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 HCO 3 − , 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 HCO 3 − 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 HCO 3 − . The reaction process between Ag NPs and HCO 3 − was revealed by H 2 O 2 mediated oxidation experiments. An ultrathin Ag 2 CO 3 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.