Volume 8 Issue 4, April 2016

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.

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.

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.

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.

By mass, iron is the most common element on earth and the most widely utilized metal in industry. Over 30 years of research have shown that iron is a poor choice for practical applications in solar energy conversion. Hematite and other ferric oxide polymorphs are competent for water oxidation in photoelectrochemical cells, but just barely. Photovoltaics based on iron oxide or sulfide materials are inefficient and the inclusion of even trace iron in silicon significantly lowers the efficiency of today’s commercial photovoltaics. In dye-sensitized solar cells (DSSCs), inclusion of an iron center in a dye molecule results in devices with poor efficiencies that are of no practical value.¹ Iron-based materials and compounds function for light-driven electron transfer and catalysis, but just well enough to give some hope to highly optimistic scientists in academic labs. In the final analysis, iron consistently continues to disappoint and one can safely conclude that it is best to keep iron out of solar cells. Until now Harlang et al.² found that the iron compound shown in Figure 1 harvests sunlight through most of the visible region with subsequent excited state electron transfer to a TiO₂ semiconductor with efficiencies >90%. Such a breakthrough in efficiency is remarkable, particularly when one considers the decades of prior research that failed to accomplish anything even close. This breakthrough raises the question, are we on a path to solar cells that utilize iron? Before addressing this question, it is worthwhile to consider the impact an iron center has on a dye molecule.

PHAs are natural biodegradable polyesters synthesized by microorganisms. However, several disadvantages such as their poor mechanical properties and limited functionalities limit their competition with traditional synthetic plastics or their application as ideal biomaterials. To circumvent these drawbacks, PHAs need to be modified to ensure improved performance in specific applications. Well-established modification methods of PHAs are summarized and discussed. The improved properties of PHA that blends with natural raw materials or other biodegradable polymers are summarized. The functionalization of PHAs by block copolymerization and graft copolymerization is described. The expanded utilization of the modified PHAs as (bio)engineering materials is addressed.