Norma C. Adragna (Committee Member), Steven R. Higgins (Committee Chair), Ioana E.P. Sizemore (Advisor)
Master of Science (MS)
Silver nanoparticles (AgNPs) are currently widely-used in consumer products, therapeutics, biomedical devices, and electronics. Yet, one application for which AgNPs have been used extensively is surface-enhanced Raman spectroscopy (SERS)-based sensing. However, AgNP size and aggregation state are known to greatly influence these applications. This works aimed 1) to synthesize a large volume of unfunctionalized, Creighton AgNPs, to characterize their chemical and physical properties, 2) then to size-select AgNPs of 1-50 nm and 50-100 nm in diameter and to concentrate them using a three-step, "green" tangential flow ultrafiltration (TFU) process. 3) Finally, to determine and compare the SERS-based sensing capabilities of the Creighton AgNPs of various sizes (1-50 nm, 50-100 nm, and 1-100 nm). It was hypothesized that the concentrated colloidal AgNPs (1-50 nm and 50-100 nm) will lead to greater SERS enhancement factors compared to that of the original Creighton colloid due the presence of a significantly larger number of SERS "hot spots" within the focal volume. The three aims were successfully accomplished, and the proposed hypothesis was validated. AgNPs of 50-100 nm in diameter were found to have the best SERS-based sensing capabilities in non-resonant conditions due to a greater abundance of optimally sized AgNPs. The surface enhancement factor of these AgNPs was 2.1 x 106 at 10-8 M of rhodamine 6G, which facilitated the detection of ~11 molecules within the focal volume.
Department or Program
Department of Chemistry
Year Degree Awarded
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