We demonstrate the synthesis of silica nanosheets (SiONSs) by exfoliation and oxidation with layered polysilane, (SiH)(n). The resulting silica was produced in the form of amorphous nanosheets with a uniform thickness of 0.68 nm, which was constructed of six-membered rings of SiO4 tetrahedra. The thickness is an order magnitude smaller than previously reported silica nanoparticles prepared by a variety of other methods. Strong photoluminescence (PL) was observed, and the PL spectra had maxima at 2.7 and 3.1 eV. This strong emission may be because of the defect center of oxygen deficiency in the sheets. The SiONSs may have potential applications in future integrated optical devices.