Synthesis of multi-branched gold nanoparticles by reduction of tetrachloroauric acid with Tris base, and their application to SERS and cellular imaging

We show that tris base (TB), a widely used buffer substance, can act as a reducing agent to synthesize multi-branched gold nanoparticles (mb-AuNPs) from tetrachloroauric acid in a one-step process. The method is simple, fast, and inexpensive and produces mb-AuNPs that are virtually monodisperse, have a size of about 90 nm and typically >6 branches. Their UV-vis absorption peaks can be fine-tuned from the visible to the near-infrared (NIR) region by controlling the concentration of TB. The mb-AuNPs represent an efficient substrate for surface-enhanced Raman scattering (SERS), with an enhancement factor of 1.2 × 105. They were applied as substrates for SERS-based imaging of kidney cells.