Color-tunable Upconversion Properties of Tb~(3+)/Er~(3+)/Yb~(3+) Tri-doped Na_5Gd(WO_4)_4 Crystals

In this work, novel phosphors Na5Gd(WO4)4: Tb^3+/Yb^3+ and Na5Gd(WO4)4: Tb^3+/Er^3+/Yb^3+ phosphors were synthesized by the solid state reaction method. The photoluminescence properties were investigated. The introduction of Er^3+ to NGW: Tb^3+/Yb^3+ was used to modify the chromaticity coordinates, then providing a good color tunable property. The change in the chromaticity coordinates induces the shift of emission color from yellow-green to blue-green for NGW: Tb^3+/Er^3+/Yb^3+ as the temperature increases. All the results indicate that the NGW: Er^3+/Tb^3+/Yb^3+ phosphors may be used as optical temperature sensing materials.     

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.     

ZrO2：Er^3＋，Yb^3＋纳米晶的制备及Er^3＋离子能级在晶体场中的分裂

采用1，3-丁二醇低热结晶法制备了ZrO2：Er^3 ，Yb^3 纳米晶．常温下，用980nm的红外激光激发可以观察到很强的ZrO2：Er^3 ，Yb^3 纳米晶红光发射，用荧光光谱仪记录了该上转换光谱．X射线粉末衍射(XRD)结果表明，ZrO2：Er^3 ，Yb^3 纳米晶属于立方晶系．研究了纳米晶的上转换发光机理，根据晶体场理论对Er^3 的2个上转换能级进行了Stark分裂计算，对2个能级之间的谱线进行了归属，进一步证实了980nm激发Er^3 离子的上转换经历两个过程：一是连续吸收2个980nm光子的过程，二是吸收980nm光子，电子转移到亚稳态能级后，再吸收980nm光子的过程．     

Microcalorimetric Study of the Action of Yb^3＋ ion on the Growth of Staphylococcus aureus

A microcalorimetric method was used to evaluate the action of Yb^3 ions onthe growth metabolism of Staphylococcus aureus.The power-time curves of the growth metabolism of Staphylo.coccus aureus and the action of Yb^3 ions were obtained by us-ing stopped-flow method at 37 ℃. For evaluation of the action,the growth rate constants ( k1 and k2) for the log phase 1, log phase 2, and the total heat effect (Qtotal) for Staphylococcus aureus were determined. The results show that Yb^3 ions at low concentrations have the stimnlatory effect on Staphylococcus au-reus and that Yb^3 ions at higher concentration could inhibit its growth.     

Growth and Spectroscopic Characteristics of Yb3＋：LiGd（WO4）2 Crystal

The Yb3+:LiGd(WO4)2 crystal with the dimension of Φ15×35 mm3 was grown by Czochralski technique. The spectroscopic characterization and fluorescence dynamics of Yb3+ in Yb3+:LiGd(WO4)2 crystal were investigated. The Yb3+:LiGd(WO4)2 crystal exhibits a broad absorption band centered near 975 nm with the linewidths of 16 and 11 nm and maximal absorption cross-section of 3.60 × 10-20 and 2.90 × 10-20 cm2 for π- and σ-polarization, respectively. The emission broadband has an FWHM of 47 and 45 nm with the emission cross sections of 3.92 × 10-20 and 3.34 × 10-20 cm2 at 1020 nm for π- and σ-polarization, respectively. The measured fluorescence lifetime is 398 μs. The blue light emission around 480 nm through cooperative upconversion from the de-excitation of excited Yb3+-Yb3+ pairs at 4 K was observed under 932-nm excitation and demonstrated.     

Density Functional Study on the Reaction Mechanism for the Reaction of Ni^＋ with Ethane

The mechanism of the reaction of Ni^ (^2D) with ethane in the gas-phase was studied by using density functional theory.Both the B3LYP and BLYP functionals with standard all-electron basis sets are used to give the detailed information of the potential energy surface (PES) of [Ni,C2,H6]^ . The mechanisms forming the products CH4 and H2 in the reaction of Ni^ with ethane are proposed.The reductive eliminations of CH4 and H2 are typical addition-elimination reactions.Each of the two reactions consists of two elementary steps:C-C or C-H bond activations to form inserted species followed by isomerizations to from product-like intermediate.The rate determining steps for the elimination reactions of forming CH4 and H2 are the isomerization of the inserted species rather than C-C or C-H bond activations .The elimination reaction of forming H2 was found to be thermodynamically favored compared to that of CH4.     

Er3+，Ho3+和Tm3+在硫氧化钆中的余辉发光

The new Er^3 , Ho^3 and Tm^3 doped gadolinium oxysulfide phosphors with the long afterglow emission were synthesized by solid-state reaction method. The synthesized phosphors were characterized by X-ray diffraction. The excitation and photolumineseenee spectra, afterglow spectra and afterglow decay curve were examined by fluorescence spectroscopy. The afterglow spectra of Gd2O2S:Er^3 , Mg, Ti showed typical transitions of Er^3 at 528(2H11/2→4I15/2), 548 (^4S3/2 →^4I15/2) and 669 nm (^4F9/2→^4I15/2). In the afterglow spectra of Gd2O2S: Ho^3 , Mg, Ti,typical transitions of Ho^3 at 546 nm (^5S2→^5I8), 651 and 661 nm (^2F5→^5I8) were observed. In Gd2O2S:Tm^3 , Mg,Ti, the afterglow emission at 800 nm (^1G4→^3H5) of Tm^3 was seen. The meehnism and model of afterglow energy transfer were proposed.     

Enhancement of Two-photon Absorption by Ce^3＋ Sensitization in Organic Dyes

The two-photon absorption(TPA)and TPA-induced frequency upconversion emission properties of the dyes 4-[P-(dicyanoethylamino)crystal]-N-methypyrdinium iodide and the complex of 4-[P-(dicyanoethylamino)crystal]-N-methypyrdinium iodide and Ce(NO3)3 were experimentally studied.It was found that the TPA cross section for the dye sensitized by Ce3 is two factors larger than that of the dye without being sensitized.A three-level system model of the dye molecules was used to analyze the enhancement of TPA by the sensitizer Ce3 ,which indicated that the sensitizer results in the increase of the transition dipole moment from the one-photon allowed excited state(1Bu)to the two-photon allowed excited state(2Ag).     

STUDY OF THE REACTION MECHANISM OF CYCLOHEXENE HYDROGENATION CATALYZED BY RhCl(PPh_3)_3

The hydrogenation rate of styrene in benzene using RhCI(PPh_3)_3 as catalyst increases with the concentration of styrene. But the hydrogenation rate of cyclohexene is rather different, It shows a maximum. So we inquire into the reaction mechanism of cyclohexene hydrogenation catalyzed by RhCI(PPh_3)_3. The rate of hydrogenation was measured at 25±0.15℃, as a function. of catalyst concentration, olefin concentration, triphenylphosphine concentration and hydrogen pressure. The maximum of the reaction rate is interpreted by the formation of RhClL_2S_2. The rate determining step is considered to be the reaction of olefin insertion into one of the Rh-H bonds formed by hydrogenation of RhClL3 to H_2RhClL_3. The hydrogenation rate of the substrate can be described by a third order equation in terms of concentration of H_2RhClL_3. Average error between the results evaluated by this equation and experimental results is about 4.9％. The quantum chemistry calculation gives support to the present mechanism.     

Elimination of HBr from CH3Br by Cu＋ and Au＋： A DFT study

The elimination of HBr from CH3Br by ground state of Cu＋ and Au＋ has been investigated by using DFT methods. A mechanism of one-step HBr elimination leading to CuCH2＋ was identified. For the formation of AuCH2＋, besides the one-step mechanism, another two-step HBr elimination pathway through a C-Br bond insertion intermediate was also found, and this pathway is energetically more favorable than the one-step mechanism. The calculated reaction energy barriers show that the formation of AuCH2＋ is energetically much more favorable than the formation of CuCH2＋. The experimental observations are well explained.     

La_(2.4)Mo_(1.6)O_8∶Yb~(3+),Er~(3+)材料的制备及其上转换发光性质

采用高温固相法制备了La_(2.4)Mo_(1.6)O_8∶Yb~(3+),Er~(3+)荧光粉。通过X射线衍射(XRD)和上转换发射光谱对样品进行了相结构和发光性质表征。XRD实验结果表明:合成的样品为面心立方萤石结构(Fm-3m)的La_(2.4)Mo_(1.6)O_8相。在980 nm红外光激发下,La_(2.4)Mo_(1.6)O_8∶Yb~(3+),Er~(3+)荧光粉发出分别来自Er~(3+)离子的~2H1_(1/2)→~4I_(15/2)、~4S_(3/2)→~4I_(15/2)跃迁的绿光(主峰为548和529 nm)和~4F_(9/2)→~4I_(15/2)跃迁的红光(主峰为670 nm)。进一步地,对样品中可能的上转换发光机制进行了讨论。     

Effect of Zn2+ Ions on Upconversion Emission of Er3+ in Zn/Er:LiNbO3 Crystal

The effect of Zn2+ ions codoped on the upconversion emission of Er3+ ions in Er:LiNbO3 crystal under different excitation wavelength was reported.The upconversion emission spectra of Zn/Er:LiNbO3 follo...     

Yb ion as a sensitizer for the upconversion luminescence in nanocrystalline Gd3Ga5O12:Ho

The effect of Yb³⁺ co-doping on the upconversion luminescence in nanocrystalline Gd₃Ga₅O₁₂:Ho³⁺ was examined. Strong and efficient NIR to green anti-Stokes luminescence was noted in nanocrystalline Gd₃Ga₅O₁₂:Ho³⁺, Yb³⁺ after excitation into the ²F_5/2 level of Yb³⁺ with 978 nm radiation. Weaker blue, red and NIR anti-Stokes luminescence was also observed after 978 nm excitation. An enhancement of the red ⁵F₅ → ⁵I₈ luminescence was observed in the anti-Stokes spectrum compared to the Stokes emission spectrum. This enhancement was attributed to two distinct energy transfer upconversion (ETU) mechanisms which preferentially populate the (⁵F₄, ⁵S₂) and ⁵F₅ levels.     

1.54 and 1.75 μm infrared luminescence of Y2O3:Er

A new 1.75 μm infrared emission transition of Y₂O₃:Er³⁺ is assigned to the ⁴S_3/2 → ⁴I_9/2 transition of Er³⁺ ions situated at the C₂ sites of cubic RE₂O₃ (RE = Y, Gd, Lu). The intensities of features in the 1.54 μm ⁴I_15/2–⁴I_13/2 absorption transition due to Er³⁺ at S₆ and C₂ sites are consistent with the site occupation ratio and the relative magnetic dipole–electric dipole intensity contributions of Er³⁺ at the different sites. The 1.54 μm emission lines are predominantly from Er³⁺ ions at C₂ sites. The different behaviours of the emission intensities 1.75 and 1.54 μm groups with change in Er³⁺ dopant ion concentration, preparation technique, Yb³⁺ co-doping, temperature change and different excitation line are rationalized.     

Effects of Surface Modification of Upconversion Nanoparticles on Cellular Uptake and Cytotoxicity

Lanthanide-doped upconversion nanoparticles(UCNPs) are great promising to apply to biomedical imaging and therapy. We prepared NaYF₄:Yb³⁺,Er³⁺ nanoparticles with different surface ligands, i.e., without any ligands(bare), coordinated with 2-aminoethyl dihydrogen phosphate(AEP), polyacrylic acid(PAA) or polyallylamine (PAAm), via a simple two-step ligand exchange of oleic acid capped NaYF₄:Yb³⁺,Er³⁺ nanoparticles. Although the surface modification retained the crystal structure and transimission electron microscope(TEM) size distribution of the nanoparticles, and good dispersibility in aqueous solution and did not significantly change the upconversion luminescence, distinct differences were observed in the surface charge and hydrodynamic diameter. The cellular uptake and cytotoxicity of the nanoparticles were studied on two different cell lines, breast cancer MCF-7 and fibroblast 3T3. Confocal microscopy images demonstrate that PAAm-coordinated UCNPs can enhance the cellular uptake and endocytosis, whereas AEP- and PAA-coordinated UCNPs show a very low level of nonspecific adsorption. Biocompatibility studies based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay, however, indicate that PAAm-coordinated UCNPs are more toxic than the other two, and thus need further modifiaction(like PEG coordinating) to improve their biocompatibility. These results are important to the knowledge base required for the biomedical application of the UCNPs.     

基于上转换发光共振能量转移的CRISPR/Cas12a生物传感系统用于HPV16 DNA双信号检测

传统的纯核结构的上转换纳米材料用于生物传感时, 存在表面猝灭效应或者因发光共振能量转移(LRET)效率不高导致灵敏度低等缺点, 对目标物的灵敏检测有一定的局限性. 本文通过多步高温共沉淀, 介导壳层外延成长法, 合成了NaYF₄∶Yb³⁺,Er³⁺(C-UCNPs)核层发光和NaYF₄@NaYF₄∶Yb³⁺,Er³⁺@NaYF₄(CSS-UCNPs)内壳层发光能量限域型上转换纳米材料, 并表征了材料的晶型、 形貌、 表面配体、 元素组成和发光共振能量转移效率. 结果表明, 该材料具有表面猝灭效应低、 发光共振转移效率较高的优势, 随后将其与成簇规律间隔的短回文重复序列及其相关蛋白(CRISPR/Cas)12a-纳米金系统结合, 实现了人乳头瘤病毒DNA(HPV16 DNA)的比色定性和上转换发光定量分析, 检出限为69.8 pmol/L, 双信号检测有效提高了检测结果的准确性. 此外, 本方法不仅特异性强, 还能识别单碱基错配的HPV16 DNA, 提高了DNA片段的容错率.     

Highly efficient blue up-conversion of Tm in Nd–Yb–Tm co-doped ZrF4-based fluoride glass

Up-conversion luminescence and energy-transfer processes in Nd³⁺, Yb³⁺ and Tm³⁺ co-doped ZrF₄-based fluoride glasses have been studied under 800 nm light excitation. Blue up-converted emission around 478 nm which can be assigned to the Tm³⁺:¹G₄→³H₆ transition, was strongly observed. Up-conversion luminescence intensity exhibited an YbF₃-concentration dependence. Among the Nd³⁺, Yb³⁺ and Tm³⁺, Nd³⁺ and Tm³⁺ have ground state absorption bands due to the (²H_9/2,⁴F_5/2)←⁴I_9/2 and ³F₄←³H₆ transitions, respectively, which can be directly pumped by 800 nm radiation. However, no emissions were observed in Tm³⁺ singly-doped and Tm³⁺–Yb³⁺ doubly-doped glasses under 800 nm excitation. Therefore, a possible up-conversion mechanism may be proposed as follows: energy-transfer firstly occurs from Nd³⁺ to Yb³⁺ when Nd³⁺ is excited by 800 nm light, then the energy is transferred from Yb³⁺ to Tm³⁺ which is in the excited state and, finally, blue up-conversion emission of Tm³⁺ is observed through the Tm³⁺:¹G₄→³H₆ transition.     

LD激发的ZnWO4:Er3+晶体上转换发光

采用Czochralski法生长出ZnWO₄:Er³⁺(Er=0.02mol)单晶,测量了吸收光谱和激发光谱。在波长966nm功率500mW的激光二极管(LD)激发下观察到上转换发光。强度最大的发射峰位于547和558nm,发射光谱分析表明,上转换激发过程与双光子步进吸收有关。     

NaYF4:Nd3+,Yb3+纳米粒子用于生物体系温度测量

采用溶剂热法制备了Nd³⁺敏化Yb³⁺的近红外纳米探针NaYF₄:Nd³⁺,Yb³⁺,观察到材料在980与865 nm两处发光峰的强度比值随温度的升高而降低。通过对探针中Nd³⁺/Yb³⁺比例的调节,综合考虑材料的发光强度与温敏效率,确定了NaYF4:2%Nd, 20%Yb为所测条件下适用于测量生物体系温度的较优组成。材料转水相前后温敏效率均随着Yb³⁺离子掺杂增加而提高,环己烷中最高可达1.9%·K^-1,水相中最高为0.46%·K^-1。通过盖肉片模拟及激光加热活体成像实验,研究了温敏材料在生物环境中发光随温度的变化情况,以及组织遮挡前后荧光比值未发生明显变化的结果,初步验证了使用该探针测量生物体系温度的可行性。     

Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)单基质白光荧光粉的制备与发光性能

为了探究在Dy~(3+)掺杂Ba_3Y(PO_4)_3荧光粉中共掺Eu~(3+)离子对其发光性能的影响,我们采用传统高温固相法制备了一系列Dy~(3+)、Eu~(3+)单掺杂和共掺杂Ba_3Y(PO_4)_3荧光粉。通过X射线衍射(XRD)、荧光发射光谱和荧光衰减曲线对样品进行了表征。结果表明,所制备的荧光粉呈闪铋矿立方相。在近紫外光激发下,Ba_3Y(PO_4)_3∶Dy~(3+)发射光谱在487和578 nm处有两个窄带发射峰,呈冷白光发射;Ba_3Y(PO_4)_3∶Eu~(3+)发射光谱的窄带发射位于594和616 nm处,呈发橙红光。在Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)中,由于Eu~(3+)离子补偿Dy~(3+)冷白光发射所缺的红色组分,从而实现了色纯度高、色温适中的暖白光发射。进一步探索了Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)荧光粉发光机理。所制备的Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)单基质白光荧光粉在白光近紫外激发白光二极管(UVWLED)领域具有潜在应用价值。