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This work reports the successful preparation of a new type of crystalline luminescent organic nanodot (<3.5 nm) by kinetically trapped self‐assembly, which is then used as a simplified π‐packing model to simulate the structure of CDs. The precise structure and J‐aggregation‐induced photoluminescence (PL) of the nanodots are revealed by investigating the structural relationship between the nanodots and the corresponding single crystals and their properties. Compared with the single crystals, crystalline organic nanodots show longer PL lifetime, higher PL quantum yield, and narrower PL peak, indicating that they are potential organic quantum nanodots. In addition, the efficient π‐stacking environment in the corresponding single crystals can promote π‐aggregation‐induced PL anisotropy. This work indicates crystalline organic nanodots with precise structures to be potentially useful for understanding the structures of CDs and to be attractive potential luminescent materials. [ABSTRACT FROM AUTHOR]

As a promising color converter in warm white LEDs, phosphors-in-glass (PiG) thick film is still suffering from the deficiency of high-efficient red phosphors. Herein, commercial Ce 3+ :Y 3 Al 5 O 12 and/or Eu 2+ :Sr 2 Si 5 N 8 phosphors were successfully embedded into a phosphate glass matrix coated on a soda-lime-silicate glass substrate. Their structural and luminescent properties were respectively investigated by XRD, SEM and photoluminescence spectra analysis. Color-tunable emission was achieved by varying the weight ratio of red to yellow phosphors. After fabricating LED devices with the optimal sample, considerable luminous performance was achieved with luminous efficacy of 72.1 lm/W, correlated color temperature of 5612 K and color rendering index Ra of 82.5. It suggested that the Ce 3+ :Y 3 Al 5 O 12 /Eu 2+ :Sr 2 Si 5 N 8 PiG thick film exhibits a significant potential for high-power warm white LEDs. [ABSTRACT FROM AUTHOR]

Ce 3+ : Y 3 Al 5 O 12 (Ce-YAG) phosphors-in-glass (PiG), which serves as both luminescent convertor and encapsulating material in the remote white light-emitting diodes (LEDs), has become a promising research field. However, the challenges in processing and mechanical strength still remain due to its submillimeter thickness. Herein, a novel transparent Ce-YAG PiG thick film was coated on a common glass substrate through conventional screen printing process and subsequent heat treatment. The introduced commercial Ce-YAG phosphors almost kept intact in a lead-free glass matrix. The microstructures and luminescent properties of as-prepared samples were investigated systematically. White LED device was also fabricated via mounting the optimal sample on the InGaN blue-emitting chips, which yielded bright white light with considerable luminous efficiency and color quality. The resulting screen-printed Ce-YAG PiG thick film will be a promising candidate for applications in the high-power remote white LEDs. [ABSTRACT FROM AUTHOR]

• 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]

Er3+/Yb3+ co-doped SiO 2 –Al 2 O 3 –AlF 3 -Gd 2 O 3 –Na 2 O glass with different F/O ratios were prepared. The effect of F/O ratio on the structure and optical properties of the glasses was investigated. The amorphous nature of the glasses was determined by XRD, and the glass transition temperature (T g) and the crystallization peak temperature (T c) were obtained from the DSC curves. The change in the structure of the glass network was analyzed by infrared spectroscopy. The density and absorption spectra of the bulk glass was also investigated. The excitation spectrum, emission spectrum and 4S 3/2 level fluorescence lifetime of Er3+ ions in the glasses were tested by a Xenon lamp with adjustable wavelength. The up-conversion luminescence spectrum of Er3+ ions was measured under excitation of a 980 nm laser. The results show that the green (2H 11/2 , 4S 3/2) and red (4F 9/2) up-conversion luminescence intensity is the highest when the F/O ratio is 0.214. According to the variation law of up-conversion luminescence intensity and pump power, it is confirmed that the up-conversion green (2H 11/2 → 4I 15/2 , 4S 3/2 → 4I 15/2) and red (4F 9/2 → 4I 15/2) light of Er3+ ions are the three-photon absorption process based on excited state absorption (ESA) and energy transfer up-conversion (ETU) mechanism. Finally, energy transfer transitions between Er3+ and Yb3+ are also analyzed. The CIE chromaticity coordinates were calculated from the emission spectrum obtained at two different excitation wavelengths of 378 nm and 980 nm. • Er3+/Yb3+ co-doped fluorosilicate glass with different F/O ratios was synthesized. • Excitation, emission spectrum and lifetime of Er3+ ions in the glass were tested. • Up-conversion luminescence properties were measured under a 980 nm laser excitation. • CIE chromaticity coordinates were calculated from the emission spectrum obtained. • Glass obtained can be a potential candidate for yellow-green color display devices. [ABSTRACT FROM AUTHOR]