Synthesis and luminescent properties of Eu-complexes with 2-acyl-1,3-indandionates (ACIND) and TPPO ligands: The first X-ray structure of Eu–ACIND complex

Europium complexes presenting general formulas [Eu(ACIND)₃(H₂O)₂] and [Eu(ACIND)₃(TPPO)₂] have been synthesized and characterized. In these formulas ACIND is stands for the ligands 2-acetyl-1,3-indandionate (AIND), 2-isovaleryl-1,3-indandionate (ISOVIND) or 2-benzyl-1,3-indandionate (BIND). The [Eu(ISOVIND)₃(H₂O)(EtOH)] complex was also prepared and its structure determined by single crystal X-ray analysis, showing that this complex crystallize in a monoclinic space group P2₁/n with the water molecules bridging through the hydrogen bond. The Eu(III) ion is eight-coordinate in a bicapped trigonal prismatic geometry defined by the oxygen donor atoms with a site of symmetry close to C_2ν. Isovaleryl groups in the ISOVIND molecules in the structure are disordered over two positions of the europium complex. Carbon atoms in ethanol molecule are disordered by the thermal vibration. Photoluminescence properties of these complexes in solid state were investigated both experimentally and theoretically, suggesting an efficient ligand-to-metal intramolecular energy transfer process.     

The electrochemical reduction of some substituted π-cyclopentadienylnickel(II) complexes

The electrochemical reduction of the complexes [CpNi(PR₃)₂]⁺, where R = C₂H₅, C₃H₇, C₄H₉ or [C₆Ni,(diphos)]⁺ and [CpNi(diars)⁺ in acetonitrile is described and the data are compared with those for the complexes Cp₂Ni, [Ni(PR₃)₄]²⁺ and Ni(diphos)²⁺₂.     

Glucose sensors based on enzyme immobilization onto biocompatible membranes obtained by radiation-induced polymerization

Amperometric glucose biosensors based on glucose oxidase immobilized onto poly(2-hydroxyethylmethacrylate) membranes obtained by γ radiation-induced polymerization were constructed. In a threeelectrode configuration, smooth or platinized platinum electrodes with different shapes were used, in order to detect the amount of hydrogen peroxide produced in the glucose oxidation. A saturated calomel electrode and a platinum foil were used as a reference and counterelectrode, respectively. The biocompatible obtained sensors were characterized as regards the temperature effect, the response, and lifetime. The determination of glucose in standard solutions was carried out, and linear calibration curves were obtained. Depending on the electrode configuration, the sensor had a response time of 1–4 min, and the measuring range extended from 5 × 10^?5 to 4 × 10^?3M.     

Mercury(II) selective sensors based on AlGaN/GaN transistors

This work presents the first polymer approach to detect metal ions using AlGaN/GaN transistor-based sensor. The sensor utilised an AlGaN/GaN high electron mobility transistor-type structure by functionalising the gate area with a polyvinyl chloride (PVC) based ion selective membrane. Sensors based on this technology are portable, robust and typically highly sensitive to the target analyte; in this case Hg²⁺. This sensor showed a rapid and stable response when it was introduced to solutions of varying Hg²⁺ concentrations. At pH 2.8 in a 10⁻² M KNO₃ ion buffer, a detection limit below 10⁻⁸ M and a linear response range between 10⁻⁸ M-10⁻⁴ M were achieved. This detection limit is an order of magnitude lower than the reported detection limit of 10⁻⁷ M for thioglycolic acid monolayer functionalised AlGaN/GaN HEMT devices. Detection limits of approximately 10⁻⁷ M and 10⁻⁶ M in 10⁻² M Cd(NO₃)₂ and 10⁻² M Pb(NO₃)₂ ion buffers were also achieved, respectively. Furthermore, we show that the apparent gate response was near-Nernstian under various conditions. X-ray photoelectron spectroscopy (XPS) experiments confirmed that the sensing membrane is reversible after being exposed to Hg²⁺ solution and rinsed with deionised water. The success of this study precedes the development of this technology in selectively sensing multiple ions in water with use of the appropriate polymer based membranes on arrays of devices.     

Linearization of a class of non-linear systems modelled by multibond graphs

Based on non-linear systems described by multibond graphs, a procedure designed to present symbolic linearization of these multibond graphs, is presented in this paper. Firstly, a junction structure of a multibond graph with multiport gyrators that represent Eulerian junction structures is proposed. In addition, non-linear multiport resistors are considered. By knowing the non-linear causal paths and loops of the non-linear multibond graph, the linearization is obtained by two steps: (1) The original multibond graph on the nominal operating point is evaluated; (2) New and additional paths based on the non-linear causal paths and loops are included. The state space representation of the linearized multibond graph using the corresponding junction structure is presented. An advantage of this methodology is its ability to allow the user to define a nominal operating point in which the linearization will be carried out.

In order to apply the proposed methodology, two physical systems are modelled and linearized by multibond graphs: a synchronous generator and a two degrees of freedom PUMA. Simulation results of these non-linear and linearized systems are shown.     

A novel approach to obtain analytical-numerical solutions of nonlinear Lorenz system

In this research we apply an analytic approach to solve the well-known Lorenz system in the non-chaotic regime. The proposed approach is based on modal expansion by infinite series. The analytical-numerical results show that for real initial conditions and under the non-convective regime the modal expansion series reproduce correctly the dynamical behavior of the solution of the Lorenz system. The validity and reliability of the proposed analytical approach with few terms is tested by its application to the convective and non-convective regime with various parameter values. The main advantage is that the obtained solution is global and is presented in analytical form.     

A new Eu(III)/Tb(III) binuclear coordination compound with crown ethers and bridging 4,4′-dipyridyl

A new Eu(III)/Tb(III) binuclear coordination compound with red and yellow emissions in solution and solid state, respectively, has been prepared. The lanthanide (Ln) ions are coordinated to crown ethers (C) and bridged by a dipyridyl (dipy) ligand. Ln/C and Ln/C/dipy complexes were also synthesized as precursors for the bimetallic compounds. The homo- and heterobimetallic Ln(III) complexes were characterized by elemental analysis as well as infra-red, absorption (UV-visible) and emission spectroscopies. The heterobimetallic complex geometry was predicted using the Sparkle/AM1 model and suggested to a chemical environment of very low symmetry around the lanthanide ions (C₁), in agreement with the luminescence spectrum. The Eu(III) and Tb(III) complexes display intense red and green emissions, respectively, in the solid state at room temperature.     

Harmonic Generation Via χ3 Intermodal Phase Matching in Microfibers

Abstract

Intermodally phase-matched up- and down-conversion processes based on third-order non-linearity have been proposed to efficiently generate light in the ultraviolet (UV) and mid-infrared (IR) wavelength regions in solid-core silica optical fibers and optical microfibers. Waveguide parameters and practical considerations required for optimum conversion are studied.