Assembly-Induced Emission in Mercaptosuccinic Acid-Templated Silver Nanoclusters: Metal Ion Selectivity and pH Sensitivity

The phenomenon of aggregation-induced emission (AIE) is an emerging strategy used to tune the optical properties of luminescent metal nanoclusters (MNCs). Various external factors such as cations, hydrophobicity, and solvents provide impetus for AIE in MNCs. Our present investigations delineate the remarkable tuning of the photophysical properties of weakly luminescent mercaptosuccinic acid (MSA)-templated silver nanoclusters (AgNCs). Upon AIE of AgNCs through the introduction of Zn2+ ions, the emission maximum of AgNCs was shifted from ∼465 to ∼670 nm with an unusual augmentation in photoluminescence intensities (∼3000 times). The minimization of energy dissipation due to the formation of the Zn2+-induced rigid assembly mainly accounts for these unprecedented optical signatures. As a consequence of this, the otherwise weakly emissive AgNC system (quantum yield, QY ∼ 0.1%) gets converted to a highly luminescent red-emitting Zn2+-induced AgNC assembly (Zn–AgNCs, QY ∼ 2%). Our MSA-templated AgNCs demonstrated the selectivity toward Zn2+ ions in forming the Zn–AgNC assemblies, which in turn were highly sensitive toward the pH of the medium in the pH range of 5–8.