| 1. |
- Cimatu, Katherine A., et al.
(författare)
-
Chemical Microscopy of Surfaces by Sum Frequency Generation Imaging
- 2009
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society. - 1932-7447 .- 1932-7455. ; 113:38, s. 16575-16588
-
Tidskriftsartikel (refereegranskat)abstract
- Sum frequency generation imaging microscopy has been developed and implemented in different systems from self-assembled monolayer on metal surfaces to reaction of a metal surface upon exposure to a corrosive material (cyanide solution). It also helped the fundamental issues of heterogeneity to be understood by using mapping analysis that considers an acquired spectrum in a chosen region-of-interest to be independent of its neighboring ROIs. The construction of the microscope has been utilized and modified to accommodate the improvement of its spatial resolution, signal-to-noise ratio, and faster accumulation time. The latter aspect is more dependent toward the kind of sample to be analyzed. Finally, the current resolution of this diffraction-limited microscope is similar to 2 mu m and there is still some room for improvement to reach its ultimate resolution of similar to 800 nm. The main and final goal of this study is to provide chemical sensitivity, interfacial specificity, and a two-dimensional image based on the chemical properties of the adsorbed molecules on the surface and also the substrate itself.
|
|
| 2. |
- Hedberg, Jonas, et al.
(författare)
-
Adsorption and Structure of Octadecanethiol on Zinc Surfaces As Probed by SumFrequency Generation Spectroscopy, Imaging, and Electrochemical Techniques
- 2007
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 111:47, s. 17587-17596
-
Tidskriftsartikel (refereegranskat)abstract
- Octadecanethiol (ODT) adsorbed onto zinc has been studied with sum frequency generation (SFG), sum frequency generation imaging microscopy (SFG-IM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrical impedance spectroscopy (EIS) in order to investigate its corrosion protective ability and conformational ordering. SFG shows that ODT forms an ordered adsorbate on both reduced and oxidized zinc within short times after immersion in 1 mM ODT/ethanol solution. The corrosion protection, deduced by EIS, is also improved after immersion in the ODT solution. After longer immersion times, the corrosion protection decreases as well as the conformational order of the adsorbed ODT. Increasing the ODT concentration avoids this degradation with prolonged immersion time. The ODT is seen in the XPS spectra to adsorb to the reduced as well as the oxidized zinc by forming a Zn-S bond for both short and long immersion times. The SFG-IM completes the picture, showing a heterogeneous surface with areas corresponding to ordered ODT as well as disordered or uncovered regions. The density of adsorbed ODT after 24 h immersion time for both reduced and oxidized zinc was deduced from CV and was found to be approximately 6.7 x 10(-9) mol/cm(2).
|
|
| 3. |
- Hedberg, Jonas, et al.
(författare)
-
Evidence for the Molecular Basis of Corrosion of Zinc Induced by Formic Acid using Sum Frequency Generation Spectroscopy
- 2010
-
Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 1:10, s. 1679-1682
-
Tidskriftsartikel (refereegranskat)abstract
- In situ observations of surface hydroxyl groups and the subsequent ligand exchange during initial atmospheric corrosion conditions of Zn are reported. The data have been obtained with sum frequency generation spectroscopy (SFG) during exposure of polycrystalline zinc to humidified or dry nitrogen gas, N-2, to which 100 parts per billion of formic acid, HCOOH, was added. The SFG data provide evidence of surface hydroxyl groups and their gradual replacement by formate species through a ligand exchange, representing the initial step of formate-induced dissolution of zinc. In addition, the aqueous adlayer on the Zn surface is probed, and the occurrence of the free OH vibration confirms a bulk-like water film.
|
|
| 4. |
- Hedberg, Jonas, et al.
(författare)
-
Initial Atmospheric Corrosion of Zn : Influence of Humidity on the Adsorption of Formic Acid Studied by Vibrational Sum Frequency Spectroscopy
- 2009
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113, s. 6169-6173
-
Tidskriftsartikel (refereegranskat)abstract
- The ZnO/Zn surface exposed to formic acid undergoes a partial, reversible dissociation to formate ion, and a protonated surface oxide and is seen to have different hydration states depending on the relative humidity. Under high relative humidity conditions it exists as a formate coordinated to the surface with the oxygen atoms toward the surface and the C-H directed away into the vapor. In a dry environment a formic acid/formate intermediate is formed, although a substantial amount of dissociated species still are present, in both hydrated and nonhydrated form. The results may have implications on the initial atmospheric corrosion of Zn and emphasize that the ZnO/Zn surface is heterogeneous with a range of acid and basic sites for the adsorption of formate and the proton.
|
|
| 5. |
- Hedberg, Jonas, et al.
(författare)
-
Molecular Structural Information of the Atmospheric Corrosion of Zinc Studied by Vibrational Spectroscopy Techniques I. Experimental Approach
- 2010
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:10, s. C357-C362
-
Tidskriftsartikel (refereegranskat)abstract
- As the nature of the interactions taking place on a metal surface during atmospheric corrosion is inherently complex, it imposes demands on the analytical studies that are needed to understand the fundamentals on a molecular level. Corrosion products may spread on the metal surface forming two-and three-dimensional structures. Thus, it is imperative to use different techniques to resolve the different types of growth. In this first part of a series of two papers, a systematic investigation is made to obtain detailed information on the mechanisms of the onset of atmospheric corrosion of zinc exposed to 115 ppb acetic acid in either dry or humidified air. The vibrational spectroscopy techniques used were vibrational sum frequency spectroscopy (VSFS, interface sensitive), infrared reflection absorption spectroscopy (IRAS, near-surface sensitive), and confocal Raman microspectroscopy (CRM, bulk sensitive). The VSFS selectively targeted the two-dimensional structures, IRAS followed the growth of three-dimensional corrosion products, and CRM could provide a laterally resolved chemical map on localized aggregates of zinc hydroxy acetate and ZnO with bulk character. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3479207] All rights reserved.
|
|
| 6. |
- Hedberg, Jonas, et al.
(författare)
-
Molecular Structural Information of the Atmospheric Corrosion of Zinc Studied by Vibrational Spectroscopy Techniques II. Two and Three-Dimensional Growth of Reaction Products Induced by Formic and Acetic Acid
- 2010
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:10, s. C363-C373
-
Tidskriftsartikel (refereegranskat)abstract
- In an effort to obtain a more molecular view of atmospheric corrosion, we present experimental data from three complementary acting vibrational spectroscopy techniques that have been used in parallel exposures to follow the initial atmospheric corrosion of zinc during exposure in dry or humid air to which formic acid or acetic acid was added, with the primary aim to simulate indoor exposure conditions. The techniques used were vibrational sum frequency spectroscopy (interface sensitive), IR reflection absorption spectroscopy (near-surface sensitive), and confocal Raman microspectroscopy (bulk sensitive with submicrometer surface lateral resolution). The growth of two-dimensional interface species of zinc formate or zinc acetate could be monitored in situ and distinguished from three-dimensional growth of ZnO and zinc hydroxy formate or acetate. These interface species are believed to act as precursors of the dissolution of aqueous zinc carboxylate species that subsequently deposit at the surface and result in local growth of crystalline or amorphous ZnO and local zinc hydroxy carboxylate. Differences in the growth of corrosion products induced by acetic or formic acid were mainly attributed to differences in pH of the aqueous adlayer and in different deposition velocities of the acids into the aqueous adlayer. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3479255] All rights reserved.
|
|
| 7. |
- Hosseinpour, Saman, 1981-, et al.
(författare)
-
Initial Oxidation of Alkanethiol-Covered Copper Studied by Vibrational Sum Frequency Spectroscopy
- 2011
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:48, s. 23871-23879
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation of octadecanethiol (ODT, CH3-(CH2)17SH)-covered copper in dry air has been studied by in situ vibrational sum frequency spectroscopy (VSFS), infrared reflection absorption spectroscopy (IRAS), and cathodic reduction (CR). During the first 10 h of exposure, the VSF spectral line shape in the CH stretching region changed significantly, with resonances observed as dips being transformed into peaks. This was attributed to a phase change in the nonresonant sum frequency signal due to the formation of a thin layer of copper(I) oxide beneath the ODT. Complementary cathodic reduction and infrared reflection/absorption spectroscopy studies yielded a thickness of the oxide layer of <2 nm after 19 h exposure. An orientation analysis on the adsorbed molecules by VSFS indicated a decreased tilt angle of the terminating methyl groups with respect to the surface normal during the formation of the oxide layer.
|
|
| 8. |
|
|
| 9. |
- Wakeham, Deborah, et al.
(författare)
-
Surface structure of a "non-amphiphilic" protic ionic liquid
- 2012
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 14:15, s. 5106-5114
-
Tidskriftsartikel (refereegranskat)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 -CH2- moieties, with the -NH3+ 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.
|
|
