Characterization of Various Noncovalent Polyphenol-Starch Complexes and Their Prebiotic Activities during In Vitro Digestion and Fermentation.

This study explores the structural characterization of six noncovalent polyphenol-starch complexes and their prebiotic activities during in vitro digestion and fermentation. Ferulic acid, caffeic acid, gallic acid, isoquercetin, astragalin, and hyperin were complexed with sweet potato starch (SPS). The polyphenols exhibited high binding capacity (>70%) with SPS. A partial release of flavonoids from the complexes was observed via in vitro digestion, while the phenolic acids remained tightly bound. Molecular dynamics (MD) simulation revealed that polyphenols altered the spatial configuration of polysaccharides and intramolecular hydrogen bonds formed. Additionally, polyphenol-SPS complexes exerted inhibitory effects on starch digestion compared to gelatinized SPS, owing to the increase in resistant starch fraction. It revealed that the different complexes stimulated the growth of Lactobacillus rhamnosus and Bifidobacterium bifidum, while inhibiting the growth of Escherichia coli. Moreover, in vitro fermentation experiments revealed that complexes were utilized by the gut microbiota, resulting in the production of short-chain fatty acids and a decrease in pH. In addition, the polyphenol-SPS complexes altered the composition of gut microbiota by promoting the growth of beneficial bacteria and decreasing pathogenic bacteria. Polyphenol-SPS complexes exhibit great potential for use as a prebiotic and exert dual beneficial effects on gut microbiota.

Antimony nanocrystals self-encapsulated within bio-oil derived carbon for ultra-stable sodium storage.

Integrating carbon-coating and nanostructuring has been considered as the most promising strategy to accommodate the dramatic volume expansion represented by high-capacity antimony (Sb) upon sodiation. Suitable coating source and synthetic strategy that are both economical and strong are yet to be explored. In this regard, by using renewable bio-oil as carbon source and self-wrapping precursor, robust Sb@C composite anode with Sb nanoparticles homogeneously impregnated into the cross-linked 2D ultrathin carbon nanosheets is developed via a facile NaCl template-assisted self-assembly and followed carbothermal reduction method. Such judiciously crafted interconnected macroporous framework can mitigate of mechanical stress and alleviate the volume change of inner Sb, guaranteeing high-performance sodium-ion battery anode. At a current density of 0.1 A g-1, ultrahigh reversible capacity of 520 mAh g-1 can be achieved. Notably, a stable capacity of 391 mAh g-1 is even retained after 500 cycles at 1 A g-1. Such a facile and cost-effective synthetic method is promising for high-performance sodium-ion batteries.

A free-standing manganese cobalt sulfide@cobalt nickel layered double hydroxide core-shell heterostructure for an asymmetric supercapacitor.

Rational design of self-supported electrode materials is important to develop high-performance supercapacitors. Herein, a free-standing MnCo2S4@CoNi LDH (MCS@CN LDH) core-shell heterostructure is successfully prepared on Ni foam using the hydrothermal reaction and electrodeposition. In this architecture, the inner MnCo2S4 nanotube provides an ultra-high electrical conductivity and the CoNi LDH nanosheets can offer more electrochemical active sites for better faradaic reactions. Moreover, the core-shell heterostructure can also maintain the structural integrity during the processes of continuous charge/discharge. The MCS@CN LDH electrode displays a satisfactory specific capacitance of 1206 C g-1 and excellent cycling performance with ∼92% retention after 10 000 cycles. In addition, an asymmetric supercapacitor (ASC), in which MCS@CN LDH and N-doped rGO are used as the positive electrode and the negative electrode, was assembled which exhibits an energy density of 48.8 W h kg-1 with superior cycling stability, indicating the potential of this electrode in practical energy storage.

Weld Formation Mechanism and Microstructural Evolution of TC4/304 Stainless Steel Joint with Cu-Based Filler Wire and Preheating.

Ti-Fe intermetallic compounds were effectively suppressed with Cu-based filler wire and weld formation was greatly improved with the preheating of substrates when joining TC4 titanium alloy and 304 stainless steel. A Ti/Cu transition zone consisting of complex TiCu, Ti2Cu3, TiFe, and TiFe2 phases was formed between Cu-weld/TC4 interface, while Cu-weld/304ss interface was mainly composed of α-Fe and ε-Cu solid solution. At lower heat input, the undercut defect in back surface had potential to cause crack initiation and joint fracture. Though increasing heat input would improve weld morphology, the formation of thick interfacial reaction layer and weld cracking led to low weld quality and joint strength. The preheating of substrates had an obvious effect on wetting ability of liquid filler metal and could achieve a better weld quality at lower heat input. The back formation of weld was improved to decrease the occurrence of weld defects. The highest tensile strength of 365 MPa occurred at welding heat input of 0.483 kJ/cm, increasing by 47% compared to the joint without preheating. The interfacial reaction mechanism was discussed to reveal the relationship between microstructural characteristics and fracture behavior of Ti/steel welded joints with Cu-based filler wire.

Oxygen-vacancy-rich nickel-cobalt layered double hydroxide electrode for high-performance supercapacitors.

The introduction of oxygen vacancies into electrode materials has been proven to be a valid way to enhance the electrochemical performance. However, the traditional methods to introduce oxygen vacancies require severe conditions that may be harmful to hydroxides. Herein, the oxygen vacancy-rich nickel-cobalt (NiCo) layered double hydroxide (denoted as Vo-NiCo LDH) nanowire array electrode is synthesized using the chemical reduction method. Owing to the reduction of NaBH4 solution, we can create oxygen vacancies under milder conditions, thus avoiding any damage to the hydroxide. The as-synthesized electrode shows a specific capacitance of 1563.1 F g-1 at 1 A g-1, which is much higher than that of the pristine electrode (995.4 F g-1 at 1 A g-1). Moreover, the cycling performance and rate performance are also enhanced. The as-fabricated asymmetric supercapacitor (Vo-NiCo LDH//Fe2O3) is able to deliver a maximum energy density of 56.2 W h kg-1 at a power density of 800 W kg-1 with a voltage window of 1.6 V.