Gradient-structure-enhanced dielectric energy storage performance of flexible nanocomposites containing controlled preparation of defective TiO_(2) and ferroelectric KNbO_(3) nanosheets

Next generation power system needs dielectrics with increased dielectric energy density.However,the low energy density of dielectrics limits their development.Here,an asymmetric trilayered nanocomposite,with a transition layer(TL),an insulation layer(IL),and a polarization layer(PL),is designed based on poly(vinylidene fluoride)-polymethyl methacrylate(PVDF-PMMA)matrix using KNbO_(3)(KN)and TiO_(2)(TO)as the nanofillers.The morphology and defect control of the two-dimensional nano KN and nano TO fillers are realized via a hydrothermal method to increase the composite breakdown strength(E_(b))and the composite energy density(U_(e)).The asymmetric trilayered structure leads to a gradient electric field distribution,and the KN and TO nanosheets block charges transfer along z direction.As a result,the development path of the electrical trees is greatly curved,and E_(b) is effectively improved.And the Ue value of the nanocomposites reaches 17.79 J·cm^(-3) at 523 MV·m^(-1).On the basis,the composite Ue is further improved by defect control in TO nanosheets.The nanocomposite KN/TO/PVDF-PMMA containing TO with less oxygen vacancy concentration(calcined at oxygen atmosphere)acquires a high Ue of 21.61 J·cm^(-3) at 548 MV·m^(-1).This study provides an idea for improving the energy storage performance by combining the design of the composite dielectric structure and the control of nanofillers’defect and morphology.

Supramolecular polymer network constructed by a functionalized polyimidazolium salt derived from metal-carbene template approach

In this study,we present a supramolecular templating approach for constructing polyimidazolium salt containing crown ether and cyclobutane moieties.This strategy involves the formation of metal-carbene templates,photochemical cycloaddition,and subsequent demetallation of metal ions.Driven by the host-guest chemistry between crown ether units and ammonium salts,we successfully fabricated a supramolecular polymer SPN1,which features imidazolium receptors and cyclobutane units.The obtained SPN1 demonstrates outstanding reversible stimulus-response,antibacterial behavior and conductivity.

N-Heterocyclic carbene-stabilized platinum nanoparticles within a porphyrinic nanocage for selective photooxidation

The successful construction of highly stable and active platinum nanoparticles(Pt NPs) within the confined cavity of a threedimensional porphyrinic nanocage is presented in this study. The flexible porphyrinic nanocage containing eight N-heterocyclic carbene(NHC) precursors was prepared using a metal-carbene-templated ring-closing metathesis(RCM) approach as new capping materials for the fabrication/stabilization of Pt NPs. Notably, the NHC-stabilized Pt NPs within the porphyrinic nanocage exhibited high catalytic activity for selective oxidation of 2-chloroethyl ethyl sulfide to nontoxic 2-chloroethyl ethyl sulfoxide with excellent stability and recyclability.

Supramolecular Template-Assisted Catalytic[2+2]Photocycloaddition in Homogeneous Solution

Supramolecular interactions can help recognize and organize substrates around an enzyme’s active sites and subsequently assemble a new molecule in a certain way.Inspired by nature’s control of reactions,in this work we designed a template catalyst equipped with ditopic Au(I)–N-heterocyclic carbene(NHC)functional sites that direct olefin substrates into reactive geometries via collaboration of coordination-driven interactions.Notably,this catalyst enables the realization of catalytic[2+2]photocycloadditions with as low as 2 mol%catalyst loading in homogeneous solution and the delivery of a series of cyclobutane derivatives with excellent conversions and stereoselectivities.The success of gram-scale reactions further demonstrates the feasibility of this strategy,which lays a solid foundation for the large-scale preparation of cyclobutane derivatives in the future.

A near-infrared fluorescent probe for visualizing transformation pathway of Cys/Hcy and H2S and its applications in living system

Sulfydryl-contained(-SH)substances including hydrogen sulfide(H_(2)S),cysteine(Cys),homocysteine(Hcy)and glutathione(GSH)play crucial roles in living systems,and their variations are closely associated with various diseases.Herein,we developed a near-infrared intramolecular charge transfer(ICT)based fluorescent probe Y-NBD,achieving detection of Cys/Hcy and H_(2)S with different fluorescent signals(green-red for Cys/Hcy,red for H_(2)S),large Stokes shifts(∼100/105nm or 191 nm)and high signal-background-ratio,but not responding to GSH.Y-NBD was successfully applied to image exogenous/endogenous Cys/Hcy and H_(2)S in various living cancer cells(HeLa,A549,and HepG2)and in zebrafish.It not only visualized the transformation pathway of several thiols in HepG2 cells but also verified that the intestine is the main site for the activation and metabolism of Y-NBD in zebrafish,as well as realized to evaluate the degree of drug-induced liver injury.This work provides a promising tool for imaging Cys/Hcy and H_(2)S in living systems and shows great potency in evaluating drug-induced liver injury and its treatment.

Electrostatic Encapsulation of Cobalt Ions into Crystalline Framework Derived Polymer Aerogel:Ultra-light,Pressure Resistant,Hydrophobic,Photothermal Conversion,Heat Insulation and Infrared Stealth

A variety of electromagnetic wave absorption materials(EMWAs)have been reported,but the integration of powder materials and multifunctional devices should be investigated in-depth to adapt to practical demands.Herein,carbon-coated cobalt composites were prepared by adsorbing magnetic metal cations into an anionic crystalline framework through an electrostatic encapsulate process.Excellent reflection loss(RL_(min))of-40.49 d B and effective absorption bandwidth(EAB)of 5.36 GHz(RL<-10 d B,10.4-15.76 GHz)was achieved with an optimal radar cross section(RCS)reduction of 34.9 dB·m^(2) for the sample tested.For commercial applications,Co@CN-4 was integrated into sodium carboxymethyl cellulose(CMC)aerogel to create an ultra-lightweight composite aerogel that is compressive resistant and heat-holding while also having photothermal conversion capabilities.The hydrophobic modification makes it more widely useful.This study provides a new strategy for EWAMs to integrate versatility and improve their application prospects.

NHC-derived carbon-centered luminescent radicals with shortwavelength emission via suppression of Kasha's rule

Luminescent organic radicals have garnered increasing attention owing to their versatile applications in sensing, imaging, and organic light-emitting diodes(OLEDs), attributed to their unique emission properties originating from the doublet spin state.However, the natural narrow bandgap of organic free radicals typically limits their emission to the long-wavelength region.Designing luminescent organic radicals with short-wavelength emission remains a significant challenge. Herein, a series of carbon-centered radicals with short-wavelength emission(383–476 nm) by combining N-heterocyclic carbenes with various polycyclic aromatic hydrocarbons(PAHs)(2-naphthyl, 2a~Ⅰ and 2b~Ⅰ;2-phenanthryl, 2a~Ⅱand 2b~Ⅱ;2-anthryl, 2a~Ⅲand 2b~Ⅲ;3-phenanthryl, 2a~Ⅳand 2b~Ⅳ). Theoretical calculations reveal that the introduction of PAHs significantly increases the ΔE_(D2-D1) in 2a^(Ⅰ–Ⅲ)and 2b^(Ⅰ–Ⅲ)compared to that in phenyl-derived radical congeners. Consequently, the internal transition from D2 to D1 is impeded, leading to a high yield of D2 emission and a suppressed Kasha's rule, thereby overcoming the limitations imposed by their narrow bandgap. For 2a~Ⅳ and 2b~Ⅳ, despite a moderately large ΔED2-D1value, the ΔED3-D1value exceeds 1 e V, indicating that their emission likely originates from the D3 state. Furthermore, we utilized 2a~Ⅲand 2b~Ⅲ as emissive materials in OLEDs,resulting in blue emissions with external quantum efficiencies of 7.5% and 6.5%, respectively.

Phase-mediated controllable intramolecular and intermolecular photocycloadditions assisted by supramolecular templates

Understanding and controlling supramolecular template effect assembly via a photochemical reaction in different solid and solution phases is one of the main topics in photochemistry. Here, an interesting case of phase-mediated controllable intramolecular/intermolecular photochemical [2+2] cycloadditions assisted by supramolecular templates was demonstrated. Direct irradiation of the complexes in solution yields intramolecular photoproducts exclusively, whereas exposure of the solid powder sample under the same conditions yields intermolecular dinuclear species quantitatively. The nature of the phase and supramolecular interaction affects the geometrical arrangements of the metallacycles, leading to different cycloaddition products under photoirradiation. The crystal structures of different products were investigated by single-crystal X-ray diffraction, nuclear magnetic resonance(NMR) spectrometry, and electrospray ionization mass spectrometry(ESI-MS).