B.S., 1978, University of Chicago Ph.D., 1983, Columbia University NIH Postdoctoral Fellow, 1983-1985, University of California, Berkeley

Synthetic Organic Chemistry

Our research focuses on applications of organic chemistry to analytical chemistry. Only rarely is it possible to directly determine the concentration of a target analyte in a sample matrix. Generally, the presence of numerous interferents having similar spectral characteristics to the target necessitates sample pretreatment, followed by some form of chromatography prior to the actual detection and quantification of the target. Indeed, much of the time and effort involved in most analytical methods are spent in this type of sample "clean-up." We are investigating a number of attractive alternatives to this traditional methodology. In one broad class of applications we construct sensor molecules that comprise a molecular recognition site for the target analyte (e.g., copper), a "reporter" subunit that undergoes a spectral change to a readily detectable form upon binding of the target, and a tethering group that has a high affinity for silver or gold. When a target containing sample is combined with the sensor, followed by addition of gold nanoparticles, the target-sensor complex binds to the nanoparticles and the amount of the complex can be determined using surface enhanced Raman scattering (SERS) spectroscopy. Using this method, we have demonstrated rapid (~10 sec) detection of bioavailable copper at a part-per-billion sensitivity. In a another approach to specific and sensitive analyte detection we have designed sensor molecules that undergo very selective reactions with certain compounds (e.g., nerve gas) to give intermediates that subsequently fragment to give readily detectable dyes. With this approach, we have demonstrated detection of sub-parts-per-million levels of nerve agent analogs in less than a minute.