Formation of cyclodextrin monolayer through a host–guest interaction with tailor-made phenyltriethoxysilane self-assembled monolayer

Abstract

Abstract Host–guest systems have been widely used for nanostructure construction; however, studying host–guest behavior by immobilizing the guest molecule on a substrate's surface faces great challenges. In this study, phenyltriethoxysilane (PTES) was selected as the ideal candidate to fabricate a guest molecule self-assembled monolayer (SAM). A remarkable PTES SAM growth mechanism, which includes two growth stages, was revealed. By controlling the PTES SAM formation in the first growth stage, the residual PTES ethoxyl groups will hydrolyze in a cyclodextrin (CD) aqueous solution, and the hydrolyzed PTES SAM, as a guest molecule, can provide suitable steric space for forming α- and β-CD inclusion complexes. The experiments demonstrated that the inclusion configurations for α- and β-CD SAMs are different, with the α-CD molecule tilting relative to the silica surface in order to include the PTES phenyl group; whereas the secondary surface of the β-CD remains parallel to the silica surface due to its large cavity. The results corroborated that this simple, yet effective, platform can be readily used to investigate host–guest systems, and it has huge potential for fabricating materials containing CD monolayers.