Selective etching of gold nanorods by ferric chloride at room temperature

The chemical stability of gold nanorods in different environments is important for a variety of practical applications, because the tiny change in shape and size could directly affect the optical properties of the gold nanorods. Herein we report a chemical etching reaction of the gold nanorods induced by ferric chloride at room temperature. In the chemical etching, halide ions act as a ligand to reduce the electron potential of the gold species, which enables ferric ions to oxidize the gold nanorods and results in the etching of the gold nanorods. The redox etching leads to a significant decrease of the gold nanorods in length but little change in diameter, which could be attributed to less surface passivation or higher chemical reactivity of the tips of the gold nanorods. It is believed that the selective shortening not only provides an alternative way to obtain the gold nanorods with desirable aspect ratios and specific optical properties, but also offers a safe way to remove gold nanostructures, which is important for the preparation of hollow nanostructures with gold as a template.