Publications

A novel series of Cu(II) complexes with formula M(HLn)(ClO4)(2)center dot mH(2)O [HLn: 13-membered pentaazamacrocyclic ligand resulted from condensation ofN,N '-bis(2-aminoethyl)ethane-1,2-diamine,l-tyrosine (HL1)/l-tryptophan (HL2)/l-phenylalanine (HL3) and formaldehyde] were synthesized by one-pot method. Techniques such as ESI-MS, IR, UV-Vis and EPR spectroscopy provided data characterizing the complexes as mononuclear species. The course of thermal decomposition was followed using TG/DSC-MS analysis in air atmosphere. The TG curves showed a gradual decomposition in several stages that comprise dehydration, decomposition of perchlorate ions as well as fragmentation and oxidative degradation of the organic part. The intermediates formed after first stage of water elimination are stable on 40, 15 and 80 degrees C interval for complexes (1), (2) and (3), respectively. The compounds were tested on the eukaryotic unicellular organismSaccharomyces cerevisiae, showing variable actions in terms of toxicity, cellular uptake and capacity to alleviate growth defects associated with Cu, Zn-superoxide dismutase (SOD1) depletion.

The structural role of V in 28Li(2)O-72SiO(2) (in mol%) lithium silicate glass doped with 0.5 mol% V2O5 was assessed using Si-29 and V-51 Nuclear Magnetic Resonance (NMR), Fourier-transform infrared (FTIR), and X-ray photoelectron (XPS) spectroscopy techniques. Despite the low amount of V2O5 used, the structural information obtained or deduced from the statistical analysis of the NMR data could explain the evolution of glass properties after V2O5 addition. The XPS results indicated that all vanadium exists in 5+ oxidation state. Both the Si-29 NMR and FTIR data point toward an increase in the polymerization of the silicate network, caused by the V2O5 acting as network former, capable to form various QVn tetrahedral units (for n = 0, 1, and 2) in the glasses. These QVn units, which are similar to phosphate units, scavenge the Li+ ions and cause the silicate network to polymerize. However, in an overall balance, the entire glass network is depolymerized due to the additional nonbridging oxygens contributed by the vanadium polyhedra. The addition of vanadium causes the network to expand and increases the ionic conductivity.

The current increasing interest in portable biosensing platforms led to their development on flexible porous substrates, such as filter paper. As these devices rely on fluid transport under capillary action, without the use of an external force, studies of the diffusion process can provide useful data for optimizing their working capabilities. We present here the results obtained by experimentally studying the radial diffusion of various fluids. The diffusion in filter paper has been recorded for six fluids with different viscosity. For each of them, the displacement of the fluid front has been measured along eight radial directions and then we investigated the possibility of describing this diffusion process using Gillespie's model.

The paper presents the research results in the field of TiNiCu shape memory alloys processed by powder metallurgy techniques. The powders mixtures used to synthesize Ti50Ni30Cu20 alloys were obtained by blended constitutive elemental powders or by mechanical alloying of powder mixtures for 10 and 20 hours, respectively. Finally, a subsequent annealing process was carried out, followed by a rapid cooling in ice water. All experiments were performed under 99.9% argon atmosphere. At room temperature, the obtained materials contained monoclinic and orthorhombic martensite type. The structural and thermal investigation of these materials were discussed in view of the potential development of actuators.

Phase-change memories have reached an advanced degree of maturity, although, to be able to meet the increasing storage demand, multilevel capability is needed. A GeTe memristor is obtained in an amorphous state and it is subjected to a specific thermal treatment which initiates the transition toward the crystalline state. It is found that this crystalline state initialization process is highly beneficial for subsequently obtaining a large number of intermediate resistive states between the high and low resistive states. Multiple resistance levels are achieved by operating the devices in both DC sweeps and rectangular pulse modes in the low-voltage subthreshold regime. The conduction is modeled using a space charge limited conduction model, showing three distinct conduction regions in the high resistive state which merge toward a single conduction region as the low resistive state is approached. The obtained memristors can be used as multilevel nonvolatile memories or as synapses in neuromorphic computing.

Thin film metal-ferroelectric-metal capacitors with an equal mixture of hafnium oxide and zirconium oxide as the ferroelectric material are fabricated using iridium oxide as the electrode material. The influence of the oxygen concentration in the electrodes during crystallization anneal on the ferroelectric properties is characterized by electrical, chemical, and structural methods. Forming gas, O-2, and N-2 annealing atmospheres significantly change the ferroelectric performance. The use of oxygen-deficient electrodes improves the stabilization of the ferroelectric orthorhombic phase and reduces the wake-up effect. It is found that oxygen-rich electrodes supply oxygen during anneal and reduce the amount of oxygen vacancies, but the nonferroelectric monoclinic phase is stabilized with a negative impact on the ferroelectric properties.

The species cis-[Cu(tbg)(2)](ClO4)(2) (CuTP) (tbg: 1-(o-tolyl)biguanide) was designed as a novel antimicrobial and biocompatible agent. The single-crystal X-ray diffraction revealed a mononuclear species with a very interesting structure consisting of two tautomeric forms of tbg arranged in a cis-configuration. A complex hydrogen bond network with perchlorate anions involved in different interactions leads to a supramolecular structure. The EPR data indicated the formation of a stable cis-trans mixture in dimethylsulfoxide. Moreover, the EPR experiments evidenced no activity against the superoxide radical (O-2 center dot(-)) but scavenging ability of the hydroxyl radical (HO center dot). This complex exhibited excellent antibacterial properties against planktonic and biofilm embedded gram-negative (Klebsiella pneumoniae, Enterobacter cloacae) and gram-positive (Bacillus subtilis, Lysteria monocytogenes) bacteria. The best efficiency was noticed against E. cloacae and L. monocytogenes with minimal inhibitory concentration and minimal biofilm eradication for a concentration value of 1.95 mu g/ml. One of the possible mechanisms of antimicrobial activity is represented by reactive oxygen species (ROS) generation. The complex was not cytotoxic on L929 fibroblasts. The in silico analysis confirmed the drug-likeness and safety profile of the tested compound and its potential for developing novel antimicrobial and therapeutic tools, targeting other clinical conditions besides infectious diseases.

The chemical precipitation was used to obtain carbon fibers (CF) with surface modified by magnetite particles (Fe3O4). Processing was carried out by employing up to three subsequent coating stages of ultrasonic treatments. After each sonication stage, the coating was 17, 33, and 47 wt. % of the total weight of the modified fibers. Raman spectroscopy indicates the presence in the coating of a mixture of iron II and III states. As-decorated fibers were used to fabricate composites with an epoxy resin (ED-20) matrix cured with PEPA. The quantity of the carbon fiber filler was of 1, 3, and 6 wt %. At room temperature, the saturation magnetization of the soft magnetic samples was 0.37, 0.83, and 1.72 emu/g for the indicated compositions. Carbon fiber reinforced polymer materials with extra functions such as magnetic in this case, are expected to be useful in applications from the power and energy industries.