Preparation and molecular recognition of cyclodextrin monolayers with different cavity size on a gold wire electrode

α-, β-, and γ-cyclodextrins (CyDs) bearing a lipolyamide residue (LP-α-CyD, LP-β-CyD, and LP-γ-CyD, respectively) at their primary hydroxyl sides were chemisorbed on a gold wire electrode. Charges associated with reductive desorption waves on cyclic voltammograms (CVs) observed for the modified electrodes revealed that the surface coverage of the CyD derivatives was nearly 100% or even higher, when the CyD derivatives were chemisorbed from their 1.0 × 10−3M solutions. Surface plasmon resonance spectroscopy was applied to estimate the thickness of the LP-β-CyD adsorbed layer, indicating that the membrane would be a monolayer. Cyclic voltammetric studies on the monolayers of LP-CyDs using ferrocenecarboxylic acid (FCA) as an electroactive marker in 0.1 M H2SO4 solutions showed that FCA permeation was effectively blocked by the LP-α-CyD monolayer, while the CyD cavities in the LP-β-CyD and LP-γ-CyD monolayers made FCA permeate through the CyD monolayers. The molecular permeability was further checked by co-addition of electroinactive guests, assessed by the reduction in the anodic peak current of FCA.