Production of Carbonaceous Materials with Various Lengths in Small Spheroidal Fullerenes and Long CNTs by Tunable Multi‐walled Carbon Nanotube Cutting

Abstract

Tunable cutting of multi‐walled carbon nanotubes (CNTs) using high pressure homogenizer and/or HNO3/H2SO4 solution was accomplished, resulting in the production of short CNTs with minimum length of 35 nm. Field emission scanning electron microscopy (FE‐SEM) and Zeta sizer analysis showed significant reduction of CNT length from this tunable cutting (e.g. from long and entangled pristine CNTs at about 20 µm to ≥1000 nm, ~400 nm, ~200 nm, and ~100 nm via high pressure jet‐spraying cutting within 5 h, while chemical cutting process using greatly longer hours (48 h) showed a reduction only to about 1000 nm). When CNT sample of average 1000 nm length previously shortened by HNO3/H2SO4 was subjected to the high pressure jet‐spraying cutting process, the reduction progressed faster (≤1 h), producing ≥35 nm. Fourier transform infrared spectra and thermogravimetric analysis (TGA) indicated restricted formation of hydrophilic functional groups such as carboxylic group and hydroxyl group in the high pressure jet‐spraying cutting, whereas an intensive formation of hydrophilic functional groups on the surface of shortened CNT samples was found after chemical cutting. Such short CNT samples would fulfill the requirements for carbonaceous materials with various lengths in small spheroidal fullerenes and long CNTs. The short CNTs produced are promising for scientific and technological applications in many fields such as electronics, diagnostics, pharmaceuticals, biomedical engineering, and environmental or energy industries.