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Enhanced Red Emission in Er <sup>3+</sup> -Sensitized NaLuF <sub/>4</sub> Upconversion Crystals via Energy Trapping
摘要： Luminescence e?ciency of trivalent lanthanide-doped upconversion (UC) materials is signi?cantly limited by luminescence concentration quenching. In this work, red UC emission is dramatically enhanced in Er3+-sensitized NaLuF4 UC crystals through energy trapping under multiple excitation wavelengths. Cross-relaxation quenching and the energy migration to internal lattice defects are simultaneously suppressed by con?ning the excitation energy in the Er3+ activator after introducing the Tm3+ or Ho3+ energy trapping center. The enhanced red UC emission (Er3+: 660 nm) mainly comes from the e?ective excitation energy con?nement by Tm3+ and Ho3+ trapping centers through an easy energy transfer between Er3+ and Tm3+/Ho3+: 4I11/2 (Er3+) → 3H5 (Tm3+) → 4I13/2 (Er3+) and 4I11/2 (Er3+) → 5I6 (Ho3+) → 4I13/2 (Er3+). It is found that the con?ning e?ciency of excitation energy in Er3+-sensitized NaLuF4 crystals is higher than that in Yb3+/Er3+ cosensitized NaLuF4 crystals, and the luminescence e?ciency of Er3+-sensitized NaLuF4 crystals is much higher than that of Er3+-based host sensitization UC crystals (NaErF4). Moreover, Er3+-sensitized UC particles can be e?ciently excited by three di?erent wavelengths (808, 980, and 1532 nm), indicating huge advantages for applications in bioimaging, anticounterfeiting, and solar cells.
关键词： energy trapping,anticounterfeiting,NaLuF4,Er3+-sensitized,solar cells,bioimaging,upconversion,luminescence
更新于2025-09-09 09:28:46
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Near-infrared excited cooperative upconversion in luminescent Ytterbium(ΙΙΙ) bioprobes as light-responsive theranostic agents
摘要： Near-infrared (NIR) Ytterbium(III) complexes namely [Yb(dpq)(DMF)2Cl3] (1), [Yb(dppz)(DMF)2Cl3] (2), [Yb(dpq)(ttfa)3] (3) and [Yb(dppz)(ttfa)3] (4) based on photosensitizing antenna: dipyrido-[3,2-d:2’,3’-f]-quinoxaline (dpq), dipyrido-[3,2-a:2′,3′-c]-phenazine (dppz) and 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Httfa), were designed as NIR bioimaging agents utilizing cooperative upconversion luminescence (CUCL) of Yb(III). Their structures, detailed photophysical properties, biological interactions, photo-induced DNA cleavage, NIR photocytotoxicity and cellular internalization and bioimaging properties were examined. Discrete mononuclear complexes adopt a seven-coordinated {LnN2O2Cl3} mono-capped octahedron (1, 2) and eight-coordinated {LnN2O6} distorted square antiprism geometry (3, 4) with bidentate N, N-donor dpq, dppz and O,O-donor ttfa ligands. The designed Yb(III) probes (3, 4) having advantages of dual sensitizing antennae (dpq/dppz and Httfa) to modulate the desirable optical properties in NIR region for bioimaging in biologically transparent window and light-responsive intracellular damage with spatiotemporal control. The lack of inner-sphere water (q = 0), remarkable photostability, large Stokes’ shifts, presence of energetically rightly poised ligand 3T states allows efficient energy transfer (ET) to the emissive 2F5/2 state of Yb(III). The unique cooperative upconversion luminescence (CUCL) of Yb(III) was observed in 1-4 in the visible blue region (λem = 490 nm) upon NIR excitation at 980 nm, makes them special candidates for NIR-to-visible or NIR-to-NIR cellular imaging probes. The CUCL property of Yb(III) were observed in the discrete mononuclear complexes both in solid state and solution. We elegantly utilized this remarkable property of Yb(III) for cellular imaging application for the first time to the our knowledge including potential uses in CUC/multiphoton excitation microscopy. The complexes exhibit significant binding propensity to DNA, HSA and BSA (K ~ 105 M-1). They effectively cleave supercoiled (SC) DNA to its nicked circular (NC) form at 365 nm via photoredox pathways. The cellular uptake studies evidently displayed cytosolic and nuclear localization of the complexes. Finally, the capability of Yb(III) complexes usage for PDT were demonstrated through significant near-IR photocytotoxicity at 980 nm CW laser. The results depicted here offers an intelligent strategy towards developing light-responsive highly photostable Yb(III) probes for NIR theranostic application in the biologically transparent phototherapeutic window.
关键词： Cooperative upconversion luminescence,NIR photocytotoxicity,NIR cellular imaging,Phototherapeutic,NIR excitation,Ytterbium
更新于2025-09-09 09:28:46
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Enhancement of Red Upconversion Emission of LiGdF <sub/>4</sub> :Yb <sup>3+</sup> /Ho <sup>3+</sup> Nanorods by Doping with Ce <sup>3+</sup>
摘要： A series of tetragonal phase LiGdF4:Yb3+/Ho3+ nanorods tri-doped with Ce3+ have been successfully prepared via a facile oil heated method at 200 °C. The visible green and red upconversion emissions have been achieved and the red emission intensity is enhanced gradually with increasing Ce3+ concentration. The ratio of red to green emission of the Ho3+ ions is boosted about 20-fold due to efficient cross relaxation processes between Ho3+ and Ce3+ ions, which promote the red emission and weaken the green emission. The crystal phase and morphology of the nanorod samples were inspected by X-ray diffraction and transmission electron microscopy, respectively. This work has great potential applications in the biological imaging, biomedical and color display applications.
关键词： Energy Transfer,Upconversion Luminescence,Nanorods LiGdF4
更新于2025-09-04 15:30:14
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Color-tunable and upconversion luminescence of Gd2O2S:Er,Tm phosphor: experimental investigations and first-principles calculation
摘要： The Er3+, Tm3+ co-doped gadolinium oxysulfide phosphors were prepared using solid-state reaction in vacuum. The crystal structure, morphology, and photoluminescence characteristics were, respectively, investigated by X-ray diffraction, transmission electron microscope, upconversion luminescence spectra and Commission Internationale de L’Eclairage diagram. Under 980 nm excitation, the quenching concentration of Er3+ was revealed to be 7 mol% with highest luminescence intensity and fluorescence lifetime. The emitting color of Gd2O2S:Er,Tm phosphors can be tuned by adjusting the concentration of Er3+ and Tm3+. First-principles calculation was employed to clarify the luminescence mechanism of the impurities doped in gadolinium oxysulfide host lattice by calculated band structure, density of states and absorption spectrum.
关键词： first-principles calculation,color-tunable,Gd2O2S:Er,upconversion luminescence,Tm
更新于2025-09-04 15:30:14