Decomposition of 2-naphthol in water and its antibacterial and antiviral activities by LaMnO₃ and LaCoO₃ in the dark

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Single-phase powders of LaMnO₃ and LaCoO₃, lanthanum-based perovskites, were synthesized using the citric acid combustion method. The surface concentration of La in the obtained powder was higher in LaCoO₃ than in LaMnO₃. These samples decomposed 2-naphthol in water in the dark. The decomposition reaction is attributed to the Mars–van Krevelen (MvK) mechanism because of the temperature dependence, activation energy, valence change during the reaction, and the amount of ion elution into water. A disproportionation reaction was confirmed for Mn in LaMnO₃. Both samples exhibited antibacterial and antiviral activity against Escherichia coli, Staphylococcus aureus, bacteriophage Qβ, and bacteriophage Φ6. The antibacterial activity was higher than the antiviral activity. LaCoO₃ tended to have higher antibacterial and antiviral activity than LaMnO₃ had. Results show that these materials had less ion leakage than that reported earlier for La₂Mo₂O₉.