No abstract

Titanium dioxide nanoparticles (n-TiO2) are common ingredients of sunscreens and are often released into surface waters during usage. Once released, the surface chemistry of n-TiO2 changes by interacting with dissolved organic matter (DOM). In previous studies, these interactions were investigated using model n-TiO2 and; therefore, do not account for the complex composition of the coating of n-TiO2 aged in sunscreens. Taking advantage of a mild extraction method to provide more realistic nanoparticles, we investigated the potentials of time of flight-secondary ion mass spectrometry (ToF-SIMS) combined with high-dimensional data analysis to characterize the sorption of fulvic acids, as a model for DOM, on titanium dioxide nanoparticles extracted from ten different commercial sunscreens (n-TiO2 ⸦ sunscreen). Clustering analysis confirmed the ability of ToF-SIMS to detect the sorption of fulvic acids. Moreover, a unique sorption pattern was recognized for each n-TiO2 ⸦ sunscreen, which implied different fractionation of fulvic acids based on the initial specifications of nanoparticles, e.g., size, coating, etc. Furthermore, random forest was used to extract the most important fragments for predicting the presence of fulvic acids on the surface of n-TiO2 ⸦ sunscreen. Finally, we evaluate the potential of ToF-SIMS for characterizing the sorption layer.

A realistic exposure of n-TiO2 nanoparticles to river water by using a dialysis bag as a passive reactor: DOM of the river water diffuses inside while n-TiO2 nanoparticles remain inside.

A new complex of yttrium-salpr was synthesized through the reaction of Y(NO 3 ) 3 Á6(H 2 O) and salpr Schiff base (salpr = N,N 0 -bis(3-salicylidenaminopropyl) amine). The prepared complex was characterized by Mid and Far-IR, 13 C-NMR, 1 H-NMR, UV-Vis, XRF, and CHN. The obtained data suggested a binuclear structure for this compound. To our surprise, the catalytic activity of this complex was even lower than its precursor, Y(NO 3 ) 3 Á6(H 2 O), in one-pot synthesis of dihydropyrimidinones under solvent-free conditions. As one of the reasons of this reduced activity should pertain to the binuclear structure of the complex that reduces the availability of yttrium in the reaction, the complex was immobilized on modified Fe 3 O 4 nanoparticles, which not only increases the surface to the volume ratio of the compound, but also hinders the formation of binuclear structure due to site (Schiff base) isolation. These prepared nanoparticles depicted noticeably high catalytic activity as well as good recyclability and very easy separation.