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

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.

Influence of the electrostatic interactions in a Pickering emulsion polymerization for the synthesis of silica-polystyrene hybrid nanoparticles.

HYPOTHESIS: Silica-polystyrene hybrid nanoparticles were synthesized by Pickering emulsion polymerization. The coupling effect of initiator type and silica surface charge was studied to exhibit the predominant role of electrostatic interactions in the synthesis mechanisms. EXPERIMENTS: Non-ionic hydrophobic initiator (2,2'-azobis(2-methylpropionitrile), AIBN) or anionic hydrophilic initiator (sodium persulfate, NaPS), and positively or negatively charged silica were used as reactants with styrene for Pickering emulsion polymerization. Their interactions were evaluated by Zeta potential measurements. The droplet size and the stability of the Pickering emulsions, and the hybrid particle morphology, surface coverage, size and agglomeration were evaluated by laser granulometry and microscopy. FINDINGS: Similar surface charge between negatively charged silica particles and an anionic initiator led to strong repulsions and thus to non-covered polystyrene nanoparticles. With positively charged silica, a high decoration was obtained due to attractive interactions between the inorganic and the organic phases, but a strong agglomeration was also observed. The use of a non-ionic initiator led to a homogeneous coverage with negatively charged silica. With positively charged silica micronic sizes were formed by following two different mechanisms. These data, by enriching the existing literature, led to a more complete and robust description of the emulsion polymerization synthesis for hybrid nanostructures.

Innovative high-surface-area CuO pretreated cotton effective in bacterial inactivation under visible light.

This study presents the first report on enhanced bacterial inactivation of E. coli by RF-plasma pretreated cotton with high-surface-area CuO powders compared with nonpretreated cotton textiles. The high-surface-area CuO (65 m/g) powder was fully characterized. The E. coli inactivation proceeded in the dark and was accelerated under visible and sunlight irradiation even at very low levels of visible light irradiation. The effect the RF-plasma pretreatment of the cotton on the binding of CuO, applied light dose, the amount of CuO loading and initial E. coli concentration on the inactivation kinetics of E. coli is reported in detail.