Dielectric-metal nitride core-shell plasmonic nanostructures for photo-absorption and photothermal conversion of solar radiation

This work systematically examines dielectric-transition metal nitrides (TMNs) core $-$ shell nanocomposites (SiO₂ $-$ TiN and SiO₂ $-$ ZrN), optimized geometrically for enhanced solar absorption and reduced thermoplasmonic heating. Numerical simulations based on Mie theory demonstrate that these nanoshells, whether embedded in air or water, surpass single-component TiN, ZrN, and Au nanospheres in achieving higher figures of merit (FoM) for solar energy absorption. It is shown that SiO₂ $-$ TiN and SiO₂ $-$ ZrN nanoshells allow for broader geometric optimization, resulting in elevated FoM with lower heating. In aqueous environments, TMN nanoshells exhibit minimal temperature increases across the solar spectrum, especially within the near $-$ infrared biological window (∼700–1000 nm), making them promising for biomedical applications. Furthermore, these structures reduce the need for plasmonic materials while maintaining effective solar absorption, underscoring their cost-effectiveness. This study highlights the adaptability of TMN nanoshells in solar energy systems, including photovoltaics, photocatalysis, solar thermal power, and biomedical applications.