| dc.description.abstract | As of 2017, improvised explosive devices have accounted for almost 75% of all traumatic injuries to United States soldiers in recent conflicts, yet current biomonitoring efforts through the Embedded Fragments Registry fall well short of comprehensively monitoring personnel with potential embedded fragments. This is due, in large part, to reliance on centralized urinalysis beginning long after exposure. Furthermore, the evaluation for inclusion into the Embedded Fragments Registry is predicated on the individual’s knowledge or suspicion of retained fragments. The goal of this work is to lay the groundwork for the development of a disposable, multiplexed sensor capable of reproducibly characterizing toxic metal ions in urine via surface-enhanced Raman spectroscopy. In this project, the surface enhancement of electron beam-deposited silver nanoparticles on zinc oxide nanowires was maximized through modification of fabrication and anneal parameters. New information gained from this parameter exploration was used to simplify fabrication of silver nanoparticle-decorated zinc oxide nanowires inside channels designed to minimize spectral interference from non-target materials. These channels were used to detect micromolar concentrations of crystal violet, and analogous substrates were used to successfully detect micromolar concentrations of melamine in deionized water, demonstrating the feasibility of the channel fabrication approach for detecting dilute analytes. To develop the device for detecting toxic metals, the crown ether 4’-aminobenzo-18-crown-6 was examined as a candidate to functionalize the sensing surface as a chelator. Interaction of this crown ether with 22 different metal ions was characterized in multiple solutions by ultraviolet-visible spectrophotometry and fluorescence spectroscopy and compared with benzo-18-crown-6. These experiments demonstrated that crown ether structure and solvent properties influence metal chelation. This study demonstrates the feasibility of simple channel fabrication that is optimized for surface-enhanced Raman scattering and characterization of metal ion chelation by crown ethers. The results of this project inform the development of a portable, multiplexed sensor capable of detecting and identifying multiple dilute toxic metals in urine. | |
