Magnetic N-halamine nanocomposites were synthesized through the encapsulation of the magnetic silica nanoparticles with antibacterial N-halamine polymer. The as-synthesized sample was characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and thermogravimetric analysis (TGA). The fabricated magnetic N-halamine nanocomposites possessed enhanced antibacterial activity against both Gram-positive and Gram-negative bacteria compared with their bulk counterparts. The effect of chlorine content of the magnetic N-halamine nanocomposites on the antibacterial activity was investigated. The magnetic N-halamine nanocomposites also exhibited super-paramagnetic behavior and had a saturation magnetization of 4.728 emu g(-1) at room temperature, which made these nanocomposites separable magnetically after the antibacterial behavior. Performances derived from the synergism between magnetic core and antibacterial shell suggest that the magnetic N-halamine nanocomposites are qualified for antibacterial applications and separable by the aid of the external magnetic field. (C) 2011 Elsevier Inc. All rights reserved.