锂离子对稀土掺杂氧化物的红外激光诱导热辐射的影响

由于具有较高的可见波段荧光效率,基于稀土掺杂氧化物的红外激光诱导热辐射具有重大的应用潜力。进一步提高红外诱导热辐射效率具有重大的实用价值。设计了一种改善稀土掺杂氧化物材料中红外诱导热辐射效率的方案,即通过掺杂改性杂质,既可以改变稀土离子周围局域晶场的对称性;同时又引入了晶格缺陷。对应的效果包括：一方面,可以通过增强稀土离子周围的晶场强度来提高稀土元素对于入射光子的吸收能力;另一方面,可以利用晶格缺陷作为猝灭中心来增加材料的热转化能力,最终将显著提高杂质改性材料的光热转化效率,即获得更加高效的红外诱导热辐射材料。为了验证设计方案的可行性,利用溶胶-凝胶方法合成了不同浓度的镱离子和锂离子的共掺杂样品,通过XRD及TEM测试分析了杂质对样品结构的影响,并且基于荧光发射光谱具体研究了杂质掺杂浓度对热辐射效率的影响。该工作为高效稀土掺杂热辐射材料的制备提供一定的参考。     

Theoretical investigation on forbidden transition properties of fine-structure splitting in ~2D state for K-like ions with 26≤Z≤36

Excitation energies, magnetic dipole, and electric quadrupole transition probabilities of the 3d~2 D_(3/2)–3d~2D_(5/2) transition in the potassium-like(K-like) sequence with 26≤Z≤36 are investigated by using the multi-configuration Dirac–Hartree–Fock(MCDHF) method. The contributions of the electron correlations, Breit interaction, and the leading-order quantum electrodynamic(QED) effects on the transition properties are analyzed. The present results are interested in the laboratory tokamak and the astronomical observations. Furthermore, the feasibility of these ions for the highly charged ion(HCI) clocks is discussed. Considering the wavelength of lasers and manipulation process of the atomic clocks, Cu~(10+)and Zn~(11+)are recommended as promising candidates with achievable quality factors at the 10~(15) level.     

Pb~(2+)掺杂导致的CaF_2中Yb~(3+)离子三聚体合作发光猝灭

利用978 nm近红外光激发样品Ca F2∶Pb2+,Yb3+,在室温下观察到二价Pb2+离子在383 nm附近的紫外上转换发光。该发射峰对应于Pb2+离子的3P0"1A1g(1S0)跃迁。瞬态光谱测量结果表明:在这个材料体系中,Pb2+离子的激发来自于Yb3+离子三聚体的合作敏化。但是随着Pb2+离子掺杂浓度的提高,Yb3+离子三聚体遭到结构性破坏,导致其合作发光减弱。本文首次利用Pb2+离子掺杂造成Yb3+离子三聚体的结构性破坏,从而引起合作荧光猝灭,并对在Ca F2基质中因其他二价离子的掺入而造成的Yb3+三聚体合作发光猝灭给予了合理的解释。     

高离化Kr33+离子22P -n2S(2≤n≤9)的耦极跃迁行为

本文构造了高离化Kr33+离子 1s2ns (2≤n≤9)和1s22p 态的波函数并利用其计算了体系的非相对论能量。为了得到高精度的理论计算结果,将相对论修正和质量极化效应作为一级微扰计算了体系的总能量和22P -n2S(2≤n≤9)跃迁能,本文的结果与有限的实验数据符合的较好。在此基础上完成了22P -n2S(2≤n≤9)偶极跃迁三种规范下振子强度的理论计算,三者的一致性进一步证明所构造的波函数在整个空间的准确性和可靠性。     

利用三维荧光结合平行因子算法研究金属离子对溶解性有机物的猝灭和校正

溶解性有机物的荧光组份由于受到金属离子的影响其荧光强度受到变化,从而为溶解性有机物的定量分析带来挑战。利用三维荧光结合平行因子分析方法研究了Cu(Ⅱ), Fe(Ⅲ), Ni(Ⅱ), Sr(Ⅱ), Hg(Ⅱ), K(Ⅰ), Mg(Ⅱ) 和Mn(Ⅱ)八个金属离子对典型溶解性有机物荧光组分的荧光猝灭作用,五个水样来源各不相同。实验表明水样被平行因子成功分解为三个荧光组分(色氨酸、腐殖酸、富里酸),这三个荧光组份的荧光得分随着Fe(Ⅲ), Cu(Ⅱ), Hg (Ⅱ)和 Ni(Ⅱ)浓度的增加呈线性或指数下降。在这四种离子中,Fe(Ⅲ)和Cu(Ⅱ)对腐殖酸和富里酸的荧光猝灭作用明显大于Hg (Ⅱ)和 Ni(Ⅱ)。Sr(Ⅱ), K(Ⅰ), Mg(Ⅱ)和Mn(Ⅱ)基本没有影响。其中Fe(Ⅲ)对于三个荧光组分的荧光猝灭都有较好的分析。由于只考虑Fe(Ⅲ) 和Cu(Ⅱ)的影响,对于含有金属离子的饮用水的荧光强度的校正曲线也被建立。不同来源的饮用水中荧光组份的荧光得分的衰减规律也是不一样的,因此水样的来源也是测量时需要考虑的因素。实验证实了金属离子对溶解性有机物的荧光猝灭作用以及其他因素比如Fe(Ⅲ) 和Cu(Ⅱ)和溶解性有机物本身的多样性都是我们荧光测量典型荧光组份时需要考虑的。表明三维荧光结合平行因子分析方法是一个有效的准确测量溶解性有机物荧光组份的工具。     

Structure and switching of single-stranded DNA tethered to a charged nanoparticle surface

Using a molecular theory, we investigate the temperature-dependent self-assembly of single-stranded DNA(ss DNA)tethered to a charged nanoparticle surface. Here the size, conformations, and charge properties of ss DNA are taken into account. The main results are as follows: i) when the temperature is lower than the critical switching temperature, the ss DNA will collapse due to the existence of electrostatic interaction between ss DNA and charged nanoparticle surface; ii)for the short ss DNA chains with the number of bases less than 10, the switching of ss DNA cannot happen, and the critical temperature does not exist; iii) when the temperature increases, the electrostatic attractive interaction between ss DNA and charged nanoparticle surface becomes weak dramatically, and ss DNA chains will stretch if the electrostatic attractive interaction is insufficient to overcome the elastic energy of ss DNA and the electrostatic repulsion energy. These findings accord well with the experimental observations. It is predicted that the switching of ss DNA will not happen if the grafting densities are too high.     

Full-profile fitting of emission spectrum to determine transition intensity parameters of Yb~(3+):GdTaO_4

The Judd-Ofelt theoretic transition intensity parameters A_(tp)~k of luminescence of rare-earth ions in solids are important for the quantitative analysis of luminescence.It is very difficult to determine them with emission or absorption spectra for a long time.A "full profile fitting" method to obtain A_(tp)~k in solids with its emission spectrum is proposed,in which the contribution of a radiative transition to the emission spectrum is expressed as the product of transition probability,line profile function,instrument measurement constant and transition center frequency or wavelength,and the whole experimental emission spectrum is the sum of all transitions.In this way,the emission spectrum is expressed as a function with the independent variables intensity parameters A_(tp)~k,full width at half maximum(FWHM) of profile functions,instrument measurement constant,wavelength,and the Huang-Rhys factor S if the lattice vibronic peaks in the emission spectrum should be considered.The ratios of the experimental to the calculated energy lifetimes are incorporated into the fitting function to remove the arbitrariness during fitting A_(tp)~k and other parameters.Employing this method obviates measurement of the absolute emission spectrum intensity.It also eliminates dependence upon the number of emission transition peaks.Every experiment point in emission spectra,which usually have at least hundreds of data points,is the function with variables A_(tp)~k and other parameters,so it is usually viable to determine A_(tp)~k and other parameters using a large number of experimental values.We applied this method to determine twenty-five A_(tp)~k of Yb~(3+) in GdTaO_4.The calculated and experiment energy lifetimes,experimental and calculated emission spectrum are very consistent,indicating that it is viable to obtain the transition intensity parameters of rare-earth ions in solids by a full profile fitting to the ions' emission spectrum.The calculated emission cross sections of Yb~(3+):GdTaO_4 also indicate that the F-L formula gives larger values in the wavelength range with reabsorption.     

Potential distribution around a test charge in a positive dust-electron plasma

The electrostatic potential caused by a test-charge particle in a positive dust-electron plasma is studied, accounting for the dust-charge fluctuations associated with ultraviolet photoelectron and thermionic emissions. For this purpose, the set of Vlasov–Poisson equations coupled with the dust charging equation is solved by using the space–time Fourier transform technique. As a consequence, a modified dielectric response function is obtained for dust-acoustic waves in a positive dust-electron plasma. By imposing certain conditions on the velocity of the test charge, the electrostatic potential is decomposed into the Debye–Hückel (DH), wake-field (WF), and far-field (FF) potentials that are significantly modified in the limit of a large dust-charge relaxation rate both analytically and numerically. The results can be helpful for understanding dust crystallization/coagulation in twocomponent plasmas, where positively charged dust grains are present.     

Halide‐Anion Water Clusters in Cucurbit[6]uril Supramolecular Systems

Three types of dihalide water clusters [X₂(H₂O)₈]^2? (X=Cl, Br) and [I₂(H₂O)₁₀]^2? have been observed in cucurbit[6]uril supramolecular systems with same guest. According to the single crystal data and the quantitative theory computation, with the increase of electronegativity of halide ions, dihalide water clusters become more stable. A further comparison of three kinds of guests with different molecule length but the same anions, [p‐phenylenediamine salt, hexamethylenediamine salt and N,N′‐hexamethylenebis(pyrazinylbromide)], gives the result that the dihalide water clusters collapse from 2D to 1D with the increase of the lengths.     

Degradation of reactive,acid and basic textile dyes in the presence of ultrasound and rare earths [Lanthanum and Praseodymium]

Degradation of five textile dyes, namely Reactive Red 141 (RR 141), Reactive Blue 21 (RB 21), Acid Red 114 (AR 114), Acid Blue 113 (AB 113) and Basic Violet 16 (BV 16) in aqueous solution has been carried out with ultrasound (US) and in combination with rare earth ions (La³⁺ and Pr³⁺). Kinetic analysis of the data showed a pseudo-first order degradation reaction for all the dyes. The rate constant (k), half life (t_1/2) and the process efficiency (φ) for various processes in degradation of dyes under different experimental conditions have been calculated. The influence of concentrations of dyes (16–40 mg/L), pH (5, 7 and 9) and rare earth ion concentration (4, 12 and 20 mg/L) on the degradation of dyes have also been studied. The degradation percentage increased with increasing rare earth amount and decreased with increasing concentration of dyes. Both horn and bath type sonicators were used at 20 kHz and 250 W for degradation. The sonochemical degradation rate of dyes in the presence of rare earths was related to the type of chromophoric groups in the dye molecule. Degradation sequence of dyes was further examined through LCMS and Raman spectroscopic techniques, which confirmed the sonochemical degradation of dyes to non-toxic end products.