Effect of bicarbonate on physiochemical properties of silver nanoparticles and toxicity to Escherichia coli.

Understanding the interaction between silver nanoparticles (Ag NPs) and substances in aquatic systems enables Ag NPs to be better applied in science and industry. Moreover, it also could help us to determine the fate of Ag NPs and assess their hazards in aquatic environment. In this work, the interaction of Ag NPs with HCO3 - , ubiquitous ligand in aquatic systems, during long-term incubation was firstly studied and the possible mechanism was proposed. Results showed that the long-term incubation with HCO3 - led to the red-shifting of UV-vis spectra, the increasing of particles zeta potential (more negative), and the declining of the aqueous Ag+ concentration, as well as the decreasing in the toxicity of Ag NPs suspensions. Furthermore, the ambient temperature was found to have a great impact on the interaction of Ag NPs with HCO3 - . The reaction process between Ag NPs and HCO3 - was revealed by H2 O2 mediated oxidation experiments. An ultrathin Ag2 CO3 layer was proved to form on the surface of Ag NPs, which should be the reason for the evolution of various properties of Ag NPs described above.