Luminescent Au6 and Au8 nanoclusters from ligand induced etching of Au nanoparticles

Metal nanoclusters (NCs) with atomic precision are receiving significant attention because of their widespread applications in the field of energy-related materials, sensing and biomedicine. In this work, luminescent Au nanoclusters (NCs) are synthesized from Au nanoparticles (NPs) by core-etching process in presence of excess glutathione (GSH) ligand. Electrospray ionization (ESI) mass spectrometric study suggests the formation of polydisperse Au6 and Au8 NCs at elevated temperature (70 °C). The HOMO-LUMO band gap of Au6 and Au8 clusters are calculated from optimized structure. The photoluminescence maximum of as-prepared Au NCs is observed at 421 nm after excitation at 340 nm with 4.20% quantum yield (QY). Lifetime of the NCs is found to be 0.57 ns in excited state, which arises because of electronic transitions from low-lying d-bands to excited state sp bands of core-state only. Moreover the luminescence intensity of as-prepared Au NCs is found to be very stable both in acidic and basic medium. The synthesis of luminescent Au NCs from non-luminescent plasmonic Au NPs is beneficial for various applications such as sensing, biomedicine, and light emitting devices.