Membranes and their size-selective filtering properties are universal in nature and their behaviour is exploited to design artificial membranes suited for, e.g., molecule or nanoparticle filtering and separation. Exploring and understanding penetration and transmission mechanisms of nanoparticles in thin film systems may provide new opportunities for size selective deposition or embedding of the nanoparticles.
Here, we demonstrate an unexpected finding that metal nanoparticles can be size-selectively sieved through atomically thin nonporous alkali halide films on a metal support and that this sieving effect can be tuned via the film thickness. Specifically, relying on scanning tunneling microscopy and spectroscopy techniques, combined with density functional theory calculations, we find that defect-free NaCl films on a Au(111) support act as size-selective membranes for deposited Au nanoclusters. The observed sieving ability is found to originate from a driving force towards the metal support and from the dynamics of both the nanoparticles and the alkali halide films.