非共价修饰碳纳米管中光诱导电荷转移的第一性原理研究
First-Principles Studies of Photoinduced Charge Transfer in Noncovalently Functionalized Carbon Nanotubes
摘要：
本文研究了手性指数为（n，0）（n=7，10，13，16，19）的半导体碳纳米管（CNTs）上吸附的二硝基甲烷分子（CH $_{2}$ N $_{2}$ O $_{4}$）的能量学、电子结构、光激发和电子弛豫.采用第一性原理密度泛函理论（DFT），结合广义梯度近似和范德华修正，计算了二硝基甲烷通过脂肪链与芘连接的二硝基戊基芘在碳纳米管上的吸附能.已发现结合能为75.26 kJ/mol，这解释了为什么这种脂肪族链-芘单元可以并且已经在实验中用于将功能分子结合到CNT。计算的电子结构表明，二硝基甲烷引入了一个本地化的状态内的带隙的CNT系统的n=10，13，16和19，这样的状态可以捕获电子时，CNT是光激发的。因此，我们研究了带内弛豫的动力学与DFT结合使用的减少密度矩阵形式主义。对于原始的碳纳米管，我们已经发现，计算的电荷弛豫常数与实验时间尺度吻合得很好。吸附后，这些常数被修改，但没有一个明确的趋势的方向和幅度的变化。然而，我们的计算预测，电子弛豫在导带是快于空穴弛豫的价带碳纳米管与分子吸附。
英文摘要：
We have studied the energetics, electronic structure, optical excitation, and electron relaxation of dinitromethane molecules (CH$_{2}$N$_{2}$O$_{4}$) adsorbed on semiconducting carbon nanotubes (CNTs) of chiral index (n,0) (n=7, 10, 13, 16, 19). Using first-principles density functional theory (DFT) with generalized gradient approximations and van der Waals corrections, we have calculated adsorption energies of dinitropentylpyrene, in which the dinitromethane is linked to the pyrene via an aliphatic chain, on a CNT. A 75.26 kJ/mol binding energy has been found, which explains why such aliphatic chain-pyrene units can be and have been used in experiments to bind functional molecules to CNTs. The calculated electronic structures show that the dinitromethane introduces a localized state inside the band gap of CNT systems of n=10, 13, 16 and 19; such a state can trap an electron when the CNT is photoexcited. We have therefore investigated the dynamics of intra-band relaxations using the reduced density matrix formalism in conjunction with DFT. For pristine CNTs, we have found that the calculated charge relaxation constants agree well with the experimental time scales. Upon adsorption, these constants are modified, but there is not a clear trend for the direction and magnitude of the change. Nevertheless, our calculations predict that electron relaxation in the conduction band is faster than hole relaxation in the valence band for CNTs with and without molecular adsorbates.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
