Inactivation of E. coli by nano-Cu/MWCNTs combined with hydrogen peroxide.

This paper aims at the study on the antibacterial activity of nCu-MWCNTs combined with H2O2 against gram-negative bacteria Escherichia coli (E. coli). The antibacterial ability of nCu-MWCNTs/H2O2 was evaluated by traditional surface plating method, fluorescence and SEM imaging, and the effects of variables (contacting time, dose of nCu-MWCNTs and dose of H2O2) were investigated. By comparing with other five processes including H2O2, MWCNTs, nCu-MWCNTs, MWCNTs/H2O2 and nCu/H2O2, nCu-MWCNTs and H2O2 was proved to have superlative antimicrobial effectiveness against E. coli. The role of nano-Cu, MWCNTs and H2O2 in the antimicrobial activity of nCu-MWCNTs/H2O2 was clarified. The release of copper ions and formation of hydroxyl radicals (OH) both contributed the antibacterial ability of nCu-MWCNTs/H2O2 system. And MWCNTs as the support might be able to promote the electron transfer in nCu-MWCNTs for copper ion release.

Mitigation in the toxicity of graphene oxide nanosheets towards Escherichia coli in the presence of humic acid.

GO nanosheets have been reported to show strong cytotoxicity towards Escherichia coli (E. coli) in aqueous solution. Natural organic matters (NOMs) in water may probably coat on the surface of GO nanosheets, which possibly influence its cytotoxicity. In this study, we illustrated how humic acid (HA), a ubiquitous NOM, mitigated the toxicity of GO nanosheets towards E. coli based on the cytotoxicity mechanism of GO nanosheets. Adsorption and cell viability tests proved that HA was adsorbed by GO nanosheets and decreased the toxicity of GO nanosheets towards E. coli. It was found that HA was adsorbed on the surface of GO nanosheets by polar groups, which prevented E. coli from contacting with GO nanosheets and weakened the toxicity of GO nanosheets. Besides, HA exerted an antioxidant role in maintaining the activity of the antioxidant enzyme and decreasing the ROS generation according to the results of oxidative stress experiments. The work revealed that HA relieved the toxicity of GO nanosheets and decreased the ecological risks induced by GO nanosheets.