| 1. |
- Brown, Matthew A, et al.
(författare)
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Measure of Surface Potential at the Aqueous-Oxide Nanoparticle Interface by XPS from a Liquid Microjet
- 2013
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Ingår i: Nano letters. - 1530-6984 .- 1530-6992. ; 13:11, s. 5403-5407
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Tidskriftsartikel (refereegranskat)abstract
- We show that the surface potential at a water–oxide nanoparticle (NP) interface, long considered an immeasurable direct quantity, can be measured by X-ray photoelectron spectroscopy (XPS) from a liquid microjet. This new method does not require a priori knowledge of the particles’ surface structure or of the ion distribution throughout the electrical double layer for its interpretation and can be applied to any colloidal suspension independent of composition, particle size and shape, and solvent. We demonstrate the application for aqueous suspensions of 9 nm colloidal silica (SiO2) at pH 0.3 and 10.0, where the surface potential changes from positive to negative. The experimental results are compared with calculated surface potentials based on Guoy–Chapman theory and are shown to be in good agreement.
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| 2. |
- Zhang, Wenhua, 1981-
(författare)
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First Principles Studies on Chemical and Electronic Structures of Adsorbates
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, we focus on theoretical study of adsorbates on metal and oxide surfaces that are important for surface chemistry and catalysis. Based on first principles calculations, the adsorption ofCO, NO, NO2, C4H6S2, C22H27SH and other molecules or radicals on nobel metal surfaces (gold and silver) are investigated. Also, NO oxidation on oxygen pre-covered Au(111)surface and CO oxidation on water-oxygen covered Au(111)surface aretheoretically studied. A new mechanism of water-enhanced COoxidation is proposed. As for oxide surfaces, we first investigatethe geometric, electronic and magnetic structures of FeO ultrathin film on Pt(111) surface. The experimentally observed scanning tunneling microscopy images are well reproduced for the first timewith our model. The adsorption and dissociation of water on rutileTiO2(110) surface are investigated by quantum molecular dynamics.By theoretical X-ray photoemission spectroscopy (XPS) calculations,the surface species are properly assigned. The same strategy has applied to the study of the phase transition of water covered reconstructed anatase TiO2(001) surface, from which two different phases are theoretically identified. The structure of graphene oxideis also studied by comparing experimental and theoretical XPS spectra. Based on the novel structures identified, a new cutmechanism of graphene oxide is proposed.
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