Controllable synthesis and up-conversion properties of tetragonal BaYF5:Yb/Ln (Ln=Er, Tm, and Ho) nanocrystals

The nanocrystals (NCs) of tetragonal barium yttrium fluoride (BaYF(5)) doped 1 mol% Ln(3+) (Ln=Er, Tm, Ho) and 20 mol% Yb(3+) with different morphologies and sizes have been successfully synthesized through a facile hydrothermal method. The influences of pH values of the initial solution and fluorine sources on the final structure and morphology of the products have been well investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the size, structure and morphology of these samples prepared at different conditions. And it is found that BaYF(5):Yb/Ln NCs prepared at pH value of 10 using NaBF(4) as F(-) source have a uniform spherical morphology with average diameter of 25 nm. Additionally, the up-conversion (UC) properties of Yb/Er, Yb/Tm, and Yb/Ho doped BaYF(5) nanoparticles were also discussed. Under 980 nm laser excitation, the BaYF(5):Yb/Er, BaYF(5):Yb/Tm, and BaYF(5):Yb/Ho NCs exhibit green, whitish blue, and yellow green UC luminescence, respectively. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.     

Preparation and up-conversion luminescence of hollow La2O3:Ln (Ln = Yb/Er, Yb/Ho) microspheres

Hollow La(2)O(3):Ln (Ln = Yb/Er, Yb/Ho) microspheres with up-conversion (UC) luminescence properties were successfully synthesized via a facile sacrificial template method by employing carbon spheres as hard templates followed by a subsequent heating process. The structure, morphology, formation process, and fluorescent properties are well investigated by various techniques. The results indicate that the hollow La(2)O(3):Ln microspheres can be well indexed to the hexagonal La(2)O(3) phase. The hollow La(2)O(3):Ln microspheres with uniform diameter of about 270 nm maintain the spherical morphology and good dispersion of the carbon spheres template. The shell of the hollow microspheres consists of numerous nanocrystals with the thickness of approximately 40 nm. Moreover, the possible formation mechanism of evolution from the carbon spheres to the amorphous precursor and to the final hollow La(2)O(3):Ln microspheres has also been proposed. The Yb/Er and Yb/Ho codoped La(2)O(3) hollow spheres exhibit bright up-conversion luminescence with different colors derived from different activators under the 980 nm NIR laser excitation. Furthermore, the doping concentration of the Yb(3+) is optimized under fixed concentration of Er(3+)/Ho(3+). This material may find potential applications in drug delivery, hydrogen and Li ion storage, and luminescent displays based on the uniform hollow structure, dimension, and UC luminescence properties.     

Hydrothermal Synthesis of Monodispersed BaGdF5:Yb/Er Nanoparticles for CT and MR Imaging

In this paper, we report the development of a facile one‐pot hydrothermal method for the controlled synthesis of monodispersed BaGdF₅ :Yb/Er nanoparticles for computed tomography (CT) and magnetic resonance (MR) imaging. The as‐prepared nanoparticles have uniform size with a diameter of 20–25 nm. MTT tests show that the cell viability surpasses 90% even with a concentration of nanoparticles of 500 µg/mL, suggesting that the as‐prepared BaGdF₅ :Yb/Er nanoparticles possess low toxicity. For both BaGdF₅ :Yb/Er nanoparticles and iopromide, the Hounsfield unit (HU) values increase with the their concentration. The slope of BaGdF₅ :Yb/Er nanoparticles is about 26.47, which is much higher than that of iopromide (16.98), indicating a better CT imaging effect. Interestingly, we find that the synthesized BaGdF₅ :Yb/Er nanoparticles exhibit paramagnetism. Our in vitro and in vivo imaging experiments demonstrate that the synthesized monodispersed BaGdF₅ :Yb/Er nanoparticles can serve as effective contrast agents for CT and MR imaging.     

Novel heterometal-organic complexes as first single source precursors for up-converting NaY(Ln)F4 (Ln = Yb, Er, Tm) nanomaterials

First heterometal-organic single source precursors for NaYF(4) nanomaterials as a host matrix for up-conversion emission are reported. These novel heterobimetallic derivatives NaY(TFA)(4)(diglyme) (1), [Na(triglyme)(2)][Y(2)(TFA)(7)(THF)(2)] (2) and Na(2)Y(TFA)(5)(tetraglyme) (3) (TFA = trifluoroacetate), which were fully characterized by elemental analysis, FT-IR and (1)H NMR spectroscopy, TG-DTA data as well as single crystal X-ray structures, are advantageous in terms of being anhydrous and having lower decomposition temperatures in comparison to the homometallic precursor Y(TFA)(3)(H(2)O)(3). In addition, they also contain chelating glyme ligands, which act as capping reagents during decomposition to control the NaYF(4) particle size and render them monodisperse in organic solvents. On decomposition in 1-octadecene, the molecular derivatives 1 and 3 are converted, in the absence of any surfactant or capping reagent, to cubic NaYF(4) nanocrystals at significantly lower temperatures (below 250 °C). At higher temperature, a mixture of the cubic and hexagonal phases was obtained, the relative ratio of the two phases depending on the reaction temperature. A pure hexagonal phase, which is many folds more efficient for UC emission than the cubic phase, was obtained by calcining nanocrystals of mixed phase at 400 °C. In order to co-dope this host matrix with up-converting lanthanide cations, analogous complexes NaLn(TFA)(4)(diglyme) [Ln = Er (4), Tm (5), Yb (6)] and Na(2)Ln(TFA)(5)(tetraglyme) [Ln = Er (7), Yb (8)] were also prepared and characterized. The decomposition in 1-octadecene of suitable combinations and appropriate molar ratios of these yttrium, ytterbium and erbium/thulium derivatives gave cubic and/or hexagonal NaYF(4): Yb(3+), Er(3+)/Tm(3+) nanocrystals (NCs) capped by diglyme or tetraglyme ligands, which were characterized by IR, TG-DTA data, EDX analysis and TEM studies. Surface modification of these NCs by ligand exchange reactions with poly acrylic acid (PAA) and polyethyleneglycol (PEG) diacid 600 was also carried out to render them water soluble. The THF solutions of suitable combinations of the diglyme derivatives were also used to elaborate the thin films of NaYF(4):Yb(3+), Er(3+)/Tm(3+) on a glass or Si wafer substrate by spin coating. The multicolour up-conversion fluorescence was successfully realized in the Yb(3+)/Er(3+) (green/red) and Yb(3+)/Tm(3+) (blue/violet) co-doped NaYF(4) nanoparticles and thin films, which demonstrates that they are promising UC nanophosphors of immense practical interest. The up-conversion excitation pathways for the Er(3+)/Yb(3+) and Tm(3+)/Yb(3+) co-doped materials are discussed.     

Blue,green,red upconversion luminescence and optical characteristics of rare earth doped rare earth oxide and oxysulfide

The cold isostatic press pretreatment process was adopted to prepare fine rare earth oxysulfide up-conversion phosphors with spherical shape, narrow size distribution and high luminescence efficiency. The upconversion optical characteristics and brightness of the blue (Y2O2SYb,Tm), green (Y2O2S: Yb,Er), red (Y2O3Yb,Er) emitter were also investigated, and a novel method was successfully developed for the brightness measurement of upconversion luminescence (UPL). It is shown that a white color can be obtained by the appropriate mixture of these primary blue, green and red emissions components. The Er3 ions exhibit different upconversion mechanism in Y2O2S and Y2O3 host materials. The rare earth oxysulfide is an efficient upconversion matrix. The UPL brightness of Y2O2S: Yb,Er is 6.5 times higher than that of Y2O3: Yb,Er, and Y2O2S: Yb,Er shows UPL brightness of 1100 cd/m2 under 5.56 W/cm2 power density using a 980 nm laser diode.     

Highly uniform and monodisperse beta-NaYF(4):Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprism crystals: hydrothermal synthesis and luminescent properties

beta-NaYF4:Ln3+ (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprisms with remarkably uniform morphology and size have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. It is found that sodium citrate as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the molar ratio of citrate/RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+). Under the excitation of 397 nm ultraviolet light, NaYF4:xEu3+ (x = 1.5, 5%) shows the emission lines of Eu3+ corresponding to 5D0-3 --> 7FJ (J = 0-4) transitions from 400 to 700 nm (whole visible spectral region) with different intensity, resulting in yellow and red down-conversion (DC) light emissions, respectively. When doped with 5% Tb3+ ions, the strong DC fluorescence corresponding to 5D4 --> 7FJ (J = 6, 5, 4, 3) transitions with 5D4 --> 7F5 (green emission at 544 nm) being the most prominent group that has been observed. In addition, under 980 nm laser excitation, the Yb3+/Er3+- and Yb3+/Tm3+-codoped beta-NaYF4 samples exhibit bright green and whitish blue up-conversion (UC) luminescence, respectively. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.     

Facile synthesis and multicolor luminescent properties of uniform Lu2O3:Ln (Ln=Eu3+, Tb3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanospheres

Multicolor Lu(2)O(3):Ln (Ln=Eu(3+), Tb(3+), Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) nanocrystals (NCs) with uniform spherical morphology were prepared through a facile urea-assisted homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and photoluminescence (PL) spectra as well as kinetic decays were employed to characterize these samples. The XRD results reveal that the as-prepared nanospheres can be well indexed to cubic Lu(2)O(3) phase with high purity. The SEM images show the obtained Lu(2)O(3):Ln samples consist of regular nanospheres with the mean diameter of 95 nm. And the possible formation mechanism is also proposed. Upon ultraviolet (UV) excitation, Lu(2)O(3):Ln (Ln=Eu(3+) and Tb(3+)) NCs exhibit bright red (Eu(3+), (5)D(0)→(7)F(2)), and green (Tb(3+), (5)D(4)→(7)F(5)) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu(2)O(3):Ln (Ln=Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) NCs display the typical up-conversion (UC) emissions of green (Er(3+), (4)S(3/2),(2)H(11/2)→(4)I(15/2)), blue (Tm(3+), (1)G(4)→(3)H(6)) and yellow-green (Ho(3+), (5)F(4), (5)S(2)→(5)I(8)), respectively.     

Facile synthesis and up-conversion properties of monodisperse rare earth fluoride nanocrystals

Monodisperse rare earth (RE) fluoride colloidal nanocrystals (NCs) including REF(3) (RE = La, Pr, Nd), NaREF(4) (RE = Sm-Ho, Y) and Na(5)RE(9)F(32) (RE = Er, Yb, Lu) have been successfully synthesized by a facile one-step method using oleic acid as surfactant and 1-octadecene as solvent. The phase, morphology, size, and photoluminescence properties of as-synthesized NCs were well investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence (PL) spectra. The results reveal that the as-synthesized NCs consist of monodisperse colloidal NCs with narrow size distribution, which can easily disperse in non-polar cyclohexane solvent. The as-prepared NCs exhibit a rich variety of morphologies and different crystal phases (hexagonal or cubic), which may be related to the inherent natures of different rare earth ions. The possible formation mechanism of NCs with diverse architectures has been presented. In addition, representative Yb/Er, Yb/Tm, or Yb/Ho co-doped NaGdF(4) and Na(5)Lu(9)F(32) NCs exhibit intensive multicolor up-conversion (UC) luminescence under a single 980 nm NIR excitation, displaying potential applications in bioimaging and therapy. Moreover, transparent and UC fluorescent NCs-polydimethylsiloxane (PDMS) composites with regular dimensions were also prepared by an in situ polymerization route.     

Fluorescein-labeled fluoroapatite nanocrystals codoped with Yb(III) and Ho(III) for trimodal (downconversion,upconversion and magnetic resonance) imaging of cancer cells

The authors report on upconversion nanocrystals (NCs) based on a fluoroapatite (FAp) support that was engineered to enable multimodal imaging by fluorescence imaging (FI), magnetic resonance imaging (MRI), and upconversion luminescence imaging. A fluorescein based fluorophore (FITC) was incorporated into the FAp nanocrystals and then doped with Yb(III) and Ho(III) by microwave-assisted solution combustion synthesis. The hexagonal phase nanocrystals (FITC-FAp:Yb/Ho) exhibit spindle like morphology with an average diameter and length of 15 nm and 196 nm, respectively. The doping concentration of the Yb (5 %) and Ho (0.6 %) was determined by ICP-MS. The nanocrystals exhibit upconversion luminescence when irradiated with NIR light of wavelength 980 nm. The emission spectrum consists of two bands centered at 542 nm (green emission) and 654 nm (red emission) corresponding to two transitions of Ho(III). The pump power dependence of upconversion luminescence intensity confirmed the 2-photon process. The presence of FITC in the nanocrystal imparts green fluorescence (peaking at 521 nm) by a conventional downconversion process. The presence of Ho(III) endows the NCs with paramagnetism. The magnetization is 21.063 emu?g^?1 at room temperature. The NCs exhibit a longitudinal relaxivity (r1) of 0.12 s^?1?mM^?1, and a transverse relaxivity (r2) of 29 s^?1?mM^?1, which makes the system suitable for developing T2 MRI contrast agents. The nanocrystals are surface aminized using polyethyleneimine (PEI) and covalently conjugated to folic acid (FA) in order to target the folate receptors that are overexpressed in many cancer cells. The FA-conjugated nanocrystals have been tested for their applicability in fluorescence imaging of HeLa cells. Their biocompatibility, upconversion and downconversion luminescence, and magnetism render these NCs potentially powerful nanoprobes for trimodal imaging.

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Graphical abstract Fluorescein-labeled fluorapatite nanocrystals codoped with Yb(III) and Ho(III) ions (FITC-FAp:Yb/Ho) have been prepared through microwave route. The up and downconversion luminescence, biocompatibility and magnetism are explored. The folic acid conjugated nanocrystals are promising candidates for trimodal imaging (up- and downconversion imaging and magnetic resonance imaging)

     

Controllable synthesis and tunable luminescence properties of Y2(WO4)3:Ln3+ (Ln = Eu, Yb/Er, Yb/Tm and Yb/Ho) 3D hierarchical architectures

Yttrium tungstate precursors with novel 3D hierarchical architectures assembled from nanosheet building blocks were successfully synthesized by a hydrothermal method with the assistance of sodium dodecyl benzenesulfonate (SDBS). After calcination, the precursors were easily converted to Y(2)(WO(4))(3) without an obvious change in morphology. The as-prepared precursors and Y(2)(WO(4))(3) were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra, respectively. The results reveal that the morphology and dimensions of the as-prepared precursors can be effectively tuned by altering the amounts of organic SDBS and the reaction time, and the possible formation mechanism was also proposed. Upon ultraviolet (UV) excitation, the emission of Y(2)(WO(4))(3):x mol% Eu(3+) microcrystals can be tuned from white to red, and the doping concentration of Eu(3+) has been optimized. Furthermore, the up-conversion (UC) luminescence properties as well as the emission mechanisms of Y(2)(WO(4))(3):Yb(3+)/Ln(3+) (Ln = Er, Tm, Ho) microcrystals were systematically investigated, which show green (Er(3+), (4)S(3/2), (2)H(11/2)→(4)I(15/2)), blue (Tm(3+), (1)G(4)→(3)H(6)) and yellow (Ho(3+), (5)S(2)→(5)I(8)) luminescence under 980 nm NIR excitation. Moreover, the doping concentration of the Yb(3+) has been optimized under a fixed concentration of Er(3+) for the UC emission of Y(2)(WO(4))(3):Yb(3+)/Er(3+).     

Controllable synthesis of β-NaYF4:Yb,Er nanorods by potassium oleate as ligand

By using potassium oleate (KOL) as a part of ligand, nanorods of β-NaYF₄:Yb,Er were synthesized. The aspect ratio of β-NaYF₄:Yb,Er nanocrystals was tuned by changing the amount of KOL. We found that potassium from KOL is not only absorbed on the surface of nanocrystals, but also partially substitutes Na element in nanocrystals lattice. Different from the classical shape control mechanism that oleate ions are absorbed on different facets of nanocrystals, the anisotropic growth of β-NaYF₄:Yb,Er in current work is caused by the doping of K⁺. The incorporation of K⁺ would not lead to obvious decrease of the upconversion fluorescence intensity. Meanwhile, oleate ions promote the phase transition of nanocrystals from cubic to hexagonal phase, resulting in the simultaneous controllability of the nanocrystals size.     

超细YF_3与GdF_3纳米晶的合成及其上转换发光

当使用液固溶法(LSS法)制备分散性纳米晶时,将传统油酸/油酸钠/酒精反应体系中的NaOH用氨水取代时,氨水将会与油酸形成新的表面活性剂油酸铵,这样就可以合成各种超细分散性的REF3纳米晶(RE代表稀土元素)。在这种新的反应体系中,合成了平均直径小于10 nm的YF3和GdF3超细颗粒,X射线与透射电镜测试表明YF3是正交相,而GdF3是面心立方结构,空间群为Fm3m,晶格常数为0.582 9 nm。在980 nm半导体激光器激发下,可检测到YF3∶Yb/Er在515~570 nm处有较强的绿色发光峰、645~675 nm处有较强的红色发光峰,呈橙色发光。YF3∶Yb/Tm和GdF3∶Yb/Tm样品在460~490 nm处有较强的蓝色发光峰,而在800 nm附近有更强的近红外发光峰。由于其超细的尺寸及红外上转换发光特性,合成的样品在生物成像、生物标签等方面有潜在的应用价值。     

超细YF3与GdF3纳米晶的合成及其上转换发光

当使用液固溶法（LSS法）制备分散性纳米晶时,将传统油酸/油酸钠/酒精反应体系中的NaOH用氨水取代时,氨水将会与油酸形成新的表面活性剂油酸铵,这样就可以合成各种超细分散性的REF₃纳米晶（RE代表稀土元素）。在这种新的反应体系中,合成了平均直径小于10nm的YF₃和GdF₃超细颗粒,X射线与透射电镜测试表明YF₃是正交相,而GdF₃是面心立方结构,空间群为Fm3m,晶格常数为0.5829nm。在980nm半导体激光器激发下,可检测到YF₃：Yb/Er在515~570nm处有较强的绿色发光峰、645~675nm处有较强的红色发光峰,呈橙色发光。YF：Yb/Tm和GdF₃：Yb/Tm样品在460~490nm处有较强的蓝色发光峰,而在800nm附近有更强的近红外发光峰。由于其超细的尺寸及红外上转换发光特性,合成的样品在生物成像,生物标签等方面有潜在的应用价值。     

Lanthanide doping-facilitated growth of ultrasmall monodisperse Ba2LaF7 nanocrystals with excellent photoluminescence

Lanthanide doping not only works as sensitizer and activator, but also plays an important role to facilitate the growth of nanocrystal and to control the size, shape, and property of nanocrystals. Here, reported was the synthesis of monodisperse Ba(2)LaF(7) nanocrystals with the size of sub-10nm through a solvothermal method. We found the dopants of Ho(3+), Er(3+), or Yb(3+) facilitated the growth of Ba(2)LaF(7) nanocrystals obviously to a certain size within a shorter reaction time. Similar phenomenon can also be observed in the synthesis of LaF(3) nanocrystals. We find that Ln(3+) (e.g., Ho(3+), Er(3+), or Yb(3+)) with smaller radius can reduce the nucleation energy and lead to heterogeneous nucleation, which favors the growth of Ba(2)LaF(7) nanocrystals obviously. In addition, intense upconversion emission can be observed from Ln(3+)-doped Ba(2)LaF(7) nanocrystals under the 980 nm laser excitation, providing great potential application in biological imaging. Especially, Ba(2)LaF(7):Yb/Er (20/1 mol%) nanocrystals present more intense upconversion emission than α-NaYF(4):Yb/Er (20/1 mol%) nanocrystals under the same conditions.     

Shape,Size, and Phase‐Controlled Rare‐Earth Fluoride Nanocrystals with Optical Up‐Conversion Properties

High‐quality rare‐earth fluorides, α‐NaMF₄ (M=Dy, Ho, Er, Tm, Y, Yb, and Lu) nanocrystals and β‐NaMF₄ (M=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y, Yb, and Lu) nanoarrays, have been synthesized by using oleic acid as a stabilizing agent through a facile hydrothermal method at 130–230 °C. The phase, shape, and size of the products are varied by careful control of synthetic conditions, including hydrothermal temperature and time, and the amounts of reactants and solvents. Tuning the hydrothermal temperature, time, and the amount of NaOH can cause the transformation from the cubic α‐NaMF₄ to hexagonal phase β‐NaMF₄. Upon adjustment of the amount of NaOH, NaF, M³⁺, and ethanol, the morphologies for the β‐NaMF₄ nanoarrays can range from tube, rod, wire, and zigzagged rod, to flower‐patterned disk. Simultaneously, the size of the rare‐earth fluoride crystals is variable from 5 nm to several micrometers. A combination of “diffusion‐controlled growth” and the “organic–inorganic interface effect” is proposed to understand the formation of the nanocrystals. An ideal “1D growth” of rare‐earth fluorides is preferred at high temperatures and high ethanol contents, from which the tube‐ and rodlike nanoarrays with high aspect ratio are obtained. In contrast, the disklike β‐NaMF₄ nanoarrays with low aspect ratios are produced by decreasing the ethanol content or prolonging the reaction time, an effect probably caused by “1D/2D ripening”. Multicolor up‐conversion fluorescence is also successfully realized in the Yb³⁺/Er³⁺ (green, red) and Yb³⁺/Tm³⁺ (blue) co‐doped α‐NaYF₄ nanocrystals and β‐NaYF₄ nanoarrays by excitation in the NIR region (980 nm).     

Single‐Crystalline and Near‐Monodispersed NaMF3 (M=Mn,Co, Ni,Mg) and LiMAlF6 (M=Ca,Sr) Nanocrystals from Cothermolysis of Multiple Trifluoroacetates in Solution

We report the synthesis of single‐crystalline and near‐monodispersed NaMF₃ (M=Mn, Co, Ni, Mg), LiMAlF₆ (M=Ca, Sr), and NaMgF₃:Yb,Er nanocrystals (quasisquare nanoplates, nanorods, and nanopolygons) by the cothermolysis of multiple trifluoroacetates in hot combined organic solvents (oleic acid, oleylamine, and 1‐octadecene). The nanocrystals were characterized by XRD, TEM, superconductive quantum interference device (SQUID), and upconversion luminescence spectroscopy. By regulating the polarity of the dispersant, the NaMF₃ (M=Mn, Co, Ni) nanoplates were partially aligned to form nanoarrays on copper TEM grids. The sizes of the NaMF₃ nanocrystals were easily tuned by the use of proper synthetic conditions such as reaction temperature and time and solvent composition. On the basis of a series of experiments in which the reaction conditions were varied, together with GC–MS and FTIR analysis, the reaction pathways for the formation of these nanocrystals from trifluoroacetate precursors were proposed. The magnetic measurements showed that the differently sized NaMnF₃ square plates displayed interesting weak ferromagnetic behavior on the nanometer scale. The strong red upconversion luminescence emitted from the NaMgF₃:Yb,Er nanorods under 980‐nm near‐IR laser excitation suggests that NaMgF₃ may be a good candidate host material for red upconversion luminescence.     

相位可控的氟钪纳米晶的合成及其上转换发光性能

控制反应条件如表面活性剂的组成、加入量或反应时间,可以制得不同形态、相结构且具有上转换发光(UCL)的氟钪纳米晶(NCs)。改变表面活性剂油酸(OA)/油胺(OM)的比例有利于晶体结构从立方相ScF_3∶Yb,Er转变为具有上转换发光性能增强的正交相KSc_2F_7∶Yb,Er纳米晶,而纳米晶的形态会发生从小到大的转变。改变掺杂元素的种类及含量,在980 nm光激发下,KSc_2F_7纳米晶的上转换发光可以从蓝色变到白色,再到主要发射紫色光。     

Microwave synthesis and photoluminescent properties of Sr2CeO4/Ln3+ (Ln = Er, Ho, Tm)

Sr₂CeO₄/Ln³⁺ (Ln = Er, Ho, Tm) phosphors were synthesized with the microwave radiation method for the first time. The luminescent properties of the samples were investigated and the up-conversion luminescence of Er³⁺, Ho³⁺ and Tm³⁺ doped Sr₂CeO₄ phosphors was observed. The spectra indicate that the energy transfer takes place from the triplet excited state of MLCT (metal-to-ligand charge transfer) state for Sr₂CeO₄ (sensitizer) to the rare earth ions (activator). __________ Translated from Journal of Hebei Normal University (Natural Science Edition), 2007, 31(2): 212–216 [译自: 河北师范大学学报 (自然科学版)]     

Hydrothermal Synthesis of Rare Earth Iodates from the Corresponding Periodates: II1). Synthesis and Structures of Ln(IO3)3 (Ln = Pr,Nd, Sm,Eu, Gd,Tb, Ho,Er) and Ln(IO3)3 · 2H2O (Ln = Eu,Gd, Dy,Er, Tm,Yb)

Single crystals of lanthanide iodates have been quickly grown by decomposition of the corresponding periodates under hydrothermal conditions. Single crystal X‐ray diffraction showed that two structure types form with the elements from Pr‐Yb, an anhydrous form for Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er and a dihydrate for Eu, Gd, Dy, Er, Tm, Yb. A detailed structure study is presented for one representative of each of these types, along with structure type and lattice parameters for the other materials. Tb(IO₃)₃: Space group P2₁/c, Z = 4, lattice dimensions at 120 K: a = 7.102(1), b = 8.468(1), c = 13.355(2)Å, β = 99.67(1)°; R1 = 0.034. Yb(IO₃)₃ · 2H₂O: Space group P1¯, Z = 2, lattice dimensions at 120 K: a = 7.013(1), b = 7.370(1), c = 10.458(2)Å, α = 95.250(5), β = 105.096(5), γ = 109.910(10)°; R1 = 0.024.     

Y2O2S∶Er3+，Yb3+的制备及Er3+离子在晶场中的能级分裂

采用沉淀法制备前驱体,通过不同温度合成了上转换发光材料Y2O2S∶Er3+,Yb3+,运用XRD,SEM和上转换发射光谱对其进行表征。结果表明,所合成的Y2O2S∶Er3+Yb3+属于六方晶系晶体,随着合成温度的升高,产物的粒径不断增大,上转换发射光强度逐渐增加。研究Y2O2S∶Er3+Yb3+的上转换发光过程,红光发射和绿光发射分别源于Er3+离子的4F9/2→4I15/2以及2H11/2→4I15/2,4S3/2→4I15/2能级跃迁。利用群论计算了晶场中Er3+离子的能级分裂数目。