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Tuning and enhancing the red upconversion emission of Er3+ in LiYF4 nanoparticles
摘要： The tetragonal-phased LiYF4:Yb3+/Er3+ nanoparticles with different core-shell nanostructures have been successfully synthesized by a modified solution-based method. The upconversion emissions of LiYF4: Yb3+/Er3+ nanoparticles were precisely tuned from green to red with the increase in Yb3+ concentrations under 980 nm excitation. The corresponding intensity ratios of the red and green emissions (R/G ratios) were enhanced from 0.06 to 5.33. However, the overall integral upconversion intensity of LiYF4:Yb3+/Er3+ nanoparticles clearly decreased when the Yb3+ doping concentrations were increased. For the enhancement of the red upconversion intensity and expansion of their application, two kinds of core-shell nanostructures, namely, LiYbF4:Er3+@LiYF4 and LiYbF4:Er3+@LiYbF4, were constructed through epitaxial growth at similar experimental conditions. The LiYbF4:Er3+@LiYF4 core-shell nanostructures exhibited stronger upconversion emission and higher R/G ratios than the LiYbF4:Er3+ and LiYbF4:Er3+@LiYbF4 nanoparticles. The highest R/G ratios increased to 6.27 in LiYbF4:Er3+@LiYF4 core-shell nanostructures, increasing 104-fold. The upconversion regulation and enhancing mechanism were also discussed according to the emission spectra and fluorescence lifetimes.
关键词： upconversion,LiYF4 nanoparticles,core/shell nanostructures,cross relaxation
更新于2025-09-10 09:29:36
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Improvement in upconversion/downshifting luminescence of Gd2O3 :Ho3+/Yb3+ phosphor through Ca2+ / Zn2+ incorporation and optical thermometry studies
摘要： The Ho3+/Yb3+ doped Gd2O3 phosphor was synthesized via the hydrothermal process. Co-doping of Ca2+ and Zn2+ ions caused a change in the particle morphology and aggregation of the Ho3+/Yb3+: Gd2O3 phosphor. The structural characterization of these particles was performed using X-ray diffraction analysis, Fourier transforms infrared spectroscopy and scanning electron microscopy. The 980 nm excitation assisted upconversion luminescence and 449 nm excitation assisted downshifting luminescence of these phosphor particles were compared through the incorporation of Ca2+ and Zn2+ co-dopants. The co-dopants concentration was varied at 0, 5, 10, 15 and 20 mol %. The change in upconversion/downshifting luminescence under the influence of the optimized molar concentration of these co-dopants was studied and explained based on structural variations in the present phosphor material. The paramagnetic behavior of these particles was characterized and compared to search possible applications of these particles in the biomedical field. The samples were studied comparatively for temperature sensing.
关键词： Temperature sensing,Upconversion/Downshifting,Ca2+/Zn2+,M-H plot,Ho3+/Yb3+: Gd2O3
更新于2025-09-10 09:29:36
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Small lanthanide-doped Sr2YbF7 nanocrystals: Upconversion fluorescence and upconversion-driven photodegradation
摘要： A series of lanthanide-doped Sr2YbF7 nanocrystals were prepared conveniently via a solvothermal method using oleic acid as the stabilizing agent, which were about 15 nm of the average crystalline size at 200 °C and 24 h. Through screening the doped lanthanide ions and their concentrations, we found that the nanocrystals realized intense ultraviolet, visible and near-infrared upconversion emissions under 980 nm excitation. Based on the photo-physical property of the nanocrystals, we built the hybrid Sr2YbF7: Tm3+@TiO2 to successfully realize upconversion-driven photo-degradation of Rhodamine B, in which semiconducting TiO2 took advantage of the light emitted by Sr2YbF7: Tm3+ to produce the electron-hole pairs.
关键词： Upconversion,Photo-degradation,Sr2YbF7 nanocrystals
更新于2025-09-10 09:29:36
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Highly Erbium-Doped Nanoplatform with Enhanced Red Emission for Dual-Modal Optical-Imaging-Guided Photodynamic Therapy
摘要： Generally, luminescence quenching at high doping concentrations typically limits the concentration of doped ions in the lanthanide material to less than 0.05?20 mol %, and this is still a major hindrance in designing nanoplatforms with improved brightness. In this research, a nanoplatform capable of dual-modal imaging and synergetic antitumor cells therapy was designed. NaYF4:x%Er@NaXF4 (x = 5, 25, 50, and 100; X = Lu and Y) core@shell nanoparticles with Er3+ ion concentration up to 100 mol % were synthesized, and the luminescence properties under near-infrared (NIR) excitation were detected. The results show the strong coupled of surface and concentration quenching effects in upconversion nanoparticles (UCNP). Upconversion luminescence (UCL) and NIR-II emission intensity increased with negligible concentration quenching effect under 980 and 800 nm NIR lasers because of the growth of epitaxial shells. Therefore, the enhanced red luminescence transfers energy to photosensitizer ZnPc as the photodynamic therapy (PDT) agent for tumor inhibition efficacy.
关键词： photodynamic therapy,upconversion nanoparticles,luminescence quenching,nanoplatform,synergetic antitumor cells therapy,NaYF4:x%Er@NaXF4,dual-modal imaging
更新于2025-09-10 09:29:36
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Precise Control of Localized Surface Plasmon Wavelengths Is Needed for Effective Enhancement of Triplet-Triplet Annihilation-Based Upconversion Emission
摘要： In this study, we demonstrate that the localized surface plasmon (LSP) resonance of metal nanoparticles, depending strictly on the generating wavelength of LSP resonance, can have both beneficial enhancement and harmful quenching effects on a triplet-triplet annihilation-based upconversion (TTA-UC) emission. When the LSP resonance band of anisotropic silver nanoprisms spectrally overlapped with the photoexcitation wavelength of a sensitizer and the fluorescence of an emitter, an increase in the photoexcitation efficiency and an acceleration of the radiative decay rate were respectively induced, resulting in an effective enhancement in the TTA-UC emission. Furthermore, the overlapping with the photoexcitation wavelength led to a significant decrease (93%) in the threshold light excitation intensity, which greatly enhances the figure-of-merit in TTA-UC systems. However, when the LSP resonance band overlapped with the phosphorescence band of the sensitizer, the TTA-UC emission was extremely quenched, accompanied by the enhanced phosphorescence and the decreased phosphorescence lifetime. These results suggest that the decrease in the TTA-UC emission is a result of the competition between the triplet-triplet energy transfer to the emitter and the LSP-induced nonradiative energy transfer to the silver nanoprisms from the triplet-excited sensitizer. This discovery of the conflicting effects of LSP resonance provides an important guideline: a precise adjustment of LSP resonance wavelengths is needed for the efficient enhancement of TTA-UC emission. This requirement is different from those of other fluorescence systems such as single downconverted fluorophores and lanthanide-based upconversion nanoparticles.
关键词： solid state,fluorescence,phosphorescence,silver nanoprisms,localized surface plasmon resonance,triplet-triplet annihilation,photon upconversion
更新于2025-09-10 09:29:36
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Core/Shell Upconversion Nanocrystal Hybrids with Temperature-Dependent Emission Color Changes for Multilevel Anticounterfeiting Applications
摘要： This work presents a novel and highly secure anticounterfeiting strategy based on core/shell upconversion nanocrystal (UCNC) hybrids with temperature-responsive multicolor emissions. Opposite luminescent temperature-dependences are found for active-core@inert-shell (thermal quenching) and active-core@active-shell (thermally induced enhancement) UCNCs. Accordingly, their hybrids are designed to show obvious color changes with increasing temperature under 975 nm excitation. Various color-shifting pathways (from white to green, blue to green, etc.) are achieved by adjusting the core/shell NC combinations in the hybrids. Moreover, color changes of the printed patterns using the hybrid NC inks can be realized by the simple heating treatment, or by increasing the laser power and prolonging the irradiation time. The results indicate the great potential of these core/shell NC hybrids for anticounterfeiting applications with high-level security and convenient authentication methods.
关键词： upconversion,anticounterfeiting,nanocrystals,hybrids,luminescence
更新于2025-09-10 09:29:36
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In situ Synthesis of Dicarboxylic Acid-Functionalized Upconversion Nanoparticles for Bioimaging Applications
摘要： We report a one-step strategy to in situ synthesize highly water-dispersable NaYF4:Yb/Er upconversion nanoparticles (UCNPs) by employing dicarboxylic acids. The dicarboxylic acids serve as a type of dual-purpose surface ligand for both controlling the growth and enabling the water-dispersability of the NaYF4:Yb/Er UCNPs. It is found that the carbon chain length of the dicarboxylic acids has a marked effect on the size and morphology of the UCNPs. Among the dicarboxylic acids studied, adipic acid shows a more superior performance. The UCNPs functionalized with adipic acid exhibit comparatively uniform size and morphology, as well as excellent water-dispersability. Our results also demonstrate their minimal toxicity and great potential for bioimaging applications.
关键词： bioimaging,water-dispersable,dicarboxylic acids,upconversion nanoparticles
更新于2025-09-10 09:29:36
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Tracing of dye molecules in living plants through NaGdF4:Yb3+,Er3+ fluorescent nanoprobes
摘要： In this paper, we demonstrated trace of dye molecules in living plants. The NaGdF4:Yb3+,Er3+ nanoparticles probe was used to detect the rhodamine B(RhB) in bean sprout. It is found that the fluorescencedye can be efficiently imbibed during the growing process and the absorbance presented a position dependence effect, which was supported by the upconversion spectra and the fluorescent image characterization. In addition, the concentration of the residual RhB in bean sprout can be efficiently traced by the synthesized probe based on the fluorescent resonant energy transfer. Finally, the relation between the excitation power, concentration and the ratio of yellow to green emission are discussed in detail. These results can be helpful in understanding the RhB dye molecules absorbance process in vegetable growth and provide an efficient way to trace the residual dyes in vivo plant.
关键词： Upconversion nanoprobes,Rare-earth-doped materials,fluorescence,Biological sensing and sensors,luminescence
更新于2025-09-10 09:29:36
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A significant enhancement of middle infrared fluorescence and upconversion of Er3+-doped transparent germanate glasses containing LaF3 nanocrystals
摘要： Er3+-doped oxyfluoride germanate glass containing LaF3 nanocrystals have been prepared via heat treatment from the precursor glass. Dynamic and static spectroscopic characteristics of IR, MIR and upconversion fluorescence of Er3+ doped transparent oxyfluoride germanate glass ceramic were investigated. When heat treat temperature increased from 540 to 600 (cid:1), NIR and MIR fluorescence intensity increase about 3 times, and companied with 2060 times 550 nm and 350 times 660 fluorescence enhancement. Increasing the heat treat time at 560 (cid:1) from 2 to 12 hours, the NIR and MIR fluorescence intensity increased about 2.5 and 1.8 times. It was due to the part of Er3+ ions were incorporated into LaF3 nanocrystals, resulting in the decrease of the multi-phonon relaxation of Er3+. According to the ratio between MIR fluorescence intensity of the heat treated glass sample to that of the untreated glass sample, the number of the Er3+ which was incorporated into the LaF3 nanocrystals can be quantificationally estimated. It was estimated to be 0.98% to 5.8% when the heat treat temperature increased from 540 to 600 (cid:1), and 1.21% to 1.63% with increasing heat treat time from 2 to 12 hours.
关键词： mid-infrared,transparent glass ceramic,upconversion fluorescence
更新于2025-09-10 09:29:36
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In-situ synthesis and enhanced upconversion luminescence of Y2O3/Y2O2S:Yb3+,Er3+/Tm3+ nanocomposites by reduction of Y2O3:Yb3+,Er3+/Tm3+
摘要： Y2O3/Y2O2S:Ln3+ (Ln = Yb,Er and Yb,Tm) nanocomposites with enhanced upconversion luminescence were successfully prepared by combining hydrothermal with in-situ synthesis method. Under 980 nm excitation, the upconversion luminescence intensity of Y2O3/Y2O2S:Ln3+ increased, and then declined with the rising amount of sulfur powder. Especially, the Y2O3/Y2O2S:Ln3+ nanocomposites can emit brighter upconversion luminescence than those of Y2O3:Ln3+ and Y2O2S:Ln3+. In terms of Y2O3/Y2O2S:Yb3+,Er3+ nanocomposites which were prepared with 0.025g sulfur powder, an unusual 4G11/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ could be observed. Besides, we have constructed a simple upconversion Y2O3/Y2O2S:Yb3+,Er3+@Au nanocomposite, which can be used for rapid sensing of glucose. The limit of detection of glucose level which based on Y2O3/Y2O2S:Yb3+,Er3+@Au was only 0.066 μmol/L. The proposed approach, which we have mentioned above, holds a great practical value for diabetes mellitus detection and clinical diagnosis.
关键词： B. Upconversion luminescence,A. Y2O3/Y2O2S:Yb3+Er3+,D. Glucose detection
更新于2025-09-10 09:29:36