ZnO nanocrystals are embedded in an amorphous matrix of SiO2 using the sol-gel method and their optical properties were studied. A strong Blue-violet luminescence was observed. The photoluminescence's maximum, located at 400 nm approximately, depends on the rate of the gelation process and also shows a slight dependence with the wavelength of excitation. The mean size of ZnO particles is about 27 nm leading with a weak quantum confinement. XRD patterns did not reveal the presence of ZnO particles but TEM investigation demonstrates agglomeration of ZnO crystallites in the composite with different sizes and shapes. (c) 2006 Elsevier B.V. All rights reserved.