J. Appl. Cryst.の発刊に際して

Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical Properties

Because of its fundamental importance in many branches of science, hydrogen bonding is a subject of intense contemporary research interest. The physical and chemical properties of hydrogen bonds in the ground state have been widely studied both experimentally and theoretically by chemists, physicists, and biologists. However, hydrogen bonding in the electronic excited state, which plays an important role in many photophysical processes and photochemical reactions, has scarcely been investigated.Upon electronic excitation of hydrogen-bonded systems by light, the hydrogen donor and acceptor molecules must reorganize in the electronic excited state because of the significant charge distribution difference between the different electronic states. The electronic excited-state hydrogen-bonding dynamics, which are predominantly determined by the vibrational motions of the hydrogen donor and acceptor groups, generally occur on ultrafast time scales of hundreds of femtoseconds. As a result, state-of-the-art femtos...

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Hydrogen Bonding in the Electronic Excited State

Inspired by rich physics and functionalities of graphenes, scientists have taken an intensive interest in two-dimensional (2D) crystals of h-BN (analogue of graphite, so-called "white" graphite). Recent calculations have predicted the exciting potentials of BN nanoribbons in spintronics due to tunable magnetic and electrical properties; however no experimental evidence has been provided since fabrication of such ribbons remains a challenge. Here, we show that few- and single-layered BN nanoribbons, mostly terminated with zigzag edges, can be produced under unwrapping multiwalled BN nanotubes through plasma etching. The interesting stepwise unwrapping and intermediate states were observed and analyzed. Opposed to insulating primal tubes, the nanoribbons become semiconducting due to doping-like conducting edge states and vacancy defects, as revealed by structural analyses and ab initio simulations. This study paves the way for BN nanoribbon production and usage as functional semiconductors with a wide range of applications in optoelectronics and spintronics.

"White graphenes": boron nitride nanoribbons via boron nitride nanotube unwrapping

Water is essential in all aspects of life, being the defining characteristic of our planet and even our body. Regrettably, water pollution is increasingly becoming a challenge due to novel anthropogenic pollutants. Of particular concern are emerging organic contaminants (EOCs), the term used not only to cover newly developed compounds but also compounds newly discovered as contaminants in the environment. Aside from anthropogenic contamination, higher temperature and more extreme and less predictable weather conditions are projected to affect water availability and distribution. Therefore, wastewater treatment has to become a valuable water resource and its reuse is an important issue that must be carried out efficiently. Among the novel technologies considered in water remediation processes, metal-organic frameworks (MOFs) are regarded as promising materials for the elimination of EOCs since they present many properties that commend them in water treatment: large surface area, easy functionalizable cavities, some are stable in water, and synthesized at large scale, etc. This review highlights the advances in the use of MOFs in the elimination (adsorption and/or degradation) of EOCs from water, classifying them by the nature of the contaminant.

Metal-Organic Frameworks for the Removal of Emerging Organic Contaminants in Water.

Synthesis of mesoporous hexagonal boron nitride fibers with high surface area for efficient removal of organic pollutants

Boron nitride foam as a polymer alternative in packaging phase change materials: Synthesis, thermal properties and shape stability

A new upconversion luminescence agent, 40CdF_2·60BaF_2·0.8Er_2O_3, was synthesized and its fluorescent spectra were determined. This upconversion luminescence agent can emit five upconversion fluorescent peaks shown in the fluorescent spectra whose wavelengths are all below 387 nm under the excitation of 488 nm visible light. This upconversion luminescence agent was mixed into nano rutile TiO_2 powder by ultrasonic and boiling dispersion and the novel doped nano TiO_2 photocatalyst utilizing visible light was firstly prepared. The doped TiO_2 powder was charactered by XRD and TEM and its photocatalytic activity was tested through the photocatalytic degradation of methyl orange as a model compound under the visible light irradiation emitted by six three basic color lamps. In order to compare the photocatalytic activities, the same experiment was carried out for undoped TiO_2 powder. The degradation ratio of methyl orange in the presence of doped nano TiO_2 powder reached 32.5% under visible light irradiation at 20 h which was obviously higher than the corresponding 1.64% in the presence of undoped nano TiO_2 powder, which indicate the upconversion luminescence agent prepared as dopant can effectively turn visible lights to ultraviolet lights that are absorbed by nano TiO_2 particles to produce the electron-cavity pairs. All the results show that the nano rutile TiO_2 powder doped with upconversion luminescence agent is a promising photocatalyst using sunlight for treating the industry dye wastewater in great force.

Degradation of dyestuff wastewater using visible light in the presence of a novel nano TiO2 catalyst doped with upconversion luminescence agent.

Polystyrene-wrapped boron nitride/commercial polystyrene (BN@PS/CPS) composites with high thermal conductivity were fabricated by a novel approach. The route included two steps, BN@PS core-shell structured fillers were prepared by using modified BN and styrene (St) as the raw materials via suspension polymerization, and then the BN@PS were kneaded with the CPS by mechanically mixed method. The composite achieves a high thermal conductivity of 0.692 W/mK containing 30 wt% BN@PS (∼15.9 wt% BN), which is 3.72 times higher than that of pure CPS of ∼0.186 W/mK and 1.78 times higher than that BN/CPS blend composite with at the same BN loading of 0.332 W/mK. Compared with traditional routes, the novel preparation process requires less BN fillers when improving the same thermal conductivity. Importantly, other polymers can also encapsulate BN through this strategy, which paves a new way for preparing thermally conductive polymer-matrix composites.

Enhanced thermal conductivity of commercial polystyrene filled with core-shell structured BN@PS

Due to their high catalytic effect on the electrochemiluminescence (ECL) of luminol, noble metal nanoparticles (NPs) have been widely used in luminol-based ECL immunosensors. However the aggregation of NPs often resulted in the decrease of ECL signal and affected the stability and durability of the sensor. In this study, a microflower-like structure made of ultrathin Co/Ni-based metal-organic frameworks (MOF) nanosheets were used as a platform for luminol-functionalized AgNPs to construct an immunosensor for tumor marker alpha-fetoprotein. The nanosheet and microflower-like assembly structure of the Co/Ni-MOF greatly improved the ECL performance of the luminol-AgNPs system, attributed to their large surface area, resistance to particle agglomeration and the high catalytic activity of the Co/Ni-MOF. The ultrathin Co/Ni-MOF was full of atomically dispersed cobalt ions and nickel ions, which can catalyze the ECL reaction of luminol and H2O2. The as-fabricated immunosensor has a good sensitivity with detection limit of 0.417 pg mL−1 (S/N=3), and shows satisfactory performance in practical applications.

A highly sensitive and stable electrochemiluminescence immunosensor for alpha-fetoprotein detection based on luminol-AgNPs@Co/Ni-MOF nanosheet microflowers

Xiangdong Zhang

Papers

Synthesis of mesoporous hexagonal boron nitride fibers with high surface area for efficient removal of organic pollutants

Boron nitride foam as a polymer alternative in packaging phase change materials: Synthesis, thermal properties and shape stability

Degradation of dyestuff wastewater using visible light in the presence of a novel nano TiO2 catalyst doped with upconversion luminescence agent.

Enhanced thermal conductivity of commercial polystyrene filled with core-shell structured BN@PS

A highly sensitive and stable electrochemiluminescence immunosensor for alpha-fetoprotein detection based on luminol-AgNPs@Co/Ni-MOF nanosheet microflowers