Single-Walled Carbon Nanotubes of Controlled Diameter and Bundle Size and Their Field Emission Properties

Abstract

Field emission studies were conducted on as-produced CoMoCAT single-walled carbon nanotube/silica composites with controlled nanotube diameter and bundle size. It has been observed that the as-produced nanotube material does not need to be separated from the high-surface area catalyst to be an effective electron emitter. By adjusting the catalytic synthesis conditions, single-walled carbon nanotubes (SWNT) of different diameters and bundle sizes were synthesized. A detailed characterization involving Raman spectroscopy, optical absorption (vis-NIR), SEM, and TEM was conducted to identify the nanotube species present in the different samples. The synthesis reaction temperature was found to affect the nanotube diameter and bundle size in opposite ways; that is, as the synthesis temperature increased the nanotube average diameter became larger, but the bundle size became smaller. A gradual and consistent reduction in the emission onset field was observed as the synthesis temperature increased. It is suggested that the bundle size, more than the nanotube diameter or chirality, determines the field emission characteristics of these composites. This is a clear demonstration that field emission characteristics of SWNT can be controlled by the nanotube synthesis conditions.

Reversible Solubilization and Precipitation of Carbon Nanotubes through Oxidation–Reduction Reactions of a Solubilizing Agent

“…[13,14] These sharp van Hove peaks are a characteristic feature of debundled, individually dispersed SWNTs, and indicate that the [Cu II (1) 2 ]-SWNTs mixture has a high ability to debundle SWNTs in chloroform. The characteristic absorption bands are apparent between 550 and 1200 nm, which are similar to those of the reported spectra.…”

“…The Cu complex shows a reversible sol-gel phase transition on changing the redox state of the Cu I /Cu II complexes by chemical oxidation and reduction. [16] We report herein that the solubilization and precipitation of CoMoCAT SWNTs, [13,14] which have a uniquely narrow distribution of (n,m) and small diameter (< 1 nm), can be controlled reversibly by changing the redox state of the Cu I /Cu II complexes by chemical oxidation and reduction. We have already reported the greater solubilization and debundling of purified and pristine SWNTs through the formation of complexes with a solubilizing agent by using a mechanochemical high-speed vibration milling (HSVM) technique.…”

Field Emission Properties of Single-Walled Carbon Nanotubes with a Variety of Emitter Morphologies

“…For this structure the turn-on field was 0.6 V/μm and the current density was 1 mA/cm 2 at 1.8 V/μm. 8) This suggests that the control of emitter morphology through optimization of catalytic layers and of growth conditions is crucial for further studies.…”

Switch-on Phenomena and Field Emission from Single-Walled Carbon Nanotubes Embedded in Glass

“…There are several materials used for field electron emission but the most promising one is carbon nanotubes (CNTs) (Forbes, 2012;Forbes et al, 2015). CNTs are composed of graphite sheets rolled into seamless hollow cylinders with diameter ranging from (1 nm) to about (50 nm) (Saito & Uemura, 2000), CNTs discovered by lijima (1991) and it have been attached much attention as electron source for many reasons such as ultra-small radius, high aspect ratio, high electrical conductivity (Zhang et al, 2005), high chemical stability and high mechanical strength (Bani Ali & Mousa, 2016), CNTs offer several advantages over other emitters material such as enhanced current stability, low threshold voltage, long lifetime (Hong et al, 2009) and high emission current density. These emission characterizations are directly related to the unique structure and chemical bonding of the CNTs (Cheng & Zhou, 2003).…”