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.