Gold/oxide heterostructured nanoparticles for enhanced SERS sensitivity and reproducibility

In surface-enhanced Raman scattering (SERS), it is highly desirable to obtain Raman signals with high sensitivity and reproducibility from noble metal nanoparticle substrates, which remains a great challenge due to the inhomogeneity of the plasmonic coupling that is sensitive to the interparticle nanogaps. In this work, we report that the interparticle plasmonic coupling could be circumvented by first synthesizing Au/metal or nonmetal oxide heterostructured nanoparticles and then depositing them uniformly onto the substrates, leading to high reproducibility of the Raman signals. Strong plasmonic coupling has been found at the Au/oxide interface, which enables high sensitivity of the SERS analysis that accompanies the excellent signal reproducibility. Among different oxides investigated (SiO₂, TiO₂ and Fe₂O₃), the Au/Fe₂O₃ heterostructured nanoparticles demonstrate the highest Raman enhancement effect. We believe our strategy opens a promising route to fabricate SERS substrates that are capable of sensitively and quantitatively detecting molecules of interest in a much reliable manner.