Growth of Single‐Walled Carbon Nanotubes with Different Chirality on Same Solid Cobalt Catalysts at Low Temperature

Abstract

Single-walled carbon nanotubes (SWNTs), since reported in 1993, [1] have been regarded as a promising material owing to unique structure-dependent properties, especially in nanoelectronics applications. [2,3] Therefore, tremendous efforts have been made to pursue the specific-chirality growth of SWNTs, including designing various catalysts [4][5][6][7][8][9] and growth process con-trolling. [10][11][12] Despite of some progresses made in chirality selective synthesis of SWNTs, the mechanism for the experiment successes is far from clarification.Currently, epitaxial growth from well-defined seeds, such as solid catalysts [13][14][15][16][17] and segments of carbon nanotubes, [18][19][20][21] has been thought to be the most promising strategy to realize this goal. At present, mainly high temperature solid catalysts were developed to realize structure-controlled growth of SWNTs. For example, using Mo 2 C and WC solid catalysts, a few (2m, m) SWNTs, such as (12, 6) and (8, 4), have been Currently, designing solid catalysts at high temperature is the main strategy to realize single-walled carbon nanotubes (SWNTs) with specific chirality, meaning it is very hard and challenging to create new catalysts or faces to fit new chirality. However, low temperatures make most catalysts solid, and developing solid catalysts at low temperature is desired to realize chirality control of SWNTs. A rational approach to grow SWNTs array with different chiralities on same solid Co catalysts at low temperature (650 °C) is herein put forward. Using solid Co catalysts, near-armchair (10, 9) tubes horizontal array with ≈75% selectivity and (12, 6) tubes array with ≈82% are realized by adopting a small amount of ethanol and large amount of CO respectively. (10, 9) tubes are enriched for thermodynamic stability and (12, 6) tubes for kinetics growth rate. Both kinds of tubes show a similar symmetry to the Co (1 1 1) face with threefold symmetry for the symmetry matching nucleation mechanism proposed earlier. This method provides a new strategy to study the nucleation mechanism and more possibilities for preparing new solid catalysts to control the structure of SWNTs.

Horizontal Single-Walled Carbon Nanotube Arrays: Controlled Synthesis, Characterizations, and Applications

“…However, to utilize their template effects during the CVD process, a low reaction temperature is required to preserve the solid state. For example, Zhang et al reported a rational approach to grow horizontally aligned SWNTs with different chiralities on Co catalysts at a temperature of 650 °C, 233 as schematically illustrated in Figure 41a. On the Co(111) facet, armchair SWNTs possess the most stable edge structure because of the tight SWNT−catalyst contact.…”

“…Raman spectra of SWNTs grown using (b) thermodynamic control and (c) kinetic control. Reproduced with permission from ref . Copyright 2019 John Wiley and Sons.…”

Low temperature growth of carbon nanotubes – A review

“…Zhang et al reported chirality-controlled growth of SWCNTs by keeping the Co catalyst in solid state using lower temperature (650°C) [171]. Their method is based on the symmetry matching mechanism [172], where Co (100) face is used as template to grow horizontal arrays of near-armchair tubes (10,9) with 75% selectivity and (12, 6) with 82% selectivity.…”

“…The catalyst was spin coated on quartz substrate using Co(NO 3 ) 2 ethanol solution. In order to achieve (10,9) tubes requiring slower growth rate, they used minimum concentration of ethanol to tune the thermodynamic selectivity, whereas for (12, 6) tubes requiring higher growth rate, they used CO to provide higher concentration of carbon while etching away the excessive amorphous carbon by oxygen radicals to maintain the catalytic activity [171].…”

Assessing the reliability of the Raman peak counting method for the characterization of SWCNT diameter distributions: a cross-characterization with TEM

“…Because these methods were not easy to implement as a routine evaluation of a large number of samples, many research groups have shifted towards using variations of the same micro-Raman mapping-based alternative methodology. This methodology relies on accumulating spectra at the nodes of a grid over the surface of the sample in a Raman microscopy setup using several discrete laser lines, and counting RBM peaks as individual SWCNTs regardless of their intensity [17,18,19,20,21,22,23,24,25,26,27]. We will refer to this as the Raman peak counting, or RBM peak counting methodology.…”