Vibrational and Structural Studies of Environmentally Persistent Free Radicals Formed by Phenol-Dosed Metal Oxide Nanoparticles

Nadra I. Sakr; Matthew C. Patterson; Luke Daemen; Erwin D. Poliakoff; Phillip T. Sprunger

doi:10.1021/acs.langmuir.9b02948

Vibrational and Structural Studies of Environmentally Persistent Free Radicals Formed by Phenol-Dosed Metal Oxide Nanoparticles

Nadra I. Sakr, Matthew C. Patterson, Luke Daemen, Erwin D. Poliakoff, Phillip T. Sprunger

Research output: Contribution to journal › Article › peer-review

13 Scopus citations

Abstract

Environmentally persistent free radicals (EPFRs) are formed by the adsorption of substituted aromatic precursors on the surface of metal oxides and are known to have significant health and environmental impact due to their unique stability. In this article, the formation of EPFRs is studied by adsorption of phenol on ZnO, CuO, Fe₂O₃, and TiO₂ nanoparticles (â'¼10-50 nm) at high temperatures. Electron paramagnetic resonance indicates the formation of phenoxyl-type radicals. Fourier transform infrared spectroscopy provides further evidence of EPFR formation by the disappearance of-OH groups, indicating the chemisorption of the organic precursor on the metal oxide surface. These results are further confirmed by inelastic neutron scattering, which shows both ring out-of-plane bend and C-H in-plane bend motions characteristic of phenol adsorption on the studied systems. Also, the changes in the oxidation state of the metal cations are investigated by X-ray photoelectron spectroscopy, which shows that the direction of electron transfer (redox) during phenol chemisorption is strongly dependent on surface properties as well as surface defects of the metal oxide surface.

Original language	English
Pages (from-to)	16726-16733
Number of pages	8
Journal	Langmuir
Volume	35
Issue number	51
DOIs	https://doi.org/10.1021/acs.langmuir.9b02948
State	Published - Dec 24 2019
Externally published	Yes

Funding

The authors acknowledge support from the National Institute of Environmental Health Science Superfund Research Program through grant P42 ES013648-03. The INS material is based upon work supported by the U.S. Department of Energy under EPSCoR grant no. DE-SC0012432 with additional support from the Louisiana Board of Regents. This research utilized the VISION beamline at ORNL’s Spallation Neutron Source, which is supported by the scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy under contract no. DE-AC0500OR22725. The authors also thank F. Hassan, Z. Wang, and M. DiTusa for help in acquiring EPR data and INS data and R. Hall and R. Kurtz for helpful discussions.

Funders	Funder number
ORNL’s
Office of Basic Energy Sciences
U.S. Department of Energy
National Institute of Environmental Health Sciences	P42 ES013648-03
Office of Experimental Program to Stimulate Competitive Research
Scientific User Facilities Division

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title = "Vibrational and Structural Studies of Environmentally Persistent Free Radicals Formed by Phenol-Dosed Metal Oxide Nanoparticles",

abstract = "Environmentally persistent free radicals (EPFRs) are formed by the adsorption of substituted aromatic precursors on the surface of metal oxides and are known to have significant health and environmental impact due to their unique stability. In this article, the formation of EPFRs is studied by adsorption of phenol on ZnO, CuO, Fe2O3, and TiO2 nanoparticles ({\^a}'¼10-50 nm) at high temperatures. Electron paramagnetic resonance indicates the formation of phenoxyl-type radicals. Fourier transform infrared spectroscopy provides further evidence of EPFR formation by the disappearance of-OH groups, indicating the chemisorption of the organic precursor on the metal oxide surface. These results are further confirmed by inelastic neutron scattering, which shows both ring out-of-plane bend and C-H in-plane bend motions characteristic of phenol adsorption on the studied systems. Also, the changes in the oxidation state of the metal cations are investigated by X-ray photoelectron spectroscopy, which shows that the direction of electron transfer (redox) during phenol chemisorption is strongly dependent on surface properties as well as surface defects of the metal oxide surface.",

author = "Sakr, {Nadra I.} and Patterson, {Matthew C.} and Luke Daemen and Poliakoff, {Erwin D.} and Sprunger, {Phillip T.}",

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doi = "10.1021/acs.langmuir.9b02948",

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AU - Sakr, Nadra I.

AU - Patterson, Matthew C.

AU - Daemen, Luke

AU - Poliakoff, Erwin D.

AU - Sprunger, Phillip T.

PY - 2019/12/24

Y1 - 2019/12/24

N2 - Environmentally persistent free radicals (EPFRs) are formed by the adsorption of substituted aromatic precursors on the surface of metal oxides and are known to have significant health and environmental impact due to their unique stability. In this article, the formation of EPFRs is studied by adsorption of phenol on ZnO, CuO, Fe2O3, and TiO2 nanoparticles (â'¼10-50 nm) at high temperatures. Electron paramagnetic resonance indicates the formation of phenoxyl-type radicals. Fourier transform infrared spectroscopy provides further evidence of EPFR formation by the disappearance of-OH groups, indicating the chemisorption of the organic precursor on the metal oxide surface. These results are further confirmed by inelastic neutron scattering, which shows both ring out-of-plane bend and C-H in-plane bend motions characteristic of phenol adsorption on the studied systems. Also, the changes in the oxidation state of the metal cations are investigated by X-ray photoelectron spectroscopy, which shows that the direction of electron transfer (redox) during phenol chemisorption is strongly dependent on surface properties as well as surface defects of the metal oxide surface.

AB - Environmentally persistent free radicals (EPFRs) are formed by the adsorption of substituted aromatic precursors on the surface of metal oxides and are known to have significant health and environmental impact due to their unique stability. In this article, the formation of EPFRs is studied by adsorption of phenol on ZnO, CuO, Fe2O3, and TiO2 nanoparticles (â'¼10-50 nm) at high temperatures. Electron paramagnetic resonance indicates the formation of phenoxyl-type radicals. Fourier transform infrared spectroscopy provides further evidence of EPFR formation by the disappearance of-OH groups, indicating the chemisorption of the organic precursor on the metal oxide surface. These results are further confirmed by inelastic neutron scattering, which shows both ring out-of-plane bend and C-H in-plane bend motions characteristic of phenol adsorption on the studied systems. Also, the changes in the oxidation state of the metal cations are investigated by X-ray photoelectron spectroscopy, which shows that the direction of electron transfer (redox) during phenol chemisorption is strongly dependent on surface properties as well as surface defects of the metal oxide surface.

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Vibrational and Structural Studies of Environmentally Persistent Free Radicals Formed by Phenol-Dosed Metal Oxide Nanoparticles

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