Synthesis and Mesogenic Properties of Liquid Crystals Containing Terminal Cyclohexylmethanol,Cyclopentylmethanol, Cyclobutylmethanol and Cyclopropylmethanol Moiety

Four series of compounds 11?50 containing terminal alicyclic rings such as cyclohexylmethyl, cyclopentylmethyl, cyclobutylmethyl, and cyclopropylmethyl rings were synthesized and their liquid crystal behavior studied. The ring size and the length of flexible alkoxy chain influence the phase formation in different ways. While the smaller ring and the shorter alkoxy chain tend to favor the formation of the N phase, the larger ring and the longer alkoxy chain tend to favor the formation of the SmC phase. All the compounds except 11 and 21 exhibit SmA phases. The widest temperature range of the N, SmA, and SmC phases are found in the compounds 41 , 46 , and 20 , respectively, which are 75 °C for 41 , 115 °C for 46 , and 100 °C for 20 .     

Thermodynamic molecular switch in sequence‐specific hydrophobic interactions

This communication will demonstrate the existence of a thermodynamic molecular switch in the pairwise, sequence‐specific hydrophobic interaction of Ile–Ile, Leu–Ile, Val–Leu, or Ala–Leu over the temperature range of 273–333 K reported by Nemethy and Scheraga in 1962. Based on Chun's development of the Planck–Benzinger methodology, the change in inherent chemical bond energy at 0 K, ΔH°(T₀), is 3.0 kcal mol^?1 for Ile–Ile, 2.4 for Leu–Ile, 1.8 for Val–Leu, and 1.2 kcal mol^?1 for Ala–Leu. The value of ΔH°(T₀) decreases as the length of the hydrophobic side chain decreases. It is clear that the strength and stability of the hydrophobic interaction is determined by the packing density of the side chains, with Ala–Leu being the most stable. At 〈T_m〉, the thermal agitation energy, $\int^{T}_{0}\Delta Cp^{\circ}(T)\,dT$, is about five times greater than ΔH°(T₀) in each case. Additionally, the thermal agitation energy for the same series, evaluated at 〈T_m〉, decreases in the same order, that is, as the length of the side chain decreases. This pairwise, sequence‐specific hydrophobic interaction is highly similar in its thermodynamic behavior to that of other biological systems, except that the negative Gibbs free energy change minimum at 〈T_s〉 occurs at a considerably higher temperature, 355 K compared to about 300 K. The melting temperature, 〈T_m〉, is also high, 470 K compared to 343 K in a biological system. The implication is that the negative Gibbs free energy minimum at a well‐defined 〈T_s〉 has it origin in the hydrophobic interactions, which are highly dependent on details of molecular structure. In addition to the four specific dipeptide interactions described, we have shown in our unpublished work the existence of a thermodynamic molecular switch in the interactions of 32 dipeptides wherein a change of sign in ΔCp°(T)_reaction leads to a true negative minimum in the Gibbs free energy of reaction, and hence, a maximum in the related K_eq. Indeed, all interacting biological systems that we have thus far examined using the Planck–Benzinger approach point to the universality of thermodynamic molecular switches. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Kinetic investigation of the textile bleaching process

Volumetric H₂-uptake measurements on an Mo₂N (79 m²g^–1) sample reduced at 673 K have been carried out and the uptake isotherms in the temperature range of 308–623 K have been determined. Both the total and reversible hydrogen uptake increased with the uptake temperature. The irreversible hydrogen uptake increased abruptly when the uptake temperature was raised up to 423 K. The maximum of irreversible hydrogen uptake was measured at 473 K. The H_IR/Mo ratio calculated from the uptakes obtained in the temperature range of 308–623 K varies in the range of 0.0010–0.0202. One possible mechanism for hydrogen adsorption is proposed to be heterolytic dissociation on Mo-N paris, in which the molybdenum atoms are in unsaturated coordination.     

水中矿物元素的ICP-MS分析

用ICP－MS对地下水、地表水和饮用水中的矿物元素进行了分析测定，实验证明用ICP－MS可以同时测定地下水，地表水和饮用水中矿物元素；该法灵敏度、精密度和准确度都能满足有关标准的要求，具有多元素同时分析，样品前处理简单，干扰少，测定快速，省事省力等优点。     

金属酞菁化合物在TiO2表面的分散研究

Dispersion of copper(Ⅱ) phthalocyanine (CuPc), copper(Ⅱ) phthalocyaninesulfonate (CuPcS) and cobalt(Ⅱ)phthalocyaninetetrasulfonate (CoPcTS) on the surface of titanium dioxide was investigated by XRD, XPS, FT-IR and UV-Vis techniques. Results show that interaction between CuPc and TiO2 was very weak and CuPc was difficult to disperse on the surface of the support. While partly sulfurized CuPcS could be dispersed on the surface of support through sulfo-groups and its dispersion capacity was determined to be 0.085 g CuPcS/g TiO2. Completely sulfurlzed CoPcTS could also be dispersed on the surface of TiO2 as a monolayer and its dispersion capacity was 0.12 g CoPcTS/g TiO2. Interactions of the sulfo-groups as well as the electrons of CoPcTS with the surface of TiO2 could be evidenced by FT-IR characterization. Therefore, it was suggested that CoPcTS molecules be adsorbed on the surface of TiO2 in a flat-lying mode while CuPcS in a slanting one. UV-Vis spectra show that the dispersed CuPcS and CoPcTS molecules exist in both forms of monomers and dimers.     

胺催化下的Baylis-Hillman反应

Baylis-Hillman (B-H)反应是在催化剂作用下由活泼烯烃和亲电试剂发生的偶合反应, 其产物是一个具有多官能团的化合物. 胺类催化剂是反应中应用最广泛的一类催化剂. 综述了各种胺催化下的Baylis-Hillman反应的研究进展.     

LBL分子沉积法制备葡萄糖氧化酶电极

采用以静电力为主的逐层分子交替沉积技术制备葡萄糖氧化酶（GOD）电极.通过带有正电荷的聚二甲基二烯丙基铵盐酸盐（PDDA）和带有负电荷的GOD交替沉积在修饰有3-巯基-1-丙基磺酸钠（MPS）的金电极表面.以甲酸二茂铁为电子媒介体,用循环伏安法检测GOD电极对葡萄糖的响应.结果表明,当GOD电极组装层数小于4时,电流响应随着层数的增加而增大,超过4层时电流响应减小.其中4层GOD修饰电极的线性范围为0.55～6.63 mmol•L－1,当pH为7.0时,响应最大.同时电极的检测重现性能良好,相对标准偏差为2.4％.     

室温制备高合金化Pt-Ru/CMK-3催化剂及其对甲醇的电催化氧化

通过低温络合反应制备了高分散高合金化的Pt-Ru固溶体, 并将其均匀地担载在有序介孔碳CMK-3上, 以形成二元复合金属催化剂. XRD谱图表明,fcc结构的Pt原子部分被hcp结构的Ru原子取代形成置换固溶体， 而且几乎没有未形成合金的Ru存在. TEM和XRD研究结果表明， Pt-Ru/CMK-3催化剂中Pt-Ru合金粒子的平均粒径为27 nm, 且具有良好的均一度. 还研究了催化剂对甲醇的电催化氧化性能, 并与E-TEK公司同类催化剂进行了对比, 研究结果表明, Pt-Ru/CMK-3催化剂具有较大的电化学活性面积, 对甲醇的电催化氧化性能和抗CO中毒能力明显优于其它同类催化剂.     

Reduction and reconstruction of Co3O4 nanocubes upon carbon deposition

We describe a synthetic investigation on the formation of carbon nanofibers using a preshaped free-standing metal-oxide catalyst (single-crystal cobalt oxide (Co(3)O(4)) nanocubes). In reacting with acetylene (C(2)H(2)) vapor, Co(3)O(4) nanocubes are reduced and reconstructed into metallic cobalt. The resultant metal catalyst with a 2-fold symmetry leads to a bilateral base growth for carbon nanofibers. Our findings indicate that an understanding of catalyst-assisted chemical vapor deposition (CVD) mechanisms can be acquired, when the shape, size, and crystal orientation of pristine metal catalysts are made known to the CVD process. By tracing their evolutional changes in structure and composition, the shape-designed model catalysts may offer new opportunities for mechanistic investigations on the chemical reactivity of nanoparticles, general catalyst-assisted material synthesis, and metal intercalation chemistry.     

液晶聚酯与环氧嵌段共聚物的合成及表征

近年来 ,人们利用高分子液晶作为热固性环氧树脂的改性剂 ,不仅可以提高环氧树脂的韧性和强度 ,而且可以改善其热性能 ,为制备高性能的环氧树脂提供了一条新的途径[1,2 ] .目前报道所使用的液晶聚合物大多为液晶聚酯[3 ] 或液晶性聚氨酯[4] ,这些液晶聚合物与环氧树脂由于存在相容性不好的问题 ,给其实际应用带来了困难 .为了改善二者的相容性 ,本文采用溶液法合成了末端带有反应活性基团的聚酯型液晶聚合物 ,将它再与双酚Ａ环氧预聚物反应 ,制得了高分子液晶环氧嵌段共聚物 ,其合成路线如下 :2ＨＯＣＯＯＣＨ3+ ＨＯ(ＣＨ2 ) 6 ＯＨ　　Ｈ…