Development of a Scanning Chemical Force Microscope with Atomic and Molecular Resolution

在目前的研究中，我们一直在开发具有原子和分子分辨率的化学力显微镜（CFM），方法是：i）通过进一步锐化和化学修饰尖端尖端来制造具有真正原子和分子分辨率的化学力显微镜尖端；ii）提高原子力显微镜（AFM）在高真空下的力灵敏度。我们还成功地对空气和水中的生物表面进行高分辨率成像。为了在 i) 中实现超高分辨率，我们尝试在刚性自组装单层 (SAM) 基质中插入突出的孤立刚性单分子。突出的刚性且高的单分子充当理想的锋利 AFM 尖端。我们合成了具有双环[2.2.2]辛烷部分的二硫化物，其横向相互作用足够高以形成稳定的SAM基质，并且其分子长度足够短以容纳隔离的刚性尖端分子，例如联苯甲硫醇衍生物。检查 Au(111) 表面上 SAM 的形成。不仅可以引入氢原子，还可以引入各种具有高电负性的卤素原子作为双环[2.2.2]辛烷部分的末端原子。此外，具有不同末端原子的二元混合 SAM 被发现是测试所开发的 CFM 的原子和分子分辨率的有用样品。关于ii)中的高灵敏度，我们尚未成功获得真正的原子分辨率。不过，从目前取得的成果来看，我们可以预期，我们将在不久的将来实现这一最终目标。

In the present research, we have been developing a chemical force microscope (CFM) with atomic and molecular resolution by i) fabricating chemical force microscope tips with true atomic and molecular resolution through further sharpening and chemical modification of tip apexes and ii) improving force sensitivity of an atomic force microscope (AFM) under high vacuum. We have also succeeded in imaging biosurfaces with high resolution in air and in water. To achieve ultrahigh resolution in i), we attempted inserting an isolated rigid single molecule protruding in a rigid self-assembled monolayer (SAM) matrix. The protruding rigid and tall single molecule acts as an ideally sharpened AFM tip. We synthesized disulfides with bicyclo[2.2.2]octane moieties whose lateral interaction is high enough to form the stable SAM matrix and whose molecular length is short enough to accommodate the isolated rigid tip molecule such as biphenyl methane thiol derivatives. SAM formation was examined on Au(111) surfaces. Not only hydrogen atom but also various halogen atoms with high electronegativity could be introduced as the terminal atoms of the bicyclo[2.2.2]octane moieties. In addition, binary mixed SAMs with different terminal atoms were found to be useful samples for testing atomic and molecular resolution of the developed CFM. Regarding to the high sensitivity in ii), we have not succeeded in attaining true atomic resolution yet. However, we can expect from the results obtained so far that we will achieve this final goal in the near future.