Silicon has emerged as the most desirable material for optical dielectric metamaterials, however chemists struggle to obtain the required silicon nanoparticle dimensions. Here the average diameter of silicon nanoparticles is varied between 3 and 15 nm by changing the reaction solvent. Electrochemistry and NMR elucidate the role of solvent on the synthetic mechanism. Surprisingly the solvent does not stabilize the nanoparticles and there is no trend associated with chain length or open-chain versus cyclical solvent molecules. The solvent's main role is to stabilize the by-products, which prolongs the reaction lifetime.