在SWCNT生长过程中局部性的动态:扶手椅与齐格扎格的纳米管相比
Joonghan Kim1, Alister J Page, Stephan Irle
1Fukui Institute for Fundamental Chemistry, Kyoto University, Japan.
Journal of the American Chemical Society
|May 11, 2012
概括
缺陷治愈至关重要,但不足以控制单壁碳纳米管 (SWCNT) 的生长. 在这个过程中,齐格扎格SWCNTs比扶手椅SWCNTs更容易失去奇拉性.
科学领域:
- 材料科学 材料科学 材料科学
- 纳米技术纳米技术
- 计算化学计算化学
背景情况:
- 控制单壁碳纳米管 (SWCNTs) 的奇拉性对于定制它们的电子和机械性能至关重要.
- 在SWCNT生长期间的性动态仍然不完全理解.
- 当地性指数 (LOCI) 方法为分析性演变提供了一种新的方法.
研究的目的:
- 调查缺陷愈合在性控制的SWCNT生长中的作用.
- 分析在模拟生长过程中SWCNT度的时间演变.
- 为了比较长椅和曲的SWCNT在生长过程中的性稳定性.
主要方法:
- 使用量子化学分子动力学 (QM/MD) 模拟来建模SWCNT生长.
- 用局部性指数 (LOCI) 方法追踪SWCNT性随时间变化.
- 模拟使用 (5,5) 扶手椅和 (8,0) 曲的SWCNT碎片在Fe(38) 催化剂上.
主要成果:
- 缺陷愈合是一个必要的,但不足的条件,以控制chirality的SWCNT增长.
- 在生长过程中观察到性变化,即使缺陷愈合.
- 与扶手椅SWCNT相比,齐格扎格SWCNT显示出明显较差的奇拉性保留.
结论:
- 在SWCNT生长过程中缺陷清除的过程会影响局部和整体SWCNT性.
- 扶手椅SWCNTs表现出优越的稳定性,在成长过程中保持其奇拉性,而不是曲的SWCNTs.
- 了解这些动态对于开发特定SWCNT状性精确合成方法至关重要.
相关概念视频
02:05Prochirality
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
02:02Chair Conformation of Cyclohexane
The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
02:30Chirality in Nature
Chirality is the most intriguing yet essential facet of nature, governing life’s biochemical processes and precision. It can be observed from a snail shell pattern in a macroscopic world to an amino acid, the minutest building block of life. Most of the snails around the world have right-coiled shells because of the intrinsic chirality in their genes. All the amino acids present in the human body exist in an enantiomerically pure state, except for glycine - the sole achiral amino acid. The...
02:11Conformations of Cyclohexane
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
02:25Chirality
Chirality is a term that describes the lack of mirror symmetry in an object. In other words, chiral objects cannot be superposed on their mirror images. For example, our feet are chiral, as the mirror image of the left foot, the right foot, cannot be superposed on the left foot.
Chiral objects exhibit a sense of handedness when they interact with another chiral object. For example, our left foot can only fit in the left shoe and not in the right shoe. Achiral objects — objects that have...
Chiral objects exhibit a sense of handedness when they interact with another chiral object. For example, our left foot can only fit in the left shoe and not in the right shoe. Achiral objects — objects that have...