Type- and Species-Selective Air Etching of Single-Walled Carbon Nanotubes Tracked with in Situ Raman Spectroscopy

Abstract

The thermal oxidation of carbon nanotubes in air is investigated by in situ Raman spectroscopy. Etching rates are directly seen to be diameter, chirality, and type dependent. We directly track the evolution of bundled nanotube networks that undergo air etching from 300 to 600 °C. Some species are more robust than others. Changes to radial breathing mode (RBM) and G– peak structures suggest that metallic species etch away more rapidly, with smaller diameter semiconducting species etching more slowly and large diameter nanotubes, including semiconductors, etching last. The decay in integrated G and D band intensities is tracked and fit reasonably well with biexponential decay. The RBM evolution is better represented by a single exponential. All bands are fit to activation plots with RBMs showing significantly different rates.

Ni2P Entwined by Graphite Layers as a Low-Pt Electrocatalyst in Acidic Media for Oxygen Reduction

“…Raman spectroscopy provides the degree of graphitization of carbon. As displayed in Figure b, the intensity ratio of the G-band (1575 cm –1 ) and D-band (1360 cm –1 ) peaks ( I G / I D ) is 1.38 for Ni 2 P/GC, implying good graphitization of carbon in the Ni 2 P/GC composite . In addition, the symmetric 2D-band at 2722 cm –1 is in accord with that of graphitic carbon in the literature .…”

Purification, separation and extraction of inner tubes from double-walled carbon nanotubes by tailoring density gradient ultracentrifugation using optical probes

“…For purification, the DWCNT samples were first exposed to hydrochloric acid to remove remaining catalysts followed by annealing in air flow at 400 °C for 2 h to remove amorphous carbon and after another acid treatment annealed at 500 °C in air for 2 h to remove SWCNT impurities (pristine sample). The effectiveness of the latter step to remove SWNT has been shown by Li-Pook-Than et al [25] , where the intensity of the integrated Raman signal for SWNT is much less than 1%. After this, four different individualization techniques were applied:…”

Synthesis of semiconducting or metallic single-walled carbon nanotubes by gas-phase selective etching

“…(1) 均一直径单壁碳纳米管的控制制备. 单壁碳 纳米管的反应活性与直径和导电属性相关 [86] , 对相 [90,91] 相关, 所以最核心的问题是如何设 计、制备尺寸、形貌、组分均一且在高温下保持稳定 的纳米催化剂.…”