Immobilization of β-cyclodextrin on gold surfaces by chemical derivatization of an 11-amino-1-undecanthiol self-assembled monolayer

Abstract

A new methodology for the covalent functionalization of a SAM of 11-amino-1-undecanethiol, previously adsorbed on polycrystalline Au, was successfully applied in order to immobilize a β-CD layer on surface. A two steps synthetic strategy is proposed based on the activation of the SAM with di-(N-succinimidyl) carbonate for the further inclusion of the β-CD. The modification of the SAM was followed by PM-FTIRRAS, AFM imaging, CV, and EIS which confirmed the introduction of β-CD layer. The AFM images allowed the identification of homogeneously distributed β-CD aggregates over the Au grain microstructure. The electrode was characterized in the presence of electroactive species in solution, with the ability to form inclusion complexes with the β-CD cavity. Contrary to the reported for other thiolated CD derivative films, the results of this study showed the formation of well-packed and compact structures which strongly reduce non-specific adsorption phenomena. The redox response of the probes at the β-CD electrode was shown to appear at higher potentials with respect to the response at bare Au. Good correlation was found between the increase of the hydroquinone oxidation peak and, both, the scan rate used in CV experiments (typical behavior of surface-confined species) and the hydroquinone concentration. In the case of dopamine, the processes seem to shifted out of the potential window of SAM stability. The results suggest that this problem could be overcome by improving the design of the device.