title: Unraveling the dynamics and structure of functionalized self-assembled monolayers on gold using 2D IR spectroscopy and MD simulations.
abstract: Functionalized self-assembled monolayers (SAMs) are the focus of ongoing investigations because they can be chemically tuned to control their structure and dynamics for a wide variety of applications, including electrochemistry, catalysis, and as models of biological interfaces. Here we combine reflection 2D infrared vibrational echo spectroscopy (R-2D IR) and molecular dynamics simulations to determine the relationship between the structures of functionalized alkanethiol SAMs on gold surfaces and their underlying molecular motions on timescales of tens to hundreds of picoseconds. We find that at higher head group density, the monolayers have more disorder in the alkyl chain packing and faster dynamics. The dynamics of alkanethiol SAMs on gold are much slower than the dynamics of alkylsiloxane SAMs on silica. Using the simulations, we assess how the different molecular motions of the alkyl chain monolayers give rise to the dynamics observed in the experiments.
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305.
authors.forename: Chang
authors.initials: C
authors.lastname: Yan
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305.
authors.forename: Rongfeng
authors.initials: R
authors.lastname: Yuan
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305.
authors.forename: William C
authors.initials: WC
authors.lastname: Pfalzgraff
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305.
authors.forename: Jun
authors.initials: J
authors.lastname: Nishida
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305.
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Markland
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305 fayer@stanford.edu.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Fayer
keywords: 2D IR spectroscopy; MD simulation; dynamics; self-assembled monolayer