石墨烯基生物分子传感器件的第一性原理研究

基于第一性原理模拟, 我们构建了一种具有石墨烯电极的纳米间隙生物分子传感器件的理论模型. 研究发现,当碱基分子胞嘧啶、甲基化胞嘧啶和羟甲基化胞嘧啶分别通过器件时, 器件横向电流的大小差异约有1个数量级, 器件对此类分子具有一定的分辨能力. 分子之间的区分度大小受单链脱氧核糖核酸(DNA)中相邻碱基分子间的相互作用及碱基分子构型的影响. 研究工作表明, 此类石墨烯基分子传感器可准确高效地区分具有不同结构的碱基分子, 为准确定位DNA链中的变异碱基分子提出了一种新的思路.     

扶手椅型缺陷硫化钼纳米带电子性质的第一性原理计算

基于密度泛函理论的第一性原理计算,研究了含空位缺陷的扶手椅型二硫化钼纳米带的电子性质.发现缺陷会导致纳米带结构稳定性降低,单空位钼缺陷和三空位缺陷使得纳米带从半导体变成金属性,而单空位硫缺陷和两种双空位缺陷仅减小纳米带的带隙;电子态密度和能带的本征态表明缺陷纳米带费米能级附近的杂质态主要是缺陷态的贡献.研究了四类半导体性质的纳米带带隙与宽度的关系,对于完整的纳米带,带隙随宽度以3为周期振荡变化;而引入空位缺陷后,纳米带的带隙振荡不再具有周期且振荡幅度变小.同时发现,当缺陷的浓度变小后,缺陷仅使纳米带的带隙减小,不会使其变为金属性.这些结果有望打开其在新型纳电子器件中的应用潜能.     

A biosensor based on graphene nanoribbon with nanopores: a first-principles devices-design

A biosensor device,built from graphene nanoribbons(GNRs) with nanopores,was designed and studied by firstprinciples quantum transport simulation.We have demonstrated the intrinsic transport properties of the device and the effect of different nucleobases on device properties when they are located in the nanopores of GNRs.It was found that the device’s current changes remarkably with the species of nucleobases,which originates from their different chemical compositions and coupling strengths with GNRs.In addition,our first-principles results clearly reveal that the distinguished ability of a device’s current depends on the position of the pore to some extent.These results may present a new way to read off the nucleobases sequence of a single-stranded DNA(ssDNA) molecule by such GNRs-based device with designed nanopores     

孔洞石墨烯纳米带的电子输运性质

基于密度泛函理论的计算模拟, 对含有孔洞的zigzag型石墨烯纳米带(N=17, N为碳链数目)结构进行优化, 进一步计算得到体系存在不同孔洞时的电子输运性质. 研究结果表明: 当存在单个孔洞时, 体系的导电性不仅与量子限域效应有关, 还受到孔洞对称性的束缚, 且斜向对称比纵向对称受到的束缚更大; 对于双孔洞的情况, 由于孔洞间的耦合作用, 体系的导电性在较大距离范围内大体上随孔洞间距的增大而增强, 同时会出现一些量子现象, 这可用一维对称双势垒模型来解释.     

Boron/nitrogen pairs Co-doping in metallic carbon nanotubes: a first-principle study

By using the first-principles calculations, the electronic structure and quantum transport properties of metallic carbon nanotubes with B/N pairs co-doping have been investigated. It is shown that the total energies of metallic carbon nanotubes are sensitive to the doping sites of the B/N pairs. The energy gaps of the doped metallic carbon nanotubes decrease with decreasing the concentration of the B/N pair not only along the tube axis but also around the tube. Moreover, the I--V characteristics and transmissions of the doped tubes are studied. Our results reveal that the conducting ability of the doped tube decreases with increasing the concentrations of the B/N pairs due to symmetry breaking of the system. This fact opens a new way to modulate band structures of metallic carbon nanotubes by doping B/N pair with suitable concentration and the novel characteristics are potentially useful in future applications.     

碳纳米管对接成异质结器件的计算模拟

基于Stone-Wales缺陷演变理论与分子动力学、Monte Carlo计算方法, 进行了碳纳米管(CNTs)对接成异质结器件的计算模拟.首先, 提出了一种模拟CNTs端帽位置变化的新算法, 并计算模拟了单根CNT的端帽从开口到闭合的过程. Stone-Wales缺陷演变被设计模拟这些端帽变化的跃变过程, 以模拟C–C键的生成与断裂, 而分子动力学则作为跃变后构型弛豫的渐变模拟. 同时, 研究了不同管型CNTs的端帽打开并对接形成异质结的过程.研究结果显示, 对接初期在对接处先产生大量的缺陷, 以促进反应的发生. 这些缺陷趋向于演变成稳定的六元环结构, 或者五元环/七元环的结构, 使异质结趋于稳定. 关键词： 碳纳米管 Monte Carlo Stone-Wales缺陷 分子动力学