Fluorescence microscopy of individual silver quantum clusters on the surface of silver nanoparticles reveals strong photoactivated emission under blue light excitation [1-4]. In this work, silver nanoparticles are produced by annealing silver thin films deposited on a glass substrate and silver quantum clusters are subsequently synthesized at the surface of the nanoparticles by photoactivation in presence of Ag⁺ cations in solution. The photogeneration of these silver quantum clusters leads to a great increase in the fluorescent signal. This photoactivated surface can then be used for sensing purposes. It was found, that in presence of a strong nucleophile (such as CN^-), silver quantum clusters are dissolved into non-fluorescing AgCN complexes, resulting in a fast and observable decrease of the fluorescent signal.