稀土对PVC热稳定机理的光谱研究

稀土ＰＶＣ热稳定剂量是最近才发展起来的一类高效、无毒的稳定体系。本文通过对稀土化合物作用下ＰＶＣ降解的光声光谱和ＰＶＣ傅里叶红外光谱的分析证明,稀土热稳定剂具有优越的稳定性能。稀土作用下ＰＶＣ降解的光声光谱研究显示了稀土热稳定剂比其他热稳定剂具有更好的初色性能;红外光谱研究表明,稀土化合物的稳定作用是由于改变了ＰＶＣ分子的构象,从而增加了ＰＶＣ的稳定性。     

稀土离子与二棕榈酰磷脂酰胆碱脂质体相互作用的分子机制

用傅里叶变换红外光谱法研究了稀土离子Ｎｄ＾３＋，Ｇｄ＾３＋和Ｙｂ＾３＋与二棕榈酰磷脂酰胆碱脂质体的相互作用。结果表明这三种稀土离子的掺入都使磷脂的凝胶－液晶相转变温度明显升高，同时相变的协同隆降低。稀土离子与磷脂极性头部的ＰＯ２＾－基团产生了键合作用，这种键合稳定，不受磷脂质体相态的影响。无论在凝胶相或液晶相，稀土离子的掺入都增加了磷脂双分子层的构象有序度。     

用FT-IR研究DBP增塑的聚氯乙烯

用FT-IR差谱技术研究了邻苯二甲酸二丁酯(DBP)增塑的聚氯乙烯(PVC)的分子结构。结果表明,DBP增塑后PVC的结晶度略有增加。碳-氯伸缩谱带向低频位移,因而稳定构象增加;在无定形区存在着DBP和PVC分子间的相互作用,从而证明两者是相容的。     

水溶液中L-半胱氨酸与稀土离子作用的NMR研究

本文测定了在八种不同稀土离子存在下(La、Pr、Nd、Eu、Dy、Ho、Er和Tm)L-半胱氨酸的¹H和¹³C稀土诱导位移。络合物生成位移和诱导位移的pH依赖关系说明L-半胱氨酸通过离子化的羧基与稀土离子配位,络合物稳定常数说明巯基的存在有利于氨基酸的配位作用。对偶极位移模拟结果表明,在半胱氨酸稀土络合物中,羧基和巯基成旁式,羧基以单齿形式与稀土离子配位。     

甘氨酸在纳米碳管中的吸附及性质的分子模拟

采用分子力学、分子动力学方法模拟研究了甘氨酸分子在单壁纳米碳管中的吸附和扩散行为 ,并对甘氨酸分子在纳米碳管中的构象和能量进行了优化 .模拟计算结果表明 ,甘氨酸在纳米碳管中的构象发生了伸缩和扭转 ,这种构象的改变将会导致氨基酸生物性能的改变 ;纳米碳管对氨基酸分子具有较强的吸附作用 ,其中纳米碳管和甘氨酸分子之间的π -π相互作用增加了纳米碳管对氨基酸的吸附能 .模拟过程中氨基酸分子和纳米碳管之间的运动会保持很强的协同效应 ,使模拟体系构型在能量上处于最稳定的状态     

水溶液中甘氨酰替亮氨酸与Ho(ClO43和Yb(ClO43相互作用的NMR研究

本文用¹³C NMR方法研究了水溶液中三价顺磁性稀土离子Ho³⁺和Yb³⁺与二肽甘氨酰替亮氨酸之间的相互作用。对稀土诱导位移中的接触位移和偶极位移进行了分离。实验表明,与羧基相连的碳核所受的接触作用很大,因此不能把镱诱导的位移直接用于肽的构象分析。在水溶液中,肽通过羧基与稀土离子配位,在弱酸性条件下肽键和氨基均不参与配位。根据结构因子确定了肽在溶液中的构象,结果表明,分子片段C1-C2-C5-C6,C2-N-C3-C4和C2-C5-C6-C8为反式,而C2-C5-C6-C7和C1-C2-N-C3成旁式。     

玻璃基质与纳米颗粒相互影响的光谱学研究

通过低温选择激发玻璃陶瓷中的LaF3:Tm3+的1D2能级,成功地分开了两种局域环境中Tm3+离子的发射谱,使一些频率的发射谱仅来自于晶相,而另一些则仪来自于玻璃相.讨论了玻璃陶瓷中形成玻璃的氧化物和以晶相析出的氟化物之间的相互作用对两种局域环境中Tm3+离子的光学性能的影响.结果表明:晶粒较大时,氧化物玻璃对处于纳米晶体局域环境的稀土离子的影响减弱,纳米晶体对处于氧化物玻璃局域环境的稀土离子的影响增强;晶粒较小时,氧化物玻璃和晶粒接触面的增加会降低处于纳米晶体局域环境的稀土离子的发光效率,但纳米晶体对处于氧化物玻璃局域环境的稀土离子的影响减弱.晶粒越大,氧化物玻璃对处于纳米品体局域环境的稀土离子的发光影响越小,发光性能越好.玻璃基质中SiO2的含量能影响两种局域环境的Tm3+离子发光效率.     

稀土离子对tRNA熔融曲线和熔融温度的影响

采用光谱技术就稀土离子对大肠杆菌ｔＲＮＡ＾ｌｅｕ和酵母ｔＲＮＡ＾ｐｈｅ的熔融曲线和熔融温度的影响进行了研究，结果表明：在低浓度条件ｔＲＮＡｓ在２６０ｎｍ的吸光度值随温度的升高而升高，稀土离子对ｔＲＮＡ分子结构起稳定作用；     

钛表面FHAP涂层的电沉积制备及其FTIR特征研究

在含有Ca2+,PO3-₄和F-的电解液中,用电化学恒电流方法,在工作电流为0.9 mA温度为60 ℃的条件下沉积60 min,在医用钛(Ti)表面上制得含氟羟基磷灰石(FHAP)涂层。采用扫描电镜(SEM)、能量弥散X射线谱(EDS)、X射线衍射(XRD)对涂层进行表征,用傅里叶变换红外光谱(FTIR)考察了氟离子的引入对涂层构象和生物活性的影响。结果表明：氟部分取代磷灰石中的羟基,FHAP晶格常数变小,涂层相貌由疏松的微米级的菊花瓣状变化为致密的纳米级的尖锥状。FTIR分析表明,涂层中羟基的伸缩和弯曲振动模式的对称性发生了改变,模拟体液浸泡后涂层覆盖碳磷灰石,涂层生物活性良好。     

FTIR光学信息研究PLD蛋白分子冻干胁迫下的二级结构变化

通过FTIR光学信息研究液态和固态磷脂酶D的二级结构,结果表明FTIR光学信息是一种有效的蛋白质分子二级结构研究方法。FTIR的光学信息分析表明冻干胁迫下,磷脂酶D的FTIR光学信息及二级结构发生较大变化。在磷脂酶D活性构象时的pH冻干使磷脂酶Dα螺旋大大下降,无规卷曲大大上升,β折叠几乎没有变化,说明PLD蛋白质分子空间有序构象解体严重。功能性试验表明,磷脂酶D二级结构的变化直接导致了其活性发生很大变化。     

正向电压激发下ZnSe:Er3+MIS二极管的高场电致发光

本文研究了在室温下经Er离子注入ZnSe晶体的电致发光.报导了三价稀土离子在ZnSe MIS结二极管中的发光.阐明了Er3+离子是在高电场下通过过热电子直接碰撞激发的,根据分立中心是高场激发的有效发光中心,可望在这类器件中有较高的效率.     

Applications and functions of rare-earth ions in perovskite solar cells

The emerging perovskite solar cells have been recognized as one of the most promising new-generation photovoltaic technologies owing to their potential of high efficiency and low production cost. However, the current perovskite solar cells suffer from some obstacles such as non-radiative charge recombination, mismatched absorption, light induced degradation for the further improvement of the power conversion efficiency and operational stability towards practical application. The rare-earth elements have been recently employed to effectively overcome these drawbacks according to their unique photophysical properties. Herein, the recent progress of the application of rare-earth ions and their functions in perovskite solar cells were systematically reviewed. As it was revealed that the rare-earth ions can be coupled with both charge transport metal oxides and photosensitive perovskites to regulate the thin film formation, and the rare-earth ions are embedded either substitutionally into the crystal lattices to adjust the optoelectronic properties and phase structure, or interstitially at grain boundaries and surface for effective defect passivation. In addition, the reversible oxidation and reduction potential of rare-earth ions can prevent the reduction and oxidation of the targeted materials. Moreover, owing to the presence of numerous energetic transition orbits, the rare-earth elements can convert low-energy infrared photons or high-energy ultraviolet photons into perovskite responsive visible light, to extend spectral response range and avoid high-energy light damage. Therefore, the incorporation of rare-earth elements into the perovskite solar cells have demonstrated promising potentials to simultaneously boost the device efficiency and stability.     

Collapse of spherical polyelectrolyte brushes in the presence of multivalent counterions

We consider the interaction of multivalent counterions with spherical polyelectrolyte brushes (SPB). The SPB result if linear polyelectrolyte (PE) chains (contour length: 60 nm) are densely grafted to colloidal spheres of 116 nm in diameter. Dispersed in water, the surface layer consisting of chains of the strong PE poly(styrene sulfonic acid) (PSS) will swell. We demonstrate that successive addition of trivalent ions (La3+) leads to a collapse in which the surface layer is shrinking drastically. All findings are discussed on the base of a theoretical mean-field approach using the Donnan equilibrium. The ion exchange and a strong binding of trivalent ions by PE chains is followed up by a drop in the osmotic pressure inside the brush. This reduction is the driving force for the collapse. The strong ion-chain correlation is discussed with results obtained from molecular dynamics simulations.     

A Study of Mechanochemical Doping of Fluoride Crystals with a Fluorite Structure by Er3+ Ions via Electron Paramagnetic Resonance Spectra

Using electron paramagnetic resonance (EPR) spectroscopy, we have shown that, upon mecha- noactivated doping of powders of compounds CaF₂, SrF₂, and BaF₂ with Er³⁺ ions, impurity centers of single erbium ions with cubic symmetry are formed. Investigations of dependences of EPR spectra intensities on the particle size show that the process of mechanochemical doping with Er³⁺ ions proceeds differently for CaF₂, SrF₂, and BaF₂ host matrices. In the case of CaF₂, impurity centers are localized in a very thin near-surface layer of CaF₂ particles, in SrF₂, the impurity is distributed over the volume of particles, while, in BaF₂, there is a layer of a finite thickness for which the probability of doping in the course of mechanosynthesis is very small and the impurity of the rare-earth element is localized in the core of large particles. These data can be explained assuming that the result of mechanosynthesis of particles of fluorides with a fluorite structure doped with Er3+ ions at room temperature is governed by two processes—mechanoactivated diffusion of rare-earth ions into particles and segregation of impurity ions at grain boundaries. In this case, the typical scales for compounds CaF₂, SrF₂, and BaF₂ considerably differ from each other.     

Understanding the influence of nanoenvironment on luminescence of rare-earth ions

This paper presents an overview of the recent results on upconversion and photoluminescence of rare-earth ions in nanoenvironments. The role of the rare-earth ion concentration, crystal size and crystal phase on the up and downconversion emission of rare-earth ions in oxide nanocrystals and their underlying mechanisms are discussed. It is also found that the luminescence lifetime of the excited state rare-earth ions is sensitive to the particle crystalline phase and size. The analysis suggests that the modifications of radiative and nonradiative relaxation mechanisms are due to local symmetry structure of the host lattice and crystal size respectively     

Photomagnetic effect in molecular magnets based on nitrosyl complexes of ruthenium and rare-earth ions

The magnetic properties of new bifunctional molecular magnets based on nitrosyl complexes of ruthenium and thiacalix[4]arenes of rare-earth ions (Gd³⁺, Dy³⁺) have been investigated. A photoinduced decrease in the magnetization of the molecular magnet with rare-earth ions Gd³⁺ and the absence of a photomagnetic effect in crystals with rare-earth ions Dy³⁺ have been revealed at a temperature of 2 K. It has been found that, in the sample containing Dy³⁺ ions, the magnetization deviates by 6% from the calculated value for noninteracting ions. A comparison of the results obtained for two groups of isostructural samples, which differ only in the type of rare-earth ions, has demonstrated that the observed deviation of the magnetization is caused by the interaction of the orbital moment of the Dy³⁺ ions with the crystal field.     

希土离子对高功率铁磁共振的影响

本文利用关联函数方法(久保理论)来讨论高功率下铁磁共振中的非线性过程。对通常的铁磁晶体,目前的理论包含了由H.Suhl所发展起来的半经典理论的结果。对含希土离子的石榴石型铁氧体,给出了希土离子引起的自旋波的频率移动,附加的损耗,以及所谓纵向注入和横向注入的一级二级的非线性过程的临阈场。希土离子的存在使临阈场增大。一般而言,这一关系是很复杂的,但当希土离子含量很少的情形下,对临阈场的影响可归结为自旋波的损耗的增加,临阈场随温度的改变及各向异性完全与低功率下铁磁共振线宽的情况相似。对于现有的一些实验结果,理论作了定性的解释。     

Eigenmodes and thermodynamics of a Coulomb chain in a harmonic potential

The density of ions trapped in a harmonic potential in one dimension is not uniform. Consequently the eigenmodes are not phononlike waves. We calculate the long-wavelength modes in the continuum limit, and evaluate the density of states in the short-wavelength limit for chains of N>1 ions. Remarkably, the results that are found analytically in the thermodynamic limit provide a good estimate of the spectrum of excitations of small chains down to few tens of ions. The spectra are used to compute the thermodynamic functions of the chain. Deviations from the extensivity of the thermodynamic quantities are found. An analytic expression for the critical transverse frequency determining the stability of a linear chain is derived.     

Intensity of the <Emphasis Type="Italic">f-f</Emphasis> transitions of Nd<Superscript>3+</Superscript>, Er<Superscript>3+</Superscript>, and Tm<Superscript>3+</Superscript> rare-earth ions in calcium niobium gallium garnet crystals

This paper reports on the results of the investigation into the intensities of the f-f transitions of Nd³⁺, Er³⁺, and Tm³⁺ ions in calcium niobium gallium garnet (CNGG) crystals. The values of the oscillator strengths and line strengths obtained for hypersensitive transitions and the intensity parameters Ω _t of the rare-earth ions in the CNGG crystals are compared with the corresponding quantities for crystals of other garnets and some oxide and fluoride crystals. The assumption is made that an increase in the oscillator strengths and line strengths for the hypersensitive transitions and the intensity parameters Ω₂ of the Nd, Er, and Tm ions in the CNGG crystals as compared to those for crystals of other garnets is associated with the specific features revealed in the crystal structure of the calcium niobium gallium garnet, in particular, with the lowering of the symmetry of the positions occupied by rare-earth ions in the crystal structure.     

Er3+在氟氧化物玻璃陶瓷中的光谱性质

根据ErYb共掺氟氧化物玻璃陶瓷的吸收光谱，用Jubb-Ofelt理论计算了强度参量，产并由此计算了激发能级的自发辐射跃迁速率、辐射寿命、荧光分支比和积分发射截面等光谱参量。