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411.
Nanxi Miao Prof. Yutong Gong Huaiyu Zhang Qing Shen Rui Yang Prof. Jianping Zhou Prof. Hideo Hosono Prof. Junjie Wang 《Angewandte Chemie (International ed. in English)》2023,62(36):e202308436
The practical applications of two-dimensional (2D) transition-metal borides (MBenes) have been severely hindered by the lack of accessible MBenes because of the difficulties in the selective etching of traditional ternary MAB phases with orthorhombic symmetry (ort-MAB). Here, we discover a family of ternary hexagonal MAB (h-MAB) phases and 2D hexagonal MBenes (h-MBenes) by ab initio predictions and experiments. Calculations suggest that the ternary h-MAB phases are more suitable precursors for MBenes than the ort-MAB phases. Based on the prediction, we report the experimental synthesis of h-MBene HfBO by selective removal of In from h-MAB Hf2InB2. The synthesized 2D HfBO delivered a specific capacity of 420 mAh g−1 as an anode material in lithium-ion batteries, demonstrating the potential for energy-storage applications. The discovery of this h-MBene HfBO added a new member to the growing family of 2D materials and provided opportunities for a wide range of novel applications. 相似文献
412.
Junjie Wang Prof. Dr. Tianping Ying Dr. Jun Deng Dr. Cuiying Pei Dr. Tongxu Yu Dr. Xu Chen Yimin Wan Mingzhang Yang Dr. Weiyi Dai Dr. Dongliang Yang Prof. Dr. Yanchun Li Prof. Dr. Shiyan Li Prof. Dr. Soshi Iimura Prof. Dr. Shixuan Du Prof. Dr. Hideo Hosono Prof. Dr. Yanpeng Qi Prof. Dr. Jian-gang Guo 《Angewandte Chemie (International ed. in English)》2023,62(10):e202216086
Searching for functional square lattices in layered superconductor systems offers an explicit clue to modify the electron behavior and find exotic properties. The trigonal SnAs3 structural units in SnAs-based systems are relatively conformable to distortion, which provides the possibility to achieve structurally topological transformation and higher superconducting transition temperatures. In the present work, the functional As square lattice was realized and activated in Li0.6Sn2As2 and NaSnAs through a topotactic structural transformation of trigonal SnAs3 to square SnAs4 under pressure, resulting in a record-high Tc among all synthesized SnAs-based compounds. Meanwhile, the conductive channel transfers from the out-of-plane pz orbital to the in-plane px+py orbitals, facilitating electron hopping within the square 2D lattice and boosting the superconductivity. The reorientation of p-orbital following a directed local structure transformation provides an effective strategy to modify layered superconducting systems. 相似文献
413.
Exchange between oxygen molecules embedded in amorphous SiO2 (interstitial O2) and oxygen atoms in the a-SiO2 network is found to be remarkably slow at 500 °C. Thermal loading of 18O2 at this temperature yields a-SiO2 containing 18O-labeled interstitial O2 whose 18O fraction is as high as ~ 90%. The 18O fraction of interstitial O2 in this sample is quickly decreased by thermal annealing at or above 700 °C because of the oxygen exchange accompanied by the release of 16O from the a-SiO2 network. This finding indicates that the oxygen exchange starts at much lower temperatures than indicated by previous works, based on monitoring of the isotopic composition of oxygen atoms in the a-SiO2 network. 相似文献
414.
The differences in formation and structural properties of polymer networks consisting of end-linked flexible or rigid chains were studied by molecular dynamics simulation. Networks were formed from monodisperse, linear, short, flexible or rigid chains with functional end groups and a stoichiometric ratio of trifunctional cross-linkers. The rigid chains had a rodlike shape defined by an angle potential, while the flexible chains had no angle potential. In order to understand the influence of chain rigidity, all parameters of precursor chains (length, reactivity, bond potential, nonbonding potential) were the same, with the exception of the angle potential. The system density rho, corresponding to the concentration of monomer in solvent, was varied from 0.01 to 0.11. Different network structures resulting from the different processes of network formation were observed. Simulations showed that the flexible chains created an inhomogeneous network on a large scale via microgel cluster formation, in agreement with experimental observations, whereas the rigid chains rapidly created a homogeneous network in the entire system volume without first generating microgel clusters, with the additional difference that they gave rise to mutually interpenetrating networks at the local scale. 相似文献
415.
Hidetaka Tobita 《Macromolecular Symposia》2008,261(1):36-45
Summary : For the controlled/living radical polymerization (CLRP) in which the active period during the chain formation is extremely small, ϕA < 1, such as the cases of usual SFRP and ATRP, the polymerization rate can be made larger by increasing the average number of monomeric units added during a single active period, . The -value is inversely proportional to the trapping agent concentration [X], and the polymerization rate is controlled by [X]. For small particles, even with a single trapping agent, [X] in the particle could be larger than that in corresponding bulk polymerization, and the polymerization rate decreases with D, where Dp is the particle diameter. On the other hand, for CLRPs whose ϕA-value is not very much smaller than unity, say ϕA>0.01, such as some of RAFT polymerization systems, the polymerization rate can be made larger by increasing the kinetic chain length for a given initiation frequency. For such reaction systems, the polymerization rate can be enhanced significantly by employing the emulsified polymerization systems. 相似文献
416.
Dr. Nobuhiko Hosono Dr. Patrick J. M. Stals Dr. Anja R. A. Palmans Prof. Dr. E. W. Meijer 《化学:亚洲杂志》2014,9(4):1099-1107
ABA‐ and BAB‐type triblock copolymers possessing pendant, self‐assembling motifs in the A and B blocks were synthesized, with 2‐ureidopyrimidinone (UPy) and benzene‐1,3,5‐tricarboxamide (BTA) for the A and B block, respectively. They were investigated to assess if and how the polymer’s microstructure influences the self‐assembly behavior of the supramolecular motifs and, as a result, the single‐chain folding process. BAB‐type triblock copolymers were synthesized via atom transfer radical polymerization (ATRP) with molecular weights ranging from 30 to 120 kg mol?1; the BTA and UPy motifs were attached using a post‐functionalization approach. The ABA‐type triblock copolymers were available from previous work. In highly dilute solutions, both types of triblock copolymers fold into single‐chain polymeric nanoparticles (SCPNs) via thermally induced BTA self‐assembly and photo‐triggered UPy dimerization. Chain collapse induced by intramolecular UPy dimerization was evaluated using size‐exclusion chromatography (SEC). The BTA self‐assembly was monitored by circular dichroism (CD) spectroscopy. The microstructures of SCPNs were visualized by atomic force microscopy (AFM). SEC analysis indicated a more loose packing for the BAB‐type folded nanoparticles than for the ABA‐type ones, which implies that topological differences in the polymer architecture do affect the folding behavior, although only slightly. The facile synthetic protocol developed here provides topologically different triblock architectures and opens up the area for single‐chain folding technology that is applicable in artificial enzymatic systems with compartmentalized domains. 相似文献
417.
Shibayama M Kawada H Kume T Matsunaga T Iwai H Sano T Osaka N Miyazaki S Okabe S Endo H 《The Journal of chemical physics》2007,127(14):144507
The microscopic structure of shear-induced gels for a mixed solution of 2-hydroxyethyl cellulose and nanometer-size spherical droplets has been investigated by in situ small-angle neutron scattering (SANS) with a Couette geometry as a function of shear rate gamma. With increasing gamma, the viscosity increased rapidly at gamma approximately 4.0 s(-1), followed by a shear thinning. After cessation of shear, the system exhibited an extraordinarily large steady viscosity. This phenomenon was observed as a shear-induced sol-gel transition. Real-time SANS measurements showed an increase in the scattering intensity exclusively at low scattering angle region. However, neither orientation of polymer chains nor droplet deformation was detected and the SANS patterns remained isotropic irrespective of gamma. It took about a few days for the gel to recover its original sol state. A possible mechanism of gelation is proposed from the viewpoint of shear-induced percolation transition. 相似文献
418.
Watanabe T Yanagi H Kamiya T Kamihara Y Hiramatsu H Hirano M Hosono H 《Inorganic chemistry》2007,46(19):7719-7721
A layered oxyphosphide, LaNiOP, was synthesized by solid-state reactions. This crystal was confirmed to have a layered structure composed of an alternating stack of (La(3+)O(2-))(+) and (Ni(2+)P(3-))(-). We found that the resulting LaNiOP shows a superconducting transition at approximately 3 K. This material exhibited metallic conduction and Pauli paramagnetism in the temperature range of 4-300 K. The resistivity sharply dropped to zero and the magnetic susceptibility became negative at <4 K, indicating that a superconducting transition occurs. The volume fraction of the superconducting phase estimated from the diamagnetic susceptibility reached approximately 40 vol % at 1.8 K, substantiating that LaNiOP is a bulk superconductor. 相似文献
419.
Nakai H Uemura S Miyano Y Mizuno M Irie M Isobe K 《Dalton transactions (Cambridge, England : 2003)》2011,40(10):2177-2179
A photoreactive rhodium dithionite complex [(RhCp(Et))(2)(μ-CH(2))(2)(μ-O(2)SSO(2))] (1(Et)) with Cp(Et) (η(5)-C(5)Me(4)Et) ligands was newly synthesized. Upon short-time irradiation with low intensity light, two kinds of stepwise surface morphology changes of the crystal 1(Et) were observed. Prolonged irradiation with high intensity light caused cracking and breaking down of the crystal. 相似文献
420.
Single nucleotide polymorphisms (SNPs) are base differences in the human genome. These differences are favorable markers for
genetic factors including those associated with risks of complex diseases and individual responses to drugs. When two duplex
DNAs with different types of SNPs are mixed and reannealed, the two novel heteroduplexes containing mismatched base pairs
are formed in addition to the two initial perfectly matched homoduplexes. Heteroduplex analysis recognizing the newly formed
mismatched base pairs is useful for SNP detection. Various strategies to detect the mismatched base pairs were devised due
to the potential applications of SNPs. However, they were not always convenient and accurate. Here, we propose a novel strategy
to detect the mismatched base pairs by the specific interaction between the Hg2+ ion and a T:T mismatched base pair and that between the Ag+ ion and a C:C mismatched base pair. UV melting indicated that the melting temperature of only the heteroduplexes with the
T:T and C:C mismatched base pair specifically increased on adding the Hg2+ and Ag+ ion, respectively. Fluorescence resonance energy transfer analyses indicated that the intensity of fluorophore emission of
only the fluorophore and quencher-labeled heteroduplexes with the T:T and C:C mismatched base pair specifically decreased
on adding the Hg2+ and Ag+ ion, respectively. We propose that the addition of the metal ion could be a convenient and accurate strategy to detect the
mismatched base pair in the heteroduplex. This novel strategy might make the heteroduplex analysis easy and eventually lead
to better SNP detection. 相似文献