• 한국염색가공학회지
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• 제24권1호
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• pp.33-38
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• 2012

In this study, to increase flame retardation of poly(ethylene terephthalate) (PET) in burning, bisphenol A bis(diphenyl phosphate) (BDP), a well known flame retardant containing phosphorous, was reacted on end groups of PET by radical pathway. End-capping mechanism of PET with BDP was suggested and confirmed by spectroscopic and thermal analysis. From 400 MHz $^{31}P$ solid state FT-NMR spectrum of end-capped PET (PET-BDP), phosphorus spectra peak in BDP was found at ca. -20 ppm. Furthermore, P-C bond stretching vibration peaks were found ca. $600cm^{-1}$ in FT-IR spectrums of PET-BDP. These results showed that BDP can be chemically added on end groups of PET by our method. Thermal characteristics of pure PET (pPET) and PET-BDP were measured and evaluated by TGA analysis. There was not significant changes in thermal characteristics of PET-BDP compared to that of pPET.

• 한국염색가공학회지
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• 제24권1호
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• pp.39-44
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• 2012

To improve flame retardation of poly(ethylene terephthalate) (PET) against burning, resorcinol bis(diphenyl phosphate) (RDP), phosphorous containing flame retardant, was incorporated into PET backbone by radical reaction pathway. Radical endcapping of PET with RDP was confirmed by spectroscopic and thermal analysis. From 400 MHz $^{31}P$ solid state FT-NMR spectrum of PET with RDP (PET-RDP), phosphorus spectra peak in RDP was found at ca. -10 ppm. Furthermore, P-C bond stretching vibration peaks were found ca. $530cm^{-1}$ in FT-IR spectrums of PET-RDP. These results indicated that RDP can be chemically bound at the ends of PET by radical addition method. Thermal characteristics of pure PET (pPET) and PET-RDP were measured and evaluated by TGA thermal analysis. There was not significant changes in thermal characteristics of PET-RDP compared to that of pPET.

• 한국자기공명학회논문지
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• 제10권2호
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• pp.141-154
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• 2006

A solid-state reaction of $V_2O_5$ with AlMCM-41 followed by calcinations generated $V^{5+}$ species in the mesoporous materials. Dehydration results in the formation of a vanadyl species, $VO^{2+}$, that can be characterized by electron spin resonance (ESR). The chemical environment of the vanadium centers in V-AlMCM-41 was investigated by XRD, EDX, diffuse reflectance UV-VIS, ESR, $^{29}Si,\;^{27}Al,\;and\;^{51}V$ NMR. It was found that the vanadium species on the wall surface and inside the wall of the hexagonal tubular wall of the V-AlMCM-41 were completely oxidized to tetrahedral $V^{5+}$ and transformed to square pyramidal by additional coordination to water molecules upon hydration. The oxidized $V^{5+}$ species on the wall surfaces and inside the wall were also reversibly reduced to $VO^{2+}$ species or lower valences by thermal process.

• 한국자기공명학회논문지
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• 제26권4호
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• pp.51-58
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• 2022

The baseline flattened NMR spectrum has been achieved by several methodologies including pulse manipulation with a series of phase cycling. The background signal inherent in the probe is also main source of baseline distortion both in solution and solid NMR. The simple direct polarization with 90° pulse flipping the magnetization from the z-axis onto the receiver coil requires the strong rf pulse enough to encompass the wide frequency range to excite the resonance of interest nuclei. Albeit the perfect polarization 90° pulse, the signal from the unwanted magnetic fields such as background signal can not be completely suppressed by suitable phase cycling. Moreover, slowly baseline wiggling signal from the low 𝛾 nuclei is not easy to eliminate with multiple pulse manipulation. So there is still need to contrive the new scheme for that purpose in an adroit manner. In this article new triple pulse excitation schemes for TIP and modified DEPTH pulse sequence are analytically examined in terms of arbitrary phase and flip angle of pulse. The suitable phase cycling for these pulse trains is necessary for the good sensitivity and resolution of the spectrum. It is observed that the ¹³C sensitivity TIP experiment is almost equal to the CP/MAS with modified DEPTH sequence, both of which are applicable to both solid and solution state NMR.

• 한국자기공명학회논문지
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• 제14권1호
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• pp.38-44
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• 2010

In liquids NMR, $^{1}H$ is the most widely observed nucleus, which is not the case in solids NMR. The reason is due to the strong homo-dipolar interactions between the hydrogen atoms which mask the useful chemical shift information. Therefore we must remove the strong homo-dipolar interactions in order to get structural information, which can be investigated by the isotropic chemical shift. There are two ways of obtaining it. One is the ultra-fast MAS of ca. 70 kHz spinning speed, which has become available only recently. The other way is devising a pulse sequence which can remove the strong homo-dipolar interaction. In the latter way, MAS with a moderate spinning rate of a few kHz, is enough to remove the chemical shift anisotropy. In this report, 1D-CRAMPS and 2D MASFSLG techniques are utilized and their results will be compared. This kind of highresolution $^{1}H$ NMR for solids, should become a valuable analytical tool in the understanding and the developing of a new class of hydrogen storage materials. Here ammonium borane $-NH_{3}BH_{3}$, whose hydrogen content is high, is used as a sample.

• 분석과학
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• 제15권1호
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• pp.36-42
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• 2002

부식질 농도가 매우 높은 지하수로 부터 humic acid (HA) 와 fulvic acid (FA)를 분리 정제한 후 각각의 물리 화학적 특성을 조사하였다. 원소분석, 자외선/가시광선과 적외선 스펙트럼분석 및 $^{13}C-NMR$ 분광법으로 HA 와 FA의 구조 및 작용기를 확인하였다. 또한 양성자 교환능력과 분자 크기분포 측정 실험을 통하여 HA와 FA의 특성 외에 산출지 특성을 나타내며, 상당한 양성자 교환능력을 갖는 다분산계임을 확인하였다.

• 한국자기공명학회논문지
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• 제6권1호
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• pp.38-44
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• 2002

60% Pt on Vulcan XC-72 with similar Pt sizes to fuel cell grade Pt black was investigated by $\^$13/C nuclear magnetic resonance spectroscopy (NMR), cyclic voltammery (CV), transmission electron microscopy (TEM). Experiments were carried out on electrochemically cleaned samples as well as as-received. The TEM and CV results showed that the average particle sizes were changed by cleaning. However, the chemical shift （$\delta$$\_$G/） of $\^$13/C of $\^$13/CO absorbed on Pt surfaces did not show any appreciable variation with particle size change as did in Pt black. These results indicate that a combination of different analytic techniques is essential to understand the properties of the metal particle catalysts and that the presence of carbon black support strongly influences the NMR data, probably through metal-support interaction.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1317-1322
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• 2014

Membrane disruption by an antimicrobial peptide (AMP) was investigated by measuring the $^2H$ solid-state nuclear magnetic resonance spectra of 1-palmitoyl-$d_{31}$-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC_$d_{31}$) in mixtures of POPC_$d_{31}$/cholesterol and either magainin 2 or aurein 3.3 deposited on thin cover-glass plates. The line shapes of the experimental $^2H$ solid-state nuclear magnetic resonance (SSNMR) spectra were best simulated by assuming the coexistence of a mosaic spread of bilayers containing pore structures and a fasttumbling isotropic phase or a hexagonal phase. Within a few days of incubation in a hydration chamber, an isotropic phase and a pore structure were induced by magainin 2, while in case of aurein 3.3 only an isotopic phase was induced in the presence of a bilayer phase. After an incubation period of over 100 days, alignment of the bilayers increased and the amount of the pore structure decreased in case of magainin 2. In contrast with magainin 2, aurein 3.3 induced a hexagonal phase at the peptide-to-lipid ratio of 1/20 and, interestingly, cholesterol was not found in the hexagonal phase induced by aurein 3.3. The experimental results indicate that magainin 2 is more effective in disrupting lipid bilayers containing cholesterol than aurein 3.3.

• Macromolecular Research
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• 제15권7호
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• pp.633-639
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• 2007

A variety of NMR techniques were applied to the micro-chemical structural characterization of polyanilines prepared via an efficient synthetic method in a self-stabilized dispersion medium in which the polymerization was conducted in a heterogeneous organic/aqueous biphasic system without any stabilizers. Here, the monomer and growing polymer chain were shown to function simultaneously as a stabilizer, imparting compatibility for the dispersion of the organic phase, and as a form of flexible template in an aqueous reaction medium. Polymerizations predicated on this concept generated polyanilines with a low defect content: solution state $^{13}C-NMR$ and solid $^{13}CDD/CP/MAS$ spectroscopy indicated that the synthesized HCPANi and its soluble derivative, HCPANi-t-BOC, evidenced distinctly different NMR spectra with fewer side peaks, as compared to conventionally prepared PANis, and the complete structural assignments of the observed NMR peaks could be determined via the combination of both 1D and 2D techniques. Ortho-linked defects in HCPANi were estimated to be as low as 7%, as shown by a comparison of the integration of the carbonyl carbon resonance peaks.

• 한국세라믹학회지
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• 제40권5호
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• pp.434-440
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• 2003

초거대 자기 저항 물질인 페로브스카이트 L $a_{0.8}$C $a_{0.2}$Mn $O_3$의 분말을 졸-겔방법으로 제조하였다. Lanthanum(III), Calcium(II) 그리고 Manganese(III) 2,4-Pentanedionate를 Propionic acid와 methane떠 혼합용매를 사용하고 PEG (l5 wt%) 용액을 첨가 하여 안정한 졸용액을 합성하였고 FT-IR spectroscopy로 반응의 진행 정도를 관찰하였다. L $a_{0.8}$C $a_{0.2}$Mn $O_3$ 겔 분말에 대해 온도를 변화시키면서 열처리하여 FT-IR, CP/MAS $^{13}$C solid state NMR spectroscopy와 XRD등을 이용해 구조변화를 관찰하였다. 열분석은 TG/DTA로 측정하였으며, FE-SEM을 통해 입자크기와 균일도를 관찰하였고, 양이온 조성 비율을 알아보기 위해 ICP-AES를 측정하였다. 자성 특성을 규명하기 위해 VSM을 이용하여 자기 모멘트를 측정하였으며, 상자기성 에서 강자기성으로 전이되는 큐리온도( $T_{c}$)를 관찰하였다.