Solid-state 13C Nuclear Magnetic Resonance Research Articles

Bacterial Cellulose Hybrid Composites with Calcium Phosphate for Bone Tissue Regeneration.

Bacterial cellulose (BC) is a unique microbial biopolymer with a huge number of significant applications in the biomedical field, including bone tissue engineering. The present study proposes to obtain and characterize BC hybrid composites with calcium phosphate as biocompatible and bioactive membranes for bone tissue engineering. BC precursor membranes were obtained in static culture fermentation, and after purification, were oxidized to obtain 2,3-dialdehyde bacterial cellulose (DABC). Calcium phosphate-BC oxidized membranes were produced by successive immersion in precursor solutions under ultrasonic irradiation. The samples were characterized for their physicochemical properties using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy grazing incidence X-ray diffraction (GI-XRD), solid-state 13C nuclear magnetic resonance (CP/MAS 13C NMR), and complex thermal analysis. In vitro cell studies were also performed to evaluate the influence of modified morphological characteristics on cell adhesion and proliferation. The results showed an increase in porosity and biodegradability for DABC hybrid composites compared with BC. In vitro cell studies have revealed that both hybrid composites favor cell adhesion to the surface. The new BC and DABC hybrid composites with calcium phosphate could be considered promising materials for bone tissue regeneration.

Spectroscopic, thermal, and mechanical characterization of the polymeric fabrics used in extreme low-temperature protective garments

This paper presents the study of the chemical and physico-mechanical properties of the natural and synthetic fabrics used in extreme low-temperature (−20 °C) gloves. The essential properties, such as the weight of the gloves, cold insulation, and surface water repellency, were studied. In-depth analysis by 13C solid-state nuclear magnetic resonance spectroscopy (13C SSNMR), attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR), and differential scanning calorimetry (DSC) techniques were undertaken to understand the chemical and thermal characteristics of the fabrics. The physico-mechanical properties, such as thickness, weight, softness, tear strength, abrasion resistance, blade cut resistance, and puncture resistance, of each fabric used in the gloves, were also studied. Finally, the physico-mechanical properties were correlated with the chemical nature of the fabrics and the garment's performance properties.The present study will guide in the selection of materials for designing low-temperature protective garments. The in-depth analysis presented in this work will also help the researchers in the chemical identification of natural and synthetic polymeric fabrics using solid-state NMR, ATR-FTIR, and DSC techniques.

Adsorption and Release Properties of Drug Delivery System Naproxen-SBA-15: Effect of Surface Polarity, Sodium/Acid Drug Form and pH.

Mesoporous silica SBA-15 was prepared via sol-gel synthesis and functionalized with different types of organosilanes containing various organic functional groups: (3-aminopropyl)triethoxysilane (SBA-15-NH2), (3-mercaptopropyl)triethoxysilane (SBA-15-SH), triethoxymethylsilane (SBA-15-CH3), triethoxyphenylsilane (SBA-15-Ph), and (3-isocynatopropyl)triethoxysilane (SBA-15-NCO). The prepared materials were investigated as drug delivery systems for naproxen. As model drugs, naproxen acid (HNAP) and its sodium salt (NaNAP) were used. Mentioned medicaments belong to the group of non-steroidal anti-inflammatory drugs (NSAIDs). The prepared materials were characterized by different analytical methods such as transmission electron microscopy (TEM), infrared spectroscopy (IR), nitrogen adsorption/desorption analysis (N2), thermogravimetric analysis (TG), 1H, 13C and 23Na solid-state nuclear magnetic resonance spectroscopy (1H, 13C and 23Na ss-NMR). The abovementioned analytical techniques confirmed the successful grafting of functional groups to the SBA-15 surface and the adsorption of drugs after the impregnation process. The BET area values decreased from 927 m2 g-1 for SBA-15 to 408 m2 g-1 for SBA-15-NCO. After drug encapsulation, a more significant decrease in surface area was observed due to the filling of pores with drug molecules, while the most significant decrease was observed for the SBA-15-NH2 material (115 m2 g-1 for NaNAP and 101 m2 g-1 for HNAP). By combining TG and nitrogen adsorption results, the occurrence of functional groups and the affinity of drugs to the carriers' surface were calculated. The dominant factor was the volume of functional groups and intermolecular interactions. The highest drug affinity values were observed for phenyl and amine-modified materials (SBA-15-Ph = 1.379 μmol m-2 mmol-1 for NaNAP, 1.761 μmol m-2 mmol-1 for HNAP and SBA-15-NH2 = 1.343 μmol m-2 mmol-1 for NaNAP, 1.302 μmol m-2 mmol-1 for HNAP) due to the formation of hydrogen bonds and π-π interactions, respectively. Drug release properties and kinetic studies were performed at t = 37 °C (normal human body temperature) in different media with pH = 2 as simulated human gastric fluid and pH = 7.4, which simulated a physiological environment. Determination of drug release quantity was performed with UV-VIS spectroscopy. The surface polarity, pH and naproxen form influenced the total released amount of drug. In general, naproxen sodium salt has a higher solubility than its acid form, thus significantly affecting drug release from surface-modified SBA-15 materials. Different pH conditions involved surface protonation and formation/disruption of intermolecular interactions, influencing both the release rate and the total released amount of naproxen. Different kinetic models, zero-order, first-order, Higuchi and Hixson-Crowell models, were used to fit the drug release data. According to the obtained experimental results, the drug release rates and mechanisms were determined.

Pharmaceutical Co-crystal of Antiviral Agent Efavirenz with Nicotinamide for the Enhancement of Solubility, Physicochemical Stability, and Oral Bioavailability.

The present research work attempted to improve the oral bioavailability of the antiviral drug Efavirenz (EFV) using a pharmaceutical cocrystallization technique. EFV comes under BCS-II and has extremely low water solubility, and results in low oral bioavailability. EFV and nicotinamide (NICO) were selected in a (1:1) stoichiometric ratio and efavirenz nicotinamide cocrystal (ENCOC) was prepared through the liquid-assisted grinding method (LAG). The confirmation of the formation of a new solid phase was done through spectroscopic techniques like Fourier transmission infrared (FTIR), Raman, and 13C solid-state nuclear magnetic resonance (13C ssNMR). Thermal techniques like differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and hot stage microscopy (HSM) illustrated the thermal behavior and melting patterns of ENCOC, EFV, and NICO. The X-ray powder diffraction (XRPD) confirms the formation of a new crystalline phase in ENCOC. The Morphology was determined through scanning electron microscopy (FESEM). The results of saturated solubility studies andin vitro drug release studies exhibited 8.9-fold enhancement in solubility and 2.56-fold enhancement in percentage cumulative drug release. The percentage drug content of ENCOC was found higher than 97% and cocrystal exhibits excellent accelerated stability. The oral bioavailability of EFV (Cmax, 799.08ng/mL) exhibits significant enhancement after cocrystallization (Cmax, 5597.09ng/mL) than EFV and Efcure®-200 tablet (2896.21ng/mL). The current work investigates the scalable and cost-effective method for enhancement of physicochemical stability, solubility, and oral bioavailability of an antiviral agent EFV.

Effect of citric acid esterification on the structure and physicochemical properties of tigernut starch

In this work, esterified tigernut starch with citric acid (ETSC) was prepared for the first time, and its structure, in vitro digestibility, and Pickering emulsifying capacity were investigated. The formation of ETSC was confirmed by SEM (Scanning electron microscopy), XRD (X-ray diffraction), FTIR (Fourier-transform infrared spectroscopy), and solid-state 13C NMR (Nuclear magnetic resonance), and the citric acid dosage in the preparation process was positively correlated with the degree of substitution (DS) of ETSC. With an increase in DS, the solubility and swelling power of ETSC decreased, the crystallinity degree declined, and the proportion of resistant starch (RS) increased rapidly. The increase in DS could also enhance the wettability of ETSC, thus improving the Pickering emulsifying ability of ETSC. The high ETSC concentration (c) and suitable oil phase volume ratio (φ) of the Pickering emulsion were beneficial to its formation and stability. Moreover, the macroscopic viscosity index (MVI) and elastic index (EI) of the emulsion were also positively related to the DS of ETSC.

Solid-State Nuclear Magnetic Resonance of Triple-Cation Mixed-Halide Perovskites.

Mixed-cation lead mixed-halide perovskites are the best candidates for perovskite-based photovoltaics, thanks to their higher efficiency and stability compared to the single-cation single-halide parent compounds. TripleMix (Cs0.05MA0.14FA0.81PbI2.55Br0.45 with FA = formamidinium and MA = methylammonium) is one of the most efficient and stable mixed perovskites for single-junction solar cells. The microscopic reasons why triple-cation perovskites perform so well are still under debate. In this work, we investigated the structure and dynamics of TripleMix by exploiting multinuclear solid-state nuclear magnetic resonance (SSNMR), which can provide this information at a level of detail not accessible by other techniques. 133Cs, 13C, 1H, and 207Pb SSNMR spectra confirmed the inclusion of all ions in the perovskite, without phase segregation. Complementary measurements showed a peculiar longitudinal relaxation behavior for the 1H and 207Pb nuclei in TripleMix with respect to single-cation single-halide perovskites, suggesting slower dynamics of both organic cations and halide anions, possibly related to the high photovoltaic performances.

Flocculation performance and evaluation of a sulfur-containing tannin flocculant for Cu2+ removal

To introduce sulfur compounds into tannin-based flocculants, thiosemicarbazide (TC) was selected as a raw material to react with black wattle bark tannin and formaldehyde through the Mannich reaction in order to synthesize a sulfur-containing tannin flocculant (TFA) with the functions of chelation, flocculation and precipitation. The physicochemical characteristics of TFA were characterized by elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR), 13C solid-state nuclear magnetic resonance (13C NMR) and zeta potential to identify the successful synthesis. The flocculation performance of TFA was evaluated by measuring the Cu2+ removal rate. The effects of pH, initial Cu2+ concentration, TFA dosage, coexisting inorganic compounds and organic complexing agents on the Cu2+ removal rate were investigated through flocculation experiments. The results showed that the Cu2+ removal rate increased with increasing pH and the maximum Cu2+ removal rate for 5, 10 and 25 mg/L initial Cu2+ reached 100 % by raising the TFA dosage. Coexisting inorganic compounds, such as KCl, NaCl, CaCl2, MgCl2, NaNO3, and Na2SO4, had a negligible impact on Cu2+ removal, while the presence of organic complexing agents (humic acid, disodium ethylenediamine tetraacetate, citric acid and aminoacetic acid) had a significant influence on Cu2+ removal. The flocculation mechanisms of Cu2+ by TFA mainly involved a combination of bridge-aggregation and chelating precipitation, accompanied by a sweeping effect.

Structure identification of binary (cyclic alcohol guests + methane) clathrate hydrates using Rietveld analysis with the direct space method

Herein, the alcohol inclusion and interactions occurring in binary (cyclobutanol + CH4), (cyclopentanol + CH4), and (cyclohexanol + CH4) clathrate hydrates were investigated using Rietveld analysis with the direct space method. The alcohol geometry in the hydrate cages of the binary-hydrates was examined using 13C solid–state nuclear magnetic resonance spectroscopy and density function theory calculations. Structural characterization of the binary-hydrates indicated that OH groups of the alcohols may interact with the host-framework via hydrogen-bonding. Additionally, the possibility of OH group incorporation of cyclic alcohols into the host framework should be conducted in the future.

Maturity trends for the Late Devonian Duvernay Formation and identification of the Willesden-Green Maturity High

Maturity trends appearing in the literature for the Late Devonian Duvernay Formation within the Western Canada Sedimentary Basin (WCSB) are inconsistent and do not reflect hydrocarbon production. To address these inconsistencies and more accurately delineate Duvernay maturity trends, this study produces solid-state 13C Nuclear Magnetic Resonance (NMR) spectroscopy and Rock-Eval Tmax data from 38 wells throughout the WCSB. The Duvernay is divided into three different assessment areas that include, from east to west, Innisfail, Willesden-Green, and Kaybob. Based upon the proportion of aromatic to aliphatic carbon of the source rock organic matter, the Duvernay maturity generally increases towards the southwest and mimics structural depth, except within the Willesden-Green area. The Innisfail area has the shallowest depths and only the southern portion reaches oil maturity. The Willesden-Green and Kaybob areas range from oil to dry gas maturity. Although Willesden-Green and Kaybob have similar structural depths (P = 0.24), they have a significant difference in solid-state 13C NMR proportion of aromatic to aliphatic (P = 0.05) and Tmax values (P = 0.00). The average residuals from the depth vs solid-state 13C NMR proportion of aromatic carbon and Tmax best fit line show an increase of 0.09 and 10 °C respectively in Willesden-Green compared to Kaybob. Maps of the maturity indicators show the increase in maturity within Willesden-Green is perpendicular to structural strike. This study names this anomalous feature the Willesden-Green Maturity High.

Evolution of mechanical properties of kerogen with thermal maturity

Kerogen is the most abundant form of naturally occurring organic matter in organic-rich shale, and it can affect the macro-mechanical characteristics of shale reservoirs during the whole shale thermal evolution process. However, the magnitude and mechanism of this effect are not clear. Here, a relatively low-maturity kerogen isolated from an organic-rich shale was used to prepare a series of kerogen samples of different maturities in an artificial pyrolysis experiment. Raman spectroscopy and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy were used to determine changes in the chemical structures of the kerogen samples, and in situ nanoindentation analysis was employed to characterize the evolution of their mechanical properties. Raman spectral analyses indicate that Raman band separation (RBS) is very sensitive to thermal maturity, increasing with maturity and displaying a strong linear correlation with mechanical properties of kerogen such as hardness and Young's modulus. Based on the solid-state 13C NMR and nanoindentation analysis, the evolution of kerogen mechanical properties with maturity can be divided into two stages: oil-generation wet-gas stage (corresponding to 0.7%–2.5% EasyRo), and dry-gas stage (2.5%–4.5% EasyRo). In the former, kerogen exhibits a soft nature with relatively low hardness and Young's modulus, possibly attributable to its relatively large proportion of aliphatic carbon and long-chain alkanes. When maturity reaches the gas stage, kerogen becomes increasingly stiff due to the markedly increased proportion of aromatic and bridgehead carbon. Considering the strong positive correlation between mechanical parameters and chemical-structure parameters (RBS, and aromatic and bridgehead carbon ratios) of kerogen during the overall thermal evolution process, we suggest that the stiffening of kerogen may result from the decreasing content of aliphatic chains and increasing aromatic carbon. This study will be beneficial to the development of rock mechanical models that are critical for accurately evaluating borehole stability and optimizing hydraulic fracture design.

Impact of residual extractives on the thermal stability of softwood Kraft pulp

Wood extractives are known to cause problems during the production of pulp and paper and to impact their mechanical properties. In the present work, we systematically explored whether minute residual amounts of extractives that reprecipitate on the fiber surface in the final stages of the pulping process would lower the thermal resilience of softwood Kraft pulp. Pulp samples subjected to different extraction methods were characterized by means of thermogravimetric analysis. The compound classes constituting the respective extracts were identified and quantified via gas chromatography-mass spectrometry/flame ionization detector (GC-MS/FID) and the influence of the individual compound classes on the thermal stability of the samples was investigated separately. Soxhlet extraction with an ethanol/toluene solvent system clearly led to increased thermal stability. Besides fatty acids and resin acids also sterols and sterol esters that do not carry carboxylic acid functionalities contributed to the deterioration of the thermal pulp properties. Lateral order indices derived from Fourier transformed infrared spectra and crystallinity indices derived from solid-state 13C nuclear magnetic resonance spectra indicate that upon thermal degradation, the presence of even minute amounts of extractives leads to an increased degree of supramolecular disorder. Moreover, the characterization of the samples’ carbohydrate composition by means of acidic hydrolysis showed a tendency towards facilitated pyrolysis of the hemicelluloses if extractives were present in the pulp.

Hydration of Wheat Flour Water-Unextractable Cell Wall Material Enables Structural Analysis of Its Arabinoxylan by High-Resolution Solid-State 13C MAS NMR Spectroscopy.

To enable its structural characterization by nuclear magnetic resonance (NMR) spectroscopy, the native structure of cereal water-unextractable arabinoxylan (WU-AX) is typically disrupted by alkali or enzymatic treatments. Here, WU-AX in the wheat flour unextractable cell wall material (UCWM) containing 40.9% ± 1.5 arabinoxylan with an arabinose-to-xylose ratio of 0.62 ± 0.04 was characterized by high-resolution solid-state NMR without disrupting its native structure. Hydration of the UCWM (1.7 mg H2O/mg UCWM) in combination with specific optimizations in the NMR methodology enabled analysis by solid-state 13C NMR with magic angle spinning and 1H high-power decoupling (13C HPDEC MAS NMR) which provided sufficiently high resolution to allow for carbon atom assignments. Spectral resonances of C-1 from arabinose and xylose residues of WU-AX were here assigned to the solid state. The proportions of un-, mono-, and di-substituted xyloses were 59.2, 19.5, and 21.2%, respectively. 13C HPDEC MAS NMR showed the presence of solid-state fractions with different mobilities in the UCWM. This study presents the first solid-state NMR spectrum of wheat WU-AX with sufficient resolution to enable assignment without prior WU-AX solubilization.

Burn Intensity Drives the Alteration of Phenolic Lignin to (Poly) Aromatic Hydrocarbons as Revealed by Pyrolysis Gas Chromatography-Mass Spectrometry (Py-GC/MS).

High-intensity wildfires alter the chemical composition of organic matter, which is expected to be distinctly different from low-intensity prescribed fires. Herein, we used pyrolysis gas chromatography/mass spectrometry (Py-GC/MS), in conjunction with solid-state 13C nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopy, to assess chemical alterations from three wildfires and a long-term frequent prescribed fire site. Our results showed that black ash formed under moderate intensity burns contained less aromatic (ArH), polyaromatic hydrocarbon (PAH), and nitrogen-containing compounds (Ntg) but more lignin (LgC) and phenol compounds (PhC), compared to white ash formed under high intensity burns. Both 13C NMR and FT-IR confirmed a higher relative percentage of carboxyl carbon in white ash, indicating the potential for higher water solubility and more mobile carbon, relative to black ash. Compared to wildfires, ash from low-intensity prescribed fire contained less ArH, PAH, and Ntg and more LgC and PhC. Controlled laboratory burning trials indicated that organic matter alteration was sensitive to the burn temperature, but not related to the fuel type (pine vs fir) nor oxygen absence/presence at high burn temperatures. This study concludes that higher burn temperatures resulted in higher (poly)aromatic carbon/nitrogen and lower lignin/phenol compounds.

Alder encroachment alters subsoil organic carbon pool and chemical structure in a boreal peatland of Northeast China

Boreal peatlands have been experiencing increased abundances of symbiotic dinitrogen-fixing woody plants (mainly alder species). However, how alder encroachment alters soil organic carbon (C) pool and stability is unclear. To examine the effects of alder encroachment on soil organic C, we measured soil organic C pool, phenol oxidase (POX) activity, organic C mineralization rate, and organic C chemical structure (alkyl C, O-alkyl C, aromatic C, and carbonyl C) using solid-state 13C nuclear magnetic resonance spectroscopy in the 0–10 cm, 10–20 cm, and 20–40 cm depths in the Alnus sibirica islands and adjacent open peatlands in the north of Da'xingan Mountain, Northeast China. A. sibirica islands had 28 %, 25 %, and 30 % greater POX activity and 36 %, 31 %, and 100 % higher organic C mineralization than open peatlands in the 0–10 cm, 10–20 cm, and 20–40 cm soil depths, respectively. Despite no significant changes in the 0–10 cm and 10–20 cm depths, alder encroachment reduced soil organic C pool in the 20–40 cm depth. Soil organic C pool in the 0–40 cm depth was lower in A. sibirica islands (298 Mg ha−1) than in the open peatlands (315 Mg ha−1). Moreover, alder encroachment increased alkyl (7 %) and carbonyl (57 %) C fractions but reduced O-alkyl C fraction (16 %) in the 20–40 cm depth, resulting in increased aliphaticity and recalcitrance indices. These findings suggest that alder encroachment will reduce soil organic C accumulation by accelerating microbial decomposition, and highlight that increased biochemical stabilization would attenuate soil organic C loss after alder expansion in boreal peatlands. Our results will help assess and project future C budgets in boreal peatlands.

Removal of anionic and cationic dyes using porous copolymer networks made from a Sonogashira cross‐coupling reaction of diethynyl iron (II) clathrochelate with various arylamines

AbstractFour copolymers containing alternating units of iron(II) clathrochelate with various arylamine CLA1‐4 were synthesized via a palladium‐catalyzed Sonogashira cross‐coupling reaction using an iron(II) clathrochelate synthon end‐capped with ethynyl groups with various brominated arylamine derivatives. Target copolymers CLA1‐4 were characterized by various instrumental analysis techniques, such as, solid‐state 13C‐nuclear magnetic resonance (SSNMR), Fourier transform infrared (FTIR), and X‐ray photoelectron spectroscopy (XPS). Thermogravimetric analysis (TGA) disclosed the superior thermal stability of the target copolymers with 10% weight loss temperature values up to ~340°C. Nitrogen adsorption measurements of CLA1‐4 using Brunauer–Emmet–Teller (BET) model revealed their porous nature with a surface area and porosity up to ~411 m2 g−1 and 0.411 cm3 g−1, respectively. Interestingly, CLA1‐4 disclose efficient adsorption of both cationic and anionic organic dyes, such as, Methylene Blue (MEB), Rhodamine B (RB), Congo Red (CR), Methyl orange (MO), and Acid orange 7 (AO7) from aqueous solutions. Furthermore, the isothermal adsorption study divulges the CLA4 uptake from aqueous solution of MEB and CR following the Langmuir model with a maximum adsorption capacity (qm) of 146.63 mg g−1 and 787.40 mg g−1, respectively.

Organic matter biomarker and 13C NMR characteristics of soil and sediment standard reference materials from China.

Soil and sediment organic matter (OM) in terrestrial environments represent two critical organic carbon pools on Earth and are likely subject to distinct degrees of oxidation and modification. However, few studies have identified critical molecular-level characteristics that differentiate soil and sediment OM from various climate zones. Using biomarkers and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy analyses, we studied the OM characteristics of 11 soil and 7 sediment standard reference materials (SRMs) originating from various geographical locations in China. Results showed significantly higher concentrations of lignin phenols in sediment OM than in soil OM, which may result from protection by higher contents of CaO and less microbial degradation in sediments. Nevertheless, the relative abundances of solvent-extractable lipids (alkanes, alkanols, and alkanoic acids) and ester-bound cutin and suberin biomarkers did not differ significantly between soil and sediment SRMs. The concentrations of lignin biomarkers decreased with increasing weathering degree of the soil, while cutin biomarkers increased with mean annual temperature and precipitation. This phenomenon was not observed in sediment SRMs. This study reveals the distinct OM characteristics between Chinese soil and sediment SRMs and provides fundamental data for future studies to link OM characteristics and functions.

Baloxavir Marboxil Shows Anomalous Conversion of Crystal Forms from Stable to Metastable through Formation of Specific Solvate Form

Baloxavir marboxil is a novel cap-dependent endonuclease inhibitor of influenza. This study aimed to identify its polymorphs and their relationship with crystal engineering. Polymorph screening by evaporation gave forms I–III and solvate forms IV and V. Heating enabled the conversion of form III to form II, but did not enable that of forms I and II. The solvent-mediated transformation of the forms I–III by magnetic stirring in various solvents resulted in the formation of form I. These results indicate that form I is the stable form. However, all crystal forms transformed to form II after magnetic stirring in a 50% acetonitrile aqueous solution, which was not obtained from water or acetonitrile. The suspension in a 50% acetonitrile aqueous solution exhibited a novel X-ray diffraction pattern as shown in form VI. The measurement of the suspension by solid-state 13C-nuclear magnetic resonance revealed that the spectra of forms II and VI were similar. From these results, we conclude that the drug forms a solvate with both water and acetonitrile and spontaneously transforms to form II upon rapid desolvation under ambient conditions. This study elucidates the mechanism of unexpected convergence to a metastable form in a specific solvent and contributes to the crystal engineering of baloxavir marboxil.

Role of the sedimentary organic matter structure and microporosity on the degradation of nonylphenol by potassium ferrate

In this study, the role of organic matter structure and microporosity in the adsorption and degradation of radioactive nonylphenol in sediments treated with potassium ferrate solutions was investigated. The demineralized fractions and acid non-hydrolyzable fractions were isolated and characterized via advanced solid-state 13C nuclear magnetic resonance and CO2 gas adsorption technology, respectively. Radioactive nonylphenol in the sediments was also fractionated into 14CO2, water-soluble residues, extractable residues, and strongly bound residues after treatment with potassium ferrate. A first-order, two-compartment kinetic model well described the mineralization and degradation kinetics of radioactive nonylphenol in the sediment (R2 > 0.99). The degradation percentages of spiked nonylphenol were highly negatively correlated with aromatic carbon, aliphatic carbon, and microporosity estimated from acid-non-hydrolyzable fractions in the bulk sediments (R2 > 0.82, p < 0.01). The percentages of adsorbed parent nonylphenol residues were highly positively correlated with aromatic carbon, aliphatic carbon, and microporosity estimated from acid-non-hydrolyzable fractions in the bulk sediments (R2 > 0.90, p < 0.01). The parent nonylphenol compound desorbed into the aqueous phase and was completely degraded. This study is the first to demonstrate the important role of aromatic carbon, aliphatic carbon, and microporosity in acid non-hydrolyzable fractions on the degradation of nonylphenol during the potassium ferrate oxidation treatment process.

Solid-state 1H and 13C NMR studies of novel ionic rotator-crystals of [NEt x Me(3−x)R][BEt4] (R = Pr, Bu. x = 1, 2)

Abstract Four new ionic rotator-crystals of [NEt x Me(3−x)R][BEt4] (R = Pr, Bu; x = 1, 2) were observed. Rotator crystals (two-dimensional plastic crystals) are mesophases between solid and isotropic liquid phases. Solid-state 1H and 13C nuclear magnetic resonance (NMR) measurements revealed that the ellipsoidal cations of [NEt x Me(3−x)R]+ undergo uniaxial rotation about their N–R axis and libration motion of the axis, and the anions perform isotropic reorientations in the highest-temperature solid-phase (rotator phase). Differential scanning calorimetry (DSC) measurements showed small entropy changes of 8–11 J K−1 mol−1 at the melting point of the compounds. These results suggest that the cations and anions have large degrees of freedom of motion in the rotator phase. The diffraction patterns of X-ray diffraction (XRD) could be indexed to the trigonal structure (space group of P31c). Compared with the reported data for [NEt x Me(3−x)Pr][BEt3Me] (x = 1, 2) compounds, which also have rotator-crystal phases and transform to a plastic crystalline phase, a model that explains why the cations of [BEt4] salts hardly perform isotropic reorientation in the solid phases was proposed.

Preparation and characterization of a bio-based rigid plastic based on gelatinized starch cross-linked with furfural and formaldehyde

The extensive use and rapid consumption of energy especially with the shortage of oil-derived resources pushed researchers to focus on developing more biomass-based plastics. The current article presents the possibility to undergo polycondensation of gelatinized starch and corn-derived furfural in presence of formaldehyde under acidic conditions to produce a thermoplastic material, starch–furanic resin. The structure of resulting product was studied intensively using solid-state 13C nuclear magnetic resonance (NMR) and Raman spectroscopy. The glass transitions, molecular weight, and thermal stability of the developed material were investigated with techniques such as differential scanning calorimetry (DSC), gel permeation chromatograph (GPC) and thermogravimetric analysis (TGA). In addition, the morphological features of the material’s surface were studied with scanning electron microscopy (SEM). Moreover, the related properties of the plastic were characterized by the measurements of Brinell hardness and compression resistance. The plastic shows a smooth appearance without crack and bubbles, and exhibited a glass transition temperature as high as 129 °C and a 12% weight loss temperature of 200 ℃ in nitrogen. All these results support that the condensation reactions between the gelatinized starch and aldehydes were more appropriate under acidic conditions to yield more complicated network structure with better homogeneous microstructure, which revealed superior and comparable results to that of phenol-formaldehyde plastics.