Optical properties of metal nitrides plasmonic nanoparticles synthesized by femtosecond laser ablation in liquids

Alternative plasmonic nanomaterials based on Transition Metal Nitrides (TMNs), such as TiN, ZrN, and HfN, exhibit red-shifted absorption and scattering properties compared to conventional plasmonic nanomaterials. This characteristic makes them highly promising for various biomedical applications, including photothermal therapy and photoacoustic imaging. However, the biomedical potential of TMNs has remained largely unexplored, primarily due to the lack of straightforward synthesis techniques capable of producing stable, uncontaminated colloidal solutions of these materials. Recently, we managed to address this challenge by employing ultrafast (femtosecond) laser ablation in liquids to synthesize colloidal TMN Nanoparticles (NPs). Here, we compare the optical properties of these NPs within the biologically relevant range of tissue transparency (650-950 nm). Our results demonstrate that all synthesized NPs exhibit a significant plasmonic response in this region, with TiN NPs showing particularly strong absorption in the longer-wavelength portion of the spectrum. This enhanced performance underscores the potential of TMNs for advancing biomedical applications.