金属性碳纳米管的脱缠结空位氧化
Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes
摘要：
原始的单壁碳纳米管（SWCNT）对O $_2$和N $_2$是相当惰性的，其对于低剂量仅在ppm水平下化学吸附在SWCNT的缺陷位点或空位上。然而，非常低的掺杂对单壁碳纳米管的电子性质和导电性具有主要影响。已经在低O $_2$剂量（80 L）下，X射线光电子能谱学（XPS）O 1 s信号变得饱和，表明几乎所有SWCNT的空位已经被氧化。因此，通过XPS探测单壁碳纳米管上的空位氧化产生具有相当低的信噪比的光谱，即使对于金属性分选的单壁碳纳米管也是如此。我们表明，即使在这些条件下，第一性原理密度泛函理论计算的Kohn-Sham O 1 s结合能可用于分配的XPS O 1 s光谱的单壁碳纳米管上的氧化空位到其单独的组件。这使得人们能够确定所测量的特定官能团或键合环境。我们发现XPS O 1 s信号主要是由于单壁碳纳米管空位上的三个含O官能团：环氧基（C $_2$ $>$ O）、羰基（C $_2$ $>$ C $=$ O）和烯酮（C $=$ C $=$ O），按丰度排序。在氧化几乎所有的单壁碳纳米管的空位，金属单壁碳纳米管样品的中心峰的强度是60%以上的半导体单壁碳纳米管样品。这表明在金属SWCNT样品上更大丰度的含O缺陷结构。对于金属和半导体单壁碳纳米管，我们发现O $_2$对XPS O~ 1 s谱没有贡献。
英文摘要：
Pristine single-walled carbon nanotubes (SWCNTs) are rather inert to O$_2$ and N$_2$, which for low doses chemisorb only on defect sites or vacancies of the SWCNTs at the ppm level. However, very low doping has a major effect on the electronic properties and conductivity of the SWCNTs. Already at low O$_2$ doses (80 L), the X-ray photoelectron spectroscopy (XPS) O 1s signal becomes saturated, indicating nearly all the SWCNT's vacancies have been oxidized. As a result, probing vacancy oxidation on SWCNTs via XPS yields spectra with rather low signal-to-noise ratios, even for metallicity-sorted SWCNTs. We show that, even under these conditions, the first principles density functional theory calculated Kohn-Sham O 1s binding energies may be used to assign the XPS O 1s spectra for oxidized vacancies on SWCNTs into its individual components. This allows one to determine the specific functional groups or bonding environments measured. We find the XPS O 1s signal is mostly due to three O-containing functional groups on SWCNT vacancies: epoxy (C$_2$$>$O), carbonyl (C$_2$$>$C$=$O), and ketene (C$=$C$=$O), as ordered by abundance. Upon oxidation of nearly all the SWCNT's vacancies, the central peak's intensity for the metallic SWCNT sample is 60\% greater than for the semiconducting SWCNT sample. This suggests a greater abundance of O-containing defect structures on the metallic SWCNT sample. For both metallic and semiconducting SWCNTs, we find O$_2$ does not contribute to the measured XPS O~1s spectra.
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