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HiPco single-walled carbon nanotube (HPNT) containing Fe was purified by one-step purification with HCl-washing (D-method) and two-step purification with HCl-washing after air oxidation (GD-method). The N 2 adsorption isotherm of HPNT at 77 K is of type II and it changes to type IV after purification. Purification by the D and GD methods increases the total surface area and micropore volume, and it decreases the average pore width from 3.5 nm to 1.7 and 1.0 nm, respectively.Introduction. Carbon nanotubes, 1 which are one of the recently discovered novel carbon nanomaterials, have received much attention both from scientific and technological aspects and they are expected to hold a great potential for application in various fields. In particular, the reversible storage of hydrogen on carbon nanotubes has been studied extensively. [2][3][4] Because the pore structure of carbon nanotube aggregates plays an essential role in gas adsorption, it is necessary to determine accurately the pore structure of carbon nanotube. The single-walled carbon nanotubes (SWCNTs) with catalytic method contain metallic impurities such as Fe, Ni, and Co in addition to various forms of carbon such as graphite, amorphous carbon, and nanoparticles. [5][6][7] These authors have studied gas adsorption using single-walled carbon nanohorns (SWNHs) which can be obtained in a pure form. 8,9 As SWNH has a slightly different morphology from SWCNT, we need highly pure SWCNTs to understand the gas adsorption properties exactly. A better purification method must be developed in order to study intrinsic properties of carbon nanotubes. Hence, various purification techniques for carbon nanotubes have been reported. [10][11][12][13] However, many purification methods such as chemical and mechanical treatments give rise to structure change of carbon nanotubes. Yudasaka et al. reported that metal content of HiPco SWCNT (HPNT), which was about 30 wt. %,

Coexistence of metallic and semiconducting carbon nanotubes has often been a bottleneck in many applications and much fundamental research. Single-walled carbon nanotubes (SWCNTs) were dissolved in HNO3/H2SO4 mixture to confirm differing reactivity between metallic (m) and semiconducting (s) SWCNTs. With HNO3/H2SO4 treatment, s-SWCNTs remained intact, while m-SWCNTs were completely removed for SWCNTs with small diameters less than 1.1 nm, which was confirmed by resonant Raman and optical absorption spectra. We also showed that nitronium ions (NO2+) dissolved in the HNO3/H2SO4 solution could preferably attack the m-SWCNTs, which was supported by our theoretical calculation. This clear selectivity can be explained by the preferential adsorption of positively charged NO2+ on m-SWCNTs due to more available electron densities at the Fermi level in the m-SWCNTs. We report for the first time a selective removal of small-diameter m-SWCNTs by using HNO3/H2SO4 solution, which presented a striking contrast to the diameter-selective removal of SWCNTs by oxidative etching reported previously.

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MXene and graphene based thin, flexible and low-density composite were prepared by cost effective spray coating and solvent casting method. The fabricated composite was characterized using Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray (EDX). The prepared composites showed hydrophobic nature with higher contact angle of 126°, −43 mN·m−1 wetting energy, −116 mN·m−1 spreading Coefficient and 30 mN·m−1 lowest work of adhesion. The composites displayed excellent conductivity of 13.68 S·cm−1 with 3.1 Ω·sq−1 lowest sheet resistance. All the composites showed an outstanding thermal stability and constrain highest weight lost until 400 °C. The MXene-graphene foam exhibited excellent EMI shielding of 53.8 dB (99.999%) with reflection of 13.10 dB and absorption of 43.38 dB in 8–12.4 GHz. The single coated carbon fabric displayed outstanding absolute shielding effectiveness of 35,369.82 dB·cm2·g−1. The above results lead perspective applications such as aeronautics, radars, air travels, mobile phones, handy electronics and military applications.

Rechargeable aqueous Zn-ion batteries (ZiBs) have received significant attention owing to their low cost and environmental friendliness. The charge storage mechanism of ZiBs generally depends on the cationic redox conversion. The anodic redox conversion is still rare due to the lack of suitable cathode materials and electrolytes, which may impede the ZiB performance. The present investigation focuses on enhancing the ZiB performance through in situ involvement of disulfide redox chemistry from a patronite Mn-doped VS4 crystal in a 1 M Zn­(OTf)2 water/acetonitrile (ACN) hybrid electrolyte. Simultaneous involvement of cationic and anionic redox conversion during the charging/discharging process enhances the specific capacity as high as ∼547 mA h g–1 at 0.2 A g–1 current density. The water/ACN hybrid solvent effectively improves the working voltage and suppresses Zn dendrite formation, resulting in superior cycling performance. The conversion of the VS4 crystal phase and intercalation of H+/Zn2+ in the cathode have been investigated through ex situ X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman studies.

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HiPco single-walled carbon nanotubes (HPNTs) containing Fe were purified by a one-step process with HClwashing (D-method) and a two-step process with HCl-washing after air oxidation (GD-method). The HPNT samples before and after purification were characterized using the N 2 adsorption at 77 K, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The TGA results showed a decreased Fe content after purification. In addition, the XPS results provided evidence that oxygen-based functional groups were introduced to the nanotube surface by both purification methods. The purification treatments also altered the N 2 adsorption isotherms from type II to type IV; this accompanied the development of microporosity. Thus, purification considerably affects the surface chemistry and pore structures of HPNT aggregates. The effects of purification on the adsorption properties of HPNT aggregates with regard to CH 3 OH and C 2 H 5 OH vapors were examined at 303 K. The purification greatly enhanced the adsorptivity for CH 3 OH and C 2 H 5 OH vapors at 303 K under a low relative pressure. We associated this with the enhanced microporosity and the oxygenbased functional groups introduced on the surface.