Highly efficient NIR to NIR and VIS upconversion in Er3+ and Yb3+ doped in M2O2S (M = Gd, La, Y)

Pokhrel, Madhab; Kumar, Gaurav; Sardar, Dhiraj K.

doi:10.1039/c3ta12205k

Cited by 97 publications

(74 citation statements)

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“…These phosphors not only enable near-IR imaging but at the same time can be used as contrast agents in MRI imaging, thus making them effective bimodal imaging contrast agents. 15 We found that UC QY in these M 2 O 2 S:Yb 3+ /Er 3+ (M = Gd, La, Y) solid phosphors are 3-4 times higher than that of β-NaYF 4 :20%Yb 3+ /2%Er 3+ at lower excitation power densities, especially under 980 nm excitation. [14][15][16][17] Under different pump power densities and a wide range of Yb 3+ and Er 3+ concentrations, we explored the static and dynamic spectral properties as well as the UC quantum yield (QY) to understand the optimum oxysulphide compositions for the highest UC efficiency.…”

Section: Introductionmentioning

confidence: 69%

“…13 Recently, we explored the multifunctional features of several oxysulphide materials with their possible applications in medical imaging, with Gd 2 O 2 S:Yb/Er showing the most potential to replace existing halide based upconverting phosphors for infrared based biomedical imaging. [14][15][16][17] Under different pump power densities and a wide range of Yb 3+ and Er 3+ concentrations, we explored the static and dynamic spectral properties as well as the UC quantum yield (QY) to understand the optimum oxysulphide compositions for the highest UC efficiency. 13 Furthermore, we explored the UC efficiency of M 2 O 2 S:Yb/Er under 980 and 1550 nm excitation in comparison with NaYF 4 :Yb/Er.…”

Section: Introductionmentioning

confidence: 99%

“…[14][15][16][17] Under different pump power densities and a wide range of Yb 3+ and Er 3+ concentrations, we explored the static and dynamic spectral properties as well as the UC quantum yield (QY) to understand the optimum oxysulphide compositions for the highest UC efficiency. 18,19 Moreover, the threshold excitation power density was found to be essential to generate the highest UC QY for these compositions. 18 We also demonstrate the highest UC QY (6.20 ± 0.90)% in La 2 O 2 S:1%Yb 3+ /1%Er 3+ at the excitation power density of 22 ± 3 W/cm 2 .…”

Section: Introductionmentioning

confidence: 99%

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Electronic and optical properties of Er-doped Y₂O₂S phosphors

Pokhrel

Kumar

et al. 2015

J. Mater. Chem. C

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In this paper, we report a detailed computational and experimental investigation of the structural, electronic and dynamic properties of undoped and Er 3+ -doped Y 2 O 2 S phosphors by using computational crystal field (CF) calculations and electronic density of states by density functional theory (DFT), combined with optical measurements including excitation spectra, emission spectra from X-ray, ultraviolet and near infrared (NIR) excitations, and quantum yield determination under ultraviolet and NIR excitations. Emission decays and quantum yields of the visible and NIR bands were measured for different Er 3+ doping concentrations in the Er 3+ -doped Y 2 O 2 S phosphors. Results show that green (550 nm) and red (667 nm) emission intensity and the respective ratio of these emission intensities depend on both the excitation wavelength and the Er 3+ doping concentration. Although the total emission efficiency does not appreciably depend on the excitation wavelength, the excitation wavelength that provided the highest efficiency was found to be 250 nm in these Er 3+ -doped Y 2 O 2 S phosphors with both 1% and 10% Er doping concentrations.4 efficient light output. The measured QY showed that these Er-doped Y 2 O 2 S phosphors possess 3-4 times higher QYs under UV excitations compared to that of 980 nm excitation. EXPERIMENTAL SECTIONSynthesis: A high temperature solid state flux fusion method was used for the syntheses of the undoped and Er 3+ -doped Y 2 O 2 S phosphors. The starting materials are Y 2 O 3 , Er 2 O 3 (Sigma Aldrich, all 99.99%), both Na 2 CO 3 (30-50wt%) and K 3 PO 4 (20wt%) (Sigma Aldrich, 99.99%) salts were used with S as flux. More details regarding the synthesis was reported in our earlier work. 21 The Er 3+ doping concentration was varied from 0 to 10 mol % of Y 2 O 3 . The starting chemicals were thoroughly mixed using an agate mortar and then heated in a muffle furnace at 1150 °C for 60 min. When the furnace was cooled down, the samples were taken out and washed 6 times with distilled water, and finally with dilute hydrochloric acid. The washed powder was subsequently dried and sieved.Characterization: Powder x-ray diffraction (XRD) of the prepared undoped and Er 3+ -doped Y 2 O 2 S samples was measured by a Rigaku-Miniflex TM II X-ray diffractometer with CuKα 1 radiation (λ = 0.15406 nm). The morphologies of these samples were observed using a a field emission scanning electron microscope (Carl Zeiss Sigma VP FE-SEM) equipped with a field emission gun operated at 5 kV. Absorption spectra were measured in the 300-1700 nm range using a UV-VIS-NIR spectrophotometer (Cary, Model 14R) in transmission mode. Electronic absorption spectral samples were prepared by pressing the synthesized undoped and Er 3+ -doped Y 2 O 2 S phosphor powders to form pellets. For low temperature (T = 8 K) absorption measurements, the formed pellets were mounted in a closed-cycle helium cryostat (Janis, Wilmington, MA) with fused silica. The excitation and emission spectra of the as-prepared Graphic AbstractGreen emission...

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Section: Introductionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electronic and optical properties of Er-doped Y₂O₂S phosphors

Pokhrel

Kumar

et al. 2015

J. Mater. Chem. C

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“…The conventional way to prepare R 2 O 2 S is the solid state reaction with or without flux agent [13,[20][21][22][23][24][25]. Reduction of rare-earth oxysulfates under hydrogen-helium mixture or sulfurization of rare-earth oxides or other precursors (e.g.…”

Section: Introductionmentioning

confidence: 99%

Combustion synthesis and up-conversion luminescence of La2O2S:Er3+,Yb3+ nanophosphors

Hakmeh

Chlique

Merdrignac‐Conanec

et al. 2015

Journal of Solid State Chemistry

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Cite this article as: Noha Hakmeh, Christophe Chlique, Odile MerdrignacConanec, Bo Fan, François Cheviré, Xianghua Zhang, Xianping Fan, Xusheng Qiao, Combustion synthesis and up-conversion luminescence of La 2 O 2 S:Er 3 þ , Yb 3 þ nanophosphors, Journal of Solid State Chemistry, http://dx. AbstractLa 2 O 2 S:Er 3+ ,Yb 3+ nanocrystalline up-converting phosphors were synthesized by a combustion method at low temperature, using ethanol as pre-ignition fuel and thioacetamide as sulfurizing agent and organic fuel. The phosphors were characterized by powder X-ray diffractometry, scanning electron microscopy, UV/Vis/NIR spectroscopy and fluorescence spectroscopy. Pure and well-crystallized La 2 O 2 S:Er 3+ ,Yb 3+ nanoparticles, of the order of 50-200 nm, are obtained after a post-treatment in a H 2 S/N 2 flow for 2h at 1000°C. The efficient energy transfer from Yb 3+ to Er 3+ results in a strong up-conversion upon excitation at 980 nm. The emission spectra show the intense green emissions corresponding to the ( 2 H 11/2 , 4 S 3/2 ) → 4 I 15/2 transitions and a red emission corresponding to the 4 F 9/2 → 4 I 15/2 transition. Additionally, within the investigated codoping concentrations, no significant concentration quenching effect and back energy transfer from Er 3+ to Yb 3+ were evidenced. This research highlights the influence of the sulfurization treatment on the purity/crystallinity/morphology of the nanocrystals and the luminescence efficiency.

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“…RE 2 O 2 S with stable thermal and chemical properties, high refractive index (~2.2)21, wide band-gap and low average phonon energy (~520 cm −1 )22 has become an efficient phosphor for visible and NIR emission232425. For UC emission, RE 2 O 2 S with optimized Yb 3+ /Er 3+ doping ratio has shown a comparable or even higher quantum yield with respect to the well-known brightest NaYF 4 at a reasonable low excitation density26272829. Their NIR emission is also demonstrated with measured quantum yield higher than 100% in Er 3+ /Yb 3+ co-doped La 2 O 2 S30.…”

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confidence: 99%

Regulating Mid-infrared to Visible Fluorescence in Monodispersed Er3+-doped La2O2S (La2O2SO4) Nanocrystals by Phase Modulation

Pan

Yang

Kang

et al. 2016

Sci Rep

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Rare earth doped mid-infrared (MIR) fluorescent sources have been widely investigated due to their various potential applications in the fields of communication, chemical detecting, medical surgery and so forth. However, with emission wavelength extended to MIR, multiphonon relaxation process that strongly quenched the MIR emission is one of the greatest challenges for such practical applications. In our design, we have described a controllable gas-aided annealing strategy to modulate the phase, crystal size, morphology and fluorescent performance of a material simultaneously. Uniform and monodispersed Er3+-doped La2O2S and La2O2SO4 nanocrystals with a similar lattice structure, crystallinity, diameter and morphology have been introduced to investigate the impact of multiphonon relaxation on luminescence performance. Detailed spectroscopic evolutions in the region of MIR, near-infrared (NIR), visible upconversion (UC) and their corresponding decay times provide insight investigation into the fluorescent mechanism caused by multiphonon relaxation. A possible energy transfer model has also been established. Our results present direct observation and mechanistic investigation of fluorescent evolution in multiphonon relaxation process, which is conductive to design MIR fluorescent materials in the future. To the best of our knowledge, it is the first investigation on MIR fluorescent performance of La2O2S nanocrystals, which may find various applications in many photoelectronic fields.

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Highly efficient NIR to NIR and VIS upconversion in Er3+ and Yb3+ doped in M2O2S (M = Gd, La, Y)

Cited by 97 publications

References 48 publications

Electronic and optical properties of Er-doped Y₂O₂S phosphors

Electronic and optical properties of Er-doped Y₂O₂S phosphors

Combustion synthesis and up-conversion luminescence of La2O2S:Er3+,Yb3+ nanophosphors

Regulating Mid-infrared to Visible Fluorescence in Monodispersed Er3+-doped La2O2S (La2O2SO4) Nanocrystals by Phase Modulation

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Highly efficient NIR to NIR and VIS upconversion in Er3+ and Yb3+ doped in M2O2S (M = Gd, La, Y)

Cited by 97 publications

References 48 publications

Electronic and optical properties of Er-doped Y2O2S phosphors

Electronic and optical properties of Er-doped Y2O2S phosphors

Combustion synthesis and up-conversion luminescence of La2O2S:Er3+,Yb3+ nanophosphors

Regulating Mid-infrared to Visible Fluorescence in Monodispersed Er3+-doped La2O2S (La2O2SO4) Nanocrystals by Phase Modulation

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Electronic and optical properties of Er-doped Y₂O₂S phosphors

Electronic and optical properties of Er-doped Y₂O₂S phosphors