Unexpected Magnetic Moments in Manganese-Doped (CdSe)₁₃ Nanoclusters: Role of Ligands

This study explores the enhancement in magnetic and photoluminescence properties of Mn²⁺-doped (CdSe)₁₃ nanoclusters, significantly influenced by the introduction of paramagnetic centers through doping, facilitated by optimized precursor chemistry and precisely controlled surface ligand interactions. Using a cost-effective and scalable synthesis approach with elemental Se and NaBH₄ (Se-NaBH₄) in n-octylamine, we tailored bonding configurations (Cd-O, Cd-N, and Cd-Se) on the surface of nanoclusters, as confirmed by EXAFS analysis. These bonding configurations allowed for tunable Mn²⁺-doping with tetrahedral coordination, further stabilized by hydrogen-bonded acetate ligands, as evidenced by ¹³C NMR and IR spectroscopy. Mulliken charge analysis indicates that the charge redistribution on Se^2- suggests electron transfer between surface ligands and the nanocluster, contributing to spin fluctuations. These tailored configurations markedly increased the nanoclusters' magnetic susceptibility and photoluminescence efficiency. The resulting nanoclusters demonstrated a clear concentration-dependent response in emission lifetimes and intensities upon exposure to magnetic field effects (MFE) and spin-spin coupling, alongside a large magnetic moment exceeding 40 μ_B at 180 K. These findings highlight the potential of these nanoclusters for magneto-optical devices and spintronic applications, showcasing their tunable magnetic properties and exciton dynamics.