Electrochemical and structural properties of Ni(II)-alumina composites as an annealing temperature function

Alumina powders, pure and doped with nickel, were synthetized by sol-gel method and calcined at 500, 900 and 1100°C in order to obtain mesoporous structures with a high specific surface area, well adapTab. to catalytic application. The characterization of samples was performed by XRD, EPR spectroscopy and electrochemical impedance spectroscopy (EIS). XRD analysis showed that the addition of Ni2+, as well as the annealing temperature, affects the structural properties of the obtained composites. EPR analysis revealed the traces of Fe3+ impurities, the presence of oxy defects in alumina and Ni2+ in tetrahedral position for samples calcined at 1100°C. The impedance of the Nafion/alumina modified GCE depended on combined effect of porous structure and surface properties of alumina samples. The electrochemical behavior of a glassy carbon electrode modified with Ni (II)-doped aluminas was studied in 0.5 M NaOH solution, with and without methanol. The electrochemical activity of nickel-doped alumina composites was dictated by the amount of present NiO impurity.Прахови алумине, без додатка и са додатком никла, синтетисани су сол-гел методом и жарени на 500, 900 и 1100 oC с циљем да се добију мезопорозне структуре са високом специфичном површином, применљиве у каталитичке сврхе. Карактеризација узорака вршена је са XRD, EPR и EIS спектроскопијом. XRD анализа показала је да и додатак Ni2+-јона, као и температура жарења, утичу на структурне особине добијених композита. EPR анализом утврђено је присуство Fe3+-јона у траговима, окси-дефеката у алумини и Ni2+-јона у тетраедарским позицијама у узорцима жареним на 1100 oC. Импеданса стакло-карбон електроде модификоване нафион/алумином, зависила је од комбинованог ефекта порозне структуре и површинских карактеристика узорака алумине. Електрохемијско понашање модификоване стакло-карбон електроде испитивано је у 0.5M раствору NaOH, без и са метанолом. Електрохемијска активност никл-алумина композита диктирана је присуством NiO фазе

Electrochemical behavior of different types of alumina

This work presents the investigation of electrochemical properties of three alumina samples with different structure and crystal water content. The samples were characterized by XRD and FTIR-ATR analysis, confirming the presence of trihydrate, monohydrate and anhydrous alumina. The samples were used as modifiers of carbon paste electrodes. Their electrochemical behavior toward ferricyanide/ferrocyanide redox probe was evaluated by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behavior toward ruthenium hexamine redox probe was investigated by cyclic voltammetry. The response toward quinone/hydroquinone redox probe was evaluated in buffered and unbuffered solution by cyclic voltammetry. It was found that the surface chemistry of investigated samples influenced their electrochemical properties

Cobalt-doped alumina catalysts in catalytic oxidation of tartrazine induced by Oxone®

Porous cobalt-doped alumina catalysts were synthetized using the sol-gel method. The synthesized materials were calcined at 500 °C, 1000 °C and 1100 °C and denoted as CoA-500, CoA-1000 and CoA-1100, respectively. Catalysts were characterized using XRPD, H2-TPR and low temperature N2 physisorption techniques. Applied techniques showed that the annealing temperature affects the structural and textural properties of the catalysts. The synthesized catalysts were investigated in the degradation of tartrazine in the presence of Oxone®. The influence of the mass of catalyst, reaction time, reaction temperature and initial pH were investigated. The temperature increase was beneficial for the dye degradation rate. CoA-500 was proved to be the most efficient among the investigated catalysts. The reaction followed the pseudo-first order kinetics for all investigated temperatures for all three catalysts. All cobalt-doped alumina catalysts were found to be efficient in the Oxone® induced catalytic degradation of tartrazine with CoA-500 showing the best performance

Antimicrobial Nanocomposites Based on Oxidized Cotton Fabric and in situ Biosynthesized Copper Oxides Nanostructures Using Bearberry Leaves Extract

The aim of this study was to develop antimicrobial nanocomposite textile material comprising of Cu-based nanostructures synthesized on oxidized cotton fabric using Arctostaphylos uva-ursi (L.) Spreng., Ericaceae (bearberry leaves) as a green reducing agent for adsorbed Cu2+-ions. In order to provide sufficient number of carboxyl groups for complexation with Cu2+-ions a two-step oxidation process with NaIO4 and NaClO2 was carried out. The influence of NaIO4 concentration on content of carboxyl groups and Cu-based nanoparticles was studied by FTIR and AAS. HPLC analysis identified the gallic acid known as a reducing agent in bearberry leaves extract. FESEM and XRD analyses revealed that using bearberry leaves extract and gallic acid solution as reducing agents led to a formation of spherical Cu2O/CuO nanoparticles and CuO nanosheets, respectively. These nanoparticles and nanosheets provided excellent antibacterial activity against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus. Cytotoxicity on human keratinocyte cells was shown to depend on their copper content