Bulk scale fabrication of sodium tungsten bronze nanoparticles for applications in plasmonics

In order to advance plasmon-based technologies, new materials with low damping losses and high chemical stability are needed. In this letter, we report the bulk scale fabrication of sodium tungsten bronze (Na _x WO₃) nanoparticles with high Na content (x ≤ 0.83) using a furnace-assisted method. Phase purity and morphology is confirmed with x-ray diffraction and scanning electron microscopy. Plasmon responses are characterized using spectrophotometry and spatially-resolved electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope. Experimental EELS maps of individual nanoparticles show the excitation of distinct plasmon resonances at visible and near-infrared (NIR) frequencies, and these observations are supported by boundary element method simulations. Na _x WO₃ is a promising alternative material for plasmonics due to its strong plasmon resonances when compared to Au, its simple nanofabrication, and low cost. In particular, their high NIR extinction makes these materials ideal for applications in solar control window coatings or plasmonic photocatalysis.