This work presents the observation of a photo-activated fluorescence from core/shell quantum dots of CdSe/CdS incorporated in a poly(butylmethacrylate) matrix. Upon illumination with UV-light, the intensity of fluorescence from the quantum dots increases as seen by naked eyes at ambient conditions. This allows its utilization in optical memory media based on thin films of CdSe/CdS polymer nanocomposites suitable for practical application. The quantum dots are synthesized by the hot-injection method and embedded in poly(butylmethacrylate) matrix by radical polymerization with 1,1.1'-azobis-(cyclohexanecarbonitrile). The fluorescence of quantum dots quenched during the polymerization process, but appeared again after illumination of the nanocomposite material with UV-light. The fluorescence properties of quantum dots are governed by the presence of trioctylphosphine oxide in the matrix, which allows control of the optical memory effect. (C) 2008 Elsevier B.V. All rights reserved.