Aligned Gold Nanorods in Silica Made by Ion Irradiation of Core–Shell Colloidal Particles

Colloidal particles with a 14 nm diameter Au core surrounded by a 72 nm thick silica shell have been irradiated with 30 MeV heavy ions. The shell deforms into an oblate ellipsoid, while the core becomes rod‐shaped (aspect ratio up to 9) with the major axis along the beam. Optical extinction measurements show evidence for split plasmon bands, characteristic for anisotropic metal nanoparticles.