High-Efficiency Ion Enrichment inside Ultra-Short Carbon Nanotubes

Abstract

The ion-enrichment inside carbon nanotubes (CNTs) offers the possibility of applications in water purification, ion batteries, memory devices, supercapacitors, field emission and functional hybrid nanostructures. However, the low filling capacity of CNTs in salt solutions due to end caps and blockages remains a barrier to the practical use of such applications. In this study, we fabricated ultra-short CNTs that were free from end caps and blockages using ball milling and acid pickling. We then compared their ion-enrichment capacity with that of long CNTs. The results showed that the ion-enrichment capacity of ultra-short CNTs was much higher than that of long CNTs. Furthermore, a broad range of ions could be enriched in the ultra-short CNTs including alkali-metal ions (e.g., K+), alkaline-earth-metal ions (e.g., Ca2+) and heavy-metal ions (e.g., Pb2+). The ultra-short CNTs were much more unobstructed than the raw long CNTs, which was due to the increased orifice number per unit mass of CNTs and the decreased difficulty in removing the blockages in the middle section inside the CNTs. Under the hydrated-cation–π interactions, the ultra-short CNTs with few end caps and blockages could highly efficiently enrich ions.

Open‐Cage Fullerene as a Selective Molecular Trap for LiF/[BeF]+

“…Hydroxylated multiwall carbon nanotubes (MWCNTs) have been found to absorb various salts efficiently, such as NaCl, when soaked in a salt solution [50, 51] . The salt together with some water molecules formed aggregates inside the MWCNTs, as detected by electron microscopy.…”

“…[49] Hydroxylated multiwall carbon nanotubes (MWCNTs) have been found to absorb various salts efficiently, such as NaCl, when soaked in a salt solution. [50,51] The salt together with some water molecules formed aggregates inside the MWCNTs, as detected by electron microscopy. The area close to the carbon inner wall is mainly occupied by water, which connects the salt in the center area inside the MWCNTs.…”

Versatile Surface Chemistry of Carbon-Based Nanoplatforms by Covalent Bonding, Non-Covalent Linking, Crosslinking, and Self-Assembling

“…In this manner, graphene could act as a non-covalent platform to interact with their close surroundings for different targeted applications such as ion doping of surfaces and targeted ion interactions. Recently, high-efficiency ion enrichment inside ultra-short carbon nanotubes was reported [55]. This ion enrichment based on ion-polar interactions offered the possibility to assay alternative ways of water purification and develop ion batteries, super-capacitors, and memory devices where controlled doping of ions showed important roles in charge transfer and detection.…”