Materials
·
2019
·Vol. 12
·期 22
·3765
·
IF 2.972
Wei Liao,Wenqing Li,Zhenggang Fang,Chunhua Lu,Zhongzi Xu
Tobermorite and Al-substituted tobermorite with varying Al/(Si + Al) molar ratios were synthesized via the static hydrothermal method. The effect of different Al substitution ratios on the structure of tobermorite was investigated by XRD, SEM–EDS, TG–DSC, FT–IR,29Si, and27Al MAS–NMR. The interplanar crystal spacing of (002) increased with the increment of the Al substitution ratio. The maximum ratio of the Al substitution for Si in the structure of tobermorite was about 15 at %, which was limited by the compositions of tobermorite and the electrostatic repulsive forces caused by Al substitution. The DSC curve of the tobermorite with an Al/(Al + Si) molar ratio of 0.15 showed a larger exothermic peak area at 850 °C, indicating that the Al-O-Si bond was formed in the structure of tobermorite and the Al participated in the recrystallization. The29Si and27Al MAS–NMR results confirmed that tetrahedral Al was introduced into the structure of the tobermorite. New silicon sites, Q2(1Al) and Q3(1Al), formed by the Al substitution for Si in bridging and non-bridging sites, were detected. Compared to the tobermorite without Al substitution, the adsorption capacity of Al-substituted tobermorite with Al/(Al + Si) = 0.15 to Na+was improved by 44%.Keywords:hydrothermal synthesis;Al-substituted tobermorite;29Si MAS–NMR;27Al MAS–NMR;adsorption capacity
研究领域:
材料科学
·
化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2017
·
IF 2.843
Xubao Jiang,Xiaoli Zhu,Alexandre A. Arnold,Xiang Zheng Kong,Jerome P. Claverie
Owing to the presence of abundant interchain interactions such as hydrogen bonds, polyureas (PU) are only swellable or soluble in a limited number of highly protonic solvents, and the viscosity of the solutions obtained is very high, making their chemical structure characterization hard or even impossible by standard NMR. Accurate structure analysis is also hard by solid-state NMR due to low spectral resolution. The presence of a side reaction in their synthesis generating biuret cross-links is often invoked to explain their insolubility. Here we demonstrate that High Resolution Magic Angle Spinning (HR-MAS) NMR is an efficient tool for the chemical structure analysis even for cross-linked PU. With 1H, 13C, and 1H–15N HSQC combined, a variety of linear and cross-linked PU is analyzed by HR-MAS NMR, and conclusive information on their chemical structure is obtained, which reveals for the first time that the biuret group is absent in all PU.
研究领域:
材料科学
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分析化学
✓ 已验证
产品关联
DOI
高影响因子
Current Analytical Chemistry
·
2024
·Vol. 20
·期 9
·686-696
·
IF 1.7
Xin Ye,Zhenyu Xu,Da Xu,Jibao Cai,Shuiping Dai,Yuting Luo,Lei Guo,Ying Wang,Jiakun Su,Jun Yang
Background: As one of the most important economic crops, tobacco products have a long history and dominate the development of the world economy. Pectin, as a complex colloidal substance widely present in plant cell walls, its content is an important factor affecting the safety of tobacco smoking. Objective: This study aimed to analyze the content and structure of pectin in tobacco samples. Methods: In this study, tobacco pectin was extracted by ultrasonic-assisted ionic liquid extraction, and the 13C MultiCP/MAS NMR spectral analysis of pectin was conducted. Results: The type of extractant, duration of ultrasonication, extraction temperature, and solid-liquid ratio were optimized. Under the conditions of using 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) as the extractant, the solid-liquid ratio of 1:20 g/mL, and the ultrasonic power of 600 w for 30 min at 30°C, the yield of 23.7% of tobacco stem pectin and the purity of 54.2% could be obtained. The optimized MultiCP sequence parameters, with 10 CP cycles of 1.0 ms and the repolarization time of 50 ms could obtain high-resolution spectra within a time of 1.0 h. The C-6 peaks of the pectin in spectra were fitted using the spectral deconvolution technique and calculated the methylesterification (DM) of the tobacco pectin, which was generally less than 50% and belonged to the low methyl esterification pectin. The pectin content of the tobacco sample was calculated using the standard curve method with the addition of dimethyl sulfone (DMS) as an internal reference. The results of this method were consistent with the colorimetric method. Conclusion: The 13C MultiCP/MAS NMR method has the advantages of being green, fast, and accurate and provides a new technical tool for quantitative and qualitative studies of cell wall substances in tobacco samples.
研究领域:
植物化学
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分析化学
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烟草科学
✓ 已验证
DOI
高影响因子
Magnetic Resonance Letters
·
2023
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IF 0
Suyu Gu,Guozhong Lu,Nianrui Guo,Juncheng Xu,Yu Jiang,Ming Shen,Bingwen Hu
LiCoO 2 is an important category of active cathode materials in lithium-ion batteries due to its high compacted electrode density, good thermal stability , and stable voltage platform. Recent works on LiCoO 2 have focused on the realization of higher charging voltages to fully utilize its high theoretical capacity. However, an unambiguous atomic-level local probe is essential for the understanding of structure-function correlation. Here we employ high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy to study the local atomic environments in LiCoO 2 synthesized with three common sintering methods. While one-dimensional 7 Li NMR shows distinct linewidth and subtle dependence on lithium over-stoichiometry, both 7 Li and 59 Co relaxation times are highly dependent on the sintering method. We prove that the two-step sintering method favors the elimination of unreacted Co 3 O 4 , thereby enabling the best discharge capacity in all-solid-state lithium batteries assembled with LiCoO 2 /LGPS/LiIn, which is in accordance with its narrowest 7 Li linewidth and the longest 7 Li/ 59 Co T 1 .
研究领域:
材料科学
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电化学
·
能源存储
✓ 已验证
DOI
JOURNAL OF MEMBRANE SCIENCE
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2017
·
IF 6.035
Li Peng,Xiaohan Xu,Xun Yao,Hua Liu,Xuehong Gu
A series of novel hierarchical ZSM-5 zeolite membranes with tunable mesopore sizes have been prepared successfully by using amphiphilic organosilane 3-[(trimethoxysilyl) propyl]octyldimethyl-ammonium chloride (TPOAC) as the mesogenous template and part of the Si source. The effects of several synthesis parameters, such as the TPOAC/SiO 2 ratio, synthesis temperature and crystallization time, on the microstructures and rejection performance of the hierarchical ZSM-5 zeolite membranes were systematically investigated. Multiple techniques, such as XRD , SEM, N 2 adsorption techniques, TEM, IR, 13 C MAS NMR and 29 Si MAS NMR were employed for the characterizations. The filtration of dextran in water shows that the membranes have molecular weight cutoff (MWCO) ranging from 9500 to 943,000, corresponding to the molecular size in the range of 4.5–37 nm. The sharp increase in the rejection of dextran with the increase of molecular weight indicated narrow pore size distribution of the membrane. These results show that the hierarchical mesoporous ZSM-5 zeolite membranes have a great potential for ultrafiltration with high performance.
研究领域:
材料科学
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化学工程
·
膜技术
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE CHINESE CHEMICAL SOCIETY
·
2024
·
IF 1.6
Ying Wang,Lan Huang,Zhenfeng Tian,Shaolin Ge,Bing Zhang,Zhao Zhang,Mingxi Chen,Bingxia Xu,Jinghang Hao,Jun Yang
As the main structural component of tobacco cell wall, lignin content is an important factor affecting the safety of tobacco smoking. However, it is time-consuming to quantify lignin by conventional wet chemical analysis methods. In this work, a 13 C multiCP/MAS NMR spectral analysis method for tobacco lignin was established. The multiCP/MAS NMR sequence was optimized for tobacco lignin. The optimized nuclear magnetic sequence parameters were 9 CP cycles of 1.5 ms, repolarization time of 0.7 s, and a total acquisition time of 130 min. Subsequently, TMSP was used as the internal standard substance to establish the working curve, and the correlation coefficient was 0.9946. The relative standard deviation (RSD, n = 5) was 3.26%. This method was applied to the determination of lignin content in different types of tobacco samples. The relative error in the determination of lignin content by this method did not exceed 4.46% compared to the results of the chemical method. The results showed that the 13 C multiCP/MAS NMR spectral analysis method had the advantages of accuracy and rapidity, which provided a new technical means for the quantitative study of tobacco cell wall substances.
研究领域:
植物化学
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烟草科学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Physical Chemistry C
·
2021
·
IF 4.126
Xin Chen,Daofeng Huang,Lulu He,Li Zhang,Yuanhang Ren,Xueying Chen,Bin Yue,Heyong He
Niobium oxides and tantalum oxides are typical solid acid catalysts that exhibit high activity and high water-resistance in the aqueous environment. To understand their acid catalytic performance, several niobium oxides and tantalum oxides and their hydrates were prepared, and the effects of adsorbed water on the acidity were investigated by 31P MAS NMR under controlled atmospheres. The results show that the introduction of water can convert the strong Lewis acid sites of Nb2O5·nH2O, Nb2O5-350, Ta2O5·nH2O, and Ta2O5-350 into weak Lewis acid sites with the induction of new Brønsted acid sites, whereas the strong Lewis acid sites of Nb2O5-450 and Ta2O5-450 convert into weak Lewis acid sites only. The obtained information may provide a unique insight into the role of water in many heterogeneous catalytic reactions that directs toward the rational design of water-resistant catalysts.
研究领域:
催化化学
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材料化学
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物理化学
·
无机化学
✓ 已验证
DOI
高影响因子
Green Energy & Environment
·
2018
·
IF 0
Wei Hui,Yan Zhou,Yan Dong,Zhi-Jun Cao,Fei-Qiang He,Min-Zhong Cai,Duan-Jian Tao
Novel superacid SO 4 H-functionalized ionic liquids (SFILs) were designed and prepared in this work. The catalytic activities of SFILs were evaluated in xylan hydrolysis and xylose dehydration to produce furfural. Combined with the results of acid strength of SFILs characterized by solid-state 31 P MAS NMR, it was found that the catalytic performance of SFILs was positively correlated to their acid strength. The superacid SFIL [Ch-SO 4 H][CF 3 SO 3 ] displayed the best catalytic performance with more than 80% yield of furfural, and it was also obviously superior to usual SO 3 H-functionalized acidic ILs, mineral liquid acids, and acidic resin Amberlyst-15 catalysts in catalytic activity under optimized conditions. In addition, the superacid SFIL [Ch-SO 4 H][CF 3 SO 3 ] could be easily separated from reaction system and reused at least five times without obvious decrease.
研究领域:
化学工程
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催化
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绿色化学
·
可再生能源
✓ 已验证
产品关联
DOI
Molecular Catalysis
·
2023
·
IF 4.6
Shiwei Feng,Chengping Zhang,Hengdao Quan
As an environmentally friendly cleaning agent, Z -1-chloro-3,3,3-trifluoropropene (HCFO-1233zd( Z )) can realize industrial production by the isomerization of HCFO-1233zd( E ). Herein, various isomerization catalysts with different structures, compositions and acid properties were prepared through the fluorination of γ-Al 2 O 3 with CHF 3 by controlling the activation conditions. For the first time, the catalysts for HCFO-1233zd( E ) isomerization were systematically studied by XRD, N 2 physisorption, XPS, SEM, MAS NMR spectroscopy, NH 3 -TPD and py-IR. The active site of this reaction was revealed and the catalyst deactivation mechanism was proposed. It turned out that HCFO-1233zd( E ) isomerization prefers to occur at Lewis acid sites with moderate density and strength. The amorphous particles composed of γ-Al 2 O 3 , Al 2 O 3 (F) and α-AlF 3 ( R 3 ¯ c ) at 450 °C exhibit highly catalytic activity for HCFO-1233zd( E ) isomerization. After 100 h evaluation, it was found that residual γ-Al 2 O 3 can be fluorinated by HCFO-1233zd( E ) to form needle-like structures which could induce the amorphous Al 2 O 3 (F) particles to reorganize and give cubic structures, where the Lewis acid properties were enhanced, leading to catalyst deactivation.
研究领域:
催化
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化学工程
·
材料科学
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环境化学
✓ 已验证
产品关联
DOI
高影响因子
CHEMOSPHERE
·
2021
·
IF 7.086
Yanan Yang,Yu Zhang,Hong Zheng,Baichao Zhang,Qi Zuo,Kaiyue Fan
A key challenge in trace heavy metals removal from drinking water by adsorption technology is to achieve high adsorption capacity and rapid uptake speed of adsorbent. Herein, we report a functionalized double modified covalent organic framework (DMTD–COF–SH) bearing high-density sulfur and nitrogen chelating groups provided simultaneously by 2,5-dimercapto-1,3,4-thiadiazole (DMTD) and 1,2-ethanedithiol, which was prepared via a facile one-pot thiol-ene “click” reaction. PXRD , FTIR, XPS, SEM, BET and 13 C MAS NMR confirmed their successful graft, and DMTD was found to be more easily grafted on the COF surface layer than 1,2-ethanedithiol. The as-prepared DMTD–COF–SH showed remarkable adsorption capacity and ultrafast uptake dynamics to trace heavy metals owing to the synergistic effects resulting from densely populated sulfur and nitrogen chelating groups within ordered COF mesopores and at the COF surface. On the basis of the drinking water treatment units standard NSF/ANSI 53–2020, when the adsorbent dosage was 10 mg/30 mL and 20 mg L −1 calcium ions coexisted, the lead concentration decreased from initial 150 μg L −1 to 2.89 μg L −1 within 10 s, far below the allowable limit of world health organization (WHO) drinking water standard (10 μg L −1 ), and the maximum adsorption capacity meeting the standard attained 14.22 mg g −1 . The adsorbent also exhibited excellent stability, wide applicable pH range and outstanding adsorption performance for coexisting trace lead, mercury, cadmium, chromium (VI) and copper in tap water, indicating that the DMTD–COF–SH material has excellent application prospect for trace heavy metals removal from drinking water.
研究领域:
环境科学
·
材料科学
·
水处理
·
化学工程
✓ 已验证
DOI
高影响因子
JOURNAL OF POWER SOURCES
·
2019
·
IF 7.467
Zonghui Zhang,Lili Hu,Haizheng Tao,Jinjun Ren
Glassy precursors in the Li 1+ x Ga x Ge 2- x P 3 O 12 system are prepared by melting and casting. The glasses are annealed at the crystallization peak temperatures to obtain glass ceramics with Na-superionic conducting structure. The ionic conductivity can be significantly increased by substituting Ge with Ga and Li. The highest ionic conductivity of the glass ceramics is 9.74 × 10 −5 S cm −1 at 20 °C. Multiple magic angle spinning nuclear magnetic resonance (MAS NMR) techniques are used to characterize the structural transitions from glasses to their glass ceramic counterparts. 71 Ga and 31 P MAS NMR spectra have shown that the local structures of the glasses are distinctly modified after crystallization. The second coordinated shells of Ga 3+ ions are consisted of phosphorus in both glasses and glass ceramics although their coordination numbers change. The glassy precursors show homonuclear segregations such as P-O-P and Ge-O-Ge linkages. However, the glass ceramics are homogeneous, in which per phosphorus tetrahedron connects with total four Ga and Ge, forming four different phosphorus species (Q 0 (4-n)Ge, nGa (n = 0, 1, 2, and 3)). A random distribution model can be used to quantitatively predict the population of every Q 0 (4-n)Ge, nGa species, if the compositions are known. A correlation between local structure and ionic conductivity is proposed.
研究领域:
材料科学
·
固体化学
·
电化学
·
核磁共振光谱学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）