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• The AMF with different densities was prepared by liquid-liquid interface self-assembly method. • A series of AMF@SiO 2 @NaYbF 4 : 2%Er3+ composite structures were constructed to enhance UC emission intensity of Er3+ ions. • The UC emission intensity of the single NaYbF 4 : 2%Er3+ microdisk was enhanced by 6.98 time. • The physics mechanism of the plasmon-enhanced UC luminescence is carefully studied. [Display omitted] Harnessing the precious metal plasmon effect is a powerful way to enhance the upconversion luminescence of rare-earth materials, so it has received extensive attention from researchers. In this study, a series of AMF@SiO 2 @NaYbF 4 : Er3+ composite structures were constructed with an Au mono-layer film (AMF) as the substrates and SiO 2 as the isolation layer to enhance the upconversion emission intensity of a single NaYbF 4 : 2%Er3+ microdisk. When the size of Au nanoparticles was 72 nm and the thickness of the SiO 2 isolation layer was 24 nm, the upconversion emission enhancement factor of the single NaYbF 4 : 2%Er3+ microdisk reached 6.98 under 980 nm laser excitation, due mainly to the enhancement of the local electromagnetic field. The upconversion luminescence properties of a single NaYbF 4 : 2%Er3+ microdisk were significantly affected by the size of Au nanoparticles, the density of the AMF substrate, and the thickness of the SiO 2 isolation layer. The plasmon-enhanced upconversion luminescence mechanism was studied according to its luminescence properties, dynamic tests, and theoretical simulation. The synergistic effects in the local electromagnetic field, luminescence quenching, and local surface plasmon resonance effect are also discussed. The results of this research provide an invaluable theoretical basis for enhancing the upconversion luminescence of rare-earth materials with the help of AMF substrates. [ABSTRACT FROM AUTHOR]

In this work, the energy transfer process and upconversion luminescence properties of NaYF 4 : Ln3+@NaYF 4 : Ln3+ (Ln = Yb3+, Er3+, Tm3+) core-shell microcrystals were studied through introducing different Yb3+ ions in core and shell. Compared with Yb3+/Tm3+/Er3+ co-doped NaYF 4 microcrystals, the NaYF 4 :Yb3+/Tm3+@NaYF 4 : Yb3+/Er3+ core-shell microcrystals displays greater stability spectral characteristics under NIR 980 nm excitation. This is because the core-shell structures can control the excitation energy acquisition channel and avoid interactions between Er3+ and Tm3+ ions. Meanwhile, the luminescence properties of NaYF 4 @NaYF 4 core-shell microcrystals can also be precisely controlled by changing concentrations of Yb3+ ions in the core and shell, respectively. The experimental results further indicate that upconversion emission of microcrystals can also be precisely controlled by constructing core-shell structures. The multicolor emission core-shell microcrystals may have great potential in display, anti-counterfeiting and micro-photoelectric technology applications. [Display omitted] • The core-shell microrods with doping different ions were successfully built by epitaxial growth technology. • The upconversion emission properties of doping ions can be accurately regulated in the NaYF 4 @NaYF 4 core-shell microrods. • The regulation mechanism was carefully discussed by spectral characteristics. • This study provides important experimental support for precise regulation of upconversion luminescence of microcrystals. [ABSTRACT FROM AUTHOR]

The construction of core-shell structure helps in enhancing upconversion luminescence in lanthanide-doped micro/nanomaterials. This study aimed to synthesize a series of NaYF 4 and NaErF 4 core-shell microrods based on epitaxial growth technology so as to enhance the upconversion emission. The upconversion luminescence properties of single NaYF 4 :Yb3+/Er3+ and NaErF 4 microrods with different core-shell structures were carefully studied using a confocal microscope spectroscopy test system under 980-nm near-infrared excitation. The upconversion emission intensity and red-to-green emission intensity ratio of Er3+ ions were remarkably enhanced in different single microrods by building different inert and active core-shell structures. The higher red-to-green ratio was mainly due to the cross-relaxation between Er3+ ions and the energy back-transfer process from Er3+ to Yb3+ ions, which were explained on the basis of spectral characteristics and rate equations. These tunable NaYF 4 and NaErF 4 core-shell microrods had the potential to be applied to displays, micro-lasers, and anti-counterfeiting. Image 1 • A series of NaY/ErF 4 core-shell microrods have been successfully synthesized via hydrothermal method. • The upconversion luminescence properties of single NaY/ErF 4 microrod with different core-shell structures are investigated. • The stronger upconversion emission and higher R/G ratio were obtained in NaErF 4 core-shell microrods. • The luminescence mechanisms of Er3+ ions in different core-shell structures have been carefully discussed. • The construction of micron core-shell can not only enhance the luminescence, but also provide a new way to construct new micro-materials. [ABSTRACT FROM AUTHOR]