Direct Observation of Transition Metal Dichalcogenides in Liquid with Scanning Tunneling Microscopy

We present atomic-resolution images of TiSe\begin{document}$_2$\end{document}, MoTe\begin{document}$_2$\end{document} and TaS\begin{document}$_2$\end{document} single crystals in liquid condition using our home-built scanning tunneling microscopy (STM). By facilely cleaving of single crystals in liquid, we were able to keep the fresh surface not oxidized within a few hours. Using the high-stable home-built STM, we have obtained atomic resolution images of TiSe\begin{document}$_2$\end{document} accompanied with the single atom defects as well as the triangle defects in solution for the first time. Besides, the superstructure of MoTe\begin{document}$_2$\end{document} and hexagonal charge-density wave domain structure in nearly commensurate phase of TaS\begin{document}$_2$\end{document} were also obtained at room temperature (295 K). Our results provide a more efficient method in investigating the lively surface of transition metal dichalcogenides. Besides, the high stable liquid-phase STM will support the further investigations in liquid-phase catalysis or electrochemistry.     

Hypersurfaces in a sphere with constant mean curvature

Let be a closed hypersurface of constant mean curvature immersed in the unit sphere . Denote by the square of the length of its second fundamental form. If , is a small hypersphere in . We also characterize all with .

     

Asymmetric ring-opening reaction of oxabicyclic alkenes with aryl boronic acids catalyzed by P-containing palladacycles

The chiral phosphine-containing palladacycle, synthesized easily from H-MOP, showed its high catalytic activity as well as asymmetric induction ability in ring-opening reaction of oxabicyclic alkenes with arylboronic acids, providing corresponding products in high yields and high ee.     

Facile synthesis and high d33 of single-crystalline KNbO3 nanocubes

Single-crystalline KNbO(3) nanocubes with orthorhombic phase were prepared in a large scale by a simple one-step molten salt route without using any surfactant as template; the nanostructures exhibited high piezoelectric properties such as d(33)=105 pC/N and k(p)=0.34 as piezoelectric materials.     

Evaluation of tungsten coil electrothermal vaporization-Ar/H2 flame atomic fluorescence spectrometry for determination of eight traditional hydride-forming elements and cadmium without chemical vapor generation

A tungsten coil electrothermal vaporizer (W-coil ETV) was coupled to an Ar/H(2) flame atomic fluorescence spectrometer for the determination of eight traditional hydride-forming elements (i.e., As, Bi, Ge, Pb, Sb, Se, Sn, and Te) as well as cadmium without chemical vapor generation. A small sample volume, typically 20muL, was manually pipetted onto the W-coil and followed by a fixed electric heating program. During the vaporization step, analyte was vaporized off the coil surface and swept into the quartz tube atomizer of AFS for further atomization and excitation of atomic fluorescence by a flow of Ar/H(2) gas, which was ignited to produce the Ar/H(2) flame. The tungsten coil electrothermal vaporizer and Ar/H(2) flame formed a tandem atomizer to produce reliable atomic fluorescence signals. Under the optimal instrumental conditions, limits of detection (LODs) were found to be better than those by flame atomic absorption spectrometry (FAAS) or inductively coupled plasma optical emission spectrometry (ICP-OES) for all the nine elements investigated. The absolute LODs are better or equivalent to those by hydride generation atomic fluorescence spectrometry (HG-AFS). Possible scattering interferences were studied and preliminary application of the proposed method was also reported.     

A novel morphology of aragonite and an abnormal polymorph transformation from calcite to aragonite with PAM and CTAB as additives

The abnormal structure conversion of CaCO3 from calcite to aragonite was investigated with a mixture of polyacrylamide (PAM) and cetyltrimethylammonium bromide (CTAB) as additives by a hydrothermal method. A novel morphology of aragonite, "magnified" cubic shape, was observed. In order to investigate the effects of PAM and experimental temperature on the morphology and phase of CaCO3, the samples were synthesized without any additives and with PAM as template at 90 and 120 degrees C, respectively. The results indicate that both the interaction between the mixed template and the CaCO3 and the elevated experiment temperature play important roles in the process of polymorph transformation.     

Site-specific fluorescent labeling approaches for naringenin, an essential flavonone in plant nitrogen-fixation signaling pathways

In search of an appropriate position for the fluorescent labeling, six chemically available positions of the flavonone core of naringenin have been examined. A number of azido-containing naringenin derivatives were accordingly prepared in various site-specific fashions, and the mild Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition successfully served as the common "Click" labeling tool in the final steps. On the basis of the biological activities of the first batch of labeled compounds, further optimization at the C-6 position of naringenin finally afforded naringenin-flu (27), which acquired 20% of the potency of naringenin and presented good optical properties. Entry of naringenin-flu into living Rhizobium cells was demonstrated by in vitro fluorescent imaging experiments.