Helical Carbon Nanotubes: Catalytic Particle Size-Dependent Growth and Magnetic Properties

Abstract

The exact knowledge of helical carbon nanotube (HCNT) growth mechanism has not yet been completely clarified, and effective synthesis of high-purity helical carbon nanotubes in high yield still remains a tremendous challenge. In this study, HCNTs were synthesized via a catalytic chemical vapor deposition method using Fe nanoparticles as catalysts. We performed systematic experiments to investigate the specific effect of catalytic particle size (CPS) on the selective growth of HCNTs, such as on the morphology, yield, mobility of carbon atoms, and HCNT purity of carbon products. Our study showed that the CPS plays a key role in the selectivity to HCNTs, yield, and morphology of the carbon products, and a small catalytic particle is favorable to HCNT formation. We hope that this result may give a beneficial suggestion to obtain highly pure HCNTs. A CPS-dependent growth mechanism for HCNTs was finally proposed. Magnetic measurements demonstrated that the HCNTs are ferromagnetic properties and show high magnetization at room temperature.

Helical Carbon Nanotubes: Intrinsic Peroxidase Catalytic Activity and Its Application for Biocatalysis and Biosensing

“…Similar phenomena have also been noted in previous reports. [22,31] Although HCNTs have been prepared for many years, to the best of our knowledge, their application in bioassay has not hitherto been reported. One possible reason may be their poor solubility in water.…”

Engineering of Micro‐ and Nanostructured Surfaces with Anisotropic Geometries and Properties

“…Thermal CVD on substrate bound Fe catalyst nanoparticles was also be used to fabricate helical CNTs, though the alignment was poor compared to the co-pyrolysis method. [ 168 ] CVD of helical CNTs from fl oating catalyst was achieved by injecting a xylene-ferrocene mixture having dissolved indium isopropoxide and tin isopropoxide (sources for In and Sn respectively) in a CVD furnace. Formation of helices was explained by asymmetric growth on compound catalyst nanoparticles (Fe-In) due to different carbon precipitation rates in the segregated phases of the particle.…”

Carbon nanotubes and helical carbon nanofibers grown by chemical vapour deposition on C60 fullerene supported Pd nanoparticles

“…al synthesized coiled CNFs with additives like tiophene and H 2 S and suggested a growth mechanism for coiled carbon fibers based on the anisotropic extrusion of carbon over a catalyst particle [18,19]. It has been shown that it is possible to synthesize HCNTs and HCNFs on Fe nano particles at temperatures below 500° C [20,21].…”