Self-assembling monolayers on SAW devices for selective chemical detection

The authors have utilized gold-coated, 98-MHz surface acoustic wave (SAW) devices on ST-cut quartz substrates to monitor in real time the self-assembly of organized alkanethiol monolayer films. The kinetics of assembly of these films indicate that the self-assembly process is dominated by the interaction between the thiol head group and the gold layer, rather than interactions between adjacent alkanethiol molecules. SAW devices modified with a self-assembled monolayer (SAM) of mercaptoundecanoic acid provide a response specific to the presence of organophosphonates (OPs) relative to water and a range of common volatile organic compounds (VOCs): the OP response is characteristic of increased mass loading of the device, while water and VOCs yield responses indicative of changes in the mechanical properties of the SAM film.<>