Measuring concentration depth profiles at liquid surfaces: Comparing angle resolved X-ray photoelectron spectroscopy and neutral impact collision scattering spectroscopy

Wang, Chuangye; Andersson, Gunther G.

doi:10.1016/j.susc.2011.01.035

Cited by 21 publications

(22 citation statements)

References 30 publications

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“…As a result, the surfactant surface/bulk concentration gradients obtained were much less pronounced than those given by the classical equation, thus by partitioning models. Such small gradients have been confirmed experimentally by ion scattering32 and angle resolved X-ray photoelectron3334 spectroscopies, which have observed surface/bulk concentration ratios between 2 and 8. These ratios will be compared with those predicted by partitioning models in the Discussion section.…”

Section: Resultsmentioning

confidence: 64%

“…For a particle with a radius of 300 nm and a surface layer of 3 nm, for instance, a number ratio of 11 corresponds to a concentration ratio of 352. The concentration ratios of 2–8 measured experimentally for surfactants 32 33 34 thus indicate that those calculated by the partitioning models are overestimated by a factor 100 in average (44–176), and the corresponding values of n b are underestimated by the same factor. The Raoult’s term should thus be also underestimated by about 100, as it is proportional to n b , which should substantially underestimate the cloud-forming efficiency of surfactants.…”

Section: Discussionmentioning

confidence: 84%

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The dynamic surface tension of atmospheric aerosol surfactants reveals new aspects of cloud activation

2014

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The activation of aerosol particles into cloud droplets in the Earth’s atmosphere is both a key process for the climate budget and a main source of uncertainty. Its investigation is facing major experimental challenges, as no technique can measure the main driving parameters, the Raoult’s term and surface tension, σ, for sub-micron atmospheric particles. In addition, the surfactant fraction of atmospheric aerosols could not be isolated until recently. Here we present the first dynamic investigation of the total surfactant fraction of atmospheric aerosols, evidencing adsorption barriers that limit their gradient (partitioning) in particles and should enhance their cloud-forming efficiency compared with current models. The results also show that the equilibration time of surfactants in sub-micron atmospheric particles should be beyond the detection of most on-line instruments. Such instrumental and theoretical shortcomings would be consistent with atmospheric and laboratory observations and could have limited the understanding of cloud activation until now.

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Section: Resultsmentioning

confidence: 64%

Section: Discussionmentioning

confidence: 84%

The dynamic surface tension of atmospheric aerosol surfactants reveals new aspects of cloud activation

2014

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“…ARXPS can be used to determine the layer thicknesses. 37 Eschen et al have described the procedure in detail. 38 The concentration depth profile of aTiO 2 -Cr 2 O 3 is shown in Figure S9.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Investigation of the Diffusion of Cr₂O₃ into Different Phases of TiO₂ upon Annealing

Alotabi

Gibson

Metha

et al. 2021

ACS Appl. Energy Mater.

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Chromium oxide (Cr 2 O 3 ) can be used as a protective layer for photocatalysts to improve photocatalytic water splitting activity and is commonly photodeposited. However, it is not known how the conditions of the Cr 2 O 3 formation affect the formation of the protective layer and potential diffusion into the substrate onto which Cr 2 O 3 has been deposited. We have investigated the stability of Cr 2 O 3 photodeposited onto the surface of different crystal phases of TiO 2 with subsequent annealing at a range of temperatures up to 600 °C. X-ray photoelectron spectroscopy and synchrotron near-edge X-ray absorption fine structure were used to analyze the chemical composition of the sample, neutral impact collision ion scattering spectroscopy was used to study the concentration depth profile of the elements in the sample, and atomic force microscopy was used to investigate the morphology of the surface. Under annealing conditions, the Cr 2 O 3 layer diffuses into the amorphous and anatase phases of TiO 2 but remains at the surface of the rutile phase. This finding is attributed to differences in surface energy with Cr 2 O 3 being higher in surface energy than the amorphous and anatase phases of TiO 2 but lower in surface energy than the rutile phase of TiO 2 . Reduction of Cr 2 O 3 to Cr metal was observed after annealing with no observation of the formation of higher oxidized forms of chromium oxide like CrO 2 and CrO 3 . These findings are of general interest to researchers utilizing a protective overlayer to augment photocatalytic water splitting.

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“…In (a) the concentration depth profiles of Bu 4 P + measured with NICISS and ARXPS and in (b) the concentration depth profiles of Br − are compared . For comparison the Bu 4 N + concentration depth profile measured by Eschen et al.…”

Section: Concentration Depth Profilesmentioning

confidence: 99%

Thermodynamics and structure of liquid surfaces investigated directly with surface analytical tools**

Andersson

Morgner²

2017

Annalen der Physik

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Measuring directly the composition, the distribution of constituents as function of the depth and the orientation of molecules at liquid surfaces is essential for determining physicochemical properties of liquid surfaces. While the experimental tools that have been developed for analyzing solid surfaces can in principal be applied to liquid surfaces, it turned out that they had to be adjusted to the particular challenges imposed by liquid samples, e.g. by the unavoidable vapor pressure and by the mobility of the constituting atoms/molecules. In the present work it is shown, how electron spectroscopy and ion scattering spectroscopy have been used for analyzing liquid surfaces. The emphasis of this review is on using the structural information gained for determining the physicochemical properties of liquid surfaces.

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Measuring concentration depth profiles at liquid surfaces: Comparing angle resolved X-ray photoelectron spectroscopy and neutral impact collision scattering spectroscopy

Cited by 21 publications

References 30 publications

The dynamic surface tension of atmospheric aerosol surfactants reveals new aspects of cloud activation

The dynamic surface tension of atmospheric aerosol surfactants reveals new aspects of cloud activation

Investigation of the Diffusion of Cr₂O₃ into Different Phases of TiO₂ upon Annealing

Thermodynamics and structure of liquid surfaces investigated directly with surface analytical tools**

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Measuring concentration depth profiles at liquid surfaces: Comparing angle resolved X-ray photoelectron spectroscopy and neutral impact collision scattering spectroscopy

Cited by 21 publications

References 30 publications

The dynamic surface tension of atmospheric aerosol surfactants reveals new aspects of cloud activation

The dynamic surface tension of atmospheric aerosol surfactants reveals new aspects of cloud activation

Investigation of the Diffusion of Cr2O3 into Different Phases of TiO2 upon Annealing

Thermodynamics and structure of liquid surfaces investigated directly with surface analytical tools**

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Product

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Investigation of the Diffusion of Cr₂O₃ into Different Phases of TiO₂ upon Annealing