Molecular interactions in self-assembly monolayers on gold-coated microcantileverelectrodes

Abstract

An electrochemical microcantilever (EMC) was used to study theintermolecular interaction of self-assembly monolayers (SAMs) with differentn-alkanethiolschain lengths (n = 0, 4, 6, 8, 12, 16) on a Au-coated microcantilever surface. Comparing potential cycling and steps inNaClO4 solution within the same potential range, the deflection rate of bare microcantilevers ismuch smaller for the former which revealed that potential excitation, i.e. the surface charge,played the dominant role in driving the instant and large deflection of the bare microcantilever,while the smaller deflection amplitude of the former implied that adsorption ofClO4 − had an adverse effect on the potential-induced stress. Upon adsorption of SAMs, thedeflection amplitude of the microcantilever under the potential step was much smaller thanthat of a bare microcantilever, and linearly decreased with the chain length increasing forn ≤ 8 (the linear correlation coefficient and the slope are 0.98 and about − 10.4 nm perCH2 unit, respectively),following a transition (8 ≤ n ≤ 12) to a stable state (n ≥ 12). The decrease of deflection amplitude and faster decay of deflection rate of the SAMsmodified microcantilever under the potential step implyed increasing compactness of theSAMs with longer chains.