Paper Title: Plasmonic Metal Oxide Nanocrystals via SurfaceAnchoring of Redox-Active Phosphorus Species
Corresponding Authors: Li Yang, Hangzhou Institute for Advanced Study, UCAS; Jin Yizheng, Zhejiang University;
Authors: Hui Du, Yang Li, Ning Zhou, Chaodan Pu, Jinglin Yin, Xueqian Kong, He Tian, and Yizheng Jin
Metal oxide nanocrystals with localized surface plasmon resonance (LSPR) properties are widely used in optoelectronic fields such as sensing, smart windows, photothermal therapy, and catalysis. At present, the regulation of free carriers in semiconductor nanocrystals is mainly achieved by chemical doping in reactions or post-treatment based on redox reactions and photochemical reactions. Chemical doping largely depends on the reactivity of the acceptor nanocrystalline with the doped precursor. In addition to making full use of the chemical advantages of colloidal nanocrystal synthesis, post-treatment based on redox reactions can also take into account the effective control of nanocrystal size, morphology, and carrier concentration. However, there are few reports on the molecular mechanism of redox reaction strategy to realize plasmonic metal oxide nanocrystals, which greatly restricts the further development of this synthesis strategy.
In response to the above problems,Li Yang, a distinguished associate research fellow from Hangzhou Institute for Advanced Study (HIAS), UCAS, cooperated with Prof. Jin Yizheng from Zhejiang University and others todevelop a universal method based on surface-active phosphine redox reaction strategy, realizing the controllable preparation of plasmonic metal oxide nanocrystals (Fig. 1).Taking indium oxide nanocrystals and tris (trimethylsilyl) phosphate with strong reducibility as a model reaction system, the authors can realize the localized surface plasmon resonance absorption characteristics in the near-infrared to mid-infrared region by adjusting the feed ratio during the reaction process.
Fig.1 Schematic diagram of synthesis of surface-active phosphine redox reaction strategy & LSPR spectral regulation of indium oxide nanocrystals.
It was found from the structure and surface characterization (Fig. 2) that the indium oxide nanocrystals after tris(trimethylsilyl)phosphine post-treatment maintained the crystal structure, size and morphology before treatment. Different from traditional chemical doping methods, however, P atoms are not diffused throughout the nanocrystal, but only distributed on its surface. It was also found from the solid nuclear magnetic and X-ray photoelectron spectroscopy that P on the surface of indium oxide nanocrystals exists in the form of -PO4 or -PO3with a positive valence of 5, rather than the precursor molecules with a negative valence of 3.
Fig. 2 Structure and surface characterization results of indium oxide before and after active phosphine post-treatment.
Based on the above spectral and structural characterization results, the authors proposed a mechanism based on the two-step reaction of surface-active phosphine (Fig. 3): First, tris(trimethylsilyl)phosphine with high reaction activity reacted with the hydroxyl functional group on the surface of nanocrystal to form a nanocrystal intermediate with redox reactive phosphine on the surface. Then, the active phosphine on the surface underwent a redox reaction with the nanocrystals, and the active phosphine was oxidized from -3 to +5. It contributed electrons to the nanocrystals, thus making them have local surface plasmon resonance characteristics. Meanwhile, the redox reaction is accompanied by a side reaction process in which surface-active phosphine reduces the residual or self-generated water in the system to hydrogen.
Fig.3 Reaction mechanism based on surface-active phosphine redox reaction strategy.
This reaction strategy is also applicable to the synthesis of other LSPR metal oxides. The reaction between tris(trimethylsilyl)phosphine and cadmium oxide nanocrystals can not only maintain the size and morphology of the original nanocrystals but also generate cadmium oxide nanocrystals with LSPR (Fig. 4).
Fig.4 Spectral and electron microscopy results of cadmium oxide nanocrystals prepared based on surface-active phosphine redox reaction strategy.
Published in Chemistry of Materials, the paper was funded by the Key R&D Program of the Ministry of Science and Technology of the People's Republic of China (2016YFB0401600), National Natural Science Foundation of China (21975220, 91833303, 51911530155, 22005267) and Fundamental Research Funds for the Central Universities.
Publication information: Chem. Mater. 2021, 33, 13, 5290-5297Publication Date: July 2, 2021https://doi.org/10.1021/acs.chemmater.1c01393
Copyright © 2021 American Chemical Society
Article link:https://pubs.acs.org/doi/10.1021/acs.chemmater.1c01393
Source | School of Physics and Optoelectronic Engineering
Typesetter | Wang Zhe
Executive Editor | Yan Hao
Scan the QR code and follow the official account of "HIAS-UCAS"!HIAS-UCAS
WeChat ID: UCAS-HIAS
Official website丨http://hias.ucas.ac.cn/
Email: hangzhou@ucas.ac.cn
Published in Zhejiang
Scan with WeChat
Follow us
