Synthesis and optical properties of branched gold nanocrystals

We report the synthesis of new branched gold nanocrystals in high yield (over 90%) via a wet-chemical route. The branched nanocrystals exhibit a shape-dependent plasmon resonance that is red-shifted by 130-180 nm from the spherical particle wavelength. Discrete dipole approximation (DDA) calculations qualitatively replicate the observed optical extinction spectra of the nanocrystals, indicating that the surface plasmon resonance is mainly determined by in-plane dipole excitation associated with the sharp tips.