Dragica M. Minić

Study of the Dendritic Growth of Ni–Co Alloys Electrodeposited on Cu Substrates

Ni–Co alloy deposits and their parent metals were formed on Cu substrates by electrolysis under different current densities applied in the galvanostatic regime. A quantitative scanning electron microscopy technique was employed to study the morphology and surface roughness of the obtained deposits. The structure of the deposits is governed by the nature of depositing ions and quantity of evolved hydrogen. The cauliflower morphology and the highest mean surface roughness values are the results of electrodeposition from the Ni containing bath. The structure of the Co deposits formed under the same conditions and determined by the formation of the hexagonal close-packed phase results in a more uniform grain size distribution and formation of smoother platelet deposits. The mean surface values of the parent metals are independent of the current density. The dendritic growth is a special case of a structure formed only in the Ni–Co alloy deposition at selected, high current densities of 220 and 400 mA cm �2 . The dendrites obtained at a higher current density of 400 mA cm �2 have shown more developed structures with smaller dendrites that

PREPARATION AND CHARACTERIZATION OF FACIAL AND MERIDIONAL ISOMERS OF UNS-CIS-(ETHYLENEDIAMINE-N,N'-DI-3-PROPIONATO)(GLYCINATO)COBALT(III) SEMIHYDRATE

Abstract Both theoretically possible geometrical isomers, facial and meridional, of uns-cis-(ethylenediamine-N, N′-di-3-propionato)(glycinato)cobalt(III) semi hydrate have been prepared by reaction of sodium uns-cis-(ethylenediamine-N, N′-di-3-propionato) (carbonato) cobaltate(III) with glycine at 75°C. The complexes have been isolated chromatographically and characterized by elemental analysis, electron absorption, infrared and nuclear magnetic spectra.

Electric and electrochemical properties of solid LiH2PO4

Abstract Electrical and electrochemical properties of solid LiH 2 PO 4 conductor were investigated in the temperature range from room temperature to 373 K. It was found that high conductivity throughout the temperature range, with activation energy 17.23 kJ/mol, originates from the movement of hydrogen ions (protons). The movement of protons in the correlation with phosphate groups rotation was considered. The slopes of Tafel lines and exchange current densities both for cathodic hydrogen and anodic oxygen evolution were determined (by means of usual electrochemical kinetic methods) at various temperatures. The energy of activation at the equilibrium potentials both for the cathodic and the anodic processes have been assessed to be 17.23 kJ/mol (0.18 eV) and 2.9 kJ/mol (0.03 eV), respectively.

Protonic conductivity of solid UO2HPO4·3H2O

Abstract The electrical and electrochemical properties of the solid ionic conductor UO 2 HPO 4 ·3H 2 O were investigated within the temperature range from room temperature up to 673 K. The conductivity of a nondehydrated sample within the temperature range from 303 K (6.5 × 10 -3 S/m) to 350 K (2.5 × 10 -2 S/m), with the activation energy of 23 kJ/mol, is a consequence of the presence of crystal water, and originates, mostly, from the fast movement of protons across the network of molecules of water in a tunneling mechanism pattern. When heated, the conductor loses crystal water, which leads to a final change in the nature of the conductor and in the conductivity mechanism. The conductivity of the dehydrated salt UO 2 HPO 4 (2.5 × 10 -4 S/m at 488 K), with the activation energy 44.04 kJ/mol, is considerably lower than the one mentioned above and can be attributed, to a great extent, to the movement of protons, most likely by a tunneling mechanism, through the less favourable structure formed by phosphate groups of the dehydrated salt. On being heated above 623 K for a certain time, the acid phosphate transforms into pyrophosphate, the conductivity of which is lower than that mentioned above. By means of electrochemical methods, the electrode processes were studied. It has been shown that H + and UO 2+ ions are reduced at the cathode, while the phosphate groups oxidize at the anode and O 2 is evolved.

Kinetic aspects of the thermal treatment of acid crystallohydrate, MgHPO4 · 3H2O: Part 2. Dehydration and accompanying effects

Abstract Dehydration of MgHPO4·3H2O takes place in the temperature interval from 120° C to 250° C. Continuous water loss in a wide temperature range results in the formation of MgHPO4 at 250 °C. Dehydration was studied under non-isothermal conditions, using differential scanning calorimetry (DSC). The reaction kinetics were followed by making a number of DSC patterns at different heating rates. Activation energy was found to be 144 kJ mol−1 by the Kissinger method and 149 kJ mol−1 by the Ozawa method. The order of reaction was 0.7. Dehydration increases disorder of the system, changes the actual symmetry of PO4 groups and causes breakdown of the crystal structure.

Thermal stability and kinetic studies of new dinuclear copper(II) complexes with octaazamacrocyclic and multidonor bidentate ligands

Abstract The thermal properties of four copper(II) complexes with N , N ′, N ″, N ‴-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane (tpmc) and several bidentate ligands N,S (thiosemicarbazide and thiourea) or N,O donors (semicarbazide and urea), of the general formula [Cu 2 (X)tpmc](ClO 4 ) 4 , have been investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). The thermal stability order can be recognized for the examined complexes, depending on coordinated bidentate bridging N,S or N,O ligand. Kinetic data demonstrated first-order thermal decomposition. A plausible mechanism has been proposed which explains the major products of the degradation.

Kinetic and Thermodynamic Studies of Facial and Meridional uns-cis-[Co(eddp)gly] Complexes

Thermal properties of facial and meridional uns-cis-[Co(eddp)gly]0.5H2O complexes were investigated by means of DSC and TG techniques. It wasshown that the processes of thermal decomposition of these complexes are multi-stepdegradation processes, which can also be well separated into individual steps, depending onthe molecular symmetry. Thus, the process of thermal degradation of the meridional isomerof the above complex consists of 4 well-separated steps in the temperature interval from 100to 500°C. The corresponding kinetic and thermodynamic parameters of this process weredetermined, and a possible mechanism is discussed.

Kinetic aspects of the thermal treatment of acid crystallohydrate, MgHPO4·-3H2O. part 1. changes in the IR spectra and proton delocalization

Abstract Changes in the IR spectra of acid magnesium phosphate trihydrate heated to progressively higher temperatures point to increased proton mobility. A strong band, of complex structure, in the region of OH stretching vibrations is convoluted. Components of this band are supposed to be due to vibrations of different hydrogen bonded hydroxyl groups. From the changes of relative band intensities with temperature, using the Boltzmann equation, the activation energy is calculated and possible mechanism of proton delocalization discussed. It has been found that proton delocalization is a complex process which includes the following steps: dissociation of hydrogen bond, proton tunnelling effect and orientation of acceptor sites.

Hydrogen Economy: Modern Concepts, Challenges and Perspectives

Identifying and building a sustainable energy system are two of the most critical issues for any modern society. Ideally, current energy system, based mostly on fossil fuels, which have limited supply and considerable negative environmental impact, would be replaced with a system based on a renewable fuel. Hydrogen, as an energy carrier primarily derived from water, can address the issues of sustainability, environmental emissions and energy security. If one assumes a full hydrogen economy the size of United States, the amount of hydrogen for just purposes of transportation would be about 150 million tons per year, which would amount to consuming, with current production efficiency, between 2 and 5 billion tons of water. As a comparison, current water consumption in United States for purpose of thermoelectric power generation in power plants is around 300 billion tons, with another 1.2 billion tons consumed for gasoline production. Therefore, rather than consume, a hydrogen economy would most likely significantly reduce water consumption for purposes of energy generation (Turner, 2004).

Ni(II) complex with bishydrazone ligand: synthesis, characterization, DNA binding studies and pro-apoptotic and pro-differentiation induction in human cancerous cell lines

A new Ni(II) complex, [Ni(L)(H2O)] (1), with diethyl 3,3′-(2,2′-(1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))bis(hydrazin-1-yl-2-ylidene))bis(3-oxopropanoate) ligand (H2L) was synthesized as a potential chemotherapeutic agent. Polidentate ligand was coordinated to Ni(II) NNN-tridentately, in dianionic form, while monodentate water coordination completed square-planar geometry around metal. Structure in the solution was determined by NMR spectroscopy and the same coordination mode was observed in the solid state using IR spectroscopy and further verified by DFT calculations and electrochemical studies. Thermal stability of 1 was determined in both air and nitrogen atmosphere. Anticancer activity of 1 was investigated on acute monocytic leukemia (THP-1) and pancreatic adenocarcinoma (AsPC-1) cell lines. On THP-1 cells 1 induced powerful apoptotic response (ED50 = 10 ± 3 μM), which was revealed to be only partially caspase-dependent, with activation of caspase-8 as the dominant course. This suggested that experimentally validated covalent binding of 1 to DNA is not the only mechanism responsible for programmed cell death. This was supported with experiments on AsPC-1 cells. Although treatment of those cells with 1 resulted in poor apoptotic response, cell cycle changes showed concentration-dependent shifts indicating a dual mechanism of activity. This study also reviews the results of preliminary biological screening, which demonstrates that 1 displays a unique pattern of anticancer activity with at least two mechanisms involved.