Plasmonic Core–Shell Zirconium Nitride–Silicon\nOxynitride Nanoparticles

Abstract

We\ndiscuss the synthesis and properties of plasmonic zirconium\nnitride nanocrystals produced using a nonthermal plasma reactor. The\nprocess enables the continuous conversion of chemical precursors into\nfree-standing ∼10 nm diameter nanoparticles. Oxidation limits\nthe resonant plasmon energy from ∼2.6 eV for ideal unoxidized\nparticles to ∼2.1 eV for particles exposed to air at room temperature.\nA simple modification to the plasma process allows the in-flight growth\nof a conformal silicon oxynitride shell onto the zirconium nitride\ncore. The shell inhibits the oxidation of the core, resulting in particles\nwith a plasmon energy of 2.35 eV. These particles show good plasmonic\nbehavior even after annealing in air at 300 °C, largely improved\nwhen compared to unprotected particles that oxidize and lose plasmonic\nactivity at the same temperature. This work represents a step toward\nthe development of earth-abundant, thermally and chemically resistant\nnanoparticles that can offer an inexpensive alternative to gold and\nsilver and extended applicability in harsh environments.