Synthesis and mesomorphic properties of fluorinated Schiff's base liquid crystals containing vinyl end groups

Three kinds of fluorinated Schiff＇s base esters, 4-allyloxy-2-X-6-X-benzoic acid 4-[（2, 3, 4-trifluorophenylimino）methyl]phenyl ester, where X=H or F, were synthesized and characterized. Their chemical structures were identified by Fourier transform infrared spectroscopy （FTIR） and ^1H nuclear magnetic resonance （^1H NMR）. Their mesomorphic properties were studied by polarized optical microscopy （POM） and differential scanning calorimetry （DSC）. It was found that all the three compounds exhibited enantiotropic nematic phases only. And their cleating point temperature and thermal range of mesophase decreased with the number of fluorine atoms on the rigid core of the compounds; while their melting point temperature showed no distinct regularity.

Preparation of bunched CeO_(2) and study on microwave absorbing properties with MWCNTs binary composite

A novel bunched cerium oxide(CeO_(2))was prepared and its binary composite material with multi-walled carbon nanotubes presented an excellent microwave absorbing properties.The morphology,structure,and absorbing properties of the composite material were investigated.It was found that the minimum reflection loss(RL)of the composite material at 15.79 GHz was−45.7 dB when the thickness was 5.5 mm.It was worth noting that when the composite material was in the thickness range of 5.0-7.5 mm and the frequency was 11.36-17.77 GHz,the electromagnetic wave RL was<−30 dB,which illustrated that the composite material had a good absorbing effect over a wide thickness range.The results of the study contributed to the design and preparation of efficient microwave absorbing materials(MAM)with rare earth oxide composites and their applications,which demonstrated the importance of new composites with special structures in the field of MAM.

One-Step High-Temperature-Synthesized Single-Atom Platinum Catalyst for Efficient Selective Hydrogenation

Although single-atom catalysts significantly improve the atom utilization efficiency,the multistep preparation procedures are complicated and difficult to control.Herein,we demonstrate that one-step in situ synthesis of the single-atom Pt anchored in single-crystal MoC(Pt_(1)/MoC)by using facile and controllable arc-discharge strategy under extreme conditions.The high temperature(up to 4000℃)provides the sufficient energy for atom dispersion and overall stability by forming thermodynamically favourable metal-support interactions.The high-temperature-stabilized Pt1/MoC exhibits outstanding performance and excellent thermal stability as durable catalyst for selective quinoline hydrogenation.The initial turnover frequency of 3710 h^(-1)is greater than those of previously reported samples by an order of magnitude under 2 MPa H_(2)at 100℃.The catalyst also shows broad scope activity toward hydrogenation containing unsaturated groups of C=C,C=N,and C=O.The facile,one-step,and fast arc-discharge method provides an effective avenue for single-atom catalyst fabrication that is conventionally challenging.

Electrodes with Electrodeposited Water-excluding Polymer Coating Enable High-Voltage Aqueous Supercapacitors

Aqueous supercapacitors are powerful energy sources,but they are limited by energy density that is much lower than lithium-ion batteries.Since raising the voltage beyond the thermodynamic potential for water splitting(1.23 V)can boost the energy density,there has been much effort on water-stabilizing salvation additives such as Li_(2)SO_(4) that can provide an aqueous electrolyte capable of withstanding~1.8 V.Guided by the first-principles calculations that reveal water can promote hydrogen and oxygen evolution reactions,here,we pursue a new strategy of covering the electrode with a dense electroplated polymerized polyacrylic acid,which is an electron insulator but a proton conductor and proton reservoir.The combined effect of salvation and coating expands the electrochemical window throughout pH 3 to pH 10 to 2.4V for both fast and slow proton-mediated redox reactions.This allows activated carbon to quadruple the energy density,a kilogram of nitrogen-doped graphene to provide 127 Watt-hour,and both to have improved endurance because of suppression of water-mediated corrosion.Therefore,aqueous supercapacitors can now achieve energy densities quite comparable to that of a lithium-ion battery,but at 100 times the charging/discharging speed and cycle durability.

Fluorination strategy enables greatly improved performance for organic solar cells based on polythiophene derivatives

The power conversion efficiencies(PCEs)of organic solar cells(OSCs)have reached 18%recently,which have already met the demand of practical application.However,these outstanding results were generally achieved with donor-acceptor(D-A)type copolymer donors,which can hardly fulfill the low-cost largescale production due to their complicated synthesis processes.Therefore,developing polymer donors with simple chemical structures is urgent for realizing low-cost OSCs.Polythiophene(PT)derivatives are currently regarded as promising candidates for such kind of donor materials,which has been illustrated in many works.In this work,two new alkylthio substituted PT derivatives,P301 and P302,were synthesized and tested as donors in the OSCs using Y5 as the accepto r.In comparison,the introduction of fluorine atoms on the backbone of P302 can not only downshift the energy levels,but also greatly improve the phase separation morphologies of the active layers,which is ascribed to the enhanced aggregation effect and the reduced miscibility with the non-fullerene acceptor.As a result,the P302:Y5-based OSC exhibits a significantly improved PCE of 9.65%than that of P301:Y5-based one,indicating the important role of fluorination in the construction of efficient PT derivative donors.