Localized Surface Plasmon Resonance in Ag-In-Te Based Quantum Dots and Core/Shell Nanocrystals

Localized surface plasmon resonance (LSPR) in plasmonic nanomaterials can concentrate light in the nano-dimension, leading to an enhancement of the light intensity by order of magnitude. While LSPR is a subject of extensive research in chalcogenide semiconductor nanocrystals (NCs), research on tellurium multinary chalcogenides (MnCs) remains elusive, possibly due to non-availability of the corresponding quantum dots (QDs). In this report, we show the sequential switching of plasmonic to non-plasmonic properties during the colloidal synthesis of AgInTe₂ QDs. The reaction passes through several intermediates including AgInTe₂/AgIn₅Te₈ core/shell NCs, AgInTe₂ microrods (MRs), AgInTe₂ QDs, and finally AgInTe₂ quantum dot chain (QDC). Here, the AgInTe₂/AgIn₅Te₈ core/shell NCs and AgInTe₂ QDs depict strong LSPR absorption in the visible-NIR region until ~2000 nm. We propose that small-size quantum confined and cation deficient AgInTe₂ particles are responsible for the observation of LSPR modes in both cases due to presence of the free carriers (holes). Our work on developing Te-based plasmonic MnC QDs may find significant advancement in the nanoscale light-matter interaction in semiconductor research.