We synthesized Fe3O4@C@Ag nanocomposites through a combination of solvothermal, hydrothermal, and chemical redox reactions. Characterization of the resulting samples by X-ray diffraction, Fourier-transform infrared spectroscopy, field-emission scanning and transmission electron microscopy, and magnetic measurement is reported. Compared to Fe3O4@Ag nanocomposites, the Fe3O4@C@Ag nanocomposites showed enhanced antibacterial activity. The Fe3O4@C@Ag nanocomposites were able to almost entirely prevent growth of Escherichia coli when the concentration of Ag nanoparticles was 10 mu g/mL. Antibacterial activity of the Fe3O4@C@Ag nanocomposites was maintained for more than 40 h at 37 degrees C. The intermediate carbon layer not only protects magnetic core, but also improves the dispersion and antibacterial activity of the silver nanoparticles. The magnetic core can be used to control the specific location of the antibacterial agent (via external magnetic field) and to recycle the residual silver nanoparticles. The Fe3O4@C@Ag nanocomposites will have potential uses in many fields as catalysts, absorbents, and bifunctional magnetic-optical materials. (C) 2011 Elsevier B. V. All rights reserved.