The nucleation and growth of solids from solutions impacts many natural processes and is fundamental to applications in materials engineering and medicine. For a crystalline solid, the nucleus is a nanoscale cluster of ordered atoms that forms through mechanisms still poorly understood. In particular, it is unclear whether a nucleus forms spontaneously from solution via a single- or multiple-step process. Here, using in situ electron microscopy, we show how gold and silver nanocrystals nucleate from supersaturated aqueous solutions in three distinct steps: spinodal decomposition into solute-rich and solute-poor liquid phases, nucleation of amorphous nanoclusters within the metal-rich liquid phase, followed by crystallization of these amorphous clusters. Our ab initio calculations on gold nucleation suggest that these steps might be associated with strong gold–gold atom coupling and water-mediated metastable gold complexes. The understanding of intermediate steps in nuclei formation has important implications for the formation and growth of both crystalline and amorphous materials.
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This work was supported by the Singapore National Research Foundation's Competitive Research Program funding (NRF-CRP9-2011-04) and the Young Investigator Award (NUSYIA-FY14-P17) from the National University of Singapore. C.A.N. and M.B. acknowledge support from grant No. NRF-CRP8-2011-07, U.M. and P.M. acknowledges support from the Microbiology Institute (Singapore) and the Centre for Bioimaging Sciences. N.D.L. thanks the support of the Lee Kuan Yew Endowment Fund, and National University of Singapore internal grant No. 154-000-606-112. The work of P.K. was supported by the National Science Foundation Division of Materials Research Grant No. 1309765 and by the American Chemical Society Petroleum Research Funding Grant No. 53062-ND6.
The authors declare no competing financial interests.
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Loh, N., Sen, S., Bosman, M. et al. Multistep nucleation of nanocrystals in aqueous solution. Nature Chem 9, 77–82 (2017). https://doi.org/10.1038/nchem.2618
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