title: Distance-dependent plasmon-enhanced fluorescence of upconversion nanoparticles using polyelectrolyte multilayers as tunable spacers.
abstract: Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted widespread interests in bioapplications due to their unique optical properties by converting near infrared excitation to visible emission. However, relatively low quantum yield prompts a need for developing methods for fluorescence enhancement. Plasmon nanostructures are known to efficiently enhance fluorescence of the surrounding fluorophores by acting as nanoantennae to focus electric field into nano-volume. Here, we reported a novel plasmon-enhanced fluorescence system in which the distance between UCNPs and nanoantennae (gold nanorods, AuNRs) was precisely tuned by using layer-by-layer assembled polyelectrolyte multilayers as spacers. By modulating the aspect ratio of AuNRs, localized surface plasmon resonance (LSPR) wavelength at 980 nm was obtained, matching the native excitation of UCNPs resulting in maximum enhancement of 22.6-fold with 8 nm spacer thickness. These findings provide a unique platform for exploring hybrid nanostructures composed of UCNPs and plasmonic nanostructures in bioimaging applications.
authors.affiliation: 1] The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, P.R. China [2] Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, P.R. China.
authors.forename: Ai Ling
authors.initials: AL
authors.lastname: Feng
authors.affiliation: 1] The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, P.R. China [2] Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, P.R. China.
authors.forename: Min Li
authors.initials: ML
authors.lastname: You
authors.affiliation: Department of Mechanical Engineering and Materials Science, Institute of Materials Science and Engineering, Washington University in St. Louis, St Louis, MO 63130, USA.
authors.forename: Limei
authors.initials: L
authors.lastname: Tian
authors.affiliation: Department of Mechanical Engineering and Materials Science, Institute of Materials Science and Engineering, Washington University in St. Louis, St Louis, MO 63130, USA.
authors.forename: Srikanth
authors.initials: S
authors.lastname: Singamaneni
authors.affiliation: Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education &International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, P.R. China.
authors.forename: Ming
authors.initials: M
authors.lastname: Liu
authors.affiliation: Center for Sarcoma and Connective Tissue Oncology, Massachusetts General Hospital, Harvard Medical School, MA 02114, USA.
authors.forename: Zhenfeng
authors.initials: Z
authors.lastname: Duan
authors.affiliation: Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, P.R. China.
authors.forename: Tian Jian
authors.initials: TJ
authors.lastname: Lu
authors.affiliation: 1] The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, P.R. China [2] Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, P.R. China.
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
authors.affiliation: 1] The Key Laboratory of Biomedical Information Engineering, Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, P.R. China [2] Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, P.R. China [3] Center for Sarcoma and Connective Tissue Oncology, Massachusetts General Hospital, Harvard Medical School, MA 02114, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Lin
mesh_terms: D004573:Electrolytes / Q000737:chemistry*; D006046:Gold / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D018625:Microscopy, Atomic Force; D009757:Nylons / Q000737:chemistry; D019047:Phantoms, Imaging; D013050:Spectrometry, Fluorescence; D013997:Time Factors
chemical_list: D004573:Electrolytes; D009757:Nylons; D006046:Gold