Chemically modified STM tips for molecular imaging of DNA and cytochrome c

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Cheniistry-iacilitated intermolecular electron tunneling is another approach to molecular imaging that is reported herein. The chemical imaging was obtained from a distinctive chemical affinity between the imaging tip of scanning tunneling microscopy (STM) and the substrate that afters the tunneling current. This was achieved by tailored chemical modification of the STM tips. When chemically modified tips are used for STM measurements, contrast enhancements at specific regions in STM images occur on the basis of hydrogen bond, charge-transfer, and metal-coordination interactions, and as a result, allowed to detect not only the distribution of specific chemical species and functional groups but also the orientation of functional groups. The contrast enhancements reflect the increase in a tunneling current due to the overlap of electronic wave functions induced by the chemical interactions between tip and sample. The molecular imaging of oligonucleotides was achieved therefrom.