Inhibiting the Jahn-Teller Effect of Manganese Hexacyanoferrate via Ni and Cu Codoping for Advanced Sodium-Ion Batteries.

Manganese (Mn)-based Prussian blue analogs (PBAs) are of great interest as a prospective cathode material for sodium-ion batteries (SIBs) due to their high redox potential, easy synthesis, and low cost. However, the Jahn-Teller effect and low electrical conductivity of Mn-based PBA cause poor structure stability and unsatisfactory performance during the cycling. Herein, a novel nickel- and copper-codoped K2Mn[Fe(CN)6] cathode is developed via a simple coprecipitation strategy. The doping elements improve the electrical conductivity of Mn-based PBA by reducing the bandgap, as well as suppress the Jahn-Teller effect by stabilizing the framework, as verified by the density functional theory calculations. Simultaneously, the substitution of sodium with potassium in the lattice is beneficial for filling vacancies in the PBA framework, leading to higher average operating voltages and superior structural stability. As a result, the as-prepared Mn-based cathode exhibits excellent reversible capacity (116.0 mAh g-1 at 0.01 A g-1) and superior cycling stability (81.8% capacity retention over 500 cycles at 0.1 A g-1). This work provides a profitable doping strategy to inhibit the Jahn-Teller structural deformation for designing stable cathode material of SIBs.

Selection of yeast strains in naturally fermented cured meat as promising starter cultures for fermented cured beef, a traditional fermented meat product of northern China.

BACKGROUND: Fermented meat products are meat products with a unique flavor, color, and texture as well as an extended shelf life under natural or artificially controlled conditions. Microorganisms or enzymes are used to ferment the raw meat so that it undergoes a series of biochemical and physical changes. Common fermentation strains are lactic acid bacteria, yeasts, staphylococci, molds, and so forth. Studies on the inhibitory effect of yeast fermentation strain on N-nitrosamines in fermented meat products have not been reported. Two excellent yeast starters were identified to solve the problem of nitrosamines in fermented meat products. RESULTS: Meyerozyma guilliermondii and Debaryomyces hansenii led to weak acid production, strong resistance to NaCl and NaNO2 , and high tolerance to low acidic conditions. The inoculated fermented beef exhibited decreased lightness, moisture content, water activity, pH, protein content, nitrite content, and N-nitrosamine content in comparison with the control group fermented bacon. M. guilliermondii had a better effect, reducing pH from 5.69 to 5.41, protein content from 254.24 to 221.92 g·kg-1 , nitrite content from 28.61 to 25.33 mg·kg-1 and N-nitrosamine by 18.97%, and giving the fermented beef the desired meat color, mouthfeel, odor, taste, and tissue quality. CONCLUSION: In this study, two strains of yeast fermenters that can degrade N-nitrosamine precursors were identified, which to some extent solves the problem of the high risk of generating nitrosamines such as N-nitrosodiethylamine (NDEA) by processing fermented meat products with nitrites as precursors. These two strains are likely to be used as starter cultures for fermented meat products. © 2023 Society of Chemical Industry.

Developing Enzyme Immobilization with Fibrous Membranes: Longevity and Characterization Considerations.

Fibrous membranes offer broad opportunities to deploy immobilized enzymes in new reactor and application designs, including multiphase continuous flow-through reactions. Enzyme immobilization is a technology strategy that simplifies the separation of otherwise soluble catalytic proteins from liquid reaction media and imparts stabilization and performance enhancement. Flexible immobilization matrices made from fibers have versatile physical attributes, such as high surface area, light weight, and controllable porosity, which give them membrane-like characteristics, while simultaneously providing good mechanical properties for creating functional filters, sensors, scaffolds, and other interface-active biocatalytic materials. This review examines immobilization strategies for enzymes on fibrous membrane-like polymeric supports involving all three fundamental mechanisms of post-immobilization, incorporation, and coating. Post-immobilization offers an infinite selection of matrix materials, but may encounter loading and durability issues, while incorporation offers longevity but has more limited material options and may present mass transfer obstacles. Coating techniques on fibrous materials at different geometric scales are a growing trend in making membranes that integrate biocatalytic functionality with versatile physical supports. Biocatalytic performance parameters and characterization techniques for immobilized enzymes are described, including several emerging techniques of special relevance for fibrous immobilized enzymes. Diverse application examples from the literature, focusing on fibrous matrices, are summarized, and biocatalyst longevity is emphasized as a critical performance parameter that needs increased attention to advance concepts from lab scale to broader utilization. This consolidation of fabrication, performance measurement, and characterization techniques, with guiding examples highlighted, is intended to inspire future innovations in enzyme immobilization with fibrous membranes and expand their uses in novel reactors and processes.

Biocatalytic Membranes for Carbon Capture and Utilization.

Innovative carbon capture technologies that capture CO2 from large point sources and directly from air are urgently needed to combat the climate crisis. Likewise, corresponding technologies are needed to convert this captured CO2 into valuable chemical feedstocks and products that replace current fossil-based materials to close the loop in creating viable pathways for a renewable economy. Biocatalytic membranes that combine high reaction rates and enzyme selectivity with modularity, scalability, and membrane compactness show promise for both CO2 capture and utilization. This review presents a systematic examination of technologies under development for CO2 capture and utilization that employ both enzymes and membranes. CO2 capture membranes are categorized by their mode of action as CO2 separation membranes, including mixed matrix membranes (MMM) and liquid membranes (LM), or as CO2 gas-liquid membrane contactors (GLMC). Because they selectively catalyze molecular reactions involving CO2, the two main classes of enzymes used for enhancing membrane function are carbonic anhydrase (CA) and formate dehydrogenase (FDH). Small organic molecules designed to mimic CA enzyme active sites are also being developed. CO2 conversion membranes are described according to membrane functionality, the location of enzymes relative to the membrane, which includes different immobilization strategies, and regeneration methods for cofactors. Parameters crucial for the performance of these hybrid systems are discussed with tabulated examples. Progress and challenges are discussed, and perspectives on future research directions are provided.

Carbonic Anhydrase Enhanced UV-Crosslinked PEG-DA/PEO Extruded Hydrogel Flexible Filaments and Durable Grids for CO2 Capture.

In this study, poly (ethylene glycol) diacrylate/poly (ethylene oxide) (PEG-DA/PEO) interpenetrating polymer network hydrogels (IPNH) were extruded into 1D filaments and 2D grids. The suitability of this system for enzyme immobilization and CO2 capture application was validated. IPNH chemical composition was verified spectroscopically using FTIR. The extruded filament had an average tensile strength of 6.5 MPa and elongation at break of 80%. IPNH filament can be twisted and bent and therefore is suitable for further processing using conventional textile fabrication methods. Initial activity recovery of the entrapped carbonic anhydrase (CA) calculated from esterase activity, showed a decrease with an increase in enzyme dose, while activity retention of high enzyme dose samples was over 87% after 150 days of repeated washing and testing. IPNH 2D grids that were assembled into spiral roll structured packings exhibited increased CO2 capture efficiency with increasing enzyme dose. Long-term CO2 capture performance of the CA immobilized IPNH structured packing was tested in a continuous solvent recirculation experiment for 1032 h, where 52% of the initial CO2 capture performance and 34% of the enzyme contribution were retained. These results demonstrate the feasibility of using rapid UV-crosslinking to form enzyme-immobilized hydrogels by a geometrically-controllable extrusion process that uses analogous linear polymers for both viscosity enhancement and chain entanglement purposes, and achieves high activity retention and performance stability of the immobilized CA. Potential uses for this system extend to 3D printing inks and enzyme immobilization matrices for such diverse applications as biocatalytic reactors and biosensor fabrication.

Advances in 3D Gel Printing for Enzyme Immobilization.

Incorporating enzymes with three-dimensional (3D) printing is an exciting new field of convergence research that holds infinite potential for creating highly customizable components with diverse and efficient biocatalytic properties. Enzymes, nature's nanoscale protein-based catalysts, perform crucial functions in biological systems and play increasingly important roles in modern chemical processing methods, cascade reactions, and sensor technologies. Immobilizing enzymes on solid carriers facilitates their recovery and reuse, improves stability and longevity, broadens applicability, and reduces overall processing and chemical conversion costs. Three-dimensional printing offers extraordinary flexibility for creating high-resolution complex structures that enable completely new reactor designs with versatile sub-micron functional features in macroscale objects. Immobilizing enzymes on or in 3D printed structures makes it possible to precisely control their spatial location for the optimal catalytic reaction. Combining the rapid advances in these two technologies is leading to completely new levels of control and precision in fabricating immobilized enzyme catalysts. The goal of this review is to promote further research by providing a critical discussion of 3D printed enzyme immobilization methods encompassing both post-printing immobilization and immobilization by physical entrapment during 3D printing. Especially, 3D printed gel matrix techniques offer mild single-step entrapment mechanisms that produce ideal environments for enzymes with high retention of catalytic function and unparalleled fabrication control. Examples from the literature, comparisons of the benefits and challenges of different combinations of the two technologies, novel approaches employed to enhance printed hydrogel physical properties, and an outlook on future directions are included to provide inspiration and insights for pursuing work in this promising field.

Synthesis and Characterization of High-Purity Mesoporous Alumina with Excellent Adsorption Capacity for Congo Red.

We explore a more concise process for the preparation of high-purity alumina and to address the problem of some conventional micro- and nano-adsorbents having difficulty in exposing their adsorption sites to target pollutants in solution due to the heavy aggregation of the adsorbent, which confers poor adsorption properties. The methods of using gamma-phase high-purity mesoporous alumina (HPMA), with its excellent adsorption properties and high adsorption rates of Congo Red, and of using lower-cost industrial aluminum hydroxide by direct aging and ammonium salt substitution were successfully employed. The results showed that the purity of HPMA was as high as 99.9661% and the total removal rate of impurities was 98.87%, a consequence of achieving a large specific surface area of 312.43 m2 g-1, a pore volume of 0.55 cm3 g-1, and an average pore diameter of 3.8 nm. The adsorption process was carried out at 25 °C, the concentration of Congo Red (CR) dye was fixed at 250 mg L-1 and the amount of adsorbent used was 100 mg. The HPMA sample exhibited an extremely fast adsorption rate in the first 10 min, with adsorption amounts up to 476.34 mg g-1 and adsorption efficiencies of 96.27%. The adsorption equilibrium was reached in about 60 min, at which time the adsorbed amount was 492.19 mg g-1 and the dye removal rate was as high as 98.44%. One-hundred milligrams of adsorbent were weighed and dispersed in 200-mL CR solutions with mass concentrations ranging from 50-1750 mg L-1 to study the adsorption isotherms. This revealed that the saturation adsorption capacity of the produced HPMA was 1984.64 mg g-1. Furthermore, the process of adsorbing Congo Red in the synthesized product was consistent with a pseudo-second order model and the Langmiur model. It is expected that this method of producing HPMA will provide a productive, easy and efficient means of treating toxic dyes in industrial wastewater.

Study on Oxygen Evolution Reaction Performance of Jarosite/C Composites.

In the electrolysis of water process, hydrogen is produced and the anodic oxygen evolution reaction (OER) dominates the reaction rate of the entire process. Currently, OER catalysts mostly consist of noble metal (NM) catalysts, which cannot be applied in industries due to the high price. It is of great importance to developing low-cost catalysts materials as NM materials substitution. In this work, jarosite (AFe3(SO4)2(OH)6, A = K+, Na+, NH4+, H3O+) was synthesized by a one-step method, and its OER catalytic performance was studied using catalytic slurry (the weight ratios of jarosite and conductive carbon black are 2:1, 1:1 and 1:2). Microstructures and functional groups of synthesized material were analyzed using XRD, SEM, FI-IR, etc. The OER catalytic performance of (NH4)Fe3(SO4)2(OH)6/conductive carbon black were examined by LSV, Tafel, EIS, ECSA, etc. The study found that the OER has the best catalytic performance when the weight ratio of (NH4)Fe3(SO4)2(OH)6 to conductive carbon black is 2:1. It requires only 376 mV overpotential to generate current densities of 10 mA cm-2 with a small Tafel slope (82.42 mV dec-1) and large Cdl value (26.17 mF cm-2).

Study on the Synthesis of High-Purity γ-Phase Mesoporous Alumina with Excellent CO2 Adsorption Performance via a Simple Method Using Industrial Aluminum Oxide as Raw Material.

To mitigate the global greenhouse effect and the waste of carbon dioxide, a chemical raw material, high-purity γ-phase mesoporous alumina (MA) with excellent CO2 adsorption performance was synthesized by the direct aging method and ammonium salt substitution method. With this process, not only can energy consumption and time be shortened to a large extent but the final waste can also be recycled to the mother liquor by adding calcium hydroxide. Reaction conditions, i.e., pH value, calcination temperature, and desodium agent, were investigated in detail with the aid of X-ray fluorescence spectrum (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and Barret-Joyner-Hallender (BJH) methods, nonlocal density functional theory (NLDFT), transmission electron microscopy (TEM), temperature-programmed desorption of CO2 (CO2-TPD), and presented CO2 adsorption measurement. The results of this study are summarized as follows: the impurity content of the MA synthesized under optimal conditions is less than 0.01%, and its total removal rate of impurities is 99.299%. It was found that the MA adsorbent has a large specific surface area of 377.8 m2/g, pore volume of 0.55 cm3/g, and its average pore diameter is 3.1 nm. Under the condition of a gas flow rate of 20 cm3/min, its CO2 adsorption capacity is 1.58 mmol/g, and after 8 times of cyclic adsorption, the amount of CO2 adsorption remained basically unchanged, both of which indicate that the material has excellent adsorption properties and can be widely used for the adsorption of carbon dioxide.

Delivery of pharmaceuticals and other active ingredients with their crystalline cyclodextrin inclusion compounds.

In honor of Prof. Thorsteinn Loftsson's 70th birthday, we offer this personal review of our work using cyclodextrins (CDs) complexed with a variety of active ingredients, including pharmaceuticals, for the purpose of improving their delivery to polymer materials, e.g., fibers, films, hydrogels, etc. Using the affinity of CDs to host and form non-covalent inclusion complexes (ICs) with guest molecules, including a variety of high molecular weight polymers, it is possible to readily deliver these guest molecules into polymer materials via either melt or solution processing of their crystalline or soluble guest molecule-CD-ICs or -rotaxanes. This provides the following advantages: i. CDs are non-toxic, implantable, and biodegradable and have earned the GRAS rating from the FDA. ii. Guest molecules, even those that are neat liquids, can form solid crystalline CD-ICs that are thermally stable to ~ 200 °C and above. This approach permits facile melt-processing into polymer materials for delivery without migration, loss, or degradation of the active guest ingredient. iii. For guests harmful and toxic to their users and the environment, delivery in the form of crystalline CD-ICs can limit any contact with and release of the included toxic guests before they function and are used. iv. It has been demonstrated that, by simple precipitation methods, neat as-received CDs that adopt cage crystal structures can be readily transformed to their columnar crystal structures containing only water in their channels, which can be easily displaced by small molecule, as well as polymer guests. v. Guest-CD-rotaxanes are water soluble, they protect the threaded guest from sources of degradation, and the CD hydroxyl groups may be modified to direct the guest-CD-rotaxane to specific substrates. For these reasons, here we summarize our contributions to the study of CD inclusion and delivery of a variety of guest molecules, including antibacterials, spermicides, insecticides, flame retardants, and dyes, that can more usefully functionalize polymer materials.

Multi-layer dressing made of laminated electrospun nanowebs and cellulose-based adhesive for comprehensive wound care.

In this work, multi-layer wound dressing was made of laminated layers of electrospun fibers supported by adhesive sheet. Graft copolymerization of methyl methacrylate (MMA) and 2-Ethyl-1-hexyl acrylate (EHA) onto carboxymethyl cellulose (CMC) was conducted to obtain an adhesive sheet with 1.52 (N/cm2) loop tack, 1.7 (N/cm) peel strength and 25 s shear strength. Diclofenac sodium, anti-inflammatory drug, was loaded to the adhesive sheet with encapsulation efficiency 73%. The contact layer to wound was made of synthesized anti-bleeding agents, chitosan iodoacetamide (CI) loaded into electrospun polyvinyl alcohol (PVA) fibers. It was fabricated from fiber diameter 300 nm by electrospinning of 5% wt/v of CI (D.S. 18.7%) mixed with 10% wt/v PVA, at 20 kV and 17 cm airgap. The second, pain-relief layer was fabricated by encapsulating up to 50% wt/wt of capsaicin into gelatin nanofibers (197 nm) crosslinked by glyoxal. The third, antimicrobial layer was fabricated from PVA electrospun fibers loaded with 2% wt/wt gentamicin. Biocompatibility test showed insignificant adverse effects of the fabricated layers on fibroblast cells. Animal test on rat showed accelerated wound healing from 21 to 7 days for the multi-layer dressing. Histopathological findings corroborated the intactness of the epidermis layer of the treated samples.

Synthesis of chitosan iodoacetamides via carbodiimide coupling reaction: Effect of degree of substitution on the hemostatic properties.

Uncontrolled hemorrhage continues to be the leading cause of death from traumatic injuries both in the battlefield and in the civilian life. Chitosan is among the very few materials that have made the short list of military recommended field-deployable hemostatic dressings. However, the detailed mechanism of its action is still not fully understood. Moreover, in the cases when patients developed coagulopathy, the efficacy of the dressings rely solely on those mechanisms that work outside of the regular blood coagulation cascade. In addition to the well-known erythrocyte agglutination, we proposed to use the reactive N-iodoacetyl group on a new chitosan derivative to accelerate hemostasis. In this paper, we describe the synthesis of chitosan iodoacetamide (CI) with considerations of the stoichiometry among the reagents, the choice of solvent, the pH of the reaction medium, and the reaction time. The reaction was confirmed by FT-IR, 1H and 13C NMR, elemental analysis, iodine content analysis, and SEM-EDS. Water contact angle measurements and Erythrocyte Sedimentation Rate (ESR) method were used to evaluate the hemostatic potential of the newly synthesized CI as a function of their degree of substitution (DS). The range of DS was 5.9% to 27.8% for CI. The mid-range of DS gave the best results for the ESR. CIs exhibit favorable cytocompatibilities up to DS 18.7 compared to the generic unmodified chitosan. In general, the biocompatibility of chitosan iodoacetamide slightly declined with increasing the iodide content up to DS 21.5 owing to its affinity to SH groups of cells.

Aliphatic Polyester Nanofibers Functionalized with Cyclodextrins and Cyclodextrin-Guest Inclusion Complexes.

The fabrication of nanofibers by electrospinning has gained popularity in the past two decades; however, only in this decade, have polymeric nanofibers been functionalized using cyclodextrins (CDs) or their inclusion complexes (ICs). By combining electrospinning of polymers with free CDs, nanofibers can be fabricated that are capable of capturing small molecules, such as wound odors or environmental toxins in water and air. Likewise, combining polymers with cyclodextrin-inclusion complexes (CD-ICs), has shown promise in enhancing or controlling the delivery of small molecule guests, by minor tweaking in the technique utilized in fabricating these nanofibers, for example, by forming core⁻shell or multilayered structures and conventional electrospinning, for controlled and rapid delivery, respectively. In addition to small molecule delivery, the thermomechanical properties of the polymers can be significantly improved, as our group has shown recently, by adding non-stoichiometric inclusion complexes to the polymeric nanofibers. We recently reported and thoroughly characterized the fabrication of polypseudorotaxane (PpR) nanofibers without a polymeric carrier. These PpR nanofibers show unusual rheological and thermomechanical properties, even when the coverage of those polymer chains is relatively sparse (~3%). A key advantage of these PpR nanofibers is the presence of relatively stable hydroxyl groups on the outer surface of the nanofibers, which can subsequently be taken advantage of for bioconjugation, making them suitable for biomedical applications. Although the number of studies in this area is limited, initial results suggest significant potential for bone tissue engineering, and with additional bioconjugation in other areas of tissue engineering. In addition, the behaviors and uses of aliphatic polyester nanofibers functionalized with CDs and CD-ICs are briefly described and summarized. Based on these observations, we attempt to draw conclusions for each of these combinations, and the relationships that exist between their presence and the functional behaviors of their nanofibers.

Nanoscale considerations responsible for diverse macroscopic phase behavior in monosubstituted isobutyl-POSS/poly(ethylene oxide) blends.

Nanocomposites prepared by incorporating functionalized polyhedral oligomeric silsesquioxane (POSS) into polymer matrices afford a wide range of versatile hybrid materials for use in technologies ranging from cosmetics and pharmaceuticals to sensors and batteries. Here, we investigate the phase behavior of nanocomposites composed of poly(ethylene oxide) (PEO) and monosubstituted isobutyl POSS (iPOSS) modified with different functional moieties. Microscopic analyses of blends containing these iPOSS variants reveal the existence of different macroscopic morphologies and surface topologies. In the presence of octa-iPOSS, a POSS-rich surface cell motif reminiscent of breath patterns develops, whereas addition of allyl-iPOSS promotes the formation of surface plates. While aminopropyl-iPOSS forms dispersed aggregates, maleamic acid-iPOSS disperses in PEO with little effect on PEO crystal morphology. We perform rotational isomeric state Monte Carlo simulations to discern the effect of monosubstitution on the interaction energy between iPOSS and PEO, and establish the molecular-level origin for these observed differences in phase behavior.

Reorganizing Polymer Chains with Cyclodextrins.

During the past several years, we have been utilizing cyclodextrins (CDs) to nanostructure polymers into bulk samples whose chain organizations, properties, and behaviors are quite distinct from neat bulk samples obtained from their solutions and melts. We first form non-covalently bonded inclusion complexes (ICs) between CD hosts and guest polymers, where the guest chains are highly extended and separately occupy the narrow channels (~0.5⁻1.0 nm in diameter) formed by the columnar arrangement of CDs in the IC crystals. Careful removal of the host crystalline CD lattice from the polymer-CD-IC crystals leads to coalescence of the guest polymer chains into bulk samples, which we have repeatedly observed to behave distinctly from those produced from their solutions or melts. While amorphous polymers coalesced from their CD-ICs evidence significantly higher glass-transition temperatures, Tgs, polymers that crystallize generally show higher melting and crystallization temperatures (Tms, Tcs), and some-times different crystalline polymorphs, when they are coalesced from their CD-ICs. Formation of CD-ICs containing two or more guest homopolymers or with block copolymers can result in coalesced samples which exhibit intimate mixing between their common homopolymer chains or between the blocks of the copolymer. On a more practically relevant level, the distinct organizations and behaviors observed for polymer samples coalesced from their CD-ICs are found to be stable to extended annealing at temperatures above their Tgs and Tms. We believe this is a consequence of the structural organization of the crystalline polymer-CD-ICs, where the guest polymer chains included in host-IC crystals are separated and confined to occupy the narrow channels formed by the host CDs during IC crystallization. Substantial degrees of the extended and un-entangled natures of the IC-included chains are apparently retained upon coalescence, and are resistant to high temperature annealing. Following the careful removal of the host CD lattice from each randomly oriented IC crystal, the guest polymer chains now occupying a much-reduced volume may be somewhat "nematically" oriented, resulting in a collection of randomly oriented "nematic" regions of largely extended and un-entangled coalesced guest chains. The suggested randomly oriented nematic domain organization of guest polymers might explain why even at high temperatures their transformation to randomly-coiling, interpenetrated, and entangled melts might be difficult. In addition, the behaviors and uses of polymers coalesced from their CD-ICs are briefly described and summarized here, and we attempted to draw conclusions from and relationships between their behaviors and the unique chain organizations and conformations achieved upon coalescence.

Coalesced poly(ε-caprolactone) fibers are stronger.

Melt-spun fibers were made from poly(ε-caprolactone) (PCL) coalesced from stoichiometric inclusion complex crystals formed with host urea. Melting and crystallization behaviors, mechanical properties, and the birefringence of undrawn and cold-drawn fibers were investigated. Undrawn coalesced PCL fibers were observed to have 500-600% higher moduli than undrawn as-received (asr) PCL fibers and a modulus comparable to drawn asr PCL fibers. Drawn coalesced PCL fibers have the highest crystallinity, orientation, and 65% higher moduli than drawn asr PCL fibers. Drawn coalesced PCL fibers have only a 5% higher crystallinity than drawn asr PCL fibers, yet they have 65% higher moduli and lower elongation at break values. Clearly, the intrinsic alignment of the coalesced polymers is the reason for their higher moduli and lower elongation, as confirmed by the birefringence observed in drawn coalesced and asr-PCL fibers. The improved mechanical properties of coalesced PCL fibers make them a better candidate for use in tissue engineering as scaffolds.