Photoluminescent water-soluble silicon nanocrystals were synthesized using solution-phase wet chemistry techniques. Adjustment of the mean size and size distribution was achieved by adjusting the rate of addition of the hydride reducing agent. When the reducing agent was added slowly the mean size of the silicon nanocrystals was 1.4nm with a monodisperse size distribution. However, when the reducing agent was added rapidly the size distribution enlarged and concomitantly the
mean sized also increased. The photoluminescence and photoluminescence excitation spectra from the monodisperse sample show narrower features when compared to the solution with the large size distribution. This provides direct evidence for size dependant effects on the photoluminescence of silicon nanocrystals.