Reactive-Oxygen-Species-Mediated Surface Oxidation of Single-Molecule DNA Origami by an Atomic Force Microscope Tip-Mounted C60 Photocatalyst

A tripod molecule incorporating a C-60 photocatalyst into a rigid scaffold with disulfide legs was designed and synthesized for the stable and robust attachment of C-60 onto an Au-coated atomic force microscope (AFM) tip. The "tripod-C-60" was immobilized onto the tip by forming S-Au bonds in the desired orientation and a dispersed manner, rendering it suitable for the oxidation and scission of single molecules on a countersurface, thereby functioning as "molecular shears". A DNA origami with a well-defined structure was chosen as the substrate for the tip-induced oxidation. The gold-coated, C-60-functionalized AFM tip was used for both AFM imaging and oxidation of DNA origami upon visible-light irradiation. The localized and temporally controlled oxidative damage of DNA origami was successfully performed at the single-molecule level via singlet-oxygen (O-1(2)) generation from the immobilized C-60 on the AFM tip. This oxidative damage to DNA origami can be carried out under ambient conditions in a fluid cell at room temperature, rendering it well-suited for the manipulation of a variety of species on surfaces via a spatially and temporally controlled oxidation reaction triggered by O-1(2) locally generated from the immobilized C-60 on the AFM tip.