An amazing phenomenon of the relative magnitude of modulus of two liquid-crystal (LC) gels is found inverted under/above their phase transition temperature TLC-iso, which is further proved to be caused by their diverse morphology flexibility. By testing the polarity of two LCs, gelator POSS-G1-Boc (POSS=polyhedral oligomeric silsesquioxane) was discovered to self-assemble into more flexible structures in a relatively low polar LC, whereas more rigid ones are formed in higher polar LC. Hence, a fitting function to connect morphology flexibility with solvent polarity was established, which can even be generalized to a number of common solvents. Experimental observations and coarse-grained molecular dynamics simulations revealed that solvent polarity mirrors a “Morse code”, with each “code” corresponding to a specific morphology flexibility. 相似文献
Implementing sustainable energy conversion and storage technologies is highly reliant on crucial oxygen electrocatalysis, such as the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). However, the pursuit of low cost, energetic efficient and robust bifunctional catalysts for OER and ORR remains a great challenge. Herein, the novel Na-ion-deficient Na2−xCoP2O7 catalysts are proposed to efficiently electrocatalyze OER and ORR in alkaline solution. The engineering of Na-ion deficiency can tune the electronic structure of Co, and thus tailor the intrinsically electrocatalytic performance. Among the sodium cobalt phosphate catalysts, the Na1.95CoP2O7 (NCPO5) catalyst exhibits the lowest ΔE (EJ10,OER−EJ−1,ORR) of only 0.86 V, which favorably outperforms most of the reported non-noble metal catalysts. Moreover, the Na-ion deficiency can stabilize the phase structure and morphology of NCPO5 during the OER and ORR processes. This study highlights the Na-ion deficient Na2−xCoP2O7 as a promising class of low-cost, highly active and robust bifunctional catalysts for OER and ORR. 相似文献
This paper presents the stabilization effects of inorganic filler, cerium-doped lead zirconate titanate on high-density polyethylene. The filler was loaded in two concentrations (1 and 3 wt%). The dopant contents in PbZrO3 were 0, 0.05, 0.075, 0.1 and 0.125 mol%. The degradation of hybrid samples was accomplished by γ-irradiation at various doses up to 200 kGy. The isothermal and nonisothermal chemiluminescence (CL) and thermal analysis (TG-DSC) were applied for the thermal stability characterization of modified HDPE samples. The mechanistic considerations and radiochemical consequences caused by the variation of filler concentration and doping level are discussed. The results demonstrate that the filler acts efficiently as stabilizer at low concentration of additive when the lower filler amount is present. The start of degradation precedes melting by four processes through which the chain scission and radical oxidation represent the essential degradation stage. The filler concentration influences the degradation due to the intimate interaction between solid-state defects and free radicals. The polymer protection against oxidation is based on the scavenging of radicals by the doping elements, that is, they trap and block radicals delaying material aging. The present results open a new perspective in the quality amelioration of organic products toward high durability.
CO2 is considered as the primary greenhouse gas, resulting in a series of serious environmental problems that affect people's life and health. Carbon capture and sequestration has been implemented as one of the most appealing pathways to control and use CO2. Here, we rationally integrate various functional sites within the confined nanospace of a microporous metal–organic framework (MOF) material, which is constructed by mixed-ligand strategy based on metal-adeninate vertices. It not only exhibits excellent stability but also can efficiently transform CO2 and epoxides to cyclic carbonates under mild and cocatalyst-free conditions. Additionally, this catalyst shows extraordinary recyclability for the CO2 cycloaddition reaction. 相似文献
Flexible control of building blocks of photonic crystals enables achieving desirable band structures. Exploration of photonic band extrema has brought many fantastic features to design artificial optical materials, such as Brillouin‐zone‐corner extrema for valley photonic materials and zone‐center extremum for zero‐index metamaterials. However, two such kinds of extrema are always found independently in different photonic crystals. In this work, a kind of valley photonic crystals possessing both zone‐center and zone‐corner band extrema almost at the same frequency is proposed. Inspired by antennas theory, a three‐antenna array (TAA) source is devoted to individually manipulate each extremum. The correlation coefficient is given to determine the coupling efficiency between the TAA source and extrema eigenmodes. By using a source with a high correlation coefficient, these extrema bulk states are selectively excited consistent with their eigenfields. Furthermore, three control cases are shown that multiple extrema points are simultaneously excited, in order to confirm the validity of the correlation coefficient. Finally, a potential application of a beam‐steering device is proposed through selective excitation of ternary extrema. This work develops binary valley states into ternary mix states, rendering more degrees of freedom for on‐chip optical information transport, particularly for beam steering and mode division multiplexing. 相似文献
Lead-free halide double perovskites have gathered wide scientific interest since they are environmentally friendly and stable.However,compared to the lead perovskites,their optoelectronic properties are compromised.Herein we report a series of bulk lead-free mixed Bi-In halide double perovskites:Cs_2AgBi_(1-x)In_xCl_6(0x1).The Cs_2AgBi_(0.125)In_(0.875)Cl_6breaks the parity-forbidden transition and retains direct band gap structure,having warm-white light emission,with photoluminescence quantum efficiency(PLQE)of 70.3%,much higher than the PLQE of reported lead perovskite materials.Its exciton self-trapping dynamics is investigated.Meanwhile,the Cs_2AgBi_(0.125)In_(0.875)Cl_6nanocrystals and Cs_2AgBi_(0.125)In_(0.875)Cl_6microcrystals can be synthesized by modified hot injection and rapid cooling crystallization,respectively.The size effect of Cs_2AgBi_(0.125)In_(0.875)Cl_6is studied on the photoluminescence(PL)property.Additionally,the bulk material exhibits excellent stability on exposure to light,humidity and air for more than 3 months.It is a promising candidate as highly efficient warm white-light emitting material for road lighting. 相似文献
A copper-catalyzed trifunctionalization of alkynes that provides rapid access to oxindoles bearing a geminal diboronate side chain, highlighted by the simultaneous formation of one C−C bond and two C−B bonds, is reported. This new reaction features simple reaction conditions (ligand-free catalysis), a general substrate scope, and excellent chemoselectivity. Mechanistic study revealed a reaction sequence constituted by, in the order, borylation, intramolecular cross-coupling, hydroboration, which has been rarely documented. 相似文献
[2+2] Photocycloaddition of two olefins is a general method to assemble the core scaffold, cyclobutane, found in numerous bioactive molecules. A new approach to synthesize cyclobutanes through multicomponent cascade reactions by merging aldol reaction and Witting reaction with visible-light-induced [2+2] cycloaddition is reported. An array of cyclobutanes with high selectivity has been achieved from commercially available aldehydes, ketones (or phosphorus ylide), and olefins with visible-light irradiation of a catalytic amount of (fac-tris(2-phenylpyridinato-C2,N)iridium) ([Ir(ppy)3]) at room temperature. Control experiments and spectroscopic studies revealed that the triplet–triplet energy transfer from the excited [Ir(ppy)3]* to enones, generated in situ from aldehyde and ketone or aldehyde and phosphorus ylide, is responsible for these simple and efficient muticomponent transformations. 相似文献