Metal nanoclusters—precisely defined groups of just a few dozen metal atoms—hold enormous promise as catalysts because their tiny size gives them a huge surface area and highly tunable electronic properties. But nanoclusters are typically synthesized with protective organic ligand shells that stabilize the metal core and prevent it from aggregating. While necessary for synthesis, these ligands often block the very active sites needed for catalytic reactions to occur, creating a persistent trade-off between stability and performance.

A collaborative Japanese research team from Tohoku University, Tokyo University of Science, Tokyo Metropolitan University, and the Japan Fine Ceramics Center has developed a ligand engineering strategy that resolves this trade-off, creating gold-platinum nanocluster catalysts with substantially improved activity. The findings are published in Nano Letters.

Mixing Ligands for Selective Removal

The team worked with Au24Pt nanoclusters, protected by a combination of two different ligand types: a dithiolate (TDT) bridging ligand that anchors more strongly to the cluster surface and provides structural stability, and a weaker-binding thiolate ligand called TBBT. By combining these two ligand types rather than using a single, uniform ligand shell as in conventional nanocluster synthesis, the researchers created a system where the weaker TBBT ligands could be selectively removed at lower temperatures during activation, exposing catalytically active sites while the stronger TDT ligands preserved the overall structural integrity of the cluster.

When the researchers tested the resulting catalysts on carbon monoxide oxidation, a benchmark reaction for evaluating catalytic activity, after supporting the nanoclusters on cerium oxide (CeO2) and undergoing thermal pretreatment, the dual-ligand nanoclusters showed markedly improved performance. The temperature required to achieve 50% CO conversion dropped by 39°C, from 301°C down to 262°C, compared to conventional nanoclusters protected by a single monothiolate ligand shell.

The researchers say this ligand engineering approach, using a mix of strongly and weakly bound protecting groups to enable selective, low-temperature activation, offers a generalizable design principle for developing more active nanocluster catalysts without sacrificing the structural stability that ligands provide during synthesis. The strategy could inform the design of nanocluster catalysts for a range of industrially important thermocatalytic reactions beyond CO oxidation.

Journal: Nano Letters
DOI: 10.1021/acs.nanolett.6c01977
Article Title: Ligand Engineering of Dithiolate-Protected Au24Pt Nanoclusters for Improved Thermocatalytic Activity
Publication Date: 29-Jun-2026