Sorption of Fulvic Acids onto Titanium Dioxide Nanoparticles Extracted from Commercial Sunscreens: ToF-SIMS and High-Dimensional Data Analysis

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.

Application of Potentiometric and Electrophoretic Measurements to Evaluate the Reversibility of Adsorption of Divalent Ions from a Solution on Titanium Dioxide

“…It is produced in large quantities by industry and used as a white pigment in paints, a sunscreen in cosmetics, and a photocatalyst [ 21 ]. Therefore, large amounts of nanoparticles end up in the aquatic environment, where they are an important adsorbent of metal ions [ 22 , 23 , 24 , 25 ]. Titanium dioxide is a durable and water-insoluble oxide that is stable over a wide pH range, unlike oxides such as or [ 26 ].…”

Direct Visualization of Homogeneous Chemical Distribution in Functional Polyradical Microspheres

“…[4,10] To the best of our knowledge, past analyses of postmodified microspheres focused on changes in their surface chemistry, evidenced by techniques such as X-ray photoelectron spectroscopy (XPS) and time-offlight secondary-ion mass spectrometry (ToF-SIMS). [7,[11][12][13][14][15][16] Answering the question how postmodification affects the inner chemical distribution of microspheres is a far more challenging task, which we address herein.…”