Electrokinetic Charging and Evidence for Charge Evaporation in Liquid Microjets of Aqueous Salt Solution

Preissler, Natalie; Buchner, Franziska; Schultz, Thomas; Lübcke, A.

doi:10.1021/jp304773n

Cited by 47 publications

(66 citation statements)

References 23 publications

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“…In line with previous measurements [23][24][25] it was found that charge carriers were needed to measure the photoelectron spectrum of a water sample. The high resistivity (18 M ) of the high performance liquid chromatography (HPLC) grade water used produced a large charging of the sample by the motion over the polyether ether ketone (PEEK) liquid jet tubing and fused silica nozzle.…”

Section: Results and Analysissupporting

confidence: 83%

A simple electron time-of-flight spectrometer for ultrafast vacuum ultraviolet photoelectron spectroscopy of liquid solutions

Arrell

Ojeda

Sabbar

et al. 2014

Review of Scientific Instruments

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Articles you may be interested inWe present a simple electron time of flight spectrometer for time resolved photoelectron spectroscopy of liquid samples using a vacuum ultraviolet (VUV) source produced by high-harmonic generation. The field free spectrometer coupled with the time-preserving monochromator for the VUV at the Artemis facility of the Rutherford Appleton Laboratory achieves an energy resolution of 0.65 eV at 40 eV with a sub 100 fs temporal resolution. A key feature of the design is a differentially pumped drift tube allowing a microliquid jet to be aligned and started at ambient atmosphere while preserving a pressure of 10 −1 mbar at the micro channel plate detector. The pumping requirements for photoelectron (PE) spectroscopy in vacuum are presented, while the instrument performance is demonstrated with PE spectra of salt solutions in water. The capability of the instrument for time resolved measurements is demonstrated by observing the ultrafast (50 fs) vibrational excitation of water leading to temporary proton transfer.

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Section: Results and Analysissupporting

confidence: 83%

A simple electron time-of-flight spectrometer for ultrafast vacuum ultraviolet photoelectron spectroscopy of liquid solutions

Arrell

Ojeda

Sabbar

et al. 2014

Review of Scientific Instruments

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“…Lübcke and co-workers reached a similar conclusion in 2013 [61]. Our choice to add 50-mM electrolyte to the NP dispersions, besides providing a platform for the investigation of specific ion effects, is, therefore, in part chosen to ensure that streaming potentials associated with the operation of the liquid microjet are largely suppressed [22,61]. We include a more detailed discussion, including the calculation of the streaming potential, in Appendix A 6.…”

Section: Discussionmentioning

confidence: 84%

“…Under essentially identical experimental conditions to ours (flow rate and capillary diameter), Kurahashi et al showed streaming potentials of −1.5 V in 5-mM electrolyte (NaCl, NaBr, and NaI) but concluded the addition of at least 30-mM salt rendered the magnitude of this potential insignificant, allowing them to refine the 1b 1 orbital binding energy of liquid water to two decimal places (i.e., AE0.04 eV) [22]. Lübcke and co-workers reached a similar conclusion in 2013 [61]. Our choice to add 50-mM electrolyte to the NP dispersions, besides providing a platform for the investigation of specific ion effects, is, therefore, in part chosen to ensure that streaming potentials associated with the operation of the liquid microjet are largely suppressed [22,61].…”

Section: Discussionmentioning

confidence: 93%

Determination of Surface Potential and Electrical Double-Layer Structure at the Aqueous Electrolyte-Nanoparticle Interface

et al. 2016

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The structure of the electrical double layer has been debated for well over a century, since it mediates colloidal interactions, regulates surface structure, controls reactivity, sets capacitance, and represents the central element of electrochemical supercapacitors. The surface potential of such surfaces generally exceeds the electrokinetic potential, often substantially. Traditionally, a Stern layer of nonspecifically adsorbed ions has been invoked to rationalize the difference between these two potentials; however, the inability to directly measure the surface potential of dispersed systems has rendered quantitative measurements of the Stern layer potential, and other quantities associated with the outer Helmholtz plane, impossible. Here, we use x-ray photoelectron spectroscopy from a liquid microjet to measure the absolute surface potentials of silica nanoparticles dispersed in aqueous electrolytes. We quantitatively determine the impact of specific cations (Li þ , Na þ , K þ , and Cs þ ) in chloride electrolytes on the surface potential, the location of the shear plane, and the capacitance of the Stern layer. We find that the magnitude of the surface potential increases linearly with the hydrated-cation radius. Interpreting our data using the simplest assumptions and most straightforward understanding of Gouy-Chapman-Stern theory reveals a Stern layer whose thickness corresponds to a single layer of water molecules hydrating the silica surface, plus the radius of the hydrated cation. These results subject electrical double-layer theories to direct and falsifiable tests to reveal a physically intuitive and quantitatively verified picture of the Stern layer that is consistent across multiple electrolytes and solution conditions.

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“…To avoid charging of the liquid jet due to photoionization and electrokinetic charging, 29 all solutions contained 25 mM sodium chloride (purity 99 %, Sigma Aldrich).…”

Section: Methodsmentioning

confidence: 99%

Alcohols at the aqueous surface: chain length and isomer effects

Walz

Werner

Ekholm

et al. 2016

Phys. Chem. Chem. Phys.

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Surface-active organic molecules at the liquid-vapor interface are of great importance in atmospheric science. Therefore, we studied the surface behavior of alcohol isomers with different chain lengths (C4-C6) in aqueous solution with surfaceand chemically sensitive X-ray photoelectron spectroscopy (XPS), which reveals information about the surface structure on a molecular level. Gibbs free energies of adsorption and surface concentrations are determined from the XPS results using a standard Langmuir adsorption isotherm model. The free energies of adsorption, ranging from around -15 to -19 kJ/mol (C4-C6), scale linearly with the number of carbon atoms within the alcohols with ΔGAds per -CH2-≈ -2 kJ/mol. While for the linear alcohols, surface concentrations lie around 2.4 x 10 14 molecules/cm 2 at the bulk concentrations where monolayers are formed, the studied branched alcohols show lower surface concentrations of around 1.6 x 10 14 molecules/cm 2 , both of which are in line with the molecular structure and their orientation at the interface. Interestingly, we find that there is a maximum in the surface enrichment factor for linear alcohols at low concentrations, which is not observed for the shorter branched alcohols. This is interpreted in terms of a cooperative effect, which we suggest to be the result of more effective van der Waals interactions between the linear alcohol alkyl chains at the aqueous surface, making it energetically even more favorable to reside at the liquid-vapor interface.

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Electrokinetic Charging and Evidence for Charge Evaporation in Liquid Microjets of Aqueous Salt Solution

Cited by 47 publications

References 23 publications

A simple electron time-of-flight spectrometer for ultrafast vacuum ultraviolet photoelectron spectroscopy of liquid solutions

A simple electron time-of-flight spectrometer for ultrafast vacuum ultraviolet photoelectron spectroscopy of liquid solutions

Determination of Surface Potential and Electrical Double-Layer Structure at the Aqueous Electrolyte-Nanoparticle Interface

Alcohols at the aqueous surface: chain length and isomer effects

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