quercetin on titanium dioxide nanoparticles.
abstract: Adsorption of quercetin on colloidal titanium dioxide nanoparticles in ethanol and its excited-state electronic structure were investigated by means of electronic and vibrational spectroscopies. The changes in electronic charge redistribution as reflected by the dipole moment difference, ∆μ, between the ground and excited electronic states were measured with electroabsorption spectroscopy and analyzed using results of TD DFT computations. Adsorption of quercetin causes a red shift of its absorption spectrum. Raman spectra of quercetin analyzed with reference to analogous data for morin indicate binding of quercetin through the hydroxy groups of the catechol moiety. The difference dipole moment, which is 5.5D in free quercetin, increases to 11.8D in opposite direction in adsorbed quercetin, and is associated with charge-transfer to the Ti atom. The computed transition energy, intensity, vector Δμ and molecular orbitals involved in the electronic transition at different molecular configurations indicate a bidentate chelating mode of binding of quercetin.
authors.affiliation: Lublin University of Technology, Faculty of Environmental Engineering, Nadbystrzycka 40B, 20-618 Lublin, Poland. Electronic address: a.zdyb@pollub.pl.
authors.forename: Agata
authors.initials: A
authors.lastname: Zdyb
authors.affiliation: Maria Curie-Skłodowska University, Institute of Physics, Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland. Electronic address: skraw@hektor.umcs.lublin.pl.
authors.forename: Stanisław
authors.initials: S
authors.lastname: Krawczyk
keywords: Charge transfer; Dipole moment; Quercetin; Stark effect; TiO(2) nanoparticles