Chemical and Biological Point Sensors for Homeland Defense

As part of an effort to develop a portable probe for real-time detection of chemical agents using Raman spectroscopy, the kinetics of adsorption of selected volatile organic molecules on high surface area silica supports was studied using Raman spectroscopy with 785-nm excitation. Two aspects of this work are described. First, the affinity of organic molecules in a flowing gas stream to ultraporous mineralized wood stubstrates was shown to be very high under a variety of respresentative conditions, suggesting that a sensor based on in-situ Raman measurement of adsorption rates may be feasible. Moreover, the mechanism of adsorption was found to vary for different molecules, thereby promoting a high degree of chemical specificity. Second, the possibility of using Surface-Enhanced Raman Spectroscopy (SERS) to enhance Raman signals and thereby improve the sensitivity of an in-situ Raman probe even further was demonstrated.