Imaging of Chemical Kinetics at the Water–Water Interface in a Free-Flowing Liquid Flat-Jet

Schewe, H. Christian; Credidio, Bruno; Ghrist, Aaron; Malerz, Sebastian; Ozga, Christian; Knie, André; Haak, Henrik; Meijer, Gerard; Winter, Bernd; Osterwalder, Andreas

doi:10.1021/jacs.2c01232

Cited by 16 publications

(14 citation statements)

References 44 publications

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“…We note that it is also possible to use pairs of miscible liquids with this nozzle geometry. Due to the small length scales involved in the liquid sheets, this configuration provides for fast diffusive mixing between two liquids or solutions and allows for the monitoring of, e.g., fast chemical kinetics. , A full description of this capability will be discussed in a future publication. Similarly, interfacial kinetics could be examined across the immiscible liquid–liquid interfaces, as has been previously examined for the liquid–vapor interfaces in liquid microjets. , …”

Section: Resultsmentioning

confidence: 99%

Liquid Heterostructures: Generation of Liquid–Liquid Interfaces in Free-Flowing Liquid Sheets

et al. 2022

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Chemical reactions and biological processes are frequently governed by the structure and dynamics of the interface between two liquid phases, but these interfaces are often difficult to study due to the relative abundance of the bulk liquids. Here, we demonstrate a method for generating multilayer thin film stacks of liquids, which we call liquid heterostructures. These free-flowing layered liquid sheets are produced with a microfluidic nozzle that impinges two converging jets of one liquid onto opposite sides of a third jet of another liquid. The resulting sheet consists of two layers of the first liquid enveloping an inner layer of the second liquid. Infrared microscopy, white light reflectivity, and imaging ellipsometry measurements demonstrate that the buried liquid layer has a tunable thickness and displays well-defined liquid–liquid interfaces and that this inner layer can be only tens of nanometers thick. The demonstrated multilayer liquid sheets minimize the amount of bulk liquid relative to their buried interfaces, which makes them ideal targets for spectroscopy and scattering experiments.

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Section: Resultsmentioning

confidence: 99%

Liquid Heterostructures: Generation of Liquid–Liquid Interfaces in Free-Flowing Liquid Sheets

et al. 2022

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“…19 Fascinating alternative approaches include tiny holes drilled in a microfluidic channel 20 and flat jets 21 for gas−dodecane scattering 22 and liquid−liquid reactions (at atmospheric pressure). 23 Gas−microjet scattering methods may be used to interrogate interfacial interactions and reactions, often building on studies of gas−solid surface dynamics 24,25 and gas−liquid kinetics. 26,27 Microjet experiments span measurements of reaction probabilities and solvation times, collisional energy transfer involving translational and internal motions, 28,29 and the observation of intermediates and final products escaping into the gas phase after interfacial and bulk phase reactions.…”

Section: ■ Introductionmentioning

confidence: 99%

“…These cylindrical jets can also be used to investigate liquid ammonia and organic liquids, , including kerosene fuels . Fascinating alternative approaches include tiny holes drilled in a microfluidic channel and flat jets for gas–dodecane scattering and liquid–liquid reactions (at atmospheric pressure) …”

Section: Introductionmentioning

confidence: 99%

Exploring Gas–Liquid Reactions with Microjets: Lessons We Are Learning

Gao

Nathanson

2022

Acc. Chem. Res.

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Conspectus Liquid water is all around us: at the beach, in a cloud, from a faucet, inside a spray tower, covering our lungs. It is fascinating to imagine what happens to a reactive gas molecule as it approaches the surface of water in these examples. Some incoming molecules may first be deflected away after colliding with an evaporating water molecule. Those that do strike surface H2O or other surface species may bounce directly off or become momentarily trapped through hydrogen bonding or other attractive forces. The adsorbed gas molecule can then desorb immediately or instead dissolve, passing through the interfacial region and into the bulk, perhaps diffusing back to the surface and evaporating before reacting. Alternatively, it may react with solute or water molecules in the interfacial or bulk regions, and a reaction intermediate or the final product may then desorb into the gas phase. Building a “blow by blow” picture of these pathways is challenging for vacuum-based techniques because of the high vapor pressure of water. In particular, collisions within the thick vapor cloud created by evaporating molecules just above the surface scramble the trajectories and internal states of the gaseous target molecules, hindering construction of gas–liquid reaction mechanisms at the atomic scale that we strive to map out. The introduction of the microjet in 1988 by Faubel, Schlemmer, and Toennies opened up entirely new possibilities. Their inspired solution seems so simple: narrow the end of a glass tube to a diameter smaller than the mean free path of the vapor molecules and then push the liquid through the tube at speeds of a car on a highway. The narrow liquid stream creates a sparse vapor cloud, with water molecules spaced far enough apart that they and the reactant gases interact, at most, weakly. Experimentalists, however, confront a host of challenges: nozzle clogging, unstable jetting, searching for vacuum-compatible solutions, measuring low signal levels, and teasing out artifacts because the slender jet is the smallest surface in the vacuum chamber. In this Account, we describe lessons that we are learning as we explore gases (DCl, (HCOOH)2, N2O5) reacting with water molecules and solute ions in the near-interfacial region of these fast-flowing aqueous microjets.

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“…Figure A sketches the essential parts of an LJ-PES experiment. The LJ or liquid sheet/flatjet , is injected into vacuum via an appropriate nozzle, held and fine-adjusted using a μm-precision XYZ-manipulator within an electrically and magnetically shielded vacuum chamber. The laminar-phase of the jet is photoionized, and the PEs are detected by an electron spectrometer, with its entrance aperture positioned a few hundred micrometers from the LJ surface.…”

Section: Introductionmentioning

confidence: 99%

Absolute Electronic Energetics and Quantitative Work Functions of Liquids from Photoelectron Spectroscopy

2023

Self Cite

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Conspectus Liquid-jet photoelectron spectroscopy (LJ-PES) enabled a breakthrough in the experimental study of the electronic structure of liquid water, aqueous solutions, and volatile liquids more generally. The novelty of this technique, dating back over 25 years, lies in stabilizing a continuous, micron-diameter LJ in a vacuum environment to enable PES studies. A key quantity in PES is the most probable energy associated with vertical promotion of an electron into vacuum: the vertical ionization energy, VIE, for neutrals and cations, or vertical detachment energy, VDE, for anions. These quantities can be used to identify species, their chemical states and bonding environments, and their structural properties in solution. The ability to accurately measure VIEs and VDEs is correspondingly crucial. An associated principal challenge is the determination of these quantities with respect to well-defined energy references. Only with recently developed methods are such measurements routinely and generally viable for liquids. Practically, these methods involve the application of condensed-matter concepts to the acquisition of photoelectron (PE) spectra from liquid samples, rather than solely relying on molecular-physics treatments that have been commonly implemented since the first LJ-PES experiments. This includes explicit consideration of the traversal of electrons to and through the liquid’s surface, prior to free-electron detection. Our approach to measuring VIEs and VDEs with respect to the liquid vacuum level specifically involves detecting the lowest-energy electrons emitted from the sample, which have barely enough energy to surmount the surface potential and accumulate in the low-energy tail of the liquid-phase spectrum. By applying a sufficient bias potential to the liquid sample, this low-energy spectral tail can generally be exposed, with its sharp, low-energy cutoff revealing the genuine kinetic-energy-zero in a measured spectrum, independent of any perturbing intrinsic or extrinsic potentials in the experiment. Together with a precisely known ionizing photon energy, this feature enables the straightforward determination of VIEs or VDEs, with respect to the liquid-phase vacuum level, from any PE feature of interest. Furthermore, by additionally determining solution-phase VIEs and VDEs with respect to the common equilibrated energy level in condensed matter, the Fermi level—the generally implemented reference energy in solid-state PES—solution work functions, eΦ, and liquid-vacuum surface dipole effects can be quantified. With LJs, the Fermi level can only be properly accessed by controlling unwanted surface charging and all other extrinsic potentials, which lead to energy shifts of all PE features and preclude access to accurate electronic energetics. More specifically, conditions must be engineered to minimize all undesirable potentials, while maintaining the equilibrated, intrinsic (contact) potential difference between the sample and apparatus. The establishment of these liquid-phase,...

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Imaging of Chemical Kinetics at the Water–Water Interface in a Free-Flowing Liquid Flat-Jet

Cited by 16 publications

References 44 publications

Liquid Heterostructures: Generation of Liquid–Liquid Interfaces in Free-Flowing Liquid Sheets

Liquid Heterostructures: Generation of Liquid–Liquid Interfaces in Free-Flowing Liquid Sheets

Exploring Gas–Liquid Reactions with Microjets: Lessons We Are Learning

Absolute Electronic Energetics and Quantitative Work Functions of Liquids from Photoelectron Spectroscopy

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