Size Effect of Hydroxide Nanobuilding Blocks and Nonionic Block Copolymer Templates on the Formation of Ordered Mesoporous Structures

The use of precrystallized nanoparticles as nanobuilding blocks (NBBs) is a promising way to obtain mesoporous materials with crystalline walls. In this study, the size effects of both hydroxide NBBs and nonionic block copolymer (BCP) templates on the formation of ordered mesostructures are investigated. The diameter of layered nickel hydroxide NBBs was controlled at the sub-2 nm scale by an epoxidemediated alkalinization process. Commercially available nonionic BCPs (gyration radii in the range of 11.9−43.9 Å) were used. Mesoperiodic structures were formed by the evaporation-induced self-assembly process. A proper size combination of hydroxide NBBs, smaller than 12.5 Å, and BCPs, larger than 19.9 Å, is shown to be necessary to form ordered mesostructures.The present work is partially supported by JSPS KAKENHI Grant Number JP20K15368 and Core-to-Core Program, MEXT Leading Initiative for Excellent Young Researchers, the Foundation for the Promotion of Ion Engineering, and the Izumi Science and Technology Foundation (2019-J-112)

Ammonolysis-free synthesis of La2O2CN2 by cyanamidation of La(OH)3 using urea, and its photoluminescence properties

A facile method was successfully developed to prepare lanthanum oxycyanamide, La2O2CN2. Urea was selected as a cyanamidation agent, instead of gaseous NH3 with graphite containers, to achieve a safe and simple synthetic strategy. Through the optimization of reaction conditions, including content of urea and heat-treatment temperature, single-phase La2O2CN2 could be obtained without any impurities. We also prepared a La2O2CN2:Eu3+ phosphor. The Eu3+-doped La2O2CN2 matrix showed a red emission. Furthermore, in comparison with La2O3:Eu3+, the photoluminescence excitation bands corresponding to the Eu3+–ligand charge transfer region were broadened. These results suggested that La2O2CN2 prepared via the urea route will offer superb application prospects for photoluminescence materials such as white light-emitting diodes.This work was supported by JSPS KAKENHI Grant Numbers JP17H05483 and JP17H03392. This work was partly supported by the Center for Functional Nano Oxide at Hiroshima University, Japan.アクセプト後にキーワードの変更あり

Preparation of LaTiO2N Using Hydrothermally Synthesized La2Ti2O7 as a Precursor and Urea as a Nitriding Agent

A facile method was successfully developed to prepare perovskite‐type metal oxynitrides, LaTiO2N, from La2Ti2O7 as a precursor in an atmosphere of N2. Urea was employed as a solid‐state nitriding agent, instead of gaseous NH3, to increase the safety of the reaction. The hydrothermally prepared La2Ti2O7 precursor had a nanosheet morphology and contained La(OH)3 as a by‐product. Through the optimization of reaction conditions including heat‐treatment temperature and content of urea, single‐phase LaTiO2N could be obtained. In addition, we revealed that the La(OH)3 present in the La2Ti2O7 precursor played an important role in the nitriding process using urea. La2O2CN2 was generated by the reaction of La(OH)3 with the thermal decomposition products of urea at the medium temperature range. This indicated that the NH3 gas released from the thermal decomposition of urea did not directly cause nitridation of the La2Ti2O7 precursor.This work was supported by JSPS KAKENHI Grant Numbers JP16H06439, JP17H05483, and JP17H03392. This work was partly supported by the Center for Functional Nano Oxide at Hiroshima University.アクセプト後にキーワードの変更あり

The suppression of superconductivity in MgCNi3 by Ni-site doping

The effects of partial substitution of Cu and Co for Ni in the intermetallic perovskite superconductor MgCNi3 are reported. Calculation of the expected electronic density of states suggests that electron (Cu) and hole (Co) doping should have different effects. For MgCNi3-xCux, solubility of Cu is limited to approximately 3% (x = 0.1), and Tc decreases systematically from 7K to 6K. For MgCNi3-xCox, solubility of Co is much more extensive, but bulk superconductivity disappears for Co doping of 1% (x = 0.03). No signature of long range magnetic ordering is observed in the magnetic susceptibility of the Co doped material.Comment: submitted, Solid State Communication

STRUCTURAL COLOR COATING FILMS COMPOSED OF AN AMORPHOUS ARRAY OF SILICA AND CARBON BLACK PARTICLES BY ELECTROPHORETIC DEPOSITION

The color of a dye or pigment is an inherent property of the material that depends on its chemical nature. Some of these paints, especially those containing organic dye molecules, easily fade over time or upon exposure to light. In addition, there is concern over unfavorable influences on health and the environment, as some paints contain harmful substances. Therefore, coloration free from photo-bleaching or toxic materials is a central goal of paint research. Structural color is one of the most promising candidates to solve this challenge [1]. Submicron-sized microstructures reflect or scatter light so that waves of certain frequencies can constructively interfere to form this type of color. Because electronic excitation is not involved in the coloration mechanism, the structural color is not susceptible to fading unless the microstructure is destroyed. Structural color from particle arrays is advantageous in the sense that the color can be tuned merely by choosing the size of the microstructure without changing the material design. However, structural color from crystalline array of particles typically exhibits angular dependence, which is unfavorable for general purposes. Commonly used paints ideally appear the same color regardless of the viewing angle. In this study, we describe a novel and simple procedure to create a low angular dependence structural color coating by the electrophoretic deposition (EPD) process using SiO2 particles. A homogeneous coating film composed of an amorphous array of SiO2 particles was obtained by the EPD. However, the structural colors emitted from these arrays are very pale because the incoherent light scattering across the entire visible region is very strong. To reduce the contribution of incoherently scattered light to the overall scattering spectrum and to enhance the structural color of the colloidal amorphous arrays, black components, which absorb light uniformly across the entire visible region, can be incorporated into the films. Carbon black (CB) is one of the most common and environmentally preferable black substances and reflects very little light in the visible region of the spectrum. Sufficient visibility of the structural color was achieved by the co-deposition of carbon CB. The thickness of the coating films can be controlled by varying the applied voltage and/or deposition time. When the EPD process is carried out with a low applied voltage, a close-packed array of SiO2 particles that exhibits an iridescent structural color is obtained (Figure1a). However, an amorphous packing state can be acquired at a high applied voltage condition (Figure1b). The structural color generated from such coating films has a low angle dependence. These results indicate that the arrangement of particles in the array and the iridescence of the resultant structural color can also be controlled by varying the EPD conditions. Various vividly colored coatings can be produced from SiO2 particles with diameters between 200 and 300 nm. Moreover, coatings on materials with curved surfaces and complicated shapes, which are difficult to obtain by commonly used techniques were also successfully prepared via the EPD process. Please click Additional Files below to see the full abstract

Interconnection of organic–inorganic hybrid nano-building blocks towards thermally robust mesoporous structures

The use of organic–inorganic hybrid nanoparticles will enable a control of the characteristics of both the nanoparticles and constructed fine structures. In this study, we report the synthesis of acrylate-intercalated layered manganese, cobalt, and nickel hydroxide nanoparticles and their assembly into ordered mesoporous structures. Polymerization of the intercalated acrylates takes place by means of a radical initiator. The formed organic network improved the thermal stability of the layered hydroxides, which results in thermally robust mesoporous structures. Additionally, it is found that the polymerization can be initiated and progressed at 200 °C without any initiators for the layered nickel hydroxide system. This allows for the scalable solid-state thermal polymerization of intercalated acrylates and the formation of thermally robust hierarchically ordered meso/macroporous powders as well as mesoporous films. The electrochemical characterization reveals that the thermally robust mesoporous films having regulated mesopores allow for the effective diffusion of molecules/solvent compared with the films having collapsed mesoporous structures.The present work is partially supported by JSPS KAKENHI Grant Number JP20K15368, JSPS Core-to-Core Program, MEXT Leading Initiative for Excellent Young Researchers, the Foundation for the Promotion of Ion Engineering, International Network on Polyoxometalate Science at Hiroshima University, and the Izumi Science and Technology Foundation (2019-J-112)