A New Weak Field Double Resonance NMR Spectrometer

Akay, Cengiz; Yalçiner, Aytaç

doi:10.1515/zna-1995-2-309

Cited by 17 publications

(7 citation statements)

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“…[19] This home-built spectrometer, which operates with the continuous-wave technique of has a resonance frequency, 61.2 kHz for protons and 40.3 MHz for electrons. The observations in this spectrometer are concerned with pure and double resonance NMR signals that have P 0 and P z signal intensities, respectively.…”

Section: Methodsmentioning

confidence: 99%

The Effect of Sample Age and Neutron Radiation to Dynamic Nuclear Polarization Parameters in Some Asphaltene Suspensions

Ovalıoğlu

2011

Journal of Dispersion Science and Technology

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Nuclear magnetic resonance and the Overhauser effect type dynamic nuclear polarization experiments were performed to study suspensions of asphaltene in the xylene isomers at a low magnetic field of 1.44 mT at room temperature. Intermolecular spin-spin interactions occur between nuclear spins of hydrogen in the solvent medium and the free electron spins in the asphaltene micelles. The samples were prepared in three different asphaltene concentrations at vacuum. The samples were waited for four years and dynamic nuclear polarization parameters were found via dynamic nuclear polarization experiments performed again. Thus, it was investigated the effect of sample age to dynamic nuclear polarization parameters. In addition, the medium concentrations of each sample were exposed to radiation for 48 hours and neutron radiation effects to the dynamic nuclear polarization parameters were investigated. The results are discussed.

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Section: Methodsmentioning

confidence: 99%

The Effect of Sample Age and Neutron Radiation to Dynamic Nuclear Polarization Parameters in Some Asphaltene Suspensions

Ovalıoğlu

2011

Journal of Dispersion Science and Technology

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“…The external magnetic field is swept by a digital sweep generator. [19] The spectrometer has also an automatic temperature control system using the liquid nitrogen vapor or heated air flow. [20] The spectrometer is also described in the previous articles.…”

Section: Methodsmentioning

confidence: 99%

“…[20] The spectrometer is also described in the previous articles. [3,19,21] In the low field DNP investigations, the observations are based on the pure and the double resonance NMR signal intensities (P 0 and P z ). The usual amplitude modulation technique gives the signals as the derivatives of the central bands, first and second side bands.…”

Section: Methodsmentioning

confidence: 99%

Dynamic Nuclear Polarization in Highly Fluorinated Solutions

Ovalıoğlu

Peksöz

Kırımlı

et al. 2010

Journal of Dispersion Science and Technology

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The Overhauser effect type dynamic nuclear polarization experiments were performed to study solutions of the stable free radical a,c-Bisdiphenylene-b-phenyl allyl complex with benzene (1:1) in some highly fluorinated aliphatic and aromatic solvents. In solutions examined in this study, it occurs mainly the Overhauser effect, which normally arises due to both dipolar and scalar interactions between the unpaired electrons of the free radical molecules and fluorine nuclei of solvent molecules. 1-Iodotridecafluorohexane, N-Methyl-bis-trifluoroacetamide, Octafluorotoluene and Hexafluorobenzene were used as the solvents. The experiments were performed at a low field double resonance NMR spectrometer, which operates at 1.53 mT. The NMR enhancements depend on competition between intermolecular magnetic interactions. It was studied to investigate variation of EPR spectra with four different temperatures. It was found as temperature increases, peak points of EPR spectra decreases.

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“…The equipment and technical details of the double resonance spectrometer used in this work have been extensively described in prior publications [4][5][6]. Further * corresponding author; e-mail: hengin@uludag.edu.tr information on the theory and applications of DNP for liquid samples is available in literature [6][7][8][9].…”

Section: Materials and Equipmentmentioning

confidence: 99%

Intermolecular Effects of Fluorocarbons on MC800 Asphaltene and their Characterization

2017

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TurkeyNuclear magnetic resonance and dynamic nuclear polarization experiments were performed to study suspensions of asphaltene in the fluorocarbons at a low magnetic field of 1.53 mT, at room temperature. The asphaltene was extracted from MC800 liquid asphalt, which was of Heavy Iran origin. The elemental composition and the surface morphology of the asphaltene were determined by scanning electron microscopy and energy dispersive X-ray analysis. Intermolecular spin-spin interactions occur between nuclear spins of hydrogen in the solvent medium and the free electron spins in the asphaltene micelles. The electron paramagnetic resonance spectrum of the asphaltene was obtained and the saturation experiments were applied to the samples prepared in vacuum. The main 1 H DNP parameters were listed. Chemical composition and molecular structure of the asphaltene were analyzed. Scanning electron microscope images have shown that asphaltenes are constituted of agglomerated particles and smooth surfaces. Energy dispersive X-ray analysis has shown that the most abundant element is carbon. IntroductionAsphaltenes, which are a part of petroleum, are regarded to be polar species, have larger aromatic structures and are containing alkyl chains, heteroatoms (such as O, S and N) and some metals [1]. Asphaltenes have unpaired electrons, which are observed using the electron spin resonance (ESR) experiments in crude petroleum [2].Dynamic nuclear polarization (DNP) utilizes the liquid state interaction between nuclei and unpaired electron spins to generate an increased nuclear polarization upon the saturation of ESR transitions of the radicals. The maximum DNP enhancement of the NMR signal is given by the electron-to-nuclear gyromagnetic ratios γ e /γ n . This ratio for proton spin is 660. In this study, the nuclear spins are the proton spins, which are the 1 H nuclei of the solvent medium and the electron spins belong to the free electrons on the asphaltene micelles. The unpaired electrons were delocalized on the incomplete carbon bonds of the condensed aromatic structure of the asphaltene particles [3]. By DNP method we have revealed dipolar interaction between hydrogen atoms of the solvent and unpaired electrons of colloidal asphaltene. Electron spin saturation and DNP enhancements have been obtained and DNP parameters determined in low magnetic field. Chemical composition and morphology of MC800 asphaltene were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis.

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A New Weak Field Double Resonance NMR Spectrometer

Cited by 17 publications

References 0 publications

The Effect of Sample Age and Neutron Radiation to Dynamic Nuclear Polarization Parameters in Some Asphaltene Suspensions

The Effect of Sample Age and Neutron Radiation to Dynamic Nuclear Polarization Parameters in Some Asphaltene Suspensions

Dynamic Nuclear Polarization in Highly Fluorinated Solutions

Intermolecular Effects of Fluorocarbons on MC800 Asphaltene and their Characterization

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