Unveiling Plasmon-Enhanced Localized Fields of Titanium Nitride via Complementary Electron Microscopy Techniques

Titanium nitride nanoparticles (TiN NPs) are promising alternatives to noble metals for visible-range plasmonic applications, yet their structure-property relationships remain insufficiently understood. Here, we combine ultrafast transmission electron microscopy (UTEM) and monochromated TEM to investigate plasmon-enhanced localized fields in TiN NPs. Photon-induced near-field electron microscopy (PINEM) enables the visualization and quantification of near fields in individual NPs while also serving as a tool to fuse smaller NPs with an ultrafast pulsed laser, creating larger NPs to explore the maximum near-field enhancement under a specific excitation wavelength. Our findings also reveal that the surface oxidation of TiN NPs, induced by initial high-energy laser synthesis in water, could contribute to a red-shift of their plasmon resonance toward the near-infrared region. By correlating nanoparticle size and composition with plasmonic response, this study provides new insights into light-TiN interactions and highlights the potential of tunable-laser-integrated TEM for investigating plasmonically and photothermally responsive nanomaterials.