Design,fabrication and characterization of a Schottky diode on an AlGaAs/GaAs HEMT structure for on-chip RF power detection

A Schottky diode was designed and fabricated on an n-AlGaAs/GaAs high electron mobility transistor (HEMT) structure for RF power detection. The processing steps used in the fabrication were the conventional steps used in standard GaAs processing. Current–voltage measurements showed that the devices had rectifying properties with a barrier height of 0.5289–0.5468 eV. The fabricated Schottky diodes detected RF signals well and their cut-off frequencies up to 20 GHz were estimated in direct injection experiments. To achieve a high cut-off frequency, a smaller Schottky contact area is required. The feasibility of direct integration with the planar dipole antenna via a coplanar waveguide transmission line without insertion of matching circuits was discussed. A higher cut-off frequency can also be achieved by reducing the length of the coplanar waveguide transmission line. These preliminary results represent a breakthrough as regards direct on-chip integration technology, towards the realization of a ubiquitous network society.     

Synthesis and Crystal Structure Analysis of 9-Phenyl-β-carboline

An efficient method is described for the synthesis of 9-phenyl-9H-pyrido[3,4-b]indole and 9-(4-chlorophenyl)-9H-pyrido[3,4-b]indole by employing a catalytic amount of CuI (10 mole%) without any ligand. The single crystal of 9-phenyl-9H-pyrido[3,4-b]indole was produced by crystallization from hexane and ethyl acetate mixture that was investigated by single X-ray diffraction (XRD). The compound crystallizes in monoclinic P21/c space group with unit cell dimensions a = 11.3132(5) Å, b = 12.0061(5) Å, c = 9.2498(4) Å, α = 90°, β = 103.187(3)°, γ = 90°. ¹H and ¹³C NMR, IR, and mass spectroscopic methods of the compounds are also discussed.     

Electroanalysis of Caffeic Acid in Red Wine and Investigation of Thermodynamic Parameters Using an Ag Nanoparticles Modified Poly(Thiophene) Film Glassy Carbon Electrode

A silver nanoparticle decorated poly(thiophene) modified glassy carbon electrode (GCE) was prepared for determination of caffeic acid. The Ag/PTh/GCE surface was characterized by scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX) spectroscopy. The modified electrode has shown higher electrocatalytic activity towards the oxidation of caffeic acid. The peak current of was found linear in the concentration range from 1.00×10^?8 to 4.83×10^?6 M with a detection limit of 5.3×10^?9 M (S/N=3). The modified electrode was used for determination of CA concentration in red wine samples. The thermodynamic constants, entropy change (ΔS), enthalpy change (ΔH) and Gibbs free energy change (ΔG) were calculated as ?166.34 J/(mol K), ?154.24 kJ/mol and ?104.75 kJ/mol at 25 °C, respectively.     

trans‐Diaquabis(nicotinamide‐κN)bis(salicylato‐κO)cobalt(II)

The title compound, [Co(C₇H₅O₃)₂(C₆H₆N₂O)₂(H₂O)₂], forms a three‐dimensional hydrogen‐bonded supramolecular structure. The Co^II ion is in an octahedral coordination environment comprising two pyridyl N atoms, two carboxylate O atoms and two O atoms from water molecules. Intermolecular N—H...O and O—H...O hydrogen bonds produce R₂²(8), R₂²(12) and R₂²(14) rings, which lead to two‐dimensional chains. An extensive three‐dimensional supramolecular network of C—H...O, N—H...O and O—H...O hydrogen bonds and C—H...π interactions is responsible for crystal structure stabilization. This study is an example of the construction of a supramolecular assembly based on hydrogen bonds in mixed‐ligand metal complexes.     

Production of Magnetic Nano‐bioconjugates via Ball Milling of Commercial Boron Powder with Biomolecules

Mechanochemical preparation and characterization of surface‐functionalized magnetic boron nanoparticles for biomedical applications are presented. Alloying with the stainless steel ball milling material during mechanochemical activation proved to be an alternative route to introduce magnetic properties to the nanomaterials, while functionalization with biomolecules provided biocompatible surfaces for bioconjugation.     

Oxidative Cleavage and Rearrangement of Aryl Epoxides Using Iodosylbenzene: on Criegee's Trail

Aryl epoxides undergo rearrangement and oxidative cleavage when reacted with in situ prepared hydroxy‐λ³‐iodane complexes. The presence of H₂O plays a decisive role in steering the reaction path. A mechanistic scheme is proposed that accounts for the observed chemoselectivities.     

Synthesis,Spectral, Thermal and Structural Study of Monoaquabis(Acetylsalicylato-κO)bis(Nicotinamide-κN)Copper(II)

Abstract  

The compound has been formed by mononuclear [Cu(C₉H₇O₄)₂(C₆H₆N₂O)₂(H₂O)] units in which the metal ion as well as the water ligand lies on a twofold symmetry axis, so that only one acetylsalicylate ligand and one nicotinamide ligand are independent. The distortion from ideal five-coordinate geometries can be described best by the degree of trigonality τ. For a regular square-pyramidal (SQP) geometry the trigonality parameter is 0 and for a trigonal–bipyramidal (TBP) structure it increases to 1. The copper coordination geometry is that of a square pyramid (τ = 0.23), with the N atoms from nicotinamide ligands and the bonded carboxylate O atoms from acetylsalicylate ligands defining the quasi-planar square base. The apical site is occupied by the aqua ligand, a bond which coincides with the twofold symmetry axis and is thus exactly perpendicular to the basal plane. The thermal decomposition takes place in four steps: removing of moisture, dehydration of aqua ligand, the elimination of the nicotinamide (na) ligand and the decomposition of acetyl-groups and oxidation of salicylate ion ligands. In complex, all ligands are coordinated to the metal ion as monodendate. The IR spectra of the intermediate products showed similar results.     

Electrochemical Determination of Dicofol at Nickel Nanowire Modified Poly(p‐aminophenol) Film Electrode

An electrochemical sensor was fabricated by construction of nickel nanowires on the surface of poly(p‐aminophenol) (PPAP) modified glassy carbon electrode. The electrochemical response of dicofol, a known pesticide and used for agricultural activities such as cyclic voltammetry and differential pulse voltammetry, were investigated and the results were compared with those obtained unmodified electrodes. Following the optimization of NaOH concentration, polymerization cycle number, Ni nanowire amount, the linear range for the dicofol was studied and found as 0.83–30.7 μmol L^?1 (R²=0.9981) at Ni/PPAP/GCE with a 0.08 μmol L^?1 detection limit according to S/N=3. Finally, the proposed Ni/PPAP/GCE sensor was successfully applied for the dicofol analysis in soil samples. The characterization of the developed surface was carried out by scanning electron microscopy and X‐Ray photoelectron spectroscopy.     

Mixed-ligand complexes of boric acid with organic biomolecules

Boric acid forms meta-stable complexes with biomolecules like amino and hydroxy acids and stable complexes with the diol group containing carbohydrates, vitamins, and nucleotides, yielding mono-chelate (1: 1 complex) or bis-chelate (1: 2 complex) structures with negatively charged tetrahedral borate anions. Here we report water-soluble, bio-available mixed-ligand boron adducts for potential nutritional and/or pharmaceutical applications. The complexes were prepared by complete esterification of boric acid with a number of acyclic- and cyclic hydroxy-functionalized biomolecules employing sodium as the counter ion. Structural and thermal properties of the complexes were investigated using chemical analysis, ¹¹B NMR, FTIR, and TGA-DTA techniques. Complexes containing salicylic acid as one of the ligands displayed higher thermal and hydrolytic stabilities.     

Investigation of fast neutron shielding characteristics depending on boron percentages of MgB<Subscript>2</Subscript>, NaBH<Subscript>4</Subscript> and KBH<Subscript>4</Subscript>

The macroscopic cross-section Σ and average neutron fluence in matter Φ are usable factors to comment neutron shielding property of samples. In this paper, we have used MgB₂, NaBH₄ and KBH₄ samples including different percentages of boron. Neutron macroscopic cross-section measurements of them have been done by using a source of mono-energetic neutrons (E _eff = 4.5 MeV ²⁴¹Am–Be). Average neutron fluence values and double differential fast neutron flux distributions of each samples calculated by using FLUKA Monte Carlo code. Also half value layers (HVLs) of samples are compared to paraffin which is one of the most neutron moderators. As a result, growing boron concentration can raise neutron shielding property of materials.