Department of Chemical Engineering, Kansas State University, 66506, USA.
Small. 2013 Nov 25;9(22):3823-8. doi: 10.1002/smll.201300857. Epub 2013 May 28.
The molecular dipole moment plays a significant role in governing important phenomena like molecular interactions, molecular configuration, and charge transfer, which are important in several electronic, electrochemical, and optoelectronic systems. Here, the effect of the change in the dipole moment of a tethered molecule on the carrier properties of (functionalized) trilayer graphene--a stack of three layers of sp(2)-hybridized carbon atoms--is demonstrated. It is shown that, due to the high carrier confinement and large quantum capacitance, the trans-to-cis isomerisation of 'covalently attached' azobenzene molecules, with a change in dipole moment of 3D, leads to the generation of a high effective gating voltage. Consequently, 6 units of holes are produced per azobenzene molecule (hole density increases by 440 000 holes μm(-2)). Based on Raman and X-ray photoelectron spectroscopy data, a model is outlined for outer-layer, azobenzene-functionalized trilayer graphene with current modulation in the inner sp(2) matrix. Here, 0.097 V are applied by the isomerisation of the functionalized azobenzene. Further, the large measured quantum capacitance of 72.5 μF cm(-2) justifies the large Dirac point in the heavily doped system. The mechanism defining the effect of dipole modulation of covalently tethered molecules on graphene will enable future sensors and molecular-machine interfaces with graphene.
分子偶极矩在控制分子相互作用、分子构型和电荷转移等重要现象方面起着重要作用，这些现象在许多电子、电化学和光电系统中都很重要。在这里，展示了连接分子的偶极矩变化对（功能化）三层石墨烯载流子性质的影响，三层石墨烯是由三个 sp(2)杂化碳原子层堆叠而成。结果表明，由于高载流子限制和大量子电容，具有 3D 偶极矩变化的“共价连接”偶氮苯分子的反式-顺式异构化导致产生高有效栅极电压。因此，每个偶氮苯分子产生 6 个空穴（空穴密度增加 440000 个空穴/μm(-2))。基于拉曼和 X 射线光电子能谱数据，提出了一种在外层、偶氮苯功能化的三层石墨烯中进行电流调制的模型，其内层 sp(2)矩阵中的偶氮苯发生异构化。在这里，通过功能化偶氮苯的异构化施加 0.097 V 的电压。此外，所测量的大量子电容 72.5 μF cm(-2) 证明了在高度掺杂系统中大的狄拉克点。共价键合分子偶极矩调制对石墨烯影响的定义机制将为未来具有石墨烯的传感器和分子机器接口提供支持。
