Plasmonic Focusing in Rod−Sheath Heteronanostructures

This paper describes the fabrication of plasmonic focusing, free-standing rod-sheath hetero-nanostructures based on electrochemical templated synthesis and selective chemical etching. These hetero-nanostructures take advantage of plasmon interference together with field enhancements due to sharp junction structures to function as stand-alone SERS substrates containing Raman hot spots at the interface of the rod and sheath segments. This result is investigated with empirical and theoretical (discrete dipole approximation, DDA) methods, and we show how plasmon interference can be tuned by varying the sheath and rod lengths.