Edited by Catherine J. Murphy, University of Illinois at Urbana–Champaign, Urbana, IL, and approved September 6, 2018 (received for review April 2, 2018)
Here, by real-time monitoring with single-molecule fluorescence microscopy the size-dependent catalytic process of individual Au clusters at single-turnover resolution, we study the size-dependent catalytic behaviors of gold (Au) clusters at the single-cluster level, and then observe the strong unique size effect on the catalytic properties of individual Au clusters, in both catalytic product formation and dissociation processes. Such a unique size effect on the nanocatalysis could be attributed intrinsically to the size-dependent electronic structure of Au clusters, leading to a more comprehensive understanding of the catalytic mechanism of Au particles.
Atomically precise metal clusters have attracted increasing interest owing to their unique size-dependent properties; however, little has been known about the effect of size on the catalytic properties of metal clusters at the single-cluster level. Here, by real-time monitoring with single-molecule fluorescence microscopy the size-dependent catalytic process of individual Au clusters at single-turnover resolution, we study the size-dependent catalytic behaviors of gold (Au) clusters at the single-cluster level, and then observe the strong size effect on the catalytic properties of individual Au clusters, in both catalytic product formation and dissociation processes. Surprisingly, indicated by both experiments and density functional theory (DFT) calculations, due to such a unique size effect, besides observing the different product dissociation behaviors on different-sized Au clusters, we also observe that small Au clusters [i.e., Au15(MPA)13; here, MPA denotes 3-mercaptopropionic acid] catalyze the product formation through a competitive Langmuir–Hinshelwood mechanism, while those relatively larger Au clusters [e.g., Au18(MPA)14 and Au25(MPA)18] or nanoparticles catalyze the same process through a noncompetitive Langmuir–Hinshelwood mechanism. Such a size effect on the nanocatalysis could be attributed intrinsically to the size-dependent electronic structure of Au clusters. Further analysis of dynamic activity fluctuation of Au clusters reveals more different catalytic properties between Au clusters and traditional Au nanoparticles due to their different size-dependent structures.
↵1Y.Z. and P.S. contributed equally to this work.
Author contributions: W.X. designed research; Y.Z. and X.L. performed research; Tiankai Chen, Z.W., Y.W., J.X., and W.X. contributed new reagents/analytic tools; Y.Z., P.S., X.L., and Tao Chen analyzed data; and Y.Z., P.S., J.X., and W.X. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1805711115/-/DCSupplemental.
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