Synthesis and upconversion luminescence of Lu_2O_3:Yb^(3+),Tm^(3+) nanocrystals

Lutetium oxide nanocrystals codoped with Tm3＋ and Yb3＋ were synthesized by the reverse-like co-precipitation method, using ammonium hydrogen carbonate as precipitant. Effects of the Tm3＋, Yb3＋ molar fractions and calcination temperature on the structural and upconversion luminescent properties of the Lu2O3 nanocrystals were investigated. The XRD results show that all the prepared nanocrystals can be readily indexed to pure cubic phase of Lu2O3 and indicate good crystallinity. The experimental results show that concentration quenching occurs when the mole fraction of Tm3＋ is above 0.2%. The optimal Tm3＋ and Yb3＋ doped molar fractions are 0.2% and 2%, respectively. The strong blue （490 nm） and the weak red （653 nm） emissions from the prepared nanocrystals were observed under 980 nm laser excitation, and attributed to the 1G4→3H6 and IG4→3F4 transitions of Tm3＋, respectively. Power-dependent study reveals that the 1G4 levels of Tm3＋ can be populated by three-step energy transfer process. The upconversion emission intensities of 490 nm and 653 nm increase gradually with the increase of calcination temperature. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing number of OH- groups and the enlarged nanoerystal size.

Energy-Transfer in CsPbBr_(3) Nanocrystals:Sensitization of Porphyrin Triplets

Sensitizing molecular triplets by colloidal nanocrystals via triplet energy transfer is important for applications such as upconversion or organic synthesis.Typically two step triplet energy transfer(TET)are included in these applications:firstly the triplet energy stored in nanocrystals are extracted into surface ligands,and then the ligands further transfer triplet energy into molecules in bulk solution.Here we report one-step TET application from CsPbBr_(3) perovskite nanocrystals(NCs)to surface-anchored metalloporphyrin derivative molecules(MP).Compared to conventional two-step TET,the one-step TET mechanism possess lower energy loss and higher TET efficiency which is more generally implementable.In this scheme,photoexcitation of CsPbBr_(3)NCs leads to the sensitization of MP ligands triplets which efficiently emit phosphorescence.The enhanced light absorption of MP ligands and down-shifted photon emission can be useful in devices such as luminescent solar concentrators.

Surface Treatment of Inorganic CsPbI_(3) Nanocrystals with Guanidinium Iodide for Efficient Perovskite Light-Emitting Diodes with High Brightness

The remarkable evolution of metal halide perovskites in the past decade makes them promise for next-generation optoelectronic material.In particular,nanocrystals(NCs)of inorganic perovskites have demonstrated excellent performance for light-emitting and display applications.However,the presence of surface defects on the NCs negatively impacts their performance in devices.Herein,we report a compatible facial post-treatment of CsPbI_(3) nanocrystals using guanidinium iodide(GuI).It is found that the GuI treatment effectively passivated the halide vacancy defects on the surface of the NCs while offering effective surface protection and exciton confinement thanks to the beneficial contribution of iodide and guanidinium cation.As a consequence,the film of treated CsPbI_(3) nanocrystals exhibited significantly enhanced luminescence and charge transport properties,leading to high-performance light-emitting diode with maximum external quantum efficiency of 13.8%with high brightness(peak luminance of 7039 cd m^(−2) and a peak current density of 10.8 cd A^(−1)).The EQE is over threefold higher than performance of untreated device(EQE:3.8%).The operational half-lifetime of the treated devices also was significantly improved with T50 of 20 min(at current density of 25 mA cm^(−2)),outperforming the untreated devices(T50~6 min).

Spectroscopic properties and mechanism of Tm^(3+)/Er^(3+)/Yb^(3+) co-doped oxyfluorogermanate glass ceramics containing BaF_2 nanocrystals

Transparent Tm^3＋/Er^3＋/yb^3＋ co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals are prepared. Under excitation of a 980-nm laser diode （LD）, compared with the glass before heat treatment, the Tm^3＋/Er^3＋/yb^3＋ co-doped oxyfluorogermanate glass ceramics can emit intense blue, green and red up-conversion luminescence and Stark- split peaks; X-ray diffraction （XRD） and transmission electron microscope （TEM） results show that BaF2 nanocrystals with an average diameter of 20 nm are precipitated from the glass matrix. Stark splitting of the up-conversion luminescence peaks in the glass ceramics indicates that Tm^3＋, Er^3＋ and （or） Yb^3＋ ions are incorporated into the BaF2 nanocrystals. The up-conversion luminescence intensities of Tm^3＋, Er^3＋ and the splitting degree of luminescence peaks in the glass ceramics increase significantly with the increase of heat treat temperature and heat treat time extension. In addition, the possible energy transfer process between rare earth ions and the up-conversion luminescence mechanism are also proposed.

Upconversion Luminescence of Er^(3+), Tm^(3+) and Yb^(3+)Co-doped Gd_3Ga_5O_(12) Nanocrystals

A series of Er3＋, Tm3＋ and Yb3＋ doped Gd3Ga5O12 nanocrystals were prepared by a combustion method. The X-ray diffraction （XRD）, field emission scanning electron microscope （FESEM） and upconversion （UC） emission spectra were used to characterize the samples. The results of XRD indicate that Gd3Ga5O12：Er3＋, Tm3＋, Yb3＋ nanocrystals with cubic phase can be obtained. Under the excitation of a 980 nm laser, the different rare earth ions doped Gd3Ga5O12 nanoerystals show upconversion luminescence involving the green emission attributed to the ^2H11/2→^4I15/2, 4^S3/2→^4I15/2 transitions of Er3＋ ions, respectively, the red emissions assigned to the ^4F9/2→^4I15/2 transitions of Er3＋ ions and the ^1G4→^3F4 as well as 3F2,3→^3H6 transitions of Tm3＋ ions, respectively, the blue emission attributed to ^1G4→^3H6 transitions of Tm3＋ ions, and the near-infrared assigned to the ^3H4→^3H6 transitions of Tm3＋ ions. The CIE coordinates for the samples are calculated. The dependence of their upconversion luminescence properties on Yb3＋ ion concentration is investieated.

双酚A通过上调Apoa 1基因的表达抑制TM3细胞睾酮合成

旨在从脂质代谢的角度探讨载脂蛋白A1(apolipoprotein A1,Apoa 1)是否介导了双酚A(bisphenol A,BPA)暴露所致小鼠睾丸间质细胞株(TM3)睾酮合成的降低。将TM3细胞随机分为不同浓度的BPA暴露剂量(0、5、10、20、40、60、80μmol·L^(-1))组,0μmol·L^(-1)BPA为对照组(CON)。给予相应剂量处理24 h后,运用CCK-8法检测TM3细胞活力,确定BPA最适染毒剂量;通过ELISA检测TM3细胞培养上清液睾酮(testosterone,T)含量;利用RT-qPCR检测TM3细胞脂质代谢相关基因Apoa1、Apoa 2(apolipoprotein A2)、Apoc 3(apolipoprotein C3)的mRNA表达水平;运用Western blot和免疫荧光方法检测APOA1蛋白表达水平;采用油红O染色观察细胞内脂滴累积情况。结果表明,20μmol·L^(-1)BPA处理24 h对TM3细胞活力无显著影响,40μmol·L^(-1)BPA处理24 h后,TM3细胞活力受到极显著抑制(P<0.01);此外,20μmol·L^(-1)BPA处理TM3细胞24 h后,培养上清液中睾酮含量极显著低于对照组(P<0.01),Apoa 1基因的mRNA表达水平及蛋白表达量极显著升高(P<0.001),但Apoa 2和Apoc 3基因的mRNA表达水平无显著变化;与对照组相比,20μmol·L^(-1)BPA处理24 h,TM3细胞的脂滴累积量极显著降低(P<0.0001)。综上,BPA可通过上调Apoa 1基因的表达水平,增强胆固醇逆向转运(reverse cholesterol transport,RCT),引起TM3细胞内的脂滴含量减少,导致TM3细胞的睾酮合成分泌降低。

Upconversion Luminescence Properties of Ho^(3+),Tm^(3+),Yb^(3+) Co-Doped Nanocrystal NaYF_4 Synthesized by Hydrothermal Method

Nanocrystal of upconversion （UC） phosphor Ho^3＋, Tm^3＋ , and Yb^3＋ co-doped NaYF4 was prepared by the hydrothermal method in the presence of the complexing agent EDTA. Under 980 nm diode laser excitation, the impact of different concentrations of Ho^3＋ ion on the UC luminescence intensity was discussed. The law of luminescence intensity versus pump power shows that the 474 nm blue emission, 538 nm green emission, and 642 nm red emission are all due to the two-photon process, while the 450 nm blue emission is a three-photon process. The UC mechanism and processes were also analyzed. The sample was characterized by transmission electron microscopy （TEM） and X-ray diffraction （XRD）. The result shows that Ho^3＋ ,Tm^3＋ , and Yb^3＋ co-doped NaYF4 prepared by the hydrothermal method exhibits a hexagonal nanocrystal.

Solution-Phase Synthesis and Characterization of Perovskite LaCoO_3 Nanocrystals via A Co-Precipitation Route

A facile co-precipitation route for the synthesis of well-dispersed LaCoO3 nanocrystals was developed. The asprepared products were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, energy dispersive X-ray spectrometer （EDX）, and laser Raman spectroscopy （LRS）. The resuks showed that modulating the growth parameters, such as the addition of surfactants as well as the adding manner of the precipitator had a significant effect on the overall shape and size of the obtained nanocrystals. The nanorods with the diameter of 20 nm and spherical LaCoO3 nanocrystals with the size of about 25 nm could be obtained at a relatively low calcining temperature of 600℃. Furthermore, the Raman properties of LaCoO3 products obtained at different calcining temperatures were investigated.

Synthesis of colloidal LaF_3: 0.04Yb^(3+), 0.01Er^(3+) nanocrystals with green upconversion luminescence

A synthesis of LaF3：0.04Yb^3＋,0.01Er^3＋ nanocrystals with oleic acid as a capping ligand was presemed. The X-Ray Diffraction （XRD） pattern indicated that the power was a single hexagonal phase. Transmission Electron Microscopy （TEM） demonstrated that the average size of the nanocrystals was less than 10 nm, with a narrow size distribution. The nanocrystals were dispersible in nonpolar solvents and form a fully transparent colloidal solution, and the solution was stable for several months without any aggregates. The Yb^3＋-Er^3＋ codoped nanocrystal colloidal solution exhibited a bright green upconversion fluorescence under 980 nm excitation from a diode laser. The nanocrystals were potentially applicable in biolabeling and bioimaging.

Theoretical Study of La , Ca modified and Pure PbTiO_3 Nanocrystals

Quantum chemistry calculations of La , Ca modified and pure PbTiO\-3 nanocrystals were carried out by means of the cluster model in DFT DVM calculating program on which the regularity of the charge distribution was drawn. The analysis of the density of state(DOS) showed that when the cubic phase PbTiO 3 nanocrystal is changed into tetragonal phase, the interaction among Ti 3d , O 2p , and Pb 6p atomic orbitals causes the dipole moment and spontaneous polarization on the axis of the crystal, which resulted in the appearance of ferroelectric phase. At the same time, the dipole moment and the intensity of the spontaneous polarization were calculated as well.

Controlled Synthesis and Optical Properties of Lanthanide-doped Na3ZrF7 Nanocrystals

In this paper,we report for the first time the controlled synthesis of lanthanide ion(Ln3+)-doped tetragonal-phase Na3Zr F7nanocrystals(NCs)via a high-temperature co-precipitation approach.The as-synthesized Na3Zr F7NCs are systematically studied by utilizing the XRD,TEM as well as high-resolution photoluminescence(PL)spectroscopy.The morphology and size for the as-synthesized Na3Zr F7NCs can be finely controlled by changing the experimental parameters such as the amount of precursor,solvent ratio,reaction temperature and time.By utilizing the red-emitting Eu3+ion as an efficient optical/structural probe,the successful hetero-valence doping of Ln3+activators in the lattices of Na3Zr F7NCs is well-established regardless of their different valences and radii between host Zr4+ion and Ln3+dopant.As a result,intense upconversion(UC)luminescence(UCL)ranging from UV to visible and to NIR spectral regions can be readily achieved after the doping of typical UCL couples of Yb3+/Er3+,Yb3+/Tm3+and Yb3+/Ho3+into the lattices of Na3Zr F7NCs when excited by using a 980-nm NIR diode laser.

Upconversion Luminescence Properties and Mechanism of Er^(3+) Doped Ba_(0.65)Sr_(0.35)TiO_3 Ferroelectric Oxide Nanocrystals

Ba0.65Sr0.35TiO3（BST） nanocrystals doped with different concentrations of Er^3＋ ion were fabricated using sol-gel method. The structure and morphology of these BST nanocrystals were studied using X-ray diffraction（XRD）, field emission scanning electron microscopy（FESEM） and transmission electron microscopy（TEM）. The X-ray diffraction patterns of all the nanocrystals prepared in the study correspond to polycrystalline perovskite BST structure. The blue and green upconversion luminescence properties of Er^3＋ doped BST nanocrystals were investigated under excitation by a 785-nm laser. The upconversion emission bands centered at 407, 523, and 547 nm can be attributed to ^2H9/2, ^4I15/2, ^2H11/2, ^4I15/2, and ^4S3/2, 4I15/2 transitions of Er^3＋ ion, respectively. The upconversion mechanism was studied in detail, based on the laser power dependence of the upconverted emissions. In addition, we examined the dependence of the intensity of green upconverted luminescence on the doping concentration of Er^3＋ ions, and discussed the mechanism underlying the process.

Lu_(2)O_(3):Yb,Tm/MC540纳米材料的制备及研究

以水热反应及后续的高温煅烧过程为合成手段,成功制备了Lu_(2)O_(3):Yb,Tm纳米材料。XRD结果显示所得样品为纯Lu2O3晶相。且SEM结果表明所得样品由不规则形状组成,粒径在100nm左右。随后通过搅拌吸附过程负载部花青(MC540)光敏剂,得到Lu_(2)O_(3):Yb,Tm/MC540纳米材料。然后以肺癌细胞(A-549细胞)为模型,研究了Lu_(2)O_(3):Yb,Tm/MC540纳米材料的抗肿瘤活性。结果表明,在650nm的红光照射下,上述材料对肺癌A-549细胞具有明显的光动力杀伤疗效。

Grain Growth Kinetics of BaTiO3 Nanocrystals During Calcining Process

BaTiO3 nanocrystals were synthesized by sol-gel method using barium acetate （Ba（CH3COO2） and tetrabutyl titanate （Ti（OC4H9）4） as raw materials. Xerogel precursors and products were characterized by means of thermogravimetric/differential scanning calorimetry （TG/DSC）, X-ray diffraction （XRD） and transmission electron microscope （TEM）. The influence of the calcination temperature and duration on the lattice constant, the lattice distortion, and the grain size of BaTiO3 nanocrystals was discussed based on the XRD results. The grain growth kinetics of BaTiO3 nanocrystals during the calcination process were simulated with a conventional grain growth model which only takes into account diffusion, and an isothermal model proposed by Qu and Song, which takes into account both diffusion and surface reactions. Using these models, the pre-exponential factor and the activation energy of the rate constant were estimated. The simulation results indicate that the isothermal model is superior to the conventional one in describing the grain growth process, implying that both diffusion and surface reactions play important roles in the grain growth process.

Polymer waveguide thermo-optical switch with loss compensation based on NaYF_4: 18% Yb^(3+), 2% Er^(3+) nanocrystals

A polymer waveguide thermo-optical switch with loss compensation based on NaYF_4： 18% Yb^（3＋）, 2% Er^（3＋）nanocrystals, fabricated by traditional semiconductor processes, has been investigated. NaYF4： 18% Yb^（3＋）, 2% Er^（3＋）nanocrystals were prepared by a pyrolysis method. The morphology and luminescent properties of the nanocrystals were characterized.The nanocrystals were doped into SU-8 as the core material of an optical waveguide amplifier. The size of the device was optimized for its optical and thermal fields as well as its transmission characteristics. The device was fabricated on a silica substrate by spin coating, photolithography, and wet etching. The insertion loss of the switch device is～15 dB. The rise and fall times of the device are 240 μs and 380 μs, respectively, as measured by application of a 304 Hz square wave voltage. The extinction ratio of the device is about 14 dB at an electrode-driving power of 7 mW. When the pump light power is 230 mW and the signal light power is 0.1 mW, the loss compensation of the device is 3.8 dB at a wavelength of1530 nm. Optical devices with loss compensation have important research significance.

Two-photon absorption of FAPbBr_(3) perovskite nanocrystals

Perovskite nanocrystals(NCs) with high two-photon absorption(TPA) cross-section are of great interest due to their potential applications in three-dimensional optical data storage and multiphoton fluorescence microscopy. Among various perovskite materials, FAPbBr_(3) NCs show a better development prospect due to their excellent stability. However, there are few reports on their nonlinear optical properties. In this work, the nonlinear optical behavior of FAPbBr_(3) NCs is studied.The methods of multiphoton absorption photoluminescence saturation and open aperture Z-scan technique were applied to determine the TPA cross-section of FAPbBr_(3)NCs, which was around 2.76 × 10^(-45)cm^(4)·s·photon^(-1) at 800 nm. In addition,temperature-dependent photoluminescence induced by TPA was investigated, and the small longitudinal optical phonon energy and electron–phonon coupling strength was obtained, which confirm the weak Pb–Br interaction. Meanwhile, it is found that the exciton binding energy in FAPbBr_(3) NCs was 69.668 me V, which may be ascribed to the strong hydrogen bond interaction. It is expected that our findings will promote the application of FAPbBr_(3) NCs in optoelectronic devices.

Fluorescence Quantum Efficiency Enhancement in CaWO_4:Eu^(3+),Na^+ Nanocrystals by Tridoping with F^- Ions

We demonstrated that tridoping with F- ions is an effective way to improve the fluorescence quantum efficiency of CaWO4：Eu3＋,Na＋ nanocrystals. F--tridoped samples with different F- concentrations were synthesized by a hydrothermal process. The fluorescence spectra and decay curves were measured at room temperature. The fluorescence intensity of F--tridoped samples is about 3 times that for the non F--doped sample. The fluorescence quantum efficiency can be enhanced by 21% when the atomic ratio of F to W was 0.7.

Tm^(3+)高掺杂的NaYF_(4)纳米颗粒制备与发光性能研究

为了研究Tm^(3+)高掺杂浓度下NaYF_(4)纳米颗粒的上转换发光性能,采用热分解法合成了六方相的NaYF_(4)∶Yb^(3+)/Tm^(3+)(20%/8%)纳米颗粒,并用X射线衍射对其结构进行了表征,用透射电子显微镜对其形貌和大小进行了表征.通过搭建上转换光谱测试系统,研究了在980 nm激光激发下NaYF_(4)∶Yb^(3+)/Tm^(3+)纳米颗粒的上转换发光光谱,并分析了其发光机制.通过计算475,513,650,744,805 nm处发光强度与激发光功率间的依赖关系,证明了其上转换发光过程为双光子过程.

基于转录组学探讨Calpeptin在睾丸间质细胞系TM3中的作用机制

目的:探究Calpeptin对睾丸间质细胞(TM3)的分子调控及其机制。方法:选取对数生长期的TM3细胞分为空白对照组、Calpeptin处理组(浓度为10μmol/L),处理20min后收集细胞提取总RNA,在进行RNA质量检测后上机执行测序程序,获得mRNA表达谱。通过生物信息学技术,分析Calpeptin处理后的信号通路变化以及通路内基因的表达水平。此外应用实时荧光定量PCR(qRT-PCR)对选取的差异表达mRNA进行验证。结果:经转录组学测序分析,发现Calpeptin处理后共有63个差异表达基因,其中包括38个显著上调基因和25个显著下调基因,KEGG通路分析揭示,这些差异基因主要富集于甲状旁腺激素的合成与分泌、IL-17信号通路、Apelin信号通路、昼夜节律干扰、醛固酮的合成和分泌等相关经典通路。并通过qRT-PCR对其中12个差异mRNA基因进行表达量的验证。结论:Calpeptin能够导致TM3细胞中mRNA差异表达,这一作用可能与调控激素合成、分泌及炎症反应等过程密切相关。

Preparation and Spectroscopic Properties of Pr^(3＋)-doped Transparent Glass-ceramic Containing LiYF_4 Nanocrystals

Pr^（3＋）-doped transparent oxyfluoride glass-ceramic containing tetragonal LiYF_4 nanocrystals has been synthesized by melting-quenching method and subsequent thermal treatment and spectroscopic properties of Pr^（3＋） ions were investigated. The crystalline phase and microstructure of the LiYF_4 nanocrystals were studied by X-ray diffraction（XRD） and transmission electron microscopy（TEM）, respectively. Compared with those of Pr^（3＋）-doped glass（Pr^（3＋）：PG）, the sharp absorption and emission bands of Pr^（3＋）-doped glass-ceramic（Pr^（3＋）：GC） reveal parts of Pr^（3＋） ions are incorporated into LiYF_4 nanocrystals. The peak absorption cross-section at 443 nm（~3H_4 → ~3P_2） adds to 110% and the full width at half maximum（FWHM） for the band around 443 nm reduces from 22 to 14 nm after crystallization. The fluorescence lifetime of the ~3P_0 multiplet of Pr^（3＋） ions increases from 5.35 to 11.14 μs after crystallization. The results indicate that this glass-ceramic is promising to be a visible laser material.