基于分数阶流变模型的铁基块体非晶合金黏弹性行为研究

采用分数阶黏弹单元替代经典模型中的黏壶, 结合非晶合金在外加载荷作用下的微观结构演化, 建立了以分数阶微积分表示的非晶合金黏弹性本构模型. 并根据Hertz弹性理论及分数阶黏弹性本构模型, 推导了块体非晶合金在纳米压痕球形压头下的位移与载荷及时间关系式. 基于推导的解析式, 对铁基块体非晶合金在表观弹性区的纳米压痕位移与载荷及时间曲线进行了非线性拟合分析. 相较于整数阶模型, 分数阶模型不仅具有较高的拟合精度, 其拟合参数能敏锐地反应加载速率对块体非晶合金黏弹性行为的影响, 且参数的变化规律与载荷作用下非晶合金微观结构演化呈现出较强的相关性.     

核壳纳米结构壳中Yb离子对稀土上转换发光温度特性的影响

采用油酸盐法分别制备出均匀的上转换发光裸核纳米粒子及其包覆具有不同Yb³⁺浓度掺杂的NaYF₄:Yb³⁺,Er³⁺核壳纳米结构的上转换纳米粒子。在不同温度下(90~450 K),研究分析了在壳中掺杂不同浓度Yb³⁺的NaYF₄:Yb³⁺,Er³⁺@NaYF₄:x%Yb³⁺核壳纳米体系的上转换发光特性。结果表明:在NaYF₄:Yb³⁺,Er³⁺上转换体系中,惰性壳中的525 nm(²H_11/2 →⁴I_15/2)发射峰呈现出与活性壳中不一样的趋势。壳层中掺杂的Yb³⁺通过声子对纳米粒子内部发光与表面及外界之间的相互作用起到了重要的"桥"连作用。     

全光谱白光发光二极管用Eu3+掺杂Ca2KZn2(VO4)3黄色荧光粉的制备及光学性能

基于蓝光芯片激发黄色荧光粉或近紫外芯片激发三基色荧光粉构建的白光发光二极管(WLED)在青光区域呈现明显的凹口,导致白光的色彩性能不够理想。为了弥补这一缺陷,实现全光谱白光,我们设计了Eu³⁺掺杂Ca₂KZn₂(VO₄)₃黄色荧光粉,其发射波长范围为400~750 nm。在387 nm激发下,在所制荧光粉中可同时获得来自VO₄^3-基团和Eu³⁺的发射光。Eu³⁺在Ca₂KZn₂(VO₄)₃基质中的最佳掺杂浓度(物质的量分数)为0.05,且VO₄^3-基团向Eu³⁺的能量传递效率达到64.9%。基于变温的发射光谱,揭示了所制荧光粉的热稳定性并发现VO₄^3-基团和Eu³⁺的激活能分别为0.538和0.510 eV。此外,将所制黄色荧光粉与商用蓝色荧光粉和近紫外芯片进行封装整合,得到可发射暖白光的WLED器件,其色温和显色指数分别为3843 K和85.8。     

Raman spectroscopic characteristics of octa-substituted bis(phthalocyaninato) rare earth complexes peripherally substituted with (4-methoxy)phenoxy derivatives

The Raman spectroscopic data in the range 500-1800 cm⁻¹ for a series of 15 rare earth double-deckers with tervalent rare earths M^III[Pc(MeOPhO)₈]₂ (M = Y, La, …, Lu, except Ce, Pr and Pm), reduced state HPr[Pc(MeOPhO)₈]₂ and intermediate-valent cerium Ce[Pc(MeOPhO)₈]₂ have been collected using laser excitation source emitting at 632.8 nm. With excitation at 632.8 nm, which is in close resonance with the main Q absorption band of the phthalocyanine ligand, typical Raman marker bands of the monoanion radical [Pc(MeOPhO)₈]⁻ were observed at 1500-1528 cm⁻¹ as very strong bands resulting from the coupling of pyrrole CC and aza CN stretchings. For Ce[Pc(MeOPhO)₈]₂ and HPr[Pc(MeOPhO)₈]₂, a very strong band at 1499 cm⁻¹ with contributions from both pyrrole CC and aza CN stretchings and also isoindole stretching was the marker Raman band of [Pc(MeOPhO)₈]²⁻. In addition, the influence of ionic radius of the rare earth metal and substituent species on the Raman scatting characteristics of sandwich-type compounds has also been tentatively studied.     

Tunable photoluminescence of NaYF4:Eu nanocrystals by Sr codoping

NaYF₄:Eu/Sr nanocrystals were synthesized by a hydrothermal method. Tunable photoluminescence of the NaYF₄:Eu nanocrystals was successfully achieved by codoping with Sr²⁺ ions. With increasing Sr²⁺ concentration, not only the X-ray diffraction peaks of the nanocrystals become broader, but also the positions of them shift toward larger lattice parameters. Eu³⁺ and Eu²⁺ have been found to coexist in an NaYF₄:Eu/Sr. The Eu³⁺/Eu²⁺ emission intensity ratio changed with the Sr²⁺ concentration and excitation wavelength. More interestingly, the spectral configurations of Eu²⁺ and Eu³⁺ also varied with the excitation wavelength, indicating that the nanocrystals have multiple luminescence centers or emitting states.     

Photoluminescence and energy transfer in Tb/Mn co-doped ZnAl2O4 glass ceramics

We report on Tb³⁺ as efficient sensitizer for red photoemission from Mn²⁺-centers in ZnO-B₂O₃-Al₂O₃-Si₂O-Na₂O-SrO glasses and corresponding gahnite glass ceramics. In comparison to singly or co-doped glasses, the glass ceramics exhibit significantly increased emission intensity. Structural considerations, ESR, and dynamic luminescence spectroscopy indicate partial incorporation of Mn²⁺ as well as Tb³⁺ into the crystalline phase, the former on octahedral Zn²⁺-sites. Interionic distance and charge transfer probability between both species depend on crystallization conditions. This enables control of the energy transfer process and, hence, tunability of the color of photoemission by simultaneous emission from Tb³⁺ and Mn²⁺ centers. Concentration quenching in Mn²⁺-singly doped materials was found at a critical dopant concentration of about 1.0 mol%. The energy transfer process was studied in detail by dynamic as well as static luminescence spectroscopy. Spectroscopic results suggest the application of the studied materials as single or dual-mode emitting phosphor for luminescent lighting.     

Synthesis and characterisation of a chiral lanthanoid cluster with an unusually exposed cubane core via concomitant deesterification of ethyl acetate

An unusual chiral lanthanoid cluster has been synthesised and characterised that exhibits a cubane cage motif with a remarkably exposed central core. This discovery stems from the use of a new asymmetric diketone ligand, (Z)-3-hydroxy-3-methyl-1-(1,2:3,4-di-O-isopropylidene-α-d-galactopyranose)prop-2-en-1-one (Hmgp), which incorporates both a methyl terminus and a protected d-galactose moiety to induce chirality. Reaction of this ligand with hydrated holmium chloride results in the formation of a cubane cluster, [Ho₄(μ₃-OH)₄(η²-mgp)₆(μ-η²-mgp)(μ-η²-Ac)(H₂O)₂] (1), which bears seven chiral ligands that form a highly shielded hemisphere and an acetate co-ligand that is postulated to form via deesterification of ethyl acetate.     

弱酸阳离子交换纤维柱富集-电感耦合等离子体原子发射光谱法测定水样中的稀土

提出了聚丙烯基弱酸性阳离子交换纤维柱富集痕量稀土元素,1.0 mol/L HCl溶液作为洗脱剂,电感耦合等离子体原子发射光谱法测定水样中稀土元素的方法。在优化的试验条件下,弱酸性阳离子交换纤维对La、Nd、Eu、Gd、Er和Yb的吸附容量分别为86.5,98.2,98.7,99.2,84.9,91.5 mg/g;La、...     

低结晶度聚ε-己内酯电纺膜的制备及其药物控释行为

以芳氧基稀土三(2,6-二叔丁基-4-甲基苯氧基)镧(La(OAr)3)为催化剂,通过加入少量(8.5 mol%)碳酸2,2-二甲基三亚甲基酯(DTC)与ε-己内酯(CL)进行无规共聚合,成功制备了低结晶度的脂肪族内酯-碳酸酯无规共聚酯(PCD)材料,并用1H-NMR、SEC、DSC和WAXS证明了产物的结构和性能.以...     

一类新型冠醚稀土配合物的合成、表征及与DNA作用研究

合成了四种双(N,N′-乙基,苯基)-2,3-萘-二(氧杂乙酰胺)(L=C30H30N2O4)稀土配合物。通过元素分析、红外光谱、差热-热重及摩尔电导值的分析,确定配合物的组成为[RE(pic)3L],RE=Eu(Ⅲ),Tb(Ⅲ),Ce(Ⅲ),Y(Ⅲ)。电化学实验表明:配体无电化学活性,配合物则呈现出一准可逆的氧化还原过程,在10～1000 mV.s-1扫速范围内配合物的氧化还原峰电流与扫描速度的平方根(ν1/2)呈良好的线性关系,表明其在玻碳电极(GCE)上的伏安行为受扩散控制。另外,通过循环伏安法、光谱法及粘度法研究了配合物与DNA的作用方式,结果表明:配合物均以插入方式与DNA作用,并且作用大小次序是Ce(pic)3L>Tb(pic)3L>Y(pic)3L>Eu(pic)3L。在pH=3.0适宜酸度条件下,建立了以Ce(pic)3L为探针定量测定DNA的分析方法。