A novel numerical simulation method for predicting compressive properties of 3D multiaxial braided composites considering various defects

This paper reports a novel manufacturing process of preparing the Three-Dimensional Multiaxial Braided Composites(3DMBCs) and the effects of various defects generated in the manufacturing process on the compressive mechanical properties of 3DMBCs through the experimental and numerical methods. The five-step fabrication process of the 3D multiaxial braided preform was firstly introduced in detail. Then, the influences of various defects such as voids, waviness, and fiber breakage defects on the compressive properties of 3DMBCs were discussed. It is found that the fiber breakage defect and waviness defects were the two primary factors on the decrease of compressive properties of 3DMBCs. However, void defects in the resin and interface had little effect on the composites. When the fiber breakage defect content was 25% and the waviness was 7°, the composite compressive modulus decreased by 51%. The progressive damage process and failure mechanism of the composite under 90° compressive loading confirmed the validity of the numerical model by comparing with the experiments.

氨基酸基防污可注射自融合水凝胶的制备及其在术后防粘连中的应用

设计和制备具有优异防污能力的可注射防粘连材料对预防手术后组织和器官的粘连具有重要的意义.在此,我们将含有羟基的氨基酸衍生物引入水凝胶的制备中,通过N-丙烯酰丝氨酸(ASer)的自由基聚合制备了一种新型的氢键交联水凝胶(PASer).结果发现一个甲基取代基的存在会对分子间氢键相互作用产生明显的影响:与聚(N-丙烯酰苏氨酸)(PAThr)水凝胶相比,PASer水凝胶具有较低的成胶浓度和增强的力学性能.值得一提的是,亲水性羟基使PASer水凝胶能够有效抵抗蛋白质吸附和细胞粘附.PASer水凝胶具有优异的力学性能、可注射性、自融合性、良好的生物相容性和适宜的体内停留时间,符合临床对术后抗粘连材料的要求.体内研究实验结果表明,PASer水凝胶在建立的小鼠腹壁缺损模型中可以有效预防术后腹膜粘连发生.

In-situ growth of N-doped graphene-like carbon/MOF nanocomposites for high-performance supercapacitor

Graphene-like materials and metal-organic framework(MOF)materials hold significant promise for advanced energy systems.However,the accumulation of two-dimensional(2D)material and the low conductivity of MOF have seriously affected their practical application.The universal method for synthesizing homogeneous nitrogen-doped graphene-like carbon/metal-organic framework(N-GLC/MOF)composites,including N-GLC/MOF-74,N-GLC/ZIF-8,N-GLC/Cu-BTC,and N-GLC/Fe Co-PBA was presented.Thanks to the synergistic effect of the two components,the N-GLC/MOF-74 composite exhibits a specific capacitance of470.18 F/g at 1 A/g and maintains a coulombic efficiency of 95.04%at 5 A/g over 5500 cycles.Our work lays a solid foundation for the design and synthesis of N-GLC-based composites.We anticipate that this research will furnish valuable insights for the advancement of N-GLC/MOF composites,with a primary focus on enhancing supercapacitor performance.

A series of formic acid MOFs/polylactic acid blending composites with the improved dielectric performance in Co(Ⅱ)systems

In order to improve the limited compatibility of existing polymer/ceramic dielectric composites and further enhance the energy storage density,MOF/polymer composite dielectrics have been explored,which exhibit good compatibility to the polymer matrix from abundant organic groups of the inorganic–organic hybrid metal-organic framework(MOF)fillers.However,they still lack a clear composition–structure–property rule,and the precise design of MOF fillers and polymer matrix becomes a prominent problem in these composites due to the diversity of the metal ions and the organic groups.Thus,in this paper,we present a series of formic acid MOFs/polylactic acid dielectric composites in which ferroelectric formic acid MOFs,namely PDLLA/[NH_(3)(CH_(2))_(4)NH_(3)][M^(Ⅱ)(HCOO)_(3)]_(2)and PDLLA/[CH_(3)NH_(3)][M^(Ⅱ)(HCOO)_(3)]_(2),in which the formic acid MOFs are with different structures and different metal ions as fillers,including[NH_(3)(CH_(2)T_(4)NH_(3))][M^(Ⅱ)(HCOO)_(3)]_(2)(namely MOF–Co(M=Co),MOF–Mg(M=Mg),MOF–Mn(M=Mn),with 1,4-butanediamine ion as guest)and[CH_(3)NH_(3)][M^(Ⅱ)(HCOO)_(3)]_(2)(namely MOF–Co_(2)(M=Co),MOF–Ni_(2)(Ni),with methylamine ion as guest).The composition and morphology of composite films were characterized by XRD,IR,SEM,DSC and UV,respectively,while the dielectric characterizations of the composites including the dielectric permittivity,the dielectric loss,the breakdown field strength and the energy density were also performed.The composition–structure–property relationships were also investigated including the influence of MOF content and MOF category.With the introduction of MOFs,the dielectric constant of the polylactic acid substrate was improved slightly while the breakdown field strength can be improved in some systems.Interestingly,the Co(Ⅱ)-containing formic acid MOF has advantages over other formic acid MOFs with similar structure for the enhancement of the dielectric constant and breakdown field strength.Also,in some composite films with methylamine ion guest MOF fillers and low-MOF content(MOF–Co_(2)(1 vol.%)and MOF–Ni_(2)(1 vol.%)),the breakdown electric field enhanced significantly and further led to improved energy storage density which was about 43%higher than that of the polylactic acid matrix.The possible reason is that in these composites,the orientation of C–H bonds of MOFs seems more beneficial to the formation of hydrogen bonds between the carboxyl group of formic acid and the polylactic acid matrix.These relationships obtained from formic acid MOFs/polylactic acid composites are valuable to the design of high-performance polymer/MOF energy storage composites and may be a new perspective to the practical use of ferroelectric MOFs.

Enhancing blocking temperature using inverse hydrogen bonds for non-radical bridged dimeric Dy(Ⅲ)single-molecule magnets

Single-molecule magnets(SMMs)are a kind of nanosized magnetic materials that are capable of storing massive bytes of information.Strongly coupling the spin centers in a proper manner is a usual approach to promote the working temperature(or blocking temperature)for SMMs.Electron delocalized radicals have been widely employed to accomplish this job.Here,we show a new manner by using weak but multiple B–H^(δ-)···Dy^(3+)inverse hydrogen bonding(IHB)interactions to control the magnetic couplings in a series of dimeric dysprosiacaborane SMMs.This approach leads to a record high T_(B)^(100s)of 10 K among non-radical bridged dimeric SMMs,which is mainly ascribed to strong ferromagnetic coupling(4.38 cm^(-1))and the proper alignment of the magnetic principle axes of the adjacent dysprosium(Ⅲ)ions.In verifying by theoretical calculations,these results demonstrate that IHB interactions can be used to construct strong axial ferromagnetic coupling and enhancing magnetic blocking temperature for SMMs.

Nonflammable PVDF-based gel polymer electrolytes modified by dimethyl methylphosphate for wide temperature range,long cycle-life and high-safety lithium metal batteries

Gel polymer electrolytes(GPEs)has been considered as a promising candidate for the development of lithium metal batteries(LMBs)with high energy density and high safety,yet most reported GPEs is flammable,making the LMBs still facing great safety hazards.Herein,we used dimethyl methylphosphate(DMMP)as the functional flame retardant and plasticizer for poly(vinylidene fluoride)(PVDF)matrix to develop a novel nonflammable PVDF-DMMP GPEs for LMBs.The DMMP not only highly enhances the flame resistance of PVDF-DMMP GPEs,the efficient dissociation of lithium salt and the rapid transport of lithium ions,but also helps to form stable and robust CEI/SEI layers.As a result,the ultrathin PVDF-DMMP GPEs(∼20µm)present superb flame resistance,high ionic conductivity(1.34×10^(−3) S cm^(−1) at 30℃),fast lithium ion transport(t_(Li^(+))=0.59at 30℃),high electrochemical stability voltage window(over 4 V)at 30–80℃ and uniform lithium deposition.When used in Li∥Li symmetric cells,Li∥LiFePO_(4)(LFP)and Li∥LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) full cells,the nonflammable PVDF-DMMP GPEs could endow these cells with long-term cycle stability,high rate capability,wide-temperature operation ranges(from−20 to 80℃)and high safety simultaneously.Even when suffering from harsh deconstructive tests,the Li∣PVDF-DMMP GPEs∣LFP pouch cells still work normally without any safety hazards.The actual energy density of the packed pouch cell is as high as 508 Wh kg^(−1).Therefore,our work can provide a promising strategy for the design of high safety and high-energy-density LMBs.

Tough Polymeric Hydrogels Based on Amino Acid Derivative Mediated Dynamic Metal Coordination Bonds

Abstract The development of physically crosslinked hydrogels with excellent mechanical and sensing properties is of importance for expanding the practical applications of intelligent soft hydrogel materials.Herein,after copolymerization of hydroxyl-containing amino acid derivative N-acryloyl serine(ASer)with acrylamide(AM),we introduce Zr4+through an immersion strategy to construct metal ion-toughened non-covalent crosslinked hydrogels(with tensile strength of up to 5.73 MPa).It is found that the synergistic coordination of hydroxyl and carboxyl groups with Zr^(4+)substantially increases the crosslinking density of the hydrogels,thereby imparting markedly superior mechanical properties compared to hydroxyl-free Zr^(4+)-crosslinked hydrogels,such as N-acryloyl alanine(AAla)copolymerized with AM hydrogels(with tensile strength of 2.98 MPa)Through the adjustment of the composition of the copolymer and the density of coordination bonds,the mechanical properties of the hydrogels can be modulated over a wide range.Additionally,due to the introduction of metal ions and the dynamic nature of coordination bonds,the hydrogels also exhibit excellent sensing performance and good self-recovery properties,paving the way for the development of flexible electronic substrates with outstanding comprehensive performances.

Gd-based molecular coolants:Aggregating for better magnetocaloric effect

Two series of 3d-Gd mixed-metal phosphonate complexes with either only two gadolinium centers such as{Gd_(2)},{Ni_(2)Gd_(2)},{Co_(4)Gd_(2)},{Co_(8)Gd_(2)},{Fe_(6)Gd_(2)},and{Fe_(17)Gd_(2)}or more than two gadoliniums such as{Co_(8)Gd_(4)},{Mn_(8)Gd_(4)},{Co_(4)Gd_(6)},{Mn_(4)Gd_(6)},{Co_(6)Gd_(8)},{Ni_(5)Gd_(8)},{Ni_(6)Gd_(6)},{Co_(8)Gd_(8)},and{Mn_(9)Gd_(9)}have been solvothermally prepared and magnetothermally studied.The nearly identical environments of the Gd(III)dimer in thefirst series allow us to qualitatively analyze the effect of magnetic exchange coupling on the magne-tocaloric effect(MCE).By doubling,tripling,or quadrupling of the Gd(III)centers,the second series of 3d-Gd mixed-metal complexes was built to further test the other effects of exchange couplings on MCE in more complicated circumstances.For the antiferromagnetic coupling cases,the results are nearly identical but diversify when topological spin frustrations are created,whose massive low-lying excited spin states help enhance MCE.For presumably ferromagnetically coupled ones,albeit are rare in phosphonate complexes,they do exhibit excellent MCE.Meanwhile,the com-plexes with weakly coupled metal centers serve as excellent examples for studying the effect of molecular mass on MCE when its magnitude is expressed in the unit of Joule per kilogram,from which we can see the values are directly proportional to the percentage of the Gd(III)ions in molecular weight.

Tailoring component incorporation for homogenized perovskite solar cells

Deep-level traps at the buried interface of perovskite and energy mismatch problems between the perovskite layer and heterogeneous interfaces restrict the development of ideal homogenized films and efficient perovskite solar cells(PSCs)using the one-step spin-coating method.Here,we strategically employed sparingly soluble germanium iodide as a homogenized bulk in-situ reconstruction inducing material preferentially aggregated at the perovskite buried interface with gradient doping,markedly reducing deep-level traps and withstanding local lattice strain,while minimizing non-radiative recombination losses and enhancing the charge carrier lifetime over 9μs.Furthermore,this gradient doping assisted in modifying the band diagram at the buried interface into a desirable flattened alignment,substantially mitigating the energy loss of charge carriers within perovskite films and improving the carrier extraction equilibrium.As a result,the optimized device achieved a champion power conversion efficiency of 25.24% with a fill factor of up to 84.65%,and the unencapsulated device also demonstrated excellent light stability and humidity stability.This work provides a straightforward and reliable homogenization strategy of perovskite components for obtaining efficient and stable PSCs.

An ultra-thin piezoelectric nanogenerator with breathable,superhydrophobic,and antibacterial properties for human motion monitoring

Piezoelectric nanogenerators(PENGs)are promising for harvesting renewable and abundant mechanical energy with high efficiency.Up to now,published research studies have mainly focused on increasing the sensitivity and output of PENGs.The technical challenges in relation to practicability,comfort,and antibacterial performance,which are critically important for wearable applications,have not been well addressed.To overcome the limitations,we developed an all-nanofiber PENG(ANF-PENG)with a sandwich structure,in which the middle poly(vinylidene fluoride-co-hexafluoropropylene(P(VDF-HFP))/ZnO electrospun nanofibers serve as the piezoelectric layer,and the above and below electrostatic direct-writing P(VDF-HFP)/ZnO nanofiber membranes with a 110 nm Ag layer on one side that was plated by vacuum coating technique serve as the electrode layer.As the ANF-PENG only has 91μm thick and does not need further encapsulating,it has a high air permeability of 24.97 mm/s.ZnO nanoparticles in ANF-PENG not only improve the piezoelectric output,but also have antibacterial function(over 98%).The multifunctional ANF-PENG demonstrates good sensitivity to human motion and can harvest mechanical energy,indicating great potential applications in flexible self-powered electronic wearables and body health monitoring.

Bioactive skin-mimicking hydrogel band-aids for diabetic wound healing and infectious skin incision treatment

The treatment of diabetic chronic wounds remains a global challenge due to the up-regulated inflammation response,oxidant stress,and persistent infection during healing process.Developing wound dressing materials with ideal biocompatibility,adequate mechanical strength,considerable under-water adhesion,sufficient anti-inflammation,antioxidant,and antibacterial properties is on-demand for clinical applications.In this study,we developed a bioactive skin-mimicking hydrogel band-aid through the combination of tannic acid(TA)and imidazolidinyl urea reinforced polyurethane(PMI)(TAP hydrogel)and explored its potentials in various medical applications,including hemostasis,normal skin incision,full-thickness skin wounds,and bacterial-infection skin incision on diabetic mice.TA was loaded into PMI hydrogel network to enhance the mechanical properties of TAP hydrogels through multiple non-covalent interactions(break strength:0.28-0.64 MPa;elongation at break:650-930%),which could resist the local stress and maintain the structural integrity of wound dressings during applications.Moreover,owing to the promising moisture-resistant adhesiveness and organ hemostasis,outstanding anti-inflammation,antibacterial,and antioxidant properties,TAP hydrogels could efficiently promote the recovery of skin incision and defects on diabetic mice.To further simulate the practical situation and explore the potential in clinical application,we also verified the treatment efficiency of TAP hydrogel in S.aureus-infected skin incision model on diabetic mice.

Robust hydrogel adhesives for emergency rescue and gastric perforation repair

Development of biocompatible hydrogel adhesives with robust tissue adhesion to realize instant hemorrhage control and injury sealing,especially for emergency rescue and tissue repair,is still challenging.Herein,we report a potent hydrogel adhesive by free radical polymerization of N-acryloyl aspartic acid(AASP)in a facile and straightforward way.Through delicate adjustment of steric hindrance,the synergistic effect between interface interactions and cohesion energy can be achieved in PAASP hydrogel verified by X-ray photoelectron spectroscopy(XPS)analysis and simulation calculation compared to poly(N-acryloyl glutamic acid)(PAGLU)and poly(N-acryloyl amidomalonic acid)(PAAMI)hydrogels.The adhesion strength of the PAASP hydrogel could reach 120 kPa to firmly seal the broken organs to withstand the external force with persistent stability under physiological conditions,and rapid hemostasis in different hemorrhage models on mice is achieved using PAASP hydrogel as physical barrier.Furthermore,the paper-based Fe^(3+)transfer printing method is applied to construct PAASP-based Janus hydrogel patch with both adhesive and non-adhesive surfaces,by which simultaneous wound healing and postoperative anti-adhesion can be realized in gastric perforation model on mice.This advanced hydrogel may show vast potential as bio-adhesives for emergency rescue and tissue/organ repair.

Chelating Guanidinates for Dysprosium(Ⅲ) Single-Molecule Magnets

Two chelating guanidinate-based dysprosium(Ⅲ)complexes,namely the monomeric{(Me_(3)Si)_(2)NC(N^(i)Pr)_(2)}_(2)Dy(μ-CI)_(2)Li(THF)_(2) 1 and the dimeric[{(Me_(3)Si)_(2)NC(N^(i)Pr)_(2)}_(2)Dy(μ-CI)]_(2) 2,have been confirmed to be single-molecule magnets.Moreover,the alteration from 1 to 2 leads to an obvious mitigated quantum tunnelling of magnetization at zero field of the hysteresis loop and much enhanced magnetic relaxation barrier(up to 312 K).5%dilution with the yttrium(Ⅲ)analogue for 2 shows no clear change for the hysteresis,indicating the single-ion nature of the magnetic behavior.

Recent Advances of Nanoelectrodes for Single-Cell Electroanalysis:From Extracellular, Intercellular to Intracellular

Detection at single-cell level plays a critical role in revealing cell behavior in different organisms.Nanoelectrodes with high temporal–spatial resolution can precisely and dynamically monitor the physiological and pathological processes of various single cells.The field of using nanoelectrodes in single-cell electroanalysis is blooming in recent years.In this review,we mainly summarize the recent advances of nanoelectrodes for single-cell electroanalysis from extracellular,intercellular to intracellular levels in the past decade.First,we introduce the main types of nanoelectrodes based on their geometry and characteristics for single-cell electroanalysis.Then,the representative works of using nanoelectrodes to investigate cellular signaling biomolecules and to understand various cellular processes from the extracellular,intercellular,and intracellular levels are introduced.Finally,the challenges and future prospects of nanoelectrodes for single-cell electroanalysis are proposed.This review gives a comprehensive summary of nanoelectrodes for single-cell electroanalysis in the prospects of monitoring cell physiological topography,understanding communication mechanism and revealing physiological functions,which can provide new insights into cell-based pharmacological screening and fundamental studies of disease development mechanisms.

Cationic telluroviologen derivatives as type-I photosensitizers for tumor photodynamic theranostics

The hypoxia of the tumor microenvironment(TME)seriously restricts the photodynamic therapy(PDT)effect of conventional type-II photosensitizers,which are highly dependent on O_(2).In this work,a new type-I photosensitizer(TPE-TeVPPh3)consisting of a tetraphenylethylene group(TPE)as a bioimaging moiety,triphenyl-phosphine(PPh3)as a mitochondria-targeting group,and telluroviologen(TeV2+)as a reactive oxygen species(O_(2)•−,•OH)generating moiety is developed.The luminescence intensity of TPE-TeV-PPh3 increased significantly after specific oxidation by excess H2O2 in the TME without responding to normal tissues via the formation of Te═O bond,which can be used for monitoring abnormal H2O2,positioning,and imaging of tumors.TPE-TeV-PPh3 with highly reactive radicals generation and stronger hypoxia tolerance realizes efficient cancer cell killing under hypoxic conditions,achieving 88%tumor growth inhibition.Therefore,TPE-TeV-PPh3 with low phototoxicity in normal tissue achieves tumor imaging and effective PDT toward solid tumors in response to high concentrations of H_(2)O_(2)in the TME,which provides a new strategy for the development of type-I photosensitizers.