Man-made superheavy elements(SHE)are produced as energetic recoils in complete-fusion reactions and need to be thermalized in a gas-filled chamber for chemical studies.The ever-shorter half-lives and decreasing produc...Man-made superheavy elements(SHE)are produced as energetic recoils in complete-fusion reactions and need to be thermalized in a gas-filled chamber for chemical studies.The ever-shorter half-lives and decreasing production rates of the elements beyond Fl(atomic number Z=114)-the heaviest element chemically studied today-require the development of novel techniques for quantitative thermalization and fast extraction efficiency.The Universal high-density gas stopping Cell(UniCell),currently under construction,was proposed to achieve this.Within this work,we propose an Ion Transfer by Gas Flow(ITGF)device,which serves as a UniCell ejector to interface with a gas chromatography detector array for chemical studies.Detailed parameter optimizations,using gas dynamics and Monte Carlo ion-trajectory simulations,promise fast(within a few ms)and highly efficient(up to 100%)ion extraction across a wide mass range.These ions can then be transmitted quantitatively through the ITGF into the high-pressure environment needed for further chemical studies.展开更多
Abundant efforts have been devoted to improving the efficiency of organic light-emitting diodes(OLEDs),however,approaches to control the device efficiency roll-off are still extremely limited,especially in nondoped bl...Abundant efforts have been devoted to improving the efficiency of organic light-emitting diodes(OLEDs),however,approaches to control the device efficiency roll-off are still extremely limited,especially in nondoped blue OLEDs.In this work,three blue emitters(TAT,TAMT and TAMT-CN)with"hot exciton"properties are designed and synthesized based on[1,2,4]triazolo[1,5-a]pyridine(TP)as a regulating unit as well as anthracene-triphenylamine(An-TPA)as the chromophore.By adjusting the linkage mode and modifying the TP unit,the excited state properties,carrier transfer abilities,horizontal orientation,and device efficiency roll-off were precisely controlled.Among these materials,emitters that directly connect the fused TP unit exhibit balanced charge-transporting ability,higher photoluminescent quantum yield and improved horizontal orientation,resulting in better electroluminescence(EL)performance in non-doped blue OLEDs.As a result,non-doped blue OLEDs exhibit excellent performance with external quantum efficiencies of over 6%,brightness of over 30,000 cd/m2and EL peaks of around 476 nm.More importantly,the device based on TAMT-CN exhibits an ultra-low efficiency roll-off of 2.97%at a high brightness of10,000 cd/m2.The accessible molecular unit and feasible design strategy in this work are of great significance for designing highly efficient and ultra-low efficiency roll-off non-doped blue OLEDs.展开更多
Acephate pesticide contamination in agricultural production has caused serious human health problems.Metal oxide semiconductor(MOS)gas sensor can be used as a portable and promising alternative tool for efficiently de...Acephate pesticide contamination in agricultural production has caused serious human health problems.Metal oxide semiconductor(MOS)gas sensor can be used as a portable and promising alternative tool for efficiently detection of acephate.In this study,hierarchical assembled SnO_(2)nanosphere,SnO_(2)hollow nanosphere and SnO_2 nanoflower were synthesized respectively as high efficiency sensing materials to build rapid and selective acephate pesticide residues sensors.The morphologies of different SnO_(2)3 D nanostructures were characterized by various material characterization technology.The sensitive performance test results of the 3 D SnO_(2)nanomaterials towards acephate show that hollow nanosphere SnO_(2)based sensor displayed preferable sensitivity,selectivity,and rapid response(9 s)properties toward acephate at the optimal working temperature(300℃).This SnO_(2)hollow nanosphere based gas sensor represents a useful tool for simple and highly effective monitoring of acephate pesticide residues in food and environment.According to the characterization results,particularly Brunauer-Emmett-Teller(BET)and Ultraviolet-Visible Spectroscopy(UV-vis),the obvious and fast response can be attributed to the mesoporous hollow nanosphere structure and appropriate band gap of SnO_2 hollow nanosphere.展开更多
Raman probing of carbon electrode and electrolyte under dynamic conditions is performed here using different aqueous electrolytes to elucidate the fundamental events occurring in electrochemical supercapacitor during ...Raman probing of carbon electrode and electrolyte under dynamic conditions is performed here using different aqueous electrolytes to elucidate the fundamental events occurring in electrochemical supercapacitor during charge–discharge processes.The areal capacitance ranges from 1.54 to 2.31μF cm^(-2)μm and it is determined using different techniques.These findings indicate that the Helmholtz capacitance governs the overall charge-storage process instead of the space charge(quantum)capacitance commonly verified for HOPG electrodes in the range of~3 to 7μF cm^(-2).Molecular dynamics simulations are employed to elucidate the origin of the reversible Raman spectral changes during the charge–discharge processes.A correlation is verified between the reversible Raman shift and the surface excesses of the different ionic species.A theoretical framework is presented to relate the effect of the applied potential on the Raman shift and its correlation with the surface ionic charge.It is proposed that the Raman shift is governed by the interaction of solvated cations with graphite promoted by polarization conditions.It is the first time that a comparative study on different aqueous electrolyte p H and cation ion size has been performed tracking the Raman spectra change under dynamic polarization conditions and contrasting with comprehensive electrochemistry and dynamic molecular simulations studies.This study shines lights onto the charge-storage mechanism with evidence of Kohn anomaly reduction in the carbon electrode during the reversible adsorption/desorption and insertion/extraction of ionic species.展开更多
Vacuum Stability Test(VST)was used to determine the thermal behavior and kinetic parameters of 1,3,5,7-tetranitro-1,3,5,7-tetrazocine(HMX)and its mixture with hydroxyl-terminated polybutadiene(HTPB)as a binder coded a...Vacuum Stability Test(VST)was used to determine the thermal behavior and kinetic parameters of 1,3,5,7-tetranitro-1,3,5,7-tetrazocine(HMX)and its mixture with hydroxyl-terminated polybutadiene(HTPB)as a binder coded as HMX/HTPB.Model fitting and isoconversional method were applied to determine the kinetic parameters based on VST results.For comparison,non-isothermal thermogravimetry analysis data(TGA)was also used to calculate the kinetic parameters by using Kissinger,OFW(Ozawa,Flynn,and Wall)and KAS(Kissinger-Akahira-Sunose)methods.Advanced Kinetics and Technology Solution(AKTS)software was also used to determine the decomposition kinetics of the studied samples.Differential Scanning Calorimetry(DSC)was employed to determine the decomposition heat flow properties of the studied samples.Results show that the activation energies obtained using VST results is 360.1kJ/mol for pure HMX and 186.9kJ/mol for HMX/HTPB.The activation energies obtained by the three different methods using TGA results are in the range of 360-368kJ/mol for pure HMX and 190-206kJ/mol for HMX/HTPB.It is concluded that values of kinetic parameters obtained by VST are close to that obtained by the different techniques using TG/DTG results.The onset decomposition peak of HMX/HTPB is lower than that of HMX where the HTPB binder has negative effect on the thermal stability of HMX.The results of all the applied techniques prove that HMX/HTPB has lower activation energy and heat release than the pure HMX.HTPB polymeric matrix has negative effect on the kinetic parameters of HMX.展开更多
The title compound was synthesized by the base catalyzed reaction of 5-（（quinolin- 8-yloxy）methyl）-1,3,4-oxadiazole-2（3H）-thione with methyl chloroacetate. The structure was supported by the spectroscopic data a...The title compound was synthesized by the base catalyzed reaction of 5-（（quinolin- 8-yloxy）methyl）-1,3,4-oxadiazole-2（3H）-thione with methyl chloroacetate. The structure was supported by the spectroscopic data and unambiguously confirmed by single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the triclinic space group Pi with unit cell dimensions a = 7.4509（9）, b = 10.2389（12）, c = 12.2299（15）A, a = 74.771（2）, β = 77.956（2）, 7 = 69.263（2）°, V = 834.98（17） A3 and Z = 2. In order to gain some valuable insights into the molecular structure, the quantum mechanical calculations were performed using both HF and time-dependent density functional theory at the B3LYP/6-31G（d,p） level. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree-Fock （HF） and density functional theory （DFT） with the 6-31G（d） basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. The energetic behavior of the title compound was examined using the B3LYP method with the 6-31G（d） basis set. The harmonic vibrational frequencies calculated have been compared with the experimental FTIR and FT-Raman spectra. The restricted Hartree-Fock and density functional theory-based nuclear magnetic resonance （NMR） calculation procedure was also performed, and it was used for assigning the 13C and 1H NMR chemical shifts of the title compound. Moreover, molecular electrostatic potential and thermodynamic parameters of the title compound were investigated by theoretical calculations.展开更多
Eight species of brown algae(Phaeophyceae)from the coast of Madagascar have been investigated for their chemical constituents.Fucosterol(3)was obtained as the most abundant compound.The brown alga Sargassum ilicifoliu...Eight species of brown algae(Phaeophyceae)from the coast of Madagascar have been investigated for their chemical constituents.Fucosterol(3)was obtained as the most abundant compound.The brown alga Sargassum ilicifolium was the source for the first isolation of the terpenoid C27-alcohol 1,10,2-trinorsqualenol(1)from marine sources.From S.incisifolium we isolated the highly unsaturated glycolipid 1-O-palmitoyl-2-O-stearidonoyl-3-O-β-D-galactopyranosylglycerol(4)and we report the first full assignment of its ^(1)H and ^(13)C NMR data.Apo-90-fucoxanthinone(8)along with 24-ketocholesterol(5),(22E)-3b-hydroxycholesta-5,22-dien-24-one(6),and saringosterol(7)were obtained from Turbinaria ornata.The crude extracts of all eight species of brown algae exhibited a pronounced antimicrobial activity against the Gram-positive bacteria Bacillus cereus,Staphylococcus aureus,and Streptococcus pneumoniae.展开更多
The title compound was synthesized by the direct reaction of 3,5-dichlorobenzoic acid with 2-methoxyaniline in the presence of DCC and HOBT. The structure was supported by the spectroscopic data and unambiguously conf...The title compound was synthesized by the direct reaction of 3,5-dichlorobenzoic acid with 2-methoxyaniline in the presence of DCC and HOBT. The structure was supported by the spectroscopic data and unambiguously confirmed by the single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the monoclinic space group P21/c with unit cell dimensions of a = 4.9369（16）, b = 13.351（5）, c = 20.168（7） A, β = 96.755（8）°, V= 1320.1（8） A^3 and Z=4.展开更多
The synthesis of the title molecule was achieved by the reaction of 2,4-dichloro- benzoyl chloride with potassium thiocyanate in 1：1 molar ratio in dry acetonitrile to afford the corresponding isothiocyante in situ f...The synthesis of the title molecule was achieved by the reaction of 2,4-dichloro- benzoyl chloride with potassium thiocyanate in 1：1 molar ratio in dry acetonitrile to afford the corresponding isothiocyante in situ followed by the treatment with 2-aminobiphenyl. The structure of the target compound was established by elemental analysis, FTIR, 1H, 13C NMR and mass spectroscopy and unequivocally confirmed by the crystallographic data. The title compound crystallizes in the monoclinic space group P21/n with a = 13.356（2）, b = 7.0761（11）, c = 20.539（3） A, β = 105.723（4）°, V= 1868.5（5） A3 and Z = 4.展开更多
Chalcone derivatives are of immense importance owing to their superior pharmacological profile. Minor changes in their structures create high degree of diversity that results in a broader spectrum of biological activi...Chalcone derivatives are of immense importance owing to their superior pharmacological profile. Minor changes in their structures create high degree of diversity that results in a broader spectrum of biological activities. The present research paper presents the synthesis of 3-（4-chloro-3-nitrophenyl）-1-phenylprop-2-en-1-one chalcone（I）, single crystal XRD analysis and the evaluation of its possible biological activities like cytotoxic（LD（50） = 5.40 ug/m L）and antileishmanial（LD（50） = 0.81 ug/m L） activities. The results indicate the tested chalcone（I）shows superior inhibition values against leishmanial promastigotes. Further, the possible interaction sites of chalcone（I） with Try R enzyme involved in the redox metabolism of the leishmanial parasite were determined using docking simulation technique. Docking computations demonstrate that the compound establishes prominent binding interactions with the key residues of Try R and possesses the potential to effectively inhibit the catalytic activities of enzyme. Thus the results suggest that the chalcone（I） can serve as a potential scaffold for the treatment of leishmaniasis and deserve further development.展开更多
The title compound was synthesized from 3-（2-methylphenyl）-2-thioxo-2,3-dihy- droquinazolin-4（1H）-one （4） which was prepared from 2-methylaniline in two steps. The structure was supported by the spectroscopic da...The title compound was synthesized from 3-（2-methylphenyl）-2-thioxo-2,3-dihy- droquinazolin-4（1H）-one （4） which was prepared from 2-methylaniline in two steps. The structure was supported by the spectroscopic data and unambiguously confirmed by single-crystal X-ray diffraction studies. It crystallizes in the orthorhombic space group Pbca with unit cell dimensions a = 6.687（4）, b = 24.788（16）, c = 30.453（19） V = 5048（5） 3 and Z = 8.展开更多
Objective: To examine the potential antimicrobial activity of Euphorbia paralias L. (Euphorbiaeae) leaves and stems extracts. Methods: The antimicrobial activity was tested against six microbial strains:Escherichia co...Objective: To examine the potential antimicrobial activity of Euphorbia paralias L. (Euphorbiaeae) leaves and stems extracts. Methods: The antimicrobial activity was tested against six microbial strains:Escherichia coli ATCC 8739, Bacillus subtilis ATCC 6633, Salmonella enterica CIP 8039, Staphy-lococcus aureus ATCC 6538, Pseudomonas aeruginosa ATCC 9027 and Candida albicans ATCC 90028 by two different methods, the disk method and the dilution method. Results: Our results showed the important antimicrobial activity of the chloroform extract of the stems towards the majority of the strains by using both methods. Bacillus subtilis was the most sensitive strain (MIC=MBC=15μg/mL). Conclusion: Thus, some extracts of Euphorbia paralias can be used in the treatment of infectious diseases caused by microbes.展开更多
Photoelectron diffraction(PED)is a powerful technique for resolving surface structures with subangstrom precision.At high photon energies,angle-resolved photoemission spectroscopy(ARPES)reveals PED effects,often chall...Photoelectron diffraction(PED)is a powerful technique for resolving surface structures with subangstrom precision.At high photon energies,angle-resolved photoemission spectroscopy(ARPES)reveals PED effects,often challenged by small cross-sections,momentum transfer,and phonon scattering.X-ray PED(XPD)is not only an advantageous approach but also exhibits unexpected effects.We present a PED implementation for the spin-polarized relativistic Korringa-Kohn-Rostoker(SPRKKR)package to disentangle them,employing multiple scattering theory and a one-step photoemission model.Unlike conventional real-space approaches,our method uses a k-space formulation via the layer-KKR method,offering efficient and accurate calculations across a wide energy range(20-8000 eV)without angular momentum or cluster size convergence issues.Additionally,the alloy analogymodel enables simulations of finite-temperature XPDand effects in soft/hard X-ray ARPES.Applications includemodeling circular dichroism in angular distributions(CDAD)in core-level photoemission of Si(100)2p and Ge(100)3p,excited by 6000 eV photons with circular polarization.展开更多
Eneyne is one of the most prevalent building blocks in synthetic chemistry.Alkenyl C−H alkynylation affords an efficient synthesis of eneynes,however,the direct use of styrenes as the synthon has remained much unexplo...Eneyne is one of the most prevalent building blocks in synthetic chemistry.Alkenyl C−H alkynylation affords an efficient synthesis of eneynes,however,the direct use of styrenes as the synthon has remained much unexplored so far.We present the firstα-/β-C−H alkynylation of E-and Z aryl alkenes as well asα-substituted aryl alkenes,producing complex eneynes with excellent regio-and E/Z ratio selectivity,assisted by N,N-bidentate directing group under palladium catalysis.Notably,disubstituted E-aryl alkenes underwentα-C−H alkynylation and thenβ-C−H alkenylation to produce conjugated dieneynes.The robustness of the protocol was further demonstrated by the successful C−H conversion of substrates including 2-alkenyl benzyl amides and anilides,proceeding by five-to seven-membered endo-/exo-palladacycles.展开更多
Lithium-ion batteries have emerged as the best portable energy storage device for the consumer electronics market. Recent progress in the development of lithium- ion batteries has been achieved by the use of selected ...Lithium-ion batteries have emerged as the best portable energy storage device for the consumer electronics market. Recent progress in the development of lithium- ion batteries has been achieved by the use of selected anode materials, which have driven improvements in performance in terms of capadty, cyclic stability, and rate capability. In this regard, research focusing on the design and electrochemical performance of full cell lithium-ion batteries, utilizing newly developed anode materials, has been widely reported, and great strides in development have been made. Nanostructured anode materials have contributed largely to the development of full cell lithium-ion batteries. With this in mind, we summarize the impact of nanostructured anode materials in the performance of coin cell full lithium-ion batteries. This review also discusses the challenges and prospects of research into full cell lithium-ion batteries.展开更多
By controlling the amorphous-to-crystalline relative volume,chalcogenide phase-change memory materials can provide multi-level data storage(MLS),which offers great potential for high-density storageclass memory and ne...By controlling the amorphous-to-crystalline relative volume,chalcogenide phase-change memory materials can provide multi-level data storage(MLS),which offers great potential for high-density storageclass memory and neuro-inspired computing.However,this type of MLS system suffers from high power consumption and a severe time-dependent resistance increase(‘‘drift")in the amorphous phase,which limits the number of attainable storage levels.Here,we report a new type of MLS system in yttriumdoped antimony telluride,utilizing reversible multi-level phase transitions between three states,i.e.,amorphous,metastable cubic and stable hexagonal crystalline phases,with ultralow power consumption(0.6–4.3 p J)and ultralow resistance drift for the lower two states(power-law exponent<0.007).The metastable cubic phase is stabilized by yttrium,while the evident reversible cubic-to-hexagonal transition is attributed to the sequential and directional migration of Sb atoms.Finally,the decreased heat dissipation of the material and the increase in crystallinity contribute to the overall high performance.This study opens a new way to achieve advanced multi-level phase-change memory without the need for complicated manufacturing procedures or iterative programming operations.展开更多
Objective： To evaluate the antimicrobial activity of the methanol extract from the stem bark of Drypetes tessmanniana, fractions （DTB1-5） as well as compounds [friedelin （2）, 3,7-dioxofriedelane （3）, 3,15-dioxo...Objective： To evaluate the antimicrobial activity of the methanol extract from the stem bark of Drypetes tessmanniana, fractions （DTB1-5） as well as compounds [friedelin （2）, 3,7-dioxofriedelane （3）, 3,15-dioxofriedelane （4）, 313 -O-（E）-3,5-dihydroxycinnamoyl-11 -oxo-olean-12-ene （6）, and 313,6 α -dihydroxylup- 20（29）-ene （7）. Methods： Agar disc diffusion was used to determine the sensitivity of the above samples, whilst the microdilution method was used for the determination of the minimal inhibitory concentration （MIC） and the minimal microbicidal concentrations （MMC）. Results： The diffusion test showed that the crude extract was able to prevent the growth of all tested organisms. All other samples showed selective activity. The inhibitory effect of the fraction DTB2 was noted on 63.7%, that of DTB1 and DBT3 on 54.6%, whilst DTB4 and DTB5 were active on 9.1% of the 11 tested organisms. The tested compounds prevented the growth of 81.8% of the tested microbial species for compounds 3 and 4, 36.7% for compound 6, and 18.2% for compound 7. The results of the MIC determinations indicated perceptible values for DTB and compound 4 on 81.8% of the tested organisms. For other samples, MICs were detected on 0-63.7%. The lowest MIC value （78.12 μg/mL） for the crude extract and fractions （DTB2） was observed on M. audouinii. The corresponding value for isolated compounds （156.25 μg/ mL） was noted with compounds 3 on S. faecalis and 4 on M. audouinii. The results of the MMC determination suggested that the microbicidal effect of most of the tested samples on the studied microorganisms could be expected. Conclusion： The methanol extract from the stem bark of Drypetes. tessmanniana （Euphorbiaceae） as well as some of the isolated compounds might be potential sources of new antimicrobial drues.展开更多
Ultralong organic room-temperature phosphorescence(RTP)materials have attracted tremendous attention recently due to their diverse applications.Several ultralong organic RTP materials mimicking the host-vip architec...Ultralong organic room-temperature phosphorescence(RTP)materials have attracted tremendous attention recently due to their diverse applications.Several ultralong organic RTP materials mimicking the host-vip architecture of inorganic systems have been exploited successfully.However,complicated synthesis and high expenditure are still inevitable in these studies.Herein,we develop a series of novel host-vip organic phosphorescence systems,in which all luminophores are electron-rich,commercially available and halogen-atom-free.The maximum phosphorescence efficiency and the longest lifetime could reach 23.6%and 362 ms,respectively.Experimental results and theoretical calculation indicate that the host molecules not only play a vital role in providing a rigid environment to suppress non-radiative decay of the vip,but also show a synergistic effect to the vip through Förster resonance energy transfer(FRET).The commercial availability,facile preparation and unique properties also make these new host-vip materials an excellent candidate for the anti-counterfeiting application.This work will inspire researchers to develop new RTP systems with different wavelengths from commercially available luminophores.展开更多
DNA modified nanoparticles(Au NPs) are an established and widely used type of nucleotide sensor. We sought to improve the design by applying short rigid DNA duplexes near the surface of the Au NPs forming a so called ...DNA modified nanoparticles(Au NPs) are an established and widely used type of nucleotide sensor. We sought to improve the design by applying short rigid DNA duplexes near the surface of the Au NPs forming a so called double-anchored Au NP sensor, and compared it with other conventional DNA modified Au NPs. The improved design exhibited higher assembly efficiency, and consequently increased its sensitivity to target DNA.展开更多
Supramolecular self-assembly in water based on non-covalent bonding is attracting major attention due to the potential of hydrogels and aqueous polymers in biomedical applications.Although supramolecular polymerizatio...Supramolecular self-assembly in water based on non-covalent bonding is attracting major attention due to the potential of hydrogels and aqueous polymers in biomedical applications.Although supramolecular polymerization in organic solvents is well established,the key design features,the assembly mechanisms in water and achieving control over the aggregate structures remain challenging.Here,we present the assembly and disassembly of geometrical isomers of a stiff-stilbene bis-urea amphiphile(SA)in pure water.A remarkable feature of this system is that the(E)-isomer forms supramolecular polymers in both pure water and organic solvents.Taking advantage of this unique property,the hydrophobic effect was studied by comparing the supramolecular assembly in both systems.The assembly process inwater follows an enthalpy-driven nucleation-elongation(cooperative)supramolecular polymerization mechanism with a standard Gibbs free energy(ΔG°=−53 kJ mol^(−1))double the value of the one found in toluene.We attributed this distinctive feature to the hydrophobic effect in water.Furthermore,we discovered an isomer-dependent assembly process,which can be used to control aggregation in aqueous media.Due to the substantial geometric difference between(E)-SA and(Z)-SA,we compared their assembly in water to study the influence of different driving forces involved in the process.The supramolecular polymerization of(E)-SA was cooperatively influenced by hydrogen bonding,π-stacking,and hydrophobic effects,whereas the assembly of(Z)-SAwasmainly driven by hydrophobic effects.As a result,the fiber length of(E)-SA in water is much longer than that of(Z)-SA,presenting opportunities for geometrical control of aggregation in aqueousmedia.展开更多
基金This work was supported by the German BMBF (No.05P21UMFN2)
文摘Man-made superheavy elements(SHE)are produced as energetic recoils in complete-fusion reactions and need to be thermalized in a gas-filled chamber for chemical studies.The ever-shorter half-lives and decreasing production rates of the elements beyond Fl(atomic number Z=114)-the heaviest element chemically studied today-require the development of novel techniques for quantitative thermalization and fast extraction efficiency.The Universal high-density gas stopping Cell(UniCell),currently under construction,was proposed to achieve this.Within this work,we propose an Ion Transfer by Gas Flow(ITGF)device,which serves as a UniCell ejector to interface with a gas chromatography detector array for chemical studies.Detailed parameter optimizations,using gas dynamics and Monte Carlo ion-trajectory simulations,promise fast(within a few ms)and highly efficient(up to 100%)ion extraction across a wide mass range.These ions can then be transmitted quantitatively through the ITGF into the high-pressure environment needed for further chemical studies.
基金the financial support from the National Natural Science Foundation of China(Nos.52273187 and 51973107)the Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme 2019(No.GDUPS2019)。
文摘Abundant efforts have been devoted to improving the efficiency of organic light-emitting diodes(OLEDs),however,approaches to control the device efficiency roll-off are still extremely limited,especially in nondoped blue OLEDs.In this work,three blue emitters(TAT,TAMT and TAMT-CN)with"hot exciton"properties are designed and synthesized based on[1,2,4]triazolo[1,5-a]pyridine(TP)as a regulating unit as well as anthracene-triphenylamine(An-TPA)as the chromophore.By adjusting the linkage mode and modifying the TP unit,the excited state properties,carrier transfer abilities,horizontal orientation,and device efficiency roll-off were precisely controlled.Among these materials,emitters that directly connect the fused TP unit exhibit balanced charge-transporting ability,higher photoluminescent quantum yield and improved horizontal orientation,resulting in better electroluminescence(EL)performance in non-doped blue OLEDs.As a result,non-doped blue OLEDs exhibit excellent performance with external quantum efficiencies of over 6%,brightness of over 30,000 cd/m2and EL peaks of around 476 nm.More importantly,the device based on TAMT-CN exhibits an ultra-low efficiency roll-off of 2.97%at a high brightness of10,000 cd/m2.The accessible molecular unit and feasible design strategy in this work are of great significance for designing highly efficient and ultra-low efficiency roll-off non-doped blue OLEDs.
基金financially funded by the National Natural Science Foundation of China(No.31701678)the Key Project of Shanghai Agriculture Prosperity through Science and Technology(No.2019-02-08-00-15-F01147)+3 种基金the project of Shanghai Science and Technology Committee(No.19391901600)the Key Basic Research Program of Science and Technology Commission of Shanghai Municipality(No.20JC1415300)the State Key Laborato ry of Transducer Technology of China(No.SKT1904)the Research Support Project number(No.RSP-2020/155),King Saud University,Riyadh,Saudi Arabia。
文摘Acephate pesticide contamination in agricultural production has caused serious human health problems.Metal oxide semiconductor(MOS)gas sensor can be used as a portable and promising alternative tool for efficiently detection of acephate.In this study,hierarchical assembled SnO_(2)nanosphere,SnO_(2)hollow nanosphere and SnO_2 nanoflower were synthesized respectively as high efficiency sensing materials to build rapid and selective acephate pesticide residues sensors.The morphologies of different SnO_(2)3 D nanostructures were characterized by various material characterization technology.The sensitive performance test results of the 3 D SnO_(2)nanomaterials towards acephate show that hollow nanosphere SnO_(2)based sensor displayed preferable sensitivity,selectivity,and rapid response(9 s)properties toward acephate at the optimal working temperature(300℃).This SnO_(2)hollow nanosphere based gas sensor represents a useful tool for simple and highly effective monitoring of acephate pesticide residues in food and environment.According to the characterization results,particularly Brunauer-Emmett-Teller(BET)and Ultraviolet-Visible Spectroscopy(UV-vis),the obvious and fast response can be attributed to the mesoporous hollow nanosphere structure and appropriate band gap of SnO_2 hollow nanosphere.
基金the financial support from the Brazilian funding agencies CNPq(301486/2016-6)the FAEPEX(2426/17),the FAPESP(2016/25082-8,2017/11958-1,2014/02163-7,2018/20756-6,2018/02713-8)and CAPES(1740195)+6 种基金the‘‘Funda??o ao AmparoàPesquisa do Estado de Minas Gerais-FAPEMIG”(Project CEX112-10)the‘‘Secretaria de Estado de Ciência,Tecnologia e Ensino Superior de Minas Gerais-SECTES/MG”(Support for the LMMA Laboratory)the‘‘Conselho Nacional de Desenvolvimento Científico e Tecnológico–CNPq”(PQ-2 grant)support Shell and the strategic importance of the support given by ANP(Brazil’s National Oil,Natural Gas and Biofuels Agency)through the R&D levy regulationthe Center for Research Computing(CRC)at the University of Notre Dame for the computational resources,and the Brazilian agencies CNPq(Reference Number 203393/2018-0)and CAPES(Finance Code 001)for the financial supportfinancial support from the FAPEMIG,CNPq(307742/2017-2 and 432384/2018-9)Brazilian Institute of Science and Technology in Carbon Nanomaterials(INCTNanocarbono)。
文摘Raman probing of carbon electrode and electrolyte under dynamic conditions is performed here using different aqueous electrolytes to elucidate the fundamental events occurring in electrochemical supercapacitor during charge–discharge processes.The areal capacitance ranges from 1.54 to 2.31μF cm^(-2)μm and it is determined using different techniques.These findings indicate that the Helmholtz capacitance governs the overall charge-storage process instead of the space charge(quantum)capacitance commonly verified for HOPG electrodes in the range of~3 to 7μF cm^(-2).Molecular dynamics simulations are employed to elucidate the origin of the reversible Raman spectral changes during the charge–discharge processes.A correlation is verified between the reversible Raman shift and the surface excesses of the different ionic species.A theoretical framework is presented to relate the effect of the applied potential on the Raman shift and its correlation with the surface ionic charge.It is proposed that the Raman shift is governed by the interaction of solvated cations with graphite promoted by polarization conditions.It is the first time that a comparative study on different aqueous electrolyte p H and cation ion size has been performed tracking the Raman spectra change under dynamic polarization conditions and contrasting with comprehensive electrochemistry and dynamic molecular simulations studies.This study shines lights onto the charge-storage mechanism with evidence of Kohn anomaly reduction in the carbon electrode during the reversible adsorption/desorption and insertion/extraction of ionic species.
文摘Vacuum Stability Test(VST)was used to determine the thermal behavior and kinetic parameters of 1,3,5,7-tetranitro-1,3,5,7-tetrazocine(HMX)and its mixture with hydroxyl-terminated polybutadiene(HTPB)as a binder coded as HMX/HTPB.Model fitting and isoconversional method were applied to determine the kinetic parameters based on VST results.For comparison,non-isothermal thermogravimetry analysis data(TGA)was also used to calculate the kinetic parameters by using Kissinger,OFW(Ozawa,Flynn,and Wall)and KAS(Kissinger-Akahira-Sunose)methods.Advanced Kinetics and Technology Solution(AKTS)software was also used to determine the decomposition kinetics of the studied samples.Differential Scanning Calorimetry(DSC)was employed to determine the decomposition heat flow properties of the studied samples.Results show that the activation energies obtained using VST results is 360.1kJ/mol for pure HMX and 186.9kJ/mol for HMX/HTPB.The activation energies obtained by the three different methods using TGA results are in the range of 360-368kJ/mol for pure HMX and 190-206kJ/mol for HMX/HTPB.It is concluded that values of kinetic parameters obtained by VST are close to that obtained by the different techniques using TG/DTG results.The onset decomposition peak of HMX/HTPB is lower than that of HMX where the HTPB binder has negative effect on the thermal stability of HMX.The results of all the applied techniques prove that HMX/HTPB has lower activation energy and heat release than the pure HMX.HTPB polymeric matrix has negative effect on the kinetic parameters of HMX.
文摘The title compound was synthesized by the base catalyzed reaction of 5-（（quinolin- 8-yloxy）methyl）-1,3,4-oxadiazole-2（3H）-thione with methyl chloroacetate. The structure was supported by the spectroscopic data and unambiguously confirmed by single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the triclinic space group Pi with unit cell dimensions a = 7.4509（9）, b = 10.2389（12）, c = 12.2299（15）A, a = 74.771（2）, β = 77.956（2）, 7 = 69.263（2）°, V = 834.98（17） A3 and Z = 2. In order to gain some valuable insights into the molecular structure, the quantum mechanical calculations were performed using both HF and time-dependent density functional theory at the B3LYP/6-31G（d,p） level. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree-Fock （HF） and density functional theory （DFT） with the 6-31G（d） basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. The energetic behavior of the title compound was examined using the B3LYP method with the 6-31G（d） basis set. The harmonic vibrational frequencies calculated have been compared with the experimental FTIR and FT-Raman spectra. The restricted Hartree-Fock and density functional theory-based nuclear magnetic resonance （NMR） calculation procedure was also performed, and it was used for assigning the 13C and 1H NMR chemical shifts of the title compound. Moreover, molecular electrostatic potential and thermodynamic parameters of the title compound were investigated by theoretical calculations.
文摘Eight species of brown algae(Phaeophyceae)from the coast of Madagascar have been investigated for their chemical constituents.Fucosterol(3)was obtained as the most abundant compound.The brown alga Sargassum ilicifolium was the source for the first isolation of the terpenoid C27-alcohol 1,10,2-trinorsqualenol(1)from marine sources.From S.incisifolium we isolated the highly unsaturated glycolipid 1-O-palmitoyl-2-O-stearidonoyl-3-O-β-D-galactopyranosylglycerol(4)and we report the first full assignment of its ^(1)H and ^(13)C NMR data.Apo-90-fucoxanthinone(8)along with 24-ketocholesterol(5),(22E)-3b-hydroxycholesta-5,22-dien-24-one(6),and saringosterol(7)were obtained from Turbinaria ornata.The crude extracts of all eight species of brown algae exhibited a pronounced antimicrobial activity against the Gram-positive bacteria Bacillus cereus,Staphylococcus aureus,and Streptococcus pneumoniae.
基金a research grant from the Higher EducationCommission of Pakistan under project No. 4-279/PAK-US/HEC 2010-917
文摘The title compound was synthesized by the direct reaction of 3,5-dichlorobenzoic acid with 2-methoxyaniline in the presence of DCC and HOBT. The structure was supported by the spectroscopic data and unambiguously confirmed by the single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the monoclinic space group P21/c with unit cell dimensions of a = 4.9369（16）, b = 13.351（5）, c = 20.168（7） A, β = 96.755（8）°, V= 1320.1（8） A^3 and Z=4.
文摘The synthesis of the title molecule was achieved by the reaction of 2,4-dichloro- benzoyl chloride with potassium thiocyanate in 1：1 molar ratio in dry acetonitrile to afford the corresponding isothiocyante in situ followed by the treatment with 2-aminobiphenyl. The structure of the target compound was established by elemental analysis, FTIR, 1H, 13C NMR and mass spectroscopy and unequivocally confirmed by the crystallographic data. The title compound crystallizes in the monoclinic space group P21/n with a = 13.356（2）, b = 7.0761（11）, c = 20.539（3） A, β = 105.723（4）°, V= 1868.5（5） A3 and Z = 4.
文摘Chalcone derivatives are of immense importance owing to their superior pharmacological profile. Minor changes in their structures create high degree of diversity that results in a broader spectrum of biological activities. The present research paper presents the synthesis of 3-（4-chloro-3-nitrophenyl）-1-phenylprop-2-en-1-one chalcone（I）, single crystal XRD analysis and the evaluation of its possible biological activities like cytotoxic（LD（50） = 5.40 ug/m L）and antileishmanial（LD（50） = 0.81 ug/m L） activities. The results indicate the tested chalcone（I）shows superior inhibition values against leishmanial promastigotes. Further, the possible interaction sites of chalcone（I） with Try R enzyme involved in the redox metabolism of the leishmanial parasite were determined using docking simulation technique. Docking computations demonstrate that the compound establishes prominent binding interactions with the key residues of Try R and possesses the potential to effectively inhibit the catalytic activities of enzyme. Thus the results suggest that the chalcone（I） can serve as a potential scaffold for the treatment of leishmaniasis and deserve further development.
基金a research grant from the Higher Education Commission of Pakistan under project No. 4-279/PAK-US/HEC 2010-917
文摘The title compound was synthesized from 3-（2-methylphenyl）-2-thioxo-2,3-dihy- droquinazolin-4（1H）-one （4） which was prepared from 2-methylaniline in two steps. The structure was supported by the spectroscopic data and unambiguously confirmed by single-crystal X-ray diffraction studies. It crystallizes in the orthorhombic space group Pbca with unit cell dimensions a = 6.687（4）, b = 24.788（16）, c = 30.453（19） V = 5048（5） 3 and Z = 8.
基金Supported by the Ministry of High Education and Scientific Research,MHSSR of Tunisia(Grant No.11/TM06)
文摘Objective: To examine the potential antimicrobial activity of Euphorbia paralias L. (Euphorbiaeae) leaves and stems extracts. Methods: The antimicrobial activity was tested against six microbial strains:Escherichia coli ATCC 8739, Bacillus subtilis ATCC 6633, Salmonella enterica CIP 8039, Staphy-lococcus aureus ATCC 6538, Pseudomonas aeruginosa ATCC 9027 and Candida albicans ATCC 90028 by two different methods, the disk method and the dilution method. Results: Our results showed the important antimicrobial activity of the chloroform extract of the stems towards the majority of the strains by using both methods. Bacillus subtilis was the most sensitive strain (MIC=MBC=15μg/mL). Conclusion: Thus, some extracts of Euphorbia paralias can be used in the treatment of infectious diseases caused by microbes.
基金supported by the project Quantum materials for applications in sustainable technologies(QM4ST),funded as project No.CZ.02.01.01/00/22_008/0004572 by Program Johannes Amos Commenius,call Excellent Research(T.-P.V.,J.M.,A.P.)the Czech Science Foundation Grant No.GAČR 23-04746S(T.-P.V.)+3 种基金In addition,T.-P.V.,S.T.,D.S.,A.P.,and J.M.acknowledge partial funding from Horizon Europe MSCA Doctoral network grant n.101073486,EUSpecLab,funded by the European UnionThis work was also supported by the Deutsche Forschungsgemeinschaft,Grant No.TRR288–422213477(Project B04)by the Federal Ministry of Education and Research(BMBF,Project 05K22UM2)A.W.was supported by the Polish National Science Center(NCN),grant no.2020/37/B/ST5/03669.
文摘Photoelectron diffraction(PED)is a powerful technique for resolving surface structures with subangstrom precision.At high photon energies,angle-resolved photoemission spectroscopy(ARPES)reveals PED effects,often challenged by small cross-sections,momentum transfer,and phonon scattering.X-ray PED(XPD)is not only an advantageous approach but also exhibits unexpected effects.We present a PED implementation for the spin-polarized relativistic Korringa-Kohn-Rostoker(SPRKKR)package to disentangle them,employing multiple scattering theory and a one-step photoemission model.Unlike conventional real-space approaches,our method uses a k-space formulation via the layer-KKR method,offering efficient and accurate calculations across a wide energy range(20-8000 eV)without angular momentum or cluster size convergence issues.Additionally,the alloy analogymodel enables simulations of finite-temperature XPDand effects in soft/hard X-ray ARPES.Applications includemodeling circular dichroism in angular distributions(CDAD)in core-level photoemission of Si(100)2p and Ge(100)3p,excited by 6000 eV photons with circular polarization.
基金the National Natural Science Foundation of China(NSFC Nos.22278103,21502037 and 21672048)Natural Science Foundation of Zhejiang Province(ZJNSF)(LY20B020010,LY19B020006 and LY15B020008)+2 种基金Key Subject of Stomatology in HangzhouHangzhou Normal University for financial supportKey Subject of Stomatology in Hangzhou for financial support.
文摘Eneyne is one of the most prevalent building blocks in synthetic chemistry.Alkenyl C−H alkynylation affords an efficient synthesis of eneynes,however,the direct use of styrenes as the synthon has remained much unexplored so far.We present the firstα-/β-C−H alkynylation of E-and Z aryl alkenes as well asα-substituted aryl alkenes,producing complex eneynes with excellent regio-and E/Z ratio selectivity,assisted by N,N-bidentate directing group under palladium catalysis.Notably,disubstituted E-aryl alkenes underwentα-C−H alkynylation and thenβ-C−H alkenylation to produce conjugated dieneynes.The robustness of the protocol was further demonstrated by the successful C−H conversion of substrates including 2-alkenyl benzyl amides and anilides,proceeding by five-to seven-membered endo-/exo-palladacycles.
基金This work was supported by the National Natural Science Foundation of China （Nos. 21273290 and 21476271）, the Natural Science Foundation of Guangdong Province （Nos. S2013030013474 and 2014KTSCX004） and the Science and Technology Plan Project of Guangdong Province （Nos. 2014B101123002, 2014B050505001 and 2015B010118002）. We thank the Middle School Student Talent Plan.
文摘Lithium-ion batteries have emerged as the best portable energy storage device for the consumer electronics market. Recent progress in the development of lithium- ion batteries has been achieved by the use of selected anode materials, which have driven improvements in performance in terms of capadty, cyclic stability, and rate capability. In this regard, research focusing on the design and electrochemical performance of full cell lithium-ion batteries, utilizing newly developed anode materials, has been widely reported, and great strides in development have been made. Nanostructured anode materials have contributed largely to the development of full cell lithium-ion batteries. With this in mind, we summarize the impact of nanostructured anode materials in the performance of coin cell full lithium-ion batteries. This review also discusses the challenges and prospects of research into full cell lithium-ion batteries.
基金the National Key Research and Development Program of China(2017YFB0701700)the National Natural Science Foundation of China(51872017)the High-Performance Computing(HPC)Resources at Beihang University。
文摘By controlling the amorphous-to-crystalline relative volume,chalcogenide phase-change memory materials can provide multi-level data storage(MLS),which offers great potential for high-density storageclass memory and neuro-inspired computing.However,this type of MLS system suffers from high power consumption and a severe time-dependent resistance increase(‘‘drift")in the amorphous phase,which limits the number of attainable storage levels.Here,we report a new type of MLS system in yttriumdoped antimony telluride,utilizing reversible multi-level phase transitions between three states,i.e.,amorphous,metastable cubic and stable hexagonal crystalline phases,with ultralow power consumption(0.6–4.3 p J)and ultralow resistance drift for the lower two states(power-law exponent<0.007).The metastable cubic phase is stabilized by yttrium,while the evident reversible cubic-to-hexagonal transition is attributed to the sequential and directional migration of Sb atoms.Finally,the decreased heat dissipation of the material and the increase in crystallinity contribute to the overall high performance.This study opens a new way to achieve advanced multi-level phase-change memory without the need for complicated manufacturing procedures or iterative programming operations.
基金Supported by International Foundation for Science(No.IFS/ 2624-3F).
文摘Objective： To evaluate the antimicrobial activity of the methanol extract from the stem bark of Drypetes tessmanniana, fractions （DTB1-5） as well as compounds [friedelin （2）, 3,7-dioxofriedelane （3）, 3,15-dioxofriedelane （4）, 313 -O-（E）-3,5-dihydroxycinnamoyl-11 -oxo-olean-12-ene （6）, and 313,6 α -dihydroxylup- 20（29）-ene （7）. Methods： Agar disc diffusion was used to determine the sensitivity of the above samples, whilst the microdilution method was used for the determination of the minimal inhibitory concentration （MIC） and the minimal microbicidal concentrations （MMC）. Results： The diffusion test showed that the crude extract was able to prevent the growth of all tested organisms. All other samples showed selective activity. The inhibitory effect of the fraction DTB2 was noted on 63.7%, that of DTB1 and DBT3 on 54.6%, whilst DTB4 and DTB5 were active on 9.1% of the 11 tested organisms. The tested compounds prevented the growth of 81.8% of the tested microbial species for compounds 3 and 4, 36.7% for compound 6, and 18.2% for compound 7. The results of the MIC determinations indicated perceptible values for DTB and compound 4 on 81.8% of the tested organisms. For other samples, MICs were detected on 0-63.7%. The lowest MIC value （78.12 μg/mL） for the crude extract and fractions （DTB2） was observed on M. audouinii. The corresponding value for isolated compounds （156.25 μg/ mL） was noted with compounds 3 on S. faecalis and 4 on M. audouinii. The results of the MMC determination suggested that the microbicidal effect of most of the tested samples on the studied microorganisms could be expected. Conclusion： The methanol extract from the stem bark of Drypetes. tessmanniana （Euphorbiaceae） as well as some of the isolated compounds might be potential sources of new antimicrobial drues.
基金This work was supported by the National Natural Science Foundation of China(21788102 and 21525417)the Natural Science Foundation of Guangdong Province(2019B030301003 and 2016A030312002)the Innovation and Technology Commission of Hong Kong(ITC-CNERC14S01).
文摘Ultralong organic room-temperature phosphorescence(RTP)materials have attracted tremendous attention recently due to their diverse applications.Several ultralong organic RTP materials mimicking the host-vip architecture of inorganic systems have been exploited successfully.However,complicated synthesis and high expenditure are still inevitable in these studies.Herein,we develop a series of novel host-vip organic phosphorescence systems,in which all luminophores are electron-rich,commercially available and halogen-atom-free.The maximum phosphorescence efficiency and the longest lifetime could reach 23.6%and 362 ms,respectively.Experimental results and theoretical calculation indicate that the host molecules not only play a vital role in providing a rigid environment to suppress non-radiative decay of the vip,but also show a synergistic effect to the vip through Förster resonance energy transfer(FRET).The commercial availability,facile preparation and unique properties also make these new host-vip materials an excellent candidate for the anti-counterfeiting application.This work will inspire researchers to develop new RTP systems with different wavelengths from commercially available luminophores.
基金supported by the National Basic Research Program of China (2013CB932803)the National Natural Science Foundation of China (91427302, 21421064)the National Natural Science Foundation of China-Deutsche Forschungsgemeinschaft (NSFC-DFG) joint project TRR61
文摘DNA modified nanoparticles(Au NPs) are an established and widely used type of nucleotide sensor. We sought to improve the design by applying short rigid DNA duplexes near the surface of the Au NPs forming a so called double-anchored Au NP sensor, and compared it with other conventional DNA modified Au NPs. The improved design exhibited higher assembly efficiency, and consequently increased its sensitivity to target DNA.
基金Financial support from the Netherlands Organization for Scientific Research(NWO-CW)the European Research Council(ERC,advanced grant no.694345 to B.L.F.)+2 种基金the Dutch Ministry of Education,Culture and Science(Gravitation program no.024.001.035)the China Scholarship Council(CSC,no.201707040064 to F.X.)the Marie Skłodowska-Curie Actions(Individual Fellowships no.838280 to S.C.and no.793082 to L.P.)is gratefully acknowledged.
文摘Supramolecular self-assembly in water based on non-covalent bonding is attracting major attention due to the potential of hydrogels and aqueous polymers in biomedical applications.Although supramolecular polymerization in organic solvents is well established,the key design features,the assembly mechanisms in water and achieving control over the aggregate structures remain challenging.Here,we present the assembly and disassembly of geometrical isomers of a stiff-stilbene bis-urea amphiphile(SA)in pure water.A remarkable feature of this system is that the(E)-isomer forms supramolecular polymers in both pure water and organic solvents.Taking advantage of this unique property,the hydrophobic effect was studied by comparing the supramolecular assembly in both systems.The assembly process inwater follows an enthalpy-driven nucleation-elongation(cooperative)supramolecular polymerization mechanism with a standard Gibbs free energy(ΔG°=−53 kJ mol^(−1))double the value of the one found in toluene.We attributed this distinctive feature to the hydrophobic effect in water.Furthermore,we discovered an isomer-dependent assembly process,which can be used to control aggregation in aqueous media.Due to the substantial geometric difference between(E)-SA and(Z)-SA,we compared their assembly in water to study the influence of different driving forces involved in the process.The supramolecular polymerization of(E)-SA was cooperatively influenced by hydrogen bonding,π-stacking,and hydrophobic effects,whereas the assembly of(Z)-SAwasmainly driven by hydrophobic effects.As a result,the fiber length of(E)-SA in water is much longer than that of(Z)-SA,presenting opportunities for geometrical control of aggregation in aqueousmedia.
