A Microwave-Assisted, Solvent-Free Approach for the Versatile Functionalization of Carbon Nanotubes

Abstract

While the functionalization of carbon nanotubes (CNTs) has attracted extensive interest for a wide range of applications, a facial and versatile strategy remains in demand. Here, we report a microwave-assisted, solvent-free approach to directly functionalize CNTs both in raw form and in arbitrary macroscopic assemblies. Rapid microwave irradiation was applied to generate active sites on the CNTs while not inducing excessive damage to the graphitic network, and a gas-phase deposition afforded controllable grafting for thorough or regioselective functionalization. Using methyl methacrylate (MMA) as a model functional group and a CNT sponge as a model assembly, homogeneous grafting was exhibited by the increased robust hydrophobicity (contact angle increase from 30 to 140°) and improved structural stability (compressive modulus increased by 135%). Therefore, when our MMA-functionalized CNTs served as a solar absorber for saline distillation, high operating stability with a superior water evaporation rate of ∼2.6 kg m–2 h–1 was observed. Finally, to highlight the efficacy and versatility of this functionalization approach, we fabricated asymmetrically hydrophobic CNT sponges by regioselective functionalization to serve as a moisture-driven generator, which demonstrated a stable open-circuit voltage of 0.6 mV. This versatile, solvent-free approach can complement conventional solution-based techniques in the design and fabrication of multifunctional nanocarbon-based materials.

Chromatographic Assessment of Organic Compounds Using Carbon Nanotubes: The Relationship between Affinity and Dispersibility

“…Apparently, the retention times on both columns, in particular the MWCNT column, exhibited a trend similar to that of the pristine SWCNT column. The MWCNTs used in this study show relatively low crystallinity and long length [27], and both structural features can also be seen in the characteristics of the supergrowth SWNCTs. The results suggest that CNT curvature has an insignificant effect on the retention of these aromatic compounds.…”

Stable dispersion of carbon nanotubes in a molten salt of KNO3–NaNO3–NaNO2–LiNO3–LiOH

“…Moreover, some solventfree approaches for the controllable functionalization of CNTs have also been developed, which also do not destroy the CNT length. 14 Looking for dispersion methods of the CNTs with high length-to-diameter ratios will be very important to fully analyze the nature of the CNTs, and bring opportunities for the better use of the CNTs. 15 In dispersion technology with no damage to the length of CNTs, researchers have proposed using super acids such as oleum and chlorosulfonic acid as the solvents, because CNTs are rich in π electrons, and the electrons can interact with the H + of the super acids.…”

“…Moreover, some solvent-free approaches for the controllable functionalization of CNTs have also been developed, which also do not destroy the CNT length. 14 Looking for dispersion methods of the CNTs with high length-to-diameter ratios will be very important to fully analyze the nature of the CNTs, and bring opportunities for the better use of the CNTs. 15…”