Ni,Ru掺杂CePO4纳米材料的合成与仿酶性质

通过水热方法合成了具有高比表面积的Ni, Ru掺杂CePO₄纳米粒子(NiRu-CePO₄). 结合纳米粒子的X射线衍射(XRD)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)和X射线能谱(EDX)的表征结果发现, NiRu-CePO₄符合六方相磷酸铈, 纳米粒子长轴尺寸约为20 nm, Ni和Ru均匀分布于纳米CePO₄中; 样品的BET表面积高达178.4 m²/g, ζ电势为-18.2 mV. 以3,3',5,5'-四甲基联苯胺(TMB)作为电子供体和显色剂, 通过分光光度法监测652 nm处的吸光度值对产物浓度进行分析, 结果表明, NiRu-CePO₄催化剂在宽泛的pH范围内表现出类过氧化物酶和类氧化酶活性. 对催化后的催化剂进行表征, 发现样品形貌、 元素分散性和表面Ce的价态均未显著变化, 表明NiRu-CePO₄具有较高的稳定性.     

Imidazolium chloride-catalyzed synthesis of benzimidazoles and 2-substituted benzimidazoles from o-phenylenediamines and DMF derivatives

A facile, general, and economical synthesis of diversely functionalized benzimidazoles and 2-substituted benzimidazoles has been realized via the imidazolium chloride-catalyzed cyclization of o-phenylenediamines with DMF derivatives. This protocol shows a broad substrate scope for aliphatic, aromatic, and heteroaromatic amides. A series of benzimidazoles and 2-substituted benzimidazoles have been obtained in moderate to excellent yields.     

Assessment of radioactivity level and associated radiation exposure in topsoil from eastern region of Shangrao Prefecture,China

Natural and fallout radioactivity were estimated in topsoil samples collected in eastern region of Shangrao Prefecture, China. The average activity concentrations of ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K in the soil were nearly 2 times the world median value and Chinese average. The ¹³⁷Cs activity concentration decreased compared with the previously reported value in the same region. The absorbed dose rate and annual effective dose rate estimated in the study area are found to be both higher than the world average values. ²³⁸U/²²⁶Ra and ²³²Th/²²⁶Ra activity ratios were also considered in this study.

     

Sinter-resistant and high-efficient Pt/CeO_2/NiAl_2O_4/Al_2O_3@SiO_2 model catalysts with “composite energy traps”

The stability of nanosized catalysts at high temperature is still a challenging topic and is a crucial criterion to evaluate their suitability for industrial use. Currently, the strategy to improve the high-temperature stability of nano-sized catalysts is to restrict the migration of particles on the surface, which, however, lacks theoretical knowledge and directions. Herein, we reported a new approach that can effectively inhibit the migration and agglomeration of supported nanoparticles by fabrication of a model catalyst Pt/CeO_2/NiAl_2O_4/Al_2O_3@SiO_2. This catalyst is highly stable with the microstructure unchanged even after being aged at 1000 °C. Density functional theory calculations indicate that two types of confinement effects exist in the catalyst and their mechanisms were well explained from the viewpoint of "energy traps" which can also be applied to other supported catalysts.     

基于流电沉积法制备的Pt/Ni/Al_2O_3催化剂及其对CO催化性能

以水滑石为前驱体,通过流电沉积法制备了Pt负载型催化剂。在该催化剂中,贵金属Pt具有良好的分散性。此外,以CO氧化为探针反应考查了不同Pt负载量对CO催化氧化性能的影响。结果表明,当Pt的负载量为5%时,催化剂对CO的完全转化温度仅为90℃。     

原子吸收光谱法测定有机锗（Ge─132）中的锗及其杂质

火焰原子吸收法测定有机锗（Ｇｅ．１３２）①中的锗，线性浓度范围为０－１．２５ｍｇ／ｍＬ，方法精度为１．２％，相对标准偏差＜２％，平均回收率为９９．５％。杂质Ｐｂ和Ａｓ用塞曼石墨炉原子吸收测定，Ｐｂ用（ＮＨ_４）_２ＨＰＯ_４＋Ｍｇ作改进剂，Ａｓ用Ｐｄ作改进剂，特征质量分别为８．２ｐｇ和８ｐｇ，相对标准偏差分别为２．１％和２．２％，并讨论了有关机理问题。     

火焰原子吸收光谱法测定光学新材料钛酸钡锶中钡和锶

本文介绍了火焰原子吸收光谱法测定光学新材料钛酸钡锶中钒和锶，研究样品制备、测试条件和共存元素干扰，本法的准确度和精密度均满意。     

调控尖晶石Co3+和Ni3+表面密度来提高催化甲烷氧化活性

天然气资源丰富、价格低廉, 因而被广泛用作燃料. 天然气的主要成分是甲烷, 未燃烧完的甲烷所产生的温室效应是二氧化碳的 21 倍, 所带来的环境问题引起越来越多的研究者关注. 但甲烷是最稳定的非极性有机小分子, C–H 键能高达434 kJ/mol, 大多数催化剂很难将其在很低的温度在完全转化. C–H 键的活化解离是催化甲烷燃烧最关键的一步, 而活化C–H 键方式主要有两大类: (1) 均裂活化机制, 一般用在贵金属催化剂上; (2) 异裂活化机制, 往往发生在过渡金属氧化物上. 比较而言, 贵金属催化剂, 尤其是 Pd, 往往具有更优异的低温催化活性, 但价格昂贵, 从而限制了其广泛使用. 因此, 开发更加高效的非贵金属催化剂用于废气中未转化的甲烷完全氧化是亟待解决的问题.含有 Co 和 Ni 的尖晶石氧化物具有良好的催化甲烷燃烧活性, 有望代替贵金属催化剂, 但要求在低于 400 °C 完全转化, 仍具有一定挑战. 另一方面, Ni3+和 Co3+哪个是活性中心, 还具有一定争议. 因此, 我们通过水热法和共沉淀法合成一系列表面暴露不同数目的 Ni3+和 Co3+来探究表面高氧化态 Co 和 Ni 跟活性之间的关系. XRD 和 TEM 结果表明, 相比于水热法合成的 Co3O4, 水热法合成的 NiCo2O4发生明显的晶格收缩现象, 这是由于在尖晶石体相中大量小半径 Ni3+(0.053 nm) 取代了大半径 Co3+(0.055 nm) 所致. 同时还发现, 水热合成的尖晶石具有多孔纳米片层结构, 相比于共沉淀法合成的尖晶石具有更大的比表面积, 催化活性也更高. XPS 分析发现, 催化甲烷燃烧的活性随着表面 (Ni3++ Co3+) 含量增加而提高. 结合文献分析和本文的实验结果推测, 表面的 Ni3+和 Co3+都可作为解离 C–H 键的活性中心. 水热 60 小时合成的 NiCo2O4纳米片表面 Ni3++ Co3+的数量最多, 所以具有最优异的催化性能, 大约在 280 °C甲烷转化 50%. 当加入 10%(体积比) 的水, 在高空速工况下对催化活性影响不大, 主要是因为长时间水热合成的尖晶石表面缺陷少, 对水的吸附弱, 这可通过 O 1s 图谱得到印证. 总之, 这些研究结果能够给甲烷活化和开发更加高效和低成本催化剂一些启示.     

Evaluation of the natural radioactivity in food and soil around uranium mining region

Journal of Radioanalytical and Nuclear Chemistry - To evaluate the radiological risk to human health associated with the ingestion of radionuclides in foods, some different plant foods cultivated...