Direct measurement of the surface energy of single-walled carbon nanotubes through atomic force microscopy.

Surface energy in nanomaterials is an essential parameter demonstrating a key role in their surface interactions and their functionalization aptitude. In this work, a new and facile methodology based on atomic force microscopy for the measurement of the surface energy of single-walled carbon nanotubes (SWCNTs) is reported. The proposed approach starts with the calibration based on a well-studied material, graphite, and the precision of the technique is confirmed by the measurement of the surface energy of multiwalled carbon nanotubes. Our measurements show that SWCNTs display a surface energy of 52.8 mJ/m2, which is in very good agreement with theoretical predictions of the measured property. Our experimental approach is essentially applicable to other nano-objects in contrast to conventional wet angle methods which are currently employed mainly in bulk materials. [ABSTRACT FROM AUTHOR]