Realization of monolayer ZrTe5 topological insulators with wide band gaps.

Two-dimensional topological insulators hosting the quantum spin Hall effect have application potential in dissipationless electronics. To observe the quantum spin Hall effect at elevated temperatures, a wide band gap is indispensable to efficiently suppress bulk conduction. Yet, most candidate materials exhibit narrow or even negative band gaps. Here, via elegant control of van der Waals epitaxy, we have successfully grown monolayer ZrTe5 on a bilayer graphene/SiC substrate. The epitaxial ZrTe5 monolayer crystalizes in two allotrope isomers with different intralayer alignments of ZrTe3 prisms. Our scanning tunneling microscopy/spectroscopy characterization unveils an intrinsic full band gap as large as 254 meV and one-dimensional edge states localized along the periphery of the ZrTe5 monolayer. First-principles calculations further confirm that the large band gap originates from strong spin-orbit coupling, and the edge states are topologically nontrivial. These findings thus provide a highly desirable material platform for the exploration of the high-temperature quantum spin Hall effect.

Observation of Electronic Strong Correlation in VTe_{2}-2sqrt[3]×2sqrt[3] Monolayer.

Strong electron correlation under two-dimensional limit is intensely studied in the transition metal dichalcogenides monolayers, mostly within their charge density wave (CDW) states that host a star of David period. Here, by using scanning tunneling microscopy and spectroscopy and density functional theory calculations with on-site Hubbard corrections, we study the VTe_{2} monolayer with a different 2sqrt[3]×2sqrt[3] CDW period. We find that the dimerization of neighboring Te-Te and V-V atoms occurs during the CDW transition, and that the strong correlation effect opens a Mott-like full gap at Fermi energy (E_{F}). We further demonstrate that such a Mott phenomenon is ascribed to the combination of the CDW transition and on-site Coulomb interactions. Our work provides a new platform for exploring Mott physics in 2D materials.

MnO(x)-modified ZnAl-LDOs as high-performance adsorbent for the removal of methyl orange.

MnO(x) modified ZnAl layered double oxides (M-LDO) nanocomposites were prepared through an intercalation/reduction/calcination process. The morphology and crystal structure of M-LDO were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) analysis methods. The results confirmed that the manganese oxide nanoparticles were well distributed on the LDO support. Methyl orange (MO) was chosen as a common water-soluble azo dye probe to evaluate the adsorption performance of M-LDO. The effects of MO initial concentration, agitation time, and temperature on MO adsorption were investigated. It was found that adsorption equilibrium data were best represented by the Langmuir and Redlich-Peterson isotherms and the maximum adsorption capacity was 617.28 mg g(-1) obtained from the Langmuir isotherm, which was much larger than some reported adsorbents. Besides, the adsorption process was spontaneous and endothermic in nature and followed a pseudo-second-order kinetic model. The mechanism of the adsorption process was elaborated by an intraparticle diffusion model. Moreover, the regeneration test of M-LDO was carried out and it showed that the used M-LDO was feasible for at least five times. In principle, this adsorbent with a high adsorption capacity and great reutilization performance could be a very promising adsorbent for wastewater treatment.