title: Single-molecule spectroscopic study of enhanced intrinsic phycoerythrin fluorescence on silver nanostructured surfaces.
abstract: In this paper, we report on steady-state and time-resolved single-molecule fluorescence measurements performed on a phycobiliprotein, R-phycoerythrin (RPE), assembled on silver nanostructures. Single-molecule measurements clearly show that RPE molecules display a 10-fold increase in fluorescence intensity, with a 7-fold decrease in lifetime when they are assembled on silver nanostructured surfaces, as compared to control glass slides. The emission spectrum of individual RPE molecules also displays a significant fluorescence enhancement on silver nanostructures as compared to glass. From intensity and lifetime histograms, it is clear that the intensities as well as lifetimes of individual RPE molecules on silver nanostructures are more heterogeneously distributed than that on glass. This single-molecule study provides further insight on the heterogeneity in the fluorescence intensity and lifetimes of the RPE molecules on both glass and SiFs surfaces, which is otherwise not possible to observe using ensemble measurements. Finite-difference time-domain calculations have been performed to study the enhanced near-fields induced around silver nanoparticles by a radiating excited-state fluorophore, and the effect of such enhanced fields on the fluorescence enhancement observed is discussed.
authors.affiliation: Center for Fluorescence Spectroscopy, Department of Biochemistry and Molecular Biology, University Maryland School of Medicine, 725 West Lombard Street, Baltimore, Maryland 21201, USA. krishanu@cfs.umbi.umd.edu
authors.forename: Krishanu
authors.initials: K
authors.lastname: Ray
authors.forename: Mustafa H
authors.initials: MH
authors.lastname: Chowdhury
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Lakowicz
mesh_terms: D000818:Animals; D001681:Biological Assay; D002417:Cattle; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000378:metabolism; D053768:Metal Nanoparticles / Q000737:chemistry*; D018613:Microscopy, Confocal; D010799:Phycoerythrin / Q000378:metabolism*; D012680:Sensitivity and Specificity; D012834:Silver / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis / Q000379:methods*; D013499:Surface Properties
chemical_list: D005456:Fluorescent Dyes; D010799:Phycoerythrin; D012834:Silver