title: Effect of natural organic matter and green microalga on carboxyl-polyethylene glycol coated CdSe/ZnS quantum dots stability and transformations under freshwater conditions.
abstract: The influence of pH, ionic strength, presence of humic or alginic acids, extracellular polymeric substances (EPS), or freshwater microalga Chlorella kesslerii on the stability and transformation of carboxyl-PEG-CdSe/ZnS core/shell quantum dots (QDs) in terms of number, hydrodynamic size and fluorescence of individual particles, was studied by fluorescence correlation spectroscopy. Obtained results demonstrated that QDs form stable dispersions at nanomolar concentrations under conditions typical for freshwaters. The presence of 5 or 15 mg C L(-1) of humic acid or 50 mg C L(-1) EPS did not significantly affect these parameters. In contrast, 5 or 50 mg C L(-1) alginate at ionic strength of 10 mM shifted the hydrodynamic radius toward larger values, suggesting a possible capture of QDs by the linear alginate chains. The addition of microalga to the QD dispersions resulted in a slight reduction of the number of QDs and a significant decline in the fluorescence of individual QDs.
authors.affiliation: Environmental Biophysical Chemistry, IIE-ENAC, Ecole Polytechnique Fédérale de Lausanne, Station 2, CH-1015 Lausanne, Switzerland. vera.slaveykova@epfl.ch
authors.forename: Vera I
authors.initials: VI
authors.lastname: Slaveykova
authors.forename: Konstantin
authors.initials: K
authors.lastname: Startchev
mesh_terms: D002708:Chlorella / Q000737:chemistry*; D005618:Fresh Water / Q000737:chemistry; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D058086:Microalgae / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D009994:Osmolar Concentration; D011092:Polyethylene Glycols / Q000737:chemistry; D045663:Quantum Dots
chemical_list: D006812:Humic Substances; D011092:Polyethylene Glycols