Ag_(60)纳米颗粒[{Cl@Ag_(12)}@Ag_(48)(dppm)_(12)]的结构(其中dppm=双(二苯基膦基)甲烷)（英文）

本文合成一种新的双膦连接Ag_(60)纳米团簇[{Cl@Ag_(12)}@Ag_(48)(dppm)_(12)],并通过X射线晶体学进行表征.二十面体的银处于核心位置,里面是中心氯化物组成,外面有48个银原子/离子的包裹,顶端是12个双(二苯基膦基)甲烷(dppm)配体.同时利用密度泛函理论对阳离子[{Cl@Ag_(12)}@Ag_(48)(dppm)_(12)]~+进行计算,以确定该结构是否对应于核心数n=58的超原子.DFT计算的优化结构与X射线一致,但是HOMO-LUMO的能差并不能保证共超级稳定性.     

低温耦合固相氮化反应合成β-Sialon

本研究拟在氮化气氛下,以金属Al粉、Si粉、α-Al2O3为原料,添加Y2O3,耦合氮化反应制备β-Sialon.通过在不同温度下的氮化反应烧结试验,研究了Y3+对β-Sialon晶相组成、晶粒大小、晶格常数及显微结构的影响.采用XRD和SEM表征试样中的晶相和显微结构,利用X'Pert Plus软件对试样进行晶胞参数分析,通过Semi-quantification法对试样各晶相组成进行计算.结果表明:随着温度的升高,合成β-Sialon相的含量不断提高,在1550℃时达到最高;添加Y2O3可以在相对较低温度条件下合成β-Sialon相,y3+对Al3+的置换作用导致β-Sialon相结构畸变,且随耦合氮化反应烧成温度的升高,晶胞体积可由1350℃时的0.208448 nm3增大到1550℃时的0.236776 nm3,合成β-Sialon相呈现增加的趋势.同时在合成β-Sialon结构中,由于过量助烧结剂Y2O3易与原料中Al2O3形成针状YAG.     

散射的原子捕获d波

正与非常规超导机制类似的d波相互作用在冷原子气体中得到了实现。超冷原子气体提供了一个精妙的实验平台,可以用于探索凝聚态物理中的多种模型。研究人员可以精细地控制这些原子,使它们成为固体与液体中的电子或其他自由度的替身,从而利用这一系统来模拟磁性、量子相变以及其他常规凝聚态现象。但是,模拟高温超导可是块难啃的骨头。这是由于这种状态     

Electrochemical "signal-on" reporter for amyloid aggregates

The synthesis and characterization of four new Ferrocene (Fc) bioconjugates, bearing a podant (Lys)-Leu-Val-Phe-Phe motif, namely the hydrophobic sequence of amyloid-β-peptides (Aβ), is reported. The Fc-peptide conjugates are characterized by a reversible redox activity and the ability to undergo hydrophobic and hydrogen bonding interactions. Biomolecular interactions between Fc-bioconjugates with Aβ(12-28) fragments were studied by circular dichroism (CD), transmission electron microscopy (TEM), and electrochemistry. All four Fc-peptides interacted favourable with Aβ(12-28) and prevented fibril formation, the extent of which depended on the length of the peptide and the nature of the C-terminal group. The aggregates obtained for the Aβ(12-28)/Fc-peptide mixtures range from short fibrils to spherical aggregates. We demonstrated that in solution the peptide sequence and peptide charge affect the biomolecular interactions. Fc-peptide interactions with immobilized Aβ(12-28)-Cys films on Au surfaces were detected by measuring the current response of the Fc redox process. The formal redox potential, E(0), at ~440 (10) mV and i(pc)/i(pa) at 0.9 were observed characteristic for the monosubstituted Fc-derivative undergoing a one-electron redox process. On the surface, methyl ester-protected Fc-peptides (1 and 3) interacted only weakly with Aβ(12-28)-Cys films, giving rise to minimal redox activity. In contrast, charged Fc-peptides (2 and 4) gave a significant electrochemical readout following the interaction with Aβ(12-28)-Cys films. Interestingly, the Fc-peptide charge dictates the surface-assisted interactions, while hydrophobic and ionic effects contribute to the overall solution behaviour of the Fc-bioconjugates with Aβ(12-28).     

Impact of Single Basepair Mismatches on Electron‐Transfer Processes at Fc‐PNA⋅DNA Modified Gold Surfaces

Gold‐surface grafted peptide nucleic acid (PNA) strands, which carry a redox‐active ferrocene tag, present unique tools to electrochemically investigate their mechanical bending elasticity based on the kinetics of electron‐transfer (ET) processes. A comparative study of the mechanical bending properties and the thermodynamic stability of a series of 12‐mer Fc‐PNA?DNA duplexes was carried out. A single basepair mismatch was integrated at all possible strand positions to provide nanoscopic insights into the physicochemical changes provoked by the presence of a single basepair mismatch with regard to its position within the strand. The ET processes at single mismatch Fc‐PNA?DNA modified surfaces were found to proceed with increasing diffusion limitation and decreasing standard ET rate constants k⁰ when the single basepair mismatch was dislocated along the strand towards its free‐dangling Fc‐modified end. The observed ET characteristics are considered to be due to a punctual increase in the strand elasticity at the mismatch position. The kinetic mismatch discrimination with respect to the fully‐complementary duplex presents a basis for an electrochemical DNA sensing strategy based on the Fc‐PNA?DNA bending dynamics for loosely packed monolayers. In a general sense, the strand elasticity presents a further physicochemical property which is affected by a single basepair mismatch which may possibly be used as a basis for future DNA sensing concepts for the specific detection of single basepair mismatches.     

Multisubband transport and magnetic deflection of Fermi electron trajectories in three terminal junctions and rings

We study the electron transport in three terminal junctions and quantum rings looking for the classical deflection of electron trajectories in the presence of intersubband scattering. We indicate that although the Aharonov-Bohm oscillations and the Lorentz force effects co-exist in the low subband transport, for higher Fermi energies a simultaneous observation of both effects is difficult and calls for carefully formed structures. In particular, in quantum rings with channels wider than the input lead the Lorentz force is well resolved but the Aharonov-Bohm periodicity is lost in chaotic scattering events. In quantum rings with equal lengths of the channels and T-shaped junctions the Aharonov-Bohm oscillations are distinctly periodic but the Lorentz force effects are not well pronounced. We find that systems with wedge-shaped junctions allow for observation of both the periodic Aharonov-Bohm oscillations and the magnetic deflection.