title: Enhanced Fluorescence Properties of Carbon Dots in Polymer Films.
abstract: Carbon dots of small carbon nanoparticles surface-functionalized with 2,2'-(ethylenedioxy)bis(ethylamine) (EDA) were synthesized, and the as-synthesized sample was separated on an aqueous gel column to obtain fractions of the EDA-carbon dots with different fluorescence quantum yields. As already discussed in the literature, the variations in fluorescence performance among the fractions were attributed to the different levels and/or effectiveness of the surface functionalization-passivation in the carbon dots. These fractions, as well as carbon nanoparticles without any deliberate surface functionalization, were dispersed into poly(vinyl alcohol) (PVA) for composite films. In the PVA film matrix, the carbon dots and nanoparticles exhibited much enhanced fluorescence emissions in comparison with their corresponding aqueous solutions. The increased fluorescence quantum yields in the films were determined quantitatively by using a specifically designed and constructed film sample holder in the emission spectrometer. The observed fluorescence decays of the EDA-carbon dots in film and in solution were essentially the same, suggesting that the significant enhancement in fluorescence quantum yields from solution to film is static in nature. Mechanistic implications of the results, including a rationalization in terms of the compression effect on the surface passivation layer (similar to a soft corona) in carbon dots when embedded in the more restrictive film environment resulting in more favorable radiative recombinations of the carbon particle surface-trapped electrons and holes, and also potential technological applications of the brightly fluorescent composite films are highlighted and discussed.
authors.affiliation: Department of Chemistry and Laboratory for Emerging Materials and Technology, Clemson University, Clemson, South Carolina 29634.
authors.forename: Yamin
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Chemistry and Laboratory for Emerging Materials and Technology, Clemson University, Clemson, South Carolina 29634.
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.affiliation: University of Dayton Research Institute, Sensors Technology Office, Dayton, Ohio 45469.
authors.forename: K A
authors.initials: KA
authors.lastname: Shiral Fernando
authors.affiliation: Department of Chemistry and Laboratory for Emerging Materials and Technology, Clemson University, Clemson, South Carolina 29634.
authors.forename: Gregory E
authors.initials: GE
authors.lastname: LeCroy
authors.affiliation: Department of Chemistry and Laboratory for Emerging Materials and Technology, Clemson University, Clemson, South Carolina 29634.
authors.forename: Halidan
authors.initials: H
authors.lastname: Maimaiti
authors.affiliation: University of Dayton Research Institute, Sensors Technology Office, Dayton, Ohio 45469.
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Harruff-Miller
authors.affiliation: Air Force Research Laboratory, Propulsion Directorate, Wright-Patterson Air Force Base, Ohio 45433.
authors.forename: William K
authors.initials: WK
authors.lastname: Lewis
authors.affiliation: Air Force Research Laboratory, Propulsion Directorate, Wright-Patterson Air Force Base, Ohio 45433.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Bunker
authors.affiliation: Department of Chemistry and Laboratory for Emerging Materials and Technology, Clemson University, Clemson, South Carolina 29634.
authors.forename: Zhi-Ling
authors.initials: ZL
authors.lastname: Hou
authors.affiliation: Department of Chemistry and Laboratory for Emerging Materials and Technology, Clemson University, Clemson, South Carolina 29634.
authors.forename: Ya-Ping
authors.initials: YP
authors.lastname: Sun