Ortho-para hydrogen conversion characteristics of amorphous and mesoporous Cr 2 O 3 powders at a temperature of 77 K

Kim, Jung Hyun; Karng, Sarng Woo; Oh, In‐Hwan; Nah, In Wook

doi:10.1016/j.ijhydene.2015.08.105

Cited by 20 publications

(13 citation statements)

References 33 publications

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“…[16, 18] The spin-conversion catalyst is typically made of iron oxides [19] or other metal oxides [20] and is stored in a metal tube, [21] aluminum cylinder [16b, 22] or a glass-trap. The spin conversion catalyst should be completely immersed in the cooling liquid/jacket to avoid back conversion at room temperature.…”

Section: How It Work: Principles Of Parahydrogen-based Polarizationmentioning

confidence: 99%

“…[16] rtH 2 is converted into about 51 %pH 2 by flowing the gas through as pin-conversion catalyst at 77 K. [17] Alternatively, rtH 2 can be passed through ac atalyst-containing chamber cryogenically chilled to about 22 Kt oa chieve > 95 % pH 2 . [16,18] Thes pin-conversion catalyst is typically made of iron oxides [19] or other metal oxides [20] and is stored in ametal tube, [21] aluminum cylinder, [16b, 22] or ag lass-trap.T he spinconversion catalyst should be completely immersed in the cooling liquid/jacket to avoid back conversion at room temperature.N ote that ah igh pH 2 enrichment is favorable because the level of hyperpolarization directly depends on it.…”

Section: Production Of Parahydrogenmentioning

confidence: 99%

“…Alternatively, rtH 2 can be passed through a catalyst‐containing chamber cryogenically chilled to about 22 K to achieve >95 % pH 2 . The spin‐conversion catalyst is typically made of iron oxides or other metal oxides and is stored in a metal tube, aluminum cylinder, or a glass‐trap. The spin‐conversion catalyst should be completely immersed in the cooling liquid/jacket to avoid back conversion at room temperature.…”

Section: How It Work: Principles Of Parahydrogen‐based Polarizationmentioning

confidence: 99%

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Parahydrogen‐Based Hyperpolarization for Biomedicine

et al. 2018

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Magnetic resonance (MR) is one of the most versatile and useful physical effects used for human imaging, chemical analysis, and the elucidation of molecular structures. However, its full potential is rarely used, because only a small fraction of the nuclear spin ensemble is polarized, that is, aligned with the applied static magnetic field. Hyperpolarization methods seek other means to increase the polarization and thus the MR signal. A unique source of pure spin order is the entangled singlet spin state of dihydrogen, parahydrogen (pH ), which is inherently stable and long-lived. When brought into contact with another molecule, this "spin order on demand" allows the MR signal to be enhanced by several orders of magnitude. Considerable progress has been made in the past decade in the area of pH -based hyperpolarization techniques for biomedical applications. It is the goal of this Review to provide a selective overview of these developments, covering the areas of spin physics, catalysis, instrumentation, preparation of the contrast agents, and applications.

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Section: How It Work: Principles Of Parahydrogen-based Polarizationmentioning

confidence: 99%

Section: Production Of Parahydrogenmentioning

confidence: 99%

Section: How It Work: Principles Of Parahydrogen‐based Polarizationmentioning

confidence: 99%

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Parahydrogen‐Based Hyperpolarization for Biomedicine

et al. 2018

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“…The fact that these opto-electronic measurements were registered on non-magnetic solids (a few tenths of experiments) and very few on magnetic ones [53][54][55] proceeds from the conversion times magnitudes. Efficient magnetic catalysts, even commercial ones, affect quickly the hydrogen mixture's concentration, in times shorter than the minute.…”

Section: The New Conversion Measures Of the XXI Th Centurymentioning

confidence: 99%

Hydrogen Conversion in Nanocages

Ilisca

2021

Hydrogen

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Hydrogen molecules exist in the form of two distinct isomers that can be interconverted by physical catalysis. These ortho and para forms have different thermodynamical properties. Over the last century, the catalysts developed to convert hydrogen from one form to another, in laboratories and industries, were magnetic and the interpretations relied on magnetic dipolar interactions. The variety concentration of a sample and the conversion rates induced by a catalytic action were mostly measured by thermal methods related to the diffusion of the o-p reaction heat. At the turning of the new century, the nature of the studied catalysts and the type of measures and motivations completely changed. Catalysts investigated now are non-magnetic and new spectroscopic measurements have been developed. After a fast survey of the past studies, the review details the spectroscopic methods, emphasizing their originalities, performances and refinements: how Infra-Red measurements characterize the catalytic sites and follow the conversion in real-time, Ultra-Violet irradiations explore the electronic nature of the reaction and hyper-frequencies driving the nuclear spins. The new catalysts, metallic or insulating, are detailed to display the operating electronic structure. New electromagnetic mechanisms, involving energy and momenta transfers, are discovered providing a classification frame for the newly observed reactions.

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“…B. durch einen Helium‐Kryostaten auf ≈22 K gekühlt werden, um einen para‐Anteil von mehr als 95 % zu erhalten . Der Katalysator für die ortho‐para‐Umwandlung besteht typischerweise aus granularem Eisenoxid oder einem anderen Metalloxid in einem Metallröhrchen, Aluminiumzylinder oder Glasgefäß. Der Katalysator sollte sich nur in der gekühlten Kammer befinden, um eine Rückumwandlung bei höheren Temperaturen zu vermeiden.…”

Section: Wie Es Funktioniert: Prinzipien Der Parawasserstoff‐basierteunclassified

Parawasserstoff‐basierte Hyperpolarisierung für die Biomedizin

et al. 2018

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Die Magnetresonanz (MR) von Kernspins ist einer der nützlichsten physikalischen Effekte für die humane Bildgebung, ebenso wie für die Aufklärung von molekularen Strukturen und die chemische Analyse. Das volle Potential der MR kann jedoch kaum genutzt werden, da nur ein geringer Bruchteil aller Kernspins polarisiert, sprich in einem äußeren magnetischen Feld ausgerichtet werden. Hyperpolarisierungsmethoden versuchen, die Polarisierung und damit das MR‐Signal auf anderem Wege zu erhöhen. Eine einzigartige Quelle reiner Spinordnung ist das langlebige, verschränkte Kernspin‐Singulett‐Isomer des Wasserstoffmoleküls, genannt Parawasserstoff (pH2). Mithilfe dieser “Spinordnung auf Abruf” kann das MR‐Signal um mehrere Größenordnungen verstärkt werden, wenn pH2 in Kontakt mit einem anderen Molekül gebracht wird. In Bezug auf eine biomedizinische Anwendung von pH2‐hyperpolarisierten Kontrastmitteln haben in den letzten zehn Jahren beeindruckende Fortschritte stattgefunden. Das Ziel dieses Aufsatzes ist es, diese Entwicklungen in den Bereichen der Spinphysik, Katalyse, Instrumentierung, Kontrastmittel und Anwendungen gebündelt und verständlich darzustellen.

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Ortho-para hydrogen conversion characteristics of amorphous and mesoporous Cr 2 O 3 powders at a temperature of 77 K

Cited by 20 publications

References 33 publications

Parahydrogen‐Based Hyperpolarization for Biomedicine

Parahydrogen‐Based Hyperpolarization for Biomedicine

Hydrogen Conversion in Nanocages

Parawasserstoff‐basierte Hyperpolarisierung für die Biomedizin

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