Iron-carbon hybrid capacitor: A proof-of-concept study

In the present study, cost-intensive Ni electrode is replaced by high surface-area activated carbon (AC) cathode and the possibility of the Fe anode, used in Ni-Fe battery, to function as Fe-C hybrid capacitor has been examined. The electrochemical properties of Fe-C hybrid capacitor assembly are studied using cyclic voltammetry (CV) and galvanostatic charge-discharge cycles. Over 100 galvanostatic charge-discharge cycles for Fe-C hybrid capacitor are carried out and a maximum capacitance of 24 F g(-1) is observed.

Role of applied potentials on bioleaching of chalcopyrite concentrate and growth of Acidithiobacillus ferrooxidans

The effect of applied DC potentials on the bioleaching of a chalcopyrite concentrate in the presence of Acidithiobacillus ferrooxidans is discussed. Copper dissolution was the highest at an applied potential of +600mV (SCE), while all the dissolved copper got cathodically deposited at a negative potential of -600mV (SCE). Electrobioleaching at an applied potential of +600mV (SCE) was established at different pulp densities as a function of time. The effect of applied potentials and electrolytic currents on the activity and growth of bacterial cells was assessed Preadaptation of bacterial cells to the concentrate slurry and electrolytic growth conditions significantly enhanced copper dissolution. Electrochemical and biochemical mechanisms involved in electrobioleaching are illustrated with respect to oxidative dissolution and biocatalysis of anodic oxidation.

Synthesis and electrocatalytic properties of manganese dioxide for non-enzymatic hydrogen peroxide sensing

Manganese dioxide nanoparticles were synthesized by chemical reduction route at different growth temperatures of 40 degrees C, 80 degrees C, 100 degrees C and were characterized using X-ray Diffraction (XRD), Field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Cyclic Voltammetry (CV) and chronoamperometry (CA) analysis. FESEM results show that on increasing growth temperature the morphology changes from clusters into mixture of rods and flakes. XPS analysis reveals the formation of MnO2. Then these particles were immobilized on Pt electrode. A platinum (Pt) electrode modified with low dimensional MnO2 was investigated as a chronoamperometric (CA) sensor for hydrogen peroxide sensing (H2O2). The sample prepared at 100 degrees C shows good electrocatalytic ability for H2O2 sensing when compared with the samples prepared at 40 degrees C and 80 degrees C. At an operating potential of 0.3 V vs. Ag/AgCl catalytic oxidation of the analyte is measured for chronoamperometric (CA) monitoring. The CA signals are linearly proportional to the concentration of H2O2. It is also found that the morphology of the nanostructure plays a vital role in the detection of H2O2. (C) 2014 Elsevier Ltd. All rights reserved.

Highly sensitive and rapid detection of acetylcholine using an ITO plate modified with platinum-graphene nanoparticles

Determining the concentrations of acetylcholine (ACh) and choline (Ch) is clinically important. ACh is a neurotransmitter that acts as a key link in the communication between neurons in the spinal cord and in nerve skeletal junctions in vertebrates, and plays an important role in transmitting signals in the brain. A bienzymatic sensor for the detection of ACh was prepared by co-immobilizing choline oxidase (ChO) and acetylcholinesterase (AChE) on graphene matrix/platinum nanoparticles, and then electrodepositing them on an ITO-coated glass plate. Graphene nanoparticles were decorated with platinum nanoparticles and were electrodeposited on a modified ITO-coated glass plate to form a modified electrode. The modified electrode was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies. The optimum response of the enzyme electrode was obtained at pH 7.0 and 35 degrees C. The response time of this ACh-sensing system was shown to be 4 s. The linear range of responses to ACh was 0.005-700 mu M. This biosensor exhibits excellent anti-interferential abilities and good stability, retaining 50% of its original current even after 4 months. It has been applied for the detection of ACh levels in human serum samples.

Synthesis, X-ray structure and in vitro cytotoxicity studies of Cu(I/II) complexes of thiosemicarbazone: special emphasis on their interactions with DNA

4-(p-X-phenyl)thiosemicarbazone of napthaldehyde {where X = Cl (HL1) and X = Br (HL2)}, thiosemicarbazone of quinoline-2-carbaldehyde (HL3) and 4-(p-fluorophenyl) thiosemicarbazone of salicylaldehyde (H2L4) and their copper(I) {Cu(HL1)(PPh3)(2)Br]center dot CH3CN (1) and Cu(HL2)(PPh3)(2)Cl]center dot DMSO (2)} and copper(II) {((Cu2L2Cl)-Cl-3)(2)(mu-Cl)(2)]center dot 2H(2)O (3) and Cu(L-4)(Py)] (4)} complexes are reported herein. The synthesized ligands and their copper complexes were successfully characterized by elemental analysis, cyclic voltammetry, NMR, ESI-MS, IR and UV-Vis spectroscopy. Molecular structures of all the Cu(I) and Cu(II) complexes have been determined by X-ray crystallography. All the complexes (1-4) were tested for their ability to exhibit DNA-binding and - cleavage activity. The complexes effectively interact with CT-DNA possibly by groove binding mode, with binding constants ranging from 10(4) to 10(5) M-1. Among the complexes, 3 shows the highest chemical (60%) as well as photo-induced (80%) DNA cleavage activity against pUC19 DNA. Finally, the in vitro antiproliferative activity of all the complexes was assayed against the HeLa cell line. Some of the complexes have proved to be as active as the clinical referred drugs, and the greater potency of 3 may be correlated with its aqueous solubility and the presence of the quinonoidal group in the thiosemicarbazone ligand coordinated to the metal.

Synthesis and Characterization of Au@Pt Nanoparticles with Ultrathin Platinum Overlayers

Gold-core platinum-shell (Au@Pt) nanoparticles with ultrathin platinum overlayers, ranging from submonolayer to two monolayers of platinum atoms, were prepared at room-temperature using a scalable, wet-chemical synthesis route. The synthesis involved the reduction of chloroauric acid with tannic acid to form 5 nm (nominal dia.) gold nanoparticles followed by addition of desired amount of chloroplatinic acid and hydrazine to form platinum overlayers with bulk Pt/Au atomic ratios (Pt surface coverages) corresponding to 0.19 (half monolayer), 0.39 (monolayer), 0.58 (1.5 monolayer) and 0.88 (2 monolayers). The colloidal particles were coated with octadecanethiol and phase-transferred into chlroform-hexane mixture to facilitate sample preparation for structural characterization. The structure of the resultant nanoparticles were determined to be Au@Pt using HRTEM, SAED, XPS, UV-vis and confirmed by cyclic voltammetry (CV) studies. Monolayers of octadecanethiol coated Au@Pt nanoparticles were self-assembled at an air-water interface and transfer printed twice onto a gold substrate to form bilayer films for electrochemical characterization. Electrochemical activity on such films was observed only after the removal of the octadecanethiol ligand coating the nanoparticles, using a RF plasma etching process. The electrochemical activity (HOR, MOR studies) of Au@Pt nanoparticles was found to be highest for particles having a two atom thick platinum overlayer. These nanoparticles can significantly enhance platinum utilization in electrocatalytic applications as their platinum content based activity was three times higher than pure platinum nanoparticles.

A Comparative Study on Electrochemical Behaviour of Co3O4 and Co3O4-MWCNTs for Supercapacitors

Co3O4 and Co3O4/MWCNTs were prepared by hydrothermal process under autogenous pressure in Teflon lined autoclave and calcined at 250 degrees C. Both samples were characterized by PXRD, FT-IR, SEM-EDS, TEM & FT-Raman to evaluate their surface and bulk properties. The PXRD pattern of the materials indicated the formation of cubic phase of Co3O4. FT-IR results showed the presence of metal oxygen bond in the samples. The SEM and TEM images of the Co3O4 / MWCNTs indicated spherical and cubic aggregates of metal oxide particles (10-30 nm) decorated both on the surface and inside the tubes of carbon nanotubes. The characteristic Ig and Id (graphitic and defects) Raman bands indicated the retention of tubular structure of MWCNTs even after the deposition of Co3O4. The calcined Co3O4-MWCNTs composites and Co3O4 exhibited specific capacitance of 284 & 205 F/g at a sweep rate of 2mVs(-1) in 6M KOH by cyclic voltammetry. The psuedocapacitance performances of calcined Co3O4-MWCNTs were found to be better than Co3O4. Chronopotentiometric studies made for the materials at a current density of 500mA/g indicated 100% columbic efficiency at 2000th cycle for Co3O4/ MWCNTs which is a better electrode material than Co3O4.

Synthesis of cadmium oxide and carbon nanotube based nanocomposites and their use as a sensing interface for xanthine detection

Xanthine oxidase (XOD) extracted from bovine milk was immobilized covalently via N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry onto cadmium oxide nanoparticles (CdO)/carboxylated multiwalled carbon nanotube (c-MWCNT) composite film electrodeposited on the surface of an Au electrode. The nanocomposite modified Au electrode was characterized by Fourier transform infrared (FTIR), cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of XOD. Under optimal operation conditions (25 degrees C, + 0.2 V vs. Ag/AgCl, sodium phosphate buffer, pH 7.5), the following characteristics are attributed to the biosensor: linearity of response up to xanthine concentrations of 120 mu M, detection limit of 0.05 mu M (S/N = 3) and a response time of at most 4 s. After being used 100 times over a period of 120 days, only 50% loss of the initial activity of the biosensor was evaluated when stored at 4 degrees C. The fabricated biosensor was successfully employed for the determination of xanthine in fish meat.

Porous Flower-like alpha-Fe2O3 Nanostructure: A High Performance Anode Material for Lithium-ion Batteries

Porous flower-like alpha-Fe2O3 nanostructures have been synthesized by ethylene glycol mediated iron alkoxide as an intermediate and studied as an anode material of Li-ion battery. The iron alkoxide precursor is heated at different temperatures from 300 to 700 degrees C. The alpha-Fe2O3 samples possess porosity and high surface area. There is a decrease in pore volume as well as surface area by increasing the preparation temperature. The reversible cycling properties of the alpha-Fe2O3 nanostructures have been evaluated by cyclic voltammetry, galvanostatic charge discharge cycling, and galvanostatic intermittent titration measurements at ambient temperature. The initial discharge capacity values of 1063, 1168,1183, 1152 and 968 mAh g(-1) at a specific current of 50 mA g(-1) are obtained for the samples prepared at 300, 400, 500, 600 and 700 degrees C, respectively. The samples prepared at 500 and 600 degrees C exhibit good cycling performance with high rate capability. The high rate capacity is attributed to porous nature of the materials. As the iron oxides are inexpensive and environmental friendly, the alpha-Fe2O3 has potential application as anode material for rechargeable Li batteries. (C) 2015 Elsevier Ltd. All rights reserved.

Ni Nano-particle Encapsulated in Hollow Carbon Sphere Electrocatalyst in Polymer Electrolyte Membrane Water Electrolyzer

The present study evaluates the synthesis by solvo-thermal method and electrocatalytic activity of nickel nano-particles encapsulated in hollow carbon sphere, in hydrogen and oxygen evolution reaction in PEM water electrolyzer. The XRD patterns have ascertained the formation of nickel metal with different planes in face centered cubic (fcc) and hexagonal closed pack (hcp) form. SEM and TEM images have confirmed the nickel nano-particles with diameter of 10-50 nm inside the 0.2 mu m sized hollow carbon spheres. The BET surface area values gradually decreased with greater encapsulation of nickel; although the electrochemical active surface area (ECSA) values have been calculated as quite higher. It confirms the well dispersion of nickel in the materials and induces their electrocatalytic performance through the active surface sites. The cyclic voltammetric studies have evaluated hydrogen desorption peaks as five times more intense in nickel encapsulated materials, in comparison to the pure hollow carbon spheres. The anodic peak current density value has reached the highest level of 1.9 A cm(-2) for HCSNi10, which gradually decreases with lesser amount of nickel in the electrocatalysts. These electrocatalysts have been proved electrochemically stable during their usage for 48 h long duration under potentiostatic condition. (C) 2015 Elsevier Ltd. All rights reserved.

Simultaneous Determination of Catecholamines in Presence of Uric Acid and Ascorbic Acid at a Highly Sensitive Electrochemically Activated Carbon Paste Electrode

A simple yet remarkable, electrochemically activated carbon paste electrode (EACPE) was prepared by successive potential cycling of carbon paste in a 0.1 M NaOH solution and was effectively used for the simultaneous determination of catecholamines such as dopamine (DA), epinephrine (E) and Norepinephrine (NE) in presence of uric acid (UA) and ascorbic acid (AA). Taking DA as the ideal catecholamine, the electrochemical behaviors of DA, UA and AA such as scan rate and pH variation was studied by cyclic voltammetry (CV) in phosphate buffer solution (PBS, pH 7.1). This electrochemical sensor exhibited strong electrocatalytic activity towards the oxidation of a mixture of catecholamines, UA and AA with apparent reduction of overpotentials. Crider optimum conditions, limit of detection (S/N = 3) of DA, E, NE, UA and AA was found to be 0.08, 0.08, 0.07, 0.1 and 6.0 mu M, respectively by differential pulse voltammetry (DPV). The analytical performance of this modified electrode as a biosensor was also demonstrated for the determination of DA, UA and AA in dopamine injection, human urine and vitamin C tablets, respectively, in presence of other interfering substances. (C) 2015 The Electrochemical Society. All-rights reserved.

Synergistic effect of colchicine and iodide ions on the corrosion of mild steel in 0.5 M H2SO4

The inhibition behavior of colchicine (CC) on the corrosion of mild steel in 0.5 M H2SO4 was evaluated by electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopic measurements. The inhibition efficiency increases with increasing concentration of CC. The potentiodynamic polarization results reveal that CC act as a mixed-type inhibitor by retarding both cathodic and anodic corrosion reactions. Additionally, the synergism was carried out between CC and KI to improve the corrosion inhibition behavior of CC on mild steel. The adsorption of both CC alone and the combined inhibitor (CC + KI) on mild steel surface follows Langmuir adsorption isotherm. The synergism parameter (S (theta) ) was calculated to recognize the existence of synergism between CC and iodide ions. Lastly, an adsorption mechanism of CC molecules with iodide ions is discussed.

Pt-Doped and Pt-Supported La1-xSrxCoO3: Comparative Activity of Pt4+ and Pt-0 Toward the CO Poisoning Effect in Formic Acid and Methanol Electro-oxidation

Pt-supported La1-xSrxCoO3 and Pt-doped La1-xSrxCoO3 are synthesized using chemical reduction and solution combustion method, respectively. Chemical reduction is carried out using formaldehyde as a reducing agent giving Pt-supported La1-xSrxCoO3. Solution combustion method is used to prepare Pt-doped La1-xSrxCoO3. Detailed characterization using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface area measurement, and transmission electron microscopy (TEM) is carried out to distinguish the Pt-supported and Pt-doped compounds in terms of their morphology and Pt oxidations states. TEM results indeed show the differences in their morphology. Further, electrochemical measurements are performed in neutral medium to differentiate their electrochemical activity. Cyclic voltammetry (CV) shows noticeable differences between Pt-supported La1-xSrxCoO3 and Pt-doped La1-xSrxCoO3. Importantly, our results show that Pt4+ in doped compound has poor to zero electrocatalytic activity toward formic acid and methanol electro-oxidation in comparison to Pt-0 in supported compound. This study shows that metallic Pt in zero oxidation state is a superior catalyst to Pt in +4 oxidation state.

High T-g fluoranthene-based electron transport materials for organic light-emitting diodes

In this study, fluoranthene-based derivatives with a high thermal stability were synthesized for applications in organic electroluminescent devices. The two derivatives synthesized in this study, bis(4-(7,9,10-triphenylfluoranthen-8-yl)phenyl)sulfane (TPFDPS) and 2,8-bis(7,9,10-triphenylfluoranthen-8-yl)dibenzob,d]thiophene (TPFDBT), were characterized by cyclic voltammetry, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). TPFDPS exhibits a high T-g of 210 degrees C while TPFDBT is crystalline in nature. Both the derivatives are thermally stable up to 500 degrees C. The charge transport studies reveal predominant electron transport properties. Subsequently, we fabricated blue OLEDs with 2-tert-butyl-9,10-bis-(beta-naphthyl)-anthracene (TBADN) as the emitting layer to demonstrate the applications of these molecules as an electron transporting layer.

High Catalytic Activity of Amorphous Ir-Pi for Oxygen Evolution Reaction

Large-scale production of hydrogen gas by water electrolysis is hindered by the sluggish kinetics of oxygen evolution reaction (OER) at the anode. The development of a highly active and stable catalyst for OER is a challenging task. Electrochemically prepared amorphous metal-based catalysts have gained wide attention after the recent discovery of a cnbalt-phosphate (Co-Pi) catalyst: Herein, an amorphous iridium-phosphate (Ir-Pi) is investigated as an oxygen evolution catalyst. The catalyst is prepared by the anodic polarization of carbon paper electrodes in neutral phosphate buffer solutions containing IrCl3. The Ir-Pi film deposited on the substrate has significant amounts of phosphate and It centers in an oxidation state higher than +4. Phosphate plays a significant role in the deposition of the catalyst and also in its activity toward OER. The onset potential of OER on the Ir-Pi is about 150 mV lower in comparison with the Co-Pi under identical experimental conditions. Thus, Ir-Pi is a promising catalyst for electrochemical oxidation of water.