Effect of ethanol soaking on the structure and physical properties of carbon nanocoils

Abstract

Carbon nanocoils (CNCs), which are quasi-one-dimensional nanomaterials, exhibit a unique helical morphology and polycrystalline-amorphous structure. In this study, we investigated the effect of ethanol soaking on the structure and physical properties of CNCs. The CNCs were soaked in ethanol for up to one year. Structural examinations revealed that ethanol permeated into the CNCs through defects and vacancies. The permeation of ethanol molecules increased the stress inside the CNCs, resulting in the rearrangement of their sp2 grains, which alleviated the stress. This improved the coherence of graphite grains. Meanwhile, the permeation of ethanol molecules separated the sp2 grains and graphite layers within the grains. Prolonged soaking resulted in a gradual change in the chemical structure of the CNCs. After 346 days of soaking, the contents of both the C-O- and C=O bonds increased, resulting in a decrease in the C:O atomic ratio from 48 to 29. The increase in the C-O- and C=O bond contents facilitated the transformation of the sp2 sites to other saturation sites. These physical and chemical changes in the structure of the CNCs reduced the concentration of conduction electrons and enhanced the electron hopping barrier and phonon scattering, thus reducing their electrical conductivity and thermal diffusivity significantly.