Atomically precise palladium(Pd)clusters are emerging as versatile nanomaterials with applications in catalysis and biomedicine.This study explores the synthesis,structure evolution,and catalytic properties of Pd clus...Atomically precise palladium(Pd)clusters are emerging as versatile nanomaterials with applications in catalysis and biomedicine.This study explores the synthesis,structure evolution,and catalytic properties of Pd clusters stabilized by cyclohexanethiol(HSC_(6)H_(11))ligands.Using electrospray ionization mass spectrometry(ESI-MS)and single-crystal X-ray diffraction(SXRD),structures of the Pd clusters ranging from Pd4(SC_(6)H_(11))8 to Pd18(SC_(6)H_(11))36 were determined.This analysis revealed a structure evolution from polygonal to elliptical geometries of the PdnS2n frameworks as the cluster size increased.UV-Vis-NIR spectroscopy,combined with quantum chemical calculations,elucidated changes in the electronic structure of the clusters.Catalytic studies on the Sonogashira cross-coupling reactions demonstrated a size-dependent decline in activity attributed to variations in structural arrangements and electronic properties.Mechanistic insights proposed a distinctive Pd(Ⅱ)-Pd(Ⅳ)catalytic cycle.This research underscores how ligands and cluster size influence the structures and properties of Pd clusters,offering valuable insights for the future design and application of Pd clusters in advanced catalysis and beyond.展开更多
A new cyclometalated platinum complex containing 2, 5-bis(naphthalene-1-yl)-1,3,4-oxadiazole ligand was synthesized and characterized. The UV-Vis absorptions and photoluminescent properties of the ligand and its plati...A new cyclometalated platinum complex containing 2, 5-bis(naphthalene-1-yl)-1,3,4-oxadiazole ligand was synthesized and characterized. The UV-Vis absorptions and photoluminescent properties of the ligand and its platinum complex were investigated. A characteristic metal-ligand charge transfer absorption peak at 439 nm in the UV spectrum and a strong emission peak at 625 nm in the photoluminescence spectrum were observed for this complex in dichloromethane. Cyclic voltammtry (CV) analysis shows that the EHOMO (energy level of the highest occupied molecular orbital) and ELUMO (energy level of the lowest unoccupied molecular orbital) of the platinum complex are about 、5.69 and 、3.25 eV, respectively, indicating that the oxadiazole-based platinum complex has a potential application in electrophosphorescent devices used as a red-emitting material.展开更多
Two cationic iridium（Ⅲ） complexes, [（pqcm）2Ir（pybz）]（PF6） （Ir1） and [（pqcm）2Ir（apybz）]（PF6） （Ir2） （pqcmH = 2-phenyl-quinoline-4-carboxylic acid methyl ester, pybz = 2-pyridyl-benzimidazole, apybz =...Two cationic iridium（Ⅲ） complexes, [（pqcm）2Ir（pybz）]（PF6） （Ir1） and [（pqcm）2Ir（apybz）]（PF6） （Ir2） （pqcmH = 2-phenyl-quinoline-4-carboxylic acid methyl ester, pybz = 2-pyridyl-benzimidazole, apybz = 1-allyl-2-pyridyl-benzimidazole）, were readily synthesized from the reaction of IrⅢ-μ-chloro-bridged dimer [Ir（pqcm）2（Cl）]2 and corresponding ancillary ligands, and characterized by NMR and mass spectroscopies. The structure of It2 was also confirmed by single-crystal X-ray diffraction. The photophysical properties of the two complexes were also investigated. Irl shows deep red emission peaked at around 652 nm with the phosphorescence quantum yield of ca. 0.29 and the emission lifetime of 233 ns, while Ir2 shows red emission peaked at around 615 nm with the phosphorescence quantum yield of ca. 0.13 and the emission lifetime of 430 ns. The active hydrogen on pybz ligand is believed to have a great influence on the photophysical properties of Ir1.展开更多
8-Oxoguanine （8-oxoG）, a critical mutagenic DNA lesion induced by reactive oxy- gen species, gives rise to a G·C→T·A transversion during replication and thereby must be repaired. The effects of explicit a...8-Oxoguanine （8-oxoG）, a critical mutagenic DNA lesion induced by reactive oxy- gen species, gives rise to a G·C→T·A transversion during replication and thereby must be repaired. The effects of explicit and implicit solvent molecules on the hydrolysis cleavage of N-Glycosidic bond in 8-oxo-7,8-dihydro-2＇-deoxyguanosine （8-oxo-dG） have been systematically clarified in the present work based upon two types of computational models. Detailed potential energy surface （PES） scans and full unconstraint optimizations for all the representative points on PESs were carried out at the B3LYP/6-31＋G（d） level of theory. The effect of implicit solvent was tested by single-point calculation at the SCRF/IEF-PCM model. The results illustrate that the direct hydrolysis model involving one explicit water molecule can’t provide a complete depiction of the hydrolysis process of 8-oxo-dG, attributed to the insufficiency of nucleophile activation and leaving group stabilization. The expansion hydrolysis model involving four explicit water molecules, however, facilitates discrete proton transfer and therefore produces smooth reaction surfaces for both the dissociative （SN1） and concerted （SN2） pathways. The presence of the implicit solvent substantially lowers all activation energies and the SN1 process is more favorable than the SN2 process. The data and insights present here agree well with the experimental results and have given out a baseline for the enzymatic deglycosylation reaction of 8-oxo-dG.展开更多
Uranyl peroxide clusters,formed from uranyl ions,peroxide and other ligands,exhibit complex structural diversity and have significant potential in nuclear chemistry applications.Theoretical prediction is essential for...Uranyl peroxide clusters,formed from uranyl ions,peroxide and other ligands,exhibit complex structural diversity and have significant potential in nuclear chemistry applications.Theoretical prediction is essential for atomic-level understanding of their formation and stability,offering insights where experiments face challenges from uranium's radioactivity and complex coordination.However,their large size and varied topologies pose challenges for theoretical study.In this work,we introduce Uni-Gen,a deep learning model based on the Uni-Mol framework,which generates uranyl cluster structures by leveraging topological similarities with carbon clusters,particularly fullerene.This newly-developed Uni-Gen not only validates the stability of the U28 uranyl cluster consistent with previous experimental data,but also discovers a more stable U44 uranyl cluster than the previously reported structure,and most notably,predicts the previously unreported isomers of the U38 uranyl cluster.Our results demonstrate that Uni-Gen is a powerful tool for predicting diverse potentially stable uranyl cluster structures,thereby enriching our understanding of the stability landscape of uranyl clusters and offering potential for further exploration of novel uranyl materials and chemical phenomena.展开更多
The Ni single-atom catalyst dispersed on nitrogen doped graphene support has attracted much interest due to the high selectivity in electro-catalyzing CO_(2)reduction to CO,yet the chemical inertness of the metal cent...The Ni single-atom catalyst dispersed on nitrogen doped graphene support has attracted much interest due to the high selectivity in electro-catalyzing CO_(2)reduction to CO,yet the chemical inertness of the metal center renders it to exhibit electrochemical activity only under high overpotentials.Herein,we report P-and S-doped Ni single-atom catalysts,i.e.symmetric Ni_(1)/PN_(4)and asymmetric Ni1/SN_(3)C can exhibit high catalytic activity of CO_(2)reduction with stable potential windows.It is revealed that the key intermediate*COOH in CO_(2)electroreduction is stabilized by heteroatom doping,which stems from the upward shift of the axial d_(z2)orbital of the active metal Ni atom.Furthermore,we investigate the potential-dependent free energetics and dynamic properties at the electrochemical interface on the Ni1/SN3C catalyst using ab initio molecular dynamics simulations with a full explicit solvent model.Based on the potential-dependent microkinetic model,we predict that S-atom doped Ni SAC shifts the onset potential of CO_(2)electroreduction from–0.88 to–0.80 V vs.RHE,exhibiting better activity.Overall,this work provides an in-depth understanding of structure-activity relationships and atomic-level electrochemical interfaces of catalytic systems,and offers insights into the rational design of heteroatom-doped catalysts for targeted catalysis.展开更多
Dual-atom catalysts(DACs),a natural extension of single-atom catalysts(SACs),have emerged as a prominent focal point in the field of heterogeneous catalysis,particularly in the context of chemical and energy conversio...Dual-atom catalysts(DACs),a natural extension of single-atom catalysts(SACs),have emerged as a prominent focal point in the field of heterogeneous catalysis,particularly in the context of chemical and energy conversion processes.Despite the fact that the catalytic activity of DACs is significantly modulated by the electronic structure of the catalyst,understanding how electron spin states are affected by variations in topology and geometric structure remains challenging and relatively unexplored.Herein,we propose the rational design of stable DACs composed of two iron atoms anchored on pristine graphdiyne(GDY),Fe_(2)-GDYn.A comprehensive and systematic investigation was carried out to elucidate the electronic configuration and spin states involved in the deliberate convergence towards the magnetic ground state,with the aim of uncovering the structure-spin relationship.Through an in-depth analysis of spin populations,electronic localization/delocalization,and the chemical bonding characteristics of the central metal atoms and the GDY skeleton,it was revealed that the spin coupling between the two iron atoms is preponderantly dictated by adjacent short-range Fe-Fe interactions.Conversely,spin decoupling can be attributed to the long-rangeπ-bond component within the linkage.Moreover,geometric and chemical bonding asymmetries were found to induce orbital and spin splitting in iron atoms possessing an electronic configuration of d8.These findings provide important insights into the relationship between topology and spin,thereby presenting novel strategies for the rational design of spin-manipulated DACs.展开更多
A layered perovskite oxide Y0.8Ca0.2BaCoFeO5＋δ（YCBCF） was synthesized as a novel cathode material for intermedi-ate-temperature solid oxide fuel cells （IT-SOFCs） by citric acid-nitrates self-propagating combusti...A layered perovskite oxide Y0.8Ca0.2BaCoFeO5＋δ（YCBCF） was synthesized as a novel cathode material for intermedi-ate-temperature solid oxide fuel cells （IT-SOFCs） by citric acid-nitrates self-propagating combustion method. The phase and micro-structure of YCBCF were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The aver-age thermal expansion coefficient （TEC） of YCBCF was 14.6×10–6 K–1, which was close to other materials of SOFC at the range of RT–1000 oC. An open-circuit potential of 0.75 V and a maximum output power density of 426 mW/cm2 were obtained at 650 oC in a Sm0.2Ce0.8O1.9 （SDC）-based anode-supported SOFC by using humidified （~3%H2O） hydrogen as fuel and static air as oxidant. The results indicated that the YCBCF was a promising cathode candidate for IT-SOFCs.展开更多
The thermal equilibrium state of the reference electrode was investigated. The results show that the temperature difference between the inside and the outside of zirconia tube was very small and the Seebeck effect can...The thermal equilibrium state of the reference electrode was investigated. The results show that the temperature difference between the inside and the outside of zirconia tube was very small and the Seebeck effect can be ignored after the sensor was dipped into liquid steel for more than 2 s. A special sensor was designed to test the relation between the EMF （electromotive force） of sensor and the thermal equilibrium state of the reference elec- trode. Based on these results, it is suggested that the peak in EMF curve was caused by the change of oxygen potential in reference electrode before the thermal equilibrium was reached. If NiO was added by 2 M- 5 M to the Cr/Cr2O3 reference electrode, the peak in EMF curve could be eliminated.展开更多
Two distinct copper coordination polymers, namely [Cu^Ⅱ2（2,5-pydc）2（bpp）2]·H2O（1） and Cu2^ⅠCu^Ⅱ（2,5-pydc）2（bpp）2（2）（2,5-pydc = pyridine-2,5-dicarboxylic acid, bpp = 1,3-bi（4-pyridyl）propane）, h...Two distinct copper coordination polymers, namely [Cu^Ⅱ2（2,5-pydc）2（bpp）2]·H2O（1） and Cu2^ⅠCu^Ⅱ（2,5-pydc）2（bpp）2（2）（2,5-pydc = pyridine-2,5-dicarboxylic acid, bpp = 1,3-bi（4-pyridyl）propane）, have been successfully synthesized through hydrothermal conditions under different temperatures. Single-crystal X-ray structural analysis revealed that both complexes 1 and 2 are 3D frameworks. Complex 1 is an 8-connected 2-fold interpenetrating network based on [Cu（2,5-pydc）]4 molecular building block（MBB）, and also can be simplified as a 4-connected net if the Cu（Ⅱ） ion is regarded as an independent node, whereas 2 shows a（4,4）-connected non-interpenetrated framework which contains mixed valence Cu（Ⅰ/Ⅱ） centers. The results demonstrate that temperature plays a significant role in the final structures of the complexes.展开更多
Two new metal-organic frameworks（MOFs）, namely, [Co_2（L_1）（bix）（μ_3-OH）]·2H_2O（1） and [Co_2（L_2）（bix）（μ_3-OH）]·2.5H_2O（2）（H_3L_1 = 5-oxyacetate isophthalic acid, H_3L_2 = 3,5-bis-oxyacet...Two new metal-organic frameworks（MOFs）, namely, [Co_2（L_1）（bix）（μ_3-OH）]·2H_2O（1） and [Co_2（L_2）（bix）（μ_3-OH）]·2.5H_2O（2）（H_3L_1 = 5-oxyacetate isophthalic acid, H_3L_2 = 3,5-bis-oxyacetate-benzoic acid, bix = 1,4-bis（imidazol-1-ylmethyl）benzene）, have been synthesized under hydrothermal conditions. Their structures were determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, and powder X-ray diffraction（PXRD） analysis. Both complexes 1 and 2 demonstrate identical three-dimensional（3D）（3,8）-connected tfz-d nets with（4~3）_2（4~6·6^（18）·8~4） topologies, where the tetranuclear [Co_4（μ_3-OH）_2] clusters act as 8-connected nodes and aromatic multicarboxylic ligands as 3-connected nodes. The results show that the ligands with different geometrical conformations can form products with the same topological structures. Their thermal and magnetic properties were also investigated.展开更多
The reduction of N2 to NH_(3) is an important reaction for the industrial production of ammonia gas.Here,we theoretically study the thermal synthesis of ammonia catalyzed by Ru1@Mo_(2)CO_(x)single-atom catalyst(SAC),w...The reduction of N2 to NH_(3) is an important reaction for the industrial production of ammonia gas.Here,we theoretically study the thermal synthesis of ammonia catalyzed by Ru1@Mo_(2)CO_(x)single-atom catalyst(SAC),where Ru atoms are anchored on the oxygen vacancy of the defective Mo2COx.The results show that Ru1@Mo_(2)CO_(x)exhibits excellent stability,and can effectively adsorb and activate N2,owing to up to0.87|e|charge transfer from it to N2.The optimal pathway of N2-to-NH_(3) conversion is association pathway I,of which the rate-determining step is*NH_(2)→*NH_(3) with the barrier energy of 1.26 eV.Especially,the Mo_(2)CO_(x)center functions as an electron reservoir,donating electrons to the NxHy species,while the Ru single atom serves as a charge transfer pathway,thereby enhancing the reaction activity.This finding provides a theoretical foundation for the rational design of MXene-based SACs for thermal catalytic NH_(3) synthesis.展开更多
Three new triterpenes, 3β,21α-dihydroxylupen-18（19）-en （1）, 3β,25-dihydroxytirucalla- 7,23（24）-dien （2）, and 21α-hydroxy-19α-hydrogentaraxastero1-20（30）-en （3） were obtained from an ethyl acetate extr...Three new triterpenes, 3β,21α-dihydroxylupen-18（19）-en （1）, 3β,25-dihydroxytirucalla- 7,23（24）-dien （2）, and 21α-hydroxy-19α-hydrogentaraxastero1-20（30）-en （3） were obtained from an ethyl acetate extract of the whole plant of Siyekucai （Ixeris chinensis）. The structures of 1-3 were determined by spectroscopic methods （EIMS, IR, 1D and 2D NMR）.展开更多
Uniform rice-like CdS particles were synthesized in cyclohexane/Triton X-100/n-pentanol/water quaternary microemulsions. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscop...Uniform rice-like CdS particles were synthesized in cyclohexane/Triton X-100/n-pentanol/water quaternary microemulsions. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, and electron diffraction. The results indicate that the size and the shape of the rice-like CdS particles can be influenced by the molar ratio of water to the surfactant（w value） and the reactant concentrations.展开更多
A red-emitting heteroleptic cyclometalated platinum（II） complex containing an ancillary ligand of pyra- zol-based diketone derivative was synthesized. Its optophysical and electroluminescent properties were studied....A red-emitting heteroleptic cyclometalated platinum（II） complex containing an ancillary ligand of pyra- zol-based diketone derivative was synthesized. Its optophysical and electroluminescent properties were studied. Compared to the reported （piq）Pt（acac） complex, this platinum（II） complex exhibited a blue-shifted UV absorption band at 300--450 nm, a low LUMO energy level and improved electroluminescent property. Using this platinum（II） complex as a single doping emitter and a blend of ploy（9,9-dioctylfluorene） and 2-tert-butylphenyl-5-phenyl- 1,3,4-oxadiazole as a host matrix, the fabricated polymer light-emitting devices displayed saturated red emission with a peak at 648 um and a shoulder at 601 nm. Furthermore, the emission quenching of the platinum（II） complex was significantly suppressed in these devices at high current density due to an introduction of the non-planar pyra- zol group into the ancillary ligand.展开更多
Electrocatalytic CO_(2) reduction reaction(CO_(2)RR)to high-value-added products is a crucial approach for promoting carbon recycling and mitigating energy challenges.Here,extensive theoretical screenings were conduct...Electrocatalytic CO_(2) reduction reaction(CO_(2)RR)to high-value-added products is a crucial approach for promoting carbon recycling and mitigating energy challenges.Here,extensive theoretical screenings were conducted on the nitrogen-doped graphene-supported heteronuclear dual-atom catalysts(DACs)M_(1)/M_(2)-NC(M=V,Cr,Mn,Fe,Co,Ni,and Cu)for CO_(2)RR using density functional theory(DFT)calculations.The calculations indicate that Mn/Cu-NC exhibits superior catalytic activity and selectivity for the CO_(2)RR to HCOOH with a limiting potential as low as−0.15 V.The superior performance is attributed to the strong d-electron coupling between Mn and Cu dual atoms in Mn/Cu-NC,which results in an upward shift of the d-band center of the Mn single atom closer to the Fermi level.Moreover,the adsorption of the key intermediate*OCHO on the Mn single atom was further enhanced,thereby reducing the limiting potential and improving the catalytic performance for CO_(2)RR.This work offers a comprehensive theoretical insight into the catalytic mechanism of the novel Mn/Cu-NC DAC for CO_(2)RR and establishes a critical descriptor of d-band center of the catalytic active center to determine the catalytic activity of DACs for CO_(2)RR,thereby providing guidance for the future design and fabrication of graphene-based metal DACs for CO_(2)RR.展开更多
The rare-earth elements are generally trivalent,but some,like cerium,praseodymium,and terbium,can also exhibit the tetravalent state.However,tetravalent rare earth(RE)metal-carbonσ-bond complexes remain elusive and h...The rare-earth elements are generally trivalent,but some,like cerium,praseodymium,and terbium,can also exhibit the tetravalent state.However,tetravalent rare earth(RE)metal-carbonσ-bond complexes remain elusive and have not been synthesized without the use of chelating ligands to stabilize them.In contrast,the synthesis of numerous trivalent RE-C bond complexes has been achieved and reported.Herein,we report the first synthesis and structural characterization of a complete series of cerium(IV)alkyl,aryl,and alkynyl complexes without chelate-assisted stabilization.The Ce^(IV)-Cσ-bond complexes are synthesized from reactions of imidazolin-2-iminato cerium(IV)chlorides with lithium alkyl,aryl,or alkynyl reagents,and they have all been characterized by single crystal X-ray diffraction.The investigation of the decomposition of cerium(IV)alkyl complexes shows the generation of alkyl radicals,indicating a homolytic cleavage mechanism of Ce^(IV)-C(sp^(3))σ-bond,which is significantly different from the decomposition mechanism of the REⅢ-C(sp^(3))σ-bond.Quantum theoretical studies were performed to provide insights into the Ce^(IV)-C(sp^(n))(n=1,2,3)σ-bonding properties as well as the high ^(13)C{^(1)H}nuclear magnetic resonance(NMR)chemical shifts of Ce^(IV)-C signals.The electronic influence of the supporting ligands was also studied theoretically,which revealed that the strong electron-donating imidazolin-2-iminato ligand enhanced the energylevel match of the Ce(IV)5d orbitals with the alkyl group.This energy-level match strategy provides insights into the preparation of RE complexes with unusual chemical bonds.展开更多
A growing population necessitates the development of sustainable agriculture,which requires achieving atom economy in pesticide delivery,fertilization,and so on.To this end,we focus on single-atom materials(SAMs)to en...A growing population necessitates the development of sustainable agriculture,which requires achieving atom economy in pesticide delivery,fertilization,and so on.To this end,we focus on single-atom materials(SAMs)to enhance atom utilization within agricultural systems.In this study,we report a novel pesticide for plants,a single-atom copper(Cu_(1))formulation,by employing a precipitation-equilibrium-driven(K_(sp)-driven)method to anchor Cu_(1)onto a calcium carbonate(CaCO_(3))carrier.Thanks to its high atom dispersion and utilization efficiency,the Cu_(1)formulation(Cu_(1)/CaCO_(3))significantly enhances crop disease resistance while exhibiting minimal phytotoxicity in the tested species.Notably,this formulation leads to nearly 20-fold less copper residue in the soil after field application compared to traditional copper formulations.It inhibits microbial growth potentially by targeting key bacterial membrane components through interactions with phosphate groups(–PO42–)in membrane phospholipids and binding to sulfhydryl(–SH)residues in respiratory chain proteins.Cu_(1)/CaCO_(3)represents SAMs as a promising tool for designing green pesticides to manage crop diseases and a novel interdisciplinary approach to promoting sustainable agriculture.展开更多
Electrochemical conversion of CO_(2)into valuable hydrocarbon fuel is one of the key steps in solving carbon emission and energy issue.Herein,we report a non-noble metal catalyst,nickel single-atom catalyst(SAC)of Ni_...Electrochemical conversion of CO_(2)into valuable hydrocarbon fuel is one of the key steps in solving carbon emission and energy issue.Herein,we report a non-noble metal catalyst,nickel single-atom catalyst(SAC)of Ni_(1)/UiO-66-NH_(2),with high stability and selectivity for electrochemical reduction of CO_(2)to CH_(4).Based on ab initio molecular dynamics(AIMD)simulations,the CO_(2)molecule is at first reduced into CO_(2)-when stably adsorbed on a Ni single atom with the bidentate coordination mode.To evaluate its activity and selectivity for electrocatalytic reduction of CO_(2)to different products(HCOOH,CO,CH3OH,and CH_(4))on Ni_(1)/UiO-66-NH_(2),we have used density functional theory(DFT)to study different reaction pathways.The results show that CH_(4) is generated preferentially on Ni_(1)/UiO-66-NH_(2)and the calculated limiting potential is as low as-0.24 V.Moreover,the competitive hydrogen evolution reaction is unfavorable at the activation site of Ni_(1)/UiO-66-NH_(2)owing to the higher limiting potential of-0.56 V.Furthermore,the change of Ni single atom valence state plays an important role in promoting CO_(2)reduction to CH_(4).This work provides a theoretical foundation for further experimental studies and practical applications of metal-organic framework(UiO-66)-based SAC electrocatalysts with high activity and selectivity for the CO_(2)reduction reaction.展开更多
As an innovative development of single-atom catalysts(SACs),single-cluster catalysts(SCCs)such as dualatom catalysts have attracted considerable interest due to their excellent performance in catalysis.As one of the m...As an innovative development of single-atom catalysts(SACs),single-cluster catalysts(SCCs)such as dualatom catalysts have attracted considerable interest due to their excellent performance in catalysis.As one of the most powerful and visualizable tools,scanning transmission electron microscopy(STEM)has been widely applied in the characterization of SCCs.Herein,the nitrogen-doped carbonsupported FeFe and CoFe,two representative examples of homonuclear and heteronuclear SCCs,are characterized by STEM.Furthermore,an image processing program is developed to analyze the STEM images and to obtain the locations of atoms,as well as the projected distances between atoms in possible dual-atom pairs.The dimer distances of both CoFe and FeFe catalysts exhibit a trimodal distribution,which can correspond to the energy-favorable atomic structures of the theoretical simulations.Our work offers an avenue for directly revealing the possible atomic configurations of dual-atom sites in SCCs via big data statistics of STEM images and strong theoretical simulations.展开更多
基金supported by the Start-Up Research Funding of Fujian Normal University(No.Y0720326K13)the National Natural Science Foundation of China(Nos.22103035 and 22033005)+2 种基金the National Key R&D Program of China(No.2022YFA1503900)Shenzhen Science and Technology Program(No.RCYX20231211090357078)Guangdong Provincial Key Laboratory of Catalysis(No.2020B121201002).
文摘Atomically precise palladium(Pd)clusters are emerging as versatile nanomaterials with applications in catalysis and biomedicine.This study explores the synthesis,structure evolution,and catalytic properties of Pd clusters stabilized by cyclohexanethiol(HSC_(6)H_(11))ligands.Using electrospray ionization mass spectrometry(ESI-MS)and single-crystal X-ray diffraction(SXRD),structures of the Pd clusters ranging from Pd4(SC_(6)H_(11))8 to Pd18(SC_(6)H_(11))36 were determined.This analysis revealed a structure evolution from polygonal to elliptical geometries of the PdnS2n frameworks as the cluster size increased.UV-Vis-NIR spectroscopy,combined with quantum chemical calculations,elucidated changes in the electronic structure of the clusters.Catalytic studies on the Sonogashira cross-coupling reactions demonstrated a size-dependent decline in activity attributed to variations in structural arrangements and electronic properties.Mechanistic insights proposed a distinctive Pd(Ⅱ)-Pd(Ⅳ)catalytic cycle.This research underscores how ligands and cluster size influence the structures and properties of Pd clusters,offering valuable insights for the future design and application of Pd clusters in advanced catalysis and beyond.
基金Project(50473046) supported by the National Natural Science Foundation of ChinaProject(204097) supported by the Science Foundation of the Ministry of Education of China+1 种基金Project(04JJ1002) supported by the Outstanding Youth Foundation of Hunan Province,ChinaProject(06JJ2008) supported by the Natural Science Foundation of Hunan Province,China
文摘A new cyclometalated platinum complex containing 2, 5-bis(naphthalene-1-yl)-1,3,4-oxadiazole ligand was synthesized and characterized. The UV-Vis absorptions and photoluminescent properties of the ligand and its platinum complex were investigated. A characteristic metal-ligand charge transfer absorption peak at 439 nm in the UV spectrum and a strong emission peak at 625 nm in the photoluminescence spectrum were observed for this complex in dichloromethane. Cyclic voltammtry (CV) analysis shows that the EHOMO (energy level of the highest occupied molecular orbital) and ELUMO (energy level of the lowest unoccupied molecular orbital) of the platinum complex are about 、5.69 and 、3.25 eV, respectively, indicating that the oxadiazole-based platinum complex has a potential application in electrophosphorescent devices used as a red-emitting material.
基金financially supported by the National Natural Science Foundation of China (No. 50903001)the Guangxi Department of Education research project (200911MS281, 200911MS282)
文摘Two cationic iridium（Ⅲ） complexes, [（pqcm）2Ir（pybz）]（PF6） （Ir1） and [（pqcm）2Ir（apybz）]（PF6） （Ir2） （pqcmH = 2-phenyl-quinoline-4-carboxylic acid methyl ester, pybz = 2-pyridyl-benzimidazole, apybz = 1-allyl-2-pyridyl-benzimidazole）, were readily synthesized from the reaction of IrⅢ-μ-chloro-bridged dimer [Ir（pqcm）2（Cl）]2 and corresponding ancillary ligands, and characterized by NMR and mass spectroscopies. The structure of It2 was also confirmed by single-crystal X-ray diffraction. The photophysical properties of the two complexes were also investigated. Irl shows deep red emission peaked at around 652 nm with the phosphorescence quantum yield of ca. 0.29 and the emission lifetime of 233 ns, while Ir2 shows red emission peaked at around 615 nm with the phosphorescence quantum yield of ca. 0.13 and the emission lifetime of 430 ns. The active hydrogen on pybz ligand is believed to have a great influence on the photophysical properties of Ir1.
基金supported by the National Natural Science Foundation of China(21203153 and 21173151)Science&Technology Department(2011JY0136)+1 种基金Department of Education(12ZA174)of Sichuan ProvinceChina West Normal University(11B002)
文摘8-Oxoguanine （8-oxoG）, a critical mutagenic DNA lesion induced by reactive oxy- gen species, gives rise to a G·C→T·A transversion during replication and thereby must be repaired. The effects of explicit and implicit solvent molecules on the hydrolysis cleavage of N-Glycosidic bond in 8-oxo-7,8-dihydro-2＇-deoxyguanosine （8-oxo-dG） have been systematically clarified in the present work based upon two types of computational models. Detailed potential energy surface （PES） scans and full unconstraint optimizations for all the representative points on PESs were carried out at the B3LYP/6-31＋G（d） level of theory. The effect of implicit solvent was tested by single-point calculation at the SCRF/IEF-PCM model. The results illustrate that the direct hydrolysis model involving one explicit water molecule can’t provide a complete depiction of the hydrolysis process of 8-oxo-dG, attributed to the insufficiency of nucleophile activation and leaving group stabilization. The expansion hydrolysis model involving four explicit water molecules, however, facilitates discrete proton transfer and therefore produces smooth reaction surfaces for both the dissociative （SN1） and concerted （SN2） pathways. The presence of the implicit solvent substantially lowers all activation energies and the SN1 process is more favorable than the SN2 process. The data and insights present here agree well with the experimental results and have given out a baseline for the enzymatic deglycosylation reaction of 8-oxo-dG.
基金supported by the National Key Research and Development Project(No.2022YFA1503900)the National Natural Science Foundation of China(Nos.22222605 and 22076095).
文摘Uranyl peroxide clusters,formed from uranyl ions,peroxide and other ligands,exhibit complex structural diversity and have significant potential in nuclear chemistry applications.Theoretical prediction is essential for atomic-level understanding of their formation and stability,offering insights where experiments face challenges from uranium's radioactivity and complex coordination.However,their large size and varied topologies pose challenges for theoretical study.In this work,we introduce Uni-Gen,a deep learning model based on the Uni-Mol framework,which generates uranyl cluster structures by leveraging topological similarities with carbon clusters,particularly fullerene.This newly-developed Uni-Gen not only validates the stability of the U28 uranyl cluster consistent with previous experimental data,but also discovers a more stable U44 uranyl cluster than the previously reported structure,and most notably,predicts the previously unreported isomers of the U38 uranyl cluster.Our results demonstrate that Uni-Gen is a powerful tool for predicting diverse potentially stable uranyl cluster structures,thereby enriching our understanding of the stability landscape of uranyl clusters and offering potential for further exploration of novel uranyl materials and chemical phenomena.
文摘The Ni single-atom catalyst dispersed on nitrogen doped graphene support has attracted much interest due to the high selectivity in electro-catalyzing CO_(2)reduction to CO,yet the chemical inertness of the metal center renders it to exhibit electrochemical activity only under high overpotentials.Herein,we report P-and S-doped Ni single-atom catalysts,i.e.symmetric Ni_(1)/PN_(4)and asymmetric Ni1/SN_(3)C can exhibit high catalytic activity of CO_(2)reduction with stable potential windows.It is revealed that the key intermediate*COOH in CO_(2)electroreduction is stabilized by heteroatom doping,which stems from the upward shift of the axial d_(z2)orbital of the active metal Ni atom.Furthermore,we investigate the potential-dependent free energetics and dynamic properties at the electrochemical interface on the Ni1/SN3C catalyst using ab initio molecular dynamics simulations with a full explicit solvent model.Based on the potential-dependent microkinetic model,we predict that S-atom doped Ni SAC shifts the onset potential of CO_(2)electroreduction from–0.88 to–0.80 V vs.RHE,exhibiting better activity.Overall,this work provides an in-depth understanding of structure-activity relationships and atomic-level electrochemical interfaces of catalytic systems,and offers insights into the rational design of heteroatom-doped catalysts for targeted catalysis.
文摘Dual-atom catalysts(DACs),a natural extension of single-atom catalysts(SACs),have emerged as a prominent focal point in the field of heterogeneous catalysis,particularly in the context of chemical and energy conversion processes.Despite the fact that the catalytic activity of DACs is significantly modulated by the electronic structure of the catalyst,understanding how electron spin states are affected by variations in topology and geometric structure remains challenging and relatively unexplored.Herein,we propose the rational design of stable DACs composed of two iron atoms anchored on pristine graphdiyne(GDY),Fe_(2)-GDYn.A comprehensive and systematic investigation was carried out to elucidate the electronic configuration and spin states involved in the deliberate convergence towards the magnetic ground state,with the aim of uncovering the structure-spin relationship.Through an in-depth analysis of spin populations,electronic localization/delocalization,and the chemical bonding characteristics of the central metal atoms and the GDY skeleton,it was revealed that the spin coupling between the two iron atoms is preponderantly dictated by adjacent short-range Fe-Fe interactions.Conversely,spin decoupling can be attributed to the long-rangeπ-bond component within the linkage.Moreover,geometric and chemical bonding asymmetries were found to induce orbital and spin splitting in iron atoms possessing an electronic configuration of d8.These findings provide important insights into the relationship between topology and spin,thereby presenting novel strategies for the rational design of spin-manipulated DACs.
基金Project supported by the National Natural Science Foundation of China(51102107,51202080)Anhui Science and Technology Project(1206c0805038)
文摘A layered perovskite oxide Y0.8Ca0.2BaCoFeO5＋δ（YCBCF） was synthesized as a novel cathode material for intermedi-ate-temperature solid oxide fuel cells （IT-SOFCs） by citric acid-nitrates self-propagating combustion method. The phase and micro-structure of YCBCF were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The aver-age thermal expansion coefficient （TEC） of YCBCF was 14.6×10–6 K–1, which was close to other materials of SOFC at the range of RT–1000 oC. An open-circuit potential of 0.75 V and a maximum output power density of 426 mW/cm2 were obtained at 650 oC in a Sm0.2Ce0.8O1.9 （SDC）-based anode-supported SOFC by using humidified （~3%H2O） hydrogen as fuel and static air as oxidant. The results indicated that the YCBCF was a promising cathode candidate for IT-SOFCs.
文摘The thermal equilibrium state of the reference electrode was investigated. The results show that the temperature difference between the inside and the outside of zirconia tube was very small and the Seebeck effect can be ignored after the sensor was dipped into liquid steel for more than 2 s. A special sensor was designed to test the relation between the EMF （electromotive force） of sensor and the thermal equilibrium state of the reference elec- trode. Based on these results, it is suggested that the peak in EMF curve was caused by the change of oxygen potential in reference electrode before the thermal equilibrium was reached. If NiO was added by 2 M- 5 M to the Cr/Cr2O3 reference electrode, the peak in EMF curve could be eliminated.
基金supported by the application basis research key project of Yunnan Province science and technology department(201401CB00299)the major project of Qujing Normal University(2012ZD002)
文摘Two distinct copper coordination polymers, namely [Cu^Ⅱ2（2,5-pydc）2（bpp）2]·H2O（1） and Cu2^ⅠCu^Ⅱ（2,5-pydc）2（bpp）2（2）（2,5-pydc = pyridine-2,5-dicarboxylic acid, bpp = 1,3-bi（4-pyridyl）propane）, have been successfully synthesized through hydrothermal conditions under different temperatures. Single-crystal X-ray structural analysis revealed that both complexes 1 and 2 are 3D frameworks. Complex 1 is an 8-connected 2-fold interpenetrating network based on [Cu（2,5-pydc）]4 molecular building block（MBB）, and also can be simplified as a 4-connected net if the Cu（Ⅱ） ion is regarded as an independent node, whereas 2 shows a（4,4）-connected non-interpenetrated framework which contains mixed valence Cu（Ⅰ/Ⅱ） centers. The results demonstrate that temperature plays a significant role in the final structures of the complexes.
基金supported by the application basis research key project of Yunnan Province science and technology department(201401CB00299)the major project of Qujing Normal University(2012ZD002)
文摘Two new metal-organic frameworks（MOFs）, namely, [Co_2（L_1）（bix）（μ_3-OH）]·2H_2O（1） and [Co_2（L_2）（bix）（μ_3-OH）]·2.5H_2O（2）（H_3L_1 = 5-oxyacetate isophthalic acid, H_3L_2 = 3,5-bis-oxyacetate-benzoic acid, bix = 1,4-bis（imidazol-1-ylmethyl）benzene）, have been synthesized under hydrothermal conditions. Their structures were determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, and powder X-ray diffraction（PXRD） analysis. Both complexes 1 and 2 demonstrate identical three-dimensional（3D）（3,8）-connected tfz-d nets with（4~3）_2（4~6·6^（18）·8~4） topologies, where the tetranuclear [Co_4（μ_3-OH）_2] clusters act as 8-connected nodes and aromatic multicarboxylic ligands as 3-connected nodes. The results show that the ligands with different geometrical conformations can form products with the same topological structures. Their thermal and magnetic properties were also investigated.
基金the financial support from National Natural Science Foundation of China(22479032,22363001 and 22250710677)the NSFC Center for Single-Atom Catalysis(22388102)+2 种基金the National Key R&D Project(2022YFA1503900)the Natural Science Special Foundation of Guizhou University(No.202140)Guizhou Provincial Key Laboratory Platform Project(ZSYS[2025]008).
文摘The reduction of N2 to NH_(3) is an important reaction for the industrial production of ammonia gas.Here,we theoretically study the thermal synthesis of ammonia catalyzed by Ru1@Mo_(2)CO_(x)single-atom catalyst(SAC),where Ru atoms are anchored on the oxygen vacancy of the defective Mo2COx.The results show that Ru1@Mo_(2)CO_(x)exhibits excellent stability,and can effectively adsorb and activate N2,owing to up to0.87|e|charge transfer from it to N2.The optimal pathway of N2-to-NH_(3) conversion is association pathway I,of which the rate-determining step is*NH_(2)→*NH_(3) with the barrier energy of 1.26 eV.Especially,the Mo_(2)CO_(x)center functions as an electron reservoir,donating electrons to the NxHy species,while the Ru single atom serves as a charge transfer pathway,thereby enhancing the reaction activity.This finding provides a theoretical foundation for the rational design of MXene-based SACs for thermal catalytic NH_(3) synthesis.
文摘Three new triterpenes, 3β,21α-dihydroxylupen-18（19）-en （1）, 3β,25-dihydroxytirucalla- 7,23（24）-dien （2）, and 21α-hydroxy-19α-hydrogentaraxastero1-20（30）-en （3） were obtained from an ethyl acetate extract of the whole plant of Siyekucai （Ixeris chinensis）. The structures of 1-3 were determined by spectroscopic methods （EIMS, IR, 1D and 2D NMR）.
文摘Uniform rice-like CdS particles were synthesized in cyclohexane/Triton X-100/n-pentanol/water quaternary microemulsions. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, and electron diffraction. The results indicate that the size and the shape of the rice-like CdS particles can be influenced by the molar ratio of water to the surfactant（w value） and the reactant concentrations.
基金Project supported by the National Natural Science Foundation of China （Nos. 50973093, 20772101, 20872124）, Research Fund and the New Teacher Fund for the Doctoral Program of Higher Education of China （Nos. 20094301110004, 200805301013）, Science Foundation of Hunan Province （No. 2009FJ2002）, Scientific Research Fund of Hunan Provincial Education Department （No. 10A 119, 11CY023） and the Postgraduate Science Foundation for Innovation in Hunan Province （No. CX2009B124）.
文摘A red-emitting heteroleptic cyclometalated platinum（II） complex containing an ancillary ligand of pyra- zol-based diketone derivative was synthesized. Its optophysical and electroluminescent properties were studied. Compared to the reported （piq）Pt（acac） complex, this platinum（II） complex exhibited a blue-shifted UV absorption band at 300--450 nm, a low LUMO energy level and improved electroluminescent property. Using this platinum（II） complex as a single doping emitter and a blend of ploy（9,9-dioctylfluorene） and 2-tert-butylphenyl-5-phenyl- 1,3,4-oxadiazole as a host matrix, the fabricated polymer light-emitting devices displayed saturated red emission with a peak at 648 um and a shoulder at 601 nm. Furthermore, the emission quenching of the platinum（II） complex was significantly suppressed in these devices at high current density due to an introduction of the non-planar pyra- zol group into the ancillary ligand.
基金supported by the National Key R&D Project(2022YFA1503900)the National Natural Science Foundation of China(22363001,22479032 and 22250710677)+1 种基金the NSFC Center for SingleAtom Catalysis(22388102)the Natural Science Special Foundation of Guizhou University(202140)。
文摘Electrocatalytic CO_(2) reduction reaction(CO_(2)RR)to high-value-added products is a crucial approach for promoting carbon recycling and mitigating energy challenges.Here,extensive theoretical screenings were conducted on the nitrogen-doped graphene-supported heteronuclear dual-atom catalysts(DACs)M_(1)/M_(2)-NC(M=V,Cr,Mn,Fe,Co,Ni,and Cu)for CO_(2)RR using density functional theory(DFT)calculations.The calculations indicate that Mn/Cu-NC exhibits superior catalytic activity and selectivity for the CO_(2)RR to HCOOH with a limiting potential as low as−0.15 V.The superior performance is attributed to the strong d-electron coupling between Mn and Cu dual atoms in Mn/Cu-NC,which results in an upward shift of the d-band center of the Mn single atom closer to the Fermi level.Moreover,the adsorption of the key intermediate*OCHO on the Mn single atom was further enhanced,thereby reducing the limiting potential and improving the catalytic performance for CO_(2)RR.This work offers a comprehensive theoretical insight into the catalytic mechanism of the novel Mn/Cu-NC DAC for CO_(2)RR and establishes a critical descriptor of d-band center of the catalytic active center to determine the catalytic activity of DACs for CO_(2)RR,thereby providing guidance for the future design and fabrication of graphene-based metal DACs for CO_(2)RR.
基金supported by the National Natural Science Foundation of China(grant nos.21890721,21732007,and 22033005)the Shanghai Municipal Committee of Science and Technologysupported by the Xuetang Program of the Department of Chemistry,Tsinghua University。
文摘The rare-earth elements are generally trivalent,but some,like cerium,praseodymium,and terbium,can also exhibit the tetravalent state.However,tetravalent rare earth(RE)metal-carbonσ-bond complexes remain elusive and have not been synthesized without the use of chelating ligands to stabilize them.In contrast,the synthesis of numerous trivalent RE-C bond complexes has been achieved and reported.Herein,we report the first synthesis and structural characterization of a complete series of cerium(IV)alkyl,aryl,and alkynyl complexes without chelate-assisted stabilization.The Ce^(IV)-Cσ-bond complexes are synthesized from reactions of imidazolin-2-iminato cerium(IV)chlorides with lithium alkyl,aryl,or alkynyl reagents,and they have all been characterized by single crystal X-ray diffraction.The investigation of the decomposition of cerium(IV)alkyl complexes shows the generation of alkyl radicals,indicating a homolytic cleavage mechanism of Ce^(IV)-C(sp^(3))σ-bond,which is significantly different from the decomposition mechanism of the REⅢ-C(sp^(3))σ-bond.Quantum theoretical studies were performed to provide insights into the Ce^(IV)-C(sp^(n))(n=1,2,3)σ-bonding properties as well as the high ^(13)C{^(1)H}nuclear magnetic resonance(NMR)chemical shifts of Ce^(IV)-C signals.The electronic influence of the supporting ligands was also studied theoretically,which revealed that the strong electron-donating imidazolin-2-iminato ligand enhanced the energylevel match of the Ce(IV)5d orbitals with the alkyl group.This energy-level match strategy provides insights into the preparation of RE complexes with unusual chemical bonds.
基金supported by the Ministry of Science and Technology of China(2021YFA1500404)the University of Science and Technology of China(USTC)Research Funds of the Double First-Class Initiative(YD2060006005)+3 种基金the Joint Funds of the National Natural Science Foundation of China(NSFC)(U23A2081,92261105,and 22221003)the NSFC Center for Single-Atom Catalysis(22388102)the Fundamental Research Funds for the Central Universities(WK2060000088)the Anhui Provincial Key Research and Development Project(2023z04020010).
文摘A growing population necessitates the development of sustainable agriculture,which requires achieving atom economy in pesticide delivery,fertilization,and so on.To this end,we focus on single-atom materials(SAMs)to enhance atom utilization within agricultural systems.In this study,we report a novel pesticide for plants,a single-atom copper(Cu_(1))formulation,by employing a precipitation-equilibrium-driven(K_(sp)-driven)method to anchor Cu_(1)onto a calcium carbonate(CaCO_(3))carrier.Thanks to its high atom dispersion and utilization efficiency,the Cu_(1)formulation(Cu_(1)/CaCO_(3))significantly enhances crop disease resistance while exhibiting minimal phytotoxicity in the tested species.Notably,this formulation leads to nearly 20-fold less copper residue in the soil after field application compared to traditional copper formulations.It inhibits microbial growth potentially by targeting key bacterial membrane components through interactions with phosphate groups(–PO42–)in membrane phospholipids and binding to sulfhydryl(–SH)residues in respiratory chain proteins.Cu_(1)/CaCO_(3)represents SAMs as a promising tool for designing green pesticides to manage crop diseases and a novel interdisciplinary approach to promoting sustainable agriculture.
基金This work was supported by the National Key Research and Development Project(Nos.2022YFA1503900 and 2022YFA1503000)the National Natural Science Foundation of China(Nos.22033005 and 21963005)+2 种基金the Natural Science Special Foundation of Guizhou University(No.202140)the Guangdong Provincial Key Laboratory of Catalysis(No.2020B121201002)The calculations were performed using supercomputers at the Center for Computational Science and Engineering of SUSTech and Shanghai Supercomputing Center.
文摘Electrochemical conversion of CO_(2)into valuable hydrocarbon fuel is one of the key steps in solving carbon emission and energy issue.Herein,we report a non-noble metal catalyst,nickel single-atom catalyst(SAC)of Ni_(1)/UiO-66-NH_(2),with high stability and selectivity for electrochemical reduction of CO_(2)to CH_(4).Based on ab initio molecular dynamics(AIMD)simulations,the CO_(2)molecule is at first reduced into CO_(2)-when stably adsorbed on a Ni single atom with the bidentate coordination mode.To evaluate its activity and selectivity for electrocatalytic reduction of CO_(2)to different products(HCOOH,CO,CH3OH,and CH_(4))on Ni_(1)/UiO-66-NH_(2),we have used density functional theory(DFT)to study different reaction pathways.The results show that CH_(4) is generated preferentially on Ni_(1)/UiO-66-NH_(2)and the calculated limiting potential is as low as-0.24 V.Moreover,the competitive hydrogen evolution reaction is unfavorable at the activation site of Ni_(1)/UiO-66-NH_(2)owing to the higher limiting potential of-0.56 V.Furthermore,the change of Ni single atom valence state plays an important role in promoting CO_(2)reduction to CH_(4).This work provides a theoretical foundation for further experimental studies and practical applications of metal-organic framework(UiO-66)-based SAC electrocatalysts with high activity and selectivity for the CO_(2)reduction reaction.
基金supported by the National Key Research and Development Project(2022YFA1503900,2022YFA1503000,and 2022YFA1203400)Shenzhen Fundamental Research Funding(JCYJ20210324115809026,JCYJ20220818100212027,and JCYJ20200109141216566)+7 种基金Shenzhen Science and Technology Program(KQTD20190929173815000)Guangdong scientific program with contract no.2019QN01L057Guangdong Innovative and Entrepreneurial Research Team Program(2019ZT08C044)to Gu Msupported by the National Natural Science Foundation of China(22033005)to Li Jpartially sponsored by Guangdong Provincial Key Laboratory of Catalysis(2020B121201002).support from Presidential fund and Development and Reform Commission of Shenzhen Municipalitysupported by the Center for Computational Science and Engineering at SUSTechthe CHEM high-performance supercomputer cluster(CHEMHPC)located at the Department of Chemistry,SUSTech。
文摘As an innovative development of single-atom catalysts(SACs),single-cluster catalysts(SCCs)such as dualatom catalysts have attracted considerable interest due to their excellent performance in catalysis.As one of the most powerful and visualizable tools,scanning transmission electron microscopy(STEM)has been widely applied in the characterization of SCCs.Herein,the nitrogen-doped carbonsupported FeFe and CoFe,two representative examples of homonuclear and heteronuclear SCCs,are characterized by STEM.Furthermore,an image processing program is developed to analyze the STEM images and to obtain the locations of atoms,as well as the projected distances between atoms in possible dual-atom pairs.The dimer distances of both CoFe and FeFe catalysts exhibit a trimodal distribution,which can correspond to the energy-favorable atomic structures of the theoretical simulations.Our work offers an avenue for directly revealing the possible atomic configurations of dual-atom sites in SCCs via big data statistics of STEM images and strong theoretical simulations.
