Studying how small silver clusters grow and their optical properties

Understanding the mechanisms of cluster growth and precisely tailoring the structure-property relationship at the atomic level is challenging and essentially important in chemistry. In this study, we present a combined experimental and theoretical investigation into the structural stability, optical properties, and growth mechanisms of a series of small silver clusters coordinated with halides and nitrates along with 2-(diphenylphosphino)pyridine (dppy) protection ligands. Using single-crystal X-ray diffraction (XRD), we uncovered the structural evolution of these clusters and elucidated the factors contributing to their stability. Interestingly, all these small clusters displayed dual emissions in the UV and red regions, with the UV emission showing enhanced intensity relative to the red emission at around 620 nm when strong σ-donating ligands or polynuclear metallic cores were introduced. The unique optical properties were further analysed through comprehensive UV-visible spectroscopy, revealing red shifts in the dominant absorption band as the cluster size increases. Density functional theory (DFT) simulations corroborated the observed UV spectra and confirmed the occurrence of ligand-to-metal charge transfer (LMCT). This multidisciplinary study merges experimental and computational methods to deepen our understanding of the structural and optical properties of small silver clusters, shedding light on their growth mechanisms and enabling the targeted design of novel clusters for applications in nanotechnology and materials science.