Nanometer-Sized Probes in Chemistry and Biology

Carbon nanotubes combine a range of properties that make them well suited for use as probe tips in applications such as atomic force microscopy (AFM)1, 2, 3. Their high aspect ratio, for example, opens up the possibility of probing the deep crevices4 that occur in micro-electronic circuits, and the small effective radius of nanotube tips sig-nificantly improves the lateral resolution beyond what can be achieved using commercial silicon tips5. Another characteristic feature of nano-tubes is their ability to buckle elastically4,6, which makes them very robust while limiting the maximum force that is applied to delicate organic and biological samples. Earlier investigations into the per-formance of nanotubes as scanning probe microscopy tips have fo-cused on topographical imaging, but a potentially more significant is-sue is the question of whether nanotubes can be modified to create probes that can sense and manipulate matter at the molecular level7. Here we demonstrate that nanotube tips with the capability of chemi