Surface Enhanced Raman Spectroscopy of a Au@Au Core-Shell Structure Containing a Spiky Shell

We have synthesized a novel Au@Au core-shell structure containing a spiky shell and characterized the surface enhanced Raman spectroscopy (SERS) of such a structure. The experimental and calculated SERS intensities for probe molecules residing between the core and shell are considerably higher in this structure containing a spiky shell, when compared to the smooth shell counterpart. Moreover, the SERS intensities for probe molecules residing on the outside of the spiky core-shell structure are comparable to those measured for the dye residing between the core and shell and similar to that of a gold nanostar. Finite-difference time-domain calculations in combination with hybridization theory are able to predict the extinction spectral features and show that the field enhancements are considerably larger than the smooth core-shell structure throughout the visible and infrared regions of the spectrum. This spiky Au@Au core-shell system shows excellent promise as a next generation SERS nanotag, in which encapsulated probe molecules yield increased SERS signal and the increased surface area of the shell allows for a greater degree of functionalization.