title: Tuning Acid-Base Properties Using Mg-Al Oxide Atomic Layer Deposition.
abstract: Atomic layer deposition (ALD) was used to coat γ-Al2O3 particles with oxide films of varying Mg/Al atomic ratios, which resulted in systematic variation of the acid and base site areal densities. Variation of Mg/Al also affected morphological features such as crystalline phase, pore size distribution, and base site proximity. Areal base site density increased with increasing Mg content, while acid site density went through a maximum with a similar number of Mg and Al atoms in the coating. This behavior leads to nonlinearity in the relationship between Mg/Al and acid/base site ratio. The physical and chemical properties were elucidated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 physisorption, and CO2 and NH3 temperature-programmed desorption (TPD). Fluorescence emission spectroscopy of samples grafted with 1-pyrenebutyric acid (PBA) was used for analysis of base site proximity. The degree of base site clustering was correlated to acid site density. Catalytic activity in the self-condensation of acetone was dependent on sample base site density and independent of acid site density.
authors.affiliation: †Materials Science Program, and ‡Department of Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States.
authors.forename: David H K
authors.initials: DH
authors.lastname: Jackson
authors.affiliation: †Materials Science Program, and ‡Department of Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States.
authors.forename: Brandon J
authors.initials: BJ
authors.lastname: O'Neill
authors.affiliation: †Materials Science Program, and ‡Department of Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States.
authors.forename: Jechan
authors.initials: J
authors.lastname: Lee
authors.affiliation: †Materials Science Program, and ‡Department of Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States.
authors.forename: George W
authors.initials: GW
authors.lastname: Huber
authors.affiliation: †Materials Science Program, and ‡Department of Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States.
authors.forename: James A
authors.initials: JA
authors.lastname: Dumesic
authors.affiliation: †Materials Science Program, and ‡Department of Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Kuech
keywords: acetone self-condensation; atomic layer deposition; gamma alumina; magnesium aluminum oxide; pyrene butyric acid; solid base