title: Surface structure of a "non-amphiphilic" protic ionic liquid.
abstract: The nanostructure of the ethanolammonium nitrate (EtAN)-air surface has been investigated using X-ray reflectometry (XRR), vibrational sum frequency spectroscopy (VSFS) and neutral impact collision ion scattering spectroscopy (NICISS). The XRR data decays more rapidly than expected for a perfectly sharp interface, indicating a diffuse electron (scattering length) density profile. Modelling of the XRR data using three different fitting routines produced consistent interfacial profiles that suggest the formation of interfacial EtAN clusters. Consistent with this, VSFS reveals that the EtAN surface is predominantly covered by -CH(2)- moieties, with the -NH(3)(+) and -OH groups of the cation buried slightly deeper in the interface. The elemental profiles determined using NICISS also show enrichment of carbon relative to nitrogen and oxygen in the outermost surface layer, which is consistent with the surface cation orientation deduced from VSFS, and with the presence of EtAN aggregates at the liquid surface.
authors.affiliation: Centre for Organic Electronics, The University of Newcastle, Callaghan, NSW 2308, Australia.
authors.forename: Deborah
authors.initials: D
authors.lastname: Wakeham
authors.forename: Petru
authors.initials: P
authors.lastname: Niga
authors.forename: Christiaan
authors.initials: C
authors.lastname: Ridings
authors.forename: Gunther
authors.initials: G
authors.lastname: Andersson
authors.forename: Andrew
authors.initials: A
authors.lastname: Nelson
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Warr
authors.forename: Steven
authors.initials: S
authors.lastname: Baldelli
authors.forename: Mark W
authors.initials: MW
authors.lastname: Rutland
authors.forename: Rob
authors.initials: R
authors.lastname: Atkin
mesh_terms: D000388:Air; D052578:Ionic Liquids / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry; D013499:Surface Properties
chemical_list: D052578:Ionic Liquids; D009566:Nitrates; C006568:ammonium nitrate