Synthesizing Gold Nanorods for Enhanced Detection

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Stevie Norcross, Westminster College

Chemistry

Gold nanostructures exhibit tunable optical properties that depend on a nanomaterial’s composition, shape, and size. These optical properties arise from a phenomenon known as the localized surface plasmon resonance (LSPR), which contributes to surface enhanced Raman scattering (SERS) spectra. SERS enhances detection by up to 9 orders of magnitude vs. normal Raman scattering thereby routinely improving detection limits of target molecules to nM μM concentrations. In this study, gold nanorods, which exhibit tunable LSPR properties from the visible to near-IR regions, were synthesized using a solution phase seed-mediated growth method. LSPR tunability was achieved by varying gold nanorod growth temperature, silver ion concentration, or reducing agent (ascorbic acid) concentration. Systematically varying these parameters yielded gold nanorods with LSPR wavelength maximums ranging from 692 to 763 nm. By increasing the concentration of ascorbic acid from 0.54 mM to 0.63 mM, gold nanorods with an average LSPR wavelength maximum of 755 ± 8 nm were synthesized. Following the synthesis, the gold nanorods were used for the direct and enhanced detection of the anti-cancer drug, 6-mercaptopurine and one of its metabolites, 6-thiouric acid. It was observed that as molecular concentrations were increased signal intensities systematically increased; therefore, the identification and quantification of each molecule individually as well as in a mixture of the molecules in buffer was achieved.