Tuning bimetallic catalysts for a selective growth of SWCNTs

Abstract

Recent advances in structural control during the synthesis of SWCNTs have in common the use of bimetallic nanoparticles as catalysts, despite the fact that their exact role is not fully understood. We therefore analyze the effect of the catalyst's chemical composition on the structure of the resulting SWCNTs by comparing three bimetallic catalysts (FeRu, CoRu and NiRu). A specific synthesis protocol is designed to impede the catalyst nanoparticle coalescence mechanisms and stabilize their diameter distributions throughout the growth. Owing to the ruthenium component which has a limited carbon solubility, tubes grow in tangential mode and their diameter is close to that of their seeding nanoparticle. By using as-synthesized SWCNTs as a channel material in field effect transistors, we show how the chemical composition of the catalysts and temperature can be used as parameters to tune the diameter distribution and semiconducting-to-metallic ratio of SWCNT samples. Finally, a phenomenological model, based on the dependence of the carbon solubility as a function of catalyst nanoparticle size and nature of the alloying elements, is proposed to interpret the results.

Ultra-sensitive NO2 gas sensors based on single-wall carbon nanotube field effect transistors: Monitoring from ppm to ppb level

“…The SWCNT diameter distribution has been extracted using the empirical law reported by Jorio [33] and co-workers, expressed as ωRBM = 248/dt, where ωRBM is the resonance frequency of the nanotube on the radial breathing mode (RBM) expressed in cm −1 and dt is the tube diameter expressed in nanometer. The reproducibility of the obtained diameter distributions have been reported in previous work [32].…”

“…SWCNT synthesis was carried out by double-hot-filament-assisted chemical vapor deposition (dHF-CVD) technique [30] in a horizontal tube furnace following similar procedure described in our previous works [31,32]. Briefly, 200 nm thermal silica coated silicon wafers (SiMat) used as…”

“…Here, we fixed the gate voltage at 15 V and the voltage between the source and drain gradually swept between 0 and 20V. A statistical analysis of the characteristic of our devices has been reported in prior work [32].…”

A deep learning approach for determining the chiral indices of carbon nanotubes from high-resolution transmission electron microscopy images

“…Such an easy-to-use tool will be of great interest to the CNT community in different research fields. A typical case is the lack of control of CNT chirality during synthesis, which is a major obstacle to the widespread use of CNTs in technological applications 46,[64][65][66][67] . This critically depends on the reliable analysis of the chirality distribution of CNT samples.…”

Melting properties of Ag$_x$Pt$_{1-x}$ nanoparticles

“…However, the complex interaction of catalyst NPs exposed to reactive carbon makes it a challenge to achieve tube growth with a specific structure [12][13][14] . For the past few years, use of bimetallic catalysts is presented by different groups as a key to achieve a structural or property control 15 . Typically, true metallic W-Co alloy NPs, seem to favour the formation of semiconducting tubes with defined chiralities 16,17 .…”