Colloidal Second Near‐Infrared‐Emitting Mn‐Doped Ag₂S Quantum Dots

Abstract Incorporation of transition metal dopants within a semiconductor nanocrystal has a tremendous effect on the optical and magnetic properties of the semiconductor nanocrystals. Herein, we report on a novel synthesis of second near‐infrared‐emitting photoluminescent Mn²⁺‐doped Ag₂S quantum dots via co‐pyrolysis of silver and manganese single‐source precursors. The Mn²⁺ doping level was flexibly tuned in Ag₂S quantum dots, which was confirmed by elemental analysis and electron paramagnetic resonance spectroscopy. The Mn²⁺ doping induced negligible change in the pristine monoclinic acanthite Ag₂S crystal structure but significantly decreased the photoluminescent intensity. Mn²⁺‐doped Ag₂S QDs exhibit second near‐infrared emission and ferromagnetic ordering, which show the potential applicability for multimodal fluorescence/MRI probes.