Enhanced Luminescence in Zn<sup>+2</sup>-Induced Au<sub>14</sub> Nanocluster Aggregates
Dipankar Bain, Aarti Devi, Rashi Rashi, Sikta Chakraborty, Sarita Kolay, Amitava Patra
Abstract
Aggregation-induced emission (AIE) is an emerging strategy used for the creation of superstructures constructed by the self-assemblies of metal nanoclusters (NCs) to tune their photophysical properties. Here, we explored the AIE of d -penicillamine-capped Au 14 NCs by introducing Zn 2+ ions with intriguing photophysical properties. The electrostatic interaction between the carboxylate (−COO – ) groups of penicillamine ligands in the NCs with Zn 2+ ions formed large cross-linked aggregated structures evident from microscopic studies. X-ray photoelectron spectroscopy corroborates the fact of charge transfer from electron-rich −COO – to Zn 2+ ions. We observed the huge photoluminescence enhancement (50-fold) in the Zn-induced Au 14 NCs compared to Au 14 NCs, with a photoluminescence quantum yield enhancement from 0.56 to 4.31% due to the surface rigidification of Au 14 NCs that suppresses nonradiative relaxation. We found that pH (in the range of pH∼3−10) controls the photophysical properties of these aggregates. The disaggregation of Zn-induced Au 14 NCs in the presence of a chelating ligand, which can be reversed by reintroducing Zn +2 ions, further supports the coordinating mechanism of Zn +2 ions with Au 14 NCs. These nanoaggregates are used as a probe for the detection of Zn 2+ ions in the linear concentration range 0.5–0.25 μM with a limit of detection of 754 nM.