Blue-green luminescent carbon nanodots entrapped in silica matrix were produced by the pyrolysis of methyl groups well dispersed on the edges of nanometric grains of silica (Aerosil® R974) previously cold sintered under high pressure. Selected Area Electron Diffraction and Electron Energy Loss Spectroscopy analyses confirmed the formation of carbon nanodots with graphitic sp2 bonds, without additional passivation technique. Photoluminescence spectra were dependent on the excitation wavelength and the higher emission intensity was observed in the range between 450-500 nm for the sample cold sintered at 7.7 GPa and thermal treated at 800°C, corresponding to a total fluorescence quantum yield of about 11%.