ULTRAFINECOPPER AND NICKEL POWDERS INTHE ELECTRO-CATALYTICHYDROGENATIONOF ORGANIC COMPOUNDS

Ultrafine copper and nickel powders are synthesized by a chemical reduction of the metal cations from their salts in an aqueous ethanol solution without and with the addition of a polymer stabilizer (polyvinylpyrrolidone and polyvinyl alcohol). The structure and morphological features of the prepared metal powders were investigated by X-ray phase analysis and electron microscopy. The electrocatalytic properties of the Cu and Ni powders have been studied in the electrohydrogenation of acetophenone, nitrobenzene, p-nitroaniline, and cyclohexanone. A higher electrocatalytic activity of Cu powders, as well as skeletal copper, was established in the electrohydrogenation of the first three of the listed compounds in comparison with nickel powders, which is explained by the ability of copper cations to be reduced from its oxides in the electrochemical system under investigation. It is shown that the use of polymer stabilizers in the synthesis of Cu and Ni powders contributes to reducing metal particle sizes, but does not increase the electrocatalytic activity of the corresponding metal powders.

Hexanuclear copper(II) complex of 2-hydroxy-N,N′-bis[1-(2-hydroxyphenyl)ethylidene]propane-1,3-diamine incorporating an open-cubane core

The title molecular structure, namely, diaquatris(μ3-1,3-bis{[1-(2-oxidophenyl)ethylidene]amino}propan-2-olato)-μ3-hydroxido-dinitratohexacopper(II) ethanol trisolvate, [Cu6(C19H19N2O3)3(NO3)2(OH)(H2O)2]·3C2H5OH, corresponds to a non-symmetric hexanuclear copper complex. The complex exhibits one core in which three CuII metal centres are mutually interconnected, two by two, via three phenolato oxygen anions acting in a μ2-mode. These three copper cations are interconnected in a μ3-mode by one hydroxyl group. An open-cube structure is generated in which each of the CuII cations of the three CuO4N units is connected by two μ2-O anions from phenolate groups and one μ3-O atom from a hydroxy anion. Each of the three pentacoordinated CuII cations situated in the open-cube unit has a distorted NO4 square-pyramidal environment. Each of these three CuII centres is interconnected with another CuII cation via one enolate O atom in μ2-mode, yielding one CuNO4 unit and two CuNO3 units. The pentacoordinated CuII atom has a distorted square-pyramidal environment while the two tetracoordinated copper(II) cations are situated in a square-planar environment. A series of intramolecular O—H...O hydrogen bonds are observed. In the crystal, the units are connected two by two by intermolecular C—H...O and O—H...O hydrogen bonds, thus forming sheets parallel to the ac plane.

COMPARATIVE OF NATURAL ZEOLITE – CLINOPTILOLITE ELIMINATION OF METAL IONS/ESPECIALLY Cu (II) WITH D-PENICILLAMINE FROM BIOLOGICAL ENVIRONMENTS

Clinoptilolite is used as an adsorbent to remove heavy metal cations due to its function as a molecular sieve. This molecular sieve characteristic has made it possible to study the efficiency of clinoptilolite and D-Penicillamine in a comparative way in terms of the adsorption of heavy metals (especially copper) from a biological medium. For this purpose, clinoptilolite was subjected to grinding to produce a homogenized micronized powder in two sizes with d90=75 and 150 μm. Then, initial adsorption tests in an aqueous medium were performed on 10 ppm solutions of iron, zinc, copper, cadmium and nickel cations in single cation solutions, as well as a mixture of cations. In the next step, tests were performed to evaluate the adsorption of Cu2+ on clinoptilolite under different conditions. Experiments have been performed to investigate the effect of pH, temperature (T), adsorbent dosage, time and cation concentration in a simulated biological medium. According to the results, clinoptilolite has a high ability to remove metal cations from aqueous solutions. The 99.71% removal of copper cations by clinoptilolite indicates the high ability of this mineral to remove copper from any environment. In a simulated biological medium at pH=7 and 5, the copper adsorption rate was 98.18% and 97.45% respectively, which indicates the high ability of zeolite to absorb copper cations under biological conditions. An examination of the mass balance calculations has also shown the ability to replace clinoptilolite with penicillamine; 15 mg of clinoptilolite removes 214 mg of Cu from aqueous solutions, which is equivalent to the formation of copper-penicillamine chelate.

Ferrierite and Its Delaminated Forms Modified with Copper as Effective Catalysts for NH3-SCO Process

Ferrierites and their delaminated forms (ITQ-6), containing aluminum or titanium in the zeolite framework, were synthetized and modified with copper by an ion-exchange method. The obtained samples were characterized with respect to their chemical composition (ICP-OES), structure (XRD, UV-Vis DRS), textural parameters (N2-sorption), surface acidity (NH3-TPD), form and reducibility of deposited copper species (UV-Vis DRS and H2-TPR). Ferrierites and delaminated ITQ-6 zeolites modified with copper were studied as catalysts for the selective catalytic oxidation of ammonia to dinitrogen (NH3-SCO). It was shown that aggregated copper oxide species, which were preferentially formed on Ti-zeolites, were catalytically active in direct low-temperature ammonia oxidation to NO, while copper introduced into Al-zeolites was present mainly in the form of monomeric copper cations catalytically active in selective reduction of NO by ammonia to dinitrogen. It was postulated that ammonia oxidation in the presence of the studied catalysts proceeds according to the internal-selective catalytic reduction mechanism (i-SCR) and therefore the suitable ratio between aggregated copper oxide species and monomeric copper cations is necessary to obtain active and selective catalysts for the NH3-SCO process. Cu/Al-ITQ-6 presented the best catalytic properties possibly due to the most optimal ratio of these copper species.

Radiation-modified wool for adsorption of redox metals and potentially for nanoparticles

Electron beam irradiated sheep wool with absorbed radiation doses ranging from 0 to 165 kGy showed good adsorption properties toward copper cations. The Cu(ii) being Lewis acid generated several types of complex salts based on carboxylates or cysteinates with ligands available in keratin. Under these conditions, cross-links were formed between the keratin chains. Experimental data obtained from Cu(ii) adsorption using the concentration of 800–5,000 mg/L were tested for fitting to 10 isotherm models. Various compositions and architectures of the Cu(ii)-complexes were specified to be responsible for different isotherm model fittings. The copper cation showed adherence to Langmuir, Flory–Huggins, and partially Redlich–Peterson models. The latter clearly distinguished the native wool from the modified ones. Another aim is to investigate the conditions for the adsorption of anti-microbial nanoparticles in addition to the redox-active metals on radiation-modified wool taking into account that the diffusion of nanoparticles into the modified wool is governed by electrostatic interactions.

Saccharide-capped Superparamagnetic Copper Cations-doped Magnetite Nanoparticles for Biomedical Applications: A Novel and Simple Synthesis Procedure, In-situ Surface Engineering and Characterization

Background: Recently, superparamagnetic and electromagnetic nano-materials have been extensively studied and their potential applications have also been investigated in various fields. In this regard, currently, Fe3O4 NPs are valuable candidates as diagnostic agents such as magnetic resonance imaging, enzyme immobilization, biosensing and cell labeling, and therapeutic probes, including drug delivery, bacteria detection, magnetic separation, and hyperthermia agents. Objective: In this study, electrochemical synthesis of Cu2+ cations-doped superparamagnetic magnetite nanoparticles (Cu-SMNPs) and their in situ surface coating with saccharides (i.e., glucose, sucrose and starch) are reported. The prepared glucose/Cu-SMNPs, sucrose/Cu-SMNPs and starch/Cu-SMNPs samples are characterized by structural, magnetic and morphological analyses by XRD, FT-IR, FE-SEM, EDAX and VSM. The suitability of the prepared samples for biomedical use is also proved. Methods: A simple cathodic electrochemical set-up was used to fabricate the iron oxide samples. The bath electrolyte was one litre deionized water containing 1.5g iron chloride, 3g iron nitrate, 0.5g copper chloride and 0.5g saccharide (i.e., glucose or sucrose or starch). The cathode and anode electrodes were connected to a DC power supply (PROVA 8000) as the power source. The deposition experiments were conducted at 10 mA cm-2 for 30 min. For the preparation of glucose/Cu-SMNPs, sucrose/Cu-SMNPs and starch/Cu-SMNPs samples, three electrodeposition experiments were carried out in three similar baths with only a change in the dissolved saccharide type. The prepared SMNPs samples were characterized by structural, morphological and magnetic analyses including X-ray powder diffraction (XRD, a Phillips PW-1800 diffractometer Smart Lab), field-emission scanning electron microscopy (FE-SEM, Mira 3-XMU with accelerating voltage of 100 kV), transmission electron microscopy (TEM, model Zeiss EM900 with an accelerating voltage of 80 kV), fourier transform infrared (FT-IR, a Bruker Vector 22 Fourier transformed infrared spectrometer) and vibrating sample magnetometers (VSM, model Lakeshore 7410). Results: Three types of metal-cations doped superparamagnetic magnetite nanoparticles (SMNPs), glucosegrafted Cu2+-doped MNPs (glucose/Cu-SMNPs), sucrose-grafted Cu2+-doped SMNPs (sucrose/Cu-SMNPs) and starch-grafted Cu2+-doped SMNPs (starch/Cu-SMNPs), were prepared for the first time. Fourier-transform infrared spectroscopy, field-emission scanning electron microscopy and energy dispersive X-ray techniques proved the presence of saccharide capped layer on the surface of deposited SMNPs and also copper cations doping on their crystal structures. Superparamagnetic behaviors, including low coercivity and remanence values, were observed for all the prepared samples. Conclusion: SMNPs capped with saccharides (i.e., glucose, sucrose and starch) were successfully synthesized via one-pot simple deposition procedures. These particles showed suitable superparamagnetic properties with negligible remanence values and proper saturation magnetization, thus proving that they all have required physicochemical and magnetic characteristics for biomedical purposes.

PARADOXAL ACTIVITY OF AMINOGUANIDINE IN THE MODEL OF GLYCOXIDATION WITH COPPER CATIONS

The well-known inhibitor of advanced glycation-end products (AGEs) formation aminoguanidine, was studied using a previously tuned model of glycoxidation in copper-contained media (glucose 0,5 M, HEPES 0,1 M, CuSO4×5H2O 40 μM). As a result of the research, it was confirmed that aminoguanidine (1, 3, 10 mM) under conditions of glyoxidation with copper does not suppress the formation of argpyrimidine by detection of argpirimidine’s self-fluorescence (λex 330 nm, λem 360–450 nm). Possible reasons of the enormous reaction are discussed.

Simultaneous adsorption of Cu2+ and Cr (VI) using HDTMA-modified zeolite: isotherm, kinetic, mechanism, and thermodynamic studies

Clinoptilolite modified by hexadecyltrimethylammonium bromide (HDTMA-Br) was used to simultaneously remove copper and hexavalent chromium from aqueous solutions. The surface properties of HDTMA-modified natural zeolite (HMNZ) were characterized using scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), zeta potential and Fourier transform infrared spectroscopy (FTIR) techniques. SEM images showed that surfactant is adsorbed on the surface of the zeolite, which is confirmed by the FTIR result. The results from BET demonstrated a reduction in the specific surface area and pore volume due to the presence of surfactant molecules on the external surface of zeolite. The effects of important parameters on adsorption efficiency of Cu2+ and Cr (VI) were evaluated by Box-Behnken design. The Langmuir isotherm provided the best fit to the equilibrium data of Cu2+ and Cr (VI), with the maximum adsorption capacity of 0.068 and 0.0093(mmol), respectively. The film diffusion mechanism was found to control the mass transfer, and the adsorption reactions were computed as endothermic for Cu2+ ( = 17.58 kJ) and exothermic for Cr (VI) ( −26.18 kJ). The results indicated that surfactant modification changes the surface charge of zeolite from negative to positive, which makes zeolites economic adsorbents with the possibility of simultaneous removal of cations and oxyanions. The results also showed that the removal efficiency of Cr (VI) increases in the presence of copper cations due to there being more positive sites on the adsorbent surface.

Coordination Compounds Featuring Non-Toxic Chiral 1,4-Dicarboxylic Acids and Copper(II)

Six new coordination compounds of copper cations and 1,4-dicarboxylic acids have been synthesized and structurally investigated. Aspartic acid (H2asp), enantiopure, racemic and meso tartaric acid (H2tart), di-para-toluyltartaric acid (H2dptta) and dibenzoyltartaric acid (H2dbta) represent environmentally benign water-soluble proligands which may be deprotonated for oxygen coordination. Chelating ligands such as tetramethylethylenediamine (TMEDA) and 2-aminomethylpyridine (AMPY) efficiently reduce the dimensionality of the target compounds, and additional aqua ligands complete the coordination environments. In this line of argument, the discrete mononuclear complexes [Cu(AMPY)(asp)(H2O)] and [Cu(Hdbta)2(H2O)4] were obtained; for the latter, only a preliminary structure model can be presented which, however, agrees with the powder diffraction pattern of the bulk. From enantiopure and racemic tartaric acid and TMEDA the closely related chain polymers [CuII(H2tart)(TMEDA)(H2O)2)]n were obtained; the racemic compound consists of individual homochiral strands of opposite chirality. The high steric demand of di-para-toluyltartaric acid leads to one-dimensional [Cu(dptta)(EtOH)(H2O)2]n with coordinated ethanol (EtOH) in the distant Jahn–Teller site of the coordination sphere. Cu(II), meso-tartaric acid and TMEDA aggregate to a trinuclear coordination compound [CuII2CuI(H2tart)(Htart)(TMEDA)2]. Its peripheral cations show the expected Jahn–Teller geometry of Cu(II), but the unambiguous assignment of the oxidation state +I for central cation required susceptibility measurements: their results prove the presence of only two and only very weakly interacting divalent cations, separated by a diamagnetic center.