Secondary nucleation and growth of ZnO

Recently we discovered that under certain conditions new crystal growth (branch) can be induced on specific crystalline planes of the same material. This is a new phenomenon and is in sharp contrast to typical nucleation and growth in which a crystal will simply grow larger in preferred directions depending on the surface energy of the specific crystalline planes. Based on our observation, we developed a sequential nucleation and growth technique offering the power to assemble complex hierarchical crystals step-by-step. However, the key questions of when and how the secondary nucleation takes place have not been answered. Here we systematically study secondary ZnO crystal growth using organic diamine additives with a range of chain lengths and concentration. We found that ZnO branches form for a narrow diamine concentration range with a critical lower and upper critical nucleation concentration limit, which increases by about a factor of 5 for each additional carbon in the diaminoalkane chain. Our results suggest that the narrow window for secondary growth is dictated by the solubility of the ZnO crystals, where the low critical nucleation concentration is determined by slight etching of the surface to produce new nucleation sites, and the upper critical concentration is determined by the supersaturation concentration. Kinetic measurements show that the induction time and growth rate increase with increasing diamine concentration and follow classical nucleation and growth theory. Observations of branch morphological evolution reveal the mechanisms guiding the tunable crystal size and morphology.     

Self-organization of double-C60 end-capped poly(ethylene oxide) in chloronaphthalene and benzene solvent mixtures

Well-defined and narrowly distributed double-C60 end-functionalized poly(ethylene oxide) (C60-PEO-C60) was prepared by reacting azido-terminated PEO with C60. The self-organization behavior of such C60-modified copolymers in different mixtures of chloronaphthalene (CN) and benzene (BN) was studied by a combination of static and dynamic laser light scattering. For C60-PEO-C60 in pure CN, a selective solvent only for C60, self-organization occurred to form a large micelle-like core-shell aggregate, probably with some C60 interlocking with each other with the collapsed PEO chains as the core. The addition of BN, a second selective solvent for core-forming PEO chains, has a significant effect on the structures and compactness of the resultant aggregates because the introduction of BN increases the stretching of the PEO chains inside the core and modifies the interfacial energy of the core-corona interface. On the other hand, for C60-PEO-C60 in pure BN, a non-solvent of C60, several smaller flower-like micelles may self-organize to form a large spherical-like aggregation complex.     

红外光谱辐射计探测器高阶非线性响应校正方法

针对傅里叶变换红外光谱辐射计辐射定标需要黑体辐射面充满仪器视场的技术特点,分析了由于入射光子流较高导致红外探测器产生非线性响应误差的机理.通过仿真包含非线性误差的黑体辐射数据,研究了非线性误差对光谱产生的影响,并根据卷积和交叉迭代两种校正方法,提出了适合校正高阶非线性响应误差的迭代方法—梯度下降法.利用傅里叶变换红外光谱辐射计进行辐射定标实验,对比卷积、交叉迭代和梯度下降法三种校正方法的效果,结果显示三种校正方法均可有效减小非线性误差,分别使拟合优度提高了0.15%,0.29%和0.39%,梯度下降法校正后的光谱数据更为准确.     

Cobalt–Nitrogen‐Doped Helical Carbonaceous Nanotubes as a Class of Efficient Electrocatalysts for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is of significant importance in the development of fuel cells. Now, cobalt–nitrogen‐doped chiral carbonaceous nanotubes (l/d ‐CCNTs‐Co) are presented as efficient electrocatalysts for ORR. The chiral template, N‐stearyl‐l/d ‐glutamic acid, induces the self‐assembly of well‐arranged polypyrrole and the formation of ordered graphene carbon with helical structures at the molecular level after the pyrolysis process. Co was subsequently introduced through the post‐synthesis method. The obtained l/d ‐CCNTs‐Co exhibits superior ORR performance, including long‐term stability and better methanol tolerance compared to achiral Co‐doped carbon materials and commercial Pt/C. DFT calculations demonstrate that the charges on the twisted surface of l/d ‐CCNTs are widely separated; as a result the Co atoms are more exposed on the chiral CCNTs. This work gives us a new understanding of the effects of helical structures in electrocatalysis.     

A new cinnamic acid glycoside from roots of Heracleum dissectum

From the roots of Heracleum dissectum Lebb., one new cinnamic acid glycoside derivative named dissectumoside (1), together with eight known compounds including three phenolics, three phenolic glycosides and two phenylpropanoic glycoside were isolated using various chromatographic methods. Among them compound 2–9 was isolated from the plant for the first time. Their structures were elucidated and identified on the basis of their physicochemical properties and by extensive analyses of NMR spectroscopy and high-resolution mass spectrometry. The results of triglyceride accumulation screening in 3T3-L1 cells showed that compounds 1, 5 and 9 exhibited significantly accelerating activities of adipogenesis in adipocytes.     

Metal-free catalytic enantioselective silylation of aromatic aldehydes in water

One-step access to chiral α-hydroxysilanes by metal-free catalytic enantioselective silylation of aromatic aldehydes in water was achieved for the first time.     

Influence of monomer structure on the properties of blue phase liquid crystal

In this paper, four kinds of polymer-stabilized blue phase liquid crystals (PS-BPLCs) with different monomer were designed and prepared. The morphology, temperature ranges and electro-optical properties of the blue phase were studied and discussed. The temperature ranges of four BPLCs are more than 90°C, and all samples can be stabilized well at room temperature. Referring to electro-optical performance, on-state voltage for mono-functional monomers systems is reduced from 75 V to 65 V at 497 nm. On-state voltage for tri-functional monomers systems is reduced from 107 V to 85 V at 497 nm. These results are helpful to the application of display and photonic devices.     

截断调和Bergman空间上小Hankel算子的代数性质

本文主要研究了截断调和Bergman空间$b_{n}^{2}$上以拟齐次函数为符号的小Hankel算子的有限秩乘积、换位子和半换位子问题.我们得到以拟齐次函数为符号的小Hankel算子的换位子和半换位子的秩总是有限的良好结论.     

蘑菇多酚氧化酶的性质及其催化反应动力学的研究

本文用二次丙酮法从磨菇中提取多酚氧化酶，用分光光度法测定多酚氧化酶催化邻苯二酚的氧化反应。实验结果表明：酶作用的最佳条件是pH等于7、温度30℃，反应活化能等于21．20kJ．mol-1。