The reduction of RE3+ in SrB6O10 prepared in air and the luminescence of SrB6O10 : RE2+ (RE=Eu, Sm, Tm)

The reduction of RE3+ to RE2+ (RE=Eu, Sm and Tm) in SrB6O10 prepared in air by high-temperature solid state reaction was observed. The luminescent properties of Eu2+ and Tm2+ show f-d transition and Sm2+ shows f-f transition at room temperature. Three crystallographic sites for Sm2+ in matrix are available. Vibronic transition of D-5(0)-F-7(0) of Sm2+ was studied. The coupled phonon energy about 108 cm(-1), was determined: from the vibronic transition. Due to the thermal population from D-5(0) level, (D1-FJ)-D-5-F-7 (J=0, 1, 2) transitions of Sm2+ were observed at room temperature. A charge compensation mechanism is proposed as a possible explanation.

A mechanistic study of electrochemical oxidation processes of (OEP)Mg(II) in the presence of anions

In the presence of F-, OH-, Cl-, electrochemical redox of (OEP)Mg(II) [2,3, 7,8,12,13,17,18 octaethyl-21H, 23H-porphine magnesium (II)] are investigated in DCE/0.1 mol/L solution by cyclic voltammetry and spectroelectrochemistry, In the presence of anions, anions are axially coordinated to (OEP)Mg(II) generate (OEP)Mg(II)Y, the E-1/2 of (OEP)MS(II)Y oxidation are negatively shifted. A chemical reaction following the second oxidation step is observed, the E-1/2 of the reaction product is obtained. Mechanism of (OEP)Mg(II) in the halogen and OH- anions titration process has been proposed.

A study on the mechanism of the abnormal reduction of Eu3+ -> Eu2+ in Sr2B5O9Cl prepared in air at high temperature

This paper reports a new observation of the abnormal reduction of Eu3+ --> Eu2+ in Sr2B5O9Cl when prepared in air at high temperature. A model based on the nature of substitution defects is proposed to explain this abnormal reduction. Electrons, which reduced the Eu3+ ions, are created by the substitution of cations first and then transferred to the target Eu3+ ions via tetrahedral berate anion groups. Codoping experiments are designed and performed. The results of these experiments support the model proposed. (C) 1999 Academic Press.

以水滑石为前体的Mg-Al-M复合氧化物对催化消除NOx的活性

通过H2-TPR，XRD，TG-DTA及比表面积测定等对ＭｇＡｌ水滑石化合物进行了表征，研究了焙烧温度对水滑石物理性质的影响．在此基础上，研究了ＭｇＡｌ水滑石中加入过渡金属（Ｍ）离子后对ＮＯ＋ＣＯ反应的催化活性．结果发现，含有Ｃｕ离子的样品对ＮＯ＋ＣＯ反应有较高的催化活性，并与ＣｏＡｌＭ的催化性能进行了比较

阴离子存在下(OEP)MG(Ⅱ)的电化学氧化机理研究

用电化学滴定和现场光谱电化学方法研究考察了DCE中OH~－，F~-和Cl-等阴离子存在下的（OEP）Mg（Ⅱ）的电极氧化过程．发现阴离子能与（OEP）Mg（目）轴向配位，形成五配位化合物，从而引起（OEP）Mg（Ⅱ）的氧化峰电位的负移；在生成二价环阳离子的过程中伴随后行化学反应．获得了反应产物的氧化还原峰电位.

Study on the self-packing of SnO2 nanoparticles at the air-hydrosol interface and its composite LB films with arachidic acid

SnO2 nanoparticles were found to self-pack at the air-hydrosol interface and form a nanoparticulate film. The self-packed films were observed under a Brewster angle microscope, and investigated by recording the time evolution of surface pressure and pi-A isotherms. The results show that SnO2 nanoparticles take 3 h to form a complete film at the air-hydrosol interface. Composite monolayers of SnO2 and arachidic acid were obtained by spreading arachidic acid onto a fresh hydrosol surface. Composite Y-type LB films were transferred from the air-hydrosol interface onto substrates, and characterized by FTIR, UV-vis, X-ray diffraction spectroscopy and TEM techniques. The results show that the composite films have good structure, with SnO2 nanoparticles uniformly and compactly distributed in the arachidate matrix. (C) 1998 Elsevier Science S.A. All rights reserved.