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1.
The spectroscopic properties of LaAlO 3 polycrystals doped with Er 3+, Ho 3+ and Yb 3+ ions have been investigated. Very efficient up-conversion emission occurs upon IR excitation. The strongest luminescence has been observed for a sample doped with Er 3+, Ho 3+, and Yb 3+ ions simultaneously and annealed at 1500 °C. An efficient energy transfer to Yb 3+ ions is observed when Er 3+ or Ho 3+ ions are excited. The energy transfer mechanisms are proposed. 相似文献
2.
Lanthanide (Ln 3+)‐doped upconversion nanoparticles (UCNPs) as a new generation of multimodal bioprobes have attracted great interest for theranostic purpose. Herein, red emitting nonstoichiometric Na 0.52YbF 3.52:Er UCNPs of high luminescence intensity and color purity are synthesized via a facile solvothermal method. The red UC emission from the present nanophosphors is three times more intense than the well‐known green emission from the ≈30 nm sized hexagonal‐phase NaYF 4:Yb,Er UCNPs. By utilizing Na 0.52YbF 3.52:Er@SrF 2 UCNPs as multifunctional nanoplatforms, highly efficient in vitro and in vivo 915 nm light‐triggered photodynamic therapies are realized for the first time, with dramatically diminished overheating yet similar therapeutic effects in comparison to those triggered by 980 nm light. Moreover, by virtue of the high transverse relaxivity ( r 2) and the strong X‐ray attenuation ability of Yb 3+ ions, these UCNPs also demonstrate good performances as contrast agents for high contrast magnetic resonance and X‐ray computed tomography dual‐modal imaging. Our research shows the great potential of the red emitting Na 0.52YbF 3.52:Er UCNPs for multimodal imaging‐guided photodynamic therapy of tumors. 相似文献
3.
The Mn 2+, Yb 3+, Er 3+: ZnWO 4 green phosphors are synthesized successfully through the high temperature solid state reaction method. The micro-structure and morphology have been investigated by means of XRD and EDS. The doped concentrations of Mn 2+, Yb 3+, Er 3+ are measured by ICP. The absorption spectra and emission spectra with different doped concentrations of Mn 2+ are presented to reveal the influence of Mn 2+ on the green up-conversion performance. Excited with 970 nm LED, the up-conversion emission peak at 547 nm is obtained and the CIE spectra as well as the green light photo are also presented. The results indicate that the Mn 2+ ions play the role of the luminescence adjustment in the up-conversion process, which can improve the up-conversion green emission intensity effectively. The luminescence adjustment mechanism of Mn 2+ ions in Mn 2+, Yb 3+, Er 3+: ZnWO 4 green phosphors has been discussed. The crystal parameters of Dq, B and C are calculated to evaluate the energy level split effect. 相似文献
4.
This article reports the luminescence properties of amphipathic YVO 4:Er 3+/Yb 3+ nanoparticles (average grain size ca. 20 nm) obtained by an oleate-aided hydrothermal process. Depending on the upconversion
(UPC) and downconversion (DWC) processes, they show luminescence in the visible and near-infrared (NIR) regions, respectively,
by 980-nm excitation. The sample doped with Er 3+:2.5 mol% and Yb 3+:10 mol% showed the highest luminescence intensity in both the visible and NIR regions as a result of efficient energy transfer
from Yb 3+ to Er 3+ ions. The hydrothermal treatment greatly enhanced both the DWC and UPC luminescence efficiencies. This is due to the reduction
in the concentration of surface defects and ligands, accompanied by grain growth. NIR Fluorescence microscopy revealed for
the first time that DWC luminescence is sufficiently intense for application of these nanocrystals as a NIR bioprobe. 相似文献
5.
Here a multifunctional nanoplatform (upconversion nanoparticles (UCNPs)‐platinum(IV) (Pt(IV))?ZnFe 2O 4, denoted as UCPZ) is designed for collaborative cancer treatment, including photodynamic therapy (PDT), chemotherapy, and Fenton reaction. In the system, the UCNPs triggered by near‐infrared light can convert low energy photons to high energy ones, which act as the UV–vis source to simultaneously mediate the PDT effect and Fenton's reaction of ZnFe 2O 4 nanoparticles. Meanwhile, the Pt(IV) prodrugs can be reduced to high virulent Pt(II) by glutathione in the cancer cells, which can bond to DNA and inhibit the copy of DNA. The synergistic therapeutic effect is verified in vitro and in vivo results. The cleavage of Pt(IV) from UCNPs during the reduction process can shift the larger UCPZ nanoparticles (NPs) to the smaller ones, which promotes the enhanced permeability and retention (EPR) and deep tumor penetration. In addition, due to the inherent upconversion luminescence (UCL) and the doped Yb 3+ and Fe 3+ in UCPZ, this system can serve as a multimodality bioimaging contrast agent, covering UCL, X‐ray computed tomography, magnetic resonance imaging, and photoacoustic. A smart all‐in‐one imaging‐guided diagnosis and treatment system is realized, which should have a potential value in the treatment of tumor. 相似文献
6.
It is shown that the ion implantation of phosphorus into thin amorphous films of germanium dioxide doped with Er 3+ and Yb 3+ ions can be used for enhancing luminescence from Er 3+ ions at ∼1.53 μm. 相似文献
7.
Data are presented on the 300-K photoluminescence in GaS crystals doped with Er 3+ or codoped with Er 3+ and Yb 3+. IR excitation (λ ex = 976 nm) gives rise to anti-Stokes luminescence in GaS:Er 3+ (0.1 at %) and GaS:Er 3+,Yb 3+ (0.1 + 0.1 at %) and leads to an increased intensity of the emission due to the 4 I 11/2 → 4 I 15/2 transitions. The anti-Stokes luminescence is shown to result from consecutive absorption of two photons by one Er 3+ ion, and the increased intensity of Er 3+ luminescence in GaS: Er 3+,Yb 3+ is due to energy transfer from Yb 3+ to Er 3+. 相似文献
8.
The Stokes and anti-Stokes luminescence of undoped and rare-earth-doped (Er 3+ and Yb 3+) BaSiO 3 has been studied in the temperature range 78–450 K under excitation at 10–1000 mV. The results indicate that the emission
mechanism in BaSiO 3 crystals is hole recombination and that the anti-Stokes luminescence is due to consecutive sensitization; that is, the Yb 3+ ions in the BaSiO 3 compound act as luminescence sensitizers, and the Er 3+ ions, as activators. 相似文献
9.
In search of new contrast materials for NMR and fluorescence diagnostics and neutron capture therapy of cancer, we have synthesized ultrafine Er 3+- and Yb 3+-doped Gd 11SiP 3O 26 and Gd 14B 6Ge 2O 34 particles and studied their luminescence properties. We measured the Er 3+ upconversion luminescence spectra of the gadolinium erbium ytterbium phosphosilicates and borate germanates in the visible range and evaluated the absolute quantum yield of their luminescence. The quantum yield of luminescence in the gadolinium phosphosilicate Gd 11SiP 3O 26 doped with 5.0 at % Yb and 2.5 at % Er is comparable to that in known Yb 3+/Er 3+ codoped fluorides. The nonradiative Yb 3+ ?? Er 3+ energy transfer efficiency is evaluated. 相似文献
10.
Near‐infrared lights have received increasing attention regarding imaging applications owing to their large tissue penetration depth, high spatial resolution, and outstanding signal‐to‐noise ratio, particularly those falling in the second near‐infrared window (NIR II) of biological tissues. Rare earth nanoparticles containing Er 3+ ions are promising candidates to show up‐conversion luminescence in the first near‐infrared window (NIR I) and down‐conversion luminescence in NIR II as well. However, synthesizing particles with small size and high NIR II luminescence quantum yield (QY) remains challenging. Er 3+ ions are herein innovatively combined with Yb 3+ ions in a NaErF 4@NaYbF 4 core/shell manner instead of being codoped into NaLnF 4 matrices, to maximize the concentration of Er 3+ in the emitting core. After further surface coating, NaErF 4@NaYbF 4@NaYF 4 core/shell/shell particles are obtained. Spectroscopy studies are carried out to show the synergistic impacts of the intermediate NaYbF 4 layer and the outer NaYF 4 shell. Finally, NaErF 4@NaYbF 4@NaYF 4 nanoparticles of 30 nm with NIR II luminescence QY up to 18.7% at room temperature are obtained. After covalently attaching folic acid on the particle surface, tumor‐specific nanoprobes are obtained for simultaneously visualizing both subcutaneous and intraperitoneal tumor xenografts in vivo. The ultrahigh QY of down‐conversion emission also allows for visualization of the biodistribution of folate receptors. 相似文献
11.
The upconversion luminescence (UCL) of nanocrystalline gadolinium oxide (Gd 2O 3) doped with Er 3+ and Yb 3+ ions has been studied in the temperature range of 90–400 K. The nanocrystals were synthesized by chemical vapor deposition and possessed a cubic crystalline structure with an average particle size within 48–57 nm. It is established that the USL intensity in the red ( 4F9/2 → 4I15/2 transition in Er3+ ion) and green ( 4S3/2 → 4I15/2 transition) spectral regions depends on the sample temperature and concentration of dopant ions, as well as on the additional structural defects (anion vacancies) created in the crystal lattice by the introduction of Zn 2+ ions or irradiation with high-energy (10 MeV) electrons. The luminescence efficiency and spectrum of the upconversion phosphor are determined by energy transfer processes. 相似文献
12.
A new phosphor CaSnO 3: Yb 3+ was synthesized by a traditional solid-state reaction and the luminescent properties were investigated. The phosphors are well crystallized at 1200?°C. The excitation and the emission spectra show the characteristic broad of the Sn 2+ ion and the X-ray photoelectron spectroscopy demonstrate the existence of Sn 2+ ions caused by the doping of Yb 3+ ions. The CaSnO 3: Yb 3+ phosphor showed a typical afterglow behavior when the UV source was switched off. Thermal simulated luminescence study indicated that the persistent afterglow of CaSnO 3: Yb 3+ phosphor was generated by the suitable electron or hole traps which were resulted from doping the calcium stannate host with rare-earth ions (Yb 3+). 相似文献
13.
Yb 3+/Er 3+ and Yb 3+/Tm 3+ co-doped LaF 3 nanoparticles with upconversion luminescence properties were prepared via the co-precipitation method, followed by heat treatment at different temperatures in the range of 180°C to 600°C. We investigated the influence of heat treatment temperatures on the size, morphology, and upconversion luminescence intensity of the nanoparticles. Significant increases of the particle size and upconversion luminescence intensity of the nanoparticles were observed with increasing heat treatment temperature. The upconversion mechanism of the LaF 3:Yb 3+,Er 3+ and LaF 3:Yb 3+,Tm 3+ nanoparticles was also discussed. 相似文献
14.
In this paper, Ho3+/Yb3+ co-doped Sodium Gadolinium Fluoride (NaGdF4) phosphors were synthesized by a facile and efficient hydrothermal method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy spectrum (EDS), and photoluminescence (PL). The results of XRD and SEM indicated that the prepared NaGdF4 samples have the hexagonal structure and good orientation in the case of changing the concentration of Yb3+. The results of pump power dependence of up-conversion intensity indicated that the energy transfer mechanism from Yb3+ to Ho3+ is a two-photon process. The energy transfer between Ho3+ and Yb3+ under 448 nm excitation was determined by PL spectra and fluorescence lifetimes. All the results proved that the doping of Yb3+ ions can effectively improve the up-conversion luminescence of NaGdF4 phosphors and achieve quantum cutting efficiency of up to 179.8%. Overall, NaGdF4:Ho3+/Yb3+ have potential application in the field of optoelectronic materials. 相似文献
15.
The codoping of KY 3F 10 with Pr 3+ and Yb 3+ ions is investigated as a possible quantum cutting system to enhance solar cells efficiency. For one visible photon absorbed by Pr ions, two ytterbium ions are expected to be excited by two consecutive energy transfers. The subsequent emission of two infrared photons reduces thus the thermalization losses usually observed in Si solar cells. Emission spectra and lifetime decays in KY 3F 10 doped with 0.5% Pr 3+ and codoped with 0%, 1%, 10% and 20% Yb 3+ show an increase of the energy transfer efficiency from Pr 3+ to Yb 3+ with the Yb 3+ concentration. For the first Pr 3+ to Yb 3+ energy transfer, an efficiency close to 100% is achieved in KY 3F 10: 0.5%Pr 3+, 20%Yb 3+. However, this promising result faces challenging issues since an increase in Yb concentration induces energy migration between Yb 3+ ions which impairs the Yb 3+ luminescence. 相似文献
16.
The present work is devoted to the characterization of the thermal and spectroscopic properties of tellurite glasses, codoped with Er 3+, Yb 3+ and Tm 3+ rare-earth ions and silver nanoparticles (NPs). The techniques used for this investigation were UV–visible and infrared absorption, time-resolved luminescence and thermal lens. Time-resolved luminescence studies indicate efficient Yb 3+ → Er 3+ and Yb 3+ → Tm 3+ energy transfers and intense Er 3+ and Tm 3+ mid-infrared emissions around 1550 nm and 1860 nm, respectively. The presence NPs is found to increase the thermal diffusivity of the materials and to shorten the mid-infrared emission lifetime of both the Er 3+ and Tm 3+ ions. 相似文献
17.
The influence of activation of the Y 2O 3 matrix of the Y 2O 3:Eu 3+ phosphor by Bi 3+ ions on the luminescence of Eu 3+ and Bi 3+ ions in it and on conditions of the excitation energy transfer to luminescence centers is studied. It is shown that the presence of Bi 3+ ions leads to the appearance of recombination luminescence with participation of bismuth ions at low concentrations (up to 6–8 at %) of the dominant activator europium and to an increase in the threshold of intrinsic concentration quenching of its luminescence. 相似文献
18.
Infrared-to-ultraviolet upconversion luminescence agent Y 2O 3:Yb 3+,Tm 3+ was prepared by a combustion method using citrate as a fuel/reductant. The prepared sample was characterized by X-ray diffraction,
SEM, and fluorescence spectrophotometer. Two unusual 1I 6 → 3H 6 (~297 nm) and 1D 2 → 3H 6 (~363 nm) emissions from Tm 3+ ions were observed at room temperature under 980-nm laser excitation. The change of upconversion emission intensity depending
on the Yb 3+ concentrations was discussed. The results showed that modest Yb 3+ doping could make the upconversion emission of Tm 3+ intense, and high Yb 3+ concentrations might lead to fluorescence quenching. Moreover, the influence of ultraviolet upconversion luminescence on
the photodegradation of methyl orange aqueous solution under solar light irradiation in the presence of TiO 2 catalyst doped with Y 2O 3:Yb 3+,Tm 3+ was also investigated. It was concluded from the experiment of this study that TiO 2/Y 2O 3:Yb 3+,Tm 3+ composite had higher photocatalytic activity than pure TiO 2 under solar light. This study would make TiO 2 utilize sunlight more efficiently and accelerate the practical application of photocatalytic technology in water treatment
region. 相似文献
19.
The upconversion luminescence spectra of nanocrystallite MgAl 2O 4 doped with 1% of Ho 3+ and 5% of Yb 3+ ions after excitation at 980 nm were measured. Influence of excitation regime either continuous or pulse on upconversion mechanisms was shown. For continuous wave (CW) laser excitation upconversion process is due to phonon assisted Excited State Absorption (ESA). For pulse laser excitation upconversion emission is due to Energy Transfer Upconversion (ETU). 相似文献
20.
Zinc aluminate co-doped with Yb 3+/Er 3+ for potential application in upconversion lasers was prepared in proportions of 2:1, 5:1, and 10:1 by combustion reaction. The samples were characterized by X-ray diffraction, transmission electron microscopy, and optical spectroscopy. The results reveal the formation of crystalline ZnAl 2O 4 primary phase and trace amounts of ZnO and Yb 3Al 5O 12 secondary phases. They also indicate that increasing the Yb 3+/Er 3+ ratio favored the increase of secondary phases. The optical spectroscopy analysis revealed that red emission predominated over green, and that emission intensity was directly influenced by the infrared intensity of the diode laser. These results indicate that ZnAl 2O 4 doped with rare earth ions may also be an interesting material for luminescence obtained by energy upconversion. 相似文献
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