TiO₂ Nanoparticles Co-Doped with Silver and Nitrogen for Antibacterial Application

We have prepared a series of TiO₂ nanoparticles for antibacterial applications. These TiO₂ nanoparticles were prepared by the hydrolysis precipitation method with Ti(OBu)₄, silver nitrate and ammonia. Crystal structure, particle size, interfacial structure and UV-visible light response of the prepared nanoparticles were characterized by X-ray diffraction measurements (XRD), Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRs). The XRD spectra showed that all samples were anatase structure calcined at 450 °C for 3 hours. The Ag doping made the peak of diffraction wider. The results of TEM showed that the nanoparticles of TiO₂, N–TiO₂ and 1% Ag–N–TiO₂ were all spherical in shape and well distributed with a mean size of 19.8 nm, 39.2 nm and 20.7 nm, respectively. N doping caused the nanoparticle size to increase, while, when the doped amount of Ag⁺ increased, the TiO₂ particle size decreased. The FTIR revealed that Ag and N doping of TiO₂ appeared to have strong absorption by –OH group and showed the characteristic absorption band of NH⁺ ₄ and Ag. The UV-Vis-DRs indicated that the absorption band of Ag-N co-doped TiO₂ had red shift and that the optical absorption response (between 400 nm and 700 nm) had obvious enhancement. The antibacterial properties of nanoparticles were investigated by agar diffusion method toward Escherichia coli and Bacillus subtilis. The results indicated that both Ag- and N-doped TiO₂ could increase the antibacterial properties of TiO₂ nanoparticles under fluorescent light irradiation. A 1% Ag–N–TiO₂ had the highest antibacterial activity with a clear antibacterial circle of 33.0 mm toward Escherichia coli and 22.8 mm toward Bacillus subtilis after cultivation for 24 hours.