The impact of material design on the photocatalytic removal efficiency and toxicity of two textile dyes.

This study deals with the toxicity of the treated solutions of two types of dyes, namely, the anthraquinonic Reactive Bleu 19 dye (RB19) and the bi-azoic Direct Red 227 dye (DR227), which are treated in single and binary mixture systems. The target molecules were removed by the photocatalysis process using ZnO as a catalyst, which was calcined at two temperatures 250 and 420 °C (ZnO250 and ZnO420) prepared in the lab by the one-step calcination method. XRD, TEM, EDX, XPS, FT-IR, BET, RAMAN, and EPR analyses were carried out to characterize the catalyst material. While the phytotoxicity was being conducted using watercress seeds, the cytotoxicity took place using a cell line (raw) and an intestinal cell (caco-2). The XRD analysis showed the partial calcination of ZnO250 and the presence of anhydrous zinc acetate along with the ZnO nanoparticles (NPs). This result was not observed for ZnO420. Despite the complete discoloration (100%) of all the final solutions, ZnO250 exhibited a high cytotoxicity and phytotoxicity against the RB19 dye after the photocatalytic treatment; however, it was not the case of ZnO420 which was selected as an eco-friendly photocatalyst for the degradation of organic dyes based on the results of removal efficiency, cytotoxicity, and phytotoxicity.

Enhanced concentration of dispersed carbon nanofibres in organic solvents through their functionalization by fluorination.

Covalent functionalization through pure molecular gaseous fluorination has been applied on carbon nanofibres. Nuclear magnetic resonance and thermal gravimetric analysis investigations have been performed on fluorinated carbon nanofibres in order to determine the chemical and thermal stability of the C-F bonding. The high covalency obtained allows no significant modification of the physicochemical nanostructure of fluorinated carbon nanofibres after sonification. Such modification of surface chemistry leads to a high increase in the limit concentration of dispersed carbon nanofibres in organic solvents without surfactant. An exciting maximum of 570 mg L(-1) of fluorinated nanofibres can be homogeneously dispersed in N-methylpyrrolidone, whereas 310 mg L(-1) is the maximum for non-fluorinated carbon nanofibres. In order to understand such dispersibility differences, Hildebrand and Hansen solubility theory has been used.

Direct fluorination applied to wood flour used as a reinforcement for polymers.

Direct fluorination was applied to wood flour in order to improve its compatibility with polymers and thus enhance the properties of wood-polymer composites. Fourier-transform infrared spectra and (19)F solid-state nuclear magnetic resonance results underlined a successful covalent grafting of fluorine atoms onto the wood chemical structure. No physical damage of the wood particles was observed during scanning electron microscopy analysis. The thermal behaviour of the wood flour was also studied by thermogravimetric analysis. The hydrophilic property changes of wood flour were examined by evaluating the water content and the rate of water uptake of samples under different relative humidity conditions. A decrease in the wood flour water content was noted after fluorination. All these studies tend to prove the efficiency of this treatment on wood hydrophilia.

Origin of the photo-cross-linking process in dichromated polyacrylamide under conventional and laser irradiation.

This work is devoted to determining the contribution of amide groups in the photoredox and cross-linking process of dichromated polyacrylamide based on the fate of the photoactive species and of the polymer under conventional and laser irradiation. It was shown that, in parallel to the reduction of chromium(VI) into chromium(V), the cross-linking of the matrix occurred through a complexation reaction around chromium(V) and through formation of covalent bonds between macromolecular chains. A comparison with dichromated poly(vinyl alcohol) was also reported to highlight the role of the chemical structure of the polymeric matrix in the mechanism of hologram formation. Moreover, for the first time it was demonstrated by in situ infrared spectroscopy that the physicochemical modifications undergone by the photosensitive materials were similar for the two modes of irradiation.