Strong Micro-Dielectric Environment Effect on the Band Gaps of (n,m)Single-Walled Carbon Nanotubes
Strong Micro-Dielectric Environment Effect on the Band Gaps of (n,m)Single-Walled Carbon Nanotubes
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DOI：
10.1021/ja105980a
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发表时间：
2010-09-22
影响因子：
15
通讯作者：
Nakashima, Naotoshi
中科院分区：
文献类型：
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作者：
Hirana, Yasuhiko;Tanaka, Yasuhiko;Nakashima, Naotoshi
碳纳米管的电子态是碳纳米管最基本的性质之一。我们现在描述的发现，（n，m）单壁碳纳米管的带隙的强烈影响周围孤立的纳米管的微介电环境的变化。在DMSO、乙腈、DMF、THF和氯仿等有机溶剂中，对15个孤立的（n，m）单壁碳纳米管（SWNTs）在ITO电极上的原位光致发光（PL）光谱电化学进行了研究，测定了（n，m）SWNTs在溶剂中的氧化还原电位和带隙（Δ E-electr）。我们已经发现，随着溶剂介电常数的降低，（n，m）SWNT的Δ E-electr变得更大，这与几乎不显示溶剂依赖性的光学带隙（Δ E-opt）形成鲜明对比。电化学带隙的这种强溶剂依赖性是由于电化学过程中产生的带电SWNT的溶剂化能的差异。mod = 1和mod = 2的两种mod类型的单壁碳纳米管的Δ E-electr随管径的倒数线性增加，这与理论一致。此外，在单壁碳纳米管中的π电子的状态进行了评估，从带隙的直径的单壁碳纳米管的依赖性。此外，使用γ（0）值（表示SWNT侧壁中的π电子的稳定性或离域程度的量度的参数）评估SWNT侧壁上的π电子的状态，并且揭示了mod = 1和mod = 2的SWNT的γ（0）值随着溶剂的介电常数在38- 100范围内的降低而增加。79.这项研究使我们能够了解碳纳米管的基本电子性质。
The electronic states of carbon nanotubes are one of the most fundamental properties of the nanotubes. We now describe the finding that the band gaps of (n,m)SWNTs are strongly affected by the change in microdielectric environments around the isolated nanotubes. In situ photoluminescence (PL) spectroelectrochemistry of the films containing 15 isolated (n,m)single-walled carbon nanotubes (SWNTs) cast on ITO electrodes in organic solvents including DMSO, acetonitirile, DMF, THF, and chloroform was completed and then the oxidation and reduction potentials, and band gaps (Delta E-electr) of the (n,m)SWNTs in the solvents were determined. We have discovered that the Delta E-electr, of the (n,m)SWNTs become greater as the solvent dielectric constants decreased, which is in sharp contrast to the optical band gaps (Delta E-opt) that show virtually no solvent dependence. Such a strong solvent dependence of the electrochemical band gaps is due to the difference in the solvation energy of the charged SWNTs produced during the electrochemical processes. The Delta E-electr, of both mod types of the SWNTs, mod = 1 and mod = 2, linearly increased versus the reciprocal of the tube diameter, which agrees with the theory. Moreover, the states of the pi-electrons in the SWNTs were evaluated from the dependence of the band gaps on the diameter of the SWNTs. Furthermore, the states of the pi-electrons on the sidewalls of the SWNTs were evaluated using the gamma(0) values, a parameter representing the measure of the stability or the degree of delocalization of pi-electrons in the sidewall of the SWNTs, and revealed that the gamma(0) values of the mod = 1 and mod = 2 SWNTs increased with a decrease in the dielectric constants of the solvents in the range of 38-79. This study has enabled us to understand the essential electronic properties of the carbon nanotubes.