A Quartz Crystal Microbalance Study of the Adsorption of Fluorescein‐5‐Isothiocyanate onto Gold Surfaces

The interaction of fluorescein‐5‐isothiocyanate (F5ITC) with gold surfaces—either uncoated or pre‐coated with passivating layers of either sodium citrate (citrate), bis(p‐sulfonatophenyl)phenylphosphine dihydrate dipotassium (BSPP), Pluronic P123 (EO20PO70EO20), or Pluronic F127 (EO100PO70EO100)—was studied using quartz crystal microbalance (QCM) measurements in order to determine the surface coverage of F5ITC in each case. Adsorption isotherms of the polymers (P123 and F127) binding to a gold surface were also obtained. Binding of F5ITC to the gold surfaces was found to be highly dependent on the passivating layer. The surface coverage ΓF5ITC of F5ITC on gold surfaces can be listed in decreasing order as ΓF5ITC, Au>ΓF5ITC, citrate>ΓF5ITC, P123>ΓF5ITC, BSPP>ΓF5ITC, F127. Mechanisms for binding of F5ITC to the gold surfaces are also discussed.