Synthesis,characterization and magnetic properties of MFe2O4 (M=Co,Mg, Mn,Ni) nanoparticles using ricin oil as capping agent

We focused on obtaining MFe₂O₄ nanoparticles using ricin oil solution as surfactant and on their structural characterization and magnetic properties. The annealed samples at 500 °C in air for 6 h were analyzed for the crystal phase identification by powder X-ray diffraction using CuKα radiation. The particle size, the chemical composition and the morphology of the calcinated powders were characterized by scanning electron microscopy. All sintered samples contain only one phase, which has a cubic structure with crystallite sizes of 12–21 nm. From the infrared spectra of all samples were observed two strong bands around 600 and 400 cm⁻¹, which correspond to the intrinsic lattice vibrations of octahedral and tetrahedral sites of the spinel structure, respectively, and characteristic vibration for capping agent. The magnetic properties of fine powders were investigated at room temperature by using a vibrating sample magnetometer. The room temperature M–H hysteresis loops show ferromagnetic behavior of the calcined samples, with specific saturation magnetization (M_s) values ranging between 11 and 53 emu/g.     

Novel fluorescence nanostructured materials obtained by entrapment of an ornamental bush extract in hybrid silica glass

Synthesis of some novel fluorescence nanomaterials loaded with photoactive polyphenols originated from plants with a high spectrum of biological activity, by replacing synthetic chemicals, may open new opportunities for optical and bio-medical applications. This paper presents the synthesis, characterization and fluorescence properties of a new class of materials based on host hybrid matrices obtained through templated sol–gel route, by hydrolysis and co-condensation of tetraorthoethylsilicate with octaisobutyltetracyclo [7.3.3.1^5,11] octasiloxane-endo-3,7-diol. The aim of paper is focused on the evaluation of the behavior of the fluorescence properties of ornamental bush extract at immobilization in a templated silica matrix and in a silica-silsesquioxane network, using as templates a neutral, non-toxic and biodegradable surfactant from poly(ethyleneglycol) class and a high biocompatible non-surfactant from glucidic class. The proofs of ornamental bush extract entrapment by physical interactions in silica based networks were provided by FT-IR and UV–VIS spectroscopy. The changes of polymer network due to the hydrogen bond interactions between residual Si–OH groups and functional groups of organic molecules from extract were evidenced by shifts of specific vibrations. In UV–VIS-NIR domain, the chromophore groups from ornamental bush extract were also evidenced by similar small shifts. As a result of ornamental bush extract entrapment, in all the immobilized samples the fluorescence intensity was more than 10 times amplified in samples templated with poly(ethylenglycol) surfactant) and of about 5 times in samples with glucidic template due to the physical adsorption of polyphenolic molecules from extract, excellent synergistic optical properties of SiO₂ and silsesquioxane compound and also due to a favorable conformational arrangement. The size of synthesized polymeric materials, estimated by dynamic light scattering technique showed main diameters less then 1.4 μm, namely 1,060 and 211 nm—for samples with d-glucose template and 1,330 and 531 nm—for samples with poly(ethyleneglycol) template, respectively, with a narrow size distribution and a polidispersity varying between 0.022 and 0.426. These results are in good accordance with TEM images that evidenced the presence of some polymeric aggregates which contain the vegetal extract immobilized inside hybrid SiO₂-Sq polymeric network of about hundred nanometers size. This study bring new contributions to the development of the sol–gel procedure by entrapment of a complex vegetable mixture in polymeric matrices as integral component of silica and hybrid silica-silsesquioxane networks which leads to a significant enhancement of the functional properties of the final material, thus diversifying the potential applications of organic doped sol–gel glasses.     

Consideration concerning interlaboratory test for cement in the last 20 years

Since 1988, over 40 laboratories representing research institutes, cement plants, pre-cast units, hydro plant construction companies, industrial construction companies, building companies, etc. from nine countries—Romania, Republic of Moldova, Croatia, Serbia, Macedonia, Bulgaria, Hungary, Ukraine and Lebanon—take part every year in an interlaboratory test organized by our laboratory. The subject of the interlaboratory test for cement was 37 laboratory tests: 12 chemical determinations, 7 physical tests and 9 mechanical tests carried out with 2 types of sand, from CEPROCIM and from each participant laboratory. The paper presents the evolution of two statistical parameters (standard deviation of reproducibility and/or coefficient of variation) for a period of 20 years and for 11 laboratory tests. The results strongly prove that interlaboratory test is one of the most efficient tools to establish a common language for all the participant laboratories performing cement testing procedures.     

Electrical conduction mechanism and gas sensing properties of Pd-doped TiO2 films

Undoped and Pd-doped titanium oxide thin films (0.5 wt.%) were prepared by the sol-gel technique (dip-coating) on glass and silicon substrates. The as-deposited thin films were compacted by subjecting them to different annealing temperatures (300 °C, 500 °C). The dependences of the electrical conductivity vs. inverse temperature were investigated in air and in vacuum. A study of the effects of Pd-doping, annealing temperature and ambient conditions on their electrical properties was performed. The sensing behavior of titanium oxide thin films exposed to some reducing gases (methane, acetone, ethanol, formaldehyde and liquefied petroleum gas) was carried out, by means of electrical conductivity measurements. All the studied films are most sensitive to formaldehyde, with a special remark for the Pd-doped ones deposited on silicon substrates.     

Permeation of gases through metallized polymer membranes

The permeation of He, H₂, CO₂, Ar, N₂ and Kr at 50°C through polyethyleneterephthalate, PET, membranes metallized with Pd, Ni and Cu was studied. It was found that metallizing a PET membrane changed its permeability for the gases studied, and that the permeability for H₂ varied slightly with differing H₂ pressure. In the range of 0-50°C the temperature dependence of the permeability for He and H₂ was determined. The results obtained were interpreted by assuming that the permeation of all gases, including H₂, through the metal layers of the membranes takes place by diffusion through fine defects which exist in their structure and, moreover, that H₂ also permeates through the Pd and Ni layers themselves. An important point is that by this method an increase of up to an order of magnitude of the membrane selectivity for H₂ was obtained     

Design and synthesis of water-soluble bioconjugatable trans-AB-porphyrins

Three free base porphyrins have been prepared that bear a polar and facially encumbering 2,4,6-tris-(carboxymethoxy)phenyl motif at one meso (5-) position. The only other substituent (15-position) comprises phenyl, formyl, or p-aminophenyl. The porphyrins exhibit solubility in water (or aqueous buffer solutions) at pH ≥7 and concentrations >1 mM at room temperature. The concise syntheses, water solubility, and bioconjugatable handle make these porphyrin constructs suitable for biological applications.     

Univalence criterion and convexity for an integral operator

For analytic functions f and g in the open unit disk U, a new integral operator I₁(f,g)(z) is introduced. The main object of this paper is to obtain a univalence condition and the order of convexity for the integral operator I₁(f,g)(z).     

Nondestructive imaging of a type I optical fiber Bragg grating

Nondestructive images of refractive-index variation within a type I fiber Bragg grating have been recorded by the differential interference contrast imaging technique. The images reveal detailed structure within the fiber core that is consistent with the formation of Talbot planes in the diffraction pattern behind the phase mask that had been used to fabricate the grating.     

Thermal behaviour and characterisation of new biologically active Cu(II) complexes with benzimidazole as main ligand

Four coordination compounds of copper(II) were synthesised and characterised in solid state by elemental analysis, infrared, electronic and EPR spectroscopy, as well as by thermal analysis (TG/DTA). The complexes were formulated on the basis of experimental data as: [Cu(BzIm)₂(H₂O)]·H₂O (1), [Cu₂(Acr)₄(HBzIm)₂] (2), [Cu(Acr)₂(HBzIm)₂] (3) and [Cu(Acr)₂(HBzIm)₂(H₂O)]·H₂O (4). IR data are in accordance with the unidentate nature of benzimidazole, in complexes (2), (3) and (4), and bridge bidentate nature of benzimidazole, in complex (1), while acrylato acts as uni- or bridge/chelate ligand. The electronic spectra display the characteristic pattern of square planar, square pyramidal, or octahedral stereochemistry, also confirmed by EPR spectra. Thermal decomposition evidenced several well-defined steps as dehydration of complexes (1) and (4), benzimidazole molecule releases for all complexes and acrylate decomposition in carbonate for complexes (3) and (4). In all four cases, the final residue after thermal treatment in air flow is copper(II) oxide, formed during the decomposition steps for complexes (3) and (4), and, respectively, after the oxidation of the metallic copper for complexes (1) and (2). Antimicrobial activities of the complexes have been determined by in vitro assays, against various Gram-negative and Gram-positive bacterial and fungal strains. Copper(II) complexes were also evaluated for their cytotoxicity on eukaryotic cells.     

Antioxidant activity evaluation by physiologically relevant assays based on haemoglobin peroxidase activity and cytochrome c-induced oxidation of liposomes

Two new protocols for exploring antioxidant-related chemical composition and reactivity are described: one based on a chronometric variation of a haemoglobin ascorbate peroxidase assay and one based on cytochrome c-induced oxidation of lecithin liposomes. Detailed accounts are given on their design, application, critical correlations with established methods and mechanisms. These assays are proposed to be physiologically relevant and bring new information regarding a real sample, both qualitative and quantitative. The well-known assays used for evaluation of antioxidant (re)activity are revisited and compared with these new methods. Extracts of the Hedera helix L. are examined as test case, with focus on seasonal variation and on leaf, fruit and flower with respect to chromatographic, spectroscopic and reactivity properties. According to the set of assays performed, winter are the most antioxidant, followed by summer leaves, and then by flowers and fruits.