Engineering Atomically Precise Copper Nanoclusters with Aggregation Induced Emission

Abstract

Controlled synthesis of atomically precise metal nanoclusters (MNCs) and fundamental understanding of their physical properties have emerged as an active area of research because of their potential applications in healthcare and energy-related materials. In the present study, atomically precise copper nanoclusters (Cu NCs) have been synthesized from nonluminescent plasmonic copper nanoparticles (Cu NPs) by core etching with excess reduced glutathione (GSH). Electrospray ionization (ESI) mass spectrometry confirms the formation of kinetically controlled, polydisperse Cu34–32(SG)16–13 NCs at room temperature and monodisperse Cu25(SG)20 NCs at elevated temperature (70 °C). Cu34–32(SG)16–13 NCs exhibit weak red emission (625 nm), while Cu25(SG)20 NCs emit intense blue luminescence at 442 nm with 9.7% quantum yield. Rational tuning of reaction temperature, pH, GSH concentration, and reaction time are crucial for the composition and emission band tuning of atomically precise Cu NCs. Interestingly, Cu34–32(SG)16–13 NCs exhibit an aggregation induced emission (AIE) with addition of a less polar solvent, ethanol (EtOH), and the enhancement in the luminescence is attributed to the alteration in the excited state dynamics with the change in solvent polarity. The unique and low cost synthetic methodology of Cu NCs with interesting AIE property may open up new possibilities for their applications in the field of bioimaging, photocatalysis, photosensors, and light emitting devices.