Electronic interactions between "pea" and "pod": the case of oligothiophenes encapsulated in carbon nanotubes

One of the most challenging strategies to achieve tunable nanophotonic devices is to build robust nanohybrids with variable emission in the visible spectral range, while keeping the merits of pristine single-walled carbon nanotubes (SWNTs). This goal is realized by filling SWNTs ("pods") with a series of oligothiophene molecules ("peas"). The physical properties of these peapods are depicted by using aberration-corrected high-resolution transmission electron microscopy, Raman spectroscopy, and other optical methods including steady-state and time-resolved measurements. Visible photoluminescence with quantum yields up to 30% is observed for all the hybrids. The underlying electronic structure is investigated by density functional theory calculations for a series of peapods with different molecular lengths and tube diameters, which demonstrate that van der Waals interactions are the bonding mechanism between the encapsulated molecule and the tube.     

Why semiconducting single-walled carbon nanotubes are separated from their metallic counterparts

The separation of single-walled carbon nanotubes (SWNTs) according to their electronic structure has attracted much recent attention. In many cases, metallic SWNTs are separated from semiconducting SWNTs and enriched in the supernatant due to stronger interaction between metallic SWNTs and adsorbates. However, the inverse separation of semiconducting from metallic SWNTs is often observed. In this computational study, the underlying mechanism is elucidated by density functional theory. We show that the shape of an aromatic molecule, the degree of hybridization between a molecule and a SWNT, and the oxidative state of SWNTs can affect the type of enriched SWNTs. In principle, one can control the type of enriched SWNTs by selecting a structurally compatible aromatic molecule or changing the hole concentration of the SWNTs.     

碳纳米管及其掺杂氧化物半导体气敏传感器

碳纳米管气敏传感器以其工作温度低和最低检出限较低等优点而备受关注,而碳纳米管掺杂氧化物半导体气敏传感器兼备了氧化物半导体气敏传感器和碳纳米管气敏传感器二者的优点,具有灵敏度较高、最低检出限低和工作温度低等特性。综述了这两类传感器的研究进展,介绍了其气敏机理,并对相应存在的问题及今后的发展趋势进行了概述。     

Physical properties of CVD boron-doped multiwalled carbon nanotubes

The effects of boron doping and electron correlation on the transport properties of CVD boron-doped multiwalled carbon nanotubes are reported. The boron-doped multiwalled carbon nanotubes were characterized by TEM as well as Raman spectroscopy using different laser excitations (viz. 488, 514.5 and 647 nm). The intensity of the D-band laser excitation line increased after the boron incorporation into the carbon nanotubes. The G-band width increased on increasing the boron concentration, indicating the decrease of graphitization with increasing boron concentration. Electrical conductivity of the undoped and boron-doped carbon nanotubes reveal a 3-dimensional variable-range-hopping conductivity over a wide range of temperature, viz. from room temperature down to 2 K. The electrical conductivity is not found to be changed significantly by the present levels of B-doping. Electron Paramagnetic Resonance (EPR) results for the highest B-doped samples showed similarities with previously reported EPR literature measurements, but the low concentration sample gives a very broad ESR resonance line.     

Electronic structure of boron-doped diamond with B–H complex and B pair

The electronic structure of boron–hydrogen complex and boron pair in diamond are studied by first-principles density-functional calculations with supercell models. The electronic structure calculated for the B–H complexes with C_2v or C_3v symmetry and the nearest-neighbor B pair is used to interpret recent experimental results such as B 1s x-ray photoemission spectroscopy, ¹¹B nuclear quadruple resonance and B K-edge x-ray absorption spectroscopy, which cannot be explained solely by the isolated substitutional boron.     

Encapsulation of cellulose chain into carbon nanotubes and boron nitride nanotubes

Encapsulation of cellulose chain into carbon nanotubes and boron nitride nanotubes was investigated to find out the possibility of band gap engineering in these nanotubes. The structural stability and the electronic properties of the zigzag carbon nanotubes and boron nitride nanotubes filled with cellulose chain were studied using density functional theory. It was found that encapsulation of cellulose chain into nanotubes was an exothermic process. The metallic properties of the carbon nanotubes did not change by cellulose encapsulation. The semiconductor and insulator nanotubes filled with cellulose were shown semiconducting properties. The energy band gap of these tubes was decreased by cellulose encapsulation. The results demonstrated the ability of band gap engineering through the encapsulation of cellulose chain into carbon nanotubes and boron nitride nanotubes.     

Synthesis of individual ultra-long carbon nanotubes and transfer to other substrates

In this article, we report the synthesis of ultra-long carbon nanotubes (CNTs) by thermal chemical vapour deposition method. Ultra-long, individual and aligned CNTs were directly grown on a flat silicon substrate. The orientation of the nanotubes was found parallel to the gas flow direction. The ultra-long CNTs were grown with different transition metallic salts, such as nickel chloride, iron (III) chloride, cobalt acetate and ruthenium acetate, as the catalysts. The influence of the growth conditions, such as growth temperature, reactive gas flow on the length and alignment of the CNTs was studied in detail. By using different catalysts, ultra-long single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) were successfully grown. These ultra-long CNTs were transferred to other substrates by two methods. (1) The first method is to use polydimethylsiloxane as a stamp. (2) The second method is to use KOH as an etching agent. The diameter and length of the CNTs were characterised by transmission electron microscope, scanning electron microscope, atomic force microscope and Raman spectroscopy. The results indicate that the length of the CNTs can reach up to 4?mm. The diameter of the SWCNTs is in the range of 0.7–2.1?nm and the diameter of the MWCNTs is approximately 150?nm.     

纳米碳管与活性炭复合电极电吸附脱盐性能的研究

为考察纳米碳管（CNTs）、活性炭（AC）及其复合电极的电吸附脱盐性能，将其粉末压制成电极，组装成脱盐器，比较电极电吸附脱盐能力和脱盐能耗。结果表明，在活性炭电极中添加纳米碳管有效地降低了电极电阻和脱盐能耗，少量纳米碳管的添加能在一定程度上提高其电极比表面积、孔容以及在盐水中的比电容；当复合电极中纳米碳管的含量为10％时，其电极在盐水中的电吸附比电容达到113.5F/g，其电极脱盐效果最为显著，其脱盐耗能比活性炭电极降低约67％左右。     

碳纳米管的组装

碳纳米管具有很多奇异的物理、化学性能．组装后的碳纳米管在光、磁、电、催化、机械等方面都展现出更加优异的特性，具有广泛的应用前景。本文对碳纳米管组装技术的现状和最新研究进展情况进行了综述，也讨论了组装机理．并对碳纳米管组装的未来进行了展望。     

Strategies for post-synthesis alignment and immobilization of carbon nanotubes

Carbon nanotubes (CNTs) have developed into a standard material used as a building block for nanotechnological developments. Based on the unique properties that make CNTs useful for many different applications in nanotechnology, optics, electronics, and material science, there has been a rapid development of this research area and many different applications have emerged in the past few years. Frequently, the alignment and immobilization of CNTs play an important role for many applications and different strategies, in particular post-synthesis approaches, can be applied. Recent developments of different techniques to immobilize and align carbon nanotubes are discussed and classified into three main categories: chemical immobilization and alignment, physical immobilization and alignment, and the use of external fields for these purposes. Many of the techniques involve multiple steps and may also cross these rather crudely defined boundaries. As such, the techniques are classified according to their most important or unique step.