Research Article


2022, 15(2): 838–844


Aluminum nanocrystals evolving from cluster to metallic state: Size tunability and spectral evidence

Hao Wu1, Xiaoyu Cheng1,2 (✉), Hongguang Dong1, Songjun Xie2, and Sailing He1,2 (✉)

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1 National Engineering Research Centre for Optical Instruments, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310058, China
2 Ningbo Research Institute, Ningbo 315100, China

Keywords: aluminum, nanocrystals, plasmon, nanoclusters, photoluminescence
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  • Abstract
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Sub-3 nm aluminum (Al) nanocrystal is an emerging class of nanomaterial with properties distinct to noble metal nanoclusters. The complete solution synthesis of aluminum nanoclusters was recently reported, and their photoluminescence (PL) observed for the first time. At the moment, there exists no method to tune the size of ultrasmall aluminum nanocrystals in solution thus no knowledge on the boundary state between aluminum nanoclusters to plasmonic nanoparticles. In this work, it is demonstrated a study of size-controlled solution synthesis of ultrasmall aluminum nanocrystals with size controlled between ~ 2.2 to ~ 3.8 nm. Increasing the size results in three sets of spectral responses: (1) absorption due to nascent plasmons generated at ~ 340 nm for larger particles, confirmed by Mie theory calculations; (2) significant decreased quantum yield of PL from ~ 7.8% to ~ 2.4%, indicating reduced quantum confinement effects and increased metallicity; (3) drop of fluorescence lifetime was observed, especially when the diameter of aluminum nanoparticles was changed from ~ 3.0 to ~ 3.8 nm. This study provides experimental evidence and insights to the transitional state between aluminum nanoclusters to plasmonic nanoparticles, which seems to occur at size larger than gold nanoclusters.
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Aluminum nanocrystals evolving from cluster to metallic state: Size tunability and spectral evidence. Nano Res. 2022, 15(2): 838–844

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