Incorporating Oxygen Atoms in a SnS2 Atomic Layer to Simultaneously Stabilize Atomic Hydrogen and Accelerate the Generation of Hydroxyl Radicals for Water Decontamination.

Photoelectrocatalysis (PEC) is an efficient way to address various pollutants. Surface-adsorbed atomic hydrogen (H*) and hydroxyl radicals (•OH) play a key role in the PEC process. However, the instability of H* and low production of •OH considerably limit the PEC efficiency. In this study, we noted that incorporating oxygen atoms could regulate the behavior of H* by creating a locally favorable electron-rich state of S atoms in the SnS2 catalyst. The finely modulated H* led to a 12-fold decrease in the overpotential of H2O2 generation (H*-OOH*-H2O2-•OH) by decreasing the activation energy barrier of OOH* (rate-determining step). Considering density functional theory calculations, an H*-•OH redox pair suitable for a wide pH range (3-11) was successfully constructed based on the photocathode. The optimal SnS1.85O0.15 AL@TNA photocathode exhibited a ∼90% reduction in Cr(VI) in 10 min and ∼70% TOC removal of 4-nitrophenol, nearly 2- and 3-fold higher than that without oxygen incorporation. Electron spin resonance spectrometry and radical quenching experiments verified that H* and the derived •OH via 1-electron and 3-electron reduction were the main active species. Operando Raman spectroscopy confirmed that the stable SnO2 phase helped constantly activate the production of H* and •OH.

Unveiling the transformative influence of sonochemistry on formation of whey protein isolate and green tea extract (WPI-GTE) conjugates.

This study investigated the formation of conjugates between whey protein isolate (WPI) and green tea extract (GTE) using three methods: redox-pair (R), ultrasound-assisted redox-pair (RU), and ultrasonication (UL). Ultrasonication significantly reduced the reaction time for synthesizing WPI-GTE conjugates compared to the standard R method (p < 0.05). The UL methods had the highest conjugate yield determined by polyphenol binding (p < 0.05). Fourier-transform infrared spectroscopy (FTIR) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirmed the conjugate formation, indicating an increased molecular weight due to protein binding with polyphenols through covalent and non-covalent bonds. Conjugates produced via ultrasonication exhibited enhanced solubility, smaller particle size, better emulsifying capacity, and improved foaming ability compared to those formed using the traditional R method (p < 0.05). However, conjugates from the R method showed higher antioxidant activity, as evidenced by DPPH•and ABTS•+ scavenging activities (p < 0.05). In conclusion, WPI-GTE conjugates created through ultrasonic treatment demonstrate potential as dual-functional ingredients, serving as both antioxidant and emulsifier.

Array of individually addressable two-electrode electrochemical cells sharing a single counter/reference electrode for multiplexed enzyme activity measurements.

This work reports on the fabrication and performance of a new on-chip array of gold thin-film electrodes arranged into five individually addressable miniaturized electrochemical cells. Each cell shows a two-electrode configuration comprising a single working electrode and a counter/pseudo-reference electrode that is compartmentalized to be shared among all the cells of the array. Using this configuration, just six contact pads are required, which significantly reduces the chip overall surface area. Electrochemical characterization studies are carried out in solutions containing the two species of reversible redox pairs. The concentration of one redox species can reliably be measured at the working electrode by applying potentiostatic techniques to record the current due to the corresponding electrochemical reaction. The redox counterpart in turn undergoes an electrochemical process at the counter/pseudo-reference electrode, which, under optimized experimental conditions, injects current and keeps the applied potential in the electrochemical cell without limiting the current being recorded at the working electrode. Under these conditions, the electrode array shows an excellent performance in electrochemical detection studies without any chemical or electrical cross-talk between cells. The enzymatic activity of horseradish peroxidase, alkaline phosphatase and myeloperoxidase enzymes is analyzed using different redox mediators. Quasi-simultaneous measurements with the five electrochemical cells of the array are carried out within 1 s time frame. This array layout can be suitable for multiplexed electrochemical immunoassays and immunosensor approaches and implementation in simplified electrochemical ELISA platforms that make use of enzyme labels. Moreover, the array reduced dimensions facilitate the integration into compact fluidic devices.

Copper Collector Generated Cu+/Cu2+ Redox Pair for Enhanced Efficiency and Lifetime of Zn-Ni/Air Hybrid Battery.

Although Zn-Ni/air hybrid batteries exhibit improved energy efficiency, power density, and stability compared with Zn-air batteries, they still cannot satisfy the high requirements of commercialization. Herein, the Cu+/Cu2+ redox pair generated from a copper collector has been introduced to construct the hybrid battery system by combining Zn-air and Zn-Cu/Zn-Ni, in which CuXO@NiFe-LDH and Co-N-C dodecahedrons are respectively adopted as oxygen evolution (OER) and oxygen reduction (ORR) electrodes. For fabricating CuXO@NiFe-LDH, the Cu foam collector is oxidized to in situ form 1D CuXO nanoneedle arrays, which could generate the Cu+/Cu2+ redox pair to enhance battery efficiency by providing an extra charging-discharging voltage plateau to reduce the charging voltage and increase the discharge voltage. Then, the 2D NiFe hydrotalcite nanosheets grow on the nanoneedle arrays to obtain 3D interdigital structures, facilitating the intimate contact of the ORR/OER electrode and electrolyte by providing a multichannel structure. Thus, the battery system could endow a high energy efficiency (79.6% at 10 mA cm-2), an outstanding energy density (940 Wh kg-1), and an ultralong lifetime (500 h). Significantly, it could stably operate under harsh environments, such as oxygen-free and any humidity. In situ X-ray diffraction (XRD) combined with ex situ X-ray photoelectron spectroscopy (XPS) analyses demonstrate the reversible process of Cu-O-Cu ↔ Cu-O and Ni-O ↔ Ni-O-O-H during the charging/discharging, which are responsible for the enhanced efficiency and lifetime of battery.

Optimization of Methods for the Production and Refolding of Biologically Active Disulfide Bond-Rich Antibody Fragments in Microbial Hosts.

Antibodies have been used for basic research, clinical diagnostics, and therapeutic applications. Escherichia coli is one of the organisms of choice for the production of recombinant antibodies. Variable antibody genes have canonical and non-canonical disulfide bonds that are formed by the oxidation of a pair of cysteines. However, the high-level expression of an antibody is an inherent problem to the process of disulfide bond formation, ultimately leading to mispairing of cysteines which can cause misfolding and aggregation as inclusion bodies (IBs). This study demonstrated that fragment antibodies are either secreted to the periplasm as soluble proteins or expressed in the cytoplasm as insoluble inclusion bodies when expressed using engineered bacterial host strains with optimal culture conditions. It was observed that moderate-solubilization and an in vitro matrix that associated refolding strategies with redox pairing more correctly folded, structured, and yielded functionally active antibody fragments than the one achieved by a direct dilution method in the absence of a redox pair. However, natural antibodies have canonical and non-canonical disulfide bonds that need a more elaborate refolding process in the presence of optimal concentrations of chaotropic denaturants and redox agents to obtain correctly folded disulfide bonds and high yield antibodies that retain biological activity.

A redox cycle meets insulin fibrillation in vitro.

Studies of amyloid proteins have gradually become a hot topic. Nevertheless, very few effective drugs and treatments is available to cope with amyloid diseases. New molecules that can inhibit the protein fibrillation are highly anticipated. Insulin is one of the popular amyloid protein research models. On the other hand, resazurin and resorufin are widely known as a redox pair. We describes here an unexpected finding that resazurin plays a role in modulating insulin fibrillation, whereas resorufin doesn't. We hypothesize that the positively charged insulin at low pH can combine with the negatively charged resazurin due to electrostatic interaction, through which resazurin inhibited the process of insulin fibrillation. This effect was characterized and verified by using various biochemical, spectroscopic and imaging tools. This inhibition of this biocompatible dye can be achieved at various stages of fibrillation, suggesting the toxicity of the protein fibrils can be eliminated by using resazurin.

Simultaneous Photoelectrocatalytic Water Oxidation and Oxygen Reduction for Solar Electricity Production in Alkaline Solution.

The photoelectrochemical (PEC) method offers an alternative approach to photovoltaic devices for solar electricity generation. The water oxidation reaction (WOR) on the anode and oxygen reduction reaction (ORR) on the cathode is an ideal design for energy transfer owing to their superiority in terms of cleanliness, eco-friendliness, and natural abundance. However, solar electricity production based on O2 circulation by a fuel-free PEC cell is very challenging because it is extremely hard to extract electrons from water molecules owing to the uphill and sluggish WOR together with enormous overpotential for the cathodic ORR. Herein, a PEC cell based on the OH- /O2 redox pair is reported for efficient and sustainable solar electricity production by using two photoelectrodes of TiO2 and polyterthiophene in alkaline electrolyte. This fuel-free PEC cell delivers an open-circuit voltage up to 0.90 V and a maximum power density of 222 µW cm-2 with O2 -saturated NaOH electrolyte under AM 1.5 G solar irradiation. A record solar-to-electricity conversion efficiency of 0.22 % is achieved in the case of tandem illumination of the two photoelectrodes. In addition, the dual photoelectrode remains robust in accelerated and day-night cycling operation under natural atmosphere for more than a week. This PEC cell is free of fuel, separating membranes, and cocatalyst, which may guide future designs for clean and simple devices for solar energy conversion.

Neutral Red and Ferroin as Reversible and Rapid Redox Materials for Redox Flow Batteries.

Neutral red and ferroin are used as redox indicators (RINs) in potentiometric titrations. The rapid response and reversibility that are prerequisites for RINs are also desirable properties for the active materials in redox flow batteries (RFBs). This study describes the electrochemical properties of ferroin and neutral red as a redox pair. The rapid reaction rates of the RINs allow a cell to run at a rate of 4 C with 89 % capacity retention after the 100th  cycle. The diffusion coefficients, electrode reaction rates, and solubilities of the RINs were determined. The electron-transfer rate constants of ferroin and neutral red are 0.11 and 0.027 cm s-1 , respectively, which are greater than those of the components of all-vanadium and Zn/Br2 cells.

Direct Conversion of Wheat Straw into Electricity with a Biomass Flow Fuel Cell Mediated by Two Redox Ion Pairs.

In this paper, a biomass flow fuel cell to directly convert wheat straw to electricity at low temperature (80-90 °C) and atmospheric pressure is presented. Two redox ion pairs, Fe3+ /Fe2+ and VO2+ /VO2+ , acting as redox catalysts and charge carriers, were used in the anode and cathode flow tanks, respectively. The wheat straw was first oxidized by Fe3+ in the anode tank at approximately 100 °C. The reduced Fe2+ in the anode was used to construct a fuel cell with VO2+ in the cathode. The VO2+ ions were reduced to VO2+ and regenerated to VO2+ by oxygen oxidation. The wheat straw flow fuel cell showed a power output of 100 mW cm-2 . Mediated with liquid Fe3+ carriers, the solid powder of wheat straw could be gradually degraded into low-molecular-weight organic molecules and even oxidized to CO2 at the anode without using noble-metal catalysts. The overpotential for the electrodes of the flow fuel cell was examined and the energy cost was estimated.

Ferrocene and cobaltocene derivatives for non-aqueous redox flow batteries.

Ferrocene and cobaltocene and their derivatives are studied as new redox materials for redox flow cells. Their high reaction rates and moderate solubility are attractive properties for their use as active materials. The cyclability experiments are carried out in a static cell; the results showed that these materials exhibit stable capacity retention and predictable discharge potentials, which agree with the potential values from the cyclic voltammograms. The diffusion coefficients of these materials are 2 to 7 times higher than those of other non-aqueous materials such as vanadium acetylacetonate, iron tris(2,2'-bipyridine) complexes, and an organic benzene derivative.

Synthesis, characterization and in vitro anti-diabetic activity of catechin grafted inulin.

In this study, a novel biological macromolecule with strong in vitro anti-diabetic activity was developed by grafting catechin onto inulin via a free radical mediated method. The characterization, α-glucosidase and α-amylase inhibitory activities of catechin grafted inulin (catechin-g-inulin) were investigated. Results showed that the grafting ratio of catechin-g-inulin was 124.8 mg CAE/g. UV-vis spectrum of catechin-g-inulin exhibited a new band at 280 nm, attributing to B ring of catechin moiety. FT-IR spectrum of catechin-g-inulin showed new absorption bands between 1540 and 1418 cm(-1), attributing to CC stretching vibration of catechin moiety. (1)H NMR spectrum of catechin-g-inulin preserved all the characteristic proton signals of inulin and partial signals of catechin. These all confirmed the successful grafting copolymerization. Conjugation probably occurred between OH of inulin (C-6) and H-6/H-8 of catechin (A ring). Catechin-g-inulin also exhibited increased thermal stability and crystallinity as compared to inulin. Moreover, in vitro anti-diabetic assays showed the α-glucosidase inhibitory activity decreased in the order of catechin-g-inulin>catechin>acarbose>inulin, and α-amylase inhibitory activity decreased in the order of catechin-g-inulin>acarbose>catechin>inulin. These indicated the potential of catechin-g-inulin in the development of a novel effective anti-diabetic agent.

Guar gum-g-N,N'-dimethylacrylamide: synthesis, characterization and applications.

The graft copolymerization of N,N'-dimethylacrylamide onto guar gum initiated by potassium peroxymonosulphate/glycolic acid redox pair in an aqueous medium was studied gravimetrically under a nitrogen atmosphere. Grafting ratio, grafting efficiency and add on increase on increasing the concentration of potassium peroxymonosulphate (8.0 × 10(-3) to 24.0 × 10(-3) mol dm(-3)) and glycolic acid concentration (4.4 × 10(-3) to 7.6 × 10(-3) mol dm(-3)). On increasing the hydrogen ion concentration from 4 × 10(-3) to 12.0 × 10(-3) mol dm(-3), grafting ratio, efficiency, add on and conversion were increased. Maximum grafting was obtained when guar gum and N,N'-dimethylacrylamide concentration were 1.0 × 10(-2) g dm(-3) and 14.0 × 10(-2) mol dm(-3), respectively. An increase in temperature from 25 °C to 45 °C, the grafting ratio increases but conversion and homopolymer decrease. The optimum time period for graft copolymerization was 2h. The graft copolymers were characterized by IR spectroscopy and thermogravimetric analysis.

Synthesis of chitosan-gallic acid conjugate: structure characterization and in vitro anti-diabetic potential.

In this study, chitosan grafted copolymer with gallic acid (GA) was synthesized by a novel and efficient free radical mediated method. The optimal grafting conditions, structural characterization, α-glucosidase and α-amylase inhibitory activities of chitosan grafted copolymers were investigated. Results showed that the maximum grafting ratio (128.3 mg GA equivalents/g) was obtained at 12 h with 5 g/L chitosan, 16 g/L GA, 2 g/L ascorbic acid and 0.2 M hydrogen peroxide. UV-vis, Fourier-transform infrared and nuclear magnetic resonance spectroscopy all confirmed the successful grafting of GA onto chitosan. The conjugation of GA onto chitosan probably occurred between amine (C-2), hydroxyl groups (C-3 and C-6) of chitosan and carboxyl groups of GA, forming amide and ester linkages, respectively. Differential scanning calorimetry and X-ray diffraction spectra indicated that GA grafted chitosan (GA-g-chitosan) had decreased thermal stability and crystallinity as compared to chitosan. Notably, GA-g-chitosan showed increased α-glucosidase and α-amylase inhibitory activity with the increase of grafting ratio. These results indicated the potential of GA-g-chitosan in the development of an effective anti-diabetic agent.