Solid-state Carbon-13 Nuclear Magnetic Resonance Research Articles

Organo acid-activated clays for water treatment as removal agent of Eosin-Y: Properties, regeneration, and single batch design absorber

Organoclays have been proposed as efficient removal agents for colored wastewater treatment. In this study, organo-acid-activated clays were investigated for their ability to remove eosin Y dye molecules. Firstly, the clay was acid activated using sulfuric solution at 90 °C for overnight. Secondly, the resulting materials were treated by hexadecyltetramethylammonium bromide solutions to obtain organo-acid-activated clays. Several techniques were used, such as X-ray diffraction, carbon hydrogen nitrogen analysis, silicon-29 and carbon-13 solid-state nuclear magnetic resonance, and nitrogen adsorption isotherms. The cation exchange capacity values were reduced and the specific surface area values increased from 80.1 m2/g to 183.2 m2/g during the acid activation process. The resulting organo-acid-activated clays had a similar expansion of interlayer spacing of 3.90 nm with less intercalated hexadecyltetramethylammonium surfactants, ranging from 0.80 mmol/g to 1.22 mmol/g; 13C solid NMR indicated that the intercalated surfactants exhibited different degree of conformation. Many factors, including the solid dose, solution pH, amount of intercalated surfactants, and starting eosin-Y concentrations, were studied in relation to the removal capabilities of organo acid-activated clays. Based on the Langmuir model, the removal capacity of the organo acid-activated clays ranged from a minimum of 43.5 mg/g to a maximum of 79.3 mg/g, dependent on the surfactant quantities and acid activation degree. , and the pH. The removal percentage of eosin-Y was increased from 50.5 % to 80.8 % by treating the organo acid-activated clay with HCl solution before the removal procedure. Regeneration and reuse of two selected organo acid-activated clays were carried out for seven successive cycles, and a reduction in the initial efficiency was in the range of 26.4 %–30.1 %. However, for organoclay (without acid activation), approximately 52.1 % efficiency was maintained. Using the Langmuir model and mass balance equations, a single-stage adsorber design was suggested for different dye volumes at a constant starting concentration.

Preparation of chitosan-graft N-hydroxyethyl acrylamide copolymers as an in vitro-engineered skin

Amino-polysaccharides derivatives such as grafted chitosan (CS) have attracted increasing interest in biotechnology. The work aims to assess the novel CS-g-PHEAA as a model for in vitro-engineered skin. Gamma radiation-induced copolymerization has achieved N-hydroxyethyl acrylamide (HEAA) grafting onto CS. The functionalization of CS by the amino group has been confirmed through solid-state carbon-13 nuclear magnetic resonance. As evidenced by cell metabolic activity, viability, and proliferation results of human dermal fibroblast (HDF) co-cultivated with the biomaterials, the biological assays are independent of the choice of solvent. Also, the grafting degree, the HDF growth, and monolayer migration favored using CS-g-PHEAA prepared in bulk. Hence, it has potential as a future bioengineered skin substitute material.

Mechanism of carbon structure transformation in plastic layer and semi-coke during coking of Australian metallurgical coals

The transformation of the carbon structure of coal during the coking process influences the coke microstructure and microtexture, and ultimately, the coke quality. This study investigates the impacts of parent coal properties on the evolution of carbon structures of selected Australian coals from the plastic layer to semi-coke stage during coking using electron spin resonance (ESR), Synchrotron attenuated total reflection Fourier transform infrared microspectroscopy (Synchrotron ATR-FTIR) and solid-state carbon-13 nuclear magnetic resonance (13C NMR) analyses. The stable radical concentration, the g-value, and the linewidth measured by ESR were combined with IR and Solid-state 13C NMR results to improve the understanding of carbon structural transformation at the plastic and post-resolidification stages of coke formation. In addition, micro gas chromatography (micro-GC) was used to study the evolution of gaseous species. The results suggested that the coal undergoes crosslinking reaction, condensation, and re-polymerization within the thermoplastic range, resulting in loss of oxygen to form condensed carbon-bearing crosslinking structures. Due to differences in their chemical structure, macerals significantly influenced crosslinking structures during plastic layer formation. Higher rank coals generated more stable radicals in the plastic phase due to their lower H/C and O/C ratios than low-rank coals with higher vitrinite contents. Lower fluidity and lower rank coals formed oxygen-bearing cross-links at the early plastic stages, hindering fluidity development and carbon ordering at high temperatures. Above the resolidification point, the continuous transformation of C-O and C–H bonds to C–C bonds was accompanied by the release of H2 and CO2, leading to increased ordering and anisotropy of coke carbon structures.

Characterisation of compound middle lamella isolated by a combination of wet-beating, sedimentation, and methanol dialysis

Abstract A simple method was developed to isolate the compound middle lamella (CML) in its natural state using wet-beating, sedimentation, and methanol dialysis. The isolated CML fraction was characterised. The CML was isolated in 2.0% yield from the mature wood of Ginkgo biloba. Scanning electron microscopy (SEM) images of the isolated CML fraction showed the presence of flake-like structures. However, some small amounts of secondary wall substance was observed. The lignin content of the CML fraction was approximately 45%. Thioacidolysis reactions with the isolated CML fraction revealed that the lignin β-O-4 structure was scarce in the isolated fraction and that numerous structures with two or more consecutive condensed-type bonds were present. Results from the solid-state carbon-13 nuclear magnetic resonance (13C NMR) experiments indicated that the CML fraction had low crystallinity, indicating low cellulose content. Liquid-state NMR analysis of the lignin from the CML fraction revealed the absence of p-hydroxyphenyl (H) units.

Decomposition of woody debris in Mediterranean ecosystems: the role of wood chemical and anatomical traits

Data about woody debris (WD) decomposition are very scarce for the Mediterranean basin. The specific aim of this work is to explore the relationships between WD traits with the decay rate. We carried out a three-year litterbag decomposition experiment using ten WD types incubated in two plant communities (i.e. shrubland and woodland) and in laboratory conditions. WD was characterized for 31 chemical and anatomical traits, including macro- and micronutrients, lignin, and cellulose as well as organic chemistry by Solid-state Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance (13C CPMAS NMR) and Fourier transform infrared spectroscopy/ Attenuated Total Reflection (FT-IR/ATR spectroscopy). WD decay rate was negatively associated with di-O-alkyl, lignin/N and C/N ratios, but positively with N concentration. Less consistent but positive correlations were recored for K, Mn, and Na concentration. The alkyl C and carboxylic C regions, associated with aliphatic and amide compounds, was positively correlated with WD decomposition. Conversely, di-O-alkyl C and O-alkyl C fractions, largely associated with cellulose and hemicellulose, were negatively correlated with WD decay rate. Finally, the positive correlation between Na concentration and WD mass loss in field conditions suggest a role of this neglected micronutrient for wood decomposition. WD specific density and anatomical features, have a minor capability to explain decomposition rate. Our findings demonstrate a major role of WD chemical traits in explaining the variability of decomposition in Mediterranean ecosystems.

13C CP/MAS NMR Can Discriminate Genetic Backgrounds of Rice Starch

Solid-state cross-polarization magic-angle spinning carbon-13 nuclear magnetic resonance (13C CP/MAS NMR) spectroscopy is used to analyze starch derived from plants including wheat, maize, and potato, but few reports have described its application to rice starch. Here, we combined 13C CP/MAS NMR with deconvolution and subtraction methods to analyze rice lines including mutants that are deficient in at least one enzyme involved in amylose and/or amylopectin biosynthesis. We found that differences in the content of ordered structures between rice lines could be evaluated using C1 signal deconvolution and subtraction. The content of the V-type ordered structure increased with increasing amylose content. Furthermore, starch derived from a starch synthase (SS) IIIa/starch branching enzyme (BE) IIb-deficient mutant formed B- and V-type ordered structures and significantly more nonordered structures than the other rice lines. These data indicate that 13C CP/MAS NMR analysis is useful for discriminating the genetic backgrounds of starch derived from different rice cultivars.

Room-Temperature Reduction of Graphene Oxide in Water by Metal Chloride Hydrates: A Cleaner Approach for the Preparation of Graphene@Metal Hybrids.

Headed for developing minimalistic strategies to produce graphene@metal hybrids for electronics on a larger scale, we discovered that graphene oxide (GO)-metal oxide (MO) hybrids are formed spontaneously in water at room temperature in the presence of nothing else than graphene oxide itself and metal ions. Our observations show metal oxide nanoparticles decorating the surface of graphene oxide with particle diameter in the range of 10–40 nm after only 1 h of mixing. Their load ranged from 0.2% to 6.3% depending on the nature of the selected metal. To show the generality of the reactivity of GO with different ions in standard conditions, we prepared common hybrids with GO and tin, iron, zinc, aluminum and magnesium. By means of carbon-13 solid-state nuclear magnetic resonance using magic angle spinning, we have found that graphene oxide is also moderately reduced at the same time. Our method is powerful and unique because it avoids the use of chemicals and heat to promote the coprecipitation and the reduction of GO. This advantage allows synthesizing GO@MO hybrids with higher structural integrity and purity with a tunable level of oxidization, in a faster and greener way.

Hydrothermal Synthesis and Structure of a Dinuclear Molybdenum(III) Hydroxy Squarate with a Mo-Mo Bond.

The reaction of molybdenum(II) and chromium(II) acetates with squaric acid in degassed and deionized water under hydrothermal conditions at 150 °C is described. The products have been formulated as M2(μ-OH)2(μ-C4O4)2(H2O)4·2H2O, where M = Cr (1) and Mo (2), based on combustion elemental analysis, infrared spectroscopy, magic angle spinning (MAS) solid-state carbon-13 nuclear magnetic resonance (NMR), and single-crystal X-ray diffraction. The edge-shared bioctahedral structures involve doubly bridging hydroxide ligands and μ-squarate ligands. The chromium compound lacks a direct metal–metal-bonding interaction, while in contrast the molybdenum compound contains a Mo–Mo bond [2.491(2) Å]. The nature of the Mo–Mo-bonding interaction is compared with that of other similar d3–d3 dimers.

Differences in swelling of chemical pulp fibers and cotton fibers – Effect of the supramolecular structure

The swelling and dissolution of cellulose are key parameters in the production of regenerated cellulose fibers. Since cotton is almost pure cellulose, it has been proposed that the recycling of cotton textiles may be accomplished through incorporating the cotton textiles into the production of regenerated cellulosic fibers. In this study, the supramolecular structure before and after pretreatment was characterized using solid-state carbon-13 nuclear magnetic resonance (13C NMR), and the findings related to the swelling of dissolving pulp and cotton were quantified with a fiber analyzer. The cotton and dissolving pulp samples were subjected to three different pretreatments: mild acid hydrolysis, acid hydrolysis in ethanol, and a hydrothermal treatment. The results showed that cotton was harder to swell than the dissolving pulp. This indicated that either waste cotton requires another type of activating pretreatment than those included in this study or very good solvents if it is to be included in the production of regenerated fibers.

Spectroscopic-Chemical Fingerprint and Biostimulant Activity of a Protein-Based Product in Solid Form.

A solid biostimulant (AA309) obtained through thermobaric hydrolysis applied on trimmings and shavings of bovine hides tanned with wet-blue technology was chemically characterized, and its effects in maize (Zea mays L.) were evaluated. AA309 contained 13.60% total nitrogen (N), mainly in organic forms (13.40%), and several amino acids, especially lysine, phenylalanine, glycine, aspartate, and isoleucine. AA309 was further analyzed using Fourier Transform Infrared (FT-IR) spectroscopy, which revealed the presence of amide I and amide II bands, indicative of peptide structures. When supplied to maize plants for 15 days at two N dosages (2.1 or 4.2 mg/kg), AA309 induced positive physiological responses, likely because of its content in amino acids functioning as signaling molecules. The low dosage was the most effective in improving leaf (+24%) and root (+98%) dry weight, photosynthetic activity (+70%), and accumulation of N (+80%), proteins (+65–75%) and antioxidants (+60%). Spectroscopic analyses (Solid-state Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance, CP/MAS 13C–NMR, and High resolution-magic angle spinning nuclear magnetic resonance, HR-MAS NMR) on plant tissues revealed the increase in proteins, lignin structures and cutin in AA309-treated plants compared to untreated plants. Our results indicate that AA309 could be used as a valuable biostimulant in agriculture.

Effect of composition and microstructure of humic acid on 3,3',4,4'-tetrachlorobiphenyl sorption.

The fate and transport of polychlorinated biphenyls (PCBs), a class of persistent organic compounds, in soils was markedly affected by their sorption/desorption on soil organic matters (SOM) due to high hydrophobicity of PCBs. Humic acid (HA), an important fraction of SOM, has no steady composition and microstructure from different origins, resulting in their diverse sorption capacity. Therefore, the effect of composition and microstructure of HA on sorption of 3,3',4,4'-tetrachlorobiphenyl (PCB77) was investigated in this study. The primary sorption mechanism of PCB77 on HAs was also demonstrated by using Fourier transform infrared (FTIR) and solid-state carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy analysis. Elemental content analysis of three HAs showed that the content of unsaturated C (the total of aromatic, carboxylic, and carbonyl carbon) followed an order of YHA>SHA>AHA. Furthermore, YHA and SHA had remarkably rough and complicated particle surfaces but AHA had relatively smooth surface and the well-proportioned and interspersed particle sizes. The results of the sorption experiment showed that the sorption capacity of PCB77 on HAs followed a similar order of YHA>SHA>AHA, indicating the content of unsaturated C of HAs controlled the sorption of PCB77 on HAs. Sorption of PCB77 on either AHA or SHA did not change with increasing ionic strength of background solution, implying that there was no H-bond or electrostatic interaction between PCB77 and HAs. The result of FTIR and 13C-NMR spectra showed the primarily possible mechanism was π-π conjugative interaction and hydrophobic binding between PCB77 and HAs.

Electrooxidative Copolymerization of 3,4-Ethylenedioxithiophene and Benzene from a Mixture of Each Monomer

Abstract Electrooxidative copolymerization of 3,4-ethylenedioxithiophene (EDOT) and benzene from a mixture of the monomers with concentrations of 5 mM EDOT and 5 M benzene produced copolymer films on an anode surface. The formation of copolymer films and characterization of their electrochemical properties was confirmed using Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible absorption (UV–vis) spectroscopy, energy dispersive X-ray (EDX) spectroscopy, cyclic voltammetry (CV), and solid-state carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy measurements. Furthermore, the copolymerization ratio could be controlled by selection of the oxidation potential applied for copolymerization.

Spectroscopic and Thermal Studies of Polyalkoxysilanes and Silica-Chitosan Hybrid Materials

Polymers of organoalkoxysilanes (or polyalkoxysilanes) were synthesized through sol-gel process using different organosilanes: Tetraethylorthosilicate (TEOS), (3-Glycidyloxypropyl) trimethoxysilane (GPTMS), Trimethoxy(propyl)silane (TMPS), and/or Triethoxy(octyl)silane (EOS). Different carboxylic acids (acetic, formic, and citric) were used to prepare polyalkoxysilanes, with citric acid acting as a reactant rather than a catalyst for the sol-gel reaction. Silica-chitosan hybrid materials were synthesized reacting polyalkoxysilanes and chitosan, one of the most important and most studied natural polymers, through sol-gel process. The synthesized materials were characterized using Fourier transform infrared spectroscopy (FT-IR), thermogravimetrical analysis (TGA), differential Scanning Calorimetric (DSC) and solid-state Carbon-13 Nuclear Magnetic Resonance (solid-state   13C-NMR) spectroscopy, obtaining information on the structural properties of each modified materials. The results obtained by NMR indicate that the oxirane group of GPTMS remains in all reaction products to form different polyalkoxysilanes.

Distinctive organic matter pools among particle-size fractions detected by solid-state 13C-NMR, δ13C and δ15N analyses only after strong dispersion in an allophanic Andisol

We previously showed the first clear evidence of aggregate hierarchy in an Andisol by comparing the particle-size fractions released upon different levels of dispersion energy up to the maximum dispersion – sonication at 5 kJ mL−1 following sodium saturation. While smaller particles (< 2 μm) appeared to act as major binding agents, the variation in organic matter (OM) chemistry among the size fractions remains unstudied. Here, we focused on comparing the carbon structure and carbon and nitrogen stable isotope ratio (δ13C and δ15N) among the particle-size fractions isolated by limited dispersion (mechanical shaking) and by the maximum dispersion treatments for the allophanic Andisol previously examined. Both solid-state carbon-13 nuclear magnetic resonance (13C NMR)and stable isotope ratios showed clear differences among the size fractions after the maximum dispersion but not after the limited dispersion. From 2–53 μm toward the < 0.2 μm fraction, we observed a progressive decline in the proportion of aromatic-C and an increase in that of O-alkyl-C. Similarly, the enrichment of 13C and 15N toward the smaller particle size fractions was observed after the maximum dispersion. While δ15 N had progressive enrichment from 3.6‰ (53–4000 μm) to 6.4‰ (< 0.2 μm fraction), δ13C showed a 2.5–3.0‰ enrichment from the 53–4000 μm fraction (−24.0‰) to 2–53 μm fraction and remained largely constant between 0.2–2 μm and < 0.2 μm fractions. The sonication-induced redistribution and chemical alternation of OM appeared to be minor due to the small pool sizes of low-density materials (e.g., plant litter) and microbial biomass. The emergence of the size-dependent changes in C chemistry after the maximum dispersion was consistent with the Andisol aggregate hierarchy model we previously proposed. The observed difference in C/N ratio and isotopic ratios as well as C composition implies that the OM present in the sonication-resistant particles of < `2 μm sizes (that account for roughly 70% of total C and N) are highly recycled by and/or largely originated from soil microbes. The applicability of current findings to other samples (e.g., non-allophanic Andisols) should be examined to establish the unique role of OM-enriched, micron to submicron particles in the aggregate hierarchy of Andisols.

Chemical Investigation on Various Aromatic Compounds Polymerization in Low Pressure Helium Plasma

Remarkable properties of plasma polymer films are greatly dependent not only on the chemical structure of precursor but also on the reactor design and the deposition conditions. In many industrial applications it is a challenge to control the plasma polymer structure. In this paper we investigate the chemical transformation of various aromatic compounds, such as activation and fragmentation of substituent-part, aromatic ring opening, during plasma polymerization process. Polymerized films are deposited in a low- frequency capacitively coupled plasma-enhanced chemical vapour deposition reactor, working at low pressure. The chemical composition of plasma-polymerized films is elu- cidated by Fourier-transform infrared spectroscopy, solid-state carbon-13 nuclear magnetic resonance spectroscopy, and X-ray photoelectron spectroscopy. Based on spectroscopic measurements, the intermediary reactions during film growth may be presumed.

Decomposition differences of labile carbon from litter to soil in a tropical rain forest and rubber plantation of Xishuangbanna, southwest China

We used solid-state carbon-13 nuclear magnetic resonance (NMR) to compare chemical compositions of carbon in plant litter, forest floor and soil in a native seasonal rain forest (SR) with those in a rubber plantation (RP) in Xishuangbanna, southwest China. We also applied a sequential fumigation–incubation (SFI) procedure to characterize the chemical compositional change of soil organic carbon (SOC) during soil degradation. It was found that RP had 1.5–1.7 times greater in alkyl C0–45ppm proportions and smaller O-alkyls C45−110 fractions in litter and forest floor materials than SR. Degradation of labile organic carbon (LOC) in fresh litter was primarily limited to O-alkyl C and O2-alkyl C in both forests, suggesting litters of RP were less decomposable than that of SR. SOC in RP was 2.3 percent higher in aromatics C110–160ppm proportions and 0.03 percent in aromaticity value than those in SR. With the absence of new C input and fauna, degradation of soil LOC companied with loss of carbonyls C160−220ppm in RP, and alkyl C and aromatics C110–160ppm in SR. Our data indicated that rubber planting induced carbon loss and extensive humification in the soil. Sources of the decomposed soil LOC can compose of both simple and complex chemical compounds.

Characterization of Spent Catalysts during Hydrodemetallization of Atmosphere Residue

The deactivation behavior of industrial hydrodemetallization catalysts was investigated in the presented work. The main objective of the study is to contribute to a better understanding of the nature of the coke and metal deposition on the used catalysts by applying chemical analysis and various advanced analytical techniques, such as X-ray diffraction analysis (XRD), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), and solid-state carbon-13 nuclear magnetic resonance spectroscopy (13C NMR). The results are discussed scientifically based on the physico–chemical properties of origin and used catalysts.

Self-Assembled Columnar Structures of Swallow-Shaped Tetrathiafulvalene-Based Molecules

A series of swallow-shaped tetrathiafulvalene (TTF)-based liquid crystal (LC) molecules (a-6TTFn, where 6 represents the number of carbon atoms in the two tails of a-6TTFn and n is the even number of carbon atoms in the alkyl chains attached to the side of the asymmetric TTF mesogen, n = 6−12) was designed and synthesized. One of this series of swallow-shaped asymmetric TTF molecules (abbreviated as a-6TTF12) having 12 carbon atoms in the alkyl chains attached to the side of the asymmetric TTF mesogen served as an example in this study. Major phase transitions and their origins in a-6TTF12 were studied with combined techniques of differential scanning calorimetry (DSC), one-dimensional (1D) wide-angle X-ray diffraction (WAXD) and solid-state carbon-13 (13C) nuclear magnetic resonance (NMR) experiments. a-6TTF12 formed a highly ordered liquid crystalline (ΦLC) phase at higher temperatures and a crystalline (ΦCr) phase at lower temperatures. On the basis of the experimental results, it was found that the hi...

Atmospheric plasma deposition of diamond-like carbon coatings

The atmospheric pressure plasma-enhanced chemical vapor deposition of diamond-like carbon (DLC) has been investigated. The DLC coatings were grown with a mixture of acetylene, hydrogen and helium that was fed through a linear plasma source. The plasma was driven with radio frequency power at 27.12 MHz. Deposition rates exceeded 0.10 µm/min at substrate temperatures between 155 and 200 °C. Solid-state carbon-13 nuclear magnetic resonance revealed that the coatings contained approximately 43% sp 2-bonded carbon and 57% sp 3-bonded carbon. Coefficient of friction values for the coatings were found to be 0.24 ± 0.02, which is within the range observed for vacuum deposited DLC.

Synthesis, X-ray crystal structure, spectroscopic characterization, and thermal chemistry oftrans-diaqua-bis-(2-hydroxyiminopropionato-N,O)zinc(II),trans-{(H2O)2[H3CC([dbnd]NOH)COO)]2Zn}–A precursor for nano-crystalline zincite

Zinc(II) 2-oximinopropionate dihydrate [Zn(PAO)2(H2O)2] was precipitated by treatment of an aqueous solution of zinc sulfate with sodium pyruvate oxime, Na(PAO) · H2O. The product was characterized by infrared spectroscopy, solid-state carbon-13 nuclear magnetic resonance spectroscopy, X-ray diffraction (XRD), and thermal gravimetric and differential thermal analyses (TGA and DTA). A stepwise decomposition pathway was observed in the TGA trace of this complex. The product produced at each step was investigated by IR, XRD, solid-state, 13C NMR, and scanning and transmission electron microscopy (SEM and TEM). The crystallite size of the zincite was measured by XRD. Surface area of the zincite was also measured. Furthermore, the structure of the Zn(PAO)2(H2O)2 complex was established for the first time by X-ray single crystal diffraction of suitable crystals obtained in aqueous medium.