title: Control of Surface and Edge Oxidation on Phosphorene.
abstract: Phosphorene is emerging as an important two-dimensional semiconductor, but controlling the surface chemistry of phosphorene remains a significant challenge. Here, we show that controlled oxidation of phosphorene determines the composition and spatial distribution of the resulting oxide. We used X-ray photoemission spectroscopy to measure the binding energy shifts that accompany oxidation. We interpreted these spectra by calculating the binding energy shift for 24 likely bonding configurations, including phosphorus oxides and hydroxides located on the basal surface or edges of flakes. After brief exposure to high-purity oxygen or high-purity water vapor at room temperature, we observed phosphorus in the +1 and +2 oxidation states; longer exposures led to a large population of phosphorus in the +3 oxidation state. To provide insight into the spatial distribution of the oxide, transmission electron microscopy was performed at several stages during the oxidation. We found crucial differences between oxygen and water oxidants: while pure oxygen produced an oxide layer on the van der Waals surface, water oxidized the material at pre-existing defects such as edges or steps. We propose a mechanism based on the thermodynamics of electron transfer to interpret these observations. This work opens a route to functionalize the basal surface or edges of two-dimensional (2D) black phosphorus through site-selective chemical reactions and presents the opportunity to explore the synthesis of 2D phosphorene oxide by oxidation.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Kaci L
authors.initials: KL
authors.lastname: Kuntz
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Rebekah A
authors.initials: RA
authors.lastname: Wells
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Jun
authors.initials: J
authors.lastname: Hu
authors.affiliation: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, P.R. China.
authors.forename: Teng
authors.initials: T
authors.lastname: Yang
authors.affiliation: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, P.R. China.
authors.forename: Baojuan
authors.initials: B
authors.lastname: Dong
authors.affiliation: College of Sciences, Liaoning Shihua University , Fushun 113001, P.R. China.
authors.forename: Huaihong
authors.identifier: http://orcid.org/0000-0001-7094-2878
authors.initials: H
authors.lastname: Guo
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Adam H
authors.initials: AH
authors.lastname: Woomer
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Druffel
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Anginelle
authors.initials: A
authors.lastname: Alabanza
authors.affiliation: Physics and Astronomy Department, Michigan State University , East Lansing, Michigan 48824, United States.
authors.forename: David
authors.identifier: http://orcid.org/0000-0003-1131-4788
authors.initials: D
authors.lastname: Tománek
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.|Department of Applied Physical Sciences, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Scott C
authors.identifier: http://orcid.org/0000-0002-2883-0204
authors.initials: SC
authors.lastname: Warren
keywords: 2D materials; DFT; binding energy shift; black phosphorus; edge functionalization; oxidation; phosphorene; surface functionalization