title: Alleviating Luminescence Concentration Quenching in Upconversion Nanoparticles through Organic Dye Sensitization.
abstract: The phenomenon of luminescence concentration quenching exists widely in lanthanide-based luminescent materials, setting a limit on the content of lanthanide emitter that can be used to hold the brightness. Here, we introduce a concept involving energy harvesting by a strong absorber and subsequent energy transfer to a lanthanide that largely alleviates concentration quenching. We apply this concept to Nd3+emitters, and we show both experimentally and theoretically that the optimal doping concentration of Nd3+in colloidal NaYF4:Nd upconverting nanoparticles is increased from 2 to 20 mol% when an energy harvestor organic dye (indocyanine green, ICG) is anchored onto the nanoparticle surface, resulting in ∼10 times upconversion brightness. Theoretical analysis indicated that a combination of efficient photon harvesting due to the large absorption cross section of ICG (∼30 000 times higher than that of Nd3+), non-radiative energy transfer (efficiency ∼57%) from ICG to the surface bound Nd3+ions, and energy migration among the Nd3+ions was able to activate Nd3+ions inside the nanoparticle at a rate comparable with that of the pronounced short-range quenching interaction at elevated Nd3+concentrations. This resulted in the optimal concentration increase to produce significantly enhanced brightness. Theoretical modeling shows a good agreement with the experimental observation. This strategy can be utilized for a wide range of other lanthanide-doped nanomaterials being utilized for bioimaging and solar cell applications.
authors.affiliation: Institute for Lasers, Photonics, Biophotonics, University at Buffalo, State University of New York , Buffalo, New York 14260, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.affiliation: Institute for Lasers, Photonics, Biophotonics, University at Buffalo, State University of New York , Buffalo, New York 14260, United States.|School of Chemistry and Chemical Engineering, Harbin Institute of Technology , Harbin, Heilongjiang 150001, People's Republic of China.
authors.forename: Guanying
authors.initials: G
authors.lastname: Chen
authors.affiliation: Institute for Lasers, Photonics, Biophotonics, University at Buffalo, State University of New York , Buffalo, New York 14260, United States.
authors.forename: Alexander
authors.initials: A
authors.lastname: Baev
authors.affiliation: Institute for Lasers, Photonics, Biophotonics, University at Buffalo, State University of New York , Buffalo, New York 14260, United States.
authors.forename: Guang S
authors.initials: GS
authors.lastname: He
authors.affiliation: Institute for Lasers, Photonics, Biophotonics, University at Buffalo, State University of New York , Buffalo, New York 14260, United States.|School of Chemistry and Chemical Engineering, Harbin Institute of Technology , Harbin, Heilongjiang 150001, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Shao
authors.affiliation: Institute for Lasers, Photonics, Biophotonics, University at Buffalo, State University of New York , Buffalo, New York 14260, United States.
authors.forename: Jossana
authors.initials: J
authors.lastname: Damasco
authors.affiliation: Institute for Lasers, Photonics, Biophotonics, University at Buffalo, State University of New York , Buffalo, New York 14260, United States.
authors.forename: Paras N
authors.initials: PN
authors.lastname: Prasad