A fluorescent magnetic core–shell nanosensor for detection of copper ions in natural waters

[Display omitted] •A luminescent nanosensor based on a magnetite core and a SiO2 shell with a modified Rhodamine B molecule covalently bonded to the silica layer.•The sensor presents high sensitivity and selectivity to Cu(II) ion.•The magnetic core allows straightforward separation of the sensor, which can be recovered for subsequent use. A nanosensor based on magnetic core–shell nanoparticles functionalized with rhodamine derivative, N-(3-carboxy)acryloyl rhodamine B hydrazide (RhBCARB), using (3-aminopropyl)triethoxysilane (APTES) as a linker, has been synthesized for detection of Cu(II) ions in water. The magnetic nanoparticle and the modified rhodamine were fully characterized, showing a strong orange emission sensitive to Cu(II) ions. The sensor shows a linear response from 10 to 90 µg L−1, detection limit of 3 µg L−1 and no interference of Ni(II), Co(II), Cd(II), Zn(II), Pb(II), Hg(II) and Fe(II) ions. The nanosensor performance is similar to those described in the literature, being a viable option for the determination of Cu(II) ions in natural waters. In addition, the magnetic sensor can be easily removed from the reaction medium with the aid of a magnet and its signal recovered in acidic solution, allowing its reuse in subsequent analysis.