Upconversion Luminescence Performance Research Articles

Morphology controlled synthesis of Ba4Bi3F17:Er3+,Yb3+ and the dual-functional temperature sensing and optical heating applications

Design and synthesis of new fluoride upconversion (UC) luminescent materials with controllable morphologies remains a challenge. Here, novel Ba4Bi3F17:Er3+/Yb3+ UC nanoparticles (UCNPs) were discovered and prepared using a simple one-step solvothermal strategy, and the modulation of the morphology and particle size was investigated in detail. Upon 980 nm excitation, the influence of dosage amounts of Yb3+/Er3+, and the environmental temperatures on the UC luminescent performance were studied in the temperature range of 293–393 K. The maximum relative sensitivities (Sr) of Ba4Bi3F17:1 mol%Er, 13 mol%Yb material are calculated to be 0.0122 K-1 and 0.0167 K−1 at 293 K, respectively, based on the two energetic levels of (2H11/2, 4S13/2) and (2H11/2, 4F9/2). In addition, the internal heating performance of the Ba4Bi3F17:Er3+/Yb3+ UCNPs was also evaluated in the pump power range of 112–901 mW, and the internal temperature of the UCNPs increased from 296 to 367 K with the increase of excitation power. This work initiates the discovery of the new bismuth-based fluoride nanothermometers and demonstrates the great potential for bifunctional applications in temperature sensing and optical heater devices.

Adjusting white light in Er3+/Tm3+/Yb3+ tridoped ZrO2/WO3 nanocrystals

To develop a white light-emitting diode (LED) phosphor with a better performance, we will make an Er3 + / Tm3 + / Yb3 + tridoped ZrO2 / WO3 composite nanophosphor through the sol–gel method. Using a 975-nm laser diode, we analyze the upconversion luminescence performance of the sample. The result shows that the Er3 + / Tm3 + / Yb3 + tridoped sample can emit strong white light and its color temperature is adjustable. The study helps to explore efficient, complex nanophosphors for white LEDs.

Effect of the doping of Al3+ ions on up-conversion luminescent performance of ZnGa2O4:Yb3+,Er3+ Phosphors

Al3+ doped ZnGa2O4:Yb3+,Er3+ powder phosphors with different Al3+ doping content were synthesized by solid-state method with subsequent thermal treatment at 1300 ℃. The morphology, structural characterization and up-conversion luminescent properties of as-prepared samples were investigated by scanning electron microscope (SEM), x-ray diffraction (XRD) and LSP920 spectrofluorometer under the excitation of a 980 nm laser with different power density. In brief, all samples have good crystallinity and consist of long rods with width of 600–900 nm and length of 1–3 µm. Under the 980 nm excitation, all phosphors can generate strong green emission at 524 nm, 549 nm (attributed to 2H11/2→ 4I15/2 transition, 4S3/2→4I15/2 transition of Er3+), red emission at 659 nm (corresponding to 4F9/2→4I15/2 transition of Er3+) and slight blue emission at 410 nm (attributed to 2H9/2→4I15/2 transition of Er3+). By contrast, the up-conversion efficiency and intensity raises with the doping of Al3+ ions. Accordingly, the doping of Al3+ ions has no effect on up-conversion emission peaks, but improve the up-conversion efficiency and intensity of phosphors.

Controllable synthesis of lanthanide Yb3+ and Er3+ co-doped AWO4 (A = Ca, Sr, Ba) micro-structured materials: phase, morphology and up-conversion luminescence enhancement.

Lanthanide ion (Yb3+, Er3+) co-doped AWO4 (A = Ca, Sr, Ba) up-conversion (UC) luminescent materials have been synthesized using a hydrothermal method and characterized by various microstructural and optical techniques. The results indicate that AWO4:Yb3+,Er3+ samples have an identical body-centered tetragonal scheelite structure with different morphologies, including CaWO4:Yb3+,Er3+ microspheres, dumbbell-like SrWO4:Yb3+,Er3+ and bipyramid-like BaWO4:Yb3+,Er3+. These samples exhibit visible emissions via an UC process under near-infrared (NIR) light (980 nm) excitation. Interestingly, the UC luminescence properties of AWO4:Yb3+,Er3+ can be prominently increased after combination with fluorescent carbon dots (CDs) to form CDs@AWO4:Yb3+,Er3+ composites. Compared to the corresponding samples without combination with CDs, the UC emission intensities of CDs@CaWO4:Yb3+,Er3+, CDs@SrWO4:Yb3+,Er3+ and CDs@BaWO4:Yb3+,Er3+ composites increase about three, six and seven fold in the green emission area, and two, three and four fold in the red emission area, respectively. The mechanism of UC luminescence enhancement is probably that the loss of non-radiative transitions from the higher energy levels to the lower excited levels could be effectively reduced through the energy capture by the CD energy levels. The fluorescence enhancement for Yb3+ and Er3+ co-doped AWO4 through combination with CDs provides a simple strategy for the tungstate system and other UC luminescent host systems.

Fabrication of Er/Tm/Yb/Y2O3 upconversion luminescence enhanced 3C-SiC composites as highly UV–Vis–NIR light responsive photocatalysts

New UV–Vis–NIR light responsive Er/Tm/Yb/Y2O3-SiC composites are designed by coupling different structured Er/Tm/Yb/Y2O3 upconversion luminescence materials (UCLMs) with 3C-SiC ultrafine nanocrystals (NCs) and explored as an efficient photocatalytic material. The Er/Tm/Yb/Y2O3 UCLMs can convert near-infrared (NIR) light into visible light which can be absorbed by 3C-SiC NCs, thus extend the optical responsive range of the photocatalysts to NIR light region. The structure effect of UCLMs on their upconversion luminescence performance is explored, indicating that the chain-like Er/Tm/Yb/Y2O3 UCLMs display much more preferable luminescence activity than flake-like structure. Compared with pure 3C-SiC NCs, both the two hybrid structures offer excellent performance in catalyzing decomposition of methylene blue (MB) under illumination of NIR light as well as UV–Vis–NIR light. Moreover, the photocatalytic activity of chain-like Er/Tm/Yb/Y2O3-SiC composites is better than that of the flake-like composites, profiting from the high light absorption efficiency induced by the multiple reflection-absorption effect. It is anticipated that this work provides new insights into the fabrication of photocatalysts with excellent light responses to a broader spectral range.

Lanthanide-Doped KLu2F7 Nanoparticles with High Upconversion Luminescence Performance: A Comparative Study by Judd-Ofelt Analysis and Energy Transfer Mechanistic Investigation

The development, design and the performance evaluation of rare-earth doped host materials is important for further optical investigation and industrial applications. Herein, we successfully fabricate KLu2F7 upconversion nanoparticles (UCNPs) through hydrothermal synthesis by controlling the fluorine-to-lanthanide-ion molar ratio. The structural and morphological results show that the samples are orthorhombic-phase hexagonal-prisms UCNPs, with average side length of 80 nm and average thickness of 110 nm. The reaction time dependent crystal growth experiment suggests that the phase transformation is a thermo-dynamical process and the increasing F−/Ln3+ ratio favors the formation of the thermo-dynamical stable phase - orthorhombic KLu2F7 structure. The upconversion luminescence (UCL) spectra display that the orthorhombic KLu2F7:Yb/Er UCNPs present stronger UCL as much as 280-fold than their cubic counterparts. The UCNPS also display better UCL performance compared with the popular hexagonal-phase NaREF4 (RE = Y, Gd). Our mechanistic investigation, including Judd-Ofelt analysis and time decay behaviors, suggests that the lanthanide tetrad clusters structure at sublattice level accounts for the saturated luminescence and highly efficient UCL in KLu2F7:Yb/Er UCNPs. Our research demonstrates that the orthorhombic KLu2F7 is a promising host material for UCL and can find potential applications in lasing, photovoltaics and biolabeling techniques.

Structure and upconversion luminescence investigation of cubic Y3.2Yb0.4Er0.08Al0.32F12 codoped with Mg2+/Zn2+/Cu2+

In this paper, we report the divalent ions Mg2+, Zn2+, and Cu2+ as dopants to manipulate the crystal field asymmetry in a new cubic Y3.2Yb0.4Er0.08Al0.32F12 phase which features two different coordination sites for rare earth ions. X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and fluorescence spectrophotometer were employed for the crystal structure analysis and luminescence performance investigation. Results reveal that the phase transition from cubic to orthogonal of Y3.2Yb0.4Er0.08Al0.32F12 is promoted by Mg2+ doping. Among Mg2+, Zn2+, and Cu2+, Mg2+ is found to be the most effective dopant for the upconversion performance enhancement. The crystal lattice structure asymmetry increases with the rising of Mg2+ doping concentration and reaches the peak when 6 mol% Mg2+ is introduced; correspondingly, the brightness of 408 and 654 nm emissions are strikingly enhanced over 20 times, and the lifetime of 540 nm emission is shortened to half of that in the Mg2+-free sample. The investigation results establish the understanding of divalent ions as dopants for adjusting upconversion luminescence performance and may be helpful for researchers to develop quick responsive upconversion luminescence materials.

The Effect of Phase Structures on the Enhanced Red Upconversion Luminescence in NaLuF4:Yb-Er Nanocrystals.

In this work, α-NaLuF4:Yb,Er (NLF) nanocomposites (NCs) and β-NLF NCs with diameter about ~13 nm were fabricated by a high temperature decomposition reaction method. The effects of NLF structure on the enhanced red upconversion luminescence performance were investigated. Under 980 nm excitation from a laser diode, the α-NLF emitted dominant red UC emission. Furthermore, the possible energy transfer mechanism was proposed on the basis of our experimental results.

Magnetic-upconversion luminescent bifunctional flexible coaxial nanoribbon and Janus nanoribbon: One-pot electrospinning preparation, structure and enhanced upconversion luminescent characteristics

Abstract Two kinds of new-typed magnetic-upconversion luminescent bifunctional one-dimensional nanostructures, including [Fe3O4/PMMA]@[NaYF4:Yb3+,Er3+/PMMA] coaxial nanoribbons and [Fe3O4/PMMA]//[NaYF4:Yb3+,Er3+/PMMA] Janus nanoribbons, have been successfully synthesized by one-pot electrospinning technology using specifically-designed spinnerets. The morphologies and properties of the final products were investigated in detail by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), biological microscopy (BM), fluorescence spectroscopy, vibrating sample magnetometry (VSM) and thermogravimetry (TG). The results show the coaxial nanoribbons and Janus nanoribbons possess superior magnetic and luminescent properties owing to their special nanostructures. Compared with Fe3O4/NaYF4:Yb3+,Er3+/PMMA composite nanoribbons, both coaxial nanoribbons and Janus nanoribbons provide better upconversion luminescent performance. The novel-typed magnetic-upconversion luminescent bifunctional coaxial nanoribbons and Janus nanoribbons have potential applications as new nano-bio-label materials, drug target delivery materials and other peculiar bifunctional materials due to their excellent magnetic and upconversion luminescent properties. Moreover, the reported construction concepts and fabrication methods are of universal significance for fabrication of other multifunctional coaxial and Janus nanoribbons.

One‐Step Hydrothermal Synthesis of Carboxyl‐Functionalized Upconversion Phosphors for Bioapplications

In this paper, we report a facile one-step hydrothermal method to synthesize phase-, size-, and shape-controlled carboxyl-functionalized rare-earth fluorescence upconversion phosphors by using a small-molecule binary acid, such as malonic acid, oxalic acid, succinic acid, or tartaric acid as capping agent. The crystals, from nano- to microstructures with diverse shapes that include nanospheres, microrods, hexagonal prisms, microtubes, microdisks, polygonal columns, and hexagonal tablets, can be obtained with different reaction times, reaction temperatures, molar ratios of capping agent to sodium hydroxide, and by varying the binary acids. Fourier transform infrared, thermogravimetric analysis, and upconversion luminescence spectra measurements indicate that the synthesized NaYF(4):Yb/Er products with hydrophilic carboxyl-functionalized surface offer efficient upconversion luminescent performance. Furthermore, the antibody/secondary antibody conjugation can be realized by the carboxyl-functionalized surfaces of the upconversion phosphors, thus indicating the potential bioapplications of these kinds of materials.