• Journal of Korean Ophthalmic Optics Society
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• v.2 no.1
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• pp.17-24
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• 1997

The Voight function which results from the convolution of the Gauss and Lorentz function is applied the MAS-NMR simulation of mixed alkali glasses and the glasses doped transition metal oxides. It is well known that the convolution of the Gauss and Lorentz function cannot be integrated in closed form for arbitrary values. So we make the new computer simulation program from which the Voight lineshape is obtained. The results are accorded well with the MAS-NMR spectra and we can find out the very small change of MAS-NMR lineshape.

• Journal of the Korean Magnetic Resonance Society
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• v.19 no.1
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• pp.18-22
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• 2015

The structural geometry of $[N(CH_3)_4]_2CdCl_4$ in a hexagonal phase is studied by $^1H$ MAS NMR, $^{13}C$ CP/MAS NMR, and $^{14}N$ NMR. The changes in the chemical shifts for $^{13}C$ and $^{14}N$ in the hexagonal phase are explained by the structural geometry. In addition, the temperature dependencies of the spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for $^1H$ MAS NMR and $^{13}C$ CP/MAS NMR are measured.

• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3644-3649
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• 2011

Multinuclear solid-state nuclear magnetic resonance (NMR) experiments were performed to investigate the local structure changes of nanoporous silica during hydrothermal treatment and surface modification with 3-aminopropyltriethoxysilane (3-APTES). The nanoporous silica was prepared by sol-gel polymerization using inexpensive sodium silicate as a silica precursor. Using $^1H$ magic angle spinning (MAS) NMR spectra, the hydroxyl groups, which play an important role in surface reactions, were probed. Various silicon sites such as $Q^2$, $Q^3$, $Q^4$, $T^2$, and $T^3$ were identified with $^{29}Si$ cross polarization (CP) MAS NMR spectra and quantified with $^{29}Si$ MAS NMR spectra. The results indicated that about 25% of the silica surface was modified. $^1H$ and $^{29}Si$ NMR data proved that the hydrothermal treatment induced dehydration and dehyroxylation. The $^{13}C$ CP MAS and $^1H$ MAS NMR spectra of 3-APTES attached on the surface of nanoporous silica revealed that the amines of the 3-aminopropyl groups were in the chemical state of ${NH_3}^+$ rather than $NH_2$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.1
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• pp.15-20
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• 2011

[ $^7Li$ ]Magic Angle Spinning (MAS) NMR spectroscopy has been used to study the lithium local environments in $Li_4P_2O_7$ and$LiFePO_4$ materials. The purpose of this study was to know the structure of the solid electrolyte interphase (SEI) in lithium ion cells composed of $LiFePO_4$ as cathode material. $Li_4P_2O_7$ and $LiFePO_4$ were prepared by a solid-state reaction. The $^7Li$ MAS NMR experiments were carried out at variable temperatures in order to observe the local structure changes at the temperatures in $Li_4P_2O_7$ system. The $^7Li$ MAS NMR spectra of in $Li_4P_2O_7$ indicate that the lithium local environments in $Li_4P_2O_7$ were not changed in the temperature range between $27^{\circ}C$ and $97^{\circ}C$ Through this work, we confirmed that the small amount of $Li_4P_2O_7$ less than 5.0 wt% in $LiFePO_4$ could be clearly measured by the $^7Li$ MAS NMR spectroscopy at high spinning rate over than 11 kHz.

• Journal of the Korean Wood Science and Technology
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• v.29 no.4
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• pp.60-66
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• 2001

For examine anti-degradation factors of acetylated wood, acetylated wood was incubated on Trametes versicolor. The laccase activity was examined in broth culture and solid fermentation that contain acetylated chips. The change of acetyl groups and chemical composition in the acetylated wood having massloss analysed by $^{13}C$-CP/MAS NMR. The laccase activity was detected in broth culture. When the T. versicolor contact to acetylated wood directly, the laccase activity was very low and couldn't maintain during test periods. Through the analysing of $^{13}C$-CP/MAS NMR, the acetylation took place carbohydrates as well as lignin and hydroxyl group of amorphous region was more easily substituted that of crystalline region The spectral analyses of $^{13}C$-CP/MAS NMR were shown that introduced acetyl bond was stable against fungal attack.

• Journal of the Korean Magnetic Resonance Society
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• v.1 no.1
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• pp.45-58
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• 1997

Heteropoly compounds, H3PMo12O40, CsxH3-xPMo12O40, and vanadium containing heteropoly compound were characterized by Solid-state broad line 1H MAS NMR, 31P MAS NMR, and High Speed MAS 51V NMR spectroscopy of quadrupolar nuclei. The effects of calcination, dehydration, and the number of protons on the structure of heteropoly compounds were studied. The results of this study demonstrate that these Solid-state NMR techniques are very useful tools to study heteropoly compounds.

• Bulletin of the Korean Chemical Society
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• v.28 no.4
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• pp.662-666
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• 2007

Poly(vinyl butyral) (PVB) with different wt% water was studied gravimetrically as well as with 1H magic angle spinning (MAS) nuclear magnetic resonance (NMR). The composition of PVB samples changes during MAS NMR because of the centrifugal force. As MAS time progresses, initially free water was removed fast but bound water also was gradually depleted. More water was diminished at faster spinning speeds, longer spinning time, higher temperatures, and higher initial water contents. As water in PVB was reduced, the chemical shifts and line widths of different types of water and also those of PVB changed. Our results demonstrate that 1H MAS NMR carried out at 10 kHz in less than about 5 minutes is a convenient and sensitive technique to measure: (a) the content variations of different types of water in polymers, (b) the degree of the interaction of water and polymer, and (c) the molecular dynamics of the polymer. Our study can be extended to different soft polymers with other small molecules than water in them.

• Journal of the Korean Magnetic Resonance Society
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• v.17 no.2
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• pp.86-91
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• 2013

Detailed information about the structural nature of three-coordinate borons in ${\beta}-BaB_2O_4$ is obtained through $^{11}B$ MAS NMR and $^{11}B$ single-crystal NMR. The three-coordinate $BO_3$ of the two borons B(1) and B(2) in ${\beta}-BaB_2O_4$ were distinguished. The spin-lattice relaxation time in the laboratory frame $T_1$ for B(1) and B(2) slowly decreases with increasing temperature, whereas the spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for B(1) and B(2), which differs from $T_1$, is nearly constant. The B(1) and B(2) of the two types were distinguished by $^{11}B$ MAS NMR and $^{11}B$ single-crystal NMR.

• Journal of the Korean Magnetic Resonance Society
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• v.25 no.2
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• pp.12-16
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• 2021

Daphnia magna is used as target organism for environmental metabolomics. The metabolome of D. magna was studied with NMR spectroscopy. Most studies used the extract of D. magna, but the reproducibility cannot be obtained using extracted sample. In this study, lyophilized D. magna samples were analyzed with two different ¹H NMR techniques, HR-MAS on intact tissues and solution NMR on extracted tissues. Samples were measured three times using 600 MHz NMR spectrometer. Metabolite extraction required more than twice as many D. magna, but the metabolite intensity was lower in solution NMR. In the spectra of HR-MAS NMR, the lipid signal was observed, but they did not interfere with metabolite profiling. We also confirmed the effect of swelling time on signal intensities of metabolites in HR-MAS NMR, and the results suggest that appropriate swelling should be used in lyophilized D. magna to improve the accuracy of metabolite profiles.

• Journal of the Korean Magnetic Resonance Society
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• v.17 no.1
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• pp.19-23
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• 2013

The temperature dependences of the NMR spectrum and the spin-lattice relaxation times in $KH_2PO_4$ were investigated via single-crystal NMR and MAS NMR. The stretched-exponential relaxation that occurred because of the distribution of correlation times was indicative of the degree of the distribution of the double-well potential on the hydrogen bond. The behaviors responsible for the strong temperature dependences of the $^1H$ and $^{31}P$ spin-lattice relaxation times in the rotating frame $T_{1{\rho}}$ in $KH_2PO_4$ are likely related to the reorientational motion of the hydrogen-bond geometry and the $PO_4$ tetrahedral distortion.