Ultrasensitive Detection of CrO4^2- Using a Microcantilever Sensor

Microcantilevers modified with a self-assembled monolayer respond sensitively to specific ion concentrations. Here, we report the detection of trace amounts of CrO4^2using microcantilevers modified with a self-assembled monolayer of triethyl-12-mercaptododecylammonium bromide. The self-assembled monolayer was prepared on a silicon microcantilever coated with a thin layer of gold on one side. The microcantilever undergoes bending due to sorption of CrO4^2- ions on the monolayer-modified side. It was found that a concentration of 10^-9 M CrO4^2- can be detected using this technology in a flow cell. Other anions, such as Cl^-, Br^-, CO3^2- (or HCO3^-), and SO4^2-, have minimal effect on the deflection of this cantilever. The mechanics of the bending and the chemistry of cantilever modification are discussed.