Exciton Localization and Optical Emission in Aryl-Functionalized Carbon Nanotubes
Exciton Localization and Optical Emission in Aryl-Functionalized Carbon Nanotubes
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DOI：
10.1021/acs.jpcc.7b09558
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发表时间：
2018-01-25
影响因子：
3.7
通讯作者：
Tretiak, Sergei
中科院分区：
文献类型：
--
作者：
Gifford, Brendan J.;Kilina, Svetlana;Tretiak, Sergei
最近的光谱研究显示，单壁碳纳米管(SWCNTs)被芳基共价官能化后，在荧光中出现了多个低能峰。这些低能光学带的光物理性质对于了解它们的外观和通过化学修饰单壁碳纳米管实现它们的精确控制具有重要的意义。这一理论研究解释了化学功能化的(6，5)单壁碳纳米管在不同构象和不同介电介质中引入的芳基溴化物的特定能量依赖关系。密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)的计算表明，特定的异构体几何构型--官能团在碳纳米管碳环上的相对位置--对于控制官能化引入的光学跃迁的能量和强度是关键的，而介电环境和官能团的化学组成对其影响不大。官能化构象对光学性质的主要影响是通过激子局域化在掺杂缺陷附近的单壁碳纳米管表面而不是官能团本身来合理化的。
Recent spectroscopic studies have revealed the appearance of multiple low-energy peaks in the fluorescence of single-walled carbon nanotubes (SWCNTs) upon their covalent functionalization by aryl groups. The photophysical nature of these low energy optical bands is of significant interest in the quest to understand their appearance and to achieve their precise control via chemical modification of SWCNTs. This theoretical study explains the specific energy dependence of emission features introduced in chemically functionalized (6,5) SWCNTs with aryl bromides at different conformations and in various dielectric media. Calculations using density functional theory (DFT) and time dependent DFT (TD-DFT) show that the specific isomer geometry- the relative position of functional groups on the carbon-ring of the nanotube- is critical for controlling the energies and intensities of optical transitions introduced by functionalization, while the dielectric environment and the chemical composition of functional groups play less significant roles. The predominant effects on optical properties as a result of functionalization conformation are rationalized by exciton localization on the surface of the SWCNT near the dopant spa-defect but not onto the functional group itself.