喹啉缩氨基硫脲Co(Ⅲ)/Cd(Ⅱ)配合物的合成、结构和DNA结合性质

合成并通过单晶衍射、元素分析、红外光谱表征了配合物 [CoL₂]Cl·2CH₃OH (1)和[CdL₂] (2)的结构(HL为喹啉-8-甲醛缩硫代氨基脲).单晶衍射结果表明,配合物1和2中金属离子采取相同的配位模式,分别与来自硫醇化脱质子的配体L^-的4个N原子和2个S原子配位,采取扭曲的八面体配位构型.配合物1和2能够与DNA结合,结合模式分别为静电结合和部分插入.     

Fabrication of double- and multi-walled carbon nanotube transparent conductive films by filtration-transfer process and their property improvement by acid treatment

Double-walled carbon nanotubes (DWCNTs) and two kinds of vertically aligned multi-walled carbon nanotubes were employed as raw materials to fabricate transparent conductive films (TCFs). DWCNTs constructed the densest conductive network at the same transmittance, and the corresponding TCFs showed the best performance (320 Ω/□ at 75.0% T). The ratio of dc conductivity to optical conductivity (σ _dc/σ _op) of the as-dispersed DWCNTs was 3.88. The as-obtained TCFs were dipped in HNO₃ solution to improve their performances. Attributed to the removal of sodium dodecyl sulfate molecules, reduction of film thickness, and doping with electron acceptors (such as oxygen), the surface resistance after HNO₃ treatment decreased. The σ _dc/σ _op ratio of the DWCNTs was further increased to 5.24.     

Embedded high density metal nanoparticles with extraordinary thermal stability derived from guest-host mediated layered double hydroxides

A chemical precursor mediated process was used to form catalyst nanoparticles (NPs) with an extremely high density (10(14) to 10(16) m(-2)), controllable size distribution (3-20 nm), and good thermal stability at high temperature (900 °C). This used metal cations deposited in layered double hydroxides (LDHs) to give metal catalyst NPs by reduction. The key was that the LDHs had their intercalated anions selected and exchanged by guest-host chemistry to prevent sintering of the metal NPs, and there was minimal sintering even at 900 °C. Metal NPs on MoO(4)(2-) intercalated Fe/Mg/Al LDH flakes were successfully used as the catalyst for the double helix growth of single-walled carbon nanotube arrays. The process provides a general method to fabricate thermally stable metal NPs catalysts with the desired size and density for catalysis and materials science.     

喹啉缩氨基硫脲Co(Ⅲ)/Cd(Ⅱ)配合物的合成、结构和DNA结合性质

合成并通过单晶衍射、元素分析、红外光谱表征了配合物 [CoL₂]Cl·2CH₃OH (1)和[CdL₂] (2)的结构(HL为喹啉-8-甲醛缩硫代氨基脲).单晶衍射结果表明,配合物1和2中金属离子采取相同的配位模式,分别与来自硫醇化脱质子的配体L-的4个N原子和2个S原子配位,采取扭曲的八面体配位构型.配合物1和2能够与DNA结合,结合模式分别为静电结合和部分插入.     

Large scale intercalated growth of short aligned carbon nanotubes among vermiculite layers in a fluidized bed reactor

Short aligned carbon nanotubes (CNTs) were intercalated grown among vermiculite layers from ethylene using a simple fluidized bed chemical vapor deposition (CVD) process. The length of CNTs ranged from 0.5 to 1.5 μm after a synthesizing duration of 1-5 min at 650 °C. The as-grown CNTs vertically aligned to the vermiculite layers were with the mean outer and inner diameter of 6.7 and 3.7 nm, respectively. A CNT yield of 0.22 g/g_cat was obtained for a 5-min growth. Those indicated that the fluidized bed CVD was an effective way for mass production of short CNTs.     

Permittivity and its temperature dependence in hexagonal structure BN dominated by the local electric field

This paper presents an analysis of the local electric field in hexagonal boron nitride (h-BN) by introducing a modified parameter. Based on the determination of the modified parameter of h-BN, the revised Lorenz equation is developed. Then the permittivity at high temperature and in the microwave frequency is investigated. In addition, this equation is derived for evaluating the temperature coefficient of the permittivity of h-BN. The analyses show that the permittivity increases with increasing temperature, which is mainly attributed to the positive temperature coefficient of the ionic polarizability.     

用密度泛函和XANES计算研究Zn2+在水锰矿表面的吸附和沉淀

用密度泛函理论(density function theory, DFT)和X射线近边结构(X-ray absorption near edge structure, XANES)模拟计算了不同酸度(pH = 7.0, 7.5 和 8.0)下Zn(II)在水锰矿表面的吸附. 优化的几何结构表明, 只有双边吸附方式的水解簇既能解释H+ 释放机制, 又能与扩展X射线吸收精细结构(extended X-ray absorption fine structure, EXAFS)实验键长值相吻合. 吸附能计算表明, 各种吸附方式的稳定性双边(DE)>双角(DC)>B型单边(SE-B)>A型单边(SE-A)；水解能计算表明各种吸附态Zn2+ 均比溶液中水合锌离子易水解. 各种吸附簇模型的XANES计算谱未能与实验谱吻合, 即, 表面发生的并不是简单的吸附. pH=7.5和pH=8.0吸附样品的XANES实验谱与Zn5(OH)6(CO3)2的实验谱非常接近, 因此认为pH=7.5和pH=8.0下Zn(II)在水锰矿表面发生沉淀, Zn(II)是Zn—O八面体和Zn—O四面体的混合, 它们按类似Zn5(OH)6(CO3)2结构中的八面体和四面体排列方式排列. pH=7.0时, Zn(II)在水锰矿表面发生的主要是边连接方式的吸附.     

Modulating the diameter of carbon nanotubes in array form via floating catalyst chemical vapor deposition

Based on the analysis of catalyst particle formation and carbon nanotube (CNT) array growth process in floating catalyst chemical vapor deposition (CVD), delicately controlled gaseous carbon sources and catalyst precursors were introduced into the reactor for the controllable growth of CNT array. The low feeding rate of ferrocene was realized through low-temperature sublimation. With less ferrocene introduced into the reactor, the collision among the in situ formed iron atoms decreased, which led to the formation of smaller catalyst particles. The mean diameter of the CNT array, grown at 800^oC, decreased from 41 to 31 nm when the ferrocene-sublimed temperature reduced from 80 to 60^oC. Furthermore, low growth temperature was adopted in synthesis, through the modulation of the CNT diameter, by controlling the sintering of catalyst particles and the collision frequency. When the growth temperature was 600^oC, the as-grown CNTs in the array were with a mean diameter of 10.2 nm. If propylene was used as carbon source, the diameter can be modulated in similar trends. The diameter of CNT can be modulated by the parameter of the operation using the same substrate and catalyst precursor without other equipment or previous treatment. Those results provide the possibility for delicately controllable synthesis of CNT array via simple floating catalyst CVD.     

Coupled process of plastics pyrolysis and chemical vapor deposition for controllable synthesis of vertically aligned carbon nanotube arrays

Efficient conversion of waste plastics into advanced materials is of conspicuous environmental, social and economic benefits. A coupled process of plastic pyrolysis and chemical vapor deposition for vertically aligned carbon nanotube (CNT) array growth was proposed. Various kinds of plastics, such as polypropylene, polyethylene, and polyvinyl chloride, were used as carbon sources for the controllable growth of CNT arrays. The relationship between the length of CNT arrays and the growth time was investigated. It was found that the length of aligned CNTs increased with prolonged growth time. CNT arrays with a length of 500 μm were obtained for a 40-min growth and the average growth rate was estimated to be 12 μm/min. The diameter of CNTs in the arrays can be modulated by controlling the growth temperature and the feeding rate of ferrocene. In addition, substrates with larger specific surface area such as ceramic spheres, quartz fibers, and quartz particles, were adopted to support the growth of CNT arrays. Those results provide strong evidence for the feasibility of conversion from waste plastics into CNT arrays via this reported sustainable materials processing.     

EXAFS研究不同酸度下Zn2+在水锰矿表面的吸附和沉淀

用EXAFS(extended X-ray absorption fine structure)研究了pH 7.00、7.50、8.00时Zn(II)在水锰矿表面的吸附和沉淀. Zn第一层配位Zn—O距离约为0.202 nm, 不随pH变化, 表明Zn的构型为四面体和八面体的混合物. 在pH 7.00 条件下, Zn—Mn距离约为0.300 nm, Zn主要以双边形式吸附在水锰矿(010)或(110)面. pH 7.50和pH 8.00时, 大部分的Zn在表面形成了结构类似于沉淀样品的多核羟基络合物, 其中0.311 nm Zn—Zn距离对应两个Zn八面体连接, 而0.353 nm Zn—Zn距离对应Zn八面体和Zn四面体连接.