IBM Research-Zurich, CH-8803 Rüschlikon, Switzerland.
Science. 2012 Sep 14;337(6100):1326-9. doi: 10.1126/science.1225621.
We show that the different bond orders of individual carbon-carbon bonds in polycyclic aromatic hydrocarbons and fullerenes can be distinguished by noncontact atomic force microscopy (AFM) with a carbon monoxide (CO)-functionalized tip. We found two different contrast mechanisms, which were corroborated by density functional theory calculations: The greater electron density in bonds of higher bond order led to a stronger Pauli repulsion, which enhanced the brightness of these bonds in high-resolution AFM images. The apparent bond length in the AFM images decreased with increasing bond order because of tilting of the CO molecule at the tip apex.
我们通过使用一氧化碳（CO）功能化针尖的非接触原子力显微镜（AFM）表明，多环芳烃和富勒烯中各个碳-碳键的不同键序可以通过该方法区分。我们发现了两种不同的对比机制，这两种机制得到了密度泛函理论计算的证实：较高键序的键中的电子密度较大，导致更强的 Pauli 排斥力，从而增强了这些键在高分辨率 AFM 图像中的亮度。由于针尖顶端处 CO 分子的倾斜，AFM 图像中的表观键长随键序的增加而减小。
