A type of fluorescent-magnetic dual-function nanocomposite, Fe3O4@SiO2@P-2, was successfully obtained by Cu+-catalyzed click reaction between acetylene (CCH)-substituted carbazole-based conjugated polymer (P-2) and azide-terminated silica-coated magnetic iron oxide nanoparticles (Fe3O4@SiO2-N-3). Optical and magnetization analyses indicate that Fe3O4@SiO2@P-2 exhibits stable fluorescence and rapid magnetic response. The fluorescence of Fe3O4@SiO2@P-2 was quenched significantly in the presence of I- and gave a detection limit (DL) of approximate to 8.85 x 10(-7) M. Given the high binding constant and matching ratio between Hg2+ and I-, the fluorescence of Fe3O4@SiO2@P-2/I- complex recovered efficiently with the addition of Hg2+. A DL of approximate to 4.17 x 10(-7) M was obtained by this probing system. Recycling of Fe3O4@SiO2@P-2 probe was readily achieved by simple magnetic separation. Results indicate that Fe3O4@SiO2@P-2 can be used as an on-off-on fluorescent switchable and recyclable Hg2+ probe. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3636-3645