Silyl Radical Abstraction in the Functionalization of Plasma-Synthesized Silicon Nanocrystals

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• 作者：Lance M. Wheeler ; Nicholas C. Anderson ; Peter K. B. Palomaki ; Jeffrey L. Blackburn ; Justin C. Johnson ; Nathan R. Neale
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：October 13, 2015
• 年：2015
• 卷：27
• 期：19
• 页码：6869-6878
• 全文大小：554K
• ISSN：1520-5002

文摘

Many silicon nanostructures have exhibited favorable optical properties following surface functionalization with molecular groups through a silicon鈥揷arbon bond. Here, we show the mechanism of functionalization of silicon nanocrystals synthesized in a nonthermal radiofrequency plasma is fundamentally different than in other silicon systems. In contrast to hydrosilylation, where homolytic cleavage of Si鈥揌 surface bonds is typically a prerequisite to functionalization, we demonstrate the dominant initiation step for plasma-synthesized silicon nanocrystals is abstraction of a silyl radical, 路SiH₃, and generation of radical at the silicon nanocrystal surface. We experimentally trap the abstracted silyl radical and show this initiation mechanism occurs for both radical- and thermally-initiated reactions of alkenes using complementary FTIR and ¹H NMR spectroscopies. These data additionally indicate that silylsilylation, addition of a Si鈥揝iH₃ group across an unsaturated hydrocarbon, competes with hydrosilylation. We also present a new empirical sizing curve as a convenient method to determine Si NC size from photoluminescence peak energy.