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

Abstract

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 Zn2+ ions, which function as an intermediate acid that can regulate metal ion acidity to enhance the doping efficiency of Mn2+ 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 (Mn2+ ions), wherein photogenerated electrons nonradiatively transfer to the 4T1 level of Mn dopant and then recombine with the Cux 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.