Fabrication of hollow metal nanocaps and their red-shifted optical absorption spectra

Cap-shaped metal nanoparticles (see Figure) have optical spectra with significant absorption in the infrared. Such shapes, produced by physical vapor deposition onto a polymer-particle template, can be readily separated from one another provided that deposition is carried out at an inclination to the plane of the template. The effect of composition, angle of deposition, and thickness on the properties of the cap-shaped particles is discussed.