Unveiling the stability of Ag42+ cluster and the protective role of DNA against oxygen quenching: a comprehensive spectroscopic analysis

Abstract

Sub-nanometer metal nanoclusters exhibit molecule-like optical properties and hold strong promise for biomedical and photonic applications. DNA templates can stabilize silver nanoclusters and enable modulation of their optical response; however, the interplay between oligonucleotide sequences, cluster structure and emissive behavior remains uncompleted understood. Here, we present a comprehensive spectroscopic investigation (UV–vis absorption, steady-state fluorescence and time-resolved fluorescence) of the interaction between electrochemically synthesized, ligand-free tetrahedral nanoclusters and the oligonucleotide (Og, 5′-CCTCCTTCCTCC-3′) template. Binding isotherms derived from both absorption and fluorescence measurements reveal a strong and specific interaction between and Og. Notably, complex formation does not induce structural reshaping of the tetrahedral cluster into the zig-zag configuration previously reported for Ag nanoclusters synthesized by chemical reduction of Ag+ in presence of the same Og. This observation underscores the influence of the synthesis route on cluster structure and highlights the intrinsic stability of free tetrahedral species. Furthermore, dissolved oxygen selectively quenches the fluorescence of bare , whereas complexation with Og effectively suppresses oxygen-induced quenching, indicating a protective role of the oligonucleotide. These findings provide insight into structure-stability relationships and are relevant for ensuring photostability and reliable performance of hybrid nanocluster in oxygenated environments.