Interfacial Supramolecular Self-Assembled Monolayers of C_(60) by Thiolated β-Cyclodextrin on Gold Surfaces via Monoanionic C_(60)

摘要

The supramolecular self-assembled monolayers (SAMs) of C_(60) by thiolated β-cyclodextrin (CD) on gold surfaces were constructed for the first time using C_(60) monoanion. The results indicate that monoanionic C_(60) plays a crucial role in the formation of the C_(60)-containing self-assembled monolayers. The generation of C_(60) monoanion and the formation process of C_(60) SAMs were monitored in-situ by UV- visible and near-IR spectroscopy. The resulting C_(60) SAMs were fully characterized by spectroscopic ellipsometry (SE), cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and water contact angle measurements. After the immobilization of C_(60) by the SAMs of thiolated β-CD, the film thickness increased by approximately 1 nm from 0.8 to 1.8 nm as determined by SE, demonstrating the formation of the supramolecular self-assembled monolayers of thiolated β-CD/C_(60). The new C_(60) SAMs exhibited one quasi-reversible redox couple at half wave potential of -0.57 V vs SCE in aqueous solution containing 0.1 M KCI. The surface coverage of C_(60) on the gold surfaces was estimated to be 1.1 x 10~(-10) mol cm~(-2). The XPS showed the assembly of C_(60) over the thiolated β-CD SAMs. The surface hydrophobicity increased greatly upon the formation of the C_(60)-containing SAMs as analyzed by water contact angle measurements. The results are in agreement with the formation of 1:1 complex of C_(60) and cyclodextrin on gold surfaces, though it also reveals some non-homogeneous features of the monolayers.