Optical trapping of plasmonic mesocapsules: Enhanced optical forces and SERS

Donatella Spadaro, Maria A. Iatì, Javier Pérez-Piñeiro, Carmen Vázquez-Vázquez, Miguel A. Correa-Duarte, Maria G. Donato, Pietro G. Gucciardi, Rosalba Saija, Giuseppe Strangi, and Onofrio M. Maragò

J. Phys. Chem. C 2017, 121, 691‒700

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.