title: Attractive double-layer forces and charge regulation upon interaction between electrografted amine layers and silica.
abstract: Amine functionalities have been introduced on glassy carbon surfaces through electrografting of 4-(2-aminoethyl)benzenediazonium tetrafluoroborate. The grafted layers were characterized by ellipsometry and by nanomechanical mapping in air and aqueous solutions using the atomic force microscopy PeakForce QNM mode. The layer was found to be 2.5 nm thick with low roughness, comparable to that of the glassy carbon substrate. However, small semi-spherical features were observed in the topographical image, indicating a clustering of the grafted amine compound. The nanomechanical mapping also demonstrated some swelling of the layer in water and pointed toward an important contribution of electrostatic interactions for the tip-surface adhesion. The forces between an aminated glassy carbon surface and a μm-sized silica particle in aqueous solutions were measured at different ionic strength and pH-values. The results demonstrate that an attractive double-layer force predominates at large separations, and that the surface charge densities increase as the separation between the surfaces decreases. The degree of charge regulation on the aminated glassy carbon is significant. The relatively low surface charge density of the aminated glassy carbon is attributed to significant incorporation of counterions in the water-rich grafted layer.
authors: KTH Royal Institute of Technology, School of Chemical Sciences and Engineering, Department of Chemistry, Surface and Corrosion Science, Stockholm, Sweden. gduner@kth.se
authors: Gunnar
authors: G
authors: Dunér
authors: Joseph
authors: J
authors: Iruthayaraj
authors: Kim
authors: K
authors: Daasbjerg
authors: Steen Uttrup
authors: SU
authors: Pedersen
authors: Esben
authors: E
authors: Thormann
authors: Andra
authors: A
authors: Dėdinaitė