Luke D. Doucette

REAGENTLESS BIO-SAMPLING METHODS FOR IR DETECTION

Currently there exists a critical need within the military and homeland defense for highly sophisticated yet, small, lightweight portable sensors and detection systems for identifying and quantifying biological and biowarfare agents (BWA) in both liquid and aerosolized form. Our proposed BWA detection system is based upon Fourier Transform Infrared Spectroscopy (FTIR), where the main advantages of this approach are that it is reagentless, operates in heterogeneous aqueous environments, and provides fast detection and high sensitivity/selectivity to bacterial spores with minimal false alarms. The key enabler to using FTIR for BWA detection is to develop selective and robust sampling protocols coupled to a miniaturized, portable FTIR unit. To that end, we have developed front-end liquid flow cells which incorporate electric field (E-Field) concentration methods for spores onto the surface of an Attenuated Total Reflection (ATR) IR crystal. IR spectra are presented which show collection and detection results with BG spores in water. The approaches we have developed take advantage of the fact that all spores are negatively charged in neutral pH solutions. Therefore, E-Field concentration of spores directly onto an ATR sampling element enables low level concentration measurements to be possible.

The Use of Reactive Thin Films for an IR-Based Detection of Toxic Compounds in Water

We are currently developing a detection system based on the principles of infrared (IR) spectroscopy that operates in heterogeneous aqueous environments and provides fast detection (<10 min) and high sensitivity/selectivity to nonvolatile toxic materials with minimal false alarms. The key enablers to using IR spectroscopy for aqueous-based detection are the development of selective and robust sampling protocols. In this paper, we describe a new sampling approach based on the use of reactive thin films sublimed onto an IR amenable support. The films chemically react with a predefined class of compounds and identification of the specific chemical is provided by IR spectral analysis. Proof of concept of this approach is demonstrated for the detection of cyanide in water. Specifically, CuI has been vacuum sublimed on silicon wafers, and upon exposure to solutions of NaCN, CuCN is formed producing a single sharp band at 2173 cm-1. The intensity of this band varies linearly with NaCN concentration, and it is shown that a detection limit below 100 ppb (parts per billion) is achievable.

Collection and Detection of Airborne Microorganisms by Combining Electrostatic Precipitation With IR Spectroscopy

A novel reagentless system for detecting airborne microorganisms and biowarfare agents is proposed (patent pending) in this paper. The system is capable of collecting and concentrating airborne agents using electrostatic precipitation (ESP), and presenting the sample to an IR spectrometer for detection. The ESP collector module is designed to provide high collection efficiencies while optimizing optical throughput matching with the concentrated sample to achieve very low detection limits. Specifically, our study shows that by measuring the amide I absorption band at 1650 cm-1 that is associated with bacterial spores, the ESP-IR collection and detection system would be capable of detecting approximately 8300 spores/l in 10 min.

DEVELOPMENT OF MATERIALS AND SAMPLING METHODS FOR IR-BASED DETECTION OF TOXIC COMPOUNDS IN WATER

A detection approach based on the principles of Fourier Transform Infrared Spectroscopy (FTIR) is presented for the trace level detection of toxic compounds in water. The main advantages of this approach are that it operates in heterogeneous aqueous environments, provides fast detection (< 10 min), and exhibits high sensitivity/selectivity to nonvolatile toxic materials with minimal false alarms. The key enablers to using FTIR for aqueous-based detection is the development of a selective and robust sampling protocol coupled to a miniaturized portable FTIR unit. The sampling approaches involve synthesizing and tailoring microporous, mesoporous, and nonporous metal oxide powders/films that are amenable for in situ FTIR measurements. In this paper we provide an overview of the material synthesis and surface modification strategies, and present results obtained using these materials for the low level detection of the organophosphate pesticide phosmet. Phosmet is used as a surrogate for the nerve agent VX.