Near‐Infrared Emissive CuInS2/ZnS Quantum Dot‐Embedded Polymer Scaffolds for Photon Upconversion Imaging

Abstract A facile synthesis and application of photon upconversion (UC) probes, CuInS₂/ZnS quantum dots (nCIS QDs) is presented, which exhibits near‐infrared (NIR) spectral emission. The nCIS QDs are synthesized via a template‐assisted cation‐exchange reaction during a heating process, resulting in NIR‐I emission with a large Stokes shift (≈650 meV) and a high photoluminescence quantum yield (PLQY, ≈0.95). This behavior is attributed to a template‐assisted cation‐exchange mechanism that produces a wurtzite crystal structure and deep defect states, leading to a relatively long fluorescence lifetime (≈5 µs ). The quantum confinement effect allows for the emission of light at different wavelengths by adjusting the size of the nanocrystals. Moreover, their deep defect states facilitate photon UC via a self‐trapping triplet‐triplet annihilation mechanism. The promising potential of the nCIS QDs is explored in UC imaging, demonstrating high‐contrast NIR imaging under IR vision modules, even in the presence of interference layers. It suggests potential applications in surgical guidance and future biomedical imaging.