One-step synthesis of star-shaped gold nanoparticles

In this paper we report on a simple synthesis procedure with which to fabricate stable gold nanostars (AuNS). Gold nanostars were synthesized by the reduction of a gold precursor in a basic environment using hydroxylamine as a reducing agent. Our investigation revealed that the pH of the solution is a crucial parameter in order to obtain stable gold nanostars suspension in water. At pH between 12 and 12.5 the nanostars formed a strong blue colored suspensions in water. The nanoparticles showed an intense absorption band in the red region of the visible spectrum. Numerical simulations attributed the strong absorption at around 610 nm to the plasmon resonance localized on the nanoparticles tips. Finally, star-shaped gold nanostructures showed a higher amplification of the Raman scattering of Rhodamine 6G molecules with respect to spherical nanoparticles of the same dimension.