Size-Dependent Room-Temperature Hydrosilylation of Silicon Nanocrystals without UV Light Excitation

Covalent alkene addition to silicon (Si) nanocrystals typically requires high temperature, UV light, or a radical initiator. Here, we show that hydride-terminated Si nanocrystals with diameters smaller than about 5 nm can be terminated with alkyl ligands (dodecene) at room temperature. This occurs when nanocrystals are transferred into chloroform after etching with hydrofluoric acid and then dispersed in neat dodecene. The presence of trace chloroform provides radicals that promote hydrosilylation without additional photoactivation. This reaction is size-dependent, and larger nanocrystals cannot be passivated at room temperature. The nanocrystals passivated at room temperature disperse in nonpolar solvents with photoluminescence (PL) quantum yields similar to those of nanocrystals capped by conventional thermal hydrosilylation at high temperature.