Impact of Sc3+-Modified Local Site Symmetries on Er3+ Ion Upconversion Luminescence in Y2O3 Nanoparticles
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ABSTRACT:
SUBMITTER: Wang Y
PROVIDER: S-EPMC9327094 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:To develop novel luminescent materials for optical temperature measurement, a series of Yb3+- and Er3+-doped Ca3Sc2Si3O12 (CSS) upconversion (UC) phosphors were synthesized by the sol-gel combustion method. The crystal structure, phase purity, and element distribution of the samples were characterized by powder X-ray diffraction and a transmission electron microscope (TEM). The detailed study of the photoluminescence emission spectra of the samples shows that the addition of Yb3+ can greatly enhance the emission of Er3+ by effective energy transfer. The prepared Yb3+ and Er3+ co-doped CSS phosphors exhibit green emission bands near 522 and 555 nm and red emission bands near 658 nm, which correspond to the 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions of Er3+, respectively. The temperature-dependent behavior of the CSS:0.2Yb3+,0.02Er3+ sample was carefully studied by the fluorescence intensity ratio (FIR) technique. The results indicate the excellent sensitivity of the sample, with a maximum absolute sensitivity of 0.67% K-1 at 500 K and a relative sensitivity of 1.34% K-1 at 300 K. We demonstrate here that the temperature measurement performance of FIR technology using the CSS:Yb3+,Er3+ phosphor is not inferior to that of infrared thermal imaging thermometers. Therefore, CSS:Yb3+,Er3+ phosphors have great potential applications in the field of optical thermometry.
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Project description:Internal hydroxyl impurity is known as one of the main detrimental factors affecting the upconversion (UC) efficiency of upconversion luminescence (UCL) nanomaterials. Different from surface/ligand-related emission quenching which can be effectively diminished by, e.g., core/shell structure, internal hydroxyl is easy to be introduced in synthesis but difficult to be quantified and controlled. Therefore, it becomes an obstacle to fully understand the relevant UC mechanism and improve UC efficiency of nanomaterials. Here we report a progress in quantifying and large-range adjustment of the internal hydroxyl impurity in NaYF4 nanocrystals. By combining the spectroscopy study and model simulation, we have quantitatively unraveled the microscopic interactions underlying UCL quenching between internal hydroxyl and the sensitizers and activators, respectively. Furthermore, the internal hydroxyl-involved UC dynamical process is interpreted with a vivid concept of "Survivor effect," i.e., the shorter the migration path of an excited state, the larger the possibility of its surviving from hydroxyl-induced quenching. Apart from the consistent experimental results, this concept can be further evidenced by Monte Carlo simulation, which monitors the variation of energy migration step distribution before and after the hydroxyl introduction. The new quantitative insights shall promote the construction of highly efficient UC materials.
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Project description:Rare earth (RE3+)-doped phosphors generally suffer from thermal quenching, in which their photoluminescence (PL) intensities decrease at high temperatures. Herein, we report a class of unique two-dimensional negative-thermal-expansion phosphor of Sc2(MoO4)3:Yb/Er. By virtue of the reduced distances between sensitizers and emitters as well as confined energy migration with increasing the temperature, a 45-fold enhancement of green upconversion (UC) luminescence and a 450-fold enhancement of near-infrared downshifting (DS) luminescence of Er3+ are achieved upon raising the temperature from 298 to 773 K. The thermally boosted UC and DS luminescence mechanism is systematically investigated through in situ temperature-dependent Raman spectroscopy, synchrotron X-ray diffraction and PL dynamics. Moreover, the luminescence lifetime of 4I13/2 of Er3+ in Sc2(MoO4)3:Yb/Er displays a strong temperature dependence, enabling luminescence thermometry with the highest relative sensitivity of 12.3%/K at 298 K and low temperature uncertainty of 0.11 K at 623 K. These findings may gain a vital insight into the design of negative-thermal-expansion RE3+-doped phosphors for versatile applications.
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Project description:GdSr2AlO5:Yb3+/Er3+ micro-particles were synthesized by a simple solid state method. The structure, morphology, size and upconversion luminescence features have been characterized. These results indicated that GdSr2AlO5 has a contracted tetragonal cell and has irregular block shaped particles with sizes of about 5 μm. During upconversion, green (2H11/2, 4S3/2 → 4I15/2) (527 nm, 549 nm) and red (4F9/2 → 4I15/2) (665 nm) emissions had been observed, both of which occurred via a two-photon population process. In addition, green UC emission characteristics were studied, and it was found that its temperature ranged from 293 K to 473 K and the sensitivity was 0.0054 K-1 at 473 K. This indicated that GdSr2AlO5:Yb3+/Er3+ micro-particles may have potential application in high temperature environments for safety signs.
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Project description:Chirality, universal characteristics of nature, introduces asymmetry in synthetic materials. Revealing the microscopic asymmetry of macroscopically symmetric materials is the key to control the growth of chiral materials and give full play to their application potential. Materials for photon upconversion (UC) are of great interest for many applications owing to their anti-Stoke luminescence process, especially for chiral UC materials. For the preparation of UC materials, a tiny change in reaction parameters will lead to variations in morphology, phase components, and fluorescence intensity, as well as its chirality. Because of the strict reaction conditions for the formation of chiral UC materials, there are no reports of the successful synthesis of chiral UC materials. Therefore, a facile method for the controllable synthesis of chiral UC materials is highly desired. Herein, chiral-assembled hexagonal prisms of β-NaYF4:Er3+/Yb3+ microcrystals were synthesized to realize the smart manipulation of their morphology as well as a great improvement of the fluorescence efficiency. We proposed a three-stage doped β-NaYF4 crystal growth mechanism on mesoscale regulation, where the fluorescence enhancement principle of chirality was revealed. The enhancement of fluorescence efficiency of chiral UC materials endows their promising application in luminescent displays.
| S-EPMC6644319 | biostudies-literature
Project description:In this work, various LiZnPO4:0.5 mol% Ln3+ (Ln = Ho, Er) phosphors with different Yb3+ ion doping concentrations were synthesized by a sol-gel/Pechini method. X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques were used to evaluate the phase and morphology of the samples. The UC process was mentioned as the typical emission peaks of Er3+ and Ho3+. For Er3+ and Ho3+, different optical temperature sensing methods are included. The Boltzmann distribution was accompanied by the fluorescence intensity ratio (FIR) for the two green Er3+ emissions originating from thermally-coupled levels. The effect of pump power on sensor sensitivities was extensively studied. The temperature uncertainty is also evaluated. The red and green emissions generated from non-thermally-coupled levels were used for temperature sensing in the Ho3+-activated LiZnPO4. High sensitivities were obtained in the phosphors, and the LiZnPO4:Yb3+/Ho3+ showed the largest absolute sensitivities. LiZnPO4:Yb3+-Er3+/Ho3+ phosphors may be useful in the development of new luminescent materials for optical temperature sensing.
| S-EPMC9041328 | biostudies-literature
Project description:Surface modified NaYF4:Yb3+/Er3+/Zn2+ upconversion nanoparticles were obtained by using branched polyethylenimine (PEI). Strong fluorescence emission was observed and the influence of copper ions on the fluorescence emission of the PEI-modified NaYF4:Yb3+/Er3+/Zn2+ nanoparticles was investigated. It was found that the fluorescence emission can be quenched through luminescence resonance energy transfer from the particle to the copper ions. The results show that the PEI modified NaYF4:Yb3+/Er3+/Zn2+ nanoparticle can be used as a fluorescent probe for highly sensitive and selective detection of copper ions.
| S-EPMC9089350 | biostudies-literature
Project description:Phase-pure eulytite-type Sr3Y0.88(PO4)3:0.10Yb3+,0.02Ln3+ upconversion (UC) phosphors (Ln = Ho, Er, Tm) were synthesized via gel-combustion and subsequent calcination at 1250°C. Their UC luminescence, temperature-dependent fluorescence intensity ratio of thermally and/or non-thermally coupled energy levels, and performance of optical temperature sensing were systematically investigated. The phosphors typically exhibit green, orange-red and blue luminescence under 978 nm NIR laser excitation for Ln = Er, Ho and Tm, respectively, which were discussed from two- and three-photon processes. The 524 nm green (Er3+), 657 nm red (Ho3+) and 476 nm blue (Tm3+) main emissions were analyzed to have average decay times of ~52 ± 2, 260.6 ± 0.7 and 117 ± 1 ?s, respectively. It was shown that (1) the Er3+ doped phosphor has a better overall performance of temperature sensing with thermally coupled 2H11/2 and 4S3/2 energy levels, whose maximum absolute (S A) and relative (SR ) sensitivities are ~5.07 × 10-3 K-1 at 523 K and ~1.16% at 298 K, respectively; (2) the Ho3+ doped phosphor shows maximum S A and SR values of ~0.019 K-1 (298-573 K) and 0.42% at 573 K for the non-thermally coupled energy pairs of 5F5/(5F4,5S2) and 5I4/5F5, respectively; (3) the Tm3+ doped phosphor has a maximum S A of ~12.74 × 10-3 K-1 at 573 K for the non-thermally coupled 3F2,3/1G4 energy levels and a maximum SR of ~1.74% K-1 at 298 K for the thermally coupled 3F2,3/3H4 levels. Advantages of the current phosphors in optical temperature sensing were also revealed by comparing with other typical UC phosphors.
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Project description:Er3+/Yb3+ co-doped Bi5O7I uniform porous microsphere photocatalysts were synthesized by a two-step chemical method, which possesses excellent photocatalytic performance and upconversion luminescence property. The photocatalytic performance of the photocatalysts was studied by degradation of bisphenol A in aqueous solution under visible light and different monochromatic light irradiation. The photocatalytic performance of Er3+/Yb3+ co-doped Bi5O7I sample is better than that of the pristine Bi5O7I and Er3+-doped Bi5O7I samples. Moreover, Er3+/Yb3+ co-doped Bi5O7I possesses photocatalytic ability with a red light monochromatic LED lamp (3 W, λ = 630 nm) and an infrared monochromatic LED lamp (100 W, λ = 940 nm) irradiation whose wavelength is longer than the absorption-limiting wavelength of pristine Bi5O7I sample. This phenomenon further verified that the upconversion property of Er3+ and Yb3+ causes the improved photocatalytic efficiency of Er3+/Yb3+ co-doped Bi5O7I sample.
| S-EPMC7496766 | biostudies-literature
Project description:Lanthanide-doped upconversion (UC) phosphors absorb low-energy infrared light and convert it into higher-energy visible light. Despite over 10 years of development, it has not been possible to synthesize nanocrystals (NCs) with UC efficiencies on a par with what can be achieved in bulk materials. To guide the design and realization of more efficient UC NCs, a better understanding is necessary of the loss pathways competing with UC. Here we study the excited-state dynamics of the workhorse UC material β-NaYF4 co-doped with Yb3+ and Er3+. For each of the energy levels involved in infrared-to-visible UC, we measure and model the competition between spontaneous emission, energy transfer between lanthanide ions, and other decay processes. An important quenching pathway is energy transfer to high-energy vibrations of solvent and/or ligand molecules surrounding the NCs, as evidenced by the effect of energy resonances between electronic transitions of the lanthanide ions and vibrations of the solvent molecules. We present a microscopic quantitative model for the quenching dynamics in UC NCs. It takes into account cross-relaxation at high lanthanide-doping concentration as well as Förster resonance energy transfer from lanthanide excited states to vibrational modes of molecules surrounding the UC NCs. Our model thereby provides insight in the inert-shell thickness required to prevent solvent quenching in NCs. Overall, the strongest contribution to reduced UC efficiencies in core-shell NCs comes from quenching of the near-infrared energy levels (Er3+: 4I11/2 and Yb3+: 2F5/2), which is likely due to vibrational coupling to OH- defects incorporated in the NCs during synthesis.
| S-EPMC5968434 | biostudies-literature