scholarly journals Structure and Properties of Oxidized Chitosan Grafted Cashmere Fiber by Amide Covalent Modification

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3812
Author(s):  
Jifeng Li ◽  
Ting Fang ◽  
Wenjing Yan ◽  
Fei Zhang ◽  
Yunhui Xu ◽  
...  
Keyword(s):  
Magic Angle Spinning ◽  
Covalent Modification ◽  
Primary Amines ◽  
Carboxyl Groups ◽  
Hydroxyl Groups ◽  
Magic Angle ◽  
Structure And Properties ◽  
Carboxyl Content ◽  
Moisture Regain ◽  
Degree Structure

In this study, oxidized chitosan grafted cashmere fibers (OCGCFs) were obtained by crosslinking the oxidized chitosan onto cashmere fibers by amide covalent modification. A novel method was developed for the selective oxidation of the C6 primary hydroxyls into carboxyl groups for chitosan. The effect of oxidization reaction parameters of HNO3/H3PO4–NaNO2 mediated oxidation system on the oxidation degree, structure, and properties of chitosan were investigated. The chemical structure of the oxidized chitosan was characterized by solid-state cross-polarization magic angle spinning carbon-13 Nuclear Magnetic Resonance (CP/MAS 13C-NMR), Fourier transform infrared spectroscopy (FT-IR), and its morphology was investigated by scanning electron microscopy (SEM). Subsequently, the effect of the oxidized chitosan grafting on OCGCF was examined, and the physical properties, moisture regain, and antibacterial activity of OCGCFs were also evaluated. The results showed that oxidation of chitosan mostly occurred at the C6 primary hydroxyl groups. Moreover, an oxidized chitosan with 43.5–56.8% carboxyl content was realized by ranging the oxidation time from 30 to 180 min. The resulting OCGCF had a C–N amido bond, formed as a result of the reaction between the primary amines in the cashmere fibers and the carboxyl groups in the oxidized chitosan through the amide reaction. The OCGCF exhibited good moisture regain and remarkable bacteriostasis against both Staphylococcus aureus and Escherichia coli bacteria with its durability.

Effect of Acid on Surface Hydroxyl Groups on Kaolinite and Montmorillonite

2018 ◽  
Vol 232 (3) ◽  
pp. 409-430 ◽  
Author(s):  
Sarah K. Sihvonen ◽  
Kelly A. Murphy ◽  
Nancy M. Washton ◽  
Muhammad Bilal Altaf ◽  
Karl T. Mueller ◽  
...  
Keyword(s):  
Functional Groups ◽  
Acid Treatment ◽  
Atmospheric Transport ◽  
Magic Angle Spinning ◽  
Resonance Spectroscopy ◽  
Hydroxyl Groups ◽  
Magic Angle ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Angle Spinning

AbstractMineral dust aerosol participates in heterogeneous chemistry in the atmosphere. In particular, the hydroxyl groups on the surface of aluminosilicate clay minerals are important for heterogeneous atmospheric processes. These functional groups may be altered by acidic processing during atmospheric transport. In this study, we exposed kaolinite (KGa-1b) and montmorillonite (STx-1b) to aqueous sulfuric acid and then rinsed the soluble reactants and products off in order to explore changes to functional groups on the mineral surface. To quantify the changes due to acid treatment of edge hydroxyl groups, we use19F magic angle spinning nuclear magnetic resonance spectroscopy and a probe molecule, 3,3,3-trifluoropropyldimethylchlorosilane. We find that the edge hydroxyl groups (OH) increase in both number and density with acid treatment. Chemical reactions in the atmosphere may be impacted by the increase in OH at the mineral edge.

scholarly journals Structure and properties of strontium-doped phosphate-based glasses

2008 ◽  
Vol 6 (34) ◽  
pp. 435-446 ◽  
Author(s):  
Ensanya A Abou Neel ◽  
Wojciech Chrzanowski ◽  
David M Pickup ◽  
Luke A O'Dell ◽  
Nicola J Mordan ◽  
...  
Keyword(s):  
Cellular Response ◽  
Cell Activity ◽  
Positive Control ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Structure And Properties ◽  
Ionic Size ◽  
Angle Spinning ◽  
Oxygen Distance ◽  
Free Glass

Owing to similarity in both ionic size and polarity, strontium (Sr 2+ ) is known to behave in a comparable way to calcium (Ca 2+ ), and its role in bone metabolism has been well documented as both anti-resorptive and bone forming. In this study, novel quaternary strontium-doped phosphate-based glasses, containing 1, 3 and 5 mol% SrO, were synthesized and characterized. 31 P magic angle spinning (MAS) nuclear magnetic resonance results showed that, as the Sr 2+ content is increased in the glasses, there is a slight increase in disproportionation of Q 2 phosphorus environments into Q 1 and Q 3 environments. Moreover, shortening and strengthening of the phosphorus to bridging oxygen distance occurred as obtained from FTIR. The general broadening of the spectral features with Sr 2+ content is most probably due to the increased variation of the phosphate–cation bonding interactions caused by the introduction of the third cation. This increased disorder may be the cause of the increased degradation of the Sr-containing glasses relative to the Sr-free glass. As confirmed from elemental analysis, all Sr-containing glasses showed higher Na 2 O than expected and this also could be accounted for by the higher degradation of these glasses compared with Sr-free glasses. Measurements of surface free energy (SFE) showed that incorporation of strontium had no effect on SFE, and samples had relatively higher fractional polarity, which is not expected to promote high cell activity. From viability studies, however, the incorporation of Sr 2+ showed better cellular response than Sr 2+ -free glasses, but still lower than the positive control. This unfavourable cellular response could be due to the high degradation nature of these glasses and not due to the presence of Sr 2+ .

scholarly journals The Effects of the Crystalline Phase of Zirconia on C–O Activation and C–C Coupling in Converting Syngas into Aromatics

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 262
Author(s):  
Sheng Wang ◽  
Yue Fang ◽  
Zhen Huang ◽  
Hualong Xu ◽  
Wei Shen
Keyword(s):  
Co Adsorption ◽  
Chemical Precipitation ◽  
Magic Angle Spinning ◽  
Hydroxyl Groups ◽  
Magic Angle ◽  
Efficient Catalyst ◽  
Syngas Conversion ◽  
Acid And Base ◽  
Zro2 Catalyst ◽  
Angle Spinning

Zirconia has recently been used as an efficient catalyst in the conversion of syngas. The crystalline phases of ZrO2 in ZrO2/HZSM-5 bi-functional catalysts have important effects on C–O activation and C–C coupling in converting syngas into aromatics and been investigated in this work. Monoclinic ZrO2 (m-ZrO2) and tetragonal ZrO2 (t-ZrO2) were synthesized by hydrothermal and chemical precipitation methods, respectively. The results of in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTs) revealed that there were more active hydroxyl groups existing on the surface of m-ZrO2, and CO temperature programmed desorption (CO-TPD) results indicated that the CO adsorption capacity of m-ZrO2 was higher than that of t-ZrO2, which can facilitate the C–O activation of m-ZrO2 for syngas conversion compared to that of t-ZrO2. And the CO conversion on the m-ZrO2 catalyst was about 50% more than that on the t-ZrO2 catalyst. 31P and 13C magic angle spinning nuclear magnetic resonance (MAS NMR) analysis revealed a higher acid and base density of m-ZrO2 than that of t-ZrO2, which enhanced the C–C coupling. The selectivity to CH4 on the m-ZrO2 catalyst was about 1/5 of that on the t-ZrO2 catalyst in syngas conversion. The selectivity to C2+ hydrocarbons over m-ZrO2 or t-ZrO2 as well as the proximity of the ZrO2 sample and HZSM-5 greatly affected the further aromatization in converting syngas into aromatics.

A MAS NMR investigation of aluminosilicate, silicophosphate, and aluminosilicophosphate gels and the evolution of crystalline structures on heating the gels

1991 ◽  
Vol 6 (3) ◽  
pp. 592-601 ◽  
Author(s):  
S. Prabakar ◽  
K.J. Rao ◽  
C.N.R. Rao
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Structural Changes ◽  
Orthophosphoric Acid ◽  
Magic Angle Spinning ◽  
Hydroxyl Groups ◽  
Magic Angle ◽  
Major Phase ◽  
Higher Temperature ◽  
Angle Spinning

Gels of various composition containing SiO2, Al2O3, and P2O5 have been investigated by employing high resolution magic-angle-spinning (MAS) 27Al, 29Si, and 31P NMR spectroscopy. Changes occurring in the NMR spectra as the gels are progressively heated have been examined to understand the nature of structural changes occurring during the crystallization of the gels. 27Al resonance is sensitive to changes in the coordination number even when the Al concentration is as low as 1 mol%. As the percentage of Al increases, the hydroxyl groups tend to be located on the Al sites while Si remains as SiO4/2 (Q4). Mullite is the major phase formed at higher temperature in the aluminosilicate gels. In the case of the silicophosphate gels, Si is present in the form of Q4 and Q3 species. There is a change in the coordination of Si from four to six as the gel is heated. The formation of six-coordinated Si is facilitated even at lower temperatures (∼673 K) when the P2O5 content is high. The phosphorus atoms present as orthophosphoric acid units in the xerogels change over to metaphosphate-like units as the gel is heated to higher temperatures. In aluminosilicophosphates, Si is present as Q4 and Q3 species while P is present as metaphosphate units; Al in these gels seems to be inducted into the tetrahedral network positions.

scholarly journals Synthesis of highly active ETS-10-based titanosilicate for heterogeneously catalyzed transesterification of triglycerides

2019 ◽  
Vol 10 ◽  
pp. 2039-2061
Author(s):  
Muhammad A Zaheer ◽  
David Poppitz ◽  
Khavar Feyzullayeva ◽  
Marianne Wenzel ◽  
Jörg Matysik ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Active Sites ◽  
Variable Temperature ◽  
Textural Properties ◽  
Active Surface ◽  
Magic Angle Spinning ◽  
Hydroxyl Groups ◽  
Magic Angle ◽  
Highly Active ◽  
The Impact

In this contribution, the preparation of hierarchically structured ETS-10-based catalysts exhibiting notably higher activity in the conversion of triolein with methanol compared to microporous titanosilicate is presented. Triolein, together with its unsaturated analog trilinolein, represent the most prevalent triglycerides in oils. The introduction of mesopores by post-synthetic treatment with hydrogen peroxide and a subsequent calcination step results in the generation of an additional active surface with Brønsted basic sites becoming accessible for triolein and enhancing the rate of transesterification. The resulting catalyst exhibits a comparable triolein conversion (≈73%) after 4 h of reaction to CaO (≈76%), which is reportedly known to be highly active in the transesterification of triglycerides. In addition, while CaO showed a maximum conversion of 83% after 24 h, the ETS-10-based catalyst reached 100% after 8 h, revealing its higher stability compared to CaO. The following characteristics of the catalysts were experimentally addressed – crystal structure (X-ray diffraction, transmission electron microscopy), crystal shape and size (scanning electron microscopy, laser diffraction), textural properties (N2 sorption, Hg porosimetry), presence of hydroxyl groups and active sites (temperature-programmed desorption of NH3 and CO2, 29Si magic angle spinning nuclear magnetic resonance (NMR)), mesopore accessibility and diffusion coefficient of adsorbed triolein (pulsed field gradient NMR), pore interconnectivity (variable temperature and exchange spectroscopy experiments using hyperpolarized 129Xe NMR) and oxidation state of Ti atoms (electron paramagnetic resonance). The obtained results enabled the detailed understanding of the impact of the post-synthetic treatment applied to the ETS-10 titanosilicate with respect to the catalytic activity in the heterogeneously catalyzed transesterification of triglycerides.

scholarly journals Reactions with Wood Carbohydrates and Lignin of Citric Acid as a Bond Promoter of Wood Veneer Panels

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 833 ◽  
Author(s):  
Claudio Del Menezzi ◽  
Siham Amirou ◽  
Antonio Pizzi ◽  
Xuedong Xi ◽  
Luc Delmotte
Keyword(s):  
Citric Acid ◽  
Model Compound ◽  
Magic Angle Spinning ◽  
Hydroxyl Groups ◽  
Magic Angle ◽  
Wood Veneer ◽  
Ionization Time ◽  
Angle Spinning ◽  
Wood Surfaces ◽  
Cp Mas 13C Nmr

The reaction of citric acid with wood veneers was studied by Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP MAS 13C NMR) and matrix assisted laser desorption ionization time of flight (MALDI ToF) mass spectrometry. The analysis showed that reactions of citric acid occurred with both lignin and carbohydrate constituents of wood. The reactions occurring are esterifications between the carboxylic acid functions of citric acid and the numerous aromatic and aliphatic hydroxyl groups of the main wood constituents. Reaction of citric acid with glucose as a simple model compound of carbohydrates hydroxyl groups also yielded reactions leading to linear and branched oligomers by esterification. The result indicate that the reactions of esterification are accompanied in parallel by some internal rearrangements of lignin. The applied results on bonding wide flat wood surfaces such as veneers to obtain LVL panels yielded excellent strength results even if the conditions of pressing were more drastic than what is usual for this application. The applied bonding results have shown that citric acid has great potential to be used as a bio-binder for wood veneers.

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