Improved photocatalytic and antibacterial performance of Cr doped TiO₂ nanoparticles

Abstract

The effect of Cr and N doping in the adsorption capacity, photocatalytic properties and antibacterial response of TiO₂ anatase nanoparticles is analyzed. The nanoparticles (N-TiO₂, Cr-TiO₂ and Cr/N-TiO₂) were prepared by the sol-gel method. The structural (X-ray diffraction and TEM) and magnetic (SQUID magnetometry) characterization confirms the nanosized nature of the anatase nanoparticles and the absence of secondary phases. The enhancement of the adsorption capacity of the dye (methyl orange) on the surface of the catalysts for the Cr and Cr/N doped samples, together with the redshift of the UV-Vis absorbance spectra promote a high photocatalytic performance under visible light in these nanocatalysts. The culturability and viability of the Escherichia coli DH5α in a medium supplemented with the nanoparticles was characterized and compared with the evolution under visible light (both without and with nanoparticles). The results show that Cr-TiO₂ nanoparticles under visible light display antibacterial activity that cannot be accounted by the toxicity of the nanoparticles alone. However the antibacterial effect is not observed in N-TiO₂ and Cr/N-TiO₂. The differences in the electrostatic charge (isoelectric point) and the degree of nanoparticle dispersion are invoked as the main origins of the different antibacterial response in the Cr-TiO₂ nanoparticles.