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1.
Spectrochim Acta A Mol Biomol Spectrosc ; 323: 124935, 2024 Dec 15.
Article in English | MEDLINE | ID: mdl-39116594

ABSTRACT

The development of white phosphors that can be activated in near-ultraviolet light is highly important in the field of LED lighting. In this work, a series of color-tunable Y2(Ti1-xHfx)2O7:Eu phosphors were prepared by adjusting the HfO2 and Eu3+ concentrations. In particular, white Y2(Ti0.8Hf0.2)2O7:Eu phosphors were successfully synthesized and emitted a broad band covering the entire visible light region upon excitation with 340 nm UV light. The white banded materials were composed of Eu2+ and Eu3+ emissions and HfO2 defect emission. The formation of Eu2+ ions was caused by the introduction of HfO2, which causes self-reduction of Eu3+ ions but does not require additional reducing agents. The white Y2(Ti0.8Hf0.2)2O7:Eu phosphors exhibit low color shifting at high temperature, which is very important for LED applications. The chromaticity shift of the Y2(Ti0.8Hf0.2)2O7:0.2Eu phosphor is 2.83 × 10-2 at 503 K, which is only 54.8 % that of commercial three-color white phosphors at the same temperature. The Ra value did not decrease significantly with increasing temperature and reached 90.2 at 383 K. Y2 (Ti0.8Hf0.2)2O7:0.2Eu phosphors were assembled with a 365 nm LED chip to fabricate a WLED device that showed excellent white-colored coordinates (0.345, 0.358) and a high Ra value of 90.1 under a 300 mA current.

2.
Cell Death Discov ; 10(1): 319, 2024 Jul 11.
Article in English | MEDLINE | ID: mdl-38992027

ABSTRACT

Graft availability from donation after circulatory death (DCD) is significantly limited by ischaemia reperfusion (IR) injury. Effective strategies to mitigate IR injury in DCD grafts are essential to improve graft quality and expand the donor pool. In this study, liver grafts from DCD pigs were preserved in the University of Wisconsin (UW) solution saturated with 0.1 nM dexmedetomidine (Dex) and various concentrations of noble gases Argon (Ar) and/or Xenon (Xe) at 4 °C for 24 or 72 h. The combined 50% Ar and Dex provided maximum protection to liver grafts by reducing morphological damage, apoptosis, necroptosis, ferroptosis, hepatocyte glycogen depletion, reticulin framework collapse, iron deposition, and oxidative stress. In vitro, human liver Hep G2 cells were preserved in the UW solution saturated with 0.1 nM Dex and 50% Ar in combination at 4 °C for 24 h, followed by recovery in medium at 37 °C for up to 48 h to mimic clinical IR injury. This treatment significantly increased the expression of anti-oxidative stress proteins by promoting the translocation of thioredoxin-interacting protein (TXNIP) to mitochondria, thereby inhibiting ferroptosis, increasing plasma membrane integrity, and maintaining cell viability.In summary, The combination of 0.1 nM Dex and 50% Ar may be a promising strategy to reduce ferroptosis and other form cell death, and preserve liver grafts.

3.
Dalton Trans ; 52(44): 16388-16397, 2023 Nov 14.
Article in English | MEDLINE | ID: mdl-37870179

ABSTRACT

Fluorescent CDs tend to undergo solid-state aggregation quenching in powder form. This is caused by the stacking of π-π conjugate structures and excessive resonant energy transfer. Moreover, various forms of N play an important role in white CDs suitable for LED applications. White, single-component, non-N-doped CDs have never been reported for LED application. In this study, to overcome this limitation, we developed Ga-doped CD powders containing no N element that exhibit ultra-wideband white emission in the range of 420-800 nm for LED applications and were able to resist solid-state aggregation quenching. Furthermore, the Ga-doped CD powders demonstrated excellent luminescence stability under high temperatures. Another strength of the Ga-doped CD powders is their large Stokes shift, where the peak center of white emission shifts from 550 nm to 650 nm under 365 nm excitation as the Ga doping concentration is adjusted from 0.05 to 0.6 (Ga : H2O, mass ratio). The full width at half-maximum can reach 262 nm. Additionally, the Ga-doped CD powders exhibit good luminescence stability under long-time exposure to an air atmosphere. Their luminescent intensity retained 70%-74% of the initial values even after being left in natural placement for 100 days. Moreover, the Ga-doped CDs demonstrate afterglow features.

4.
Spectrochim Acta A Mol Biomol Spectrosc ; 260: 119951, 2021 Nov 05.
Article in English | MEDLINE | ID: mdl-34049007

ABSTRACT

GdNbTiO6: Sm3+ phosphors with various Sm3+ concentrations were prepared via a high temperature solid-state reaction method. The crystal structure of the samples was characterized by means of X-ray diffraction (XRD) and the as-prepared samples were confirmed to be orthorhombic phase GdNbTiO6. Photoluminescence properties were investigated by measuring the concentration- and temperature-dependent photoluminescence spectra. Concentration-dependent luminescence quenching and luminescent thermal quenching behaviors were observed and they were respectively ascribed to the electric dipole-dipole interaction between Sm3+ ions and the cooperation of energy transfer and crossover process. The chromatic characteristics were found to be dependent on the excitation wavelength and Sm3+ concentration. In addition, temperature-induced redshift of charge transfer band of GdNbTiO6 host was found in temperature-dependent excitation spectra and the opposite variations of different excitation peaks were utilized for optical thermometry. Finally, the optical transition property was studied on the basis of the diffuse reflectance spectra and Judd-Ofelt (J-O) theory, meanwhile, its accuracy was evaluated by the result of emission spectra.

5.
Phys Chem Chem Phys ; 22(43): 25177-25183, 2020 Nov 21.
Article in English | MEDLINE | ID: mdl-33124640

ABSTRACT

Usually, the optical transition properties of trivalent rare earth (RE) ions in transparent hosts can be quantitatively investigated in the framework of Judd-Ofelt theory. A standard and commonly accepted calculation procedure based on the absorption spectrum has already been established. However, it is hard to assess the optical transition properties of trivalent RE ions doped in powdered and film materials owing to the difficulty in the absolute absorption spectrum measurements. In this work, we proposed a new route to calculate the Judd-Ofelt parameters of trivalent RE ion-doped materials in any morphological and shaped forms. In this method, the fluorescence decay values bridging the radiative transition rates and the Judd-Ofelt parameters were used. As an application example of the proposed Judd-Ofelt calculation method, the Judd-Ofelt parameters of Er3+ in NaYF4 were calculated via the proposed route, and it was found that the obtained results are in reasonable accordance with those derived from other routes. It was also proved that this proposed Judd-Ofelt calculation method is a practicable and effective route for evaluating optical transition properties of trivalent RE ions in non-transparent hosts as long as the fluorescence decay values can be measured.

6.
Phys Chem Chem Phys ; 22(15): 7844-7852, 2020 Apr 15.
Article in English | MEDLINE | ID: mdl-32227059

ABSTRACT

The optical transition properties of trivalent rare earth (RE3+) doped luminescent materials have received extensive attention. The Judd-Ofelt theory is an effective tool for exploring the optical transition properties for the 4f-4f transitions of lanthanides. The aim of this work is to discover the effect of Er3+ concentration and different Ln3+ ions on the Judd-Ofelt parameters in LnOCl:Er3+ (Ln = Y, La, Gd) phosphors. Oxychloride LnOCl:Er3+ (Ln = Y, La, Gd) phosphors were produced via a single displacement reaction technique. The Judd-Ofelt calculation procedure for RE3+ doped powders was modified and then adopted to obtain the Judd-Ofelt parameters of Er3+ in the studied phosphors. Meanwhile, a new route for examining the Judd-Ofelt calculation quality was proposed and used. It was found that the Er3+ doping concentration slightly affects the optical transition properties of Er3+ in YOCl and LaOCl, but greatly affects the optical transition properties in GdOCl. Moreover, it was also found that the optical transition properties of Er3+ depend also on Ln3+ (Ln = Y, La, Gd) though the crystal structure of these compounds is similar. The Judd-Ofelt parameters of Er3+ are the smallest in LaOCl:Er3+, medium in YOCl:Er3+, but the biggest in GdOCl:Er3+ when the doping concentration is the same.

7.
Phys Chem Chem Phys ; 21(20): 10840-10845, 2019 May 28.
Article in English | MEDLINE | ID: mdl-31089636

ABSTRACT

In this Reply, we truthfully respond to the comments on our recent paper entitled "A universal approach for calculating the Judd-Ofelt parameters of RE3+ in powdered phosphors and its application for the ß-NaYF4:Er3+/Yb3+ phosphor derived from auto-combustion-assisted fluoridation" published in Phys. Chem. Chem. Phys. [Y. Zhang, B. Chen, S. Xu, X. Li, J. Zhang, J. Sun, X. Zhang, H. Xia, R. Hua, A universal approach for calculating the Judd-Ofelt parameters of RE3+ in powdered phosphors and its application for the beta-NaYF4:Er3+/Yb3+ phosphor derived from auto-combustion-assisted fluoridation, Phys. Chem. Chem. Phys., 20, 2018, 15876-15883]. In the Comment, the authors oppugned partial calculation results we reported in our original paper, thus we redid the calculations and compared the presently obtained results with the original ones and the author provided ones. The recalculations and comparisons confirmed that our calculations are reproducible and the results are correct. In the Comment, the authors also made some comments on the Judd-Ofelt calculation approaches for powdered samples reported by other researchers. Following the authors' train of thought we added some supplements to the comments to understand the application strategy of Judd-Ofelt theory. Furthermore, we extended some points of view regarding the fluorescence lifetime measurements the authors presented in the Comment.

8.
Spectrochim Acta A Mol Biomol Spectrosc ; 217: 107-112, 2019 Jun 15.
Article in English | MEDLINE | ID: mdl-30928835

ABSTRACT

Usually, the luminescence intensity and mechanism of rare-earth ions doped materials are dependent on both doping concentration and sample temperature. In this study, we attempt to explore the concentration effect on up-conversion (UC) luminescence and the dependence of luminescence temperature quenching on excitation wavelength in YNbO4: Ho3+/Yb3+ phosphors. The YNbO4: Ho3+/Yb3+ phosphors with various Ho3+ and Yb3+ concentrations were synthesized via a high-temperature solid-state reaction technique. Intense green UC emission peaked at 543 nm was observed, accompanying with weak red and near infrared (NIR) UC emissions centered at 659 and 745 nm. Based on the laser working current dependence of UC luminescence, two-photon processes were responsible for both the green and the red UC emissions under 980 nm excitation, which have no apparent dependence on both Ho3+ and Yb3+ concentrations. According to the Arrhenius model, crossover process was responsible for the temperature-dependent down-conversion (DC) luminescence quenching of Ho3+ under 452 nm excitation. However, the temperature quenching processes of the green and the red UC luminescence cannot be well explained by Arrhenius model. It was found that the UC luminescence intensity decayed with increasing sample temperature, which was caused by both the crossover and temperature-dependent energy transfer processes.

9.
Phys Chem Chem Phys ; 20(23): 15876-15883, 2018 Jun 13.
Article in English | MEDLINE | ID: mdl-29845990

ABSTRACT

It is difficult to calculate the Judd-Ofelt (J-O) parameters for trivalent rare earth (RE)-doped powders due to the unavailable absorption spectrum that is necessarily used in the conventional J-O calculation procedure. In this study, a universal method starting from the diffuse-reflection spectrum for calculating the J-O parameters of RE3+-doped powdered samples was proposed. In this proposed method, by taking the Kubelka-Munk function into account, the absorption cross-section spectrum was derived from the diffuse-reflection spectrum in the RE3+-doped powdered sample using the connection between the absorption cross section and the radiative transition rate of RE3+. Then, the J-O parameters might be calculated from the absorption cross-section spectrum via the traditional J-O calculation technique. The NaYF4:Er3+/Yb3+ and NaYF4:Er3+ phosphors were prepared via an auto-combustion-assisted fluoridation technique, and the J-O calculation was carried out for the obtained samples. The obtained J-O parameters were compared with those reported in the literature and also verified by comparing the calculated radiative transition lifetimes with the experimental values. Finally, it was deduced that the proposed J-O calculation route was practicable.

10.
Sci Rep ; 8(1): 5736, 2018 Apr 10.
Article in English | MEDLINE | ID: mdl-29636498

ABSTRACT

YNbO4 phosphors with various Er3+ and Yb3+ concentrations were synthesized via a traditional high-temperature solid-state reaction method. Their crystal structure was investigated by means of X-ray diffraction (XRD) and Rietveld refinements, and it was confirmed that the obtained samples exist in monoclinic phase. The Er3+ and Yb3+ concentration-dependent up-conversion (UC) luminescence was studied under 1550 nm excitation. By inspecting the dependence of UC intensity on the laser working current, it was found that four-photon and three-photon population processes were co-existent for generating the green UC emissions in the samples with higher Yb3+ concentrations. In addition, it was observed that the temperature sensing properties of YNbO4: Er3+/Yb3+ phosphors were sensitive to both Er3+ and Yb3+ doping concentrations. Furthermore, based on the obtained temperature response of the UC luminescence phosphors, 1550 nm laser-irradiation-induced thermal effect was studied, and it was discovered that the sample temperature was very sensitive to the doping concentrations of Er3+ and Yb3+ and the excitation power.

11.
Opt Express ; 26(2): 1870-1881, 2018 Jan 22.
Article in English | MEDLINE | ID: mdl-29401909

ABSTRACT

Ag-Eu3+ co-doped fluoroborate glass phosphors doped with various Eu3+-concentrations were prepared by a melt-quenching technique. The luminescent properties of these glass phosphors were characterized by excitation and emission spectra. Broad excitation and emission bands located, respectively, at 300-450 nm and 390-700 nm originating from silver aggregates were observed. Strong red emissions were detected under 404 nm violet light-emitting diode (LED) excitation for those Ag-Eu3+ co-doped samples. It was found that these red emissions of Eu3+ well compensated the deficiency of the red spectral components in glasses containing Ag aggregates. In addition, it was confirmed that stable white light could be achieved from the combination of a specific Ag-Eu3+ co-doped fluoroborate glass phosphor and LEDs with different output wavelengths. By adjusting the luminescence intensity ratio of the glass phosphor to the 404 nm violet LED, tunable emitting color was realized, and the studied glass phosphors showed excellent emitting color stability toward LED drive currents. Our results demonstrated that this kind of easy fabrication, low-cost, and highly stable Ag-Eu3+ co-doped fluoroborate glass phosphors had potential application in white LED.

12.
Sci Rep ; 7(1): 11849, 2017 09 19.
Article in English | MEDLINE | ID: mdl-28928385

ABSTRACT

To realize photothermal therapy (PTT) of cancer/tumor both the photothermal conversion and temperature detection are required. Usually, the temperature detection in PTT needs complicated instruments, and the therapy process is out of temperature control in the present investigations. In this work, we attempt to develop a novel material for achieving both the photothermal conversion and temperature sensing and control at the same time. To this end, a core-shell structure with NaYF4:Er3+/Yb3+ core for temperature detection and NaYF4:Tm3+/Yb3+ shell for photothermal conversion was designed and prepared. The crystal structure and morphology of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Furthermore, the temperature sensing properties for the NaYF4:Er3+/Yb3+ and core-shell NaYF4:Er3+/Yb3+@NaYF4:Tm3+/Yb3+ nanoparticles were studied. It was found that the temperature sensing performance of the core-shell nanoparticles did not become worse due to coating of NaYF4:Tm3+/Yb3+ shell. The photothermal conversion behaviors were examined in cyclohexane solution based on the temperature response, the NaYF4:Er3+/Yb3+@NaYF4:Tm3+/Yb3+ core-shell nanoparticles exhibited more effective photothermal conversion than that of NaYF4:Er3+/Yb3+ nanoparticles, and a net temperature increment of about 7 °C was achieved by using the core-shell nanoparticles.


Subject(s)
Hyperthermia, Induced , Nanoparticles , Phototherapy , Animals , Erbium/chemistry , Fluorides/chemistry , Humans , Nanoparticles/chemistry , Nanoparticles/therapeutic use , Thermometers , Ytterbium/chemistry , Yttrium/chemistry
13.
Opt Express ; 25(14): 16047-16058, 2017 Jul 10.
Article in English | MEDLINE | ID: mdl-28789113

ABSTRACT

A core-shell structure with a NaYF4:Sm3+/Yb3+ core for photothermal conversion nanocalorifier and a NaYF4:Er3+/Yb3+ shell as temperature probe for potential applications in photothermal therapy (PTT) were synthesized by a thermal decomposition technique of rare-earth oleate complexes. The optical temperature reading-out property for the NaYF4:Sm3+/Yb3+@NaYF4:Er3+/Yb3+ core-shell structure was systematically investigated and it was found that in comparison with pure NaYF4:Er3+/Yb3+ particles, the temperature sensing performance of the NaYF4:Er3+/Yb3+ shell did not become worse due to the presence of NaYF4:Sm3+/Yb3+ core. Furthermore, the photothermal conversion behavior for core-shell nanoparticles was successfully examined by dint of temperature sensing of the NaYF4:Er3+/Yb3+ shell, and it was found that an excitation-power-density-dependent temperature increase of up to several tens degrees can be achieved. All the experimental results suggested that the core-shell structure may be an excellent nanocalorifier candidate for advanced temperature-controllable PTT.

14.
J Nanosci Nanotechnol ; 16(4): 3534-41, 2016 Apr.
Article in English | MEDLINE | ID: mdl-27451662

ABSTRACT

Nanosized Gd6WO12 phosphors containing various Er3+ concentrations and fixed Yb3+ concentration were synthesized by a co-precipitation method. The crystal structure and microscopic morphology of the obtained nanophosphors were characterized by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Two-photon processes for both the green and red upconversion (UC) emissions were confirmed by analyzing the dependence of UC intensities on 980 nm laser working current. UC emission intensity changing with temperature displays different trends for the samples with different Er3+ concentrations. The experimental results indicated that thermal quenching behavior of UC luminescence could not be simply explained by crossover mechanism. The enhancement for green UC emission in the sample with higher Er3+ concentration was discussed. Finally, the ErS+ concentration dependence of UC luminescence was experimentally observed, and its mechanisms were analyzed.

15.
J Nanosci Nanotechnol ; 15(6): 4717-21, 2015 Jun.
Article in English | MEDLINE | ID: mdl-26369102

ABSTRACT

A modified Judd-Ofelt theory is used in this paper to treat the electric dipole transitions within the 4f8 configuration of Tb3+ by considering the main perturbing components. Through the energy-level calculation and the strandard tensorial analysis, the explicit distances between the 4f7 5d configuration and the 5D4 state and other lower 4f8 energy levels are determined. The rare-earth ion Tb3+ substituted at Y3+ sites in KY3F10 has the site symmetry of C4v. The standard Judd-Ofelt parameters A2(10), A2(30), A4(30), A4(50), A6(50), A4(54) and A6(54) are included in the calculation together with odd-λ parameters A1(10), A3(30), A5(50) and A5(54). The fluorescence branching ratios originating from 5D4 are calculated. Compared with the experimental measurements, the modified model yields better results than the standard Judd-Ofelt theory.

16.
J Nanosci Nanotechnol ; 15(1): 281-9, 2015 Jan.
Article in English | MEDLINE | ID: mdl-26328346

ABSTRACT

In this paper, Tm3+ and Dy3+ single- and double-doped nano-sized GdVO4 phosphors were prepared via a co-precipitation reaction. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and photoluminescence (PL) were utilized to characterize the as-prepared samples. The XRD and FE-SEM results reveal that the samples are single phase and that the average size is about 30 nm, respectively. Under 280 nm ultraviolet excitation, Dy3+ and Tm3+ single-doped nano-sized GdVO4 phosphors show the characteristic emissions of Dy3+ (4F9/2 --> 6H15/2 and 4F9/2 -*6H13/2 transitions) and Tm3+ (1G4 --> 3H6 transition), respectively. All the luminescence results from efficient energy transfer from the GdVO4 host to the doped Dy3+ and Tm3+ ions. Moreover, the interaction types for Dy3+ and Tm3+ ions in nano-sized GdVO4 host are confirmed as exchange and electrical dipole-dipole interaction by theoretical calculation. In Tm3+ and Dy3+ co-doped nanosized GdVO4 phosphors, the luminescence intensities of Dy3+ ions increase with increasing Tm3+ ion doping concentration, which suggests that energy transfer from Tm3+ to Dy3+ ions occurs. The responding luminescence mechanisms have been proposed in this paper. Finally, in order to evaluate the luminescence of Tm3+ and Dy3+ co-doped nano-sized GdVO4 phosphors, the color coordinates were calculated.

17.
J Nanosci Nanotechnol ; 15(1): 373-7, 2015 Jan.
Article in English | MEDLINE | ID: mdl-26328363

ABSTRACT

Transparent Eu(3+)-doped borate glasses containing Ag nanoparticles and Ag aggregates with composition (40 - x) CaO-59.5B2O3-0.5Eu2O3-xAgNO3 were prepared by a simple one-step melt-quenching technique. The X-ray diffraction (XRD) patterns of the glasses reveal amorphous structural properties and no diffraction peaks belonging to metal Ag particles. Ag particles and Ag aggregates were observed from the absorption spectra. Effective energy transfers from the Ag aggregates to the Eu3+ ions were observed in the excitation spectra from monitoring the intrinsic emission of Eu3+x .5D0 --> 7F2. The glasses with higher Ag content can be effectively excited by light in a wide wavelength region, indicating that these glasses have potential application in the solid state lighting driven by semiconductor light emitting diodes (LEDs). The emission spectra of the samples with higher Ag contents exhibit plenteous spectral components covering the full visible region from violet to red, thus indicating that these glass materials possess an excellent and tunable color rendering index. The color coordinates for all the glass samples were calculated by using the intensity-corrected emission spectra and the standard data issued by the CIE (Commission International de l' Eclairage) in 1931. It was found that the color coordinates for most samples with higher Ag contents fall into the white region in the color space.

18.
J Colloid Interface Sci ; 420: 27-34, 2014 Apr 15.
Article in English | MEDLINE | ID: mdl-24559696

ABSTRACT

Laurustinus shaped NaY(WO4)2 micro-particles assembled by nanosheets were synthesized via a microwave-assisted hydrothermal (MH) route. The growing mechanisms for the obtained resultants with various morphologies were proposed based on the observation of scanning electron microscopic (SEM) images. It was found that Na3Cit added into the reaction solution greatly influenced the formation and size dimension of the nano-sheets, furthermore determined assembling of the laurustinus shaped micro-particles. The temperature sensing performance of NaY(WO4)2:Er(3+)/Yb(3+) was evaluated. Thermal effect induced by the 980nm laser irradiation in laurustinus-shaped NaY(WO4)2:Er(3+)/Yb(3+) phosphor was studied. It was found that the green upconversion luminescence intensity increased in the first stage of laser irradiation, and then decreased after reaching a maximum. Based on the thermal sensing technology the laurustinus NaY(WO4)2:Er(3+)/Yb(3+) microparticles were used as thermal probe to discover thermal effect of upconversion luminescence in laurustinus NaY(WO4)2:Tm(3+)/Yb(3+) micro-particles.

19.
J Colloid Interface Sci ; 393: 44-52, 2013 Mar 01.
Article in English | MEDLINE | ID: mdl-23151384

ABSTRACT

Persimmon-like NaLa(WO(4))(2) microarchitectures were prepared via hydrothermal process with using trisodium citrate (Na(3)Cit) as chelated reagent and characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), photoluminescence (PL), and fluorescent dynamics. The influences of Na(3)Cit concentration, organic additivities, and reaction time on the morphologies of NaLa(WO(4))(2) phosphor were studied. The results revealed that Na(3)Cit species had double functions of strong ligand and structure-directing reagent that could efficiently control the formation of persimmon-like NaLa(WO(4))(2) microarchitectures. The possible mechanism for the growth of persimmon-like NaLa(WO(4))(2) microarchitectures was attributed to the Ostwald ripening mechanism. The energy transfer from Tb(3+) to Eu(3+) in the persimmon-like NaLa(WO(4))(2) phosphors was observed. The energy transfer efficiencies and emission colors can be tuned by changing the concentration of Eu(3+). Finally, it was deduced that the electric dipole-dipole interaction (D-D) is the main mechanism for energy transfer between Tb(3+) and Eu(3+) in the persimmon-like NaLa(WO(4))(2) phosphor.

20.
J Colloid Interface Sci ; 360(2): 586-92, 2011 Aug 15.
Article in English | MEDLINE | ID: mdl-21621217

ABSTRACT

Three-dimensional (3D) nanostructured CaWO(4):Tb(3+)microspheres assembled by submicrospindles were synthesized via a mild sonochemical route from an aqueous solution of CaCl(2), TbCl(3) and Na(2)WO(4) with the aid of surfactant Polyglycol 600 (PEG-600). The crystal structure and morphology of the as-prepared products were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Rietveld refinement was carried out on the XRD data. The results showed that the CaWO(4):Tb(3+)nanoparticles can be formed without ultrasonic irradiation or addition of PEG-600. With continuously increasing irradiation time the submicrospindles and microspheres could be self-assembled. The central diameter and length of the submicrospindles are around 190 and 500 nm, respectively. The 3D CaWO(4):Tb(3+)nanostructured microspheres with diameter of 2-4 µm were assembled by the submicrospindles. A possible formation mechanism for the 3D-structured CaWO(4):Tb(3+)microspheres was proposed. The Photoluminescent (PL) properties of Tb(3+) ions in the nanostructured CaWO(4) microspheres were studied. The energy transfer processes in CaWO(4):Tb(3+)microspheres were analyzed. The electric dipole-dipole energy transfers related to (5)D(3) level were studied by inspecting the fluorescence decay of (5)D(3) level. The energy transfer critical distance was estimated.

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