title: Probing distance-dependent plasmon-enhanced near-infrared fluorescence using polyelectrolyte multilayers as dielectric spacers.
abstract: Owing to their applications in biodetection and molecular bioimaging, near-infrared (NIR) fluorescent dyes are being extensively investigated. Most of the existing NIR dyes exhibit poor quantum yield, which hinders their translation to preclinical and clinical settings. Plasmonic nanostructures are known to act as tiny antennae for efficiently focusing the electromagnetic field into nanoscale volumes. The fluorescence emission from NIR dyes can be enhanced by more than thousand times by precisely placing them in proximity to gold nanorods. We have employed polyelectrolyte multilayers fabricated using layer-by-layer assembly as dielectric spacers for precisely tuning the distance between gold nanorods and NIR dyes. The aspect ratio of the gold nanorods was tuned to match the longitudinal localized surface plasmon resonance wavelength with the absorption maximum of the NIR dye to maximize the plasmonically enhanced fluorescence. The design criteria derived from this study lays the groundwork for ultrabright fluorescence bullets for in vitro and in vivo molecular bioimaging.
authors.affiliation: Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, 1 Brooking Drive, St. Louis, MO 63130 (USA).
authors.forename: Naveen
authors.initials: N
authors.lastname: Gandra
authors.forename: Christopher
authors.initials: C
authors.lastname: Portz
authors.forename: Limei
authors.initials: L
authors.lastname: Tian
authors.forename: Rui
authors.initials: R
authors.lastname: Tang
authors.forename: Baogang
authors.initials: B
authors.lastname: Xu
authors.forename: Samuel
authors.initials: S
authors.lastname: Achilefu
authors.forename: Srikanth
authors.initials: S
authors.lastname: Singamaneni
mesh_terms: D000042:Absorption; D045744:Cell Line, Tumor; D004573:Electrolytes / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006046:Gold / Q000737:chemistry; D006801:Humans; D007259:Infrared Rays; D018625:Microscopy, Atomic Force; D043942:Nanotubes / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D020349:Surface Plasmon Resonance
chemical_list: D004573:Electrolytes; D005456:Fluorescent Dyes; D011108:Polymers; D006046:Gold
keywords: dyes; fluorescence; gold nanorods; layer-by-layer technique; surface plasmon resonances