Near Single-Molecule SERS-Based Detection Using Ultrafiltered, Unfunctionalized Silver Nanoparticles
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
Copyright 2012, all rights reserved. This open access ETD is published by Wright State University and OhioLINK.