Surface-Induced
Alkene Oligomerization: Does Thermal
Hydrosilylation Really Lead to Monolayer Protected Silicon Nanocrystals?
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Abstract
Surface
functionalization of hydride-terminated silicon nanocrystals
(SiNCs) with dodecene via thermal hydrosilylation has been reexamined.
We observed the formation of dodecyl oligomers (<i>n</i> ≤ 4) during the reaction under an argon atmosphere at various
predesigned temperatures (100–190 °C). In a comparative
study, surface hydrosilylation and ligand oligomerization were found
to be more pronounced under air (<i>n</i> ≤ 7) at
the same temperatures. These observations strongly suggest that hydrogen
abstraction by oxygen accelerates hydrosilylation and generates sufficient
silyl radical as initiator to interact with unsaturated bonds, promote
chain propagation, and generate ligand oligomers. We further propose
that, to inhibit ligand oligomerization and obtain monolayer coverage
on SiNC surfaces, it is feasible to apply comparatively low temperatures,
inert atmosphere, and dilute ligand concentration during thermal hydrosilylation