Facile, tunable, and SERS-enhanced HEPES gold nanostars

Gold nanoparticles have shown promise as effective tools in biomedicine for drug delivery, imaging, and photo thermal therapy. We present the preparation of gold nanostars (AuNSs) through a two-step approach utilizing a common Good's buffer, HEPES, as a weak reducing agent. AuNSs with tunable branch-lengths up to 30 nm in length were produced in a two-step synthesis. We have investigated the effect of the ionic strength on the AuNS growth and branch length. AuNSs were found to be near-infrared responsive and provide an augmented SERS signal, with an enhancement factor, defined as the magnitude of SERS signal amplification, of approximately 10(7). The unique branched morphology of the AuNSs confers optical properties advantageous for in vivo biomedical applications.