MPQ, Université Paris Diderot-Paris 7, Sorbonne Paris Cité, CNRS, UMR 7162, 10, rue A. Domon et L. Duquet, 75205 Paris 13, France.
Research Center in Physics of Matter and Radiation (PMR), Université de Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium.
Sci Rep. 2016 Apr 21;6:24796. doi: 10.1038/srep24796.
Graphene-based sensors are among the most promising of graphene's applications. The ability to signal the presence of molecular species adsorbed on this atomically thin substrate has been explored from electric measurements to light scattering. Here we show that the adsorbed molecules can be used to sense graphene properties. The interaction of porphyrin molecules with nitrogen-doped graphene has been investigated using scanning tunneling microscopy and ab initio calculations. Molecular manipulation was used to reveal the surface below the adsorbed molecules allowing to achieve an atomic-scale measure of the interaction of molecules with doped graphene. The adsorbate's frontier electronic states are downshifted in energy as the molecule approaches the doping site, with largest effect when the molecule sits over the nitrogen dopant. Theoretical calculations showed that, due to graphene's high polarizability, the adsorption of porphyrin induces a charge rearrangement on the substrate similar to the image charges on a metal. This charge polarization is enhanced around nitrogen site, leading to an increased interaction of molecules with their image charges on graphene. Consequently, the molecular states are stabilized and shift to lower energies. These findings reveal the local variation of polarizability induced by nitrogen dopant opening new routes towards the electronic tuning of graphene.
基于石墨烯的传感器是石墨烯应用中最有前途的应用之一。已经从电测量到光散射探索了在这种原子薄基底上吸附的分子种类存在的信号的能力。在这里，我们表明吸附的分子可用于感测石墨烯性质。使用扫描隧道显微镜和从头算计算研究了卟啉分子与氮掺杂石墨烯的相互作用。分子操纵用于揭示吸附分子下方的表面，从而实现了对分子与掺杂石墨烯相互作用的原子级测量。当分子接近掺杂位置时，吸附物的前沿电子态在能量上向下移动，当分子位于氮掺杂剂上时，效果最大。理论计算表明，由于石墨烯的高极化率，吸附的卟啉在底物上诱导类似于金属上的像电荷的电荷重排。这种电荷极化在氮位周围增强，导致分子与其在石墨烯上的像电荷之间的相互作用增强。因此，分子状态稳定并移至较低的能量。这些发现揭示了氮掺杂剂诱导的极化率的局部变化，为电子调谐石墨烯开辟了新途径。
