CTAB stabilizes silver on gold nanorods

Abstract

We present a study that allows us to explain the chemical changes behind the often observed but so far ununderstood drift of the plasmon resonance of chemically prepared gold nanorods in microfluidic devices. We systematically monitored the evolution of the plasmon scattering signal from thousands of single nanoparticles in parallel, from different gold nanorod batches, prepared by both, silver-assisted and silver-free seeded growth. By varying the experimental conditions, we confirmed the presence of a silver surface layer for nanorods prepared by the silver-assisted method. Although the silver layer is initially protected by the surfactant CTAB, it gets oxidized as soon as CTAB desorbs because of a reduced concentration in the flowing solution.