Browsing by Author "Bai, Shi"
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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 Evolution of multiple spillover hydrogen species on anatase titanium dioxide(Cell Reports Physical Science, 2022-12-21) Liu, Kairui; Hou, Guangjin; Gao, Pan; Nie, Xuezhong; Bai, Shi; Janik, Michael J.; Zhang, Z. ConradHydrogen spillover is a widespread phenomenon on reducible metal oxide surfaces, with numerous observations confirming its occurrence. However, direct physical characterization of the spillover hydrogen species on an oxide catalyst support remains challenging. Differentiating the binding sites of specific spillover hydrogen species has been elusive. Herein, we vary temperature and reductive conditions, then quench and detect the physicochemical character of three distinct spillover hydrogen species on anatase titanium dioxide (TiO2-A) by deuterium magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, aided by density functional theory. Fast cooling during the sample preparation is crucial in quenching the spillover deuterium species to enable MAS NMR detection. Energetically favorable spillover deuterium species evolve from deuteron to deuteride states with increasing reduction temperature. Prevailing deuteron species reside on the 2-fold-coordinated O2c site of the TiO2-A (101) surface at low reduction temperature. At high reduction temperature, deuterides residing at oxygen vacancies (Ti6c–D–Ti5c) are formed.Item A one-shot double-slice selection NMR method for biphasic systems(Physical Chemistry Chemical Physics, 2022-07-18) Doolittle Catlin, Kaitlyn; Simmons, Julia; Bai, ShiWe propose a new and robust one-shot double-slice selection experiment to detect 1H NMR signals of biphasic systems simultaneously. The resultant spectrum contains opposite-phased peaks representing the chemical species from the two phases, respectively.