Functionalization of atomic force microscopy cantilevers and tips by activated vapour silanization

Abstract Atomic force microscopy (AFM) is a powerful tool in Biology due to the possibility of identifying and locating single molecules at a subnanometer scale. Performing these experiments requires the usage of functionalized AFM tips to which sensing molecules can be attached. In this work the possibility of functionalizing AFM cantilevers and tips using the activated vapour silanization (AVS) process is explored. Functionalized thin films are deposited on commercial silicon nitride chips and their presence is assessed by measuring the variation in the resonance frequency of the cantilever. Subsequently, the presence and functionality of the films is studied through the covalent immobilization of a fluorescein-derived molecule to the amine reactive groups on the surface. With regard to its sensing ability, the functionalized tips are shown to sustain repetitive interactions with a model graphite substrate (HOPG) under relatively harsh conditions, while no apparent damage is observed in the tip. It is also found that the substrate-tip interaction may be modified by covalently attaching a molecule to the latter. Consequently, AVS functionalized AFM tips are found to be robust and reliable candidates for their use in the affinity (or chemical) atomic force microscopy (AF-AFM) mode.