自制三种物理实验装置及演示

1演示超重现象 取透明塑料瓶一个，截去瓶底，并改用一张白纸封住底部（可用细线捆扎）．再取一段橡皮筋，一端和一柱形金属重物连结，并将重物放入瓶中，橡皮筋另一端固定在瓶口处．静止时重物不和白纸接触，约保持1cm距离．整个装置如图1所示．     

Beam focusing through a tapered subwavelength aperture surrounded by dielectric surface gratings

A novel plasmonic nanolens formed by a tapered subwavelength metal slit surrounded by surface dielectric gratings is proposed and demonstrated numerically. By patterning surface corrugations on the output surface, the beam can be focused, by regulating the aperture, the focal length can be controlled effectively. Numerical simulations using Finite-Difference Time-Domain (FDTD) method coupled with anisotropic perfectly matched layer (APML) boundary conditions verify that the proposed metallic lens can focus the radiation on the scale of a wavelength below the substrate and the method is effective for the design of nano-optical devices such as optical microprobes.     

Local field enhancement of pair arrays of silver nanospheres

Local field surface plasmon excitation of pair arrays of silver nanospheres was studied using three-dimensional finite-difference time-domain method. The near-field enhancement was associated with the radius of nanosphere and the incident wavelength, the highest of which always appeared in the penultimate gaps, regardless of the number of the pairs. The surface plasmon resonance could be controlled and tuned by radius of nanosphere and incident wavelength.     

Grain size of nanocrystalline YSZ buffer layers fabricated by ion beam deposition

Amorphous or nanocrystalline thin films are capable to be efficient diffusion barrier layers for YBCO coated conductors of ion beam assisted deposition route. Nanocrystalline Yttria-Stabilized Zirconia (YSZ) buffer layers were fabricated by the ion beam deposition. Kr and Ar gases were utilized for the dual Kaufman type sputtering ion sources sequently. Both of the ion beams were fixed at 200 mA, while the ion energy was in the range of 450–2000 eV. The thickness of the YSZ buffer layers was several hundreds of nanometers. The grain size of YSZ thin films, which varied from 2 to 20 nm, was calculated by Scherrer Formulation based on the X-ray diffraction measurement results. The grain size always decreased at first and then increased when the ion energy was increased. In the cases Kr gas was utilized and Ar gas was utilized, the grain size reached its minimum value at the ion energy of about 1800 eV and 1000 eV, respectively. Such phenomenon was discussed using the thermodynamic theory of thin film nucleation. Deposition rate and substrate temperature were the two chief variables of the critical nuclei concentration and grain size.     

Double-stranded helical lanthanide(III) supramolecular networks with rigid diimine ligands: Synthesis, structure, and physical properties

Two lanthanide coordination complexes [Nd(NO₃)₃(CH₃OH)₂(4,4′-bipy)₂] (1) (4,4′-bipy=4,4′-bipyridine) and [4,4′-Hbipy][La(NO₃)₄(H₂O)₂(4,4′-bipy)] (2), with a salt of cationic diprotonated 4,4′-bipy, [2(4,4′-H₂bipy)][4(NO₃)] (3), have been identified and isolated from a methanol solution of Ln(NO₃)₃·6H₂O, 4,4′-bipyridine and pyrazine in 1:2:1 ratio. Their structures have been determined by single-crystal X-ray diffraction analyses, which reveal that 1 has an interesting three-dimensional supramolecular architecture containing 2₁ double-stranded helical chains through hydrogen bonding and π–π interactions, while 2 and 3 have well defined infinite chiral 3D open networks that undergo self-interpenetration. The electrospray ionization mass spectra (ESI-MS) indicate that the covalent complex has higher stability than the electrostatic bonding one. ESI-MS/MS of these ions reveal that the Ln–O bond forms a stronger coordinated bonding than that of Ln–N system and the nitrate anion remains bound to the lanthanide centers after complete dissociation in methanol solution.     

First-principles prediction of the magnetism of 3d transition-metal-doped Rocksalt MgO

Using first-principles band structure methods, we have systematically studied the electronic structures, magnetic stabilities, and half-metal properties of 3d transition-metal (TM) doped Rocksalt MgO compounds TMMg₃O₄ (TM=V, Cr, Mn, Fe, Co, and Ni). The calculations reveal that only CrMg₃O₄ has a ferromagnetic stability among the six compounds, which is explained by double-exchange mechanism. The magnetic stability is affected by the doping concentration of TM if the top valance band is composed of partially occupied t2g states. In addition, CrMg₃O₄ is a half-metallic ferromagnet. The origins of half-metallic and ferromagnetic properties are explored. The Curie temperature (Tc) of CrMg₃O₄ is 182 K. And it is hard for CrMg₃O₄ to deform due to the large bulk modulus and shear modulus, so it is a promising spintronic material. Our calculations provide the first available information on the magnetic properties of 3d TM-doped MgO.     

Corannulene derivatives for organic electronics: From molecular engineering to applications

This paper intends to provide an overview for using corannulene derivatives in organic electronics such as organic field-effect transistors (OFETs), organic solar cells (OSCs), and organic light-emitting diodes (OLEDs). We highlight the rational design strategies, tuning molecular orbital energy levels and arrangement in single crystals of corannulenes. The topological structure and properties of corannulene make it a unique candidate for organic electronics.     

Palladium‐Initiated Radical Cascade Stereoselective Iodofluoroalkylation/Cycloisomerization of Ene‐vinylidenecyclopropanes

A novel and convenient palladium‐initiated radical cascade stereoselective iodofluoroalkylation/cycloisomerization of ene‐vinylidenecyclopropanes with fluoroalkyl iodides has been developed. The reaction proceeds under mild reaction conditions with high atom economy and stereoselectivity, thereby allowing an efficient access to a variety of difluoromethylated or perfluoroalkylated pyrrolidines tethered with an alkyl iodide. Two plausible radical pathways for the transformation have been proposed on the basis of the results of control experiments and previous reports, which in one case it was thought that palladium(0) was an initiator rather than a catalyst.     

Kinetic Resolution of Racemic Allylic Alcohols by Catalytic Asymmetric Substitution of the OH Group with Monosubstituted Hydrazines

A new strategy has been established for the kinetic resolution of racemic allylic alcohols through a palladium/sulfonyl‐hydrazide‐catalyzed asymmetric OH‐substitution under mild conditions. In the presence of 1 mol % [Pd(allyl)Cl]₂, 4 mol % (S)‐SegPhos, and 10 mol % 2,5‐dichlorobenzenesulfonyl hydrazide, a range of racemic allylic alcohols were smoothly resolved with selectivity factors of more than 400 through an asymmetric allylic alkylation of monosubstituted hydrazines under air at room temperature. Importantly, this kinetic resolution process provided various allylic alcohols and allylic hydrazine derivatives with high enantiopurity.