In this study, a sensitive fluorescence sensor was synthesized for the detection of Cu2+ ions based on the quenching of fluorophore. The sensor is composed of pyranine functionalized amino silane shell modified magnetite (Fe3O4) core nanostructures. The synthesized nanomaterials were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Powder Diffraction (XRD), Vibrating Sample Magnetometer (VSM) and Transmission Electron Microscopy (TEM). The fluorescent magnetic nano particles were analyzed by fluorescence spectroscopy. The characterization data showed that the magnetic core was highly superparamagnetic with an average particles diameter up to 10 nm. The fluorescence response of Fe3O4@-SiO2-NH2-Pyr nanosensor towards Cu2+ ions showed an enhanced and selective fluorescence quenching. Pyranine functionalized magnetic nanoparticles were found to be highly selective for Cu2+ ions without giving any response to other interfering cations and biomolecules. The nanosensor not only provided a sensitive (LOD = 6 nM), fast and selective detection of Cu2+ ions but a new fluorescent and biocompatible material with potential uses in biological and environmental fields. (C) 2018 Elsevier B.V. All rights reserved.