title: Calixarene monolayers as quartz crystal microbalance sensing elements in aqueous solution.
abstract: We have examined p-tert-butylcalix[4]arenetetrathiolate (BCAT) monolayers for their potential use as molecular recognition elements for in situ aqueous chemical sensors. Spectroscopic and wetting studies of BCAT monolayers on Au{111} reveal that the calixarene molecules exist in monolayers, preferentially oriented with their phenyl rings parallel to the surface normal axis. Using quartz crystal microbalance (QCM) sensors with gold-coated electrodes, the chemical specificity of monolayers and thin films to a variety of aromatic and aliphatic analytes in aqueous solution was examined. The response of BCAT sensors was compared to the responses of p-tert-butylcalix[4]arene (BCA)- and decanethiolate (DT)-coated QCM electrodes. BCAT is very selective for alkylbenzenes, much more so than either its spray-coated thin-film analogue, BCA, or the highly ordered DT monolayer. From these measurements, the factors behind molecular differentiation in each film are explored. Drawing upon these findings, the roles of cavitation and film order in molecular recognition for calixarene films are discussed.
authors.affiliation: Chemistry Division, Naval Research Laboratory, Code 6116, Washington, D.C. 20375-5342, 185 Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, and Texas Christian University, P.O. Box 32908, Fort Worth, Texas 76129.
authors.forename: M T
authors.initials: MT
authors.lastname: Cygan
authors.forename: G E
authors.initials: GE
authors.lastname: Collins
authors.forename: T D
authors.initials: TD
authors.lastname: Dunbar
authors.forename: D L
authors.initials: DL
authors.lastname: Allara
authors.forename: C G
authors.initials: CG
authors.lastname: Gibbs
authors.forename: C D
authors.initials: CD
authors.lastname: Gutsche