Multi-branched gold nanoparticles for Surface Enhanced Raman scattering characterization

Abstract

Surface enhanced Raman scattering (SERS) is a sensitive and reproducible vibrational spectroscopic technique used to detect and characterize molecules near the surface of noble metals like Au, Ag, Pt, Cu, etc. SERS enhances Raman signals through light-induced plasmonic vibrations occurring on irregular metal surfaces and localized electromagnetic augmentation. To better define nano-scale regions of the Raman signal enhancement, we generated gold nanoparticles with a unique multi-branched configuration along with surface-adsorbed fluorescent reporter molecules. The reporter molecules included a set of near-infra red active fluorescent dyes IR820 (green cynanine, photo electronic dye), DTTC (3, 3'-diethylthiatricarbocyanine iodide) and DTDC (3, 3'-diethylthiadicarbocyanine iodide). We employed a one-pot synthesis method in order to generate a stellate configuration in gold nanoparticles through the reduction of HAuCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> with Good's buffer, HEPES, at pH 7.4 and room temperature. A cell viability assay was performed with normal esophageal cells exposed to the multi-branched gold nanoparticles and SERS molecules to assess their toxicity. Our results demonstrate the capacity of multi-branched gold nanoparticles linked to Raman reporter molecules to generate distinct signature spectra and, with the exception of the gold nanoparticles functionalized with DTTC, remain non-toxic to normal esophageal cells.