In this paper, experimental investigations of stimulated Raman scattering in silicon quantum dots and nanocomposites based Si-materials are reported. Two Raman amplifiers are realized and amplifications due to stimulated Raman scattering are measured. For both of them, a significant enhancement of Raman gain and a significant reduction in threshold power are demonstrated. Our findings indicate that nanostructured materials show great promise for Si-based Raman lasers.