Enhanced infrared spectroscopy for the detection of chemical and biological analytes

Since its discovery in 1980 Surface Enhanced Infrared Absorption (SEIRA) spectroscopy has generated a large amount of interest. Surface enhancement is generated when analytes are attached to thin metal films. Metal films, which are sufficiently thin, exist as small islands. The incident infrared light generates an electric field surrounding these metal islands. This field serves to channel the energy into the analyte where it is absorbed. The effect has been demonstrated using gold, silver, copper and tin films. This dissertation will discuss recent research conducted using (SEIRA) spectroscopy to monitor both biological and chemical analytes. Colloidal gold filtrates were used as a novel SEIRA biosensor for the detection of salmonella. By establishing the metal-antibody and the antibody-antigen attachment in solution, greater sensitivity was achieved. Furthermore, the colloidal filtrates offer substantial cost savings over gold sputter-coated silicon wafer. For chemical analytes, organic monolayers on the thin gold films were used to isolate analytes that do not naturally bind to gold. The largest enhancements reported previously have been with chemicals which chemically attach to the metal surface. In order to gain greater enhancement with chemicals that won't bind to the metal surface, organic monolayers were used to link analytes to a gold coating. A primary study was conducted to determine which analytes showed surface enhancement when bound to a monolayer gold system. Afterwards, a more detailed study was conducted to determine variables in the analytes and coating which determined the degree of surface enhancement. The results of the comparison were used to apply self-assembled monolayer coated substrates to the detection and quantification of trinitrotoluene (TNT).