Optical Properties of Metacrystals Based on Protein Nanocages

The optical properties of 3D metacrystals made of gold nanoparticles in protein nanocages are studied. These metacrystals have sizes of tens of micrometers and are of high structural and optical quality. Through microspectroscopy measurements and model calculations it is demonstrated that the metacrystals show plasmonic absorption in the green wavelength range and are largely transparent in the red and infrared ranges. By using empty nanocages as placeholders in the metacrystal lattice, it is possible to control how strongly the metamaterial absorbs. Measurements on a pyramidal metacrystal show that it deflects visible light. The deflection shows evidence for anomalous refraction at short wavelengths and normal refraction at long wavelengths. The refractive dispersion is ascribed to the optical dispersion relation of the plasmonic metamaterial.

Automated summary

The optical properties of 3D metacrystals made of gold nanoparticles in protein nanocages are investigated. These metacrystals have good structural and optical quality with sizes in the tens of micrometers range. Through microspectroscopy measurements and model calculations, it is shown that the metacrystals exhibit plasmonic absorption in the green wavelength range and are mostly transparent in the red and infrared ranges. By using empty nanocages as placeholders in the metacrystal lattice, the absorption strength of the metamaterial can be controlled. Measurements on a pyramidal metacrystal demonstrate deflection of visible light, indicating anomalous refraction at short wavelengths and normal refraction at long wavelengths. The refractive dispersion is attributed to the optical dispersion relation of the plasmonic metamaterial.