Lu Jin-You, Olukan Tuza, Tamalampudi Srinivasa Reddy, Al-Hagri Abdulrahman, Lai Chia-Yun, Ali Al Mahri Mariam, Apostoleris Harry, Almansouri Ibraheem, Chiesa Matteo
Laboratory for Energy and Nano Science, Department of Mechanical and Materials Engineering, Khalifa University, Abu Dhabi, United Arab Emirates.
Nanoscale. 2019 Apr 23;11(16):7944-7951. doi: 10.1039/c9nr00155g.
In this work, we study the surface energy of monolayer, bilayer and multilayer graphene coatings, produced through exfoliation of natural graphite flakes and chemical vapor deposition. We employ bimodal atomic force microscopy and micro-Raman spectroscopy for high spatial resolution and large area scanning of force of adhesion on the regions of the graphene/SiO2 surface with different graphene layers. Our measurements show that the interface conditions between graphene and SiO2 dominate the experimentally observed graphene surface energy. This finding sheds new light on the controversy surrounding graphene transparency studies. By separating the surface energy into polar and non-polar interactions, our findings suggest that monolayer graphene is nearly van der Waals opaque but partially transparent (near 60%) to polar interactions, which is further supported by characterizing graphene on the copper surface and two levels of density functional theory simulation. In addition to providing quantitative insight into the surface interactions of complicated graphene coatings, this work demonstrates a new route to nondestructively monitor the interface between graphene and coated substrates.
在这项工作中，我们研究了通过天然石墨薄片的剥离和化学气相沉积制备的单层、双层和多层石墨烯涂层的表面能。我们采用双峰原子力显微镜和显微拉曼光谱对具有不同石墨烯层数的石墨烯/二氧化硅表面区域进行高空间分辨率和大面积的粘附力扫描。我们的测量结果表明，石墨烯与二氧化硅之间的界面条件主导了实验观察到的石墨烯表面能。这一发现为围绕石墨烯透明度研究的争议提供了新的线索。通过将表面能分为极性和非极性相互作用，我们的研究结果表明，单层石墨烯对范德华力几乎是不透明的，但对极性相互作用部分透明（接近60%），这一结论在对铜表面的石墨烯进行表征以及两级密度泛函理论模拟中得到了进一步支持。除了对复杂的石墨烯涂层的表面相互作用提供定量的见解外，这项工作还展示了一种无损监测石墨烯与涂层基底之间界面的新途径。
