Dynamic Equilibria between DNA-Stabilized Silver Nanoclusters and Silver-Carrying DNA Strands

DNA-stabilized silver nanoclusters (DNA-AgNCs) are versatile emitters whose photophysical properties are defined by the DNA template. In this study, we explore the unusual temperature- and concentration-dependent behavior of two NIR-emissive DNA-AgNCs: one stabilized by two 16-base DNA oligomers (16mer), and another embedded within a 3-base shortened version of these strands (13mer). Using a combination of optical spectroscopy and mass spectrometry, we show that Ag⁺-carrying DNA strands can reversibly attach to DNA-AgNCs and fine-tune their photophysical properties. For 13mer-AgNC, we demonstrate the presence of three different species, (13mer)₂-[Ag₂₀]¹⁰⁺, (13mer)₃-[Ag₂₇]¹⁷⁺, and (13mer)₄-[Ag₃₄]²⁴⁺, depending on concentration and temperature. For the AgNC stabilized by two 16-base DNA strands, (16mer)₂-[Ag₂₀]¹⁰⁺, emission wavelength and intensity vary with temperature, although no significant concentration-dependent spectral shifts are observed. While mass-spectrometry revealed the existence of (16mer)₃-[Ag₂₇]¹⁷⁺, time-resolved anisotropy uncovered the formation of aggregates of (16mer)₂-[Ag₂₀]¹⁰⁺. These findings demonstrate the presence of dynamic equilibria between Ag⁺-carrying DNA strands and DNA-AgNCs.