Atomically self-healing of structural defects in monolayer WSe_(2)

Minimizing disorder and defects is crucial for realizing the full potential of two-dimensional transition metal dichalcogenides(TMDs) materials and improving device performance to desired properties. However, the methods in defect controlcurrently face challenges with overly large operational areas and a lack of precision in targeting specific defects. Therefore,we propose a new method for the precise and universal defect healing of TMD materials, integrating real-time imaging withscanning transmission electron microscopy (STEM). This method employs electron beam irradiation to stimulate the diffusionmigration of surface-adsorbed adatoms on TMD materials grown by low-temperature molecular beam epitaxy (MBE),and heal defects within the diffusion range. This approach covers defect repairs ranging from zero-dimensional vacancydefects to two-dimensional grain orientation alignment, demonstrating its universality in terms of the types of samples anddefects. These findings offer insights into the use of atomic-level focused electron beams at appropriate voltages in STEMfor defect healing, providing valuable experience for achieving atomic-level precise fabrication of TMD materials.

Molecular and atomic manipulation of metal-organic framework-derived LiCoMnO_(4):An oxygen-deficient strategy for advanced lithium storage

As a novel class of high-voltage cathode materials,spinel lithium transition metal oxides have been faced with demerits including pronounced structural instability caused by Jahn-Teller distortion(especially at the lower voltage region)and severe capacity degradation despite their intriguing electrochemical properties.To extend their functionalities as broad-voltage cathodes,the sacrificial template method has been regarded as a promising way to realize structural and compositional control for desirable electrochemical behaviors.Herein,we report a synthetic protocol to directionally prepare Li Co Mn O_(4)(LCMO)using carboxyl-based metal-organic frameworks(MOFs)as self-sacrificing templates.Impressively,LCMO derived from Co Mn-BDC(H_(2)BDC=1,4-benzenedicarboxylate)displays superior electrochemical performances with a specific capacity of 151.6 m Ah g^(-1)at 1 C(150 m A g^(-1))after 120 cycles and excellent rate capacity of 91.9 m Ah g^(-1)at 10 C due to the morphology control,microstructural modulation,and atomic manipulation of the MOF precursor.Bestowed by the optimized atomic and electronic structure,abundant oxygen vacancies,and the nanostructure retained from MOF precursors,LCMO materials display extraordinary electrochemical properties,which have been extensively verified by both experimental and theoretical studies.This work not only provides guidelines for the directional design of spinel materials at molecular and atomic levels but also sheds light on the practical use of LIBs with broad range voltage.

Microwave coherent manipulation of cold atoms in optically induced fictitious magnetic traps on an atom chip

We propose a novel on-chip platform for controlling and manipulating cold atoms precisely and coherently. The scheme is achieved by producing optically induced fictitious magnetic traps（OFMTs） with 790 nm（for -（87）Rb） circularly polarized laser beams and state-dependent potentials simultaneously for two internal atomic states with microwave coplanar waveguides. We carry out numerical calculations and simulations for controlled collisional interactions between OFMTs and addressable single atoms＇ manipulation on our designed hybrid atom chips. The results show that our proposed platform is feasible and flexible, which has wide applications including collisional dynamics investigation, entanglement generation,and scalable quantum gates implementation.

Revealing the Atomic Site-Dependent g-Factor within a Single Magnetic Molecule

The Lande g-factor of a free atom determines the effective magnetic moment of an electron or atom with both spin and orbital angular momentum,which can be calculated by Lande formula,for a transition metal ion in the crystal field,the spin-orbital interaction can mix the non-zero orbital angular momentum of excited states with the＂pure spin＂ground state,resulting in an effective g-factor.Thus,the ability to probe the fine structure of the g-factor allows us to understand the internal spin properties of a magnetic system,such as the spin-orbital interaction.However,for molecular systems,traditional experimental methods for g-factor measurement,like EPR.

Atomically-precise Au_(24)Ag_(1) Clusterzymes with Enhanced Peroxidase-like Activity for Bioanalysis

Atomically-precise clusterzymes have been widely studied for their special physicochemical properties,but it is still a challenge to enhance their peroxidase-like activity.Herein,we demonstrated that by substituting a single Ag atom into Au25 nanoclusters to form Au_(24)Ag_(1) nanoclusters,the peroxidase-like activity was enhanced greatly.In the presence of H_(2)O_(2),Au_(24)Ag_(1) could produce reactive oxygen species(ROS)to oxidize colorless 3,3'5,5'-tetramethylbenzidine(TMB)to the blue oxidized TMB(oxTMB).It is worth mentioning that pyrophosphate compounds inhibit the activity of Au_(24)Ag_(1).Since alkaline phosphatase(ALP)can dephosphorylate the substrate phosphate compound,that is,remove the phosphate group on the substrate by hydrolysis,the enzymatic activity of the clusterzyme is restored.Based on this,we have developed a sensitive and reliable colorimetric sensing system for the detection of pyrophosphate ion(PPi),adenosine triphosphate(ATP),adenosine diphosphate(ADP)and ALP,respectively.Importantly,the detection limit of the assay system is lower than those of most of the assays that have been reported.In addition,we also built a simple optical logic gate on this basis,further extending the application of metal nanoclusters as peroxidase mimics in bioanalysis.This work could help to shed light on the structure-activity relationship of nanozyme.

Writing with atoms： Oxygen adatoms on the MoO2/Mo（110） surface

Writing at the nanoscale using the desorption of oxygen adatoms from the oxygen-rich MoO2＋x/Mo（110） surface is demonstrated by scanning tunnelling microscopy （STM）. High-temperature oxidation of the Mo（110） surface results in a strained, bulk-like MOO2（010） ultra-thin film with an O-Mo-O trilayer structure. Due to the lattice mismatch between the Mo（110） and the MOO2（010）, the latter consists of well-ordered molybdenum oxide nanorows separated by 2.5 nm. The MoO2（010）/Mo（110） structure is confirmed by STM data and density functional theory calculations. Further oxidation results in the oxygen-rich MoOa^x/Mo（110） surface, which exhibits perfectly aligned double rows of oxygen adatoms, imaged by STM as bright protrusions. These adatoms can be removed from the surface by scanning （or pulsing） at positive sample biases greater than 1.5 V. Tip movement along the surface can be used for controlled lithography （or writing） at the nanoscale, with a minimum feature size of just 3 nm. By moving the STM tip in a predetermined fashion, information can be written and read by applying specific biases between the surface and the tip.

Topological Defects Induced HighSpin Quartet State in Truxene-Based Molecular Graphenoids

Topological defects in graphene materials introduce exotic properties with both fundamental importance and technological implications,absent in their defect-free counterparts.Although individual topological defects have been widely studied,collective magnetic behaviors originating from well-organized multiple topological defects remain a great challenge.Here,we examined the collective magnetic properties originating from three pentagon topological defects in truxene-based molecular graphenoids using scanning tunneling microscopy(STM)and non-contact atomic force microscopy.Unpairedπelectrons were introduced into the aromatic topology of truxene molecular graphenoids one by one by dissociating hydrogen atoms at the pentagon defects via atom manipulation.STM measurements,together with density functional theory calculations,suggested that the unpaired electrons were ferromagnetically coupled,forming a collective highspin quartet state of S=3/2.Our work demonstrates that collective spin ordering could be realized through engineering regular patterned topological defects in molecular graphenoids,providing a new platform for designing one-dimensional ferromagnetic spin chains and two-dimensional ferromagnetic networks.

Recent advances in optical-based and force-based single nucleic acid imaging

The capability to image, as well as control and manipulate single molecules such as nucleic acids(DNA or RNA) can greatly enrich our knowledge of the roles of individual biomolecules in cellular processes and their behavior in native environments. Here we summarize the recent advances of single nucleic acid imaging based on optical observation and force manipulation. We start by discussing the superiority of single molecule image, the central roles nucleic acids play in biosystems, and the significance of single molecule image towards nucleic acids. We then list a series of representative examples in brief to illustrate how nucleic acid of various morphologies has been imaged from different aspects, and what can be learned from such characterizations. Finally,concluding remarks on parts of which should be improved and outlook are outlined.