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Silver-loaded MnO_2 nanomaterials(Ag/MnO_2),including Ag/α-MnO_2,Ag/β-MnO_2,Ag/γ-MnO_2and Ag/δ-MnO_2 nanorods,were prepared with hydrothermal and impregnation methods.The bactericidal activities of four types of Ag/MnO_2 nanomaterials against Escherichia coli were investigated and an inactivation mechanism involving Ag~+ and reactive oxygen species(ROS)was also proposed.The bactericidal activities of Ag/MnO_2 depended on the MnO_2 crystal phase.Among these nanomaterials,Ag/β~-MnO_2 showed the highest bactericidal activity.There was a 6-log decrease in E.coli survival number after treatment with Ag/β~-MnO_2 for120 min.The results of 5,5-dimethyl-l-pyrroline-N-oxide spin-trapping measurements by electron spin resonance indicate OH and O_2~- formation with addition of Ag/β-MnO_2,Ag/γ-MnO_2 or Ag/δ-MnO_2.The strongest peak of OH appeared for Ag/β-MnO_2,while no OH or ·O_2~-signal was found over Ag/α-MnO_2.Through analysis of electron spin resonance(ESR) and Ag+elution results,it could be deduced that the toxicity of Ag~+ eluted from Ag/MnO_2 nanomaterials and ROS played the main roles during the bactericidal process.Silver showed the highest dispersion on the surface of β-MnO_2,which promoted ROS formation and the increase of bactericidal activity.Experimental results also indicated that Ag/MnO_2 induced the production of intracellular ROS and disruption of the cell wall and cell membrane.
Silver-loaded MnO 2 nanomaterials (Ag / MnO 2), including Ag / α-MnO 2, Ag / β-MnO 2, Ag / γ-MnO 2 and Ag / δ-MnO 2 nanorods, were prepared with hydrothermal and impregnation methods.The bactericidal activities of four types of Ag / MnO_2 nanomaterials against Escherichia coli were investigated and an inactivation mechanism involved Ag ~ + reactive oxygen species (ROS) was also proposed. The bactericidal activities of Ag / MnO_2 depended on the MnO 2 crystal phase. Amm these nanomaterials, Ag / β ~ -MnO_2 showed the highest bactericidal activity. Here was a 6-log decrease in E. coli survival number after treatment with Ag / β ~ -MnO_2 for 120 min. These results of 5,5-dimethyl-l-pyrroline-N-oxide spin-trapping measurements by electron spin resonance indicate OH and O_2 ~ - formation with addition of Ag / β-MnO_2, Ag / γ-MnO_2 or Ag / δ-MnO_2.The strongest peak of OH was for Ag / β-MnO_2, while no OH or · O 2 ~ -signal was found over Ag / α-MnO_2.Through analysis of electron spin resonance (ESR) and Ag + elution results, i t could be deduced that the toxicity of Ag ~ + eluted from Ag / MnO 2 nanomaterials and ROS played the main roles during the bactericidal process. Silica showed the highest dispersion on the surface of β-MnO 2, which promoted ROS formation and the increase of bactericidal activity. Experimental results also indicated that Ag / MnO 2 induced the production of intracellular ROS and disruption of the cell wall and cell membrane.