Key Laboratory of Radio Frequency and Micro-Nano Electronics of Jiangsu Province, College of Electronic and Optical Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China.
Nanoscale. 2019 Nov 28;11(46):22482-22492. doi: 10.1039/c9nr08071f.
Although many graphene derivatives have sizable band gaps, their electrical or mechanical properties are significantly degraded due to the low degree of π-conjugation. Besides the π-π conjugation, there exist hyperconjugative interactions arising from the delocalization of σ electrons. Inspired by the structural characteristics of a hyperconjugated molecule, dimethyl ether, we design a two-dimensional oxocarbon (named graphether) by the assembly of dimethyl ether molecules. Our first-principles calculations reveal the following findings: (1) monolayer graphether possesses excellent dynamic and thermal stabilities as demonstrated by its favourable cohesive energy, the absence of soft phonon modes, and high melting point. (2) It has a direct wide-band-gap energy of 2.39 eV, indicating its potential applications in ultraviolet optoelectronic devices. Interestingly, the direct band gap feature is rather robust against the external strains (-10% to 10%) and stacking configurations. (3) Due to the hyperconjugative effect, graphether has the high intrinsic electron mobility. More importantly, its in-plane stiffness (459.8 N m-1) is even larger than that of graphene. (4) The Pt(100) surface exhibits high catalytic activity for the dehydrogenation of dimethyl ether. The electrostatic repulsion serves as a driving force for the rotation and coalescence of two dehydrogenated precursors, which is favourable for the bottom-up growth of graphether. (5) Replacement of the C-C bond with an isoelectronic B-N bond can generate a stable Pmn21-BNO monolayer. Compared with monolayer hexagonal boron nitride, Pmn21-BNO has a moderate direct band gap energy (3.32 eV) and better mechanical property along the armchair direction.
虽然许多石墨烯衍生物具有相当大的带隙，但由于 π 键共轭程度低，它们的电学或力学性质会显著下降。除了 π-π 共轭，还有由 σ 电子离域引起的超共轭相互作用。受超共轭分子二甲醚结构特征的启发，我们通过二甲醚分子的组装设计了一种二维氧碳（命名为graphether）。我们的第一性原理计算揭示了以下发现：（1）单层 graphether 具有出色的动力学和热稳定性，表现为有利的内聚能、不存在软声子模式和高熔点。（2）它具有直接的宽能隙为 2.39eV，表明其在紫外光电子器件中的潜在应用。有趣的是，直接带隙特征对外部应变（-10%至 10%）和堆叠构型具有很强的鲁棒性。（3）由于超共轭效应，graphether 具有高的本征电子迁移率。更重要的是，其面内刚度（459.8N m-1）甚至大于石墨烯。（4）Pt(100)表面对二甲醚的脱氢反应表现出高催化活性。静电排斥作用作为两个脱氢前体旋转和合并的驱动力，有利于 graphether 的自下而上生长。（5）用等电子 B-N 键取代 C-C 键可以生成稳定的 Pmn21-BNO 单层。与单层六方氮化硼相比，Pmn21-BNO 具有适度的直接带隙能（3.32eV）和沿扶手椅方向更好的力学性能。
