Building a multi-walled carbon nanotube-based mass sensor with the atomic force microscope

We report an approach for building a mass sensor based on multi-walled carbon nanotubes (MWCNT). We propose a method with a great potential for the positioning of MWCNTs based on self-assembly onto patterned hydrophilic areas. For the experiments ultra flat mica substrates covered with gold are used. The gold substrate is first covered with hydrophobic thiol molecules: octadecanthiol. The octadecanthiol molecules are then selectively removed from small areas by nanoshaving the gold substrate with the tip of an atomic force microscope (AFM) operating in contact mode. Hydrophilic thiols (2-mercaptoethanesulfonic acid) are then self-assembled onto the cleaned area. Next, the substrate, comprised of hydrophobic and hydrophilic areas, is immersed in MWCNTsdispersed in N, N-dimethylformamide. The MWCNTs are self-assembled on the hydrophilic areas.