title: Intraparticulate Metal Speciation Analysis of Soft Complexing Nanoparticles. The Intrinsic Chemical Heterogeneity of Metal-Humic Acid Complexes.
abstract: The counterion condensation-Donnan (CCD) model for the electrostatic features of soft, charged nanoparticles (NPs) is applied to the determination of the intrinsic stability constants, K̅int, for inner-sphere Cd(II) and Cu(II) complexes with humic acid NPs. The novel CCD model accounts for the strong ion condensation potential for higher valency counterions within the intraparticulate double layer zone of the soft NP. The approach offers new insights into the intrinsic heterogeneity of the HA complexes, as revealed by the intraparticulate speciation as a function of the true degree of inner-sphere complexation, θM. The ensuing intrinsic heterogeneity parameters, Γ, for CdHA and CuHA complexes are in very good agreement with those obtained from dynamic electrochemical stripping chronopotentiometric measurements. The overall intraparticulate metal ion speciation is found to depend on θM: at low θMthe strong inner-sphere complexes predominate whereas at higher θMvalues, electrically condensed M may be an equally significant or even larger fraction of the particle-associated M.
authors.affiliation: Department of Physics, Chemistry and Pharmacy, University of Southern Denmark , Campusvej 55, 5230 Odense, Denmark.|Physical Chemistry and Soft Matter, Wageningen University & Research , Stippeneng 4, 6708 WE Wageningen, The Netherlands.|Systemic Physiological and Ecotoxicological Research (SPHERE), Department of Biology, University of Antwerp , Groenenborgerlaan 171, 2020 Antwerp, Belgium.
authors.forename: Raewyn M
authors.initials: RM
authors.lastname: Town
authors.affiliation: Physical Chemistry and Soft Matter, Wageningen University & Research , Stippeneng 4, 6708 WE Wageningen, The Netherlands.
authors.forename: Herman P
authors.initials: HP
authors.lastname: van Leeuwen
mesh_terms: D002104:Cadmium / Q000737:chemistry* / Q000378:metabolism; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D006812:Humic Substances; D053758:Nanoparticles / Q000737:chemistry* / Q000378:metabolism
chemical_list: D006812:Humic Substances; D002104:Cadmium; D003300:Copper