Possibilities for In-situ Observation of Basic Deformation Processes and of Other Dynamic Processes

The purposes of this paper are to discuss the possibilities of HVEM in-situ observation for deriving meaningful results on basic deformation processes by illustrating some examples which have been obtained so far and to assess the capabilities of this method to investigate crystal deformation as well as other dynamic processes. First, the experimental procedures developed by our group in Nagoya to study the dynamic behaviour of dislocations are introduced. Research subjects which have been studied effectively by this method so far are illustrated. The lower safety limit of specimen thickness for deriving information typical of bulk materials, the effects of size and free surfaces of a specimen and the effects of electron irradiation etc. are to be discussed to assess the validity of in situ observation of dislocation behaviours. Some prospects on new applications and extensions of in-situ HVEM for physical and materials research are to be presented, including possibilities for in-situ observation of other subjects such as diffusion, environmental effects, interface reaction, chemical reaction, defect formation during growing or processing of semi-conductors, surface treatment and micro fabrication by electron beam etc.     

Demonstration of diamond field effect transistors by AlN/diamond heterostructure

This is the first report on an AlN/diamond heterojunction field effect transistor (HFET). The AlN epilayer is grown on oxygen‐terminated (111) diamond substrates using metalorganic vapor phase epitaxy at a temperature as high as 1240 °C. The transistor and gate capacitance–voltage characteristics indicate that the HFET behaves as a p‐channel FET with a normally‐on depletion mode. The HFET channel is located at the AlN/diamond interface, and holes are accumulated in diamond close to the interface. The development of the AlN/diamond HFET creates a new possibility for diamond‐based power electronics. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dual Soft‐Template System Based on Colloidal Chemistry for the Synthesis of Hollow Mesoporous Silica Nanoparticles

A new dual soft‐template system comprising the asymmetric triblock copolymer poly(styrene‐b‐2‐vinyl pyridine‐b‐ethylene oxide) (PS‐b‐P2VP‐b‐PEO) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) is used to synthesize hollow mesoporous silica (HMS) nanoparticles with a center void of around 17 nm. The stable PS‐b‐P2VP‐b‐PEO polymeric micelle serves as a template to form the hollow interior, while the CTAB surfactant serves as a template to form mesopores in the shells. The P2VP blocks on the polymeric micelles can interact with positively charged CTA⁺ ions via negatively charged hydrolyzed silica species. Thus, dual soft‐templates clearly have different roles for the preparation of the HMS nanoparticles. Interestingly, the thicknesses of the mesoporous shell are tunable by varying the amounts of TEOS and CTAB. This study provides new insight on the preparation of mesoporous materials based on colloidal chemistry.     

Controlled Crystallization of Cyano‐Bridged Cu–Pt Coordination Polymers with Two‐Dimensional Morphology

Two‐dimensional (2D) coordination polymers (CPs) have a highly accessible surface area that permits guest molecules to effectively access the micropores in the CPs. Here we report a bottom‐up synthesis of 2D cyano‐bridged Cu–Pt CP nanoflakes using trisodium citrate as a chelating agent, which controls the nucleation rate and the crystal growth. The lateral sizes of the CP nanoflakes are controlled by changing the amount of trisodium citrate used. We strongly believe that our method will be useful for the preparation of other types of 2D CP nanoflakes. The 2D CPs have many active sites for catalytic and electrochemical reactions, and furthermore the assembled CPs can be used as membrane filters.     

Synthesis of Nanoporous Carbon–Cobalt‐Oxide Hybrid Electrocatalysts by Thermal Conversion of Metal–Organic Frameworks

Nanoporous carbon–cobalt‐oxide hybrid materials are prepared by a simple, two‐step, thermal conversion of a cobalt‐based metal–organic framework (zeolitic imidazolate framework‐9, ZIF‐9). ZIF‐9 is carbonized in an inert atmosphere to form nanoporous carbon–metallic‐cobalt materials, followed by the subsequent thermal oxidation in air, yielding nanoporous carbon–cobalt‐oxide hybrids. The resulting hybrid materials are evaluated as electrocatalysts for the oxygen‐reduction reaction (ORR) and the oxygen‐evolution reaction (OER) in a KOH electrolyte solution. The hybrid materials exhibit similar catalytic activity in the ORR to the benchmark, commercial, Pt/carbon black catalyst, and show better catalytic activity for the OER than the Pt‐based catalyst.     

Oxygen‐Assisted Synthesis of Mesoporous Palladium Nanoparticles as Highly Active Electrocatalysts

Mesoporous Pd nanoparticles (MPNs) enclosed by high‐index facets have been successfully prepared by taking advantage of successive oxygen adsorption and desorption caused by the oxidative etching effect. The as‐prepared MPNs exhibit excellent performance toward formic acid electro‐oxidation, which is due to the synergetic effect between the diffusion‐feasible tubular mesochannels and the high index facets.     

Effects of lysozyme and bovine serum albumin on membrane characteristics of dipalmitoylphosphatidylglycerol liposomes

The effects of adsorption of two kinds of proteins on the membrane characteristics of liposomes were examined at pH 7.4 in terms of adsorption amounts of proteins on liposomes, penetrations of proteins into liposomal bilayer membranes, phase transition temperature, microviscosity and permeability of liposomal bilayer membranes, using positively charged lysozyme (LSZ) and negatively charged bovine serum albumin (BSA) as proteins and negatively charged L-alpha-dipalmitoylphosphatidylglycerol (DPPG) liposomes. The saturated adsorption amount of LSZ was 720 g per mol of liposomal DPPG, while that of BSA was 44 g per mol of liposomal DPPG. The penetration of LSZ into DPPG lipid membranes was greater than that of BSA. The microviscosity in the hydrophobic region of liposomal bilayer membranes increased due to adsorption (penetration) of LSZ or BSA, while the permeability of liposomal bilayer membranes increased. The gel-liquid crystalline phase transition temperature of liposomal bilayer membranes was not affected by adsorption of LSZ or BSA, while the DSC peak area (heat of phase transition) decreased with increasing adsorption amount of LSZ or BSA. It is suggested that boundary DPPG makes no contribution to the phase transition and that boundary DPPG and bulk DPPG are in the phase-separated state, thereby increasing the permeability of liposomal bilayer membranes through adsorption of LSZ or BSA. A possible schematic model for the adsorption of LSZ or BSA on DPPG liposomes was proposed.     

Effect of adsorption of bovine serum albumin on liposomal membrane characteristics

The effect of adsorption of bovine serum albumin (BSA) on the membrane characteristics of liposomes at pH 7.4 was examined in terms of zeta potential, micropolarity, microfluidity and permeability of liposomal bilayer membranes, where negatively charged L-alpha-dipalmitoylphosphatidylglycerol (DPPG)/L-alpha-dipalmitoylphosphatidylcholine (DPPC), negatively charged dicetylphosphate (DCP)/DPPC and positively charged stearylamine (SA)/DPPC mixed liposomes were used. BSA with negative charges adsorbed on negatively charged DPPG/DPPC mixed liposomes but did not adsorb on negatively charged DCP/DPPC and positively charged SA/DPPC mixed liposomes. Furthermore, the adsorption amount of BSA on the mixed DPPG/DPPC liposomes increased with increasing the mole fraction of DPPG in spite of a possible electrostatic repulsion between BSA and DPPG. Thus, the adsorption of BSA on liposomes was likely to be related to the hydrophobic interaction between BSA and liposomes. The microfluidity of liposomal bilayer membranes near the bilayer center decreased by the adsorption of BSA, while the permeability of liposomal bilayer membranes increased by the adsorption of BSA on liposomes. These results are considered to be due to that the adsorption of BSA brings about a phase separation in liposomes and that a temporary gap is consequently formed in the liposomal bilayer membranes, thereby the permeability of liposomal bilayer membranes increases by the adsorption of BSA.