title: Distance-dependent interactions between gold nanoparticles and fluorescent molecules with DNA as tunable spacers.
abstract: Using stoichiometrically controlled 1:1 functionalization of gold nanoparticles with fluorescent dye molecules in which the dye molecule is held away from the particle surface by a rigid DNA spacer allows precise determination of the distance-dependent effect of the metal nanoparticles on fluorescence intensity. Two dyes were studied, Cy3 and Cy5, with two sizes of nanoparticles, 5 and 10 nm. The larger the particle, the more quenching of the photoluminescence (PL) intensity, due to increased overlap of the dye's emission spectrum with the Au surface plasmon resonance. Fluorescence is quenched significantly for distances somewhat larger than the particle diameter, in good agreement with the predictions of an electrodynamics model based on interacting dipoles. The distance dependence of surface energy transfer behavior, i.e. quenching efficiency, is proportional to 1/d(4), which involves no consideration of the size of the particle and the spectral overlap of the dye and AuNp. This surface energy transfer model is found qualitatively and agrees with the electrodynamic model, though the exponent is greater than 4 for the smaller nanoparticles (5 nm), and smaller than 4 for the larger nanoparticles (10 nm).
authors.affiliation: The Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA. Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA.
authors.forename: Rahul
authors.initials: R
authors.lastname: Chhabra
authors.forename: Jaswinder
authors.initials: J
authors.lastname: Sharma
authors.forename: Haining
authors.initials: H
authors.lastname: Wang
authors.forename: Shengli
authors.initials: S
authors.lastname: Zou
authors.forename: Su
authors.initials: S
authors.lastname: Lin
authors.forename: Hao
authors.initials: H
authors.lastname: Yan
authors.forename: Stuart
authors.initials: S
authors.lastname: Lindsay
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
mesh_terms: D002232:Carbocyanines / Q000737:chemistry; D003198:Computer Simulation; D004247:DNA / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D009693:Nucleic Acid Hybridization; D013056:Spectrophotometry, Ultraviolet
chemical_list: D002232:Carbocyanines; D005456:Fluorescent Dyes; C089187:cyanine dye 3; C085321:cyanine dye 5; D006046:Gold; D004247:DNA