Two-dimensional (2D) metallic transition-metal dichalcogenides (TMDCs), such as 1T-TiSe , have recently emerged as unique platforms for exploring their exciting properties of superconductivity and the charge density wave (CDW). 2D 1T-TiSe undergoes rapid oxidation under ambient conditions, significantly affecting its CDW phase-transition behavior. We comprehensively investigate the oxidation process of 2D TiSe by tracking the evolution of the chemical composition and atomic structure with various microscopic and spectroscopic techniques and reveal its unique selenium-assisting oxidation mechanism. Our findings facilitate a better understanding of the chemistry of ultrathin TMDCs crystals, introduce an effective method to passivate their surfaces with capping layers, and thus open a way to further explore the functionality of these materials toward devices.

Atomically thin transition-metal dichalcogenides are of great interest due to their intriguing physical properties and potential applications. Here, we report our findings from scanning tunneling microscopy and spectroscopy investigations on molybdenum disulfide (MoS2) mono- to few-layers and pyramid nanostructures synthesized through chemical vapor deposition. On the few-layered MoS2 nanoplatelets grown on gallium nitride (GaN) and pyramid nanostructures on highly oriented pyrolytic graphite, we observed an intriguing curved region near the edge terminals. The measured band gap on these curved regions is 1.96 ± 0.10 eV, consistent with the value of the direct band gap in MoS2 monolayers. The curved features near the edge terminals and the associated electronic properties may contribute to the catalytic behaviors of MoS2 nanostructures and have potential applications in future electronic devices and energy-related products based on MoS2 nanostructures.

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Objective: Regional dissemination is the major cause of the widespread prevalence of a plasmid-encoding NDM-1 enzyme. We investigated the drug resistance, joint efficiency, and gene environment of a Klebsiella pneumoniae strain carrying bla NDM-1 gene. Materials and Methods: Carbapenem-non-susceptible strains were analyzed using the VITEK 2 Compact. Strains carrying bla NDM-1 were identified using polymerase chain reaction and sequencing. Antimicrobial susceptibility testing and plasmid conjugation experiments were then conducted. Strains carrying bla NDM-1 were subjected to Southern blot analysis. After the gene mapping of bla NDM-1 , library construction, and sequencing, plasmids were subsequently spliced and genotyped using the software Glimmer 3.0, and then analyzed using Mauve software. Results: Among 1735 carbapenem-non-susceptible strains, 54 strains of bla NDM-1positive bacteria were identified, which consisted of 44 strains of K. pneumoniae, 8 strains of Acinetobacter baumannii and 2 strains of Escherichia coli. Strains carrying bla NDM-1 had a resistance rate of more than 50% in most antibiotics. Plasmid conjugation between strains carrying bla NDM-1 and E. coli strain J53 had a success rate of 50%. Southern blot analysis indicated that each strain had multiple plasmids containing bla NDM-1. Among the five plasmids containing bla NDM-1 in K. pneumoniae for sequencing, two plasmids with complete sequences were obtained. The findings were as follows: (i) The p11106 and p12 plasmids were highly similar to pNDM-BTR; (ii) the p11106 and p12 plasmids showed differences in the 20-30 kb region (orf00032-orf00043) from the other six plasmids; and (iii) bla NDM-1 was located at orf00037, while ble was found at orf00038. Two tnpA genes were located in the upstream region, and orf00052 (tnpA) in the 36 kb region was in the downstream sequence. Conclusion: bla NDM-1-containing bacteria exhibit multidrug resistance, which rapidly spreads and is transferred through efficient plasmid conjugation; the multidrug

Tw o-dimensional (2D) metallic transition-metal dichalcogenides (TMDCs), such as 1T-TiSe 2 ,h ave recently emerged as unique platforms for exploring their exciting properties of superconductivity and the charge density wave (CDW). 2D 1T-TiSe 2 undergoes rapid oxidation under ambient conditions,s ignificantly affecting its CDWp hase-transition behavior.W ec omprehensively investigate the oxidation process of 2D TiSe 2 by tracking the evolution of the chemical composition and atomic structure with various microscopic and spectroscopic techniques and reveal its unique seleniumassisting oxidation mechanism. Our findings facilitate abetter understanding of the chemistry of ultrathin TMDCs crystals, introduce an effective method to passivate their surfaces with capping layers,a nd thus open aw ay to further explore the functionality of these materials towardd evices.Several transition-metal dichalcogenides (TMDCs), such as TiSe 2 ,NbSe 2 and TaS 2 ,are known to exhibit two fundamental low-temperature ground states in bulk crystals:t he charge density wave (CDW) and superconductivity,which have been extensively studied for decades. [1] In the last two years,t wodimensional (2D) TiSe 2 ,N bSe 2 ,a nd TaS 2 have attracted intensive interest in condensed-state physics for exploring their complex many-body electronic ground states at low dimensions. [2] Besides providing new insights into the fundamentals of superconductivity and CDW, [2] these 2D metallic TMDCs also show potential applications in advanced lowpower electronics,e specially for 2D TiSe 2 which allows for tuning the phase transitions over ab road range of temperatures by applying gate voltage. [2a] However,e xperimental studies on these metallic 2D TMDCs are still very limited, compared with semiconducting 2D TMDCs,such as MoS 2 and WSe 2 ,m ainly due to the challenges of preserving their pristine properties as these metallic thin flakes undergo rapid oxidations upon exposure to air. [2d,3] 2D black phosphorus (BP) is known to degrade easily under ambient conditions, and great efforts have been made on understanding its oxidation details, [4] which provides important insights into the protection of 2D BP to preserve its intrinsic properties for device applications. [5] Actually,m etallic TMDCs show even higher oxidation tendency than BP under ambient conditions. However,t odate, the oxidation mechanism of these 2D metallic TMDCs is still unknown and the effects of oxidation on their CDW/superconductivity phase transitions are also unexplored.Herein, we explore the oxidation behavior, mechanism, and protection of 2D metallic transition metal diselenides with 1T-TiSe 2 as an example,w hich is one of the most extensively studied CDW-bearing TMDCs. [6] We demonstrated that CDWp hase transitions in 2D TiSe 2 were gradually suppressed in the progress of surface oxidation. We tracked the evolution of the morphology,s tructure,a nd composition of 2D TiSe 2 during oxidation by combining several surface analysis tools with atomically resolved microscopic imaging and...