Dual Luminescent Mn(II)‐Doped Cu‐In‐Zn‐S Quantum Dots as Temperature Sensors in Water

Abstract CuInS₂ quantum dots have emerged in the last years as non‐toxic alternative to traditional Pb and Cd based quantum dots, especially for biological applications. In this work, the hydrothermal synthesis of alloyed Cu‐In‐Zn‐S quantum dots (CIZS) doped with manganese(II) is explored, with different metal ratios (Mn‐CIZSy). The doped quantum dots show the sensitized emission of Mn²⁺ (approximately ms lifetime), together with the emission of the CIZS structure (approximately µs lifetime). The relative contribution of Mn²⁺ emission is highly dependent on the composition of the CIZS hosting structure (In:Cu ratio). In addition to that, it is shown that Mn²⁺ sensitization requires a threshold energy, which suggests the involvement of an intermediate state in the sensitization mechanism. The long‐lived emission intensity decay of Mn²⁺ shows a stable and reversible temperature response in physiological conditions (25–45 °C, pH = 7.4). Mn‐CIZSy quantum dots are thus interesting candidates as biological luminescent temperature probe thanks to their easy synthesis, high colloidal stability, insensitivity to dioxygen quenching and quantitative time‐gated detection.