Synthesis of near-infrared zinc-induced manganese-doped Cu-In-Se quantum dots and their photoluminescence mechanism

Manganese ion-doped quantum dots (QDs) with wide band gaps have been widely investigated to modify their electronic, magnetic, and photophysical properties. The research on Mn-doped Cu-In-Se QDs with narrow band gaps has been minimal due to the profound differences in the reaction reactivity of cations. In this work, photoluminescent and magnetic Cu-In-Se QD nanoprobes were designed and synthesized by introducing Zn 2+ ions, which function as an intermediate acid that can regulate metal ion acidity to enhance the doping efficiency of Mn 2+ ions in a facile phosphine-free hot-injection protocol. The emission peaks of Zn-doped Cu-In-Se QDs and MnZn-doped Cu-In-Se QDs exhibit significant composition-dependent shifts. Moreover, incorporating manganese ions confers a paramagnetic character to MnZn-doped Cu-In-Se QDs and provides a quasi-core shell structure with an Mn-rich alloy shell layer, as demonstrated by the micro-structural surface analysis and electron paramagnetic resonance spectroscopy . Analyzing the decay lifetime and quantum yield reveals that this host-dopant coupling involves a preferential energy transfer from the host material to the dopant (Mn 2+ ions), wherein photogenerated electrons nonradiatively transfer to the 4 T 1 level of Mn dopant and then recombine with the Cu x state above the valance band of host QDs. The ability to serve as nanoprobes for the visualization of tumors through fluorescence and magnetic resonance dual-modality imaging makes these ternary MnZn-doped Cu-In-Se QDs strong candidates for practical applications in biology/biomedicine field.