Controllable synthesis of sea urchin-like gold nanoparticles and their optical characteristics

We reported a controlled synthesis and characterization of high-yield sea urchin-like gold nanoparticles (SGNPs) and their optical characteristics. The morphology of the SGNPs can be readily tuned by varying the experimental parameters, i.e., seeds growth time, proportion of precursors in silver/gold seeds, and amount of gold precursor used for spikes growth. Detailed statistical analysis such as TEM and SEM measurements unravels the average diameter and spike length of the SGNPs were ~150 and ~25 nm, respectively. Their corresponding optical properties were studied in detail. The absorption spectra of the SGNPs comprising a short and long plasmon band showed that the localized surface plasmon resonance (LSPR) peaks were red-shifted with the increasing spike length of SGNPs. In addition, the surface-enhanced Raman scattering (SERS) of the resulting SGNPs were also investigated using 4-mercaptobenzoic acid as a Raman reporter molecule, which exhibited a distinctive surface plasmon resonance band in the visible and near-infrared region depending on their morphologies. It is shown that the SGNPs with sharp and numerous spikes can be used as excellent SERS substrates for single-molecule detection.