Rapid Ultrasensitive Chemical-Fingerprint Detection of Chemical and Biochemical Warfare Agents

Abstract

Vibrational spectra can serve as chemical fingerprints for positive identification of chemical and biological warfare molecules. The required speed and sensitivity might be achieved with surface-enhanced Raman spectroscopy (SERS) using nanotextured metal surfaces. Systematic and reproducible methods for preparing metallic surfaces that maximize sensitivity have not been previously developed. This work sought to develop methods for forming highefficiency metallic nanostructures that can be integrated with either gas or liquidphase chem-lab-on-a-chip separation columns to provide a highly sensitive, highly selective microanalytical system for detecting current and future chem/bio agents. In addition, improved protein microchromatographic systems have been made by the creation of acrylate-based porous polymer monoliths that can serve as protein preconcentrators to reduce the optical system sensitivity required to detect and identify a particular protein, such as a bacterial toxin. 6 Executive SummaryUnambiguous identification of chemicals and biochemicals usable as chem/ bio weapons (CBW) is essential at nanomolar levels with short analysis times (<5 min.) Vibrational spectra can serve as chemical fingerprints for positive identification of CBW molecules. The required speed and sensitivity might be achieved with surface-enhanced Raman spectroscopy (SERS) using nanotextured metal surfaces. Although ordinary SERS produces sensitivity enhancements on the order of 10 3 vs. normal Raman spectroscopy, a properly nanotextured metal surface can increase sensitivity up to 10 14 -fold.Systematic and reproducible methods for preparing stationary metallic surfaces that maximize sensitivity have not been previously developed. This LDRD program was to investigate the integration of chemical-fingerprint identification of CBW molecules using SERS as the detector in the chip-scale microseparation columns developed under the Sandia MicroChemLab program. To this end, this program was to develop methods for forming high-efficiency metallic nanostructures that could be integrated with either gas or liquid-phase chem-lab-on-a-chip separation columns to provide a highly sensitive, highly selective microanalytical system for detecting current and future chem/bio agents. In addition to speed and sensitivity, the chemical fingerprinting provided by SERS would enable rapid identification of new, non-standard CBW agents that might be introduced to avoid detection by established sensor systems.Improved methods for on-chip separation of biomolecules, such as proteins, were a prerequisite for the application of SERS as a detector in microchromatograpic systems. Chromatographic separation media based on porous polymer monoliths were to be developed in this program to insure efficient separation and purification of proteins, such as biotoxins, prior to their detection and identification using SERS.The goals of this LDRD were three-fold: 1) Development of a manufacturable surface that possessed a very high density of metallic nanostructure...