Life Sciences Division
Oak Ridge National Laboratory

Highly Selective Microcantilever Sensor for Cesium Ion Detection (May 1999)

Researchers in the Nanoscale Science and Devices Group of Life Sciences Division’s Biochemistry and Biophysics Section have demonstrated a novel, extremely sensitive sensor with a wide dynamic range for detecting cesium (Cs) ion concentrations in water. This sensor concept based on microcantilever platform is highly selective for cesium. To make the microcantilevers selective for Cs, the cantilevers were coated with cesium-selective ionophores (which have selectivities for cesium over sodium in the range of 20,000 to 50,000). We have used chemically modified 1,3-alternate 25,27-dialkoxy —26,28-calix[4]-benzo-crown-6 ionophores, for attachment to the microcantilever. The ionophores were synthetically modified with long-chain alkanethiols for attachment to a gold-coated microcantilever for the detection of cesium ions. The octyl chains were derivatized with terminal thiols for adsorption onto gold.

It was found that the cantilever responded to Cs concentrations ranging from 10^-2 to 10^-11M. From the response curves it is clear that Cs concentrations as low as 10^-12 M could be detected using this unique approach. These sensors were so selective that we were able discern small concentrations of Cs even in the presence of high concentrations of Na and K ions. We have also demonstrated that this sensor can detect small amounts of cesium in simulated tank waste (pH 14).

One clear advantage of this sensor concept is its suitability for the development of a multi-ion sensor with wide ranging applications. Currently available micromachining technologies can be used to make sensor arrays with hundreds of cantilevers without significantly increasing the size, complexity, or cost of the overall sensor package. The large number of sensing elements in a sensor array will result in lower noise, much higher selectivity, and increased robustness. (Contact: Thomas Thundat, 574-6201 or thundattg@ornl.gov; Funding Source: KP)