title: Metal-Enhanced Near-Infrared Fluorescence by Micropatterned Gold Nanocages.
abstract: In metal-enhanced fluorescence (MEF), the localized surface plasmon resonances of metallic nanostructures amplify the absorption of excitation light and assist in radiating the consequent fluorescence of nearby molecules to the far-field. This effect is at the base of various technologies that have strong impact on fields such as optics, medical diagnostics, and biotechnology. Among possible emission bands, those in the near-infrared (NIR) are particularly intriguing and widely used in proteomics and genomics due to its noninvasive character for biomolecules, living cells, and tissues, which greatly motivates the development of effective and, eventually, multifunctional NIR-MEF platforms. Here, we demonstrate NIR-MEF substrates based on Au nanocages micropatterned with a tight spatial control. The dependence of the fluorescence enhancement on the distance between the nanocage and the radiating dipoles is investigated experimentally and modeled by taking into account the local electric field enhancement and the modified radiation and absorption rates of the emitting molecules. At a distance around 80 nm, a maximum enhancement up to 2-7 times with respect to the emission from pristine dyes (in the region 660-740 nm) is estimated for films and electrospun nanofibers. Due to their chemical stability, finely tunable plasmon resonances, and large light absorption cross sections, Au nanocages are ideal NIR-MEF agents. When these properties are integrated with the hollow interior and controllable surface porosity, it is feasible to develop a nanoscale system for targeted drug delivery with the diagnostic information encoded in the fluorophore.
authors.affiliation: Istituto Nanoscienze-CNR, Euromediterranean Center for Nanomaterial Modelling and Technology (ECMT) , via Arnesano, I-73100 Lecce, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Camposeo
authors.affiliation: Istituto Nanoscienze-CNR, Euromediterranean Center for Nanomaterial Modelling and Technology (ECMT) , via Arnesano, I-73100 Lecce, Italy.
authors.forename: Luana
authors.initials: L
authors.lastname: Persano
authors.affiliation: Istituto Nanoscienze-CNR, Euromediterranean Center for Nanomaterial Modelling and Technology (ECMT) , via Arnesano, I-73100 Lecce, Italy.|Dipartimento di Matematica e Fisica "Ennio De Giorgi", Università del Salento , via Arnesano, I-73100 Lecce, Italy.
authors.forename: Rita
authors.initials: R
authors.lastname: Manco
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia 30332, United States.|Key Laboratory of Green Synthesis and Applications, College of Chemistry, Chongqing Normal University , Chongqing 401331, P. R. China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Istituto Nanoscienze-CNR, Euromediterranean Center for Nanomaterial Modelling and Technology (ECMT) , via Arnesano, I-73100 Lecce, Italy.
authors.forename: Pompilio
authors.initials: P
authors.lastname: Del Carro
authors.affiliation: Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, P. R. China.
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, P. R. China.|College of Physics and Optoelectronics, South China University of Technology , Guangzhou 510641, P. R. China.
authors.forename: Zhi-Yuan
authors.initials: ZY
authors.lastname: Li
authors.affiliation: Istituto Nanoscienze-CNR, Euromediterranean Center for Nanomaterial Modelling and Technology (ECMT) , via Arnesano, I-73100 Lecce, Italy.|Dipartimento di Matematica e Fisica "Ennio De Giorgi", Università del Salento , via Arnesano, I-73100 Lecce, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Pisignano
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia 30332, United States.
authors.forename: Younan
authors.initials: Y
authors.lastname: Xia
mesh_terms: D006046:Gold / Q000737:chemistry*; D007259:Infrared Rays; D008027:Light; D046228:Microarray Analysis; D055616:Microtechnology; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology; D055095:Optics and Photonics; D020349:Surface Plasmon Resonance
chemical_list: D006046:Gold
keywords: fluorescence enhancement; nanocages; near-infrared emission; soft lithography