Direct synthesis and characterization of titanium-substituted mesoporous molecular sieve SBA-15

Ti-substituted mesoporous SBA-15 (Ti-SBA-15) materials have been synthesized by using a new approach in which the hydrolysis of the silicon precursor (tetramethoxysilane, TMOS) is accelerated by fluoride. These materials were characterized by powder X-ray diffraction patterns (XRD), X-ray fluorescence spectroscopy (Y-RF), N-2 sorption isotherms, diffuse-reflectance UV-visible (UV-vis) and UV-Raman spectroscopy, Si-29 MAS NMR, and the catalytic epoxidation reaction of styrene. Experiments show that Ti-SBA-15 samples of high quality can be obtained under the following conditions: F/Si greater than or equal to 0.03 (molar ratio), pH less than or equal to 1.0, aging temperature less than or equal to 80 degreesC, and Ti/Si less than or equal to 0.01. It was found that the hydrolysis rate of TMOS was remarkably accelerated by fluoride, which was suggested to play the main role in the formation of Ti-SBA-15 materials of high quality. There is no stoichiometric incorporation of Ti, and the Ti contents that are obtained are quite low in the case of the approach that is proposed. The calcined Ti-SBA-15 materials show highly catalytic activity in the epoxidation of styrene.

Direct synthesis of highly ordered Fe-SBA-15 mesoporous materials under weak acidic conditions

Iron-substituted SBA-15 (Fe-SBA-15) materials have been synthesized via a simple direct hydrothermal method under weak acidic conditions. The powder X-ray diffraction (XRD), NZ sorption and transmission electron microscopy (TEM) characterizations show that the resultant materials have well-ordered hexagonal meso-structures. The diffused reflectance UV-vis and UV resonance Raman spectroscopy characterizations show that most of the iron ions exist as isolated framework species for calcined materials when the Fe/Si molar ratios are below 0.01 in the gel. The presence of iron species also has significant salt effects that can greatly improve the ordering of the mesoporous structure. Different iron species including isolated framework iron species, extraframework iron clusters and iron oxides are formed selectively by adjusting the pH values of the synthesis solutions and Fe/Si molar ratios. (c) 2005 Elsevier Inc. All rights reserved.

Alkanes-assisted low temperature formation of highly ordered SBA-15 with large cylindrical mesopores

Highly ordered SBA-15 silicas with large cylindrical mesopores (similar to 15 nm) are successfully obtained with the help of NH4F by controlling the initial reaction temperatures in the presence of excess amounts of alkanes.

Factors influencing the catalytic activity of SBA-15-supported copper nanoparticles in CO oxidation

Copper nanoparticles were deposited onto mesoporous SBA-15 support via two different routes: post-grafting method and incipient wet impregnation method. Both XRD and TEM reveal that the post-grafting can make Cu particles very small in size and highly dispersed into channels of SBA-15, while the impregnation method mainly forms large Cu particles on the external surface of SBA-15. TPR experiments show that CuO species formed by the post-grafting method is more reducible than that prepared by the impregnation method. The catalytic activity tests for CO oxidation manifests that the sample prepared by the post-grafting method has a much higher activity than that prepared by the impregnation method, with a lowering of 50 degrees C for T-50, showing a strong dependence of catalytic activity on the size and dispersion of Cu particles. Besides the preparation procedure, other factors including calcination temperature, reduction treatment, copper loading as well as the feed composition, have an important effect on the catalytic activity. The best performance was obtained when the catalyst was calcined at 500 degrees C and reduced at 550 degrees C. The calcination and reduction treatment at high temperature have been found to be necessary to completely remove the organic residue and to generate active metallic copper particles. (c) 2005 Elsevier B.V. All rights reserved.

Large-pore mesoporous SBA-15 silica particles with submicrometer size as stationary phases for high-speed CEC separation

A new mesoporous sphere-like SBA-15 silica was synthesized and evaluated in terms of its suitability as stationary phases for CEC. The unique and attractive properties of the silica particle are its submicrometer particle size of 400 nm and highly ordered cylindrical mesopores with uniform pore size of 12 nm running along the same direction. The bare silica particles with submicrometer size have been successfully employed for the normal-phase electrochromatographic separation of polar compounds with high efficiency (e.g., 210 000 for thiourea), which is matched well with its submicrometer particle size. The Van Deemeter plot showed the hindrance to mass transfer because of the existence of pore structure. The lowest plate height of 2.0 mu m was obtained at the linear velocity of 1.1 mm/s. On the other hand, because of the relatively high linear velocity (e.g., 4.0 mm/s) can be generated, high-speed separation of neutral compounds, anilines, and basic pharmaceuticals in CEC with C-18-modified SBA-15 silica as stationary phases was achieved within 36, 60, and 34 s, respectively.

辐射增强 PP/LDPE 共混体系力学性能的研究

研究了在多官能团单体—三烯丙基异腈脲酸酯存在下，ＰＰ／ＬＤＰＥ共混物的辐射效应，并用ＳＥＭ、ＤＳＣ和动态力学性能对其形态结构和相容性进行了表征。结果表明：通过添加三烯丙基异腈脲酸酯，用辐射可以强化ＰＰ／ＬＤＰＥ共混物的相间结合力，改善共混物的相容性，从而提高共混物的力学性能。

EPDM对PP/LDPE���混物力学阻尼及结晶行为的影响

用动态粘弹谱仪和DSC研究了聚丙烯/三元乙丙橡胶(PP/EPDM)的动态力学性能,考察了EPDM对PP/LDPE(低密度聚乙烯)的力学行为的影响。结果表明,EPDM对PP有增塑作用,在PP/LDPE/EPDM共混物中,PP和LDPE���非晶部分与EPDM具有部分相容性;PP有两个结晶温度(T_c),较低的一个T_c随共混物中EPDM含量(5～25质量份)的增加逐渐向更低温度区迁移,说明EPDM具有加快冷却速率的作用。

稀土(Er, Nd, Yb, Pr, Ho, Sm)有机/无机杂化材料的制备及发光性能研究

目前，国内外对于铕和铽等稀土配合物的可见区发光和应用都有大量研究，但对具有近红外发光（800-1700 nm）性能的稀土配合物的研究还处于起步阶段。由于稀土的近红外发光在光纤通讯、激光系统及诊断学等方面应用具有特殊的优点，越来越引起人们的兴趣和重视。 稀土近红外发光配合物的致命弱点是其光、热和化学稳定性较差，从而限制了其在很多领域的实际应用。而溶胶－凝胶材料和介孔材料具有良好的光、热和化学稳定性，能改善客体分子的结构环境和化学微环境，从而能有效提高客体分子的发光性能。因此，本论文将具有优良近红外发光性能的稀土配合物分别与上述两种基质复合，从实验和理论研究稀土近红外发光杂化材料的性能和应用价值，制备出具有良好稳定性的高效稀土近红外发光杂化材料，以期为光纤通讯、激光等领域提供潜在的候选材料。围绕这一宗旨，开展了如下工作： 通过原位技术分别得到了掺杂和嫁接[Ln(dbm)3phen]化合物（Ln = Er, Nd, Yb）的杂化凝胶材料，Ln-D-P gel和Xerogel-Ln。通过对其近红外发光性能的研究，表明材料中配体能很好的保护稀土离子，并将能量有效的传递给稀土离子。采用Judd-Ofelt理论对所得部分材料进行了光谱分析，基于实验数据和理论分析表明其具有潜在的光放大和激光应用价值。 选择了两种含全氟化烷基链的β-二酮配体Hhfth和Htfnb，通过功能化的phen-Si配体，将三元配合物[Ln(hfth)3phen] (Ln = Er, Nd, Yb, Sm)和[Pr(tfnb)3phen]成功共价嫁接到介孔MCM-41和SBA-15���化材料中，得到的衍生材料Ln(hfth)3phen–MCM-41、Pr(tfnb)3phen–MCM-41和Ln(hfth)3phen–SBA-15���Pr(tfnb)3phen–SBA-15���保持了高度有序的介孔p6mm结构，并展现出稀土离子特征的近红外发射。所得稀土配合物功能化的材料的发射光谱能完全覆盖对光通讯极具应用价值的1300-1600nm区域。 通过对Er(dbm)3phen–M41(X, Y) (X = 1~14, Y = 3, 6, 12, 18, 24 h)材料系统的比较研究，选择了X = 12, Y = 6作为合成目标材料的优化参数，通过功能化的phen-Si配体将[Ln(dbm)3phen]配合物共价嫁接于有序介孔MCM-41和SBA-15���(Ln = Er, Nd, Yb)，所得两类材料Ln(dbm)3phenM41和Ln(dbm)3phenS15都保持了很好的介孔有序性，并具有良好的近红外发光性能。通过对Ln(dbm)3phenM41和Ln(dbm)3phenS15两类材料发光行为的比较，以及两类材料中稀土离子的含量及孔结构的分析，推出以SBA-15���载体得到的材料在相对发光强度和荧光寿命上，均比以MCM-41为载体的材料有所提高。 通过对8－羟基喹啉配体进行改性，合成了具有双功能的配体Q-Si，继而合成了共价嫁接8－羟基喹啉衍生物的介孔杂化材料Q–SBA-15���其形貌均一，并具有高度有序的介孔p6mm结构。通过配体交换反应，得到了嫁接稀土喹啉配合物的具有近红外发光性能的介孔杂化材料LnQ3–SBA-15 (Ln = Er, Nd, Yb)，其仍然保持高度有序的介孔结构，且外形呈现与母体材料Q–SBA-15���似的弯曲圆柱状。激发配体的吸收，LnQ3–SBA-15���料都分别展现出相应稀土离子特征的近红外发射，并详细分析和讨论了所得介孔杂化材料的近红外发光性能。

酶生物燃料电池载体选择及其应用基础研究

酶生物燃料电池（EBFC）是利用酶作为催化剂将化学能转化为电能的装置。由于氧化还原蛋白质和酶通常具有复杂的空间结构，活性中心深埋在它们的肽链中，很难与基底电极进行直接电子传递，从而影响了电池的性能。但使用适当的载体对电极表面进行修饰，可以实现直接的、快速的电子传递。因此，开发稳定性好、成本低、能够有效促进氧化还原蛋白质或酶与基底电极进行直接电子传递的载体成为EBFC发展中的重要课题之一。 本论文主要集中于EBFC中蛋白质或酶载体的选择方面的研究。探讨不同性质的载体，包括半导体电物质、生物相容性物质和导电物质对氧化还原蛋白质或酶的直接电子传递的影响。同时以SiO2纳米粒子为例，探讨了载体促进氧化还原蛋白质直接电子传递的作用机理。通过对不同载体的考察，最终选择了一种合适的材料组装成葡萄糖/O2 EBFC，并考察了EBFC的性能。主要结果如下： 1．将SiO2纳米粒子固定在GC电极上，成功实现了细胞色素c（Cyt c）的准可逆的直接电化学反应，并在这基础上提出双功能机理模型，说明了半导体对氧化还原蛋白质和电极之间的直接电子迁移的影响。 2．发现Cyt c能够在SBA-15���修饰的电极上实现准可逆的直接电化学反应，并能够对H2O2产生较好的电催化还原效果。 3．以生物相容性物质壳聚糖为载体，分别研究了Cyt c、微过氧化物酶（MP-11）和葡萄糖氧化酶（GOD）的准可逆的直接电化学反应。并发现固载在壳聚糖上的Cyt c和MP-11对H2O2和O2还原有很好的电催化活性，而固载在壳聚糖上的GOD对葡萄糖氧化有很好的电催化活性。 4．以碳纳米管（CNT）为载体，实现了GOD的准可逆的直接电化学反应。并在氧化还原媒介体的作用下实现了其对葡萄糖的电催化氧化。 5．将筛选出的最佳载体组装成葡萄糖/O2 EBFC，分别以葡萄糖氧化酶和漆酶作为阳极和阴极的催化剂，制得有隔膜和无隔膜的EBFC。