Synthesis, Characterization, And Photocatalytic Antibacterial Performance Of Ag-N-codoped TiO₂

In this paper, a new method of sol-gel combined hydrothermal was used to prepare TiO2 photocatalyst codoped with metal of sliver and non-metal of nitrogen elements. The samples prepared under different technological conditions were characterized by XRD, SEM, EDS, TEM, IR. The rhodamine B(RhB) was used for the objective pollutant to evaluate the photocatalytic degradation effect of Ag-N-TiO2 photocatalyst, and the Escherichia coli and Staphylococcus aureus were used for the target bacterias to evaluate the photocatalytic antibacterial performance of Ag-N-TiO2 photocatalyst. The main results were obtained as follows:(1) Ag-N-TiO2 nanoparticles with highly visible-light response were successfully synthesized by the method of sol-gel combined hydrothermal. The influence of N/Ag doped dosages, calcination temperatures, calcination times to the preparation of Ag-N-TiO2 nanoparticles were investigated using the decoloration efficiency of RhB as the evaluation index. The results indicated the optimal doped dosage was n(Ti):n(Ag):n(N)=1:0.05:1, the optimal calcination temperature was 450℃, the optimal calcination time was 2h.(2) The crystal structure, morphological structure, element composition of Ag-N-TiO2 was characterized by XRD, SEM, EDS, TEM, IR. It turned out that Ag-N-TiO2 showed good crystal shape, high crystallinity, small particle size(11.32nm) and homogeneous distribution.(3) Using RhB as the objective pollutant, the photocatalytic activity of Ag-N-TiO2 were investigated. The effects of different catalyst dosages, the initial concentrations and pH values of RhB on the decoloration efficiency of RhB were discussed. The experiments suggested that Ag-N-TiO2 had high photocatalytic activity on the decoloration efficiency of RhB reaching 96.51% after 4h under visible light irradiation as the dosage of catalyst being 1.00g/L, the initial concentration of RhB being 10mg/L and the initial pH value of the reaction solution being 3. Furthermore, Ag-N-TiO2 exhibited certain availablity of reusing and had a good degradation effect on methylene blue(MB) and acid orange 7(AO7) under visible light irradiation. The photocatalytic degradation reaction process of different catalysts followed the first order reaction kinetics model and the apparent reaction rate constant of Ag-N-TiO2 was greater than that of undoped and single-doped TiO2.(4) Using Escherichia coli and Staphylococcus aureus as the target bacterias, the visible photocatalytic antibacterial performance of Ag-N-TiO2 were studied, and the effects on the diameter of inhibition zone for bacterias under different catalysts and different N/Ag doped dosages was analysed. The results revealed that Ag-N-TiO2 had good visible photocatalytic antibacterial performance on the diameter of inhibition zone for Escherichia coli to be 15.2mm and the diameter of inhibition zone for Staphylococcus aureus to be 21.9mm under visible light irradiation as the doped dosages being n(Ti): n(Ag):n(N)=1:0.05:1. Besides, Ag-N-TiO2 had certain antibacterial effects on Escherichia coli and Staphylococcus aureus under dark condition with the diameter of inhibition zone to be 14.7mm and 19.2mm respectively. SEM morphological characterization showed that the surface of bacterial cells appeared concaves, ruffles or holes, and missing flagellum with catalyst.