Mechanistic study of nitrogen-modified titanium dioxide nanoparticles for enhancing the degradation of organic dyes and antibacterial properties under visible-light irradiation

Titanium oxide sulfate, the raw material for one of the industrial preparation methods of titanium dioxide (TiO2), and urea as the nitrogen source were used to synthesize N-modified TiO2 materials (N-TiO2) with different chemical bonding of N elements by a relatively simple homogeneous co-precipitation method, providing a theoretical basis and experimental foundation for the industrial preparation of N-TiO2 photocatalytic materials. According to the analysis of its microscopic morphology, structural composition, and optoelectronic properties, the material consisted of porous spherical clusters formed by the aggregation of spherical nanoparticles. Nitrogen atoms were uniformly distributed on the surface of the material, causing a red shift in its optical response range and a reduction in the electron-hole recombination rate, which contributed to the photocatalytic performance of the material. The conducted photocatalytic degradation experiments of methyl orange and rhodamine B revealed that both dyes can be effectively degraded under visible-light conditions. Methyl orange interacted with the oxygen vacancies and Brønsted acid sites on the surface of the material, converting from an azo structure to a more degradable quinoid structure. In antibacterial experiments, N-TiO2 demonstrated excellent antibacterial properties, which led to a preliminary discussion of its antibacterial mechanism. According to electron paramagnetic resonance investigations and reactive oxygen species (ROS) scavenging experiments, the material can generate multiple ROS at the same time, among which·OH is the key active substance.