Synthesis and Characterization of Au@MnO2 Nanoparticles as Plasmon Enhanced Spectroscopy Substrates

The plasmonic properties of Au nanoparticles (AuNP), which allow the observation of enhanced spectroscopic effects, are strongly affected by the aggregation and precipitation caused by the strong interactions between nanoparticles. To avoid AuNP aggregation and precipitation, the present study proposes coating with MnO2, forming AuNP@MnO2 core-shell structures. The MnO2 layers presented 1-10 nm thickness so that highly surface-enhanced fluorescence was obtained with maximum intensity given by 5 nm thick MnO2. The decrease in Raman intensity could be controlled, despite the inherent reduction in surface-enhanced Raman scattering (SERS) intensity with increasing adsorbate-surface distance. The decrease in Raman intensity was compensated by increasing AuNP stability caused by the MnO2 shell.