TY - JOUR
T1 - Oxidant-Activated Reactions of Nucleophiles with Silicon Nanocrystals
AU - Dasog, Mita
AU - Thompson, Jonathan R.
AU - Lewis, Nathan S.
N1 - Funding Information:
The authors acknowledge the National Science Foundation (Grant CHE-1214152) and Dalhousie University for providing financial support. Instrumentation support was provided by the Molecular Materials Research Center of the Beckman Institute at the California Institute of Technology and by the Institute for Research in Materials at Dalhousie University. M.D. acknowledges a postdoctoral fellowship from the National Sciences and Engineering Research Council of Canada. J.R.T. acknowledges support from the U.S. Department of Energy “Light-Material Interactions in Energy Conversion” Energy Frontier Research Center under Grant DE-SC0001293. We thank Dr. A. C. Nielander and Azhar Carim for insightful discussions during the preparation of this work.
PY - 2017/8/22
Y1 - 2017/8/22
N2 - The oxidant-activated reactivity of Si toward nucleophiles was evaluated for Si nanocrystals (Si-NCs) of differing diameters, d. In the presence of ferrocenium as a one-electron, outer-sphere oxidant, d ≥ 8 nm Si-NCs readily reacted with nucleophiles, including methanol, butanol, butylamine, butanoic acid, butylthiol, and diethylphosphine. However, d < 8 nm Si-NCs did not undergo such reactions, and stronger oxidants such as acetylferrocenium or 1,1′-diacetylferrocenium were required. Butylamine-, butylthiol-, and butanol-functionalized d ≥ 8 nm Si-NCs were partially oxidized and exhibited photoluminescence originating from defect states. In contrast, butanoic acid-functionalized Si-NCs were minimally oxidized and displayed core emission resulting from the excitation and relaxation of electrons across the Si-NC bandgap. Diethylphosphine-functionalized Si-NCs were stable only under inert conditions and showed core emission, with the Si-P bonds being highly susceptible to oxidation and rapidly decomposing upon exposure to ambient conditions. The general reactivity is consistent with the redox potential of the one-electron oxidant and the valence band edge position of the Si-NCs. The trends in reactivity thus provide an example of differential chemical reactions of nanoparticles relative to bulk materials, reflecting the differences in electronic structure and the continuum of electronic properties between variously sized Si nanoparticles and bulk Si samples.
AB - The oxidant-activated reactivity of Si toward nucleophiles was evaluated for Si nanocrystals (Si-NCs) of differing diameters, d. In the presence of ferrocenium as a one-electron, outer-sphere oxidant, d ≥ 8 nm Si-NCs readily reacted with nucleophiles, including methanol, butanol, butylamine, butanoic acid, butylthiol, and diethylphosphine. However, d < 8 nm Si-NCs did not undergo such reactions, and stronger oxidants such as acetylferrocenium or 1,1′-diacetylferrocenium were required. Butylamine-, butylthiol-, and butanol-functionalized d ≥ 8 nm Si-NCs were partially oxidized and exhibited photoluminescence originating from defect states. In contrast, butanoic acid-functionalized Si-NCs were minimally oxidized and displayed core emission resulting from the excitation and relaxation of electrons across the Si-NC bandgap. Diethylphosphine-functionalized Si-NCs were stable only under inert conditions and showed core emission, with the Si-P bonds being highly susceptible to oxidation and rapidly decomposing upon exposure to ambient conditions. The general reactivity is consistent with the redox potential of the one-electron oxidant and the valence band edge position of the Si-NCs. The trends in reactivity thus provide an example of differential chemical reactions of nanoparticles relative to bulk materials, reflecting the differences in electronic structure and the continuum of electronic properties between variously sized Si nanoparticles and bulk Si samples.
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U2 - 10.1021/acs.chemmater.7b02572
DO - 10.1021/acs.chemmater.7b02572
M3 - Article
AN - SCOPUS:85027998446
VL - 29
SP - 7002
EP - 7013
JO - Chemistry of Materials
JF - Chemistry of Materials
SN - 0897-4756
IS - 16
ER -