Deciphering surface enhanced Raman scattering activity of gold nanoworms through optical correlations

Surface enhanced Raman scattering (SERS) “hot spots” are the regions where the electromagnetic field is significantly enhanced, resulting in much greater SERS activity than other areas. Therefore, the engineering and characterization of “hot spots” have attracted much attention. Herein, we have synthesized nanoworms formed by connecting hollow gold nanospheres and investigated their composition as well as their SERS properties, including their potential for simultaneous analysis of multiple species. The three-dimensional nanostructures that led to different SERS activities were investigated using correlated optical/SERS and SEM imaging. Gold nanoworms with hollow nanosphere segments and partial tube formation were confirmed. All highly SERS-active structures were found to be three-dimensional arrays consisting of inter-/intrananoworm interactions; no individual nanospheres were found to give significant SERS signal under the experimental conditions. The major SERS contribution was found to be the electromagnetic coupling effect within the three-dimensional arrays and the localized surface plasmon resonance of the nanostructure was found to have a minimal effect. This study gives insight into the basis of enhancement for these nanoworm structures and adds to the growing body of evidence in relation to nanostructures and surface enhancement of Raman scattering