Figure 6: Molecular orbital picture.
From: Hypervalent surface interactions for colloidal stability and doping of silicon nanocrystals
The Cl termination of the Si NC surface effectively lowers the LUMO energy in comparison with the H-terminated Si NC surface (that is, the Si–Cl group is more Lewis acidic). Molecule A represents a molecule with favourable energetic alignment for hypervalent interactions. In this study, we find ketones, aldehydes and nitriles to fit this criteria. B molecules are strong Lewis base donors such as dimethylformamide and pyridine. These molecules also donate electron density but to an extent where the Si–Cl surface is not preserved. C molecules are chemically inert molecules such as hydrocarbon and chlorinated hydrocarbon solvents, and D molecules represent protic solvents, such as alcohols, that contain acidic hydrogens, which hydrolyse the Si–Cl group. HOMO, highest occupied molecular orbital.
