Original Article in 2016

MoS₂-coated vertical graphene nanosheet nanocomposites are successfully designed and synthesized as high-performance electrode materials for both lithium-ion batteries and hydrogen production. The unique three-dimensional hybrid structure is the key to the high performance for energy storage and conversion.

Bi-layer intercalation in Bi₂Se₃ nanoplatelets gives rise to an intriguing crystal structure comprised of randomly stacked Bi₂Se₃ and Bi₂Se₂. Detailed conduction electron spin resonance (CESR) and AC/DC magnetization studies prove that controlling Bi intercalation results in fine tuning the two-dimensional electron gas parabolic Rashba states, which enables the appearance of extraordinary orbital magnetism, through the coupling of the spin and orbital degrees of freedom. The methodology presented herein provides a unique and simple way for efficient spin engineering, with important potential applications.

Graphene quantum dots (GQDs) decorated sulfur–carbon hierarchical structure serve as a high sulfur/sulfide utilization in Li–S battery. The oxygen rich functionalities of the GQDs induced structural integrity of the sulfur–carbon electrode composite. This hierarchical structure enables fast charge transfer, minimizes the loss of soluble polysulfides and completes reaction of sulfur/sulfide.

Nanorod NiC₂O₄·2H₂O/rGO composite exhibits good cyclability with high capacity and reasonable rate performance. These characteristics are originated from the high electric conductivity and buffering effect of rGO that promote the reversible lithiation and delithiation processes associated with conversion reaction.

The polytypes P2-Na_0.62Ti_0.37Cr_0.63O₂ and P3-Na_0.63Ti_0.37Cr_0.63O₂ with nearly the same composition and different layered structures are successfully synthesized, their sodium storage performance are systematically investigated and compared and the bridge between crystal structures, migration paths and electrochemical properties is well set up for the first time.

Selective decoration of palladium nanoparticles on diverse graphene-defect sites. Graphene grown by chemical vapor deposition method has structural imperfections, such as grain boundaries, wrinkles and topological cracks, which cause reduced graphene-based device performance. Herein, we selectively decorated graphene defects with metal nanoparticles (Pd and Ag) by using a wet-chemistry-based galvanic displacement reaction within a few minutes without generating damage on graphene. The defect-decorated graphene showed a noticeable improvement in electrical characteristics, and defect-decorated graphene-based transparent heater showed better heating performance than a heater fabricated using pristine graphene.

A sacrificial strategy is developed for preparing layer-controlled MoS₂ on three-dimensional Bi₂S₃ micro-flowers using a facile method. The nanostructured hybrid enables adsorption-promoted photocatalysis under visible light irradiation for excellent degradation of low-concentration organic pollutants, because of the increased mass transfer, robust light-harvesting capacity, improved charge separation, reduced oxygen-activation barrier and enhanced active oxygen yield.

Currently, among all known quantum spin Hall (QSH) insulators, square and hexagonal atomic rings are the dominant structural motifs, and QSH insulators composed of pentagonal rings have not yet been reported. Here, we propose a family of large-gap QSH insulators in the SnX₂ (X=S, Se, Te) two-dimensional (2D) crystals (121–224 meV). Remarkably, different from all the known QSH insulators, the QSH insulators predicted here are composed entirely of pentagonal rings. Additionally, the considered 2D crystals retain their QSH properties in a quantum well obtained by sandwiching monolayers between two BiOBiS₂ sheets, thus providing a viable way for further experimental studies.

Drug-encapsulated nanoparticles (NPs) are emerging as therapeutic agents to deliver DNA\drugs into cells. However, clinical applications demand a technique to concentrate NPs at the diseased cells that are beneath other tissues. We report a strategy to achieve this goal with magnetic- and therapeutic NP-coated microbubbles as carriers. Although external magnetic field concentrates them at the targeted tissue, moderate ultrasound irradiation at their resonance frequency drives stable oscillation and microstreaming flow. Consequently, the NP armor detaches, penetrates into tissues and is later internalized by the cells. This technique would greatly improve the on-target delivery of nanomedicine, thereby reduces cost and side effects.

We demonstrate our recent progress in the newly emerging and intriguing research field of developing graphene-based functional membranes with the ability to effectively filtrate and separate molecules or ions in solutions based on a simple criterion (for example, the size or charge of solutes) for various engineering-relevant applications ranging from wastewater purification and reuse to chemical refinement.

Nitrogen doping of nanostructured carbon-based membranes allows to produce ultrathin reverse osmosis membranes, which exhibit high robustness for water desalination applications. Structural and chemical characterization, water permeation and salt rejection tests, and computational modeling of these carbon-based membranes is discussed. Their salt rejection performance and degradation resistance reveal a strong dependency on the amount of nitrogen doping within the carbon structure. The properties shown by our nanostructured carbon membranes render them a potential alternative to current polymer-based membranes.

Planar arrays of optofluidic vortices are generated with photothermal gradients from an array of graphene oxide heaters to achieve multiform manipulations. As a tweezer, each vortex can rapidly capture and confine particles without any restriction on shapes or materials. As a motor, it can actuate any trapped particle to persistently rotate/spin in clockwise or anti-clockwise mode. Such a high-performance ‘workshop’ can be used for various self-assembly ranging from colloid-based clusters, chains, capsules, shells, and ultra-thin films, through particles’ surface modification and fusion, to nanowires-based architectures.

Our study reveals the first experimental evidence that charge transport can be tuned from partially to fully coherent. We used pentacene, a soft organic material, to measure transport properties depending on temperature and pressure. Under ambient conditions, charge transport was only partially coherent. At 1 GPa and below 220 K fully coherent charge transport emerged. Microscopically, we find that the thermal fluctuations are reduced so that the charge carriers start moving around freely leading to a coherent charge transport.

Naturally occurring and magnetically induced optical activities (the Faraday effect) have contributed to our understanding of molecular electronic states, and have also had various applications in photonics. It has been generally considered that the Faraday effect is not affected by natural optical activity originating from chirality. Herein we describe for the first time a relationship between the Faraday rotation angles and chirality in a chiral lanthanide cluster. This finding provides new insights into the design of next-generation molecular Faraday materials and may lead to the development of a novel area of study within the field of chiral science.

Formation of a strained Si membrane with oxidation-induced residual strain by releasing a host Si substrate of a silicon-on-insulator (SOI) wafer is demonstrated. To do this, we construct suspended Si/SiO₂ structures and induce over 0.5% tensile strain on the top Si membrane. The fabricated thin-film transistor (TFTs) with strained Si channels are transferred on plastics using a roll-based transfer technique, and they exhibit a mobility enhancement factor of 1.2–1.4 in comparison with an unstrained Si TFT.

It can be found that the Mn/Si ratio is a crucial factor affecting the morphology of the as-obtained products. The pristine Si nanoparticles are sphere-like particles of ~100 nm in diameter. When the Mn/Si molar ratio is 4:1, ultrafine MnCO₃ nanowires less than 10 nm in diameter are obtained. The MnO@C nanowires were synthesized via polymerization–pyrolysis steps, and the excellent high-rate performance and stability of the MnO@C nanowires used as an anode in the lithium-ion battery are attributed to the unique interconnected nanostructure.

The effects of structural relaxation (SR) on the electronic state of oxygen vacancies (V_O s) in amorphous oxide semiconductors is investigated. Without redox reactions, the concentration of V_O s in the shallow-donor state (N_DS) increases about 10³ times with increases in the annealing temperature from 300 to 450 °C. The reduction in the free volume size and transformation of V_O s in either deep-donor or electron-trap states into the shallow-donor state during SR is the primary mechanism responsible for the increase in N_DS.

A novel strategy is demonstrated to produce silicon nanosheets on a large scale through the simultaneous molten-salt-induced exfoliation and chemical reduction of natural clay. The thus-synthesized silicon nanosheets have a high surface area, are ultrathin (~5 nm), and contain mesoporous structures derived from the oxygen vacancies in the clay. These advantages make the nanosheets a highly suited photocatalyst with an exceptionally high activity (723 μmol H₂ per h per g Si) for the generation of hydrogen from a water–methanol mixture.

A hydrophobic porous coordination polymer (PCP) has been synthesized and its growth throughout the graphene oxide (GO)-modified sponge yields a macroscopic PCP@GO@sponge sorbent, which repels water and exhibits superior adsorption for diverse oils. Remarkably, the sorbent is further assembled with tubes and a self-priming pump to build a model apparatus that can afford consecutive and efficient oil recovery from water.

The cell adhesion and growth were studied on vertically aligned silicon nanowires with different diameter. Varying the diameter of nanowires affected their elasticity, resulting in a difference in cell morphology and adhesion. The formation of focal adhesion and anisotropic cell growth was promoted on thin silicon nanowires. Fluorescence analysis demonstrated that the cytoskeletal actin dynamics was affected by the mechanical tension of elastic nanotopography.