Ag@CeO2 nanocomposites were synthesized by a biogenic and green approach using electrochemically active biofilms (EABs) as a reducing tool. The as-synthesized Ag@CeO2 nanocomposites were characterized and used in antimicrobial, visible light photocatalytic and photoelectrode studies. The Ag@CeO2 nanocomposites showed effective and efficient bactericidal activities and survival test against Escherichia coli 0157:H7, and Pseudomonas aeruginosa. The as-synthesized Ag@CeO2 nanocomposites also exhibited enhanced visible light photocatalytic degradation of 4-nitrophenol and methylene blue than pure CeO2. A photocatalytic investigation showed that the Ag@CeO2 nanocomposites possessed excellent visible light photocatalytic activities compared to pure CeO2. Electrochemical impedance spectroscopy and photocurrent measurements showed that the as-synthesized Ag@CeO2 nanocomposites exhibited excellent and enhanced responses to visible light irradiation. These results suggest that the AgNPs anchored at CeO2 induced visible light photoactivity by decreasing the recombination of photogenerated electrons and holes, and extending the response of pure CeO2 to visible light. Overall, as-synthesized Ag@CeO2 nanocomposites are smart materials that can be used for a range of applications, such as antimicrobial activity, visible light photocatalysis and photoelectrode. (C) 2014 Elsevier Inc. All rights reserved.