Waterborne infectious diseases caused by pathogens such as E. coli and salmonella are among the major causes of death in humans worldwide. In an effort to rapidly and reliably detect common pathogens in water, we synthesized antibody conjugated gold nanoparticles and by using the resulting materials, we are constructing a sensor. This sensor will utilize both antibody-pathogen recognition and optical properties of gold nanoparticles to detect trace amounts of E. coli and Salmonella in water. The gold nanoparticles and gold-antibody conjugate nanomaterials were characterized with infrared spectroscopy, X-ray photoemission spectroscopy, transmission electron microscopy (TEM) and thermogravimetric analyses (TGA). By using 1H NMR spectroscopy, we demonstrated that the alkane thiol modified gold nanoparticle reacts with EDC coupling agents, to produce a urea product, indicating that the pendant carboxyl groups on the surface of the nanoparticle can be activated by the carbodiimide and that antibody coupling with the gold particle has been achieved. The materials' ability to detect E. coli samples in water is being currently demonstrated