Oxidant-Activated Reactions of Nucleophiles with Silicon Nanocrystals

Journal Article · 10 July 2017 · Chemistry of Materials

DOI: https://doi.org/10.1021/acs.chemmater.7b02572 · OSTI ID:1470406

Dasog, Mita  ^[1]; Thompson, Jonathan R. ^[2]; Lewis, Nathan S.  ^[3]

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1. California Inst. of Technology (CalTech), Pasadena, CA (United States). Division of Chemistry and Chemical Engineering; Dalhousie Univ., Halifax, NS (Canada). Dept. of Chemistry
2. California Inst. of Technology (CalTech), Pasadena, CA (United States). Division of Engineering and Applied Sciences
3. California Inst. of Technology (CalTech), Pasadena, CA (United States). Division of Chemistry and Chemical Engineering, Kavli Nanoscience Inst., and Beckman Inst.

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.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Light-Material Interactions in Energy Conversion (LMI)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: SC0001293
• OSTI ID: 1470406
• Journal Information: Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 16 Vol. 29; ISSN 0897-4756
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English