Strain Engineering: A Pathway for Tunable Functionalities of Perovskite Metal Oxide Films.

Perovskite offers a framework that boasts various functionalities and physical properties of interest such as ferroelectricity, magnetic orderings, multiferroicity, superconductivity, semiconductor, and optoelectronic properties owing to their rich compositional diversity. These properties are also uniquely tied to their crystal distortion which is directly affected by lattice strain. Therefore, many important properties of perovskite can be further tuned through strain engineering which can be accomplished by chemical doping or simply element substitution, interface engineering in epitaxial thin films, and special architectures such as nanocomposites. In this review, we focus on and highlight the structure-property relationships of perovskite metal oxide films and elucidate the principles to manipulate the functionalities through different modalities of strain engineering approaches.

Phospholipase-catalyzed hydrolysis in an artificial cell membrane in the presence of melittin.

Biomimicry involves the use of the structure and function of biological systems as models for the design and engineering of materials and machines. An artificial cell membrane was developed using biomembrane components, and the membrane, formed by a lipid bilayer, was analyzed using surface plasmon resonance (SPR) to monitor hydrolysis by phospholipase (PL). The simultaneous atomic force microscope (AFM) images show that PL catalyzed the nanometer-scale hydrolysis of the artificial lipid biomembranes through enzymatic hydrolysis. In addition, it was confirmed that the combination of PL and melittin allowed the control of enzyme hydrolysis for the degradation of the lipid bilayer. Regarding the expected activating effect of melittin on hydrolysis, no difference with respect to the non-treated lipid membrane was observed in the AFM images. It is assumed that the partitioning of melittin into the membrane might prevent the binding or hydrolysis of Phospholipase A2 (PLA2). This study provides basic knowledge on a new approach for patterning biomimicking lipid membranes on a nano-scale.

A simple device unit consisting of all NiO storage and switch elements for multilevel terabit nonvolatile random access memory.

Present charge-based silicon memories are unlikely to reach terabit densities because of scaling limits. As the feature size of memory shrinks to just tens of nanometers, there is insufficient volume available to store charge. Also, process temperatures higher than 800 °C make silicon incompatible with three-dimensional (3D) stacking structures. Here we present a device unit consisting of all NiO storage and switch elements for multilevel terabit nonvolatile random access memory using resistance switching. It is demonstrated that NiO films are scalable to around 30 nm and compatible with multilevel cell technology. The device unit can be a building block for 3D stacking structure because of its simple structure and constituent, high performance, and process temperature lower than 300 °C. Memory resistance switching of NiO storage element is accompanied by an increase in density of grain boundary while threshold resistance switching of NiO switch element is controlled by current flowing through NiO film.

Synthesis of selenium nanowires morphologically directed by Sinorhizobial oligosaccharides.

Shinorhizobial cyclosophoraose (cyclic beta-(1-->2)-glucan) or succinoglycan monomer (SGM 2), which has one acetyl, pyruvyl, and succinyl group, functions as a morphology-directing agent for the synthesis of pure trigonal selenium nanowires by using ascorbic acid (vitamin C) as the reducing agent. The synthesis was achieved in water at room temperature. Under these experimental conditions, the diameters of the as-prepared Se nanowires were varied in the range of 34-120 nm by cyclosophoraose and of 33-66 nm by SGM 2, in which the nanowires were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Through this study, we propose that Shinorhizobial cyclic and linear oligosaccharides have morphologically directing functions for the synthesis of single-crystalline selenium nanowires by green chemical methods.

Agarose and gellan as morphology-directing agents for the preparation of selenium nanowires in water.

Commercially available polysaccharides, agarose and gellan, were used as morphology-directing agents for the synthesis of t-Se nanowires in water at room temperature in the presence of ascorbic acid as reducing agent. The nanostructures were characterized using XRD, SEM, and TEM. The diameter of the nanowires varied from 100 to 208 nm for nanowires obtained in the presence of agarose and from 51 to 145 nm for nanowires from gellan, as evidenced by SEM and TEM. Agarose and gellan have then a potential as environmentally acceptable morphology-directing agents to generate Se nanostructures in water.