Dy3+在Ba3La(BO3)3 中的光致发光

研究了Ba3La(BO3)3 基质中Dy3 的光致发光特性; 探讨了RE3 的电荷半径比(z/r)和Ce3 , Dy3 含量对Dy3 发光强度及发光颜色的影响; 分析了Ba3La(BO3)3 中Ce3 对Dy3 发光的敏化作用; 确定了Dy3 的 4F9/2→6H15/2及4F9/2→6H13/2跃迁发射的浓度猝灭机制均为电偶极-电四极相互作用.     

钙钛矿CH3NH3PbI3晶体的电化学

Perovskite CH₃NH₃PbI₃ is an ionic crystal with suitable band gap and conductivity for optoelectronic applications. The sensitivity of the CH₃NH₃PbI₃ crystal and its derivatives to chemical composition, film-forming process, and even moisture lead to difficulties in evaluating its electronic structure and redox behavior using electrochemical techniques. Nevertheless, full understanding of the electrochemical behavior of the perovskite crystal is certainly beneficial for tuning its redox properties and chemical stability, especially for device fabrication. We show that the band structure of CH₃NH₃PbI₃ can be successfully evaluated based on electrochemical square wave voltammetry. The energy level of the bottom of the conduction band of the perovskite crystal was determined directly from the onset reduction potential with reference to the onset oxidation potential of ferrocene, and estimated to be −3.56 eV; the top of the valence band, at –5.07 eV, was determined indirectly after taking into consideration the bandgap, because the oxidation current of the iodide ions shields that corresponding to the valence band of the CH₃NH₃PbI₃ crystal. The overlap of the oxidation currents from the iodide ions and the valence band of the crystal suggests that there are excess iodide ions in CH₃NH₃PbI₃ not involved in the development of the valence band. In addition, the alternating current (AC) impedance spectra of CH₃NH₃PbI₃ indicate that the iodide ions are not completely immobilized. These imply that the defects in the crystal are related to the iodide ions to a large extent. The electrochemistry of CH₃NH₃PbI₃ in an organic electrolyte reveals its coupling degradation during the redox processes in square wave and cyclic voltammetry. The degradation reactions result from the reduction of lead ions and oxidation of iodide ions in the perovskite crystal. In electrochemical reduction, along with the reduction that occurs in the conduction band, the lead ions in the crystal are reduced to metallic lead, which introduces a phase change in the crystal, as revealed in cyclic voltammetry; the metallic lead can be re-oxidized electrochemically. In the case of electrochemical oxidation, the iodide ions, as well as the valence band of CH₃NH₃PbI₃, lose electrons. The electrochemically generated iodine diffuses into the organic electrolyte gradually, which results in the loss of iodide ions in the crystal. Such loss of iodide ions continues during the cyclic redox reaction. Apparently, the electrochemical investigations on perovskite CH₃NH₃PbI₃ show that the crystal is extremely reactive during the redox process; attention should be paid on controlling the excess iodide ions and the irreversible phase change resulting from the oxidation of lead ions.     

Non-Isothermal Kinetics of the Decomposition Reaction of Cluster [Ag3WS3Br]（PPh3）3 and [Cu3WS3Br]（PPh3）3

The thermal behaviors of clusters [Ag3WS3Br](PPh3)3 and [Cu3WS3Br](PPh3)3 (PPh3=triphenyl phosphine) in a nitrogen atmosphere were studied under the non-isothermal conditions by simultaneous TG-DTG-DSC and EDS techniques. The results showed that the evolution of PPh3 generally proceeded before the release of the other moiety in one or two step-mode. The mechanisms, the kinetic and the thermodynamic parameters for decomposition of PPh3 of both clusters were determined and calculated by jointly using several methods, which showed that its evolution was controlled by Avrami-Erofeev equation. The results also showed that there was no new stable phase composed of W-Ag(Cu)-S-Br after release of organic moiety PPh3 and that CVD method was not applicable to their further processing.     

有关NdCl_3·3ROH-AlEt_3催化体系的活性

<正> 我们曾指出,在NdCl_3·3ROH-AlEt_3体系中,醇的作用在于它的给电子性将会降低稀土离子的正电性,从而减弱Nd-Cl键的离子性,同时引起晶格的变化,使之有利于烷基化作用的发生,导致活性提高。本实验采用一种简便的方法证实了这种作用的发生。 这个方法所根据的原理是一般Ziegler-Natta型催化组分的熟知反应形式:     

KMgF3:Ce3+,Tb3+纳米粒子中Ce3+→Tb3+的发光及能量传递

利用微乳液方法,合成了铈、铽共掺杂的氟镁钾纳米粒子,研究了体系中Ce3+→Tb3+的发光特性以及它们之间的相互作用,结果表明KMgF3:Ce3+Tb3+纳米粒子中存在Ce3+→Tb3+的能量传递过程,即Ce3+可以将吸收的能量直接传递给Tb3+离子,使得Tb3+的绿色发光强度大为增加.     

LaVO3和NdVO3的合成

以Ｖ２Ｏ３为起始原料，在氩气中合成了ＡＢＯ３型稀土钒化合物，对加热前通氩气的时间，Ｖ２Ｏ３∶Ｌａ２Ｏ３的配比等进行了探讨，得到了适宜的制备条件。首次报道了ＬｎＶＯ３（Ｌｎ＝Ｌａ，Ｎｄ）的热学性质，发现ＬａＶＯ３具有吸附二氧化碳的特性。     

Growth and Spectral Properties of Yb^3＋-doped Ba3Gd（BO3）3 Crystal

Crystal of Yb3+-doped Ba3Gd(BO3)3 has been grown by the Czochralski method. The spectroscopic characterizations have been investigated at room temperature. The Yb3+:Ba3Gd(BO3)3 crystal exhibits broad absorption at 976nm with FWHM of 7nm and large overall spitting of 2F7/2 manifold (823cm-1). The absorption and emission cross sections are 5.09×10-21cm2 at 976nm and 0.97×10-21cm2 at 1040nm,respectively. The fluorescence lifetime is 2.84 ms.