The combination of molecular self-assembly and electron beam lithography is very useful to build supramolecular nanostructures. Our starting points are aromatic self-assembled monolayers (SAMs) that are modified by electrons. In nitrobiphenyl-SAMs, the impinging electrons dehydrogenate and cross-link the underlying aromatic cores, and chemically convert the terminal nitro groups to amino groups (chemical lithography). On these amino templates, we coupled tris-nitrilotriacetic acid (tris-NTA) chelators. These were then used to reversibly immobilize His6-tagged 20S proteosome. The functionality of the surface-bound protein is demonstrated.
Cross-linked aromatic SAMs can also be released from the surface, for example by dissolving the substrate. The resulting free-standing ‘carbon nanosheets’? have the thickness of a single molecule. We have found that nanosheets are mechanically and thermally stable. They can be transferred onto arbitrary surfaces. A first technical application of carbon nanosheets is to use them as ultrathin sample supports for transmission electron microscopy (TEM). We tested their applicability by placing Co and Au nanoparticles on 1.6 nm thick nanosheets. The corresponding TEM images show significant improvements over a conventional 15 nm thick film. The contrast of Co and Au clusters, as well as of single diffusing gold atoms is much higher on the nanosheet than on any conventional support.