State 13C Nuclear Magnetic Resonance Research Articles

The Molecular Model of Organic Matter in Coal-Measure Shale: Structure Construction and Evaluation Based on Experimental Characterization

To investigate the molecular structure and micropore structure of organic matters in coal-measure shale, the black shale samples of the Shanxi formation were collected from Xishan Coalfield, Taiyuan, and a hybrid experimental–simulation method was used for realistic macromolecular models of organic matter (OM). Four experimental techniques were used to determine the structural information of OM, including elemental analysis, state 13C nuclear magnetic resonance (13CNMR), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). With structural parameters, two-dimensional (2D) average molecular models of OM were established as C177H160O8N2S with a molar weight of 2474, which agreed well with the experimental 13C-NMR spectra. A realistic three-dimensional (3D) OM macromolecular model was also reconstructed, containing 20 2D molecules with a density of 1.41 g/cm3. To determine the connectivity and spatial disposition of the OM pores, focused ion beam microscope (FIB-SEM) and transmission electron micrographs (TEM) were utilized. The 3D OM pores models were developed. The results show that whether the OM pores varied from 20 to 350 nm as obtained from FIB-SEM images or less than 10 nm as observed in the TEM images, both were of poor connectivity. However, the ultra-micro pores from the 3D OM macromolecular model varied from 3Å to 10 Å and showed certain connectivity, which may be the main channel of diffusion. Furthermore, with the pressure increased, the methane adsorption capacity of the 3D OM model increased with a maximum value of 103 cm3/g at 7 MPa, indicating that OM pores less than 1 nm have a huge methane adsorption capacity. Therefore, our work provides an analysis method that is a powerful and superior tool in further research on gas migration.

Development of highly-reproducible hydrogel based bioink for regeneration of skin-tissues via 3-D bioprinting technology

3-D Bioprinting is employed as a novel approach in biofabrication to promote skin regeneration following chronic-wounds and injury. A novel bioink composed of carbohydrazide crosslinked {polyethylene oxide-co- Chitosan-co- poly(methylmethacrylic-acid)} (PEO-CS-PMMA) laden with Nicotinamide and human dermal fibroblast was successfully synthesized via Free radical-copolymerization at 73 °C. The developed bioink was characterized in term of swelling, structural-confirmation by solid state 13C-Nuclear Magnetic Resonance (NMR), morphology, thermal, 3-D Bioprinting via extrusion, rheological and interaction with DNA respectively. The predominant rate of gelation was attributed to the electrostatic interactions between cationic CS and anionic PMMA pendant groups. The morphology of developed bioink presented a porous architecture satisfying the cell and growth-factor viability across the barrier. The thermal analysis revealed two-step degradation with 85 % weight loss in term of decomposition and molecular changes in the bioink moieties By applying low pressure in the range of 25–50 kPa, the optimum reproducibility and printability were determined at 37 °C in the viscosity range of 500–550 Pa. s. A higher survival rate of 92 % was observed for (PEO-CS-PMMA) in comparison to 67 % for pure chitosan built bioink. A binding constant of K ≈ 1.8 × 106 M−1 recognized a thermodynamically stable interaction of (PEO-CS-PMMA) with the Salmon-DNA. Further, the addition of PEO (5.0 %) was addressed with better self-healing and printability to produce skin-tissue constructs to replace the infected skin in human.

Chemical structure characteristics and multidimensional model construction of Fushun oil shale kerogen: An experimental and simulation study

Solid state 13C nuclear magnetic resonance (13C NMR), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) were carried out to characterize the chemical structure characteristics and to establish the average molecular structure of kerogen extracted from Fushun oil shale. NMR predictor was used to calculate the chemical shift of carbon atoms to verify the rationality of the constructed model. And the stability of 3D model was studied by molecular dynamics (MD) simulations. 13C NMR results demonstrate that Fushun kerogen consists of 76.98% of aliphatic structure dominated by long linear methylene and 21.6% of aromatic structure (mainly protonated aromatic carbon). Functional groups observed in 13C NMR spectra were also detected in FT-IR spectra at wavenumber range of 1800-1000 cm−1. XPS analysis indicates that nitrogen-containing groups were pyrrole, pyridine and primary amines, and sulfur existed as sulfoxides, thiophenes and mercaptans. By comparing the calculated 13C NMR and experimental 13C NMR, it was found that the aromatic structure condensed in two aromatic rings and the aliphatic structure without alicyclic and epoxy ether were more rational for the chemical structure model of Fushun kerogen. A new method to evaluate the average methylene chain length was proposed. Finally, a relatively rational 2D molecular structure with a molecular formula of C228H350O10N6S3 was constructed. The most stable 3D periodic structure (20 optimized molecules, 48.44 × 49.63 × 50.28 Å3) with the lowest total potential energy was obtained by MD simulation and density of it was 0.943 g/cm3.

Chlorine-free extraction and structural characterization of cellulose nanofibers from waste husk of millet (Pennisetum glaucum)

This study aims to extract cellulose nanofibers (CNFs) from a sustainable source, i.e. millet husk, which is an agro-waste worthy of consideration. Pre-treatments such as mercerisation, steam explosion, and peroxide bleaching (chlorine-free) were applied for the removal of non-cellulosic components. The bleached millet husk pulp was subjected to acid hydrolysis (5% oxalic acid) followed by homogenization to extract CNFs. The extracted CNFs were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Dynamic Light Scattering (DLS), Energy Dispersive X-ray Spectroscopy (EDX), Thermogravimetry (TG and DTG), Differential scanning calorimetry (DSC), and Solid state 13C nuclear magnetic resonance spectroscopy (solid state 13C NMR). The isolated CNFs show a typical cellulose type-I structure with a diameter of 10-12 nm and a crystallinity index of 58.5%. The appearance of the specific peak at 89.31 ppm in the solid state 13C NMR spectra validates the existence of the type-I cellulose phase in the prepared CNFs. The prepared CNFs had a maximum degradation temperature (Tmax) of 341 °C, that was 31 °C greater than raw millet husk (RMH). The outcome of the study implies that the nanofibers are prominent alternatives for synthetic fibers for assorted potential applications, especially in manufacturing green composites.

Folic acid and sodium folate salts: Thermal behavior and spectroscopic (IR, Raman, and solid-state 13C NMR) characterization

Folic acid (FA; vitamin B9) and its associated sodium salts, strongly relevant for many scientific and technological applications - from nutrition to pharmacology and nanomedicine, suffer from a lack of characterization combining experimental and theoretical. In this work, a spectroscopic investigation of FA and its synthesized sodium salts in the form of dianion (Na2HFol) or trianion (Na3Fol) was scrutinized in their solid state. The spectroscopic (infrared, Raman, and solid state 13C-nuclear magnetic resonance) data interpretation was supported by theoretical calculations using the Density Functional Theory (DFT). Additionally, the compounds were characterized by UV–VIS diffuse-reflectance spectroscopy, combined thermal analysis (TG/DTG-DSC) coupled to mass spectrometry, and X-ray diffractometry. The main signatures of each species were identified, as well as the influence of the protonation level on their physicochemical properties. These distinct properties for the three compounds are mainly based on signals assigned to glutamic acid (glutamate) and pterin (neutral or anionic) moieties. This work should help developing new products based on FA or its anionic forms, such as theragnostic/drug delivery systems, supramolecular structures, nanocarbons, or metal complexes.

The Thermo-Oxidative Behavior of Cotton Coated with an Intumescent Flame Retardant Glycine-Derived Polyamidoamine: A Multi-Technique Study

Linear polyamidoamines (PAAs) derived from the polyaddition of natural α-amino acids and N,N′-methylene bis(acrylamide) are intumescent flame retardants for cotton. Among them, the glycine-derived M-GLY extinguished the flame in horizontal flame spread tests at 4% by weight add-on. This paper reports on an extensive study aimed at understanding the molecular-level transformations of M-GLY-treated cotton upon heating in air at 300 °C, 350 °C and 420 °C. Thermogravimetric analysis (TGA) identified different thermal-oxidative decomposition stages and, coupled to Fourier transform infrared spectroscopy, allowed the volatile species released upon heating to be determined, revealing differences in the decomposition pattern of treated and untreated cotton. XPS analysis of the char residues of M-GLY-treated cotton revealed the formation of aromatic nanographitic char at lower temperature with respect to untreated cotton. Raman spectroscopy of the char residues provided indications on the degree of graphitization of treated and untreated cotton at the three reference temperatures. Solid state 13C nuclear magnetic resonance spectroscopy (NMR) provided information on the char structure as a function of the treatment temperature, clearly indicating that M-GLY favors the carbonization of cotton with the formation of more highly condensed aromatic structures.

Belowground allocation and dynamics of recently fixed plant carbon in a California annual grassland

Plant roots and the organisms that surround them are a primary source for stabilized soil organic carbon (SOC). While grassland soils have a large capacity to store organic carbon (C), few field-based studies have quantified the amount of plant-fixed C that moves into soil and persists belowground over multiple years. Yet this characteristic of the soil C cycle is critical to C storage, soil water holding capacity, nutrient provisions, and the management of soil health. We tracked the fate of plant-fixed C following a five-day 13CO2 labeling of a Northern California annual grassland, measuring C pools starting at the end of the labeling period, at three days, four weeks, six months, one year, and two years. Soil organic carbon was fractionated using a density-based approach to separate the free-light fraction (FLF), occluded-light fraction (OLF), and heavy fraction (HF). Using isotope ratio mass spectrometry, we measured 13C enrichment and total C content for plant shoots, roots, soil, soil dissolved organic carbon (DOC), and the FLF, OLF, and HF. The chemical nature of C in the HF was further analyzed by solid state 13C nuclear magnetic resonance (NMR) spectroscopy.At the end of the labeling period, a substantial portion of the 13C (40%) was already found belowground in roots, soil, and soil DOC. By 4 weeks, the highest isotope enrichment and 27% of the total amount of 13C remaining in the system was associated with the mineral-rich HF. At the 6-month sampling—after the dry summer period during which plants senesced and died—the amount of label in the FLF increased to an amount similar to that in the HF. The FLF 13C then declined substantially by 1 year and further decreased in the second year. By the end of the 2-year experiment, 67% of remaining label was in the HF, with 19% in the FLF and 14% in the OLF. While the 13C content in the HF was stable over the final year, the chemical forms associated with the HF evolved with time. The relative proportion of aliphatic/alkyl C functional groups declined in the newly formed SOC over the 2 years in the field; simultaneously, aromatic and carbonyl/carboxylic C functional groups increased and the proportion of carbohydrate (O-alkyl C) groups remained relatively constant.Our results indicate that plant-fixed C moved into soil within days of its fixation and was associated with the soil mineral fraction within weeks. While most of the annual plant C input in these grasslands cycles rapidly (<2-year timescale), a sizeable proportion (about 23% of the 13C present at day 0) persisted in the soil for longer than 2 years. While decadal studies would allow improved assessment of the long-term stabilization of newly fixed plant C, our 2-year field study reveals surprisingly rapid movement of plant C into the HF of soil, followed by subsequent evolution of the chemical forms of organic C in the HF.

Bionanocomposite Beads Based on Montmorillonite and Biopolymers as Potential Systems for Oral Release of Ciprofloxacin

AbstractThe number of studies of controlled drug-release systems is growing constantly. Bionanocomposite materials which can be prepared from the combination of biopolymers with inorganic solids such as clay minerals offer interesting alternatives for use as drug-delivery systems. In the present study, new bionanocomposite drug-release systems were prepared from the intercalation of the antibiotic drug ciprofloxacin into montmorillonite using an ion-exchange reaction. In order to prepare more stable systems for oral ciprofloxacin release, this ciprofloxacin-clay intercalation compound was incorporated into i-carrageenan-gelatin biopolymer blend to produce bionanocomposite materials. Bionanocomposites of two distinct i-carrageenan and gelatin mass ratios were conformed as beads through an ionic gelification reaction with Ca2+ ions, and dried by freeze-drying where liquid nitrogen or conventional freezing was adopted in the freezing step. The resulting ciprofloxacin-clay hybrid was characterized by X-ray diffraction (XRD) analysis, Fourier-transform infrared (FTIR) spectroscopy, solid state 13C Nuclear Magnetic Resonance (NMR), thermal analysis, and scanning electron microscopy (SEM). The montmorillonite-ciprofloxacin hybrid incorporated into the bionanocomposite beads was evaluated by in vitro release studies which showed a significant difference in the release profiles in the aqueous medium used to simulate the gastrointestinal tract, depending on the blend composition and the freezing method employed in the preparation of the beads. The results point to bionanocomposite systems based on ciprofloxacin-clay hybrids and biopolymers that may be used as devices in the biomedical area.

Structural Developments of the Reversible Confinement of Ionic Liquids in Nylon 6 Fibres: Solid State 13C Nuclear Magnetic Resonance

Reversible confinement of ionic liquids (ILs) among the polyamide molecules is used for suppressing or weakening the hydrogen bonds during the low-speed melt spinning process for the structural improvements of the nylon 6 fibres. The melt spinning process is followed by a hot drawing process and a subsequent extraction of the ILs. Afterwards, the resulting fibres are thermally stabilized so as to produce high performance nylon 6 fibres. Interestingly, the molecular structural developments of the IL-confined nylon 6 fibres took place during the stress-induced phase transformation (i.e. during the hot-drawing stage) – these developments lead to an ultimate molecular orientation which in turn caused improvements of the overall fibres’ properties. The solid state 13C nuclear magnetic resonance (NMR) tests revealed that non-aliphatic carbonyl chemical shifts at 172.6 ×10-6 and 172.9 ×10-6 took place and they are believed to be due to the γ crystal phases of the neat and of the 2% IL-confined nylon 6 fibres, respectively. Moreover, during the γ to α crystal phase transitions, the NMR peaks’ shift for the IL-confined fibres are either remained unchanged or are slightly increased. The Structural developments of the IL-confined and the reverted nylon 6 fibres have, also, been discussed.

Evaluation of commercial composts and potting mixes and their ability to support arbuscular mycorrhizal fungi with maize (Zea mays) as host plant.

The use of composts and potting mixes in food production systems is a promising way to counteract the effects of soil degradation and allows crop growth in soilless culture systems. Arbuscular mycorrhizal fungi (AMF) are a well-studied group of beneficial plant symbionts that have been shown to provide important ecosystem services. This study analysed the properties of nine commercial Australian potting mixes and composts and investigated whether they support colonization of maize plants with AMF in a plant growth bioassay. Physicochemical analyses showed highly variable properties between the substrates, with some extreme values that limited plant growth. DNA-based analysis revealed the presence of various plant pathogens, which was linked to inhibited plant growth in one substrate. Some substrates did not meet national quality standards, due to the concentrations of plant nutrients, heavy metals, or substrate maturity. Plant growth was mostly limited due to nitrogen immobilization, which required weekly fertilizer applications. Solid state 13C nuclear magnetic resonance spectroscopy gave insight into the decomposition state of the substrates. Plant roots in most substrates were well colonized with AMF (>60% root length), regardless of most substrate properties. Root colonization was negatively affected in only one substrate, likely due to ammonium toxicity. Results of this study show that not all commercial substrates adhered to national quality standards. Potting mixes and composts can support high mycorrhizal root colonization when plant growth is otherwise not limited.

Isolation and characterization of cellulose nanomaterials from jute bast fibers

This work describes a simple yet effective pathway for extracting cellulose nanomaterials from jute bast fibers by chemical pretreatment to isolate microfibrillated cellulose followed by either mechanical or acid hydrolysis to ultimately isolate cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs), respectively. Analyses carried out through Fourier transform infrared spectroscopy (FTIR), X-ray photon spectroscopy (XPS) and solid state 13C nuclear magnetic resonance (NMR) demonstrated that the pretreatments gradually removed lignins and hemicelluloses from the fibers. The yield of microfibrillated cellulose was 56.5% with respect to the initial dry mass of untreated fibers. Scanning electron microscopy (SEM) evaluated the morphological variation in the fiber dimension during the initial chemical pretreatment stages leading to extraction of microfibril 12–15 µm in average width. Transmission electron microscopy (TEM) images confirmed the nano-scale dimension of these nanocelluloses. The thermal stability of jute fibers at different stages of treatment was studied by thermogravimetric analysis. The high yield and high crystallinity of the nanocelluloses demonstrated effective isolation protocol confirming that jute bast fibers can be a valuable source for generation of nanomaterials.

Synthesis of hydrogel from sugarcane bagasse extracted cellulose for swelling properties study

Insolubility of cellulose in common solvent had been a challenge in generating cellulose hydrogels. In the present work, hydrogels from sugarcane bagasse extracted cellulose and modify with synthetic polymer, poly (vinyl alcohol) (PVA) and cross-linker, glutaraldehyde (GA) was synthesize. Cellulose was isolated from sugarcane bagasse via pre-treatment with 4 vol% sulphuric acid (H2SO4) and 10 wt% sodium hydroxide (NaOH) solution. The cellulose extracted was dissolved in ZnCl2/CaCl2 solution at 65 ℃ to fabricate self-standing cellulose hydrogel without cross-linker. Another cellulose hydrogel was generated and immersed into 5 wt% GA solution to cross-link the cellulose chains. To improve the stability and swelling properties of cellulose, PVA was introduced into the hydrogel by using GA to cross-link cellulose chains with PVA chains. The resulting hydrogels were characterized with Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and solid state 13C Nuclear Magnetic Resonance (NMR) spectroscopy for structural determination. Three self-standing cellulose-based hydrogels, including regenerated cellulose (RC), GA cross-linked cellulose (C-GA), followed by PVA and GA cross-linked cellulose (C-GA-PVA) were successfully generated from ZnCl2/CaCl2 dissolution system and each hydrogel possessed different physical aspects. The occurrence of chemical cross-linking reaction between cellulose, GA and PVA was further evidenced by the data analyzed from ATR-FTIR and NMR spectra. The swelling degree of hydrogels generally increase after the addition of PVA and GA into cellulose suspension, showing 52 % (RC), 80 % (C-GA) and 135 % (C-GA-PVA). C-GA-PVA possessed the best swelling capability and potential for possible application as water reservoir in agriculture.

Construction of a Macromolecular Structure Model for Zhundong Subbituminous Coal

Understanding the coal molecular structure is of paramount importance for the effective utilization of coal. In this paper, the molecular structure of Zhundong coal (ZD) was characterized by physical detection techniques, such as solid state 13C nuclear magnetic resonance spectroscopy (13C-NMR), fourier transform infrared resonance spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The occurrence and distribution of aromatic carbocyclic frameworks were analyzed by 13C-NMR. Based on the FTIR and XPS analysis, the existing forms and the length of the aliphatic chain, the substitution forms of aromatic carbocyclic rings, and different types of functional groups were confirmed. The aliphatic chains and functional groups were introduced into these aromatic carbocyclic frameworks, and the 2D molecular structures model of ZD with the molecular chemical formula as C179H124O21N4 were constructed. The simulated 13C-NMR spectra of which were consistent with the experimental spectra, indicating the accuracy of the 2D ZD molecular structure model. Efforts were made to obtain the energy-minimum conformation of the 3D molecular structure by molecular mechanics (MM) and molecular dynamics (MD). The simulated FTIR spectra of the model were in good agreement with the experimental results, which fully verified the accuracy of the ZD molecular structure. The molecular structure provides a deep reference to understand the structural characteristics of ZD coal at the molecular micro-scale, which would be helpful to understand the reactivity of ZD coal.

The comparison study of multiple biochar stability assessment methods

Biochar produced from thermochemical processing biomass is being developed as an effective way to mitigate climate change. The stability of biochar means the potential capability of fixing biochar carbon in the soil environment. The method for biochar stability assessment is significant to its climate change mitigation potential. However, there is no standard method available to use, and the stability of biochar assessed by the diverse methods has a significant difference. Nevertheless, the comparative study on the diversified stability assessment methods is limited. In the present study, the biochars were pyrolyzed from soybean straw, wood sawdust, and Chlorella Vulgaris at temperatures ranging from 300 to 800 °C. Then, the evaluation methods, such as ultimate analysis, proximate analysis, the Edinburgh stability tool, X-ray photoelectron spectroscopy (XPS), solid state 13C nuclear magnetic resonance (NMR), and thermogravimetric analysis, were compared to assess the stability of biochars. The stability indicators obtained by most methods, excluding aromatic C from NMR and C–C/C = C/ C–H from XPS, were closely related to the pyrolysis temperature (ANOVA analysis, p < 0.05). The volatile matter/(fixed carbon + volatile matter) had high correlations with other indicators (Pearson coefficient, |r|>0.36, p < 0.05) except for C–C/C = C/C–H from XPS. The cluster analysis indicates the studied stability methods could be divided into three categories, according to which the proximate analysis may be developed as an alternative to O/C and H/C. These research findings help provide the reference for the classification and selection of stability assessment method for the accurate and efficient evaluation of biochar stability.

Fourier Transform Infrared and Solid State 13C Nuclear Magnetic Resonance Spectroscopic Characterization of Defatted Cottonseed Meal-Based Biochars

Conversion to biochar may be a value-added approach to recycle defatted cottonseed meal, a major byproduct from the cotton industry. In this work, complete slow pyrolysis at seven peak temperatures ranging from 300 to 600&amp;deg;C in batch reactors was implemented to process cottonseed meal into biochar products. Elemental analysis, attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy and quantitative solid state 13C nuclear magnetic resonance (NMR) spectroscopy were applied to characterize raw meal and its derived biochar products. The biochar yield and organic C and total N recoveries decreased as the peak pyrolysis temperatures was elevated. However, most of the mineral elements including P in cottonseed meal were retained during pyrolysis and became enriched in biochar as a result of the decreased mass yield. The spectral data showed that pyrolysis removed the functional groups of biopolymers in cottonseed meal, producing highly aromatic structures in biochars. With increasing pyrolysis temperature, alkyl structures decreased progressively in the biochar products and became negligible at higher temperatures (550 and 600&amp;deg;C). Quantitative analysis of FT IR data revealed that the values of a simple 3-band (1800,1700, and 650 cm-1)-based R reading of the biochars were linearly related to the pyrolysis temperature, and showed strong correlations with decreasing aromaticity and increasing alkyl, aliphatic C-O/N and carbonyl signal intensities in the 13C NMR spectra. Therefore, the cheaper and faster FT-IR measurement could be used as a routine conversion indicator of pyrolysis of lignocellulosic biomass instead of the more expensive and time-consuming NMR spectroscopy.

A novel elemental composition based prediction model for biochar aromaticity derived from machine learning

The measurement of aromaticity in biochars is generally conducted using solid state 13C nuclear magnetic resonance spectroscopy, which is expensive, time-consuming, and only accessible in a small number of research-intensive universities. Mathematical modelling could be a viable alternative to predict biochar aromaticity from other much easier accessible parameters (e.g. elemental composition). In this research, Genetic Programming (GP), an advanced machine learning method, is used to develop new prediction models. In order to identify and evaluate the performance of prediction models, an experimental data set with 98 biochar samples collected from the literature was utilized. Due to the benefits of the intelligence iteration and learning of GP algorithm, a kind of underlying exponential relationship between the elemental compositions and the aromaticity of biochars is disclosed clearly. The exponential relationship is clearer and simpler than the polynomial mapping relationships implicated by Maroto-Valer, Mazumdar, and Mazumdar-Wang models. In this case, a novel exponential model is proposed for the prediction of biochar aromaticity. The proposed exponential model appears better prediction accuracy and generalization ability than existing polynomial models during the statistical parameter evaluation.

Facile approach to the solid support photografting coating of citric acid as a novel biomimetic iron chelator film

Herein, the facile photografting coating method was used to develop a novel metal biochelator film by covalent immobilization of citric acid (CA) onto polypropylene (PP) surface. First, PP film underwent a surface modification by UV-grafting of glycidyl methacrylate (GMA) in the presence of benzophenone (BP). The concentrations of GMA (bifunctional monomer) and BP (photoinitiator) were appropriately optimized to achieve the breath-figure-array structure and brush-like grafting configuration with a high availability of the reactive oxirane ring. Subsequently, CA was immobilized onto the PP-g-GMA surface via the ring-opening reaction to obtain the biochelator film (PP-g-GMA-g-CA). Fourier-transform infrared spectroscopy and solid state 13C nuclear magnetic resonance spectroscopy elucidated the chemical structure and grafting mechanism of grafted samples. X-ray photoelectron spectroscopy was used to detect the chemical composition of the surface of the grafted samples, by which the grafting density was relatively estimated. In addition, the uniformity of the grafting pattern and morphology of the grafting unit were observed using scanning electron microscopy and atomic force microscopy. Furthermore, the carboxylic acid density of the biochelator film (PP-g-GMA-g-CA) was quantified using a toluidine blue O assay, in which approximately 327 ± 58 nM carboxylic acid was detected per each film. The metal chelating activity of the film was also investigated using the colorimetric ferrozine assay, by which PP-g-GMA-g-CA film chelated approximately 215 ± 11 nM of Fe3+. Therefore, this newly developed system can be used as a versatile metal biochelator in a wide range of biomedical, cosmetic, and packaging applications.11Citric acid (CA), benzophenone (BP), glycidyl methacrylate (GMA), Fourier-transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance (13C NMR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscopy (AFM), polypropylene (PP), toluidine blue O (TBO), breath figure array (BFA)

Fabrication of starch-based high-performance adsorptive hydrogels using a novel effective pretreatment and adsorption for cationic methylene blue dye: Behavior and mechanism

Herein, NaOH solution of a finite concentration was used to pretreat starch, which serves a novel effective pretreatment. A starch-based high-performance adsorptive hydrogel (STAH) was successfully prepared by grafting polyacrylic acid (PAA) onto starch and then crosslinking with N,N'-methylene-bisacrylamide (MBA). This adsorbent was employed to adsorb typical organic cationic dye contaminants (methylene blue (MB)) from high concentration effluents. The effect of the pretreatment time of starch on adsorption capacity of STAH was investigated in detail based on starch molecular weight, solid state 13C nuclear magnetic resonance spectra and grafting parameters. The results suggested that the optimal adsorbent (STAH20) presented the highest grafting parameters (50.06% reaction ratio of C6 in starch, 90.79% grafting efficiency, and 248.49% grafting ratio of PAA). STAH20 exhibited maximum adsorption capacity (2967.66 mg/g) in optimal conditions and excellent reusability after 4 rounds of recycling. The adsorption process of STAH20 for MB was consistent with the Langmuir model, obeyed the pseudo-first order model with intra-particle diffusion, and was endothermic and spontaneous. Using this pretreatment, the semi-crystalline structure of starch was destroyed, and numerous hydroxyl groups were gradually exposed with time, which is conducive to the graft reactions. The number of –COOH/ –COO– groups increased, which significantly enhances the hydrogen-bonding interaction and electrostatic interaction between STAH and MB and improves the adsorption capacity. Our study provides a method for low-energy, inexpensive, effective and simple starch pretreatment for the fabrication of STAH that exhibits significant potential for application in the removal of organic cationic dye contaminants.

Photografting of p-anisidine-glycidyl methacrylate onto polymeric substrate for developing free-radical scavenging films

In this study, we present a facile approach for the development of a non-migratory antioxidant film via photografting of a conducing polymer (p-anisidine (PA)) onto polypropylene (PP). Initially, the surface of the PP film was functionalized via UV grafting (365 nm) of glycidyl methacrylate (GMA) in the presence of benzophenone (BP) into the methanol or mixed solvents (methanol and water). The addition of 40 v/v% of water into the coating solution led to an increase in grafting density, a reduction in UV-irradiation time, and changes in the grafting morphology. Scanning electron microscopy and atomic force microscopy were used in the identification of the breath figure array structure and brush-like grafting configuration on the surface of the films that were grafted in the mixed solvent (40 v/v % water). Subsequently, PA was immobilized onto the PP-g-GMA films via a ring-opening reaction wherein the PP-g-GMA films developed in the mixed solvent (40 % water) immobilized a higher amount of PA (2.114 ± 0.0013 μM), compared with those developed in methanol (1.760 ± 0.0070 μM). Fourier-transform infrared spectroscopy and solid state 13C nuclear magnetic resonance showed the chemical structure of the grafted surface and identified the grafting mechanism. Moreover, PP-g-GMA-g-PA films presented a strong free-radical scavenging activity using the DPPH assay. Furthermore, cyclic voltammetry analysis exhibited strong oxidation and reduction potential peaks, which proved the antioxidant activity of the films. Therefore, this newly developed free-radical scavenging film can be used as a non-migratory antioxidant film for a variety of applications, such as biomedical, cosmetic, and packaging.

Monitoring a Mechanochemical Reaction Reveals the Formation of a New ACC Defect Variant Containing the HCO3– Anion Encapsulated by an Amorphous Matrix

Amorphous calcium carbonate (ACC) is an important precursor in the biomineralization of crystalline CaCO3. In nature, it serves as a storage material or as a permanent structural element, whose lifetime is regulated by an organic matrix. The relevance of ACC in materials science is primarily related to our understanding of CaCO3 crystallization pathways and CaCO3/(bio)polymer nanocomposites. ACC can be synthesized by liquid–liquid phase separation, and it is typically stabilized with macromolecules. We have prepared ACC by milling calcite in a planetary ball mill. Phosphate “impurities” were added in the form of monetite (CaHPO4) to substitute the carbonate anions, thereby stabilizing ACC by substitutional disorder. The phosphate anions do not simply replace the carbonate anions. They undergo shear-driven acid/base and condensation reactions, where stoichiometric (10%) phosphate contents are required for the amorphization to be complete. The phosphate anions generate a strained network that hinders ACC recrystallization kinetically. The amorphization reaction and the structure of BM-ACC were studied by quantitative Fourier transform infrared spectroscopy and solid state 31P, 13C, and 1H magic angle spinning nuclear magnetic resonance spectroscopy, which are highly sensitive to symmetry changes of the local environment. In the first—and fast—reaction step, the CO32– anions are protonated by the HPO42– groups. The formation of unprecedented hydrogen carbonate (HCO3–) and orthophosphate anions appears to be the driving force of the reaction, because the phosphate group has a higher Coulomb energy and the tetrahedral PO43– unit can fill space more efficiently. In a competing second—and slow—reaction step, pyrophosphate anions are formed in a condensation reaction. No pyrophosphates are formed at higher carbonate contents. High strain leads to such a large energy barrier that any reaction is suppressed. Our findings aid in the understanding of the mechanochemical amorphization of calcium carbonate and emphasize the effect of impurities for the stabilization of the amorphous phases in general. Our approach allowed the synthesis of new amorphous alkaline earth defect variants containing the unique HCO3– anion. Our approach outlines a general strategy to obtain new amorphous solids for a variety of carbonate/phosphate systems that offer promise as biomaterials for bone regeneration.