SERS induced by Au/ZnO plasmonic nanorods coupled to Au nanoparticles

We study the surface enhanced Raman scattering of Methylene Blue (MB) dye molecules induced by 3D array of "hot spots" made of vertical Au/ZnO core-shell nanorods coupled to self-assembled plasmonic Au nanoparticles. SERS substrates based on array of nanorods coupled to nanoparticles show much better performance compared with bare Au/ZnO nanorods. The hybrid 3D SERS substrate perfectly resolve Raman spectra of MB molecules chemisorbed from solutions with analyte concentrations of ∼10^-7 M even upon washing of a sample i.e. when only chemisorbed molecules were remained. Raman signal enhancement results from the superposition of two effects, namely, the ability of a plasmonic coupled system to enhance the Raman scattering via local field enhancement and from the large 3D surface which provides more adsorption sites compared with traditional 2D surfaces. (paper)