查看更多>>摘要：Exciton behavior is crucial to the exploitation of light-emitting conjugated polymer(LCPs)for optoelec-tronic devices.Singlet excitons are easily trapped by the intrinsically defect structures.Herein,we set a polyfluorenol(PPFOH)as an example to systematically investigate its photophysical behavior to check the role of defect structures in LCPs.According to time-resolved photoluminescence analysis,the feature emission peaks from individual chain of PPFOH in diluted DMF solution is effectively avoided the influ-ence of fluorenone formation,but the residual green-band emission at 550 nm is easily observed in the PL spectra of PPFOH dilute toluene solution obtained delay 1.5 ns,confirmed the formation of"guest"physical aggregation-induced defect structure.Remarkably,efficient and ultrafast energy transfer from in-dividual chain to defect structure is observed in PPFOH films.Interestingly,the efficient energy transfer happened for the film obtained from DMF solution(200ps)than those of toluene ones(600ps).Mean-while,compared to relatively stable green-band emission in PPFOH film from toluene solution,red-shifted emission peak(11 nm)of PPFOH film from DMF solutions exposed to saturated DNT vapor also confirmed their different aggregation-induced green-band emission.Therefore,this aggregation defect structures are influenced on the photophysical property of LCPs in solid states.
查看更多>>摘要：Carbon aerogels prepared from renewable nano building blocks are rising-star materials and hold great promise in many fields.However,various defects formed during carbonization at high temperature dis-favor the stress transfer and thus the fabrication of flexible carbon aerogel from renewable nano build-ing blocks.Herein,a structural defect-reducing strategy is proposed by altering the pyrolysis route of cellulose nanofiber.Inorganic salt that inhibits the generation of tar volatilization during pyrolysis can prevent the formation of various structural defects.Microstructure with fewer defects can reduce stress concentration and remarkably enhance the compressibility of carbon aerogel,thus increasing the max-imum stress retention of carbon aerogel.The carbon aerogel also has high stress sensor sensitivity and excellent temperature coefficient of resistance.The structural defect-reducing strategy will pave a new way to fabricate high-strength carbon materials for various fields.
查看更多>>摘要：Folding of molecules is an essential process in nature,and various molecular machines achieve their chemical and mechanical function via controlled folding of molecular conformations.The electric field offers a unique strategy to drive the folding of molecular conformation and to control charge transport through single molecules but remains unexplored.The single-molecule break junction technique provides access to detect the conformational changes via the monitoring of single-molecule conductance,and the electric field between two metal electrodes with nanoscale spacing can provide an extremely strong to achieve in-situ control and detection of molecular folding at the single-molecule level.Here,we use the electric field to control the single-molecule folding using the scanning tunneling microscope break junc-tion(STM-BJ)technique.The electric fields induced folding could lead to a～1400％conductance change of the single-molecule junctions,and the folding/unfolding process can be in-situ switched at the scale of milliseconds.DFT calculations suggest the conformational control originates from the electric field-induced charge injection,and the formation of homoconjugated conformation with the overlapped or-bitals.This work provides the first demonstration of electric field-driven molecular folding,which is es-sential for the understanding of molecular machines in nature and for the design of artificial molecular machines.
查看更多>>摘要：Atomization energy(AE)is an important indicator for measuring material stability and reactivity,which refers to the energy change when a polyatomic molecule decomposes into its constituent atoms.Predict-ing AE based on the structural information of molecules has been a focus of researchers,but existing methods have limitations such as being time-consuming or requiring complex preprocessing and large amounts of training data.Deep learning(DL),a new branch of machine learning(ML),has shown promise in learning internal rules and hierarchical representations of sample data,making it a potential solution for AE prediction.To address this problem,we propose a natural-parameter network(NPN)approach for AE prediction.This method establishes a clearer statistical interpretation of the relationship between the network's output and the given data.We use the Coulomb matrix(CM)method to represent each com-pound as a structural information matrix.Furthermore,we also designed an end-to-end predictive model.Experimental results demonstrate that our method achieves excellent performance on the QM7 and BC2P datasets,and the mean absolute error(MAE)obtained on the QM7 test set ranges from 0.2kcal/mol to 3kcal/mol.The optimal result of our method is approximately an order of magnitude higher than the accuracy of 3 kcal/mol in published works.Additionally,our approach significantly accelerates the pre-diction time.Overall,this study presents a promising approach to accelerate the process of predicting structures using DL,and provides a valuable contribution to the field of chemical energy prediction.
查看更多>>摘要：The development of core-shell nanoclusters with controllable composition is of utmost importance as the material properties depend on their constituent elements.However,precisely tuning their compositions at the atomic scale is not easily achieved because of the difficulty of using limited macroscopic synthetic methods for atomic-level modulation.In this work,we report an interesting example of precisely regu-lating the core composition of an inorganic core-shell-type cobalt polyoxoniobate[Co26Nb36O140]32-by controlling reaction conditions,in which the inner Co-core composition could be tune while retaining the outer Nb-shell composition of resulting product,leading to a series of isostructural species with a general formula of {Co26-nNb36+nO140)(n=0-2).These rare species not only can display good powder and single-crystal proton conductivities,but also might provide helpful and atomic-level insights into the syntheses,structures and composition modifications of inorganic amorphous core-shell heterometal oxide nanoparticles.
查看更多>>摘要：Herein,two antimony sulfates,named RbSb(SO4)2(1)and CsSb(SO4)2(2),have been successfully synthe-sized with the introduction of Sb3+cation with stereochemically active lone pairs(SCALP)into sulfates by the conventional hydrothermal method.Both two compounds endow short ultraviolet(UV)absorption edges(281 nm and 278 nm,respectively)and large birefringence(0.171@546 nm and 0.174@546 nm,re-spectively),which means that they are promising short-wave UV optical materials.Interestingly,though both of the two compounds exhibit similar 1D chained structures,and possess the same functional moi-eties including SbO4 seesaws and SO4 tetrahedral groups,they exhibit significantly opposite macroscopic symmetries,i.e.,compound 1 crystallizes in a centrosymmetric(CS)manner(P21/n)and compound 2 in a noncentrosymmetric(NCS)manner(P212121),due to the size of cations[r(Rb+)=1.56 Å,r(Cs+)=1.67 Å]affects the orientation of SCALP of the adjacent Sb3+.
查看更多>>摘要：Metal-organic frameworks(MOFs)with inherent porosity and suspended acidic groups are promising pro-ton conducting materials in water or aqua-ammonia media.Herein we report a new lanthanide phospho-nate,namely,Dy2(amp2H2)2(mal)(H2O)2-5H2O(MDAF-6).It possesses a 3D open-framework structure,and shows a high NH3 adsorption capacity of 142.4 cm3/g at P/P0=0.98 at 298K due to acid-base in-teraction.Interestingly,the proton conductivity of MDAF-6-NH3 is enhanced by five orders of magnitude compared to MDAF-6 after 8.5 h exposure in saturated NH3-H2O vapor,indicating the importance of coex-istent conjugate acid-base pairs of H3O+-H2O and NH4+-NH3 in promoting proton conduction.Magnetic studies of MDAF-6 revealed slow magnetization relaxation under zero dc field,characteristic of single-molecule magnet behavior.This work provides not only a new multifunctional MOF material,but also a new strategy to improve proton conduction in aqua-ammonia medium.
查看更多>>摘要：Polycyclic aromatic hydrocarbons(PAHs)play an important role in the industry,and the development of new materials for the selective separation of PAHs is of great significance.In this work,we report a hex-ahedral metal-organic cage with low symmetry by subcomponent self-assembly.In this cage,the eight ZnⅡ centers adopt an interesting ∧∧/△△△△△△ or ∧∧∧∧∧∧/△△ configuration.This cage with a cav-ity volume of 520 Å3 can bind anthracene,phenanthrene,and pyrene to form 1:1 host-guest complexes,while the bigger triphenylene,chrysene,perylene,and coronene cannot be encapsulated.The binding constant Ka of pyrene is about 1.110 x 103(mol/L)-1,which is more than an order of magnitude larger than that of anthracene and phenanthrene(111(mol/L)-1,277(mol/L)-1,respectively).X-ray structure studies reveal that the pyrene is located in the cavity and stabilized by multiple C-H---π interactions.After separation from a mixture of PAHs,pyrene with＞96.1％purity can be obtained.This work provides a useful method for the first time for the selective separation of pyrene from PAHs mixture by utiliz-ing a metal-organic cage as the material,making it a useful tool for purifying and separating specific compounds from complex mixtures.
查看更多>>摘要：We have synthesized two copper nanoclusters(NCs)with a protection of the same ligand diphenylphosphino-2-pyridine(C17H14NP,dppy for short),formulated as Cu4(dppy)4Cl2 and Cu21(dppy)10,respectively.The former one bears a distorted tetrahedron Cu4 core with its six edges fully protected by chlorine and dppy ligands,while the latter presents a symmetric Cu21 core on which ten dppy molecules function as monolayer protection via well-organized monodentate or bidentate coordination.Interestingly,the Cu4(dppy)4Cl2 cluster exhibits a strong yellow emission at～577 nm,while Cu21(dppy)10 displays dual emissions in purple(～368nm)and green(～516nm)regions respectively.In combination with TD-DFT calculations,we demonstrate the origin of altered emissions and unique stability of the two copper nan-oclusters pertaining to the ligand coordination and metallic superatomic states.
查看更多>>摘要：It is challenging to cooperatively improve the nonlinear optical(NLO)efficiency and the laser-induced damage threshold(LIDT).This work reports a novel IR NLO materials CslnP2S7(CIPS)designed by combination the strategies of alkali metals substitution and microscopic NLO units PS4 introduction based on AgGaS2.CIPS was composed of strongly distorted[InS6]9-octahedra and[P2S7]4-dimers con-structed by corner-sharing[PS4]3-,which increase the NLO efficiency and decrease thermal expansion anisotropy simultaneously.Compared with AgGaS2,CIPS exhibited strong phase matchable NLO response ca.1.1 × AGS@2.1 μm,high LIDT ca.20.8×AgGaS2,and IR transparency up to 15.3 μm.Structural analysis and theoretical investigation confirmed that large SHG effect and ultrahigh LIDT of CIPS originated from the synergistic contribution of[InS6]9-octahedra and[P2S7]4-dimers.These results indicate that CIPS is a promising NLO candidate in the mid-IR region,and this study provides a new approach for developing potential NLO-LIDT compatible materials.
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