Mn-Doped Quinary Ag-In-Ga-Zn-S Quantum Dots for Dual-Modal Imaging

Doping of transition metals within a semiconductor quantum dot (QD) has a high impact on the optical and magnetic properties of the QD. In this study, we report the synthesis of Mn²⁺-doped Ag-In-Ga-Zn-S (Mn:AIGZS) QDs via thermolysis of a dithiocarbamate complex of Ag⁺, In³⁺, Ga³⁺, and Zn²⁺ and of Mn(stearate)₂ in oleylamine. The influence of the Mn²⁺ loading on the photoluminescence (PL) and magnetic properties of the dots are investigated. Mn:AIGZS QDs exhibit a diameter of ca. 2 nm, a high PL quantum yield (up to 41.3% for a 2.5% doping in Mn²⁺), and robust photo- and colloidal stabilities. The optical properties of Mn:AIGZS QDs are preserved upon transfer into water using the glutathione tetramethylammonium ligand. At the same time, Mn:AIGZS QDs exhibit high relaxivity (r ₁ = 0.15 mM^-1 s^-1 and r ₂ = 0.57 mM^-1 s^-1 at 298 K and 2.34 T), which shows their potential applicability for bimodal PL/magnetic resonance imaging (MRI) probes.