單壁奈米碳管製成時，其中約有1/3比例為金屬性，2/3為半導體性。藉由單壁與雙壁奈米碳管之共振拉曼散射光譜，我們探討單壁與雙壁奈米碳管管徑大小與導電性。藉由介電泳實驗，我們研究金屬性與半導體性單壁奈米碳管的分離情況。
從單壁與雙壁奈米碳管的共振拉曼散射光譜研究中，我們發現：第一、由分析Stokes與anti-Stokes徑向呼吸模(RBM)的相對強度比，推算單壁與雙壁奈米碳管的導電性，與利用Kataura能隙圖的判斷結果皆大致吻合，但雙壁奈米碳管內外管徑差過小，外管的RBM拉曼光譜不明顯；第二、G-mode拉曼光譜所推測出的單壁奈米碳管導電性與前述結果具一致性；第三、入射雷射光子能量增加時，D-mode及G’-mode峰值皆呈現藍移現象，但在單壁奈米碳管中，D-mode及G’-mode峰值變化斜率與二維石墨層(薄膜)相似，而雙壁奈米碳管的峰值變化斜率與三維石墨層(鉛筆心)相似。
從單壁奈米碳管的介電泳研究中，我們發現：第一、銅電極會產生電解現象，而金電極維持穩定狀態；第二、單壁奈米碳管僅附著在兩側電極邊緣上，中央電極邊緣上無附著物的蹤影；第三、經由G-mode拉曼光譜分析，介電泳實驗所收集的單壁奈米碳管之二維特性比裁剪前後更加明顯。

Selection of the metallic and semiconducting single-walled carbon nanotubes (SWNTs) from bundle forms is important for technological applications in nanoscale devices. This works reports resonance Raman spectroscopy measurements of SWNTs and double-walled carbon nanotubes (DWNTs) addressing the identification of their diameters and electronic structures. Dielectrophoresis on SWNTs has also been demonstrated to separate these nanotubes.

The electric conductivity of these nanotubes can be determined from the spectra of the Stokes and anti-Stokes radial breathing mode (RBM) and tangential mode (G-mode), which correlates well with the analysis of Kataura plot. However, the difference of the inner and outer DWNTs tubes is too small to obtain the detailed structural and electronic properties of DWNTs. Interestingly, the peak position of disorder mode (D-mode) and its overtone (G’-mode) shows a shift to higher frequencies with increasing laser photon energy. The slope of SWNTs(DWNTs) is similar to 2-dimensional(3-dimensional) graphite.

Dielectrophoresis experiment of SWNTs show the gold electrode is more stable than the cooper one. The G-mode spectra of adherent SWNTs on the side electrode (no SWNTs on the middle electrode) exhibit characteristic 2-dimensional behavior.

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