title: Two-color, laser excitation improves temporal resolution for detecting the dynamic, plasmonic coupling between metallic nanoparticles.
abstract: The ability of two, scattering gold nanoparticles (GNPs) to plasmonically couple in a manner that is dependent on the interparticle separation has been exploited to measure nanometer-level displacements. However, despite broad applicability to monitoring biophysical dynamics, the long time scales (<5 Hz) with which plasmonic coupling are typically measured are not suitable for many dynamic molecular processes, generally occurring over several milliseconds. Here, we introduce a new technique intended to overcome this technical limitation: ratiometric analysis using monochromatic, evanescent darkfield illumination (RAMEDI). As a proof-of-principle, we monitored dynamic, plasmonic coupling arising from the binding of single biotin- and neutravidin-GNPs with a temporal resolution of 38 ms. We also show that the observable bandwidth is extendable to faster time scales by demonstrating that RAMEDI is capable of achieving a signal-to-noise ratio greater than 20 from individual GNPs observed with 200 Hz bandwidth.
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States. dianemariewiener@gmail.com
authors.forename: Diane M
authors.initials: DM
authors.lastname: Wiener
authors.forename: Troy A
authors.initials: TA
authors.lastname: Lionberger
mesh_terms: D001360:Avidin / Q000737:chemistry; D001710:Biotin / Q000737:chemistry; D003116:Color; D031541:Fluorescence Resonance Energy Transfer; D007834:Lasers; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry*; D012542:Scattering, Radiation
chemical_list: C093483:neutravidin; D001360:Avidin; D001710:Biotin