Abstract
Chirality-selective synthesis of single-walled carbon nanotubes (SWNTs) has been a research goal for the last two decades and is still challenging due to the difficulty in controlling the atomic structure in the one-dimensional material. Here, we develop an optimized approach for controlling the chirality of species by tuning the oxidation degree of Co catalyst. Predominant synthesis of (6,4) SWNTs is realized for the first time. The detailed mechanism is investigated through a systematic experimental study combined with first-principles calculations, revealing that the independent control of tube diameter and chiral angle achieved by changing the binding energy between SWNTs (cap and tube edge) and catalyst causes a drastic transition of chirality of SWNTs from (6,5) to (6,4). Since our approach of independently controlling the diameter and chiral angle can be applied to other chirality species, our results can be useful in achieving the on-demand synthesis of specific-chirality SWNTs.
Highlights
Owing to the excellent electrical and optical properties reported by many researchers[1, 2], single-walled carbon nanotubes (SWNTs) are expected to be utilized in a wide range of applications, e.g., in thin film transistors, photodetectors in THz range, and chemical sensors[3,4,5]
It is still challenging to develop a method for synthesizing SWNTs with a specific chirality, which can be used for producing various chiral species, especially in the case of species for which a preferential synthesis has not yet been realized
Our result is very important in terms of achieving the dominant growth of (6,4) SWNTs and providing a new strategy for the chirality-selective synthesis of SWNTs, thereby contributing to the on-demand for the synthesis of specific-chirality SWNTs, which is regarded as an ultimate goal
Summary
Owing to the excellent electrical and optical properties reported by many researchers[1, 2], single-walled carbon nanotubes (SWNTs) are expected to be utilized in a wide range of applications, e.g., in thin film transistors, photodetectors in THz range, and chemical sensors[3,4,5]. We report the preferential growth of (6,4) SWNTs with high purity (∼57%) achieved by precisely controlling the oxidation degree of Co, where the basic concept itself is different from previous catalyzed growth controlling (1-1) catalyst type, (1-2) gas phase reaction, and (1-3) crystal phase of catalyst. The high quantum yield (calculated from theoretically predicted value of photoluminescence (PL) intensity (IPL) and absorption efficiency (Wab) (IPL/Wab)) of (6,4) SWNTs23 (1.89 times higher than that of (6,5), which is the highest value achieved for the preferential synthesis of specific-chirality SWNTs) can contribute in developing future high-performance optoelectrical devices using chirality-controlled SWNTs (Fig. 1c). Surface states of the catalysts were examined using X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectrometry (EDX), X-ray absorption fine structure (XAFS), and extended XAFS (EXAFS) (see Methods section for detailed information)
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