Synthesis and characterization of fluorinated anatase nanoparticles and subsequent N-doping for efficient visible light activated photocatalysis

Abstract

Fluorinated-titanium dioxide (TiO₂-F) nanoparticles in a pure anatase polymorph was precipitated from solution by hydrolysis of titanium oxychloride, using urea and ammonia as precipitation agents and potassium fluoride as a source of fluorine anion. A further wet attrition milling in presence of glycine completed by a heat treatment allowed an additional nitrogen doping of TiO₂ (TiO₂-F&N-HT). The morphology and crystalline structure of the as-synthesized powder was determined by transmission electron microscopy (TEM) and X-ray diffraction (XRD) and showed that TiO₂ powder was composed of nanoparticles with narrow size distribution which crystallized in the anatase phase. X-ray photoelectron spectroscopy (XPS) revealed that fluorine and nitrogen are present in TiO₂ as surface fluorination and interstitial doping, respectively. UV–vis diffuse reflectance spectroscopy (DRS) showed an increased optical absorption in the visible for TiO₂-F&N-HT sample. Under visible light irradiation, TiO₂-F nanoparticles showed a high photocatalytic performance, showing the high potential of an improved surface fluorination for Escherichia coli (E. coli) disinfection in suspension. These results show the importance of anatase-TiO₂ nanoparticles synthesis and modification by using a wet chemical approach leading to low aggregation and high specific surface area for effective bacterial inactivation. The co-doped TiO₂-F&N-HT powder showed slightly improved performance compared to the fluorinated sample. The significant degree of aggregation after the heat treatment is postulated as being a limiting factor in its photocatalytic activity.