Co-reporter:Yang Feng, Hongda Chen, Lina Ma, Baiqi Shao, Shuang Zhao, Zhenxin Wang, and Hongpeng You
ACS Applied Materials & Interfaces May 3, 2017 Volume 9(Issue 17) pp:15096-15096
Publication Date(Web):April 14, 2017
DOI:10.1021/acsami.7b03411
In this work, we developed the surfactant-free aqueous synthesis of novel polyethylene glycol (PEG) coated Ba2GdF7:Yb3+, Er3+ upconversion nanoparticles (named as, Ba2GdF7:Yb3+, Er3+@PEG UCNPs) for in vivo multimodality imaging including upconversion luminescence (UCL), X-ray computed tomography (CT), and T1-weighted magnetic resonance (MR). The as-prepared Ba2GdF7:Yb3+, Er3+@PEG UCNPs not only present bright UCL and reasonably high CT/MR enhancements but also exhibit excellent colloidal stability, inappreciable cytotoxicity, and negligible organ toxicity. In particular, the Ba2GdF7:Yb3+, Er3+@PEG UCNPs emit red UCL with high intensity in the tumor site after intravenous injection via the tail vein of a nude mouse. The Ba2GdF7:Yb3+, Er3+@PEG UCNPs as contrast agents exhibit high-performance for in vivo trimodality (UCL/CT/MR) imaging of a tumor during HepG2 tumor-bearing nude mouse experiments.Keywords: Ba2GdF7:Yb3+, Er3+@PEG UCNPs; in vivo trimodality imaging; red emission;
Co-reporter:Yan Song, Baiqi Shao, Yang Feng, Wei Lü, Jiansheng Huo, Shuang Zhao, Man Liu, Guixia Liu, and Hongpeng You
Inorganic Chemistry 2017 Volume 56(Issue 1) pp:282-291
Publication Date(Web):December 19, 2016
DOI:10.1021/acs.inorgchem.6b02125
The surface modification can realize systematically the emission enhancement of GdVO4:Ln3+ (Ln = Dy, Eu) microstructures and multicolor emission at single component. The structure, morphology, composition, and the surface ligands modification of as-prepared samples were studied in detail. It is found that the surface-modified ligands can act as sensitizer to improve the emission of the Eu3+ and Dy3+ ions via the energy transfer besides the VO43––Eu3+/Dy3+ process. More importantly, under a single wavelength excitation, the emission color can be effectively tuned by manipulating the doping ratio of the Eu3+ ions in the internal crystal lattice and the Tb3+ ions in the external surface ligands, simultaneously. And further, multicolor emissions are obtained under single wavelength excitation due to the high overlapping between the VO43– absorption and the π–π* electron transition of the ligands. These findings may open new avenues to design and develop new highly efficient luminescent materials.
Co-reporter:Lingfei Zhao;Ying Tao
CrystEngComm (1999-Present) 2017 vol. 19(Issue 15) pp:2065-2071
Publication Date(Web):2017/04/10
DOI:10.1039/C7CE00097A
In this paper, a rationally designed low temperature and surfactant-free ion-exchange strategy to synthesize monodisperse hexagonal NaGdF4 nanorods from a layered gadolinium hydroxynitrate precursor is reported for the first time. This novel synthetic process takes advantage of the structural similarity between the precursor and the hexagonal NaGdF4 to avoid the formation of the kinetically favored cubic phase. The formation mechanisms were discussed in detail by tracking the phase and morphology evolution during the reaction process. In addition, the downconversion and upconversion properties were investigated under laser excitation, and the products exhibited intense characteristic luminescence.
Co-reporter:Wei Lü;Huawei Xu;Jiansheng Huo;Baiqi Shao;Yang Feng;Shuang Zhao
Dalton Transactions 2017 vol. 46(Issue 28) pp:9272-9279
Publication Date(Web):2017/07/18
DOI:10.1039/C7DT01086A
A tunable white light emitting Na2Ca3Si2O8:Ce3+,Tb3+,Mn2+ phosphor with a high color rendering index (CRI) has been prepared. Under UV excitation, Na2Ca3Si2O8:Ce3+ phosphors present blue luminescence and exhibit a broad excitation ranging from 250 to 400 nm. When codoping Tb3+/Mn2+ ions into Na2Ca3Si2O8, energy transfer from Ce3+ to Tb3+ and Ce3+ to Mn2+ ions is observed from the spectral overlap between Ce3+ emission and Tb3+/Mn2+ excitation spectra. The energy-transfer efficiencies and corresponding mechanisms are discussed in detail. The mechanism of energy transfer from Ce3+ to Tb3+ is demonstrated to be a dipole–quadrupole mechanism by the Inokuti–Hirayama model. The wavelength-tunable white light can be realized by coupling the emission bands centered at 440, 550 and 590 nm ascribed to the contribution from Ce3+, Tb3+ and Mn2+, respectively. The commission on illumination value of color tunable emission can be tuned by controlling the content of Ce3+, Tb3+ and Mn2+. Temperature-dependent luminescence spectra proved the good thermal stability of the as-prepared phosphor. White LEDs with CRI = 93.5 are finally fabricated using a 365 nm UV chip and the as-prepared Na2Ca3Si2O8:Ce3+,Tb3+,Mn2+ phosphor. All the results suggest that Na2Ca3Si2O8:Ce3+,Tb3+,Mn2+ can act as potential color-tunable and single-phase white emission phosphors for possible applications in UV based white LEDs.
Co-reporter:Mengmeng Jiao;Qinfeng Xu;Chuanlu Yang
RSC Advances (2011-Present) 2017 vol. 7(Issue 46) pp:28647-28654
Publication Date(Web):2017/05/30
DOI:10.1039/C7RA04105E
By partially substituting Ga3+ ions at Al1(2a) and Al2/Si1(4e) sites in gehlenite Ca2Al2SiO7, novel Ca2GaAlSiO7:Eu2+/Ce3+ phosphors with efficient green and blue emissions have been prepared for the first time. Structure and luminescence properties of these newly obtained samples have been investigated in detail together with the effect of Ga3+ substitution which has caused a decrement of Eu–O bond length and covalency. The excitation spectra suggested that both the Eu2+ and Ce3+ doped Ca2GaAlSiO7 samples had broad excitation bands in the UV range, which are favourable properties for application as UV-WLED phosphors. Under 350 nm irradiation, the Ca2GaAlSiO7:Eu2+ had intense emission peaking at 510 nm, while Ca2GaAlSiO7:Ce3+ emitted bright blue light. The energy migration mechanism of the Eu2+ ions was confirmed to be electric dipole–dipole interaction in terms of the experimental results and analysis. The thermal quenching mechanism, and quantum efficiency of the composition-optimized samples have been investigated. Moreover, a white LED device has been obtained by coating our prepared phosphors with CaAlSiN3 red phosphor on a UV chip. The experimental results suggested that the Ca2GaAlSiO7:Eu2+ and Ca2GaAlSiO7:Ce3+ samples might have potential value in serving as green and blue phosphors for UV-WLEDs, respectively.
Co-reporter:Jiansheng Huo, Wei Lü, Baiqi Shao, Yang Feng, Shuang Zhao, Hongpeng You
Dyes and Pigments 2017 Volume 139(Volume 139) pp:
Publication Date(Web):1 April 2017
DOI:10.1016/j.dyepig.2016.12.012
•Ce3+ & Tb3+ co-doped MgYSi2O5N oxynitrides was successfully synthesized by the solid-state method for the first time.•MgYSi2O5N: Ce3+, Tb3+ can emit green light upon n-UV excitation via energy transfer from Ce3+ to Tb3+ ions.•The MgYSi2O5N: Ce3+, Tb3+ phosphors may be good candidates as potential green component for application in n-UV WLEDs.An oxynitride phosphor MgYSi2O5N co-doped with Ce3+ and Tb3+ was successfully synthesized by the conventional solid-state reaction at 1623 K for 2 h in NH3 atmosphere. X-ray powder diffraction profiles, photoluminescence spectra, luminescence decay curves and chromaticity variation of the samples were investigated in detail. The photoluminescence properties showed that the Tb3+ ions exhibited characteristic green emission peaks at 545 nm corresponding to the strong excitation band of Ce3+ ions over a broad spectral range between 220 and 380 nm which matched well with the dominant emission band of near UV LED chips. The efficient energy transfer from Ce3+ to Tb3+ was verified by the excitation and emission spectra together with the luminescence decay curves. The corresponding efficiencies of energy transfer and energy transfer mechanisms were also calculated and analyzed according to the variations of the lifetime values of Ce3+. With the doping content of Tb3+ ions increasing, the emitting color of phosphors can be tuned from purplish-blue to green upon 365 nm excitation. All the results indicated that the developed phosphors have a potentiality to be a kind of near UV-convertible phosphor for application in phosphor-converted white-light-emitting diodes.
Co-reporter:Jiansheng Huo;Langping Dong;Wei Lü;Baiqi Shao
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 26) pp:17314-17323
Publication Date(Web):2017/07/05
DOI:10.1039/C7CP02507F
A series of novel Ce3+, Tb3+ and Eu3+ ion doped Y4SiAlO8N-based oxynitride phosphors were synthesized by the solid-state method and characterized by X-ray powder diffraction, scanning electron microscopy, photoluminescence, lifetimes and thermo-luminescence. The excitation of the Ce3+/Tb3+ co-doped and Ce3+/Tb3+/Eu3+ tri-doped phosphor with near-UV radiation results in strong linear Tb3+ green and Eu3+ red emission. The occurrence of Ce3+–Tb3+ and Ce3+–Tb3+–Eu3+ energy transfer processes is responsible for the bright green or red luminescence. The Tb3+ ion acting as an energy transfer bridge can alleviate MMCT quenching between the Ce3+–Eu3+ ion pairs. The lifetime measurements demonstrated that the energy-transfer mechanisms of Ce3+ → Tb3+ and Tb3+ → Eu3+ are dipole–quadrupole and quadrupole–quadrupole interactions, respectively. The temperature dependent luminescence measurements showed that as-prepared green/red phosphors have good thermal stability against temperature quenching. The obtained results indicate that these phosphors might serve as promising candidates for n-UV LEDs.
Co-reporter:Mengmeng Jiao;Chuanlu Yang;Yalin Li;Dongxu Wang
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 36) pp:24566-24573
Publication Date(Web):2017/09/20
DOI:10.1039/C7CP04691J
Color tunable Sr3LaNa(PO4)3F:Eu2+,Tb3+ and Sr3LaNa(PO4)3F:Tb3+,Mn2+ phosphors were prepared by a high temperature solid state reaction. The crystal structure, luminescence properties, and energy transfer mechanism of the samples were investigated in detail. The Eu2+ doped phosphors can be efficiently excited in the range from 250 to 410 nm, which matches well with the commercial n-UV LED chips. Utilizing the energy transfer from Eu2+ to Tb3+ ions, tunable colors from blue to green were obtained under the irradiation of 405 nm. The mechanism of the Eu2+ → Tb3+ energy transfer was demonstrated to be a dipole–quadrupole interaction in terms of the experimental results and analysis of the photoluminescence spectra and decay curves of the phosphors. Moreover, the thermal stability and quantum efficiency of the Eu2+ and Tb3+ co-doped phosphors were studied. For the Sr3LaNa(PO4)3F:Tb3+,Mn2+ samples, tunable green-orange emissions were obtained by changing the relative ratio of Tb3+ and Mn2+ ions under 230 nm irradiation. The investigation results suggest that color tunable phosphors with potential for WLEDs were obtained utilizing the energy transfer process.
Co-reporter:Baiqi Shao, Yang Feng, Yan Song, Mengmeng Jiao, Wei Lü, and Hongpeng You
Inorganic Chemistry 2016 Volume 55(Issue 4) pp:1912-1919
Publication Date(Web):February 3, 2016
DOI:10.1021/acs.inorgchem.5b02817
A novel nonorganic wet route for direct synthesis of uniform hexagonal β-NaYF4:Ln3+ (Ln = Eu, Tb, Ce/Tb, Yb/Er, and Yb/Tm) microcrystals with various morphologies has been developed wherein the intermediate routine cubic–hexagonal (α → β) phase transfer process was avoided. The morphology can be effectively tuned into hexagonal disc, prism, and novel hierarchical architectures by systematically fine manipulating the Na2CO3/F– feeding ratio. It has been found that the routine α → β phase transfer for NaYF4 was not detected during the growth, while NaY(CO3)F2 emerged in the initial reaction stage and fast transformed into β-NaYF4 via a novel topotactic transformation behavior. Detailed structural analysis showed that β-NaYF4 preferred the [001] epitaxial growth direction of NaY(CO3)F2 due to the structural matching of [001]NaY(CO3)F2//[0001]β-NaYF4. Besides, the potential application of the as-prepared products as phosphors is emphasized by demonstrating multicolor emissions including downconversion, upconversion, and energy transfer (Ce–Tb) process by lanthanides doping.
Co-reporter:Xiaopeng Fu, Wei Lü, Mengmeng Jiao, and Hongpeng You
Inorganic Chemistry 2016 Volume 55(Issue 12) pp:6107-6113
Publication Date(Web):June 1, 2016
DOI:10.1021/acs.inorgchem.6b00648
A series of Ba4Gd3Na3(PO4)6F2:Eu2+ phosphors with a broad emitting band have been synthesized by a traditional solid state reaction. The crystal structural and photoluminescence properties of Ba4Gd3Na3(PO4)6F2:Eu2+ are investigated. The different crystallographic sites of Eu2+ in Ba4Gd3Na3(PO4)6F2:Eu2+ phosphors have been verified by means of their photoluminescence (PL) properties and decay times. Energy transfer between Eu2+ ions, analyzed by excitation, emission, and PL decay behavior, has been indicated to be a dipole–dipole mechanism. Moreover, the luminescence quantum yield as well as the thermal stability of the Ba4Gd3Na3(PO4)6F2:Eu2+ phosphor have been investigated systematically. The as-prepared Ba4Gd3Na3(PO4)6F2:Eu2+ phosphor can act as a promising candidate for n-UV convertible white LEDs.
Co-reporter:Wei Lü, Jiansheng Huo, Yang Feng, Shuang Zhao and Hongpeng You
Dalton Transactions 2016 vol. 45(Issue 23) pp:9676-9683
Publication Date(Web):17 May 2016
DOI:10.1039/C6DT01652A
New tuneable light-emitting Ca3Al8Si4O17N4:Ce3+/Tb3+/Eu2+ oxynitride phosphors with high brightness have been prepared. When doped with trivalent cerium or divalent europium they present blue luminescence under UV excitation. The energy transfer from Ce3+ to Tb3+ and Ce3+ to Eu2+ ions is deduced from the spectral overlap between Ce3+ emission and Tb3+/Eu2+ excitation spectra. The energy-transfer efficiencies and corresponding mechanisms are discussed in detail, and the mechanisms of energy transfer from the Ce3+ to Tb3+ and Ce3+ to Eu2+ ions are demonstrated to be a dipole–quadrupole and dipole–dipole mechanism, respectively, by the Inokuti–Hirayama model. The International Commission on Illumination value of color tuneable emission as well as luminescence quantum yield (23.8–80.6%) can be tuned by controlling the content of Ce3+, Tb3+ and Eu2+. All results suggest that they are suitable for UV light-emitting diode excitation.
Co-reporter:Yan Song, Baiqi Shao, Yang Feng, Wei Lü, Guixia Liu and Hongpeng You
Dalton Transactions 2016 vol. 45(Issue 23) pp:9468-9476
Publication Date(Web):04 May 2016
DOI:10.1039/C6DT01206J
Promoting excitation efficiency is a direct route to enhance the luminescence properties of lanthanide doped materials. Here, we describe a novel strategy to enhance the luminescence performance of NaGdF4:Ln3+ (Ln = Tb, Eu, Dy) nanoparticles by surface modification with benzoate (BA) and 1,10-phenanthroline (Phen) ligands via the sensitization of surface dopants. It was found that the surface ligands provide a new path for energy transfer to the activators due to the matching in energy levels between the two. Moreover, the overlap in excitation peaks for both Gd3+ ions and ligands ensures the simultaneous energy transfer of Gd3+ → Ln3+ and ligands → Ln3+ under a single wavelength excitation. The obtained NaGdF4 nanocomposite was characterized in detail using XRD, FT-IR, TGA, SEM, and EDS. The luminescence performance of the surface modified NaGdF4:Ln3+ nanoparticles was also optimized by tuning the loading amount of modified ligands. In addition, luminescence thermometry was realized by monitoring emission intensity at different temperatures.
Co-reporter:Baiqi Shao, Yang Feng, Mengmeng Jiao, Wei Lü and Hongpeng You
Dalton Transactions 2016 vol. 45(Issue 6) pp:2485-2491
Publication Date(Web):11 Dec 2015
DOI:10.1039/C5DT03708E
GdOF:Ln3+ (Ln = Eu, Tb, Eu/Tb, Ce/Tb, Yb/Er, and Yb/Tm) nanocrystals with a hexagonal prism morphology have been readily synthesized by a novel topotactic transformation route. The Gd(OH)2F precursor was first synthesized and structurally analyzed by the Rietveld refinement method. It has been found that the Gd(OH)2F precursor was formed by a novel type of ion-exchange from the brucite-like Gd2(OH)5NO3·0.9H2O (LGdH). Such an ion-exchange behavior is different from the traditional case for the layered double hydroxides (LDHs) in which the intercalated anions are exchanged by the external ions. The detailed structural analysis showed that GdOF prefered [0001] epitaxial growth direction of Gd(OH)2F due to the structural matching of [0001]Gd(OH)2F//[110]GdOF. Furthermore, the potential application of the as-prepared nanocrystals as phosphors is emphasized by demonstrating strong multicolor emissions including both down-conversion and upconversion, and energy transfer (Ce–Tb) processes by GdOF:Ln3+ in detail. Our nonorganic green synthetic strategy based on the novel ion-exchange for the LDHs may enrich the synthetic methodology for nanomaterials.
Co-reporter:Wei Lü, Mengmeng Jiao, Baiqi Shao, Lingfei Zhao, Yang Feng and Hongpeng You
Dalton Transactions 2016 vol. 45(Issue 2) pp:466-468
Publication Date(Web):17 Nov 2015
DOI:10.1039/C5DT03465E
To date, most current reports on the development and optimization of solar spectral converters have described the utilization of energy transfer among rare-earth ions. Here, we introduce non-rare-earth ion Mn4+ to transfer energy to Yb3+, which can exhibit strong near-infrared luminescence. It can harvest UV-blue photons and exhibits intense NIR emission of Yb3+ around 1000 nm, perfectly matching the maximum spectral response of Si solar cells. It demonstrates for the first time that efficient energy transfer occurs with a decrease in the excited state lifetime and red photoluminescence (PL) from Mn4+ with increasing Yb3+ concentration. These results demonstrate that the Mn4+ ions can be an efficient and direct sensitizer harvesting UV-blue photons. It could provide new avenues for developing harvesting Si-based solar cells.
Co-reporter:Qipeng Liu, Huijun Yin, Tao Liu, CuiQing Wang, Riqiang Liu, Wei Lü, Hongpeng You
Journal of Luminescence 2016 Volume 177() pp:349-353
Publication Date(Web):September 2016
DOI:10.1016/j.jlumin.2016.05.014
We have synthesized yellow–orange CaO:Ce3+,Mn2+ phosphors by solid-state reaction. Photoluminescence properties and energy transfer mechanism from Ce3+ to Mn2+ ions have been investigated. The Ce3+ activated phosphors exhibit strong absorption in the range of 250–490 nm and a yellow emission centered at 554 nm. When Mn2+ ions were codoped, CaO:Ce3+,Mn2+ phosphors exhibit yellow emission band of Ce3+ as well as orange emission band centered at 600 nm of Mn2+. We observed an efficient energy transfer from Ce3+ to Mn2+ ions in CaO:Ce3+,Mn2+, which was verified from the lifetime decay curves and was discussed by Dexter׳s energy transfer theory. The critical distance of the energy transfer from Ce3+ to Mn2+ ions has also been calculated to be 12.3 Å by spectral overlap methods following Dexter׳s theory and by concentration quenching mechanism to be 15.2 Å. Moreover, by combining the synthesized phosphors and InGaN blue chip (460 nm), warm-white light has been created.
Co-reporter:Wei Lü, Mengmeng Jiao, Jiansheng Huo, Baiqi Shao, Lingfei Zhao, Yang Feng and Hongpeng You
New Journal of Chemistry 2016 vol. 40(Issue 3) pp:2637-2643
Publication Date(Web):08 Jan 2016
DOI:10.1039/C5NJ02893K
We have synthesized a series of Eu2+ and Eu2+/Tb3+ activated novel GdAl12O18N oxynitride phosphors by a traditional solid state reaction. The structural and photoluminescence properties related to the crystal of GdAl12O18N:Eu2+/Tb3+ phosphor are investigated. Rietveld structure refinement and photoluminescence properties of the obtained phosphor indicate that the GdAl12O18N host has only one type of Gd site. GdAl12O18N:Eu2+,Tb3+ samples exhibit a blue emission band that peaks at 460 nm and a green line that peaks at 550 nm, originating from the Eu2+ and Tb3+ ions, respectively. This energy transfer from Eu2+ to Tb3+ was confirmed by the decay times of energy donor Eu2+. In addition, the mechanism of energy transfer from Eu2+ to Tb3+ ions is demonstrated to be a dipole–quadrupole mechanism by the Inokuti–Hirayama (I–H) model. All the results indicate that the Eu2+ and Tb3+ activated phosphor may be a good candidate for blue-green components in UV white LEDs.
Co-reporter:Wei Lü, Wenzhen Lv, Qi Zhao, Mengmeng Jiao, Baiqi Shao and Hongpeng You
Journal of Materials Chemistry A 2015 vol. 3(Issue 10) pp:2334-2340
Publication Date(Web):13 Jan 2015
DOI:10.1039/C4TC02652G
Utilizing Mn2+ and Tb3+ ions as energy-transfer acceptors, we report a series of emission color-tunable Ca2GdZr2(AlO4)3:Ce3+, Mn2+, Tb3+ aluminate garnets. Incorporating Mn2+ and Tb3+ into Ca2GdZr2(AlO4)3:Ce3+ phosphor generates an orange emission band peaking at 572 nm and a green line peaking at 550 nm. The energy transfers from Ce3+ to Mn2+ and Ce3+ to Tb3+ ions are deduced from the spectral overlap between the Ce3+ emission and Mn2+/Tb3+ excitation spectra. Fluorescence decay patterns are studied as a function of Mn2+ and Tb3+ concentration. The calculated values based on the luminescence dynamical process indicate that the intensity ratios of the orange to green bands as a function of Mn2+ concentration are in good agreement with those obtained directly from the emission spectra. We have demonstrated that the color emission as well as the luminescence external quantum yield (20.4–48.9%) can be tuned by precisely controlling the content of Ce3+, Mn2+, and Tb3+. The energy transfer significantly enables the achievement of a broad emission spectrum covering an orange spectral region. It is suitable for near-UV light-emitting diode (LED) excitation.
Co-reporter:Baiqi Shao, Qi Zhao, Wenzhen Lv, Mengmeng Jiao, Wei Lü and Hongpeng You
Journal of Materials Chemistry A 2015 vol. 3(Issue 5) pp:1091-1098
Publication Date(Web):21 Nov 2014
DOI:10.1039/C4TC02477J
Monodisperse β-NaYF4:Ln3+ (Ln = Eu, Tb, Yb/Er, or Yb/Tm) nanocrystals with multiform novel morphologies have been synthesized for the first time by a novel two-step ion-exchange route expressed as Y2(OH)5NO3·nH2O (LYH) → Y(OH)xF3−x → β-NaYF4. In step I (LYH → Y(OH)xF3−x), the Y(OH)xF3−x is fabricated using a one-pot method from the starting point of a unit layer at low temperature through a novel style of ion-exchange from LYH based on the special crystal structural similarity between the LYH unit layer and the Y(OH)xF3−x {0001} plane. Of particular interest is that the ion-exchange process in step I can be completed within the initial few minutes, and the unique two-dimensional layered structure of LYH greatly favors the ion-exchange reaction by exfoliating into atomically thick monolayers. Meanwhile, the identical structural framework between Y(OH)xF3−x and β-NaYF4 ensures the in situ ion-exchange reaction in step II. The composition of the intermediate precursor Y(OH)xF3−x can be tuned in a wide range, which gives the synthetic parameters high maneuverability and greatly simplifies the experimental variables. In addition, the luminescence properties showed that the as-prepared β-NaYF4:Ln3+ nanocrystals exhibited strong characteristic multicolor emissions through upconversion and downconversion.
Co-reporter:Baiqi Shao;Qi Zhao;Wenzhen Lv;Mengmeng Jiao;Wei Lü
Advanced Optical Materials 2015 Volume 3( Issue 4) pp:583-592
Publication Date(Web):
DOI:10.1002/adom.201400638
A novel two-step topotactic transformation (TT) synthetic route, Y2(OH)5NO3•nH2O (LYH)Y(OH)2.02F0.98YOF, is first developed for the monodisperse YOF:Re3+ (Re = Eu, Tb, Yb/Er, and Yb/Tm) nanostructure with bundle, tube, and atomically thick sheet morphologies. The intermediate Y(OH)2.02F0.98 precursor is synthesized from the starting point of the {0001} plane, which forms by a novel type of ion-exchange from the brucite-like LYH due to the structural similarity between the [Y2(OH)5(H2O)n]+ unit layer and the Y(OH)2.02F0.98 {0001} plane. Such ion-exchange behavior is different from the traditional case for LYH exchanging the intercalated anions. The detailed structural characterization reveals that the formation of YOF is attributed to an in situ TT with the structural matching of [0001]Y(OH)2.02F0.98//[110]YOF. Moreover, this novel synthetic route can be also extended to other lanthanides oxyfluorides series (LnOF, Ln = Pr–Lu), and the as-prepared YOF:Re3+ products exhibit intense characteristic down/upconversion luminescence. Our synthetic strategy dovetails well with the green concept in the current nanoscience and nanotechnology, which may bring new opportunity to LRHs and open a new avenue in the synthetic methodology for micro/nanomaterials.
Co-reporter:Wei Lü; Mengmeng Jiao; Baiqi Shao; Lingfei Zhao
Inorganic Chemistry 2015 Volume 54(Issue 18) pp:9060-9065
Publication Date(Web):September 2, 2015
DOI:10.1021/acs.inorgchem.5b01402
Eu2+-doped SrSi2O2N2 has recently been identified as a viable green phosphor that in conjunction with a blue-emitting diode can be used in solid-state white-lighting sources. In this study, we attempt to improve the photoluminescence and thermal quenching behavior by codoping Re3+ (Re = La, Gd, Y, Dy, Lu, Sc) and Li+ instead of Sr2+. Trivalent cation substitution at the Sr2+ site enhances the photoluminescence intensities and also achieves better thermal stability at high temperature. The lifetime decay properties in the related substituted phosphors are investigated. Furthermore, under the 460 nm blue light irradiation, this green phosphor exhibits excellent luminescence properties with absorption and internal/external efficiencies. High-color-rendition warm-white LEDs using the phosphor have the color temperature and color rendition of 4732 K and 91.2, respectively, validating its suitability for use in solid-state white lighting.
Co-reporter:Mengmeng Jiao, Wenzhen Lv, Wei Lü, Qi Zhao, Baiqi Shao and Hongpeng You
Dalton Transactions 2015 vol. 44(Issue 9) pp:4080-4087
Publication Date(Web):14 Jan 2015
DOI:10.1039/C4DT03906H
A new langbeinite-type phosphate KSrSc2(PO4)3 has been synthesized by conventional high temperature solid state reaction. Rietveld structure refinement, a field emission scanning electron microscope, photoluminescence spectra, quantum efficiency as well as lifetimes were used to characterize the samples. Structure refinement reveals that KSrSc2(PO4)3 has two kinds of Sr2+ and Sc3+ sites for the doped ions to occupy, forming emission centers. The KSrSc2(PO4)3:Ce3+ and KSrSc2(PO4)3:Eu2+ phosphors both have broad excitation and emission bands due to spin- and orbit-allowed electron transitions. Phosphors with tunable blue to blue-green colors were obtained by codoping the Tb3+ ions into the KSrSc2(PO4)3:0.03Ce3+ and KSrSc2(PO4)3:0.03Eu2+ phosphors with varying contents. The mechanism of Eu2+→Tb3+ energy transfer is determined to be a dipole–quadrupole interaction in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors by using the Inokuti–Hirayama theoretical model. Our prepared KSrSc2(PO4)3:Ce3+,Tb3+ and KSrSc2(PO4)3:Eu2+,Tb3+ phosphors are of potential value for UV excited WLEDs.
Co-reporter:Qi Zhao, Baiqi Shao, Wei Lü, Wenzhen Lv, Mengmeng Jiao, Lingfei Zhao and Hongpeng You
Dalton Transactions 2015 vol. 44(Issue 8) pp:3745-3752
Publication Date(Web):07 Jan 2015
DOI:10.1039/C4DT03619K
Hexagonal-phase NaGdF4 nanotubes were successfully fabricated through a template- and catalyst-free method in a hydrothermal environment. The intrinsic and external factors contributing to the formation of tubular nanocrystals were discussed, namely the anisotropic crystal structure of the hexagonal-phase NaGdF4 and the insufficient supply of reagents. Furthermore, the addition of ethylene glycol and hydrazine had a significant effect on the morphological variation. The desirable multicolor outputs were achieved by co-doping Ce3+ and Ln3+ (Ln = Eu, Tb, and Dy) ions in the NaGdF4 crystal, in which the Gd3+ ions acted as an intermediate medium transforming the excitation energy to the activator ions. Finally, the upconversion luminescence and magnetic performance of the sodium rare earth fluoride were demonstrated.
Co-reporter:Wei Lü, Yongchao Jia, Wenzhen Lv, Qi Zhao, Hongpeng You
Optical Materials 2015 Volume 42() pp:62-66
Publication Date(Web):April 2015
DOI:10.1016/j.optmat.2014.12.019
Co-reporter:Dr. Mengmeng Jiao;Wenzhen Lv;Wei Lü;Qi Zhao;Baiqi Shao; Hongpeng You
ChemPhysChem 2015 Volume 16( Issue 4) pp:817-824
Publication Date(Web):
DOI:10.1002/cphc.201402788
Abstract
A series of Eu2+-, Ce3+-, and Tb3+-doped Ca2Ga2SiO7 phosphors is synthesized by using a high-temperature solid-state reaction. The powder X-ray diffraction and structure refinement data indicate that our prepared phosphors are single phased and the phosphor crystalizes in a tetrahedral system with the (113) space group. The Eu2+- and Ce3+-doped phosphors both have broad excitation bands, which match well with the UV light-emitting diodes chips. Under irradiation of λ=350 nm, Ca2Ga2SiO7:Eu2+ and Ca2Ga2SiO7:Ce3+, Li+ have green and blue emissions, respectively. Luminescence of Ca2Ga2SiO7:Tb3+, Li+ phosphor varies with the different Tb3+ contents. The thermal stability and energy-migration mechanism of Ca2Ga2SiO7:Eu2+ are also studied. The investigation results indicate that the prepared Ca2Ga2SiO7:Eu2+ and Ca2Ga2SiO7:Ce3+, Li+ samples show potential as green and blue phosphors, respectively, for UV-excited white-light-emitting diodes.
Co-reporter:Dr. Mengmeng Jiao;Wei Lü;Baiqi Shao;Lingfei Zhao; Hongpeng You
ChemPhysChem 2015 Volume 16( Issue 12) pp:2663-2669
Publication Date(Web):
DOI:10.1002/cphc.201500387
Abstract
A series of novel KBaSc2(PO4)3:Ce3+/Eu2+/Tb3+phosphors are prepared using a solid-state reaction. X-ray diffraction analysis and Rietveld structure refinement are used to check the phase purity and crystal structure of the prepared samples. Ce3+- and Eu2+-doped phosphors both have broad excitation and emission bands, owing to the spin- and orbital-allowed electron transition between the 4f and 5d energy levels. By co-doping the KBaSc2(PO4)3:Eu2+ and KBaSc2(PO4)3:Ce3+ phosphors with Tb3+ ions, tunable colors from blue to green can be obtained. The critical distance between the Eu2+ and Tb3+ ions is calculated by a concentration quenching method and the energy-transfer mechanism for Eu2+Tb3+ is studied by utilizing the Inokuti–Hirayama model. In addition, the quantum efficiencies of the prepared samples are measured. The results indicate that KBaSc2(PO4)3:Eu2+,Tb3+ and KBaSc2(PO4)3:Ce3+,Tb3+ phosphors might have potential applications in UV-excited white-light-emitting diodes.
Co-reporter:Baiqi Shao, Qi Zhao, Yongchao Jia, Wenzhen Lv, Mengmeng Jiao, Wei Lü and Hongpeng You
Journal of Materials Chemistry A 2014 vol. 2(Issue 36) pp:7666-7673
Publication Date(Web):18 Jul 2014
DOI:10.1039/C4TC00808A
Highly monodisperse YF3:Ln3+ (Ln = Eu, Ce, Tb, Yb/Er, Yb/Ho, and Yb/Tm) nano/microcrystals with controllable size and morphology have been synthesized by an innovative low-temperature (≤0 °C) precipitation route free of any surfactant. Interestingly, the monodispersity and morphology are independent of the pH value and reactant concentration at a low temperature even when the reactant concentrations are close to saturation. This allows for a high yield production at 150 g L−1 of reaction system. A detailed investigation of the growth process reveals that a low temperature can ensure a more definite separation of nucleation and growth. Simultaneously, the low temperature-induced diffusion-controlled growth model gives rise to a size focusing effect, which further insures the monodispersity of the final products. Furthermore, our synthetic strategy can be extended to other lanthanide fluorides (REF3, RE (rare earth) = Ce, Nd, Sm-Lu), and the obtained YF3:Ln3+ samples exhibit strong down/upconversion emissions. Such a facile synthetic strategy fits well with the green concept in current synthetic innovations for nanocrystals and may provide some guidance in the kinetically controlled synthesis of inorganic nanocrystals.
Co-reporter:Mengmeng Jiao, Yongchao Jia, Wei Lü, Wenzhen Lv, Qi Zhao, Baiqi Shao and Hongpeng You
Journal of Materials Chemistry A 2014 vol. 2(Issue 21) pp:4304-4311
Publication Date(Web):01 Apr 2014
DOI:10.1039/C4TC00401A
A series of Eu2+ and Ce3+/Tb3+ doped Ca2NaSiO4F (CNSOF) phosphors have been synthesized and their structure and photoluminescence properties have been investigated in detail. Rietveld structure refinement indicates that the phosphors crystalized in an orthorhombic system with a space group of Pnma (no. 62) and there are two kinds of cation sites for the doped ions to occupy in forming emission centers. The CNSOF:Eu2+ and CNSOF:Ce3+ phosphors both have broad excitation bands, which match well with the commercial UV LED chips. The CNSOF:Eu2+ phosphor can have intense green emission with a maximum at 530 nm under irradiation at 380 nm, while the CNSOF:Ce3+ sample can emit intense blue light, peaking at 470 nm with excitation at 365 nm. By codoping the Tb3+ and Ce3+ ions into an CNSOF host and varying their relative ratio, tunable blue-green colors are obtained due to efficient energy transfer from the Ce3+ to Tb3+ ions. Moreover, energy transfer mechanisms for the Eu2+ ions in CNSOF:Eu2+ and Ce3+ → Tb3+ in CNSOF:Ce3+,Tb3+ have been studied systematically. Our investigation indicates that CNSOF:Eu2+ and CNSOF:Ce3+,Tb3+ may be potential green and blue-green phosphors for UV WLEDs, respectively.
Co-reporter:Mengmeng Jiao, Yongchao Jia, Wei Lü, Wenzhen Lv, Qi Zhao, Baiqi Shao and Hongpeng You
Journal of Materials Chemistry A 2014 vol. 2(Issue 1) pp:90-97
Publication Date(Web):23 Oct 2013
DOI:10.1039/C3TC31837K
A series of Eu2+ and Mn2+ activated novel Sr3GdNa(PO4)3F phosphors have been prepared through a high temperature solid state reaction. The investigation revealed that Sr3GdNa(PO4)3F crystallized in a hexagonal crystal system with the space group P (no. 147). The Eu2+ activated phosphors can be efficiently excited in the range of 250 to 420 nm, which matches well with the commercial n-UV LED chips, and give intense blue emission centering at 470 nm. By codoping the Eu2+ and Mn2+ ions into the SGNPF host and singly varying the doping content of the Mn2+ ion, tunable colors from blue to white and then to yellow are obtained in SGNPF:Eu2+,Mn2+ phosphors under the irradiation of 390 nm. The energy transfer from the Eu2+ to Mn2+ ions is demonstrated to be a dipole–quadrupole mechanism in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors. The critical distance between the Eu2+ and Mn2+ ions in SGNPF:Eu2+,Mn2+ was determined by the spectral overlap method. The investigation indicates that our prepared samples might have potential application in WLEDs.
Co-reporter:Baiqi Shao, Qi Zhao, Yongchao Jia, Wenzhen Lv, Mengmeng Jiao, Wei Lü and Hongpeng You
Chemical Communications 2014 vol. 50(Issue 84) pp:12706-12709
Publication Date(Web):29 Aug 2014
DOI:10.1039/C4CC05191B
Monodisperse β-NaYF4:Ln3+ (Ln = Yb/Er, Yb/Tm) single micro/nanocrystals were first one-pot fabricated at 50 °C through a novel synthetic route containing two pivotal processes: (a) synthesis of a β-NaYF4 {0001} unit layer through a novel style of ion-exchange from Y2(OH)5NO3·nH2O (LYH) and (b) the subsequent oriented-assembly process.
Co-reporter:Qi Zhao, Zhen Lei, Sa Huang, Xueli Han, Baiqi Shao, Wei Lü, Yongchao Jia, Wenzhen Lv, Mengmeng Jiao, Zhenxin Wang, and Hongpeng You
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 15) pp:12761
Publication Date(Web):July 10, 2014
DOI:10.1021/am502718b
Multifunctional BaGdF5 nanospheres with mesoporous, luminescent, and magnetic properties have been successfully synthesized with the assistance of trisodium citrate by a hydrothermal method. The mesoporous structure is revealed by scanning electron microscope and transmission electron microscope images as well as N2 adsorption–desorption isotherm. The as-synthesized BaGdF5 nanospheres exhibit an intense broad bluish emission (centered at 450 nm) under the excitation of 390 nm, which might originate from the CO2·– radical-related defect produced by Cit3– groups. It is also shown that these BaGdF5 nanospheres brightened the T1-weighted images, suggesting that they could act as T1 contrast agents for magnetic resonance imaging. Using metformin hydrochloride as the model drug, the luminescent porous spheres show good drug storage/release capability. Furthermore, the emission intensity varies as a function of the cumulative drug release, making the drug-carrying system easily trackable and monitorable by detecting the luminescence intensity. Additionally, the paramagnetic property, originating from the unpaired electrons of Gd3+ ions, opens the possibility of directing the magnetic targeted carrier to the pathological site by magnetic field gradient.Keywords: BaGdF5; drug delivery; luminescence; magnetism; multifunctional material; porosity
Co-reporter:Wenzhen Lv, Mengmeng Jiao, Qi Zhao, Baiqi Shao, Wei Lü, and Hongpeng You
Inorganic Chemistry 2014 Volume 53(Issue 20) pp:11007-11014
Publication Date(Web):September 26, 2014
DOI:10.1021/ic501423p
In this paper, Eu2+-doped and Eu2+/Mn2+-codoped Ba1.3Ca0.7SiO4 phosphors were synthesized by means of a conventional solid-state reaction process. The single-phase purity was checked by means of X-ray diffraction and the Rietveld method. Under excitation at 390 nm, the emission spectra of the Eu2+-doped phosphors exhibit a broad-band emission centered at 500 nm caused by the electric dipole allowed transition of the Eu2+ ions. The emission spectra of codoped phosphors show one more broad emission centered at 600 nm attributable to the transitions from the 4T1(4G) → 6A1(6S) of Mn2+ ions. The luminescent color of the codoped phosphors can be easily adjusted from blue to red with variation of the Mn2+ content. The energy transfer mechanism from the Eu2+ to Mn2+ ions in Ba1.3Ca0.7SiO4 phosphors has been confirmed to be the resonant type via dipole–quadrupole interaction, and the critical distance has been calculated quantitatively. All these results demonstrate that the Eu2+/Mn2+-codoped Ba1.3Ca0.7SiO4 phosphors can be a promising single-phase, color-tunable phosphor for near-UV white-light-emitting diodes after a further optimization process. Additionally, a great red shift from 593 to 620 nm has been observed following the increase of Mn2+ content, and the phenomenon has been discussed in relation to the changes in the crystal field surrounding the Mn2+ ions and the exchange interactions caused by the formation of Mn2+ pairs.
Co-reporter:Wei Lü, Wenzhen Lv, Qi Zhao, Mengmeng Jiao, Baiqi Shao, and Hongpeng You
Inorganic Chemistry 2014 Volume 53(Issue 22) pp:11985-11990
Publication Date(Web):October 28, 2014
DOI:10.1021/ic501641q
A new, highly efficient deep red-emitting phosphor Ca14Al10Zn6O35:Mn4+ was developed as a component of solid-state white light-emitting diodes (LEDs). The structural and optical characterization of the phosphor is described. The phosphor exhibits strong emission in the range of 650–700 nm when excited by 460 nm excitation, with a quantum efficiency approaching 50%. Concentration dependence of Mn4+ luminescence in Ca14Al10Zn6O35:Mn4+ is investigated. Attempts to understand the thermal stability on the basis of the thermal quenching characteristics of Ca14Al10Zn6O35:Mn4+ is presented. The results suggest that phosphors deriving from Ca14Al10Zn6O35:Mn4+ have potential application for white LEDs. In addition, influence of cation substitution on the luminescence intensity of these phosphors is elucidated.
Co-reporter:Wenzhen Lv;Yongchao Jia;Qi Zhao;Mengmeng Jiao;Baiqi Shao;Wei Lü
Advanced Optical Materials 2014 Volume 2( Issue 2) pp:183-188
Publication Date(Web):
DOI:10.1002/adom.201300448
In this paper, a novel green phosphor Ca8Mg3Al2Si7O28:Eu2+ is synthesized via a conventional high-temperature solid-state reaction. The crystal structure of the phosphor is confirmed from the Rietveld method. The obtained phosphor has a wide absorption band from the UV to the visible spectral region, ranging from 230 to 450 nm, which fits well with the characteristic emission of UV light-emitting diode (LED) chips. Upon excitation at 420 nm, the phosphor shows a bright and broad green color emission band with a maximum centered at 535 nm, which is attributed to the parity and spin allowed 5d–4f transition. The longer emission wavelength is caused by both the d orbital preferential orientation and the lowered symmetry of the Eu2+ ions caused by the discrepancy of the tetrahedrons composed of MgO4, SiO4, and AlO4. Additionally, the energy transfer mechanism among Eu2+ ions is demonstrated via a dipole–dipole interaction by the luminescence spectra and the fluorescence decay analysis calculations on the basis of the Inokuti–Hirayama model. Furthermore, the thermal stability of the phosphor is investigated in detail. These results suggest that the Ca8Mg3Al2Si7O28:Eu2+ phosphor has great potential to be a green phosphor for white light emitting diodes (WLEDs).
Co-reporter:Qi Zhao, Baiqi Shao, Wei Lü, Yongchao Jia, Wenzhen Lv, Mengmeng Jiao, and Hongpeng You
Crystal Growth & Design 2014 Volume 14(Issue 4) pp:1819-1826
Publication Date(Web):March 3, 2014
DOI:10.1021/cg401933m
Pseudo-octahedrons of Ba2GdF7 were successfully synthesized through a solution-based method in a hydrothermal environment for the first time. The preferential adsorption of ethylene glycol (EG) molecules on the {111} planes contributed to the formation of the octahedral shape. Hydrazine was employed as the alkaline source to adjust the adsorption affinity of EG and the hydrolysis rate of NaBF4 (fluorine supply), thereby controlling the morphology and phase structure. A series of contrast experiments were conducted to investigate the growth mechanism of the Ba2GdF7 nanocrystals. As a proof-of-concept experiment, Eu3+, Tb3+, Dy3+, and Yb3+/Er3+ ions were doped to demonstrate the potential of the Ba2GdF7 crystals as host material for phosphors.
Co-reporter:Baiqi Shao, Qi Zhao, Ning Guo, Yongchao Jia, Wenzhen Lv, Mengmeng Jiao, Wei Lü and Hongpeng You
CrystEngComm 2014 vol. 16(Issue 2) pp:152-158
Publication Date(Web):04 Sep 2013
DOI:10.1039/C3CE41456F
Well-defined t-LaVO4:Eu3+ microcrystals have been synthesized through a facile hydrothermal route using La0.95Eu0.05(1,3,5-BTC)(H2O)6 as a precursor for the first time. It was found that the pH value and temperature have a remarkable influence on the morphology determination. By tuning the initial pH value, uniform micro cubes and cuboid rods can be obtained. The possible growth mechanism has been discussed, underlying the systematic time-dependent phase transition and morphological evolution. In addition, the luminescence properties showed that the cuboid rod-shaped LaVO4:Eu3+ sample shows a slightly stronger red emission than the cube-shape one. Our novel synthetic route may provide some new guidance in the design and controlled synthesis of inorganic nano/micromaterials.
Co-reporter:Mengmeng Jiao, Yongchao Jia, Wei Lü, Wenzhen Lv, Qi Zhao, Baiqi Shao and Hongpeng You
Dalton Transactions 2014 vol. 43(Issue 8) pp:3202-3209
Publication Date(Web):02 Dec 2013
DOI:10.1039/C3DT52832D
A series of Ca2SrAl2O6:Ce3+,Li+,Mn2+ phosphors have been synthesized by traditional solid state reactions. The structure and photoluminescence properties of the samples together with the energy transfer from Ce3+ to Mn2+ ions have been investigated in detail. The obtained phosphors can be excited efficiently by UV excitation and exhibit a broad blue-green emission band peaking at 470 nm and an orange-red emission band at 610 nm, which result from the f–d transition of the Ce3+ and the 4T1–6A1 transition of the Mn2+ ions, respectively. By varying the doping concentration of the Mn2+ ion, a series of tunable colors including white are obtained at an irradiation of 355 nm. The possible energy transfer mechanism was proposed in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors. The critical distance between the Ce3+ and Mn2+ ions has been calculated by both the concentration quenching method and the spectral overlap method. Preliminary studies on the properties of the phosphor indicated that our prepared Ca2SrAl2O6:Ce3+,Li+,Mn2+ phosphor might have potential application as a single-phase white-emitting phosphor for WLEDs.
Co-reporter:Xinhao Yin, Qi Zhao, Baiqi Shao, Wei Lv, Yunhui Li and Hongpeng You
CrystEngComm 2014 vol. 16(Issue 25) pp:5543-5550
Publication Date(Web):03 Apr 2014
DOI:10.1039/C3CE42571A
Uniform monodisperse YBO3:Eu3+/Tb3+ microspheres have been successfully synthesized via a facile ethylene glycol-mediated solvothermal method. The crystal structure, morphology and luminescence properties of the prepared products have been characterized by X-ray diffraction, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, and photoluminescence excitation and emission spectra. It was found that the size and morphology of the products could be effectively controlled by adjusting the reaction parameters, such as reaction temperature, pH value and the amount of ethylene glycol. It could be noted that ethylene glycol plays an extremely critical role in the morphology determination. The possible growth mechanism of YBO3 microspheres was further discussed in detail on the basis of a series of time-dependent experiments. Furthermore, the luminescence properties reveal that the YBO3:Eu3+ and YBO3:Tb3+ phosphors show strong orange and green emissions under ultraviolet excitation, respectively.
Co-reporter:Wei Lü, Yongchao Jia, Wenzhen Lv, Qi Zhao, Hongpeng You
Journal of Luminescence 2014 Volume 147() pp:159-162
Publication Date(Web):March 2014
DOI:10.1016/j.jlumin.2013.11.001
•A novel full-color emitting phosphor CaScAlSiO6:Ce3+, Tb3+, Eu3+ are synthesized and investigated.•The obtained phosphor exhibits three emission bands.•The CIE chromaticity coordinates (0.30, 0.30) and high color rendering index CRI=88 can be achieved.•These results indicated that CSAS:Ce3+, Tb3+, Eu3+ is a promising single-composition full-color emitting phosphor.We reported a single-phased CaScAlSiO6:Ce3+, Tb3+, Eu3+ as a potential full-color emitting phosphor for the application in fluorescent lamps. The CaScAlSiO6:Ce3+, Tb3+, Eu3+ phosphor exhibits three bands under 254 nm excitation: one band situated at 380 nm is attributed to the 5d→4f transitions of Ce3+ ions, the second band with sharp lines peaked at 542 nm is assigned to the 5D4→7FJ transitions of Tb3+ ions, the third band in the orange–red region (580–700 nm) is originated from 5D0→7FJ transitions of Eu3+ ions. The Commission Internationale de I’Eclairage (CIE) chromaticity coordinates (0.30, 0.30) and high color rendering index (CRI=88) can be achieved upon excitation of 254 nm light. It is suggested that CaScAlSiO6:Ce3+, Tb3+, Eu3+ can serve as a potential single-phased full-color emitting phosphor for phosphor-converted fluorescent lamps.
Co-reporter:Wei Lü, Yongchao Jia, Wenzhen Lv, Qi Zhao and Hongpeng You
New Journal of Chemistry 2014 vol. 38(Issue 7) pp:2884-2889
Publication Date(Web):01 Apr 2014
DOI:10.1039/C4NJ00314D
Emission-tunable Mg2Al4Si5O18:Eu2+, Mn2+ and Mg2Al4Si5O18:Eu2+, Tb3+ cordierite phosphors have been synthesized by a high-temperature solid-state reaction technique. Photoluminescence and energy transfer in Mg2Al4Si5O18:Eu2+, Mn2+ occur via a resonance-type dipole–quadrupole interaction mechanism, and the critical distance of the energy transfer is calculated to be 11.1 A. We found that the emission colors could be tuned from blue (0.19, 0.26) to white (0.41, 0.37) via the energy transfer of Eu2+ → Mn2+ and from blue to green (0.28, 0.45) via the energy transfer of Eu2+ → Tb3+. The green emission is realized in the Mg2Al4Si5O18:Eu2+, Tb3+ phosphors on the basis of the highly efficient energy transfer from the Eu2+ to Tb3+ ions. Finally, the color tunable emission with varied hues has been obtained in Eu2+, Tb3+, or Mn2+ activated Mg2Al4Si5O18 phosphors, making them potential emission-tunable phosphors for near-UV LEDs.
Co-reporter:Yang Zhang, Qi Zhao, Baiqi Shao, Wei Lü, Xiangting Dong and Hongpeng You
RSC Advances 2014 vol. 4(Issue 67) pp:35750-35756
Publication Date(Web):07 Aug 2014
DOI:10.1039/C4RA04185B
Large-scale CaF2–YF3 alkaline-earth ternary fluoride microspheres with diameters of about 2.5 μm were prepared by a facile hydrothermal method in the presence of disodium ethylenediamine tetraacetate (Na2H2L). The influences of several experimental parameters, such as reaction time, amount of Na2H2L, pH values, and fluoride source on the final products were investigated. The formation mechanism of the as-obtained microspheres was proposed on the basis of all these studies. It is also found that the addition amount of the Y3+ ions had an effect on the morphology of CaF2–YF3. The luminescence spectrum of Eu3+-doped CaF2–YF3 microspheres showed the strong characteristic dominant emission of the Eu3+ ions at 590 nm, indicating that the Eu3+ ions occupy a site of inversion symmetry in the CaF2–YF3 matrix.
Co-reporter:Wenzhen Lv, Yongchao Jia, Qi Zhao, Mengmeng Jiao, Baiqi Shao, Wei Lv and Hongpeng You
RSC Advances 2014 vol. 4(Issue 27) pp:14074-14080
Publication Date(Web):28 Feb 2014
DOI:10.1039/C4RA01381F
In this paper, Ce3+ doped and Ce3+,Mn2+ co-doped Na2Ba6(Si2O7)(SiO4)2 phosphors were synthesized via a high temperature solid-state reaction. The Rietveld refinement analysis of the X-ray diffraction patterns confirmed the formation of the single phase of Na2Ba6(Si2O7)(SiO4)2. The PL spectrum of the Ce3+ single-doped phosphor shows a broad asymmetric band extending from 350 to 600 nm peaking at 420 nm under the excitation of UV light. Also, the low temperature (5 K) PL spectrum shows clearly three peaks at 375, 420, and 451 nm, which is in accordance with the Ce3+ ion site in the host. The Ce3+,Mn2+ co-doped phosphors show a blue emission band and an orange emission band, and the corresponding CIE coordinates intuitively indicate the tunable colors from the blue to green area. And the energy transfer mechanism from Ce3+ to Mn2+ in the host has been verified to be a dipole–quadrupole interaction. In addition, the emission intensity of Na2Ba6(Si2O7)(SiO4)2:0.01Ce3+ phosphor slightly changed with the temperature increase from 300 to 450 K, revealing that the obtained phosphor possesses an excellent thermal stability, which makes it an attractive candidate phosphor for white lighting emitting diodes.
Co-reporter:Wenzhen Lv, Yongchao Jia, Qi Zhao, Mengmeng Jiao, Baiqi Shao, Wei Lü and Hongpeng You
RSC Advances 2014 vol. 4(Issue 15) pp:7588-7593
Publication Date(Web):08 Jan 2014
DOI:10.1039/C3RA46474A
In this paper, a novel single-phased white light emitting phosphor Na2Ca4Mg2Si4O15:Eu2+, Mn2+ was prepared successfully via the high temperature solid state reaction. The obtained Na2Ca4Mg2Si4O15:Eu2+ phosphor exhibits a broad excitation band ranging from 200 to 450 nm and a blue light emission band peaking at 480 nm, originating from 4f7 ↔ 4f65 d1 (f-d) electric dipole allowed transitions of Eu2+ ions. Due to the energy transfer from Eu2+ to Mn2+ ions, the co-doped Eu2+ ions in the Na2Ca4Mg2Si4O15:Eu2+, Mn2+ phosphors markedly enhances the luminescence intensity of Mn2+ ions, providing highly attractive tunable color. The luminescent mechanism invoking the energy transfer between Eu2+ ions and Mn2+ ions has been certified to be dipole–quadrupole interaction predominantly through the investigations of the luminescence spectra and the fluorescence decay curves. Our results show that the novel Na2Ca4Mg2Si4O15:Eu2+, Mn2+ phosphor is a very promising candidate for UV white light emitting diodes.
Co-reporter:Wenzhen Lv ; Yongchao Jia ; Qi Zhao ; Wei Lü ; Mengmeng Jiao ; Baiqi Shao
The Journal of Physical Chemistry C 2014 Volume 118(Issue 9) pp:4649-4655
Publication Date(Web):February 17, 2014
DOI:10.1021/jp500662a
In this paper, a novel divalent europium-doped green emitting blue convertible K2Ba7Si16O40:Eu2+ phosphor has been synthesized successfully via high-temperature solid-state reaction. The structure of K2Ba7Si16O40:Eu2+ has been refined on the basis of X-ray powder diffraction by Rietveld refinement method, which consists of two infinite dimensional layers of corner-sharing [SiO4] tetrahedral parallel to (201) linked together through eight-coordinate K and seven- and nine-coordinate Ba atoms. Under excitation of blue light, the K2Ba7Si16O40:Eu2+ phosphor emits a strong green emission band peaking at 500 nm. The concentration quenching mechanism of the Eu2+ ion was discussed and the critical distance was calculated. Furthermore, the phosphor exhibits high quantum efficiency and good thermal stability, indicating that the K2Ba7Si16O40:Eu2+ phosphor can serve as an effective green emitting candidate for blue light down-conversion white light emitting diodes.
Co-reporter:Qi Zhao, Baiqi Shao, Wei Lü, Yongchao Jia, Wenzhen Lv, Mengmeng Jiao and Hongpeng You
CrystEngComm 2013 vol. 15(Issue 46) pp:9930-9937
Publication Date(Web):03 Oct 2013
DOI:10.1039/C3CE41598H
The monodisperse submicroplates of Gd1−yCayF3−y solid solution were successfully synthesized by a simple and facile hydrothermal method for the first time. The structure of the as-synthesized Gd1−yCayF3−y was determined to be tysonite-type instead of the usual fluorite-type via a Rietveld refinement method with GSAS. Detailed contrast experiments revealed that the addition amounts of ethylene glycol, calcium chloride, and sodium fluoroborate played critical roles in the formation of the Gd1−yCayF3−y solid solution. Desirable multicolor outputs were successfully realized by doping activator ions (Eu3+, Tb3+, and Dy3+) in the Gd1−yCayF3−y crystals where the Gd3+ ions served as an energy intermediate. Furthermore, the energy transfer from the Gd3+ to Eu3+ ions in the obtained Gd1−yCayF3−y solid solution was more efficient than that in the orthorhombic GdF3.
Co-reporter:Qi Zhao, Baiqi Shao, Wei Lü, Yongchao Jia, Wenzhen Lv, Mengmeng Jiao and Hongpeng You
Dalton Transactions 2013 vol. 42(Issue 43) pp:15482-15488
Publication Date(Web):12 Sep 2013
DOI:10.1039/C3DT51967H
Hexagonal GdF3 is a more efficient phosphor host compared with the traditional orthorhombic form but the hexagonal phase is thermodynamically unstable at room temperature. Herein, we present a strategy to stabilize hexagonal GdF3 by doping with alkaline-earth ions in a mild hydrothermal reaction system. The selection of the dopant, effect of the dopant amount and the mechanism of the phase transition was discussed in detail. The luminescence variation of GdF3:Eu was demonstrated to verify the phase transformation. Furthermore, the upconversion luminescence of the Sr-doped and undoped GdF3:Yb/Er was investigated.
Co-reporter:Wenzhen Lv, Wei Lü, Ning Guo, Yongchao Jia, Qi Zhao, Mengmeng Jiao, Baiqi Shao and Hongpeng You
RSC Advances 2013 vol. 3(Issue 36) pp:16034-16039
Publication Date(Web):03 Jul 2013
DOI:10.1039/C3RA41662C
A new blue-green emitting phosphor Ca12Al14O33Cl2:Eu2+,Mn2+ has been synthesized by the solid-state reaction technique method under a reductive atmosphere. The X-ray diffraction measurement results indicate that the crystal structure of the phosphor is a single phase of Ca12Al14O33Cl2. The phosphors can be efficiently excited by near ultraviolet (n-UV) light and show a blue emission band at about 450 nm and a green emission band at about 550 nm, which originated from the Eu2+ ions and the Mn2+ ions. The efficient energy transfer from the Eu2+ ions and the Mn2+ ions was observed and its mechanism should be a resonant type via a nonradiative dipole–quadrupole interaction. The critical distance between the Eu2+ ions and Mn2+ ions has been calculated to be about 10.83 Å as well. In addition, the temperature dependent photoluminescence of the as-prepared phosphors has been investigated in detail. Our results indicate that the developed phosphor may be used as a potential blue-green emitting phosphor for UV-based white LEDs.
Co-reporter:Wei Lü, Yongchao Jia, Wenzhen Lv, Qi Zhao and Hongpeng You
New Journal of Chemistry 2013 vol. 37(Issue 11) pp:3701-3705
Publication Date(Web):22 Aug 2013
DOI:10.1039/C3NJ00758H
An orange-emitting phosphor was obtained via efficient Ce3+–Mn2+ and Eu2+–Mn2+ energy transfers in La9.33(SiO4)6O2, and has been developed for solid state UV/near-UV white lighting applications. The luminescence properties and energy transfer from Ce3+ to Mn2+ and Eu2+ to Mn2+ are investigated. The La9.33(SiO4)6O2:Ce3+, Mn2+ phosphor shows a blue emission centered at 380 and an orange emission peaking at 590 nm, which could be ascribed to the allowed 5d → 4f transition of the Ce3+ ion and the 4T1g(4G) → 6A1g(6S) transition of the Mn2+ ion, respectively. Upon excitation at 365 nm, the Eu2+, Mn2+ co-doped La9.33(SiO4)6O2 phosphor exhibits the Eu2+ green emission band and the Mn2+ orange emission band. Non-radiative transitions between the Ce3+/Eu2+ and Mn2+ ions in the La9.33(SiO4)6O2 host are both demonstrated to be attributable to dipole–quadrupole interactions. The intensity ratio of the Mn2+ emission bands can be enhanced through the increase of the Mn2+ content, which is attributed to the efficient energy transfer from Ce3+/Eu2+ to Mn2+, and the corresponding chromaticity coordinates (0.50, 0.38), (0.51, 0.46) were obtained with the La9.33(SiO4)6O2:Ce3+, Mn2+ and La9.33(SiO4)6O2:Eu2+, Mn2+ samples. Results indicated that the as-prepared phosphors might have promising applications in white-light LEDs as an orange-emitting phosphor.
Co-reporter:Baiqi Shao, Qi Zhao, Yongchao Jia, Wenzhen Lv, Mengmeng Jiao, Wei Lü and Hongpeng You
Journal of Materials Chemistry A 2014 - vol. 2(Issue 36) pp:NaN7673-7673
Publication Date(Web):2014/07/18
DOI:10.1039/C4TC00808A
Highly monodisperse YF3:Ln3+ (Ln = Eu, Ce, Tb, Yb/Er, Yb/Ho, and Yb/Tm) nano/microcrystals with controllable size and morphology have been synthesized by an innovative low-temperature (≤0 °C) precipitation route free of any surfactant. Interestingly, the monodispersity and morphology are independent of the pH value and reactant concentration at a low temperature even when the reactant concentrations are close to saturation. This allows for a high yield production at 150 g L−1 of reaction system. A detailed investigation of the growth process reveals that a low temperature can ensure a more definite separation of nucleation and growth. Simultaneously, the low temperature-induced diffusion-controlled growth model gives rise to a size focusing effect, which further insures the monodispersity of the final products. Furthermore, our synthetic strategy can be extended to other lanthanide fluorides (REF3, RE (rare earth) = Ce, Nd, Sm-Lu), and the obtained YF3:Ln3+ samples exhibit strong down/upconversion emissions. Such a facile synthetic strategy fits well with the green concept in current synthetic innovations for nanocrystals and may provide some guidance in the kinetically controlled synthesis of inorganic nanocrystals.
Co-reporter:Mengmeng Jiao, Yongchao Jia, Wei Lü, Wenzhen Lv, Qi Zhao, Baiqi Shao and Hongpeng You
Journal of Materials Chemistry A 2014 - vol. 2(Issue 21) pp:NaN4311-4311
Publication Date(Web):2014/04/01
DOI:10.1039/C4TC00401A
A series of Eu2+ and Ce3+/Tb3+ doped Ca2NaSiO4F (CNSOF) phosphors have been synthesized and their structure and photoluminescence properties have been investigated in detail. Rietveld structure refinement indicates that the phosphors crystalized in an orthorhombic system with a space group of Pnma (no. 62) and there are two kinds of cation sites for the doped ions to occupy in forming emission centers. The CNSOF:Eu2+ and CNSOF:Ce3+ phosphors both have broad excitation bands, which match well with the commercial UV LED chips. The CNSOF:Eu2+ phosphor can have intense green emission with a maximum at 530 nm under irradiation at 380 nm, while the CNSOF:Ce3+ sample can emit intense blue light, peaking at 470 nm with excitation at 365 nm. By codoping the Tb3+ and Ce3+ ions into an CNSOF host and varying their relative ratio, tunable blue-green colors are obtained due to efficient energy transfer from the Ce3+ to Tb3+ ions. Moreover, energy transfer mechanisms for the Eu2+ ions in CNSOF:Eu2+ and Ce3+ → Tb3+ in CNSOF:Ce3+,Tb3+ have been studied systematically. Our investigation indicates that CNSOF:Eu2+ and CNSOF:Ce3+,Tb3+ may be potential green and blue-green phosphors for UV WLEDs, respectively.
Co-reporter:Baiqi Shao, Qi Zhao, Wenzhen Lv, Mengmeng Jiao, Wei Lü and Hongpeng You
Journal of Materials Chemistry A 2015 - vol. 3(Issue 5) pp:NaN1098-1098
Publication Date(Web):2014/11/21
DOI:10.1039/C4TC02477J
Monodisperse β-NaYF4:Ln3+ (Ln = Eu, Tb, Yb/Er, or Yb/Tm) nanocrystals with multiform novel morphologies have been synthesized for the first time by a novel two-step ion-exchange route expressed as Y2(OH)5NO3·nH2O (LYH) → Y(OH)xF3−x → β-NaYF4. In step I (LYH → Y(OH)xF3−x), the Y(OH)xF3−x is fabricated using a one-pot method from the starting point of a unit layer at low temperature through a novel style of ion-exchange from LYH based on the special crystal structural similarity between the LYH unit layer and the Y(OH)xF3−x {0001} plane. Of particular interest is that the ion-exchange process in step I can be completed within the initial few minutes, and the unique two-dimensional layered structure of LYH greatly favors the ion-exchange reaction by exfoliating into atomically thick monolayers. Meanwhile, the identical structural framework between Y(OH)xF3−x and β-NaYF4 ensures the in situ ion-exchange reaction in step II. The composition of the intermediate precursor Y(OH)xF3−x can be tuned in a wide range, which gives the synthetic parameters high maneuverability and greatly simplifies the experimental variables. In addition, the luminescence properties showed that the as-prepared β-NaYF4:Ln3+ nanocrystals exhibited strong characteristic multicolor emissions through upconversion and downconversion.
Co-reporter:Mengmeng Jiao, Yongchao Jia, Wei Lü, Wenzhen Lv, Qi Zhao, Baiqi Shao and Hongpeng You
Dalton Transactions 2014 - vol. 43(Issue 8) pp:NaN3209-3209
Publication Date(Web):2013/12/02
DOI:10.1039/C3DT52832D
A series of Ca2SrAl2O6:Ce3+,Li+,Mn2+ phosphors have been synthesized by traditional solid state reactions. The structure and photoluminescence properties of the samples together with the energy transfer from Ce3+ to Mn2+ ions have been investigated in detail. The obtained phosphors can be excited efficiently by UV excitation and exhibit a broad blue-green emission band peaking at 470 nm and an orange-red emission band at 610 nm, which result from the f–d transition of the Ce3+ and the 4T1–6A1 transition of the Mn2+ ions, respectively. By varying the doping concentration of the Mn2+ ion, a series of tunable colors including white are obtained at an irradiation of 355 nm. The possible energy transfer mechanism was proposed in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors. The critical distance between the Ce3+ and Mn2+ ions has been calculated by both the concentration quenching method and the spectral overlap method. Preliminary studies on the properties of the phosphor indicated that our prepared Ca2SrAl2O6:Ce3+,Li+,Mn2+ phosphor might have potential application as a single-phase white-emitting phosphor for WLEDs.
Co-reporter:Mengmeng Jiao, Wenzhen Lv, Wei Lü, Qi Zhao, Baiqi Shao and Hongpeng You
Dalton Transactions 2015 - vol. 44(Issue 9) pp:NaN4087-4087
Publication Date(Web):2015/01/14
DOI:10.1039/C4DT03906H
A new langbeinite-type phosphate KSrSc2(PO4)3 has been synthesized by conventional high temperature solid state reaction. Rietveld structure refinement, a field emission scanning electron microscope, photoluminescence spectra, quantum efficiency as well as lifetimes were used to characterize the samples. Structure refinement reveals that KSrSc2(PO4)3 has two kinds of Sr2+ and Sc3+ sites for the doped ions to occupy, forming emission centers. The KSrSc2(PO4)3:Ce3+ and KSrSc2(PO4)3:Eu2+ phosphors both have broad excitation and emission bands due to spin- and orbit-allowed electron transitions. Phosphors with tunable blue to blue-green colors were obtained by codoping the Tb3+ ions into the KSrSc2(PO4)3:0.03Ce3+ and KSrSc2(PO4)3:0.03Eu2+ phosphors with varying contents. The mechanism of Eu2+→Tb3+ energy transfer is determined to be a dipole–quadrupole interaction in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors by using the Inokuti–Hirayama theoretical model. Our prepared KSrSc2(PO4)3:Ce3+,Tb3+ and KSrSc2(PO4)3:Eu2+,Tb3+ phosphors are of potential value for UV excited WLEDs.
Co-reporter:Qi Zhao, Baiqi Shao, Wei Lü, Wenzhen Lv, Mengmeng Jiao, Lingfei Zhao and Hongpeng You
Dalton Transactions 2015 - vol. 44(Issue 8) pp:NaN3752-3752
Publication Date(Web):2015/01/07
DOI:10.1039/C4DT03619K
Hexagonal-phase NaGdF4 nanotubes were successfully fabricated through a template- and catalyst-free method in a hydrothermal environment. The intrinsic and external factors contributing to the formation of tubular nanocrystals were discussed, namely the anisotropic crystal structure of the hexagonal-phase NaGdF4 and the insufficient supply of reagents. Furthermore, the addition of ethylene glycol and hydrazine had a significant effect on the morphological variation. The desirable multicolor outputs were achieved by co-doping Ce3+ and Ln3+ (Ln = Eu, Tb, and Dy) ions in the NaGdF4 crystal, in which the Gd3+ ions acted as an intermediate medium transforming the excitation energy to the activator ions. Finally, the upconversion luminescence and magnetic performance of the sodium rare earth fluoride were demonstrated.
Co-reporter:Wei Lü, Mengmeng Jiao, Baiqi Shao, Lingfei Zhao, Yang Feng and Hongpeng You
Dalton Transactions 2016 - vol. 45(Issue 2) pp:NaN468-468
Publication Date(Web):2015/11/17
DOI:10.1039/C5DT03465E
To date, most current reports on the development and optimization of solar spectral converters have described the utilization of energy transfer among rare-earth ions. Here, we introduce non-rare-earth ion Mn4+ to transfer energy to Yb3+, which can exhibit strong near-infrared luminescence. It can harvest UV-blue photons and exhibits intense NIR emission of Yb3+ around 1000 nm, perfectly matching the maximum spectral response of Si solar cells. It demonstrates for the first time that efficient energy transfer occurs with a decrease in the excited state lifetime and red photoluminescence (PL) from Mn4+ with increasing Yb3+ concentration. These results demonstrate that the Mn4+ ions can be an efficient and direct sensitizer harvesting UV-blue photons. It could provide new avenues for developing harvesting Si-based solar cells.
Co-reporter:Wei Lü, Jiansheng Huo, Yang Feng, Shuang Zhao and Hongpeng You
Dalton Transactions 2016 - vol. 45(Issue 23) pp:NaN9683-9683
Publication Date(Web):2016/05/17
DOI:10.1039/C6DT01652A
New tuneable light-emitting Ca3Al8Si4O17N4:Ce3+/Tb3+/Eu2+ oxynitride phosphors with high brightness have been prepared. When doped with trivalent cerium or divalent europium they present blue luminescence under UV excitation. The energy transfer from Ce3+ to Tb3+ and Ce3+ to Eu2+ ions is deduced from the spectral overlap between Ce3+ emission and Tb3+/Eu2+ excitation spectra. The energy-transfer efficiencies and corresponding mechanisms are discussed in detail, and the mechanisms of energy transfer from the Ce3+ to Tb3+ and Ce3+ to Eu2+ ions are demonstrated to be a dipole–quadrupole and dipole–dipole mechanism, respectively, by the Inokuti–Hirayama model. The International Commission on Illumination value of color tuneable emission as well as luminescence quantum yield (23.8–80.6%) can be tuned by controlling the content of Ce3+, Tb3+ and Eu2+. All results suggest that they are suitable for UV light-emitting diode excitation.
Co-reporter:Jiansheng Huo, Langping Dong, Wei Lü, Baiqi Shao and Hongpeng You
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 26) pp:NaN17323-17323
Publication Date(Web):2017/06/12
DOI:10.1039/C7CP02507F
A series of novel Ce3+, Tb3+ and Eu3+ ion doped Y4SiAlO8N-based oxynitride phosphors were synthesized by the solid-state method and characterized by X-ray powder diffraction, scanning electron microscopy, photoluminescence, lifetimes and thermo-luminescence. The excitation of the Ce3+/Tb3+ co-doped and Ce3+/Tb3+/Eu3+ tri-doped phosphor with near-UV radiation results in strong linear Tb3+ green and Eu3+ red emission. The occurrence of Ce3+–Tb3+ and Ce3+–Tb3+–Eu3+ energy transfer processes is responsible for the bright green or red luminescence. The Tb3+ ion acting as an energy transfer bridge can alleviate MMCT quenching between the Ce3+–Eu3+ ion pairs. The lifetime measurements demonstrated that the energy-transfer mechanisms of Ce3+ → Tb3+ and Tb3+ → Eu3+ are dipole–quadrupole and quadrupole–quadrupole interactions, respectively. The temperature dependent luminescence measurements showed that as-prepared green/red phosphors have good thermal stability against temperature quenching. The obtained results indicate that these phosphors might serve as promising candidates for n-UV LEDs.
Co-reporter:Wei Lü, Huawei Xu, Jiansheng Huo, Baiqi Shao, Yang Feng, Shuang Zhao and Hongpeng You
Dalton Transactions 2017 - vol. 46(Issue 28) pp:NaN9279-9279
Publication Date(Web):2017/06/21
DOI:10.1039/C7DT01086A
A tunable white light emitting Na2Ca3Si2O8:Ce3+,Tb3+,Mn2+ phosphor with a high color rendering index (CRI) has been prepared. Under UV excitation, Na2Ca3Si2O8:Ce3+ phosphors present blue luminescence and exhibit a broad excitation ranging from 250 to 400 nm. When codoping Tb3+/Mn2+ ions into Na2Ca3Si2O8, energy transfer from Ce3+ to Tb3+ and Ce3+ to Mn2+ ions is observed from the spectral overlap between Ce3+ emission and Tb3+/Mn2+ excitation spectra. The energy-transfer efficiencies and corresponding mechanisms are discussed in detail. The mechanism of energy transfer from Ce3+ to Tb3+ is demonstrated to be a dipole–quadrupole mechanism by the Inokuti–Hirayama model. The wavelength-tunable white light can be realized by coupling the emission bands centered at 440, 550 and 590 nm ascribed to the contribution from Ce3+, Tb3+ and Mn2+, respectively. The commission on illumination value of color tunable emission can be tuned by controlling the content of Ce3+, Tb3+ and Mn2+. Temperature-dependent luminescence spectra proved the good thermal stability of the as-prepared phosphor. White LEDs with CRI = 93.5 are finally fabricated using a 365 nm UV chip and the as-prepared Na2Ca3Si2O8:Ce3+,Tb3+,Mn2+ phosphor. All the results suggest that Na2Ca3Si2O8:Ce3+,Tb3+,Mn2+ can act as potential color-tunable and single-phase white emission phosphors for possible applications in UV based white LEDs.
Co-reporter:Qi Zhao, Baiqi Shao, Wei Lü, Yongchao Jia, Wenzhen Lv, Mengmeng Jiao and Hongpeng You
Dalton Transactions 2013 - vol. 42(Issue 43) pp:NaN15488-15488
Publication Date(Web):2013/09/12
DOI:10.1039/C3DT51967H
Hexagonal GdF3 is a more efficient phosphor host compared with the traditional orthorhombic form but the hexagonal phase is thermodynamically unstable at room temperature. Herein, we present a strategy to stabilize hexagonal GdF3 by doping with alkaline-earth ions in a mild hydrothermal reaction system. The selection of the dopant, effect of the dopant amount and the mechanism of the phase transition was discussed in detail. The luminescence variation of GdF3:Eu was demonstrated to verify the phase transformation. Furthermore, the upconversion luminescence of the Sr-doped and undoped GdF3:Yb/Er was investigated.
Co-reporter:Mengmeng Jiao, Yongchao Jia, Wei Lü, Wenzhen Lv, Qi Zhao, Baiqi Shao and Hongpeng You
Journal of Materials Chemistry A 2014 - vol. 2(Issue 1) pp:NaN97-97
Publication Date(Web):2013/10/23
DOI:10.1039/C3TC31837K
A series of Eu2+ and Mn2+ activated novel Sr3GdNa(PO4)3F phosphors have been prepared through a high temperature solid state reaction. The investigation revealed that Sr3GdNa(PO4)3F crystallized in a hexagonal crystal system with the space group P (no. 147). The Eu2+ activated phosphors can be efficiently excited in the range of 250 to 420 nm, which matches well with the commercial n-UV LED chips, and give intense blue emission centering at 470 nm. By codoping the Eu2+ and Mn2+ ions into the SGNPF host and singly varying the doping content of the Mn2+ ion, tunable colors from blue to white and then to yellow are obtained in SGNPF:Eu2+,Mn2+ phosphors under the irradiation of 390 nm. The energy transfer from the Eu2+ to Mn2+ ions is demonstrated to be a dipole–quadrupole mechanism in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors. The critical distance between the Eu2+ and Mn2+ ions in SGNPF:Eu2+,Mn2+ was determined by the spectral overlap method. The investigation indicates that our prepared samples might have potential application in WLEDs.
Co-reporter:Wei Lü, Wenzhen Lv, Qi Zhao, Mengmeng Jiao, Baiqi Shao and Hongpeng You
Journal of Materials Chemistry A 2015 - vol. 3(Issue 10) pp:NaN2340-2340
Publication Date(Web):2015/01/13
DOI:10.1039/C4TC02652G
Utilizing Mn2+ and Tb3+ ions as energy-transfer acceptors, we report a series of emission color-tunable Ca2GdZr2(AlO4)3:Ce3+, Mn2+, Tb3+ aluminate garnets. Incorporating Mn2+ and Tb3+ into Ca2GdZr2(AlO4)3:Ce3+ phosphor generates an orange emission band peaking at 572 nm and a green line peaking at 550 nm. The energy transfers from Ce3+ to Mn2+ and Ce3+ to Tb3+ ions are deduced from the spectral overlap between the Ce3+ emission and Mn2+/Tb3+ excitation spectra. Fluorescence decay patterns are studied as a function of Mn2+ and Tb3+ concentration. The calculated values based on the luminescence dynamical process indicate that the intensity ratios of the orange to green bands as a function of Mn2+ concentration are in good agreement with those obtained directly from the emission spectra. We have demonstrated that the color emission as well as the luminescence external quantum yield (20.4–48.9%) can be tuned by precisely controlling the content of Ce3+, Mn2+, and Tb3+. The energy transfer significantly enables the achievement of a broad emission spectrum covering an orange spectral region. It is suitable for near-UV light-emitting diode (LED) excitation.
Co-reporter:Yan Song, Baiqi Shao, Yang Feng, Wei Lü, Guixia Liu and Hongpeng You
Dalton Transactions 2016 - vol. 45(Issue 23) pp:NaN9476-9476
Publication Date(Web):2016/05/04
DOI:10.1039/C6DT01206J
Promoting excitation efficiency is a direct route to enhance the luminescence properties of lanthanide doped materials. Here, we describe a novel strategy to enhance the luminescence performance of NaGdF4:Ln3+ (Ln = Tb, Eu, Dy) nanoparticles by surface modification with benzoate (BA) and 1,10-phenanthroline (Phen) ligands via the sensitization of surface dopants. It was found that the surface ligands provide a new path for energy transfer to the activators due to the matching in energy levels between the two. Moreover, the overlap in excitation peaks for both Gd3+ ions and ligands ensures the simultaneous energy transfer of Gd3+ → Ln3+ and ligands → Ln3+ under a single wavelength excitation. The obtained NaGdF4 nanocomposite was characterized in detail using XRD, FT-IR, TGA, SEM, and EDS. The luminescence performance of the surface modified NaGdF4:Ln3+ nanoparticles was also optimized by tuning the loading amount of modified ligands. In addition, luminescence thermometry was realized by monitoring emission intensity at different temperatures.
Co-reporter:Baiqi Shao, Yang Feng, Mengmeng Jiao, Wei Lü and Hongpeng You
Dalton Transactions 2016 - vol. 45(Issue 6) pp:NaN2491-2491
Publication Date(Web):2015/12/11
DOI:10.1039/C5DT03708E
GdOF:Ln3+ (Ln = Eu, Tb, Eu/Tb, Ce/Tb, Yb/Er, and Yb/Tm) nanocrystals with a hexagonal prism morphology have been readily synthesized by a novel topotactic transformation route. The Gd(OH)2F precursor was first synthesized and structurally analyzed by the Rietveld refinement method. It has been found that the Gd(OH)2F precursor was formed by a novel type of ion-exchange from the brucite-like Gd2(OH)5NO3·0.9H2O (LGdH). Such an ion-exchange behavior is different from the traditional case for the layered double hydroxides (LDHs) in which the intercalated anions are exchanged by the external ions. The detailed structural analysis showed that GdOF prefered [0001] epitaxial growth direction of Gd(OH)2F due to the structural matching of [0001]Gd(OH)2F//[110]GdOF. Furthermore, the potential application of the as-prepared nanocrystals as phosphors is emphasized by demonstrating strong multicolor emissions including both down-conversion and upconversion, and energy transfer (Ce–Tb) processes by GdOF:Ln3+ in detail. Our nonorganic green synthetic strategy based on the novel ion-exchange for the LDHs may enrich the synthetic methodology for nanomaterials.
Co-reporter:Baiqi Shao, Qi Zhao, Yongchao Jia, Wenzhen Lv, Mengmeng Jiao, Wei Lü and Hongpeng You
Chemical Communications 2014 - vol. 50(Issue 84) pp:NaN12709-12709
Publication Date(Web):2014/08/29
DOI:10.1039/C4CC05191B
Monodisperse β-NaYF4:Ln3+ (Ln = Yb/Er, Yb/Tm) single micro/nanocrystals were first one-pot fabricated at 50 °C through a novel synthetic route containing two pivotal processes: (a) synthesis of a β-NaYF4 {0001} unit layer through a novel style of ion-exchange from Y2(OH)5NO3·nH2O (LYH) and (b) the subsequent oriented-assembly process.
