Electromagnetically Porous Infrared Plasmonic F,Sn-Doped In₂O₃ Semiconductor Nanocrystals for Infrared Optoelectronic Sensors

We report dopant-induced complex hierarchical shell growth in metal oxide nanocrystal cubes, leading to a high-density infrared near-field localized surface plasmonic resonance (LSPR) response per film area with an interparticle 41.25% film porosity. We synthesize electromagnetically porous infrared plasmonic nanocrystals via hierarchical cube-on-cube surface growth in highly aliovalently doped semiconductor nanocrystals. In indium oxide colloidal nanocrystal systems, under low Sn dopant, we observe uniform Frank–van der Merwe type shelling. While exceeding 4% Sn atomic dopant, excessive Sn on (400) nanocrystalline achieves a Volmer–Weber island formation-type growth. Through surface XPS analysis, we exclude Stranski–Krastanov-type growth, an intermediary between uniform and island surface growth. Through complex hierarchical shapes in infrared plasmonic semiconductor nanocrystal surfaces, infrared range optical extinction is observed around the 2500 nm wavelength. Direct electromagnetic near-field was imaged through the infrared STEM-EELS electron microscopy technique in single nanocrystals. Due to the intrinsic interparticle gap under monolayer film architecture, electromagnetically dense near-field plasmonic response was directly observed via STEM-EELS.