Ultrathin gold nanowires (1.7 nm) with unique physical properties can be stabilised using a specific organic ligand (oleylamine) layer. To understand the key role of the organic layer at the surface of these ultrathin gold nanowires, SANS time-resolved experiments will be performed during their synthesis. The thickness of the organic layer will be determined using a shell contrast by matching the scattering length density of the solvent with the one of gold. This layer thickness will be compared to the one of spherical gold nanoparticles obtained in similar synthesis conditions.