title: Adsorption of cellulose derivatives on flat gold surfaces and on spherical gold particles.
abstract: The adsorption of hydroxyethylcellulose (HEC), ethyl(hydroxyethyl)cellulose (EHEC), and their hydrophobically modified counterparts HM-HEC and HM-EHEC has been studied on planar gold and citrate-covered gold surfaces by means of quartz crystal microbalance with dissipation monitoring (QCM-D), and on citrate-covered gold particles with the aid of dynamic light scattering (DLS). The QCM-D results indicate that larger amounts of polymer are adsorbed from aqueous solutions of HM-HEC and HM-EHEC on both substrates than from solutions of their unmodified analogues. The adsorption affinity for all the polymers, except EHEC, is higher on the citrate-covered surfaces than on the bare gold substrate. This indicates that more adsorption sites are activated in the presence of the citrate layer. The experimental adsorption data for all the polymers can be described fairly well by the Langmuir adsorption isotherm. However, at very low polymer concentrations significant deviations from the model are observed. The value of the hydrodynamic thickness of the adsorbed polymer layer (delta h), determined from DLS, rises with increasing polymer concentration for all the cellulose derivatives; a Langmuir type of isotherm can be used to roughly describe the adsorption behavior. Because of good solvent conditions for HEC the chains extend far out in the bulk at higher concentrations and the value of delta h is much higher than that of HM-HEC. The adsorption of EHEC and HM-EHEC onto gold particles discloses that the values of delta h are considerably higher for the hydrophobically modified cellulose derivative, and this finding is compatible with the trend in layer thickness estimated from the QCM-D measurements.
authors.affiliation: Department of Chemistry, University of Oslo, PO Box 1033, Oslo, Norway.
authors.forename: Masoud
authors.initials: M
authors.lastname: Amirkhani
authors.forename: Sondre
authors.initials: S
authors.lastname: Volden
authors.forename: Kaizheng
authors.initials: K
authors.lastname: Zhu
authors.forename: Wilhelm R
authors.initials: WR
authors.lastname: Glomm
authors.forename: Bo
authors.initials: B
authors.lastname: Nyström
mesh_terms: D000327:Adsorption; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000493:pharmacokinetics; D019343:Citric Acid; D006046:Gold; D008027:Light; D008863:Microspheres; D012542:Scattering, Radiation; D013499:Surface Properties
chemical_list: C462399:ethyl(hydroxyethyl)cellulose; D019343:Citric Acid; D006046:Gold; D002482:Cellulose; C002283:hydroxyethylcellulose