高氯酸与硫酸溶液中铂电极上氧阳极析出动力学与机理

本文研究了不同浓度的HClO₄和H₂SO₄溶液中铂电极上氧阳极析出过程的动力学。稳态极化曲线上有三个区域:电位突跃前的低极化区,突跃区和突跃后的高极化区。前两个区域内对于α_w的反应级数均为1,在后一区域内对于α_w·α_ClO4^-或αw·α_HSO4^-的反应级数接近于1/2。文中对在各区域内的反应机理和产生电位突跃的原因进行了探讨。     

臭氧提高纳米TiO2光催化活性的ESR分析

以5,5-二甲基-1-吡咯啉-N-氧化物(DMPO)为自由基捕获剂,分别以去离子水和二甲基亚砜(DMSO)为溶剂,利用电子自旋共振(ESR)方法对UV、O₃、TiO₂/O₃、TiO₂/UV/O₂、UV/O₃和TiO₂/UV/O₃这6种体系中形成的羟基自由基(·OH)和超氧阴离子自由基(·O₂^-)进行了检测,同时考察了反应时间、催化剂投量以及体系溶解氧对TiO₂/UV/O₃体系形成·OH和·O₂^-的影响.结果显示,在纳米TiO₂光催化体系中加入臭氧,能显著增加反应体系中·OH和·O₂^-自由基的生成量,6种体系中DMPO-·OH和DMPO-·O₂^-加合物的ESR波谱峰信号强度分别为:TiO₂/UV/O₃>TiO₂/UV/O₂>UV/O₃>UV>TiO₂/O₃>O₃和TiO₂/UV/O₃≈TiO₂/UV/O₂>TiO₂/O₃>UV>UV/O₃>O₃,在TiO₂/UV/O₃体系中成功监测到·O₃^-自由基的存在.     

2.7NaF-AlF3(7wt%CaF2)-Al2O3-YM2O3体系物理化学性质的研究

本文系统研究了冰晶石熔体中添加钇族稀土碳酸盐即2.7NaF·AlF₃(7Wt%CaF₂)-Al₂O₃-YM₂O₃体系的一系列物理化学性质。 应用最优化设计原理,研究了该体系的初晶温度、表面张力、密度、粘度和电导率,分别得到了表征该体系初晶温度、粘度与Al₂O₃、YM₂O₃浓度关系的回归方程以及该体系表面张力、密度、电导率与Al₂O₃、YM₂O₃浓度和温度关系的回归方程。     

一些氮氧自由基和受阻胺化合物对单重态氧的猝灭能力及其与光稳定作用的关系

本工作测定了一系列稳定氟氧自由基( )化合物及一些受阻胺光稳定剂对单重态氧(¹O₂)的猝灭速率常数(k_q^1O₂),发现不同结构的 对¹O₂的猝灭能力很接近,但它们对聚丙烯(PP)膜的光稳定作用却相差很大。四甲基哌啶醇(TMP)及其衍生物对¹O₂的猝灭能力远不如相应的五甲基哌啶醇(PMP)及其衍生物,但前者对PP的光稳定能力却胜于后者。这说明在对聚合物的光稳定作用中, 和受阻胺光稳定剂对¹O₂的粹灭作用不占重要地位,也说明¹O₂在PP的光氧化过程中很可能不是主要因素。     

Cr(Ⅲ)盐在Pt电极和PbO电极上阳极氧化为铬酸盐的机理的研究

在[H₂SO₄]和[SO₄^2-]恒定的不同浓度Cr₂(SO₄)₃溶液中测定了Cr³⁺在光滑Pt和PbO₂电极上的稳态极化曲线和分解极化曲线,得到了氧的阳极发生和Cr⁶⁺阳极形成的动力学数据,提出了Cr(Ⅵ)是由Cr(Ⅲ)通过"活性氧"的氧化形成的反应机理。测得了PbO₂电极上不同过电位下电极反应的有效活化能,其数值均在41.9kJ/mol以上,且随着极化的增大而减小,据此在动力学处理中可以忽略扩散的作用。测得了在不同电位极化下PbO₂电极的阻抗频谱。在较高电位下阻抗谱呈现明显的两个半圆,表明电极过程包括了中间吸附物的形成。吸附电容C_ad比双层电容C_d大1-2个数量级;C_d比通常光滑电极表面的C_d大得多,这可能与阴离子的特性吸附有关。     

明胶大分子的还原性与抽提的关系

用不同抽提次序的一系列明胶样品,用电位法测定了它们的还原性,用氨基酸分析仪测定了蛋氟酸(Met)、蛋氨酸亚砜(Metsox)和砜(Metson)的含量,用SDS-PAGE电泳法测定了它们的不同构象组份的相对含量。发现:明胶的还原性随抽提次序的增加出现一极大值,而这个极大值与α₁,α₁+α₂和α₁/α₂的比值互呈正并行性的对应关系。仔细考察和对比α₁和α₂的一级构型表明:α₁比α₂含有较多的Met。这个极大值的出现,是与第2道抽提出来的明胶中含有较多的α₁组份(从而较多的Met)有关。     

硼化合物的研究——ⅩⅩⅧ.十八氢二十硼酸α,α′-联吡啶合稀土(Ⅲ)配合物的合成和性质

作者曾报导一系列不同类型的配体稀土阳离子同闭式氢硼酸B₁₀H₁₀^2-、B₁₂H₁₂^2-相结合的化合物.B₂₀H₁₈^-氢硼酸根的dipy稀土(Ⅲ)配合物迄今未见报道.     

电化学合成己二腈与其阴极极化曲线的测定

恒电位电解法制备己二腊可能有许多反应发生:阳极 H₂O→1/2O₂+2H⁺+2e 2Br^-→Br₂+2e 阴极 2CH₂=CHCN+2H₂O+2e→2CN(CH₂)₄CN+2OH^- CH₂=CHCN+2H⁺+2e→CH₃CH₂CN 2H⁺+2e→H₂ nCH₂=CHCN+H₂O+2e→齐聚物要使己二腈的收率有效的提高,除严格控制溶液体系的半波电位外,反应溶液体系最好是中性偏酸,即应控制pH=6-7为宜。同时,为了抑制氢气的生成,阴极材料应采用氢超电势高的铅等。     

硼化合物的研究Ⅹ。B10H102-、B10H122-及B3H8-双二茂铁季铵盐及环状二茂铁季铵盐的合成

众所周知,二茂铁类和硼氢类化合物都具有特殊的化学结构,并且有可能作为高能材料得到应用。作者通过B₁₀H₁₀^2-、B₁₂H₁₂^2-及B₃H₈^-与(N,N-二甲基胺甲基)二茂铁和1,1'-双(N,N-二甲基胺甲基)二茂铁卤化铵反应,曾合成了一系列新的化合物并研究了它们的反应性能和晶体结构^[1-4]。     

在非质子溶剂中竹红菌甲素敏化光氧化胆红素

胆红素IX_α(胆红素)是哺乳动物体内血红素的代谢产物,由于它与小儿黄疸病光疗的直接关系,以及近来发现它在体内可能作为生物抗氧剂,所以一直受到科学家的重视。在非质子溶剂中胆红素的光氧化可以生成胆绿素IX_α(胆绿素)及一系列单吡咯、双吡咯的衍生物。对于生成单、双吡咯小分子衍生物,用类型Ⅱ(¹O₂为中间体)的光氧化机制很好解释,但对胆绿素的生成到底是经过单重态氧途径,还是离子自由基途径尚不完全清楚。     

导数－同步荧光光谱法同时测定三种B族维生素的研究

研究了维生素B₁的氧化产物(硫色素)、维生素B₂和B₆混合物体系的导数-同步荧光光谱,提出了混合物体系荧光光谱被分辨开的同时测定方法。该法可不经分离直接测定复合维生素片剂中维生素B₁、B₂及B₆,其线性范围均为0～1.0μg/mL,检出限分别为0.5、1.5及4.0ng/mL.     

Anti-cooperativity of the two water OH groups

This paper presents the results concerning anti-cooperativity effects between two H-bonds of a water molecule. The IR OH stretching band shifts Δν—as a measure of the H-bond energy—are compared for HOD with different bases B of 1:1 complexes B…HOD…Cl₄ (Δν₁₁) and 1:2 complexes B…HOD…B (Δν₁₂). We found that Δν₁₂ of the 1:2 complexes for different bases B are 25% smaller than Δν₁₁ for the 1:1 complexes. Corrections for the solvent shifts are introduced. This effect is in line with different observations concerning cooperativity effects of OH H-bonds by polarization with neighbouring molecules. The reduction of Δν₁₂ in 1:2 complexes can be understood on the assumption of a negative polarization by the first H-bond to the second OH or OD group and is called anti-cooperativity. This anti-effect has been already detected by NMR observation on NH₂.

We already observe a decrease of the CCl₄ solvent shift by van der Waals forces OH…CCl₄ of 1:1 complexes, induced by the H-bond of the other OH or OD group. This decrease is measured by the CCl₄ solvent effect for monomers. This indicates a real negative polarization by the H-bond in 1:1 complexes on the second OH/OD. This experiment establishes the real polarization and excludes the importance of repulsions of the bases as the cause. The dependence of intermolecular forces is known on the polarizability. Our method demonstrates directly the polarization by interactions.

The anti-cooperativity of symmetric complexes B₁…HOD…B₁ by a strong base B₁ can be reduced in unsymmetric 1:2 complexes B₁…HOD…B₂ by weaker bases B₂. This weakening of the anti-cooperativity of the stronger base could be predicted quantitatively. Similarly, the anti-cooperativity of the weaker base B₂ is strengthened in unsymmetric 1:2 complexes by stronger bases B₁.

It is known that H-bonds XH…B can be strengthened by cooperativity with a second H-bond XH…XH…B. They can be weakened for water by anti-cooperativity of two H-bonds B…HOH…B. The H-bond B₁…HO of 1:2 complexes B₁…HOH…B₂ can be weakened if the base strength of B₂ is stronger than of B₁ or strengthened if B₂ is weaker than B₁. Nature may use these possibilities in biochemistry.     

高精度定量毛细管电泳法同时测定复合维生素B片中B1、B2、B6、烟酰胺及泛酸钙

建立了高精度定量毛细管电泳法同时测定复合维生素B片中维生素B₁、B₂、B₆、烟酰胺和泛酸钙的方法。样品经乙腈-水（20∶80，v/v）超声提取后，采用全自动高精度定量毛细管电泳仪，以高精度进样阀定量进样，以40 mmol/L硼砂-硼酸缓冲液（pH 9.0）为背景电解质溶液，以工作电压为-10 kV电泳分离。维生素B₁、B₂、B₆、烟酰胺的检测波长为280 nm，然后切换至检测波长210 nm检测泛酸钙。结果表明，各组分之间均得到良好分离，峰面积日内重复性（RSD）为1.3%~1.9%，显著优于普通毛细管电泳。维生素B₁、B₂、B₆、烟酰胺及泛酸钙的浓度在各自线性范围内的相关系数（r）为0.9968~0.9998，检出限2.5~36.0 mg/L，平均回收率为94.1%~98.9%。该法准确可靠，可用于实际复合维生素B片中维生素B₁、B₂、B₆、烟酰胺和泛酸钙含量的同时测定。     

基于加压毛细管电色谱-激光诱导荧光联用技术研究离子强度对维生素B_2光解反应的影响

基于加压毛细管电色谱-激光诱导荧光检测法建立了分析维生素B2及其荧光性光解产物的方法,并用于研究维生素B2在水溶液和磷酸盐缓冲液中的光解反应速率与离子强度之间的关系。发现在C18毛细管色谱柱,流动相为含0.1%(v/v)三氟乙酸的乙腈水溶液,梯度洗脱,激发波长为488 nm,发射波长为520 nm的条件下,维生素B2及多种荧光性光解产物均得到很好的分离和检测,维生素B2的定量限为5×10-8mol/L。在此基础上研究了维生素B2的光降解反应受光照时间和离子强度等的影响。发现离子强度对维生素B2溶液的光解反应有显著影响,离子强度越大,光解速度越快。并进一步通过动力学计算得到维生素B2在水溶液和磷酸盐缓冲液中光解反应的表观速率常数。该研究为维生素B2的光稳定研究提供了一种高效分离和检测的方法,并为维生素B2的保存及临床使用提供了参考。     

Orthorhombic B2CN crystal synthesized by high pressure and temperature

B_0.54C_0.28N_0.18 precursor powder with turbostratic structure was prepared by using melamine and boric acid. The precursor was transformed into orthorhombic B₂CN under definite high pressure and temperature conditions. The composition of the orthorhombic B₂CN powder is B_0.47C_0.23N_0.30. Its lattice parameters are a=0.4776 nm, b=0.4585 nm and c=0.3629 nm. A strong absorption band from 1088 to 1385 cm⁻¹ of orthorhombic B₂CN was observed by infrared measurement. In the photoluminescence (PL) spectrum of orthorhombic B₂CN powder measured at room temperature, a broad peak corresponding to its band-edge emission centers at 374 nm.     

Transitions between the B2 phase and more usual smectic phases in binary systems of banana-shaped with calamitic mesogens

Three phase diagrams of binary systems are presented where one of the mixing components is a bent-core mesogen and the other is a calamitic mesogen. In two of these systems transitions between the 'banana phase' B₂ and more usual smectic phases in the sequences B₂-SmA, B₂-SmC, B₂-SmC-SmA, B₂-SmC-SmA-N could be observed. The mesophases have been identified by their textures, by X-ray investigations and by electro-optical measurements.     

Detection of higher excited states of p-fluorotoluene with (3 + 1)RMPI spectra

In this paper the results of detection of higher excited states of p-fluorotoluene in the gas phase are presented. Within a laser scanning range of 547.0–570.0 nm (3+1) RMPI spectra are obtained, and some vibrational structures on the third electronically excited valence state are observed. According to the polarization characteristic of the multiphoton transition the symmetry of the electronic state is determined as A₁+B₁+3pB₂. Correlated to excited states of benzene, the results show that A₁+B₁ corresponds to ¹E_1u and 3pB₂ to 3p ¹A_2u. It indicates that the double degeneracy of ¹E_1u state does not yet degrade in p-fluorotoluene. Moreover, it occasionally degenerates with 3p¹ A_2u. Furthermore, the electron distribution in the phenyl ring maintains the symmetry of the D_6h point group consistently like in benzene.     

Synthesis and characterization of achiral banana-shaped liquid crystalline molecules containing bisnaphthyl moieties

Three analogous series of symmetric banana-shaped liquid crystalline molecules containing bisnaphthyl units were synthesized and characterized. The effects of linking groups (on the side wings) and lateral meta-fluoro substitutions (on the middle outer rings) on the mesogenic properties were examined. The type of mesophase depends on the lengths of terminal alkoxy chains. Thus, achiral molecules with shorter flexible chains (n = 8) exhibit a rectangular columnar (B₁) phase, while analogous derivatives with longer flexible chains (n = 12) display the B₂ phase. All lateral meta-fluoro substituted analogues (series II) possess the lowest isotropization temperatures and the narrowest mesophasic ranges of the B₁ and B₂ phases. The B₁ and B₂ phases were confirmed by X-ray diffraction, polarizing optical microscopy (POM) and electro-optical (EO) switching experiments. An electric field-induced transition from an antiferroelectric (tristable) state to a ferroelectric (bistable) state was observed in the EO measurements. Spontaneous polarization (by switching current response), tilt angle of chiral domains (by POM), and transmittance-voltage measurements of the B₂ phase in related compounds have been surveyed in this study.     

Coupled Hartree-Fock calculations of the electric dipole polarizability and first hyperpolarizability of some “inorganic benzenes”

Extended basis sets of gaussian functions were used to calculate near Hartree-Fock estimates of the electric dipole polarizabilities, , and first hyperpolarizabilities, β, of the “inorganic benzenes” B₃N₃H₆, B₃O₃H₃, B₃P₃H₃ and Al₃N₃H₆. Assuming that electron delocalization is responsible for the enhanced polarizabilities of aromatic systems, an aromaticity scale can be set up according to the trend of theoretical polarizabilities obtained in this work, i.e. (B₃O₃H₃) < (B₃N₃H₆ ) < (C₆H₆ ), which is consistent with previous calculations of the degree of delocalization in these compounds.     

The B2-B7 phase transition in symmetrical bent-shaped mesogens with methoxy substitution

New mesogens composed of achiral bent molecules with thermally stable ester linkages, and laterally substituted by a methoxy group symmetrically near the central benzene ring, were synthesized. Texture, calorimetric, electro-optical, X-ray and dielectric measurements were performed. In most of studied compounds the antiferroelectric B₂ phase was found on cooling from the isotropic phase, followed by the B₇ phase at lower temperatures. Undulation of layers in the B₇ phase was confirmed by precise synchrotron studies.