• Title/Summary/Keyword: $^1H$ nuclear magnetic resonance

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Thermodynamic and Physical Properties of (NH4)2MnCl4·2H2O by Nuclear Magnetic Resonance Relaxation Times

  • Kim, Yoo Young
    • Journal of the Korean Magnetic Resonance Society
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    • v.23 no.2
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    • pp.40-45
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    • 2019
  • The phase transition temperatures and thermodynamic properties of $(NH_4)_2MnCl_4{\cdot}2H_2O$ grown by the slow evaporation method were studied using differential scanning calorimetry and thermogravimetric analysis. A structural phase transition occurred at temperature $T_{C1}$ (=264 K), whereas the changes at $T_{C2}$ (=460 K) and $T_{C3}$ (=475 K) seemed to be chemical changes caused by thermal decomposition. In addition, the chemical shift and the spin-lattice relaxation time $T_{1{\rho}}$ were investigated using $^1H$ magic-angle spinning nuclear magnetic resonance (MAS NMR), in order to understand the role of $NH_4{^+}$ and $H_2O$. The rise in $T_{1{\rho}}$ with temperature was related to variations in the symmetry of the surrounding $H_2O$ and $NH_4{^+}$.

Nuclear Magnetic Resonance of a Layered Organic-Inorganic Hybrid System (C8H17NH3)2SnCl6

  • Lee, Kyu Won;Lee, Cheol Eui
    • Journal of Magnetics
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    • v.9 no.1
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    • pp.1-4
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    • 2004
  • Three successive phase transitions in bis-n-octhylammonium hexachlorostannate, $(n-C_8H_{17}NH_3)_2SnCl_6$, were studied by means of the ^1H nuclear magnetic resonance linewidth and spin-lattice relaxation measurements. Unlike the compounds with longer hydrocarbon chains, the order-disorder and conformational nature were found to coexist in the phase transitions.

Solid State Dynamic Nuclear Polarization of 1H Nuclear Spins at 0.3 T and 4.2 K

  • Shim, Jeong Hyun
    • Journal of the Korean Magnetic Resonance Society
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    • v.21 no.4
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    • pp.114-118
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    • 2017
  • Here, I report solid state Dynamic Nuclear Polarization (DNP) of $^1H$ nuclear spins at 0.3 T and 4.2 K. The DNP polarizer was developed based on a commercial X-band Electron Spin Resonance (ESR) modified for DNP, in combination with a NMR console and a liquid-Helium cryostat. By detuning magnetic field, DNP spectrum was measured to find the optimal condition. At +3 mT detuned from on-resonance field, $^1H$ NMR signal of 60:40 glycerol/water frozen solution doped with 20 mM perdeuterated-Tempone was amplified 43 times. The $^1H$ spin polarization obtained at 4.2 K is over 3100 times higher than that at 300 K. The width of the DNP spectrum, which is five times broader than ESR spectrum, is inconsistent with solid effect or thermal mixing, and presumably suggests a different DNP mechanism.

Ferroelectric-Paraelectric Phase Transition of CsH2PO4 studied by Static NMR and MAS NMR

  • Lim, Ae Ran;Lee, Kwang-Sei
    • Journal of the Korean Magnetic Resonance Society
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    • v.19 no.1
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    • pp.29-35
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    • 2015
  • The microscopic dynamics of $CsH_2PO_4$, with two distinct hydrogen bond lengths, are studied by static nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR. The proton dynamics of the two crystallographically inequivalent hydrogen sites were discussed in terms of the $^1H$ NMR and $^1H$ MAS NMR spectra. Although the hydrogen bonds have two inequivalent sites, H(1) and H(2), distinct proton dynamics for the two sites were not found. Further, the $^{133}Cs$ spectrum is more or less continuous near $T_{C1}$ (=153 K). Finally, the phase transition mechanism of $T_{C1}$ in $CsH_2PO_4$ is related to the ordering of protons.

Thermodynamic properties and structural geometry of KMgCl3·6H2O single crystals

  • Yoon, Hyo In;Lim, Ae Ran
    • Journal of the Korean Magnetic Resonance Society
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    • v.19 no.3
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    • pp.119-123
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    • 2015
  • The thermodynamic properties and structural geometry of $KMgCl_3{\cdot}6H_2O$ were investigated using thermogravimetric analysis, differential scanning calorimetry, and nuclear magnetic resonance. The initial mass loss occurs around 351 K ($=T_d$), which is interpreted as the onset of partial thermal decomposition. Phase transition temperatures were found at 435 K ($=T_{C1}$) and 481 K ($=T_{C2}$). The temperature dependences of the spin-lattice relaxation time $T_1$ for the $^1H$ nucleus changes abruptly near $T_{C1}$. These changes are associated with changes in the geometry of the arrangement of octahedral water molecules.

Use of Nuclear Magnetic Resonance Spectroscopy in Analysis of Fennel Essential Oil

  • AbouZid, Sameh
    • Natural Product Sciences
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    • v.22 no.1
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    • pp.30-34
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    • 2016
  • A simple and rapid method based on proton nuclear magnetic resonance spectroscopy was developed for determination of trans-anethole content in fennel essential oil. Spectra of pure trans-anethole, of the pure essential oil of fennel, and of the pure oil of fennel with thymol internal standard were recorded. The signal of $H-1^/$ was used for quantification of trans-anethole. This proton signal is well separated in the proton magnetic resonance spectrum of the compound. No reference compound is needed and cheap internal standard was used. The results obtained from spectroscopic analysis were compared with those obtained by gas chromatography. Additionally, the developed method was used for determination of the type of vegetable oil used as a carrier in commercial products, which cannot be quantified as such by gas chromatography. This study demonstrates the application of proton nuclear magnetic resonance spectroscopy as a quality control method for estimation of essential oil components.

Study of molecular motion by 1H NMR relaxation in ferroelectric LiH3(SeO3)2, Li2SO4·H2O, and LiN2H5SO4 single crystals

  • Park, Sung Soo
    • Journal of the Korean Magnetic Resonance Society
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    • v.20 no.1
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    • pp.1-6
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    • 2016
  • The proton NMR line widths and spin-lattice relaxation rates, $T_1^{-1}$, of ferroelectric $LiH_3(SeO_3)_2$, $Li_2SO_4{\cdot}H_2O$, and $LiN_2H_5SO_4$ single crystals were measured as a function of temperature. The line width measurements reveal rigid lattice behavior of all the crystals at low temperatures and line narrowing due to molecular motion at higher temperatures. The temperature dependences of the proton $T_1^{-1}$ for these crystals exhibit maxima, which are attributed to the effects of molecular motion by the Bloembergen - Purcell - Pound theory. The activation energies for the molecular motions of $^1H$ in these crystals were obtained. From these analysis, $^1H$ in $LiH_3(SeO_3)_2$ undergoes molecular motion more easily than $^1H$ in $LiN_2H_5SO_4$ and $Li_2SO_4{\cdot}H_2O$ crystals.

Constructing Overhauser Dynamic Nuclear Polarization-Nuclear Magnetic Resonance System Using Benchtop Electron Paramagnetic Resonance Spectrometer

  • Saun, Seung-Bo;Kim, JiWon;Han, Oc Hee
    • Journal of the Korean Magnetic Resonance Society
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    • v.22 no.2
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    • pp.34-39
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    • 2018
  • The Nuclear Magnetic Resonance (NMR) technique using Dynamic Nuclear Polarization (DNP) procedures is one of the promising techniques that enable overcoming low sensitivity problems in NMR spectroscopy. We constructed an ODNP-NMR system using a commercial benchtop EPR spectrometer. The $^1H$ NMR peak area of water in aqueous solutions of 4-hydroxy-TEMPO was enhanced more than 95 times in the ODNP-NMR experiments. Our signal enhancement results were about 55% of the previously reported result. This could be due to non-uniform microwave power over a sample and unwanted sample heating by microwave. However, this portable ODNP-NMR spectrometer will be eventually useful for site-specific detection with nano-scale spatial resolutions and molecular dynamics studies with significantly improved signal sensitivity.

Study on nuclear magnetic resonance of superionic conductor NH4HSeO4 in rotating frame

  • Choi, Jae Hun;Lim, Ae Ran
    • Journal of the Korean Magnetic Resonance Society
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    • v.18 no.1
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    • pp.41-46
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    • 2014
  • In order to obtain information on the structural geometry of $NH_4HSeO_4$ near the phase transition temperature, the spectrum and spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for the ammonium and hydrogen-bond protons were investigated through $^1H$ MAS NMR. $T_{1{\rho}}$ for the hydrogen-bond protons abruptly decreased at high temperature and it is associated with the change in the structural geometry in $O-H{\cdots}O$ bonds. This mobility of the hydrogen-bond protons may be the main reason for the high conductivity.

133Cs Nuclear Magnetic Resonance Relaxation Study of the Phase Transition of Cs2MnCl4·2H2O Single Crystals

  • Heo, Cheol;Lim, Ae-Ran
    • Journal of the Korean Magnetic Resonance Society
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    • v.14 no.2
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    • pp.76-87
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    • 2010
  • The structural phase transition of $Cs_2MnCl_4{\cdot}2H_2O$ single crystals was investigated by determining the $^{133}Cs$ spin-lattice relaxation time $T_1$. The number of resonance lines in the $^{133}Cs$ spectrum changes from seven to one near 375 K, which means that above 375 K the Cs sites are symmetric. Further, the $T_1$ of the $^{133}Cs$ nucleus undergoes a significant change near 375 K, which coincides with the change in the splitting of the $^{133}Cs$ resonance lines. The change in $T_1$ near $T_C$ is related to the loss of $H_2O$, and means that the forms of the octahedra of water molecules surrounding $Cs^+$ are disrupted.