The present article describes the immobilization of chemically shortened single-walled carbon nanotubes (SWNTs) onto atomic force microscopy (AFM) tips using a novel wet chemistry procedure. Preliminary results on the measurement of dissociation properties of carboxylic acid groups at the open end of the shortened SWNTs in aqueous solution by chemical force microscopy (CFM) are also described. The as-prepared long SWNTs were cut into short tubes by chemical oxidation, which produced -COOH groups at the open ends of the tubes. The shortened SWNTs were covalently attached to AFM tips by surface condensation between AFM tips modified with primary amino-terminated self-assembled monolayers (SAMs) and the carboxylic groups at the exposed end of the tube. The nanotube orientation on the AFM tips was demonstrated using AFM force calibration mode. The dissociation properties of carboxylic groups at the end of SWNTs were investigated by measuring the adhesion force between SWNTs modified AFM tips and hydroxyl-terminated SAMs surfaces as a function of pH (force titration measurement). The results showed a different force titration behavior and variable pK1/2 values between different SWNTs tips, indicating variations in the chemistry of the oxidized tubes from sample to sample. Successful attachment of carbon nanotubes to AFM tips has opened up a considerable number of possibilities in increasing the resolution of AFM procedures. Most importantly, the present investigation has provided a means of investigating the chemical properties of nanotubes attached to AFM tips.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry