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.

Improving photocatalytic activity by combining upconversion nanocrystals and Mo-doping: a case study on β-NaLuF4:Gd,Yb,Tm@SiO2@TiO2:Mo

“…36 The photocatalytic activities of β-UCNCs@SiO 2 @TiO 2 :Mo and β-UCNCs@SiO 2 @TiO 2 are higher than β-UCNCs-TiO 2 physical mixture, which can be ascribed to the difference in their energy transfer efficiencies. The RhB is almost completely degraded (99.44%) in the present of β-UCNCs @SiO 2 @TiO 2 :Mo after exposing under Xe lamp for 210min, whereas the degradation ratios of P25, TiO 2 , β-UCNCs-TiO 2 physical mixture and NaLuF 4 : Gd, Yb, Tm@SiO 2 @TiO 2 are 30%, 25%, 55% and 82%, respectively.…”

“…36 In typically, 10 ml each of the coordinating oleic acid (90%) ligand and the non-coordinating solvent 1-octadecene (90%) were added to the reaction vessel (Solution A). 36 In typically, 10 ml each of the coordinating oleic acid (90%) ligand and the non-coordinating solvent 1-octadecene (90%) were added to the reaction vessel (Solution A).…”

“…3. 36,37 For Mo 6+ -doped TiO 2 , the incorporation of Mo 6+ ions into TiO 2 lattice usually results in a formation of oxygen vacancies. 29 Based on these UV-visible spectra, it can be speculated that the UV photos generated from the upconversion process of β-UCNCs can be absorbed by the anatase TiO 2 via an energy transfer.…”

“…8, both the simulated solar and NIR-driven photocatalytic activities of the product are very stable. 36 Furthermore, Mo 6+ ions replacing Ti 4+ ions in the lattice act as electron traps to promote the charge separation and to reduce the recombination rate of the photogenerated carriers. One is the function of the upconversion nanocrystal β-UCNCs and the other is the effect of Mo-doping.…”

Large enhanced photocatalytic activity of g-C3N4 by fabrication of a nanocomposite with introducing upconversion nanocrystal and Ag nanoparticles

“…The samples of UCNPs, UCNPs@SiO 2 /g-C 3 N 4 , and UCNPs@SiO 2 @Ag/g-C 3 N 4 show multiple characteristic diffraction peaks (100, 110, 101, 111, 200, 210, 002, 211, 112), which match well with the standard of b-NaLuF 4 (JCPDS 27-0726). 37 Both Ag/g-C 3 N 4 and UCNPs@SiO 2 @Ag/g-C 3 N 4 show a typical face-centered cubic phase of silver (JCDS 04-0783), 38 conrming the formation of Ag NPs. All of the XRD results are in good agreement with the measured TEM results.…”