A DNA-based approach to the carbon nanotube sorting problem

Carbon nanotube sorting, i.e., the separation of a mixture of tubes into different electronic types and further into species with a specific chirality, is a fascinating problem of both scientific and technological importance. It is one of those problems that are easy to describe but difficult to solve. Single-stranded DNA forms stable complexes with carbon nanotubes and disperses them effectively in water. A particular DNA sequence of alternating guanine (G) and thymine (T) nucleotides ((GT) _n , with n = 10 to 45) self-assembles into an ordered supramolecular structure around an individual nanotube, in such a way that the electrostatic properties of the DNA-carbon nanotube hybrid depend on tube structure, enabling nanotube separation by anion-exchange chromatography. This review provides a summary of the separation of metallic and semiconducting tubes, and purification of single (n, m) tubes using the DNA-wrapping approach. We will present our current understanding of the DNA-carbon nanotube hybrid structure and separation mechanisms, and predict future developments of the DNA-based approach. This article is published with open access at Springerlink.com     

掺杂对钛酸锶压敏陶瓷性能的影响

研究了施主掺杂和受主掺杂对SrTiO3压敏陶瓷材料微观结构和电性能的作用。研究结果表明，La、Nb进行双施主掺杂时按一定比例能获得较低的压敏电压；以La进行单施主掺杂，含量为1．2mol％时，压敏电压最低。双施主掺杂的压敏电压要高于单施主的电压。以CuO进行受主掺杂的效果要好于以MnCO3进行受主掺杂的效果。     

ZnO纳米线阵列的侧面生长机理

通过一种简单的无催化剂存在的气相生长工艺制备了侧面长成梳状结构的ZnO纳米线阵列。沿[0001]方向生长的ZnO纳米线按照100～500nm的间隔有规律地排列在梳底一侧。单晶梳底沿着[2110]方向生长到±(0110)和±(0001)面终止。所得均一纳米线的直径和长度分别为40～100nm和0.5～2.0μm。纳米线阵列的侧面生长成为微米梳,是气体分子自组装成纳米线和一步法组装成微米结构的重要例子。本文详细讨论了ZnO纳米线阵列生长成为微米梳的生长机理。     

TiO2气敏传感器研究进展

TiO2气敏传感器具有工作温度低、灵敏度高、响应速度快、制备简单等独特优点,已经成为人们关注的热点.本文概述了TiO2材料的导电类型和气敏机理,介绍了TiO2气敏传感器两个方面的研究进展:运用传统掺杂方法和利用纳米技术改善传感器性能;展望了TiO2气敏传感器今后的研究和发展方向.     

太阳能电池中单分散性PbSe量子点的微波法合成和表征(英文)

量子点PbSe被提出能应用于太阳能电池中,采用微波方法,用乙二醇作为溶剂来合成单分散性的纳米晶体PbSe,并用X射线衍射、红外光谱、透射电镜、同步热分析仪、原子力显微镜、扫描电镜,X射线能谱仪来表征。实验证明,在PbSe的合成过程中,乙二醇是良好的还原剂和分散剂。     

Mapping of Domain Orientation and Molecular Order in Polycrystalline Semiconducting Polymer Films with Soft X‐Ray Microscopy

We utilize scanning transmission X‐ray microscopy (STXM) to study the domain structure of polycrystalline films of the semiconducting polymer poly(9,9’‐dioctylfluorene‐co‐benzothiadiazole) (F8BT). By taking several images at different orientations of the film with respect to the polarization of the X‐ray beam, we are able to compute quantitative maps of molecular alignment/order and molecular orientation, including both the backbone direction and phenyl ring plane orientation, as well as the in‐plane and out‐of‐plane components. We show that polycrystalline F8BT films consist of well‐ordered micron‐sized domains with the transition from one domain orientation to another characterized either by a smooth transition of orientation or by ～ 200 nm wide disordered domain boundaries. The morphology of the disordered domain boundaries resemble the electroluminescence patterns observed previously in F8BT light‐emitting field‐effect transistors suggesting that charge trapping at these disordered domain boundaries facilitates charge recombination in ambipolar operation. A relatively narrow distribution of local average tilt angles is observed that correlates with film structure, with the ordered domains in general showing a higher tilt angle than the disordered domain boundaries. We also use secondary electron detection to image the surface domain structure of polycrystalline F8BT films and demonstrate that the polycrystalline structure extends to the film/air interface. Finally, we calculate ideal NEXAFS spectra corresponding to a perfect F8BT crystal oriented with the 1s – π^* transition dipole moment parallel and perpendicular to the electric field vector of a perfectly linearly polarized X‐ray beam.