A polytetrafluoroethylene capillary viscometer

A polytetrafluoroethylene(PTFE) capillary Ubbelohde viscometer was designed and constructed. The relative viscosities of aqueous solutions of a polyethylene oxide and a polyvinylpyrrolidone sample were carefully determined down to an extremely dilute concentration region. In comparison with the data obtained from the common glass capillary viscometer, slippage is believed to occur in the PTFE capillary due to its hydrophobic nature. While for the glass capillary viscometer, conventional viscous flow is operative and adsorption phenomena occur since both the solvent water and aqueous solution are wet and/or adsorbed onto the glass capillary surface due to the existence of hydroxyl groups on glass surface. The data were analyzed with a recently developed wall-effect theory and satisfactory results were obtained.

Synthesis of the complex fluoride LiBaF3 and optical spectroscopy properties of LiBaF3 : M(M = Eu,Ce) through a solvothermal process

The complex fluoride LiBaF3 and LiBaF3:M(M = Eu, Ce) is solvothermally synthesized at 180 degreesC and characterized by means of X-ray powder diffraction, scanning electron microscopy, thermogravimetric analysis and infrared spectroscopy. In the solvothermal process, the solvents, molar ratios of initial mixtures and reaction temperature play important roles in the formation of products. The excitation and emission spectra of the LiBaF3:M(M= Eu,Ce) have been measured by fluorescence spectrophotometer. In the LiBaF3: Eu emission spectra, there is one sharp line emission located at 360 nm arising from f --> f transition of Eu2+ in the host lattice, and typical doublet 5d-4f emission of Ce3+ in LiBaF3 powder is shown.

Capillary liquid chromatographic-high-resolution mass spectrometric analysis of ribonucleotides

A method of capillary HPLC-high-resolution MS was developed for the trace analysis of ATP, GTP, dATP and dGTP Dimethylhexylamine (DMHA) was used as ion-pairing agent for the HPLC retention and separation of the nucleotides and positive ion electrospray time-of-flight MS was used for the detection. The application of capillary HPLC allowed minimal usage of DMHA while providing excellent peak retention and resolution, which significantly reduced the ion suppression in electrospray ionization-MS analysis and thus increased the sensitivity. Adduct ions of nucleotides and DMHA were used as quantitative ions in order to achieve the best sensitivity. DMHA concentration at 5 mM in the aqueous mobile phase at pH 7 was found to be the optimal conditions for the C Is capillary column. The method was applied to determine ATP level in cultured C6 glioma cells that were treated with toxic concentrations of Zn. The results showed that the cellular ATP level decreased from 2.7 pmol/cell (<10% cell death) in average control cell samples to 0.36 pmol/cell as the concentration of Zn increased to 120 mg/l (>35% cell death) in culture medium.

Synthesis-dependent luminescence properties of Y3Al5O12 : Re3+ (Re=Ce, Sm, Tb) phosphors

By using metal nitrates and oxides as the starting materials, Y2Al5O12 (YAG) and YAG:Re3+ (Re = Ce, Sm, Th) powder phosphors were prepared by solid-state (SS), coprecipitation (CP) and citrate gel (CG) methods. The resulting YAG and YAG-based phosphors were characterized by XRD, FT-IR, SEM and photoluminescent excitation and emission spectra. The purified crystalline phases of YAG were obtained at 800 degreesC (CG) and 900 degreesC (CP, SS). At an identical annealing temperature and doping concentration, the doped rare-earth ions showed the stronger emission intensity in the CP- and SS-derived phosphors than the CG-derived YAG phosphors. The poor emission intensity for the CG-derived phosphors is mainly caused by the contamination of carbon impurities from citric acid in the starting materials.

Zn_4B_6O_(13)∶Ce~(3+),Tb~(3+)的合成与发光

高温固相扩散方法首次合成了Zn4 B6 O1 3:Ce3+ ,Tb3+ 光致发光材料。通过XRD分析获得晶胞参数 :a =0 7472nm ,V =0 .4172nm3,为立方晶系。研究Ce3+ 和Ce3+ ,Tb3+ 在Zn4 B6 O1 3中的激发和发射光谱 ,发现Ce3+ 在Zn4 B6 O1 3中的激发和发射带比Ce3+ 在其他基质中红移2 3 8～ 4.94KK ,Ce3+ 的发射带与Tb3+ 的 7F6 → 5G2 ,5D1 ,5H7吸收带有很好的重叠 ,使Ce3+ 对Tb3+ 有良好的敏化作用。Ce3+ ,Tb3+ 在基质中的能量传递机理为 :Ce3+ →Ce3+ 和Ce3+ →Tb3+ 之间的偶极子—偶极子的电多级相互作用的共振传递机理。色坐标为 :x =0 2 81,y =0 .619。SEM摄取产物的晶貌 ,颗粒均匀 ,平均粒度为 0 .2 3 μm ,接近纳米级。

TG-DTA properties of new nonlinear optical materials: K(2)Ln(NO3)(5)center dot 2H(2)O (Ln = La, Ce, Pr, Nd, Sm)

Single crystals of K(2)Ln(NO3)(5). 2H(2)O (KLnN) (Ln = La, Ce, Pr, Nd, Sm) were grown from aqueous solution. The thermogravimetric analysis and differential thermal analysis curves of KLnN demonstrate that the processes of dehydration, melting, irreversible phase transformation and decomposition of NO3- take place in sequence in the heating processes (except KCN). There are three stages in the decomposition of NO3- in KLnN (Ln = La, Nd, Sm) while two in KLnN (Ln = Ce, Pr). K(2)Ln(NO3)(5) is formed at about 225 degrees C by the reaction of KNO3 and Ln(NO3)(3). nH(2)O (Ln = La, Ce, Pr, Nd). (C) 2000 Elsevier Science Ltd. All rights reserved.

P-6(7/2)-excited-state decay mechanism and energy-transfer processes in KMgF3 : Eu2+ and KMgF3 : EuX (X = Gd, Ce, Cr)

A four-level decay model in KMgF3:Eu2+ is proposed. The decay profiles of the P-6(7/2) excited state of Eu2+ are biexponential, and the physical implication of each term in the fit equation responsible for the model is interpreted. The evidence obtained spectroscopically for supporting the model is presented. A new method to study energy transfer between Eu2+ and X3+ in KMgF3:Eu-X (X = Gd, Ce, Cr) is established on the basis of the proposed model.

Vibronic transitions and site substitution of Eu2+ and codoped ions in KMgF3 : Eu-X (X=Ce, Cr, Gd, Cu) system

The high-resolution emission spectra of KMgF3 : Eu and KMgF3 : Eu-X(X = Ce, Cr, Gd, Cu) single crystals were measured at 300 and 77 K. The vibronic side bands of Eu2+ were characterized and an assignment of the normal mode frequencies to particular vibrations has been made. The correlation between the vibronic frequencies of Eu2+ and the site substitution of other co-dopcd ions was first found. The relationship between vibronic intensity of Eu2+ and other doped ions concentration showed that Cr3+, Gd3+ ions competed K+ sites with Eu2+ ions. Ce3+ and Eu3+ occurred the electron transference. The introduction of Cu+ made for Eu2+ substuting for K+ sites.

Site substitution and energy transfer of Eu2+ and Ce3+ in KMgF3 : Eu and KMgF3 : Eu-Ce single crystals

The high-resolution emission spectra of KMgF3 : Eu and KMgF3 : Eu-Ce single crystals were measured at 77 K. The site substitution of Eu2+ and Eu2+-Ce3+ co-doped system in KMgF3 was discussed. Eu2+ substituted for K+ sites on three different site-symmetry: cubic, trigonal and tetragonal. The attribution of all lines occurring in the emission spectra were ascertained. The indirect energy transfer from P-6(5/2) states of Eu2+ to 4f5d states of Ce3+ in KMgF3 : Eu-Ce was observed and the energy transfer mechanism was studied. The d-d interaction among levels was proposed.

Energy transfer from Ce3+ to Eu2+ and electron transfer from Ce3+ to Eu3+ in BaY2F8 : Ce, Eu systems

Phorsphors of BaY2F8 : Ce3+, BaY2F8: EU2+ and BaY2F8 : Ce, Eu were prepared by higher temperature solid reaction and their excitation, emission and diffuse reflection spectra were made. We firstly found that the competition of energy transfer from Ce3+ to Eu2+ and electron transfer from Ce3+ to EU3+ existed in CeF3 and EuF3-co-doped BaY2F8 systems. The f-f transition emission of EU2+ was increased with increasing x in systems BaY2F8 : 0. 03Ce, xEU. Ce4+ ions coexist,with Ce3+ ions and substitute Y3+ for Ce4+ in the systems BaY2F8 : Eu, Cc.

Study of energy transfer in KMgF3 : Eu-X (X = Gd, Cr, Ce) by the decay model of P-6(7/2) exited state of Eu2+

Energy transfer processes between Eu2+ and Gd3+, Cr3+, Ce3+ ions in KMgF3, which are difficult to study spectroscopically, have been investigated by using the proposed four-level decay model of the P-6(7/2) excited state of the Eu2+ ion. Gd3+ and Ce3+ transfer its energy to the vibronic transition of the P-6(7/2) --> S-8(7/2) transition of Eu2+, whereas Cr3+ receive energy from Eu2+ via the d-d interaction. The energy transfer from the Eu2+ 4f(6)5d level to the Ce3+ 4f5d state is observed spectroscopically, and the energy transfer mechanism is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

BaY_2F_8∶Ce,Eu中Ce~(3+)→Eu~(2+)的能量传递和Ce~(3+)→Eu~(3+)的电子转移

采用高温固相反应法制备了 Ba Y2 F8∶ Ce3 + ,Ba Y2 F8∶ Eu2 + 和 Ba Y2 F8∶ Ce,Eu,测定了它们的激发、发射和漫反射光谱 .首次发现并研究了在 Ba Y2 F8共掺 Ce F3 和 Eu F3 体系中存在 Ce3 + → Eu2 + 的能量传递和Ce3 +→ Eu3 +的电子转移两种过程及其竞争 .根据光谱数据 ,讨论了 Ce4 +的可能取代格位

KMgF_3∶Eu和KMgF_3∶Eu-Ce单晶体中Eu~(2+)与Ce~(3+)的格位取代和能量传递

在 77K测定了两个晶体的高分辨发射光谱 ,讨论了单掺杂 Eu2 + 和双掺杂 Eu2 + 及 Ce3+ 的 KMg F3中的格位取代问题 .在 KMg F3∶ Eu-Ce中观察到了 Eu2 + 的 6P5/ 2 能级到 Ce3+ 的 4 f 5 d能级间的间接能量传递 ,讨论了能量传递机理

KMgF_3∶Eu,X(X=Ce,Cr,Gd,Cu)体系中Eu~(2+)振动光谱和共掺离子的格位取代

测定了一系列单掺杂 Eu2 +和双掺杂 Eu,X( X=Ce,Cr,Gd,Cu)的 KMg F3晶体在 30 0 K和 77K的高分辨发射光谱以及伴随的振动光谱 ,据此研究了 Eu2 + 在这些体系中的振动跃迁特征 ,并指认了每一振动峰所对应的正则振动模式 .首次发现了在共掺杂体系中 Eu2 +振动频率与其它掺杂离子格位取代间的相关性