title: Fabrication of a novel nanocomposite Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er for large enhancement upconversion luminescence.
abstract: Upconversion nanocrystals have a lot of advantages over other fluorescent materials. However, their applications are still limited due to their comparatively low upconversion luminescence (UCL). In the present study, a novel nanocomposite of Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er for enhancing UCL was fabricated successfully, and its morphology, crystalline phase, composition, and fluorescent property were investigated. It is interesting to find that the Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er and Ag@SiO2-NaLuF4:Yb,Gd,Er nanocomposites showed high UCL enhancements of 52- and 10-fold compared to the control of Ag-free nanocomposite SiO2-NaLuF4:Yb,Gd,Er, respectively. The enhancement of 52-fold is greater than those reported in our previous studies and some papers. Moreover, the measured life times of the Ag-presented nanocrystals were longer than that of Ag-absent counterparts. These enhancements of UCL can be ascribed to the effect of metal-enhanced fluorescence, which is caused by the enhancement of the local electric field. The UCL intensity of Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er was 5.2-fold higher than that of Ag@SiO2-NaLuF4:Yb,Gd,Er, indicating that graphene presented in the fabricated nanocomposite structure favors metal-enhanced UCL. The small-sized Ag nanoparticles anchored on the graphene sheet mutually enhanced each other's polarizability and surface plasmon resonance, resulting in a big metal-enhanced UCL. This study provides a new strategy for effectively enhancing the UCL of upconversion nanocrystals. The enhancement potentially increases the overall upconversion nanocrystal detectability for highly sensitive biological, medical, and optical detections.
authors.affiliation: School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China. ydg@shu.edu.cn.
authors.forename: Dongguang
authors.initials: D
authors.lastname: Yin
authors.forename: Xianzhang
authors.initials: X
authors.lastname: Cao
authors.forename: Lu
authors.initials: L
authors.lastname: Zhang
authors.forename: Jingxiu
authors.initials: J
authors.lastname: Tang
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Huang
authors.forename: Yanlin
authors.initials: Y
authors.lastname: Han
authors.forename: Minghong
authors.initials: M
authors.lastname: Wu
mesh_terms: D006108:Graphite / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D049449:Luminescence; D049408:Luminescent Agents / Q000737:chemistry*; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D012822:Silicon Dioxide / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*
chemical_list: D028581:Lanthanoid Series Elements; D049408:Luminescent Agents; D012834:Silver; D012822:Silicon Dioxide; D006108:Graphite