| The band gap structure of semiconductor is composed of a valence band with full electrons and an empty conduction band.When the semiconductor particles are radiated by light whose energy is not less than the band gap of the particles,the electrons in the valence band can be excited to the conduction band,forming the photoinduced electron-hole pairs,and the electrons and the holes in interior are transferred to the surface of the particles.The electrons can reduct the electron acceptor,and the holes can be combined with the electron donor to form reactive oxygen species(ROS)with strong oxidizability.The ROS can react with most organics and decompose them.The semiconductor materials can be used as photocatalyst and photocatalytic antibacterial agent based on the photocatalytic mechanism in some fields such as wastewater treatment and killing bacteria.Zinc ferrites(ZnFe2O4),a typical spinel ferrite with broad light response range,has become a new type of semiconductor photocatalyst.However,some inherent defects limit its application for photocatalysis,such as the large density,electron and hole easy to combinate.Graphene(GE),the two-dimensional structure material in the carbon family,has been attracted extensive attention worldwide since it was found.The large surface area and unique layered structure make GE possess strong adsorption capacity.What's more,GE can promote electrons and holes separate as an electron receptor.Polyaniline '(PANI)not only can produce the additional electron-hole pair with irradiation but also can stabilize photogenerated electrons and holes,which contribute to improve the degradation efficiency.Considering the excellent properties of GE,ZnFe2O4 and PANI,the GE/ZnFe2O4 binary and GE/ZnFe2O4/PANI ternary composites are prepared,and their photocatalytic and antibacterial activities also are studied in this paper.Based on the topic above,the contents of this paper are as follows:(1)GE was prepared by oxidation-reduction method.Using GE as substrate,the GE/ZnFe2O4 composites with different mass ratio of GE to ZnFe2O4(mG/Z)were prepared by chemical coprecipitation method.There are some interactions between the two components proved by characterization using modern testing techniques.Photocatalytic performances of the samples were researched taking Rhodamine B(RhB)as simulated organic pollutant in water.The composite with mG/Z = 0.4 had the best photocatalytic activity on the acidic RhB solution,and had good performance for repeated use in the same experimental conditions.(2)GE/ZnFe2O4 composite with mG/Z = 0.4 were coated with PANI by in situ polymerization method to prepare GE/ZnFe2O4/PANI composites with different mass ratio of PANI to GE/ZnFe2O4(/mP/GZ).There are some interactions between the two components proved by characterization using modern testing techniques..Photocatalytic experiments showed that the photocatalytic activities of the ternary composites were better than the binary composites.And the ternary composite with mP/GZ=0.6 had the best the photocatalytic effect on the acidic RhB solution,and alsoexhibited good repeated performance.(3)Taking the binary and ternary composites as antibacterial agents,the antibacterial properties of the samples were studied agaist Escherichia coli,Staphylococcus aureus and Candida albicans.The experiments indicated that the antimicrobial activities were affected by the component ratio of composites and the strain.The antibacterial effect of the binary composite with mG/Z=0.4 and the ternary composite with mP/GZ= 0.6 were the best among their series composites.And the ternary composites had better antibacterial activity than the binary ones.In addition,all the samples had the best antibacterial activity against Candida albicans among three strains.(4)The photocatalytic and antibacterial mechanisms of the samples were studied in detail.The essence of the photocatalytic and antibacterial property was the photodegradation of ROS produced by the samples upon illumination. |
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