Electrochemically assisted photocatalytic inactivation of Escherichia coli under visible light using a ZnIn2S4 film electrode

ZnIn(2)S(4) film was fabricated on Ti substrate by a two-step approach including electrodeposition and annealing. The film obtained after electrodeposition was composed of Zn, In, and S. Then this precursor film was gradually converted to hexagonal phase ZnIn(2)S(4) during the process of annealing in a nitrogen flow. The crystallographic structures and photoresponse ability of the film could be affected significantly by the annealing temperature. From diffuse reflection spectra, ZnIn(2)S(4) film annealed at 500 degrees C exhibited the highest absorption intensity in visible light region among all the samples, resulting in a high photoresponse in the electrochemical measurement. The microstructures of ZnIn(2)S(4) were characterized by transmission electron microscopy, and the results indicated that the interlayer distance was 0.295 nm, corresponding to d(104) space of hexagonal ZnIn(2)S(4). Energy-dispersive X-ray spectra showed that the atomic ratio of Zn:In:S was 9.3:20.3:39.5, which was close to the stoichiometry ZnIn(2)S(4). The photocatalytic ability of ZnIn(2)S(4) was investigated by photoelectrocatalytic inactivation of Escherichia coli (E. coli) with the initial concentration of similar to 3 x 10(8) colony forming units per milliliter. More than 3 logs of E. coli were killed within 60 min with the ZnIn(2)S(4) film under visible light, and when the photocatalytic process was assisted by a 0.6 V positive potential, no surviving bacteria were detected after 60 min of inactivation.