Optical Trapping of Plasmonic Mesocapsules: Enhanced Optical Forces and SERS

Donatella Spadaro, Maria Antonia Iatì, Javier Perez-Pineiro, Carmen Vázquez-Vázquez, Miguel A. Correa-Duarte, Maria Grazia Donato, Pietro Giuseppe Gucciardi, Rosalba Saija, Giuseppe Strangi, and Onofrio M Marago

We demonstrate optical trapping of plasmonic silica-gold mesocapsules and their use as local SERS probes in Raman tweezers. These novel hybrid dielectric-metal particles, designed for optoplasmonic applications, are mesoscopic porous silica shells embedding gold nanospheres in their inner wall. We observe a high trapping efficiency due to plasmon-enhanced optical trapping of the gold component. Furthermore, we develop an accurate model of optical trapping of this hybrid system in the T-matrix framework studying how the plasmon-enhanced optical forces scale with gold nanoparticle number in the mesocapsule. The relevance of effective optical trapping in hollow plasmonic mesocapsules is twofold for detection and delivery technologies: Positioning and activation processes. In fact, the presented system allows for the opportunity to drag and locate cargo mesocapsules embedded with specific molecules that can be activated and released in-situ when a precise localization is required.

DOI