Surface evolution of thermoelectric material KCu_(4)Se_(3) explored by scanning tunneling microscopy

Novel two-dimensional thermoelectric materials have attracted significant attention in the field of thermoelectric due to their low lattice thermal conductivity.A comprehensive understanding of their microscopic structures is crucial for driving further the optimization of materials properties and developing novel functional materials.Here,by using in situ scanning tunneling microscopy,we report the atomic layer evolution and surface reconstruction on the cleaved thermoelectric material KCu_(4)Se_(3) for the first time.We clearly revealed each atomic layer,including the naturally cleaved K atomic layer,the intermediate Se^(2-)atomic layer,and the Se^(-)atomic layer that emerges in the thermodynamic-stable state.Departing from the maj ority of studies that predominantly concentrate on macroscopic measurements of the charge transport,our results reveal the coexistence of potassium disorder and complex reconstructed patterns of selenium,which potentially influences charge carrier and lattice dynamics.These results provide direct insight into the surface microstructures and evolution of KCu_(4)Se_(3),and shed useful light on designing functional materials with superior performance.

Effects of atomic corrugations on electronic structures in Pb_(1-x)Bi_(x) thin films

We carried out experimental investigations of the geometric effect on the electronic behavior in Pb_(1-x)Bi_(x) thin films by scanning tunneling microscopy and spectroscopy.Single crystal monolayer Pb_(0.74)Bi_(0.26) and two-monolayer Pb_(0.75)Bi_(0.25)Pb_(1-x)Bi_(x) thin films were fabricated by molecular beam epitaxy,where large surface corrugations were observed.Combined with tunneling spectroscopic measurements,it is found that atomic corrugations can widely change the electronic behaviors.These findings show that the Pb_(1-x)Bi_(x) system can be a promising platform to further explore geometry-decorated electronic behavior in two-dimensional metallic thin films.

Interplay between the atomic structures and superconductivity of two-monolayer Pb films

Superconductors with reduced dimensionality have been widely explored for their exotic superconducting behaviors.Especially,at the two-dimensional limit,two-monolayer Pb films with two types of structures provide an ideal platform to unveil the underlying superconducting mechanism[Science 324,1314(2009)].Here,by combining scanning tunneling microscopy(STM)with the first-principle calculations,we successfully identify that these two types have different atomic lattice structures with varying stacking phases,which further enables us to calculate the phonon spectrum and electron phonon coupling strength of each type.The theoretical calculations are in good agreement with tunneling spectroscopy measurements of the superconducting transition temperatures(T_(c)),which established a correlation between atomic structures and superconductivity.Moreover,it was observed that the higher T_(c)of these two types also possess higher out-of-plane upper critical magnetic fields(Hc2).These findings will provide important new insights into two-dimensional superconductivity at the atomic level.

Self-assembled natural phytochemicals for synergistically antibacterial application from the enlightenment of traditional Chinese medicine combination

The application of nanotechnology for antimicrobial delivery has capacity to improve anti-bacterial efficacy.Currently,the usage of various inorganic and organic carriers,such as metal ions,nano-silicon and surfactants,might increase the potential toxicity of nanoparticles and make their clinical transformation more difficult.Herein,a nano-delivery system was constructed by direct self-assembly of antibacterial phytochemicals(berberine and rhein)originated from traditional Chinese medicine Coptis chinensis Franch.and Rheum palmatum L.,respectively.Combining X-ray single crystal diffraction,nuclear magnetic resonance and other spectra characterizations,the stacked structure of nanoparticles was profoundly demonstrated.Briefly,rhein acted as the layered backbone and berberine embedded in it.In vitro bacteriostasis experiment showed the minimum bactericidal concentration of nanoparticles was 0.1μmol/mL,which was lower than that of berberine and rhein.The results of confocal laser scanning microscope,biofilm quantitive assay and scanning electron microscopy indicated that nanoparticles had strong inhibitory effects on Staphylococcus aureus biofilm.More importantly,transmission electron microscopy and mass spectra indicated the further bacteriostatic mechanism of nanoparticles.Meanwhile,the nanoparticles had well biocompatibility and safety.Current study will open up new prospect that the design of self-assemblies between active phytochemicals can be originated from traditional Chinese medicine combination.

Design of multidimensional nanocomposite material to realize the application both in energy storage and electrocatalysis

The development of clean,sustainable and renewable energy storage systems is in urgent need with the fast-growing energy demand in the areas of electric vehicles and mobile electronics etc.Lithium-ion batteries(LIBs)have been deemed to be the most promising energy storage devices for their high power density,long cycle life and fast charge-discharge rates[1].Transition