title: Heterogeneous translational dynamics of rhodamine B in polyelectrolyte multilayer thin films observed by single molecule microscopy.
abstract: The lateral diffusion dynamics of rhodamine B (RB) in polyelectrolyte multilayer (PEM) thin films has been studied with single-molecule confocal fluorescence microscopy. The films were made with sodium poly(sodium 4-styrenesulfonate) (PSS) and poly(diallydimethlyammonium chloride) (PDDA). Analysis of the real-time emission intensity traces reveals three diverse components of translational motion: (1) fast diffusion of RB through the confocal detection volume; (2) reversible tracer adsorption processes; and (3) nanoconfined diffusion. These processes cover a wide range of time scales. Analysis via fluorescence correlation spectroscopy (FCS) involves multicomponent fitting of the autocorrelated emission data. The model includes a free Brownian diffusion parameter, D, and two rate constants of desorption, k(-1) and k(-2). For RB in a PSS/PDDA thin film made with 0.01 M NaCl in the polyelectrolyte buildup solutions, D = 1.7 x 10(-7) cm(2)/s, k(-1) = 30 s(-1), and k(-2) = 0.1 s(-1). FCS was also performed on RB/PEM samples made with NaCl concentrations of the buildup solutions ranging from 0.01 to 0.7 M. A weak dependence of D and k(-1) on NaCl concentration was observed while k(-2) increased linearly with [NaCl].
authors.affiliation: Department of Chemistry, Wheaton College, Wheaton, IL 60187, USA.
authors.forename: Joshua K
authors.initials: JK
authors.lastname: Carr
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Himes
authors.forename: Connie H
authors.initials: CH
authors.lastname: Keung
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Burden
authors.forename: Peter K
authors.initials: PK
authors.lastname: Walhout