Preparation of Silica-Coated Ultrathin Gold Nanowires with High Morphological Stability

We demonstrated a preparation method of silica-coated straight ultrathin Au nanowires (NWs). Water-dispersive ultrathin Au NWs capped with a long-chain amidoamine derivative (C18AA) were used for silica coating. The Au NWs were partially covered with 3-mercaptopropanoic acid by the ligand exchange method, and silica coating of the Au NWs was carried out by the hydrolysis of tetraethoxysilane (TEOS) at pH > 6.7 because the shape of the Au NWs was changed under acidic conditions. The thickness of the silica layer depended on the concentration of TEOS, and the layer was able to decrease to 6-10 nm thick. We also demonstrated that the silica-coated Au NWs had high morphological stabilities against external stimuli such as a TEM electron beam, heat, and pH compared with the bare Au NWs.