Mesoscopic cage-like structured single-wall carbon nanotube cryogels

We fabricated mesoscopic cage-like structured Single-Wall Carbon Nanotube (SWCNT) cryogels having ultra-microporous necks using highly concentrated SWCNT-water inks with the aid of Zn-Al sol-gel dispersant. High-resolution transmission electron microscopy (TEM) image shows the presence of three-dimensional cage-like structures in the SWCNT cryogels, which are quite different from the bundle structures of pristine SWCNTs. Average bundle size of the SWCNT cryogels is 30% smaller than that of pristine SWCNTs according to the TEM observation. Adsorption isotherms of N-2 at 77 K and Ar at 87 K for SWCNT cryogels and pristine SWCNTs have explicit adsorption hysteresis in low and high relative pressure regions, indicating the presence of necked ultramicropores and mesopores. Ar adsorption isotherms show that the SWCNT cryogels have predominant low and high relative pressure hysteresis, suggesting the presence of mesopores with necked entrances of ultramicropores. Surface areas of SWCNT cryogels by Ar and N-2 adsorption are about two times larger than those of pristine SWCNTs which is in agreement with the geometrically evaluated surface area from SWCNT bundles. Mesopore volumes evaluated by adsorption of N-2 and Ar are 3 and 2.3 times larger than those of pristine SWCNTs in the mesopore range above 15 nm. The marked increase in the mesoporosity of the SWCNT assemblies by freeze-drying supports the mesoscopic three-dimensional cage-like structures observed by TEM.