Abstract
Localized electric filed enhancement by surface plasmon resonance (SPR) of noble metal nanoparticles is an effective method to amplify the upconversion luminescence (UCL) strength of upconversion nanoparticles (UCNPs), whereas the highly effective UCL enhancement of UCNPs in colloids has not been realized until now. Here, we designed and fabricated the colloidal Au-Ag nanocage@NaYF4@NaYF4:Yb,Er core-shell hybrid with different intermediate thickness (NaYF4) and tunable SPR peaks from visible wavelength region to NIR region. After the optimization of the intermediate spacer thickness (~7.5 nm) of NaYF4 NPs and the SPR peak (~950 nm) of noble metal nanoparticles, an optimum enhancement as high as ~25 folds was obtained. Systematic investigation indicates that UCL enhancement mainly originates from the influence of the intermediate spacer and the coupling of Au-Ag nanocages with the excitation electromagnetic field of the UCNPs. Our findings may provide a new thinking on designing highly effective metal@UCNPs core-shell hybrid in colloids.
Highlights
Various upconversion nanoparticles (UCNPs)@metal core-shell structures have been designed to boost upconversion luminescence (UCL) in colloids, the luminescent enhancements for those hybrid UCNPs are not obvious in colloidal solutions[21,22,23,24,25]
Au-Ag nanocage@ NaYF4@NaYF4:Yb,Er structures were prepared based on the galvanic replacement reaction between the silver nanocubes and HAuCl4 solution[34]
Energy-dispersive X-ray (EDX) analysis and X-ray diffraction (XRD) pattern of Au-Ag nanocage@NaYF4@NaYF4:Yb,Er in Fig. S2 indicate that the core-shell structure consists of cubic phase Au/Ag and cubic phase NaYF4
Summary
Xu Chen[1], Donglei Zhou[1], Wen Xu1,2, Jinyang Zhu[3], Gencai Pan[1], Ze Yin[1], He Wang[3], Yongsheng Zhu[4], Cui Shaobo5 & Hongwei Song[1]. We designed and fabricated the colloidal Au-Ag nanocage@NaYF4@ NaYF4:Yb,Er core-shell hybrid with different intermediate thickness (NaYF4) and tunable SPR peaks from visible wavelength region to NIR region. After the optimization of the intermediate spacer thickness (~7.5 nm) of NaYF4 NPs and the SPR peak (~950 nm) of noble metal nanoparticles, an optimum enhancement as high as ~25 folds was obtained. Systematic investigation indicates that UCL enhancement mainly originates from the influence of the intermediate spacer and the coupling of Au-Ag nanocages with the excitation electromagnetic field of the UCNPs. Our findings may provide a new thinking on designing highly effective metal@UCNPs core-shell hybrid in colloids. After the optimization of the intermediate spacer thickness (~7.5 nm) of undoped NaYF4 and the SPR peak (~950 nm) of noble metal NPs, an optimum enhancement as high as ~25 folds was obtained
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