Browsing by Author "Quinn, Caitlin M."
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Item Attachment Chemistry of 4-Fluorophenylboronic Acid on TiO2 and Al2O3 Nanoparticles(Chemistry of Materials, 2022-12-13) Byron, Carly; Silva-Quinones, Dhamelyz; Sarkar, Sucharita; Brown, Scott C.; Bai, Shi; Quinn, Caitlin M.; Grzenda, Zachary; Chinn, Mitchell S.; Teplyakov, Andrew V.Surface modification of nanoparticulate TiO2 and Al2O3 materials with 4-fluorophenylboronic acid is investigated in order to both evaluate the novel surface modification schemes and develop spectroscopic labels for surface characterization. The chemistry of the modification is followed on all these surfaces using X-ray photoelectron spectroscopy, multinuclear (11B, 19F, and 13C) solid-state and solution NMR, and infrared spectroscopy to determine the binding modes of this compound using boron and fluorine as probe atoms. Density functional theory model calculations are utilized to visualize predicted surface species and to interpret the results of spectroscopic measurements. A comparison is made among TiO2 rutile, TiO2 anatase, and γ-Al2O3. On all three materials, the modification proceeds via the boronic functional groups, with metal oxide-controlled surface chemistry. The bonding configuration depends on the material and is dominated by a monodentate species for titania and by bidentate species for alumina. The surface structures determined to form on all the oxide semiconductors investigated suggest that sensitization or monolayer doping approaches with a well-defined chemical interaction via a boronic functionality can be developed.Item Total and Class-Specific Determination of Fluorinated Compounds in Consumer and Food Packaging Samples Using Fluorine-19 Solid-State Nuclear Magnetic Resonance Spectroscopy(Analytical Chemistry, 2024-05-28) Thijs, Mike; Laletas, Ernest; Quinn, Caitlin M.; Raguraman, Subbu V.; Carr, Bryan; Bierganns, PatricHamburger wrapping paper, coated with water-based barrier coatings, used in the food packaging industry was studied by using the total organic fluorine (TOF) method based on combustion ion chromatography and fluorine-19 solid-state nuclear magnetic resonance (19F ss-NMR) spectroscopy. Although the TOF method is a fast and affordable method used to screen for per- and polyfluoroalkyl substances (PFAS), the amount of fluorine it measures is heavily dependent on the extraction step and, therefore could lead to inaccurate results. Fluorine-19 ss-NMR spectroscopy can differentiate between organic and inorganic fluorinated sources, eliminating the need for sample clean up. To illustrate this, the 19F ss-NMR spectra of clean coated paper samples that contained naturally occurring F- ions from the talc raw material and spiked samples containing perfluorooctanoic acid were compared. A range of experimental conditions was explored to improve sensitivity for low PFAS concentrations (in the order of 10–20 mg/kg). Despite the disadvantages of ss-NMR spectroscopy, such as the low limit of detection and resolution, the results demonstrate it can be a viable tool to directly detect PFAS moieties in consumer and food packaging. Therefore, 19F solid-state NMR spectroscopy challenges and complements current methods, which only provide indirect evidence of the presence of PFAS.