Ion-Mediated Photoluminescence Enhancement in CuInS₂ Quantum Dots and Its Use as Heavy Metal Ion Sensor

High Resolution Image Download MS PowerPoint Slide The absence of heavy metal ions and excellent photoluminescent (PL) properties make CuInS 2 quantum dots (QDs) ideal candidates for a wide range of PL applications. One of these applications stems from their inherent capacity to respond to the presence of Cd 2+ ions, which significantly enhances their photoluminescence emission. This property enables the creation of Cd 2+ sensors based on the detection of variations in the PL emission or PL lifetime. Aiming to understand the enhancement effect that the presence of Cd 2+ exerts on these CuInS 2 QDs, we synthesized and characterized a set of CuInS 2 QDs covered with varying ZnS shell thicknesses, which were used as Cd 2+ probes. The analysis of PL features demonstrated that the presence of Cd 2+ ions blocks surface traps on the CuInS 2 QDs, minimizing nonradiative decay pathways and therefore increasing both the PL lifetimes and the PL emission of the QDs. In contrast, the incorporation of a ZnS shell passivates the surface of the QDs, reduces the number of accessible surface traps, and diminishes the sensitivity toward the Cd 2+ ions. This knowledge has been used to create a sensor that can be used to selectively detect the presence of Cd 2+ in the micromolar range, which can even be seen with the naked eye, and exhibits a linear range from 0.05 to 10 μM.