Selective Plasmonic Sensing and Highly Ordered Metallodielectrics via Encapsulation of Plasmonic Metal Nanoparticles with Metal Oxides

Novel materials for sensing and metallodielectric arrays have been prepared by encapsulation of gold-protected shape-selected silver nanoparticles with a diverse range of shells including iron, manganese, and iridium oxides using a versatile deposition procedure. These shells of varying thickness, porosity, and smoothness encapsulating metal nanoparticles advantageously combine functionalities of plasmonic cores and oxide shells into resulting functional materials. In particular, the size-uniform metal oxide encapsulated metal nanoparticles (MO-MNPs) assemble into well-ordered metallodielectric arrays for plasmonic applications. The shape and the localized surface plasmon resonance (LSPR) of the metal cores are well preserved, while the chemical and colloidal stability are enhanced by the formation of oxide shells. Metal oxide shells impart the selectivity of detection in surface-enhanced Raman spectroscopy (SERS) and surface plasmon resonance (SPR) sensing. Notably, selective sub-millimolar SPR detection of phosphate ions has been demonstrated.