Many-body potential for point defect clusters in Fe-C alloys

Modeling the consequences of crystalline defects requires efficient interaction sampling. Empirical potentials can identify relevant pathways if the energetics and configurations of competing defects are captured. Here, we develop such a potential for an alloy of arbitrary point defect concentration, body-centered cubic alpha-Fe supersaturated in C. This potential successfully calculates energetically favored defects, and predicts formation energies and configurations of multicarbon-multivacancy clusters that were not attainable with existing potentials or identified previously via ab initio methods.     

Manipulating Nonlinear Photocurrent from Interlayer Coupling in Bilayer Metamaterials for Polarized Terahertz Generation

Polarized terahertz (THz) wave generation is of great significance for chiral and anisotropic sensing applications. However, how to manipulate amplitude, polarization, and ellipticity of the THz generation is still a fundamental challenge. Herein, polarized THz wave generation is achieved from a bilayer metamaterial consisting of T-shaped structure (TSS) and split resonator rings (SRRs) by combining Maxwell and hydrodynamic equations. The elliptically polarized THz wave can be synthetized directly from horizontally and vertically polarized THz components due to the orthogonal nonlinear photocurrents along the arm-directions of TSS and SRRs, respectively. Besides, the ellipticity and the orientation angle of the THz polarization ellipse can be modulated by the twist angle between the SRRs and TSS layers. The maximum ellipticity can reach 0.34 while the orientation angle is tunable from −0.45 to 0.48π by tuning the twist angle. This work proposes an interlayer coupling method for the polarized THz sources based on metamaterials in potential circular dichroism and chiral sensing applications.     

A theoretical solution for axially symmetric problems in elastodynamics

This paper presents a theoretical solution for the basic equation of axisymmetric problems in elastodynamics. The solution is composed of a quasi-static solution which satisfies inhomogeneous boundary conditions and a dynamic solution which satisfies homogeneous boundary conditions. After the quasi-static solution has been obtained an inhomogeneous equation for dynamic solution is found from the basic equation. By making use of eigenvalue problem of a corresponding homogeneous equation, a finite Hankel transform is defined. A dynamic solution satisfying homogeneous boundary conditions is obtained by means of the finite Hankel transform and Laplace transform. Thus, an exact solution is obtained. Through an example of hollow cylinders under dynamic load, it is seen that the method, and the process of computing are simple, effective and accurate.     

A Chemically Triggered and Thermally Switched Dielectric Constant Transition in a Metal Cyanide Based Crystal

A dielectric constant transition is chemically triggered and thermally switched in (HPy)₂[Na(H₂O)Co(CN)₆] ( 2 , HPy=pyridinium cation) by single‐crystal‐to‐single‐crystal transformation and structural phase transition, respectively. Upon dehydration, (HPy)₂[Na(H₂O)₂Co(CN)₆] ( 1 ) transforms to its semi‐hydrated form 2 , accompanying a transition from a low‐dielectric state to a high‐dielectric state, and vice versa. This dielectric switch is also realized by a structural phase transition in 2 that occurs between room‐ and low‐temperature phases, and which corresponds to high‐ and low‐dielectric states, respectively. The switching property is due to the variation in the environment surrounding the HPy cation, that is, the hydrogen‐bonding interactions and the crystal packing, which exert predominant influences on the dynamics of the cations that transit between the static and motional states.     

Direct Conversion of Bulk Metals to Size‐Tailored,Monodisperse Spherical Non‐Coinage‐Metal Nanocrystals

Monodisperse non‐noble metal nanocrystals (NCs) that are highly uniform in shapes and particle size are much desired in various advanced applications, and are commonly prepared by either thermal decomposition or reduction, where reactive organometallic precursors or/and strong reducing agents are mandatory; however, these are usually toxic, costly, or suffer a lack of availability. Bulk Group 12 metals can now be converted into ligand‐protected, highly crystalline, monodisperse spherical metal NCs with precisely controlled sizes without using any precursors and reducers. The method is based on low‐power NIR‐laser‐induced size‐selective layer‐by‐layer surface vaporization. The monodisperse Cd NCs show pronounced deep‐UV (DUV) localized surface plasmon resonance making them highly competitive DUV‐plasmonic materials. This approach will promote appreciably the emergence of a wide range of monodisperse technically important non‐coinage metal NCs with compelling functionalities.     

Three‐Component Reaction of Pyrimidin‐2‐yl Sulfonates with Sodium Azide and Alkynes: An Efficient Approach to C2–Triazolo Functionalized Pyrimidines

Pyrimidin‐2‐yl sulfonate, as an efficient reaction partner, can be easily prepared from cheap commercial materials, reacted with sodium azide and alkynes to give C2‐triazolo functionalized pyrimidines in good yields under mild reaction conditions. This procedure eliminates the need to handle organic halides or organic azides, as they are generated in situ, making this already powerful click process even more user‐friendly and safe.     

Ultrasensitive non-enzymatic glucose sensing at near-neutral pH values via anodic stripping voltammetry using a glassy carbon electrode modified with Pt3Pd nanoparticles and reduced graphene oxide

We describe an anodic stripping voltammetric (ASV) method for glucose sensing that widely expands the typical amperometric i-t response of glucose sensors. The electrode is based on a working electrode consisting of a glassy carbon electrode modified with Pt-Pd nanoparticles (NPs; in an atomic ratio of 3:1) on a reduced graphene oxide (rGO) support. The material was prepared via the spontaneous redox reaction between rGO, PdCl₄ ²⁻ and PtCl₄ ²⁻ without any additional reductant or surfactant. Unlike known Pt-based sensors, the use of Pt₃Pd NPs results in an ultrasensitive ASV approach for sensing glucose even at near-neutral pH values. If operated at a working voltage as low as 0.06 V (vs. SCE), the modified electrode can detect glucose in the 2 nM to 300 μM concentration range. The lowest detectable concentration is 2 nM which is much lower than the LODs obtained with other amperometric i-t type sensing approaches, most of which have LODs at a μM level. The sensor is not interfered by the presence of 0.1 M of NaCl.

We describe an anodic stripping voltammetric method for glucose sensing that widely expands the typical amperometric i-t response of glucose sensors (2 nM to 300 μM). The electrode is based on a glassy carbon electrode modified with Pt-Pd nanoparticles on a reduced graphene oxide (rGO) support.

     

Clean and Efficient Synthesis of Pyrazole Derivatives in Aqueous Media

A series of 5‐aryl‐1H‐pyrazole derivatives were synthesized via the reaction of 3‐(dimethylamino)‐1‐arylprop‐2‐en‐1‐one with hydrazine in aqueous media without using any catalyst. This method has the advantages of easier work‐up, mild reaction condition, high yields, and an environmentally benign procedure.