Unveiling\nSpatial and Temporal Dynamics of Plasmon-Enhanced\nLocalized Fields in Metallic Nanoframes through Ultrafast Electron\nMicroscopy

Plasmonic\nnanomaterials, particularly noble metal nanoframes (NFs),\nare important for applications such as catalysis, biosensing, and\nenergy harvesting due to their ability to enhance localized electric\nfields and atomic efficiency via localized surface plasmon resonance\n(LSPR). Yet the fundamental structure–function relationships\nand plasmonic dynamics of the NFS are difficult to study experimentally\nand thus far rely predominately on computational methodologies, limiting\ntheir utilization. This study leverages the capabilities of ultrafast\nelectron microscopy (UEM), specifically photon-induced near-field\nelectron microscopy (PINEM), to probe the light-matter interactions\nwithin plasmonic NF structures. The effects of shape, size, and plasmonic\ncoupling of Pt@Au core–shell NFs on spatial and temporal characteristics\nof plasmon-enhanced localized electric fields are explored. Importantly,\ntime-resolved PINEM analysis reveals that the plasmonic fields around\nhexagonal NF prisms exhibit a spatially dependent excitation and decay\nrate, indicating a nuanced interplay between the spatial geometry\nof the NF and the temporal evolution of the localized electric field.\nThese results and observations uncover nanophotonic energy transfer\ndynamics in NFs and highlight their potential for applications in\nbiosensing and photocatalysis.