We present a quantum dynamics study on the isotope effects of hydro-gen transfer isomerization in the formic acid dimer,and this is achieved by multidimensional dy-namics calculations with an efficient quantum mechani...We present a quantum dynamics study on the isotope effects of hydro-gen transfer isomerization in the formic acid dimer,and this is achieved by multidimensional dy-namics calculations with an efficient quantum mechanical theoretical scheme developed by our group,on a full-dimensional neural network ab initio potential energy surface.The ground-state and fundamental tun-neling splittings for four deuterium isotopologues of formic acid dimer are considered,and the calculated results are in very good general agreement with the avail-able experimental measurements.Strong isotope effects are revealed,the mode-specific funda-mental excitation effects on the tunneling rate are evidently influenced by the deuterium sub-stitution of H atom with the substitution on the OH bond being more effective than on the CH bond.Our studies are helpful for acquiring a better understanding of isotope effects in the double-hydrogen transfer processes.展开更多
This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature....This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature. Five different methods, namely, mechanical mixing, impregnation,hydrothermal treatment, co‐precipitation, and a sol‐gel technique, were used to synthesizeMnOx‐CeO2 catalysts. The catalysts were characterized in detail, and an NH3‐SCR model reaction waschosen to evaluate the catalytic performance. The results showed that the preparation methodsaffected the catalytic performance in the order: hydrothermal treatment > sol‐gel > co‐precipitation> impregnation > mechanical mixing. This order correlated with the surface Ce3+ and Mn4+ content,oxygen vacancies and surface adsorbed oxygen species concentration, and the amount of acidic sitesand acidic strength. This trend is related to redox interactions between MnOx and CeO2. The catalystformed by a hydrothermal treatment exhibited excellent physicochemical properties, optimal catalyticperformance, and good H2O resistance in NH3‐SCR reaction. This was attributed to incorporationof Mnn+ into the CeO2 lattice to form a uniform ceria‐based solid solution (containing Mn‐O‐Cestructures). Strengthening of the electronic interactions between MnOx and CeO2, driven by thehigh‐temperature and high‐pressure conditions during the hydrothermal treatment also improved the catalyst characteristics. Thus, the hydrothermal treatment method is an efficient and environment‐friendly route to synthesizing low‐temperature denitrification (deNOx) catalysts.展开更多
The modification mechanism of the water/alcohol cathode interlayer is one of the most complicated problems in the field of organic photovoltaics,which has not been clearly elucidated yet;this greatly restricts the fur...The modification mechanism of the water/alcohol cathode interlayer is one of the most complicated problems in the field of organic photovoltaics,which has not been clearly elucidated yet;this greatly restricts the further enhancement of the PCE for polymer solar cells.Herein,we clarified the different effects of PFN and its derivatives,namely,poly[(9,9-bis(3’-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN-Br) in modifying fullerene-free PSCs.It is found for the first time that doping on IT-4F by the amino group of PFN leads to the unfavorable charge accumulation,and hence,forms a dense layer of electronegative molecule due to the poor electron transport capacity of the non-fullerene acceptor IT-4F.The electronegative molecular layer can block the electron transfer from the active layer to the interlayer and cause serious charge recombination at the active layer/cathode interface.This mechanism could be verified by the ESR measurement and electron-only devices.By replacing PFN with PFN-Br,the excessive doping effect between the cathode interlayer and IT-4F is eliminated,by which the charge transport and collection can be greatly improved.As a result,a high PCE of 13.5%was achieved in the fullerene-free PSCs.展开更多
The catalytic activities are generally believed to be relevant to the electronic states of their active center, but understanding this relationship is usually difficult. Here, we design two types of catalysts for elec...The catalytic activities are generally believed to be relevant to the electronic states of their active center, but understanding this relationship is usually difficult. Here, we design two types of catalysts for electrocatalytic urea via a coordination strategy in a metal–organic frameworks: Cu^(Ⅲ)-HHTP and Cu^(Ⅱ)-HHTP. Cu^(Ⅲ)-HHTP exhibits an improved urea production rate of 7.78 mmol h^(−1)g^(−1) and an enhanced Faradaic efficiency of 23.09% at-0.6 V vs. reversible hydrogen electrode, in sharp contrast to Cu^(Ⅱ)-HHTP.Isolated CuⅢspecies with S = 0 spin ground state are demonstrated as the active center in Cu^(Ⅲ)-HHTP, different from Cu^(Ⅱ) with S = 1/2 in Cu^(Ⅱ)-HHTP. We further demonstrate that isolated Cu^(Ⅲ)with an empty dx2-y20orbital in Cu^(Ⅲ)-HHTP experiences a single-electron migration path with a lower energy barrier in the C–N coupling process, while Cu^(Ⅱ)with a single-spin state( d_(x2-y2)^(1)) in Cu^(Ⅱ)-HHTP undergoes a two-electron migration pathway.展开更多
Some color centers in diamond can serve as quantum bits which can be manipulated with microwave pulses and read out with laser,even at room temperature.However,the photon collection efficiency of bulk diamond is great...Some color centers in diamond can serve as quantum bits which can be manipulated with microwave pulses and read out with laser,even at room temperature.However,the photon collection efficiency of bulk diamond is greatly reduced by refraction at the diamond/air interface.To address this issue,we fabricated arrays of diamond nanostructures,differing in both diameter and top end shape,with HSQ and Cr as the etching mask materials,aiming toward large scale fabrication of single-photon sources with enhanced collection efficiency made of nitrogen vacancy(NV) embedded diamond.With a mixture of O2 and CHF3 gas plasma,diamond pillars with diameters down to 45 nm were obtained.The top end shape evolution has been represented with a simple model.The tests of size dependent single-photon properties confirmed an improved single-photon collection efficiency enhancement,larger than tenfold,and a mild decrease of decoherence time with decreasing pillar diameter was observed as expected.These results provide useful information for future applications of nanostructured diamond as a single-photon source.展开更多
Ring polymer molecular dynamics(RPMD)calculations for the C(^(1)D)+H_(2)reaction are performed on the Zhang-Ma-Bian ab initio potential energy surfaces(PESs)recently constructed by our group,which are unique in very g...Ring polymer molecular dynamics(RPMD)calculations for the C(^(1)D)+H_(2)reaction are performed on the Zhang-Ma-Bian ab initio potential energy surfaces(PESs)recently constructed by our group,which are unique in very good descriptions of the regions around conical intersections and of van der Waals(vdW)interactions.The calculated reaction thermal rate coefficients are in very good agreement with the latest experimental results.The rate coefficients obtained from the ground˜a^(1)A′ZMB-a PES are much larger than those from the previous RKHS PES,which can be attributed to that the vdW saddles on our PESs have very different dynamical effects from the vdW wells on the previous PESs,indicating that the RPMD approach is able to include dynamical effects of the topological structures caused by vdW interactions.The importance of the excited˜b^(1)A′′ZMB-b PES and quantum effects in the title reaction is also underscored.展开更多
The photoabsorption and photodissociation of carbon monoxide(CO)in the vacuum ultraviolet(VUV)region is one of the most important photochemical processes in the interstellar medium,thus it has attracted numerous exper...The photoabsorption and photodissociation of carbon monoxide(CO)in the vacuum ultraviolet(VUV)region is one of the most important photochemical processes in the interstellar medium,thus it has attracted numerous experimental and theoretical studies.Here,we employed the two-color VUV-VUV laser pump-probe time-slice velocity-map ion imaging method to measure the relative branching ratios[C(3P0)+O(1D)]/{[C(3P0)+O(3P)]+[C(3P0)+O(1D)]}and[C(3P2)+O(1D)]/{[C(3P2)+O(3P)]+[C(3P2)+O(1D)]}in the VUV photoexcitation energy range of 108000-113200 cm^−1.Here,one tunable VUV laser beam is used to excite CO to speci c rovibronic states,and a second independently tunable VUV laser beam is used to state-selectively ionize C(3P0)and C(3P2)for detection.State-selective photoionization through the 1VUV+1UV/visible resonance-enhanced multiphoton ionization scheme has greatly enhanced the detection sensitivity,which makes many new weak absorption bands observable in the current study.The branching ratio measurement shows that the spin-forbidden channels C(3P0)+O(1D)and C(3P2)+O(1D)only open at several discrete narrow energy windows.This might be caused by certain accidental resonanceenhanced spin-orbit interactions between the directly excited Rydberg states and valence states of triplet type which nally dissociate into the spin-forbidden channels.展开更多
The interaction between Amyloid β(Aβ) peptide and acetylcholine receptor is the key for our understanding of how Aβ fragments block the ion channels within the synapses and thus induce Alzheimer’s disease.Here,mol...The interaction between Amyloid β(Aβ) peptide and acetylcholine receptor is the key for our understanding of how Aβ fragments block the ion channels within the synapses and thus induce Alzheimer’s disease.Here,molecular docking and molecular dynamics(MD)simulations were performed for the structural dynamics of the docking complex consisting of Aβ and α7-n ACh R(α7 nicotinic acetylcholine receptor),and the inter-molecular interactions between ligand and receptor were revealed.The results show that Aβ_(25-35) is bound toα7-n ACh R through hydrogen bonds and complementary shape,and the Aβ_(25-35) fragments would easily assemble in the ion channel of α7-n ACh R,then block the ion transfer process and induce neuronal apoptosis.The simulated amide-I band of Aβ_(25-35) in the complex is located at 1650.5 cm^(-1),indicating the backbone of Aβ_(25-35) tends to present random coil conformation,which is consistent with the result obtained from cluster analysis.Currently existing drugs were used as templates for virtual screening,eight new drugs were designed and semi-flexible docking was performed for their performance.The results show that,the interactions between new drugs and α7-n ACh R are strong enough to inhibit the aggregation of Aβ_(25-35) fragments in the ion channel,and also be of great potential in the treatment of Alzheimer’s disease.展开更多
The treatment of chronic and non-healing wounds in diabetic patients remains a major medical problem.Recent reports have shown that hydrogel wound dressings might be an effective strategy for treating diabetic wounds ...The treatment of chronic and non-healing wounds in diabetic patients remains a major medical problem.Recent reports have shown that hydrogel wound dressings might be an effective strategy for treating diabetic wounds due to their excellent hydrophilicity,good drug-loading ability and sustained drug release properties.As a typical example,hyaluronic acid dressing(Healoderm)has been demonstrated in clinical trials to improve wound-healing efficiency and healing rates for diabetic foot ulcers.However,the drug release and degradation behavior of clinically-used hydrogel wound dressings cannot be adjusted according to the wound microenvironment.Due to the intricacy of diabetic wounds,antibiotics and other medications are frequently combined with hydrogel dressings in clinical practice,although these medications are easily hindered by the hostile environment.In this case,scientists have created responsive-hydrogel dressings based on the microenvironment features of diabetic wounds(such as high glucose and low pH)or combined with external stimuli(such as light or magnetic field)to achieve controllable drug release,gel degradation,and microenvironment improvements in order to overcome these clinical issues.These responsive-hydrogel dressings are anticipated to play a significant role in diabetic therapeutic wound dressings.Here,we review recent advances on responsive-hydrogel dressings towards diabetic wound healing,with focus on hydrogel structure design,the principle of responsiveness,and the behavior of degradation.Last but not least,the advantages and limitations of these responsive-hydrogels in clinical applications will also be discussed.We hope that this review will contribute to furthering progress on hydrogels as an improved dressing for diabetic wound healing and practical clinical application.展开更多
For practicable elastomeric polyethylene,achieving high catalyst thermal stability and activity,along with precise control of polymer properties such as branching density,molecular weights,and distribution,is crucial ...For practicable elastomeric polyethylene,achieving high catalyst thermal stability and activity,along with precise control of polymer properties such as branching density,molecular weights,and distribution,is crucial but challenging.In this study,two sets of symmetricalα-diimine nickel complexes,each comprising four nickel bromide or chloride complexes,were synthesized and investigated their performance for ethylene polymerization under various reaction conditions.Upon activation with either Et2AlCl or MMAO cocatalysts,these complexes displayed not only high activity but also generated high molecular weight polyethylenes with controlled polydispersity and a substantial number of branches.The catalyst with the least steric hindrance displayed the remarkable high activity(up to 1.2×10^(7) g·mol^(-1)·h^(-1)).Notably,nickel bromides demonstrated higher activity compared to their chloride counterparts.The investigation into the effect of reaction temperature on catalytic performance revealed that NiBrMe-MMAO system displayed high thermal stability(activity up to 2.51×10^(6) g·mol^(-1)·h^(-1) at 100℃)and consistently yielded high polymer molecular weights with narrow polydispersity over a broad temperature range of 30-100℃.Of significant note,mechanical analysis of the resulting polyethylene demonstrated excellent ultimate tensile strength and high strain at break.Particularly,the polyethylene sample prepared at 100℃exhibited ultimate tensile strength up to 10 MPa with 1863%maximum strain at break and a strain recovery of up to 54.9%after ten cycles at a fixed strain of 300%,indicating excellent material properties of prepared thermoplastic polyethylene elastomers(TPE).展开更多
Based on the in-situ self-reduction and chemical stability,graphdiyne(GDY)and graphdiyne oxide(GDYO)are used as trapping agents to investigate the ability for recovering Au^(3+),Ag^+,and Pd^(2+)under different pH valu...Based on the in-situ self-reduction and chemical stability,graphdiyne(GDY)and graphdiyne oxide(GDYO)are used as trapping agents to investigate the ability for recovering Au^(3+),Ag^+,and Pd^(2+)under different pH values and interfering ions.Under strong acidity at pH=1,these two agents demonstrate high select recovery towards the three precious metal ions,which could be insitu reduced to nanoparticles(NPs).In addition,superparamagnetic Fe_(3)O_(4)NPs are deposited on the surfaces of GDY and GDYO.The magnetic responses enable GDYFe_(3)O_(4)to recover precious metals conveniently and efficiently by the aid of an external magnetic field.This study also confirms the antibacterial activity of the as-recovered NPs deposited on GDY and GDYO against Escherichia coli and Staphylococcus aureus(1×10^(5)colony-forming unit(CFU)·mL^(-1)),and the antibacterial rates are 100%.This strategy of recovering precious metals and subsequently reusing to combat pathogens will be of great significance for environmental remediation and biomedical applications.展开更多
Lithium-sulfur(Li-S) batteries belong to one of the promising technologies for high-energy-density rechargeable batteries.However,sulfur cathodes suffer from inherent problems of its poor electronic conductivity and...Lithium-sulfur(Li-S) batteries belong to one of the promising technologies for high-energy-density rechargeable batteries.However,sulfur cathodes suffer from inherent problems of its poor electronic conductivity and the shuttling of highly dissoluble lithium polysulfides generated during the cycles.Loading sulfur into porous carbons has been proved to be an effective approach to alleviate these issues.Mesoporous and microporous carbons have been widely used for sulfur accommodation,but mesoporous carbons have poor sulfur confinement,whereas microporous carbons are impeded by low sulfur loading rates.Here,a core-shell carbon,combining both the merits of mesoporous carbon with large pore volume and microporous carbon with effective sulfur confinement,was prepared by coating the mesoporous CMK-3 with a microporous carbon(MPC) shell and served as the carbon host(CMK-3 @MPC) to accommodate sulfur.After sulfur infusion,the as-obtained S/(CMK-3@MPC) cathode delivered a high initial capacity of up to 1422 mAh·g-1 and sustained 654 mAh·g-1 reversible specific capacity after 36 cycles at 0.1 C.The good performance is ascribed to the unique core-shell structure of the CMK-3@MPC matrix,in which sulfur can be effectively confined within the meso/microporous carbon host,thus achieving simultaneously high electrochemical utilization.展开更多
A series of experiments were conducted in a self-made smog chamber at (300 + 1) K and 1.01 × 10^5 Pa to simulate the photochemical reaction of ethyl methyl sulfide (EMS) and NOx. The results showed that the ...A series of experiments were conducted in a self-made smog chamber at (300 + 1) K and 1.01 × 10^5 Pa to simulate the photochemical reaction of ethyl methyl sulfide (EMS) and NOx. The results showed that the higher the initial concentration of EMS, the more ozone was generated in the simulative reactions. It was found that the light intensity plays a very important role in the evaluation of ozone formation potential for EMS. The parameters of d(Oa-NO) and IR (incremental reactivity) were used to quantify the potential of EMS on ozone formation. The obtained maximum IR values in this article for the five simulative reactions were 1.55 × 10^-2, 0.99 × 10^-2, 1.36 × 10^-2, 2.47 × 10^-2, and 1.65 × 10^-2, respectively. A comparison between the results we obtained here and the results we obtained previously for di-tert-butyl peroxide and acetylene showed that the potential reactivity of EMS on ozone formation was at a relatively low level.展开更多
Perovskite solar cells(PSCs)are regarded as promising candidates for future renewable energy production.High-density defects in the perovskite films,however,lead to unsatisfactory device performances.Here,poly(propyle...Perovskite solar cells(PSCs)are regarded as promising candidates for future renewable energy production.High-density defects in the perovskite films,however,lead to unsatisfactory device performances.Here,poly(propylene glycol)bis(2-aminopropyl ether)(PEA)additive is utilized to passivate the trap states in perovskite.The PEA molecules chemically interact with lead ions in perovskite,considerably passivate surface and bulk defects,which is in favor of charge transfer and extraction.Furthermore,the PEA additive can efficiently block moisture and oxygen to prolong the device lifetime.As a result,PEA-treated MAPbI3(MA:CH3NH3)solar cells show increased power conversion efficiency(PCE)(from 17.18 to 18.87%)and good longterm stability.When PEA is introduced to(FAPbI3)1-x(MAPbBr3)x(FA:HC(NH2)2)solar cells,the PCE is enhanced from 19.66 to 21.60%.For both perovskites,their severe device hysteresis is efficiently relieved by PEA.展开更多
This present study reviewed the chemical diversity of marine ascidians and their pharmacological applications,challenges and recent developments in marine drug discovery reported during 1994–2014,highlighting the str...This present study reviewed the chemical diversity of marine ascidians and their pharmacological applications,challenges and recent developments in marine drug discovery reported during 1994–2014,highlighting the structural activity of compounds produced by these specimens.Till date only 5%of living ascidian species were studied from\3000 species,this study represented from family didemnidae(32%),polyclinidae(22%),styelidae and polycitoridae(11–12%)exhibiting the highest number of promising MNPs.Close to 580 compound structures are here discussed in terms of their occurrence,structural type and reported biological activity.Anti-cancer drugs are the main area of interest in the screening of MNPs from ascidians(64%),followed by anti-malarial(6%)and remaining others.FDA approved ascidian compounds mechanism of action along with other compounds status of clinical trials(phase 1 to phase 3)are discussed here in.This review highlights recent developments in the area of natural products chemistry and biotechnological approaches are emphasized.展开更多
An efficient synthetic method was developed to synthesize 2-substituted benzimidazoles and benzo- xazoles with β-keto esters as starting materials under mild reaction conditions, during which other functional groups ...An efficient synthetic method was developed to synthesize 2-substituted benzimidazoles and benzo- xazoles with β-keto esters as starting materials under mild reaction conditions, during which other functional groups are bearable from reactants to products.展开更多
The N,N -(phenyl-2-pyridinylmethylene)-3,3 ,5,5 -tetramethylbenzidine and its dimeric Co(Ⅱ)and Ni(Ⅱ) complexes were synthesized.The organic compound was characterized by elemental analyses,IR and NMR spectra,while t...The N,N -(phenyl-2-pyridinylmethylene)-3,3 ,5,5 -tetramethylbenzidine and its dimeric Co(Ⅱ)and Ni(Ⅱ) complexes were synthesized.The organic compound was characterized by elemental analyses,IR and NMR spectra,while the bimetal complexes were determined by elemental analyses,IR spectra as well as the single-crystal X-ray diffraction.The nickel complex showed high activity for ethylene polymerization and its cobalt analogue showed negligible active in ethylene activation.展开更多
Recent progress in improving Li-S batteries' cathodes, anodes, and electrolytes via different approaches is summa- rized. The poor conductivity of sulfur cathodes, the dissolution of polysulfide intermediates, and th...Recent progress in improving Li-S batteries' cathodes, anodes, and electrolytes via different approaches is summa- rized. The poor conductivity of sulfur cathodes, the dissolution of polysulfide intermediates, and the high reactivity of metal Li anodes currently motivate a great deal of research. Urgent challenges concerning Li anodes are also emphasized.展开更多
The photodissociation dynamics of Br-C bond cleavage for BrCN in the wavelength region from 225 nm to 260 nm has been studied by our homebuilt time-slice velocity-map imaging setup.The images for both of the ground st...The photodissociation dynamics of Br-C bond cleavage for BrCN in the wavelength region from 225 nm to 260 nm has been studied by our homebuilt time-slice velocity-map imaging setup.The images for both of the ground state Br(^(2)P_(3/2))and spin-orbit excited Br^(*)(^(2)P_(1/2))channels are obtained at several photodissociation wavelengths.From the analysis of the translational energy release spectra,the detailed vibrational and rotational distributions of CN products have been measured for both of the Br and Br^(*) channels.It is found that the internal excitation of the CN products for the Br^(*) channel is colder than that for the Br channel.The most populated vibrational levels of the CN products are v=0 and 1 for the Br and Br^(*) channels,respectively.For the Br channel,the photodissociation dynamics at longer wavelengths are found to be different from those at shorter wavelengths,as revealed by their dramatically different vibrational and rotational excitations of the CN products.展开更多
The environmentally important free radical reaction of chlorinated methyl CHCl2 with NO2 was investigated by step-scan time-resolved FTIR (TR-FTIR) emission spectroscopy. Vibrationally excited products of CHClO, NO,...The environmentally important free radical reaction of chlorinated methyl CHCl2 with NO2 was investigated by step-scan time-resolved FTIR (TR-FTIR) emission spectroscopy. Vibrationally excited products of CHClO, NO, CO, and HCl are observed in the high-resolution IR emission spectra and three possible reaction channels are therefore elucidated. In particular, the product CO is newly detected and the product HCl is identified explicitly as a yield from the CHCl2+NO2 reaction, taking advantage of the sensitive detection of HCl and CO with TR-FTIR. These results are of particular interests to understand the related realistic chemical processes including atmospheric photochemistry, biofuel combustion, waste destruction, and smoking fire.展开更多
基金supported by the National Natural Sci-ence Foundation of China(No.21973098 and No.22133003)the Beijing National Laboratory for Molecular SciencesJianwei Cao acknowledges the Youth Innovation Promotion Association CAS(No.2018045).
文摘We present a quantum dynamics study on the isotope effects of hydro-gen transfer isomerization in the formic acid dimer,and this is achieved by multidimensional dy-namics calculations with an efficient quantum mechanical theoretical scheme developed by our group,on a full-dimensional neural network ab initio potential energy surface.The ground-state and fundamental tun-neling splittings for four deuterium isotopologues of formic acid dimer are considered,and the calculated results are in very good general agreement with the avail-able experimental measurements.Strong isotope effects are revealed,the mode-specific funda-mental excitation effects on the tunneling rate are evidently influenced by the deuterium sub-stitution of H atom with the substitution on the OH bond being more effective than on the CH bond.Our studies are helpful for acquiring a better understanding of isotope effects in the double-hydrogen transfer processes.
基金supported by the National Natural Science Foundation of China (No. 21507130)the Open Project Program of Beijing National Laboratory for Molecular Sciences (No. 20140142)+3 种基金the Open Project Program of Chongqing Key Laboratory of Environmental Materials and Remediation Technology from Chongqing University of Arts and Sciences (No. CEK1405)the Open Project Program of Jiangsu Key Laboratory of Vehicle Emissions Control (No. OVEC001)the Open Project Program of Chongqing Key Laboratory of Catalysis and Functional Organic Molecules from Chongqing Technology and Business University (1456029)the Chongqing Science & Technology Commission (Nos. cstc2016jcyj A0070, cstc2014pt-gc20002, cstckjcxljrc13)~~
文摘This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature. Five different methods, namely, mechanical mixing, impregnation,hydrothermal treatment, co‐precipitation, and a sol‐gel technique, were used to synthesizeMnOx‐CeO2 catalysts. The catalysts were characterized in detail, and an NH3‐SCR model reaction waschosen to evaluate the catalytic performance. The results showed that the preparation methodsaffected the catalytic performance in the order: hydrothermal treatment > sol‐gel > co‐precipitation> impregnation > mechanical mixing. This order correlated with the surface Ce3+ and Mn4+ content,oxygen vacancies and surface adsorbed oxygen species concentration, and the amount of acidic sitesand acidic strength. This trend is related to redox interactions between MnOx and CeO2. The catalystformed by a hydrothermal treatment exhibited excellent physicochemical properties, optimal catalyticperformance, and good H2O resistance in NH3‐SCR reaction. This was attributed to incorporationof Mnn+ into the CeO2 lattice to form a uniform ceria‐based solid solution (containing Mn‐O‐Cestructures). Strengthening of the electronic interactions between MnOx and CeO2, driven by thehigh‐temperature and high‐pressure conditions during the hydrothermal treatment also improved the catalyst characteristics. Thus, the hydrothermal treatment method is an efficient and environment‐friendly route to synthesizing low‐temperature denitrification (deNOx) catalysts.
基金the financial support from NSFC(21325419,21504095,and 51373181)the Chinese Academy of Science(XDB12030200,KJZD-EW-J01)。
文摘The modification mechanism of the water/alcohol cathode interlayer is one of the most complicated problems in the field of organic photovoltaics,which has not been clearly elucidated yet;this greatly restricts the further enhancement of the PCE for polymer solar cells.Herein,we clarified the different effects of PFN and its derivatives,namely,poly[(9,9-bis(3’-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN-Br) in modifying fullerene-free PSCs.It is found for the first time that doping on IT-4F by the amino group of PFN leads to the unfavorable charge accumulation,and hence,forms a dense layer of electronegative molecule due to the poor electron transport capacity of the non-fullerene acceptor IT-4F.The electronegative molecular layer can block the electron transfer from the active layer to the interlayer and cause serious charge recombination at the active layer/cathode interface.This mechanism could be verified by the ESR measurement and electron-only devices.By replacing PFN with PFN-Br,the excessive doping effect between the cathode interlayer and IT-4F is eliminated,by which the charge transport and collection can be greatly improved.As a result,a high PCE of 13.5%was achieved in the fullerene-free PSCs.
基金supported by“Key Program for International S&T Cooperation Projects of China”from the Ministry of Science and Technology of China(Grant No.2019YFE0123000)the National Natural Science Foundation of China(Grant Nos.91961125 and 21905019)+2 种基金Science and Technology Project of Guangdong Province(No.2020B0101370001)Chemistry and Chemical Engineering Guangdong Laboratory(No.1932004)the Project from China Petrochemical Corporation(No.S20L00151).
文摘The catalytic activities are generally believed to be relevant to the electronic states of their active center, but understanding this relationship is usually difficult. Here, we design two types of catalysts for electrocatalytic urea via a coordination strategy in a metal–organic frameworks: Cu^(Ⅲ)-HHTP and Cu^(Ⅱ)-HHTP. Cu^(Ⅲ)-HHTP exhibits an improved urea production rate of 7.78 mmol h^(−1)g^(−1) and an enhanced Faradaic efficiency of 23.09% at-0.6 V vs. reversible hydrogen electrode, in sharp contrast to Cu^(Ⅱ)-HHTP.Isolated CuⅢspecies with S = 0 spin ground state are demonstrated as the active center in Cu^(Ⅲ)-HHTP, different from Cu^(Ⅱ) with S = 1/2 in Cu^(Ⅱ)-HHTP. We further demonstrate that isolated Cu^(Ⅲ)with an empty dx2-y20orbital in Cu^(Ⅲ)-HHTP experiences a single-electron migration path with a lower energy barrier in the C–N coupling process, while Cu^(Ⅱ)with a single-spin state( d_(x2-y2)^(1)) in Cu^(Ⅱ)-HHTP undergoes a two-electron migration pathway.
基金Project supported by the National Key Research and Development Plan of China(Grant No.2016YFA0200402)the National Natural Science Foundation of China(Grants Nos.11574369,11574368,91323304,11174362,and 51272278)the FP7 Marie Curie Action(project No.295208)sponsored by the European Commission
文摘Some color centers in diamond can serve as quantum bits which can be manipulated with microwave pulses and read out with laser,even at room temperature.However,the photon collection efficiency of bulk diamond is greatly reduced by refraction at the diamond/air interface.To address this issue,we fabricated arrays of diamond nanostructures,differing in both diameter and top end shape,with HSQ and Cr as the etching mask materials,aiming toward large scale fabrication of single-photon sources with enhanced collection efficiency made of nitrogen vacancy(NV) embedded diamond.With a mixture of O2 and CHF3 gas plasma,diamond pillars with diameters down to 45 nm were obtained.The top end shape evolution has been represented with a simple model.The tests of size dependent single-photon properties confirmed an improved single-photon collection efficiency enhancement,larger than tenfold,and a mild decrease of decoherence time with decreasing pillar diameter was observed as expected.These results provide useful information for future applications of nanostructured diamond as a single-photon source.
基金supported by the National Natural Science Foundation of China(No.21773251 and No.21973098)the Youth Innovation Promotion Association CAS(No.2018045)the Beijing National Laboratory for Molecular Sciences。
文摘Ring polymer molecular dynamics(RPMD)calculations for the C(^(1)D)+H_(2)reaction are performed on the Zhang-Ma-Bian ab initio potential energy surfaces(PESs)recently constructed by our group,which are unique in very good descriptions of the regions around conical intersections and of van der Waals(vdW)interactions.The calculated reaction thermal rate coefficients are in very good agreement with the latest experimental results.The rate coefficients obtained from the ground˜a^(1)A′ZMB-a PES are much larger than those from the previous RKHS PES,which can be attributed to that the vdW saddles on our PESs have very different dynamical effects from the vdW wells on the previous PESs,indicating that the RPMD approach is able to include dynamical effects of the topological structures caused by vdW interactions.The importance of the excited˜b^(1)A′′ZMB-b PES and quantum effects in the title reaction is also underscored.
基金the National Natural Science Foundation of China(No.21803072)the Program for Young Outstanding Scientists of Institute of Chemistry,Chinese Academy of Science(ICCAS),and Beijing National Laboratory for Molecular Sciences(BNLMS).+1 种基金the National Aeronautics and Space Administration Award #80NSSC18K0592 and National Science Foundation under CHE-1763319.Yu SongWilliam.M.Jackson gratefully acknowledge the support of NSF under grants CHE-1301501 and AST-1410297.
文摘The photoabsorption and photodissociation of carbon monoxide(CO)in the vacuum ultraviolet(VUV)region is one of the most important photochemical processes in the interstellar medium,thus it has attracted numerous experimental and theoretical studies.Here,we employed the two-color VUV-VUV laser pump-probe time-slice velocity-map ion imaging method to measure the relative branching ratios[C(3P0)+O(1D)]/{[C(3P0)+O(3P)]+[C(3P0)+O(1D)]}and[C(3P2)+O(1D)]/{[C(3P2)+O(3P)]+[C(3P2)+O(1D)]}in the VUV photoexcitation energy range of 108000-113200 cm^−1.Here,one tunable VUV laser beam is used to excite CO to speci c rovibronic states,and a second independently tunable VUV laser beam is used to state-selectively ionize C(3P0)and C(3P2)for detection.State-selective photoionization through the 1VUV+1UV/visible resonance-enhanced multiphoton ionization scheme has greatly enhanced the detection sensitivity,which makes many new weak absorption bands observable in the current study.The branching ratio measurement shows that the spin-forbidden channels C(3P0)+O(1D)and C(3P2)+O(1D)only open at several discrete narrow energy windows.This might be caused by certain accidental resonanceenhanced spin-orbit interactions between the directly excited Rydberg states and valence states of triplet type which nally dissociate into the spin-forbidden channels.
基金supported by the National Natural Science Foundation of China(No.21103021)the New Century Excellent Talent Project in University of Fujian Province,Opening Project of PCOSS,Xiamen University(No.201904)。
文摘The interaction between Amyloid β(Aβ) peptide and acetylcholine receptor is the key for our understanding of how Aβ fragments block the ion channels within the synapses and thus induce Alzheimer’s disease.Here,molecular docking and molecular dynamics(MD)simulations were performed for the structural dynamics of the docking complex consisting of Aβ and α7-n ACh R(α7 nicotinic acetylcholine receptor),and the inter-molecular interactions between ligand and receptor were revealed.The results show that Aβ_(25-35) is bound toα7-n ACh R through hydrogen bonds and complementary shape,and the Aβ_(25-35) fragments would easily assemble in the ion channel of α7-n ACh R,then block the ion transfer process and induce neuronal apoptosis.The simulated amide-I band of Aβ_(25-35) in the complex is located at 1650.5 cm^(-1),indicating the backbone of Aβ_(25-35) tends to present random coil conformation,which is consistent with the result obtained from cluster analysis.Currently existing drugs were used as templates for virtual screening,eight new drugs were designed and semi-flexible docking was performed for their performance.The results show that,the interactions between new drugs and α7-n ACh R are strong enough to inhibit the aggregation of Aβ_(25-35) fragments in the ion channel,and also be of great potential in the treatment of Alzheimer’s disease.
基金This work was supported by the National Key Research and Development Program of China(2020YFA0908100)the National Natural Science Foundation of China(81972081,81971724,81773661,51973226 and 82173750)+2 种基金the Youth Innovation Promotion Association CAS(2019031)the Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang(2020R01018,2021B42001 and 2022C02037)the A*STAR Research Grant for Support of This Project.
文摘The treatment of chronic and non-healing wounds in diabetic patients remains a major medical problem.Recent reports have shown that hydrogel wound dressings might be an effective strategy for treating diabetic wounds due to their excellent hydrophilicity,good drug-loading ability and sustained drug release properties.As a typical example,hyaluronic acid dressing(Healoderm)has been demonstrated in clinical trials to improve wound-healing efficiency and healing rates for diabetic foot ulcers.However,the drug release and degradation behavior of clinically-used hydrogel wound dressings cannot be adjusted according to the wound microenvironment.Due to the intricacy of diabetic wounds,antibiotics and other medications are frequently combined with hydrogel dressings in clinical practice,although these medications are easily hindered by the hostile environment.In this case,scientists have created responsive-hydrogel dressings based on the microenvironment features of diabetic wounds(such as high glucose and low pH)or combined with external stimuli(such as light or magnetic field)to achieve controllable drug release,gel degradation,and microenvironment improvements in order to overcome these clinical issues.These responsive-hydrogel dressings are anticipated to play a significant role in diabetic therapeutic wound dressings.Here,we review recent advances on responsive-hydrogel dressings towards diabetic wound healing,with focus on hydrogel structure design,the principle of responsiveness,and the behavior of degradation.Last but not least,the advantages and limitations of these responsive-hydrogels in clinical applications will also be discussed.We hope that this review will contribute to furthering progress on hydrogels as an improved dressing for diabetic wound healing and practical clinical application.
基金This work was financially supported by the Chemistry and Chemical Engineering Guangdong Laboratory(Nos.2111018 and 2132012)Q.M.would like to express gratitude towards the Foreign Youth Talent Program(No.QN2022030008L)for their support.
文摘For practicable elastomeric polyethylene,achieving high catalyst thermal stability and activity,along with precise control of polymer properties such as branching density,molecular weights,and distribution,is crucial but challenging.In this study,two sets of symmetricalα-diimine nickel complexes,each comprising four nickel bromide or chloride complexes,were synthesized and investigated their performance for ethylene polymerization under various reaction conditions.Upon activation with either Et2AlCl or MMAO cocatalysts,these complexes displayed not only high activity but also generated high molecular weight polyethylenes with controlled polydispersity and a substantial number of branches.The catalyst with the least steric hindrance displayed the remarkable high activity(up to 1.2×10^(7) g·mol^(-1)·h^(-1)).Notably,nickel bromides demonstrated higher activity compared to their chloride counterparts.The investigation into the effect of reaction temperature on catalytic performance revealed that NiBrMe-MMAO system displayed high thermal stability(activity up to 2.51×10^(6) g·mol^(-1)·h^(-1) at 100℃)and consistently yielded high polymer molecular weights with narrow polydispersity over a broad temperature range of 30-100℃.Of significant note,mechanical analysis of the resulting polyethylene demonstrated excellent ultimate tensile strength and high strain at break.Particularly,the polyethylene sample prepared at 100℃exhibited ultimate tensile strength up to 10 MPa with 1863%maximum strain at break and a strain recovery of up to 54.9%after ten cycles at a fixed strain of 300%,indicating excellent material properties of prepared thermoplastic polyethylene elastomers(TPE).
基金financially supported by the National Natural Science Foundation of China(Nos.22062017 and 22164015)Inner Mongolia Autonomous Region Program for Key Science and Technology(No.2020GG0161)+3 种基金Ordos City Program for Key Science and Technology(No.2022YY003)the Program of Higher-Level Talents of Inner Mongolia University(No.10000-22311201/035)the Research Program of science and technology at Universities of Inner Mongolia Autonomous Region(No.NJZZ23091)the Program for Innovative Research Team in Universities of Inner Mongolia Autonomous Region(No.NMGIRT2210)。
文摘Based on the in-situ self-reduction and chemical stability,graphdiyne(GDY)and graphdiyne oxide(GDYO)are used as trapping agents to investigate the ability for recovering Au^(3+),Ag^+,and Pd^(2+)under different pH values and interfering ions.Under strong acidity at pH=1,these two agents demonstrate high select recovery towards the three precious metal ions,which could be insitu reduced to nanoparticles(NPs).In addition,superparamagnetic Fe_(3)O_(4)NPs are deposited on the surfaces of GDY and GDYO.The magnetic responses enable GDYFe_(3)O_(4)to recover precious metals conveniently and efficiently by the aid of an external magnetic field.This study also confirms the antibacterial activity of the as-recovered NPs deposited on GDY and GDYO against Escherichia coli and Staphylococcus aureus(1×10^(5)colony-forming unit(CFU)·mL^(-1)),and the antibacterial rates are 100%.This strategy of recovering precious metals and subsequently reusing to combat pathogens will be of great significance for environmental remediation and biomedical applications.
基金supported by the National Natural Science Foundation of China(Grant No.51225204,91127044,U1301244 and 21121063)the National Key Project on Basic Research(Grant No.2011CB935700,2013AA050903 and 2012CB932900)the"Strategic Priority Research Program"of CAS(Grant No.XDA09010300)
文摘Lithium-sulfur(Li-S) batteries belong to one of the promising technologies for high-energy-density rechargeable batteries.However,sulfur cathodes suffer from inherent problems of its poor electronic conductivity and the shuttling of highly dissoluble lithium polysulfides generated during the cycles.Loading sulfur into porous carbons has been proved to be an effective approach to alleviate these issues.Mesoporous and microporous carbons have been widely used for sulfur accommodation,but mesoporous carbons have poor sulfur confinement,whereas microporous carbons are impeded by low sulfur loading rates.Here,a core-shell carbon,combining both the merits of mesoporous carbon with large pore volume and microporous carbon with effective sulfur confinement,was prepared by coating the mesoporous CMK-3 with a microporous carbon(MPC) shell and served as the carbon host(CMK-3 @MPC) to accommodate sulfur.After sulfur infusion,the as-obtained S/(CMK-3@MPC) cathode delivered a high initial capacity of up to 1422 mAh·g-1 and sustained 654 mAh·g-1 reversible specific capacity after 36 cycles at 0.1 C.The good performance is ascribed to the unique core-shell structure of the CMK-3@MPC matrix,in which sulfur can be effectively confined within the meso/microporous carbon host,thus achieving simultaneously high electrochemical utilization.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(No. KZCX2-YW-205)the National Natural Sci-ence Foundation of China (No. 20577052, 20673123,20503035).
文摘A series of experiments were conducted in a self-made smog chamber at (300 + 1) K and 1.01 × 10^5 Pa to simulate the photochemical reaction of ethyl methyl sulfide (EMS) and NOx. The results showed that the higher the initial concentration of EMS, the more ozone was generated in the simulative reactions. It was found that the light intensity plays a very important role in the evaluation of ozone formation potential for EMS. The parameters of d(Oa-NO) and IR (incremental reactivity) were used to quantify the potential of EMS on ozone formation. The obtained maximum IR values in this article for the five simulative reactions were 1.55 × 10^-2, 0.99 × 10^-2, 1.36 × 10^-2, 2.47 × 10^-2, and 1.65 × 10^-2, respectively. A comparison between the results we obtained here and the results we obtained previously for di-tert-butyl peroxide and acetylene showed that the potential reactivity of EMS on ozone formation was at a relatively low level.
基金Financial support for this research is provided by the National Key Research Program of China(2016YFA0200104)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB12030200).
文摘Perovskite solar cells(PSCs)are regarded as promising candidates for future renewable energy production.High-density defects in the perovskite films,however,lead to unsatisfactory device performances.Here,poly(propylene glycol)bis(2-aminopropyl ether)(PEA)additive is utilized to passivate the trap states in perovskite.The PEA molecules chemically interact with lead ions in perovskite,considerably passivate surface and bulk defects,which is in favor of charge transfer and extraction.Furthermore,the PEA additive can efficiently block moisture and oxygen to prolong the device lifetime.As a result,PEA-treated MAPbI3(MA:CH3NH3)solar cells show increased power conversion efficiency(PCE)(from 17.18 to 18.87%)and good longterm stability.When PEA is introduced to(FAPbI3)1-x(MAPbBr3)x(FA:HC(NH2)2)solar cells,the PCE is enhanced from 19.66 to 21.60%.For both perovskites,their severe device hysteresis is efficiently relieved by PEA.
文摘This present study reviewed the chemical diversity of marine ascidians and their pharmacological applications,challenges and recent developments in marine drug discovery reported during 1994–2014,highlighting the structural activity of compounds produced by these specimens.Till date only 5%of living ascidian species were studied from\3000 species,this study represented from family didemnidae(32%),polyclinidae(22%),styelidae and polycitoridae(11–12%)exhibiting the highest number of promising MNPs.Close to 580 compound structures are here discussed in terms of their occurrence,structural type and reported biological activity.Anti-cancer drugs are the main area of interest in the screening of MNPs from ascidians(64%),followed by anti-malarial(6%)and remaining others.FDA approved ascidian compounds mechanism of action along with other compounds status of clinical trials(phase 1 to phase 3)are discussed here in.This review highlights recent developments in the area of natural products chemistry and biotechnological approaches are emphasized.
基金Supported by the National Natural Science Foundation of China(No.20874105)the Foundation of Hebei Education Department China(No.2010268)
文摘An efficient synthetic method was developed to synthesize 2-substituted benzimidazoles and benzo- xazoles with β-keto esters as starting materials under mild reaction conditions, during which other functional groups are bearable from reactants to products.
文摘The N,N -(phenyl-2-pyridinylmethylene)-3,3 ,5,5 -tetramethylbenzidine and its dimeric Co(Ⅱ)and Ni(Ⅱ) complexes were synthesized.The organic compound was characterized by elemental analyses,IR and NMR spectra,while the bimetal complexes were determined by elemental analyses,IR spectra as well as the single-crystal X-ray diffraction.The nickel complex showed high activity for ethylene polymerization and its cobalt analogue showed negligible active in ethylene activation.
基金supported by the Ministry of Science and Technology(Grant Nos.2012CB932900 and 2013AA050903)the National Natural Science Foundation of China(Grant Nos.51225204 and U1301244)the“Strategic Priority Research Program”of the Chinese Academy of Sciences(Grant No.XDA09010300)
文摘Recent progress in improving Li-S batteries' cathodes, anodes, and electrolytes via different approaches is summa- rized. The poor conductivity of sulfur cathodes, the dissolution of polysulfide intermediates, and the high reactivity of metal Li anodes currently motivate a great deal of research. Urgent challenges concerning Li anodes are also emphasized.
基金supported by the Beijing Municipal Natural Science Foundation(No.8212043)the support from Program for Young Outstanding Scientists of Institute of Chemistry,Chinese Academy of ScienceBeijing National Laboratory for Molecular Sciences。
文摘The photodissociation dynamics of Br-C bond cleavage for BrCN in the wavelength region from 225 nm to 260 nm has been studied by our homebuilt time-slice velocity-map imaging setup.The images for both of the ground state Br(^(2)P_(3/2))and spin-orbit excited Br^(*)(^(2)P_(1/2))channels are obtained at several photodissociation wavelengths.From the analysis of the translational energy release spectra,the detailed vibrational and rotational distributions of CN products have been measured for both of the Br and Br^(*) channels.It is found that the internal excitation of the CN products for the Br^(*) channel is colder than that for the Br channel.The most populated vibrational levels of the CN products are v=0 and 1 for the Br and Br^(*) channels,respectively.For the Br channel,the photodissociation dynamics at longer wavelengths are found to be different from those at shorter wavelengths,as revealed by their dramatically different vibrational and rotational excitations of the CN products.
基金Ⅴ. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (No.20733005 and No.20673126), the National Basic Research Program of China (No.2007CB815200 and No.2007AA02Z116), and the Chinese Academy of Sciences.
文摘The environmentally important free radical reaction of chlorinated methyl CHCl2 with NO2 was investigated by step-scan time-resolved FTIR (TR-FTIR) emission spectroscopy. Vibrationally excited products of CHClO, NO, CO, and HCl are observed in the high-resolution IR emission spectra and three possible reaction channels are therefore elucidated. In particular, the product CO is newly detected and the product HCl is identified explicitly as a yield from the CHCl2+NO2 reaction, taking advantage of the sensitive detection of HCl and CO with TR-FTIR. These results are of particular interests to understand the related realistic chemical processes including atmospheric photochemistry, biofuel combustion, waste destruction, and smoking fire.