title: Dual-Mode Luminescent Nanopaper Based on Ultrathin g-C3N4 Nanosheets Grafted with Rare-Earth Upconversion Nanoparticles.
abstract: Ultrathin graphite-like carbon nitride (g-C3N4) nanosheets have attracted considerable attention due to the enhanced intrinsic photoabsorption and photoresponse with respect to bulk g-C3N4. For the first time, a dual-mode of down- and upconversion luminescent g-C3N4 nanopaper with high optical transparency and mechanical robustness was successfully fabricated through a simple thermal evaporation process using chitosan as a green cross-linking agent. The dual-mode of down- and upconversion fluorescence emission originated from the amino terminated ultrathin g-C3N4 nanosheets functionalized with carboxylic acid modified multicolored rare-earth upconversion nanoparticles (cit-UCNPs) via EDC/NHS coupling chemistry. The homogeneously distributed cit-UCNPs@g-C3N4 nanoconjugates with excellent hydrophilicity displayed good film-forming ability and structural integrity; thus, the photoluminescence of each ingredient was substantially maintained. Results indicated that the freestanding chitosan cross-linked cit-UCNPs@g-C3N4 luminescent nanopaper possessed high transmittance, excellent mechanical properties, and remarkable dual-mode emission. The smart design of high performance luminescent nanopaper based on ultrathin g-C3N4 nanosheets grafted with multicolored UCNPs offers a potential strategy to immobilize other multifunctional luminescent materials for easily recognizable and hardly replicable anticounterfeiting fields.
authors: Research Center of Nano Science and Technology, Shanghai University , Shanghai 200444, P.R. China.
authors: Yafei
authors: Y
authors: Zhao
authors: Research Center of Nano Science and Technology, Shanghai University , Shanghai 200444, P.R. China.
authors: Ruoyan
authors: R
authors: Wei
authors: Research Center of Nano Science and Technology, Shanghai University , Shanghai 200444, P.R. China.
authors: Xin
authors: X
authors: Feng
authors: Research Center of Nano Science and Technology, Shanghai University , Shanghai 200444, P.R. China.
authors: Lining
authors: L
authors: Sun
authors: Department of Chemistry, College of Science, Shanghai University , Shanghai 200444, P.R. China.
authors: Panpan
authors: P
authors: Liu
authors: Department of Chemistry, College of Science, Shanghai University , Shanghai 200444, P.R. China.
authors: Yongxiang
authors: Y
authors: Su
authors: Research Center of Nano Science and Technology, Shanghai University , Shanghai 200444, P.R. China.
authors: Liyi
authors: L
authors: Shi
keywords: chitosan; dual-mode luminescent nanopaper; mechanical properties; rare-earth upconversion nanoparticles; ultrathin g−C3N4 nanosheets