title: Probing the interaction of caffeic acid with ZnO nanoparticles.
abstract: The binding of ZnO nanoparticles (NPs) and caffeic acid (CFA) was investigated using fluorescence quenching, UV/vis absorption spectrscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS) at different temperatures. The study results indicated fluorescence quenching between ZnO NPs and CFA rationalized in terms of a static quenching mechanism or the formation of non-fluorescent CFA-ZnO. From fluorescence quenching spectral analysis, the binding constant (K(a)), number of binding sites (n) and thermodynamic properties were determined. Values of the quenching (K(SV)) and binding (K(a)) constants decrease with increasing temperature and the number of binding sites n = 2. The thermodynamic parameters determined using Van't Hoff equation indicated that binding occurs spontaneously involving the hydrogen bond, and van der Waal's forces played a major role in the reaction of ZnO NPs with CFA. The FTIR, TEM and DLS measurements also indicated differences in the structure, morphology and size of CFA, ZnO NPs and their corresponding CFA-ZnO.
authors.affiliation: Department of Nanomaterial Engineering & BK 21 Plus Nanoconvergence Technology Division, Pusan National University, Miryang, 627-706, Korea.|Department of Applied Physics, School of Applied Natural Sciences, Adama Science and Technology University, P.O.Box 1888, Adama, Ethiopia.
authors.forename: Abebe
authors.initials: A
authors.lastname: Belay
authors.affiliation: Department of Nanomaterial Engineering & BK 21 Plus Nanoconvergence Technology Division, Pusan National University, Miryang, 627-706, Korea.
authors.forename: Hyung Kook
authors.initials: HK
authors.lastname: Kim
authors.affiliation: Department of Nanomaterial Engineering & BK 21 Plus Nanoconvergence Technology Division, Pusan National University, Miryang, 627-706, Korea.
authors.forename: Yoon-Hwae
authors.initials: YH
authors.lastname: Hwang
mesh_terms: D001665:Binding Sites; D002109:Caffeic Acids / Q000737:chemistry*; D005453:Fluorescence; D053758:Nanoparticles / Q000737:chemistry*; D013816:Thermodynamics; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D002109:Caffeic Acids; D015034:Zinc Oxide; C040048:caffeic acid
keywords: DLS; FTIR; TEM; ZnO nanoparticles; caffeic acid; fluorescence quenching