title: Direct studies of liquid flows near solid surfaces by total internal reflection fluorescence cross-correlation spectroscopy.
abstract: We present a new method to study flow of liquids near solid surface: Total internal reflection fluorescence cross-correlation spectroscopy (TIR-FCCS). Fluorescent tracers flowing with the liquid are excited by evanescent light, produced by epi-illumination through the periphery of a high numerical aperture oil-immersion objective. The time-resolved fluorescence intensity signals from two laterally shifted observation volumes, created by two confocal pinholes are independently measured. The cross-correlation of these signals provides information of the tracers' velocities. By changing the evanescent wave penetration depth, flow profiling at distances less than 200 nm from the interface can be performed. Due to the high sensitivity of the method fluorescent species with different size, down to single dye molecules can be used as tracers. We applied this method to study the flow of aqueous electrolyte solutions near a smooth hydrophilic surface and explored the effect of several important parameters, e.g. tracer size, ionic strength, and distance between the observation volumes.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128, Mainz, Germany.
authors.forename: Stoyan
authors.initials: S
authors.lastname: Yordanov
authors.forename: Andreas
authors.initials: A
authors.lastname: Best
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Butt
authors.forename: Kaloian
authors.initials: K
authors.lastname: Koynov
mesh_terms: D004573:Electrolytes; D004867:Equipment Design; D005456:Fluorescent Dyes / Q000494:pharmacology; D007477:Ions; D007834:Lasers; D008027:Light; D015233:Models, Statistical; D009821:Oils; D055095:Optics and Photonics; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013499:Surface Properties
chemical_list: D004573:Electrolytes; D005456:Fluorescent Dyes; D007477:Ions; D009821:Oils