Diameter-controlled growth of aligned single-walled carbon nanotubes on quartz using molecular nanoclusters as catalyst precursors

Abstract

Molecular nanoclusters containing Fe and Mo atoms have been used as catalyst precursors for the growth of single-walled carbon nanotubes (SWNTs) on stable temperature (ST)-cut quartz substrates by chemical vapor deposition. Attribute to the uniform catalyst nanoparticles and the confinement effect of the crystalline substrates, well-aligned SWNTs with narrow diameter distribution have been synthesized. Atomic force microscopy measurements show that the mean diameter of the nanotubes obtained by thermal decomposition of ethanol at 900°C is 0.76 ± 0.16 nm, which is the smallest among all reported results for aligned SWNTs. The mean diameter of the nanotubes increases with growth temperature. In addition to using identical nanoclusters as the catalyst precursors, the avoidance of annealing treatment of catalyst precursors is also a key point for obtaining SWNTs with controlled diameters. Using these identical nanoclusters as catalyst precursors and carefully tuning the growth parameters make us closer to the ultimate goal of controlling the chirality of SWNTs. molecular nanoclusters, single-walled carbon nanotubes, diameter control, quartz, catalysts Citation:Peng F, Luo D, Sun H, et al. Diameter-controlled growth of aligned single-walled carbon nanotubes on quartz using molecular nanoclusters as catalyst precursors.

Understanding the “Activation” of the Nanocluster [HxPMo12O40⊂H4Mo72Fe30(O2CMe)15O254(H2O)98-y(EtOH)y] for Low Temperature Growth of Carbon Nanotubes

“…6 compare the same FeMoC sample before and after a 15 min dwell at 925°C under a 5% hydrogen atmosphere. The AFM images provided no evidence of catalyst coarsening prior to injection of carbon precursor, in agreement with prior work with FeMoC [17,21]. This suggests that catalyst coarsening is occurring during CNT growth.…”

“…We show that the mechanism for FeMoC ''activation'' is due to the sufficient reduction of the metal oxide components. Consideration of prior reports, including our own, of using FeMoC as a single source molecular procatalyst precursor [16][17][18][19][20][21] suggest that their partial failures to perform as expected were due to insufficient activation or partial sublimation of the metal oxide resulting in a smaller than necessary catalyst size [45]. These reports underline the importance of the catalyst pre-treatment step in ''activating'' FeMoC and related pro-catalyst for growth of CNTs.…”

“…8, and clearly show MWCNT growth at all growth Fig. 9 The approximate CVD heating profile and conditions employed by a An et al [16], b Anderson et al [17], c Edgar et al [18], d Peng et al [21], and e, f this work. The CVD temperature profile is depicted by the red line, and the CVD conditions for air (blue), H 2 gas (green), inert gas (orange), and carbon precursor (black) are also depicted (Color figure online) temperatures tested.…”

“…The excessive growth temperatures required with FeMoC appear to counter previous work with Fe-Mo catalyst systems demonstrating CNT growth at temperatures as low as 550°C [22][23][24]. It should be noted that both Fe and Mo have been shown to be efficient catalysts both independently and as mixed metal nanoparticles [25][26][27][28][29][30]; thus, FeMoC should be ''active'' for CNT growth, but under the prior growth conditions studied it is not [16][17][18][19][20][21].…”

“…As with the report by Liu, we found that additional Fe is required in order to achieve SWNT growth at 900°C. Later, Edgar et al [18], Jeon et al [19], Goss et al [20], Peng et al [21], demonstrated CNT growth by employing growth temperatures in the range of 880-1010°C without the use of additional catalyst promoters. The excessive growth temperatures required with FeMoC appear to counter previous work with Fe-Mo catalyst systems demonstrating CNT growth at temperatures as low as 550°C [22][23][24].…”