Enhanced plasmonic behavior of incomplete nanoshells: Effect of local field irregularities on the far-field optical response

Abstract

Plasmonic behavior of core-shell-type nanostructures is currently the focus of intense research, particularly because of the tunable optical response of such materials suitable for emerging applications such as laser-induced interstitial thermotherapy, surface-enhanced Raman scattering, and biosensing. In this work, we report on the plasmonic behavior of incomplete nanoshells, providing insight into their evolution and growth. During the initial stages of formation, well-separated, noninteracting metallic nanoparticles at the surface of a dielectric core behave like isolated particles, but irregular and intense local electric fields (hot spots) are created when the number of metallic spheres increases, dramatically affecting the far-field optical response of the integral structure. Under the action of these local fields, the position of the surface plasmon resonance (SPR) suffers a dramatic red shift up to 50% higher than that of a complete nanoshell. The presented results open up the possibility of fabricating metallic nanoshells that are more efficient than the conventional ones for biological applications. © 2011 American Chemical Society.