In situ tracking of defect healing and purification of single-wall carbon nanotubes with laser radiation by time-resolved Raman spectroscopy

Abstract

a Defects and impurities in carbon nanotubes (CNTs), inherent to all synthesis routes, are generally addressed by thermal and/or chemical post treatments. These require atmosphere control, time-consuming temperature ramping, chemical handling, and often incur further defects. Furthermore, certain applications require nanotube treatments, such as dispersion, that cause further unwanted damage. Laser radiation was found to drastically increase purity, crystallinity and mean inter-defect distance while reducing defects, as indicated by Raman spectroscopy, effectively annealing our single-wall CNTs. Laser power density and radiation times, in other words, fluence, were optimised. When applied to CNTs with mechanically induced defects, these were almost fully eliminated. In addition to the tuned annealing of CNTs, unintentional sample modification can occur during Raman measurements if the influence of the power density and the exposure time are underestimated or disregarded. Fast laser radiation times and simple manipulation outdo common purification treatments. Additionally, selective shape and sitespecific parameters come into play such as interference patterns. Such arrangements of alternating tube quality, that is, in a CNT mat, could be interesting for preferred electronic conduction paths and find applications in, for example, interdigitated electrodes or sensors.

Chirality-independent characteristic crystal length in carbon nanotube textiles measured by Raman spectroscopy

“…There are other established methodologies for similar purification [33] [34] [35] [36] [37]. The point of this report is not the purification process itself, but the fact a high degree of graphitic crystallinity and species homogeneity may be required in CNT textiles before the λ 4 relationship applies and may be used to characterize the material.…”

Upcycling spent petroleum cracking catalyst: pulsed laser deposition of single-wall carbon nanotubes and silica nanowires

“…Raman spectra from 100 to 3500 cm À1 were obtained in a Raman spectrometer (Renishaw inVia) with 532 nm (2.33 eV) CW excitation through a 50Â objective with a numerical aperture of 0.75, producing a 2.91 mm spot (calculated in ref. 92) on the sample. The power was set to 8.8 mW (0.13 kW m À2 ), below a threshold of 2.65 kW cm À2 , beyond which modication was observed in SWCNTs.…”

“…The power was set to 8.8 mW (0.13 kW m À2 ), below a threshold of 2.65 kW cm À2 , beyond which modication was observed in SWCNTs. 92 All Raman spectra were baselinecorrected with a straight line through the middle of the base noise over the complete range, if not specied otherwise, and peaks were tted with Lorentzian functions.…”

Scaling up single-wall carbon nanotube laser annealing: effect on electrical resistance and hydrogen adsorption

“…Point (1) easily nds proponents in CNT electronics and threads. In the previous iteration of this study, 20 we examined current purication techniques, arguing points (2) to (5). Additionally, most are limited to purication and do not heal crystal defects.…”

“…Accordingly, we presented the rst in-depth study of CNT purication and healing, with power-and timeresolved laser radiation, standing out as fast, contactless and ambient. 20 A thorough review of the state of the art, including sample, atmosphere and laser characteristics, revealed a limited body of literature with understudied phenomena, oen tangential to other core subjects.…”