Seed-Mediated Synthesis of Photoluminescent Cu–Zn–In–S Nanoplatelets

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Ternary and quaternary colloidal nanocrystals (NCs) based on I–III–VI group semiconductors are promising low-toxic luminescent materials attracting huge interest as alternatives to cadmium- and lead-chalcogenide-based NCs. Despite significant progress in the synthesis of three-dimensionally confined quantum dots based on I–III–VI semiconductors with intensive photoluminescence (PL) in a broad spectral range, all attempts to prepare one-dimensionally confined nanoplatelets (NPLs) or nanosheets have resulted in rather nonemitting two-dimensional (2D) NCs. Since 2D NCs of the II–VI group exhibit unique anisotropic optical properties, exploring synthetic strategies to obtain 2D I–III–VI-based NPLs might also reveal interesting optical and electronic features. In this work, we demonstrate the synthesis of luminescent In-rich Cu–Zn–In–S (CZIS) NPLs using a one-pot approach. The synthesis includes the formation of Cu–In–S NPLs from In2S3 seeds, followed by the incorporation of zinc to form quaternary NPLs with improved stability and optical properties. The synthetic strategy implemented results in the formation of ∼1 nm thick NPLs with lateral sizes of ∼30 × 10 nm2 and a tetragonal crystal structure. As-synthesized NPLs are stable at ambient conditions and demonstrate PL in the range of 700–800 nm with a large Stokes shift. An additional shell of ZnS grown on CZIS NPLs resulted in the enhancement of their PL quantum yield reaching 29%.