Size-refinement enhanced flexibility and electrochemical performance of MXene electrodes for flexible waterproof supercapacitors

Increasing mechanical flexibility without sacrificing electrochemical performance of the electrode material is highly desired in the design of flexible electrochemical energy storage devices.In metal-related materials science,decreasing the grain size introduces more grain boundaries;this stops dislocations and crack propagation under deformation,and results in increased strength and toughness.However,such a size refinement effect has not been considered in the mechanical properties,particle stacking,wetting,and electrochemical performances of flexible supercapacitor electrodes.In this paper,MXene was used as an electrode material to study the size refinement effect of flexible supercapacitors.Size refinement improved the strength and toughness of the MXene electrodes,and this resulted in increased flexibility.Finite elemental analysis provided a theoretical understanding of size refinement-increased flexibility.Moreover,the size refinement also improved the specific surface area,electric conductance,ion transportation,and water wetting properties of the electrode,and the size refinement provided highly increased energy density and power density of the MXene supercapacitors.A highly flexible,water-proof supercapacitor was fabricated using size-refined MXene.The current study provides a new viewpoint for designing tough and flexible energy storage electrodes.The size refinement effect may also be applicable for metal ion batteries and electronic and photo devices composed of MXene and other nanoparticles.

A Hybrid Conjugate Gradient Algorithm for Solving Relative Orientation of Big Rotation Angle Stereo Pair

The fast convergence without initial value dependence is the key to solving large angle relative orientation.Therefore,a hybrid conjugate gradient algorithm is proposed in this paper.The concrete process is:①stochastic hill climbing(SHC)algorithm is used to make a random disturbance to the given initial value of the relative orientation element,and the new value to guarantee the optimization direction is generated.②In local optimization,a super-linear convergent conjugate gradient method is used to replace the steepest descent method in relative orientation to improve its convergence rate.③The global convergence condition is that the calculation error is less than the prescribed limit error.The comparison experiment shows that the method proposed in this paper is independent of the initial value,and has higher accuracy and fewer iterations.

UV light-driven asymmetric vinylogous aldol reaction of isatins with 2-alkylbenzophenones and enantioselective synthesis of 3-hydroxyoxindoles

Chiral 3-hydroxyoxindoles are biologically important molecular motifs which are frequently present in natural products and artificial compounds.Herein,we report an ultraviolet light-driven asymmetric vinylogous aldol reaction between versatile isatins and 2-alkylbenzophenones.Under mild conditions.

Recent developments in artificial spider silk and functional gel fibers

It is highly desirable to develop fiber materials with high strength and toughness while increasing fiber strength always results in a decrease in toughness.Spider silk is a natural fiber material with an excellent combination of high strength and toughness,which is produced from the spinning dope solution by gelation and drawing spinning process.This encourages people to prepare artificial fibers by mimicking the material,structure,and spinning of natural spider silk.In this review,we first summarized the preparation of artificial spider silk prepared via such a gelation process from different types of materials,including nonrecombinant proteins,recombinant proteins,polypeptides,synthetic polymers,and polymer nanocomposites.In addition,different spinning approaches for spinning artificial spider silk are also summarized.In the third section,some novel application scenarios of the artificial spider silk were summarized,such as artificial muscles,sensing,and smart fibers.

Spider Silk Supercontraction‑Inspired Cotton‑Hydrogel Self‑Adapting Textiles

Smart textiles are able to self-adapt to an irregular surface.So,they found new applications in intelligent clothes and equipments,where the properties and functionality of traditional polymeric fibers are insufficient,and hard to be realized.Inspired by the supercontraction behavior of the spider silk,we prepared a spinnable hydrogel to form a sheath-core-like composite yarn,after being coated on cotton yarn.The strong hydrogen bonding between the cotton yarn and the polar groups of the hydrogel provides an outstanding mechanical stability,and the twists insertion forms a spiral-like architecture,which exhibited moisture-responsive super contraction behavior.By structural tailoring the chirality of the fiber twists and coiling extends into homo-chiral and heterochiral architectures,as displays contraction and expansion when is exposed to the moisture.Once the relative humidity is increased from 60 to 90%,a homochiral yarn exhibits 90%contraction,while a heterochiral yarn shows 450% expansion,and the maximum work capacity reached up to 6.1 J/Kg.The super contracted yarn can be re-stretched to its original length manifesting cyclability,which can be exploited to build a smart textile,selfadaptive to irregular surfaces.Such a strategy may be further extended to a wide variety of materials to achieve intelligent textiles from common fiber or yarns.